TW200826019A - Light emitting diode driver - Google Patents

Abstract

This invention relates to a driving system used for light emitting diodes, and more particularly, this invention relates to a controllable driver which can detect the voltage desire from application and adjust driving voltage (Vapp1-Vapp2) automatically in order to reach a steady driving current. Additionally, user scan adjust the setting of driving current and the output value of DC voltage source for application with different voltage and current requirements through a control interface. The over-temperature and over-current protections (e.g. cutting off driving current or setting the upper limit of driving current) are also included in the present invention for prevention of possible harms. In the present invention, a driving system is also disclosed for integration of all the mentioned functions but no need of massive space and can be used in LED lighting system or LED backlight system for constant power emitting.

Description

200826019 ' IX, invention description: [Technical field of invention] The present invention relates to a light-emitting diode driver, especially a controllable driver, which has a drive control for automatically adjusting a driving voltage to stabilize a driving current. The technology can be applied to high-power light-emitting diodes such as lighting and backlights. [Prior Art] There are two types of constant current drivers in the traditional industry: one is the constant voltage mode, which limits the value of the drive current flowing through the application body by setting the voltage value; the other is

The constant current mode limits the value of the drive current by setting the value of the current source. As shown in Fig. 2A, the constant voltage mode (the application body shown in the figure is a light-emitting diode), the external input voltage VDD first generates a current through the output voltage of the light-emitting diode controller 210, VLEI^g At the same time, the LED controller further controls the voltage drop Vset on the electric group R connected in series with the LED, and stabilizes the current flowing through the resistor rv by stabilizing the value of the set voltage Vset (also illuminating) The current value on the diode is Iled). The second type is the constant current mode. As shown in Figure 2B, the external input voltage vLED directly drives the light-emitting diode to generate current.

