LED dynamic switching protection circuit and control method

Abstract

The invention relates to a control circuit for a switching circuit. The switching circuit receives an input signal and converts the input signal into an output current flowing through an LED load by controlling on and off of at least one switch. Wherein the control circuit comprises an error amplification circuit, a current control circuit and an overcurrent control circuit, and the error amplification circuit receives a detection signal representing output current and a reference signal and compares the detection signal with the reference signal to generate a current control signal. The current control circuit receives a current control signal and a triangular wave signal, and generates a switch control signal according to the current control signal and the triangular wave signal to control the on and off of the at least one switch. The over-current control circuit controls the current control signal according to a comparison result of the detection signal and the over-current signal, and when the detection signal is larger than the over-current signal, the current control signal is reduced to a preset voltage. According to the technical scheme, rapid adjustment of the output current when the load LED changes is achieved, and the reliability and the service life of the LED are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to a control circuit for a switching circuit used to drive an LED load. Background Technology

[0002] In modern LED applications, switching circuits are widely used to drive matrix headlights (ADB) and various LED strings. These applications require frequent and rapid switching of the number of LEDs to meet varying brightness requirements. However, in existing technologies, whenever the number of LEDs in a string decreases, the constant current drive loop of the switching circuit cannot keep up with the sudden voltage change across the LED string, resulting in a large current surge on the LEDs. This overcurrent phenomenon persists for a long time, accelerating the aging of the LED chips, severely impacting their long-term reliability and lifespan, and increasing equipment maintenance costs and replacement frequency.

[0003] Therefore, a control circuit for driving LED load switching circuitry is needed, whose control circuitry can reduce the duration of overcurrent and effectively protect the LED string. Summary of the Invention

[0004] The main objective of this invention is to provide a control circuit for a switching circuit, wherein the switching circuit has an input terminal for receiving an input signal and an output terminal for providing an output current. The switching circuit includes at least one switch, and converts the input signal into an output current flowing through an LED load by controlling the on and off states of the at least one switch. The control circuit includes: an error amplifier circuit that receives a detection signal and a reference signal characterizing the output current and compares them to generate a current control signal; a current control circuit that receives the current control signal and a triangular wave signal, and generates a switch control signal based on the current control signal and the triangular wave signal to control the on and off states of the at least one switch; and an overcurrent control circuit that receives a detection signal and an overcurrent signal, and controls the current control signal based on the comparison result of the detection signal and the overcurrent signal, wherein when the detection signal is greater than the overcurrent signal, the current control signal is reduced to a preset voltage.

[0005] This invention employs a switching circuit to rapidly reduce the output current when it exceeds a certain value, thereby minimizing current spikes. The current control circuit achieves high-precision regulation of the output current, and the overcurrent control circuit quickly adjusts the output current upon detecting a current spike. This significantly shortens the LED overcurrent time, substantially reducing the risk of accelerated aging of the LED chip due to overcurrent, thus improving the reliability and lifespan of the LED over long-term use. Attached Figure Description

[0006] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0007] Figure 1 A schematic diagram of the circuit structure of a control circuit for a switching circuit according to an embodiment of the present invention is provided;

[0008] Figure 2 Given Figure 1 The waveform diagram of each signal in the control circuit shown;

[0009] Figure 3 A schematic diagram of the circuit structure of a control circuit for a switching circuit according to another embodiment of the present invention is provided;

[0010] Figure 4 A schematic diagram of the circuit structure of a control circuit for a switching circuit according to another embodiment of the present invention is provided;

[0011] Figure 5 A schematic diagram of the circuit structure of a control circuit for a switching circuit according to another embodiment of the present invention is provided;

[0012] Figure 6 A schematic diagram of the circuit structure of a control circuit for a switching circuit according to an embodiment of the present invention is provided;

[0013] Figure 7 A schematic diagram of the circuit structure of a control circuit for a switching circuit according to another embodiment of the present invention is provided. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0015] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0016] In modern LED lighting systems, dynamically adjusting the number or type of LED strings has become a key requirement for achieving advanced lighting functions. Matrix headlights (ADB) achieve intelligent beam adjustment by precisely controlling the on / off state and brightness of multiple LEDs, effectively avoiding glare for oncoming vehicles and significantly improving nighttime driving safety. However, LED loads are often subjected to large current surges when changing, greatly increasing the risk to long-term lifespan.

[0017] Based on this, the present invention proposes a control circuit for a switching circuit used to drive an LED load, which can reduce current spikes when the load LED changes and increase LED reliability.

