Current limiting circuit, lighting driving circuit and lighting device

Abstract

The invention belongs to the technical field of power electronics, and particularly provides a current limiting circuit, a lighting driving circuit and lighting equipment, the current limiting circuit is provided with a current limiting control loop and a short circuit control loop, and under the condition that a power supply loop is not short-circuited, the current limiting control loop is controlled by a switching module to act on a current limiting module, so that the current limiting control loop is controlled to act on the lighting driving circuit; the current of the power supply loop is limited below a first preset current, and under the condition that the power supply loop is short-circuited, the switching module controls the current-limiting control loop to stop acting on the current-limiting module, so that the short-circuit control loop acts on the current-limiting module, and the current of the power supply loop is limited below a second preset current. Under normal current-limiting and short-circuit current-limiting working conditions, corresponding current-limiting values are directly adjusted according to corresponding current-limiting requirements, actual current-limiting fluctuation is reduced, the service life of a product is prolonged, and the energy efficiency of the product is improved.

Description

Technical Field

[0001] This application belongs to the technical field of electronic circuits, and particularly relates to a current-limiting circuit, a lighting drive circuit, and a lighting device. Background Art

[0002] The DALI (Digital Addressable Lighting Interface) protocol is an internationally public lighting control protocol that defines the digital communication method between lighting devices (drive circuits for various lamps) and control devices (such as lighting controllers). Among them, the DALI protocol stipulates that the current of each lighting interface cannot exceed 250 mA, which means that the control device (host) can not only communicate but also limit the current of the lighting interface. Usually, semiconductor devices are used to configure current limiting. However, because the actual parameters of the semiconductor devices during operation cannot be determined or fluctuate, the actual current limiting fluctuates unstably, which is not conducive to debugging and damages the product life. In addition, the current limiting fluctuation will also cause the temperature of the semiconductor devices to rise, which is not conducive to the reliability and energy efficiency of the products. Summary of the Invention

[0003] The purpose of this application is to provide a current-limiting circuit, a lighting drive circuit, and a lighting device, aiming to solve the problem that the actual current limiting of the current-limiting scheme in the prior art fluctuates unstably, which is not conducive to debugging and temperature control, and will damage the product life and energy efficiency.

[0004] In a first aspect, an embodiment of this application provides a current-limiting circuit, including a current-limiting control, a short-circuit control loop, a current-limiting module, and a switching module;

[0005] The current-limiting module is connected in series with the load on the power supply loop;

[0006] The switching module is connected to the current-limiting control loop and the current-limiting module, and is used to control the current-limiting control loop to be coupled to the current-limiting module when the power supply loop does not have a short circuit; and is used to control the current-limiting control loop to stop being coupled to the current-limiting module when the power supply loop has a short circuit;

[0007] The current-limiting control loop is used to act on the current-limiting module when coupled to the current-limiting module, and limit the current of the power supply loop below a first preset current;

[0008] The short-circuit control loop is connected to the current-limiting module, and is used to act on the current-limiting module when the power supply loop has a short circuit, and limit the current of the power supply loop below a second preset current.

[0009] In one embodiment, the current limiting module includes a first switching tube and a current limiting resistor. The load, the first switching tube, and the current limiting resistor are connected in series between the positive and negative poles of the power supply port. The switching module is connected between the connection node of the load and the first switching tube. The input end of the current limiting control loop and the input end of the short - circuit control loop are connected to the series node of the first switching tube and the current limiting resistor. The output end of the current limiting control loop is connected to the control end of the first switching tube through the switching module, and the output end of the short - circuit control loop is connected to the control end of the first switching tube.

[0010] In one embodiment, the current limiting control loop accesses a first reference voltage. Specifically, when coupled to the current limiting module, the current limiting control loop forms a negative feedback loop, generating a first voltage applied to the current limiting module to limit the current in the power supply circuit below a first preset current.

[0011] In one embodiment, the short - circuit control loop accesses a second reference voltage. Specifically, when a short - circuit occurs in the power supply circuit, the short - circuit control loop forms a negative feedback loop, generating a second voltage applied to the current limiting module to limit the current in the power supply circuit below a second preset current.

