Overcurrent protection circuit and power supply system

Abstract

The invention relates to the technical field of power electronics, and discloses an overcurrent protection circuit and a power supply system, the overcurrent protection circuit comprises a driving unit, a first switch circuit, a second switch circuit, a first detection unit, a second detection unit and a level conversion circuit, the first end of the driving unit is connected with the first end of a load, and the second end of the driving unit is connected with the second end of the load. The second end is connected with the first end of the second switching circuit, and the third end is connected with the first end of the second detection unit; the second end of the second switching circuit is connected with the second end of the load, and the third end is connected with the first end of the first switching circuit; the second end of the first switch circuit is connected with the first end of the level conversion circuit, and the third end is connected with the first end of the first detection unit; the second end of the first detection unit is connected with the second end of the second detection unit. Load power supply can be cut off when any one of the first switching circuit or the second switching circuit is short-circuited and loses turn-off capacity, energy output is limited, and the reliability of the overcurrent protection circuit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to an overcurrent protection circuit and a power supply system. Background Art

[0002] When designing a constant voltage LED power supply, a necessary output energy limiting circuit is generally added to meet the energy limiting requirements. Even if any component in the output energy limiting circuit fails, the output energy limiting capability cannot be affected. Therefore, an additional output energy limiting circuit is required to ensure that the output energy can still be limited after the original energy limiting circuit fails. The two output energy limiting circuits are independent of each other in function and operate in coordination during the operation of the LED power supply. The following methods are used in the prior art to achieve the above functions:

[0003] (1) Combine the output current monitoring of the power supply output terminal with the overcurrent monitoring of the power supply control IC: Figure 1 As shown, for a constant voltage power supply, the output voltage is generally constant. When the output current is limited, the output power can be limited. Therefore, adding an output current detection unit at the output end can achieve this function. The main component of the output current detection unit is generally a resistor. After the output current flows through the output current detection unit, a voltage will be generated at both ends of the output current detection unit. After the reference voltage of the voltage processing unit is compared with the voltage, the corresponding voltage signal is output to the input end of the feedback unit, so that the feedback unit works according to the set conditions. The main component of the voltage processing unit is generally an op amp or an MCU. The output end of the feedback unit is connected to the power supply main control chip. The power supply main control chip turns off or turns on Q according to the signal given by the feedback unit to achieve output energy limitation. It is usually set that when the current value detected by the output current detection unit is greater than the design value, the power supply main control chip turns off Q. When the power supply main control IC is used to limit the power output, the pin design requirements are usually high, and this method is basically difficult to achieve the requirements.

[0004] (2) Output current detection at dual output terminals: Figure 2As shown, the output end is designed with two current detection units and two voltage processing units. The two current detection units are connected in series, the output ends of the two voltage processing units are connected to each other, and the input ends are respectively connected to the two current detection units. When a short circuit occurs in any current detection unit, the operation of the other current detection unit is not affected. When any current detection unit is open, the output circuit is disconnected and the output energy is controlled. The two voltage processing units work independently of each other, and an abnormality in any working process will not affect the normal operation of the other. The output ends of the two voltage processing units are connected to the input ends of the feedback unit, and the output ends of the feedback unit are connected to the power supply main control chip. The power supply main control chip turns off or turns on Q according to the signal given by the feedback unit, so as to achieve output energy limitation. The defect of this solution is that it is more suitable for use in a power supply with a single output, because when the main control chip turns off Q, all output energies will be limited. When the LED power supply needs to provide multiple outputs, it needs to be able to turn off any output without affecting the operation of any other output, and the technical implementation will become difficult. Summary of the invention

[0005] In view of this, the present invention provides an overcurrent protection circuit and a power supply system to solve the problem of low reliability of the overcurrent protection circuit.

[0006] In a first aspect, the present invention provides an overcurrent protection circuit, comprising: a driving unit, a first switch circuit, a second switch circuit, a first detection unit, a second detection unit and a level conversion circuit, wherein a first end of the driving unit is connected to a first end of a load and inputs a power supply voltage, a second end of the driving unit is connected to a first end of the second switch circuit, and a third end of the driving unit is connected to a first end of the second detection unit; a second end of the second switch circuit is connected to a second end of the load, and a third end of the second switch circuit is connected to a first end of the first switch circuit; a second end of the first switch circuit is connected to a first end of the level conversion circuit, and a third end of the first switch circuit is connected to a first end of the first detection unit; The second end of the first detection unit is connected to the second end of the second detection unit, and the third end of the first detection unit is connected to the second end of the level conversion circuit; the third end of the level conversion circuit is connected to the third end of the second detection unit and then grounded, and the level conversion circuit adjusts the voltage of the second end of the first switch circuit so that the first switch circuit operates in a safe operating area; when the first detection unit determines that the load is overcurrent, the level conversion circuit controls the first switch circuit to disconnect based on the overcurrent signal output by the first detection unit, so that the load stops working; when the second detection unit determines that the load is overcurrent, the driving unit controls the second switch circuit to disconnect based on the overcurrent signal output by the second detection unit, so that the load stops working.

