Disconnection detection circuit of pressure detection device
A disconnection detection circuit includes: a pull-up resistor to which the detection signal is fed and which connects a signal line connected to the wiring cable to a power supply or a pull-down resistor which connects the signal line to a GND; and a voltage clip circuit 105 which includes a high-voltage clip circuit which is connected between the signal line and the power supply and which clips the voltage of the signal line to the maximum specified voltage and a low-voltage clip circuit which is connected between the signal line and the GND and which clips the voltage of the signal line to the minimum specified voltage.
1. A disconnection detection circuit of a pressure detection device, with the pressure detection device including at least: a pressure detection portion having a pressure detection element which receives pressure so as to output a charge signal corresponding to the pressure; and a wiring cable which transmits a detection signal output from the pressure detection portion to an external circuit, the disconnection detection circuit detecting a disconnection of the wiring cable in the pressure detection device,
wherein the disconnection detection circuit comprises:
a pull-up resistor to which the detection signal is fed and which connects a signal line connected to the wiring cable to a power supply or a pull-down resistor which connects the signal line to a GND; and
a voltage clip circuit which includes a high-voltage clip circuit which is connected between the signal line and the power supply and which clips the voltage of the signal line to a maximum specified voltage and a low-voltage clip circuit which is connected between the signal line and the GND and which clips the voltage of the signal line to a minimum specified voltage,
wherein the voltage clip circuit includes an output resistor which is connected in series to the signal line on the input side of the high-voltage clip circuit and the low-voltage clip circuit.
2. The disconnection detection circuit of a pressure detection device according to claim 1 ,
wherein the high-voltage clip circuit includes a high voltage-side resistor voltage dividing circuit which sets the maximum specified voltage and which is connected between the power supply and the GND.
3. The disconnection detection circuit of a pressure detection device according to claim 2 ,
wherein the high-voltage clip circuit uses a transistor pair of a pnp transistor and an npn transistor to which divided voltage obtained from the high voltage-side resistor voltage dividing circuit is fed.
4. The disconnection detection circuit of a pressure detection device according to claim 3 ,
wherein the transistor pair is formed with complimentary transistors.
5. The disconnection detection circuit of a pressure detection device according to claim 2 ,
wherein the high-voltage clip circuit uses a diode to which divided voltage obtained from the high voltage-side resistor voltage dividing circuit is fed.
6. The disconnection detection circuit of a pressure detection device according to claim 1 ,
wherein the low-voltage clip circuit includes a low voltage-side resistor voltage dividing circuit which sets the minimum specified voltage and is connected between the power supply and the GND.
7. The disconnection detection circuit of a pressure detection device according to claim 6 ,
wherein the low-voltage clip circuit uses a transistor pair of a pnp transistor and an npn transistor to which divided voltage obtained from the low voltage-side resistor voltage dividing circuit is input.
8. The disconnection detection circuit of a pressure detection device according to claim 7 ,
wherein the transistor pair is formed with complimentary transistors.
9. The disconnection detection circuit of a pressure detection device according to claim 6 ,
wherein the low-voltage clip circuit uses a diode to which divided voltage obtained from the low voltage-side resistor voltage dividing circuit is fed.
10. The disconnection detection circuit of a pressure detection device according to claim 1 ,
wherein the external circuit is a control board which outputs a control signal based on the detection signal.
11. The disconnection detection circuit of a pressure detection device according to claim 1 ,
wherein the wiring cable includes a signal line connected to the signal line, a power supply line connected to the power supply and a GND line connected to the GND.
12. The disconnection detection circuit of a pressure detection device according to claim 1 ,
wherein the disconnection detection circuit is applied to a pressure detection device which detects a combustion pressure of an engine mounted in an automobile.
13. The disconnection detection circuit of a pressure detection device according to claim 1 ,
wherein the high-voltage clip circuit includes a high voltage-side resistor voltage dividing circuit connected between the power supply and the GND for setting the maximum specified voltage, and a diode or a transistor circuit connected between the high voltage-side resistor voltage dividing circuit and the signal line, the low-voltage clip circuit includes a low voltage-side resistor voltage dividing circuit connected between the power supply and the GND for setting the minimum specified voltage, and a diode or a transistor circuit connected between the low voltage-side resistor voltage dividing circuit and the signal line.