Patent Publication Number: US-8111015-B2

Title: Brightness-adjustable illumination driving system

Description:
FIELD OF THE INVENTION 
     The present invention relates to an illumination driving system, and more particularly to a brightness-adjustable illumination driving system. 
     BACKGROUND OF THE INVENTION 
     Incandescent lamps such as tungsten filament lamps or halogen lamps are widely used as sources of artificial light. In the early stage, incandescent lamps are used for simply providing a bright place. With diversified living attitudes, incandescent lamps having difference brightness are developed. For adjusting brightness of respective incandescent lamp, a brightness-adjustable circuit is used to drive the incandescent lamp and control the brightness of the incandescent lamp. 
       FIG. 1  is a schematic circuit diagram illustrating a brightness-adjustable circuit for a conventional incandescent lamp. As shown in  FIG. 1 , the brightness-adjustable circuit  1  includes a switch element  11  and a triggering circuit  12 . The switch element  11  is for example a solid semiconductor component such as a silicon-controlled rectifier (SCR) or a TRIode for Alternating Current (TRAIC) component. Take a TRAIC component as the switch element  11  for example. The control terminal G is the gate of the switch element  11 . The first terminal N 1  and the control terminal G of the switch element  11  are coupled to the incandescent lamp  13  and the triggering circuit  12 , respectively. The second terminal N 2  of the switch element  11  can receive the electric energy from the input voltage V in . The triggering circuit  12  can control the on phase or on duration of the switch element  11 , thereby controlling the electricity to be transmitted to the incandescent lamp  13 . 
     Please refer to  FIG. 1  again. The triggering circuit  12  includes a resistor R, a variable resistor R var  a capacitor C and a bidirectional diode thyristor D. The resistor R, the variable resistor R var  and the capacitor C are connected in serried with each other to form a charging loop. Both ends of these serially-connected components are coupled to the second terminal N 2  of the switch element  11  and the incandescent lamp  13 , respectively. An end of the bidirectional diode thyristor D is coupled to the control terminal G of the switch element  11 . The other end of the bidirectional diode thyristor D is coupled to the capacitor C. Through the charging loop which is defined by the resistor R, the variable resistor R var  and the capacitor C, the input voltage V in  can charge the capacitor C. Until the capacitor C is charged to the turn-on voltage of the bidirectional diode thyristor D, the bidirectional diode thyristor D is conducted and thus a triggering signal is transmitted to the control terminal G of the switch element  11 . In response to the triggering signal, the switch element  11  is conducted. That is, the on phase or on duration of the switch element  11  can be controlled by adjusting the resistance of the resistor R, thereby controlling the electricity to be transmitted to the incandescent lamp  13  and adjusting the brightness of the incandescent lamp  13 . 
     In recent years, light emitting diodes (LEDs) and cold cathode fluorescent lamps (CCFLs) that emit light with high brightness values and high illuminating efficiency have been developed. With the maturity of the LED or CCFL technology, LEDs and CCFLs will replace all conventional lighting devices in many aspects such as home-use lighting devices. 
     The conventional brightness-adjustable circuit  1 , however, is only applicable to the incandescent lamp with the pure resistive property. If the conventional brightness-adjustable circuit  1  is applied to a cold cathode fluorescent lamp or a light emitting diode, the cold cathode fluorescent lamp or the light emitting diode fails to be normally operated and is possibly burnt out. In other words, the conventional brightness-adjustable circuit is not feasible to adjust brightness values of the cold cathode fluorescent lamp or the light emitting diode. 
     Therefore, there is a need of providing an improved brightness-adjustable illumination driving system so as to obviate the drawbacks encountered from the prior art. 
     SUMMARY OF THE INVENTION 
     An object of the present invention provides a brightness-adjustable illumination driving system for adjusting the brightness value of a cold cathode fluorescent lamp or a light emitting diode. 
