CN104244503B - Apparatus for driving light-emitting diode strings using high voltage - Google Patents

Abstract

An apparatus for driving a plurality of light emitting diodes to which a high voltage is applied includes a plurality of light emitting diodes divided into a plurality of light emitting diode segments connected in series, and a plurality of voltage-controlled current limiters having three connection terminals. Each current limiter corresponds to a light emitting diode segment and has a first connection end connected to the negative end of the corresponding light emitting diode segment, a bias voltage is applied to the second connection end, a third connection end is connected to a common node in the light emitting diode device, and a current source connects the common node to ground. A power dissipation reduction circuit including a plurality of LED segments controlled by an LED control circuit may be added between the common node and the current source to reduce power dissipation of the current source due to the high voltage at the common node.

Description

Apparatus for driving light-emitting diode strings using high voltage

technical field

The present invention relates to a light emitting diode (LED) lighting device, especially a driving device for a lighting device using a high voltage LED string.

Background technique

Light-emitting diode (LED) is a semiconductor-based light source, which is often used in low-power consumption meters and indicators of home appliances. The application of light-emitting diodes in various lighting devices has become more and more common. For example, high-brightness light-emitting diodes have been widely used in traffic lights, vehicle lights, and brake lights. In recent years, lighting fixtures using strings of high-voltage LEDs have also been developed to replace traditional incandescent and fluorescent bulbs.

The current-to-voltage (I-V) characteristic curve of a light-emitting diode is similar to that of an ordinary diode. When the voltage applied to the light-emitting diode is less than the forward voltage of the diode, only a very small current flows through the light-emitting diode. When the voltage exceeds the forward voltage, the current through the LED increases significantly. In general, the luminous intensity of an LED-based lighting device is proportional to the current passing through most of the operating range, but not when operating at high currents. Generally, the driving device designed for LED-based lighting devices is mainly to provide a constant current so as to emit stable light and prolong the life of the LED.

In order to improve the brightness of LED-based lighting devices, it is usually to connect multiple LEDs in series to form a LED-based lighting unit, and multiple LED-based lighting units can be further connected in series to form a lighting unit. device. The working voltage required for each lighting device usually depends on the forward voltage of the light-emitting diodes in the lighting unit, how many light-emitting diodes are in each lighting unit, how each lighting unit is connected to each other, and the How a lighting unit receives voltage from a power source in a lighting fixture.

Therefore, in most applications, some type of mains voltage conversion device is required to convert the generally more common high voltage power supply to a lower voltage for supplying one or more LED based lighting units. Because of the need for such a voltage conversion device, the efficiency of the lighting equipment based on the light-emitting diode is reduced, the cost is increased, and it is difficult to reduce its volume.

In order to improve the efficiency and reduce the size of the LED-based lighting device, many technologies have been developed so that the LED-based lighting device can use AC power such as 120V or 240V without a voltage conversion device. Generally, the LEDs in LED-based lighting devices are segmented into a plurality of LED segments. Each LED segment can be selectively switched on and off as the AC voltage increases or decreases under the control of an associated switch or current source. All switches or current sources in the lighting device are controlled by a controller.

In the prior art, most LED-based lighting devices that use high voltage use the detection of the voltage value of the input AC power or the current value flowing through the lighting device to control the switch or the current source, thereby selectively connecting Toggle LED segments on and off. For example, US Patent Nos. 6,989,807 and 8,324,840, and US Patent Publication No. 2011/0089844, all have an integral controller capable of detecting the voltage value of an input voltage to control a switch or a current source connected to a light-emitting diode. US Patent Publications No. 2012/0056559 and No. 2012/0217887 use an integral controller to control the current limiter or switch according to the detected local current.

Since more and more light-emitting diode-based lighting units have been applied to high-brightness lighting equipment using high voltage, how to use the existing AC power on the wall to flexibly and effectively increase the utilization rate of light-emitting diodes and reduce Design methods and apparatus to drive and connect multiple LED-based lighting units with low power consumption, and provide stability and high brightness, have formed an integral need.

