Random number generating device

The present invention relates to a random number generator and a random number generator.

It is known that random numbers are used for IDs (identification numbers) used in communication devices such as IC cards and non-contact communication. When a random number is used for such an ID, a random number with high irregularity is required. In response to such a requirement, in a regulated power supply that supplies a constant output voltage to a load circuit, a configuration is known in which a random number is generated using a control signal generated by amplifying the fluctuation of the output voltage with respect to the reference voltage. (See, for example, Patent Document 1).

FIG. 17 is a circuit diagram showing the configuration of a conventional random number generator. As shown in FIG. 17, a random number generator as in Patent Document 1 includes a regulator 900, a voltage controlled oscillator (VCO) 930, and a random number generator 940. The regulator 900 amplifies the error between the reference voltage Vref and the feedback voltage S93 with the amplifier 91 to generate the control voltage S91 in order to supply a constant output voltage Vout as the power supply for the load circuit 920, and outputs based on this. Adjusting the voltage Vout. The VCO930 outputs an output signal CLK in which the frequency of the oscillation frequency is changed according to the fluctuation of the voltage level of the control voltage S91. The random number generator 940 generates a pseudo-random number based on the output signal CLK of the VCO 930. In this way, the pseudo-random number generated by the random number generator 940 changes according to the oscillation frequency of the VCO 930 (that is, changes according to the control voltage S91 of the regulator 900), so as long as the control voltage S91 constantly fluctuates. Random numbers with high irregularity can be generated.

Further, Patent Document 2 also shows a configuration in which different pseudo-random numbers are generated according to fluctuations in the voltage level of the control voltage input to the control terminal of the VCO.

<p><patcit num="1"><text>JP-A-2007-122560</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 10-340183</text></patcit></p>

<p> However, in the above-mentioned random number generator, in order to obtain a random number with high irregularity, it is necessary that the fluctuation of the control voltage of the VCO is large. Patent Document 1 assumes that the control voltage changes due to an increase or decrease in the load or a fluctuation in the power supply voltage, but when the increase or decrease in the load is small and the power supply voltage is stable, the change in the control voltage almost disappears. It ends up. If the change in the control voltage is small, the fluctuation of the oscillation frequency in the output voltage of the VCO is also small, so that the irregularity of the random numbers is low. Further, Patent Document 2 also describes that a power source having a large voltage change is used as the control voltage of the VCO, but a specific mode of the power source is not disclosed.</p><p> The present invention solves such a conventional problem, and an object of the present invention is to provide a random number generator and a random number generation method capable of generating highly irregular random numbers with a simple configuration.</p>

<p> The random number generator according to a certain embodiment of the present invention has a receiving mechanism that receives energy sent from the transmitting unit in a non-contact manner, and has a receiving unit that converts the energy received by the receiving mechanism into a receiving voltage, and the receiving voltage. Based on the above, a voltage-controlled oscillator that outputs an oscillating output signal and a pseudo-random number generator that generates a pseudo-random number that fluctuates according to the oscillation frequency of the output signal of the voltage-controlled oscillator are provided.</p><p> According to the above configuration, the oscillation frequency of the output signal output by the voltage controlled oscillator fluctuates according to the reception voltage of the receiving unit that receives the energy transmitted from the transmitting unit in a non-contact manner. Since the reception voltage fluctuates according to the distance between the transmission unit and the reception unit, the reception voltage can be significantly changed by changing the distance. Since the pseudo-random number can be generated based on the reception voltage that fluctuates greatly in this way, it is possible to generate a random number with high irregularity with a simple configuration.</p><p> A limiter circuit that limits the reception voltage of the reception unit to a predetermined voltage range may be provided. As a result, the voltage input to the voltage controlled oscillator (voltage based on the received voltage) can be within the operating range of the voltage controlled oscillator.</p><p> The limiter circuit may have a temperature-dependent characteristic in which the output voltage value fluctuates according to the temperature. As a result, the voltage input to the voltage controlled oscillator fluctuates even when the temperature changes, so that a random number with higher irregularity can be generated.</p><p> The receiving mechanism may include a coil that receives electromagnetic waves from the transmitting unit in a non-contact manner. As a result, the induced electromotive force generated in the coil easily fluctuates according to the distance between the transmitting unit and the receiving unit. Moreover, the induced electromotive force generated in the coil can be easily used as a power source for the receiving unit.</p><p> The receiving mechanism may include a light receiving element that receives light from the transmitting unit in a non-contact manner. As a result, the amount of light received by the light receiving element easily varies depending on the distance between the transmitting unit and the receiving unit.</p><p> The voltage controlled oscillator is configured to switch between an on period for outputting the output signal based on the received voltage and an off period for outputting the output signal fixed at a predetermined voltage level based on the operation signal, and the pseudo-random number. The generator may be configured to generate a pseudo-random number that fluctuates based on the number of waves of the output signal input during the on period. As a result, a period in which the reception voltage fluctuation is large can be set as the on period, so that a pseudo-random number can be generated based on the period in which the reception voltage fluctuation is large, and as a result, the irregularity of the random number is further increased. Can be enhanced.</p><p> The pseudo-random number generator may include an M-sequence bit string arithmetic unit having a shift register and an exclusive OR gate. As a result, a complicated pseudo-random number sequence can be easily generated with a simple configuration.</p><p> Further, the random number generation method according to another embodiment of the present invention oscillates based on a reception step of receiving energy from a transmission unit in a non-contact manner and converting the received energy into a reception voltage, and the reception voltage. It includes a voltage-controlled oscillation step that outputs an output signal and a pseudo-random number generation step that generates a pseudo-random number that fluctuates according to the oscillation frequency of the output voltage.</p><p> According to the above method, the oscillation frequency of the output signal fluctuates according to the received voltage obtained by converting the energy received from the transmitting unit in a non-contact manner. Since the reception voltage fluctuates according to the distance to and from the transmission unit, the reception voltage can be greatly fluctuated by changing the distance. Since the pseudo-random number can be generated based on the reception voltage that fluctuates greatly in this way, it is possible to generate a random number with high irregularity with a simple configuration.</p>

