TWI868511B - Method of controlling charging device and charging system - Google Patents

Abstract

A method of controlling charging device is adapted to a charging device including an AC/DC converter and a DC/DC converter, the method includes performing, by a controlling device: performing a first efficiency adjustment procedure when the charging device is in a constant current mode, wherein the first efficiency adjustment procedure includes: adjusting a DC side voltage of the AC/DC converter and simultaneously obtaining a first working frequency of the DC/DC converter; and determining whether the first working frequency falls within a lowest frequency range. When the first working frequency does not fall within a lowest frequency range, performing the first efficiency adjustment procedure again; and when the first working frequency falls within a lowest frequency range, boosting the DC side voltage. The present disclosure further provides a charging system.

Description

Charging device control method and charging system

The present invention relates to a charging device control method and a charging system.

In the current two-stage charging device, the operation mode is to boost the power input to the charging device to a high voltage, and then reduce the output voltage, resulting in unnecessary power waste. Although the correspondence between the output voltage and the load rate can be determined by looking up a table, this method is not suitable for a wide range of variable output voltage/current, nor is it suitable for adjusting the operation of AC-DC converters and DC-DC converters in different ways. Therefore, the table lookup method can only partially optimize the conversion efficiency of the charging device, and actually lacks the flexibility to adjust the AC-DC converter and DC-DC converter.

In view of the above, the present invention provides a charging device control method and a charging system to meet the above needs.

According to an embodiment of the present invention, a charging device control method is applicable to a charging device including an AC-DC converter and a DC-DC converter. The method includes executing with a control device: when the charging device is in a constant current mode, executing a first efficiency adjustment procedure, wherein the first efficiency adjustment procedure includes: adjusting the DC side voltage of the AC-DC converter, and simultaneously obtaining the first operating frequency of the DC-DC converter; and determining whether the first operating frequency falls within the lowest frequency interval; when the first operating frequency does not fall within the lowest frequency interval, executing the first efficiency adjustment procedure again; and when the first operating frequency falls within the lowest frequency interval, increasing the DC side voltage.

A charging system according to an embodiment of the present invention includes: a charging device including an AC-DC converter and a DC-DC converter; and a control device connected to the charging device, the control device being used to execute: when the charging device is in a constant current mode, executing a first efficiency adjustment procedure, wherein the first efficiency adjustment procedure includes: adjusting the DC side voltage of the AC-DC converter and simultaneously obtaining the first operating frequency of the DC-DC converter; and determining whether the first operating frequency falls within the minimum frequency range; when the first operating frequency does not fall within the minimum frequency range, executing the first efficiency adjustment procedure again; and when the first operating frequency falls within the minimum frequency range, increasing the DC side voltage.

In summary, the charging device control method and charging system shown in one or more embodiments of the present invention can adjust the DC side voltage of the AC-DC converter according to the conversion efficiency (operating frequency) of the DC-DC converter through feedback, thereby optimizing the charging efficiency of the charging device. In addition, it can reduce the energy wasted during the charging process and increase the charging rate.

The above description of the disclosed content and the following description of the implementation method are used to demonstrate and explain the spirit and principle of the present invention, and provide a further explanation of the scope of the patent application of the present invention.

1: Charging system

10: Power supply

11: Charging device

12: Control device

13:Battery

111: AC-DC converter

112: DC-DC converter

V _dc ,V _cc : DC side voltage

W _o : First historical output power

_Wi : First historical input power

S201,S203,S205,S301,S303,S305,S307,S601,S603,S701,S703,S705,S901,S903,S905,S907,S1001,S1003: Steps

FIG1 is a schematic diagram of a charging system according to an embodiment of the present invention.

Figure 2 is a flow chart of a charging device control method according to an embodiment of the present invention.

FIG3 is a flow chart of a method for adjusting the DC side voltage of an AC-DC converter according to an embodiment of the present invention.

FIG4 is a schematic diagram showing the connection between the components in FIG1.

