CN102625548A - Multi-output heavy-power LED constant-current drive power supply - Google Patents

Abstract

The invention discloses a multi-output heavy-power LED constant-current drive power supply which comprises an AC-AC frequency conversion unit, wherein the AC-AC frequency conversion unit is used for converting an AC electric supply into a high-frequency AC voltage with stable frequency and peak to form a high-frequency AC bus, the output of the high-frequency AC bus is respectively connected with input ends of multiple paths of LCL passive resonance rectifiers, each path of LDL passive resonance rectifier is used for driving a corresponding LED string to emit light and comprises an LCL resonance network unit and a rectifier unit, and the rectifier unit is used for rectifying an AC output by the LCL resonance network unit into a DC and then driving the LED string of the corresponding string. The invention can avoid problem of uneven current caused by parallel connection of a plurality of strings of LEDs, has the characteristics of simple circuit structure and low cost, can work in a high-frequency state, and has the advantages of small volume, high power density and the like.

Description

A multi-output high-power LED constant current drive power supply

technical field

The invention relates to a driving power supply for semiconductor lighting, specifically a high-power LED constant current driving power supply with multi-channel output function, and belongs to the technical field of driving power supply.

the

Background technique

Semiconductor lighting, also known as solid-state lighting, mainly refers to lighting that uses high-power high-brightness light-emitting diodes (High-Brightness Light Emitting Diode, HB-LED) as the light source. LED has the advantages of high luminous efficiency, small size, light weight, good optical performance, long life (about 100,000 hours), and environmental friendliness. It is a new generation of green and energy-saving lighting sources with great development prospects. In October 2009, the National Development and Reform Commission and other six ministries and commissions issued the "Opinions on the Development of Semiconductor Lighting Energy-saving Industry", marking that the semiconductor lighting industry has officially risen to a national strategy, and it also means that China's semiconductor lighting industry will enter a stage of accelerated development. On January 6, 2012, the China Semiconductor Lighting/LED Industry and Application Alliance was established, which means that China's semiconductor lighting industry will enter the stage of large-scale application.

The driving power supply is the power source of the LED, and its output current determines the photometric performance indicators such as the brightness, luminous flux, and luminous efficiency of the LED. Since the fluctuation of the forward voltage at both ends of the LED will lead to a wide range of changes in the forward current, a consensus has gradually been formed on the use of constant current drive for LEDs. Therefore, the LED drive power supply must have a constant current output function. In addition, due to the limitations of current packaging and heat dissipation technologies, the power level of a single LED is watt level, so it is an inevitable measure to connect multiple LEDs in series, parallel, or series-parallel in practical applications. Considering safety regulations and reliability requirements, it is a common solution to connect multiple LEDs in series and then connect them in series and parallel. However, due to the discrete conduction voltage drop of the LED itself, the application of connecting multiple LEDs in series and then in parallel will inevitably cause the current imbalance of each string of LEDs, which will cause the total light output and quality of the LED to decline. Reduced reliability and shortened lifespan. Therefore, the LED drive power supply must also have the function of multiple constant current outputs.

At present, most of the LED drive power supplies used in commercial lighting use AC input through a power frequency AC/DC conversion unit and then pass through a multi-channel isolated DC/DC conversion unit to drive multiple strings of LED loads. Configure an independent driving power supply to realize the multi-channel constant current output function. Such a driving power supply will increase the cost of LED driving because the main circuit topology, control circuit, and driving power supply of each driving power supply are completely independent. In addition, there is also a drive power supply that uses a power frequency transformer to achieve the purpose of stepping down, but the use of a power frequency transformer has the defect that the drive power supply is too large.

the

Contents of the invention

Aiming at the problems of complex structure, large volume and high cost of the existing LED drive power supply, the purpose of the present invention is to provide a high-power LED constant current drive with simple structure, small size, low cost and easy realization with multi-channel output function. power supply.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A multi-output high-power LED constant current drive power supply, including an AC-AC alternating frequency conversion unit, used to convert the AC mains into a high-frequency AC voltage with stable frequency and peak value to form a high-frequency AC bus, and the output of the high-frequency AC bus They are respectively connected to the input ends of multiple LCL passive resonant rectifiers, and each LCL passive resonant rectifier is used to drive a corresponding LED string to emit light.

