Patent Publication Number: US-2005142508-A1

Title: Automatic power-off control circuit for essential oil burner

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a control circuit for essential oil burner and, more particularly, to an automatic power-off control circuit for essential oil burner.  
      2. Description of the Prior Art  
      As more and more people are concerned with improving the quality of life in the recent years, many novel equipments and facilities are manufactured to meet the growing need for those seeking quality lifestyle. The essential oil burner is one of the items that have gained much popularity due to its ease of use and reputable effects.  
      Conventional essential oil burners provide different designs to meet different purposes. For example, Taiwan patent publication No. 437,917 disclosed a design of essential oil burner whose burning base is placed on a container with a heating wick in the middle. The other end of the heating wick is soaked in the essential oil in the container. The burning base can be covered with an outer cap. The top rink of the burning base includes a net cover, which is padded with a specially treated platinized asbestos layer. The layer is directly in contact with the heating wick, and is air-permeable. Taiwan patent publication No. 474,182 disclosed a new structure of an essential oil burner, including a main body, which is single-mold of a cap base and a container. The cap base is a hollow case, and inside the cap base is a heating device. The upper part of the cap base is to support the open container, which is for containing water and essential oil. An AC power source is rectified and voltage lowered to generate a DC voltage, which is passed through a regulator for filtering and regulation. The final DC current is to supply the microprocessor and the impedance detection components of the heating device. The microprocessor is preset with a range of impedance resulted from contacting water. The impedance detection component detects the impedance with or without contacting water, which determines whether the microprocessor issues control signal to activate or deactivate the heating device. The impedance detection component is embedded in the bottom of the container wall of the main body in order to detect the presence of the water in the container for activating or deactivating the heating device.  
     SUMMARY OF THE INVENTION  
      In the conventional essential oil burner design, the safety and the convenience of the circuit is not well considered. For example, it is a safety hazard if the user forgets to turns off the power when the essential oil in the essential oil burner is used up.  
      Because of the shortcomings in the conventional designs, the first object of the present invention is to provide an essential oil burner with an automatic power-off control circuit. With the automatic power-off control circuit, the safety and the convenience of using essential oil burners can be improved.  
      Another object of the present invention is to provide an automatic power-off control circuit for an essential oil burner. When the users use an essential oil burner, they only need to press a simple power-on switch to activate the essential oil burner. When the essential oil is used up, the control circuit can automatic detects its state and cut off the power supply.  
      Yet another object of the present invention is to provide an automatic power-off control circuit with a self-holding circuit for an essential oil burner. When the users press the power-on switch to activate the essential oil burner, the control circuit can keep supplying power to the heating device of the essential oil burner in a self-holding manner. This improves the operational simplicity.  
      To solve the aforementioned problems and achieve the objects, the present invention of a control circuit includes a power-on switch, an AC/DC transformer, a signal detection circuit, a signal amplifier, and a heating device. The power-on switch is connected in series between an AC power source and the AC/DC transformer. The power-on switch is connected in parallel with a power self-holding circuit so that the AC power supply keeps supplying power to the heating device to heat the essential oil in the bowl when the switch is pressed and the signal detection circuit detects the presence of essential oil in the bowl of the essential oil burner. When the signal detection circuit detects that essential oil is used up in the bowl, the self-holding circuit relieves its self-holding state and cuts off the supplying of the power to the heating device.  
      For the preferred embodiment of the present invention, the control circuit can further include a heating indicator to indicate the heating state of the heating device and a night light circuit so that the essential oil burner can also serve as a night light.  
      Through the technologies adopted in the present invention, the essential oil burner can detect that the essential oil in the burner is used up and automatically cut off the power when it is in use. This greatly improves the safety of essential oil burner usage. Furthermore, the self-holding circuit of the control circuit of the present invention allows the user only need to press the power-on switch to activate the essential oil burner. The self-holding feature of the control circuit can keep the power supplied to the heating device. This improves the operational convenience.  
