Abstract:
An AC-to-DC voltage converter as power supply for lamp converts an AC input voltage to a constant DC voltage at predetermined value set by potentiometer. The converter includes input power supply  210,  input protection circuit  201,  EMI filter  202,  rectifier  203,  filter  204,  converter  206,  output filter  214,  lamp  211,  start circuit  208,  control circuit  209,  biasing circuit  212,  sampling circuit  207,  output protection circuit  200,  feedback and dimming circuit  205  and input monitor circuit  213.  This version is a flyback converter; versions from other topologies etc are also provided. The converter has feedback function that can regulate output voltage at predetermined value. The converter has dimming function and can adjust lamp brightness for conformability. The output constant brightness decreases peoples&#39; eyes fatigue to minimum level.

Description:
[0001]     This application is a continuation in part of application Ser. No. 11/204,307 filed on Aug. 15, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention is an AC-to-DC converter as lamp power supply that converts an AC input voltage to a constant DC voltage at predetermined value set by potentiometer. The lamp has constant brightness, no low frequency or high frequency flicker light in the output, no electromagnetic radiation, thus reduce eye&#39;s fatigue to minimum level and protect eyesight and health to maximum level.  
       BACKGROUND OF THE INVENTION  
       [0003]     Currently, the power supply for lamp has three main categories: 
        1) Output has only low frequency (less than a few hundred Hz) voltage;     2) Output has only high frequency (more than a few hundred Hz and usually around KHz) voltage;     3) Output has high frequency voltage in low frequency envelope.        
 