Each LCL passive resonant rectifier is composed of an LCL resonant network unit and a rectifier unit. The rectifier unit is used to rectify the alternating current output by the LCL resonant network unit into a DC current and then drive the corresponding LED string; the LCL resonant network unit consists of two A resonant inductor L ₁ , L _a1 and a resonant capacitor C _O are formed, and the rectification unit is composed of a full-bridge rectifier circuit composed of four rectifier diodes D _r1 , D _r2 , D _r3 , D _r4 and a filter capacitor C _f ;

The first end of the high-frequency AC bus is connected to the first end of the resonant inductance L ₁ in the LCL resonant network unit, and the second end of the resonant inductance L ₁ is connected to the first end of another resonant inductance L _a1 and the first end of the resonant capacitor C _O The second end of the resonant inductor L _a1 is connected to the anode of the rectifier diode D _r1 in the rectifier unit and the cathode of the rectifier diode D _r2 ; the second end of the capacitor C _O is connected to the second end of the high-frequency AC bus and then connected to the rectifier unit The anode of the rectifier diode D _r3 in the rectifier unit is connected to the cathode of the rectifier diode D _r4 ; the cathode of the rectifier diode D _r1 in the rectifier unit is connected to the cathode of the rectifier diode D _r3 and then connected to the first end of the filter capacitor C _f , and the filter capacitor C The first terminal of _f is used to connect with the positive terminal of the LED string; the positive terminal of the rectifier diode D _r2 in the rectification unit is connected to the positive terminal of the rectifier diode D _r4 and then connected to the second terminal of the filter capacitor C _f , the filter capacitor C _f is the first The two terminals are used to connect with the negative terminal of the LED string.

The AC-AC frequency conversion unit is composed of a power factor correction unit and a high-frequency DC/AC resonant inverter, and the DC power obtained after the AC mains passes through the power factor correction unit is used as the input of the high-frequency DC/AC resonant inverter , the high-frequency DC/AC resonant inverter is composed of a full-bridge topology composed of four power switch tubes S ₁ , S ₂ , S ₃ , and S ₄ , a resonant network, and a high-frequency isolation transformer T. The power switch tube S The input terminal of ₁ is connected to the input terminal of the power switch tube _S2 , and then connected to the positive pole of the DC power output of the power factor correction unit, and the output terminal of the power switch tube _S1 is connected to the input terminal of the power switch tube _S4 , and then connected to the resonance The first end of the input end of the network is connected, the output end of the power switch tube _S2 is connected with the input end of the power switch tube _S3 and then connected with the second end of the input end of the resonant network, the power switch tube _S3 is connected with the power switch tube S ₄ and then connected to the negative pole of the DC power output of the power factor correction unit; the first end of the output end of the resonant network is connected to the first end of the input end of the primary side of the high-frequency isolation transformer T, and the second end of the output end of the resonant network is connected to the high The second terminal of the input terminal of the primary side of the frequency isolation transformer T is connected; the output terminal of the secondary side of the high frequency isolation transformer T forms a high frequency AC bus, and the output terminal of the secondary side of the high frequency isolation transformer T is connected to the four power switch tubes S through a feedback circuit. _1. S ₂ , S ₃ , and S ₄ are connected in a full-bridge topology to control the on-off of the four power switch tubes, so that the high-frequency AC bus voltage is set at a constant frequency and constant peak value. frequency AC voltage.

In the case of small and medium power, in order to reduce the cost, the front-stage AC/DC power factor correction unit can be integrated with the rear-stage high-frequency DC/AC resonant inverter on the basis of the basic scheme of the present invention, that is, a single-stage AC/AC The high-frequency inverter structure enables it to output high-frequency AC voltage to form a high-frequency AC bus under the direct input of industrial frequency AC power, and then drive multiple strings of LCL resonant rectifiers.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention is formed by connecting a single high-frequency DC/AC inverter or a single-stage AC/AC frequency converter and multiple LCL passive resonant rectifiers through a high-frequency AC bus. Since each LCL passive resonant rectifier drives a string of LEDs Therefore, the problem of current unevenness caused by the parallel use of multiple strings of LEDs can be avoided, and since the LCL passive resonant rectifier can realize constant current output without any switching components and control circuits, the circuit structure of the present invention is simple and the cost is low.

