Short-circuit protection circuit and lighting equipment

Abstract

The utility model provides a short circuit protection circuit and a lighting device, the short circuit protection circuit comprises a comparison circuit, a current sampling circuit and a control circuit, the control circuit comprises a thyristor and a switch tube; the comparison circuit is electrically connected with a power supply, one end of the current sampling circuit and one end of the thyristor, the other end of the current sampling circuit is electrically connected with a first end of the switch tube, and a second end of the switch tube is electrically connected with a second end of the thyristor. The third end of the switch tube is used for being electrically connected with an external load. Through the implementation of the utility model, the on-off of the switch tube is controlled by the thyristor capable of continuously keeping the conduction state, so that the complete disconnection of the switch tube can be ensured, and the effectiveness and the reliability of short-circuit protection are effectively improved.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, in particular to a short - circuit protection circuit and a lighting device. Background Art

[0002] During the process of a power supply system supplying power to a load, problems such as a short - circuit in the power supply loop or a failure of the load may occur, resulting in damage to the load or the power supply system. Therefore, in order to avoid the above - mentioned situations, a short - circuit protection is usually set in the power supply loop to switch the power supply when the loop current is too large. When the related - art short - circuit protection circuit detects that the current is too large through current sampling, the connection switch of the loop is turned off by a triode, thereby disconnecting the power supply loop. However, the triode will respond instantaneously to the drive. When there is a drive, the triode conducts instantaneously, and when the drive stops, the triode cuts off instantaneously. If the drive supply time is short, the connection switch of the loop may not be turned off completely, resulting in low reliability of the short - circuit protection. Summary of the Utility Model

[0003] The utility model provides a short - circuit protection circuit and a lighting device, aiming to solve the problem of low reliability of the short - circuit protection circuit in the related art.

[0004] To solve the above - mentioned technical problems, in the first aspect of the utility model, a short - circuit protection circuit is provided, including: a comparison circuit, a current sampling circuit and a control circuit. The control circuit includes a thyristor and a switching tube; the comparison circuit is electrically connected to the power supply, one end of the current sampling circuit and the first end of the thyristor respectively. The other end of the current sampling circuit is electrically connected to the first end of the switching tube. The second end of the switching tube is electrically connected to the second end of the thyristor. The third end of the switching tube is used for electrically connecting to an external load.

[0005] Further, the comparison circuit includes a reference voltage supply circuit, a comparator, a first resistor, a second resistor, a third resistor and a first capacitor; the positive input terminal of the comparator is electrically connected to the third resistor, the first capacitor and one end of the current sampling circuit respectively. The negative input terminal of the comparator is electrically connected to one end of the reference voltage supply circuit. The output terminal of the comparator is electrically connected to the other end of the third resistor, the first resistor and one end of the second resistor respectively. The power supply terminal of the comparator, the first resistor and the other end of the reference voltage supply circuit are all electrically connected to the power supply. The other end of the second resistor is electrically connected to the thyristor. The other end of the first capacitor is grounded.

[0006] Further, the control circuit further includes a tenth resistor and a second capacitor; one end of the tenth resistor and the second capacitor are both electrically connected to the first end of the thyristor, and the other end of the tenth resistor and the second capacitor are both grounded.

[0007] Further, a voltage stabilizing circuit is further included, and the voltage stabilizing circuit is electrically connected to the power supply and the comparison circuit respectively.

[0008] Further, the voltage stabilizing circuit includes a triode, a voltage stabilizing diode, a diode, an eleventh resistor and a twelfth resistor; the collector of the triode is electrically connected to the positive electrode of the diode, the emitter of the triode is electrically connected to one end of the eleventh resistor and the comparison circuit respectively, the base of the triode is electrically connected to the first end of the voltage stabilizing diode, the negative electrode of the diode is electrically connected to the power supply, the second end of the voltage stabilizing diode is electrically connected to the other end of the eleventh resistor and one end of the twelfth resistor respectively, and the third end of the voltage stabilizing diode and the other end of the twelfth resistor are both grounded.

