Output voltage automatic regulating circuit and lighting lamp

Abstract

The invention provides an output voltage automatic regulation circuit and an illumination lamp, and the circuit comprises a constant voltage module which is used for converting an external alternating current into a constant voltage direct current; the linear constant current module is used for converting the constant voltage direct current into constant current; a voltage threshold value is set in the MCU control module, and the MCU control module is used for detecting the voltage to ground of the linear constant current module and outputting a PWM signal with a corresponding duty ratio according to a comparison result of the voltage to ground and the voltage threshold value; and the constant-voltage loop regulation module is connected in series between the MCU control module and the constant-voltage module and is used for receiving the PWM signal and carrying out voltage division and RC filtering on the PWM signal to obtain a processing voltage, and the processing voltage is used as a reference voltage of an operational amplifier in the constant-voltage loop regulation module. Compared with the prior art, the output voltage of the constant-voltage module can be intelligently and dynamically adjusted in real time, the loss of the linear constant-current module is reduced, and the purposes of improving the driving efficiency and reducing heating are achieved.

Description

TECHNICAL FIELD

[0001] The application relates to an output voltage automatic regulating circuit and a lighting lamp, and belongs to the technical field of lamp driving. BACKGROUND

[0002] With the improvement of living standards, LED lighting is increasingly applied in many scenes, and intelligent lighting solutions with MCUs also appear in more application scenarios.

[0003] Constant voltage + linear constant current driving is one of many LED driving solutions. In this solution, the linear constant current IC sets the constant current value of the LED. Since the linear constant current IC works in the linear region, its loss is the voltage multiplied by the LED current. The voltage of the front-stage constant voltage part is usually fixed, but the Vf values of the LED particles in different LED lamps are different, the number is different, and the working environment is different, resulting in different voltages added to the linear constant current IC. The higher the voltage of the linear constant current IC, the greater the loss, the lower the driving efficiency, and the greater the heat generation.

[0004] Therefore, it is necessary to provide a novel output voltage automatic regulating circuit to solve the above problems. SUMMARY

[0005] The application aims to provide an output voltage automatic regulating circuit to reduce the loss of the linear constant current module, so as to improve the driving efficiency and reduce the heat generation.

[0006] To achieve the above-mentioned purpose, the application provides an output voltage automatic regulating circuit applied to a lighting lamp, comprising:

[0007] A constant voltage module is configured to convert external alternating current into constant voltage direct current.

[0008] A linear constant current module is connected in series with the LED light source and connected to the output end of the constant voltage module, and is configured to convert the constant voltage direct current into constant current to supply power to the LED light source.

[0009] An MCU control module is connected with the linear constant current module and internally set with a voltage threshold, and is configured to detect the voltage of the linear constant current module to ground and output a PWM signal with a corresponding duty cycle according to the comparison result of the voltage to ground and the voltage threshold.

[0010] A constant voltage loop regulating module is connected in series between the MCU control module and the constant voltage module, and is configured to receive the PWM signal, divide and RC filter the PWM signal to obtain a processing voltage, take the processing voltage as the reference voltage of an operational amplifier in the constant voltage loop regulating module, and make the constant voltage module output a voltage according to the reference voltage.

[0011] As a further improvement of the present application, it further comprises a voltage detection line connected between the MCU control module and the linear constant current module, for detecting the voltage of the linear constant current module to ground.

[0012] As a further improvement of the present application, when the MCU control module outputs the PWM signal with the corresponding duty cycle according to the comparison result of the voltage to ground and the voltage threshold, it further comprises that the MCU control module detects, divides and ADC converts the voltage of the linear constant current module to ground, forms a digital voltage, compares it with the voltage threshold, and the voltage threshold comprises a maximum voltage threshold and a minimum threshold; when the digital voltage is greater than the maximum voltage threshold, the MCU control module reduces the duty cycle of the current PWM signal; when the digital voltage is less than the minimum voltage threshold, the MCU control module increases the duty cycle of the current PWM signal.

