Abstract:
An AC-to-DC converter with PFC or without PFC generates an output constant voltage at any predetermined value (no matter less or more than input line peak voltage, or even equal to input line peak voltage) with an input line AC voltage with wide range (Typical sinusoidal 110 VAC, 60 Hz or 220 VAC, 50 Hz). It is mainly used as power supply for lamp. Previous power supply for lamp has low frequency component or high frequency component. (1) Low frequency light cause eyes pupil and crystalline lens will adjust 60 times, 120 or many times per second to cause eyes tired. Pupil open wide and crystalline lens adjust to collect more light to focus on retina for seeing clearly at weak light while pupil open narrow and crystalline lens adjust to collect less light to focus on retina at strong light to prevent retina from strong light harm and hurt. In the long run, muscles to control pupil and crystalline lens become very tired and become flabby. Then the muscle can&#39;t adjust pupil and crystalline according to distance and brightness so that myopia is caused. (2) High frequency voltage causes lamp brightness changes too fast. Eyes can not adjust fast enough to follow the brightness change of lamp for high frequency voltage. But high frequency large current on the secondary cause high EMI that has risk to harm people&#39;s health. High frequency light causes EMI issue. Peoples&#39; eyes can&#39;t keep up with high frequency light. Peak strong light shine on the retina for pupil can&#39;t shrink at high frequency light. In the long run, retina will be harmed and affect eyesight is affected, cornea dryness or crystalline lens opacity is caused. My invention of power supply lamp has only DC constant voltage on lamp. Lamp&#39;s brightness is constant and has no low frequency or high frequency component Thus peoples&#39; eyes and health are protected to maximum extent. The output voltage is regulated at predetermined DC constant value by feedback. You can adjust feedback potentiometer value to set output voltage. Potentiometer and resistor voltage divider with auxiliary winding, (opto-coupler, digital isolator or direct feedback) compose the dimming feedback circuit. It is convenient to adjust the brightness of lamp for eyes&#39; comfort by adjusting the potentiometer resistance value. My invention can be used directly on second category lamp that doesn&#39;t need high voltage with ballast to start the lamp. Most of them use heat generated by filament or diode etc to create light. Such as Halogen, Incandescent, LED, PAR lamp, miniature sealed beam lamp, Projection lamp, automotive lamp, some stage and studio lamp, DC fluorescent lamp etc. The converter realized pulse-by-pulse or other current limit protection by sense the current sense resistor or signal transformer.  
     One stage DC sinusoidal to DC constant converter  206  can be implemented by all kinds of topologies other than the following topologies as long as they can convert DC sinusoidal voltage to DC constant voltage. Buck, Boost, Buck-boost, Noninverting buck-boost ,H-Bridge, Watkins-Johnson, Current-fed bridge, Inverse of Watkins-Johnson, Cuk, SEPIC, Inverse of SEPIC, Buck square, full bridge, half bridge, Forward, Two-transistor Forward, Push-pull, Flyback, Push-pull converter basedon Watkins-Johnson, Isolated SEPIC, Isolated Inverse SEPIC, Isolated Cuk, Two-transistor Flyback etc  
     One stage AC to DC converter  206  can be realized by discrete components without controller  209 , active startup circuit, feedback circuit or sample circuit. Main switch and active startup circuit can be integrated in IC controller. The AC to DC converter is not used only for lamp. It is can also be used for any device requires DC power supply in all the industrial areas. (Telecommunication, Storage, Personal computer, cell phone power supply and charger, video game etc) For example, Bus AC to DC converter, PFC converter, PFC converter for lighting Computer power supply, Monitor power supply, notebook adapter, LCD TV, AC/DC adapter, adjusted voltage charger, Power tool charger, Electronic ballast, Video game power supply etc.

Description:
CROSS-REFERENCE AND CORRECTION TO RELATED APPLICATIONS  
       [0000]     The present application claims priority to U.S. Patent Application No. 11/204,307, filed on Aug. 15, 2005, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND  
       [0001]     The following disclosure relates to electrical circuits and signal processing.  
         [0002]     Power supplies are used to power many types of electronic devices, for example, lamps. Conventional power supplies (e.g., for halogen lamps) typically include a converter. A converter is a power supply switching circuit.  
         [0003]     Lamps have two categories: 
    First category uses ballast to strike the lamp to start. Most of them use gas to create light such as Fluorescent, HID, Compact, metal halide lamp etc. Bulbs need ballast because they use gas to create light. When the gas is excited by electricity, it emits invisible ultraviolet light that hits the white coating inside the bulb. The coating changes the ultraviolet light into light you can see. It needs a very high voltage strike to startup the operation of the lamp. But my invention is not applied directly to this category. The invention must be combined with second stage ballast to drive the lamp.     Second category doesn&#39;t need ballast to start the lamp. Most of them use heat generated by filament or diode etc to create light. Such as Halogen, Incandescent, LED, PAR lamp, miniature sealed beam lamp, Projection lamp, automotive lamp, some stage and studio lamp, DC fluorescent lamp etc.     My patent can be used directly on second category lamp.     Because Halogen lamp is the typical lamp of second category (filament or diode etc), all the discussion starts from the application of the power supply on Halogen lamp.    
 
         [0008]      FIG. 1  shows a conventional half bridge converter  100  that receives AC sinusoidal voltage from a power source Vin. Converter  100  includes transistors Q 1 , Q 2 , transformer TI 1 , Coupled inductor T 1 A, T 1 B and T 1 C; DC blocking Capacitor C 4 , C 5 ; Timing circuit C 2 , R 2  and C 3 , R 3 ; startup circuit D 5 , R 4 , Q 3 ; R 1 , C 1 ; bridge rectifier D 1 , D 2 , D 3  and D 4 ; AC power source 120Vac 60 Hz sinusoidal (or 220Vac 50 Hz) and Halogen lamp. (low voltage, for example 12v)  
         [0009]     Q 1  and Q 2  complementary on/off with 50% duty cycle. Output voltage waveform is 120 Hz low frequency envelope with high switching frequency square waveform in it. As shown in  FIG. 2  and  FIG. 3 .
 
 Vo= 60*(4/3.14159)* ns/np  ( np  is primary turns and  ns  is secondary turns.)
 
         [0010]     Dimming is realized by applying phase cut dimmer in the converter in trailing edge mode. This means that at the beginning of the line voltage half cycle, the switch inside the dimmer is closed and mains voltage is supplied to the converter allowing the converter to operate normally. At some point during the half cycle, the switch inside the dimmer is opened and voltage is no longer applied. The DC bus inside the converter almost immediately drops to 0 V and the output is no longer present. In this way, bursts of high frequency output voltage are applied to the lamp. The RMS voltage across the lamp will naturally vary depending on the phase angle at which the dimmer switch switches off. In this way the lamp brightness may easily be varied from zero to maximum output as shown in  FIG. 5  and  6 .  
         [0011]     Advantage of this typical low-voltage halogen-lamp converter  100  is simple without IC controller.  
         [0012]     Disadvantage: 
        1. Output voltage has low frequency (120 Hz) envelope, voltage change from valley to peak 120 times per second. Lamp brightness is proportional to lamp voltage. So lamp brightness will change from darkest to brightest 120 times per second. Eyes pupil will open wide (mydriasis) when lamp becomes dark while eyes pupil will contract (myosis) while the crystalline lens also adjust according to different brightness. Thus the pupil will open and close 120 times per second. The muscle to control pupil and crystalline lens will become very tired for several hours. For long run, the muscle to control pupil and crystalline lens become limp and can&#39;t control well. Thus myopia is caused for crystalline lens can&#39;t be adjusted well according to distance.     2. High frequency (switching frequency) square waveform in the envelope cause EMI issue and has risk to harm people&#39;s health. Pupil open wide at darkness and contract at brightness to protect retina. Eyes pupil can&#39;t keep pace with high frequency light. Thus the retina will be harmed by peak brighness light in high frequency light.     3. Crest factor is high (17/12=1.4167) and shorten lamp&#39;s life.     4. Variation output voltage for No Feedback;     5. Dimming needs external dimmer based on turn on/off line voltage. So cost increases.     6. Power factor is very low during dimming at low voltage.     7. Inrush current during turn on is high and shortens the lamp life.        
 
