A voltage sampling tracking adjustment circuit

Abstract

A voltage sampling tracking adjustment circuit, comprising an input end, the input end outputs voltage to a plurality of LEDs through an AC / DC constant voltage converter; one end of the AC / DC constant voltage converter is connected with the light-emitting positive electrode of a photo-coupler U2, and the negative electrode is grounded; one end of the output end of the AC / DC constant voltage converter is connected with the collector of the photo-coupler U2 through a resistor R7, and the emitter of the photo-coupler U2 is grounded through a reference unit; one end of the output end of the AC / DC constant voltage converter is connected with the emitter of a triode Q1 through a resistor R1, the collector of the triode Q1 is connected with the reference end of the reference unit, and one end of the output end of the AC / DC constant voltage converter is also connected with the base of the triode Q1 through a resistor R2; the resistor R2 is also connected with the collector of a triode Q2, the emitter of the triode Q2 is grounded, and the base is connected with the output end of an operational amplifier U1 through a MOS tube Q3; the inverting end of the operational amplifier U1 is connected with the output end, the non-inverting end is connected with a voltage Vup through a resistor R5, and the resistor R5 is also connected with the plurality of LEDs.

Description

Technical Field

[0001] This invention relates to the field of LED driver power supply technology, specifically a voltage sampling and tracking adjustment circuit. Background Technology

[0002] Linear constant current chips are increasingly favored in LED applications due to their excellent constant current accuracy control and superior dimming performance. However, the large range of voltage distribution between LED power supply and LED chips can lead to relatively high operating voltages at the ends of linear chips. In this case, the linear chip suffers from excessive power loss, resulting in severe heat generation and reduced power efficiency. In severe cases, it may trigger the over-temperature protection or over-temperature current reduction function of the linear chip, affecting normal use and significantly limiting its application.

[0003] The commonly used solution is to use multiple chips in parallel to share the power loss. Another method is to manually adjust the power supply voltage according to the different LED voltages to achieve more accurate control of the operating voltage across the linear chip.

[0004] The specific drawbacks are: 1. While parallel connection of multiple linear constant current chips to share heat can solve the heat dissipation problem, the high heat generation leads to low power supply efficiency, which is inconvenient for users or may not meet requirements. 2. Manually adjusting the power supply voltage according to different LED voltages is a rather troublesome method during production and is not conducive to mass production.

[0005] 3. Even if the power supply voltage is manually adjusted, after working for a period of time, the voltage of the LED beads will decrease due to their own heat generation, resulting in greater chip loss and heat generation. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a voltage sampling and tracking adjustment circuit, including an input terminal, which outputs voltage to multiple LEDs via an AC / DC constant voltage converter; One end of the AC / DC constant voltage converter is connected to the positive terminal of the light-emitting terminal of the optocoupler U2, and the negative terminal is grounded. One end of the output terminal of the AC / DC constant voltage converter is connected to the collector of the optocoupler U2 through resistor R7. The emitter of the optocoupler U2 is grounded through the reference unit. One end of the output terminal of the AC / DC constant voltage converter is connected to the emitter of transistor Q1 through resistor R1, the collector of transistor Q1 is connected to the reference terminal of the reference unit, and the other end of the output terminal of the AC / DC constant voltage converter is also connected to the base of transistor Q1 through resistor R2. The resistor R2 is also connected to the collector of the transistor Q2, the emitter of the transistor Q2 is grounded, and the base is connected to the output of the operational amplifier U1 through the MOS transistor Q3. The inverting input of the operational amplifier U1 is connected to the output, and the non-inverting input is connected to the voltage Vup through a resistor R5. The resistor R5 is also connected to multiple LEDs.

[0007] In some embodiments, one end of the output terminal of the AC / DC constant voltage converter is grounded through resistors R10 and R11 in sequence, wherein resistor R10 is also connected to the reference unit through capacitor C2 and resistor R9.

[0008] In some embodiments, the base of the transistor Q2 is grounded through capacitor C1 and resistor R3.

[0009] In some embodiments, the other end of the output terminal of the AC / DC constant voltage converter is provided with a plurality of constant current circuits corresponding one-to-one with LEDs.

[0010] Beneficial effects

[0011] This invention provides a voltage sampling and tracking adjustment circuit. Compared with the prior art, it has the following advantages: This application designs a sampling tracking adjustment circuit. When using a linear constant current chip, this circuit can automatically adjust the power supply voltage according to different power supply voltages and LED bead voltages, keeping the voltage across the linear chip at a low value, reducing heat generation, improving driving efficiency, and expanding the application range of the linear chip. Attached Figure Description

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

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Please see Figure 1 The present invention provides a technical solution: a voltage sampling and tracking adjustment circuit includes an input terminal, wherein the input terminal outputs voltage to multiple LEDs through an AC / DC constant voltage converter; One end of the AC / DC constant voltage converter is connected to the positive terminal of the light-emitting terminal of the optocoupler U2, and the negative terminal is grounded. One end of the output terminal of the AC / DC constant voltage converter is connected to the collector of the optocoupler U2 through resistor R7. The emitter of the optocoupler U2 is grounded through the reference unit. One end of the output terminal of the AC / DC constant voltage converter is connected to the emitter of transistor Q1 through resistor R1, the collector of transistor Q1 is connected to the reference terminal of the reference unit, and the other end of the output terminal of the AC / DC constant voltage converter is also connected to the base of transistor Q1 through resistor R2. The resistor R2 is also connected to the collector of the transistor Q2, the emitter of the transistor Q2 is grounded, and the base is connected to the output of the operational amplifier U1 through the MOS transistor Q3. The inverting input of the operational amplifier U1 is connected to the output, and the non-inverting input is connected to the voltage Vup through a resistor R5. The resistor R5 is also connected to multiple LEDs.

