TW201244538A - Circuits for driving light sources - Google Patents

Abstract

A circuit for driving LED light source is disclosed. The PCB includes a bridge rectifier rectifying an AC voltage to a rectified AC voltage, an LED light source, and a first switch coupled to the LED light source in series controlling a current through the LED light source according to a predetermined current reference. The LED light source and the first switch coupled in series receive the rectified AC voltage while the first switch is controlled linearly.

Description

201244538 VI. Description of the Invention: [Technical Field] The present invention relates to the field of light source driving technology, and more particularly to a light emitting diode light source driving circuit. [Prior Art] In recent years, 'light-emitting diodes (LEDs) have been utilized in many fields of application, for example, general illumination. Compared to conventional light sources (eg, fluorescent and incandescent lamps, etc.), LEDs have several advantages, such as lower power dissipation. Conventional white woven lamps use a significant portion of the power to heat the metal filaments to cause the filaments to illuminate at very high temperatures, while the LEDs are almost non-heating, producing light of the same brightness as incandescent lamps with minimal power consumption. For example, in a bulb application, if you want to produce light of the same brightness, using LK) as a light source consumes only 7 watts of power, while a traditional incandescent bulb consumes about 60 watts. In addition, LEDs have a service life of more than 50,000 hours, while incandescent lamps have an average life of only 5,000 hours, and fluorescent lamps have an average life of approximately 15,000 hours. Compared to traditional light sources, LEDs have a much higher lifetime. In addition, LEDs do not contain harmful substances such as mercury, and do not generate ultraviolet radiation. Using LEDs as a light source can protect the environment and save energy. The traditional line-to-line/disambiguation (AG/DG) conversion converts the AC voltage from the AC source to a -DC voltage to power the (10) source. Figure 1 shows a schematic diagram of a conventional light source driving circuit, a drive-source γ, for example, an LED array (1). The light source driving circuit 1A includes a bridge rectifier 104 for rectifying an alternating voltage. The light source driving circuit is also known as 0796-TW CH Spec+Claim(filed-20120424).doc 3 201244538 includes an electrolytic capacitor & (10) coupled to the bridge rectifier 1〇4, the electrolytic capacitor Cbulk is larger in size and The rectified AC voltage is filtered and produces a DC voltage VIN. The light source drive circuit 100 also includes a DC/阢 converter 122 operating in a switching mode for converting the DC voltage VIN to a DC output voltage VOUT across the capacitor 116 to power the LED array 108. In operation, controller 118 generates an on/off signal (〇n/〇FF) to fully turn the switch or fully open switch 106' to control the power delivered to LED array 1〇8. Since the switches 106 are alternately turned on and off to cause electromagnetic interference, it is necessary to use the electromagnetic interference filter 130 to suppress noise on the power line. In addition to the EMI filter 130, the DC/DC converter 122 typically also includes components such as the inductor 112 and the capacitor 116 for energy storage and filtering. These components are generally bulky and difficult to place in conventional lighting devices such as the E12. , E13, E17 and other types of bulbs or Τ-5, T-8 and other types of lamps. SUMMARY OF THE INVENTION An object of the present invention is to provide a light source driving circuit comprising: a rectifier for converting an input AC voltage into a rectified AC voltage; a light emitting diode (LED) light source, the light emitting diode light source Receiving, by the terminal, the rectified AC voltage; and a first switch coupled in series to the LED light source, and linearly controlling a current flowing through the LED source according to a preset current reference value, wherein the current is The rectifier and the light emitting diode light source are disposed on a printed circuit board. [Embodiment] 0796-TW CH Spec+Claim(filed-20120424).doc 4 201244538 A detailed description will be given below of embodiments of the present invention. While the present invention will be carried out in conjunction with the embodiments, it should be understood that this is not intended to limit the present invention to these embodiments. On the contrary, the invention is intended to cover various modifications, modifications and equivalents of the invention as defined by the scope of the invention. In addition, in the following detailed description of the embodiments of the invention However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these. The other methods, procedures, components and circuits are not described in detail in order to highlight the gist of the present invention. The present invention provides a control circuit for a crane or a plurality of wires (e.g., a light emitting diode). The circuit provided by the invention can be applied to the bulbs of the E12, E13, E17 and the like, or the lamps of the T-5, T-8 and the like, but it is not limited thereto. In the embodiment, the light source driving circuit includes an alternating current/ DC linear conversion benefits. The AC/DC linear converter can achieve high power efficiency and high power factor at the same time. In an embodiment, the AC/DC linear converter can be configured on a relatively thin (eg, a printed circuit board (PCB) having a thickness less than (4)' and can be placed in a bulb of the E12, E13, ei7, etc. or Τ_5 In addition, compared with the traditional light source drive circuit, the switch mode DC/DC converter works with the ac/dc converter. 