[0012] In one embodiment, the current limiting control loop includes a first voltage comparator and a first unidirectional conduction device. The non - inverting input terminal of the first voltage comparator accesses the first reference voltage, the inverting input terminal is connected to the series node, and the output terminal is connected to the switching module. The first unidirectional conduction device is connected between the switching module and the control end of the first switching tube.

[0013] In one embodiment, the short - circuit control loop includes a second voltage comparator and a second unidirectional conduction device. The non - inverting input terminal of the second voltage comparator accesses the second reference voltage, the inverting input terminal is connected to the series node, and the output terminal is connected to the control end of the first switching tube through the second unidirectional conduction device.

[0014] In one embodiment, the switching module includes a first switching module and a second switching module. The first switching module is connected in series between the current limiting control loop and the current limiting module. The control end of the second switching module is connected to the connection node of the current limiting module and the load. The first end of the second switching module is connected to the control end of the first switching module, and the second end of the second switching module is connected to the positive or negative pole of the first power supply.

[0015] In one embodiment, the first switch module includes a second switching transistor, which is connected in series between the current limiting control loop and the current limiting module. The control terminal of the second switching transistor is connected to the first end of the second switch module.

[0016] The second switch module includes a third switching transistor and a fourth switching transistor. The control terminal of the third switching transistor forms the control terminal of the second switch module and is connected to the connection node. The first end of the third switching transistor forms the second end of the second switch module and is connected to the positive pole of the first power supply. The second end of the third switching transistor is connected to the control terminal of the fourth switching transistor. The first end of the fourth switching transistor forms the first end of the second switch module and is connected to the positive pole of the first power supply and the control terminal of the first switch module. The second end of the fourth switching transistor is connected to the negative pole of the first power supply.

[0017] In a second aspect, an embodiment of the present application provides an illumination driving circuit, which is connected to a light emitting device. The illumination driving circuit includes the current limiting circuit as described above, and the current limiting circuit is connected in series with the light emitting device on the power supply loop.

[0018] In a third aspect, an embodiment of the present application provides an illumination device, which includes a light emitting device and the current limiting circuit as described above. The current limiting circuit is connected in series with the light emitting device on the power supply loop.

[0019] Compared with the prior art, the beneficial effect of the chip testing device provided by the present application is that: by setting a current limiting control loop and a short - circuit control loop, when there is no short - circuit in the power supply loop, the current limiting control loop is controlled by the switching module to act on the current limiting module, and the current of the power supply loop is limited below a first preset current. When there is a short - circuit in the power supply loop, the current limiting control loop is controlled by the switching module to stop acting on the current limiting module, so that the short - circuit control loop acts on the current limiting module, and the current of the power supply loop is limited below a second preset current. In normal current limiting and short - circuit current limiting conditions, the corresponding current limiting values are directly adjusted according to the corresponding current limiting requirements, reducing the actual current limiting fluctuation and improving the product life and energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a schematic structural diagram of a current limiting circuit provided by an embodiment of the present application;

[0022] Figure 2 The structural schematic diagram of the current limiting circuit provided by an embodiment of the present application;

[0023] Figure 3 The structural schematic diagram of the current limiting circuit provided by an embodiment of the present application. Specific embodiments

[0024] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application.

[0025] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application 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 thus should not be construed as limiting the present application.

[0026] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0027] In the present application, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0028] Please refer to Figure 1 , an embodiment of the present application provides a current limiting circuit for a lighting device applicable to the DALI protocol. The current limiting circuit is connected in series with the light emitting device of the lighting device on the power supply loop. The current limiting circuit includes a current limiting control loop 110, a short circuit control loop 120, a current limiting module 130, and a switching module 140.

