JPH0855721A - Dc-operated switch controller - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a switch element connected in series with the exciting coil of a switch by an opening surge impressed upon the element. CONSTITUTION:Voltage divider circuits R2 and R3 which generate a control voltage V3 by dividing the voltage applied across the exciting coil Lx of a DC-operated switch are provided and a transistor Q4 which is conducted by the voltage V3 is connected to the route of a reflux current. When a reset command is issued to the switch, the application of the voltage is stopped after the voltage applied across the coil Lx is once switched to a holding voltage. Therefore, the opening surge impressed upon the switch element is sufficiently suppressed and the breakdown of the transistor Q4 is prevented when the transistor Q4 breaks a reflux current, because the transistor Q4 is never cut off when an actuating voltage is applied across the coil Lx.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC electrically operated switch controller for supplying and controlling operating power to a DC electrically operated switch.

[0002]

2. Description of the Related Art FIG. 8 shows a configuration example of a conventional DC electrically operated switchgear control device. In general, a DC electric operation type switch has a lower voltage (holding voltage) required to hold a state than a voltage required for starting (starting voltage). As shown in FIG. 8, it has a configuration including two power supply circuits. In FIG.
Reference numeral 11 is a first power supply circuit that outputs a starting voltage, and 12 is a second power supply circuit that outputs a holding voltage. Also, Q1
Is a transistor serving as a first switching element that outputs a starting voltage, and Q2 is a transistor serving as a second switching element that outputs a holding voltage.

In FIG. 8, when the exciting coil 15 of the DC electric operation type switch (hereinafter simply referred to as "switch") is activated, the control unit 13 turns on the transistor Q1 and turns off the transistor Q2 to turn on the first switch. The starting voltage which is the output voltage of the power supply circuit 11 is applied to the exciting coil 15 of the switch connected to the output terminal 14. As a result, when the switch starts responding (starts the transition from the open state to the closed state) and then the switch completes responding (when the switch enters the closed state), the control unit 13 causes the transistor Q2 to operate. Is turned on, the transistor Q1 is turned off, and the second power supply circuit 1
The holding voltage which is the output voltage of 2 is applied to the exciting coil 15 of the switch through the diode D2, and the holding voltage for keeping the switch in the closed state is applied. Second power supply circuit 12
Uses the first power supply circuit 11 as an input power supply and steps down the input voltage and outputs it. Therefore, a holding voltage lower than the starting voltage is applied to the exciting coil 15 of the switch. The switch maintains the closed state by continuing to apply the holding voltage. After that, when the switch is restored, the control unit 13 turns off the transistor Q2 to stop the voltage application from both the power supply circuits 11 and 12, and the switch is switched from the closed state to the open state (non-excitation state). Move to. In this way, the DC electric operation type switch control device controls the state of the switch.

[0004]

DISCLOSURE OF THE INVENTION In the conventional DC electric operation type switch control device, when the DC electric operation type switch is restored, when the voltage application to the exciting coil is stopped by shutting off the switch element, An open surge due to the stored energy of is applied to the switch element. In the example shown in FIG. 8, when the voltage applied to the exciting coil is switched from the starting voltage to the holding voltage, the transistor Q1 is turned off, thereby adding an open surge to the transistor Q1 and changing the applied voltage to the exciting coil. When stopping, the transistor Q2 is turned off to turn off the transistor Q2.
An open surge is applied to. However, since the energy of these open surges is usually small, there is no particular problem. However, when a switch return command is applied immediately after applying a starting voltage to the exciting coil in response to the switch drive command, the transistor Q1 is turned off without the transistor Q2 being turned on, so that the voltage is high. Transistor Q due to large open energy surge due to starting voltage
There was a risk that 1 would be destroyed.

The above-mentioned problem is solved in an apparatus which separately includes a power supply for generating a starting voltage and a power supply for generating a holding voltage as shown in FIG. 8 and selectively outputs the output voltage via a switch element. Not limited to this, as will be described below, the power supply for generating the starting voltage and the power supply for generating the holding voltage are configured by one switching regulator, and the output voltage is controlled by controlling the on-duty ratio of the switching transistor. The same occurs in a device in which the voltage and the holding voltage are switched.

