Short-circuit protection circuits, LED power supply circuits and LED lighting fixtures

Abstract

To provide a short-circuit protection circuit, an LED power supply circuit including the short-circuit protection circuit, and an LED illumination apparatus including the LED power supply circuit.SOLUTION: A short-circuit protection circuit in the present invention includes a power supply, a step-up inductor connected to the power supply and including a main coil and an auxiliary coil, an LED load circuit connected to the main coil, a feedback circuit connected to the auxiliary coil, and a field effect transistor having a drain connected to the LED load circuit, a gate connected to the auxiliary coil through the feedback circuit, and a source grounded. The short-circuit protection circuit further includes a protection circuit connected between the auxiliary coil and the gate of the field effect transistor. The short-circuit protection circuit in the present invention can protect the circuit from short-circuit so as to prevent, in the occurrence of short-circuit on the load side, the field effect transistor from keeping heat generation due to excess current and damaging the circuit significantly.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the electrical technology field, and more particularly to a short-circuit protection circuit, an LED power supply circuit including the short-circuit protection circuit, and an LED lighting fixture using the LED power supply circuit. [Background technology]

[0002] When a power supply such as a battery or a stabilized power supply is used, a field-effect transistor is usually connected in series to the output terminal of the power supply circuit to remove ripple in the circuit and stabilize the output voltage of the power supply circuit.

[0003] In the prior art, in a power supply circuit provided with a field effect transistor 6 as shown in FIG. 1, if a large voltage is applied to the field effect transistor 6 when the load circuit 4 is short-circuited, a large amount of heat is generated in a short time due to the excessive current, which may damage the field effect transistor 6 and ultimately cause serious damage to the power supply circuit.

[0004] In response to this problem, a conventional solution has been proposed in which a voltage dividing resistor 41 is connected in series to one end of the load circuit 4 to prevent a large voltage from being applied to the field effect transistor 6 when the load circuit 4 is short-circuited, as shown in Figure 2. However, to obtain a good voltage dividing effect, the voltage dividing resistor 41 connected in series must have a large resistance value, and if the resistance value of the voltage dividing resistor 41 is too high, there is a risk of excessive power consumption during normal circuit operation.

[0005] Therefore, it is desirable to provide a technology that not only achieves the short circuit protection effect by preventing a large voltage from being applied to the field effect transistor 6 when the load circuit 4 is short-circuited, but also prevents excessive power consumption from affecting the normal output of the circuit itself. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a short-circuit protection circuit that can protect a circuit from short circuits by preventing serious damage to the circuit caused by a field-effect transistor continuing to heat up due to excessive current when a short circuit occurs on the load side. [Means for solving the problem]

[0007] The short-circuit protection circuit provided by the present invention includes a power supply, a boost inductor connected to the power supply and having a main coil and an auxiliary coil, an LED load circuit connected to the main coil, a feedback circuit connected to the auxiliary coil, and a field-effect transistor having a drain connected to the LED load circuit, a gate connected to the auxiliary coil via the feedback circuit, and a source grounded, and further including a protection circuit connected between the auxiliary coil and the gate of the field-effect transistor.

[0008] With the above circuit structure, in the short-circuit protection circuit provided by the present invention, when the LED load circuit operates normally, the normal operating voltage is applied to the auxiliary coil of the boost inductor, the protection circuit does not operate, and the gate voltage of the field-effect transistor is provided by the feedback circuit, turning on the field-effect transistor. Also, when a short circuit occurs in the LED load circuit, the voltage applied to the auxiliary coil of the boost inductor disappears, the auxiliary coil does not operate, and its voltage value becomes zero, so the protection circuit connected between the auxiliary coil and the gate of the field-effect transistor turns on, and by grounding the gate of the field-effect transistor, the gate voltage becomes zero and the field-effect transistor turns off, preventing the large voltage generated by the short circuit in the LED load circuit from being directly applied to the field-effect transistor, thereby realizing short-circuit protection for the circuit.

