CN112838624B

CN112838624B - Power supply circuit

Info

Publication number: CN112838624B
Application number: CN201911156710.2A
Authority: CN
Inventors: 谭磊; 易新敏
Original assignee: SG Micro Beijing Co Ltd
Current assignee: SG Micro Beijing Co Ltd
Priority date: 2019-11-22
Filing date: 2019-11-22
Publication date: 2024-02-06
Anticipated expiration: 2039-11-22
Also published as: CN112838624A

Abstract

The invention discloses a power supply circuit, which comprises a first battery, a second battery and a conditioning circuit which are sequentially connected in series, wherein the conditioning circuit comprises: the first to fourth switches, the flying capacitor and the circulation control circuit are sequentially connected in series between the positive electrode of the first battery and the negative electrode of the second battery, the middle node between the second switch and the third switch is connected to the middle nodes of the first battery and the second battery, the flying capacitor comprises a first polar plate connected with the middle nodes of the first switch and the second switch and a second polar plate connected with the middle nodes of the third switch and the fourth switch, and the circulation control circuit is beneficial to reducing the manufacturing cost by controlling the working circulation of the first to fourth switches so as to balance the positive electrode voltage of the second battery to half of the positive electrode voltage of the first battery, and the first battery and the second battery can be charged to the same level under the low-voltage charging type, so that the first battery and the second battery can be compatible with universal 5V chargers which are widely popularized on the market.

Description

Power supply circuit

Technical Field

The invention relates to the technical field of integrated circuits, in particular to a power supply circuit.

Background

Lithium ion batteries are increasingly used in the fields of notebook computers, mobile phones, robots, electric tools and the like because of the advantages of high energy storage capacity and the like. However, with the development of technology, the requirement of users on battery capacity and voltage increases, the design of only adopting a single lithium ion battery cannot meet the requirement of users, and the design of connecting a plurality of lithium ion batteries in series can improve the charging speed and the power supply voltage on the premise of ensuring that the total capacity of the batteries is equivalent. The lithium ion batteries are connected in series, so that the charging and discharging functions can be realized only by matching with a special charger and a high-voltage circuit, and the universal 5V charger and the low-voltage circuit which are widely popularized in the market cannot be compatible.

Therefore, improvements are needed in the prior art to solve the problem that the universal 5V charger and the low-voltage circuit cannot be compatible when the dual batteries are used in series, and reduce the circuit scale and the manufacturing cost.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a power circuit, which is provided with a conditioning circuit connected to a series battery, and the conditioning circuit provides a low-voltage charging scheme for charging from the middle of the series battery, so that the dual-battery series can be compatible with a universal 5V charger which has been widely popularized in the market, and the manufacturing cost is reduced.

According to an embodiment of the present invention, there is provided a power supply circuit including: a first battery and a second battery connected in series in sequence; and a conditioning circuit, wherein the conditioning circuit comprises: first to fourth switches connected in series in sequence between a positive electrode of the first battery and a negative electrode of the second battery, an intermediate node between the second switch and the third switch being connected to intermediate nodes of the first battery and the second battery; a flying capacitor comprising a first plate connected to the intermediate nodes of the first switch and the second switch, and a second plate connected to the intermediate nodes of the third switch and the fourth switch; and a cycle control circuit for balancing the positive electrode voltage of the second battery to half of the positive electrode voltage of the first battery by controlling the duty cycles of the first to fourth switches.

Preferably, the cycle control circuit includes: a voltage difference detection module for detecting a voltage difference between positive voltages of the first battery and the second battery and generating a compensation control signal based on the voltage difference; the cyclic time sequence adjusting module is connected with the voltage difference detecting module and used for generating a cyclic adjusting signal according to the compensation control signal; and the driving module is connected with the cycle time sequence adjusting module and used for adjusting the working cycle of the first switch, the second switch and the fourth switch according to the cycle adjusting signal so as to balance the positive voltage of the second battery to be half of the positive voltage of the first battery.

Preferably, the cyclic timing adjustment module has a continuous adjustment mode and a stepwise adjustment mode.

