CN102821526A - Circuit for realizing voltage-self-adaptation PWM (Pulse Width Modulation) light adjustment of LED (Light Emitting Diode) under drive of prepositive constant-current source - Google Patents
Circuit for realizing voltage-self-adaptation PWM (Pulse Width Modulation) light adjustment of LED (Light Emitting Diode) under drive of prepositive constant-current source Download PDFInfo
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Abstract
The invention relates to a PWM (Pulse Width Modulation) light adjusting technology for an LED (Light Emitting Diode) and aims at providing a circuit for realizing the voltage-self-adaptation PWM light adjustment of the LED under the drive of a prepositive constant-current source. The circuit comprises an output load LED string LED1, an output filter capacitor Co1, a forestage controlled direct-current (DC) source Is1 and a PWM light adjusting control circuit which is connected with the LED string LED1, wherein the filter capacitor Co1 is in parallel connection with the two terminals of the controlled DC source Is1, the LED string LED1 is in series connection with the PWM light adjusting control circuit and then in parallel connection with the two terminals of the Is1, and a light adjusting signal input terminal is connected to the control terminal of the controlled DC source Is1. According to the circuit for realizing the voltage-self-adaptation PWM light adjustment of the LED under the drive of the prepositive constant-current source, the forestage constant-current source and the rear-stage PWM control circuit are out of additional signal circuit connection, besides being in power connection, so that the control is simple; the average terminal of the rear-stage PWM pulse constant current source obtains the minimum voltage through self adaptation, so that the conduction losses are reduced; the PWM light adjustment of the LED can be realized without PWM light adjusting signals; the M light adjusting function is realized in an analog mode, so that the cost is low; and the multichannel PWM light adjusting control can be realized by adopting a multichannel output constant current source, and only light adjusting signals of one channel are used.
Description
Technical field
The present invention relates to the implementation of pulse duration (PWM) light modulation of a kind of LED, LED realizes the control mode of PWM light modulation under a kind of specifically constant-current source pre-driver.
Background technology
Great power LED becomes the new generation of green light source with characteristics such as its long-life, high light efficiency, environmental friendliness.LED not only is applied in traditional illumination occasion, substitutes common existing light source, and is applied in the occasion that light modulation is had relatively high expectations more, such as the back lighting of LCD.Owing to the colour temperature of LED can change along with the magnitude of drive current, therefore, require when light modulation, to maintain the amplitude of electric current in order to guarantee the consistency of colour temperature, carry out light modulation through the ON time that changes electric current, PWM dimming mode promptly commonly used.Owing to the diode characteristic of LED, need the constant amplitude of Control current during its conducting, can equivalence become constant-current source.When the PWM dimming mode is worked, then can equivalence become the pulse current source of constant amplitude.
The PWM dimming mode of LED commonly used carries out at present, and input side adopts constant pressure source that energy is provided, and during the LED multi-path load, is connected in parallel on the same voltage bus; Linear switch of realizing constant current control of series connection in the LED string is as shown in Figure 1 simultaneously.This series connection constant-current source can pass through pwm control signal, makes this linear switch work in the state of pulsed constant current supply, and the amplitude of its current impulse is controlled by Vref.In order to reduce the conduction voltage drop of linear switch, thereby reduce the wastage, need the pressure drop through the sampling pulse current source, come the amplitude of adaptive regulation voltage bus, the pressure drop when making this linearity constant-current source work as far as possible is minimum.But; Because the LED multi-path load relies on a public voltage bus that energy is provided; So when the pressure drop difference of multi-string LED is big; Linear constant-current source such as causing series connection in the less LED string of wherein pressure drop bears itself and the voltage difference with maximum forward pressure drop LED string, causes the linear current source loss to increase.In addition; Owing to will regulate the output voltage of prime current transformer through the voltage that detects the linear current source two ends; The output signal of voltage detecting circuit is restricted with the distance of corresponding linear constant-current source; Influence the reliability that the prime current transformer is regulated, also increased the difficulty that the signal transmission is connected with circuit in addition, and the independence and the standardization of restriction prime driver.
Summary of the invention
The technical problem that the present invention will solve is, overcomes the deficiency of prior art, and a kind of PWM light modulation solution that can carry out high efficiency self adaptation adjustment busbar voltage is provided.And promptly use analog signal also can realize the PWM light modulation.
