JPH0226267A - Protective circuit for parallel operation - Google Patents

Abstract

PURPOSE:To enhance reliability by providing second and third comparators to compare output voltage with second and third reference voltage and by continuing, etc., the ON-OFF operation of switching elements. CONSTITUTION:A power device connects switching power supply sections 6-1 to 6-n in parallel equipped with a transistor(Tr) 2 connected to the primary winding of a transformer 1 and controlling the current in turning ON and OFF from a DC power source DC, a rectifying and smoothing circuit 3 on the secondary winding side of the transformer 1, a first comparison section 4 to compare the output voltage of this circuit 3 with a first reference voltage Vr1 and a switching control circuit 5 to turn ON and OFF the above Tr 2 by a pulse width control, and the power device supplies stabilized output voltage to a load. In this connection, a voltage detection section 7 for the transformer secondary winding and second and third comparison sections 8 and 9 to compare the output voltage of the circuit 3 with the second and third reference voltage Vr2 to Vr3 (where Vr2>Vr3) are provided. The output voltage applied to the 1st comparison section 4 is thus reduced by the 2nd comparison section 8, and by the third comparison section 9 the occurrence of failure is detected and displayed, etc., accordingly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a power supply device in which a plurality of switching power supply units are connected in parallel to supply a stabilized output voltage to a load. The present invention relates to a parallel operation protection circuit that detects and controls parallel operation so that only a normal switching power supply unit can continue parallel operation.

For large computers, semiconductor integrated circuit testers, etc., low voltage, high current DC power supplies, such as 5V,
Although a power supply device of 3000A or the like is required, from the point of view of cost and reliability, the power supply device is configured by connecting six switching power supply units of 5V, 500A, etc. in parallel, for example. In this case, a failure of one unit immediately causes a shortage of power supply capacity, so one or more units are connected in parallel for redundant parallel operation to improve reliability. In a power supply device in which switching power supply units are connected in parallel in this manner, it is necessary to prevent a failure of one switching power supply unit from adversely affecting the operation of other switching power supply units operating in parallel.

[Conventional technology]

As mentioned above, in a power supply device that supplies a stabilized output voltage to a large-capacity load by connecting a plurality of relatively small-capacity switching power supply units in parallel, conventionally, for example, as shown in FIG. When the load 40 requires 5"i?2000A, four switching power supply units 41 to 44 with an output capacity of 500A at 5V are connected in parallel to supply a stabilized output voltage to the load 40. Note that 45 indicates an AC power supply, and each of the switching power supply units 41 to 44 rectifies an AC voltage to provide a DC power supply.

The output voltages of the switching power supply units 41 to 44 are, for example,
The relationship is set such that Vl > V2 > Vs > V4, and the difference between the respective voltages is selected to be approximately several IQmV. In addition, the current supplied from the switching power supply units 41 to 44 is 50O.
When it comes to A, when the configuration is configured such that the overcurrent protection function operates,
When a current of 200 OA flows through the load 40, the output current I, ~■4 of each switching power supply section 41 to 44 is 50 OA.
However, if a current of 500 A or less flows through the load 40, the current It is supplied only from the switching power supply section 41 with the highest output voltage (Vl'').

Therefore, the relationship between the current and voltage of the load is as shown in FIG. 4, and OCP 1 to OCP 4 are overcurrent protection operating values of the switching power supply units 41 to 44. For example, A
If point is taken as the operating point, the voltage of the load 40 will be a value between V and ■4, the switching power supply sections 41 and 42 will supply the maximum rated current, and the switching power supply section 43 will supply a few minutes of the maximum rated current. 1 of the switching power supply unit 4.
4 is a state in which no current is supplied.

As mentioned above, each switching power supply unit 4 connected in parallel
1-44 does not share the load equally, and the switching power supply unit 41 set to the maximum output voltage always supplies current, and is often in the maximum current supply state.
The life of this switching power supply section 41 is the shortest.

