JPH04317216A - Driver circuit - Google Patents

Abstract

PURPOSE:To detect the malfunction of a switching transistor and to prevent a load and the switching transistor from burning by disconnecting the power supply. CONSTITUTION:When an input signal (a) has low potential, a switching transistor 1 is turned off and collector voltage is made to have high potential. One input of exclusive OR circuits 4, becomes a high potential signal from a Zener diode 3. Since a low potential input signal (a) is inputted to the other of the circuits 4, the output signal (b) of the exclusive OR signal 4 is changed into a high potential normal signal. When failure occurs in the switching transistor, a low potential alarming signal is generated as the output signal (b) of the exclusive OR circuit 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driver circuit using switching elements.

0002

2. Description of the Related Art Conventional driver circuits have not been provided with a malfunction detection function.

0003

[Problems to be Solved by the Invention] The conventional driver circuit described above does not include a malfunction detection circuit, so if the switching element remains on due to a failure of the switching element, current continues to flow to the load. However, the disadvantage is that there is a possibility that accidents such as load burnout or switching element burnout may occur.

0004

[Means for Solving the Problems] A driver circuit according to a first aspect of the invention is a driver circuit that turns on and off a switching element according to an input signal of a logic signal to flow current to a load or cut off current to the load. , by detecting the on or off state of the switching element by a Zener diode, and inputting the input signal and the output signal of the Zener diode to an exclusive OR circuit, the output differs from the expected output according to the input signal. The exclusive OR circuit outputs an alarm signal when an output occurs in the switching element.

[0005] Further, in the driver circuit of the second aspect of the invention, in the driver circuit which turns on and off a switching element according to an input signal to intermittent current flowing to a load, the on or off state of the switching element is detected by a comparator. , the output signal of the comparator and the input signal are compared by the exclusive OR circuit, and if an output different from the expected output is generated in the switching element due to the input signal, an alarm is generated from the exclusive OR circuit. It is configured by outputting a signal.

Furthermore, in a driver circuit according to a third aspect of the invention, in a driver circuit that turns on and off a switching element according to an input signal to intermittent a current flowing to a load, the on or off state of the switching element is detected by a photocoupler. The output signal of the photocoupler and the input signal are compared by the exclusive OR circuit, and if an output different from the expected output is generated in the switching element due to the input signal, the exclusive OR circuit It is configured by outputting an alarm signal from.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a driver circuit according to the first invention.

In the embodiment shown in FIG. 1, when the input signal a is at a low potential, the switching transistor 1 is turned off.
Its collector voltage becomes high potential due to the power supply voltage VP. Therefore, one input of the exclusive OR circuit 4 receives a high potential output signal from the 4V Zener diode 3. Since the low potential input signal a is input to the other input, the output signal b of the exclusive OR circuit 4 is at the high potential of the normal signal. In this manner, when the switching transistor 1 is normally turned on and off according to the input signal, the output signal b of the exclusive OR circuit 4 becomes a normal signal with a high potential. However, the output of switching transistor 1 is input signal a
If the output is different from the expected output, the output signal b of the exclusive OR circuit 4 becomes a low potential and outputs an alarm signal.

FIG. 2 is a time chart showing an example of signal waveforms in the embodiment shown in FIG.

As shown in FIG. 2, for input signal a,
If the collector voltage of the switching transistor 1 is normal, the output signal b of the exclusive OR circuit 4 is at a high potential, but if a failure occurs in the switching transistor 1, an alarm signal at a low potential is generated.

FIG. 3 is a circuit diagram showing an embodiment of the driver circuit of the second invention. Further, FIG. 4 is a time chart showing an example of a signal waveform in the embodiment of FIG.

