Patent Abstract:
An alternating current (AC) light-emitting diode (LED) lamp includes a first AC power end, a second AC power end, a lighting module and a direct current (DC) power output circuit. The lighting module has a first end, a second end and at least one LED unit, wherein the first end is electrically coupled to the first AC power end. The at least one LED unit has one or more LEDs connected in series. The DC power output circuit has a first end and a second end, wherein the second end of the DC power output circuit is electrically coupled to the second AC power end, while the first end of the DC power output circuit is electrically coupled to the second end of the lighting module. The DC power output circuit has a DC output side.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to an alternating current (AC) light-emitting diode (LED) lamp and, more particularly, to an AC LED lamp that has a direct current (DC) power output circuit. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional AC LED lamp includes two AC power ends P 1  and P 2  and a lighting module  9 . The AC power ends P 1  and P 2  are connected to the lighting module  9  so that an AC power can be directly supplied to the lighting module  9 . The lighting module  9  includes a first LED unit  91  and a second LED unit  92 . Both the first LED unit  91  and second LED unit  92  comprise at least one LED. The first LED unit  91  and second LED unit  92  are inversely connected in parallel. Based on this, the lighting module  9  may be directly connected to the AC power, allowing the first LED unit  91  and second LED unit  92  to emit light in an alternating manner as the AC power alternates between positive and negative voltage cycles. 
     Referring to  FIG. 1  again, the conventional AC LED lamp requires at least a cooling device  8  for cooling the lighting module  9  as the at least one LED generates heat when being electrified. The cooling device  8  is generally a DC device such as a cooling fan, cooling module or cooling chip. As a result, at least an extra power supply circuit is irreversibly needed to generate a DC power for the cooling device  8 . 
     In light of this, the conventional AC LED lamp needs a power converter  7  disposed between the AC power and the cooling device  8  for converting the AC power into the DC power. 
     Specifically, the power converter  7  includes a transformer  71  and a rectifying and filtering circuit  72 . After the AC power has gone through voltage conversion, rectifying and regulating procedures performed by the transformer  71  and the rectifying and filtering circuit  72 , the stable DC power can be provided to the cooling device  8 . 
     However, the conventional AC LED lamp has some drawbacks. For example, since the root mean squared voltage (VRMS) of the cooling device  8  is usually smaller than that of the AC power, the transformer  71  is required for converting the AC power into a smaller voltage suitable for the cooling device  8 . However, usage of the transformer  71  will increase the costs, volume and weight of the conventional AC LED lamp. Therefore, it is desired to improve the conventional AC LED lamp. 
     SUMMARY OF THE INVENTION 
     It is therefore the primary objective of this invention to provide an AC LED lamp which avoids use of a transformer by providing a DC power output circuit that is connected to a certain node of the AC LED lamp for outputting a DC power required for driving a cooling device. Thus, costs, circuit volume and weight of the AC LED lamp are reduced. 
     The invention discloses an AC LED lamp including a first AC power end, a second AC power end, a lighting module and a DC power output circuit. The lighting module has a first end, a second end and at least one LED unit, wherein the first end is electrically coupled to the first AC power end. The at least one LED unit has one or more LEDs connected in series. The DC power output circuit has a first end and a second end, wherein the second end of the DC power output circuit is electrically coupled to the second AC power end, while the first end of the DC power output circuit is electrically coupled to the second end of the lighting module. The DC power output circuit has a DC output side. 
     Furthermore, the invention discloses an AC LED lamp including a first AC power end, a second AC power end, a lighting module and a DC power output circuit. The lighting module has at least one LED unit and first and second ends electrically coupled to the first and second AC power ends, respectively. The at least one LED unit has a plurality of LEDs connected in series. The DC power output circuit is electrically coupled in parallel to at least one of the plurality of LEDs and has a DC output side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  shows a circuit diagram of a conventional AC LED lamp with a cooling device. 
         FIG. 2   a  shows a circuit diagram of an AC LED lamp according to a first embodiment of the invention. 
         FIG. 2   b  shows a circuit diagram of another AC LED lamp according to the first embodiment of the invention. 
         FIG. 3  shows a circuit diagram of an AC LED lamp according to a second embodiment of the invention. 
         FIG. 4  shows a circuit diagram of an AC LED lamp according to a third embodiment of the invention. 
         FIG. 5  shows a circuit diagram of an AC LED lamp according to a fourth embodiment of the invention. 
         FIG. 6  shows a circuit diagram of an AC LED lamp according to a fifth embodiment of the invention. 
