CN203423823U

CN203423823U - Led drive circuit

Info

Publication number: CN203423823U
Application number: CN201320069021.XU
Authority: CN
Inventors: 村中将浩
Original assignee: Rohm Co Ltd
Current assignee: Rohm Co Ltd
Priority date: 2013-02-06
Filing date: 2013-02-06
Publication date: 2014-02-05
Anticipated expiration: 2023-02-06

Abstract

The utility model provides an LED drive circuit, comprising: a first LED; a second LED connected between a power supply and the ground; and an inductor in a serial connection with the first LED and then connected between the power supply and the ground, wherein, when the power supply is switched on, the first LED is in a forward bias state, and the second LED is in a reverse bias state. Via the LED drive circuit, power supply utilization rate is improved, luminescence can be performed under the condition of low voltage drive, and function of improving power factor is also provided.

Description

LED drive circuit

Technical field

The utility model relates to LED(Light Emitting Diode: light-emitting diode) drive circuit, and be particularly related to the LED drive circuit and the ligthing paraphernalia that comprises this LED drive circuit with low voltage drive LED.

Background technology

In recent years, LED illumination has obtained developing rapidly.In LED ligthing paraphernalia, in order to reduce the loss bringing due to resistive element, not only need to reduce the value of resistive element, also need to reduce the drive current of LED.Therefore, wish to reduce the electric current that flows in LED string in ligthing paraphernalia.

On the other hand, at Triac(triac) etc. in dimming mode, the misoperation when reducing driving LED, wishes directly to use Triac light modulation machine to drive, and for this reason, need to reduce LED driving voltage, and raising LED drive current.

Fig. 1 is the schematic diagram that existing LED drive circuit 100 is shown.As shown in Figure 1, existing LED drive circuit 100 comprises: power supply 101, capacitor 102,

LED

103a, 103b, 103c, inductor 104, controller 105, MOSFET(mos field effect transistor) 106, diode 107 and resistor 108.Controller 105 is connected to source electrode and the grid of MOSFET 106, to control conducting (ON) and the cut-off (OFF) of MOSFET 106, comes with pulse

mode driving LED

103a, 103b, 103c.

Fig. 2 illustrates the schematic diagram that drives the LED drive circuit 100 shown in Fig. 1 by DC power supply.The first half in Fig. 2 represents to be applied to driving voltage on LED drive circuit 100 over time, and the electric current that the latter half represents to flow in inductor 104 over time.As shown in Figure 2, power supply 101 generation direct voltage Vs(are shown in broken lines).See figures.1.and.2, when controller 105 control MOSFET 106 are conducting state, current flowing is in the loop consisting of power supply 101,

LED

103a, 103b, 103c, inductor 104, MOSFET 106, resistor 108, thereby driving

LED

103a, 103b, 103c are luminous.Now, diode 107 is in reverse blocking state, prevents that electric current from crossing and

short circuit LED

103a, 103b, 103c and inductor 104 via the circuit flow on right side.Now, 101 pairs of inductors of power supply 104 charge, and flow through the Current rise of inductor 104, and after elapsed time Tr, Current rise is to default maximum Imax, and this Time Controller 105 makes MOSFET 106 cut-offs.Owing to flowing in the electric current of inductor 104, can not suddenly change, therefore, inductor 104 makes diode 107 conductings, thereby to

LED

103a, 103b, 103c electric discharge, driving

LED

103a, 103b, 103c are luminous, flow through the current reduction of inductor 104.After elapsed time Td, current reduction is to default minimum value Imin, and this Time Controller 105 makes MOSFET 106 conducting again.Repeat said process, so the electric current that flows in

LED

103a, 103b, 103c changes between maximum Imax and minimum value Imin.Thereby can reduce the loss on resistive element and prevent from averaging out between the misoperation of Triac dimmer.

Fig. 3 illustrates the schematic diagram that drives the LED drive circuit 100 shown in Fig. 1 by the AC power of full-wave rectification.The first half in Fig. 3 represents to be applied to driving voltage on LED drive circuit 100 over time, and the electric current that the latter half represents to flow in inductor 104 over time.As shown in Figure 3, the alternating voltage Vs(that power supply 101 produces full-wave rectification is shown in broken lines).With reference to Fig. 1 and Fig. 3, when the instantaneous value of alternating voltage Vs is higher, the charging rate of inductor 104 is fast, and Current rise is fast, and the charging interval, Tr was short; Yet when the instantaneous value of alternating voltage Vs is lower, inductor 104 charging rates are slack-off, Tr is elongated.When the instantaneous value of alternating voltage Vs is reduced to the required voltage threshold Vth of driving

LED

103a, 103b, 103c when following (the time period To in Fig. 3), can not driving

LED

103a, 103b due to brownout, 103c, even now still conducting of MOSFET 106, can not be to inductor 104 chargings, circuit 100 is not worked, thereby LED is 103a, 103b, 103c extinguish.