         [0020]      FIG. 4  shows another way to drive the halogen lamp. A low frequency transformer is connected directly to the halogen lamp. 
    Advantage: Component is only one transformer and cost is less.     Disadvantage:     1. Output voltage has low frequency sinusoidal waveform, thus human&#39;s eyes will feel tired under the low frequency flicker; it cause myopia for long term.     2. Variation output voltage for No Feedback;     3. Dimming needs external dimmer based on turn on/off line voltage, so the Power factor is very low during dimming, Inrush current during turn on is high and shorten the lamp life.     4. Transformer is too big and heavy for low frequency use.      
       SUMMARY  
       [0027]     In general, in one aspect, this specification describes new block diagram for Halogen lamp converter as  FIG. 7  and new topology as  FIG. 11 , 12 , 13 , 14 , 15 , 16 , 17 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ,  47 , 48 , 49 , 50 , 51 , 52  and  53 .  
         [0028]     Implementations can include one or more of the following advantages. 
    1. Output voltage is DC constant voltage. No low frequency component and no high frequency component. It protects peoples&#39; eyesight and health to maximum extent.     (Low frequency component cause eyes tired and myopia for long term.     High frequency component cause EMI issue and harm to people&#39;s health. Eyes pupil can&#39;t keep pace with high frequency light. Thus the retina will be harmed by peak bright light under high frequency light.)     2. Output voltage has feedback control and is constant without varying voltage magnitude in normal operation or dimming. Crest factor is 1 so that lamp&#39;s life is extended to maximum degree.     3. Dimming is realized by changing potentiometer resistance value. No need for external dimmer and save cost. Dimming does not turn on/off circuit and does not cause inrush current or ugly waveform. So lamp&#39;s life is prolonged.     3. Power factor correction circuit is included in one implementation like IW2202, So power factor is unity even at dimming and efficiency is high; Power factor correction is not included in one implementation like IW2210, LNK302/304-306, LNK362-364 or UCC28600 etc    
 
         [0035]     Traditional PFC only use boost ( FIG. 34 ) converter to realize AC to DC conversion. But boost converter can only output DC voltage higher than the peak of input AC voltage. Most of lamps rating voltage are less than peak of input AC line voltage (170v). So traditional PFC boost converter can&#39;t be directly used for low voltage lamp. My invention can buck down the voltage. Output DC voltage can be lower or higher than input AC peak voltage or equal to input AC peak voltage. My invention can be directly used for any rating voltage lamp of any kind without ballast requirement.  
         [0036]     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0037]      FIG. 1 : typical low-voltage halogen-lamp power supply based on conventional half bridge converter  100 .  
         [0038]      FIG. 2 : Output voltage waveform of typical halogen lamp power supply based on half bridge converter  100  is high frequency square waveform contained in low frequency (120 Hz) envelope. 
    Top graph: Blue or red curve-rms value of output voltage across lamp;     Red shade-output voltage waveform across lamp.     Bottom table: VP 1 -Peak value of output voltage; SQRT(AVG-rms value of output voltage.      
         [0042]      FIG. 3 : amplified high frequency square waveform contained in the low frequency envelope of output voltage in typical halogen lamp converter  100 . 
    Top: Red waveform-high frequency square waveform in output voltage     Bottom: rms value of output voltage      
         [0045]      FIG. 4 : The halogen lamp converter driven directly by a big low frequency transformer and output voltage on the lamp. 
    Top table: V 2 -peak value of output voltage; SQRT(AVG-rms value of output voltage.     Top waveform: red-sinusoidal output voltage; blue-rms value of output voltage     Bottom waveform: red-rms value of output voltage      
         [0049]      FIG. 5 : input bus voltage and lamp output voltage waveform during dimming with external dimmer for typical Halogen lamp converter  100 . 
    Left: trailing edge dimming     Right: Leading edge dimming      
         [0052]      FIG. 6 : Output voltage and current of lamp during dimming of typical halogen lamp converter  100 . 
    Top: trailing edge dimming     Bottom: Leading edge dimming      
         [0055]      FIG. 7 : Block diagram of my invention, Power Supply  200 , AC to DC power supply with PFC (or without PFC) for Lamp  
         [0056]      FIG. 8 . Voltage waveform across A and A′ on block diagram  FIG. 7   
         [0057]      FIG. 9 . Voltage waveform across C and C′ on block diagram  FIG. 7   
         [0058]      FIG. 10 . Voltage waveform across D and D′ on block diagram  FIG. 7   
         [0059]      FIG. 11 . Flyback converter used as converter  206  in block diagram  FIG. 7  Vo=Vg*D*n 2 /(D′*n 1 )  
         [0060]      FIG. 12 . One implementation schematic of my invention using Flyback topology for converter  206  and IW2202 for controller  209  with PFC function.(primary dimming control)  
         [0061]      FIG. 13 . One implementation schematic of my invention using Flyback topology for converter  206  and IW2202 for controller  209  with PFC ftinction.(secondary dimming control)  
         [0062]      FIG. 14 . One implementation schematic of my invention using Flyback topology for converter  206  and IW2202 for controller  209  with PFC function.(secondary dimming control)  
         [0063]      FIG. 15 . One implementation schematic of my invention using Flyback topology for converter  206  and IW2210 for controller  209  without PFC function.(primary dimming control)  
         [0064]      FIG. 16 . One implementation schematic of my invention using Flyback topology for converter  206  and IW2210 for controller  209  without PFC function.(secondary dimming control)  
         [0065]      FIG. 17 . One implementation schematic of my invention using Flyback topology for converter  206  and IW2210 for controller  209  without PFC function. (secondary dimming control)  
         [0066]      FIG. 18 . Pulse train algorithm in IW2210 for controller  209 .  
         [0067]      FIG. 19 . The input current waveform with input voltage through switching Mosfet, Vinrms=input rms voltage; Lm=magnetic inductance of transformer; d(t):duty cycle; Ts: period. Ipeak=peak value of current through switching Mosfet iav(t):average value of current through switch Mosfet. Slope: Mosfet switch current slope.  
         [0068]      FIG. 20 . One implementation schematic of active startup circuit  208   
         [0069]      FIG. 21 . One implementation schematic of active startup circuit  208   
         [0070]      FIG. 22 . One implementation schematic of active startup circuit  208   
         [0071]      FIG. 23 . Startup Timing Diagram on pins of IC controller in one implementation with IW2202  
         [0072]      FIG. 24 . One implementation schematic of my invention using Flyback topology for converter  206  and UCC28600 for controller  209  without PFC function.(secondary dimming control)  
         [0073]      FIG. 25 . One implementation schematic of my invention using Flyback topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK362, LNK363 or LNK364 etc.  
         [0074]      FIG. 26 . Buck converter for converter  206  Vo/vin=D  
         [0075]      FIG. 27 . One implementation schematic of my invention using Buck topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK302, LNK304, LNK305 or LNK306 etc. Direct feedback.  
         [0076]      FIG. 28 . One implementation schematic of my invention using Buck topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK302, LNK304, LNK305 or LNK306 etc. High side buck-opto coupler feedback  
         [0077]      FIG. 29 . One implementation schematic of my invention using Buck topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK302, LNK304, LNK305 or LNK306 etc. Low side buck-opto coupler feedback  
         [0078]      FIG. 30 . Buck-boost converter for converter  206  Vo/vin=-D/(1−D)  
         [0079]      FIG. 31 . One implementation schematic of my invention using Buck-Boost topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK302, LNK304, LNK305 or LNK306 etc. High side buck boost-direct feedback  
         [0080]      FIG. 32 . One implementation schematic of my invention using Buck-Boost topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK302, LNK304, LNK305 or LNK306 etc. High-Side Buck Boost-Constant current feedback  
         [0081]      FIG. 33 . One implementation schematic of my invention using Buck-Boost topology for converter  206  and U 1  for controller  209  without PFC function. In one implementation, U 1  is IC controller LNK302, LNK304, LNK305 or LNK306 etc. Low-Side Buck Boost-Optocoupler feedback  
         [0082]      FIG. 34 . Boost converter for converter  206  Vo/vin=1(1−D)  
         [0083]      FIG. 35  Noninverting buck-boost converter for converter  206  Vo/vin=D/(1−D)  
         [0084]      FIG. 36  H-Bridge converter for converter  206  Vo/Vin=2D−1  
         [0085]      FIG. 37  Watkins-Johnson converter for converter  206  Vo/vin=(2D−1)/D  
         [0086]      FIG. 38  Current-fed bridge converter for converter  206  Vo/vin=1/(2D−1)  
         [0087]      FIG. 39  Inverse of Watkins-Johnson converter for converter  206  Vo/vin=D/(2D−1)  
         [0088]      FIG. 40 . Cuk converter for converter  206  Vo/vin=−D/(1−D)  
         [0089]      FIG. 41 . SEPIC converter for converter  206  Vo/vin=D/(1−D)  
         [0090]      FIG. 42 . Inverse of SEPIC converter for converter  206  Vo/vin=D/(1−D)  
         [0091]      FIG. 43 . Buck square converter for converter  206  Vo/Vin=D*D  
         [0092]      FIG. 44 . Full bridge converter for converter  206  Vo/Vin=n 2 *D/n 1   
         [0093]      FIG. 45  Half bridge converter for converter  206  Vo/Vin=0.5*n 2 *D/n 1   
         [0094]      FIG. 46  Forward converter for converter  206  Vo/Vin=(n 3 /n 1 )*D  
         [0095]      FIG. 47  Two transistor forward converter for converter  206  Vo/Vin=n 2 *D/n1  
         [0096]      FIG. 48  Push pull converter for converter  206  Vo/Vin=n 2 *D/n 1   
         [0097]      FIG. 49 . Push pull based on Watkins-Johnson for converter  206 ; Vo/Vin=(n 2 /n 1 )*(2*D−1)/D  
         [0098]      FIG. 50 . Isolated SEPIC converter for converter  206  Vo/Vin=(n 2 /n 1 )*D/D′ 
         [0099]      FIG. 51 . Isolated Inverse SEPIC converter for converter  206  Vo/Vin=(n 2 /n 1 )*D/D′ 
         [0100]      FIG. 52  Isolated Cuk converter for converter  206  Vo/Vin=(n 2 /n 1 )*D/D′ 
         [0101]      FIG. 53  Two-transistor Flyback converter for converter  206  Vo/Vin=(n 2 /n 1 )*D/D′ 
     