For addressing the above problem, the invention provides a kind of prime constant-current source output current that passes through to regulate, just can realize the adjusting of busbar voltage self adaptation, thereby obtain the distributed PWM light regulating technology of minimum output voltage.Be specially:
The circuit of realizing LED voltage adaptive PWM light modulation under a kind of constant-current source pre-driver is provided, comprises output loading LED string LED1 and output filter capacitor Co1; This circuit also comprises the controlled DC current source Is1 of prime, and the PWM adjusting control circuit that joins with output loading LED string LED1; Output filter capacitor Co1 is connected in parallel on the two ends of controlled DC current source Is1, output loading LED string LED1 and the two ends that are connected in parallel on controlled DC current source Is1 after the PWM adjusting control circuit is connected; The input of dim signal is connected to the control end of controlled DC current source Is1; Said PWM adjusting control circuit comprises: pulse current source ID1, voltage sampling circuit, voltage control and PWM duty ratio generation circuit that pulsewidth is controlled; The anode of pulse current source ID1 is connected to the negative terminal of output loading LED string LED1 and the input of voltage sampling circuit simultaneously, and the output of voltage sampling circuit is as the input of voltage control and PWM duty ratio generation circuit; The output signal of voltage control and PWM duty ratio generation circuit is duty ratio D, and the duty cycle signals of this output is connected to the control end of pulse current source ID1.
Among the present invention, said pulse current source ID1 is the adjustable pulse current source of frequency and pulse amplitude.
Among the present invention, the controlled DC current source Is1 of said prime is linear controlled source, or constitutes the constant-current source of switching circuit through output current control.
Among the present invention; The controlled DC current source of prime is except that said controlled DC current source Is1; Also comprise the multichannel arranged side by side output with it controlled DC current source Is2, Is3 ..., Isn; The back level on each road all has output filter capacitor Co1, output loading LED string and PWM adjusting control circuit, and its circuit structure is identical.
Among the present invention, the controlled DC current source Is1 of said multichannel output, Is2, Is3 ..., among the Isn, the amplitude of each controlled DC current source is identical, or has different ratios.
Among the present invention, the controlled DC current source Is1 of said multichannel output, Is2, Is3 ..., Isn receives same control signal Vdim control.
Compare as the PWM light modulation strategy of prestage with the traditional voltage source, the beneficial effect of current source forward voltage adaptive optimization PWM adjusting control circuit of the present invention is:
(1) between prime constant-current source and the back level pwm control circuit except power is connected, no extra signal circuit connects, and controls simply;
(2) the average terminal voltage self adaptation of back level pwm pulse constant-current source obtains minimum value, reduces conduction loss.
(3) need not the PWM light modulation that the PWM dim signal just can be realized LED; Analog form is realized the PWM dimming function, and cost is low;
(4) adopt the constant-current source of multichannel output just can realize the multi-channel PWM brightness adjustment control, and only use one road dim signal.
Description of drawings
Fig. 1: the voltage adaptive PWM dimming controlling method that the traditional voltage source is preposition.
Fig. 2: the preposition distributed Voltage adaptive optimization of the current source PWM adjusting control circuit that the present invention proposes.
Fig. 3: dim signal Vdim and duty ratio D.
Fig. 4: the preposition multichannel output of current source distributed Voltage adaptive optimization PWM adjusting control circuit.
Fig. 5: the PWM brightness adjustment control execution mode of terminal voltage self-adapting closed loop control.
Fig. 6: a kind of execution mode of controlled constant-current source Is1.
Specific embodiment
Below in conjunction with accompanying drawing embodiment of the present invention are specifically set forth.
