Abstract:
Disclosed are an alternating current rectifying circuit and an alternating current rectifying method for driving an LED module. The method comprises: when an alternating current module is in a positive half cycle, after an alternating current output by the alternating current module is rectified, outputting the alternating current to a positive half cycle rectifying branch circuit of an external LED module; when the alternating current module is in a negative half cycle, carrying out charging according to the alternating current output by the alternating current module, and when the alternating current module is in the positive half cycle, carrying out discharging, and outputting the alternating current to a positive half cycle feed branch circuit of the external LED module; when the alternating current module is in the negative half cycle, rectifying the alternating current output by the alternating current module, and outputting the alternating current to a negative half cycle rectifying branch circuit of the external LED module; when the alternating current module is in the positive half cycle, carrying out charging according to the alternating current output by the alternating current module, and when the alternating current module is in the negative half cycle, carrying out discharging, and outputting the alternating current to a negative half cycle feed branch circuit of the external LED module. By using the present invention, stability of an output voltage can be improved, and luminous efficiency of the LED module can be improved.

Description:
The present application is a National Stage Application of PCT/CN2013/090330, filed Dec. 24, 2013, which claims priority of Chinese Patent Application No. 201310037188.2, filed Jan. 31, 2013. The entirety of the aforementioned applications is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to the technique of alternating current rectification, and more particularly, to an alternating current rectifying circuit and an alternating current rectifying method for driving an LED (Light Emitting Diode) module. 
     BACKGROUND 
     As one kind of new light sources with high-efficiency, LED (Light Emitting Diode) modules are widely applied in illumination in commercial, industrial and domestic fields due to advantages such as a long lifespan, a low energy consumption, energy-saving and environmental protection. 
     When the LED module acts as a light source of an illumination device, the lifespan of the illumination device not only depends on an illumination performance of the LED, but also depends on stability of driving circuit components for providing a working voltage for the LED module. In conventional application solutions, the bottleneck of the lifespan of the LED module still lies in the stability of the voltage provided by the driving circuit. In order to reduce the influence of fluctuation of the driving voltage to the lifespan of the LED module, it is necessary to design a new alternating current rectifying circuit for providing a stable driving voltage to drive the LED module based on the widely applied alternating current at present. 
     In a bridge rectifier circuit, semiconductor rectifier diodes (or named diodes) are connected to form a simple rectifying circuit. The bridge rectifier circuit is widely applied in various voltage-stabilizing applications for AC-DC conversion. Through the bridge rectifier circuit, the alternating current (AC) is rectified into the direct current (DC), so as to provide a relatively stable voltage for the LED module and thus lengthen the service life of the LED module. 
       FIG. 1  is a schematic diagram illustrating a structure of a conventional alternating current rectifying circuit for driving an LED module. The LED module is connected to a DC output terminal of the alternating current rectifying circuit. The alternating current is rectified by the alternating current rectifying circuit so as to be capable of directly driving the LED module. Referring to  FIG. 1 , the alternating current rectifying circuit is a bridge rectifier circuit, and includes an alternating current module (AC), a first diode D 1 , a second diode D 2 , a third diode D 3  and a fourth diode D 4 . 
     A positive terminal of the first diode D 1  is connected with a negative terminal of the second diode D 2 , and a negative terminal of the first diode D 1  is connected with a negative terminal of the third diode D 3  and an input terminal (V+) of an external LED module. 
     A positive terminal of the second diode D 2  is connected with a positive terminal of the fourth diode D 4  and an output terminal (V−) of the external LED module. 
     A positive terminal of the third diode D 3  is connected with a negative terminal of the fourth diode D 4 . 
     One end (A 1 ) of the alternating current module is connected with the positive terminal of the first diode D 1 , and the other end (A 2 ) thereof is connected with the positive terminal of the third diode D 3 . 
     A cycle of the alternating current includes a positive half cycle and a negative half cycle, wherein the positive half cycle is a time period during which the alternating current ascends to a positive peak value from a zero value and descends from the positive peak value to the zero value; and the negative half cycle is a time period during which the alternating current descends to a negative peak value from the zero value and ascends from the negative peak value to the zero value. 
     During the positive half cycle of the alternating current, the alternating current outputted from the alternating module passes through the first diode D 1 , the external LED module and the fourth diode D 4  so as to form a current loop for providing working voltage for the external LED module. 
     During the negative half cycle of the alternating current, the alternating current outputted from the alternating module passes through the third diode D 3 , the external LED module and the second diode D 2  so as to form another current loop for providing working voltage for the external LED module. 