[0009] In a preferred technical means of the present invention, the protection circuit in the short-circuit protection circuit further includes a diode having an anode connected to the auxiliary coil, a voltage inverting circuit connected between the cathode of the diode and the gate of the field-effect transistor and connected to a DC power supply, and a first capacitor having one end connected to the cathode of the diode and the other end grounded.

[0010] According to this preferred technical solution, when the LED load circuit operates normally, i.e., when a normal operating voltage is applied to the auxiliary coil of the boost inductor, the gate of the field-effect transistor receives the normal operating voltage output from the voltage inverter and / or feedback circuit. When the LED load circuit is short-circuited, i.e., when the auxiliary coil voltage of the boost inductor becomes zero, the voltage inverter inverts the high-level signal transmitted from the DC power source and grounds the gate of the field-effect transistor, turning it off. This prevents the large voltage generated by the short circuit of the LED load circuit from being directly applied to the field-effect transistor, thereby realizing short-circuit protection. Here, the first capacitor and the voltage inverter are connected in parallel, and the memory function of the capacitor ensures that the voltage inverter circuit does not malfunction when the circuit is started. The diode ensures unidirectional conduction between the auxiliary coil of the boost inductor and the voltage inverter circuit, preventing the voltage inverter circuit or the first capacitor from inputting a reverse voltage to the boost inductor.

[0011] Furthermore, in a preferred technical means of the present invention, the voltage inverting circuit further includes a first bipolar transistor having a base connected to the cathode of the diode, a collector connected to a DC power supply, and an emitter grounded, and a second bipolar transistor having a base connected to the collector of the first bipolar transistor, a collector connected to the gate of the field effect transistor, and an emitter grounded.

[0012] According to the preferred technical means, a voltage inversion circuit formed by a first bipolar transistor and a second bipolar transistor controls the on and off of the first bipolar transistor and the second bipolar transistor depending on whether a normal operating voltage is applied to the auxiliary coil of the boost inductor, i.e., whether the LED load circuit is operating normally. When a normal operating voltage is applied to the auxiliary coil of the boost inductor, i.e., when the LED load circuit is operating normally, the first bipolar transistor is on and the second bipolar transistor is off, the protection circuit does not send a signal to the gate of the field-effect transistor, and the gate voltage of the field-effect transistor is provided by the feedback circuit, turning the field-effect transistor on. When the operating voltage of the auxiliary coil of the boost inductor becomes zero, i.e., when the LED load circuit is short-circuited, the first bipolar transistor is off and the second bipolar transistor is on, the protection circuit outputs a voltage to the gate that becomes zero, turning the field-effect transistor off. This prevents a large voltage generated by a short circuit in the LED load circuit from being directly applied to the field-effect transistor, thereby realizing short-circuit protection for the circuit.

[0013] In particular, in a preferred technical means of the present invention, the short circuit protection circuit may further include a second capacitor having one end connected to the main coil and the other end grounded.

[0014] According to this preferred technical means, the second capacitor and the boost inductor are connected in parallel, so that the charging and discharging of the second capacitor can be used to achieve the effects of voltage stabilization and noise removal.

[0015] A preferred technical solution of the present invention further provides an LED power supply circuit including the above short circuit protection circuit, which turns off the field effect transistor when the LED load is short-circuited, thereby preventing a large voltage from being applied to the field effect transistor, which would cause continuous heat generation and damage to electrical components in the LED load circuit.

[0016] In a preferred technical solution of the present invention, an LED lighting fixture is further provided, in which the power supply circuit is equipped with the above-mentioned short-circuit protection circuit, which turns off the field-effect transistor when the LED load is short-circuited, thereby preventing a large voltage from being applied to the field-effect transistor, which continues to generate heat and damages electrical components in the circuit, and ultimately damaging the structure of the LED lighting fixture. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of a power supply circuit in the prior art. [Figure 2] FIG. 2 is a schematic diagram of one power supply circuit including short circuit protection in the prior art. [Figure 3] FIG. 3 is a schematic diagram of a short-circuit protection circuit provided in the first embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a short-circuit protection circuit provided in the second embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram of a short-circuit protection circuit provided in the third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. It is obvious to those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention and do not limit the scope of protection of the present invention. Those skilled in the art can adjust these embodiments as necessary to meet specific application cases.

