CN114583940A - Power-off circuit of low-voltage direct-current power supply - Google Patents
Power-off circuit of low-voltage direct-current power supply Download PDFInfo
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- CN114583940A CN114583940A CN202210495893.6A CN202210495893A CN114583940A CN 114583940 A CN114583940 A CN 114583940A CN 202210495893 A CN202210495893 A CN 202210495893A CN 114583940 A CN114583940 A CN 114583940A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
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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
- H02H9/045—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage adapted to a particular application and not provided for elsewhere
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
- H03K17/082—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit
- H03K17/0822—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit in field-effect transistor switches
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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
- H03K17/6871—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 the output circuit comprising more than one controlled field-effect transistor
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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
- H03K17/6877—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 the control circuit comprising active elements different from those used in the output circuit
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/16—Information or communication technologies improving the operation of electric vehicles
Abstract
The invention discloses a power-down circuit of a low-voltage direct-current power supply, which comprises a main circuit and a control circuit, wherein the main circuit comprises a direct-current input end, a power-down switch and a direct-current output end; the control circuit comprises a microcontroller, the lower electric switch comprises an MOS (metal oxide semiconductor) tube, and the MOS tube is connected between the direct current input end and the direct current output end in series; the control circuit comprises an overcurrent protection circuit and an MOS tube drive circuit, the overcurrent protection circuit comprises a current sampling circuit of a main circuit, the output end of the current sampling circuit is connected with the overcurrent protection signal input end of the microcontroller, the control end of the MOS tube drive circuit is connected with the control signal output end of the microcontroller, and the grid electrode of the MOS tube is connected with the drive signal output end of the MOS tube drive circuit. The lower electric switch of the invention adopts MOS tube, the lower circuit cost is low, the volume is small; the overcurrent protection circuit can protect the MOS tube which is used as the lower electric switch, and the reliability of the lower electric switch is improved.
Description
Technical Field
The invention relates to a low-voltage direct-current power supply, in particular to a power-down circuit of the low-voltage direct-current power supply.
Background
Market demand for power electronics technology and devices is increasing, wherein power supplies are one of the main application areas of power electronics technology; with the continuous progress of power semiconductor manufacturing technology, computer technology and control theory; high frequency, miniaturization, modularization and intellectualization are development directions of the switching power supply; nowadays, outdoor communication power supplies, charging piles and various charging power supplies have been in close relation with the work and life of people for a long time; users have higher and higher requirements on the intellectualization of the power supplies, and want the power supplies to control the output switches of the power supplies without switching off the mains supply, for example, in the field of charging piles, users want to automatically turn off the power supply output after the battery of the electric automobile is fully charged to protect the battery, or can reserve charging time at any time, or have multiple outputs in an outdoor 5G communication power supply, and want each output to be controllable, and can control power-on and power-off through communication equipment such as bluetooth and WIFI at any time, and can power-off and turn off the output when not in use. When the power-saving switch is needed, the power can be turned on to output, and the power can be saved. Nowadays each big power supply manufacturer almost all uses relay or contactor as output electronic switch, and the reason is that the relay is not fragile like the MOS pipe, and the drawback of relay is bulky, and is with high costs, thereby appears striking sparks phenomenon easily when going up and down the electricity and lead to the life of relay not high. Although the switch MOS tube is low in cost, small in size and free of ignition phenomenon, the switch MOS tube is very easy to damage, and although short-circuit protection is provided when a power supply is short-circuited, the high-frequency switch tube inside the power supply, such as an LLC MOS tube and a synchronous rectification MOS tube, are protected; however, the lower electric switching tube for circuit output cannot be protected, and the lower electric switching MOS tube cannot bear short-circuit large current or surge current impact to cause damage, which is also the reason why many power supply manufacturers do not adopt the MOS tube as an output electronic switch.
Disclosure of Invention
The invention aims to provide a power-off circuit of a low-voltage direct-current power supply, which can protect an output electronic switch.
