A dimming circuit and working method thereof

Abstract

The present invention relates to a dimming circuit and a working method thereof. The circuit includes a main circuit unit and a dimming improvement unit. The dimming improvement unit includes a voltage adjustment subunit and a three-in-one dimming subunit. The voltage adjustment subunit is connected to the three-in-one dimming subunit, and the three-in-one dimming subunit is connected to the main circuit unit. The voltage adjustment subunit is used to lower the reference voltage of the three-in-one dimming subunit to increase the dimming range of the main circuit unit. The present invention lowers the reference voltage of the three-in-one dimming subunit through the voltage adjustment subunit to increase the dimming range of the main circuit unit, improve the dimming range, and adjust the output current within the entire voltage range to avoid affecting the user experience. An over-temperature protection unit is added to improve the reliability of the power supply, an isolated power supply unit is added to improve the safety of operation, and a dial current adjustment unit is added to enable the user to adjust the current in multiple gears without using a dimmer.

Description

Technical Field

[0001] The present invention relates to a dimming circuit, and more particularly to a dimming circuit and a working method thereof. Background Art

[0002] LED lamps are increasingly being used in applications that require them to be dimmed, and the 0V to 10V dimming method is widely used, such as Figure 1 The figure shows the application of a three-in-one dimming circuit. The dimming pin of U1A is connected to the dimming input signal. The dimming signal output pin outputs a 5V PWM signal after internal processing by U1A. The signal is transmitted to the primary side of the power supply through an optocoupler and connected to the receiving pin to achieve a change in the output current.

[0003] Using the above three-in-one dimming circuit, if the control signal is added to the dimming input pin, the signal is processed internally to obtain the voltage on the reference pin, and this reference is added to the offset voltage of 0.5V, and then compared with the internal ramp voltage to generate a PWM signal. When the input signal pin voltage is ≥9V, the signal output pin outputs a 100% PWM duty cycle, so that when the dimming control signal is 9V, the power supply has reached the maximum current output, and the actual dimming range is only 0V to 9V, while the dimmers on the market are generally 0V to 10V, which means that the dimmer cannot adjust the output current between 9V and 10V, which reduces the entire dimming range and affects the user experience.

[0004] Therefore, it is necessary to design a new circuit to improve the dimming range so that the output current can be adjusted within the entire voltage range to avoid affecting the user experience. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a dimming circuit and a working method thereof.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solutions: a dimming circuit, comprising a main circuit unit and a dimming improvement unit, the dimming improvement unit comprising a voltage adjustment subunit and a three-in-one dimming subunit, the voltage adjustment subunit is connected to the three-in-one dimming subunit, the three-in-one dimming subunit is connected to the main circuit unit, and the reference voltage of the three-in-one dimming subunit is lowered by the voltage adjustment subunit to increase the dimming range of the main circuit unit.

[0007] A further technical solution is as follows: the voltage adjustment subunit comprises a pull-down resistor R7, one end of the pull-down resistor R7 is grounded, and the other end of the pull-down resistor R7 is connected to the three-in-one dimming subunit.

[0008] Its further technical solution is: the three-in-one dimming sub-unit includes a dimming chip U1, a resistor R4, a resistor R6, a capacitor C2, a capacitor C3 and a capacitor C4, and the dimming chip U1 is provided with a signal input terminal pin, a power supply terminal pin, a signal output terminal pin and a reference terminal pin; the reference terminal pin of the dimming chip U1 is connected to the pull-down resistor R7, the reference terminal pin of the dimming chip U1 is connected to the capacitor C3, and the dimming chip U1 is respectively connected to the capacitor C4, the capacitor C2, the resistor R6 and the resistor R4.

[0009] A further technical solution is: the dimming improvement unit is connected to an isolation power supply unit.

[0010] A further technical solution is as follows: the isolation power supply unit includes an isolation winding NP and an isolation diode D1, the isolation diode D1 is connected to the isolation winding NP, and the isolation diode D1 is connected to the power supply pin of the dimming chip U1.

[0011] A further technical solution is: the dimming improvement unit is also connected to a dial current adjustment unit.

[0012] A further technical solution is: a signal conversion unit is connected between the dimming improvement unit and the main circuit unit.

[0013] A further technical solution is: the signal conversion unit is also connected to an over-temperature protection unit.

