Sinusoidal modulation circuit for driving LEDs on optical analytical instrumentation

Abstract

A sinusoidal modulation circuit for driving LEDs on optical analysis instruments includes: a sinusoidal voltage, a conversion circuit structure, a voltage follower, a bypass capacitor, and a light-emitting diode (LED). The sinusoidal voltage is connected to the conversion circuit structure, the voltage follower is connected to the conversion circuit structure, the bypass capacitor is connected to both the conversion circuit structure and the voltage follower, and the LED is connected to both the conversion circuit structure and the voltage follower. The conversion circuit structure includes: resistors R1, R2, R3, and R5, capacitors C1 and C2, and a power operational amplifier. Compared with traditional technologies, this invention reduces total harmonic distortion (THD), eliminates the need to adjust circuit hardware parameters when driving multiple LED loads, simplifies the circuit design, and achieves the function of driving LEDs with a sinusoidal current source at a lower cost.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and more specifically to a sinusoidal modulation circuit for driving LEDs on optical analysis instruments. Background Technology

[0002] There are two common types of sinusoidal modulation circuits for LED drivers: The first type consists of a rectifier module, a phase detection module, a sine wave generation module, a constant current source module, and an LED string. Its principle is that the phase detection module samples the line voltage and outputs the corresponding phase signal to the sine wave generation module. The sine wave generation module then generates the required sine wave signal, which finally controls the constant current source module to adjust the operating current flowing through the LEDs. This ensures that the operating current is a near-sine wave with the same frequency and phase as the line voltage, thereby reducing total harmonic distortion and eliminating LED flicker. However, this principle uses a large number of components and modules, including a rectifier module, phase detection module, sine wave generation module, constant current source driver module, and LED string, resulting in a relatively complex circuit design and higher cost.

[0003] The second circuit consists of dual operational amplifiers (Op-Amplifier 1 and Op-Amplifier 2), an N-channel MOSFET, an LED power supply, and LED chips. Its principle involves a closed-loop feedback circuit formed by the two operational amplifiers (Op-Amplifier 1 and Op-Amplifier 2). Op-Amplifier 1 and a capacitor form an integrating circuit, while Op-Amplifier 2 and some capacitors and resistors form a voltage sampling circuit. This sampled voltage is fed back to Op-Amplifier 1 via Op-Amplifier 2 and compared with a reference voltage. The resulting control voltage adjusts the gate-source voltage of the N-channel MOSFET, which in turn controls the current flowing through the sampling resistor, ultimately achieving constant current control of the LED. However, this principle requires an external power supply and MOSFET to expand the current, and the provided reference voltage is constant. This also results in a constant current value for the constant current source, which cannot be modified, thus limiting its ability to drive only a single LED as a load.

[0004] To address the aforementioned issues, we have made a series of improvements. Summary of the Invention

[0005] The purpose of this invention is to provide a sinusoidal modulation circuit for driving LEDs on optical analysis instruments, so as to overcome the above-mentioned shortcomings and deficiencies of the prior art.

[0006] A sinusoidal modulation circuit for driving LEDs on an optical analysis instrument includes: a sinusoidal voltage, a conversion circuit structure, a voltage follower, a bypass capacitor, and a light-emitting diode. The sinusoidal voltage is connected to the conversion circuit structure, the voltage follower is connected to the conversion circuit structure, the bypass capacitor is connected to both the conversion circuit structure and the voltage follower, and the light-emitting diode is connected to both the conversion circuit structure and the voltage follower.

[0007] The conversion circuit structure includes: resistor R1, resistor R2, resistor R3, resistor R5, capacitor C1, capacitor C2, and a power operational amplifier. One end of resistor R1 and capacitor C1 is connected to a sine wave voltage, and the other end of resistor R1 and capacitor C1 is connected to the positive input terminal of the power operational amplifier. One end of resistor R3 and capacitor C2 is connected to the output terminal of the power operational amplifier. The other end of resistor R2, resistor R3, and capacitor C2 is connected to the negative input terminal of the power operational amplifier. One end of resistor R5 is connected to the output terminal of the power operational amplifier, and the other end of resistor R5 is connected to a light-emitting diode.

[0008] Furthermore, the voltage follower includes: a resistor R4 and a precision operational amplifier. One end of the resistor R4 is connected to the output terminal of the precision operational amplifier, and another end of the resistor R4 is connected to the negative input terminal of the precision operational amplifier. The other end of the resistor R4 is connected to the positive input terminal of the power operational amplifier. The resistor R4 is connected to a resistor R1 and a capacitor C1.

