CN103702477A - Multi-color LED (Light-emitting Diode) illumination system and LED driving circuit based on PFM (Pulse Frequency Modulation) dimming - Google Patents

Abstract

The invention discloses a multi-color LED (Light-emitting Diode) illumination system and an LED driving circuit based on PFM (Pulse Frequency Modulation) dimming. The illumination system comprises LED light sources in at least two colors, at least two LED driving circuit parts and a control unit, wherein each LED light source is coupled to one LED driving circuit part; the control unit generates at least two PFM dimming signals and inputs the signals to the LED driving circuit parts; and the LED driving circuit parts receive input voltage and the PFM dimming signals to control average current of the LED light sources in at least two colors. The LED driving circuit comprises a switch, and the switch receives the PFM dimming signals to control on-off of the switch. Compared with the prior art, the average current of the LED light sources is accurately controlled in a PFM mode; the PFM mode is different from a PWM (Pulse Width Modulation) mode; and the PFM mode is more efficient than the PWM mode at light load and low current.

Description

Multiple color LED illumination system based on PFM light modulation and LED drive circuit

Technical field

The present invention relates to LED lighting field, particularly a kind of multiple color LED illumination system and LED drive circuit based on PFM light modulation.

Background technology

LED due to have energy-saving and environmental protection, can be light-operated, the lot of advantages such as solidification, long-life, in the today of advocating low-carbon (LC) life, be widely used in various lighting fields.

At present, development along with LED industry, constantly bringing forth new ideas of LED control mode, various LED products appear on the market in a large number, the brilliance control to monochromatic light LED of generally using at present can not meet people's needs, in order to meet user's demand, adopt the color LED technology of more than one monochromatic LED mixed lights to become the important topic of LED industry development, the light modulating device of polychromatic source can make LED lamp produce different colour temperatures and brightness, take three color scheme light as example, existing technology is mainly to adopt three road PWM(Pulse Width Modulation, pulse width modulation) mode is controlled the average current of three kinds of color LED light sources, PWM controls simple, flexibly, in LED field, there are a lot of advantages, but under certain conditions, PWM is not the optimal selection that LED controls, as underload and the low current in the situation that, PFM more has superiority than PWM.

Summary of the invention

The present invention is directed to above-mentioned the deficiencies in the prior art, a kind of multiple color LED illumination system and LED drive circuit of controlling at least two kinds of color LED light sources based on two-way PFM signal is at least provided.

Technical scheme of the present invention is achieved in that

A kind of multiple color LED illumination system based on PFM light modulation, comprise the LED light source of at least two kinds of colors, at least two LED drive circuits and control unit, the LED light source of described every kind of color is coupled to a LED drive circuit, described control unit produces at least two-way PFM dim signal and also inputs to respectively LED drive circuit, described LED drive circuit receives input voltage and PFM dim signal, thereby controls the average current of at least two kinds of color LED light sources.

As preferably, described LED drive circuit comprises a switch, and this switch is transistor or field effect transistor.

As preferably, described switch is field effect transistor, and it comprises grid, source electrode and drain electrode, and described grid receives PFM dim signal and carries out break-make with control switch.

As preferably, described LED light source comprises red LED, green LED and blue led, corresponding three LED drive circuits of the LED light source of these three kinds of colors, and the LED light source of three kinds of colors to connect separately a LED drive circuit luminous to control respectively red LED, green LED and blue led.

As preferably, described control unit produces three road PFM dim signals, and the switch that each road PFM dim signal is controlled in LED drive circuit carries out break-make, thereby controls the average current of three kinds of color LED light sources, reaches the object that regulates LED light source color and brightness.

A LED drive circuit based on PFM light modulation, it is for receiving input voltage and PFM dim signal driving LED light source, and described LED drive circuit comprises a switch, and described switch receives PFM dim signal and carries out break-make with control switch.

As preferably, described LED drive circuit adopts BUCK circuit.

Based on above-mentioned BUCK circuit, described LED drive circuit comprises switch, the diode being connected with switch, inductance and the electric capacity being connected in parallel with LED light source.

As preferably, described LED drive circuit adopts BUCK-BOOST circuit.

Based on above-mentioned BUCK-BOOST circuit, as preferably, described LED drive circuit comprises switch, the inductance being connected with switch, diode and the electric capacity being connected in parallel with LED light source.

