CN110769564B - Circuit capable of automatically adjusting output current along with input voltage and LED driving power supply - Google Patents
Circuit capable of automatically adjusting output current along with input voltage and LED driving power supply Download PDFInfo
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- CN110769564B CN110769564B CN201911085314.5A CN201911085314A CN110769564B CN 110769564 B CN110769564 B CN 110769564B CN 201911085314 A CN201911085314 A CN 201911085314A CN 110769564 B CN110769564 B CN 110769564B
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Abstract
The invention relates to a circuit capable of automatically adjusting output current along with input voltage and an LED driving power supply. The voltage comparison circuit in the circuit compares the sampling voltage acquired by the voltage sampling circuit with the reference voltage and outputs a voltage error signal capable of reflecting the voltage variation trend; the optocoupler feedback circuit controls the on-off of the optocoupler according to the voltage error signal; the switch control circuit controls the output current of the reference voltage according to the switch of the photoelectric coupler, and the current comparison circuit compares the output current of the switch control circuit with the reference current collected by the current sampling circuit and outputs a current error signal capable of reflecting the current change trend. The invention automatically adjusts the output current according to the input voltage, effectively prevents the influence of the input voltage fluctuation on the driving power supply, prolongs the service life of the LED driving power supply and greatly improves the reliability and the stability of the LED driving power supply.
Description
Technical Field
The invention relates to the field of LED power supplies, in particular to a circuit capable of automatically adjusting output current along with input voltage and an LED driving power supply.
Background
LEDs are gradually replacing traditional lighting sources and are finding wider and wider application in various lighting fields. Along with the increasing development of social and economic construction, the level of urban road infrastructure illumination construction becomes an important sign of the speed and the level of urban development, and the quality of illumination engineering not only influences the safety of vehicles and pedestrians, but also relates to the realization of energy-saving and environment-friendly targets.
In the daily use process, the LED power supply output caused by the fluctuation of the power grid voltage is unstable, so that the whole lamp cannot work normally. In addition, in addition to the basic electrical performance of the driving power supply, some protection measures are necessary, such as abnormal protection functions of over-temperature, over-current, short circuit, over-voltage, under-voltage, etc., and more importantly, some driving power supply labels clearly indicate the range of the input voltage, such as: the input voltage marked on the label is 220-240Vac, and as a result, the driving power supply is sold to regions such as North America or Japan, when the input voltage is low, the driving power supply can not be damaged due to excessive temperature rise for a few hours, and the label time of some driving power supplies is unclear for a long time or the result of no label is improper, so that the driving power supplies can be damaged to cause serious accidents such as customer complaints or casualties.
Disclosure of Invention
The present invention provides a circuit for automatically adjusting an output current according to an input voltage and an LED driving power supply, which address the above-mentioned drawbacks of the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: a circuit capable of automatically adjusting output current along with input voltage is constructed and comprises a voltage sampling circuit, a voltage comparison circuit, an optocoupler feedback circuit, a loop compensation circuit, a switch control circuit, a current comparison circuit, a reference voltage circuit and a current sampling circuit;
the input end of the voltage sampling circuit receives input voltage, and the output end of the voltage sampling circuit is connected with the input end of the voltage comparison circuit; the output end of the voltage comparison circuit is connected with the input end of the optocoupler feedback circuit; a first output end of the optical coupling feedback circuit is connected with an input end of the switch control circuit, and a second output end of the optical coupling feedback circuit is connected with the voltage comparison circuit through the loop compensation circuit; the output end of the switch control circuit is connected with the first input end of the current comparison circuit, the second input end of the current comparison circuit is connected with the current sampling circuit, and the reference voltage circuit is connected with the third input end of the current comparison circuit;
the voltage comparison circuit compares the sampling voltage acquired by the voltage sampling circuit with a reference voltage and outputs a voltage error signal capable of reflecting the voltage change trend, and the loop compensation circuit is used for reducing the loop voltage return difference range; the optocoupler feedback circuit controls the on-off of the optocoupler according to the voltage error signal; the switch control circuit controls the output current of the reference voltage according to the switch of the photoelectric coupler, the current comparison circuit compares the output current of the switch control circuit with the reference current collected by the current sampling circuit and outputs a current error signal capable of reflecting the current variation trend, and the reference voltage circuit is used for generating a preset voltage reference signal to control the current error signal.