In order to solve the technical problems, the invention adopts the technical scheme that the power-down circuit of the low-voltage direct-current power supply comprises a main circuit and a control circuit, wherein the main circuit comprises a direct-current input end, a power-down switch and a direct-current output end; the control circuit comprises a microcontroller, the lower electric switch comprises an MOS (metal oxide semiconductor) tube, and the MOS tube is connected between the direct current input end and the direct current output end in series; the control circuit comprises an overcurrent protection circuit and an MOS tube drive circuit, the overcurrent protection circuit comprises a current sampling circuit of a main circuit, the output end of the current sampling circuit is connected with the overcurrent protection signal input end of the microcontroller, the control end of the MOS tube drive circuit is connected with the control signal output end of the microcontroller, and the grid electrode of the MOS tube is connected with the drive signal output end of the MOS tube drive circuit.
In the power-off circuit of the low-voltage direct-current power supply, the current sampling circuit comprises a current sampling resistor, an operational amplifier circuit and a current sampling resistor which are connected in series in the main circuit, two input ends of the operational amplifier circuit are respectively connected with two ends of the current sampling resistor, and an output end of the operational amplifier circuit is connected with an overcurrent protection signal input end of the microcontroller.
In the power-down circuit of the low-voltage direct-current power supply, the current sampling circuit comprises a first voltage division circuit, a first double-series switch diode and two filter circuits, and the operational amplification circuit comprises an operational amplifier; the non-inverting input end of the operational amplifier is connected with the first end of the current sampling resistor through a first balance resistor and is grounded through a second balance resistor, and the first balance capacitor is connected with the second balance resistor in parallel; the inverting input end of the operational amplifier is connected with the second end of the current sampling resistor through a third balance resistor, is connected with the non-inverting input end of the operational amplifier through a first filter capacitor, and is connected with the output end of the operational amplifier through a fourth balance resistor, and the second balance capacitor is connected with the fourth balance resistor in parallel; the first end of the first voltage division circuit is connected with the output end of the operational amplifier, the second end of the first voltage division circuit is grounded, and the voltage output end of the first voltage division circuit is connected with the overcurrent protection signal input end of the microcontroller; the anode of the first double-series switch diode is grounded, the cathode of the first double-series switch diode is connected with a chip power supply, and the middle of the first double-series switch diode is connected with the voltage output end of the first voltage division circuit; the first filter circuit is connected between the output end of the operational amplifier and the ground, and the second filter circuit is connected between the voltage output end of the first voltage division circuit and the ground.
In the power-off circuit of the low-voltage direct-current power supply, the control circuit comprises a short-circuit protection circuit, the short-circuit protection circuit comprises a current transformer, a demagnetization circuit and a rectification circuit, a primary winding of the current transformer is connected in series in the main circuit, a first end of a secondary winding of the current transformer is grounded, a second end of the secondary winding of the current transformer is connected with an input end of the rectification circuit, and an output end of the rectification circuit is connected with a short-circuit protection signal input end of the microcontroller; the demagnetization circuit is connected with the secondary winding of the current transformer in parallel.
In the power-down circuit of the low-voltage direct-current power supply, the short-circuit protection circuit comprises a voltage output resistor, a second voltage division circuit, a second filter capacitor and a second double-series switch diode, the demagnetization circuit comprises a first rectifier diode and a demagnetization resistor, and the rectification circuit comprises a second rectifier diode; the anode of the first rectifier diode is connected with the first end of the secondary winding of the current transformer, and the cathode of the first rectifier diode is connected with the second end of the secondary winding of the current transformer through a demagnetizing resistor; the anode of the second rectifier diode is connected with the second end of the secondary winding of the current transformer, the cathode of the second rectifier diode is connected with the first end of the voltage output resistor, and the second end of the voltage output resistor is grounded; the first end of the second voltage division circuit is connected with the cathode of the second rectifying diode, and the second end of the second voltage division circuit is grounded; the output end of the second voltage division circuit is connected with the short-circuit protection signal input end of the microcontroller; the second filter capacitor is connected between the output end of the second voltage-dividing circuit and the ground, the anode of the second double-series-connection switch diode is grounded, the cathode of the second double-series-connection switch diode is connected with the chip power supply, and the middle of the second double-series-connection switch diode is connected with the voltage output end of the second voltage-dividing circuit.