An example using a step-down switching regulator is shown in FIG. In FIG. 9, Q3 is a switching transistor, D1 is a flywheel diode,
L is a choke coil, C1 is a smoothing capacitor, and Lx is an exciting coil of a switch. In FIG. 9, when power is supplied to the exciting coil of the switch, the exciting current IL flows, but the energy accumulated in the exciting coil of the switch even after the power supply is stopped is the return current I1. Is discharged as. Therefore, the switch recovery time becomes long.
In order to prevent this, a configuration in which the transistor Q4 is inserted in the path of the return current I1 and the transistor Q4 is cut off in synchronization with the stop of power supply to the exciting coil Lx can be considered. However, when the transistor Q4 is cut off, an open surge voltage of the switch exciting coil is applied between the collector and the emitter of the transistor Q4, and when the voltage exceeds the safe operating area of the transistor, the transistor Q4
There is a problem that 4 is destroyed.

An object of the present invention is to provide a DC electrically operated switch control device in which an open surge to a switch element due to stored energy of an exciting coil of a DC electrically operated switch is reduced to prevent destruction of the switch element. To do.

Another object of the present invention is to generate a starting voltage and a holding voltage using a single power supply circuit, and
It is an object of the present invention to provide a DC electric operation type switch control device which shortens the release time of the energizing current to the exciting coil of the DC electric operation type switch and prevents the delay of the return response of the DC electric operation type switch.

[0009]

According to a first aspect of the present invention, there is provided a direct current electrically operated switch control device which generates a startup voltage required to start up a direct current electrically operated switch and outputs the startup voltage as a first voltage. A first power supply circuit for applying to the exciting coil of the DC electric operation type switch via the switch element of No. 1 and for maintaining the state of the DC electric operation type switch after starting the DC electric operation type switch. A second power supply circuit that generates a required holding voltage and applies the holding voltage to the exciting coil via a second switch element; and a first switch element and a second switch that receives a drive command or a return command. A switch element control means for controlling ON / OFF of the switch element to select an applied voltage to the exciting coil, the voltage applied to the exciting coil is a voltage applied to the exciting coil. After switching from the holding voltage to the holding voltage, a time measuring means for measuring a fixed time until the holding voltage stabilizes, and the switch element when receiving the return command after the time measuring means measures the fixed time. A means for controlling the control means to immediately stop the voltage application to the exciting coil; and a means for controlling the switch element control means to control the switching element when the return command is received before the time measuring means measures the fixed time. Means for stopping the voltage application to the exciting coil after applying the holding voltage to the coil for the fixed time.

A DC electrically operated switch controller according to a second aspect of the present invention is a DC electrically operated switch controller for generating a voltage applied to an exciting coil of a DC electrically operated switch at a switching power supply section. A switching element control circuit for connecting the switching element for shutting off the reflux current in series with the exciting coil and for shutting off the switching element for shutting off the circulating current in conjunction with the stop of the voltage applied to the exciting coil. When a command is received, the switching transistor of the switching power supply circuit is driven at the on-duty ratio required to generate the starting voltage of the DC electrically operated switch, and then the state of the DC electrically operated switch is maintained. Means for driving the switching transistor with an on-duty ratio required to generate a holding voltage; After the voltage applied to the exciting coil is switched from the starting voltage to the holding voltage, the time keeping means counts a fixed time until the holding voltage stabilizes, and the time keeping means measures the fixed time. Means for immediately keeping the switching transistor in an off state when receiving a return command, and generating the holding voltage for the fixed time only when the return command is received by the time counting means for counting the fixed time. Means for keeping the switching transistor in the off state after driving the switching transistor at the duty ratio required for.

[0011]