Preferably, the conditioning circuit further comprises an inductance connected in series between an intermediate node between the second switch and the third switch and an intermediate node of the first battery and the second battery.

Preferably, the power supply circuit further includes a low voltage terminal connected to an intermediate node of the first battery and the second battery, and a ground terminal connected to a negative electrode of the second battery, wherein the low voltage terminal and the ground terminal are used to be connected to an external low voltage charger in a low voltage charging type of the power supply circuit and to be connected to an external low voltage load in a low voltage power supplying type of the power supply circuit.

Preferably, the power supply circuit further includes a high voltage terminal connected to the positive electrode of the first battery, wherein the high voltage terminal and the ground terminal are used to be connected to an external high voltage charger in a high voltage charging type of the power supply circuit and to be connected to an external high voltage load in a high voltage supplying type of the power supply circuit.

Preferably, the conditioning circuit further includes first to third capacitors, wherein the first capacitor is connected in series between the positive electrode and the negative electrode of the first battery, the second capacitor is connected in series between the positive electrode and the negative electrode of the second battery, and the third capacitor is connected in series between the positive electrode of the first battery and the negative electrode of the second battery.

Preferably, the first to fourth switches are respectively selected from metal oxide semiconductor field effect transistors or complementary metal oxide semiconductor field effect transistors.

Preferably, the inductance is selected from small inductance values.

The power supply circuit of the embodiment of the invention is provided with the conditioning circuit connected with the batteries in series, and the conditioning circuit not only can balance the positive voltage of the upper battery to be twice of the positive voltage of the lower battery under the low-voltage charging type, but also ensures that the upper battery and the lower battery can be charged to the same level. And the battery voltages of the upper battery and the lower battery can be balanced under the high-voltage charging type, so that the charging voltages of the upper battery and the lower battery are kept consistent. On the one hand, a low-voltage charging scheme for charging from the middle of the series battery is provided, so that the battery can be compatible with a universal 5V charger which is widely popularized in the market, and the manufacturing cost is reduced. On the other hand, the power supply circuit of the embodiment can be compatible with chargers of two different charging schemes of low-voltage charging and high-voltage charging, is convenient for users to select, and improves the diversity of products.

Furthermore, the conditioning circuit of the power supply circuit in this embodiment is further configured to equalize the voltages between the upper and lower batteries under the low-voltage power supply type, so as to avoid the occurrence of inconsistent output power of the upper and lower batteries due to the output of electric energy from the intermediate node of the series-connected batteries. On the one hand, the power supply circuit of the embodiment can directly supply power to the low-voltage load, and the low-voltage load is not required to be matched with a corresponding step-down circuit, so that the manufacturing cost of the circuit is reduced. On the other hand, the power supply circuit of the embodiment can also reduce the extra power consumption caused by the inconsistent output power of the upper battery and the lower battery.

Furthermore, the conditioning circuit further comprises an inductor with a small inductance value, the voltage difference between the positive voltages of the upper battery and the lower battery is adjusted through follow current action of the inductor with the small inductance value and fine adjustment of the duty ratio of the circulating control circuit to the charge pump, and the voltage can be slightly increased in the output direction of the conditioning circuit, so that balance of the positive voltages of the upper battery and the lower battery is further promoted.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the present invention with reference to the accompanying drawings.

Fig. 1 shows a schematic structure of a power circuit application according to an embodiment of the invention;

FIG. 2 shows a schematic circuit diagram of the conditioning circuit of FIG. 1;

FIG. 3 shows a duty cycle timing diagram of the operational mode of the conditioning circuit of FIG. 2;

FIG. 4 shows another circuit schematic of the conditioning circuit of FIG. 1;

FIGS. 5A and 5B illustrate voltage build-up for the charge pump operating waveform and underdamped second order circuit, respectively, of the conditioning circuit of FIG. 4 away from the charge balance state during the switching cycle;

fig. 6A and 6B show small signal circuit schematic diagrams of the conditioning circuit of fig. 4, respectively.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. Like elements are denoted by like reference numerals throughout the various figures. For clarity, the various features of the drawings are not drawn to scale. Furthermore, some well-known portions may not be shown in the drawings.

