FREQUENCY JITTERING CONTROL CIRCUIT AND A METHOD FOR A PULSE FREQUENCY MODULATION POWER SUPPLY CAPABLE OF GENERATING A CONTROL SIGNAL FOR FREQUENCY JITTERING

摘要

PURPOSE: A frequency jittering control circuit and a method for a pulse frequency modulation (PFM) power supply prevent electromagnetic interference (EMI) of the PFM power supply by jittering a switching frequency of a power switch.;CONSTITUTION: A current detector (14) generates a current detection signal (Vcs) by detecting a current (Ip) of a power switch (M1). An output voltage feedback circuit (16) generates a feedback signal (VFB) by detecting an output voltage (Vo). A comparator (20) generates a first signal (S1) by comparing the feedback signal with a reference voltage (Vref). A current limit signal generator (18) provides a jittering current limit signal (VL). A comparator (22) generates a second signal (S2) by comparing the current limit signal with the current detection signal. A pulse frequency modulator (12) generates a control signal (Vg) by the first and second signals.;COPYRIGHT KIPO 2013