CN101505563A

CN101505563A - LED driving circuit

Info

Publication number: CN101505563A
Application number: CNA2009100086586A
Authority: CN
Inventors: 黄华南
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-02-10
Filing date: 2009-02-10
Publication date: 2009-08-12
Also published as: WO2010091621A1

Abstract

The invention discloses an LED driving circuit, and belongs to the LED driving circuit. The LED driving circuit comprises a switching power circuit and a transformer, wherein the switching power circuit is used for accessing AC input and a feedback control signal, and converting the AC input into AC or pulsating direct current output according to the feedback control signal; and an inphase end of primary winding and an opposite phase end of secondary winding of the transformer access the AC or pulsating direct current output, an opposite phase end of the primary winding of the transformer and a first rectifier cell are connected with a first LED load to form a loop, and an inphase end of the secondary winding of the transformer is connected to a second LED load through a second rectifier cell. The invention provides an LED driving circuit which can generate two paths of proportional current output.

Description

LED driving circuit

Technical field

The invention belongs to a kind of LED driving circuit, concretely, belong to a kind of light-emitting diode current-sharing drive circuit.

Background technology

Up to now, the application of light-emitting diode (LED) has had the history in more than 40 year, owing to be mainly used in demonstration in the past, its power utilization efficiency belongs to secondary cause, this is such a case, caused the control of light-emitting diode drive current all fairly simple, generally only use the fixed voltage source power supply, the resistance current limliting that is aided with serial connection, there is the low side design even not add any current limiting measures, only utilize power supply or control device internal resistance to reach the purpose of current limliting, except at power-efficient, outside the compromise on reliability and the stability, this typical scenario is in daily low-power, still enough in using cheaply.

Have benefited from the high speed development of new material and new technology, light-emitting diode had had bigger improvement more in the past in the brightness performance, because light-emitting diode is a solid state device, its life-span can reach more than 100,000 hours, and its composition do not contain harmful heavy metal, and above factor makes light-emitting diode become a kind of very attractive lighting source.

As light source, the chromatogram of brightness and light source (perhaps color call, colour temperature) is the key factor whether the decision light source has practicality, though white light-emitting diode is not the highest light source of luminous efficiency at present, its efficient has also reached the twice of incandescent lamp, add reliability with height, it possesses the condition of using light source that becomes fully, in order to make LED source produce nature, Huang warm colour is necessary that the light-emitting diode of sneaking into different colours when the design light source has reached the effect of optimizing colour temperature partially.For example, need simultaneously red diodes and white light-emitting diodes as load.

LED source belongs to high efficiency light source, general 1/2 watt or above LED light lamp use Switching Power Supply power supply, and therefore, power supply and relevant circuit efficiency problem become the important technology index.LED for illumination is compared with general light-emitting diode, when especially adopting different types of light-emitting diode as load, there is following technical difficulty, promptly because the employed semi-conducting material difference of light-emitting diode of different colours, so the pressure drop by diode also has than big difference, when sneaking into the diode of two or more different colours, voltage and electric current all have different, are difficult to reach simultaneously current-sharing and efficient.In addition, because the performance parameter of different diodes is variant, and temperature rise is different during work, and simple parallel connection is not easy to reach effective current-sharing, causes light-emitting diode to be unfavorable for being connected in parallel.

Shown in Figure 1 is a kind of design of Switching Power Supply of simple light-emitting diode, this Switching Power Supply is a flyback, it comprises: transformer T2, be connected in the input circuit on the former limit of transformer T2 and be connected in the current rectifying and wave filtering circuit of forming by rectifier diode D3 and decoupling zero capacitor C 3 of transformer secondary, comprise in the input circuit that power supply BT1 presses in order to a galvanic current to be provided, and switching device U1 produces pulsating dc voltage in order to the former limit of control transformer, switching device U1 is the device of known technology, its operation principle is, have a control end and one and spill end, spilling end can present ground connection and the two states that opens circuit under the control of control end.Such device can be NCP 1013 switches of ONSEMI company.

The Switching Power Supply of light-emitting diode has one first output CN5 and feedback input end CN6, the one LED load is in parallel with the 2nd LED load, the one LED load can be red light-emitting diode string D6, D7, and the 2nd LED load can be white light emitting diode D5.

