WO2019062262A1

WO2019062262A1 - Dc solid state relay

Info

Publication number: WO2019062262A1
Application number: PCT/CN2018/094817
Authority: WO
Inventors: 尹向阳; 王保均; 陶小丽
Original assignee: 广州金升阳科技有限公司
Priority date: 2017-09-29
Filing date: 2018-07-06
Publication date: 2019-04-04
Also published as: CN107707229A; CN107707229B

Abstract

A solid state relay comprises a DC input positive terminal (Vin+), a DC input negative terminal (Vin-), a DC output positive terminal (Vout+), a DC output negative terminal (Vout-), a control end positive terminal (K+), a control end negative terminal (K-), an isolation circuit (2), a drive circuit (3), a first switch (S1), a second switch (S2), a first diode (D1), and a second diode (D2). A cross connection of double switches and double flyback diodes is used, preventing a sudden change to the energy stored in a load end circuit. A new path is searched for a continuous current flow by means of a flyback diode, and the energy stored in the load end circuit is fed back to a DC grid by means of the path so as to realize no-loss energy recovery. In addition, the product has a small volume and low costs and may be applied in medium and high power scenarios.

Description

DC solid state relay

Technical field

This invention relates to solid state relays, and more particularly to DC solid state relays.

Background technique

The schematic diagram of the existing solid state relay is shown in Fig. 1. The control terminal positive terminal K+ and the control terminal negative terminal K-, the load terminal positive terminal L+ and the load terminal negative terminal L-, the outer casing 1, the internal isolation circuit 2, the driving circuit 3 And switch S. The isolation circuit 2 is used for isolating the low voltage control terminal from the high voltage load terminal, and the driving circuit 3 is used for amplifying the weak control signal input from the low voltage control terminal and supplying the high current load to the load terminal of the switch S.

When the existing solid state relay is disconnected, a very large peak voltage is generated at both ends of the switch S. For this reason, the absorption circuit 4 needs to be connected in parallel across the switch S, and the solid state in which the absorption circuit 4 is integrated is shown in FIG. The relay schematic diagram is composed of a resistor R and a capacitor C connected in series.

The working principle of the absorbing circuit 4 shown in FIG. 2 is: when the steady state, the current at the load end flows through the switch S; when the fault occurs, the switch S is disconnected, the current at the load end is transferred to the RC branch, and the capacitor C is charged through the RC branch. Since the voltage across the capacitor C cannot be abruptly changed, the voltage across the switch S starts to rise slowly from 0, thereby suppressing the spike voltage across the switch S, reducing the impact of the short-circuit current on the switch S, and protecting other power electronic components on the line from being protected. damage.

The problems with the above circuits are as follows:

(1) A part of the energy stored in the load line is consumed by the resistor R, and the other part is stored and absorbed by the capacitor C. When the fault is eliminated, the switch S is turned on, the capacitor C is discharged, and the absorbing circuit 4 is damaged. Conducive to energy saving in the power system;

(2) When the energy stored in the load line is large, the volume of the RC is required to be large, and the cost is high, which is not applicable to the medium and high power solid state relay.

With the rapid development of China's economy and the gradual modernization of the industrial transportation sector, the DC power load capacity has also continued to increase. With the increase of voltage level and rated current, the breaking of large-capacity DC short-circuit current becomes extremely difficult, and its breaking time The requirements are becoming more and more demanding, and DC solid-state relays have become the bottleneck restricting high-voltage, large-capacity DC power supply systems.

For example, new energy vehicles use high-voltage (400-1200V), medium-high current (10-1000A) and high-power DC solid-state relays. At present, the electric motor power of the electric vehicle is generally around 100Kw. The highest speed is the motor. The greater the power required; such as solar photovoltaic power station, DC bus voltage up to 800-1500V, lightning protection DC cabinet power up to 30-500Kw; military aviation, ship medium voltage DC integrated power system, bus voltage up to 3000V or more, power is extremely The traditional power demarcation point for selecting whether the motor adopts the medium voltage power standard is 450Kw; the UHV long-distance DC transmission system has a line voltage of up to ±800kV, a current of up to 10kA, and a power of up to 8000Mw.

In the above high-voltage and high-current applications, high-power DC solid-state relays are required, and the prior art has no technical solution of small size, low cost, and energy saving.

