Jules_Theone
Member
I've solved the diode heating problem, but having new problems... The modified spec is as follows:
40v - 75v input
10v @ 200mA output, stepped down to 3v3 through a L200CV regulator
5v @ 10mA (with isolated gnd) output, stepped down to 3v3 through a LM1117 regulator.
I'm using a LM5020MM-2 controller, Wurth Elektronik power over ethernet tranformer part number 749119133, FCD4N60 MOSFET for the power switch. The circuit is attached.
The circuit powers up ok, with stable 10v regulated, 5.2v outputs with desired resistive loading. This works fine at ambient temperature (22deg C) but the output voltage gradually decreases with increasing temperature (maximum 150deg C). I have tested the L200 regulator with 10v input and a 22R load, ramped up the temp and measured the output voltage. this decreased with temp, i believe it's a feedback resistor issue. The output voltages from the SMPS also decreases with temp by approx the same amount so when I connect it all together the problem is compounded. Although the LM1117 3v3 reg doesn't change at all (I didn't build it, so naturally it works perfectly!) But i cannot use a LM1117 for the 200mA because the input voltage is too high and the current it needs to pass causes it to drop out at 135deg C.
Are there any ways to stabilise or compensate for the output change?
Any ideas?
Thanks.
40v - 75v input
10v @ 200mA output, stepped down to 3v3 through a L200CV regulator
5v @ 10mA (with isolated gnd) output, stepped down to 3v3 through a LM1117 regulator.
I'm using a LM5020MM-2 controller, Wurth Elektronik power over ethernet tranformer part number 749119133, FCD4N60 MOSFET for the power switch. The circuit is attached.
The circuit powers up ok, with stable 10v regulated, 5.2v outputs with desired resistive loading. This works fine at ambient temperature (22deg C) but the output voltage gradually decreases with increasing temperature (maximum 150deg C). I have tested the L200 regulator with 10v input and a 22R load, ramped up the temp and measured the output voltage. this decreased with temp, i believe it's a feedback resistor issue. The output voltages from the SMPS also decreases with temp by approx the same amount so when I connect it all together the problem is compounded. Although the LM1117 3v3 reg doesn't change at all (I didn't build it, so naturally it works perfectly!) But i cannot use a LM1117 for the 200mA because the input voltage is too high and the current it needs to pass causes it to drop out at 135deg C.
Are there any ways to stabilise or compensate for the output change?
Any ideas?
Thanks.