Therefore, hope can provide such LED drive circuit, this LED drive circuit can be disposed at the small space of LED electric light inside, can under low-voltage, also not make LED extinguish works, can reduce the electric current of LED drive circuit and raise the efficiency, and improve the power factor (power factor, PF) of LED drive circuit.

Utility model content

The utility model is made in view of above-mentioned situation.

In the utility model, a kind of LED drive circuit has been proposed, comprising: a LED; The 2nd LED, the 2nd LED is connected in series between VDD-to-VSS; And inductor, inductor and a LED are connected in series between VDD-to-VSS, and wherein when power connection, the one LED is in forward bias state, and the 2nd LED is in reverse-bias state.

In the utility model, a kind of illuminating circuit has also been proposed, comprising: the first light-emitting component; The second light-emitting component, the second light-emitting component is connected in series between VDD-to-VSS; And inductor, inductor and a LED are connected in series between VDD-to-VSS, and wherein when power connection, the first light-emitting component is in conducting state, and the second light-emitting component is in not on-state.

In the utility model, a kind of ligthing paraphernalia that comprises foregoing circuit has also been proposed.

The utility model is by above-mentioned LED drive circuit, illuminating circuit and ligthing paraphernalia, improved power utilization rate, even also can be luminous in the situation that using low voltage drive, and, when input voltage is high, power output is large, when input voltage is low, power output is low, so be improved the function of PF.

Accompanying drawing explanation

By describe embodiment of the present utility model with reference to accompanying drawing, in the accompanying drawings, similar element like Reference numeral representation class.

Fig. 1 is the schematic diagram that existing LED drive circuit is shown.

Fig. 2 illustrates the schematic diagram that drives the LED drive circuit shown in Fig. 1 by DC power supply.

Fig. 3 illustrates the schematic diagram that drives the LED drive circuit shown in Fig. 1 by the AC power of full-wave rectification.

Fig. 4 is the schematic diagram that the LED drive circuit of embodiment 1 of the present utility model is shown.

Fig. 5 is the schematic diagram that the LED drive circuit of embodiment 2 of the present utility model is shown.

Fig. 6 is the schematic diagram that the LED drive circuit of embodiment 3 of the present utility model is shown.

Description of reference numerals

100,400,500,600 LED drive circuits; 101,401 power supplys; 102,502,609 capacitors; 103a, 103b, 103c, 403a, 403b, 403c LED; 104,404 inductors; 105,405 controllers; 106,406 MOSFET; 107,407 diodes; 108,408 resistors.

Embodiment

Below, with specific embodiment, exemplary embodiment of the present utility model is described.Yet, should recognize, the utility model is not limited to following described embodiment, but also comprises other mode of texturing that some those skilled in the art can expect.

" connection " word using in the utility model refers to two connections between element, has both comprised the direct connection between two elements, also comprises via the indirect connection between three-element two elements.

(embodiment 1)

First, with reference to Fig. 4, embodiment 1 of the present utility model is described.

Fig. 4 is the schematic diagram that the LED drive circuit 400 of embodiment 1 of the present utility model is shown.As shown in Figure 4, the LED drive circuit 400 of embodiment 1 of the present utility model comprises: power supply 401,

LED

403a, 403b, 403c, inductor 404, controller 405, MOSFET 406, diode 407 and resistor 408.

LED

403a, 403b are connected in series; The anodic bonding of LED 403c is to the negative electrode of LED 403a; One end of inductor 404 is connected to the anode of LED 403b, and the other end of inductor 404 is connected to the negative electrode of diode 407; The anodic bonding of diode 407 is to the negative electrode of LED 403c; LED 403c, MOSFET 406 and resistor 408 are connected in series between power supply 401 and ground; Controller 405 is connected between the source electrode and grid of MOSFET 406, in pulse width modulation (pulse width modulation, PWM) mode, controls MOSFET 406.