     
    
    
     In the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the term “first”, “second”, “third”, “fourth”, “inner”, “outer” “top”, “bottom” and similar terms are used hereinafter, it should be understood that these terms refer only to the structure shown in the drawings as it would appear to a person viewing the drawings, and are utilized only to facilitate describing the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 2   a , an AC LED lamp is disclosed according to a first embodiment of the invention. The AC LED lamp includes a first AC power end AC 1 , a second AC power end AC 2 , a lighting module  1  and a DC power output circuit  2 . The first AC power end AC 1  and second AC power end AC 2  are connected to an AC power. The lighting module  1  has a first end V 1  and a second end V 2 , with the first end V 1  connected to the first AC power end AC 1 . The DC power output circuit  2  also includes a first end V 3  and a second end V 4 , with the second end V 4  connected to the second AC power end AC 2 . The second end V 2  of the lighting module  1  is electrically connected to the first end V 3  of the DC power output circuit  2 . The DC power output circuit  2  has a DC output side  20  to be connected to a cooling device  8 , which is usually a cooling fan, cooling module or cooling chip. The lighting module  1  and the DC power output circuit  2  can receive the AC power so that the lighting module  1  may emit light and the DC power output circuit  2  may generate a DC power at the DC output side  20  thereof for the cooling device  8 . 
     Specifically, referring to  FIG. 2   a , the lighting module  1  includes a first LED unit  11  and a second LED unit  12 . Both the first LED unit  11  and second LED unit  12  comprise at least one LED. The first LED unit  11  and second LED unit  12  are inversely connected in parallel between the first end V 1  and second end V 2 . 
     The DC power output circuit  2  includes a rectifying unit  21  and a voltage limiting and filtering unit  22 . The rectifying unit  21  and the voltage limiting and filtering unit  22  are connected to the lighting module  1  in series, with the lighting module  1  connected to the first AC power end AC  1  and the DC power output circuit  2  connected to the second AC power end AC 2  to form a series loop. 
     Referring to the  FIG. 2   a , the rectifying unit  21  is implemented as a half-wave rectifying circuit having a diode. The diode has an anode connected to the first end V 3 , and is connected in the same direction as the at least one LED of the first LED unit  11  or the second LED unit  12 . In this way, the first LED unit  11  will turn on during positive voltage cycle of the AC power if the diode is connected in the same direction as the at least one LED of the first LED unit  11 , or the second LED unit  12  will turn on during negative voltage cycle of the AC power if the diode is connected in the same direction as the at least one LED of the second LED unit  12 . 
     The voltage limiting and filtering unit  22  further includes a voltage-limiting element  221  and a filtering capacitor  222 . The voltage-limiting element  221  is connected to the filtering capacitor  222  in parallel. Then, the voltage-limiting element  221  and the filtering capacitor  222  are connected to the rectifying unit  21  in series. Specifically, the voltage-limiting element  221  and filtering capacitor  222  share one end connected to a cathode of the diode of the rectifying unit  21 , as well as the other end connected to the second end V 4 . In particular, the two ends where the voltage-limiting element  221  and filtering capacitor  222  are connected in parallel serve as the DC output side  20 . The voltage-limiting element  221  keeps the DC power of the DC output side  20  in a predetermined value. The voltage-limiting element  221  may be a Zener diode, but is not limited thereto. The filtering capacitor  222  is also parallel to the DC output side  20  for filtering the DC power. 
     Referring to  FIG. 2   b , another lighting module  1 ′ including a rectifying unit  11 ′ and an LED unit  12 ′ is disclosed. The rectifying unit  11 ′ is a full-wave rectifier and includes four diodes  111 ′ and  112 ′. Two of the diodes  111 ′ turn on under a positive voltage cycle of the AC power and the other two diodes  112 ′ turn on under a negative voltage cycle of the AC power. One diode  111 ′ has an anode connected to a cathode of one diode  112 ′, with the lighting module  1 ′ having an end V 1 ′ connected to the node where the diodes  111 ′ and  112 ′ are connected. In addition, the other diode  111 ′ also has an anode connected to a cathode of the other diode  112 ′, with the lighting module  1 ′ having an end V 2 ′ connected to the node where the diodes  111 ′ and  112 ′ are connected. The LED unit  12 ′ includes at least an LED. The rectifying unit  11 ′ is electrically connected to the LED unit  12 ′ to form a full-wave rectifying circuit. 
     Referring to  FIG. 2   b  again, the DC power output circuit  2  is connected to the end V 2 ′ of the lighting module  1 ′ via the first end V 3  thereof. In this way, operation of the AC LED lamp is available. 
     Referring to  FIG. 3 , an AC LED lamp is disclosed according to a second embodiment of the invention. In comparison with the first embodiment, the AC LED lamp in the second embodiment further includes an inverse diode  23 . The inverse diode  23  has one end connected to the rectifying unit  21  and the other end connected to the voltage limiting and filtering unit  22 . In addition, the inverse diode  23  is connected in an opposite direction to the diode of the rectifying unit  21 . 
     Referring to  FIG. 3 , when the AC power is supplied to the AC LED lamp, the inverse diode  23  can be turned on under the negative voltage cycle of the AC power so that the second LED unit  12  will also be turned on and driven to emit light. 