[0013] As a further improvement of the present application, the constant voltage loop adjustment module comprises:

[0014] an operational amplifier;

[0015] peripheral elements, including a first voltage dividing resistor, a second voltage dividing resistor and a first filter capacitor, one end of the first voltage dividing resistor is connected with the positive input terminal of the operational amplifier, the other end of the first voltage dividing resistor is connected with the PWM output port of the MCU control module, the second voltage dividing resistor is connected with one end of the first voltage dividing resistor and grounded, and the first filter capacitor is connected at one end of the second voltage dividing resistor and grounded.

[0016] As a further improvement of the present application, the peripheral elements further comprise a current limiting resistor connected between the first voltage dividing resistor and the positive input terminal of the operational amplifier, and a second filter capacitor connected at one end of the current limiting resistor and grounded.

[0017] As a further improvement of the present application, the constant voltage loop adjustment module is further used for dividing the output voltage of the constant voltage module and serving as the negative terminal of the operational amplifier, the operational amplifier is used for amplifying the error between the reference voltage and the divided output voltage of the constant voltage module to form a low voltage signal, and the output terminal of the operational amplifier outputs the low voltage signal to control the output voltage of the constant voltage module.

[0018] As a further improvement of the present application, the linear constant current module comprises a linear constant current IC connected in series with the LED light source.

[0019] As a further improvement of the present application, the reference voltage is in a proportional relationship with the duty cycle of the PWM signal, and the output voltage of the constant voltage module is also in a proportional relationship with the reference voltage, and the reference voltage is an adjustable change value in a preset range.

[0020] As a further improvement of the present application, the loss of the linear constant current module is in a linear proportional relationship with the output voltage of the constant voltage module.

[0021] Another object of the present application is to provide a lighting fixture using the above-mentioned output voltage automatic adjustment circuit.

[0022] To achieve the above-mentioned objects, the present application provides a lighting fixture using the above-mentioned output voltage automatic adjustment circuit.

[0023] The beneficial effects of the present application are: the output voltage automatic adjustment circuit of the present application detects the voltage of the linear constant current module to the ground through the MCU control module, and outputs a PWM signal with a corresponding duty cycle according to the comparison result of the voltage to the ground and the voltage threshold, so that the constant voltage loop adjustment module can receive the PWM signal and perform voltage division and RC filtering on the PWM signal to obtain a processing voltage, and the processing voltage is used as the reference voltage of the operational amplifier in the constant voltage loop adjustment module, and the constant voltage module outputs a voltage according to the reference voltage, thereby realizing the automatic adjustment of the output voltage of the constant voltage module. Compared with the prior art, the output voltage automatic adjustment circuit of the present application can intelligently and dynamically adjust the output voltage of the constant voltage module in real time, reduce the loss of the linear constant current module, and achieve the purposes of improving the driving efficiency and reducing the heat generation. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of the output voltage automatic adjustment circuit of the present application.

[0025] Figure 2 is Figure 1 the circuit principle diagram of the output voltage automatic adjustment circuit shown in FIG.

[0026] Figure 3 is Figure 2 the circuit principle diagram of the constant voltage loop adjustment module in FIG. DETAILED DESCRIPTION

[0027] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described in detail below with reference to the drawings and specific embodiments.

[0028] This invention discloses an automatic output voltage adjustment circuit and a lighting fixture using this circuit. After applying the automatic output voltage adjustment circuit, the lighting fixture can improve driving efficiency, reduce heat generation, and reduce energy loss. Other structures of the lighting fixture can adopt existing technologies, which will not be described in detail here.

[0029] like Figure 1 As shown, the automatic output voltage adjustment circuit mainly consists of a constant voltage module 1, a constant voltage loop adjustment module 5, an MCU control module 4, an LED light source 2, and a linear constant current module 3. In specific implementation, the power supply and light source sections of the lighting fixture can be in two states: 1. The power supply and light source sections are separate. In this case, the power supply section consists of the constant voltage module 1, the constant voltage loop adjustment module 5, and the MCU control module 4, while the light source section consists of the LED light source 2 and the linear constant current module 3. The power supply and light source sections are connected via three lines: V_LED+, the voltage detection line, and GND. 2. The power supply and light source sections are integrated. In this case, the constant voltage module 1, the constant voltage loop adjustment module 5, the MCU control module 4, the LED light source 2, and the linear constant current module 3 form a complete lighting fixture. However, these two states of the power supply and light source sections do not affect the implementation effect of the present invention and are not considered limitations here.

