Sharp AE-XM24HR, Service Manual, Page: 15 / 50

AEXM24HR
2 – 7
1. Brief explanation of bootstrap system (single power drive system)
To supply power to the upper-phase IC, the microcomputer (IC1) turns ON the lower-phase IGBT (LU, LV, LW).
It results in a charging current that flows through the electrolytic capacitor in each upper-phase IC input and charges the bootstrap capacitor up to
15V voltage.
The power supply for the subsequent stages is stored when the lower-phase IGBT is ON in common drive control of the compressor.
2.5.2
1. DC overcurrent detection circuit
When a current about 32A or higher flows through the shunt resistance (R100) on IPM printed circuit board (PWB), the voltage on this resistance
is input to IPM CIN pin (16). Then, the gate voltage of the lower-phase IGBT (LU, LV, LW) inside the IPM turns OFF to cut the overcurrent off.
At the same time, an L output which lasts about 1.8 ms is generated from IPM Fo pin (18), and it results in an L level input to overcurrent detection
input pin (53) of the microcomputer (IC1) and then turns OFF the compressor driving signal output (IC1 from pins (65) to (70)) to the IGBT gate.
2.6.
2.6.1 120
°
energizing control (digital position detection control)
This control system detects the digital position detection signal and adjusts the rate of acceleration/deceleration accordingly.
The motor's induced voltage waveform is input to the comparator in the form of PWM-switched pulse, and a position detection signal is generated as
a reference voltage which is equal to 1/2 of 370 VDC. However, since there is no induced voltage waveform when the PWM waveform is OFF, the
P(Vcc)
U,V,W,
V
D
V
DB
V
CIN
(
n
)
N-side
IGBT
N(GND)
Bootstrap capacitor
High-voltage-withstanding,
high-speed recovery diode
LVIC
(LU,LV,LW)
HVIC
(HU,HV,HW)
Bootstrap circuit
Initial charge period
Charging current group
SET
RESET
About 32A
SC
SC reference voltage
Delay by CR time constant circuit
About 1.8 ms
a1
Protection circuit status
Output current Ic (A)
Sense voltage relative
to shunt resistance
Error output Fo
(Lower phase)
Internal IGBT gate