     Referring to  FIG. 4 , an AC LED lamp is disclosed according to a third embodiment of the invention. In comparison with the first and second embodiments, the AC LED lamp in the third embodiment includes a DC power output circuit  3  having a rectifying unit  31  and a voltage limiting and filtering unit  32 . The rectifying unit  31  is a full-wave rectifying circuit. The full-wave rectifying circuit, voltage limiting and filtering unit  32  and lighting module  1  are connected in series. Moreover, the way the voltage limiting and filtering unit  32  is connected and operated is the same as that of the voltage limiting and filtering unit  22  in the first and second embodiments, so it is not described herein again. 
     The third embodiment differs from the first and second embodiments in that the full-wave rectifying circuit can rectify the AC power to generate a rectified waveform, and the voltage limiting and filtering unit  32  will then filter the ripples of the rectified waveform. Thus, a stable DC power will be generated at a DC output side  30  of the voltage limiting and filtering unit  32 . 
     Furthermore, since the third embodiment uses the full-wave rectifying circuit to rectify the AC power in a full-wave manner, a small-capacity filtering capacitor of the voltage limiting and filtering unit  32  may be chosen. 
     Referring to  FIG. 5 , an AC LED lamp is disclosed according to a fourth embodiment of the invention. A DC power output circuit  4  in the fourth embodiment includes a rectifying unit  41  connected to the lighting module  1  in series and having a forward rectifying diode unit  411 . The forward rectifying diode unit  411  includes a plurality of diodes connected in series and has two ends connected to the first end V 3  and second end V 4 , respectively. Furthermore, the DC power output circuit  4  includes a DC output side  40  connected in parallel to at least one diode of the forward rectifying diode unit  411 . Each diode of the forward rectifying diode unit  411  has a rated voltage value (such as 3V). Thus, the voltage value of the DC power at the DC output side  40  can be adjusted by changing the number of the diodes of the forward rectifying diode unit  411  to which the DC output side  40  is connected. 
     The DC power output circuit  4  further includes a filtering capacitor  42  connected in parallel to the DC output side  40 . Based on this, the ripples of the DC power generated by the DC power output circuit  4  may be filtered by the filtering capacitor  42  to provide a stable DC power for the cooling device  8 . 
     Furthermore, the rectifying unit  41  in the fourth embodiment further includes a reverse rectifying diode unit  412  connected in parallel to the forward rectifying diode unit  411 . The reverse rectifying diode unit  412  also includes a plurality of diodes connected in series in an opposite direction to the diodes of the forward rectifying diode unit  411 . Thus, the reverse rectifying diode unit  412  can be turned on under the negative cycle of the AC power so that the second LED unit  12  will also be turned on and driven to emit light. 
     Moreover, the reverse rectifying diode unit  412  preferably has the same number of diodes as the forward rectifying diode unit  411  has, so as to ensure that the current passing through the lighting module  1  under positive voltage cycle of the AC power will be equal to that passing through the lighting module  1  under negative voltage cycle of the AC power. In this arrangement, the luminance of the lighting module  1  will be consistent. 
     Referring to  FIG. 6 , an AC LED lamp is disclosed according to a fifth embodiment of the invention. In comparison with the first to fourth embodiments, both the first LED unit  11  and second LED unit  12  include a plurality of LEDs, and the first AC power end AC 1  and second AC power end AC 2  are respectively connected to the first end V 1  and second end V 2  for providing power supply thereto. 
     Additionally, in comparison with the fourth embodiment, a DC power output circuit  5  in the fifth embodiment includes a filtering capacitor  51  connected in parallel to at least one LED of the first LED unit  11  or second LED unit  12 . 
     In general, each LED in the lighting module  1  has a rated voltage value. Therefore, the voltage value of a DC power at a DC output side  50  of the filtering capacitor  51  can be adjusted by connecting the filtering capacitor  51  to a proper number of the LEDs. 
     For example, referring to  FIG. 6 , the filtering capacitor  51  of the DC power output circuit  5  of the invention is connected to two LEDs of the first LED unit  11  so that a 6V voltage can be generated at the DC output side  50 . Similarly, the filtering capacitor  51  may also be connected to two LEDs of the second LED unit  12  to obtain a 6V voltage at the DC output side  50 . 
     In comparison with the fourth embodiment, since the filtering capacitor  51  in the fifth embodiment is connected to at least one LED of the lighting module  1  in parallel, the forward rectifying diode unit  411  and reverse rectifying diode unit  412  can be omitted to simplify the circuit complexity of the AC LED lamp. 
     In conclusion, the power supply required by the cooling device  8  may be provided at a DC output side of a DC power output circuit without using the transformer  71 , thereby reducing the costs, circuit volume and weight of the AC LED lamp. 
     Similarly, the DC power output circuit  2 ,  3 ,  4  or  5  may be connected to the other lighting module  1 ′ in  FIG. 2   b . Similar operation of this modification may be obtained by referring to the above description, so it is not described herein again. 
     Although the invention has been described in detail with reference to its presently preferable embodiment, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims.

Technology Classification (CPC): 8