         [0007]     The first category has serious low frequency flicker problem, the crystalline lens and pupil muscle will adjust to the flicker light and become very tired. In the long run, the crystalline and pupil muscle becomes slack and can&#39;t adjust accurately then myopia is caused.  
         [0008]     The second category has high frequency flicker, the crystalline lens and pupil muscle is not fast enough to adjust at such a high frequency. The intense peak light will hurt retina for long run and dry cornea or opacity of the crystalline lens are caused. High frequency electromagnetic radiation will hurt health.  
         [0009]     The third category has low frequency flicker to cause myopia and high frequency flicker to hurt retina or cause electromagnetic radiation that will hurt health.  
       SUMMARY OF THE INVENTION  
       [0010]     The invention is an AC-to-DC converter as lamp power supply that converts an AC input voltage to a constant DC voltage at predetermined value set by potentiometer. The output lamp has neither low frequency flicker nor high frequency flicker. So the constant brightness light reduces eyes&#39; fatigue to minimum level to prevent myopia. And the constant brightness light can be set to comfortable value that has no intense light to hurt retina by adjusting dimming and feedback circuit. There is no electromagnetic radiation on output.  
         [0011]     In order to realize the above object, the invention provides an AC-to-DC voltage converter as power supply for lamp. The converter includes input power supply  210 , input protection circuit  201 , EMI filter  202 , rectifier  203 , filter  204 , converter  206 , output filter  214 , lamp  211 , start circuit  208 , control circuit  209 , biasing circuit  212 , sampling circuit  207 , output protection circuit  200 , feedback and dimming circuit  205 , input monitor circuit  213 .  
         [0012]     Input power source  210  is connected to input protection circuit  201 ,  201  is connected to EMI filter  202 ,  202  is connected to rectifier  203 ,  203  is connected to filter  204 ,  204  is connected to input of converter  206 , the output of converter  206  is connected to output filter  214 ,  214  is connected to lamp  211 , the input of sampling circuit  207  is connected to the output of converter  206  or lamp  211 , the output of sampling circuit  207  is connected to input of feedback and dimming circuit  205 , the output of feedback and dimming circuit  205  is connected to input of control circuit  209 , input of start circuit  208  is connected to output of rectifier  203  or the output of filter  204 , output of start circuit  208  is connected to input of control circuit  209  or output of biasing circuit  212 , input of biasing circuit  212  is connected to output of converter  206  or lamp  211 , input of output protection circuit  200  is connected to output of converter  206  or lamp  211 , output of output protection circuit is connected to input of control circuit  209 , input of input monitor circuit  213  is connected to output of rectifier  203  or output of filter  204 , output of input monitor circuit  213  is connected to input of control circuit  209 , the output of control circuit  209  is connected with converter  206  input.  
         [0013]     The position or connection way of circuit Block  200 ,  201 ,  202 ,  203 ,  204 ,  205 ,  206 ,  207   208 ,  209 ,  210 ,  211 ,  212 ,  213 ,  214  can be changed, some block can be removed, or new block can be added in or attached. Some block can be integrated into one circuit, part of some block can be integrated with part of another block into one circuit. Every block can use any circuit that has the required function.  
         [0014]     In the invention, input voltage source comes from line voltage that is usually low frequency AC voltage such as 110 volt, 60 Hz or 220 volt, 50 Hz; Over current protection circuit becomes open to cut off the connection between voltage source  210  and power supply input when input current is above predetermined value, over voltage protection circuit clamp input voltage under predetermined value to prevent over voltage damage on power supply circuit, they compose input protection circuit  201 ; EMI filter  202  prevents high frequency component from entering low frequency input power supply  210 ; rectifier  203  converts AC voltage to varying magnitude DC voltage; filter  204  prevents high frequency component from entering start circuit  208  and control circuit  209 ; converter  206  converts varying magnitude DC voltage to constant DC voltage; sampling circuit  207  collect voltage signal proportional to output voltage; Feedback and dimming circuit  205  regulates output voltage at constant value while changes output voltage and dims lamp by changing potentiometer resistor value to change the ratio between output voltage and interior reference voltage in control circuit  209 ; control circuit  209  control turn on time or switching frequency of the main switch in converter  206  to regulate the output voltage at a constant value or use other control way such as pulse train control or DSP; Output filter  214  prevents high frequency component from entering output lamp; start circuit  208  supplies power to control circuit  209  to startup the power supply before stable operation, after the power supply enter stable state, the start circuit  208  is reverse biased and doesn&#39;t work and biasing circuit  212  supply power to control circuit  209 , some circuit can use biasing circuit  212  to supply power to control circuit  209  from very beginning to stable state; lamp  211  can use any kind of lamp; output protection circuit  200  can have over voltage protection circuit, over current protection circuit, over temperature protection circuit, when output voltage, output current or board temperature is above predetermined value, control circuit  209  turns off the main switch in voltage converter  206 ; input monitor circuit  213  monitor the input voltage and send the signal to control circuit  209  to control duty cycle or frequency response to input voltage in order that the output voltage is regulated at constant predetermined value. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  the block diagram of the invention;  
         [0016]      FIG. 2  one implementation of the invention, Flyback topology used as converter  206 , integrated circuit controller IW2202 for control circuit  209 ; feedback is realized with auxiliary winding;  
