Patent Publication Number: US-8994332-B2

Title: Battery heating circuits and methods using voltage inversion based on predetermined conditions

Description:
1. CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is continuation-in-part of U.S. patent application Ser. No. 13/187,279, which claims priority to Chinese Patent Application No. 201010245288.0, filed Jul. 30, 2010, Chinese Patent Application No. 201010274785.3, filed Aug. 30, 2010, and Chinese Patent Application No. 201110137264.8, filed May 23, 2011, all these four applications being incorporated by reference herein for all purposes. 
     Additionally, this application is related to International Application Publication No. WO2010/145439A1 and Chinese Application Publication No. CN102055042A, both these two applications being incorporated by reference herein for all purposes. 
    
    
     2. BACKGROUND OF THE INVENTION 
     The present invention pertains to electric and electronic field, in particular related to a battery heating circuit. 
     Considering cars need to run under complex road conditions and environmental conditions or some electronic devices are used under harsh environmental conditions, the battery, which serves as the power supply unit for electric-motor cars or electronic devices, need to be adaptive to these complex conditions. In addition, besides these conditions, the service life and charge/discharge cycle performance of the battery need to be taken into consideration; especially, when electric-motor cars or electronic devices are used in low temperature environments, the battery needs to have outstanding low-temperature charge/discharge performance and higher input/output power performance. 
     Usually, under low temperature conditions, the resistance of the battery will increase, and so will the polarization; therefore, the capacity of the battery will be reduced. 
     To keep the capacity of the battery and improve the charge/discharge performance of the battery under low temperature conditions, some embodiments of the present invention provide a battery heating circuit. 
     3. BRIEF SUMMARY OF THE INVENTION 
     The objective of certain embodiments of the present invention is to provide a battery heating circuit, in order to solve the problem of decreased capacity of the battery caused by increased resistance and polarization of the battery under low temperature conditions. 
     The battery heating circuit provided in certain embodiments of the present invention comprises a switch unit, a switching control module, a damping component, an energy storage circuit, and an energy superposition unit; the energy storage circuit is configured to connected with the battery to form a loop, and comprises a current storage component and a charge storage component; the damping component R 1 , the switch unit, the current storage component L 1 , and the charge storage component C 1  are connected in series; the switching control module is connected with the switch unit, and is configured to control ON/OFF of the switch unit, so as to control the energy that flows between the battery and the energy storage circuit; the energy superposition unit is connected with the energy storage circuit, and configured to superpose the energy in the energy storage circuit with the energy in the battery after the switch unit switches on and then switches off; the switching control module is configured to control the switch unit to switch off after the first positive half cycle of current that flows through the switch unit after the switch unit switches on, and the voltage that is applied to the switch unit at the time the switch unit switches off is lower than the voltage rating of the switch unit. 
     The heating circuit provided in certain embodiments of the present invention can improve the charge/discharge performance of the battery; in addition, since the energy storage circuit is connected with the battery in series in the heating circuit, when the battery is heated, safety problem related to failures and short circuit caused by failures of the switch unit can be avoided due to the existence of the charge storage component connected in series, and therefore the battery can be protected effectively according to some embodiments. 
     In addition, owing to the existence of the current storage component in the loop, switching off the switch unit when there is a current flowing in the loop may cause the current to drop abruptly to zero, and therefore induce high voltage on the current storage component in the loop, which may cause damage to other circuit components in the loop (e.g., the switch unit). In the heating circuit provided according to certain embodiments of the present invention, since the switching-off timing of the switch unit is chosen according to the voltage rating of the switch unit, the high induced voltage on the current storage component in the loop and the resultant damage to the switch unit can be prevented, and therefore the heating circuit is safer, and the adverse effect to the entire circuit can be reduced according to some embodiments. 
     In addition, an energy superposition unit is provided in the heating circuit in certain embodiments of the present invention, and the energy superposition unit can superpose the energy in the energy storage circuit with the energy in the battery after the switch unit switches on and then switches off; thus, when the switch unit is controlled to switch on at the next time, the discharging current in the heating loop is increased, and therefore the working efficiency of the heating circuit is improved according to some embodiments. 
     Other characteristics and advantages of the present invention will be further described in detail in the following section for embodiments. 
    
    
     
       4. BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, as a part of this description, are provided here to facilitate further understanding of the present invention, and are used in conjunction with the following embodiments to explain the present invention, but shall not be comprehended as constituting any limitation on the present invention. In the figures: 
         FIG. 1  is a schematic diagram showing a battery heating circuit according to one embodiment of the present invention; 
         FIG. 2  is a schematic diagram showing the switch unit as part of the battery heating circuit as shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 3  is a schematic diagram showing the switch unit as part of the battery heating circuit as shown in  FIG. 1  according to another embodiment of the present invention; 
         FIG. 4  is a schematic diagram showing the switch unit as part of the battery heating circuit as shown in  FIG. 1  according to yet another embodiment of the present invention; 
         FIG. 5  is a schematic diagram showing the switch unit as part of the battery heating circuit as shown in  FIG. 1  according to yet another embodiment of the present invention; 
         FIG. 6  is a schematic diagram showing the switch unit as part of the battery heating circuit as shown in  FIG. 1  according to yet another embodiment of the present invention; 
         FIG. 7  is a schematic diagram showing a battery heating circuit according to another embodiment of the present invention; 
         FIG. 8  is a schematic diagram showing the freewheeling circuit as part of the battery heating circuit as shown in  FIG. 7  according to one embodiment of the present invention; 
         FIG. 9  is a schematic diagram showing the freewheeling circuit as part of the battery heating circuit as shown in  FIG. 7  according to another embodiment of the present invention; 
         FIG. 10  is a schematic diagram showing the energy superposition unit as part of the battery heating circuit as shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 11  is a schematic diagram showing the polarity inversion unit as shown in  FIG. 10  as part of the battery heating circuit as shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 12  is a schematic diagram showing the polarity inversion unit as shown in  FIG. 10  as part of the battery heating circuit as shown in  FIG. 1  according to another embodiment of the present invention; 
         FIG. 13  is a schematic diagram showing the polarity inversion unit as shown in  FIG. 10  as part of the battery heating circuit as shown in  FIG. 1  according to yet another embodiment of the present invention; 
         FIG. 14  is a schematic diagram showing the first DC-DC module as shown in  FIG. 13  as part of the battery heating circuit as shown in  FIG. 1  according to one embodiment of the present invention; 
         FIG. 15  is a schematic diagram showing a battery heating circuit according to yet another embodiment of the present invention; 
         FIG. 16  is a schematic diagram showing the energy consumption unit as part of the battery heating circuit as shown in  FIG. 15  according to one embodiment of the present invention; 
         FIG. 17  is a schematic diagram showing a battery heating circuit according to yet another embodiment of the present invention; 
         FIG. 18  is a timing diagram of waveforms of the battery heating circuit as shown in  FIG. 17  according to one embodiment of the present invention; 
         FIG. 19  is a schematic diagram showing a battery heating circuit according to yet another embodiment of the present invention; 
         FIG. 20  is a timing diagram of waveforms of the battery heating circuit as shown in  FIG. 19  according to one embodiment of the present invention; 
         FIG. 21  is a schematic diagram showing a battery heating circuit according to yet another embodiment of the present invention; 
         FIG. 22  is a timing diagram of waveforms of the battery heating circuit as shown in  FIG. 21  according to one embodiment of the present invention. 
