Sharp AY-XPC18LR Service Manual page 18

Split type room air conditioner

Operation manual (164 pages)

Table of Contents

AYXPC18LR

29. PFC MODULE CIRCUIT

These model's circuit uses PFCM (Power Factor Correction Module) and IPM as the figure below for the high efficiency operation of compressor.

Noise filter

200V

circuit

29.1. PFC Module

In the case the direct current is obtained by the diode bridge and smooth capacitor from the commercial power source, the current wave shape will be

the pulse shape at the peak of the voltage wave shape as shown in the figure below. For this reason, the harmonic current will be generated and at

the same time the power factor will be deteriorated. While monitoring the AC input voltage in the control circuit, in order to be the same phase and

wave shape as this voltage wave shape, IGBT is made ON/OFF by the carrier frequency of approximately 20 kHz. By adoption of this PFC Module,

the current wave shape can be made to the sine wave synchronized to the commercial power source and the power factor can be made to almost

99%. As a result of this, reactor can be disused. PFC Module works for the improvement of power factor and as the countermeasures for the har-

monic current.

29.2. PFC Module Voltage Raise Circuit

The IGBT in the figure below is the switching transistor of the PFC Module. By adding ON signal to the gate of IGBT from the control IC, IGBT turns

ON and the collector current Ic flows. This current flows from the + side of the diode bridge DB to the Choke coil, the - side of the diode bridge DB

through IGBT from the Choke coil L. At this time, energy is stored in the choke coil L. Next, when gate signal of IGBT turned OFF, IGBT will be turned

OFF and the energy stored in L during the ON time of IGBT will be discharged through the diode D, electrolytic capacitor C, load, primary side and the

+ side of DB. Assuming the input voltage of PFC Module (voltage between + and - of DB) as Ei, the output voltage (voltage at the both ends of smooth

capacitor) as Vo, switching cycle of IGBT as T and ON time of IGBT as ton, the voltage between collector emitter of IGBT Vs will be as follows;

Vs= 0 (during ON of IGBT: ton)

Vs= Vo (during OFF of IGBT: T-ton)

Here, assuming no loss in L and IGBT, average value of Vs turns equal to Ei,

Ei = (T-ton)/T x Vo

Therefore

Vo = T/(T-ton) x Ei

As ton is a smaller value than T, output voltage Vo will be higher than input voltage Ei.

Choke coil

Rectifica-

tion circuit