FIG5 shows the relationship between the adjustment of the DC side voltage (V _d ) and the conversion efficiency (EFF).

FIG6 is a flow chart of a method for adjusting the DC side voltage of an AC-DC converter according to another embodiment of the present invention.

FIG7 is a flow chart of a charging device control method according to another embodiment of the present invention.

FIG8 is a waveform diagram showing the drive signal for adjusting the DC-DC converter.

FIG9 is a flow chart of a method for adjusting the phase angle difference between driving signals of a DC-DC converter according to an embodiment of the present invention.

FIG. 10 is a flow chart of a method for adjusting the phase angle difference between driving signals of a DC-DC converter according to another embodiment of the present invention.

Figures 11a to 11d show the relationship between the adjustment of the phase angle difference and the conversion efficiency.

The detailed features and advantages of the present invention are described in detail in the following implementation method. The content is sufficient for anyone familiar with the relevant technology to understand the technical content of the present invention and implement it accordingly. According to the content disclosed in this specification, the scope of the patent application and the drawings, anyone familiar with the relevant technology can easily understand the relevant purposes and advantages of the present invention. The following embodiments are to further illustrate the viewpoints of the present invention, but do not limit the scope of the present invention by any viewpoint.

Please refer to FIG. 1, which is a schematic diagram of a charging system according to an embodiment of the present invention. The charging system 1 is electrically connected to a power source 10 and a battery 13. The charging system 1 is used to convert the output power of the power source 10 and output the converted power to the battery 13 to charge the battery 13, wherein the power source 10 is, for example, a mains power source.

The charging system 1 includes a charging device 11 and a control device 12. The charging device 11 is a two-stage charging device, including an AC/DC converter 111 and a DC/DC converter 112. The charging device 11 may be a charging pile, etc., but the present invention is not limited thereto. The control device 12 may be a controller, such as a programmable logic controller (PLC). The control device 12 adjusts the DC side voltage (e.g., the DC side voltage V _dc in FIG. 1 ) of the AC/DC converter 111 during the stage of charging at a constant current, and adjusts the phase angle difference of the DC/DC converter 112 during the stage of charging at a constant voltage, so as to improve the conversion efficiency of the charging device 11.

To explain the content of adjusting the DC side voltage in more detail, please refer to FIG. 1 and FIG. 2 , wherein FIG. 2 is a flow chart of a charging device control method according to an embodiment of the present invention. The charging device control method includes executing by the control device 12: when the charging device is in a constant current mode, executing a first efficiency adjustment procedure, wherein the first efficiency adjustment procedure includes: step S201: adjusting the DC side voltage of the AC-DC converter, and obtaining the first operating frequency of the DC-DC converter; and step S203: judging whether the first operating frequency falls within the minimum frequency range; if the judgment result of step S203 is "yes", executing step S205: increasing the DC side voltage; and if the judgment result of step S203 is "no", executing the first efficiency adjustment procedure again.

In step S201, in the constant current mode, the control device 12 increases or decreases the DC side voltage of the AC-DC converter 111, and obtains the first operating frequency of the DC-DC converter 112 corresponding to the adjusted DC side voltage.

In step S203, the control device 12 determines whether the first operating frequency of the DC-DC converter 112 falls within the lowest frequency range. In other words, the control device 12 determines whether the first operating frequency falls within the lowest frequency range in order to determine whether the DC-DC converter has reached the control boundary.

If the first operating frequency does not fall within the minimum frequency range, the control device 12 executes the first efficiency adjustment procedure again, i.e., executes step S201 again. If the first operating frequency falls within the minimum frequency range, because the control boundary of the DC-DC converter has been touched, the DC side voltage is increased to avoid entering the control saturation phenomenon, so the control device 12 executes step S205 to increase the DC side voltage of the AC-DC converter 111.