Numerous specific details of the invention, such as construction, materials, dimensions, processing techniques and technologies, may be set forth in the following description in order to provide a thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.

It should be appreciated that in the following description, a "circuit" may include a single or multiple combined hardware circuits, programmable circuits, state machine circuits, and/or elements capable of storing instructions for execution by the programmable circuits. When an element or circuit is referred to as being "connected to" another element or being "connected between" two nodes, it can be directly coupled or connected to the other element or intervening elements may be present, the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements present between the two.

Fig. 1 shows a schematic structure of a power circuit application according to an embodiment of the invention. As shown in fig. 1, the power supply circuit 200 of the present embodiment includes a high-voltage terminal 221, a low-voltage terminal 222, a ground terminal 223, and a battery 211 and a battery 212 sequentially connected in series between the high-voltage terminal 221 and the ground terminal 223 of the power supply circuit 200, the positive electrode of the battery 211 is connected to the high-voltage terminal 221, the negative electrode of the battery 211 is connected to the positive electrode of the battery 212, and the positive electrode and the negative electrode of the battery 212 are connected to the low-voltage terminal 222 and the ground terminal 223, respectively. The power circuit 200 also includes a conditioning circuit 230, the conditioning circuit 230 for balancing current and voltage between the battery 211 and the battery 212 under different operating types of the power circuit 200.

In the present embodiment, the different operation types of the power supply circuit 200 include a high-voltage charge type, a low-voltage charge type, a high-voltage power supply type, and a low-voltage power supply type. Wherein the terms "high voltage" and "low voltage" are used herein in a relative sense, and different terminal devices may be different. Taking mobile terminals such as mobile phones as an example, a voltage of more than 5V is generally referred to as "high voltage"; voltages less than 5V are referred to as "low voltages".

Specifically, when the power supply circuit 200 operates in the high-voltage charging type, the high-voltage terminal 221 and the ground terminal 223 of the power supply circuit 200 are connected to the high-voltage charger 131 to supply electric power to the battery 211 and the battery 212 via the high-voltage terminal 221. The conditioning circuit 230 is now used to equalize the voltage between the battery 211 and the battery 212 so that the charging voltages of the battery 211 and the battery 212 remain consistent.

It should be noted that the power supply circuit 200 of the present embodiment may be applied to a mobile terminal, where the high voltage terminal 221 and the ground terminal 223 may be connected to a high voltage charging interface on the mobile terminal, and then connected to the high voltage charger 131 via the high voltage charging interface, where the type of the high voltage charging interface is matched with the type of the connection port of the high voltage charger 131.

The high-voltage charger 131 is, for example, a charger capable of outputting a predetermined high voltage. Taking a mobile terminal such as a mobile phone as an example, the high voltage charger 131 can output a voltage higher than 5V, preferably 9-12V.

When the power supply circuit 200 operates in the low-voltage charging type, the low-voltage terminal 222 and the ground terminal 223 of the power supply circuit 200 are connected with the low-voltage charger 132 to supply electric power to the battery 212 via the low-voltage terminal 222. The conditioning circuit 230 is now used to balance the positive voltage of the battery 211 to twice the positive voltage of the battery 212, thereby charging the battery 211 to the same level as the battery 212 as well. It should be noted that the power supply circuit 200 of the present embodiment may be applied to a mobile terminal, where the low voltage terminal 221 and the ground terminal 223 may be connected to a low voltage charging interface on the mobile terminal, and then connected to the low voltage charger 132 via the low voltage charging interface, where the type of the low voltage charging interface is matched with the type of the connection port of the low voltage charger 132.

The low-voltage charger 132 is, for example, a charger capable of outputting a predetermined low voltage. Taking a mobile terminal such as a cell phone as an example, the low voltage charger 132 can output a voltage of less than 5V, preferably 4-5V.

When the power supply circuit 200 operates in the high-voltage power supply type, the high-voltage terminal 221 and the ground terminal 223 of the power supply circuit 200 are connected with the high-voltage load 121 to supply electric power to the high-voltage load 121 via the high-voltage terminal 221. The conditioning circuit 230 is used for equalizing the voltages between the battery 211 and the battery 212, so that the output power of the battery 211 and the output power of the battery 212 are consistent, and the extra loss caused by the difference of the individual batteries is reduced. The high-voltage load 121 is, for example, a load circuit whose rated operating voltage is a predetermined high voltage. Taking a mobile terminal such as a cell phone as an example, the high voltage load 121 may have a rated operating voltage higher than 5V.

