CN202183892U - Driver with single inductor and multiple LED light strings - Google Patents

Abstract

The utility model discloses a driver with a single inductor and multiple LED light strings, which comprises a switching control circuit and a current detection control circuit, wherein the switching control circuit is used for generating a plurality of digital control signals, so as to control a plurality of switches which are coupled to a plurality of LED light strings, each switch is controlled to be conducted or cut off by the corresponding digital signal, and the current detection circuit is used for determining the sum of electric quantity passing by each LED light string, each switch, a common module inductor, a main switch and the ground from an input voltage end in sequence, and controlling the conductive time of each switch according to the determined sum of the electric quantity so as to lead average current passing by each LED light string is the same, therefore, the total current passing by each LED light string is controlled to be in a pre-set value.

Description

The driver of single many LED of inductor lamp string

The application is a priority of advocating that, application number that submit first to the U.S. on August 23rd, 2010 is 61/402,106, the utility model name is called the utility model patent of " Single Inductor Multiple LED StringDriver ".

Technical field

The utility model relates to the correlation technique of the power supply of a kind of LED lamp, control and protective circuit, refers to a kind of in order to use single inductor to drive the controller of many LED lamp string especially.

Background technology

In the general lighting field, the application of light-emitting diode or LED lamp is more and more universal, for example, the LED lamp is applied to the back lighting of LCD TV, frivolous laptop display screen and DLP light source of projector.Along with of the use of LED lamp in field of backlights, the more and more thinning design of television set and computer display screen curtain.The many LED lamp string that uses the LED-backlit design is for laterally arranging, and each the LED lamp in each LED lamp string is for being connected in series.For obtaining high-quality effect backlight, control flows through the various controllers of the electric current of many LED lamp string just and arise at the historic moment.

As shown in Figure 1, it comprises the sketch map in order to many LED lamp string driver 10 of the boost converter 11 that drives a plurality of LED lamp strings through steady resistance for demonstration is existing.This boost converter 11 is by 14 drivings of feedback signal that provided between resistor 16 and one of them LED lamp string 15 of being connected in series with it, to adjust the output voltage (VOUT) of the required electric current of these boost converter 11 outputs.For other LED lamp strings that above-mentioned feedback signal 14 is not provided, all has the resistor series connection with it with this resistor similar resistance, so that the electric current basically identical of each LED lamp string of flowing through.The matching degree of forward voltage and the feedback voltage of LED is depended in the variation of LED lamp string stream, and for example, when total forward voltage of two LED lamp strings differs 1 volt (V), feedback voltage is 2V, and then the mismatch degree of LED lamp current is 1V/2V=50%.

As shown in Figure 2; It comprises the sketch map in order to many LED lamp string driver 20 of the LED lamp offset controller 21 that passes through a plurality of LED lamp strings of electric current synchronous (current sync) driving separately for demonstration is existing; Wherein, This electric current is arranged at this LED lamp offset controller 21 inside synchronously, and connects with the CTRL1-CTR6 port 22-27 lotus root of this LED lamp offset controller 21.A power supply changeover device provides the front end that gives LED lamp string through adjusted output voltage (VOUT), and adjusts the electric current of each LED lamp string synchronously by above-mentioned electric current.For reaching better efficient; Adjust the output voltage (VOUT) of power supply changeover device adaptively, so, then this electric current synchronously end can produce certain operating voltage and fall; So; Make the electric current between LED lamp string that very high matching degree arranged, still, the fluctuation of LED lamp total forward voltage between string and string is very big.Therefore, electric current is the change in voltage of end synchronously, can cause the very high power loss and the generation of heat; For example; Total forward voltage of two long LED lamp strings is respectively 200V and 180V, and the synchronous end of electric current that then has the LED lamp string of 180V forward voltage will have the additional electrical pressure reduction of 20V, so; Then when the bias current circulation of 120mA, the existence of aforementioned electric pressure reduction will cause the LED lamp string with 200V forward voltage to produce the power loss up to 2.4W than the LED lamp string with 180V forward voltage.