[0007] The overcurrent protection circuit provided by the present invention realizes output energy limitation at the power supply voltage output end, omitting the conventional feedback unit circuit structure; when either the first switch circuit or the second switch circuit is open-circuited, the power supply circuit of the load is directly disconnected, which limits the output energy from the root and solves the overcurrent problem of the load; when either the first switch circuit or the second switch circuit is short-circuited and loses the shutdown capability, the other switch circuit can still work normally, ensuring that the output energy is limited, thereby improving the reliability of the overcurrent circuit.

[0008] In an optional embodiment, the first detection unit includes: a first voltage detection circuit and a first current detection circuit, wherein the first end of the first voltage detection circuit is connected to the third end of the first switch circuit and the first end of the first current detection circuit, and the second end of the first voltage detection circuit is connected to the second end of the level conversion circuit; the second end of the first current detection circuit is connected to the second end of the second detection unit; when the voltage drop across the first current detection circuit is greater than the first reference voltage, the first voltage detection circuit determines that the load is overcurrent and outputs an overcurrent signal, so that the first switch circuit is disconnected.

[0009] In an optional embodiment, the first voltage detection circuit includes: a voltage comparison unit and a control unit, wherein the first reference voltage is input into the positive input terminal of the voltage comparison unit, the reverse input terminal of the voltage comparison unit is connected to the first end of the first current detection circuit and the output end of the control unit, and the output end of the voltage comparison unit is connected to the input end of the control unit; when the voltage comparison unit determines that the voltage drop across the first current detection circuit is greater than the first reference voltage, the control unit outputs an overcurrent signal.

[0010] In an optional embodiment, the second detection unit includes: a second voltage detection circuit and a second current detection circuit, wherein the first end of the second current detection circuit is connected to the second end of the first current detection circuit and the first end of the second voltage detection circuit, and the second end of the second current detection circuit is connected to the second end of the second voltage detection circuit and the third end of the level conversion circuit and then grounded; the third end of the second voltage detection circuit is connected to the third end of the driving unit; when the voltage drop across the second current detection circuit is greater than the second reference voltage, the second voltage detection circuit determines that the load is overcurrent and outputs an overcurrent signal, so that the second switch circuit is disconnected.

[0011] In an optional embodiment, the second voltage detection circuit includes: a first resistor, a second resistor, a third resistor, a first capacitor, a second capacitor and an operational amplifier, wherein the first end of the first resistor is connected to the first end of the second current detection circuit, and the second end of the first resistor is connected to the first end of the first capacitor and the positive input end of the operational amplifier; the second reference voltage is input to the reverse input end of the operational amplifier, the output end of the operational amplifier is connected to the first end of the second resistor, and the operational amplifier is used to output an overcurrent signal when the voltage drop across the second current detection circuit is greater than the second reference voltage; the second end of the second resistor is connected to the third end of the driving unit, the first end of the second capacitor and the first end of the third resistor; the second end of the second capacitor is connected to the second end of the third resistor, the second end of the first capacitor and the third end of the level conversion circuit and then grounded.

[0012] In an optional embodiment, the driving unit includes: a fourth resistor, a fifth resistor, a first diode and a first controllable switch, wherein the first end of the fourth resistor is connected to the first end of the load and inputs the supply voltage, the second end of the fourth resistor is connected to the first end of the fifth resistor, the cathode of the first diode, the first end of the first controllable switch and the first end of the second switch circuit; the second end of the fifth resistor is connected to the anode of the first diode and the second end of the first controllable switch; the control end of the first controllable switch is connected to the first end of the second detection unit; when the second detection unit determines that the load is overcurrent, the first controllable switch controls the second switch circuit to disconnect based on the overcurrent signal output by the second detection unit, so that the load stops working.

