Solenoid drive device

Abstract

To provide a solenoid drive device capable of suppressing an overcurrent, and driving a solenoid.SOLUTION: A first switch part connected in parallel to a current limit resistance is provided. The first switch part is turned off before a voltage is applied to a solenoid from a power supply circuit, a detection result is acquired from a current detection part when the voltage is applied. It is determined whether a current value based on the acquired detection result is equal to or more than a preset reference value. In the case where the current value is less than the reference value, the current limit resistance is bypassed by turning on the first switch part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a solenoid drive device. [Background technology]

[0002] There is a solenoid driving device for driving a solenoid (see, for example, Patent Document 1). When driving a solenoid, a circuit is sometimes provided to prevent an overcurrent when the solenoid is started. For example, by connecting a current limiting resistor in series with the solenoid and supplying power, even if an overcurrent occurs when the solenoid is started, the current can be limited by the current limiting resistor. Such a current limiting resistor is set to a certain level of resistance value because it is necessary to limit the overcurrent. Incidentally, in recent years, in order to simplify power supply circuits, there are cases where a power supply circuit for driving other electronic components is shared rather than a separate power supply circuit for the solenoid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-302358 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a power supply circuit for the solenoid and a power supply circuit for other electronic components are provided as a common power supply circuit, the power supply voltage may be set to match the other electronic components. In this case, the set voltage may be lower than the voltage output from the individual power supply circuit for the solenoid, and depending on the relationship between the resistance value of the current limiting resistor and the internal resistance value of the solenoid, the voltage supplied from the power supply circuit may be divided and may not reach a voltage at which the solenoid can be driven. In this case, the solenoid cannot be driven normally. In addition, if the resistance value of the current limiting resistor is reduced to increase the voltage applied to the solenoid, it may be possible to drive the solenoid normally, but since the resistance value of the current limiting resistor is small, it may not be possible to suppress overcurrent.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solenoid driving device that can suppress overcurrent and can drive a solenoid. [Means for solving the problem]

[0006] A solenoid drive device according to one embodiment of the present invention includes a power supply circuit that applies a voltage to a solenoid, a current limiting resistor connected in series with the solenoid to suppress overcurrent, a current detection unit that detects the current flowing through the solenoid, a first switch unit connected in parallel to the current limiting resistor, and a control circuit that turns off the first switch unit before applying voltage to the solenoid from the power supply circuit, acquires a detection result from the current detection unit when the voltage is applied, determines whether a current value based on the acquired detection result is equal to or greater than a predetermined reference value, and if the current value is less than the reference value, bypasses the current limiting resistor by turning on the first switch unit. Effect of the Invention

[0007] According to the present invention, when the solenoid is started, the current is limited by passing through a current limiting resistor connected to the solenoid, and when it is detected that no overcurrent is occurring, the current limiting resistor is bypassed. As a result, when an overcurrent occurs, the current from the power supply passes through the current limiting resistor, and the overcurrent can be suppressed by the current limiting resistor. On the other hand, when no overcurrent is occurring, the current limiting resistor is bypassed, so that the voltage is not divided by the current limiting resistor, and a voltage capable of driving the solenoid can be applied to the solenoid from the power supply circuit. Therefore, a higher voltage can be applied to the solenoid compared to when the current limiting resistor is not bypassed, and it is possible to obtain the voltage required to drive the solenoid while suppressing the overcurrent. [Brief description of the drawings]

[0008] [Figure 1] 1 is a circuit diagram showing a configuration of a solenoid drive device according to a first embodiment of the present invention. [Diagram 2] 1 is a circuit diagram used to explain a solenoid drive device according to a first embodiment of the present invention. [Diagram 3] 3 is a waveform diagram of each part of the solenoid drive device according to the first embodiment of the present invention. FIG. [Figure 4] 3 is a waveform diagram of each part of the solenoid drive device according to the first embodiment of the present invention. FIG. [Diagram 5] 1 is a circuit diagram used to explain a solenoid drive device according to a first embodiment of the present invention. [Figure 6] 1 is a circuit diagram used to explain a solenoid drive device according to a first embodiment of the present invention. [Figure 7] FIG. 5 is a circuit diagram showing a configuration of a solenoid drive device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. <First embodiment> Fig. 1 is a diagram showing the configuration of a solenoid drive device according to a first embodiment of the present invention, Fig. 2 is an explanatory diagram of the solenoid drive device according to the first embodiment of the present invention.

