LIGHT-EMITTING DIODE (LED) DIMMING APPARATUS AND LED LIGHTING SYSTEM

Abstract

 Embodiments of the present disclosure provide a light-emitting diode (LED) dimming apparatus and an LED lighting system. The LED dimming apparatus includes: a voltage monitoring module configured to be connected between a positive terminal and a negative terminal of an LED power supply for an LED light or light string to sample an output voltage of the LED power supply; and a current controller with a voltage input terminal connected to a voltage output terminal of the voltage monitoring module, the current controller being configured to be connected in series with the LED light or light string to control a current of the LED light or light string according to the output voltage of the LED power supply. According to the embodiments of the present disclosure, the light intensity of the LED light or light string can be regulated by adjusting the output voltage of the LED power supply.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the technical field of current control, and in particular, to a light-emitting diode (LED) dimming apparatus and an LED lighting system.

BACKGROUND

[0002] Efficient control of the light intensity of an LED lighting circuit or system has always been challenging, especially in an application scenario where a plurality of LED light strings are driven by one LED power supply (LED driver). As LED lights demonstrate a nearly linear relationship between their brightness and the current flowing therethrough, embodiments of the present disclosure provide an apparatus for adjusting the brightness of one or more LED lights by controlling the current of the LED light(s), to provide more efficient and reliable LED lighting or lighting systems.

SUMMARY

[0003] Embodiments of the present disclosure provide an LED dimming apparatus and an LED lighting system to resolve or alleviate one or more technical problems in the prior art.

[0004] According to one aspect, an embodiment of the present disclosure provides an LED dimming apparatus, including: a voltage monitoring module configured to be connected between a positive terminal and a negative terminal of an LED power supply for an LED light or light string to sample an output voltage of the LED power supply; and a current controller with a voltage input terminal connected to a voltage output terminal of the voltage monitoring module, the current controller being configured to be connected in series with the LED light or light string to control a current of the LED light or light string according to the output voltage of the LED power supply.

[0005] In some embodiments, the voltage monitoring module includes a first resistor and a second resistor connected in series which are configured to be connected between the positive terminal and the negative terminal of the LED power supply, and a node between the first resistor and the second resistor is the voltage output terminal of the voltage monitoring module.

[0006] In some embodiments, the current controller includes: at least one switch including a controlled terminal and at least one pair of switch contacts, the at least one pair of switch contacts being configured to be connected in series with the LED light or light string; and a switch control circuit including a control terminal and a voltage input terminal, the voltage input terminal of the switch control circuit being connected to the voltage output terminal of the voltage monitoring module, and the control terminal of the switch control circuit being connected to the controlled terminal of the at least one switch to control a duty cycle of the switch according to the output voltage of the LED power supply for the LED light or light string, so as to control the current of the LED light or light string.

[0007] In some embodiments, the switch control circuit includes a current setter, an error amplifier, and a switch driver. The current setter is configured to set a corresponding current according to a voltage input to the current setter and output the set current. A voltage input terminal of the current setter is connected to the voltage output terminal of the voltage monitoring module. A current output terminal of the current setter is connected to a positive input terminal of the error amplifier. A negative input terminal of the error amplifier is connected to a current feedback loop of the LED light or light string to sample the current of the LED light or light string. An output terminal of the error amplifier is connected to an input terminal of the switch driver. A drive terminal of the switch driver is connected to the controlled terminal of the switch to control opening and closing of the switch.

[0008] In some embodiments, the current controller further includes a smoothing circuit, and the smoothing circuit is configured to be connected to the LED light or light string and then connected in series with the switch, so that the smoothing circuit and the LED light or light string form a closed circuit when the switch is opened, allowing energy stored in the smoothing circuit to power the LED light or light string.

[0009] In some embodiments, the smoothing circuit includes a capacitor, a diode, and an inductor. The inductor and the diode are connected in series and then connected in parallel to the capacitor. The capacitor is configured to be connected in parallel to the LED light or light string. A direction from a positive terminal of the diode to a negative terminal of the diode is opposite to a current direction of the LED light or light string. The inductor is configured to be connected in series with the LED light or light string.