In the DC electrically operated switchgear controller according to the first aspect of the present invention, the starting voltage generated by the first power supply circuit is the same as that shown in FIG. The holding voltage generated by the second power supply circuit is applied to the exciting coil via the second switch element. When the drive command of the DC electric operation type switch is received, the first switch element is turned on and the starting voltage is applied to the exciting coil, and after the start, the second switch element is turned on and the first switch element is turned on. When turned off, the holding voltage is applied to the exciting coil. After that, when the return command of the DC electric operation switch is received, the second switch element is also turned off and the voltage application to the exciting coil is stopped. However, even if a return command is received while the starting voltage is being applied to the exciting coil, the applied voltage to the exciting coil is not immediately stopped, but is switched to the holding voltage once and the holding voltage stabilizes. Only after that, the voltage application is stopped. The reason why the voltage application is stopped after the holding voltage is stabilized is to surely suppress the open surge applied to the switch element. That is, immediately after switching from the starting voltage to the holding voltage, the applied voltage to the exciting coil becomes unstable due to the transient phenomenon determined by the circuit constant including the inductance component of the exciting coil. , The open surge applied to the switch element may not be suppressed sufficiently. Therefore, the voltage applied to the exciting coil is switched to the holding voltage, and the voltage application is stopped after a fixed time required for the holding voltage to stabilize.

According to the direct-current electrically operated switchgear controller according to claim 1 of the present invention, the switch is activated when the starting voltage is applied to the exciting coil or immediately after the starting voltage is switched to the holding voltage. Since the element is not interrupted, the open surge applied to the switch element when the switch element is interrupted is sufficiently suppressed, and the switch element is prevented from being destroyed.

According to the direct-current electrically operated switch controller of the second aspect of the present invention, the switching transistor is turned on at an on-duty ratio of, for example, 100% when a drive command for the direct-current electrically operated switch is received. Then, the starting voltage is applied to the exciting coil, the switching transistor is turned on at a predetermined on-duty ratio after the starting, and the holding voltage is applied to the exciting coil. After that, when the return command of the DC electric operation switch is received, the switching transistor is kept in the OFF state, and the voltage application to the exciting coil is stopped. However, even if a return command is received while the starting voltage is being applied to the exciting coil, the applied voltage to the exciting coil is not immediately stopped, but is switched to the holding voltage once and the holding voltage stabilizes. Only after that, the voltage application is stopped.

According to the second aspect of the present invention, there is provided the direct-current electrically operated switch control device, in which the switch is activated when the starting voltage is applied to the exciting coil or immediately after the starting voltage is switched to the holding voltage. Since the element is not interrupted, the open surge applied to the switch element when the switch element is interrupted is sufficiently suppressed, and the switch element is prevented from being destroyed. Further, after the application of the voltage to the exciting coil is stopped, the return current cutoff switch element cuts off the return current, so that a delay in the return response of the DC electrically operated switch caused by the return current flowing through the exciting coil is prevented.

FIG. 1 is a waveform chart showing an example of the operation of the DC electric operation type switchgear controller of the present invention.

In FIG. 1, the vertical axis represents the voltage applied to the exciting coil of the DC-electrically operated switch, and the horizontal axis represents time.
As shown in (a), when a drive command is given at t1 to drive a DC electrically operated switch, a starting voltage is first applied, and a holding voltage is applied after t2 when the response of the switch is completed. To do. After that, if there is a return command at t3, the voltage application to the exciting coil is stopped. If shown in (c),
Even if there is a return command while applying the starting voltage to the exciting coil, the voltage application is not immediately stopped at that point, but the applied voltage to the exciting coil is once switched to the holding voltage and then the holding voltage is maintained. The voltage application to the exciting coil is stopped only after a predetermined time T1 required for the voltage to stabilize. Further, as shown in (b), there is a return command from when the voltage applied to the exciting coil is switched from the starting voltage to the holding voltage until the time T1 required for stabilizing the applied voltage to the exciting coil elapses. However, the voltage application is not stopped at that point, and T1
The voltage application to the exciting coil is stopped only after the lapse of time.

[0017]

FIG. 2 shows the configuration of the voltage control circuit portion of the DC electric operation type switchgear control apparatus according to the first embodiment of the present invention. In FIG. 2, 11 is a first power supply circuit that outputs a starting voltage, 12 is a second power supply circuit that outputs a holding voltage, Q1 is a transistor as a first switch element that outputs a starting voltage, and Q2. Is the second that outputs the holding voltage
Is a transistor as a switch element. The transistor control circuit 6 controls conduction / cutoff of the transistors Q1 and Q2. Further, Lx is an exciting coil of the DC electric operation switch controller, and the circuit composed of Lx, R1 and D3 is a discharging circuit for discharging the stored energy of the exciting coil Lx when the voltage application to the exciting coil Lx is stopped.

