Circuits and methods for heating batteries in parallel using resonance components in series

1. CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No. 201010245288.0, filed Jul. 30, 2010, Chinese Patent Application No. 201010274785.3, filed Aug. 30, 2010, Chinese Patent Application No. 201010603669.1, filed Dec. 23, 2010, and Chinese Patent Application No. 201010604677.8, filed Dec. 23, 2010, 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.

Certain embodiments of the present invention provide a battery heating circuit, wherein: the battery comprises a first battery and a second battery; the heating circuit comprises a first switch unit, a second switch unit, a damping component R 1 , a damping component R 2 , a current storage component L 3 , a current storage component L 4 , a switching control module and an energy storage component V 1 ; the first battery, damping component R 1 , current stage component L 3 , energy storage component V 1 and first switch unit are connected in series to constitute a first charging/discharging circuit; the second battery, damping component R 2 , current stage component L 4 , energy storage component V 1 and second switch unit are connected in series to constitute a second charging/discharging circuit; when the energy storage component V 1 is charged or discharges, the direction of charging/discharging current in the second charging/discharging circuit is reverse to the direction of charging/discharging current in the first charging/discharging circuit; the switching control module is electrically connected with the first switch unit and second switch unit, and is configured to control the first switch unit and second switch unit to switch on in alternate, so as to control the electric energy to flow among the first battery, energy storage component V 1 and second battery.

In the heating circuit provided in certain embodiments of the present invention, the first switch unit and second switch unit can be controlled by the switching control module to switch on in alternate, so that the electric energy can flow back-and-forth among the first battery, energy storage component V 1 and second battery in alternate, and thereby causes the damping component R 1 and damping component R 2 to generate heat, so as to heat up the first battery and second battery. Since the direction of charging/discharging current in the second charging/discharging circuit is reverse to the direction of charging/discharging current in the first charging/discharging circuit when viewed from the aspect of the energy storage component V 1 , the energy charged from the first battery into the energy storage component V 1 can be transferred successfully to the second battery, so that the heating efficiency is improved.

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 of the heating circuit in the first embodiment of the present invention;

FIG. 2 is a schematic diagram of a heating circuit in the first embodiment of the present invention;

FIG. 3 is a timing sequence diagrams of waveform of the heating circuit in FIG. 2 ;

FIG. 4 is a schematic diagram of another heating circuit in the first embodiment of the present invention;

FIG. 5 is a timing sequence diagrams of waveform of the heating circuit in FIG. 4 ;

FIG. 6 is a schematic diagram of the heating circuit in the second embodiment of the present invention;

FIG. 7 is a schematic diagram of a heating circuit in the second embodiment of the present invention;

FIG. 8 is a timing sequence diagrams of waveform of the heating circuit in FIG. 7 ;

FIG. 9 is a schematic diagram of another heating circuit in the second embodiment of the present invention;

FIG. 10 is a timing sequence diagrams of waveform of the heating circuit in FIG. 9 ; and

FIG. 11 is a circuit diagram of one embodiment of the first and/or second switch unit in the heating circuit provided in 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 R 1 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.

FIG. 1 is a schematic diagram of the heating circuit in the first embodiment of the present invention. As shown in FIG. 1 , one embodiment of the present invention provides a battery heating circuit, wherein: the battery comprises a first battery E 1 and a second battery E 2 ; the heating circuit comprises a first switch unit 10 , a second switch unit 20 , a damping component R 1 , a damping component R 2 , a current stage component L 3 , a current stage component L 4 , a switching control module 100 and an energy storage component V 1 ; the first battery E 1 , damping component R 1 , current stage component L 3 , energy storage component V 1 and first switch unit 10 are connected in series to constitute a first charging/discharging circuit; the second battery E 2 , damping component R 2 , current stage component L 4 , energy storage component V 1 and second switch unit 20 are connected in series to constitute a second charging/discharging circuit; when the energy storage component V 1 is charged or discharges, the direction of charging/discharging current in the second charging/discharging circuit is reverse to the direction of charging/discharging current in the first charging/discharging circuit; the switching control module 100 is electrically connected with the first switch unit 10 and second switch unit 20 , and is configured to control the first switch unit 10 and second switch unit 20 to switch on in alternate, so as to control the electric energy to flow among the first battery E 1 , energy storage component V 1 and second battery E 2 .

wherein: the damping component R 1 and the damping component R 2 can be the parasitic resistances in the first battery E 1 and the second battery E 2 respectively, and the current storage component L 3 and the current storage component L 4 can be the parasitic inductances in the first battery E 1 and the second battery E 2 respectively.

