A deep LED dimming control circuit and dimming method

Abstract

The present invention discloses a deep LED dimming control circuit and a dimming method, belonging to the technical field of novel light source control circuits. By further optimizing the dimming depth and optimizing the fluctuation of the dimming depth caused by load changes, no high-frequency ripple and low dimming depth can be achieved at the same time, and no high-frequency ripple and low dimming depth are compatible, and the requirements for system cost, efficiency and system versatility in practical applications are optimized to the greatest extent.

Description

Technical Field

[0001] The present invention relates to the application scope of novel electric light sources, belonging to the technical field of novel light source control circuits, and more specifically to a deep LED dimming control circuit and a dimming method. Background Art

[0002] At present, LED lighting sources are the most advanced electric light sources in modern times. Due to the characteristics of low power consumption, light weight, and constant current drive, LED lighting sources will be more and more widely used. In order to meet the dimming function and no low-frequency flicker, the existing technology usually adopts a two-level architecture to achieve it. The front stage adopts an isolated constant voltage system of AC to DC, and the back stage uses a DC-DC constant current system that can support dimming.

[0003] However, the existing DC-DC constant current system that supports dimming uses two methods for deep dimming, one is to perform chopping dimming output, and the other is to reduce the reference voltage. For the chopping dimming output method, the advantage is that the dimming depth is low, and the disadvantage is that the LED current has high-frequency ripple. For the method of reducing the reference voltage, the advantage is that the LED current has no high-frequency and low-frequency ripples, and the disadvantage is that the dimming depth is low and the dimming depth is poor. When the load voltage changes, the dimming depth will also fluctuate. In some high-end dimming markets, the requirements for LED current ripple and dimming depth are very high. How to be compatible with no high-frequency ripple and low dimming depth has become a difficult problem that the market needs to solve.

[0004] Among them, in the existing DC-DC dimming constant current control circuit structure, there are two reasons why the dimming depth cannot be very low. One is the influence of the offset voltage on the minimum reference voltage, and the other is the influence of the junction capacitance of the MOS tube M1 and the diode D1. During deep dimming, the MOS tube M1 is turned on, the inductor L is excited, and the excitation voltage ΔV=VDC-VCO. After the excitation is completed, the inductor L and the junction capacitance of the MOS tube M1 resonate, and the inductor L and the junction capacitance of the freewheeling diode D1 resonate. The inductor L charges the junction capacitance of the MOS tube M1, and the junction capacitance of the freewheeling diode D1 discharges the inductor L. As a result, after the MOS tube M1 is turned off, the inductor current will continue to increase, causing the LED current to increase, and the dimming depth cannot be reduced. Moreover, as the ΔV voltage and the junction capacitance increase, the switching frequency increases, the inductor current increases, the LED current increases, and the dimming depth becomes worse.

[0005] Therefore, how to provide a deep LED dimming control circuit and a dimming method is a problem that those skilled in the art need to solve urgently. Summary of the invention

[0006] In view of this, the present invention provides a deep LED dimming control circuit and a dimming method, which further optimizes the dimming depth and the fluctuation of the dimming depth caused by load changes for the deep dimming method of reducing the benchmark, so that no high-frequency ripple and low dimming depth can be achieved at the same time, and is compatible with no high-frequency ripple and low dimming depth, and optimizes to the greatest extent to meet the requirements of system cost, efficiency and system versatility in practical applications.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A deep LED dimming control circuit comprises: a power supply circuit, a constant current control circuit, a dimming depth control circuit, and an LED load, wherein the power supply circuit, the constant current control circuit, the dimming depth control circuit, and the LED load are connected in sequence.