Further, in the circuit for automatically adjusting output current according to input voltage of the present invention, the voltage sampling circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R26, and a capacitor C1;
a first end of the resistor R1 receives an input voltage, a second end of the resistor R1 is connected with a first end of the resistor R26 through the resistor R2, and a second end of the resistor R26 is grounded through the resistor R3; the second end of the resistor R26 is connected with the first end of the resistor R4, and the second end of the resistor R4 is grounded through the capacitor C1; the second end of the resistor R4 is grounded through the resistor R5, and the connection point of the resistor R4 and the resistor R5 outputs the sampling voltage.
Further, in the circuit for automatically adjusting the output current according to the input voltage, the voltage comparison circuit comprises a TL431 chip, a resistor R6, a capacitor C2 and a resistor R7;
the anode of the TL431 chip is grounded, and the reference pole of the TL431 chip is connected with the connection point of the resistor R4 and the resistor R5 through the resistor R6 and receives the sampling voltage; the cathode of the TL431 chip is connected with the reference electrode of the TL431 chip through the capacitor C2, and a reference voltage is provided inside the TL431 chip; the cathode of the TL431 chip is connected with the optical coupler feedback circuit through the resistor R7;
if the sampling voltage is greater than the reference voltage, the TL431 chip is conducted to work; and if the sampling voltage is smaller than the reference voltage, the TL431 chip is not conducted.
Further, in the circuit for automatically adjusting output current according to input voltage, the optocoupler feedback circuit comprises a triode Q4, an optocoupler, a resistor R8, a resistor R11 and a resistor R13;
the base electrode of the triode Q4 is connected with the cathode of the TL431 chip through the resistor R7, the base electrode of the triode Q4 is connected with the emitter electrode of the triode Q4 through the resistor R8, and the emitter electrode of the triode Q4 is connected with a first power supply VCC 1; the collector of the triode Q4 is connected with the first input end of the photoelectric coupler through the resistor R11, and the second input end of the photoelectric coupler is grounded; the first output end of the photoelectric coupler is connected with a second power supply VCC2 through the resistor R13, the first output end of the photoelectric coupler is connected with the input end of the switch control circuit, and the second output end of the photoelectric coupler is grounded;
if the TL431 chip is conducted to work, current flows into the input end of the photoelectric coupler, and the output end of the photoelectric coupler is conducted; if the TL431 chip is not conducted, no current flows into the input end of the photoelectric coupler, and the output end of the photoelectric coupler is disconnected.
Further, in the circuit for automatically adjusting output current according to input voltage of the present invention, the loop compensation circuit includes a resistor R9 and a resistor R10;
the collector of the transistor Q4 is connected to the first end of the resistor R10 through the resistor R9, and the second end of the resistor R10 is connected to the connection point between the resistor R4 and the resistor R5.
Further, in the circuit for automatically adjusting output current according to input voltage of the present invention, the switch control circuit includes a resistor R14, a resistor R15, a diode D1, and a transistor Q6;
the anode of the diode D1 is connected with the first output end of the photoelectric coupler, the cathode of the diode D1 is connected with the second output end of the photoelectric coupler through the resistor R14, and the second output end of the photoelectric coupler is grounded; the cathode of the diode D1 is connected with the base of the triode Q6, and the emitter of the triode Q6 is grounded; the collector of the transistor Q6 is connected with the current comparison circuit through the resistor R15;
if the output end of the photoelectric coupler is conducted, the triode Q6 is not conducted; if the output end of the photoelectric coupler is not conducted, the triode Q6 is conducted.
