CN103762548B - Short-circuit protection circuit for low-voltage direct current system - Google Patents
Short-circuit protection circuit for low-voltage direct current system Download PDFInfo
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- CN103762548B CN103762548B CN201410014338.2A CN201410014338A CN103762548B CN 103762548 B CN103762548 B CN 103762548B CN 201410014338 A CN201410014338 A CN 201410014338A CN 103762548 B CN103762548 B CN 103762548B
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Abstract
The invention discloses a kind of short-circuit protection circuit for low-voltage direct current system, side of the positive electrode current sampling resistor one end and low-voltage direct-current system cathode output end, positive pole short-circuit protection circuit current sampling end connects, the other end is through side of the positive electrode voltage sampling resistor, common resistance, negative side voltage sampling resistor is connected with low-voltage direct-current system cathode output end, side of the positive electrode voltage sampling resistor is connected with positive pole short-circuit protection circuit voltage sampling end with the common port of common resistance, negative side voltage sampling resistor is connected with negative pole short-circuit protection circuit voltage sampling end with the common port of common resistance, low-voltage direct-current system cathode output end is connected with negative pole short-circuit protection circuit current sampling end through negative side current sampling resistor, just, the synchronizing signal input of negative pole short-circuit protection circuit, the corresponding connection of output, just, negative pole short-circuit protection circuit has outside spill current protection electronic circuit and/or low-impedance protection electronic circuit simultaneously, also can have overcurrent protection electronic circuit, to realize spill current, overcurrent and low-impedance protection.
Description
Technical field
The present invention relates to a kind of short-circuit protection circuit, espespecially a kind of short-circuit protection circuit being applied to low-voltage direct-current system, belongs to electrical engineering field.
Background technology
Low-voltage direct-current system is common electric power system in electrical engineering field.At present, the protective device supporting for low-voltage direct-current system mainly contains frame type automatic air circuit breaker, breaker of plastic casing, Mini-size circuit breaker with plastic shell, its release has operating current at 8 times of electromagnetic type momentary excess current releases to more than 10 times rated current, the time delay overcurrent trip of operating current rated current more than 3 times, operating current is 1.1 ~ 1.3 times and above rated current, operate time the thermal overload release etc. more than 1 hour, these devices are all for low-voltage direct-current system provides a kind of overcurrent protection based on current detecting, realize the short-circuit protection to low-voltage direct-current system.
Along with the development of photovoltaic generation industry, implementing short-circuit protection accurately to the low-voltage direct-current system be provided with in it becomes a great problem.Specifically; because the voltage-current characteristic of the photovoltaic electrification component adopted in photovoltaic generating system has nonlinear characteristic; the electric current of its output when short circuit and the running current before short circuit very nearly the same; thus external short circuit fault cannot be judged according to the curent change of photovoltaic electrification component output; that is; come to implement short-circuit protection to the low-voltage direct-current system in photovoltaic generating system according to current existing overcurrent protection; then cannot excise short trouble accurately and effectively, there is very large potential safety hazard.
Summary of the invention
The object of the present invention is to provide a kind of short-circuit protection circuit for low-voltage direct current system; this circuit is that low-voltage direct-current system provides spill current protection, overcurrent protection and low-impedance protection (i.e. under-voltage protection) three kinds of short circuit protection measures, and low-impedance protection is wherein specially adapted to the low-voltage direct-current system in photovoltaic generating system.
To achieve these goals, present invention employs following technical scheme:
A kind of short-circuit protection circuit for low-voltage direct current system, it is characterized in that: it comprises positive pole short-circuit protection circuit, negative pole short-circuit protection circuit, one end of side of the positive electrode current sampling resistor and the cathode output end of low-voltage direct-current system, the current sampling end of this positive pole short-circuit protection circuit connects, the other end of this side of the positive electrode current sampling resistor is successively via side of the positive electrode voltage sampling resistor, common resistance, negative side voltage sampling resistor is connected with the cathode output end of this low-voltage direct-current system, the common port of this side of the positive electrode current sampling resistor and this side of the positive electrode voltage sampling resistor is as load positive terminal, this side of the positive electrode voltage sampling resistor is connected with the voltage sampling end of this positive pole short-circuit protection circuit with the common port of this common resistance, the synchronous signal output end of this positive pole short-circuit protection circuit is connected with the synchronous signal input end of this negative pole short-circuit protection circuit, this negative side voltage sampling resistor is connected with the voltage sampling end of this negative pole short-circuit protection circuit with the common port of this common resistance, the cathode output end of this low-voltage direct-current system to be connected with the current sampling end of this negative pole short-circuit protection circuit via negative side current sampling resistor and the current sampling end of this negative pole short-circuit protection circuit simultaneously as load negative pole end, the synchronous signal output end of this negative pole short-circuit protection circuit is connected with the synchronous signal input end of this positive pole short-circuit protection circuit, this positive pole short-circuit protection circuit, the breaking coil that the trip signal output of this negative pole short-circuit protection circuit is corresponding to this low-voltage direct-current system respectively connects, wherein: this positive pole short-circuit protection circuit, this negative pole short-circuit protection circuit has spill current protection electronic circuit and/or low-impedance protection electronic circuit simultaneously.
In actual applications, breaking coil described in each is same breaking coil or different breaking coils.
