WO2009057343A1

WO2009057343A1 - Resonant mode switching controller circuit for driving red led, green led and blue led connected in series

Info

Publication number: WO2009057343A1
Application number: PCT/JP2008/061084
Authority: WO
Inventors: Yen-Tang Hsu
Original assignee: Ultimax Corporation (Hk) Limited
Priority date: 2008-06-11
Filing date: 2008-06-11
Publication date: 2009-05-07
Also published as: JP2010507903A; JP4527798B2

Abstract

A resonant mode switching controller circuit for driving a Red LED, a Green LED and a Blue LED connected in series, comprises a DC power source, a step down circuit comprising a first transistor, a first diode and a first choke coil, a polarity reversal circuit comprising a second transistor, a second diode and a second choke coil, a Red LED, a Green LED and a Blue LED connected in series between the positive output terminal of the step down circuit and the negative output terminal of the polarity reversal circuit, and filter units, each including a Xu element and respectively connected in parallel to the first or second choke coil, wherein the step down circuit and the polarity reversal circuit are connected in parallel to the DC power source.

Description

DESCRIPTION

RESONANT MODE SWITCHING CONTROLLER CIRCUIT FOR DRIVING RED LED, GREEN LED AND BLUE LED CONNECTED IN SERIES

TECHNICAL FIELD

[0001] The invention relates to the field of LED driving circuitry. More particularly, this invention relates to LED driving circuitry for driving R, G, and B LEDs connected in series.

BACKGROUND ART

[0002] Conventionally, in order to generate white light using Red LED (Light Emission Diode) , Green LED and Blue LED, these LEDs are connected in parallel as is shown in Fig. 1 (see, Japanese Patent Laid-Open No. 2005-302712) . This is because each color LED has its own characteristic regarding driving voltage.

DISCLOSURE OF INVENTION

[0003] The present invention provides a LED driver circuitry to drive serially connected Red LED, Green LED and Blue LED.

[0004] According to one aspect of the present invention, there is provided a resonant mode switching controller circuit for driving Red LED, Green LED and Blue LED connected in series, comprising a DC power source, a step down circuit comprising a first transistor, a first diode and a first choke coil, a polarity reversal circuit comprising a second transistor, a second diode and a second, choke coil, a Red LED, a Green LED and a Blue LED connected in series between the positive output terminal of the step down circuit and the negative output terminal of the polarity reversal circuit, a first filter unit including a Xu element connected in parallel to the first choke coil and a second filter unit including a Xu element connected in parallel to the second choke coil, wherein the step down circuit and the polarity reversal circuit are connected in parallel to the DC power source.

[0005] According to another aspect of the present invention, the first transistor and the second transistor may be switched by input signals having frequencies in a mega hertz (MHz) bandwidth. The frequencies of the input signals may fall within 50 MHz through 100 MHz.

[0006] According to a further aspect of the present invention, the Xu element may comprise, a first dielectric material, wherein impedance of the first dielectric material decreases with increase in frequency, and a second dielectric material, wherein the second dielectric material is located adjacent to the first dielectric material and impedance of the second dielectric material increases with increase in frequency, wherein the first and second dielectric materials are sintered.

[0007] According to further aspect of the present invention, the Xu element may comprise, a mixed dielectric material, wherein the mixed dielectric material is a mixture of a first dielectric material and a second dielectric material, impedance of the first dielectric material decreasing with increase in frequency and that of the second dielectric material increasing with increase in frequency, wherein the mixed dielectric material is sintered.

[0008] According to further aspect of the present invention, the Xu element may comprises, a mixed dielectric material, wherein the mixed dielectric material is a mixture of a first dielectric material and a second dielectric material, impedance of the first dielectric material decreasing with increase in frequency and that of the second dielectric material increasing with increase in frequency, wherein the first and second dielectric materials are sintered prior to the mixture.

[0009] According to further aspect of the present invention, the first dielectric material may have a negative temperature coefficient of resistance, and the second dielectric material has a positive temperature coefficient of resistance. [0010] According to further aspect of the present invention, the first dielectric material may be a metal oxide or a metal nitride and the second dielectric material may be a metal dielectric material or a gallium arsenide.

[0011] The preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Electronic elements in some embodiments can be applied to various electronic circuitry (including electrical circuitry) .

BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1 shows a traditional circuit to drive a Red LED, a Green LED, and a Blue LED each connected in parallel.

[0013] Fig. 2 shows a resonant mode switching controller circuit for driving a Red LED, a Green LED and a Blue LED connected in series. [0014] Fig. 3 shows a variation of resistance (impedance) of a positive type (p-type) dielectric material as a function of temperature. [0015] Fig. 4 shows a variation of temperature (current I) of a p-type dielectric material as a function of time. This corresponds to a capacitance charge or inductance discharge curve. [0016] Fig. 5 shows a variation of resistance (impedance) of a negative type (n-type) dielectric material as a function of temperature. [0017] Fig. 6 shows a variation of temperature

(voltage V) of a v-type dielectric material as a function of time. This corresponds to an inductance charge or capacitance discharge curve.

[0018] Fig. 7 shows I-V characteristics of a p- type dielectric material.

[0019] Fig. 8 shows V-I characteristics of an n- type dielectric material.

[0020] Fig. 9 shows dual tunnel effect with hysteresis .

[0021] Fig. 10 shows RF power applied to the Xu element as a function of time.

[0022] Fig. 11 shows RF power applied to the Xu element as a function of frequency, corresponding to

Fig. 10.

[0023] Fig. 12 is a flowchart illustrating a manufacturing method of an electronic element according to a first embodiment of the invention.

[0024] Fig. 13 is a flowchart illustrating a manufacturing method of an electronic element according to a second embodiment of the invention.

[0025] Fig. 14 shows a variation of amplitude of series notch oscillators as a function of frequency.

[0026] Fig. 15 shows a variation of amplitude of parallel notch oscillators as a function of frequency.

BEST MODE FOR CARRYING OUT THE INVENTION [0027] Hereinafter, embodiments of the present invention shall be described in detail with reference to the appended drawings.

[0028] Fig. 2 shows a resonant mode switching controller circuit for driving Red LED, Green LED and

Blue LED connected in series. The circuit has filter units including Xu elements. The circuit also has a DC power source DC, transistors TrI and Tr2, and diodes Dl and D2, choke coils Ll and L2, capacitors Cl, C2, C3 and C4.

[0029] The transistor TrI, diode Dl and choke coil

Ll and capacitors Cl and C2 are connected to arrange a step down circuit 201. One Xu element XuI is connected in parallel to the choke coil Ll with a capacitor C5 to arrange a filter unit Fl.

[0030] The transistor Tr2, diode D2 and choke coil

L2 and capacitors C3 and C4 are connected to arrange a polarity reversal circuit 202. Another Xu element Xu2 is connected in parallel to the choke coil L2 with a capacitor C6 to arrange a filter unit F2.

[0031] The step down circuit 201 and the polarity reversal circuit 202 are connected in parallel to the power source DC.

[0032] Regarding Xu elements, detailed description will be provided in the following.

[0033] A red LED R, a green LED G and a blue LED B are connected in series to the positive output terminal Vo of the step down circuit 201 and negative output terminal -Vo of the polarity reversal circuit 202. The order of series connection is not limited to the pattern shown in Fig. 2.

[0034] The red, green and blue LEDs may be integrated into one element or divided into each dependent element, as long as these red and green and blue LEDs are connected in series. [0035] The transistor TrI is switched by a switching signal Sl inputted to a base. The transistor Tr2 is also switched by a switching signal S2 inputted to a base. The switching signals Sl and S2 have frequencies in MHz bandwidth. Preferably, frequencies of Sl and S2 fall within 50 MHz through 100 MHz. [0036] In a conventional LED circuitry, the transistor TrI and Tr2 cannot be switched by signals of MHz frequencies, because of the Lenz's law. Further, when RF power is applied to the choke coil, the RF power is consumed in the inductor of the choke coil. [0037] On the other hand, according to the preferred embodiment, the transistors TrI and Tr2 are switched by MHz frequency signals by using the filter Fl and F2. Since the filter units Fl and F2 are connected in parallel to the inductor of the choke coils Ll and L2, the RF power applied to the inductor is not consumed due to the function of the filter units. [0038] A spectrum of the emitted light by the red LED R, green LED G and blue LED B can be controlled to fall within a range from IR to UV.