Wherein: the energy storage component V 1 can be an inductor L 1 or a capacitor C 1 . FIG. 2 and FIG. 4 show the circuit diagrams in the case that the energy storage component V 1 is an inductor L 1 or capacitor C 1 , respectively; FIG. 3 and FIG. 5 show the timing sequence diagrams of waveform corresponding to FIG. 2 and FIG. 4 , respectively. Hereunder the heating circuit in the first embodiment of the present invention will be described, with reference to FIG. 2 to FIG. 5 .

As shown in FIG. 2 , the energy storage component V 1 can be an inductor L 1 , the switching control module 100 can control the first switch unit 10 and second switch unit 20 to switch theirs ON/OFF states when the current in the inductor L 1 reaches a preset value, for example, the first switch unit 10 switches from ON state to OFF state, while the second switch unit 20 switches from OFF state to ON state, so that the electric energy stored in the inductor L 1 from one battery can flow into the other battery. As the electric energy flows, current is generated; by keeping current flowing through the damping component R 1 and damping component R 2 continuously, the damping component R 1 and damping component R 2 generate heat, and thereby heat up the first battery E 1 and second battery E 2 .

FIG. 3 is a timing sequence diagram of the waveform of the circuit shown in FIG. 2 . Hereunder the working process of the heating circuit provided in one embodiment of the present invention will be described, with reference to FIG. 3 . First, the switching control module 100 controls the first switch unit 10 to switch on, and controls the second switch unit 20 to switch off; thus, the first battery E 1 charges the inductor L 1 , and therefore the current in the inductor L 1 increases gradually (as indicated by the time period t 1 shown in FIG. 3 ). When the current I L1 in the inductor L 1 rises to a preset value, the switching control module 100 controls the first switch unit 10 to switch off and controls the second switch unit 20 to switch on; the inductor L 1 transfers the energy charged in it to the second battery E 2 , and therefore the current in the inductor L 1 decreases slowly (as indicated by the time period t 2 ). Then, after the energy in the inductor L 1 is released, the second battery E 2 starts charging the inductor L 1 , and therefore the current I L1 in the inductor L 1 increases slowly. At this time, the flow direction of the current I L1 in the inductor L 1 is reverse to the flow direction in the time period t 1 and t 2 (as indicated by the time period t 3 ). Then, when the current I L1 in the inductor L 1 rises to a preset value, the switching control module 100 controls the first switch unit 10 to switch on and controls the second switch unit 20 to switch off; the inductor L 1 transfers the energy charged in it to the first battery E 1 , and therefore the current I L1 in the inductor L 1 decreases slowly (as indicated by the time period t 4 ; now, the heating circuit has accomplished a complete working cycle). In that way, the cycles continue on and on, so that the current flows through damping component R 1 and damping component R 2 continuously; as a result, the damping component R 1 and damping component R 2 generate heat, and thereby heat up the first battery E 1 and second battery E 2 to the expected condition. It should be noted: U L1 in FIG. 3 represents the voltage of the inductor L 1 , which is a constant value in forward direction when the current I L1 through the inductor L 1 increases in forward direction or decreases in reverse direction, and is a constant value in reverse direction when the current I L1 through the inductor L 1 decreases in forward direction or increases in reverse direction.

