The OPA2189 is used as the main control operational amplifier, and the LM339 is used as the OVP/OCP/OTP protection comparator. Diodes are used to combine the CV/CC loop. Simulated crossover frequencies are 190kHz/100kHz. The output stage uses four parallel TIP41C transistors in conjunction with an 8050 as a Darlington output stage to reduce amplifier’s current load.
The 12V 50% current step test shows that the CV loop’s dominant pole frequency is approximately 27kHz with good phase margin, and the instantaneous undershoot is 1.1%. The 5A 50% voltage step test shows a 60% instantaneous current overshoot and loop is unstable, with a dominant pole frequency of 91kHz and an amplitude of 32%.
After changing the CC loop compensation, the dominant pole frequency is 3kHz, the loop is stable, but the response is poor. Note: The first peak is caused by capacitor discharge, and the first undershoot is caused by OCP recovery.
