can we follow der289 to make a dimmable driver

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     We made a 15w (24v/0.7a) dimmable highly accurate ISOLATED  led driver using lnk406 with the guidance of DER296 and PI forum. It is working fine but efficiency is low as 76% due to the series resistance drop. We need a Dimmable   highly accurate constant current driver with efficiency >80%. Shall we follow DER289 for achieving our goals? Is there any drawback with DER289?(currently it is not available in the design examples list ). If I add dimmer and bleeder and change the device to 407, let me know whether DER289 will work as a dimmable driver.   Please guide me to make a dimmable highly accurate CC driver with efficiency >80%. Also I would like to know what are the changes need to add in rdr195(90-265v input) to make it 90v-277v input design.



I also can't find DER-289. I guess they are making an update. Anyway, since the circuit is already working fine, then let me try to help how you can improve efficiency.

First, you may use an active damper circuit to lower the power dissipation of the series resistance ( I assume the series resistance you mention refers to damping resistor). Please implement active damper circuit used on RDR-195 and see how much the efficiency improves.

Second, please review your transformer design. Efficiency can be improved by using lower loss core material, minimizing interwinding capacitance and minimizing leakage inductance.

Third, please check your design if you can use schottky diode for the output rectifier. If the PIVS on the PIXLS spreadsheet is less than 180V, then you can use a 200V schottky diode which can help increase efficiency as well.(need to verify actual voltage stress)


For RD195 operation up to 277VAC, you have to change the voltage ratings of RV1 and C1 to 300VAC.Please check the voltage stress of the output diode at 277VAC. Do surge testing to verify effectiveness of the new varistor.