[0009] In the second aspect of the present invention, an illumination device is provided, which includes the short-circuit protection circuit as described in the first aspect of the present invention.

[0010] As can be seen from the above description, the present invention collects the current in the power supply loop through the current sampling circuit, compares it through the comparison circuit, and outputs a short-circuit protection signal to the control circuit when a short circuit occurs in the power supply loop. After receiving the short-circuit protection signal, the control circuit disconnects the connection between the power supply loop and the load to achieve short-circuit protection. Among them, the thyristor of the control circuit remains in the conducting state continuously after receiving the short-circuit protection signal, so as to ensure that the switching tube is completely disconnected, effectively improving the effectiveness and reliability of short-circuit protection. Description of the Drawings

[0011] Figure 1 is a schematic structural diagram of a short-circuit protection circuit according to an embodiment of the present invention;

[0012] Figure 2 is a circuit schematic diagram of a short-circuit protection circuit according to an embodiment of the present invention;

[0013] Figure 3 is a circuit schematic diagram of another short-circuit protection circuit according to an embodiment of the present invention;

[0014] Figure 4 is a circuit schematic diagram of a power supply system of an illumination device according to an embodiment of the present invention. Detailed Embodiments

[0015] In order to make the objectives, technical solutions and advantages of the present utility model clearer and more understandable, the present utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model. In addition, the technical features involved in the various embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0016] In the related art, due to the problem that the short-circuit protection circuit has low reliability of short-circuit protection because the switching tube cannot be completely turned off, for this reason, the embodiment of the present utility model provides a short-circuit protection circuit.

[0017] As Figure 1 shown is a schematic structural diagram of a short-circuit protection circuit provided by an embodiment of the present utility model. The short-circuit protection circuit includes: a comparison circuit 100, a current sampling circuit 200 and a control circuit 300. The control circuit 300 includes a thyristor 310 and a switching tube 320; the comparison circuit 100 is electrically connected to the power supply, one end of the current sampling circuit 200 and the first end of the thyristor 310 respectively. The other end of the current sampling circuit 200 is electrically connected to the first end of the switching tube 320. The second end of the switching tube 320 is electrically connected to the second end of the thyristor 310. The third end of the switching tube 320 is used to be electrically connected to an external load 400.

[0018] Specifically, in this embodiment, the current sampling circuit 200 collects the current in the power supply loop and transmits it to the comparison circuit 100. The comparison circuit 100 determines whether a short circuit occurs in the power supply loop. When a short circuit occurs in the power supply loop, a short-circuit protection signal is output and transmitted to the control circuit 300. The control circuit 300 disconnects the connection between the power supply loop and the load 400. Among them, when the thyristor 310 in the control circuit 300 receives the short-circuit protection signal transmitted by the comparison circuit 100, it will continuously maintain the conducting state until it receives a shutdown signal, so that the switching tube 320 is completely turned off, ensuring that the power supply loop is completely disconnected from the load 400, realizing short-circuit protection, and improving the effectiveness and reliability of short-circuit protection.

[0019] As Figure 2 shown is a circuit schematic diagram of a short-circuit protection circuit provided by this embodiment. Please refer to Figure 2, the comparison circuit 100 includes a reference voltage supply circuit, a comparator U2, a first resistor R5, a second resistor R6, a third resistor R15, and a first capacitor C13; the positive input terminal of the comparator U2 is electrically connected to one end of the third resistor R15, the first capacitor C13, and the current sampling circuit 200 respectively, the negative input terminal of the comparator U2 is electrically connected to one end of the reference voltage supply circuit, the output terminal of the comparator U2 is electrically connected to the other end of the third resistor R15, one end of the first resistor R5, and one end of the second resistor R6 respectively, the power supply terminal of the comparator U2, one end of the first resistor R5, and the other end of the reference voltage supply circuit are all electrically connected to the power supply, the other end of the second resistor R6 is electrically connected to the thyristor 310 (i.e., Q4), and the other end of the first capacitor C13 is grounded.