Please refer to FIG. 3 and FIG. 4 together, wherein FIG. 3 is a flow chart of a method for adjusting the DC side voltage of an AC-DC converter according to an embodiment of the present invention; and FIG. 4 is a schematic diagram showing the connection between the components in FIG. 1. As shown in FIG. 3, the step S201 of FIG. 2 for adjusting the DC side voltage of the AC-DC converter 111 may include: step S301: obtaining the continuous first historical conversion efficiency and the second historical conversion efficiency of the AC-DC converter; step S303: calculating the efficiency slope according to the first historical conversion efficiency and the second historical conversion efficiency; step S305: multiplying the efficiency slope by a preset voltage to obtain a voltage change value; and step S307: adding the voltage change value to the DC side voltage.

In step S301, the control device 12 obtains a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter 111, wherein the first historical conversion efficiency and the second historical conversion efficiency respectively represent conversion efficiencies after the DC side voltage (e.g., the DC side voltage _Vcc in FIG. 4) is adjusted. The time point of the first historical conversion efficiency (hereinafter referred to as the first time point) and the time point corresponding to the second historical conversion efficiency (hereinafter referred to as the second time point) are earlier than the time point corresponding to the first operating frequency. In other words, the first historical conversion efficiency and the second historical conversion efficiency may be two consecutive conversion efficiencies at a time point closest to the first operating frequency, and when the second historical conversion efficiency is later than the first historical conversion efficiency, the time difference between the first historical conversion efficiency and the second historical conversion efficiency is preferably the same as the time difference between the second historical conversion efficiency and the first operating frequency.

Further, as shown in FIG4 , for the first historical conversion efficiency, the control device 12 obtains the first historical input power _Wi input from the power source 10 to the charging device 11, and obtains the first historical output power W _o output from the charging device 11 to the battery 13, divides the first historical output power W _o by the first historical input power _Wi , and uses the obtained ratio as the first historical conversion efficiency. Similarly, the control device 12 can obtain the second historical conversion efficiency based on the ratio of the historical output power to the historical input power.

Next, in step S303, the control device 12 obtains an efficiency slope according to the rate of change from the first historical conversion efficiency to the second historical conversion efficiency. The efficiency slope is used to represent the change in the historical conversion efficiency of the AC-DC converter 111. In the case where the second time point is later than the first time point, the efficiency slope is calculated as the change in efficiency from the first historical conversion efficiency to the second historical conversion efficiency divided by the change in the DC side voltage from the first historical conversion efficiency to the second historical conversion efficiency. If the efficiency slope is a positive value, it means that the adjustment method of increasing the DC side voltage corresponding to the first time point to the DC side voltage corresponding to the second time point improves the conversion efficiency of the charging device 11; if the efficiency slope is a negative value, it means that the adjustment method of increasing the DC side voltage corresponding to the first time point to the DC side voltage corresponding to the second time point reduces the conversion efficiency of the charging device 11; if the efficiency slope is equal to 0, it means that the adjustment method of increasing the DC side voltage corresponding to the first time point to the DC side voltage corresponding to the second time point does not change the conversion efficiency of the charging device 11.

In step S305, the control device 12 multiplies the preset voltage by the efficiency slope obtained according to the first historical conversion efficiency and the second historical conversion efficiency to obtain a voltage change value, wherein the preset voltage is, for example, 5V. In step S307, the control device 12 adds the voltage change value to the DC side voltage of the AC-DC converter 111.

As described above, if the efficiency slope is a positive value, it means that the efficiency increases with the increase of the DC side voltage, and the control device 12 adjusts the DC side voltage in that direction; conversely, if the efficiency slope is a negative value, it means that the efficiency decreases with the increase of the DC side voltage, and the control device 12 adjusts the DC side voltage in the opposite direction. After adding the voltage change value to the DC side voltage, the control device 12 can execute the step S201 of FIG2 to obtain the first operating frequency, and then execute the step S203 of FIG2.

