TPS92513: Non linear dimming by external mosfet using tps92513 driver ic

Since the laber day is from 5.1 to 5.5, our expert will reply you on 5.6 

Driver Board.pdf

Hi, 

Attached the schematics , led connection and capture images on dso.

Images between anode and cathode points with 25,50,75 and 100%dimming.

Issues when dimming dimming by q1, q3, q5, q7 mosfet. 

Thanks, 

Irfan

Hi Robin, could you help in this case.

Hi Irfan,

Could you mark the above waveform clearly? Thanks!

BTW, TPS92513 is a peak current control mode device and shunt FET dimming performance may be not good.

BR,

Robin

Hi, 

Actually we had design complete bulb with Bluetooth controller. Also FCc test pass but above issue not seen design stage. Please help us to do complete this product. 

Please help us how to improve this performance. 

Yellow colour waveform is Anode and Red for cathode of LED .

Thanks, 

Irfan

Hi, 

We are waiting for reply. Please reply.. 

Regards, 

Irfan

Hi Robin, please help to keep following this case

Hi Irfan,

Could you decrease the external  FET switching frequency to see if there is any improvement?

BR,

Robin

Hi, 

We have tried with 4khz, 2khz1khz, ,250hz but no improvement. 

Regards, 

Irfan

Hi Robin, please help to keep following this case.

Hi 

We are waiting for response. Please reply. 

Regards, 

Irfan

Hi Robin, please help to keep following this case

Hi Irfan,

There are some suggestions that may be helpful. 1). Change C3 with a bigger one and X7R is better. 2). Add phase shift to these four MOSFT gate signals, and the phase shift should be 0/90/180/270. 3). Keep low external MOSFET switching frequency.

BR,

Robin

Hi, 

1)we have increased c3 value up to 220uf but not improvement found, 2) we have problem with single mosfet other keep off (we have not apply phase shifting in 4ch signal), 3)we have decreased External midget pwm signal Frequency as 4k, 2k, 1k, 500hz, 250,125,60hz But improvement found. 

Please advise more. 

Thanks, 

Irfan