    
     DETAILED DESCRIPTION  
       [0102]      FIG. 7  is a block diagram of a power supply  200  for a connected output device (e.g., lamp  211 ). In one implementation, power supply  200  receives an AC source voltage from a voltage source  210 . In one implementation, power supply  200  includes an RF 1   201 , an input filter  202 , a rectifier  203 , an one stage substantially DC sinusoidal to constant DC voltage converter  206 , a controller  209 , feedback and dimmer circuit  205 , sample circuit  207 , active startup circuit  208  and Lamp  211 . The power supply can have more blocks or fewer blocks than  FIG. 7 . (For example,  206 , 208 , 209  can be an integrated block  204  or  208  can be removed in some implementation. Main switch of converter  206  and  208  can be integrated into the controller  209  as in LNK302/304-306 or LNK362-364). The sequence and position of some blocks can be exchanged. (For example, position of  202  and  203  can be exchanged). Each block can use all kinds of different circuits with function as the following.  
         [0103]     Input RF 1   201  provides input current protection for converter  200 . In particular, in one implementation, input fise is designed to provide current protection for converter  206  by cutting off current flow to converter  206  in an event that current being drawn through input fuse  201  exceeds a predetermined design rating. In another implementation, RF 1   201  is a flameproof, fusible, wire wound type and functions as a fuse, inrush current limiter. In another implementation, RF 1   210  can be a NTC or PTC thermistor.  
         [0104]     Input filter  202  minimizes an effect of electromagnetic interference (EMI) on power supply  200 , converter  206  and exterior power system. Input filter  202  can be LC filter π filter, common mode filter, differential mode filter or any type filter that provide a low impedance path for high-frequency noise to protect power supply  200  and exterior power system from EMI. Input filter  202  can be placed in front of rectifier  203  or behind rectifier  203 .  
         [0105]     Rectifier  203  converts the input AC source voltage from voltage source  210  (like  FIG. 8 ) into a substantially DC sinusoidal voltage (like  FIG. 9 ).  
         [0106]     In one implementation, rectifier  203  is a full-wave rectifier that includes four rectifiers in a bridge configuration as in  FIG. 12, 13  or  14  etc. In another implementation, rectifier  203  contains 2 diodes as shown in  FIG. 27,28  or  29  etc. Rectifier can be any type or bridgeless PFC.  
         [0107]     One stage DC sinusoidal voltage to constant DC voltage converter  206  converts the substantially DC sinusoidal voltage like  FIG. 9  received from rectifier  203  into a DC constant voltage at predetermined value suitable to support an output device (e.g., halogen lamp  211 ). In one implementation, converter  206  converts the substantially DC sinusoidal voltage received from rectifier  203  into DC constant voltage 12 volts. ( FIG. 10 ) Usually the input voltage source  210  comes from 60 Hz 110v AC or 50 Hz 220v AC sinusoidal line voltage in power system.  
         [0108]     Controller  209  is operable to regulate output voltage at predetermined value.  
         [0109]     Controller  209  can be any type and have any type of control with PFC or without PFC function. (Such as digital control, analogy control, DSP, bang-bang control, skipping switching cycles as in LNK302/304-306, Pulse Train control as in IW2210 etc.)  
         [0110]     In such an implementation, controller  209  is operable to adjust the duty cycle, switching frequency or on time of main switch of converter  206  so that converter  206  outputs a DC constant output voltage having a predetermined voltage value. Controller  209  can control an output voltage level of converter  206  responsive to a predetermined value set by voltage divider composed of potentiometer and resistor at dimming or normal operating.  
         [0111]     Normal operating; predetermined value set to rating voltage of lamp; dimming operating, predetermined value set to lower voltage than rating voltage of lamp.  
         [0112]     Feedback control voltage comes from feedback circuit  205 , as discussed in greater detail below.  
         [0113]     Sample circuit  207  sense the signal proportional to output DC constant voltage or directly sense the voltage cross the lamp.  
         [0114]     Feedback and dimmer circuit  205  is operable to provide a feedback dimming control voltage to controller  209  for dimming (or reducing) output voltage (e.g., halogen lamp  211 ) by changing potentiometer value to change voltage divider ratio. Duty cycle, switching frequency or on time of main switch are changed to change output voltage.  
         [0115]     In one implementation (non-isolated feedback),  205  can be realized by a voltage divider composed of potentiometer and resistor (or zener diode and resistor voltage divider) and voltage cross one resistor goes to Feedback pin of controller  209 ;  
         [0116]     In one implementation (isolated feedback),  205  can be realized by a voltage divider composed of potentiometer and resistor (or zener diode and resistor voltage divider) and voltage across one resistor or voltage across secondary winding is coupled to Feedback pin of controller  209  by auxiliary winding, opto-coupler or digital isolator etc  
         [0117]     In real application, block can be more or less than  FIG. 7 . Some blocks maybe different from  FIG. 7 . For example, some application had no feedback function.  
       Type I. Isolated Converter  
     I-1 Part 1 Flyback Converter Used as Converter  206   
       [0118]     Flyback converter is shown in  FIG. 11 . The function is described as the following: when Q 1  on, all magnetic winding has positive voltage on no ‘•’ end with respect to the other end. D 1  is off; when Q 1  off, all magnetic winding has positive voltage on ‘•’ end with respect to the other end, D 1  turns on, energy transfer to output load.  
         [0119]     During Q 1  on, 0&lt;t&lt;DTs, voltage across transformer primary winding is Vg. (Vg input voltage). During Q 1  off, DTs&lt;t&lt;Ts, voltage across transformer primary winding is −Vo*n 1 /n 2 . (Vo is output voltage, n 1  is primary turns; n 2  is secondary turns.) In continues conduction mode, primary winding balance: D is duty cycle, D′=1−D
 
 Vg*D*Ts−Vo*D′*Ts*n 1/n2=0 Vo=Vg*D*n   2 /( D′*n   1 )
 
