CN109168216B - Constant-power LED driving circuit and LED driving power supply - Google Patents

Constant-power LED driving circuit and LED driving power supply Download PDF

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Publication number
CN109168216B
CN109168216B CN201811070446.6A CN201811070446A CN109168216B CN 109168216 B CN109168216 B CN 109168216B CN 201811070446 A CN201811070446 A CN 201811070446A CN 109168216 B CN109168216 B CN 109168216B
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resistor
circuit
voltage
output
operational amplifier
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CN109168216A (en
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邹超洋
王宗友
莫永福
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Shenzhen Sosen Electronics Co Ltd
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Shenzhen Sosen Electronics Co Ltd
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Priority to PCT/CN2019/080579 priority patent/WO2020052223A1/en
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    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00Circuit arrangements for operating light-emitting diodes [LED]

Abstract

The invention relates to a constant-power LED driving circuit and an LED driving power supply, wherein the driving circuit comprises an AC-DC conversion circuit, a reference setting circuit, a current sampling circuit, a voltage sampling circuit, a signal processing circuit and a constant-power regulating circuit; the positive output end of the AC-DC conversion circuit is respectively connected with the input end of the reference setting circuit and the input end of the voltage sampling circuit, and the negative output end of the AC-DC conversion circuit is connected with the input end of the current sampling circuit; the current reference end of the reference setting circuit is connected with the input end of the signal processing circuit, and the voltage reference end of the reference setting circuit is connected with the voltage input end of the voltage sampling circuit; the output end of the current sampling circuit is connected with the output end of the voltage sampling circuit and then connected with the first input end of the constant power regulating circuit; the output end of the signal processing circuit is connected with the second input end of the constant power regulating circuit; the constant power regulating circuit is also connected with the feedback end of the AC-DC conversion circuit. The invention can realize constant power output and improve the application field of power supply.

Description

Constant-power LED driving circuit and LED driving power supply
Technical Field
The invention relates to the technical field of driving power supplies, in particular to a constant-power LED driving circuit and an LED driving power supply.
Background
In daily life, a power supply is generally used to convert a commercially available ac power source (such as ac power from a mains outlet) into a dc power source for supplying to an electrical device. For example, a conversion technique of a power supply used in a personal computer is based on a switching operation using a switching device to provide a plurality of predetermined prepared dc output voltages. This type of power supply is commonly referred to as a switching power supply.
The LED driving power supply is a power supply for converting external primary electric energy into secondary electric energy required by the LEDs. The input power to the LED drive power supply includes alternating current and direct current, while the output power is typically a constant current that varies in voltage as the LED forward voltage varies. The LED driving power supply is mainly applied to the fields of LED illumination, LED display screens and LED backlight, wherein the LED illumination has the highest requirements on the driving control technology, is the current most main application field of the LED driving power supply, and has the most broad market prospect. The stability of the driving power quality is a key factor of the service life of the LED lighting lamp.
Because the LED lamp industry lacks unified standard, the serial and parallel quantity designs of the lamp beads are determined by each manufacturer, so that LED lamp modules designed by most manufacturers are different, great challenges are brought to the universality and the matching performance of the power supply, most of the power supplies used by customers have different requirements on output voltage and output constant current value, and great inconvenience is brought to professional power supply factories in production.
The existing constant power supply technology mainly comprises the steps of manually setting a voltage range, then adjusting an output current value, manually calculating the output voltage multiplied by the current to obtain power, and judging whether the maximum output power value of the power supply is exceeded.
The traditional LED power supply output is divided into two independent units of constant current control and constant voltage control, when the output constant current is adjusted, the constant voltage control is not affected, and because the current specifications of the client-side lamp are different, the product is convenient for a client to apply when in design, the reserved current is adjusted, and when the output current is increased, the risk of over-power application exists in the use process because the voltage is unchanged.
In addition, the constant power circuit of the singlechip is adopted, so that the phenomenon of program run-off or the problem of resetting of the singlechip is always a difficult problem in the industry because the singlechip is in a severe electromagnetic environment and an outdoor unpredictable temperature environment is likely to be caused.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a constant-power LED driving circuit and an LED driving power supply.
The technical scheme adopted for solving the technical problems is as follows: a constant power LED driving circuit is constructed, comprising: an AC-DC conversion circuit, a reference setting circuit, a current sampling circuit, a voltage sampling circuit, a signal processing circuit, and a constant power adjusting circuit;
The positive output end of the AC-DC conversion circuit is respectively connected with the input end of the reference setting circuit and the input end of the voltage sampling circuit, and the negative output end of the AC-DC conversion circuit is connected with the input end of the current sampling circuit; the current reference end of the reference setting circuit is connected with the input end of the signal processing circuit, and the voltage reference end of the reference setting circuit is connected with the voltage input end of the voltage sampling circuit; the output end of the current sampling circuit is connected with the output end of the voltage sampling circuit and then connected with the first input end of the constant power regulating circuit; the output end of the signal processing circuit is connected with the second input end of the constant power regulating circuit; the constant power regulating circuit is also connected with the feedback end of the AC-DC conversion circuit;
the AC-DC conversion circuit is used for converting alternating current into direct current and outputting the direct current to a load, the reference setting circuit is used for generating a reference signal, and the current sampling circuit is used for collecting and amplifying a current signal output by the AC-DC conversion circuit and outputting the amplified current signal to the constant power regulating circuit; the voltage sampling circuit is used for collecting the voltage signal output by the AC-DC conversion circuit and outputting the collected voltage signal to the constant power regulating circuit, the dimming circuit is used for receiving and processing the dimming signal and transmitting the processed dimming signal to the signal processing circuit, and the signal processing circuit is used for receiving the reference signal output by the reference setting circuit and outputting a direct current signal to the constant power regulating circuit; the constant power regulating circuit is used for outputting feedback signals to the AC-DC converting circuit according to the received current signals, voltage signals and direct current signals so as to enable the AC-DC converting circuit to keep constant power output.