     
    
    
     5. DETAILED DESCRIPTION OF THE INVENTION 
     Certain embodiments of the present invention are described in detail below, with reference to the accompanying drawings. It should be appreciated that the embodiments described here are only provided to describe and explain the present invention, but shall not be deemed as constituting any limitation on the present invention. 
     It is noted that, unless otherwise specified, when mentioned hereafter in this description, the term “switching control module” may refer to any controller that can output control commands (e.g., pulse waveforms) under preset conditions or at preset times and thereby control the switch unit connected to it to switch on or switch off accordingly, according to some embodiments. For example, the switching control module can be a PLC. Unless otherwise specified, when mentioned hereafter in this description, the term “switch” may refer to a switch that enables ON/OFF control by using electrical signals or enables ON/OFF control on the basis of the characteristics of the component according to certain embodiments. For example, the switch can be either a one-way switch (e.g., a switch composed of a two-way switch and a diode connected in series, which can be conductive in one direction) or a two-way switch (e.g., a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or an IGBT with an anti-parallel freewheeling diode). Unless otherwise specified, when mentioned hereafter in this description, the term “two-way switch” may refer to a switch that can be conductive in two directions, which can enable ON/OFF control by using electrical signals or enable ON/OFF control on the basis of the characteristics of the component according to some embodiments. For example, the two-way switch can be a MOSFET or an IGBT with an anti-parallel freewheeling diode. Unless otherwise specified, when mentioned hereafter in this description, the term “one-way semiconductor component” may refer to a semiconductor component that can be conductive in one direction, such as a diode, according to certain embodiments. Unless otherwise specified, when mentioned hereafter in this description, the term “charge storage component” may refer to any device that can enable charge storage, such as a capacitor, according to some embodiments. Unless otherwise specified, when mentioned hereafter in this description, the term “current storage component” may refer to any device that can store current, such as an inductor, according to certain embodiments. Unless otherwise specified, when mentioned hereafter in this description, the term “forward direction” may refer to the direction in which the energy flows from the battery to the energy storage circuit, and the term “reverse direction” may refer to the direction in which the energy flows from the energy storage circuit to the battery, according to some embodiments. Unless otherwise specified, when mentioned hereafter in this description, the term “battery” may comprise primary battery (e.g., dry battery or alkaline battery, etc.) and secondary battery (e.g., lithium-ion battery, nickel-cadmium battery, nickel-hydrogen battery, or lead-acid battery, etc.), according to certain embodiments. Unless otherwise specified, when mentioned hereafter in this description, the term “damping component” may refer to any device that inhibits current flow and thereby enables energy consumption, such as a resistor, etc., according to some embodiments. Unless otherwise specified, when mentioned hereafter in this description, the term “main loop” may refer to a loop composed of battery, damping component, switch unit and energy storage circuit connected in series according to certain embodiments. 
     It should be noted specially that, considering different types of batteries have different characteristics, in some embodiments of the present invention, “battery” may refer to an ideal battery that does not have internal parasitic resistance and parasitic inductance or has very low internal parasitic resistance and parasitic inductance, or may refer to a battery pack that has internal parasitic resistance and parasitic inductance; therefore, those skilled in the art should appreciate that if the battery is an ideal battery that does not have internal parasitic resistance and parasitic inductance or has very low internal parasitic resistance and parasitic inductance, the damping component  121  may refer to a damping component external to the battery and the current storage component L 1  may refer to a current storage component external to the battery; if the battery is a battery pack that has internal parasitic resistance and parasitic inductance, the damping component R 1  may refer to a damping component external to the battery or refer to the parasitic resistance in the battery pack, and the current storage component L 1  may refer to a current storage component external to the battery or refer to the parasitic inductance in the battery pack, according to certain embodiments. 
     To ensure the normal service life of the battery, according to some embodiments, the battery can be heated under low temperature condition, which is to say, when the heating condition is met, the heating circuit is controlled to start heating for the battery; when the heating stop condition is met, the heating circuit is controlled to stop heating, according to certain embodiments. 
     In the actual application of battery, the battery heating condition and heating stop condition can be set according to the actual ambient conditions, to ensure normal charge/discharge performance of the battery, according to some embodiments. 