[0019] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the present invention. As used herein, the singular forms "a," "one," and "the" are intended to include the plural, unless the context clearly dictates otherwise. In this description, "plurality" means two or more than two, unless other specific limitations are clear. Furthermore, it is understood that the terms "comprising" and / or "including," when used in this description, specify the presence of the stated features, integers, steps, operations, components, and / or elements, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, elements, and / or elements.

[0020] For a complete understanding of the present invention, detailed steps and detailed configurations are shown in the following description, so as to explain in detail the technical means shown by the present invention. Detailed descriptions of more preferred embodiments of the present invention are as follows, but in addition to these detailed descriptions, the present invention can also include other embodiments.

[0021] (Embodiment 1) As shown in FIG. 3 , the short-circuit protection circuit 1 provided in the first embodiment of the present invention includes a power supply 2 connected to a filter circuit 21; a boost inductor 3 connected to the power supply 2 and having a main coil 31 and an auxiliary coil 32, for increasing the voltage in the circuit and supplying power to a downstream circuit; an LED load circuit 4 connected at one end to the main coil 31 and at the other end to a field-effect transistor 6; a feedback circuit 5 connected between the auxiliary coil 32 and the field-effect transistor 6 and including two control IC chips 51; and the field-effect transistor 6, whose drain is connected to the LED load circuit 4, whose gate is connected to the auxiliary coil 32 via the feedback circuit 5, and whose source is grounded. The filter circuit 21 can remove noise from the voltage output by the power supply 2, thereby further stabilizing the output voltage of the power supply 2. The short-circuit protection circuit 1 also includes a protection circuit 7 connected between the auxiliary coil 32 and the gate of the field-effect transistor 6 and connected in parallel with the feedback circuit 5.

[0022] With the above circuit structure, the short circuit protection circuit 1 provided by the present invention can achieve the function of short circuit protection by preventing a large voltage from being applied to the field effect transistor 6 when the LED load circuit 4 is short-circuited.

[0023] The field effect transistor 6 is an NMOS transistor and a voltage controlled device, and the gate voltage determines the operating state of the field effect transistor 6. When the gate voltage is at a high level, the field effect transistor 6 is turned on, and when the gate voltage is at a low level (0), the field effect transistor 6 is turned off.

[0024] When the LED load circuit 4 operates normally, a normal operating voltage is applied to the auxiliary coil 32 of the boost inductor 3, and the protection circuit 7 connected to the auxiliary coil 32 of the boost inductor 3 can receive a high-level signal from the auxiliary coil 32. At this time, the protection circuit 7 is inactive, and the gate voltage of the field-effect transistor 6 is provided by the feedback circuit 5, which is also connected to the auxiliary coil 32 of the boost inductor 3, turning the field-effect transistor 6 on. When a short circuit occurs in the LED load circuit 4, the voltage applied to the auxiliary coil 32 of the boost inductor 3 disappears, the voltage value of the auxiliary coil 32 of the boost inductor 3 becomes zero, and the field-effect transistor 6 stops operating. The protection circuit 7, connected to the auxiliary coil 32 of the boost inductor 3, can no longer receive the signal from the auxiliary coil 32. This turns on the protection circuit 7, grounding the gate of the field-effect transistor 6, causing the gate voltage to become zero, turning the field-effect transistor 6 off and no longer operating. This prevents the large voltage generated by a short circuit in the LED load circuit 4 from being directly applied to the field-effect transistor 6, thereby achieving short-circuit protection.