Summary of the invention

In view of this, the technical problem to be solved by the present invention is to provide a DC solid state relay, which can realize small volume, low cost, energy saving and is suitable for medium and large power applications.

The technical solution of the present invention to solve the above technical problems is as follows:

A DC solid state relay characterized by:

It includes at least six terminals, which are DC input positive terminal, DC input negative terminal, DC output positive terminal, DC output negative terminal, control terminal positive terminal and control terminal negative terminal;

The method further includes: an isolation circuit, a driving circuit, a first switch, a second switch, a first diode and a second diode; the first switch is connected between the DC input positive terminal and the DC output positive terminal, and the second switch is connected Between the DC input negative terminal and the DC output negative terminal, the anode of the first diode is connected to the DC output negative terminal, the cathode of the first diode is connected to the DC input positive terminal, and the anode of the second diode is connected to the DC input negative terminal. The cathode of the second diode is connected to the positive terminal of the DC output, the first input end of the isolation circuit is connected to the positive terminal of the control terminal, the second input end of the isolation circuit is connected to the negative terminal of the control terminal, and the output end of the isolation circuit is connected to the driving circuit, and the driving circuit is first. The output end is connected to the control end of the first switch, and the second output end of the drive circuit is connected to the control end of the second switch;

The isolation circuit receives the control signal inputted by the positive terminal of the control terminal and the negative terminal of the control terminal, and is isolated and transmitted to the driving circuit;

The driving circuit receives the control signal transmitted by the isolation circuit and is amplified and supplied to the first switch and the second switch.

As a first equivalent replacement of the above solution, the DC input negative terminal therein is shared, thereby reducing one terminal.

As a second equivalent replacement of the above solution, the two terminals of the control terminal positive terminal and the control terminal negative terminal are replaced by three terminals of an auxiliary power supply positive terminal, an auxiliary power supply negative terminal and an enable terminal, thereby A terminal is added; at this time, the isolation circuit has three input terminals, the first input end of the isolation circuit is connected to the auxiliary power supply positive terminal, the second input end of the isolation circuit is connected to the auxiliary power supply negative terminal, and the third input end of the isolation circuit is connected to the enable terminal. .

As a third equivalent replacement of the above solution, the DC input negative terminal is common to the ground, and one terminal is reduced here; the control terminal positive terminal and the control terminal negative terminal are replaced by the auxiliary power supply. The positive terminal, the auxiliary power supply negative terminal and the enable terminal, a terminal is added here, and the isolation circuit has three input ends, the first input end of the isolation circuit is connected to the auxiliary power supply positive terminal, and the second input end of the isolation circuit is connected auxiliary. The power supply negative terminal is connected to the third input terminal of the isolation circuit to enable the terminal.

An equivalent replacement of the third equivalent alternative described above is characterized in that the auxiliary power supply negative terminal is also common, thereby reducing one terminal.

As a first improvement of the above scheme, the first diode and the second diode are composed of a plurality of diodes connected in series.

As a second modification of the above solution, the first switch has a series circuit composed of a first resistor and a first capacitor connected in parallel; the second switch has a second resistor and a second capacitor connected in parallel at both ends thereof. Series circuit.

An equivalent replacement of the second modification described above is characterized in that: a first capacitor is connected in parallel at both ends of the first switch, and a second capacitor is connected in parallel at both ends of the second switch.

A further improvement of the second modification described above and its equivalent replacement is characterized in that a third capacitor is connected in parallel between the anode of the first diode and the cathode of the first diode, and the anode of the second diode A fourth capacitor is connected in parallel between the cathodes of the second diode.

A further improvement of the above-described second modification and its equivalent replacement, characterized in that it further comprises a first negative temperature coefficient thermistor and a second negative temperature coefficient thermistor, the first negative temperature coefficient The thermistor is connected in series with the first switch, and then a series circuit composed of the first resistor and the first capacitor is connected in parallel at both ends thereof, and the second negative temperature coefficient thermistor is connected in series with the second switch and then at both ends thereof. A series circuit consisting of a second resistor and a second capacitor is connected in parallel.

An equivalent replacement of the further improvement of the third modification described above, characterized in that it further comprises a first negative temperature coefficient thermistor and a second negative temperature coefficient thermistor, a first negative temperature coefficient thermistor and The first switch is connected in series and then the first capacitor is connected in parallel at both ends thereof, and the second negative temperature coefficient thermistor is connected in series with the second switch, and then the second capacitor is connected in parallel at both ends thereof.