[0009] Preferably, the dimming depth control circuit includes: a first resistor, a second resistor, a third resistor, a fourth resistor, a first voltage regulator tube, a first NMOS tube, a second NMOS tube and a capacitor, wherein:

[0010] One end of the first resistor is connected to one end of the constant current control circuit, and is connected to the drain of the first NMOS tube, the drain of the second NMOS tube and one end of the capacitor, the other end of the first resistor is connected to the cathode of the first voltage regulator tube, and is connected to the gate of the first NMOS tube and the gate of the second NMOS tube, one end of the second resistor is connected to the source of the first NMOS tube, the other end of the second resistor is connected to the anode of the first voltage regulator tube, and one end of the fourth resistor is connected to the other end of the constant current control circuit, one end of the third resistor is connected to the source of the second NMOS tube, and the other end of the third resistor is connected to the other end of the fourth resistor and the other end of the capacitor;

[0011] The LED load is connected in parallel with the capacitor.

[0012] Preferably, the first resistor, the first voltage regulator, the first NMOS transistor, and the second resistor form a first constant current source.

[0013] Preferably, the first resistor, the first voltage regulator, the second NMOS transistor, and the third resistor form a second constant current source.

[0014] In another aspect, the present invention provides a deep LED dimming control method, comprising:

[0015] S100: The power supply circuit provides a DC power supply and inputs it into the constant current control circuit (2);

[0016] S200: The constant current control circuit performs constant current control on the connected DC power supply and outputs a constant current;

[0017] S300: The dimming depth control circuit receives a constant current and performs control to achieve dimming depth control of the LED load.

[0018] Preferably, the step S300 specifically includes:

[0019] S310: the dimming depth control circuit inputs the received constant current into the first constant current source and the second constant current source to form a first current and a second current respectively, and sets a third current as the difference between the constant current output by the constant current control circuit and the first current;

[0020] S320: When the second current is close to the third current, the output current of the LED load is the difference between the third current and the second current, thereby achieving dimming of the LED load.

[0021] It can be known from the above technical scheme that compared with the prior art, the present invention discloses a deep LED dimming control circuit and a dimming method, which is improved based on the dimming method of lowering the reference, and the implementation method is simple, low cost, and can be flexibly configured. At the same time, the first resistor, the first voltage regulator, the first NMOS tube, and the second resistor form a first constant current source. Compared with the discharge of ordinary resistors, the same current can be discharged in a larger load range, which is beneficial to improve the consistency of the dimming depth. The first resistor, the first voltage regulator, the first NMOS tube, and the second resistor form a second constant current source. Compared with the discharge of ordinary resistors, the same current can be discharged in a larger load range, which is beneficial to improve the consistency of the dimming depth and achieve the technical effect of maintaining a low dimming depth when the load changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 The accompanying drawing is a schematic diagram of the structure of a deep LED dimming control circuit provided by the present invention;

[0024] Figure 2 The accompanying drawing is a structural diagram of a DC-DC dimming constant current control circuit in the prior art provided by Example 1 of the present invention;

[0025] Figure 3The accompanying drawing is a circuit diagram of a deep LED dimming control according to embodiment 1 of the present invention.

[0026] In the attached Figure 1 Middle: 1-power supply circuit, 2-constant current control circuit, 3-dimming depth control circuit, 4-LED load. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] In a specific embodiment, the present invention is based on a dimmable DC-DC constant current circuit with a switching frequency of 100K-1MHZ, which is a dimming method for reducing the reference.

[0030] See attached Figure 1 As shown, embodiment 1 of the present invention provides a deep LED dimming control circuit, including: a power supply circuit 1, a constant current control circuit 2, a dimming depth control circuit 3, and an LED load 4. The power supply circuit 1, the constant current control circuit 2, the dimming depth control circuit 3, and the LED load are connected in sequence.

[0031] In a specific embodiment, the constant current control circuit 2 can refer to the attached Figure 2 As shown, it is a structure diagram of a DC-DC dimming constant current control circuit in the prior art, including: a control module 21, a diode D1, an inductor L1, and a MOS tube M1;

[0032] The input end of the control module 21 is connected to the power supply circuit 1 and the MOS tube M1; the drain of the MOS tube M1 is connected to one end of the inductor L1 and the positive electrode of the diode D1, and the other end of the inductor L1 is connected to the negative output end of the control module 21; the negative electrode of the diode D1 is connected to the positive output end of the control module 21.

