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With nominal load 10mA, I am not getting regulated (10V) output voltage.

Posted by: NITESH FUNDE on 11/24/2021

Hi Team,

I have build an offline buck converter using an LNK306 regulator. I have design it for 10V, 100mA output.

It should output a voltage of around 10V. To meet this voltage the feedback circuit consists of a 2K bias resistor and a 10K feedback resistor. I use a 10K load resistor(4mA). I have used a 10uF feedback capacitor.

With nominal load 10mA, I am not getting regulated (10V) output voltage.

PFA schematic of design.
 

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Untitled_6.png 61.93 KB

Comments

Submitted by NITESH FUNDE on 11/24/2021

The output voltage more than 20V at 50V input.

Submitted by NITESH FUNDE on 11/24/2021

PFA waveform across Drain and source.

Attachment Size
tek01112.png 241.81 KB
Submitted by PI-Hiro on 11/26/2021

Hello NITESH FUNDE, 

Upon checking of the schematic, I have noticed that you have connected capacitor C8 in reverse. The negative polarity of the capacitor should be connected to both inductor L2 and diode D8. 

As for the pre-load resistor, a minimum load current of 3mA may be required to ensure output regulation. For 10 V output, 10 V / 3 mA = 3333 Ω. You can try connecting 3.3 kΩ or 3 kΩ as pre-load resistor. 

Thank you.

Regards,

PI-Hiro