In the above working process of the heating circuit provided in one embodiment of the present invention, the current can be kept flowing back-and-forth between the first battery E 1 and the second battery E 2 , so that the two batteries are heated up in alternate, and therefore the heating efficiency is improved. In addition, owing to the existence of the inductor L 1 , the current flowing through the first and second batteries and the first and second switch units is limited; alternatively, the current flowing through the first and second batteries and the first and second switch units can be limited by using the preset value, so as to reduce the current flowing through the first and second batteries and the first and second switch units, to attain the purpose of protecting the first and second batteries and the first and second switch units.

As shown in FIG. 4 , the energy storage component V 1 is a capacitor C 1 , the switching control module 100 can control the first switch unit 10 and second switch unit 20 to switch their ON/OFF states when the current in the capacitor C 1 reaches zero after each pair of continuous positive and negative half cycles or each pair of continuous negative and positive half cycles, for example, the first switch unit 10 can switch from ON state to OFF state, while the second switch unit 20 can switch from OFF state to ON state, so that the electric energy stored in the capacitor C 1 from one battery can flow into the other battery. As the electric energy flows, current is generated; by keeping current flowing through the damping component R 1 and damping component R 2 continuously, the damping component R 1 and damping component R 2 generate heat, and thereby heat up the first battery E 1 and second battery E 2 .

FIG. 5 is a timing sequence diagram of the waveform of the circuit shown in FIG. 4 . Hereunder the working process of the heating circuit provided in one embodiment of the present invention will be described, with reference to FIG. 5 . First, the switching control module 100 controls the first switch unit 10 to switch on, and controls the second switch unit 20 to switch off; the first battery E 1 , damping component R 1 , current stage component L 3 , capacitor C 1 and first switch unit 10 form a charging/discharging circuit, which performs charging/discharging operations (as indicated by the time period t 1 in FIG. 5 ). After the charging/discharging circuit completes a charging/discharging cycle (at this point, the current I C1 through the capacitor C 1 reaches zero after the negative half cycle, the voltage U C1 of the capacitor C 1 has passed the peak value in the positive half cycle), the switching control module 100 controls the first switch unit 10 to switch off and controls the second switch unit 20 to switch on; thus, the second battery E 2 , damping component R 2 , current stage component L 4 , capacitor C 1 and second switch unit 20 form a charging/discharging circuit, which performs charging/discharging operations (as indicated by the time period t 2 in FIG. 5 ). After the charging/discharging circuit completes a charging/discharging cycle (at this point, the current I C1 through capacitor C 1 reaches zero after the positive half cycle, and the entire heating circuit accomplishes a complete working cycle), the switching control module 100 controls the first switch unit 10 to switch on and controls the switch unit 20 to switch off again; in that way, the cycles continue on, so that the current flows through the damping component R 1 and damping component R 2 continuously; as a result, the damping component R 1 and damping component R 2 generate heat, and thereby heat up the first battery E 1 and second battery E 2 to the expected condition.

In the above working process of the heating circuit shown in FIG. 4 , the current can be kept flowing back-and-forth between the first battery E 1 and the second battery E 2 , so that the two batteries are heated up in alternate, and therefore the heating efficiency is improved. In addition, in the heating circuit shown in FIG. 4 , the capacitor is connected in series with the battery. When the battery is heated, safety problems related with failure or short circuit of the switch unit can be avoided owing to the existence of the serially connected capacitor, and therefore the battery can be protected effectively.

FIG. 6 is a schematic diagram of the heating circuit in the second embodiment of the present invention. Preferably, as shown in FIG. 6 , the heating circuit provided in one embodiment of the present invention can further comprise an energy storage component V 2 ; the first battery E 1 , damping component R 1 , current stage component L 3 , energy storage component V 2 and second switch unit 20 are connected in series to form a third charging/discharging circuit; the second battery E 2 , damping component R 2 , current stage component L 4 , energy storage component V 2 and first switch unit 10 are connected in series to form a fourth charging/discharging circuit; when the energy storage component V 2 is charged or discharges, the direction of charging/discharging current in the third charging/discharging circuit is reverse to the direction of charging/discharging current in the fourth charging/discharging circuit; the switching control module 100 also controls the electric energy to flow among the first battery E 1 , energy storage component V 1 , energy storage component V 2 and second battery E 2 by controlling the first switch unit 10 and second switch unit 20 to switch on in alternate.