Preferably, the method further comprises: a dimming circuit connected to the signal processing circuit;
the dimming circuit is used for receiving and processing the dimming signal and transmitting the processed dimming signal to the signal processing circuit.
Preferably, the reference setting circuit includes: a linear voltage stabilizing circuit, a voltage generating circuit and a reference signal generating circuit;
the input end of the linear voltage stabilizing circuit is connected with the positive output end of the AC-DC conversion circuit, the output end of the linear voltage stabilizing circuit is connected with the input end of the voltage generating circuit, the output end of the voltage generating circuit is connected with the input end of the reference signal generating circuit, the first output end of the reference signal generating circuit is connected with the input end of the signal processing circuit, and the second output end of the reference signal generating circuit is connected with the reference voltage end of the voltage sampling circuit;
the input end of the linear voltage stabilizing circuit is the input end of the reference setting circuit, the first output end of the reference signal generating circuit is the current reference end of the reference setting circuit, and the second output end of the reference signal generating circuit is the voltage reference end of the reference setting circuit.
Preferably, the linear voltage stabilizing circuit includes: resistor R5, triode Q2, voltage stabilizing tube ZD1 and electrolytic capacitor CE3;
the first end of the resistor R5 and the collector of the triode Q2 are connected with the positive output end of the AC-DC conversion circuit, the second end of the resistor R5 and the base of the triode Q2 are connected with the negative electrode of the voltage stabilizing tube ZD1, the positive electrode of the voltage stabilizing tube ZD1 and the second end of the electrolytic capacitor CE3 are grounded, and the emitter of the triode Q2 and the first end of the electrolytic capacitor CE3 are connected with the input end of the voltage generating circuit;
the first end of the resistor R5 and the collector electrode of the triode Q2 are the input end of the linear voltage stabilizing circuit, and the emitter electrode of the triode Q2 and the first end of the electrolytic capacitor CE3 are the output end of the linear voltage stabilizing circuit.
Preferably, the voltage generating circuit includes: resistor R6, reference voltage regulator U2, resistor R7, resistor R8 and capacitor C2;
the first end of the resistor R6 is connected with the input end of the linear voltage stabilizing circuit, the second end of the resistor R6 is respectively connected with the third end of the reference voltage stabilizer U2, the first end of the resistor R7 and the first end of the capacitor C2, the second end of the reference voltage stabilizer U2, the second end of the resistor R8 and the second end of the capacitor C2 are grounded, and the first end of the reference voltage stabilizer U2 is connected with the second end of the resistor R7 and the first end of the resistor R8; the second end of the resistor R6 and the connecting end of the first end of the capacitor C2 are also connected with the input end of the reference signal generating circuit;
The first end of the resistor R6 is an input end of the voltage generating circuit, and the connection end of the second end of the resistor R6 and the first end of the capacitor C2 is an output end of the voltage generating circuit.
Preferably, the reference signal generating circuit includes: resistor R9, adjustable potentiometer VR1 and resistor R10;
the first end of the resistor R9 is connected with the output end of the voltage generation circuit, the second end of the resistor R9 is connected with the first end of the adjustable potentiometer VR1, the second end of the adjustable potentiometer VR1 is connected with the first end of the resistor R10, and the second end of the resistor R10 is grounded; the second end of the resistor R9 and the connecting end of the first end of the adjustable potentiometer VR1 are also connected with the input end of the signal processing circuit, and the second end of the adjustable potentiometer VR1 and the connecting end of the first end of the resistor R10 are also connected with the reference voltage end of the voltage sampling circuit;
the connection end of the second end of the resistor R9 and the first end of the adjustable potentiometer VR1 is the first output end of the reference signal generating circuit, and the connection end of the second end of the adjustable potentiometer VR1 and the first end of the resistor R10 is the second output end of the reference signal generating circuit.
Preferably, the signal processing circuit includes: resistor R24, resistor R25, operational amplifier U5-A, resistor R26 and capacitor C4;
the first end of the resistor R24 is connected with the current reference end of the reference setting circuit, the second end of the resistor R24 is grounded through the capacitor C4, the connecting end of the resistor R24 and the capacitor C4 is connected with the positive input end of the operational amplifier U5-A through the resistor R25, the negative input end of the operational amplifier U5-A is in short circuit with the output end of the operational amplifier U5-A, the output end of the operational amplifier U5-A is connected with the first end of the resistor R26, and the second end of the resistor R26 is connected with the second input end of the constant power regulating circuit; at this time, the first end of the resistor R24 is an input end of the signal processing circuit, and the second end of the resistor R26 is an output end of the signal processing circuit;
or the signal processing circuit comprises a photoelectric coupler OT2-B, a resistor R21, a resistor R22, a MOS tube Q3, a resistor R23, a resistor R24, a resistor R25, a capacitor C4, an operational amplifier U5-A and a resistor R26;
the photoelectric coupler OT2-B is coupled to the dimming circuit, the third end of the photoelectric coupler OT2-B is grounded, the fourth end of the photoelectric coupler OT2-B is connected with the connection node of the resistor R21 and the resistor R22 and is connected to the base electrode of the MOS tube Q3, the first end of the resistor R21 is connected with VCC, the second end of the resistor R22 is grounded, the drain electrode of the MOS tube Q3 is connected with the second end of the resistor R23, the source electrode of the MOS tube Q3 is grounded, the first end of the resistor R23 is connected with the current reference end of the reference setting circuit, the first end of the resistor R24 is connected with the first end of the resistor R23, the second end of the resistor R24 is grounded through the capacitor C4, the connection end of the resistor R24 and the capacitor C4 is connected with the positive input end of the operational amplifier U5-A through the resistor R25, the negative input end of the operational amplifier U5-A is shorted with the output end thereof, the output end of the operational amplifier U5-A is connected with the first end of the resistor R26, and the first end of the constant power regulator circuit is connected with the second end of the resistor R26; at this time, the connection end of the first end of the resistor R23 and the first end of the resistor R24 is the input end of the signal processing circuit, and the second end of the resistor R26 is the output end of the signal processing circuit.
