JPH0623160Y2 - Switching signal abnormality detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to an abnormality detection circuit for detecting an abnormality of an input AC signal (hereinafter referred to as an input signal) of a switching regulator. When the input signal is abnormal, the switching regulator operates. An abnormality detection circuit that detects an abnormality in the input signal and a switching regulator that boosts the DC voltage by switching the output signal of the abnormality detection circuit for the purpose of automatically stopping and protecting the destruction of the switching transistor In the power supply device having the first abnormality detection circuit, the abnormality detection circuit includes a first comparison circuit having means for comparing the input signal with a predetermined reference voltage;
A second comparator circuit having means for comparing the output voltage of the comparator circuit with the input signal, and the operation of the switching regulator by the output signal of the second comparator circuit in response to the abnormality of the input signal. Is configured to stop.

[Industrial application field]

The present invention relates to an abnormality detection circuit that detects an abnormality in an input AC signal (hereinafter referred to as an input signal) of a switching regulator.

For example, in a logic circuit of an exchange, an information device, etc., a method is widely used in which a DC voltage is controlled to switch a transistor on and off by an AC voltage which is an input signal such as a pulse signal to obtain another DC voltage. .

The method of obtaining this DC voltage is required to be a simple circuit and not to destroy the power supply circuit even if the logic circuit becomes abnormal.

[Conventional technology]

FIG. 3 is a circuit diagram showing an example of the conventional method of the present invention. In the figure, 1 is an abnormality detection circuit, 2 is a switching regulator, and 3 is a logic circuit.

Conventionally, in the abnormality detection circuit 1, when the input signal of the base of the switching transistor Tr21 of the switching regulator 2 becomes abnormal and the transistor Tr21 continues to be turned on, and when an overcurrent flows in the collector of the transistor Tr21, the collector Resistor R connected in series with
21 detects overcurrent and converts it to overvoltage. Next,
The two voltages of the converted overvoltage and the preset reference voltage Vr are applied to the comparator H11, and their levels are compared and judged. Further, the output signal of the comparator H11 is set to the logic circuit 3
, The operation of the logic circuit 3 is stopped, and the switching transistor Tr21 is turned off to stop the operation of the switching regulator 2 for protection.

The switching regulator 2 has a switching transistor Tr21, a resistor R21 at the collector, and a capacitor C.
21 and the diode D21 are connected in a loop, and a negative DC voltage (for example, -24V) is applied to the intermediate connection point between the resistor R21 and the capacitor C21 via the choke L21. The required DC output is from both ends of the capacitor C21. I was getting.

[Problems to be solved by the invention]

As described above, the conventional switching regulator 2 is protected from the logic circuit 3 by the switching transistor Tr.
The output signal of turning off 21 was added to stop the switching operation.

Therefore, there is no problem if the logic circuit 3 outputs a signal for turning off the switching transistor Tr21 at the time of abnormality. For example, when the output transistor of the output stage of the logic circuit 3 fails, the switching transistor T21
The switching signal for turning off r21 is no longer output, and an excessive current flows through the switching transistor Tr21, causing destruction. Also, in some cases, a choke L
There was a problem of destroying up to 21.

The purpose of this invention is to provide a circuit for automatically stopping the operation of the switching regulator 2 when an input signal is abnormal, for protection.

[Means for solving problems]

The above object of the present invention is to provide an abnormality detection circuit (1) in a power supply device having an abnormality detection circuit (1) to which an AC signal is input and a switching regulator (2) controlled by the output signal to generate a DC voltage. ) Is the first comparison circuit
(11) and the second comparison circuit (12), the first comparison circuit
(11) compares the judgment signal in which the input AC signal is converted to the reference voltage or higher with the reference voltage, and the judgment signal is the normal signal if the judgment signal is a normal input AC signal or higher than the reference voltage value. In the case of an abnormal input AC signal that is less than or equal to the voltage, the abnormal voltage is output, and the second comparison circuit outputs the AC voltage corresponding to the input AC signal as a switching signal according to the normal signal output from the first comparison circuit. Generate a blocking signal as a switching signal, the switching regulator generates a DC output by being controlled by an AC voltage as a switching signal from the second comparison circuit, and stops the generation of a DC output by the blocking signal as a switching signal. Is achieved by the switching signal abnormality detection circuit.

[Action]

The first comparison circuit 11 detects the AC component of the input signal, that is, "presence" and "absence" of the signal for turning on and off the switch ig regulator 2. Then, while the first comparison circuit 11 indicates the AC component “present”, the second comparison circuit 12 operates the switch ig regulator 2 based on the input signal.

When the first comparison circuit 11 indicates that there is no AC component, the second
The comparison circuit 12 stops the operation of the switch ignition regulator 2.

〔Example〕

FIG. 2 (a) is a circuit diagram showing an embodiment of the present invention, 1 is an abnormality detection circuit, 2 is a switching regulator,
FIG. 2 (b) is an explanatory diagram of the operation of FIG. 2 (a).

