Abstract:
A sauna that reduces EMI emissions in the sauna room by, in the preferred embodiment, passing the AC current through an EMI filter, converting it to DC current, and passing it through another EMI filter to remove any remaining irregularities.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. 119(a) to Chinese Patent No. 2012 2 0471712.8, filed on Sep. 14, 2012 and issued on Apr. 17, 2013. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to sauna technology, and particularly to low EMI saunas. 
       BACKGROUND 
       [0003]    Various heating devices are used in sauna rooms around the world. Typically, the heaters used for that purpose are mica heaters, carbon fiber heaters, ceramic rods, film heaters, iron heat pipes, light tubes, and so on. These heating appliances usually use 110V-130V or 220V-240V alternating current. Testing shows that this makes these heaters produce electromagnetic radiation at 30 Hz-3 GHz at 10-300 mGs (milligauss). This electromagnetic radiation has undesirable effects on the human body. Neurological effects include headaches, dizziness, pain, fatigue and weakness, insomnia and sleep disturbances, and memory problems; other effects include dry mouth, numbness, and menstrual disturbances in women. In some people, electromagnetic radiation causes increases or decreases in blood pressure, bradycardia or tachycardia, sinus arrythmia, and other cardiovascular effects. It is therefore important to reduce the electromagnetic radiation emitted within a sauna room. 
         [0004]    Some sauna designs already address this issue. Some sauna manufacturers put two carbon fiber heaters back to back with the AC current being of opposite phase, so that the electromagnetic waves cancel each other out and reduce the overall electromagnetic radiation emitted by the sauna. However, this kind of sauna still produces an average electromagnetic radiation value that can be as high as 50 mGauss, or even up to 200 mGauss in some cases. This is partly due to the fact that it is difficult to ensure that the two paired heaters are exactly identical in their electromagnetic radiation emissions. If they are not exactly identical, the electromagnetic fields do not fully cancel each other out. Furthermore, not all sauna rooms use carbon fiber heaters—80% of all existing saunas use other technologies, such as heating pipes, mica heaters, light tubes, and other heating devices that cannot be used in this kind of design. 
         [0005]    A need therefore exists for a low-EMF sauna room that is not limited to carbon fiber heater technology and that does not require precision manufactured heaters. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide a low-EMF sauna room that avoids the detrimental effects of EMF emissions on the human body while providing beneficial heat. 
         [0007]    The present invention comprises an AC input, an AC to DC converter circuit, and an EMI filter circuit. The filtered DC current is then used to power at least one heater in a sauna. 
         [0008]    In another embodiment, the present invention comprises an AC input, an AC to DC converter circuit, and two EMI filter circuits—a first EMI filter circuit connected between the AC input and the AC to DC converter circuit, and a second EMI filter circuit connected between the DC output of the AC to DC converter circuit and at least one heater in a sauna. 
         [0009]    In another embodiment, the AC input, AC to DC converter circuit, and the EMI filter circuit or circuits are located at such a distance from the sauna room that any EMF radiation produced by them is further reduced. 
         [0010]    In another embodiment, the present invention can also comprise additional EMF shielding in the sauna room. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]      FIG. 1  shows a structural diagram of the preferred embodiment of the present invention. AC current comes in through AC connector  100 . The AC connector is connected, through a fuse  110 , to a first-pass EMI filter  120 . The first-pass EMI filter is connected to an AC to DC transformer  130 , which converts the AC power to DC. After the DC conversion, the signal goes through a second-pass EMI filter  140  to filter the EMI from the DC signal. After that, the DC signal is used to power the heater  150 . The AC to DC transformer  130  preferably comprises a heat sink to discharge some of the heat generated by the AC to DC conversion. 
         [0012]    The heater  150  can be any type of heater that can provide therapeutic levels of heat for a sauna and that can be powered by DC current. Such a heater can be a heating pipe, mica heater, light tube, carbon fiber heater, or any other heater known in the art of sauna manufacture. 
         [0013]      FIG. 2  shows an electrical schematic of the preferred embodiment of the present invention. AC current comes in through an AC power supply  100  and goes through the AC input controller. After going through the fuse  110 , the signal goes through the first-pass EMI filter  120 . The first-pass EMI filter  120  preferably comprises capacitors CX 1 , CX 2 , and CX 3 , inductor L 1 , and resistors R 1  and R 2 . The capacitor CX 1  is connected in parallel with resistor R 1  in between the two ends of the power supply. The inductor L 1  input connects to both ends of the capacitor CX 1  and resistor R 1 , and its output connects to the capacitors CX 2  and CX 3  connected in series, and resistor R 2  connected in parallel with the capacitors CX 2  and CX 3 ; the circuit is grounded between capacitors CX 2  and CX 3 . 
         [0014]    The AC/DC transformer  130  is preferably a full-wave rectifier circuit. The input end of the full-wave rectifier circuit connects to the output end of the inductor L 1 , and its output end connects to the second-pass EMI filter  140 . 
         [0015]    The second-pass EMI filter  140  preferably includes at least a filter capacitor and a decoupling capacitor, connected in parallel. The filter capacitor and decoupling capacitor then cross on the output end of the full-wave rectifier circuit. The filter capacitor is a broadband electromagnetic radiation filter, which filters the DC current to smooth it out. The decoupling capacitor is a low-pass power filter. The second-pass EMI filter  140  not only filters out the high-frequency noise of the power grid, but also ensures that the sauna receives pure DC power. This effectively reduces the intensity of the electromagnetic radiation and its hazards to the human body. 
         [0016]    In the preferred embodiment, the second-pass EMI filter comprises filter capacitors C 1 , C 2 , C 3 , C 4 , C 5 , and C 6 , and decoupling capacitor CX 4 . The filter capacitors C 1 -C 6  and decoupling capacitor CX 4  are all connected in parallel, as shown in  FIG. 2 ; this ensures that a smooth DC output is obtained. 
         [0017]    The sauna preferably also includes an AC input controller  200  that sets AC input levels, a DC output controller  210  that sets DC output levels, or both. The AC input controller  200  is connected between the AC power supply and first-pass EMI filter. The DC output controller  210  is connected between the second-pass EMI filter and the heater or heaters. This ensures that both the AC input and the DC output are set to the correct level. 
         [0018]    An overcurrent protection device  110  may be connected between the AC input controller and the EMI filter. Such an overcurrent protection device may be a fuse, a circuit breaker, a temperature sensor, a current limiter, or any other device known in the art to prevent overcurrent. 
         [0019]    The present invention reduces the EMI levels within the sauna from 200 mGauss to less than 2 mGauss. This is a much safer level of EMI exposure for the human body. 
         [0020]    Those of reasonable skill in the art will realize that some changes and alterations can be made to the embodiment described above while still staying within the scope of the invention. For instance, while specific types of EMI filters are described, any other EMI filters that reduce EMF to safe levels for the human body can also be used either as a first-pass or second-pass EMI filter.