CN104619087A - Multi-LED series-connection drive circuit and control method thereof - Google Patents
Multi-LED series-connection drive circuit and control method thereof Download PDFInfo
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Abstract
The invention relates to a multi-LED (light emitting diode) series-connection drive circuit and a method for controlling the circuit. The drive circuit is characterized in that the lowest feedback voltage channel is selected by a selecting module and corresponding continuity signals are output, so that the switch circuit in a series-connection channel including the lowest feedback voltage is always connected; switch circuits in the series-connection channels excluding the lowest feedback voltage series-connection channel are intermittently connected by a duty ratio control module according to feedback voltage in the series-connection channels, so that the average feedback voltage in the series-connection channels is equal to the feedback voltage of the lowest feedback voltage series-connection channel. Because the average current of the series-connection channels is related with the ratio of the average feedback voltage to the on-resistance value of the series-connection channel and the luminance of the LED is directly related with the average current of the LED, the light emitting diodes in series connected are uniform in luminance when the average feedback voltage of each channel is equal; besides the addition power consumption is relatively low, and the system efficiency is greatly improved.
Description
Technical field
The present invention relates to a kind of LED control field, particularly a kind of many LED strip drive circuit and control method thereof.
Background technology
Widely, profit is as being used as backlight, big screen LED advertisement screen etc. in all kinds of computer liquid-crystal display in the application of light-emitting diode (being called for short LED) in various product.
In many applications, usually multiple LED strip is joined, form a LED strip connection branch road, and drive several LED strip to join branch road (hereinafter referred to as LED strip) work at the same time or separately by drive circuit, due to particularity during LED processing and manufacturing, electric current, the voltage characteristic of the LED causing even same manufacturer of different manufacturers to produce in a collection of product all have larger individual difference.Conducting voltage just because of each LED is different, so the electric current that will realize each LED strip is equal, needs to adjust each LED strip.
In prior art, normally to connect again in each LED strip a NMOS tube or bipolar transistor, output services voltage VO is adjusted to higher than the minimum operating voltage needed for LED, then by adjusting the conducting state of NMOS tube or the bipolar transistor that each LED branch road is connected and then adjusting its voltage drop, and the unnecessary pressure drop of electric current is set by NMOS tube or bipolar transistor adjustment consumption by maintaining LED.The shortcoming of this mode is that these NMOS tube or bipolar transistor are in half conducting state, will consume extra efficiency, and multiple LED strip will lower consumption more power, thus causes system effectiveness on the low side.
Summary of the invention
Instant invention overcomes above-mentioned shortcoming, provide that a kind of loss is little, efficiency is high, and realize the consistent many LED strip drive circuit of each LED luminance and control method thereof.
The present invention solves the technical scheme that its technical problem takes: a kind of many LED strip drive circuit, for connecting and driving some LED strip, comprises
Some switching circuits, for turning on and off the channels in series at each LED strip place;
Some feedback resistances, obtain the feedback voltage of place channels in series for dividing potential drop;
Wherein, a LED strip, a switching circuit and a feedback resistance channels in series in series;
Also comprise,
Voltage control circuit, its output is connected with each described channels in series, for providing operating voltage to each channels in series;
Select module, its input is connected with the feedback resistance in described each channels in series, output is directly or indirectly connected with the control end of described switching circuit, for selecting minimum feedback voltage in each channels in series, and export corresponding Continuity signal, control the switching circuit conducting all the time in the channels in series at described minimum feedback voltage place;
Control circuit of duty ratio, its input is connected with the feedback resistance in described each channels in series, its output is directly or indirectly connected with the control end of described switching circuit, for according to the feedback voltage in each channels in series, control the described switching circuit interval conducting in all the other each channels in series except minimum feedback voltage channels in series, make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series.
Also can comprise the first error amplifier, its input connects the minimum feedback voltage output of described selection module, its output is connected with described voltage control circuit, for minimum feedback voltage that described selection module is obtained compared with reference voltage, obtain error voltage, and feed back to described voltage control circuit, the operating voltage that described voltage control circuit exports according to described error voltage adjustment; After circuit stability, make described minimum feedback voltage, described average feedback equal with described reference voltage.