     Another object of the present invention provides a brightness-adjustable illumination driving system, in which the control unit including a brightness-adjustable circuit is separated from the base, so that the control unit can remotely control the brightness value of the light-emitting devices. 
     In accordance with an aspect of the present invention, there is provided an illumination driving system for driving at least one light-emitting device and controlling a brightness value of the light-emitting device. The illumination driving system includes a control unit and at least one base. The control unit includes a first converter and a brightness-adjustable circuit. An input AC voltage is converted into a regulated DC voltage by the first converter. The brightness-adjustable circuit is connected to the first converter. The base is separated from the control unit for supporting the at least one light-emitting device. The base includes a second converter. The second converter is connected with the first converter and the light-emitting device for converting the regulated DC voltage into an output voltage. The light-emitting device is driven to illuminate by the output voltage. The brightness-adjustable circuit generates a brightness adjusting signal to the first converter. The magnitude of the regulated DC voltage is adjusted according to the brightness adjusting signal, thereby adjusting the brightness value of the light-emitting device. 
     The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic circuit diagram illustrating a brightness-adjustable circuit for a conventional incandescent lamp; 
         FIG. 2  is a schematic circuit diagram illustrating a brightness-adjustable illumination driving system for use in an indoor environment according to a preferred embodiment of the present invention; 
         FIG. 3  is a schematic circuit diagram illustrating the brightness-adjustable illumination driving system as shown in  FIG. 2 ; and 
         FIG. 4  is a schematic detailed circuit diagram of the brightness-adjustable illumination driving system as shown in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
       FIG. 2  is a schematic circuit diagram illustrating a brightness-adjustable illumination driving system for use in an indoor environment according to a preferred embodiment of the present invention. The brightness-adjustable illumination driving system  2  is used for driving at least one light-emitting device  9  in the indoor environment  3  and controlling the brightness value of the light-emitting device  9 . An example of the light-emitting device  9  includes but is not limited to a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED). The brightness-adjustable illumination driving system  2  can be also applied to outdoor environments. 
     Please refer to  FIG. 2  again. The brightness-adjustable illumination driving system  2  principally comprises a control unit  20  and at least one base  21 . In this embodiment, the brightness-adjustable illumination driving system  2  has a plurality of bases  21  and a plurality of light-emitting devices  9 . The control unit  20  comprises a first converter  22  and a brightness-adjustable circuit  23 . The light-emitting devices  9  are mounted on respective bases  21 . In accordance with a key feature of the present invention, the bases  21  are separated from the control unit  20 . For example, as shown in  FIG. 2 , the control unit  20  is disposed on a wall  31  of the indoor environment  3  and the bases  21  are disposed on the ceiling  32 . As a consequence, the control unit  20  can remotely control the light-emitting devices  9 . The configurations and the relations of the control unit  20  and the bases  21  will be illustrated in more details as follows. 
       FIG. 3  is a schematic circuit diagram illustrating the brightness-adjustable illumination driving system as shown in  FIG. 2 . Please refer to  FIG. 2  and  FIG. 3 . The control unit  20  comprises a first converter  22  and a brightness-adjustable circuit  23 . The control unit  20  is used for driving illumination of the light-emitting devices  9  and adjusting the brightness values of the light-emitting devices  9 . A first input terminal of the first converter  22  is connected to a power source (e.g. a utility source) for receiving an input AC voltage V ac  and converting the input AC voltage V ac  into a regulated DC voltage V d . A second input terminal of the first converter  22  is connected to the brightness-adjustable circuit  23  for receiving a brightness adjusting signal V dim  from the brightness-adjustable circuit  23 . According to the brightness adjusting signal V dim , the magnitude of the regulated DC voltage V d  is adjusted by the first converter  22 . In some embodiments, the control unit  20  further comprises a user operation interface (not shown) such as a knob. Via the user operation interface, the user can control the brightness-adjustable circuit  23  to generate various brightness adjusting signals V dim . 
