KR20020059135A - Sensing circuit for badness of power supply - Google Patents

Abstract

PURPOSE: A failure monitoring circuit of a power supply is provided to find a failed power supply among many power supplies in an equipment or a system in real time to notify over-voltage. CONSTITUTION: A failure monitoring circuit of a power supply comprises a switching controller, a switch, a transformer, a rectifier, a first photo diode, a first photo transistor, a second photo transistor and a low voltage detecting circuit(100). The low voltage detecting circuit(100) includes a third photo diode(PD3), a fourth photo diode(PD4), a third zener diode(ZD3), a third photo transistor(PTR3) and a fourth photo transistor(PTR4). The anode of the third photo diode(PD3) is coupled in parallel to the positive output of the rectifier. The anode of the fourth photo diode(PD4) is coupled in parallel to the cathode of the third photo diode(PD3). The cathode and the anode of the zener diode(ZD3) are coupled to the cathode of the fourth photo diode(PD4) and the negative output of the rectifier, respectively. The third photo transistor(PTR3) is optically coupled to the third photo diode(PD3) and the collector and the emitter are coupled to the external light emitting device and ground, respectively. The fourth photo transistor(PTR4) is optically coupled to the fourth photo diode(PD4) and the collector and the emitter are coupled to the external controller and ground, respectively.

Description

SENSING CIRCUIT FOR BADNESS OF POWER SUPPLY}

The present invention relates to a power supply, and more particularly, to a failure detection circuit of the power supply to notify the outside when the voltage output from the failure detection circuit used in the power supply is out of the limit value range.

In general, a switch mode power supply (SMPS) is provided with a failure detection circuit for protecting the device and the circuit connected to the output terminal of the over voltage or over current output.

As shown in FIG. 1, the power supply 10 includes a switching control unit 11, a switching unit 12, a transformer 13, a rectifier 14, and a failure detection circuit 15.

The switching controller 11 controls each switch (not shown) of the switching unit 12 through pulse width modulation according to the magnitude of the current input from the outside. Each switch of the switching unit 12 is switched in accordance with a pulse width modulation signal output from the switching control unit 11 to apply AC power to the transformer 13, and the transformer 13 is connected to each of the switching units 12. According to the switching of the switch, the AC voltage is increased or reduced and outputted.

The rectifier 14 rectifies and outputs the alternating voltage output from the transformer 13 into direct current voltages (+,-). The failure detection circuit 15 is configured to feed back the DC voltage output from the rectifier 14 to inform the switching controller 11 of the DC voltage failure according to the magnitude of the voltage.

This failure detection circuit 15 is composed of an overvoltage protection circuit 16 of + DC voltage and an overvoltage protection circuit 17 of -DC voltage as shown in FIG.

The overvoltage protection circuit 16 of the + DC voltage includes a first resistor R1 connected in parallel to the + output terminal (OUTPUT + VDC) of the rectifier 14 and an anode connected in series to a rear end of the first resistor R1. A first zener diode ZD1 having a cathode connected in series to the first photodiode PD1 of the first photocoupler PTC, a cathode of the first photodiode PD1, and an anode grounded to ground; The first photo transistor PTR1 corresponds to the first photo diode PD1 of the photo coupler V.

The overvoltage protection circuit 17 of the DC voltage has a cathode connected to the cathode of the second Zener diode ZD2 and the anode of the second Zener diode ZD2 connected in parallel with the output terminal (-VDC) of the rectifier 14. A second photodiode PD2 of the second photocoupler PTC2 connected in series, a second resistor R2 having one end connected to an anode of the second photodiode PD2 and the other end grounded to ground; The second photo transistor PTR2 corresponds to the second photodiode PD2 of the second photo coupler PTC2.

Hereinafter, the operation of the conventional failure detection circuit will be described in detail with reference to FIGS. 1 and 2.

First, when a normal output voltage is output from the rectifier 14 outputting power from the transformer 13 under the control of the switching unit 12 of the switching controller 11, the overvoltage protection circuit of the + DC voltage of the failure detection circuit 15 is output. The first Zener diode ZD1 of (16) or the second Zener diode ZD2 of the overvoltage protection circuit 17 of the -DC voltage is kept in the OFF state.

Then, the first photodiode PD1 of the first photocoupler PTC1 or the second photodiode PD2 of the second photocoupler PTC2 is also kept off so that the first phototransistor PTR1 or the second phototransistor ( The PTR2 is kept in the off state, and a high signal is input to the switching controller 11. In other words, it indicates the normal state.

On the contrary, if an abnormal output voltage (voltage exceeding a user-specified voltage range) is output from the power supply 10, the first zener diode ZD1 of the overvoltage protection circuit 16 of the + DC voltage of the failure detection circuit 15 or The second zener diode ZD2 of the overvoltage protection circuit 17 of the DC voltage is turned on.

