Adaptive linear dimming power supply system

Abstract

The present invention provides an adaptive linear dimming power supply system, comprising an adaptive voltage output module and an LED linear dimming module with at least one LED linear dimming branch. The adaptive voltage output module is a dual-controller architecture, wherein a first controller and a second controller are respectively located on different integrated circuit main cores, and the second controller can receive a sampling signal generated by a common end of an LED load and a dimming switch tube in the LED linear dimming branch, and transmit a corresponding adjustment control signal to the first controller. Thus, on the one hand, it can avoid the problem that the DC output voltage cannot be fed back in real time and the system dynamic response performance is poor due to the ground terminal potential of the first controller being higher than the system ground. On the other hand, it can ensure that the chip where the first controller is located and the chip where the second controller is located only need a very small voltage-resistant area, and do not need to withstand excessively high voltage, thereby reducing the cost of the control chip and improving the flexibility of system design.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, and in particular to an adaptive linear dimming power supply system. Background Art

[0002] With the continuous progress of society, LEDs are widely used in our daily lives, such as backlights of electronic products, and daily lighting at home and in public places. The reason why LEDs are widely used by humans is because of their small size, low power consumption, long service life, high brightness, low heat, environmental protection, durability and brilliant colors.

[0003] Figure 1 This is a multi-line linear dimming power supply system that is currently commonly used on the market. The AC side voltage of the power grid is rectified by a rectifier bridge composed of diodes D1, D2, D3, and D4, and then output as an output voltage Vo after being controlled by the controller and power switch tube Q1 in the control chip, and Vo is a fixed value. The output voltage Vo supplies power to the subsequent n-line linear LED dimming circuit, and the n-line linear LED dimming circuit corresponds to the dimming signals PWM1~PWMn one by one. Taking the first-line linear dimming circuit as an example, the dimming signal PWM1 is converted into a reference signal Vref1 proportional to the duty cycle of the dimming signal PWM1 through a low-pass filter. The analog error amplifier EA is adjusted according to the size of Vref1 and Vcs1, and finally the linear dimming of the first-line linear dimming circuit is realized.

[0004] To ensure that the n-line linear dimming can work properly, the value of the output voltage Vo must be greater than the minimum supply voltage required in the n-line linear LED dimming circuit (i.e. full-range LED linear dimming). However, this will cause the drain-source voltage of each dimming switch tube S1, S2...Sn in the n-line linear LED dimming circuit to be relatively large when the voltage difference between the conduction voltage drop of the LED load and the output voltage Vo is large or the dimming is deep, such as 1%, resulting in a relatively large overall system efficiency and shortening the life of the entire system.

[0005] At the same time, for the controller at the front stage, the existing technology usually adopts the topology of the power switch tube Q1 source grounding as the front stage topology. If the topology of the power switch tube Q1 is not directly grounded at both ends as the front stage topology, the driving potential of the Q1 gate is high, which will require the entire control chip to have the ability to withstand and output high voltage, and put forward higher requirements on the voltage resistance of the control chip, raising the cost. This habit limits the flexibility of system design. Summary of the invention

[0006] The object of the present invention is to provide an adaptive linear dimming power supply system, which can reduce the voltage resistance performance requirements of the control chip, provide system design flexibility, and realize real-time feedback to improve the overall efficiency and dynamic response speed of the system.

[0007] In order to solve the above technical problems, the present invention provides an adaptive linear dimming power supply system, including an adaptive voltage output module and an LED linear dimming module, wherein:

[0008] The LED linear dimming module comprises at least one LED linear dimming branch, wherein the LED linear dimming branch comprises an LED load and a dimming switch tube, wherein the LED load is connected in series with the dimming switch tube, and the LED linear dimming branch generates a sampling signal from a common end of the LED load and the dimming switch tube;

[0009] The adaptive voltage output module includes a first controller and a second controller respectively located on different integrated circuit main cores, the second controller is used to generate a corresponding adjustment control signal according to the sampling signal generated by the corresponding LED linear dimming branch, the first controller is used to receive an input voltage and the adjustment control signal, and adjust the input voltage to a DC output voltage according to the adjustment control signal to power each LED linear dimming branch, and the input voltage is greater than the DC output voltage.

[0010] Optionally, the LED linear dimming module has n LED linear dimming branches, n≥2; the adaptive linear dimming power supply system also includes a multiplexer with n input terminals, each input terminal of the multiplexer is connected one-to-one to the common terminal of the LED load and the dimming switch tube in the corresponding LED linear dimming branch to receive the sampling signal generated by the LED linear dimming branch, the output terminal of the multiplexer is connected to the corresponding input terminal of the adaptive voltage output module, and the multiplexer is used to receive and compare the sizes of the sampling signals generated by all the LED linear dimming branches, and filter out the minimum value therefrom as the sampling signal transmitted to the adaptive voltage output module, so that the adaptive voltage output module adjusts the DC output voltage according to the minimum value.

[0011] Optionally, the multiplexer includes n diodes, the cathode of each diode serves as a corresponding input end of the multiplexer and is connected to the common end of the LED load and the dimming switch tube in a corresponding LED linear dimming branch, and the node formed by the anodes of all the diodes being connected together serves as the output end of the multiplexer.

[0012] Optionally, the multiplexer further includes a resistor, one end of which is connected to the node, and the other end of which is connected to the DC output voltage output by the adaptive voltage output module or to a DC voltage.

[0013] Optionally, the multiplexer includes n-1 levels of voltage comparators, n-1 levels of first switches and n-1 levels of second switches, wherein two input ends of the first level voltage comparator are respectively connected to sampling signals generated by the first LED linear dimming branch and the second LED linear dimming branch, the control end of each level of the first switch and the control end of the second switch are connected to the output end of the voltage comparator at the same level, and one end of each level of the first switch and one end of the second switch are respectively connected to two input ends of the voltage comparator at the same level; and for all comparators except the first level voltage comparator, one input end of the i-th level voltage comparator is connected to the sampling signal generated by the i+1th LED linear dimming branch, and the other input end of the i-th level voltage comparator is connected to the other end of the i-1th level first switch and the other end of the i-1th level second switch, 2≤i≤n-1; the other end of the n-1th level first switch and the other end of the n-1th level second switch are connected together to form the output end of the multiplexer.

[0014] Optionally, the second controller includes a first PWM generator and a drive signal converter, the first PWM generator is used to generate a corresponding original PWM signal according to the sampling signal generated by the corresponding LED linear dimming branch, the drive signal converter is connected to the first PWM generator, and is used to convert the original PWM signal into the adjustment control signal, the ground terminal of the first PWM generator is the ground terminal of the second controller and is connected to the system ground; the first controller includes a drive signal detector, a driver and a power switch tube, the drive signal detector is used to convert the adjustment control signal into a drive signal synchronized with the original PWM signal, the driver is used to control the conduction and cutoff of the power switch tube according to the control of the drive signal to adjust the DC output voltage, and the ground terminal potential of the first controller is higher than the potential of the system ground.

[0015] Optionally, the first PWM generator includes an error amplifier and a voltage comparator, the non-inverting input of the error amplifier is connected to a reference voltage, the inverting input is connected to the minimum value, the output of the error amplifier is connected to the non-inverting input of the voltage comparator, the inverting input of the voltage comparator is connected to a triangle wave signal, and the output of the voltage comparator outputs the original PWM signal.

[0016] Optionally, the drive signal converter includes a switch control unit and a current pulse generating unit connected in sequence, the switch control unit is used to access the original PWM signal and perform switching under the control of the original PWM signal, and the current pulse generating unit is used to generate a current pulse signal according to the switching of the switch control unit to serve as the regulation control signal.

[0017] Optionally, the current pulse generating unit includes a first MOS tube and a current limiting resistor, and the switch control unit includes a second MOS tube, the first MOS tube is a depletion-type field effect tube whose gate terminal is connected to the system ground, the drain terminal of the first MOS tube is the output terminal of the current pulse generating unit for outputting the adjustment control signal, the source terminal of the first MOS tube is connected to one end of the current limiting resistor, the other end of the current limiting resistor is connected to the drain terminal of the second MOS tube, the source terminal of the second MOS tube is connected to the system ground, and the gate terminal of the second MOS tube is connected to the first PWM generator.

