Patent Publication Number: US-2011074306-A1

Title: Led dimming apparatus, circuit, and method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a LED dimming apparatus, in particular, to a dimming apparatus concentrating on LED light sources. 
     2. Description of Related Art 
     As technology advances, as well as the trend of energy saving, all kinds of lamps and a variety of new types of light sources are developed continuously, for example, from the traditional incandescent bulbs to the latest white LED elements. With the expanded application range of these light sources, such as, stage lighting or home lighting and so on, all kinds of dimming apparatuses for adjusting the brightness level of light have also been widely applied. However, the drive modes of different light sources are not the same, and therefore, these dimming apparatuses also must be improved and adapted for a variety of light sources correspondingly. 
     Conventional light sources, such as incandescent light sources, have the general service life of 1,000 hours or more. Incandescent light sources are the most widely applied light source for an ordinary family or in commercial use. A new type of light source, such as LED (Light Emitting Diode) light source, has a service life up to 100,000 hours, and also has both advantages of energy-saving and short reaction time. With the energy-saving issue prevailing, LED light sources have also become progressively more appealing and popular. 
       FIG. 1  illustrates a schematic diagram of the dimming apparatus in accordance with the conventional light source apparatus. 
     A conventional dimming apparatus  1  primarily focuses on performing illumination brightness adjustment of a conventional light source apparatus  12 . Generally, the aforementioned conventional light source apparatus  12  is the incandescent light source. The conventional light source apparatus  12  can be triggered and emits light by applying the public electricity (AC power signal) and AC signals, therefore, it&#39;s merely required to add a light modulator  11  between the AC power source  10  and the conventional light source apparatus  12  so as to provide illumination brightness adjustment for the conventional light source apparatus  12  via applying the light modulator  11 . 
     Generally speaking, the light modulator  11  can be a TRIAC (Triode for Alternating Current) or a SCR (Silicone Controlled Rectifier), or even a simple rheostat to achieve the objective of adjusting illumination brightness of the conventional light source apparatus  12  by regulating the current value, voltage level, or phase angle of the input AC power source. Because the conventional light source apparatus  12  can be triggered by applying AC signals directly, the output signal of the light modulator  11  is an AC signal. 
       FIG. 2  illustrates a schematic diagram of the dimming apparatus in accordance with the conventional LED light source apparatus. 
     A LED light source apparatus  24  is a kind of apparatus by taking LED&#39;s as its light source. Because LED light sources cannot be Illuminated by AC power, though they emit light by applying DC power sources, it can not utilize AC signals to drive directly unlike the conventional filament-illuminating light source. Therefore, it is necessary to add an analog/digital converter  21  (AC to DC converter, ADC) between the AC power source  10  and the LED light source apparatus  24  so as to convert AC power signals to DC power signals, thereby driving the LED light source apparatus  24  smoothly. However, the current conversion circuit is commercially available, for example, for the incandescent lamp of the stabilizer without supporting for the power signal conversion functions, such that the public can not replace the conventional incandescent light sources into a variety of new types of LED light sources directly. 
     Furthermore, simply driving the LED light source apparatus  24  to emit light can not satisfy requirements in use completely, a dimming function must be added so as to meet applications at home, in commercial, display settings, or on stage. Therefore, the rear side of the light modulator as shown in  FIG. 1  connects with a conventional LED dimming circuit  25  to convert AC signals to DC signals and perform dimming operations for the LED light source apparatus  24 . Therein, the conventional LED dimming circuit  25  and the light modulator  11  can be composed or arranged to be a conventional LED dimming apparatus  2 , wherein the conventional LED dimming circuit  25  includes an analog/digital converter circuit  21 , a pulse width modulation circuit  22  and a pulse width modulated control signal circuit  23 . 
     The light modulator  11  of the conventional LED dimming apparatus  2  connects with the AC power source  10  for receiving the AC power signal of the AC power source  10  and performing current, voltage, and phase adjustment of the AC power source  10  so as to form a dimming signal. The analog/digital converter circuit  21  connects with the light modulator  11  for receiving the dimming signal of the light modulator  11  and performing analog to digital conversion so as to generate a DC conversion signal. The pulse width modulation circuit  22  connects with the analog/digital converter circuit  21  and the pulse width modulated control signal circuit  23  for receiving the conversion signal of the analog/digital converter circuit so as to generate a pulse width modulation signal. Finally, the conventional LED light source apparatus  24  connects with the pulse width modulation circuit  22  for receiving the pulse width modulation signal to drive the LED light source apparatus  24  for emitting light. Therein, the pulse width modulation circuit  22  generally utilizes a DC/DC converted pulse width modulation circuit for receiving and taking the DC conversion signal as a reference voltage level of outputting conversion signals, and for receiving and taking the pulse width modulated control signal of the pulse width modulated control signal circuit  23  as a reference duty cycle of outputting conversion signals. 