Described selection module can have and the input of the equal number of described channels in series and Continuity signal output, the feedback voltage of each channels in series is obtained by described input, and the minimum feedback voltage therefrom obtained, control the Continuity signal output corresponding with described minimum feedback voltage channels in series and export useful signal, all the other Continuity signal outputs export invalid signals;
Described control circuit of duty ratio can have the some duty cycle control module identical with described channels in series number, the input of each duty cycle control module is corresponding with the feedback resistance in described each channels in series respectively to be connected, the output of each duty cycle control module, according to the feedback voltage in the corresponding channels in series received, export corresponding duty cycle signals by its output;
Described many LED strip drive circuit also can comprise some logic gates, correspond respectively to each channels in series, each described logic gates has first input end, the second input and output, described output is connected with the control end of the switching circuit in corresponding channels in series, described first input end is connected with the output of corresponding described duty cycle control module, and described second output is connected with the Continuity signal output of corresponding described selection module;
For each gate, any one in the described Continuity signal that it receives and described duty cycle signals is for time effective, this logic gates exports control signal and controls corresponding switching circuit conducting, otherwise, export control signal and control corresponding switching circuit cut-off.
Described selection module also can have an initializing signal output, and the initializing signal that described initializing signal output exports is one and continues a section time effective pulse signal;
Each described logic gates also has the 3rd input, and described 3rd input is connected with the initializing signal output of described selection module; For each logic gates, any one in described initializing signal, Continuity signal and duty cycle signals exports as time effective, this logic gates exports control signal and controls corresponding switching circuit conducting, otherwise, export control signal and control corresponding switching circuit cut-off.
Described selection module can comprise the comparison module and output module that connect in turn further; Described comparison module, for the feedback voltage of more each channels in series, obtain the channels in series at minimum feedback voltage place, described output module, for exporting corresponding Continuity signal according to the channels in series at minimum feedback voltage place, and minimum feedback voltage is exported.
Described selection module also can comprise initialization module, and described initialization module is used for providing initializing signal, and its clock signal exported directly or indirectly is connected to the control end of described switching circuit; The initializing signal that described initialization module exports is the time period of a continuous and effective, when described effective time, section was initial, control the switching circuit conducting in each channels in series, and by the feedback voltage of the more each channels in series of described comparison module, obtain the channels in series at minimum feedback voltage place, at the end of described effective time section, export corresponding Continuity signal by described output module according to the passage at minimum feedback voltage place.
Each described duty cycle control module can comprise the filter, the second error amplifier and the comparator that connect in turn, described second error amplifier input and described filter output be connected, another input access reference voltage, output is connected to an input of described comparator, another input access triangular signal of described comparator, output is namely as the output of control circuit of duty ratio.
Each described logic gates can be or door, input that is each or door connects the output of the initializing signal output of described selection module, one of them Continuity signal output and a described control circuit of duty ratio respectively, and output that is described or door connects the control end of corresponding described channels in series breaker in middle circuit; Described initializing signal represents effective when being high level, described duty cycle signals represents effective when being high level, described Continuity signal represents effective when being high level, when described or door exports as high level, the switching circuit conducting of its correspondence, when described or door exports as low level, the switching circuit cut-off of its correspondence.
A kind of many LED strip drived control method, comprises the steps:
The whole conducting of channels in series at each LED strip place;
Obtain the feedback voltage of each channels in series, relatively and select feedback voltage minimum in each channels in series;
Control the channels in series conducting all the time that feedback voltage is minimum, according to feedback voltage and the reference voltage of all the other each channels in series, produce duty cycle signals, control the conducting of corresponding channels in series interval, and make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series.
The step of the whole conducting of channels in series at described each LED strip place, can comprise the steps: further
When circuit powers on or be enabled, produce an initializing signal,
An optional channels in series, and obtain the current feedback voltage of this channels in series,
Current feedback voltage and reference voltage compare, and obtain error voltage, and produce operating voltage, for each channels in series is powered according to described error voltage;
At the feedback voltage of each channels in series of described acquisition, relatively and after selecting feedback voltage step minimum in each channels in series, also comprise the step that initializing signal terminates.
