A 24 VDC, 10 A AC/DC converter design has been done using the eDesignSuite on the ST website.
In this design, L6566B controller has been used. After production of the prototype converter, we tested the converter using loads 4-5 amps. There was no problem at first. But later, we encountered some problems.
The output voltage is increasing gradually starting from 8VDC to 24VDC with no load. But when we connected a load, the output voltage drops to 2-6 VDC level for 20mA load (0 VDC for loads more than 2 amps) and then tries to restart.
We have seen that there should be an accurate voltage reference (5V ± 2%) at the Vref pin (10) of the L6566B in accordance with the datasheet, Table 1 and Table 4.
We have checked the pin 10 of the L6566B and there was no 5V even though there was no load at the output. No matter what we did, we couldn't get it solved.
We have the following questions:
- We could not see any information for Vref in datasheet timing diagrams of L6566B. When does Vref voltage reference become stabil? After Vin > VHVstart, VCC > VCCON, HV_EN, or Vcc_OK?
- What should we pay attention to in this case? Do you have any recommendation for us?
Thanks in advance for your help.
Erdogan Dokmeci
