Control circuit for sectional type LED driving and sectional type LED driving circuit

Abstract

The utility model provides a sectional type LED drive circuit and a control circuit thereof. The control circuit comprises N first subtraction circuits, and each first subtraction circuit receives voltage detection signals of voltages of two adjacent LED nodes and provides compensation signals; n second subtraction circuits, each second subtraction circuit receiving the reference signal and one compensation signal and providing a compensated reference signal; and N operational amplification circuits, each operational amplification circuit receives the compensated reference signal and the current detection signal, the output end of the operational amplification circuit is coupled with the corresponding transistor, the transistor is coupled between the corresponding LED module and the first end of the current detection resistor, the second end of the current detection resistor is grounded, and the first end of the current detection resistor is grounded. The first end of the current detection resistor provides a current detection signal. According to the segmented LED drive circuit and the control circuit thereof, the phenomenon of unbalanced compensation in segmented LED lamp control can be eliminated, and self-adaptive power compensation is realized.

Description

Technical Field

[0001] This utility model relates to the field of electronics, specifically but not limited to a segmented LED driving circuit and its control circuit. Background Technology

[0002] To improve the power factor and efficiency of linear LED (light-emitting diode) drivers, a segmented driving method is typically used. A typical two-segment linear constant-current LED application system is as follows: Figure 1 As shown, two LED modules are connected in series. When the input voltage Vbus gradually increases to a level greater than the lamp voltage of LED1, the channel of transistor Q1 is turned on, while the channel of transistor Q2 is turned off, LED1 is lit, and LED2 is off. When the input voltage Vbus is greater than the sum of the lamp voltages of LED1 and LED2, transistor Q2 is turned on, and both LED1 and LED2 are lit simultaneously. Typically, the threshold signal Vref2 for transistor Q2 to turn on is set to be greater than the threshold signal Vref1 for transistor Q1 to turn on. In this case, transistor Q1 will be turned off under the closed-loop control of the first operational amplifier (Op-amp 1).

[0003] When Vref1 and Vref2 remain constant, the voltage drop and output current of each LED module are fixed. When the input voltage Vbus increases, the conduction time of the LEDs increases, and the voltage across transistors Q1 and Q2 also increases, leading to an increase in input power. To ensure that the input power does not change with the input voltage Vbus, input power compensation is usually required.

[0004] In view of this, there is a need to provide a new structure or control method in order to solve at least some of the above problems. Utility Model Content

[0005] In response to at least one or more problems in the background art, this utility model proposes a segmented LED driving circuit and its control circuit.

[0006] According to one aspect of this utility model, a control circuit for segmented LED driving is proposed. The control circuit includes: N first subtraction circuits, wherein each first subtraction circuit receives a voltage detection signal characterizing the node voltage of two adjacent LED nodes in N LED modules and provides a compensation signal, wherein N is an integer greater than or equal to 2; N second subtraction circuits, wherein each second subtraction circuit receives a reference signal and a corresponding compensation signal and provides a compensated reference signal; and N operational amplifier circuits, wherein the first input terminal of each operational amplifier circuit receives the corresponding compensated reference signal, the second input terminal of the operational amplifier circuit receives a current detection signal, the output terminal of the operational amplifier circuit is coupled to a corresponding transistor, the transistor is coupled between the corresponding LED module and the first terminal of the current detection resistor, the second terminal of the current detection resistor is grounded, and the first terminal of the current detection resistor provides a current detection signal.

[0007] According to another aspect of this utility model, an LED driving circuit is proposed, comprising: a rectifier circuit, the two input terminals of which are coupled to the two ports of a mains power supply, the first output terminal of which provides a DC bus voltage, and the second output terminal of which is coupled to a reference ground; N LED modules connected in series, wherein the anodes of the multiple LED modules connected in series are coupled to the first output terminal of the rectifier circuit, and N is an integer greater than or equal to 2; multiple transistors, the first terminal of each transistor is coupled to the cathode of each LED module, and the second terminal of each transistor is grounded through a current sensing resistor; and a control circuit, comprising a compensation signal generation unit, a compensation unit, and N control units, wherein the compensation signal generation unit generates N compensation signals, the compensation signals being proportional to the lamp voltages at both ends of the corresponding LED module, the compensation unit receiving N reference signals and N compensation signals, each compensation signal compensating the corresponding reference signal to obtain a compensated reference signal; the output terminal of each control unit is coupled to the control terminal of the corresponding transistor, and each control unit receives the corresponding compensated reference signal to control the corresponding LED module.