Contents of the invention

The invention is made to provide a device for driving light-emitting diode strings that can use high voltage and has low power consumption. The device provided by the invention comprises a plurality of LEDs divided into a plurality of LED segments connected in series, and a plurality of voltage-controlled current limiters corresponding to the LED segments and each having three connection terminals.

Each LED section has a positive terminal and a negative terminal, the first connection terminal of each current limiter is connected to the negative terminal of the corresponding LED section, a bias voltage is applied to the second connection terminal, and the third connection terminal Then connect to a common node in the LED device. An input voltage source is connected to the first LED segment in the entire device to provide the required power.

In a first preferred embodiment of the present invention, the common node in the LED device is grounded via a current source. It is preferable that all three-connection voltage-controlled current limiters in the entire installation have the same characteristics and that the bias voltage applied to the second connection is from the most leading first LED segment to the last A LED segment increases gradually in sequence.

As the input voltage increases, the voltage at the common node also increases. Since the bias voltage applied to the second connection terminal of the current limiter is gradually increased sequentially, the current limiter in the first preferred embodiment has at most two current limiters partially turned on at any one time, Or only one current limiter is fully on. Therefore, when the input voltage rises, the LED segments in the LED device can be sequentially turned on one by one, and when the input voltage drops, the opposite segments are sequentially turned off.

The bias voltage applied to the second connection terminal in the first preferred embodiment of the invention cannot be from the most The lead from the first LED segment to the last LED segment increases gradually in sequence. Therefore, at the same time, more than one current limiter is partially on.

According to the second preferred embodiment of the present invention, a power loss reducing circuit is added between the common terminal and the current source to reduce the power loss in the current source caused by the increase of the voltage of the common terminal. The power loss reduction circuit includes a plurality of light emitting diodes divided into a plurality of light emitting diode segments controlled by a light emitting diode control circuit, which are connected in series between the common terminal and the current source.

In the first fabrication of the second preferred embodiment of the present invention, the light-emitting diode control circuit includes a plurality of switches corresponding to the plurality of light-emitting diode segments in the power loss reduction circuit, each of which switches from The positive end of the corresponding LED segment in the reduction circuit is connected to the current source. A controller in the LED control circuit selectively turns on or off the switches to convert the power to be dissipated in the first preferred embodiment into LED power for the LED section in the power loss reduction circuit.

In the second fabrication of the second preferred embodiment of the present invention, the light emitting diode control circuit also includes a plurality of switches corresponding to the plurality of light emitting diode segments in the power loss reduction circuit, each switch being connected to the The corresponding light-emitting diode segment in the power loss reduction circuit is connected in parallel. Therefore, each LED segment in the power loss reduction circuit can be selectively turned on or off.

In the third fabrication of the second preferred embodiment of the present invention, the light-emitting diode control circuit is a current controlled by a plurality of voltages with three connection terminals corresponding to a plurality of light-emitting diode segments in the power loss reduction circuit limiter composition. A third fabrication of the second preferred embodiment is similar to joining together two wires of the first preferred embodiment.

Description of drawings

FIG. 1 is a block diagram showing a device for driving LED strings with a high voltage according to a first preferred embodiment of the present invention;

Fig. 2 is to show the characteristic curve of the electric current to the voltage (I-V) of the current limiter that contains the voltage control of three connection terminals in the present invention;

Fig. 3 shows that in the device of the first preferred embodiment of Fig. 1, the simulated voltage waveform of the input voltage and the voltage of the common terminal;

FIG. 4A shows the respective current values flowing through the seven current limiters when the input voltage varies according to the input voltage shown in FIG. 3;

Figure 4B is an enlarged view showing the top two current values of Figure 4A;

Figure 5 shows the current value flowing through the light-emitting diode in the device when the input voltage changes;

Fig. 6 shows several examples designed according to the first preferred embodiment of the present invention;

Fig. 7 shows the efficiency under different numbers of LED segments in the device of the first preferred embodiment;

Fig. 8 shows the luminance (the power of the light emitting diode) under different LED segment numbers in the device of the first preferred embodiment;

FIG. 9 is a block diagram showing a device for driving LED strings with a high voltage according to a second preferred embodiment of the present invention;

