Auto-switching converter with PWM and PFM selection
An auto-switching converter with PWM and PFM selection supplies a boosted DC power to a load through a power switch unit. A starter outputs a starting-enabling signal. An auto PWM/PFM controller is connected to the starter for outputting a selection signal. A controller and a PFM controller are connected to the auto PWM/PFM controller, the power switch unit and the load for transmitting a PWM control signal and a PFM control signal to the power switch unit, respectively, for controlling the switching action of the power switch unit.
1. An auto-switching converter with PWM and PFM selection, connected to a load through a power switch unit for supplying DC power to the load by controlling a switching action of the power switch unit, comprising:
a starter outputting a starting-enabling signal;
an auto PWM/PFM controller connected to the starter for receiving the starting-enabling signal and outputting a selection signal;
a PWM controller connected to the auto PWM/PFM controller, the power switch unit and the load for receiving a feedback voltage signal, a load current signal and the selection signal, outputting an error signal to the auto PWM/PFM controller, and outputting a PWM control signal to the power switch unit for controlling the switching action of the power switch unit; and
a PFM controller connected to the auto PWM/PFM controller, the power switch unit and the load for receiving the feedback voltage signal, the load current signal and the selection signal, outputting a current comparison signal to the auto PWM/PFM controller, and outputting a PFM control signal to the power switch unit for controlling the switching action of the power switch unit;
wherein, the auto PWM/PFM controller comprises:
a reference voltage generator outputting a reference voltage signal;
a PWM comparator connected to the reference voltage generator, the starter and the PWM controller for receiving the reference voltage signal, the starting-enabling signal and the error signal, and outputting a PWM comparison signal;
a PFM comparator connected to the reference voltage generator, the starter and the PWM controller for receiving the reference voltage signal, the starting-enabling signal and the error signal, and outputting a PFM comparison signal;
a first flip-flop connected to the PWM comparator and the PFM comparator for outputting a reset signal;
an AND circuit outputting an AND signal; and
a second flip-flop connected to the first flip-flop and the AND circuit for receiving the reset signal and the AND signal, and outputting the selection signal.
2. The auto-switching converter of claim 1 , wherein the error signal is produced by comparing the feedback voltage signal with a reference voltage.
3. The auto-switching converter of claim 1 , wherein the current comparison signal is produced by comparing the load current signal with a reference current.
4. The auto-switching converter of claim 1 , wherein the second flip-flop is a R-S flip-flop.
5. The auto-switching converter of claim 1 , wherein the AND circuit is connected to the PFM controller and the second flip-flop for receiving the current comparison signal and the selection signal, and outputting the AND signal by an AND-operation.
6. The auto-switching converter of claim 1 , wherein the first flip-flop is an R-S flip-flop.
7. An auto PWM/PFM controller receiving a feedback signal from a PWM controller and a PFM controller, and outputting a selection signal to the PWM controller and the PFM controller to select one controller for operating by a starter, the auto PWM/PFM controller comprising:
a reference voltage generator for outputting outputs a reference voltage signal;
a PWM comparator connected to the reference voltage generator, the starter and the PWM controller for receiving the reference voltage signal, the starting-enabling signal and the error signal, and outputting a PWM comparison signal;
a PFM comparator connected to the reference voltage generator, the starter and the PWM controller for receiving the reference voltage signal, the starting-enabling signal and the error signal, and outputting a PFM comparison signal;
a first flip-flop connected to the PWM comparator and the PFM comparator for outputting a reset signal;
an AND circuit outputs an AND signal; and
a second flip-flop connected to the first flip-flop and the AND circuit for receiving the reset signal and the AND signal, and outputting the selection signal.
8. The controller of claim 7 , wherein the second flip-flop is an R-S flip-flop.
9. The controller of claim 7 , wherein the AND circuit is connected to the PFM controller and the second flip-flop for receiving the feedback signal and the selection signal, and outputting the AND signal by AND-operation.
10. The controller of claim 7 , wherein the first flip-flop is an R-S flip-flop.