Patent ID: 7486493
Filing Date: 2009-02-03
Classification: H02M

Abstract:
1. An over-power protection circuit for a power converter, comprising: an oscillator, generating a clock signal; a current comparator having a pair of inputs respectively coupled to a current sense signal and a first threshold signal for generating a protection signal at an output thereof responsive said current sense signal exceeding said first threshold signal; an accumulating trigger unit having a first input coupled to said output of said current comparator and a second input coupled to said oscillator for generating an off signal in response to receipt of said protection signal for a time period defined by a number of pulses of said clock signal; a latch unit coupled to said accumulating trigger unit for generating a latch signal in response to said off signal; a driving output unit coupled to said latch unit and said oscillator for generating a switching signal in response to said clock signal and said latch signal; wherein said latch signal is used to disable said switching signal to a power switch; and a driving control unit having an output coupled to said driving output unit for generating a clear signal for periodically disabling said switching signal, said driving control unit having respective inputs coupled to a voltage feedback signal, said current sense signal and a second threshold signal, wherein said clear signal disables said switching signal to said power switch responsive to said current sense signal being higher than said second threshold signal; wherein said accumulating trigger unit initiates a count of clock pulses responsive to receipt of said protection signal, said latch unit controls said driving output unit to latch off said switching signal to said power switch responsive to said protection signal being received by said accumulating trigger unit for a period defined by said number of clock pulses.