Direct-current-direct-current converter

Abstract

The present application relates to a kind of direct current-direct current converters, it includes: first capacitor;First switch, second switch, third switch and fourth switch, it is connected in series between the first electrode and second electrode of first capacitor;Second capacitor, it is connected to the connection node of first switch and second switch and the connection node of third switch and fourth switch;Inductance, it is connected to the connection node of second switch and third switch;And controller, based on the calculation result using the difference between first detection voltage and first voltage instruction value, the difference between second detection voltage and second voltage instruction value and the reciprocal of detection current, the conduction / shut-off state of each of first switch to fourth switch is controlled, the detection current is the measured current flowing through the inductance.

Description

Technical Field

[0001] This invention relates to a DC-DC converter, and more specifically, to a DC-DC converter with a flying capacitor having improved controllability. Background Technology

[0002] DC-DC converters, which convert direct current (DC) power from one voltage level to another, are widely used in a variety of electronic devices.

[0003] Regarding conventional DC-DC converters, a known technique involves converting a DC power supply voltage to another voltage by controlling the energy accumulation and release of an inductor through the on / off operation of a semiconductor switch. This type of DC-DC converter suffers from the disadvantages of large inductance and bulkiness.

[0004] To address this problem—that is, to reduce the size and weight of the inductor—it is necessary to reduce the inductance value. To this end, techniques have been developed to reduce the voltage applied to the inductor by charging and discharging the capacitor.

[0005] Among the various DC-DC converters utilizing this technology, there exists a DC-DC converter that includes a series of switches and a flying capacitor disposed between two of the series of switches.

[0006] This type of DC-DC converter with a flying capacitor has the following problems: Because the voltage across the flying capacitor needs to be kept at a constant level, it is difficult to control. When the voltage across the flying capacitor deviates significantly from a certain level, a high voltage will be applied to the switch, potentially burning it out.

[0007] Therefore, a technique is needed to improve the controllability of the voltage applied to the flying capacitor.

[0008] The above statements are merely intended to help understand the background technology of the present invention and are not intended to imply that the present invention falls within the scope of related technologies known to those skilled in the art. Summary of the Invention

[0009] One object of the present invention is to provide a DC-DC converter with improved controllability of a flying capacitor.

[0010] To achieve this objective, according to one aspect of the present invention, a DC-DC converter is provided, comprising: a first capacitor; a first switch, a second switch, a third switch, and a fourth switch connected in series between a first electrode and a second electrode of the first capacitor; a second capacitor, the first electrode of which is connected to a connection node of the first switch and the second switch, and the connection node of the third switch and the fourth switch, respectively; an inductor, the first terminal of which is connected to the connection node of the second switch and the third switch; and a controller that controls the on / off state of each of the first to fourth switches based on a calculation result using the difference between a first detected voltage and a first voltage command value, the difference between a second detected voltage and a second voltage command value, and the reciprocal of a detected current, wherein the detected current is a measured current flowing through the inductor; wherein the first detected voltage is a measured voltage between the first electrode and the second electrode of the first capacitor or a measured voltage between the second terminal of the inductor and the connection node of the first capacitor and the fourth switch, and the second detected voltage is a measured voltage between the first electrode and the second electrode of the second capacitor.

[0011] According to one embodiment of the present invention, the controller can control the on / off state of each of the first to fourth switches based on the value obtained by applying a preset proportional control constant to the difference between the second detection voltage and the second voltage command value, and by multiplying the result of applying the preset proportional control constant by the reciprocal of the detection current.

[0012] According to one embodiment of the present invention, when the magnitude of the detected current is within a preset range near zero, the controller can determine the reciprocal of the detected current as a preset constant value.

[0013] According to one embodiment of the present invention, when the magnitude of the detected current is within a preset range near zero, the controller can determine the reciprocal of the detected current as a preset constant value that changes linearly within the preset range.

[0014] According to one embodiment of the present invention, the controller may include: a voltage controller that generates a current command value as a target current flowing through an inductor based on the difference between a first detected voltage and a first voltage command value; a current controller that generates a first control voltage command value based on the difference between the current command value and a detected current; and a flying capacitor voltage controller that generates a second control voltage command value based on the difference between a second detected voltage and a second voltage command value and the reciprocal of the detected current.

