CN111181136A - Short-circuit protection circuit and power supply system - Google Patents
Short-circuit protection circuit and power supply system Download PDFInfo
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- CN111181136A CN111181136A CN202010117554.5A CN202010117554A CN111181136A CN 111181136 A CN111181136 A CN 111181136A CN 202010117554 A CN202010117554 A CN 202010117554A CN 111181136 A CN111181136 A CN 111181136A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/125—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers
- H02H7/1257—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers responsive to short circuit or wrong polarity in output circuit
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- Emergency Protection Circuit Devices (AREA)
Abstract
The invention discloses a short-circuit protection circuit and a power supply system. Wherein, this short-circuit protection circuit includes: an auxiliary winding, a switching unit and a relay; the auxiliary winding, a primary coil and a secondary coil of the transformer are wound on the same iron core, the first end of the auxiliary winding is connected with the switch unit through a first resistor, and the second end of the auxiliary winding is grounded; the switch unit is connected between the first end of the auxiliary winding and the coil of the relay and used for controlling the relay to be electrified when the load is short-circuited and controlling the relay to be powered off when the load works normally; and a coil of the relay is connected between a voltage source and a reference ground, a second contact of the relay is connected with a live wire of the alternating current power supply, and a third contact of the relay is suspended, wherein the second contact is a normally closed contact. According to the invention, all elements in the power supply system can be protected, the problem that the power supply chip is seriously heated due to the short circuit of the load is solved, and the safety is improved.
Description
Technical Field
The invention relates to the technical field of electronic power, in particular to a short-circuit protection circuit and a power supply system.
Background
In the actual production test process, the phenomenon of short circuit at the power output end of the controller caused by the problems of wrong connection or poor welding and the like often occurs. In addition, when breakdown failure occurs in semiconductor elements such as an IC, a transistor, and a voltage regulator chip, the semiconductor elements often show a low impedance power supply terminal and a near short circuit state. When the short circuit occurs in the circuit, the controller can not work normally, and the circuit or components of the controller can be damaged due to overcurrent, and serious accidents such as fire disasters can be caused in serious cases.
At present, components such as a switching power supply chip and a voltage reduction chip in a controller have a short-circuit protection function. If the load is detected to be short-circuited and the short-circuit fault is not released all the time, the power supply chip can work in a hiccup state all the time, and the chip can generate heat and even be damaged for a long time. In addition, the power supply chip can only protect the local circuit of the output end of the power supply chip and block the output path, but the power supply chip can also cause the problems of false triggering and the like.
Aiming at the problem that the power supply chip generates heat seriously due to the short circuit of the load in the prior art, an effective solution is not provided at present.
Disclosure of Invention
The embodiment of the invention provides a short-circuit protection circuit and a power supply system, which are used for solving the problem that a power supply chip is seriously heated due to short circuit of a load in the prior art.
In order to solve the above technical problem, the present invention provides a short-circuit protection circuit, wherein the short-circuit protection circuit includes: an auxiliary winding, a switching unit and a relay;
the auxiliary winding, a primary coil and a secondary coil of the transformer are wound on the same iron core, the first end of the auxiliary winding is connected with the switch unit through a first resistor, and the second end of the auxiliary winding is grounded;
the switch unit is connected between the first end of the auxiliary winding and the coil of the relay and used for controlling the relay to be electrified when the load is short-circuited and controlling the relay to be powered off when the load works normally;
the coil of the relay is connected between a voltage source and a reference ground, a first contact of the relay is connected with a zero line of an alternating current power supply, a second contact of the relay is connected with a live line of the alternating current power supply, a third contact of the relay is suspended, and the second contact is a normally closed contact.
Further, the switching unit includes:
a first switch having a first pole connected to the first resistor, a second pole connected between the voltage source and the first end of the coil of the relay through a second resistor, and a third pole grounded through a voltage dividing unit;
and a second switch, a first pole of which is connected between a third pole of the first switch and the voltage division unit through a third resistor, a second pole of which is grounded, and a third pole of which is connected with a second end of the coil of the relay.
Further, the switching unit further includes:
a third switch having a first pole connected to the third pole of the second switch, a second pole connected to the second end of the coil of the relay, and a third pole connected between the first pole of the second switch and the third resistor.