At the same time, another external input voltage vDD is generated via the LED controller 22 to circulate a reference current on the set resistor Rset, and the reference current is used to lock the current value Iled on the LED. However, for some of the more sophisticated applications (for example, high-wattage illumination or backlight LEDs), the temperature rise caused by the illumination, the drive voltage disturbance _ fine _ and the light-emitting diode material The similarities and differences of attributes will affect the driving current and cannot maintain a fixed value normally. 6 200826019 In addition, using a reference current source to clamp the drive current through a current mirror is also a method of directly controlling the current. As shown in Fig. 6A, two currents which are also a 1:N ratio amplifying the current source u of the reference current source u and clamped up can clamp the drive current Iled to the value of N*Iref. However, the space occupied by two 1:N ratio current mirrors is too large; at the same time, only the clamping current can only cope with a small amount of current fluctuations, which may cause electrical changes to the application (eg, special effects). The resistance, the current-voltage curve i_v curve, and the chemical and physical changes) have caused the voltage requirements of the entire driver (the age of the read), and the conventional current mirror circuit cannot cope with such a complicated situation. SUMMARY OF THE INVENTION An object of the present invention is to provide a highly stable controlled drive and drive system for a light-emitting diode. In addition to constant current clamping technology, the unique voltage adjuster technology automatically adjusts the drive voltage of the application, even in the face of potentially elevated temperatures or sudden conditions. When the circuit is loaded, the adjusted driving voltage can also stably drive the set driving current value. The drive system of the present invention can successfully integrate the above functions without occupying too much system space, and is suitable for use in various portable devices. Moreover, with the unique voltage regulator technology of the present invention, the adjustable-voltage source controlled by the user interface further deepens the application range of the present invention; in the present invention, the user can pass through the control interface (c〇 Ntr〇l interface) controls the variable voltage source to directly select the driving voltage applicable to different applications. In addition, for high-wattage lighting and moonlight source LEDs and other common over-temperature and over-current 7200826019 (-_« gift, this wealth also set up overheated bribe current In order to prevent serious damage to the application body directly from the drive control system. * In order to make the above contents, objects, advantages and other features of the present invention more comprehensible, the following detailed description of the drawings and the preferred embodiments [Embodiment] The present invention is a high-low potential end current Iapp of a driving application body (a_cation) 520, which mainly includes a (8) DC power supply terminal 51〇, For the input DC V. '(b) first; ^ effect transistor (pt effect Du (10) curry, for use as a voltage regulator (voltage adjust 〇 r), the source of the helium is also adjustable The voltage across the application body (Vappi_Vapp2), which satisfies the voltage requirement of the application and achieves a stable driving current effect; (6) a controller 530' is provided to control the first power The gate of the crystal (4) (6) voltage; (6) -^t>^f»Il(cuirentcontroller) 140 ^ fixed value, wherein the controller can also detect the voltage change 532 of the application body to generate a negative feedback voltage domain of the first field effect transistor gate The voltage difference automatically generates a compensation voltage between the source and the drain source to relieve the voltage demand of the application body. Through the negative feedback loop, the control driver of the present invention can be spontaneous Maintaining the drive current value of the stable temperature, even in the face of objective and subjective conditions such as large voltage source fluctuations, application equivalent resistance changes, etc., the appropriate driving voltage can be automatically adjusted. In conjunction with the set drive current value, the control driver of the present invention can also be combined with a variable voltage source 200826019 (adjustable-voltage source) 110 for receiving a power input of an external voltage Vdd, and outputting a variable DC voltage. V. to the DC power input; plus a control interface 160, the control driver of the present invention can accept user commands, (user co Mmand) directly controls the value of the DC voltage V. Thus, the range in which the driving voltage can be adjusted is more flexible, and the range of application of the physical energy application is greatly improved. The same day, in order to make the control type driver of the present invention operate more stably ( 〇perati〇n), over-temperature protection and over_current protection can be installed on the gate voltage connection 534 of the first effect transistor or the current controller. In the event of overheating and overcurrent, the drive current is cut off at the appropriate time or the upper limit of the set current is set. A temperature sensor 552 and a current monitor 553 that cooperate with the protection device can also be included in the control type driver of the present invention. The invention is a driving system that drives an application body to generate a stable driving current. The driving system mainly comprises the following six parts: (a) a DC power input terminal 510 for inputting a DC voltage. V. (9) an application output terminal (〇 putput f〇r application) 501 for connecting the application body at a high potential and the voltage at the place is; (6) an application input (input for application) 502 for connecting the application body at a low potential The voltage at this location is; (9) a first field effect transistor field effect transist〇r, FET) 131 'supplied as a voltage regulator (v〇乜agea (jjust〇r); (8) a first operational amplification state (1st) Operation amplifier, OpAmp) 132, can detect the voltage change of the application body to generate a negative feedback voltage to the gate of the first field effect transistor, and automatically compensate the voltage difference between the source and the source (draint〇 source) The voltage is used to relieve the voltage demand of the application body 200826019 (voltage desire) to achieve the effect of stabilizing the driving current Iapp; and 1 a current controller (currentC〇ntr〇ller) 140 for clamping the driving current In order to achieve the purpose of the current controller, the current controller can be placed between the application body and the ground to input the driving current as shown in FIG. 3 (the application body in the figure is a light-emitting diode group) 120), its And includes: (8) a reference current source 147 for outputting a reference current Iref; and (8) a current mirror for amplifying the reference current u by a ratio of 1:N (4) for the clamped input (4)' for the clamp input The current is the reference current ^^❶ In order to accurately grasp the 1··Ν amplification ratio, the control of the drive current is more precise. As shown in the figure, the current mirror further includes a second operational amplifier (2nd 〇pAmp) 144. The positive input is common to the output of the reference current source and the output is common to the common gate of the current mirror (c〇mm〇n_ga(6), and its negative input (negative input) The voltage is equal to the potential of the positive input terminal of the first operational amplifier 132 (Vset2 = Vsetl), in addition to accurately grasping the effect of clamping, and avoiding the large amount of the current mirror design (see Figure 6A). System space. In addition, the meter current source further includes (8) a third operational amplifier (3rd OpAmp) 141 whose positive input 钿 inputs an energy gap reference v〇kage and its negative input terminal Instead of losing The terminal connection forms a negative feedback circuit; (b) a second field effect transistor (2ndFET) 142 whose gate source is located on the negative _ line of the third operational amplifier ,, and its gate and the third τττ The amplified output is connected and the source thereof is connected to the negative input terminal of the third operational amplifier. The voltage of the negative input terminal of the third operational amplifier is fixed, and is positively affected by the second operational amplifier. Voltage control at the input end; (C)-a resistor Rsee is located between the negative wheel of the third differential amplifier 3 and the ground terminal for generation - through the second field power 200826019

