Patent Publication Number: US-2003234622-A1

Title: Safety output device of electronic ballast

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a safety output device of electronic ballast.  
       [0003] 2. Description of the Related Art  
       [0004] Electronic ballasts are extensively publicized because they are significantly more energy efficient and less in weight; nevertheless, in the course of utilization, ordinary electronic ballasts yield high output voltage at the output terminals surpassing the safety limit of human body despite the device are under inoperative mode and not loaded with lamp. Particularly during installation of high power detachable electronic energy saving lamp, for example, sizable lamp of E 39 , E 40 , and etc., accident of bodily injury or even death is very easy to be happened especially when working high above ground, and people may fall down because of electric shock. Electric shock will most likely occur while bare hands come into contact with the terminals of lamp socket. Consequently, the present invention innovates a safety output device for the electronic ballasts wherein casualty of electric shock can be virtually eradicated by means of insolating transformer, relay, and induction circuit.  
       SUMMARY OF THE PRESENT INVENTION  
       [0005] An object of the present invention is to provide a safety output device of electronic ballast, which can ensure that two output terminals of the electronic ballast provide a safety voltage limit under the conditions of without loading a lamp to the electronic ballast, or in any circumstances. In accordance with the present invention, this object is accomplished through the following technical solution: the safety output device includes an insolating transformer B, a relay J 1 , a control circuit and an induction circuit controlling the relay J 1 ; the primary winding of the transformer (B) connects to the input terminal of electronic ballast, the secondary winding B- 2  of transformer B supplies low voltage direct current source through the rectification diodes D 1 -D 4 , electrolytic capacitor C 1 , current source input terminal of control circuit connects to anode of low voltage direct current source, output terminal of control circuit connects to the coil of relay J 1 , another side of relay&#39;s J 1  coil connects to cathode of low voltage direct current source; input terminal of control circuit connects to the output terminal G 2  of the device through the normal-open contact J 1 -b of relay J 1 ; the said induction circuit is composed of inductive transformer T 1 , diode D 5  and electrolytic capacitor C 3 , one terminal of primary winding T 1 - 1  of the inductive transformer T 1  connects with the output terminal G 2  of the device through the normal-close contact J 1 -d of relay J 1 , another terminal of primary winding T 1 - 1  connects to one of the output terminal of the electronic ballast; one terminal of secondary winding T 1 - 2  of the inductive transformer T 1  connects to cathode of low voltage direct current source, another terminal thereof connects to the input terminal of control circuit through diode D 5 , electrolytic capacitor C 3  is connected between the input terminal of control circuit and cathode of low voltage direct current source; anode of low voltage direct current source connects to the output terminal G 1  of the device through the normal-open contact J 1 -a of relay J 1 ; normal-close contact J 1 -c of the relay J 1  is connected between the device&#39;s output terminal G 1  of the device and another output terminal of electronic ballast. Two output terminals BL 1 , BL 2  of electronic ballast are connected to the safety output device. While the circuit is not loaded with lamp, two output terminals G 1 , G 2  of safety output device present low voltage which is below the safe voltage of human body. While the circuit is loaded with lamp, due to function alternation of relay J 1 , two output terminals G 1 , G 2  of the safety output device are changed to high frequency high voltage output of electronic ballast in order to enable the lamp loaded circuit to operate normally.  
       [0006] In accordance with the present invention, control circuit which controls relay J 1  composed of transistors Q 1 , Q 2 , resistor R 1  and electrolytic capacitor C 2 . Collector c of transistor Q 1  is connected with anode of low voltage direct current source, and emitter e thereof is the output terminal of the circuit connecting to the coil of relay J 1 . Resistor R 1  is connected to collector c of transistor Q 2 . Node X is connected to base b of transistor Q 1 . Electrolytic capacitor C 2  is connected between the base b of transistor Q 1  and cathode of low voltage direct current source. Emitter e of transistor Q 2  is connected to cathode of low voltage direct current source. The base b thereof becomes the output terminal of the circuit.  
       [0007] In accordance with the present invention the control circuit controlling relay J 1  is composed of comparator IC, resistors R 1 , R 2 , R 3  and electrolytic capacitor C 2 . Anode and cathode of the comparator IC are connected to the anode and cathode of direct current low voltage source respectively. Output terminal of comparator IC is the output terminal of the circuit connects to relay&#39;s J 1  coil. Output terminal of comparator IC is respectively connected to anode and cathode of the direct current low voltage source through resistor R 3 , electrolytic capacitor C 2 . Resistors R 1 , R 4  is in series connected between anode and cathode of direct current low voltage source. Reference voltage input terminal of comparator IC is connected to resistors R 1 , R 4  at node Y; sampling voltage input terminal of comparator IC is the input terminal of the circuit. As a further improvement of the present invention, relay J 2  is in parallel connected between anode and cathode of the low voltage direct current source. Normal-open contact J 2 -a thereof is connected between the normal-close contact J 1 -c of relay J 1  and output terminal G 1  of the device; another normal-open contact J 2 -b of relay J 2  is connected between the normal-close contact J 1 -d of relay J 1  and output terminal G 2  of the device.  
