Switching power supply control
A switching power supply controller includes a comparator to compare a feedback signal to a first limit and a second limit, one of which includes a ramp. Limit generators may be used to generate limit signals in response to power supply signals, control signals, and/or output signals. An error amplifier may be used to generate the feedback signal in response to an output signal and an input control signal. A switching power supply may alternatively include an oscillator that shifts the switching frequency in response to the input control signal.
1. A switching power supply controller comprising:
a first comparator to compare a feedback signal to a first limit to set a flip-flop to a first operating state of the power supply controller and a second comparator to compare the feedback signal to a second limit to set the flip-flop to a second operating state of the power supply controller, wherein the first limit comprises a ramp.
2. The controller of claim 1 where the second limit comprises a ramp.
3. The controller of claim 1 where the second limit comprises a bias signal.
4. The controller of claim 1 where the feedback signal comprises an error signal.
5. The controller of claim 1 further comprising a feedback network coupled to the comparator to generate the feedback signal responsive to an output signal.
6. The controller of claim 5 where the feedback network comprises an error amplifier to generate the feedback signal responsive to an input control signal and an output signal.
7. The controller of claim 6 where the output signal represents a voltage.
8. The controller of claim 6 where the output signal represents a current.
9. The controller of claim 1 further comprising a limit generator coupled to the comparator to generate the first limit.
10. The controller of claim 9 where the limit generator is to generate the first limit in response to a power supply signal.
11. The controller of claim 9 where the limit generator is to generate the first limit in response to an input control signal.
12. The controller of claim 9 where the limit generator is to generate the first limit in response to an output signal.
13. The controller of claim 9 further comprising a second limit generator coupled to the comparator to generate the second limit.
14. The controller of claim 13 where the second limit generator is to generate the second limit in response to a power supply signal.
15. The controller of claim 13 where the second limit generator is to generate the second limit in response to an input control signal.
16. A switching power supply controller comprising:
a comparator to compare a feedback signal to a first limit to set a first operating state of the power supply controller and to a second limit to set a second operating state of the power supply controller, wherein the first limit comprises a ramp;
a first limit generator coupled to the comparator to generate the first limit in response to a power supply signal, an input control signal, and/or an output signal;
a second limit generator coupled to the comparator to generate the second limit in response to a power supply signal and/or an input control signal; and
an error amplifier coupled to the comparator to generate the feedback signal in response to an output signal and an input control signal.
17. A method comprising:
operating a switching power supply between first and second states in order to regulate an output voltage by comparing a feedback signal to a first limit to set a modulation signal used to regulate the output voltage and comparing the feedback signal to a second limit to reset the modulation signal, wherein the second limit is a ramp.
18. The method of claim 17 where the second limit is a ramp.
19. The method of claim 17 where the second limit is a bias signal.
20. The method of claim 17 further comprising generating the feedback signal in response to an output signal and an input control signal.
21. The method of claim 17 further comprising generating the first limit in response to an output signal.
22. A switching power supply controller comprising:
a means for comparing an error signal to a bias signal and responsively setting a modulation signal used to regulate an output voltage; and
a separate means for comparing the error signal to a ramp signal and responsively resetting the modulation signal.
23. The controller of claim 22 further comprising means for generating the error signal in response to an output signal and an input control signal.
24. The controller of claim 22 further comprising means for generating the ramp signal.
25. The controller of claim 22 further comprising means for generating the bias signal.