Preferably, the current sampling circuit includes: resistor R11, resistor R12, resistor R13, resistor R14, operational amplifier U4-A and resistor R15;
the first end of the resistor R11 is grounded, the second end of the resistor R11 is connected with the output end of the operational amplifier U4-A through the resistor R14, and the second end of the resistor R11 is also connected with the negative input end of the operational amplifier U4-A; the first end of the resistor R12 is connected with the negative output end of the AC-DC conversion circuit, the second end of the resistor R12 is connected with the positive input end of the operational amplifier U4-A, the positive input end of the operational amplifier U4-A is grounded through the resistor R13, the output end of the operational amplifier U4-A is connected with the first end of the resistor R15, and the second end of the resistor R15 is connected with the first input end of the constant power regulating circuit;
the first end of the resistor R12 is the input end of the current sampling circuit, and the second end of the resistor R15 is the output end of the current sampling circuit;
the voltage sampling circuit includes: resistor R16, resistor R17, resistor R18, resistor R19, capacitor C3, resistor R20 and operational amplifier U4-B;
the first end of the resistor R16 is connected with the positive output end of the AC-DC conversion circuit, the second end of the resistor R16 is connected with the positive input end of the operational amplifier U4-B, the positive input end of the operational amplifier U4-B is grounded through the resistor R17, the first end of the resistor R18 is connected with the voltage reference end of the reference setting circuit, the second end of the resistor R18 is connected with the negative input end of the operational amplifier U4-B, the second end of the resistor R18 is connected with the output end of the operational amplifier U4-B sequentially through the capacitor C3 and the resistor R19, the output end of the operational amplifier U4-B is connected with the first end of the resistor R20, and the second end of the resistor R20 is connected with the output end of the current sampling circuit and then is connected with the first input end of the constant power regulating circuit;
The first end of the resistor R16 is an input end of the voltage sampling circuit, the first end of the resistor R18 is a voltage input end of the voltage sampling circuit, and the second end of the resistor R20 is an output end of the voltage sampling circuit.
Preferably, the constant power regulating circuit includes: a capacitor C5, a resistor R27, a resistor R28, a photoelectric coupler OT1-A and an operational amplifier U5-B;
the capacitor C5 is connected in series with the resistor R27 and then connected in parallel between the negative input end and the output end of the operational amplifier U5-B, the negative input end of the operational amplifier U5-B is also connected with the output end of the current sampling circuit and the output end of the voltage sampling circuit, the positive input end of the operational amplifier U5-B is connected with the output end of the signal processing circuit, the output end of the operational amplifier U5-B is connected with the second end of the photoelectric coupler OT1-A through the resistor R28, the first end of the photoelectric coupler OT1-A is connected with VCC, and the photoelectric coupler OT1-A is coupled to the feedback end of the AC-DC conversion circuit;
the negative input end of the operational amplifier U5-B is a first input end of the constant power regulating circuit, and the positive input end of the operational amplifier U5-B is a second input end of the constant power regulating circuit.
The invention also provides an LED driving power supply, which comprises the constant-power LED driving circuit.
The constant-power LED driving circuit has the following beneficial effects: the invention can realize automatic adjustment of output voltage and output current, realize constant power output, and the output power is irrelevant to the input voltage, thereby greatly improving the application field of the LED driving power supply. In addition, the constant power LED driving circuit adopts a mode of automatically detecting voltage and current, automatically adjusts output voltage and output voltage, and performs constant power control so as to realize the purpose of constant power output, thereby effectively saving labor cost and avoiding misoperation caused by manual operation.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic diagram of a first embodiment of a constant power LED driver circuit of the present invention;
FIG. 2 is a schematic diagram of a second embodiment of a constant power LED driver circuit according to the present invention;
fig. 3 is a schematic circuit diagram of a constant power LED driving circuit according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a schematic diagram of a constant power LED driving circuit according to an embodiment of the present invention is shown. As shown in fig. 1, the constant power LED driving circuit includes: an AC-DC conversion circuit 10, a reference setting circuit 20, a current sampling circuit 40, a voltage sampling circuit 50, a signal processing circuit 60, and a constant power adjusting circuit 70. Wherein, the positive output end (LED+) of the AC-DC conversion circuit 10 is respectively connected with the input end of the reference setting circuit 20 and the input end of the voltage sampling circuit 50, and the negative output end (LED-) of the AC-DC conversion circuit 10 is connected with the input end of the current sampling circuit 40; the current reference terminal of the reference setting circuit 20 is connected with the input terminal of the signal processing circuit 60, and the voltage reference terminal of the reference setting circuit 20 is connected with the voltage input terminal of the voltage sampling circuit 50; the output end of the current sampling circuit 40 is connected with the output end of the voltage sampling circuit 50 and then connected with the first input end of the constant power regulating circuit 70; an output end of the signal processing circuit 60 is connected with a second input end of the constant power regulating circuit 70; the constant power regulating circuit 70 is also connected to the feedback terminal of the AC-DC conversion circuit 10.
In the embodiment of the present invention, the AC-DC conversion circuit 10 is used for converting AC power into DC power and outputting the DC power to a load.
The reference setting circuit 20 is used for generating a reference signal. The reference signals generated by the reference setting circuit 20 include a current reference signal and a voltage reference signal, and the output voltage and the output current of the LED driving power supply can be controlled by generating corresponding current reference signals and voltage reference signals by the reference setting circuit 20.
The current sampling circuit 40 is used for amplifying and collecting the current signal output from the AC-DC conversion circuit 10, and outputting the amplified current signal to the constant power adjustment circuit 70. In the embodiment of the present invention, the current sampling circuit 40 may amplify the collected current signal according to a certain proportion, and then transmit the amplified signal to the constant power adjusting circuit 70, and the constant power adjusting circuit 70 performs corresponding comparison and amplification processing and feeds back the amplified signal to the AC-DC converting circuit 10, so as to adjust the output current of the AC-DC converting circuit 10, thereby achieving the purpose of automatically adjusting the output current of the LED driving power supply. The output current of the AC-DC conversion circuit 10 is the output current of the LED driving power supply.