[0014] Its further technical solution is: the over-temperature protection unit includes a comparator U3, a thermistor NTC1, a thermistor NTC2 and a diode D2, the reverse input end of the comparator U3 is connected to the thermistor NTC1, the output end of the comparator U3 is connected to the thermistor NTC2, and the diode D2 is respectively connected to the signal conversion unit and the thermistor NTC2.

[0015] The present invention also provides a working method of a dimming circuit, comprising:

[0016] The voltage of the main circuit unit is adjusted by the dimming improvement unit, and the reference voltage of the three-in-one dimming subunit is lowered by the voltage adjustment subunit to increase the dimming range of the main circuit unit.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention increases the dimming range of the main circuit unit by adding a conversion subunit in the dimming improvement unit connected to the main circuit unit, and lowers the reference voltage of the three-in-one dimming subunit through the voltage adjustment subunit, thereby improving the dimming range, so that the output current can be adjusted within the entire voltage range to avoid affecting the user experience, and an over-temperature protection unit is added to improve the reliability of the power supply, and an isolated power supply unit is added to improve the safety of operation, and a dial-code current adjustment unit is added to enable the user to adjust the current in multiple gears without a dimmer.

[0018] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0020] Figure 1 It is a specific circuit principle diagram of the three-in-one dimming circuit in the prior art;

[0021] Figure 2 A schematic block diagram of a dimming circuit provided in a specific embodiment of the present invention;

[0022] Figure 3 A specific circuit schematic diagram of a dimming circuit provided by a specific embodiment of the present invention;

[0023] Figure 4 A schematic diagram comparing the output duty cycle of a dimming circuit provided in a specific embodiment of the present invention and an application circuit in the prior art. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0027] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0028] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be connected, detachably connected, or integrated; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0030] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms should not be understood as necessarily referring to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0031] like Figures 2 to 4 The specific embodiment shown in the present embodiment provides a dimming circuit, which increases the dimming range of the main circuit unit 10 by adding a voltage adjustment sub-unit 21 to lower the reference voltage of the three-in-one dimming sub-unit 22, so that the adjustable voltage range of the entire dimming circuit is 0V to 10V, and the adjustment range is increased.

[0032] See also Figure 2 The above-mentioned dimming circuit includes a main circuit unit 10 and a dimming improvement unit 20. The dimming improvement unit 20 includes a voltage adjustment subunit 21 and a three-in-one dimming subunit 22. The voltage adjustment subunit 21 is connected to the three-in-one dimming subunit 22, and the three-in-one dimming subunit 22 is connected to the main circuit unit 10. The reference voltage of the three-in-one dimming subunit 22 is lowered by the voltage adjustment subunit 21 to increase the dimming range of the main circuit unit 10.

[0033] In one embodiment, see Figure 3 The voltage adjustment subunit 21 includes a pull-down resistor R7 , one end of the pull-down resistor R7 is grounded, and the other end of the pull-down resistor R7 is connected to the three-in-one dimming subunit 22 .

[0034] A MΩ-class pull-down resistor R7 is added to the reference terminal pin of the three-in-one dimming sub-unit 22 to the ground, and the reference voltage compared with the internal ramp voltage of the dimming chip U1 of the three-in-one dimming sub-unit 22 is pulled down, so that the output signal pin outputs 100% duty cycle only when the input signal is 10V, thereby improving the dimming range and solving the problem that the dimming signal 9V to 10V cannot adjust the current.

[0035] In one embodiment, see Figure 3The above-mentioned three-in-one dimming sub-unit 22 includes a dimming chip U1, a resistor R4, a resistor R6, a capacitor C2, a capacitor C3 and a capacitor C4. The dimming chip U1 is provided with a signal input terminal pin, a power supply terminal pin, a signal output terminal pin and a reference terminal pin; the reference terminal pin of the dimming chip U1 is connected to the pull-down resistor R7, the reference terminal pin of the dimming chip U1 is connected to the capacitor C3, and the dimming chip U1 is respectively connected to the capacitor C4, the capacitor C2, the resistor R6 and the resistor R4.

