JP7199573B2 - Electromagnetic coil drive circuit - Google Patents

Description

The present invention relates to an electromagnetic coil drive circuit for driving electromagnetic coils such as electromagnetic solenoids and operating coils of electromagnetic contactors.

Conventionally, the excitation current that flows through the operation coil that drives the movable iron core of an electromagnetic contactor is held during the adsorption operation in which the movable iron core is attracted to the fixed iron core, and the state in which the movable iron core is attracted to the fixed iron core. There is known a technique for differentiating between the time of adsorption and holding. For example, Japanese Patent Application Laid-Open No. 2002-200000 discloses that, regarding a pulse signal to be applied to a switching element that controls an exciting current flowing through an operation coil, the ratio of the ON time is relatively increased during the adsorption operation, and the ON time is increased during the adsorption holding operation. By relatively reducing the ratio of , the excitation current to the operating coil is changed.

JP 2004-186052 A

However, in Patent Document 1, in order to change the exciting current flowing through the operation coil between when the movable iron core is being attracted and when it is being held, the pulse width of the pulse signal is controlled according to the magnitude of the exciting current. A pulse width modulation (PWM) technique is required. Therefore, there is a problem that the circuit becomes complicated and large-scaled, and the manufacturing cost and power consumption increase.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electromagnetic coil drive circuit that can suppress the complexity and scale of the circuit and reduce the manufacturing cost and power consumption. .

In order to solve the above-described problems and achieve the object, an electromagnetic coil drive circuit according to the present invention includes first and second switching elements, first and second drive circuits, and a step-down circuit. The first switching element is arranged between the first power line on the high potential side and the second power line on the low potential side via the electromagnetic coil, and is arranged on the lower potential side than the electromagnetic coil. be. The first drive circuit drives the first switching element using a first voltage applied between the first power line and the second power line. The second switching element is arranged between the first power supply line and the third power supply line on the low potential side via the electromagnetic coil, and is arranged on the lower potential side than the electromagnetic coil. The second drive circuit drives the second switching element using a second voltage applied between the first power line and the third power line. The step-down circuit uses the first voltage to step down the first voltage to generate a second voltage.

According to the electromagnetic coil drive circuit of the present invention, it is possible to suppress the complexity and scale of the circuit, and to reduce the manufacturing cost and power consumption.

FIG. 2 shows an example of the electromagnetic coil drive circuit according to the first embodiment; 1 is a diagram showing a configuration example of an electromagnetic coil drive circuit according to Embodiment 1; FIG. Time chart used for explaining the operation of the electromagnetic coil drive circuit according to the first embodiment FIG. 10 is a diagram showing a configuration example of an electromagnetic coil and an inductor according to Embodiment 2; Sectional view showing a section of the electromagnetic coil and the inductor shown in FIG. The figure which shows the structural example of the electromagnetic coil drive circuit which concerns on Embodiment 3.

An electromagnetic coil drive circuit according to Embodiment 1 of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the first embodiment described below. Also, hereinafter, the term “connection” is simply used for explanation without distinguishing between electrical connection and physical connection.

Embodiment 1.
FIG. 1 is a diagram showing an example of an electromagnetic coil drive circuit according to Embodiment 1. FIG. FIG. 1 shows an AC power supply 1, a full-wave rectifier circuit 2, an electromagnetic coil drive circuit 3, an electromagnetic coil 5, and a driven portion 6 having a fixed iron core 61 and a movable iron core 62. ing.

An example of the electromagnetic coil 5 is a solenoid coil provided in a circuit breaker. Another example of an electromagnetic coil is the operating coil of an electromagnetic contactor.

The electromagnetic coil drive circuit 3 has DC input terminals T1 and T2. A rectified voltage rectified by the full-wave rectifier circuit 2 is applied between the DC input terminals T1 and T2. The full-wave rectifier circuit 2 uses the AC voltage output from the AC power supply 1 to generate a rectified voltage. The electromagnetic coil drive circuit 3 controls the exciting current flowing through the electromagnetic coil 5 based on the rectified voltage. The details of the control of the exciting current will be described later.