In actual design, for described positive pole short-circuit protection circuit:
Described spill current protection electronic circuit comprises current amplitude comparator, an input of this current amplitude comparator is connected with the current sampling end of described positive pole short-circuit protection circuit and another input is connected with the output of Saw-tooth Signal Waveform Generator, the pulse signal input terminal of this Saw-tooth Signal Waveform Generator is connected with the output of phased lock loop clock signal generator, the Synchronization Control input of this phased lock loop clock signal generator is connected with the synchronous signal output end of described negative pole short-circuit protection circuit, two inputs of difference between current comparator respectively with the output of this current amplitude comparator, the synchronous signal input end of described positive pole short-circuit protection circuit connects, the output of this difference between current comparator is successively via spill current protection decision circuit, the time relay, spill current protection start-up circuit is connected with corresponding described breaking coil,
Described low-impedance protection electronic circuit comprises voltage magnitude comparator, an input of this voltage magnitude comparator is connected with the voltage sampling end of described positive pole short-circuit protection circuit via inverter and another input is connected with the output of this Saw-tooth Signal Waveform Generator, an input of sense of current discriminator is connected with the current sampling end of described positive pole short-circuit protection circuit and another inputs termination benchmark voltage, this sense of current discriminator, the output of this voltage magnitude comparator is connected with the corresponding signal receiving terminal of current direction switches respectively, the signal output part of this current direction switches is successively via low-impedance protection decision circuit, the time relay, low-impedance protection start-up circuit is connected with corresponding described breaking coil,
For described negative pole short-circuit protection circuit:
Described spill current protection electronic circuit comprises current amplitude comparator, an input of this current amplitude comparator is connected with the current sampling end of described negative pole short-circuit protection circuit and another input is connected with the output of Saw-tooth Signal Waveform Generator, the pulse signal input terminal of this Saw-tooth Signal Waveform Generator is connected with the output of phased lock loop clock signal generator, the Synchronization Control input of this phased lock loop clock signal generator is connected with the synchronous signal output end of described positive pole short-circuit protection circuit, two inputs of difference between current comparator respectively with the output of this current amplitude comparator, the synchronous signal input end of described negative pole short-circuit protection circuit connects, the output of this difference between current comparator is successively via spill current protection decision circuit, the time relay, spill current protection start-up circuit is connected with corresponding described breaking coil,
Described low-impedance protection electronic circuit comprises voltage magnitude comparator, an input of this voltage magnitude comparator is connected with the voltage sampling end of described negative pole short-circuit protection circuit and another input is connected with the output of this Saw-tooth Signal Waveform Generator, an input of sense of current discriminator is connected with the current sampling end of described negative pole short-circuit protection circuit and another inputs termination benchmark voltage, this sense of current discriminator, the output of this voltage magnitude comparator is connected with the corresponding signal receiving terminal of current direction switches respectively, the signal output part of this current direction switches is successively via low-impedance protection decision circuit, the time relay, low-impedance protection start-up circuit is connected with corresponding described breaking coil.
Preferably, in actual design, the synchronous signal output end of described positive pole short-circuit protection circuit is connected via the synchronous signal input end of photoelectrical coupler with described negative pole short-circuit protection circuit; The synchronous signal output end of described negative pole short-circuit protection circuit is connected via the synchronous signal input end of photoelectrical coupler with described positive pole short-circuit protection circuit.
In actual design, except having spill current protection electronic circuit and/or low-impedance protection electronic circuit, described positive pole short-circuit protection circuit, described negative pole short-circuit protection circuit also can have overcurrent protection electronic circuit simultaneously.
In actual design, for described positive pole short-circuit protection circuit: described overcurrent protection electronic circuit comprises overcurrent protection decision circuit, the input of this overcurrent protection decision circuit is connected with the output of the described current amplitude comparator of described positive pole short-circuit protection circuit, and the output of this overcurrent protection decision circuit is connected with corresponding described breaking coil via the time relay, overcurrent protection start-up circuit successively;
For described negative pole short-circuit protection circuit: described overcurrent protection electronic circuit comprises overcurrent protection decision circuit; the input of this overcurrent protection decision circuit is connected with the output of the described current amplitude comparator of described negative pole short-circuit protection circuit, and the output of this overcurrent protection decision circuit is connected with corresponding described breaking coil via the time relay, overcurrent protection start-up circuit successively.
The present invention, except the simulation that has a synchronous sequence feature by above-mentioned and logical hybrid circuit are formed, can also adopt single-chip microcomputer to mix with simulation, logical circuit and form, be implemented as:
Described phased lock loop clock signal generator in described positive pole short-circuit protection circuit, described difference between current comparator, described spill current protection decision circuit, monostable flipflop, overcurrent judgement timer, described overcurrent protection decision circuit, described sense of current discriminator, Low ESR judgement timer, described current direction switches, described low-impedance protection decision circuit, all described time relays are substituted by a single-chip microcomputer; Described phased lock loop clock signal generator in described negative pole short-circuit protection circuit, described difference between current comparator, described spill current protection decision circuit, monostable flipflop, overcurrent judgement timer, described overcurrent protection decision circuit, described sense of current discriminator, Low ESR judgement timer, described current direction switches, described low-impedance protection decision circuit, all described time relays are substituted by a single-chip microcomputer.
Advantage of the present invention is:
The present invention is according to the circuit structure feature of low-voltage direct-current system and the circuit feature of short trouble; for low-voltage direct-current system provide spill current protection, overcurrent protection and low-impedance protection (i.e. under-voltage protection) three kinds of short circuit protection measures and the visual actual needs selection of this three kinds of short-circuit protections enable; low-impedance protection is wherein specially adapted to the low-voltage direct-current system in photovoltaic generating system; the short trouble accuracy of judgement that the present invention realizes, reliable; electric short circuit fault can be excised with prestissimo, fault harm is limited in lowest range.
When being applied to as the present invention in the low-voltage direct-current system in photovoltaic generating system; the present invention can solve the problem of the protection sensitivity deficiency that existing overcurrent protection exists to the loop of the photovoltaic electrification component in photovoltaic generating system and external short circuit fault, strange land ground short circuit fault in district, outside district and inside and outside district is provided to reliable and has and optionally protects.
Accompanying drawing explanation
Fig. 1 is composition frame chart of the present invention.
Fig. 2 is the circuit diagram of a preferred embodiment of the present invention.
Fig. 3 is the circuit diagram of another preferred embodiment of the present invention.
Embodiment
Short-circuit protection circuit for low-voltage direct current system of the present invention is used for carrying out short-circuit protection to low-voltage direct-current system, and this low-voltage direct-current system is conventionally in electrical engineering field know electric power system, comprises basic powered appliance equipment, therefore it specifically forms and does not here describe in detail.