When the power supply circuit 200 operates in the low voltage power supply type, the low voltage terminal 222 and the ground terminal 223 of the power supply circuit 200 are connected with the low voltage load 122 to supply electric power to the low voltage load 122 via the low voltage terminal 222. The conditioning circuit 230 is used for equalizing the voltages between the battery 11 and the battery 212, so as to avoid inconsistent output power of the battery 211 and the battery 212 caused by output of electric energy from the intermediate node of the battery 211 and the battery 212. The low-voltage load 122 is, for example, a load circuit whose rated operating voltage is a specified low voltage. Taking a mobile terminal such as a cell phone as an example, the low voltage load 122 may have a rated operating voltage below 5V.

The power supply circuit 200 of the embodiment of the invention is provided with the conditioning circuit 230 connected with the batteries in series, and the conditioning circuit 230 not only can balance the positive voltage of the upper battery to be twice of the positive voltage of the lower battery under the low-voltage charging type, so as to ensure that the upper battery and the lower battery can be charged to the same level. And the battery voltages of the upper battery and the lower battery can be balanced under the high-voltage charging type, so that the charging voltages of the upper battery and the lower battery are kept consistent. On the one hand, a low-voltage charging scheme for charging from the middle of the series battery is provided, so that the battery can be compatible with a universal 5V charger which is widely popularized in the market, and the manufacturing cost is reduced. On the other hand, the power supply circuit of the embodiment can be compatible with chargers of two different charging schemes of low-voltage charging and high-voltage charging, is convenient for users to select, and improves the diversity of products.

Further, the conditioning circuit 230 of the power supply circuit 200 of the present embodiment is further configured to equalize the voltages between the upper and lower batteries under the low-voltage power supply type, so as to avoid the occurrence of inconsistent output power of the upper and lower batteries due to the output of electric energy from the intermediate node of the series-connected batteries. On the one hand, the power supply circuit of the embodiment can directly supply power to the low-voltage load, and the low-voltage load is not required to be matched with a corresponding step-down circuit, so that the manufacturing cost of the circuit is reduced. On the other hand, the power supply circuit of the embodiment can also reduce the extra power consumption caused by the inconsistent output power of the upper battery and the lower battery.

Fig. 2 shows a schematic circuit diagram of the conditioning circuit of fig. 1. As shown in fig. 2, conditioning circuit 230 includes switches M11-M14, flying capacitor CF1, and a cycle control circuit 231 connected in series in sequence.

The first end of the switch M11 and the positive electrode of the battery 211 are connected to the first coupling node T, the intermediate nodes of the switch M12 and the switch M13 and the positive electrode of the battery 212 are connected to the second coupling node C, and the second end of the switch M14 and the negative electrode of the battery 212 are connected to the third coupling node B.

The flying capacitor CF1 has an upper plate connected to the intermediate node of the switch M11 and the switch M12, and a lower plate connected to the intermediate node of the switch M13 and the switch M14.

The circulation control circuit 231 is connected to the switches M11-M14, and is configured to balance the positive voltage of the battery 212 to half the positive voltage of the battery 211 by controlling the duty cycle of the switches M11-M14, so that the battery 211 and the battery 212 can maintain balanced voltages and currents under different operation types of the power supply circuit.

In the example of fig. 2, in order to promote the balance of voltages between the battery 211 and the battery 212, a cycle control circuit 231 is connected to the anodes of the battery 211 and the battery 212, respectively, to detect the anode voltages of the battery 211 and the battery 212, and when the anode voltages of the battery 211 and the battery 212 deviate from a predetermined integral multiple relationship, the duty cycles of the switches M11 to M14 are feedback-adjusted in a predetermined ratio to promote the balance between the anode voltages of the two.