When an exciting current flows through the electromagnetic coil 5, the movable iron core 62 is attracted by the electromagnetic force caused by the exciting current. Thereby, the movable iron core 62 is attracted to the fixed iron core 61 . In the first embodiment, the electromagnetic coil drive circuit is operated during the adsorption operation in which the movable iron core 62 is attracted to the fixed iron core 61 and in the adsorption holding state in which the movable iron core 62 is attracted to the fixed iron core 61 . 3 operates differently. Details of each operation will be described later.

FIG. 2 is a diagram showing a configuration example of an electromagnetic coil drive circuit according to Embodiment 1. FIG. The electromagnetic coil drive circuit 3 according to Embodiment 1 includes, as main components, a first capacitor 31, a step-down circuit 32, a second capacitor 33, a switching element drive circuit 34, and a first switching element 41. and a second switching element 42 . Furthermore, the electromagnetic coil drive circuit 3 includes a first diode 43 , a second diode 44 , a current suppression circuit 45 and a third diode 46 .

The switching element drive circuit 34 includes a first drive circuit 341 , a second drive circuit 342 and a voltage detection circuit 343 . The step-down circuit 32 includes a diode 321 , an inductor 322 , a power supply IC 323 and a voltage detection circuit 324 .

One end of the first capacitor 31 is connected to the first power line 36 . The other end of the first capacitor 31 is connected to the second power line 37 via the third diode 46 . The anode of the third diode 46 is connected to the other end of the first capacitor 31 . A cathode of the third diode 46 is connected to the second power supply line 37 .

The first power line 36 is a high-potential power line connected to the DC input terminal T1. The second power line 37 is a low potential side power line connected to the DC input terminal T2. As described above, a rectified voltage rectified by the full-wave rectifier circuit 2 is applied between the DC input terminals T1 and T2. The rectified voltage is determined by the AC voltage output from the AC power supply 1 and the forward voltage drop of the diode provided in the full-wave rectifier circuit 2 . A rectified voltage is applied between the first power line 36 and the second power line 37 . Ignoring the forward drop voltage of the third diode 46, the voltage across the first capacitor 31 is also equal to the rectified voltage. In the following description, the voltage applied between the first power line 36 and the second power line 37 may be referred to as "first voltage".

Also, in the step-down circuit 32 , the cathode of the diode 321 is connected to the first power supply line 36 . The anode of diode 321 is connected to one end of inductor 322 . The other end of inductor 322 is connected to third power line 38 . The third power line 38 is grounded. A power supply IC 323 is inserted between a connection point 325 between the anode of the diode 321 and one end of the inductor 322 and the anode of the third diode 46 . Inside the power supply IC 323, a switch section 323a for opening and closing the connection between the first power supply line 36 and the second power supply line 37 is provided. Details of the operation of the step-down circuit 32 will be described later.

One end of the second capacitor 33 is connected to the first power line 36 . The other end of the second capacitor 33 is connected to the third power line 38 . The voltage detection circuit 324 is connected between the first power line 36 and the third power line 38 so as to measure the voltage across the second capacitor 33 . In the following description, the voltage applied between the first power line 36 and the third power line 38 may be referred to as "second voltage".

Also, in the switching element drive circuit 34 , one end of the first drive circuit 341 is connected to the first power supply line 36 . The other end of the first drive circuit 341 is connected to the second power line 37 . One end of the second drive circuit 342 is connected to the first power line 36 . The other end of the second drive circuit 342 is connected to the third power line 38 . The voltage detection circuit 343 is connected between the first power line 36 and the second power line 37 so as to measure the voltage across the first capacitor 31 . Details of the operation of the switching element drive circuit 34 will be described later.

The first drive circuit 341 drives the first switching element 41 . A second drive circuit 342 drives the second switching element 42 . An example of each of the first switching element 41 and the second switching element 42 is the illustrated metal oxide semiconductor field effect transistor (MOSFET). A bipolar transistor may be used instead of the MOSFET.

