WO1989001256A1

WO1989001256A1 - Electric power supply device with regulated alternating-current voltage output

Info

Publication number: WO1989001256A1
Application number: PCT/FR1988/000405
Authority: WO
Inventors: Edouard Serras-Paulet
Original assignee: Merrillton Corporation N.V.
Priority date: 1987-08-05
Filing date: 1988-08-04
Publication date: 1989-02-09
Also published as: NL8701846A

Abstract

An electric power supply device with regulated alternating-current voltage output comprises a transformer (T) connected to an electrical distribution network and a linear regulator (R) mounted in series with the secondary winding (S1) of the transformer and controlled by the difference between its output voltage (Vs) and a reference voltage (Vc) which is synchronous and in phase with the voltage (Ve) of the electrical distribution network with which it varies with a predetermined alternation factor, for example equal to 2. The invention is also applicable to power supply devices for computers.

Description

ELECTRICAL SUPPLY APPARATUS WITH OUTPUT

The invention relates to an electrical supply device with regulated alternating voltage output, comprising a single transformer for connection to an electrical distribution network, and is particularly intended for supplying computer systems, of which it is known that they are very sensitive to a large and / or sudden variation in the voltage of the electrical distribution network.

It is therefore imperative to connect a computer system to the electrical distribution network by means of a supply device with alternating voltage output, which allows, on the one hand, to absorb voltage variations and micro- network outages and, on the other hand, to supply the computer system in the event of a prolonged outage of the electrical distribution network. Devices have already been proposed for this, comprising ferro-resonant type transformers, or inverters supplied by a rectifier and associated with an electro-chemical accumulator, switching type inverters, or alternatively switching systems making it possible to switch on an auxiliary source of energy such as an electro-chemical accumulator, in the event of a cut in the distribution network.

All of these known devices have their own drawbacks: significant weight and size, generation of radiated or conducted disturbances, poor stabilization of the AC voltage delivered, low efficiency, high price.

The invention aims to avoid the drawbacks of these known devices, while offering greater reliability and efficiency.

To this end, it offers an electrical supply device with regulated alternating voltage output, comprising a transformer for connection to an electrical distribution network and means for regulating the output voltage, characterized in that these means include in series a transformer winding and a linear regulator circuit, a control input of which is connected to a circuit generating a variable corrugated voltage setpoint which is synchronous and in phase with the voltage of the distribution network and which varies as the latter with a predetermined attenuation factor, for example equal to 2.

The apparatus according to the invention differs from the previously known devices essentially by its simplicity and its excellent performance. The simplicity results in a saving in weight and size and a lowering of the cost price (the apparatus includes only one transformer) and the high value of the yield comes from a significant reduction in losses, due to the fact that the regulated alternating output voltage of the device follows, with a predetermined attenuation, the variations in the voltage of the distribution network.

We know that in general, computer systems are designed to operate with a supply voltage whose value can vary by plus or minus 10% compared to its nominal value. The apparatus according to the invention makes it possible to supply the computer systems with a voltage the variation of which is plus or minus 5% relative to its nominal value when the variation in voltage of the network is plus or minus 10%, and guarantees therefore the correct functioning of the computer systems, while reducing the losses which are a function of the difference between the network voltage and the voltage supplied. Furthermore, micro-cuts in the distribution network are absorbed by the aforementioned transformer. In the event of a prolonged outage, the invention provides for automatically substituting an auxiliary source of electrical energy, such as an electro-chemical accumulator, for the distribution network. The device according to the invention is therefore also characterized in that it comprises means for storing electrical energy, associated with a charging circuit supplied by the distribution network by means of a winding of the transformer, and an inverter comprising a primary winding of said transformer, at the midpoint of which is connected a terminal of the energy storage means, and two contactors operating alternately at a predetermined frequency, mounted between the other terminal of the energy storage means and each end of the aforementioned primary winding.

This apparatus also comprises a detector of variation of the voltage of the distribution network, connected to a switch, as well as to a means inhibiting the load circuit and to means for controlling the aforementioned contactors, for actuating them when the network voltage varies beyond predetermined limits compared to its nominal value.

According to a preferred embodiment of the invention, the linear regulator connected in series to the transformer winding, comprises a diode bridge in the diagonal of which is connected at least one transistor, for example of the MOS or bipolar type.

When the power to be treated is large, several MOS transistors are mounted in parallel in the diagonal of the bridge.

According to another characteristic of the invention, the circuit generating the setpoint voltage comprises a circuit for producing a stable reference voltage and means for combining this reference voltage with a voltage proportional to the voltage of the distribution network .

