CN103917028B - A kind of LED constant current source and control method thereof - Google Patents
A kind of LED constant current source and control method thereof Download PDFInfo
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Abstract
The present invention relates to a kind of LED constant current source and control method thereof, wherein: constant-current source includes rectification module and the sample resistance (Rcs) being serially connected on rectification module output loop and switch (Q1) and the output capacitance (C1) in parallel with load (LEDs)；Sample resistance electrical connection average current detection controls module, and the control end of switch electrically connects voltage detecting and switch drive module；Average current detection controls module and includes the first operational amplifier, the negative input end of the first operational amplifier is sequentially connected electrically the high voltage link of integrating resistor (R3) and sample resistance, positive input terminal connects reference voltage (VREF), bridges integrating capacitor (C2) between outfan and negative input end；Voltage detecting and switch drive module include the second comparator, and the positive input terminal of the second comparator electrically connects the outfan of the first operational amplifier, and negative input end electrically connects the positive output end of described rectification module, and outfan electrically connects the control end of described switch.
Description
Technical field
The present invention relates to electronic circuit and signal processing technology, be specifically related to a kind of light emitting diode (LED) constant-current source and control method thereof.
Background technology
Along with a large amount of universal and application of LED drive power, LED also occurs in that multifaceted development, and except LED point light source, LED area light source, HV-LED are also subject to the favor in market gradually.And most LED drive power is Switching Power Supply in the market, although its constant-current driving effect is better, but Switching Power Supply is relatively costly, the particularly cost of inductance；Then occurring in that again the simple application of similar current regulator diode (CRD), it is applied in the low power LED power module of small area analysis, very low cost, without inductance.
Traditional CRD Constant Current Control System, circuit structure as it is shown in figure 1, by LED load with exchange between (AC) rectifying and wave-filtering voltage one chip of series connection, include at least a high-voltage MOS pipe inside it, one current sampling resistor, and a constant-current control circuit.
From figure 1 it appears that chip is by the electric current on sampling current sample resistance, thus controlling the conduction impedance of high-voltage MOS pipe, and then reach the effect of current constant control.
Conventional art be technically characterized in that alternating current input power supplying rectifying and wave-filtering after voltage be applied in load LEDs and CRD control system, chip controls the conduction impedance of high-voltage MOS pipe and obtains constant current effect by sampling load current.
Conventional art have drawbacks in that chip be by change high-voltage MOS pipe conduction impedance obtain constant current effect, if the voltage after rectifying and wave-filtering is bigger with the voltage difference of load LEDs, then the loss on pressure reduction can be applied on high-voltage MOS pipe, so that inefficient, and high-voltage MOS pipe can generate heat more serious.
On the other hand, Switching Power Supply is to utilize modern power electronics technology, control the time that switching tube turns on and off, maintain a kind of power supply of stable output, Switching Power Supply is generally made up of pulse width modulation (PWM) control chip (IC) and inductance and switching tube and continued flow tube, Switching Power Supply all need inductance, reach the purpose of stable output by the storage of inductance energy with release；And its switching signal is not taken from exchange input, generally higher, at more than 10kHz.
Summary of the invention
The technical issues that need to address of the present invention are, how to provide a kind of LED constant current source and control method thereof, are avoided that switching tube excessive heating while not increasing considerably system cost, promote the utilization rate of energy and solve chip cooling problem.
Above-mentioned first technical problem of the present invention so solves, build a kind of LED constant current source, rectification module including electrical connection alternating current input power supplying, it is characterized in that, also include being serially connected in the sample resistance on described rectification module output loop and switch and the output capacitance in parallel with external LED constant current source load；Described sample resistance electrical connection average current detection controls module, and the control end of described switch electrically connects voltage detecting and switch drive module；Described average current detection controls module and includes the first operational amplifier, the negative input end of the first operational amplifier is sequentially connected electrically the high voltage link of integrating resistor and described sample resistance, the positive input terminal of the first operational amplifier device connects reference voltage, bridges integrating capacitor between outfan and the negative input end of the first operational amplifier；Described voltage detecting and switch drive module include the second comparator, the positive input terminal of the second comparator electrically connects the outfan of the first operational amplifier, the negative input end of the second comparator electrically connects the positive output end of described rectification module, the outfan of the second comparator electrically connects the control end of described switch: the second comparator output " 1 " then closes described switch, and the second comparator output " 0 " then disconnects described switch.
