STR-A6351 SanKen, STR-A6351 Datasheet - Page 15

• Manufacturer Part Number: STR-A6351
• Description: STR-A6300 Series
• Manufacturer: SanKen

STR-A6300 Application Notes
either a wire with small diameter or a Litz wire. Resonant capacitors and electrolytic capacitors for high
ripple applications, or for low impedance for the power supply should be selected.
9.2 Switching speed control
The source terminal is isolated, and switching noise can be reduced by adding a ferrite bead(FB) to the
source terminal, which enables to control switching speed. However, with the ferrite bead only, switching
speed is decreased not only at turn-ON but also at turn-OFF, resulting in the increase of switching loss.
In order to prevent this, adding a diode between pin 1 and pin 2,5(GND) is recommended as displayed on Fig.
11. The small signal switching diode having high speed and small junction capacitance, or a Schottky Barrier
diode(such as AK 03 manufactured by Sanken) is recommended.
9.3 Maximum switching current
The voltage between the source and GND terminal shall be dropped by inserting a current detecting resistor
and a ferrite bead. Due to the voltage drop, gate drive voltage of the MOSFET falls, and maximum switching
current for MOSFET operation decreases, accordingly. Therefore, as shown on Fig. 11, the maximum
switching current needs to be de-rated in accordance with the de-rating curve listed In each data sheet,
measuring the voltage drop between the source and the GND terminal.
Make sure the voltage drop and the maximum switching current measured at both the normal operation and
the overcurrent protection operation are within the de-rating curve.
9.4 Phase compensation
Current mode control circuit is applied in
the STR-A6300 Series; therefore, it
requires no special phase
compensation, and gain adjustments by
a secondary side error-amplifier shall be
enough.
Furthermore, in case a Sanken’s
error-amplifier is applied, thanks to its
excellent response and low gain, phase
compensation might not be required at
all.
ＯＣＰ／ＦＢ
Fig. 12 Phase compensation circuit
ＧＮＤ
Ｓ
②⑤
①
④
D5
C5
Fig. 11 Voltage waveform of each part
R4
FB
Ｖｉｎ（ＡＣ）
図11 各部電圧波形
R5
③
Page 15
コントロール部
Control part
VIN
0
Additional
追加部品
図12 位相補正回路
C6
OCP/FB
GND
D
S
D6
R2
⑦
⑧
①
④
②⑤
470pF
C5
680
R4
PC
R5
（Ver.1.2）
C2
D2
R8
D
C4
P