TWI626806B - Charging circuit and capacitive power conversion circuit and charging control method thereof - Google Patents

Abstract

A charging circuit for providing a charging current to a battery includes a power transmitting unit and a capacitive power conversion circuit. The power transmitting unit converts an input power into a DC output current and adjusts the DC output current to a preset output current level. The capacitive power conversion circuit includes a transfer switch circuit having a plurality of transfer switches. Or a complex conversion capacitor, and a conversion control circuit for correspondingly operating the complex conversion switch during the complex conversion period, so that the one or complex conversion capacitor is periodically correspondingly coupled to one or a plurality of voltage dividing nodes, the The DC output voltage and one of the pair of nodes of the ground point generate the charging current through one of the one or more voltage dividing nodes, where the level of the charging current is the preset output current level One of the preset boosting times.

Description

Charging circuit, capacitive power conversion circuit and charging control method

The invention relates to a charging circuit, in particular to a charging circuit capable of multiplying current. The invention also relates to a capacitive power conversion circuit and a charging control method used in a charging circuit.

FIG. 1 illustrates a prior art charging circuit (charging circuit 1), which includes a power adapter 11 with direct charging capability, and can provide a charging current IBAT via a cable 20 (such as a USB cable) and a load A switch 40 (load switch) charges a battery 50 with a constant current (CC). However, in the prior art shown in Figure 1, when a standard cable such as a USB cable is used, the current limit of the cable is generally relatively low, for example, about 5A or less, so the charging time is longer. . If you want to speed up the charging time and increase the charging current (for example, 8A or more), you must use a special fast charging cable with a thicker diameter. In addition to the inconvenience caused by the use of non-standard cables, the fast charging cable also has It is not easy to use because the wire diameter is thick and it is not easy to bend.

FIG. 2 shows another charging circuit (charging circuit 2) of the prior art, which includes a switching charging circuit 60, which can supply the power provided by the power adapter 11 (such as, but not limited to, 5V or 9V or 12V VBUS of USB PD) ) Is converted into a charging current IBAT, and the battery 50 is charged with a constant current (CC, constant current). The disadvantage of the prior art shown in FIG. 2 is that in the switching charging circuit 60, it is difficult to select an inductor and a switch (not shown) of appropriate specifications to take into account the amount of charging current and current ripple. The optimization of various parameters such as the amplitude, the on-resistance of the switch, and the energy conversion efficiency makes design optimization difficult to achieve.

Compared with the prior art of FIG. 1, the present invention has the advantage that it can provide a multiplied charging current to charge the battery and shorten the charging time. However, it can use standard cables such as USB cables. Operation under current is convenient for users. Compared with the prior art of FIG. 2, the present invention has no inductor, reduces size, reduces cost, and is easy to optimize parts selection to achieve the best energy conversion efficiency. Etc.

In one aspect, the present invention provides a charging control method for controlling a charging circuit to provide a battery with a charging power source. The charging power source includes a charging voltage and a charging current. The charging circuit includes a power transmitting circuit. Unit, and one or more capacitive power conversion circuits, wherein the power transmitting unit converts an input power into a DC output power, the DC output power includes a DC output voltage and a DC output current; wherein the capacitive power conversion circuit The charging control method includes the following steps: adjusting the DC output current to a preset output current level by the power transmitting unit; and The capacitive power conversion circuit converts the DC output power into the charging power so that the level of the charging current is a preset current scale-up factor, which is one of the preset output current levels, where The charging current is greater than the DC output current; wherein the DC output power The step of converting to the charging power source includes: correspondingly operating the complex conversion switch during the complex conversion period, so that the one or more conversion capacitors are correspondingly coupled to one or more voltage dividing nodes, the DC output voltage, and the periodically The ground point is between one pair of nodes, and the charging power source is coupled to one of the one or more voltage dividing nodes.

In a preferred embodiment, the step of converting the DC output power into the charging power further includes: generating a synchronous control signal; and controlling each of the multiple conversion periods of the complex capacitive power conversion circuit according to the synchronous control signal. Time is synchronized.

In a preferred embodiment, the step of converting the DC output power into the charging power further includes: in the capacitive power conversion circuit, in any conversion period, at the one or more voltage division nodes, the DC output The voltage and any pair of nodes of the ground point are coupled at most to one of the complex conversion capacitors.