Further, the switching unit further includes:
and the first end of the reset switch is connected with the second end of the coil of the relay, the second end of the reset switch is grounded, and the reset switch is used for controlling the relay to recover the power-off state after the fault of the load short circuit is relieved.
Further, the switching unit further includes:
and a fourth resistor, a first end of which is connected between the first pole of the second switch and the third resistor, and a second end of which is grounded.
Furthermore, the voltage dividing unit is at least one voltage dividing diode, an anode of the voltage dividing diode is connected with a third pole of the first switch, and a cathode of the voltage dividing diode is grounded.
Further, the short-circuit protection circuit further includes:
a fifth resistor disposed between the voltage source and the first end of the coil of the relay for limiting current flow through the coil of the relay.
Further, the short-circuit protection circuit further includes:
and the unidirectional conduction element is connected between the first end and the second end of the coil of the relay in parallel and used for limiting the direction of current flowing through the coil of the relay.
Further, the short-circuit protection circuit further includes:
and the rectifying unit is connected between the first end of the auxiliary winding and the first resistor and is used for converting the alternating current output by the auxiliary winding into direct current.
Further, the short-circuit protection circuit further includes:
a first capacitor, a first end of which is connected between the rectifying unit and the first resistor;
the first end of the first capacitor is connected with the first resistor, and the second end of the first capacitor is connected with the first end of the first resistor and then grounded;
the first capacitor and the second capacitor are used for filtering the current output by the rectifying unit.
Further, the short-circuit protection circuit further includes:
and a sixth resistor, a first end of which is connected between the first resistor and the switch unit, and a second end of which is grounded, for controlling the voltage input to the switch unit.
Further, the short-circuit protection circuit further includes:
and a first end of the indicating unit is connected between the auxiliary winding and the first resistor through a seventh resistor and is used for indicating the state of the short-circuit protection circuit.
The invention also provides a power supply system which comprises an alternating current power supply, a protective tube, a third capacitor, a piezoresistor, a voltage source output circuit and the short-circuit protection circuit.
Further, the voltage source output circuit includes: the voltage stabilizing diode, the eighth resistor, the ninth resistor, the fourth capacitor, the fifth capacitor and the sixth capacitor;
the anode of the voltage-stabilizing diode is connected with a live wire of the alternating-current power supply, the cathode of the voltage-stabilizing diode is respectively connected with the first end of the eighth resistor and the anode of the diode, the ninth resistor and the fourth capacitor are connected between the second end of the eighth resistor and a reference ground after being connected in parallel, one end of the fifth capacitor is connected with the cathode of the diode after being connected in parallel with the sixth capacitor, and the other end of the fifth capacitor is grounded; and the common connection point of the cathodes of the fifth capacitor, the sixth capacitor and the diode outputs a voltage source for supplying power to the short-circuit protection circuit.
By applying the technical scheme of the invention, based on the principle that the output of the auxiliary winding is unbalanced and the output voltage of the auxiliary winding approaches to zero when the load is in short circuit, the relay is controlled to be electrified by the switch unit connected with the output of the auxiliary winding, the global power supply input of the power supply system is controlled to be cut off, and the cut-off state is locked, so that all elements in the power supply system can be protected, the problem that the power supply chip is seriously heated when the load is in short circuit is solved, and the safety is improved.
Drawings
Fig. 1 is a circuit configuration diagram of a short-circuit protection circuit according to an embodiment of the present invention;
fig. 2 is a circuit configuration diagram of a short-circuit protection circuit according to another embodiment of the present invention;
fig. 3 is a circuit configuration diagram of a power supply system according to an embodiment of the present invention;
fig. 4 is a circuit schematic diagram of the short-circuit protection circuit according to the present embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, third, etc. may be used to describe the resistors in the embodiments of the present invention, the resistors should not be limited to these terms. These terms are only used to distinguish between different resistances. For example, a first resistance may also be referred to as a second resistance, and similarly, a second resistance may also be referred to as a first resistance, without departing from the scope of embodiments of the present invention.
The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.
It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.
