DEPLETION MOSFET DRIVER

• US 20140266321A1
• Filed: 06/26/2013
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Flextronics America LLC (Flextronics International Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Telefus, Mark
• Granted Patent: US 9,806,553 B2
• Time in Patent Office: Days
• US Class Current: 327/108
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A driver circuit is configured using a depletion-mode MOSFET to supply an output voltage across an output capacitor. The driver circuit includes a resistor positioned between two terminals of the MOSFET. In the case of an n-channel depletion-mode MOSFET, the resistor is coupled to the source and the gate. The circuit is a current controlled depletion driver that turns OFF the depletion-mode MOSFET by driving a reverse current through the resistor to establish a negative potential at the gate relative to the source. A Zener diode is coupled between the source of the depletion-mode MOSFET and the output capacitor to establish a voltage differential between the output and the MOSFET source.

Claims

1. A current driven depletion-mode MOSFET-based driver circuit comprising:

a. a depletion-mode MOSFET having a first terminal, a second terminal and a gate, wherein the first terminal is coupled to a power supply;

b. an output capacitor coupled to the second terminal of the depletion-mode MOSFET;

c. a transistor having a first terminal to receive a driving voltage, a second terminal and a third terminal coupled to ground, wherein the first terminal of the transistor is coupled to the output capacitor, and the second terminal of the transistor is coupled to the gate of the depletion-mode MOSFET; and

d. a resistor having a first terminal and a second terminal, wherein the first terminal of the resistor is coupled to the output capacitor and the second terminal of the depletion-mode MOSFET, and the second terminal of the resistor is coupled to the gate of the depletion-mode MOSFET and the second terminal of the transistor.

4. The driver circuit of claim 1 further comprising a voltage divider coupled between the output capacitor and the first terminal of the transistor.

5. The driver circuit of claim 4 wherein the voltage divider is configured to supply a turn ON voltage to a gate of the transistor when a voltage across the output capacitor is equal to or greater than a threshold voltage.

6. The driver circuit of claim 1 wherein when the transistor is turned ON, a reverse current flows through the resistor, thereby resulting in a negative voltage potential between the gate and the second terminal of the depletion-mode MOSFET which turns OFF the depletion-mode MOSFET.

7. The driver circuit of claim 6 wherein the reverse current flows from the output capacitor, through the resistor, and through the transistor.

8. The driver circuit of claim 6 wherein the reverse current flow results in the voltage across the output capacitor dropping, further wherein when the voltage across the output capacitor drops below a minimum value, the voltage supplied to the gate of the transistor drops below the turn ON voltage and the transistor turns OFF.

9. The driver of claim 8 wherein when the transistor turns OFF, the reverse current stops and the depletion-mode MOSFET turns ON.

10. The driver circuit of claim 1 further comprising a Zener diode having a cathode coupled to the second terminal of the depletion-mode MOSFET and an anode coupled to the output capacitor.

11. The driver circuit of claim 10 wherein the first terminal of the resistor is coupled to the cathode of the Zener diode and the second terminal of the depletion-mode MOSFET.

2. The driver circuit of claim 2 wherein the depletion-mode MOSFET is a N-channel MOSFET, and the first terminal of the resistor is coupled to a source of the depletion-mode MOSFET.

3. The driver circuit of claim 2 wherein the depletion-mode MOSFET is a P-channel MOSFET, and the first terminal of the resistor is coupled to a drain of the depletion-mode MOSFET.

12. A current driven depletion-mode MOSFET-based driver circuit comprising:

a. a depletion-mode MOSFET having a first terminal, a second terminal and a gate, wherein the first terminal is coupled to a power supply;

b. an output capacitor;

c. a Zener diode having a cathode coupled to the second terminal of the depletion mode MOSFET and an anode coupled to a first terminal of the output capacitor;

d. a voltage divider coupled to the first terminal of the output capacitor;

e. a transistor having a first terminal to receive a driving voltage, a second terminal and a third terminal coupled to ground, wherein the first terminal of the transistor is coupled to the voltage divider, and the second terminal of the transistor is coupled to the gate of the depletion-mode MOSFET; and

f. a resistor having a first terminal and a second terminal, wherein the first terminal of the resistor is coupled to the cathode of the Zener diode and the second terminal of the depletion-mode MOSFET, and the second terminal of the resistor is coupled to the gate of the depletion-mode MOSFET and the second terminal of the transistor.

13. A method of driving a depletion-mode MOSFET based driver circuit, the method comprising:

a. configuring a driver circuit including a depletion-mode MOSFET, an output capacitor, a transistor and a resistor, wherein the depletion-mode MOSFET comprises a first terminal coupled to a power supply, a second terminal coupled to the output capacitor and a gate, wherein the transistor comprises a gate coupled to the output capacitor, a first terminal coupled to the gate of the depletion-mode MOSFET and a second terminal coupled to ground, wherein the resistor comprises a first terminal coupled to the output capacitor and the second terminal of the depletion-mode MOSFET and a second terminal coupled to the gate of the depletion-mode MOSFET and the first terminal of the transistor; and

b. turning ON the transistor, thereby driving a reverse current through the resistor from the first terminal to the second terminal, resulting in a negative voltage potential between the gate of the depletion-mode MOSFET and the second terminal of the depletion-mode MOSFET which turns OFF the depletion-mode MOSFET.

14. The method of claim 13 wherein the reverse current flows from the output capacitor, through the resistor, and through the transistor.

15. The method of claim 14 wherein the reverse current flow results in the voltage across the output capacitor dropping, further wherein when the voltage across the output capacitor drops below a minimum value, the voltage supplied to the gate of the transistor drops below a turn ON voltage of the transistor and the transistor turns OFF.

16. The method of claim 15 wherein when the transistor turns OFF, the reverse current stops and the depletion-mode MOSFET turns ON.

17. The method of claim 13 further comprising supplying a turn ON voltage to the gate of the transistor when a voltage across the output capacitor is equal to or greater than a threshold voltage.