[0030] The constant voltage module 1 is used to convert external AC power into constant voltage DC power. The linear constant current module 3 is connected in series with the LED light source 2 and connected to the output terminal of the constant voltage module 1. It is used to convert the constant voltage DC power into constant current power to supply power to the LED light source 2. Here, the linear constant current module 3 and the LED light source 2 are connected in series and in parallel with the constant voltage module 1. The MCU control module 4 is connected to the linear constant current module 3 and has an internal voltage threshold. The MCU control module 4 is used to detect the voltage to ground of the linear constant current module 3 and output a PWM signal with a corresponding duty cycle based on the comparison result between the voltage to ground and the voltage threshold. The constant voltage loop adjustment module 5 is connected in series between the MCU control module 4 and the constant voltage module 1. The constant voltage loop adjustment module 5 is used to receive the PWM signal and perform voltage division and RC filtering on the PWM signal to obtain a processed voltage. The processed voltage is used as the reference voltage of the operational amplifier in the constant voltage loop adjustment module 5. The constant voltage module 1 outputs a voltage based on the reference voltage to realize the automatic adjustment of the output voltage of the constant voltage module 1.

[0031] The constant voltage module 1 can be composed of different power supply topologies, and can be either isolated or non-isolated; no limitation is made here. The LED light source 2 is composed of LED chips. The forward conduction voltage of the LED chips has a negative temperature coefficient; the higher the operating temperature, the lower the forward conduction voltage Vf, and the lower the operating temperature, the higher the forward conduction voltage. Because different LED chips have different color temperatures, are from different manufacturers, and have different Vf values, and because the number of LED light sources 2 connected in series and parallel varies in different applications, the power output voltage required for different lighting fixtures also varies.

[0032] Using a fixed voltage to adapt each lighting fixture will result in increased losses in low-voltage fixtures and a lack of constant current in high-voltage fixtures. These losses are specifically manifested in the losses of the linear constant current module 3. Since the linear constant current module 3 operates in the linear region, its loss is the sum of the conduction voltage and the fixture's operating current, expressed as I_led*V_led-. Here, I_led is the fixture's operating current, a fixed value, and V_led- is directly proportional to the output voltage of the constant voltage module 1. In other words, the losses of the linear constant current module 3 are linearly proportional to the output voltage of the constant voltage module 1. The higher the output voltage of the constant voltage module 1, the higher the V_led-, and the greater the losses of the linear constant current module 3. The manufacturer and model of the linear constant current module 3 are not limited; any module with linear constant current functionality is acceptable.

[0033] The function of the MCU control module 4 is to detect the voltage to ground at the negative terminal of the LED light source 2, which is the voltage to ground of the linear constant current module 3. Based on the comparison between this voltage and a voltage threshold set internally by the MCU control module 4, the MCU control module 4 outputs PWM signals with different duty cycles. In this embodiment, the voltage to ground at the negative terminal of the LED light source 2 is equivalent to the voltage to ground of the linear constant current module 3, and this voltage originates from the output voltage of the constant voltage module 1. Furthermore, the MCU of the MCU control module 4 has no specific restrictions on model, bit width, or manufacturer, as long as it has ADC detection and PWM output functions. In addition, the MCU has other functions in smart lighting applications; this invention only describes the function of adjusting the power supply output voltage, and other functions are not within the scope of this invention. That is to say, in smart lighting applications, the application of this invention is only a small part of the application of the MCU.

[0034] A voltage detection line is connected between the MCU control module 4 and the linear constant current module 3 to detect the voltage to ground of the linear constant current module 3. When the MCU control module 4 outputs a PWM signal with a corresponding duty cycle based on the comparison result of the voltage to ground and the voltage threshold, the process further includes: the MCU control module 4 detecting, dividing, and ADC-converting the voltage to ground of the linear constant current module 3 to form a digital voltage, and comparing it with the voltage threshold, which includes a maximum voltage threshold and a minimum voltage threshold. When the digital voltage is greater than the maximum voltage threshold, the MCU control module 4 reduces the duty cycle of the current PWM signal; when the digital voltage is less than the minimum voltage threshold, the MCU control module 4 increases the duty cycle of the current PWM signal.

