POWER TRANSISTOR GATE DRIVER

• US 20140300413A1
• Filed: 06/13/2012
• Published: 10/09/2014
• Est. Priority Date: 06/14/2011
• Status: Active Grant

• Current Assignee: Infineon Technologies Austria Ag (Infineon Technologies AG)
• Original Assignee: Merus Audio ApS (Infineon Technologies AG)
• Inventors: Hyerby, Mikkel, Jakobsen, Jrgen Kragh
• Granted Patent: US 9,231,583 B2
• Time in Patent Office: Days
• US Class Current: 330/251
• 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 7/4837 Flying capacitor converters
• CPC Class Codes: H03F 3/2171 with field-effect devices H03F3/2173 - H03F3/2178 take precedence
• CPC Class Codes: H03F 3/2173 of the bridge type
• CPC Class Codes: H03K 17/063 in field-effect transistor switches
• CPC Class Codes: H03K 17/687 the devices being field-effect transistors
• CPC Class Codes: H03K 17/6871 the output circuit comprising more than one controlled field-effect transistor

Abstract

The present invention relates to a gate driver for a power transistor comprising a first charging path operatively connected between a first voltage supply and a gate terminal of the power transistor for charging the gate terminal to a first gate voltage. A second charging path is connectable between the gate terminal of the power transistor and a second supply voltage to charge the gate terminal from the first gate voltage to a second gate voltage larger or higher than the first gate voltage. A voltage of the second voltage supply is higher than a voltage of the first voltage supply.

Claims

1. A gate driver for a power transistor, comprising:

a first charging path electrically connectable between a first voltage supply and a gate terminal of the power transistor for charging the gate terminal to a first gate voltage; and

a second charging path electrically connectable between a second voltage supply and the gate terminal of the power transistor for charging the gate terminal from the first gate voltage to a second gate voltage larger than the first gate voltage,

wherein a voltage of the second voltage supply is higher than a voltage of the first voltage supply.

2. A gate driver according to claim 1, wherein the first voltage supply comprises a drain voltage of the power transistor.

3. A gate driver according to claim 1, comprising a voltage or charge pump adapted to generate the second voltage supply based on a DC supply voltage of the gate driver.

4. A gate driver according to claim 1, further comprising a controllable discharge path adapted to switch the power transistor to an OFF-state/non-conducting state, wherein the controllable discharge path is connectable between the gate terminal of the power transistor and a source terminal of the power transistor.

5. A gate driver according to claim 1, comprising a controller or sequencer adapted to control supply of charging current to the gate terminal through the first charging path and control supply of charging current to the gate terminal through the second charging path, and optionally, the OFF-state and ON-state of the controllable discharge path.

6. A gate driver according to claim 5, wherein the controller or sequencer is adapted to control the supply of charging currents to the gate terminal of the power transistor through the first and second charging paths by comparing the gate voltage of the power transistor with a predetermined threshold voltage.

7. A gate driver according to claim 6, wherein the controller or sequencer is adapted to derive the predetermined threshold voltage from a drain voltage of the power transistor electrically coupled to the first charging path.

8. A gate driver according to claim 5, wherein the controller or sequencer is adapted to:

supply charging current to the gate terminal of the power transistor through the first charging path for a predetermined charging time period such as a time period between 5 and 100 nanoseconds to reach the first gate voltage; and

subsequently supply charging current to the gate terminal of the power transistor through the second charging path for a predetermined time period.

9. A gate driver according to claim 5, wherein each of the first and second charging paths comprises a controllable series connected FET transistor controlled by the controller or sequencer.

10. A gate driver according to claim 6, wherein the controller or sequencer is adapted to disrupt the supply of charging current from the second voltage supply until the gate voltage reaches the first gate voltage.

11. A gate driver according to claim 1, wherein the voltage of the second voltage supply is at least one gate-to-source voltage drop of the power transistor higher than a voltage of the first voltage supply during a conducting state or ON-state of the power transistor.

12. A gate driver according to claim 1, wherein the voltage of the second voltage supply is at least 2 Volts higher than the voltage of the first voltage supply during a conducting state or ON-state of the power transistor.

13. A gate driver according to claim 1, wherein the first charging path is adapted to charge the gate terminal to the first gate voltage in less than 100 nanoseconds.

14. A gate driver according to claim 1, wherein the voltage level on the second voltage supply is at least 2.5 Volt higher than the voltage level on the first voltage supply at all times during operation of the gate driver.

15. A load driving assembly, comprising:

a plurality of gate drivers according to claim 1;

a plurality of power transistors each having a gate terminal electrically connected to a first node of the first charging path and to a first node of the second charging path of a gate driver;

a drain terminal of each power transistor being electrically coupled to a second node of the first charging path to provide the first supply voltage for the power transistor;

a plurality of assembly input terminals coupled to respective inputs of the plurality of gate drivers to supply modulated input signals thereto;

the plurality of power transistors being coupled in cascade with an upper leg formed between a first DC supply voltage and an output terminal and a lower leg formed between the output terminal and the second DC supply voltage; and

the output terminal being electrically coupled between the upper and lower legs.

16. A load driving assembly according to claim 15, further comprising:

a DC voltage source configured to set a predetermined DC voltage difference between a first node, situated between a pair of cascaded power transistors of the upper leg, and a second node, situated between a pair cascaded power transistors of the lower leg.

17. A load driving assembly according to claim 16, wherein the DC voltage sources comprises at least one device or component selected from a group consisting of a charged capacitor, a floating DC supply rail, and a battery.

18. A load driving assembly according to claim 17, wherein the DC voltage source comprises a charged capacitor with a capacitance between 100 nF and 10 μ

F.

19. A load driving assembly according to claim 17, wherein the predetermined DC voltage difference is substantially equal to one half of a DC voltage difference between the first and second DC supply voltages so as to enable the generation of a 3-level output signal at the output terminal.

20. A load driving assembly according to claim 15, adapted to operate at a DC voltage difference between 5 Volt and 120 Volt between the first and second DC supply voltages.

21. A load driving assembly according to claim 15, wherein the plurality of power transistors comprise at least one N-channel field effect transistor such as a NMOS or IGBT deposited on semiconductor substrate such as Silicon, Gallium Nitride or Silicon Carbide.

22. A load driving assembly according to claim 15, wherein the second voltage supplies of the plurality of gate drivers are electrically connected to a common charge pump capacitor of the second voltage supply.

23. A semiconductor substrate comprising a load driving assembly according to claim 15 coupled to an external charge pump capacitor.

24. A class D audio amplifier comprising:

a load driving assembly according to claim 15.