Abstract:
An LED control circuit with auto ON/OFF function has a power module, a control module, a timer module, a driver module and an LED module with a first LED unit and a second LED unit. The control module generates a time control signal and an LED control signal to respectively activate the timer module and the LED module. The LED module is activated by the LED control signal only when the timer module is turned ON. The timer module can be automatically turned ON/OFF by the time control signal. Moreover, the LED control signal has high potentials and low potentials. The driver module activates the first LED unit and the second LED unit based on two the different potentials of the LED control signal respectively. Both high and low potentials of the LED control are used. The performance of the LED module is improved.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an LED control circuit, and more particularly to an LED control circuit with auto ON/OFF function. 
         [0003]    2. Description of Related Art 
         [0004]    A light-emitting diode (LED) device has advantages of high brightness and low power dissipation. The LEDs can be applied for illumination and decoration. For example, an LED string can have multiple LED devices connected in series. Such LED string can be used as a decoration light string during festive occasions. 
         [0005]    The LED device is an electric device that is activated by a forward bias voltage. For example, the LED string can be activated by a PWM signal. The PWM signal comprises multiple high potentials and low potentials changed alternately. The LED string is activated in the high potentials but inactivated in the low potentials. Therefore, the LED string flashes. 
         [0006]    However, the flashing performance of the LED string is poor because the LED string is only activated in the high potentials of the PWM signal. The LED string is not actuated in the low potentials. Hence, the use of the PWM signal is inefficient. 
         [0007]    In additional, the LED string is usually connected to a power source via a switch. In the daytime, the LED string does not need to be activated. A user can press the switch to turn OFF the LED string. At night, the user has to press the button again to turn ON the LED string. The user may press the button several times in a day, especially in a shopping area where variations in flow of customers need to be taken into account. Hence, it is inconvenient for the user to manually turn ON/OFF the LED string. 
       SUMMARY OF THE INVENTION 
       [0008]    An objective of the LED control circuit of the present invention is to improve the illumination efficiency of the LED module and to automatically turn ON/OFF the LED module. 
         [0009]    The LED control circuit of the present invention comprises a power module, a control module, a timer module, a driver module and an LED module. 
         [0010]    The power module provides a working voltage. 
         [0011]    The control module is connected to the power module to receive the working voltage and synchronously generates a time control signal and an LED control signal. The LED control signal comprises multiple high potentials and low potentials changed alternately. 
         [0012]    The timer module is connected to the power module and the control module and is activated by the time control signal. 
         [0013]    The driver module is connected to the timer module and is activated by the LED control signal. 
         [0014]    The LED module is connected to the driver module and has at least one LED assembly. The LED assembly comprises a first LED unit and a second LED unit. The first LED unit has an anode and a cathode. The second LED unit has an anode and a cathode. The anode of the second LED unit is connected to the cathode of the first LED unit. The cathode of the second LED unit is connected to the anode of the first LED unit. 
         [0015]    The controller automatically turns ON and OFF the timer module according to the time control signal to connect or disconnect the LED module to or from the power module at certain times. The LED module is activated by the LED control signal only when the timer module is turned ON. The first LED unit and the second LED unit are respectively activated by the high and low potentials of the LED control signal through the driver module. 
         [0016]    The LED control circuit of the present invention has advantages of: 
         [0017]    1. The timer module can be turned ON/OFF by the time control signal. When the timer module is turned ON, the LED module can be connected to the power module to receive the working voltage. When the timer module is turned OFF, the LED module is disconnected from the power module to be inactivated. Hence, the user can setup a working time of the time control signal. The control module then automatically turns ON/OFF the LED module at a certain time. 
         [0018]    2. Both the high potentials and the low potentials of the LED control signal can activate the LED module. Because both of the potentials are efficiently used, the performance of the LED module is beneficial. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a block diagram of an LED control circuit of the present invention; 
           [0020]      FIG. 2  is a detailed circuit diagram of a first embodiment of the present invention; 
           [0021]      FIG. 3  is a detailed circuit diagram of a second embodiment of the present invention; 
           [0022]      FIG. 4  is a detailed circuit diagram of a wireless control module of the present invention; 
           [0023]      FIG. 5  is a wave diagram of the LED control signal; and 
           [0024]      FIG. 6  is a wave diagram of the time control signal. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    With reference to  FIGS. 1 ,  2  and  4 , the LED control circuit of the present invention comprises a power module  10 , a control module  20 , a timer module  30 , a driver module  40 , an LED module  50 , a wireless receiver  60  and a wireless control module  70 . 