The operation principle of Switching Power Supply is as follows, under the effect of switching device U1, the electric energy that input power supply BT1 provides produces Rectified alternating current by the circuit that transformer is delivered in secondary, this pulsation alternating current is that Rectified alternating current is a LED load, the 2nd LED electric by the current rectifying and wave filtering circuit rectification, drives white light-emitting diodes respectively and red diodes is luminous.

In sort circuit, for the pressure drop of balance the one LED load and the 2nd LED load, i.e. the pressure drop of red light-emitting diode branch road and white light emitting diode branch road reaches the effect of current-sharing, needs to add balance resistance Rm on the branch road of white light-emitting diodes therein.

Yet, can see, must not only consume a part of power at the Rm on the road of white light-emitting diodes as equilibrium pressure drop, and this part power has been converted into heat, this is very disadvantageous to the LED power supply, its reason is: the pressure drop that is positioned at the road of white light-emitting diodes can not be followed the change in pressure drop on the road of red diodes when variations in temperature, thereby makes the current-sharing stability of Switching Power Supply not good enough.

Summary of the invention

One object of the present invention is to solve weak point of the prior art, provide a kind of two-way electric current output of producing, and the two-way electric current is exported proportional LED driving circuit.

For achieving the above object, LED driving circuit of the present invention comprises

Switching power circuit in order to incoming transport input and a feedback control signal, and will exchange input according to feedback control signal and be converted to and exchange or pulsating direct current is exported;

According to the present invention, LED driving circuit also comprises transformer, the in-phase end of the former limit winding of described transformer and the end of oppisite phase of secondary winding insert described interchange or pulsating direct current output, the former limit winding end of oppisite phase of described transformer is connected first LED load and forms the loop with first rectifier cell, the in-phase end of the secondary winding of described transformer is connected to second LED load by second rectifier cell.

Preferably, determine the number of turn of former limit of transformer and secondary by the electric current demand of first LED load or second LED load.

Preferably, be connected with between the in-phase end of the secondary winding of described transformer and the end of oppisite phase in order to control the absorption circuit of due to voltage spikes.

Preferably, described switching power circuit is anti-energizing switch translation circuit.

Preferably, described switching power circuit is the normal shock switch transformed circuit.

Preferably, also comprise a testing circuit, be connected between feedback end and the load, in order to detecting the magnitude of current of second load, and according to the height of detected magnitude of current Control and Feedback terminal voltage.

Beneficial effect of the present invention is, just can control another load current by the electric current of monitoring a load.Like this, just avoid traditional for the power on each bar load branch is equated, and on branch road, increase the way of devices such as resistance.And therefore, it is low to have avoided adding the power-efficient that resistance causes, and the problem that causes of resistance heating.

Description of drawings

Fig. 1 is the structure chart of a kind of Switching Power Supply of the prior art.

Fig. 2 is the circuit diagram according to the LED driving circuit of a kind of embodiment of the present invention.

Fig. 3 is the circuit diagram according to the LED driving circuit of another kind of embodiment of the present invention.

Embodiment

The present invention relates to a kind of LED driving circuit, in order to utilize a transformer that inserts, by the electric current in branch road of monitoring load, and the electric current that makes another branch road of load is kept constant, therefore and reduce the inspection stream magnitude of current, reach the purpose that reduces power consumption,, feature of the present invention elaborated below in conjunction with accompanying drawing:

Fig. 2 is the circuit diagram according to the LED driving circuit of a kind of embodiment of the present invention, and with reference to Fig. 1, the LED driving circuit in this embodiment comprises the first power input CN1, second source input CN4; The first output CN5, the second output CN7 and feedback input end CN6; Wherein, the first power input CN1 is connected reverse exciting switching voltage regulator circuit 100 with CN2, in order to external power source is connected into LED driving circuit.First output connects a LED load, the one LED load can be white light LEDs or white light LEDs string, second output connects the 2nd LED load, and the 2nd LED load can be that red-light LED, yellow light LED or red-light LED string, yellow light LED string or red-light LED yellow light LED mix string.Feedback input end CN6 is in order to connecting any one of a LED load or the 2nd LED load, thereby obtains feedback signal from load.

Described reverse exciting switching voltage regulator circuit 100 comprises power interface part 101 and switching device U1, this part inserts in order to DC power supply or the AC power with the outside, to encourage the former limit winding of the first transformer T2, this power interface part 101 can be to insert the voltage stabilizing circuit of DC power supply as shown in Figure 2, can certainly be the current rectifying and wave filtering circuit in order to the incoming transport electricity.

