Patent Publication Number: US-10791601-B2

Title: Light-emitting device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the right of priority based on Provisional Application Ser. No. 62/643,039, filed on Mar. 14, 2018, which is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a light-emitting device, and more particularly to a light-emitting device including a current source of a high electron mobility transistor. 
     DESCRIPTION OF BACKGROUND ART 
     In recent years, light-emitting diode has gradually replaced cathode lamp or tungsten as light sources for various lighting systems because of good electro-optical conversion efficiency and small product volume. The advantages and disadvantages of these lighting systems depend on whether stable lighting can be provided. For lighting system with dimmable luminous intensity, it usually needs a circuit that does not flicker the lighting system at low luminance. 
     SUMMARY OF THE DISCLOSURE 
     A light-emitting device comprises a light source, a stabilizing-current circuit and a current source. The light source has a first terminal and a second terminal. The stabilizing-current circuit is connected with the first terminal. The stabilizing-current circuit has a first transistor connected with the light source. The current source is connected with the second terminal. The current source has a second transistor connected with the light source. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIG. 2A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIG. 2B  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIGS. 2C to 2F  are waveform diagrams of a light-emitting device under different operation conditions in accordance with an embodiment of the present disclosure. 
         FIG. 3A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIG. 3B  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIGS. 3C to 3E  are waveform diagrams of a light-emitting device under different operation conditions in accordance with an embodiment of the present disclosure. 
         FIG. 4A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIGS. 4B-4D  are the waveform diagrams of different terminals in a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIG. 5A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIGS. 5B-5C  are the waveform diagrams of different terminals in a light-emitting device in accordance with an embodiment of the present disclosure. 
         FIG. 6  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE 
       FIG. 1  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. Referring to  FIG. 1 , a light-emitting device  1000  includes a driving circuit  100  and a light source  18  having light-emitting diodes, and the light-emitting device  1000  is coupled to an power supply VAC to activate the light source  18 . The power supply VAC is alternating current (AC) power source. The light source  18  can be a light source having endurance for high voltage. The light source  18  can also be formed by connecting a plurality of light-emitting diodes of the same or different sizes in series. For example, light source  18  includes two light-emitting diodes of the same size and connected in series, and the equivalent forward voltage of the light source  18  is 130 volts. The light-emitting diode include III-V group semiconductor material, such as Al x In y Ga (1-x-y) N or Al x In y Ga (1-x-y) P, wherein 0≤x, y≤1; (x+y)≤1. Based on the material of the semiconductor material, the light-emitting diode can emit a red light with a peak wavelength or dominant wavelength of 610˜650 nm; emit a green light with a peak wavelength or dominant wavelength of 530˜570 nm; emit a blue light with a peak wavelength or dominant wavelength of 450˜490 nm; emit a purple light with a peak wavelength or dominant wavelength of 400˜440 nm, or emit a UV light with a peak wavelength of 200˜400 nm. In an embodiment, the light-emitting diode further includes a wavelength conversion layer. The wavelength conversion layer includes one or more of phosphor, quantum dot material, or combinations thereof. The phosphor includes yellow-greenish phosphor, red phosphor, or blue phosphor. The yellow-greenish phosphor includes YAG, TAG, silicate, vanadate, alkaline-earth metal selenide, or metal nitride. The red phosphor includes fluoride (K 2 TiF 6 :Mn 4+ , K 2 SiF 6 :Mn 4+ ), silicate, vanadate, alkaline-earth metal sulfide, oxynitride, or a mixture of tungstate and molybdate. The blue phosphor includes BaMgAl 10 O 17 :Eu 2+ . The quantum dot material can be ZnS, ZnSe, ZnTe, ZnO, CdS, CdSe, CdTe, GaN, GaP, GaSe, GaSb, GaAs, AlN, AlP, AlAs, InP, InAs, Te, PbS, InSb, PbTe, PbSe, SbTe, ZnCdSeS, CuInS, CsPbCl 3 , CsPbBr 3 , CsPbI 3 . In an embodiment, the light-emitting diode including a wavelength conversion material can emit a white light, wherein the white light has a color temperature between 10000K and 20000K, and has a color point coordinate (x, y) in the CIE 1931 chromaticity diagram, 0.27≤x≤0.285; 0.23≤y≤0.26. In one embodiment, the white light emitted by the light-emitting diode has a color temperature between 2200 and 6500K (for example, 2200K, 2400K, 2700K, 3000K, 5700K, 6500K) and has a color point coordinate (x, y) located in the 7-step MacAdam ellipse in the CIE1931 chromaticity diagram. In an embodiment, the equivalent forward voltage of the light source  18  is between 260 and 265 volts. In an embodiment, the light source  18  is a filament. The driving circuit  100  includes a bridge rectifier  12 , a first filter  14 , an electronic device  16  having a high electron mobility transistor (HEMT) T 1  and a second filter  15 . When the power supply VAC is activated, the input alternating current voltage is converted into an input voltage VIN via the bridge rectifier  12 , and the electronic device  16  is turned on by the input voltage VIN and the light source  18  is turned on, so that the electronic device  16  is a current source to supply current to the light source  18 . The input voltage VIN is direct current (DC) voltage signal. 
     The bridge rectifier  12  includes four diodes DB 1 -DB 4  for converting the power supply VAC into the input voltage VIN. In an embodiment, the diodes DB 1 -DB 4  are Schottky diodes. In an embodiment, the power supply VAC is 110V, 220V, or 230V. A first filter  14  is disposed between the bridge rectifier  12  and the light source  18 . The first filter  14  is connected to the bridge rectifier  12 , and has a capacitor C 11  and two series-connected resistors R 11  and R 12 . The first filter  14  can avoid sudden surges and the noise voltage directly into the light source  18 , thereby avoiding damage or abnormal flicker caused by sudden surges and the noise voltage in the light source  18 . 
     Two sides of the electronic device  16  are respectively connected to the light source  18  and the second filter  15 . The electronic device  16  includes a high electron mobility transistor T 1 . The transistor T 1  generates a current IDS to the light source  18  when it is turned on. The current IDS is a substantially constant current. In the case of conduction, the value of the current IDS is almost not changed under the variation of the voltage difference between the drain and the source. Therefore, the transistor T 1  can provide a constant current to the light source  18 . In an embodiment, the electronic device  16  includes two high electron mobility transistors electrically insulated from each other, and each of the two transistors can provide a constant current. The second filter  15  includes a resistor R 13  and a capacitor C 12  connected in parallel with each other, wherein the capacitor C 12  can provide a voltage stabilizing effect and avoid flicker. 