     To heat up the battery E in a low temperature environment, one embodiment of the present invention provides a heating circuit for battery E, as shown in  FIG. 1 ; the heating circuit comprises a switch unit  1 , a switching control module  100 , a damping component R 1 , an energy storage circuit, and an energy superposition unit, the energy storage circuit is configured to connect with the battery to form a loop, and comprises a current storage component L 1  and a charge storage component C 1 ; the damping component R 1 , the switch unit  1 , the current storage component L 1 , and the charge storage component C 1  are connected in series; the switching control module  100  is connected with the switch unit  1 , and is configured to control ON/OFF of the switch unit  1 , so as to control the energy flowing between the battery and the energy storage circuit; the energy superposition unit is connected with the energy storage circuit, and is configured to superpose the energy in the energy storage circuit with the energy in the battery when the switch unit  1  switches on and then switches off; the switching control module  100  is also configured to control the switch unit  1  to switch off after the first positive half cycle of the current flow through the switch unit  1  after the switch unit  1  switches on, and the voltage applied to the switch unit  1  when the switch unit  1  switches off is lower than the voltage rating of the switch unit  1 . 
     With the technical scheme of certain embodiments of the present invention, when the heating condition is met, the switching control module  100  controls the switch unit  1  to switch on, and thus the battery E is connected with the energy storage circuit in series to form a loop, and can discharge through the loop (i.e., charge the charge storage component C 1 ); when the current in the loop reaches zero in normal direction after the peak current, the charge storage component C 1  begins to discharge through the loop, i.e., charge the battery E; in the charge/discharge process of the battery E, the current in the loop passes through the damping component R 1  in both normal direction and reversed direction, and thus the battery E is heated up by the heat generated in the damping component R 1 ; when the condition for heating stop is met, the switching control module  100  can control the switch unit  1  to switch off, so that the heating circuit stops heating. 
     To achieve to-and-fro energy flow between the battery E and the energy storage circuit, in one embodiment of the present invention, the switch unit  1  is a two-way switch K 3 , as shown in  FIG. 2 . The switching control module  100  controls ON/OFF of the two-way switch K 3 ; when the battery E is to be heat up, the two-way switch K 3  can be controlled to switch on; if heating is to be paused or is not needed, the two-way switch K 3  can be controlled to switch off. 
     Employing a separate two-way switch K 3  to implement the switch unit  1  can simplify the circuit, reduce system footprint, and simplify the implementation; however, to implement cut-off of reverse current, the following embodiment of the switch unit  1  is further provided in the present invention. 
     Preferably, the switch unit  1  comprises a first one-way branch configured to enable energy flow from the battery E to the energy storage circuit, and a second one-way branch configured to enable energy flow from the energy storage circuit to the battery E; wherein: the switching control module  100  is connected to the first one-way branch and the second one-way branch respectively, and is configured to control ON/OFF the switch unit  1  by controlling ON/OFF of the connected branches. 
     When the battery is to be heated, both the first one-way branch and the second one-way branch can be controlled to switch on; when heating is to be paused, either or both of the first one-way branch and the second one-way branch can be controlled to switch off; when heating is not needed, both of the first one-way branch and the second one-way branch can be controlled to switch off. Preferably, both of the first one-way branch and the second one-way branch are subject to the control of the switching control module  100 ; thus, energy flow cut-off in normal direction and reversed direction can be implemented flexibly. 
     In another embodiment of the switch unit  1 , as shown in  FIG. 3 , the switch unit  1  comprises a two-way switch K 4  and a two-way switch K 5 , wherein: the two-way switch K 4  and two-way switch K 5  are connected in series opposite to each other, to form the first one-way branch and the second one-way branch; the switching control module  100  is connected with the two-way switch K 4  and the two-way switch K 5  respectively, to control ON/OFF of the first one-way branch and the second one-way branch by controlling ON/OFF of the two-way switch K 4  and two-way switch K 5 . 
     When the battery E is to be heated, the two-way switches K 4  and K 5  can be controlled to switch on; when heating is to be paused, either or both of the two-way switch K 4  and the two-way switch K 5  can be controlled to switch off; when heating is not needed, both of the two-way switch K 4  and the two-way switch K 5  can be controlled to switch off. In such an implementation of switch unit  1 , the first one-way branch and the second one-way branch can be controlled separately to switch on and off, and therefore energy flow in normal direction and reversed direction in the circuit can be implemented flexibly. 
     In another embodiment of switch unit  1 , as shown in  FIG. 4 , the switch unit  1  comprises a switch K 6 , a one-way semiconductor component D 11 , a switch K 7 , and a one-way semiconductor component D 12 , wherein: the switch K 6  and the one-way semiconductor component D 11  are connected in series with each other to form the first one-way branch; the switch K 7  and the one-way semiconductor component D 12  are connected in series with each other to form the second one-way branch; the switching control module  100  is connected with the switch K 6  and the switch K 7 , to control ON/OFF of the first one-way branch and the second one-way branch by controlling ON/OFF of the switch K 6  and the switch K 7 . In the switch unit  1  shown in  FIG. 4 , since switches (i.e., the switch K 6  and the switch K 7 ) exist in both one-way branches, energy flow cut-off function in normal direction and reversed direction is implemented. 
     Preferably, the switch unit  1  can further comprise a resistor, which is connected in series with the first one-way branch and/or second one-way branch and configured to reduce the current in the heating circuit for the battery E and avoid damage to the battery E resulted from over-current in the circuit. For example, a resistor R 6  connected in series with the two-way switch K 4  and the two-way switch K 5  can be added in the switch unit  1  shown in  FIG. 3 , to obtain another implementation of the switch unit  1 , as shown in  FIG. 5 .  FIG. 6  shows one embodiment of the switch unit  1 , which is obtained by connecting the resistor R 2  and the resistor R 3  in series in the two one-way branches in the switch unit  1  shown in  FIG. 4 , respectively. 