Therefore, we have previously proposed a current-balanced switching regulator in which each switching power supply unit can supply load current at a predetermined burden rate. That is, as shown in FIG.
The switching power supply units 50-1 and 50-2 connected in parallel to supply a stabilized output voltage to the load 71 have the same configuration, 51 is a transformer, 52 is a transistor as a switching element, and 53 is a DC Power source (for example, a power source that rectifies alternating current using a rectifier circuit not shown)
, 54 is a diode, 55 is a pulse width control circuit (PWM
), 56 is an error amplifier, 57 is a resistor adder consisting of resistors R1 and R2, 58 is a voltage setting circuit consisting of resistor RO and variable reference voltage E, 59 is a current transformer, 60 is a diode, 61 is a resistor, and 62 is a capacitor. , 63 is a resistor for determining the unbalanced component, 64 is a differential amplifier, 65 is an integrating circuit consisting of a resistor R3 and a capacitor C, 66 is a limiter circuit, 67 and 68 are rectifier diodes, 69 is a choke coil, and 70 is a smoothing circuit. capacitor, SL is slave terminal, M
A is a mask terminal, CB is a current balance terminal, and CM is a common terminal (ground terminal), indicating a forward type case.

The configuration is shown in which the switching power supply section 50-1 is used as a mask switching power supply section and the switching power supply section 50-2 is operated in parallel as a slave switching power supply section, and the mask terminal M of the mask switching power supply section 50-1 is
A and the slave terminal SL of the slave switching power supply unit 50-2 are connected, and the current balance terminals CB are connected to each other, and the common terminals CM are connected to each other. Therefore, in the slave switching power supply section 50-2, stabilization control of the output voltage is performed in accordance with the voltage set in the voltage setting section 58 of the mask switching power supply section 50-1.

The error amplifier 56 has a stabilized output voltage and a resistance adder 57.
The pulse width control circuit 55 compares the set voltage of the voltage setting circuit 58 via the
The DC current from the DC power supply 53 is supplied to the primary winding of the transformer 51, and the voltage induced in the secondary winding is controlled by a rectifying and smoothing circuit consisting of a diode 67, 68, a choke coil 69, and a capacitor 70. The transformer 51 is rectified via the diode 54 connected to the auxiliary winding of the transformer 51, and as described above, control is performed so that the output voltage corresponds to the set voltage of the voltage setting circuit 58. be exposed.

Furthermore, since the current supplied to the load 71 is proportional to the current flowing through the transistor 52 on the primary side of the transformer 51, this current is detected by the current transformer 59, and the diode 6
0. Resistance 61. It is added to the resistor 63 as a DC component using a capacitor 62 or the like.

This resistor 63 is connected to the switching power supply unit 50-1゜50-
The settings are made in accordance with the current capacity of No. 2, and the settings are made so that the same terminal voltage (for example, No. IV) occurs when the maximum rated current is supplied.

Therefore, when the current burdens of the mask switching power supply section 50-1 and the slave switching power supply section 50-2 are in a balanced state, the terminal voltage of the resistor 63 is It becomes 0. In this case, only the voltage set by the voltage setting circuit 58 is applied to the error amplifier 56.

Also, when the current burden becomes unbalanced, the output voltage of the differential amplifier 64 with a larger current burden becomes monopolar, and conversely, the output voltage of the differential amplifier 64 with a smaller current burden becomes unipolar. Therefore, an integration circuit 65 integrates it so as not to be affected by sudden load fluctuations, a limiter circuit 66 limits it to the maximum allowable value or less so as not to be affected by startup or failure, and a resistor adder 57, it is added to the set voltage from the voltage setting circuit 58 to lower the output voltage with a larger current burden and to increase the output voltage with a smaller current burden. In addition, it is possible to balance the current burden.

(Problem to be solved by the invention) Plural switching power supply units 41 to 44.50-1.50
-2 connected in parallel to supply a stabilized output voltage to the load 40.71, it is necessary to detect a faulty switching power supply section at an early stage and replace it.