[0036] The dimming chip U1, resistor R4, resistor R6, capacitor C2, capacitor C3 and capacitor C4 are a typical three-in-one dimming circuit. The pull-down resistor R7 is added to form an improved 0-10V dimming circuit, which mainly solves the problem that the output current cannot be adjusted when the dimming signal is 9V to 10V. The pull-down resistor R7 is connected to the reference terminal of the dimming chip U1 to the ground, and is connected in series with the 500KΩ resistor inside the dimming chip U1. When an analog signal is input to the signal input terminal, the pull-down resistor R7 plays a role in voltage division. The voltage reduced by the pull-down resistor R7 is added to the 0.5V offset voltage after processing and compared with the ramp voltage inside the dimming chip U1 to generate a correspondingly reduced duty cycle PWM signal. Selecting a suitable resistance value of the pull-down resistor R7 can make the signal output pin start to output 100% duty cycle only when the analog signal on the signal input terminal is 10V, such as Figure 4 As shown, avoid affecting the user experience.

[0037] In one embodiment, see Figure 2 The dimming improvement unit 20 is connected to an isolation power supply unit 30. The isolation power supply unit 30 is provided to completely isolate the dimming circuit from the power output circuit to ensure the safety of operation and to ensure compliance with the latest certification safety regulations.

[0038] In one embodiment, see Figure 3 The above-mentioned isolation power supply unit 30 includes an isolation winding NP and an isolation diode D1. The isolation diode D1 is connected to the isolation winding NP, and the isolation diode D1 is connected to the power supply pin of the dimming chip U1.

[0039] The dimming circuit isolation unit uses an isolated transformer winding to power the dimming chip U1 to achieve electrical isolation from the output circuit. The isolation winding NP and the isolation diode D1 form the power supply circuit of the dimming chip U1. The isolation winding NP is the isolation winding of the transformer, which is proportional to the output winding but completely isolated to achieve electrical isolation between the dimming circuit and the main power circuit. The isolated power supply method is adopted, and the circuit topology meets the new safety certification requirements.

[0040] In one embodiment, see Figure 2 The dimming improvement unit 20 is also connected to a dial current adjustment unit 40.

[0041] The DIP current adjustment unit 40 utilizes the resistor dimming property of the dimming chip U1. Different resistance values ​​are added to the input signal pin through a switch to achieve different current outputs. The user can adjust the current in multiple gears without using a dimmer.

[0042] In one embodiment, see Figure 3 The above-mentioned code-controlled current adjustment unit 40 includes a switch S1, a switch S2, a switch S3 and resistors R1, R2 and R3, wherein one end of the switch S1 is connected to the resistor R1, and the other end of the switch S1 is connected to the signal input pin of the dimming chip U1; one end of the switch S2 is connected to the resistor R2, and the other end of the switch S2 is connected to the signal input pin of the dimming chip U1; one end of the switch S3 is connected to the resistor R3, and the other end of the switch S3 is connected to the signal input pin of the dimming chip U1; utilizing the resistor dimming characteristic of the dimming chip U1, when the switch S1 is closed, the signal input pin is grounded through the resistor R1, and the signal output controls the output current with a PWM duty cycle signal corresponding to the resistance value of the resistor R1; when the switch S2 is closed, the signal input pin is grounded through the resistor R2, and the signal output controls the output current with a PWM duty cycle signal corresponding to the resistance value of the resistor R2; when the switch S3 is closed, the signal input pin is grounded through the resistor R3, and the signal output controls the output current with a PWM duty cycle signal corresponding to the resistance value of the resistor R3. The dip switches S1, S2, and S3 are connected in series to the dimming control input, and each switch node is connected in series with a resistor to the ground.

[0043] In one embodiment, see Figure 2 A signal conversion unit 50 is connected between the dimming improvement unit 20 and the main circuit unit 10 .

[0044] In one embodiment, see Figure 3 The signal conversion unit 50 includes a filter subunit and an optocoupler chip U2. The optocoupler chip U2 is connected to the signal output pin of the dimming chip U1. The optocoupler chip U2 is connected to the filter subunit. The filter subunit is connected to the main circuit unit 10. The filter subunit includes a filter capacitor C5 and a resistor R8. The resistor R8 and the filter capacitor C5 are an RC filter circuit. The PWM of the signal output pin is converted into an analog dimming signal of 0V to 5V through the optocoupler chip U2, the resistor R8, and the filter capacitor C5.

[0045] In one embodiment, see Figure 2 The signal conversion unit 50 is also connected to an over-temperature protection unit 60 .

