LED linear driving circuit and system

Abstract

The utility model provides an LED linear driving circuit and system, and the circuit comprises a diode which is connected in series with a bus capacitor between the two output ends of a rectifier bridge; the first linear constant current module and the LED lamp are connected in series and coupled between the two ends of the bus capacitor; the second linear constant current module and the LED lamp are connected in series and coupled between the two output ends of the rectifier bridge; wherein when the input voltage is smaller than or equal to the load voltage of the LED lamp, the bus capacitor provides a first driving current for the LED lamp through the first linear constant current module; and when the input voltage is greater than the load voltage of the LED lamp, the input voltage provides a second driving current for the LED lamp through the second linear constant current module. According to the invention, better current THD can be provided by switching the driving current of the LED load, and the stability and reliability of the system are improved.

Description

Technical Field

[0001] The present application relates to the field of LED lighting, and in particular to an LED linear drive circuit and system. Background Art

[0002] Compared with traditional light sources, LED (Light Emitting Diode) has the advantages of small size, energy saving, long life, high brightness and environmental protection, so it is widely used in indoor and outdoor lighting.

[0003] The brightness of an LED lamp is related to its driving current, and the corresponding driving schemes are a linear driving scheme and a switch driving scheme, which respectively use a linear regulating transistor and a switch controlling transistor to adjust the driving current of the LED lamp.

[0004] As people's living standards improve, the requirements for the luminous quality of LED lamps are getting higher and higher, and how to provide high-quality driving current is the key to achieving high-quality driving of LED lamps. Utility Model Content

[0005] In order to solve the above technical problems, the present application provides an LED linear drive circuit and system, which provides better current THD by switching the driving current of the LED load, thereby improving the stability and reliability of the system.

[0006] According to a first aspect of the present application, there is provided an LED linear drive circuit, characterized in that it includes:

[0007] A diode, wherein the diode and the bus capacitor are connected in series between a first output terminal and a second output terminal of a rectifier bridge, and an input voltage is provided between the first output terminal and the second output terminal of the rectifier bridge;

[0008] A first linear constant current module, wherein the first linear constant current module is coupled in series with the LED lamp between the first input end and the second end of the bus capacitor;

[0009] A second linear constant current module, wherein the second linear constant current module is coupled in series with the LED lamp between the first output terminal and the second output terminal of the rectifier bridge;

[0010] Wherein, when the input voltage is less than or equal to a preset third reference voltage, the first linear constant current module is turned on, the second linear constant current module is turned off, a first current loop is formed between the bus capacitor, the first linear constant current module and the LED lamp, and the bus capacitor provides a first driving current to the LED lamp through the first current loop;

[0011] When the input voltage is greater than a preset third reference voltage, the first linear constant current module is turned off, the second linear constant current module is turned on, a second current loop is formed between the rectifier bridge, the second linear constant current module and the LED lamp, and the input voltage provides a second driving current to the LED lamp through the second current loop.

[0012] Optionally, the second driving current is equal to the first driving current.

[0013] Optionally, when the input voltage is greater than the bus capacitor voltage, the input voltage charges the bus capacitor through the diode, and when the input voltage is lower than the bus capacitor voltage, the input voltage stops charging the bus capacitor.

[0014] Optionally, the current output end of the first linear constant current module and the current output end of the second linear constant current module are both connected to the current input end of the LED lamp through a first resistor.

[0015] Optionally, the first linear constant current module includes:

[0016] a first transistor, wherein a current input end of the first transistor is connected to a first end of the bus capacitor, and a current output end of the first transistor is connected to the LED lamp through the first resistor;

[0017] a first amplifier, wherein the positive input terminal receives a first reference voltage, the negative input terminal is connected to the current output terminal of the first transistor, and the output terminal of the first amplifier is connected to the control terminal of the first transistor,

[0018] The first amplifier is used to drive the first transistor according to a comparison result between the first reference voltage and the voltage across the first resistor to obtain the first driving current.

[0019] Optionally, the second linear constant current module includes:

[0020] a second transistor, wherein a current input end of the second transistor is connected to the first output end of the rectifier bridge, and a current output end of the second transistor is connected to the LED lamp through the first resistor;

[0021] a second amplifier, wherein the positive input terminal receives a second reference voltage, the negative input terminal is connected to the current output terminal of the second transistor, and the output terminal of the second amplifier is connected to the control terminal of the second transistor,

[0022] The second amplifier is used to drive the second transistor according to a comparison result between the second reference voltage and the voltage across the first resistor to obtain the second driving current;

[0023] The first reference voltage is equal to the second reference voltage.

[0024] Optionally, the LED linear drive circuit further includes:

[0025] an enabling control module, connected to the first output end of the rectifier bridge, the first linear constant current module and the second linear constant current module respectively, the enabling control module receives the input voltage and a preset third reference voltage, and is used to control the first linear constant current module and the second linear constant current module to be turned on in turn according to the magnitude relationship between the input voltage and the preset third reference voltage,

[0026] Among them, when the input voltage is less than or equal to a preset third reference voltage, the enable control module controls the first linear constant current module to turn on and the second linear constant current module to turn off; when the input voltage is greater than the preset third reference voltage, the enable control module controls the first linear constant current module to turn off and the second linear constant current module to turn on.

[0027] Optionally, the enabling control module includes:

[0028] A sampling unit, receiving the input voltage, and outputting a sampling signal of the input voltage based on a first reference ground of the LED linear driving circuit;

[0029] A comparator, wherein the positive input terminal receives the sampling signal of the input voltage, the negative input terminal receives the third reference voltage, and the output terminal is connected to the enable terminal of the second linear constant current module;

[0030] The first inverter has an input end connected to the output end of the comparator, and the output end of the first inverter is connected to the enable end of the first linear constant current module.