Further, in the circuit for automatically adjusting the output current according to the input voltage, the current comparison circuit comprises a resistor R20, a resistor R21, a resistor R50, a variable resistor VR1, a capacitor C18 and a second comparator U2-B;
the first end of the resistor R20 is connected with the collector of the triode Q6 through the resistor R15, and the first end of the resistor R20 is connected with the reference voltage circuit; a second end of the resistor R20 is connected with a non-inverting input end of the second comparator U2-B, a second input end of the resistor R20 is connected with a first end of the variable resistor VR1 through the resistor R21, and a second end of the variable resistor VR1 is grounded; the inverting input end of the second comparator U2-B is connected with the output end of the second comparator U2-B through the series connection of the capacitor C18 and the resistor R50;
if the transistor Q6 is not conducting, the branch of the resistor R15 is disconnected, and current flows only through the resistor R20; if the transistor Q6 is turned on, the resistor R15 shunts the current loop, and the current of the resistor R20 decreases; the second comparator U2-B outputs a current error signal capable of reflecting the trend of current change according to the current of the resistor R20 and the reference current.
Further, in the circuit for automatically adjusting output current according to input voltage of the present invention, the current sampling circuit includes a resistor R23; the inverting input end of the second comparator U2-B is connected with the detection output end through the resistor R23 and receives the reference current.
Further, in the circuit for automatically adjusting the output current according to the input voltage, the reference voltage circuit comprises a first comparator U2-A, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R22, a resistor R24, a resistor R25, a capacitor C41, a diode D2, a diode D3 and a second photoelectric coupler;
the positive electrode of the first comparator U2-A is connected with a second power supply VCC2, the negative electrode of the first comparator U2-A is grounded, and the non-inverting input end of the first comparator U2-A is connected with the first end of the resistor R20 through the resistor R19; the inverting input end of the first comparator U2-A is connected with the anode of the LED through the resistor R16, and the inverting input end of the first comparator U2-A is grounded through the resistor R17; the inverting input end of the first comparator U2-A is connected with the first end of the resistor R18 through the capacitor C41, and the second end of the resistor R18 is connected with the output end of the first comparator U2-A; the output end of the first comparator U2-A is connected with the cathode of the diode D2 through the resistor R22, the anode of the diode D2 is connected with the second input end of the second photoelectric coupler, and the first input end of the second photoelectric coupler is connected with a second power supply VCC2 through the resistor R25; the anode of the diode D3 is connected to the anode of the diode D2, and the cathode of the diode D3 is connected to the output terminal of the second comparator U2-B through the resistor R24.
In addition, the invention also provides an LED driving power supply which comprises the circuit for automatically adjusting the output current along with the input voltage.
The circuit for automatically adjusting the output current along with the input voltage and the LED driving power supply have the following beneficial effects: the invention automatically adjusts the output current according to the input voltage, effectively prevents the influence of the input voltage fluctuation on the driving power supply, prolongs the service life of the LED driving power supply and greatly improves the reliability and the stability of the LED driving power supply.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a schematic structural diagram of a circuit for automatically adjusting an output current according to an input voltage according to an embodiment;
fig. 2 is a circuit diagram of a circuit for automatically adjusting an output current according to an embodiment of the invention.
Detailed Description
For a more clear understanding of the technical features, objects and effects of the present invention, embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Examples
Referring to fig. 1, the technical solution adopted by the embodiment to solve the technical problem is as follows: a circuit capable of automatically adjusting output current along with input voltage is constructed, and comprises a voltage sampling circuit 10, a voltage comparison circuit 20, an optical coupling feedback circuit 30, a loop compensation circuit 40, a switch control circuit 50, a current comparison circuit 60, a reference voltage circuit 70 and a current sampling circuit 80.
The input end of the voltage sampling circuit 10 receives an input voltage, and the output end of the voltage sampling circuit 10 is connected with the input end of the voltage comparison circuit 20; the output end of the voltage comparison circuit 20 is connected with the input end of the optocoupler feedback circuit 30; a first output end of the optical coupling feedback circuit 30 is connected with an input end of the switch control circuit 50, and a second output end of the optical coupling feedback circuit 30 is connected with the voltage comparison circuit 20 through the loop compensation circuit 40; the output terminal of the switch control circuit 50 is connected to the first input terminal of the current comparison circuit 60, the second input terminal of the current comparison circuit 60 is connected to the current sampling circuit 80, and the reference voltage circuit 70 is connected to the third input terminal of the current comparison circuit 60.
