Systems and methods for regulating output currents of power conversion systems
Systems and methods are provided for regulating a power conversion system. An example system controller includes a first controller terminal and a second controller terminal. The first controller terminal is configured to receive a first signal associated with an input signal for a primary winding of a power conversation system. The second controller terminal is configured to output a drive signal to a switch to affect a first current flowing through the primary winding of the power conversion system, the drive signal being associated with an on-time period, the switch being closed during the on-time period. The system controller is configured to adjust a duration of the on-time period based on at least information associated with the first signal.
1. A system controller for a power converter, the system controller comprising:
a first controller terminal configured to output a drive signal to a switch to affect a first current flowing through a primary winding of a power converter, the drive signal being associated with an on-time period, the switch being closed during the on-time period;
a first current-signal generator configured to generate a second current based at least in part on a first signal; and
a ramp-signal generator configured to generate a ramping signal based at least in part on the second current, the ramping signal being associated with a ramping slope;
wherein the system controller is configured to:
adjust a duration of the on-time period based at least in part on the first signal, the first signal being associated with an input signal for the primary winding of the power converter, the input signal corresponding to an input voltage; and
adjust the duration of the on-time period by adjusting the ramping slope of the ramping signal based at least in part on the first signal.
2. The system controller of claim 1 , further comprising:
a second controller terminal configured to provide a compensation signal based at least in part on the first current; and
a second current-signal generator configured to generate a third current based at least in part on the compensation signal.
3. The system controller of claim 2 wherein the ramp-signal generator is configured to generate the ramping signal based at least in part on the second current and the third current.
4. The system controller of claim 2 wherein:
the ramp-signal generator is configured to increase the ramping signal at the ramping slope from a first magnitude to a second magnitude during the on-time period;
the first magnitude is equal to a reference signal in magnitude; and
the second magnitude is equal to the compensation signal in magnitude.
5. The system controller of claim 2 wherein the ramp-signal generator includes:
a third current-signal generator configured to generate a fourth current based at least in part on the second current and the third current; and
a capacitor configured to be charged in response to the fourth current to generate the ramping signal, the capacitor being associated with a capacitance.
6. The system controller of claim 5 wherein the ramping slope of the ramping signal is related to the fourth current and the capacitance.
7. The system controller of claim 5 wherein the duration of the on-time period is related to the compensation signal, the fourth current and the capacitance.
8. The system controller of claim 5 wherein the third current-signal generator includes one or more current-mirror circuits.
9. The system controller of claim 5 , further comprising a modulation signal generator configured to receive the ramping signal and the compensation signal and output a modulation signal based at least in part on the ramping signal and the compensation signal to affect the drive signal.
10. The system controller of claim 5 , further comprising an error amplifier configured to receive a sensing signal associated with the first current and a reference signal and outputs the compensation signal based at least in part on the sensing signal and the reference signal.
11. The system controller of claim 5 , further comprising:
a transistor including a first transistor terminal, a second transistor terminal and a third transistor terminal;
wherein:
the first transistor terminal is configured to receive a control signal;
the second transistor terminal is configured to receive a second signal associated with a reference signal; and
the third transistor terminal is coupled to a first capacitor terminal of the capacitor and is configured to receive the ramping signal.
12. The system controller of claim 2 wherein:
the first current-signal generator is further configured to generate the second current flowing into the first current-signal generator; and
the second current-signal generator is further configured to generate the third current flowing into the second current-signal generator.
13. The system controller of claim 2 wherein:
the first current-signal generator is further configured to generate the second current flowing out of the first current-signal generator; and
the second current-signal generator is further configured to generate the third current flowing out of the second current-signal generator.
14. The system controller of claim 1 , further comprising:
a jittering-signal generator configured to generate a jittering signal associated with multiple jittering cycles corresponding to a predetermined jittering frequency related to a predetermined jittering period;
wherein:
the drive signal is associated with multiple modulation cycles corresponding to a modulation frequency related to a modulation period; and
the system controller is further configured to:
change the ramping slope based at least in part on the jittering signal so that, within a same jittering cycle of the multiple jittering cycles, the ramping slope is changed by different magnitudes corresponding to the multiple modulation cycles respectively; and
adjust the modulation frequency based at least in part on the changed ramping slope.