       I-1.1 Power Supply with PFC Based on Flyback Converter  
     (In One Implementation, IW2202 is Used as Controller)  
       [0120]     The detail is discussed below.  
         [0121]      FIG. 12,13  and  14  illustrate one implementation of a converter that can be used within power supply  200 . Referring to  FIG. 12,13  and  14 , my invention converter  200  is implemented with Flyback topology for converter  206  and IC IW2202 for controller  209 . The following discussion starts from IC IW2202. In application, the circuit can have more or less components than  FIG. 12,13  and  14 . We started the discussion with  FIG. 11 .  
         [0122]     During the period when Q 1  is on (0&lt;t&lt;=DTs), the ‘•’ end is negative with respect to no ‘•’ end of primary and secondary transformer windings, thus diode D 3  could not turn on. Energy is saved in the magnetic inductance Lm. The voltage cross primary winding is Vg. (Vg is voltage after AC voltage rectified, In one implementation, Vg is DC sinusoidal voltage like  FIG. 9 )  
         [0123]     During the period when Q 1  is off (DTs&lt;=t&lt;Ts), the polarity of the transformer winding changes. ‘•’ end is positive with respect to no ‘•’ end for both primary and secondary winding of transformer. Thus D 3  turns on; energy is delivered to the output. The voltage cross primary winding is Vo*np/ns. (Vo is output DC voltage and np is primary turns; ns is secondary turns).  
         [0124]     For normal operating, transformer set and reset must be balanced. It can be shown by ∫vdt=0. That is Vg*DTs−(Vo*np/ns)*D′Ts=0 
    D is duty cycle. D=Ton/Ts.     Ts is the switching period.
 
 D′= 1−D. 
   
 
         [0127]                                                            So Vo = Vg*D*ns/(D′*np)   (3.1)           Vop is defined as the output voltage reflected to           primary during Q1 off time,           Vop = (np/ns)*(Vo + ΔV)   (3.2)           ΔV represents the voltage drop across diode and trace.           Vg = {square root over ( 2 )}*Vinrms*sin(ωt)   (3.3)           Usually, ΔV is small enough compared with Vo.           Vop ≈ (np/ns)*Vo   (3.4)           From (3.1) and (3.4), we know Vop = Vg*D/D′   (3.5)           Vop = Vg*D/(1 − D) derive 1 − D = (Vg/Vop)*D   (3.6)           D = 1/(1 + Vg/Vop)   (3.7)           Substitute Vg, we get D(t) = 1/(1 +   (3.8)           {square root over ( 2 )}*Vinrms*sin(ωt)/(np*Vo/ns))                        
 From (3.8), for a predetermined constant DC value Vo, we can adjust duty cycle D(t) according to value of input voltage to guarantee the output voltage constant. Thus the converter converters a 120 Hz or 100 Hz DC sinusoidal waveform to a DC constant voltage. 
 
         [0128]     Dimming can be realized by adjust potentiometer. In  FIG. 12 , potentiometer R 15 ,R 6  and R 12  form a voltage divider. During Q 1  off, Auxiliary winding ‘•’ end is positive with respect to no ‘•’ end, so does secondary winding. The output voltage Vo is coupled to auxiliary winding for D 20  is on. Voltage on top of R 6  equals to N 2 *Vo. (N 2  is turns ratio of auxiliary winding and transformer secondary winding. N 2 =Na/Ns, Na: auxiliary winding turns, Ns: secondary winding turns). So voltage Vs sensed on R 12  is N 2 *Vo*R 12 /(R 12 +R 15 +R 6 ). Vs is compared with interior reference voltage Vr by CMP. If Vs greater than Vr, that show Vo is greater than predetermined value, so duty cycle decreases or fs changes, Vo is decreased until Vo equals to predetermined value; If Vs less than Vr, that shows Vo is less than predetermined value, so duty cycle increases or fs changes, Vo is increased until Vo equals to predetermined value.  
         [0000]     So Vs=Vr=N 2 *Vo*R 12 /(R 12 +R 15 +R 6 ) for steady state. Vr is constant and N 2  is constant.
 
 So Vo=Vr *( R 12 +R 15 +R 6)/( R 12 *N 2).  (3.9)
 
 We can adjust potentiometer R 15  to change value of (R 12 +R 15 +R 6 )/R 12 =1+(R 15 +R 6 )/R 12  to change predetermined Vo. Increase R 15 , Vo increase; decreases R 15 , Vo decrease. Thus lamp can be dimmed by change R 15  to set output voltage and it is stable with constant voltage. R 6  can be potentiometer, then increase R 6  to increase Vo, Vice versa. R 12  can be potentiometer, we can decrease R 12  resistance to increase output voltage or increase R 12  resistance to decrease output voltage. Dimming voltage is also DC constant voltage. There is no low frequency component. So the eyes will not feel fatigue due to the low frequency flicker. There is no high frequency light. No EMI issue or no retina harm by peak brightness because eyes pupil can&#39;t keep pace with high frequency light. Thus eyes are protected to maximum extent to avoid myopia or retina harm. 
 
         [0129]     Sometimes opto-coupler is used as isolated feedback. In  FIG. 13 , dimming is realized by changing potentiometer R 21  to change feeback signal on Vsense pin to dim voltage. Increase R 21  will decrease opto-diode current, then voltage on Vsense pin increases. Controller decreases duty cycle or change frequency to decrease output voltage; Decrease R 21  will increase opto-diode current, then voltage on Vsense pin decreases. Controller increases duty cycle or change frequency to increase output voltage. R 22  can be potentiometer too. It behaves similar to R 21 .  
         [0130]     In  FIG. 14 , dimming is realized by changing potentiometer R 23 . Optocoupler current Ioc=Vref*(R 22 +R 23 )/R 23 /R 21 =Vref*(1+R 22 /R 23 )/R 21 ; Vsense=Vref−Ioc*R 12 . Output voltage is set by reference voltage times (1+R 22 /R 23 ). Increase R 23 , Vo decreases; Vice versa. Vo has small ΔVo increase, Ioc has small increase, Vsense has small decrease. Vo+ΔV has small decreases until equals to Vo.  
         [0131]     In one implementation, PFC (power factor correction) can be realized by modulating the average input current ipr(t)av in phase with the input line voltage Vin(t). Thus power factor is unity. PFC also can be done by multiplier, μPFC as in IR1150S or DSP.  
         [0132]     Please see  FIG. 14 , the input current waveform with input voltage through switching Mosfet  
                                                       Slope = {square root over ( 2 )}*Vinrmssin(ωt)/Lm   (3.10)           Ipeak = Slope*d(t)*Ts   (3.11)           Ipr(t)av = ipeak*d(t)*Ts/2/Ts   (3.12)           So we get ipr(t)av =   (3.13)           ({square root over ( 2 )}*Vinrmssin(wt)/(2Lm))*d(t)*d(t)*Ts(t)           Let k = d(t)*d(t)*Ts(t), ipr(t)av =   (3.14)           ({square root over ( 2 )}*Vinrmssin(wt)/(2Lm)*k                      
 
 We know the input current is in phase with the AC line if k is constant. The converter accomplishes by modulating the average input current iin(t) in phase with the input line voltage Vin(t). Thus the power factor is very near to unity no matter in normal operation or dimming. 
 