The voltage comparison circuit 20 compares the sampling voltage acquired by the voltage sampling circuit 10 with a reference voltage, and outputs a voltage error signal capable of reflecting the voltage variation trend, and the loop compensation circuit 40 is used for reducing the loop voltage return difference range; the optocoupler feedback circuit 30 controls the on-off of the optocoupler according to the voltage error signal; the switch control circuit 50 controls the output current of the reference voltage according to the switch of the photoelectric coupler, the current comparison circuit 60 compares the output current of the switch control circuit 50 with the reference current collected by the current sampling circuit 80 and outputs a current error signal capable of reflecting the current variation trend, and the reference voltage circuit 70 is used for generating a preset voltage reference signal to control the current error signal.
According to the embodiment, the output current is automatically adjusted according to the input voltage, the influence of input voltage fluctuation on the driving power supply is effectively prevented, the service life of the LED driving power supply is prolonged, and the reliability and the stability of the LED driving power supply are greatly improved.
Examples
Referring to fig. 2, in the circuit for automatically adjusting output current according to the input voltage of the present embodiment, the voltage sampling circuit 10 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R26, and a capacitor C1, a first end of the resistor R1 receives an input voltage HV, and the input voltage HV is a bus voltage rectified in the LED driving power supply. The second end of the resistor R1 is connected with the first end of the resistor R26 through a resistor R2, and the second end of the resistor R26 is grounded through a resistor R3; the second end of the resistor R26 is connected with the first end of the resistor R4, and the second end of the resistor R4 is grounded through the capacitor C1; the second end of the resistor R4 is grounded through a resistor R5, and the connection point of the resistor R4 and the resistor R5 outputs a sampling voltage.
In the circuit for automatically adjusting the output current according to the input voltage of the embodiment, the voltage comparison circuit 20 includes a TL431 chip (ZT 1 in fig. 2), a resistor R6, a capacitor C2 and a resistor R7, an anode of the TL431 chip is grounded, a reference electrode of the TL431 chip is connected to a connection point of the resistor R4 and the resistor R5 through the resistor R6, and receives the sampling voltage; the cathode of the TL431 chip is connected with the reference electrode of the TL431 chip through a capacitor C2, and a reference voltage is provided inside the TL431 chip; the cathode of the TL431 chip is connected with the optical coupling feedback circuit 30 through a resistor R7; if the sampling voltage is greater than the reference voltage, the TL431 chip is conducted to work; if the sampling voltage is less than the reference voltage, the TL431 chip is not conducted.
In the circuit for automatically adjusting output current according to input voltage of the present embodiment, the optocoupler feedback circuit 30 includes a transistor Q4, an optocoupler, a resistor R8, a resistor R11, and a resistor R13, where an input end of the optocoupler is OT2-a in fig. 2, a first input end of the optocoupler is pin 1, and a second input end of the optocoupler is pin; the output terminal of the photoelectric coupler is OT2-B, the first output terminal of the photoelectric coupler is pin 4, and the second output terminal of the photoelectric coupler is pin 3. The base electrode of the triode Q4 is connected with the cathode of the TL431 chip through a resistor R7, the base electrode of the triode Q4 is connected with the emitting electrode of the triode Q4 through a resistor R8, and the emitting electrode of the triode Q4 is connected with a first power supply VCC 1; the collector of the triode Q4 is connected with the first input end of the photoelectric coupler through a resistor R11, and the second input end of the photoelectric coupler is grounded; the first output end of the photoelectric coupler is connected with a second power supply VCC2 through a resistor R13, the first output end of the photoelectric coupler is connected with the input end of the switch control circuit 50, and the second output end of the photoelectric coupler is grounded. If the TL431 chip is conducted to work, current flows into the input end of the photoelectric coupler, and the output end of the photoelectric coupler is conducted; if the TL431 chip is not conducted, no current flows into the input end of the photoelectric coupler, and the output end of the photoelectric coupler is disconnected. The chip pin structure and function of the TL431 chip can be referred to in the prior art.