     From above, in the conventional alternating current rectifying circuit for driving the LED module, the alternating current, after being rectified by the diodes, directly drives the LED module to operate. The alternating current fluctuates periodically, and the LED module has a certain switching-on voltage, i.e., only when the voltage applied across the LED module exceeds the switching-on voltage, the LED module may be turned on and may emit light; and if the voltage applied across the LED module does not exceed the switching-on voltage, the LED module is in a cut-off status, i.e., in a status of not emitting light. Thereby, the voltage which can be provided by the conventional alternating current rectifying circuit to the external LED module when the current loop reverses its current direction is smaller than the switching-on voltage, thus the luminous efficiency of the LED module is relatively low; further, through the rectification by the diodes in the alternating current rectifying circuit, the voltage value outputted to the LED module fluctuates as the fluctuation of the alternating voltage, thereby the stability of the output voltage is relatively low, and obvious flickering phenomenon appears in the LED module, which shortens the service life of the LED module. 
     SUMMARY 
     The embodiments of the present disclosure provide an alternating current rectifying circuit for driving an LED module, which improves stability of an output voltage and improves luminous efficiency of the LED module. 
     The embodiments of the present disclosure also provide an alternating current rectifying method for driving an LED module, which improves stability of an output voltage and improves luminous efficiency of the LED module. 
     In order to achieve the above purposes, the embodiments of the present disclosure provide an alternating current rectifying circuit for driving an LED module, the alternating current rectifying circuit including: an alternating current module, a positive half cycle rectifying branch, a positive half cycle feeding branch, a negative half cycle rectifying branch, and a negative half cycle feeding branch, wherein: 
     the positive half cycle rectifying branch is configured to, when the alternating current module is in a positive half cycle, rectify an alternating current outputted from the alternating current module, and output the rectified voltage signal to an external LED module; 
     the positive half cycle feeding branch is configured to perform charging according to the alternating current outputted from the alternating current module when the alternating current module is in a negative half cycle; and perform discharging and output the discharged voltage signal to the external LED module when the alternating current module is in the positive half cycle; 
     the negative half cycle rectifying branch is configured to, when the alternating current module is in the negative half cycle, rectify the alternating current outputted from the alternating current module, and output the rectified voltage signal to the external LED module; and 
     the negative half cycle feeding branch is configured to perform charging according to the alternating current outputted from the alternating current module when the alternating current module is in the positive half cycle; and perform discharging and output the discharged voltage signal to the external LED module when the alternating current module is in the negative half cycle. 
     Preferably, the positive half cycle rectifying branch includes a first rectifying tube, a second rectifying tube and a sixth rectifying tube, wherein: 
     a positive terminal of the second rectifying tube is connected with one end of the alternating current module, and a negative terminal of the second rectifying tube is connected with a positive terminal of the first rectifying tube; 
     a negative terminal of the first rectifying tube is connected with an input terminal of the external LED module; 
     a positive terminal of the sixth rectifying tube is connected with an output terminal of the external LED module, and a negative terminal of the sixth rectifying tube is connected with the other end of the alternating current module. 
     Preferably, the negative half cycle rectifying branch includes a third rectifying tube, a fourth rectifying tube and a fifth rectifying tube, wherein: 
     a negative terminal of the third rectifying tube is connected with the one end of the alternating current module, and a positive terminal of the third rectifying tube is connected with the output terminal of the external LED module; 
     a positive terminal of the fifth rectifying tube is connected with the other end of the alternating current module, and a negative terminal of the fifth rectifying tube is connected with a positive terminal of the fourth rectifying tube; and 
     a negative terminal of the fourth rectifying tube is connected with the input terminal of the external LED module. 
     Preferably, the positive half cycle feeding branch includes a first capacitor and a fourth capacitor, wherein: 
     one end of the first capacitor is connected with the positive terminal of the fourth rectifying tube, and the other end of the first capacitor is connected with the one end of the alternating current module; and 
     one end of the fourth capacitor is connected with the other end of the alternating current module, and the other end of the fourth capacitor is connected with the output terminal of the external LED module. 
     Preferably, the negative half cycle feeding branch includes a second capacitor and a third capacitor, wherein: 
     one end of the second capacitor is connected with the one end of the alternating current module, and the other end of the second capacitor is connected with the output terminal of the external LED module; and 
     one end of the third capacitor is connected with the positive terminal of the first rectifying tube, and the other end of the third capacitor is connected with the other end of the alternating current module. 