At the feedback voltage of each channels in series of described acquisition, relatively and after selecting feedback voltage step minimum in each channels in series, also can comprise and comparing according to described minimum feedback voltage and reference voltage, obtain error voltage, and adjust the step of operating voltage.
The present invention by the minimum feedback voltage passage of described selection model choice, and exports corresponding Continuity signal, controls the switching circuit conducting all the time in the channels in series at described minimum feedback voltage place; Again by described duty cycle control module, according to the feedback voltage in each channels in series, control the described switching circuit interval conducting in all the other each channels in series except minimum feedback voltage channels in series, make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series.Average current due to channels in series is relevant to the ratio of conducting resistance in average feedback voltage and channels in series, and the brightness of LED is directly related to the average current size of LED, therefore, equal by controlling average feedback voltage in each passage, and then the brightness realizing string LED is consistent, and extra power consumption is less, also substantially increases system effectiveness.
Accompanying drawing explanation
Fig. 1 is the circuit theory diagrams of many LED strip drive circuit in the present invention;
Fig. 2 is the circuit theory diagrams of duty cycle control module in Fig. 1;
Fig. 3 is the oscillogram of each output signal in described duty cycle control module;
Fig. 4 is the circuit theory diagrams selecting module in Fig. 1;
Fig. 5 is the flow chart of many LED strip drived control method in the present invention.
Embodiment
The invention provides a kind of many LED strip drive circuit, for connecting and driving several LED strip.
As shown in fig. 1, for the circuit theory diagrams of a kind of preferred implementation of many LED strip drive circuit provided by the invention, in the present embodiment, many LED strip drive circuit is for driving three LED strip, each LED strip is formed by three LED strip connection, be respectively the first LED strip be in series by LED1A, LED1B and LED1C, the second LED strip be in series by LED2A, LED2B and LED2C, the 3rd LED strip be in series by LED3A, LED3B and LED3C.Described LED strip can be reduced to a single LED, or also can be other series-parallel systems.
This preferred embodiment comprises three switching circuits for turning on and off each LED strip connection branch road, with obtain three feedback resistances of the feedback voltage of place channels in series for dividing potential drop, described switching circuit comprises three nmos pass transistors corresponding with LED strip number, one group of LED strip, a switching circuit and a feedback resistance channels in series in series, i.e. the first LED strip, nmos pass transistor MN1 and feedback resistance R1 connects, form the first channels in series, other channels in series by that analogy, second LED strip, nmos pass transistor MN2 and feedback resistance R2 connects, form the second channels in series, 3rd LED strip, nmos pass transistor MN3 and feedback resistance R3 connects, form the 3rd channels in series.Wherein, the resistance value of resistance R1 ~ R3 is identical, is r.This preferred embodiment also comprises voltage control circuit U1, selects module U2, control circuit of duty ratio, error amplifier EA and logic gates.
The input of described voltage control circuit U1 connects power voltage terminal VIN, and output VO is connected to the voltage input end of described each channels in series, and provides operating voltage to each channels in series.
Described selection module U2 has and input FB1, FB2, FB3 of the equal number of described channels in series (in the present embodiment being three) and Continuity signal output ON1, ON2, ON3, minimum feedback voltage output Min, an initializing signal output Init.Input FB1, FB2, FB3 of described selection module U2 are connected with feedback resistance R1, R2, the R3 in described each channels in series, for obtaining the feedback voltage of each channels in series in each channels in series, and the minimum feedback voltage that will therefrom obtain, Continuity signal output simultaneously by corresponding to minimum feedback voltage passage in Continuity signal output ON1, ON2, ON3 exports useful signal, control the switching circuit conducting all the time in the channels in series of described minimum feedback voltage place, all the other Continuity signal outputs export invalid signals; Again minimum feedback voltage is exported to the input of error amplifier EA from described minimum feedback voltage output Min, the output of described error amplifier EA is connected to the error voltage input EAO of described voltage control circuit U1, for minimum feedback voltage that described selection module is obtained compared with reference voltage, the error voltage of acquisition is fed back to described voltage control circuit, the operating voltage that described voltage control circuit exports according to described error voltage adjustment.
