JPH07213060A - Switching power unit - Google Patents

Abstract

PURPOSE:To quickly detect the abnormality occurring in individual switching power units in parallel operation by constituting a pulse voltage detection circuit out of a capacitor for DC cut, a photocoupler, a resistor, and a Zener diode, and detecting the pulse voltage generated in a transformer or a choke transformer. CONSTITUTION:The pulse voltage waves outputted by a rectifier circuit 5 is transmitted to a pulse voltage detecting circuit 13 through a capacitor 14 for DC cut, and the pulse voltage is clamped by the Zener diode 16. At this time, while a charge current is flowing to the capacitor 14, a photocoupler 15 is turned on and transmits it to a primary switching control circuit 4. The diode 17 makes the pulse voltage to be applied to a pulse voltage detection circuit 13 only the positive pulse voltage. And, in the case that the switching power source stops by abnormality, the photocoupler 15 is tuned of, and the alarm circuit inside the switching control circuit 4 is operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply unit for operating a plurality of switching power supplies in parallel by a wired OR to obtain a large current, and in particular, when the output of one switching power supply is stopped due to a failure or the like, The present invention relates to a switching power supply capable of surely detecting a failed switching power supply.

[0002]

2. Description of the Related Art FIG. 6 shows a system configuration in which a plurality of switching power supplies are connected in parallel and supplied to a load.

Conventionally, in the case of configuring such a switching power supply, a method has been known in which a wired OR connection is made at the output of the switching power supply in order to suppress heat generation and increase efficiency.

As a low voltage detection circuit for the output voltage of the switching power supply for parallel operation which makes such a wired OR connection, there is disclosed a method of detecting the output voltage at the output terminal and Japanese Patent Laid-Open No. 3-159566. As described above, a method is proposed in which a voltage value that is resistance-divided via a diode is input to the comparator from the middle of the route from the secondary side of the transformer to the rectifier diode, and the abnormality of the switching power supply is detected by the comparator output. Has been done.

[0005]

However, in the circuit configuration in which the comparator is used for the detection circuit, when it is necessary to insulate the primary side and the secondary side from each other, in order to operate the comparator even when the power supply is stopped, a load is required. Power cannot be taken from the main circuit that supplies power to the. Therefore, it is necessary to form an auxiliary power supply circuit different from the main circuit from the primary side by using a transformer or the like, which causes a problem that the number of parts is significantly increased.

In view of the above problems, the present invention is a power supply capable of quickly detecting an abnormality of a switching power supply with a simple circuit configuration even when a part of the switching power supplies stop operating due to an abnormality during parallel operation. To provide a device.

[0007]

In order to achieve the above object, a low voltage detection circuit for a switching power supply according to the present invention comprises a DC cut capacitor or diode, a photocoupler, a resistor, a zener diode or a transistor, and a transformer or The pulse voltage generated in the choke transformer is detected to determine whether or not the switching power supply is operating.

[0008]

According to this structure, since the pulse voltage generated in the transformer or the choke transformer is monitored, the pulse voltage does not occur in the transformer or the choke transformer when the own power supply stops due to an abnormality. The detection circuit constantly monitors the pulse voltage, and while the voltage is being generated, it is transmitted to the control circuit on the primary side using a photocoupler, and when the pulse voltage does not occur due to an abnormality, it is transmitted to the control circuit on the primary side. Stop. In the control circuit on the primary side, the alarm circuit is not operated while the pulse voltage is being transmitted by the photocoupler, and when the transmission of the pulse voltage is stopped, it is regarded as a power supply abnormality and the alarm circuit is operated.

In the present invention, since the abnormality is monitored by using the capacitor or the diode so as not to be influenced by the sneak of the output voltage from the other power source, it is possible to accurately detect the abnormality of the own power source.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a switching power supply showing an embodiment of the present invention. The input is converted into a DC voltage stabilized by the rectifying / smoothing circuit 1, converted into a pulse voltage by the switching element 3 and applied to the transformer 2.
The transformer 2 outputs a voltage according to the winding ratio to the secondary side, and the rectifier circuit 5 and the smoothing circuit 6 output a predetermined voltage. On the other hand, the output voltage is taken into the error amplifier 12 at the output terminals 42 and 43, the difference from the internal reference voltage is feedback-controlled to the primary side switching control circuit 4 through the photocoupler 11, and when the output voltage rises, the switching element is switched. 3 operates so as to narrow the ON period, and when the output voltage drops, it operates so as to widen the ON period, and stabilizes the voltage. The pulse voltage detection circuit 13 is
It is connected in parallel to the commutation diode 8 in the rectifier circuit 5.
The pulse voltage detection circuit 13 includes a DC cut capacitor 1
4, a resistor 18 for limiting current, a light emitting element of the photocoupler 15, a Zener diode 16 and a diode 17.

