CN112822818A - Circuit structure for realizing stepless dimming function - Google Patents
Circuit structure for realizing stepless dimming function Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention relates to a circuit structure for realizing a stepless dimming function, which comprises a first current generation circuit module, a second current generation circuit module and a control circuit module, wherein the first current generation circuit module is used for realizing the continuous linear change output of a first current; the second current generation circuit module is used for realizing the continuous linear change output of the second current; the first switch module is used for controlling the charging and discharging time of the capacitor; the second switch module is used for controlling the charging and discharging time of the capacitor; the frequency modulation module is used for carrying out frequency modulation on the first current and the second current; and the LED driving module is used for realizing dimming of the LED light source. By adopting the circuit structure for realizing the stepless dimming function, the invention provides the dimming circuit and the realization method based on the PFM mode, the working frequency of the circuit is modulated, the turn-off time of the switch tube is increased to change the duty ratio of the turn-on time of the switch tube, finally the dimming of the LED is realized, the output current of the LED can be linearly changed along with the dimming control signal, and the stepless dimming scheme can be realized.
Description
Technical Field
The invention relates to the field of smart homes, in particular to the field of LED dimming, and specifically relates to a circuit structure for realizing a stepless dimming function.
Background
Along with the development and popularization of the Internet of things and smart homes, the light source dimming requirement is more and more, and the dimming quality requirement is higher and higher. Therefore, the dimming technology of the LED needs to be continuously improved to exert the advantages of the LED, and the LED intelligent lighting system is in line with the development trend of intelligent home.
The existing common dimming technologies include linear dimming, PWM dimming, and thyristor dimming, among which the linear dimming circuit is relatively simple, and changes the peak current of the inductor by changing the voltage or the resistance to change the LED driving current, but the drawback is that the decrease of the peak current increases the operating frequency of the driving circuit, increases the switching loss, and simultaneously decreases the LED current and causes the white light to shift to the yellow spectrum.
The PWM dimming method is a method of changing an output current by controlling a duty ratio of a PWM wave, and a power circuit of a circuit operates when the PWM is high, and stops operating when the PWM is low. When the PWM frequency is lower, the stroboscopic can appear in the LED light source, can send the noise that the human ear can perceive moreover, is difficult to realize higher dimming precision and degree of depth when the frequency is higher.
The circuit structure of the prior invention d is shown in fig. 1, an adjustable resistor is used for changing the size of a current source 1/a current source 2, a switch 1 is closed, a capacitor C1 is charged by an I1, the switch 1 is opened, the switch 2 is closed, and a capacitor C1 discharges through an I2. The charge-discharge time of the capacitor is related to the magnitudes of I1 and I2, and the duty ratio of the on-time of the switching tube is changed by controlling and increasing the off-time of the switching tube through the charge-discharge time of the capacitor.
As shown in fig. 2, for a non-isolated LED driving circuit, one implementation of dimming based on PFM mode is as follows: no need of frequency modulation circuit during non-dimming, LED current ILED_100％＝IPK/2，IPKThe inductance peak current. The LED drive control method includes the steps that a frequency modulation circuit controls LED drive when dimming is needed, one working period of the circuit when dimming is not needed is t1, in the time t1, a capacitor is charged, the time t1 is finished, namely inductance demagnetization is finished, the capacitor discharges, an adjustable resistor is set to be I2-I1/N, the discharge time t 2-Nt 1, an LED drive control circuit controls a switching tube to enter the next period after the time t2 is delayed after inductance current is reduced to 0, and I drive control is conducted on the switching tube, and the next period is started when the time t2 is delayedLED＝IPK/2(1+N)＝ILED_100％/(1+N)。
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a circuit structure which has high precision, simple structure and wider application range and realizes the stepless dimming function.
In order to achieve the above object, the circuit structure of the present invention for realizing the stepless dimming function is as follows:
the circuit structure for realizing the electrodeless dimming function is mainly characterized by comprising the following components:
the first current generation circuit module is used for realizing continuous linear change output of the first current;
the second current generation circuit module is used for realizing the continuous linear change output of the second current;
the first switch module is connected with the first current generation circuit module and used for controlling the charging and discharging time of the capacitor;
the second switch module is connected with the second current generation circuit module and used for controlling the charging and discharging time of the capacitor;
the frequency modulation module is connected with the first current generation circuit module, is connected with the second current generation circuit module and is used for carrying out frequency modulation on the first current and the second current;
and the LED driving module is connected with the frequency modulation module and is used for realizing dimming of the LED light source.
