IRPLCFL5U

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7

Figure 6.3 shows the VS (HB) Voltage, the lamp voltage and the lamp current during Run Mode.

Figure 6.3: VS (HB) Voltage (blue), Lamp Voltage (yellow) and the Lamp Current (green) during

Run Mode.

7. Fault Conditions

In case of fault conditions such as open filaments, failure to strike, deactivated lamp or no lamp, the

IR2520D will go into Fault Mode. In this mode the oscillator is latched off. To reset the IC back to

preheat mode, VCC must be recycled below and above the UVLO thresholds. This is done by

resetting the mains. In case of low AC line, the IR2520D will automatically increase the frequency to

maintain ZVS. In this way, the ballast will work at a lower power during a low AC line condition and

will operate at the proper power again when the line increases again.

7.1. Failure To Strike/ Deactivated Lamp Protection

This protection relies on the crest factor protection together with the non-ZVS circuit of the IR2520D,

both enabled when the voltage at the VCO pin reaches 4.6V.