     Preferably, the rectifying tubes are diodes, transistors or silicon controlled rectifiers. 
     Preferably, the first capacitor, the second capacitor, the third capacitor and the fourth capacitor are non-polar capacitors. 
     Preferably, the first capacitor, the second capacitor, the third capacitor and the fourth capacitor have the same capacitance value. 
     Preferably, during the positive half cycle of the alternating current, the current passes through the second rectifying tube, the first rectifying tube, the LED module and the sixth rectifying tube to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of voltage of the alternating current, the alternating current passes through the second diode and the third capacitor to form a loop so as to charge the third capacitor; meanwhile, the alternating current passes through the second capacitor and the sixth diode to form a loop so as to charge the second capacitor; meanwhile, the fourth capacitor, the first capacitor, the fourth diode and the LED module form a loop so as to supply power to the LED module; 
     during the negative half cycle of the alternating current, the current passes through the fifth rectifying tube, the fourth rectifying tube, the LED module and the third rectifying tube to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of an absolute value of voltage, the alternating current in the alternating current module passes through the fifth rectifying tube and the first capacitor to form a loop so as to charge the first capacitor; meanwhile, the alternating current passes through the fourth capacitor and the third rectifying tube to form a loop so as to charge the fourth capacitor; meanwhile, the second capacitor, the third capacitor, the first rectifying tube and the LED module form a loop so as to supply power to the LED module. 
     Preferably, the alternating current rectifying circuit further includes: a current regulative diode, 
     a positive terminal of the current regulative diode is connected with the output terminal of the LED module, and a negative terminal of the current regulative diode is connected with the positive terminal of the third rectifying tube. 
     Preferably, the alternating current rectifying circuit further includes: an electrolytic capacitor, 
     a positive terminal of the electrolytic capacitor is connected with the input terminal of the LED module, and a negative terminal of the electrolytic capacitor is connected with the output terminal of the LED module. 
     An alternating current rectifying method for driving a light emitting diode LED module is provided, wherein the LED module is driven by an alternating current rectifying circuit and the alternating current rectifying circuit includes: an alternating current module, a positive half cycle rectifying branch, a positive half cycle feeding branch, a negative half cycle rectifying branch, and a negative half cycle feeding branch, the method including: 
     when the alternating current module is in a positive half cycle, the positive half cycle rectifying branch rectifies an alternating current outputted from the alternating current module, and outputs the rectified voltage signal to an external LED module; 
     the negative half cycle feeding branch performs charging according to the alternating current outputted from the alternating current module, and the positive half cycle feeding branch performs discharging and outputs the discharged voltage signal to the external LED module; 
     when the alternating current module is in the negative half cycle, the negative half cycle rectifying branch rectifies the alternating current outputted from the alternating current module, and outputs the rectified voltage signal to the external LED module; and 
     the negative half cycle feeding branch performs discharging, and outputs the discharged voltage signal to the external LED module, and the positive half cycle feeding branch performs charging according to the alternating current outputted from the alternating current module. 
     The positive half cycle rectifying branch includes a first rectifying tube, a second rectifying tube and a sixth rectifying tube, wherein: 
     a positive terminal of the second rectifying tube is connected with one end of the alternating current module, and a negative terminal of the second rectifying tube is connected with a positive terminal of the first rectifying tube; 
     a negative terminal of the first rectifying tube is connected with an input terminal of the external LED module; and 
     a positive terminal of the sixth rectifying tube is connected with an output terminal of the external LED module, and a negative terminal of the sixth rectifying tube is connected with the other end of the alternating current module. 
     The negative half cycle rectifying branch includes a third rectifying tube, a fourth rectifying tube and a fifth rectifying tube, wherein: 
     a negative terminal of the third rectifying tube is connected with the one end of the alternating current module, and a positive terminal of the third rectifying tube is connected with the output terminal of the external LED module; 
     a positive terminal of the fifth rectifying tube is connected with the other end of the alternating current module, and a negative terminal of the fifth rectifying tube is connected with a positive terminal of the fourth rectifying tube; and 
     a negative terminal of the fourth rectifying tube is connected with the input terminal of the external LED module. 
     The positive half cycle feeding branch includes a first capacitor and a fourth capacitor, wherein: 
     one end of the first capacitor is connected with the positive terminal of the fourth rectifying tube, and the other end of the first capacitor is connected with the one end of the alternating current module; and 
     one end of the fourth capacitor is connected with the other end of the alternating current module, and the other end of the fourth capacitor is connected with the output terminal of the external LED module. 