[0020] Specifically, the reference voltage supply circuit includes a fourth resistor R12 and a fifth resistor R23; one end of the fourth resistor R12 is electrically connected to the power supply, the other end of the fourth resistor R12 is electrically connected to the negative input terminal of the comparator U2 and one end of the fifth resistor R23 respectively, and the other end of the fifth resistor R23 is grounded.

[0021] In this embodiment, the negative input terminal of the comparator U2 is used to receive the reference voltage, the positive receiving terminal of the comparator U2 is used to receive the feedback voltage of the power supply loop transmitted by the current sampling circuit 200. After the comparator U2 compares the feedback voltage with the reference voltage, if the feedback voltage is larger, the comparator U2 outputs a short-circuit protection signal such as a high-level signal to the control circuit 300 through the second resistor R6.

[0022] Further, please refer to Figure 2 , the control circuit 300 further includes a sixth resistor R7 and a seventh resistor R16; the switching transistor 320 (i.e., Q3) is an NMOS transistor, one end of the sixth resistor R7 is electrically connected to the power supply, the other end of the sixth resistor R7 is electrically connected to the gate of the NMOS transistor, the second terminal of the thyristor Q4, and one end of the seventh resistor R16 respectively, the other end of the seventh resistor R16 is electrically connected to the source of the NMOS transistor, and the third terminal of the thyristor Q4 is grounded.

[0023] Further, please refer to Figure 2 , the current sampling circuit 200 includes an eighth resistor R19 and a ninth resistor R25; one end of the eighth resistor R19 is electrically connected to the comparison circuit 100, the other end of the eighth resistor R19 is electrically connected to one end of the ninth resistor R25 and the source of the NMOS transistor respectively, and the other end of the ninth resistor R25 is grounded.

[0024] Further, please refer to Figure 2, the control circuit 300 further includes an interference suppression circuit, and the interference suppression circuit is electrically connected to the first end of the thyristor Q4. Among them, the interference suppression circuit includes a tenth resistor R10 and a second capacitor C6. One ends of the tenth resistor R10 and the second capacitor C6 are both electrically connected to the first end of the thyristor Q4, and the other ends of the tenth resistor R10 and the second capacitor C6 are both grounded.

[0025] Specifically, in this embodiment, the switching transistor Q3 can be a MOS transistor, such as Figure 2 the NMOS transistor in. When the comparator U2 determines that the output current is too large, that is, a short circuit occurs in the power supply circuit, a high-level signal is output to the thyristor Q4 through the second resistor R6, causing the thyristor Q4 to conduct, so that the gate voltage of the NMOS transistor is pulled low and turned off. And since the thyristor Q4 can maintain the conduction state even after the drive is removed, it can ensure that the switching transistor Q3 is completely turned off. The sixth resistor R7 and the seventh resistor R16 are used to provide a bias voltage for the switching transistor Q3 to ensure that the switching transistor Q3 is within the normal operating range, and can also play a role in preventing static electricity, avoiding electrostatic damage when the gate and the source are in a high-impedance state, and ensuring the safety of the device. The eighth resistor R19 and the ninth resistor R25 are used to collect the current of the source of the switching transistor Q3 and convert it into a voltage and transmit it to the positive input terminal of the comparator U2. The tenth resistor R10 and the second capacitor C6 are used to suppress interference signals and prevent the thyristor Q4 from being mis-triggered. At the same time, the tenth resistor R10 can also provide a discharge circuit.

[0026] As Figure 3 shown is the circuit schematic diagram of another short-circuit protection circuit provided by this embodiment. Please refer to Figure 3 , the short-circuit protection circuit further includes a voltage stabilization circuit, and the voltage stabilization circuit is electrically connected to the power supply and the comparison circuit 100 respectively.

[0027] Specifically, the voltage stabilization circuit includes a triode Q2, a voltage stabilizing diode U3, a diode D2, an eleventh resistor R9, and a twelfth resistor R20; the collector of the triode Q2 is electrically connected to the positive pole of the diode D2, the emitter of the triode Q2 is electrically connected to one end of the eleventh resistor R9 and the comparison circuit 100 respectively, the base of the triode Q2 is electrically connected to the first end of the voltage stabilizing diode U3, the negative pole of the diode D2 is electrically connected to the power supply, the second end of the voltage stabilizing diode U3 is electrically connected to the other end of the eleventh resistor R9 and one end of the twelfth resistor R20 respectively, and the third end of the voltage stabilizing diode U3 and the other end of the twelfth resistor R20 are both grounded.