A source that is a first terminal of the first switching element 41 is connected to the second power supply line 37 . The first terminal is the terminal on the low potential side of the first switching element 41 . A drain, which is a second terminal of the first switching element 41 , is connected to the first power supply line 36 via the electromagnetic coil 5 . A second terminal is a terminal on the high potential side of the first switching element 41 . A gate, which is a drive terminal of the first switching element 41 , is connected to the first drive circuit 341 . A first diode 43 is connected across the electromagnetic coil 5 .

As described above, the first switching element 41 is arranged on the lower potential side than the electromagnetic coil 5 . The first switching element 41 is arranged between the first power supply line 36 on the high potential side and the second power supply line 37 on the low potential side through the electromagnetic coil 5 .

A source, which is a first terminal of the second switching element 42 , is connected to the third power supply line 38 via the current suppression circuit 45 . The first terminal is the terminal on the low potential side of the second switching element 42 . A drain, which is a second terminal of the second switching element 42 , is connected to the first power line 36 via the electromagnetic coil 5 and the second diode 44 . A second terminal is a terminal on the high potential side of the second switching element 42 . A gate, which is a drive terminal of the second switching element 42 , is connected to the second drive circuit 342 and the current suppression circuit 45 . The anode of the second diode 44 is connected to the electromagnetic coil 5 . The cathode of the second diode 44 is connected to the drain of the second switching element 42 .

As described above, the second switching element 42 is arranged on the lower potential side than the electromagnetic coil 5 . The second switching element 42 is arranged between the first power supply line 36 on the high potential side and the third power supply line 38 on the low potential side through the electromagnetic coil 5 .

Next, a preparatory operation of the electromagnetic coil drive circuit 3 according to Embodiment 1 will be described. First, the first capacitor 31 holds a first voltage approximately equal to the rectified voltage. As described above, the rectified voltage is determined by the AC voltage output from the AC power supply 1 and the forward voltage drop of the diode provided in the full-wave rectifier circuit 2 . In this specification, the case where the first voltage is 200 [V] is exemplified.

A first voltage is applied to the step-down circuit 32 . The step-down circuit 32 uses the first voltage to step down the first voltage to generate a second voltage. A second voltage is held by a second capacitor 33 . When the switch portion 323a of the power supply IC 323 is turned on, current flows through the path of the DC input terminal T1, the second capacitor 33, the inductor 322, the power supply IC 323, and the DC input terminal T2. At this time, electromagnetic energy is stored in the inductor 322 . When the switch section 323a is controlled to be off, the electromagnetic energy stored in the inductor 322 becomes an electromotive force, and a current flows through the path of one end of the inductor 322, the diode 321, the second capacitor 33, and the other end of the inductor 322. flow.

A specified second voltage is maintained across the second capacitor 33 by controlling the ratio of the ON time to the sum of the ON time and the OFF time of the switch section 323a. While the second voltage is maintained, the on/off operation of the switch section 323a is stopped. The second voltage is monitored by voltage detection circuit 324 . The second voltage drops when the charge in the second capacitor 33 is used. When the second voltage drops, the on/off operation of the switch section 323a is resumed.

In this specification, the case where the second voltage is 20 [V] is exemplified, but the present invention is not limited to this. The second voltage may be any voltage lower than the first voltage, and may be other than 20 [V].

Next, the main operation of the electromagnetic coil drive circuit 3 according to Embodiment 1 will be described. FIG. 3 is a time chart used for explaining the operation of the electromagnetic coil drive circuit according to the first embodiment. From the top, (a) is the gate voltage of the first switching element 41, (b) is the drain-source voltage of the first switching element 41, (c) is the gate voltage of the second switching element 42, (d) shows the drain-source voltage of the second switching element 42, and (e) shows the waveform of the exciting current flowing through the electromagnetic coil 5, respectively.

In the switching element drive circuit 34, the voltage detection circuit 343 constantly monitors whether the voltage of the first capacitor 31 has reached the first voltage. The first voltage is a voltage that is necessary and sufficient for the attracting operation of attracting the movable iron core 62 to the fixed iron core 61 . In other words, the first voltage is a voltage that allows the electromagnetic coil 5 to flow a current required to attract the movable iron core 62 to the fixed iron core 61 .