As Fig. 1, the present invention is connected between the cathode output end X1 of low-voltage direct-current system and cathode output end X3, as figure, short-circuit protection circuit for low-voltage direct current system of the present invention comprises positive pole short-circuit protection circuit 100, negative pole short-circuit protection circuit 200, one end of side of the positive electrode current sampling resistor 301 and the cathode output end X1 of low-voltage direct-current system, the current sampling end of this positive pole short-circuit protection circuit 100 connects, the other end of this side of the positive electrode current sampling resistor 301 (i.e. R1 shown in Fig. 2) is successively via side of the positive electrode voltage sampling resistor 302 (i.e. R2 shown in Fig. 2), common resistance 305 (i.e. R5 shown in Fig. 2), negative side voltage sampling resistor 304 (i.e. R4 shown in Fig. 2) is connected with the cathode output end X3 of this low-voltage direct-current system, the cathode output end X3 of this low-voltage direct-current system is as the local-reference ground (as shown in Figure 2 G2) of this negative pole short-circuit protection circuit 200, the common port of this side of the positive electrode current sampling resistor 301 and this side of the positive electrode voltage sampling resistor 302 is as load positive terminal X2 and as the local-reference ground (as shown in Figure 2 G1) of this positive pole short-circuit protection circuit 100, this side of the positive electrode voltage sampling resistor 302 is connected with the voltage sampling end of this positive pole short-circuit protection circuit 100 with the common port of this common resistance 305, the synchronous signal output end of this positive pole short-circuit protection circuit 100 is connected with the synchronous signal input end of this negative pole short-circuit protection circuit 200, this negative side voltage sampling resistor 304 is connected with the voltage sampling end of this negative pole short-circuit protection circuit 200 with the common port of this common resistance 305, the cathode output end X3 of this low-voltage direct-current system to be connected with the current sampling end of this negative pole short-circuit protection circuit 200 via negative side current sampling resistor 303 (i.e. R3 shown in Fig. 2) and the current sampling end of this negative pole short-circuit protection circuit 200 simultaneously as load negative pole end X4, be used for being connected load between load positive terminal X2 with load negative pole end X4, the synchronous signal output end of this negative pole short-circuit protection circuit 200 is connected with the synchronous signal input end of this positive pole short-circuit protection circuit 100, this positive pole short-circuit protection circuit 100, the breaking coil that the trip signal output of this negative pole short-circuit protection circuit 200 is corresponding to this low-voltage direct-current system respectively connects, wherein: this positive pole short-circuit protection circuit 100, this negative pole short-circuit protection circuit 200 has spill current protection electronic circuit and/or low-impedance protection electronic circuit simultaneously, in other words, this positive pole short-circuit protection circuit 100, this negative pole short-circuit protection circuit 200 can be provided with spill current protection electronic circuit together, or be provided with low-impedance protection electronic circuit together, or be provided with spill current protection electronic circuit and low-impedance protection electronic circuit together.
In actual design; as Fig. 1; preferably; the synchronous signal output end of positive pole short-circuit protection circuit 100 is connected via the synchronous signal input end of photoelectrical coupler 306 with negative pole short-circuit protection circuit 200, and the synchronous signal output end of negative pole short-circuit protection circuit 200 is connected via the synchronous signal input end of photoelectrical coupler 307 with positive pole short-circuit protection circuit 100.
The present invention is that low-voltage direct-current system provides three kinds of short circuit protection measures, except the low-impedance protection (also referred to as under-voltage protection) that the spill current protection realized except above-mentioned spill current protection electronic circuit and above-mentioned low-impedance protection electronic circuit realize, also has the overcurrent protection that overcurrent protection electronic circuit realizes, that is, at this positive pole short-circuit protection circuit 100, this negative pole short-circuit protection circuit 200 has on the basis of spill current protection electronic circuit and/or low-impedance protection electronic circuit simultaneously, this positive pole short-circuit protection circuit 100, negative pole short-circuit protection circuit 200 also can have overcurrent protection electronic circuit simultaneously.
As Fig. 1, for positive pole short-circuit protection circuit 100:
Spill current protection electronic circuit comprises current amplitude comparator 104, an input (negative input end) of this current amplitude comparator 104 is connected with the current sampling end of positive pole short-circuit protection circuit 100, for receiving the current sampling signal that low-voltage direct-current system cathode output end X1 place gathers via side of the positive electrode current sampling resistor 301, and another input (positive input terminal) of current amplitude comparator 104 is connected with the output of Saw-tooth Signal Waveform Generator 103, the pulse signal input terminal of this Saw-tooth Signal Waveform Generator 103 is connected with the output of phased lock loop clock signal generator 101, the Synchronization Control input of this phased lock loop clock signal generator 101 is connected with the synchronous signal output end of negative pole short-circuit protection circuit 200, for receiving the synchronizing current signal that negative pole short-circuit protection circuit 200 exports, positive and negative reference voltage source 102 for this Saw-tooth Signal Waveform Generator 103 provide positive negative two reference voltage signals (one of them reference voltage signal can by another reference voltage signal through operational amplifier export or via divider resistance split produce), the intermediate contact of this positive and negative reference voltage source 102 is connected with local-reference ground G1, two inputs of difference between current comparator 105 respectively with the output of this current amplitude comparator 104, the synchronous signal input end of positive pole short-circuit protection circuit 100 connects, be respectively used to the current amplitude compare result signal receiving the output of this current amplitude comparator 104, the synchronizing current signal that negative pole short-circuit protection circuit 200 exports, the output of this difference between current comparator 105 is successively via spill current protection decision circuit 107, the time relay 108, spill current protection start-up circuit 109 is connected with the terminals of corresponding breaking coil 401.
Overcurrent protection electronic circuit comprises overcurrent protection decision circuit 111; the input of this overcurrent protection decision circuit 111 is connected with the output of the current amplitude comparator 104 of positive pole short-circuit protection circuit 100, and the output of this overcurrent protection decision circuit 111 is connected with the terminals of corresponding breaking coil 402 via the time relay 112, overcurrent protection start-up circuit 113 successively.
Low-impedance protection electronic circuit comprises voltage magnitude comparator 115, an input (negative input end) of this voltage magnitude comparator 115 is connected with the voltage sampling end of positive pole short-circuit protection circuit 100 via inverter 121, for receiving the voltage sampling signal that low-voltage direct-current system cathode output end X1 place gathers via side of the positive electrode voltage sampling resistor 302, and another input (positive input terminal) of voltage magnitude comparator 115 is connected with the output of this Saw-tooth Signal Waveform Generator 103, an input of sense of current discriminator 114 is connected with the current sampling end of positive pole short-circuit protection circuit 100 and another inputs termination benchmark voltage (V0 as shown in Figure 2
+), the output of this sense of current discriminator 114, this voltage magnitude comparator 115 is connected with the corresponding signal receiving terminal of current direction switches 117 respectively, and the signal output part of this current direction switches 117 is connected with the terminals of corresponding breaking coil 403 via low-impedance protection decision circuit 118, the time relay 119, low-impedance protection start-up circuit 120 successively.