         [0133]     Active startup circuit is used to start up the circuit. In other implementation, Active startup circuit can be realized by other way or removed. In other circuit, active startup circuit can have more or less component than  FIG. 20,21  or  22 .  
         [0134]      FIG. 20  shows active startup circuit. ASU pin is designed to drive the Mosfet of the active startup circuit. An external zener diode is to clamp the ASU pin.  
         [0135]     Before startup, ASU is floating. Once a voltage is supplied to Vg(t) (DC sinusoidal voltage after bridge rectifier like  FIG. 9 ). The gate capacitor C 31  starts to charge via the startup resistor R 31 . When Vcc reaches the threshold voltage of Q 2 , transistor Q 2  conducts. (Q 2  can be NPN transistor or N channel Mosfet). The startup capacitor C 32  starts to be charged via the charge resistor R 32  and R 33  (R 32  can be removed). When Vcc reaches the startup threshold voltage, PWM (IW2202) starts operating. Converter main switch Q 1  switches and auxiliary winding has voltage coupled from secondary output. ASU goes lower than secondary coupled voltage, thus turns off Q 2 . Vcc is supplied from C 32  that is charged by auxiliary winding and D 4 .  
         [0136]     Thus, supply voltage for PWM (IW2202) no longer uses linear regulator Q 2  and the efficiency is improved.  FIG. 23  Startup Timing Diagram on pins of IC controller shows that. By select auxiliary winding and secondary winding turns ratio carefully, we guarantee the voltage on the auxiliary winding during minimum dimming is larger than Vcc threshold+Voltage drop on D 4 ; We guarantee the voltage on the auxiliary winding during normal operating is not high enough to damage R 33  and Z 2 . Thus, we can guarantee PWM (IW2202) works well no matter in normal operation or dimming.  
         [0137]     In  FIG. 12 , AC Power line functions as  210  in  FIG. 7   
         [0138]     In  FIG. 12 , F 1  is a fuse to prevent too much current drawn from power line.(function as RF 1201  in  FIG. 7 ) If the current through F 1  is larger than its rating current, it melts and open the circuit.  
         [0139]     L 1 , C 1  and C 2  become a II filter and EMI filter to prevent high frequency component enter line. (function as Filter  202  in  FIG. 7 )  
         [0140]     BR is a full bridge rectifier to rectify AC sinusoidal voltage ( FIG. 8 ) to DC sinusoidal voltage ( FIG. 9 ). (Functions as rectifier  203  in  FIG. 7 ). BR can be realized by other circuit as in  FIG. 27,28  or  29 .  
         [0141]     Q 1 , T 1 , D 20  compose a flyback power converter. (function as Converter  206  in  FIG. 7 ) C 20  is to eliminate high frequency noise.  
         [0142]     Halogen lamp is parallel with C 20 . (function as Lamp  211  in  FIG. 7 ) Auxiliary winding (functions as Sample  207  in  FIG. 7 ) and D 4 ,Q 3 ,D 5  supply voltage to PWM and connect to Vcc pin. (Pin 1 -Vcc is power supply for the controller).  
         [0143]     R 6 , R 12  and Potentiometer R 15  compose a voltage divider and connect to pin 2 -Vsense. (function as Feedback and dimmer  205  in  FIG. 7 ) ( Vsense senses signal input from auxiliary winding. This provides the secondary feedback used for output regulation).  
         [0144]     Active startup circuit is shown in  FIG. 20 , 21 , 22 . (functions as Active Startup circuit  208  in  FIG. 7 ). Other circuit such as valley-filled, linear regulator can replace circuit as  FIG. 20 , 21 , 22 .  
         [0145]     Controller use IW2202 (function as  209  in  FIG. 7 ).  
         [0146]     Pin 3 -SCL is secondary current-limit feedback input. It is pulled up to Vrega through a 10 kohm resistor when secondary current limit function is not used.  
         [0147]     Pin 4 -ASU is gate drive for the external Mosfet in the active start-up circuit. Similar to  FIG. 22 .  
         [0148]     Scaled voltage from line by voltage divider R 3 , R 4  and filter R 5 , C 4  is sent to pin  5 -Vindc.  
         [0149]     (Sense signal input representing the average line voltage for line regulation, under voltage and over voltage protection.).  
         [0150]     Scaled voltage from line by voltage divider R 1 , R 2  is sent to pin  6 -Vinac (sense signal input representing AC line voltage.) that is for input current shaping.  
         [0151]     R 13  and C 5  are connected to pin 7 -Vref (2.0v reference voltage output).  
         [0152]     Pin  8 -AGND (Analog ground) is grounded.  
         [0153]     Pin 9 -SD (shut down pin. The input signal on SD is sampled during every switching cycle. When the voltage is above the shutdown threshold, the converter goes in a latched shutdown mode). SD can be used as OVP and OTP.  
         [0154]     The voltage on R 9  is sent to Pin  10 -Isense (Primary power switch current limit. This is used to provide cycle-by-cycle current limit). It is used as current limit or over current protection.  
         [0155]     C 7  is connected to Pin  11 -Vrega (Analog regulator output. The internal 3.3v regulator is used for internal analog circuits.)  
         [0156]     C 6  is connected to Pin  12 -Vregd (Digital regulator decoupling pin. Internal 3.3v regulator is used for internal digital circuits.)  
         [0157]     Pin  13 -PGND is power ground and is grounded.  
         [0158]     Pin  14 -Output is gate drive signal for the external Mosfet switch. CY 1  is a Y cap between primary and secondary ground.  
         [0159]     We can also use  FIG. 13  to realize similar function. The only difference is the dimming is realized in secondary with opto-coupler. In  FIG. 13 , R 21  is a potentiometer and can be adjusted to set the current in diode of opto-coupler. Suppose current transfer ratio of opto-coupler is CTR. Vsense=Vref−(Vo*CTR*R 12 )/(R 21 +R 22 ),  
         [0160]     so we get Vo=(Vref−Vsense)*(R 21 +R 22 )/(CTR*R 12 ). All other values except R 21  are fixed. R 21  is a potentiometer that can be adjusted to adjust output voltage Vo. If we want to dim down lamp, we just need to decrease R 21  value, vice versa. Of Course we can select R 22  as potentiometer. We can add components or delete component on  FIG. 13 .  
         [0161]     In real application, components can be more or less than  FIG. 12 , 13 , 14 . Component value can be different from  FIG. 12 , 13 , 14 . Topology or component connection way may be different from  FIG. 12 , 13 , 14 .  
         [0162]     Other controllers with PFC function can be used in power supply with PFC based on Flyback converter. Components, connection way or components value may be different from  FIG. 12,13  or  14  etc.  
       I-1.2 Power Supply without PFC Based on Flyback Converter  
     (In One Implementation, IW2210 is Used as Controller)  
       [0163]     In one implementation, AC to constant DC power supply without PFC for Lamp can be realized with IW2210 as in  FIG. 15 , 16 , 17 ;  
         [0164]     Full bridge rectifier D 1 ˜D 4  rectify AC sinusoidal input line voltage (shown in  FIG. 8 ) to DC sinusoidal voltage (shown in  FIG. 9 ). Full bridge rectifier D 1 ˜D 4  functions as Rectifier  203  in  FIG. 7 ; Filter can be other circuit.  
         [0165]     C 1  is a filter to pass high frequency component caused by switching to avoid EMI on line voltage. C 1  functions as Filter  202  in  FIG. 7 ;  
         [0166]     R 3  connect between line voltage and Vcc to startup the controller IW2210, after it operates, Auxiliary winding will charge C 3  through D 5 . This functions as Active Startup Circuit  208  in  FIG. 7 ; Vcc: power supply for the controller IW2210.  
         [0167]     Transformer T 1 , D 8 , C 4  and Q 1  compose flyback topology. That works as One Stage DC Sinusoidal to DC Constant Converter  206  in  FIG. 7   
         [0168]     IW2210 works as controller  209  in  FIG. 7 ;  
         [0169]     Output voltage can be coupled to primary through auxiliary winding and connect to Vsense pin by voltage divider composed of R 9 , R 10  and R 11 . Vsense: Sense signal input from auxiliary winding. This provides the secondary voltage feedback used for output regulation.  
         [0170]     Auxiliary winding works as Sample  207  in  FIG. 7 .  
         [0171]     Voltage divider R 9 , R 10  and R 11  works as Feedback and dimmer  205  in  FIG. 7 . R 10  is a potentiometer.  
         [0172]     R 1  and R 2  voltage divider connect to Vin pin that is used for line regulation, under voltage and over voltage protection;  
         [0173]     Vref is reference voltage output and connected with decoupling capacitor C 2  and R 4  in parallel;  
         [0174]     GND (Analog ground) is grounded;  
         [0175]     Isense senses primary switch current to provide cycle-by-cycle current limit.  
         [0176]     Output pin output square waveform to switching on/off Main Switch Mosfet Q 1 .  
         [0177]     R 6 , R 7  and R 8  become a voltage divider and connect to pin OVP/OTP. When output voltage is higher than a threshold, the voltage coupled on OVP/OTP pin through auxiliary winding will reach a threshold of interior controller, it shuts down. So it functions as OVP. It can also function as OTP. For example, if R 8  is a thermistor and changes to a very high value during high temperature, then the voltage on pin OVP/OTP can reach threshold and shuts down controller. Any of R 6 , R 7  or R 8  can be a thermistor, thermal resistor; NTC (negative temperature coefficient) or PTC (positive temperature coefficient) depends on the OTP function requirement;  
         [0178]     During the period when Q 1  is on (0&lt;t&lt;=DTs), the ‘•’ end voltage is negative with respect to no ‘•’ end of both primary and secondary transformer windings, thus diode D 3  could not turn on. Energy is saved in the magnetic inductance Lm. The voltage cross primary winding is Vg. (Vg is DC sinusoidal voltage as  FIG. 9  after AC voltage rectified). During the period when Q 1  is off (DTs&lt;=t&lt;Ts), the polarity of the transformer winding changes. ‘•’ end voltage is positive with respect to no ‘•’ end for both primary and secondary windings of transformer. Thus D 3  turns on and energy is delivered to the output. The voltage cross primary winding is Vo*n. (Vo is output DC voltage and n is transformer turns ratio n=np/ns, np is primary turns; ns is secondary turns). The voltage coupled cross auxiliary winding is Vo*Na/Ns. Voltage on Vsense=(Vo*Na/Ns)*R 11 /(R 9 +R 10 +R 11 ).  
         [0179]     As shown in  FIG. 18 , if the auxiliary voltage is higher than the threshold set by the reference at tn, the next pulse the controller generates is a sense pulse. This is a much shorter pulse. The frequency of the operation is kept constant pulse by pulse, which result in discontinuous operation during sense cycles.  
         [0180]     As shown in  FIG. 18 , if the auxiliary voltage at tn+1 is below the threshold, the next pulse is a power pulse.  
         [0181]     If the voltage is still too high, the controller sends more sense pulses. If the feedback voltage is still too high after 12 sense pulse, the converter transitions into SmartSkip mode operation, sending out very narrow skip pulses and gradually decreasing the operating frequency until the generated power is in balance with the load. The minimum operating period at no load is about 2 ms.  
         [0182]     Thus the feedback guarantees the output voltage is constant at predetermined value. Vsense=(Vo*Na/Ns)*R 11 /(R 9 +R 10 +R 11 )=Vinterior ref.(Vinterior ref is interior reference voltage).
 