[0010] In some embodiments, the smoothing circuit includes a diode and an inductor connected in series with the diode. The inductor is connected in series with the LED light or light string. The diode is connected in parallel to the LED light or light string. A direction from a positive terminal of the diode to a negative terminal of the diode is opposite to a current direction of the LED light or light string.

[0011] In some embodiments, the switch is a field-effect transistor, including a gate connected to the control terminal of the switch control circuit and a drain and a source connected in series in the current feedback loop of the LED light or light string to open or close the current feedback loop.

[0012] According to another aspect, an embodiment of the present disclosure further provides an LED lighting system, including an LED power supply, at least one LED light or at least one LED light string, and the LED dimming apparatus provided in the embodiments mentioned above of the present disclosure. Two ends of the at least one LED light or at least one LED light string are connected to a positive terminal and a negative terminal, respectively, of the LED power supply. The voltage monitoring module of the LED dimming apparatus is connected between the positive terminal and the negative terminal of the LED power supply. The current controller of the LED dimming apparatus is connected to the at least one LED light or at least one LED light string.

[0013] In some embodiments, the LED power supply includes one of an alternating current/direct current (AC/DC) switched-mode power supply (SMPS) and a DC/DC SMPS.

[0014] According to the embodiments of the present disclosure, the current controller is provided to be connected in series with the LED light or light string, and the voltage monitoring module monitors the output voltage of the LED power supply for the LED light(s), which output voltage is then used as a constant current control instruction or control signal to control the current of the LED light(s), so as to control the brightness of the LED light(s).

[0015] The summary section is only for illustration and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the present disclosure will become apparent with reference to the accompanying drawings and the detailed description below.

BRIEF DESCRIPTION OF DRAWINGS

[0016] In the accompanying drawings, the same reference numerals throughout the figures indicate the same or similar components or elements unless otherwise specified. The accompanying drawings are not necessarily drawn to scale. It should be understood that these accompanying drawings depict only some embodiments of the present disclosure and should not be considered as limiting the scope of the present disclosure.

Fig. 1 is a schematic diagram of an embodiment of an LED dimming apparatus according to the present disclosure;

Fig. 2 is a schematic diagram of an embodiment of an LED lighting system according to the present disclosure; and

Fig. 3 is a schematic diagram of an embodiment of an LED lighting system according to the present disclosure.

DETAILED DESCRIPTION

[0017] Hereinafter, some embodiments are briefly described by way of example only. As will be appreciated by those skilled in the art, the embodiments described may be modified in various ways without departing from the principle or scope of the present disclosure. Therefore, the accompanying drawings and descriptions are regarded as illustrative in nature rather than restrictive.

[0018] Referring to Figs. 1 and 2, Fig. 1 is a schematic diagram of an LED dimming apparatus according to an embodiment of the present disclosure, and Fig. 2 is a schematic diagram of an LED lighting system according to an embodiment of the present disclosure. The LED dimming apparatus 100 includes a voltage monitoring module 110 and a current controller 120. The voltage monitoring module is configured to be connected between a positive terminal and a negative terminal of an LED power supply 210 of an LED light or light string 220 to sample an output voltage of the LED power supply 210. A voltage input terminal of the current controller 120 is connected to a voltage output terminal of the voltage monitoring module 110. The current controller 120 is configured to be connected in series with the LED light or light string 220 to control a current of the LED light or light string 220 according to the output voltage of the LED power supply 210. The LED dimming apparatus 100 in Fig. 1 is applied to the LED lighting system. The current of the LED light or light string 220 may be configured to vary as a function of the output voltage of the LED power supply 210. If the output voltage of the LED power supply 210 is V and the current of the LED light or light string is I, then I = f(V). For example, I = aV + b. Here, a and b are preset values and may be preset according to an average current of the LED light or light string 220. Therefore, in the embodiments of the present disclosure, the light intensity of the LED light(s) can be adjusted by adjusting the output voltage of the LED power supply.

[0019] Where one LED power supply simultaneously drives a plurality of LED light strings connected in parallel, the light intensity of all the LED light strings can be adjusted by adjusting the output voltage of the LED power supply without the need to additionally configuring any other relevant parameter.