[0033] In a specific embodiment, the dimming depth control circuit 3 can refer to the attached Figure 3 As shown, the structure diagram of the deep LED dimming control circuit of the present invention provided in this embodiment includes: a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor Rcs, a first voltage regulator tube Z1, a first NMOS tube Q1, a second NMOS tube Q2 and a capacitor C1, wherein,

[0034] One end of the first resistor R1 is connected to the positive output end of the constant current control circuit 2, and is connected to the drain of the first NMOS tube Q1, the drain of the second NMOS tube Q2 and one end of the capacitor C1, the other end of the first resistor R1 is connected to the cathode of the first voltage regulator tube Z1, and is connected to the gate of the first NMOS tube Q1 and the gate of the second NMOS tube Q2, one end of the second resistor R2 is connected to the source of the first NMOS tube Q1, the other end of the second resistor R2 is connected to the anode of the first voltage regulator tube Z1, and one end of the fourth resistor Rcs is connected to the negative output end of the constant current control circuit 2, one end of the third resistor R3 is connected to the source of the second NMOS tube Q2, and the other end of the third resistor R3 is connected to the other end of the fourth resistor Rcs and the other end of the capacitor C1;

[0035] Specifically, the LED load 4 is connected in parallel with the capacitor C1.

[0036] In a specific embodiment, the first resistor R1, the first voltage regulator Z1, the first NMOS transistor Q1, and the second resistor R2 form a first constant current source.

[0037] Specifically, the first constant current source mainly functions to discharge the current of the LED load 4 caused by the resonance of the junction capacitance between the discharge inductor L1 and the MOS tube M1 and the diode D1.

[0038] In a specific embodiment, the first resistor R1, the first voltage regulator Z1, the second NMOS transistor Q2, and the third resistor R3 form a second constant current source.

[0039] Specifically, the second constant current source mainly functions to discharge the current of the LED load 4 caused by the minimum reference voltage.

[0040] More specifically, the first constant current source and the second constant current source work simultaneously, so as to maintain a relatively low dimming depth when the output LED load 4 changes.

[0041] On the other hand, Embodiment 1 of the present invention discloses a deep LED dimming control method, characterized by comprising:

[0042] S100: The power supply circuit 1 provides a DC power supply to the circuit;

[0043] S200: The constant current control circuit 2 performs constant current control according to the connected DC power supply and outputs a constant current;

[0044] S300 : The dimming depth control circuit 3 is used to control the received constant current to achieve dimming depth control of the LED load 4 .

[0045] Preferably, step S300 specifically includes:

[0046] S310: the dimming depth control circuit 3 forms a first constant current source and a second constant current source according to the received constant current;

[0047] S320: The first constant current source and the second constant current source provide a stable direct current to the LED load 4, so that the LED load 4 maintains a certain dimming depth.

[0048] In a specific embodiment, the working principle is as follows: set the current IL as the inductor current, the current I1 as the drain current of the first NMOS transistor Q1, the current I2 as the drain current of the second NMOS transistor Q2, and the current I3 as the current difference between the inductor current IL and the drain current I1 of the first NMOS transistor Q1;

[0049] When the first NMOS transistor Q1 operates in the saturation region and the gate-source voltage of the first NMOS transistor Q1 is fixed, the drain current thereof will not change with the drain-source voltage.

[0050] The drain current I1 of the first NMOS tube Q1 is:

[0051]

[0052] BVz is the reverse breakdown voltage of the first voltage regulator tube Z1, and Vth1 is the gate opening threshold voltage of the first NMOS tube Q1.

[0053] The second NMOS transistor Q2 operates in a saturation region. When the gate-source voltage of the second NMOS transistor Q2 is fixed, the drain current thereof does not change with the drain-source voltage.