When a command to energize the electromagnetic coil 5 is received from the host control device and the voltage of the first capacitor 31 reaches the first voltage, the switching element drive circuit 34 performs the first drive at time t1. The circuit 341 is operated to apply a gate voltage to the first switching element 41 to make the first switching element 41 conductive. When the first switching element 41 conducts, the drain-source voltage of the first switching element 41 drops to near zero [V]. Also, when the first switching element 41 is turned on, an exciting current necessary for the attracting operation flows through the electromagnetic coil 5 . As a result, the movable iron core 62 is attracted to the fixed iron core 61, and the attraction operation is completed.

Note that when the first switching element 41 is turned on, the potential of the drain of the second switching element 42 greatly fluctuates. Therefore, a so-called reverse voltage may be applied to the second switching element 42 . A second diode 44 is provided to prevent this. That is, the second diode 44 operates as a reverse voltage application prevention diode.

At time t2, in order to reduce the excitation current flowing through the electromagnetic coil 5, the first switching element 41 is controlled from conducting to non-conducting, and the second switching element 42 is controlled from non-conducting to conducting. . That is, at time t2, the first drive circuit 341 releases the gate voltage to the first switching element 41 to make the first switching element 41 non-conductive. The second drive circuit 342 applies a gate voltage to the second switching element 42 to make the second switching element 42 conductive. As a result, a second voltage (20 [V]) lower than the first voltage (200 [V]) is applied across the electromagnetic coil 5, and the excitation current flowing through the electromagnetic coil 5 gradually decreases. Then, at time t3, when the second switching element 42 is completely turned on, the electromagnetic coil 5 receives an attracting and holding current necessary to maintain the state in which the movable iron core 62 is attracted to the fixed iron core 61. .

If the first switching element 41 is made non-conductive and the second switching element 42 is made conductive, the exciting current will drop sharply. 5 generates a back electromotive force. Due to this back electromotive force, a current exceeding the rated current may flow through the step-down circuit 32 . More specifically, there is a possibility that a current exceeding the rated current will flow through the step-down circuit 32 through the circuit that passes through the electromagnetic coil 5 →second diode 44 →second switching element 42 →inductor 322 →diode 321 →electromagnetic coil 5 . A current suppression circuit 45 is provided to prevent this. Between times t2 and t3, the waveform of the drain-source voltage of the second switching element 42 gently decreases. This waveform is obtained by the action of the current suppression circuit 45. FIG.

An example of a component of the current suppression circuit 45 is a resistor. For example, it can be configured by inserting a resistor between the source of the second switching element 42 and the third power supply line 38 . When current flows through the second switching element 42 , the voltage generated across the resistor can reduce the ON voltage between the gate and source of the second switching element 42 . As a result, it is possible to prevent a current exceeding a certain value from flowing through the second switching element 42 . As a result, the components of the step-down circuit 32 can be selected without being greatly affected by the back electromotive force generated in the electromagnetic coil 5, and the step-down circuit 32 can be configured with the minimum necessary rated components.

Also, although not shown in the time chart of FIG. 3, the attraction of the movable iron core 62 to the fixed iron core 61 can be released by making the second switching element 42 non-conductive. When the second switching element 42 is made non-conductive, a back electromotive force is generated in the electromagnetic coil 5 while the current flowing through the electromagnetic coil 5 is decreasing. A first diode 43 is provided in the electromagnetic coil 5 to circulate this back electromotive force. That is, the first diode 43 operates as a flywheel diode.

A third diode 46 is provided so that the first capacitor 31 is not discharged when the first switching element 41 is turned on. That is, the third diode 46 operates as a discharge prevention diode that prevents the first capacitor 31 from being discharged. Thereby, the power supply to the step-down circuit 32 can be performed smoothly.

