LED dimming circuit, dimming method and LED control circuit

Abstract

The present invention proposes an LED dimming circuit, a dimming method and an LED control circuit, wherein the LED dimming circuit comprises an impedance circuit and a conversion circuit, wherein the impedance circuit is connected in series with the LED; the conversion circuit receives a dimming signal and outputs a switch control signal, wherein the switch control signal controls the on and off of a corresponding switch or a corresponding switch tube in the impedance circuit; the dimming signal is a PWM signal or an analog signal. The present invention has high dimming accuracy, a wide dimming range and a simple dimming scheme.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to an LED dimming circuit, a dimming method and an LED control circuit. Background Art

[0002] LED dimming circuits commonly used in the prior art are as follows: Figure 1 As shown, the compensation signal Vcomp is obtained by the error between the output current sampling signal Vs and the reference voltage VREF to control the LED load current. If you want to reduce the output current, you need to reduce the reference voltage VREF synchronously. However, due to the error amplifier U01 device itself, there is an offset voltage Vos, which makes it difficult to control the accuracy of adjusting the reference voltage VREF. In particular, when the output current needs to be adjusted to close to 0, the reference voltage VREF also needs to be adjusted to close to 0, then the ratio of the offset voltage Vos to the reference voltage VREF will be very large, which is equivalent to a large deviation between the output current and the expected value, which also indicates that the influence of uncontrollable factors such as the offset voltage Vos is very large. Summary of the invention

[0003] The object of the present invention is to provide an LED dimming circuit, a dimming method and an LED control circuit, so as to solve the problem of inaccurate dimming accuracy in the prior art.

[0004] To achieve the above-mentioned purpose, the present invention provides an LED dimming circuit, including an impedance circuit and a conversion circuit, wherein the impedance circuit is connected in series with the LED; the conversion circuit receives a dimming signal and outputs a switch control signal, and the switch control signal controls the on and off of a corresponding switch or a corresponding switch tube in the impedance circuit; the dimming signal is a PWM signal or an analog signal.

[0005] Optionally, the LED dimming circuit also includes a compensation circuit, wherein a first input terminal of the compensation circuit receives a feedback signal representing a load current, and a second input terminal of the compensation circuit receives a reference signal. The compensation circuit compensates for an error between the feedback signal and the reference signal and outputs a compensation signal, and the compensation signal controls the load current.

[0006] Optionally, the impedance circuit includes multiple parallel circuits, each of which is connected in series, and each parallel circuit is composed of a switch and a resistor in parallel.

[0007] Optionally, the impedance circuit includes a plurality of series circuits, each of which is connected in parallel, and each series circuit is composed of a resistor and a switch connected in series.

[0008] Optionally, the impedance circuit includes a plurality of switching tubes connected in parallel.

[0009] Optionally, the LED dimming circuit also includes a first control circuit and a feedback circuit, wherein the first end of the first control circuit is connected to the first end of the impedance circuit, the second end of the first control circuit receives a first reference voltage, and the output end of the first control circuit is connected to the control end of the impedance circuit; the first end of the feedback circuit is connected to the first end of the impedance circuit, the second end of the feedback circuit is connected to the control end of the first control circuit, and the feedback circuit outputs the feedback signal.

[0010] Optionally, the feedback circuit includes a first operational amplifier, a first adjustment tube and a second adjustment tube, the first end of the first adjustment tube is connected to the first input end of the compensation circuit, the second end of the first adjustment tube is connected to the first end of the second adjustment tube, the second end of the second adjustment tube is grounded, and the control end of the second adjustment tube is connected to the output end of the first control circuit; the first input end of the first operational amplifier is connected to the first end of the impedance circuit, the second input end of the first operational amplifier is connected to the common connection end of the first adjustment tube and the second adjustment tube, and the output end of the first operational amplifier is connected to the control end of the first adjustment tube; the current flowing through the second adjustment tube is the feedback signal.

[0011] Optionally, the impedance circuit includes a plurality of switch modules connected in parallel, each switch module includes an adjustment tube and two switches, the first ends of each adjustment tube are connected, and the connection end thereof is the first end of the impedance circuit, the control end of each adjustment tube is connected to the output end of the second operational amplifier through one of the switches, and the control end of each adjustment tube is connected to its second end through another switch and then grounded; the switch control signal controls the on and off of the two switches in each switch module, and the switch control signals received by the two switches are opposite signals.

[0012] The present invention also provides an LED dimming method, in which an impedance circuit is connected in series with an LED, and a conversion circuit converts a dimming signal into a switch control signal, and the switch control signal controls the on and off of a corresponding switch or a corresponding switch tube in the impedance circuit; the dimming signal is a PWM signal or an analog signal.

[0013] The present invention also provides an LED control circuit, comprising any one of the above LED dimming circuits.

