SWITCH MODE POWER SUPPLY CONTROLLERS

摘要

This invention relates to Switch Mode Power Supply (SMPS) controllers, especially analogue controllers employing a combination of Pulse Width Modulation (PWM) and Pulse Frequency Modulation (PFM) . A switch mode power supply (SMPS) controller circuit for controlling a power switching device of said SMPS, the circuit comprising: a current input to receive a feedback signal current (IFB) dependent upon an output voltage of said SMPS; a ramp generator circuit coupled to said current control input to generate responsive to said feedback current signal (IFB) consecutive first and second voltage ramps (202, 204) , one (202) rising the other (204) falling; and a control output responsive to said voltage ramps (202, 204) from said voltage ramp generator to provide a drive signal for controlling said power switching device. The ramp generator circuit is configured to initialise said first voltage ramp (202) at a voltage level (202a) dependent upon said feedback signal current (IFB) .