[0031] Optionally, the enabling control module includes:

[0032] A sampling unit, receiving the input voltage, and outputting a sampling signal of the input voltage based on a first reference ground of the LED linear driving circuit;

[0033] A reference voltage generating unit, wherein the first input terminal receives the sampling signal of the input voltage, the second input terminal receives the third reference voltage, the first input terminal outputs the first reference voltage to the first linear constant current module, and the second input terminal outputs the second reference voltage to the second linear constant current module;

[0034] When the first reference voltage is greater than the second reference voltage, the first linear constant current module is turned on and the second linear constant current module is turned off.

[0035] When the first reference voltage is less than the second reference voltage, the first linear constant current module is turned off, and the second linear constant current module is turned on.

[0036] Optionally, the sampling unit includes:

[0037] A second resistor and a third resistor are connected in series between the first output end of the rectifier bridge and the first reference ground, and the sampling unit outputs a sampling signal of the input voltage at a connection node between the second resistor and the third resistor.

[0038] Optionally, the sampling unit includes:

[0039] The third transistor has a drain connected to the first output end of the rectifier bridge and a control end connected to the first reference ground. The sampling unit outputs a sampling signal of the input voltage at the source of the third transistor.

[0040] Optionally, the first linear constant current module includes a first transistor and a first amplifier, the second linear constant current module includes a second transistor and a second amplifier, and the first linear constant current module, the second linear constant current module and the enable control module are integrated in the same chip.

[0041] Optionally, at least one of the diode and the rectifier bridge is sealed with the chip in a package.

[0042] Optionally, the current input terminal of the LED lamp serves as the first reference ground, and the second output terminal of the rectifier bridge serves as the second reference ground.

[0043] According to a second aspect of the present application, there is provided an LED linear drive system, comprising:

[0044] a rectifier bridge for rectifying an AC voltage to provide an input voltage between a first output terminal and a second output terminal;

[0045] LED lights;

[0046] As described in any embodiment of the present application, the LED linear driving circuit is connected in series with the LED lamp between the first output terminal and the second output terminal of the rectifier bridge to provide a driving current to the LED lamp.

[0047] The beneficial effects of this application include at least:

[0048] The linear LED driving circuit provided in the embodiment of the present application is provided with a first current loop from the bus capacitor to the first linear constant current module and then to the load LED lamp, and a second current loop from the input voltage to the second linear constant current module and then to the load LED lamp, and the first linear constant current module and the second linear constant current module are set to be turned on in turn according to the different magnitude relationships between the input voltage and the third reference voltage, so that the bus capacitor can be controlled to supply power to the load only when the input voltage is less than or equal to the load voltage, and the input voltage is used to supply power to the load at other times, such as when the input voltage is greater than the load. Compared with the prior art, the power supply time of the bus capacitor to the load is reduced and the power supply time of the input voltage to the load is increased, thereby reducing the capacitance requirement of the bus capacitor, so that the capacitance of the bus capacitor can be set to be smaller, while reducing the system cost, the current distortion at the input end of the system is also reduced, the power factor of the circuit is improved, the flicker on the load current is reduced, the total harmonic distortion (THD) of the current in the LED linear driving circuit is improved, and the stability and reliability of the system are improved;

[0049] In the embodiment of the present application, the power supply current of the bus capacitor to the load is set to be equal to or similar to the power supply current of the input voltage to the load, which can keep the load current stable when the power supply source is switched, further eliminating flicker.

[0050] It should be noted that the above general description and the following detailed description are merely exemplary and explanatory and do not limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic circuit diagram of an LED linear driving system according to the prior art is shown;

[0052] Figure 2 A schematic waveform diagram of an LED linear driving system according to the prior art is shown;

[0053] Figure 3 A schematic block diagram of an LED linear driving system according to the present application is shown;

[0054] Figure 4 A schematic circuit diagram of an LED linear driving system according to a first embodiment of the present application is shown;

[0055] Figure 5 A schematic circuit diagram of an LED linear driving system according to a second embodiment of the present application is shown;

[0056] Figure 6 A schematic circuit diagram of an LED linear driving system according to a third embodiment of the present application is shown;

[0057] Figure 7 A schematic waveform diagram of an LED linear driving system according to the present application is shown. DETAILED DESCRIPTION

[0058] In order to facilitate the understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0059] References to "one embodiment" or "some embodiments" etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear at different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0060] In the description of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment described as "exemplary" or "for example" in the present application should not be interpreted as being more preferred or more advantageous than other embodiments. "Multiple" refers to two or more than two. In addition, in order to facilitate the clear description of the technical solutions of the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not limit them to be necessarily different.

[0061] In addition, the same reference numerals in the figures represent the same or similar structures, and thus their repeated description will be omitted, that is, the various parts in this specification are described in a combination of parallel and progressive manner, and each part focuses on the differences from other parts, and the same or similar parts between the various parts can refer to each other. The words expressing position and direction described in this application are all explained using the accompanying drawings as examples, but they can also be changed as needed, and the changes made are all included in the scope of protection of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportion.

[0062] In the present application, the term "LED lamp" refers to, for example, an LED lamp string formed by connecting a plurality of LEDs in series. If a plurality of LEDs form an LED lamp string, the cathode of the preceding LED in the LED lamp string is connected to the anode of the next LED. The anode of the LED lamp refers to the anode of the first LED lamp in the LED lamp string, and the cathode of the LED lamp refers to the cathode of the last LED lamp in the LED lamp string.

[0063] This application may be presented in a variety of forms, some examples of which are described below.

