Method and apparatus switching a semiconductor switch with a multi-stage drive circuit

• US 20060261878A1
• Filed: 05/12/2006
• Published: 11/23/2006
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Giao Minh Pham
• Original Assignee: Giao Minh Pham
• Inventors: Pham, Giao Minh
• Granted Patent: US 8,207,760 B2
• Time in Patent Office: Days
• US Class Current: 327/427
• CPC Class Codes: H03K 17/04206 in field-effect transistor switches
• CPC Class Codes: H03K 17/164 using parallel switching arrangements
• CPC Class Codes: H03K 17/167 using parallel switching arrangements

Abstract

A method and an apparatus for implementing a semiconductor switch multi-stage drive circuit. The disclosed method and an apparatus reduce losses in a semiconductor switch when it is turned from an off state to an on state or from an on state to an off state. The reduction in losses is achieved without influencing the dv/dt across the semiconductor switch during a first time period while the semiconductor switch is switching. This reduction in losses is therefore achieved with very little increase in the noise generated due to rapid dv/dt during the first time period when the semiconductor switch is switching. The configuration of the circuitry to achieve this reduction in switching losses is such that benefits are less sensitive to manufacturing tolerances and temperature effects than alternative semiconductor switch drive schemes to achieve similar results.

Claims

1. An apparatus, comprising:

a semiconductor switch to be switched between on and off states;

a plurality of drive circuits having a drive circuit impedance and coupled to provide a plurality of drive signals to switch the semiconductor switch; and

a selector circuit coupled to the semiconductor switch and coupled to each of the plurality of drive circuits to select in response to a sensing of the semiconductor switch the drive circuits that provide the plurality of drive signals to the semiconductor switch to reduce the drive circuit impedance as the semiconductor switch switches.

2. The circuit of claim 1 wherein the plurality of drive circuits comprise a first drive circuit and a second drive circuit, wherein the first drive circuit provides a first drive signal for a first time period and the second drive circuit provides a second drive signal for a second time period while the semiconductor switch switches.

3. The circuit of claim 2 wherein the first drive circuit provides the first drive signal during both the first and second time periods.

4. The circuit of claim 2 wherein the semiconductor switch includes a drive terminal and a reference voltage terminal, wherein the first and second drive signals are coupled to be received by the drive terminal of the semiconductor switch.

5. The circuit of claim 4 wherein the second time period starts when the voltage between the drive terminal and reference voltage terminal reaches a first voltage threshold value.

6. The circuit of claim 1 further comprising a current sensor coupled between the semiconductor switch and the selector circuit.

7. The circuit of claim 6 wherein the second time period starts when a current through the semiconductor switch is sensed to cross a current threshold value.

8. The circuit of claim 2 wherein the second time period starts when a voltage across the semiconductor switch crosses a second voltage threshold value as the semiconductor switch switches from the first state to the second state.

9. The circuit of claim 2 wherein the second time period starts when a change in voltage across the semiconductor switch over a time period (dv/dt) occurs as the semiconductor switch switches from the first state to the second state.

10. The circuit of claim 2 wherein the first time period is a fixed time period.

11. The circuit of claim 1 wherein the semiconductor switch comprises a metal oxide field effect transistor (MOSFET).