Hello everyone,
I'm working on an LED driver circuit using the TPS923653, designed to drive a string of LEDs with a constant current of 350mA. The LED load varies between 8.8V and 13.28V, and the circuit is powered with an input voltage range of 12-16V, potentially extending up to 24V.
My goal is to utilize the buck-boost mode, considering that the input voltage might sometimes be above or below the required output voltage to maintain a 350mA output. However, I've encountered issues in buck-boost mode where the LED panel flickers every second or so but doesn't stay on, suggesting a recurring fault condition, although no specific fault criteria appear to be met.
To troubleshoot, I switched the circuit to operate exclusively in boost mode, which stabilized the operation somewhat, but there were still issues with setting the correct current:
- Initially, I used a 576mR RSENSE resistor calculated to set the LED current around 347mA (_ = x = 0.2 / 0.576Ω = 347mA), but instead, I measured 608mA through the LEDs and 315mV across the RSENSE.
- After changing the RSENSE to 1.2Ω, the current dropped to 250mA, and VSENSE was 300mV.
Currently, I have both PWM and ADIM pins tied high since I don’t require adjustable brightness — the LEDs need to be either fully on or off, controlled by the power supply to the driver. Could I be misunderstanding the function of the RSENSE resistor, or is there something else at play affecting the output current relative to changes in the input voltage?
Any insights or suggestions would be greatly appreciated as I continue to diagnose and resolve these issues.
Thank you in advance for your help!
AEIPSU60.pdf
