A LED load current sharing protection circuit

Abstract

The present invention discloses an LED load current sharing protection circuit, comprising: a power supply module; a circuit break detection module connected to an LED load branch and used to detect open circuit fault information or normal operation information of the LED load branch; a switch module connected to the power supply module and the circuit break detection module and used to disconnect according to an open circuit fault or close according to normal operation information; a constant current drive module connected to the switch module and the LED load branch and used to disconnect the constant current drive module from the power supply module when the switch module is disconnected; when the switch module is closed, the constant current drive module is connected to the power supply module via the switch module and drives the LED load branch; a current sharing module connected to the constant current drive module and used to be driven by the constant current drive module to achieve current sharing control for the LED load branch when the switch module is closed; the present invention can protect the LED load while achieving high-precision current sharing of multiple LED loads.

Description

Technical Field

[0001] The present invention belongs to the technical field of LED loads, and in particular relates to an LED load current sharing protection circuit. Background Art

[0002] Switching power supplies are a common application in circuits. They are widely used in various drive circuits due to their high efficiency and energy-saving advantages. To save circuit costs, it is important to maximize the use of switching circuits. LED load current sharing protection circuits are an example of this application in switching circuits. In a switching circuit, when there are a large number of LEDs in series and parallel, the number of LEDs in each branch of the LED load is different, and the models of LEDs connected in parallel in each branch of the LED load are different, current sharing in each branch becomes a major problem, resulting in the LED loads in the switching power supply having to be connected in series. In some fields, it is also required that if one LED load is disconnected, all LED loads are disconnected. For a switching power supply, disconnecting all LED loads at once is also a problem. In a switching power supply, when the LED load is divided into multiple branches, a certain voltage difference is generated due to the different number or model of LEDs in each branch, resulting in uneven current flow in each branch. The current shunting accuracy and cost of the existing technology increase proportionally. In a switching power supply, it is impossible to divide the LEDs into multiple branches and they can only be connected in series. Moreover, when one LED is disconnected, it is impossible to disconnect the protection of all LED loads. In some fields, it does not meet the lighting distribution requirements of customers. Summary of the Invention

[0003] In order to overcome the above technical defects, the present invention provides an LED load current sharing protection circuit, aiming to solve the above problems.

[0004] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0005] An LED load current sharing protection circuit is used to protect an LED load while achieving high-precision current sharing. The LED load includes one or more different LED load branches. The circuit includes:

[0006] Power module;

[0007] a circuit breaker detection module, connected to the LED load branch, for detecting open circuit fault information or normal working information of the LED load branch;

[0008] a switch module, connected to the power module and the circuit breaker detection module, configured to open the circuit according to the open circuit fault or close the circuit according to normal operating information;

[0009] a constant current driving module connected to the switch module and the LED load branch; when the switch module is disconnected, the constant current driving module is disconnected from the power module; when the switch module is closed, the constant current driving module is connected to the power module through the switch module and drives the LED load branch;

[0010] The current sharing module is connected to the constant current driving module and is used to realize current sharing control on the LED load branch under the drive of the constant current driving module when the switch module is closed.

[0011] As a further improvement of the present invention, the power supply module includes: a filtering and anti-reverse module;

[0012] The input end of the filtering and anti-reverse module is connected to the power module, and the output end of the filtering and anti-reverse module is connected to the switch module.

[0013] As a further improvement of the present invention, the current balancing module includes a current balancing resistor and a number of current balancing transistors with the same number as the LED load branches; one end of the current balancing resistor is connected to the base of the current balancing transistor, and the LED load branch is grounded through the CE junction of the current balancing transistor; the other end of the current balancing resistor is connected to the constant current driving module, so as to make the current balancing transistor operate in the amplification area when turned on and make the base current of the current balancing transistor consistent. Adjusting the resistance value of the resistor can achieve high-precision current balancing.

[0014] As a further improvement of the present invention, the circuit break detection module includes a detection transistor, a detection diode, a second MOS transistor, a third MOS transistor, a pull-up resistor, a first voltage divider resistor, and a second voltage divider resistor;

[0015] The number of the detection transistors and the detection diodes is the same as the number of the LED load branches; the base of the detection transistor is connected to the LED load branch, the emitter of the detection transistor is grounded, the collector of the detection transistor is connected to the positive end of the detection diode, the negative end of the detection diode is connected to the gate of a third MOS transistor, the source of the third MOS transistor is grounded, the drain of the third MOS transistor is connected to the gate of the second MOS transistor, the source of the second MOS transistor is grounded, and the drain of the second MOS transistor is connected to the switch module; the positive end of the detection diode is connected to the power module through the pull-up resistor; the gate of the second MOS transistor is grounded through the first voltage divider resistor, and the gate of the second MOS transistor is connected to the power module through the second voltage divider resistor.