Further, the loop control circuit 231 of the present embodiment includes a voltage difference detection module 2311, a loop timing adjustment module 2312, and a driving module 2313. The voltage difference detection module 2311 is connected to the anodes of the battery 211 and the battery 212, respectively, to detect a voltage difference between the positive voltage of the battery 211 and the positive voltage of the battery 212, and generate a compensation control signal based on the voltage difference. The cycle timing adjustment module 2312 is coupled to the voltage difference detection module 2311 to receive the compensation control signal and generate a cycle adjustment signal in response to the compensation control signal. The driving module 2313 is coupled to the cycle timing adjustment module 2312 to receive the cycle adjustment signal and adjust the duty cycle of the switches M11-M14 in response to the cycle adjustment signal to facilitate voltage balancing between the battery 211 and the battery 212.

In the example of fig. 2, the driving module 2313 is understood to apply the first driving signal D1 to drive the control terminal of the switch M11, the second driving signal D2 to drive the control terminal of the switch M12, the third driving signal D3 to drive the control terminal of the switch M13, and the fourth driving signal D4 to drive the control terminal of the switch M13. The first driving signal D1 and the third driving signal D3 are the same signals, the second driving signal D2 and the fourth driving signal D4 are the same signals, and the first driving signal D1 and the third driving signal D3 are opposite signals to the second driving signal D2 and the fourth driving signal D4. Thus, the driving module 2313 of the present embodiment is understood to adjust the duty ratios of the first to fourth driving signals D1 to D4 in response to the cyclic adjustment signal to adjust the on or off times of the switches M11 to M14 at each switching period.

Fig. 3 shows a duty cycle timing diagram of the operational mode of the conditioning circuit of fig. 2. In fig. 3, time T1 and time T2 constitute a complete switching period T of the conditioning circuit, and the first to fourth driving signals D1 to D4 are square wave signals having a certain duty cycle. The following description will be made of the operation of the power supply circuit in the low-voltage charging type.

At time t1, the first driving signal D1 and the third driving signal D3 are at low level, and the second driving signal D2 and the fourth driving signal D4 are at high level. At this time, the first switch M11 and the third switch M13 are turned off, and the second switch M12 and the fourth switch M14 are turned on. The flying capacitor CF1 is connected in parallel with the battery 212, the battery 212 charges the flying capacitor CF1, the voltage vcf1_h of the upper plate of the flying capacitor CF1 is equal to the voltage VC of the second coupling node C, and the voltage vcf1_l of the lower plate of the flying capacitor CF1 is equal to the reference ground voltage.

At time t2, the first driving signal D1 and the third driving signal D3 are at high level, and the second driving signal D2 and the fourth driving signal D4 are at low level. At this time, the first switch M11 and the third switch M13 are turned on, and the second switch M12 and the fourth switch M14 are turned off. The flying capacitor CF1 is connected in parallel with the battery 211, and the upper plate voltage vcf1_h of the flying capacitor CF1 is equal to the voltage VT of the first coupling node T, and the lower plate voltage vcf1_l of the flying capacitor CF1 is equal to the voltage VC of the second coupling node C. Since the voltage difference between the upper and lower plates of the flying capacitor CF1 is kept constant, the upper plate voltage vcf1_h of the flying capacitor CF1 is equal to 2×vc at this time, and thus the voltage VT of the first coupling node T is equal to 2×vc. After a plurality of switching cycles, the positive voltage of the battery 211 is balanced by 2 times the positive voltage of the battery 212, so that the battery 211 can be charged to the same level as the battery 212 in the low voltage charging type.

The charge transfer direction on the flying capacitor CF1 of the conditioning circuit in this embodiment may be any direction, for example, the charge transfer direction on the flying capacitor CF1 is determined by the load or power supply connected to the high voltage terminal 221 and the low voltage terminal 222.

In addition, the voltage detecting circuit is also used for detecting the positive voltages of the battery 211 and the battery 212 during the operation of the conditioning circuit, and when the voltage difference between the positive voltage of the battery 211 and the positive voltage of the battery 212 deviates from a predetermined integral multiple (for example, 2 times), the duty ratios of the first to fourth driving signals D1 to D4 are feedback-adjusted to promote the balance between the positive voltages.