As described above, the electromagnetic coil drive circuit according to Embodiment 1 includes first and second switching elements, first and second drive circuits, and a step-down circuit. The first switching element is arranged between the first power supply line on the high potential side and the second power supply line on the low potential side via the electromagnetic coil, and is arranged on the lower potential side than the electromagnetic coil. The first drive circuit drives the first switching element using a first voltage applied between the first power line and the second power line. The second switching element is arranged between the first power supply line and the third power supply line on the low potential side via the electromagnetic coil, and is arranged on the low potential side with respect to the electromagnetic coil. The second drive circuit drives the second switching element using a second voltage applied between the first power line and the third power line. The step-down circuit uses the first voltage to step down the first voltage to generate a second voltage. As is clear from these techniques, the technique of Embodiment 1 does not use PWM techniques like the prior art. Therefore, a control microcomputer and complicated control circuits are not required. As a result, the complexity and scale of the circuit can be suppressed, and the manufacturing cost and power consumption can be reduced.

In the electromagnetic coil drive circuit according to the first embodiment, when starting to drive the electromagnetic coil, the first drive circuit drives the first switching element to attract the movable iron core of the electromagnetic coil. Further, the electromagnetic coil drive circuit stops driving by the first drive circuit after the movable iron core is attracted, and the second drive circuit drives the second switching element to maintain the attraction of the movable iron core. do.

Due to the above operation, a back electromotive force is generated in the electromagnetic coil. Therefore, even if the electromagnetic coil drive circuit according to the first embodiment includes the current suppression circuit between the first terminal, which is the terminal on the low potential side of the second switching element, and the third power supply line, good. The current suppression circuit operates to suppress entry of current into the step-down circuit due to back electromotive force of the electromagnetic coil. As a result, the step-down circuit can be configured with the minimum necessary rated components.

Also, a diode may be provided whose anode is connected to the other end of the first capacitor and whose cathode is connected to the second power supply line. This diode acts as an anti-discharge diode to prevent discharge of the charge of the first capacitor. This prevents the first capacitor from being discharged, so that the first capacitor holds the voltage necessary for the operation of the step-down circuit. This allows smooth power supply to the step-down circuit.

In addition, when the driving force of the movable iron core 62 is small, the excitation current flowing through the electromagnetic coil 5 can be reduced. In such a case, at least one of the first diode 43, the second diode 44 and the third diode 46 can be omitted.

Embodiment 2.
FIG. 4 is a diagram showing a configuration example of an electromagnetic coil and an inductor according to the second embodiment. 5 is a sectional view showing a section of the electromagnetic coil and the inductor shown in FIG. 4. FIG. In Embodiment 1, the electromagnetic coil 5 and the inductor 322 are configured as separate parts. When the electromagnetic coil drive circuit 3 is used with a high power supply voltage such as AC440V, a voltage obtained by adding the input voltage and the surge voltage due to the back electromotive force of the electromagnetic coil 5 is applied to the inductor 322 . Therefore, it is necessary to use an inductor 322 having a rated performance equal to or higher than the summed voltage. Selecting a commercially available inductor results in a large external size and a high manufacturing cost.

Therefore, in the second embodiment, as shown in FIG. 4, a winding 350 is wound around the outer periphery of the electromagnetic coil 5 to form an inductor 322, and an inductor component 50 is formed by using the electromagnetic coil 5 and the inductor 322 as the same component. doing. More specifically, as shown in FIG. 5, an inductor component 50 is configured with a bobbin 51, a yoke 52, a fixed iron core 53, a movable iron core 54, and a shaft 55. As shown in FIG.

A through hole is provided in the central portion of the bobbin 51 . A winding 56 for forming the electromagnetic coil 5 is wound around the bobbin 51 . The yoke 52 is arranged outside the bobbin 51 . A through hole is provided in the central portion of the fixed iron core 53 . The fixed iron core 53 is provided inside the through hole of the bobbin 51 . The movable iron core 54 is provided in the through hole of the bobbin 51 and is provided movably in the through hole of the bobbin 51 . The shaft 55 is held by the movable iron core 54 and movably penetrates through the through hole of the fixed iron core 53 . The inductor 322 is provided between the electromagnetic coil 5 and the yoke 52 and is composed of a winding 350 wound around the outside of the electromagnetic coil 5 .