     The negative half cycle feeding branch includes a second capacitor and a third capacitor, wherein: 
     one end of the second capacitor is connected with the one end of the alternating current module, and the other end of the second capacitor is connected with the output terminal of the external LED module; and 
     one end of the third capacitor is connected with the positive terminal of the first rectifying tube, and the other end of the third capacitor is connected with the other end of the alternating current module. 
     The rectifying tubes are diodes, during the positive half cycle of the alternating current, the current passes through the second diode, the first diode, the LED module and the sixth diode to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of voltage of the alternating current, the alternating current passes through the second diode and the third capacitor to form a loop so as to charge the third capacitor; meanwhile, the alternating current passes through the second capacitor and the sixth diode to form a loop so as to charge the second capacitor; meanwhile, the fourth capacitor, the first capacitor, the fourth diode and the LED module form a loop so as to supply power to the LED module; 
     during the negative half cycle of the alternating current, the current passes through the fifth diode, the fourth diode, the LED module and the third diode to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of an absolute value of voltage, the alternating current in the alternating current module passes through the fifth diode and the first capacitor to form a loop so as to charge the first capacitor; meanwhile, the alternating current passes through the fourth capacitor and the third diode to form a loop so as to charge the fourth capacitor; meanwhile, the second capacitor, the third capacitor, the first diode and the LED module form a loop so as to supply power to the LED module. 
     It can be seen from the above technical solutions, the alternating current rectifying circuit and the alternating current rectifying method for driving a light emitting diode LED module provided by the embodiments of the present disclosure include: an alternating current module, a positive half cycle rectifying branch, a positive half cycle feeding branch, a negative half cycle rectifying branch, and a negative half cycle feeding branch, wherein: the positive half cycle rectifying branch is configured to rectify an alternating current outputted from the alternating current module and output the rectified voltage signal to an external LED module when the alternating current module is in a positive half cycle; the positive half cycle feeding branch is configured to perform charging according to the alternating current outputted from the alternating current module when the alternating current module is in a negative half cycle; and perform discharging and output the discharged voltage signal to the external LED module when the alternating current module is in the positive half cycle; the negative half cycle rectifying branch is configured to rectify the alternating current outputted from the alternating current module and output the rectified voltage signal to the external LED module when the alternating current module is in the negative half cycle; and the negative half cycle feeding branch is configured to perform charging according to the alternating current outputted from the alternating current module when the alternating current module is in the positive half cycle; and perform discharging and output the discharged voltage signal to the external LED module when the alternating current module is in the negative half cycle. In this way, on the basis of the conventional circuit in which the alternating current directly drives the LED module, by utilizing the charging and discharging of the capacitors, the stability of the output voltage is improved, the utilization rate of each half cycle of the alternating current is improved, the conduction time of the LED is increased, the fluctuation of light emitted by the LED is reduced, the relatively high power factor is ensured, and the luminous efficiency of the LED module is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to explain the technical solutions in the embodiments of the present disclosure or in the prior art more clearly, the drawings necessary for describing the embodiments or the prior art will be simply introduced below. Apparently, the drawings in the following description only illustrate some embodiments of the present disclosure, for the person skilled in the art, other embodiments and drawings may also be obtained according to the embodiments shown in these drawings. 
         FIG. 1  is a schematic diagram illustrating a structure of a conventional alternating current rectifying circuit for driving an LED module. 
         FIG. 2  is a schematic diagram illustrating a structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. 
         FIG. 3  is a schematic diagram illustrating a detailed structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. 
         FIG. 4  is a schematic diagram illustrating another detailed structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. 
         FIG. 5  is a schematic diagram illustrating further another detailed structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. 
         FIG. 6  is a flow chart of an alternating current rectifying method for driving an LED module according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the technical solutions of respective embodiments in the present disclosure will be described clearly and completely in combination with the accompanying drawings. Apparently, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the preset disclosure, all the other embodiments which could be obtained by the person skilled in the art without paying inventive labor belong to the scope protected by the present disclosure. 
     In the conventional alternating current rectifying circuit for driving the LED module, since the alternating current fluctuates periodically, and the LED module has a certain switching-on voltage, the voltage which can be provided to the external LED module when the current loop turns its direction is smaller than the switching-on voltage, thus the luminous efficiency of the LED module is relatively low; further, through the rectification by the diodes in the alternating current rectifying circuit, the voltage value outputted to the LED module fluctuates as the fluctuation of the alternating voltage, thereby the stability of the output voltage is relatively low, which influences the service life of the LED module. 