       FIG. 3  illustrates a signal diagram of the dimming apparatus in accordance with the conventional LED light source apparatus. 
     The AC power signal of the AC power source  10  is usually the sinusoidal wave or cosine wave, herein, the sinusoidal wave is taken as an embodiment for illustration. Please refer to  FIG. 2  in conjunction with  FIG. 3 , as the light modulator  11  receives the AC power signal of the AC power source  10 , users can regulate the light modulator  11  to generate a dimming signal. In general, the light modulator  11  can be classified into several types based on modulating voltage, current and phase of AC power signals; herein, a phase type light modulator  11  is taken as an embodiment for illustration. Therefore, while the light modulator  11  receives the AC power signal of the AC power source  10  and generates a dimming signal having the successive half cycles of the positive sinusoidal half-cycle waveform and the successive half cycles of the negative sinusoidal half-cycle waveform, the analog/digital converter circuit  21  receives the dimming signal and then generates a conversion signal with DC voltage after rectification, voltage transformation and voltage stabilization are processed by the analog/digital converter circuit  21  the pulse width modulation circuit  22  receives the conversion signal and is cooperated with the pulse width modulated control signal outputted from the pulse width modulated control signal circuit  23  so as to generate a pulse width modulation signal. Therein, the pulse width modulation circuit  22  can regulate the illumination brightness of the LED light source apparatus  24  by adjusting the voltage level or duty cycle ratio of the pulse width modulation signal. 
     The conventional LED light source apparatus  23  can apply the commonly seen light regulators  11  in combination with the conventional dimming circuit to form a conventional LED dimming apparatus  2  and produce a pulse width modulation signal so as to trigger the LED light source apparatus  24 . However, as the conduction angle of the light modulator  11  is modulated to be too small, the current value of the dimming signal generated from different brands, specifications and standards of light regulators will be too small as well. Consequently, if the analog/digital converter circuit  21  receives the current value of the dimming signal which is lower than the threshold value of operating current thereof, the conversion signal outputted from the analog/digital converter circuit  21  is unstable; if the pulse width modulation circuit  22  receives the conversion signal with the current value lower than the threshold value of operating current associated with the pulse width modulation circuit  22 , the pulse width modulation signal outputted from the pulse width modulation circuit  22  is a unstable signal. The unstable conversion signal and the pulse width modulation signal cause the LED light source apparatus  24  twinkle or simply become non-functional. Additionally, the DC/DC converted pulse width modulation circuit  22  is applied according to the prior art. This kind of pulse width modulation circuit  22  does not have transformer coils, thus does not have the isolation effect, and therefore, it would result in a leakage problem for the conventional LED light source apparatus  24 . 
     SUMMARY OF THE INVENTION 
     To solve the aforementioned issues, an embodiment of a LED dimming apparatus according to the present invention, comprising: a light modulation, connected with a AC power source, for receiving a AC power signal and generating a dimming signal; a rectification circuit, connected with the light modulator, for receiving the dimming signal and rectifying the dimming signal to generate a rectification signal; a matching circuit, connected with the light modulator, for receiving the rectification signal and matching the rectification signal to generate a matching signal respectively; an analog/digital converter circuit, connected with the matching circuit, for receiving the matching signal and converting the matching signal to form a conversion signal with positive half cycles of a sinusoidal waveform; and a pulse width modulation circuit, connected with the analog/digital converter circuit, for receiving the conversion signal, generating a modulation signal according to the conversion signal, and transferring the modulation signal to a LED light source apparatus so as to drive the LED light source apparatus emitting light. 
     To solve the aforementioned issues, an embodiment of a LED dimming circuit according to the present invention, comprising: a matching circuit, connected with the light modulator, for receiving a dimming signal of the light modulator and converting the dimming signal to a matching signal; an analog/digital converter circuit, connected with the matching circuit, for receiving the matching signal and converting the matching signal to form a conversion signal with positive half cycles of a sinusoidal waveform; and a pulse width modulation circuit, connected with the analog/digital converter circuit, for receiving the conversion signal, generating a modulation signal according to the conversion signal, and transferring the modulation signal to a LED light source apparatus so as to drive the LED light source apparatus emitting light. 
