Switching power supply control
View Patent ↗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 modulation circuit to generate a modulation signal in response to an input control signal and a frequency signal; and
a timer to generate the frequency signal in response to the input control signal.
2. The controller of claim 1 where the modulation circuit implements PWM control.
3. The controller of claim 1 where the modulation circuit implements PFM control.
4. The controller of claim 1 where:
the modulation circuit comprises a comparator to compare a feedback signal to a first limit and a second limit; and
the first limit comprises a ramp.
5. The controller of claim 4 where the timer comprises a bias generator coupled to the modulation circuit.
6. The controller of claim 5 where the bias generator comprises:
a divider coupled between the input control signal and a voltage source; and
a summing circuit coupled between the divider and the modulation circuit.
7. The controller of claim 1 where the modulation circuit comprises:
a PWM comparator to generate a modulation signal in response to a frequency signal and an error signal; and
an error amplifier coupled to the PWM comparator to generate the error signal in response to the input control signal and a feedback signal.
8. The controller of claim 1 where the modulation circuit comprises:
a switch circuit coupled to the time to control the modulation signal in response to an error signal; and
an error amplifier coupled to the switch circuit to generate the error signal in response to the input control signal and a feedback signal.