Not getting full load cureent

Posted by: SA Hameed on 09/27/2014

Dear Sir..,

I'm using TOP258EN in my one of product design in flyback mode. its output range is 12V 2A. In some of the cards I'm not getting 2A. it is giving 0.7A or something near to that.

Please give me a suggestion in which area can I concetrate to solve this.

please do needful as it is very uregent requirements.

Thanks & Regards,

S. Abdul Hameed

Mob: +91 97039 64595

email : sahameed@areca.in

Comments

Hello,

there can be a number of reasons why some of your power supplies have these problems.

I am providing a list below and I hope this helps you to resolve:

1. If the current limit programming resistors are not of the correct value.

2. If some of the transformers are wound incorrectly ( start and end of one or more of the windings is reversed)

3. Layout issues are causing noise to be coupled in the feedback loop causing drop in voltage as load is applied.

4. Primary inductance is incorrect.

5. Number of turns of one or more windings is incorrect.

It should be possible for you to find out the source of the problem by evaluating the drain current waveform when you see the output fall out of regulation as you load the power supply.

Hope this helps with your debug.

Regards PI-Sarek

Thank you sir.

I will check that and please tell me that how to check drain current. can I monitor it with CRO.

Regards

SA Hameed.

Hello,

The most appropriate method to measure drain current is using a current probe.

There are several current probes available for this purpose and you may be able to get more specific information from the Oscilloscope vendor.

You will need a current probe capable of measuring AC as well as Dc currents as the drain current waveform being unidirectional, has a strong DC component.

Regards

PI-Sarek