     With respect to the deficiencies in the prior art in which the alternating current directly drives the circuit, the embodiments of the present disclosure provide a driving circuit for directly driving the LED module by using an alternating current which provides a driving current for the LED module, i.e., charging and discharging of capacitors are used to increase a conduction angle and fill a trough of the alternating current, so as to improve efficiency of power supply and reduce flickering phenomenon in the LED. 
       FIG. 2  is a schematic diagram illustrating a structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. Referring to  FIG. 2 , the alternating current rectifying circuit includes: an alternating current module, a positive half cycle rectifying branch, a positive half cycle feeding branch, a negative half cycle rectifying branch, and a negative half cycle feeding branch, wherein: 
     the positive half cycle rectifying branch rectifies an alternating current outputted from the alternating current module and outputs the rectified voltage signal to an external LED module when the alternating current module is in a positive half cycle; 
     the positive half cycle feeding branch performs charging according to the alternating current outputted from the alternating current module when the alternating current module is in a negative half cycle; and performs discharging and outputs the discharged voltage signal to the external LED module when the alternating current module is in the positive half cycle; 
     the negative half cycle rectifying branch rectifies the alternating current outputted from the alternating current module and outputs the rectified voltage signal to the external LED module when the alternating current module is in the negative half cycle; and 
     the negative half cycle feeding branch performs charging according to the alternating current outputted from the alternating current module when the alternating current module is in the positive half cycle; and performs discharging and outputs the discharged voltage signal to the external LED module when the alternating current module is in the negative half cycle. 
     In the embodiments of the present disclosure, the external LED module may also be other load modules, such as other loads which need to be in a stable working voltage. 
     The positive half cycle rectifying branch includes a first rectifying tube D 1 , a second rectifying tube D 2  and a sixth rectifying tube D 6  (not shown in the drawing), wherein: 
     a positive terminal of the second rectifying tube D 2  is connected with one end (A 1 ) of the alternating current module, and a negative terminal of the second rectifying tube D 2  is connected with a positive terminal of the first rectifying tube D 1 ; 
     a negative terminal of the first rectifying tube D 1  is connected with an input terminal of the external LED module; 
     a positive terminal of the sixth rectifying tube D 6  is connected with an output terminal of the external LED module, and a negative terminal of the sixth rectifying tube D 6  is connected with the other end (A 2 ) of the alternating current module. 
     The negative half cycle rectifying branch includes a third rectifying tube D 3 , a fourth rectifying tube D 4  and a fifth rectifying tube D 5  (not shown in the drawing), wherein: 
     a negative terminal of the third rectifying tube D 3  is connected with the one end (A 1 ) of the alternating current module, and a positive terminal of the third rectifying tube D 3  is connected with the output terminal of the external LED module; 
     a positive terminal of the fifth rectifying tube D 5  is connected with the other end (A 2 ) of the alternating current module, and a negative terminal of the fifth rectifying tube D 5  is connected with a positive terminal of the fourth rectifying tube D 4 ; 
     a negative terminal of the fourth rectifying tube D 4  is connected with the input terminal of the external LED module. 
     The positive half cycle feeding branch includes a first capacitor C 1  and a fourth capacitor C 4  (not shown in the drawing), wherein: 
     one end of the first capacitor C 1  is connected with the positive terminal of the fourth rectifying tube D 4 , and the other end of the first capacitor C 1  is connected with the one end (A 1 ) of the alternating current module; and 
     one end of the fourth capacitor C 4  is connected with the other end (A 2 ) of the alternating current module, and the other end of the fourth capacitor C 4  is connected with the output terminal of the external LED module. 
     The negative half cycle feeding branch includes a second capacitor C 2  and a third capacitor C 3  (not shown in the drawing), wherein: 
     one end of the second capacitor C 2  is connected with the one end (A 1 ) of the alternating current module, and the other end of the second capacitor C 2  is connected with the output terminal of the external LED module; and 
     one end of the third capacitor C 3  is connected with the positive terminal of the first rectifying tube D 1 , and the other end of the third capacitor C 3  is connected with the other end (A 2 ) of the alternating current module. 