In this case, in multiple switching power supply units running in parallel, even if the output voltage drops to zero due to a failure that stops the switching operation in one of the switching power supply units, the output voltage of the other switching power supply units will remain normal. Then load 4
Since the output voltage applied to 0.71 does not become zero, it is difficult to detect a faulty switching power supply section.

Therefore, a method has been proposed that utilizes the fact that the switching element is turned on and off at a predetermined cycle, and determines that a failure has occurred when the operation stops.

However, when the output voltage of the switching power supply section increases, other switching power supply sections will detect the output voltage and apply it to, for example, the error amplifier 56 in FIG. If the voltage is sufficiently high, the on-period of the transistor 52 is controlled to be zero. That is, the on/off operation of the switching element based on pulse width control is stopped. Also, in the conventional example shown in Fig. 3, the switching element is constantly turned on and off in the switching power supply section where the output voltage is set to the highest level, but in the switching power supply section where the output voltage is set to the lowest, the switching element is constantly turned on and off. In the power supply section, when the load current is small, the switching elements stop turning on and off.

According to the above-described method of determining that a failure has occurred when the on/off operation stops, there is a drawback that it is determined that a failure has occurred also in this case.

An object of the present invention is to detect a faulty switching power supply unit during parallel operation and disconnect it from the parallel operation.

[Means to solve the problem]

The parallel operation protection circuit of the present invention is capable of reliably detecting a faulty switching power supply unit during parallel operation in which a plurality of switching power supply units are connected in parallel to supply a stabilized output voltage to a load. Yes, and will be explained with reference to FIG.

A switching element 2 such as a transistor that is connected to the primary winding of the transformer 1 and controls on and off a current from a DC power supply such as a rectified power supply, and a rectification and smoothing circuit 3 that is connected to the secondary winding of the transformer 1. A first voltage that compares a voltage proportional to the output voltage of this rectifying and smoothing circuit 3 with a first reference voltage Vrl.
a switching power supply unit 6-1 to 6-, comprising a comparison unit 4 and a switching control circuit 5 such as a pulse width control circuit that controls on/off of the switching element 2 based on the output signal of the first comparison unit 4; In a power supply device that supplies a stabilized output voltage to a load by connecting two voltage detectors in parallel, a voltage detection section 7 detects the induced voltage of the secondary winding of the transformer 1, and a voltage detected by the voltage detection section 7 and a , the first reference voltage Vrl
When the detected voltage is lower than the second reference voltage r2 by comparing it with the lower second reference voltage Vr2, the first comparison unit 4
A second comparator 8 reduces the voltage proportional to the output voltage of the rectifier and smoothing circuit 3 applied to the output voltage, the voltage detected by the voltage detector 7, and a third reference voltage Vr3 lower than the second reference voltage Vr2. A third controller controls the switch circuit SW to cut off parallel operation information such as the first reference voltage and the current detection signal from the current detector CT when the detected voltage becomes lower than the third reference voltage Vr3. It is equipped with a comparing section 9.

[Effect]

Each of the switching power supply units 6-1 to 6-n compares a voltage proportional to the output voltage applied to the load with a first reference voltage Vrl to control on/off of the switching element 2, and outputs a set output voltage. When the detection signal from the current detection section CT is used, it is possible to balance the current burden of the switching power supply sections 6-1 to 6-n.

In addition, when the output voltage of another switching power supply unit running in parallel increases and a situation occurs in which the switching control circuit 5 stops turning on and off the switching element 2, the voltage detection unit 7 detects that the two of the transformer 1 The induced voltage of the next winding is detected, and the voltage proportional to the output voltage applied to the first comparator 4 is reduced by the second comparator 8. As a result, the output voltage becomes lower than the set voltage, and in a normal state, at least the on/off operation of the switching element 2 is not stopped.