'According to the AC/DC, the linear converter does not produce Electromagnetic wave interference' does not require electromagnetic waves to interfere with the ship, nor does it require a volumetric element such as an inductor. Therefore, the light source driving circuit and method provided by the present invention provide efficiency and reduce cost. 0796-TW CH Spec+Claim( Filed-20120424).doc 5 201244538 Figure 2 is not a circuit schematic of a light source driving circuit 2 according to an embodiment of the present invention. In the example of Fig. 2, the light source driving circuit 2 includes AC/DC linear conversion. The device 240 is configured to receive an alternating voltage and control a current flowing through the light source. In the example of FIG. 2, the light source may be an LED array 210 including a plurality of sets of LED chains, but not limited thereto, and other types may be used. Light source. AC/DC linear rotation The device 240 includes a rectifier (eg, a bridge rectifier 204) for converting the AC voltage Vac into a rectified AC voltage Vrec 'switch qi' in series with the LED array 210 for controlling flow through the LED according to a preset current reference value The current of array 210; a control circuit (eg, operational amplifier 206) for linearly controlling switch Q1; and a current monitor (eg, monitoring resistor rset) for monitoring current flowing through the source and providing a monitoring for the control circuit Signal 220. In one embodiment, the switch qi is a metal oxide semiconductor field effect transistor (M〇SFET). Figure 3 shows the rectified AC voltage Vrec corresponding to the AC voltage Vac in the range of 〇 to 27 Γ. Waveform diagram. Figure 3 will be described in conjunction with Figure 2. In one embodiment, VRE (; is a periodic voltage signal with a peak voltage of Vp. The forward voltage drop V? of LED array 210 intersects VREC. When the voltage across the LED array 210 is greater than the forward voltage drop V of the LED array 210, the LED array 210 is illuminated. Specifically, in the example of FIG. 3, when the rectified AC voltage Vrec is greater than the LED array 210 When the voltage drops to V., the LED array 210 is illuminated. In one embodiment, the voltage drop across the monitoring resistor rset is small and negligible. Therefore, whether the LED array 210 is illuminated depends on the rectified AC voltage. The size of Vrec. When the rectified AC voltage Vrec is greater than the forward voltage drop V〇 of the LED array 210, the LED array 210 is illuminated. In an embodiment, 0796-TW CH Spec+Claim(filed-20120424).doc 6 In 201244538, a current monitor (e.g., monitoring resistor Rset) is coupled in series with array 21A for providing a monitoring signal 220 indicative of current flowing through LED array 21A. The control circuit compares the monitor signal 22 and the reference AD§ADJ indicating the preset current reference value and linearly controls the switch 卩丨 to adjust the current flowing through the LEd array 210 so that the current magnitude is equal to the preset current reference value. In one embodiment, the operational amplifier 206 in the control circuit compares the monitor signal 220 with the reference signal ADj and generates an error signal to linearly control the switch Q. In the example of FIG. 3, the rectified AC voltage vREC is a half wave. Sinusoidal voltage "No. In other examples, the rectified AC voltage Vre (: can be other types of periodic signals, and is not limited to the type shown in Figure 3. Under normal operating conditions, the monitoring resistor Rset The voltage drop can be ignored, and the forward voltage drop v〇 of the light source (eg, 'LED array 210) intersects the rectified AC voltage VREc. In other words, the peak value of the rectified AC voltage Vrec is greater than the source V〇 and the valley value is smaller than the LED array. The forward voltage drop v 210 of 210. In one embodiment, the current I flowing through the LED array 210 can be expressed as: I 〇 = ADJ / Rset (1) where 'ADJ in equation (1) represents the voltage of the reference signal ADJ The value ' Rset represents the resistance value of the monitoring resistor Rset. The forward voltage drop Vo of the LED array 21〇 can be expressed as: V〇= VpxSin0 (.2) where Vp in the equation (2) represents the rectified AC voltage vREC Peak, representative The rectified AC voltage Vre is equal to the conduction angle of the forward voltage drop V of the LED array 21〇. Here, “the rectified AC power 0796-TW CH Spec+Claim(filed-20120424).doc 7 201244538 Vrec is equal to the forward voltage drop V〇 of the LED array 210. It is established under the premise of ignoring the voltage drop across the switch Q1 and the monitoring resistor Rset and ignoring the non-ideal factors of the circuit components. Therefore, in the interval of 0 to 7 Γ The average input power Pin can be expressed as: 7t ^ =-*/〇*^*(-c〇s^)|re (3) π 1 丄*/ *F *2*cos0 π ° p at 0 to 7Γ Within the interval, the output power PDUt of the LED array 210 can be expressed as Ι0*ν0*(π-Θ-Θ) (4) π 2*θ π W(1——) according to equations (3) and (4), AC/ The power efficiency 7 of the DC linear converter 240 can be calculated by the following equation:

