My customer is using TPS61169 to light up 8s series, 2 parallel total 16 LEDs. Input voltage is 4V not 5V shown in the picture below.
The schematic is as below.
At lowest duty cycle of 1%, the waveform is as below:
At brightest dimming, the waveform is as below:
They also measured the input current with multimeter. They've already limited the output current to 40mA. So with input current =450mA, the output current should be 450mA*4V*efficiency/22.5=80mA if efficiency=100%. which is far bigger than limited.
It seems that the problem is at the abnormal current waveform, so could you please tell what may cause this abnormal?
|
darkest dimming VIN current |
brightest dimming VIN current |
|
|
32mA |
450mA |
