JPH0578190U - Power supply abnormality display circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a power supply abnormality display circuit that accurately stores a power supply abnormality mode and has a simple circuit configuration. [Configuration] An overload detection circuit (OLP) for detecting an overload current of a power supply, an overvoltage detection circuit (OVP) for detecting an overvoltage state of the output voltage of the power supply, and an abnormal alarm when one outputs an alarm signal A latch circuit for continuously outputting a signal is provided, and the first LE is provided while the abnormality alarm signal is valid.
In the abnormality display circuit of the power supply that lights up D and shuts down the operation of the power supply, when the alarm feedback circuit is used to output the abnormal alarm signal by the alarm signal of the overvoltage detection circuit, LED
The feature is that it lights continuously.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an abnormality display circuit used in a switching power supply device and the like, and more particularly to a circuit for storing an abnormal mode and displaying it even after the power supply is shut down.

[0002]

[Prior Art]

 The applicant of the present invention has proposed a power supply protection circuit in, for example, Japanese Utility Model Publication No. 1-69383. FIG. 3 is a block diagram of such a protection circuit. The overload detection circuit OLP10 operates when the output current of the power supply becomes larger than the allowable value, such as when the load is short-circuited. The overvoltage detection circuit OVP20 operates when the output voltage of the power supply becomes excessive, and the overvoltage causes damage to the electronic circuit on the load side, so an alarm is required. The timer circuit 30, which is connected to the output of the overload detection circuit OLP10, does not have the possibility of damaging the power supply or issuing an alarm if the overload is for an extremely short time. Only the overload condition is recognized and an alarm is output. The latch circuit 40 inputs the output signals of the timer circuit 30 and the overvoltage detection circuit OVP20, and when either one outputs an alarm signal, the LED 41 is turned on. The latch circuit 42 inputs the output signal of the overvoltage detection circuit OVP20 and turns on the LED 43 when the alarm signal is output once. Therefore, the determination of the abnormal mode depends on the number of lights of the LEDs 41 and 43. The latch circuit is provided to store the abnormal mode.

[0003]

[Problems to be solved by the device]

 However, if the overvoltage is transient, there is a risk of latch malfunction such as not being latched or too sensitive due to the difference in the operation time of the latch circuits 40 and 42, and the abnormal mode may not be accurately stored. was there. Also, since there are multiple latch circuits, simplification of the circuits has been desired. The present invention solves such a problem, and an object thereof is to provide a power supply abnormality display circuit that accurately stores a power supply abnormality mode and has a simple circuit configuration.

[0004]

[Means for Solving the Problems]

 The present invention that achieves such an object includes an overload detection circuit (OLP) that detects an overload current of a power supply, an overvoltage detection circuit (OVP) that detects an overvoltage state of an output voltage of the power supply, and an overload detection circuit (OVP). A timer circuit that outputs an overload alarm signal when the overload condition continues for a certain period of time in the detection circuit, and an output of this timer circuit and the output signal of the overvoltage detection circuit. A power supply abnormality display circuit that has a latch circuit that continuously outputs and that turns on the first LED and shuts down the operation of the power supply while the abnormality alarm signal is valid has the following configuration. Is.

That is, the second LED mounted between the warning signal output of the overvoltage detection circuit and the latch circuit input, the abnormality warning signal of the latch circuit, and the warning signal of the overvoltage detection circuit are input, and both are valid. If an abnormal alarm signal is output by the alarm signal of the overvoltage detection circuit, an alarm feedback circuit for returning the alarm signal to the overvoltage detection circuit is provided. It is characterized by continuous lighting.

[0006]

[Action]

 In the present invention, the first LED indicates that the power supply is in an abnormal state due to overload or overvoltage, and if the second LED is lit, it indicates that it is due to overvoltage. The alarm feedback circuit performs the same function as the latch circuit by ANDing the latch circuit and the overvoltage detection circuit.

[0007]

【Example】

 The present invention will be described below with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of the present invention. Incidentally, in FIG. 1, those having the same functions as those in FIG. In the figure, a shutdown circuit 44 receives an abnormality alarm signal from the latch circuit 40 and suppresses the power supply to the power supply. For example, in a switching power supply, the switching control output of the switching control circuit is suppressed. The alarm feedback circuit 50 inputs the abnormality alarm signal of the latch circuit 40 and the alarm signal of the overvoltage detection circuit 20, and when both are displaying an alarm state, returns the alarm signal to the overvoltage detection circuit 20. The LED 22 is provided between the overvoltage detection circuit 20 and the latch circuit 40. The LED 22 lights up in the overvoltage state and continues when the alarm feedback circuit 50 issues an abnormal alarm signal due to the overvoltage. Light. Due to the logic level, it is connected to the voltage source Vcc via the resistor R5, connected to the latch circuit 40 via the diode D6, and connected to the LED 22 via the diode D7.