[0035] The constant voltage loop adjustment module 5 receives the PWM signal output by the MCU control module 4 and performs voltage division and RC filtering on the PWM signal to obtain a processed voltage. This processed voltage is used as the reference voltage for the operational amplifier in the constant voltage loop adjustment module 5. The constant voltage module 1 outputs a voltage based on this reference voltage, thus automatically adjusting the output voltage of the constant voltage module 1. The constant voltage loop adjustment module 5 utilizes its voltage feedback control loop function to perform voltage division and RC filtering on the PWM signal output by the MCU control module 4 in real time to obtain a processed voltage, which is then provided to the positive terminal of the operational amplifier as a reference voltage.

[0036] It is understood that the constant voltage loop adjustment module 5 is also a voltage feedback control loop, which is a necessary circuit of the constant voltage power supply. The constant voltage loop adjustment module 5 detects the output voltage of the constant voltage module 1, divides it to the negative terminal, compares it with the positive terminal reference voltage, and then adjusts the feedback pin of the constant voltage module 1 to achieve the purpose of stabilizing the output voltage of the constant voltage module 1. In traditional applications, the positive terminal reference voltage of the operational amplifier is a fixed value. This invention uses the voltage feedback control loop circuit to adjust the output voltage of the constant voltage module 1 by adjusting the positive terminal reference voltage of the operational amplifier. The output voltage of the constant voltage module 1 is directly proportional to the reference voltage. In this invention, the positive terminal reference voltage of the operational amplifier is an adjustable value within a certain preset range.

[0037] The constant voltage loop adjustment module 5 is also used to divide the output voltage of the constant voltage module 1 and use it as the negative terminal of the operational amplifier. At the same time, it provides the processed voltage to the positive terminal of the operational amplifier as a reference voltage. The operational amplifier is used to amplify the error between the reference voltage and the output voltage of the constant voltage module 1 after voltage division to form a low voltage signal. The output terminal of the operational amplifier outputs the low voltage signal to control the output voltage of the constant voltage module 1, so that the output voltage of the constant voltage module 1 is constant.

[0038] likeFigures 2-3 As shown, the constant voltage loop adjustment module 5 includes an operational amplifier and peripheral components. The peripheral components include a first voltage divider resistor R4, a second voltage divider resistor R5, and a first filter capacitor C2. One end of the first voltage divider resistor R4 is connected to the positive input terminal of the operational amplifier, and the other end of the first voltage divider resistor R4 is connected to the PWM output port of the MCU control module. The second voltage divider resistor R5 is connected to one end of the first voltage divider resistor R4 and grounded. The first filter capacitor C2 is connected to one end of the second voltage divider resistor R5 and grounded.

[0039] In this embodiment, the MCU control module 4 is 3.3V, so the PWM signal is 3.3V. The first voltage divider resistor R4 and the second voltage divider resistor R5 form a voltage divider circuit. This voltage divider circuit is used to reduce the received PWM signal to a set voltage PWM signal according to a fixed ratio. The only difference between this and the input PWM signal is the voltage. The first filter capacitor C2 is used to perform RC filtering on the stepped-down PWM signal to obtain a stable voltage, which is the processed voltage. The processed voltage serves as the positive terminal reference voltage of the operational amplifier. The reference voltage after RC filtering is proportional to the duty cycle of the PWM signal. The larger the duty cycle of the PWM signal, the larger the positive terminal reference voltage of the operational amplifier, and the higher the output voltage of the constant voltage module 1. Conversely, the smaller the duty cycle of the PWM signal, the smaller the positive terminal reference voltage of the operational amplifier, and the lower the output voltage of the constant voltage module 1.