In a preferred embodiment, the capacitive power conversion circuit includes a first capacitive power conversion circuit, the conversion capacitor includes a first conversion capacitor, and the complex conversion period includes a first conversion period and a second conversion period. ; Wherein the step of converting the DC output power into the charging power further includes: operating the complex conversion switch of the first capacitive power conversion circuit, so that the first end of the first conversion capacitor and the The second conversion period is respectively switched between the DC output voltage and the charging voltage, and the second end of the first conversion capacitor is respectively switched to the charging during the first conversion period and the second conversion period. Between the voltage and the ground point; wherein the level of the charging current is twice the level of the preset output current.

In a preferred embodiment, the conversion capacitor further includes a second conversion capacitor; wherein the step of converting the DC output power into the charging power further includes: operating the complex conversion switch of the first capacitive power conversion circuit, The first end of the second conversion capacitor is switched between the DC output voltage and the charging voltage respectively in the second conversion period and the first conversion period, and the second end of the second conversion capacitor is switched between The second conversion period and the first conversion period are respectively switched between the charging voltage and the ground point.

In a preferred embodiment, the charging control method further includes: sensing the DC output current or the charging current to generate a current-related signal; and using the power transmitting unit to adjust the DC output current in accordance with the current-related signal. The preset output current level.

According to another aspect, the present invention also provides a charging circuit including the power transmitting unit and the corresponding capacitive power conversion circuit controlled by the charging control method; and a cable for coupling the power transmitting Unit and the capacitive power conversion circuit.

In a preferred embodiment, the cable is a cable conforming to the universal serial bus power supply specification (USB PD cable), which includes a power cable, wherein the power cable is used to transmit the DC output power.

In a preferred embodiment, the cable includes a signal line, wherein the signal line is used to transmit the current-related signal.

In another aspect, the present invention also provides a capacitive power conversion circuit for a charging circuit. The charging circuit is used to provide a battery with a charging power source. The charging power source includes a charging voltage and a charging current. The charging circuit includes a power transmitting unit, wherein the power transmitting unit converts an input power into a DC output power, and the DC output power includes a DC output voltage and a DC output current; wherein the power transmitting unit regulates the DC output current At a preset output current level; the capacitive power conversion circuit includes: a transfer switch circuit including a complex transfer switch coupled to one or a plurality of transfer capacitors; and a transfer control circuit for generating a switch control signal For correspondingly operating the complex conversion switch during the complex conversion period, so that the one or complex conversion capacitor is periodically correspondingly coupled to one of a pair of one or more voltage dividing nodes, the DC output voltage, and a ground point Between nodes, so that the level of the charging current is the preset output current The quasi-one preset fold increase flow (current scale-up factor), wherein the charging current is larger than the DC output current; wherein the charging power supply coupled to the one or a plurality of partial pressure of one of the nodes in the node.

In a preferred embodiment, the conversion control circuit further generates a synchronization control signal, and controls synchronization between each of the plurality of conversion periods of the plurality of capacitive power conversion circuits according to the synchronization control signal.

In a preferred embodiment, during any conversion period, at most one of the pair of nodes of the one or more voltage dividing nodes, the DC output voltage, and the ground point is coupled to the plurality of conversion capacitors. One.

In a preferred embodiment, the capacitive power conversion circuit includes a first capacitive power conversion circuit, the conversion capacitor includes a first conversion capacitor, and the complex conversion period includes a first conversion period and a second conversion period. ; Wherein the conversion control circuit controls the plurality of conversion switches so that the first end of the first conversion capacitor is correspondingly switched between the first conversion period and the second conversion period and is electrically connected to the DC output voltage and the charging Between the voltage and the second end of the first conversion capacitor is switched between the first conversion period and the second conversion period respectively and is electrically connected between the charging voltage and the ground point; wherein the charging current The level is twice the preset output current level.

In a preferred embodiment, the conversion capacitor further includes a second conversion capacitor; wherein the conversion control circuit controls the plurality of conversion switches, so that the first end of the second conversion capacitor is connected to the first conversion period during the second conversion period. The switching period is correspondingly switched and electrically connected between the DC output voltage and the charging voltage, and the second end of the second conversion capacitor is switched correspondingly during the second conversion period and the first conversion period. It is electrically connected between the charging voltage and the ground point.

In a preferred embodiment, the conversion control circuit further senses the DC output current or the charging current to generate a current-related signal, wherein the power transmitting unit adjusts the DC output current to the pre-measurement according to the current-related signal. Set the output current level.