As shown in Figure 2, comprise the controlled DC current source Is1 of prime, output filter capacitor Co1, output loading LED among the present invention and go here and there LED1.The back level is the constant controlled PWM adjusting control circuit of pulsewidth of pulse amplitude of terminal voltage adaptive control, comprises voltage sampling circuit, voltage control and the PWM duty ratio generation circuit of pulse current source ID1, acquisition pulse current source terminal voltage.Controlled DC current source Is1 receives the control of dim signal Vdim.Output filter capacitor Co1 is connected in parallel on the two ends of controlled DC current source Is1, output loading LED string LED1 and the two ends that are connected in parallel on controlled DC current source Is1 after the PWM adjusting control circuit is connected.The anode that just terminates to output filter capacitor Co1 of controlled DC current source Is1 is received the anode of output loading LED string LED1 simultaneously; The negativing ending grounding of output filter capacitor Co1; The negative terminal of output loading LED string LED1 is connected to the anode of pulse current source ID1; The negativing ending grounding of pulse current source ID1; Its anode is also connected to the input of voltage sampling circuit simultaneously; The output of voltage sampling circuit is received the input of voltage control and PWM duty ratio generation circuit, and the Voltage Reference of voltage control and PWM duty ratio generation circuit terminates to reference voltage Vref.Voltage control and PWM duty ratio generation circuit are output as duty ratio D, receive the control end of the pulse current source of pulse width control, are used for controlling the pulse duration of ID1.
Technical scheme among the present invention also is applicable to the PWM dimmer application of multichannel output; Prime is the controlled constant-current source Is1 of multichannel output, Is2 ..., can there be certain proportion in Isn between each constant-current source, and proportionality coefficient is a1, a2 ..., an.And the multiple constant current source receives same control signal Vdim control.The connected mode of each road constant-current source and back level terminal voltage adaptive PWM adjusting control circuit is identical with the connected mode of single channel.
The pulse current of brightness adjustment control of the present invention also can be the adjustable pulse current source of frequency and pulse amplitude.Controlled DC current source can be linear controlled source, also can be the constant-current source that any switching circuit constitutes through output current control.
Fig. 5 is a kind of execution mode of PWM light modulation of the terminal voltage adaptive control among the present invention.The negative terminal of LED load LED1 is connected to an end of switch S 12, receives the collector electrode of Q1 simultaneously, and the other end of S12 is received an end of capacitor C 13, is connected to an end of resistance R 16 simultaneously, and the control end of S12 is received the output of rest-set flip-flop FP1; The other end ground connection of capacitor C 13, resistance R 17 is parallelly connected with capacitor C 13; The other end of resistance R 16 is connected to the negative input end of error amplifier EA1, is connected to the end of C12 simultaneously, and the other end of C12 is connected to an end of resistance R 15, and the other end of R15 is connected to the output of EA1.The positive input termination voltage reference Vref of EA1.The negative input end of comparator C omp1 is received in the output of EA1, the positive input termination sawtooth signal source of Comp1, and the S end of the output side joint rest-set flip-flop FP1 of comparator C omp1, the output of FP1 is received the control end of switch S 12 and S11 simultaneously.The end ground connection of S11, the positive input terminal of another termination error amplifier EA2 and an end of resistance R 14, resistance R 13 is connected in parallel on the two ends of S11.Another termination current reference Iref of resistance R 14.Error is amplified the negative input end of its EA2 and is received an end of capacitor C 11 and the end of R18, and the other end of C11 is received an end of resistance R 11, and the other end of resistance R 11 is connected to the output of EA2 and an end of resistance R 12 simultaneously.The other end of R12 is received the base stage of Q1, and the emitter-base bandgap grading of Q1 is received the end of sampling resistor Rs1 and the other end of R18, the other end ground connection of Rs1.Q1 in this execution mode can be a bipolar transistor, also can be field-effect transistor.
Fig. 6 is a kind of execution mode of controlled dc constant current power supply.The end that just terminates to switching tube S of input source Vin, the negative electrode of another terminating diode D of S is received inductance L d one end simultaneously, and the anode of diode D is received input ground.The other end of inductance L is received the end of output capacitance Co, and the other end of Co is received input ground; Load is connected in parallel on the two ends of Co; The sampled signal of inductive current is received the Rsen end of controller, and dim signal is received its moral of control Iref end, and output D receives the control end of S.
Should be noted that employed specific term should not be used to be illustrated in when explanation some characteristic of the present invention or scheme defines this term here again with restriction of the present invention some certain features, characteristic or the scheme relevant with this term.In a word, should be with the terminological interpretation of in the claims of enclosing, using for the present invention not being limited to disclosed specific embodiment in the specification, only if above-mentioned detailed description part defines these terms clearly.Therefore, actual range of the present invention not only comprises the disclosed embodiments, also is included in to implement or carry out all equivalents of the present invention under claims.
