CIRCUIT SYSTEM AND METHOD FOR ENERGIZING AND DISCHARGING A COIL

Abstract

A circuit includes a rectifier, e.g., including four diodes; a semiconductor switch; a coil that is chargeable, is dischargeable, and has (a) a first terminal connected to a first output terminal of the rectifier and (b) a second terminal connected via the semiconductor switch to a second output terminal of the rectifier; a first resistor via which a control terminal of the semiconductor switch is connected to the first output terminal of the rectifier; a second resistor connected between the second output terminal of the rectifier and the control terminal of the semiconductor switch; and a discharge unit connected between the second terminal of the coil and the control terminal of the semiconductor switch. The charging and discharging is implemented by, respectively, connecting both of, and disconnecting one or both of, first and second input terminals of the rectifier to/from the voltage source.

Claims

1-12. (canceled)

13. A circuit comprising: a rectifier that is connectable via a first input terminal and a second input terminal to an AC voltage source; a semiconductor switch; a coil that is chargeable, is dischargeable, and has (a) a first terminal connected to a first output terminal of the rectifier and (b) a second terminal connected via the semiconductor switch to a second output terminal of the rectifier; a first resistor via which a control terminal of the semiconductor switch is connected to the first output terminal of the rectifier; a second resistor connected between the second output terminal of the rectifier and the control terminal of the semiconductor switch; and a discharge unit connected between the second terminal of the coil and the control terminal of the semiconductor switch.

14. The circuit of claim 13, wherein the discharge unit includes at least one first Zener diode having an inverse direction from the second terminal of the coil in a direction of the control terminal of the semiconductor switch.

15. The circuit of claim 14, wherein a breakdown voltage of the at least one first Zener diode is lower than a predefined voltage that drops across the semiconductor switch.

16. The circuit of claim 13, wherein the discharge unit includes at least one third resistor.

17. The circuit of claim 13, wherein the discharge unit includes a series connection of a third resistor and a diode having a conducting direction from the second terminal of the coil in a direction of the control terminal of the semiconductor switch, the circuit further comprsing a fourth resistor connected between (a) a terminal situated between the third resistor and the diode and (b) the second output terminal of the rectifier.

18. The circuit of claim 13, further comprising a capacitor connected between the second output terminal of the rectifier and the control terminal of the semiconductor switch.

19. The circuit of claim 13, further comprising a Zener diode connected in a conducting direction between the second output terminal of the rectifier and the control terminal of the semiconductor switch.

20. The circuit of claim 13, wherein the semiconductor switch is a MOSFET.

21. The circuit of claim 13, wherein the first output terminal of the rectifier is a positive terminal, and the second output terminal of the rectifier is a negative terminal.

22. The circuit of claim 13, wherein the first output terminal of the rectifier is a negative terminal and the second output terminal of the rectifier is a positive terminal.

23. The circuit of claim 13, wherein the coil is part of a solenoid valve.

24. A method for a circuit that includes a rectifier, a semiconductor switch, a coil that has (a) a first terminal connected to a first output terminal of the rectifier and (b) a second terminal connected via the semiconductor switch to a second output terminal of the rectifier, a first resistor via which a control terminal of the semiconductor switch is connected to the first output terminal of the rectifier, a second resistor connected between the second output terminal of the rectifier and the control terminal of the semiconductor switch, and a discharge unit connected between the second terminal of the coil and the control terminal of the semiconductor switch, the method comprising: energizing the coil by connecting the rectifier via first and second input terminals of the rectifier to an AC voltage source; and discharging the coil by disconnecting one or both of the first and second input terminals of the rectfier from the AC voltage source.

25. The method of claim 24, wherein the energixing and discharging are carried out during an operation of a solenoid valve of which the coil is a part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 schematically shows a circuit system according to an example embodiment of the present invention.

[0021] FIG. 2 schematically shows a circuit system according to another example embodiment of the present invention.

[0022] FIG. 3 schematically shows a circuit system according to another example embodiment of the present invention.

[0023] FIG. 4 schematically shows a current curve when using a method according to an example embodiment of the present invention compared to a method not according to the present invention.

DETAILED DESCRIPTION

[0024] FIG. 1 schematically shows a circuit system according to an example embodiment of the present invention. Circuit system 100 includes a rectifier 110, which is connectable, and also connected here, to an AC voltage source 120 via a first input terminal 111 and a second input terminal 112. The AC voltage source can be disconnected from rectifier 110 here by way of example using a switch element 121. AC voltage source 120 can provide a voltage of 230 V, for example.

[0025] Rectifier 110 includes four diodes D1, D2, D3 and D4 arranged, by way of example, in such a way that a positive voltage is always present on a first output terminal 115 of rectifier 110, whereas a negative voltage is always present on a second output terminal 116 of rectifier 110.

[0026] Furthermore, circuit system 100 includes a coil 140, which is connected via a first terminal 141 to first output terminal 115 of rectifier 110. Coil 140 is connected via a second terminal 142 to a semiconductor switch 150, and semiconductor switch 150 is connected to second output terminal 116 of rectifier 110. In other words, second terminal 142 of coil 140 is connected via semiconductor switch 150 to second output terminal 116 of rectifier 110.

[0027] Semiconductor switch 150 is, for example, an enhancement-type N-channel MOSFET including a control terminal 153 designed as a gate terminal. Control terminal 153 of semiconductor switch 150 is connected via a first resistor R1 to first output terminal 115 of rectifier 110.