     Owing to the existence of the current storage component L 1  in the loop, switching off the switch unit  1  when there is current flow in the loop will cause abrupt current drop to zero and therefore induces high induced voltage on the current storage component in L 1  the loop, which may cause damage to other circuit components in the loop (e.g., the switch unit  1 ). To improve safety of the heating circuit, in the technical scheme of certain embodiments of the present invention, the switching control module  100  can choose the switching-off opportunity of the switch unit  1 , so as to enable the voltage applied to the switch unit  1  lower than the voltage rating of the switch unit  1  at the time the switch unit  1  switches off. The switching-off opportunity of the switch unit  1  can be determined according to the voltage rating of the switch unit  1 , so as to prevent high induced voltage on the current storage component L 1  and the resultant damage to the switch unit  1 ; therefore, the heating circuit is safer, and the adverse effect to the entire circuit can be reduced. 
     Wherein: for example, the switching-off opportunity can be the time interval from the time the current flow through the switch unit  1  reaches degree 30 before zero after the peak value in the negative half cycle to the time the current flow reaches degree 30 after zero before the peak value in the next positive half cycle, and the switch unit  1  can switch off at any time within the said time interval. Of course, the present invention is not limited to that. The specific time interval should be determined according to the voltage rating of the switch unit  1 ; for example, the time interval can be from the time the current flow through the switch unit  1  reaches degree 60 before zero after the peak value in the negative half cycle to the time the current flow reaches degree 60 after zero before the peak value in the next positive half cycle, depending on the voltage rating of the switch unit  1 . 
     In the cyclic charge/discharge process of the battery E, since the energy will not be charged back completely into the battery E when the battery E is charged in reversed direction, the energy discharged from the battery E in the next discharge cycle in positive direction will be reduced, and therefore the heating efficiency of the heating circuit will be degraded. Therefore, preferably, the switching control module  100  is configured to control the switch unit  1  to switch off when the current flow through the switch unit  1  reaches zero after the peak value in the negative half cycle after the switch unit  1  switches on, so as to improve the heating efficiency of the heating circuit, and minimize the induced voltage on the current storage component L 1 , and thereby minimize the voltage applied to the switch unit  1  when the switch unit  1  switches off, in order to prevent the damage of high induced voltage to the switch unit  1 . 
     Preferably, as shown in  FIG. 7 , the heating circuit further comprises a freewheeling circuit  20 , which is configured to form a serial loop with the battery E and the current storage component L 1  to sustain current flow in the battery E after the switch unit  1  switches on and then switches off. Thus, after the switch unit  1  switches off, the current flow can be sustained by controlling the freewheeling circuit  20  to operate, so as to protect other circuit components (e.g., switch unit  1 ) in the circuit, and ensure safety of the heating circuit. The utilization of the freewheeling circuit widens the range of switching-off opportunity of the switch unit  1 . 
     In one embodiment of the present invention, the switching control module  100  is configured to control the switch unit  1  to switch off before the current flow through the switch unit  1  reaches zero after the peak value in the negative half cycle after the switch unit  1  switches on. As shown in  FIG. 8 , the freewheeling circuit  20  can comprises a switch K 20  and a one-way semiconductor component D 2  connected in series with each other; the switching control module  100  is connected with the switch K 20 , and is configured to control the switch K 20  to switch on after the switch unit  1  switches on and then switches off, and control the switch K 20  to switch off after the current flow to the battery E reaches a preset value of current (e.g., zero). The freewheeling circuit  20  can be connected in parallel between the ends of the battery E; or, one end of the freewheeling circuit  20  can be connected between the switch K 7  and the one-way semiconductor component D 12  in the second one-way branch of the switch unit  1 , and the other end of the freewheeling circuit  20  can be connected to the battery E, as shown in  FIG. 4 . 
     The preset value of current is a value that will not make the voltage applied to the switch unit  1  higher than or equal to the voltage rating of the switch unit  1  at the time the switch unit  1  switches off, and can be set according to the voltage rating of the switch unit  1 . 
     In another embodiment of the present invention, the switching control module  100  is configured to control the switch unit  1  to switch off after the current flow through the switch unit  1  reaches zero before the peak value in the positive half cycle of the switch unit  1  after the switch unit  1  switches on. As shown in  FIG. 9 , the freewheeling circuit  20  can comprise a one-way semiconductor component D 21 , a damping component R 21 , and a charge storage component C 21 , the one-way semiconductor component D 21  and the damping component R 21  are connected in parallel with each other, and then connected in series with the charge storage component C 21 ; after the switch unit  1  switches on and then switches off, the current storage component L 1  can sustain the current flow via the one-way semiconductor component D 21  and the charge storage component C 21 ; the damping component R 21  is configured to release the energy stored in the charge storage component C 21 . The freewheeling circuit  20  can be connected in parallel between the ends of the battery E; or, one end of the freewheeling circuit  20  can be connected between the switch K 6  and the one-way semiconductor component D 11  in the first one-way branch of the switch unit  1 , and the other end of the freewheeling circuit  20  can be connected to the battery E, as shown in  FIG. 4 . 
     The energy superposition unit is connected with the energy storage circuit, and is configured to superpose the energy in the energy storage circuit with the energy in the battery E after the switch unit  1  switches on and then switches off, so that the discharging current in the heating circuit will be increased when the switch unit  1  is controlled to switch on at the next time, and thereby the working efficiency of the heating circuit is improved. 
     In one embodiment of the present invention, as shown in  FIG. 10 , the energy superposition unit comprises a polarity inversion unit  102 , which is connected with the energy storage circuit, and is configured to invert the voltage polarity of the charge storage component C 1  after the switch unit  1  switches on and then switches off; since the voltage of the charge storage component C 1  can be superposed in series with the voltage of the battery E after polarity inversion, the discharging current in the heating circuit will be increased when the switch unit  1  switches on at the next time. 