As Fig. 1, for negative pole short-circuit protection circuit 200:
Spill current protection electronic circuit comprises current amplitude comparator 204, an input (negative input end) of this current amplitude comparator 204 is connected with the current sampling end of negative pole short-circuit protection circuit 200, for receiving the current sampling signal that low-voltage direct-current system cathode output end X3 place gathers via negative side current sampling resistor 303, and another input (positive input terminal) of current amplitude comparator 204 is connected with the output of Saw-tooth Signal Waveform Generator 203, the pulse signal input terminal of this Saw-tooth Signal Waveform Generator 203 is connected with the output of phased lock loop clock signal generator 201, the Synchronization Control input of this phased lock loop clock signal generator 201 is connected with the synchronous signal output end of positive pole short-circuit protection circuit 100, for receiving the synchronizing current signal that positive pole short-circuit protection circuit 100 exports, positive and negative reference voltage source 202 for this Saw-tooth Signal Waveform Generator 203 provide positive negative two reference voltage signals (one of them reference voltage signal can by another reference voltage signal through operational amplifier export or via divider resistance split produce), the intermediate contact of this positive and negative reference voltage source 202 is connected with local-reference ground G2, two inputs of difference between current comparator 205 respectively with the output of this current amplitude comparator 204, the synchronous signal input end of negative pole short-circuit protection circuit 200 connects, be respectively used to the current amplitude compare result signal receiving the output of this current amplitude comparator 204, the synchronizing current signal that positive pole short-circuit protection circuit 100 exports, the output of this difference between current comparator 205 is successively via spill current protection decision circuit 207, the time relay 208, spill current protection start-up circuit 209 is connected with the terminals of corresponding breaking coil 404.
Overcurrent protection electronic circuit comprises overcurrent protection decision circuit 211; the input of this overcurrent protection decision circuit 211 is connected with the output of the current amplitude comparator 204 of negative pole short-circuit protection circuit 200, and the output of this overcurrent protection decision circuit 211 is connected with the terminals of corresponding breaking coil 405 via the time relay 212, overcurrent protection start-up circuit 213 successively.
Low-impedance protection electronic circuit comprises voltage magnitude comparator 215, an input (negative input end) of this voltage magnitude comparator 215 is connected with the voltage sampling end of negative pole short-circuit protection circuit 200, for receiving the voltage sampling signal that low-voltage direct-current system cathode output end X3 place gathers via negative side voltage sampling resistor 304, and another input (positive input terminal) of voltage magnitude comparator 215 is connected with the output of this Saw-tooth Signal Waveform Generator 203, an input of sense of current discriminator 214 is connected with the current sampling end of negative pole short-circuit protection circuit 200 and another inputs termination benchmark voltage (V0 as shown in Figure 2
+), the output of this sense of current discriminator 214, this voltage magnitude comparator 215 is connected with the corresponding signal receiving terminal of current direction switches 217 respectively, and the signal output part of this current direction switches 217 is connected with the terminals of corresponding breaking coil 406 via low-impedance protection decision circuit 218, the time relay 219, low-impedance protection start-up circuit 220 successively.
As Fig. 2, preferably, in positive pole short-circuit protection circuit 100: difference between current comparator 105 can comprise biconditional gate U1; Spill current protection decision circuit 107 comprises d type flip flop U2, the input of this d type flip flop U2 is connected through the output of inverter (NOR gate U3 is as inverter) with this biconditional gate U1 herein, and the clock end of this d type flip flop U2 is connected via the output of monostable flipflop 106 with this biconditional gate U1; Current direction switches 117 comprises and door U7; Low-impedance protection decision circuit 118 comprises d type flip flop U8, the input of this d type flip flop U8 be connected with the output of door U7 with this, and the clock end of this d type flip flop U8 is connected via the Low ESR judgement output of timer 116 with phased lock loop clock signal generator 101; Overcurrent protection decision circuit 111 comprises d type flip flop U5, the input of this d type flip flop U5 is connected with the output of current amplitude comparator 104 through inverter (NOR gate U4 is as inverter) herein, and the clock end of this d type flip flop U5 is connected through the electric current judgement output of timer 110 with phased lock loop clock signal generator 101; Spill current protection start-up circuit 109 comprises auxiliary relay K1, and overcurrent protection start-up circuit 113 comprises auxiliary relay K2, and low-impedance protection start-up circuit 120 comprises auxiliary relay K3.
In like manner, preferably, in negative pole short-circuit protection circuit 200: difference between current comparator 205 comprises biconditional gate; Spill current protection decision circuit 207 comprises d type flip flop, and the input of this d type flip flop is connected with the output of this biconditional gate through inverter, and the clock end of this d type flip flop is connected with the output of this biconditional gate via monostable flipflop 206; Current direction switches 217 comprises and door; Low-impedance protection decision circuit 218 comprises d type flip flop, and the input of this d type flip flop be connected with the output of door with this, and the clock end of this d type flip flop is connected via the Low ESR judgement output of timer 2 16 with phased lock loop clock signal generator 201; Overcurrent protection decision circuit 211 comprises d type flip flop, the input of this d type flip flop is connected through the output of inverter with current amplitude comparator 204, and the clock end of this d type flip flop is connected through the electric current judgement output of timer 2 10 with phased lock loop clock signal generator 201; Spill current protection start-up circuit 209, overcurrent protection start-up circuit 213, low-impedance protection start-up circuit 220 include auxiliary relay.
In the present invention, phased lock loop clock signal generator 101 and 201, positive and negative reference voltage source 102 and 202 (as adopted TL431), Saw-tooth Signal Waveform Generator 103 and 203, current amplitude comparator 104 and 204, sense of current discriminator 114 and 214, voltage magnitude comparator 115 and 215 etc. are the electronic device of knowing of this area, therefore its concrete formation does not here describe in detail.
It should be noted that; in the present invention; except because of the polarity of sampling point voltage signal contrary; positive pole short-circuit protection circuit 100 is than negative pole short-circuit protection circuit more than 200 outside an inverter 121; positive pole short-circuit protection circuit 100 forms identical with the internal circuit of negative pole short-circuit protection circuit 200; their operation principle is also substantially identical, therefore in Fig. 2 and Fig. 3, the internal circuit of not shown negative pole short-circuit protection circuit 200 constructs.
In actual applications, as Fig. 1, each breaking coil 401 ~ 406 can be same breaking coil or different breaking coils.Breaking coil can be the breaking coil in the protection devices such as release.
Preferably; selector switch can be set in corresponding position of the present invention; selector switch can select protection pressing plate to realize; according to actual needs the spill current protection of positive pole short-circuit protection circuit 100, negative pole short-circuit protection circuit 200, overcurrent protection, low-impedance protection function are carried out independence and opened or closing control; certainly, the function that positive pole short-circuit protection circuit 100, negative pole short-circuit protection circuit 200 are opened should be synchronously consistent.Such as, for positive pole short-circuit protection circuit 100 explanation, as shown in Figure 2, selector switch S1 is provided with in Fig. 2, S2 and S3, be used for respectively controlling spill current defencive function, excess current protective function, the open and close of low-impedance protection function, in fig. 2, when selecting switch S 1 to connect high level, open spill current defencive function, otherwise, when selecting switch S 1 to connect low level, close spill current defencive function, in like manner, when selecting switch S 2 to connect high level, open excess current protective function, otherwise, when selecting switch S 2 to connect low level, close excess current protective function, when selecting switch S 3 to connect high level, open low-impedance protection function, otherwise, when selecting switch S 3 to connect low level, close low-impedance protection function.