[0028] Furthermore, circuit system 100 includes a second resistor R2, a second Zener diode Z2, and a capacitor C, each of which is connected to second output terminal 116 of rectifier 110 and to control terminal 153 of semiconductor switch 150. As a result, these components are also connected in parallel among one another. Second Zener diode Z2 is connected in such a way that the conducting direction is present from second output terminal 116 of rectifier 110 in the direction of control terminal 153 of semiconductor switch 150. Accordingly, the situation is converse with the inverse direction of second Zener diode Z2.

[0029] Furthermore, a discharge unit 130 is connected between second terminal 142 of coil 140 and control terminal 153 of semiconductor switch 150. In the illustrated example embodiment, discharge unit 130 includes four first Zener diodes Z11, Z12, Z13 and Z14 connected in series, and a resistor R6 furthermore connected in series thereto. An inverse direction of the first Zener diodes is present from second terminal 142 of coil 140 in the direction of control terminal 153 of semiconductor switch 150.

[0030] If circuit system 100 is now used to energize coil 140, switch 121 can be closed. Via first output terminal 115 of rectifier 110, a voltage is applied to control terminal 153 of semiconductor switch 150 or between control terminal 153 and a source terminal of semiconductor switch 150, which is the rectifier-side terminal of semiconductor switch 150. In this way, semiconductor switch 150 becomes conducting, and current is able to flow through coil 140.

[0031] Capacitor C ensures that a voltage is continuously present at control terminal 153, since the voltage provided at first output terminal 115 of rectifier 110 is generally only present in the form of positive sine half waves. Second Zener diode Z2, in contrast, ensures a voltage limitation at control terminal 153. The breakdown voltage of second Zener diode Z2 can be 10 V for this purpose, for example.

[0032] If AC voltage source 120 is disconnected from rectifier 110 by opening of switch element 121, capacitor C initially discharges via second resistor R2. Semiconductor switch 150 thus becomes high-resistance, and an induction voltage at the drain terminal of semiconductor switch 150, which is the coil-side terminal of semiconductor switch 150 here, immediately begins to rise steeply.

[0033] As soon as this voltage reaches a value which is higher than the breakdown voltage of the four first Zener diodes Z11, Z12, Z13 and Z14 and the threshold voltage of the semiconductor switch, control terminal 153 of semiconductor switch 150 is supplied with voltage. The semiconductor switch thus becomes conductive again, and the voltage dropping across the semiconductor switch, i.e., the source-drain voltage, adjusts to the value of the breakdown voltage of the first Zener diodes. With it, an extinction current flows through the semiconductor switch.

[0034] This voltage should be set in such a way that a predefined or permissible source-drain voltage is not exceeded. The value can be 400 V, for example, when a 500 V MOSFET is used as the semiconductor switch. The chain of the first Zener diodes can also be replaced with a single Zener diode. However, in general a series connection made up of multiple 100 V Zener diodes is more cost-effective.

[0035] As was already mentioned at the outset, the polarity of circuit system 100, and in particular of rectifier 110, can also be reversed, for example then using a P-channel MOSFET as semiconductor switch 150 and with appropriate adaptation of the remaining components.

[0036] FIG. 2 schematically shows a circuit system according to another example embodiment of the present invention. Circuit system 200 essentially corresponds to circuit system 100, so that reference is made to the description there for this purpose. Identical elements are denoted by identical reference numerals. In contrast to circuit system 100, however, a different discharge unit 230, which includes a third resistor R3 here, is provided in circuit system 200. Third resistor R3 can have a value of several M; for example, 3.3 M is conceivable. The values of first and second resistors R1 and R2 can then be 220 k and 50 k, for example. The voltage at control terminal 153 is now determined here by the ratio of the values of third and second resistors R3 and R2.

[0037] FIG. 3 schematically shows a circuit system according to another example embodiment of the present invention. Circuit system 300 essentially corresponds to circuit system 100, so that reference is made to the description there for this purpose. Identical elements are denoted by identical reference numerals. In contrast to circuit system 100, however, a different discharge unit 330, which includes a fourth resistor R4 and a diode D5 here, is provided in circuit system 300. A conducting direction of diode D5 is present from second terminal 142 of coil 140 in the direction of control terminal 153 of semiconductor switch 150.

[0038] Moreover, a fifth resistor R5 is provided, which is connected between a terminal 331 situated between fourth resistor R4 and diode D5 and second output terminal 116 of rectifier 110. By using diode D5, the voltage divider made up of fifth and fourth resistor R5 and R4 now becomes lower resistance, while a voltage, however, is provided at control terminal 153 during the discharging of the coil.

[0039] FIG. 4 schematically shows a current curve when using a method according to the present invention in an example embodiment compared to a method not according to the present invention. For this purpose, a current I is plotted against time t.

[0040] Initially, a start of the energization of the coil is apparent here. The current rises slowly. During the energization, the current then remains constant, at least on average.

[0041] Furthermore, a discharge is shown. I.sub.1 shows a curve as it occurs without the use of a circuit system according to the present invention when the coil is only being discharged via two diodes of the rectifier. The current decreases comparatively slowly here.

[0042] I.sub.2 shows a curve when using one of the circuit systems, for example, as they were described with respect to FIGS. 1-3. It is apparent here that the current drops considerably more quickly due to the corresponding circuit system, since it is not limited by the maximum voltage drop across the diodes of the rectifier. The illustration of curve I.sub.2 is schematic, and the actual curve cvary, depending on the specific configuration of the circuit system.