Alternative embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Example 1
The present embodiment provides a short-circuit protection circuit, and fig. 1 is a circuit structure diagram of the short-circuit protection circuit according to the embodiment of the present invention, as shown in fig. 1, the short-circuit protection circuit includes: an auxiliary winding T1, a switch unit 11, and a relay K;
an auxiliary winding T1 wound on the same core as the primary winding T2 and the secondary winding T3 of the transformer 12 in the power supply system and wound on the same side of the core as the primary winding T2, and having a first end connected to the switch unit 11 through a first resistor R1 and a second end grounded; the switch unit 11 is connected between the first end of the auxiliary winding T1 and a coil T4 of the relay K, when a load is in short circuit, because the voltage output by the auxiliary winding T1 approaches zero, the switch unit 11 can control the coil T4 of the relay K to be electrified, so that the first contact 1 and the third contact 3 are switched on, the zero line AC-N and the live line AC-L of a power supply system are switched off, the system does not supply power, when the load works normally, the coil T4 of the relay K is controlled to be powered off, the first contact 1 and the second contact 2 of the relay K are switched on, the zero line and the live line of the power supply system are switched on, and the system supplies power normally; and a coil T3 of the relay K is connected between a voltage source VCC and a reference ground, a first contact 1 of the relay K is connected with a zero line of an alternating current power supply, a second contact 2 of the relay K is connected with a live line of the alternating current power supply, and a third contact of the relay K is suspended, wherein the second contact 2 is a normally closed contact.
By applying the technical scheme of the invention, based on the principle that the output of the auxiliary winding T1 is unbalanced when the load is in short circuit, so that the output voltage of the auxiliary winding T1 approaches zero, when the load is in short circuit, the relay is controlled to be electrified through the switch unit connected with the output of the auxiliary winding T1, the global power supply input of the power supply system is controlled to be cut off, and the cut-off state is locked, so that all elements in the power supply system can be protected, the problem that the power supply chip is seriously heated when the load is in short circuit is solved, and the safety is improved.
Example 2
In this embodiment, another short-circuit protection circuit is provided, and fig. 2 is a circuit structure diagram of a short-circuit protection circuit according to another embodiment of the present invention, wherein in order to realize that a coil T4 of a relay K is controlled by a switch unit 11 to be energized when a load is short-circuited and to be de-energized when the load is normally operated, as shown in fig. 2, the switch unit 11 includes: a first switch Q1, the base of which is connected to a first resistor R1, the emitter of which is connected between the voltage source VCC and the first end of the coil T4 of the relay K through a second resistor R2, and the third pole of which is grounded through a voltage dividing unit; a second switch Q2, the base of which is connected between the collector of the first switch Q1 and the voltage dividing unit through a third resistor R3, the emitter of which is grounded, the collector of which is connected with the second end of the coil T4 of the relay K, when the load works normally, the base of the first switch Q1 is in a high level state, the first switch Q1 is turned off, the base of the second switch Q2 is in a low level state, the second switch Q2 is turned off, the coil T4 of the relay K is not energized, the contact 1 is connected with the normally closed contact 2, the zero line AC-N and the live line AC-L of the AC power supply are connected, the power supply system supplies power normally, when the load is short-circuited, the output unbalance of the transformer 12 is caused, the output voltage of the auxiliary winding T1 approaches, the base of the first switch Q1 is in a low level, therefore, the first switch Q1 is turned on, and due to the voltage dividing effect of the unit, the base of the second switch Q2 is in, the second switch Q2 is turned on to energize the coil T4 of the relay K, and further to turn on the contact 1 and the suspended contact 3, which results in the disconnection of the zero line and the live line of the ac power supply, and the power supply system is turned off to realize the power supply of the whole power supply system.
In order to achieve the accelerated saturation of the second switch Q2, and to bring the short-circuit protection circuit into a short-circuit protection state and lock, the switching unit 11 further includes: a third switch Q3, a base of which is connected to the collector of the second switch Q2, an emitter of which is connected to the second end of the coil T4, and a collector of which is connected between the base of the second switch Q2 and the third resistor R3, when the second switch Q2 is turned on, the base of the third switch Q3 is pulled to a low level state, the third switch Q3 is turned on, and when the third switch Q3 is turned on, current flows from the emitter to the collector and then flows through the base of the second switch Q2, so that the turn-on of the second switch Q2 is accelerated, and then the turn-on of the third switch Q3 is accelerated by forming positive feedback. Finally, the second switch Q2 and the third switch Q3 quickly enter a saturation state in a short time, so that the short-circuit protection circuit enters a short-circuit protection state and is locked, and in the embodiment, the third switch Q3 is a PNP type triode, and is cut off when the base of the PNP type triode is at a high level and is turned on when the base of the PNP type triode is at a low level.