The cycle timing adjustment module of the present embodiment includes a step adjustment mode and a continuous adjustment mode. In the step adjustment mode, when the voltage difference between the battery 211 and the battery 212 deviates from a preset integral multiple relation, the cycle time adjustment module adjusts the duty ratio of the first to fourth driving signals D1-D4 according to a preset proportion until the voltage difference between the battery 211 and the battery 212 reaches the preset integral multiple relation, and then the cycle time adjustment module restores the duty ratio of the first to fourth driving signals D1-D4 to 50%; in the continuous adjustment mode, the cycle timing adjustment module adjusts the duty cycles of the first through fourth drive signals D1-D4 according to the voltage difference feedback between the battery 211 and the battery 212 to promote voltage balance therebetween.

With continued reference to fig. 2, conditioning circuit 230 also includes a capacitor C1-C3 for high voltage decoupling of the power supply circuit. Wherein the capacitor C1 is connected in series between the first coupling node T and the second coupling node C, the capacitor C2 is connected in series between the second coupling node C and the third coupling node B, and the capacitor C3 is connected in series between the first coupling node T and the third coupling node B.

Fig. 4 shows another circuit schematic of the conditioning circuit of fig. 1. As shown in FIG. 4, the conditioning circuit 240 of another embodiment includes switches M21-M24, flying capacitor CF2, circulation control circuit 241, capacitors C1-C3, and inductor L1 connected in series. The structures and connection manners of the switches M21-M24, the flying capacitors CF2, the capacitors C1-C3, and the circulation control circuit 241 are identical to those of the conditioning circuit in fig. 2, and are not described herein.

The inductor L1 is connected in series between the intermediate node S of the switch M22 and the switch M23 and the positive electrode of the battery 212 to construct a voltage difference boosting circuit and an underdamped second-order circuit to boost the voltage in the output direction of the conditioning circuit. When there is no inductance L1, the total parasitic resistance R of the switches M21-M24 and the flying capacitor CF2 in the conditioning circuit form a first order circuit, and there is an unavoidable voltage drop between the input voltage and the output voltage, resulting in a deviation of a predetermined integer multiple relationship between the positive voltages of the battery 211 and the battery 212.

Fig. 5A and 5B illustrate the voltage build-up process of the charge pump operating waveform and underdamped second order circuit, respectively, of the conditioning circuit of fig. 4 away from the charge balance state during the switching cycle. In fig. 5A, the solid line represents the variation curves of the flying capacitor current ICF2 and the flying capacitor voltage VCF2 in the switching period, and the broken line represents the progressive course of the flying capacitor current and the flying capacitor voltage after one switching without switching. In fig. 5B, the solid line represents the voltage build-up process of the under-damped second order circuit, and the dotted line represents the critical damped line of the under-damped ringing. In the embodiment, an inductor L1 is added between the intermediate node S of the switch M22 and the switch M23 and the positive electrode of the battery 212, and the voltage difference between the positive voltages of the battery 211 and the battery 212 is adjusted by the freewheeling action of the inductor L1 and by adjusting the duty ratios of the first to fourth driving signals D1 to D4, so as to increase the voltage in the output direction of the conditioning circuit by a small margin.

Fig. 6A and 6B show small signal circuit schematic diagrams of the conditioning circuit of fig. 4, respectively. In fig. 6A and 6B, the capacitor C1, the capacitor C2 and the flying capacitor CF2 are all large enough, the voltage on them will not change when the charge transfer occurs, the time constants of the flying capacitor CF2 and the inductor L1 are large enough relative to the switching period of the conditioning circuit, the voltage on the flying capacitor CF2 changes with a linear slope, and the resistor R is the total parasitic resistance on the switching path.