[0018] Optionally, the drive signal detector includes a current mirror, a pull-down resistor and a Schmitt trigger, the power supply end of the current mirror is connected to the drain end of the power switch tube, the input end of the current mirror is connected to the output end of the drive signal converter, the output end of the current mirror is connected to one end of the pull-down resistor and the input end of the Schmitt trigger, the other end of the pull-down resistor is connected to the source end of the power switch tube, and the output end of the Schmitt trigger is connected to the control end of the power switch tube and is used to output the drive signal.

[0019] Optionally, the current mirror includes a third MOS tube and a fourth MOS tube, the third MOS tube and the fourth MOS tube are PMOS, the gate end of the third MOS tube is connected to the gate end of the fourth MOS tube and the drain end of the third MOS tube to form the input end of the current mirror, the drain end of the fourth MOS tube serves as the output end of the current mirror, and the source end of the third MOS tube is connected to the source end of the fourth MOS tube to form the power supply end of the current mirror.

[0020] Optionally, the drive signal converter is used to convert the original PWM signal into two synchronous narrow pulse current control signals, and the drive signal detector includes two current mirrors, two buffers and a D flip-flop. The input ends of the two current mirrors are connected to the two narrow pulse current control signals one by one, and the output ends of the two current mirrors are respectively connected to the input ends of the two buffers, and the output ends of the two buffers are respectively connected to the clock input and the clear input of the D flip-flop. The data input end of the D flip-flop is connected to logic "1", and the output end of the D flip-flop is the output end of the drive signal detector and is used to output the drive signal.

[0021] Optionally, each of the current mirrors includes two PMOS tubes connected with a common gate and a resistor, wherein the drain end of one of the PMOS tubes is connected to an output end of the drive signal converter, the drain end of the other PMOS tube is connected to one end of the resistor and forms the output end of the current mirror, and the other end of the resistor is connected to the source end of the power switch tube. The source ends of the two PMOS tubes are connected to each other and serve as the power supply end of the current mirror, and are connected to the drain end of the power switch tube.

[0022] Optionally, the adaptive voltage output module also includes a freewheeling diode, a filter inductor and a filter capacitor, the cathode of the freewheeling diode is connected to the source end of the power switch tube in the first controller and one end of the filter inductor, the source end of the power switch tube serves as the ground end of the first controller, the other end of the filter inductor is connected to one end of the filter capacitor, and the anode of the freewheeling diode and the other end of the filter capacitor are both connected to the system ground.

[0023] Optionally, each LED linear dimming branch also includes a low-pass filter, an error amplifier and a sampling resistor, the positive end of the LED load is connected to the DC output voltage, the negative end of the LED load is connected to the drain end of the dimming switch tube to form a common end of the LED load and the dimming switch tube, the source end of the dimming switch tube is connected to one end of the sampling resistor and the inverting input end of the error amplifier, the gate end of the dimming switch tube is connected to the output end of the error amplifier, the other end of the sampling resistor is connected to the system ground, the in-phase input end of the error amplifier is connected to the output end of the low-pass filter, and the input end of the low-pass filter is connected to a dimming signal.

[0024] Compared with the prior art, the technical solution of the present invention has one of the following beneficial effects:

[0025] 1. The adaptive linear dimming power supply system of the present invention includes an adaptive voltage output module and an LED linear dimming module with at least one LED linear dimming branch. The adaptive voltage output module is a dual-controller architecture, wherein the first controller and the second controller are respectively located on different integrated circuit main cores and are separated from each other. The second controller can receive a sampling signal generated by the common end of the LED load and the dimming switch tube in the LED linear dimming branch, and transmit a corresponding adjustment control signal (i.e., a current signal) to the first controller according to the sampling signal. Thus, on the one hand, it can avoid the problem that the DC output voltage cannot be fed back in real time and the system dynamic response performance is poor due to the ground terminal potential of the first controller being higher than the system ground. On the other hand, it can ensure that the chip where the first controller is located and the chip where the second controller is located (i.e., the control chip of the adaptive linear dimming power supply system) only need a very small voltage-resistant area, without having to withstand excessively high voltage, thereby reducing the cost of the control chip and improving the flexibility of the system design.

[0026] 2. The DC output voltage output by the adaptive voltage output module can change in real time with the feedback sampling signal to adapt to the dimming depth of the LED load in the LED linear dimming branch and the number of LED light-emitting diodes in series in the LED load (the voltage drop of the LED light-emitting diodes). It has good dynamic response, simple system design and wide application occasions.

[0027] 3. The deeper the linear dimming depth (the smaller the current flowing through the LED load) or the smaller the LED load (that is, the fewer the number of LEDs in series), the smaller the DC output voltage output by the adaptive voltage output module. Compared with the constant DC output voltage value in the prior art, the voltage from the drain end of the dimming switch tube in each LED linear dimming branch to the ground can be adaptively set to a minimum value to ensure that the dimming switch tube operates in the saturation zone. Therefore, the temperature rise, thermal stress and voltage stress of the dimming switch tube can be controlled to a minimum, and the efficiency and reliability of the entire system can be improved.

[0028] 4. When there are more than two LED linear dimming branches, the adaptive linear dimming power supply system also has a multiplexer, which can filter out the minimum value from the sampling signals generated by all the LED linear dimming branches (i.e., the drain voltage of the dimming switch tube), so that the adaptive voltage output module can adaptively adjust the DC output voltage it outputs according to the minimum value. As a result, the adaptive voltage output module can adaptively adjust the DC output voltage according to the dimming depth of the LED load and the size of the LED load. While ensuring the normal operation of each LED linear dimming branch, the overall dynamic response performance and efficiency of the system are improved.

[0029] 5. Since the sampling signal comes directly from the common end of the LED load and the dimming switch tube in each LED linear dimming branch (that is, the voltage from the drain end of the dimming switch tube to the ground), the voltage stress of the power switch tube in the first controller under different load conditions can be kept constant, thereby increasing system reliability and improving dynamic response. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The invention is a circuit structure diagram of a multi-channel linear dimming power supply system.

[0031] Figure 2 Schematic diagram of the circuit structure of the adaptive linear dimming power supply system according to the first embodiment of the present invention.

[0032] Figure 3A This is an exemplary schematic diagram of the circuit structure of the multiplexer according to the first embodiment of the present invention.

[0033] Figure 3BThis is another exemplary schematic diagram of the circuit structure of the multiplexer according to the first embodiment of the present invention.

[0034] Figure 4 It is a schematic diagram of the circuit structure of the PWM generator of the first embodiment of the present invention.

[0035] Figure 5 Schematic diagram of the circuit structure of the driving signal converter according to the first embodiment of the present invention.

[0036] Fig. 6A FIG. 1 is a schematic diagram showing an example of a circuit structure of a driving signal detector according to a first embodiment of the present invention.

[0037] Figure 6B is another exemplary schematic diagram of the circuit structure of the driving signal detector according to the first embodiment of the present invention.

[0038] Figure 7 Schematic diagram of the circuit structure of the adaptive linear dimming power supply system according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0039] As described in the background technology, in the existing multi-channel linear dimming power supply system, since the output voltage can be sampled by the sampling capacitor C3 through the diode D6 only in the demagnetization stage, there are problems such as low sampling accuracy, poor dynamic response, low overall system efficiency and short life.