As a fourth improvement of the above aspect, the synchronous rectifier is connected in parallel across the first diode and the second diode.

Preferably, the isolation circuit uses an opto-isolated circuit, a coil, a magnetoelectric isolation circuit or a piezoelectric ceramic isolation circuit.

Preferably, the first switch and/or the second switch may be an electronic switch such as a MOS transistor, an IGBT or a thyristor.

Preferably, the DC solid state relay is packaged with a housing.

As a specific embodiment of the outer casing, it may be square or circular.

Preferably, the six terminals are evenly distributed on the side or bottom of the outer casing.

Preferably, a control circuit is further connected between the control terminal and the isolation circuit.

Compared with the existing solid-state relay lossy absorption scheme, the present invention proposes a completely new technical concept: a double-switch and a double free-wheeling diode cross-connection is adopted, and the energy stored in the load terminal line cannot be mutated, and the freewheeling diode is used. The continued flow of this current finds a new path that enables the energy stored in the load line to be fed back into the DC grid, thereby achieving a non-destructive recovery of energy.

The present application has the following outstanding advantages over the prior art:

(1) When the first switch and the second switch are turned off, the first diode and the second diode provide a freewheeling path for the energy flow stored in the load line, such that the first switch and the second switch are generated The peak voltage is small, so that the first switch and the second switch need to withstand a small voltage stress;

(2) The first diode and the second diode are clamped by the DC input voltage, and the voltage stress to be withstood is smaller than the prior art;

(3) The freewheeling path formed by the first diode and the second diode realizes that the energy stored in the load line is fed back to the DC grid, and the energy stored in the load line is realized when the switch is disconnected. Non-destructive recycling makes the system more energy efficient, especially when the DC solid state relays frequently operate, the energy saving effect is more obvious;

(4) The circuit is extremely simple, the implementation is very easy, and the volume is small, the cost is low, and the advantages of the present invention are more obvious in the case of a high voltage and a large current;

(5) further accelerating the energy in the transfer switch by the capacitor, so that the current in the switch is reduced, the peak voltage is reduced, and du/dt and overvoltage are further suppressed, so that the reverse voltage of the diode and the reverse voltage are not excessively broken. damage.

DRAWINGS

Figure 1 shows the schematic diagram of the existing solid state relay;

Figure 2 is a schematic diagram of an integrated internal absorption circuit of a solid state relay;

Figure 3 is a schematic diagram of a first embodiment of the present invention;

Figure 4-1 shows the simulated voltage and current waveforms at both ends of the switch when the circuit of Figure 1 is short-circuited;

Figure 4-2 shows the simulated voltage and current waveforms at both ends of the switch when the circuit of Figure 2 is short-circuited;

Figure 4-3 shows the simulated voltage and current waveforms at both ends of the switch when the circuit of Figure 3 is short-circuited;

Figure 5 is a schematic diagram of a second embodiment of the present invention;

Figure 6 is a schematic diagram of a third embodiment of the present invention;

Figure 7 is a schematic diagram of a fourth embodiment of the present invention.

Detailed ways

In order to make the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

First embodiment

3 is a schematic diagram of a first embodiment of the present invention, which includes six terminals, namely a DC input positive terminal Vin+, a DC input negative terminal Vin-, a DC output positive terminal Vout+, a DC output negative terminal Vout-, The control terminal positive terminal K+ and the control terminal negative terminal K-; further comprising: a casing 1, an isolation circuit 2, a driving circuit 3, a first switch S1, a second switch S2, a first diode D1 and a second diode D2; The first switch S1 is connected between the DC input positive terminal Vin+ and the DC output positive terminal Vout+, and the second switch S2 is connected between the DC input negative terminal Vin- and the DC output negative terminal Vout-, the anode of the first diode D1 Connect the DC output negative terminal Vout-, the cathode of the first diode D1 is connected to the DC input positive terminal Vin+, the anode of the second diode D2 is connected to the DC input negative terminal Vin-, and the cathode of the second diode D2 is connected to the DC output The positive terminal Vout+, the first input end of the isolation circuit 2 is connected to the positive terminal K+ of the control terminal, the second input end of the isolation circuit 2 is connected to the negative terminal K- of the control terminal, the output end of the isolation circuit 2 is connected to the drive circuit 3, and the first output end of the drive circuit 3 is connected. First switch S1 Control terminal Ki1, 3 the second output of the driver circuit is connected to the second switch control terminal is Ki2 S2.