The number that described control circuit of duty ratio comprises duty cycle control module AvgReg1, AvgReg2, AvgReg3 is also identical with channels in series number, the input of each duty cycle control module is connected with feedback resistance R1, R2, the R3 in described each channels in series, and output is connected to the control end of described nmos pass transistor through logic gates.According to the feedback voltage in each channels in series, control the described switching circuit interval conducting in all the other each channels in series except minimum feedback voltage channels in series, after whole circuit stability, make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series, and equal with described reference voltage.
Described logic gates is used for the output of described selection module and duty cycle control module the control signal controlling described switching circuit (i.e. nmos pass transistor), the control end of the corresponding described each channels in series breaker in middle circuit of access, the i.e. grid of nmos pass transistor, it comprises three or OR1, OR2, OR3.Three inputs that are described or door OR1 connect respectively selects initializing signal output Init, the Continuity signal output ON1 of module U2 and the output of duty cycle control module AvgReg1, output is connected to the grid of described nmos pass transistor MN1, by that analogy, three inputs that are described or door OR2 connect respectively selects initializing signal output Init, the Continuity signal output ON2 of module U2 and the output of duty cycle control module AvgReg2, and output is connected to the grid of described nmos pass transistor MN2; Three inputs that are described or door OR3 connect respectively selects initializing signal output Init, the Continuity signal output ON3 of module U2 and the output of duty cycle control module AvgReg3, output is connected to the grid of described nmos pass transistor MN3, when or door described three inputs input signal in any one be effective time, control the switching circuit conducting of correspondence.
Based on foregoing circuit structure, its course of work is as follows:
First, select the initializing signal output Init of module U2 to export an initializing signal, produce initializing signal when each circuit power powers on or is enabled, namely when power supply electrifying or when being enabled, Init end becomes high level, continues for some time, then becomes low level.Now the grid outputting to nmos pass transistor MN1, MN2, MN3 of this high level signal warp or door OR1, OR2, OR3 all becomes high level, the whole conducting of switch MN1 ~ MN3, makes the whole conducting of all channels in series.
Now described selection module U2 selects the feedback voltage of any channels in series (namely in input FB1 ~ FB3 any one) to export minimum feedback voltage output Min to, carry out loop feedback control, because although current each channels in series is in conducting state, but now voltage control circuit U1 does not have output services voltage, each channels in series electric current is zero, therefore this feedback voltage is 0, compare with reference voltage VR through described error amplifier EA, the error voltage (being equivalent to VR) produced is input to the error voltage input EAO of described voltage control circuit U1, then described voltage control circuit U1 produces operating voltage according to error voltage, be that LED strip is powered by voltage output end VO.This process utilizes negative feedback, makes voltage control circuit and LED strip enter operating state from off state.Wherein, described voltage control circuit U1 can adopt Boost DC-direct current switching controller, buck DC to dc switching controller or AC-DC switching controller to realize.
Now described selection module U2 compares the feedback voltage of three inputs FB1, FB2, FB3, namely, find out that channels in series that feedback voltage is minimum, then minimum feedback voltage is exported to minimum feedback voltage output MIN, and the Continuity signal output controlling corresponding channels in series exports high level, other Continuity signal outputs are low level.Such as described selection module U2 judges that the feedback voltage (i.e. the feedback voltage of input FB1) of the first channels in series is minimum, then the voltage of input FB1 is outputted to minimum feedback voltage output Min, and Continuity signal output ON1 is set to high level, all the other two Continuity signal output ON2 and ON3 are set to low level.
Wherein, the initializing signal of the initializing signal output Init output of described selection module U2, it is the time period (namely high level is effective) of a high level, be used to select minimum feedback voltage channels in series, when this time period is initial, namely when the saltus step of initializing signal output is high level, the switching circuit conducting in each channels in series is controlled by described logic gates, and the control of loop is used for the feedback voltage of optional channels in series, compare with reference voltage VR by realizing this feedback voltage with error amplifier EA, produce error voltage, described voltage control circuit U1 produces according to described error voltage and adjusts operating voltage, by voltage output end VO, for LED strip is powered, again by the feedback voltage of the more each channels in series of described comparison module, obtain the channels in series at minimum feedback voltage place.At the end of this time period, when namely the saltus step of initializing signal output is low level, export corresponding Continuity signal by described output module according to the passage at minimum feedback voltage place.This high level time section is used for judging and selecting minimum feedback voltage and minimum feedback voltage channels in series, and described initializing signal output is low level always afterwards.