Switching signal in this LED constant current source, it is consistent that its frequency exports half-wave voltage waveform frequency (domestic for 100Hz) with rectification module, its principle is to utilize linear voltage-stabilizing circuit principle (as tradition CRD controls system) and suitable loop conducting and closing control, reaches the constant current effect of optimum and the efficiency of optimum.
According to LED constant current source provided by the invention, the electric current forward being directly connected with the described LED constant current source load wire protection diode also including and being serially connected on described rectification module output loop；It is noted that the electric current forward protection diode D1 in this system can omit under suitable conditions, the output that premise is rectification module does not have other loads.
According to LED constant current source provided by the invention, include, but are not limited to following three kinds of concrete forms:
(i) the simplest:
Described LED constant current source load is sequentially connected electrically the negative output terminal of electric current forward protection diode, switch, sample resistance and described rectification module；The negative input end of the second comparator electrically connects the positive output end of described rectification module by partial pressure unit, and described partial pressure unit includes the first resistance and the second resistance that are serially connected between positive output end and the negative input end of described rectification module.
(ii) source drive+(i)
Described switch is injectron, and this LED constant current source also includes source drive module；Described source drive module includes the second switch pipe being connected between electric current forward protection diode and switch; the end that controls of second switch pipe is connected with the positive output end of described rectification module by the 4th resistance, is connected with the negative output terminal of described rectification module by Zener diode simultaneously；Described 4th resistance and Zener diode are serially connected between the positive output end negative input end of described rectification module.
Drive (iii) floatingly
The positive output end of described rectification module is sequentially connected electrically switch, sample resistance, electric current forward protection diode and described LED constant current source load；This LED constant current source also includes the 3rd operational amplifier and mirror current source, the low-voltage link of the positive input terminal electrical connection sample resistance of the 3rd operational amplifier, the negative input end of the 3rd operational amplifier electrically connects described rectification module by the second resistance, bridges the source current terminal of described mirror current source between outfan and the negative input end of the 3rd operational amplifier；The follow current end of described mirror current source is connected between the negative input end of the second comparator and the low-voltage link of described sample resistance, is also connected with the second Zener diode between the negative input end and the low-voltage link of described sample resistance of the second comparator；The negative input end of the second comparator electrically connects the positive output end of described rectification module also by the first resistance.
Another technical problem above-mentioned of the present invention so solves, and builds a kind of LED constant current source control method, it is characterised in that is adopted as and solves the described LED constant current source that first technical problem of the present invention builds, including by formula ILED=VREF/RCSSet or adjust output electric current, wherein: VREFIt is reference voltage level, RcsIt it is sample resistance value.
According to LED constant current source control method provided by the invention, it is adopted as and solves the described LED constant current source comprising forward protection diode D1 that first technical problem of the present invention builds, also include passing through formulaSet overvoltage protection voltage VOVP, wherein: R1 is the first resistance value, R2 is the second resistance value, VOPA_MAXBeing the voltage max of integrating capacitor, this maximum can set maximum reference voltage level by chip.
LED constant current source provided by the invention and control method thereof, compared with prior art, have the advantage that
1, avoid switching tube excessive heating, solve chip cooling problem and saved chip cost；
2, improve the utilization rate that LED constant current source energy uses；
3, LED constant current source zero load and short circuit problem are effectively stably solved.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail further.
Fig. 1 is the circuit block diagram of traditional CRD Constant Current Control System；
Fig. 2 is the circuit block diagram of LED constant current source of the present invention；
Fig. 3 is that LED constant current source system of the present invention controls and output waveform figure；
Fig. 4 is the electrical block diagram of first embodiment of the invention；
Fig. 5 is the electrical block diagram of second embodiment of the invention；
Fig. 6 is the electrical block diagram of third embodiment of the invention.
