JPS61141103A - Driving circuit for solenoid - Google Patents

Abstract

PURPOSE:To reduce power consumption while maintaining the speeding-up properties of the speed of response by using a first power supply having high voltage when a solenoid is driven and flowing holding currents through the solenoid by employing a second power supply lower than the first power supply after the solenoid is operated once. CONSTITUTION:When a driving signal D is transmitted, Tr1-Tr3 are all turned ON, currents flow through a first power supply E1, the transistor Tr2, a solenoid L, R, the transistor Tr1 and a resistor RS, and currents flowing through the solenoid rapidly increase. When currents flowing through the solenoid reach a fixed value, the transistor Tr2 is turned OFF by the working of a comparator 1 and an AND gate 2, and currents flow through a second power supply E2, the transistor Tr3, a diode D1, the solenoid L, R, the transistor Tr1 and the resistor RS. Currents gradually reduce owing to a resistance section made to be contained in the solenoid, a current value finally reach E2/R (where RS is neglected because of a small value), and only the holding currents of the solenoid flow.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a solenoid drive circuit.

[Conventional technology]

Solenoids are used for various purposes, and are known, for example, as electromagnetic valves with relays or plungers, and as air guns with a drawer. However, in a solenoid drive circuit, problems include response speed, holding current, power consumption, and transient voltage during disconnection. In order to increase the response speed, the L/R time constant may be reduced or the power supply voltage may be increased.

Therefore, in order to increase the power supply voltage and limit the holding current, a resistor R is externally attached to increase the size.

For this reason, the power loss in the resistor R is large (increased power consumption and heat generation in the drive circuit become a problem).Furthermore, various arc extinguishing circuits have been proposed to absorb the high voltage when the solenoid current is cut off. However, all of them temporarily attenuate and absorb the electromagnetic energy of the solenoid, and do not actively utilize this energy.

[Problem that the invention seeks to solve]

Therefore, an object of the present invention is to provide a highly efficient solenoid drive circuit that reduces power consumption while maintaining high response speed.

[Means for solving problems]

The solenoid drive circuit of the present invention uses a first power source with a high voltage when driving the solenoid, and once activated, uses a second power source with a lower voltage to flow a holding current through the solenoid. . For this reason, it has a first switch for driving the solenoid to open and close this current path, and second and third switches for switching and using the first and second power sources, respectively. An external solenoid drive signal directly actuates the first switch. Further, a second switch is provided to supply the first power to the solenoid in response to the solenoid drive signal. A third switch is provided to supply the second power source to the solenoid in response to a signal from a current detection means for detecting a current flowing through the solenoid and the solenoid drive signal.

Additionally, an arc extinguishing circuit is provided which returns the electromagnetic energy to the first power source and/or the second power source when the solenoid current is disconnected.

[For production]

When the drive signal is input, it passes through the first and second switches,
A high voltage first current power source is provided to the solenoid. Due to the high voltage, the time required for the solenoid drive circuit to flow is short. Therefore, the high speed of the circuit is maintained.

When the signal from the current detection means reaches a predetermined level, this signal and the drive signal cause the third switch to supply the second DC power to the solenoid. A holding current for the solenoid is ensured by this second DC power supply. In this way, since the first and second DC power supplies are used, high speed can be maintained and power consumption can be reduced without using a large external resistor.

Furthermore, since the arc-extinguishing circuit provided in the solenoid returns its electromagnetic energy to the first and/or second DC power source, the solenoid drive circuit becomes extremely efficient.

〔Example〕

Embodiments of the solenoid drive circuit of the present invention will be described below with reference to FIGS. 1 and 2.

In the figure, R indicates the inductance and internal resistance of the solenoid; the first, second, and third switches are TrlsTrz and T, respectively.

It is an NPN (NPN) transistor. A resistor R6 having a small value is connected between the emitter of the transistor ('r, , ) and ground, and serves as a current detection means for the solenoid.

The voltage of this resistor R8 is input to one input terminal of a comparator, for example, a Schmitt circuit, and the reference voltage E0 is input to the other input terminal. The output of the comparator 1 and the drive signal R are input to an AND gate 2, and the output thereof is input to the base of the Trt transistor. Further, drive signals are input to the bases of the 'r, , T, and tl transistors, respectively.

