Driver circuit

• US 9,742,388 B2
• Filed: 02/17/2015
• Issued: 08/22/2017
• Est. Priority Date: 05/28/2014
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kihara, Seiichiro
• Primary Examiner(s): Hernandez, William
• Application Number:
  US15/127,979
• Publication Number:
  US 20170093389A1
• Time in Patent Office: 917 Days
• Field of Search: 326 82, 326 83, 327108
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 13/4072 Drivers or receivers G06F13/4086 takes precedence; for multistate logic circuits H03K19/0002
• CPC Class Codes: G06F 13/4081 Live connection to bus, e.g. hot-plugging current or voltage limitation during live insertion H02H9/004
• CPC Class Codes: H03K 17/0406 in composite switches
• CPC Class Codes: H03K 17/063 in field-effect transistor switches
• CPC Class Codes: H03K 17/08122 in field-effect transistor switches
• CPC Class Codes: H03K 17/08128 in composite switches
• CPC Class Codes: H03K 17/162 without feedback from the output circuit to the control circuit
• CPC Class Codes: H03K 2217/0081 Power supply means, e.g. to the switch driver
• CPC Class Codes: H03K 3/014 Modifications of generator to ensure starting of oscillations

Abstract

A driver circuit includes normally-on transistors (Q1, Q2), control circuits (1, 2) that control the transistors (Q1, Q2), a capacitor (4) connected between power source nodes (1c, 1d) of the control circuit (1), a power source (7) connected between power source nodes (2c, 2d) of the control circuit (2), a MOSFET (16) connected between the power source nodes (1d, 2d), a control circuit (3) that turns on the MOSFET (16) when an output voltage VO reaches approximately 0 V, and a startup circuit that includes a Zener diode (20) connected in parallel to the capacitor (4) and that can charge the capacitor (4) with a Zener voltage even when the MOSFET (16) is off.

Claims

1. A driver circuit, comprising:

a first transistor connected between a line of a first voltage and an output terminal;

a second transistor connected between the output terminal and a line of a second voltage lower than the first voltage;

a first control circuit having first and second power source nodes and configured to provide a voltage of the first power source node to a control electrode of the first transistor in response to an input signal being set to a first logic level so as to turn on the first transistor and to provide a voltage of the second power source node to the control electrode of the first transistor in response to the input signal being set to a second logic level so as to turn off the first transistor; and

a second control circuit having third and fourth power source nodes and configured to provide a voltage of the fourth power source node to a control electrode of the second transistor in response to the input signal being set to the first logic level so as to turn off the second transistor and to provide a voltage of the third power source node to the control electrode of the second transistor in response to the input signal being set to the second logic level so as to turn on the second transistor,

wherein each of the first and second transistors is a normally-on transistor,

wherein the first power source node is connected to the output terminal,

wherein the third power source node receives the second voltage,

wherein the fourth power source node receives a third voltage lower than the second voltage, and

wherein the driver circuit further includes

a capacitor connected between the first and second power source nodes,

a switching element connected between the second and fourth power source nodes,

a third control circuit configured to turn on the switching element so as to charge the capacitor in response to a voltage corresponding to a difference between a voltage of the output terminal and the second voltage falling below a preset voltage, and

a startup circuit having a voltage generating component connected between the first and second power source nodes and a current passing component connected between the second and third power source nodes and capable of charging the capacitor on the basis of a generated voltage of the voltage generating component even when the switching element is off by causing a current that is based on a voltage across the first and third power source nodes to pass through the voltage generating component and the current passing component.

2. The driver circuit according to claim 1,

wherein the voltage generating component includes

a Zener diode having a cathode and an anode connected to the first and second power source nodes, respectively, or

a series circuit of a plurality of diodes connected between the first and second power source nodes with a direction from the first power source node to the second power source node being a forward direction.

3. The driver circuit according to claim 2,

wherein the current passing component includes a resistance element connected between the second and third power source nodes.

4. The driver circuit according to claim 2,

wherein the current passing component includes a series circuit of a resistance element and a starting switching element, and

wherein the series circuit is connected between the second and third power source nodes.

5. The driver circuit according to claim 2,

wherein the third control circuit turns on the switching element when the voltage corresponding to the difference between the voltage of the output terminal and the second voltage falls below the preset voltage and the input signal is at the second logic level.

6. The driver circuit according to claim 2,

wherein each normally-on transistor is an n-channel FET formed by a wide band gap semiconductor.

7. The driver circuit according to claim 1,

wherein the voltage generating component includes a voltage generating resistance element connected between the first and second power source nodes.

8. The driver circuit according to claim 7,

wherein the current passing component includes a resistance element connected between the second and third power source nodes.

9. The driver circuit according to claim 7,

wherein the current passing component includes a series circuit of a resistance element and a starting switching element, and

wherein the series circuit is connected between the second and third power source nodes.

10. The driver circuit according to claim 7,

wherein the third control circuit turns on the switching element when the voltage corresponding to the difference between the voltage of the output terminal and the second voltage falls below the preset voltage and the input signal is at the second logic level.

11. The driver circuit according to claim 7,

wherein each normally-on transistor is an n-channel FET formed by a wide band gap semiconductor.

12. The driver circuit according to claim 1,

wherein the current passing component includes a resistance element connected between the second and third power source nodes.

13. The driver circuit according to claim 12,

wherein the third control circuit turns on the switching element when the voltage corresponding to the difference between the voltage of the output terminal and the second voltage falls below the preset voltage and the input signal is at the second logic level.

14. The driver circuit according to claim 1,

wherein the current passing component includes a series circuit of a resistance element and a starting switching element, and

wherein the series circuit is connected between the second and third power source nodes.

15. The driver circuit according to claim 14,

wherein the starting switching element is a normally-on transistor that is turned on/off on the basis of a voltage across a positive electrode and a negative electrode of a power source that is to generate the third voltage, and the starting switching element is turned on before the power source is started and is turned off after the power source is started.

16. The driver circuit according to claim 15,

wherein the third control circuit turns on the switching element when the voltage corresponding to the difference between the voltage of the output terminal and the second voltage falls below the preset voltage and the input signal is at the second logic level.

17. The driver circuit according to claim 14,

wherein the third control circuit turns on the switching element when the voltage corresponding to the difference between the voltage of the output terminal and the second voltage falls below the preset voltage and the input signal is at the second logic level.

18. The driver circuit according to claim 1,

wherein the third control circuit turns on the switching element when the voltage corresponding to the difference between the voltage of the output terminal and the second voltage falls below the preset voltage and the input signal is at the second logic level.

19. The driver circuit according to claim 1,

wherein each normally-on transistor is an n-channel FET formed by a wide band gap semiconductor.

20. The driver circuit according to claim 1,

wherein the switching element is an n-channel MOSFET.