HV9922 Supertex, Inc., HV9922 Datasheet - Page 6

• Manufacturer Part Number: HV9922
• Description: 3-pin Switch-mode Led Lamp Driver Ic
• Manufacturer: Supertex, Inc.

Step 1. Calculating L1.
The output voltage V
(1) assuming a 30% peak-to-peak ripple.
L1 = (30V • 10.5µs) / (0.3 • 50mA) = 21mH
Select L1 22mH, I = 60mA. Typical SRF = 270KHz. Calculate
the coil capacitance.
Step 2. Selecting D1
Select D1 MUR160 with V
(V
Step 3. Calculating total parasitic capacitance using (3)
C
Step 4. Calculating the leading edge spike duration using
(4), (5)
Step 5. Estimating power dissipation in HV9922 at 135VAC
using (8) and (10)
Let us assume that the overall effi ciency η = 0.7.
Figure 2. Universal 85-264VAC LED Lamp Driver
C
T
P
SPIKE
L
F
=
= 5pF + 5pF + 15pF + 8pF = 33pf
> 50V).
L1 x (2π x SRF)
= 135V x √2 x 33pF + 50ns ≈ 113ns < T
1
85-264V
AC Line
100mA
2
O
= 12 x V
=
22mH x ( 2π x 270kHz)
R
VRD1
= 600V, t
D2
D4
F1
F
= 30V (max.). Use equation
1
D3
D5
rr
≈ 50ns and C
C
DD
3
BLANK(MIN)
2
HV9922
VDD
≈ 15pF
C
IN2
J
≈ 8pF
U1
L
IN
DRAIN
GND
6
P
Switching power loss:
P
Minimum duty ratio:
D
Conduction power loss:
P
P
Total power dissipation in HV9922:
P
Step 6. Selecting input capacitor C
Output Power = 30V • 50mA = 1.5W
Select C
2
C
SWITCH
SWITCH
COND
COND
TOTAL
M
IN
= 30V / (0.7 • 135V • √2) ≈ 0.23
1
= 32 • (50mA)
≈ 175mW
= 65mW + 175mW = 240mW
=
≈ 65mW
IN
2 x 10.5µs
0.22µF, 250V.
1
D1
(135V x 33pF + 2 x 100mA x 50ns)
C
2
O
• 200Ω + 0.62 • 200µA • 135V
IN
LED
L1
1
-LED
HV9922
12
(
135V - 30V
0.7
)