DC-DC Converter that Includes a High Frequency Power MESFET Gate Drive Circuit

• US 20080203991A1
• Filed: 02/18/2008
• Published: 08/28/2008
• Est. Priority Date: 01/26/2006
• Status: Abandoned Application

• Current Assignee: Advanced Analogic Technologies Incorporated (Skyworks Solutions Incorporated)
• Original Assignee: Advanced Analogic Technologies Incorporated (Skyworks Solutions Incorporated)
• Inventors: Williams, Richard K.
• Application Number:
  US12/032,939
• Publication Number:
  US 20080203991A1
• Time in Patent Office: Days
• US Class Current: 323/288
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H03K 17/08122 in field-effect transistor switches

Abstract

A DC-DC converter that includes a high frequency power MESFET gate drive circuit is provided. The gate drive circuits are intended to be used in switching regulators where at least one switching device is an N-channel MESFET. For regulators of this type, the gate drive circuits provide gate drive at the correct voltage to ensure that MESFETs are neither under driven (resulting in incorrect circuit operation) nor over driven (resulting in MESFET damage or excess current or power loss).

Claims

1. A DC-to-DC converter comprising series-connected low-side and high-side MESFETs where:

the low-side MESFET is powered by a low-side gate drive circuit that limits the maximum forward biasing of the Schottky gate intrinsic to the low side MESFET to a maximum voltage or maximum current;

where the low-side gate drive circuit is ground referenced;

the low-side gate drive circuit is powered from the battery; and

where

the high-side MESFET is powered by a floating gate drive circuit that limits the maximum forward biasing of the Schottky gate intrinsic to the high side MESFET to a maximum voltage or maximum current;

where

the high-side gate drive circuit is referenced to the source of the high-side MESFET and to the drain of the low-side MESFET;

the high-side gate drive circuit is powered from a bootstrap capacitor charged through a bootstrap diode.

2. A circuit as recited in claim 1 where the bootstrap capacitor is charged to a voltage less than the battery voltage.

3. A DC-to-DC converter as recited in claim 1 where the floating gate drive circuit limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a voltage where no substantial DC conduction current flows.

4. A DC-to-DC converter as recited in claim 1 where the floating gate drive circuit limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a voltage less than the voltage powering the gate drive circuit

5. A DC-to-DC converter as recited in claim 1 where the floating gate drive circuit limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a maximum voltage provided by a switched capacitor network and a LDO regulator.

6. A DC-to-DC converter as recited in claim 1 where the floating gate drive circuit comprises:

a bootstrap capacitor;

a bootstrap diode with its anode connected to an input voltage and with its cathode connected to the positive terminal of the bootstrap capacitor; and

a floating gate buffer driving the gate of the MESFET where the floating gate buffer is powered by the bootstrap capacitor and shares a common electrical node with the MESFET and the negative terminal of the bootstrap capacitor;

where the gate buffer limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a maximum gate to source voltage.

7. A DC-to-DC converter as recited in claim 1 where the floating gate drive circuit comprises:

a bootstrap capacitor;

a bootstrap diode with its anode connected to an input voltage and with its cathode connected to the positive terminal of the bootstrap capacitor; and

a floating gate buffer driving the gate of the MESFET where the floating gate buffer is powered by the bootstrap capacitor and shares a common electrical node with the MESFET and negative terminal of the bootstrap capacitor;

where the gate buffer limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a maximum gate to a maximum current.

8. A DC-to-DC converter as recited in claim 1 where the MESFET is a normally off type.

9. A DC-to-DC converter as recited in claim 1 where the MESFET comprises GaAs.

10. A DC-to-DC converter comprising series-connected low-side and floating MESFETs where:

the low-side MESFET is powered by a low-side gate drive circuit that limits the maximum forward biasing of the Schottky gate intrinsic to the low-side MESFET to a maximum voltage or maximum current;

where

the low-side gate drive circuit is ground referenced;

the low-side gate drive circuit is powered from the battery; and

where

the floating-side MESFET is powered by a floating gate drive circuit that limits the maximum forward biasing of the Schottky gate intrinsic to the floating-side MESFET to a maximum voltage or maximum current;

where

the floating gate drive circuit is referenced to the source of the floating-side MESFET whenever the floating-side MESFET is on;

the floating gate drive circuit is powered from a bootstrap capacitor charged through a bootstrap diode; and

the floating drive circuit and bootstrap capacitor are referenced to ground whenever the floating side MESFET is not on.

11. A circuit as recited in claim 10 where the bootstrap capacitor is charged to a voltage less than the battery voltage.

12. A DC-to-DC converter as recited in claim 10 where the floating gate drive circuit limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a voltage where no substantial DC conduction current flows.

13. A DC-to-DC converter as recited in claim 10 where the floating gate drive circuit limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a voltage less than the voltage powering the gate drive circuit

14. A DC-to-DC converter as recited in claim 10 where the floating gate drive circuit limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a maximum voltage provided by a switched capacitor network and a LDO regulator.

15. A DC-to-DC converter as recited in claim 10 where the floating gate drive circuit comprises:

a bootstrap capacitor;

a bootstrap diode with its anode connected to an input voltage and with its cathode connected to the positive terminal of the bootstrap capacitor; and

a floating gate buffer driving the gate of the MESFET where the floating gate buffer is powered by the bootstrap capacitor and shares a common electrical node with the MESFET and the negative terminal of the bootstrap capacitor;

where the gate buffer limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a maximum gate to source voltage.

16. A DC-to-DC converter as recited in claim 10 where the floating gate drive circuit comprises:

a bootstrap capacitor;

a bootstrap diode with its anode connected to an input voltage and with its cathode connected to the positive terminal of the bootstrap capacitor; and

a floating gate buffer driving the gate of the MESFET where the floating gate buffer is powered by the bootstrap capacitor and shares a common electrical node with the MESFET and negative terminal of the bootstrap capacitor;

where the gate buffer limits the maximum forward biasing of the Schottky gate intrinsic to the MESFET to a maximum gate to a maximum current.

17. A DC-to-DC converter as recited in claim 10 where the MESFET is a normally off type.

18. A DC-to-DC converter as recited in claim 10 where the MESFET comprises GaAs.