Patent Document

CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to International Application No. PCT/CN2009/073722, filed on Sep. 3, 2009, which claims priority to Chinese Patent Application No. 200820147332.2, filed on Sep. 9, 2008. 
     FIELD OF THE INVENTION 
     The present invention relates to electronic circuits field, more particular to a reversal connection protecting circuit. 
     BACKGROUND OF THE INVENTION 
     Continuous power supplying is very important to many electronic equipments, especially to communication systems, internet servers etc. When the unexpected event results in power supply interruption, the backup power has to be activated by protecting circuit. Therefore, the power supplying for protecting circuit is especially important. At present, the combination of transient voltage suppressor (TVS) and fuse is used for protecting the circuit when the power supply is reversed. But the fuse is broken after once protection, and it must be replaced for using next time. The maintenance is inconvenience. 
     SUMMARY OF THE INVENTION 
     In viewing thereof, the present invention is directed to solve at least one of the problems existing in the prior art. Therefore, a reversal connection protecting circuit is needed, which may overcome the inconvenience brought by substituting a fuse that is melted in a protecting circuit under the condition that the power supply of the protecting circuit is reversely connected in prior art. 
     According to an embodiment of the invention, a reversal connection protecting circuit is provided, comprising: a power supply interface, which may comprise a first positive terminal and a first negative terminal; a secondary battery, which may comprise a second positive terminal and a second negative terminal; a reversal connection driving unit coupled to the power supply interface, which may be configured to output driving signals while the first positive terminal and the first negative terminal may be reversed; and a power switching unit coupled to the reversal connection driving unit, which may be configured to switch the secondary battery to supply power according to the driving signal from the reversal connection driving unit. 
     According to an embodiment of the invention, the reversal connection driving unit may comprise a first current-limiting resistor and a protecting diode. One end of the first current-limiting resistor may be coupled to either of the first negative terminal and the first positive terminal, and the other end of the first current-limiting resistor may be coupled to the power switching unit. A cathode of the protecting diode may be coupled to the first positive terminal or the first negative terminal, and an anode of the protecting diode may be coupled to the power switching unit. 
     According to another embodiment of the invention, the power switching unit may comprise: a MOS transistor, a drain of which is coupled to the first positive terminal, and a source of which is coupled to the second positive terminal; a first divider resistor, which is connected between a gate of the MOS transistor and the source of the MOS transistor in parallel; a second divider resistor, with one end being coupled to the source of the MOS transistor; and a first photoelectric coupling unit comprising a first light emitting diode and a first phototransistor. An anode of the first light emitting diode is coupled to the first current-limiting resistor, a cathode of the first light emitting diode is coupled to the anode of the protecting diode, a collector of the first phototransistor is coupled to the second divider resistor, and an emitter of the first phototransistor is coupled to the second negative terminal. 
     According to some embodiments of the invention, the reversal connection protecting circuit further comprises an anti-reversal unit coupled to the power switching unit. In these embodiments, the anti-reversal unit comprises at least one of a first anti-reversal part and a second anti-reversal part. 
     According to an embodiment of the invention, the first anti-reversal part comprises a first diode. An anode of the first diode is coupled to the first positive, and a cathode of the first diode is coupled to the drain of the MOS transistor. 
     According to another embodiment of the invention, the second anti-reversal part comprises a second diode. An anode of the second diode is coupled to the second positive terminal, and a cathode of the second diode is coupled to the source of the MOS transistor. 
     According to some embodiments of the invention, the reversal connection protecting circuit further comprises a processing unit coupled to the reversal connection driving unit for processing the driving signals from the reversal connection driving unit; and a warning interface coupled to the processing unit for transferring the processed signals from the processing unit to the field monitoring device or remote monitoring device. 
     According to an embodiment of the invention, the processing unit comprises: a second photoelectric coupling unit comprising a second light emitting diode and a second phototransistor, a second current-limiting resistor, and a MCU (microprocessor control unit). An anode of the second light emitting diode is coupled to the first current-limiting resistor, a cathode of the second light emitting diode is coupled to the anode of the protecting diode. An emitter of the second phototransistor is grounded. An end of the second current-limiting resistor is coupled to the collector of the second phototransistor, and the other end of the same is coupled to the first positive terminal. A detecting pin of the MCU is coupled to the collector of the second phototransistor, a supply pin of the MCU is coupled to the first positive terminal, and a grounding pin of the MCU is grounded. In another embodiment, the processing unit further comprises a depressing voltage module coupled between the first positive terminal and the second current-limiting resistor. 