The voltage sampling circuit 50 is used for collecting the voltage signal output from the AC-DC conversion circuit 10 and outputting the collected voltage signal to the constant power adjustment circuit 70. The voltage sampling circuit 50 can adopt a resistor voltage division mode to feed back the voltage value of the voltage signal output by the AC-DC conversion circuit 10 and the change condition of the voltage signal, and transmit the fed back voltage value or the change condition of the voltage signal to the constant power regulating circuit 70, so as to realize the regulation of the voltage signal output by the AC-DC conversion circuit 10, namely the regulation of the output voltage of the LED driving power supply, and achieve the purpose of automatically regulating the output voltage of the LED driving power supply. The output voltage of the AC-DC conversion circuit 10 is the output voltage of the LED driving power supply.
The signal processing circuit 60 processes and converts the received reference signal output from the reference setting circuit 20 into a dc signal, and sends the dc signal to the constant power adjustment circuit 70.
The constant power regulating circuit 70 is configured to output a feedback signal to the AC-DC converting circuit 10 according to the received current signal, voltage signal, and DC signal, so that the AC-DC converting circuit 10 maintains a constant power output. The feedback signal output by the constant power adjusting circuit 70 is sent to the AC-DC converting circuit 10, so that the AC-DC converting circuit 10 can adjust the output current of the LED driving power according to the actual output signal (voltage signal and current signal) of the LED driving power, so that the LED driving power achieves the purpose of constant power output.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a second embodiment of the constant power LED driving circuit provided by the present invention.
This embodiment further includes, on the basis of the first embodiment: a dimmer circuit 30.
The dimming circuit 30 is connected to the signal processing circuit 60 for receiving and processing the dimming signal and transmitting the processed dimming signal to the signal processing circuit 60. The dimming circuit 30 may process different dimming signals (e.g., any one or more of a resistive dimming signal, a voltage dimming signal, a PWM dimming signal) into a linearly varying PWM dimming signal. Wherein the dimming signal is provided by an external circuit.
The signal processing circuit 60 mainly converts the linearly-varying PWM signal outputted from the dimming circuit 30 into a direct current signal of a certain ratio, and sends the direct current signal to the constant power adjusting circuit 70.
By adding the dimming circuit on the basis of the first embodiment, the constant-power LED driving circuit can adjust the output current of the LED driving power supply according to different dimming signals, so that the LED driving power supply can still realize constant-power output under the action of different dimming signals.
Specifically, referring to fig. 3, a schematic circuit diagram of a preferred embodiment of a constant power LED driving circuit according to an embodiment of the present invention is shown, where the schematic circuit diagram is a dimming constant power output, that is, the constant power can adjust the output current of the LED driving power according to different dimming signals, so that the LED driving power can still achieve constant power output under the action of different dimming signals.
As shown in fig. 3, in the embodiment of the present invention, the AC-DC conversion circuit 10 includes a fuse F1, a common-mode inductor LF1, a rectifier bridge BD1, an electrolytic capacitor CE1, a diode D2, an electrolytic capacitor CE2, a switching MOS Q1, a resistor R4, a photo-coupler OT1-B, and a control IC U1.
The specific working principle is as follows: the alternating current AC passes through a fuse F1 and a common mode inductor LF1 to a rectifier bridge BD1, the rectified voltage filters direct current voltage through an electrolytic capacitor CE1, the filtered direct current voltage is coupled to a secondary side through a transformer according to a certain proportion, the secondary side is rectified through a diode D2, the electrolytic capacitor CE2 filters direct current output voltage and current, a switch MOS tube Q1 controls the output voltage and the output current according to a switch PWM signal, specifically, a photoelectric coupler OT1-B controls a feedback end (FB) of a control IC U1, the control IC U1 outputs a PWM signal to a resistor R3 according to a feedback signal of the feedback end to control the duty ratio of the switch MOS tube Q1, and therefore the purpose of stabilizing the output voltage and the current is achieved, and constant power output is achieved.
In the embodiment of the present invention, the reference setting circuit 20 includes: a linear voltage stabilizing circuit 201, a voltage generating circuit 202, and a reference signal generating circuit 203.
The input end of the linear voltage stabilizing circuit 201 is connected with the positive output end of the AC-DC conversion circuit 10, the output end of the linear voltage stabilizing circuit 201 is connected with the input end of the voltage generating circuit 202, the output end of the voltage generating circuit 202 is connected with the input end of the reference signal generating circuit 203, the first output end of the reference signal generating circuit 203 is connected with the input end of the signal processing circuit 60, and the second output end of the reference signal generating circuit 203 is connected with the reference voltage end of the voltage sampling circuit 50; the input terminal of the linear voltage stabilizing circuit 201 is the input terminal of the reference setting circuit 20, the first output terminal of the reference signal generating circuit 203 is the current reference terminal of the reference setting circuit 20, and the second output terminal of the reference signal generating circuit 203 is the voltage reference terminal of the reference setting circuit 20.
Specifically, as shown in fig. 3, the linear voltage stabilizing circuit 201 includes: resistor R5, triode Q2, voltage regulator ZD1, electrolytic capacitor CE3.
The first end of the resistor R5 and the collector of the triode Q2 are connected with the positive output end of the AC-DC conversion circuit 10 together, the second end of the resistor R5 and the base of the triode Q2 are connected with the negative electrode of the voltage stabilizing tube ZD1 together, the positive electrode of the voltage stabilizing tube ZD1 and the second end of the electrolytic capacitor CE3 are grounded, and the emitter of the triode Q2 and the first end of the electrolytic capacitor CE3 are connected with the input end of the voltage generating circuit 202 together; the first end of the resistor R5 and the collector of the triode Q2 are the input end of the linear voltage stabilizing circuit 201, and the first end of the emitter of the triode Q2 and the electrolytic capacitor CE3 are the output end of the linear voltage stabilizing circuit 201.