The main circuit of the power-off circuit of the low-voltage direct-current power supply comprises a lightning stroke protection circuit, and the positive electrode of the direct-current input end of the main circuit is connected with the positive electrode of the direct-current output end through a direct-current bus; the lightning stroke protection circuit comprises an absorption capacitor, a discharge tube, two piezoresistors and a fast recovery diode; the source electrode of the MOS tube is connected with the negative electrode of the direct current input end, the drain electrode of the MOS tube is connected with the negative electrode of the direct current output end, and the source electrode of the MOS tube is connected with the grid electrode of the MOS tube through a grounding resistor; the absorption capacitor is connected between the anode and the cathode of the direct current input end, after the two piezoresistors are connected in series, one end of the absorption capacitor is connected with the direct current bus, the other end of the absorption capacitor is connected with the source electrode of the MOS tube, the connection point of the two piezoresistors is connected with the input end of the discharge tube, and the output end of the discharge tube is connected with the ground; the anode of the fast recovery diode is connected with the drain electrode of the MOS tube, and the cathode of the fast recovery diode is connected with the direct current bus.
In the power-down circuit of the low-voltage direct-current power supply, the power-down switch comprises a plurality of MOS (metal oxide semiconductor) tubes, the drains of the MOS tubes are connected together, the sources of the MOS tubes are connected together, and the gates of the MOS tubes are connected together.
In the lower circuit of the low-voltage direct-current power supply, the MOS transistor driving circuit includes an NPN transistor, a collector of the NPN transistor is connected to the auxiliary power supply through a current-limiting resistor, and is connected to a gate of the MOS transistor through an MOS transistor driving resistor; the base electrode of the NPN triode is connected with the control signal output end of the microcontroller through a base electrode resistor; the emitter of the NPN triode is grounded.
In the lower circuit of the low-voltage direct-current power supply, the MOS tube driving circuit comprises a reverse pumping diode, the anode of the reverse pumping diode is connected with the base electrode of the NPN triode, and the cathode of the reverse pumping diode is connected with the control signal output end of the microcontroller; the grid electrode of the NPN triode is grounded through a pull-down resistor.
The lower electric switch of the invention adopts MOS tube, the lower circuit cost is low, the volume is small; the overcurrent protection circuit can protect the MOS tube which is used as the lower electric switch, and the reliability of the lower electric switch is improved.
Drawings
The invention is described in further detail below with reference to the drawings and the detailed description.
Fig. 1 is a circuit diagram of a power-down circuit of a low-voltage dc power supply according to an embodiment of the present invention.
Fig. 2 is a circuit diagram of an overcurrent protection circuit according to an embodiment of the invention.
Fig. 3 is a circuit diagram of a short-circuit protection circuit according to an embodiment of the invention.
FIG. 4 is a circuit diagram of a main circuit and a MOS transistor driving circuit of an embodiment of the invention.
Detailed Description
The structure and principle of the power-down circuit of the low-voltage direct-current power supply of the embodiment of the invention are shown in fig. 1 to 4, and the power-down circuit comprises a main circuit and a control circuit.
The main circuit comprises a direct current input end, a down switch, a lightning stroke protection circuit and a direct current output end. The positive pole of the direct current input end of the main circuit is connected with the positive pole VO + of the direct current output end through a direct current bus.
The lower electric switch comprises 4 MOS tubes Q95, Q93, Q55 and Q47, and is connected between the direct current input end and the direct current output end in series. The 4 MOS tubes Q95, Q93, Q55 and Q47 are connected in parallel, namely the drains of the 4 MOS tubes Q95, Q93, Q55 and Q47 are connected together, the sources are connected together, and the gates are connected together. The source electrode of 4 MOS tubes is connected with the negative electrode of the direct current input end, the drain electrode of 4 MOS tubes is connected with the negative electrode VO-of the direct current output end, and the source electrode of 4 MOS tubes is connected with the grid electrode of the MOS tube through a grounding resistor R495.
The control circuit comprises a microcontroller (a single chip microcomputer, not shown in the figure), an overcurrent protection circuit, a short-circuit protection circuit and an MOS tube drive circuit.
The overcurrent protection circuit comprises a current sampling circuit, the current sampling circuit samples the current of the main circuit, the output end of the current sampling circuit is connected with the overcurrent protection signal input end ISENSE of the microcontroller, the control end of the MOS tube driving circuit is connected with the control signal output end of the microcontroller, and the grid electrode of the MOS tube is connected with the driving signal output end of the MOS tube driving circuit.
