Vout and OVP for HSTNS-PF43

[ogni846]

Added a change to OVP and Vout. Now I'm looking for a solution to control the output current!

[darwinbeing]

This can be achieved using a constant current-constant voltage (CC-CV) control scheme with two feedback loops: one regulating the maximum output voltage (CV control) and the other regulating the maximum output current (CC control). These two control loops are combined using an OR logic function, where the loop with the smaller error takes priority and controls the output.

Under light load conditions, the voltage loop dominates, maintaining a stable output voltage. As the load increases and the output current reaches its limit, the current loop takes over, holding the output current constant while the output voltage drops gradually to prevent overloading. This design ensures stability and safety across varying operational conditions.

PMP9622 350W Constant Voltage - Constant Current (CVCC) Phase-Shifted Full Bridge reference design https://www.ti.com/lit/df/tidrde5/tidrde5.pdf

[IceShiva]

Dont forget about the complex poles and zeros in compensation. Of course you can use +1uf cap integrator in current loop. Psu would be very slow but will works. Second way is use mcu in the loop, extract parameters from analog voltage loop, implement it in digital way and tune it, or open the loop and design new one. Most of server psu's has a current share loop which is not acceptable for charnig batteries and powering leds, because it's implemented as kind of constant resistance, so if impedance of reciver changes current grows up then you need to adjust reference for current share loop. Another limitation is CCM/DCM mode and frequency of operation (Ton/Tof). Good point of start is having oscilloscope, signal generator, dummy load and alot calculations.

[darwinbeing]

Thanks for the insights! Regarding hardware modifications, I completely agree that they can introduce instability and unreliability into the power supply. It’s interesting that the HP HSTNS-PL30 doesn’t use the UCC28950 Phase-shifted full-bridge and instead implements control in the secondary MCU firmware. Secondary Side Control Loop consists of three subsections

• Voltage Control Loop
• Current Control Loop
• Load Feed-forward

Reimplementing the secondary firmware might enable constant current mode with minimal hardware changes.