Detailed descriptions will be provided below through specific embodiments to make it easier to understand the purpose, technical content, features and effects of the present invention.

1,2,3,4,5‧‧‧Charging circuit

10‧‧‧ Power Transmission Unit

11‧‧‧ Power Adapter

20‧‧‧cable

21‧‧‧Power cord

22‧‧‧Signal line

30A, 30B, 30 ’, 30” ‧‧‧Capacitive power conversion circuit

31A, 31B, 31 ’, 31” ‧‧‧transfer switch circuit

32A, 32B, 32 ’, 32” ‧‧‧Conversion control circuit

40‧‧‧Load Switch

50‧‧‧ battery

60‧‧‧Switching charging circuit

CA1-CAN‧‧‧ Conversion Capacitor

CB1-CBN‧‧‧ Conversion Capacitor

CTRLA, CTRLB‧‧‧Switch control signal

IBAT‧‧‧Charging current

IDC‧‧‧DC output current

ISENA, ISENB‧‧‧ Current related signals

NDA1-NDAM‧‧‧Divided voltage node

NDB1-NDBM ‧‧‧ Divided Voltage Node

SW11-14, SW21-24‧‧‧ transfer switch

SYNC‧‧‧Synchronous control signal

VBUS‧‧‧DC output voltage

VBAT‧‧‧Charging voltage

Figure 1 shows a schematic diagram of a prior art charging circuit.

Figure 2 shows a schematic diagram of a prior art charging circuit.

FIG. 3 is a schematic diagram of an embodiment of a charging circuit of the present invention.

FIG. 4 shows a schematic diagram of an embodiment of a charging circuit of the present invention.

FIG. 5 shows a schematic diagram of an embodiment of a charging circuit and a capacitive power conversion circuit of the present invention.

FIG. 6 is a schematic diagram of an embodiment of a capacitive power conversion circuit in a charging circuit of the present invention.

Please refer to FIG. 3, which shows a schematic diagram of an embodiment of the charging circuit (charging circuit 3) of the present invention. The charging circuit 3 is used to provide a charging power to a battery 50, which includes a charging current IBAT; charging The circuit 3 includes a power transmitting unit 10 and a capacitive power conversion circuit 30A. The power transmitting unit 10 converts an input power (not shown) into a DC output power. The DC output power includes a DC output voltage VBUS and a DC output current IDC. The power transmitting unit 10 may be, for example, a power adapter. The input power in the form of AC is converted into the aforementioned DC output power, or may be a direct current DC conversion circuit that converts input power from, for example, a power bank into the aforementioned DC output power; the power transmitting unit 10 adjusts the DC Output current IDC at a preset output current Level. In one embodiment, the power transmitting unit 10 may support a constant current direct charging mode, and directly charge the battery 50 without the control of the capacitive power conversion circuit 30A (the related lines are not shown). The capacitive power conversion circuit 30A converts a DC output power into a charging power, wherein the charging power includes a charging voltage VBAT and a charging current IBAT; the capacitive power conversion circuit 30A includes a transfer switch circuit 31A, which includes a plurality of transfer switches (not (Shown), coupled with a conversion capacitor (such as CA1 in FIG. 3) or a complex conversion capacitor (such as CA1-CAN in FIG. 3, where N is a natural number); and a conversion control circuit 32A for Generate a switch control signal CTRLA for correspondingly operating the complex conversion switch during the complex conversion period, so that one or the complex conversion capacitor CA1 or CA1-CAN is correspondingly coupled to the one or the complex voltage dividing node periodically (for example, corresponding to the third NDA1 or NDA1-NDAM in the picture, where M is a natural number), the DC output voltage VBUS, and one or more pairs of nodes of the ground point GND, so that the level of the charging current IBAT is the DC output One of the preset output current levels of the current IDC is a preset current scale-up factor K, where K is a real number greater than 1, where the charging current IBAT is greater than the DC output current IDC Wherein the charging power supply coupled to one of the one or plurality of sub-nodes (e.g. NDA1 corresponding to the FIG. 3) in the pressure node, and generate the charging current IBAT via the node. In one embodiment, the capacitive power conversion circuit 30A may include, for example, but not limited to, a divider charge pump.