     The bases  21  are separated from the control unit  20  and used for supporting respective light-emitting devices  9 . Each base  21  comprises a second converter  24 . The second converters  24  of these bases  24  are connected with each other in parallel. The input terminals of the second converters  24  are connected to the output terminals of the first converter  22 . The output terminals of the second converters  24  are connected to respective light-emitting devices  9 . The regulated DC voltage V d  is received by the second converter  24  and converted into an output voltage V o  for driving illumination of a corresponding light-emitting device  9 . Moreover, in a case that the magnitude of the regulated DC voltage V d  is adjusted by the first converter  22 , the magnitude of the output voltage V o  is adjusted and thus the brightness value of the light-emitting device  9  is changed. 
     Please refer to  FIG. 2  and  FIG. 3  again. The brightness-adjustable circuit  23  can generate various brightness adjusting signals V dim  to the first converter  22 . According to the brightness adjusting signals V dim , the input AC voltage V ac  is converted into corresponding regulated DC voltages V d . The regulated DC voltage V d  are received by the second converter  24  and converted into an output voltage V o  for driving illumination controlling the brightness value of a corresponding light-emitting device  9 . That is, the control unit  20  can remotely adjust the brightness value of the light-emitting devices  9  by controlling the brightness-adjustable circuit  23 . 
       FIG. 4  is a schematic detailed circuit diagram of the brightness-adjustable illumination driving system as shown in  FIG. 3 . As shown in  FIG. 4 , the first converter  22  of the control unit  20  comprises a feedback circuit  220 , an AC-to-DC converting circuit  221  and a DC-to-DC converting circuit  222 . The input AC voltage V ac  is received by the AC-to-DC converting circuit  221  and converted into a transition DC voltage V 3  by the AC-to-DC converting circuit  221 . An example of the AC-to-DC converting circuit  221  includes but is not limited to a boost converting circuit. The AC-to-DC converting circuit  221  principally comprises a rectifying circuit  223 , an inductor L 1 , a first switching circuit  224 , a first pulse width modulation (PWM) controller  225  and a first rectifying and filtering circuit  226 . The rectifying circuit  223  is connected to the input terminal of the AC-to-DC converting circuit  221  for rectifying the input AC voltage V ac  into a rectified DC voltage V 1 . An end of the inductor L 1  is connected to the rectifying circuit  223 . The other end of the inductor L 1  is connected to the first switching circuit  224  and the first rectifying and filtering circuit  226 . The rectified DC voltage V 1  is transmitted from the rectifying circuit  223  to the inductor L 1 . According to the switching statuses of the first switching circuit  224 , the electric energy of the rectified DC voltage V 1  is charged into the inductor L 1  or the inductor L 1  discharges the stored electric energy to generate a boost voltage V 2 . 
     The first switching circuit  224  is connected to the inductor L 1 , the first rectifying and filtering circuit  226 , the first PWM controller  225 , and a common terminal. Under control of the first PWM controller  225 , the first switching circuit  224  is alternately conducted or shut off. In this embodiment, the first switching circuit  224  includes a first switch element Q 1 . 
     The first rectifying and filtering circuit  226  is connected to the inductor L 1  and the output terminal of the AC-to-DC converting circuit  221 . The first rectifying and filtering circuit  226  is used for rectifying and filtering the boost voltage V 2 , thereby generating the transition DC voltage V 3 . In this embodiment, the first rectifying and filtering circuit  226  comprises a first diode D 1  and a first capacitor C 1 . The positive end of the first diode D 1  is connected to the inductor L 1  and the first switching circuit  224 . The negative end of the first diode D 1  is connected to an end of the first capacitor C 1 . The other end of the first capacitor C 1  is connected to the common terminal. 