As preferably, described LED drive circuit adopts BOOST circuit.

Based on above-mentioned BOOST circuit, described LED drive circuit comprises switch, the diode being connected with switch, inductance and the electric capacity being connected in parallel with LED light source.

As preferably, described LED drive circuit adopts Flyback circuit.

Based on above-mentioned Flyback circuit, described LED drive circuit comprises switch, transformer, diode and the electric capacity being connected in parallel with LED light source, described transformer comprises primary and secondary, and described switch is connected with primary, and described transformer secondary output is connected with diode.

Based on above-mentioned each circuit, described switch is a kind of in transistor or field effect transistor.

As preferably, described switch is field effect transistor, and it comprises grid, source electrode and drain electrode, and described grid receives PFM dim signal and carries out break-make with control switch.

Compared to prior art, the present invention adopts the mode of pulse frequency modulated PFM accurately to control the average current of LED light source, is different from PWM mode, and the in the situation that of underload and low current, PFM mode has more efficiency than PWM mode.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of multiple color LED illumination system of the present invention;

Fig. 2 is the first embodiment circuit diagram of LED drive circuit of the present invention;

Fig. 3 is another circuit diagram of the first embodiment of LED drive circuit of the present invention;

Fig. 4 is the current waveform schematic diagram of the LED drive circuit shown in Fig. 2 and Fig. 3;

Fig. 5 is the second embodiment circuit diagram of LED drive circuit of the present invention;

Fig. 6 is another circuit diagram of the second embodiment of LED drive circuit of the present invention;

Fig. 7 is the current waveform schematic diagram of the LED drive circuit shown in Fig. 5 and Fig. 6;

Fig. 8 is the 3rd embodiment circuit diagram of LED drive circuit of the present invention;

Fig. 9 is the current waveform schematic diagram of the LED drive circuit shown in Fig. 8;

Figure 10 is the 4th embodiment circuit diagram of LED drive circuit of the present invention;

Figure 11 is the current waveform schematic diagram of the LED drive circuit shown in Figure 10.

Embodiment

The specific embodiment of the present invention is as follows:

Fig. 1 is the structured flowchart of multiple color LED illumination system of the present invention, and as shown in Figure 1, multiple color LED illumination system of the present invention comprises the LED light source 1 of at least two kinds of colors, at least two LED drive circuits 2 and control units 3.LED light source 1 correspondence of described every kind of color is coupled to a LED drive circuit 2, described control unit 3 is for generation of two-way PFM dim signal at least and input to respectively LED drive circuit 2, every road PFM dim signal is controlled the LED light source 1 of independent a kind of color, thereby the LED light source of every kind of color is controlled; The LED light source of every kind of color is comprised of the LED of a plurality of colors of the same race again.Described LED drive circuit 2 receives input voltage vin and PFM dim signal, thereby controls the average current of at least two kinds of color LED light sources 1.

Preferably, described LED light source 1 comprises red LED, green LED, and blue led, such as LED1 in Fig. 1 represents red coloration LED, LED2 is representing green LED, LED3 is representing blue led, this red LED, green LED, be connected separately a LED drive circuit 2 with blue led, to control respectively red LED, green LED, luminous with blue led, PFM1, PFM2, PFM3 represents Zhe San road PFM dim signal separately, the switch that each road PFM dim signal is controlled in LED drive circuit 2 carries out break-make, thereby the LED to LED light source 1 interior every kind of color controls, reach the object of modulation LED light source color and brightness.

Figure 2 shows that the circuit diagram of the first embodiment of LED drive circuit of the present invention, as shown in Figure 2, in the present embodiment, LED drive circuit of the present invention adopts BUCK circuit, circuit working is in DCM pattern, and LED drive circuit comprises switch 21, diode 22, inductance 23 and electric capacity 24.Described switch 21 can be transistor or field effect transistor, in the present embodiment, switch 21 adopts field effect transistor, described switch 21 comprises grid, source electrode and drain electrode, the grid of described switch 21 receives PFM dim signal, this PFM dim signal carries out break-make for control switch 21, the drain electrode of described switch 21 connects input voltage vin, the source electrode of switch 21 is connected with one end of inductance 23 with the negative electrode of diode 22, the inductance other end is connected with electric capacity 24, and described LED light source 1 is connected in parallel with electric capacity 24.

