Patent ID: 6278597
Filing Date: 2001-08-21
Classification: H02M

Abstract:
An over-voltage protection circuit for a switching power supply, said over-voltage protection circuit comprising:a first comparator having first and second inputs, said first input of said first comparator receptive to an output voltage signal from the switching power supply, said second input of said first comparator connected to a first reference voltage signal, said first comparator having an output for providing a control signal indicative of a difference between said signals at said first and second inputs of said first comparator,a second comparator having first and second inputs said first input of said second comparator connected to said output of said first comparator to receive said control signal, said second input of said second comparator connected to a second reference voltage signal, said second comparator having an output for providing a zero oscillator signal indicative of a difference between said signals at said first and second inputs of said second comparator;an oscillator capacitor; anda controller having a control input connected to said output of said first comparator to receive said control signal, said controller having an oscillator input connected to said capacitor, said controller having a plurality of outputs for connection to inputs of the switching power supply, each of said outputs of said controller providing a pulse train signal, said capacitor defining a frequency of said pulse train signals, said control signal defining a phase-shift between said pulse train signals, said oscillator input of said controller connected to said output of said second comparator, wherein said zero oscillator signal drives the frequency of said pulse train signals to zero.