In the figure, the abnormality detection circuit indicated by 1 indicates a first comparison circuit 11 having a first comparator H11 for comparing the input signal with a reference voltage and making a decision, and the input signal and the output of the first comparator H11. A second comparison circuit 12 having a second comparator H12 for comparison and judgment is provided.

Here, each of the comparators H11 and H12 uses an opn collector type operational amplifier. Therefore, a negative power supply voltage of -5 V is output when turned on, and the output stage transistor is turned on when turned off.

The time constant of the integrating circuit composed of C11 and R12 connected to the input terminal a of the first comparator H11 is set to the charging time of C11 <C11
The discharge time is set to.

With this setting, when the input signal is normal and the level changes from "L" level to "H" level, the level of the determination signal gradually increases to the level divided by the resistors R12 and R13. Rise to. Next, when the level is inverted to "L" level, D11 is cut, the voltage stored in C11 is discharged by R12, and the determination signal is gradually lowered. When the level changes to "H" level again, the voltage is again stored in C11 and the determination signal gradually rises. That is, the AC component of the input signal can be detected by the integrating circuit of C11 and R12.

When the circuit is normal, the determination signal becomes a triangular wave voltage in which these states are repeated and is input to the a terminal of the comparator H11. The reference voltage Vref divided by R13 and R14 is input to the input terminal b of H11. By adjusting R13 and R14, the reference voltage Vref is set to be always lower than the determination voltage which is the triangular wave voltage. Therefore, if the input signal is normal, the comparator H11 is turned off and is in the open state, and the comparator H11
The voltage divided by R15 and R16 is input as a normal signal to the level of the terminal c of 11, that is, the terminal b of H12.

Therefore, the second comparison circuit 12 repeats the open state and the on state in synchronization with the input signal input in parallel with the first comparison circuit 11, and the input AC shown in FIG. A switching signal corresponding to the signal is input. Therefore, the transistor Tr21 also repeats the normal ON / OFF switching operation, and the switch ignition regulator 2 outputs a normal DC voltage.

In the present embodiment, the abnormal case where the input signal keeps turning on the transistor Tr21 is the abnormal signal output state in which the level continues to be the "L" level. (Because the switch ignition regulator is used with a negative voltage.) Now, when the level drops to "L" level, D11 of the first comparison circuit 11 turns off, and the voltage stored in C11 changes due to R12. After being discharged, the determination signal gradually decreases toward the ground level, and the comparator 11 operates at the specified time T when the level of the determination signal matches the reference voltage Vr.
Is turned on and turned on, and the voltage at the terminal c becomes -5 V as an abnormal signal.

As a result, since the input signal is directly input to the output a terminal of the second comparison circuit 12, the b terminal voltage becomes less than the a terminal voltage, H12 is turned off, and the switch is in the open state, and the switching signal is at the "L" level. Becomes As a result, + is provided as a blocking signal to the base of the switching transistor via R23.
5V is applied, and the switching transistor Tr21 is turned on and is not destroyed.

[Effect of device]

According to the present invention, when the input signal from the logic circuit becomes abnormal, the switching regulator sets the switching transistor to an open state to stop the switching operation, so that it does not cause overcurrent and is not destroyed.

Therefore, it is effective in improving the reliability of the device and the system.

[Brief description of drawings]

 FIG. 1 is a block diagram showing the principle configuration of the present invention, FIG. 2 (a) is a circuit diagram showing an embodiment of the present invention, FIG. 2 (b) is an explanatory view of the operation of the present invention, and FIG. 1 is a circuit diagram showing an example of a conventional method. In FIG. 1, 1 is an abnormality detection circuit, 11 is a first comparison circuit, 12 is a second comparison circuit, and 2 is a switching regulator.

Claims (1)

[Scope of utility model registration request] 1. An abnormality detection circuit (1) to which an AC signal is input
In a power supply device having a switching regulator (2) that generates a DC voltage controlled by its output signal, the abnormality detection circuit (1) includes a first comparison circuit (11) and a second comparison circuit (12). The first comparison circuit (11) is configured to compare the judgment signal in which the input AC signal is converted to the reference voltage or higher with the reference voltage, and the judgment signal is normal when the input AC signal is the reference voltage value or higher. If the signal is an abnormal input AC signal whose judgment signal is less than or equal to the reference voltage, the abnormal voltage is output, and the second comparison circuit switches the AC voltage corresponding to the input AC signal by the normal signal output from the first comparison circuit. The signal is output as a signal, a blocking signal is generated as a switching signal according to the abnormal signal, and the switching regulator is controlled by the AC voltage as the switching signal from the second comparison circuit. Switching signal abnormality detection circuit, characterized in that the DC output generated, stops generating the DC output by the blocking signal as a switching signal.