With reference to Fig. 2, the former limit winding connection method of the first transformer T2 is the connection of typical flyback converter, promptly is parallel with by capacitor C 4, and the leakage inductance spike that resistance R 2 and diode D2 form absorbs circuit.The leakage inductance spike absorbs circuit in order to the due to voltage spikes that leakage inductance caused of control owing to transformer.Wherein, the anode of diode D2 connects the negative pole on the former limit of the first transformer T2, and the negative electrode of D2 is connected the positive pole on the former limit of the first transformer T2 with capacitor C 4 by parallel resistor R2.

Switching device U1 exports a high level or low level signal in order to the feedback signal of reception feedback input end CN6 and according to switching device U1 of this signal output in order to the feedback signal of reception feedback input end CN6 and according to this signal; In this example, with reference to Fig. 2, it can be NCP 1013 switches of ONSEMI company, this switch has feedback end FB, spills end DRAIN, power end Vcc and earth terminal GND, wherein feedback end FB is in order to receive the feedback signal of load, spill end DRAIN and export the former limit end of oppisite phase of high level or low level to the first transformer T2 accordingly in order to the feedback signal of foundation feedback end FB, thereby to electric.Power end Vcc connects external power source, earth terminal GND ground connection.By the output of control DRAIN end, can control the former limit of first transformer T2 winding and produce pulsating current, thereby induce pulsating current at the secondary of the first transformer T2.

Feedback end FB can be by a triode Q1 control, the grounded collector of triode Q1, and emitter connects the feedback input end of switching device U1, and base stage connects the second load link, and by inspection leakage resistance R1 ground connection.

Present embodiment adopts the reverse exciting switching voltage regulator circuit, the therefore in-phase end ground connection of the secondary winding of the first transformer T2, with end of oppisite phase as output.

With reference to Fig. 2, the end of oppisite phase of the first transformer T2 connects the in-phase end of secondary of the second transformer T3 and the end of oppisite phase on former limit, the in-phase end of the former limit winding of the second transformer T3 must be exported by the first rectifier diode D3 rectification and by decoupling capacitance C10 filtering decoupling zero, is connected to first output CN5 output then; The output of the end of oppisite phase of the secondary winding of the second transformer T3 is by the second rectifier diode D5 rectification and pass through decoupling capacitance C3 filtering decoupling zero, and connects second output CN7 output.In the present embodiment, the second transformer T3 will be decomposed into two by the pulsating direct current of first transformer T2 output in proportion and wait waveform, equiphase pulsating direct current output as a current-sharing device.

Decomposition to electric current is to determine according to the number of turn of second transformer former limit winding and secondary winding, promptly, determine according to the former secondary current relation equation of current transformer N1*I1=N2*I2, wherein, N1 represents the number of turn of the former limit of second transformer winding, N2 represents the number of turn of the second transformer secondary winding, and I1 represents the electric current of the first rectifier cell D3 that flows through, and I2 represents the electric current of the second rectifier cell D5 that flows through.

According to the above-mentioned relation formula as can be known, by determining the number of turn of former limit of transformer or secondary, can determine the ratio of the current amplitude of first output circuit and second output circuit.

Filter capacitor C8 is connected between switching device controller U feedback input end and ground, and C9 is connected between triode Q1 base stage and ground, and C10 is connected between second output and ground.

The operation principle of the LED driving circuit of present embodiment is as follows: at first insert current source at the first power input CN1 and second source input CN4, between the first output CN5 and feedback input end CN6, insert a LED load, between the second output CN7 and ground, insert the 2nd LED load, because the former limit umber of turn of the second transformer T3 and good fortune limit umber of turn are determined, therefore, in the selection of LED load, need to note to some extent.Always be output as 1000mA as T3, cutting turn ratio is 1/5, and the electric current demand of a selected LED load is 750mA, and then the electric current of the 2nd LED load is 150mA, and therefore, the maximum permissible current of the 2nd LED load is about 180mA.