That is,, in the LED drive circuit of Fig. 4, comprising:

LED

403a, 403b; LED 403c; Diode 407, and LED 403c is connected in series between power supply 401 and ground; And inductor 404, and

LED

403a, 403b be connected in series between power supply 401 and ground, and wherein the negative electrode of

LED

403a, 403b is connected with power supply 401, makes when from power supply 401 input positive voltage, and

LED

403a, 403b are in forward bias state; And the anode of LED 403c is connected with power supply 401, make when from power supply 401 input positive voltage, LED 403c is in reverse-bias state.

In addition, in the LED drive circuit of Fig. 4, MOSFET 406 and

LED

403a, 403b, inductor 404 are connected in series between power supply 401 and ground, and MOSFET 406 and LED 403c, diode 407 are connected in series between power supply 401 and ground.

In addition,

LED

403a, 403b in Fig. 4 can also be considered as to a LED string, LED 403c is considered as to the 2nd LED string, thereby, in the LED drive circuit of Fig. 4, comprising: a LED string, comprises a plurality of 403a, 403b; The 2nd LED string, comprises a LED 403c; Diode 407, and the 2nd LED is connected in series between power supply 401 and ground; And inductor 404, and a LED is connected in series between power supply 401 and ground, for

example LED

403a, 403b of each LED(in a LED string wherein) negative electrode is connected with power supply 401, make when from power supply 401 input positive voltage, each LED in a LED string is in forward bias state; And each LED(in the 2nd LED string LED 403c for example) anode is connected with power supply 401, make when inputting positive voltage from power supply 401, each LED during the 2nd LED goes here and there is in reverse-bias state.

The driving process of the LED drive circuit 400 of the embodiment 1 in Fig. 4 then, is described.The alternating voltage Vs(that power supply 401 produces full-wave rectification is as shown in Figure 3 shown in broken lines).When controller control MOSFET 406 is conducting state, current flowing is in the loop consisting of power supply 101,

LED

403a, 403b, inductor 404, MOSFET 406, resistor 408, thereby driving

LED

403a, 403b are luminous.Now, diode 407, in reverse blocking state, prevents from being applied to the overtension on LED 403c and destroys LED 403c.Now, 101 pairs of inductors of power supply 404 charge, and flow in the Current rise of inductor 404, and after elapsed time Tr, Current rise is to default maximum Imax, and this Time Controller 405 makes MOSFET 406 cut-offs.Owing to flowing in the electric current of inductor 404, can not suddenly change, therefore, inductor 404 makes diode 407 conductings, thereby to

LED

403c, 403a, 403b electric discharge, driving

LED

403a, 403b, 403c are luminous, flow in the current reduction of inductor 404, after elapsed time Td, current reduction is to default minimum value Imin, and this Time Controller 405 makes MOSFET conducting again.So repeat, by using controller 405 speed-sensitive switch MOSFET 406, thereby driving

LED

403a, 403b, 403c are luminous, and make the electric current that flows through each LED between maximum Imax and minimum value Imin, therefore, can reduce the loss on resistive element and prevent from averaging out between the misoperation of Triac dimmer.

When adopting the alternating current of full-wave rectification as shown in Figure 3 to drive, when the instantaneous value of alternating voltage Vs is higher, inductor 404 charging rates are fast, and Current rise is fast, and r is short for induction charging time T; When the instantaneous value of alternating voltage Vs is lower, inductor 404 charging rates are slack-off.Herein, compare with existing LED drive circuit 100, because the quantity of the LED of MOSFET 406 conduction period demand motive becomes 2 from 3, thus relatively high at the voltage at inductor 404 two ends, cause the charging rate of inductor 404 faster than existing inductor 104.In addition, because the quantity of the LED of MOSFET 406 conduction period demand motive becomes 2 from 3, so the needed voltage threshold Vth of driving LED reduces, the inoperable time period To of LED drive circuit 400 shortens, thereby reduced unavailable voltage amplitude in power supply, can improve the utilance of power supply.

In addition, compare with existing LED drive circuit 100, quantity decline due to the LED at MOSFET 406 conduction period demand motive, so can reduce required drive current, thereby reduced the power consuming on resistor 408, reduce the loss of drive circuit 400, thereby improved the efficiency of drive circuit 400.