     In one embodiment of the polarity inversion unit  102 , as shown in  FIG. 11 , the polarity inversion unit  102  comprises a single-pole double-throw switch J 1  and a single-pole double-throw switch J 2  located on the two ends of the charge storage component C 1  respectively; the input wires of the single-pole double-throw switch J 1  are connected in the energy storage circuit, the first output wire of the single-pole double-throw switch J 1  is connected with the first pole plate of the charge storage component C 1 , and the second output wire of the single-pole double-throw switch J 1  is connected with the second pole plate of the charge storage component C 1 ; the input wires of the single-pole double-throw switch J 2  are connected in the energy storage circuit, the first output wire of the single-pole double-throw switch J 2  is connected with the second pole plate of the charge storage component C 1 , and the second output wire of the single-pole double-throw switch J 2  is connected with the first pole plate of the charge storage component C 1 ; the switching control module  100  is also connected with the single-pole double-throw switch J 1  and single-pole double-throw switch J 2  respectively, and is configured to invert the voltage polarity of the charge storage component C 1  by altering the connection relationships between the respective input wires and output wires of the single-pole double-throw switch J 1  and the single-pole double-throw switch J 2 . 
     According to this embodiment, the connection relationships between the respective input wires and output wires of the single-pole double-throw switch J 1  and single-pole double-throw switch J 2  can be set in advance, so that the input wires of the single-pole double-throw switch J 1  are connected with the first output wire of the switch unit K 1  and the input wires of the single-pole double-throw switch J 2  are connected with the first output wire of the switch unit K 1  when the switch unit K 1  switches on; the input wires of the single-pole double-throw switch J 1  are switched to connect with the second output wire of the switch unit K 1  and the input wires of the single-pole double-throw switch J 2  are switched to connect with the second output wire of the switch unit K 1  under control of the switching control module  100  when the switch unit K 1  switches off, and thereby the voltage polarity of the charge storage component C 1  is inverted. 
     As another embodiment of the polarity inversion unit  102 , as shown in  FIG. 12 , the polarity inversion unit  102  comprises a one-way semiconductor component D 3 , a current storage component L 2 , and a switch K 9 ; the charge storage component C 1 , current storage component L 2 , and switch K 9  are connected sequentially in series to form a loop; the one-way semiconductor component D 3  is connected in series between the charge storage component C 1  and the current storage component L 2  or between the current storage component L 2  and the switch K 9 ; the switching control module  100  is also connected with the switch K 9 , and is configured to invert the voltage polarity of the charge storage component C 1  by controlling the switch K 9  to switch on. 
     According to the above embodiment, when the switch unit  1  switches off, the switch K 9  can be controlled to switch on by the switching control module  100 , and thereby the charge storage component C 1 , one-way semiconductor component D 3 , current storage component L 2 , and switch K 9  form a LC oscillation loop, and the charge storage component C 1  discharges through the current storage component L 2 , thus, the voltage polarity of the charge storage component C 1  will be inverted when the current flowing through the current storage component L 2  reaches zero after the current in the oscillation circuit flows through the positive half cycle. 
     As yet another embodiment of the polarity inversion unit  102 , as shown in  FIG. 13 , the polarity inversion unit  102  comprises a first DC-DC module  2  and a charge storage component C 2 ; the first DC-DC module  2  is connected with the charge storage component C 1  and the charge storage component C 2  respectively; the switching control module  100  is also connected with the first DC-DC module  2 , and is configured to transfer the energy in the charge storage component C 1  to the charge storage component C 2  by controlling the operation of the first DC-DC module  2 , and then transfer the energy in the charge storage component C 2  back to the charge storage component C 1 , so as to invert the voltage polarity of the charge storage component C 1 . 
     The first DC-DC module  2  is a DC-DC (direct current to direct current) conversion circuit for voltage polarity inversion commonly used in the field. Certain embodiments of the present invention do not impose any limitation to the specific circuit structure of the first DC-DC module  2 , as long as the module can accomplish voltage polarity inversion of the charge storage component C 1 . Those skilled in the art can add, substitute, or delete the components in the circuit as needed. 
       FIG. 14  shows one embodiment of the first DC-DC module  2  provided in the present invention. As shown in  FIG. 14 , the first DC-DC module  2  comprises: a two-way switch Q 1 , a two-way switch Q 2 , a two-way switch Q 3 , a two-way switch Q 4 , a first transformer T 1 , a one-way semiconductor component D 4 , a one-way semiconductor component D 5 , a current storage component L 3 , a two-way switch Q 5 , a two-way switch Q 6 , a second transformer T 2 , a one-way semiconductor component D 6 , a one-way semiconductor component D 7 , and a one-way semiconductor component D 8 . 
     In the embodiment, the two-way switch Q 1 , two-way switch Q 2 , two-way switch Q 3 , and two-way switch Q 4  are MOSFETs, and the two-way switch Q 5  and two-way switch Q 6  are IGBTs. 
     The Pin  1 ,  4 , and  5  of the first transformer T 1  are dotted terminals, and the pin  2  and  3  of the second transformer T 2  are dotted terminals. 
     Wherein: the positive electrode of the one-way semiconductor component D 7  is connected with the end ‘a’ of the charge storage component C 1 , and the negative electrode of the one-way semiconductor component D 7  is connected with the drain electrodes of the two-way switch Q 1  and two-way switch Q 2 , respectively; the source electrode of the two-way switch Q 1  is connected with the drain electrode of the two-way switch Q 3 , and the source electrode of the two-way switch Q 2  is connected with the drain electrode of the two-way switch Q 4 ; the source electrodes of the two-way switch Q 3  and two-way switch Q 4  are connected with the end ‘b’ of the charge storage component C 1  respectively. Thus, a full-bridge circuit is formed, here, the voltage polarity of end ‘a’ of the charge storage component C 1  is positive, while the voltage polarity of end ‘b’ of the charge storage component C 1  is negative. 