Also, when the on/off operation of the switching element 2 stops,
Since the induced voltage in the secondary winding of the transformer 1 becomes 0, the voltage detected by the voltage detection section 7 also becomes 0, and the third comparison section 9 detects the occurrence of a failure. By displaying a lamp or the like using the output signal of the third comparison section 9 as a failure detection signal, it becomes possible to immediately identify the switching power supply section in which the failure has occurred. In addition, in the switching power supply section where the failure has occurred, the switch circuit SW is controlled to cut off the reference voltage Vrl for parallel operation, the current detection signal from the current detection section CT, etc., and other normal It is possible to prevent the switching power supply section from being adversely affected.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention, in which 11 is a transformer, 12 is a transistor as a switching element, 13 is a DC power source such as a rectified power source, 14 is a voltage detection section, 1
5 is a pulse width control circuit (P
WM), 16 is the first comparator, 17 is the resistance adder, 1
8 is a voltage setting circuit, 19 is a current transformer, 20 is a second comparator, 21 is a third comparator, 22 is a fourth comparator, 23 is a fifth comparator, 24 is an operational amplifier, 25 is a AND circuit, R1, R2, R4-R12 are resistors, 01 to C5
is a capacitor, Ll is a choke coil, D1 to D6 are diodes, ZDl and ZD2 are Zener diodes, RL
is a relay, rj21. r12 is the relay contact, Vrl~
Vr5 is a reference voltage, SL is a slave terminal, MA is a mask terminal, and CB is a current balance terminal.

In this embodiment, in correspondence with FIG. 1, the switching element 2 connected to the primary winding of the transformer 1 corresponds to the transistor 12 connected to the primary winding of the transformer 11, and A rectifying and smoothing circuit 3 connected to the secondary winding corresponds to a rectifying and smoothing circuit consisting of diodes Di, D2, choke coil L1, and capacitor C1 connected to the secondary winding of the transformer 11, and the first comparison section 4 corresponds to the first comparator 16, the switching control circuit 5 corresponds to the pulse width control circuit 15, and the voltage detection section 7 corresponds to the diode D.
5. The second and third comparison sections 8 and 9 correspond to the voltage detection section 14 consisting of resistors R11, R12 and capacitor C3.
．． It corresponds to the third comparator 20°21.

In addition, during normal operation, relay RL continues to operate due to the output signal "1" of AND circuit 25, and its contacts r/ll,
r12 is in the meter state, and as explained with reference to FIG. 5, the mask terminal MA of the mask switching power supply section and the slave terminal SL of the slave switching power supply section are connected, and the current balance terminals CB are connected to each other. Thus, parallel operation information is transmitted between switching power supply units. Note that a common terminal serving as a ground terminal is omitted from illustration. Also, connect the output terminal of the rectifying and smoothing circuit in parallel with the output terminal of another switching power supply section to connect the output terminal of the rectifying and smoothing circuit to a load (not shown).
It is connected to.

In addition, the reference voltage Vrl is generally adjustable in order to set the output voltage, as in the conventional example, and the set voltage is applied to the positive terminal of the comparator 16 via the resistor R1 of the resistor adder 17. , an output voltage is applied to its negative terminal via a resistor R10, an error voltage is applied to a pulse width control circuit 15, and the on-period in the switching period of the transistor 12 is controlled so that the error becomes zero. In this case, the output voltage is divided by a resistor voltage divider, etc., and then passed through the resistor RIO to the first comparator 1.
It is also possible to have a configuration in which it is added to the negative terminal of No. 6.

Also, since the load current is proportional to the current flowing through the primary winding of the transformer 11, the current supplied to the load is detected by the current transformer 19, and converted into a DC component by the diode D4, resistor R5, and capacitor C2, and the load current is Add to resistor R4 for detecting unbalance. The terminal voltage of this resistor R4 is applied to the operational amplifier 24 via resistors R6 and R7, and is integrated by the integral action of resistor R8 and capacitor C4, and resistor R9 and capacitor C5, and then is applied to the operational amplifier 24 by the limiter circuit of Zener diodes ZDI and ZD2. Limiting the maximum positive and negative values and adding an unbalanced current detection signal to the positive terminal of the comparator 16 via the resistor R2 of the resistor adder 17,
As explained with reference to FIG. 5, control is performed so that the current burden corresponds to the set rated current ratio.