       FIG. 2A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. Referring to  FIG. 2A , the light-emitting device  2000  includes a driving circuit  200  and light sources  180 - 183  having light-emitting diodes. The light sources  180 - 183  can be a light source having endurance for high voltage. The light sources  180 - 183  can also be formed by connecting a plurality of light-emitting diodes of the same or different sizes in series. For example, light sources  180 - 183  respectively includes 24 light-emitting diodes of the same size and connected in series. The equivalent forward voltage of each light-emitting diode is 3 volts, therefore the respectively equivalent forward voltage of light sources  180 - 183  is 72 volts. In an embodiment, each of the light sources  180 - 183  is a filament. In an embodiment, the light-emitting device  2000  is a light-emitting device adapting DOB (Driver On Board) technology with both the driving circuit  200  and the light sources  180 - 183  disposed on the same board. The driving circuit  200  includes a bridge rectifier  12 , filters  140 - 149 , electronic devices  160 - 165 , diode D 0  and diode groups DP 0 , DP 1 , DP 2 . The electronic devices  160 - 165  include transistors such as high electron mobility transistors and are used as a current source for providing current to the light sources  180 - 183 . The bridge rectifier  12  also converts the power supply VAC into an input voltage VIN. Related detailed descriptions can be referred to the above-mentioned paragraphs. 
     Referring to  FIG. 2A , in the light-emitting device  2000 , as the voltage of the power supply VAC increases, the input voltage VIN also increases and the light sources  180 - 183  are illuminated in sequence. More particularly, the input voltage VIN is increased enough to turn on the light source  180  but the light sources  181 - 183  are not illuminated. At this time, the current I 1  flows through the light source  180  and the electronic devices  160 - 165  in sequence. The magnitude of the current I 1  is limited by the electronic devices  160 - 165 . In an embodiment, the current I 1  is equal to the minimum value of the current supplied by the electronic devices  160 - 165 . In another aspect, the electronic device includes a transistor that can be a high electron mobility transistor (HEMT). For example, the electronic device  160  includes a transistor T 201 , the electronic device  161  includes transistors T 202  and T 203 , the electronic device  162  includes a transistor T 204 , the electronic device  163  includes transistors T 205  and T 206 , the electronic device  164  includes transistors T 207  and T 208 , and the electronic device  165  includes transistors T 209  and T 210 . 
     As the input voltage VIN increases, the electronic device  160  is turned off, and the light sources  180 ,  181  are illuminated but the light sources  182 ,  183  are not illuminated. At this time, the current I 2  flowing through the light source  181  is limited by the electronic devices  161 - 165 . In an embodiment, the current I 2  is equal to the maximum value of the current that can be supplied by the electronic device  161  under normal operation, or the maximum value of the sum of the currents that can be supplied by the transistors T 202  and T 203 . 
     As the input voltage VIN increases again, the electronic devices  160 ,  161  are turned off, and the light sources  180 - 182  are illuminated but the light source  183  is not illuminated. At this time, the current I 3  flowing through the light source  182  is limited by the electronic devices  162 - 165 . In an embodiment, the current I 3  is equal to the maximum value of the sum of the currents that can be supplied by the transistors T 204 -T 206  under normal operation. When the input voltage VIN increases again, the electronic devices  160 - 163  are turned off, and the light sources  180 - 183  are illuminated. At this time, the current I 4  flowing through the light source  183  is limited by the electronic devices  164  and  165 . In an embodiment, the current I 4  is equal to the maximum value of the sum of the currents that can be supplied by the transistors T 207 -T 210  under normal operation. However, when the input voltage VIN gradually decreases, the electronic devices  160 - 165  are turned on in the sequence of the electronic devices  164 - 165 , the electronic devices  162 - 163 , the electronic device  161  and the electronic device  160 . For example, the electronic devices  162 - 163  are turned on and then electronic device  161  is turned on as the input voltage VIN decreasing. 
     During the operation of the light-emitting device  2000 , the electronic devices  160 - 165  are sequentially turned off as the input voltage increases, and then sequentially turned on in the reverse order as the input voltage decreases. In an embodiment, the input voltage is a DC power source that is variable in value. The current I 1  is controlled by the transistor T 201  of the electronic device  160 , the current I 2  is controlled by the transistors T 202 , T 203  of the electronic device  161 , the current I 3  is controlled by the transistors T 204 -T 206  of the electronic device  162  and  163 , and the current I 4  is controlled by the transistors T 207 -T 210  of the electronic devices  164 ,  165 . The current I 2  is substantially averaged by the transistors T 202  and T 203 . 
     The diode D 0  is connected to the electronic devices  160 - 163 . A fixed voltage existing between the two terminals of the diode D 0  in the breakdown condition is provided to the electronic devices  160 - 163 . More particularly, the diode D 0  is connected to all the gates of the transistors of the electronic devices  160 - 163 . In an embodiment, the diode D 0  is a Zener diode. Each of the filters  140 - 149  is connected to each source of the transistors of the electronic devices  160 - 163  for filtering noise when the current passes through the electronic devices  160 - 163 , thereby avoiding the light source  180 - 183  flickers due to noise. The filters  140 - 149  are similar to the filter  15 , and each of filters  140 - 149  includes a resistor and a capacitor connected in parallel. The related descriptions can be referred to the above-mentioned paragraphs. The diode groups DP 0 , DP 1 , DP 2  are connected to the electronic devices  160 - 163  and the filters  140 - 145  of the same electronic device  160 - 163 . More particularly, each of the diode group DP 0 , DP 1 , DP 2  has a first terminal and a second terminal. Each first terminal of the diode group DP 0 , DP 1 , DP 2  is connected to each gate of the transistors of the electronic devices  160 - 163 , and each second terminal of the diode group DP 0 , DP 1 , DP 2  is connected to each source of the transistors of the electronic devices  160 - 163  through the filter  140 - 145 . The diode groups DP 0 -DP 2  are used to maintain the voltage between the gate and the source of the transistors of the electronic devices  160 - 163  not exceeding a certain value, for example, below 6.5 volts, to limit the operating range of the electronic device, thereby preventing the electronic device from generating excessive current to burn the light source or abnormally turning off the power to cause the flicker. Each of the diode groups DP 0 -DP 2  respectively includes diodes in reverse series, such as Zener diodes in reverse series. 
