IR2159S datasheet(21/25 Pages) IRF

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IR21592/IR21593(S)

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BLANK

Switching

Noise

Dimming

Range

Fault Mode (FAULT)

During dimming, the peak current regulation circuit

active during preheat and ignition is disabled.

Should non-zero voltage switching at the output

of the half-bridge occur (Figure 17), high current

spikes will result. A lamp filament failure, lamp

end-of-life, lamp removal, or a deadtime shorter

than what is required for commutation, can all

cause hard-switching.

1.6V

NORMAL

OPERATION

HARD

SWITCHING

FAULT

LOAD

REMOVAL

Figure 17, hard-switching with latch off

Figure 16, Current sense timing diagram.

Should the peak voltage on pin CS exceed 1.6V

at any time during dimming, the IR21592/IR21593

enters FAULT mode and the high and low-side

driver outputs, HO and LO, are both turned off.

Cycling the supply voltage on VCC below UVLO-

or the voltage on pin SD above and below SD+

and SD- will reset the IR21592/IR21593 to preheat

(PH) mode (see STATE DIAGRAM).

Ballast Design

Lamp Requirements

Before selecting component values for the ballast

output stage and the programmable inputs of

the IR21592/IR21593, the following lamp

requirements must first be defined:

Variable

Description

Units

Filament pre-heat current

Arms

Filament pre-heat time

max

Maximum lamp pre-heat voltage

Vpp

ign

Lamp ignition voltage

Vpp

100

Lamp power at 100% brightness

100

Lamp voltage at 100% brightness

Vpp

Lamp power at 1% brightness

Lamp voltage at 1% brightness

Vpp

min

Cath

Minimum cathode heating current

Arms

Table I, Typical lamp requirements

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