[0064] Figure 1 FIG. 2 shows a schematic circuit diagram of an LED linear driving circuit according to the prior art. Figure 1 As shown, the LED linear drive circuit 100 includes a rectifier bridge B1, a bus capacitor C1, a diode D10, a linear constant current module 110 and a linear constant current module 120. The rectifier bridge B1 is used to rectify the AC voltage Vac to obtain an input voltage Vin. The bus capacitor C1 and the diode D10 are connected in series and connected between the two output ends of the rectifier bridge B1 to store the input voltage Vin output by the rectifier bridge B1. The linear constant current module 110 is connected in parallel with the diode D10. The linear constant current module 120 and the LED light string 130 are connected in series between the two output ends of the rectifier bridge B1. The linear constant current module 110 includes a power tube Q10, an amplifier 111 and a resistor R10. The linear constant current module 120 includes a power tube Q11, an amplifier 121 and a resistor R11. The linear constant current module 110 provides a charging circuit for the bus capacitor C1, and the diode D10 provides a discharge path for the bus capacitor C1.

[0065] Under AC voltage input, the input current Iin charges the bus capacitor C1, and at the same time, discharges through the LED light string 130. The charging current Iq1 of the bus capacitor C1 is determined by the linear constant current module 110, and the load current Iled of the LED light string 130 is determined by the linear constant current module 120. The linear constant current module 110 is used to compare the voltage across the resistor R10 with the reference voltage Vrefa, generate a linear drive signal according to the difference between the two, control the drive current flowing through the power tube Q10, and finally maintain the charging current Iq1 of the bus capacitor C1 at Vrefa / R10. The linear constant current module 120 is used to compare the voltage across the resistor R11 with the reference voltage Vrefb, generate a linear drive signal according to the difference between the two, control the drive current Iq2 flowing through the power tube Q11, and finally maintain the load current Iled of the LED light string 130 at Vrefb / R11.

[0066] Figure 2 FIG. 4 shows a schematic waveform diagram of an LED linear driving circuit according to the prior art. Figure 2As shown, the LED linear drive circuit 100 of the prior art only needs the voltage Vc1 on the bus capacitor C1 to be always greater than the voltage Vled on the LED lamp 130 so that the load current Iled of the LED lamp 130 can be maintained at a constant value. The input current Iin starts to build up when the input voltage Vin is greater than the voltage Vled on the LED lamp 130; when the input voltage Vin is greater than the voltage Vc1 on the bus capacitor C1, it quickly reaches a peak value as the input voltage Vin rises. It can be seen from the current waveform that, on the one hand, when the capacitance of the bus capacitor C1 is large, since the driving current Iq2 provided by the linear constant current module 120 is fixed, the load current Iled passing through the LED lamp string 130 is always fixed, and flicker-free driving is achieved at this time. However, in each half-wave of the AC power, the bus capacitor C1 with a larger capacitance will produce very large current distortion at the input end of the system, which is easy to reduce the power factor of the circuit and cause the THD (Total High Voltage HDD) of the current. The total harmonic distortion (THR) of the LED light string 130 is poor, which makes it unable to meet the requirements of various environmental certifications for subharmonics, reducing the stability and reliability of the system. When the capacitance of the capacitor C1 is small, the voltage ripple of the bus capacitor C1 in each half cycle will be large, which is easy to generate flicker on the load current Iled. On the other hand, after the input AC voltage of the LED linear drive circuit 100 of the prior art reaches the peak value, as long as the voltage Vc1 on the bus capacitor C1 exceeds the input voltage Vin, the discharge path of the bus capacitor C1 will always exist. At this time, the load current Led of the LED light string 130 is jointly provided by the bus capacitor C1 and the input voltage Vin, which will cause the waveform distortion of the input current Iin to increase. In order to take into account the LED drive circuit for flicker removal and meet the harmonic requirements of the input current, it is usually necessary to set a bus capacitor C1 with a larger capacitance in the LED drive circuit, which is costly.

[0067] Figure 3 FIG. 1 is a schematic block diagram of an LED linear drive system according to the present application. Figure 3 As shown, the LED linear drive system 200 includes a rectifier bridge B1, a bus capacitor C1, an LED linear drive circuit 210 and an LED lamp 240. The rectifier bridge B1 is used to rectify the AC voltage Vac to obtain an input voltage Vin. The bus capacitor C1 is coupled to the output end of the rectifier bridge B1 and is used to store the input voltage Vin output by the rectifier bridge B1. The LED linear drive circuit 210 includes a diode D1, a first linear constant current module 21220 and a second linear constant current module 230. The diode D1 and the bus capacitor C1 are connected in series between the first output end and the second output end of the rectifier bridge B1; the first linear constant current module 220 and the LED lamp 240 are coupled in series between the first input end and the second end of the bus capacitor C1; the second linear constant current module 230 and the LED lamp 240 are coupled in series between the first output end and the second output end of the rectifier bridge B1.

[0068] The first linear constant current module 220 and the second linear constant current module 230 are both configured to selectively start one according to the comparison result between the input voltage Vin and the load voltage of the LED lamp 240, so as to provide driving current to the LED lamp 240 according to different power sources in different time periods. In some preferred examples, the first linear constant current module 220 and the second linear constant current module 230 provide equal driving current to the LED lamp 240 in different time periods, so as to keep the current of the LED lamp 240 stable when the power source is switched, and eliminate flicker.

[0069] Among them, when the input voltage Vin is less than or equal to the load voltage of the LED lamp 240, the first linear constant current module 220 is turned on, the second linear constant current module 230 is turned off, and a first current loop is formed between the bus capacitor C1, the first linear constant current module 220 and the LED lamp 240. At this time, the bus capacitor C1 provides the first drive current Iq1 to the LED lamp 240 through the first current loop; when the input voltage Vin is greater than the load voltage of the LED lamp 240, the first linear constant current module 220 is turned off, the second linear constant current module 230 is turned on, and a second current loop is formed between the rectifier bridge B1, the second linear constant current module 230 and the LED lamp 240. At this time, the input voltage Vin provides the second drive current Iq2 to the LED lamp 240 through the second current loop.

