IRPLCFL5E Просмотр технического описания (PDF) - International Rectifier

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IRPLCFL5E

CFL Ballast for 26W/Spiral Lamp, 220VAC Input

International Rectifier 

IRPLCFL5E

7.2. Open Filaments Protection

The open filament protection relies on the non-ZVS circuit of the IR2520D, enabled when pin VCO

reaches 4.6V. Should an open filament lamp fault occur, hard-switching will occur at the half-bridge

and the non-ZVS circuit inside the IR2520 will detect this condition, increase the frequency each

cycle and shut down when VCO decreases below 0.85V; both gate driver outputs will be latched

‘low’. This will prevent hard-switching and damaging of the half-bridge MOSFETs.

Fig. 7.3 shows the VCO pin and VS pin at the shutdown with open filament. As you can see, at

startup the VCO pin charges from 0V up to 4.6V, at 4.6V the non-ZVS circuit is enabled, CVCO

discharges and the frequency increases. When the voltage at the VCO pin decreases below 0.85V

we have latched shutdown. Fig. 7.4 shows the voltage at the VCO pin (HB Voltage) at the shutdown

with a shorter time scale. The FMIN pin can be used as trigger as this pin transitions from 5V to

COM when the IC enters fault mode or UVLO-.

Fig. 7.3: 3 is the voltage in pin VCO and 2 is pin VS

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