Abstract:
An electronic candle includes a power source, and two circuit assemblies electrically coupled to the power source in parallel and respectively including a waveform generator, a drive circuit and a first light-emitting diode being electrically connected in series. By means of controlling the two waveform generators to respectively generate a triangle wave, square wave, T wave or sawtooth wave, synchronously or asynchronously, the electronic candle simulates the flashing candlelight of a real wax candle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    (a) Field of the Invention 
         [0002]    The present invention relates to electronic candles and more particularly to an electronic candle driving circuit design, which effectively simulates the flashing candlelight of a real wax candle in the presence of an air flow. 
         [0003]    (b) Description of the Prior Art 
         [0004]    Conventional electronic candles use a lamp bulb as the light source. After a long use, the brightness of the lamp bulb may deteriorate and become dim. Nowadays, power-saving light-emitting diodes have been widely used in electronic candles to replace conventional lamp bulbs for the advantage of long durability and constant brightness. There are electronic candles using a control circuit to control the supply of intermittent electric current to light-emitting diodes, thereby simulating the flaming of a real wax candle. However, because the circuit breaking time interval is very short, the intermittent lighting effect may be not significantly visible. Further, this intermittent lighting effect cannot simulate flying flickering flame. Further, the variation of lighting mode between high brightness and dimness is still not attractive. Improper operation control may result in an off status of light, thus losing the sense of the electronic candle. Therefore, there is a strong demand for an electronic candle that eliminates the aforesaid drawbacks. 
       SUMMARY OF THE INVENTION 
       [0005]    The objective of the present invention is to provide an electronic candle, which effectively simulates the flashing candlelight of a real wax candle. 
         [0006]    To achieve this and other objects of the present invention, an electronic candle according to the present invention comprises a power source, a first circuit assembly and a second circuit assembly electrically coupled to the power source in parallel. The first circuit assembly comprises a first waveform generator controllable to generate a first waveform, a first drive circuit electrically connected to the first waveform generator, and a first light-emitting diode electrically connected in series to the first drive circuit and the first waveform generator and drivable by the first drive circuit to emit light in a first lighting mode subject to the first waveform. The second circuit assembly comprises a second waveform generator controllable to generate a second waveform, a second drive circuit electrically connected to the second waveform generator, and a second light-emitting diode electrically connected in series to the second drive circuit and the second waveform generator and drivable by the second drive circuit to emit light in a second lighting mode subject to the second waveform. 
         [0007]    To achieve this and other objects of the present invention, an alternate form of the electronic candle comprises a power source, a first circuit assembly and a second circuit assembly electrically coupled to the power source in parallel. The first circuit assembly comprises a first waveform generator controllable to generate a first waveform, a first pulse wave generator controllable to generate a first pulse-width modulation signal, a first wave mixer electrically coupled with the first waveform generator and the first pulse wave generator and adapted for mixing the first waveform and the first pulse-width modulation signal, a first drive circuit electrically connected to the first wave mixer, and a first light-emitting diode electrically connected to the first drive circuit and drivable by the first drive circuit to emit light in a first lighting mode. The second circuit assembly comprises a second waveform generator controllable to generate a second waveform, a second pulse wave generator controllable to generate a second pulse-width modulation signal, a second wave mixer electrically coupled with the second waveform generator and the second pulse wave generator and adapted for mixing the second waveform and the second pulse-width modulation signal, a second drive circuit electrically connected to the second wave mixer, and a second light-emitting diode electrically connected to the second drive circuit and drivable by the second drive circuit to emit light in a second lighting mode. 
         [0008]    Further, the first waveform generator is controllable to generate one of triangle wave, square wave, T wave and sawtooth wave. 
         [0009]    Further, the second waveform generator is controllable to generate one of triangle wave, square wave, T wave and sawtooth wave. 
         [0010]    Further, the waveforms generated by the first waveform generator and the second waveform generator have a frequency difference and an amplitude difference. 
         [0011]    By means of controlling the two light-emitting diodes to emit light in different lighting modes, a visual decussation effect is produced, and thus the electronic candle can simulate the flashing candlelight of a real wax candle in an air flow. 