In the device thus configured, only the LED 41 is turned on when the abnormality warning signal is output due to the overload current. Further, when the abnormality warning signal is output due to the overvoltage, the LED 41 lights up, and the abnormality feedback signal is fed back to the overvoltage detection circuit 20 by the alarm feedback circuit 50 so that the LED 22 continues to light up. Therefore, the abnormal mode can be easily grasped by the lighting state of the LED.

FIG. 2 shows an abnormality display device for a multi-output power supply. Here is directed to the power of 3 output, it represents the load current of each power supply I _1, I _2, I _3, represents the output voltage at _{V 1, V 2, V 3} . The overload detection circuit 10 has an OLP circuit using a comparator. The OLP1 inputs the load current I ₁ to the plus terminal via the resistor R1, compares it with the reference voltage Vref connected to the minus terminal, and outputs an alarm signal to the diode D1 when it is recognized as an overload state. The same applies to the OLPs _{2 and 3} , but the load currents I _{2 and} I ₃ are level-converted because the reference voltage Vref is shared. By abutting the cathode terminals of the diodes D1 to D3, if any one of the comparators is H, OR is taken and the logic level becomes H. The timer circuit 30 is a CR time constant circuit, and the H logic signal of the overload detection circuit 10 is stored in the capacitor C1 via the resistor R3. The output of the time constant circuit 30 is sent to the latch circuit 40 via the diode D4, and the signal of the overvoltage detection circuit 20 is sent to the latch circuit 40 via the diode D5. If either one is H, the LED 41 is turned on. At the same time, the shutdown circuit 44 is operated.

The overvoltage detection circuit 20 has an OVP circuit using a comparator. The OV P1 divides the output voltage V ₁ by the voltage dividing resistors R11 and R12, inputs it to the plus terminal, compares it with the reference voltage Vref connected to the negative terminal, and turns on the LE D22 when it is recognized as an overvoltage state. To do. OVP2,3 is similar, but the reference level conversion of the output voltage V _2, V ₃ the voltage Vref in relation to share with is performed by using the voltage dividing resistors, diodes D11 to the output side of the comparator over data, D12 Are connected. By abutting the cathode terminals of the LED 22 and the diodes D11 and D12, if any one of the comparators is H, OR is taken and the logic level becomes H. This output is sent to the latch circuit 40 via the diode D5.

In the alarm feedback circuit 50, the cathode side of the diode D6 is connected to the output side of the latch circuit 40, and the cathode side of the diode D7 is connected to the output signal line of the overvoltage detection circuit 20 via the ground resistance R17. The anode sides of the diodes D6 and D7 are fed back to the plus terminal of OVP1 via the diode D8. The resistor R5 is a pull-up resistor, and when the abnormality alarm signal of the latch circuit 40 is caused by the H logic of the overvoltage detection circuit 20, the LED 22 is turned on by the OVP1.

In the device configured as described above, the LED 22 is only connected to the OVP 1, but when an abnormality in the overvoltage mode occurs at any output, the LED 22 is turned on by the action of the alarm feedback circuit 50. Preferably, displaying which output the overvoltage mode has occurred is convenient for identifying the cause of the failure.

[0013]

[Effect of the device]

 As described above, according to the present invention, the alarm signal of the true latch circuit 40 which sends the control signal to the shutdown circuit is fed back to the alarm feedback circuit 50 to turn on the LED, thereby displaying the abnormal mode. In addition, the reliability of the trigger mode judgment is high, and the single latch circuit has a unique effect that the number of parts is small and the cost is low compared to the conventional example.

[Brief description of drawings]

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

FIG. 2 is an abnormality display device for a multi-output power supply.

FIG. 3 is an explanatory diagram of a conventional device.

[Explanation of symbols]

 10 ... Overload detection circuit 20 ... Overvoltage detection circuit 30 ... Timer circuit 40 ... Latch circuit 50 ... Alarm feedback circuit

Claims (1)

[Scope of utility model registration request] 1. An overload detection circuit (OLP) for detecting an overload current of a power supply, an overvoltage detection circuit (OVP) for detecting an overvoltage state of an output voltage of the power supply, and an overload detection circuit for a predetermined time. A timer circuit that outputs an overload alarm signal when the load condition continues, and a latch that inputs the output signal of this timer circuit and the overvoltage detection circuit and continuously outputs an abnormal alarm signal when at least one outputs an alarm signal Circuit, and while the abnormal alarm signal is valid, the first LE
In the power supply abnormality display circuit that lights D and shuts down the operation of the power supply, a second LED mounted between the alarm signal output of the overvoltage detection circuit and the latch circuit input, and the latch circuit abnormality alarm signal And an alarm signal of the overvoltage detection circuit are input, and an alarm feedback circuit that returns the alarm signal to the overvoltage detection circuit when both are valid, and an abnormal alarm signal is output by the alarm signal of the overvoltage detection circuit. If the alarm returns, the second LE
A power supply abnormality display circuit characterized by continuously lighting D.