The circuit schematic in Figure 8 shows a high power-factor LED driver based on a LNK413EG from the LinkSwitch-PH family of devices. It was optimized to drive an LED string at a voltage of 21 V with a constant current of 0.33 A, ideal for PAR20/PAR30 lamp retro-fit applications. The design operates over the universal input voltage range of 90 VAC to 265 VAC and is a non-dimming application. A non-dimming application has tighter output current variation with changes in the line voltage than a dimming application. It’s key to note that, although
pin provides excellent line regulation over the entire 90 VAC to 265 VAC input range.
The VOLTAGE MONITOR pin current is also used by the device to set the line input overvoltage and undervoltage protection thresholds.
Diode D1 and VR1 clamp the drain voltage to a safe level due to the effects of leakage inductance. A Zener clamp was selected for lowest component count and highest efficiency. Diode D5 is necessary to prevent reverse current from flowing through U1 during the period when the AC input voltage is lower than the
not specified for dimming, no circuit damage will result if the
reflected output voltage (V
). A space efficient RM6 core was
end user does operate the design with a phase controlled dimmer.