SENSOR SIGNAL OUTPUT CIRCUIT AND METHOD FOR ADJUSTING IT

摘要

A sensor signal output circuit includes: a buffer amplifier which amplifies an output of a temperature sensor; an operational amplifier which amplifies an output of the buffer amplifier; an oscillator which generates a triangular wave signal; and a comparator which compares the triangular wave signal with an output of the operational amplifier to generate a PWM signal. After an offset adjusting resistor of the operational amplifier is adjusted at first temperature, the amplitude of the triangular wave signal is set to adjust the pulse width of the PWM signal at the first temperature. After that, a gain adjusting resistor of the operational amplifier is set to adjust the pulse width of the PWM signal at a second temperature.

主权项

1. A sensor signal output circuit for use with a temperature sensor, comprising:
a buffer amplifier which amplifies and outputs an output signal of the temperature sensor; an operational amplifier which has an inverting input terminal, a non-inverting input terminal, and an output terminal, an output voltage of the buffer amplifier being inputted to the inverting input terminal through a resistor, a reference voltage divided by an offset adjusting resistor being inputted to the non-inverting input terminal, and a gain adjusting resistor being provided between the inverting input terminal and the output terminal; an oscillator which generates a triangular wave signal with a predetermined amplitude; a comparator which compares the triangular wave signal with an output voltage of the operational amplifier and generates a PWM signal with a pulse width corresponding to the output voltage of the operational amplifier; an offset adjusting unit which adjusts the offset adjusting resistor to make the output voltage of the buffer amplifier at a first temperature equivalent to the voltage at the inverting input terminal of the operational amplifier; an amplitude adjusting unit which adjusts the amplitude of the triangular wave signal to make the pulse width of the PWM signal equivalent to a defined first pulse width at the first temperature after the offset adjusting resistor has been set; and a gain adjusting unit which adjusts the gain adjusting resistor to make the pulse width of the PWM signal equivalent to a defined second pulse width at a second temperature that different from the first temperature after the amplitude of the triangular wave signal has been set.