APPARATUS AND METHOD FOR LOWERING DC RIFFLE VOLTAGE FOR THREE PHASE STEP-DOWN TYPE DIODE RECTIFIER

摘要

PURPOSE: An apparatus and a method for lowering a DC riffle voltage for three phase step-down type diode rectifier are provided to improve efficiency of a rectifier and supply stably an output voltage by controlling a turning-on time and a turning-off time. CONSTITUTION: The low pass filter(209) receives a DC voltage(VDC) from a three phase step-down type diode rectifier and outputs the current without riffle of 360Hz. The current without riffle and DC current(iDC) of a rectifier according to the DC voltage(VDC) are applied to an output load calculator(208). The output load calculator(208) generates an output power to indicate the amount of output load and applies the output power to a low pass filter(204) of a preliminary switching frequency decision loop(A1) and a high pass filter(207) of a voltage riffle suppression loop(A2). The filtered output power is applied to a power/frequency function block(203). An auxiliary switching frequency(fff) is determined by a predetermined function value. The power/frequency function block(203) controls the auxiliary switching frequency(fff) according to the amount of output of the low pass filter(204). The high pass filter(207) extracts a desired riffle power signal by filtering the output load of the output load calculator(208). A riffle gain calculator(206) determines a frequency(fcomp) to indicate the variable amount of a final switching frequency(Fsw). A PI control loop(A3) controls an output voltage.