It should be noted that, due to the parasitic effect of the circuit parts themselves or the mutual matching between the parts, it is not necessarily ideal. Therefore, although the level of the charging current IBAT is intended to be preset to one of the preset output current levels Increase current multiplier K, but the actual level of charging current IBAT may not be the exact K times of the preset output current level, but only close to K times. Therefore, the “ … A preset current-increasing multiple K ”may allow errors in implementation, rather than having to be an extremely accurate K-fold, the same below. It is also worth noting that, in the embodiment having a plurality of voltage dividing nodes, the current-increasing multiplier K will be different depending on the node to which the charging power source is coupled; while there is only one voltage dividing node In the embodiment of the node, the current increase multiple K is 2, that is, the level of the charging current IBAT is twice the preset output current level, but in other embodiments, K is not limited to an integer.

Please continue to refer to FIG. 3. In one embodiment, in the charging circuit (for example, charging circuit 3) of the present invention, the power transmitting unit 10 is further coupled to a capacitive power conversion circuit (for example, a capacitive type) through a cable 20. Power conversion circuit 30A), wherein the cable 20 may be, for example, but not limited to, a cable complying with the Universal Serial Bus Power Supply Specification (USB PD) or the Universal Serial Bus Specification (USB), which includes a power line 21 and a signal line 22, The power line 21 is used for transmitting DC output power.

Please continue to refer to FIG. 3. In one embodiment, the conversion control circuit (eg, the conversion control circuit 32A) detects a DC output current IDC to generate a current-related signal (eg, ISANA), and the power transmitting unit 10 is based on the current-related signal ISANA The DC output current IDC is adjusted at a preset output current level. In another embodiment, the current-related signal ISENA can also be obtained by detecting the charging current IBAT. In a preferred embodiment, the conversion control circuit transmits the current-related signal ISANA to the power transmitting unit 10 through the signal line 22. It should be noted that the aforementioned cable 20 may be omitted in other embodiments.

The charging circuit of the present invention may include a plurality of capacitive power conversion circuits. For example, please refer to FIG. 4, which shows a schematic diagram of an embodiment (charging circuit 4) of the charging circuit of the present invention. In one embodiment, The charging circuit 4 further includes a capacitive power conversion circuit 30B, which can be coupled in parallel with the capacitive power conversion circuit 30A to collectively generate the aforementioned charging power. In the embodiment having a complex capacitive power conversion circuit, the ripple of the charging voltage can be reduced and the equivalent resistance on the charging path can be reduced to improve the conversion efficiency. In a preferred embodiment, the conversion control circuit (for example, the conversion control circuit 32A or the conversion control circuit 32B) can further generate or receive a synchronization control signal SYNC, and control the complex capacitive power conversion circuit (for example, according to the synchronization control signal SYNC) Capacitive power conversion circuits 30A and 30B) are synchronized between complex conversion periods; the term “synchronization” means that the phases of each complex conversion period have There are preset phase relationships, such as but not limited to in-phase, reverse phase, interleaving phase, or other forms of phase relationships.

In an embodiment having a complex conversion capacitor (such as CA1-CAN in FIG. 3), when the complex conversion capacitor is periodically correspondingly coupled between the aforementioned complex pair nodes, each complex conversion capacitor is at any time There is no parallel coupling between them. In other words, during any conversion period, at most one of the foregoing or a plurality of voltage-dividing nodes, a DC output power source, and a ground point is coupled to one of the plurality of conversion capacitors. .

Please refer to FIG. 5, which shows a schematic diagram of an embodiment of a capacitive power conversion circuit (capacitive power conversion circuit 30 ′) in a charging circuit (for example, charging circuit 3) of the present invention. In the power conversion circuit 30 ′, the transfer switch circuit 31 ′ includes a plurality of transfer switches (such as SW11, SW12, SW13, and SW14 shown in the figure), which are coupled to the transfer capacitor CA1. In this embodiment, as described above, The complex conversion period includes a first conversion period and a second conversion period. The conversion control circuit 32 'controls the plurality of conversion switches SW11, SW12, SW13, and SW14 so that the first end of the conversion capacitor CA1 is in the first conversion period. Correspondingly switched in the second conversion period and electrically connected between the DC output voltage VBUS and the charging voltage VBAT, and the second end of the conversion capacitor CA1 is switched between the first conversion period and the second conversion period The corresponding switching is electrically connected between the charging voltage VBAT and the ground point GND, so that the level of the charging current IBAT is twice the preset output current level.