[0009] Furthermore, the bypass capacitors include: capacitor C3, capacitor C4, capacitor C5, and capacitor C6. Capacitors C3 and C4 are connected to the power supply terminal of the power operational amplifier, and capacitors C5 and C6 are connected to the power supply terminal of the precision operational amplifier.

[0010] The beneficial effects of this invention are:

[0011] Compared with traditional technologies, this invention reduces total harmonic distortion, and when driving multiple LED loads, there is no need to adjust the circuit hardware parameters. At the same time, the circuit design is relatively simple, and the function of driving LEDs with a sinusoidal current source is realized at a lower cost. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention.

[0013] Figure label:

[0014] The circuit consists of a sine wave voltage of 100, a conversion circuit structure of 200, a resistor of 210 R1, a resistor of 220 R2, a resistor of 230 R3, a resistor of 240 R5, a capacitor of 250 C1, a capacitor of 260 C2, and a power operational amplifier of 270.

[0015] Voltage follower 300, resistor R4 310 and precision operational amplifier 320.

[0016] Bypass capacitor 400, capacitor C3 410, capacitor C4 420, capacitor C5 430, capacitor C6 440 and LED 500. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] Example 1

[0019] Figure 1 This is a schematic diagram of the structure of the present invention.

[0020] like Figure 1 As shown, the sinusoidal modulation circuit for driving LEDs on an optical analysis instrument includes: a sinusoidal voltage 100, a conversion circuit structure 200, a voltage follower 300, a bypass capacitor 400, and a light-emitting diode 500. The sinusoidal voltage 100 is connected to the conversion circuit structure 200, the voltage follower 300 is connected to the conversion circuit structure 200, the bypass capacitor 400 is connected to both the conversion circuit structure 200 and the voltage follower 300, and the light-emitting diode 500 is connected to both the conversion circuit structure 200 and the voltage follower 300.

[0021] The conversion circuit structure 200 includes: resistor R1 210, resistor R2 220, resistor R3 230, resistor R5 240, capacitor C1 250, capacitor C2 260, and power operational amplifier 270. One end of resistor R1 210 and capacitor C1 250 is connected to the sinusoidal voltage 100, and the other end of resistor R1 210 and capacitor C1 250 is connected to the positive input terminal of power operational amplifier 270. One end of resistor R3 230 and capacitor C2 260 is connected to the output terminal of power operational amplifier 270. The other end of resistor R2 220, resistor R3 230, and capacitor C2 260 is connected to the negative input terminal of power operational amplifier 270. One end of resistor R5 240 is connected to the output terminal of power operational amplifier 270, and the other end of resistor R5 240 is connected to light-emitting diode 500.

[0022] The voltage follower 300 includes: resistor R4 310 and precision operational amplifier 320. One end of resistor R4 310 is connected to the output terminal of precision operational amplifier 320, and another end of resistor R4 310 is connected to the negative input terminal of precision operational amplifier 320. The other end of resistor R4 310 is connected to the positive input terminal of power operational amplifier 270. Resistor R4 310 is connected to resistor R1 210 and capacitor C1 250.

[0023] The bypass capacitor 400 includes: capacitor C3 410, capacitor C4 420, capacitor C5 430 and capacitor C6 440. The capacitors C3 410 and C4 420 are connected to the power supply terminal of the power operational amplifier 270, and the capacitors C5 430 and C6 440 are connected to the power supply terminal of the precision operational amplifier 320.

[0024] The working principle of this invention is as follows: a microcontroller pin outputs a sinusoidal voltage of 100Vin, where Vin <= Vo1 / 2. To prevent waveform distortion, this sinusoidal voltage 100 includes a bias DC voltage component greater than 0V, ensuring that the voltage at the lowest point of the sinusoidal voltage 100 is higher than 0V. This DC-biased sinusoidal voltage 100 is input to the non-inverting input of a power operational amplifier 270 via resistor R1 210 and capacitor C1 250. After processing by the non-inverting adder operational amplifier circuit of the power operational amplifier 270, it outputs a sinusoidal voltage of 100Vo1, where VoL <= Vo1 <= VoH. VoL and VoH are the high and low output voltages of the operational amplifier, respectively. The operational amplifier can only output an undistorted voltage if the value of Vo1 falls within this range. Because this circuit design uses positive and negative feedback, oscillation may occur. To stabilize the circuit, resistor R3 (230Ω) and small-value capacitors C1 (250Ω) and C2 (260Ω) are added, with values ​​approximately 10pF. Based on the operational amplifier's "virtual short" and "virtual open" concepts, the voltage Vo1 = (1 + R3 / R2) * Vp1. The output sinusoidal voltage 100Vo1, after passing through resistor R5 (240Ω), achieves voltage-to-current conversion, forming a constant current source. The current flows from Vo1 to Vp2 through resistor R5 (240Ω).

