Capacitive load driving device

• US 4,733,106 A
• Filed: 04/01/1985
• Issued: 03/22/1988
• Est. Priority Date: 03/30/1984
• Status: Expired due to Term

• Current Assignee: Hitachi Engineering Co.,Ltd (Hitachi, Ltd.), Hitachi, Ltd.
• Original Assignee: Hitachi Engineering Co.,Ltd (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Kariya, Tadaaki, Okutsu, Mitsuhiko, Shimura, Tatsuo
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Davis, B. P.
• Application Number:
  US06/718,283
• Time in Patent Office: 1,086 Days
• Field of Search: 307/246, 307/252 B, 307/270, 328/67, 330/255, 330/262
• US Class Current: 327/111
• CPC Class Codes: H03K 17/0403 in thyristor switches
• CPC Class Codes: H03K 17/732 Measures for enabling turn-off

Abstract

A device for driving a capacitive load, comprising a first switching element responsive to an external control signal for selectively conducting a charge current therethrough to the load, a second switching element responsive to the external control signal for conducting a discharge current from the load and a generator for generating from the discharge current a cutoff signal to be applied to the first switching element to ensure turn-off of the latter.

Claims

1. A device for driving a capacitive load in response to an external control signal, comprising:

charging circuit means being connectable with the capacitive load for charging the latter and including a switching element, said switching element being arranged to be rendered electrically conductive to supply a charge current to the capacitive load when the device receives said control signal; and

discharging circuit means connectable with the capacitive load for discharging the latter with a discharge current passing therethrough when said control signal ceases, said discharging circuit means including means for generating a cutoff signal from said discharge current and applying the cutoff signal to said switching element to ensure turn-off of said switching element, in which said switching element is constituted by a unidirectional tetrode thyristor having an anode connectable with a power source, a cathode connectable with the capacitive load, a first gate for receiving said control signal and a second gate, and said cutoff signal generating means is constituted by a diode having its anode connected with the cathode of said thyristor and its cathode connected with said second gate.

2. A device according to claim 1, in which said discharging circuit means further includes a switch connected with the cathode of said diode and operable to be electrically non-conductive when said control signal exists and electrically conductive when said control signal ceases.

3. A device according to claim 2, in which said switch is constituted by a transistor.

4. A device according to claim 2, in which said switch is constituted by a unidirectional tetrode thyristor.

5. A switching circuit for a capacitive load, comprising:

a thyristor having a gate, and a cathode, responsive to an external control signal to selectively conduct a charge current to the capacitive load;

a switch responsive to said external control signal to conduct a discharge current from the capacitive load; and

means connected with said thyristor and passing therethrough said condcuted discharge current to generate therefrom a cutoff signal to be applied to said thyristor to ensure turn-off of the latter.

10. A device according to claim 5, in which said cutoff signal generating means is constituted by a diode having its anode connected with the cathode of said thyristor and its cathode connected with said gate of said thyristor, and said discharging means further includes a switch connected with the cathode of said diode and operable to be electrically non-conductive when said control signal exists and electrically conductive when said control signal ceases.

11. A device according to claim 10, in which said switch is constituted by a transistor.

12. A device according to claim 10, in which said switch is constituted by a second unidirectional thyristor.

13. A device according to claim 5, further comprising means for selectively applying said external control signal to said gate of said thyristor for a charging operation and to said switch for a discharging operation.

6. A device for driving a capacitive load in response to an external control signal, comprising:

charging circuit means being connectable with the capacitive load for charging the latter and including a switching element, said switching element being arranged to be rendered electrically conductive to supply a charge current to the capacitive load when the device receives said control signal; and

discharging circuit means connectable with the capacitive load for discharging the latter with a discharge current passing therethrough when said control signal ceases, said discharging circuit means including means for generating a cutoff signal from said discharge current and applying the cutoff signal to said switching element to ensure turn-off of said switching element, in which said switching element is constituted by a unidirectional tetrode thyristor having a cathode connectable with a power source, an anode connectable with the capacitive load, a first gate and a second gate for receiving said control signal, and said cutoff signal generating means is constituted by a diode having its anode connected with the first gate of said thyristor and its cathode connected with the anode of said thyristor.

7. A device according to claim 6, in which said discharging circuit means further includes a switch connected with the anode of said diode and operable to be electrically non-conductive when said control signal exists and electrically conductive when said control signal ceases.

8. A device according to claim 7, in which said switch is constituted by a transistor.

9. A device according to claim 7, in which said switch is constituted by a unidirectional tetrode thyristor.