[0046] The PWM signal output by the three-in-one dimming sub-unit 22 is converted into a 5V analog dimming signal, and a comparator U3 and an NTC resistor are added. At high temperatures, the NTC resistor is activated to divide the 5V dimming signal, and the voltage of the main power dimming receiving pin becomes smaller, thereby reducing the output current and playing the role of over-temperature protection; when the power supply temperature is too high, the output current is adaptively reduced, thereby achieving the purpose of controlling the power supply output power.

[0047] In one embodiment, see Figure 3 The over-temperature protection unit 60 includes a comparator U3, a thermistor NTC1, a thermistor NTC2 and a diode D2. The reverse input end of the comparator U3 is connected to the thermistor NTC1, the output end of the comparator U3 is connected to the thermistor NTC2, and the diode D2 is respectively connected to the signal conversion unit 50 and the thermistor NTC2.

[0048] Thermistors NTC1 and NTC2 are thermistors with negative temperature coefficients, a voltage-dividing resistor R9 is connected between the non-inverting input terminal of the comparator U3 and the thermistor NTC1, and the other end of the thermistor NTC1 is grounded through a resistor R11, and a capacitor C6 with one end grounded is connected between the thermistor NTC1 and the reverse input terminal of the comparator U3, a voltage-dividing resistor R10 is connected to one end of the voltage-dividing resistor R9, and the other end of the voltage-dividing resistor R10 is grounded, a pull-down resistor R12 is connected between the thermistor NTC2 and the diode D2, and a pull-down resistor R13 is also connected between the output terminal of the comparator U3 and the diode D2.

[0049] The voltage-dividing resistors R9 and R10 divide the 5V reference voltage and add it to the in-phase input terminal of the comparator U3. The thermistor NTC1 and the resistor R11 divide the 5V reference voltage and add it to the reverse input terminal of the comparator U3. During normal operation, the voltage at the reverse input terminal is greater than the in-phase input terminal, the comparator U3 outputs a high level, and the diode D2 is cut off without over-temperature protection. When the temperature rises, the resistance of the thermistor NTC1 gradually decreases, and the voltage at the reverse input terminal gradually increases. When the voltage at the reverse input terminal is greater than the 3rd pin of the in-phase input terminal, the comparator U3 outputs a low level, the diode D2 is turned on, and the diode D2, the thermistor NTC2, the pull-down resistor R12, and the pull-down resistor R13 pull down the analog dimming signal voltage on the filter capacitor C5, and the voltage signal of the dimming received by the main power supply becomes smaller, so that the output current is reduced accordingly. The higher the temperature, the lower the resistance of thermistor NTC2, the greater the voltage division on the filter capacitor C5, and the more the output current decreases. Selecting appropriate parameters of resistor R11 and thermistor NTC1 can realize the setting of the over-temperature switch node, and selecting appropriate parameters of thermistor NTC2, pull-down resistor R12, and pull-down resistor R13 can control the over-temperature derating curve.

[0050] Specifically, the over-temperature protection unit 60 divides the reference voltage through the voltage-dividing resistors R9 and R10 and adds it to the positive end of the comparator U3. The negative temperature coefficient thermistor NTC1 and the conventional resistor divide the reference voltage and add it to the negative end of the comparator U3. The output end of the comparator U3 is connected in series with the thermistor NTC2 and the diode D2 and then connected to the analog dimming signal after the filter sub-unit to form the over-temperature protection unit 60. When the temperature is high, the protection circuit is activated, and the analog dimming signal is divided to reduce the voltage of the main power dimming receiving pin and the output current. Adding over-temperature protection improves the reliability of the power supply, and adding a recoverable over-temperature protection circuit enables the power supply to adaptively reduce the current output under abnormal high working temperature, ensuring the reliability of the power supply for long-term operation.

[0051] In one embodiment, the main circuit unit 10 includes a rectifier unit 11 , a converter unit 12 and an output unit 13 , wherein the rectifier unit 11 and the output unit 13 are respectively connected to the converter unit 12 , and the converter unit 12 is connected to the signal conversion unit 50 .

[0052] The rectifier unit 11 is a bridge rectifier circuit. A transformer is connected between the conversion unit 12 and the output unit 13 .

[0053] The above-mentioned dimming circuit enables the power supply to adjust the voltage of the dimming control terminal at the maximum output current, or adjust the output current of the power supply through the DIP switch outside the power supply. When the temperature of the power supply is too high, the output current is adaptively reduced. The long-term working reliability of the power supply can be guaranteed even under abnormal high working temperature, thereby achieving the purpose of controlling the output power of the power supply, improving the reliability of the power supply, diversifying the current adjustment method, and increasing the dimming range. At the same time, the dimming circuit is completely isolated from the power supply output circuit to ensure the safety of operation.