[0010] In Fig. 1, a current detection resistor R2 and an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Q1 (second switch unit), which is an example of an N-type semiconductor switch, are connected in series between one end of a solenoid L1 and the positive electrode of a DC power supply voltage V1. As shown in Fig. 2, the solenoid L1 includes an inductance La and an internal resistance Ra. A current limiting resistor R1 and an N-channel MOSFET Q2 (first switch portion) are connected in parallel between the other end of the solenoid L1 and the negative electrode of the DC power supply voltage V1.

[0011] The DC power supply voltage V1 is realized by a power supply circuit that applies a voltage to the solenoid L1. The DC voltage V1 may be configured to be shared with a power supply circuit for driving other electronic components, rather than being a separate power supply circuit for the solenoid.

[0012] The MOSFET Q1 is a switching element that turns the power supply on and off. A control signal V2 is supplied to the gate of the MOSFET Q1 from the control circuit 12. When the control signal V2 goes to H level, the MOSFET Q1 turns on, and the voltage from the DC power supply voltage V1 is applied to the solenoid L1.

[0013] The current detection resistor R2 detects the current I1 flowing through the solenoid L1. The voltage across the current detection resistor R2 is sent to the current detection circuit 11. The output signal V3 of the current detection circuit 11 is sent to the control circuit 12. When the control circuit 12 sets the output signal V2 to H level and the output signal V4 to L level to turn on the MOSFET Q1 and turn off the MOSFET Q2, the current I1 flowing through the solenoid L1 becomes less than the threshold. When the output signal V3 of the current detection circuit 11 is less than the threshold, the control circuit 12 sets the output signal V4 to H level to maintain the MOSFET Q2 in the on state. When the current I1 flowing through the solenoid L1 increases due to the occurrence of a solenoid short-circuit failure or the like, and the output signal V3 of the current detection circuit 11 becomes equal to or greater than the threshold, the control circuit 12 sets the control signal V2 to L level to turn off the MOSFET Q1. This makes it possible to cut off the power supplied to the solenoid L1, thereby preventing an overcurrent from flowing through the solenoid L1.

[0014] The current limiting resistor R1 limits the current flowing through the circuit when the power supply is started. The MOSFET Q2 bypasses the current flowing through the current limiting resistor R1. A control signal V4 is sent from the control circuit 12 to the gate of the MOSFET Q2. Immediately after the MOSFET Q1 is turned on and the DC power supply voltage V1 is applied to the solenoid L1, the control signal V4 is at the L level. When the control signal V4 is at the L level, the MOSFET Q2 is turned off. When the MOSFET Q2 is off, the current of the solenoid L1 flows through the current limiting resistor R1 as shown by the current I2. This makes it possible to prevent an overcurrent from flowing into the solenoid L1 when the power supply is turned on. During the subsequent steady state, if the output signal V3 of the current detection circuit 11 is less than the threshold value, the control signal V4 becomes the H level and the MOSFET Q2 is turned on. When the MOSFET Q2 is turned on, the current of the solenoid L1 flows through the MOSFET Q2 as shown by the current I3, bypassing the current limiting resistor R1. This makes it possible to suppress a drop in the applied voltage of the solenoid L1.

[0015] 3 and 4 are waveform diagrams of the various parts of the solenoid driving device according to the first embodiment of the present invention.

[0016] Figure 3 shows the waveforms of each part in a normal state. In Figure 3, the power supply is off before time T1. When the power supply is off, the DC power supply voltage V1 is not driven and is 0 V. Also, when the power supply is off, the control signal V2 is at the L level and the MOSFET Q1 is off. Therefore, the current I1 flowing through the solenoid L1 is zero.

[0017] At time T1, the DC power supply voltage V1 is driven, and at time T2, the control signal V2 from the control circuit 12 goes to H level. When the control signal V2 goes to H level, the MOSFET Q1 turns on.

[0018] Immediately after time T2 when the control signal V2 becomes H level, the control signal V4 is at L level. When the control signal V4 is at L level, the MOSFET Q2 is turned off. Therefore, the current from the DC power supply voltage V1 passes through the current detection resistor R2, the MOSFET Q1, and the solenoid L1, and then flows as the current I2 through the current limiting resistor R1.

[0019] At this time, the current I1 flowing through the solenoid L1 is detected by the current detection circuit 11. Normally, as shown in Fig. 3, the detection voltage V3 of the current detection circuit 11 is less than a predetermined threshold value. Therefore, the control signal V2 from the control circuit 12 becomes H level, and the MOSFET Q1 is maintained in the on state.

[0020] Here, as shown in FIG. 2, the solenoid L1 includes not only a pure inductance La component, but also an internal resistance Ra. Also, the resistance value of the current detection resistor R2 and the on-resistance of the MOSFET Q1 are small enough that they can be ignored. Therefore, the resistance component of the circuit in this case is the sum (R1+Ra) of the current detection resistor R1 component and the internal resistance Ra component of the solenoid L1. Therefore, the current I1 flowing through the solenoid L1 immediately after the power is turned on is, I1=V1 / (R1+Ra) … (1) is limited to.