[0039] The resonant mode switching controller circuit of the present invention can work as a RF (radio frequency: very high frequency) power source or a resonant mode RF generator.

[0040] In the present invention, the filter unit Fl and F2 are enough and there is no need to have a multistage filter. The number of stages has limitations, and therefore the power loss remains. In addition, the number of filters, the size and the cost increase as the number of stages increases. According to the present invention, the power loss can be reduced with a simple structure and it is possible to reduce the heat. [0041] In the following, detailed descriptions regarding the Xu elements are provided. [0042] Fig. 3 shows a variation of resistance (impedance) of a positive type (p-type) dielectric material as a function of temperature. For lower temperature below T_R^_IΠ, the resistance decreases with temperature. However, for temperature over TR_mi_n, the resistance increases with temperature and positive slope is obtained. The temperature T₃ is the temperature that the corresponding resistance is twice that of R 25 degrees C. Fig. 4 shows a variation of temperature (current I) of a p-type dielectric material as a function of time. As shown in Fig. 4, the temperature (current I) gradually increases with time. [0043] Fig. 5 shows a variation of resistance (impedance) of a negative type (n-type) dielectric material as a function in temperature. Note that resistance of the n-type dielectric material decreases with the increase of temperature and negative slope is obtained. Fig. 6 shows a variation of temperature (voltage V) of a v-type dielectric material as a function of time. As shown in Fig. 6, the temperature (voltage V) gradually decreases with time. [0044] Fig. 7 shows I-V characteristics of a p- type dielectric material. When the applied voltage is smaller than 10 V, the current increases with the increase in voltage. When the applied voltage is greater than 10 V, the current gradually decreases with the increase in voltage. Therefore, the p-type dielectric material functions as a dielectric inductor. [0045] Fig. 8 shows V-I characteristics of an retype dielectric material. At the voltage across the n- type dielectric material is highest at the current Io- When the current is smaller than Io, the voltage increases with the current. When the current is greater than Io, the voltage gradually decreases with the current. Therefore, the n-type dielectric material functions as a dielectric capacitor. [0046] As will be further discussed herein, the p- type dielectric material and the n-type dielectric material are sintered and are arranged adjacent to each other. Such an arrangement advantageously allows the sintered materials to function as a filter, the cutoff frequency of which varies effectively according to the frequency of an input signal. This effect is explained in Fig. 9.

[0047] Fig. 9 shows the dual tunnel effect with hysteresis in a time domain. A in Fig. 9 shows I-V characteristics of p-type and n-type dielectric materials, corresponding to Figs 7 and 8. When the p- type and n-type dielectric materials are sintered and are arranged adjacent to each other, the resultant materials shows hysteresis effect of resistance as shown in B in Fig. 9 in a frequency domain. The frequency response as shown in B in Fig. 9 behaves a circle feature and be changed according to the frequency of an input signal input. We call the sintered material the "Xu element." According to the preferred embodiments of the present invention, a plurality of LC filters are not necessary to handle a plurality of cutoff frequencies. Such a dynamically- regulated cutoff frequency may also be advantageous for electronic devices such as a cellular phone, a computer, a light-emitting diode and a solar cell. [0048] Fig. 10 shows RF power applied to the Xu element as a function of time. Note that the RF power allied to the Xu element decreases in a very short time. If the input RF power with another frequency is applied, the cutoff frequency of Xu element is changed to conform that, and therefore the RF power decreases without an additional filter, which has the cutoff frequency to cancel the input RF power with another frequency.

[0049] Fig. 11 shows RF power applied to the Xu element as a function of frequency, corresponding to Fig. 10. As shown in Fig. 11, the applied RF power gradually decreases with change in frequency. This may be caused by the excellent change of the cutoff frequency of Xu element. As a result, the applied RF power vanishes in a very short time. [0050] Fig. 12 is a flowchart illustrating a manufacturing method of an electronic element according to the preferred embodiment of the invention. [0051] In step 13a, a first dielectric material (n-type dielectric material) 101 is prepared. The impedance of the first dielectric material 101 decreases with increase in frequency. The first dielectric material 101 may be, for example, a metal oxide (e.g., AI₂O₃) or a metal nitride (e.g., AlN), although the present invention is not limited to these materials .

