Load Switch System Driven by a Charge Pump

• US 20110163796A1
• Filed: 01/06/2011
• Published: 07/07/2011
• Est. Priority Date: 01/06/2010
• Status: Active Grant

• Current Assignee: Aptus Power Semiconductor
• Original Assignee: Aptus Power Semiconductor
• Inventors: Floyd, Brian Harold
• Granted Patent: US 8,487,689 B2
• Time in Patent Office: Days
• US Class Current: 327/536
• CPC Class Codes: H03K 17/08122 in field-effect transistor switches
• CPC Class Codes: H03K 17/166 Soft switching

Abstract

A method for operating a load switch, wherein a charge pump drives a gate of the load switch, comprises the steps of: controlling a charge pump frequency as a function of states of the load switch; generating a charge pump output as a function of the charge pump frequency; and providing the charge pump output to the gate of the load switch.

Claims

1. A method for operating a load switch, wherein a charge pump drives a gate of the load switch, comprising the steps of:

controlling a charge pump frequency as a function of states of the load switch;

generating a charge pump output as a function of the charge pump frequency; and

providing the charge pump output to the gate of the load switch.

3. The method of claim 1 wherein the states of the load switch comprise a steady state and a transient state.

4. The method of claim 3 wherein during the steady state, the charge pump frequency is at a minimum frequency.

5. The method of claim 3 wherein during the transient state, the charge pump frequency decreases as an output of the load switch increases.

6. The method of claim 5 wherein the charge pump frequency decreases at one of the following rates:

an inversely proportional rate, a constant rate, and a step-wise rate.

7. The method of claim 3 wherein the load switch is an N-channel load switch and during the transient state, the charge pump frequency decreases as the gate voltage of the load switch increases.

8. The method of claim 7 wherein the charge pump frequency decreases at one of the following rates:

an inversely proportional rate, a constant rate, and a step-wise rate.

9. The method of claim 3 wherein the load switch is an N-channel load switch and during the transient state, the charge pump frequency decreases as the gate voltage of the load switch increases and an output of the load switch increases.

10. The method of claim 1 wherein the charge pump output is regulated to a value proportional to an input voltage of the load switch.

11. The method of claim 10 wherein the load switch is an N-channel load switch and the value is also proportional to an output of the load switch.

14. The method of claim 1 wherein the load switch is an N-channel load switch, wherein if an on signal of the load switch exceeds an input voltage of the load switch by a predetermined threshold, the charge pump is disabled and the on signal supplies voltage to the gate of the load switch.

2. The method of 1 wherein the charge pump output is filtered before it is provided to the gate of the load switch.

12. The method of 1 wherein the load switch is a P-channel load switch and wherein the charge pump is disabled when the gate of the load switch is at or below a threshold value.

13. The method of 12 wherein the charge pump is enabled when the gate of the load switch exceeds the threshold value.

15. A method for operating a load switch, wherein a charge pump drives a gate of the load switch, comprising the steps of:

controlling a charge pump frequency as a function of states of the load switch, wherein the states of the load switch comprise a steady state and a transient state;

generating a charge pump output as a function of the charge pump frequency, wherein during the steady state, the charge pump frequency is at a minimum frequency and wherein during the transient state, the charge pump frequency decreases as an output of the load switch increases;

filtering the charge pump output; and

providing the filtered charge pump output to the gate of the load switch.

16. The method of claim 15 wherein the load switch is an N-channel load switch and during the transient state, the charge pump frequency further decreases as the gate voltage of the load switch increases.

17. The method of claim 16 wherein the charge pump frequency decreases at one of the following rates:

an inversely proportional rate, a constant rate, and a step-wise rate.

18. The method of claim 15 wherein the charge pump output is regulated to a value proportional to an input voltage of the load switch.

19. The method of claim 15 wherein the load switch is an N-channel load switch and the value is also proportional to an output of the load switch.

21. The method of claim 15 wherein the load switch is an N-channel load switch, wherein if an on signal of the load switch exceeds an input voltage of the load switch by a predetermined threshold, the charge pump is disabled and the on signal supplies voltage to the gate of the load switch.

20. The method of 15 wherein the load switch is a P-channel load switch and wherein the charge pump is disabled when the gate of the load switch is at or below a threshold value and wherein the charge pump is enabled when the gate of the load switch exceeds the threshold value.