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3

The pre-heat time is determined by an RC combination formed by R3 and C3 and the voltage of

zener diode D1. When the voltage across C3 reaches the magnitude of the zener diode D1 + the

turn-on threshold of Q1, capacitor C6 is shorted out and the frequency shifts to the final running

frequency. The final running frequency is given by the formula:

)

5

)(

6

(

4

.

1

1

C

R

f

The final component values, shown in Bill of Materials, were chosen to operate a 13 watt compact

fluorescent lamp with a cathode resistance at cold of 4 ohms. If a lamp is used which has a different

cathode resistance the component values for the pre-heat frequency selection will need to be changed.

The ballast circuit was operated at various temperatures from 25 degrees C to 105 degrees C with

little or no change in the operating characteristics.

The IR Family of Integrated Half-Bridge Products (9-pin SIP Package)

Part Number

Maximum

Voltage

Rds(on)

at 25C

Target Applications

(Spec only for ZVS)

IRxxH214, HD214

250V

2.0

Ω

110VAC, 5W-15W

IRxxH224, HD224

250V

1.1

Ω

110VAC, 15W-25W

IRxxH737, HD737

300V

0.75

Ω

110VAC, 25W-35W

IRxxH310, HD310

400V

3.6

Ω

220VAC, 5W-15W

IRxxH320, HD320

400V

1.8

Ω

220VAC, 15W-25W

IRxxH420, HD420

500V

3.0

Ω

220VAC, 10W-20W

1) IC options for the half-bridge products include IR2101, IR2102, IR2103, IR2104, IR2151, IR2152,

IR2153, IR2154. Use the last two digits of the IC part number for the “xx” designator.

2) The “H” option contains only the Control IC and MOSFET half-bridge. The “HD” option contains

the Control IC, Bootstrap Diode and MOSFET half-bridge.