Solenoid Drive Circuit

Abstract

To provide a solenoid drive circuit that can increase the responsiveness and speed of the solenoid while minimizing as much as possible the increase in manufacturing costs and the enlargement of housings and boards.SOLUTION: Since a capacitor 25 is provided in a solenoid drive circuit 10 to supply power from a drive power supply 20 and discharge current from the capacitor 25 simultaneously, the voltage rises much faster and the amount of current supplied increases until the discharge from the capacitor 25 is completed, compared to when power is supplied only from the drive power supply 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a solenoid drive circuit, and more particularly to a solenoid drive circuit capable of improving the responsiveness and high speed of a solenoid. [Background technology]

[0002] In solenoids, various solenoid drive circuits have been invented with the objectives of shortening the time until the plunger starts to operate and increasing the initial speed of the plunger operation. Figure 6 is a circuit diagram of a solenoid drive circuit according to the prior art. In Figure 6, 51 is a DC power supply, 52 is a transistor, 53 is a transistor, 54 is a current limiting resistor, 55 is a solenoid valve, 55a is a solenoid coil, 56 is a boost chopper circuit, 57 is a reactor, 58 is a diode, 59 is a capacitor, 60 is a chopper NPN transistor, and 61 is a reverse current blocking diode.

[0003] Fig. 6 shows a drive circuit for a solenoid incorporated in a solenoid valve, which is disclosed in Japanese Patent Laid-Open Publication No. 6-026589. As shown in Fig. 3, this solenoid drive circuit is configured such that the DC voltage of a DC power supply 51 is boosted by a boost chopper circuit 56, and the boosted voltage is supplied as a pull-up voltage to a solenoid valve 55 via a transistor 52, which is a switching element for pulling up the solenoid valve. The boost chopper circuit 56 is composed of a reactor 57, a diode 58, a capacitor 59, and a chopper NPN transistor 60. The reverse current blocking diode 61 prevents the generation of a high voltage due to the counter electromotive force of a solenoid coil 55a provided in the solenoid valve 55.

[0004] When the transistors 52 and 53 are turned on, the voltage is boosted by the boost chopper circuit 56 and the voltage charged in the capacitor 59 is applied to the solenoid coil 55a of the solenoid valve 55 via the transistor 52. Therefore, in response to the voltage boosted by the boost chopper circuit 56, it is possible to shorten the time until the plunger of the solenoid valve 55 starts to operate and to increase the initial speed of the plunger operation.

[0005] However, when the circuit configuration described above is adopted, the boost chopper circuit 56 must be newly provided, which increases the manufacturing cost and requires additional space to accommodate the boost chopper circuit 56. In particular, the reactor 57 has a relatively large capacity, and the housing or board in which the reactor 57 is provided must be large, which in itself increases the manufacturing cost. Furthermore, it is surprisingly difficult to turn on a bipolar transistor accurately, and it can be said that bipolar transistors are not very suitable for applications that require a fast response. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 6-026589 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to solve the above-mentioned problems, the present invention aims to provide a solenoid drive circuit that can improve the responsiveness and high speed of a solenoid while minimizing increases in manufacturing costs and increases in the size of the housing and board. [Means for solving the problem]

[0008] The invention described in claim 1 relates to a solenoid coil provided in a solenoid, a driving power supply having a positive terminal connected to one end of the solenoid coil and a negative terminal connected to the other end of the solenoid coil and supplying a current to the solenoid coil, a capacitor having a negative terminal connected to the other end of the solenoid coil and a positive terminal connected to the negative terminal of the driving power supply and provided in series with the solenoid coil, a charging power supply having a positive terminal connected to the positive terminal of the capacitor and a negative terminal connected to the negative terminal of the capacitor and supplying a current to the capacitor, and a switch element provided between the positive terminal of the driving power supply and the one end of the solenoid coil, a first diode having one terminal connected to the other end of the solenoid coil and the other terminal connected to the negative side of the charging power supply and the positive side of the charging power supply, and arranged in a forward direction with respect to the direction of the output current of the driving power supply, the negative side of the driving power supply, the positive side of the charging power supply, the positive terminal of the capacitor, and the other terminal of the first diode are grounded, and when the switch element is off, the capacitor is charged by the charging power supply, and when the switch element is on, the sum of the output voltage of the driving power supply and the charging voltage of the capacitor is applied to the solenoid coil.