[0028] In this embodiment, in order to ensure that the comparator U2 can obtain a stable operating voltage to improve the stability of the short - circuit protection circuit, the short - circuit protection circuit is also provided with a voltage - stabilizing circuit for converting and stabilizing the input voltage to the operating voltage required by the comparison circuit 100, such as 5V. The voltage - stabilizing circuit mainly consists of a voltage - stabilizing diode U3, a triode Q2, and a sampling circuit. Among them, the eleventh resistor R9 and the twelfth resistor R20 sample the voltage input to the comparison circuit 100 and transmit it to the voltage - stabilizing diode U3. After comparing the sampled voltage with its own reference voltage, the voltage - stabilizing diode U3 controls the output of the triode Q2 to adjust the voltage input to the comparison circuit 100. The diode D2 is used to limit the voltage so that the input voltage does not exceed the maximum allowable voltage of the voltage - stabilizing diode U3 to protect the voltage - stabilizing diode U3. The voltage - stabilizing circuit also includes capacitors C4, C5, C9, C7 and a resistor R8. The resistor R8 is used to provide a bias current for the triode Q2, and the capacitors C4, C5, C7 are used for filtering, and the capacitor C9 can be used to stabilize the feedback loop.

[0029] The short - circuit protection circuit provided by the embodiment of the present utility model collects the current in the power supply loop through the current sampling circuit and transmits it to the comparison circuit. The comparison circuit determines whether the power supply loop has a short - circuit. When the power supply loop has a short - circuit, it outputs a short - circuit protection signal to the control circuit, and the control circuit disconnects the connection between the power supply loop and the load. Among them, when the thyristor in the control circuit receives the short - circuit protection signal transmitted by the comparison circuit, it will continuously maintain the conducting state until it receives the shutdown signal, so that the switching tube is completely turned off, ensuring that the power supply loop is completely disconnected from the load, realizing short - circuit protection, and improving the effectiveness and reliability of short - circuit protection.

[0030] The embodiment of the present utility model also provides an illumination device, which includes the above - mentioned short - circuit protection circuit. Among them, the illumination device can be an emergency light. The illumination device may also include a boost circuit, that is, the short - circuit protection circuit is connected between the output terminal of the boost circuit and the load, and the input voltage of the short - circuit protection circuit is the output voltage of the boost circuit (i.e., Figure 2 +48V in Figure 4As shown in the circuit schematic diagram of the power supply system of the lighting device, the boost circuit includes a controller U1, a MOS transistor Q5, and a boost inductor L1. The output pin of the controller U1 transmits a driving signal to the MOS transistor Q5 to cause the MOS transistor Q5 to perform periodic switching. In each switching cycle, when the MOS transistor Q5 is turned on, the boost inductor L1 stores energy to increase the output voltage. When the MOS transistor Q5 is turned off, the boost inductor L1 releases energy and transmits the stored energy to an external load such as an LED unit. The voltage feedback terminal of the controller also receives the voltage sampled by the voltage sampling circuit, generates a control voltage through comparison, adjusts the duty cycle or pulse width of the driving signal, and thus adjusts the conduction time of the MOS transistor Q5 to regulate the magnitude of the output voltage. The current detection terminal of the controller is also used to receive the feedback voltage collected by the current sampling circuit to adjust the duty cycle or pulse width of the driving control signal according to the feedback voltage. The output voltage of the boost circuit is rectified by a diode D1 and then transmitted to the short-circuit protection circuit and the external load to provide a power supply voltage for the device.

[0031] It should be noted that the various embodiments in the content of the present invention are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0032] It should also be noted that in the content of the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0033] The above description of the disclosed embodiments enables those skilled in the art to implement or use the content of the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined in the content of the present invention can be implemented in other embodiments without departing from the spirit or scope of the content of the present invention. Therefore, the content of the present invention will not be limited to these embodiments shown in the content of the present invention, but will conform to the widest scope consistent with the principles and novel features disclosed in the content of the present invention.