Pou, 2*0 π η = - Ρ'» 丄 */β* 匕 *2*〇w0 π 2*θ =___π_ L*I0*VD*2*Cose π (5)

ΐΒηθ*(π -2Θ) In the interval of 0 to 7 ,, the total power consumed by the switch Q1 and the monitoring resistor Rset can be expressed as:

Pl〇sS=Pin-Pmu= [(1/7)-1]^ (6) According to equation (5), the power efficiency as shown in Fig. 4 can be obtained. 7? 0796-TW CH Spec+Claim(filed-20120424 ).doc 8 201244538 Diagram of the relationship between the conduction angle θ and . (5) If the power efficiency 77 is known, the conduction angle " can be obtained according to the equation). If the peak voltage & of the rectified AC voltage Vrec is known, the forward voltage drop Vq can be calculated according to equation (2). If the output power of a standby device is known, for example, pQut=5w, according to the equation (two to the current I flowing through the LED array 210. Therefore, if the amount of the LED is known), it can be calculated to generate 5W output power. For example, if you want to design a power with 5W output and a power of 8_lamps, suppose that the AC power supply 2Q2 provides a frequency of (9) secret cut = special AC voltage vAe, and the peak value of the rectified AC dust w is 155 ^ Then according to equation (5), the conduction angle Θ is approximately 〇 81 intensity (46. 43 according to equation (2), the forward voltage drop v of the LED array is sin (〇.81) 'about ι 12 volts. According to equation (4) The current is ι〇, and the spoon is 92 mA. If the forward voltage drop of each single LED is & 2v, the number of LEDs that can be included in each group of LEDs in 21G is 35 _|35). If the LED is rated at 20 mA, the array can include 5 sets of LED chains, and each set of LED chains includes 35 passes. The power consumption of the switch Q1 and the monitoring resistor is 1.25 W.丨 ia ia - The power factor PF of the system can be expressed as ·· PF=v\~ (7) Let 7Pi: represent the average input power, which can be passed through equation (7): to 'L represents the root mean square of the input REC into the array 21G The root mean squares of the currents, seven and U, can be expressed as: 0796-TW CH Spec+Claim(filed-20120424).d〇c (8)201244538