As shown in Figure 3, it comprises the sketch map in order to many LED lamp string driver 30 of the DC-DC controller 31 that drives a plurality of LED lamp strings for demonstration is existing.Adopt a boost converter 32 input direct voltage of 24V to be converted into for example 100 to 200V the VD (VOUT) of the appointment that exports LED lamp string front end to; And the rear end of each LED lamp string is driven by the LED lamp string switch transducer of for example dc-dc converter 35 respectively; This LED lamp string switch transducer is to be made up of MOSFFET transistor 36, inductor 37, diode rectifier 38 and current sensing resistor 39; Each LED lamp string switch transducer is with the operation of the operation principle of step-down controller, is complementary with the total forward voltage of LED lamp string to reduce main output voltage, and then adjusts each LED lamp string and flow to desired value; So; Promptly do not have the power loss that causes because of the voltage difference between main output voltage and the total forward voltage of LED lamp string, right, each LED lamp string all need dispose a LED lamp string switch transducer with independent inductor; So, promptly increased whole cost.

The utility model content

The utility model provides the driver of single many LED of inductor lamp string, and it comprises ON-OFF control circuit and current detection control circuit, wherein; This ON-OFF control circuit is in order to produce a plurality of digital controlled signals; Be coupled to a plurality of switches of a plurality of LED lamp strings with control, and each switch be respectively by its its conducting of corresponding digital controlled signal control with end, and this current detection circuit is in order to confirm flowing to each LED lamp string by Input voltage terminal successively; Again to each switch; Then to common-mode inductor, the quantity of total electric weight of the electric current supply through main switch to ground again, and according to the quantity of determined total electric weight; The ON time of controlling each switch is all identical with the flow through average current of each LED lamp string of order, and then makes the total current of each LED lamp string of flowing through be controlled at a predetermined value.

In an embodiment of the utility model, the driver of many LED of this list inductor lamp string has single inductor and a plurality of LED lamp string combination (Single-Inductor-Multiple-Output of a timesharing; SIMO) framework; This framework adopts common-mode inductor electric current to be injected the maintenance capacitor of each LED lamp string respectively; So that each LED lamp string produces identical average current; The current uniform of feasible each the LED lamp string of flowing through of the multiplexing property of this common-mode inductor does not obtain adjustment, and every road phase place of this common-mode inductor is the step-down translate phase, to drive the conducting of each LED lamp string respectively.Preferably, because main output voltage is different with total forward voltage of LED lamp, make the biasing of each LED lamp string not have power loss.In addition, the utility model only need adopt single inductor can reach above-mentioned effect.

In an embodiment of the utility model; The driver of many LED of this list inductor lamp string is the part of integrated circuit, and this ON-OFF control circuit is a PDM keyer, and a plurality of LED switches and this main switch are arranged on the inside or the outside of this integrated circuit; Preferably; Adopt AC/DC converter (AC-to-DC converter) to export unjustified direct voltage (VHIGH), so, need not to adopt dc/dc boost converter (DC-to-DC boostconverter); Be that this unregulated direct voltage VHIGH capable of using directly drives a plurality of LED lamp strings, and then avoid the loss of added efficiency.

Below promptly specify other structures and the method for the utility model, the rights protection scope of the utility model is not limited to above stated specification, and the scope of the claims that should like enclosed is listed.

Description of drawings

Below in conjunction with accompanying drawing the utility model embodiment is done further explain, and similar components is used similar label.