Preferably, the means for applying the reference voltage to the input of the control of the linear regulator comprise a photo-coupler, such as for example a photo-transistor associated with a photo-emissive diode.

The invention will be better understood and other details, characteristics and advantages thereof will emerge more clearly on reading the explanatory description which follows, given by way of example with reference to the appended drawings in which:

- Figure 1 schematically shows an apparatus according to the invention;

- Figure 2 schematically shows the means for controlling the output voltage of the device to the voltage of the electrical distribution network;

- Figure 3 shows schematically the means for producing the setpoint voltage;

FIG. 4 represents a variant of the circuit of FIG. 3,

- Figure 5 shows an alternative embodiment of the device

Reference is first made to FIG. 1 in which the device according to the invention comprises a transformer T for connection to an electrical distribution network which delivers an alternating voltage Ve which is for example 220 V at a frequency of 50 Hz The transformer T comprises a primary winding P1 associated with a secondary winding S1 to which a capacitor C is connected in parallel. The secondary winding S1 of the transformer T is connected in series to a linear regulator R comprising a diode bridge 10 in which each diode is mounted in opposition with respect to the neighboring diodes. A MOS transistor 12 is mounted in the diagonal of the diode bridge 10 by its drain and its source, while its gate is connected to the output of a control circuit 14 making it possible to control the voltage Ve of the electrical distribution network the output voltage Vs of the device, which is produced between the output of the regulator circuit R and the other end of the primary winding S1 of the transformer.

The control circuit 14 comprises a circuit 16 generating a stable alternating reference voltage Vr, which is synchronous and in phase with the voltage Ve of the electrical distribution network. Such a circuit 16 is within the reach of those skilled in the art and comprises for example a pilot oscillator operating at the frequency of the distribution network and a synchronization circuit.

The output of circuit 16 is connected to an input of a circuit 18 for producing a setpoint voltage Vc, another input of which receives the voltage Ve from the electrical distribution network, or a voltage proportional to this voltage Ve. The setpoint voltage Vc is rippled and synchronous with the voltage Ve of the electrical distribution network, and varies like the latter, with a predetermined attenuation factor which is for example equal to 2, the variations of the setpoint voltage Vc thus being two times less important than the variations of the voltage Ve compared to its nominal value. The setpoint voltage Vc and the output voltage Vs of the device, or a voltage proportional to this output voltage, are applied to the inputs of a circuit 20 for driving the MOS transistor 12 placed in the diagonal of the diode bridge 10 The circuit 20 is for example of the type represented in FIG. 2 and comprises an operational amplifier 22 whose inputs receive the set voltage Vc and the output voltage of the device Vs (or a voltage proportional to the latter) and whose the output is connected to the MOS transistor 12 via a photo-coupler 24 comprising a photo-emissive diode 26 associated with a photo-transistor 28 connected to the MOS transistor 12 by an impedance matching circuit, the photo - coupler 24 allowing analog isolation between the control circuit 20 and the MOS transistor 12. The circuit 18 for producing the set voltage Vc is of the type shown in FIG. 3 and then comprises an operational amplifier 30, an input of which is connected on the one hand to the output of the circuit 16 to receive the reference voltage Vr and on the other hand to a controlled inverter 32 to receive the voltage Ve of the electrical distribution network, or a voltage proportional to Ve. A feedback loop 34 is provided on the operational amplifier 30, with a gain sufficient for the variations in current not to cause variations in voltage. The setpoint voltage Vc obtained at the output of the operational amplifier 30 is then the summation of the voltages Ve and Vr.

Alternatively, the circuit 18 can be as shown in Figure 4 and then includes one. multiplier circuit 36, one input of which receives the stable reference voltage Vr and another input of which receives a continuous signal U which is the sum of a stable continuous signal Ul and a continuous signal U2 representing the mean peak value of the voltage Ve of the electrical distribution network. The continuous signal U2 can be produced from the voltage Ve by means of a circuit 38, which can be a peak rectifier circuit without threshold or a rectifier circuit associated with an integrator. The continuous signals U1 and U2 are applied to a semiconductor circuit comprising an operational amplifier 40 and a feedback loop 42, of the same type as in the circuit of FIG. 3. The output of the operational amplifier 40 provides the continuous signal U applied to the multiplier circuit 36 with the stable reference signal Vr, so that the multiplier circuit 36 outputs a reference signal Vc which is proportional to the product of the voltages Vr and U.