Detailed description of the invention
First, circuit of the present invention and operation principle are described:
As in figure 2 it is shown, LED constant current source of the present invention includes the rectification module of electrical connection alternating current input power supplying, the sample resistance Rcs also including being serially connected on described rectification module output loop and switch Q1, and with external output capacitance C1 in parallel for LED constant current source load LEDs；Described sample resistance Rcs electrically connects average current detection and controls module, and the control end of described switch Q1 electrically connects voltage detecting and switch drive module；Described average current detection controls module and includes the first operational amplifier, and the negative input end of the first operational amplifier is sequentially connected electrically integrating resistor R3 and the high voltage link of described sample resistance Rcs, and the positive input terminal of the first operational amplifier connects reference voltage VREF, between outfan and the negative input end of the first operational amplifier, bridge integrating capacitor C2；Described voltage detecting and switch drive module include the second comparator, the positive input terminal of the second comparator electrically connects the outfan of the first operational amplifier, the negative input end of the second comparator electrically connects the positive output end of described rectification module, the control end of the outfan electrical connection described switch Q1 of the second comparator: the second comparator output " 1 " then closes described switch Q1, the second comparator output " 0 " then disconnects described switch Q1.This circuit core is:
Make use of the alternating current input power supplying half waveform after rectification, by detecting the voltage of this half waveform so that switch Q1 is in the state of Push And Release；Simultaneously by the electric current on value current sampling resistor, and then control to switch the open state time of Q1, obtain the purpose of constant current output.This system maintains low system cost and good constant current effect, has reached again high efficiency simultaneously, has efficiently solved chip cooling problem.The present invention is technically characterized in that by detecting exchange AC rectified half-waves voltage, controls the on off state of switching tube, by detecting the average voltage of current sampling resistor, controls the comparative level of exchange AC rectified half-waves voltage, thus reaching the purpose of constant current output.The design of Novel constant-flow origin system, its difficult point is in that how to be controlled the purpose of the comparative level of AC rectified half-waves voltage by sensed current signal.
This circuit operation principle is specifically: the half-wave voltage source signal obtained after rectifier bridge rectification when exchange AC power supplies, its waveform is as shown in Figure 3.
From figure 3, it can be seen that in conjunction with the system block diagram in Fig. 2, system detection exchange AC input rectifying half waveform, after it controls the output signal ' control level ' of module more than current average detection, output drive waveforms is ' L ', and switching tube turns off；After it is less than ' control level ', output drive waveforms is ' H ', switch Q1 conducting.
When switching tube turns off, output capacitance C1 passes through load discharge, and therefore the voltage above it is gradually reduced (with reference to output voltage waveforms in Fig. 3).
When switching Q1 conducting, owing to exchange AC input rectifying half-wave voltage now is more than voltage in output capacitance, therefore electric capacity is charged by half-wave voltage, and then output capacitance voltage can quickly rise；When exchanging AC input rectifying half-wave voltage and output capacitance voltage close to or smaller than output capacitance voltage, now the diode owing to being connected in conducting loop is in reverse blocking state, and output capacitance voltage is gradually reduced；End along with exchange AC input rectifying half wave cycles, the arrival of next half wave cycles, then exchange AC input rectifying half-wave voltage now is gradually increasing, when exchanging AC input rectifying half-wave voltage more than voltage in output capacitance, due to now switch Q1 and be connected on conducting loop in diode be in conducting state, therefore electric capacity is charged by half-wave voltage again, and output capacitance voltage can quickly rise, until switch Q1 turns off.
When output is stablized, the voltage waveform meansigma methods on output capacitance C1 remains unchanged, and therefore the mean charge on electric capacity C1 remains unchanged, it is believed that do not have DC current to flow through on electric capacity C1, only ac current signal；Then all of DC current current-sharing overload LEDs.
Second, it is described in detail with circuit in conjunction with specific embodiments:
First embodiment
By the circuit in Fig. 4 it is recognised that the electric current flowing through output capacitance C1 and load LEDs can flow through sample resistance Rcs；By the voltage on sample resistance Rcs is integrated, integral contrast level is a base reference level VREF(in figure the value of datum VREF), integrating resistor R3, integrating capacitor C2.Therefore when the voltage ratio on sample resistance Rcs is higher, its sampling voltage and base reference level VREFDifference by resistance R2, electric capacity C2 is discharged；When the voltage ratio on sample resistance Rcs is relatively low, its sampling voltage and base reference level VREFDifference by resistance R2, electric capacity C2 is charged.
As the average voltage on sample resistance Rcs and reference voltage VREFTime consistent, system is in steady statue；When stablizing, the level on electric capacity C2 remains unchanged, thus obtaining a stable comparative level ' control level ', this level is for controlling the on off state of switching tube.
Then output electric current during system stability is
ILED=VREF/RCS
Wherein VREFFor chip internal base reference level, therefore output electric current is only relevant with the current sampling resistor Rcs that outside is arranged.
When output no-load, by the maximum of the level on chip internal setting electric capacity C2, it is possible to obtain load maximum output voltage, i.e. overvoltage protection voltage VOVP, it is assumed that the voltage max on electric capacity C2 is VOPA_MAX, then
When output short-circuit, the level on electric capacity C2 is made to tend to 0V by the voltage on sample resistance Rcs, so that injectron is in very of short duration conducting state, and exchange AC input rectifying half-wave voltage is very low during its conducting, therefore input power consumption is only small, and output electric current can be defined within the specific limits.