       [0008] As a further improvement of the present invention, stabilivolt DZ or voltage division resistor R 2  is connected between said anode of low voltage direct current source and normal-open contact J 1 -a of relay J 1 .  
       [0009] At the time of inputting alternating current to the electronic ballast while the lamp not to be loaded in the loading circuit, relay J 1  is closed by transistor Q 1 , so that the connection between both output terminals BL 1 , BL 2  of electronic ballast and both output terminals G 1 , G 2  of the device is cut off, in the mean time, anode of low voltage source is safely separated from the output terminal G 1  of the device through the normal-open contact J 1 -a of relay J 1 . The base b of transistor Q 2  adjoins the output terminal G 2  of the device through the other normal-open contact J 1 -b of relay J 1 , whereby making voltage existed between the output terminalG 1  and G 2  to be much less that the safe voltage of human body. At this point, human body does not sense the presence of voltage even if the output terminals G 1 , G 2  are contacted by human body at the same time, thus ensuring the safety of human body. However after the lamp is loaded, safe low voltage source conducts transistor Q 2  through the output terminal G 1 , loading of lamp, output tenninal G 2 , the base b of transistor Q 2 , cuts off transistor Q 1 , releases relay J 1 , thus cutting off the connection of anode of low voltage source and output terminal G 1 , as well as the connection of output terminal G 2  and base b of transistor Q 2 . In the mean time, a resonant circuit is established through the connection of output terminal BL 1  of electronic ballast, output terminal G 1 , loading of lamp, output terminal G 2  and another output terminal BL 2  of electronic ballast, whereby keeping the electronic ballast and lamp loaded circuit in normal operation. Simultaneously, induction circuit provides induction direct current voltage for the base b of transistor Q 2 , in order to make the transistor Q 2  under the state of continuous conduction. Hence, during no load of lamp, or in any circumstances, both output terminals of electronic ballast do not supply voltage over the safe voltage of human body, while when loaded with lamp, it is able to ensure the loading of lamp under operation condition, thus accomplishing safety usage of energy saving electronics lighting, and making sure of safety of human body. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] Some exemplary embodiments of the present invention will be in detail described below in connection with the accompanying drawings, in which:  
     [0011]FIG. 1 is a schematic diagram of electric circuit showing the first example of the present invention.  
     [0012]FIG. 2 is a schematic diagram of electric circuit showing the second example of the present invention.  
     [0013]FIG. 3 is a schematic diagram of electric circuit showing the third example of the present invention.  
     [0014]FIG. 4 is a schematic diagram of electric circuit showing the fourth example of the present invention.  
     [0015]FIG. 5 is a schematic diagram of electric circuit showing the fifth example of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0016] As shown in FIG. 1, secondary B 1 - 2  of isolating transformer B is connected to anode of direct current low voltage source through rectification diodes D 1 -D 4 , electrolytic capacitor C 1  in order for processing rectification filtration, and collector c of transistor Q 1 . Emitter e connects to one terminal of relay&#39;s J 1  coil, and another terminal thereof connects to cathode of direct current low voltage source. Resistor R 1  connects to collector c of transistor Q 2  via node X and to base b of transistor Q 1 . Electrolytic capacitor C 2  is connected between the base b of transistor Q 1  and cathode of direct current low voltage source, in order for causing the delay-action. Direct current low voltage source connects to the output terminal G 1  of the device through anode of stabilivolt DZ, and normal-open contact J 1 -a of relay J 1 , and output terminal BL 1  of electronic ballast connects to the output terminal G 1  of the device through normal-close contact J 1 -c of relay. Base b of transistor Q 2  connects to output terminal G 2  of the device through normal-open contact J 1 -b of relay J 1 . Another terminal BL 2  of electronic ballast connects to another output terminal G 2  of the device through the primary T 1 - 1  of inductive transformer T 1 , and the normal-close contact J 1 -d of relay J 1 . One terminal of secondary T 1 - 2  of inductive transformer T 1  connects to cathode of direct current low voltage source, and another one connects to the base b of transistor Q 2  through diode D 5 . Electrolytic capacitor C 3  is connected between the base b of transistor Q 2  and cathode of direct current low voltage source, in order for causing the delay-action.  
     [0017] When alternating-current power supply is applied to primary coil B- 1  of isolating transformer B, secondary coil of isolating transformer B outputs low alternating current voltage, whereby building up direct current low voltage source which is below the safe voltage limit of human body through rectification diodes D 1 -D 4  and electrolytic capacitor C 1 . At this point, if the circuit has no load of lamp, both of the output terminals G 1 , G 2  of the device are under the state of open circuit, transistor Q 1  is conducted by inputting high potential through resistor R 1 , and relay J 1  is closed. The normal-close contact J 1 -c of relay J 1  cuts off the connection of output terminal BL 1  of electronic ballast and output terminal G 1  of the installation. The other normal-close contact J 1 -d of relay J 1  cuts off the connection of another output terminal BL 2  of electronic ballast and another output terminal G 2  of the device. Anode of direct current low voltage source connects to the base b of the transistor Q 2  through the normal-open contact J 1 -b of the already closed relay J 1 . Hence, direct current source exists between both of the output terminal G 1 , G 2  of the device to be much less than the safe voltage of human body, even if hands are directly in contact with both of the output terminals G 1 , G 2 , feeling of electric shock does not exist, thus ensuring safe usage of electronic ballast under any circumstance.  