Fig. 10A is the first example showing the first kind of manufacture of the second preferred embodiment of the present invention;

FIG. 10B is a second example showing the first manufacture of the second preferred embodiment of the present invention;

Fig. 11 A is the first example showing the second kind of manufacture of the second preferred embodiment of the present invention;

FIG. 11B is a second example showing a second manufacture of the second preferred embodiment of the present invention;

Figure 12 is a third fabrication showing the second preferred embodiment of the present invention;

Fig. 13 shows the comparison of the efficiency under certain numbers of light-emitting diode segments in the first preferred embodiment and the second preferred embodiment of the present invention;

Fig. 14 shows that corresponding to Fig. 13, the luminance (light-emitting diode power) comparison under certain number of light-emitting diode segments;

FIG. 15A shows the input voltage V _IN and the voltage values at the common terminal and the current source in the first preferred embodiment with 20 LED segments;

Figure 15B shows the voltage values at the common terminal and the current source in the second preferred embodiment with 20 LED segments.

Wherein, the reference signs are explained as follows:

100 LED segments

200 Voltage-controlled current limiter with three terminals

300 current source

400, 500, 600, 700 LED control circuit

401 LED segment

501, 601 switch

502, 602 controller

701 Voltage-controlled current limiter with three terminals

detailed description

This specification provides accompanying drawings for a better understanding of the present invention, and the accompanying drawings also constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a block diagram showing an apparatus for driving LED strings with a high voltage according to a first preferred embodiment of the present invention. The device of this embodiment comprises a plurality of LEDs connected in series and is divided into a plurality of LED segments 100 connected in series, each LED segment 100 has a positive terminal and a negative terminal, each connected to a leading LED the negative terminal of a segment and the positive terminal of a subsequent LED segment.

As shown in FIG. 1, the negative terminal of each LED segment is also connected to the first connection terminal of a three-connection voltage-controlled current limiter 200, the second connection terminal of which is applied with a current limiter. bias voltage, and the third connection terminal is connected to a common node in the LED device. A current source 300 is connected between the common node and ground.

FIG. 2 is a graph showing the current versus voltage (IV) characteristic curve of the voltage-controlled current limiter 200 with three terminals of the present invention. When the voltage V _bc between the second connection terminal and the third connection terminal (connection terminals b and c) of the current limiter 200 is less than or equal to the threshold voltage V _th of the current limiter, the current limiter is closed, and The current I _a flowing through the current limiter is zero.

When the voltage V _bc between the second connection terminal and the third connection terminal (connection terminals b and c) of the current limiter 200 is greater than the threshold voltage V _th of the current limiter, and the first connection terminal and the third connection terminal of the current limiter When the voltage V _ac between the three connection terminals (connection terminals a and c) is less than the saturation voltage V _sat of the current limiter, the current limiter behaves like a resistor. In other words, the current _Ia flowing through the current limiter is linearly proportional to the voltage _Vac .

It can be seen from Figure 2 that when the voltage V _bc is greater than the threshold voltage V _th of the current limiter, and the voltage V _ac is also greater than the saturation voltage V _sat of the current limiter, the current limiter of the voltage control with three terminals The device 200 forms a fixed current source, and the current I _a is a function of the voltage V _bc , that is to say, I _a =f(V _bc ). It is worth noting that the saturation voltage V _sat of the current limiter is also proportional to the voltage V _bc .

It can also be understood from Fig. 2 that different bias voltages V ₁ , V ₂ , ..., and V _N are respectively applied to the first voltage-controlled current limiter in the device shown in Fig. 1 . On the two connection terminals, each current limiter can be cut off or on at different times according to the change of the input voltage with time.

In the present invention, the voltage-controlled current limiter with three connection terminals has a characteristic that when the current flowing through each current limiter is I, its respective V _bc and V _th can be expressed by V _bc1 = V _th1 + ΔV ₁ , V _bc2 = V _th2 + ΔV ₂ , V _bc3 = V _th3 + ΔV ₃ , ..., and V _bcN = V _thN + ΔV _N , where N is the voltage of all three terminals in the entire device Total number of current limiters controlled.

