Regulated inverter circuit for standby power supply - uses four-arm bridge inverter to generate AC with adjustment of frequency or pulse width to regulate output

FRENCH REPUBLIC

498 024

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY (h) Publication number:

(To be used only for reproduction commands).

PARIS

REQUEST

INVENTION PATENT © N° 81 00597 θ Converter interface for emergency lighting from a DC power supply with storage battery.

(5t) International classification (Int. CL³). H 02 D 9/06.

(22) Date of filing.................. January 13, 1981.

(33) (^2) (3l) Priority claimed:

Date the application was made available to the public.... ...........

BOPI - “Lists” n° 28 of 16-7-1982.

(71) Applicant: ETABLISSEMENTS HENNENQUIN & CIE SA, residing in France.

(72) Invention by: Maurice Budin and Jacques Chantelot.

(73) Holder: Idem (5l) (73) Agent:

D

Sale of booklets at the PRINTING NATIONAL. 27. rue de la Convention — 75732 PARIS CEDEX 15 i

LIGHTING OVEN CONVERTER INTERFACE

SAFETY FROM A POWER SUPPLY

CONTINUOUS WITH ACCUMULATOR BATTERY

The present invention relates to a new design of electrical equipment intended for the emergency lighting of premises open to the public.

Currently, these lights are frequently produced by a floating battery charger assembly, constituting a central continuous source, which during a power outage, has an autonomy depending on the capacity of the accumulator battery.

This source then supplies incandescent lamps through a suitable distributio n box.

This design of the emergency lighting function has several drawbacks.

It is necessary to use either conventional incandescent lamps, the voltages of which are poorly suited to the number of cells in the battery, or lamps of different voltages, but specific to this type of application, and therefore more expensive. This principle therefore excludes the use of mass-produced industrial lighting devices such as fluorescent tubes or bulbs designed exclusively for 220V 5θ Hz alternating networks, whereas this type of lighting has a much higher luminous efficiency than incandescent bulbs.

Furthermore, these lamps, regardless of their nominal voltage, must be subjected, without possible regulation, to the variations in accumulator battery voltage between the charging mode and the autonomy mode. Network present these lamps are supercharged which leads to short lifespans.

A poor performance of these luminaires, a limited range of choices on low-diffusion equipment, an impossibility of controlling an optimal operating point between luminous efficiency and lifespan, all these various cumulative insufficiencies constitute a burden for the operator of these systems.

The invention proposes to add to the battery charger assembly equipment which can be designated as a converter interface and which makes it possible to reduce the above drawbacks. This system is inserted directly without any other protection device between the lighting lines and the battery charger assembly. Figure 1 shows an example of an installation, comprising a conventional battery charger assembly 1, then this system 2, connected to L lighting lines 3 ·

For this, the invention incorporates in a single piece of equipment, five essential functions and characteristics of the invention: a non-sinusoidal AC DC conversion function, a control and regulation function, a filter function for reducing radio-electric disturbances, a protection function at the short circuit on each feeder, a slow overload protection function for display and alarm in the event of a risk of this nature. Figure 2 gives an example of the organization of such a system, one finds there, from the arrival of the battery 1, the AC DC conversion function 2, then a transformer or auto-transformer 3, necessary according to the DC voltage used, and the need for galvanic isolation between DC and AC, this element is not characteristic of the invention, an h filter, a function 5 for controlling slow overloads that may affect the system, then the divisional protections 6, finally a regulation and control block 7, this receives as a measure the output voltage 8, then a setpoint 9 by potentiometer, and acts on the basis of these two pieces of information following the power block 2 , it additionally allows the characteristic magnitude of light operation to be displayed.

The AC DC conversion function uses a bridge assembly, made up of four static switches, two of which are connected to the positive half-terminal DC source, two to the negative terminal, these positive and negative switches are associated in series, the load is connected to the point of meeting of each of these associations. Each of these static switches is made by a power thyristor, or by several bipolar transistors, or even by power mos technology transistors, in parallel with this element there is a diode mounted in reverse, called recovery, the elements of power can be triggered and controlled at high frequency, which justifies the term static switches, they are connected to a control circuit either by a pulse transformer or else by a photo-coupler, through one or more amplification elements. According to the control sequence of each of these stages, in particular for a diagonal control, a non-sinusoidal alternating voltage generator is obtained at the terminals of the load. From a direct voltage of determined amplitude, it is possible to produce an alternating voltage converter whose frequency and effective value can be controlled from the control signals coming from the regulation function.