[0029] The current limiting module 130 is connected in series with the load 200 (such as a light emitting device) on the power supply circuit (i.e., between Vin and GND); the switching module 140 is connected to the current limiting control loop 110 and the current limiting module 130, and is used to control the current limiting control loop 110 to be coupled to the current limiting module 130 when there is no short circuit in the power supply circuit (mainly referring to a short circuit of the load 200); and is used to control the current limiting control loop 110 to stop being coupled to the current limiting module 130 when there is a short circuit in the power supply circuit; the current limiting control loop 110 is used to act on the current limiting module 130 when coupled to the current limiting module 130 to limit the current in the power supply circuit below a first preset current; the short circuit control loop 120 is connected to the current limiting module 130 and is used to act on the current limiting module 130 when there is a short circuit in the power supply circuit to limit the current in the power supply circuit below a second preset current.

[0030] Among them, the power supply voltage provided by the power supply port is almost loaded on the current limiting module 130, which can be considered a short circuit condition. The current limiting control loop 110 can work independently under non-short circuit conditions, and the short circuit control loop 120 can work independently under short circuit conditions, and the two will not interfere with each other. Moreover, the preset currents under different working conditions can be set independently. In addition, the circuit parameters of the current limiting control loop 110 and the short circuit control loop 120 can be adjusted respectively to configure the corresponding preset currents, and the current limiting value is set below the preset current to reduce the actual current limiting fluctuation, which is beneficial to debugging and temperature control, and improves the product life and energy efficiency.

[0031] Please refer to Figure 2 , in one embodiment, the current limiting module 130 includes a first switching transistor Q1 and a first current limiting resistor R1. The load 200, the first switching transistor Q1, and the first current limiting resistor R1 are connected in series between the positive and negative poles (Vin - GND) of the power supply port. The switching module 140 is connected to the connection node between the load 200 and the first switching transistor Q1. The input ends of the current limiting control loop 110 and the short circuit control loop 120 are connected to the series node of the first switching transistor Q1 and the first current limiting resistor R1. The output end of the current limiting control loop 110 is connected to the control end of the first switching transistor Q1 through the switching module 140, and the output end of the short circuit control loop 120 is connected to the control end of the first switching transistor Q1.

[0032] Exemplarily, the first switching transistor Q1 is, for example, a MOS transistor.

[0033] When the current in the power supply circuit is 0, both the current limiting control loop 110 and the short circuit control loop 120 can be coupled to the current limiting module 130. However, since there is no current in the power supply circuit, the current limiting control loop 110 and the short circuit control loop 120 do not start to feedback and regulate the current flowing through the first current limiting resistor R1.

[0034] When the current in the power supply circuit gradually increases, exceeds the second preset current and is lower than the first preset current, the switching module 140 controls the current limiting control loop 110 to act on the first switching transistor Q1 and the first current limiting resistor R1. At this time, the first switching transistor Q1 is fully turned on (operating in the variable resistance region), equivalent to a wire, and the short - circuit control loop 120 does not act on the first current limiting resistor R1. When the current in the power supply circuit attempts to exceed the first preset current, the voltage drop across the first current limiting resistor R1 increases, and the current limiting control loop 110 starts negative feedback regulation, controlling the first switching transistor Q1 to enter a semi - conducting state (operating in the saturation region) to limit the current in the power supply circuit, and finally making the voltage across the first current limiting resistor R1 stable at the first preset voltage, thereby limiting the current in the power supply circuit below the first preset current. This process can be called the normal current limiting working condition.

[0035] In the case of a short - circuit in the power supply circuit, the supply voltage is almost applied to the current limiting module 130. The switching module 140 controls the current limiting control loop 110 to stop acting on the current limiting module 130 according to this voltage, so that the short - circuit control loop 120 acts on the current limiting module 130. When the supply voltage is almost applied to the first current limiting resistor R1, the short - circuit control loop 120 starts negative feedback regulation, controlling the first switching transistor Q1 to enter a semi - conducting state to limit the current in the power supply circuit, and finally making the voltage across the first current limiting resistor R1 stable at the second preset voltage, thereby limiting the current in the power supply circuit below the second preset current. This process can be called the short - circuit current limiting working condition.

[0036] It can be understood that whether it is the normal current limiting working condition or the short - circuit current limiting working condition, the current limiting is mainly achieved by controlling the conduction degree of the first switching transistor Q1 through the current limiting control loop 110 or the short - circuit control loop 120.

