JP2019197718A - Reed relay hybrid switch - Google Patents

Abstract

To perform hybrid switching of a reed relay characterized by high insulation resistance.SOLUTION: In a hybrid switch in which a semiconductor switch and a reed relay are connected in parallel, a leakage current is eliminated by using an auxiliary reed relay in series with the semiconductor switch, and the current and voltage at the time of switching are controlled by a gate control circuit of the semiconductor switch.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a small-sized relay switchgear, and in particular, a reed relay having a high speed, a long life, and high reliability is used in many electronic circuits because of its small size. However, the power capacity ranged from several tens of watts to a maximum of 100 watts. In order to increase the current that can be opened and closed, semiconductor switches are connected in parallel, and the semiconductor switches are turned off when on and off. A direct-current hybrid switchgear.

  The present invention relates to a direct current switchgear and takes advantage of a reed switch to solve the disadvantage of being unable to cut off an energization current. The current interruption capability of the reed switch is extremely small, and the control of DC power is limited considering the consumption of contacts.

  The feature of the reed switch is that the electrode sealed in the glass tube is driven by a magnetic field from the outside, the insulation resistance is very high, it is 10 12 ohms or more, and this is hybridized Ingenuity that is not lost is necessary.

  A conventional hybrid switch is a power MOSFET or IGBT having an insulated gate and can turn on / off direct current, but a semiconductor device has a larger leakage current than a reed switch. In order not to lose the characteristics of the reed switch, it is necessary to secure the insulation resistance by inserting the reed switch in series in the semiconductor circuit.

  The present invention intends to apply the principle of the arc-free switch disclosed in Japanese Patent No. 5864006 to the reed relay switch having a high frequency, high frequency, and high insulation resistance.

Patent 5864006 "DC power system safety device" Japanese Patent Application No. 2015-199768 “Restart Voltage Control Device” Japanese Patent Application No. 2016-13814 “Arc-free switchgear”

Since the DC current switching circuit in parallel with the mechanical contact and the semiconductor switch shown in Patent Document 1 controls the semiconductor switch using the b-throw of the double throw contact, the energization of the semiconductor is changed from the a-contact to the b-contact. Only transfer time to contact. In addition, the a-contact is an ideal procedure in which a contact voltage is opened and the maximum distance is reached, and then it is cut off later to generate a re-emergence voltage.
However, in the cut-off state, a slight current flows from the b-contact through the pull-up resistor (100 kΩ or more) although it has a high resistance. The current becomes a leakage current and is continuous at the time of interruption, so that there is a problem that the high resistance interruption characteristic which is a feature of the reed switch is lost.

  Also, the reed switch basically has a configuration of a normally open a contact only because of the drive structure, and since there is no b contact, it is necessary to prepare a gate drive circuit for the semiconductor switch separately. Further, a reed switch S1 for cutting off a leakage current is provided in series with the semiconductor circuit for the purpose of eliminating the leakage current, but it is also necessary to separately drive the drive. Further, since it is necessary to prevent the pulse current from flowing to the semiconductor circuit with the voltage when the reed switch S1 for cutting off the leakage current is turned on, it is also necessary to turn on the reed switch S1 after the gate is turned off.

  The present invention has been made in view of the above points. The object of the present invention is to provide a highly reliable isolated power source such as a sequence, a gate drive power source, and a timer circuit, which is necessary when the reed switch is applied to a hybrid switch. It is to provide a means for raising

  An auxiliary reed relay S1 is placed in series with the semiconductor switch circuit, and after the current is cut off by the semiconductor switch, S1 is quickly opened to ensure a high insulation resistance. Since the auxiliary reed relay S1 is short in energization time and has almost no current such as leakage current or leakage current of the pull-up resistor of the semiconductor switch, it can be interrupted without arc.

  When the load is opened and closed, an overvoltage occurs when the load is cut off when the inductance is large, and a rush current is generated when the capacitor is loaded. In the gate control circuit 4 of the semiconductor switch S2, various current / voltage controls are performed. can do. The gate control circuit 4 performs, for example, control that also serves as overcurrent and overvoltage protection, and can also perform functions of current pattern control, regenerated voltage pattern control, overpower protection, and high temperature protection of the semiconductor switch itself. Here, a gate control circuit having a small number of components, simply connecting a capacitor C1 between the drain and gate to form a Miller integrating circuit, and controlling the on / off of the semiconductor switch slowly with R1 and C1 is explained. To do.