In addition, the induced voltage of the secondary winding of the transformer 11 is detected by the voltage detection section 14.
, and in addition to the positive terminal of the second comparator 20, it is compared with the reference voltage Vr2. This reference voltage Vr2 can also be changed in accordance with the reference voltage Vrl, and the induced voltage in the secondary winding of the transformer 11 during normal operation due to the set reference voltage Vrl is determined from the value detected by the voltage detection unit 14. It should be set to a low value. Alternatively, it is set to a value lower than the value corresponding to the lowest value of the setting range of the reference voltage Vrl. Therefore, under normal conditions, the output signal of the comparator 20 is at a high level and the diode D6 is in a reverse bias state, so the second comparator 20 is disconnected from the first comparator 16. The output voltage is controlled to be the set voltage and the load current is controlled to be the load sharing ratio.

In addition, the induced voltage of the secondary winding of the transformer 11 is detected by the voltage detection section 14.
The voltage V detected by is the reference voltage Vr for abnormality detection.
3, and the output voltage is the reference voltage V for overvoltage detection.
Reference voltage Vr5 smaller than r4 and for undervoltage detection
Since the relationship becomes larger and the output signals of the comparators 21 to 23 become "1", the output signal of the AND circuit 25 becomes "1".
Then, relay RL operates and its contact rj! l, rl
'1 is the meter status. Therefore, in the mask switching power supply section, the set reference voltage Vrl is
The voltage is applied to the slave terminal SL of the slave switching power supply unit via Ill, and the resistor R4 is connected to each other via the contact r12 and the current balance terminal CB. That is,
Parallel operation information between switching power supply units is at contact rj! 1.
transmitted via rl'l.

When the output voltage of the other switching power supply increases compared to the set voltage, the negative terminal of the first comparator 16 is connected to the resistor RI.
The output voltage applied through O also increases, and the pulse width control circuit 15 sets the on period of the transistor 12 to zero, stops the on/off operation, and controls the output voltage to decrease. As a result, the induced voltage in the secondary winding of the transformer 11 decreases, and the detected voltage V1 of the voltage detection section 14 also decreases. When this detection voltage V becomes lower than the reference voltage Vr2,
The output signal of the comparator 20 becomes “O”, and the diode I>
6 is forward biased, the input voltage at the positive terminal of the first comparator 16 will be low.

That is, the input state to the comparator 16 is equivalent to that when the output voltage decreases. Therefore, the on/off operation of the transistor 12 by the pulse width control circuit 15 continues, and the transistor 12 is completely turned on.

It is possible to prevent the off operation from stopping. In that case, the output signal of the comparator 21 will continue to be "1" by setting the detection voltage V to maintain the reference voltage Vr3 or higher.

Also, failure of the pulse width control circuit 15, etc., or failure of the transistor 12
When the on/off operation of the transistor 120 stops due to a failure or the like, the induced voltage in the secondary winding of the transformer 11 becomes zero, and its detected voltage V also becomes zero. In that case, the output signal of the comparator 21 becomes "O", so the AND circuit 25
The output signal also becomes "0" and the relay RL is restored. Therefore, contact r11. rl'l enters a break state, and parallel operation information with other switching power supply units is cut off.

Therefore, in the case of a failure in the mask switching power supply section,
The reference voltage Vrl set by the voltage setting circuit 18 is the contact rf
Since the output voltage is not applied to the slave switching power supply unit via Vrl, the output voltage is continuously stabilized by the set reference voltage Vrl in the slave switching power supply unit. Also, since the resistor R4 is separated from the resistor R4 of the other switching power supply section by the contact rl'l,
Control is performed so that the burden current of the faulty switching power supply section is borne by other normal switching power supply sections.