[0013] In an optional embodiment, the level conversion circuit includes: a state indication circuit, a third switch circuit, a sixth resistor and a seventh resistor, wherein the first end of the state indication circuit is connected to the first end of the third switch circuit and the first end of the sixth resistor and then inputs the first external voltage, the second end of the state indication circuit is connected to the second end of the third switch circuit and then inputs the second external voltage, the third end of the state indication circuit is connected to the third end of the third switch circuit, the third end of the second detection unit and the first end of the seventh resistor, and the state indication circuit is used to be turned on and always on when there is an external voltage; the fourth end of the third switch circuit is connected to the second end of the sixth resistor, the fifth end of the third switch circuit is connected to the second end of the first switch circuit, and the sixth end of the third switch circuit is connected to the second end of the seventh resistor; when the first detection unit determines that the load is overcurrent, the third switch circuit is turned off, so that the voltage at the second end of the first switch circuit is reduced to less than the on-state voltage drop of the internal switch of the first switch circuit, and then the first switch circuit is disconnected, so that the load stops working; the resistance value of the seventh resistor is greater than the resistance value of the sixth resistor.

[0014] In an optional implementation, when the first switch circuit or the second switch circuit fails and opens, the load is powered off and stops working.

[0015] In an optional embodiment, when the first switch circuit fails and short-circuits, and the second detection unit determines that the load is overcurrent, the driving unit controls the second switch circuit to disconnect based on the overcurrent signal output by the second detection unit, so that the load stops working; when the second switch circuit fails and short-circuit, and the first detection unit determines that the load is overcurrent, the level conversion circuit controls the first switch circuit to disconnect based on the overcurrent signal output by the first detection unit, so that the load stops working.

[0016] In a second aspect, the present invention provides a power supply system, comprising: a power supply and an overcurrent protection circuit according to the first aspect or any corresponding embodiment thereof, wherein the output end of the power supply is connected to the first end of the driving unit, and the power supply is used to output a supply voltage.

[0017] The power supply system provided by the present invention realizes output energy limitation at the output end of the power supply, thereby eliminating the need for a conventional feedback unit circuit structure. When either the first switch circuit or the second switch circuit is open-circuited, the power supply circuit of the load is directly disconnected, thereby limiting the output energy from the root and solving the overcurrent problem of the load. When either the first switch circuit or the second switch circuit is short-circuited and loses its shutoff capability, the other switch circuit can still work normally, thereby ensuring that the output energy is limited and improving the reliability of the overcurrent circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of a power supply circuit with an overcurrent protection circuit in the related art;

[0020] Figure 2 It is a schematic diagram of another power supply circuit with an overcurrent protection circuit in the related art;

[0021] Figure 3 is a composition diagram of an overcurrent protection circuit according to an embodiment of the present invention;

[0022] Figure 4 2 is another composition diagram of an overcurrent protection circuit according to an embodiment of the present invention.

[0023] Figure 5 is a specific circuit structure diagram of a first voltage detection circuit according to an embodiment of the present invention;

[0024] Figure 6is another composition diagram of the overcurrent protection circuit according to an embodiment of the present invention;

[0025] Figure 7 is a specific circuit structure diagram of an overcurrent protection circuit according to an embodiment of the present invention;

[0026] Figure 8 is a specific circuit structure diagram of a level conversion circuit according to an embodiment of the present invention;

[0027] Fig. 9 is a composition diagram of a power supply system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] In constant voltage LED power supply control, it is usually necessary to design an output energy limiting circuit to protect the LED from overcurrent. Existing energy limiting circuits, such as Figure 1 and Figure 2 As shown, Figure 1 The circuit in the circuit has high requirements on the design parameters and is highly dependent on the experience and professional ability of the designer; Figure 2 The circuits in the circuit affect each other, and when some of the components fail, the entire circuit will lose its energy limiting function.

[0033] In order to improve the reliability of the overcurrent protection circuit, this embodiment provides an overcurrent protection circuit, such as Figure 3 As shown, it includes: a driving unit 1, a first switch circuit 2, a second switch circuit 3, a first detection unit 4, a second detection unit 5 and a level conversion circuit 6.

[0034] Figure 3 In the embodiment, the first end of the driving unit 1 is connected to the first end of the load and the power supply voltage is input, the second end of the driving unit 1 is connected to the first end of the second switch circuit 3, and the third end of the driving unit 1 is connected to the first end of the second detection unit 5; the second end of the second switch circuit 3 is connected to the second end of the load, and the third end of the second switch circuit 3 is connected to the first end of the first switch circuit 2; the second end of the first switch circuit 2 is connected to the first end of the level conversion circuit 6, and the third end of the first switch circuit 2 is connected to the first end of the first detection unit 4; the second end of the first detection unit 4 is connected to the second end of the second detection unit 5, and the third end of the first detection unit 4 is connected to the second end of the level conversion circuit 6; the third end of the level conversion circuit 6 is connected to the third end of the second detection unit 5 and then grounded.