2. Since the resonant converter is easy to realize soft switching, the present invention can work in a high-frequency state, so it has the advantages of small size and high power density.

the

Description of drawings

Fig. 1 - schematic diagram of the circuit of the present invention.

Fig. 2 - Circuit structure diagram of Embodiment 1 of the present invention.

Fig. 3 - a structural diagram of Embodiment 2 of the present invention, that is, the high-frequency DC/AC resonant inverter adopts a half-bridge topology with voltage equalizing capacitors.

Fig. 4 - a structural diagram of Embodiment 3 of the present invention, that is, the high-frequency DC/AC resonant inverter adopts a half-bridge topology without voltage equalizing capacitors.

Fig. 5 is a structure diagram of Embodiment 4 of the present invention, that is, a circuit structure diagram of a high-frequency AC bus formed by a single-stage AC/AC inverter structure.

Fig. 6 - The steady-state voltage and current waveforms of the present invention when driving two strings of LED loads with two outputs; wherein, each string of LED loads is 10 LEDs connected in series.

Fig. 7 - a waveform diagram of the transient change in output current and voltage when a single LCL passive resonant rectifier of the present invention drives an LED load when the number of LEDs changes from 1 to 10.

the

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing.

Referring to Figure 1-2, it can be seen from the figure that the present invention is a high-power LED constant current drive power supply with commercial power as the input power supply, including an AC-AC alternating frequency conversion unit, which is used to convert AC commercial power into frequency and peak value The stable high-frequency AC voltage forms a high-frequency AC bus, and the outputs of the high-frequency AC bus are respectively connected to the input terminals of multiple LCL passive resonant rectifiers, and each LCL passive resonant rectifier is used to drive the corresponding LED string to emit light. The AC-AC frequency conversion unit is composed of a power factor correction unit and a high-frequency DC/AC resonant inverter. The DC power obtained from the AC mains through the power factor correction unit is used as the input of the high-frequency DC/AC resonant inverter. Through the constant frequency phase-shift control of the high-frequency DC/AC resonant inverter, the high-frequency AC voltage output by it passes through the high-frequency isolation transformer to form a high-frequency AC bus to drive multiple LCL passive resonant rectifiers, and each The LCL passive resonant rectifier drives a single string of LED loads, so it can drive multiple strings of LEDs to emit light.

Therefore, this power supply consists of three parts:

The first part is the power frequency AC/DC rectification link, that is, the power factor correction link (PFC), and its output DC voltage is about 400V. Since the current PFC technology is relatively mature, it will not be repeated here.

The second part is the link of the high-frequency DC/AC resonant inverter. The high-frequency DC/AC resonant inverter is composed of four power switch tubes S ₁ , S ₂ , S ₃ , and S ₄ with a full-bridge topology and a resonant network. It is composed of a high-frequency isolation transformer T; the input end of the power switch tube _S1 is connected to the input end of the power switch tube _S2 and then connected to the positive pole of the DC voltage source, and the output end of the power switch tube _S1 is connected to the power switch tube _S4 After the input end is connected, it is connected to the first end of the input end of the resonant network, and the output end of the power switch tube _S2 is connected to the input end of the power switch tube _S3 , and then connected to the second end of the input end of the resonant network. S ₃ is connected to the output end of the power switch tube S ₄ and then connected to the negative pole of the DC voltage source. The resonant network can adopt a second-order, third-order or above-order resonant network structure. The first end of the output end of the resonant network is connected to the first end of the input end of the primary side of the high-frequency isolation transformer T, and the second end of the output end is isolated from the high-frequency The second end of the input end of the primary side of the transformer T is connected. The output terminal _of the secondary side of the high _- frequency isolation transformer T forms _a high- _frequency AC bus. Bridge topology connection, through the acquisition, rectification and comparison control of the secondary side voltage of the transformer, to control the opening and closing of the four power switch tubes, so that the high-frequency AC bus voltage is a constant frequency and a constant peak value under the setting high frequency AC voltage. It can be seen from Figure 2-Figure 5 that the voltage controller, constant-frequency phase-shift regulator and high-frequency gate driver form a feedback circuit. In addition, the high-frequency DC/AC resonant inverter in the present invention may also have other topological structures or control methods as long as it is to obtain an AC voltage with a constant frequency and peak value.

The third part is a plurality of LCL passive resonant rectifiers for driving LED loads, and each LCL passive resonant rectifier includes two parts: an LCL resonant network unit and a rectification unit. The rectification unit is used to rectify the alternating current output by the LCL resonant network unit into a DC current and then drive the corresponding LED string; the LCL resonant network unit is composed of two resonant inductors L ₁ , L _a1 and a resonant capacitor C _O , rectifying The unit is composed of a full-bridge rectifier circuit composed of four rectifier diodes D _r1 , D _r2 , D _r3 , D _r4 and a filter capacitor C _f . Taking one of the LCL resonant rectifiers as an example, the first end of the high-frequency AC input power is connected to the first end of the resonant inductor L ₁ in the LCL resonant network unit, and the second end of the resonant inductor L ₁ is connected to the second end of the other resonant inductor L _a1 One end is connected to the first end of the resonant capacitor C _O , the second end of the resonant inductor L _a1 is connected to the anode of the rectifier diode D _r1 in the rectifier unit and the cathode of the rectifier diode D _r2 , the second end of the resonant capacitor C _O is connected to the high The second terminal of the frequency AC input power supply is connected to the anode of the rectifier diode D _r3 and the cathode of the rectifier diode D _r4 in the rectifier unit, and the cathode of the rectifier diode D _r1 in the rectifier unit is connected to the cathode of the rectifier diode D _r3 It is connected to the first end of the filter capacitor C _f , and then connected to the positive end of the LED array. The anode of the rectifier diode D _r2 in the rectification unit is connected to the anode of the rectifier diode D _r4 , and then connected to the second end of the filter capacitor C _f , and then connected to the negative terminal of the LED array. Wherein, the filter capacitor C _f connected to the LED array can also be omitted, so that the obtained driving current of the LED is a constant and pulsating direct current.

All power switches are fully-controlled devices such as Mosfet and IGBT, and the diodes can be replaced by the above-mentioned fully-controlled devices.

Referring to Fig. 3, the first expansion scheme of the present invention is different from Fig. 2 in that the high-frequency DC/AC resonant inverter adopts a capacitor equalizing half-bridge topology, that is, the power switch tubes S ₂ and S ₃ use two A voltage equalizing capacitor C _b1 and C _b2 instead.

Referring to Fig. 4, the second expansion scheme of the present invention is different from Fig. 2 in that the high-frequency DC/AC resonant inverter adopts a capacitor-free voltage-balancing half-bridge topology, that is, only two power switch tubes S are used to realize chopping. wave function.

Referring to Fig. 5, the third expansion scheme of the present invention is different from Fig. 2 in that the front-stage AC/DC power factor correction unit is integrated with the rear-stage DC/AC high-frequency inverter unit, that is, the high-frequency AC/AC AC single-stage inverter structure.

Describe working principle and working process of the present invention below according to Fig. 2:

(1). The present invention is a high-power LED constant-current driving power supply using commercial power as the input power supply. The first stage is a power factor correction (PFC) link, and its function is to convert the alternating AC power supply into a constant DC power supply. That is to realize the power factor correction (PFC) function. Since the current PFC technology is relatively mature, it will not be described in detail here, and this link is also omitted in FIG. 2 .

(2). The second stage structure of the present invention is a DC/AC high-frequency resonant inverter. After collecting, rectifying, and comparing the secondary voltage of the transformer, the power switch is controlled by constant frequency phase shifting or constant frequency Variable duty cycle control, so that the frequency and peak value of the high-frequency AC voltage output by the resonant network meet the set target, and then pass through the high-frequency isolation transformer to form a high-frequency AC bus to drive multiple LCL passive resonant rectifiers, and then drive multiple String LEDs glow.

(3). The LCL passive resonant rectifier unit is composed of an LCL resonant network unit and a rectifier unit. The LCL resonant network unit is composed of two resonant inductors and a resonant capacitor, and its input terminal is connected to the high-frequency AC bus. The rectification unit is composed of a full-bridge rectification circuit composed of four rectification diodes and a filter capacitor, its input end is connected with the output end of the LCL resonant network, and its output end is connected with the LED array.

，即输入的高频交流电源使谐振电感，谐振电容处于谐振状态，此时LCL谐振网络可以输出幅值大小恒定，频率与其输入交流电源频率相同的交变电流，并且高频交流电源输出功率完全为有功功率，即实现了功率因数校正功能，后面的整流单元将LCL谐振网络单元输出的交变电流整流成直流电流后进而驱动LED阵列。理论上LCL无源谐振整流器后面接入的LED颗数无论多大值，其输出的电流幅值大小都保持恒定不变，但实际应用时，由于非理想因素的影响（如两个电感感值不可能绝对相同，电感与电容取值不可能与理论值绝对相同等），LCL无源谐振整流器后面所接入的负载值必须限制在一定范围内，其输出的电流可以恒流输出。 (4). When the frequency f of the high-frequency AC power supply and the peak value U _m are a certain value, the resonant inductance L and the resonant capacitance C in the LCL resonant network are designed to satisfy the formula

, that is, the input high-frequency AC power makes the resonant inductor and resonant capacitor in a resonant state. At this time, the LCL resonant network can output an alternating current with a constant amplitude and the same frequency as the frequency of the input AC power, and the output power of the high-frequency AC power is completely For active power, that is to say, the power factor correction function is realized, and the rectification unit at the back rectifies the alternating current output by the LCL resonant network unit into a direct current, and then drives the LED array. Theoretically, no matter how large the number of LEDs connected behind the LCL passive resonant rectifier is, the magnitude of the output current remains constant. However, in practical applications, due to the influence of non-ideal factors (such as the It may be absolutely the same, the value of the inductance and capacitance cannot be absolutely the same as the theoretical value, etc.), the load value connected behind the LCL passive resonant rectifier must be limited within a certain range, and the output current can be output at a constant current.

(5). Other expansion schemes of the present invention, such as a half-bridge resonant inverter with a voltage-balancing capacitor can be used instead of a full-bridge resonant inverter, as shown in Figure 3; a half-bridge resonant inverter without a voltage-balancing capacitor can also be used The inverter replaces the full-bridge resonant inverter, as shown in Figure 4; in small and medium power applications, a single-stage AC/AC high-frequency converter can also be used to replace the PFC and DC/AC high-frequency inverter links, thereby saving funds, as shown in Figure 5.

The experimental waveform diagram of the present invention is as shown in Figure 6 and Figure 7, and Figure 6 is the steady-state voltage and current waveform when two-way LCL resonant rectifiers are connected behind the high-frequency DC/AC resonant inverter to drive two strings of LED loads As shown in the figure, each string of LED loads is 10 LEDs connected in series. Figure 7 is a single LCL passive resonant rectifier driving an LED load without any switching elements and feedback control loop. When the number of LEDs changes from 1 to 10, the waveform diagram of the output current and voltage changes shows that it basically realizes Constant current output.

It can be seen from the above that compared with the existing LED drive unit, the present invention has the advantages of simple structure, low cost, high reliability, small volume, high power density, etc., so it has good practicability.

Most of the above implementations of the present invention are examples for illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other changes in various forms can also be made on the basis of the above description. It is not possible to exhaustively list all implementation manners here. All obvious changes or changes that are derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims (4)

1. A multi-channel output high-power LED constant current drive power supply is characterized in that: it includes an AC-AC alternating frequency conversion unit, which is used to convert the AC mains power into a high-frequency AC voltage with stable frequency and peak value to form a high-frequency AC busbar, The output of the high-frequency AC bus is respectively connected to the input ends of multiple LCL passive resonant rectifiers, and each LCL passive resonant rectifier is used to drive a corresponding LED string to emit light. 2. The multi-channel output high-power LED constant current drive power supply according to claim 1, characterized in that: each LCL passive resonant rectifier is composed of an LCL resonant network unit and a rectifier unit, and the rectifier unit is used to convert the LCL resonant network unit The output alternating current is rectified into a direct current and then drives the corresponding LED string; the LCL resonant network unit is composed of two resonant inductors L ₁ , L _a1 and a resonant capacitor C _O , and the rectifier unit is composed of four rectifier diodes D _r1 , D _r2 , D _r3 , D _r4 constitute a full-bridge rectifier circuit and a filter capacitor C _f ; The first end of the high-frequency AC bus is connected to the first end of the resonant inductance L ₁ in the LCL resonant network unit, and the second end of the resonant inductance L ₁ is connected to the first end of another resonant inductance L _a1 and the first end of the resonant capacitor C _O The second end of the resonant inductor L _a1 is connected to the anode of the rectifier diode D _r1 in the rectifier unit and the cathode of the rectifier diode D _r2 ; the second end of the capacitor C _O is connected to the second end of the high-frequency AC bus and then connected to the rectifier unit The anode of the rectifier diode D _r3 in the rectifier unit is connected to the cathode of the rectifier diode D _r4 ; the cathode of the rectifier diode D _r1 in the rectifier unit is connected to the cathode of the rectifier diode D _r3 and then connected to the first end of the filter capacitor C _f , and the filter capacitor C The first terminal of _f is used to connect with the positive terminal of the LED string; the positive terminal of the rectifier diode D _r2 in the rectification unit is connected to the positive terminal of the rectifier diode D _r4 and then connected to the second terminal of the filter capacitor C _f , the filter capacitor C _f is the first The two terminals are used to connect with the negative terminal of the LED string. 3. The multi-output high-power LED constant current drive power supply according to claim 1 or 2, characterized in that: the AC-AC frequency conversion unit is composed of a power factor correction unit and a high-frequency DC/AC resonant inverter , the DC power obtained by the AC mains through the power factor correction unit is used as the input of the high-frequency DC/AC resonant inverter, and the high-frequency DC/AC resonant inverter consists of four power switch tubes S ₁ , S ₂ , The full-bridge topology composed of S ₃ and S ₄ , the resonant network and the high-frequency isolation transformer T are composed. The input end of the power switch tube S ₁ is connected to the input end of the power switch tube S ₂ and then connected to the DC output of the power factor correction unit. The positive pole of the power supply is connected, the output end of the power switch tube _S1 is connected to the input end of the power switch tube _S4 , and then connected to the first end of the input end of the resonant network, the output end of the power switch tube _S2 is connected to the input end of the power switch tube _S3 After the input terminal is connected, it is connected to the second terminal of the input terminal of the resonant network, and the power switch tube _S3 is connected to the output terminal of the power switch tube _S4 , and then connected to the negative pole of the DC power output of the power factor correction unit; the second terminal of the output terminal of the resonant network One end is connected to the first end of the input end of the primary side of the high-frequency isolation transformer T, and the second end of the output end of the resonant network is connected to the second end of the input end of the primary side of the high-frequency isolation transformer T; the output end of the secondary side of the high-frequency isolation transformer T forms a high high-frequency AC bus, and the output terminal of the secondary side of the high-frequency isolation transformer T is connected to the full-bridge topology composed of four power switch tubes S ₁ , S ₂ , S ₃ , and S ₄ through a feedback circuit, so as to control the four power switches The on-off of the tube is controlled so that the high-frequency AC bus voltage is a high-frequency AC voltage with a constant frequency and a constant peak value under the setting. 4. The multi-output high-power LED constant current drive power supply according to claim 1, 2 or 3, characterized in that: the AC-AC frequency conversion unit is a single-stage AC/AC high-frequency converter.

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