[0025] In a preferred technical solution of the present invention, the short circuit protection circuit 1 preferably further includes a second capacitor 8, one end of which is connected to the main coil 31 and the other end of which is grounded. The second capacitor 8 is connected in parallel with the boost inductor 3, and the charging and discharging effect of the second capacitor 8 itself can be used to provide voltage stabilization and noise removal effects. Here, the second capacitor 8 is usually an electrolytic capacitor, which has a large capacitance per unit volume and is low in cost.

[0026] (Embodiment 2) Referring to FIG. 4, as one preferred embodiment of the present invention, embodiment 2 of the present invention differs from embodiment 1 of the present invention in that, in the preferred technical means of the present invention, protection circuit 7 in short-circuit protection circuit 1 further includes a diode 71 having an anode connected to auxiliary coil 32, a voltage inversion circuit 72 connected between the cathode of diode 71 and the gate of field-effect transistor 6 and connected to a DC power supply, and a first capacitor 73 having one end connected to the cathode of diode 71 and the other end grounded.

[0027] The other circuit structures of the short-circuit protection circuit 1 in the second embodiment are all the same as those in the first embodiment, and will not be described again.

[0028] The voltage inversion circuit 72 realizes control over the gate voltage of the field-effect transistor 6. When the LED load circuit 4 operates normally, that is, when a normal operating voltage is applied to the auxiliary coil 32 of the boost inductor 3, the voltage inversion circuit 72 can receive a high-level signal transmitted from the auxiliary coil 32. At this time, the voltage inversion circuit 72 does not transmit a signal to the gate of the field-effect transistor 6, or transmits a high-level signal to the gate of the field-effect transistor 6, and correspondingly, the gate of the field-effect transistor 6 only receives a high-level signal transmitted from the feedback circuit 5, or simultaneously receives the normal operating voltage, i.e., a high-level signal, transmitted from the voltage inversion circuit 72 and the feedback circuit 5, and the field-effect transistor 6 is turned on. When the LED load circuit 4 is short-circuited, i.e., when the voltage across the auxiliary coil 32 of the boost inductor 3 is zero, the auxiliary coil 32 of the boost inductor 3 stops operating, and the voltage inversion circuit 72 connected to the auxiliary coil 32 of the boost inductor 3 cannot receive the signal from the auxiliary coil 32. Instead, the voltage inversion circuit 72 starts operating and inverts the high-level signal transmitted from the DC power supply 723. This causes the voltage inversion circuit 72 to ground the gate of the field-effect transistor 6, turning it off. This prevents the large voltage generated by the short circuit in the LED load circuit 4 from being directly applied to the field-effect transistor 6, thereby achieving short-circuit protection. The voltage inversion circuit 72 uses the DC power supply circuit design of the short-circuit protection circuit 1, eliminating the need for complex circuitry.

[0029] The protection circuit 7 further includes a first capacitor 73, and the first capacitor 73 and the voltage inversion circuit 72 are connected in parallel. Due to the charge / discharge characteristics of the first capacitor 73 itself, the protection circuit 7 connected to the auxiliary coil 32 of the boost inductor 3 at the time of circuit startup is preferably prevented from receiving a signal transmitted from the auxiliary coil 32, causing the voltage inversion circuit 72 to malfunction and turn off the field-effect transistor 6.

[0030] The protection circuit 7 further includes a diode 71, the unidirectional conduction characteristics of which can ensure unidirectional conduction between the auxiliary coil 32 of the boost inductor 3 and the voltage inversion circuit 72, and more preferably, prevent the voltage inversion circuit 72 or the first capacitor 73 from inputting a reverse voltage to the boost inductor 3.