As shown in fig. 4, the current sampling circuit includes a current sampling resistor RS9, an operational amplifier circuit, and a current sampling resistor RS9 connected in series in the main circuit, two input terminals of the operational amplifier circuit are respectively connected to two ends of the current sampling resistor RS9, and an output terminal of the operational amplifier circuit is connected to an overcurrent protection signal input terminal ISENSE of the microcontroller.
As shown in fig. 2, the current sampling circuit further includes a first voltage divider circuit formed by a resistor R353 and a resistor R2 connected in series, a first double-series-connected switch diode D126, and two filter capacitors. The operational amplification circuit comprises an operational amplifier U18-A. The non-inverting input terminal of the operational amplifier U18-a is connected to the first terminal of the current sampling resistor RS9 through the first balancing resistor R323, and is connected to ground (AGND) through the second balancing resistor R324, and the first balancing capacitor C166 is connected in parallel to the second balancing resistor R324. The inverting input end of the operational amplifier U18-A is connected with the second end of the current sampling resistor RS9 through a third balance resistor R322, is connected with the non-inverting input end of the operational amplifier U18-A through a first filter capacitor C165, is connected with the output end of the operational amplifier U18-A through a fourth balance resistor R327, and is connected with the fourth balance resistor R327 in parallel. The first end of the first voltage division circuit is connected with the output end of the operational amplifier U18-A, the second end is grounded, and the voltage output end (the connection point of the resistor R353 and the resistor R2) of the first voltage division circuit is connected with the overcurrent protection signal input end ISENSE of the microcontroller. The anode of the first double-series switch diode D126 is grounded, the cathode is connected with the chip power supply SMCU _3.3V, and the middle connection point is connected with the voltage output end of the first voltage division circuit. The first filter capacitor C177 is connected between the output terminal of the operational amplifier U18-A and ground, and the second filter capacitor MH C188 is connected between the voltage output terminal of the first voltage divider circuit and ground.
As shown in fig. 3 and 4, the short-circuit protection circuit comprises a current transformer TR1, a demagnetization circuit and a rectification circuit, wherein a primary winding TR1-B of the current transformer TR1 is connected in series in a main circuit, a first end of a secondary winding TR1-a of the current transformer TR1 is grounded, a second end of the secondary winding TR1 is connected with an input end of the rectification circuit, and an output end of the rectification circuit is connected with a short-circuit protection signal input end of the microcontroller. The demagnetization circuit is connected with a secondary winding TR1-A of the current transformer TR1 in parallel.
As shown in fig. 3, the short-circuit protection circuit includes a voltage output resistor formed by connecting a resistor R221 and a resistor 111 in parallel, a second voltage divider circuit formed by connecting a resistor R190 and a resistor 191 in series, a second filter capacitor C118, and a second double-series-connected switching diode D27, the demagnetization circuit includes a first common-cathode rectifier diode D52 and a demagnetization resistor R196, and the rectifier circuit has a second common-cathode rectifier diode D24. The anode of the first common cathode rectifier diode D52 is connected with the first end of the secondary winding TR1-A of the current transformer TR1, and the cathode is connected with the second end of the secondary winding TR1-A of the current transformer TR1 through a demagnetization resistor R196. The anode of the second common cathode rectifier diode D24 is connected with the second end of the secondary winding TR1-A of the current transformer TR1, the cathode is connected with the first end of the voltage output resistor, and the second end of the voltage output resistor is grounded. The first end of the second voltage division circuit is connected with the cathode of the second common cathode rectifier diode D24, and the second end is grounded. The output end (the connection point of the resistor R190 and the resistor 191) of the second voltage division circuit is connected with the short-circuit protection signal input end CS of the microcontroller. The second filter capacitor C118 is connected between the output end of the second voltage-dividing circuit and the ground, the anode of the second double-series switch diode D27 is grounded, the cathode of the second double-series switch diode D27 is connected with the chip power supply SMCU _3.3V, and the middle of the second double-series switch diode D27 is connected with the voltage output end of the second voltage-dividing circuit.