     According to an embodiment of the invention, the warning interface comprises a bus-line. An input interface of the bus-line is coupled to the output end of the processing unit, and the output interface of the bus-line is coupled to a field monitoring device or a remote monitoring device. 
     Additional aspects and advantages of the embodiments of present invention will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantages of the invention will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which: 
         FIG. 1  shows a block diagram of a reversal connection protecting circuit according to an embodiment of the present invention; 
         FIG. 2  shows a block diagram of a reversal connection protecting circuit according to another embodiment of the present invention; 
         FIG. 3  shows a block diagram of a reversal connection protecting circuit according to yet another embodiment of the present invention; and 
         FIG. 4  shows a detailed circuit diagram of the reversal connection protecting circuit in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will be made in detail to embodiments of the present invention. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present invention. The embodiments shall not be construed to limit the present invention. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions. 
       FIG. 1  illustrates a reversal connection protecting circuit according to one embodiment of the invention, the circuit comprises: a power supply interface  1100 , a secondary battery  1200 , a power switching unit  1400  coupled to the power supply interface  1100  and the secondary battery  1200 , and a reversal connection driving unit  1500  coupled to the power switching unit  1400 . 
     When the interface  1100  is reversal connected, the unit  1500  may output driving signals to unit  1400 ; and then the unit  1400  can switch the battery  1200  to supply power for the reversal connection protecting circuit and other protecting circuits (not shown) according to the driving signals. 
     As shown in  FIG. 2 , according to another embodiment of the invention, the reversal connection protecting circuit further comprises an anti-reversal unit  1300  coupled to the power switching unit  1400 . 
     The unit  1300  can avoid the interaction between the interface  1100  and the battery  1200 , if one of them is reversal connected. 
     As shown in  FIG. 3 , according to yet another embodiment of the invention, the reversal connection protecting circuit further comprises a processing unit  1600  and a warning interface  1700 . 
     The unit  1600  is coupled to the unit  1500  for processing the driving signals from the unit  1500 . The interface  1700  is coupled to the unit  1600  for transferring the processed signals from unit  1600  to a field monitoring device or a remote monitoring device (not shown). When the interface  1100  was reversely connected, the abnormal condition may be shown and be corrected promptly. 
       FIG. 4  illustrates a circuit diagram of the reversal connection protecting circuit according to one embodiment of the present invention. As shown, the interface  1100  includes a first positive terminal P+ and a first negative terminal P−. The terminal P+ and P− provide interface for external power. The external power can supply power for the reversal connection protecting circuit and other protecting circuits (not shown). The battery  1200  includes n (n≧1) single batteries. The single batteries are series connected. The positive of battery  1  provides a second positive terminal B+, the negative of battery n provides a second negative terminal B−. The unit  1300  includes a first diode D 10  and a second diode D 20 . The terminal P+ is coupled to the anode of the diode D 10 , the terminal B+ is coupled to the anode of the diode D 20 . The unit  1400  comprises a MOS transistor, the cathode of the diode D 10  is coupled to the drain of the MOS transistor, and the cathode of the diode D 20  is coupled to the source of the MOS transistor. In some embodiments, diode  10  or diode  20  can be removed, where terminal P+ is coupled to the drain of the MOS transistor, or terminal B+ is coupled to the source of the MOS transistor. 
     As shown in  FIG. 4 , the unit  1400  further comprises a first divider resistor R 10 , a second divider resistor R 20 , and a first photoelectric coupling unit U 10 . The unit U 10  may comprise a first phototransistor a 10  and a first light emitting diode b 10 . One end of the resistor R 10  is coupled to the source of the MOS transistor, the other end of the resistor R 10  is coupled to the gate of the MOS transistor and one end of the resistor R 20 . The other end of the resistor R 20  is coupled to the collector of the phototransistor a 10 . The emitter of the phototransistor a 10  is coupled to the terminal B−. 