[0009] The invention described in claim 2 is a solenoid drive circuit according to the invention described in claim 1, further comprising a second diode arranged in parallel with the solenoid coil, one terminal of which is connected to the positive side of the drive power supply and the other terminal of which is connected to the negative terminal of the capacitor, the negative side of the drive power supply, and the positive side of the charging power supply, and is arranged in the opposite direction to the direction of the output current of the drive power supply. Effect of the Invention

[0010] According to the invention described in claim 1, the capacitor is charged in advance by the charging power source, and by turning on the switch element, the voltages of both the driving power source and the capacitor are applied to the solenoid coil, so that the time until the plunger of the solenoid starts to operate can be shortened and the initial speed of the plunger can be increased. Furthermore, since the charging power source can be made to continuously charge the capacitor, the solenoid can be repeatedly operated in a relatively short time. In addition, although it is necessary to add a charging power source, a capacitor, and a first diode to a general solenoid driving circuit, the charging power source can be various primary or secondary batteries, or a direct current supplied from the power circuit of the device in which the solenoid is mounted can be used as the charging power source, and the mounting area of ​​the capacitor, the first diode, and the third diode is extremely small, so that the housing and the board do not become large. In addition, since it is composed of only inexpensive batteries and circuit elements, the increase in manufacturing cost is also extremely small.

[0011] According to the invention as recited in claim 2, it is possible to prevent the generation of high voltage due to the counter electromotive force of the solenoid coil. [Brief description of the drawings]

[0012] [Figure 1] 1 is a circuit diagram of a solenoid drive circuit according to an embodiment of the present invention. [Diagram 2] 4 is a circuit diagram showing a charging state of a capacitor in the solenoid drive circuit according to the embodiment of the present invention. FIG. [Diagram 3] 1 is a circuit diagram (1) showing a state in which current is applied to a solenoid coil of a solenoid drive circuit according to an embodiment of the present invention. FIG. [Figure 4] 4 is a circuit diagram (2) showing a state in which current is applied to a solenoid coil of the solenoid drive circuit according to the embodiment of the present invention. FIG. [Diagram 5] 5 is a graph showing characteristics of a solenoid drive circuit according to an embodiment of the present invention when current is applied; [Figure 6] FIG. 1 is a circuit diagram of a solenoid drive circuit according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The solenoid drive circuit according to the embodiment of the present invention can be applied to various solenoids, but is particularly suitable for solenoids that require extremely high response or high speed, such as vehicle solenoid valves. The solenoid drive circuit according to the embodiment of the present invention will be described below. FIG. 1 is a circuit diagram of the solenoid drive circuit according to the embodiment of the present invention. In FIG. 1, 10 is a solenoid drive circuit, 20 is a drive power source, 21 is a charging power source, 22 is a solenoid coil, 23 is a second diode, 24 is a switch element, 25 is a capacitor, 26 is a first diode, 27 is a ground point, 28 is a first resistor, 29 is a FET driver, 30 is an electrical component of the solenoid, and 31 is an initial drive acceleration unit. In the claims and specification of the present application, the term "one terminal" or "one end" refers to the side closer to the positive electrode of the drive power source 20, and the term "the other terminal" or "the other end" refers to the side closer to the negative electrode of the drive power source 20.

[0014] First, an overview of a solenoid drive circuit 10 according to an embodiment of the present invention will be described. As shown in Fig. 1, the solenoid drive circuit 10 is a DC circuit including a solenoid coil 22, and functions as a drive circuit for a plunger (not shown). This plunger operates only with power supplied from a drive power source 20, but in the present invention, a charging power source 21 is also provided, thereby shortening the time until the plunger starts to operate and increasing the initial speed of the plunger operation.

[0015] As described later, the driving power supply 20 supplies power to the solenoid coil 22 when the switch element 24 is turned on. The charging power supply 21 is always on and continues to supply power to the capacitor 25. The negative electrode side of the driving power supply 20, the positive electrode side of the charging power supply 21, the positive terminal side of the capacitor 25, and the other terminal side of the first diode 26 are each grounded at a ground point 27. The driving power supply 20 and the charging power supply 21 can be appropriately selected from power supply from the power supply circuit of the device in which the solenoid is mounted, power supply from a primary battery or a secondary battery, etc., depending on the situation of the device in which the solenoid is mounted, and further, the driving power supply 20 and the charging power supply 21 may be different types of power supplies. The charging power supply 21 may be configured to be turned on only when necessary, for example, in a device in which the solenoid operates infrequently.