Fig. 1 is the existing sketch map that comprises in order to many LED lamp string driver of the boost converter that drives a plurality of LED lamp strings through steady resistance;

Fig. 2 for existing comprise in order to the electric current through separately synchronously (current syncs) drive the sketch map of many LED lamp string driver of the LED lamp offset controller of a plurality of LED lamp strings;

Fig. 3 is the existing sketch map that comprises in order to many LED lamp string driver of the DC-DC controller that drives a plurality of LED lamp strings through each LED lamp string switch transducer;

Fig. 4 is the sketch map of first embodiment of single many LED of inductor lamp string driver of the utility model;

Fig. 5 is the more detailed circuit diagram of single many LED of inductor lamp string driver of Fig. 4;

Fig. 6 is the different conditions sketch map in the PWM switch circulation of single many LED of inductor lamp string driver of Fig. 5;

Fig. 7 is the voltage corresponding with it of the different switches in the circulation of PWM switch, the oscillogram of electric current;

Fig. 8 drives the flow chart of the method for many LED lamp string for the single inductor of the employing of the utility model;

Fig. 9 is the sketch map of second embodiment of single many LED of inductor lamp string driver of the utility model; And

Figure 10 is the sketch map of the 3rd embodiment of single many LED of inductor lamp string driver of the utility model.

Embodiment

As shown in Figure 4, it is the sketch map of first embodiment of single many LED of inductor lamp string driver of demonstration the utility model.Single many LED of inductor lamp string driver 40 comprises a plurality of LED lamp string 41-46, integrated circuit 47, AC/DC converter 48, output capacitor 51, diode rectifier 52 and common-mode inductor 53.Each LED lamp string comprises the LED lamp of a plurality of series connection links.As shown in the figure, the front end of each LED lamp string all connects direct voltage VHIGH end, and the rear end of each LED lamp string connects the LED lamp switch terminal S1-S6 of integrated circuit 47 respectively, and the rear end of each LED lamp string also electrically connects maintenance capacitor 61-66 respectively.Except above-mentioned 6 LED lamp switch terminal S1-S6, integrated circuit 47 also comprises CTRL terminal as control interface, the ISET terminal as reference current, main switch terminal SW, input terminal LIN, power supply voltage terminal VCC and two earth terminal GND and GP.

In the present embodiment, AC/DC converter 48 receives the voltage of the alternating-current voltage source 49 that exchanges from for example 110V, and exports the 5V direct voltage of an adjustment, and this 5V direct voltage generally can be applicable in many electronic equipments.This AC/DC converter 48 can also be exported a unjustified secondary direct voltage VHIGH.The value of VHIGH depends on the turn ratio of this AC/DC converter 48 basically.Preferably, need not to use additional dc/dc boost converter, can directly this unjustified direct voltage VHIGH be used to drive a plurality of LED lamp strings; For example; If each LED lamp string has 45 LED lamp serial connections, total forward voltage of this LED lamp string then is approximately 45 * 3.3=150V, and this supply voltage VHIGH is approximately 190V; Then can be left 40V voltage as normal operation; Compared to LED lamp string driver 30 shown in Figure 3, the utility model directly uses from unjustified voltage VHIGH in the AC/DC converter 48, can reduce by 20% loss in efficiency.

Single many LED of inductor lamp string driver 40 general back lightings of using LCD TV, LCD monitor, frivolous laptop display screen and DLP light source of projector.In order effectively to adjust the electric current of above-mentioned 6 the LED lamp strings of flowing through, each LED lamp string is to realize biasing through LED lamp switch terminal S1-S6, common mode inductance 53 and main switch terminal SW respectively.At first; Each LED lamp switch terminal electrically connects a LED lamp switch (not shown) that can provide active current to give corresponding LED lamp string synchronously; Secondly, this main switch terminal SW electrically connects the main switch (not shown) that can drive common mode inductance 53, so; Then when one of them switch conductions of main switch and all LED lamp switches, can form I as shown in the figure _LED1, I _LED2... I _LED6Etc. many LED lamp string streams, this electric current flows into LED lamp string from voltage VHIGH end, flows into corresponding LED lamp switch again, passes through common-mode inductor 53 then, arrives ground via this main switch at last.This main switch cooperates 6 LED lamp switches and single inductor, reaches synchronously with the electric current of controlling these 6 LED lamp strings respectively.