Then, the first photodiode PD1 of the first photocoupler PTC1 or the second photodiode PD2 of the second photocoupler PTC2 is turned on, thereby causing the first phototransistor PTR1 or the second phototransistor. When PTR2 is turned on, a low signal is input to the switching controller 11. Eventually, the switching control unit 11 informs the abnormal state. Then, the switching controller 11 performs an operation corresponding to an abnormal state.

However, the failure detection circuit of such a conventional power supply does not know from the outside by processing the overvoltage only in the power supply, and does not find a specific power supply that has a problem when a plurality of power supplies are used simultaneously in the equipment or the system. There is this.

In addition, such a conventional failure detection circuit has only another problem of not only detecting an overvoltage but not a low voltage.

An object of the present invention is to solve the above problems, it is possible to inform whether the overvoltage to the outside so that when using a plurality of power supplies in the equipment or system at the same time to find a specific power supply in which the problem occurs in real time It is.

In addition, another object of the present invention is to be able to detect both overvoltage and undervoltage in the failure detection circuit.

1 is a block diagram schematically showing a general power supply

FIG. 2 is a circuit diagram illustrating a configuration of a failure detection circuit of FIG. 1.

Figure 3 is a circuit diagram showing the configuration of the failure detection circuit of the power supply according to the present invention

<Explanation of symbols for main parts of the drawings>

10: power supply 11: switching control unit

12: switching unit 13: transformer

14: rectifier 15: failure detection circuit

100: low voltage detection circuit PD1 to PD4: first to fourth photodiode

PTC1 to PTC4: First to Fourth Photo Coupler PTR1 to PTR4: First to Fourth Phototransistor

R1 to R4: First to fourth resistors ZD1 to ZD3: First to third Zener diodes

Features of the present invention for achieving the above objects,

Step-up the switching control unit for performing a pulse width modulation according to the magnitude of the current input from the outside, the switching unit is switched according to the pulse width modulation of the switching control unit, the AC power applied to the primary side according to the switching of the switching unit A transformer for outputting to the secondary side, a rectifying unit for rectifying and outputting an AC voltage output from the transformer as a DC voltage, and a DC voltage output from the rectifying unit and feeding back the DC voltage output from the transformer to the switching controller according to the magnitude of these voltages. A power supply comprising a failure detection circuit having a first photodiode, a first phototransistor, a second photodiode and a second phototransistor to indicate a magnitude of a DC voltage to be provided,

The failure detection circuit is,

A third photodiode having an anode connected in parallel to the positive output terminal of the rectifying unit;

A fourth photodiode having an anode connected to the cathode of the third photodiode;

A zener diode having a cathode connected to the cathode of the fourth photodiode and an anode connected to a negative output terminal of the rectifying unit;

A third photo transistor optically coupled to the third photodiode, a collector connected to an external light emitting element, and an emitter grounded to ground;

And a low voltage sensing circuit comprising a fourth photo transistor optically coupled to the fourth photo diode, a collector connected to an external controller, and an emitter grounded to ground.

Here, the low voltage detection circuit,

A first resistor for protecting the third photodiode and the fourth photodiode from overvoltage between the positive output terminal of the rectifier and the anode of the first photodiode;

A second resistor is further provided between the rear end of the first resistor and the cathode of the fourth photodiode and the cathode of the zener diode to protect the first photodiode and the fourth photodiode from overcurrent.

Hereinafter, the configuration of the failure detection circuit of the power supply according to the present invention will be described in detail with reference to FIG. Here, about the same structure as the conventional one, the same code | symbol is attached | subjected and the duplication description is abbreviate | omitted.

3 is a circuit diagram showing the configuration of a failure detection circuit of the power supply according to the present invention.

Referring to FIG. 3, the low voltage detection circuit 100 of the failure detection circuit 15 according to the present invention may include a third photo coupler PTC3, a fourth photo coupler PTC4, a third zener diode ZD3, It consists of a 3rd resistor R3 and a 4th resistor R4.

The third photodiode PD3 of the third photocoupler PTC3 has an anode connected in parallel to the + output terminal + VDC of the rectifier 14 of the power supply 10. The third phototransistor PTR3 is optically coupled to the third photodiode PD3, the collector is connected to an external light emitting device (not shown), and the emitter is grounded to the ground.

An anode of the fourth photodiode PD4 of the fourth photocoupler PTC4 is connected to the cathode of the third photodiode PD3. The fourth photo transistor PTR4 is optically coupled to the fourth photo diode PD4, the collector is connected to an external controller (not shown), and the emitter is grounded to the ground.

The third Zener diode ZD3 has a cathode connected to the cathode of the fourth photodiode PD4 and an anode connected to the -output terminal (-VDC) of the rectifier 14.