         [0026]    The power module  10  is electrically connected to the control module  20 , the timer module  30 , the driver module  40 , the LED module  50  and the wireless receiver  60  to provide a working voltage VCC. In this embodiment, the working voltage VCC is positive. 
         [0027]    The control module  20  has an oscillator Y 1 , a mode switch S 1 , a controller  21  and a regulator D 2 . 
         [0028]    The oscillator Y 1  has two terminals and generates a clock signal. 
         [0029]    The mode switch S 1  can be a normally open switch. 
         [0030]    With reference to  FIG. 2 , the controller  21  has multiple input pins and multiple output pins. The input pins include a first pin, a second pin, a third pin, a fourth pin, a sixth pin and an eighth pin. The output pins include a fifth pin and a seventh pin. 
         [0031]    The first pin and the eighth pin are power pins. The first pin is connected to the power module  10  to receive the working voltage VCC. The eighth pin is grounded. The controller  21  is activated by the working voltage VCC. 
         [0032]    The second pin and the third pin are respectively connected to the two terminals of the oscillator Y 1  to receive the clock signal. 
         [0033]    The fourth pin is connected to the wireless receiver  60  to receive signals from the wireless control module  70 . 
         [0034]    The sixth pin is connected to the mode switch S 1 . 
         [0035]    The wireless control module  70  has a wireless transmitter  71 , multiple buttons  72  and a controller  73 . The wireless transmitter  71  wirelessly communicates with the wireless receiver  60 . The controller  73  stores multiple mode signals and is electrically connected to the buttons  72  and the wireless transmitter  71 . The controller  73  of the wireless control module  70  sends the mode signal to the controller  21  of the control module  20  via the wireless transmitter  71  according to the button  72  which is pressed by a user. 
         [0036]    When the controller  21  is working, the controller  21  generates an LED control signal and a time control signal. The clock signal of the oscillator Y 1  is a reference for normalizing the timing of the LED control signal and the time control signal, so that the clock signal is adapted to synchronize the LED control signal with the time control signal. 
         [0037]    The LED control signal is sent out via the fifth pin and is a PWM signal comprising multiple high potentials and multiple low potentials changed alternately. With reference to  FIG. 5 , the high potentials (Von) and the low potentials (Voff) respectively perform in short intervals, such as seconds. Under the control of the LED control signal, the LED module  50  may be operated in a full light mode, a repeating mode or a flashing mode. The modes are changed sequentially when the mode switch S 1  is pressed or changed according the mode signal sent from the wireless control module  70 . 
         [0038]    The time control signal is sent out via the seventh pin and comprises high potentials and low potentials changed alternately. With reference to  FIG. 6 , the high potentials (Von) and the low potentials (Voff) are respectively maintained for a certain time, such as several hours. For example, the low potential occurs in the night while the high potential occurs in the daytime. 
         [0039]    The regulator D 2  can be a Zener diode and is connected between the first pin and the eighth pin of the controller  21 . The regulator D 2  is used to protect the controller  21  from unusually high voltages. 
         [0040]    The timer module  30  is connected to the power module  10  in series. In this embodiment, the timer module  30  has a fifth electric switch Q 5  which is a PNP bipolar junction transistor (BJT). The fifth electric switch Q 5  has a base, an emitter and a collector. The emitter is connected to the power module  10 . The base is connected to the seventh pin through a resistor R 1  to receive the time control signal from the controller  21 . When the fifth electric switch Q 5  receives the low potentials of the time control signal, the fifth switch Q 5  is turned ON. 
         [0041]    The driver module  40  is connected to the timer module  30  in series. In this embodiment, the driver module  40  has a first electric switch Q 1 , a second electric switch Q 2 , a third electric switch Q 3  and a fourth electric switch Q 4 . In the embodiment, the first electric switch Q 1  and the fourth electric switch Q 4  are PNP BJT having a base, a collector and an emitter respectively. The second electric switch Q 2  and the third electric switch Q 3  are NPN BJT having a base, a collector and an emitter respectively. 
         [0042]    The base of the first electric switch Q 1  is connected to the fifth pin of the controller  21  through a resistor R 2  to receive the LED control signal. The emitter of the first electric switch Q 1  is connected to the collector of the fifth electric switch Q 5 . 