Iset3; Channel current _3, for accepting the current through the second field effect transistor, and outputting the reference current at the other end of the positive carrier current mirror. In order to make the voltage demand generated by the application body (¥〇1_如(4) can be resolved in time, the first field effect transistor miscellaneous (SQUrce) can be connected to the lying wheel end, and its immersed (dmm) and The DC input is connected to the terminal, and the voltage difference between the DC output of the application and the output of the application Vappl, and the negative input of the first operational amplifier (ist 〇perati〇n 卿 O OpAmp) can be input. The system inputs the terminal voltage %ρ2, and inputs A #. ^(negative feedback voltage)^lt^-#, tt (gate) at the output end thereof, and can also make the drain of the first field effect transistor and the Applying the input terminal connection, and the source is connected to the input of the first operational amplifier, for the difference between the input terminal of the application and the negative input terminal of the first operational amplifier, and The output of the operational amplifier outputs a negative feedback voltage (negative feedbackv〇ltage) to the gate of the first field effect transistor, which enables the first field effect transistor to automatically coordinate its source 咏ain t〇s 〇_) The voltage difference is supplied to relieve the pressure demand to achieve a stable drive current. In the circuit configuration, a power valley is connected to the source or drain of the first field effect transistor and grounded to adjust the voltage of the source or the immersion. In order to solve the overheating phenomenon and overcurrent phenomenon that often occur in high wattage applications, the system can be equipped with a thermal sensor to monitor the system temperature Tsys, so that the system can be cut off when the system is overheated (Tsys%). And after the system temperature is lower than the safe temperature (Τ^<Τ2), the drive current is restarted (as indicated by the arrow in Figure 4A); the system can also be equipped with a current monitor for current current. Cut off the drive current (as in Figure 4b 11 200826019) or hold the current (as in Figure 4C) to prevent serious damage to the application directly from the drive system. In the driving system of the present invention, the overvoltage protection and overcurrent protection can be directly installed on the gate voltage connection line 534 of the first field effect transistor or the wheel terminal of the second operational amplifier 144. There is no need to set up a separate circuit for overheat protection and overcurrent protection. The driving system of the present invention can also be combined with a variable voltage source (adjustaW please (s) sourCe) 110, which includes an external power input terminal for receiving the external voltage VDD of the electric f. source input, as shown in the figure The DC voltage is converted by a DC-DC converter (DC_DC converteDlll or a voltage regulator (the voltage of the current or the AC-DC converter), which is supplied with an external input voltage. Then cooperate with a voltage selection circuit 112 #a analog switch lion switch) digital control (digitalcontr 〇 1) circuit, accept the external input voltage selection signal 113 'to select the appropriate voltage loop (four) ring, and according to The selected voltage loop feedback voltage 114 is connected to the circuit between the external input voltage vDD and the output voltage & V, so that the wheel voltage % can be modulated by the voltage selection signal. To select the variable voltage source The voltage is more convenient to use, and can be combined with a control interface (c〇ntr〇i interface) 160 negative to accept the user command (userc〇mmand) via a voltage controller 551 The user command outputs a voltage selection signal of the external input to the variable voltage source to change the voltage loop. In addition, the DC-to-DC converter 111 or the voltage regulator or the AC-to-DC/Melon conversion state can have a low-dropout voltage regulator. Function (1〇w dr〇p_〇ut) for voltage dissipation caused by stable low input voltage; it may also include one or more charge pumps 'for voltage rise and fall. Thus, drive The range of voltage energy adjustment is further flexible. The scope of application of physical energy is also greatly enhanced. In summary, according to the above-mentioned drawings and descriptions, the present invention can achieve the intended purpose, and provide a high stability control. Type driver and drive system can be used in the industry. • [Simplified description of the drawing] Figure 1A is a circuit diagram of the driving system of the present invention (the application body in the figure is the illumination for backlight or backlight) In the polar body, this circuit diagram is not limited to this application.) Fig. 1B is a circuit diagram of the first embodiment of the variable voltage source of the present invention. Γ Figure 2A is a conventional constant voltage drive. Dynamic system (prior art). Fig. 2B is a conventional constant current drive system (prior art). Fig. 3 is a circuit diagram of a current controller embodiment of the present invention (the application body shown in the figure is illumination or backlight) With the light-emitting diode, the circuit diagram is not limited to this application.) Figure 4A is a diagram showing the temperature change of the drive current corresponding to the overheat protection operation of the present invention. Figure 4B is the overcurrent protection operation of the present invention. A driving current change diagram. Fig. 4C is a diagram showing the driving current variation of the overcurrent protection operation of the present invention. Fig. 5 is a program explanatory diagram of the control type driver of the present invention. The 6A picture is a conventional current mirror circuit (prior art). Figure 6B is a modified current mirror circuit of the present invention. [Main component symbol description] 110 : Variable voltage source 120 ··Light-emitting diode group 140 Gas control is 16〇 ·Control interface