     The electronic device may include one or more transistors, wherein the transistor may be a high electron mobility transistor (HEMT).  FIG. 2B  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. In  FIG. 2B , the electronic devices  160 - 165  of  FIG. 2A  are replaced by transistors to form the light-emitting device  2002 . For example, the electronic device  160  is replaced by the transistor T 201 , the electronic device  161  is replaced by the transistors T 202  and T 203 , the electronic device  162  is replaced by the transistor T 204 , the electronic device  163  is replaced by the transistors T 205  and T 206 , the electronic device  164  is replaced by the transistors T 207  and T 208 , and the electronic device  165  is replaced by the transistors T 209  and T 210 . More particularly, the gate of the transistor T 201  is connected to the diode group DP 0 , the drain is connected to the light source  180 , and the source is connected to the filter  140 . The gates of the transistors T 202  and T 203  are connected to the diode group DP 1 , the two drains are also connected to the light source  181 , the source of the transistor T 202  is connected to the filter  142 , and the source of the transistor T 203  is connected to the filter  141 . In addition, the electrical connection relationship between the transistor T 204  and other components in the light-emitting device  2002  is similar to that of the electronic device  160 , and the electrical connection relationship between the transistors T 205 -T 210  and other components is similar to that of the electronic device  161 . The related circuit operation can be referred to the above-mentioned paragraphs of  FIG. 2A . 
       FIGS. 2C to 2F  are waveform diagrams of a light-emitting device under different operation conditions in accordance with an embodiment of the present disclosure. These operation conditions are differentiated by different input conditions. More particularly,  FIGS. 2C to 2F  show the waveforms of a transient state when the light-emitting device of  FIG. 2A or 2B  is operated under different input conditions. 
     Referring to  FIG. 2C , the root-mean-square (RMS) value of the voltage output from the power supply VAC is 69.7V, and the average output current is 89.2 mA. In  FIG. 2C , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the operation condition of  FIG. 2C , only the light source  180  emits light, and the current I 1  passes through the light source  180 , the electronic device  160  (the transistor T 201 ), the filter  140 , the electronic device  161  (the transistors T 202 , T 203 ), the filters  141  and  142 , the electronic devices  162  and  163  (the transistors T 204 -T 206 ), the filters  143 - 145 , electronic devices  164  and  165  (the transistors T 207 -T 210 ) and the filters  146 - 149 . The 1st area in the figure indicates the current under the condition disclosed in  FIG. 2C . 
     Referring to  FIG. 2D , the RMS value of the voltage output from the power supply VAC is 140V, and the average output current is 131 mA. In  FIG. 2D , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the operation condition of  FIG. 2D , the light sources  180  and  181  emit light and the electronic device  160  (the transistor T 201 ) is turned off. The current I 2  passes through the light sources  180  and  181 , the electronic device  161  (the transistors T 202 , T 203 ), the filters  141  and  142 , the electronic devices  162  and  163  (the transistors T 204 -T 206 ), the filters  143 - 145 , the electronic devices  164  and  165  (the transistors T 207 -T 210 ), and the filters  146 - 149 . 
     In  FIG. 2D , the RMS value of the voltage output from the power supply VAC is 140V. When the voltage output from the power supply VAC is gradually increased from a lower voltage (for example, 0V) to 140V, it goes through the voltage 69.7V output from the power supply VAC disclosed in  FIG. 2C  first. That means in a continuous boosting voltage process, the condition disclosed in  FIG. 2C  is occurred earlier than the condition disclosed in  FIG. 2D . Such operation is also reflected in the waveform diagram. Referring to  FIG. 2D , the 1st area in the figure indicates the current under the condition disclosed in  FIG. 2C , and the 2nd area indicates the current under the condition disclosed in  FIG. 2D . 
     Referring to  FIG. 2E , the RMS value of the voltage output from the power supply VAC is 180V, and the average output current is 190 mA. In  FIG. 2E , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the condition of  FIG. 2E , the light sources  180 - 182  emit light and the electronic device  160  and  161  (the transistors T 201 -T 203 ) are turned off. The current I 3  passes through the light sources  180 - 182 , the electronic devices  162  and  163  (the transistors T 204 -T 206 ), the filters  143 - 145 , the electronic devices  164  and  165  (the transistors T 207 -T 210 ), and the filters  146 - 149 . 
     Similarly, when the voltage output from the power supply VAC is gradually increased from a lower voltage to 180V, it goes through the voltage 69.7V and the voltage 140V respectively output from the power supply VAC disclosed in  FIGS. 2C and 2D  first. Therefore the conditions disclosed in  FIGS. 2C and 2D  will be occurred earlier than the condition disclosed in  FIG. 2E . Referring to  FIG. 2E , the 1st area in the figure indicates the current under the condition disclosed in  FIG. 2C , the 2nd area indicates the current under the condition disclosed in  FIG. 2D , and the 3rd area indicates the current under the condition disclosed in  FIG. 2E . 
     Referring to  FIG. 2F , the RMS value of the voltage output from the power supply VAC is 230V, and the average output current is 218 mA. In  FIG. 2F , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the operation condition of  FIG. 2F , the light sources  180 - 183  emit light and the electronic device  160 - 163  (the transistors T 201 -T 206 ) are turned off. The current I 4  passes through the light sources  180 - 183 , the electronic devices  164  and  165  (the transistors T 207 -T 210 ), and the filters  146 - 149 . 
     Similarly, when the voltage output from the power supply VAC is gradually increased from a lower voltage to 230V, it goes through the conditions disclosed in  FIG. 2C to 2E . Referring to  FIG. 2F , the 1st area in the figure indicates the current under the condition disclosed in  FIG. 2C , the 2nd area indicates the current under the condition disclosed in  FIG. 2D , the 3rd area indicates the current under the condition disclosed in  FIG. 2E , and the 4th area indicates the current under the condition disclosed in  FIG. 2F . In contrast, when the voltage output from the power supply VAC is gradually decreased from the higher voltage, the electronic devices  160 - 163  are turned on in the sequence of the electronic devices  162 - 163 , the electronic device  161  and the electronic device  160 . 