     [0018] Having been loaded with lamp, a high potential at the base b of transistor Q 2  is introduced by anode of direct current low voltage source through stabilivolt DZ, normal-open contact J 1 -a of relay J 1 , output terminal G 1  of the device, lamp filament M 2 , preheat circuit, lamp filament M 1 , another output terminal G 2  of the device, normal-open contact J 1 -b of relay J 1 . So transistor Q 2  is conducted, and the base of transistor Q 1  is changed from high potential to low potential. Transistor Q 1  is cut off, and relay J 1  is released. In this instance, a resonant circuit is established through the connection of output terminal BL 1  of electronic ballast, the normal-close contact J 1 -c of relay J 1 , output terminal G 1  of the device, lamp filament M 2 , resonant capacitor C 4 , lamp filament M 1 , output terminal G 2  of the device, normal-close contact J 1 -d of relay J 1 , primary T 1 - 1  of inductive transformer T 1 , and another output terminal BL 2  of electronic ballast, whereby keeping lamp loading circuit in normal operation. Due to formation of resonance of electronic ballast, high frequency induction voltage is built up at the secondary T 1 - 2  of inductive transformer T 1 , while the base b of transistor Q 2  is continuously kept at high potential through diode D 5  and electrolytic capacitor C 3  in order for continuously keeping the transistor Q 2  in the state of conduction, thus ensuring electronic ballast and loaded circuit under normal condition.  
     [0019] As shown in FIG. 2, separated transistors Q 1 , Q 2  are replaced by comparator IC. Anode and cathode of comparator IC are connected to anode and cathode of direct current low voltage source respectively. Resistor R 3  and relay&#39;s J 1  coil are first in series and then in parallel connected between the anode and cathode of direct current low voltage source. The reference input of comparator IC connects to the series connection node Y of resistors R 1 , R 4 , and output of the induction circuit connects to the voltage sampling input terminal of comparator IC. When the power supply source is connected without the lamp in the loading circuit, primary of inductive transformer T 1  has no current flowing through, and induction circuit has no output voltage. In this instance, input of reference voltage of comparator IC is higher than sampling voltage, so that output voltage is in the state of high potential, and relay J 1  is closed. After the lamp is plugged into the loading circuit, the sampling voltage is higher than the reference due to that anode of direct current low voltage source goes through stabilivolt diode D 2 , normal-open contact J 1 -a of relay J 1 , output terminal G 1  of the device, lamp filament M 1 , output terminal G 2 , normal-open contact J 1 -b of relay J 1  to the voltage sampling input terminal of comparator IC. As a result, output voltage of comparator IC is changed from high potential to low potential, and relay J 1  is released. Thus, the electronic ballast is in normal operation through the connection of output terminal BL 1  of electronic ballast, the normal-close contact J 1 -c of relay J 1 , output terminal G 1  of the device, lamp filament M 2 , resonant capacitor C 4 , lamp filament M 1 , output terminal G 2  of the device, normal-close contact J 1 -d of relay J 1 , primary T 1 - 1  of inductive transformer T 1 , and another output terminal BL 2  of electronic ballast. In the mean time, due to current flowing through the primary T 1 - 1  of inductive transformer T 1 , induction circuit produces voltage output, so that the input of voltage sampling of integrated circuit is still higher than the reference voltage, and output voltage of comparator IC keeps at low potential. Under this circumstance relay cannot be closed, thus ensuring electronic ballast under normal operation.  
     [0020] As shown in FIG. 3, coil of relay J 2  is in parallel connected between the anode and cathode of low voltage direct current source, the normal-open contact J 2 -a thereof is connected between the normal-close contact J 1 -c of relay J 1  and output terminal G 1  of the device, and the other normal-open contact J 2 -b of relay J 2  is connected between the normal-close contact J 1 -d of relay J 1  and output terminal G 2  of the device. The function thereof is that while power source is not available, connecting between the output terminals BL 1 , BL 2  of electronic ballast and output terminals G 1 , G 2  of the device is cut off by both normal-open contacts J 2 -a, J 2 -b of relay J 2 , thus preventing connection from neutral wire to the switch. When live wire connects to electronic ballast directly, output terminals G 1 , G 2  of the device still have voltage higher than the safe voltage of human body.  
     [0021] As shown in FIG. 4, primary T 1 - 1  of inductive transformer T 1  is connected between the output terminal BL 1  of electronic ballast and the normal-close contact J 1 -c of relay J 1 . As shown in FIG. 5, stabilivolt DZ is replaced by voltage-dividing resistor R 2 . The principle of operation of the embodiments shown in FIG. 4 and  5  is same as that shown in FIG. 1.