Preferably, the first current generating circuit module includes a first constant voltage source unit and a first resistance unit, the first constant voltage source unit is connected to the first resistance unit, and the first resistance unit is connected to the first switch module.
Preferably, the second current generating circuit module includes a variable voltage source unit and a variable resistance unit, the variable voltage source unit is connected to the variable resistance unit, and the variable resistance unit is connected to the second switch module.
Preferably, the first current generating circuit module further includes a first current mirror unit, an input end of the first current mirror unit is connected to the first resistance unit, and an output end of the first current mirror unit is connected to the first switch module for adjusting a direction of the first current.
Preferably, the first constant voltage source unit includes a first operational amplifier and a first triode, the first resistance unit includes a first resistor, a positive input terminal of the first operational amplifier is connected to a constant voltage and a negative input terminal is connected to the first resistor, an output terminal of the first operational amplifier is connected to the first triode, one end of the first resistor is connected to the first triode, the other end of the first resistor is grounded, and the first current mirror unit is connected to the first triode.
Preferably, the second current generating circuit module further includes a second current mirror unit, an input end of the second current mirror unit is connected to the variable resistance unit, and an output end of the second current mirror unit is connected to the second switch module for adjusting a direction of the second current.
Preferably, the variable resistance unit includes a digital-to-analog converter, a second operational amplifier and a second triode, the variable resistance unit includes a variable resistance, an input end of the digital-to-analog converter is connected to the constant voltage and the dimming control signal respectively, an output end of the digital-to-analog converter is connected to a positive input end of the second operational amplifier, the variable resistance is connected to a negative input end of the second operational amplifier, the dimming control signal and the second triode and is grounded, and the second current mirror unit is connected to the second triode and the variable resistance.
Preferably, the voltage value of the variable voltage source unit satisfies the formula:
V2＝V1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
wherein, V2Is the voltage value of the variable voltage unit, V1Is a voltage value of a constant voltage.
Preferably, the resistance value of the variable resistance unit satisfies the formula:
R2＝R1－R1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
wherein R is2Is the resistance value of the variable resistance unit, R1Is the resistance of the first resistor.
By adopting the circuit structure for realizing the stepless dimming function, the invention provides the dimming circuit based on the PFM mode and the realization method, the working frequency of the circuit is modulated, the turn-off time of the switch tube is increased to change the duty ratio of the turn-on time of the switch tube, finally the dimming of the LED is realized, the output current of the LED can be linearly changed along with the dimming control signal, and the stepless dimming scheme can be realized.
Drawings
Fig. 1 is a circuit configuration diagram of the prior art.
Fig. 2 is a waveform diagram of the prior art.
Fig. 3 is a schematic diagram of a circuit structure for implementing the stepless dimming function according to the present invention.
Fig. 4 is a structural diagram of a first current generation circuit module of the circuit structure for implementing the stepless dimming function according to the present invention.
Fig. 5 is a structural diagram of a second current generation circuit module of the circuit structure for implementing the stepless dimming function according to the present invention.
Detailed Description
In order to more clearly describe the technical contents of the present invention, the following further description is given in conjunction with specific embodiments.
In a specific embodiment of the present invention, a circuit structure for implementing an electrodeless dimming function is disclosed, as shown in fig. 3, the circuit structure includes a first current generation circuit module, a second current generation circuit module, a first switch module, a second switch module, a frequency modulation module, and an LED driving module. The first current generation circuit module is connected with the first switch module and the frequency modulation module, the second current generation circuit module is connected with the second switch module and the frequency modulation module, and the frequency modulation module is further connected with the LED driving module.
As shown in fig. 4, the first current generation circuit module of the present invention includes a first constant voltage source unit, a first resistance unit, and a first current mirror unit, and is configured to generate a first current and realize a continuous linear change output of the first current. The first resistance unit is connected with the first switch module and the first constant voltage source unit respectively, the input end of the first current mirror image unit is connected with the first resistance unit, and the output end of the first current mirror image unit is connected with the first switch module and used for adjusting the direction of the first current.