The relationship between i 2*0 (9) 2*0 and the guide (r can be expressed as: The tomb L5 shows a relationship diagram between the power factor of the system and the quotient of the quotient (four) 0 according to an embodiment of the present invention. As shown in FIG. 4 and FIG. 5, the light source driving circuit 200 provided by the present invention can achieve higher power efficiency and a higher power factor PF through the selection of the right angle 0. For example, when 0 is Q.81, The power efficiency is about 80%, and the power pF is about 疋0.89. In addition, the light source driving circuit 00 provided by the present invention does not require an additional power factor correction circuit (generally including an inductor, a switch, and a control element) to obtain a comparison. High power factor. In one embodiment, the switch Q1 and the operational amplifier 2〇6 constitute a controller, and the controller can be integrated in the integrated circuit 23A. In addition, the bridge rectifier 204 and the integrated circuit 230 The monitoring resistor beating can be configured on a printed circuit board, and the light source (such as the LED array 21A of Figure 2) can be disposed on another printed circuit board. Figure 6 shows another implementation in accordance with the present invention. A schematic diagram of a circuit of the light source driving circuit 600 of the example. Elements of the same reference number have similar functions in Figure 2. The light source drive circuit 6A includes an ac/DC linear converter 640. The AC/DC linear converter 640 includes a control circuit for controlling the switch qi. In one embodiment, When the signal indicating the rectified AC voltage % is greater than the DC voltage, the light source driving circuit 600 illuminates the LED array 210; 0796-TW CH Spec+Claim (61ed-20120424).doi 10 201244538 When the rectified AC voltage is indicated When the signal of Vrec is less than the DC voltage, the light source driving circuit 600 turns off the LED array 210. Specifically, when the signal Vi of the 乂 voltage Vrec that is not rectified the next day is greater than the DC voltage Vdc, the output of the operational amplifier 206 is linearly controlled. Switch Q1. However, when the signal V indicating the rectified AC voltage VREC is less than the DC voltage Vdc, the output of the operational amplifier 206 is low, thus opening the switch Q1. In the example of Fig. 6, the 'AC/DC linear converter 640 includes a comparator 610 for comparing the signal Vi and the DC voltage Vdc to control the switch Q3 coupled to the operational amplifier 206. The signal Vi is proportional to the rectified AC voltage vREC. The dynamic circuit 600 includes a voltage divider formed by resistors R1, R2 for receiving the rectified AC voltage VREC and generating a signal V!. In one embodiment, the average of the DC voltage Vdc and the rectified AC voltage Vm: The light source driving circuit 600 further includes a voltage divider composed of resistors R3 and R4. The average filter capacitor C1 is connected in parallel with the resistor R4. Therefore, the DC voltage Vdc is proportional to the average value of the rectified AC voltage Vm: In the embodiment, when the signal Vi is greater than the DC voltage Vdc, the comparator 610 turns off the switch Q3, and the operational amplifier 206 linearly controls the switch Q1. When the signal Vi is less than the DC voltage Vdc, the comparator 610 turns on the switch Q3, the output of the operational amplifier 206 is connected to ground, and the switch Q1 is turned off. Therefore, even if the input AC voltage Vac changes, the light source driving circuit 600 can control the LED array 210 to produce a relatively stable brightness. Fig. 7 is a waveform diagram showing the rectified AC voltage VREC1 and the rectified AC voltage VREc2 in the interval of 0 to 2ττ. Figure 7 is described in conjunction with Figure 6. In one embodiment, the rectified AC voltages Vmn and VREC2 are periodic voltage signals, such as half-wave sinusoidal voltage signals. Assume that the input AC is 0796-TW CH Spec+Claim(filed-20120424).doc 11 201244538 The pressure Vac changes from Vaci to Vac2, and the rectified AC voltage changes from Vreci to Vrec2 accordingly. The peak value of Vrec丨 is Vpi ’Vrec2 and the peak value is Vp2. Since the DC voltage Vdc is proportional to the average value of the rectified AC voltage Vrec, its voltage value also changes from Vdci to Vdc2. As shown in the example of FIG. 7, regardless of whether the rectified AC voltage is Vreci or Vrec2, in the range of 〇~0, (π_0)~(7Γ + 0), and (2 7Γ - Θ)~2 7Γ, The switch Q3 is turned on; in the interval of (7 Γ +0) 〜 (27 Γ - 0), the switch Q3 is turned off. In one embodiment, when switch Q3 is turned on, switch Q1 is turned off; when switch Q3 is turned off, operational amplifier 206 compares reference signal ADJ and monitor signal 220 to linearly control switch Q1' to adjust the current flowing through LED array 210. In other words, even if the rectified AC voltage Vrec changes due to a change in the input AC voltage Vac, the switch Q1 is turned on at the same conduction angle, so the brightness of the LED array 210 is relatively stable. In the example shown in Figure 6, the DC voltage Vdc can be expressed as:

R3 + R4 (11) where R3 represents the resistance of resistor R3 and R4 represents the resistance of resistor R4. In one embodiment, the resistance values of R3 and R4 are selected based on the integrated circuit design conditions (e.g., the input voltage of the non-inverting input of comparator 610 is required to be 2.0 V, i.e., Vdc is 2.0 V). If the peak value νΡ of the rectified AC voltage Vrec is 155V, according to equation (11), the proportional relationship between R3 and R4 can be expressed as: = 0.02 (12) R3 + R4 —*155 Known when rectified AC voltage VREc is greater than the forward voltage drop V of the LED array 210. When the switch Q1 is turned on. The inverting input of the comparator 610 is 0796-TW CH Spec+Claim(filed-20120424).doc 12 201244538 The voltage Vi is proportional to the rectified AC voltage Vrec and is determined by the resistance of the resistors R1, R2. The forward voltage drop V of the LED array 210 is assumed. For 112V, the peak value Vp of the rectified AC voltage Vrec is 155V, and the proportional relationship between R1 and R2 can be expressed as: R2 RI + R2 2.0 ΤΪ2 0.0178 (13) Assume that the rectified AC is changed due to the change of the input AC voltage Vac The peak value Vp of the voltage Vrec is changed from 155V to 180V. According to equation (11), the DC voltage Vdc: will also change accordingly:

π R3 R3 + R4 *180 = 2.322 Factory (14) According to the square (2) ' Stn9 = x ', therefore 0 = 0.81 intensity (46.43 degrees), equal to the conduction angle of Vp of 155V ‘. From the above analysis, it can be seen that even if the rectified AC voltage Vreg changes, the switch Q] is always turned on at the same conduction angle, so the brightness of the LED array 210 is relatively stable. Referring to FIG. 2, for the light source driving circuit 2A of FIG. 2, if the peak value Vp of the rectified AC voltage Vrec changes from 155V to 180V due to the change of the AC voltage Vac, the conduction angle 0 can be obtained according to the following calculation. Approximately 0.67 intensity (38.48 degrees) · (15) Output power (16) V0 = Vp x Sin0 ^ 112V = 180F xsin^ 0 = 0.67 Therefore, if the light source driving circuit 200 of Fig. 2 is employed, Pout can be expressed as: P〇m =^〇Χ^〇Χ(1-^^·) 7t τ 2x0.67 = ^〇Χ^〇Χ(1--) π =5J5Watis This shows that if rectified due to changes in AC voltage Vac AC 0796-TW CH Spec+Claim(filed-20120424).doc 13 201244538 The peak VP of the voltage Vrec changes from 155V to 180V, which causes the LED array 210 to change its shell. The power loss is:

Pioss = Pin --^= [(1 -77)-= 2.35^ (17) And if the light source driving circuit 600 of Fig. 6 is employed, the power efficiency is further improved. For the light source driving circuit 6〇〇, if the rectified AC voltage is VREC2' and its peak value is 180V, then