<p> The present invention is configured as described above, and has the effect of being able to generate highly irregular random numbers with a simple configuration.</p>

<figref num="1">FIG. 1 is a circuit diagram showing a schematic configuration example of a random number generator according to the first embodiment of the present invention.</figref><figref num="2">FIG. 2 is a circuit diagram showing a specific configuration example of the receiving unit in the random number generator shown in FIG.</figref><figref num="3">FIG. 3 is a graph showing a change in the receiving voltage according to the distance between the receiving unit and the transmitting unit in the random number generator of FIG.</figref><figref num="4">FIG. 4 is a circuit diagram showing a specific configuration example of the pseudo-random number generator in the random number generator shown in FIG.</figref><figref num="5">FIG. 5 is a circuit diagram showing a schematic configuration example of a random number generator according to a modified example of the first embodiment of the present invention.</figref><figref num="6">FIG. 6 is a circuit diagram showing a schematic configuration example of the random number generator according to the second embodiment of the present invention.</figref><figref num="7">FIG. 7 is a graph showing the oscillation frequency characteristics with respect to the control voltage of the voltage controlled oscillator of the random number generator shown in FIG.</figref><figref num="8">FIG. 8 is a circuit diagram showing a specific configuration example of the limiter circuit shown in FIG.</figref><figref num="9">FIG. 9 is a graph showing the simulation results of the input / output voltage characteristics of the limiter circuit shown in FIG.</figref><figref num="10">FIG. 10 is a graph showing the simulation results of the output voltage characteristics with respect to the temperature of the limiter circuit shown in FIG.</figref><figref num="11">FIG. 11 is a circuit diagram showing a schematic configuration example of a random number generator according to a modified example of the second embodiment of the present invention.</figref><figref num="12">FIG. 12 is a graph showing the simulation results of the input / output voltage characteristics of the limiter circuit shown in FIG.</figref><figref num="13">FIG. 13 is a graph showing the simulation results of the output voltage characteristics with respect to the temperature of the limiter circuit shown in FIG.</figref><figref num="14">FIG. 14 is a circuit diagram showing a schematic configuration example of a receiving unit in the random number generator according to the third embodiment of the present invention.</figref><figref num="15">FIG. 15 is a circuit diagram showing a configuration example of a communication device to which the random number generator according to the embodiment of the present invention is applied.</figref><figref num="16">FIG. 16 is a schematic diagram showing an example of the relationship between the primary coil and the secondary coil.</figref><figref num="17">FIG. 17 is a circuit diagram showing the configuration of a conventional random number generator.</figref>

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, the same or corresponding elements will be designated by the same reference numerals throughout all the figures, and duplicate description thereof will be omitted.

&lt;First Embodiment&gt; First, the random number generator according to the first embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing a schematic configuration example of a random number generator according to the first embodiment of the present invention.

As shown in FIG. 1, the random number generator 10 in the present embodiment has a receiving mechanism 101 that receives the energy sent from the transmitting unit 20 in a non-contact manner, and the energy received by the receiving mechanism 101 is set to the receiving voltage VIN. The receiving unit 100 to be converted, the voltage controlled oscillator (VCO) 110 that outputs the oscillating output signal CKIN based on the received voltage VIN, and the pseudo-random number (pseudo-random number) that fluctuates according to the oscillation frequency of the output signal CKIN of the voltage controlled oscillator 110. It is equipped with a pseudo-random number generator 120 that generates pseudorandom numbers).

When energy is transmitted from the transmitting unit 20 in a non-contact manner, the receiving unit 100 receives the energy in the receiving mechanism 101 and converts the energy into a receiving voltage VIN. A control voltage VCOIN based on the received voltage VIN is input to the voltage controlled oscillator 110. In this embodiment, the control voltage VCOIN is equal to the reception voltage VIN. The voltage controlled oscillator 110 outputs an output signal (clock signal) CKIN that oscillates based on the input control voltage VCOIN. The pseudo-random number generator 120 generates a pseudo-random number sequence that fluctuates according to the output signal CKIN of the voltage controlled oscillator 110, and outputs a pseudo-random number of the pseudo-random number sequence for each bit. In this embodiment, it has 20 output terminals S1 to S20 and generates a pseudo-random number sequence composed of 20-bit pseudo-random numbers.

According to the above configuration, the oscillation frequency of the output signal CKIN output by the voltage controlled oscillator 110 fluctuates according to the reception voltage VIN of the reception unit 100 that receives the energy transmitted from the transmission unit 20 in a non-contact manner. Since the reception voltage VIN fluctuates according to the distance between the transmission unit 20 and the reception unit 100, the reception voltage VIN can be greatly fluctuated by changing the distance. Since the pseudo-random number can be generated based on the reception voltage VIN that fluctuates greatly in this way, it is possible to generate a random number with high irregularity with a simple configuration.