Then, the high level signal of the Continuity signal output ON1 output of described selection module U2, warp or door OR1 control described nmos pass transistor MN1 conducting always (being namely equivalent to its duty ratio is 100%), feedback voltage is minimum means that the series connection conducting voltage of this branch road LED strip is maximum, when described nmos pass transistor MN1 conducting always, after closed loop feedback, the feedback voltage of the first channels in series equals reference voltage VR, and the electric current of this first LED strip is constantly equal to VR/r.And select all the other two Continuity signal output ON2 and ON3 of module U2 to be low level, now by duty cycle control module AvgReg2, AvgReg3 output duty cycle signal, through described or door OR2, OR3 controls nmos pass transistor MN2 in all the other two channels in series, MN3, make this two-way channels in series batch (-type) conducting, because the conducting voltage of LED strip in these two channels in series is all lower than the series connection conducting voltage of the LED strip in described minimum feedback voltage channels in series, 1 is less than by described duty cycle control module adjustment nmos pass transistor conducting period duty ratio, and the average voltage meeting feedback voltage equals reference voltage VR, then the average current of the LED strip of all the other two channels in series described also equals VR/r.
As shown in Figure 2, for the schematic diagram of duty cycle control module in this preferred embodiment, described duty cycle control module comprises the filter Filter connected in turn, second error amplifier OP and comparator Comp, wherein, the input of described filter is connected with described feedback resistance, obtain feedback voltage, output is connected to the inverting input of described second error amplifier OP, the in-phase input end access reference voltage VR of described second error amplifier OP, output is connected to the in-phase input end of described comparator Comp, the inverting input access triangular signal of described comparator Comp.The peripheral circuit of described error amplifier and comparator is routine techniques, not shown in the drawings, and those skilled in the art can carry out design according to actual needs and suitably choose.
The specific works process of described duty cycle control module is as follows, the described feedback voltage signal of each channels in series, average-voltage signal AVFB is produced after filtering after device Filter filtering, described filter Filter is by the waveform shaping signal of input, make this waveform more stable, so that the second error amplifier OP steady operation.Described filter Filter can adopt conventional various low pass filters, and such as RC filter or other low-pass active filter, belong to routine techniques, herein omit specific descriptions.Average-voltage signal AVFB compares with reference voltage VR by described second error amplifier OP, voltage difference according to them produces error signal OPO, error signal OPO and triangular signal Ramp is compared by described comparator Comp, produce corresponding duty cycle signals D, then export to corresponding logic gates.
When described average-voltage signal AVFB voltage is higher than reference voltage VR, error amplifier OP reduces its error signal OPO exported, comparator Comp reduces the duty ratio of duty cycle signals D according to the reduction of error signal OPO, composition graphs 1 is known, when the duty ratio of described duty cycle signals D reduces, through or behind the door, cause corresponding switching circuit, namely the ON time of nmos pass transistor reduces, the high level time of corresponding voltage feedback signal is caused to reduce like this, the average-voltage signal AVFB signal after low pass filter Filter is caused to reduce further, result in formation of negative feedback.Otherwise, when described average-voltage signal AVFB signal is lower than reference voltage VR, error amplifier OP increases its error signal OPO exported, the duty ratio causing described comparator Comp to output signal D increases, cause through or signal dutyfactor behind the door increase, control corresponding nmos pass transistor ON time to increase, thus cause the high level time of corresponding feedback voltage signal to increase, cause the average-voltage signal AVFB signal after low pass filter Filter to increase further, also show as negative feedback.When this feedback loop is stablized, average-voltage signal AVFB must be met equal with reference voltage VR.So when final all control loops are stablized, the mean value of the electric current of each LED strip equals VR/r, therefore, as long as the resistance arranging feedback resistance R1, R2, the R3 in all channels in series is all identical, then the average current that can realize all LED strip is all equal.