Vdd: External input voltage V. : Voltage of the DC voltage source input terminal 13 200826019 131 : The first field effect transistor (1stFET) C · The younger one of the transistor or the source (source) before the grounding capacitor VLED: the light-emitting diode Group driving voltage Iled: driving current of the LED group 132: first operational amplifier (lst〇pAmp)

Vseti · The positive input voltage of the differential amplifier 111 : DC-DC converter 112 : Voltage selection circuit 113 · Voltage selection signal 114 · · Feedback voltage

Ra · Select the resistance in the circuit 1 Rb : Select the resistance in the circuit 2

Rc: Select the resistance in the circuit 3 Rd · Select the resistance in the circuit 4 210, 220: LED driver R: the resistance of the constant voltage drive system Vset: the set voltage of the constant voltage drive system Rset: the resistance of the constant current drive system 141 : third operational amplifier (3rd〇pAmp) 142: second field effect transistor (2nd FET) 143: positive channel current mirror (p channel current mirror) 144: second operational amplifier (2nd〇pAmp) 145 Current mirror of 1:N ratio reference current 146 : Reference current input 147 : Reference current source 14 200826019 vset3: Positive input voltage of the third operational amplifier RSet3 : Reference current source setting Resistor ISet3: reference current source setting resistor current Iref: reference current source output reference current Vset2: second op amp negative input terminal voltage Vsetl: first operational amplifier positive input terminal voltage TSyS: 糸 system temperature T] [ : Start-up temperature T2 of over-temperature protection: release temperature of overheat protection

Iapp: application current of the application

Imax: Drive current upper limit value 500 for overcurrent protection: Control driver 501: Application output 502: Application input 510: DC power input 520: Application 530: Controller 534: Gate Voltage switch 532: Negative feedback controller 551: Voltage controller 552: Temperature sensor 553 · Current monitoring

Vappi: voltage at the output of the application 15 200826019

Vapp2: voltage at the input of the application 611, 612: conventional current mirror

Claims (1)