FIG. 2 is a circuit diagram showing a specific configuration example of the receiving unit in the random number generator shown in FIG. As shown in FIG. 2, the transmission unit 20 in the present embodiment has a coil (primary side coil) L2 to which a voltage based on electric power supplied from a power source (not shown) is applied. Correspondingly, the receiving unit 100 in the present embodiment includes a coil (secondary side coil) L1 that receives electromagnetic waves as energy from the transmitting unit 20 in a non-contact manner as the receiving mechanism 101. As a result, energy can be transferred and received by electromagnetic induction between the coil L2 of the transmitting unit 20 and the coil L1 of the receiving unit 100. Therefore, an induced electromotive force E is generated in the coil L1 of the receiving unit 100 by transmitting energy due to electromagnetic waves from the coil L2 of the transmitting unit 20 to the coil L1 of the receiving unit 100 in a non-contact manner. In this way, since the induced electromotive force E is generated in the coil L1 of the receiving unit 100 by non-contact, the induced electromotive force E generated in the coil L1 is easily generated according to the distance between the transmitting unit 20 and the receiving unit 100. Fluctuates to. As a result, the received voltage VIN easily fluctuates. Moreover, it is easy to use the induced electromotive force E generated in the coil L1 as a power source for the random number generator 10.

Further, the receiving unit 100 includes a rectifier circuit 102 that rectifies the induced electromotive force E received by the coil L1 of the receiving mechanism 101. Specifically, the rectifier circuit 102 is composed of a diode bridge circuit in which four diodes D1 to D4 are connected in a bridge type. The anode of the diode D1 and the cathode of the diode D3 are connected to one end of the coil L1, and the anode of the diode D2 and the cathode of the diode D4 are connected to the other end of the coil L1. Further, the cathodes of the diode D1 and the diode D2 are connected to each other, and the anodes of the diode D3 and the diode D4 are connected to each other. The rectifier circuit 102 full-wave rectifies the induced electromotive force E received by the coil L1 of the receiving mechanism 101.

Further, the receiving unit 100 includes a capacitive element C1 for stabilizing the induced electromotive force E rectified by the rectifier circuit 102. The cathodes of the diodes D1 and D2 are connected to one end of the capacitive element C1, and the anodes of the diodes D3 and D4 are connected to the other end of the capacitive element C1. The other end of the capacitive element C1 is connected to the ground, and the voltage at one end of the capacitive element C1 is output as the received voltage VIN of the receiving unit 100.

Here, the relationship between the distance d between the coil L1 of the receiving unit 100 and the coil L2 of the transmitting unit 20 and the induced electromotive force E generated in the coil L1 of the receiving unit 100 will be described. FIG. 16 is a schematic diagram showing an example of the relationship between the primary coil and the secondary coil. In the following description, the coil L2 of the transmitting unit 20 is simply referred to as the primary coil L2, and the coil L1 of the receiving unit 100 is referred to as the secondary coil L1. In FIG. 16, the primary side coil L2 and the secondary side coil L1 are shown as circular coils, but the same applies to coils having other shapes.

As shown in FIG. 16, the distance between the primary coil L2 and the secondary coil L1 (distance between the coils) is d, and the radius of each coil L1 and L2 is a. At this time, the mutual inductance M is M = μ using the Neumann formula.₀It is represented by a (log (8a / d) -2). In addition, μ₀Indicates the magnetic permeability of the vacuum. In this way, it can be understood that the mutual inductance M changes according to the distance d between the coils. Further, the AC current I from the AC power supply P1 of the primary coil L2 is the maximum value (amplitude) I of the current.₀I = I using₀It can be expressed as sinωt. At this time, the induced electromotive force e generated in the secondary coil L1 is e = -M (dI / dt) = -MI.₀It becomes ωcosωt and e₀= MI₀If you set ω, e = -e₀It becomes cosωt.

Since the effective value E of the generated induced electromotive force e is equal to 1 / 2 of the maximum value, E = e₀/ 2 = MI₀ω / 2 = (μ₀aI₀ω / 2) (log (8a / d) -2), which is a constant μ₀aI₀If ω / 2 is C, then E = C (log (8a / d) -2). In this way, it can be understood that the effective value E of the induced electromotive force e generated in the secondary coil L1 changes according to the distance d between the coils. Therefore, the reception voltage VIN determined based on the effective value E of the induced electromotive force e generated in the secondary coil L1 also changes according to the distance d between the primary coil L2 and the secondary coil L1. Can be understood.

FIG. 3 is a graph showing a change in the receiving voltage according to the distance between the receiving unit and the transmitting unit in the random number generator of FIG. In the example of FIG. 3, the maximum current I of the AC current I from the AC power supply P1 of the primary coil L2₀= 100mA, frequency f = ω / 2π = 100kHz, number of turns N1 = N2 = 30 of primary coil L1 and secondary coil L2, radius a1 = a2 = 30mm of primary coil L1 and secondary coil L2 ..

As shown in FIG. 3, the reception voltage VIN decreases as the inter-coil distance d increases (that is, the distance d between the transmitting unit 20 and the receiving unit 100), and the smaller the inter-coil distance d (that is, the transmitting unit). The reception voltage VIN increases (the closer the 20 and the reception unit 100 are). In this way, when the distance d between the coil (primary side coil) L2 of the transmission unit 20 and the coil (secondary side coil) L1 of the reception unit 100 changes, the mutual inductance M changes, resulting in an induced electromotive force. Since the magnitude of e fluctuates greatly, the received voltage VIN also fluctuates greatly. Therefore, by generating a pseudo-random number based on the reception voltage VIN that fluctuates greatly depending on the distance between the transmission unit 20 and the reception unit 100, it is possible to generate a highly irregular random number.