When the short-circuit protection circuit enters the locked state, it cannot recover to the normal state by itself, and in order to recover the normal state of the short-circuit protection circuit after the load short-circuit fault is removed, that is, the state of the relay K being powered off, the switch unit 11 further includes: and a reset switch Kr having a first end connected to the second end of the coil T4 of the relay K and a second end grounded, and configured to return to the power-off state by manually controlling the relay K after the load short-circuit failure is resolved.
In addition, in order to define the voltage of the base input of the second switch Q2 in cooperation with the third resistor R3, the switching unit 11 further includes: a fourth resistor R4 has a first end connected between the base of the second switch Q2 and the third resistor R3, and a second end grounded.
In this embodiment, the voltage dividing unit is at least one voltage dividing diode D1, an anode of the diode is connected to a collector of the first switch Q1, a cathode of the diode is grounded, and the diode is used for defining an input voltage of a base of the first switch Q1, and another voltage dividing diode D2 may be further included, and the voltage dividing diode D1 and the voltage dividing diode D2 are connected in series in the same direction.
Since the coil T4 of the relay K has a limitation of the maximum operating current, in order to avoid an excessive current flowing through the coil T4 of the relay K, the short-circuit protection circuit further includes: and a fifth resistor R5 disposed between the voltage source VCC and the first end of the coil T4 for limiting the current flowing through the coil T4.
In this embodiment, in order to limit the direction of the current flowing through the coil T4, the short-circuit protection circuit further includes: and a one-way conductive element D3 connected in parallel between the first and second terminals of the coil T4 of the relay K for limiting the direction of current flowing through the coil T4 of the relay K, the one-way conductive element D3 may be a diode.
Since the auxiliary winding T1 outputs dc power, and the dc power is preferably used to turn on or off the control switch tube in this embodiment, the short-circuit protection circuit further includes: and a rectifying unit D4 connected between the first end of the auxiliary winding T1 and the first resistor R1 for converting the alternating current output from the auxiliary winding T1 into direct current, wherein the rectifying unit D4 may be a diode.
Since noise exists in the voltage output from the auxiliary winding T1, in order to eliminate the noise, the short-circuit protection circuit further includes: a first capacitor C1 having a first end connected between the rectifying unit D4 and the first resistor R1; a second capacitor C2 connected in parallel with the first capacitor C1, wherein a first end of the second capacitor C2 is connected between a first end of the first capacitor C1 and the first resistor R1, and a second end of the second capacitor C2 is connected to the second end of the first capacitor C1 and then grounded; the first capacitor C1 and the second capacitor C2 are used together to filter the current outputted from the rectifying unit.
In order to further limit the input voltage to the base of the first switch Q1, the short-circuit protection circuit further comprises: a sixth resistor R6, having a first end connected between the first resistor R1 and the switch unit 11 and a second end connected to ground, for controlling the voltage inputted to the switch unit 11.
In order to visually observe the state of the protection circuit, the short-circuit protection circuit further comprises: and the first end of the indicating unit LED1 is connected between the auxiliary winding T1 and the first resistor R1 through a seventh resistor R7 and is used for indicating the state of the short-circuit protection circuit, namely when the short-circuit protection circuit is in the short-circuit protection state, the indicating unit LED1 is turned off, and when the short-circuit protection circuit is recovered to be normal, the indicating unit LED1 is turned on.
Example 3
Fig. 3 is a circuit structure diagram of a power supply system according to an embodiment of the present invention, and as shown in fig. 3, the power supply system includes an AC power source AC, a FUSE1, a third capacitor C3, a voltage dependent resistor RV1, a voltage source output circuit 12, and further includes the short-circuit protection circuit in the above embodiments.