     The input terminal of the DC-to-DC converting circuit  222  is connected to the output terminal of the AC-to-DC converting circuit  221 . The transition DC voltage V 3  is transmitted from the AC-to-DC converting circuit  221  to the DC-to-DC converting circuit  222  and converted into the regulated DC voltage V d  by the DC-to-DC converting circuit  222 . In this embodiment, the DC-to-DC converting circuit  222  is a buck converting circuit, but it is not limited thereto. The DC-to-DC converting circuit  222  comprises a second switching circuit  227 , a first transformer T 1 , a second PWM controller  228  and a second rectifying and filtering circuit  229 . The second switching circuit  227  is connected to the output terminal of the AC-to-DC converting circuit  221 , the second PWM controller  228  and the first transformer T 1 . Under control of the second PWM controller  228 , the second switching circuit  227  is alternately conducted or shut off. 
     The primary winding assembly N p  of the first transformer T 1  is connected to the second switching circuit  227  and the common terminal. During the second switching circuit  227  is alternately conducted or shut off, the transition DC voltage V 3  is transmitted from the AC-to-DC converting circuit  221  to the primary winding assembly N p  of the first transformer T 1 . The electric energy stored in the primary winding assembly N p  is magnetically transmitted to the secondary winding assembly N s  of the first transformer T 1 . As such, the secondary winding assembly N s  generates a converted voltage V 4 . The second rectifying and filtering circuit  229  is connected to the secondary winding assembly N s  of the first transformer T 1 , the feedback circuit  220  and the output terminal of the DC-to-DC converting circuit  222 . The second rectifying and filtering circuit  229  is used for rectifying and filtering the converted voltage V 4 , thereby generating the regulated DC voltage V d . 
     The DC-to-DC converting circuit  222  further comprises a reset capacitor C c . The reset capacitor C c  is connected to the second switching circuit  227  and the primary winding assembly N p  of the first transformer T 1 . By discharging the electrical energy stored in the reset capacitor C c , the electric energy of the primary winding assembly N p  of the first transformer T 1  is reset. The second switching circuit  227  comprises a second switch element Q 2  and a third switch element Q 3 . The second switch element Q 2  is connected to the output terminal of the AC-to-DC converting circuit  221 , the reset capacitor C c , the third switch element Q 3  and the second PWM controller  228 . The third switch element Q 3  is connected to the second switch element Q 2 , the reset capacitor C c , the second PWM controller  228  and the common terminal. Under control of the second PWM controller  228 , the second switch element Q 2  and the third switch element Q 3  are alternately conducted or shut off. In this embodiment, the second rectifying and filtering circuit  229  comprises a second diode D 2 , a third diode D 3  and a second capacitor C 2 . The positive ends of the second diode D 2  and the third diode D 3  are connected to the secondary winding assembly N s  of the first transformer T 1 . The negative ends of the second diode D 2  and the third diode D 3  are connected to an end of the second capacitor C 2 . The other end of the second capacitor C 2  is connected to the common terminal. 
     A first input terminal of the feedback circuit  220  is connected to the output terminal of the DC-to-DC converting circuit  222 . A second input terminal of the feedback circuit  220  is connected to the brightness-adjustable circuit  23 . The output terminal of the feedback circuit  220  is connected to the second PWM controller  228  of the DC-to-DC converting circuit  222 . According to the regulated DC voltage V d  issued from the DC-to-DC converting circuit  222  and the brightness adjusting signal V dim  issued from the brightness-adjustable circuit  23 , the feedback circuit  220  generates a feedback signal V fb  to the second PWM controller  228 . According to the feedback signal V fb , the second PWM controller  228  controls the duty cycle of the second switching circuit  227 , thereby adjusting the magnitude of the regulated DC voltage V d . In this embodiment, the feedback circuit  220  comprises a first resistor R 1 , a signal controlling circuit  220   a  and an isolation circuit  220   b . A first input terminal of the signal controlling circuit  220   a  is connected to the output terminal of the DC-to-DC converting circuit  222 . A second input terminal of the signal controlling circuit  220   a  is connected to the brightness-adjustable circuit  23 . The output terminal of the signal controlling circuit  220   a  is connected to the input terminal of the isolation circuit  220   b . According to the regulated DC voltage V d  issued from the DC-to-DC converting circuit  222  and the brightness adjusting signal V dim  issued from the brightness-adjustable circuit  23 , the signal controlling circuit  220   a  generates a control signal V c  to the isolation circuit  220   b.    