[0015] In this embodiment, one end of the output terminal of the AC / DC constant voltage converter is grounded through resistors R10 and R11 in sequence, wherein resistor R10 is also connected to the reference unit through capacitor C2 and resistor R9.

[0016] In this embodiment, the base of the transistor Q2 is grounded through capacitor C1 and resistor R3.

[0017] In this embodiment, the other end of the output terminal of the AC / DC constant voltage converter is provided with multiple constant current circuits corresponding to LEDs.

[0018] Referring to the attached diagram, LED+ is the output voltage of the AC / DC constant voltage converter, and also the power supply voltage for the LED beads and the linear constant current circuit. Constant current circuits 1-n are linear constant current circuits; V1-Vn are the voltages across linear constant current circuits 1-n respectively. The voltage at point A is the base voltage of transistor Q2, serving as the reference voltage for V1-Vn sampling and tracking adjustment. Vup is the pull-up voltage (powered by other lines). The constant holding value set for the linear constant current circuits V1-Vn must be lower than the Vup voltage. The voltage at point B in the circuit is tracked and output to point C by operational amplifier U1. The voltage at point C is divided and filtered by R3, R4, and C1, and then fed to point A for comparison. The comparison result affects the collector voltage of Q2 at point D (i.e., the base voltage of Q1). Q1 outputs a feedback signal Vf based on the voltage at point D, which is given to the control loop to adjust the output voltage of the AC / DC constant voltage converter. Changes in the output voltage of the AC / DC constant voltage converter will cause changes in the voltages of V1-Vn, thus achieving the purpose of adjusting V1-Vn. In the initial power-on state, LED+ is at the set maximum value, the PWM signal is set to low level, and the voltage at point B is pulled high to Vup. When the linear constant current circuit 1-n is turned on, the PWM signal is simultaneously set to high level. At this time, the voltage values ​​of V1-Vn will be higher than the voltage at point B. The voltage of LED+ continues to decrease under the feedback effect of the voltage of Vnp. When the voltage of V1-Vn drops below the voltage of VB, the voltage at point B will automatically follow the lowest value among V1-Vn. Finally, the voltage values ​​of V1-Vn will be fixed near the set expected voltage value.

[0019] Since the losses of a linear chip are mainly the product of the voltage difference between its two ends (LED + voltage minus LED bead voltage) and the current flowing through it (i.e., the current of the LED bead), when the maximum current of the LED bead is fixed, the greater the operating voltage across the linear chip, the greater the losses and the higher the chip heats up. In severe cases, this can lead to overheating protection or even damage to the chip.

[0020] Based on the above principles, if the power supply voltage LED+ to the LED bead is constant, the linear chip will overheat significantly when the LED bead voltage is low due to the wide voltage distribution range of the LED bead (e.g., the voltage distribution range of a typical COB LED bead in a downlight is generally 33-38V). This invention fundamentally solves this problem. Without the circuit of this invention, the operating voltage of the linear chip would also vary depending on the LED bead voltage. The circuit of this invention automatically adjusts the LED+ voltage value in real time based on the sampled operating voltage across the linear chip. For example, if an increase in the voltage across the linear chip is detected, the LED+ voltage is lowered; conversely, the output voltage of LED+ is increased. This ensures that the operating voltage across the linear chip is ultimately maintained at a relatively ideal set value. This value guarantees both the normal operation of the linear chip and keeps its heat generation within a reasonable range, thereby ensuring the normal and safe operation of the circuit.

[0021] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

Claims

1. A voltage sampling and tracking adjustment circuit, characterized in that: Includes an input terminal, which outputs voltage to multiple LEDs via an AC / DC constant voltage converter; One end of the AC / DC constant voltage converter is connected to the positive terminal of the light-emitting terminal of the optocoupler U2, and the negative terminal is grounded. One end of the output terminal of the AC / DC constant voltage converter is connected to the collector of the optocoupler U2 through resistor R7. The emitter of the optocoupler U2 is grounded through the reference unit. One end of the output terminal of the AC / DC constant voltage converter is connected to the emitter of transistor Q1 through resistor R1, the collector of transistor Q1 is connected to the reference terminal of the reference unit, and the other end of the output terminal of the AC / DC constant voltage converter is also connected to the base of transistor Q1 through resistor R2. The resistor R2 is also connected to the collector of the transistor Q2, the emitter of the transistor Q2 is grounded, and the base is connected to the output of the operational amplifier U1 through the MOS transistor Q3. The inverting input of the operational amplifier U1 is connected to the output, and the non-inverting input is connected to the voltage Vup through a resistor R5. The resistor R5 is also connected to multiple LEDs.

2. The voltage sampling and tracking adjustment circuit according to claim 1, characterized in that: One end of the output terminal of the AC / DC constant voltage converter is grounded through resistors R10 and R11 in sequence, wherein resistor R10 is also connected to the reference unit through capacitor C2 and resistor R9.

3. The voltage sampling and tracking adjustment circuit according to claim 1, characterized in that: The base of the transistor Q2 is grounded through capacitor C1 and resistor R3.

4. The voltage sampling and tracking adjustment circuit according to claim 1, characterized in that: The output terminal of the AC / DC constant voltage converter is equipped with multiple constant current circuits corresponding to LEDs.

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