[0016] As a further improvement of the present invention, the circuit break detection module further includes a base diode; each of the LED load branches is provided with the base diode; and the base of the detection transistor is grounded via the base diode.

[0017] As a further improvement of the present invention, the switch module includes a first MOS transistor; the gate of the first MOS transistor is connected to the drain of the second MOS transistor, the source of the first MOS transistor is connected to the power module, and the drain of the first MOS transistor is connected to the constant current drive module;

[0018] As a further improvement of the present invention, the filtering and anti-reverse module includes a first capacitor, a second capacitor, a bleeder resistor, a TVS tube, an anti-reverse diode, and a third capacitor;

[0019] The power supply module is grounded through the first capacitor and the second capacitor; the power supply module is grounded through the bleeder resistor; the power supply module is grounded through the TVS tube; the power supply module is grounded through the anti-reverse diode and the third capacitor; the negative end of the anti-reverse diode is the output of the filtering anti-reverse module.

[0020] As a further improvement of the present invention, the current-sharing transistor is an NPN transistor.

[0021] Compared with the prior art, the present invention has the following beneficial effects: first, the circuit break detection module detects whether the LED load branch is operating normally. When a fault occurs in a certain LED load branch, the fault information is fed back to the switch module, and the switch module directly shuts off the constant current output of the constant current drive module, thereby protecting the LED load; second, a constant current drive module and a current balancing module are provided. For a situation where there are multiple LED load branches and each LED load branch contains a different number of LEDs or different LED models, each LED load branch can achieve high-precision current balancing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0023] Figure 1 This is a structural block diagram of the LED load current sharing protection circuit described in Example 1;

[0024] Figure 2 This is a circuit schematic diagram of the LED load current sharing protection circuit described in Example 1;

[0025] Figure 3 This is a circuit diagram of the filtering and anti-reverse circuit described in Example 1;

[0026] Figure 4 This is a circuit schematic diagram of the switch module described in Example 1;

[0027] Figure 5 This is a circuit schematic diagram of the circuit break detection module described in Example 1;

[0028] Figure 6 This is a circuit schematic diagram of the LED load branch and the current balancing module described in Example 1.

[0029] Marking description: 1. Power module; 2. Filter and anti-reverse module; 3. Switch module; 4. Constant current drive module; 5. LED load branch; 6. Circuit break detection module; 7. Current sharing module. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] Example 1

[0032] This embodiment provides an LED load current sharing protection circuit for sharing the current of each branch load while protecting the LED load. The LED load includes one or more different LED load branches. The multi-channel LED load protection circuit includes:

[0033] Power module 1;

[0034] A circuit breaker detection module 6 is connected to the LED load branch 5 and is used to detect open circuit fault information or normal working information of the LED load branch 5;

[0035] The switch module 3 is connected to the power module 1 and the circuit breaker detection module 6, and is used to open according to an open circuit fault or close according to normal working information;

[0036] The constant current driving module 4 is connected to the switch module 3 and the LED load branch 5. When the switch module 3 is disconnected, the constant current driving module 4 is disconnected from the power module 1. When the switch module 3 is closed, the constant current driving module 4 is connected to the power module 1 through the switch module 3 and drives the LED load branch 5.

[0037] The current sharing module 7 is connected to the constant current driving module 4 and is used to realize current sharing control on the LED load branch 5 under the drive of the constant current driving module 4 when the switch module 3 is closed.

[0038] Specifically, the bases of the current-sharing transistors are connected to the current-sharing resistors to balance the voltage differences of the branches, thereby providing high-precision current-sharing control for the LED load branch 5 .

[0039] For example, in a multi-channel LED load, when a large number of LEDs are connected in series or parallel, the number of LEDs in each branch of the LED load varies, or the models of LEDs connected in parallel vary, current sharing within each LED load branch 5 becomes an urgent issue. This embodiment uses three LED load branches 5 as an example. The first LED load branch 5 comprises six LEDs connected in series (LED1, LED2, ..., LED6), the second LED load branch 5 comprises five LEDs connected in series (LED7, LED8, ..., LED11), and the third LED load branch 5 comprises four LEDs connected in series (LED12, LED13, ..., LED15). This embodiment is further described.