     Preferably, the rectifying tubes may be diodes, or may be transistors, or may be any devices having a unidirectional conductive characteristic, such as silicon controlled rectifiers. The semiconductor rectifier diode is preferably adopted, since the semiconductor rectifier diode has a low cost, and is convenient to be secondarily integrated with the LED module to constitute an integrated LED illumination device directly driven by the alternating current. 
     For example, the diode is used as the rectifying tube. In this case, the detailed explanation of the embodiments of the present disclosure will be given below. 
       FIG. 3  is a schematic diagram illustrating a detailed structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. Referring to  FIG. 3 , the alternating current rectifying circuit for driving an LED module includes: a first diode D 1 , a second diode D 2 , a third diode D 3 , a fourth diode D 4 , a fifth diode D 5 , a sixth diode D 6 , a first capacitor C 1 , a second capacitor C 2 , a third capacitor C 3 , a fourth capacitor C 4 , and an LED module, wherein: 
     a positive terminal of the second diode D 2  is connected with one end (A 1 ) of the alternating current module, and a negative terminal of the second diode D 2  is connected with a positive terminal of the first diode D 1  and one end of the third capacitor C 3 ; 
     a negative terminal of the first diode D 1  is connected with a negative terminal of the fourth diode D 4  and an input terminal (V+) of an external LED module; 
     the other end of the third capacitor C 3  is connected with the other end (A 2 ) of the alternating current module; 
     a positive terminal of the fourth diode D 4  is connected with a negative terminal of the fifth diode D 5  and one end of the first capacitor C 1 ; 
     the other end of the first capacitor C 1  is connected with the one end (A 1 ) of the alternating current module; 
     a positive terminal of the fifth diode tube D 5  is connected with a negative terminal of the sixth diode D 6 , one end of the fourth capacitor C 4  and the other end (A 2 ) of the alternating current module; 
     a negative terminal of the third diode D 3  is connected with the one end of the second capacitor C 2  and the one end (A 1 ) of the alternating current module; and 
     an output terminal (V−) of the LED module is connected with a positive terminal of the third diode D 3 , the other end of the second capacitor C 2 , the other end of the fourth capacitor C 4 , and a positive terminal of the sixth diode D 6 . 
     In the embodiments of the present disclosure, the first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3  and the fourth capacitor C 4  operate in an alternating state, and need to endure an inverse voltage. Preferably, the first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3  and the fourth capacitor C 4  are non-polar capacitors, so as to be adaptable to the alternating working circumstance. The alternating withstanding voltage value of the non-polar capacitor should be greater than or at least equal to the alternating input voltage value. 
     Preferably, the first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3  and the fourth capacitor C 4  have the same or similar capacitance value. 
     Hereinafter, the operational principle of the circuit in the embodiments of the present disclosure will be described: 
     during the positive half cycle of the alternating current, current passes through the second diode D 2 , the first diode D 1 , the LED module and the sixth diode D 6  to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of the alternating current voltage, the alternating current passes through the second diode D 2  and the third capacitor C 3  to form a loop so as to charge the third capacitor C 3 ; meanwhile, the alternating current passes through the second capacitor C 2  and the sixth diode D 6  to form a loop so as to charge the second capacitor C 2 ; meanwhile, the fourth capacitor C 4 , the first capacitor C 1 , the fourth diode D 4  and the LED module form a loop so as to supply power to the LED module, i.e., electric charges stored in the first capacitor C 1  and the fourth capacitor C 4  are discharged to the LED module through the fourth diode D 4 , so as to provide the working voltage for the LED module. 
     In the embodiments of the present disclosure, during the ascending stage of the alternating current voltage, in the circuit structure, the second capacitor C 2  and the third capacitor C 3  are connected in parallel, the first capacitor C 1  and the fourth capacitor C 4  are connected with the alternating current module in series so as to supply power to the LED module, such that the voltage of the alternating current is increased when the alternating current module initially supplies power or switches the positive and negative half cycles, so as to enable the LED module to be turned on in advance, in this way, the quality factor of the circuit is improved, the stability of the output voltage is improved, the luminous efficiency of the LED module is improved, and the service life of the LED module is prolonged. 
     During the negative half cycle of the alternating current, current passes through the fifth diode D 5 , the fourth diode D 4 , the LED module and the third diode D 3  to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of an absolute value of voltage, the alternating current in the alternating current module passes through the fifth diode D 5  and the first capacitor C 1  to form a loop so as to charge the first capacitor C 1 ; meanwhile, the alternating current passes through the fourth capacitor C 4  and the third diode D 3  to form a loop so as to charge the fourth capacitor C 4 ; meanwhile, the second capacitor C 2 , the third capacitor C 3 , the first diode D 1  and the LED module form a loop so as to supply power to the LED module, i.e., electric charges stored in the second capacitor C 2  and the third capacitor C 3  are discharged to the LED module through the first diode D 1 , so as to provide the working voltage for the LED module. 