Main for positive pole short-circuit protection circuit 100 below, what spill current defencive function that the present invention realizes, excess current protective function, low-impedance protection function were described realizes principle.
As Fig. 2, if phased lock loop clock signal generator 101 receives the synchronizing current signal that the other side's (negative pole short-circuit protection circuit 200) sends, then only play synchronous effect (being synchronized with trailing edge) at the trailing edge of synchronizing current signal.Phased lock loop clock signal generator 101 is to Saw-tooth Signal Waveform Generator 103 output clock pulse signal, Saw-tooth Signal Waveform Generator 103 is made to trigger output sawtooth waveforms at the rising edge of each clock pulse, the lower summit of sawtooth waveforms is corresponding with negative reference voltage, and upper summit is corresponding with positive reference voltage.
At phased lock loop clock signal generator 101 to while Saw-tooth Signal Waveform Generator 103 output clock pulse signal, it also carries clock pulse signal (namely overcurrent judgement timer 110 is synchronoused working with Saw-tooth Signal Waveform Generator 103) to overcurrent judgement timer 110, and overcurrent judgement triggers the pulse of an output rising edge time delay to the rising edge of each clock pulse with timer 110.
The positive and negative input of current amplitude comparator 104 receives the periodic serrations ripple signal that Saw-tooth Signal Waveform Generator 103 exports, the current sampling signal gathered via side of the positive electrode current sampling resistor 301 respectively, then amplitude com parison is carried out between the two to it, exporting with pulse duration is that the current amplitude compare result signal of feature is (when sawtooth signal is greater than current sampling signal, current amplitude comparator 104 exports high level, namely exports with high level displacement in current amplitude compare result signal).Then, this current amplitude compare result signal divides three tunnels.
The first via exports to negative pole short-circuit protection circuit 200 after photoelectrical coupler U9 Phototube Coupling as synchronizing current signal.
Second road direction d type flip flop U5 carries, when opening excess current protective function (selector switch S2 connects high level), this current amplitude compare result signal sends into the input (D end) of d type flip flop U5 after NOR gate U4 is anti-phase, set according to the delay time of setting current to overcurrent judgement timer 110, and the delay pulse signal exported by overcurrent judgement timer 110 is as the clock signal of d type flip flop U5, so, d type flip flop U5 realizes measuring to the pulse duration in the inversion signal of current amplitude compare result signal based on the delay pulse signal received, and measurement result is exported.When the continuing current flow flowing through current sampling resistor R1 is greater than setting current; d type flip flop U5 continues to export high level and driving time relay 112; after elapsed time relay 112 carries out time restriction; namely after the time that the continuing current flow flowing through side of the positive electrode current sampling resistor R1 is greater than setting current reaches the limiting time of the time relay 112; to the coil conveying high level of auxiliary relay K2; so coil obtains electric, overcurrent trip, realizes overcurrent protection.After the electric current flowing through side of the positive electrode current sampling resistor R1 is lower than setting current, before delay time arrives, the output of d type flip flop U5 be low level " 0 ", thus the coil dead electricity at once of this auxiliary relay K2, stopping overcurrent protection.This overcurrent protection for photovoltaic electrification component and between positive and negative electrode output X1, X3 (in the other direction) electric current of one-point short circuit or 2 strange land ground short circuits transfinite and have reliable overcurrent protection; and for the short trouble outside district; owing to not having enough fault currents to flow through, thus overcurrent protection is inoperative.
One end conveying of the 3rd road direction biconditional gate U1, the other end of this biconditional gate U1 receives the synchronizing current signal (the current amplitude compare result signal that negative pole short-circuit protection circuit 200 exports) that negative pole short-circuit protection circuit 200 is sent, so biconditional gate U1 aligns, negative pole short-circuit protection circuit 100, the 200 current amplitude compare result signals exported respectively compare, if both pulse durations are the same, namely the electric current flowing through side of the positive electrode current sampling resistor R1 is the same with the electric current flowing through negative side current sampling resistor R3, then output low level, otherwise output high level.When opening spill current defencive function (selector switch S1 connects high level); the level signal that this biconditional gate U1 exports sends into the input (D end) of d type flip flop U2 after NOR gate U3 is anti-phase; the level signal that simultaneously biconditional gate U1 exports also flows to monostable flipflop 106, and the pulse signal that the negative logic output terminal of monostable flipflop 106 exports is as the clock signal of d type flip flop U2.By the width of the pulse signal that monostable flipflop 106 is exported set (as setting pulse signal width be tested electric current allow measure error and coefficient of reliability product); make d type flip flop U2 based on the pulse signal receiving monostable flipflop 106 output; pulse-width difference carries out measuring (the pulse duration difference in the current amplitude compare result signal namely exported respectively positive and negative electrode short-circuit protection circuit 100,200 is measured), and measurement result is exported.Under normal circumstances; the electric current flowing through side of the positive electrode current sampling resistor R1 is the same with the electric current flowing through negative side current sampling resistor R3; before monostable flipflop 106 output pulse signal terminates; the output of d type flip flop U2 has been low level " 0 "; thus the coil of this auxiliary relay K1 is power failure state, does not carry out spill current protection.When pulse duration difference continues to be greater than setting discrepancy threshold (when namely terminating at monostable flipflop 106 output pulse signal; d type flip flop U2 still receives high level; difference still exists) time; d type flip flop U2 continues to export high level and driving time relay 108; after elapsed time relay 108 carries out time restriction; namely after the time that pulse duration difference continues to be greater than setting discrepancy threshold reaches the limiting time of the time relay 108; to the coil conveying high level of auxiliary relay K1; so coil obtains electric; spill current trips, and realizes spill current protection.When recovering normal after spill current protection, d type flip flop U2 is output low level " 0 " again, so spill current protection stops.In spill current protection, two photoelectrical couplers U9, U10 serve the effect of the synchronous working that to be linked together by both positive and negative polarity short-circuit protection.2 strange land earth faults that the protection of this spill current can align, any point is formed in cathode output end X1, X3 play spill current protective effect; the short trouble occurred the current imbalance between positive and negative electrode output X1, X3 caused because of any reason is all effective, has high sensitivity to minimum fault current.