The first constant-voltage source unit comprises a first operational amplifier and a first triode, the first resistance unit comprises a first resistor, the positive input end of the first operational amplifier is connected with a constant voltage, the negative input end of the first operational amplifier is connected with the first resistor, the output end of the first operational amplifier is connected with the first triode, one end of the first resistor is connected with the first triode, the other end of the first resistor is grounded, and the first current mirror unit is connected with the first triode. In FIG. 4, AMP is a first operational amplifier, M1 is a first transistor, and R1 is a first resistor.
The second current generating circuit module of the invention is shown in fig. 5, and includes a variable voltage source unit, a variable resistance unit and a second current mirror unit, and is configured to generate a second current, and linearly change an output current by adjusting the variable voltage source and the variable resistance, so as to implement continuous linear change output of the second current. The variable resistance unit is connected with the variable voltage source unit and the second switch module respectively, the input end of the second current mirror image unit is connected with the variable resistance unit, and the output end of the second current mirror image unit is connected with the second switch module and used for adjusting the direction of the second current.
The variable resistance unit comprises a digital-to-analog converter, a second operational amplifier, a second triode and a variable resistance, the input end of the digital-to-analog converter is respectively connected with a constant voltage and a dimming control signal, the output end of the digital-to-analog converter is connected with the positive input end of the second operational amplifier, the variable resistance is connected with the negative input end of the second operational amplifier, the dimming control signal and the second triode and is grounded, and the second current mirror unit is connected with the second triode and the variable resistance. In fig. 5, the DAC is a digital-to-analog converter, the AMP is a second operational amplifier, the M2 is a second transistor, and the R2, i.e., the R _ DAC, is a variable resistor.
The voltage value of the variable voltage source unit satisfies the formula:
V2＝V1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
wherein, V2Is the voltage value of the variable voltage unit, V1Is a voltage value of a constant voltage.
The resistance value of the variable resistance unit satisfies the formula:
R2＝R1－R1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
wherein R is2Is the resistance value of the variable resistance unit, R1Is the resistance of the first resistor.
According to the invention, the first switch module and the frequency modulation module are both connected with the first current generation circuit module, the frequency modulation module is also connected with the second current generation circuit module, the first switch module is used for controlling the charging and discharging time of the capacitor, and the frequency modulation module is used for carrying out frequency modulation on the first current and the second current. The second switch module is connected with the second current generation circuit module and used for controlling the charging and discharging time of the capacitor. The LED driving module is connected with the frequency modulation module and used for dimming the LED light source.
The prior art can easily realize the setting of a certain current value, but can not realize the continuous linear change of the output current, so the methodThe scheme is applicable to a switching dimming scheme and not applicable to an electrodeless dimming scheme. As shown in fig. 2, a waveform diagram of the prior art is shown, a frequency modulation circuit is not needed to operate when dimming is not performed, one operating cycle of the circuit is t1, the capacitor is charged within time t1, and the inductor demagnetization is finished when time t1 is finished, and the capacitor is discharged. LED Current ILED_100％＝IPK/2，IPKThe inductance peak current. When dimming is needed, the frequency modulation circuit controls the LED drive, the adjustable resistor is set to be I2-I1/N, the discharge time t 2-Nt 1, the capacitor is charged in the time t1, the time t1 is over, namely the LED drive control circuit controls the switching tube to delay the time t2 after the inductive current is reduced to 0, and then the next period is started, ILED＝IPK/2(1+N)＝ILED_100％/(1+ N). To achieve 50% output current, the resistor sets the discharge current I2＝I1，ILED＝50％×ILED_100％。
The invention aims to realize continuous linear change of output current, and supposes ILED＝X×ILED_100％(X represents a percentage), the dimming signal controls the variable voltage source and the variable resistor to simultaneously change, so that I2＝I1X/(1-X), wherein, I1For charging current, I2Is a discharge current.
The voltage value of the first constant voltage source is V1The first resistance value is R1If the output current is decreased linearly, the voltage variation range of the variable voltage source is V1Linearly decreasing to 0V, and the variable resistance is in the range of 0 to R1Linearly increasing.
Constant voltage V1Generating a charging current I by an LDO circuit1：I1＝V1/R1；
The n-bit dimming control signal controls the DAC to output a variable voltage signal V2＝V1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
The n-bit dimming control signal controls the R _ DAC to obtain the variable resistor R2＝R1－R1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
Variable voltage V2And a variable resistor R2The discharging current I is obtained after the current mirror image is generated by the LDO circuit2。
Is provided with (b)n－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2nX, then I2And I1Satisfy the relation I2＝I1×X/(1－X)。
The charging current I is obtained by controlling the variable voltage source and the variable resistor to simultaneously and linearly change through the dimming signal1Constant, discharge current I2And I1Has a relationship of2＝I1X/(1-X) can make the LED output current ILEDLinearly changing.
