UM0670 datasheet(19/43 Pages) STMICROELECTRONICS

Part #	UM0670

Description	80 W offline LED driver with PFC

PDF	43 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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19 / 43 page

Measurement

UM0670

19/43

Doc ID 15327 Rev 2

Measurement

9.1

Output waveform measurement

Figure 13 shows the output LED current waveform. The LED current was set to 350 mA and,

as shown, the current ripple is 92 mA and the switching frequency for the modified buck

converter is 125 kHz. The input voltage was 230 VAC and 12 LEDs were used as the load

(OSTAR LED LE UW E3B; see Section 11: References and related materials 6).

The output LED current slightly varies with the output voltage, as explained in detail in

application note AN2928, (Section 11: References and related materials 2) and therefore

this design is optimal for a fixed number of LEDs. The output LED current accuracy for

different LED voltages is demonstrated in Figure 14.

Figure 13.

Output LED current waveform (ILED = 350 mA)

UM0670 Datasheet(PDF) 19 Page - STMicroelectronics