Furthermore, the apparatus according to the invention also comprises (FIG. 1) an auxiliary source of electrical energy constituted by an electro-chemical accumulator 44 associated with a charging circuit 46 supplied by the network. of electrical distribution by means of a secondary winding S2 of the transformer T and which is dimensioned to ensure the charge of the accumulator 44. A terminal of the latter is connected to the midpoint of a primary winding P2 of the transformer T, whose two ends are each connected to the other terminal of the accumulator 44 by a contactor 48, the two contactors being controlled alternately at a frequency of 50 Hz for example, by a circuit itself controlled by a circuit 50 for detecting variation of the voltage Ve of the electrical distribution network. The detector circuit 50 also controls an inhibitor means of the charging circuit 46 and a switch 52 mounted in series in the circuit connecting the transformer T to the electrical distribution network. The two contactors 48 may be transistors controlled to be alternately conductive and blocked, and operating in alternation with each other at a frequency equal to that of the electrical distribution network. The assembly constituted by the accumulator 44, the contactors 48, the primary winding P2 and the secondary winding S1 of the transformer constitutes an inverter delivering square voltage signals to the linear regulator R, which transforms them into an undulated voltage.

It is understood that the detector circuit 50 will also control the inverter 32 of FIG. 3.

This circuit 50 is intended to limit the admissible variation of the voltage Ve of the electrical distribution network to a value which is for example plus or minus 10% relative to its nominal value. For this, different operating modes are possible:

- a corrected reference corrugated voltage can be compared to the rectified voltage Ve;

- or compare the undulated undulated voltage Ve to two reference undulated voltages representing the upper and lower admissible limits of variation of the voltage Ve.

The realization of such a detection circuit is within the reach of those skilled in the art, and it is only important to point out that this circuit must be rapid, with a response time of less than one millisecond.

The operation of the device which has just been described is as follows:

When the voltage Ve of the electrical distribution network remains within the abovementioned limits, the switch 52 is closed under control of the detection circuit 50, the contactors 48 are open, and the circuit 46 charges the accumulator 44. The voltage produced by the secondary S1 of the transformer T is regulated and subject to slight variations in the voltage Ve of the distribution network, via the linear regulator R whose MOS transistor 12 is controlled by the difference between the output voltage Vs of the device and the setpoint voltage Vc, which is itself produced from the stable reference voltage Vr (synchronous and in phase with the voltage Ve) so that the variations in the setpoint voltage Vc are half that of the voltage Ve. This limits losses in the linear rectifier R and the overall efficiency of the device reaches a value of 85% for the nominal value of the voltage Ve. It will be noted that the transformer T, as regards its windings P1 and S1, is slightly boosted, of the order of 15%, so as to compensate for the voltage drop produced in the linear regulator R by the MOS transistor 12 which is in fact behaves as a variable resistor as a function of the difference between the output voltage Vs and the setpoint voltage Vc.

The micro-cuts likely to appear in the voltage Ve are absorbed by the transformer T.

When the variation of the input voltage Ve exceeds the predetermined limit values, good in case of prolonged interruption of the electrical distribution network, the detection circuit 50 controls the opening of the switch 52, the blocking of the circuit 46 for charging the accumulator 44 and the control of the contactors 48 which constitute with the winding P2 of the transformer T a PUSH-PULL converter which borrows its energy from the accumulator 44 and which operates at a frequency equal to that of the electrical distribution network. The square voltage signals delivered by this converter are transformed by the regulator R into a rippled voltage regulated to the value of the setpoint voltage Vc.

The apparatus according to the invention has the following advantages in particular:

- It only includes a transformer, which results in weight gain and vol ume;

- It has a high efficiency (80 to 35% in operation on the electrical distribution network and of the order of 50% in operation on the accumulator 44);

- It has very good reliability; - The output voltage Vs is regulated and filtered during operation on the electrical distribution network;

- The device does not produce radiated or produced electrical disturbances which would be likely to disturb the operation of computer systems or weak signal processing systems.

The variant embodiment shown in FIG. 5 differs from the circuit of FIG. 1 in that the linear regulator R is mounted in series, no longer with the secondary of the transformer, but with the primary. As before, the transistor 12 of the regulator is controlled by a circuit 54 for producing a reference voltage V _c from the network voltage Ve and a reference voltage which is preferably synchronous with the voltage Ve. The circuits used for this are of the same type as those of FIGS. 2 to 4, but the output voltage Vs is replaced (for comparison with the setpoint voltage) by the output voltage of the linear regulator R.

The charger 46 of the accumulator 44 is supplied by a primary winding P'a of the transformer, under the control of a circuit 56 for comparing the network voltage with a stable reference voltage (which may be the nominal value of network voltage).

A circuit 58 mounted on the output of circuit 54, controls the comparison of the grid voltage with the reference voltage, either the operation of the inverter or that of the regulator R.