[0035] Optionally, Figure 3 In the figure, the level conversion circuit 6 can be a boost circuit for adjusting the voltage at the second end of the first switch circuit 2. The level conversion circuit 6 can convert the internal low-voltage power supply into a higher-level voltage to drive the first switch circuit 2, so as to avoid the voltage level being too low to exceed the on-state voltage drop of the first switch circuit 2, or causing the startup working area of ​​the MOS inside the first switch circuit 2 to fall to the Miller platform and fail to work in a reasonable working area.

[0036] Specifically, Figure 3 In the embodiment, when the first detection unit 4 determines that the load is overcurrent, the level conversion circuit 6 controls the first switch circuit 2 to disconnect based on the overcurrent signal output by the first detection unit 4, so that the load stops working; when the second detection unit 5 determines that the load is overcurrent, the drive unit 1 controls the second switch circuit 3 to disconnect based on the overcurrent signal output by the second detection unit 5, so that the load stops working.

[0037] Specifically, Figure 3In the figure, since the first switch circuit 2 and the second switch circuit 3 are connected in series, the power supply circuit of the load is a power supply circuit in which the power supply voltage passes through the second switch circuit 3, the first switch circuit 2, the first detection unit 4, and the second detection unit 5 in sequence before reaching the ground. Therefore, when either the first switch circuit 2 or the second switch circuit 3 is open, regardless of whether the power supply voltage exceeds the rated working voltage of the load, the power supply circuit of the load is in an open circuit state, and no overcurrent flows to achieve output energy limitation, thereby protecting the load from overcurrent damage; when either the first switch circuit 2 or the second switch circuit 3 is short-circuited, the other switch circuit can still work normally without being affected, the power supply circuit of the load is still open, and the overcurrent protection circuit can work normally to limit the output energy.

[0038] The overcurrent protection circuit provided in this embodiment realizes output energy limitation at the power supply voltage output end, eliminating the conventional feedback unit circuit structure and simplifying it; when either the first switch circuit or the second switch circuit is open, the power supply circuit of the load is directly disconnected, which limits the output energy from the source and solves the overcurrent problem of the load; when either the first switch circuit or the second switch circuit is short-circuited and loses the shutdown capability, the other switch circuit can still work normally, ensuring that the output energy is limited and improving the reliability of the overcurrent circuit.

[0039] In some optional embodiments, such as Figure 4 As shown, the first detection unit 4 includes: a first voltage detection circuit 41 and a first current detection circuit 42, wherein the first end of the first voltage detection circuit 41 is connected to the third end of the first switch circuit 2 and the first end of the first current detection circuit 42, the second end of the first voltage detection circuit 41 is connected to the second end of the level conversion circuit 6; the second end of the first current detection circuit 42 is connected to the second end of the second detection unit 5.

[0040] Optionally, Figure 4 In the embodiment, the first current detection circuit 42 may be a collection circuit composed of resistors.

[0041] Specifically, Figure 4 In the embodiment, when an overcurrent occurs in the load, after the overcurrent flows through the first current detection circuit 42, the voltage drop on the first current detection circuit 42 increases. When the first voltage detection circuit 41 recognizes that the voltage at the first end of the first current detection circuit 42 is greater than the first reference voltage, the first voltage detection circuit 41 determines that the load is overcurrent and outputs an overcurrent signal. The level conversion circuit 6 controls the first switch circuit 2 to disconnect based on the overcurrent signal output by the first voltage detection circuit 41, so that the load stops working.

[0042] In some optional embodiments, such as Figure 5As shown, the first voltage detection circuit 41 includes: a voltage comparison unit 411 and a control unit 412, wherein the first reference voltage is input to the positive input terminal of the voltage comparison unit 411, the reverse input terminal of the voltage comparison unit 411 is connected to the first terminal of the first current detection circuit 42 and the output terminal of the control unit 412 (i.e., R79), and the output terminal of the voltage comparison unit 411 is connected to the input terminal of the control unit 412 (i.e., D8).

