ZERO CURRENT DETECTION CIRCUIT FOR BRIDGELESS TOTEM-POLE POWER FACTOR IMPROVING CONVERTER, AND BRIDGELESS TOTEM-POLE POWER FACTOR IMPROVING CONVERTER

摘要

To provide a zero current detection circuit for an improving converter of bridgeless totem-pole power factor and a bridgeless totem-pole power factor improving converter, in which low noise zero current detection is performed in one detection winding.SOLUTION: A zero current detection circuit 13 includes: a detection winding 21 that is magnetically coupled to a boost inductor 4 of a power factor improving converter 1 which converts an AC input voltage into a DC output voltage and outputs, is connected to ground at one end and is proportional to the voltage across the boost inductor 4 at the other end, and generates a zero current detection signal S7; a resistor 22 of which one end is connected to the other end of the detection winding 21; a clump portion 23 that is constituted of two diodes connected in series with each other in a forward direction, clumps the zero current detection signal S7 inputted via the resistor 22 with a potential of ground G (zero voltage) and a positive power supply voltage, and converts the signal into a rectangular signal S8 and outputs; and a pulse output portion 24 that includes a comparator for comparing a comparison voltage and the rectangular signal S8, and outputs detection pulses S1 and S2 which are synchronized with timing when an inductor current Iflowing a falling edge through the boost inductor 4 becomes zero.SELECTED DRAWING: Figure 1