     In general, the operation state of the light-emitting device is varied with the value of the input voltage. An operation state corresponding to a higher voltage output from the power supply VAC can be accompanied with an operation state corresponding to a lower voltage. For example, when observing the waveform of the 100V RMS value of the voltage output from the power supply VAC, the waveform of the 69.7V RMS value of the voltage output from the power supply VAC output in  FIG. 2C  can also be observed. When observing the waveform of the 175V RMS value of the voltage output from the power supply VAC, the waveform of the 69.7V RMS value of the voltage output from the power supply VAC output in  FIG. 2C  and the waveform of the 140V RMS value of the voltage output from the power supply VAC output in  FIG. 2D  can also be observed. 
       FIG. 3A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. Referring to  FIG. 3A , the light-emitting device  3000  includes a driving circuit  300  and light sources  184 - 186  having light-emitting diodes. The light sources  184 - 186  can be formed by connecting a plurality of light-emitting diodes of the same or different sizes in series. The light sources  184 - 186  can also be a filament or a light source having endurance for high voltage. The related detailed descriptions can be referred to the above-mentioned paragraphs. In an embodiment, the light-emitting device  3000  is a light-emitting device adapting DOB (Driver On Board) technology with both the driving circuit  300  and the light sources  184 - 186  disposed on the same board. The driving circuit  300  includes a bridge rectifier  12 , filters  150 - 152 , electronic devices  166 - 168  having high electron mobility transistors, diode D 1 , resistors RA and RB, and diode groups DP 3 -DP 5 . The electronic devices  166 - 168  are similar to the electronic device  16 , and are used as a current source to provide current to the light sources  184 - 186 . The electronic device  166  includes a transistor T 301 , the electronic device  167  includes transistors T 302  and T 303 , and the electronic device  168  includes a transistor T 304 .  FIG. 3B  is a circuit diagram of a light-emitting device  3002  in accordance with an embodiment of the present disclosure. In  FIG. 3B , the electronic devices  166 - 168  of  FIG. 3A  are replaced by transistors to form the light-emitting device  3002 . For example, the electronic device  166  is replaced by a transistor T 301 , the electronic device  167  is replaced by transistors T 302  and T 303 , and the electronic device  168  is replaced by transistors T 304  and T 305 . The bridge rectifier  12  converts the power supply VAC into an input voltage VIN. The related detailed descriptions can be referred to the above-mentioned paragraphs. A fixed voltage existing between the two terminals of the diode D 1  in the breakdown condition is provided to the electronic devices  166  and  167 . In an embodiment, the diode D 1  is a Zener diode. 
     Referring to  FIG. 3A , the light-emitting device  3000  is electrically connected to the power supply VAC and a dimmer DI. The dimmer DI can adjust the luminous intensity of the light-emitting device  3000  by changing the electrical signal into the light-emitting device  3000 , wherein the dimmer DI is a TRIAC dimmer. In an embodiment, the light-emitting device  3000  is electrically connected to a digital dimmer and a power supply. After receiving an input signal, the dimmer DI changes the waveform of the signal by cutting off part of the input signal, and then outputs the remaining waveform to change a signal received by the load end. For example, after receiving a sine wave (for example, an AC signal), taking phase angle of 0 to 180 degrees for consideration, the dimmer DI cuts off the phase angle of the sine wave from 0 to 90 degrees, so that the waveform output from the dimmer DI only retains the phase angle of the sine wave from 90 degrees to 180 degrees. Therefore only half of the energy of the sine wave can pass through the dimmer DI. The dimmer DI further includes a minimum current for maintaining operation. It can prevent the current passed through the light-emitting device  3000  from being lower than the minimum current for maintaining the operation when the light-emitting device  3000  is at low luminance, which makes the dimmer DI abnormally turned off causing the light-emitting device  3000  flickering. The driving circuit  300  includes a bleeder circuit to generate a latching current for the dimmer DI. The bleeder circuit includes electronic devices  166 - 168  and filters  150 - 152 . When the voltage supplied by the power supply VAC is low, and the light sources  184 - 186  have not yet illuminated and only a very low current passes through the dimmer DI, the bleeder circuit is electrically connected to the dimmer DI and provides a latching current. More particularly, a latching current flows through the dimmer DI, the bridge rectifier  12 , the resistor RA, the electronic device  166 , the resistor RB, the electronic device  167 , the filters  150  and  151 , the electronic device  168  and the filter  152 , wherein the electronic device  166 - 168  is used as the current source and the resistor RA and RB are connected in series with the electronic devices  166 - 168  for adjusting the current. In an embodiment, the bleeder circuit is used as a current source. 
     As the value of the power supply VAC increases, the input voltage VIN also increases and the light sources  184 - 186  are sequentially illuminated. In particular, referring to  FIGS. 3A, 3B , the input voltage VIN is increased sufficiently to turn on the light source  184  but the light sources  185  and  186  are not illuminated. At this time, the electronic device  166  is turned off. The current I 5  flows through the light source  184 , the transistor T 302  of the electronic device  167 , the filter  150 , the transistor T 303  of the electronic device  167 , the filter  151 , the electronic device  168  and the filter  152 . As the input voltage VIN increases again, the transistor T 302  of the electronic device  167  and the electronic device  166  are turned off and the light sources  184 ,  185  are illuminated but the light source  186  is not illuminated. At this time, the current I 6  flows through the light sources  184  and  185 , the transistor T 303  of the electronic device  167 , the filter  151 , the electronic device  168 , and the filter  152 . The input voltage VIN is then increased to turn off the electronic devices  166  and  167 , and the electronic device  168  remains turned on. The light sources  184 - 186  are illuminated and the current I 7  flows through the light sources  184 - 186 , the electronic device  168 , and the filter  152 . 