[0043] Specifically, Figure 5 In the figure, the voltage 5VDC1 is divided by resistors R1, R7 and R4 to form a first reference voltage which is input to the positive input terminal of the comparator U1B. The voltage of the first end of the first current detection circuit 42 is filtered by resistor R13 and capacitor C1 and input to the reverse input terminal of the comparator U1B. When the comparator U1B determines that the voltage of the first end of the first current detection circuit 42 is greater than the first reference voltage, it outputs a low-level signal to the control unit 412. The control unit 412 performs level conversion based on the low-level signal and outputs an overcurrent signal, that is, the control chip U4 outputs an ADJ1 signal of a low level. After the ADJ1 signal is input to the second end of the level conversion circuit 6, the level conversion circuit 6 performs level conversion on the voltage drop of the ADJ1 signal so that when the driving voltage of the switch inside the first switch circuit 2 is reduced to below the conduction voltage drop, the first switch circuit 2 is disconnected and the load stops working.

[0044] In some optional embodiments, such as Figure 6 As shown, the second detection unit 5 includes: a second voltage detection circuit 51 and a second current detection circuit 52, wherein a first end of the second current detection circuit 52 is connected to a second end of the first current detection circuit 42 and a first end of the second voltage detection circuit 51, a second end of the second current detection circuit 52 is connected to a second end of the second voltage detection circuit 51 and a third end of the level conversion circuit 6 and then grounded; a third end of the second voltage detection circuit 51 is connected to a third end of the driving unit 1.

[0045] Optionally, Figure 6 In the embodiment, the second current detection circuit 52 may be a collection circuit composed of resistors.

[0046] Specifically, Figure 6 In the embodiment, when an overcurrent occurs in the load, after the overcurrent flows through the second current detection circuit 52, the voltage drop on the second current detection circuit 52 increases. When the second voltage detection circuit 51 recognizes that the voltage at the first end of the second current detection circuit 52 is greater than the second reference voltage, the second voltage detection circuit 51 determines that the load is overcurrent and outputs an overcurrent signal. The drive unit 1 controls the second switch circuit 3 to disconnect based on the overcurrent signal output by the second voltage detection circuit 51, so that the load stops working.

[0047] It should be noted that, when the first voltage detection circuit 41, the first current detection circuit 42, the second voltage detection circuit 51 and the second current detection circuit 52 are not faulty, the first switch circuit 2 and the second switch circuit 3 can both cut off the power supply circuit of the load based on the overcurrent signal in time; when the first voltage detection circuit 41 or the first current detection circuit 42 fails, the first switch circuit 2 is no longer controlled, and the second voltage detection circuit 51 and the second current detection circuit 52 detect the overcurrent and control the second switch circuit 3 to cut off the power supply circuit of the load; when the second voltage detection circuit 51 or the second current detection circuit 52 fails, the second switch circuit 3 is no longer controlled, and the first voltage detection circuit 41 and the first current detection circuit 42 detect the overcurrent and control the second switch circuit 3 to cut off the power supply circuit of the load.

[0048] In some optional embodiments, such as Figure 7 As shown, the second voltage detection circuit 51 includes: a first resistor R3, a second resistor R12, a third resistor R2, a first capacitor C3, a second capacitor C2 and an operational amplifier U2B, wherein the first end of the first resistor R3 is connected to the first end of the second current detection circuit 52, and the second end of the first resistor R3 is connected to the first end of the first capacitor C3 and the positive input end of the operational amplifier U2B; the second reference voltage Vref is input to the reverse input end of the operational amplifier U2B, the output end of the operational amplifier U2B is connected to the first end of the second resistor R12, and the operational amplifier U2B is used to output an overcurrent signal when the voltage drop across the second current detection circuit 52 is greater than the second reference voltage Vref; the second end of the second resistor R12 is connected to the third end of the driving unit 1, the first end of the second capacitor C2 and the first end of the third resistor R2; the second end of the second capacitor C2 is connected to the second end of the third resistor R2, the second end of the first capacitor C3 and the third end of the level conversion circuit 6 and then grounded.

[0049] Specifically, Figure 7 In the embodiment, the first switch circuit 2 includes a MOS transistor Q1, the second switch circuit 3 includes a MOS transistor Q2, the first current detection circuit 42 includes a resistor R25, and the second current detection circuit 52 includes a resistor R26. The driving unit 1 includes: a fourth resistor R8, a fifth resistor R11, a first diode D2, and a first controllable switch Q3, wherein a first end of the fourth resistor R8 is connected to a first end of a load and inputs a 24V power supply voltage, a second end of the fourth resistor R8 is connected to a first end of a fifth resistor R11, a cathode of the first diode D2, a first end of the first controllable switch Q3, and a first end of the second switch circuit 3; a second end of the fifth resistor R11 is connected to an anode of the first diode D2 and a second end of the first controllable switch Q3; and a control end of the first controllable switch Q3 is connected to a first end of the second detection unit 5.