Ploss =Pin ~P〇ut = ~xI〇xVpx^cos0-5Watts 1 λ (18) = -x/〇xl8〇x2x cos(〇.81) - SWatts =lllWatts In one embodiment, switches Q1 and Q3, The operational amplifier 2〇6, the comparator 610, and the resistors m, R2, R3, and R4 constitute a health controller, and the controller can be integrated in the integrated circuit 630. In another embodiment, resistors R1 and/or R3 may also be disposed external to the integrated circuit. Further, the bridge rectifier 204 filter valley C1, the monitor resistor Rset, and the integrated circuit 63A can be disposed on a printed circuit board. The light source (e.g., array (10) shown in Figure 6) can be configured on another printed circuit board. Figure 8 is a circuit diagram of the light source driving circuit surface splicing the lighting switch 808 according to an embodiment of the present invention. The light source driving circuit is similar to the driving circuit shown in Fig. 2, and a current path is connected in parallel with (10)_. In an implementation, this current path is connected to a resistor 8〇2. Illumination switch 808 includes an illuminating indicator (e.g., IF 2 in Figure 8, body 806 or other type of source such as a xenon lamp), and the LED is connected to the resistor pair. The lighting switch 808 also includes a switch _, which is lightly connected between the AC power source 2G2 and the bridge rectifier 2〇4. 0796-TW CH Spec+Claim(fi]ed-20120424).d〇c 201244538 804 is also connected in parallel with the light-emitting diode 806 and the resistor 8i〇. In operation, when the switch 804 is turned on and the rectified AC voltage Vrec is greater than the forward voltage drop Vfl of the LED array 210, the LED array 21 is illuminated. When the switch 804 is turned off, current flows from the AC power source 2〇2 through the resistor 81〇, the light-emitting body 806, the bridge rectifier 2〇4, the current path including the resistor 802, and then flows to the ground. At this time, the light-emitting diodes 8〇6 are illuminated, making it easy for the user to determine the position of the switch even in the dark. The resistance of the resistor 8 〇 2 is selected such that, in the case where the switch 804 is off, the rectified voltage VREe reaches its peak value Vp ′. The voltage drop across the LED array 210 must be less than the forward voltage V LE of the LEd array 21 〇. Thus, when the switch 8〇4 is turned off, the LED array 21〇 remains off. Figure 9 is a circuit diagram showing the driving circuit 9A coupled to the illumination switch 808 in accordance with another embodiment of the present invention. The light source driving circuit 9A is similar to the light source driving circuit 600 shown in Fig. 6, and based on this, a current path is connected in parallel at both ends of the LED array 21. In an embodiment, this current path includes a resistor 802. Similarly, as shown in the above figure, the light source driving circuit 9 is used in conjunction with the illumination switch 808 using a current path coupled between the bridge rectifier 204 and the switch Q1. Fig. 10 is a schematic view of a lamp 1 根据 according to an embodiment of the present invention, and Fig. 11 is an exploded view of the lamp 1 图 shown in Fig. 10. The lamp unit 1 includes an electric portion 111 that receives an AC signal, a printed circuit board 11〇4, an LED array 1106, a plastic sleeve 11〇2, and a metal portion nog on which the printed circuit board 11〇4 and the LED array 1106 are placed. In an embodiment, the light source driving circuit 200 (or the light source driving circuit 6A) is disposed on the printed circuit board.

On 1104. In another embodiment, an AC/DC linear converter 240 (or AC/DC 0796-TW CH Spec+Claim (filed-20120424).doc 201244538 linear converter 640) and LED array 1106 are disposed on printed circuit board 1104. on. As described, the present invention provides a light source driving circuit suitable for driving one or more light sources, such as LED light sources. The light source drive circuit utilizes an AC/DC linear converter to achieve high power efficiency and high power factor at the same time. Compared with the conventional light source driving circuit, a DC/DC converter which adopts an inductor, a capacitor, a switch and the like to form a switching mode is required, and the circuit of the present invention does not require a switching mode DC/DC converter, thereby reducing the size and reducing the cost. . Moreover, the AC/team linear converter employed in the circuit of the present invention does not generate electromagnetic interference. It is not necessary to use an electromagnetic dry thief. Because of its small size, the light source driving circuit provided by the invention can be applied to bulbs of the E12, E13, E17 and the like, or lamps of the type τ_5, τ_8 and the like. The above detailed description and the drawings are merely illustrative of the common embodiments of the invention. It is apparent that various additions, modifications and substitutions are possible without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood by those skilled in the art that the present invention may be modified in form, structure, arrangement, ratio, material, element, element, and other aspects in accordance with the specific environmental and operational requirements without departing from the invention. Therefore, the embodiments disclosed herein are intended to be illustrative and not limiting, and the scope of the invention is defined by the appended claims BRIEF DESCRIPTION OF THE DRAWINGS The following is a detailed description of the present invention, and the features and advantages of the present invention will become more apparent. Its order: 0796-TW CH Spec+Claim(ftled-20120424).doc 201244538 Figure 1 shows a schematic diagram of a conventional light source driving circuit. Figure 2 is a schematic illustration of a light source driving circuit in accordance with an embodiment of the present invention. 3 is a waveform diagram of the rectified AC voltage Vrec corresponding to the AC voltage Vac in the interval of 〇2ττ according to an embodiment of the present invention. 4 is a graph showing the relationship between power efficiency and conduction angle 0 in accordance with an embodiment of the present invention. Figure 5 is a graph showing the relationship between system power factor and conduction angle 根据 according to an embodiment of the present invention. Fig. 6 is a circuit diagram showing a light source driving circuit according to another embodiment of the present invention. Fig. 7 is a waveform diagram of the rectified AC voltage and the rectified AC voltage VrEC2 in the interval of 〇2; r. Figure 8 is a circuit diagram of a drive circuit coupled switch in accordance with an embodiment of the present invention. *, ,, and Figure 9 is a circuit diagram showing a driving circuit of a switch according to another embodiment of the present invention. Money Figure 10 is a schematic view of a lamp tube in accordance with an embodiment of the present invention. Figure 11 is an exploded view of the lamp of Figure 10. [Main component symbol description] 100: Light source driving circuit 104: Bridge rectifier 106: Switch 108: LED array 0796-TW CH Spec+Claim (filed-20120424) doc 17 201244538 112: Inductance 116: Capacitor 118: Controller 122: DC/DC converter 130: EMI filter 200: Light source drive circuit 202: AC power supply 204: Bridge rectifier 206: Operational amplifier 210: LED array 220: Monitoring signal 230: Integrated circuit 240: AC/DC linear converter 600: light source driving circuit 610: comparator 630: integrated circuit 640 · AC/DC linear converter 800: light source driving circuit 802: resistor 804: switch 806: light emitting diode 808: lighting switch 810: resistor 900: light source Drive circuit 1000: tube 0796-TW CH Spec+Claim(filed-20120424).doc 18 201244538 1110: electrical part 1102: plastic sleeve 1104: printed circuit board 1106: LED array 1108: metal part 0796-TW CH Spec+ Claim(filed-20120424).doc 19