[0020] Referring to Fig. 2, the embodiments of the present disclosure will be described in detail below by using one LED light string as an example as shown in Fig. 2. A plurality of LED light strings 220 may each be provided with one current controller 120. The plurality of LED light strings may be powered by one LED power supply. Alternatively, one current controller 120 may control a plurality of LED light strings 220. In addition, a voltage division circuit formed by connecting a first resistor R1 and a second resistor R2 in series may feed the output voltage of the LED power supply 210 to the current controller 120 as a reference. The current controller 120 adjusts and stabilizes the average current of the LED light string 220 according to the output voltage of the LED power supply 210 to control or adjust the brightness of the LED light. LED lights demonstrate a nearly linear relationship between the current flowing therethrough and their light intensity. Therefore, in this embodiment, the dimming control of the LED light(s) is performed by controlling the current of the LED light string 220.

[0021] In the embodiments of the present disclosure, the voltage division circuit may serve as a voltage sensing circuit. Voltage monitoring may also be realized in other ways. When one LED power supply 210 drives a plurality of LED light strings 220, each LED light string 220 may be provided with one current controller 120 and connected in parallel to the LED power supply 210. A circuit for each current controller 120 to sense the output of the LED power supply 210 may come from the same sensing point of the same voltage division circuit. Alternatively, each current controller 120 may have its own voltage sensing circuit.

[0022] The LED power supply 210 can convert a power input into a DC voltage with sufficient power to drive the LED light to emit light. The input to the LED power supply 210 may be an AC or DC voltage, while output is a DC voltage for powering the LED light(s). The LED power supply 210 may be any type of DC power supply, for example, any form of a circuit that can efficiently provide sufficient power for the LED light string 220, such as a linear power supply, an AC/DC SMPS, a DC/DC SMPS, a pulse width modulation (PWM) type SMPS, a buck-boost converter, or an LC or LRC resonator.

[0023] The LED lighting system includes the LED power supply 210, the at least one LED light string 220, and the LED dimming apparatus 100. The LED power supply 210 can supply the LED light string 220 with a voltage that meets a power requirement of the LED light string. The current controller 120 in the LED dimming apparatus 100 may include a switch control circuit 130 and at least one switch (for example, a field-effect transistor Q1 in Fig. 3). When one current controller 120 controls one LED light string 220, one switch may be provided to be connected in series with the LED light string 220. When one current controller 120 controls a plurality of LED light strings 220, a plurality of switches may be provided, and each LED light string 220 is connected to one switch such that the current of the plurality of LED light strings 220 can be controlled by one current controller 120.

[0024] As shown in Fig. 3, the switch control circuit 130 includes a current setter 131, an error amplifier 132, and a switch driver 133. The current setter 131 may set a corresponding current according to an input voltage. A voltage input terminal of the current setter 131 is connected to the voltage output terminal of the voltage monitoring module, and a current output terminal of the current setter 131 is connected to a positive input terminal of the error amplifier 132. A negative input terminal of the error amplifier 132 may be connected in series with the LED light string 220 through a sampling resistor R3 to monitor the current of the LED light string 220. The error amplifier 132 amplifies an error that is based on the difference between currents inputted into the positive input terminal and the negative input terminal. The amplified signal is output to the switch driver 133. The switch driver 133 determines a duty cycle of the switch according to the amplified signal. Then, opening and closing of the switch are controlled according to the duty cycle to acquire the required average current of the LED light string 220.

[0025] In the embodiments of the present disclosure, a field-effect transistor Q1 may be used as the switch. A gate of the field-effect transistor Q1 is connected to a control terminal of the switch driver 133. A drain and a source are connected in series in a current feedback loop of the LED light string 220.