 Vo=V interior  ref *( Ns/Na )*(1+( R 9 +R 10)/ R 11).
 
         [0183]     In one implementation, R 10  is a potentiometer. So decrease R 10  value to decrease Vo to realize dimming with feedback. R 9  or R 11  can be a potentiometer, then decrease R 9  or increase R 11  value to decrease Vo to realize dimming.  
         [0184]     In one implementation, Controller  209  is IW2210 that uses Pulse Train control algorithm, which is a discrete time bang-bang type control that provides ultra-fast transient response, and guarantees loop stability without external loop compensation components. The controller provides three types of pulses to output driver, depending on the real-time value of the output voltage. (1) If output voltage Vo is too low, the controller sends out a power pulse that is high-energy pulses that transfer enough energy to the output to provide up to 130% of the rated output power for the converter; (2) If the output voltage Vo is too high, the controller sends out a sense pulse which represents significantly less energy than the power pulses. While in regulation, the controller adjusts the average mix of power and sense pulses to balance the energy provided by the converter and used by the load, thus regulating the output voltage within its specified limits. (3) If the load is very light, the controller operates in Smart Skip mode which generates ultra-narrow skip pulses and gradually reduces the frequency to keep the output in regulation down to zero load current.  
         [0185]      FIG. 18  shows the Vsense waveform over four switching cycles. The voltage feedback block and the digital controller make a cycle-by-cycle determination of the type of pulse that will be generated in the next switching cycle. The first cycle shown is a power pulse. It is sampled close to the edge of the “flat portion” of the waveform, before the flux in the transformer collapses and the Vsense voltage falls. This time point is labeled tn. The controller turns on the switch again at the first minimum point of the auxiliary voltage. This point is calculated by the digital controller based on input from the Zero Voltage Detector block. This operation corresponds to valley-mode voltage switching (VMS) on the main power switch. VMS minimizes switching losses and increases the efficiency of the converter. The controller operates in critical discontinuous mode during power cycles. This operation maximizes the power density of the magnetic and minimizes its size for a given power level. If the auxiliary voltage is higher than the threshold set by the reference at tn, the next pulse the controller generates is a sense pulse. This is a much shorter pulse. The frequency of the operation is kept constant pulse by pulse, which results in discontinuous operation during sense cycles. If the auxiliary voltages at tn+1 is below the threshold, the next pulse is a power pulse, as shown in  FIG. 18 . However, if the voltage is still too high, the controller sends more sense pulses. If the feedback voltage is still too high after 12 sense pulses, the converter transitions into SmartSkiptm mode operation, sending out very narrow skip pulses and gradually decreasing the operating frequency until the generated power is in balance with the load. The minimum operating period at no load is about 2 ms.  
         [0186]     We can also use  FIG. 16  to realize similar function. The only difference is the dimming is realized in secondary with opto-coupler. In  FIG. 16 , R 21  is a potentiometer and can be adjusted to set the current in diode of opto-coupler. Suppose current transfer ratio of opto-coupler is CTR. Vsense=Vref−(Vo*CTR*R 10 )/(R 21 +R 20 ),  
         [0187]     so we get Vo=(Vref−Vsense)*(R 21 +R 20 )/(CTR*R 10 ). All other values except R 21  are fixed. R 21  is a potentiometer that can be adjusted to adjust output voltage Vo. If we want to dim down lamp, we just need to decrease R 21  value, vice versa. Of Course we can select R 20  as potentiometer then we can decrease R 20  value to realize dimming.  
         [0188]     In  FIG. 17 , dimming is realized by changing potentiometer R 22 . Optocoupler current Ioc=Vref*(R 22 +R 23 )/R 23 /R 20 =Vref*(1+R 22 /R 23 )/R 20 ; Vsense=Vicref−Ioc*R 10  Output voltage is set by reference voltage times (1+R 22 /R 23 ). Decrease R 22 , Vo decreases; Vice versa. Vo has small ΔVo increase, Ioc has small increase, Vsense has small decrease. Vo+ΔV has small decreases until equals to Vo. Feedback guarantees the voltage in regulation. R 23  can be a potentiometer, increase R 23  to decrease Vo to realize dimming.  
         [0189]     In real application, component can be more or less than  FIG. 15 , 16 , 17 . Component value can be different from  FIG. 15 , 16 , 17 . Topology or component connection way may be different from  FIG. 15 , 16 , 17 .  
         [0190]     Other controllers without PFC function can be used in power supply without PFC based on Flyback converter (such as Iw1688). Components, connection way or components value may be different from  FIG. 15,16  or  17  etc. For example, UCC28600 is used with schematic as  FIG. 24  and the function is similar to  FIG. 17 . In real application, components or values or connection way may be different from  FIG. 24 .  
       I-1.3 Power Supply Based on Flyback Converter with Switch Integrated in Controller  
     (In One Implementation, LNK362-364 is Used as Controller with Switch Integrated)  
       [0191]      FIG. 25  is the schematic in one implementation.  
         [0192]     The AC input is rectified by D 1  to D 4  (as Rectifier block  203  in schematic  7 ) and filtered by the bulk storage capacitors C 1  and C 2 .  
         [0193]     Resistor RF 1  is a fuse, PTC or NTC thermistor, or inrush current limiter or other over current protection. (As RF 1  block  201  in schematic  7 ).  
         [0194]     Together with the π filter formed by C 1 , C 2 , L 1  and L 2 , differential mode noise attenuator. (as Filter block  202  in schematic  7 ) Other type of filter can also be used here.  
         [0195]     Resistor R 1  damps ringing caused by L 1  and L 2 .  
         [0196]     The rectified and filtered input voltage is applied to the primary winding of T 1 .  
         [0197]     The other side of the primary is driven by the integrated MOSFET in U 1 . The secondary of the flyback transformer T 1  is rectified by D 5 , and filtered by C 4 . (All these are as block  204  in schematic  7 ). U 1 ,T 1 ,D 5 ,C 4  compose a flyback converter as  206  in  FIG. 7 .  
         [0198]     The combined voltage drop across VR 1 , R 4 , R 5  and the LED of U 2  determines the output voltage. R 4  and R 5  are as Sample block  207  in schematic  7 .  
         [0199]     VR 1 , R 2 , R 3 , U 2 , R 4 , R 5  and C 3  are Feedback and Dimmer block  205  in schematic  7 .  
         [0200]     Suppose VR 1  rating voltage=Vzener. Vr 2  is voltage across resistor R 2 . Vu 2 led is voltage across LED in opto-coupler U 2 .
 