In the switching power supply connected as described above, the operation of the pulse voltage detection circuit 13 in the normal state will be described. During normal operation, a pulse voltage waveform appears on the secondary side of the transformer 2, and the rectifier circuit 5 outputs a positive pulse voltage waveform. This positive pulse voltage waveform is transmitted to the pulse voltage detection circuit 13 through the DC cut capacitor 14. The resistor 18 limits the current flowing when the pulse is applied and clamps the pulse voltage applied by the Zener diode 16. At this time, the capacitor 14
The photocoupler 15 is turned on while the current for charging is transmitted to the switching control circuit 4 on the primary side. In the switching control circuit 4, since the power supply is operating normally while the pulse voltage is being input, the alarm circuit and the like are prevented from operating. Since the pulse voltage passing through the DC cut capacitor 14 becomes a positive and negative pulse centered on 0 V, the diode 17 is made conductive when the pulse is a negative pulse, so that the pulse voltage applied to the pulse voltage detection circuit 13 is a positive pulse. Only voltage is used.

Next, when the switching power supply is stopped due to an abnormality, no pulse voltage appears in the output of the rectifier circuit 5 on the secondary side. On the other hand, the normal DC voltage of the other power source
Although it wraps around through 2, 43, it does not affect the pulse voltage detection circuit 13 because of the DC cut capacitor 14. At this time, since the pulse voltage detection circuit 13 cannot detect a pulse, the photocoupler 15 remains off and a signal of level L is constantly input on the switching control circuit 4 side. Therefore, the alarm circuit in the switching control circuit 4 is input. To operate.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of a switching power supply showing a second embodiment of the present invention. The operation of the power supply is the same as in FIG. The pulse voltage detection circuit 13 is connected in parallel with the choke transformer 9 and is composed of a diode 19, a smoothing capacitor 20, a resistor 21 for limiting a current, a photocoupler 15 and a Zener diode 16.
During normal operation, a pulse voltage waveform appears on the secondary side of the transformer 2 and a positive pulse voltage waveform is output from the rectifier circuit 5 and transmitted to the pulse voltage detection circuit 13 via the diode 19. The pulse voltage is smoothed by the capacitor 20 into a DC voltage, which is applied to the photocoupler 15 and the like. While the positive pulse voltage is being applied, a current flows through the diode 19 to the photocoupler 15 to turn it on. The resistor 21 is for limiting the current for protecting the photocoupler 15, and the Zener diode 16 clamps the applied DC voltage.
Further, during the period when the pulse voltage is not applied, the capacitor 2
Current is supplied from 0. The operation on the primary side when the photocoupler 15 is on is the same as in FIG.

Next, when the switching power supply is stopped due to an abnormality, no pulse voltage appears in the output of the rectifier circuit 5 on the secondary side. On the other hand, the normal DC voltage of the other power source
Although it goes around 2 and 43, since the anode potential of the diode 19 and the anode potential of the Zener diode 16 are the same potential, the photocoupler 15 is not turned on. The operation on the primary side when the photocoupler 15 is off is the same as in FIG.

Next, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram of a switching power supply showing a third embodiment of the present invention. The operation of the power supply is the same as in FIG. The pulse voltage detection circuit 13 is connected in parallel to the secondary side of the transformer 2, and has a diode 19, a smoothing capacitor 24, current limiting resistors 22, 23, and
It is formed of a photocoupler 15 and a Zener diode 16. During normal operation, since a pulse voltage waveform appears on the secondary side of the transformer 2, it is transmitted to the pulse voltage detection circuit 13 via the diode 19. As for the pulse voltage, a positive voltage is generated during the ON period of the switching element 3 and the resistors 22, 23
Limits the current that charges the capacitor 24 and the current that flows in the photocoupler 15, and
Stabilizes the voltage across. During the OFF period of the switching element 3, current is supplied from the capacitor 24 to the photocoupler 15, and the photocoupler 15 is turned on during the ON / OFF period. In the switching control circuit 4 on the primary side, since the signal of level H is input during this period, the alarm circuit is not operated at this time.

Next, when the switching power supply is stopped due to an abnormality, no pulse voltage appears on the secondary side of the transformer 2. On the other hand, the normal DC voltage of the other power source is output to the output terminals 42 and 43.
It wraps around, but is blocked by the rectifying diode 7. Therefore, the photocoupler 15 never turns on. The operation on the primary side when the photocoupler 15 is off is the same as in FIG.

Next, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 4 is a block diagram of a switching power supply showing a fourth embodiment of the present invention. The operation of the power supply is the same as in FIG. The pulse voltage detection circuit 13 is connected in parallel to the commutation diode 8 in the rectifier circuit 5. The pulse voltage detection circuit 13 is formed of a DC cut capacitor 14, current limiting resistors 26 and 27, a capacitor 29, a transistor 25, a light emitting element of the photocoupler 15, a resistor 28, and a diode 17. During normal operation of the power supply, a positive pulse voltage waveform appears at the output of the rectifier circuit 5. This positive pulse voltage waveform is transmitted to the pulse voltage detection circuit 13 through the DC cut capacitor 14. Resistance 26,
27 limits the current that flows when a pulse is applied and sets the bias potential applied to the base of transistor 25. In this circuit format, the capacitor 1
Even if the current for charging 4 is small, it is amplified by the transistor 25, so that a sufficient current flows to turn on the photocoupler 15 connected to the collector side of the transistor 25. The resistor 28 is for protecting the photocoupler 15. Further, during the period when the pulse voltage waveform is not displayed in the output of the rectifier circuit 5, the operation of the transistor 25 is continued by the discharge from the capacitor 29, and the photocoupler 15 is continuously turned on. The function of the diode 17 is the same as in the case of FIG. The operation on the primary side is the same as in FIG.