Next, FIG. 3 is a block diagram showing the configuration of the control section of the DC electric operation type switchgear control apparatus according to the first embodiment.
Shown in In FIG. 3, the CPU 1 executes a program written in advance in the ROM in the memory 2 to perform the processing described later. The timer circuit 3 corresponds to the time measuring means according to the present invention, and measures the elapsed time after switching from the starting voltage to the holding voltage. The I / O port 4 inputs switch opening and closing commands from the outside. The contact input unit 5 inputs the state of the auxiliary contact of the switch. Transistor control circuit 6
Outputs a control signal to the transistors Q1 and Q2 shown in FIG. 2 to generate a starting voltage or a holding voltage. The CPU 1 sends a signal representing three states, that is, a state in which a starting voltage is generated, a state in which a holding voltage is generated, and a stop state, through the I / O port 7 to the transistor control circuit 6
Give to.

FIG. 4 is a flow chart showing the processing procedure of the CPU shown in FIG. First, the transistors Q1 and Q2 shown in FIG.
1 → n2). If there is a closing command, Q1 is turned on and clocking is started (n3 → n4). After that, it is determined whether or not there is an opening command, the state of the auxiliary contact, and whether or not the switch inability determination time has elapsed (n5, n6, n7). If the auxiliary contact is closed, the second transistor Q2
Is turned on and the first transistor Q1 is turned off (n6 →
n8). If there is an opening command before the auxiliary contact is turned on, the process moves to step n8 (n5 → n).
8). If the auxiliary contact remains in the open state even after the predetermined closing failure determination time, it is considered that the switch cannot be closed, and the process proceeds to step n8 (n).
7 → n8). If Q2 is turned on and Q1 is turned off in step n8, time counting is started from that point (n9). Then, it is determined whether or not a time T1 until the applied voltage to the exciting coil stabilizes at a predetermined holding voltage is reached,
Then, the presence / absence of the opening command is determined (n10, n11).
If there is an open command after T1 has already passed, the transistor Q2 is turned off (n10 → n11 → n12). The steps n11 and n12 correspond to the "means for immediately stopping the voltage application to the exciting coil" according to claim 1.
Even if an opening command is issued before T1 elapses, the presence or absence of the opening command is not determined in step n11 until T1 elapses, so that the transistor Q2 is turned off after T1 elapses ( n10 → n11 → n
12). The steps n10, n11 and n12 correspond to the "means for stopping the voltage application to the exciting coil after applying the holding voltage for a certain period of time". Q2
After turning off, the state of the auxiliary contact is judged, and if it is opened, a series of processing is ended (n13). Although not shown in FIG. 4, if the auxiliary contact remains in the closed state for a certain period of time after the transistor Q2 is turned off, it is considered that the switch cannot be opened, and a predetermined abnormality process is performed. I do.

Next, FIG. 5 shows the configuration of the voltage control circuit portion of the DC electrically operated switchgear control apparatus according to the second embodiment of the present invention. In FIG. 5, AC is an AC power supply, and DB is a diode bridge circuit. In the device shown in FIG. 5, a switching transistor Q3, a choke coil L, and a smoothing capacitor C1 are connected in this order in series on the output side of the power supply, and the choke coil L and the smoothing capacitor C1 are in parallel when viewed from the switching transistor Q3 side. In this way, the flywheel diode D1 is connected, and the series circuit of the transistor Q4 as a return current cutoff switch element and the exciting coil Lx of the switch is connected to both ends of the smoothing capacitor C1. The switching transistor Q3 is switching-controlled by the control signal S1 output from the transistor control circuit 6. A voltage dividing circuit including resistors R2 and R3 is connected to both ends of the smoothing capacitor C1, and the divided voltage is connected to the base of the transistor Q4 as a control voltage V3. A discharge circuit including a diode D3 and a resistor R1 is connected to the exciting coil Lx of the switch.