[0040] In order to improve the overall efficiency and dynamic response performance of the system, the core idea of ​​the present invention is that: the LED linear dimming module includes at least one LED linear dimming branch, the LED linear dimming branch has an LED load and a dimming switch tube, the LED load is connected in series with the dimming switch tube, and the LED linear dimming branch generates a sampling signal from the common end of the LED load and the dimming switch tube; the adaptive voltage output module includes a first controller and a second controller respectively located on different integrated circuit main cores, the second controller is used to generate a corresponding adjustment control signal according to the sampling signal generated by the corresponding LED linear dimming branch, the first controller is used to receive an input voltage and the adjustment control signal, and adjust the input voltage to a DC output voltage according to the adjustment control signal to power each LED linear dimming branch, and the input voltage is greater than the DC output voltage.

[0041] In the whole system of the present invention, the collected voltage is not the DC output voltage output by the adaptive voltage output module, but the voltage of the common end of the LED load and the dimming switch tube in each LED linear dimming branch (i.e., the drain voltage of the dimming switch tube). Therefore, the adaptive voltage output module can adaptively adjust the output voltage according to the dimming depth of the LED load of the LED linear dimming branch and the number of LED light-emitting diodes connected in series to ensure that the drain voltage of the dimming switch tube is relatively low. Therefore, the overall dynamic response performance and efficiency of the system are improved, and the application requirements of different dimming depths and different LED load sizes can be met. The adaptive linear dimming power supply system of the present invention can be applied to various adaptive linear dimming occasions, especially in the application occasions where the input is connected to AC voltage or high voltage DC voltage (>80V) and the constant voltage output is connected to multiple linear dimming loads.

[0042] Furthermore, when the LED linear dimming module includes n LED linear dimming branches, and n≥2, the adaptive linear dimming power supply system of the present invention also has a multiplexer, which is connected to the common end of the LED load and the dimming switch tube in each LED linear dimming branch (i.e., the drain end of the dimming switch tube), and is used to receive and compare the sampling signals generated by all the LED linear dimming branches (i.e., the drain end voltage of the dimming switch tube), and filter out the minimum value therefrom and transmit it to the adaptive voltage output module; the adaptive voltage output module is connected to the positive end of the LED load of each LED linear dimming branch, and is used to convert the grid side voltage (e.g., an AC voltage or a DC voltage greater than 80V) into a DC output voltage, to power each LED linear dimming branch, and automatically adjust the DC output voltage according to the minimum value.

[0043] The technical solution proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0044] It should be noted that, in this application document, unless the context clearly indicates an exception, the words "a", "an", "a kind" and / or "the" do not specifically refer to the singular, but may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of clearly identified steps and elements, and these steps and elements do not constitute an exclusive list, and the method or device may also include other steps or elements.

[0045] Unless otherwise specifically stated, the relative arrangement of the parts, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0046] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0047] It should be understood that when a component is referred to as being "connected to another component," it may be directly on, coupled to, coupled to, or contacting the other component, or there may be intervening components. An electrical path exists between the two connected components that allows current to flow. The electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even without direct contact between the conductive components.

[0048] Embodiment 1

[0049] Figure 2 FIG. 4 is a circuit diagram of the adaptive linear dimming power line system of this embodiment.

[0050] Please refer to Figure 2 This embodiment provides an adaptive linear dimming power supply system based on a buck circuit (step-down circuit), which includes an adaptive voltage output module 1, an LED linear dimming module 2 and a multiplexer 3.

[0051] The LED linear dimming module 2 has n parallel LED linear dimming branches 21-2n, where n is a natural number not less than 2. Each LED linear dimming branch includes a low-pass filter, an error amplifier, a dimming switch tube, a sampling resistor and an LED load, wherein the positive end of the LED load is connected to the output end of the adaptive voltage output module 1 to access the DC output voltage Vo output by the adaptive voltage output module 1, the negative end of the LED load is connected to the drain end of the dimming switch tube to form a source end of the dimming switch tube connected to one end of the sampling resistor and the inverting input end of the error amplifier, the other end of the sampling resistor is connected to the system ground, the in-phase input end of the error amplifier is connected to the output end of the low-pass filter, the input end of the low-pass filter is connected to a dimming signal, and the sampling resistor is used to provide the error amplifier with a corresponding sampling voltage signal (i.e., the voltage from the source end of the dimming switch tube to the ground). Specifically, the first LED linear dimming branch 21 includes a low-pass filter 210, an error amplifier EA1, a dimming switch tube S1, a sampling resistor Rcs1 and an LED load LED1. The LED load LED1 can be an LED light string, which is formed by a number of LED light-emitting diodes connected in series. The dimming switch tube S1 can be an NMOS tube. The positive end of the LED load LED1 is connected to the DC output voltage Vo, and the negative end of the LED load LED1 is connected to the drain end of the dimming switch tube S1 to form a common end of the LED load LED1 and the dimming switch tube S1 to generate a sampling signal Vf1 of the first LED linear dimming branch 21. The source end of the dimming switch tube S1 is connected to the sampling resistor One end of Rcs1 and the inverting input end of the error amplifier EA1, the gate end of the dimming switch tube S1 is connected to the output end of the error amplifier EA1, the other end of the sampling resistor Rcs1 is connected to the system ground, the non-inverting input end of the error amplifier EA1 is connected to the output end of the low-pass filter 210, the input end of the low-pass filter 210 is connected to a dimming signal PWM1, the low-pass filter 210 converts the dimming signal PWM1 into a reference voltage signal Vref1, Vref1 is proportional to the duty cycle of PWM1, through the adjustment of the error amplifier EA1, in steady state, the sampling voltage signal Vcs1 = I1*Rcs1 = Vref1, and finally linear dimming is achieved, wherein I1 is the current flowing through the LED load LED1.The second LED linear dimming branch 22 includes a low-pass filter 220, an error amplifier EA2, a dimming switch tube S2, a sampling resistor Rcs2 and an LED load LED2. The LED load LED2 can be an LED lamp string, which is formed by a plurality of LED lamps connected in series. The dimming switch tube S2 can be an NMOS tube. The positive end of the LED load LED2 is connected to the DC output voltage Vo, and the negative end of the LED load LED2 is connected to the drain end of the dimming switch tube S2 to form a common end of the LED load LED2 and the dimming switch tube S2 to generate a sampling signal Vf2 of the second LED linear dimming branch 22. The source end of the dimming switch tube S2 is connected to one end of the sampling resistor Rcs2 to generate a sampling signal Vf2 of the second LED linear dimming branch 22. And the inverting input end of the error amplifier EA2, the gate end of the dimming switch tube S2 (that is, the control end of S2) is connected to the output end of the error amplifier EA2, the other end of the sampling resistor Rcs2 is connected to the system ground, the non-inverting input end of the error amplifier EA2 is connected to the output end of the low-pass filter 220, the input end of the low-pass filter 220 is connected to a dimming signal PWM2, the low-pass filter 220 converts the dimming signal PWM2 into a reference voltage signal Vref2, Vref2 is proportional to the duty cycle of PWM2, through the adjustment of the error amplifier EA2, in steady state, the sampling voltage signal Vcs2 = I2*Rcs2 = Vref2, and finally linear dimming is achieved, wherein I2 is the current flowing through the LED load LED2. The nth LED linear dimming branch 2n includes a low-pass filter 2n0, an error amplifier EAn, a dimming switch tube Sn, a sampling resistor Rcsn and an LED load LEDn. The LED load LEDn can be an LED lamp string, which is formed by a number of LED lamps connected in series. The dimming switch tube Sn can be an NMOS tube. The positive end of the LED load LEDn is connected to the DC output voltage Vo, and the negative end of the LED load LEDn is connected to the drain end of the dimming switch tube Sn to form a common end of the LED load LEDn and the dimming switch tube Sn to generate a sampling signal Vfn of the nth LED linear dimming branch 2n. The source end of the dimming switch tube Sn is connected to one end of the sampling resistor Rcsn to generate a sampling signal Vfn of the nth LED linear dimming branch 2n. And the inverting input end of the error amplifier EAn, the gate end of the dimming switch tube Sn (that is, the control end of Sn) is connected to the output end of the error amplifier EAn, the other end of the sampling resistor Rcsn is connected to the system ground, the non-inverting input end of the error amplifier EAn is connected to the output end of the low-pass filter 2n0, and the input end of the low-pass filter 2n0 is connected to a dimming signal PWMn. The low-pass filter 2n0 converts the dimming signal PWMn into a reference voltage signal Vrefn, and Vrefn is proportional to the duty cycle of PWMn. Through the adjustment of the error amplifier EAn, in steady state, the sampling voltage signal Vcsn=In*Rcsn=Vrefn, and finally linear dimming is achieved, wherein In is the current flowing through the LED load LEDn.In addition, the specific structures of the 3rd to n-1st LED linear dimming branches are similar to the structures of the 1st, 2nd, and nth LED linear dimming branches described above, and will not be described in detail here. It should be noted that the technical solution of the present invention is not limited to the solution of using a sampling resistor as a sampling unit in each LED linear dimming branch to sample the source voltage of the dimming switch tube, but can also be other sampling solutions well known to those skilled in the art. For example, in other embodiments of the present invention, the sampling resistor in each LED linear dimming branch is replaced by a MOS transistor.