Diodes 60 are mounted in parallel on the contactors 48, to connect the charger to the primary P2, P'2 of the transformer. When the variation of Ve with respect to the stable reference voltage exceeds a predetermined value, the output voltage Vs is produced from the voltage delivered by the inverter, and the regulator R is blocked to avoid any reinjection of voltage on the network. The operation of the charger 46 is also stopped. When the network voltage Ve varies little with respect to the stable reference voltage, the output voltage Vs is produced from the voltage Ve by the regulator R. The operation of the charger 46 is controlled. When the load supplied by the voltage Vs is purely resistive, the voltage Vs is regulated by the circuit R. When this load is reactive, the reactive power which it develops is absorbed by the charger 46, using diodes 60 mounted in parallel on the contactors 48 of the inverter. In the case where the reactive energy is important, it is desirable to mount, in parallel on the winding P1, a second linear regulator R ', of the same type as the first and controlled like this which will dissipate all of the reactive energy supplied by the load, without altering the form of the voltage Vs. The following advantages result:

- the operating efficiency on the network is high (80%),

- the reactive power developed by the load is absorbed,

- the isolation of the output from the network is reinforced (no feedback from the secondary to the primary for regulation),

- operation on the accumulator has a high efficiency of around 65% (the voltage supplied by the inverter does not pass through the linear regulator).

Claims

1. Electric power supply device with regulated alternating voltage output, comprising a transformer (T) for connection to an electrical distribution network, and means for regulating the output voltage (Vs), characterized in that these means comprise , in series, a winding (P1; S1) of the transformer and a linear regulator (R), a control input of which is connected to a circuit (18; 54) which generates a variable reference corrugated voltage (Vc) which is synchronous and is in phase with the voltage (Ve) of the distribution network and which varies like the latter with a predetermined attenuation factor, for example equal to 2.

2. Apparatus according to claim 1, characterized in that the linear regulator (R) comprises a diode bridge (10) in the diagonal of which is connected at least one transistor (12), for example of the MOS or bipolar type.

3. Apparatus according to claim 1 or 2, characterized in that it comprises a feedback loop between the output of the linear regulator (R) and its control input.

4. Apparatus according to one of the preceding claims, characterized in that the circuit (18) generating the setpoint voltage comprises a circuit (16) for producing a stable reference voltage (Vr) and means for combining this reference voltage with a voltage equal to or proportional to the voltage (Ve) of the distribution network.

5. Apparatus according to claim 4, characterized in that the combining means comprise a summing circuit (30, 34).

6. Apparatus according to claim 4, characterized in that the combining means comprise a multiplier circuit (36), one input of which receives the stable reference voltage (Vr) and one of which another input is connected to a circuit producing a continuous signal

(ϋ) function of the mean peak voltage value

(Ve) from the supply network.

7. Apparatus according to one of claims 1 to 6, characterized in that the reference voltage (Vc) is applied to the control input of the linear regulator (R) by a photo-coupler (24).

8. Apparatus according to one of the preceding claims, characterized in that it also comprises means (44) for storing electrical energy, associated with a charging circuit (46) supplied by the distribution network by means of a winding (P'2; S2) of the transformer, at the midpoint of which is connected a terminal of said energy storage means (44), and two controlled contactors (48) operating alternately at a predetermined frequency, mounted between the another terminal of the energy storage means (44) and each end of the aforementioned primary winding (P2).

9. Apparatus according to claim 8, characterized in that it also comprises a detector

(50) variation of the voltage (Ve) of the distribution network, connected to a switch (52) mounted in series in the network connection to the transformer (T), as well as to a means inhibiting the load circuit (46 ) and to means for controlling the aforementioned contactors, for actuating them when the network voltage varies beyond predetermined limits with respect to its nominal value.

10. Apparatus according to claim 8 or 9, characterized in that the energy storage means comprise an electrochemical accumulator (44), substitutable for the distribution network during a prolonged outage thereof.

11. Apparatus according to one of the preceding claims characterized in that the linear regulator (R) is mounted in series with a secondary winding (S1) of the transformer.

12. Apparatus according to one of claims 1 to

10, characterized in that the linear regulator (R) is mounted in series with a primary winding (P1) of the transformer.

13. Apparatus according to claim 12, characterized in that it comprises a second regulator (R ') mounted in parallel on the primary (P1) of the transformer.

14. Apparatus according to claim 12 or 13, characterized in that diodes (60) are mounted in parallel on the contactors (48) of the inverter, to connect the charger (46) to the primary winding (P2, P '2) of the transformer.