The voltage generation circuit 202 includes: resistor R6, reference voltage regulator U2, resistor R7, resistor R8, and capacitor C2.
The first end of the resistor R6 is connected with the input end of the linear voltage stabilizing circuit 201, the second end of the resistor R6 is respectively connected with the third end of the reference voltage stabilizer U2, the first end of the resistor R7 and the first end of the capacitor C2, the second end of the reference voltage stabilizer U2 and the second end of the resistor R8 are grounded, and the first end of the reference voltage stabilizer U2 is connected with the second end of the resistor R7 and the first end of the resistor R8; the second end of the resistor R6 and the connection end of the first end of the capacitor C2 are also connected with the input end of the reference signal generating circuit 203; the first end of the resistor R6 is an input end of the voltage generating circuit 202, and the connection end between the second end of the resistor R6 and the first end of the capacitor C2 is an output end of the voltage generating circuit 202.
The reference signal generating circuit 203 includes: resistor R9, adjustable potentiometer VR1, and resistor R10.
The first end of the resistor R9 is connected with the output end of the voltage generation circuit 202, the second end of the resistor R9 is connected with the first end of the adjustable potentiometer VR1, the second end of the adjustable potentiometer VR1 is connected with the first end of the resistor R10, and the second end of the resistor R10 is grounded; the second end of the resistor R9 and the connecting end of the first end of the adjustable potentiometer VR1 are also connected with the input end of the signal processing circuit 60, and the second end of the adjustable potentiometer VR1 and the connecting end of the first end of the resistor R10 are also connected with the reference voltage end of the voltage sampling circuit 50; the connection between the second end of the resistor R9 and the first end of the adjustable potentiometer VR1 is a first output end of the reference signal generating circuit 203, and the connection between the second end of the adjustable potentiometer VR1 and the first end of the resistor R10 is a second output end of the reference signal generating circuit 203.
The working principle is as follows: the output voltage passes through the linear voltage stabilizing circuit 201 to output a stabilized voltage VCC, which passes through a resistor R6, a reference voltage stabilizer U2 (TL 431), a resistor R7, a resistor R8, and a capacitor C2 to generate a stabilized reference voltage, which outputs a current reference signal (IREF) and a voltage reference signal (VREF) through a resistor R9, an adjustable potentiometer VR1, and a resistor R10. The current reference signal (IREF) and the voltage reference signal (VREF) are obtained by the constant proportional change of the adjustable potentiometer VR1, and the constant output power can be realized by setting the constant maximum output voltage and the constant maximum output current when the adjustable potentiometer VR1 is set to be at a certain potentiometer value.
The stabilized voltage VCC is also transmitted to the control IC U1 and other circuits inside the LED driving power supply, and is used as a power supply voltage for the control IC U1 and other circuits inside the LED driving power supply.
As shown in fig. 3, the signal processing circuit 60 includes a photo coupler OT2-B, a resistor R21, a resistor R22, a MOS transistor Q3, a resistor R23, a resistor R24, a resistor R25, a capacitor C4, an operational amplifier U5-a, and a resistor R26;
the photoelectric coupler OT2-B is coupled to the dimming circuit 30, the third end of the photoelectric coupler OT2-B is grounded, the fourth end of the photoelectric coupler OT2-B is connected with a connecting node of a resistor R21 and a resistor R22 and is connected to a base electrode of a MOS tube Q3, the first end of the resistor R21 is connected with VCC, the second end of the resistor R22 is grounded, the drain electrode of the MOS tube Q3 is connected with the second end of a resistor R23, the source electrode of the MOS tube Q3 is grounded, the first end of the resistor R23 is connected with a current reference end of the reference setting circuit 20, the first end of the resistor R24 is connected with the first end of the resistor R23, the second end of the resistor R24 is grounded through a capacitor C4, the connecting ends of the resistor R24 and the capacitor C4 are connected with the positive input end of an operational amplifier U5-A through a resistor R25, the negative input end of the operational amplifier U5-A is in short circuit with the output end of the operational amplifier U5-A, the output end of the operational amplifier U5-A is connected with the first end of a resistor R26, and the second end of the resistor R26 is connected with the second input end of the constant power regulating circuit 70; the connection between the first end of the resistor R23 and the first end of the resistor R24 is an input end of the signal processing circuit 60, and the second end of the resistor R26 is an output end of the signal processing circuit 60.
The working principle is as follows: the stabilized voltage VCC is passed through resistor R21, resistor R22, photo coupler OT2-B to the base (driving pin) of MOS transistor Q3, and the drain of MOS transistor Q3 is connected to resistor R23 to the current reference signal (IREF). The resistor R23 mainly plays a role in setting the minimum dimming output current. The photo coupler OT2-B receives the linear dimming signal (PWM signal) output by the dimming circuit 30, and after passing the PWM signal through the MOS transistor Q3, makes the current reference signal (IREF) on the first end of the resistor R23 be a PWM voltage with a constant amplitude, the PWM voltage with the constant amplitude is filtered into a dc voltage through the resistor R24 and the capacitor C4, the dc voltage is passed through the resistor R25 to the positive input end of the operational amplifier U5-a, the U5-a realizes voltage following, and outputs a dc voltage signal to the positive input end of the operational amplifier U5-B (i.e., the second input end of the constant power adjusting circuit 70) through the resistor R26.
Of course, it will be appreciated that in other embodiments, when the constant power LED driving circuit is a constant power output LED driving circuit that does not dim, the signal processing circuit 60 only includes: resistor R24, resistor R25, op-amp U5-A, resistor R26 and capacitor C4.