[0050] Specifically, Figure 7In the embodiment, when the 24V power supply voltage is applied to the first end of the fourth resistor R8, the 24V power supply voltage is divided by the fourth resistor R8 and the fifth resistor R11, and the divided voltage is applied to the G pole of Q2, so that Q2 is turned on. The voltage stabilization value of the D2 voltage regulator tube is selected to be lower than the maximum voltage that can be applied to the G pole of Q2, thereby ensuring that the G pole will not be damaged by high voltage. The first controllable switch Q3 is a unidirectional thyristor switch. When the trigger end of the first controllable switch Q3 receives the overcurrent signal of the second voltage detection circuit 51, the first controllable switch Q3 is turned on.

[0051] Specifically, Figure 7 In the embodiment, when the load is overcurrent, the voltage drop across the resistor R26 increases, causing the voltage input to the positive input terminal of the operational amplifier U2B to increase to a value greater than the second reference voltage Vref. The operational amplifier U2B outputs a high-level overcurrent signal, which is divided by the second resistor R12 and the third resistor R2 and input to the trigger pin of the first controllable switch Q3 to turn on the first controllable switch Q3. After the G-pole voltage of Q2 is reduced to a value lower than the on-state voltage drop of Q2, Q2 is disconnected, thereby cutting off the power supply circuit of the load. At this time, even if the overcurrent signal disappears, due to the existence of the holding current, the first controllable switch Q3 remains on to prevent Q2 from starting repeatedly.

[0052] In some optional embodiments, such as Figure 8 As shown, the level conversion circuit 6 includes: a state indicating circuit 61, a third switch circuit 62, a sixth resistor R128 and a seventh resistor R127, wherein a first end of the state indicating circuit 61 is connected to a first end (i.e., Q29) of the third switch circuit 62 and a first end of the sixth resistor R128 and then inputs a first external voltage, a second end of the state indicating circuit 61 is connected to a second end (i.e., R16) of the third switch circuit 62 and then inputs a second external voltage (i.e., ADJ1), a third end of the state indicating circuit 61 is connected to a third end (i.e., R124) of the third switch circuit 62, a third end of the second detection unit 5 and a first end of the seventh resistor R127, and the state indicating circuit 61 is used to be turned on and always on when there is an external voltage; a fourth end of the third switch circuit 62 is connected to a second end of the sixth resistor R128, a fifth end of the third switch circuit 62 is connected to a second end of the first switch circuit 2, and a sixth end of the third switch circuit 62 is connected to a second end of the seventh resistor R127.

[0053] Figure 8 In the embodiment, the resistance of the seventh resistor R127 is greater than the resistance of the sixth resistor R128; when the first detection unit 4 determines that the load is overcurrent, the third switch circuit 62 is turned off, so that the voltage at the second end of the first switch circuit 2 is reduced to a level lower than the on-state voltage drop of the internal switch of the first switch circuit 2, and then the first switch circuit 2 is disconnected, so that the load stops working.

[0054] Specifically, Figure 8In the embodiment, the third switch circuit 62 is composed of transistors Q28, Q29 and Q31. The first external voltage is 12V, and the second external voltage is the voltage of the ADJ1 signal output by the control chip U4. The level amplitude of the signal is determined by the power supply voltage of the control chip U4. Figure 5 The power supply voltage of the control chip U4 is 5V. If the MOS tube Q1 in the first switch circuit is directly driven by the 5V ADJ1 signal, the driving start working area of ​​Q1 may fall on the Miller platform. In this driving platform, the working current capacity of Q1 will be much lower than the rated level. At this time, Q1 is not used reasonably.

[0055] therefore, Figure 8 In the figure, when the ADJ1 signal is applied to the base of Q31, Q29 and Q31 will be turned on, Q28 will be turned on by the base drive current, and the 12V voltage will be applied to the G pole of Q1 through the sixth resistor R128, the transistor Q28, the seventh resistor R127, and the diode D5. Since the seventh resistor R127 is much larger than the resistance of the seventh resistor R127, the G pole voltage of Q1 is approximately equal to 12V minus the conduction voltage drop of Q28 minus the forward voltage drop of the diode D5, that is, the G pole voltage applied to Q1 will be maintained at about 11V, so that the driving voltage of Q1 is increased from 5V to 11V, ensuring that Q1 works in a reasonable working range.

