CIRCUIT FOR FORCING TURNOFF OF THYRISTOR

• US 3,582,764 A
• Filed: 12/10/1968
• Issued: 06/01/1971
• Est. Priority Date: 12/13/1967
• Status: Expired due to Term

• Current Assignee: Erich Huber
• Original Assignee: Erich Huber
• Inventors: Huber, Erich
• Application Number:
  US04/782,634
• Time in Patent Office: 903 Days
• US Class Current: 323/351
• CPC Class Codes: H02M 1/06 Circuits specially adapted for rendering non-conductive gas discharge tubes or equivalent semiconductor devices, e.g. thyratrons, thyristors
• CPC Class Codes: H02P 7/29 using pulse modulation
• CPC Class Codes: H03K 17/72 having more than two PN junctions; having more than three electrodes; having more than one electrode connected to the same conductivity region

Abstract

A control circuit for extinguishing current flow in thyristors in which a capacitor discharges through a load current switching thyristor and compensates load current therein, and wherein the discharge current is augmented beyond the value available after an initial charge from the power supply subsequent to a turn off of load current flow, by providing additional energy, for example, from the load current and/or additional, appropriately timed sources other than the main voltage source directly but connected thereto.

Claims

1. A circuit for intermittent operation of an electric load circuit from a source supply voltage comprising:

first means including a thyristor for operatively connecting the load of the load circuit to the source to control current flow through the load, the thyristor having conductive and nonconductive states;

second means connected to control the thyristor to change from the nonconductive to the conductive state;

third means including a capacitor and switching means connected across the thyristor to control discharge of the capacitor through the thyristor when conductive to extinguish current flow therein and to render the thyristor nonconductive the discharge current reversing the charge on the capacitor;

fourth means connected to the capacitor and operating concurrently with operation of the second means to reverse the polarity of the charge on the capacitor through the conducting thyristor; and

fifth means connected to the load circuit and to the capacitor to augment the charge on the capacitor, for the capacitor to obtain a charge on the capacitor in excess of the charge as resulting from the supply voltage for the load.

2. A circuit as set forth in claim 1, the fifth means coupling the capacitor to the load circuit to provide to the capacitor a charging voltage in excess of the voltage of the source during onset of load current flow in the thyristor, there being additional circuit means for augmenting the charge on the capacitor further.

3. A circuit as set forth in claim 1, the fifth means including a first inductance in the load circuit and a second inductance connected in series with the capacitor and inductively coupled to the first inductance.

4. A circuit as set forth in claim 1, the fifth means including a voltage-to-voltage conversion means having its input connected to the load circuit to be controlled in phase opposition to the thyristor, and having its output connected to the capacitor to increase the charge on the voltage during the period of nonconduction of the thyristor.

5. A circuit as set forth in claim 1, the fifth means including a voltage-to-voltage conversion means connected to be controlled in synchronism with the thyristor to control the charging of the capacitor during period of conduction of the thyristor.

6. A circuit for inTermittent operation of an electric load circuit from a source supply voltage comprising:

first means including a thyristor for operatively connecting the load of the load circuit to the source to control current flow through the load, the thyristor having conductive and nonconductive states;

second means connected to control the thyristor to change from the nonconductive to the conductive state;

third means including a capacitor and switching means connected across the thyristor to control discharge of the capacitor through the thyristor when conductive to extinguish current flow therein and to render the thyristor nonconductive;

fourth means connected to the load circuit and providing a particular current pulse in response to the decaying load current as the current flow in the thyristor is being extinguished; and

fifth means connecting the fourth means to the capacitor to add the current pulse to the capacitor discharge through the thyristor to augment the discharge current beyond the value available by discharge of the capacitor alone.

7. In a circuit for forcing turnoff of load current flow in a first semiconductor element controllable for load current flow command by triggering through a control electrode, there being a capacitor connected to the first semiconductor element through a second semiconductor element for controlling current flow through the first element for extinguishing load current flow therein, there being a third controllable semiconductor element for control of the reversal of the charge on the capacitor obtained during current conduction through the second semiconductor element, the combination comprising:

first, second and third inductances respectively connected in series with the first, second and third semiconductor elements and magnetically coupled to each other for inducing auxiliary voltages in the second and third inductances respectively upon commencement and decay of the load current flow through the first inductance and the first semiconductor element, augmenting the respective current flow through the second and third inductances.

8. A circuit as set forth in claim 7, the inductances being coupled to each other through air gaps.

9. A circuit as set forth in claim 7, including circuit means controlled in phase opposition to the states of current conduction and nonconduction of the first semiconductor element for controlling charge of the capacitor during conduction phases of the first semiconductor element.

10. The circuit as set forth in claim 9, the circuit means being controllable by means of a control circuit connected through a Zener diode to the first semiconductor element for control of the circuit means in direct response to the current flow through the first semiconductor element.

11. The circuit as set forth in claim 7, including circuit means connected to the capacitor and connected to be operated in phase synchronism with current flow through the first semiconductor element for charging the capacitor to a voltage at least equal to the operating voltage effective in the load circuit.

12. A circuit for the control of current pulses through a load, using a semiconductor element of the thyristor type comprising:

a first inductance connected in the load circuit;

a series circuit including a capacitor, a second controllable semiconductor element and a second inductance, the series circuit being connected in parallel to the first semiconductor element to control capacitor discharge through the thyristor-type element for extinguishing load current therein and subsequently recharging the capacitor at opposite polarity, the first and second inductances being inductively coupled to each other to increase the capacitor discharge current during decay of load current through the first inductance and the first semiconductor element; and

means connected for producing polarity reversal of the charge on the capacitor after recharging thereof.

13. A circuit as set forth in claim 12, the means for producing charge reversal including means for augmenting the capacitor voltage beyond value obtainable by charge reversal alone.

14. A circuit as set forth in claim 12, including means operating at least during charge reversal to augment the capacitor charge.

15. A circuit as set forth in claim 14, the means to augment including means coupled to the load circuit to derive from the onsetting load current energy to be included as additional charge in the capacitor upon charge reversal.

16. A circuit as set forth in claim 14, the augmenting means including a voltage-to-voltage conversion means operated in synchronism with current conduction through the first semiconductor element.

17. A circuit for the control of current pulses through a load using a semiconductor element of the thyristor type, there being means to intermittently fire the thyristor, comprising:

a first inductance connected in the load circuit;

a capacitor having one electrode connected to the thyristor;

a controllable discharge circuit for the capacitor to force discharge current flow therefrom through the thyristor to compensate load current therein and to extinguish the load current flow; and

a recharge circuit for the capacitor, including a controllable semiconductor element and a second inductance coupled to the first inductance to provide a recharge voltage component in the response to load current increase after firing of thyristor and as effective in the first inductance.

18. A circuit as set forth in claim 17, wherein the discharge circuit operates to recharge the capacitor and the recharge circuit reverses the polarity of the charge, including means operated in response to current flow in the load circuit to augment the charge on the capacitor prior to charge reversal.

19. A circuit as set forth in claim 18, the means to augment being voltage-to-voltage conversion means operated in synchronism with a load current pause to additionally charge the capacitor prior to charge reversal.

20. A circuit as set forth in claim 17, the discharge circuit being coupled to the load circuit to augment the discharge current by drawing energy from the decaying load current.