IR2159 datasheet(16/25 Pages) IRF

16 / 25 page

IR2159/IR21591 (S)

www.irf.com

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Lamp Pow er [Watts]

Figure 4, Lamp power vs. phase of output stage.

Under-voltage Lock-Out (UVLO)

The IR2159 undervoltage lock-out is designed to

maintain an ultra low quiescent current of less

than 200uA, while guaranteeing the IC is fully

functional before the high and low side output

drivers are activated. Figure 5 shows an efficient

supply voltage using the start-up current of the

IR2159 together with a charge pump from the

ballast output stage (R1, C1, C2, D1 and D2).

11 LO

COM

VCC

Rectified

AC Line

Half-Bridge

Output

RVDC

BUS(+)

RCS

BUS(-)

VDC

CVDC

DISCHARGE

TIME

INTERNAL

CLAMP VOLTAGE

VHYST

UVLO+

UVLO-

CHARGE PUMP

OUTPUT

R1 & C1 TIME

CONSTANT

DISCHARGE

Figure 6, Start-up capacitor (C1) voltage.

During the discharge cycle, the rectified current

from the charge pump charges the capacitor above

the minimum operating voltage of the device and

the charge pump and internal 15.6V zener clamp

of the IC take over as the supply voltage. The

start-up capacitor and snubber capacitor must be

selected such that worst case IC conditions are

satisfied. A bootstrap diode (D3) and supply

capacitor (C3) comprise the supply voltage for

the high side driver circuitry. To guarantee that

the high-side supply is charged up before the first

pulse on pin HO, the first pulse from the output

drivers comes from the LO pin. During UVLO,

the high and low side driver outputs are low, pin

VCO is pulled-up internally to 5V resetting the

starting frequency to the maximum, and pin CPH

is short-circuited internally to COM resetting the

preheat time.

Figure 5, Typical application of start-up circuitry.

The start-up capacitor (C1) is charged by current

through resistor (R1) minus the start-up current

drawn by the IC. This resistor is typically chosen

to provide 2X the maximum start-up current at

low line to guarantee start-up under the worst case

condition. Once the capacitor voltage reaches the

start-up threshold, and, the voltage on pin VDC is

above 5.1V (see Brown-out Protection), the IC

turns on and HO and LO begin to oscillate. The

capacitor begins to discharge due to the increase

in IC operating current (Figure 6).

IR2159 Datasheet(PDF) 16 Page - International Rectifier

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