     In the full-bridge circuit, the two-way switch Q 1 , two-way switch Q 2  constitute the upper bridge arm, while the two-way switch Q 3  and two-way switch Q 4  constitute the lower bridge arm. The full-bridge circuit is connected with the charge storage component C 2  via the first transformer T 1 ; the pin  1  of the first transformer T 1  is connected with the first node N 1 , the pin  2  of the first transformer T 1  is connected with the second node N 2 , the pin  3  and pin  5  of the first transformer T 1  are connected to the positive electrode of the one-way semiconductor component D 4  and the positive electrode of the one-way semiconductor component D 5  respectively; the negative electrode of one-way semiconductor component D 4  and the negative electrode of one-way semiconductor component D 5  are connected with one end of the current storage component L 3 , and the other end of the current storage component L 3  is connected with the end ‘d’ of the charge storage component C 2 ; the pin  4  of the transformer T 1  is connected with the end ‘c’ of the charge storage component C 2 , the positive electrode of the one-way semiconductor component D 8  is connected with the end ‘d’ of the charge storage component C 2 , and the negative electrode of the one-way semiconductor component D 8  is connected with the end ‘b’ of the charge storage component C 1 ; here, the voltage polarity of end ‘c’ of the charge storage component C 2  is negative, while the voltage polarity of end ‘d’ of the charge storage component C 2  is positive. 
     Wherein: the end ‘c’ of the charge storage component C 2  is connected with the emitter electrode of the two-way switch Q 5 , the collector electrode of the two-way switch Q 5  is connected with the pin  2  of the transformer T 2 , the pin  1  of the transformer T 2  is connected with end ‘a’ of the charge storage component C 1 , the pin  4  of the transformer T 2  is connected with end ‘a’ of the charge storage component C 1 , the pin  3  of the transformer T 2  is connected with the positive electrode of the one-way semiconductor component D 6 , the negative electrode of the one-way semiconductor component D 6  is connected with the collector electrode of the two-way switch Q 6 , and the emitter electrode of the two-way switch Q 6  is connected with the end ‘b’ of the charge storage component C 2 . 
     Wherein: the two-way switch Q 1 , two-way switch Q 2 , two-way switch Q 3 , two-way switch Q 4 , two-way switch Q 5 , and two-way switch Q 6  are controlled by the switching control module  100  respectively to switch on and switch off. 
     Hereafter the working process of the first DC-DC module  2  will be described: 
     1. After the switch unit  1  switches off, the switching control module  100  controls the two-way switch Q 5  and two-way switch Q 6  to switch off, and controls the two-way switch Q 1  and two-way switch Q 4  to switch on at the same time to form phase A; controls the two-way switch Q 2  and two-way switch Q 3  to switch on at the same time to form phase B. Thus, by controlling the phase A and phase B to switch on alternately, a full-bridge circuit is formed; 
     2. When the full-bridge circuit operates, the energy in the charge storage component C 1  is transferred through the first transformer T 1 , one-way semiconductor component D 4 , one-way semiconductor component D 5 , and current storage component L 3  to the charge storage component C 2 ; now, the voltage polarity of end ‘c’ of the charge storage component C 2  is negative, while the voltage polarity of end ‘d’ of the charge storage component C 2  is positive. 
     3. The switching control module  100  controls the two-way switch Q 5  to switch on, and therefore a path from the charge storage component C 1  to the charge storage component C 2  is formed via the second transformer T 2  and the one-way semiconductor component D 8 , thus, the energy in the charge storage component C 2  is transferred back to the charge storage component C 1 , wherein: some energy will be stored in the second transformer T 2 , Now, the switching control module  100  controls the two-way switch Q 5  to switch off and controls the two-way switch Q 6  to switch on, and therefore the energy stored in the second transformer T 2  is transferred to the charge storage component C 1  by the second transformer T 2  and the one-way semiconductor component D 6 ; now, the voltage polarity of the charge storage component C 1  is inverted such that end ‘a’ is negative and end ‘b’ is positive. Thus, the purpose of inverting the voltage polarity of the charge storage component C 1  is attained. 
     In one embodiment of the present invention, the working efficiency of the heating circuit can be improved by superposing the energy in the charge storage component C 1  with the energy in the battery E directly, or superposing the remaining energy in the charge storage component C 1  with the energy in the battery E after some energy in the charge storage component C 1  is consumed. 
     Therefore, as shown in  FIG. 15 , the heating circuit further comprises an energy consumption unit, which is connected with the charge storage component C 1 , and is configured to consume the energy in the charge storage component C 1  after the switch unit  1  switches on and then switches off and before the energy in the energy superposition unit is superposed. 
     In one embodiment of the present invention, as shown in  FIG. 16 , the energy consumption unit comprises a voltage control unit  101 , which is configured to convert the voltage across the charge storage component C 1  to a predetermined voltage value after the switch unit  1  switches on and then switches off and before the energy superposition unit performs energy superposition. The predetermined voltage value can be set as needed. 
     As shown in  FIG. 16 , the voltage control unit  101  comprises a damping component R 5  and a switch K 8 , wherein: the damping component R 5  and switch K 8  are connected in series with each other and then connected in parallel across the charge storage component C 1 ; the switching control module  100  is also connected with the switch K 8 , and is configured to control the switch K 8  to switch on after the switch unit  1  switches on and then switches off. Thus, the energy in the charge storage component C 1  can be consumed via the damping component R 5 . 
     The switching control module  100  can be a separate controller, which, by using internal program setting, enables ON/OFF control of different external switches; or, the switching control module  100  can be a plurality of controllers, for example, a switching control module  100  can be set for each external switch correspondingly; or, the plurality of switching control modules  100  can be integrated into an assembly. Certain embodiments of the present invention do not impose any limitation to the forms of implementation of the switching control module  100 . 
