GENERATING CIRCUIT FOR PWM SIGNAL

摘要

PURPOSE:To attain a high degree of resolution with a clock of a low frequency by counting the two types of clocks having a slight difference of frequencies within a prescribed carrier frequency and generating pulses when the coincidence is obtained between the numbers of both types of clocks. CONSTITUTION:A counter 1 supplies the clock pulses of the 1st frequency and counts the number of these pulses within a prescribed carrier period. While the 2nd counter 2 supplies the clock pulses having the smaller frequency than the 1st frequency and counts these clock pulses within a prescribed carrier period. A CPU7 sets '1' and '2' are set to registers 3 and 4 as the initial value respectively. Then clocks are supplied to both counters 1 and 2 for start of actuation. When the 1st clock is supplied, the pulses are delivered from a coincidence circuit 5. Then a flip-flop 8 is set. Then the pulses are delivered from a coincidence circuit 6 with input of the 2nd clock, and the flip-flop 8 is also reset. Thus a PWM signal is delivered. Then the values of both registers 3 and 4 are replaced by the CPU7 and set at '2' and '3' respectively.