12 volt 10 amps

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I have constructed a PSU 12v @ 10 amps with TOP249Y. Circuit works on no load, on connecting a halogen lamp 12 V 50W the PSU shuts down like an over current trip. I have tried wiring the device in 3 terminal mode, and still the same shut down happens. Component values are as per PIexpert 6.6. Transformer has been constructed by me. Do let me know if this can be corrected. I havent faced this problem with older devices and the current TINY devices. Regards Shashi Menon
hello mr shashi, pls do check following points: 1: check the primary voltage waveform & secondry wavefor for voltage. if it is flyback topology based, pls do confirm that both the waveforms are in phase. 2: short the X pin to ground without connecting any resistor. If it works with load, then adjust the X pin resistor value in between 5k to 12 k suitably. 3: pls confirm the output rectifier diode rating as- a: diode current rating should be 3 times the output average current. in your case, to acheive 5A load, pls see the diode is 15A diode. b: output diode voltage should be 1.5 times the PIV of the output. you can find PIV in spreadsheet in OUTPUT section specification column. c: trr of diode should also be confirmed suitably. 4: input capacitor should be choosen properly to drive the concern output load. C input must be 3 times the output power for universal line operation & 1 times for 230V operation. pls go through the application note for designing with Gx series available on website. or else pls mail me at prasun@spectraind.com
Hello, if all else is ok, the reason for this shutdown is the high inrush current, "many times more" than its steady state 4 Amps, through the lamp filament in a cold start. more over, to run a halogen lamp with this topology is not the way to go, unless you are intending to use this power supply for some other purpose. rgds gpm

GPM's comments are correct - there's similar issues driving DC motor or similar loads. If your supply will always be started up with the lamp connected then you can use a long soft-start time (by adding a cap and small signal transistor).

However a simpler trick to try first is to increase the size of the control pin capacitor from 47uF to 220 uF. This will allow the TOPSwitch to run for 200 ms instead of 47 ms before entering auto-restart. This may increase output ripple (due to reduced bandwidth) but if the load is a lamp this won't be an issue.

Cheers

Chekov