Synchronous rectifier control with second assertion of drive signal during conduction phase

1. A method for controlling a drive signal in a synchronous rectifier controller (SRC), the method comprising:

detecting a beginning of a conduction phase using a current sense signal;

performing, in response to detecting the beginning of the conduction phase, a first assertion of the drive signal; and

during the conduction phase:

detecting an occurrence of an OFF condition after performing the first assertion of the drive signal,

performing a de-assertion of the drive signal in response to detecting the occurrence of the OFF condition,

detecting an occurrence of an ON condition after performing the de-assertion of the drive signal, and

performing a second assertion of the drive signal in response to the ON condition being detected.

2. The method of claim 1 , further comprising:

commencing an exception timer in response to detecting the beginning of the conduction phase, the exception timer running for an exception timer duration,

wherein performing the second assertion of the drive signal requires the exception timer be running.

3. The method of claim 2 , further comprising:

detecting an end of the conduction phase using the current sense signal,

wherein detecting the end of the conduction phase requires the exception timer not be running.

4. The method of claim 1 , further comprising:

detecting an end of the conduction phase using the current sense signal; and

commencing a minimum off timer in response the detecting the end of the conduction phase, the minimum off timer having a predetermining minimum off duration,

wherein detecting the beginning of the conduction phase requires the minimum off timer not be running.

5. The method of claim 1 , further comprising:

commencing a minimum on timer in response the first assertion of the drive signal, the minimum on timer having a predetermining minimum on duration,

wherein detecting the OFF condition requires the minimum on timer not be running.

6. The method of claim 1 , further comprising:

commencing a half minimum on timer, in response the de-assertion of the drive signal, the half minimum on timer having a predetermining half minimum on duration,

wherein detecting the occurrence of the ON condition requires the half minimum on timer not be running.

7. The method of claim 1 , wherein detecting the occurrence of the ON condition includes comparing a voltage of the current sense signal an ON threshold.

8. The method of claim 1 , wherein detecting the occurrence of the OFF condition includes comparing a voltage of the current sense signal an OFF threshold.

9. A Synchronous Rectifier Controller (SRC), comprising:

a comparator; and

a control logic circuit that:

receives an output of the comparator,

detects a beginning of a conduction phase,

performs a first assertion of a drive signal in response to the detection of the beginning of the conduction phase,

de asserts the drive signal in response to detecting an OFF condition, and

performs a second assertion of the drive signal during the conduction phase.

10. The SRC of claim 9 , further comprising:

an exception timer,

wherein the control logic circuit:

directs the exception timer to generate an exception interval in response to the detection of the beginning of the conduction phase, the exception interval having a predetermined duration, and

performs the second assertion of the drive signal only during the exception interval.

11. The SRC of claim 10 , wherein the predetermined duration is externally configurable.

12. The SRC of claim 9 , further comprising:

a minimum time timer,

wherein the control logic circuit:

directs the minimum time timer to generate an off interval in response to the control logic circuit de asserting the drive signal; and

performs the second assertion of the drive signal only after an end of the off interval.

13. The SRC of claim 9 , further comprising:

a sensing circuit that receives a current sense signal and produces a sensed voltage according to the received current sense signal,

wherein the control logic circuit:

detects the beginning of the conduction phase using the sensed voltage,

detects the OFF condition using the sensed voltage,

detects an ON condition using the sensed voltage, and

performs the second assertion in response to detecting the ON condition.

14. The SRC of claim 13 ,

wherein the SRC detects the beginning of the conduction phase by comparing the sensed voltage to a first predetermined value,

wherein the SRC detects the OFF condition by comparing the sensed voltage to a second predetermined value different from the first predetermined value, and

wherein the SRC detects the ON condition by comparing the sensed voltage to the first predetermined value.

15. A semiconductor device including a synchronous rectifier controller, comprising:

a first comparator that detects a reset condition;

a second comparator that detects an ON condition;

a third comparator that detects an OFF condition; and

a control logic circuit that:

enters a wait state in response to a first detection of the reset condition,

performs a first assertion of a drive signal and exits the wait state in response to a first detection of the ON condition when the control logic circuit is in the wait state,

performs a de-assertion of the drive signal in response to the detection of the OFF condition, and

performs a second assertion of a drive signal in response to a second detection of the ON condition before a second detection of the reset condition,

wherein the second detection of the reset condition is a next detection of the reset condition after the first detection of the reset condition.

16. The semiconductor device of claim 15 , further comprising:

an exception timer,

wherein the control logic circuit:

directs the exception timer to generate an exception interval in response to the first detection of the ON condition when the control logic circuit is in the wait state, the exception interval having a predetermined duration, and

prevents the assertion of the gate signal in an interval that begins at an end of the exception interval and ends at the second detection of the reset condition.

17. The semiconductor device of claim 15 , further comprising:

a minimum time timer,

wherein the control logic circuit:

directs the minimum time timer to generate a blanking interval in response to the control logic circuit de asserting the drive signal, and

performs the second assertion of the drive signal only after the blanking interval.

18. The semiconductor device of claim 15 , further comprising:

a minimum time timer,

wherein the control logic circuit:

directs the minimum time timer to generate a minimum on interval in response to the first assertion of the drive signal, the minimum on interval having a predetermined duration, and

performs the de-assertion of the drive signal only after an expiration of the minimum on interval.

19. The semiconductor device of claim 15 , further comprising:

a minimum time timer,

wherein the control logic circuit enters the wait state by:

directing the minimum time timer to generate a minimum off interval in response to the first detection of the reset condition, the minimum off interval having a predetermined duration, and

entering the wait state in response to the expiration of the minimum off interval.

20. The semiconductor device of claim 15 ,

wherein the first comparator detects the reset condition by comparing a current sense voltage to a first predetermined value;

wherein the second comparator detects the ON condition by comparing the current sense voltage to a second predetermined value; and

wherein the third comparator detects the OFF condition by comparing the current sense voltage to a third predetermined value,

wherein the first, second, and third predetermined values are different from each other.