CN109618463B - LED driving power supply dimming method without electrolytic capacitor - Google Patents
LED driving power supply dimming method without electrolytic capacitor Download PDFInfo
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- CN109618463B CN109618463B CN201910011062.5A CN201910011062A CN109618463B CN 109618463 B CN109618463 B CN 109618463B CN 201910011062 A CN201910011062 A CN 201910011062A CN 109618463 B CN109618463 B CN 109618463B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
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Abstract
The invention relates to a dimming method of an LED driving power supply without electrolytic capacitor. The dimming control signal is generated by combining the dimming input signal and the PFC input voltage signal, when the PFC input voltage is larger than the set voltage value, the constant-current resonant converter starts to work, and the resonant converter stops working after the set time, and the steps are repeated in a circulating mode. The set voltage value, the set time and the set dimming output signal are calculated by the duty ratio of the dimming input signal, the clock current duty ratio of the rated output current and the PFC input voltage. By adjusting the working time and the continuous working time of the constant-current resonant converter, the dimming control of the LED lamp is realized, and the voltage ripple of the energy storage capacitor is inhibited. The method has the advantages of wide dimming range, long service life, high reliability and the like.
Description
Technical Field
The invention relates to a dimming method of an LED driving power supply without electrolytic capacitor.
Background
With the deep research on the related technologies of the LED, the application range of the LED is also wider and wider, and the LED gradually becomes a mainstream lighting device, and the demand of people on energy conservation, personalized light, intelligent control and the like requires that the LED must have a dimming function, and the power consumption and the temperature of the LED during dimming are reduced, which is beneficial to improving the service life and the reliability of the LED lamp. Therefore, the research on the dimming scheme of the LED driving power supply has very important significance for the popularization and the use of the LED.
At present, research on LED dimming modes mainly focuses on three types, namely silicon controlled dimming, analog dimming and PWM dimming. The PWM dimming is to change the average brightness of the LED by controlling the ratio of the on time to the off time of the LED in a fixed period. In the dimming scheme, the current flowing through the LED is alternately changed between the maximum driving current and the zero current, the amplitude of the output current is constant, and only the duty ratio is changed, so that the chromaticity basically cannot deviate, the dimming linearity is good, and the dimming range is wide.
In a two-stage LED driving power supply consisting of a PFC stage and a constant-current resonant converter, because the output current of the resonant converter is only related to the input voltage and the resonant parameters of a resonant network at a constant-current frequency, the dimming (analog dimming) cannot be carried out by adjusting the frequency, the output current of the resonant converter cannot be adjusted by changing the resonant parameters in practical application, and because the resonant converter is in constant-current output and cannot directly change the output current by controlling the on-off of a switching tube, the dimming can be realized by changing the input voltage of the resonant network. The input voltage of the resonant network and the output voltage of the PFC are in a linear relation, but the PFC circuit usually adopts a Boost converter, and the regulation range of the output voltage is limited, so that the dimming control of the LED lamp can be realized only by controlling the constant-current resonant converter to work in a pulse density modulation mode so as to change the input voltage of the resonant network.
Disclosure of Invention
The invention aims to provide an electrolytic capacitor-free LED driving power supply dimming method, which is characterized in that a dimming control signal is generated by combining a dimming input signal and a PFC input voltage signal, and when the PFC input voltage is greater than a set voltage value VeWhen the constant current resonant converter starts to work, the set time t passesaThe rear resonant converter stops working, and the operation is repeated in a circulating way; the method realizes dimming control of the LED lamp by adjusting the working time and the continuous working time of the constant-current resonant converter, and suppresses the voltage ripple of the energy storage capacitor. The method has the advantages of wide dimming range, long service life, high reliability and the like.