[0040] Specifically, the current-sharing module 7 includes a current-sharing resistor R14 and three current-sharing transistors: a seventh transistor Q7, an eighth transistor Q8, and a ninth transistor Q9. The current-sharing transistors can be, but are not limited to, NPN transistors. The first LED load branch 5 is grounded via the CE junction of the ninth transistor Q9, the second LED load branch 5 is grounded via the CE junction of the eighth transistor Q8, and the third LED load branch 5 is grounded via the CE junction of the seventh transistor Q7. The constant-current drive module 4 is connected to the bases of the seventh transistor Q7, the eighth transistor Q8, and the ninth transistor Q9 via the current-sharing resistor R14, ensuring that the current-sharing transistors operate in the amplification region when conducting. The bases of the branch transistors are connected together, and the current-sharing resistor R14 draws power from the LED input terminal. The resistance value of the current-sharing resistor R14 can be set according to the actual LED load conditions and can be used to adjust the current-sharing accuracy, so that the seventh transistor Q7, the eighth transistor Q8, and the ninth transistor Q9 are always in the amplification region. Since the bases of the seventh transistor Q7, the eighth transistor Q8, and the ninth transistor Q9 are the same, the collector currents are also the same, which can balance the voltage differences generated by each branch and achieve high-precision current sharing.

[0041] In the above embodiment, the power module 1 includes: a filter and anti-reverse module 2; the input end of the filter and anti-reverse module 2 is connected to the power module 1, and the output end of the filter and anti-reverse module 2 is connected to the switch module 3. The filter and anti-reverse module 2 includes a first capacitor C1, a second capacitor C2, a bleeder resistor R1, a TVS tube TVS1, an anti-reverse diode D1, and a third capacitor C3; the power module 1 is grounded through the first capacitor C1 and the second capacitor C2; the power module 1 is grounded through the bleeder resistor R1; the power module 1 is grounded through the TVS tube; the power module 1 is grounded through the anti-reverse diode D1 and the third capacitor C3; the negative end of the anti-reverse diode D1 is the output of the filter and anti-reverse module 2. The anti-reverse filter circuit can provide a stable power input for subsequent circuits.

[0042] In the above embodiment, the circuit breaker detection module 6 includes detection transistors (fourth transistor Q4, fifth transistor Q5, sixth transistor Q6), detection diodes (second diode D2, third diode D3, fourth diode D4), second MOS transistor Q2, third MOS transistor Q3, pull-up resistors (eighth resistor R8, ninth resistor R9, tenth resistor R10), first voltage divider resistor R6, second voltage divider resistor R5, base diodes (fifth diode D5 and sixth diode D6, seventh diode D7 and eighth diode D8, ninth diode D9 and tenth diode D10);

[0043] The base of the fourth transistor Q4 is connected to the negative terminal of LED6 in the first LED load branch 5, the emitter is grounded, and the collector is connected to the positive terminal of the second diode D2. The base of the fifth transistor Q5 is connected to the negative terminal of LED11 in the second LED load branch 5, the emitter is grounded, and the collector is connected to the positive terminal of the third diode D3. The base of the sixth transistor Q6 is connected to the negative terminal of LED15 in the third LED load branch 5, the emitter is grounded, and the collector is connected to the positive terminal of the fourth diode D4. The negative terminals of the second diode D2, the third diode D3, and the fourth diode D4 are all connected to the gate of the third MOS transistor Q3. The source of the third MOS transistor Q3 is grounded. The drain of the third MOS transistor Q3 is connected to the gate of the second MOS transistor Q2. The source of the second MOS transistor Q2 is grounded. The drain of the second MOS transistor Q2 is connected to the switch module 3. The gate of the second MOS transistor Q2 is grounded via a first voltage divider resistor R6. The gate of the second MOS transistor Q2 is connected to the power module 1 via a second voltage divider resistor R5.

[0044] The base of the detection transistor is grounded through a group of base diodes and current-sharing transistors. The sum of the voltage drops of the base diodes and the current-sharing transistors is the base of the detection transistor. The sum of the voltage drops of the base diodes and the current-sharing transistors only needs to meet the conduction voltage drop of the detection transistor.

[0045] In the above embodiment, the switch module 3 includes a first MOS transistor Q1 ; the gate of the first MOS transistor Q1 is connected to the drain of the second MOS transistor Q2 , the source of the first MOS transistor Q1 is connected to the power module 1 , and the drain of the first MOS transistor Q1 is connected to the constant current drive module 4 .

[0046] Specifically, in the circuit breaker detection module 6, the base diode provides a detection voltage for the detection transistor. When the LED loads of each branch are working normally, the voltage detected by the base of the detection transistors Q4, Q5, and Q6 is the sum of the voltage drops of the base diodes and the current-sharing transistors of the LED loads of each branch. The sum of the voltage drops satisfies the conduction voltage drop of the detection transistor. At this time, the detection transistors Q4, Q5, and Q6 are turned on, and the voltage of the collector of the detection transistor is pulled to the ground, outputting a low level to the detection diodes D2, D3, and D4 to the third MOS transistor Q3. Q3 can be, but is not limited to, N-MOS, since the MOS tube is a voltage-controlled device, at this time there is no conduction voltage difference between the gate and source of Q3, Q3 is in the cut-off region, and the drain feeds back a high level to the second N-MOS MOS tube Q2. There is a conduction voltage difference between the gate and source of Q2, Q2 is in the on state, the drain of Q2 is pulled to the ground, and a low level is fed back to the gate of the first P-MOS MOS tube Q1 in the switch module 3. There is a conduction voltage difference between the gate and source of Q1, Q1 is turned on and provides operating voltage to the constant current drive module 4, and the LED load works normally.