In the circuit for automatically adjusting the output current according to the input voltage of the present embodiment, the loop compensation circuit 40 includes a resistor R9 and a resistor R10, a collector of the transistor Q4 is connected to a first end of the resistor R10 through the resistor R9, and a second end of the resistor R10 is connected to a connection point of the resistor R4 and the resistor R5.
In the circuit for automatically adjusting the output current according to the input voltage of the embodiment, the switch control circuit 50 includes a resistor R14, a resistor R15, a diode D1 and a triode Q6, wherein the positive electrode of the diode D1 is connected to the first output end of the photoelectric coupler, the negative electrode of the diode D1 is connected to the second output end of the photoelectric coupler through a resistor R14, and the second output end of the photoelectric coupler is grounded; the negative electrode of the diode D1 is connected with the base electrode of the triode Q6, and the emitting electrode of the triode Q6 is grounded; the collector of the transistor Q6 is connected to the current comparator circuit 60 through a resistor R15. If the output end of the photoelectric coupler is conducted, the triode Q6 is not conducted; if the output end of the photoelectric coupler is not conducted, the triode Q6 is conducted.
In the circuit for automatically adjusting the output current according to the input voltage of the embodiment, the current comparison circuit 60 comprises a resistor R20, a resistor R21, a resistor R50, a variable resistor VR1, a capacitor C18 and a second comparator U2-B, wherein a first end of the resistor R20 is connected with a collector of a triode Q6 through a resistor R15, and a first end of a resistor R20 is connected with the reference voltage circuit 70; a second end of the resistor R20 is connected with a non-inverting input end of a second comparator U2-B, a second input end of the resistor R20 is connected with a first end of the variable resistor VR1 through the resistor R21, and a second end of the variable resistor VR1 is grounded; the inverting input terminal of the second comparator U2-B is connected to the output terminal of the second comparator U2-B through a series capacitor C18 and a resistor R50. If the transistor Q6 is not turned on, the branch of the resistor R15 is disconnected, and current flows only through the resistor R20; if the triode Q6 is turned on, the resistor R15 shunts the current loop, and the current of the resistor R20 decreases; the second comparator U2-B outputs a current error signal reflecting the trend of current change according to the current of the resistor R20 and the reference current.
In the circuit for automatically adjusting the output current in accordance with the input voltage of the present embodiment, the current sampling circuit 80 includes a resistor R23; the inverting input terminal of the second comparator U2-B is connected to the detection output terminal through a resistor R23 and receives the reference current.
In the circuit for automatically adjusting the output current according to the input voltage of the embodiment, the reference voltage circuit 70 includes a first comparator U2-a, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R22, a resistor R24, a resistor R25, a capacitor C41, a diode D2, a diode D3, and a second photocoupler, wherein an anode of the first comparator U2-a is connected to a second power supply VCC2, a cathode of the first comparator U2-a is grounded, and a non-inverting input terminal of the first comparator U2-a is connected to a first end of the resistor R20 through the resistor R19; the inverting input end of the first comparator U2-A is connected with the anode of the LED through a resistor R16, and the inverting input end of the first comparator U2-A is grounded through a resistor R17; the inverting input end of the first comparator U2-A is connected with the first end of the resistor R18 through the capacitor C41, and the second end of the resistor R18 is connected with the output end of the first comparator U2-A; the output end of the first comparator U2-A is connected with the cathode of the diode D2 through a resistor R22, the anode of the diode D2 is connected with the second input end of the second photoelectric coupler, and the first input end of the second photoelectric coupler is connected with a second power supply VCC2 through a resistor R25; the anode of the diode D3 is connected with the anode of the diode D2, and the cathode of the diode D3 is connected with the output end of the second comparator U2-B through the resistor R24. Alternatively, the first comparator U2-A has a model number AP4310 and the second comparator U2-B has a model number AP 4310.