  In order to manage these operations collectively, there is a sequence control circuit (not shown in the figure), and a sequence determined internally by a single external on / off signal like a conventional single reed relay. By operating sequentially with a programmed sequencer that operates, the conventional maximum reed relay had a withstand voltage of 1 kV, an energization current of about 2 A, and a cutoff current of 0.1 A, because the current cutoff capacity increased. The power capacity is greatly increased from about 100 W to about 1 kW, and an arc-free interrupted reed relay switching device capable of switching DC power at high speed is realized.

Because the reed switch is small, has a long life, and is sealed in a glass tube in an inert gas, it is a metal contact, so there is no problem of contamination such as water and seawater regardless of the external environment. There are few contact failures. Furthermore, the drive mechanism of the reed relay is simple, so there is little failure at high speed.
If a reed relay is used in a hybrid switchgear, a reed relay that can hardly be expected to have a current interruption capability can obtain a current interruption capability with a hybrid interruption with a semiconductor switch, and power can be turned on and off at high speed. become.

  If the hybrid of the present invention is applied to a reed switch, the field of use of the reed switch is expanded. Since the energization capacity is determined by the temperature rise due to the heat generation at the contact portion, the contact pressure at the contact portion, that is, the magnetic field may be increased and further cooling may be performed in order to increase the energization capacity. Further development of the reed switch is conceivable, such as filling the reed switch sealed in an inert gas with a glass tube with insulating oil to increase cooling and insulation capacity.

FIG. 4 is a diagram showing a hybrid switchgear circuit having a semiconductor switch and a gate control circuit using two reed relays according to the present invention and an on / off sequence of each switch. 1 is a circuit diagram in which an optical coupling switch or the like is added to a gate of a semiconductor switch as an embodiment of a reed relay hybrid switchgear according to the present invention. It is a circuit diagram which shows the detailed sequence of each switch of the reed relay hybrid switchgear concerning this invention. 1 is a circuit diagram showing a reversible current embodiment of a reed relay hybrid switchgear according to the present invention. It is a circuit diagram which shows the details of semiconductor switch S2 of the reed relay hybrid switchgear according to the present invention, and shows an embodiment in which the rise of the regenerative voltage starts and slows with a non-linear capacitor and then rises rapidly thereafter. It is a circuit diagram which shows the detail of semiconductor switch S2 of the reed relay hybrid switchgear apparatus concerning this invention, and shows embodiment which turns off a gate drive by an insulated gate drive power supply, MOSFET in a saturation region, and a negative voltage. The function of the gate control circuit according to the present invention is shown in a block diagram.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment: FIG. 1] FIG. 1 is a circuit diagram showing an embodiment of a reed relay hybrid switchgear according to the present invention. (Claim 1)
FIG. 1 shows a DC power circuit in which the switch is formed by connecting terminals 1 and 2 between two wires. Current can flow from terminal 1 to terminal 2. To pass the current, the auxiliary reed relay S1 is turned on, and then the semiconductor switch S2 is turned on by the gate control circuit. The current then flows from terminal 1 to terminal 2. Finally, when the reed relay S3 is turned on, most of the current flows through the reed relay S3 because the electric resistance of the current path of the reed relay S3 is smaller or there is an ON voltage of the semiconductor switch. There is no need for measures for slow heating of large-scale semiconductors.

  In order to cut off the current flowing from the terminal 1 to the terminal 2, S3 is first turned off in the reverse sequence. When the contact of the reed switch is opened, an arc voltage Varc is generated between the contacts, and the voltage is about 10 V to 20 V when the current is about several A to 100 A, and varies depending on the type and condition of the metal.

  By this voltage Varc, the current of S3 is commutated to S1 and the semiconductor switch circuit. The time Tn required for the commutation is about several tens of nH and the current Iarc is several A in the loop circuits S1 and S2 and S3. Therefore, the commutation time Tn = Ln * Iarc / Varc is several tens of nanoseconds or less. It is a short time. During this time, no arc is generated, or even if an arc is generated, the temperature of the electrode does not rise, so the electrode is not consumed.