In an embodiment of the utility model, the driver 40 of many LED of this list inductor lamp string has single inductor and a plurality of LED lamp string combination (Single-Inductor-Multiple-Output of a timesharing; SIMO) framework; This framework adopts common-mode inductor 53 electric current to be injected the maintenance capacitor 61-66 of each LED lamp string 41-46 respectively; So that each LED lamp string produces identical average current, the electric current I LED1-ILED6 of feasible each the LED lamp string of flowing through of the multiplexing property of this common-mode inductor 53 obtains adjustment respectively, for example; The one LED lamp switch promptly produces LED lamp string stream I in the first ON time conducting _LED1, this electric current I _LED1Flow into a LED lamp string 41 from voltage VHIGH end successively, flow into LED lamp switch terminal S1 again, pass through common-mode inductor 53 then, arrive ground (shown in the thick dashed line among Fig. 4 91) via main switch terminal SW at last, when above-mentioned electric current I _LED1Total electric weight when reaching desired value, promptly by a LED lamp switch.Then, the 2nd LED lamp switch promptly produces the 2nd LED lamp string stream I in the second ON time conducting _LED2, this electric current I _LED2Flow into the 2nd LED lamp string 42 from voltage VHIGH end successively, flow into LED lamp switch terminal S2 again, pass through common-mode inductor 53 then, arrive ground (shown in the thick dashed line among Fig. 4 92) via main switch terminal SW at last, in like manner, when above-mentioned electric current I _LED2Total electric weight when reaching desired value, promptly by the 2nd LED lamp switch, each LED lamp string repeats above-mentioned steps.When its corresponding LED lamp switch conducting or by the time, each LED lamp string fails to be convened for lack of a quorum and changes, and each keeps the balanced always LED lamp string stream of capacitor 61-66.Keep the electric weight of capacitor to be equal to identical desired value owing to inject each, make that the average current of each LED lamp string is all identical.Therefore, every road phase place of this common-mode inductor 53 is the step-down translate phase, to drive the conducting of each LED lamp string respectively.Preferably, because main output voltage is different with total forward voltage of LED lamp, make the biasing of each LED lamp string not have power loss.In addition, compared to the use of many inductors shown in Figure 3, the utility model only need adopt single inductor 53 to get final product.

As shown in Figure 5, be the more detailed circuit diagram of single many LED of inductor lamp string driver 40 of displayed map 4.In the present embodiment, integrated circuit 47 comprises interface module 55, oscillator 56, benchmark and biasing module 57, reference current IREF module 58, ON-OFF control circuit 60, a plurality of switch QS1-QS6 (71-76), discharge switch QD 77, main switch QM 78 and current detection control circuit 80.These a plurality of switch QS1-QS6 are to described 6 the LED lamp switches of Fig. 4 part (but not shown); And main switch QM 78 is to the described main switch of Fig. 4 part (but not shown), though, in the present embodiment; Above-mentioned switch QSn, main switch QM and discharge switch QD all are arranged on the inside of integrated circuit 47; But, in other circuit embodiments, also can switch QSn, QM and QD be arranged on the outside of integrated circuit 47 not as limit.

As shown in Figure 5, ON-OFF control circuit 60 is pulse-width modulation (PWM) controller, this ON-OFF control circuit 60 comprise shift unit 68 and with door 69.This ON-OFF control circuit 60 (being the PWM controller) receives the clock signal TCLK101 from oscillator 56, the cycle period of these oscillator 56 control PWM switches.This ON-OFF control circuit 60 (being the PWM controller) also receives the ON time control signal QTON102 from current detection control circuit 80, and produces a plurality of switch controlling signal 111-116 according to this, to control a plurality of LED lamp switch QS 1-QS6 respectively.Switch controlling signal 111-116 supplies to provide to give and door 69 and buffer 82, to produce first a main switch control signal 103 in order to control main switch QM78.Switch controlling signal 111-116 also supplies to provide and gives and door 69 and inverter 81, to produce a main switch control signal 104 in order to control discharge switch QD77.