 Vo=[V zener+ Vr 2 +Vu 2 led ]*( R 4 +R 5)/ R 5 =[V zener+ Vr 2 +Vu 2 led ]*(1 +R 4 /R 5)
 
 Vr 2 &lt;&lt;V zener,  VU 2 LED&lt;&lt;V zener,  So Vo≈V zener*(1 +R 4 /R 5)
 
         [0201]     We can increase R 5  to decrease Vo to realize dimming. If R 4  is a potentiometer, we can decrease R 4  to decrease Vo for dimming.  
         [0202]     In one implementation, when the output voltage exceeds this level, current will flow through the LED of U 2 . As the LED current increases, the current fed into the FEEDBACK pin of U 1  increases until the turnoff threshold current is reached, disabling further switching cycles, and at very light loads, almost all the switching cycles will be disabled, giving a low effective frequency and providing high light load efficiency and low no-load consumption. Resistor R 2  provides 1 mA through VR 1  to bias the Zener closer to its test current. Resistor R 3  allows the output voltage to be adjusted to compensate for designs where the value of the zener may not be ideal, as they are only available in discrete voltage ratings. For higher output accuracy, the Zener may be replaced with a reference IC such as the TL431. The LinkSwitch-XT is completely self-powered from the DRAIN pin, requiring only a small ceramic capacitor C 3  connected to the BYPASS pin. No auxiliary winding on the transformer is required.  
         [0203]     Several implementations are listed in  FIG. 25 . Feedback can use opto-coupler as shown in first schematic in  FIG. 25 ; Feedback can use auxiliary winding as shown in second schematic in  FIG. 25 ; Feedback can directly comes from secondary voltage divider as third schematic in  FIG. 25 .  
         [0204]     In real application, component can be more or less than  FIG. 25 . Component value can be different from  FIG. 25 . Topology or component connection way may be different from  FIG. 25 .  
         [0205]     Other controllers with switch integrated into the controller can also be used in power supply based on Flyback converter with switch integrated in controller.  
         [0206]     As above part 1 , power supply for lamp can be realized by flyback converter with or without PFC and can use all kinds of controllers with any kind of control method or algorithm for controller  209  in  FIG. 7 .  
       I-2 Part 2. Other Topology Converter Used As Converter  206   
     I-2.1 Power Supply Based on Full-bridge Converter (FIG.  44 ) 
       [0207]        Vo =( n 2 /n   1 )* D *Vg,    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; Vg: input voltage      
         [0210]     Any Full-bridge controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.2 Power Supply Based on Half-bridge Converter (FIG.  45 ) 
       [0211]        Vo= 0.5*( n 2 /n   1 )* D *Vg,    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; Vg: input voltage      
         [0214]     Any Half-bridge controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.3 Power Supply Based on Forward Converter (FIG.  46 ) 
       [0215]        Vo =( n 3 /n   1 )* D *Vg,    Vo: output voltage; n 3 : secondary winding turns; n 1 : primary winding turns;     D: duty cycle; Vg: input voltage      
         [0218]     Any Forward controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.4 Power Supply Based on Two-transistor Forward Converter (FIG.  47 ) 
       [0219]        Vo =( n 2 /n   1 )* D *Vg,    Vo: output voltage; n 1  :primary winding turns; n 2 : secondary winding turns;     D: duty cycle; Vg: input voltage      
         [0222]     Any two-transistor Forward controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.5 Power Supply Based on Push-pull Converter (FIG.  48 ) 
       [0223]        Vo =( n 2 /n   1 )* D *Vg,    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; Vg: input voltage      
         [0226]     Any two-transistor Forward controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.6 Power Supply Based on Push-pull Converter Based on Watkins-Johnson Converter 
       [0000]     ( FIG. 49 )
 
 Vo =( n 2 /n 1 )*( 2 D− 1) Vg/D, 
    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; Vg: input voltage    
 
         [0229]     Any Push-pull converter based on Watkins-Johnson controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.7 Power Supply Based on Isolated SEPIC Converter (FIG.  50 ) 
       [0230]        Vo =( n 2 /n   1 )* D *Vg/D′,    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; D′= 1 −D; Vg: input voltage      
         [0233]     Any Isolated SEPIC controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.8 Power Supply Based on Isolated Inverse SEPIC Converter (FIG.  51 ) 
       [0234]        Vo =( n 2 /n   1 )* D *Vg/D′,    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; D′= 1 −D; Vg: input voltage      
         [0237]     Any Isolated Inverse SEPIC controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.9 Power Supply Based on Isolated Cuk Converter (FIG.  52 ) 
       [0238]        Vo =( n 2 /n   1 )* D *Vg/D′,    Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; D′= 1 −D; Vg: input voltage      
         [0241]     Any Cuk controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       I-2.10 Power Supply Based on Two-transistor Flyback Converter (FIG.  53 ) 
       [0242]        Vo=Vg*D *( n 2 /n   1 )/ D′      Vo: output voltage; n 1 : primary winding turns; n 2 : secondary winding turns;     D: duty cycle; D′= 1 −D; Vg: input voltage      
         [0245]     Any Two-transistor flyback controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
         [0246]     As above, components can be more or less than  FIG. 44  to  FIG. 53 . Other isolated topologies also can be used here. Any controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       Type II. Non-Isolated Converter  
     II-1 Part 1. Buck Converter Used As Converter  206   
       [0247]     Buck converter is shown in  FIG. 26 . The function is described as the following:  
         [0248]     Transistor Q 1  on, 0&lt;t&lt;DTs, voltage on point A equals to Vg, diode D 1  is off, voltage on point A is positive with respect to point B on inductor L 1 , VA=Vg;  
         [0249]     Transistor Q 1  off, DTs&lt;t&lt;Ts, polarity of inductor change, voltage on point A is negative with respect to point B on inductor L 1 , diode D 1  turns on, VA= 0 .  
         [0250]     Output voltage is average value of VA for the filter composed of L 1 , C 1 . So Vo=(Vg*DTs+0*D′Ts)/Ts=DVg.  
       II-1.1 Power Supply Based on Buck Converter with Switch Integrated in Controller  
     (In One Implementation, LNK302/304-306 is Used as Controller)  
       [0251]     The circuits shown in  FIG. 27 , 28 , 29  are typical implementations of non-isolated power supply.  
         [0252]     The input stage comprises fusible resistor RF 1  (as RF 1   201  block in  FIG. 7 ); Resistor RF 1  is a flame proof, fusible, wire wound resistor. It accomplishes several functions: 
    a) Inrush current limitation to safe levels for rectifiers D 3  and D 4 ;     b) Differential mode noise attenuation;     c) Input fuse should blow up when any other component fail for short circuit    
 
