FC9920 datasheet(5/7 Pages) FS

5 / 7 page

FC9920

2012. 10. 31

5/7

Revision No : 0

L1 = (60V · 10.5µs) / (0.3 · 100mA) = 21mH

Select L1 = 22mH, I = 150mA. Typical SRF =

270KHz. Calculate the coil capacitance.

CL = 1/[L1· (2π · SRF)2] = 1 / [22mH · (2π ·

270KHz)2] ≈ 15pF

Step 2. Selecting D1.

Select D1 MUR160 with VR = 600V,

trr ≈ 50ns

and CJ ≈ 8pF (VR>50V).

Step 3. Calculating total parasitic capacitance

using (3).

CP = 5pF + 5pF + 15pF + 8pF = 33pF

Step 4. Calculating the leading edge spike duration

using (4), (5).

TSPIKE = (135V · √2 · 33pF) / 150mA + 50ns ≈

92ns < TBLANK(MIN)=200ns

Step 5. Estimating power dissipation in An9920 at

135VAC using (8) and (10).

Let us assume that the overall efficiency η = 0.7.

Switching Power Loss

PSWITCH = (135V · 33pF + 2 · 150mA · 50ns) ·

(135V – 60V/0.7) / (2 · 10.5µs) ≈ 46mW

Minimum Duty Ratio

DM = 60V / (0.7 · 135V · √2) ≈ 0.45

Conduction Power Loss

PCOND = 0.42 · (100mA)

2· 100Ω + 0.57 · 2

0 0µA ·

135V ≈ 435

Total Power Dissipation in An9920:

PTOTAL = 46mW + 435mW = 481mW

Step 6. Selecting input capacitor CIN

Output Power = 60V · 100mA = 6W

Select CIN = 0.68µF, 250V

1N4007*4

10nF

250V

33nF

250V

0.68µF

250V

CIN

LED1-LED24

LIN

CIN2

AC Line

85-135V

VRD1

CDD

VDD

GND

DRAIN

FC9920

Figure 2. Universal 85 - 135VAC LED Lamp Driver

22mH

150mA

2.2mH

150mA

MUR

160

600V

VF=2.5V

0.1µF

50V

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