A PWM switch circulation comprises leading logical time and main deadline; When this main switch QM conducting, 6 switch QSn are given in this leading logical time multiplexing, in main deadline; Main switch QM and 6 switch QSn all end, and discharge switch QD conducting.In other words, in the leading logical time of PWM, and main switch QM also conducting and discharge switch QD by the time, shift unit 68 is a switch among the conducting LED lamp switch QS1-QS6 optionally.On the other hand, in PWM master deadline, has only discharge switch QD conducting.Be to be controlled by PWM clock or minimum mechanism deadline the leading logical and deadline of this PWM switch circulation.In addition, the conducting of each LED lamp switch QSn and deadline are to be controlled by ON time control signal QTON102, so, can make the average current of each LED lamp switch QSn that flows through identical.ON time control signal QTON102 is controlled by current detection control circuit 80 successively, and this current detection control circuit 80 is in order to detect at the flow through LED lamp string stream (I of main switch QM of leading logical time _LED1I _LED6).

This current detection control circuit 80 comprises current mirror 83, error amplifier 86, comparator 87, compensation condenser CCOMP 88, integrating condenser CINT 89 and single-shot circuit 93.In the leading logical time of PWM,, promptly form by the VHIGH voltage end and flow to one of them selected LED lamp string (electric current I of the LED lamp string 41 of promptly flowing through when through one of them LED lamp switch QSn (for example QS1) of switch controlling signal 111-116 (for example control signal 111) conducting _LED1), through selected LED lamp switch QSn, flow to common-mode inductor 53 then again, arrive ground (shown in the thick dashed line among Fig. 5 91) through main switch QM at last.In other words, if LED lamp switch QS1 conducting, average inductor current I _LXThe electric current I LED1 of LED lamp string 41 equals to flow through.Current mirror 83 detects the inductive current I of the main switch QM that flows through _LX, and export two image currents (be designated as 1X, be also referred to as current detection signal), and these two image currents have two different application targets, and one of them image current flows into integrating condenser CINT 89, and another image current flows into error amplifier 86.

At first, as inductive current I _LXCurrent detection signal when flowing into integrating condenser CINT 89, the voltage VCINT at this integrating condenser CINT 89 two ends risings of starting from scratch, wherein, voltage VCINT representes inductive current I _LX(the electric current I when also can be LED lamp switch QS1 conducting _LED1) the lasting electric weight of accumulating.Then,, when voltage VCOMP is higher than voltage VCINT, promptly produce ON time switch controlling signal QTON102, to end one of them selected LED lamp switch QSn (for example QS1) through comparator 87 comparative voltage VCINT and voltage VCOMP.Then voltage VCINT is reset to 0V, for next LED lamp switch QSn prepares, for example, can be through the single-shot reset signal 106 switch driven 90 reset voltage VCINT of ON time switch controlling signal QTON102 generation.Because each LED lamp string is current offset, so, can adjust average LED lamp string stream through the flow through electric weight of electric current accumulation of LED lamp string of adjustment.If voltage VCOMP is constant voltage values, then through comparative voltage VCINT and voltage VCOMP controlling the ON time of each LED lamp switch, the start-up time of each LED lamp switch the electric weight that the electric current of each LED lamp string accumulates of flowing through still keep unanimity.The average LED lamp string stream that gets final product each LED lamp string of will flowing through by the way all is adjusted into identical.

Secondly, compare inductive current I through error amplifier 86 _LXCurrent detection signal and reference current IREF 105.This error amplifier 86 produces the output voltage signal VCOMP that acts on all LED lamp strings.If overall average inductive current I _LXLess than reference current IREF 105, then the voltage signal VCOMP of these error amplifier 86 outputs can increase.Otherwise, if overall average inductive current I _LXGreater than reference current IREF 105, then the voltage signal VCOMP of these error amplifier 86 outputs can reduce.Therefore, be reference current IREF 105 through adjustment total current detected value (being the overall average inductive current), voltage signal VCOMP can be consistent, and the total current of each LED lamp string of flowing through can be adjusted to a predetermined value.LED lamp string stream I _LEDnBe to equal reference current IREF to multiply by a constant.Therefore, through selected suitable reference current IREF value, can adjust LED lamp string stream I _LEDnTo an ideal value.