[0037] Please refer to Figure 3 , in one of the embodiments, the current limiting control loop 110 is connected to the first reference voltage V1 (i.e., the above - mentioned first preset voltage). The current limiting control loop 110 is specifically used for forming a negative feedback loop when coupled to the current limiting module 130, generating a first voltage applied to the current limiting module 130 to limit the current in the power supply circuit below the first preset current.

[0038] The current limiting control loop 110 is specifically used for forming a negative feedback loop in response to the current applied to the current limiting module 130 (specifically the first current limiting resistor R1) when coupled to the current limiting module 130, generating a first voltage applied to the current limiting module 130.

[0039] In one embodiment, the current limiting control loop 110 forms a negative feedback loop. The negative input terminal and the output terminal are connected through the conducting first switching transistor Q1, and the voltage applied to the first current limiting resistor R1 is accessed. The positive input terminal is connected to the first reference voltage V1. Through negative feedback regulation, finally, the first voltage is applied to the current limiting module 130 (specifically, the first switching transistor Q1), achieving the purpose of limiting the current below the first preset current.

[0040] When the current in the power supply circuit attempts to or just exceeds the first preset current, initially, the voltage at the negative input terminal of the negative feedback loop is greater than the first reference voltage V1. Through negative feedback regulation, the first switching transistor Q1 is controlled to operate in a semi-conducting state. Finally, the voltage across the two ends of the first current limiting resistor R1 is stabilized at the first reference voltage V1, that is, the voltages at the positive and negative input terminals of the negative feedback loop gradually stabilize at the same voltage, making the current in the power supply circuit stable. Therefore, the magnitude of the first preset current can be adjusted by adjusting the magnitude of the first reference voltage V1. Exemplarily, the first preset current is set to 250 mA, the first current limiting resistor R1 is 5 ohms, the first reference voltage V1 is set to 1.24 V. When the voltage across the two ends of the first current limiting resistor R1 is stabilized at the first reference voltage V1, the current flowing through the first current limiting resistor R1 is 248 mA, which is less than the first preset current.

[0041] Please refer to Figure 3 , in one embodiment, the short-circuit control loop 120 accesses the second reference voltage V2 (i.e., the above-mentioned second preset voltage). The short-circuit control loop 120 is specifically configured to form a negative feedback loop in the case of a short circuit in the power supply circuit, and form a second voltage applied to the current limiting module 130 to limit the current in the power supply circuit below the second preset current.

[0042] The short-circuit control loop 120 is specifically configured to, when coupled to the current limiting module 130, in response to the current applied to the current limiting module 130 (specifically, the first current limiting resistor R1), form a negative feedback loop and form a second voltage applied to the current limiting module 130.

[0043] In one embodiment, the short-circuit control loop 120 forms a negative feedback loop. The negative input terminal and the output terminal are connected through the conducting first switching transistor Q1, and the voltage applied to the first current limiting resistor R1 is accessed. The positive input terminal is connected to the second reference voltage V2. Through negative feedback regulation, a second voltage is formed and applied to the current limiting module 130 (specifically, the first switching transistor Q1), achieving the purpose of limiting the current below the second preset current.

[0044] In the case of a short circuit in the power supply loop, the supply voltage is almost applied to the current limiting module 130 (the voltage at the negative input terminal of the negative feedback loop is greater than the second reference voltage V2). The switching module 140 controls the current limiting loop to stop acting on the current limiting module 130. At this time, the short circuit control loop 120 acts on the current limiting module 130 to start negative feedback regulation, controls the first switching transistor Q1 to operate in a semi-conducting state, and finally stabilizes the voltage across the first current limiting resistor R1 at the second reference voltage V2, that is, the positive and negative input terminal voltages of the negative feedback loop gradually stabilize at the same voltage, so that the current in the power supply loop stabilizes. Therefore, the magnitude of the second preset current can be adjusted by adjusting the magnitude of the second reference voltage V2. Exemplarily, the second preset current is set to 60 mA, the first current limiting resistor R1 is 5 ohms, the first reference voltage V1 is set to 0.3 V, and when the voltage across the first current limiting resistor R1 stabilizes at the second reference voltage V2, the current flowing through the first current limiting resistor R1 is 60 mA.