In order to achieve the purpose, the technical scheme of the invention is as follows: the method combines a dimming input signal and a PFC input voltage signal through a control unit to generate a dimming control signal, and when the PFC input voltage is greater than a set voltage value VeWhen the constant current resonant converter is started, the constant current resonant converter is controlled to start working, and the set time t passesaThe rear constant-current resonant converter stops working, and the operation is repeated in such a circulating way, so that the constant-current resonant converter works in a pulse density modulation mode, and the LED is driven in a pulsating current mode, thereby realizing the dimming workAt any dimming position, the corresponding dimming output signal I is set according to the duty ratio of the dimming input signale(ii) a Wherein the set voltage value VeSet time taAnd a set dimming output signal IeThe duty ratio of the dimming input signal, the clock current-driving duty ratio of the rated output current and the PFC input voltage are calculated.
In one embodiment of the invention, two input ends of the rectifying circuit are connected with a power supply, and two output ends of the rectifying circuit are connected with two input ends of the LED lamp through the PFC circuit, the energy storage capacitor and the constant-current resonant converter; the control unit comprises a single chip microcomputer and a control module; the control module comprises an error amplifier, a subtracter and a control circuit; one input end of the single chip microcomputer is connected with the positive input end of the PFC circuit and used for detecting PFC input voltage, the other input end of the single chip microcomputer serves as a dimming signal input end, one output end of the single chip microcomputer is connected with the constant-current resonant converter and used for generating a driving signal for driving a switching tube in the constant-current resonant converter, the other output end of the single chip microcomputer serves as a dimming control signal output end and is connected with the non-inverting input end of the error amplifier, the inverting input end of the error amplifier serves as a sampling end of the LED lamp current, the output end of the error amplifier is connected with the inverting input end of the subtracter, the non-inverting input end of the subtracter serves as a sampling end of PFC output voltage, the output end of the subtracter is.
In an embodiment of the invention, the set voltage value VeAnd a set time taThe calculation formula of (a) is as follows:
ta＝kiDa/2f
in the formula, VmFor inputting amplitude of AC voltage, DaFor dimming the duty cycle of the input signal, kiThe duty ratio of the clock current is rated as the rated output current, and f is the input crossThe frequency of the streaming voltage.
In an embodiment of the present invention, k isiK is not less than 0.6i＜1。
In an embodiment of the present invention, a relation between the duty ratio of the dimming output signal and the duty ratio of the dimming input signal is as follows: i ise＝I0*DaWherein, I0Is the rated output current.
Compared with the prior art, the invention has the following beneficial effects: the method generates the dimming control signal by combining the dimming input signal with the PFC input voltage signal, and when the PFC input voltage is greater than the set voltage value VeWhen the constant current resonant converter starts to work, the set time t passesaAnd the rear resonant converter stops working, and the operation is repeated in a circulating mode. Wherein the set voltage value VeThe set time taAnd a set dimming output signal IeThe duty ratio of the dimming input signal, the clock current-driving duty ratio of the rated output current and the PFC input voltage are calculated. By adjusting the working time and the continuous working time of the constant-current resonant converter, the dimming control of the LED lamp is realized, and the voltage ripple of the energy storage capacitor is inhibited. The method has the advantages of wide dimming range, long service life, high reliability and the like.
Drawings
Fig. 1 is a schematic diagram of a dimming method of an electrolytic capacitor-free LED driving power supply according to the present invention.
Fig. 2 shows an embodiment of a dimming method for an electrolytic capacitor-free LED driving power supply according to the present invention.
Fig. 3 shows waveforms of the storage capacitor voltage and the output current during dimming.
Fig. 4 is a graph showing maximum and minimum voltage variations of the energy storage capacitor under different dimming input signals.
Detailed Description
The technical scheme of the invention is specifically explained below with reference to the accompanying drawings.