In this embodiment, the voltage source output circuit includes: a zener diode ZD1, a diode D5, an eighth resistor R8, a ninth resistor R9, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6; the anode of the zener diode ZD1 is connected to the live wire of the ac power supply, the cathode of the zener diode ZD1 is connected to the first end of the eighth resistor R8 and the anode of the diode D5, the ninth resistor R9 and the fourth capacitor C4 are connected in parallel and then connected between the second end of the eighth resistor R8 and the reference ground, the ninth resistor R9 is a bleeder resistor, the electric energy stored at the two ends of the fourth capacitor C4 is released after power failure, after the fifth capacitor C5 and the sixth capacitor C6 are connected in parallel, one end of the ninth resistor R9 is connected to the cathode of the diode, and the other end of the fifth capacitor C; the common connection point of the fifth capacitor C5, the sixth capacitor C6 and the cathode of the diode D5 outputs a voltage source VCC for supplying power to the short-circuit protection circuit.
Example 4
In the present embodiment, another short-circuit protection circuit is provided, and fig. 4 is a schematic circuit diagram of the short-circuit protection circuit according to the present embodiment, as shown in fig. 4, after an ac power is input, the ac power first passes through the short-circuit self-protection circuit 400 and then is output to a transformer, and an auxiliary winding T41 of the transformer provides a voltage signal to be fed back to the short-circuit self-protection circuit 400. When the load circuit is detected to be short-circuited, the short-circuit self-protection circuit can cut off the input of the alternating current power supply, and meanwhile, the circuit enters a protection locking state. In the case where the short-circuit fault is not released, the lock-up protection is maintained until the short-circuit fault is released, and the transformer can normally output.
The short-circuit protection circuit of the embodiment specifically works as follows:
the AC power is input by two terminals of AC-L, AC-N. The AC-L terminal is connected with a live wire, the N terminal is connected with a zero wire, and the input voltage is 220V. A resistor-capacitor voltage reduction circuit 410 is formed by the zener diode ZD41, the diode D45, the eighth resistor R48, the ninth resistor R49, the fourth capacitor C44, the fifth capacitor C45 and the sixth capacitor C46, a voltage source VCC is provided to supply power to the short-circuit protection circuit 400, in the figure, PGND is a power ground, the ninth resistor R49 is a bleeder resistor, and the electric energy stored at two ends of the capacitor C44 is released after power failure.
When the ac power supply is not turned on, the contact 1 of the relay K1 and the normally closed contact 2 are turned on. The reset button Kr1 keeps the normally open state, and after the ac power is switched on, 220V ac will flow through the contact 1, the contact 2 of the relay K1, the fuse FSUE1, the main loop capacitor C43, the voltage dependent resistor RV1 and the primary winding T42 of the transformer, and supply the secondary winding T43, so that the transformer starts to work as a load to supply power, and the rc step-down circuit 410 provides the voltage source VCC.
An alternating current voltage signal output by the auxiliary winding T41 is rectified by a rectifying element D44, filtered by a filter capacitor C41 and a filter capacitor C42, and then a smooth direct current voltage is output to the base of the PNP type triode Q41 and one end of an LED41, and an LED41 indicator lamp is turned on. Since the base of the PNP transistor Q41 is in a high state, the PNP transistor Q41 is turned off, which results in the base potential of the NPN transistor Q42 being zero, and the NPN transistor Q42 is also turned off, which results in the base of the PNP transistor Q43 being in a high state and thus also in a turned off state. The relay K1 does not work, the normally closed contact 2 is connected, and the transformer normally supplies power to the load circuit.
When the internal power output circuit of the load circuit is short-circuited, the output imbalance of the transformer is caused, i.e., the output voltage of the auxiliary winding T41 approaches zero. At this time, the base of the PNP transistor Q41 is in a low level state, the PNP transistor Q41 is turned on, the diode D41 and the diode D42 with certain parameters are selected, so that the diode D41 and the diode D42 respectively obtain a voltage of 0.7V, the base voltage of the NPN transistor Q42 is 1.4V, the NPN transistor Q42 is turned on, the base of the PNP transistor Q43 is pulled to a low level state, and the PNP transistor Q43 is turned on. After the PNP transistor Q43 is turned on, current flows from the emitter to the collector of the PNP transistor Q42 and then flows through the base of the NPN transistor Q42, so that the conduction of the NPN transistor Q42 is accelerated, and then positive feedback is formed to accelerate the conduction of the PNP transistor Q43, and finally the NPN transistor Q42 and the PNP transistor Q43 rapidly enter a saturation state in a short time. The voltage source VCC is not affected by the short circuit of the load circuit and always keeps a stable output state, that is, the voltage source VCC forms a loop to the power supply through the fifth resistor R45, the coil T44 of the relay K1, the PNP transistor Q43 and the NPN transistor Q42. Therefore, the relay K1 is electrically engaged, the contact 1 and the contact 2 are opened, and the contact 1 and the contact 3 are closed. The global power supply circuit is cut off due to the cut-off of the input of the live line.
