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RD0801

10. Fault Conditions

In case of fault conditions such as open filaments, failure to strike, or lamp removal, the

IRS2530D will go into Fault Mode. In this mode, the internal fault latch is set, HO is off,

LO is open circuit, and the IRS2530D consumes an ultra-low micro-power current. The

IRS2530D can be reset with a lamp exchange (as detected by the LO pin) or a recycling

of VCC below and back above the UVLO thresholds.

Failure to Strike

resonance frequency. When the lamp fails to strike, the VCO voltage continues to

increase and the frequency continues to decrease until the VCO voltage exceeds

VVCOFLT+ (4.0V, typical), and the IRS2530D enters Fault Mode and shuts down

(Figure 10.1). It should be noted that in case of failure to strike, the system will operate

in capacitive side of resonance, but only for short period of time.

Figure 10.1: Lamp non-strike: CH1 is the VCO voltage, CH4 is the voltage across lamp

AC Mains Interrupt / Brown-Out Conditions

This protection relies on the non-ZVS circuit of IRS2530D, enabled in the Dim Mode.

During an AC mains interrupt or brown-out condition, the DC bus can decrease and

cause the system to operate too close to, or, on the capacitive side of resonance. The

result is non-ZVS switching that causes high peak currents to flow in the half-bridge

MOSFETs that can damage or destroy them.

To protect against this, the IRS2530D will detect non-ZVS by measuring the VS voltage

at each rising edge of LO. If the voltage is greater than VZVSTH (4.5V, typical), the IC

will reduce the voltage at VCO pin, and thus increase the frequency until ZVS is

reached again (Figure 10.2).