The voltage controlled oscillator 110 is not particularly limited, but for example, a ring oscillator type voltage controlled oscillator can be applied. Although not shown, the ring oscillator type voltage control oscillator 110 is based on a voltage-current conversion circuit that receives a control signal VCOIN based on the received voltage VIN and converts the voltage level of the control signal VCOIN into a current, and a converted current value. It also has an inverter chain circuit that sets the frequency clock of the output signal CKIN. The inverter chain circuit is configured by connecting multiple inverters in succession, and the delay decreases as the converted current value increases (the frequency of the output signal CKIN increases), and the converted current value increases. The output signal CKIN is output so that the decrease increases the delay (the frequency of the output signal CKIN decreases).

FIG. 4 is a circuit diagram showing a specific configuration example of the pseudo-random number generator in the random number generator shown in FIG. As shown in FIG. 4, the pseudo-random number generator 120 in this embodiment includes an M-sequence bitwise operation unit having a shift register 122 and an exclusive OR (XOR) gate 123. In the present embodiment, the shift register 122 is a shift register having an output of a plurality of bits (20 bits in the example of FIG. 4) by sequentially connecting a plurality of (20 in the example of FIG. 4) registers 121. It is configured.

Each register 121 is composed of, for example, a D flip-flop circuit. The output signal CKIN of the voltage controlled oscillator 110 is input to the clock input terminal of each register 121. Further, the output signal of the XOR gate 123 is input to the input terminal of the register 121 in the first stage. The output signal of the previous stage is input to the input terminal of each register 121 of the other stage. Therefore, each register 121 sets the signal level (either L level or higher H level) input from the input terminal each time the clock pulse of the output signal CKIN of the voltage controlled oscillator 110 is input. Output to 121. Further, the output of each register 121 is output from the output terminals S1 to S20 of the pseudo-random number generator 120, and a 20-bit pseudo-random number that differs depending on the wave number (number of clock pulses) of the output signal CKIN of the voltage controlled oscillator 110 is generated. Generated.

Further, at the input terminal of the XOR gate 123, the output signal of the register 121 of the predetermined stage (17th stage in the example of FIG. 4) and the output of the register 121 of the final stage (20th stage in the example of FIG. 4) A signal is input.

The register 121 connected to the input terminal of the XOR gate 123 is set as follows. That is, the M-sequence bit string applied in the pseudo-random number generator 120 of the present embodiment is a bit number sequence represented by the following linear recurrence formula.

X_n= (X_np) XOR (X_nq) However, p&gt; q&gt; 0 The period of the M-sequence bit string shown in this way is 2^pIndicated by -1. In the example of Fig. 4, p = 20 and q = 17, and the period is 2.²⁰-1 = 1048575. Since the values of p and q can be set as needed, the register 121 connected to the input terminal of the XOR gate 123 can be changed accordingly.

Here, the number of waves (the number of clock pulses) of the output signal CKIN of the voltage controlled oscillator 110 input to the shift register 122 of the pseudo-random number generator 120 in a predetermined period is between the transmitting unit 20 and the receiving unit 100. The induced electromotive force generated in the coil L1 easily fluctuates according to the distance of the coil L1.

As described above, in the random number generator 10 of the present embodiment, even if the input period of the output signal CKIN to the pseudo-random number generator 120 is constant, the number of waves of the output signal CKIN input to the pseudo-random number generator 120 is Since it fluctuates, the pseudo-random number generated by the pseudo-random number generator 120 fluctuates greatly, and a highly irregular random number can be output. The input period of the output signal CKIN to the pseudo-random number generator 120 may be determined by whether or not the voltage controlled oscillator 110 is operated as described later, or the output terminal of the voltage controlled oscillator 110 is set only for a predetermined period. It may be connected to the input terminal of the pseudo-random number generator 120. Further, it may have a configuration for acquiring the output values of the output terminals S1 to S20 of the pseudo-random number generator 120 at a predetermined timing.

Here, an example in which the voltage controlled oscillator 110 outputs the output signal CKIN in response to a predetermined operating signal will be described. FIG. 5 is a circuit diagram showing a schematic configuration example of a random number generator according to a modified example of the first embodiment of the present invention. In the random number generator 10B of the example of FIG. 5, the voltage controlled oscillator 110B outputs an on-period T1 that outputs an output signal CKIN based on the received voltage VIN and an off-period T2 that outputs the output signal fixed at a predetermined voltage level. It is configured to switch based on VCOON. Further, the pseudo-random number generator 120 is configured to generate different pseudo-random numbers based on the wave number of the output signal CKIN input in the on-period T1.

The operation signal VCOON is not particularly limited, but may be a signal having a constant on-period T1 or a signal having a different on-period T1 each time. When the ON period T1 becomes a constant signal, the operating signal VCOON is the predetermined time after the reception voltage VIN becomes equal to or higher than the predetermined first voltage due to, for example, the transmission unit 20 approaching the reception mechanism 101 of the reception unit 100. It may be a signal whose on-period is T1 until the elapse of. When the ON period T1 is different each time, the operating signal VCOON is set to, for example, a predetermined second voltage or higher in which the received voltage VIN is higher than the first voltage after the received voltage VIN becomes the predetermined first voltage or higher. It may be a signal that has an on-period T1 until it becomes. Such an operation signal VCOON may be generated in the random number generator 10B, or an externally generated signal may be input.

As a result, the period in which the change in the received voltage VIN is large can be set as the on period T1, so that a pseudo-random number can be generated based on the period in which the change in the received voltage VIN is large, and as a result, the random numbers are irregular. You can improve your sex.

Next, how much the wave number changes in the output signal CKIN of the voltage controlled oscillator 110B due to the fluctuation of the induced electromotive force E generated in the receiving mechanism 101 of the receiving unit 100 in such a random number generator will be described. Here, the on-period T1 is constant (50 ms), and the frequency gain G (details will be described later) of the voltage controlled oscillator 110B is 20 MHz / V.