         [0012]    Other advantages and features of the present invention will be fully understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like components of structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a circuit block diagram of an electronic candle in accordance with a first embodiment of the present invention. 
           [0014]      FIG. 2  is a detailed circuit diagram of the electronic candle in accordance with the first embodiment of the present invention. 
           [0015]      FIG. 3  illustrates a triangle wave generated by the first waveform generator of the electronic candle in accordance with the present invention. 
           [0016]      FIG. 4  illustrates a triangle wave generated by the second waveform generator of the electronic candle in accordance with the present invention. 
           [0017]      FIG. 5  is a schematic drawing illustrating two waveforms respectively outputted by the first waveform generator and the second waveform generator and overlapped according to the present invention. 
           [0018]      FIG. 6  is a schematic drawing illustrating another triangle wave generated by the first waveform generator of the electronic candle in accordance with the present invention. 
           [0019]      FIG. 7  is a schematic drawing illustrating a square wave generated by the second waveform generator of the electronic candle in accordance with the present invention. 
           [0020]      FIG. 8  is a schematic drawing illustrating two different waveforms respectively outputted by the first waveform generator and the second waveform generator and overlapped according to the present invention. 
           [0021]      FIG. 9  is a circuit block diagram of an electronic candle in accordance with a second embodiment of the present invention. 
           [0022]      FIG. 10  is a detailed circuit diagram of the electronic candle in accordance with the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    As shown in  FIGS. 1 and 2 , an electronic candle in accordance with a first embodiment of the present invention comprises a first circuit assembly  1  and a second circuit assembly  2  that are connected in parallel to a power source  10 . The second circuit assembly  2  is adapted to generate a waveform different from that generated by the first circuit assembly  1 . For example, the first circuit assembly  1  can be designed to generate square wave; the second circuit assembly  2  can be designed to generate another full wave. The first circuit assembly  1  comprises a first waveform generator  11 , a first drive circuit  12  and a first light-emitting diode  13  that are connected in series. The second circuit assembly  2  comprises a second waveform generator  21 , a second drive circuit  22  and a second light-emitting diode  23  that are connected in series. The waveform outputted by the first waveform generator  11  (see  FIG. 3  or  FIG. 6 ) and the waveform outputted by the second waveform generator  21  (see  FIG. 4  or  FIG. 7 ) can be the same but asynchronous. Alternatively, these two waveforms can be different but synchronously outputted. 
         [0024]    During operation of the aforesaid electronic candle, the first waveform generator  11  outputs a first waveform to the first drive circuit  12 , causing the first light-emitting diode  13  to create a first lighting effect subject to the waveform outputted by the first waveform generator  11 ; the second waveform generator  21  outputs a second waveform to the second drive circuit  22 , causing the second light-emitting diode  23  to create a second lighting effect subject to the waveform outputted by the second waveform generator  21 . As the first waveform and the second waveform are different (same waveform but asynchronous, or different waveforms but synchronous), the first light-emitting diode  13  and the second light-emitting diode  23  are driven to emit different lighting frequencies, as shown in  FIG. 5  and  FIG. 8 . 
         [0025]    Referring to  FIG. 3  and  FIG. 4 , the first waveform generator  11  and the second waveform generator  21  can be set to output triangle waves asynchronously. Alternatively, as shown in  FIG. 6  and  FIG. 7 , the first waveform generator  11  and the second waveform generator  21  can be set to output a triangle wave and a square wave in a synchronous manner. In other words, these two waveform generators can be designed to output triangle wave, square wave, T-wave or sawtooth wave in a time difference or density difference for causing an unstable flashing effect. These two waveform generators can also be set to output a triangle wave and a square wave, a T-wave and a square wave, or a triangle wave and a T-wave respectively, and so on. Even the two waveform generators output the same waveform, a time interval difference can lead to a brightness difference. When the brightness of the two light-emitting diodes is enhanced at a different frequency, a flashing effect will also be produced. By means of waveform variation, a flickering, gradually brightening or gradually dimming lighting effect can be produced. 