The isolation circuit receives the control signal of the control terminal positive terminal K+ and the control terminal negative terminal K- input, and is isolated and transmitted to the driving circuit 3; the driving circuit 3 receives the isolation signal transmitted by the isolation circuit 2, and is amplified and supplied to the first switch S1. And the second switch S2; the first switch S1 and the second switch S2 are used to turn on or off the current output by the DC output positive terminal Vout+ and the DC output negative terminal Vout-.

The isolation circuit 2 can adopt an opto-isolation circuit, a coil, a magnetoelectric isolation circuit or a piezoelectric ceramic isolation circuit, etc. The driving circuit 3 can adopt a circuit composed of a relay or a bidirectional switching circuit composed of two FETs reversely connected; the first switch S1 And the second switch S2 can adopt an electronic switch such as a MOS tube, an IGBT or a thyristor, which is well known to those skilled in the art, and since it is not the innovation of the present invention, the isolation circuit 2 and the driving circuit are not drawn. 3. A specific circuit diagram of the first switch S1 and the second switch S2.

When the power system works normally, switch S1 and switch S2 are closed, diode D1 and diode D2 are cut off due to reverse bias, and the current flow in the circuit is: DC input positive terminal Vin+ → switch S1 left end → switch S1 right end → DC output positive Terminal Vout+→load→DC output negative terminal Vout-→switch S2 right end→switch S2 left end→DC input negative terminal Vin-.

To illustrate the beneficial effects of the present embodiment, the inventors conducted simulation and comparison analysis for FIG. 1, FIG. 2 and FIG. 3, and the simulation parameters are: input voltage 1 kV, inductive load with load of 1H connected to the load end, switches S1 and S2 The current at the turn-off time is 100A, the turn-off resistance of the switches S1 and S2 is 10MΩ, the turn-off process time of the switches S1 and S2 is 3ms, the resistance of the resistor R is 1kΩ, and the capacitance of the capacitor C is 1uF.

Figure 4-1 to Figure 4-3 show the simulated voltage and current waveforms at both ends of the switch when the circuit of Figure 1-3 is short-circuited, where V1 is the voltage waveform across the switch S of Figure 1, and V2 is the voltage across the switch S of Figure 2. The waveform, V3 is the voltage waveform across the switch S1 of FIG. 3, I1 is the current waveform in the switch S of FIG. 1, I2 is the current waveform in the switch S of FIG. 2, and I3 is the current waveform in the switch S1 of FIG.

The analysis of voltage waveform V3 and current waveform I3 of Figure 4-3 of the present application is as follows:

As can be seen from Fig. 4-3, 0ms is the moment when the DC circuit is short-circuited, and it is recorded as t0; the voltage across the switch S1 starts to rise at 0.9ms. For this embodiment (ie, Figure 3), the switch S1 is turned off, which is recorded as t1; The voltage across the ms switch S1 rises to the voltage of the DC output positive terminal Vout+, and the current in the switch S1 begins to decrease. In this embodiment (ie, FIG. 3), the diode D2 is turned on, which is denoted as t2.

From time t1, the voltage of the DC output positive terminal Vout+ begins to decrease, that is, the cathode voltage of the diode D2 begins to decrease. At time t2, the cathode voltage of the diode D2 is lower than the anode voltage (ie, the voltage of the DC input negative terminal Vin-), and the diode D2 leads. Pass, diode D1 is positively biased, diode D1 is turned on, forming a freewheeling circuit: diode D2 anode → diode D2 cathode → DC output positive terminal Vout + → load → DC output negative terminal Vout - → diode D1 anode → diode D1 cathode. Since the cathode of the diode D1 is connected to the DC input positive terminal Vin+, and the anode of the diode D2 is connected to the DC input negative terminal Vin-, the energy stored in the load line is fed back to the DC grid, thereby achieving non-destructive recovery of energy, making the power system more energy efficient.

It should be noted that the waveforms V3 and I3 are for the case where the switch S1 and the switch S2 are simultaneously turned off, and it is a well-known technique for those skilled in the art to set the switch S1 and the switch S2 to be linked control.

The waveforms when the switch S is disconnected in Figure 1 and Figure 2 are compared with Figure 3 as follows:

As can be seen from the above table, the switch S in Figure 1 does not take absorption measures when the peak voltage is as high as 430KV, which is 430 times of the DC input voltage, and the duration is 2ms; after the switch S in Figure 2 takes the RC absorption spike, the spike voltage is still 90KV, which is 90 times of the DC input voltage, and the duration is still 2ms. After using the absorption scheme of this embodiment, the spike voltage is clamped to the DC input voltage Vin, and the current between the switches S1 and S2 is reduced to 0. The time is 1.7 ms, and the time is also reduced. Therefore, the present embodiment can achieve the object of the invention.

It should be noted that the current diode with the highest withstand voltage can reach several thousand volts. For higher voltage applications, the voltage stress across the first diode D1 and the second diode D2 is shared, the first diode D1 And the second diode D2 can be designed to be composed of a plurality of diodes in series, and attention should be paid to the polarity in series, and a positive-negative phase connection is required, which is well known to those skilled in the art.

As can be seen from the waveform of Figure 4-3, when a short-circuit fault occurs in the DC circuit, after a certain delay (t1-t0), the switch S1 is turned off. At the time t1 to t2, since the diode D2 is not turned on at this time, The current in the inductive load cannot be abruptly changed, so the current in the switch S1 remains unchanged, and the voltage in the switch S1 increases sharply, resulting in a large instantaneous power of the switch S1. The circuit is a symmetric circuit. The instantaneous power of the S2 is also large and easily damaged. The switch S1 and the switch S2, therefore, the present invention will result in a further improved technical solution, as described in detail in the second embodiment.

Second embodiment

FIG. 5 is a schematic diagram of a second embodiment of the present invention. The difference from FIG. 1 is that a series circuit composed of a resistor R1 and a capacitor C1 is connected in parallel across the switch S1, and the switch S2 is connected in parallel with a resistor R2 and a capacitor C2. Series circuit.

It should be noted that the positions of the resistor R1 and the capacitor C1 can be exchanged, and the positions of the resistor R2 and the capacitor C2 can also be exchanged, which is equivalent for the RC series device to exchange positions, which is common knowledge to those skilled in the art. .

At t1 to t2, the current in the switch S1 is shunted through the RC buffer branch composed of the resistor R1 and the capacitor C1, which reduces the load on the switch S1, suppresses du/dt and overvoltage, and when the diode D2 is turned on at time t2 The current of the RC buffer branch is quickly transferred to the absorption circuit composed of the diodes D2 and D1, thereby protecting the switch S1 from being damaged by the overvoltage, and the same switch S2 is also protected.

When the DC input voltage is as high as several thousand to tens of thousands V and the DC input current is as high as several thousand to tens of thousands of A, the diode D1 diode and D2 will withstand very high voltage stress and current stress, which will easily damage diode D1 and diode D2. Therefore, the present invention will produce a further improved technical solution, as described in detail in the third embodiment.

It should be noted that the elimination of the resistors R1 and R2 in the two RC buffer branches can also achieve the object of the present invention. The applicant finds that the resistors R1 and R2 are removed by circuit simulation, and the voltage of the current drop process becomes small and spikes. The voltage is reduced and the implementation effect is even more ideal.

Third embodiment

6 is a schematic diagram of a third embodiment of the present invention, which differs from FIG. 5 in that a capacitor C3 is connected in parallel across the diode D1, and a capacitor C4 is connected in parallel across the diode D2.

At t1 to t2, a charging current is formed in the capacitor C3 and the capacitor C4, accelerating the currents in the absorption switches S1 and S2, causing the currents in the switches S1 and S2 to decrease and the peak voltage to decrease, further suppressing du/dt and The overvoltage causes the reverse voltages of the diodes D1 and D2 to be excessively broken and is damaged by breakdown; when the diodes D2 and D1 are turned on to form an absorption loop at time t2, the capacitor C3 and the capacitor C4 start to discharge.

In this embodiment, there is a certain problem in the process of the switch being turned on: when the switch S1 changes from off to on, the capacitor C4 is directly charged with the DC input positive and DC input negative connection through the switch S1, and the capacitor C1 is discharged through the switch S1. Since the on-resistance of the switch S1 is small, a large inrush current is generated, and the switch S1 is at risk of damage. Since the circuit is symmetrical, the switch S2 also has the same risk of damage, so the present invention will further improve. For technical solutions, see the fourth embodiment.

Fourth embodiment

7 is a schematic diagram of a fourth embodiment of the present invention, which differs from FIG. 6 in that a thermistor NTC1 having a negative temperature coefficient is connected in series between the right end of the switch S1 and the cathode of the diode D2, and the right end of the switch S2 and the diode D1 are A thermistor NTC2 with a negative temperature coefficient is connected in series between the anodes.

It should be noted that the position of the switch S1 and the thermistor NTC1 can be exchanged, that is, a thermistor NTC1 with a negative temperature coefficient is connected in series between the connection point of the resistor R1 and the DC input positive Vin+ and the left end of the switch S1; similarly, the switch The position of S2 and the thermistor NTC2 can also be exchanged, that is, a thermistor NTC2 with a negative temperature coefficient is connected in series between the connection point of the resistor R2 and the DC input negative Vin- and the left end of the switch S2, and the position is exchanged for the series device. This is common knowledge to those skilled in the art.

When the switch S1 changes from off to on, the temperature of the thermistor NTC1 is lower, the resistance is larger, the charging current of the capacitor C4 and the discharge current of the capacitor C1 are limited, the magnitude of the inrush current is limited, and the switch S1 is protected. After normal operation, the thermistor NTC1 is heated, the resistance is reduced, and the normal operation of the load is not affected, and the same switch S2 is also protected.

It should be noted that, for those skilled in the art, the above embodiments are at least six terminals, and can also be replaced by the following equivalents:

(1) comprising at least five terminals, wherein the DC input negative terminal Vin-co-located to reduce one terminal;

(2) At least seven terminals are included, and the two terminals of the control terminal positive terminal K+ and the control terminal negative terminal K- are replaced by an auxiliary power supply positive terminal, an auxiliary power supply negative terminal, and an enable terminal (also called a control terminal). The terminal has three input ends, the first input end of the isolation circuit is connected to the auxiliary power supply positive terminal, the second input end of the isolation circuit is connected to the auxiliary power supply negative terminal, and the third input end of the isolation circuit is connected to the enable terminal;

(3) At least six terminals, including DC input negative terminal Vin-common, where one terminal is reduced; replace the control terminal positive terminal K+ and the control terminal negative terminal K- terminals with auxiliary power supply The positive terminal, the auxiliary power supply negative terminal and the enable terminal (also called the control terminal) have three terminals. Here, one terminal is added. At this time, the isolation circuit has three input terminals, and the first input end of the isolation circuit is connected to the auxiliary power supply positive terminal. The second input end of the isolation circuit is connected to the auxiliary power supply negative terminal, and the third input end of the isolation circuit is connected to the enable terminal;

(4) At least five terminals are included, and the auxiliary power supply negative terminal in the above equivalent replacement (3) is also common, thereby reducing one terminal.

The above is only a preferred embodiment of the present invention, and it should be noted that the above-described preferred embodiments are not to be construed as limiting the scope of the invention, and the scope of the invention should be determined by the scope defined by the claims. It will be apparent to those skilled in the art that several modifications and refinements can be made without departing from the spirit and scope of the invention, such as designing the outer casing 1 as a square or a circle, and evening the terminals on the sides or bottom of the casing. Distribution, parallel rectifiers at both ends of the first diode D1 and the second diode D2 solve the problem of large diode voltage drop and low current withstand, and a control circuit is connected between the control terminal and the isolation circuit. These improvements and finishes should also be considered as protection of the present invention.

Claims

A DC solid state relay characterized by:

It includes at least six terminals, which are DC input positive terminal, DC input negative terminal, DC output positive terminal, DC output negative terminal, control terminal positive terminal and control terminal negative terminal;

The method further includes: an isolation circuit, a driving circuit, a first switch, a second switch, a first diode and a second diode; the first switch is connected between the DC input positive terminal and the DC output positive terminal, and the second switch is connected Between the DC input negative terminal and the DC output negative terminal, the anode of the first diode is connected to the DC output negative terminal, the cathode of the first diode is connected to the DC input positive terminal, and the anode of the second diode is connected to the DC input negative terminal. The cathode of the second diode is connected to the positive terminal of the DC output, the first input end of the isolation circuit is connected to the positive terminal of the control terminal, the second input end of the isolation circuit is connected to the negative terminal of the control terminal, and the output end of the isolation circuit is connected to the driving circuit, and the driving circuit is first. The output end is connected to the control end of the first switch, and the second output end of the drive circuit is connected to the control end of the second switch;