Please refer to FIG. 1 and FIG. 5 together, wherein FIG. 5 illustrates the relationship between the adjustment of the DC side voltage (V _d ) and the conversion efficiency (EFF) of the AC-DC converter. The efficiency value in FIG. 5 is a value obtained by dividing the output power of the AC-DC converter 111 by the input power input to the AC-DC converter 111. In the example of FIG. 5 , the AC-DC converter 111 of the charging device 11 charges the battery 13 at a constant current of 10 amperes (A), the initial DC side voltage of the AC-DC converter 111 is 650V, and the lowest frequency range is approximately 43kHz to 47kHz, and the lowest frequency range preferably includes 45kHz.

As shown in Figure 5, when the DC side voltage drops from 650V to 630V (adding the voltage change value to the DC side voltage), the corresponding conversion efficiency increases from 95.2% to 95.4%. Therefore, the control device 12 continues to reduce the DC side voltage in the same direction, so that the conversion efficiency continues to increase.

Please refer to FIG. 1 and FIG. 6 together, wherein FIG. 6 is a flow chart of a method for adjusting the DC side voltage of an AC-DC converter according to another embodiment of the present invention. As shown in FIG. 6, the step S201 of FIG. 2 for adjusting the DC side voltage of the AC-DC converter 111 may include: step S601: multiplying the preset efficiency gain by the preset voltage to obtain a voltage change value; and step S603: adding the voltage change value to the DC side voltage.

In step S601, the control device 12 multiplies the preset voltage by the preset efficiency gain to obtain the voltage change value. The preset efficiency gain can be a value less than 1, equal to 1, or greater than 1. The present invention does not limit the actual value of the preset efficiency gain. In step S603, the control device 12 adds the voltage change value to the DC side voltage.

It should be noted that in step S601, the control device 12 can first calculate the efficiency slope in the manner of step S301 and step S303 in FIG3, and when the efficiency slope is positive, set the preset efficiency gain to a positive value, and when the efficiency slope is negative, set the preset efficiency gain to a negative value. In addition to adjusting the DC side voltage according to the efficiency slope and the preset efficiency gain as described above, the control device 12 can also adjust the DC side voltage in the manner of an increasing function such as a step function or a sigmoid function.

Please refer to FIG. 1 , FIG. 7 and FIG. 8 , wherein FIG. 7 is a flow chart of a charging device control method according to another embodiment of the present invention, and FIG. 8 is a waveform diagram of a driving signal for adjusting a DC-DC converter. After executing step S205 of FIG. 2 , the control device 12 may execute: when the charging device is in the constant voltage mode, execute the second efficiency adjustment procedure, wherein the second efficiency adjustment procedure includes: step S701: adjusting the phase angle difference between the multiple driving signals of the DC-DC converter, and obtaining the second operating frequency of the DC-DC converter at the same time; and step S703: determining whether the second operating frequency falls within the lowest frequency range; if the determination result of step S703 is "yes", executing step S705: maintaining the phase angle difference; and if the determination result of step S703 is "no", executing the second efficiency adjustment procedure again.

In step S701, in the constant voltage mode, the control device 12 increases or decreases the phase angle difference between the multiple driving signals of the DC-DC converter 112, and obtains a second operating frequency corresponding to the adjusted phase angle difference. The control device 12 can be a phase angle difference between the gate driving signals of the four transistors of the full-bridge switching converter of the DC-DC converter 112. In FIG8, Q1 to Q4 represent four transistors of the full-bridge switching converter, wherein transistor Q1 and transistor Q2 are switches of the same arm, and transistor Q3 and transistor Q4 are switches of the same arm. As shown by the two dotted lines in FIG8 , the control device 12 adjusts the phase angle difference between the two arm switches, that is, the phase angle difference between transistor Q1 and transistor Q4 and the phase angle difference between transistor Q2 and transistor Q3, and the primary side voltage (VPRI) corresponding to the adjusted phase angle difference is shown in the waveform at the bottom of FIG8 .