The effect of the switching duty cycle on the voltage distribution of the conditioning circuit when deriving pure resistors and pure inductors from fig. 6A and 6B is as follows:

when the resistor is pure: v1-v2=i×r×t ² /(2×T1×T2) (1)

When the pure inductance is: v1—v2=2×i×l× (1/T1-1/T2) (2)

Wherein V1 and V2 are voltages on the capacitor C1 and the capacitor C2, T is a switching period of the conditioning circuit, T1 is a time when the flying capacitor CF2 and the capacitor C1 are turned on, T2 is a time when the flying capacitor CF2 and the capacitor C2 are turned on, and t=t1+t2. As can be seen from equation (1), when the conditioning circuit has only a pure resistance, there is an unavoidable voltage drop in the current direction of the circuit due to the effect of the parasitic resistance on the switching path, and the magnitude of the voltage drop depends on the current I and the switching parasitic resistance R, and the voltage loss of the circuit is minimal when t1=t2=t/2. As can be seen from the formula (2), when there is a pure inductance in the conditioning circuit, the voltage of the circuit in the current direction may be decreased or increased due to the freewheeling effect of the inductance, and the voltage variation in the current direction depends on the relationship between the time T1 and the time T2. The fine adjustment of the voltage distribution proportion relation of the upper section and the lower section of the conditioning circuit can be realized by utilizing the follow current action of the micro-inductor. The fine tuning ensures that the circuit can still maintain the integral multiple of the input and output relation under the condition of great switching path loss, and has high efficiency when deviating from the integral multiple of the input and output relation. Further, the inductance L1 in the conditioning circuit of the present embodiment may be a inductance with a small inductance value. Taking a battery with internal resistance of 40mΩ and current of 2.5A as an example, the inductance of the inductor L1 only needs 100nH when the circuit is operated at a switching frequency of 500kHz and in the case of current ripple of 1A.

In addition, the second-order circuit formed by the inductance L1, the flying capacitor CF2 and the total parasitic resistance R of the switches M21-M24 can make the current lifting speed of the circuit higher than that of the first-order circuit, and improve the charge transfer capability. As shown in fig. 5B, the current on the capacitor C3 maintains the original direction at the moment of switch on, the voltage variation on the capacitor C3 maintains the original direction, and the later under-damped overshoot process makes the voltage variation exceed the voltage variation of the first-order circuit, and if the period of the charge pump in the conditioning circuit approaches the characteristic frequency of the damping circuit, the damping process is beneficial to accelerating the charge transfer.

In this embodiment, the voltage difference between the positive voltages of the upper and lower batteries is adjusted by the freewheel action of the inductance L1 with a small inductance and the fine adjustment of the duty ratio of the circulation control circuit to the charge pump, so that the voltage can be raised in the output direction of the conditioning circuit with a small amplitude, and the balance of the positive voltages of the upper and lower batteries is further improved.

In the above embodiments, the switches M11-M14 and the switches M21-M24 are combinations of one or more structures such as Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) or complementary Metal-Oxide-semiconductor field effect transistor (Complementary Metal Oxide Semiconductor, CMOS). In a further embodiment, the switches M11-M14 and the switches M21-M24 are selected from, for example, P-type metal oxide semiconductor field effect transistors.

In summary, the power supply circuit of the embodiment of the invention is provided with the conditioning circuit connected with the series-connected batteries, and the conditioning circuit not only can balance the positive voltage of the upper battery to twice the positive voltage of the lower battery under the low-voltage charging type, but also ensures that the upper battery and the lower battery can be charged to the same level. And the battery voltages of the upper battery and the lower battery can be balanced under the high-voltage charging type, so that the charging voltages of the upper battery and the lower battery are kept consistent. On the one hand, a low-voltage charging scheme for charging from the middle of the series battery is provided, so that the battery can be compatible with a universal 5V charger which is widely popularized in the market, and the manufacturing cost is reduced. On the other hand, the power supply circuit of the embodiment can be compatible with chargers of two different charging schemes of low-voltage charging and high-voltage charging, is convenient for users to select, and improves the diversity of products.

It should be noted that in this document relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

Embodiments in accordance with the present invention, as described above, are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and the full scope and equivalents thereof.