At phased lock loop clock signal generator 101 to while Saw-tooth Signal Waveform Generator 103 output clock pulse signal, it also carries clock pulse signal (namely Low ESR judgement timer 116 is synchronoused working with Saw-tooth Signal Waveform Generator 103) to Low ESR judgement timer 116, and Low ESR judgement triggers the pulse of an output rising edge time delay to the rising edge of each clock pulse with timer 116.Sense of current discriminator 114 detects the sense of current flowing through side of the positive electrode current sampling resistor R1.In the present invention, setting direction shown in arrow in Fig. 2 is running current direction.So; when opening Low ESR (low-voltage) defencive function (selector switch S3 connects high level) and when actual current direction is consistent with the running current direction of setting (sense of current discriminator 114 carries high level to door U7); low-impedance protection function just can use, otherwise low-impedance protection function cannot use.The voltage sampling signal that the positive and negative input of voltage magnitude comparator 115 receives periodic serrations ripple signal that Saw-tooth Signal Waveform Generator 103 exports respectively, gather via side of the positive electrode voltage sampling resistor 302 carry out anti-phase after the signal that obtains, then amplitude com parison is carried out between the two to it, exporting with pulse duration is that the voltage magnitude compare result signal of feature is (when sawtooth signal is greater than voltage sampling signal, voltage magnitude comparator 115 exports high level, namely exports with high level displacement in voltage magnitude compare result signal).When low-impedance protection function can use, voltage magnitude compare result signal just can send into the input (D end) of d type flip flop U8.
According to adjusting, the delay time of voltage to Low ESR judgement timer 116 sets, and the delay pulse signal exported by Low ESR judgement timer 116 is as the clock signal of d type flip flop U8, so, d type flip flop U8 realizes measuring to the pulse duration in voltage magnitude compare result signal based on the delay pulse signal received, and measurement result is exported.When the voltage keeps on voltage sampling resistor R2 lower than adjust voltage time; d type flip flop U8 continues to export high level and driving time relay 119; after elapsed time relay 119 carries out time restriction; namely after the voltage keeps on side of the positive electrode voltage sampling resistor R2 reaches the limiting time of the time relay 119 lower than time of voltage of adjusting; to the coil conveying high level of auxiliary relay K3; so coil obtains electric, Low ESR trips, and realizes low-impedance protection.After the voltage on side of the positive electrode voltage sampling resistor R2 is greater than voltage of adjusting; or the running current direction of actual current direction and setting is short-circuited time reverse fault; or when selector switch S3 connects low level; before delay time arrives; the output of d type flip flop U8 has been low level " 0 "; now the coil of this auxiliary relay K3 is dead electricity, and low-impedance protection stops.This low-impedance protection is specially adapted to the low-voltage direct-current system in photovoltaic generating system.Can find in practice; photovoltaic electrification component in photovoltaic generating system is almost constant as the electric current that during power supply, it supplies before and after short circuit; and the voltage at positive and negative electrode output X1, X3 place shows as the remarkable reduction of voltage along with the reduction of external impedance; therefore; present invention utilizes the significantly reduced feature of this voltage; under-voltage protection is realized to the low-voltage direct-current system of photovoltaic generating system, for excising the short trouble of positive and negative electrode output X1, X3 place voltage reduction caused in any case.
The spill current defencive function of negative pole short-circuit protection circuit 200, excess current protective function, low-impedance protection function to realize principle substantially identical with positive pole short-circuit protection circuit 100, therefore no longer here to repeat.
In actual design, the present invention, except the simulation that has a synchronous sequence feature by above-mentioned and logical hybrid circuit are formed, can also adopt single-chip microcomputer to mix with simulation, logical circuit and form.As Fig. 3; as can be seen from Fig. 3 and Fig. 2 relatively, the phased lock loop clock signal generator 101 in positive pole short-circuit protection circuit 100, difference between current comparator 105, spill current protection decision circuit 107, monostable flipflop 106, overcurrent judgement timer 110, overcurrent protection decision circuit 111, sense of current discriminator 114, Low ESR judgement timer 116, current direction switches 117, low-impedance protection decision circuit 118, the time relay 108,112,119 can be substituted by single-chip microcomputer U0.In like manner, the phased lock loop clock signal generator 201 in negative pole short-circuit protection circuit 200, difference between current comparator 205, spill current protection decision circuit 207, monostable flipflop 206, overcurrent judgement timer 2 10, overcurrent protection decision circuit 211, sense of current discriminator 214, Low ESR judgement timer 2 16, current direction switches 217, low-impedance protection decision circuit 218, the time relay 208,212,219 can be substituted by a single-chip microcomputer.In practice, the single-chip microcomputer that can play its alternative device institute tool function selected by single-chip microcomputer.In addition, in practice, selector switch S1 ~ S3 can be set and they are connected with single-chip microcomputer, or adopting the protection pressing plate of software simulation to realize the function of selector switch.
Fig. 3 shows and mixes with simulation, logical circuit the present invention formed by single-chip microcomputer.In reality is implemented, for positive pole short-circuit protection circuit 100, single-chip microcomputer U0 can run according to the following steps, to realize various short-circuit protection function.
Step one: close all short-circuit protection functions via selector switch S1 ~ S3, single-chip microcomputer U0 powers on and closes its all output and carry out initialization (initialization data memory, on-chip timer and adaptation thereof, A/D converter and system mode), opens the Sampling interrupt function of all DI, A1 mouths;
Step 2: the sampled data checking that all DI mouths receive of rolling, if the continuous sampled data received for 3 times is consistent, then enters step 3, otherwise repeats step 2;
Step 3: open overcurrent and under-voltage protection function via selector switch S2, S3, starts Saw-tooth Signal Waveform Generator 103 simultaneously;
Step 4: if the forward position of the clock pulse of single-chip microcomputer U0 setting arrives, then receive the sampled data of DI mouth and AI mouth, and carry out computing (to voltage and current execution division arithmetic according to relay protective scheme, there is provided the distance protection based on fault localization), realize ladder, the overcurrent in multistage time limit and under-voltage protection, otherwise, wait for;
Step 5: check the synchronizing current signal that negative pole short-circuit protection circuit 200 is sent, if there is synchronizing current signal, then opens spill current defencive function via selector switch S1, enters step 6, otherwise, skip to step 7;
Step 6: single-chip microcomputer U0 synchronously processes phased lock loop clock signal and exports, receives the sampled data of DI mouth and AI mouth, and carries out computing according to relay protective scheme, realizes spill current protection;
Step 7: single-chip microcomputer U0 is to each auxiliary relay K1 ~ K3 output protection logical calculated result;
Step 8: the electric current and the voltage that calculate now sampling point;
Step 9: when the output of the d type flip flop of all software simulations is in " 0 " state, according to the request task of the network port, process advanced tasks;
Step 10: if clock pulse forward position arrives or without request task, then skips to step 4, perform circular treatment thus.