Wherein: the energy storage component V 2 can also be an inductor L 2 or a capacitor C 2 . FIG. 7 and FIG. 9 show the circuit diagrams in the case that the energy storage component V 2 is an inductor L 2 or capacitor C 2 , respectively; FIG. 8 and FIG. 10 show the timing sequence diagrams of waveform corresponding to FIG. 7 and FIG. 9 , respectively. Hereunder the heating circuit in the second embodiment of the present invention will be described, with reference to FIG. 7 to FIG. 10 .

As shown in FIG. 7 , the energy storage component V 1 is an inductor L 1 , the energy storage component V 2 is an inductor L 2 , the switching control module can control the first switch unit 10 and second switch unit 20 to switch their ON/OFF states when the current in the inductor L 1 or inductor L 2 reaches a preset value. FIG. 8 is a timing sequence diagram of the waveform of the circuit shown in FIG. 7 . Hereunder the working process of the heating circuit provided in the second embodiment of the present invention will be described, with reference to FIG. 8 .

First, the switching control module 100 controls the first switch unit 10 to switch on, and controls the second switch unit 20 to switch off; thus, the first battery E 1 charges the inductor L 1 , and the second battery E 2 charges the inductor L 2 ; as a result, the current I L1 and current I L2 in the inductor L 1 and inductor L 2 increase slowly (as indicated by the time period t 1 shown in FIG. 8 ). When the current I L1 in the inductor L 1 or the current I L2 in the inductor L 2 rises to a preset value, the switching control module 100 controls the first switch unit 10 to switch off and controls the second switch unit 20 to switch on; the inductor L 1 transfers the energy stored in it to the second battery E 2 , and the inductor L 2 transfers the energy stored in it to the first battery E 1 ; therefore the current I L1 in the inductor L 1 and the current I L2 in the inductor L 2 decrease slowly (as indicated by the time period t 2 ). Then, after the energy in the inductor L 1 and L 2 is released, the second battery E 2 turns to charge the inductor L 1 , and the first battery E 1 turns to charge the inductor L 2 ; therefore the current I L1 in the inductor L 1 and the current I L2 in the inductor L 2 increase slowly. At this time, the flow direction of the current in the inductor L 1 and L 2 is reverse to the flow direction in the time period t 1 and t 2 (as indicated by the time period t 3 ). Then, when the current I L1 in the inductor L 1 or the current I L2 in the inductor L 2 rises to a preset value, the switching control module 100 controls the first switch unit 10 to switch on and controls the second switch unit 20 to switch off; the inductor L 1 transfers the energy stored in it to the first battery E 1 , and the inductor L 2 transfers the energy stored in it to the second battery E 2 ; therefore the current I L1 in the inductor L 1 and the current I L2 in the inductor L 2 decrease slowly (as indicated by the time period t 4 ; now, the heating circuit has accomplished a complete working cycle). The cycles continue on and on, till the first battery E 1 and second battery E 2 are heated up satisfactorily. It should be noted: U L1 and U L2 in FIG. 8 represent the voltage of the inductor L 1 and the voltage of the inductor L 2 ; the voltage U L1 is a constant value in forward direction when the current I L1 through the inductor L 1 increases in forward direction or decreases in reverse direction, and is a constant value in reverse direction when the current I L1 through the inductor L 1 decreases in forward direction or increases in reverse direction. The same is true also for voltage U L2 .

By adding an inductor L 2 in the heating circuit, the first battery E 1 and second battery E 2 are always in a charging/discharging process, and current always flows through the impedance component R 1 and impedance component R 2 ; thus, the heating efficiency is further improved. Alternatively, the current flowing through the first and second batteries and the first and second switch units can be limited by the inductor L 1 and L 2 and the preset value, so that the first and second batteries and the first and second switch units are protected.

In addition, it should be noted: the “preset value” mentioned above shall be set according to the current endurable by the first battery E 1 , second battery E 2 , and other components/components in the heating circuit, with comprehensive consideration of heating efficiency and protection of the first battery E 1 and second battery E 2 against damages, as well as the size, weight and cost of the heating circuit.