Referring to fig. 2, taking an input voltage of 120Vac as an example, the specific operation principle is as follows:
A. when the input voltage is larger than or equal to 120Vac, the rectified bus voltage (HV) passes through the input voltage sampling circuit 10 consisting of the resistor R1, the resistor R2, the resistor R26, the resistor R3, the resistor R4, the capacitor C1 and the resistor R5, and the sampled voltage is input to the input end of the reference signal generator consisting of the TL431 through the resistor R6 to be compared with the reference voltage. When the sampling voltage is greater than the reference voltage, the TL431 is turned on and operates, and is input to the base of the transistor Q4 through the resistor R7, and the transistor Q4 is also turned on after being biased. After the current comparator U2-B (namely the second comparator U2-B) is turned on, the collector output of the triode Q4 is connected to the input end OT2-A of the electro-optical coupling through the resistor R11, the photoelectric coupler OT2-A has current passing, the output end OT2-B of the photoelectric coupler is also connected, the connection of the photoelectric coupler OT2-B is equivalent to the fact that the base of the triode Q6 is pulled to the ground, the triode Q6 is not connected and is in a cut-off state, the resistor R15 has no influence on a current loop and cannot shunt current to the resistor R20, and then the output current of the current comparator U2-B (namely the second comparator U2-B) is the largest, namely the.
B. When the input voltage is less than 120Vac, the rectified bus voltage (HV) passes through the input voltage sampling circuit 10 composed of the resistor R1, the resistor R2, the resistor R26, the resistor R3, the resistor R4, the capacitor C1 and the resistor R5, and the sampled voltage is input to the input end of the reference signal generator composed of the TL431 through the resistor R6 to be compared with the reference voltage. When the sampling voltage is smaller than the reference voltage, the TL431 does not conduct to work, the sampling voltage is input to the base of the triode Q4 through the resistor R7, the open circuit of the base of the triode Q4 is in a cut-off state, no output voltage exists at the collector of the triode Q4, the resistor R11 is input to the input end OT2-A of the photoelectric coupler, the photoelectric coupler OT2-A does not emit light when no current passes through the photoelectric coupler, the output end OT2-B of the photoelectric coupler does not receive light, the photoelectric coupler OT2-B is equivalent to an open circuit, VCC is input to the base of the triode Q6 through the diode D1, the triode Q6 is conducted, the current loop is changed through the resistor R15 to form shunt to the resistor R20, and the output current of the current comparator U2-B (namely the second comparator U2-B) is reduced, namely the output power is reduced.
In some embodiments, parameters in the schematic diagram can be flexibly adjusted:
A. the input voltage section can be changed by properly adjusting the resistances of the resistor R1, the resistor R2, the resistor R26, the resistor R3 and the resistor R4 in the input sampling circuit.
B. The values of the resistor R9 and the resistor R10 in the loop compensation circuit are properly adjusted, so that the size of the return difference can be changed, and the voltage precision range is also changed.
C. The percentage of the maximum current output can be changed by properly adjusting the resistance of the resistor R15 in the switch control circuit.
According to the embodiment, the output current is automatically adjusted according to the input voltage, the influence of input voltage fluctuation on the driving power supply is effectively prevented, the service life of the LED driving power supply is prolonged, and the reliability and the stability of the LED driving power supply are greatly improved.
Examples
The LED driving power supply of the present embodiment includes the circuit for automatically adjusting the output current according to the input voltage as described above.
According to the embodiment, the output current is automatically adjusted according to the input voltage, the influence of input voltage fluctuation on the driving power supply is effectively prevented, the service life of the LED driving power supply is prolonged, and the reliability and the stability of the LED driving power supply are greatly improved.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.