Figure 3 gives an example of a bridge assembly, which brings together a continuous source 5 with a load 6 through four static switches represented from 1 to 1.

FIG. 1 shows the assembly of diode 1 with respect to a power transistor 2, these two components constitute the two power elements of a static switch with bipolar transistor these transistors can be grouped in parallel according to the power.

Figure 5 represents the voltage signal 9, obtained at the terminals of a resistive load, when switches 1 and H of figure 2 are controlled according to diagram 7, and switches 2 and 3 according to diagram 8.

FIG. 6 represents the voltage signal 10, obtained at the terminals of a resistive load when switches 1 and 1 of FIG. 2 are controlled according to diagram 11 and switches 2 and 3 according to diagram 12, the period is represented in 13

The control and regulation function must make it possible to control each of the switches of the power unit. It therefore imposes the output frequency, and if necessary the effective value of the output voltage. For lighting applications to which the invention applies, there is a DC voltage source capable of varying according to the charging or discharging conditions of the accumulator battery used as energy source. Through the control and regulation function, and through the continuous conversion function, it is possible to regulate the luminous efficiency of the luminaires used, and to optimize the compromise, luminous efficiency, energy efficiency and lifespan of bulbs and tubes. despite the fluctuations of the continuous source.

For most fluorescent tubes and bulbs the significant quantity of luminous efficiency is the current, it can be frequency controlled for control without pulse width modulation, or fixed frequency, with such modulation. The figure represents the voltage signal obtained in the first case, figure 6 is an example of pulse width modulation.

The control and regulation function includes an auxiliary power supply circuit obtained from the DC source, a circuit for obtaining a stabilized reference, which can be adjusted by a potentiometer or variable resistor, a conversion circuit from the voltage signal delivered by the system, this conversion makes it possible to obtain the characteristic and significant magnitude of the luminous efficacy according to the control principles implemented, the voltage to frequency ratio is chosen when the frequency is variable, or only the effective voltage when the frequency is fixed. This quantity can be displayed, then it intervenes in a regulation loop with the reference, the error signal, resulting from this loop which incorporates the circuits of stability and damping of the system, modulates and controls a time base. The signal from this time base is then shaped, amplified and adapted for controlling the static switches of the AC DC conversion function.

FIG. 7 represents a circuit making it possible to obtain such a control function, this circuit receives the DC battery voltage at 23, the output signal at 22, and distributes the control commands to the static switches at 24, inside it is produced from the DC signal a power supply (25), a reference (26), a setpoint adjustable by potentiometer 27; this setpoint acts on a comparator amplifier 30, the latter also receives the measurement signal after conversion 28, this conversion stage makes it possible, from the output signal, to obtain a DC voltage proportional to the voltage/frequency ratio significant of the luminous efficiency in an application with a fluorescent tube, this information can be displayed in 29The comparator 30 consists of an operational amplifier with different stability networks, the output of this stage makes it possible to modulate a time base at 31, the outputs of this time base will control the power bridge after amplification and galvanic separation by transformer or optocoupler.

The filter function makes it possible to eliminate the high-frequency components generated by the power system, and to prevent the lighting lines from being liable to transmit radio-electric fields by radiation in the vicinity thereof. This filter function is essential, because it makes it possible to exploit a non-sinusoidal signal, allowing good energy efficiency during the AC DC conversion. The attenuation is obtained by a first order low pass filter.

Figure 8 and 9 give two examples of filters, at 30 we have the input signal at 31 the output after attenuation, 32 and 33 represent an LC filter, Figure 9 is a variant which includes two chokes, and at 3^ two capacitors of very low values ​​connected to earth, the chokes can be linear or saturable. The solution of FIG. 9 makes it possible to guarantee an attenuation on the asymmetrical components of the disturbance signal.

The short-circuit protection function is performed either by distribution-type fuses, or by divisional circuit breakers with thermal and magnetic release. These circuits are selected in such a way that a short-circuit on any one of the feeders allows the divisional protection device to operate without destruction and without tripping of the converter itself which, after tripping of a feeder, must make it possible to ensure power to other circuits.

The slow overload protection function consists of a thermal relay, bimetallic type, with a caliber in relation to the rated current of the converter. This protection can be achieved by an electronic current threshold relay, the overload information is displayed locally or remotely as an alarm. The protection can be limited to displaying only the current supplied, with very visible marking of the rated current.

These last three functions are characteristic of the invention because they allow a non-sinusoidal DC-AC converter to be operational for emergency lighting applications.

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