Figure 3 shows that another circuit diagram of the first embodiment of LED drive circuit of the present invention, the difference of LED drive circuit shown in Fig. 3 and Fig. 2 is: the position of switch 21 is different, the grid of switch 21 receives PFM dim signal, this PFM dim signal carries out break-make, the anodic bonding of the drain electrode of switch 21 and diode 22 for control switch 21.

Fig. 4 is the current waveform schematic diagram of the LED drive circuit shown in Fig. 2 and Fig. 3, and as shown in Figure 4, Ipk is peak current, and ton is the switch conduction time, and toff is switch opening time:

$\mathrm{ton}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vin}-\mathrm{vo}},\mathrm{toff}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vo}},T_s=\frac{1}{\mathrm{fs}}.$

$I_{\mathrm{LED}}=\frac{\frac{1}{2}\&CenterDot;I_{\mathrm{pk}}\&CenterDot;(\mathrm{ton}+\mathrm{toff})}{\mathrm{Ts}}=\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;{I_{\mathrm{<figure-callout\; id="2"\; label="pk"\; filenames="HDA0000430304480000011.png"\; state="\{\{state\}\}">pk</figure-callout>}}}^2\&CenterDot;(\frac{1}{\mathrm{vin}-\mathrm{vo}}+\frac{1}{\mathrm{vo}})\&CenterDot;\mathrm{fs}.---\left(1\right)$

In formula (1), guaranteeing

for steady state value, i.e. I _lED=k ₁in the situation of fs, can realize by the frequency f s of by-pass cock 21 the accurate control of LED electric current, reach the object of modulation LED light source color and brightness.

Figure 5 shows that the circuit diagram of the second embodiment of LED drive circuit of the present invention, as shown in Figure 5, in the present embodiment, LED drive circuit of the present invention adopts BUCK-BOOST circuit, circuit working is in DCM pattern, LED drive circuit comprises switch 41, diode 42, inductance 43 and electric capacity 44, described switch 41 can be transistor or field effect transistor, in the present embodiment, take field effect transistor as example, described switch 41 comprises grid, source electrode and drain electrode, the grid of described switch 41 receives PFM dim signal, this PFM dim signal carries out break-make for control switch 41, the drain electrode of described switch 41 connects input voltage vin, the source electrode of switch 41 is connected with one end of inductance 43 with the negative electrode of diode 42, the anode of diode is connected with electric capacity 44, described LED light source 1 is connected in parallel with electric capacity 44.

Figure 6 shows that another circuit diagram of the second embodiment of LED drive circuit of the present invention, the difference of LED drive circuit shown in Fig. 6 and Fig. 5 is: the position of switch 41 is different, the grid of switch 41 receives PFM dim signal, this PFM dim signal carries out break-make for control switch 41, and the drain electrode of switch 41 is connected with one end of inductance 43.Fig. 7 is the current waveform schematic diagram of the LED drive circuit shown in Fig. 5 and Fig. 6, and as shown in Figure 7, Ipk is peak current, and ton is the switch conduction time, and toff is switch opening time:

$\mathrm{ton}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vin}},\mathrm{toff}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vo}},T_s=\frac{1}{\mathrm{fs}}.$

$I_{\mathrm{LED}}=\frac{\frac{1}{2}\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\mathrm{toff}}{\mathrm{Ts}}=\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;{I_{\mathrm{<figure-callout\; id="2"\; label="pk"\; filenames="HDA0000430304480000011.png"\; state="\{\{state\}\}">pk</figure-callout>}}}^2\&CenterDot;\frac{1}{\mathrm{vo}}\&CenterDot;\mathrm{fs}.---\left(2\right)$

In formula (2), guaranteeing

for steady state value, i.e. I _lED=k ₂in the situation of fs, can realize by the frequency f s of by-pass cock 41 the accurate control of LED electric current, reach the object of modulation LED light source color and brightness.