[0031] Furthermore, the protection circuit 7 may also control the gate voltage of the field-effect transistor 6 using other methods, such as a chip or a voltage control circuit. For example, in a chip (not shown) that controls the output voltage according to the input voltage, when the LED load circuit 4 operates normally, a normal operating voltage is applied to the auxiliary coil 32 of the boost inductor 3, and the chip (not shown) in the protection circuit 7 connected to the auxiliary coil 32 of the boost inductor 3 can receive a high-level signal transmitted from the auxiliary coil 32, and the chip (not shown) outputs no signal or a high-level signal, and the gate voltage of the field-effect transistor 6 is similarly provided by the feedback circuit 5 connected to the auxiliary coil 32 of the boost inductor 3, turning on the field-effect transistor 6. Furthermore, when the LED load circuit 4 is short-circuited, that is, when the voltage of the auxiliary coil 32 of the boost inductor 3 is zero, the auxiliary coil 32 of the boost inductor 3 stops operating, and the chip (not shown) in the protection circuit 7 connected to the auxiliary coil 32 of the boost inductor 3 cannot receive the signal transmitted from the auxiliary coil 32. The chip (not shown) then grounds the gate of the field-effect transistor 6, turning the field-effect transistor 6 off, thereby preventing the large voltage generated by the short-circuit of the LED load circuit 4 from being directly applied to the field-effect transistor 6, and further realizing short-circuit protection for the circuit.

[0032] (Embodiment 3) Referring to FIG. 5, embodiment 3 is based on embodiment 1 and embodiment 2 of the present invention, and as a more preferable embodiment, voltage inversion circuit 72 in short circuit protection circuit 1 further includes a first bipolar transistor 721 having a base connected to the cathode of diode 71, a collector connected to a DC power supply 723, and an emitter grounded, and a second bipolar transistor 722 having a base connected to the collector of first bipolar transistor 721, a collector connected to the gate of field effect transistor 6, and an emitter grounded.

[0033] The DC power supply 723 extends from the above-mentioned short circuit protection circuit 1, and a short circuit in the LED load circuit 4 does not affect the normal operation of the DC power supply 723. Note that the other circuit structures of the short circuit protection circuit 1 in embodiment 3 are all the same as those in embodiment 1 or 2, and will not be described again.

[0034] When the LED load circuit 4 operates normally, i.e., when a normal operating voltage is applied to the auxiliary coil 32 of the boost inductor 3, the auxiliary coil 32 of the boost inductor 3 sends a high-level signal to the voltage inversion circuit 72, the base of the first bipolar transistor 721 receives the high-level signal, the first bipolar transistor 721 enters a saturated state, and the collector of the first bipolar transistor 721 goes low, i.e., the base of the second bipolar transistor 722 receives the low-level signal from the collector of the first bipolar transistor 721, the second bipolar transistor 722 goes off, the second bipolar transistor 722 does not conduct, and the voltage inversion circuit 72 does not send a level signal to the subsequent stage. The gate voltage of the field-effect transistor 6 is provided only by the feedback circuit 5, and the gate of the field-effect transistor 6 receives the high-level signal from the feedback circuit 5, turning the field-effect transistor 6 on.

[0035] When the LED load circuit 4 is short-circuited, i.e., when the auxiliary coil 32 of the boost inductor 3 stops operating, the voltage of the auxiliary coil 32 of the boost inductor 3 becomes zero, the signal of the auxiliary coil 32 received by the base of the first bipolar transistor 721 becomes low, the first bipolar transistor 721 is turned off, the first bipolar transistor 721 is not conductive, and the first bipolar transistor 721 does not transmit a signal to the circuit connected downstream. The base of the second bipolar transistor 722 receives a high-level signal from the DC power supply 723, the second bipolar transistor 722 becomes saturated, the collector of the second bipolar transistor 722 becomes low, and the gate of the field-effect transistor 6 receives a low-level signal, i.e., the gate of the field-effect transistor 6 is grounded and the field-effect transistor 6 is turned off. This prevents a large voltage generated by the short-circuit of the LED load circuit 4 from being directly applied to the field-effect transistor 6, thereby realizing short-circuit protection for the circuit. Furthermore, by using bipolar transistors to construct the voltage inverting circuit 72, a simple circuit structure and low cost can be realized.

[0036] Furthermore, the voltage inversion circuit 72 may also achieve inversion of the voltage signal using other components or circuits such as field effect transistors, integrated circuit chips, etc.