Waveforms and states of each part of the circuit shown in FIG. 5 are shown in FIG. The symbols in FIG. 6 correspond to the symbols in FIG. 5, respectively. The transistor control circuit 6 shown in FIG.
When the switch is started at the timing of 1, the switching transistor Q3 is kept in the ON state (driving at 100% on-duty ratio), and the starting voltage is applied to the exciting coil. This activates the switch. After that, when the response of the switch is completed at t2, thereafter, the switching transistor Q3 is driven at a constant on-duty ratio, and a holding voltage for holding the state of the switch is applied to the exciting coil. Here, input voltage of choke coil is V1
, V2 is the voltage of the smoothing capacitor when the switching transistor Q3 is turned on / off at a constant on-duty ratio, T is the on / off period of the switching transistor Q3, and Ton is V2 = (Ton /
T) * V1.

This is because when the switching transistor Q3 is turned on, a current is supplied to the choke coil L and the smoothing capacitor C1 so that a load current flows, and when the energy stored in the choke coil L is turned off, the switching transistor Q3 is turned off. Due to being emitted through the flywheel diode D1.

When the switch is restored at the timing of t3, the switching transistor Q3 is kept in the off state.
After t3, the divided voltage V3 given as the control voltage (base voltage) to the transistor Q4 decreases. When the voltage V3 falls below the control voltage required to maintain the on state of the transistor Q4, the transistor Q4 turns off.
At this time, an open surge voltage is applied between the collector and the emitter of the transistor Q4. However, the starting voltage applied to the exciting coil is 200 V, and the holding voltage is 24 V, for example.
If V is set, the transistor Q
The energy of the open surge is (24/200) ² ≈1 / 69, which is extremely small as compared with the case where 4 is cut off.

The configuration of the control unit of the DC electric operation type switchgear control device in the second embodiment is the same as that shown in FIG. 3 as the first embodiment. Here, the processing procedure of the control unit of the DC electric operation type switchgear control apparatus according to the second embodiment is shown as a flowchart in FIG. First, the switching transistor Q3 shown in FIG. 5 is kept in the off state, and the closing instruction is waited (n1 → n2). If there is a closing command, Q3 is kept on and time counting is started (n3 → n4).
After that, it is determined whether or not there is an opening command, the state of the auxiliary contact, and whether or not the switch inability determination time has elapsed (n
5, n6, n7). If the auxiliary contact is turned on, the switching transistor Q3 starts to be interrupted at a predetermined on-duty ratio (n6 → n8). This step n8
Corresponds to the "means for driving the switching transistor at the on-duty ratio required to generate the holding voltage". If there is an opening command before the auxiliary contact is turned on, the process moves to step n8 (n
5 → n8). If the auxiliary contact remains in the open state even after a predetermined closing failure determination time, it is considered that the switch cannot be closed, and the process proceeds to step n8 (n7 → n8). If the intermittent operation of Q3 is started at a predetermined on-duty ratio in step n8, the time counting is started from that point (n9). Then, it is determined whether or not the time T1 until the voltage applied to the exciting coil stabilizes at the predetermined holding voltage elapses, and the presence or absence of the open command is determined (n10, n11). If there is an open command after T1 has already passed, the transistor Q3 is kept off (n
10 → n11 → n12). This step n11, n12
Corresponds to the "means for immediately keeping the switching transistor in the off state". Even if the opening command is issued before T1 elapses, the presence or absence of the opening command is not determined in step n11 until T1 elapses, so that the transistor Q3 is turned off after T1 elapses ( n10 → n11 → n12). The steps n10, n11, and n12 correspond to the "means for keeping the switching transistor in the off state after driving the switching transistor at the duty ratio required to generate the holding voltage for a certain time". After Q3 is turned off, the state of the auxiliary contact is judged, and if it is opened, a series of processing is terminated (n1
3). Although omitted in FIG. 7, the transistor Q
If 3 is kept in the OFF state and the state of the auxiliary contact remains closed even after a certain period of time, it is considered that the switch cannot be opened and a predetermined abnormality process is performed.

In the first and second embodiments, an example in which the present invention is applied to a switch that shifts from an open state to a closed state when a voltage is applied is shown, but the present invention is not limited to this. However, it can also be applied to a switch that shifts from a closed state to an open state when a voltage is applied.

In the above embodiment, the bipolar type transistor is used as the switch element according to the present invention.
The present invention can be applied to the case where a switching element such as a unipolar transistor such as a MOS-FET or a thyristor is used, and the same effect can be obtained.

