lnk6766k Auto Start at Load
I have a Design based upon LNK6766K. Output Required 24 Volt 1.5 amp. The problem is
1. Output voltage reaches up to 29 Volt while no Load is connected. While the design is for 24 Volt Only. The PCB has component that is rated up to 28 Volt.
2. Even at just 200mA load SMPS goes into autostart Mode. It pulses every 1 Second.
评论
The issue at 21.5 volt( Expected 24 Volt) 100mA The power supply drawing 50mA at 100 Volt. I have added the primary side Waveform.... Is that Normal?
| Attachment | 大小 |
|---|---|
| PI-icon-30px_tv-climate-control.png (4.71 KB) | 4.71 KB |
| PI-icon-30px_battery-mgmt.png (1.8 KB) | 1.8 KB |
| PI-icon-30px_off-board-charger.png (1.86 KB) | 1.86 KB |
Hi ehsanhabib
For the audible noise, it can be solve by putting varnish to the TRF.
For your entry #3, the concern is if I get it right Vo is loaded at 100mA. at 100Vac. And the output is drops to 21.5V?
Please probe Vds waveform zoom in as indicated in the attachment.
Thanks
Regards
PI-Chloe
| Attachment | 大小 |
|---|---|
| auto-battery-management.jpg (59.06 KB) | 59.06 KB |
Hi ehsanhabib
For the audible noise, it can be solve by putting varnish to the TRF.
For your entry #3, the concern is if I get it right Vo is loaded at 100mA. at 100Vac. And the output is drops to 21.5V?
Please probe Vds waveform zoom in as indicated in the attachment.
Thanks
Regards
PI-Chloe
| Attachment | 大小 |
|---|---|
| auto-battery-management.jpg (59.06 KB) | 59.06 KB |
I am adding Pictures for 22.8 Volt Output. at 112mA load....Input is 120 volt AC,at 52.2mA Input Current... Input Power is 6.264 Watt, while the output is 2.5536 Watt.... So the efficiency is 40%. I don't think its normal,and the transformer is generating sound of switching, but when I load it around 400ma The switching sound gets away.... i get it,it can be removed by varnishing.... So let's talk about efficiency and the output volt(design was for 24 volt,1.5amp)
| Attachment | 大小 |
|---|---|
| Input Volt & Input Current (43.88 KB) | 43.88 KB |
| ZOOM picture of VDS (77.96 KB) | 77.96 KB |
| ZOOM OUT picture of vds (46.06 KB) | 46.06 KB |
| Output Voltage (34.66 KB) | 34.66 KB |
| Output Current (48.96 KB) | 48.96 KB |
Now i am adding another set of pictures where the input is 173 volt AC,at 161mA Input Current. And the output is 22.5 volt and 429mA current. The input is 27.8 watt and the output is 9.65 watt.
| Attachment | 大小 |
|---|---|
| Input Volt & Input Current (50.45 KB) | 50.45 KB |
| ZOOM picture of VDS (43.5 KB) | 43.5 KB |
| ZOOM OUT picture of vds (72.61 KB) | 72.61 KB |
| Output Current (38.45 KB) | 38.45 KB |
Hi ehsanhabib
We have available Application Notes for LNK HP AN58.
There are tips on the application notes to increase efficiency.
For regulation, it is a must to reduce the ringing of the Vds waveform during off time.
Efficiency Improvement and regulation
- Ratio of leakage inductance to primary inductance should be no greater than 2%.
Need to design a TRF with low leakage inductance.
- For D2 please use standard recovery diode reduce ringing in the Vds waveform.
- Please increase R2 this will reduce the ringing in the Vds waveform.
- Please Th1 also reduce s efficiency. If TH1 is needed for inrush, try to examine if you can lower down the resistance.
- Please check R5 and C7. R5 value seems very high
- For D4 you can use schottky diode.
Thanks
Regards
PI-CHLOE
I have solved the previous issue. The ic gone bad,maybe i distress it while soldering... So i changed it to new one. And its working.. Now i have different issue..
1. The design was for 24 volts 1.5 amp. When I give a load of 1.120 Amp using a 20 Ohm resistor,i get around 22.8 volts. At that time the SMPS draw around 212 mili Amp at 230 Volt.. So the input power is 48.76 Watt when the output is 25.536 Watt.
**I didn't put the Smps transformer to varnish, Can that be the reason for it?
***Also I hear some switching sound coming from transformer or maybe the SMPS,is that normal?
****