     When the input voltage VIN gradually decreases, the electronic devices  167  and  166  are sequentially turned on in the reverse order of the above-mentioned description about the input voltage VIN being gradually increased. For example, the electronic device  167  is turned on and then the electronic device  166  is turned on. During the illuminating process of the light sources  184 - 186 , the transistors of the electronic devices  167 - 168  provide current and limit the maximum value of the passing current, thereby preventing the light sources  184 - 186  from receiving excessive current and being damaged. During the operation, the electronic device  167  (the transistors T 302  and T 303 ), and the electronic device  168  (the transistors T 304  and T 305 ) act as part of the bleeder circuit for passing the latching current when the light sources  184 - 186  are not turned on, and as a current source when the light sources  184 - 186  are illuminated. The related descriptions can be referred to the above-mentioned paragraphs of  FIG. 3A . 
       FIGS. 3C to 3E  are waveform diagrams of a light-emitting device under different operation conditions in accordance with an embodiment of the present disclosure. These operation conditions are differentiated by the different input conditions changed by the dimmer DI. More particularly,  FIGS. 3C to 3E  show the waveforms of a transient state when the light-emitting device of  FIG. 3A or 3B  is operated under different input conditions. 
     Referring to  FIG. 3C , the RMS value of the voltage output from the power supply VAC is 50V, and the average output current is 24.3 mA. In  FIG. 3C , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the operation condition of  FIG. 3C , only the light source  184  emits light and the light sources  185  and  186  are not illuminated. At this time, the electronic device  166  is turned off and the current I 5  flows through the light source  184 , the transistor T 302  of the electronic device  167 , the filter  150 , the transistor T 303  of the electronic device  167 , the filter  151 , the electronic device  168 , and the filter  152 . 
     Referring to  FIG. 3D , the RMS value of the voltage output from the power supply VAC is 120V, and the average output current is 35.2 mA. In  FIG. 3D , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the operation condition of  FIG. 3D , the light sources  184  and  185  emit light. At this time, the electronic device  166  and the transistor T 302  of the electronic device  167  are turned off. The current I 6  flows through the light sources  184  and  185 , the transistor T 303  of the electronic device  167 , the filter  151 , the electronic device  168  and the filter  152 . In the process of increasing the voltage of power supply VAC from 0V to 120V, it goes through the voltage 50V disclosed in  FIG. 3C  first. Therefore, in the current waveform diagram, the 1st area in  FIG. 3D  indicates the current under the condition disclosed in  FIG. 3C  and the 2nd area indicates the current under the condition disclosed in  FIG. 3D . 
     Referring to  FIG. 3E , the RMS value of the voltage output from the power supply VAC is 230V, and the average output current is 46 mA. In  FIG. 3E , the left-hand side diagram is the voltage waveform diagram and the right-hand side diagram is the current waveform diagram. Under the operation condition of  FIG. 3E , the light sources  184 - 186  emit light. At this time, the electronic devices  166  and  167  are turned off. The current I 7  flows through the light sources  184  and  185 , the electronic device  168  and the filter  152 . In the process of increasing the voltage of power supply VAC from 0V to 230V, it goes through the voltage 50V disclosed in  FIG. 3C  and the voltage 120V disclosed in  FIG. 3D  first. Therefore, in the current waveform diagram, the 1st area in  FIG. 3E  indicates the current under the condition disclosed in  FIG. 3C , the 2nd area indicates the current under the condition disclosed in  FIG. 3D  and the 3rd area indicates the current under the condition disclosed in  FIG. 3E . In contrast, when the voltage output from the power supply VAC decreases, the light source and the electronic devices are turned off in the reverse order of the above-mentioned description about the voltage of the power supply VAC being increasing. The related descriptions can be referred to the above-mentioned paragraphs of  FIG. 3A . 
     In general, the operation state of the light-emitting devices  3000 ,  3002  are varied with the voltage output from the power supply VAC. An operation state corresponding to a higher voltage output from the power supply VAC must be accompanied with an operation state corresponding to a lower voltage. For example, when observing the waveform of the 75V RMS value of the voltage output from the power supply VAC, the waveform of the 50V RMS value of the voltage output from the power supply VAC in  FIG. 3C  and the waveform of the 120V RMS value of the voltage output from the power supply VAC in  FIG. 3D  can also be observed. However, when the light-emitting devices  3000  and  3002  do not emit light, for example, when the voltage output from the power supply VAC is 40V, the bleeder circuit provides a latching current through the dimmer DI. The related descriptions can be referred to paragraphs of  FIG. 2F . 
       FIG. 4A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. Referring to  FIG. 4A , the light-emitting device  4000  includes a driving circuit  400  and a light source  187  having light-emitting diodes. The light source  187  can be formed by connecting a plurality of light-emitting diodes of the same or different sizes in series. The light source  187  can also be a filament or a light source having endurance for high voltage. The related detailed descriptions can be referred to the above-mentioned paragraph. In an embodiment, the light-emitting device  4000  is a light-emitting device adapting DOB (Driver On Board) technology with both the driving circuit  400  and the light source  187  disposed on the same board. The driving circuit  400  includes a bridge rectifier  12 , a bleeder circuit  42  having a transistor T 401 , a diode D 2 , a resistor R 45 , filters  156  and  157 , and a transistor T 402 . 
     The transistors T 401  and T 402  can be high electron mobility transistors, and the transistor T 402  is used as current sources for the light source  187 . When the transistor T 402  is activated, the transistor T 402  generates a substantially constant current flow to the light source  187  and the value of the current is almost not changed under the variation of the voltage difference between the drain and the source. Therefore, the transistor T 402  can provide a constant current to the light source  187 . The bridge rectifier  12  is used to convert the power supply VAC into an input voltage VIN. The related descriptions can be referred to the above-mentioned paragraphs. The filter  156  is located between the light source  187  and the bleeder circuit  42 . The filter  156  is connected to the bridge rectifier  12  through the diode D 2 , and includes a resistor R 41  and a capacitor C 41  connected in parallel. The filter  157  connected to the transistor T 402  includes a resistor R 42  and a capacitor C 42  connected in parallel. 
