Patent ID: 6924633

Claim:
A pulse width modulation controller for powering a load comprising: at least one comparator having first and second inputs for receiving a generally repeating analog waveform having a predetermined periodic interval and a reference voltage at respective inputs, said at least one comparator operative to produce at least one output signal corresponding to a pulse width modulated output signal having a first comparator output state corresponding to a power off state in which power is not delivered to the load and a second comparator output state corresponding to a power on state in which power is delivered to the load; and a shutter circuit coupled to said at least one comparator output, said shutter circuit having a shutter circuit output, said shutter circuit receiving a periodic reset pulse at an interval that corresponds to said predetermined periodic interval, said reset signal having an asserted state and a de-asserted state, said shutter circuit output having a first logic state corresponding to said state when power is not delivered to said load and a second logic state corresponding to said state when power is delivered to said load, said shutter circuit operative: to switch said shutter circuit output from said first logic state to said second logic state and to arm said shutter circuit to permit a transition of said shutter circuit output from said second logic state to said first logic state in response to the first crossing of said reference voltage in a first direction by said analog waveform subsequent to a respective reset pulse; to cause said output of said shutter circuit output to assume said first logic state in response to the next crossing of said reference voltage by said analog waveform in a second direction opposite to said first direction subsequent to said arming of said shutter circuit; and to maintain said shutter circuit output in said first logic state for the duration of said interval.