[0056] This embodiment provides a power supply system, such as Fig. 9 As shown, it includes: a power supply and an overcurrent protection circuit of the above embodiment or any corresponding implementation method thereof, wherein the output end of the power supply is connected to the first end of the driving unit 1, and the power supply is used to output a supply voltage.

[0057] It should be noted that the load can be an LED, the power supply can be an existing common constant voltage LED power supply, and the overcurrent protection circuit is used to limit the output energy of the constant voltage LED power supply to prevent overcurrent from damaging the LED. The specific working mode of the power supply system will not be repeated here.

[0058] The power supply system provided in this embodiment realizes output energy limitation at the output end of the power supply, eliminating the conventional feedback unit circuit structure. When either the first switch circuit or the second switch circuit is open, the power supply circuit of the load is directly disconnected, which limits the output energy from the source and solves the overcurrent problem of the load. When either the first switch circuit or the second switch circuit is short-circuited and loses the shutdown capability, the other switch circuit can still work normally, ensuring that the output energy is limited and improving the reliability of the overcurrent circuit.

[0059] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An overcurrent protection circuit, characterized in that: include: A driving unit (1), a first switching circuit (2), a second switching circuit (3), a first detection unit (4), a second detection unit (5) and a level conversion circuit (6), wherein: The first end of the driving unit (1) is connected to the first end of the load and inputs a supply voltage, the second end of the driving unit (1) is connected to the first end of the second switch circuit (3), and the third end of the driving unit (1) is connected to the first end of the second detection unit (5); The second end of the second switch circuit (3) is connected to the second end of the load, and the third end of the second switch circuit (3) is connected to the first end of the first switch circuit (2); The second end of the first switch circuit (2) is connected to the first end of the level conversion circuit (6), and the third end of the first switch circuit (2) is connected to the first end of the first detection unit (4); The second end of the first detection unit (4) is connected to the second end of the second detection unit (5), and the third end of the first detection unit (4) is connected to the second end of the level conversion circuit (6); The third end of the level conversion circuit (6) is connected to the third end of the second detection unit (5) and then grounded, and the level conversion circuit (6) adjusts the voltage of the second end of the first switch circuit (2) so that the first switch circuit (2) operates in a safe working area; When the first detection unit (4) determines that the load is overcurrent, the level conversion circuit (6) controls the first switch circuit (2) to be disconnected based on the overcurrent signal output by the first detection unit (4), so that the load stops working; When the second detection unit (5) determines that the load is overcurrent, the drive unit (1) controls the second switch circuit (3) to disconnect based on the overcurrent signal output by the second detection unit (5), so that the load stops working.

2. The overcurrent protection circuit according to claim 1, characterized in that: The first detection unit (4) comprises: a first voltage detection circuit (41) and a first current detection circuit (42), wherein: A first end of the first voltage detection circuit (41) is connected to a third end of the first switch circuit (2) and a first end of the first current detection circuit (42), and a second end of the first voltage detection circuit (41) is connected to a second end of the level conversion circuit (6); The second end of the first current detection circuit (42) is connected to the second end of the second detection unit (5); When the voltage drop across the first current detection circuit (42) is greater than the first reference voltage, the first voltage detection circuit (41) determines that the load is overcurrent and outputs an overcurrent signal, causing the first switch circuit (2) to be disconnected.

3. The overcurrent protection circuit according to claim 2, characterized in that: The first voltage detection circuit (41) comprises: a voltage comparison unit (411) and a control unit (412), wherein: A first reference voltage is input to a positive input terminal of the voltage comparison unit (411), a negative input terminal of the voltage comparison unit (411) is connected to a first terminal of the first current detection circuit (42) and an output terminal of the control unit (412), and an output terminal of the voltage comparison unit (411) is connected to an input terminal of the control unit (412); When the voltage comparison unit (411) determines that the voltage drop across the first current detection circuit (42) is greater than the first reference voltage, the control unit (412) is controlled to output an overcurrent signal.

4. The overcurrent protection circuit according to claim 2, characterized in that: The second detection unit (5) comprises: a second voltage detection circuit (51) and a second current detection circuit (52), wherein: The first end of the second current detection circuit (52) is connected to the second end of the first current detection circuit (42) and the first end of the second voltage detection circuit (51), and the second end of the second current detection circuit (52) is connected to the second end of the second voltage detection circuit (51) and the third end of the level conversion circuit (6) and then grounded; A third end of the second voltage detection circuit (51) is connected to a third end of the drive unit (1); When the voltage drop across the second current detection circuit (52) is greater than the second reference voltage, the second voltage detection circuit (51) determines that the load is overcurrent and outputs an overcurrent signal, causing the second switch circuit (3) to be disconnected.