In step S703, the control device 12 searches for the highest conversion efficiency. The control device 12 determines whether the second operating frequency of the DC-DC converter 112 falls within the lowest frequency range during the process of searching for the highest conversion efficiency. If the second operating frequency of the DC-DC converter 112 reaches the lowest frequency range, the current phase angle difference is maintained. At this time, when the operating frequency falls within the lowest frequency range, the control boundary of the DC-DC converter has been touched, so the current phase angle difference is maintained. In addition, the lowest frequency range described here can be the same as the lowest frequency range described in the embodiment of FIG. 2.

If the second operating frequency does not fall within the lowest frequency range, the control device 12 executes the second efficiency adjustment procedure again, i.e., executes step S701 again. If the second operating frequency falls within the lowest frequency range, it indicates that the control boundary of the DC converter has been touched, so the control device 12 executes step S705 to maintain the current phase angle difference.

Please refer to FIG. 1 and FIG. 9 together, wherein FIG. 9 is a flow chart of a method for adjusting the phase angle difference between driving signals of a DC-DC converter according to an embodiment of the present invention. As shown in FIG. 9, the method for adjusting the phase angle difference between driving signals of a DC-DC converter in step S701 of FIG. 7 may include: step S901: obtaining a continuous first historical conversion efficiency and a second historical conversion efficiency of the DC-DC converter; step S903: calculating an efficiency slope according to the first historical conversion efficiency and the second historical conversion efficiency; step S905: multiplying a preset phase angle by the efficiency slope to obtain a phase angle change value; and step S907: adding the phase angle change value to the phase angle difference. Step S901 in FIG. 9 is similar to step S301 in FIG. 3 , so it will not be described here in detail.

After obtaining the first historical conversion efficiency and the second historical conversion efficiency, in step S903, the control device 12 obtains the efficiency slope according to the rate of change from the first historical conversion efficiency to the second historical conversion efficiency. The efficiency slope is calculated as the change in efficiency from the first historical conversion efficiency to the second historical conversion efficiency divided by the change in the phase angle difference from the first historical conversion efficiency to the second historical conversion efficiency. In the case where the second time point is later than the first time point, if the efficiency slope is a positive value, it means that the adjustment method of increasing the phase angle difference corresponding to the first time point to the phase angle difference corresponding to the second time point improves the conversion efficiency of the charging device 11; if the efficiency slope is a negative value, it means that the adjustment method of increasing the phase angle difference corresponding to the first time point to the phase angle difference corresponding to the second time point reduces the conversion efficiency of the charging device 11; if the efficiency slope is equal to 0, it means that the adjustment method of adjusting the phase angle corresponding to the first time point to the phase angle corresponding to the second time point does not change the conversion efficiency of the charging device 11.

In step S905, the control device 12 multiplies the preset phase angle by the efficiency slope obtained according to the first historical conversion efficiency and the second historical conversion efficiency to obtain a phase angle change value, wherein the preset phase angle is, for example, 5 degrees. In step S907, the control device 12 adds the phase angle change value to the current phase angle difference between the driving signals of the DC-DC converter 112.

As described above, if the efficiency slope is a positive value, it means that the efficiency increases with increasing the phase angle difference, and the control device 12 adjusts the phase angle difference in that direction; conversely, if the efficiency slope is a negative value, it means that the efficiency decreases with increasing the phase angle difference, and the control device 12 adjusts the phase angle difference in the opposite direction. After adding the phase angle change value to the phase angle difference, the control device 12 can execute the step S701 of FIG. 7 to obtain the second operating frequency, and then execute the step S703 of FIG. 7.

Please refer to FIG. 1 and FIG. 10 , wherein FIG. 10 is a flow chart of a method for adjusting the phase angle difference between driving signals of a DC-DC converter according to another embodiment of the present invention. As shown in FIG. 10 , the method for adjusting the phase angle difference between driving signals of a DC-DC converter in step S701 of FIG. 7 may include: step S1001: multiplying a preset efficiency gain by a preset phase angle to obtain a phase angle change value; and step S1003: adding the current phase angle difference to the phase angle change value.

In step S1001, the control device 12 multiplies the preset efficiency gain by the preset phase angle to obtain the phase angle change value. The preset efficiency gain can be a value less than 1, equal to 1, or greater than 1. The present invention does not limit the actual value of the preset efficiency gain. In step S1003, the control device 12 adds the phase angle change value to the current phase angle difference.