The first end of the resistor R24 is connected with the current reference end of the reference setting circuit 20, the second end of the resistor R24 is grounded through the capacitor C4, the connection end of the resistor R24 and the capacitor C4 is connected with the positive input end of the operational amplifier U5-A through the resistor R25, the negative input end of the operational amplifier U5-A is in short circuit with the output end of the operational amplifier U5-A, the output end of the operational amplifier U5-A is connected with the first end of the resistor R26, and the second end of the resistor R26 is connected with the second input end of the constant power regulating circuit; at this time, the first end of the resistor R24 is an input end of the signal processing circuit 60, and the second end of the resistor R26 is an output end of the signal processing circuit 60; also, in this embodiment, the resistance R24 is 0 ohm.
As shown in fig. 3, in the embodiment of the present invention, the current sampling circuit 40 includes: resistor R11, resistor R12, resistor R13, resistor R14, operational amplifier U4-A, and resistor R15.
The first end of the resistor R11 is grounded, the second end of the resistor R11 is connected with the output end of the operational amplifier U4-A through the resistor R14, and the second end of the resistor R11 is also connected with the negative input end of the operational amplifier U4-A; the first end of the resistor R12 is connected with the negative output end of the AC-DC conversion circuit 10, the second end of the resistor R12 is connected with the positive input end of the operational amplifier U4-A, the positive input end of the operational amplifier U4-A is grounded through the resistor R13, the output end of the operational amplifier U4-A is connected with the first end of the resistor R15, and the second end of the resistor R15 is connected with the first input end of the constant power regulating circuit 70; the first end of the resistor R12 is an input end of the current sampling circuit 40, and the second end of the resistor R15 is an output end of the current sampling circuit 40.
The working principle is as follows: the signal at the negative output end of the AC-DC conversion circuit 10 is passed through a resistor R12 and a resistor R13 to the positive input end of an operational amplifier U4-a, the negative input end of U4-a is grounded by a resistor R11, and the negative input end of U4-a is connected with a resistor R14, so that the sampling of the small current signal is realized and the voltage is amplified to a certain ratio by the operational amplifier U4-a, and the voltage with the ratio is output to the negative input end of the operational amplifier U5-B (i.e., the first input end of the constant power regulating circuit 70) through a resistor R15.
As shown in fig. 3, in the embodiment of the present invention, the voltage sampling circuit 50 includes: resistor R16, resistor R17, resistor R18, resistor R19, capacitor C3, resistor R20, and operational amplifier U4-B.
The first end of the resistor R16 is connected with the positive output end of the AC-DC conversion circuit 10, the second end of the resistor R16 is connected with the positive input end of the operational amplifier U4-B, the positive input end of the operational amplifier U4-B is grounded through the resistor R17, the first end of the resistor R18 is connected with the voltage reference end of the reference setting circuit 20, the second end of the resistor R18 is connected with the negative input end of the operational amplifier U4-B, the second end of the resistor R18 is connected with the output end of the operational amplifier U4-B through the capacitor C3 and the resistor R19 in sequence, the output end of the operational amplifier U4-B is connected with the first end of the resistor R20, and the second end of the resistor R20 is connected with the first input end of the constant power regulating circuit 70 after being connected with the output end of the current sampling circuit 40; the first end of the resistor R16 is an input end of the voltage sampling circuit 50, the first end of the resistor R18 is a voltage input end of the voltage sampling circuit 50, and the second end of the resistor R20 is an output end of the voltage sampling circuit 50.
As shown in fig. 3, in the embodiment of the present invention, the constant power adjusting circuit 70 includes: a capacitor C5, a resistor R27, a resistor R28, a photoelectric coupler OT1-A and an operational amplifier U5-B.
After being connected in series with a resistor R27, a capacitor C5 is connected in parallel between the negative input end and the output end of an operational amplifier U5-B, the negative input end of the operational amplifier U5-B is also connected with the output end of a current sampling circuit 40 and the output end of a voltage sampling circuit 50, the positive input end of the operational amplifier U5-B is connected with the output end of a signal processing circuit 60, the output end of the operational amplifier U5-B is connected with the second end of a photoelectric coupler OT1-A through a resistor R28, the first end of the photoelectric coupler OT1-A is connected with VCC, and the photoelectric coupler OT1-A is coupled to the feedback end of an AC-DC conversion circuit 10; the negative input of the operational amplifier U5-B is the first input of the constant power regulating circuit 70, and the positive input of the operational amplifier U5-B is the second input of the constant power regulating circuit 70.
The working principle is as follows: the signal output by the current sampling circuit 40 is input to the negative input end of the operational amplifier U5-B, and the signal output by the voltage sampling circuit 50 is input to the negative input end of the operational amplifier U5-B; the direct-current voltage signal output by the signal processing circuit 60 is output to the positive input end of the operational amplifier U5-B through the resistor R26; the operational amplifier U5-B performs loop compensation through a resistor R27 and a capacitor C5, the output end of the operational amplifier U5-B is connected to the photoelectric coupler OT1-A through a resistor R28, a feedback signal is coupled to the photoelectric coupler OT1-B through the photoelectric coupler OT1-A, the feedback signal is fed back to the feedback end (FB) of the control IC U1 through the photoelectric coupler OT1-B, the control IC U1 outputs a PWM signal to the resistor R3 according to the feedback signal of the feedback end to control the duty ratio of the switching MOS tube Q1, and therefore the purposes of stabilizing output voltage and current are achieved, and constant power output is achieved. Here, when the dimming circuit 30 receives any one of the PWM dimming signal, the voltage dimming signal, and the resistance dimming signal, the constant power LED driving circuit of the present invention can stably linearly scale the output voltage and the output current of the LED driving power source, thereby realizing constant power output.
The constant-power LED driving circuit uses the pure analog circuits of the operational amplifier and the sensor, can automatically adjust the output voltage and the output current, realizes constant output of the output power through different positions of the operational amplifier, has no relation with the input voltage, and can greatly improve the application field of the LED driving power supply. Meanwhile, the invention adopts the design of automatically detecting the output voltage and the output current, automatically adjusts the output voltage and the output current in real time according to the actual change of the output voltage and the output current, realizes the purpose of constant current output, does not need manual adjustment, effectively saves labor cost and can avoid errors caused by manual operation.