Also, if the output voltage rises abnormally due to a failure, comparator 2
3 becomes "O", the output signal of AND circuit 25 becomes "0", the relay RL is restored, and the contact rj! l
, rg2 interrupts parallel operation information with other switching power supplies. Also, if the output voltage drops abnormally due to a malfunction such as a short circuit in the rectifying and smoothing circuit, the comparator 22
The output signal of the AND circuit 25 becomes "0", and the output signal of the AND circuit 25 becomes "0", and the relay RL is restored.

Therefore, when the relay RL is restored, a lamp or the like is turned on to indicate the occurrence of a failure, thereby making it possible to simplify the identification of the switching power supply unit in which the failure has occurred, and to quickly recover from the failure.

The present invention is not limited to the above-described embodiments, and can be modified in various ways, such as a configuration that performs load sharing control using a configuration other than the current balance type,
The present invention can also be applied to a configuration in which only the reference voltage is shared.

〔Effect of the invention〕

As explained above, the present invention includes a voltage detection unit 7 that detects the induced voltage of the secondary winding of the transformer l, and a second voltage detection unit that compares the detected voltage of the voltage detection unit 7 with the second reference voltage r2. , a third reference voltage Vr3 lower than the second reference voltage Vr2, and a third comparison section 9 that compares the detected voltage of the voltage detection section 7 are connected to the switching power supply sections 6-1 to 6-6. −
n, when the detected voltage of the voltage detection section 7 becomes lower than the second reference voltage Vr2, by reducing the voltage proportional to the output voltage applied to the first comparison section 4, the switching element 20 It is possible to make the on/off operation continue so that it can be distinguished from the occurrence of a failure.

Furthermore, when the detected voltage of the voltage detection section 7 becomes lower than the third reference voltage Vr3, it is a failure that stops the on/off operation, so the parallel operation information is cut off by the switch circuit SW, etc. It is possible to prevent an adverse effect on the switching power supply section during parallel operation.

Therefore, it is possible to detect a faulty switching power supply unit during parallel operation and to disconnect it from a normal switching power supply unit, making it possible to quickly recover from a fault.
There is an advantage that the reliability of the power supply device can be improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is an explanatory diagram of a conventional example, Fig. 4 is an explanatory diagram of current-voltage characteristics, and Fig. 5 is a diagram illustrating the current-voltage characteristics. FIG. 2 is a block diagram of the proposed switching regulator. 1 is a transformer, 2 is a switching element, 3 is a rectifier and smoothing circuit, 4 is a first comparison section, 5 is a switching control circuit, 6
-1 to 6-n are switching power supply units, 7 is a voltage detection unit,
8 is a second comparison section, 9 is a third comparison section, SW is a switch circuit, CT is a current detection section, DC is a direct current power supply, Vrl~V
r3 is a reference voltage. Fig. 1, explanatory diagram of the principle of the present invention

Claims (1)

[Claims] A switching element (2) connected to the primary winding of the transformer (1), a rectifying and smoothing circuit (3) connected to the secondary winding of the transformer (1), and the rectifying and smoothing circuit ( A first comparison section (4) that compares a voltage proportional to the output voltage of step 3) with a first reference voltage, and an output signal of the first comparison section (4) turns on the switching element (2). , a switching control circuit (5) for controlling off-state, and a plurality of switching power supplies (6-1 to 6-n) connected in parallel to supply a stabilized output voltage to a load. A voltage detection unit (7) detects the induced voltage in the secondary winding of the transformer (1).
), the detected voltage by the voltage detection section (7) is compared with a second reference voltage lower than the first reference voltage, and when the detected voltage is lower than the second reference voltage, the first Comparison part (
4), a second comparison section (8) that reduces a voltage proportional to the output voltage of the rectification and smoothing circuit (3) applied to the voltage detection section (7), and a voltage detected by the voltage detection section (7) and the second reference voltage. a third comparison unit (9) that compares the detected voltage with a lower third reference voltage and shuts off the parallel operation control information based on a power supply abnormality detection signal when the detected voltage becomes lower than the third reference voltage; A parallel operation protection circuit characterized by comprising: