CN112332823B - DC switch - Google Patents
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- CN112332823B CN112332823B CN202011121582.0A CN202011121582A CN112332823B CN 112332823 B CN112332823 B CN 112332823B CN 202011121582 A CN202011121582 A CN 202011121582A CN 112332823 B CN112332823 B CN 112332823B
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for DC systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/041—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage using a short-circuiting device
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/16—Modifications for eliminating interference voltages or currents
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Abstract
The embodiment of the invention discloses a direct current switch, relates to the technical field of switches, and aims to improve the safety of a metal-oxide semiconductor field effect transistor in the direct current switch. The switching device comprises a switching main circuit, a driving control circuit and a switching sampling circuit, wherein the switching main circuit comprises an MOS tube, the input end of the driving control circuit is used for being connected with the output end of a controller, and the output end of the driving control circuit is connected with the MOS tube; the switch sampling circuit comprises an input voltage sampling circuit and an output current sampling circuit, the input voltage sampling circuit comprises a first voltage dividing resistor and a second voltage dividing resistor, the first voltage dividing resistor and the second voltage dividing resistor are connected in series, the input end of the first voltage dividing resistor is connected to the output end of the power supply, and a node between the first voltage dividing resistor and the second voltage dividing resistor is used for being connected with the input end of the controller; the output current sampling circuit includes a sampling resistor. The invention is suitable for the on-off control occasion of the current loop.
Description
Technical Field
The invention relates to the technical field of switches, in particular to a direct current switch.
Background
The DC switch is also called as a DC fast switch or a DC fast automatic switch, and can perform opening and closing operations on a DC circuit and play a role in tripping protection in the case of short circuit and overload.
In some applications of the power system, such as power distribution, a dc relay and a dc ammeter are generally used as a dc switch to control on/off of a large current loop, so as to indirectly control running and stopping of a load.
The inventor finds in the process of realizing the invention: the direct current relay is easy to cause direct current arc problem in the heavy current switching scene, in order to solve the harm of the arc, usually an arc extinguishing device is needed; the direct current relay and the contactor are mechanical devices, so that the problem of switching service life exists, and the direct current relay and the contactor are not suitable for being applied to frequent switching occasions; the action time of the direct current relay and the contactor is longer, and the accident expansion is easy to be caused when the load is short-circuited.
Disclosure of Invention
Therefore, the embodiment of the invention provides a direct current switch, which can solve the problem that the large current of the existing direct current relay is easy to cause direct current arc.
The embodiment of the invention provides a direct current switch, which comprises: the switching device comprises a switching main circuit, a driving control circuit and a switching sampling circuit, wherein the switching main circuit comprises MOS (metal oxide semiconductor) tubes arranged in an input and output loop, the input end of the driving control circuit is used for being connected with the output end of a controller, and the output end of the driving control circuit is connected with the MOS tubes;
the switch sampling circuit comprises an input voltage sampling circuit and an output current sampling circuit, the input voltage sampling circuit comprises a first voltage dividing resistor and a second voltage dividing resistor, the first voltage dividing resistor is connected in series with the second voltage dividing resistor, the input end of the first voltage dividing resistor is connected with a power supply, the output end of the second voltage dividing resistor is connected with the power supply ground, and a node between the first voltage dividing resistor and the second voltage dividing resistor is used for being connected with the input end of the controller;
the output current sampling circuit comprises a sampling resistor, a first end of the sampling resistor is connected to the source electrode of the MOS tube, a second end of the sampling resistor is grounded, and two ends of the sampling resistor are also used for being connected with the input end of the controller.
According to an alternative mode of the embodiment of the invention, the output current sampling circuit further comprises an input resistor, an operational amplifier and a feedback resistor, wherein the input end of the input resistor is connected with the first end of the sampling resistor, the output end of the input resistor is connected with the non-inverting input end of the operational amplifier, the first end of the feedback resistor is connected with the inverting input end of the operational amplifier, the second end of the feedback resistor is connected with the output end of the operational amplifier, and the first end of the feedback resistor is also grounded.
According to a further alternative of the embodiment of the present invention, a bias circuit is further connected to the non-inverting input terminal of the operational amplifier.
According to an alternative mode of the embodiment of the invention, the bias circuit comprises a direct current power supply, a first bias resistor and a second bias resistor, wherein the first bias resistor is connected in series with the second bias resistor, the input end of the first bias resistor is connected with the direct current power supply, the output end of the first bias resistor is also connected with the non-inverting input end of the operational amplifier, and the output end of the second bias resistor is connected with the power supply ground.
According to an alternative manner of the embodiment of the present invention, a first resistor is further connected in series with the first end of the feedback resistor and the inverting input end of the operational amplifier, and the first end of the feedback resistor is further grounded through the first resistor.
According to an alternative way of the embodiment of the present invention, the switch sampling circuit further includes: the switch state sampling circuit comprises a third voltage dividing resistor and a fourth voltage dividing resistor, the third voltage dividing resistor is connected with the fourth voltage dividing resistor in series, the input end of the third voltage dividing resistor is connected with the drain electrode of the MOS tube, the output end of the fourth voltage dividing resistor is connected with the power supply ground, and a node between the third voltage dividing resistor and the fourth voltage dividing resistor is further used for being connected with the input end of the controller.
According to an alternative manner of the embodiment of the present invention, the switch main circuit further includes a freewheeling diode, wherein a cathode of the freewheeling diode is connected to an output end of the power supply, and an anode of the freewheeling diode is connected to a drain electrode of the MOS transistor.
According to an alternative mode of the embodiment of the present invention, the switch further includes an input lightning protection circuit, the input lightning protection circuit is disposed in an input loop of the switch main circuit, and the input lightning protection circuit includes: the power supply comprises a power supply, a first piezoresistor and a first capacitor, wherein the power supply is connected with the positive electrode and the negative electrode of the power supply in parallel, the positive electrode of the power supply is grounded, and the negative electrode of the power supply is grounded.
According to an alternative mode of the embodiment of the invention, the MOS transistor further comprises an output lightning protection circuit, wherein the output lightning protection circuit is arranged in an output loop of the switch main circuit, the output lightning protection circuit comprises a second piezoresistor and a second capacitor, the second piezoresistor and the second capacitor are respectively connected in parallel with an output end of the switch main circuit, one end of each of the second piezoresistor and the second capacitor is connected with a positive electrode of a power supply, and the other end of each of the second piezoresistor and the second capacitor is connected with a drain electrode of the MOS transistor.
According to an optional manner of the embodiment of the present invention, the drain electrode of the MOS transistor is further connected to an inductance element.
According to an alternative mode of the embodiment of the invention, a first diode is connected in parallel between the drain electrode of the MOS tube and the second end of the sampling resistor.
According to an alternative mode of the embodiment of the present invention, the switch driving control circuit includes: the device comprises a first control signal input circuit, a second control signal input circuit and a triode, wherein a second resistor is arranged on the first control signal input circuit, the input end of the second resistor is used for being connected with the first output end of the controller, and the output end of the second resistor is connected with the base electrode of the triode through a second diode;
the second control signal input circuit is provided with a third resistor, the input end of the third resistor is used for being connected with the second output end of the controller, the output end of the third resistor is connected with the base electrode of the triode, the collector electrode of the triode is connected with a pull-up resistor, and the emitting electrode of the triode is grounded;
and a clamping diode is further connected to a node between the second resistor and the second diode, and the other end of the clamping diode is connected with the drain electrode of the MOS tube.
The direct current switch provided by the embodiment of the invention comprises a switch main circuit, a drive control circuit and a switch sampling circuit, wherein a semiconductor switching device MOS tube is arranged between an input loop and an output loop of the switch main circuit to control the on-off of a current loop, so that an arc phenomenon does not exist when a load is powered on or powered off.
Furthermore, the switch sampling circuit is arranged, and the switch sampling circuit comprises an input voltage sampling circuit and an output current sampling circuit which are connected with the controller, so that the voltage and the current can be sampled, and the controller is convenient to automatically and accurately control the on-off of the MOS tube, namely the on-off of a control loop, so that loads and other electronic elements in the circuit are effectively protected to a certain extent.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic circuit diagram of a DC switch according to an embodiment of the present invention;
FIG. 2 is a schematic circuit diagram of one embodiment of the switch main circuit of FIG. 1;
FIG. 3 is a schematic circuit diagram of an embodiment of the switch main circuit with the switch sampling circuit of FIG. 1;
FIG. 4 is a schematic circuit diagram of another embodiment of the switch main circuit of FIG. 1;
fig. 5 is a schematic circuit diagram of an embodiment of the switch main circuit with input and output lightning protection circuits in fig. 1.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
It should be apparent that numerous technical details are set forth in the following detailed description in order to provide a more thorough explanation of the invention, and it should be understood by those skilled in the art that the invention may be practiced without some of these details. In addition, some methods, means, components, applications thereof, etc. which are well known to those skilled in the art are not described in detail in order to highlight the gist of the present invention, but do not affect the implementation of the present invention. The embodiments described herein are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
FIG. 1 is a schematic circuit diagram of a DC switch according to an embodiment of the present invention; FIG. 2 is a schematic circuit diagram of one embodiment of the switch main circuit of FIG. 1; fig. 3 is a schematic circuit diagram of an embodiment of the switch main circuit with the switch sampling circuit in fig. 1.
As shown in fig. 1 to 3, the dc switch provided by the embodiment of the present invention is suitable for use in an electric power distribution system, and is used for controlling on-off of a current loop, thereby controlling work and shutdown of a load.
In the figure, vin is the input end of a DC switch, VCC is used for connecting with the positive electrode of a power supply, the grounding side is connected with the negative electrode of the power supply, V O Is the output of the dc switch and RL is the load.
The dc switch may include: the switch main circuit comprises a Metal-Oxide-semiconductor field effect transistor M1 (Metal-Oxide-Semiconductor Field-Effect Transistor, commonly referred to as MOS (Metal Oxide semiconductor) tubes, which are used for convenience of description, wherein the MOS tube M1 is a core switching device of a direct current switch, an input end of the drive control circuit is used for connecting an output end of a controller, the controller can also be regarded as a processor, and the controller is represented by a CPU (Central processing Unit) in the figure; the output end of the drive control circuit is connected to the MOS tube M1.
According to the requirements, when the equipment adopts the direct current switch, when the load RL needs to supply power to work, the MOS tube M1 is conducted, the main circuit of the switch is conducted, and the load RL works; when the load RL needs to stop working, the MOS tube M1 is turned off, the main circuit of the switch is disconnected, and the load RL is stopped. Because the core switching device is the power MOS tube M1 of the semiconductor device, the arc phenomenon can not exist when the load RL is powered on or powered off. Further, the characteristics of the power MOS tube M1 can basically realize unlimited power supply and power off operation to the load RL, so that the power MOS tube M can be suitable for frequent current on-off switching occasions.
The switch sampling circuit comprises an input voltage sampling circuit and an output current sampling circuit.
The input voltage sampling circuit is used for converting high voltage into low voltage which is easy to identify by the controller, so that input voltage acquisition is realized, and the controller can automatically control the on-off of the circuit according to a set overvoltage protection threshold value, so that input overvoltage protection is realized.
The input voltage sampling circuit adopts voltage dividing resistor sampling, and specifically comprises a first voltage dividing resistor R10 and a second voltage dividing resistor R12, wherein the first voltage dividing resistor R10 and the second voltage dividing resistor R12 are connected in series, the input end of the first voltage dividing resistor R10 is connected to a power supply VCC, the output end of the second voltage dividing resistor R12 is connected to the power supply ground, and a node between the first voltage dividing resistor R10 and the second voltage dividing resistor R12 is used for being connected with the input end of the controller. Thus, input overvoltage protection is realized through the input voltage sampling circuit, and load RL damage caused by input power supply overvoltage is prevented.
Specifically, an under-voltage protection threshold value can be set, and the controller compares the acquired input voltage value with the set under-voltage protection threshold value, so that input under-voltage protection can be realized, and load RL damage caused by input power under-voltage is prevented; similarly, if the input power supply is a battery power supply, the battery power supply can also play a role in protecting the battery from being discharged deeply, and the battery is prevented from being damaged by discharging deeply.
The output current sampling circuit is used for sampling output current and comprises a sampling resistor Rs, a first end of the sampling resistor Rs is connected with a source electrode of the MOS tube M1, a second end of the sampling resistor Rs is connected with a power supply ground, and two ends of the sampling resistor Rs are also connected with an input end of a controller, namely a CPU sampling interface in the figure, so that the controller can sample and monitor the output current, and the circuit can be automatically cut off when necessary, thereby realizing overcurrent protection of a load RL.
Specifically, an overcurrent protection threshold may be set, and the controller compares and judges according to the collected actual current value and the set overcurrent protection threshold, so as to realize overcurrent protection control on the load RL.
The direct current switch provided by the embodiment of the invention comprises a switch main circuit, a drive control circuit and a switch sampling circuit, wherein the semiconductor switching device MOS tube M1 is arranged between the input and output loops of the switch main circuit to control the on-off of the current loop, so that an arc phenomenon does not exist when the load RL is powered on or powered off.
Further, the switch sampling circuit is arranged, and the switch sampling circuit comprises an input voltage sampling circuit and an output current sampling circuit which are connected with the controller, so that the voltage and the current can be sampled, and the controller is convenient to automatically and accurately control the on-off of the MOS tube M1, namely the on-off of a control loop, so that a load RL and other electronic elements in the circuit are effectively protected to a certain extent.
Wherein, referring to fig. 4, A1 and A2 are respectively controller or processor CPU control ports, in some embodiments, the switch driving control circuit comprises: the device comprises a first control signal input circuit, a second control signal input circuit and a triode N1, wherein a second resistor R1 is arranged on the first control signal input circuit, the input end of the second resistor R1 is used for being connected with a port of a first output end A1 of the controller, and the output end of the second resistor R1 is connected with a base electrode of the triode N1 through a second diode D2;
the second control signal input circuit is provided with a third resistor R2, the input end of the third resistor R2 is connected with a port of a second output end A2 of the controller, the output end of the third resistor R2 is connected with the base electrode of the triode N1, the collector electrode of the triode N1 is connected with a pull-up resistor R3, the input end of the pull-up resistor R3 is connected with an auxiliary power supply VCC1, the auxiliary power supply VCC1 is used for supplying power for driving M1, and the emitter electrode of the triode N1 is grounded;
and a clamping diode D1 is further connected to a node M between the second resistor R1 and the second diode D2, and the other end of the clamping diode D1 is connected with the drain electrode of the MOS tube M1.
The working principle of the switch driving control circuit is as follows:
the MOS tube M1 is forced to conduct: when the controller ports A1 and A2 are both at low level, the triode N1 is turned off, the auxiliary power supply VCC1 charges Vgs (voltage of the gate G relative to the source S) of the MOS transistor M1 through the pull-up resistor R3, and the pull-up resistor R3 plays a certain current limiting role, so that the MOS transistor M1 is gradually turned on. The current flowing through the MOS transistor M1 rises slowly, so that di/dt is smaller. Therefore, the method can not generate great electromagnetic interference, and meanwhile, the method also can not have great current abrupt change to interfere other circuits to work, so that the problem of inter-shunt interference caused by switching of a switch, short-circuit protection and the like when the multi-way switch operates in parallel is avoided. By extension, the different devices can be ensured to independently work without mutual interference when the different devices are connected in parallel.
The forced turn-off process of the MOS tube M1: when the controller ports A1 and A2 (or only A2) are at high level, the triode N1 is immediately turned on, so that the power MOS tube M1 can be effectively turned off, and false triggering is prevented.
The safe operation state process of the MOS tube M1 comprises the following steps: when the forced conduction state of the MOS tube M1 is executed, the controller port A1 is set to be at a high level, the controller port A2 is kept at a low level, and the MOS tube M1 is kept at a conduction state at the moment, but if the output current is suddenly increased instantly to reach a hardware protection current threshold value Im due to short circuit or other abnormal conditions of the output load RL, the MOS tube M1 can be automatically protected and turned off from the aspect of hardware, the MOS tube M1 and a power supply VCC can be effectively protected to safely operate, and other parallel branches can not be influenced to normally operate, so that the state is called a safe operation state, and the problem that the semiconductor devices such as the MOS tube M1 are directly applied to equipment ports and are easy to damage is solved.
Wherein, set up: vds: MOS tube M1 is conducted for voltage drop; rdson: the on-resistance of the MOS transistor M1; vd1: the clamp diode D1 is conducted for voltage drop; vd2: the second diode D2 is conducted for voltage drop; vbe: the conduction voltage drop between the base and the emitter of the triode N1. Then, the hardware protection current threshold is: im= (vd2+vbe-Vd 1)/Rdson, i.e. the formula basis for setting the overcurrent protection threshold.
When the switch is normally turned on, the MOS tube M1 works in a safe running state, at the moment, the A1 is in a high level, the A2 is in a low level, the triode N1 is turned off, the MOS tube M1 is turned on, the power supply supplies power to the load RL, and the load is in a working state.
The principle of realizing protection of the switch driving control circuit is as follows: let load RL current be I, then MOS transistor M1 drain voltage is: vmd= (rdson+rs) ×i.
When the conduction voltage between the base b and the emitter e of the triode N1 is Vbe, and when Vd1+Vmd is smaller than Vd2+Vbe, the M point voltage is clamped by Vd1+Vmd, the second diode D2 and the triode N1 are not conducted, and the MOS tube M1 is continuously conducted.
When Vd1+Vmd > Vd2+Vbe, the M point voltage is clamped by Vd2+Vbe, the second diode D2 and the triode N1 are conducted, the MOS tube M1 is turned off, and the drain voltage of the MOS tube M1 is equal to the power supply voltage. Because Vmd is far greater than Vd2+Vbe, the MOS tube M1 is kept in an off state, and therefore the protection and locking functions are achieved.
In the embodiment of the invention, the circuit topology formed by the combination of the resistor, the triode and the diode realizes a driving control scheme of the power MOS tube M1 with 3 working states, and can effectively protect the switch, mainly the safe operation of the MOS tube M1 and the load RL.
The switch driving control circuit provided in this embodiment is used for driving control of a single controller or a CPU port and a non-isolated MOS transistor M1. In practical application, isolation driving can be realized through signal isolation devices such as an optical coupler, and the signal isolator can be a photoelectric coupler, a magnetic coupler or a capacitive coupler; some of the electronic components in the circuit may be simplified, and the modified circuit should be considered as an extension of the embodiments of the present invention.
With continued reference to fig. 1 or fig. 2, when the load RL is a relay, the MOS transistor M1 is turned off suddenly (including normal turn-off and protection turn-off generated when the current is too large), and a larger induced voltage still exists on the relay, and the induced voltage is applied to the drain electrode of the MOS transistor M1, so that the MOS transistor M1 is easy to break down. Therefore, in some embodiments, the switch main circuit further includes a freewheeling diode D3, where a cathode of the freewheeling diode D3 is connected to the output terminal of the power supply VCC and an anode of the freewheeling diode D3 is connected to the drain of the MOS transistor M1. When the load RL needs to stop working, the MOS tube M1 is turned off; the freewheeling diode D3 freewheels the load RL and other electronic elements at the output end of the switch main circuit when the MOS tube M1 is turned off, so that overvoltage breakdown of the MOS tube M1 can be effectively prevented, and protection of the MOS tube M1 is realized.
With continued reference to fig. 1 and 3, the output current sampling circuit further includes an input resistor R6, an operational amplifier U1, and a feedback resistor R5, where the operational amplifier U1 includes a non-inverting input terminal and an inverting input terminal; the input end of the input resistor R6 is connected to the first end of the sampling resistor Rs for realizing impedance matching, the output end of the input resistor R6 is connected to the non-inverting input end of the operational amplifier U1, the first end of the feedback resistor R5 is connected to the inverting input end of the operational amplifier U1, the second end of the feedback resistor R5 is connected to the output end of the operational amplifier U1, and the first end of the feedback resistor R5 is also grounded. Thus, the output current is converted into the voltage Virs (namely, the voltages at two ends of Rs) after passing through the sampling resistor Rs and is converted into the sampling voltage Vio which is easy to identify by the controller after passing through the operational amplifier U1, so that the sampling voltage Vio is in a voltage range which is easy to identify by the controller, and the current sampling precision can be improved.
It can be understood that, in order to ensure that the operational amplifier U1 amplifies the signal without distortion and improve the sampling precision of the output port CPU of the operational amplifier U1 on the signal, the input voltage of the input stage of the operational amplifier U1 and the output voltage of the operational amplifier U1 need to be ensured, so in some embodiments, the non-inverting input end of the operational amplifier U1 is further connected with a bias circuit, so that the input current of the input stage of the operational amplifier is increased by the bias circuit, which can improve the non-distortion degree after the signal is amplified, thereby improving the precision of current sampling.
Specifically, the bias circuit adopts a direct current bias circuit, and comprises a direct current power supply, a first bias resistor R8 and a second bias resistor R7, wherein the direct current power supply can be 3.3V, the first bias resistor R8 is connected with the second bias resistor R7 in series, the input end of the first bias resistor R8 is connected with the direct current power supply, the output end of the first bias resistor R8 is also connected with the non-inverting input end of the operational amplifier U1, and the output end of the second bias resistor R7 is connected with the power supply ground.
With continued reference to fig. 1 or 3, in some embodiments, a first resistor R4 is further connected in series with the inverting input terminal of the operational amplifier U1, and the first terminal of the feedback resistor R5 is further connected to the power ground through the first resistor R4. The first resistor R4 and the feedback resistor R5 together form an amplifying feedback.
In order to realize the monitoring to the switch state, the switch sampling circuit further comprises: the switch state sampling circuit comprises a third voltage dividing resistor R9 and a fourth voltage dividing resistor R11, wherein the third voltage dividing resistor R9 and the fourth voltage dividing resistor R11 are connected in series, the input end of the third voltage dividing resistor R9 is connected to the drain electrode of the MOS tube M1, the output end of the fourth voltage dividing resistor R11 is connected with the power supply ground, and a node between the third voltage dividing resistor R9 and the fourth voltage dividing resistor R11 is also used for being connected with the input end of the controller. The third voltage dividing resistor R9 and the fourth voltage dividing resistor R11 divide the voltage to form a switch state sampling circuit, the switch state sampling circuit is used for collecting voltage conditions, and the controller judges whether the circuit is actually in an on state or an off state according to the voltage sampling conditions, so that the monitoring of the actual running state of the circuit is realized.
In addition to one of the prior art described in the background art, there is a scheme of using a solid state relay in combination with dc detection as a switch to control the on/off of a current in an existing current distribution system. However, the loop formed by the method has small through flow, cannot bear lightning stroke, is easy to damage and cannot bear large current impact.
Referring to fig. 1 and 5, PE represents the earth; to reduce the likelihood of a lightning strike on the dc switch in this embodiment, in some embodiments, the dc switch further includes an input lightning protection circuit disposed in an input loop of the switch main circuit, the input lightning protection circuit comprising: the voltage-sensitive resistor comprises a first voltage-sensitive resistor RV1 and a first capacitor C1, wherein the first voltage-sensitive resistor RV1 and the first capacitor C1 are respectively connected in parallel with the positive electrode and the negative electrode of a power supply VCC, the positive electrode of the power supply VCC is grounded, and the negative electrode of the power supply VCC is grounded.
In other embodiments, the switch further comprises an output lightning protection circuit, the output lightning protection circuit is arranged in an output loop of the switch main circuit, the output lightning protection circuit comprises a second piezoresistor RV2 and a second capacitor C2, the second piezoresistor RV2 and the second capacitor C2 are respectively connected in parallel with an output end of the switch main circuit, one end of each of the second piezoresistor RV2 and the second capacitor C2 is connected with a positive electrode of a power supply VCC, and the other end of each of the second piezoresistor RV2 and the second capacitor C2 is connected with a drain electrode of the MOS tube M1.
When the lightning surge current passes, the tail end can be preferentially started to release current when the line voltage reaches a preset value, and when the line voltage is continuously increased, if the distance between the input and output two-stage lightning protection devices is too short (the essence is that the impedance is too low), the current passes quickly, and the tail end is easily damaged due to oversized bearing current. Therefore, in order to better realize lightning protection, the lightning protection circuit further comprises an inductance element, and specifically, the drain electrode of the MOS tube M1 is further connected with the inductance element. Because the current passing through the inductance element cannot jump, the current can be prevented from passing through quickly, so that the current splitting capacity can be balanced relatively, and the lightning protection effect is improved.
In order to increase the lightning-proof shunt branch, in some embodiments, a first diode D4 is connected in parallel between the drain of the MOS transistor M1 and the second end of the sampling resistor Rs.
The principle of lightning protection in the scheme is that surge current is introduced into the ground, so that the damage of the excessive surge current to elements in the direct current switch, mainly the MOS tube M1, is avoided, and equipment with the direct current switch is further protected.
The input lightning protection circuit has the following specific working principle:
(1) When a lightning surge current is input into Vin-output from vin+, the surge current first flows through the branch: vin+ & gt, a first capacitor C1- & gt, vin-; when the voltage across the first capacitor C1 increases, the first varistor RV1 is triggered, and thus the second current branch is added to shunt: vin + → first varistor RV1 → Vin-. Further, since the second voltage dependent resistor RV2 may be triggered early or late, a third current branch may be added, vin+ →the second voltage dependent resistor RV2→l1→the MOS transistor m1→rs→vin-; the inrush current injection causes the switching main circuit input voltage to increase, so that the output voltage also increases, and then accompanies the fourth current branch: vin+ & gtRL- & gtL 1- & gtMOS transistor M1- & gtRs- & gtvin-.
In the input lightning protection, the current divided by the third branch and the fourth branch is relatively small due to the existence of the decoupling inductance element, and the MOS tube M1 is switched off for protection along with the increase of the current flowing through the MOS tube M1, and then the third branch and the fourth branch of the circuit are also disconnected, so that the surge current is mainly born by the first branch and the second branch and flows into the ground in the input lightning protection, thereby realizing the lightning protection.
(2) When a lightning surge current is input by Vin-, vin+ is output, the surge current firstly flows through the branch: vin- & gt, a first capacitor C1- & gt vin+; along with the electric energy in the first capacitor C1 of the capacitor is released, after the voltages at two ends of the first capacitor C1 are reversely biased, the freewheeling diode D3 and the first diode D4 are turned on, so that the first current branch is gradually turned off, and the second branch is turned on, namely: vin- & gt, D4- & gt, D3- & gt, vin+; meanwhile, due to the parallel connection, the third branch circuit also divides a small part of current, and the branch circuit is as follows: vin- & gtRS- & gtMOS tube M1- & gtD3- & gtvin+, surge current is led into the ground through the branch circuit, and lightning protection is realized.
The specific working principle of the output lightning protection is as follows:
(1) When a lightning surge current is output from vo+ to Vo-, the surge current first flows through the branch: vo + → second capacitance c2→vo-; when RV2 is triggered as the voltage across the second capacitor C2 rises, then a second current leg is added: vo + → RV2→vo-; meanwhile, RV1 can be triggered early or late, so that a third current branch is added, and vo+ & fwdarw RV1- & gtD4- & gtL1- & gtvo-; the inrush current injection causes the circuit to reverse charge, so that the switching main circuit input voltage also increases, and then accompanies the fourth current branch: vo + → c1→ d4→ l1→ Vo-; in addition, rs and MOS tube M1 connected in parallel with D4 also divide a small amount of current to form fifth and sixth current branches.
(2) When a lightning surge current is output by Vo-vo+, the surge current first flows through the branch: vin- & gt, a second capacitor C2- & gt, vin+; after the second capacitor C2 is discharged and the voltage at two ends reversely rises to RV2, adding a second current branch: vo- →rv2- →vo+; the third current branch due to the presence of the surge current in parallel relationship is also discharging, i.e.: vo- & gtL1- & gtMOS tube M1- & gtRs- & gtC1- & gtvo+; when C1 finishes discharging, the diode D3 is positively biased to conduct, and a 4 th current branch is formed: vo- →l1- →d3- →vo+. Because of the decoupling inductance L1, the currents of the third branch and the fourth branch are relatively small, and the MOS tube M1 is turned off for protection along with the current increase of the MOS tube M1 of the main switch tube, then the third current branch of the circuit is disconnected, and the surge current is mainly born by the first branch, the second branch and the fourth branch so as to carry out surge current division, thereby realizing output lightning protection.
The direct current switch provided by the embodiment of the invention uses the power MOS tube M1 as a main switching device, can realize the switching of direct current heavy current, and has the advantages of small volume, low cost, convenience in integration and the like. The safe operation of the switch itself and the load RL can be effectively protected.
Therefore, the design can be widely applied to the scene of high-current direct-current relay switching and hot plug butt joint of a power circuit.
The device has the characteristics of strong lightning surge resistance, timely protection and convenient remote automatic control, and can be suitable for occasions such as household branching control of the current 5G product, outdoor pole-holding tower installation scenes, tidal power control of living area working areas and the like so as to save power.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "mounted," "connected," "coupled," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
In this specification, each embodiment is described in a related manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (10)
1. A dc switch, comprising: the switching device comprises a switching main circuit, a driving control circuit and a switching sampling circuit, wherein the switching main circuit comprises a MOS tube arranged in a loop, the input end of the driving control circuit is used for being connected with the output end of a controller, and the output end of the driving control circuit is connected with the MOS tube;
the switch sampling circuit comprises an input voltage sampling circuit and an output current sampling circuit, the input voltage sampling circuit comprises a first voltage dividing resistor and a second voltage dividing resistor, the first voltage dividing resistor is connected in series with the second voltage dividing resistor, the input end of the first voltage dividing resistor is connected with a power supply, the output end of the second voltage dividing resistor is connected with the power supply ground, and a node between the first voltage dividing resistor and the second voltage dividing resistor is used for being connected with the input end of the controller;
the output current sampling circuit comprises a sampling resistor, a first end of the sampling resistor is connected with a source electrode of the MOS tube, a second end of the sampling resistor is grounded, and two ends of the sampling resistor are also used for being connected with an input end of the controller;
a first diode is connected in parallel between the drain electrode of the MOS tube and the second end of the sampling resistor;
the switch drive control circuit includes: the device comprises a first control signal input circuit, a second control signal input circuit and a triode, wherein a second resistor is arranged on the first control signal input circuit, the input end of the second resistor is used for being connected with the first output end of the controller, and the output end of the second resistor is connected with the base electrode of the triode through a second diode;
the second control signal input circuit is provided with a third resistor, the input end of the third resistor is used for being connected with the second output end of the controller, the output end of the third resistor is connected with the base electrode of the triode, the collector electrode of the triode is connected with a pull-up resistor, and the emitting electrode of the triode is grounded;
and a clamping diode is further connected to a node between the second resistor and the second diode, and the other end of the clamping diode is connected with the drain electrode of the MOS tube.
2. The dc switch of claim 1, wherein the output current sampling circuit further comprises an input resistor, an operational amplifier, and a feedback resistor, wherein the input terminal of the input resistor is connected to the first terminal of the sampling resistor, the output terminal is connected to the non-inverting input terminal of the operational amplifier, the first terminal of the feedback resistor is connected to the inverting input terminal of the operational amplifier, the second terminal is connected to the output terminal of the operational amplifier, and the first terminal of the feedback resistor is further connected to the power supply ground.
3. The dc switch of claim 2, wherein a bias circuit is further connected to the non-inverting input of the operational amplifier.
4. The direct current switch of claim 3, wherein the bias circuit comprises a direct current power supply, a first bias resistor and a second bias resistor, the first bias resistor is connected in series with the second bias resistor, an input end of the first bias resistor is connected with the direct current power supply, an output end of the first bias resistor is further connected with a non-inverting input end of the operational amplifier, and an output end of the second bias resistor is grounded.
5. The dc switch of claim 4 wherein a first resistor is connected in series before the first end of the feedback resistor and the inverting input of the operational amplifier, the first end of the feedback resistor being further connected to power ground through the first resistor.
6. The direct current switch of claim 1, wherein the switch sampling circuit further comprises: the switch state sampling circuit comprises a third voltage dividing resistor and a fourth voltage dividing resistor, the third voltage dividing resistor is connected with the fourth voltage dividing resistor in series, the input end of the third voltage dividing resistor is connected with the drain electrode of the MOS tube, the output end of the fourth voltage dividing resistor is connected with the power supply ground, and a node between the third voltage dividing resistor and the fourth voltage dividing resistor is further used for being connected with the input end of the controller.
7. The direct current switch of claim 1, wherein the switch main circuit further comprises a freewheeling diode, a cathode of the freewheeling diode is connected to a power supply output terminal, and an anode of the freewheeling diode is connected to a drain of the MOS transistor.
8. The direct current switch of claim 1 or 7, further comprising an input lightning protection circuit provided in an input loop of the switch main circuit, the input lightning protection circuit comprising: the power supply comprises a power supply, a first piezoresistor and a first capacitor, wherein the power supply is connected with the positive electrode and the negative electrode of the power supply in parallel, the positive electrode of the power supply is grounded, and the negative electrode of the power supply is grounded.
9. The direct current switch according to claim 1 or 7, further comprising an output lightning protection circuit, wherein the output lightning protection circuit is arranged in an output loop of the switch main circuit, the output lightning protection circuit comprises a second piezoresistor and a second capacitor, the second piezoresistor and the second capacitor are respectively connected in parallel with an output end of the switch main circuit, one end of each of the second piezoresistor and the second capacitor is connected with a positive electrode of a power supply, and the other end of each of the second piezoresistor and the second capacitor is connected with a drain electrode of the MOS tube.
10. The direct current switch of claim 9, wherein the drain of the MOS transistor is further connected to an inductive element.
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