2
Total power dissipation in HV9925:
PSWITCH = 35pF⋅ 135V +135V ⋅ 2 ⋅100mA ⋅35ns ⋅78kHz
(
)
PTOTAL = 52mW + 217mW = 269mW
PSWITCH ≈ 52mW
Minimum duty ratio:
Step 6. Selecting input capacitor CIN
Output Power = 30V ⋅50mA = 1.5W
Dm = 30V /(0.7⋅135V ⋅ 2) ≈ 0.23
Select CIN 3.3µF, 250V.
Conduction power loss:
30V ⋅(50mA)2 ⋅ 200Ω
30V
0.7
PCOND
=
+ 0.5mA ⋅ 85V ⋅ 2 −
0.7⋅85V ⋅ 2
PCOND = 217mW
Figure 2. Universal 85-264VAC LED Lamp Driver
(IO = 20mA, VO = 50V) from Example 1
LIN
LED1 -LED10
D2
D4
D3
D5
CIN
CIN2
CO
D1
8
7
3
L1
AC Line
85-264V
VRD1
F1
HV9925
U1
4
6
CDD
1
2
RSENSE
Figure 3. 85-135VAC LED Lamp Driver with PWM Dimming
LED1 -LED12
D2
D4
D3
D5
CIN
CO
D1
AC Line
85-135V
R1
L1
8
7
3
HV9925
100~200Hz
U1
4
6
CDD
1
2
RSENSE
NR021506
8
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