[0070] Specifically, refer to Figure 7 The LED linear driving system 200 of this embodiment has three working states:

[0071] When the input voltage Vin is in the first interval from being greater than the load voltage of the LED lamp 240 and slowly rising to the maximum value, the LED linear drive system 200 is in the first working state. In this stage, the input voltage Vin is greater than the voltage Vc1 of the bus capacitor C1, and the first linear constant current module 220 is turned off, and the second linear constant current module 230 is turned on, that is, the first current loop is disconnected, and the second current loop is connected. The input voltage Vin charges the bus capacitor C1 through the diode D1, and at the same time, the input voltage Vin supplies power to the LED lamp 240 through the second linear constant current module 230. At this time, the current in the LED lamp 240 is equal to the second drive current Iq2 provided by the second linear constant current module 230;

[0072] When the input voltage Vin is in the second interval where it slowly decreases from the maximum value to a load voltage greater than the LED lamp 240, the LED linear drive system 200 is in the second working state. In this stage, the first linear constant current module 220 is turned off, and the second linear constant current module 230 is turned on, that is, the first current loop is disconnected, and the second current loop is connected. Since the input voltage Vin is less than the voltage Vc1 on the bus capacitor C1 at this time, the input voltage Vin stops charging the bus capacitor C1, and the input voltage Vin only supplies power to the LED lamp 240 through the second linear constant current module 230. At this time, the current in the LED lamp 240 is equal to the second drive current Iq2 provided by the second linear constant current module 230. At the same time, in this stage, due to the unidirectional conduction characteristic of the diode D1, the bus capacitor C1 does not have a discharge path, and the voltage Vc1 on the bus capacitor C1 remains unchanged;

[0073] When the input voltage Vin is in a third interval less than or equal to the load voltage of the LED lamp 240, the LED linear drive system 200 is in a third working state. During this stage, the first linear constant current module 220 is turned on and the second linear constant current module 230 is turned off, that is, the first current loop is connected and the second current loop is disconnected. Only the bus capacitor C1 supplies power to the LED lamp 240 through the first linear constant current module 220. At this time, the current in the LED lamp 240 is equal to the first drive current Iq1 provided by the first linear constant current module 220.

[0074] In some preferred examples, the first driving current Iq1 is equal to the second driving current Iq2.

[0075] Figure 4 , Figure 5 and Figure 6 Schematic circuit diagrams of LED linear drive systems in the first embodiment, the second embodiment and the third embodiment based on the basic implementation scheme of the present application are shown respectively, and the main difference between the three is the internal structure of the LED linear drive circuit 210. It should be noted that these three embodiments are only three specific circuit implementations based on the concept of the present application, and do not constitute a limitation on the basic implementation scheme of the present application.

[0076] When implementing it, Figure 4 , Figure 5 and Figure 6 As shown, the LED linear drive system 200 includes a rectifier bridge B1, a bus capacitor C1, an LED linear drive circuit 210, and an LED lamp 240. The rectifier bridge B1, the LED linear drive circuit 210, and the bus capacitor C1 are connected to the LED lamp 240. Figure 3The LED linear driving circuit 210 includes not only a diode D1, a first linear constant current module 220 and a second linear constant current module 230, but also an enabling control module 250, which is used to realize the aforementioned function of turning on the first linear constant current module 220 and the second linear constant current module 230 in turn according to the comparison result between the input voltage Vin and the load voltage of the LED lamp 240, so as to provide driving current to the LED lamp 240 according to different power sources in different time periods. Exemplarily, the enable control module 250 is respectively connected to the first output end of the rectifier bridge B1, the enable end of the first linear constant current module 220 and the enable end of the second linear constant current module 230, and the enable control module 250 receives the input voltage Vin and the preset third reference voltage Vref3, and is used to control the first linear constant current module 220 and the second linear constant current module 230 to be turned on alternately according to the magnitude relationship between the input voltage Vin and the preset third reference voltage Vref3, wherein the preset third reference voltage Vref3 is used to characterize the load voltage of the LED lamp 240, and the enable control module 250 controls the first linear constant current module 220 to be turned on and the second linear constant current module 230 to be turned off when the input voltage Vin is less than or equal to the preset third reference voltage Vref3; when the input voltage Vin is greater than the preset third reference voltage Vref3, the enable control module 250 controls the first linear constant current module 220 to be turned off and the second linear constant current module 230 to be turned on.

[0077] exist Figure 4 In the example shown, the first linear constant current module 220 specifically includes: a transistor Q1 and an amplifier 221. Among them, the current input terminal (for example, drain) of the transistor Q1 is connected to the first end of the bus capacitor C1, the second end of the bus capacitor C1 is connected to the second output end of the rectifier bridge B1, the current output terminal (for example, source) of the transistor Q1 is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the current input terminal (for example, anode) of the LED lamp 240, and the current output terminal (for example, cathode) of the LED lamp 240 is connected to the second output terminal of the rectifier bridge B1; the positive input terminal of the amplifier 221 receives the first reference voltage Vref1, the negative input terminal of the amplifier 221 is connected to the current output terminal of the transistor Q1, and the output terminal of the amplifier 221 is connected to the control terminal (for example, gate) of the transistor Q1.

[0078] The amplifier 221 is used to drive the transistor Q1 according to the comparison result between the first reference voltage Vref1 and the voltage formed at both ends of the resistor R1 by the current flowing through the resistor R1, so as to obtain the first driving current Iq1. Exemplarily, the first reference voltage Vref1 is provided by a reference voltage source provided inside or outside the LED linear driving circuit 210. Of course, other implementations are also possible. The first reference voltage Vref1 can also be obtained by appropriately processing any node voltage in the LED linear driving system 200.

[0079] The second linear constant current module 230 specifically includes: a transistor Q2 and an amplifier 231. The current input terminal (e.g., drain) of the transistor Q2 is connected to the first output terminal of the rectifier bridge B1, the current output terminal (e.g., source) of the transistor Q2 is connected to the first end of the resistor R1, the second end of the resistor R1 is connected to the current input terminal (e.g., anode) of the LED lamp 240, and the current output terminal (e.g., cathode) of the LED lamp 240 is connected to the second output terminal of the rectifier bridge B1; the positive input terminal of the amplifier 231 receives the second reference voltage Vref2, the negative input terminal of the amplifier 231 is connected to the current output terminal of the transistor Q2, and the output terminal of the amplifier 231 is connected to the control terminal (e.g., gate) of the transistor Q2.