As shown in Figure 3, be the oscillogram of each output signal in described duty cycle control module, Ramp is periodic triangular ripple signal, and in one cycle, when in the time period of error signal OPO higher than Ramp signal, duty cycle signals D is high level; In one-period, when in the time period of error signal OPO lower than Ramp signal, duty cycle signals D is low level.Illustrate in figure that the rising time of Ramp signal is longer, the trailing edge time shorter (almost nil), but in actual design, also can design rising time shorter, the trailing edge time is longer.
As shown in Figure 4, for selecting the circuit theory diagrams of module described in this preferred embodiment.Described selection module comprises comparison module, output module and initialization module, described comparison module is used for the feedback voltage of more each channels in series, obtain the channels in series of minimum feedback voltage, described output module, feedback voltage for the channels in series by minimum feedback voltage exports corresponding Continuity signal, and is exported by minimum feedback voltage.Described initialization module, for providing starting clock signal, its clock signal exported is connected to the control end of described switching circuit through described logic gates.
Described comparison module comprise comparator CM1 ~ CM3, inverter inv1, NOR gate nor1, nor2 and with door and1.The feedback voltage of three channels in series accesses the input of three comparators respectively, and when the feedback voltage signal FB1 voltage of the first channels in series is minimum, or the output MIN1 of door nor1 is high level, and output MIN2 and MIN3 is low level.When the feedback voltage signal FB2 voltage of the first channels in series is minimum, be high level with the output MIN2 of door and1, MIN1 and MIN3 is low level.When the voltage of the feedback voltage signal FB3 of the 3rd channels in series is minimum, the output MIN3 of NOR gate nor2 is high level, MIN1 and MIN2 is low level.Three output signals MIN1, MIN2, MIN3 output to the d end of three d type flip flop ffdf1 ~ ffdf3 respectively, when TL signal trailing edge, the q of MIN1 ~ MIN3 signal latch to d type flip flop holds by described d type flip flop ffdf1 ~ ffdf3, and as the Continuity signal output ON1 ~ ON3 of described selection module.
Feedback voltage signal FB1, FB2, FB3 of three channels in series output to described minimum feedback voltage output MIN hold respectively through three switch S 1, S2, S3, when initialization signal Init signal is high level, by or door OR4 control switch S1 conducting, the feedback voltage signal FB1 of the first channels in series is selected to output to MIN output, because this selection is arbitrary, FB2 or FB3 also can be selected to output to MIN end.After Init signal is low level, export the output for high level in ON1 ~ ON3, corresponding is the minimum channels in series of feedback voltage, and in control switch S1, S2, S3, minimum feedback voltage signal is outputted to MIN end by corresponding switch.
Described initialization module comprises the d type flip flop ffdf4 ~ ffdf7 of resistance R4, R5, comparator CM4, inverter INV2 or door OR5 and four serial connection.Here the number of d type flip flop just signal, can increase as the case may be in actual design or reduce d type flip flop number, the number of d type flip flop determines the time that initializing signal Init is high level, and number is more, and Init is that the time of high level is longer.Input supply voltage VIN is carried out dividing potential drop by described resistance R2, R1, then compared with reference voltage VRUV by comparator CM4, produce UV signal, when input supply voltage is lower than VRUV × (R4+R5)/R5, UV signal is high level, is therefore provided with the minimum operating voltage of circuit by the dividing potential drop of resistance R4, R5.When in supply voltage power up, generally can there is one section of virtual voltage lower than VRUV × (R4+R5)/R5, the i.e. time period of minimum operating voltage, now producing a period of time UV is high level state, and process or door OR5 produce the reset signal RST of all d type flip flops.Or when circuit enable signal EN is low level, be high level after inverter INV2, the RST signal of process or door OR5 is also high level.So circuit is prohibited work or supply voltage power up and all can produces reset signal, namely RST signal is high level, and all d type flip flops are that high level resets, and the output q of all d type flip flops can be reset to low level, output qb is reset to high level.CK is clock signal, can be produced by any oscillator structure.