In addition, the voltage threshold Vth required due to the identical LED of the total number of driving is lower than prior art, so in the situation that identical supply voltage is provided, can improves the quantity of the LED that LED drive circuit can drive, and not need to increase the quantity of main driving element and the complexity of drive circuit.

In addition, in above-mentioned LED circuit, use the alternating voltage of the full-wave rectification of not passing through capacitor filtering as power supply, when inductor 404 charging, the voltage that deducts LED 403a and LED 403b voltage with supply voltage Vs charges, and now lights LED 403a and LED403b.When inductor 404 electric discharge, by

LED

403a, 403b, 403c, discharge.Now, owing to being constant current state, so be the low state of input current when input voltage is high.

And when supply voltage step-down, slack-off due to charging, the charging interval in the cycle is elongated, thereby inductor 404 can not discharge fully, i.e. so-called sub-resonance condition.When supply voltage further reduces, only with maximum duty recently driving

LED

403a, 403b.

Compare while driving with constant-current decompression transducer with simple, the state of the load in the present invention lightens steppedly.Circuit of the present invention has not only expanded the LED load area of Triac light modulation, and by the load in two stages, has played the effect of improving PF.Especially when the forward voltage (VF) of used LED is higher, for example VF is 30 volts when above, can play more significant PF and improve effect.

Although take in embodiment 1, with alternating voltage Vs driving LED drive circuit 400, be described as example, but be to be understood that, the utility model is not limited in this, at power supply 401, be other voltage waveform, especially voltage lower (such as DC low-voltage) or portion of time lower (such as triangular wave, sawtooth waveforms etc.) in the situation that, also can play similar technique effect.

Although the 2nd LED string that comprises a LED string of two

LED

403a, 403b and comprise a LED 403c of take in embodiment 1 is described as example, but be to be understood that, the utility model is not limited in this, each LED string can comprise one or more LED, and the connected mode between LED can be the mode that series, parallel or connection in series-parallel mix.

Although take MOSFET 406 and controller 405 as example is described in embodiment 1, should be appreciated that the utility model is not limited in this, in the situation that using other switch element, also can play similar technique effect.Even can not comprise switch element, as long as can make supply voltage alternately connect and cut off.

Although take resistor 408 as example is described in embodiment 1, should be appreciated that the utility model is not limited in this, in the situation that using other resistive element, also can play similar technique effect.Even can not comprise resistive element, but utilize the spuious or dead resistance in drive circuit 400 to serve as resistive element.

Although in embodiment 1 with

LED

403a, 403b, inductor 404, MOSFET 406 and resistor 408 are connected in series between power supply 401 and ground successively, and LED 403c, diode 407, MOSFET 406 and resistor 408 are connected in series between power supply 401 and ground successively as example is described, but be to be understood that, the utility model is not limited in this, as long as

LED

403a, 403b, inductor 404, MOSFET 406 is connected in series between power supply 401 and ground, and LED 403c, diode 407, MOSFET 406 is connected in series between power supply 401 and ground.

Although take diode 407 as example is described in embodiment 1, should be appreciated that the utility model is not limited in this, in the situation that using other one-way conduction element, also can play similar technique effect.Can also replace diode 407 with switch element, as long as switch element is opened circuit when power supply 401 is connected, when power supply 401 disconnects, switch element is closed.

Although take positive supply as example is described in embodiment 1, should be appreciated that the utility model is not limited in this, in the situation that using negative supply, as long as by the polarity inversion of LED403a, 403b, 403c and diode 407.In addition, the link position of VDD-to-VSS also can exchange, as long as

LED

403a, 403b are in forward bias state while making to switch on power; And LED 403c is in reverse-bias state.

Although take LED as example is described in embodiment 1, should be appreciated that the utility model is not limited in this, in the situation that use other light-emitting component, also can play similar technique effect.Now, illuminating circuit comprises: the first light-emitting component; The second light-emitting component; Switch element, and the second light-emitting component is connected in series between VDD-to-VSS; And inductance element, and the first light-emitting component is connected in series between VDD-to-VSS, and wherein when power connection, the first light-emitting component is in conducting state, and the second light-emitting component and switch element are in not on-state.In addition,, when power supply disconnects, the first light-emitting component, the second light-emitting component and switch element are in conducting state.