     In the embodiments of the present disclosure, during the charging process in the ascending stage of the alternating current voltage, in the circuit structure, the first capacitor C 1  and the fourth capacitor C 4  are connected in parallel, the second capacitor C 2  and the third capacitor C 3  are connected with the alternating current module in series, such that the absolute value of voltage of the alternating current is increased when switching the alternating current, so as to enable the LED module to be turned on in advance. 
     In the embodiments of the present disclosure, through the alternative charging and discharging of the first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3  and the fourth capacitor C 4  during the positive and negative half cycles of the alternating current, the voltage value outputted to the LED module becomes relatively stable, and the flickering frequency of the LED module when emitting light is reduced; meanwhile, the turn-on time of the LED module within the positive and negative half cycles of the alternating current is increased, the fluctuation of light emitted by the LED module is reduced, and the power factor of the circuit is improved. Further, the circuit in the embodiments of the present disclosure has a simple structure, has a high efficiency of power supply, and is very suitable for the illumination device in which the LED module is directly driven by the alternating current. 
     In actual applications, in order to ensure that a difference between the output currents of the alternating current within the positive and negative half cycles is small, in  FIGS. 2 and 3 , the equivalent resistances of respective branches should be the same or similar, i.e., diode parameters in respective branches should be the same or similar, and respective capacitors should also have the same or similar capacitances. For example, the diode parameters in the positive half cycle rectifying branch should be the same as or similar with the diode parameters in the negative half cycle rectifying branch; and the capacitance in the positive half cycle feeding branch should be the same as or similar with the capacitance in the negative half cycle feeding branch. 
     In the embodiments of the present disclosure, selecting the capacitors having the same or similar parameters brings benefit to improve the electrical balance, and also brings benefit to balance the load, reduce the flickering and improve efficiency of power supply. In the embodiments of the present disclosure, the charging and discharging characteristic of the capacitor is mainly utilized, thereby the capacitance (capacitivity) parameters are the most important parameters. By selecting the capacitors having the same or similar capacitances, the charging and discharging characteristics can substantially reach the same or similar level. 
     Preferably, in order to further improve the stability of the voltage signal outputted to the LED module, the alternating current rectifying circuit for driving an LED module in the embodiments of the present disclosure further includes a current regulative diode (CRD). 
       FIG. 4  is a schematic diagram illustrating another detailed structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. Referring to  FIG. 4 , different from  FIG. 3 , a current regulative diode (CRD) is further included, wherein a positive terminal of the CRD is connected with the output terminal of the LED module, and a negative terminal of the CRD is connected with the positive terminal of the third diode D 3 . In this way, by adding one current regulative diode for limiting current in the DC loop, the luminous efficiency of the LED module can be greatly improved. 
     In  FIG. 3 , although the embodiments of the present disclosure can solve the problem of fluctuation of the light outputted from the LED module to a certain extent, the degree of filling the trough of the alternating current is low. The light outputted from the LED module at the trough of the alternating current is only 30%˜40% of the light outputted at the peak. 
     Thereby, a preferable solution of the present disclosure is provided as shown in  FIG. 5 . 
       FIG. 5  is a schematic diagram illustrating further another detailed structure of an alternating current rectifying circuit for driving an LED module according to an embodiment of the present disclosure. Referring to  FIG. 5 , different from  FIG. 4 , on the basic circuit of the present disclosure, an electrolytic capacitor C 5  is added as a filter capacitor, wherein a positive terminal of the electrolytic capacitor C 5  is connected with the input terminal of the LED module, and a negative terminal of the electrolytic capacitor C 5  is connected with the output terminal of the LED module. Thus, due to filtering function of the electrolytic capacitor C 5 , the current wave flowing into the LED module is smoother. Although some power factors are sacrificed, the light outputted from the LED module at the trough of the alternating current can reach more than 80% of the light outputted at the peak, thus there is mostly no difference of the sense. 