[0052] The multiplexer 3 is mainly used to receive and compare the sampling signals Vf1~Vfn (i.e., the drain voltage of the dimming switch tubes S1~Sn, which can also be called the ground voltage of the drain terminal of the dimming switch tubes S1~Sn, and also the negative terminal voltage of the LED loads LED1~LEDn) generated by the n-way LED linear dimming branches 21~2n, and select the minimum value Vfb from Vf1~Vfn, Vfb=min(Vf1, Vf2,…, Vfn), and then transmit the minimum value Vfb to the adaptive voltage output module 1.

[0053] It should be noted that the present embodiment does not limit the specific circuit implementation of the multiplexer 3 , and any suitable circuit that can implement the functions of the multiplexer 3 can be used as the multiplexer 3 of the present embodiment.

[0054] Please refer to Figure 3AAs an example of a specific circuit implementation of the multiplexer 3 of this embodiment, the multiplexer 3 can be implemented by connecting n identical diodes with a common anode. At this time, the minimum value Vfb=Vd+min(Vf1, Vf2, ..., Vfn), and Vd is the conduction voltage drop of the diode. Specifically, the multiplexer 3 includes n diodes Ds1~Dsn and a resistor R1. The cathode of each diode is used as an input end of the multiplexer 3 and is respectively connected to the drain end of the dimming switch tube of the corresponding LED linear dimming branch (that is, the negative end of the corresponding LED load, which is also the common end of the LED load and the dimming switch tube). For example, the cathode of the diode Ds1 is connected to the drain end of the dimming switch tube S1 (that is, connected to the negative end of the LED load LED1, which is also the common end of the LED1 and the dimming switch tube S1), and the cathode of the diode Ds2 is connected to the drain end of the dimming switch tube S2 (that is, connected to the negative end of the LED load LED2, which is also the common end of the LED1 and the dimming switch tube S1). The cathode of the diode Dsn is connected to the drain end of the dimming switch tube Sn (that is, connected to the negative end of the LED load LEDn, which is also the common end of the LEDn and the dimming switch tube Sn), the anodes of all diodes Ds1 to Dsn are connected together to form a node as the output end of the multiplexer for outputting the minimum value Vfb, one end of the resistor R1 is connected to the node (that is, the anodes of all diodes Ds1 to Dsn), and the other end of the resistor R1 is connected to the DC output voltage Vo output by the adaptive voltage output module 1 or to the DC voltage VCC, which is a fixed DC voltage.

[0055] Please refer to Figure 3BAs another example of the specific circuit implementation of the multiplexer 3 of this embodiment, the multiplexer 3 can also be implemented by using a multi-stage voltage comparator to compare one by one, and in this case, the minimum value Vfb=min(Vf1, Vf2, ..., Vfn). Specifically, the multiplexer 3 includes n-1 levels of voltage comparators cmp1~cmp(n-1), n-1 levels of first switches K11~K1(n-1) and n-1 levels of second switches K21~K2(n-1), wherein the non-inverting input end of the first-level voltage comparator cmp1 is connected to the drain end of the dimming switch tube S1 (i.e., the common end of LED1 and the dimming switch tube S1), and is connected to the sampling signal Vf1 (i.e., the drain end voltage of the dimming switch tube S1) generated by the first LED linear dimming branch 21, the inverting input end of the first-level voltage comparator cmp1 is connected to the drain end of the dimming switch tube S2 (i.e., the common end of LED2 and the dimming switch tube S2), and is connected to the sampling signal Vf2 (i.e., the drain end voltage of the dimming switch tube S2) generated by the second LED linear dimming branch 22, and the first The control end of the first-stage first switch K11 and the control end of the first-stage second switch K21 are both connected to the output end of the first-stage voltage comparator cmp1, one end of the first-stage first switch K11 is connected to the non-inverting input end of the first-stage voltage comparator cmp1, one end of the first-stage second switch K21 is connected to the inverting input end of the first-stage voltage comparator cmp1, and the other end of the first-stage first switch K11 is connected to the other end of the first-stage second switch K21, forming a first-stage node min1 for outputting the minimum value of Vf1 and Vf2. The voltage comparator cmp1 can compare the sizes of Vf1 and Vf2, and correspondingly control the first-stage first switch K11 or the first-stage second switch K21 to be turned on to output the minimum value min1=(Vf1, Vf2) of Vf1 and Vf2 to the first-stage node min1.The non-inverting input terminal of the second-stage voltage comparator cmp2 is connected to the first-stage node min1, the inverting input terminal of the second-stage voltage comparator cmp2 is connected to the drain terminal of the dimming switch tube S3 (i.e., the common terminal of LED3 and the dimming switch tube S3), and is connected to the sampling signal Vf3 (i.e., the drain terminal voltage of the dimming switch tube S3) generated by the third LED linear dimming branch 23, the control terminal of the second-stage first switch K12 and the control terminal of the second-stage second switch K22 are both connected to the output terminal of the second-stage voltage comparator cmp2, ​​one end of the second-stage first switch K12 is connected to the non-inverting input terminal of the second-stage voltage comparator cmp2, ​​and the second-stage second switch K22 is connected to the sampling signal Vf3 generated by the third LED linear dimming branch 23. One end of K22 is connected to the inverting input terminal of the second-stage voltage comparator cmp2, ​​and the other end of the second-stage first switch K12 is connected to the other end of the second-stage second switch K22, forming a second-stage node min2 for outputting the minimum value of Vf1~Vf3. The voltage comparator cmp2 can compare the size of Vf3 and min1=(Vf1,Vf2), and correspondingly control the conduction of the second-stage first switch K12 or the second-stage second switch K22 to output the minimum value min2=(Vf1,Vf2,Vf3) of Vf3 and min1=(Vf1,Vf2) to the non-inverting input terminal of the third-stage voltage comparator cmp3. The non-inverting input terminal of the n-1th voltage comparator cmp(n-1) is connected to the n-2th node min(n-2), and the inverting input terminal of the n-1th voltage comparator cmp(n-1) is connected to the drain terminal of the dimming switch tube Sn (i.e., the common terminal of LEDn and the dimming switch tube Sn) to access the sampling signal Vfn (i.e., the drain terminal voltage of the dimming switch tube Sn) generated by the nth LED linear dimming branch 2n. The control terminal of the n-1th first switch K1(n-1) and the control terminal of the n-1th second switch K2(n-1) are both connected to the output terminal of the n-1th voltage comparator cmp(n-1), one end of the n-1th first switch K1(n-1) is connected to the non-inverting input terminal of the n-1th voltage comparator cmp(n-1), and one end of the n-1th second switch K2(n-1) is connected to the The inverting input terminal of the n-1-th voltage comparator cmp(n-1), the other end of the n-1-th first switch K1(n-1) is connected to the other end of the n-1-th second switch K2K1(n-1), and forms the n-1-th node min(n-1) for outputting the minimum value of Vf1~Vfn. The n-1-th node min(n-1) is the output terminal of the multiplexer 3 for outputting the minimum value Vfb=(Vf1, Vf2,…, Vfn). The voltage comparator cmp(n-1) can compare the size of Vfn and min(n-2)=(Vf1, Vf2,…, Vfn-1), and accordingly control the n-1-th first switch K1(n-1) or the n-1-th second switch K2(n-1) to turn on to output Vfb=min(Vf1, Vf2,…, Vfn).That is to say, in the multiplexer 3 of this example, the control end of the first switch and the control end of the second switch of each stage are connected to the output end of the comparator of the same stage, and one end of the first switch and one end of the second switch of each stage are respectively connected to the two input ends of the comparator of the same stage; and for all comparators except the first-stage voltage comparator, one input end of the i-th-stage voltage comparator is connected to the sampling signal Vfi+1 generated by the i+1-th LED linear dimming branch, and the other input end of the i-th-stage voltage comparator is connected to the other end of the i-1-th stage first switch and the other end of the i-1-th stage second switch, 2≤i≤n-1 and i is an integer; the other end of the n-1-th stage first switch and the other end of the n-1-th stage second switch are connected together to form the output end of the multiplexer 3 for outputting the minimum value Vfb.

