Driver for driving a p-type power switch
There is presented a driver and a corresponding method for driving a p-type power switch. The driver includes a capacitor coupled to a control terminal of the power switch. The driver is configured to apply a control voltage to the control terminal and to connect the control terminal to ground to reduce the control voltage down to a target value to switch the power switch on. When identifying that the control voltage has reached the target value, the driver disconnects the control terminal from ground. The driver may be used in various circuits including switching power converters, audio amplifiers and charge-pump circuits.
1. A driver for driving a p-type power switch, the driver comprising
a capacitor coupled to a control terminal of the power switch;
the driver being adapted
to apply a control voltage to the control terminal,
to connect the control terminal to ground to reduce the control voltage down to a target value to switch the power switch on;
and to disconnect the control terminal from ground upon identifying that the control voltage has reached the target value;
wherein the capacitor has a first terminal coupled to the control terminal and a second terminal reversibly coupled to a voltage source adapted to provide a predetermined voltage.
2. The driver as claimed in claim 1 , wherein the control terminal is coupled to ground via a first switch and a second switch.
3. The driver as claimed in claim 2 , wherein the the second terminal of the capacitor is reversibly coupled to the voltage source via a third switch.
4. The driver as claimed in claim 3 , comprising a fourth switch having a first terminal adapted to receive an input voltage, and a second terminal coupled to the control terminal of the power switch.
5. The driver as claimed in claim 4 , wherein the target value is defined by a difference between the input voltage and the predetermined voltage.
6. The driver as claimed in claim 4 , the driver being operable in a sequence of states comprising a first state to turn the power switch off and a second state to turn the power switch on, wherein in the first state the control voltage is set to the input voltage and wherein in the second state the control voltage is set to a value defined by a difference between the input voltage and the predetermined voltage.
7. The driver as claimed in claim 6 , wherein in the first state the first switch is off, the third switch is on and the fourth switch is on, and wherein in the second state the first switch is on, the third switch is off and the fourth switch off.
8. The driver as claimed in claim 4 , comprising a controller adapted to generate a first logic signal configured to control the first switch and the third switch, and a second logic signal configured to control the fourth switch.
9. The driver as claimed in claim 2 , wherein the second terminal of the capacitor is coupled to a control terminal of the second switch.
10. The driver as claimed in claim 1 , wherein the predetermined voltage is set to a limit value of the power switch.
11. The driver as claimed in claim 1 , wherein a voltage across the capacitor remains substantially constant.
12. A circuit comprising a p-type power switch coupled to a first driver, the first driver comprising a capacitor coupled to a control terminal of the power switch; the first driver being adapted to apply a control voltage to the control terminal, to connect the control terminal to ground to reduce the control voltage down to a target value to switch the power switch on; and to disconnect the control terminal from ground upon identifying that the control voltage has reached the target value: wherein the capacitor has a first terminal coupled to the control terminal and a second terminal reversibly coupled to a voltage source adapted to provide a predetermined voltage.
13. The circuit as claimed in claim 12 , wherein the control terminal is coupled to ground via a first switch and a second switch, wherein the second terminal of the capacitor is reversibly coupled to the voltage source via a third switch.
14. The circuit as claimed in claim 13 , wherein the circuit is a switching power converter.
15. The circuit as claimed in claim 14 , comprising a n-type power switch coupled to a second driver.
16. The circuit as claimed in claim 15 , wherein the second driver is adapted to receive a signal from the second terminal of the capacitor.
17. The circuit as claimed in claim 16 , wherein the second driver comprises two NOT gates coupled in series and wherein the second driver is adapted to enable or disable one of the NOT gates using the signal from the second terminal of the capacitor.
18. A method for driving a p-type power switch, the method comprising
providing a capacitor coupled to a control terminal of the power switch; wherein the capacitor has a first terminal coupled to the control terminal and a second terminal reversibly coupled to a voltage source adapted to provide a predetermined voltage;
applying a control voltage to the control terminal,
connecting the control terminal to ground to reduce the control voltage down to a target value to switch the power switch on; and
disconnecting the control terminal from ground upon identifying that the control voltage has reached the target value.