Service manual

Principles of Operation
Pulse width modulation circuit
This section describes how the pulse width modulation (PWM) comparator
operates. Figure 2-19 shows the internal circuitry of the NJM2355 integrated
circuit.
In circuit 1, the output from AMP1 flows into the negative terminal of PWM
comparator 1. In circuit 2, the outputs from AMP2 and AMP3 flow into the
negative terminal of PWM comparator 2 without wired OR. The dead-time control
voltage is input to additional negative terminals of both comparators. At the same
time, a saw-tooth waveform from the oscillator is input to the positive terminals.
The saw-tooth waveform causes the comparators to generate pulses as shown in
Figure 2-20.
Figure 2-19. NJM2355 Internal Circuit
LQ-200/AP3000
2-19