The invention discloses a
pulse width modulation type
constant current source circuit. The circuit comprises a reference
voltage generation circuit and a V / I conversion circuit. The reference voltagegeneration circuit comprises an amplitude conversion circuit, a filter circuit, a
voltage amplification buffer circuit and a parallel
linear control circuit. The PWM
control signal enables an output waveform to be switched between reference
voltage VREF and 0V (ground) after passing through the amplitude conversion circuit, a
signal output by the amplitude conversion circuit is output as
direct current voltage after passing through the filter circuit, the
direct current voltage is output after being amplified and isolated, and current driving is provided for output of the reference voltage generation circuit. The V / I conversion circuit comprises a summation operation circuit, a complementary
driving circuit, a power amplification circuit, a detection
resistor and a
feedback loop, the V / I conversion circuit introduces current
negative feedback into the amplification circuit, the detection
resistor converts current into voltage, and feeds the voltage back to the summation operation circuit through the
feedback loop, so that voltage-current conversion is realized. High-resolution and high-precision current output can be achieved by controlling PWM input signals.