[0054] The above-mentioned dimming circuit increases the dimming range of the main circuit unit 10 by adding a conversion subunit 12 in the dimming improvement unit 20 connected to the main circuit unit 10, and lowers the reference voltage of the three-in-one dimming subunit 22 through the voltage adjustment subunit 21, so as to improve the dimming range, so that the output current can be adjusted within the entire voltage range to avoid affecting the user experience, and adds an over-temperature protection unit 60 to improve the reliability of the power supply, adds an isolated power supply unit 30 to improve the safety of operation, and adds a dial-code current adjustment unit 40 to enable the user to adjust the current in multiple gears without a dimmer.

[0055] In one embodiment, a working method of a dimming circuit is also provided, including:

[0056] The voltage of the main circuit unit 10 is adjusted by the dimming improvement unit 20 , and the reference voltage of the three-in-one dimming subunit 22 is pulled down by the voltage adjustment subunit 21 , so as to increase the dimming range of the main circuit unit 10 .

[0057] It should be noted that technicians in the relevant field can clearly understand that the specific implementation process of the working method of the above-mentioned dimming circuit can refer to the corresponding description in the aforementioned dimming circuit embodiment. For the convenience and conciseness of the description, it will not be repeated here.

[0058] The above examples are only used to further illustrate the technical content of the present invention, so that readers can understand it more easily, but they do not mean that the implementation of the present invention is limited to this. Any technical extension or re-creation made according to the present invention is protected by the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A dimming circuit, characterized in that: The device comprises a main circuit unit and a dimming improvement unit, wherein the dimming improvement unit comprises a voltage adjustment subunit and a three-in-one dimming subunit, wherein the voltage adjustment subunit is connected to the three-in-one dimming subunit, and the three-in-one dimming subunit is connected to the main circuit unit, and the reference voltage of the three-in-one dimming subunit is lowered by the voltage adjustment subunit to increase the dimming range of the main circuit unit; The voltage adjustment subunit includes a pull-down resistor R7, one end of the pull-down resistor R7 is grounded, and the other end of the pull-down resistor R7 is connected to the three-in-one dimming subunit; The three-in-one dimming sub-unit includes a dimming chip U1, a resistor R4, a resistor R6, a capacitor C2, a capacitor C3 and a capacitor C4. The dimming chip U1 is provided with a signal input terminal pin, a power supply terminal pin, a signal output terminal pin and a reference terminal pin; the reference terminal pin of the dimming chip U1 is connected to the pull-down resistor R7, the reference terminal pin of the dimming chip U1 is connected to the capacitor C3, and the dimming chip U1 is respectively connected to the capacitor C4, the capacitor C2, the resistor R6 and the resistor R4.

2. A dimming circuit according to claim 1, characterized in that: The dimming improvement unit is connected to an isolation power supply unit.

3. A dimming circuit according to claim 2, characterized in that: The isolation power supply unit includes an isolation winding NP and an isolation diode D1 . The isolation diode D1 is connected to the isolation winding NP. The isolation diode D1 is connected to a power supply pin of the dimming chip U1 .

4. A dimming circuit according to claim 1, characterized in that: The dimming improvement unit is also connected to a dial current adjustment unit.

5. A dimming circuit according to claim 1, characterized in that: A signal conversion unit is connected between the dimming improvement unit and the main circuit unit.

6. A dimming circuit according to claim 5, characterized in that: The signal conversion unit is also connected to an over-temperature protection unit.

7. A dimming circuit according to claim 6, characterized in that: The over-temperature protection unit includes a comparator U3, a thermistor NTC1, a thermistor NTC2 and a diode D2, the inverting input end of the comparator U3 is connected to the thermistor NTC1, the output end of the comparator U3 is connected to the thermistor NTC2, and the diode D2 is respectively connected to the signal conversion unit and the thermistor NTC2.

8. A working method using the dimming circuit according to any one of claims 1 to 7, characterized in that: include: The voltage of the main circuit unit is adjusted by the dimming improvement unit, and the reference voltage of the three-in-one dimming subunit is lowered by the voltage adjustment subunit to increase the dimming range of the main circuit unit.

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