Figure 8 shows that the circuit diagram of the 3rd embodiment of LED drive circuit of the present invention, as shown in Figure 8, in the present embodiment, LED drive circuit of the present invention adopts BOOST circuit, circuit working is in DCM pattern, LED drive circuit comprises switch 61, diode 62, inductance 63 and electric capacity 64, described switch 61 can be transistor or field effect transistor, in the present embodiment, take field effect transistor as example, described switch 61 comprises grid, source electrode and drain electrode, the grid of described switch 61 receives PFM dim signal, this PFM dim signal carries out break-make for control switch 61, the drain electrode of described switch 61 connects one end of inductance 63, the other end of inductance 63 connects input voltage vin, switch 61 also miss the anodic bonding with diode 62, the negative electrode of diode 62 is connected with electric capacity 64, described LED light source 1 is connected in parallel with electric capacity 64.Fig. 9 is the current waveform schematic diagram of the LED drive circuit shown in Fig. 8, and as shown in Figure 9, Ipk is peak current, and ton is the switch conduction time, and toff is switch opening time:

$\mathrm{ton}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vin}},\mathrm{toff}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vo}-\mathrm{vin}},T_s=\frac{1}{\mathrm{fs}}.$

$I_{\mathrm{LED}}=\frac{\frac{1}{2}\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\mathrm{toff}}{\mathrm{Ts}}=\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;{I_{\mathrm{<figure-callout\; id="2"\; label="pk"\; filenames="HDA0000430304480000011.png"\; state="\{\{state\}\}">pk</figure-callout>}}}^2\&CenterDot;\frac{1}{\mathrm{vo}-\mathrm{vin}}\&CenterDot;\mathrm{fs}.---\left(3\right)$

In formula (3), guaranteeing

for steady state value, i.e. I _lED=k ₃in the situation of fs, can realize by the frequency f s of by-pass cock 61 the accurate control of LED electric current, reach the object of modulation LED light source color and brightness.

Figure 10 is the 4th embodiment circuit diagram of LED drive circuit of the present invention, as shown in figure 10, in the present embodiment, LED drive circuit of the present invention adopts Flyback circuit, circuit working is in DCM pattern, LED drive circuit comprises switch 81, diode 82, transformer 83 and electric capacity 84, described switch 81 can be transistor or field effect transistor, in the present embodiment, take field effect transistor as example, described switch 81 comprises grid, source electrode and drain electrode, the grid of described switch 81 receives PFM dim signal, this PFM dim signal carries out break-make for control switch 81, elementary one end of drain electrode connection transformer 83 of described switch 81, the elementary other end of transformer 83 connects input voltage vin, the anode of diode 82 is connected with the secondary of transformer 83, the negative electrode of diode 82 is connected with electric capacity 84, described LED light source 1 is connected in parallel with electric capacity 84.Figure 11 is the current waveform schematic diagram of the LED drive circuit shown in Figure 10, and as shown in figure 11, Ipk is peak current, and ton is the switch conduction time, and toff is switch opening time:

$\mathrm{ton}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vin}},\mathrm{toff}=\frac{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;I_{\mathrm{pk}}}{\mathrm{vp}\&CenterDot;\frac{\mathrm{Np}}{\mathrm{Ns}}},T_s=\frac{1}{\mathrm{fs}}.$

$I_{\mathrm{LED}}=\frac{\frac{1}{2}\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\frac{\mathrm{Np}}{\mathrm{Ns}}\&CenterDot;\mathrm{toff}}{\mathrm{Ts}}=\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000430304480000011.png,HDA0000430304480000012.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\&CenterDot;{I_{\mathrm{<figure-callout\; id="2"\; label="pk"\; filenames="HDA0000430304480000011.png"\; state="\{\{state\}\}">pk</figure-callout>}}}^2\&CenterDot;\frac{1}{\mathrm{vo}}\&CenterDot;\mathrm{fs}.---\left(4\right)$

In formula (4), guaranteeing

for steady state value, i.e. I _lED=k ₄in the situation of fs, can realize by the frequency f s of by-pass cock 81 the accurate control of LED electric current, reach the object of modulation LED light source color and brightness.

Compared to prior art, the present invention adopts the mode of pulse frequency modulated PFM accurately to control the average current of LED light source, wherein PFM mode is the technology that method by regulating impulse frequency realizes voltage stabilizing output, and its pulse duration is fixed and frequency changes; And PWM mode is to utilize the output of pulse width control signal, be the wide and narrow variation of frequency, and PFM mode is the variation of having of frequency and nothing, the in the situation that of underload and low current, PFM mode has more efficiency than PWM mode.