As can be seen from foregoing description process; Saw-tooth Signal Waveform Generator 103 together provides electric current, voltage measurement function fast with current amplitude comparator 104, voltage magnitude comparator 115 respectively; two photoelectrical couplers U9, U10 provide the function of the synchronous working that to be linked together by both positive and negative polarity short-circuit protection; and single-chip microcomputer U0 passes through many covers action definite value of inner foundation and multiple time relay, provide ladder, the spill current in multistage time limit, overcurrent and under-voltage protection function.
Advantage of the present invention is:
The present invention is according to the circuit structure feature of low-voltage direct-current system and the circuit feature of short trouble; for low-voltage direct-current system provide spill current protection, overcurrent protection and low-impedance protection (i.e. under-voltage protection) three kinds of short circuit protection measures and the visual actual needs selection of this three kinds of short-circuit protections enable; low-impedance protection is wherein specially adapted to the low-voltage direct-current system in photovoltaic generating system; the short trouble accuracy of judgement that the present invention realizes, reliable; electric short circuit fault can be excised with prestissimo, fault harm is limited in lowest range.
When being applied to as the present invention in the low-voltage direct-current system in photovoltaic generating system; the present invention can solve the problem of the protection sensitivity deficiency that existing overcurrent protection exists to the loop of the photovoltaic electrification component in photovoltaic generating system and external short circuit fault, strange land ground short circuit fault in district, outside district and inside and outside district is provided to reliable and has and optionally protects.
The above know-why being preferred embodiment of the present invention and using; for a person skilled in the art; when not deviating from the spirit and scope of the present invention; any based on apparent changes such as the equivalent transformation on technical solution of the present invention basis, simple replacements, all belong within scope.
Claims (9)
1. a short-circuit protection circuit for low-voltage direct current system, it is characterized in that: it comprises positive pole short-circuit protection circuit, negative pole short-circuit protection circuit, one end of side of the positive electrode current sampling resistor and the cathode output end of low-voltage direct-current system, the current sampling end of this positive pole short-circuit protection circuit connects, the other end of this side of the positive electrode current sampling resistor is successively via side of the positive electrode voltage sampling resistor, common resistance, negative side voltage sampling resistor is connected with the cathode output end of this low-voltage direct-current system, the common port of this side of the positive electrode current sampling resistor and this side of the positive electrode voltage sampling resistor is as load positive terminal, this side of the positive electrode voltage sampling resistor is connected with the voltage sampling end of this positive pole short-circuit protection circuit with the common port of this common resistance, the synchronous signal output end of this positive pole short-circuit protection circuit is connected with the synchronous signal input end of this negative pole short-circuit protection circuit, this negative side voltage sampling resistor is connected with the voltage sampling end of this negative pole short-circuit protection circuit with the common port of this common resistance, the cathode output end of this low-voltage direct-current system to be connected with the current sampling end of this negative pole short-circuit protection circuit via negative side current sampling resistor and the current sampling end of this negative pole short-circuit protection circuit simultaneously as load negative pole end, the synchronous signal output end of this negative pole short-circuit protection circuit is connected with the synchronous signal input end of this positive pole short-circuit protection circuit, this positive pole short-circuit protection circuit, the breaking coil that the trip signal output of this negative pole short-circuit protection circuit is corresponding to this low-voltage direct-current system respectively connects, wherein: this positive pole short-circuit protection circuit, this negative pole short-circuit protection circuit has spill current protection electronic circuit and/or low-impedance protection electronic circuit simultaneously.
2. short-circuit protection circuit for low-voltage direct current system as claimed in claim 1, is characterized in that:
For described positive pole short-circuit protection circuit:
Described spill current protection electronic circuit comprises current amplitude comparator, an input of this current amplitude comparator is connected with the current sampling end of described positive pole short-circuit protection circuit and another input is connected with the output of Saw-tooth Signal Waveform Generator, the pulse signal input terminal of this Saw-tooth Signal Waveform Generator is connected with the output of phased lock loop clock signal generator, the Synchronization Control input of this phased lock loop clock signal generator is connected with the synchronous signal output end of described negative pole short-circuit protection circuit, two inputs of difference between current comparator respectively with the output of this current amplitude comparator, the synchronous signal input end of described positive pole short-circuit protection circuit connects, the output of this difference between current comparator is successively via spill current protection decision circuit, the time relay, spill current protection start-up circuit is connected with corresponding described breaking coil,
Described low-impedance protection electronic circuit comprises voltage magnitude comparator, an input of this voltage magnitude comparator is connected with the voltage sampling end of described positive pole short-circuit protection circuit via inverter and another input is connected with the output of this Saw-tooth Signal Waveform Generator, an input of sense of current discriminator is connected with the current sampling end of described positive pole short-circuit protection circuit and another inputs termination benchmark voltage, this sense of current discriminator, the output of this voltage magnitude comparator is connected with the corresponding signal receiving terminal of current direction switches respectively, the signal output part of this current direction switches is successively via low-impedance protection decision circuit, the time relay, low-impedance protection start-up circuit is connected with corresponding described breaking coil,
For described negative pole short-circuit protection circuit:
Described spill current protection electronic circuit comprises current amplitude comparator, an input of this current amplitude comparator is connected with the current sampling end of described negative pole short-circuit protection circuit and another input is connected with the output of Saw-tooth Signal Waveform Generator, the pulse signal input terminal of this Saw-tooth Signal Waveform Generator is connected with the output of phased lock loop clock signal generator, the Synchronization Control input of this phased lock loop clock signal generator is connected with the synchronous signal output end of described positive pole short-circuit protection circuit, two inputs of difference between current comparator respectively with the output of this current amplitude comparator, the synchronous signal input end of described negative pole short-circuit protection circuit connects, the output of this difference between current comparator is successively via spill current protection decision circuit, the time relay, spill current protection start-up circuit is connected with corresponding described breaking coil,
Described low-impedance protection electronic circuit comprises voltage magnitude comparator, an input of this voltage magnitude comparator is connected with the voltage sampling end of described negative pole short-circuit protection circuit and another input is connected with the output of this Saw-tooth Signal Waveform Generator, an input of sense of current discriminator is connected with the current sampling end of described negative pole short-circuit protection circuit and another inputs termination benchmark voltage, this sense of current discriminator, the output of this voltage magnitude comparator is connected with the corresponding signal receiving terminal of current direction switches respectively, the signal output part of this current direction switches is successively via low-impedance protection decision circuit, the time relay, low-impedance protection start-up circuit is connected with corresponding described breaking coil.