[0021] At this time, the potential of the negative electrode of the solenoid L1 is the resistance obtained by dividing the power supply voltage V1 by the current limiting resistor R1 and the internal resistance Ra, so the voltage applied to both ends of the solenoid L1 is V5 = V1 - (R1 / (R1 + Ra)) V1 … (2) This results in a voltage lower than the power supply voltage V1.

[0022] At time T3 when the steady state is reached, the control signal V4 goes to H level. When the control signal V4 goes to H level, the MOSFET Q2 turns on. When the MOSFET Q2 turns on, the current from the DC power supply voltage V1 passes through the current detection resistor R2, the MOSFET Q1, and the solenoid L1, and then switches to flow through the MOSFET Q2 as current I3. Thus, in the steady state, the control signal V4 goes to H level, and the current flowing through the solenoid L1 bypasses the current limiting resistor R1 and flows through the MOSFET Q2. At this time, the current I3 increases more than the current I2 because it bypasses the limiting resistor, and therefore the voltage V3 also increases.

[0023] When the current limiting resistor R1 is bypassed, the voltage V5 applied across the solenoid L1 becomes equal to the power supply voltage V1, V5 = V1 … (3) The decrease in the voltage applied to the solenoid L1 can be suppressed.

[0024] Figure 4 shows the waveforms of each part when a short circuit occurs. In Figure 4, the power supply is off before time T11. When the power supply is off, the power supply voltage V1 is not driven and is 0 V. Also, when the power supply is off, the control signal V2 is at the L level and the MOSFET Q1 is off. Therefore, the current I1 flowing through the solenoid L1 is zero.

[0025] At time T11, the DC power supply voltage V1 is driven, and at time T12, the control signal V2 from the control circuit 12 goes to H level. When the control signal V2 goes to H level, the MOSFET Q1 turns on. Immediately after time T12 when the control signal V2 goes to H level, the control signal V4 is at L level. When the control signal V4 is at L level, the MOSFET Q2 is off.

[0026] When MOSFET Q1 is turned on, a current from DC power supply voltage V1 flows through current detection resistor R2, MOSFET Q1, solenoid L1, and current limiting resistor R1. At this time, current I1 flowing through solenoid L1 is detected by current detection circuit 11. If a short circuit occurs, as shown in FIG. 4, detection voltage V3 of current detection circuit 11 will be equal to or higher than a predetermined threshold. Therefore, at time T13, control signal V2 from control circuit 12 goes to L level, and MOSFET Q1 is turned off. This prevents a large current due to a short circuit from flowing through solenoid L1.

[0027] As described above, in this embodiment, when the solenoid L1 is started, the current can be limited by passing through the current limiting resistor R1 connected to the solenoid L1, and during steady state, the current flowing through the current limiting resistor R1 is bypassed by the MOSFET Q2, so that a voltage capable of driving the solenoid L1 can be applied to the solenoid L1. This makes it possible to prevent an overcurrent from flowing through the solenoid L1, and to suppress a drop in the applied voltage to the solenoid L1. This will be further explained.

[0028] The drive circuit for solenoid L1 can basically be realized by a configuration in which a MOSFET Q1 is connected as a switching element between a DC power supply voltage V1 and solenoid L1, and an on / off drive signal is supplied to the gate of MOSFET Q1, as shown in Fig. 5. When an H-level signal is supplied to the gate of MOSFET Q1, MOSFET Q1 turns on, current flows through solenoid L1, and solenoid L1 is driven. When an L-level signal is supplied to the gate of MOSFET Q1, MOSFET Q1 turns off, and drive of solenoid L1 is stopped.

[0029] However, when the solenoid L1 starts to be driven, an overcurrent may flow into the solenoid L1. With this type of configuration, it is not possible to limit the overcurrent that flows through the solenoid L1 when the power is turned on. Also, it is necessary to prevent a large current from flowing through the circuit when a short circuit occurs.

[0030] 6, a current limiting resistor R1 is provided, as well as a current detection resistor R2 and a current detection circuit 11. As described above, the provision of the current limiting resistor R1 makes it possible to limit the current flowing through the circuit when the power is on. Furthermore, the provision of the current detection resistor R2 and the current detection circuit 11 makes it possible to prevent a large current from flowing in the event of a short circuit.