The invention provides a dimming method of an electrolytic capacitor-free LED driving power supply, wherein the electrolytic capacitor-free LED driving power supply consists of a rectifying circuit, a PFC circuit, an energy storage capacitor,The method combines a dimming input signal and a PFC input voltage signal through a control unit to generate a dimming control signal, and when the PFC input voltage is greater than a set voltage value VeWhen the constant current resonant converter is started, the constant current resonant converter is controlled to start working, and the set time t passesaThe rear constant-current resonant converter stops working, the operation is repeated in such a circulating way, so that the constant-current resonant converter works in a pulse density modulation mode, the LED is driven in a pulsating current mode, the dimming function is realized, and the corresponding dimming output signal I is set according to the duty ratio of the dimming input signal at any dimming positione(ii) a Wherein the set voltage value VeSet time taAnd a set dimming output signal IeThe duty ratio of the dimming input signal, the clock current-driving duty ratio of the rated output current and the PFC input voltage are calculated. Two input ends of the rectifying circuit are connected with a power supply, and two output ends of the rectifying circuit are connected with two input ends of the LED lamp through the PFC circuit, the energy storage capacitor and the constant-current resonant converter; the control unit comprises a single chip microcomputer and a control module; the control module comprises an error amplifier, a subtracter and a control circuit; one input end of the single chip microcomputer is connected with the positive input end of the PFC circuit and used for detecting PFC input voltage, the other input end of the single chip microcomputer serves as a dimming signal input end, one output end of the single chip microcomputer is connected with the constant-current resonant converter and used for generating a driving signal for driving a switching tube in the constant-current resonant converter, the other output end of the single chip microcomputer serves as a dimming control signal output end and is connected with the non-inverting input end of the error amplifier, the inverting input end of the error amplifier serves as a sampling end of the LED lamp current, the output end of the error amplifier is connected with the inverting input end of the subtracter, the non-inverting input end of the subtracter serves as a sampling end of PFC output voltage, the output end of the subtracter is.
The set voltage value VeAnd a set time taThe calculation formula of (a) is as follows:
ta＝kiDa/2f
in the formula, VmFor inputting amplitude of AC voltage, DaFor dimming the duty cycle of the input signal, kiThe duty cycle of the clock current is rated for the output current, in this example, kiThe value is 0.8, and f is the input alternating voltage frequency.
The relation between the duty ratio of the dimming output signal and the duty ratio of the dimming input signal is as follows: i ise＝I0*DaWherein, I0Is the rated output current.
The following is a specific embodiment of the present invention.
For a driving power supply without an electrolytic capacitor, the balance of input instantaneous power and output power needs to be considered, the voltage ripple of the energy storage capacitor is suppressed, and meanwhile, the output voltage of the PFC circuit is controlled within a certain range, so that the normal work of the PFC circuit is ensured. Therefore, the dimming input signal processing is determined by the dimming input signal and the PFC input voltage, and meanwhile, the voltage stress of the energy storage capacitor and the PFC function are considered.
As shown in fig. 1, the present invention provides an electrolytic capacitor-free LED driving power supply dimming method, which combines a dimming input signal and an input voltage signal for control, so as to implement dimming control on an output current of an LED lamp. The mechanism for controlling the output current by using the method is as follows: the singlechip detects the duty ratio of the dimming input signal in real time, when the duty ratio of the dimming input signal is maximum, the LED driving power supply is fully loaded and output, and the current of the LED lamp is maximum. When the duty ratio of the dimming input signal is DaWhen the single chip generates the signal I0*DaOf the dimming output signal IeThe reference value of the current is used as the reference value of the current, and meanwhile, a corresponding driving signal is provided for a switching tube of the constant-current resonant converter. When the PFC input voltage is instantaneous
The constant current resonance converter starts to work through ta＝kiDaPost/2 f constant current resonant converter stopAnd in the working process, the constant current resonant converter works in a pulse density modulation mode, and the LED is driven in a pulsating current mode. Wherein VmFor inputting amplitude of AC voltage, DaFor dimming the duty cycle of the input signal, kiFor the rated output current clock current duty ratio, considering the requirement of peak-to-average ratio of the LED ripple current, kiTake 0.8, f as the input AC voltage frequency. At a dimming input signal duty cycle of DaThe duty ratio of the LED pulsating current is kiDa. According to the dimming control method, the working time and the continuous working time of the constant-current resonant converter are adjusted according to the dimming input signal, the dimming control of the LED lamp is realized, and the voltage ripple of the energy storage capacitor is restrained.