200826019 X. Patent application scope: 1. A controllable driver for generating a stable driving current between the south low potential terminals (Vappl and Vapp2) of the driver application (included) (8) a DC The power input is supplied with an input DC voltage V. (b) a first field effect transistor (FET) for use as a voltage regulator or a voltage difference adjustable application between drain to source The voltage at both ends (VapprVapP2) is used to relieve the voltage requirement of the application and achieve the effect of stabilizing the driving current lapp; (c) a controller for controlling the first field effect transistor a gate voltage; and (6) a current controller (current c〇ntr〇uer) for setting the ciamp drive current to a set value. 2. The illuminating diode driver of claim 1, wherein the controller is capable of measuring a voltage change of the application body to generate a negative feedback voltage to a gate of the first field effect transistor, such that The voltage difference between the drain to source automatically generates a compensation voltage '纾 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该 该The LED driver of the present invention further includes: an adjustable voltage source for inputting an output voltage VDD of the external voltage VDD to the DC power input. 4. The LED driver of claim 2, further comprising: a control 17 200826019 interface (controlinterface) for accepting a user command (usercommand) and outputting a signal to the control 5. The light-emitting diode driver described in claim 1 of the patent application includes: an over-temperature protection (over_temperatureprotection) measure at the system temperature Tsys In the case of an over temperature phenomenon, the gate voltage of the first field effect transistor is controlled to cut off the driving current. 6. The light emitting diode driver according to claim 1, further comprising: A measure of 〇ver_current protection controls the gate voltage of the first field effect transistor to cut off the drive current when an overcurrent phenomenon occurs in the drive current. The LED driver of the first aspect of the patent includes an over-temperature protection measure for controlling the current controller to be cut off when the system temperature Tsys is over temperature (cut 〇ff The driving current is as follows: 8. The illuminating diode driver according to claim 1, further comprising: an over-current protection measure for 驱动ver current in the driving current. The current controller is controlled to cut off the driving current. 9. The light-emitting diode driver according to claim 1, further comprising: an overcurrent protection ( Over-current protection measures that the current controller controls the drive current not to exceed an upper limit when the drive current has an overcurrent (〇ver current) phenomenon. 10. The illuminating diode driver of claim 3, further comprising: a voltage controller for varying the output voltage of the variable voltage source. The value. 18 200826019 11 The light-emitting diode driver of claim 1, further comprising: a temperature sensor performing overheat protection when the system temperature Tsys is overheated. 12. The illuminating diode driver of claim 1, further comprising: a current monitoring state (currentmonitor) for monitoring the change of the driving current and performing when an over current phenomenon occurs Current protection (over_currem pr〇tecti (10). 13. The light-emitting diode driver of claim 1, wherein: the electrical capacity is connected to the source of the first field-effect transistor. The grounding voltage is used to adjust the voltage of the source. The light-emitting diode driver of claim 1, further comprising: a capacitor connected to the drain of the first field effect transistor Connected to ground, to adjust its voltage. 15 · A driving system (driving system), driving an application to generate a stable drive current, including: (8) a DC power input, for input DC voltage Vq; (b) an output for application for connecting to the application's high potential and the voltage at which is Vappl; (c) an application input (inpUt for application) for connecting applications At a low potential and at a voltage of Vapp2; (d) a first field effect transistor (FET) for use as a voltage adjustor; (e) a first operational amplifier (ft 〇 Perati〇n ampi er, 〇pAmp), which can detect the voltage change of the application of the 2008 200826019 application and generate a negative feedback voltage to the gate of the first field effect transistor to make it drain to source The voltage difference automatically generates a compensation voltage to relieve the effect of the voltage of the application to achieve a stable driving current lapp; and (f) a current controller for ciamp The driving current is a set value. 16· The driving system described in claim 15 wherein the current controller is located between the application body and the ground to input the driving current, and includes: (8) a reference turtle source Supplying a stable reference current (reference current) u; and (b) a current mirror that amplifies the reference current iref according to a ratio of 1 · ,, for clamping the input current as a reference current Iref*N 17. The driving system of claim 16, further comprising: a second operational amplification state (2 OpAmp), the positive input terminal (p〇sitiveinput) and the output terminal of the reference current source are common The output terminal (〇utput) is common to the common-gate of the current mirror, and has its negative input terminal (negativei叩(10) voltage Vs(10) and the positive input terminal voltage Vseti of the first operational amplifier (potential) I = V』, to accurately grasp the 1··Ν amplification ratio to make the control of the drive current more precise. 18. The drive system of claim 16, wherein the reference current source comprises: (8) a third operational amplifier (3rd〇pAmp) having a positive input input _gap reference voltage (energy gap reference) Voltage) and its negative input terminal is connected with its wheel terminal 20 200826019 to form a negative feedback circuit; (b) a brother of an effect transistor (2 FET) 'the gate source is located in the negative feedback of the third operational amplifier a circuit having a gate connected to an output of the third operational amplifier, and a source connected to a negative input terminal of the third operational amplifier for clamping a voltage of a negative input terminal of the third operational amplifier a fixed value and controlled by the voltage of the positive input terminal of the third operational amplifier; (C) a resistor Rset3 is located between the negative input terminal of the third operational amplifier and the ground terminal f to generate a pass through the second field The current of the effect transistor; and (d) a positive channel current mirror (p channel current mirror) for accepting the current Iset through a 5 效 one effect transistor; 3 'and the positive carrier Channel current mirror End of the output reference current Iref. 19. The driving system of claim 15, wherein the first field effect transistor is a metal-oxide-semiconductor field effect transistor (MOSFET). 