         [0017]      FIG. 3  one implementation of the invention, Flyback topology used as converter  206 , integrated circuit controller IW2210 for control circuit  209 ; feedback is realized with auxiliary winding;  
         [0018]      FIG. 4  one implementation of the invention, Flyback topology used as converter  206 , integrated circuit controller IW1688 for control circuit  209 ; feedback is realized with auxiliary winding;  
         [0019]      FIG. 5  one implementation of feedback with opto-coupler, R 15  is a potentiometer, R 6  and R 31  are resistors, point  1  is connected to Vo, point  2  is connected to Vref or Vreg, point  3  is connected to Vsense or feedback pin.  
         [0020]      FIG. 6  one implementation with DC fluorescent lamp, resistor Rs and Capacitor Cs delay voltage change, Ts is the trigger to connect the cathode filament, after lamp start, voltage goes down and Ts disconnect the cathode filament.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     In  FIG. 1 , input voltage comes from line voltage that is usually sinusoidal AC voltage, rectifier  203  converts AC sinusoidal voltage to DC sinusoidal voltage, converter  206  converts DC sinusoidal voltage to a DC constant voltage on output.  
         [0022]      FIG. 2  is one implementation of the invention, input power supply  210  comes from line voltage usually around 100 volt 60 Hz AC voltage; Fuse F 1  works as input over current protection circuit, transient absorber VR 1  works as input over voltage protection circuit, F 1 ,VR 1  constitute input protection circuit  201 ; inductor L 2  common mode filter and capacitor C 3  form the EMI filter  202 , resistor R 27  can discharge capacitor C 3 ; diodes D 7 ,D 8 ,D 9 ,D 10  compose bridge rectifier BR 1 , diodes D 15 ,D 16 ,D 17 ,D 18  compose bridge rectifier BR 2 , BR 1  or BR 2  or both become rectifier circuit  203 , resistor R 25  is the limiting current resistor; π filter composed of capacitors C 1 ,C 2  and inductor L 1  works as filter  204 ; transformer T 1 , transistor Q 1 , diode D 20  constitute Flyback topology converter that works as converter  206 , clamp circuit D 2 , diode D 1 , resistor R 24 ,R 26 , capacitor C 15  clamp the spike voltage on the drain of transistor Q 1 , resistor R 30  prevents transistor Q 1  from turning on by static electricity; common mode filter L 3  and capacitor C 20 ,C 30  constitute output filter  214 , resistor R 20  discharge capacitor C 20 ,C 30 ; auxiliary winding of transformer T 1  and diode D 6  constitute sampling circuit  207 ; resistor R 6 ,R 12  and potentiometer R 15  constitute feedback and dimming circuit  205 , capacitor C 21  remove noise signal; integrated circuit Iw2202 works as control circuit  209 , resistor R 29  and diode D 19  control delay time of turn on duration; resistors R 10 ,R 11 ,R 7 , transistor Q 2 , capacitor C 8 , zener diodes D 11 ,D 12  constitute start circuit  208 ; auxiliary winding, diodes D 4 ,D 5 , transistor Q 3 , resistor R 8 , zener diodes D 13 ,D 14 , capacitors C 9 ,C 19  constitute biasing circuit  212 ; lamp  211  can use any lamp such as Halogen, Incandescent or DC fluorescent etc; auxiliary winding, resistors R 16 ,R 17 ,R 23  and diode D 3  constitute output over voltage protection circuit, capacitors C 11 ,C 12 ,C 13 ,C 14  and resistors R 18 ,R 19 ,R 21 , NTC thermistor R 22  and transistor Q 4  constitute over temperature protection circuit, resistor R 9 , filter R 28 , C 18  constitute over current protection circuit, as above, three circuits compose output protection circuit  200 ; capacitor C 16 ,C 17 , voltage divider resistors R 1 ,R 2 ,R 3 ,R 4 , filter resistor R 5 , capacitor C 4  compose input monitor circuit  213 ; the following describes the connection with IC controller Iw2202.  
         [0023]     Output of start circuit  208  and output of biasing circuit  212  are connected to pin 1 -Vcc; output of feedback and dimming circuit  205  is connected to pin 2 -Vsense; pin 3 -SCL is secondary current limit feedback input, it is connected to pin 11 -Vrega by a 10 Kohm resistor when secondary current limit is not used; zener diode D 12  of start circuit  208  is connected to pin 4 -ASU by resistor R 7 ; the input monitor circuit  213  get signal proportional to line voltage by voltage divider R 3  and R 4  then sends to pin 5 -Vindc with filter composed of resistor R 5  and capacitor C 4 , monitor signal reflects the average voltage of line voltage and is used as under voltage protection and over voltage protection; input monitor circuit  213  gets signal proportional to line voltage by voltage divider R 1 ,R 2  and sends to pin 6 -Vinac for power factor correction to make current and voltage waveform in phase; resistor R 13  and capacitor C 5  are connected to pin 7 -Vref 2.0 volt reference voltage output; pin 8 -AGND analog circuit ground; pin 9 -SD samples input signal at every switching pulse, when sampling signal is higher than threshold voltage, converter turns off in unlatch mode, it can be used as over voltage protection, over temperature protection; the voltage across R 9  is sent to pin 10 -Isense that is used as main switch current limit, that can be used for single pulse current limit, over current protection or short circuit protection; capacitor C 7  is connected to pin 11 -Vrega that is analog regulator output; capacitor C 6  is connected to pin 12 -Vregd that is digital regulator output; pin 13 -PGND is power ground and grounded; pin 14 -ouput pulse signal to drive transistor Q 1 ; capacitor C 10  is a Y capacitor that is connected between primary and secondary side of transformer.  
         [0024]     Another implementation is shown in  FIG. 3, 4  respectively, same name component has same function, connection way is similar to  FIG. 2 .  FIG. 2, 3 ,  4  use auxiliary winding as feedback, potentiometer is on primary side; opto-coupler can be used in  FIG. 2, 3 ,  4  for feedback, potentiometer is on secondary side. One implementation with opto-coupler feedback is shown in  FIG. 5 .  
         [0025]     The principle of the implementations is as the following:  
         [0026]     When main switch Q 1  turns on, the energy is saved in primary winding of transformer, after main switch Q 1  turns off, the energy is transferred to secondary and lamp;  
         [0027]     Output voltage Vo, input voltage Vg(t), duty cycle D, D′=1−D, n is the ratio between primary and secondary winding, so 
 