After the one LED load and the 2nd LED load insert, current source input under the control of switching device controller U1, be converted to pulsating direct current, and, wherein, electric current by a LED load will be detected and input to switching device controller U1 by inspection leakage resistance R1, switching device controller U1 is than the output of adjusting MOSFET drain electrode output in view of the above, then adjust loop current value, here, because the former limit and the secondary number of windings of the second transformer T2 are constant, and equate with the ratio of the gross power of the gross power of first group of light-emitting diode and second group of light-emitting diode, therefore, electric current adjustment meeting on first group of light-emitting diode directly influences accordingly the electric current of second group of light-emitting diode, makes its also corresponding changing.Like this, reached by monitoring a load and controlled the purpose of another load.Thereby just avoid traditional for the power on each bar load branch is equated, and on branch road, increase the way of devices such as resistance.And therefore, it is low to have avoided adding the power-efficient that resistance causes, and the problem that causes of resistance heating.

Preferably, can also series zener diode ZD1 and resistance R 7 between the base stage of the negative electrode of diode D3 and triode Q1, wherein, the negative electrode of Zener diode ZD1 connects the negative electrode of diode D3, and anode connects the Q1 base stages by resistance R 7.Have a Zener diode ZD1 who is higher than the puncture voltage of loaded work piece voltage by setting, when open circuit occurring, puncture Zener diode, thereby when avoiding open circuit occurring in the loop, output voltage is out of control, the situation of output overvoltage takes place.

Preferably, defeated diode D3, D5 can be Schottky diodes, have had resume speed faster.

Preferably, can connect resistance R 10 between the positive pole of the secondary of the second transformer T2, negative pole, it also as absorbing a kind of of circuit, is used to provide the road warp of releasing of a leakage inductance energy, with control because the due to voltage spikes that leakage inductance was caused of transformer.

Preferably, switching device controller U1 accessory power supply input connects accessory power supply Vaux, this accessory power supply can be realized like this: the first transformer T2 is being provided with second secondary, the minus earth of second secondary, anodal by rectifier diode D4, the filter circuit of forming by resistance R 6 and capacitor C 7, and decoupling capacitance C6 is connected to switching device U1 as the accessory power supply input.

Fig. 3 shows another kind of embodiment of the present invention, LED driving circuit in the present embodiment comprises normal shock switching power circuit 200, and the difference of this normal shock switching power circuit and anti-energizing switch circuit is that the first transformer T2 adopts the normal shock connection; Between first rectifier cell and first output, be provided with the first afterflow inductance L 1, between second rectifier cell and second input, also be provided with the second afterflow inductance L 2.Identical with the principle of circuit of reversed excitation, the electric current of the flow through first afterflow inductance and the second afterflow inductance has identical waveform and phase place, and the ratio of amplitude equals the inverse ratio of second transformer former limit winding and secondary umber of turn.

In addition,, adopt ac power supply, therefore, partly adopt the drag flow filter circuit at power interface at power unit.

Only being preferred embodiment of the present invention in sum, is not to be used for limiting practical range of the present invention.Be that all equivalences of doing according to the content of the present patent application claim change and modification, all should belong to technology category of the present invention.

Claims

1. LED driving circuit, it comprises switching power circuit, in order to incoming transport input and a feedback control signal, and will exchange input according to feedback control signal and be converted to and exchange or pulsating direct current is exported; It is characterized in that: LED driving circuit also comprises transformer, the in-phase end of the former limit winding of described transformer and the end of oppisite phase of secondary winding insert described interchange or pulsating direct current output, the former limit winding end of oppisite phase of described transformer is connected first LED load and forms the loop with first rectifier cell, the in-phase end of the secondary winding of described transformer is connected to second LED load by second rectifier cell.

2. LED driving circuit according to claim 1 is characterized in that: the number of turn of being determined former limit of transformer and secondary by the electric current demand of first LED load or second LED load.

3. LED driving circuit according to claim 2 is characterized in that: be connected with the absorption circuit in order to the control due to voltage spikes between the in-phase end of the secondary winding of described transformer and the end of oppisite phase.

4. LED driving circuit according to claim 3 is characterized in that: described switching power circuit is anti-energizing switch translation circuit.

5. LED driving circuit according to claim 3 is characterized in that: described switching power circuit is the normal shock switch transformed circuit.

6. according to any described LED driving circuit in the above claim of claim, it is characterized in that: also comprise a testing circuit, be connected between feedback end and the load, in order to detecting the magnitude of current of second load, and according to the height of detected magnitude of current Control and Feedback terminal voltage.