         [0256]     Diodes D 3  and D 4  work as Rectifier  203  in  FIG. 7 ;  
         [0257]     Capacitors C 4  and C 5 , and inductor L 2  (as Filter block  202  in  FIG. 7 ).  
         [0258]     The power processing stage is formed by the LinkSwitch-TN, freewheeling diode D 1 , Controller U 1 , output choke L 1 , and the output capacitor C 2  compose Buck converter (as converter  206  in  FIG. 7 )  
         [0259]     The LNK302/304-306 was selected for U 1  as controller  209  in  FIG. 7  such that the power supply operates in the mostly discontinuous-mode (MDCM). Diode D 1  is an ultra-fast diode with a reverse recovery time (trr) of approximately 75 ns, acceptable for MDCM operation. For continuous conduction mode (CCM) designs, a diode with a reverse recovery time less than 35 ns is recommended. Inductor L 1  is a standard off-the-shelf inductor with appropriate RMS current rating (and acceptable temperature rise). Capacitor C 2  is the output filter capacitor; its primary function is to limit the output voltage ripple.  
         [0260]     (controller U 1  with switch integrated into, diode D 1 , inductor L 1  and capacitor C 2  become a buck converter as block  204  in schematic  7 )  
         [0261]     Active startup circuit  208  and main switch are integrated in IC controller U 1 .  
         [0262]     To a first order, the forward voltage drops of D 1  and D 2  are identical. Therefore, the voltage across C 3  tracks the output voltage. The voltage developed across C 3  is sensed and regulated via the resistor divider R 1  and R 3  (R 1  or R 3  is a potentiometer) connected to U 1 &#39;s FB pin. The values of R 1  and R 3  are selected such that, at the desired output voltage, the voltage at the FB pin is 1.65v. So Vout·R 3 /(R 1 +R 3 )=1.65v, Vout=1.65*(1+R 1 /R 3 ).  
         [0263]     If R 3  is a potentiometer, we can increase R 3  to decrease output voltage for dimming;  
         [0264]     If R 1  is a potentiometer, we can decrease R 1  to decrease output voltage for dimming.  
         [0265]     Main switch is integrated in IC LNK302/304-306.  
         [0266]     D 2 , become sample block  207  in  FIG. 7 ;  
         [0267]     C 3 , R 1 , R 3  work as Feedback and dimmer block  205  in  FIG. 7 .  
         [0268]     In one implementation, Regulation is maintained by skipping switching cycles. As the output voltage rises, the current into the FB pin will rise. If this exceeds Ifb then subsequent cycles will be skipped until the current reduces below Ifb. Thus, as the output load is reduced, more cycles will be skipped and if the load increases, fewer cycles are skipped. To provide overload protection if no cycles are skipped during a 50 ms period, LinkSwitch-TN will enter auto-restart (LNK304-306), limiting the average output power to approximately 6% of the maximum overload power. Due to tracking errors between the output voltage and the voltage across C 3  at light load or no load, a small pre-load may be required (R 4 ). For the design in  FIG. 27 , if regulation to zero load is required, then this value should be reduced to 2.4 kohm.  
         [0269]     Feedback can be realized by opto-coupler as in  FIG. 28  or  FIG. 29 .  
         [0270]     Output voltage is set by voltage divider composed of potentiometer R 3  and resistor R 1 . Voltage of reference Z 1  is Vz. Vo=Vz*(1+R 1 /R 3 ). Dimming can be realized by increasing R 3 . If R 1  is potentiometer, dimming can be realized by decreasing R 1  value.  
         [0271]     Connection or component values can be changed in application. Components can be more or less than  FIG. 27 , 28 , 29 .  
         [0272]     As above in Part 2, we can use any buck controller with any kind of control way or algorithm which can convert DC sinusoidal voltage to DC constant voltage with switch or without switch integrated in power supply for lamp with PFC or without PFC.  
       II-2 Part 2. Buck-Boost Converter Used As Converter  206   
       [0273]     Buck-Boost converter is shown in  FIG. 30 . The function is described as the following:  
         [0274]     Transistor Q 1  on, 0&lt;t&lt;DTs, voltage across L 1  equals to Vg, diode D 1  is off, voltage on point A is positive with respect to point B on inductor L 1 , VA=Vg;  
         [0275]     Transistor Q 1  off, DTs&lt;t&lt;Ts, polarity of inductor change, voltage on point A is negative with respect to point B on inductor L 1 , diode D 1  turns on, VL=−Vo.  
         [0276]     For steady state, the average of voltage across inductor L 1  should be 0. So 0=(Vg*DTs+Vo*D′Ts)/Ts; Vo=−Vg*D/D′, Vo had opposite polarity as Vg.  
       II-2.1 Power Supply Based on Buck-Boost Converter with Switch Integrated in Controller  
     (In One Implementation, LNK302/304-306 is Used As Controller)  
       [0277]     The circuits shown in  FIG. 31 , 32 , 33  are typical implementations of non-isolated power supply. Regulation and feedback is already described in II-2.  
         [0278]     Feedback can be realized by opto-coupler as in  FIG. 33 .  
         [0279]     Output voltage is set by voltage divider composed of potentiometer R 3  and resistor R 1 . Voltage of reference Z 1  is Vz. Vo=Vz*(1+R 1 /R 3 ). Dimming can be realized by increasing R 3 . If R 1  is potentiometer, dimming can be realized by decreasing R 1  value.  
         [0280]     Connection or component values can be changed in application. Components can be more or less than  FIG. 31 , 32 , 33 .  
         [0281]     As above in II-2 Part 2, we can use any buck-boost controller with any kind of control way or algorithm which can convert DC sinusoidal voltage to DC constant voltage with switch or without switch integrated in power supply for lamp.  
       II-3 Part 3. Other Non-isolated Topology Converter Used As Converter  206   
     II-3.1 Power Supply Based on Boost Converter (FIG.  34 ) 
       [0282]    
       
      
       Vo=Vg/D′, 
      
       
          Vo: output voltage; D: duty cycle; D′= 1 −D; Vg: input voltage  
       
     
         [0284]     Any Boost controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.2 Power Supply Based on Noninverting Buck-Boost Converter (FIG.  35 ) 
       [0285]    
       
      
       Vo=Vg*D/D′, 
      
       
          Vo: output voltage; D: duty cycle; D′=1−D; Vg: input voltage  
       
     
         [0287]     Any noninverting Buck-Boost controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.3 Power Supply Based on H-Bridge Converter (FIG.  36 ) 
       [0288]        Vo=Vg *(2 D− 1),    Vo: output voltage; D: duty cycle; Vg: input voltage      
         [0290]     Any H-bridge controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.4 Power Supply Based on Watkins-Johnson Converter (FIG.  37 ) 
       [0291]        Vo=Vg *(2 D− 1)/ D,      Vo: output voltage; D: duty cycle; Vg: input voltage      
         [0293]     Any Watkins-Johnson controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.5 Power Supply Based on Current-fed Bridge Converter (FIG.  38 ) 
       [0294]        Vo=Vg /(2 D− 1),    Vo: output voltage; D: duty cycle; Vg: input voltage      
         [0296]     Any current-fed bridge controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.6 Power Supply Based on Inverse of Watkins-Johnson Converter (FIG.  39 ) 
       [0297]        Vo=Vg*D /(2 D− 1),    Vo: output voltage; D: duty cycle; Vg: input voltage      
         [0299]     Any Inverse of Watkins-Johnson controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.7 Power Supply Based on Cuk Converter (FIG.  40 ) 
       [0300]    
       
      
       Vo=−Vg*D/D′, 
      
       
          Vo: output voltage; D: duty cycle; D′=1−D; Vg: input voltage  
       
     
         [0302]     Any Cuk controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.8 Power Supply Based on SEPIC Converter (FIG.  41 ) 
       [0303]    
       
      
       Vo=Vg*D/D′, 
      
       
          Vo: output voltage; D: duty cycle; D′= 1 −D; Vg: input voltage  
       
     
         [0305]     Any SEPIC controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.9 Power Supply Based on Inverse of SEPIC Converter (FIG.  42 ) 
       [0306]    
       
      
       Vo=Vg*D/D′, 
      
       
          Vo: output voltage; D: duty cycle; D′=1D; Vg: input voltage  
       
     
         [0308]     Any Inverse of SEPIC controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
       II-3.10 Power Supply Based on Buck Square Converter (FIG.  43 ) 
       [0309]    
       
      
       VO=D*D 
      
       
          Vo: output voltage; D: duty cycle; Vg: input voltage  
       
     
         [0311]     Any Buck square controller with any control way that can convert DC sinusoidal voltage to DC constant voltage can be used as controller  209 .  
         [0312]     Other non-isolated topology controller with any control which can convert DC sinusoidal voltage to DC constant voltage can also be used as controller  209 .  
         [0313]     Controller  209  can use all kinds of control method such as digital control, analog control, DSP, SmartSkip Mode, LinkSwitch-XT or LinkSwtich-TN mode etc.  
         [0314]     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Moreover, the converter topologies discussed above can be used within power supplies to supply power to devices other than lamps—For example, Bus AC to DC converter, PFC converter, PFC converter for lighting,Computer power supply, Monitor power supply, notebook adapter, LCD TV, AC/DC adapter, Adjusted output voltage Battery charger, Power tool charger, Electronic ballast, Video game power supply.