LinkSwitch CV Start-up Time
Dear Gents, I've designed an off-line SMPS using LNK626 switcher (more details upon request). The supply start-up time is very slow (roughly 3 sec) at DC input voltage about 140V .. 160V. In the datasheet, I found information about auto-restart protection OFF time about 2 .. 2.5s, which seems to be related to the observed long start-up time. The first question is, is it possible to start-up the supply quickly (within tens or hundreds of msec), i.e. without the aforementioned delay ? How can this be done ? Alternatively, can you please recommend a different low-cost switcher for comparable power level ?
Many thanks, Robert
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Dear Jedidiah,
thank you for the hint. I've been off work for some time, I will check the matter as advised.
Best regards,
Robert
Hello,
It looks like the problem occurs when the input (high voltage) supply ramp is very slow - say hundreds of miliseconds. In that case, something small appears at the output (e.g. 2 volts instead of required 22 volts) very early, but it becomes stuck at that level for the next 2 sec or more (see picture). It looks like that the auto-restart protection is activated. Can I do something to prevent from this behavior ? Many thanks, Robert
| Attachment | サイズ |
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| TEK0157.png (3.57 KB) | 3.57 KB |
Hi Robert,
Can you share to me the schematic you are using in your power supply and the transformer specs?
Regards,
Jedidiah
Dear Jedidiah,
I'm uploading the requested items.
Note that the circuit is used as a house-keeping supply within a bigger unit, powered off a bulk cap of a PFC front-end. In some cases (operation scenarios), input voltage rises very slowly (rise time hundreds of miliseconds) and here's where the mischief happens.
Thank you for your attention.
Best regards,
Robert
| Attachment | サイズ |
|---|---|
| HV_PSU.png (53.23 KB) | 53.23 KB |
| TI-EF16-4V1-22V-6W5.pdf (754.85 KB) | 754.85 KB |
Dear Jedidiah,
I'm uploading the requested items.
Note that the circuit is used as a house-keeping supply within a bigger unit, powered off a bulk cap of a PFC front-end. In some cases (operation scenarios), input voltage rises very slowly (rise time hundreds of miliseconds) and here's where the mischief happens.
Thank you for your attention.
Best regards,
Robert
| Attachment | サイズ |
|---|---|
| HV_PSU.png (53.23 KB) | 53.23 KB |
| TI-EF16-4V1-22V-6W5.pdf (754.85 KB) | 754.85 KB |
Hi Robert,
Based from your schematic, it seems you have multiple output. 22V/0.25A and 4.1V/0.25A. Is that correct? And you connect the FB divider resistors on 22V rail. LNK-CV needs an auxiliary winding to regulate the output voltage same as shown in the sample schematic of datasheet. Can you measure also the waveform across 4.1V during start-up?
Regards,
Jedidiah
Hi Robert,
Do you have waveform that can be shared capturing Vds, Ids, Vbpp, and Vbps during start-up condition? 2.5s auto-restart happens only during fault condition like stated in the datasheet.
Regards,
Jedidiah