Next, the case where the switching power supply is stopped due to an abnormality is the same as in FIG.

Next, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a block diagram of a switching power supply showing a fifth embodiment of the present invention. The operation of the power supply is the same as in FIG. The pulse voltage detection circuit 13 is connected in parallel to the commutation diode 8 in the rectifier circuit 5. The pulse voltage detection circuit 13 is composed of a DC cut capacitor 14, current limiting resistors 32 and 33, a capacitor 30, a light emitting element of a photocoupler 15, a Zener diode 16 and a diode 17. In FIG. 1, the photocoupler 15 is turned on only when the capacitor 14 is charged, but in the present circuit, the photocoupler 15 can be turned on by the discharge from the capacitor 30 even during the period when the pulse voltage waveform is not displayed in the output of the rectifier circuit 5. it can. As a result, two pulses can be transmitted to the primary side during one cycle of the switching element. Other operations are the same as those in FIG.

[0025]

According to the present invention, since a circuit for detecting a pulse voltage generated at both ends of a choke transformer or a commutation diode of each switching power supply which operates in parallel in a wired or wired manner is provided, other normal switching is performed. Abnormality of each switching power supply can be detected without being affected by the power supply. Further, since a power supply circuit for operating the detection circuit is unnecessary, there is an effect that it can be realized by a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a fifth embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a switching power supply that performs parallel operation.

[Explanation of symbols]

2 ... Transformer, 3 ... Switching element, 5 ... Rectifier circuit,
6 ... Smoothing circuit, 7 ... Rectifier diode, 8 ... Commutation diode, 9 ... Choke transformer, 10 ... Smoothing capacitor,
11, 15 ... Photocoupler, 13 ... Pulse voltage detection circuit,
14, 20, 24, 29, 30 ... Capacitors, 18, 2
1, 22, 23, 26, 27, 28, 31, 32, 3
3, ... Resistor, 16 ... Zener diode, 17, 19 ...
Diode, 25 ... Transistor, 34, 35, 36 ...
Switching power supplies, 40, 41 ... Input terminals, 42, 43
… Output terminal.

Claims (5)

[Claims] 1. A switching stabilized power supply for converting a rectified and smoothed DC voltage into a pulse voltage by a switching operation, applying the pulse voltage to a transformer for voltage conversion, and then rectifying and smoothing to generate a predetermined output voltage. In a power supply system that operates a plurality of units at the same time to obtain a large output current, for each switching power supply, in parallel with the commutation diode of the rectifier circuit on the secondary side, a DC-cutting capacitor and a current limiting resistor and transmission to the primary side It has a pulse voltage detection circuit in which a photocoupler and a zener diode of the means are connected in series, and a diode is connected in parallel with the resistor, the photocoupler, and the zener diode, and an abnormality is determined by the presence or absence of a pulse transmitted by the photocoupler on the primary side. A switching power supply device characterized by the above. 2. A pulse according to claim 1, wherein a diode, a resistor for limiting current, a photocoupler and a Zener diode of a transmission means to the primary side are connected in series, and a capacitor is connected in parallel to the resistor, the photocoupler and the Zener diode. A switching power supply device characterized in that a voltage detection circuit is connected in parallel with a choke transformer. 3. A diode, a first resistor for limiting current, a second resistor, a photocoupler of a transmitting means to the primary side, and a Zener diode are connected in series, and the second resistor and photocoupler are connected. A switching power supply device characterized in that a pulse voltage detection circuit in which a capacitor is connected in parallel to a Zener diode is connected in parallel to the output terminal on the secondary side of the transformer. 4. The direct current cut capacitor according to claim 1, wherein the current limiting first resistor and the second resistor are connected in series, a diode is provided in parallel with the first resistor and the second resistor, and a second resistor is connected in parallel. Connect a capacitor in parallel with the resistor of 2
Is connected to the base of the transistor from the connection point of the resistance of the second resistance to the base of the transistor, the emitter is connected to the other end of the second resistance, and the collector is connected to the current limiting resistance and the photocoupler of the transmission means to the primary side. A switching power supply device characterized in that a pulse voltage detection circuit connected to the positive electrode side of the switching power supply output at the other end is connected in parallel to a commutation diode of a rectification circuit on the secondary side. 5. A switching power supply device according to claim 1, wherein in the pulse voltage detection circuit for a switching power supply, a resistor is divided into two, and a capacitor is connected in parallel to the second resistor, the photocoupler and the Zener diode.