System and method for a/d conversion

An analog to digital (A/D) converter comprising:

• a ramp signal generator comprising a ramp signal output and a clock trigger input;
• an active comparator comprising a first input coupled to the ramp signal output and a second input coupled to an A/D input;
• a reference comparator comprising a first input coupled to the ramp signal output and a second input coupled to a reference signal;
• control logic coupled to an output of the reference comparator and an output of the active comparator, wherein
• the control logic is configured to assert a start signal if the output of the reference comparator or the output of the active comparator is active, and
• the control logic is further configured to assert a stop signal if both the output of the reference comparator and the output of the active comparator is active;
• and
• a delay line comprising a plurality of delay elements, the delay line coupled to a start signal and a stop signal, wherein the delay line is configured to
• activate the delay line and initiate a signal propagating through the delay line when the start signal becomes active and the stop signal is inactive, and
• deactivate the delay line and produce a state output of the delay line when the stop signal becomes active.

A method of performing an analog to digital (A/D) conversion comprising:

• comparing a reference signal to a ramp signal;
• comparing an input signal to the ramp signal;
• causing a signal to propagate through a delay line when the ramp signal crosses a first of the reference signal or the input signal;
• and
• storing a state of the delay line when the ramp signal crosses a second of the reference signal or the input signal after the ramp signal crosses the first of the reference signal or the input signal.

A delay element comprising:

• a first switch comprising a control terminal coupled to a delay element input, and an output terminal loaded by a first current source;
• a second switch comprising a control terminal coupled to the output terminal of the first switch, and an output terminal loaded by a second current source;
• a latch comprising an input coupled to the output terminal of the second switch, and an output coupled to a delay element output;
• and
• a third switch coupled in series with the second switch, the third switch comprising a control terminal coupled to a stop signal input.

A power supply system comprising:

• a power converter comprising a power input, an output, and a control terminal, the control terminal controlling the output;
• and
• a feedback network coupled between the output and the control terminal, the feedback network comprising an analog to digital (A/D) converter configured to convert a difference between a reference voltage and a voltage proportional to a voltage at the output of the power converter, the A/D converter comprising
• a ramp signal generator comprising a ramp signal output and a clock trigger input,
• an active comparator comprising a first input coupled to the ramp signal output and a second input coupled to an A/D converter input,
• a reference comparator comprising a first input coupled to the ramp signal output and a second input coupled to a reference signal,
• control logic coupled to an output of the reference comparator and an output of the active comparator, wherein
• the control logic is configured to assert a start signal if the output of the reference comparator or the output of the active comparator is active, and
• the control logic is further configured to assert a stop signal if the output of the reference comparator and the output of the active comparator is active, and
• a delay line comprising a plurality of delay elements coupled to the start signal and stop signal, wherein the delay line is configured to
• activate the delay line and initiate a signal propagating through the delay line when the start signal becomes active and the stop signal is inactive, and
• deactivate the delay line and produce a state output of the delay line when the stop signal becomes active.