Patent ID: 6205037
Filing Date: 2001-03-20
Classification: H02M

Abstract:
A switch mode power supply, comprising:a supply inductance coupled to a source of an input supply voltage and to a switching transistor for producing current pulses in said inductance that are coupled to an output of said power supply, a given current pulse having a first portion at a first polarity, that flows in said transistor, during a first portion of a cycle, when forward conduction occurs in said transistor, and a second portion, at an opposite polarity, during a second portion of said cycle, after said forward conduction ceases in said transistor;a source of a first control signal having a value that is indicative of a current limit;a control circuit coupled to said transistor and responsive to said first portion of said given current pulse and to said first control signal for limiting amplitudes of said current pulses, in a current mode on a current pulse-by-current pulse control basis, in accordance with said current limit value; anda protection circuit coupled to said control circuit and responsive to said second portion of said current pulse for varying said first control signal, in accordance with said second portion of said current pulse, to vary said current limit value, when a magnitude of said second portion is within a first range of values, the variation of said first control signal being disabled, when said magnitude of said second portion is within a second range of values.