[0014] Compared with the prior art, the present invention has the following advantages: the impedance circuit is connected in series with the LED, the conversion circuit converts the dimming signal into a switch control signal, the switch control signal controls the on and off of the corresponding switch or the corresponding switch tube in the impedance circuit; the dimming signal is a PWM signal or an analog signal. The present invention has high dimming accuracy, a wide dimming range, and a simple dimming scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1This is a schematic diagram of a dimming circuit in the prior art;

[0016] Figure 2 This is a schematic diagram of a dimming circuit embodiment 1 of the present invention;

[0017] Figure 3 For the present invention Figure 2 Schematic diagram of the first embodiment of the medium impedance circuit;

[0018] Figure 4 For the present invention Figure 2 Schematic diagram of the second embodiment of the medium impedance circuit;

[0019] Figure 5 For the present invention Figure 2 Schematic diagram of the third embodiment of the medium impedance circuit;

[0020] Figure 6 This is a schematic diagram of a second embodiment of a dimming circuit according to the present invention;

[0021] Figure 7 This is a schematic diagram of an impedance circuit in Embodiment 2 of the present invention; DETAILED DESCRIPTION

[0022] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0023] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0024] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportions, in order to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0025] like Figure 2As shown, a schematic diagram of a dimming circuit embodiment of the present invention is shown, which includes a conversion circuit U00, an impedance circuit U01, a compensation circuit, a capacitor C00 and an LED driving circuit U03. The compensation circuit includes an operational amplifier U02 and a capacitor C00. The impedance circuit U01, the LED driving circuit U03 and the LED are connected in series. The inverting input terminal of the operational amplifier U02 is connected to the first end of the impedance circuit U01, and its in-phase output terminal receives a reference signal VREF. Its output terminal is connected to the first end of the capacitor C00, and the second end of the capacitor C00 is grounded. The operational amplifier U02 outputs a control signal Vcomp to the LED driving circuit to control the LED current. The conversion circuit U04 receives the dimming signal and outputs a switch control signal Q1, Q2, Q3, ..., Qn to control the on and off of the corresponding switch or the corresponding switch tube in the impedance circuit U00. The dimming signal is a PWM signal or an analog signal Vd. When the dimming signal is a PWM signal, the conversion circuit U04 calculates the duty cycle of the PWM signal and outputs the switch control signal after decoding; when the dimming signal is an analog signal Vd, the conversion circuit U04 converts the analog signal Vd into a digital signal and outputs the switch control signal after decoding.

[0026] like Figure 3 As shown, the present invention is illustrated Figure 2 The impedance circuit embodiment 1 schematic diagram, the impedance circuit includes a plurality of parallel circuits, each parallel circuit is connected in series, each parallel circuit is composed of a switch Qi (i is 1 to n in sequence) and a resistor in parallel, and the switch control signals Q1, Q2, Q3, ..., Qn respectively control the on and off of the corresponding switch in each parallel circuit. In this embodiment, the resistance value of each resistor is proportional.

[0027] like Figure 4 As shown, the present invention is illustrated Figure 2 The schematic diagram of the second embodiment of the impedance circuit, the impedance circuit includes multiple series circuits, each of which is connected in parallel, each series circuit is composed of a resistor and a switch i in series (i is 1 to n in sequence), and the switch control signals Q1, Q2, Q3, ..., Qn respectively control the on and off of the corresponding switches in each series circuit, and the resistance value of each resistor in the embodiment is proportional.

[0028] like Figure 5 As shown, the present invention is illustrated Figure 2 The schematic diagram of the third embodiment of the medium impedance circuit includes a plurality of parallel switch tubes M1, M2, ..., Mn, and the switch control signals Q1, Q2, Q3, ..., Qn respectively control the on and off of the switch tubes M1, M2, ..., Mn to control the output current. In this embodiment, the size of each switch tube is proportional.

[0029] like Figure 6As shown, the schematic diagram of the second real-time example of the dimming circuit of the present invention is illustrated, including the first control circuit, the impedance circuit U1, the conversion circuit U3, the feedback circuit U4, the compensation circuit and the LED driving circuit U5. The impedance circuit U1 and the LED are connected in series, the first control circuit includes the second operational amplifier U2 and the capacitor C01, the in-phase input terminal of the second operational amplifier U2 is connected to the first terminal of the impedance circuit U1, the inverting input terminal of the second operational amplifier U2 receives the first reference voltage VREF1, the output terminal of the second operational amplifier U2 is connected to the first terminal of the capacitor C01, the second terminal of the capacitor C01 is grounded, and the output terminal of the second operational amplifier U2 is connected to the control terminal of the impedance circuit U1. The conversion circuit U3 receives the dimming signal and outputs the switch control signal Q1, Q2, Q3, ..., Qn, and the switch control signal controls the on and off of the corresponding switch in the impedance circuit U1. The feedback circuit includes the first operational amplifier U4, the first adjustment tube M01 and the second adjustment tube M02; the compensation circuit includes a reference current source and a capacitor C00, and the reference current source outputs a reference signal IREF. The first end of the first adjustment tube M01 is connected to the reference current source, the second end of the first adjustment tube M01 is connected to the first end of the second adjustment tube M02, the second end of the second adjustment tube M02 is grounded, and the control end of the second adjustment tube M02 is connected to the output end of the first control circuit; the first input end of the first operational amplifier U4 is connected to the first end of the impedance circuit U1, the second input end of the first operational amplifier U4 is connected to the common connection end of the first adjustment tube M01 and the second adjustment tube M02, and the output end of the first operational amplifier U3 is connected to the control end of the first adjustment tube M01; the current flowing through the second adjustment tube M02 is the feedback signal I1. The first end of the capacitor C00 is connected to the common end of the reference current source and the first adjustment tube M01, the second end of the capacitor C00 is grounded, the voltage on the capacitor C00 is the compensation signal Vcomp, and the control end of the LED drive circuit U5 receives the control signal Vcomp to drive the LED.