Claims

1. A power supply circuit, comprising:

a first battery and a second battery connected in series in sequence;

a high-voltage terminal connected to the positive electrode of the first battery;

a low-voltage terminal connected to the negative electrode of the first battery and the positive electrode of the second battery;

a ground terminal connected to the negative electrode of the second battery; and

conditioning circuitry for balancing the voltages of the first battery and the second battery under different operating types,

wherein when the power supply circuit is operated in a high-voltage charging type, the high-voltage terminal and the ground terminal are connected with a high-voltage charger to supply electric power to the first battery and the second battery via the high-voltage terminal, the conditioning circuit keeps the charging voltages of the first battery and the second battery uniform,

when the power circuit is operated in a low voltage charging type, the low voltage terminal and the ground terminal are connected with a low voltage charger to supply electric power to the second battery via the low voltage terminal, the conditioning circuit is used for balancing the positive voltage of the first battery to be twice the positive voltage of the second battery,

wherein the conditioning circuit comprises:

first to fourth switches connected in series in sequence between a positive electrode of the first battery and a negative electrode of the second battery, an intermediate node between the second switch and the third switch being connected to intermediate nodes of the first battery and the second battery;

a flying capacitor comprising a first plate connected to the intermediate nodes of the first switch and the second switch, and a second plate connected to the intermediate nodes of the third switch and the fourth switch; and

a cycle control circuit for detecting positive voltages of the first and second batteries, feedback-adjusting duty cycles of the first to fourth switches in a predetermined ratio when the positive voltages of the first and second batteries deviate from a predetermined integer-multiple relationship,

wherein the conditioning circuit has a plurality of switching cycles when the power circuit is operating in a low voltage charging type, and each switching cycle includes a first time period and a second time period,

during the first period, the first switch and the third switch are turned off, the second switch and the fourth switch are turned on, the flying capacitor is connected in parallel with the second battery, the second battery charges the flying capacitor, the voltage of a first polar plate of the flying capacitor is equal to the voltage of an intermediate node of the first battery and the second battery, and the voltage of a second polar plate of the flying capacitor is equal to a reference ground voltage;

in the second period, the first switch and the third switch are turned on, the second switch and the fourth switch are turned off, the flying capacitor is connected in parallel with the first battery, the voltage of the first plate of the flying capacitor is equal to the positive voltage of the first battery, the voltage of the second plate of the flying capacitor is equal to the voltage of the intermediate node of the first battery and the second battery, and

after the plurality of switching cycles, the conditioning circuit is configured to balance the positive voltage of the first battery to twice the positive voltage of the second battery.

2. The power supply circuit of claim 1, wherein the cycle control circuit comprises:

a voltage difference detection module for detecting a voltage difference between positive voltages of the first battery and the second battery and generating a compensation control signal based on the voltage difference;

the cyclic time sequence adjusting module is connected with the voltage difference detecting module and used for generating a cyclic adjusting signal according to the compensation control signal; and

and the driving module is connected with the cycle time sequence adjusting module and used for adjusting the working cycle of the first switch, the second switch and the fourth switch according to the cycle adjusting signal so as to balance the positive voltage of the second battery to be half of the positive voltage of the first battery.

3. The power circuit of claim 2, wherein the cyclic timing adjustment module has a continuous adjustment mode and a step adjustment mode.

4. The power circuit of claim 3, wherein the conditioning circuit further comprises an inductance connected in series between an intermediate node between the second switch and the third switch and an intermediate node of the first battery and the second battery.

5. The power supply circuit according to any one of claims 1 to 4, wherein the low voltage terminal and the ground terminal are connected to an external low voltage load at a low voltage supply type of the power supply circuit.

6. A power supply circuit according to any one of claims 1-4, characterized in that the high voltage terminal is connected to an external high voltage load under a high voltage supply type of the power supply circuit.

7. The power circuit of any one of claims 1-4, wherein the conditioning circuit further comprises first through third capacitors,

wherein the first capacitor is connected in series between the positive electrode and the negative electrode of the first battery,

the second capacitor is connected in series between the positive and negative electrodes of the second battery,

the third capacitor is connected in series between the positive electrode of the first battery and the negative electrode of the second battery.

8. The power supply circuit of claim 1, wherein the first through fourth switches are each selected from a metal oxide semiconductor field effect transistor or a complementary metal oxide semiconductor field effect transistor.

9. The power supply circuit of claim 4, wherein the inductance is selected from the group consisting of small inductance.