[0056] Please refer to Figure 2The adaptive voltage output module 1 is a buck circuit structure and adopts a dual controller architecture, which is suitable for AC / DC or >80V DC. The adaptive voltage output module 1 specifically includes a rectifier bridge 11, an input filter capacitor C1, a first controller 12, a second controller 13, a freewheeling diode D5, a filter inductor L and an output filter capacitor C2. The first controller 12 and the second controller 13 are respectively located on different integrated circuit main cores to achieve mutual separation. The ground terminal of the first controller 12 (i.e., the source terminal S of the power switch tube Q1) has a potential higher than the system ground, and the ground terminal of the second controller 13 is connected to the system ground GND. The rectifier bridge is composed of four diodes D1, D2, D3, and D4 connected to each other. The cathodes of diodes D1 and D2 are connected to each other to form the output end of the rectifier bridge 11, and are connected to one end of the input filter capacitor C1 and the drain end D of the power switch tube Q1 in the first controller 12. The anode of diode D1 is connected to the cathode of diode D3 to form an input end of the rectifier bridge 11, and is connected to the positive pole of the power grid AC. The anode of diode D2 is connected to the cathode of diode D4 to form the other input end of the rectifier bridge 11, and is connected to the negative pole of the power grid AC. The anodes of diodes D3 and D4 and the other end of C1 are all connected to the system ground GND. The cathode of the freewheeling diode D5 is connected to the source end S of the power switch tube Q1 and one end of the filter inductor L. The other end of the filter inductor L is connected to one end of the output filter capacitor C2. The anode of the freewheeling diode D5 and the other end of the output filter capacitor C2 are all connected to the system ground GND. The voltage on the AC side of the power grid is rectified by the rectifier bridge 11 and filtered by the input filter capacitor C1 to obtain a DC input voltage (also called bus voltage, not shown). The DC input voltage is controlled by the first controller 12 and the second controller 13 to generate a DC output voltage Vo that is less than the DC input voltage. Vo supplies power to each LED linear dimming branch 21 to 2n in the LED linear dimming module 2. The second controller 13 can generate a corresponding adjustment control signal IPWM (i.e., a current pulse signal) according to the minimum value Vfb output by the multiplexer 3, and transmit it to the first controller through the Sout port. The first controller 12 is used to adjust the DC output voltage Vo according to the adjustment control signal IPWM, so that Vo can be automatically adjusted according to the LED load size and light brightness in the LED linear dimming module 2.

[0057] Please refer to Figure 2In this embodiment, the second controller 13 includes a first PWM generator 131 and a drive signal converter 132. The first PWM generator 131 is connected to the output end of the multiplexer 3, and is used to access the minimum value Vfb and generate a corresponding original PWM signal according to the minimum value Vfb. The drive signal converter 132 is connected to the first PWM generator 131, and is used to convert the original PWM signal into the adjustment control signal IPWM and transmit it to the first controller 12. The ground terminal of the first PWM generator 131 is the ground terminal of the second controller 13 and is connected to the system ground GND.

[0058] Please refer to Figure 4 As an example, the first PWM generator 131 includes an error amplifier EA0 and a voltage comparator Cmp0. The non-inverting input terminal of the error amplifier EA0 is connected to a reference voltage Vref, and the inverting input terminal is connected to the output terminal of the multiplexer 3 to connect the minimum value Vfb sampled and fed back by the multiplexer 3. The output terminal of the error amplifier EA0 is connected to the non-inverting input terminal of the voltage comparator Cmp0, and the inverting input terminal of the voltage comparator Cmp0 is connected to a triangle wave signal. The output terminal of the voltage comparator Cmp0 outputs the original PWM signal. The difference between the minimum value Vfb sampled and fed back by the multiplexer 3 and the reference voltage Vref is amplified by the error amplifier EA0 to obtain the Vcomp voltage signal. The voltage comparator Cmp0 compares the Vcomp voltage signal with the triangle wave signal to obtain the original PWM signal (i.e. Figure 4 PWM in ).

[0059] Please refer to Figure 5 As an example, the drive signal converter 132 includes a switch control unit 1321 and a current pulse generating unit 1322 connected in sequence, wherein the switch control unit 1321 is used to access the original PWM signal and perform switching under the control of the original PWM signal, and the current pulse generating unit 1322 is used to generate a current pulse signal according to the switching of the switch control unit 1321 as the adjustment control signal IPWM. Specifically, the current pulse generating unit 1322 includes a first MOS tube Q0 and a current limiting resistor R1, and the switch control unit 1321 includes a second MOS tube Q2. The first MOS transistor Q0 may be a depletion-type field effect transistor, the second MOS transistor Q2 may be an enhancement-type NMOS transistor, the gate terminal of the first MOS transistor Q0 is connected to the system ground, the drain terminal of the first MOS transistor Q0 is the output terminal of the driving signal converter 132, and is used to output the adjustment control signal IPWM, the source terminal of the first MOS transistor Q0 is connected to one end of the current limiting resistor R1, the other end of the current limiting resistor R1 is connected to the drain terminal of the second MOS transistor Q2, the source terminal of the second MOS transistor Q2 is connected to the system ground, and the gate terminal of the second MOS transistor Q2 is connected to the output terminal of the first PWM generator 131 to access the original PWM signal (i.e. Figure 4 and 5 PWM in). When the original PWM signal is at a high level, Q2 is turned on, and Q0 generates a current signal IPWM=Vp / R1, where Vp is the pinch-off voltage of Q0. When the original PWM signal is at a low level, Q2 is turned off, and IPWM at Q0=0, thereby generating a current pulse signal IPWM synchronized with the original PWM signal as a regulation control signal, which is transmitted to the first controller 12 through the Sout port.

[0060] Please refer to Figure 2 The first controller 12 includes a drive signal detector 121, a driver 122, a power switch tube Q1 and a linear regulator (LDO) 123. The input terminal Sin of the drive signal detector 121 is connected to the output port Sout of the drive signal converter 132 of the second controller 13 through a lead. The drive signal detector 121 is used to convert the adjustment control signal IPWM output by the second controller 13 into a drive signal driver synchronized with the original PWM signal. The driver 122 is used to control the conduction and cutoff of the power switch tube Q1 according to the control of the drive signal. The power switch tube Q1 can be an NMOS tube. The linear regulator (LDO) 123 can convert the DC input voltage output by the rectifier bridge 11 into the voltage required by the drive signal detector 121 and the driver 122. The source terminal S of the power switch tube Q1 is the ground terminal of the first controller 12, and the ground terminal of the drive signal detector 121 and the ground terminal of the driver 122 are both connected to the source terminal S of the power switch tube Q1.