[0030] like Figure 7As shown, the schematic diagram of the impedance circuit in the second embodiment of the present invention is illustrated, including multiple switch modules, each switch module includes two switches and an adjustment tube, the first end of each adjustment tube is connected to the LED load, the control end of each adjustment tube is connected to the output end of the first control circuit through one of the switches, and the control end of each adjustment tube is connected to the second end through another switch and then grounded. According to needs, the ratio between different adjustment tubes and the second adjustment tube M02 is set. Assuming that the conversion circuit inputs a dimming signal and outputs a switch control signal 100.......0, the output end of the first control circuit is controlled to be connected to the control end of the adjustment tube M1, the control end of the adjustment tube M1 is disconnected from its second end, the adjustment tube M1 is turned on, and other adjustment tubes are controlled to be disconnected. Compared with the first embodiment of the present invention, this embodiment can adjust the voltage of the control end of the corresponding adjustment tube in the impedance circuit in real time, and the control accuracy is higher.

[0031] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0032] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. An LED dimming circuit, characterized in that: It includes an impedance circuit and a conversion circuit, wherein the impedance circuit is connected in series with the LED; the conversion circuit receives a dimming signal and outputs a switch control signal, wherein the switch control signal controls the on and off of a corresponding switch or a corresponding switch tube in the impedance circuit; the dimming signal is a PWM signal or an analog signal; The conversion circuit decodes the dimming signal and outputs a plurality of switch control signals, wherein the plurality of switch control signals respectively control the on and off of corresponding switches or corresponding switch tubes in the impedance circuit to adjust the resistance value of the impedance circuit; The LED dimming circuit also includes a compensation circuit, a first input end of the compensation circuit receives a feedback signal representing a load current, a second input end of the compensation circuit receives a reference signal, the compensation circuit compensates for an error between the feedback signal and the reference signal, and outputs a compensation signal, the compensation signal controls the load current, and the feedback signal represents a voltage of the impedance circuit.

2. The LED dimming circuit according to claim 1, characterized in that: The impedance circuit includes a plurality of parallel circuits, each of which is connected in series, and each parallel circuit is composed of a switch and a resistor in parallel.

3. The LED dimming circuit according to claim 1, characterized in that: The impedance circuit includes a plurality of series circuits, each of which is connected in parallel, and each of which is composed of a resistor and a switch connected in series.

4. The LED dimming circuit according to claim 1, characterized in that: The impedance circuit includes a plurality of switching tubes connected in parallel.

5. The LED dimming circuit according to claim 1, characterized in that: The LED dimming circuit further includes a first control circuit and a feedback circuit, wherein a first end of the first control circuit is connected to a first end of the impedance circuit, a second end of the first control circuit receives a first reference voltage, and an output end of the first control circuit is connected to a control end of the impedance circuit; a first end of the feedback circuit is connected to a first end of the impedance circuit, a second end of the feedback circuit is connected to an output end of the first control circuit, and the feedback circuit outputs the feedback signal; The first control circuit includes a second operational amplifier, a first input terminal of the second operational amplifier is connected to the first terminal of the impedance circuit, a second input terminal of the second operational amplifier receives the first reference voltage, and an output terminal of the second operational amplifier is connected to the control terminal of the impedance circuit.

6. The LED dimming circuit according to claim 5, characterized in that: The feedback circuit includes a first operational amplifier, a first adjustment tube and a second adjustment tube, wherein the first end of the first adjustment tube is connected to the first input end of the compensation circuit, the second end of the first adjustment tube is connected to the first end of the second adjustment tube, the second end of the second adjustment tube is grounded, and the control end of the second adjustment tube is connected to the output end of the first control circuit; the first input end of the first operational amplifier is connected to the first end of the impedance circuit, the second input end of the first operational amplifier is connected to the common connection end of the first adjustment tube and the second adjustment tube, and the output end of the first operational amplifier is connected to the control end of the first adjustment tube; the current flowing through the second adjustment tube is the feedback signal.

7. The LED dimming circuit according to claim 5 or 6, characterized in that: The impedance circuit includes a plurality of switch modules connected in parallel, each switch module includes an adjustment tube and two switches, the first ends of each adjustment tube are connected, and the connection end is the first end of the impedance circuit, the control end of each adjustment tube is connected to the output end of the second operational amplifier through one of the switches, and the control end of each adjustment tube is connected to the second end through another switch and then grounded; the switch control signal controls the on and off of the two switches in each switch module, and the switch control signals received by the two switches are opposite signals.

8. An LED control circuit, characterized in that: The invention comprises any one of the LED dimming circuits of claims 1 to 7.

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