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TO-247N(-4L) Half-Bridge Evaluation Board
User’s Guide
© 2022 ROHM Co., Ltd.
No. 63UG0
60E
Rev.001
2022.2
4
.
How to Set the Gate Drive Voltage
The gate drive voltage is supplied by an isolated flyback power supply mounted on-board. This flyback power supply uses a
photo-coupler-less control IC (BD7F200EFJ) manufactured by ROHM, and is equipped with transformers that output positive and
negative drive voltages on the HS and L-sides, respectively.
Figure 4 shows the layout of the on-board power supply.
Figure 4 Gate power supply configuration (Top view of PCB004P)
4.1 How to adjust the positive bias (VCC2)
The transformer (TX1, TX101) outputs of the isolated flyback power supply have a positive voltage and a negative voltage.
VCC2, which is the drive voltage (positive bias) of the MOSFET, is generated from the transformer positive output through LDO,
and the output voltage of LDO can be adjusted by the variable resistors RV51 and RV151. Rotating the variable resistors clockwise
increases the output voltage.
4.2 How to adjust the negative bias (VEE2)
The negative bias VEE2, which is the bias voltage when the MOSFET is off, is adjusted from the negative output of
transformers TX1 and TX101 by the shunt regulators SR1 and SR101 (TIV431 manufactured by TI) and by the variable resistors
RV51 and RV151 can be set in the range of -4.5 V to -2 V. VEE2 is supplied via the negative bias switching pins JP51 and JP151
to select between zero bias and VEE2 bias. The setting method is shown in Table 5.
Connector
Pin No.
Signal
Setting method
JP51
JP151
01
SOURCE
DRIVER_SOURCE
02
GND2
03
VEE
H-side VCC2
Adjustment
(RV51)
L-side isolation
Power supply
IC (U101)
L-side VCC2
Adjustment
(RV151)
L-side negative
bias switching
(JP151)
H-side isolation
Power supply
IC (U1)
L-side VEE2
Adjustment
(RV152)
H-side VEE2
Adjustment
(RV52)
H-side negative
bias switching
(JP51)
Table 5 Negative bias (VEE2) setting method
Pin 1-2 connection: 0 V bias
setting
Pin 2-3 connection: Negative
bias setting