Please refer to FIG. 6, which shows a schematic diagram of an embodiment of a capacitive power conversion circuit (capacitive power conversion circuit 30 ") in a charging circuit (such as charging circuit 3) of the present invention. The capacitive power conversion circuit 30 "is similar to the capacitive power conversion circuit 30 'of the previous embodiment, except that the transfer switch circuit 31" further includes a plurality of transfer switches such as SW21, SW22, SW23, and SW24 shown in the figure, which are coupled to another Conversion capacitor CA2, conversion control circuit 32 "controls conversion capacitor CA1 The coupling method is the same as above, and the transfer control circuit 32 "further controls the transfer switches SW21, SW22, SW23, and SW24, so that the first end of the transfer capacitor CA2 is switched correspondingly in the second conversion period and the first conversion period. And is electrically connected between the DC output voltage VBUS and the charging voltage VBAT, and the second end of the conversion capacitor CA2 is correspondingly switched between the second conversion period and the first conversion period and is electrically connected to the charging Between the voltage VBAT and the ground point GND; in other words, the switching between CA1 and CA2 between the aforementioned node pairs is opposite to each other.

The present invention has been described above with reference to the preferred embodiments, but the above is only for making those skilled in the art easily understand the content of the present invention, and is not intended to limit the scope of rights of the present invention. The described embodiments are not limited to separate applications, and can also be applied in combination. For one example, the capacitive power conversion circuits that control different numbers of conversion capacitors can be used in combination. For example, the charging circuit of the present invention may include multiple capacitive power supplies. A conversion circuit. One of the capacitive power conversion circuits can be coupled to control a conversion capacitor, and the other capacitive power conversion circuit can be coupled to control a plurality of conversion capacitors. In addition, under the same spirit of the present invention, those skilled in the art can think about various equivalent changes and various combinations. For example, the polarity of the switching capacitors can be changed according to requirements, such as sometimes being positive Sometimes it is negative, which can increase the range or resolution of the boosting factor K. For another example, the aforementioned synchronous control signal can also be an externally provided synchronous control signal, and can still achieve synchronous operation between multiple capacitive power conversion circuits. For another example, the term "processing or calculation according to a signal or generating an output result" in the present invention is not limited to the signal itself, but also includes performing voltage-current conversion, current-voltage conversion on the signal when necessary, and / Or proportional conversion, etc., and then process or calculate according to the converted signal to produce an output result. It can be seen that, under the same spirit of the present invention, those skilled in the art can think of various equivalent changes and various combinations, and there are many combinations, which are not listed here. Therefore, the scope of the invention should cover the above and all other equivalent variations.

Claims (15)

