AN4376 datasheet(28/37 Pages) STMICROELECTRONICS

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PFC waveforms

AN4376

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DocID025380 Rev 1

7.6

Short-circuit and output current limitation

During a short-circuit of the output connector, all the energy stored in the output electrolytic

capacitor is discharged into the output side loop, so that no current will flow to the external

LED, thus preventing their failure.

When the output capacitor is shorted, the HVLED815PF device works with the internal self-

supply function because no charging current came from the auxiliary winding. The controller

doesn't stop switching but reduces the on-time to its minimum level. The selection of the

R24 and R24 allows limiting the output diode current at a level of about 260 mA. Increasing

Figure 38. Short-circuit of the output connector

at 100 VAC - 50 Hz

Figure 39. Short-circuit removal

at 100 VAC - 50 Hz

CH1: output LED driver current

CH2: DMG

CH3: VOUT

CH4: VCC

CH1: output LED driver current

CH2: DMG

CH3:V OUT

CH4:V CC

Figure 40. Short-circuit of the output connector

at 230 VAC - 50 Hz

Figure 41. Short-circuit removal

at 230 VAC - 50 Hz

CH1: output LED driver current

CH2: DMG

CH3: VOUT

CH4: VCC

CH1: output LED driver current

CH2: DMG

CH3: VOUT

CH4: VCC

AN4376 데이터시트(PDF) 28 Page - STMicroelectronics