Fig. 2 shows an embodiment of a dimming method for an LED driving power supply without an electrolytic capacitor. The working process is as follows: the LED current sampling signal Vif is compared with a current reference signal Iref generated by a singlechip according to a dimming input signal, a current loop error amplification signal Vi is obtained after the current reference signal Iref is isolated by an error amplifier U1 and an optical coupler U2, then a weighted feedback signal Vw is obtained after the PFC output voltage sampling signal Uvf and the current loop error amplification signal Vi are subjected to weighted subtraction and serves as a voltage feedback signal of a PFC control chip U4, and the output voltage ripple is controlled within a certain range through dynamically adjusting the PFC output voltage; the PFC input voltage is divided by resistors R1 and R2 and then sent to the singlechip through a voltage follower U3, the PFC input voltage is collected and processed by the singlechip to control the constant-current resonant converter to work, and when the singlechip detects the instantaneous value of the PFC input voltage
The constant current resonance converter starts to work through ta＝kiDaAnd after the delay of/2 f, stopping the constant-current resonant converter to enable the constant-current resonant converter to work in a pulse density modulation mode, and driving the LED in a pulse current mode. According to the dimming control method, the working time and the continuous working time of the constant-current resonant converter are adjusted according to the dimming input signal, the dimming control of the LED lamp is realized, and the voltage ripple of the energy storage capacitor is restrained.
By controlling the working time of the constant-current resonant converter, when the input power is high, the LED lights to consume energy, and when the input power is low, the LED stops lighting, so that the output current is in a pulsating mode, the ripple value of the PFC output voltage is reduced, the capacitance value of the energy storage capacitor required under the same ripple value can be reduced, the electrolytic capacitor can be replaced by the thin-film capacitor, and the constant current of the LED lamp without the electrolytic capacitor can be realized. By controlling the continuous working time of the constant-current resonant converter, the LED driving current can be adjusted, and the dimming function is realized.
FIG. 3 shows the waveforms of the voltage of the energy storage capacitor and the output current during dimming, showing the duty ratio D of the input signal with dimmingaThe average value of the output current is gradually reduced, and the output current and the duty ratio of the dimming input signal are in a linear relation, so that the dimming control of the LED is realized. Fig. 4 is a maximum and minimum voltage variation curves of the energy storage capacitor under different dimming input signals, which shows that the voltage ripple of the energy storage capacitor can be controlled within a certain range, and the normal operation of the PFC circuit can be ensured.
The above are preferred embodiments of the present invention, and all changes made according to the technical scheme of the present invention that produce functional effects do not exceed the scope of the technical scheme of the present invention belong to the protection scope of the present invention.
