Power supply unit with autonomous input power limiting
A power supply receives AC power and generates a DC output voltage. The power supply may be divided into a primary section that converts AC power to a relatively high DC voltage. A secondary section converts this relatively high DC voltage into a well-regulated lower DC voltage. In an embodiment, the current and/or power supplied by the primary to the secondary side is used by the secondary side in a closed-loop feedback system to limit the current drawn by the secondary side to a configurable value.
1. A method, comprising:
scaling a reference current based on a constant current adjustment, the constant current adjustment generated based on an input power and an input power limit;
generating an output current adjustment based on the scaled reference current; and
regulating an output voltage based on the output current adjustment.
2. The method of claim 1 , further comprising generating the constant current adjustment via a PID controller.
3. The method of claim 2 , further comprising:
receiving, via the PID controller, an error signal based on the input power and the input power limit; and
generating, via the PID controller, the constant current adjustment based on the error signal.
4. The method of claim 3 , wherein generating the constant current adjustment based on the error signal comprises generating the constant current adjustment to indicate 100% current capacity of the output current in response to the input power being less than the input power limit.
5. The method of claim 4 , wherein the constant current adjustment does not affect the output current in response to the indication of 100% current capacity.
6. The method of claim 4 , wherein generating the constant current adjustment based on the error signal comprises generating the constant current adjustment to indicate less than 100% current capacity of the output current in response to the input power being greater than the input power limit.
7. The method of claim 6 , wherein the constant current adjustment decreases the output current in response to the indication of less than 100% current capacity.
8. The method of claim 3 , wherein the input power is a primary side input power.
9. The method of claim 1 , wherein the reference current comprises a constant current reference.
10. A method of regulating a secondary side output current, comprising:
scaling a reference current based on a current adjustment signal, the current adjustment signal generated based on a primary side input power and a target power limit;
generating an error adjustment signal based on the scaled reference current; and
regulating an output voltage based on the error adjustment signal to limit an output current of the output voltage.
11. The method of claim 10 , further comprising generating the current adjustment signal based on the primary side input power and the target power limit.
12. The method of claim 11 , further comprising:
receiving, via a PID controller, an error signal based on the primary side input power and the target power limit; and
generating, via the PID controller, the current adjustment signal based on the error signal.
13. The method of claim 12 , wherein generating the error adjustment signal comprises:
generating the current adjustment signal to indicate 100% current capacity of the output current in response to the primary side input power being less than the target power limit; and
generating the current adjustment signal to indicate less than 100% current capacity of the output current in response to the primary side input power being greater than the target power limit.
14. The method of claim 12 , wherein the reference current comprises a constant current reference.
15. A power supply system, comprising:
an error modulator configured to generate an error adjustment signal based on a primary side input power and a target power limit;
a constant current reference modulator configured to scale a reference current based on the error adjustment signal;
a current feedback combiner configured to generate an output current adjustment based on the error adjustment signal and an output current feedback; and
a secondary output voltage regulator configured to produce an output voltage based on the output current adjustment.
16. The power supply system of claim 15 , further comprising a constant current reference generator configured to generate the reference current.
17. The power supply system of claim 15 , wherein the secondary output voltage regulator comprises a pulse-width modulation controller.
18. The power supply system of claim 15 , wherein the target power limit is configurable by an external system.
19. The power supply system of claim 15 , wherein the error modulator comprises a PID controller configured to:
receive an error signal based on the primary side input power and the target power limit;
generate the error adjustment signal based on the error signal; and
provide the error adjustment signal to the error modulator.