 Vo=Vg ( t ) *D/ ( D′*n )  (1) 
 
 Vg(t) is the DC sinusoidal voltage after rectifier  203 , rms value of line voltage is Vrms(t), so w=2*π*f, f is input voltage frequency, 
 
 Vg ( t )=1.414 *V inrms*|sin(wt)|  (2) 
 
Substitute  Vg ( t ), we get  D ( t )=1/(1+1.414 *V inrms*|sin(wt)|/( n*Vo ))  (3) 
 
         [0028]     From (3), we know duty cycle D(t) an be adjusted according to Vg(t) in order to get constant predetermined value Vo. The frequency also can be adjusted to get constant predetermined value Vo. Pulse Train control or smart skip mode can also be used such as iW2210 or iW1688.  
         [0029]     Dimming is realized by changing resistance of potentiometer R 15 , Naux is turns of auxiliary winding, Ns is turns of secondary winding, according to  FIG. 2 , Vsense=Vo*R 12 *Naux/((R 6 +R 15 +R 12 )*Ns).  
         [0030]     Controller keeps Vsense=Vref. 
 
 Vo=V ref*(R6 +R 15 +R 12) *Ns /( R 12 *N aux) =V ref*(1+( R 6 +R 15) /R 12) *Ns/N aux 
 
         [0031]     Here Vref, Ns, Naux, R 6  and R 12  are all constant values, R 15  value can be changed. Vo will be changed according to R 15  change. So we can change R 15  value to change output voltage value and also lamp brightness.  
         [0032]     In one implementation, power factor correction is realized by adjusting input average current ipr(t)av to be in phase with input voltage Vin(t), power factor is almost 1.  
         [0033]     The power supply can be implemented as the following:  
         [0034]     Filter  202 , 204 , 214  can use common mode filter, differential mode filter, LC, CLC filter; rectifier  203  can use full bridge rectifier, half bridge rectifier, bridge less PFC etc; converter  206  can use any topology as the following: 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 based on Watkins-Johnson, Isolated SEPIC, Isolated Inverse SEPIC, Isolated Cuk, Two-transistor Flyback etc; sampling circuit  207  can use auxiliary winding or optocoupler or sampling voltage from the lamp; feedback and dimming circuit  205  can use voltage divider composed of resistor and potentiometer or voltage divider composed of potentiometer and reference voltage; the control circuit  209  in the power supply control suitable topology to convert sinusoidal voltage after rectified to constant DC voltage, Flyback topology can use iW2202, iW2210, iW1688, UCC28600, LNK362, LNK363, LNK364, TinySwitch, TOPSwitch, PeakSwitch, VIPer series, TEA1506,NCP1055,FSDM311,IRIS series etc IC controller; Buck or Buck-Boost topology can use LNK302,LNK304,LNK305,LNK306 etc IC controller;When using other controller or other topology, circuit maybe different from  FIG. 2 , circuit  209  can use any controller, IC controller or discrete component controller.  
         [0035]     Start circuit  208  can use linear regulator or valley-filled circuit etc; biasing circuit  212  can use auxiliary winding or zener diode; lamp  211  can use any lamp such as Halogen, incandescent, fluorescent etc; input power supply  210  usually comes from 11 volt AC 60 Hz or 220 volt AC 50 Hz. Output protection circuit  200  can have over voltage protection, over current protection, over temperature protection or other protection, it can be realized by other circuit, the power supply can have one or several protection circuits mentioned above.  
         [0036]     Many types of method have been described. But all the changes don&#39;t run away from main idea. That is the power supply that can convert from low frequency line AC voltage to DC constant voltage which has no low frequency component or high frequency component, which reduces eye&#39;s fatigue to minimum level and has no electromagnetic radiation. The invention prevents myopia and protects people&#39;s health to maximum level. The invention can be used as bus AC to DC converter, PFC converter, PFC converter for lighting, computer power supply, TV power supply, monitor power supply, notebook adapter, LCD TV, AC/DC adapter, battery charger, power tool charger, electronic ballast, video game power supply, router power supply, ballast, power tool charge power supply etc.