Claims (1)

201244538 VII. Patent application scope: 1. A light source driving circuit, comprising: a rectifier for converting an input AC voltage into a rectified AC voltage; a light emitting diode (LED) light source, the light emitting diode light source- The terminal receives the rectified AC voltage; and a first switch coupled in series to the LED light source, and linearly controlling a current flowing through the LED source according to a preset current reference value, wherein The rectifier and the light emitting diode light source are disposed on a printed circuit board. 2. The light source driving circuit of claim 1, wherein the light source driving circuit illuminates the light emitting diode light source when a signal indicating the rectified alternating voltage is greater than a direct current voltage, and wherein When the signal of the rectified AC voltage is less than the DC voltage, the light source driving circuit turns off the LED light source. 3. The light source driving circuit of claim 2, further comprising: a control circuit coupled to the first switch, the monitoring signal indicating the current flowing through the light emitting diode source and the indication A reference signal of the preset reference current linearly controls the first switch. 4. The light source driving circuit of claim 3, further comprising: a second switch coupled to the control circuit; and a comparator for comparing the rectified AC voltage and the DC voltage and generating a control The signal controls the second switch. 0796-TW CH Spec+Claim(filed-20120424).d&lt; 20 201244538 5. The light source driving circuit of claim 3, further comprising: a current monitor coupled in series to the light emitting diode light source, And generate the monitoring signal. 6. The light source driving circuit of claim 3, wherein the control circuit includes an amplifier that compares the monitoring signal with the reference signal and generates an error signal to linearly control the first switch. 7. The light source driving circuit of claim 2, wherein the direct current voltage represents a forward voltage drop of the light emitting diode source. 8. The light source driving circuit of claim 2, wherein the DC voltage is proportional to an average of the rectified AC voltage. 9. The light source driving circuit of claim 1, wherein the rectifying parent voltage comprises a periodic voltage signal. Ίο. The light source driving circuit of claim 1, wherein the turbulent voltage after the rectification comprises a half-wave sinusoidal voltage signal. 11. The light source driving circuit of claim 1, wherein the light emitting diode light source comprises a plurality of light emitting diodes connected in series. 12. The light source driving circuit of claim </ RTI> further comprising: a current path coupled in parallel to the light emitting diode source. 13. The light source driving circuit of claim 12, wherein the current path comprises a resistor. 14. The light source driving circuit of claim 12, wherein when the third switch is coupled to an off state between the AC power source and the rectifier, the current flows from the rectified H current_current path To the ground. 15. The light source driving circuit of claim </ RTI> wherein the switch is disposed on the printed circuit board. The 0796-TW CH Spec+Claim (fiIed-20120424).doc 21 201244538. 0796-TW CH Spec+Claim(filed-20120424).doc 22