[0047] More specifically, taking the case where an LED in the second LED load branch 5 is broken as an example, the base detection voltage of the transistor Q8 is in a floating state, and the collector provides a high level to the diode D3 through the pull-up resistor R9. The gate of the Q3 N-MOS is also at a high level, Q3 is turned on, and the drain of Q3 is pulled to the ground, outputting a low level to the Q2 N-MOS. Q2 does not conduct due to the lack of a voltage difference, and then the drain of Q2 outputs a high level to the switch module 3Q1 P-MOS. The voltage difference between the gate and source of Q1 is much smaller than the conduction voltage difference of the MOS, and the switch module 3Q1 is turned off. As a result, the constant current drive module 4 stops working due to the lack of operating voltage, and the entire LED load branch 5 is in a turned-off state.

[0048] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Therefore, any modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An LED load current sharing protection circuit for protecting an LED load, wherein the LED load includes one or more LED load branches of different models, characterized in that: The circuit comprises: Power module; a circuit breaker detection module, connected to the LED load branch, for detecting open circuit fault information or normal working information of the LED load branch; a switch module, connected to the power module and the circuit breaker detection module, configured to open the circuit according to the open circuit fault information or close the circuit according to normal operating information; a constant current driving module connected to the switch module and the LED load branch; when the switch module is disconnected, the constant current driving module is disconnected from the power module; when the switch module is closed, the constant current driving module is connected to the power module through the switch module and outputs a constant current to drive the LED load branch; a current sharing module connected to the constant current driving module, and configured to realize current sharing control for the LED load branch under the drive of the constant current driving module when the switch module is closed; The current balancing module includes a current balancing resistor and a number of current balancing transistors, the same number as the LED load branches; one end of the current balancing resistor is connected to the base of the current balancing transistor, and the LED load branch is grounded through the CE junction of the current balancing transistor; the other end of the current balancing resistor is connected to the constant current driving module, so as to allow the current balancing transistor to operate in the amplification area and have equal base current when turned on; the resistance value of the current balancing resistor is determined according to the LED load branch, and the current balancing resistor is used to adjust the current balancing accuracy.

2. The LED load current sharing protection circuit according to claim 1, characterized in that: The power supply module includes: a filtering and anti-reverse module; The input end of the filtering and anti-reverse module is connected to the power module, and the output end of the filtering and anti-reverse module is connected to the switch module.

3. The LED load current sharing protection circuit according to claim 1, characterized in that: The disconnection detection module includes a detection transistor, a detection diode, a second MOS transistor, a third MOS transistor, a pull-up resistor, a first voltage-dividing resistor, and a second voltage-dividing resistor; The number of the detection transistors and the detection diodes is the same as the number of the LED load branches; the base of the detection transistor is connected to the LED load branch, the emitter of the detection transistor is grounded, the collector of the detection transistor is connected to the positive end of the detection diode, the negative end of the detection diode is connected to the gate of a third MOS transistor, the source of the third MOS transistor is grounded, the drain of the third MOS transistor is connected to the gate of the second MOS transistor, the source of the second MOS transistor is grounded, and the drain of the second MOS transistor is connected to the switch module; the positive end of the detection diode is connected to the power module through the pull-up resistor; the gate of the second MOS transistor is grounded through the first voltage divider resistor, and the gate of the second MOS transistor is connected to the power module through the second voltage divider resistor.

4. The LED load current sharing protection circuit according to claim 3, characterized in that: The disconnection detection module further includes a base diode; each of the LED load branches is provided with the base diode; and the base of the detection transistor is grounded via the base diode.

5. The LED load current sharing protection circuit according to claim 3, characterized in that: The switch module includes a first MOS tube; the gate of the first MOS tube is connected to the drain of the second MOS tube, the source of the first MOS tube is connected to the power module, and the drain of the first MOS tube is connected to the constant current drive module.

6. The LED load current sharing protection circuit according to claim 2, characterized in that: The filtering and anti-reverse module includes a first capacitor, a second capacitor, a bleeder resistor, a TVS tube, an anti-reverse diode, and a third capacitor; The power supply module is grounded through the first capacitor and the second capacitor; the power supply module is grounded through the bleeder resistor; the power supply module is grounded through the TVS tube; the power supply module is grounded through the anti-reverse diode and the third capacitor; the negative end of the anti-reverse diode is the output of the filtering anti-reverse module.

7. The LED load current sharing protection circuit according to claim 2, characterized in that: The current-sharing transistor is an NPN transistor.

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