[0045] Please refer to Figure 3 , in one embodiment, the current limiting control loop 110 includes a first voltage comparator U1 and a first unidirectional conduction device D1. The non-inverting input terminal of the first voltage comparator U1 is connected to the first reference voltage V1, the inverting input terminal of the first voltage comparator U1 is connected to the series node B of the first switching transistor Q1 and the first current limiting resistor R1, the output terminal of the first voltage comparator U1 is connected to the switching module 140, and between the input terminal of the first unidirectional conduction device D1 connected to the switching module 140 and the control terminal of the first switching transistor Q1.

[0046] In this embodiment, the first voltage comparator U1 includes a first operational amplifier, and the first unidirectional conduction device D1 includes a first diode. The first unidirectional conduction device D1 functions to prevent reverse current injection. Optionally, the current limiting control loop 110 further includes a second current limiting resistor R2, which is connected in series at the output terminal of the first unidirectional conduction device D1 and is used to suppress the current supplied to the first switching transistor Q1 and plays a protective role.

[0047] Exemplarily, the non-inverting input terminal of the first operational amplifier is connected to the first reference voltage V1, the inverting input terminal of the first operational amplifier is connected to the series node B of the first current limiting resistor R1 and the first switching transistor Q1, and the output terminal of the first operational amplifier, the switching module 140, the first unidirectional conduction device D1, the second current limiting resistor R2 and the control terminal of the first switching transistor Q1 are connected in sequence. The switching module 140 is used to control whether the output terminal of the first operational amplifier is connected to the control terminal of the first switching transistor Q1 to implement whether the current limiting control loop 110 is coupled to the current limiting module 130.

[0048] Exemplarily, the operating voltage of the first voltage comparator U1 can be directly provided by the power supply interface of the power supply loop, such as 16 V and 0 V voltages.

[0049] Please refer to Figure 3 In one embodiment, the short - circuit control loop 120 includes a second voltage comparator U2 and a second unidirectional conduction device D2. The non - inverting input terminal of the second voltage comparator U2 is connected to a second reference voltage V2. The inverting input terminal of the second voltage comparator U2 is connected to the series node B of the first switching transistor Q1 and the first current - limiting resistor R1. The output terminal of the second voltage comparator U2 is connected to the control terminal of the first switching transistor Q1 through the second unidirectional conduction device D2.

[0050] In this embodiment, the second voltage comparator U2 includes a second operational amplifier, and the second unidirectional conduction device D2 includes a second diode. The second unidirectional conduction device D2 functions to prevent reverse charging. Optionally, the short - circuit control loop 120 further includes a third current - limiting resistor R3. The third current - limiting resistor R3 is connected in series at the output terminal of the second unidirectional conduction device D2 to suppress the current provided to the first switching transistor Q1 and play a protective role.

[0051] Exemplarily, the non - inverting input terminal of the second operational amplifier is connected to the second reference voltage V2, the inverting input terminal of the second operational amplifier is connected to the series node B of the first current - limiting resistor R1 and the first switching transistor Q1, and the output terminal of the second operational amplifier, the second unidirectional conduction device D2, the third current - limiting resistor R3 and the control terminal of the first switching transistor Q1 are connected in sequence.

[0052] Exemplarily, the operating voltage of the second voltage comparator U2 can be directly provided by the power supply interface of the power supply circuit, such as 16V and 0V voltages.

[0053] Please refer to Figure 3 In one embodiment, the switching module 140 includes a first switching module (Q2) and a second switching module (Q3, Q4). The first switching module is connected in series between the current - limiting control loop 110 and the current - limiting module 130. The control terminal of the second switching module is connected to the connection node A between the current - limiting module 130 and the load 200. The first terminal of the second switching module is connected to the control terminal of the first switching module, and the second terminal of the second switching module is connected to the positive or negative pole of the first power supply V0. In other embodiments, the switching module 140 can also be composed of one or more switching transistors. The present application does not limit the number and type selection of the switching transistors of the switching module 140, as long as it can cooperate to implement the control logic of the present application.