[0031] However, in the configuration shown in Fig. 6, the voltage applied to the solenoid L1 is lower than the DC power supply voltage V1. That is, as shown in Fig. 6, the solenoid L1 includes an internal resistance Ra as well as an inductance La. Therefore, the voltage V5 applied across the solenoid L1 is the voltage obtained by dividing the DC power supply voltage V1 by the current limiting resistor R1 and the internal resistance Ra. V5 = V1 - (R1 / (R1 + Ra)) V1 … (4) This results in a voltage lower than the DC power supply voltage V1.

[0032] In contrast, in this embodiment, the current limiting resistor R1 is bypassed by turning on the MOSFET Q2 in the steady state as shown in Figures 1 and 2. As a result, as shown in formula (3), the voltage V5 applied to the solenoid L1 becomes equal to the power supply voltage V1, and the drop in the voltage applied to the solenoid L1 can be suppressed.

[0033] <Second embodiment> FIG. 7 shows the configuration of a solenoid driving device according to a second embodiment of the present invention. 7, a current detection resistor R12 and an N-channel MOSFET Q11 are connected in series between one end of a solenoid L11 and the positive electrode of a DC power supply voltage V11, and a parallel circuit of a current limiting resistor R11 and a P-channel MOSFET Q12, which is an example of a P-type semiconductor switch, is connected. The other end of the solenoid L11 is connected to the negative electrode of the DC power supply voltage V11.

[0034] In the first embodiment described above, the parallel connection of the current limiting resistor R1 and the MOSFET Q2 is connected to the downstream side of the solenoid L1 (a terminal side different from the terminal connected to the power supply circuit that supplies the DC power supply voltage V1 to the solenoid L1), whereas in this embodiment, the parallel connection of the current limiting resistor R11 and the MOSFET Q12 is connected to the upstream side of the solenoid L11 (a terminal side connected to the power supply circuit that supplies the DC power supply voltage V11 to the solenoid L11). Also, a P-channel MOSFET Q12 is used as a switching element that bypasses the current limiting resistor. The other configurations are the same as those of the first embodiment described above.

[0035] In the first embodiment, an N-channel MOSFET Q2 is used as a switching element that bypasses the current limiting resistor. Since an N-channel MOSFET is less expensive than a P-channel MOSFET, the first embodiment can reduce costs. Even when a P-channel MOSFET Q12 is used as a switching element that bypasses the current limiting resistor as in the second embodiment, it is possible to suppress overcurrent and suppress a drop in the applied voltage of the solenoid, as in the first embodiment.

[0036] The DC power supply voltage V1 is realized by a power supply circuit that applies a voltage to the solenoid L1. The DC voltage V1 may be configured to be shared with a power supply circuit for driving other electronic components, rather than being a separate power supply circuit for the solenoid. In this case, since there is no need to provide a separate power supply circuit for the solenoid, the number of components can be reduced. Also, even if the voltage of the power supply circuit for driving other electronic components is lower than the voltage of the separate power supply circuit for the solenoid, as long as the voltage required to start the solenoid is secured, the solenoid can be started even at a voltage lower than the voltage of the separate power supply circuit for the solenoid.

[0037] In the above example, a MOSFET is used as the switching element, but a bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor) may also be used as the switching element.

[0038] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0039] 11...current detection circuit, 12...control circuit, L1, L11...solenoid, Q1, Q2, Q11, Q12...MOSFET, R1, R11...current limiting resistor, R2, R12...current detection resistor, V1...DC power supply voltage

Claims

1. a power supply circuit for applying a voltage to the solenoid; A current limiting resistor connected in series with the solenoid to suppress overcurrent; A current detection unit that detects a current flowing through the solenoid; A first switch unit connected in parallel to the current limiting resistor; a control circuit which turns off the first switch unit before applying a voltage from the power supply circuit to the solenoid, obtains a detection result from the current detection unit when the voltage is applied, determines whether a current value based on the obtained detection result is equal to or greater than a predetermined reference value, and, if the current value is less than the reference value, turns on the first switch unit to bypass the current limiting resistor. A solenoid drive device having a

2. a second switch portion connected in series to the solenoid; The control circuit includes: The second switch unit is turned on before a voltage is applied from the power supply circuit to the solenoid, and when the voltage is applied, if the determined result indicates that the current value is equal to or greater than the reference value, the second switch unit is turned off to cut off the power supplied to the solenoid.

2. The solenoid drive device of claim 1.

3. The current limiting resistor is connected downstream of the solenoid, The first switch section is an N-type semiconductor switch.

3. The solenoid drive device of claim 2.

4. The current limiting resistor is connected upstream of the solenoid, The first switch unit is a P-type semiconductor switch.

3. The solenoid drive device of claim 2.

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