Pressure detection device

1. A pressure detection device comprising:

a pressure detection element which receives pressure so as to output a detection signal corresponding to the pressure; and

a processing circuit which processes and outputs the detection signal output from the pressure detection element,

wherein the processing circuit includes:

a voltage transformation circuit receiving a power supply voltage fed from an external power supply and transforming the power supply voltage fed to obtain a first reference voltage with a predetermined positive voltage value;

an integrator circuit operating with the power supply voltage fed from the external power supply, receiving the first reference voltage as an operation reference and the detection signal from the pressure detection element to perform integral processing on the detection signal so as to convert the detection signal into a single output signal, differentially amplifying the detection signal and the first reference voltage, the integrator circuit having a computation amplifier circuit and integrating a detection signal to convert the detection signal to a voltage waveform; and

at least one or more amplifier circuits receiving the single output signal of the integrator circuit and a second reference voltage with a predetermined voltage value as an operation reference to perform amplification processing on the single output signal of the integrator circuit,

wherein the integrator circuit cancels out a noise component superimposed on the detection signal by differentially amplifying the detection signal and the first reference voltage,

wherein the voltage transformation circuit is formed with a voltage dividing resistor circuit in which a plurality of voltage dividing resistors are combined,

wherein the second reference voltage is obtained from an output of a second reference power supply using a regulator, and

wherein the detection signal is a charge signal which is obtained from a piezoelectric element used as the pressure detection element.

2. The pressure detection device according to claim 1 , wherein the integrator circuit is operated with a single power supply.

3. The pressure detection device according to claim 1 , wherein the second reference voltage is obtained from the voltage transformation circuit.

4. The pressure detection device according to claim 1 , wherein the processing circuit includes a voltage follower circuit in the final stage.

5. The pressure detection device according to claim 1 , wherein at least part of the processing circuit is formed with an integrated circuit, and the voltage transformation circuit is arranged outside the integrated circuit.

6. The pressure detection device according to claim 1 , wherein at least a part of the processing circuit is formed with an integrated circuit, and the voltage transformation circuit is incorporated in the integrator circuit.

7. The pressure detection device according to claim 1 , wherein the pressure detection device is applied to a pressure detection device which detects a combustion pressure of an engine mounted in an automobile.

8. The pressure detection device according to claim 1 , wherein the integrator circuit receives the first reference voltage as an operation reference to a first input and the detection signal from the pressure detection element to a second input, and

wherein the at least one amplifier circuit comprises a first amplifier circuit receiving the single output signal of the integrator circuit to a first input and the second reference voltage with a predetermined voltage value as an operation reference to a second input to perform amplification processing on the single output signal of the integrator circuit to obtain a second output voltage.