     To solve the aforementioned issues, an embodiment of a LED dimming method according to the present invention, comprising: providing a light modulator, for generating a dimming signal; providing a matching circuit, for generating a matching signal based on the dimming signal and generating the matching signal with the lowest output current value based on various dimming signals, in which the lowest output current value that is fixed at the output current value with a conduction angle greater than zero degree; providing an analog/digital converter circuit, for generating a conversion signal based on the matching signal which has a conversion signal with positive half cycles of a sinusoidal waveform; and providing a pulse width modulation circuit, for generating a pulse width modulation signal based on the signal period and the voltage level of the conversion signal so as to drive a LED light source apparatus, wherein the pulse width modulation signal has a constant output current value, so that the LED light source apparatus has a stable luminescence spectrum. 
     The concepts of the present invention as invented by the inventor are distinguishable from the standard technology according to the prior art. Accordingly, a LED dimming apparatus is provided so as to utilize the light modulator of the prior art and the LED dimming apparatus of the present invention, thereby performing dimming for LED light source apparatuses and promoting industrial upgrading. 
     In order to further understand the techniques, means and effects the present invention takes for achieving the prescribed objectives, the following detailed description and included drawings are hereby referenced, such that, through which, the purposes, features and aspects of the present invention can be thoroughly and concretely appreciated; however, the included drawings are provided solely for reference, explanation, and illustration, without any intention that they be used for limiting the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a schematic diagram of the dimming apparatus in accordance with the conventional light source apparatus; 
         FIG. 2  illustrates a schematic diagram of the dimming apparatus in accordance with the conventional LED light source apparatus; 
         FIG. 3  illustrates a signal diagram of the dimming apparatus in accordance with the conventional LED light source apparatus; 
         FIG. 4  illustrates a schematic diagram of a first embodiment of the LED dimming apparatus in accordance with the present technique; 
         FIG. 5  illustrates a signal diagram of the first embodiment of the LED dimming apparatus in accordance with the present technique; 
         FIG. 6  illustrates a schematic diagram of a second embodiment of the LED dimming apparatus in accordance with the present technique; and 
         FIG. 7  illustrates a signal diagram of the second embodiment of the LED dimming apparatus in accordance with the present technique. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 4  illustrates a schematic diagram of a first embodiment of the LED dimming apparatus in accordance with the present technique. 
     The LED dimming apparatus  3  includes a light modulator  11 , a rectification circuit  41 , an active matching circuit  42 , an analog/digital converter circuit  21  and a pulse width modulation circuit  43 . The light modulator  11  connects with the AC power source  10  to receive AC power signals and perform adjustment for AC power signal current value, voltage level and phase angle of the AC power source  10  so as to generate a dimming signal. With regard to the embodiment, the light modulator  11  for regulating the phase angle of the AC power signal is taken as an embodiment for illustration. The rectification circuit  41  connects with the light modulator  11  to receive the dimming signal and rectify the dimming signal to generate a rectification signal. The active matching circuit  42  connects with the rectification circuit  41  to receive the rectification signal and perform signal matching for the rectification signal to form a matching signal. The analog/digital converter circuit  21  connects with the matching circuit  42  to receive the matching signal and perform the analog to digital conversion to generate a DC conversion signal. The pulse width modulation circuit  43 , connects with the analog/digital conversion circuit  21  to receive the conversion signal of the analog/digital conversion circuit  21  and form a pulse width modulation signal based on the voltage level and the duty cycle of the conversion signal. Lastly, the LED dimming apparatus  3  drives the LED light source apparatus  24  based on the pulse width modulation signal generated. Therein, the rectification circuit  41  can be integrated with the light modulator  11 , or with the matching circuit  42 , so that the matching circuit  42  can either receive the rectified dimming signal or receive the dimming signal directly in advance and then perform rectification afterward inside the matching circuit. Thus, the rectification circuit  31 , the matching circuit  42 , the analog/digital conversion circuit  21  and the pulse width modulation circuit  43  is configured to be a LED dimming circuit  40 . Additionally, the light modulator  11  can be a TRIAC or a SCR light modulator. 
     Therefore, the light modulator  11  is the conventional light modulator which has a large number of brands and different specifications and standards, and even dimming signals generated and output current values for a variety of light modulators  11  in different conduction angles are not the same. As a result, the light modulator  11  fails to generate a dimming signal having the same specifications and standards, and results in the signal modulation which is required to perform specifically for each of different standards of light modulators  11  as shown in  FIG. 2 , so as to modulate the LED light source apparatus  24  successfully. 