         [0026]    An electronic candle in accordance with a second embodiment of the present invention is shown in  FIGS. 9 and 10 . The electronic candle of this second embodiment comprises a first circuit assembly la and a second circuit assembly  2   a  that are connected in parallel to a power source  10 . The first circuit assembly la comprises a first waveform generator  11   a,  a first drive circuit  12   a,  a first light-emitting diode  13   a,  a first pulse wave generator  14   a,  and a first wave mixer  15   a.  The output end of the first waveform generator  11   a  and the output end of the first pulse wave generator  14   a  are connected in parallel to the first wave mixer  15   a.  The first wave mixer  15   a  is connected in series to the first drive circuit  12   a  and the first light-emitting diode  13   a . The second circuit assembly  2   a  comprises a second waveform generator  21   a,  a second drive circuit  22   a,  a second light-emitting diode  23   a,  a second pulse wave generator  24   a,  and a second wave mixer  25   a.  The output end of the second waveform generator  21   a  and the output end of the second pulse wave generator  24   a  are connected in parallel to the second wave mixer  25   a.  The second wave mixer  25   a  is connected in series to the second drive circuit  22   a  and the second light-emitting diode  23   a.    
         [0027]    Further, the first waveform generator  11   a  is adapted to generate a triangle wave, square wave, T-wave or sawtooth wave and to output the generated waveform into the first wave mixer  15   a.  The first pulse wave generator  14   a  is adapted to generate a PWM (pulse width modulation) signal and to output the generated PWM signal into the first wave mixer  15   a.  The first wave mixer  15   a  is adapted to convert the waveform generated by the first waveform generator  11  a into a signal wave subject to the PWM signal received from the first pulse wave generator  14   a,  and then to output the signal wave to the first drive circuit  12   a  for driving the first light-emitting diode  13   a.  The second circuit assembly  2   a  is adapted to generate a triangle wave, square wave, T-wave or sawtooth wave and to output the generated waveform into the second wave mixer  25   a.  The second pulse wave generator  24   a  is adapted to generate a PWM (pulse width modulation) signal and to output the generated PWM signal into the second wave mixer  25   a . The second wave mixer  25   a  is adapted to convert the waveform generated by the second waveform generator  21   a  into a signal wave subject to the PWM signal received from the second pulse wave generator  24   a,  and then to output the signal wave to the second drive circuit  22   a  for driving the second light-emitting diode  23   a.    
         [0028]    The waveform outputted by the first waveform generator  11  and the waveform outputted by the second waveform generator  21  can be the same but asynchronous. Alternatively, these two waveforms can be different but synchronously outputted. Thus, the first waveform generated by the first waveform generator  11   a  can be modulated by the first wave mixer  15   a  subject to the PWM signal received from the first pulse wave generator  14   a,  and the second waveform generated by the second waveform generator  21   a  can be modulated by the second wave mixer  25   a  subject to the PWM signal received from the second pulse wave generator  24   a.    
         [0029]    The modulated waves from the first wave mixer  15   a  and the second wave mixer  25   a  are respectively provided to the first drive circuit  12   a  and the second drive circuit  22   a  to drive the first light-emitting diode  13   a  and the second light-emitting diodes  23   a , causing the first light-emitting diode  13   a  and the second light-emitting diodes  23   a  to create different lighting effects. As the modulated first waveform and the modulated second waveform are different (same waveform but asynchronous, or different waveforms but synchronous), the first light-emitting diode  13   a  and the second light-emitting diode  23   a  are driven to emit different lighting frequencies, 
         [0030]    In conclusion, the invention provides an electronic candle, which uses two independent circuit assemblies to produce a waveform phase difference. When the waveform, frequency and amplitude are all different, many variations between the waveforms being outputted by the two circuit assemblies are generated. Thus, by means of controlling the waveform generators of the two circuit assemblies to generate a respective waveform at a respective frequency, the respective drive circuits drive the first light-emitting diode and the second light-emitting diode to perform a respective lighting mode, producing a highly variable lighting effect.