         [0043]    The base of the second electric switch Q 2  is connected to the fifth pin of the controller  21  through a resistor R 3  to receive the LED control signal. The emitter of the second electric switch Q 2  is grounded. The collector of the second electric switch Q 2  is connected to the collector of the first electric switch Q 1 . 
         [0044]    The base of the third electric switch Q 3  is connected to the collector of the first electric switch Q 1  through a resistor R 4 . The emitter of the third electric switch Q 3  is grounded. 
         [0045]    The base of the fourth electric switch Q 4  is connected to the collector of the second electric switch Q 2  through a resistor R 5 . The emitter of the fourth electric switch Q 4  is connected to the collector of the fifth electric switch Q 5 . The collector of the fourth electric switch Q 4  is connected to the collector of the third electric switch Q 3 . 
         [0046]    The LED module  50  is connected to the driver module  40  and comprises at least one LED assembly  51 . The LED assembly  51  has a first LED unit  511  and a second LED unit  512 . In the first embodiment, the LED module  50  has an LED assembly  51 . With reference to  FIG. 3  of a second embodiment, the LED module  50  has multiple LED assemblies  51  connected in series. 
         [0047]    With reference to  FIG. 2 , the first LED unit  511  can be a single LED device or have multiple LED devices connected in series. The first LED unit  511  has an anode and a cathode. The anode is connected to the collector of the first electric switch Q 1  through a resistor R 7 . The cathode is connected to the collector of the third electric switch Q 3 . 
         [0048]    The second LED unit  512  can be an LED device or have multiple LED devices connected in series. The second LED unit  512  has an anode and a cathode. The anode of the second LED unit  512  is connected to the collector of the fourth electric switch Q 4  and the cathode of the first LED unit  511 . The cathode of the second LED unit  512  is connected to the anode of the first LED unit  511 . 
         [0049]    During the high potentials of the LED control signal, the first electric switch Q 1  and the third electric switch Q 3  are turned OFF. The second electric switch Q 2  and the fourth electric switch Q 4  are turned ON. The power module  10 , the fifth electric switch Q 5 , the fourth electric switch Q 4 , the second LED unit  512  and the second electric switch Q 2  then form a first current loop. Therefore, the second LED unit  512  is activated to light up. 
         [0050]    During the low potentials of the LED control signal, the first electric switch Q 1  and the third electric switch Q 3  are turned ON. The second electric switch Q 2  and the fourth electric switch Q 4  are turned OFF. The power module  10 , the fifth electric switch Q 5 , the first electric switch Q 1 , the first LED unit  511  and the third electric switch Q 3  then form a second current loop. Therefore, the first LED unit  511  is activated to light up. 
         [0051]    The first LED unit  511  is activated by the low potentials of the LED control signal. The second LED unit  512  is activated by the high potentials of the LED control signal. Because the high potentials and the low potentials of the LED control signal are efficiently used, the illumination performance of the LED module  50  can be improved. 
         [0052]    As long as the low potential of the time control signal ends, the time control signal turns into the high potential. The fifth electric switch Q 5  is then turned off due to the high potential of the time control signal. When the fifth electric switch Q 5  is turned OFF, the LED module  50  is disconnected from the power module  10  and cannot receive the working voltage from the power module  10 . The LED module  50  is then inactivated. 
         [0053]    In conclusion, the LED module  50  can be activated by the LED control signal only when the timer module  30  is turned ON by the time control signal. 
         [0054]    With reference to  FIG. 3 , the power module  10  of the second embodiment comprises a rectifier  11  and a filter  12 . The rectifier  11  has an input and an output. The input is connected to a power source to receive an input power VAC. The output is connected to the first pin of the controller  21  through a resistor R 8 . The rectifier  11  converts the input power VAC to the working voltage VCC. The filter  12  is connected to the output of the rectifier  11  in parallel to filter electrical noises. 
         [0055]    The timer module  30  of the second embodiment has a fifth electric switch Q 5  and a sixth electric switch Q 6 . In this embodiment, the fifth electric switch Q 5  is a PNP BJT and the sixth electric switch Q 6  is an NPN BJT. The fifth electric switch Q 5  and the sixth electric switch Q 6  respectively have a base, a collector and an emitter. 
         [0056]    The emitter of the fifth electric switch Q 5  is connected to the output of the rectifier  11 . The base of the sixth electric switch Q 6  is connected to the seventh pin of the controller  21  through a resistor R 1  to receive the time control signal. The emitter of the sixth electric switch Q 6  is grounded. The collector of the sixth electric switch Q 6  is connected to the base of the fifth electric switch Q 5  through a resistor R 9 . The sixth electric switch Q 6  can be turned ON by the high potentials of the time control signal. 