[0052] In step 13b, a second dielectric material (p-type dielectric material) 102 is located adjacent to the first dielectric material 101. The impedance of the second dielectric material 102 increases with increase in frequency. The second dielectric material 102 may be, for example, a gallium arsenide or a metal dielectric material (e.g., BaTiC>₃) , although the present invention is not limited to these materials. [0053] Then, the first dielectric material 101 and the second dielectric material 102 are sintered to form a conductor. Although the sintering temperature is dependent on the first and second dielectric materials 101 and 102, the preferable range of the sintering temperature is from 1000 degrees C to 1400 degrees C, and more preferable range of the sintering temperature is from 1100 degrees C to 1300 degrees C, and the most preferable sintering temperature is 1200 degrees C. This allows the first and second dielectric materials 101 and 102 to become conductors of an electronic element (the Xu element) .

[0054] The resonance frequency of the resultant electronic element varies effectively according to the frequency of an input signal and eventually conforms to the frequency of the input signal. Therefore, excellent impedance matching is achieved, thereby largely reducing power loss.

[0055] Although the first and second dielectric materials 101 and 102 are sintered after these materials are prepared, these materials may be located adjacent to each other after they are sintered in advance. A resistance such as a ceramic resonant element may also be arranged between the first and second dielectric materials 101 and 102. [0056] Preferably, the first dielectric material 101 has a negative temperature coefficient of resistance and the second dielectric material 102 has a positive temperature coefficient of resistance. It is also preferable that the temperature coefficient of resistance of the first dielectric material 101 and that of the first dielectric material 102 are substantially the same value. That is, it is preferable that the temperature coefficient of resistance of the first and second dielectric materials 101 and 102 have substantially the same magnitude and are opposite in sign.

[0057] Fig. 13 is a flowchart illustrating a manufacturing method of an electronic element according to the preferred embodiment of the invention. [0058] In step 14a, first dielectric material powder and second dielectric material powder are prepared. Then, these materials are mixed to form a mixed dielectric material 1301. The impedance of the first dielectric material 101 decreases with increase in frequency. The first dielectric material 101 may be, for example, a metal oxide or a metal nitride. The impedance of the second dielectric material 102 increases with increase in frequency. The second dielectric material 102 may be, for example, a gallium arsenide or a metal dielectric material (e.g., Al₂O₃ or BaTiO₃) .

[0059] In step 14b, the mixed dielectric material 1301 is formed in step 14a. This sintering process allows the dielectric materials to change from an insulator to a conductor 1302, and thereby forming an electronic element (the Xu element) according to the preferred embodiment. In step 14b, the preferable range of the sintering temperature is from 1000 degrees C to 1400 degrees C, and more preferable range of the sintering temperature is from 1100 degrees C to 1300 degrees C, and the most preferable sintering temperature is 1200 degrees C. [0060] Thus, electronic elements can be manufactured with a simple structure. The resonance frequency of the resultant electronic element varies effectively according to the frequency of an input signal and eventually conforms to the frequency of the input signal. Therefore, excellent impedance matching is achieved, thereby largely reducing the power loss. [0061] Although the powder of the first and second dielectric materials is sintered after these materials are mixed, these materials may be mixed after they are sintered in advance. [0062] Preferably, the first dielectric material has a negative temperature coefficient of resistance and the second dielectric material has a positive temperature coefficient of resistance. It is also preferable that the temperature coefficient of resistance of the first dielectric material and that of the first dielectric material have substantially the same magnitude. That is, it is preferable that the temperature coefficient of resistance of the first and second dielectric materials have substantially the same magnitude and are opposite in sign. [0063] The example of the Xu element will be described below, however, the Xu element to be used in the present invention is not limited to this example. [0064] First, a first dielectric material, the impedance of which decreases with increase in frequency, and a second dielectric material, the impedance of which increases with increase in frequency, are refined and mixed. Then, a catalyst is added to the mixed materials and the mixed materials are sintered to become a mixed dielectric material. [0065] Next, the mixed dielectric material is polished (milled) and dielectric material powder is obtained by a spray drying process. Then, the power is molded.