Claims (4)
1. A circuit capable of automatically adjusting output current along with input voltage is characterized by comprising a voltage sampling circuit (10), a voltage comparison circuit (20), an optical coupler feedback circuit (30), a loop compensation circuit (40), a switch control circuit (50), a current comparison circuit (60), a reference voltage circuit (70) and a current sampling circuit (80);
the input end of the voltage sampling circuit (10) receives an input voltage, and the output end of the voltage sampling circuit (10) is connected with the input end of the voltage comparison circuit (20); the output end of the voltage comparison circuit (20) is connected with the input end of the optical coupling feedback circuit (30); a first output end of the optical coupling feedback circuit (30) is connected with an input end of the switch control circuit (50), and a second output end of the optical coupling feedback circuit (30) is connected with the voltage comparison circuit (20) through the loop compensation circuit (40); the output end of the switch control circuit (50) is connected with the first input end of the current comparison circuit (60), the second input end of the current comparison circuit (60) is connected with the current sampling circuit (80), and the reference voltage circuit (70) is connected with the third input end of the current comparison circuit (60);
the voltage comparison circuit (20) compares the sampling voltage acquired by the voltage sampling circuit (10) with a reference voltage and outputs a voltage error signal capable of reflecting the voltage variation trend, and the loop compensation circuit (40) is used for reducing the loop voltage return difference range; the optocoupler feedback circuit (30) controls the on-off of the optocoupler according to the voltage error signal; the switch control circuit (50) controls the output current of the reference voltage according to the switch of the photoelectric coupler, the current comparison circuit (60) compares the output current of the switch control circuit (50) with the reference current collected by the current sampling circuit (80) and outputs a current error signal capable of reflecting the current variation trend, and the reference voltage circuit (70) is used for generating a preset voltage reference signal to control the current error signal;
the voltage sampling circuit (10) comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R26 and a capacitor C1; a first end of the resistor R1 receives an input voltage, a second end of the resistor R1 is connected with a first end of the resistor R26 through the resistor R2, and a second end of the resistor R26 is grounded through the resistor R3; the second end of the resistor R26 is connected with the first end of the resistor R4, and the second end of the resistor R4 is grounded through the capacitor C1; the second end of the resistor R4 is grounded through the resistor R5, and the connection point of the resistor R4 and the resistor R5 outputs the sampling voltage;
the voltage comparison circuit (20) comprises a TL431 chip, a resistor R6, a capacitor C2 and a resistor R7; the anode of the TL431 chip is grounded, and the reference pole of the TL431 chip is connected with the connection point of the resistor R4 and the resistor R5 through the resistor R6 and receives the sampling voltage; the cathode of the TL431 chip is connected with the reference electrode of the TL431 chip through the capacitor C2, and a reference voltage is provided inside the TL431 chip; the cathode of the TL431 chip is connected with the optical coupling feedback circuit (30) through the resistor R7; if the sampling voltage is greater than the reference voltage, the TL431 chip is conducted to work; if the sampling voltage is smaller than the reference voltage, the TL431 chip is not conducted;
the optocoupler feedback circuit (30) comprises a triode Q4, an optocoupler, a resistor R8, a resistor R11 and a resistor R13; the base electrode of the triode Q4 is connected with the cathode of the TL431 chip through the resistor R7, the base electrode of the triode Q4 is connected with the emitter electrode of the triode Q4 through the resistor R8, and the emitter electrode of the triode Q4 is connected with a first power supply VCC 1; the collector of the triode Q4 is connected with the first input end of the photoelectric coupler through the resistor R11, and the second input end of the photoelectric coupler is grounded; the first output end of the photoelectric coupler is connected with a second power supply VCC2 through the resistor R13, the first output end of the photoelectric coupler is connected with the input end of the switch control circuit (50), and the second output end of the photoelectric coupler is grounded; if the TL431 chip is conducted to work, current flows into the input end of the photoelectric coupler, and the output end of the photoelectric coupler is conducted; if the TL431 chip is not conducted, no current flows into the input end of the photoelectric coupler, and the output end of the photoelectric coupler is disconnected;