Assuming that the voltage V1 of the control signal VCOIN input to the voltage controlled oscillator 110B is 0.83V with respect to the received voltage VIN = 2V as shown in FIG. 9 described later, the oscillation frequency f1 of the output signal CKIN is f1. = G V1 = 16.6MHz. Therefore, the wave number (number of clock pulses) n1 of the oscillation frequency f1 in the on period T1 is n1 = T1 / (1 / f1) = 830000. Here, when the voltage of the control signal VCOIN input to the voltage controlled oscillator 110B changes by 1 mV with respect to V1 (when V2 = V1 + 0.001V = 0.831V), the oscillation frequency f2 of the output signal CKIN is f2 = G V2 = 16.62MHz. Therefore, the wave number n2 of the oscillation frequency f2 in the on period T1 is n2 = T1 / (1 / f2) = 831000.

From the above, when the voltage of the control signal VCOIN changes by 0.1 mV, the difference in the wave numbers input to the pseudo-random number generator 120 changes by n2-n1 = 1000 ( 1). If the wave numbers differ by 1 or more, different pseudo-random numbers are naturally generated, so the output random numbers become irregular. In this way, even if the on-period T1 is constant, the wave number of the output signal CKIN input to the pseudo-random number generator 120 fluctuates each time the on-period T1 is reached. Therefore, an irregular random number can be easily generated with a simple configuration. be able to.

When the operating signal VCOON becomes T2 during the off period, the voltage level of the output signal CKIN input to the pseudo-random number generator 120 becomes a predetermined voltage level (regardless of the fluctuation of the control signal VCOIN input to the voltage controlled oscillator 110). Since the pseudo-random number generator 120 does not operate (L level), the outputs of the output terminals S1 to S20 of the pseudo-random number generator 120 are held in the state when the on period T1 has elapsed. Therefore, as will be described later, the random numbers generated even after the operation signal VCOON changes to the off period T2 can be used for the identification number ID of the communication device or the like. Further, in the off period T2, the voltage controlled oscillator 110 and the pseudo-random number generator 120 are stopped, so that power saving can be achieved.

&lt;Second embodiment&gt; Next, the random number generator according to the second embodiment of the present invention will be described. FIG. 6 is a circuit diagram showing a schematic configuration example of the random number generator according to the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The random number generator 10C of the present embodiment is different from the first embodiment in that it includes a limiter circuit 130 that limits the reception voltage VIN of the reception unit 100 to a predetermined voltage range.

FIG. 7 is a graph showing the oscillation frequency characteristics with respect to the control voltage of the voltage controlled oscillator of the random number generator shown in FIG. As shown in FIG. 7, it is known that the voltage controlled oscillator 110 linearly changes the oscillation frequency of the output signal CKIN up to a predetermined voltage range with respect to the control voltage VCOIN. In the example of FIG. 7, the control voltage VCOIN changes linearly in the range of 0 to 2.0V, but when it exceeds 2.0V, the oscillation frequency approaches the upper limit due to the circuit characteristics of the voltage controlled oscillator 110, so the control voltage The rate of increase of the oscillation frequency decreases with respect to the increase of VCOIN. Therefore, if a voltage exceeding 2.0 V is input as the control voltage VCOIN, the oscillation frequency of the output signal CKIN of the voltage controlled oscillator 110 does not fluctuate so much, and the irregularity of the pseudo-random number decreases, which is not preferable.

Therefore, in the present embodiment, the reception voltage VIN of the reception unit 100 is limited to a predetermined voltage range (for example, the range of 0 to 2.0V in the example of FIG. 7) between the voltage controlled oscillator 110 and the reception unit 100. The limiter circuit 130 is provided. As a result, the voltage input to the voltage controlled oscillator 110 (voltage based on the received voltage VIN) can be set within the operating range of the voltage controlled oscillator 110 (within the range of 0 to 2.0 V). In the example of FIG. 7, the frequency gain (frequency change amount per 1V) G in the linear region of the voltage controlled oscillator 110 (control voltage VCOIN is in the range of 0 to 2.0V) is G = 40MHz / 2.0V = 20 ( MHz / V).

FIG. 8 is a circuit diagram showing a specific configuration example of the limiter circuit shown in FIG. As shown in FIG. 8, the limiter circuit 130 in this embodiment is connected in series between an input terminal into which a reception voltage VIN which is an input voltage is input and a predetermined voltage source (ground in the example of FIG. 8). It is equipped with resistors R1 and R2 and diode D5. In diode D5, the anode is connected to resistor R2 and the cathode is connected to ground. The output terminal is provided between the resistors R1 and R2, and is configured to output the voltage divided by the resistors R1 and R2 as the output voltage (control voltage VCOIN). Then, the voltage division ratio between the resistors R1 and R2 is set so that the control voltage VCOIN, which is the voltage divider output, is within the voltage range of the voltage controlled oscillator 110.

The operation of such a limiter circuit 130 will be described. When the voltage applied to the diode D5 is smaller than the region where the IV characteristics of the diode D5 change significantly (meaning the so-called on-voltage, for example, around 0.6 V for a silicon diode), the voltage applied to the diode D5. On the other hand, the forward current flowing through the diode D5 is very small. Therefore, the control voltage VCOIN output from the output terminal changes relatively significantly according to the change in the reception voltage VIN applied to the input terminal. On the other hand, when the input received voltage VIN becomes larger and the voltage applied to the diode D5 becomes higher than the on voltage, the order of flow to the diode D5 with respect to the voltage applied to the diode D5. The directional current becomes very large. Therefore, the control voltage VCOIN output from the output terminal has a smaller increase rate than the reception voltage VIN applied to the input terminal. From the above, by setting the values of resistors R1 and R2 so that the voltage applied to the diode D5 becomes the on-voltage when a voltage close to the upper limit of the desired voltage range is applied to the output terminal. The optimum limiter circuit 130 can be easily formed.