The preferred embodiment of the present invention is just for helping to set forth the present invention.Preferred embodiment does not have all details of detailed descriptionthe, and also not limiting this invention is only described embodiment.Obviously, according to the content of this specification, can make many modifications and variations.These embodiment are chosen and specifically described to this specification, is in order to explain better principle of the present invention and practical application, thereby under making, technical field technical staff can utilize the present invention well.The present invention is only subject to the restriction of claims and four corner and equivalent.Disclosed is above only several specific embodiments of the application, but the application is not limited thereto, and the changes that any person skilled in the art can think of, all should drop in the application's protection range.

Claims (16)

1. the multiple color LED illumination system based on PFM light modulation, it is characterized in that: comprise the LED light source of at least two kinds of colors, at least two LED drive circuits and control unit, the LED light source of described every kind of color is coupled to a LED drive circuit, described control unit produces at least two-way PFM dim signal and also inputs to respectively LED drive circuit, described LED drive circuit receives input voltage and PFM dim signal, thereby controls the average current of at least two kinds of color LED light sources.

2. the multiple color LED illumination system based on PFM light modulation according to claim 1, is characterized in that: described LED drive circuit comprises a switch, and this switch is transistor or field effect transistor.

3. the multiple color LED illumination system based on PFM light modulation according to claim 2, is characterized in that: described switch is field effect transistor, and it comprises grid, source electrode and drain electrode, and described grid receives PFM dim signal and carries out break-make with control switch.

4. the multiple color LED illumination system based on PFM light modulation according to claim 3, it is characterized in that: described LED light source comprises red LED, green LED and blue led, corresponding three LED drive circuits of the LED light source of these three kinds of colors, and the LED light source of three kinds of colors to connect separately a LED drive circuit luminous to control respectively red LED, green LED and blue led.

5. the multiple color LED illumination system based on PFM light modulation according to claim 4, it is characterized in that: described control unit produces three road PFM dim signals, the switch that each road PFM dim signal is controlled in LED drive circuit carries out break-make, thereby control the average current of three kinds of color LED light sources, reach the object that regulates LED light source color and brightness.

6. the LED drive circuit based on PFM light modulation, it,, for receiving input voltage and PFM dim signal driving LED light source, is characterized in that: described LED drive circuit comprises a switch, described switch receives PFM dim signal and carries out break-make with control switch.

7. the LED drive circuit based on PFM light modulation according to claim 6, is characterized in that: described LED drive circuit adopts BUCK circuit.

8. the LED drive circuit based on PFM light modulation according to claim 7, is characterized in that: described LED drive circuit comprises switch, the diode being connected with switch, inductance and the electric capacity being connected in parallel with LED light source.

9. the LED drive circuit based on PFM light modulation according to claim 6, is characterized in that: described LED drive circuit adopts BUCK-BOOST circuit.

10. the LED drive circuit based on PFM light modulation according to claim 9, is characterized in that: described LED drive circuit comprises switch, the inductance being connected with switch, diode and the electric capacity being connected in parallel with LED light source.

11. LED drive circuits based on PFM light modulation according to claim 6, is characterized in that: described LED drive circuit adopts BOOST circuit.

12. LED drive circuits based on PFM light modulation according to claim 11, is characterized in that: described LED drive circuit comprises switch, the diode being connected with switch, inductance and the electric capacity being connected in parallel with LED light source.

13. LED drive circuits based on PFM light modulation according to claim 6, is characterized in that: described LED drive circuit adopts Flyback circuit.

14. LED drive circuits based on PFM light modulation according to claim 13, it is characterized in that: described LED drive circuit comprises switch, transformer, diode and the electric capacity being connected in parallel with LED light source, described transformer comprises primary and secondary, described switch is connected with primary, and described transformer secondary output is connected with diode.

15. according to the LED drive circuit based on PFM light modulation described in claim 6-14 any one, it is characterized in that: described switch is a kind of in transistor or field effect transistor.

16. LED drive circuits based on PFM light modulation according to claim 15, is characterized in that: described switch is field effect transistor, and it comprises grid, source electrode and drain electrode, and described grid receives PFM dim signal and carries out break-make with control switch.

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