A first DC power supply E is connected to the collectors of the Tw and t transistors.
, is connected to the collector of the Tr3, and a second DC power source E2 having a lower voltage is connected to the collector of the Tr3. The emitter of the Tri transistor is directly connected to the solenoid and T
rj) The emitter of the transistor is connected to the solenoid via a diode D1. Diode D2, D
3 is connected to both ends of the solenoid, and returns the electromagnetic energy at the time of disconnection to the first power source E.

The operation of the embodiment having the above configuration will be explained.

When the drive signal R is applied, T rl , Tri , and Trj all turn ON, and first, current flows through the first power supply E, T, transistor, solenoid L, R, T□ transistor, resistor R3, and then to the solenoid. The current increases rapidly. The current change at this time corresponds to the 0 portion in FIG.

When the current flowing through the solenoid reaches a predetermined value, comparator 1
, Tr2 transistor is turned off by the action of AND gate 2
Then, current flows through the second power source E2, Trj transistor, diode Dis solenoid L, R, T, l) transistor, and resistor R8 (corresponding to the 0 part in FIG. 2). The current gradually decreases due to the resistance bone contained in the solenoid, and the current value eventually becomes Et/R (however, R8
is small, so ignore it) (corresponds to the 0 part in Figure 2),
Only the holding current of the solenoid flows.

Next, when the drive signal is cut off, T rl s Trz % T
Both the 'r3 transistors are turned off, and no current is supplied to the solenoid from the first and second DC power supplies E+ and Ex. At this time, diode D2, solenoids L, R
, diode D3, and the first DC power supply, and the energy stored in the L portion of the solenoid is E.

is released in the form of a charge.

Therefore, the arc extinguishing operation is performed and energy consumption is also prevented.

〔effect〕

Only in the initial stage of operation of the solenoid, a high voltage first DC power source is used to flow a large amount of current, and thereafter a low voltage second DC power source is used to flow a holding current. Therefore, it has the advantage of high-speed response and low power consumption without using a large external resistor as in the conventional case.

Furthermore, by setting the reference voltage with an appropriate margin, stable operation of the solenoid can be ensured.

Further, since the arc extinguishing circuit is configured to return electromagnetic energy to the power source side, it is possible to achieve the effects of further reducing power consumption and increasing efficiency.

Although the present invention has been specifically described above based on examples, it goes without saying that the present invention is not limited to the above-mentioned examples and can be modified in various ways without departing from the gist thereof.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the solenoid drive circuit of the present invention, and FIG. 2 is a diagram showing changes in solenoid current. Trl, Tr2, Trj...transistor, DI
, D z, D3... Diode, E,...
・First DC power supply, E...Second DC power supply, R3
...Resistance (current detection means), L, R1...Inductance and resistance of each solenoid, 1...Comparator, 2...AND gate, D...Drive signal, E
o...Reference voltage. 1st diagram 2nd diagram

Claims (5)

[Claims] (1) A first DC power supply for supplying current to the solenoid, a second DC power supply having a voltage lower than the first DC power supply voltage, and a current flowing to the solenoid in response to an external drive signal. a first switch for opening and closing a flow path; a current detection means provided in the flow path for detecting a current flowing through the solenoid; and supplying the first DC power source to the solenoid in accordance with the drive signal. second for
and a third switch for supplying the second DC power source to the solenoid in response to the drive signal and a signal indicating that the current detected by the current detection means has reached a predetermined level. and an arc extinguishing circuit that returns electromagnetic energy of the solenoid to the first DC power source and/or the second DC power source when the first switch is opened. (2) The solenoid drive circuit according to claim 1, wherein the first, second and third switches are transistors. (3) The drive signal is supplied to the bases of the first and third switches, the signal output by the current detection means is input to a comparator, and the logical product of the comparator output and the drive signal is applied to the base of the second switch. The solenoid drive circuit according to claim 2, which is supplied to the base of the solenoid drive circuit. (4) The solenoid drive circuit according to claim 1, wherein the current detection means is a resistor inserted in the current flow path of the solenoid. (5) The arc extinguishing circuit is formed by a diode connected to both ends of the solenoid.
Solenoid drive circuit described in section.