Untitled record

(42) Date of commencement of the patent: 15. 6.1994 (45) Date of issue: 25. 3.1996 (51) Int.Cl.⁶ : H02M 3/535 H023 7/10

<td>(56) Documents:</td><td>(73) Patent owner:</td>

<td>US 45339Θ6Α US 4967332A US 4502104A</td><td>SIEMENS AKTIENGESELLSCHAFT ÖSTERREICH</td>

<td>'' ACTIVE OVERWAVE FILTRATION FOR MAIN RECTIFIERS</td><td>A-1210 VIENNA (AT).</td>

<td>HIGHER OUTPUT POWER ", SIEMENS COHONENTS 1/86" OF THE IGBT - A POWER SIGNAL SWITCH WITH</td><td>(72) Inventor:</td>

<td>MANY ANYOD ADVANTAGES ", SIEMENS CCMONENTS 4/91</td><td>ALMEDER ERNST ING. VIENNA (AT). TÖRÖK LASZLO DIPL.ING. VIENNA (AT). S0 »€ R HELMUT DIPL.ING. DR.TECH4. VIENNA (AT). HIHLELSTOCK FELIX DIPL.ING. Dr.techn. WR. NEUDORF, LOWER AUSTRIA (AT). ZACH FRANZ DIPL.ING. Dr.techn. VIENNA (AT).</td>

(54) BATTERY CHARGER (57) The battery charger (BL) of the power supply of a passenger coach is equipped with IGB transistors as a switch. It can be designed as a voltage-fed push-pull converter, full-bridge voltage-fed, single-ended or current-fed push-pull converter. Depending on the requirements, single-loop controllers such as PI, PDI and PID controllers are installed; for complex applications, cascade control is advantageous. The high switching frequency reduces the power loss and saves weight, as well as magnetic material

ZS

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WR

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GQ

AT 400 782

KR 0078013

AT 400 782 Β

The invention relates to a Wandlerschaitung with pulse width modulation controlled switches. Clocked converter circuits are well known. Their control must be designed so that the converter circuit remains stable in all operating conditions and the electronic switches are reliably protected against overloading. Depending on the field of application, precise adjustments of the components used are required.

For example, US Pat. No. 4,533,986 shows a power supply unit with a clocked resonant converter, which is realized essentially by means of two field-effect transistors and two resonant capacitors. The US-PS 4,967,332 shows among other things a clocked full-bridge converter with an input-side capacitor, the full-bridge is implemented as well by means of field effect transistors which are connected to one disclosed in this document control device. Furthermore, US Pat. No. 4,502,104 shows a power supply device with a current-supplied push-pull converter which is embodied by means of power transistors, in particular MOSFETs. When the FET or MOSFET switches of the above-mentioned bridge circuits are clocked at high frequencies in order to realize a compact design, high switching losses occur, which are undesirable and usually require additional cooling devices.

The invention is therefore based on the object to minimize switching losses and losses due to the saturation voltage of the switch.

This is inventively achieved in that the switches are designed as IGB transistors and a battery is connected as a constant-voltage source at the output of the converter circuit.

Through the use of IGB transistors (Insulated-gate bipolar transistor) eliminates the usual in thyristors Schaltentlastungsnetzwerke. Higher switching frequencies can be used, which means that smaller transformers can cope. This leads to weight savings and a saving of magnetic material.

It is advantageous that the converter circuit is a voltage-fed push-pull converter. This circuit contains only two IGB transistors. Particularly precise control is achieved in that the converter circuit is a voltage-fed full bridge.

Only two IGB transistors are needed if the converter circuit is a single-ended converter according to the invention. If the converter circuit is a current-fed push-pull converter, two IBG transistors operated at 50% duty cycle, which are easy to relieve, require a third floating IBG transistor. However, there is no danger of a bridge short circuit and the third IGB transistor is also easier to relieve than a switch in the bridge circuit.

It is advantageous that a single-loop control circuit is connected. These controllers can be configured as PI, PTI and PID controllers. This results in a very cost-effective solution. For extended applications, such as a power supply, it is advantageous that a cascade control is connected as a double-loop control circuit. As a result, when operated as a power supply, a more favorable behavior than with einschleifiger regulation is achieved.

The invention will be explained in more detail with reference to embodiments and drawings. Show it:

1 shows a voltage-fed push-pull converter,

2 a voltage-fed full bridge,

3 a single-ended converter,

4 shows a current-fed push-pull converter,

5 shows a PTI controller,

6 shows a PI controller,

7 is an equivalent circuit diagram with closed primary switch,

8 is an equivalent circuit diagram with opened primary switch,

9 shows the controller structure in cascade control and

FIG. 10 the schematic block diagram of a battery charger in a passenger coach Fig. 1 shows a voltage-fed push-pull converter with the supply voltage U1 and two IGBTransistoren IGBT. At the output of a battery B is connected to a constant counter voltage UB. In parallel there is an output capacitor C to limit the output voltage when the battery B is removed. The input voltage U1 is between 460 and 600 V, the current varies between 10 and 220 A with a desired battery voltage of 30 V. Such a battery charger is used in the power supply of passenger cars. The control behavior of the voltage-fed push-pull converter corresponds to a voltage-fed single-ended forward converter. With the pulse width modulation of the converter is controlled by the duty cycle.

Fig. 2 shows a voltage-fed full bridge, Fig. 3 shows a single-ended converter. These two types can also be used.

AT 400 782 B

FIG. 4 shows a current-fed push-pull converter whose input circuit consists of a first IGBTransistor IGBT1, a freewheeling diode FD and a storage inductor L. The structure image of the control of the current-fed push-pull converter corresponds to that of the voltage-fed push-pull converter. Since the battery B is applied to the output of a constant counter voltage, is not the output voltage, but the current is the output. The control must take into account the transfer function between duty cycle and converter current (current in the storage inductance). Since these requirements apply to all converter types, classic single-loop controllers can be used.

Fig. 5 shows the favorable solution by means of a PTI controller. A smoothing in the current measurement can be used for the delay to be set. The current measuring element is to be considered in the controller structure. Its attenuation is reversed by increasing the gain in the PTI control.

The same applies to a PI controller, as shown in Fig. 6. Since the control circuit behaves very robust, also a smoothing can be omitted in the current detection, since it comes through the pulse width modulation to a sampling.

During the commissioning phase, the battery charger works against a purely resistive load, which is also taken into account in the converter behavior. The control circuits remain stable, but the quality of the control is getting worse with small load currents. Therefore, in this area, the gain of the controller is increased.

Even with trickle charging of the battery, a regulation of the battery voltage is necessary. Fig. 7 shows the equivalent circuit diagram for a voltage-fed push-pull converter with the primary switch closed and Fig. 8 with the primary switch open. The greater the internal resistance of the battery, the closer one gets to the situation of the idle push-pull converter with output capacitor, where, for reasons of stability, a PID regulator is more favorable.

A very favorable control behavior results in two-loop cascade control, shown in Fig. 9. The transfer function of the converter system is then divided into two sub-functions. Thus, a regulator for the current control part IR can be built while stabilizing the inner loop. The voltage regulator UR operates independently and is constructed as a linear system.

FIG. 10 shows the arrangement of the battery charger in the power supply of a passenger coach. It is supplied with one of the four UlC supply voltages via the ZS train busbar. This input voltage is converted to an internal DC circuit of 600 V via an inverter WR. With this the battery charger BL is connected. The rated voltage of battery B is 24 V. The voltage reversal in the inverter WR and battery charger BL is each electrically isolated. The IGB transistors in the battery charger BL are operated at a switching frequency between 15 and 25 kHz.