     Hereafter the working process of certain embodiments of the heating circuit for battery E will be described briefly with reference to  FIGS. 17-22 . It should be noted that though the features and components of certain embodiments of the present invention are described specifically with reference to  FIGS. 17-22 , each feature or component can be used separately without other features and components, or can be used in combination or not in combination with other features and components. The embodiments of the heating circuit for battery E provided in the present invention are not limited to those as shown in  FIGS. 17-22 . Additionally, the time intervals between the time periods in the waveform diagrams as shown in the drawings can be adjusted as needed, according to the actual circumstance in some embodiments. 
     In the heating circuit for battery E as shown in  FIG. 17 , the switch K 6  and the one-way semiconductor component D 11  are connected in series to constitute the first one-way branch of the switch unit; the one-way semiconductor component D 12  and the switch K 7  are connected in series to constitute the second one-way branch of the switch unit  1 ; the switch unit  1 , the damping component R 1 , the charge storage component C 1 , and the current storage component L 1  are connected in series; the one-way semiconductor component D 3 , the current storage component L 2 , and the switch K 9  constitute a polarity inversion unit  102 ; the one-way semiconductor component D 20  and the switch K 20  constitute a freewheeling circuit  20 ; the switching control module  100  can control ON/OFF of the switch K 6 , the switch K 7 , the switch K 9 , and the switch K 20 . For example,  FIG. 18  shows a waveform sequence diagram corresponding to the heating circuit as shown in  FIG. 17 , wherein: V C1  refers to the voltage across the charge storage component C 1 , I main  refers to the current flowing through the switch unit  1 , I L2  refers to the current flowing in the polarity inversion circuit, I C1  refers to the current flowing through the charge storage component C 1 , and I D20  refers to the current flowing through the one-way semiconductor component D 20 . In another example, the working process of the heating circuit as shown in  FIG. 17  is as follows: 
     a) The switching control module  100  controls the switch K 6  to switch on, and thus the battery E discharges in the positive direction through the loop composed by the battery E, the switch K 6 , the one-way semiconductor component D 11 , and the charge storage component C 1  (e.g., in the time period t 1  as shown in  FIG. 18 ); 
     b) The switching control module  100  controls the switch K 6  to switch off when the current flow reaches zero after the peak value in the first positive half cycle; 
     c) The switching control module  100  controls the switch K 7  to switch on, and the battery E is charged in the reversed direction through the loop composed by the battery E, the charge storage component C 1 , the switch K 7 , and the semiconductor device D 12 ; the switching control module  100  controls the switch K 7  to switch off when the current flow reaches degree 24 before zero after the peak value in the first negative half cycle (e.g., in the time period t 2  as shown in  FIG. 18 ); 
     d) The switching control module  100  controls the switch K 20  to switch on when it controls the switch K 7  to switch off, and thus the current storage component L 1  sustains the current flow via the switch K 20  and the one-way semiconductor component D 20 ; the switching control module  100  controls the switch K 20  to switch off when the current flow to the battery E reaches zero (e.g., in the time period t 3  as shown in  FIG. 18 ); 
     e) The switching control module  100  controls the switch K 9  to switch on, and thus the charge storage component C 1  discharges through the loop composed by the one-way semiconductor component D 3 , the current storage component L 2 , and the switch K 9 , and thereby achieves the purpose of voltage polarity inversion; then, the switching control module  100  controls the switch K 9  to switch off (e.g., in the time period t 4  as shown in  FIG. 18 ); 
     f) Repeat step a) to step e); the battery E is heated up continuously while it discharges and is charged, till the battery E meets the heating stop condition. 
     In the heating circuit for battery E as shown in  FIG. 19 , the switch K 6  and the one-way semiconductor component D 11  are connected in series to constitute the first one-way branch of the switch unit  1 ; the one-way semiconductor component D 12  and the switch K 7  are connected in series to constitute the second one-way branch of the switch unit  1 ; the switch unit  1 , the damping component R 1 , the charge storage component C 1 , and the current storage component L 1  are connected in series; the one-way semiconductor component D 3 , the current storage component L 2 , and the switch K 9  constitute a polarity inversion unit  102 ; the one-way semiconductor component D 21 , the damping component R 21 , and the charge storage component C 21  constitute a freewheeling circuit  20 ; the switching control module  100  can control ON/OFF of the switch K 6 , the switch K 7 , and the switch K 9 . For example,  FIG. 20  shows a waveform sequence diagram corresponding to the heating circuit as shown in  FIG. 19 , wherein: V C1  refers to the voltage across the charge storage component C 1 , I main  refers to the current flowing through the switch unit  1 , I L2  refers to the current flowing in the polarity inversion circuit, I C1  refers to the current flowing through the charge storage component C 1 , and I C21  refers to the current flowing through the charge storage component C 21 . In another example, the working process of the heating circuit as shown in  FIG. 19  is as follows: 
     a) The switching control module  100  controls the switch K 6  and the switch K 7  to switch on, and thus the battery E discharges in the normal direction through the loop composed by the battery E, the switch K 6 , the one-way semiconductor component D 11 , and the charge storage component C 1  (e.g., in the time period t 1  as shown in  FIG. 20 ), and is charged in the reversed direction through the loop composed by the battery E, the switch K 7 , the one-way semiconductor component D 12 , and the charge storage component C 1  (e.g., in the time period t 2  as shown in  FIG. 20 ); 
     b) The switching control module  100  controls the switch K 6  and the switch K 7  to switch off when the current flow reaches degree 25 after zero before the peak value in the second positive half cycle (e.g., in the time period t 3  as shown in  FIG. 20 ); the current storage component L 1  sustains the current flow via the one-way semiconductor component D 21  and the charge storage component C 21  (e.g., in the time period t 4  as shown in  FIG. 20 ); 
     c) The switching control module  100  controls the switch K 9  to switch on, and thus the charge storage component C 1  discharges through the loop composed by the one-way semiconductor component D 3 , the current storage component L 2 , and the switch K 9 , and achieves the purpose of voltage polarity inversion; then, the switching control module  100  controls the switch K 9  to switch off (e.g., in the time period t 5  as shown in  FIG. 20 ); 
     d) Repeat step a) to step c); the battery E is heated up continuously while it discharges and is charged, till the battery E meets the heating stop condition. 
