SYNCHRONOUS RECTIFIER CONTROL TECHNIQUES
Control circuitry for a synchronous rectifier includes a sensor configured to sense a current through a power switch of the synchronous rectifier or a voltage across the power switch; a phase compensation network coupled to the output of the sensor, the phase compensation network being configured to shift a phase of the output of the sensor in a leading direction to generate a phase-shifted sense signal; and drive circuitry configured to control switching of the power switch based on the phase-shifted sense signal.
1 . Control circuitry for a synchronous rectifier, the control circuitry comprising:
a sensor configured to sense a current through a power switch of the synchronous rectifier, a voltage across the power switch, or a current or voltage related to the current through the power switch or the voltage across the power switch;
a phase compensation network coupled to an output of the sensor, the phase compensation network being configured to shift a phase of the output of the sensor in a leading direction to generate a phase-shifted sense signal; and
drive circuitry configured to control switching of the power switch based on the phase-shifted sense signal.
2 . The control circuitry of claim 1 , wherein the sensor comprises a current sensor and the drive circuitry is configured to control turn-off timings for the power switch based on the phase-shifted sense signal.
3 . The control circuitry of claim 1 , further comprising comparison circuitry configured to compare the phase-shifted sense signal to a threshold voltage, and to control the drive circuitry based on the comparison between the phase-shifted sense signal and the threshold voltage.
4 . The control circuitry of claim 3 , wherein the comparison circuitry comprises a comparator.
5 . The control circuitry of claim 1 , wherein a phase shift produced by the phase compensation network is selected to compensate for a delay in a signal chain driving the power switch.
6 . The control circuitry of claim 3 , wherein the output is a first output, the control circuitry further comprises a resistor, the resistor comprising a first end and a second end, and the first end is coupled to a second output of the phase compensation network.
7 . The control circuitry of claim 6 , wherein the comparison circuitry comprises a comparator, the comparator comprising a first comparator input, a second comparator input, and a comparator output, the first comparator input being coupled to the first end of the resistor, the second comparator input being coupled to a terminal configured to receive a threshold voltage, the comparator output being coupled to an input of the drive circuitry.
8 . The control circuitry of claim 1 , wherein the sensor comprises a current sense transformer or a Rogowski coil.
9 . Control circuitry for a synchronous rectifier, the control circuitry comprising:
a sensor configured to sense a current through a power switch of the synchronous rectifier, a voltage across the power switch, or a current or voltage related to the current through the power switch or the voltage across the power switch, to produce a sense signal;
comparison circuitry configured to compare the sense signal to a non-zero threshold value;
a pulse generator configured to generate a pulse in response to an output of the comparison circuitry; and
drive circuitry configured to control switching of the power switch in response to the pulse.
10 . The control circuitry of claim 9 , wherein the non-zero threshold value is selected to compensate for a delay in a signal chain driving the power switch.
11 . The control circuitry of claim 9 , wherein the pulse generator comprises a single-shot circuit.
12 . The control circuitry of claim 9 , wherein the drive circuitry is configured to control the power switch to turn on in response to the pulse.
13 . The control circuitry of claim 9 , wherein:
a first input of the comparison circuitry is coupled to a first output of the sensor;
a second input of the pulse generator is coupled to the output of the comparison circuitry, which is a second output;
a third input of the drive circuitry is coupled to a third output of the pulse generator; and
a fourth output of the drive circuitry is coupled to the power switch.
14 . The control circuitry of claim 13 , further comprising a resistor with a first end and a second end, the first end coupled to the first output of the sensor and the first input of the comparison circuitry, and the second end coupled to a fourth input of the sensor.
15 . The control circuitry of claim 9 , wherein the sensor is a current sensor.
16 . The control circuitry of claim 15 , wherein the current sensor comprises a current sense transformer or a Rogowski coil.
17 . A wireless power receiver comprising the control circuitry of claim 1 and the synchronous rectifier.
18 . A method of controlling a synchronous rectifier, the method comprising:
sensing a current through a power switch of the synchronous rectifier, a voltage across the power switch, or a current or voltage related to the current through the power switch or the voltage across the power switch, to produce a sense signal;
shifting a phase of the sense signal in a leading direction to produce a phase shifted sense signal; and
controlling switching of the power switch based on the phase shifted sense signal.
19 . (canceled)