High Voltage Power Switches Using Low Voltage Transistors

• US 20080309307A1
• Filed: 12/04/2006
• Published: 12/18/2008
• Est. Priority Date: 12/08/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Wang, Zhenhua
• Granted Patent: US 7,911,192 B2
• Time in Patent Office: Days
• US Class Current: 323/311
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence
• CPC Class Codes: H03K 17/102 in field-effect transistor switches
• CPC Class Codes: H03K 17/6871 the output circuit comprising more than one controlled field-effect transistor

Abstract

A switching regulator having first and second power switches. The first power switch has at least two transistors connected in series, the transistors having a first maximum voltage across their terminals which is less than the input voltage of the regulator. The transistors have at least a first node at the point where they are connected, and a first control circuit controls the voltage at the first node so that the voltages across the terminals of the transistors of the first power switch do not exceed the first maximum voltage. The second power switch also has at least two transistors connected in series, the transistors having a maximum voltage across their terminals that is less than the input voltage. The transistors have at least a second node at the point where they are connected, and a second control circuit controls the voltage at the second node so that the voltages across the terminals of the transistors of the second power switch do not exceed the second maximum voltage.

Claims

1. A switching regulator having an input voltage and comprising:

a first power switch comprising;

at least two transistors connected in series, the transistors having at least a first nodes at the point where two of the transistors are connected; and

at least a first control circuit for setting the voltage at the first node to a first intermediate voltage when the first power switch is turned off; and

a second power switch comprising;

at least two transistors connected in series, and the transistors having at least a second node at the point where two of the transistors are connected; and

at least a second control circuit for setting the voltage at the second node to a second intermediate voltage when the second power switch is turned off.

2. The switching regulator of claim 1, characterized in that the first power switch is connected between an input of the switching regulator and a third node and the second power switch is connected between a common voltage and the third node.

3. The switching regulator of claim 1, characterized in that the first control circuit comprises a switch for connecting a gate terminal and a source terminal of one of the series connected transistors of the first power switch.

4. The switching regulator of claim 3, characterized in that the second control circuit comprises a switch for connecting a gate terminal and a source terminal of one of the series connected transistors of the second power switch.

5. The switching regulator of claim 1, characterized in that the series-connected transistors of the first power switch have a first maximum permitted voltage across their terminals which is less than the input voltage of the switching regulator, and in that the first intermediate voltage is greater than or equal to the input voltage less the first maximum permitted voltage.

6. The switching regulator of claim 5, characterized in that the series-connected transistors of the second power switch have a second maximum permitted voltage across their terminals which is less than the input voltage of the switching regulator, and in that the second intermediate voltage is less than or equal to the second maximum permitted voltage.

7. The switching regulator of claim 6, characterized in that the first intermediate voltage equals the input voltage less the second intermediate voltage.

8. The switching regulator of any of claim 1, characterized in that one of the series connected transistors of the first power switch has a gate terminal which is switched and another of the series connected transistors of the first power switch has a gate terminal which is not switched.

9. The switching regulator of claim 8, characterized in that the first control circuit comprises a switch for connecting a gate terminal to a source terminal of the non-switched series connected transistor of the first power switch.

10. The switching regulator of claim 1, characterized in that the first power switch comprises two transistors connected in series, the gate terminal of the first transistor being switched between the input voltage and the first intermediate voltage and the gate terminal of the second transistor being fixed at the first intermediate voltage;

and

the first control circuit comprises a transistor for electrically connecting the first node to the first intermediate voltage.

11. The switching regulator of claim 10, characterized in that the

the second power switch comprises two transistors connected in series, the gate terminal of the first transistor being switched between ground and the second intermediate voltage and the gate terminal of the second transistor being fixed at the second intermediate voltage;

and

the second control circuit comprises a transistor for electrically connecting the second node to the second intermediate voltage.

12. A power supply circuit comprising:

the switching regulator of claim 1;

a control signal generator for providing signals for switching at least one of the transistors of each of the power switches of the switching regulator; and

an internal power supply for providing the first and second intermediate voltages.

13. An audio power amplifier circuit comprising:

the switching regulator of claim 1;

a control signal generator for providing signals for switching at least one of the transistors of each of the power switches of the switching regulator; and

an internal power supply for providing the first and second intermediate voltages.

14. A method for operating a switching regulator having an input voltage, the switching regulator comprising first and second power switches each comprising at least two transistors connected in series, the transistors having a maximum permitted voltage across their terminals which is less than the input voltage, the transistors in the first power switch having a first node at the point where two of the transistors are connected, and the transistors in the second power switch having a second node at the point where two of the transistors are connected,

the method comprising the steps of:

setting the voltage at the first node to a first intermediate voltage when the first power switch is turned off, so that the voltages across the terminals of the transistors of the first power switch do not exceed the maximum permitted voltage; and

setting the voltage at the second node to a second intermediate voltage when the second power switch is turned off, so that the voltages across the terminals of the transistors of the second power switch do not exceed the maximum permitted voltage.

15. The method of claim 14, characterized in that the first intermediate voltage is greater than or equal to the input voltage less the first maximum permitted voltage.

16. The method of claim 14, characterized in that the second intermediate voltage is less than or equal to the second maximum permitted voltage.

17. The method of claim 14, characterized in that the first intermediate voltage equals the input voltage less the second intermediate voltage.