[0018] Figure 1 A schematic diagram of the control circuit of a switching circuit according to an embodiment of the present invention is provided. Figure 1 In this embodiment, a switching circuit 10 is used to drive an LED load 30. The switching circuit 10 includes at least one switch SL, which receives an input voltage VIN and converts the input voltage VIN into an output current IO to drive the LED load 30 by controlling the on / off state of the at least one switch. In one embodiment, the switching circuit 10 further includes an inductor L, wherein the current flowing through the inductor L is the inductor current IL. In one embodiment, the input voltage VIN ranges from 5V to 80V, and the output current IO ranges from 100mA to 2A. The LED load 30 has a first terminal and a second terminal, comprising N LEDs connected in series. The voltage across the first and second terminals of the LED load 30 is the load voltage VLED, where N is a natural number greater than 1. Figure 1 In the LED load 30, there are also N switches S1-SN, and the changes of each LED are realized by controlling the conduction and cutoff of the corresponding switches S1-SN.

[0019] continue Figure 1The control circuit 20 includes an error amplifier circuit EA, a current control circuit CM1, and an overcurrent control circuit 201. The error amplifier circuit EA receives a detection signal SEN and a reference signal REF1 characterizing the output current IO, and generates a current control signal COMP based on the detection signal SEN and the reference signal REF1. Figure 1 In the illustrated embodiment, the detection signal SEN is generated by a detection circuit. The detection circuit includes a detection resistor RS and a detection operational amplifier OP, wherein the detection resistor RS is connected in series between the output of the switching circuit and the LED load. The detection circuit generates the detection signal SEN, representing the output current IO, based on the current flowing through the detection resistor RS. The current control circuit 201 receives the current control signal COMP and generates a switch control signal PWM based on the current control signal COMP and a triangular wave signal VT to control the on and off of at least one switch SL, and controls the output current IO of the switching circuit by controlling the on and off of the at least one switch SL. The overcurrent control circuit 201 receives the detection signal SEN and an overcurrent signal REF2, and controls the current control signal COMP based on the comparison result of the detection signal SEN and the overcurrent signal REF2. When the detection signal SEN is greater than the overcurrent signal REF2, the current control signal COMP decreases to a preset voltage VS, wherein the value of the overcurrent signal REF2 is greater than the value of the reference signal REF1.

[0020] exist Figure 1 In the illustrated embodiment, the control circuit 20 further includes an adjustment transistor SO, which has a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the output terminal of the switching circuit 10, the second terminal is coupled to the first terminal of the LED load, and the control terminal receives a dimming signal DIM and is turned on or off under the control of the dimming signal DIM. Figure 1 In the illustrated embodiment, the regulating transistor SO is a P-type field-effect transistor. In one embodiment, an external controller, such as an MCU, provides a dimming signal DIM. In another embodiment, the external controller, such as the MCU, sends a control signal to the control circuit 20, which generates the dimming signal DIM based on the control signal. The dimming signal DIM controls the regulating transistor SO to turn on or off according to application requirements.

[0021] It should be noted that, in Figure 1 In the illustrated embodiment, the detection circuit is just one of the specific circuits that generates the detection signal SEN. Any circuit that can generate the detection signal SEN based on the output current IO is included within the scope of protection of this application. Figure 1In the illustrated embodiment, the switching circuit 10 is a SEPIC circuit. In other embodiments, the switching circuit 10 includes any switching circuit capable of driving an LED, such as a BUCK circuit, BOOST circuit, or BUCK-BOOST circuit. More specifically, when the switching circuit 10 is a BUCK circuit, the BUCK circuit includes a high-side switch and a low-side switch. The switching control signal PWM can control the output current IO by controlling the on and off states of the high-side and low-side switches. Alternatively, the switching control signal PWM can control the output current IO by controlling the on and off states of the low-side switch.

[0022] Figure 2 Given Figure 1 The waveforms of each signal in the control circuit shown are illustrated. (Reference) Figure 1 The control circuit shown is for the switching circuit. Figure 2 The waveforms of each signal in the diagram are explained. Figure 2 At time t1, a change in the LED load causes the load voltage VLED to decrease from a higher first voltage V1, and then decrease to a second voltage V2 at time t2, where the first voltage V1 is greater than the second voltage V2. Before time t1, the output current IO is constant, therefore the detection signal SEN, representing the output current, is constant IC. At time t1, the sudden decrease in the load voltage VLED causes the output current IO to increase instantaneously, and the detection signal SEN, representing the output current IO, increases instantaneously. At time t1, the detection signal SEN is greater than the overcurrent signal REF2, therefore the current control signal COMP decreases to the preset voltage VS.

[0023] Figure 3 A schematic diagram of the control circuit for a switching circuit according to another embodiment of the present invention is provided. Figure 1 The difference shown is that, Figure 3 The control circuit 20 shown includes an adjusting transistor SO having a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the second terminal of the LED load, the second terminal is coupled to reference ground GND, and the control terminal receives a dimming signal and is turned on or off under the control of the dimming signal Dim. Figure 3In the illustrated embodiment, the regulating transistor SO is an N-type field-effect transistor. In one embodiment, an external controller, such as an MCU, provides a dimming signal DIM. In another embodiment, the external controller, such as the MCU, sends a control signal to the control circuit 20, which generates the dimming signal DIM based on the control signal. The dimming signal DIM controls the regulating transistor SO to turn on or off according to application requirements. In one embodiment, the dimming control signal DIM is a square wave signal with a frequency range of 100Hz-1kHz and a duty cycle D. In one embodiment, the frequency of the dimming control signal DIM is 200Hz. In one embodiment, the average current flowing through the LED load is adjusted by changing the duty cycle of the dimming control signal DIM, i.e., the brightness of the LED load is adjusted.

[0024] Figure 4 A schematic diagram of the control circuit of a switching circuit according to another embodiment of the present invention is provided. Figure 4 In the illustrated embodiment, the overcurrent control circuit 201 includes a comparator circuit CM2. The comparator circuit CM2 receives a detection signal SEN and an overcurrent signal REF2, and compares the two signals to generate an overcurrent indication signal OC. When the detection signal SEN is greater than the overcurrent signal REF2, the overcurrent indication signal OC is in a first state; when the detection signal SEN is less than the overcurrent signal REF2, the overcurrent indication signal OC is in a second state. When the overcurrent indication signal OC is in the first state, the current control signal COMP is pulled low to a preset voltage VS; when the overcurrent indication signal OC is in the second state, the current control signal COMP remains unchanged. Figure 4 In the illustrated embodiment, the overcurrent control circuit 201 further includes an overcurrent transistor SR, which has a first terminal, a second terminal, and a control terminal. The first terminal receives a current control signal COMP, the second terminal receives a preset voltage VS, and the control terminal receives an overcurrent indication signal OC. More specifically, when the detection signal SEN is greater than the overcurrent signal REF2, the overcurrent indication signal OC is in a first state, controlling the overcurrent transistor SR to turn on, and the current control signal COMP decreases to the preset voltage VS. When the detection signal SEN is less than the overcurrent detection signal REF2, the overcurrent indication signal OC is in a second state, controlling the overcurrent transistor SR to turn off, and the current control signal COMP remains unchanged.

[0025] Figure 5 A schematic diagram of the control circuit for a switching circuit according to another embodiment of the present invention is provided. Figure 4 The difference shown is that, Figure 5The overcurrent control circuit 201 shown includes a comparator circuit CM2, a duration control circuit, and an overcurrent transistor SR. The comparator circuit CM2 receives a detection signal SEN and compares it with an overcurrent signal REF2 to generate an overcurrent indication signal OC. The duration control circuit 201 receives the overcurrent indication signal OC and generates a duration signal OT based on it. The overcurrent transistor SR has a first terminal, a second terminal, and a control terminal. The first terminal receives a current control signal COMP, the second terminal receives a preset voltage VS, and the control terminal receives the duration signal OT. When the detection signal SEN is greater than the overcurrent signal REF2, the overcurrent indication signal OC is in a first state, and the duration control signal OT controls the overcurrent transistor ST to turn on for a first time T1 and then turn off. In one embodiment, at the rising edge of the overcurrent indication signal OC, the duration control signal OT triggers the generation of a valid pulse, the length of which is the first time T1. In another embodiment, at the falling edge of the overcurrent indication signal OC, the duration control signal OT triggers the generation of a valid pulse, the length of which is the first time T1. In one embodiment, the duration of the first time T1 is adjustable and can be set according to a preset voltage VS and a current control signal COMP. In one embodiment, the duration of the first time T1 is 0.1µs-1ms.

[0026] Figure 6 A schematic diagram of the control circuit for a switching circuit according to another embodiment of the present invention is provided. Figure 5 The difference between the illustrated embodiment and the one shown is that, in Figure 6 In the illustrated embodiment, the duration control circuit further generates an overcurrent suppression signal GR based on the overcurrent indication signal OT and outputs it to the gate of the regulating transistor SO to control the regulating transistor SO to turn off for a preset time TS before turning it on again. More specifically, when the detection signal SEN is greater than the overcurrent signal REF2, the overcurrent indication signal OT switches from the second state to the first state, and the overcurrent suppression signal GR switches from a high potential to a low potential to control the regulating transistor SO to turn off for a preset time TS before turning it on again. In one embodiment, the preset time TS is 0.1µs-1ms. Figure 7 The overcurrent suppression signal GR received at the gate terminal of the regulating transistor SO and Figure 6 The dimming control signal DIM shown is different, and the overcurrent suppression signal GR is a single pulse signal, which cannot adjust the brightness of the LED load.

[0027] Figure 7 A schematic diagram of the control circuit for a switching circuit according to another embodiment of the present invention is provided. Figure 6 The difference between the illustrated embodiment and the one shown is that, in Figure 7 In the illustrated embodiment, the regulating transistor SO is coupled between the second terminal of the LED load and a reference ground. Figure 7In the illustrated embodiment, the duration control circuit also generates an overcurrent suppression signal GR based on the overcurrent indication signal OT and outputs it to the gate of the regulating transistor SO to control the regulating transistor SO to turn off for a preset time TS before turning it on again. More specifically, when the detection signal SEN is greater than the overcurrent signal REF2, the overcurrent indication signal OT jumps from the second state to the first state, and the overcurrent suppression signal GR jumps from a high potential to 0V to control the regulating transistor SO to turn off for a preset time TS before turning it on.

[0028] The control circuit of the switching circuit provided by the present invention can cope with the overshoot of the output current when the LED load changes, which greatly shortens the LED overcurrent time and significantly reduces the risk of LED chip aging accelerated due to overcurrent, thereby improving the reliability and lifespan of LED for long-term use and reducing equipment maintenance costs and replacement frequency.

[0029] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A control circuit for a switching circuit, wherein the switching circuit has an input terminal for receiving an input signal and an output terminal for providing an output current, the switching circuit including at least one switch, and converting the input signal into an output current flowing through an LED load by controlling the on and off states of the at least one switch, the control circuit comprising: The error amplifier circuit receives the detection signal and the reference signal that characterize the output current, compares them, and generates a current control signal. A current control circuit receives a current control signal and a triangular wave signal, and generates a switch control signal based on the current control signal and the triangular wave signal to control the conduction and cutoff of the at least one switch. The overcurrent control circuit receives a detection signal and an overcurrent signal, and controls the current control signal based on the comparison result of the detection signal and the overcurrent signal. When the detection signal is greater than the overcurrent signal, the current control signal is reduced to a preset voltage.

2. The control circuit as described in claim 1, wherein the preset voltage is a reference ground.

3. The control circuit as described in claim 1, wherein the overcurrent control circuit comprises: The comparator circuit receives the detection signal and the overcurrent signal, and compares the detection signal with the overcurrent signal to generate an overcurrent indication signal; When the overcurrent indication signal is in the first state, the current control signal decreases to the preset voltage; when the overcurrent indication signal is in the second state, the current control signal remains unchanged.

4. The control circuit as described in claim 3, wherein the overcurrent control circuit further includes; An overcurrent transistor has a first terminal, a second terminal, and a control terminal, wherein the first terminal receives a current control signal, the second terminal receives a preset voltage, and the control terminal receives an overcurrent indication signal.

5. The control circuit as described in claim 3, wherein the overcurrent control circuit further comprises: The duration control circuit receives the overcurrent indication signal and generates a duration signal based on the overcurrent indication signal. An overcurrent transistor has a first terminal, a second terminal, and a control terminal, wherein the first terminal receives a current control signal, the second terminal receives a preset voltage, and the control terminal receives a duration signal. When the overcurrent indication signal transitions from the second state to the first state, the duration control signal controls the overcurrent transistor to turn on for a first time and then turn it off.

6. The control circuit as described in claim 5, wherein the duration of the first time is 0.1µs-1ms.

7. The control circuit of claim 1, wherein the LED load has a first terminal and a second terminal, and the control circuit further comprises: The regulating transistor has a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the output terminal of the switching circuit to receive the output current, the second terminal is coupled to the first terminal of the LED load, and the control terminal receives a dimming signal and turns the transistor on or off under the control of the dimming signal.

8. The control circuit of claim 1, wherein the LED load has a first terminal and a second terminal, and the control circuit further comprises: The regulating transistor has a first terminal, a second terminal, and a control terminal, wherein the first terminal is coupled to the second terminal of the LED load, the second terminal is coupled to a reference ground, and the control terminal receives a dimming signal and turns on or off under the control of the dimming signal.

9. The control circuit of claim 1, wherein the LED load has a first terminal and a second terminal, and the control circuit further comprises: An regulating transistor has a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the output terminal of a switching circuit to receive the output current. The second terminal is coupled to the first terminal of an LED load. The control terminal receives an overcurrent suppression signal. When the detected signal is greater than the overcurrent signal, the overcurrent suppression signal controls the regulating transistor to turn off for a preset time and then turn it on again.

10. The control circuit of claim 1, wherein the LED load has a first terminal and a second terminal, and the current protection circuit further includes: An regulating transistor has a first terminal, a second terminal, and a control terminal. The first terminal is coupled to the second terminal of an LED load, the second terminal is coupled to a reference ground, and the control terminal receives an overcurrent suppression signal. When the detected signal is greater than the overcurrent signal, the overcurrent suppression signal controls the regulating transistor to turn off for a preset time and then turn on again.

11. The control circuit as claimed in claim 1, wherein the value of the overcurrent signal is greater than the value of the reference signal.

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