In addition, the constant-power LED driving circuit can widen the working range of a single LED power supply, so that the constant-power LED driving circuit is suitable for wider voltage and current ranges, the number of single series of machine types is reduced, lamps can be matched more flexibly, and the stock quantity of customers is reduced.
The invention also discloses an LED driving power supply, which comprises the constant-power LED driving circuit. By setting the constant-power LED driving circuit, the LED driving power supply can realize constant-power output and can automatically adjust output voltage and output current.
The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same according to the content of the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made with the scope of the claims should be covered by the claims.
It will be understood that modifications and variations will be apparent to those skilled in the art from the foregoing description, and it is intended that all such modifications and variations be included within the scope of the following claims.

Claims (8)

1. A constant power LED driving circuit, comprising: an AC-DC conversion circuit, a reference setting circuit, a current sampling circuit, a voltage sampling circuit, a signal processing circuit, a constant power adjusting circuit and a dimming circuit connected with the signal processing circuit;
the positive output end of the AC-DC conversion circuit is respectively connected with the input end of the reference setting circuit and the input end of the voltage sampling circuit, and the negative output end of the AC-DC conversion circuit is connected with the input end of the current sampling circuit; the current reference end of the reference setting circuit is connected with the input end of the signal processing circuit, and the voltage reference end of the reference setting circuit is connected with the voltage input end of the voltage sampling circuit; the output end of the current sampling circuit is connected with the output end of the voltage sampling circuit and then connected with the first input end of the constant power regulating circuit; the output end of the signal processing circuit is connected with the second input end of the constant power regulating circuit; the constant power regulating circuit is also connected with the feedback end of the AC-DC conversion circuit;
The AC-DC conversion circuit is used for converting alternating current into direct current and outputting the direct current to a load, the reference setting circuit is used for generating a reference signal, and the current sampling circuit is used for collecting and amplifying a current signal output by the AC-DC conversion circuit and outputting the amplified current signal to the constant power regulating circuit; the voltage sampling circuit is used for collecting the voltage signal output by the AC-DC conversion circuit and outputting the collected voltage signal to the constant power regulating circuit, and the signal processing circuit is used for receiving the reference signal output by the reference setting circuit and outputting a direct current signal to the constant power regulating circuit; the constant power regulating circuit is used for outputting feedback signals to the AC-DC conversion circuit according to the received current signals, voltage signals and direct current signals so as to enable the AC-DC conversion circuit to keep constant power output; the dimming circuit is used for receiving and processing the dimming signal and transmitting the processed dimming signal to the signal processing circuit;
the reference setting circuit includes: a linear voltage stabilizing circuit, a voltage generating circuit and a reference signal generating circuit;
the input end of the linear voltage stabilizing circuit is connected with the positive output end of the AC-DC conversion circuit, the output end of the linear voltage stabilizing circuit is connected with the input end of the voltage generating circuit, the output end of the voltage generating circuit is connected with the input end of the reference signal generating circuit, the first output end of the reference signal generating circuit is connected with the input end of the signal processing circuit, and the second output end of the reference signal generating circuit is connected with the reference voltage end of the voltage sampling circuit;
The input end of the linear voltage stabilizing circuit is the input end of the reference setting circuit, the first output end of the reference signal generating circuit is the current reference end of the reference setting circuit, and the second output end of the reference signal generating circuit is the voltage reference end of the reference setting circuit.
2. The constant power LED driving circuit according to claim 1, wherein the linear voltage stabilizing circuit comprises: resistor R5, triode Q2, voltage stabilizing tube ZD1 and electrolytic capacitor CE3;
the first end of the resistor R5 and the collector of the triode Q2 are connected with the positive output end of the AC-DC conversion circuit, the second end of the resistor R5 and the base of the triode Q2 are connected with the negative electrode of the voltage stabilizing tube ZD1, the positive electrode of the voltage stabilizing tube ZD1 and the second end of the electrolytic capacitor CE3 are grounded, and the emitter of the triode Q2 and the first end of the electrolytic capacitor CE3 are connected with the input end of the voltage generating circuit;
the first end of the resistor R5 and the collector electrode of the triode Q2 are the input end of the linear voltage stabilizing circuit, and the emitter electrode of the triode Q2 and the first end of the electrolytic capacitor CE3 are the output end of the linear voltage stabilizing circuit.
3. The constant power LED driving circuit according to claim 1, wherein the voltage generating circuit comprises: resistor R6, reference voltage regulator U2, resistor R7, resistor R8 and capacitor C2;
the first end of the resistor R6 is connected with the input end of the linear voltage stabilizing circuit, the second end of the resistor R6 is respectively connected with the third end of the reference voltage stabilizer U2, the first end of the resistor R7 and the first end of the capacitor C2, the second end of the reference voltage stabilizer U2, the second end of the resistor R8 and the second end of the capacitor C2 are grounded, and the first end of the reference voltage stabilizer U2 is connected with the second end of the resistor R7 and the first end of the resistor R8; the second end of the resistor R6 and the connecting end of the first end of the capacitor C2 are also connected with the input end of the reference signal generating circuit;
the first end of the resistor R6 is an input end of the voltage generating circuit, and the connection end of the second end of the resistor R6 and the first end of the capacitor C2 is an output end of the voltage generating circuit.
4. The constant power LED driving circuit according to claim 1, wherein the reference signal generating circuit comprises: resistor R9, adjustable potentiometer VR1 and resistor R10;
The first end of the resistor R9 is connected with the output end of the voltage generation circuit, the second end of the resistor R9 is connected with the first end of the adjustable potentiometer VR1, the second end of the adjustable potentiometer VR1 is connected with the first end of the resistor R10, and the second end of the resistor R10 is grounded; the second end of the resistor R9 and the connecting end of the first end of the adjustable potentiometer VR1 are also connected with the input end of the signal processing circuit, and the second end of the adjustable potentiometer VR1 and the connecting end of the first end of the resistor R10 are also connected with the reference voltage end of the voltage sampling circuit;
the connection end of the second end of the resistor R9 and the first end of the adjustable potentiometer VR1 is the first output end of the reference signal generating circuit, and the connection end of the second end of the adjustable potentiometer VR1 and the first end of the resistor R10 is the second output end of the reference signal generating circuit.