[0040] In this embodiment, the peripheral components further include: a current-limiting resistor R3, which is connected between the first voltage divider resistor R4 and the positive input terminal of the operational amplifier; and a second filter capacitor C1 connected to one end of the current-limiting resistor R3 and grounded. After the first filter capacitor C2 performs RC filtering on the PWM signal, there may still be slight fluctuations. The current-limiting resistor R3 and the second filter capacitor C1 are used to perform a second stage of RC filtering on the PWM signal that has undergone RC filtering. Of course, if the PWM signal still fluctuates after the second stage of RC filtering, another stage of RC filtering can be added. If the voltage across the first filter capacitor C2 is very flat and has no ripple, the current-limiting resistor R3 and the second filter capacitor C1 can also be removed, and only the first filter capacitor C2 can be used for RC filtering.

[0041] The peripheral components also include: a third voltage divider resistor R1 and a fourth voltage divider resistor R2. Since one end of the third voltage divider resistor R1 is connected to the negative input terminal of the operational amplifier, and the other end of the third voltage divider resistor R1 is connected to the output terminal of the constant voltage module 1, and the fourth voltage divider resistor R2 is connected to one end of the third voltage divider resistor R1 and grounded, the third voltage divider resistor R1 and the fourth voltage divider resistor R2 form a voltage divider circuit, which is used to reduce the output voltage of the constant voltage module 1.

[0042] The linear constant current module 3 includes a linear constant current IC, which is connected in series with the LED light source 2. The linear constant current IC has a minimum constant current voltage. The MCU control module 4 detects the voltage to ground on the linear constant current IC. The voltage to ground on the linear constant current IC is directly proportional to the power loss; the higher the voltage to ground, the greater the power loss. The MCU control module 4 also includes a fifth voltage divider resistor R10 and a sixth voltage divider resistor R11. The fifth voltage divider resistor R10 is located on the voltage detection line. The sixth voltage divider resistor R11 is connected to one end of the fifth voltage divider resistor R10 and grounded. The fifth voltage divider resistor R10 and the sixth voltage divider resistor R11 form a voltage divider circuit. This voltage divider circuit is used to divide the voltage to ground on the linear constant current IC, and the MCU control module 4 performs ADC conversion to form a digital voltage, which is compared with an internally set voltage threshold. When the digital voltage is greater than the maximum voltage threshold, it indicates that the voltage to ground on the linear constant current module 3 is too high. The MCU control module 4 needs to reduce the duty cycle of its output PWM signal to reduce the reference voltage of the operational amplifier, thereby reducing the output voltage of the constant voltage module 1, and then reducing the voltage on the linear constant current module 3 to reduce losses.

[0043] Since the linear constant current module 3 operates at a minimum constant current voltage, when the output voltage of the constant voltage module 1 is lower than this minimum constant current voltage, the linear constant current module 3 cannot maintain a constant current at the set value. In this case, the MCU control module 4 needs to output a PWM signal to control the output voltage of the constant voltage module 1 to increase. Therefore, when the digital voltage is less than the minimum voltage threshold, it indicates that the voltage on the linear constant current module 3 is low. The MCU control module 4 needs to increase the duty cycle of its output PWM signal to increase the operational amplifier reference voltage, thereby increasing the output voltage of the constant voltage module 1, and subsequently increasing the voltage on the linear constant current module 3.