     As shown in  FIG. 4 , the unit  1500  comprises a first current-limiting resistor R 30 , and a protecting diode D 30 . The anode of the diode b 10  is coupled to one end of the resistor R 30 . The cathode of the diode b 10  is coupled to the anode of the diode D 30 . Under normal condition (no reversal connected), the other end of the resistor R 30  is coupled to the terminal P−, and the cathode of the diode D 30  is coupled to the terminal P+. 
     The Unit  1600  and the interface  1700  are used to achieve early warning. As shown in  FIG. 4 , the unit  1600  comprises a second photoelectric U 20  including a second phototransistor a 20  and a second light emitting diode b 20 , a second current-limiting resistor R 40 , a MCU (Microprocessor Control Unit), and a depressing voltage module  1610 . The interface  1700  comprises a bus-line  1710 . 
     The diode b 20  is connected to the diode b 10  in parallel, the anode of the diode b 20  is coupled to the anode of the diode b 10 , and the cathode of the diode b 20  is coupled to the cathode of the diode b 10 . The collector of the phototransistor a 20  is coupled to one end of the resistor R 40  and the detecting pin of the MCU. The emitter of the phototransistor a 20  is coupled to the grounding pin of the MCU, and grounded. The other end of the resistor R 40  and the supply pin of the MCU are coupled to the cathode of the diode D 10  via the module  1610 . The module  1610  is used to depress voltage to supply power for the MCU. In some embodiments, the module  1610  can be removed. The output pins of the MCU are coupled to the input interface of the bus-line  1710 , and the output interface of the bus-line  1710  is coupled to a field monitoring device or a remote monitoring device (not shown). In some embodiments, the bus-line  1710  can be any type of bus-lines. According to an embodiment of the invention, the bus-line  1710  can be CAN-bus-line. 
     The following provides details protecting principle of the reversal connection protecting circuit embodiments of the present invention. 
     Under normal conditions, the terminal P+ is coupled to the anode of the diode D 10  and the cathode of the diode D 30 . Then the diode D 10  is conducted, and the diode D 30  is not conducted, the terminal P+ supplies power for the reversal connection protecting circuit and other protecting circuits. If the battery  1200  is reversed, the terminal B− is coupled to the anode of the diode D 20 , and the diode D 20  is not conducted, it can avoid the conduction between the terminal P+ and the terminal B−, and avoid damage to the battery  1200 . 
     When the interface  1100  is reversed, the terminal P− is coupled to the anode of the diode D 10 , and the diode D 10  is not conducted, it can avoid the conduction between the terminal B+ and the terminal P−, and prevents the interface  1100  from being damaged. At the same time, the terminal P+ is coupled to the resistor R 30 , the terminal P− is coupled to the cathode of the diode D 30 , and then the unit U 10  is conducted. Furthermore, the terminal B+, the diode D 20 , the resistor R 10 , the resistor R 20 , the unit U 10  and the terminal B− are conducted. The resistances of the resistor R 10  and the resistor R 20  can be selected to achieve the partial voltage of the resistor R 10  equal to the threshold voltage of the gate and drain of the MOS transistor. Then the drain and source of the MOS transistor are conducted, the terminal B+ is coupled to the power supply loop via the MOS transistor, and the battery  1200  supplies power for the reversal connection protecting circuit and other protecting circuits. 
     In addition, the unit U 20  is conducted at the same time, and the voltage of the collector of the phototransistor a 20  is changed from high-voltage to low-voltage. The MCU can receive and process the changed signal. Then the processed signal is transferred to the field monitoring device or the remote monitoring device via the bus-line  1710 . 
     According to some embodiments of the present invention, the reversal connection protecting circuit can switch the secondary battery to supply power for the reversal connection protecting circuit and other protecting circuits when the power supply interface is reversed. There is no destructive action in the protecting process, and it needs no replacement of any part, so it is convenient for use. The anti-reversal unit can prevent the interaction between the power supply interface and secondary battery if one of them is reversely connected. Furthermore, the abnormal condition can be shown and be alarmed via the warning interface and the monitoring device, and then the technicians can correct it promptly. 
     Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications may be made in the embodiments without departing from spirit and principles of the invention. Such changes, alternatives, and modifications all fall into the scope of the claims and their equivalents.

Technology Category: 5