The isolation circuit receives the control signal inputted by the positive terminal of the control terminal and the negative terminal of the control terminal, and is isolated and transmitted to the driving circuit;

The driving circuit receives the control signal transmitted by the isolation circuit and is amplified and supplied to the first switch and the second switch.
The direct current solid state relay of claim 1 wherein the DC input negative terminals are common to each other, thereby reducing one terminal.
The DC solid state relay according to claim 1, wherein two terminals of the control terminal positive terminal and the control terminal negative terminal are replaced by three terminals of an auxiliary power supply positive terminal, an auxiliary power supply negative terminal and an enable terminal. Therefore, one terminal is added; at this time, the isolation circuit has three input ends, the first input end of the isolation circuit is connected to the auxiliary power supply positive terminal, the second input end of the isolation circuit is connected to the auxiliary power supply negative terminal, and the third input connection of the isolation circuit is enabled. Terminal.
The direct current solid state relay according to claim 1, wherein the DC input negative terminal is common to the ground, wherein one terminal is reduced; and the two terminals of the control terminal positive terminal and the control terminal negative terminal are replaced with auxiliary power sources. The power supply positive terminal, the auxiliary power supply negative terminal and the enable terminal, a terminal is added here, and the isolation circuit has three input ends, the first input end of the isolation circuit is connected to the auxiliary power supply positive terminal, and the second input end of the isolation circuit is connected. The auxiliary power supply is powered by a negative terminal, and the third input of the isolation circuit is connected to the enable terminal.
The direct current solid state relay according to claim 4, wherein the auxiliary power supply negative terminal is also common to the ground, thereby reducing one terminal.
A direct current solid state relay according to claim 1, wherein the first diode and the second diode are composed of a plurality of diodes connected in series.
The direct current solid state relay according to claim 1, wherein a series circuit composed of a first resistor and a first capacitor is connected in parallel at both ends of the first switch; and a second resistor and a second capacitor are connected in parallel at both ends of the second switch. A series circuit composed of.
The direct current solid state relay according to claim 1, wherein a first capacitor is connected in parallel at both ends of the first switch, and a second capacitor is connected in parallel at both ends of the second switch.
The direct current solid state relay according to claim 7 or 8, wherein a third capacitor is connected in parallel between the anode of the first diode and the cathode of the first diode, and the anode and the second of the second diode A fourth capacitor is connected in parallel between the cathodes of the diodes.
A direct current solid state relay according to claim 9, further comprising a first negative temperature coefficient thermistor and a second negative temperature coefficient thermistor, a first negative temperature coefficient thermistor and the first switch First, after connecting in series, a series circuit composed of a first resistor and a first capacitor is connected in parallel at both ends thereof, and the second negative temperature coefficient thermistor is connected in series with the second switch, and then connected in parallel at both ends thereof by the second resistor and the first A series circuit composed of two capacitors.
A direct current solid state relay according to claim 9, further comprising a first negative temperature coefficient thermistor and a second negative temperature coefficient thermistor, a first negative temperature coefficient thermistor and the first switch After the series connection, the first capacitor is connected in parallel at both ends thereof, and the second negative temperature coefficient thermistor is connected in series with the second switch, and then the second capacitor is connected in parallel at both ends thereof.
A direct current solid state relay according to claim 1, wherein a synchronous rectifier is connected in parallel across the first diode and the second diode.
The direct current solid state relay according to claim 1, wherein the isolation circuit uses an optical isolation circuit, a coil, a magnetoelectric isolation circuit or a piezoelectric ceramic isolation circuit.
The direct current solid state relay according to claim 1, wherein the driving circuit comprises a circuit composed of a relay or a bidirectional switching circuit composed of two FETs connected in reverse.
The direct current solid state relay according to claim 1, wherein the first switch and/or the second switch employ an electronic switch such as a MOS transistor, an IGBT or a thyristor.
The direct current solid state relay of claim 1 wherein the direct current solid state relay is packaged with a housing.
The direct current solid state relay of claim 16 wherein the outer casing is square or circular.
The direct current solid state relay of claim 16 wherein the six terminals are evenly distributed on the side or bottom of the outer casing.
The direct current solid state relay according to any one of claims 1 to 5, characterized in that a control circuit is further connected between the control terminal and the isolation circuit.