Claims (6)
1. realize the circuit of LED voltage adaptive PWM light modulation under the constant-current source pre-driver, comprise output loading LED string LED1 and output filter capacitor Co1; It is characterized in that this circuit also comprises the controlled DC current source Is1 of prime, and the PWM adjusting control circuit that joins with output loading LED string LED1; Output filter capacitor Co1 is connected in parallel on the two ends of controlled DC current source Is1, output loading LED string LED1 and the two ends that are connected in parallel on controlled DC current source Is1 after the PWM adjusting control circuit is connected; The input of dim signal is connected to the control end of controlled DC current source Is1;
Said PWM adjusting control circuit comprises: pulse current source ID1, voltage sampling circuit, voltage control and PWM duty ratio generation circuit that pulsewidth is controlled; The anode of pulse current source ID1 is connected to the negative terminal of output loading LED string LED1 and the input of voltage sampling circuit simultaneously, and the output of voltage sampling circuit is as the input of voltage control and PWM duty ratio generation circuit; The output signal of voltage control and PWM duty ratio generation circuit is duty ratio D, and the duty cycle signals of this output is connected to the control end of pulse current source ID1.
2. circuit according to claim 1 is characterized in that, said pulse current source ID1 is the adjustable pulse current source of frequency and pulse amplitude.
3. circuit according to claim 1 is characterized in that, the controlled DC current source Is1 of said prime is linear controlled source, or constitutes the constant-current source of switching circuit through output current control.
4. according to the circuit described in any one of the claim 1 to 3; It is characterized in that; The controlled DC current source of prime is except that said controlled DC current source Is1; Also comprise the multichannel arranged side by side output with it controlled DC current source Is2, Is3 ..., Isn, the back level on each road all has output filter capacitor Co1, output loading LED string and PWM adjusting control circuit, and its circuit structure is identical.
5. circuit according to claim 4 is characterized in that, the controlled DC current source Is1 of said multichannel output, Is2, Is3 ..., among the Isn, the amplitude of each controlled DC current source is identical, or has different ratios.
6. circuit according to claim 4 is characterized in that, the controlled DC current source Is1 of said multichannel output, Is2, Is3 ..., Isn receives same control signal Vdim control.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201210324680.3A CN102821526B (en) | 2012-09-05 | 2012-09-05 | The circuit of LED electrical pressure adaptive PWM light modulation is realized under constant-current source pre-driver |
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| CN201210324680.3A CN102821526B (en) | 2012-09-05 | 2012-09-05 | The circuit of LED electrical pressure adaptive PWM light modulation is realized under constant-current source pre-driver |
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Cited By (7)
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| WO2016065573A1 (en) * | 2014-10-30 | 2016-05-06 | Texas Instruments Incorporated | Led current controller |
| CN105722272A (en) * | 2016-02-15 | 2016-06-29 | 深圳迈睿智能科技有限公司 | Initial voltage adaptive method for constant-voltage dimming power supply |
| CN106879127A (en) * | 2017-04-19 | 2017-06-20 | 上海晶丰明源半导体股份有限公司 | A kind of pair of controller of LED drive system, chip and method |
| CN110267392A (en) * | 2019-06-03 | 2019-09-20 | 苏州慧润百年物联科技有限公司 | A kind of circuit and method of achievable LED isolation stepless dimming |
| CN112449461A (en) * | 2020-11-19 | 2021-03-05 | 东莞华明灯具有限公司 | Wide-voltage composite light-adjusting constant-voltage power supply circuit |
| US20220101805A1 (en) * | 2020-09-29 | 2022-03-31 | Coretronic Corporation | Driving device and driving method for backlight module |
| WO2023165424A1 (en) * | 2022-03-04 | 2023-09-07 | 华为技术有限公司 | Backlight driving circuit, chip, backlight module and electronic device |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017100793A1 (en) * | 2015-12-10 | 2017-06-15 | Osram Sylvania Inc. | A multi string controller with independent current setting for each string |
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| CN114333707A (en) * | 2020-09-29 | 2022-04-12 | 中强光电股份有限公司 | Driving device and driving method of backlight module |
| CN112449461A (en) * | 2020-11-19 | 2021-03-05 | 东莞华明灯具有限公司 | Wide-voltage composite light-adjusting constant-voltage power supply circuit |
| WO2023165424A1 (en) * | 2022-03-04 | 2023-09-07 | 华为技术有限公司 | Backlight driving circuit, chip, backlight module and electronic device |
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