     In this embodiment, the signal controlling circuit  220   a  comprises a second resistor R 2 , a third resistor R 3 , a third capacitor C 3  and a signal amplifier OP. An end of the second resistor R 2  is connected to the output terminal of the DC-to-DC converting circuit  222 . The other end of the second resistor R 2  is connected to an end of the third resistor R 3 . The other end of the third resistor R 3  is connected to the common terminal. The negative end of the signal amplifier OP is connected to the node between the second resistor R 2  and the third resistor R 3 . The regulated DC voltage V d  is received by the negative end of the signal amplifier OP through the second resistor R 2 . The positive end of the signal amplifier OP is connected to the brightness-adjustable circuit  23  for receiving the brightness adjusting signal V dim . The output terminal of the signal amplifier OP is connected to the input terminal of the isolation circuit  220   b . According to the regulated DC voltage V d  and the brightness adjusting signal V dim , the signal amplifier OP issues the control signal V c  to the isolation circuit  220   b . An end of the third capacitor C 3  is connected to the second resistor R 2 , the third resistor R 3  and the negative end of the signal amplifier OP. The other end of the third capacitor C 3  is connected to the output terminal of the signal amplifier OP. 
     The input terminal of the isolation circuit  220   b  is connected to the output terminal of the DC-to-DC converting circuit  222  and the signal controlling circuit  220   a  for receiving the regulated DC voltage V d  and the control signal V c . The output terminal of the isolation circuit  220   b  is connected to the second PWM controller  228  of the DC-to-DC converting circuit  222  and the common terminal. The isolation circuit  220   b  is used for isolating the signal controlling circuit  220   a  from the primary winding assembly N p  of the first transformer T 1 . In this embodiment, the isolation circuit  220   b  is a photo coupler. Due to the voltage difference between the regulated DC voltage V d  and the control signal V c , the input terminal of the isolation circuit  220   b  will generate a first current I 1 . According to the first current I 1 , the output terminal of the isolation circuit  220   b  generates a second current I 2 . An end of the first resistor R 1  is connected to the output terminal of the isolation circuit  220   b  and the second PWM controller  228 . The other end of the first resistor R 1  is connected to a supply voltage V cc . According to the magnitude of the second current I 2 , the first resistor R 1  generates the feedback signal V fb  to the second PWM controller  228 . 
     The brightness-adjustable circuit  23  is connected to the feedback circuit  220  for generating the brightness adjusting signal V dim  to the feedback circuit  220 . In this embodiment, the brightness-adjustable circuit  23  comprises a fourth resistor R 4  and a variable resistor R var . An end of the fourth resistor R 4  receives the supply voltage V cc . The other end of the fourth resistor R 4  is connected to an end of the variable resistor R var  and the feedback circuit  220 . The other end of the variable resistor R var  is connected to the common terminal. By adjusting the resistance value of the variable resistor R var , the brightness-adjustable circuit  23  will generate various brightness adjusting signals V dim . As previously described, the control unit  20  further comprises a user operation interface (not shown) such as a knob. Via the user operation interface, the user can control the brightness-adjustable circuit  23  to generate various brightness adjusting signals V dim . 