     Thus, the first embodiment of the present invention utilizes the active matching circuit  42  based on the variation of the dimming signal in accordance with the light modulator  11  to perform full-wave rectification for the dimming signal. And when the light modulation configures in a lower conduction angle, which is below than 20 degrees, the matching circuit  42  is going to fix the output current value as the conduction angle is at 20 degrees, so as to allow the matching signal containing the lowest output current value, such that the analog/digital converter circuit  21  or the pulse width modulation circuit  43  can receive the matching signal with the lowest operating current required respectively to maintain the normal operation state thereof. For the aforementioned reasons, the matching circuit  42  is designed to perform modulation in the output current value actively for the dimming signals generated from all different kinds of the light modulators  11 , thereby adapting for all light modulators with different brands, specifications, and standards. Herein, the active matching circuit  42  can be any one kind of matching circuits, primarily utilizing a configuration containing a voltage unit (not shown), a control unit (not shown) and a current unit (not shown) to perform matching and modulation of the dimming signal, so that the light modulator  11  is able to output the matching signal with the lowest operating current in all phases and all operating voltages, and the matching circuit, connected with the analog/digital converter circuit  21  and the pulse width modulation circuit  43 , are capable of operating normally, thereby adjusting brightness of the LED light source apparatus  24  ordinarily. 
     In addition, based on the first embodiment of the present invention, the pulse width modulation circuit  43  of the LED dimming circuit  40  is an AC/DC pulse width modulation circuit  43 , which can utilize the conversion signal generated from the analog/digital conversion circuit  21  to form the corresponding pulse width modulation signal. In other words, the pulse width modulation circuit  43  can take the period of the conversion signal as the reference duty cycle of the pulse width modulation signal and take the waveform variation of the conversion signal as the reference output voltage of the pulse width modulation signal. Furthermore, because the AC to DC pulse width modulation circuit  43  contains transformer coils, and thus has an isolation effect, which means that the front end signal variation of the pulse width modulation circuit  43  and the pulse width modulation signal generated from the rear end thereof contains an isolation effect, the leakage problem of the LED power source apparatus  24  can be prevented. 
     It is worth mentioning that, the first embodiment of the present invention, the pulse width modulation circuit  43  of the LED dimming circuit  40  outputs the pulse width modulation signal as a high voltage and constant current pulse width modulation signal. As the output voltage of the pulse width modulation voltage is higher than the drive voltage of the LED light source apparatus  23 , the LED&#39;s of the LED light source apparatus  24  can be activated completely. While the pulse width modulation signal outputted is maintained at a constant current value, the LED&#39;s of the LED light source apparatus  23  has a stable luminescence spectrum. Therefore, according to the dimming apparatus  40  of the first embodiment in accordance with the present invention can contain a function to drive the LED light source apparatus  24  regularly and prevent drift for the luminescence spectrum of the LED light source due to instable current. 
       FIG. 5  illustrates a signal diagram of the first embodiment of the LED dimming apparatus in accordance with the present technique. 
     The AC power signals of the AC power source  10  are normally the sinusoidal wave or cosine wave, and the embodiment takes the sinusoidal wave as an example. Please refer to  FIG. 4  in conjunction with  FIG. 5 , the light modulator  11  connects with the AC power source  10  to receive an AC power signal and perform phase regulation for the AC power signal. As per the example of the phase type light modulator  11  of the embodiment, a dimming signal having the successive half cycles of the positive sinusoidal half-cycle waveform and the successive half cycles of the negative sinusoidal half-cycle waveform is generated. The rectification circuit  41  connects with the light modulator  11  to receive the dimming signal and perform signal rectification, so as to convert the negative half cycle signals into the positive half cycle signals to generate a rectification signal. The active matching circuit  42  connects with the rectification circuit  41  to receive the rectification signal and perform full-wave rectification to generate a matching signal with the successive half cycles of the positive sinusoidal half-cycle waveform, wherein the matching signal contains the same of operating frequency and maximum output voltage level of the rectification signal. Additionally, the matching signal has the lowest output current value, for example, as the conduction angle of the light modulator  11  modulates to be below 20 degrees, the output current value is fixed at the current value for the conduction angle of 20 degrees, and thus is guaranteed that the subsequent analog/digital converter circuit  21  and the pulse width modulation circuit  43  are capable of receiving the matching signal or the conversion signal with the lowest operating current value. The analog/digital converter circuit  21  connects to the active matching circuit  42  to receive the matching signal and output a conversion signal having the successive half cycles of the positive sinusoidal half cycle waveform via the internal transformer elements (not shown) and the rectifier elements (not shown), wherein the conversion signal and the matching signal have the same duty cycle and the maximum output voltage level. The pulse width modulation circuit  43  connects with the analog/digital converter circuit  21  to receive the conversion signal and generate a pulse width modulation signal according to the maximum output voltage level and the duty cycle of the conversion signal, wherein the pulse width modulation signal has a high voltage, which is higher than the operating voltage of the LED light source apparatus  24 , and a constant output current, which can stable the luminescent chromaticity generated by the LED light source apparatus  24 , thereby preventing drift for the luminescence spectrum of the LED light source. 