The lightning strike protection circuit comprises a absorption capacitor C33, a discharge tube F11, two voltage dependent resistors MOV18, MOV17 and two fast recovery diodes D98, D167. The absorption capacitor C33 is connected between the positive and negative poles of the direct current input end, after the two piezoresistors MOV18 and MOV17 are connected in series, one end is connected with a direct current bus, the other end is connected with the source electrodes of 4 MOS tubes, the connection point of the two piezoresistors MOV18 and MOV17 is connected with the input end of a discharge tube F11, and the output end of the discharge tube F11 is connected with the ground CHGND. The anodes of the two fast recovery diodes D98 and D167 are connected with the drains of the 4 MOS tubes, and the cathodes are connected with the direct current bus.
The MOS tube driving circuit comprises an NPN triode Q94, wherein the collector of the NPN triode Q94 is connected with a 12V auxiliary power supply through a current limiting resistor R512 and a current limiting resistor R513, and is connected with the grids of 4 MOS tubes through a MOS tube driving resistor R496. The base of NPN transistor Q94 is connected to the control signal output LOAD _ DRVER of the microcontroller through base resistor R475. The emitter of NPN transistor Q94 is grounded. The reverse diode D147 is connected in parallel with the base resistor R475, the anode of the reverse diode D147 is connected with the base of the NPN triode Q94, and the cathode is connected with the control signal output end LOAD _ DRVER of the microcontroller. The gate of NPN transistor Q94 is coupled to ground through pull-down resistor R481.
In the embodiment of the invention, when the power-off circuit of the low-voltage direct-current power supply works normally, the control signal output end LOAD _ DRVER of the singlechip is at low level, because the output of the power-off circuit is invariable direct current, the current transformer TR1 can not induce the changeable current, so the short-circuit protection circuit does not work, namely short circuit, and does not influence the normal work of the circuit, the sampling resistor RS9 transmits the current signal into the differential proportion operation circuit, the current signal is amplified and converted into a voltage signal ISENSE to be transmitted into the singlechip, the singlechip can monitor the output current in real time, when the output current of the power supply is overlarge (can be flexibly changed by a program), the single chip microcomputer can immediately set the LOAD _ DRVER signal output by the single chip microcomputer to be high, at the moment, the 4 output switch MOS tubes are immediately closed when losing the driving signal, the MOS tube can be prevented from being burnt due to overlarge current, and the overcurrent protection of the lower electric switch MOS tube is realized.
When the circuit is suddenly short-circuited under output, the current is changed greatly instantly, the differential proportional operation circuit is not applicable any more at the moment, the reason is that the delay is too high, the MOS tube is not ready to be turned off, the short-circuit protection circuit starts to work, the primary winding TR1-B of the current transformer is instantly increased due to the output short-circuit current, the current signal sensed by the secondary winding TR1-A due to the current change on the primary side passes through the common cathode rectifier diode D52, then the current signal is converted into a voltage signal through the demagnetization resistor R196 and the filter capacitor and is transmitted into the pin CS of the singlechip comparator, the singlechip receives the signal, if the signal amplitude is larger than the threshold value, the control signal LOAD _ DRVER of the singlechip is immediately increased, the 4 output switch MOS tubes lose the driving signal and are immediately turned off to prevent the MOS tube from being broken down by the short-circuit current, but the MOS tubes are forcibly turned off and protected when the current is not zero, the MOS tube has high stress, the two fast recovery diodes D98 and D167 clamp the drain electrode of the MOS tube at output VO +, and the redundant energy is reversely poured into the output electrolytic capacitor C33 to be absorbed, so that the closing stress of the switch MOS tube is greatly reduced, the MOS tube is protected from being damaged due to overhigh stress, and the short-circuit protection of the switch MOS tube is realized;
when a differential mode lightning stroke comes, firstly, a part of energy is reversely poured into an absorption capacitor (electrolytic capacitor) C33 through fast recovery diodes D98 and D167, the rest surge voltage is absorbed by two series-connected piezoresistors MOV18 and MOV17, if the surge voltage is a current type lightning stroke, if the front protection circuit can not be completely absorbed, the short-circuit protection circuit can start working, and the differential mode lightning stroke protection of the switch MOS tube is realized; when common-mode lightning strike comes temporarily, whether the common-mode lightning strike is positive to the ground or negative to the ground can pass through two series-connected piezoresistors MOV18, the MOV17 absorbs a part of energy and then passes through a discharge tube F11, the discharge tube discharges the energy to the ground after being conducted, the common-mode lightning strike is prevented from influencing a rear-stage circuit and influencing a power-down MOS tube driving circuit, and the common-mode lightning strike protection of an output switch MOS tube is realized;
the protection circuit of the power-down circuit of the low-voltage direct-current power supply is suitable for chargers with various powers and various communication power supplies or outdoor power supplies needing to control the output switch, can effectively and timely protect the output power-down switch MOS tube, and has the functions of overcurrent protection, output short-circuit protection, lightning protection and the like; the protection circuit of the power-off circuit of the low-voltage direct-current power supply is simple in structure, low in cost and convenient to popularize.