FIG. 9 is a graph showing the simulation results of the input / output voltage characteristics of the limiter circuit shown in FIG. FIG. 9 shows the input / output voltage characteristics when the resistance value of the resistor R1 of the limiter circuit 130 shown in FIG. 8 is 1000 kΩ, the resistance value of the resistor R2 is 2 kΩ, and the standard operating temperature is 25 ° C. As shown in FIG. 9, even if the reception voltage VIN, which is the input voltage, exceeds 2.0 V, the increase in the control voltage VCOIN, which is the output voltage, is suppressed. Therefore, the control voltage does not exceed the voltage range of the voltage controlled oscillator 110. Can be set.

In the present embodiment, the limiter circuit 120 is configured by using the diode D5, but the present invention is not limited to this as long as it is a rectifying element having a non-linear IV characteristic. For example, instead of the diode D5, a Schottky barrier diode or a Zener It is also possible to use a diode or the like. In the case of a Schottky barrier diode, like the diode D5, it is connected so that the direction from the resistor R2 toward the predetermined voltage source is forward, and in the case of the Zener diode, the direction from the predetermined voltage source toward the resistor R2 is. Connected in the forward direction.

Further, the limiter circuit 120 as described above may have a temperature-dependent characteristic in which the output voltage value fluctuates according to the temperature. FIG. 10 is a graph showing the simulation results of the output voltage characteristics with respect to the temperature of the limiter circuit shown in FIG. In FIG. 10, the resistance value of the resistor R1 of the limiter circuit 130 shown in FIG. 8 is 1000 kΩ, the resistance value of the resistor R2 is 2 kΩ, and the received voltage VIN, which is the input voltage, is (A) VIN = 8 V, (B) VIN = 4 V. , (C) When VIN = 2V, the voltage change of the control voltage VCOIN, which is the output voltage when the operating temperature of the limiter circuit 130 is changed between -20 ° C and 100 ° C, is shown.

As shown in FIG. 10, even if the reception voltage VIN, which is the input voltage, is the same voltage, the control voltage VCOIN, which is the output voltage, fluctuates as the temperature changes. In the example of FIG. 10, the control voltage VCOIN decreases as the temperature increases. That is, in the example of FIG. 10, the limiter circuit 130 has a negative temperature coefficient in the entire circuit. The limiter circuit may be configured so that the entire limiter circuit has a positive temperature coefficient. Such temperature dependence occurs depending on the temperature characteristics of the resistors R1 and R2 and the diode D5 constituting the limiter circuit 130. The desired temperature dependence can be obtained by combining the temperature characteristics of each component so that the desired temperature characteristics can be obtained in the entire limiter circuit 130. As a result, the voltage (control voltage VCOIN) input to the voltage controlled oscillator 110 fluctuates even when the temperature changes, so that a random number with higher irregularity can be generated.

&lt;Modified example of the second embodiment&gt; Next, a random number generator according to a modified example of the second embodiment of the present invention will be described. FIG. 11 is a circuit diagram showing a schematic configuration example of a random number generator according to a modified example of the second embodiment of the present invention. In this modification, the same components as those in the second embodiment are designated by the same reference numerals and the description thereof will be omitted. The random number generator of this modification (the entire random number generator is not shown in FIG. 11) is different from the second embodiment in that the configuration of the limiter circuit 130D is different from that of the limiter circuit 130 of the second embodiment. is there. Specifically, as shown in FIG. 11, the limiter circuit 130D includes resistors R3 and R4 connected in series between the input terminal and a predetermined voltage source (ground in the example of FIG. 11), and the resistors R3. It is equipped with a diode D6 in which an anode is connected between the resistor R4 and a predetermined voltage source (ground in the example of FIG. 11) is connected to the cathode. An output terminal is connected between the resistor R3 and the resistor R4.

According to such a configuration, the received voltage VIN applied to the input terminal is divided by the resistors R3 and R4, and the divided voltage is applied to the diode D6. The voltage applied to the diode D6 becomes the control voltage VCOIN output from the output terminal. When the voltage applied to the diode D6 is smaller than the on voltage of the diode D6, the forward current flowing through the diode D6 is very small with respect to the voltage applied to the diode D6. Therefore, the control voltage VCOIN output from the output terminal fluctuates relatively greatly according to the change in the reception voltage VIN applied to the input terminal. On the other hand, when the input received voltage VIN becomes larger and the voltage applied to the diode D6 becomes higher than the on voltage, the order of flow to the diode D6 with respect to the voltage applied to the diode D6. The directional current becomes very large. Therefore, the control voltage VCOIN output from the output terminal has a smaller increase rate than the reception voltage VIN applied to the input terminal. From the above, by setting the values of the resistors R3 and R4 so that the voltage applied to the diode D6 becomes the on-voltage when a voltage close to the upper limit of the desired voltage range is applied to the output terminal. The optimum limiter circuit 130D can be easily formed.

FIG. 12 is a graph showing the simulation results of the input / output voltage characteristics of the limiter circuit shown in FIG. FIG. 12 shows the input / output voltage characteristics when the resistance values of the resistors R3 and R4 of the limiter circuit 130D shown in FIG. 11 are both 1000 kΩ and the standard operating temperature is 25 ° C. In this modified example as well, as shown in FIG. 12, even if the received voltage VIN, which is the input voltage, exceeds 2.0 V, the increase in the control voltage VCOIN, which is the output voltage, is suppressed. The control voltage VCOIN can be set within a range that does not exceed it.