[0080] The amplifier 231 is used to drive the transistor Q2 according to a comparison result between the second reference voltage Vref2 and a voltage formed at two ends of the resistor R1 by the current flowing through the resistor R1 , so as to obtain a second driving current Iq2 .

[0081] Exemplarily, the first reference voltage Vref1 and the second reference voltage Vref2 are provided by corresponding reference voltage sources disposed inside or outside the LED linear driving circuit 210. Of course, other implementations are also possible. The first reference voltage Vref1 and the second reference voltage Vref2 can also be obtained by appropriately processing the voltage at any node in the LED linear driving system 200. In some preferred examples, the first reference voltage Vref1 is equal to the second reference voltage Vref2.

[0082] In this embodiment, the current input end of the LED lamp 240, namely the second end of the resistor R1, serves as the first reference ground GND1 of the LED linear driving system 200, and the second output end of the rectifier bridge B1 serves as the second reference ground GND2 of the LED linear driving system 200.

[0083] It should be noted that, in this embodiment, the current output end of the first linear constant current module 220 and the current output end of the second linear constant current module 230 are connected to the current input end of the LED lamp 240 through the resistor R1, so that the first linear constant current module 220 and the second linear constant current module 230 can share the same resistor element when limiting the first drive current Iq1 and the second drive current Iq2, thereby saving the number of components and helping to reduce the circuit area and reduce the circuit cost.

[0084] It can be understood that since the first reference voltage Vref1 is equal to the second reference voltage Vref2, the first linear constant current module 220 and the second linear constant current module 230 can match the same resistor R1, or the first linear constant current module 220 and the second linear constant current module 230 can match two resistors with equal resistance values ​​respectively, so that the current values ​​of the first drive current Iq1 and the second drive current Iq2 respectively defined by the first linear constant current module 220 and the second linear constant current module 230 can be equal.

[0085] In this embodiment, the enable control module 250 specifically includes: a sampling unit 260, a comparator 251 and an inverter 252. The sampling unit 260 receives an input voltage Vin, and is used to output a sampling signal Vs of the input voltage Vin based on the first reference ground GND1 of the LED linear driving circuit 210; the positive input terminal of the comparator 251 receives the sampling signal Vs of the input voltage Vin, the negative input terminal of the comparator 251 receives the third reference voltage Vref3, the output terminal of the comparator 251 outputs an enable signal EN1, and is connected to the enable terminal of the second linear constant current module 230; the input terminal of the inverter 252 is connected to the output terminal of the comparator 251 to receive the enable signal EN1, and the output terminal of the inverter 252 outputs an inverted signal EN2 of the enable signal EN1, and is connected to the enable terminal of the first linear constant current module 220.

[0086] exist Figure 4 In the example shown, the sampling unit 260 includes a resistor R2 and a resistor R3 connected in series between the first output terminal of the rectifier bridge B1 and the first reference ground GND1. At this time, the sampling unit 260 outputs a sampling signal Vs of the input voltage at the connection node of the resistor R2 and the resistor R3. At this time, the aforementioned third reference voltage Vref3 represents the load voltage of the LED lamp 240, and the enabling control module 250 determines the magnitude relationship between the input voltage Vin and the load voltage of the LED lamp 240 by comparing the sampling signal Vs of the input voltage with the third reference voltage Vref3.

[0087] Combination Figure 4 and Figure 7, when the input voltage Vin is in the first interval from the load voltage greater than the LED lamp 240 to the maximum value, the sampling signal Vs of the input voltage is greater than the third reference voltage Vref3, the comparator 251 outputs a valid enable signal EN1, and after the inverter 252 performs inversion processing, an invalid enable signal EN2 is obtained at the same time, the valid enable signal EN1 controls the second linear constant current module 230 to turn on (for example, the enable amplifier 231 performs a valid output, and controls the transistor Q2 to turn on), and the invalid enable signal EN2 controls the first linear constant current module 220 to turn off (for example, the enable amplifier 221 performs an invalid output, and controls the transistor Q1 to turn off), so that the first current loop is disconnected and the second current loop is connected. In this stage, the input voltage Vin is greater than the voltage Vc1 on the bus capacitor C1, and the input voltage Vin charges the bus capacitor C1 through the diode D1. At the same time, the input voltage Vin also supplies power to the LED lamp 240 through the second current loop formed by the transistor Q2, the resistor R1 and the LED lamp 240. The amplifier 231 controls the gate voltage of the transistor Q2 so that the voltage across the resistor R1 is equal to the second reference voltage Vref2, that is, Iq2=Vref2 / R1. Since the first linear constant current module 220 is in the off state at this time, only the second drive current Iq2 supplies power to the LED lamp 240, and thus the drive current of the LED lamp 240 is equal to the second drive current Iq2 at this time.

[0088] When the input voltage Vin is in the second interval that slowly decreases from the maximum value to a value greater than the load voltage of the LED lamp 240, the sampling signal Vs of the input voltage is still greater than the third reference voltage Vref3, and the comparator 251 continues to output a valid enable signal EN1, and after being inverted by the inverter 252, an invalid enable signal EN2 is obtained at the same time. The valid enable signal EN1 controls the second linear constant current module 230 to turn on (for example, the enable amplifier 231 performs a valid output and controls the transistor Q2 to turn on), and the invalid enable signal EN2 controls the first linear constant current module 220 to turn off (for example, the enable amplifier 221 performs an invalid output and controls the transistor Q1 to turn off), so that the first current loop is disconnected and the second current loop is connected. In this stage, the input voltage Vin is lower than the voltage Vc1 on the bus capacitor C1, so the input voltage Vin no longer charges the bus capacitor C1, and only supplies power to the LED lamp 240 through the second current loop formed by the transistor Q2, the resistor R1 and the LED lamp 240. The amplifier 231 controls the gate voltage of the transistor Q2 so that the voltage across the resistor R1 is equal to the second reference voltage Vref2, that is, Iq2 = Vref2 / R1. Similarly, since the first linear constant current module 220 is in the off state at this time, only the second drive current Iq2 supplies power to the LED lamp 240, and thus the drive current of the LED lamp 240 is equal to the second drive current Iq2 at this time.