As described above, according to the electromagnetic coil drive circuit according to the second embodiment, the inductor provided in the step-down circuit is configured by winding a wire around the outer circumference of the electromagnetic coil. As a result, the electromagnetic coil and the inductor can be configured as inductor parts, so that the number of parts and the manufacturing cost can be reduced. In addition, since the electromagnetic coil and the inductor can be configured as inductor parts, the size of the electromagnetic coil drive circuit can be reduced compared to the case where equivalent parts are selected from commercially available products.

Embodiment 3.
Embodiment 3 describes that the circuit configuration of Embodiment 1 can be simplified by using inductor 322 shown in Embodiment 2. FIG. FIG. 6 is a diagram showing a configuration example of an electromagnetic coil drive circuit according to the third embodiment.

An electromagnetic coil drive circuit 3A according to the third embodiment has the configuration of the electromagnetic coil drive circuit 3 according to the first embodiment shown in FIG. 1, in which the switching element drive circuit 34 is replaced with a switching element drive circuit 34A. The second drive circuit 342 is removed from the switching element drive circuit 34A. Accordingly, the second switching element 42 is also eliminated. Therefore, the high potential side of the current suppression circuit 45 is connected to the cathode of the second diode 44 and the low potential side of the current suppression circuit 45 is connected to the third power line 38 . The rest of the configuration is the same as or equivalent to the configuration shown in FIG. 1, and the same or equivalent components are denoted by the same reference numerals, and overlapping descriptions are omitted.

In the electromagnetic coil drive circuit 3A according to the third embodiment, when the first switching element 41 is made non-conductive, an attracting and holding current flows through the current suppressing circuit 45 . The current suppression circuit 45 operates to suppress current caused by the back electromotive force of the electromagnetic coil 5 from entering the inductor 322 of the step-down circuit 32 .

In the configuration of the third embodiment, when the inductor 322 having the configuration according to the second embodiment is used, the winding 350 of the inductor 322 is made to have a large current carrying capacity for a short time. In this way, the second switching element 42 and the second drive circuit 342 can be eliminated as in the configuration of FIG. Moreover, the current suppression circuit 45 can satisfy the required performance even if it is configured using a simple circuit element such as a resistor. Furthermore, by using a winding having a high withstand voltage for the winding 350 constituting the inductor 322, it becomes possible to use the electromagnetic coil drive circuit 3A at a high power supply voltage such as AC440V.

As described above, according to the electromagnetic coil drive circuit according to the third embodiment, the step-down circuit includes an inductor formed by winding a wire around the outer periphery of the electromagnetic coil, and the current suppression circuit has It operates to suppress the current caused by the electromotive force from entering the inductor of the step-down circuit. In this configuration, if the winding wound around the outer periphery of the electromagnetic coil is a winding having a large short-time current resistance and a high withstand voltage, the second switching element 42 and the second drive circuit 342 and can be reduced. This enables further miniaturization of the electromagnetic coil drive circuit.

It should be noted that the configuration shown in the above embodiment shows an example of the contents of the present invention, and it is possible to combine it with another known technique, and the configuration can be changed without departing from the gist of the present invention. It is also possible to omit or change part of

1 AC power supply 2 Full-wave rectifier circuit 3, 3A Electromagnetic coil drive circuit 5 Electromagnetic coil 6 Driven part 31 First capacitor 32 Step-down circuit 33 Second capacitor 34, 34A Switching element drive circuit , 36 first power supply line, 37 second power supply line, 38 third power supply line, 41 first switching element, 42 second switching element, 43 first diode, 44 second diode, 45 current suppression circuit, 46 third diode, 50 inductor component, 51 bobbin, 52 yoke, 53, 61 fixed iron core, 54, 62 movable iron core, 55 shaft, 56, 350 winding, 321 diode, 322 inductor, 323 power supply IC, 323a switch section, 324, 343 voltage detection circuit, 325 connection point, 341 first drive circuit, 342 second drive circuit, T1, T2 DC input terminals.