[0044] In summary, the automatic output voltage adjustment circuit of the present invention detects the voltage to ground of the linear constant current module 3 through the MCU control module 4, and outputs a PWM signal with a corresponding duty cycle based on the comparison result of the voltage to ground and the voltage threshold. Thus, the constant voltage loop adjustment module 5 can receive the PWM signal, perform voltage division and RC filtering on the PWM signal to obtain a processed voltage, and use the processed voltage as the reference voltage of the operational amplifier in the constant voltage loop adjustment module 5. This allows the constant voltage module 1 to output a voltage based on the reference voltage, thereby achieving automatic adjustment of the output voltage of the constant voltage module 1. Compared with the prior art, the automatic output voltage adjustment circuit of the present invention can intelligently and dynamically adjust the output voltage of the constant voltage module 1 in real time, reducing the loss of the linear constant current module 3, and achieving the purpose of improving driving efficiency and reducing heat generation.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An automatic output voltage adjustment circuit, applied to lighting fixtures, characterized in that, include: A constant voltage module (1) is used to convert external AC power into constant voltage DC power; A linear constant current module (3) is connected in series with the LED light source (2) and connected to the output terminal of the constant voltage module (1) to convert the constant voltage DC power into constant current power to power the LED light source (2); The MCU control module (4) is connected to the linear constant current module (3) and has a voltage threshold set inside. The MCU control module (4) is used to detect the voltage to ground of the linear constant current module (3) and output a PWM signal with a corresponding duty cycle according to the comparison result between the voltage to ground and the voltage threshold. A constant voltage loop adjustment module (5) is connected in series between the MCU control module (4) and the constant voltage module (1). The constant voltage loop adjustment module (5) is used to receive the PWM signal, perform voltage division and RC filtering on the PWM signal to obtain a processing voltage, and use the processing voltage as the reference voltage of the operational amplifier in the constant voltage loop adjustment module (5). The constant voltage module (1) outputs a voltage according to the reference voltage.

2. The automatic output voltage adjustment circuit according to claim 1, characterized in that, Also includes: A voltage detection line is connected between the MCU control module (4) and the linear constant current module (3) to detect the voltage to ground of the linear constant current module (3).

3. The automatic output voltage adjustment circuit according to claim 2, characterized in that, When the MCU control module (4) outputs a PWM signal with a corresponding duty cycle based on the comparison result between the voltage to ground and the voltage threshold, the MCU control module (4) further includes: detecting, dividing, and ADC converting the voltage to ground of the linear constant current module (3) to form a digital voltage, and comparing it with the voltage threshold, wherein the voltage threshold includes a maximum voltage threshold and a minimum voltage threshold; when the digital voltage is greater than the maximum voltage threshold, the MCU control module (4) reduces the duty cycle of the current PWM signal; when the digital voltage is less than the minimum voltage threshold, the MCU control module (4) increases the duty cycle of the current PWM signal.

4. The automatic output voltage adjustment circuit according to claim 1, characterized in that, The constant pressure loop regulation module (5) includes: Operational amplifier; The peripheral components include a first voltage divider resistor (R4), a second voltage divider resistor (R5), and a first filter capacitor (C2). One end of the first voltage divider resistor (R4) is connected to the positive input terminal of the operational amplifier, and the other end of the first voltage divider resistor (R4) is connected to the PWM output port of the MCU control module (4). The second voltage divider resistor (R5) is connected to one end of the first voltage divider resistor (R4) and grounded. The first filter capacitor (C2) is connected to one end of the second voltage divider resistor (R5) and grounded.

5. The automatic output voltage adjustment circuit according to claim 4, characterized in that, The peripheral components also include: a current-limiting resistor (R3) connected between the first voltage divider resistor (R4) and the positive input terminal of the operational amplifier; and a second filter capacitor (C1) connected to one end of the current-limiting resistor (R3) and grounded.

6. The automatic output voltage adjustment circuit according to claim 4, characterized in that, The constant voltage loop adjustment module (5) is also used to divide the output voltage of the constant voltage module (1) and use it as the negative terminal of the operational amplifier. The operational amplifier is used to amplify the error between the reference voltage and the output voltage of the constant voltage module (1) after voltage division to form a low voltage signal. The output terminal of the operational amplifier outputs the low voltage signal to control the output voltage of the constant voltage module (1).

7. The automatic output voltage adjustment circuit according to claim 1, characterized in that, The linear constant current module (3) includes a linear constant current IC, which is connected in series with the LED light source (2).

8. The automatic output voltage adjustment circuit according to claim 1, characterized in that, The reference voltage is directly proportional to the duty cycle of the PWM signal, and the output voltage of the constant voltage module (1) is also directly proportional to the reference voltage. The reference voltage is an adjustable value within a preset range.

9. The automatic output voltage adjustment circuit according to claim 1, characterized in that, The loss of the linear constant current module (3) is linearly proportional to the output voltage of the constant voltage module (1).

10. A lighting fixture, characterized in that, The output voltage automatic adjustment circuit according to any one of claims 1-9 is adopted.

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