[0061] The IPWM signal output by the second controller 13 is transmitted to the driving signal detector 121 of the first controller 12 through the lead wire. After receiving the IPWM signal, the driving signal detector 121 converts it into a driving signal driver, and then controls the on and off of the power switch tube Q1 through the driver 122, thereby controlling the output Vo of the Buck circuit, forming a closed-loop negative feedback loop. Finally, in steady state, Figure 4 In the first PWM generator 131 shown, Vfb=min(Vf1, Vf2, . . . , Vfn)=Vref, thereby ensuring that each LED linear dimming branch 21-2n can operate normally.

[0062] It should be noted that in Figure 2In the figure, the ground terminal of the second controller 13 is the system ground GND, and the original PWM signal generated in the second controller 13 uses the system ground GND as the reference ground, while the ground terminal of the first controller 12 is the source terminal S of the power switch tube Q1. The ground terminals of the second controller 13 and the first controller 12 are not at the same potential, or in other words, the second controller 13 and the first controller 12 do not share a common ground. If you want to drive Q1, the reference ground of the drive signal output by the driver 122 must be the S terminal, so a conversion is required between the original PWM signal and the drive signal output by the driver 122. Here, the drive signal converter 132 and the drive signal detector 121 are used to implement this function. The greatest advantages of doing so include: (1) being able to transmit the current pulse signal IPWM between the drive signal converter 132 and the drive signal detector 121, so that the chip where the first controller 12 is located and the chip where the second controller 13 is located only require a very small voltage-resistant area and do not need to withstand excessively high voltages, thereby reducing the voltage-resistant requirements and costs of the control chip; (2) being able to achieve real-time feedback and having good system dynamic response performance; (3) limiting the drain-source voltage difference of each dimming switch tube in the multi-line dimming module 2, thereby reducing the heat loss of each dimming switch tube in the multi-line dimming module 2 and improving the efficiency of the entire system.

[0063] Please refer to Figure 2 and 6A As an example of a specific circuit implementation of the drive signal detector 121 of this embodiment, the drive signal detector 121 includes a current mirror, a pull-down resistor R2 and a Schmitt trigger SMT. The current mirror is a basic current mirror, mainly composed of a third MOS tube Q3 and a fourth MOS tube Q4. The third MOS tube Q3 and the fourth MOS tube Q4 can both be PMOS tubes. The gate end of the third MOS tube Q3 is connected to the gate end of the fourth MOS tube Q4 and the drain end of the third MOS tube Q3 and is also connected to the input port Sin of the drive signal detector 121. The drain end of the fourth MOS tube Q4 is used as the output end of the current mirror, connected to one end of the pull-down resistor R2 and the input end of the Schmitt trigger SMT. The source end of the third MOS tube Q3 is connected to the source end of the fourth MOS tube Q4 and is also connected to the drain end of the power switch tube Q1 (that is, Fig. 6A The other end of the pull-down resistor R2 is connected to the source end S of the power switch tube Q1, and the source end S of the power switch tube Q1 serves as the ground end of the first controller 12 (i.e. Figure 2 and Fig. 6AThe output end of the Schmitt trigger SMT is used as the output end of the drive signal detector 121 and is used to output the drive signal driver. The current pulse signal IPWM (i.e., the adjustment control signal) output by the drive signal converter 132 is input by the Sin port of the drive signal detector 121. When the IPWM signal is in the "current state" (i.e., Figure 5 IPWM=Vp / R1), the input voltage of the Schmitt trigger SMT is pulled up by the current mirrored by the fourth MOS tube Q4, and the output of the Schmitt trigger SMT is flipped to a high level; when the IPWM signal is in a "no current state" (i.e. Figure 5 The IPWM in the circuit is 0), the input voltage of the Schmitt trigger SMT is pulled down by the pull-down resistor R2, and the output of the Schmitt trigger SMT is flipped to a low level. In this way, the IPWM signal generated by the second controller 13 is restored by the drive signal detector 121 to a drive signal driver synchronized with the IPWM signal. In other embodiments of the present invention, the current mirror can also be formed by more than three MOS tubes to form a higher level current mirror.

[0064] It should be noted that Figure 4 The first PWM generator 131 shown generates an original PWM signal. Figure 5 The drive signal converter 132 shown in FIG. 1 also outputs a regulation control signal IPWM. Fig. 6A The driving signal detector 121 shown also correspondingly restores only one channel of the regulating control signal IPWM, but the technical solution of the present invention is not limited to the above example. In other examples of the present embodiment, the first PWM generator 131 can also generate multiple channels of original PWM signals, and the regulating control signal IPWM output by the driving signal converter 132 is also multiple channels. Fig. 6A The driving signal detector 121 shown can correspondingly restore the multi-channel regulation control signals IPWM into one channel of driving signal driver.

[0065] Specifically, please refer to Figure 2 and Figure 6B The PWM generator 121 in the second controller 12 can generate two narrow pulse voltage control signals PWMon and PWMoff according to the minimum value Vfb. The PWMon and PWMoff signals can correspond to Figure 4The opening and closing of one original PWM signal in the circuit, the two narrow pulse voltage control signals PWMon and PWMoff are converted into two narrow pulse current control signals IPWMon and IPWMoff by the drive signal converter 132. At this time, as another example of the specific circuit implementation of the drive signal detector 121 of this embodiment, the drive signal detector 121 can simultaneously receive the two signals IPWMon and IPWMoff, and finally convert them into one drive signal driver. The drive signal detector 121 specifically includes two current mirrors, a D flip-flop U3, and two buffers U1 and U2. One of the current mirrors includes two MOS tubes M3 and M4 connected in common gate and a resistor R PD2 The other current mirror includes two MOS tubes M1 and M2 connected in common gate and a resistor R PD1 MOS tubes M1 to M4 can all be PMOS tubes. In the first current mirror, the drain end of M1 is connected to an input port sin1 of the drive signal detector 121, and is also connected to an output end of the drive signal converter 132 to access the IPWMon signal. The source end of M1 and the source end of M2 are connected to each other and to the drain end of the power switch tube Q1 (i.e. Figure 6B The D end of M2 is connected to the resistor R PD1 The output end of the first current mirror is connected to the input end of the buffer U1 to transmit a narrow pulse voltage signal Dri_on synchronized with PWMon to the buffer U1. The resistor R PD1 The reference ground S terminal of the first controller 12 is connected to the source terminal of the power switch tube Q1. In the second current mirror, the drain terminal of M3 is connected to another input port sin2 of the drive signal detector 121, and is also connected to another output terminal of the drive signal converter 132 to access the IPWMoff signal. The source terminal of M3 and the source terminal of M4 are connected to each other and to the drain terminal of the power switch tube Q1 (i.e. Figure 6B The D end of M4 is connected to the resistor R PD2 The output end of the second current mirror is formed by one end of the resistor R and connected to the input end of the buffer U2 to transmit a narrow pulse voltage signal Dri_off synchronized with PWMoff to the buffer U2. PD2The other end is connected to the source end S of the power switch tube Q1 (i.e., the ground end of the first controller 12). The output end of the buffer U1 is connected to the clock input end of the D flip-flop U3, the output end of the buffer U2 is connected to the reset input end R of the D flip-flop U3, the data input end D of the D flip-flop U3 is connected to the logic "1" (i.e., high level), and the output end Q of the D flip-flop U3 is the output end of the drive signal detector 121 and is used to output the drive signal driver. In this example, the falling edge of the Dri_on signal triggers the voltage signal driver output by the D flip-flop U3 to become a high level, and the narrow pulse of the Dri_off signal causes the D flip-flop U3 to be cleared, thereby the drive signal driver output by the D flip-flop U3 becomes a low level, thereby the drive signal detector 121 realizes the function of synchronously converting the two signals IPWMon and IPWMoff into one driver signal. In this example, both current mirrors are basic current mirror structures, but in other embodiments of the present invention, at least one of the two current mirrors can also be a higher-level current mirror built with more than three MOS tubes.

[0066] In the whole system of this embodiment, the sampling signal fed back by the multiplexer 3 to the adaptive voltage output module 1 is not the DC output voltage Vo, but the sampling signals (i.e., the drain voltage of the dimming switch tubes S1~Sn) Vf1~Vfn generated by each LED linear dimming branch 21~2n, and the minimum value Vfb can be screened out from Vf1~Vfn, so that the adaptive voltage output module 1 can control the value of the DC output voltage Vo to adapt to the changes of the LED dimming depth and the LED load size (i.e., the number of LED lamps connected in series) in the LED linear dimming module through the minimum value Vfb. The deeper the dimming depth (i.e., the smaller the current flowing through the LED load) or the smaller the LED load (i.e., the fewer the number of LED lamps connected in series), the smaller the value of Vo, and thus the smaller the voltage difference between the drain and source of the dimming switch tubes S1~Sn, the higher the system efficiency. The adaptability of Vo can ensure that the overall efficiency of the system is very high under different dimming depths or different numbers of LEDs connected in series. In addition, by controlling the minimum value Vfb among Vf1 to Vfn to be equal to the reference voltage Vref (this value is generally the saturation voltage drop of the dimming switch S1), it can be ensured that each LED linear dimming branch can work normally.

[0067] Embodiment 2

[0068] Please refer to Figure 7 This embodiment provides an adaptive linear dimming power supply system based on a flyback circuit, including an adaptive voltage output module 1, an LED linear dimming module 2 and a multiplexer 3. The structures of the LED linear dimming module 2 and the multiplexer 3 and their connection relationship with the adaptive voltage output module 1 are the same as those in the first embodiment, and will not be repeated here.

[0069] The adaptive voltage output module 1 of this embodiment is a flyback circuit structure, and its circuit composition and internal connection relationship are different from those of Example 1. Specifically, the adaptive voltage output module 1 of this embodiment includes a rectifier bridge 11, an input filter capacitor C1, a first controller 12, a second controller 13, a transformer T1, an optocoupler transmitter 14, an optocoupler receiver 15, a freewheeling diode D5 and an output filter capacitor C2. Among them, the first controller 12 and the second controller 13 are located on different integrated circuit main cores to achieve mutual separation. The connection relationship between the rectifier bridge 11 and the input filter capacitor C1 can refer to Example 1, and will not be repeated here.

[0070] The transformer T1 is both an energy storage device and an isolation transformer. One end of the primary coil of the transformer T1 is connected to the output end of the rectifier bridge 11, the other end of the primary coil of the transformer T1 is connected to the port D of the first controller 12, one end of the secondary coil of the transformer T1 is connected to the anode of the freewheeling diode D5, and the other end of the secondary coil of the transformer T1 is connected to the system ground. The cathode of the freewheeling diode D5 is connected to one end of the output filter capacitor C2, and the other end of the output filter capacitor C2 is connected to the system ground. The second controller 13 may include Figure 4 The error amplifier EA0 in the circuit is omitted and the voltage comparison amplifier Cmp0 is omitted to convert the error between the minimum value Vfb=min(Vf1, Vf2…Vfn) output by the multiplexer 3 and the reference voltage Vref into a Vcomp voltage signal. The input end of the optical coupler transmitter 14 is connected to the output end of the second controller 13, and the modulated signal output by the second controller 13 can be transmitted to the optical coupler receiver 15 in the form of light. The output end of the optical coupler receiver 15 is connected to an input end of the first controller 12 to convert the received light into an electrical signal comp and transmit it to the first controller 12.

[0071] In this embodiment, the first controller 13 includes a second PWM generator 124, a driver 122, a power switch tube Q1 and a linear regulator (LDO) 123. The input end of the second PWM generator 124 is connected to the output end of the optocoupler receiver 15. The second PWM generator 124 is used to generate a drive signal driver according to the electrical signal generated by the optocoupler receiver 15. The input end of the driver 122 is connected to the output end of the second PWM generator 124. The output end of the driver 122 is connected to the gate end of the power switch tube Q1. The driver 122 is used to control the conduction and cutoff of the power switch tube Q1 according to the drive signal driver.

[0072] The circuit design of the second PWM generator 124 can refer to the circuit design of the first PWM generator 131 in the first embodiment, and will not be described in detail here. Since the source terminal S of the power switch tube Q1 is the ground terminal of the first controller 13, the ground terminal of the second PWM generator 124 needs to be connected to the source terminal S of the power switch tube Q1.

[0073] In this embodiment, the value of the DC output voltage Vo is adaptive to the dimming depth of the LED linear dimming module 2 and the size of the LED loads LED1 -LEDn (ie, the number of light emitting diodes connected in series). The multiplexer 3 samples the drain voltages Vf1-Vfn of the dimming switch tubes S1-Sn in the LED linear dimming branches 21-2n, and selects the minimum voltage Vfb=min(Vf1, Vf2, ..., Vfn). The error signal between Vfb and a reference voltage Vref is converted into a Vcomp signal through the second controller 13. The Vcomp signal is transmitted to the first controller 12 through the optical coupling of the optocoupler transmitter 14 and the optocoupler receiver 15, and the second PWM generator 124 of the first controller 12 generates a corresponding PWM signal as a driving signal. The driver 122 controls the on and off of the power switch tube Q1, thereby forming a closed-loop feedback system, limiting the sampling signals generated by each LED linear dimming branch to a fixed value, which can reduce the source-drain voltage difference of the dimming switch tube, thereby making the system more efficient, and the voltage stress and thermal stress of the dimming switch tube of each LED linear dimming branch are lower, and the reliability of the entire system is higher.

[0074] It should be noted that the LED linear dimming module 2 in the above-mentioned embodiment 1 and embodiment 2 has at least two LED linear dimming branches, and the adaptive voltage output module 1 is a multi-channel output, and a multiplexer is also required to compare the sampling signals generated by all LED linear dimming branches, so that the adaptive voltage output module 1 can adaptively adjust its output voltage according to the minimum drain voltage. However, the technical solution of the present invention is not limited to this. In other embodiments of the present invention, the LED linear dimming module 2 of the adaptive linear dimming power supply system can also have only one LED linear dimming branch, that is, the adaptive linear dimming power supply system includes an adaptive voltage output module 1 and an LED linear dimming module 2 having only one LED linear dimming branch. At this time, the adaptive voltage output module 1 is a single-channel output, and a multiplexer is not required at this time, and the DC output voltage Vo of the adaptive voltage output module 1 can change with the sampling signal generated in the LED linear dimming branch (that is, the signal generated by the common end of the LED load and the dimming switch tube in the LED linear dimming branch).

[0075] It should be further explained that the adaptive voltage output module 1 in the above-mentioned Embodiment 1 and Embodiment 2 is directly connected to the AC power grid AC, and therefore requires a rectifier bridge 11 and an input filter capacitor C1 to convert the AC power into a DC input voltage. However, the technical solution of the present invention is not limited to this. In other embodiments of the present invention, a DC input voltage (for example, >80V) can also be directly provided to the adaptive voltage output module 1. In this case, the rectifier bridge 11 and the input filter capacitor C1 can be omitted in the adaptive voltage output module 1.

[0076] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. An adaptive linear dimming power supply system, characterized in that: It includes an adaptive voltage output module and an LED linear dimming module, wherein: The LED linear dimming module comprises at least one LED linear dimming branch, wherein the LED linear dimming branch comprises an LED load and a dimming switch tube, wherein the LED load is connected in series with the dimming switch tube, and the LED linear dimming branch generates a sampling signal from a common end of the LED load and the dimming switch tube; The adaptive voltage output module includes a first controller and a second controller respectively located on different integrated circuit chips separated from each other, the second controller is used to generate a corresponding adjustment control signal according to a sampling signal generated by the corresponding LED linear dimming branch, the first controller includes a power switch tube, the first controller is used to receive an input voltage and the adjustment control signal, and control the conduction and cutoff of the power switch tube according to the adjustment control signal, thereby adjusting the input voltage to output a DC output voltage to power each LED linear dimming branch, and the input voltage is greater than the DC output voltage; The source end of the power switch tube is the ground end of the first controller and has a potential higher than that of the system ground. The ground end of the second controller is connected to the system ground.

2. The adaptive linear dimming power supply system according to claim 1, characterized in that: The LED linear dimming module has n LED linear dimming branches, n≥2; the adaptive linear dimming power supply system also includes a multiplexer with n input terminals, each input terminal of the multiplexer is connected to the common terminal of the LED load and the dimming switch tube in the corresponding LED linear dimming branch one by one to receive the sampling signal generated by the LED linear dimming branch, the output terminal of the multiplexer is connected to the corresponding input terminal of the adaptive voltage output module, and the multiplexer is used to receive and compare the sizes of the sampling signals generated by all the LED linear dimming branches, and filter out the minimum value therefrom as the sampling signal transmitted to the adaptive voltage output module, so that the adaptive voltage output module adjusts the DC output voltage according to the minimum value.

3. The adaptive linear dimming power supply system according to claim 2, characterized in that: The multiplexer includes n diodes, the cathode of each diode serves as a corresponding input end of the multiplexer and is connected to the common end of the LED load and the dimming switch tube in the corresponding LED linear dimming branch, and the node formed by the anodes of all the diodes connected together serves as the output end of the multiplexer.

4. The adaptive linear dimming power supply system according to claim 3, characterized in that: The multiplexer further comprises a resistor, one end of which is connected to the node, and the other end of which is connected to the DC output voltage output by the adaptive voltage output module or to a DC voltage.

5. The adaptive linear dimming power supply system according to claim 2, characterized in that: The multiplexer includes an n-1-level voltage comparator, an n-1-level first switch and an n-1-level second switch, wherein two input ends of the first-level voltage comparator are respectively connected to sampling signals generated by the first LED linear dimming branch and the second LED linear dimming branch, the control end of each first switch and the control end of the second switch are connected to the output end of the voltage comparator at the same level, and one end of each first switch and one end of the second switch are respectively connected to two input ends of the voltage comparator at the same level; and for all comparators except the first-level voltage comparator, one input end of the i-th level voltage comparator is connected to the sampling signal generated by the i+1-th LED linear dimming branch, and the other input end of the i-th level voltage comparator is connected to the other end of the i-1-th level first switch and the other end of the i-1-th level second switch, 2≤i≤n-1; the other end of the n-1-th level first switch and the other end of the n-1-th level second switch are connected together to form the output end of the multiplexer.

6. The adaptive linear dimming power supply system according to claim 1, characterized in that: The second controller includes a first PWM generator and a drive signal converter. The first PWM generator is used to generate a corresponding original PWM signal according to a sampling signal generated by the corresponding LED linear dimming branch. The drive signal converter is connected to the first PWM generator and is used to convert the original PWM signal into the adjustment control signal. The ground terminal of the first PWM generator is the ground terminal of the second controller and is connected to the system ground. The first controller also includes a drive signal detector and a driver. The drive signal detector is used to convert the adjustment control signal into a drive signal synchronized with the original PWM signal. The driver is used to control the conduction and cutoff of the power switch tube according to the control of the drive signal to adjust the DC output voltage.

7. The adaptive linear dimming power supply system according to claim 6, characterized in that: The first PWM generator includes an error amplifier and a voltage comparator. The non-inverting input terminal of the error amplifier is connected to a reference voltage, and the inverting input terminal is connected to the sampling signal. The output terminal of the error amplifier is connected to the non-inverting input terminal of the voltage comparator, and the inverting input terminal of the voltage comparator is connected to a triangle wave signal. The output terminal of the voltage comparator outputs the original PWM signal.

8. The adaptive linear dimming power supply system according to claim 6, characterized in that: The drive signal converter includes a switch control unit and a current pulse generating unit connected in sequence, wherein the switch control unit is used to access the original PWM signal and perform switching under the control of the original PWM signal, and the current pulse generating unit is used to generate a current pulse signal according to the switching of the switch control unit to serve as the regulation control signal.

9. The adaptive linear dimming power supply system according to claim 8, characterized in that: The current pulse generating unit includes a first MOS tube and a current limiting resistor, and the switch control unit includes a second MOS tube. The first MOS tube is a depletion-type field effect tube whose gate terminal is connected to the system ground. The drain terminal of the first MOS tube is the output terminal of the current pulse generating unit for outputting the adjustment control signal. The source terminal of the first MOS tube is connected to one end of the current limiting resistor, and the other end of the current limiting resistor is connected to the drain terminal of the second MOS tube. The source terminal of the second MOS tube is connected to the system ground, and the gate terminal of the second MOS tube is connected to the first PWM generator.

10. The adaptive linear dimming power supply system according to claim 6, characterized in that: The drive signal detector includes a current mirror, a pull-down resistor and a Schmitt trigger, wherein the power supply end of the current mirror is connected to the drain end of the power switch tube, the input end of the current mirror is connected to the output end of the drive signal converter, the output end of the current mirror is connected to one end of the pull-down resistor and the input end of the Schmitt trigger, the other end of the pull-down resistor is connected to the source end of the power switch tube, and the output end of the Schmitt trigger is connected to the control end of the power switch tube and is used to output the drive signal.

11. The adaptive linear dimming power supply system according to claim 10, characterized in that: The current mirror includes a third MOS tube and a fourth MOS tube, the third MOS tube and the fourth MOS tube are PMOS, the gate end of the third MOS tube is connected to the gate end of the fourth MOS tube and the drain end of the third MOS tube to form the input end of the current mirror, the drain end of the fourth MOS tube serves as the output end of the current mirror, and the source end of the third MOS tube is connected to the source end of the fourth MOS tube to form the power supply end of the current mirror.

12. The adaptive linear dimming power supply system according to claim 6 or 8, characterized in that: The drive signal converter is used to convert the original PWM signal into two synchronous narrow pulse current control signals. The drive signal detector includes two current mirrors, two buffers and a D flip-flop. The input ends of the two current mirrors are connected to the two narrow pulse current control signals one by one. The output ends of the two current mirrors are respectively connected to the input ends of the two buffers. The output ends of the two buffers are respectively connected to the clock input end and the reset input end of the D flip-flop. The data input end of the D flip-flop is connected to logic "1". The output end of the D flip-flop is the output end of the drive signal detector and is used to output the drive signal.

13. The adaptive linear dimming power supply system according to claim 12, wherein: Each of the current mirrors includes two PMOS tubes connected with a common gate and a resistor, wherein the drain end of one of the PMOS tubes is connected to an output end of the drive signal converter, the drain end of the other PMOS tube is connected to one end of the resistor and forms the output end of the current mirror, and the other end of the resistor is connected to the source end of the power switch tube. The source ends of the two PMOS tubes are connected to each other and serve as the power supply end of the current mirror, and are connected to the drain end of the power switch tube.

14. The adaptive linear dimming power supply system according to claim 6, wherein: The adaptive voltage output module also includes a freewheeling diode, a filter inductor and a filter capacitor. The cathode of the freewheeling diode is connected to the source end of the power switch tube in the first controller and one end of the filter inductor. The source end of the power switch tube serves as the ground end of the first controller. The other end of the filter inductor is connected to one end of the filter capacitor. The anode of the freewheeling diode and the other end of the filter capacitor are both connected to the system ground.

15. The adaptive linear dimming power supply system according to claim 1, characterized in that: Each LED linear dimming branch also includes a low-pass filter, an error amplifier and a sampling resistor. The positive end of the LED load is connected to the DC output voltage, the negative end of the LED load is connected to the drain end of the dimming switch tube to form a common end of the LED load and the dimming switch tube, the source end of the dimming switch tube is connected to one end of the sampling resistor and the inverting input end of the error amplifier, the gate end of the dimming switch tube is connected to the output end of the error amplifier, the other end of the sampling resistor is connected to the system ground, the in-phase input end of the error amplifier is connected to the output end of the low-pass filter, and the input end of the low-pass filter is connected to a dimming signal.

Images