     The bleeder circuit  42  includes a transistor T 401  and resistors R 43 , R 44 . The resistor R 43  is located between the bridge rectifier  12  and the transistor T 401 . The resistor R 43  is located between the transistor T 401  and the resistor R 45 . The resistors R 43 -R 45  are used to adjust the current value of the bleeder circuit  42 . In an embodiment, the light-emitting device  4000  does not include the resistor R 45 . The transistor T 401  is further electrically connected to the transistor T 402  through the resistor R 42 . In particular, the source of the transistor T 401  is connected to the gate of the transistor T 402 , the source of the transistor T 401  is connected to the source of the transistor T 402  through the filter  157 , and the drain of the transistor T 401  is connected to the drain of the transistor T 402  through the filter  156  so that the transistor T 401  and the transistor T 402  can be considered as being connected in parallel. When the bleeder circuit  42  can be turned on or turned off by an external control signal, it can be used as an active bleeder circuit. In an embodiment, the power supply VAC is used as an external control signal, the transistor T 401  is a depletion mode transistor, and the gate of the transistor T 401  is connected to ground as shown in  FIG. 4A  to make the transistor T 401  turned on. As the voltage of the power supply VAC increases, the current flowing through the bleeder circuit  42  also increases so that the current I 8  flowing through the light source  187  increases. The current I 8  also flows through the resistor R 45 . As the current I 8  increases, the terminal voltage of the resistor R 45  connected to the bleeder circuit  42  also increases, which means that the source voltage of the transistor T 401  increases. When the voltage difference between the gate and the source of the transistor T 401  increases to a certain value, that is, when the voltage difference between the gate and the source is greater than the threshold voltage of the transistor T 401 , it causes the depletion mode transistor T 401  to be turned off. The bleeder circuit  42  is also turned off and no current flowing. In an embodiment, the bleeder circuit  42  is used as a current source. 
       FIGS. 4B-4D  are the waveform diagrams of different terminals in a light-emitting device in accordance with an embodiment of the present disclosure.  FIG. 4B  shows the current waveform W 1  and the voltage waveform W 2  provided by the power supply VAC, wherein the current waveform W 1  has a RMS value of 51.7 mA and the voltage waveform W 2  has a RMS value of 121V.  FIG. 4B  can be divided into four parts P 1 -P 4 . The phases of the parts P 1  and P 3  show that the voltage of the power supply VAC is insufficient to turn off the transistor T 401 , and the bleeder circuit  42  is activated. At the phase when the bleeder circuit  42  is activated, the current supplied by the power supply VAC is primarily dominated by the current flowing through the bleeder circuit  42  and a small portion of the current flowing to the light source  187 . However, these currents are not enough to activate the light source  187 . In an embodiment, during the phase that the bleeder circuit  42  is activated, the current supplied by the power supply VAC is all dominated by the current flowing through the bleeder circuit  42 . The phases of parts P 2  and P 4  show that the voltage of the power supply VAC is sufficient to turn off the transistor T 401  and activate the light source  187 . At this time, the bleeder circuit  42  is turned off, and the current supplied by the power supply VAC is primarily dominated by the current flowing through the light source  187  and only a small portion is by the current flowing to the bleeder circuit  42 , but it is still insufficient to activate the bleeder circuit  42 . In other words, the current flows mainly to the bleeder circuit  42  when the voltage supplied by the power supply VAC is low, and flows to the light source  187  when the voltage is high, thereby avoiding excessive current flow to light source  187  when the voltage is low. When the voltage supplied by the power supply VAC is low, excessive current flowing to light source  187  can produce blinking or low luminance condition that is considered abnormal. 
       FIG. 4C  shows the waveform W 3  of the voltage across the filter  156 , the waveform W 4  of the voltage across the light source  187 , the waveform W 5  of the voltage across the bleeder circuit  42  and the waveform W 6  of the current I 8 . The waveform W 3  has a RMS value of 138V, the waveform W 4  has a RMS value of 132V, the waveform W 5  has a RMS value of 120V, and the waveform W 6  has a RMS value of 31.3 mA. The waveform W 4  is smoother than the waveform W 3 . This is because the voltage of the power supply VAC passes through the filter  156  having the voltage regulation function before entering the two terminals of the light source  187 , so that the light source  187  can receive a relatively smooth voltage (waveform W 4 ). This makes the light source provide a stable light intensity while receiving a stable voltage. As in the operation flow described in the above-mentioned paragraphs, the bleeder circuit  42  is activated when the voltage supplied by the power supply VAC is low, and then the light source  187  is activated as the voltage increases. Therefore, the peak of the waveform W 5  of the voltage across the bleeder circuit  42  appears before the peak of the waveform W 6  of the current I 8 , that is, the normal operation of the bleeder circuit  42 . 
       FIG. 4D  shows the waveform W 8  of the voltage across the light source  187  and the waveform W 8  of the current I 8 . The waveform W 7  has a RMS value of 138V and the waveform W 8  has a RMS value of 31.3 mA. The peaks and troughs of the waveform W 7  and the waveform W 8  are appeared corresponding to each other. 
     In an embodiment, the light-emitting device  4000  is connected to a dimmer DI to adjust the luminance of the light source  187  through the dimmer DI as shown in  FIG. 3A . The bleeder circuit  42  can provide a latching current to dimmer DI, such as the phases P 1  and P 3  in  FIG. 4B , to avoid abnormal flicker or low-luminance. 
       FIG. 5A  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. Referring to  FIG. 5A , the light-emitting device  5000  includes a driving circuit  500  and a light source  188  having light-emitting diodes. The light source  188  can be formed by connecting a plurality of light-emitting diodes of the same or different sizes in series. The light source  188  can also be a filament or a light source having endurance for high voltage. The related detailed descriptions can be referred to the above-mentioned paragraph. In an embodiment, the light-emitting device  5000  is a light-emitting device adapting DOB (Driver On Board) technology with both the driving circuit  500  and the light source  188  disposed on the same board. The driving circuit  500  includes a bridge rectifier  12 , a bleeder circuit  52  having a transistor T 501 , diodes D 3  and D 4 , resistors R 55  and R 56 , filters  158  and  159 , a transistor T 402 , and a flicker reduction circuit  54 . The flicker reduction circuit  54  is regarded as a stabilizing-current circuit which can stabilize the current, thereby avoiding the light flicker caused by current vibration. 