[0066] Next, powder metallurgy (sintering) is performed by a powder metallurgical furnace at high temperature after the molding process. The powder becomes a conductor after the powder metallurgy process. [0067] Finally, the high temperature powder metallurgical material is molded and connected to the conducting wires. The finished conductive product (i.e., an electronic element) is thus obtained. [0068] The resultant finished conductive product has, for example, the nature of frequency self- oscillation, induced alternating current, magnetic phenomenon (hysteresis), polarization phenomenon of the electric and magnetic, temperature resistance variation and ambient temperature superconductivity. [0069] Conventionally, drifting cannot be controlled due to a large inductance. What is needed in design is a fixed capacitance. According to the example, equivalent inductance is obtained by a rapid change of the resistivity of the resultant conductive finished product, and thereby a drift of the inductance can be compensated.

[0070] Fig. 14 shows a variation of amplitude of series notch oscillators as a function of frequency. The series notch oscillators attenuate frequencies in a specific range. Therefore, specific noises in the specific range can be filtered out.

[0071] Fig. 15 shows a variation of amplitude of parallel notch oscillators as a function of frequency. The parallel notch oscillators pass frequencies in a specific range. Therefore, most frequencies can be filtered out except the frequencies in the specific range.

[0072] In the present invention, since the filter unit including the Xu element can work as both of the series notch oscillator and the parallel notch oscillator, the positive pulse oscillation and the negative pulse oscillation are combined to generate a resonant pulse oscillation. The filter unit can correspond to any pulse signal and can be functioned as a substantial all-pass filter. It is an object of the present invention to reduce the power loss effectively with a simple structure.

[0073] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures and functions.

Claims

1. A resonant mode switching controller circuit for driving a Red LED, a Green LED and a Blue LED connected in series, comprising: a DC power source; a step down circuit comprising a first transistor, a first diode and a first choke coil; a polarity reversal circuit comprising a second transistor, a second diode and a second choke coil; a Red LED, a Green LED and a Blue LED connected in series between the positive output terminal of the step down circuit and the negative output terminal of the polarity reversal circuit; a first filter unit including a Xu element connected in parallel to the first choke coil; and a second filter unit including a Xu element connected in parallel to the second choke coil, wherein the step down circuit and the polarity reversal circuit are connected in parallel to the DC power source.

2. The resonant mode switching controller circuit according to claim 1, wherein the first transistor and the second transistor are switched by switching signals having frequencies in a mega hertz (MHz) bandwidth.

3. The resonant mode switching controller circuit according to claim 2, wherein the frequencies of the switching signals fall within 50 MHz through 100 MHz.

4. The resonant mode switching controller circuit according to any one of claims 1 through 3, wherein the Xu element comprising: a first dielectric material, wherein impedance of the first dielectric material decreases with increase in frequency; and a second dielectric material, wherein the second dielectric material is located adjacent to the first dielectric material and impedance of the second dielectric material increases with increase in frequency, wherein the first and second dielectric materials are sintered.

5. The resonant mode switching controller circuit according to any one of claims 1 through 3, wherein the Xu element comprising: a mixed dielectric material, wherein the mixed dielectric material is a mixture of a first dielectric material and a second dielectric material, impedance of the first dielectric material decreasing with increase in frequency and that of the second dielectric material increasing with increase in frequency, wherein the mixed dielectric material is sintered.

6. The resonant mode switching controller circuit according to any one of claims 1 through 3, wherein the Xu element comprising: a mixed dielectric material, wherein the mixed dielectric material is a mixture of a first dielectric material and a second dielectric material, impedance of the first dielectric material decreasing with increase in frequency and that of the second dielectric material increasing with increase in frequency, wherein the first and second dielectric materials are sintered prior to the mixture.

7. The resonant mode switching controller circuit according to any one of claims 4 through 6, wherein the first dielectric material has a negative temperature coefficient of resistance, and the second dielectric material has a positive temperature coefficient of resistance.

8. The resonant mode switching controller circuit according to any one of claims 4 through 7, wherein the first dielectric material is a metal oxide.

9. The resonant mode switching controller circuit according to any one of claims 4 through 7, wherein the first dielectric material is a metal nitride .

10. The resonant mode switching controller circuit according to any one of claims 4 through 9, wherein the second dielectric material is a metal dielectric material.

11. The resonant mode switching controller circuit according to any one of claims 4 through 9, wherein the second dielectric material is a gallium arsenide.