According to the first preferred embodiment shown in Fig. 1 of the present invention, more appropriate bias voltages V ₁ , V ₂ , ..., and V _N should satisfy the following conditions:

V ₂ ≥ V ₁ +ΔV ₂ +(V _th2 -V _th1 ),

V ₃ ≥ V ₂ +ΔV ₃ +(V _th3 -V _th2 ),

…

V _N ≥ V _N-1 +ΔV _N +(V _thN −V _th(N-1) ).

According to the above conditions, when the input voltage V _IN increases to the voltage value that the first current limiter can start to switch on, before the current flowing through it reaches the maximum current value, the second and all subsequent current limiters , because of the relationship between the forward voltages of each LED segment therebetween, the voltage V _ac across the first and third connection terminals of these current limiters is still zero, therefore, these current limiters are still in the cut-off state .

When the input voltage V _IN increases to make the voltage V _AC across the first connection terminal and the third connection terminal of the second current limiter greater than zero, the second current limiter starts to turn on, and the current also starts to flow through the second current limiter. LED segments. When the currents flowing through the first current limiter and the second current limiter are I ₁ and I ₂ respectively, the sum of the currents is I=I ₁ +I ₂ .

As the input voltage _V continues to increase, the current I2 flowing through the _second current limiter also increases, while the current _I1 flowing through the first current limiter decreases. Because of the current vs. voltage (IV) characteristic shown in Figure 2, the current I ₂ of the second current limiter continues to increase to the highest current value I, and the voltage at the common node also increases to (V ₂ -V _th2 - ΔV ₂ )≥(V ₁ −V _th1 ), so that the first current limiter is cut off and the current I ₁ =0 flows through.

According to the above analysis, when the input voltage V _IN rises, these current limiters can be turned on sequentially from the first LED segment to the last LED segment. In a similar principle, when the input voltage V _IN decreases, the voltage at the common node also decreases, so that the current limiters are sequentially turned on one by one in the opposite direction. When the current limiter K is fully on, the current limiters 1, 2, . . . , K-1, K+1, . . . , and N are all switched off. At any one time, up to two current limiters may be partially on, or only one current limiter may be fully on.

If all three-terminal voltage-controlled current limiters in the entire installation have the same characteristics, that is, V _th1 =V _th2 =V _th3 =...=V _thN and ΔV ₁ =ΔV ₂ =ΔV ₃ = ...=ΔV _N =ΔV, then the bias voltage of the first preferred embodiment of the present invention can satisfy the following conditions:

V ₂ ≥ V ₁ +ΔV ₂ +(V _th2 −V _th1 )=V ₁ +ΔV,

V ₃ ≥ V ₂ +ΔV ₃ +(V _th3 −V _th2 )=V ₂ +ΔV,

…

V _N ≥ V _N-1 +ΔV _N +(V _thN −V _th(N-1) )=V _N-1 +ΔV.

In other words, the device can use the bias voltage V ₁ <V ₂ <...<V _N , and when the input voltage V _IN rises or falls, only one current limiter in the whole device is fully turned on, or at most two A current limiter is partially turned on.

If all the voltage-controlled current limiters with three terminals in the entire device do not have the same characteristics, the bias voltage of the first preferred embodiment of the present invention may not necessarily satisfy V ₁ <V ₂ <...< V _N , in this case, the current limiters cannot be switched on or off sequentially one by one. Such an LED lighting device is still operable and usable, however, multiple current limiters are partially turned on at the same time.

It must be emphasized that the bias voltages V ₁ , V ₂ , ..., and V _N applied to the second terminal of the three-terminal voltage-controlled current limiter do not vary with the input voltage V _IN while changing the fixed voltage. Moreover, the switching of the LED segment in the present invention is continuous, and is controlled according to the rise or fall of the voltage of the common node, rather than by detecting the voltage value of the input voltage or the current value flowing through the current limiter to control. Regardless of whether all three-terminal voltage-controlled current limiters in the device have the same characteristics, if the bias voltages V ₁ , V ₂ , ..., and V _N connected to the second terminal do not satisfy the above Conditions, at the same time, there will be more than one current limiter is partially turned on.