     The transistors T 501  and T 502  can be high electron mobility transistors, and the transistor T 502  is used as current sources for the light source  188 . When the transistor T 502  is activated, the transistor T 502  generates a substantially constant current flow to the light source  188  and the value of the current is almost not changed under the variation of the voltage difference between the drain and the source. Therefore, the transistor T 502  can provide a constant current to the light source  188 . The bridge rectifier  12  is used to convert the power supply VAC into an input voltage VIN. The related descriptions can be referred to the above-mentioned paragraphs. The filter  158  is located between the light source  188  and the bleeder circuit  52 . The filter  158  is connected to the bridge rectifier  12  through the diode D 3 , and includes a resistor R 51  and a capacitor C 51  connected in parallel. The filter  159  connected to the transistor T 502  includes a resistor R 52  and a capacitor C 52  connected in parallel. 
     The bleeder circuit  52  includes a transistor T 501  and resistors R 53 , R 54 . The resistor R 53  is located between the bridge rectifier  12  and the transistor T 501 . The resistor R 54  is located between the transistor T 501  and the transistor T 502 . The resistors R 53  and R 54  are used to adjust the current value of the bleeder circuit  52 . The bleeder circuit  52  is connected with the transistor T 502  in series. When the light source  188  has not been activated, the current supplied by the bleeder circuit  52  flows through the transistor T 502  and the filter  159 . Therefore, the current flowing through the bleeder circuit  52  is also limited by the transistor T 502 . For example, the maximum value of the current flowing through the bleeder circuit  52  cannot exceed the maximum value of the current that the transistor T 502  can withstand, and the current flowing through the bleeder circuit  52  cannot exceed the current flowing through the transistor T 502 . The gate of the transistor T 501  is connected to the resistor R 55  via a resistor R 56  and a diode D 4  connected in series. When the diode D 4  is turned on, a stable voltage is applied to the gate of the transistor T 501  through a fixed voltage across two terminals of the diode D 4 . As the voltage of the power supply VAC increases, the voltage received by the source of the transistor T 501  through the resistor R 54  also increases until the transistor T 501  is turned off to close the bleeder circuit  52 . In an embodiment, the bleed circuit  52  can be used as an active bleed circuit. The voltage of the power supply VAC can be a control signal to turn the bleed circuit  52  on or off. The related descriptions can be referred to the above-mentioned paragraphs of  FIG. 4A . In an embodiment, the bleeder circuit  52  is used as a current source. 
     The two terminals of the flicker reduction circuit  54  are respectively connected to the filter  158  and the light source  188 . The flicker reduction circuit  54  includes resistors R 57  and R 58 , a capacitor C 53 , a diode D 5  and a transistor T 503 . The transistor T 503  can be a high electron mobility transistor or a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). The diode D 5  can be a Zener diode. The voltage received by the gate of transistor T 503  is determined by the voltage division of resistors R 57  and R 58 , or by the voltage across the diode D 5 . The capacitor C 53  is used to store the charge to stabilize the voltage of the gate of transistor T 503 . When the voltage of the power supply VAC increases, the voltage between the resistors R 57  and R 58  increases, and the voltage received by the gate of the transistor T 503  also increases. Until the voltage between the resistors R 57  and R 58  increases enough to cause the breakdown of the diode D 5 , the voltage received by the gate of the transistor T 503  is fixed at the breakdown voltage of the diode D 5 . For example, when the diode D 5  receives a voltage greater than or equal to its breakdown voltage, the voltage across the diode D 5  is fixed at a constant value. That is, the breakdown of the diode D 5  causes the transistor T 503  to operate within a fixed voltage range, so that the current through the transistor T 503  is substantially fixed. For example, when the diode D 5  is broken down, the difference between the maximum value and the minimum value of the current through the transistor T 503  is less than 5% of the minimum value, and the capacitor C 53  can further reduce the variation of the current, thereby stabilizing the current I 9  to avoid the light flicker caused by peak vibration of the high voltage. In other words, the flicker reduction circuit  54  can avoid the variation of the current I 9  caused by the variation of the power supply VAC, thereby avoiding the light flicker from the light source  188  caused by the variation of the current I 9 . 
     For example, the voltage of the power supply VAC is 110V, the activation voltage of the light source  188  is 80V, the breakdown voltage of the light source is 120V, and a diode D 5  with a breakdown voltage of 18V is selected. The flicker reduction circuit  54  can be designed to be activated by turning on the transistor T 503  when the voltage of the power supply VAC reaches 98V (the sum of the activation voltage (80V) of the light source  188  and the breakdown voltage (18V) of the diode D 5 ), wherein the current is the maximum value of current I 9 . In another embodiment, the flicker reduction circuit  54  can be designed to be activated when the voltage of the power supply VAC reaches 138V (the sum of the breakdown voltage (120V) of the light source  188  and the breakdown voltage (18V) of the diode D 5 ), wherein the current is the maximum value of current I 9 . By setting the diode D 5 , the voltage fluctuation to the drain of the transistor T 503  is not directly reflected on the light source  188  so as to reduce the ripple of the current I 9  to the light source  188  for avoiding abnormal flicker caused by the ripple. The flicker reduction circuit  54  can also be applied and connected to the light source of other light-emitting devices, such as the light-emitting devices  1000 ,  2000 ,  2002 ,  3000 ,  3002 ,  4000 , to reduce the ripple of the current to the light source. 
       FIGS. 5B-5C  are the waveform diagrams of different terminals in a light-emitting device in accordance with an embodiment of the present disclosure.  FIG. 5B  shows the current waveform W 9  and the voltage waveform W 10  provided by the power supply VAC, wherein the current waveform W 9  has a RMS value of 40.6 mA and the voltage waveform W 2  has a RMS value of 230V.  FIG. 5B  is similar with  FIG. 4B , the voltage waveform W 10  can be divided into four parts P 1 -P 4  according to ON/OFF of the transistor T 501 . The phases of the parts P 1  and P 3  show that the transistor T 501  is turned on and the bleeder circuit  42  is activated. The current supplied by the power supply VAC is primarily dominated by the current flowing through the bleeder circuit  52 . The phases of parts P 2  and P 4  show that the transistor T 501  is turned off and the light source  188  is activated. The current supplied by the power supply VAC is primarily dominated by the current flowing through the light source  188  so excessive current flowing to light source  187  when the voltage is low can be avoided. When the voltage supplied by the power supply VAC is low, excessive current flowing to light source  188  can produce blinking or low luminance condition that is considered abnormal. The related description can be referred to the above-mentioned paragraphs of  FIG. 4A . 