20. The drive system of claim 18, wherein the second field effect transistor is a metal-oxide-semiconductor field effect transistor (MOSFET). 21. The driving system according to claim 15 of the patent application, further comprising: an adjustable voltage source for receiving a power input of the external voltage VDD, and outputting the adjustable DC voltage V◦ to The DC power input. 22. The drive system of claim 15 further comprising: a control interface for accepting user commands to change settings of the system. The driving system of claim 15, wherein the source of the first field effect crystal body is miscellaneous with the output end of the application, and the dfain is The DC • voltage input is connected to regulate the DC voltage V. And the voltage difference between the output terminal v_ of the application; and the first operational amplifier (lstoperatic) namplifiei> QpA_1 input is the input of the fine input terminal Vapp2, and the negative feedback voltage is outputted by the fourth (negative feedback) Voltage) to the gate of the first field effect transistor, : and the first field effect transistor automatically coordinates its 汲 source (drain t〇 voltage difference, for decompression voltage demand to achieve stable driving 24. The driving system of claim 15, wherein the first field effect transistor has a drain connected to the application input and the source and the first operational amplifier are a negative input terminal is connected to adjust a voltage difference between the application input terminal Vapp2 and a negative input terminal of the first operational amplifier; and output a negative feedback voltage to the first output of the first operational amplifier to the first The gate of the field effect transistor, so that the first field effect transistor automatically coordinates the drain to source voltage difference for the purpose of mitigating the voltage requirement to achieve a stable driving current; Patent model The driving system of claim 15 further comprising: a capacitor connected to the source of the first field effect transistor and grounded to adjust the voltage of the source thereof. The driving system of the present invention further includes: a capacitor connected to the drain of the first field effect transistor and grounded to adjust the voltage of the drain. 22 200826019 27·If the patent application is 15th The driving system described in the item further includes an over-temperature protection, which controls the gate voltage of the first field effect transistor to be cut off when the system temperature Tsys is overheated (over • temPerature). Off) The driving system described in claim 15 of the patent scope includes: an over current protection 'controlling the first field effect transistor when the driving current is over-currented The gate voltage is used to cut the drive current. 29) The drive system according to claim 15 of the patent application includes: an over-ememperation protection, which is generated at the system temperature. Overheating (blind temper sacred sequel (9) ratio Wei Mirror system depends on the reduction (four) off) drive current. 30. The drive system described in claim 15 of the patent scope, including · an overcurrent protection ΡΓ (fine ion The measure, the overcurrent occurs in the drive current - C_〇 is now controlled by the 1:N _ current mirror _long 峨 (4) _ drive current. 3L, as described in claim 15 of the scope of the patent system, includes: an overcurrent protection (_ 〇 〇 tion tion ) ) 措施 措施 措施 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动 驱动The driving current must not exceed an upper limit. 32. The driving system described in item 21 of the patent application scope, ',, and death, includes a voltage controller for controlling the variable AI. The electric house source changes the value of the output DC voltage V. 23 200826019 33. The driving system according to claim 15 of the patent application, further comprising: a temperature sensor for detecting the change of the system temperature Perform overheat protection when the system overheats • (τπ> Τι), and operate the drive current again after the system temperature is lower than the safe temperature (Tsys<T2). 34. As described in item 15 of the patent application. The drive system further includes: a current monitor for monitoring the change of the drive current and performing overcurrent protection when the overcurrent (〇ver CUrrent) phenomenon occurs (〇ver-C_ntproteetiQn) [35] The drive system of claim 21, wherein the variable voltage source comprises a voltage regulator for outputting a direct current and a rectification with an external input voltage Vdd Voltage V. 36. The drive system of claim 21, wherein the variable voltage source comprises a DC-DC converter for voltage transformation and rectification with an external input voltage Vdd The output voltage system of claim 21, wherein the variable voltage source package (including an AC-DC converter) is provided with an external input voltage. The Vdc is subjected to a voltage transformation and rectification and outputs a DC voltage V. 38. The drive system of claim 21, wherein the variable voltage source further comprises one or more charge pumps for supplying 39. The drive system of claim 21, wherein the variable voltage source further comprises a voltage selection circuit for accepting voltage signals and selecting (swkch) appropriate power a circuit that causes a feedback voltage (feedback v〇ltage) to a circuit between the external input power VDD and the output DC voltage V. The voltage of the variable voltage source output is changed to the 200826019 voltage value v. 4〇· The driving system of claim 21, wherein the variable voltage source further comprises a digital control circuit of an analog switch for receiving a voltage change command to select ( Switch) A suitable voltage circuit and its feedback voltage to the external input voltage Vdd and the output DC voltage V. The circuit between the two changes the voltage value V of the output of the variable voltage source. . 41. The drive system of claim 32, wherein the voltage controller is operative to control a switch and flicker of the application by using a pulse width adjustment (PWM) signal. form. 42. The drive system described in claim 15 is for use in driving illumination using a luminescent LED. 43. The drive system of claim 15, wherein the backlight is used to drive a backlight. 44. The drive system of claim 21, wherein the variable voltage source has a low dropout voltage regulation function (low droP-〇ut) for stabilizing the low input voltage. 25