[0008] Optionally, the control unit includes an operational amplifier circuit. The first input terminal of the operational amplifier circuit is coupled to a compensated reference signal, and the second input terminal of the operational amplifier circuit receives a current detection signal, wherein the current detection signal is the voltage difference across the current detection resistor. The output terminal of the operational amplifier circuit is coupled to the control terminal of the corresponding transistor.

[0009] Optionally, the control circuit further includes a voltage detection circuit to detect the node voltage on N+1 LED nodes corresponding to N LED modules and obtain N+1 node detection signals; wherein: the compensation signal generation unit includes N first subtraction circuits, each first subtraction circuit subtracts the two node detection signals of adjacent LED nodes to obtain a compensation signal; the compensation unit includes N second subtraction circuits, the reference signal is subtracted from the compensation signal to form a compensated reference signal.

[0010] According to another aspect of this utility model, a control circuit for segmented LED driving is proposed, comprising: a compensation signal generation unit that generates N compensation signals, each compensation signal being proportional to the lamp voltage across the corresponding LED module, wherein N is an integer greater than or equal to 2; a compensation unit that receives N reference signals and the N compensation signals, wherein each compensation signal compensates the corresponding reference signal to obtain a compensated reference signal; and N control units, each control unit receiving the corresponding compensated reference signal and a current detection signal, wherein the output terminal of the control unit is coupled to the control terminal of the corresponding transistor for controlling the corresponding LED module, wherein the current detection signal is the voltage difference across the current detection resistor.

[0011] Optionally, the control unit includes an operational amplifier circuit. The first input terminal of the operational amplifier circuit is coupled to the compensated reference signal, the second input terminal of the operational amplifier circuit receives the current detection signal, and the output terminal of the operational amplifier circuit is coupled to the control terminal of the corresponding transistor.

[0012] Optionally, the control circuit further includes a voltage detection circuit to detect the node voltage of N+1 LED nodes in the N LED modules and obtain N+1 node detection signals; wherein: the compensation signal generation unit includes N first subtraction circuits, which subtract the node detection signals of adjacent nodes to obtain a compensation signal proportional to the lamp voltage at both ends of the corresponding LED; the compensation unit includes N second subtraction circuits, which subtract the corresponding compensation signal from the corresponding reference signal to form a compensated reference signal.

[0013] The segmented LED driving circuit and its control circuit proposed in this utility model can compensate the driving current of the LED module based on the input voltage, and can perform different compensations for the voltages of different LED modules. This can eliminate the imbalance of compensation in the segmented LED lamp control, realize adaptive power compensation, and make the segmented LED lamp have higher brightness accuracy. Attached Figure Description

[0014] The accompanying drawings are provided to further illustrate the present invention and, together with the description, serve to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0015] Figure 1 A segmented LED driving circuit is shown;

[0016] Figure 2 A segmented LED driving circuit according to an embodiment of the present invention is shown. Detailed Implementation

[0017] To further understand this utility model, preferred embodiments of this utility model are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of this utility model, and not for limiting the scope of the claims of this utility model.

[0018] The description in this section pertains to only a few typical embodiments, and this utility model is not limited to the scope of the embodiments described. Combinations of different embodiments, substitution of some technical features in different embodiments, and substitution of the same or similar prior art with some technical features in the embodiments are also within the scope of the description and protection of this utility model.

[0019] The terms "coupled" or "connected" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection through an electrically conductive medium like a conductor, which may contain parasitic inductance or capacitance. It can also be a connection through intermediate circuits or components described in the embodiments of this specification. Indirect connections may also include connections through other active or passive devices that achieve the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, or other circuits or components. "Multiple" or "more" indicates two or more.

[0020] Continue reading Figure 1 To address the aforementioned issues, one compensation method involves simultaneously reducing Vref1 and Vref2 by the same amount when the input voltage Vbus exceeds a certain value. This reduction can be proportional to the input voltage Vbus, thereby lowering the LED's output current. By reducing the output current, the input power remains essentially constant even when the input voltage increases. However, when the voltage drops across the LED module differ, this compensation method is not sufficiently balanced for each LED, leading to unstable and inaccurate illumination. In multi-color control systems, this may cause color imbalances.