Claims (9)
1. A power-down circuit of a low-voltage direct-current power supply comprises a main circuit and a control circuit, wherein the main circuit comprises a direct-current input end, a power-down switch and a direct-current output end; the control circuit comprises a microcontroller and is characterized in that the lower electric switch comprises an MOS (metal oxide semiconductor) tube which is connected between a direct current input end and a direct current output end in series; the control circuit comprises an overcurrent protection circuit and an MOS tube drive circuit, the overcurrent protection circuit comprises a current sampling circuit of a main circuit, the output end of the current sampling circuit is connected with the overcurrent protection signal input end of the microcontroller, the control end of the MOS tube drive circuit is connected with the control signal output end of the microcontroller, and the grid electrode of the MOS tube is connected with the drive signal output end of the MOS tube drive circuit.
2. The power-down circuit of the low-voltage direct-current power supply according to claim 1, wherein the current sampling circuit comprises a current sampling resistor, an operational amplifier circuit, the current sampling resistor is connected in series in the main circuit, two input ends of the operational amplifier circuit are respectively connected with two ends of the current sampling resistor, and an output end of the operational amplifier circuit is connected with an overcurrent protection signal input end of the microcontroller.
3. The power-down circuit of a low-voltage direct-current power supply according to claim 2, wherein the current sampling circuit comprises a first voltage division circuit, a first double-series-connection switching diode and two filter circuits, and the operational amplification circuit comprises an operational amplifier; the non-inverting input end of the operational amplifier is connected with the first end of the current sampling resistor through a first balance resistor and is grounded through a second balance resistor, and the first balance capacitor is connected with the second balance resistor in parallel; the inverting input end of the operational amplifier is connected with the second end of the current sampling resistor through a third balance resistor, and is connected with the non-inverting input end of the operational amplifier through a first filter capacitor, and is connected with the output end of the operational amplifier through a fourth balance resistor, and the second balance capacitor is connected with the fourth balance resistor in parallel; the first end of the first voltage division circuit is connected with the output end of the operational amplifier, the second end of the first voltage division circuit is grounded, and the voltage output end of the first voltage division circuit is connected with the overcurrent protection signal input end of the microcontroller; the anode of the first double-series-connection switching diode is grounded, the cathode of the first double-series-connection switching diode is connected with the chip power supply, and the middle of the first double-series-connection switching diode is connected with the voltage output end of the first voltage division circuit; the first filter circuit is connected between the output end of the operational amplifier and the ground, and the second filter circuit is connected between the voltage output end of the first voltage division circuit and the ground.
4. The power-off circuit of the low-voltage direct-current power supply according to claim 1, wherein the control circuit comprises a short-circuit protection circuit, the short-circuit protection circuit comprises a current transformer, a demagnetization circuit and a rectification circuit, a primary winding of the current transformer is connected in series in the main circuit, a first end of a secondary winding of the current transformer is grounded, a second end of the secondary winding of the current transformer is connected with an input end of the rectification circuit, and an output end of the rectification circuit is connected with a short-circuit protection signal input end of the microcontroller; the demagnetization circuit is connected with the secondary winding of the current transformer in parallel.