As shown in FIG. 9 , the energy storage component V 1 is a capacitor C 1 , the energy storage component V 2 is a capacitor C 2 , the switching control module 100 can control the first switch unit 10 and second switch unit 20 to switch their ON/OFF states when the current in the capacitor C 1 or capacitor C 2 reaches zero after each pair of continuous positive and negative half cycles or each pair of continuous negative and positive half cycles. FIG. 10 is a timing sequence diagram of the waveform of the circuit shown in FIG. 9 . Hereunder the working process of another heating circuit in the second embodiment of the present invention will be described, with reference to FIG. 9 and FIG. 10 .

First, the switching control module 100 controls the first switch unit 10 to switch on, and controls the second switch unit 20 to switch off; the first battery E 1 , damping component R 1 , current stage component L 3 , capacitor C 1 and first switch unit 10 form a charging/discharging circuit; the second battery E 2 , damping component R 2 , current stage component L 4 , capacitor C 2 and first switch unit 10 form another charging/discharging circuit; the two charging/discharging circuits perform charging/discharging operations (as indicated by the time period t 1 shown in FIG. 10 ; please note: the voltage waveform and current waveform of capacitor C 1 are the same as those of the capacitor C 2 ). After the two charging/discharging circuits complete a charging/discharging cycle (at this point, the current I C1 through the capacitor C 1 or the current I C2 through the capacitor C 2 reaches zero after the negative half cycle, the voltage U C1 of the capacitor C 1 or the voltage U C2 of the capacitor C 2 has passed the peak value in the positive half cycle), the switching control module 100 controls the first switch unit 10 to switch off and controls the second switch unit 20 to switch on; thus, the first battery E 1 , damping component R 1 , current stage component L 3 , capacitor C 2 and second switch unit 20 form a charging/discharging circuit, and the second battery E 2 , damping component R 2 , current stage component L 4 , capacitor C 1 and second switch unit 20 form another charging/discharging circuit; the two charging/discharging circuits perform charging/discharging operations (as indicated by the time period t 2 shown in FIG. 10 ; please note: at this point, the voltage waveform and current waveform of the capacitor C 1 are the same as those of the capacitor C 2 ). After the two charging/discharging circuits complete a charging/discharging cycle (at this point, the current I C1 through the capacitor C 1 or the current I C2 through the capacitor C 2 reaches zero after the positive half cycle, and the entire heating circuit accomplishes a complete working cycle), the switching control module 100 controls the first switch unit 10 to switch on and controls the second switch unit 20 to switch off again; in that way, the cycles continue on and on, so that the current flows through the damping component R 1 and damping component R 2 continuously; thus, the damping component R 1 and damping component R 2 generate heat, and thereby heat up the first battery E 1 and second battery E 2 to the expected condition.

By adding a capacitor C 2 in the heating circuit, two charging/discharging circuits are formed at the same time in each working cycle, and therefore the first battery E 1 and second battery E 2 are always in a charging/discharging process, and the current always flows through the damping component R 1 and damping component R 2 ; thus, the heating time can be shortened.

FIG. 11 is a circuit diagram of one embodiment of the switch unit in the heating circuit provided in the present invention. As shown in FIG. 11 , the first switch unit 10 and/or the second switch unit 20 can comprise a switch K 11 and a one-way semiconductor component D 11 connected in parallel with the switch K 11 in reverse direction, wherein: the switching control module 100 is electrically connected with the switch K 11 , and is configured to control ON/OFF of the forward direction branches of the first switch unit 10 and/or the second switch unit 20 by controlling ON/OFF of the switch K 11 . The ON/OFF control of switch K 11 can be performed in the grid zone shown in FIG. 3 , FIG. 5 , FIG. 8 and FIG. 10 . In FIG. 5 and FIG. 10 , when or after the current flowing through the first switch unit 10 or the second switch unit 20 reaches zero, the switching control module 100 can control the first switch unit 10 or the second switch unit 20 to switch off respectively.

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.