[0021] Figure 2A segmented LED driving circuit according to an embodiment of the present invention is shown. The segmented LED driving circuit includes a rectifier circuit 21, two LED modules 221 and 222 connected in series, transistors Q1 and Q2, a voltage detection circuit 23, a control circuit 20, and a current detection resistor Rcs. The two input terminals of the rectifier circuit 21 are coupled to the two ports of the ACIN mains power supply. The first output terminal of the rectifier circuit 21 provides a DC bus voltage Vbus, and the second output terminal of the rectifier circuit 21 is coupled to reference ground GND. The rectifier circuit 21 is used to rectify the ACIN mains power supply into a bus input voltage Vbus with a DC pulsating voltage waveform. The voltage value of the input voltage Vbus varies sinusoidally with time over half an AC cycle. The two LED modules 221 and 222 are connected in series, wherein the anodes of the two series-connected LED modules are coupled to the first output terminal of the rectifier circuit 21 to receive the input voltage Vbus. The anodes and cathodes of the two LED modules form three LED nodes N1, N2, and N3, respectively. The voltage at LED node N1 is the input voltage Vbus. Node N2 is the cathode of LED module 221 and the anode of LED module 222. Node N3 is the cathode of LED module 222. In another embodiment, the driving circuit system includes three or more LED modules. The N LED modules have N+1 LED nodes, corresponding to the anode and cathode of the N LED modules, respectively, where N is an integer greater than or equal to 2. The voltage detection circuit 23 detects the node voltages at the N+1 LED nodes and outputs N+1 voltage detection signals proportional to the node voltages. Each LED module may include one LED device, multiple LED devices connected in series, or multiple LED devices with a hybrid series-parallel structure. The first terminal of transistor Q1 is coupled to the cathode of the first LED module 221, and the second terminal of transistor Q1 is coupled to the first terminal of the current sensing resistor Rcs, which is grounded to GND. The first terminal of transistor Q2 is coupled to the cathode of the second LED module 222, and the second terminal of transistor Q2 is also grounded to GND through the current sensing resistor Rcs. The first terminal of the current sensing resistor Rcs provides the current sensing signal Vcs.

[0022] Voltage detection circuit 23 detects the node voltages on the three LED nodes N1, N2, and N3 corresponding to LED modules 221 and 222, obtaining three node detection signals Vn1, Vn2, and Vn3. Voltage detection circuit 23 includes three detection circuits. In the illustrated embodiment, each detection circuit includes a resistor divider circuit and a capacitor connected in parallel with the lower resistor in the voltage divider circuit, used to obtain stable node detection signals characterizing the voltage of each LED node.

[0023] The control circuit 20 includes a compensation signal generation unit 24, a compensation unit 25, and control units 261 and 262. The compensation signal generation unit 24 generates two compensation signals, Vcp1 and Vcp2, which are proportional to the lamp voltages at both ends of the first LED module 221 and the second LED module 222, respectively. The compensation unit 25 generates two compensated reference signals, Vref_cp1 and Vref_cp2, based on the compensation signals Vcp1 and Vcp2 and the reference signals Vref1 and Vref2. The input terminal of the first control unit 261 receives the compensated reference signal Vref_cp1 and the current detection signal Vcs. The output terminal of the first control unit 261 is coupled to the control terminal of transistor Q1 to control the current in the first LED module 221. The input terminal of the second control unit 262 receives the second compensated reference signal Vref_cp2 and the current detection signal Vcs. The output terminal of the second control unit 262 is coupled to the control terminal of the second transistor Q2 to control the current in the first LED module 221 and the second LED module 222.

[0024] exist Figure 2 In the illustrated embodiment, the compensation signal generation unit 24 includes two first subtraction circuits 241 and 242 for generating two compensation signals Vcp1 and Vcp2. The first subtraction circuit 241 compensates for the current flowing through the LED module 221. It subtracts the node detection signals Vn1 and Vn2 at LED nodes N1 and N2 to obtain a compensation signal Vcp1 proportional to the lamp voltage across the LED module 221. The first subtraction circuit 242 compensates for the current flowing through LED modules 221 and 222. It subtracts the node detection signals Vn2 and Vn3 at LED nodes N1 and N3 to obtain a compensation signal Vcp2 proportional to the lamp voltage across the LED module 222.

[0025] The compensation unit 25 includes two second subtraction circuits 251 and 252. The compensation unit 25 receives two reference signals Vref1 and Vref2, and two compensation signals Vcp1 and Vcp2. The compensation signals Vcp1 and Vcp2 compensate for the reference signals Vref1 and Vref2 respectively, obtaining two compensated reference signals Vref_cp1 and Vref_cp2. Preferably, the reference signal Vref1 is used to define the current flowing through the first LED module 221 when transistor Q1 is turned on, and the reference signal Vref2 is used to define the current flowing through both the first LED module 221 and the second LED module 222 when transistor Q2 is turned on. The second reference signal Vref2 is greater than the first reference signal Vref1, so that transistor Q1 is in a turned-off state when transistor Q2 is turned on. The two inputs of the first second subtraction circuit 251 receive the reference signal Vref1 and the compensation signal Vcp1 respectively. The first second subtraction circuit 251 subtracts the compensation signal Vcp1 from the reference signal Vref1 to form the first compensated reference signal Vref_cp1. The second subtraction circuit 252 receives the reference signal Vref2 and the compensation signal Vcp2 at its two input terminals, respectively. The second subtraction circuit 252 subtracts the compensation signal Vcp2 from the reference signal Vref2 to form the compensated reference signal Vref_cp2. Thus, the compensation signals Vref_cp1 and Vref_cp2 are not only proportional to the input voltage Vbus, but also proportional to the voltage difference across the corresponding LED module that needs adjustment. This can be used to eliminate the problem of uneven compensation caused by different output voltages of different LED modules.

[0026] The control unit 261 includes an operational amplifier circuit. The first input terminal of the control unit 261 (i.e., the operational amplifier circuit 261) is coupled to the second subtraction circuit 251 in the compensation unit 25 to receive the compensated reference signal Vref_cp1. The second input terminal of the operational amplifier circuit 261 receives the current detection signal Vcs, where Vcs is the voltage difference across the current detection resistor Rcs. The output terminal of the operational amplifier circuit 261 (i.e., the output terminal of the control unit 261) is coupled to the control terminal of transistor Q1. When the current flowing through transistor Q1 is less than the current value represented by the compensated reference signal Vref_cp1, the operational amplifier 261 turns on transistor Q1. Of course, when the input voltage Vbus is less than the turn-on voltage of the first LED module 221, no current flows through the LED module 221 and transistor Q1. When the current flowing through transistor Q1 is greater than the current value represented by the compensated reference signal Vref_cp1, operational amplifier 261 reduces its output voltage to increase the on-resistance of transistor Q1, thus clamping the current flowing through transistor Q1 to the current value represented by the compensated reference signal Vref_cp1. Similarly, the first input terminal of the operational amplifier circuit 262 in the second control unit is coupled to the compensated reference signal Vref_cp2, its second input terminal receives the current detection signal Vcs, and its output terminal is coupled to the control terminal of transistor Q2. When the current flowing through transistor Q2 is less than the current value represented by the compensated reference signal Vref_cp2, operational amplifier 262 turns on transistor Q2. However, when the input voltage Vbus is less than the sum of the on-state voltages of the first LED module 221 and the second LED module 222, LED module 222 does not turn on, and no current flows through transistor Q2. When the input voltage Vbus is greater than the sum of the turn-on voltages of the first LED module 221 and the second LED module 222, transistor Q2 turns on, and the current detection signal Vcs increases to be greater than the first compensated reference signal Vref_cp1. Operational amplifier 261 outputs a low-level voltage to turn off transistor Q1. When the current flowing through transistor Q1 is greater than the current value represented by the compensated reference signal Vref_cp2, operational amplifier 262 decreases its output voltage to increase the on-resistance of transistor Q2, so that the current flowing through transistor Q2 is clamped to the current value represented by the compensated reference signal Vref_cp2.

[0027] In other embodiments, the voltage detection circuit 23 and the current detection resistor Rcs may be partially or wholly incorporated within the control circuit 20.

[0028] The above LED driver circuit embodiment uses two segmented LED modules, three LED node voltage detection circuits, two first subtraction circuits, two second subtraction circuits, and two operational amplifier circuits. In other embodiments, the above quantities can be extended to any N segmented LED modules, N+1 LED node voltage detection circuits, N first subtraction circuits, N second subtraction circuits, and N operational amplifier circuits, where N is an integer greater than or equal to 2. Different compensation signals are set for different LED modules according to their differential voltage, thereby ensuring that the compensation coefficients of different LED segment voltages can be adaptively adjusted to compensate for the output current, without the need for external individual settings, thus improving the flexibility of the application.

[0029] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "non-inverting input" and "inverting input" in the logic control involved in the specification or drawings can be interchanged or changed, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic control.

[0030] The description and application of this utility model herein are illustrative and not intended to limit the scope of the utility model to the above embodiments. The effects or advantages described in the specification may not be apparent in actual experimental examples due to uncertainties in specific conditions or parameters or other factors, and such descriptions are not intended to limit the scope of the utility model. Variations and modifications to the embodiments disclosed herein are possible, and various substitutions and equivalent components of the embodiments are well known to those skilled in the art. It should be clear to those skilled in the art that this utility model can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the utility model. Other variations and modifications can be made to the embodiments disclosed herein without departing from the scope and spirit of the utility model.

Claims

1. A control circuit for segmented LED driving, characterized in that, The control circuit includes: N first subtraction circuits, each of which receives a voltage detection signal representing the node voltage of two adjacent LED nodes in N LED modules and provides a compensation signal, where N is an integer greater than or equal to 2; N second subtraction circuits, each receiving a reference signal and a corresponding compensation signal to provide a compensated reference signal; and There are N operational amplifier circuits, where the first input terminal of each operational amplifier circuit receives the corresponding compensated reference signal, the second input terminal of the operational amplifier circuit receives the current detection signal, the output terminal of the operational amplifier circuit is coupled to the corresponding transistor, the transistor is coupled between the corresponding LED module and the first terminal of the current detection resistor, the second terminal of the current detection resistor is grounded, and the first terminal of the current detection resistor provides the current detection signal.

2. A segmented LED driving circuit, characterized in that, The LED driver circuit includes: The rectifier circuit has two input terminals coupled to the two ports of the mains power supply, the first output terminal of the rectifier circuit provides the DC bus voltage, and the second output terminal of the rectifier circuit is coupled to the reference ground. N LED modules connected in series, wherein the anodes of the multiple LED modules connected in series are coupled to the first output terminal of the rectifier circuit, and N is an integer greater than or equal to 2; Multiple transistors, each with its first terminal coupled to the cathode of each LED module, and its second terminal grounded via a current-sensing resistor; and The control circuit includes a compensation signal generation unit, a compensation unit, and N control units. The compensation signal generation unit generates N compensation signals, which are proportional to the lamp voltage at both ends of the corresponding LED module. The compensation unit receives N reference signals and N compensation signals, and each compensation signal compensates the corresponding reference signal to obtain a compensated reference signal. The output terminal of each control unit is coupled to the control terminal of the corresponding transistor. Each control unit receives the corresponding compensated reference signal and controls the corresponding LED module.

3. The LED driving circuit as described in claim 2, characterized in that, The control unit includes an operational amplifier circuit. The first input terminal of the operational amplifier circuit is coupled to a compensated reference signal, and the second input terminal of the operational amplifier circuit receives a current detection signal, wherein the current detection signal is the voltage difference across the current detection resistor. The output terminal of the operational amplifier circuit is coupled to the control terminal of the corresponding transistor.

4. The LED driving circuit as described in claim 2, characterized in that, The control circuit further includes a voltage detection circuit, which detects the node voltages on N+1 LED nodes corresponding to the N LED modules, and acquires N+1 node detection signals; wherein: The compensation signal generation unit includes N first subtraction circuits. Each first subtraction circuit subtracts the detection signals of two adjacent LED nodes to obtain the compensation signal. The compensation unit includes N second subtraction circuits, which subtract the compensation signal from the reference signal to form the compensated reference signal.

5. A control circuit for segmented LED driving, characterized in that, The control circuit includes: The compensation signal generation unit has its input terminal coupled to the LED module to obtain the node voltage of the corresponding LED module, and its output terminal provides multiple compensation signals. Each compensation signal is proportional to the lamp voltage at both ends of the corresponding LED module, where N is an integer greater than or equal to 2. A compensation unit, whose input is coupled to the output of a compensation signal generation unit, receives the N compensation signals. Each compensation signal compensates for a corresponding reference signal to obtain a compensated reference signal. There are N control units. Each control unit receives a corresponding compensated reference signal and a current detection signal. The output of the control unit is coupled to the control terminal of the corresponding transistor to control the corresponding LED module. The current detection signal is the voltage difference across the current detection resistor.

6. The control circuit as described in claim 5, characterized in that, The control unit includes an operational amplifier circuit. The first input terminal of the operational amplifier circuit is coupled to a compensated reference signal, the second input terminal of the operational amplifier circuit receives a current detection signal, and the output terminal of the operational amplifier circuit is coupled to the control terminal of the corresponding transistor.

7. The control circuit as described in claim 5, characterized in that, The control circuit further includes a voltage detection circuit that detects the node voltage of N+1 LED nodes in the N LED modules to obtain N+1 node detection signals; wherein: The compensation signal generation unit includes N first subtraction circuits. The first subtraction circuits subtract the node detection signals of adjacent nodes to obtain a compensation signal that is proportional to the lamp voltage at both ends of the corresponding LED. The compensation unit includes N second subtraction circuits, which subtract the corresponding compensation signal from the corresponding reference signal to form the compensated reference signal.

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