As shown in Figure 6, be the interior different conditions sketch map of PWM switch circulation that is presented at single many LED of inductor lamp string driver 40 of Fig. 5.When forbidden energy or the unripe state of power supply, single many LED of inductor lamp string driver 40 is to begin with initial cut-off state.When enabling and carrying out the power supply status of receive ready, single many LED of inductor lamp string driver 40 gets into demagnetization or discharge condition.In any PWM switch circulation, single many LED of inductor lamp string driver 40 is followed successively by ST1, ST2, ST3, ST4, ST5 and ST6 state, then, is repeating to get into erasing state before the next PWM switch circulation.As shown in Figure 6, be to show 4 PWM switch circulations, and each PWM switch circulation is to be divided into 6 switch QSn.State ST1 is that the expression first switch QS1 ON time is TON1, and state ST2 is that expression second switch QS2 ON time is TON2, and so on.No matter be in which kind of state, in case state when to be forbidden energy or power supply unripe, single many LED of inductor lamp string driver 40 promptly returns the state by OFF.

At the leading logical time durations PWM controller 60 of PWM switch circulation switch QSn of conducting only, and if only if during its corresponding switch QSn conducting, the electric current I LEDn of each LED lamp string of flowing through can flow into inductor.Therefore, in any stable state of ST1-ST6, and during its corresponding switch QSn conducting, the average current of each LED lamp string of flowing through equal the to flow through average current of inductor:

$\mathrm{Average}\left(I_{\mathrm{LEDn}}\right)=\frac{\mathrm{TONn}}{\mathrm{TPEROID}}*\mathrm{Average}\left(I_{\mathrm{LXQSn}}\right)---\left(1\right)$

Wherein, I _LEDnBe the average current of n LED lamp string, TONn is the ON time of switch QSn, and TPERIOD is the cycle of main switch circulation, I _LXQSnBe the average inductor current in switch QSn ON time.

With regard to 6 LED lamp strings, the overall average electric current of all 6 LED lamp strings of in the leading logical time, flowing through equal the to flow through overall average electric current of inductor.Therefore, the formula that adds up (1) if be directed against 6 LED lamp strings, then the result is following:

$\underset{n=1}{\overset{n=6}{\mathrm{\Σ}}}\mathrm{Average}\left(I_{\mathrm{LEDn}}\right)=\underset{n=1}{\overset{n=6}{\mathrm{\Σ}}}\frac{\mathrm{TONn}}{\mathrm{TPEROID}}*\mathrm{Average}\left(I_{\mathrm{LXQSn}}\right)---\left(2\right)$

And, be controlled owing to be used for the ON time TONn of each switch QSn, therefore; The average current of each LED lamp string of flowing through is equal to each other; And because total ON time TONn equals the leading logical time, the average current of each LED lamp string of then flowing through equals to flow through the overall average electric current of inductor divided by 6 value; At this moment, then above-mentioned formula (2) becomes as follows:

$\mathrm{Average}\left(I_{\mathrm{LED}}\right)=\frac{1}{6}*\mathrm{Average}\left(I_{\mathrm{LXQM}}\right)---\left(3\right)$

Wherein, I _LEDBe the average current of each LED lamp string, I _LXQMBe the average inductor current in the main switch ON time.

