Hi team,
Could you please kindly help to share with us the way how to test the bode plots of TPS92520-Q1 design? Since customer want to test it in lab. Thank you very much for your support.
Best regards
Jessica
Hello Jessica,
Sumeet states, the control loop is greatly simplified because the control loop regulates the inductor current.
TPS92520 Compensation Capacitor Selection
A simple integral compensator is recommended to achieve stable operation across the wide operating range. The bode plot of the loop gain with different compensation capacitors is shown in figure below. The buck converter behaves as a single pole system with additional phase lag caused by the switching behavior. The gain and phase margin is then determined by the choice of the switching frequency and is independent of other design parameters. TI recommends a 1-nF to 10-nF capacitor to achieve bandwidth between 4 kHz and 40 kHz. The choice of compensation capacitor impacts the transient response, the shunt FET dimming behavior and PWM dimming performance. A larger compensation capacitor (lower bandwidth) is recommended to limit the LED current overshoot on the rising edge of internal or external PWM signal. A smaller compensation capacitor
(higher bandwidth) is recommend to improve shunt FET dimming response.
We will be providing the Simplis model when the device is released, but in the mean time let me know via email if you would like me to forward the model to you for sharing with customers.
Measuring gain and phase to generate the bode plots is difficult for LED drivers because cutting the loop and injecting an AC signal for the measurement is difficult when using typical bode plot equipment.
-Francis Houde