The three-terminal voltage-controlled current limiter of the present invention can be fabricated using various semiconductor components. A few suitable examples are N-channel Metal Oxide Semiconductor Field Effect Transistor (MOSFET), NPN Bipolar Transistor (BJT), N-channel Insulated Gate Bipolar Transistor (IGBT). In addition, the current limiter connected to the last LED segment is optional, and the number of LEDs in each LED segment does not have to be the same.

FIG. 3 shows simulated voltage waveforms of the input voltage and the voltage of the common terminal in the apparatus of the first preferred embodiment of FIG. 1 . In the figure, it is assumed that there are 7 LED segments in the LED device, and the input voltage is a rectified AC voltage.

From top to bottom, Figure 4A shows the respective current values flowing through the seven current limiters when the input voltage varies according to the input voltage shown in Figure 3; Figure 4B shows the amplification of the top two current values in Figure 4A picture. Figure 5 shows the current values flowing through the LEDs in the device when the input voltage varies.

According to the light-emitting diode device of the present invention, the voltage of the common terminal must increase with the rise of the input voltage, so that the current limiter can be turned on or off sequentially. For a given input voltage, if the number of LED segments in the device increases, the total number of LEDs in the entire device must decrease so that enough current can still flow when only the last current limiter is switched on. via light-emitting diodes.

Fig. 6 shows several examples designed according to the first preferred embodiment of the present invention, assuming that the input voltage is 60 Hz, the AC voltage of 110 volts after rectification, the current source can provide the electric current of 350 milliamps, in the whole device The number of LED segments, the total number of LEDs, and the number of LEDs in each LED segment. Fig. 7 and Fig. 8 show the efficiency and brightness (light emitting diode power) of the device of the first preferred embodiment under different numbers of light emitting diode segments.

When the number of LED segments in the whole device is less than 7, the power loss is mainly from the voltage controlled current limiter with three connection terminals. When the number of LED segments in the whole device is greater than 7, the power loss is mainly from the current source. If the number of LED segments in the overall device increases, the voltage at the common terminal will also increase. Therefore, the power consumption from the current source is even more increased. It can be seen from the figure that the optimal number of LED segments is between 6 and 9.

As mentioned above, the voltage of the common terminal in the first preferred embodiment will increase with the increase of the input voltage V _IN , the higher the voltage of the common terminal, the more unnecessary power consumption will be. Therefore, the present invention proposes a second preferred embodiment to reduce power consumption. FIG. 9 is a block diagram showing an apparatus for driving LED strings with a high voltage according to the second preferred embodiment of the present invention. In this arrangement, the power loss in the first preferred embodiment can be converted to the power of the LEDs.

It can be seen from FIG. 9 that in the device of the second preferred embodiment, there is a power loss reduction circuit between the common terminal and the current source 300, which includes a plurality of LEDs and an LED control circuit 400 associated therewith. The plurality of LEDs are divided into a plurality of LED segments 401 . For simplicity, each LED segment 401 is shown with only one LED in the figure. According to the second preferred embodiment of the present invention, the number of turned-on LED segments 401 is controlled by the LED control circuit 400 and increases as the voltage at the common terminal rises, thereby reducing power consumption from the current source.

10A and 10B are two examples showing the first fabrication of the second preferred embodiment of the present invention. In the first example in FIG. 10A , the LED control circuit 500 includes a plurality of switches 501 controlled by a controller 502 , corresponding to a plurality of LED segments 401 . Each switch 501 is connected from the positive end of the corresponding LED segment 401 to the current source 300 , and the controller 502 controls these switches 501 to determine how to control and connect the LED segment 401 according to the voltage of the common terminal.

In the second example of FIG. 10B, the circuit is almost the same as that of the first example in FIG. 10A, only the controller 502 controls the switches 501 according to the voltage flowing through the three connection terminals. The individual currents I ₁ , I ₂ , . . . , and I _N of the current limiter 200 are not based on the voltage at the common terminal.

11A and 11B are two examples showing the second fabrication of the second preferred embodiment of the present invention. Similar to FIG. 10A, the light emitting diode control circuit 600 of the first example in FIG. 11A includes a plurality of switches 601 controlled by a controller 602, corresponding to a plurality of light emitting diode segments 401, but each switch The device 601 is connected in parallel with the corresponding LED segment 401. Therefore, in this example, each LED segment 401 can be controlled and wound separately according to the voltage of the common terminal.