After the commutation and interruption of the current, the reed relay opens, and the reed relay S3 recovers the withstand voltage. In the meantime, power is supplied at S1 and S2. After S1 is sufficiently opened, the semiconductor switch S2 cuts off the current by the gate control circuit.
Although the regenerative voltage is generated in the semiconductor switch, recent silicon carbide semiconductor MOSFETs can withstand high voltages exceeding 1 kV. In addition, since the current interruption time is several tens of nanoseconds due to the high-speed switching characteristics of the MOSFET, in the case of an inductive load, the restart voltage of L * dI / dt becomes high, but it is easy to absorb the overvoltage with a varistor or the like. .

  However, countermeasures against surges and noise in electronic circuits due to sharp current interruption are necessary. The surge overvoltage can be cut by a varistor or arrester, but the gate control circuit 4 can be a highly functional switching device that controls voltage and current during transient. The gate control circuit 4 detects the voltage and current here by PT and CT, and controls them with an FB circuit and an OP operational amplifier fed back by the analog control circuit. In addition, it is possible to protect against overcurrent by detecting abnormal voltage and having various protection functions with the conventional technology, as shown in the block diagram in FIG. 7, but here without a separate power supply A method having a large number of parts and a large effect will be described below.

  After the current is cut off by the semiconductor switch S2, the auxiliary reed relay is turned off, but there is no current, so that the arc is opened without arc. After the current interruption, since the two reed relays are open, the leakage current of the semiconductor switch and the gate control circuit is completely interrupted.

[Second Embodiment: FIG. 2] FIG. 2 is a circuit diagram showing details of the gate control circuit of the first embodiment of the reed relay hybrid switchgear according to the present invention. (Claims 2 and 3) The time sequence of control is shown in FIG. 3, but the timing according to claim 4 is shown. The reed switch has a time zone in which chattering due to mechanical vibration occurs when the contact is turned on and off, but is controlled by a sequence having a time margin “Td” to avoid the time zone. Chattering often occurs when the contact bounces when the contact is on, but there is a possibility that the chattering is off, so a necessary and sufficient time margin Td is set.

  As for the gate of the semiconductor switch S2, two of the optical coupling switches S21 and S22 control the gate of the MOSFET, and Rg suppresses parasitic oscillation of the MOSFET with a gate resistance of several hundred Ω. The capacitor C1 and the resistor R1 constitute a Miller integrating circuit that delays the on / off time of the semiconductor switch. In this embodiment, C1 is 0.02 μF, R1 is 100Ω, and R2 is several hundred kΩ. R2 is a high resistance and a discharge resistance of C1.

(Explanation of Claim 3)
The optical coupling switch S22 prevents the current from flowing through the MOSFET only at the moment when the gate potential rises via C1 due to the voltage rise when the auxiliary reed relay S1 is turned on. The timing of turning on S22 is immediately before turning on of S1, and if C1 is charged, it is quickly turned off. FIG. 3 shows the switch states from the time flow and the open / close state of the switching device to the closed state and then to the open state.

The explanation for controlling the on / off speed according to claim 5 is as follows:
If the direct current is controlled simply by a square wave with the gate voltage of the semiconductor switch, the voltage rise and fall speed of the switch is too fast, tens of nanoseconds. Add a slow gate control circuit. When the optical coupling switch S21 is turned off, the MOSFET is turned on, and S21 is turned on and the MOSFET is turned off. However, S21 is turned on, and the gate is connected to the source via R1. Since there is a high voltage current control characteristic and transconductance in the active region of the MOSFET, it is possible to achieve a resumption voltage increase speed determined by the reciprocal of R1 × C1 by the Miller integration effect at the threshold voltage Vth. The re-start voltage Vr is
Vr = Vth + Vth * (R1 × C1) ⁻¹ * Time
This is already disclosed in Patent Document 2 “Restart Voltage Control Device”.

  The explanation of claim 6 is shown in FIG. 4, but there are cases where the current flows through the switch even in the case of a DC circuit. Furthermore, in order to make this switchgear applicable to AC current of commercial frequency, the semiconductor switch unit of S2 is connected via a diode rectifier bridge after S1. In this case, since a current flows through the diode bridge only for a short time, there is no fear of heat generation or heat removal.