The TL signal that 3rd d type flip flop ffdf6 exports, is high level in four clock cycle after circuit is started working, will becomes low level at the trailing edge of the 4th clock cycle.That 4th d type flip flop ffdf7 exports and be high level in eight clock cycle that Init signal is after circuit is started working, will low level be become at the trailing edge of the 8th clock cycle.Described TL signal is for generation of the time point selection result of minimum feedback voltage channels in series be latched in d type flip flop ffdf1, ffdf2, ffdf3, in order to ensure correct selection minimum feedback Voltage Series passage, Init signal is to continue the time of high level until the trailing edge of TL signal arrives, namely the trailing edge of initializing signal Init signal should be later than the trailing edge of TL signal, concrete time of delay can be produced by analog delay circuit, also can be produced by digital circuit.Concrete time of delay can free setting according to actual needs.
As shown in Figure 5, be the flow chart of many LED strip drived control method provided by the invention, comprise the steps:
1, when circuit powers on or be enabled, produce an initializing signal, as the starting clock signal of whole driving process, this initializing signal can be the time period of a high level;
2, an optional channels in series, and obtain the current feedback voltage of this channels in series;
3, compare according to described feedback voltage and reference voltage, obtain error voltage, and be that channels in series is powered according to described error voltage generation operating voltage; Because each channels in series electric current is zero before, this process utilizes negative feedback, makes the channels in series comprising LED strip enter operating state from off state;
4, the feedback voltage of each channels in series is obtained, relatively and select feedback voltage minimum in each channels in series;
5, compare according to minimum feedback voltage and reference voltage, obtain error voltage, and adjust the output of operating voltage;
6, initializing signal terminates, and namely initializing signal is low level by high level saltus step;
7, the minimum channels in series conducting all the time of feedback voltage is controlled, according to feedback voltage and the reference voltage of all the other each channels in series, produce duty cycle signals, control all the other channels in series interval conductings, and make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series.
Above many LED strip drive circuit provided by the present invention and control method thereof are described in detail, apply specific case herein to set forth principle of the present invention and execution mode, the explanation of above embodiment just understands method of the present invention and core concept thereof for helping; Meanwhile, for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.
Claims (10)
1. the drive circuit of LED strip more than, for connecting and driving some LED strip, is characterized in that: comprise
Some switching circuits, for turning on and off the channels in series at each LED strip place;
Some feedback resistances, for obtaining the feedback voltage of place channels in series;
Wherein, a LED strip, a switching circuit and a feedback resistance channels in series in series;
Also comprise,
Voltage control circuit, its output is connected with each described channels in series, for providing operating voltage to each channels in series;
Select module, its input is connected with the feedback resistance in described each channels in series, output is directly or indirectly connected with the control end of described switching circuit, for selecting minimum feedback voltage in each channels in series, and export corresponding Continuity signal, control the switching circuit conducting all the time in the channels in series at described minimum feedback voltage place;
Control circuit of duty ratio, its input is connected with the feedback resistance in described each channels in series, its output is directly or indirectly connected with the control end of described switching circuit, for according to the feedback voltage in each channels in series, control the described switching circuit interval conducting in all the other each channels in series except minimum feedback voltage channels in series, make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series.
2. many LED strip drive circuit according to claim 1, it is characterized in that: also comprise the first error amplifier, its input connects the minimum feedback voltage output of described selection module, its output is connected with described voltage control circuit, for minimum feedback voltage that described selection module is obtained compared with reference voltage, obtain error voltage, and feed back to described voltage control circuit, the operating voltage that described voltage control circuit exports according to described error voltage adjustment; After circuit stability, make described minimum feedback voltage, described average feedback equal with described reference voltage.
