| 摘要 |
The present invention relates to a constant voltage constant current (CVCC) controller, and associated control methods. In one embodiment, a CVCC controller for a flyback converter can include: (i) a current controller configured to generate an error signal by comparing an output current feedback signal against a reference current; (ii) a voltage controller configured to receive an output voltage feedback signal and a reference voltage, and to generate a control signal; (iii) a selector configured to control the flyback converter to operate in a first or a second operation mode based on the control signal, and to further generate a constant voltage or a constant current control signal based on the error signal; and (iv) a pulse-width modulation (PWM) controller configured to generate a PWM control signal to control a main switch, and to maintain the output voltage and/or current of the flyback converter as substantially constant. |
| 主权项 |
1. A constant voltage constant current (CVCC) controller configured for a flyback converter, said CVCC controller comprising:
a) a current controller configured to generate an error signal by calculating a difference between an output current feedback signal from a current feedback circuit, and a reference current; b) a voltage controller configured to receive an output voltage feedback signal and a reference voltage, and to generate a control signal; c) a selector coupled to said current controller and said voltage controller, wherein said selector is configured to receive said error signal and said control signal, and to control said flyback converter to operate in a first operation mode or a second operation mode based on said control signal, wherein said selector is configured to generate a constant voltage control signal based on said error signal when said flyback converter is operating in said first operation mode, and wherein said selector is configured to generate a constant current control signal based on said error signal when said flyback converter is operating in said second operation mode; d) a pulse-width modulation (PWM) controller configured to generate a PWM control signal to control a main switch, wherein said PWM controller is configured to generate a constant voltage signal based on said constant voltage control signal to maintain an output voltage of said flyback converter as substantially constant when said flyback converter operates in said first operation mode, and wherein said PWM controller is configured to generate a constant current signal based on said constant current control signal to maintain an output current of said flyback converter as substantially constant when said flyback converter operates in said second operation mode; e) a voltage feedback circuit, comprising a blanking circuit configured to be controlled by said PWM control signal and to generate a blanking signal at each falling edge of said PWM control signal, a first switch configured to be controlled by said blanking signal, a resistor coupled in parallel to said first switch and configured to receive a signal representing a secondary output voltage of said flyback converter, a second switch coupled to said resistor and configured to be controlled by a timing signal, and a first capacitor coupled to said second switch and ground, wherein a common node of said second switch and said first capacitor is configured as said output voltage feedback signal; and f) a timer configured to measure a discharging time of a secondary winding of said flyback converter, and to generate said timing signal. |