In the second example in Fig. 11B, the circuit is almost the same as the first example in Fig. 11A, only the controller 602 controls the switches 601 according to the voltage flowing through the three connection terminals The individual currents I ₁ , I ₂ , . . . , and I _N of the current limiter 200 are not based on the voltage at the common terminal.

Fig. 12 is a third fabrication showing the second preferred embodiment of the present invention. It can be seen from FIG. 12 that there are multiple voltage-controlled current limiters 701 with three connection terminals in the LED control circuit 700 . The first connection terminal of each three-connection voltage-controlled current limiter 701 is connected to the positive terminal of the corresponding LED segment 401, the second connection terminal is applied with a bias voltage, and the third connection terminal is connected to a current source 300 . The bias voltages applied to the second connection terminal are V _1x , V _2x , . . . , and so on.

In the third fabrication of the second preferred embodiment, the voltage-controlled current limiter 701 with three connection terminals is the same as that described above, and can be designed using the above principles, so the description will not be repeated here. Overall, the third fabrication of the second preferred embodiment is similar to joining two wires of the first preferred embodiment together.

Fig. 13 shows the efficiency comparison of the first preferred embodiment and the second preferred embodiment of the present invention under certain numbers of LED segments. In FIG. 13, the second preferred embodiment is represented by the above-mentioned first fabrication. FIG. 14 shows, corresponding to FIG. 13 , the brightness (LED power) comparison under certain numbers of LED segments.

In order to show that the second preferred embodiment can reduce the power consumption, Fig. 15A and Fig. 15B show the input voltage V _IN and the common terminal and current source voltage values. The upper graph of FIG. 15A shows the input voltage V _IN , while the lower graph shows the voltage value at the common terminal. It can be seen from the figure that when the input voltage V _IN rises, the voltage of the common terminal also increases. In the first preferred embodiment, since the common terminal is directly connected to the current source 300, the voltage of the current source 300 is the same as the voltage of the common terminal.

The upper and lower graphs of FIG. 15B each show the voltage values of the common terminal and the current source corresponding to FIG. 15A in the first fabrication of the second preferred embodiment. It can be seen from the figure that the voltage of the common terminal in the upper figure is the same as the lower figure in FIG. 15A , but the lower figure in FIG. 15B shows the voltage value of the corresponding current source 300 in the second preferred embodiment, When the input voltage V _IN changes, it is very obvious that the voltage value at the common terminal is smaller than that. Therefore, the power loss from the current source 300 is greatly reduced.

Although the present invention is described above only by several preferred implementation examples, those skilled in the art can clearly understand that there are still many undescribed modifications and modifications, all without departing from the present invention defined below within the scope of the claims.

Claims (17)

1. a kind of device for driving multiple light emitting diodes, it is characterised in that the device includes：

Multiple light emitting diodes, are divided into multiple light-emitting diodes pipeline sections of series connection, each of which light-emitting diodes pipeline section just having one End and a negative terminal；

One input voltage source, is connected to the anode of leading the first light-emitting diodes pipeline section in above-mentioned multiple light-emitting diodes pipeline sections；

Multiple voltage-controlled demand limiters, the voltage-controlled demand limiter of each of which and above-mentioned multiple light-emitting diodes A light-emitting diodes pipeline section in pipeline section is corresponding, and the first connection end is connected to the negative of light-emitting diodes pipeline section corresponding thereto End, the second connection end is applied in a bias voltage, and the 3rd connection end is connected to a common node；

One power dissipation reduction circuit, the LED control circuit for including multiple light emitting diodes and correlating with which, on State multiple light-emitting diodes pipeline sections that multiple light emitting diodes are dividing under above-mentioned LED control circuit control, above-mentioned work( The anode and above-mentioned light-emitting diodes of the first leading light-emitting diodes pipeline section in multiple light-emitting diodes pipeline sections of rate consume reduction circuit One end of pipe control circuit is connected to above-mentioned common node；

One current source, its first end are connected to above-mentioned power dissipation and reduce in above-mentioned multiple light-emitting diodes pipeline sections of circuit last The negative terminal of individual light-emitting diodes pipeline section and the other end of above-mentioned LED control circuit, and the second termination of above-mentioned current source Ground；And

Wherein, put on bias voltage on the second connection end of above-mentioned each voltage-controlled demand limiter be respectively with The unrelated fixed voltage of change of input voltage.