The third resistor R3 is connected between the + output terminal (+ VDC) of the rectifier 14 and the anode of the third photodiode PD3, and the fourth resistor R4 is connected to the rear end of the third resistor R3. The cathode is connected between the cathode of the fourth photodiode PD4 and the cathode of the third zener diode ZD3.

Hereinafter, the operation of the failure detection circuit of the power supply according to the present invention will be described in detail with reference to FIG.

First, when the overvoltage is output from the rectifier 14 and the failure detection circuit 15 is operated to turn off the switch 12 in the switching controller 11, the voltage is not output from the rectifier 14.

Since the voltage is not applied to the low voltage sensing circuit 100, the third photodiode PD3 of the third photocoupler PT3 and the fourth photodiode PD4 of the fourth photocoupler PTC4 remain off. do.

As a result, the third phototransistor PTR3 and the fourth phototransistor PTR4 are also turned off together, so that a high signal is output to the external light emitting element side and the external controller side. As a result, the external light emitting device is turned off or the light emission color is changed to notify the overvoltage of the power supply 10 to the outside, and the external controller recognizes the overvoltage of the power supply 10 to control another device.

On the other hand, if the difference between the output voltage of the + output terminal (+ VDC) of the rectifier 14 and the output voltage of the-output terminal (-VDC) is within a range specified by the user, that is, the zener voltage of the third zener diode ZD3, the third zener The current flows from the + output terminal (+ VDC) to the-output terminal (-VDC) by the constant voltage function of the diode ZD3, thereby turning on the third photocoupler PTC3 and the fourth photo coupler PTC4.

As a result, since the third phototransistor PTR3 and the fourth phototransistor PTR4 are turned on, a low signal is output to an external light emitting device side and an external controller side. Thus, the external light emitting device is turned on or the light emission color is changed to notify the normal operation of the power supply 10 to the outside, and the external controller recognizes the normal operation of the power supply 10.

On the contrary, if the difference between the output voltage of the + output terminal (+ VDC) of the rectifier 14 and the output voltage of the-output terminal (-VDC) does not satisfy the user-specified range, the constant voltage function of the third zener diode ZD3 is lost. The current flowing from the output terminal (+ VDC) to the -output terminal (-VDC) is cut off, thereby turning off the third photocoupler (PTC3) and the fourth photo coupler (PTC4).

As a result, since the third phototransistor PTR3 and the fourth phototransistor PTR4 are turned off, a high signal is output to the external light emitting element side and the external controller side. Thus, the external light emitting device is turned off or the light emission color is changed to notify the low voltage of the power supply 10 to the outside, and the external controller recognizes the low voltage of the power supply 10 to control another device.

Therefore, the fault detection circuit can detect both the overvoltage and undervoltage of the power supply, and can easily determine whether the power supply is defective from the outside by informing the current state of the power supply to the outside.

As described above, according to the failure detection circuit of the power supply according to the present invention, by using a plurality of power supplies in the equipment or the system at the same time by allowing the external to inform whether or not the specific power supply having a problem in real time In addition, it can detect both overvoltage and undervoltage in the fault detection circuit.

Claims (2)

Step-up the switching control unit for performing a pulse width modulation according to the magnitude of the current input from the outside, the switching unit is switched according to the pulse width modulation of the switching control unit, the AC power applied to the primary side according to the switching of the switching unit A transformer for outputting to the secondary side, a rectifying unit for rectifying and outputting an AC voltage output from the transformer as a DC voltage, and a DC voltage output from the rectifying unit and feeding back the DC voltage output from the transformer to the switching controller according to the magnitude of these voltages. A power supply comprising a failure detection circuit having a first photodiode, a first phototransistor, a second photodiode and a second phototransistor to indicate a magnitude of a DC voltage to be provided, The failure detection circuit is, A third photodiode having an anode connected in parallel to the positive output terminal of the rectifying unit; A fourth photodiode having an anode connected to the cathode of the third photodiode; A zener diode having a cathode connected to the cathode of the fourth photodiode and an anode connected to a negative output terminal of the rectifying unit; A third photo transistor optically coupled to the third photodiode, a collector connected to an external light emitting element, and an emitter grounded to ground; And a low voltage sensing circuit comprising a fourth photo transistor optically coupled to the fourth photodiode, a collector connected to an external controller, and an emitter grounded to the ground. The method of claim 1, The low voltage detection circuit, A first resistor for protecting the third photodiode and the fourth photodiode from overvoltage between the positive output terminal of the rectifier and the anode of the first photodiode; And a second resistor between the rear end of the first resistor, the cathode of the fourth photodiode and the cathode of the zener diode, to protect the first photodiode and the fourth photodiode from overcurrent. Power supply failure detection circuit.