       FIG. 5C  shows the voltage waveform W 11  of the terminal connected to the bleeder circuit  52  and the diode D 3 , the waveform W 12  of the voltage received by the gate of the transistor T 503 , the waveform W 13  of the voltage across the light source  188  and the waveform W 13  of the current I 9 . The waveform W 11  has a RMS value of 228V, the waveform W 12  has a RMS value of 1.72V, the waveform W 13  has a RMS value of 260V, and the waveform W 14  has a RMS value of 17.2 mA. The bleed circuit  52  is activated when the voltage supplied by the power supply VAC is low, and then the light source  188  is activated as the voltage increases. Therefore, the peak of the waveform W 11  appears before the peak of the waveform W 14  and the peak of the waveform W 13 . That is the normal operation of the bleeder circuit  42 . The waveform W 12  is smoother than other waveforms. That means the gate of the transistor T 503  is biased with a stable voltage because of the combination of the diode D 5  and the capacitor C 53 , thereby reducing the ripple of the current to the light source  188 . As the voltage of the power supply VAC increases, the bleeder circuit  52  is activated before the light source  188  and the light source  188  is activated before the flicker reduction circuit  54 . 
     In an embodiment, the light-emitting device  5000  is connected to a dimmer DI to adjust the luminance of the light source  188  through the dimmer DI as shown in  FIG. 3A . The bleeder circuit  42  can provide a latching current to dimmer DI, such as the phases P 1  and P 3  in  FIG. 5B , to avoid abnormal flicker or low-luminance. 
       FIG. 6  is a circuit diagram of a light-emitting device in accordance with an embodiment of the present disclosure. Referring to  FIG. 6 , the light-emitting device  6000  includes a driving circuit  600  and a light source  189  having light-emitting diodes. The light source  189  can be formed by connecting a plurality of light-emitting diodes of the same or different sizes in series. The light source  189  can also be a filament or a light source having endurance for high voltage. The related detailed descriptions can be referred to the above-mentioned paragraph. In an embodiment, the light-emitting device  6000  is a light-emitting device adapting DOB (Driver On Board) technology with both the driving circuit  600  and the light source  189  disposed on the same board. The driving circuit  600  includes a bridge rectifier  12 , a bleeder circuit  62  having a transistor T 501 , diodes D 7 , a resistor RC, filters  160  and  161 , transistors T 602  and T 603 , and a flicker reduction circuit  64 . 
     The transistors T 601 -T 503  can be high electron mobility transistors. The transistor T 602  and T 603  are used as current sources for the light source  189  and can be accompanied with the filter  161  to make the voltage received by the transistors T 602  and T 603  more stable, thereby supplying a more stable current. The bridge rectifier  12  is used to convert the power supply VAC into an input voltage VIN. The related descriptions about a constant current supplied by the transistor and the bridge rectifier  12  can be referred to the above-mentioned paragraphs. In an embodiment, the transistors T 602  and T 603  can be packaged in the same electronic device. 
     The filter  160  and the flicker reduction circuit  64  are disposed between the light source  189  and the bleeder circuit  52 . The filter  160  connected to the diode D 7  includes a resistor R 61  and a capacitor C 61  connected in parallel. The filter  161  connected to the transistors T 602  and T 603  includes a resistor R 62  and a capacitor C 62  connected in parallel. 
     The bleeder circuit  62  includes a transistor T 601  and resistors R 63  and R 64  for adjusting the value of the current flowing through the bleeder circuit  62 . The gate of the transistor T 601  is connected to ground. As the voltage of the power supply VAC increase, the current through the resistor RC and the bleeder circuit  62  increases, and the voltage received by the source of the transistor T 601  through the resistor RC also increases. The transistor T 601  is turned off until the voltage of the gate and source of the transistor T 601  is greater than the threshold voltage. In an embodiment, the bleeder circuit  62  can be used as an active bleeder circuit. The voltage of the power supply VAC can be a control signal to turn the bleeder circuit  62  on or off. The related descriptions about the active bleeder circuit and the bleeder circuit  62  can be referred to the above-mentioned paragraphs of  FIG. 5A . In an embodiment, the bleeder circuit  62  is used as a current source. 
     One side of the transistors T 602  and T 603  is connected to the resistor RC through the filter  161 , and the other side is connected to the bleeder circuit  62  through the filter  160  and the diode D 5 , so that the transistors T 602 , T 603  and the bleeder circuit  62  are connected in parallel. 
     The two terminals of the flicker reduction circuit  64  are respectively connected to the filter  160  and the light source  189 , and includes resistors R 65 , R 66 , a capacitor C 63 , a diode D 6  and a transistor T 604 . The voltage received by the gate of transistor T 604  is determined by the voltage division of the resistors R 65  and R 66 , or by the voltage across the diode D 6 , thereby avoiding the light flicker caused by peak vibration of the high voltage. The related descriptions about the operation of the transistor T 604 , the diode D 6 , the capacitor C 63  and the resistors R 65 , R 66  in the flicker reduction circuit can be referred to in the above-mentioned paragraphs. The ripple of the current I 10  to the light source  188  can be reduced by setting the flicker reduction circuit  64  to stabilize the current I 10 , for avoiding abnormal flicker caused by the ripple. The flicker reduction circuit  64  can also be applied and connected to the light source of other light-emitting devices, such as the light-emitting devices  1000 ,  2000 ,  2002 ,  3000 ,  3002 ,  4000 , to reduce the ripple of the current to the light source  188 . As the voltage of the power supply VAC increases, the bleeder circuit  62  is activated before the light source  189  and the light source  189  is activated before the flicker reduction circuit  64 . 
     In an embodiment, the light-emitting device  6000  is connected to a dimmer DI to adjust the luminance of the light source  189  through the dimmer DI as shown in  FIG. 3A . The bleeder circuit  62  can provide a latching current to dimmer DI, such as the phases P 1  and P 3  in  FIG. 5B , to avoid abnormal flicker or low-luminance. The filters in the above-mentioned embodiments can provide not only the filtering function but also the function of stabilizing the voltage. The diodes in the above-mentioned embodiments also provide a function of preventing current from flowing back. 
     The above are only the preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalents, improvements, etc., which are included in the spirit and scope of the present disclosure, should be included in the scope of the present disclosure.