CONTROL CIRCUIT FOR A SWITCHING POWER SUPPLY WITH A SINUCONTROL CIRCUIT FOR A SWITCHING POWER SUPPLY WITH A SINUSOIDAL INPUT CURRENT FOR TRANSFORMING A SINUSOIDAL AC VOSOIDAL INPUT CURRENT FOR TRANSFORMING A SINUSOIDAL AC VOLTAGE INTO A REGULATED DC VOLTAGE LTAGE INTO A REGULATED DC VOLTAGE

摘要

A control circuit for controlling a known active harmonic filter operating as a step-up converter in a power supply with sinusoidal network current input and a power factor of almost unity. The step-up converter comprises: a main rectifier, a storage inductance (LS), a cross-connected high-speed transistor (TQ), a diode (D1) and a power storage capacitor (CL). The high-speed transistor (TQ) is controlled by a first threshold switch (STc) whose input is controlled by a control capacitor (C12) coupled to receive a signal representative of instantaneous rectified d.c. output voltage (UE), instantaneous power output voltage (Uo) and a signal representative of the charge state of the inductance. The inductance charge signal is obtained from a voltage jump (ringing voltage) between the inductance and the diode (D1) by sensing a flank of an oscillation voltage occurring at the diode by a RC circuit (R8, C10), which triggers a second threshold switch (STa) to control charge reversal and recharge of the capacitor (C12), thus determining the time instants of operation of the first threshold switch to control the cross-connected electronic switch (TQ) to conduction, and hence re-storing of electrical energy in the inductance.