     It should be noted that there is also a current flow in the freewheeling circuit  20  as shown in  FIG. 19  in the time periods t 1  and t 2 . To illustrate clearly the purpose of the freewheeling circuit  20  in the heating circuit provided in certain embodiments of the present invention, only the current flow in the time periods when the effect of the freewheeling circuit  20  is operative is shown in  FIG. 20 , but the current flow in the freewheeling circuit  20  in the time periods t 1  and t 2  is omitted, to avoid confusion. 
     In the heating circuit for battery E as shown in  FIG. 21 , the two-way switch K 3  is used to form the switch unit  1 ; the energy storage circuit comprises the current storage component L 1  and the charge storage component C 1 ; the damping component R 1  and the switch unit  1  are connected in series with the energy storage circuit; the one-way semiconductor component D 3 , the current storage component L 2 , and the switch K 9  constitute a polarity inversion unit  102 ; the switching control module  100  can control the switch K 9  and the two-way switch K 3  to switch on and switch off. For example,  FIG. 22  is a timing sequence diagram of the waveforms corresponding to the heating circuit as shown in  FIG. 21 , wherein: V C1  refers the voltage value across the charge storage component C 1 , I main  refers to the value of current flowing through the two-way switch K 3 , and I L2  refers to the value of current in the polarity inversion circuit. In another example, the working process of the heating circuit as shown in  FIG. 21  is as follows: 
     a) The switching control module  100  controls the two-way switch K 3  to switch on, and the energy storage circuit starts operation as indicated by the time period t 1  as shown in  FIG. 22 ; the battery E discharges in the normal direction and is charged in the reversed direction through the loop composed by the battery E, the two-way switch K 3 , and the charge storage component C 1  (e.g., in the time period t 1  as shown in  FIG. 22 ); 
     b) The switching control module  100  controls the two-way switch K 3  to switch off when the current flowing through the two-way switch K 3  reaches zero after the peak value in the negative half cycle (e.g., when the reverse current reaches zero); 
     c) The switching control module  100  controls the switch K 9  to switch on, and thus the polarity inversion unit  102  starts operation; the charge storage component C 1  discharges through the loop composed by the one-way semiconductor component D 3 , the current storage component L 2 , and the switch K 9 , and achieves the purpose of voltage polarity inversion; then, the switching control module  100  controls the switch K 9  to switch off (e.g., in the time period t 2  as shown in  FIG. 22 ); 
     d) Repeat step a) to step c); the battery E is heated up continuously while it discharges and is charged, till the battery E meets the heating stop condition. 
     Certain embodiments of the present invention provide a battery heating circuit, comprising a switch unit  1 , a switching control module  100 , a damping component R 1 , an energy storage circuit, and an energy superposition unit; the energy storage circuit is configured to connect with the battery to form a loop, and comprises a current storage component L 1  and a charge storage component C 1 ; the damping component R 1 , the switch unit  1 , the current storage component L 1 , and the charge storage component C 1  are connected in series; the switching control module  100  is connected with the switch unit  1 , and is configured to control ON/OFF of the switch unit  1 , so as to control the energy flowing between the battery and the energy storage circuit; the energy superposition unit is connected with the energy storage circuit, and is configured to superpose the energy in the energy storage circuit with the energy in the battery when the switch unit  1  switches on and then switches off; the switching control module  100  is also configured to control the switch unit  1  to switch off after the first positive half cycle of current flowing through the switch unit  1  after the switch unit  1  switches on, and the voltage that is applied to the switch unit  1  at the time the switch unit  1  switches off is lower than the voltage rating of the switch unit  1 . 
     The heating circuit provided in certain embodiments of the present invention can improve the charge/discharge performance of a battery. In addition, since an energy storage circuit is connected with the battery in series in the heating circuit, the safety problem related with short circuit caused by failures of the switch unit can be avoided when the battery is heated due to the existence of the charge storage component connected in series, and therefore the battery can be protected effectively according to some embodiments. 
     In addition, in the heating circuit provided according to certain embodiments of the present invention, since the switching-off timing of the switch unit is chosen according to the voltage rating of the switch unit, high induced voltage on the current storage component in the loop and the resultant damage to the switch unit can be prevented, and therefore the heating circuit is safer, and the adverse effect to the entire circuit can be reduced according to some embodiments. 
     In addition, an energy superposition unit is provided in the heating circuit according to certain embodiments of the present invention, and the energy superposition unit can superpose the energy in the energy storage circuit with the energy in the battery after the switch unit switches off; thus, when the switch unit is controlled to switch on at the next time, the discharging current in the heating circuit is increased, and therefore the working efficiency of the heating circuit is improved according to some embodiments. 
     For example, some or all components of various embodiments of the present invention each are, individually and/or in combination with at least another component, implemented using one or more software components, one or more hardware components, and/or one or more combinations of software and hardware components. In another example, some or all components of various embodiments of the present invention each are, individually and/or in combination with at least another component, implemented in one or more circuits, such as one or more analog circuits and/or one or more digital circuits. 
     While some embodiments of the present invention are described above with reference to the accompanying drawings, the present invention is not limited to the details of those embodiments. Those skilled in the art can make modifications and variations, without departing from the spirit of the present invention. However, all these modifications and variations shall be deemed as falling into the scope of the present invention. 
     In addition, it should be noted that the specific technical features described in the above embodiments can be combined in any appropriate way, provided that there is no conflict. To avoid unnecessary repetition, certain possible combinations are not described specifically. Moreover, the different embodiments of the present invention can be combined as needed, as long as the combinations do not deviate from the spirit of the present invention. However, such combinations shall also be deemed as falling into the scope of the present invention. 
     Hence, although specific embodiments of the present invention have been described, it will be understood by those of skill in the art that there are other embodiments that are equivalent to the described embodiments. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims.