WO2016107395A1

WO2016107395A1 - Led constant-current driving device

Info

Publication number: WO2016107395A1
Application number: PCT/CN2015/097195
Authority: WO
Inventors: 杨冕; 李东明
Original assignee: 四川新力光源股份有限公司
Priority date: 2014-12-31
Filing date: 2015-12-11
Publication date: 2016-07-07
Also published as: CN105813285A

Abstract

An LED constant-current driving device. The LED constant-current driving device comprises a rectification module (10), a constant-current module, and a lighting module (70). The lighting module (70) comprises a plurality of LED units (701, 702, 703, 704). An output end of the rectification module (10) is connected to the lighting module (70). The constant-current module is connected to the lighting module (70). The constant-current module comprises a plurality of current-limiting units (51, 52, 53, 54) and a sampling unit (20). Each current-limiting unit (51, 52, 53, 54) comprises a resistor (205, 206, 207, 208), a voltage-regulator tube (301, 302, 303, 304), a triode (501, 502, 503, 504), and a transistor (601, 602, 603, 604). In each current-limiting unit (51, 52, 53, 54), a drain of the transistor (601, 602, 603, 604) and one end of the resistor (205, 206, 207, 208) are jointly connected to an output end of the corresponding LED unit (701, 702, 703, 704); a gate of the transistor (601, 602, 603, 604) is connected to the other end of the resistor (205, 206, 207, 208), a negative end of the voltage-regulator tube (301, 302, 303, 304) and a collector of the triode (501, 502, 503, 504); a source of the transistor (601, 602, 603, 604) and a base of the triode (501, 502, 503, 504) are jointly connected to the sampling unit (20); and an emitter of the triode (501, 502, 503, 504) and a positive end of the voltage-regulator tube (301, 302, 303, 304) are connected and then are grounded. The LED constant-current driving device has a small size and low cost, and also has a high power factor.

Description

LED constant current driving device

Technical field

The invention relates to an LED driving device, in particular to an LED constant current driving device.

Background technique

Now the state advocates energy saving and emission reduction, and the lighting products of LED light source used in the lighting field are developing rapidly with its excellent energy saving, low carbon and green environmental protection effects. When an LED is used as a light source for a lighting device, the life of the lighting device depends not only on the LED but also on components such as a driving power source. In the current application scheme, the bottleneck of the life of the LED lighting device is still the driving power source. In order to reduce the impact of the life of the driving power on the life of the LED lamp, the researchers on the one hand improved the existing DC power drive device, on the other hand, designed a new AC circuit to directly drive the LED.

For ordinary people, the use of LED lighting products can save energy, but the existing LED lighting products have the problem of short drive life. Because the existing driving scheme adopted in the market is the traditional switching power supply technology, this technology is relatively mature, but the power supply has a large volume and needs good heat dissipation performance. When this power technology is introduced into an LED lighting product, it provides a small space for the driving power source and a high working environment temperature (above 60 ° C). This directly leads to a reduction in drive life, while the switching power supply is costly and has poor EMC characteristics (additional auxiliary components are required). Moreover, once the existing LED lighting products are damaged, there is basically no value for maintenance, and it is necessary to directly replace the driving power supply. However, due to the limitation of the power supply cavity of the limited LED lighting products, generally only the designated manufacturer, the designated model of the driving power source, and the maintenance can be replaced. The process is complicated.

At present, there are some AC direct drive LED circuits, which are traditionally used for RC or single-track constant current technology. Although the cost of the RC is low, these technologies have the following problems. The power factor of the LED circuit is low (generally 0.2 to 0.5). And need to use high-voltage capacitors, this capacitor is large in size, the life is far lower than the LED, once the capacitor damages the LED will all be broken down, directly causing the entire lamp to be scrapped. In addition, the single-route constant current technology solves the problem of low power factor (generally 0.8 to 0.85), but in a cycle of AC mains operation, since the circuit requires a starting voltage, and the starting voltage is generally Higher, so there is a long time the circuit is not working State (utilization below 60%).

For this to happen, an improved AC direct drive LED circuit with multiplexed switching function has now emerged. This circuit divides a string of LEDs into multiple segments, each segment has an independent constant current device, and selects different access terminals according to different voltages. This kind of driving technology can better solve the problem of the original driving technology, but this driving technology also has shortcomings. The circuit needs to have a specific input voltage sampling circuit, and the constant current part of this type of circuit uses electronic components such as an op amp, so it is necessary to provide the necessary working voltage and reference voltage for the operation of these components. However, these circuits reduce the reliability of the circuit and require a dedicated controller to control the multiplexer circuit through the detected input voltage. Once the control switch fails, the LED will be broken down by high voltage, causing the lamp to be scrapped. For example, Chinese Patent Publication No. CN201310080348.1 discloses a segmented LED driving circuit based on an AC power source, the LED driving circuit comprising a rectifying unit, a constant current driving unit and a lighting unit. The LED driving circuit needs to supply the necessary operating voltage to the operational amplifier in the constant current driving unit, and the reliability of the circuit is lowered.

Summary of the invention

In view of the deficiencies of the prior art, the present invention provides an LED constant current driving device including a rectifier module, a constant current module, and a lighting module, the lighting module including a plurality of LED units, wherein the rectifier module is The output terminal is connected to the lighting module, and the constant current module is connected to the lighting module. The constant current module includes a plurality of current limiting units and a sampling unit, and each current limiting unit includes a resistor and a voltage regulator. Tube, a triode and a transistor,

In each current limiting unit, the drain of the transistor and the end of its resistor are connected in common to the output of the corresponding LED unit, the gate of the transistor is connected to the other end of its resistor, the negative terminal of its Zener and its transistor a collector, the source of the transistor and the base of the transistor are connected to the sampling unit, and the emitter of the transistor is connected to the positive terminal of the Zener and grounded.

In each current limiting unit, the source of its transistor and the base of its transistor are connected to the source of the transistor of the next current limiting unit and the base of the transistor via corresponding sampling resistors.

According to a preferred embodiment, the rectifier module includes a first rectifier arm and a second rectifier arm composed of four diodes, and a first diode and a second diode of the four diodes are connected in series to form the first A rectifying arm, wherein the third diode and the fourth diode of the four diodes are connected in series to form the second rectifying arm.

According to a preferred embodiment, the diode is a rectifier diode or a Schottky diode.

According to a preferred embodiment, the sampling unit consists of several sampling resistors connected in series.

According to a preferred embodiment, the transistor is an N-MOSFET or an NPN type transistor.

According to a preferred embodiment, the current limiting unit further comprises a capacitor connected in parallel to the Zener.

According to a preferred embodiment, the LED unit consists of a plurality of or a single low-voltage LED, which are connected in a series or series-parallel combination.

According to a preferred embodiment, the LED unit is a high voltage LED module packaged in a COB.

The invention has at least the following advantages:

1. The LED constant current driving device does not use the input voltage sampling circuit and the control circuit, and has low cost, small volume, and high circuit reliability.

2. Electrolytic capacitors and inductors are not used in the circuit, which makes the LED lamps have a long service life and good EMC characteristics.

3, LED constant current drive circuit can adjust the number of LED conduction units with voltage changes, has a higher power factor (not less than 0.95), and can improve the voltage utilization (greater than 90%).

4. In the circuit, the input current can be adjusted by changing the resistance of the sampling resistor, thereby achieving an adjustable input power.

DRAWINGS

Figure 1 is a structural diagram of a driving circuit of the present invention;

Figure 2 is a schematic diagram of a driving circuit of the present invention;

Figure 3 is a waveform diagram of an input AC voltage in the present invention;

4 is a waveform diagram of voltages after passing through a rectifier module in the present invention; and

Figure 5 is a waveform diagram of input voltage and input current as a function of time in the present invention.

detailed description

The details will be described below with reference to the accompanying drawings. As shown in FIG. 1, the LED constant current driving device of the present invention includes a rectifier module 10, a constant current module, and a lighting module 70. The lighting module 70 includes a number of LED units. The output end of the rectifier module 10 is connected to the illumination module 70, and the constant current module is connected to the illumination module 70. Constant current The module includes a plurality of current limiting units and a sampling unit 20. Each current limiting unit includes a resistor, a Zener, a transistor, and a transistor. In each current limiting unit, the drain of its transistor and its one end of the resistor are commonly connected to the output of the corresponding LED unit. The gate of the transistor is connected to the other end of the resistor, the negative terminal of the Zener diode, and the collector of the transistor. The source of the transistor and the base of the transistor are connected to the sampling unit 20, and the emitter of the transistor is connected to the positive terminal of the Zener and grounded. The foregoing LED unit may be a plurality of single or single low voltage LEDs, or may be a high voltage LED module in a COB package.

The LED constant current driving device not only has the advantages of the conventional AC direct driving LED circuit, but also can further improve the reliability of the circuit, and does not require a dedicated control circuit, so that the cost of the circuit can be reduced. The electrolytic capacitors required in the conventional switching power supply technology are not used in the driving circuit, and thus the life is high. There is also no inductance in the drive circuit and therefore good EMC characteristics.

As shown in FIG. 1, the rectifier module 10 in the circuit includes four

rectifier diodes

101, 102, 103, and 104. The sampling unit 20 includes four sampling resistors 201, 202, 203, 204. The current limiting unit 51 includes a triode 501, a resistor 205, a Zener diode 301, and a transistor 601. The current limiting unit 52 includes a triode 502, a resistor 206, a Zener diode 302, and a transistor 602. The current limiting unit 53 includes a triode 503, a resistor 207, a Zener diode 303, and a transistor 603. The current limiting unit 54 includes a triode 504, a resistor 208, a Zener diode 304, and a transistor 604. The lighting module 70 includes

LED units

701, 702, 703, 704. The number of LEDs of each LED unit is greater than or equal to one, and the LEDs are connected in series, or may be connected in a series and a combination manner. The

diodes

101, 102, 103, 104 may be ordinary rectifier diodes, or Schottky diodes with sufficient withstand voltage or other components that can perform the same function. The transistors 601, 602, 603, 604 may be N-MOSFETs or NPN-type transistors.

The first input terminal IN1 of the rectifier module 10 is connected to the connection node of the positive terminal of the first diode 101 and the negative terminal of the second diode 102. The positive terminal of the second diode 102 is connected to the positive terminal of the fourth diode 104, and its connection node is grounded. The second input terminal IN2 of the rectifier module 10 is connected to the connection node of the positive terminal of the third diode 103 and the negative terminal of the fourth diode 104. The negative terminal of the third diode 103 is connected to the negative terminal of the first diode 101, and its connection node constitutes the output positive terminal of the rectifier module 10. The input of the LED unit 701 is connected to the output positive terminal of the rectifier module 10. The output of the LED unit 701 is connected to the input of the LED unit 702, and the output of the LED unit 701 is connected to the drain of the transistor 601 and one end of the resistor 205. The output of the LED unit 702 is connected to the input of the LED unit 703, and the LED single The output of element 702 is coupled to the drain of transistor 602 and one end of resistor 206. The output of the LED unit 703 is connected to the input of the LED unit 704, and the output of the LED unit 703 is connected to the drain of the transistor 603 and one end of the resistor 207. The output of LED unit 704 is coupled to the drain of transistor 604 and one end of resistor 208.

The other end of the resistor 205 is connected to the negative terminal of the Zener diode 301, the collector of the transistor 501, and the gate of the transistor 601. The other end of the resistor 206 is connected to the negative terminal of the Zener diode 302, the collector of the transistor 502, and the gate of the transistor 602. The other end of the resistor 207 is connected to the negative terminal of the Zener diode 303, the collector of the transistor 503, and the gate of the transistor 603. The other end of the resistor 208 is connected to the negative terminal of the Zener diode 304, the collector of the transistor 504, and the gate of the transistor 604. The positive terminal of the Zener diode 301 is connected to the emitter of the transistor 501 and then grounded. The positive terminal of the Zener diode 302 is connected to the emitter of the transistor 502 and then grounded. The positive terminal of the Zener diode 303 is connected to the emitter of the transistor 503 and then grounded. The positive terminal of the Zener diode 304 is connected to the emitter of the transistor 504 and then grounded.

The base of the transistor 501 is connected to the source of the transistor 601, and then connected to one end of the sampling resistor 201. The base of the transistor 502 is connected to the source of the transistor 602, and then connected to the other end of the sampling resistor 201 and one end of the sampling resistor 202. The base of the transistor 503 is connected to the source of the transistor 603, and then connected to the other end of the sampling resistor 202 and one end of the sampling resistor 203. The base of the transistor 504 is connected to the source of the transistor 604, and then connected to the other end of the sampling resistor 203 and one end of the sampling resistor 204. The other end of the sampling resistor 204 is grounded.

As shown in FIG. 2, each current limiting unit may further include a capacitor, and the capacitor is connected in parallel with the Zener diode, which can improve the reliability of the circuit. One end of the capacitor 401 is connected to the negative terminal of the Zener diode 301, and the other end of the capacitor 401 is connected to the positive terminal of the Zener diode 301. One end of the capacitor 402 is connected to the negative terminal of the Zener diode 302, and the other end of the capacitor 402 is connected to the positive terminal of the Zener diode 302. One end of the capacitor 403 is connected to the negative terminal of the Zener diode 303, and the other end of the capacitor 403 is connected to the positive terminal of the Zener diode 303. One end of the capacitor 404 is connected to the negative terminal of the Zener diode 304, and the other end of the capacitor 404 is connected to the positive terminal of the Zener diode 304.

Figure 3 shows the voltage waveform of the AC mains. The AC mains outputs a pulsating direct current through a bridge rectifier circuit composed of

rectifier diodes

101, 102, 103, and 104. The voltage waveform of the pulsating DC is shown in Figure 4.

The specific operation of the LED constant current driving device of the present invention is as follows: the forward conduction voltages of the

LED units

701, 702, 703, and 704 are Vf1, Vf2, Vf3, and Vf4. The pulse DC voltage has voltage values VF1, VF2, VF3, VF4 during the lifting process, and the pulse voltage value is in accordance with the characteristics: VF1=Vf1; VF2=Vf1+Vf2; VF3=Vf1+Vf2+Vf3; VF4=Vf1+Vf2+Vf3+Vf4≦Vmax.

Initially, after the pulsating DC voltage rises from 0 V to VF1, current flows through the LED unit 701, the resistor 205, and the Zener diode 301. A stable voltage V1 is obtained at the negative terminal of the Zener diode 301, so that the transistor 601 is in an on state, and current flows from the output of the LED unit 701 through the transistor 601 and the sampling resistors 201, 202, 203, and 204. Thus, the circuit is turned on, and the LED unit 701 starts to emit light. A sampling voltage Vref1 is obtained at the current input terminal of the sampling resistor 201, and Vref1 is the sum of the voltages formed by the resistors 201, 202, 203, and 204, respectively. The sampling voltage Vref1 is supplied to the base voltage of the transistor 501. When Vref1 is greater than the base forward voltage V _BE =0.6V of the transistor 501, the transistor 501 is turned on and operates in the amplification region, and the voltage of the collector of the transistor 501 is lowered to lower the transistor. The gate voltage of 601 causes the output current of the transistor 601 to drop, and the sampling voltage Vref1 of the sampling resistor 201 falls. When Vref1 < V _BE , the transistor 501 is turned off, and the gate voltage of the transistor 601 rises, turning on the transistor 601 and operating in the amplification region. At this time, the current flowing through the transistor 601 does not change, and current limiting is achieved, and the current I _in = I ₁ .

When the pulsating DC voltage rises from VF1 to VF2, the pulsating DC voltage reaches the preset turn-off voltage value of the current limiting unit 51, and the current limiting unit 51 is turned off. Current flows through the LED unit 701, the LED unit 702, the resistor 206, and the Zener diode 302. A stable voltage V2 is obtained at the negative terminal of the Zener diode 302, causing the transistor 602 to be in an on state, and current flows from the output of the LED unit 702 through the transistor 602 and the sampling resistors 202, 203, and 204. Thus, the circuit is turned on and the LED unit 702 starts to emit light. A sampling voltage Vref2 is obtained at the current input of the sampling resistor 202, and Vref2 is the sum of the voltages formed by the resistors 202, 203, and 204, respectively. The sampling voltage Vref2 is supplied to the base voltage of the transistor 502. When Vref2 is greater than the base forward voltage _VBE = 0.6V of the transistor 502, the tee 502 is turned on and operates in the amplification region, causing the collector of the transistor 502 to drop. Reducing the gate voltage of the transistor 602 causes the output current of the transistor 602 to drop, and the sampling voltage Vref2 of the sampling resistor 202 to drop. When Vref2 < V _BE , the transistor 502 is turned off. At this time, the gate voltage of the transistor 602 rises, the transistor 602 is turned on and operates in the amplification region, and the current flowing through the transistor 602 is constant, and the current limit is realized, and the current I _in = I ₂ . At this time, Vref1 ≥ Vref2, the transistor 501 operates in an on state, and the transistor 601 operates in an off state.

When the pulsating DC voltage rises from VF2 to VF3, the pulsating DC voltage reaches the preset turn-off voltage value of the current limiting unit 52, and the current limiting unit 52 is turned off. Current flows through the LED unit 701, the LED unit 702, the LED unit 703, the resistor 207, and the Zener diode 303. A stable voltage V3 is obtained at the negative terminal of the Zener diode 303, so that the transistor 603 is in an on state, and current flows from the output terminal of the LED unit 703 through the transistor 603 and the sampling resistors 203 and 204. Thus, the circuit is turned on, and the LED unit 703 starts to emit light. A sampling voltage Vref3 is obtained at the current input terminal of the sampling resistor 203, and Vref3 is the sum of the voltages formed by the resistors 203, 204, respectively. The sampling voltage Vref3 is supplied to the base voltage of the transistor 503. When Vref3 is greater than the base forward voltage _VBE = 0.6V of the transistor 503, the tee tube 503 is turned on and operates in the amplification region, causing the collector of the transistor 503 to descend. Reducing the gate voltage of the transistor 603 causes the output current of the transistor 603 to drop, and the sampling voltage Vref3 of the sampling resistor 203 to fall. When Vref3 < V _BE , the transistor 503 is turned off. At this time, the gate voltage of the transistor 603 rises, the transistor 603 is turned on and operates in the amplification region, and the current flowing through the transistor 603 does not change, and the current limit is realized, and the current I _in = I ₃ . At this time, Vref2 ≥ Vref3, the transistor 502 operates in an on state, and the transistor 602 operates in an off state.

When the pulsating DC voltage rises from VF3 to VF4, the pulsating DC voltage reaches the preset turn-off voltage value of the current limiting unit 53, and the current limiting unit 53 is turned off. Current flows through the LED unit 701, the LED unit 702, the LED unit 703, the LED unit 704, the resistor 208, and the Zener tube 304. A stable voltage V4 is obtained at the negative terminal of the Zener diode 304, causing the transistor 604 to be in an on state, and current flows from the output of the LED unit 704 through the transistor 604 and the sampling resistor 204. The circuit is thus turned on and the LED unit 704 begins to emit light. A sampling voltage Vref4 is obtained at the current input of the sampling resistor 204, and Vref4 is the voltage of the resistor 204. The sampling voltage Vref4 is supplied to the base voltage of the transistor 504. When Vref4 is greater than the base forward voltage _VBE = 0.6V of the transistor 504, the tee 504 is turned on and operates in the amplification region, causing the collector of the transistor 504 to drop. Reducing the gate voltage of transistor 604 causes the output current of transistor 604 to drop, and the sampling voltage Vref4 of sampling resistor 204 to drop. When Vref4 < V _BE , the transistor 504 is turned off. At this time, the gate voltage of the transistor 604 rises, the transistor 604 is turned on and operates in the amplification region, and the current flowing through the transistor 604 is constant, and current limiting is achieved, and the current I _in = I ₄ . At this time, Vref3 ≥ Vref4, the transistor 503 operates in an on state, and the transistor 603 operates in an off state.

The above process is a reversible process, and the pulse DC voltage starts to drop after rising to Vmax. When the voltage drops from VF4 to VF3, the transistor 504 is now operating in the amplification region and the transistor 604 is also operating in the amplification region. However, after the voltage drops, the

LED units

701, 702, 703, and 704 cannot be simultaneously lit, so that no current flows through the LED unit 704, the transistor 604, and the sampling resistor 204, so that the voltage Vref4 of the current input terminal of the sampling resistor 204 is lowered. At the same time, the sampling voltage Vref3 of the current inflow end of the sampling resistor 203 and the base voltage of the transistor 503 are also lowered. Vref4 is lowered, and transistor 504 and transistor 604 are successively turned off. At this time, the base forward voltage Vref3 < V _BE of the transistor 503, the transistor 503 is turned off, the gate voltage of the transistor 603 is thus increased, and the transistor 603 is turned on. The current limiting unit 53 is turned on and the current drops to I _in = I ₃ .

When the voltage drops from VF3 to VF2, the transistor 503 is now operating in the amplification region and the transistor 603 is also operating in the amplification region. However, after the voltage drops, the

LED units

701, 702, and 703 cannot be simultaneously lit, so that no current flows through the LED unit 703, the transistor 603, and the sampling resistor 203, so that the voltage Vref3 of the current input terminal of the sampling resistor 203 is lowered and simultaneously sampled. The sampling voltage Vref2 at the current input of the resistor 202 and the base voltage of the transistor 502 are also reduced. Vref3 is lowered, and transistor 503 and transistor 603 are successively turned off. At this time, the base forward voltage Vref2 < V _BE of the transistor 502, the transistor 502 is turned off, the gate voltage of the transistor 602 is thus increased, the current limiting unit 52 is turned on, and the current is decreased to I _in = I ₂ .

After the voltage drops from VF2 to VF1, at this time, although the transistor 502 is operating in the amplification region, the transistor 602 also operates in the amplification region. However, after the voltage drops, the

LED units

701 and 702 cannot be simultaneously lit, so that no current flows through the LED unit 702, the transistor 602, and the sampling resistor 202, so that the voltage Vref2 of the first end of the sampling resistor 202 is lowered, and the sampling resistor is simultaneously The sampling voltage Vref1 at the current input terminal of 201 and the base voltage of the transistor 501 are also lowered. Vref2 is lowered, and transistor 502 and transistor 602 are successively turned off. At this time, the base forward voltage Vref1 < V _BE of the transistor 501, the transistor 501 is turned off, the gate voltage of the transistor 601 is thus increased, the current limiting unit 51 is turned on, and the current is decreased to I _in = I ₁ .

When the voltage drops from VF1 to 0V, since the voltage drops, the LED unit 701 cannot be lit, so that no current flows through the LED unit 701, the transistor 601, and the sampling resistor 201, so that the voltage Vref1 of the current input terminal of the sampling resistor 201 is lowered. . Vref1 is lowered, and the transistor 501 and the transistor 601 are successively turned off, and no current is passed. Thus, the

LED units

701, 702, 703, and 704 are all turned off.

The driving circuit of the present invention does not require input voltage sampling, and is equipped with a dedicated controller, so the cost is low, the volume is small, and the reliability is high. The LED constant current driving circuit can adjust the number of conducting units of the LED according to the voltage change, has a high power factor (not less than 0.95), and can improve the voltage utilization rate (greater than 90%). In the circuit, the input current can be changed by changing the resistance of the sampling resistor, so the input power can be adjusted.

It should be noted that the above specific embodiments are exemplary, and those skilled in the art can make various improvements and modifications based on the above embodiments, and the improvements or modifications fall into the present application. New range of protection. Those skilled in the art should understand that the above specific The description is only for the purpose of explaining the invention and is not intended to limit the invention. The scope of the invention is defined by the claims and their equivalents.

Claims

An LED constant current driving device includes a rectifying module (10), a constant current module and a lighting module (30), the lighting module (30) comprising a plurality of LED units,

It is characterized in that

An output end of the rectifier module (10) is connected to the illumination module (30), and the constant current module is connected to the illumination module (30).

The constant current module includes a plurality of current limiting units and a sampling unit (20), each of the current limiting units including a resistor, a Zener diode, a transistor, and a transistor.

In each current limiting unit, the drain of the transistor and the end of its resistor are connected in common to the output of the corresponding LED unit, the gate of the transistor is connected to the other end of its resistor, the negative terminal of its Zener and its transistor a collector, the source of the transistor and the base of the transistor are connected to the sampling unit (20), and the emitter of the transistor is connected to the positive terminal of the Zener and grounded.

In each current limiting unit, the source of its transistor and the base of its transistor are connected to the source of the transistor of the next current limiting unit and the base of the transistor via corresponding sampling resistors.
The LED constant current driving device according to claim 1, wherein said rectifying module (10) comprises a first rectifying arm and a second rectifying arm composed of four diodes, the first of said four diodes The diode (101) and the second diode (102) are connected in series to form the first rectifying arm, and the third diode (103) and the fourth diode (104) of the four diodes are connected in series The second rectifying arm.
The LED constant current driving device according to claim 2, wherein the diode is a rectifier diode or a Schottky diode.
The LED constant current driving device according to claim 1, wherein said sampling unit (20) is composed of a plurality of sampling resistors connected in series with each other.
The LED constant current driving device according to claim 1, wherein said transistor is an N-MOSFET or an NPN type transistor.
The LED constant current driving device of claim 1 , wherein the current limiting unit further comprises a capacitor connected in parallel to the Zener diode.
The LED constant current driving device according to claim 1, wherein the LED unit is composed of a plurality of or a single low voltage LED, and the LEDs are connected by a series connection or a series-parallel combination.
The LED constant current driving device according to claim 1, wherein the LED unit is a high voltage LED module packaged in a COB.