[0054] In one embodiment, the first switching module includes a second switching transistor Q2. The second switching transistor Q2 is connected in series between the current limiting control loop 110 and the current limiting module 130. The control terminal of the second switching transistor Q2 is connected to the first end of the second switching module. The second switching module includes a third switching transistor Q3 and a fourth switching transistor Q4. The control terminal of the third switching transistor Q3 forms the control terminal of the second switching module and is connected to the connection node A between the current limiting module 130 and the load 200. The first end of the third switching transistor Q3 forms the second end of the second switching module and is connected to the positive pole of the first power supply V0. The second end of the third switching transistor Q3 is connected to the control terminal of the fourth switching transistor Q4. The first end of the fourth switching transistor Q4 forms the first end of the second switching module and is connected to the positive pole of the first power supply and the control terminal of the first switching module. The second end of the fourth switching transistor Q4 is connected to the negative pole (i.e., grounded) of the first power supply V0.

[0055] Exemplarily, the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4 are a P-channel MOS transistor, a P-channel MOS transistor, and an N-channel MOS transistor respectively. The source of the second switching transistor Q2 is connected to the output terminal of the first operational amplifier. The drain of the second switching transistor Q2 is connected to the anode of the first diode. The gate of the second switching transistor Q2 is connected to the drain of the fourth switching transistor Q4 through a resistor R4. The drain of the fourth switching transistor Q4 is connected to the positive pole of the first power supply V0 through a resistor R5, such as the power supply interface of the power supply circuit. The source of the fourth switching transistor Q4 is grounded (i.e., the negative pole of the power supply interface). The gate of the fourth switching transistor Q4 is connected to the drain of the third switching transistor Q3 through a resistor R6. The drain of the third switching transistor Q3 is also grounded through a resistor R7. The source of the third switching transistor Q3 is connected to the positive pole of the first power supply. The gate of the third switching transistor Q3 is connected to the connection node A between the current limiting module 130 and the load 200.

[0056] Exemplarily, the input power supply Vin of the power supply circuit and the first power supply V0 can use the same voltage source. At this time, the voltage of the input power supply Vin is equal to the voltage of the first power supply V0.

[0057] In other embodiments, the selection of the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4 is not limited, as long as they can cooperate to implement the control logic of the present application.

[0058] Taking the first current limiting resistor R1 as 5 ohms, the first reference voltage V1 as 1.24V, the second reference voltage V2 as 0.3V, the first power supply as 16V, and the supply voltages of the second operational amplifier and the first operational amplifier as 16V, that is, the supply of the power supply circuit is also 16V as an example, the working process of the current limiting circuit is described in detail:

[0059] When initially powered on, the current in the power supply circuit is 0:

[0060] The gate voltage of the third switching transistor Q3 is 0, the third switching transistor Q3 conducts, the fourth switching transistor Q4 conducts, the second switching transistor Q2 conducts, and the output terminal of the first operational amplifier is connected to the control terminal of the first switching transistor Q1. The voltage across the first current-limiting resistor R1 is 0, the first voltage comparator U1 and the second operational amplifier both output 16V, and the first switching transistor Q1 is fully conducting, that is, both the short-circuit control loop 120 and the current-limiting control loop 110 are effective, but the feedback regulation has not started yet.

[0061] When the current in the power supply circuit increases and exceeds 60 mA:

[0062] The gate voltage of the third switching transistor Q3 is approximately 0.3V, the third switching transistor Q3 conducts, the fourth switching transistor Q4 conducts, the second switching transistor Q2 conducts, and the output terminal of the first voltage comparator U1 is connected to the control terminal of the first switching transistor Q1. The second operational amplifier outputs a low voltage of 0V, and the first operational amplifier outputs a high level of 16V. Due to the presence of the second diode D2, the 16V output by the first operational amplifier controls the first switching transistor Q1 to be fully conducting. The first switching transistor Q1 is equivalent to a wire, and the current-limiting loop loses its regulating function at this time. The current-limiting control loop 110 is still effective, but the feedback regulation has not started yet.

