Rohm BM2P0161-EVK-003, Руководство пользователя

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© 2018 ROHM Co., Ltd.
No. 60UG092E Rev.001
JULY.2018
User’s Guide
BM2P0161-EVK-003
(3) Determination of C6
C6 G
WhJ=
Oj hH × 7 × 7 =
520
70 × 659;k × 1209Ω = 935pF
C6 voltage is VOR- input maximum voltage 520V-400=120V + surge
This time capacitor value and voltage rating is set 1000pF/1kV. Considering surge voltage margins.
(4) Determination of D1
Choose a fast recovery diode as the diode, with a withstand voltage that is at or above the MOSFET’s Vds (max) value.
This time is selected RFN1LAM7S 0.8A/700V.
2-7
．
FB terminal capacitor:C9
C16 is a capacitor for stability of FB voltage (approximately 1000pF to 0.01
µ
F)
2-8
．
Output rectification diode :D3
Choose a high-speed diode (Schottky barrier diode or fast recovery diode) as the output rectification diode. When Vf=1V,
reverse voltage applied to output diode is,
Vdr = Vout max + vf + VIN max ×
When Vout(max)=12.0V+10%=13.2V
Vdr = 13.2V + 1.0V + 400V ×
14
77 = 86.92
With consideration of margins 87/0.7=124V → 150V
Also, diode loss (approximate value) becomes Pd=Vf x Iout=1.0V x 2A=2.0W
This board is used schottky barrier diode RB088BGE-150
：
150V 10A , TO-252 package
Using a voltage margin of 70% or less and current of 50% or less is recommended.
Check the rise in temperature while assembled in the product. If necessary, reconsider the component and radiate heat by a heat
sink or similar to dissipate the heat.
2-9
．
Output capacitors: C13, C15
Determine the output capacitors based on the output load‘s allowable peak-to-peak ripple voltage ( ∆ Vpp) and ripple-current.
When the MOSFET is ON, the output diode is OFF. At that time, current is supplied to the load from the output capacitors. When
the MOSFET is OFF, the output diode is ON. At that time, the output capacitors are charged and a load current is also
supplied.
When ∆ Vpp = 200mV,
Z
n
<
∆
9 =
∆
× 9
=
0.2
77
14 × 0.9828
= 0.037Ω J 609;k: 7 min
With an ordinary switching power supply electrolytic-capacitor (low-impedance component), impedance is rated at 100kHz, so it
is converted to 100kHz.
Z
n
< 0.037Ω ×
Yq
rss
= 0.02405Ω J 1009;k