the loop compensation circuit (40) includes a resistor R9 and a resistor R10; the collector of the triode Q4 is connected to the first end of the resistor R10 through the resistor R9, and the second end of the resistor R10 is connected to the connection point of the resistor R4 and the resistor R5;
the switch control circuit (50) comprises a resistor R14, a resistor R15, a diode D1 and a triode Q6; the anode of the diode D1 is connected with the first output end of the photoelectric coupler, the cathode of the diode D1 is connected with the second output end of the photoelectric coupler through the resistor R14, and the second output end of the photoelectric coupler is grounded; the cathode of the diode D1 is connected with the base of the triode Q6, and the emitter of the triode Q6 is grounded; the collector of the transistor Q6 is connected with the current comparison circuit (60) through the resistor R15; if the output end of the photoelectric coupler is conducted, the triode Q6 is not conducted; if the output end of the photoelectric coupler is not conducted, the triode Q6 is conducted;
the current comparison circuit (60) comprises a resistor R20, a resistor R21, a resistor R50, a variable resistor VR1, a capacitor C18 and a second comparator U2-B; a first end of the resistor R20 is connected with the collector of the triode Q6 through the resistor R15, and a first end of the resistor R20 is connected with the reference voltage circuit (70); a second end of the resistor R20 is connected with a non-inverting input end of the second comparator U2-B, a second input end of the resistor R20 is connected with a first end of the variable resistor VR1 through the resistor R21, and a second end of the variable resistor VR1 is grounded; the inverting input end of the second comparator U2-B is connected with the output end of the second comparator U2-B through the series connection of the capacitor C18 and the resistor R50; if the transistor Q6 is not conducting, the branch of the resistor R15 is disconnected, and current flows only through the resistor R20; if the transistor Q6 is turned on, the resistor R15 shunts the current loop, and the current of the resistor R20 decreases; the second comparator U2-B outputs a current error signal capable of reflecting the trend of current change according to the current of the resistor R20 and the reference current.
2. The circuit of claim 1, wherein the current sampling circuit (80) comprises a resistor R23; the inverting input end of the second comparator U2-B is connected with the detection output end through the resistor R23 and receives the reference current.
3. The circuit of claim 1, wherein the reference voltage circuit (70) comprises a first comparator U2-A, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a resistor R22, a resistor R24, a resistor R25, a capacitor C41, a diode D2, a diode D3, and a second photocoupler;
the positive electrode of the first comparator U2-A is connected with a second power supply VCC2, the negative electrode of the first comparator U2-A is grounded, and the non-inverting input end of the first comparator U2-A is connected with the first end of the resistor R20 through the resistor R19; the inverting input end of the first comparator U2-A is connected with the anode of the LED through the resistor R16, and the inverting input end of the first comparator U2-A is grounded through the resistor R17; the inverting input end of the first comparator U2-A is connected with the first end of the resistor R18 through the capacitor C41, and the second end of the resistor R18 is connected with the output end of the first comparator U2-A; the output end of the first comparator U2-A is connected with the cathode of the diode D2 through the resistor R22, the anode of the diode D2 is connected with the second input end of the second photoelectric coupler, and the first input end of the second photoelectric coupler is connected with a second power supply VCC2 through the resistor R25; the anode of the diode D3 is connected to the anode of the diode D2, and the cathode of the diode D3 is connected to the output terminal of the second comparator U2-B through the resistor R24.
4. An LED driving power supply comprising the circuit for automatically adjusting an output current in accordance with an input voltage according to any one of claims 1 to 3.
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| CN112235896B (en) * | 2020-09-10 | 2023-04-18 | 深圳市崧盛电子股份有限公司 | Circuit for automatically adjusting output current by low-voltage input and driving power supply |
| CN112737297A (en) * | 2020-12-15 | 2021-04-30 | 广东新昇电业科技股份有限公司 | Driving power supply and method for improving reliability of driving power supply in abnormal environment |
| CN113267990B (en) * | 2021-05-21 | 2024-01-30 | 优利德科技(中国)股份有限公司 | Negative pressure tracking device and negative pressure tracking method |
| CN114488873B (en) * | 2021-12-24 | 2024-05-03 | 深圳市联洲国际技术有限公司 | Control circuit and device |
| CN114679815B (en) * | 2022-04-19 | 2023-05-26 | 珠海市圣昌电子有限公司 | Control circuit capable of changing response speed of feedback loop of LED dimming power supply in real time |
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