PWM control apparatus

Abstract

A Pulse Width Modulation (PWM) control circuit is used in a switched-mode power supply (SMPS) having a normal mode and a standby mode, for controlling and regulating the SMPS. An input of the PWM control circuit is arranged to receive a signal indicating an amount of current supplied by the supply. An over-current determining arrangement provides an over-current signal in the event of there being an over-current condition in the signal indicating the amount of current supplied by the supply. A further input of the PWM control circuit receives a regulation signal in the event of there being a regulation output from circuitry coupled to receive power from the SMPS. A logic circuit within the PWM control circuit compares the over-current signal and the regulation signal in order to determine whether the switched-mode power supply is in standby mode or normal mode, thus avoiding the need for a dedicated control pin to indicate standby and normal modes.

Dependencies are inferred from the claim text.