Compressor Over Current Detection Circuit - Sharp AY-X12PSR Service Manual

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advantage of being simple and inexpensive; however, the duty cycle and on-time are limited by the need to refresh the charge in the bootstrap capacitor.
The bootstrap supply is formed by a combination of and bootstrap diode, resistor, and capacitor as shown in Figure35 and Figure36. The current flow path
of the bootstrap circuit is show in Figure 35. When V is pulled down to ground (either through the low-side or the load), the bootstrap capacitor C ) is
s BS
charged through the bootstrap diode (D ) and the resistor (R ) from the V supply.
BS BS CC
(Figure 34) (Figure 35)
(Figure 36)
3.1.2

Compressor over current detection circuit

When a current of about 25 A or higher flows through the shunt resistance (R638,R642,R644) on the control printed circuit board (PCB), the voltage at
this resistance is input to IPM CSC pin (8). Then the gate voltage of the lower-phase IGBT (LU, LV, LW) inside the IPM turns OFF to cut off the over
current. At the same time, an L output of about 2ms is generated from IPM VFO pin (6), and this results in an L input to overcurrent detection input VFO of
the microcomputer and turns OFF the PWM signal output through to the IGBT gate.
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