A charging control method for controlling a charging circuit to provide a charging power to a battery. The charging power includes a charging voltage and a charging current. The charging circuit includes a power transmitting unit and one or more capacitive power conversions. A circuit in which the power transmitting unit converts an input power into a DC output power, the DC output power includes a DC output voltage and a DC output current; wherein the capacitive power conversion circuit includes a transfer switch circuit including a complex transfer switch Is coupled to one or a plurality of conversion capacitors; the charging control method includes the following steps: adjusting the DC output current to a preset output current level by the power transmitting unit; and outputting the DC output by the capacitive power conversion circuit The power source is converted into the charging power source, so that the level of the charging current is a preset current scale-up factor of one of the preset output current levels, wherein the charging current is greater than the DC output current; The step of converting the DC output power into the charging power includes: During the complex conversion period, the complex conversion switch is operated correspondingly, so that the one or complex conversion capacitor is periodically correspondingly coupled between one or more pairs of nodes, the DC output voltage, and the ground point, The charging power source is coupled to one of the one or more voltage dividing nodes. The charging control method according to item 1 of the scope of patent application, wherein the step of converting the DC output power into the charging power further includes: generating a synchronous control signal; and controlling the plurality of capacitive power conversions according to the synchronous control signal. The complex conversion periods of the circuit are synchronized. The charging control method according to item 1 of the scope of patent application, wherein the step of converting the DC output power into the charging power further includes: in the capacitive power conversion circuit, in any conversion period, in the one or more The voltage-dividing node, the DC output voltage, and any pair of nodes of the ground point are coupled at most to one of the complex conversion capacitors. The charging control method according to item 1 of the scope of patent application, wherein the capacitive power conversion circuit includes a first capacitive power conversion circuit, the conversion capacitor includes a first conversion capacitor, and the complex conversion period includes a first conversion Time period and a second conversion period; wherein the step of converting the DC output power into the charging power source further comprises: operating the plurality of transfer switches of the first capacitive power conversion circuit, so that the first end of the first conversion capacitor is at The first conversion period and the second conversion period are respectively switched between the DC output voltage and the charging voltage, and the second end of the first conversion capacitor is switched between the first conversion period and the second conversion period. Zhong respectively switches between the charging voltage and the ground point; wherein the level of the charging current is twice the level of the preset output current. The charging control method according to item 4 of the scope of patent application, wherein the conversion capacitor further includes a second conversion capacitor; wherein the step of converting the DC output power into the charging power further includes: operating the first capacitive power conversion The multiple conversion switch of the circuit causes the first end of the second conversion capacitor to switch between the DC output voltage and the charging voltage respectively during the second conversion period and the first conversion period, and enables the second The second end of the conversion capacitor is respectively switched between the charging voltage and the ground point during the second conversion period and the first conversion period. The charging control method according to item 1 of the scope of patent application, further comprising: sensing the DC output current or the charging current to generate a current-related signal; and adjusting the DC output by the power transmitting unit according to the current-related signal The current is at the preset output current level. A charging circuit comprising the power transmitting unit and the corresponding capacitive power conversion circuit controlled by the charging control method according to any one of items 1 to 6; and a cable for coupling the power transmitting unit And the capacitive power conversion circuit. The charging circuit as described in item 7 of the scope of patent application, wherein the cable is a USB PD cable that conforms to the universal serial bus power supply specification, which includes a power cord, wherein the power cord is used to transmit the DC output power supply. The charging circuit according to item 8 of the scope of patent application, wherein the cable includes a signal line, wherein the signal line is used to transmit the current-related signal. A capacitive power conversion circuit for a charging circuit. The charging circuit is used to provide a charging power to a battery. The charging power includes a charging voltage and a charging current. The charging circuit includes a power transmitting unit. The power transmitting unit converts an input power into a DC output power. The DC output power includes a DC output voltage and a DC output current. The power transmitting unit adjusts the DC output current to a preset output current level. The capacitive power conversion circuit includes: a transfer switch circuit including a complex transfer switch coupled to one or more transfer capacitors; and a transfer control circuit for generating a switch control signal for corresponding operations during the complex conversion period The complex conversion switch enables the one or more conversion capacitors to be correspondingly coupled to one or more of the voltage division nodes, the DC output voltage, and a pair of nodes of a ground point periodically, so that the charging current level Current scal which is one of the preset output current levels e-up factor), wherein the charging current is greater than the DC output current; wherein the charging power source is coupled to one of the one or more voltage dividing nodes. The capacitive power conversion circuit according to item 10 of the scope of patent application, wherein the conversion control circuit further generates a synchronous control signal, and controls between the multiple conversion periods of the multiple capacitive power conversion circuit according to the synchronous control signal. For synchronization. The capacitive power conversion circuit according to item 10 of the scope of patent application, wherein, in any conversion period, between any one of the pair of nodes of the one or more voltage division nodes, the DC output voltage, and the ground point, At most is coupled to one of the complex conversion capacitors. The capacitive power conversion circuit according to item 10 of the scope of patent application, wherein the capacitive power conversion circuit includes a first capacitive power conversion circuit, the conversion capacitor includes a first conversion capacitor, and the complex conversion period includes a first A conversion period and a second conversion period; wherein the conversion control circuit controls the plurality of conversion switches so that the first end of the first conversion capacitor is switched correspondingly between the first conversion period and the second conversion period; Is connected between the DC output voltage and the charging voltage, and the second end of the first conversion capacitor is switched correspondingly during the first conversion period and the second conversion period, and is electrically connected between the charging voltage and the Between ground points; where the level of the charging current is twice the preset output current level. The capacitive power conversion circuit according to item 13 of the scope of patent application, wherein the conversion capacitor further includes a second conversion capacitor; wherein the conversion control circuit controls the plurality of conversion switches so that the first end of the second conversion capacitor is at The second conversion period and the first conversion period are switched correspondingly and electrically connected between the DC output voltage and the charging voltage, and the second end of the second conversion capacitor is connected to the second conversion period and the The first switching periods are correspondingly switched and are electrically connected between the charging voltage and the ground point. The capacitive power conversion circuit according to item 10 of the application, wherein the conversion control circuit further senses the DC output current or the charging current to generate a current-related signal, and the power transmitting unit is based on the current-related signal. And adjust the DC output current to the preset output current level.