By adopting the circuit structure for realizing the stepless dimming function, the invention provides the dimming circuit based on the PFM mode and the realization method, the working frequency of the circuit is modulated, the turn-off time of the switch tube is increased to change the duty ratio of the turn-on time of the switch tube, finally the dimming of the LED is realized, the output current of the LED can be linearly changed along with the dimming control signal, and the stepless dimming scheme can be realized.
In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
Claims (9)
1. A circuit structure for realizing stepless dimming function is characterized in that the circuit structure comprises:
the first current generation circuit module is used for realizing continuous linear change output of the first current;
the second current generation circuit module is used for realizing the continuous linear change output of the second current;
the first switch module is connected with the first current generation circuit module and used for controlling the charging and discharging time of the capacitor;
the second switch module is connected with the second current generation circuit module and used for controlling the charging and discharging time of the capacitor;
the frequency modulation module is connected with the first current generation circuit module, is connected with the second current generation circuit module and is used for carrying out frequency modulation on the first current and the second current;
and the LED driving module is connected with the frequency modulation module and is used for realizing dimming of the LED light source.
2. The circuit structure for realizing the electrodeless dimming function as claimed in claim 1, wherein the first current generating circuit module comprises a first constant voltage power supply unit and a first resistor unit, the first constant voltage power supply unit is connected with the first resistor unit, and the first resistor unit is connected with the first switch module.
3. The circuit structure for realizing electrodeless dimming function as claimed in claim 1, wherein the second current generating circuit module comprises a variable voltage source unit and a variable resistance unit, the variable voltage source unit is connected with the variable resistance unit, and the variable resistance unit is connected with the second switch module.
4. The circuit structure for realizing the electrodeless dimming function as claimed in claim 2, wherein the first current generating circuit module further comprises a first current mirror unit, an input end of the first current mirror unit is connected with the first resistor unit, and an output end of the first current mirror unit is connected with the first switch module for adjusting a direction of the first current.
5. The circuit structure according to claim 4, wherein the first constant voltage source unit comprises a first operational amplifier and a first transistor, the first resistor unit comprises a first resistor, a positive input terminal of the first operational amplifier is connected to a constant voltage and a negative input terminal of the first operational amplifier is connected to the first resistor, an output terminal of the first operational amplifier is connected to the first transistor, one end of the first resistor is connected to the first transistor, the other end of the first resistor is grounded, and the first current mirror unit is connected to the first transistor.
6. The circuit structure for realizing the electrodeless dimming function as claimed in claim 3, wherein the second current generating circuit module further comprises a second current mirror unit, an input end of the second current mirror unit is connected to the variable resistor unit, and an output end of the second current mirror unit is connected to the second switch module for adjusting a direction of the second current.
7. The circuit structure according to claim 6, wherein the variable resistor unit comprises a digital-to-analog converter, a second operational amplifier and a second transistor, the variable resistor unit comprises a variable resistor, an input terminal of the digital-to-analog converter is connected to the constant voltage and the dimming control signal, an output terminal of the digital-to-analog converter is connected to a positive input terminal of the second operational amplifier, the variable resistor is connected to a negative input terminal of the second operational amplifier, the dimming control signal and the second transistor and is grounded, and the second current mirror unit is connected to the second transistor and the variable resistor.
8. The circuit structure for realizing the electrodeless dimming function as claimed in claim 3, wherein the voltage value of the variable voltage source unit satisfies the following formula:
V2＝V1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
wherein, V2Is the voltage value of the variable voltage unit, V1Is a voltage value of a constant voltage.
9. The circuit structure for realizing the electrodeless dimming function as claimed in claim 3, wherein the resistance value of the variable resistance unit satisfies the formula:
R2＝R1－R1×(bn－1×2n－1+bn－2×2n－2+……+bi×2i+……+b1×21+b0)/2n；
wherein R is2Is the resistance value of the variable resistance unit, R1Is the resistance of the first resistor.
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| CN201911117934.2A CN112822818B (en) | 2019-11-15 | 2019-11-15 | Circuit structure for realizing electrodeless dimming function |
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