In this modification as well, a Schottky barrier diode or a Zener diode may be used instead of the diode D6.

Further, the limiter circuit 130D of this modification may also be configured to have temperature-dependent characteristics. FIG. 13 is a graph showing the simulation results of the output voltage characteristics with respect to the temperature of the limiter circuit shown in FIG. In FIG. 13, the resistance values of the resistors R3 and R4 of the limiter circuit 130D shown in FIG. 11 are 1000 kΩ, respectively, and the received voltage VIN, which is the input voltage, is (A) VIN = 8V, (B) VIN = 4V, (C) VIN. When = 2V, the voltage change of the control voltage VCOIN, which is the output voltage when the operating temperature of the limiter circuit 130D is changed between -20 ° C and 100 ° C, is shown.

In this modification as well, as shown in FIG. 13, even if the reception voltage VIN which is the input voltage is the same voltage, the control voltage VCOIN which is the output voltage fluctuates as the temperature changes. As a result, the voltage (control voltage VCOIN) input to the voltage controlled oscillator 110 fluctuates even when the temperature changes, so that a random number with higher irregularity can be generated.

&lt;Third embodiment&gt; Next, the random number generator according to the third embodiment of the present invention will be described. FIG. 14 is a circuit diagram showing a schematic configuration example of a receiving unit in the random number generator according to the third embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The random number generator of the present embodiment differs from the first embodiment in that the receiving mechanism 101E of the receiving unit 100E includes a light receiving element PD1 that receives light as energy from the transmitting unit 20E in a non-contact manner. .. Since the configurations other than the receiving unit 100E are the same as those in the first embodiment, the illustration is omitted in FIG.

In the present embodiment, the transmission unit 20E includes a primary side power supply VCC1, a light emitting diode LED1 that emits light by the power of the primary side power supply VCC1, and an LED driver 21 that drives the light emitting diode LED1. The light receiving element PD1 of the receiving unit 100E is configured to receive (receive) the energy generated by the light emitted from the light emitting diode LED1 of the transmitting unit 20E. The light receiving element PD1 is composed of, for example, a photodiode. Further, the receiving unit 100E outputs the receiving voltage VIN by converting the secondary power supply VCC2 for applying the reverse bias to the light receiving element PD1, the protection resistor R5, and the current detected by the light receiving element PD1 into a voltage. It includes a current-voltage conversion circuit 103. In the light receiving element PD1, the cathode is connected to the protection resistor R5 (secondary power supply VCC2 side), and the anode is connected to the current-voltage conversion circuit 103.

Further, in the current-voltage conversion circuit 103, the current detected by the light receiving element PD1 is input to the inverting input terminal, the operational amplifier 104 to which the ground is connected to the non-inverting input terminal, and the inverting input terminal and the output terminal of the operational amplifier 104. It is equipped with a feedback resistor R6 provided in the feedback path between them.

In such a configuration, when light from the light emitting diode LED1 of the transmission unit 20E is incident on the light receiving element PD1 in a state where the reverse bias is applied by the secondary power supply VCC2, the light receiving element PD1 is in the opposite direction. Light current flows. The photocurrent flowing through the light receiving element PD1 fluctuates according to the sensitivity of the light received by the light receiving element PD1. The emission intensity of the light emitting diode LED1 of the transmission unit 20E fluctuates according to the control command from the LED driver 21. Therefore, the amount of light received by the light receiving element PD1 of the receiving unit 100E fluctuates according to the fluctuation of the light emitting intensity of the light emitting diode LED1. Further, even if the light emitting intensity of the light emitting diode LED1 is the same, the amount of light received by the light receiving element PD1 easily varies depending on the distance between the transmitting unit 20E and the receiving unit 100E. As described above, the current flowing through the light receiving element PD1 varies variously depending on the amount of light received by the light receiving element PD1. Then, the photocurrent flowing through the light receiving element PD1 is input to the non-inverting input terminal of the operational amplifier 104. Since the imaginary short circuit is made between the non-inverting input terminal and the inverting input terminal of the operational amplifier 104, the voltage (that is, the received voltage) VIN output from the output terminal of the operational amplifier 104 is input to the non-inverting input terminal. It is the value obtained by multiplying the current value by the resistance value of the feedback resistor R6. From the above, even in the configuration as in this embodiment, it is possible to obtain a reception voltage VIN that greatly fluctuates depending on the distance between the transmission unit 20E and the reception unit 100E. Therefore, also in the present embodiment, since the pseudo-random number can be generated based on the reception voltage VIN that fluctuates greatly, it is possible to generate a highly irregular random number with a simple configuration.

In the present embodiment, the elements constituting the receiving unit 100E may be configured to have temperature dependence, or may be provided with a limiter circuit having temperature dependence as in the second embodiment. .. As a result, the voltage (control voltage VCOIN) input to the voltage controlled oscillator 110 fluctuates even when the temperature changes, so that a random number with higher irregularity can be generated.

In the present embodiment, the configuration in which the operational amplifier 104 is used as the current-voltage conversion circuit 103 is illustrated, but the configuration is not limited to this as long as the current flowing through the light receiving element PD1 can be converted into a voltage, for example. The configuration may be such that the resistor is directly connected to the anode of the light receiving element PD1.

Further, an example in which the light emitting diode LED1 is used as the configuration of the transmission unit 20E that irradiates the light receiving element PD1 with light has been shown, but the present invention is limited to this as long as the light receiving element PD1 irradiates light that can be received. Absent. For example, it may be an incandescent light bulb or an infrared lamp.