As shown in Figure 7, be to be shown as the interior different switches of the PWM switch circulation voltage corresponding, the oscillogram of electric current with it.In the present embodiment, TON is conducting and the deadline of each LED lamp switch QSn, QM _ONBe conducting and the deadline of main switch QM, VS is the voltage of terminal S1-S6 end, I _LXBe the electric current of the common-mode inductor 53 of flowing through, I _CAP1For first of the LED lamp string 41 of flowing through keeps the electric current of capacitor 61, and I _LED1Electric current for the LED lamp string 41 of flowing through.For ease of explanation, be to represent with thick dashed line like the waveform among Fig. 7 about a LED lamp string 41.In a LED lamp switch QS1 ON time, this LED lamp string stream I _LED1Flow into a LED lamp string 41 from voltage VHIGH end successively, flow into LED lamp switch QS1 again, pass through common-mode inductor 53 then, arrive ground (shown in the thick dashed line among Fig. 5 91) via main switch QM at last.Along with inductive current I _LXIncrease the electric current I of LED lamp string gradually _LED1Also along with increase.When keeping capacitor 61 discharges, electric current (I _CAP1Be negative value) should keep capacitor 61 to flow out certainly, this keeps the voltage VS1 at capacitor 61 two ends to descend.In the 2nd LED lamp switch QS2 ON time (promptly at switch QS1 by after, the switch QS2 conducting), because electric current (I _CAP1For on the occasion of) flow into and should keep capacitor 61, make the electric current I of this LED lamp string _LED1Descend, along with keeping capacitor 61 in charging, this keeps the voltage VS1 at capacitor 61 two ends to rise.I _LED2, VS2, I _CAP2Waveform respectively with I _LED1, VS1, I _CAP1Waveform similarity.At whole main switch in the time, as LED lamp switch QS1, QS2... and QS6 one by one during conducting, this inductive current I _LXContinue to increase.

In the circulation of PWM switch, in main switch in the time all LED lamp switch QSn promptly all LED lamp switch QSn are ended by after the selected conducting one by one in main deadline.In main deadline, this discharge switch QD conducting, and this main switch QM ends.The LIIN terminal is coupled to ground through discharge switch QD, the pole reversal of inductor 53 then, (shown in the thick dashed line 97 of Fig. 5), this inductor 53 is holding current I through ground, diode rectifier 52 and the formed current branch of voltage VHIGH _LXAt this moment, because the biasing of inductor 53 negative senses, inductor 53 begins discharge and its electric current I _LXProgressively descend until next PWM switch circulation beginning.As shown in Figure 7, electric current I in the leading logical time _LXContinue to rise, and in main deadline electric current I _LXDescend fast.And, though in main deadline, electric current I _LXDescend fast, but never drop to 0.Therefore, continuing the enough short time through controlling this main deadline, can make electric current not drop to 0 all the time, is to move with the inductive current continuous mode and make this inductor 53.

As shown in Figure 7, when in the main switch ON time, along with the lasting rising of inductive current; The ON time of each LED lamp switch QSn is then descending; This is because total electric weight of each LED lamp string stream is adjusted into identically, equates with the average current of guaranteeing each LED lamp string, so when electric current increases; ON time needs to reduce, and then makes the total current of each LED lamp string identical.In the present embodiment, the conducting order of switch QSn is QS1, QS2...QS6 successively.What need explain is here and since adjustment LED lamp string average current consistent be to depend on total current, therefore, the conducting order of switch QSn does not exceed with above-mentioned, the conducting order can be any.Yet constant if the conducting order of switch QSn keeps this to implement described order, the ON time of switch QS1 is the longest (and the electric current I always _LED1In time T ON1, be minimum), the ON time of switch QS6 is the shortest (and electric current I always _LED6In time T ON6, be maximum).Preferably, each LED lamp string moves with essentially identical mode, to realize best coupling.In one embodiment, shift unit 68 produces alternate succession with conducting LED lamp switch QSn, and then makes each LED lamp switch QSn in preset time, obtain an essentially identical conducting chance.

As shown in Figure 8, it drives the flow chart of the method for many LED lamp string for the single inductor of the employing that shows the utility model.Single many LED of inductor lamp string driver comprises ON-OFF control circuit and current detection control circuit.In step 801, this ON-OFF control circuit produces a plurality of digital controlled signals, is coupled to a plurality of switches of a plurality of LED lamp strings with control, and each switch be respectively by its its conducting of corresponding digital controlled signal control with end.In step 802, this current detection control circuit is confirmed to flow to each LED lamp string by Input voltage terminal successively, again to each switch, and then to common-mode inductor, the quantity of total electric weight of the electric current supply through main switch to ground again.In step 803; Quantity according to determined total electric weight; This current detection control circuit produces ON time control signal, and controlling the ON time of each switch, and then the flow through average current of each LED lamp string of order is all identical; So, can make the total current of each LED lamp string of flowing through be controlled at a predetermined value.