[0026] The field-effect transistor Q1 is connected in series in a power supply loop of the LED power supply 210 and the LED light string 220 as a power switch to control the power supply for the LED light string 220 to be connected or disconnected. The dimming apparatus may further include a smoothing circuit 130 to smooth a voltage ripple generated upon the opening and closing of the switch. The field-effect transistor Q1 works in cooperation with the smoothing circuit 130. When the field-effect transistor Q1 turns on, the current output by the LED power supply 210 may flow from its positive terminal through the LED light string 220 and the smoothing circuit 130, in which case the smoothing circuit 130 can be charged to store electric energy. When the field-effect transistor Q1 is turned off, the power supply loop is disconnected, the LED power supply 210 stops outputting a current to the LED light string 220, the smoothing circuit 130 forms a closed circuit with the LED light string 220, the energy stored in the smoothing circuit 130 is discharged to the LED light string 220 through the formed closed circuit, so that the LED light string 220 can keep emitting light. Therefore, the average current of the LED light string 220 can be well regulated by controlling the duty cycle of the power switch, namely, the field-effect transistor Q1.

[0027] The smoothing circuit 130 may include a capacitor C1, an inductor L1, and a diode D1. The capacitor C1 and the LED light string 220 are connected in parallel, then connected in series with the inductor L1, and then connected in parallel to the diode D1. A direction from a positive terminal to a negative terminal of the diode D1 is opposite to the current direction of the LED light string 220. The diode D1 and a branch of the LED light string 220 and the inductor L1 connected in series are connected in parallel and then connected to the field-effect transistor Q1. The current direction from the drain to the source of the field-effect transistor Q1 is the same as the current direction of the LED light string 220. At a moment when the field-effect transistor Q1 turns on, the current output by the LED power supply 210 passes through a branch of the capacitor C1 and the inductor L1 and a branch of the LED light string 220 and the inductor L1. Once the capacitor C1 is fully charged, the current output by the LED power supply 210 no longer passes through the capacitor C1. Upon the cutoff of the field-effect transistor Q1, the LED power supply 210 no longer outputs a current to the LED light string 220, the inductor L1 discharges energy to the LED light string 220 through the closed circuit formed by the diode D1 and the LED light string 220. Energy is also discharged to the LED light string 220 through a closed circuit formed by the capacitor C1 and the LED light string 220. In addition, the smoothing circuit 130 formed by the capacitor C1, the inductor L1, and the diode D1 may further be used to smooth a voltage ripple generated upon the closing and opening of the field-effect transistor Q1.

[0028] The first resistor R1 and the second resistor R2 of the voltage division circuit are connected in series between the positive terminal and the negative terminal of the LED power supply 210, and provide a voltage monitoring point (a node between the first resistor R1 and the second resistor R2) for the current controller 120 to monitor the output voltage of the LED power supply 210. When the output voltage of the LED power supply 210 changes, a voltage at the voltage monitoring point changes, and the average current and light intensity of the LED light string also change along with it. The current controller 120 adjusts the average current of the LED light string 220 to stabilize the current and light intensity when a change in the voltage at the voltage monitoring point is detected.

[0029] The current setter 131 is connected between the voltage division circuit and the positive input terminal of the error amplifier 132 to convert a voltage signal at the voltage monitoring point into a corresponding current. In addition, the negative input terminal of the error amplifier 132 is connected between the LED light string 220 and the negative terminal of the power supply to input the current of the LED light string 220 to the error amplifier 132. The error amplifier 132 amplifies an error that is based on the difference between currents inputted into the positive input terminal and the negative input terminal. The duty cycle of the field-effect transistor Q1 is controlled by the switch driver 133 to acquire the required average current of the LED light string 220.

[0030] In summary, according to the embodiments of the present disclosure, the LED lighting system is provided with the smoothing circuit 130 and the switch, and the change in the output voltage is monitored through a current control circuit to control the duty cycle of the switch, so as to adjust or stabilize the average current and light intensity of the LED light string.

[0031] In this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", and "some examples" means that the specific features, structures, materials or features described in conjunction with the embodiment(s) or example(s) are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in any suitable manner. In addition, those skilled in the art may combine different embodiments or examples and features of different embodiments or examples described in this specification without contradicting each other.

[0032] In addition, the terms "first" and "second" are for the purpose of description only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the term "plurality" means two or more, unless otherwise explicitly and specifically defined.

[0033] The above are only some specific embodiments of the present disclosure, and the scope of protection of the present disclosure is not limited thereto. Any modification or replacement easily conceivable by those skilled in the art within the technical scope of the present disclosure should fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be subject to the scope of protection of the claims.