[0016] The solenoid drive circuit 10 will be described in detail. The solenoid coil 22 is provided as an electrical component in a solenoid (not shown). One end of the solenoid coil 22 is connected to the positive electrode side of the driving power source 20 via a switch element 24, and the other end of the solenoid coil 22 is connected to the negative electrode side of the driving power source 20 and the positive electrode side of the charging power source 21 via a first diode 26. A second diode 23 is provided in parallel with the solenoid coil 22 and is connected to the positive electrode side of the driving power source 20 via a switch element 24, and the other end of the solenoid coil 22 is connected to the negative electrode side of the driving power source 20 and the positive electrode side of the charging power source 21 via the first diode 26. The second diode 23 is provided in a direction opposite to the direction of the output current of the driving power source 20, and is provided as a flywheel diode that prevents the generation of high voltage due to the back electromotive force of the solenoid coil 22. A varistor or a Zener diode may be provided instead of the second diode 23. Alternatively, instead of providing a diode or the like at this position, a varistor may be provided between the drain and source of the FET that is the switch element 24, which will provide the same function.

[0017] A switch element 24 is provided between the positive electrode of the driving power supply 20 and one end of the solenoid coil 22 and one terminal of the second diode 23. The switch element 24 is a P-channel MOSFET. The P-channel MOSFET is turned on when a voltage is applied that makes the gate electrode negative with respect to the source electrode, but an N-channel MOSFET may be used that is turned on when a voltage is applied that makes the gate electrode positive. In any case, in consideration of the high speed of the ON operation, it is highly desirable to use a MOSFET as the switch element 24, rather than a bipolar transistor. The FET driver 29 is for driving the switch element 24, but since it has little relevance to the present invention, a description thereof will be omitted.

[0018] Furthermore, the solenoid drive circuit 10 is provided with an initial drive acceleration section 31 consisting of a capacitor 25 and a first diode 26. The initial drive acceleration section 31 is provided to enhance responsiveness and high speed by adding power supply from the initial drive acceleration section 31 to normal power supply from the drive power source 20 at the beginning of operation of the solenoid (not shown). The negative terminal of the capacitor 25 is connected to the negative electrode side of the charging power source 21, the other end of the solenoid coil 22, and the other terminal of the second diode 23 via a first resistor 28, and the positive terminal is connected to the positive electrode side of the charging power source 21, the negative electrode side of the drive power source 20, and the other terminal of the first diode 26. The first diode 26 is provided in parallel with the capacitor 25, with one terminal connected to the negative electrode side of the charging power source 21, the other end of the solenoid coil 22, and the other terminal of the second diode 23, and the other terminal connected to the positive electrode side of the charging power source 21 and the negative electrode side of the driving power source 20. By being connected in this manner, the first diode 26 has the role of securing a path for the solenoid current to flow after the charge of the capacitor 25 is discharged.

[0019] Next, the operation of the solenoid drive circuit 10 according to the embodiment of the present invention will be described. FIG. 2 is a circuit diagram showing the charging state of the capacitor of the solenoid drive circuit according to the embodiment of the present invention. All the symbols used in FIG. 2 are the same as those in the figure. Furthermore, FIG. 3 is a circuit diagram (1) showing the energization state of the solenoid coil of the solenoid drive circuit according to the embodiment of the present invention. All the symbols used in FIG. 3 are the same as those in the figure. In addition, FIG. 4 is a circuit diagram (2) showing the energization state of the solenoid coil of the solenoid drive circuit according to the embodiment of the present invention. All the symbols used in FIG. 4 are the same as those in the figure.

[0020] First, as shown in FIG. 2, the capacitor 25 is charged by power supply from the charging power source 21. As described above, in the solenoid driving circuit 10 according to this embodiment, the charging power source 21 is always on. Therefore, even if the switch element 24 is off, a current path is generated that returns from the positive electrode side of the charging power source 21 to the negative electrode side of the charging power source 21 via the capacitor 25 and the first resistor 28, and the capacitor 25 is charged. When the switch element 24 is turned on in a charged state of the capacitor 25, a current path is generated that returns from the positive electrode side of the driving power source 20 to the negative electrode side of the driving power source 20 via the switch element 24, the solenoid coil 22, and the capacitor 25, as shown in FIG. 3. Therefore, until the discharge of the capacitor 25 is completed, an excitation current is supplied to the solenoid (not shown) by the discharge of the driving power source 20 and the solenoid coil 22.

[0021] 4, a current path is generated that runs from the positive electrode side of the driving power supply 20 through the switch element 24, the solenoid coil 22, and the first diode 26 back to the negative electrode side of the driving power supply 20. In other words, the solenoid coil 22 continues to operate only with the power supply from the driving power supply 20.