         [0057]    The driver module  40  of the second embodiment has a first electric switch Q 1  of a PNP BJT, a second electric switch Q 2  of an NPN BJT, a third electric switch Q 3  of an NPN BJT, a fourth electric switch Q 4  of a PNP BJT, a seventh electric switch Q 7  of an NPN BJT, an eighth electric switch Q 8  of an NPN BJT and a ninth electric switch Q 9  of a PNP BJT. The electric switches Q 1 -Q 4 , Q 7 -Q 9  respectively have a base, a collector and an emitter. 
         [0058]    The base of the seventh electric switch Q 7  is connected to the fifth pin of the controller  21  through a resistor R 10  to receive the LED control signal. The emitter of the seventh switch Q 7  is grounded. The collector of the seventh switch Q 7  is connected to the collector of the fifth electric switch Q 5  through a resistor R 11 . 
         [0059]    The base of the eighth electric switch Q 8  is connected to the fifth pin of the controller  21  through a resistor R 13  to receive the LED control signal. The emitter of the eighth electric switch Q 8  is grounded. 
         [0060]    The base of the first electric switch Q 1  is connected to the collector of the eighth electric switch Q 8  through a resistor R 2 . The emitter of the first electric switch Q 1  is connected to the collector of the fifth electric switch Q 5 . 
         [0061]    The base of the second electric switch Q 2  is connected to the collector of the seventh electric switch Q 7  through a resistor R 3 . The emitter of the second electric switch Q 2  is grounded. The collector of the second electric switch Q 2  is connected to the collector of the first electric switch Q 1  and the cathode of the first LED unit  511 . 
         [0062]    The base of the third electric switch Q 3  is connected to the collector of the first electric switch Q 1  through a resistor R 4 . The emitter of the third electric switch Q 3  is grounded. 
         [0063]    The base of the ninth electric switch Q 9  is connected to the collector of the second electric switch Q 2 . The collector of the ninth electric switch Q 9  is grounded through a resistor R 12 . 
         [0064]    The base of the fourth electric switch Q 4  is connected to the emitter of the ninth electric switch Q 9  through a resistor R 5 . The emitter of the fourth electric switch Q 4  is connected to the collector of the fifth electric switch Q 5 . The collector of the fourth electric switch Q 4  is connected to the collector of the third electric switch Q 3  and the anode of the first LED unit  511 . 
         [0065]    During the high potentials of the LED control signal, the seventh electric switch Q 7  and the eighth electric switch Q 8  are turned ON. The collectors of the seventh and the eighth electric switch Q 7 , Q 8  stay at a low potential. Therefore, the first electric switch Q 1  can be turned ON and the second electric switch Q 2  can be turned OFF. The power module  10 , the fifth electric switch Q 5 , the first electric switch Q 1 , the first LED units  511  and the third electric switch Q 3  form a third current loop, wherein the collector current of the fifth electric switch Q 5  can be regarded as the current of the third current loop. The first LED units  511  are then activated to light up. 
         [0066]    During the low potentials of the LED control signal, the seventh and the eighth electric switch Q 7 , Q 8  are turned OFF. The collectors of the seventh and the eighth electric switch Q 7 , Q 8  keep at a high potential. Therefore, the first electric switch Q 1  can be turned OFF and the second electric switch Q 2  can be turned ON. The power module  10 , the fifth electric switch Q 5 , the fourth electric switch Q 4 , the second LED units  512  and the second electric switch Q 2  then form a fourth current loop, wherein the collector current of the fifth electric switch Q 5  can be regarded as the current of the fourth current loop. The second LED units  512  are then activated to light up. 
         [0067]    In the second embodiment, the sixth electric switch Q 6  and the seventh electric switch Q 7  are used to increase the current of the current loops. Taking the timer module  30  of the second embodiment as an example, the fifth electric switch Q 5  is driven by the sixth electric switch Q 6 . In general, a collector current is β times greater than a base current of a BJT. The collector current of the sixth electric switch Q 6  is regarded as the base current of the fifth electric switch Q 5 . Therefore, the collector current of the fifth electric switch Q 5  of the second embodiment is approximately β times greater than that of the first embodiment. Because the current loops of the second and the third embodiment are increased, the LED control circuit is capable of lighting more LED units  511 ,  512 .