  The explanation of claim 7 is shown in FIG. 5. In order to drive the MOSFET of the semiconductor switch S2 in saturation, a gate voltage higher than the threshold voltage Vth is applied to lower the on-voltage of the MOSFET. Loss is reduced and larger current can flow. In order to turn off the MOSFET, a stable gate cutoff state is obtained by applying a negative voltage as the gate voltage. The gate voltage generator with the optical coupling switch S21 insulated is turned on with a pulse voltage, for example, plus 15V, and the MOSFET is turned off with minus 7V. At that time, it is also possible to slow down the voltage change speed by C1, R1. Thus, generation of a surge voltage can be avoided. However, because the Joule loss in the semiconductor switch increases due to the longer cutoff time, it is necessary to pay attention to the temperature rise. As a measure for reducing the Joule loss of the semiconductor switch, a voltage nonlinear capacitor is used as C1. Some ceramic capacitors have a capacitance of 1/10. However, while the reactivation voltage is low, the capacitance of C1 is large, and as the reactivation voltage increases, the reactivation voltage increases with the J curve. Thus, the Joule loss of the semiconductor can be reduced.

  Reed relays and mercury relays have a long life with a small current, and can be turned on and off quickly with a small size. According to the present invention, it is possible to open and close a mechanical contact with no arc at the time of opening using a semiconductor switch such as a MOSFET with respect to opening and closing of current. It can be turned on and off.

  In addition, the rush current control function and regenerative voltage rise control can be applied to the gate control circuit in consideration of noise generation at the time of power switching that is important in electronic circuits. The switch made by is shown. As described above, the hybrid switch composed of the semiconductor switch and the mechanical contact does not melt or break the contact due to the arc, thereby extending the switching life of the switch and can be used as an electrically noise-free switch.

1: Auxiliary reed relay S1
2: Semiconductor switch S2
3: Reed relay S3
4: Gate control circuit 5: MOSFET
6: Diode bridge 7: Optical coupling switch 8: Insulated gate drive power supply

Claims (7)

A direct current switch, the switchgear comprising:
The DC current is turned on / off using two reed relays (S1, S3). A semiconductor switch circuit (S2) is connected in series to the first reed relay (S1). The reed relay (S3) is a contact point for continuous conduction when it is turned on. By connecting a series circuit of S1 and a semiconductor switch circuit in parallel with S3 in parallel, the reed relay (S3) It is a hybrid switch with the semiconductor switch circuit (S2), the sequence when turning on is to turn on the contact (S1), then turn on the semiconductor switch circuit (S2), and finally turn on the energizing contact (S3), After that, the main current flows through S3.
To turn it off, reverse the reverse sequence. First, by turning off the contact S3 of the reed relay, the current S1 and the semiconductor switch circuit (S2) are commutated into a series circuit, and the insulation withstand voltage is reduced by opening the contact S3. After the recovery, the semiconductor switch (S2) gate voltage control turns off S2 and cuts off the current, and then turns off the reed relay (S1) in the almost no current state to achieve high insulation resistance and resistance. Switchgear that secures voltage.   The gate drive circuit of the semiconductor switch circuit of the semiconductor switch (S2) is not only the on / off state of the semiconductor switch, but also a gate having functions of current control, reactivation voltage control, overvoltage, overcurrent, overload protection and semiconductor switch protection The switchgear according to claim 1, wherein the switchgear is a control circuit.   The semiconductor switch (S2) is driven by the gate drive circuit, but when the gate drive circuit (S1) is turned on, the semiconductor switch (S2) is turned off to cause a malfunction due to a rise in voltage when S1 is turned on. The switchgear according to claim 1 to prevent.   The reed switch has a time zone in which chattering due to mechanical vibration occurs when the contact is turned on and off, and is controlled by a sequence having a time margin "Td" to avoid the time zone. The switchgear described.   DC current is turned on / off by gate control of the semiconductor switch (S2). In order to prevent malfunction of peripheral devices due to high rise of re-start voltage, voltage change speed is achieved by connecting a capacitor between drain and gate and a resistor between gate and source. The switchgear according to any one of claims 1 to 4, wherein the switch circuit is a Miller integrating circuit that slows down, but further uses a voltage nonlinear capacitor to control the regenerative voltage waveform to reduce the power loss of the semiconductor switch.   6. The switching according to claim 1, wherein the switching device of S2 is connected via a diode rectifier bridge after S1 so that the switching device can be applied to bidirectional DC current and further to AC current. apparatus.   In order to reduce heat generation due to the conduction loss of the semiconductor switch (S2), a voltage higher than the threshold voltage Vth is applied to the gate to achieve a low on-voltage saturation drive, and a negative voltage is applied to the gate to turn it off. The switchgear according to claim 1, wherein the gate is shut off.

Images