Claims

1. A light-emitting diode (LED) dimming apparatus, comprising:

a voltage monitoring module, which is configured to be connected between a positive terminal and a negative terminal of an LED power supply for an LED light or light string to sample an output voltage of the LED power supply; and

a current controller, which has a voltage input terminal connected to a voltage output terminal of the voltage monitoring module, the current controller being configured to be connected in series with the LED light or light string to control a current of the LED light or light string according to the output voltage of the LED power supply.

2. The apparatus of claim 1, wherein the voltage monitoring module comprises a first resistor and a second resistor connected in series, which are configured to be connected between the positive terminal and the negative terminal of the LED power supply, and a node between the first resistor and the second resistor is the voltage output terminal of the voltage monitoring module.

3. The apparatus of claim 1, wherein the current controller comprises:

at least one switch comprising a controlled terminal and at least one pair of switch contacts, the at least one pair of switch contacts being configured to be connected in series with the LED light or light string; and

a switch control circuit comprising a control terminal and a voltage input terminal, the voltage input terminal of the switch control circuit being connected to the voltage output terminal of the voltage monitoring module, and the control terminal of the switch control circuit being connected to the controlled terminal of the at least one switch to control a duty cycle of the switch according to the output voltage of the LED power supply for the LED light or light string, so as to control the current of the LED light or light string.

4. The apparatus of claim 3, wherein the switch control circuit comprises a current setter, an error amplifier, and a switch driver;

the current setter is configured to set a corresponding current according to a voltage input to the current setter and output the set current, a voltage input terminal of the current setter is connected to the voltage output terminal of the voltage monitoring module, and a current output terminal of the current setter is connected to a positive input terminal of the error amplifier;

a negative input terminal of the error amplifier is configured to be connected to a current feedback loop of the LED light or light string to sample the current of the LED light or light string; and

an output terminal of the error amplifier is connected to an input terminal of the switch driver, and a drive terminal of the switch driver is connected to the controlled terminal of the switch to control opening and closing of the switch.

5. The apparatus of claim 3, wherein the current controller further comprises a smoothing circuit, and the smoothing circuit is configured to be connected to the LED light or light string and then connected in series with the switch, so that the smoothing circuit and the LED light or light string form a closed circuit when the switch is opened, allowing energy stored in the smoothing circuit to power the LED light or light string.

6. The apparatus of claim 5, wherein the smoothing circuit comprises a capacitor, a diode, and an inductor; and the inductor and the diode are connected in series and then connected in parallel to the capacitor, the capacitor is configured to be connected in parallel to the LED light or light string, a direction from a positive terminal of the diode to a negative terminal of the diode is opposite to a current direction of the LED light or light string, and the inductor is configured to be connected in series with the LED light or light string.

7. The apparatus of claim 5, wherein the smoothing circuit comprises a diode and an inductor connected in series with the diode, the inductor is connected in series with the LED light or light string, the diode is connected in parallel to the LED light or light string, and a direction from a positive terminal of the diode to a negative terminal of the diode is opposite to a current direction of the LED light or light string.

8. The apparatus of any one of claims 3 to 7, wherein the switch is a field-effect transistor comprising: a gate connected to the control terminal of the switch control circuit; and a drain and a source connected in series in the current feedback loop of the LED light or light string to open or close the current feedback loop.

9. A light-emitting diode (LED) lighting system, comprising:

an LED power supply,

at least one LED light or at least one LED light string, and

an LED dimming apparatus according to any one of claims 1 to 8, wherein

two ends of the at least one LED light or at least one LED light string are connected to a positive terminal and a negative terminal, respectively, of the LED power supply; and

the voltage monitoring module of the LED dimming apparatus is connected between the positive terminal and the negative terminal of the LED power supply, and the current controller of the LED dimming apparatus is connected to the at least one LED light or at least one LED light string.

10. The system of claim 9, wherein the LED power supply comprises one of an alternating current/direct current (AC/DC) switched-mode power supply (SMPS) and a DC/DC SMPS.

Drawing