[0025] The precision operational amplifier 320 and resistor R4 310 form a voltage follower 300. The sinusoidal voltage 100 is passed through resistor R5 240 to acquire the voltage V. L The input is given to the non-inverting input of the precision operational amplifier 320, where |VL| <= |Vo1| - R5*I. The non-inverting input of the precision operational amplifier 320 is Vp2. Voltage V L The voltage range of 1.5V-3.6V, which varies depending on the forward voltage of the load LED, basically covers all LED forward voltage drops. Based on the operational amplifier's concepts of "virtual short" and "virtual open," the output voltage Vo2 of the precision operational amplifier 320 = Vp2. The sampled voltage is fed back to the non-inverting input of the power operational amplifier 270 through the voltage follower 300, forming a closed-loop negative feedback circuit. Therefore,

[0026] Vp1 = [Vin*R4 / (R1+R4)] + [Vp2*R1 / (R1+R4)], the current value of the constant current source I = {(1+R3 / R2)*[Vin*R4 / (R1+R4) + Vp2*R1 / (R1+R4)] - Vp2} / R5. When R1=R2=R3=R4=100K, the current value of the constant current source I = Vin / R5. That is, the current value of the constant current source I = sinusoidal voltage 100Vin / R5. The advantage of a constant current source compared to a constant voltage driving the LED load is that with a constant current source driving the LED load, the number of charge carriers in the PN junction remains constant as the LED reaches its on-state voltage drop, so the luminous intensity of the LED 500 remains constant. However, with a constant voltage driving the LED load, the luminous intensity of the LED 500 changes over time. Therefore, a constant current source is ultimately chosen to drive the LED 500 load. This invention reduces total harmonic distortion, and when driving multiple LED loads, the circuit does not require adjustment of circuit hardware parameters. At the same time, the circuit design is relatively simple, and the function of driving LEDs with a sinusoidal current source is realized at a low cost.

[0027] The specific embodiments of the present invention have been described above, but the present invention is not limited thereto. Various changes can be made to the present invention as long as they do not depart from the spirit of the present invention.

Claims

1. A sinusoidal modulation circuit for driving LEDs on optical analysis instruments, characterized in that, include: The circuit includes a sinusoidal voltage (100), a conversion circuit structure (200), a voltage follower (300), a bypass capacitor (400), and a light-emitting diode (500). The sinusoidal voltage (100) is connected to the conversion circuit structure (200), the voltage follower (300) is connected to the conversion circuit structure (200), the bypass capacitor (400) is connected to both the conversion circuit structure (200) and the voltage follower (300), and the light-emitting diode (500) is connected to both the conversion circuit structure (200) and the voltage follower (300). The conversion circuit structure (200) includes: resistor R1 (210), resistor R2 (220), resistor R3 (230), resistor R5 (240), capacitor C1 (250), capacitor C2 (260), and power operational amplifier (270). One end of resistor R1 (210) and capacitor C1 (250) is connected to a sinusoidal voltage (100), and the other end of resistor R1 (210) and capacitor C1 (250) is connected to power operational amplifier (270). The positive input terminal is connected, one end of the resistor R3 (230) and capacitor C2 (260) is connected to the output terminal of the power operational amplifier (270), the other end of the resistor R2 (220) and resistor R3 (230) and capacitor C2 (260) is connected to the negative input terminal of the power operational amplifier (270), one end of the resistor R5 (240) is connected to the output terminal of the power operational amplifier (270), and the other end of the resistor R5 (240) is connected to the light-emitting diode (500).

2. The sinusoidal modulation circuit for driving LEDs on the optical analysis instrument equipment according to claim 1, characterized in that: The voltage follower (300) includes: a resistor R4 (310) and a precision operational amplifier (320). One end of the resistor R4 (310) is connected to the output terminal of the precision operational amplifier (320), and one end of the resistor R4 (310) is connected to the negative input terminal of the precision operational amplifier (320). The other end of the resistor R4 (310) is connected to the positive input terminal of the power operational amplifier (270). The resistor R4 (310) is connected to a resistor R1 (210) and a capacitor C1 (250).

3. The sinusoidal modulation circuit for driving LEDs on the optical analysis instrument equipment according to claim 2, characterized in that: The bypass capacitor (400) includes: capacitor C3 (410), capacitor C4 (420), capacitor C5 (430) and capacitor C6 (440). The capacitors C3 (410) and C4 (420) are connected to the power supply terminal of the power operational amplifier (270), and the capacitors C5 (430) and C6 (440) are connected to the power supply terminal of the precision operational amplifier (320).

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