Claims (5)

An electromagnetic coil drive circuit for driving an electromagnetic coil,
A first switching device arranged between a first power supply line on a high potential side and a second power supply line on a low potential side through the electromagnetic coil, and arranged on a lower potential side than the electromagnetic coil. an element;
a first drive circuit that drives the first switching element using a first voltage applied between the first power line and the second power line;
a second switching element arranged between the first power supply line and a third power supply line on the low potential side via the electromagnetic coil and arranged on the low potential side relative to the electromagnetic coil;
a second drive circuit that drives the second switching element using a second voltage applied between the first power line and the third power line;
a step-down circuit that steps down the first voltage using the first voltage to generate the second voltage;
It is connected between a first terminal, which is a terminal on the low-potential side of the second switching element, and the third power supply line, and suppresses a current exceeding a certain value from flowing from the electromagnetic coil to the step-down circuit. and a current suppression circuit that
The current suppression circuit operates to suppress entry of a current resulting from back electromotive force of the electromagnetic coil into the step-down circuit.
An electromagnetic coil drive circuit characterized by: An electromagnetic coil drive circuit for driving an electromagnetic coil,
A first switching device arranged between a first power supply line on a high potential side and a second power supply line on a low potential side through the electromagnetic coil, and arranged on a lower potential side than the electromagnetic coil. an element;
a first drive circuit that drives the first switching element using a first voltage applied between the first power line and the second power line;
a second switching element arranged between the first power supply line and a third power supply line on the low potential side via the electromagnetic coil and arranged on the low potential side relative to the electromagnetic coil;
a second drive circuit that drives the second switching element using a second voltage applied between the first power line and the third power line;
a step-down circuit that steps down the first voltage using the first voltage to generate the second voltage;
a first capacitor having one end connected to the first power supply line;
a diode having an anode connected to the other end of the first capacitor and a cathode connected to the second power supply line;
An electromagnetic coil drive circuit comprising: An electromagnetic coil drive circuit for driving an electromagnetic coil,
A first switching device arranged between a first power supply line on a high potential side and a second power supply line on a low potential side through the electromagnetic coil, and arranged on a lower potential side than the electromagnetic coil. an element;
a first drive circuit that drives the first switching element using a first voltage applied between the first power line and the second power line;
a second switching element arranged between the first power supply line and a third power supply line on the low potential side via the electromagnetic coil and arranged on the low potential side relative to the electromagnetic coil;
a second drive circuit that drives the second switching element using a second voltage applied between the first power line and the third power line;
a step-down circuit that steps down the first voltage using the first voltage to generate the second voltage,
The step-down circuit includes an inductor,
An electromagnetic coil drive circuit, wherein the inductor is configured by winding a wire around the outer circumference of the electromagnetic coil. When the electromagnetic coil starts to be driven, the first switching element is driven by the first drive circuit to attract the movable iron core of the electromagnetic coil, and after the movable iron core is attracted, the first driving is performed. 4. The apparatus according to any one of claims 1 to 3, wherein the drive by the circuit is stopped and the second switching element is driven by the second drive circuit to maintain the attraction of the movable iron core. Electromagnetic coil drive circuit. An electromagnetic coil drive circuit for driving an electromagnetic coil,
A first switching device arranged between a first power supply line on a high potential side and a second power supply line on a low potential side through the electromagnetic coil, and arranged on a lower potential side than the electromagnetic coil. an element;
a first drive circuit that drives the first switching element using a first voltage applied between the first power line and the second power line;
a step-down circuit including an inductor formed by winding a wire around the outer circumference of the electromagnetic coil, the step-down circuit using the first voltage to step down the first voltage to generate a second voltage;
It is arranged between the first power supply line and the third power supply line on the low potential side via the electromagnetic coil, and the current caused by the back electromotive force of the electromagnetic coil enters the inductor of the step-down circuit. a current suppression circuit operable to suppress the
An electromagnetic coil drive circuit comprising:

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