[0089] When the input voltage Vin is in the third interval less than / equal to the load voltage of the LED lamp 240, the sampling signal Vs of the input voltage is less than the third reference voltage Vref3, the comparator 251 outputs an invalid enable signal EN1, and after being inverted by the inverter 252, a valid enable signal EN2 is obtained at the same time, the invalid enable signal EN1 controls the second linear constant current module 230 to turn off (for example, the enable amplifier 231 performs invalid output, and controls the transistor Q2 to turn off), and the valid enable signal EN2 controls the first linear constant current module 220 to turn on (for example, the enable amplifier 221 performs valid output, and controls the transistor Q1 to turn on), so that the first current loop is connected and the second current loop is disconnected. In this stage, the input voltage Vin is lower than the voltage Vc1 on the bus capacitor C1, so the input voltage Vin no longer charges the bus capacitor C1, and at this time, only the bus capacitor C1 supplies power to the LED lamp 240 through the first current loop formed by the transistor Q1, the resistor R1, and the LED lamp 240. The amplifier 221 controls the gate voltage of the transistor Q1 so that the voltage across the resistor R1 is equal to the first reference voltage Vref1, and the first drive current Iq1=Vref1 / R1. Since the second linear constant current module 230 is in the off state at this time, only the first drive current Iq1 supplies power to the LED lamp 240, and the drive current of the LED lamp 240 is equal to the first drive current Iq1.

[0090] As can be seen from the above, the present application can make the first linear constant current module 220 and the second linear constant current module 230 turn on in turn, and at the same time only one power supply supplies power to the LED lamp 240 through a current loop, so that the waveform distortion of the input current can be reduced, thereby improving the power factor of the circuit. Among them, the control conversion point of the first linear constant current module 220 and the second linear constant current module 230 turning on in turn is determined by the voltage difference between the input voltage Vin and the first reference ground GND1, and / or the third reference voltage Vref3. By setting different third reference voltages Vref3, different conversion points can be controlled, thereby taking into account the requirements of the LED linear drive circuit for flicker removal and input current harmonics. In addition, by parameter design, Vref1=Vref2, that is, Vref2 / R1=Vref1 / R1, then Iq1=Iq2, so that the current of the LED lamp 24 can be kept stable when the power supply (including the input voltage Vin and the bus capacitor C1) is switched, further eliminating flicker.

[0091] In an exemplary embodiment, the first linear constant current module 220, the second linear constant current module 230 and the enable control module 250 of this embodiment can be integrated into the same chip, such as Figure 4As shown, the chip 211 may include an input terminal VIN, a bus capacitor connection terminal VC, a load connection terminal VLED, and a reference ground terminal GND1. The input terminal VIN is used to connect to the first output terminal of the rectifier bridge B1 to receive the input voltage Vin, the bus capacitor connection terminal VC is used to connect to the first end of the bus capacitor C1, the load connection terminal VLED is used to couple with the LED lamp 240 through the resistor R1, and the reference ground terminal GND1 is used to connect to the current input terminal of the LED lamp 240 to provide a reference ground potential to the package. In a further embodiment, at least one of the resistor R1, the diode D1, and the rectifier bridge B1 may be packaged with the chip 211 in a package, and at this time, the load connection terminal VLED of the package is also directly connected to the current input terminal of the LED lamp 240, that is, at this time, the load connection terminal VLED and the reference ground terminal GND1 of the package will share the same pin.

[0092] Figure 5 The second embodiment of the LED linear drive system 200 shown adopts Figure 4 The first embodiment of the LED linear drive system 200 shown has a substantially identical structure, and similarities thereto may be referenced to each other and will not be described in detail herein.

[0093] The difference is that: Figure 5 In the example shown, the sampling unit 260 in the enable control module 250 includes: a transistor Q3, the drain of the transistor Q3 is connected to the first output end of the rectifier bridge B1, the control end (for example, the gate) of the transistor Q3 is connected to the first reference ground GND1, and the sampling unit 260 outputs a sampling signal Vs of the input voltage at the source of the transistor Q3.

[0094] In this embodiment, the transistor Q3 is, for example, a junction field effect transistor (JFET), a metal-oxide-semiconductor field effect transistor (MOSFET), or any other transistor that can be in a normally-on state under the control of a predetermined voltage, so that the drain voltage (i.e., the input voltage Vin) can be sampled at the source of the transistor Q3. Figure 5 In the example shown, the transistor Q3 can be always turned on with its control terminal connected to the first reference ground GND1 .

[0095] Figure 6 The third embodiment of the LED linear drive system 200 shown adopts Figure 4 The first embodiment of the LED linear drive system 200 shown has a substantially identical structure, and similarities thereto may be referenced to each other and will not be described in detail herein.

[0096] The difference is that: Figure 6In the example shown, the enabling control module 250 includes: a sampling unit 260 and a reference voltage generating unit 253. The sampling unit 260 can be implemented as follows: Figure 4 or Figure 5 The structure shown in the Figure 4 or Figure 5 The sampling unit 260 shown in FIG. 2 has the same function; the first input terminal of the reference voltage generating unit 253 receives the sampling signal Vs of the input voltage, the second input terminal of the reference voltage generating unit 253 receives the third reference voltage Vref3, the first input terminal of the reference voltage generating unit 253 outputs the first reference voltage Vref1 to the first linear constant current module 220, and the second input terminal of the reference voltage generating unit 253 outputs the second reference voltage Vref2 to the second linear constant current module 230.