[0037] (Fourth embodiment) 3, 4 and 5, a fourth embodiment of the present invention further provides an LED power supply circuit 9 including the short-circuit protection circuit 1 of any one of the above-described first, second and third embodiments. The LED power supply circuit 9 turns off the field-effect transistor 6 when the LED load circuit 4 is short-circuited, thereby preventing a large voltage from being applied to the field-effect transistor 6, which would cause continuous heat generation and damage to electrical components in the circuit.

[0038] (Embodiment 5) A fifth embodiment of the present invention further provides an LED lighting fixture whose power supply circuit includes the short-circuit protection circuit 1 of any one of the first, second, and third embodiments, or whose power supply circuit is the LED power supply circuit 9 of the fourth embodiment. By turning off the field-effect transistor 6 when the LED load circuit 4 is short-circuited, the LED lighting fixture can prevent a large voltage from being applied to the field-effect transistor 6, which continues to generate heat and damages electrical components in the circuit, which in turn damages the structure of the LED lighting fixture and affects the service life of the LED lighting fixture.

[0039] It should be noted that throughout this specification, references to "an embodiment" or "an embodiment" indicate that the particular features, structures, functions, or characteristics described in that embodiment are included in combination in at least one embodiment of the present invention. Thus, the various appearances of the phrase "in an embodiment" in the specification do not necessarily all refer to the same embodiment of the present invention. Furthermore, particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, embodiment 1 and embodiment 2 may be combined as long as the two embodiments are not mutually exclusive.

[0040] Although the technical solutions of the present invention have been described above in conjunction with the drawings, those skilled in the art can easily understand that the scope of protection of the present invention is not limited to the specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent modifications or replacements to the relevant technical features, and all of the technical solutions after such modifications or replacements will fall within the scope of protection of the present invention. [Explanation of symbols]

[0041] 1 Short-circuit protection circuit 2 Power supply 21 Filter Circuit 3 Boost inductor 31 Main coil 32 Auxiliary coil 4 LED load circuit 41 Voltage dividing resistor 5 Feedback Circuit 51 Control IC chip 6. Field-effect transistor 7 Protection circuit 71 Diode 72 Voltage Inverter 721 First Bipolar Transistor 722 Second Bipolar Transistor 723 DC power supply 73 First Capacitor 8 Second Capacitor 9 LED power supply circuit

Claims

1. 1. A short circuit protection circuit, comprising: Power supply and a boost inductor connected to the power supply and having a main coil and an auxiliary coil; an LED load circuit connected to the main coil; a feedback circuit connected to the auxiliary coil; a field effect transistor having a drain connected to the LED load circuit, a gate connected to the auxiliary coil via the feedback circuit, and a source grounded; The short-circuit protection circuit further includes a protection circuit connected between the auxiliary coil and the gate of the field-effect transistor. Short circuit protection circuit.

2. The protection circuit further comprises: a diode having an anode connected to the auxiliary coil; a voltage inverting circuit connected between the cathode of the diode and the gate of the field effect transistor and connected to a DC power supply; a first capacitor having one end connected to the cathode of the diode and the other end grounded.

2. The short circuit protection circuit of claim 1.

3. The voltage inverting circuit further comprises: a first bipolar transistor having a base connected to the cathode of the diode, a collector connected to the DC power supply, and an emitter grounded; a second bipolar transistor having a base connected to the collector of the first bipolar transistor, a collector connected to the gate of the field effect transistor, and an emitter grounded.

3. The short circuit protection circuit of claim 2.

4. The short circuit protection circuit further comprises: and a second capacitor having one end connected to the main coil and the other end grounded. The short-circuit protection circuit according to any one of claims 1 to 3.

5. A short-circuit protection circuit according to any one of claims 1 to 4 is provided. LED power supply circuit.

6. A power supply circuit comprising the short-circuit protection circuit according to any one of claims 1 to 4. LED lighting fixture.

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