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Transient overcurrent issue on AC/DC converter designed with eDesignSuite.

EDokm
Associate III

A 24 VDC, 10 A AC/DC converter design has been done using the eDesignSuite on the ST website.

The converter gives a very stable output at 24 VDC. We did not encounter any problems when we used the converter at normal loads below 10 A.

However, when we connect loads whose normal driving current is below 10 A but transient period current is above 10 A to the output of the converter, the converter protected itself by cutting off the output current. For example, when we tried to drive two LED bulbs together, with a normal driving current of 2.5 A and a startup transient period current of around 8 A, the converter cut off the output current and protected itself. At this point, our expectation is that the converter can tolerate short-term transient currents greater than 10 A.

Although it is an excellent feature that the converter we manufactured using ST eDesignSuite protects itself by cutting off the output current at 10 A, this situation becomes a problem for loads with transient period current greater than 10 A.

We have the following questions on the subject:

  1. Are there any improvements that can be made to this converter design for loads with normal current below 10 A but transient period current greater than 10 A? For example, can a design change be made in this converter so that it can deliver up to 16 A output current for a 100 milliseconds transient period? If your answer is yes, which circuit element or elements' values ​​should be changed and what should their values ​​be?
  2. If your answer is no to our first question, would you recommend us to make a converter with higher output current or change the converter topology from QR flyback to another topology?
  3. When we reduce the value of the Rcs resistor (130 mOhm) used in current measurement, will the converter start to cut the output current at a higher current value? If so, does this negatively increase the self-protection threshold value of the converter while allowing us to drive loads higher than the 10 A transient current?

 

Thanks in advance.

2 REPLIES 2
Patrizia BELLITTO
ST Employee

Hi @EDokm ,

thanks a lot for using eDesignSuite and for your interest in our products.

I need to forward your question to the application engineers team, responsible for L6566B design.

I'll let you know as soon as possible.

Best regards,

Patrizia Bellitto

EDokm
Associate III

I appreciate your timely response. Best regards.