[0015] According to one embodiment of the present invention, the flying capacitor voltage controller may include: a subtractor that calculates the difference between a second detected voltage and a second voltage command value; a proportional controller that outputs a value obtained by applying a proportional control value to the calculation result of the subtractor; a reciprocal calculator that calculates the reciprocal of the detected current; and a multiplier that multiplies the value output by the proportional controller by the calculation result of the reciprocal calculator, and outputs the product obtained by multiplication as the second control voltage command value.

[0016] According to one embodiment of the present invention, when the magnitude of the detected current is within a preset range near zero, the reciprocal calculator can determine the reciprocal of the detected current as a preset constant value.

[0017] According to one embodiment of the present invention, when the magnitude of the detected current is within a preset range near zero, the reciprocal calculator can determine the reciprocal of the detected current as a preset constant value that changes linearly within the preset range.

[0018] According to one embodiment of the present invention, the controller may include: a first adder that adds a first control voltage command value to a second control voltage command value to generate a first duty cycle command value; a subtractor that subtracts the first control voltage command value from a first detected voltage; a second adder that adds the output value of the subtractor to the second control voltage command value to generate a second duty cycle command value; a first switch controller that determines the on / off state of each of a first switch and a fourth switch based on a comparison between the first duty cycle command value and a triangular wave signal having a predetermined frequency; and a second switch controller that determines the on / off state of each of a second switch and a third switch based on a comparison between the second duty cycle command value and the triangular wave signal.

[0019] According to one embodiment of the present invention, the DC-DC converter may further include: a voltage sensor for obtaining a measured voltage between the first electrode and the second electrode of the first capacitor or a measured voltage between the second terminal of the inductor and the connection node of the first capacitor and the fourth switch.

[0020] According to one embodiment of the invention, the DC-DC converter may further include a current sensor for obtaining a measured current flowing through the inductor.

[0021] In the DC-DC converter according to the present invention, the controllability of the voltage applied to the flying capacitor is improved. That is, since the voltage of the flying capacitor is easily maintained at the desired level, damage to the switch due to overvoltage can be avoided.

[0022] The effects and advantages that can be achieved by the present invention are not limited to those described above, and those skilled in the art will clearly understand, through the following description, other effects and advantages that can be achieved by the present invention but not described above. Attached Figure Description

[0023] The above and other objects, features, and other advantages of the present invention will become more clearly understood from the following detailed description presented in conjunction with the accompanying drawings, in which:

[0024] Figure 1 A circuit diagram illustrating a DC-DC converter according to one embodiment of the present invention is provided.

[0025] Figure 2 A block diagram of the controller of a DC-DC converter according to one embodiment of the present invention is shown in more detail;

[0026] Figures 3 to 6 A schematic diagram illustrating the current flow in a DC-DC converter according to an embodiment of the present invention; and

[0027] Figures 7 to 9 A graph illustrating the characteristics of the reciprocal of the inductor current used in the control operation of a DC-DC converter according to an embodiment of the present invention. Detailed Implementation

[0028] Hereinafter, DC-DC converters according to various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0029] Figure 1 This is a circuit diagram of a DC-DC converter according to one embodiment of the present invention.

[0030] refer to Figure 1 According to one embodiment of the present invention, the DC-DC converter converts the voltage applied between the first input / output (I / O) terminal T11 and the second I / O terminal T12 to a higher voltage, and provides the increased voltage between the third I / O terminal T21 and the fourth I / O terminal T22. Conversely, the DC-DC converter converts the voltage applied between the third I / O terminal T21 and the fourth I / O terminal T22 to a lower voltage, and provides the generated lower voltage between the first I / O terminal T11 and the second I / O terminal T12. Figure 1An exemplary converter is shown, comprising a battery BAT disposed between a first I / O terminal T11 and a second I / O terminal T12. The converter boosts the voltage of the supply current of the battery BAT to a higher voltage and provides the generated higher voltage between a third I / O terminal T21 and a fourth I / O terminal T22. For example, a load is connected between the third I / O terminal T21 and the fourth I / O terminal T22.

