DER-596 Output Compensation Calculation
Dear PI Team,
since we're not having any luck getting acceptable results using a LYTSwitch-5 Circuit based on DER-515 and have determined the transformer to be the cause of all our issues, we wish to switch to a transformer-less circuit, but using the same driver (LYT5228D). I found the DER-596, which seems ideal for our purposes. However, there is no example given for how the values for the Output Compensation circuit was calculated, and your PI Expert sheets still always assume a transformer with bias winding is used. How do I calculate the required values based on that output? I cannot use the specific values in the DER-596 sheet, I think, since we need slightly different values. Specifically, we have two different applications, once requiring a VLED of 72V and an LED current of 200mA, and once requiring a VLED of 54V and an LED current of 180mA.
I would appreciate any assistance on that front.
Hi A. Lehmann,
Good day!
To determine the Output Compensation resistor (R3) of DER-596, it is important to consider the ILOV+ (Current Threshold for Input Voltage). Based on typical values stated on page 8-9 of the datasheet, the resistor can be estimated using the following calculation:
R3 = (VOUT − Output Compensation Pin Voltage) / ILOV+
R3 = (80 V − 2.25 V) / 120 μA = 647.7 kΩ (*all typical values used)
And we can observe that the value used in the report (768 kΩ) is close to the estimation--it is reconfigured during design evaluation for the optimum value for the design. This estimation closely aligns with the value used in the report, which was later fine-tuned during the design evaluation phase to achieve optimal performance.
For your application with a 72 V output, the estimation would be:
R3 = (72 V − 2.25 V) / 120 μA = 581 kΩ
You may consider starting with this value and iterating as necessary.