It should be noted that in step S1001, the control device 12 can first calculate the efficiency slope in the manner of steps S901 and S903 in FIG. 9, and when the efficiency slope is a positive value, the default efficiency gain is set to a positive value, and when the efficiency slope is a negative value, the default efficiency gain is set to a negative value.

Please refer to Figures 11a to 11d, which show the relationship between the adjustment of the phase angle difference and the conversion efficiency. The charging parameters are all 2000 watts and 800V. Figures 11a and 11b adjust the phase angle difference in a step function manner, and Figures 11c and 11d adjust the phase angle difference in an S-shaped function manner. In Figures 11a and 11b, it can be seen that when the phase angle difference is increased in the form of a step function, the conversion efficiency of the DC-DC converter is gradually improved. In Figures 11c and 11d, it can be seen that when the phase angle difference is increased in the form of an S-shaped function, the conversion efficiency of the DC-DC converter is gradually improved.

In summary, the charging device control method and charging system shown in one or more embodiments of the present invention can adjust the DC side voltage of the AC-DC converter according to the conversion efficiency of the overall converter through feedback, thereby optimizing the charging efficiency of the charging device. In addition, it can reduce the energy wasted during the charging process and increase the charging rate. In addition, the charging device control method and charging system shown in one or more embodiments of the present invention can adjust the phase angle difference between multiple drive signals of the DC-DC converter according to the conversion efficiency of the overall converter through feedback, thereby achieving full online optimization of the charging efficiency of the charging device.

Although the present invention is disclosed as above by the aforementioned embodiments, it is not intended to limit the present invention. Any changes and modifications made within the spirit and scope of the present invention are within the scope of patent protection of the present invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

S201, S203, S205: Steps

Claims (12)