5. The constant power LED driving circuit according to claim 1, wherein the signal processing circuit comprises: resistor R24, resistor R25, operational amplifier U5-A, resistor R26 and capacitor C4;
the first end of the resistor R24 is connected with the current reference end of the reference setting circuit, the second end of the resistor R24 is grounded through the capacitor C4, the connecting end of the resistor R24 and the capacitor C4 is connected with the positive input end of the operational amplifier U5-A through the resistor R25, the negative input end of the operational amplifier U5-A is in short circuit with the output end of the operational amplifier U5-A, the output end of the operational amplifier U5-A is connected with the first end of the resistor R26, and the second end of the resistor R26 is connected with the second input end of the constant power regulating circuit; at this time, the first end of the resistor R24 is an input end of the signal processing circuit, and the second end of the resistor R26 is an output end of the signal processing circuit;
Alternatively, the signal processing circuit includes: the photoelectric coupler OT2-B, the resistor R21, the resistor R22, the MOS tube Q3, the resistor R23, the resistor R24, the resistor R25, the operational amplifier U5-A, the resistor R26 and the capacitor C4;
the photoelectric coupler OT2-B is coupled to the dimming circuit, the third end of the photoelectric coupler OT2-B is grounded, the fourth end of the photoelectric coupler OT2-B is connected with the connection node of the resistor R21 and the resistor R22 and is connected to the base electrode of the MOS tube Q3, the first end of the resistor R21 is connected with VCC, the second end of the resistor R22 is grounded, the drain electrode of the MOS tube Q3 is connected with the second end of the resistor R23, the source electrode of the MOS tube Q3 is grounded, the first end of the resistor R23 is connected with the current reference end of the reference setting circuit, the first end of the resistor R24 is connected with the first end of the resistor R23, the second end of the resistor R24 is grounded through the capacitor C4, the connection end of the resistor R24 and the capacitor C4 is connected with the positive input end of the operational amplifier U5-A through the resistor R25, the negative input end of the operational amplifier U5-A is shorted with the output end thereof, the output end of the operational amplifier U5-A is connected with the first end of the resistor R26, and the first end of the constant power regulator circuit is connected with the second end of the resistor R26; at this time, the connection end of the first end of the resistor R23 and the first end of the resistor R24 is the input end of the signal processing circuit, and the second end of the resistor R26 is the output end of the signal processing circuit.
6. The constant power LED driving circuit of claim 1, wherein the current sampling circuit comprises: resistor R11, resistor R12, resistor R13, resistor R14, operational amplifier U4-A and resistor R15;
the first end of the resistor R11 is grounded, the second end of the resistor R11 is connected with the output end of the operational amplifier U4-A through the resistor R14, and the second end of the resistor R11 is also connected with the negative input end of the operational amplifier U4-A; the first end of the resistor R12 is connected with the negative output end of the AC-DC conversion circuit, the second end of the resistor R12 is connected with the positive input end of the operational amplifier U4-A, the positive input end of the operational amplifier U4-A is grounded through the resistor R13, the output end of the operational amplifier U4-A is connected with the first end of the resistor R15, and the second end of the resistor R15 is connected with the first input end of the constant power regulating circuit;
the first end of the resistor R12 is the input end of the current sampling circuit, and the second end of the resistor R15 is the output end of the current sampling circuit;
the voltage sampling circuit includes: resistor R16, resistor R17, resistor R18, resistor R19, capacitor C3, resistor R20 and operational amplifier U4-B;
The first end of the resistor R16 is connected with the positive output end of the AC-DC conversion circuit, the second end of the resistor R16 is connected with the positive input end of the operational amplifier U4-B, the positive input end of the operational amplifier U4-B is grounded through the resistor R17, the first end of the resistor R18 is connected with the voltage reference end of the reference setting circuit, the second end of the resistor R18 is connected with the negative input end of the operational amplifier U4-B, the second end of the resistor R18 is connected with the output end of the operational amplifier U4-B sequentially through the capacitor C3 and the resistor R19, the output end of the operational amplifier U4-B is connected with the first end of the resistor R20, and the second end of the resistor R20 is connected with the output end of the current sampling circuit and then is connected with the first input end of the constant power regulating circuit;
the first end of the resistor R16 is an input end of the voltage sampling circuit, the first end of the resistor R18 is a voltage input end of the voltage sampling circuit, and the second end of the resistor R20 is an output end of the voltage sampling circuit.
7. The constant power LED driving circuit according to claim 1, wherein the constant power adjusting circuit comprises: a capacitor C5, a resistor R27, a resistor R28, a photoelectric coupler OT1-A and an operational amplifier U5-B;
The capacitor C5 is connected in series with the resistor R27 and then connected in parallel between the negative input end and the output end of the operational amplifier U5-B, the negative input end of the operational amplifier U5-B is also connected with the output end of the current sampling circuit and the output end of the voltage sampling circuit, the positive input end of the operational amplifier U5-B is connected with the output end of the signal processing circuit, the output end of the operational amplifier U5-B is connected with the second end of the photoelectric coupler OT1-A through the resistor R28, the first end of the photoelectric coupler OT1-A is connected with VCC, and the photoelectric coupler OT1-A is coupled to the feedback end of the AC-DC conversion circuit;
the negative input end of the operational amplifier U5-B is a first input end of the constant power regulating circuit, and the positive input end of the operational amplifier U5-B is a second input end of the constant power regulating circuit.
8. An LED driving power supply comprising a constant power LED driving circuit according to any one of claims 1-7.
CN201811070446.6A 2018-09-13 2018-09-13 Constant-power LED driving circuit and LED driving power supply Active CN109168216B (en)

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