Because the voltage of the voltage source VCC does not change, once the base of the NPN type triode Q42 generates high level triggering, the NPN type triode Q42 and the PNP type triode Q43 will always maintain the conducting state and not change no matter the base voltage of the subsequent NPN type triode Q42 is high or low, and it is ensured that the relay K1 will also always be in the pull-in state, so that the input live wire is broken, the transformer has no output, and the light emitting diode LED41 is extinguished. The circuit enters a protection locking state, thereby effectively protecting elements and circuits of the load circuit from being damaged, and simultaneously avoiding the circuit misoperation phenomenon caused by the local protection of the circuit.
The reset key Kr1 is used for breaking the protection lock and controlling the relay K1 to restore the power-off state. When the short-circuit fault is manually eliminated, the circuit is still in a protection locking state due to the previous short circuit. When the reset button Kr1 is pressed, the current flowing through the NPN transistor Q42 and the PNP transistor Q43 flows directly to the power ground through the reset button Kr 1. The NPN transistor Q42 and the PNP transistor Q43 lose the holding current, thereby releasing the locked state. The NPN transistor Q42 and the PNP transistor Q43 transition to the off state, and when the coil T44 loses current, the contact 1 and the contact 2 are connected, so that the entire circuit recovers to the normal operating state. If the short-circuit failure is not released, the lock state cannot be released by pressing the reset button Kr 1. After the reset key Kr1 is pressed forcibly by human, the circuit will enter the self-protection locking state instantly.
Under the condition that the load circuit is not short-circuited, when the resistance-capacitance voltage reduction circuit 410 is damaged due to other reasons and the relay K1 cannot work due to the damage of the rear end associated circuit of the auxiliary winding T41, the relay K1 is not attracted at the moment, and the contact 1 and the contact 2 are kept connected. The circuit can still work normally. Therefore, when the element of the short-circuit self-protection circuit breaks down, the normal work of the protected controller cannot be influenced, and the high-reliability and high-redundancy characteristics are achieved.
The short-circuit self-protection circuit of the embodiment is completely isolated from the load circuit, and the action circuit for detecting the short circuit and locking the protection cannot influence the output power or the working state of the load circuit.
It should be noted that the first resistor R41, the second resistor R42, the third resistor R43, the fourth resistor R44, the fifth resistor R45, the sixth resistor R46, the seventh resistor R47, and the unidirectional conducting element D43 in this embodiment have the same functions as the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, and the unidirectional conducting element D3 in the above embodiment, and are not described again.
In summary, the circuit can automatically cut off the global power supply input and lock the cut-off state when the controller power circuit is short-circuited. And the controller circuit can be recovered to be normal through manual reset until the short-circuit fault of the controller is manually relieved. The global circuit is protected from being damaged, and the occurrence of circuit misoperation is avoided.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods of the various embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (14)
1. A short-circuit protection circuit, comprising: an auxiliary winding, a switching unit and a relay;
the auxiliary winding, a primary coil and a secondary coil of the transformer are wound on the same iron core, the first end of the auxiliary winding is connected with the switch unit through a first resistor, and the second end of the auxiliary winding is grounded;
the switch unit is connected between the first end of the auxiliary winding and the coil of the relay and used for controlling the relay to be electrified when the load is short-circuited and controlling the relay to be powered off when the load works normally;
the coil of the relay is connected between a voltage source and a reference ground, a first contact of the relay is connected with a zero line of an alternating current power supply, a second contact of the relay is connected with a live line of the alternating current power supply, a third contact of the relay is suspended, and the second contact is a normally closed contact.