In the embodiment of FIG. 3, when the input signal is at a low potential, the switching transistor 31 is off.
As shown in FIG. 4, the collector voltage of the transistor 31 is at a high potential, the input signal of the comparator 33 is at a high potential, and the output of the comparator 33 is at a high potential. When the input signal and the output signal of the comparator 33 are input to the exclusive OR circuit 34, the switching transistor 3
1 is normally turned on and off according to the input signal, the output of the exclusive OR circuit 34 is at a high potential, but as shown in FIG. 4, a failure occurs in the transistor 31 and the switching transistor 31 If the state does not operate according to the input signal, the output of the exclusive OR circuit 34 becomes a low potential and is detected as an alarm.

FIG. 5 is a circuit diagram showing an embodiment of the driver circuit according to the third invention. Moreover, FIG. 6 is a time chart showing an example of a signal waveform in the embodiment of FIG.

In the embodiment of FIG. 5, when the input signal is at a low potential, the switching transistor 51 is off.
As shown in FIG. 6, the collector voltage of the transistor 51 is at a high potential, current flows through the light emitting diode of the photocoupler 53, and the output signal of the photocoupler 53 is at a low potential, as shown in FIG.

Therefore, when the input signal and the output signal of the photocoupler are input to the exclusive OR circuit 54, if the switching transistor 51 is normally turned on and off according to the input signal, the exclusive OR circuit 54 However, as shown in FIG. 6, if a failure occurs in the transistor 51 and the state of the switching transistor 51 does not operate according to the input signal, the output of the exclusive OR circuit 54 will be at a high potential. This will be detected as an alarm.

[0017]

As explained above, the driver circuit of the first invention detects the on/off state of the switching transistor using the Zener diode, and compares it with the input signal using the exclusive OR circuit. Since a malfunction of the switching transistor can be detected, the power supply can be cut off based on the detection result to prevent burnout of the load or the switching transistor.

Further, the driver circuit of the second invention can detect malfunction of the switching transistor by detecting the on/off state of the switching transistor using the comparator and comparing it with the input signal using the exclusive OR circuit. As a result, it is possible to prevent the load or the switching transistor from burning out by turning off the power.

Furthermore, the driver circuit of the third invention detects malfunction of the switching transistor by detecting the on/off state of the switching transistor using a photocoupler and comparing it with the input signal using an exclusive OR circuit. As a result, it is possible to prevent the load or the switching transistor from burning out by turning off the power.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a driver circuit of a first invention.

FIG. 2 is a time chart showing an example of a signal waveform in the embodiment of FIG. 1;

FIG. 3 is a circuit diagram showing an embodiment of the driver circuit of the second invention.

FIG. 4 is a time chart showing an example of a signal waveform in the embodiment of FIG. 3;

FIG. 5 is a circuit diagram showing an embodiment of the driver circuit of the third invention.

FIG. 6 is a time chart showing an example of a signal waveform in the embodiment of FIG. 5;

[Explanation of symbols]

1, 31, 51 switching transistor 2,
32, 52 Load 3 Zener diode 4, 34, 54 Exclusive OR circuit 33
Comparator 53 Photocoupler a Input signal b Output signal

Claims (3)

[Claims] [Claim 1] A switching element is turned on and off according to an input signal of a logic signal to cause current to flow through a load,
In the driver circuit that cuts off the current of the load,
By detecting the on or off state of the switching element using a Zener diode and inputting the input signal and the output signal of the Zener diode to an exclusive OR circuit, an output different from an expected output based on the input signal is detected. 1. A driver circuit characterized in that, when the above-mentioned switching element generates an alarm signal, the exclusive-OR circuit outputs an alarm signal. 2. In a driver circuit that turns on and off a switching element according to an input signal to intermittent current flowing through a load, the on or off state of the switching element is detected by a comparator, and the output signal of the comparator and the input When the input signal generates an output different from the expected output in the switching element,
A driver circuit characterized in that an alarm signal is output from the exclusive OR circuit. 3. In a driver circuit that turns on and off a switching element according to an input signal to intermittent current flowing through a load, the on or off state of the switching element is detected by a photocoupler, and the output signal of the photocoupler and The input signal is compared with the exclusive OR circuit, and if an output different from the expected output due to the input signal is generated in the switching element,
A driver circuit characterized in that an alarm signal is output from the exclusive OR circuit.