[0097] exist Figure 6 In the example shown, in a specific implementation, when the sampling signal Vs of the input voltage is greater than the third reference voltage Vref3, the reference voltage generating unit 253 outputs the first reference voltage Vref1 and the second reference voltage Vref2, in which the first reference voltage Vref1 is less than the second reference voltage Vref2 (for example, the output first reference voltage Vref1 is zero voltage, and the output second reference voltage Vref2 is a first voltage value greater than zero voltage value), and at this time, the first linear constant current module 220 can be equivalently triggered to be turned off, and the second linear constant current module 230 can be triggered to be turned on; and when the sampling signal Vs of the input voltage is less than or equal to the third reference voltage Vref3, the first reference voltage Vref1 and the second reference voltage Vref2 can be output, in which the first reference voltage Vref1 is greater than the second reference voltage Vref2 (for example, the output first reference voltage Vref1 is a first voltage value greater than zero voltage value, and the output second reference voltage Vref2 is zero voltage), and at this time, the first linear constant current module 220 can be equivalently triggered to be turned on, and the second linear constant current module 230 can be triggered to be turned off. Thus, the first linear constant current module 220 and the second linear constant current module 230 are turned on in turn.

[0098] Figure 7 A schematic waveform diagram of the LED linear drive system according to the present application is shown below. Figure 4 and Figure 7 The working principle of the LED linear drive system of the present application is described. Figure 7As shown, during the time period t2-t3, the sampling signal Vs of the input voltage is less than the third reference voltage Vref3, indicating that the input voltage Vin is less than the voltage Vled on the LED lamp. During this time period, the bus capacitor C1 supplies power to the LED lamp 240 through the transistor Q1 and the resistor R1, and the gate voltage of the transistor Q1 is controlled by the amplifier 221, so that the voltage across the resistor R1 is equal to the first reference voltage Vref1. At this time, the first drive current Iq1=Vref1 / R1. Since the transistor Q2 is completely turned off at this time, the current Iled in the LED lamp 240=Iq1. During the time period t1-t2, the sampling signal Vs of the input voltage is greater than the third reference voltage Vref3, indicating that the input voltage Vin is greater than the voltage Vled on the LED lamp. The input voltage Vin supplies power to the LED lamp 240 through the transistor Q2 and the resistor R1. The amplifier 231 controls the gate voltage of the transistor Q2 so that the voltage across the resistor R1 is equal to the second reference voltage Vref2, that is, the second drive current Iq2=Vref2 / R1. Since the transistor Q1 is completely turned off at this time, the current Iled in the LED lamp 240 is equal to Iq2. Preferably, by designing the first reference voltage Vref1 to be equal to the second reference voltage Vref2, the current of the LED lamp 240 during the time period t2-t3 can be equal to the current of the LED lamp 240 during the time period t1-t2, which makes it easier to realize the constant current drive of the LED lamp 240, thereby further eliminating the flicker.

[0099] from Figure 7 It can be seen from the waveform in that the input current Iin in the LED linear drive system of the present application is composed of the charging current of the bus capacitor C1 and the second drive current Iq2. Therefore, the input current Iin starts to build up when the input voltage Vin is greater than the voltage on the LED lamp 240, and quickly reaches a peak value as the input voltage Vin rises until the input voltage Vin is less than the voltage on the LED lamp 240 again. Compared with the existing LED linear drive system, the LED linear drive system of the present application controls the bus capacitor to supply power to the load only when the input voltage is less than or equal to the load voltage, and the input voltage supplies power to the load at other times. Compared with the prior art, the power supply time of the bus capacitor to the load is reduced and the power supply time of the input voltage to the load is increased, so that the capacitance of the bus capacitor can be set smaller and the input current waveform time is wider, so the THD of the current is better, the power factor is higher, and the application efficiency of the LED light-emitting device is improved. The capacitance of the bus capacitor C1 in the embodiment of the present application is generally preferably 4.7uF.

[0100] In summary, the linear LED driving circuit provided in the embodiment of the present application is provided with a first current loop from the bus capacitor to the first linear constant current module and then to the load LED lamp, and a second current loop from the input voltage to the second linear constant current module and then to the load LED lamp, and the first linear constant current module and the second linear constant current module are set to be turned on alternately according to the different size relationships between the input voltage and the third reference voltage, so that the bus capacitor can be controlled to supply power to the load only when the input voltage is less than or equal to the load voltage, and at other times, such as when the input voltage is greater than the load, the input voltage supplies power to the load. Compared with the prior art, the power supply time of the bus capacitor to the load is reduced and the power supply time of the input voltage to the load is increased, thereby reducing the capacitance requirement of the bus capacitor, so that the capacitance of the bus capacitor can be set smaller, while reducing the system cost, it also reduces the current distortion at the input end of the system, improves the power factor of the circuit, reduces the flicker on the load current, improves the total harmonic distortion (THD) of the current in the LED linear driving circuit, and improves the stability and reliability of the system.

[0101] In addition, the embodiment of the present application sets the power supply current of the bus capacitor to the load to be equal to or similar to the power supply current of the input voltage to the load, which can keep the load current stable when the power supply source is switched, further eliminating flicker.

[0102] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly explaining the present application, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present application.