[0027]

According to the direct-current electrically operated switch controller according to the first and second aspects of the present invention, when the direct-current electrically operated switch is driven, the exciting coil is operated only for the time until the response is completed. The starting voltage is applied to the coil, the holding voltage is applied after the starting, and the voltage application to the exciting coil is stopped when the DC electrically operated switch returns, but the voltage applied to the exciting coil is used for starting. The voltage application to the exciting coil is not stopped until the applied voltage to the exciting coil stabilizes after the voltage is switched to the holding voltage. Therefore, since the switch element is not interrupted when the starting voltage is applied to the exciting coil or immediately after the starting voltage is switched to the holding voltage, the open surge applied to the switch element is sufficiently suppressed. As a result, the switch element is prevented from being destroyed.

Further, according to the direct-current electrically operated switch controller according to the second aspect of the invention, the return current interruption switch element interrupts the return current after the voltage application to the excitation coil is stopped, so that the return current flows to the excitation coil. The delay of the return response of the DC electrically operated switch due to the flow of current is prevented.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing an operation example of a DC electric operation type switchgear control device of the present invention.

FIG. 2 is a diagram showing a configuration of a voltage control circuit portion of the DC electric operation type switchgear control apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a control unit of the DC electric operation type switchgear control apparatus according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing a processing procedure of a control unit of the DC electric operation type switchgear control apparatus according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a voltage control circuit portion of a DC electrically operated switchgear control device according to a second embodiment of the present invention.

6 is a diagram showing waveforms and states of respective parts of the circuit shown in FIG.

FIG. 7 is a flowchart showing a processing procedure of a control unit of the DC electric operation type switchgear control apparatus according to the second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a conventional DC electrically operated switchgear control device.

FIG. 9 is a diagram showing an example in which a step-down switching regulator is used in a voltage control circuit of a DC electrically operated switchgear control device.

[Explanation of symbols]

 6-transistor control circuit DB-diode bridge Q1-transistor (first switch element) Q2-transistor (second switch element) Q3-switching transistor Q4-transistor (switch element for shutting off return current) L-choke coil C1- Smoothing capacitor D1-Flywheel diode Lx-Exciting coil of DC electrically operated switch I1-Return current

Claims (2)

[Claims] 1. A first voltage generator for generating a starting voltage required for starting a DC electrically operated switch and applying the starting voltage to an exciting coil of the DC electrically operated switch via a first switch element. And a holding voltage required to hold the state of the DC electrically operated switch after the DC electrically operated switch has been activated, and the holding voltage is generated via the second switch element. A second power supply circuit to be applied to the exciting coil, and a switch element control for controlling on / off of the first switch element and the second switch element in response to a drive command or a return command to select an applied voltage to the exciting coil. In a DC electrically operated switchgear control device including a means, a constant voltage applied to the excitation coil after the switching from the starting voltage to the holding voltage until the holding voltage becomes stable. A clocking means for clocking the time, and a means for immediately stopping the voltage application to the exciting coil by controlling the switch element control means when the clocking means receives the return command after clocking the fixed time, When the clocking means receives the return command before timing the fixed time, it controls the switch element control means to apply the holding voltage to the exciting coil for the fixed time, and then the voltage to the exciting coil. A DC electrically operated switchgear control device comprising means for stopping the application. 2. A DC electric operation type switch controller for generating a voltage applied to an excitation coil of a DC electric operation type switch in a switching power supply unit, wherein a switching element for shutting off a return current is connected in series to the excitation coil. A switch element control circuit for disconnecting the return current interrupting switch element in conjunction with the connection of the applied voltage to the exciting coil is provided, and when the drive command is received, the DC electrically operated switch is started. The switching transistor of the switching power supply circuit is driven at an on-duty ratio required to generate a voltage, and then the switching transistor is driven at an on-duty ratio required to generate a holding voltage for holding the state of the DC electrically operated switch. A driving means, and a voltage applied to the exciting coil is held from the starting voltage. The switching transistor, the switching transistor is immediately turned off when receiving a return command after the fixed time has elapsed after the fixed voltage has been stabilized, and the time measuring means receives a return command after measuring the fixed time. And a switching unit that drives the switching transistor at a duty ratio required to generate the holding voltage for the fixed time only when the return command is received before the time counting means measures the fixed time. A DC electrically operated switchgear control device comprising: means for keeping a transistor in an off state.