[0063] When the current in the power supply circuit continues to increase and exceeds 250 mA:

[0064] The gate voltage of the third switching transistor Q3 is approximately 1.24V, the third switching transistor Q3 conducts, the fourth switching transistor Q4 conducts, the second switching transistor Q2 conducts, and the output terminal of the first voltage comparator U1 is connected to the control terminal of the first switching transistor Q1;

[0065] The second operational amplifier still outputs a low level of 0V and is in an ineffective state; the output voltage of the first voltage comparator U1 gradually decreases, and the first switching transistor Q1 gradually cuts off to a semi-conducting state. The current-limiting control loop 110 is effective, and the current in the power supply circuit (1.24V / 5Ω = 248 mA) is limited to less than 250 mA, which conforms to the DALI protocol.

[0066] Exemplarily, if the equivalent impedance of the load 200 becomes smaller (for example, several light-emitting devices are connected in parallel), the current flowing through the load 200 and the first current-limiting resistor R1 increases. When the voltage across the first current-limiting resistor R1 is greater than 1.24V, the negative feedback loop will be triggered, the voltage output by the first voltage comparator U1 becomes smaller, which will cause the first switching transistor Q1 to enter a semi-conducting state, and the current flowing through the load 200 and the first current-limiting resistor R1 will become smaller again. Eventually, the voltage across the first current-limiting resistor R1 will be equal to the first reference voltage V1, and the current in the power supply circuit will stabilize.

[0067] When an abnormal short circuit occurs in the power supply circuit:

[0068] At this time, the gate voltage of the third switching transistor Q3 approaches 16V, the third switching transistor Q3 becomes cut-off, the fourth switching transistor Q4 is cut-off, the second switching transistor Q2 is cut-off, the output terminal of the first voltage comparator U1 is disconnected from the control terminal of the first switching transistor Q1, the current limiting control loop 110 fails, and the output of the first voltage comparator U1 no longer affects the first switching transistor Q1. The output of the second operational amplifier starts to control the first switching transistor Q1, and the short-circuit control loop 120 starts feedback regulation, and the current of the power supply circuit is limited to a preset 60 mA (0.3V / 5Ω = 60 mA).

[0069] It can be understood that if the short circuit returns to normal, the working state of the current limiting circuit enters one of the above working states according to the connected lighting device. The current limit value during the short circuit can be changed by modifying the second reference voltage V2, and the negative feedback loop will automatically adjust to finally limit the current of the power supply circuit to the second preset current.

[0070] In a second aspect, an embodiment of the present application provides a lighting drive circuit. The lighting drive circuit is connected to a light emitting device. The lighting drive circuit includes the current limiting circuit as described above. The current limiting circuit is connected in series with the light emitting device on the power supply circuit.

[0071] In a third aspect, an embodiment of the present application provides a lighting device. The lighting device includes a light emitting device and the current limiting circuit as described above. The current limiting circuit is connected in series with the light emitting device on the power supply circuit.

[0072] Compared with the prior art, the beneficial effects of the chip testing device provided by the present application are as follows: By setting the current limiting control loop 110 and the short-circuit control loop 120, when there is no short circuit in the power supply circuit, the current limiting control loop 110 is controlled by the switching module 140 to act on the current limiting module 130 to limit the current of the power supply circuit below the first preset current. When a short circuit occurs in the power supply circuit, the current limiting control loop 110 is controlled by the switching module 140 to stop acting on the current limiting module 130, so that the short-circuit control loop 120 acts on the current limiting module 130 to limit the current of the power supply circuit below the second preset current. In normal current limiting and short-circuit current limiting conditions, the corresponding reference voltage is directly adjusted according to the corresponding current limiting requirements to adjust the current limit value. Moreover, the current limiting control loop 110 and the short-circuit control loop 120 do not require semiconductor devices to configure the current limit, avoiding the actual unstable current limit caused by the use of semiconductor devices, reducing the actual current limit fluctuation, and improving the product life and energy efficiency.

