POWER AMPLIFIER FOR CONTROLLING AC SERVO MOTOR Russian patent published in 1998 - IPC

FIELD: pulse technique. SUBSTANCE: amplifier has reset integrators 9, 10, operating similarly but in phase opposition, each operating in two time steps of equal length of half the mains period; control voltage is integrated during first half-cycle of time step and DC reference voltage, during second half-cycle, its polarity being reverse to that of control voltage; reference voltage is built up across output of controlled-gain switch 19 depending on polarity of voltages across outputs of integrators 9, 10 during moments corresponding to clock pulses; output pulse is shaped during second half-cycle from its origin to comparator change-over level of output voltage attained by integrator; at end of second half-cycle, integrators are reset to initial position. Variable-polarity pulse trains controlling switches of bridge-type reversing power amplifier are shaped across outputs of first and second OR gates 24, 27; length of variable-polarity pulses is adjusted between 0 at zero control signal to half the mains period T/2 at maximum control signal; phase shift of output ac voltage relative to supply mains voltage depends on polarity of control signal. EFFECT: improved noise immunity of pulse-width modulator controlling power amplifier. 3 dwg