&lt;Application example of random number generator&gt; Next, an application example of the random number generator of the above embodiment will be described. Here, an example in which a random number generator is provided in the communication device to generate an ID (identification number) used for the communication device such as non-contact communication will be described. FIG. 15 is a circuit diagram showing a configuration example of a communication device to which the random number generator according to the embodiment of the present invention is applied.

The random number generator 10F in this application example has a configuration in which the voltage controlled oscillator 110 in the random number generator 10C (FIG. 6) of the second embodiment is provided with an operating input terminal into which the operating signal VCOON is input (voltage controlled oscillator in FIG. 5). It has a configuration replaced with 110B) (in FIG. 14, the voltage controlled oscillator in this application example is referred to as 110F again). Further, in this application example, the coil L1 is adopted as the receiving mechanism 101 of the receiving unit 100, and the other configurations of the receiving unit 100 also have a circuit configuration suitable for it (the same circuit configuration as in FIG. 2). The communication device 30 in this application example is configured so that the reception voltage VIN output from the reception unit 100 can be used as a power source for each device constituting the communication device 30.

The communication device 30 in this application example includes a random number generator 10F having the above configuration and an ID storage unit 140 that stores an ID generated based on a pseudo-random number sequence generated by the pseudo-random number generator 120 of the random number generator 10F. It has. The ID storage unit 140 is composed of an internal memory of the communication device 30, and stores random number data output from the 20-bit output terminals S1 to S20 generated by the pseudo-random number generator 120 as ID data. The ID data stored in the ID storage unit 140 can be transmitted from the coil L1 of the receiving unit 100 to the coil L2 of the transmitting unit 20. In this way, the transmission unit 20 functions as a power source for supplying electric power from the coil L2 to the coil L1 of the reception unit 100 by electromagnetic induction, and also functions as a communication interface for performing ID authentication of the communication device 30.

As described in the above embodiment, the voltage controlled oscillator 110F outputs an output signal VCOIN having an oscillation frequency based on the induced electromotive force generated in the coil L1 of the receiving unit 100 while the operating signal VCOON is on period T1. The pseudo-random number generator 120 generates a 20-bit pseudo-random number based on the wave number (number of clocks) included in the oscillation frequency of the output signal VCOIN, and outputs the pseudo-random number to the output terminals S1 to S20. That is, every time the operation signal VCOON becomes the ON period T1, the pseudo-random number generator 120 generates a pseudo-random number and outputs it as random number data. The output random number data is sent to the ID storage unit 140 and stored as ID data. That is, every time the random number data output from the pseudo-random number generator 120 is sent to the ID storage unit 140, the ID data stored in the ID storage unit 140 is updated. When the operating signal VCOON of the voltage controlled oscillator 110F is in the off period T2, the output signal CKIN has a fixed output (wave number 0), so the ID data stored in the ID storage unit 140 is not updated and is turned on last time. The ID data generated during period T1 is retained.

In this application example, the timing at which the ID data is stored in the ID storage unit 140 is described as after the on-period T1 of the operation signal VCOON ends (that is, a certain time in the off-period T2), but within the on-period T1. In the pseudo-random number generator 120, a pseudo-random number may be generated based on the wave number included in the oscillation frequency of the output signal CKIN up to that time, and stored as ID data in the ID storage unit 140.

According to the communication device 30 having such a configuration, when the communication device 30 is brought close to the transmission unit 20, power is supplied to the communication device 30, depending on the distance between the reception unit 100 and the transmission unit 20 of the communication device 30. The induced electromotive force is generated in the coil L1 of the receiving unit 100. When the operating signal VCOON of the voltage controlled oscillator 110F becomes the ON period T1, the pseudo-random number generator 120 generates random number data based on the induced electromotive force generated in the coil L1, and this is stored in the ID storage unit 140 as ID data. Will be done. In particular, by setting the ON period T1 of the operation signal VCOON to include the time when the communication device 30 is approaching the transmission unit 20, the irregularity of the random number data generated by the pseudo-random number generator 120 should be further increased. Can be done. By sending the stored ID data to the transmission unit 20 via the coil L1 of the reception unit 100, the communication device 30 is authenticated by the transmission unit 20, and various communications are performed after the authentication. In this way, by authenticating the communication device 30 using the highly irregular random number data, higher security can be ensured. The ID data stored in the ID storage unit 140 may be used in a process different from the communication with the transmission unit 20.

In this application example, all 20-bit random number data output from the output terminals S1 to S20 of the pseudo-random number generator 120 is used, but the present invention is not limited to this. For example, only some predetermined bits (for example, 3 bits of S1 to S3) of the 20-bit output terminals S1 to S20 may be acquired as ID data and stored in the ID storage unit 140.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various improvements, changes, and modifications can be made without departing from the spirit of the present invention. For example, each component in the plurality of embodiments and modifications may be arbitrarily combined. Further, in the above embodiment, the configuration having the M-sequence bit string calculation unit as the pseudo-random number generator 120 has been described, but if a pseudo-random number can be generated, a pseudo-random number generator of another embodiment may be used.

The random number generator and the random number generation method of the present invention are useful for generating highly irregular random numbers with a simple configuration.

10,10B, 10C, 10D, 10F Random number generator 20,20E Transmission unit 21 LED driver 30 Communication equipment 100,100E receiving unit 101,101E Reception mechanism 102 Rectifier circuit 103 Current-voltage conversion circuit 104 op amp 110,110B, 110F Voltage Control Oscillator 120 Pseudo-random number generator 121 register 122 shift register 123 XOR gate 130,130D limiter circuit 140 ID storage C1 capacitive element D1, D2, D3, D4, D5, D6 diodes L1, L2 coil LED1 light emitting diode PD1 light receiving element R1, R2, R3, R4, R5, R6 resistors VCC1 Primary power supply VCC2 Secondary power supply