Method and apparatus for self-synchronization of a synchronous rectifier
AssigneeSemiconductor Components Industries, LLC
InventorsTomas Tichy, Karel Ptacek
Life of this patent
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Abstract
A method and synchronous rectifier controller uses minimum off and on time blanking to avoid switching the switching transistor at incorrect times responsive to transients in the current sense signal. The minimum off time timer is commenced only when the current sense signal is above a reset threshold, and is reset when the current sense voltage falls below the reset threshold. Resetting the minimum off time timer in this manner avoids false starts of the minimum off time timer due to transients and allows the SRC to properly synchronize with the conduction and blocking phases of rectifier operation.
Claims20
A method for self-synchronization in a synchronous rectifier controller (SRC), comprising:
- sensing a current sense signal;
- comparing the current sense signal to a RESET threshold;
- commencing a minimum off time timer when the current sense signal exceeds the RESET threshold;
- and
- resetting the minimum off time timer when the current sense voltage falls below the RESET threshold before the minimum off time timer has lapsed.
A synchronous rectifier controller, comprising:
- a RESET comparator that compares a current sense signal to a RESET threshold and provides an output that is asserted when the current sense signal is above the RESET threshold and de-asserted otherwise;
- a minimum off time timer;
- and
- control logic that commences the minimum off time timer when the output of the RESET comparator is asserted and resets the minimum off time timer when output of the RESET comparator is de-asserted.
A semiconductor device including a self-synchronizing synchronous rectifier controller, comprising:
- a RESET comparator that compares a current sense signal to a RESET threshold and provides an output that is asserted when the current sense signal is above the RESET threshold and de-asserted otherwise;
- a minimum off time timer;
- a minimum on time timer;
- control logic that commences the minimum off time timer when the output of the RESET comparator is asserted and resets the minimum off time timer when output of the RESET comparator is de-asserted;
- an ON comparator that compares the current sense signal to an ON threshold and provides an output to the control logic that is asserted when the current sense signal is below the ON threshold and de-asserted otherwise;
- and
- wherein the control logic commences the minimum on time timer upon the output of the ON comparator being asserted;
- wherein the control logic asserts a drive signal at the start of a conduction phase as indicated by the output of the ON comparator being asserted and the minimum off time timer elapsing prior to the start of the conduction phase.
Dependencies are inferred from the claim text.