       FIG. 6  is a flow chart of an alternating current rectifying method for driving an LED module according to an embodiment of the present disclosure. Referring to  FIG. 6 , the alternating current rectifying circuit drives a light emitting diode LED module. The current rectifying circuit includes: an alternating current module, a positive half cycle rectifying branch, a positive half cycle feeding branch, a negative half cycle rectifying branch, and a negative half cycle feeding branch. The method includes the following steps. 
     In step  601 , when the alternating current module is in a positive half cycle, the positive half cycle rectifying branch rectifies an alternating current outputted from the alternating current module, and outputs the rectified voltage signal to an external LED module. 
     In this step, the positive half cycle rectifying branch includes a first rectifying tube, a second rectifying tube and a sixth rectifying tube, wherein: 
     a positive terminal of the second rectifying tube is connected with one end of the alternating current module, and a negative terminal of the second rectifying tube is connected with a positive terminal of the first rectifying tube; 
     a negative terminal of the first rectifying tube is connected with an input terminal of the external LED module; and 
     a positive terminal of the sixth rectifying tube is connected with an output terminal of the external LED module, and a negative terminal of the sixth rectifying tube is connected with the other end of the alternating current module. 
     In step  602 , the negative half cycle feeding branch performs charging according to the alternating current outputted from the alternating current module, and the positive half cycle feeding branch performs discharging and outputs the discharged voltage signal to the external LED module. 
     In this step, the negative half cycle feeding branch includes a second capacitor and a third capacitor, wherein: 
     one end of the second capacitor is connected with one end of the alternating current module, and the other end of the second capacitor is connected with the output terminal of the external LED module; and 
     one end of the third capacitor is connected with the positive terminal of the first rectifying tube, and the other end of the third capacitor is connected with the other end of the alternating current module. 
     The positive half cycle feeding branch includes a first capacitor and a fourth capacitor, wherein: 
     one end of the first capacitor is connected with the positive terminal of the fourth rectifying tube, and the other end of the first capacitor is connected with one end of the alternating current module; and 
     one end of the fourth capacitor is connected with the other end of the alternating current module, and the other end of the fourth capacitor is connected with the output terminal of the external LED module. 
     In step  603 , when the alternating current module is in the negative half cycle, the negative half cycle rectifying branch rectifies the alternating current outputted from the alternating current module, and outputs the rectified voltage signal to the external LED module. 
     In this step, the negative half cycle rectifying branch includes a third rectifying tube, a fourth rectifying tube and a fifth rectifying tube, wherein: 
     a negative terminal of the third rectifying tube is connected with one end of the alternating current module, and a positive terminal of the third rectifying tube is connected with the output terminal of the external LED module; 
     a positive terminal of the fifth rectifying tube is connected with the other end of the alternating current module, and a negative terminal of the fifth rectifying tube is connected with a positive terminal of the fourth rectifying tube; and 
     a negative terminal of the fourth rectifying tube is connected with the input terminal of the external LED module. 
     In step  604 , the negative half cycle feeding branch performs discharging, and outputs the discharged voltage signal to the external LED module, and the positive half cycle feeding branch performs charging according to the alternating current outputted from the alternating current module. 
     Thus, in the embodiments of the present disclosure, during the positive half cycle of the alternating current, current passes through the second rectifying tube, the first rectifying tube, the LED module and the sixth rectifying tube to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of the alternating current voltage, the alternating current passes through the second rectifying tube and the third capacitor to form a loop so as to charge the third capacitor; meanwhile, the alternating current passes through the second capacitor and the sixth rectifying tube to form a loop so as to charge the second capacitor; meanwhile, the fourth capacitor, the first capacitor, the fourth rectifying tube and the LED module form a loop so as to supply power to the LED module; 
     during the negative half cycle of the alternating current, current passes through the fifth rectifying tube, the fourth rectifying tube, the LED module and the third rectifying tube to form a loop so as to supply power to the LED module, wherein: 
     during an ascending stage of an absolute value of voltage, the alternating current in the alternating current module passes through the fifth rectifying tube and the first capacitor to form a loop so as to charge the first capacitor; meanwhile, the alternating current passes through the fourth capacitor and the third rectifying tube to form a loop so as to charge the fourth capacitor; meanwhile, the second capacitor, the third capacitor, the first rectifying tube and the LED module form a loop so as to supply power to the LED module. 
     Apparently, the person skilled in the art can make various modifications and changes to the present disclosure without departing from the spirit and scope thereof. Thus, if the modifications and changes to the present disclosure are within the scope of the claims of the present disclosure and its equivalent technique, the present disclosure intends to contain such modifications and changes.