As shown in Figure 9, it is the sketch map of second embodiment of single many LED of inductor lamp string driver 900 of demonstration the utility model.Single many LED of inductor lamp string driver 900 is closely similar with single many LED of inductor lamp string driver 40 shown in Figure 4; Both differences are; Direct voltage VHIGH in the present embodiment is provided by DC-DC converter 901; For example, this DC-DC converter 901 receives a direct voltage VLOW (for example 24V), and the direct voltage VHIGH (for example 190V) of output in order to supply a plurality of LED lamp strings.The use of DC-DC converter 901 can cause 20% loss in efficiency.

Shown in figure 10, it is the sketch map of the 3rd embodiment of single many LED of inductor lamp string driver 910 of demonstration the utility model.Single many LED of inductor lamp string driver 910 is closely similar with single many LED of inductor lamp string driver 40 shown in Figure 4; Both differences are; Common-mode inductor 53 in the present embodiment is to be coupled to a main switch QM who is arranged on integrated circuit 911 outsides; And the other end of this main switch QM is coupled to the current sensing resistor Rcs that is arranged on integrated circuit 911 outsides.Therefore, when main switch QM conducting, inductive current I _LXFlow into main switch QM from common-mode inductor 53, arrive ground through resistor R cs again.Integrated circuit 911 is controlled main switch QM through terminal GATEM, and through terminal CS received current detection signal 107.

The foregoing description is the principle and the effect thereof of illustrative the utility model only, but not is used to limit the utility model.The those of ordinary skill of technical field all can be modified, changed or combine the foregoing description under the scope of appending claims under any.

Claims (9)

1. an integrated circuit is characterized in that, comprising:

Current detection control circuit, it is used to detect many electric currents of going into common-mode inductor from a plurality of LED lamp crossfires, and produces the current detecting control signal; And

ON-OFF control circuit; It is in order to receive said current detecting control signal; And export a plurality of switch controlling signals according to this; And each switch controlling signal be in order to control be coupled to corresponding LED lamp string switch conducting with end, and each switch controlling signal controls the ON time of each switch respectively, so that the current average of each LED lamp string of flowing through reaches a current target value.

2. integrated circuit according to claim 1 is characterized in that: said integrated circuit comprises a plurality of switches.

3. integrated circuit according to claim 1 is characterized in that: said ON-OFF control circuit is also in order to produce a main control signal that supplies control to be coupled to the main switch of said common-mode inductor.

4. integrated circuit according to claim 3; It is characterized in that: said ON-OFF control circuit comprises a PDM keyer; So that when said main control signal is ON time; A switch in the said main switch of conducting and the said a plurality of switch, and when said main control signal is deadline, by said main switch.

5. integrated circuit according to claim 4 is characterized in that: when said main switch conducting, inductive current rises, and when said main switch by the time, inductive current decline, and said inductance is to move with the inductive current continuous mode.

6. integrated circuit according to claim 4 is characterized in that: said PDM keyer comprises a shift unit, in order at said main control signal each said switch of conducting respectively during for ON time.

7. integrated circuit according to claim 1 is characterized in that: the conducting order of each said switch changes always, so that each said switch obtains an essentially identical conducting chance in preset time.

8. integrated circuit according to claim 4 is characterized in that: the quantity of LED lamp string is N, and N is the integer greater than 1, and the average current of each LED lamp string of the flowing through average current of the said common-mode inductor numerical value after divided by N that equals to flow through.

9. integrated circuit according to claim 1 is characterized in that: said current detection control circuit comprises a capacitor, in order to confirm the quantity by total electric weight of the electric current supply of each LED lamp string of flowing through.

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