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RD0801

In case the DC bus decreases too far and the lamp extinguishes, the VCC voltage will

go below VCCUV- (10.5V, typical) and the ignition/preheat ramp will be reset to re-

ignite the lamp reliably.

Figure 10.2: Brown-out conditions: CH1 is the VCO voltage, CH2 is the VS voltage

Lamp Removal

When the lamp is removed, the IRS2530D uses the Crest Factor Over-current

Protection to enter the Fault mode and shut down. During lamp removal, the output

stage will transition to a series-LC configuration, and the frequency will move towards

resonance until the inductor saturates. The IRS2530D uses the VS-sensing circuitry

and the RDSon of the low-side half-bridge MOSFET to measure the MOSFET current

for detecting an over-current fault. Should the peak current exceed the average current

by a factor of 5.5 (CF>5.5) during the on-time of LO, the IRS2530D will enter Fault

Mode, where the half-bridge is off. Performing crest factor measurement provides a

relative current measurement that cancels temperature and/or tolerance variations of

the RDSon of the low-side half-bridge MOSFET.

Figure 10.3 shows the voltage across the lamp and the VS voltage when the lower

filament of the lamp is removed. Figure 10.4 shows these voltages when the upper

filament of the lamp is removed. In both cases, the IRS2530D will enter the Fault Mode

and shut down after detecting that the crest factor exceeds 5 during the on-time of LO.

Figure 10.5 shows the VS pin, inductor current, and voltage across lamp when the

inductor saturates and the ballast shuts down.