3. short-circuit protection circuit for low-voltage direct current system as claimed in claim 1 or 2, is characterized in that:
The synchronous signal output end of described positive pole short-circuit protection circuit is connected via the synchronous signal input end of photoelectrical coupler with described negative pole short-circuit protection circuit; The synchronous signal output end of described negative pole short-circuit protection circuit is connected via the synchronous signal input end of photoelectrical coupler with described positive pole short-circuit protection circuit.
4. short-circuit protection circuit for low-voltage direct current system as claimed in claim 2, is characterized in that:
Described positive pole short-circuit protection circuit, described negative pole short-circuit protection circuit have overcurrent protection electronic circuit simultaneously.
5. short-circuit protection circuit for low-voltage direct current system as claimed in claim 4, is characterized in that:
For described positive pole short-circuit protection circuit:
Described overcurrent protection electronic circuit comprises overcurrent protection decision circuit, the input of this overcurrent protection decision circuit is connected with the output of the described current amplitude comparator of described positive pole short-circuit protection circuit, and the output of this overcurrent protection decision circuit is connected with corresponding described breaking coil via the time relay, overcurrent protection start-up circuit successively;
For described negative pole short-circuit protection circuit:
Described overcurrent protection electronic circuit comprises overcurrent protection decision circuit; the input of this overcurrent protection decision circuit is connected with the output of the described current amplitude comparator of described negative pole short-circuit protection circuit, and the output of this overcurrent protection decision circuit is connected with corresponding described breaking coil via the time relay, overcurrent protection start-up circuit successively.
6. short-circuit protection circuit for low-voltage direct current system as claimed in claim 2, is characterized in that:
In described positive pole short-circuit protection circuit: described difference between current comparator comprises biconditional gate; Described spill current protection decision circuit comprises d type flip flop, and the input of this d type flip flop is connected with the output of this biconditional gate through inverter, and the clock end of this d type flip flop is connected with the output of this biconditional gate via monostable flipflop; Described current direction switches comprises and door; Described low-impedance protection decision circuit comprises d type flip flop, and the input of this d type flip flop be connected with the output of door with this, and the clock end of this d type flip flop is connected via the Low ESR judgement output of timer with described phased lock loop clock signal generator; Described spill current protection start-up circuit, described low-impedance protection start-up circuit include auxiliary relay;
In described negative pole short-circuit protection circuit: described difference between current comparator comprises biconditional gate; Described spill current protection decision circuit comprises d type flip flop, and the input of this d type flip flop is connected with the output of this biconditional gate through inverter, and the clock end of this d type flip flop is connected with the output of this biconditional gate via monostable flipflop; Described current direction switches comprises and door; Described low-impedance protection decision circuit comprises d type flip flop, and the input of this d type flip flop be connected with the output of door with this, and the clock end of this d type flip flop is connected via the Low ESR judgement output of timer with described phased lock loop clock signal generator; Described spill current protection start-up circuit, described low-impedance protection start-up circuit include auxiliary relay.
7. short-circuit protection circuit for low-voltage direct current system as claimed in claim 5, is characterized in that:
In described positive pole short-circuit protection circuit: described overcurrent protection decision circuit comprises d type flip flop, the input of this d type flip flop is connected through the output of inverter with described current amplitude comparator, and the clock end of this d type flip flop is connected through the electric current judgement output of timer with described phased lock loop clock signal generator; Described overcurrent protection start-up circuit comprises auxiliary relay;
In described negative pole short-circuit protection circuit: described overcurrent protection decision circuit comprises d type flip flop, the input of this d type flip flop is connected through the output of inverter with described current amplitude comparator, and the clock end of this d type flip flop is connected through the electric current judgement output of timer with described phased lock loop clock signal generator; Described overcurrent protection start-up circuit comprises auxiliary relay.
8. short-circuit protection circuit for low-voltage direct current system as claimed in claim 5, is characterized in that:
Described phased lock loop clock signal generator in described positive pole short-circuit protection circuit, described difference between current comparator, described spill current protection decision circuit, monostable flipflop, overcurrent judgement timer, described overcurrent protection decision circuit, described sense of current discriminator, Low ESR judgement timer, described current direction switches, described low-impedance protection decision circuit, all described time relays are substituted by a single-chip microcomputer;
Described phased lock loop clock signal generator in described negative pole short-circuit protection circuit, described difference between current comparator, described spill current protection decision circuit, monostable flipflop, overcurrent judgement timer, described overcurrent protection decision circuit, described sense of current discriminator, Low ESR judgement timer, described current direction switches, described low-impedance protection decision circuit, all described time relays are substituted by a single-chip microcomputer.
9. short-circuit protection circuit for low-voltage direct current system as claimed in claim 1, is characterized in that:
Breaking coil described in each is same breaking coil or different breaking coils.
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| US6002215A (en) * | 1997-05-16 | 1999-12-14 | Koito Manufacturing Co., Ltd. | Lighting circuit for discharge lamp |
| CN202285320U (en) * | 2011-09-16 | 2012-06-27 | 新安县电业公司 | Short-circuit protection device for DC low-voltage system |
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| CN203722201U (en) * | 2014-01-13 | 2014-07-16 | 北京恺思维特科技有限责任公司 | Low-voltage direct-current system short circuit protection circuit |
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2014
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Patent Citations (4)
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|---|---|---|---|---|
| US6002215A (en) * | 1997-05-16 | 1999-12-14 | Koito Manufacturing Co., Ltd. | Lighting circuit for discharge lamp |
| CN202285320U (en) * | 2011-09-16 | 2012-06-27 | 新安县电业公司 | Short-circuit protection device for DC low-voltage system |
| CN203056903U (en) * | 2012-11-30 | 2013-07-10 | 西安智海电力科技有限公司 | High reliability DC low voltage power supply circuit |
| CN203722201U (en) * | 2014-01-13 | 2014-07-16 | 北京恺思维特科技有限责任公司 | Low-voltage direct-current system short circuit protection circuit |
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