15. The system controller of claim 1 , further comprising:
a jittering-signal generator configured to generate a random jittering signal;
wherein:
the drive signal is associated with multiple modulation cycles corresponding to a modulation frequency related to a modulation period; and
the system controller is further configured to:
change the ramping slope based at least in part on the random jittering signal so that the ramping slope is changed by random magnitudes corresponding to the multiple modulation cycles respectively; and
adjust the modulation frequency based at least in part on the ramping slope changed by the random magnitudes.
16. A system controller for a power converter, the system controller comprising:
a ramp-signal generator configured to receive a first signal associated with a compensation signal and generate a ramping signal based at least in part on the first signal, the ramping signal being associated with a ramping slope, the compensation signal being associated with a first current flowing through a primary winding of a power converter; and
a controller terminal configured to output a drive signal to a switch based at least in part on the ramping signal to affect the first current;
wherein the system controller is configured to adjust the ramping slope of the ramping signal based at least in part on the compensation signal.
17. The system controller of claim 16 wherein the system controller is coupled to a capacitor and configured to provide the compensation signal with at least the capacitor.
18. The system controller of claim 16 wherein the ramping slope is larger than 0.
19. The system controller of claim 16 , further comprising a first current-signal generator configured to generate the first signal based at least in part on the compensation signal.
20. The system controller of claim 19 wherein:
the ramp-signal generator is configured to increase the ramping signal at the ramping slope from a first magnitude to a second magnitude during an on-time period, the switch being closed during the on-time period;
the first magnitude is equal to a reference signal in magnitude; and
the second magnitude is equal to the compensation signal in magnitude.
21. The system controller of claim 19 wherein the ramp-signal generator includes:
a second current-signal generator configured to generate a second current based at least in part on the first signal; and
a capacitor configured to be charged in response to the second current to generate the ramping signal, the capacitor being associated with a capacitance.
22. The system controller of claim 21 wherein the ramping slope of the ramping signal is related to the second current and the capacitance.
23. The system controller of claim 21 wherein:
a duration of an on-time period is related to the compensation signal, the second current and the capacitance; and
the switch is closed during the on-time period.
24. The system controller of claim 21 wherein the second current-signal generator includes one or more current-mirror circuits.
25. The system controller of claim 16 , further comprising a modulation signal generator configured to receive the ramping signal and the compensation signal and output a modulation signal based at least in part on the ramping signal and the compensation signal to affect the drive signal.
26. The system controller of claim 16 , further comprising an error amplifier configured to receive a sensing signal associated with the first current and a reference signal and generate, together with a capacitor, the compensation signal based at least in part on the sensing signal and the reference signal.
27. The system controller of claim 16 wherein the controller terminal is a pin.
28. The system controller of claim 16 wherein the system controller operates in a voltage mode.
29. The system controller of claim 16 wherein the power converter operates in a quasi-resonant mode.
30. The system controller of claim 16 , further comprising:
a jittering-signal generator configured to generate a jittering signal associated with a jittering frequency;
wherein the ramp-signal generator is further configured to:
change the ramping slope associated with the ramping signal periodically based at least in part on the jittering signal so that one or more changes in the ramping slope are made in each jittering period corresponding to the jittering frequency; and
output the ramping signal associated with the changed ramping slope.
31. The system controller of claim 30 wherein the jittering signal is a current signal.
32. The system controller of claim 30 wherein the jittering signal corresponds to a triangle waveform associated with the jittering frequency.
33. The system controller of claim 30 wherein the jittering signal corresponds to a sinusoidal waveform associated with the jittering frequency.
34. The system controller of claim 16 , further comprising:
a jittering-signal generator configured to generate a jittering signal associated with a random waveform;
wherein the ramp-signal generator is further configured to:
change the ramping slope associated with the ramping signal based at least in part on the jittering signal; and
output the ramping signal associated with the changed ramping slope.
35. The system controller of claim 34 wherein the random waveform corresponds to a pseudo-random waveform associated with a jittering frequency.
36. A method for regulating a power converter, the method comprising:
receiving a first signal associated with a compensation signal, the compensation signal being associated with a current flowing through a primary winding of a power converter;
generating a ramping signal based at least in part on the first signal, the ramping signal being associated with a ramping slope;
adjusting the ramping slope of the ramping signal based at least in part on the compensation signal; and
generating a drive signal based at least in part on the ramping signal; and
outputting the drive signal to a switch to affect the current.