Claims (5)
1. The method is characterized in that a dimming control signal is generated by combining a dimming input signal and a PFC input voltage signal through a control unit, and when the PFC input voltage is greater than a set voltage value VeWhen the constant current resonant converter is started, the constant current resonant converter is controlled to start working, and the set time t passesaThe rear constant-current resonant converter stops working, the operation is repeated in such a circulating way, so that the constant-current resonant converter works in a pulse density modulation mode, the LED is driven in a pulsating current mode, the dimming function is realized, and the corresponding dimming output signal I is set according to the duty ratio of the dimming input signal at any dimming positione(ii) a Wherein the set voltage value VeSet time taAnd a set dimming output signalNumber IeThe duty ratio of the dimming input signal, the clock current-driving duty ratio of the rated output current and the PFC input voltage are calculated; the method for realizing the LED dimming function specifically comprises the following steps: the single chip microcomputer detects the duty ratio of the dimming input signal in real time, when the duty ratio of the dimming input signal is maximum, the LED driving power supply is fully loaded and outputs, and the LED current is maximum; when the duty ratio of the dimming input signal is DaWhen the single chip generates the signal I0*DaOf the dimming output signal IeThe reference value of the current is used, and meanwhile, a corresponding driving signal is provided for a switching tube of the constant-current resonant converter; when the PFC input voltage is instantaneous
The constant current resonance converter starts to work through ta＝kiDaAfter/2 f, the constant current resonant converter stops working, so that the constant current resonant converter works in a pulse density modulation mode, the LED is driven in a pulsating current mode, wherein VmFor inputting amplitude of AC voltage, DaFor dimming the duty cycle of the input signal, kiClock current duty cycle, k, for a nominal output currentiTake 0.8, f as the input AC voltage frequency, I0Is a rated output current; at a dimming input signal duty cycle of DaThe duty ratio of the LED pulsating current is kiDa(ii) a And adjusting the working time and the continuous working time of the constant-current resonant converter according to the magnitude of the dimming input signal to realize dimming control of the LED.
2. The dimming method of the LED driving power supply without the electrolytic capacitor as claimed in claim 1, wherein two input terminals of the rectifying circuit are connected to the power supply, and two output terminals of the rectifying circuit are connected to two input terminals of the LED lamp via the PFC circuit, the energy storage capacitor, and the constant current resonant converter; the control unit comprises a single chip microcomputer and a control module; the control module comprises an error amplifier, a subtracter and a control circuit; one input end of the single chip microcomputer is connected with the positive input end of the PFC circuit and used for detecting PFC input voltage, the other input end of the single chip microcomputer serves as a dimming signal input end, one output end of the single chip microcomputer is connected with the constant-current resonant converter and used for generating a driving signal for driving a switching tube in the constant-current resonant converter, the other output end of the single chip microcomputer serves as a dimming control signal output end and is connected with the non-inverting input end of the error amplifier, the inverting input end of the error amplifier serves as a sampling end of the LED lamp current, the output end of the error amplifier is connected with the inverting input end of the subtracter, the non-inverting input end of the subtracter serves as a sampling end of PFC output voltage, the output end of the subtracter is.
3. The dimming method for LED driving power supply without electrolytic capacitor as claimed in claim 1, wherein the set voltage value V iseAnd a set time taThe calculation formula of (a) is as follows:
ta＝kiDa/2f
in the formula, VmFor inputting amplitude of AC voltage, DaFor dimming the duty cycle of the input signal, kiThe duty ratio of the clock current is the rated output current, and f is the input alternating voltage frequency.
4. The dimming method for LED driving power supply without electrolytic capacitor as claimed in claim 3, wherein the k isiK is not less than 0.6i＜1。
5. The dimming method of claim 3, wherein the relationship between the duty ratio of the dimming output signal and the dimming input signal is as follows: i ise＝I0*DaWherein, I0Is the rated output current.
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| CN110536516B (en) * | 2019-09-27 | 2021-11-30 | 福州大学 | Digital control method of LED driving power supply without electrolytic capacitor |
| CN111526641B (en) * | 2020-05-15 | 2022-06-10 | 深圳市洲明科技股份有限公司 | Back pressure self-adjusting method and device |
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| GB201011081D0 (en) * | 2010-07-01 | 2010-08-18 | Macfarlane Alistair | Improved semi resonant switching regulator, power factor control and LED lighting |
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| CN101702863A (en) * | 2009-11-25 | 2010-05-05 | 中国电子科技集团公司第五十二研究所 | Frequency-modulation electronic ballast for dimmable fluorescent lamp |
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| CN103813602A (en) * | 2014-02-24 | 2014-05-21 | 福州大学 | Electroless fluorescent lamp dimming method |
| CN204090258U (en) * | 2014-11-04 | 2015-01-07 | 太仓电威光电有限公司 | Intelligent LED underwater fishing lamp |
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