(embodiment 2)

Fig. 5 is the schematic diagram that the LED drive circuit 500 of embodiment 2 of the present utility model is shown.Compare with the LED drive circuit 400 shown in Fig. 4, LED drive circuit 500 increases capacitor 502, and capacitor 502 is connected with the LED connection in series-parallel that

LED

403a, 403b form.While applying voltage on

LED

403a, 403b, capacitor 502 can be stored a part of electric charge, so by increasing capacitor 502, can strengthen the charging and discharging capabilities of LED drive circuit 500, thereby further reduce voltage threshold Vth.

Although take capacitor 502 as example is described in embodiment 2, should be appreciated that the utility model is not limited in this, in the situation that using other capacity cell, also can play similar technique effect.

Although the LED connection in series-parallel forming with capacitor 502 and

LED

403a, 403b in embodiment 2 is connected to example and is described, and should be appreciated that capacitor 502 also can be connected in parallel with LED 403a and/or LED 403b.

(embodiment 3)

Fig. 6 is the schematic diagram that the LED drive circuit 600 of embodiment 3 of the present utility model is shown.Compare with the LED drive circuit 500 shown in Fig. 5, increase capacitor 609, capacitor 609 is connected in parallel with LED 403c.Capacitor 609 can be stored a part of electric charge, so by increasing capacitor 609, can further strengthen the charging and discharging capabilities of LED drive circuit 600, thereby further reduce voltage threshold Vth.

Although used capacitor 502 and capacitor 609 to strengthen the charging and discharging capabilities of LED drive circuit 600 in embodiment 3, should be appreciated that in the present embodiment and also can not use capacitor 502.

(embodiment 4)

The utility model also relates to the ligthing paraphernalia of the LED drive circuit of a kind of embodiment of use 1-3.Thereby ligthing paraphernalia of the present utility model can lower at supply voltage (such as DC low-voltage) or is worked in portion of time lower (such as sine wave, triangular wave, sawtooth waveforms etc.) in the situation that, has improved ligthing paraphernalia adaptive capacity.In addition, owing to having reduced, consume the loss on resistive element, so improved the efficiency of ligthing paraphernalia, also improved the PF of ligthing paraphernalia.

Although the embodiment 1-4 of take above has described execution mode of the present utility model as example.But those skilled in the art will realize that and can above each embodiment be combined and be changed, and do not deviate from spirit and scope of the present utility model.Scope of the present utility model is defined by the claims.

Claims

1. a LED drive circuit, is characterized in that, comprising:

The one LED;

The 2nd LED, described the 2nd LED is connected between VDD-to-VSS; And

Inductor, described inductor and a described LED are connected in series between VDD-to-VSS,

Described in wherein when power connection, a LED is in forward bias state, and described the 2nd LED is in reverse-bias state.

2. LED drive circuit according to claim 1, is characterized in that, also comprises:

The first capacity cell, described the first capacity cell and a described LED are connected in parallel.

3. LED drive circuit according to claim 2, is characterized in that, also comprises:

The second capacity cell, described the second capacity cell and described the 2nd LED are connected in parallel.

4. LED drive circuit according to claim 1, is characterized in that, also comprises:

Diode, described diode and described the 2nd LED are connected in series between VDD-to-VSS, and described in when power connection diode in reverse-bias state.

5. LED drive circuit according to claim 4, is characterized in that, also comprises:

Switch element,

Wherein, described the 2nd LED, described diode and described switch element are connected in series between power supply and ground, and a described LED, described inductance element and described switch element are connected in series between power supply and ground.

6. LED drive circuit according to claim 1, is characterized in that, described power supply is AC power.

7. LED drive circuit according to claim 5, it is characterized in that, described switch element is that MOSFET and described LED drive circuit also comprise controller, and described controller is connected between the source electrode and grid of described MOSFET, and controls described switch element in PWM mode.

8. an illuminating circuit, is characterized in that, comprising:

The first light-emitting component;

The second light-emitting component, described the second light-emitting component is connected between VDD-to-VSS; And

Inductor, described inductor and described the first light-emitting component are connected in series between VDD-to-VSS,

Described in wherein when power connection, the first light-emitting component is in conducting state, and described the second light-emitting component is in not on-state.

9. illuminating circuit according to claim 8, is characterized in that, comprising:

The first capacity cell, described the first capacity cell and described the first light-emitting component are connected in parallel; And

The second capacity cell, described the second capacity cell and described the second light-emitting component are connected in parallel.

10. a ligthing paraphernalia, is characterized in that, comprises the circuit described in any one of claim 1 ~ 9.