2. device as claimed in claim 1, it is characterised in that have the voltage-controlled demand limiter of N number of characteristic identical according to Sequence ground corresponds to N number of light-emitting diodes pipeline section, and N is the positive integer more than 1, V₁、V₂... and V_NFor putting on above-mentioned each voltage Bias voltage on second connection end of the demand limiter of control, and V₁<V₂<···<V_N。

3. device as claimed in claim 1, it is characterised in that in above-mentioned multiple light-emitting diodes pipeline sections last luminous two Pole pipe section is not connected to a voltage-controlled demand limiter.

4. device as claimed in claim 1, it is characterised in that put on above-mentioned each voltage-controlled demand limiter Respective fixed voltage on second connection end is Yu Xianxuanding, so that the device has two modes of operation, including above-mentioned multiple In voltage-controlled demand limiter, the voltage-controlled demand limiter of only one of which is fully switched on first state, Yi Jishang There is the second state that two voltage-controlled demand limiters are part connections in stating multiple voltage-controlled demand limiters.

5. device as claimed in claim 1, it is characterised in that in above-mentioned multiple voltage-controlled demand limiters, each Voltage-controlled demand limiter has a threshold voltage V_th, a saturation voltage V_sat, one cross over its second connection end and above-mentioned common Voltage V between node_bc, and one across voltage V between its first connection end and above-mentioned common node_ac, when the demand limiter Voltage V_bcLess than the threshold voltage V of the demand limiter_thWhen, the demand limiter is to cut out, when the demand limiter Voltage V_bcMore than the threshold voltage V of the demand limiter_thAnd the voltage V of the demand limiter_acLess than the demand limiter Saturation voltage V_satWhen, the demand limiter seems a resistor, and as the voltage V of the demand limiter_bcLimit more than the electric current The threshold voltage V of device processed_thAnd the voltage V of the demand limiter_acAlso greater than the saturation voltage V of the demand limiter_satWhen, should Demand limiter has a fixed current to turn on.

6. device as claimed in claim 5, it is characterised in that have N number of voltage-controlled demand limiter to correspond to N in order Individual light-emitting diodes pipeline section, V_bci、V_thiAnd V_iIt is the voltage V of i-th voltage-controlled demand limiter respectively_bc, threshold voltage V_th And bias voltage, wherein 1≤i≤N, N are the positive integer more than 1, and for the i more than 1, work as V_bci=V_thi+ΔV_i, and Preset bias voltage V_iMake V_i≥V_i-1+ΔV_i+(V_thi-V_th(i-1)) when, △ V_i=V_bci–V_thi, this i-th voltage-controlled Demand limiter has a maximum current to turn on.

7. device as claimed in claim 1, it is characterised in that above-mentioned power dissipation reduces circuit and includes multiple light-emitting diodes Pipe, the multiple light-emitting diodes pipeline sections being dividing under LED control circuit control.

8. device as claimed in claim 7, it is characterised in that above-mentioned LED control circuit includes a controller and quilt The multiple switch device of the controller control, and each derailing switch of the plurality of derailing switch, are to reduce electricity with above-mentioned power dissipation One light-emitting diodes pipeline section of the multiple light-emitting diodes pipeline sections in road is corresponding.

9. device as claimed in claim 8, it is characterised in that controller noted above is controlled according to the magnitude of voltage of above-mentioned common node Make above-mentioned multiple switch device.

10. device as claimed in claim 8, it is characterised in that controller noted above is above-mentioned multiple voltage-controlled according to flowing through The current value of demand limiter is controlling above-mentioned multiple switch device.