[0073] It should be noted that the above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A current limiting circuit, characterized in that: It includes a current limiting control loop, a short-circuit control loop, a current limiting module and a switching module; The current limiting module and the load are connected in series on the power supply circuit; The switching module is connected to the current limiting control loop and the current limiting module, and is used to control the current limiting control loop to couple to the current limiting module when the power supply loop is not short-circuited; and is used to control the current limiting control loop to stop coupling to the current limiting module when the power supply loop is short-circuited; The current limiting control loop is used to act on the current limiting module when coupled to the current limiting module, so as to limit the current of the power supply circuit to below a first preset current; The short-circuit control loop is connected to the current limiting module, and is used to act on the current limiting module to limit the current of the power supply circuit to below a second preset current when a short circuit occurs in the power supply circuit.

2. The current limiting circuit according to claim 1, characterized in that: The current limiting module includes a first switch tube and a current limiting resistor. The load, the first switch tube and the current limiting resistor are connected in series between the positive and negative electrodes of the power supply port in sequence. The switching module is connected between the connection node between the load and the first switch tube. The input end of the current limiting control loop and the input end of the short-circuit control loop are connected to the series node of the first switch tube and the current limiting resistor. The output end of the current limiting control loop is connected to the control end of the first switch tube through the switching module, and the output end of the short-circuit control loop is connected to the control end of the first switch tube.

3. The current limiting circuit according to claim 1, characterized in that: The current limiting control loop is connected to a first reference voltage. The current limiting control loop is specifically used to form a negative feedback loop when coupled to the current limiting module, forming a first voltage loaded on the current limiting module to limit the current of the power supply loop to within a first preset current.

4. The current limiting circuit according to claim 1, characterized in that: The short-circuit control loop is connected to a second reference voltage. The short-circuit control loop is specifically used to form a negative feedback loop when a short circuit occurs in the power supply circuit, so as to form a second voltage loaded on the current limiting module to limit the current of the power supply circuit to below a second preset current.

5. The current limiting circuit according to any one of claims 1 to 4, characterized in that: The current limiting control loop includes a first voltage comparator and a first unidirectional conductive device, wherein the first voltage comparator has a non-inverting input terminal connected to a first reference voltage, a reverse input terminal connected to the series node, an output terminal connected to the switching module, and the first unidirectional conductive device connected between the switching module and the control terminal of the first switch tube.

6. The current limiting circuit according to any one of claims 1 to 4, characterized in that: The short-circuit control loop includes a second voltage comparator and a second unidirectional conducting device, the in-phase input terminal of the second voltage comparator is connected to a second reference voltage, the inverting input terminal is connected to the series node, and the output terminal is connected to the control terminal of the first switch tube through the second unidirectional conducting device.

7. The current limiting circuit according to any one of claims 1 to 4, characterized in that: The switching module includes a first switch module and a second switch module, the first switch module is connected in series between the current limiting control loop and the current limiting module, the control end of the second switch module is connected to the connection node between the current limiting module and the load, the first end of the second switch module is connected to the control end of the first switch module, and the second end of the second switch module is connected to the positive or negative pole of the first power supply.

8. The current limiting circuit according to claim 7, characterized in that: The first switch module includes a second switch tube, the second switch tube is connected in series between the current limiting control loop and the current limiting module, and the control end of the second switch tube is connected to the first end of the second switch module; The second switch module includes a third switch tube and a fourth switch tube. The control end of the third switch tube constitutes the control end of the second switch module and is connected to the connection node. The first end of the third switch tube constitutes the second end of the second switch module and is connected to the positive electrode of the first power supply. The second end of the third switch tube is connected to the control end of the fourth switch tube. The first end of the fourth switch tube constitutes the first end of the second switch module and is connected to the positive electrode of the first power supply and the control end of the first switch module. The second end of the fourth switch tube is connected to the negative electrode of the first power supply.

9. A lighting driving circuit, characterized in that: The lighting driving circuit is connected to the light emitting device, and the lighting driving circuit comprises the current limiting circuit according to any one of claims 1 to 8, and the current limiting circuit and the light emitting device are connected in series on a power supply circuit.

10. A lighting device, characterized in that: The lighting device comprises a light-emitting device and a current-limiting circuit as claimed in any one of claims 1 to 8, wherein the current-limiting circuit and the light-emitting device are connected in series on a power supply circuit.

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