     As a result, according to the LED dimming apparatus  3  of the first embodiment in accordance with the prevent invention, as the light modulator  11  has the maximum conduction angle, the dimming signal of the light regulator  11  has the sinusoidal wave entirely, the rectification circuit converts the negative half cycle wave of the dimming signal into the positive half cycle wave thereof to generate a rectification signal, the matching circuit  42  and the analog/digital converter circuit  21  generate the matching signal and the conversion signal containing the same waveform of the dimming signal, and finally, the waveform of the pulse width modulation signal associated with the pulse width modulation circuit  43  approaches a DC output voltage. Contrarily, if the conduction angle of the dimming signal outputted from the light modulator is getting smaller, the waveform ratio of the sinusoidal wave in accordance with the dimming signal is getting smaller as shown in  FIG. 5 , wherein the matching signal and the conversion signal are maintained to have the successive half cycles of the positive sinusoidal half-cycle waveform. 
       FIG. 6  illustrates a schematic diagram of a second embodiment of the LED dimming apparatus in accordance with the present technique. 
       FIG. 7  illustrates a signal diagram of the second embodiment of the LED dimming apparatus in accordance with the present technique. 
     As per the LED dimming apparatus  4  of the second embodiment according to the present invention, the principal elements and the connection relationship thereof are similar with the LED dimming apparatus  3  demonstrated in  FIG. 4 , wherein the LED dimming apparatus  4  further comprises a constant current drive circuit  61 , connected with the pulse width modulation circuit  43  and the LED light source apparatus  24 . In other words, the LED dimming circuit  60  includes the rectification circuit  42 , the matching circuit  42 , the analog/digital converter circuit  21 , the pulse width modulation circuit  43  and the constant current drive circuit  61 . The constant current drive circuit  61  is one kind of circuits for outputting a constant current and it can modulate the output current value of the constant current drive signal as shown in  FIG. 7  based on the pulse width modulation signal of the pulse width modulation circuit  43 . As per the above illustrations, as the duty cycle ratio of the pulse width modulation signal is high, the constant current drive circuit  61  outputs a constant current drive signal with higher output current value; as the duty cycle ratio of the pulse width modulation signal is low, the constant current drive circuit  61  outputs a constant current drive signal with lower output current value. Therefore, the constant current drive circuit  61  outputs different current values based on the duty cycle ratio of the pulse width modulation signal, and the LED light source apparatus  24  can modulate illumination brightness thereof according to different output current values of the constant current drive signal. Because the constant current drive circuit  61  outputs the constant current drive signal having a constant current and a high voltage level as shown in  FIG. 7 , and the high voltage of the constant current drive signal is higher than the operating voltage for the LED light source apparatus  24 , the drift for the luminescence spectrum of the LED light source  24  can be prevented and the twinkling issue caused by the pulse width modulation signal switching of the pulse width modulation circuit  43  can be avoided as well. Pursuant to the above illustrations, the LED dimming apparatus  4  of the second embodiment according to the present invention, adapts for the LED light source apparatus  24  for providing a near-by light source, for example, table lamps or the like. It can avoid the twinkling issues caused by the pulse width modulation signal of the pulse width modulation circuit  43 . When users apply the light source, the twinkling of the LED light source will not cause uncomfortable for eyes. 
     The aforementioned descriptions represent solely the preferred embodiment of the present invention, without any intention to limit the scope of the present invention thereto. Various equivalent changes, alterations, or modifications based on the claims of present invention, therefore, are all viewed as being embraced by the scope of the present invention which is fully described fully only within the claims presented here.