Claims

1. A short - circuit protection circuit, characterized in that, Comprising: A comparison circuit, a current sampling circuit and a control circuit, wherein the control circuit includes a thyristor and a switching transistor; The comparison circuit is electrically connected to the power supply, one end of the current sampling circuit and the first end of the thyristor respectively. The other end of the current sampling circuit is electrically connected to the first end of the switching transistor. The second end of the switching transistor is electrically connected to the second end of the thyristor. The third end of the switching transistor is used for electrically connecting to an external load.

2. The short-circuit protection circuit according to claim 1, characterized in that The comparison circuit includes a reference voltage supply circuit, a comparator, a first resistor, a second resistor, a third resistor and a first capacitor. The positive input terminal of the comparator is electrically connected to the third resistor, the first capacitor and one end of the current sampling circuit respectively. The negative input terminal of the comparator is electrically connected to one end of the reference voltage supply circuit. The output terminal of the comparator is electrically connected to the other end of the third resistor, the first resistor and one end of the second resistor respectively. The power supply terminal of the comparator, the first resistor and the other end of the reference voltage supply circuit are all electrically connected to the power supply. The other end of the second resistor is electrically connected to the thyristor. The other end of the first capacitor is grounded.

3. The short-circuit protection circuit according to claim 2, wherein, The reference voltage supply circuit includes a fourth resistor and a fifth resistor. One end of the fourth resistor is electrically connected to the power supply. The other end of the fourth resistor is electrically connected to the negative input terminal of the comparator and one end of the fifth resistor respectively. The other end of the fifth resistor is grounded.

4. The short-circuit protection circuit according to claim 1, characterized in that, The control circuit further includes a sixth resistor and a seventh resistor. The switching transistor is an NMOS transistor. One end of the sixth resistor is electrically connected to the power supply. The other end of the sixth resistor is electrically connected to the gate of the NMOS transistor, the second end of the thyristor and one end of the seventh resistor respectively. The other end of the seventh resistor is electrically connected to the source of the NMOS transistor. The third end of the thyristor is grounded.

5. The short-circuit protection circuit according to claim 4, wherein The current sampling circuit includes an eighth resistor and a ninth resistor. One end of the eighth resistor is electrically connected to the comparison circuit. The other end of the eighth resistor is electrically connected to one end of the ninth resistor and the source of the NMOS transistor respectively. The other end of the ninth resistor is grounded.

6. The short-circuit protection circuit according to claim 1, characterized in that, The control circuit further includes an interference suppression circuit, and the interference suppression circuit is electrically connected to the first end of the thyristor.

7. The short-circuit protection circuit according to claim 6, wherein The interference suppression circuit includes a tenth resistor and a second capacitor. One end of the tenth resistor and the second capacitor are both electrically connected to the first end of the thyristor. The other end of the tenth resistor and the second capacitor are both grounded.

8. The short-circuit protection circuit according to claim 1, wherein, It further includes a voltage stabilizing circuit, and the voltage stabilizing circuit is electrically connected to the power supply and the comparison circuit respectively.

9. The short-circuit protection circuit according to claim 8, characterized in that, The voltage stabilizing circuit includes a triode, a voltage stabilizing diode, a diode, an eleventh resistor, and a twelfth resistor; the collector of the triode is electrically connected to the positive electrode of the diode, the emitter of the triode is respectively electrically connected to one end of the eleventh resistor and the comparison circuit, the base of the triode is electrically connected to the first end of the voltage stabilizing diode, the negative electrode of the diode is electrically connected to the power supply, the second end of the voltage stabilizing diode is respectively electrically connected to the other end of the eleventh resistor and one end of the twelfth resistor, and the third end of the voltage stabilizing diode and the other end of the twelfth resistor are both grounded.

10. A lighting device, characterized in that, It includes the short-circuit protection circuit according to any one of claims 1 to 9.

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