5. The overcurrent protection circuit according to claim 4, characterized in that: The second voltage detection circuit (51) comprises: a first resistor (R3), a second resistor (R12), a third resistor (R2), a first capacitor (C3), a second capacitor (C2) and an operational amplifier, wherein: The first end of the first resistor (R3) is connected to the first end of the second current detection circuit (52), and the second end of the first resistor (R3) is connected to the first end of the first capacitor (C3) and the positive input end of the operational amplifier; A second reference voltage is input to the inverting input terminal of the operational amplifier, an output terminal of the operational amplifier is connected to the first end of the second resistor (R12), and the operational amplifier is used to output an overcurrent signal when the voltage drop across the second current detection circuit (52) is greater than the second reference voltage; The second end of the second resistor (R12) is connected to the third end of the driving unit (1), the first end of the second capacitor (C2) and the first end of the third resistor (R2); The second end of the second capacitor (C2) is connected to the second end of the third resistor (R2), the second end of the first capacitor (C3) and the third end of the level conversion circuit (6) and then grounded.

6. The overcurrent protection circuit according to claim 1, characterized in that: The driving unit (1) comprises: a fourth resistor (R8), a fifth resistor (R11), a first diode (D2) and a first controllable switch (Q3), wherein: The first end of the fourth resistor (R8) is connected to the first end of the load and inputs a supply voltage, and the second end of the fourth resistor (R8) is connected to the first end of the fifth resistor (R11), the cathode of the first diode (D2), the first end of the first controllable switch (Q3) and the first end of the second switch circuit (3); The second end of the fifth resistor (R11) is connected to the anode of the first diode (D2) and the second end of the first controllable switch (Q3); A control end of the first controllable switch (Q3) is connected to a first end of the second detection unit (5); When the second detection unit (5) determines that the load is overcurrent, the first controllable switch (Q3) controls the second switch circuit (3) to disconnect based on the overcurrent signal output by the second detection unit (5), so that the load stops working.

7. The overcurrent protection circuit according to claim 1, characterized in that: The level conversion circuit (6) comprises: a state indication circuit (61), a third switch circuit (62), a sixth resistor (R128) and a seventh resistor (R127), wherein: The first end of the state indicating circuit (61) is connected to the first end of the third switch circuit (62) and the first end of the sixth resistor (R128) and then inputs a first external voltage; the second end of the state indicating circuit (61) is connected to the second end of the third switch circuit (62) and then inputs a second external voltage; the third end of the state indicating circuit (61) is connected to the third end of the third switch circuit (62), the third end of the second detection unit (5) and the first end of the seventh resistor (R127); the state indicating circuit (61) is used to be turned on and always on when there is an external voltage; The fourth end of the third switch circuit (62) is connected to the second end of the sixth resistor (R128), the fifth end of the third switch circuit (62) is connected to the second end of the first switch circuit (2), and the sixth end of the third switch circuit (62) is connected to the second end of the seventh resistor (R127); When the first detection unit (4) determines that the load is overcurrent, the third switch circuit (62) is turned off, so that the voltage at the second end of the first switch circuit (2) is reduced to a value lower than the on-state voltage drop of the internal switch of the first switch circuit (2), and then the first switch circuit (2) is disconnected, so that the load stops working; The resistance of the seventh resistor (R127) is greater than the resistance of the sixth resistor (R128).

8. The overcurrent protection circuit according to claim 1, characterized in that: When the first switch circuit (2) or the second switch circuit (3) fails and opens, the load is powered off and stops working.

9. The overcurrent protection circuit according to claim 1, characterized in that: When the first switch circuit (2) fails and short-circuits, and the second detection unit (5) determines that the load is overcurrent, the drive unit (1) controls the second switch circuit (3) to disconnect based on the overcurrent signal output by the second detection unit (5), so that the load stops working; When the second switch circuit (3) fails and short-circuits, and the first detection unit (4) determines that the load is overcurrent, the level conversion circuit (6) controls the first switch circuit (2) to disconnect based on the overcurrent signal output by the first detection unit (4), so that the load stops working.

10. A power supply system, characterized in that: include: A power supply and an overcurrent protection circuit as claimed in any one of claims 1 to 9, wherein: The output end of the power supply is connected to the first end of the drive unit (1), and the power supply is used to output a power supply voltage.

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