[0022] Fig. 5 is a graph showing the characteristics of the solenoid drive circuit according to the embodiment of the present invention when current is applied. Fig. 5 is an analysis of the operation of the above-mentioned solenoid drive circuit 10, in which the capacitor voltage and current were obtained by simulating the fluctuations in the voltage and current between both terminals of the capacitor 25, and the solenoid voltage and current were also obtained by simulating the fluctuations in the voltage and current between both terminals of the solenoid coil 22.

[0023] As can be seen from FIG. 5, after the switch element 24 is turned on, the capacitor voltage rises extremely rapidly due to the discharge of the capacitor 25. At the same time, the capacitor current also rises rapidly. Therefore, when the switch element 24 is turned on, the sum of the output voltage from the driving power supply 20 and the charging voltage from the capacitor 25 flows to the solenoid coil 22. application Therefore, after the switch element 24 is turned on, the power supply to the solenoid coil 22 increases very rapidly, making it possible to supply power that cannot be realized by the power supply only from the driving power supply 20. Furthermore, when the discharge of the capacitor 25 is completed, the capacitor current drops very rapidly and is switched to the current from the driving power supply 20.

[0024] As described above, when the switch element 24 is turned on, the sum of the output voltage from the driving power source 20 and the charging voltage from the capacitor 25 is applied to the solenoid coil 22, so that the current supplied increases rapidly. Therefore, the magnetic flux flowing by the current passing through the solenoid coil 22 also increases, and it is possible to shorten the time until the plunger starts to operate and to increase the initial speed of the plunger. In addition, although it varies somewhat depending on the characteristics required for the solenoid, the charging power source 21, the capacitor 25, and the first diode 26 can be very small elements, so there is an advantage that the area of ​​the board and the volume of the housing are hardly increased, and the manufacturing cost is hardly increased. Furthermore, the power supply by discharging the capacitor 25 has the advantage that it is not necessary to operate the switch element for the auxiliary power source with high precision, as in the case of power supply by the auxiliary power source.

[0025] The present invention is not limited to the contents described above, and various configurations are possible without departing from the scope of the claims, such as adding a sensor to the configuration of the solenoid drive circuit according to the embodiment of the present invention. [Explanation of symbols]

[0026] 10 Solenoid drive circuit 20 Driving power supply 21 Charging power supply 22 Solenoid coil 23 Second Diode 24 Switching element 25 Capacitor 26 First Diode 27 Grounding point 28 The First Resistance 29 FET Drivers 30 Electrical components of solenoid 31 Initial drive acceleration section 51 DC power supply 52 Transistor 53 Transistor 54 Current limiting resistor 55 Solenoid valve 55a solenoid coil 56 Boost chopper circuit 57 Reactor 58 Diode 59 Capacitor 60 Chopper NPN transistor 61 Reverse current blocking diode

Claims

1. A solenoid coil provided in the solenoid; a driving power source having a positive electrode connected to one end of the solenoid coil and a negative electrode connected to the other end of the solenoid coil, the driving power source supplying a current to the solenoid coil; a capacitor having a negative terminal connected to the other end of the solenoid coil and a positive terminal connected to the negative electrode side of the driving power source, the capacitor being provided in series with the solenoid coil; a charging power source having a positive electrode connected to the positive terminal of the capacitor and a negative electrode connected to the negative terminal of the capacitor, the charging power source supplying a current to the capacitor; a switch element provided between the positive electrode side of the driving power source and the one end of the solenoid coil; a first diode having one terminal connected to the other end of the solenoid coil and the other terminal connected to the negative electrode side of the charging power source and the positive electrode side of the charging power source, the first diode being arranged in a forward direction with respect to the direction of the output current of the driving power source; the negative electrode side of the driving power supply, the positive electrode side of the charging power supply, the positive terminal of the capacitor, and the other terminal of the first diode are grounded; When the switch element is turned off, the capacitor is charged by the charging power source, a first switching element that switches on the first and second switching elements, and a second switching element that switches on the second and third switching elements, the first switching element being connected to the first and second switching elements, and the second switching element being connected to the first and second switching elements.

2. 2. The solenoid drive circuit according to claim 1, further comprising a second diode arranged in parallel with the solenoid coil, one terminal of which is connected to the positive electrode side of the drive power supply and the other terminal of which is connected to the negative terminal of the capacitor, the negative electrode side of the drive power supply, and the positive electrode side of the charging power supply, and arranged in a direction opposite to the direction of the output current of the drive power supply.

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