3. many LED strip drive circuit according to claim 1, is characterized in that:
Described selection module has and the input of the equal number of described channels in series and Continuity signal output, the feedback voltage of each channels in series is obtained by described input, and the minimum feedback voltage therefrom obtained, control the Continuity signal output corresponding with described minimum feedback voltage channels in series and export useful signal, all the other Continuity signal outputs export invalid signals;
Described control circuit of duty ratio has the some duty cycle control module identical with described channels in series number, the input of each duty cycle control module is corresponding with the feedback resistance in described each channels in series respectively to be connected, each duty cycle control module, according to the feedback voltage in the corresponding channels in series received, exports corresponding duty cycle signals by its output;
Described many LED strip drive circuit also comprises some logic gates, correspond respectively to each channels in series, each described logic gates has first input end, the second input and output, described output is connected with the control end of the switching circuit in corresponding channels in series, described first input end is connected with the output of corresponding described duty cycle control module, and described second output is connected with the Continuity signal output of corresponding described selection module;
For each gate, any one in the described Continuity signal that it receives and described duty cycle signals is for time effective, this logic gates exports control signal and controls corresponding switching circuit conducting, otherwise, export control signal and control corresponding switching circuit cut-off.
4. many LED strip drive circuit according to claim 3, is characterized in that: described selection module also has an initializing signal output, and the initializing signal that described initializing signal output exports is the time period pulse signal of a continuous and effective;
Each described logic gates also has the 3rd input, and described 3rd input is connected with the initializing signal output of described selection module;
For each logic gates, any one in described initializing signal, Continuity signal and duty cycle signals exports as time effective, this logic gates exports control signal and controls corresponding switching circuit conducting, otherwise, export control signal and control corresponding switching circuit cut-off.
5. many LED strip drive circuit according to claim 4, is characterized in that:
Each described logic gates is or door, input that is each or door connects the output of the initializing signal output of described selection module, one of them Continuity signal output and a described control circuit of duty ratio respectively, and output that is described or door connects the control end of corresponding described channels in series breaker in middle circuit;
Described initializing signal represents effective when being high level, described duty cycle signals represents effective when being high level, described Continuity signal represents effective when being high level, when described or door exports as high level, the switching circuit conducting of its correspondence, when described or door exports as low level, the switching circuit cut-off of its correspondence.
6. many LED strip drive circuit according to claim 3, it is characterized in that: each duty cycle control module comprises the filter, the second error amplifier and the comparator that connect in turn, described second error amplifier input and described filter output be connected, another input access reference voltage, output is connected to an input of described comparator, another input access triangular signal of described comparator, output is namely as the output of control circuit of duty ratio.
7. the many LED strip drive circuit according to any one of claim 1 ~ 6, is characterized in that: described selection module comprises the comparison module and output module that connect in turn further; Described comparison module, for the feedback voltage of more each channels in series, obtain the channels in series at minimum feedback voltage place, described output module, for exporting corresponding Continuity signal according to the channels in series at minimum feedback voltage place, and minimum feedback voltage is exported.
8. the drived control of LED strip a more than method, comprises the steps:
The whole conducting of channels in series at each LED strip place;
Obtain the feedback voltage of each channels in series, relatively and select feedback voltage minimum in each channels in series;
Control the channels in series conducting all the time that feedback voltage is minimum, according to feedback voltage and the reference voltage of all the other each channels in series, produce duty cycle signals, control the conducting of corresponding channels in series interval, and make the average feedback voltage of all the other each channels in series described equal with the feedback voltage of minimum feedback voltage channels in series.
9. many LED strip drived control method according to claim 8, is characterized in that: the step of the whole conducting of channels in series at described each LED strip place, comprises the steps: further
When circuit powers on or be enabled, produce an initializing signal,
An optional channels in series, and obtain the current feedback voltage of this channels in series,
Current feedback voltage and reference voltage compare, and obtain error voltage, and produce operating voltage, for each channels in series is powered according to described error voltage;
At the feedback voltage of each channels in series of described acquisition, relatively and after selecting feedback voltage step minimum in each channels in series, also comprise the step that initializing signal terminates.
10. many LED strip drived control method according to claim 8 or claim 9, it is characterized in that: at the feedback voltage of each channels in series of described acquisition, relatively and after selecting feedback voltage step minimum in each channels in series, also comprise and comparing according to described minimum feedback voltage and reference voltage, obtain error voltage, and adjust the step of operating voltage.
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| CN113329538A (en) * | 2021-04-25 | 2021-08-31 | 南京中感微电子有限公司 | LED drive circuit |
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