Patent ID: 6850401
Filing Date: 2005-02-01
Classification: H02M,Y02B

Abstract:
1. A DC-DC converter comprising: an input DC source which supplies an input DC voltage; a main switch circuit which receives said input DC voltage and performs a switching operation during a predetermined ON-period and a predetermined OFF-period; an inductor which repeats accumulation and release of magnetic energy in response to said switching operation of said main switch circuit; a rectifying and smoothing circuit which comprises a synchronous switch circuit and which rectifies and smoothes out a voltage in said main switch circuit or said inductor and supplies an output DC voltage to a load; an error amplifying circuit which compares said output DC voltage with a reference voltage and outputs an error voltage; a switch control circuit which adjusts ON and OFF-periods of said main switch circuit and said synchronous switch circuit based on said error voltage and controls said main switch circuit; a light load detecting circuit which detects that said load is in a light load state; an output power dive detecting circuit which detects an output power dive state; a synchronous switch driving circuit which receives an output from said switch control circuit, an output from said light load detecting circuit and an output from said output power dive detecting circuit, wherein (1) said synchronous switch driving circuit turns off said synchronous switch circuit when said light load detecting circuit detects a light load state and said output power dive detecting circuit fails to detect an output power dive state, (2) said synchronous switch driving circuit turns on and off said synchronous switch circuit in accordance with an output from said switch control circuit when said light load detecting circuit detects a light load state and said output power dive detecting circuit detects an output power dive state, (3) said synchronous switch driving circuit turns on and off said synchronous switch circuit in accordance with an output from said switch control circuit when said light load detecting circuit fails to detect a light load state and said output power dive detecting circuit fails to detect an output power dive state, and (4) said synchronous switch driving circuit turns on and off said synchronous switch circuit in accordance with an output from said switch control circuit when said light load detecting circuit fails to detect a light load state and said output power dive detecting circuit detects an output power dive state.