      These and other objects, features and advantages of the invention will be apparent to those skilled in the art, from a reading of the following brief description of the drawings, the detailed description of the preferred embodiment, and the appended claims.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a schematic side of an embodiment of the present invention;  
       FIG. 2  shows a block diagram of the control circuit of the present invention; and  
       FIG. 3  shows a detailed control circuit diagram of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  shows a schematic side view of the present invention of an essential oil burner with an automatic power-off control circuit. An essential oil burner  100  includes a main body  101  and an essential oil bowl  102  for placing essential oil of an appropriate quantity. The essential oil bowl  102  includes a pair of detection electrodes p 1 , p 2  at appropriate locations for detecting the presence of essential oil in essential oil bowl  102 . The signal indicating the presence of the essential oil detected by detection electrodes p 1 , p 2  is transmitted through a pair of signal lines  103 ,  104  to a circuit board  105 , which is appropriately located inside main body  101  of essential oil burner  100 .  
       FIG. 2  shows a functional block diagram of the control circuit of the present invention. The block diagram includes a power-on switch  1 , an AC/DC transformer  2 , a signal detection circuit  3 , a signal amplifier  4 , a power self-holding circuit  5 , a heating device  6 , a heating indicator  7 , and a night light circuit  8 .  
       FIG. 3  shows a detailed control circuit of the present invention. The power-on switch  1  is connected between an AC power source ACV and the AC/DC transformer  2 . The AC/DC transformer  2  can transform the AC current from AC power source ACV into a DC current with an appropriate voltage Vcc. The AC/DC transformer  2  includes a transformer  21 , four diodes  22 ,  23 ,  24 ,  25  forming a bridge-type full-wave rectifier, a capacitor  26 , and a power regulator  27 .  
      the signal detection circuit  3  is connected to the detection electrodes p 1 , p 2 , which are located appropriately on the essential oil bowl  102  of the essential oil burner  100 . The signal detection circuit  3  includes a resistor  31  and a capacitor  32 . The signal generated by the signal detection circuit  3  is amplified by the signal amplifier  4 . The signal amplifier  4  includes a diode  41  and a transistor  42  as the amplification device.  
      Both ends of the power-on switch  1  are connected, in parallel, to the power self-holding circuit  5 . When the power-on switch  1  is pressed and the signal detection circuit  3  detects the presence of essential oil in the bowl  102 , the power self-holding circuit  5  allows AC power source ACV to supply the power to the heating device  6  in order to heat the essential oil in the bowl  102 . When the signal detection circuit  3  detects that the essential oil in the bowl  102  is used up, the power self-holding circuit  5  relieves its self-holding state and cuts off the power supply to the heating device  6 .  
      The power self-holding circuit  5  includes a relay whose coil  51  is connected to the output end of the signal detection circuit  3 , and the both ends of the normally open (N/O) contact  52  is connected in parallel with both ends of the power-on switch  1 . When the power-on switch  1  is pressed and signal detection circuit  3  detects the presence of essential oil in the bowl  102 , a control signal is generated to excite the coil  51  of the relay, and N/O contact  52  is closed.  
      The present invention of essential oil burner with an automatic power-off control circuit further includes a night light circuit  7 , including a light sensitive resistor  71 , an LED indicator  72 , and relevant electronic elements. The light sensitive resistor  71  and the indicator  72  are connected in series and the connected in parallel to the heating device  6 . When the light reaches a predefined lower level (as in the evening), the resistance of the light sensitive resistor  71  changes and the LED indicator  72  lights up.  
      The present invention of essential oil burner with an automatic power-off control circuit further includes a heating indicator  8 , including a resistor  81  connected in series with an LED indicator  82 . The heating indicator  8  is connected to DC voltage Vcc generated by the AC/DC transformer  2 , so that it indicates the heating status when the power self-holding circuit  5  is in the self-holding state and power is supplied to the heating device  6 .  
      From the aforementioned embodiment, it is obvious that the present invention of an essential oil burner with an automatic power-off control circuit allows the essential oil burner to automatically power off when it detects that the essential oil in the bowl is used up. It improves the safety of the essential oil burner. Further more, the self-holding feature of the present invention allows the user to only press the power-on switch to activate the burner, and the control circuit will continue the power supply to the heating device with a self-holding feature. Hence, it improves the operational convenience and provides highly usable value to the industry.  
      While the invention has been described in connection with what is presently considered to the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangement included within the spirit and scope of the appended claims.