Second embodiment
As can be seen from the figure, when, after firm electrifying startup, on output capacitance C1, voltage gradually rises, now on load LEDs no current or electric current not up to setting value, until voltage makes after on load LEDs, electric current reaches setting value on output capacitance C1, on output capacitance C1, voltage tends towards stability.
When exchanging AC input rectifying half-wave voltage less than voltage in output capacitance, the now pressure drop on resistance R2 is exchange AC input rectifying half-wave voltage signal, and the pressure drop on R1 is close to zero, the source electric current I1 that 3rd operational amplifier Buffer outfan produces, it is amplified on follow current I2 by mirror image multiple, so that floating earth potential is zero by the negative input end of the second comparator CPA, therefore switch Q1 conducting.
When exchanging AC input rectifying half-wave voltage more than voltage in output capacitance and when being gradually increased, made by the relation of image current the negative input end of the second comparator CPA that floating earth potential is gradually increasing, now output capacitance C1 is charged；After rising to certain level, namely the negative input end of the second comparator CPA to floating earth potential more than its positive input terminal to floating earth potential time, switching tube turn off；Along with exchange AC input rectifying half-wave voltage is gradually reduced, when the negative input end of its second comparator CPA to floating earth potential less than its positive input terminal to floating earth potential time, switching tube turns on again, now output capacitance C1 is charged.
Similar with embodiment in Fig. 3, when the system is stable, the average voltage on current sampling resistor Rcs controls the first operational amplifier OPA integration and obtains a stable level, is input to the positive input terminal of the second comparator CPA.Therefore steady timing output electric current remains as
ILED=VREF/RCS
Wherein VREFFor chip internal base reference level, therefore output electric current is only relevant with the current sampling resistor Rcs that outside is arranged.
It is seen that, first embodiment and the second embodiment, it is all that the control level signal obtained with sampling output current average by exchanging AC input rectifying half-wave voltage detection signal compares the driving signal obtaining switching tube, and then obtains the output current value of setting.Its relevant technical details is not quite similar, and repeats no more herein.
3rd embodiment
3rd embodiment adds source electrode drive circuit on first embodiment basis, and other philosophy and technique details total numbers are similar, do not repeating herein.Certain present invention can also pass through other type of drive and realize.
It is an advantage of the current invention that: by detecting the voltage of this exchange AC input rectifying half waveform so that switch Q1 is in the state of Push And Release, when half-wave voltage is higher, switch Q1 turns off, it is prevented that switch Q1 heating；When half-wave voltage is low, switch Q1 conducting, it is achieved the power supply to output capacitance and load LEDs.Make this system maintain good constant current effect by detecting sampling current signal averaging, reached again high efficiency simultaneously, efficiently solved chip cooling problem.
From the above: the new A C/DCLED constant source flowing system of the present invention, while keeping good constant current effect, solve traditional current regulator diode CRD and control system problem of switching tube heating when input is bigger with output pressure reduction, improve system effectiveness, efficiently solve chip cooling problem, save chip cost.
The foregoing is only presently preferred embodiments of the present invention, all equalizations done according to the claims in the present invention scope change and modify, and all should belong to the covering scope of the claims in the present invention.
Claims (7)
1. a LED constant current source, rectification module including electrical connection alternating current input power supplying, it is characterized in that, also include the sample resistance (Rcs) and the switch (Q1) that are serially connected on described rectification module output loop and the output capacitance (C1) in parallel with external LED constant current source load (LEDs)；Described sample resistance (Rcs) electrically connects average current detection and controls module, and the control end of described switch (Q1) electrically connects voltage detecting and switch drive module；Described average current detection controls module and includes the first operational amplifier, the negative input end of the first operational amplifier is sequentially connected electrically integrating resistor (R3) and the high voltage link of described sample resistance (Rcs), the positive input terminal of the first operational amplifier connects reference voltage (VREF), bridges integrating capacitor (C2) between outfan and the negative input end of the first operational amplifier；Described voltage detecting and switch drive module include the second comparator, the positive input terminal of the second comparator electrically connects the outfan of the first operational amplifier, the negative input end of the second comparator electrically connects the positive output end of described rectification module, the outfan of the second comparator electrically connects the control end of described switch (Q1): the second comparator output " 1 " then closes described switch (Q1), and the second comparator output " 0 " then disconnects described switch (Q1).
2. LED constant current source according to claim 1, it is characterised in that also include and the electric current forward being directly connected with described LED constant current source load (Rcs) wire that is serially connected on described rectification module output loop protects diode (D1).