5. The power-down circuit of the low-voltage direct-current power supply according to claim 4, wherein the short-circuit protection circuit comprises a voltage output resistor, a second voltage division circuit, a second filter capacitor and a second double-series-connection switching diode, the demagnetization circuit comprises a first rectifier diode and a demagnetization resistor, and the rectifier circuit comprises a second rectifier diode; the anode of the first rectifier diode is connected with the first end of the secondary winding of the current transformer, and the cathode of the first rectifier diode is connected with the second end of the secondary winding of the current transformer through a demagnetizing resistor; the anode of the second rectifier diode is connected with the second end of the secondary winding of the current transformer, the cathode of the second rectifier diode is connected with the first end of the voltage output resistor, and the second end of the voltage output resistor is grounded; the first end of the second voltage division circuit is connected with the cathode of the second rectifying diode, and the second end of the second voltage division circuit is grounded; the output end of the second voltage division circuit is connected with the short-circuit protection signal input end of the microcontroller; the second filter capacitor is connected between the output end of the second voltage division circuit and the ground, the anode of the second double-series-connection switching diode is grounded, the cathode of the second double-series-connection switching diode is connected with the chip power supply, and the middle of the second double-series-connection switching diode is connected with the voltage output end of the second voltage division circuit.
6. The power-down circuit of a low-voltage direct-current power supply according to claim 1, wherein the main circuit comprises a lightning stroke protection circuit, and the positive pole of the direct-current input end of the main circuit is connected with the positive pole of the direct-current output end through a direct-current bus; the lightning stroke protection circuit comprises an absorption capacitor, a discharge tube, two piezoresistors and a fast recovery diode; the source electrode of the MOS tube is connected with the negative electrode of the direct current input end, the drain electrode of the MOS tube is connected with the negative electrode of the direct current output end, and the source electrode of the MOS tube is connected with the grid electrode of the MOS tube through a grounding resistor; the absorption capacitor is connected between the positive electrode and the negative electrode of the direct current input end, after the two piezoresistors are connected in series, one end of the absorption capacitor is connected with the direct current bus, the other end of the absorption capacitor is connected with the source electrode of the MOS tube, the connection point of the two piezoresistors is connected with the input end of the discharge tube, and the output end of the discharge tube is connected with the ground; the anode of the fast recovery diode is connected with the drain electrode of the MOS tube, and the cathode of the fast recovery diode is connected with the direct current bus.
7. The power-down circuit of a low-voltage direct-current power supply according to claim 1, wherein the power-down switch comprises a plurality of said MOS transistors, drains of said plurality of said MOS transistors are connected together, sources of said plurality of said MOS transistors are connected together, and gates of said plurality of said MOS transistors are connected together.
8. The power-off circuit of the low-voltage direct-current power supply according to claim 1, wherein the MOS tube driving circuit comprises an NPN triode, a collector of the NPN triode is connected with the auxiliary power supply through a current-limiting resistor, and the collector of the NPN triode is connected with a grid electrode of the MOS tube through an MOS tube driving resistor; the base electrode of the NPN triode is connected with the control signal output end of the microcontroller through a base electrode resistor; the emitter of the NPN triode is grounded.
9. The power-down circuit of a low-voltage direct-current power supply according to claim 8, wherein the MOS tube driving circuit comprises a reverse-pumping diode, the anode of the reverse-pumping diode is connected with the base electrode of the NPN triode, and the cathode of the reverse-pumping diode is connected with the control signal output end of the microcontroller; the grid electrode of the NPN triode is grounded through a pull-down resistor.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210495893.6A CN114583940A (en) | 2022-05-09 | 2022-05-09 | Power-off circuit of low-voltage direct-current power supply |
| CN202221842705.4U CN218386788U (en) | 2022-05-09 | 2022-07-18 | Power-off circuit of low-voltage direct-current power supply |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210495893.6A CN114583940A (en) | 2022-05-09 | 2022-05-09 | Power-off circuit of low-voltage direct-current power supply |
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| CN114583940A true CN114583940A (en) | 2022-06-03 |
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| CN202210495893.6A Pending CN114583940A (en) | 2022-05-09 | 2022-05-09 | Power-off circuit of low-voltage direct-current power supply |
| CN202221842705.4U Active CN218386788U (en) | 2022-05-09 | 2022-07-18 | Power-off circuit of low-voltage direct-current power supply |
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| Publication number | Publication date |
|---|---|
| CN218386788U (en) | 2023-01-24 |
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Application publication date: 20220603 |