Electronic device for switched DC-DC conversion having high-efficiency at high load and low load and method for operating the same
View Patent ↗An electronic device for switched DC-DC conversion of an input voltage level into an output voltage level, comprising a first power switch and a second power switch, being connected in parallel and having a different gate width, and a driving stage that is configured to selectively drive the first power switch and/or second power switch depending on a load current output.
1. An electronic device for switched DC-DC conversion of input voltage level into an output voltage level comprising:
a first power switch couplable to a load receiving a pulse width modulated (PWM) signal to generate the output voltage;
a second power switch coupled in parallel with the first power switch having a gate width larger than the first power switch and being couplable to the load, the second power switch receiving a drive signal that compares a timing signal having a switching frequency lower than that of the PWM signal with a signal level related to output current, wherein the first power switch is continually driven by the PWM signal and the second power switch is driven by a portion of the PWM signal.
2. The electronic device of claim 1 wherein the portion of the PWM signal utilized to drive the second power switch varies between approaching 0% approaching 100%.
3. The electronic device of claim 2 wherein the portion of the PWM signal utilized to drive the second transistor is defined by the ratio of the time intervals (tx minus t 1 )/(t 2 minus tx), where:
t 1 =a starting point for the low-frequency signal;
t 2 =an ending point for the low-frequency signal;
tx=a point between t 1 and t 2 where the low-frequency signal exceeds a value related to output current.
4. The electronic device of claim 2 wherein the low frequency signal is a sawtooth signal.
5. The electronic device of claim 1 wherein when the portion of the PWM signal approaches 100%, the first and second power switches operate synchronously.
6. The electronic device of claim 5 is a wherein the low frequency signal is a sawtooth signal.
7. The electronic device of claim 1 wherein the low frequency signal is a sawtooth signal.
8. A method for operating an electronic device for switched DC-DC conversion of input voltage level into an output voltage level comprising:
coupling a first power switch to a load receiving a pulse width modulated (PWM) signal to generate the output voltage;
coupling a second power switch coupled in parallel with the first power switch having a gate width larger than the first power switch and being coupled to the load;
receiving a drive signal at the second power switch that compares a timing signal having a switching frequency lower than that of the PWM signal with a signal level related to output current, wherein the first power switch is continually driven by the PWM signal and the second power switch is driven by a portion of the PWM signal.
9. The method of claim 8 wherein the portion of the PWM signal utilized to drive the second power switch varies between approaching 0% approaching 100%.
10. The method of claim 9 wherein the low frequency signal is a sawtooth signal.
11. The method of claim 9 wherein when the portion of the PWM signal approaches 100%, the first and second power switches operate synchronously.
12. The method of claim 11 is a wherein the low frequency signal is a sawtooth signal.
13. The method of claim 8 wherein the portion of the PWM signal utilized to drive the second transistor is defined by the ratio of the time intervals (tx minus t 1 )/(t 2 minus tx), where:
t 1 =a starting point for the low-frequency signal;
t 2 =an ending point for the low-frequency signal;
tx=a point between t 1 and t 2 where the low-frequency signal exceeds a value related to output current.
14. The method of claim 8 wherein the low frequency signal is a sawtooth signal.