     Please refer to  FIGS. 2 ,  3  and  4 . Each base  21  comprises a second converter  24 . The second converter  24  comprises a second transformer T 2 , a third switching circuit  241  and a third PWM controller  243 . The third switching circuit  241  is connected to the primary winding assembly N p1  of the second transformer T 2  and the output terminal of the first converter  22 . Under control of the third PWM controller  243 , the third switching circuit  241  is alternately conducted or shut off. The third switching circuit  241  comprises a fourth switch element Q 4  and a fifth switch element Q 5 . The fourth switch element Q 4  is connected to the output terminal of the first converter  22 , the third PWM controller  243 , the primary winding assembly N p1  of the second transformer T 2  and the fifth switch element Q 5 . The fifth switch element Q 5  is connected to the output terminal of the first converter  22 , the third PWM controller  243 , the primary winding assembly N p1  of the second transformer T 2  and the fourth switch element Q 4 . Under control of the third PWM controller  243 , the fourth switch element Q 4  and the fifth switch element Q 5  are alternately conducted or shut off. 
     The primary winding assembly N p1  of the second transformer T 2  is connected to the third switching circuit  241 . The secondary winding assembly N s1  of the second transformer T 2  is connected to the light-emitting device  9 . During the third switching circuit  241  is alternately conducted or shut off under control of the third PWM controller  243 , the regulated DC voltage V d  is transmitted from the DC-to-DC converting circuit  222  to the primary winding assembly N p1  of the second transformer T 2 . The electric energy stored in the primary winding assembly N p1  is magnetically transmitted to the secondary winding assembly N s1  of the second transformer T 2 . As such, the secondary winding assembly N s  generates an output voltage V o  for driving illumination of the light-emitting device  9 . In this embodiment, the second converter  24  is a push-pull inverter, but it is not limited thereto. The second converter  24  further comprises at least one current-sharing circuit  242 . The current-sharing circuit  242  is connected to the light-emitting device  9  and the secondary winding assembly N s1  of the second transformer T 2 . In a case that several light-emitting devices  9  are supported on the same base  21 , the currents flowing through these light-emitting devices  9  are substantially identical by means of the current-sharing circuit  242 . In this embodiment, the current-sharing circuit  242  includes for example a capacitor. 
     Please refer to  FIGS. 2 ,  3  and  4  again. For adjusting the brightness value of the light-emitting device  9 , the user may control the brightness-adjustable circuit  23  to generate various brightness adjusting signals V dim  via the user operation interface. According to the regulated DC voltage V d  issued from the DC-to-DC converting circuit  222  and the brightness adjusting signal V dim  issued from the brightness-adjustable circuit  23 , the signal controlling circuit  220   a  of the feedback circuit  220  generates a control signal V c  to the isolation circuit  220   b . Due to the voltage difference between the regulated DC voltage V d  and the control signal V c  at the input terminal of the isolation circuit  220   b , the output terminal of the isolation circuit  220   b  of the feedback circuit  220  generates the second current I 2 . According to the magnitude of the second current I 2 , the first resistor R 1  generates the feedback signal V fb  to the second PWM controller  228 . According to the feedback signal V fb , the second PWM controller  228  controls the duty cycle of the second switching circuit  227 , thereby adjusting the magnitude of the regulated DC voltage V d  corresponding to the brightness adjusting signal V dim . Moreover, the regulated DC voltage V d  is converted into the output voltage V o  by the second converter  24  of each base  21 . By the output voltage V o , the light-emitting device  9  is driven to illuminate a light beam with a desired brightness value. 
     From the above embodiment, the brightness-adjustable illumination driving system is capable of adjusting the brightness value of a cold cathode fluorescent lamp or a light emitting diode. Since the control unit is separated from the base, the user can control the brightness-adjustable circuit  23  to generate various brightness adjusting signals via the user operation interface. According to the brightness adjusting signal, the magnitude of the regulated DC voltage is adjusted by the first converter. The regulated DC voltage is converted by the second converters of the bases into corresponding output voltage, thereby driving illumination of the light-emitting devices and adjusting the brightness values of the light-emitting devices. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.