11. devices as claimed in claim 8, it is characterised in that each derailing switch of above-mentioned multiple switch device with above-mentioned Power dissipation is reduced in circuit and its corresponding light-emitting diodes pipeline section is in parallel.

12. devices as claimed in claim 8, it is characterised in that each derailing switch of above-mentioned multiple switch device has first end Be connected to and the anode in circuit with its corresponding light-emitting diodes pipeline section reduced in above-mentioned power dissipation, have the second end to be connected to State the negative terminal that power dissipation reduces circuit.

13. devices as claimed in claim 7, it is characterised in that above-mentioned LED control circuit includes multiple voltage controls The demand limiter of system, each the voltage-controlled demand limiter in wherein above-mentioned LED control circuit with it is above-mentioned The light-emitting diodes pipeline section that power dissipation is reduced in the multiple light-emitting diodes pipeline sections in circuit is corresponding, and has the first connection end The anode of light-emitting diodes pipeline section corresponding thereto is connected to, the second connection end is applied in a bias voltage, and the 3rd connection End is connected to the negative terminal that above-mentioned power dissipation reduces circuit, wherein puts on each in above-mentioned LED control circuit Bias voltage on second connection end of voltage-controlled demand limiter is respectively unrelated with the change of above-mentioned input voltage Fixed voltage.

14. devices as claimed in claim 13, it is characterised in that have K characteristic phase in above-mentioned LED control circuit Same voltage-controlled demand limiter reduces K light-emitting diodes pipeline section in circuit, K corresponding to above-mentioned power dissipation in order It is the positive integer more than 1, V_1x、V_2x... and V_KxFor putting on the second connection end of above-mentioned K voltage-controlled demand limiter On bias voltage, and V_1x<V_2x<···<V_Kx。

15. devices as claimed in claim 13, it is characterised in that put on each in above-mentioned LED control circuit Respective fixed voltage on second connection end of individual voltage-controlled demand limiter is Yu Xianxuanding, so that above-mentioned power consumption Damage reduce circuit have two modes of operation, including above-mentioned LED control circuit in multiple voltage-controlled current limit In device, the voltage-controlled demand limiter of only one of which is fully switched on first state, and the control of above-mentioned light emitting diode is electric There is the second shape that two voltage-controlled demand limiters are part connections in multiple voltage-controlled demand limiter in road State.

16. devices as claimed in claim 13, it is characterised in that the multiple voltage controls in above-mentioned LED control circuit In the demand limiter of system, each voltage-controlled demand limiter has a threshold voltage V_thx, a saturation voltage V_satx, one The voltage V of the negative terminal of circuit is reduced across its second connection end and above-mentioned power dissipation_bcx, and one cross over its first connection end The voltage V of the negative terminal of circuit is reduced with above-mentioned power dissipation_acx, as the voltage V of the demand limiter_bcxLess than the demand limiter Threshold voltage V_thxWhen, the demand limiter is to cut out, as the voltage V of the demand limiter_bcxMore than the demand limiter Threshold voltage V_thxAnd the voltage V of the demand limiter_acxLess than the saturation voltage V of the demand limiter_satxWhen, the electric current Limiter seems a resistor, and as the voltage V of the demand limiter_bcxMore than the threshold voltage V of the demand limiter_thxAnd And the voltage V of the demand limiter_acxAlso greater than the saturation voltage V of the demand limiter_satxWhen, the demand limiter has one admittedly Determine current lead-through.

17. devices as claimed in claim 16, it is characterised in that have K voltage control in above-mentioned LED control circuit The demand limiter of system reduces K light-emitting diodes pipeline section in circuit, V corresponding to above-mentioned power dissipation in order_bcxj、V_thxjWith V_jxIt is the voltage V of j-th voltage-controlled demand limiter respectively_bcx, threshold voltage V_thxAnd bias voltage, wherein 1≤j≤K, K is the positive integer more than 1, and for the j more than 1, works as V_bcxj=V_thxj+ΔV_jx, and preset bias voltage V_jxMake V_jx≥V_(j-1)x+ΔV_jx+(V_thxj-V_thx(j-1)) when, △ V_jx=V_bcxj–V_thxj, this j-th voltage-controlled demand limiter have One maximum current is turned on.