[0054] The drain current I2 of the second NMOS tube Q2 is:

[0055]

[0056] Wherein BVz is the reverse breakdown voltage of the first voltage regulator tube Z1, and Vth2 is the gate opening threshold voltage of the second NMOS tube Q2.

[0057] Generally, the gate turn-on threshold voltages of the first NMOS transistor Q1 and the second NMOS transistor Q2 can be selected to be equal, that is, the parameters Vth1 and Vth2 are equal.

[0058] The current I3 is the current difference between the inductor current IL and the current I1. The current I1 is set to be greater than the sum of the inductor current IL and the junction capacitance resonant current in the diode D1. In this way, when the output LED load 4 changes, that is, when the excitation voltage ΔV changes, the current I3 remains unchanged under low dimming depth. At the same time, since the output current of the LED load 4 is: ILED=I3-I2, the current I2 is further set to be close to the current I3, and the output current of the LED load 4 will be further reduced, thereby achieving a low dimming depth at a lower dimming depth and maintaining a low dimming depth under different load conditions.

[0059] It can be known from the above technical scheme that compared with the prior art, the present invention discloses a deep LED dimming control circuit and a dimming method, which is improved based on the dimming method of lowering the reference, and the implementation method is simple, low cost, and can be flexibly configured. At the same time, the first resistor, the first voltage regulator, the first NMOS tube, and the second resistor form a first constant current source. Compared with the discharge of ordinary resistors, the same current can be discharged in a larger load range, which is beneficial to improve the consistency of the dimming depth. The first resistor, the first voltage regulator, the first NMOS tube, and the second resistor form a second constant current source. Compared with the discharge of ordinary resistors, the same current can be discharged in a larger load range, which is beneficial to improve the consistency of the dimming depth and achieve the technical effect of maintaining a low dimming depth when the load changes.

[0060] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0061] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A deep LED dimming control circuit, characterized in that: include: A power supply circuit (1), a constant current control circuit (2), a dimming depth control circuit (3), and an LED load (4), wherein the power supply circuit (1), the constant current control circuit (2), the dimming depth control circuit (3), and the LED load (4) are connected in sequence; The dimming depth control circuit (3) comprises: a first resistor, a second resistor, a third resistor, a fourth resistor, a first voltage regulator tube, a first NMOS tube, a second NMOS tube and a capacitor, wherein: One end of the first resistor is connected to one end of the constant current control circuit, and is connected to the drain of the first NMOS tube, the drain of the second NMOS tube and one end of the capacitor; the other end of the first resistor is connected to the cathode of the first voltage regulator tube, and is connected to the gate of the first NMOS tube and the gate of the second NMOS tube; one end of the second resistor is connected to the source of the first NMOS tube, the other end of the second resistor is connected to the anode of the first voltage regulator tube, and one end of the fourth resistor is connected to the other end of the constant current control circuit (2); one end of the third resistor is connected to the source of the second NMOS tube, and the other end of the third resistor is connected to the other end of the fourth resistor and the other end of the capacitor; The LED load (4) is connected in parallel with the capacitor; The first resistor, the first voltage regulator, the first NMOS transistor, and the second resistor form a first constant current source; The first resistor, the first voltage regulator, the second NMOS transistor, and the third resistor form a second constant current source.

2. A control method using the deep LED dimming control circuit of claim 1, characterized in that: include: S100: the power supply circuit (1) provides a direct current power supply and inputs the direct current power supply to the constant current control circuit (2); S200: the constant current control circuit (2) performs constant current control on the connected DC power supply and outputs a constant current; S300: the dimming depth control circuit (3) receives a constant current and performs control to achieve dimming depth control of the LED load (4); The step S300 specifically includes: S310: the dimming depth control circuit (3) inputs the received constant current into the first constant current source and the second constant current source to form a first current and a second current respectively, and sets the third current to be the difference between the constant current output by the constant current control circuit (2) and the first current; S320: When the second current is close to the third current, the output current of the LED load (4) is the difference between the third current and the second current, thereby achieving dimming of the LED load (4).

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