A charging device control method is applicable to a charging device including an AC-DC converter and a DC-DC converter. The method includes executing with a control device: when the charging device is in a certain current mode, executing a first efficiency adjustment procedure, wherein the first efficiency adjustment procedure includes: adjusting the DC side voltage of the AC-DC converter and obtaining a first operating frequency of the DC-DC converter; and determining whether the first operating frequency falls within a minimum frequency range; when the first operating frequency does not fall within the minimum frequency range, executing the first efficiency adjustment procedure again; and when the first operating frequency falls within the minimum frequency range, increasing the DC side voltage. A charging device control method as described in claim 1, wherein after the control device executes the step of increasing the DC side voltage, the method further comprises: when the charging device is in a certain voltage mode, executing a second efficiency adjustment procedure, wherein the second efficiency adjustment procedure comprises: adjusting a phase angle difference between a plurality of drive signals of the DC-DC converter, and simultaneously obtaining a second operating frequency of the DC-DC converter; and determining whether the second operating frequency falls within the minimum frequency range; when the second operating frequency does not fall within the minimum frequency range, executing the second efficiency adjustment procedure again; and when the second operating frequency falls within the minimum frequency range, maintaining the phase angle difference. The charging device control method as described in claim 1, wherein adjusting the DC side voltage of the AC-DC converter includes: obtaining a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter in succession; calculating an efficiency slope according to the first historical conversion efficiency and the second historical conversion efficiency; multiplying the efficiency slope by a preset voltage to obtain a voltage change value; and adding the voltage change value to the DC side voltage. The charging device control method as described in claim 1, wherein adjusting the DC side voltage of the AC-DC converter includes: calculating an efficiency slope according to a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter; when the efficiency slope is a positive value, setting a preset efficiency gain to be positive; when the efficiency slope is a negative value, setting the preset efficiency gain to be negative; multiplying the preset efficiency gain by a preset voltage to obtain a voltage change value; and adding the voltage change value to the DC side voltage. The charging device control method as described in claim 2, wherein adjusting the phase angle difference between the driving signals of the DC-DC converter includes: obtaining a first historical conversion efficiency and a second historical conversion efficiency of the DC-DC converter; calculating an efficiency slope according to the first historical conversion efficiency and the second historical conversion efficiency; multiplying the efficiency slope by a preset phase angle to obtain a phase angle change value; and adding the phase angle difference to the phase angle change value. The charging device control method as described in claim 2, wherein adjusting the phase angle difference between the driving signals of the DC-DC converter includes: calculating an efficiency slope according to a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter; when the efficiency slope is a positive value, setting a preset efficiency gain to be positive; when the efficiency slope is a negative value, setting the preset efficiency gain to be negative; multiplying the phase angle difference by a preset efficiency gain to obtain a preset phase angle; and adding the phase angle change value to the phase angle difference. A charging system includes: a charging device including an AC-DC converter and a DC-DC converter; and a control device connected to the charging device, the control device is used to execute: when the charging device is in a certain current mode, execute a first efficiency adjustment procedure, wherein the first efficiency adjustment procedure includes: adjusting the DC side voltage of the AC-DC converter and obtaining a first operating frequency of the DC-DC converter; and determining whether the first operating frequency falls within a minimum frequency range; when the first operating frequency does not fall within the minimum frequency range, executing the first efficiency adjustment procedure again; and when the first operating frequency falls within the minimum frequency range, increasing the DC side voltage. The charging system as described in claim 7, wherein the control device further executes after executing the boosting of the DC side voltage: When the charging device is in a certain voltage mode, execute a second efficiency adjustment procedure, wherein the second efficiency adjustment procedure includes: adjusting a phase angle difference between multiple drive signals of the DC-DC converter, and simultaneously obtaining a second operating frequency of the DC-DC converter; and determining whether the second operating frequency falls within the minimum frequency range; when the second operating frequency does not fall within the minimum frequency range, executing the second efficiency adjustment procedure again; and when the second operating frequency falls within the minimum frequency range, maintaining the phase angle difference. The charging system as described in claim 7, wherein the control device performs the adjustment of the DC side voltage of the AC-DC converter, including: obtaining a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter in succession, wherein the time difference between the first historical conversion efficiency and the second historical conversion efficiency is the same as the time difference between the second historical conversion efficiency and the first operating frequency; calculating an efficiency slope according to the first historical conversion efficiency and the second historical conversion efficiency; multiplying the efficiency slope by a preset voltage to obtain a voltage change value; and adding the voltage change value to the DC side voltage. The charging system as described in claim 7, wherein the control device performs the adjustment of the DC side voltage of the AC-DC converter, including: calculating the efficiency slope according to a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter; when the efficiency slope is positive, setting a preset efficiency gain to be positive; when the efficiency slope is negative, setting the preset efficiency gain to be negative; Multiplying a preset efficiency gain by a preset voltage to obtain a voltage change value; and adding the voltage change value to the DC side voltage. The charging system as described in claim 8, wherein the control device performs the phase angle difference adjustment between the driving signals of the DC-DC converter, including: obtaining a first historical conversion efficiency and a second historical conversion efficiency of the DC-DC converter, wherein the time difference between the first historical conversion efficiency and the second historical conversion efficiency is the same as the time difference between the second historical conversion efficiency and the first operating frequency; calculating an efficiency slope according to the first historical conversion efficiency and the second historical conversion efficiency; multiplying the efficiency slope by a preset phase angle to obtain a phase angle change value; and adding the phase angle difference to the phase angle change value. The charging system as described in claim 8, wherein the control device performs the phase angle difference adjustment between the driving signals of the DC-DC converter, including: calculating the efficiency slope according to a first historical conversion efficiency and a second historical conversion efficiency of the AC-DC converter; when the efficiency slope is a positive value, setting a preset efficiency gain to be positive; when the efficiency slope is a negative value, setting the preset efficiency gain to be negative; multiplying a preset efficiency gain by a preset phase angle to obtain a phase angle change value; and adding the phase angle difference to the phase angle change value.

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