Claims

1. A LED linear drive circuit, characterized in that: include: A diode, wherein the diode and the bus capacitor are connected in series between a first output terminal and a second output terminal of the rectifier bridge, and an input voltage is provided between the first output terminal and the second output terminal of the rectifier bridge; A first linear constant current module, wherein the first linear constant current module is coupled in series with the LED lamp between the first input end and the second end of the bus capacitor; A second linear constant current module, wherein the second linear constant current module is coupled in series with the LED lamp between the first output terminal and the second output terminal of the rectifier bridge; Among them, when the input voltage is less than or equal to a preset third reference voltage, the first linear constant current module is turned on, the second linear constant current module is turned off, and a first current loop is formed between the bus capacitor, the first linear constant current module and the LED lamp, and the bus capacitor provides a first driving current to the LED lamp through the first current loop; when the input voltage is greater than the preset third reference voltage, the first linear constant current module is turned off, the second linear constant current module is turned on, and a second current loop is formed between the rectifier bridge, the second linear constant current module and the LED lamp, and the input voltage provides a second driving current to the LED lamp through the second current loop.

2. The LED linear driving circuit according to claim 1, characterized in that: The second driving current is equal to the first driving current.

3. The LED linear driving circuit according to claim 1, characterized in that: When the input voltage is greater than the bus capacitor voltage, the input voltage charges the bus capacitor through the diode, and when the input voltage is lower than the bus capacitor voltage, the input voltage stops charging the bus capacitor.

4. The LED linear driving circuit according to claim 2, characterized in that: The current output end of the first linear constant current module and the current output end of the second linear constant current module are both connected to the current input end of the LED lamp through a first resistor.

5. The LED linear driving circuit according to claim 4, characterized in that: The first linear constant current module comprises: a first transistor, wherein a current input end of the first transistor is connected to a first end of the bus capacitor, and a current output end of the first transistor is connected to the LED lamp through the first resistor; a first amplifier, wherein the positive input terminal receives a first reference voltage, the negative input terminal is connected to the current output terminal of the first transistor, and the output terminal of the first amplifier is connected to the control terminal of the first transistor, The first amplifier is used to drive the first transistor according to a comparison result between the first reference voltage and the voltage across the first resistor to obtain the first driving current.

6. The LED linear driving circuit according to claim 5, characterized in that: The second linear constant current module comprises: a second transistor, wherein a current input end of the second transistor is connected to the first output end of the rectifier bridge, and a current output end of the second transistor is connected to the LED lamp through the first resistor; a second amplifier, wherein the positive input terminal receives a second reference voltage, the negative input terminal is connected to the current output terminal of the second transistor, and the output terminal of the second amplifier is connected to the control terminal of the second transistor, The second amplifier is used to drive the second transistor according to a comparison result between the second reference voltage and the voltage across the first resistor to obtain the second driving current; The first reference voltage is equal to the second reference voltage.

7. The LED linear driving circuit according to claim 1, characterized in that: The LED linear drive circuit also includes: an enabling control module, connected to the first output end of the rectifier bridge, the first linear constant current module and the second linear constant current module respectively, the enabling control module receives the input voltage and a preset third reference voltage, and is used to control the first linear constant current module and the second linear constant current module to be turned on in turn according to the magnitude relationship between the input voltage and the preset third reference voltage, Among them, when the input voltage is less than or equal to a preset third reference voltage, the enable control module controls the first linear constant current module to turn on and the second linear constant current module to turn off; when the input voltage is greater than the preset third reference voltage, the enable control module controls the first linear constant current module to turn off and the second linear constant current module to turn on.

8. The LED linear driving circuit according to claim 7, characterized in that: The enabling control module comprises: A sampling unit, receiving the input voltage, and outputting a sampling signal of the input voltage based on a first reference ground of the LED linear driving circuit; A comparator, wherein the positive input terminal receives the sampling signal of the input voltage, the negative input terminal receives the third reference voltage, and the output terminal is connected to the enable terminal of the second linear constant current module; The first inverter has an input end connected to the output end of the comparator, and the output end of the first inverter is connected to the enable end of the first linear constant current module.

9. The LED linear driving circuit according to claim 7, characterized in that: The enabling control module comprises: A sampling unit, receiving the input voltage, and outputting a sampling signal of the input voltage based on a first reference ground of the LED linear driving circuit; A reference voltage generating unit, wherein the first input terminal receives the sampling signal of the input voltage, the second input terminal receives the third reference voltage, the first input terminal outputs the first reference voltage to the first linear constant current module, and the second input terminal outputs the second reference voltage to the second linear constant current module; When the first reference voltage is greater than the second reference voltage, the first linear constant current module is turned on and the second linear constant current module is turned off. When the first reference voltage is less than the second reference voltage, the first linear constant current module is turned off, and the second linear constant current module is turned on.

10. The LED linear driving circuit according to claim 8 or 9, characterized in that: The sampling unit comprises: A second resistor and a third resistor are connected in series between the first output end of the rectifier bridge and the first reference ground, and the sampling unit outputs a sampling signal of the input voltage at a connection node between the second resistor and the third resistor.

11. The LED linear driving circuit according to claim 8 or 9, characterized in that: The sampling unit comprises: The third transistor has a drain connected to the first output end of the rectifier bridge and a control end connected to the first reference ground. The sampling unit outputs a sampling signal of the input voltage at the source of the third transistor.

12. The LED linear driving circuit according to any one of claims 7 to 9, characterized in that: The first linear constant current module includes a first transistor and a first amplifier, the second linear constant current module includes a second transistor and a second amplifier, and the first linear constant current module, the second linear constant current module and the enable control module are integrated in the same chip.

13. The LED linear driving circuit according to claim 12, characterized in that: At least one of the diode and the rectifier bridge is sealed with the chip in a package.

14. The LED linear driving circuit according to claim 8 or 9, characterized in that: The current input terminal of the LED lamp serves as the first reference ground, and the second output terminal of the rectifier bridge serves as the second reference ground.

15. An LED linear drive system, characterized in that: include: a rectifier bridge for rectifying an AC voltage to provide an input voltage between a first output terminal and a second output terminal; LED lights; The LED linear drive circuit according to any one of claims 1 to 14, wherein the LED linear drive circuit and the LED lamp are connected in series between the first output terminal and the second output terminal of the rectifier bridge, for providing a drive current to the LED lamp.

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