2. The short-circuit protection circuit according to claim 1, wherein the switching unit includes:
a first switch having a first pole connected to the first resistor, a second pole connected between the voltage source and the first end of the coil of the relay through a second resistor, and a third pole grounded through a voltage dividing unit;
and a second switch, a first pole of which is connected between a third pole of the first switch and the voltage division unit through a third resistor, a second pole of which is grounded, and a third pole of which is connected with a second end of the coil of the relay.
3. The short-circuit protection circuit of claim 2, wherein the switching unit further comprises:
a third switch having a first pole connected to the third pole of the second switch, a second pole connected to the second end of the coil of the relay, and a third pole connected between the first pole of the second switch and the third resistor.
4. The short-circuit protection circuit of claim 2, wherein the switching unit further comprises:
and the first end of the reset switch is connected with the second end of the coil of the relay, the second end of the reset switch is grounded, and the reset switch is used for controlling the relay to recover the power-off state after the fault of the load short circuit is relieved.
5. The short-circuit protection circuit of claim 2, wherein the switching unit further comprises:
and a fourth resistor, a first end of which is connected between the first pole of the second switch and the third resistor, and a second end of which is grounded.
6. The short-circuit protection circuit of claim 2, wherein the voltage divider is at least one voltage divider diode, an anode of the voltage divider diode is connected to the third pole of the first switch, and a cathode of the voltage divider diode is grounded.
7. The short-circuit protection circuit of claim 1, further comprising:
a fifth resistor disposed between the voltage source and the first end of the coil of the relay for limiting current flow through the coil of the relay.
8. The short-circuit protection circuit of claim 1, further comprising:
and the unidirectional conduction element is connected between the first end and the second end of the coil of the relay in parallel and used for limiting the direction of current flowing through the coil of the relay.
9. The short-circuit protection circuit of claim 1, further comprising:
and the rectifying unit is connected between the first end of the auxiliary winding and the first resistor and is used for converting the alternating current output by the auxiliary winding into direct current.
10. The short-circuit protection circuit of claim 9, further comprising:
a first capacitor, a first end of which is connected between the rectifying unit and the first resistor;
the first end of the first capacitor is connected with the first resistor, and the second end of the first capacitor is connected with the first end of the first resistor and then grounded;
the first capacitor and the second capacitor are used for filtering the current output by the rectifying unit.
11. The short-circuit protection circuit of claim 1, further comprising:
and a sixth resistor, a first end of which is connected between the first resistor and the switch unit, and a second end of which is grounded, for controlling the voltage input to the switch unit.
12. The short-circuit protection circuit of claim 1, further comprising:
and a first end of the indicating unit is connected between the auxiliary winding and the first resistor through a seventh resistor and is used for indicating the state of the short-circuit protection circuit.
13. A power supply system comprising an ac power source, a fuse, a third capacitor, a varistor, a voltage source output circuit, wherein the power supply system further comprises the short-circuit protection circuit of any one of claims 1 to 12.
14. The power supply system of claim 13, wherein the voltage source output circuit comprises: the voltage stabilizing diode, the eighth resistor, the ninth resistor, the fourth capacitor, the fifth capacitor and the sixth capacitor;
the anode of the voltage-stabilizing diode is connected with a live wire of the alternating-current power supply, the cathode of the voltage-stabilizing diode is respectively connected with the first end of the eighth resistor and the anode of the diode, the ninth resistor and the fourth capacitor are connected between the second end of the eighth resistor and a reference ground after being connected in parallel, one end of the fifth capacitor is connected with the cathode of the diode after being connected in parallel with the sixth capacitor, and the other end of the fifth capacitor is grounded; and the common connection point of the cathodes of the fifth capacitor, the sixth capacitor and the diode outputs a voltage source for supplying power to the short-circuit protection circuit.
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| CN202010117554.5A CN111181136B (en) | 2020-02-25 | 2020-02-25 | Short circuit protection circuit and power supply system |
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| CN202010117554.5A CN111181136B (en) | 2020-02-25 | 2020-02-25 | Short circuit protection circuit and power supply system |
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| CN114675527A (en) * | 2022-03-17 | 2022-06-28 | 上海创米智能科技有限公司 | Control circuit, control method and device, device, and readable storage medium |
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