Charge pump and switch control circuit

1. A charge pump, comprising:

a first diode coupled to a first node to which is also coupled a device including at least one coil;

a second diode coupled to a second node, wherein the at least one coil is coupled between the second node and ground;

a pump capacitor coupled to a third node to which the first diode and the second diode are coupled;

a power supply capacitor coupled to the pump capacitor; and

a third diode coupled between the pump capacitor and the power supply capacitor,

wherein the pump capacitor is charged by a voltage of the first node that is supplied to the pump capacitor at the third node through the at least one coil,

wherein the pump capacitor is coupled between the third node and an anode of the third diode.

2. The charge pump of claim 1 , wherein one electrode of the power supply capacitor is coupled to a cathode of the third diode and a second electrode of the power supply capacitor is coupled to ground.

3. The charge pump of claim 2 , wherein a zener diode is coupled between the anode of the third diode and the second electrode of the power supply capacitor.

4. The charge pump of claim 1 , wherein the second diode is configured to block connection between the third node and the second node when a voltage of the pump capacitor reaches a predetermined level.

5. The charge pump of claim 4 , wherein the pump capacitor is discharged through the first diode when the first diode becomes electrically conductive after the voltage of the pump capacitor has reached the predetermined level.

6. A charge pump that is coupled to a first node and a second node that are coupled to both ends of a power switch, the charge pump comprising:

a first diode configured to be electrically conductive by a voltage of the first node, wherein the second node is coupled to a device including at least one coil;

a second diode configured to be electrically conductive by short-circuit of the first node and the second node;

a pump capacitor coupled to a third node to which the first diode and the second diode are coupled;

a power supply capacitor having a first end that is coupled to the third node through the pump capacitor, a second end of the power supply capacitor being coupled to ground; and

a third diode configured to be biased in a direction from the pump capacitor to the power supply capacitor,

wherein the first diode is electrically conductive by the first node voltage when the power switch is turned off, and the pump capacitor is charged by a voltage of the first node that is supplied to the third node through the first diode.

7. The charge pump of claim 6 , wherein the power supply capacitor is charged by the voltage of the first node that is supplied through the first diode.

8. The charge pump of claim 6 , wherein a zener diode is electrically conductive by a power supply voltage that is charged at the power supply capacitor to bypass the power supply capacitor.

9. The charge pump of claim 6 , wherein the difference between a voltage of the third node and a power supply voltage that is charged at the power supply capacitor is charged at the pump capacitor.

10. The charge pump of claim 6 , wherein, when the power switch is turned on, the first node and the second node are short-circuited and the second diode is electrically conductive.

11. The charge pump of claim 10 , wherein the pump capacitor is discharged through the second diode.

12. The charge pump of claim 11 , wherein discharge of the power supply capacitor is blocked by the third diode, when the pump capacitor is discharged.

13. The charge pump of claim 6 , wherein the first diode is configured to block connection between the first node and the third node when a voltage of the pump capacitor reaches a predetermined level.

14. The charge pump of claim 13 , wherein the pump capacitor is discharged through the second diode when the power switch is turned on.