3. LED constant current source according to claim 2; it is characterized in that, described LED constant current source load (LEDs) is sequentially connected electrically the negative output terminal of electric current forward protection diode (D1), switch (Q1), sample resistance (Rcs) and described rectification module；The negative input end of the second comparator electrically connects the positive output end of described rectification module by partial pressure unit, and described partial pressure unit includes the first resistance (R1) and the second resistance (R2) that are serially connected between positive output end and the negative input end of described rectification module.
4. LED constant current source according to claim 3, it is characterised in that described switch (Q1) is injectron, and this LED constant current source also includes source drive module；Described source drive module includes the second switch pipe (Q2) being connected between electric current forward protection diode (D1) and switch (Q1); the control end of second switch pipe (Q2) is connected with the positive output end of described rectification module by the 4th resistance (R4), is connected with the negative output terminal of described rectification module by Zener diode (Dz) simultaneously；Described 4th resistance (R4) and Zener diode (Dz) are serially connected between positive output end and the negative input end of described rectification module.
5. LED constant current source according to claim 2; it is characterized in that, the positive output end of described rectification module is sequentially connected electrically switch (Q1), sample resistance (Rcs), electric current forward protection diode (D1) and described LED constant current source load (LEDs)；This LED constant current source also includes the 3rd operational amplifier and mirror current source, the low-voltage link of positive input terminal electrical connection sample resistance (Rcs) of the 3rd operational amplifier, the negative input end of the 3rd operational amplifier electrically connects the negative output terminal of described rectification module by the second resistance (R2), bridges the source current terminal (I1) of described mirror current source between outfan and the negative input end of the 3rd operational amplifier；The follow current end (I2) of described mirror current source is connected between the negative input end of the second comparator and the low-voltage link of described sample resistance (Rcs), is also connected with the second Zener diode (D2) between the negative input end and the low-voltage link of described sample resistance (Rcs) of the second comparator；The negative input end of the second comparator electrically connects the positive output end of described rectification module also by the first resistance (R1).
6. a LED constant current source control method, it is characterised in that adopt the LED constant current source according to any one of claim 1-5, including by formula ILED=VREF/RCSSet or adjust output electric current ILED, wherein: VREFIt is reference voltage (VREF) value, RCSIt it is sample resistance (Rcs) value.
7. LED constant current source control method according to claim 6, it is characterised in that adopt the LED constant current source according to any one of claim 3-5, also include passing through formulaSet overvoltage protection voltage VOVP, wherein: R1 is the first resistance value, R2 is the second resistance value, VOPA_MAXIt it is the voltage max of integrating capacitor.
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| CN104582174B (en) * | 2014-12-31 | 2017-08-25 | 无锡华润矽科微电子有限公司 | The LED drive circuit and its driving method protected with sampling resistor |
| CN105263225A (en) * | 2015-10-28 | 2016-01-20 | 深圳创维－Rgb电子有限公司 | Constant current driving device and TV |
| CN105263224A (en) * | 2015-10-28 | 2016-01-20 | 深圳创维－Rgb电子有限公司 | Non-inductive BUCK constant current driving device and TV |
| CN105338718B (en) * | 2015-12-08 | 2018-09-18 | 王汉忠 | It is a kind of based on linearly with the LED constant current driving method and device of PWM operating modes |
| CN107529241B (en) * | 2016-06-22 | 2019-06-21 | 华润矽威科技（上海）有限公司 | A kind of linear Constant-power LED drive circuit of single hop and method |
| CN107529242B (en) * | 2016-06-22 | 2019-06-21 | 华润矽威科技（上海）有限公司 | A kind of LED drive circuit and method of equalization efficiency and power factor |
| CN106405242B (en) * | 2016-09-29 | 2023-08-15 | 国网山东省电力公司金乡县供电公司 | On-line monitoring device and detection method for direct-current resistance of isolating switch |
| CN107734784B (en) * | 2017-09-27 | 2024-04-23 | 泉芯电子技术(深圳)有限公司 | Control method of LED constant current source system |
| CN108024417B (en) * | 2017-12-22 | 2024-01-16 | 泉芯电子技术(深圳)有限公司 | High-voltage linear sectional type LED driving circuit |
| CN211557553U (en) * | 2019-06-06 | 2020-09-22 | 上海路傲电子科技有限公司 | Chip driving circuit, chip, linear constant current driving circuit and lighting device |
| CN116501125A (en) * | 2023-06-29 | 2023-07-28 | 荣耀终端有限公司 | Power supply voltage regulating circuit, method and electronic equipment |
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