[0031] The following description relates to an example of applying a voltage obtained by boosting the output voltage of the battery BAT between the third I / O terminal T21 and the fourth I / O terminal T22. However, those skilled in the art will understand that the reverse is also possible. That is, the voltage applied between the third I / O terminal T21 and the fourth I / O terminal T22 is stepped down, and the resulting reduced voltage is applied between the first I / O terminal T11 and the second I / O terminal T12.

[0032] A DC-DC converter according to one embodiment of the present invention includes: a first capacitor C DC The first to fourth switches S1, S2, S3 and S4, and the second capacitor C FC Inductor L and controller 10; the first capacitor C DC The first and second electrodes are respectively connected to the third I / O terminal T21 and the fourth I / O terminal T22; the first to fourth switches S1, S2, S3 and S4 are connected in series to the first capacitor C. DC Between the first electrode and the second electrode; the second capacitor C FC The first and second electrodes are respectively connected to the connection node between the first switch S1 and the second switch S2 and the connection node between the third switch S3 and the fourth switch S4; the first terminal of the inductor L is connected to the connection node between the second switch S2 and the third switch S3; the controller 10 controls the on / off state of each of the first to fourth switches S1 to S4. In one example, the outputs S1 to S4 of the controller 10 can be connected to the gates of the first to fourth switches S1 to S4 respectively.

[0033] First capacitor C DC It is a smoothing capacitor connected between the third I / O terminal T21 and the fourth I / O terminal T22. Although Figure 1 It is not shown in the figure, but an additional smoothing capacitor can be connected between the first I / O terminal T11 and the second I / O terminal T12.

[0034] The first switch S1 to the fourth switch S4 are connected to the first capacitor C. DCThe first electrode side is connected in series with the second electrode side. Each of the first switches S1 to the fourth switches S4 is implemented by an insulated gate bipolar transistor (IGBT). Each switch is turned on or off according to an on / off control signal input from the controller 10 to its gate. Alternatively, each of the first switches S1 to the fourth switches S4 can be implemented using any switching element known in the art instead of an IGBT.

[0035] Second capacitor C FC It is a flying capacitor, whose first electrode and second electrode are respectively connected to the connection node between the first switch S1 and the second switch S2 and the connection node between the third switch S3 and the fourth switch S4.

[0036] Although not shown in the accompanying drawings, a DC-DC converter according to one embodiment of the present invention may include a plurality of sensors for detecting internal circuitry information used by a controller 10 to generate an on / off control signal for each of the first switch S1 to the fourth switch S4. The plurality of sensors may include: sensors for measuring the voltage V between the first I / O terminal T11 and the second I / O terminal T12 or the voltage V between the third I / O terminal T21 and the fourth I / O terminal T22. DC A voltage sensor is used to measure the second capacitor C. FC voltage V FC A voltage sensor, and a current I used to measure the current flowing through inductor L. L The current sensor is used. The voltage and current values ​​measured by the voltage and current sensors are called the detection voltage and detection current, respectively. The detection voltage and detection current are input to the controller 10.

[0037] Controller 10 receives a first detection voltage, the first detection voltage being in the first capacitor C DC Between the first electrode and the second electrode, or at the second terminal of the inductor L and the first capacitor C DC The actual measured voltage between the connection node of the first detection voltage and the fourth switch S4. The first detection voltage corresponds to the output voltage generated by the boost operation of the DC-DC converter or the output voltage obtained by the buck operation. In the case of boost operation, the first detection voltage corresponds to the voltage between the third I / O terminal T21 and the fourth I / O terminal T22 (i.e., the voltage between the first capacitor C and the fourth I / O terminal T22). DC (The voltage). In the case of buck operation, the first detection voltage corresponds to the voltage between the first I / O terminal T11 and the second I / O terminal T12.

[0038] Controller 10 compares the first detected voltage with a first voltage command value and calculates the difference between them. The first voltage command value represents the target voltage to be output from the DC-DC converter. The first voltage command value is set by a higher-level controller. In one example, the set value or preset value may be stored in a storage device and can be read by controller 10, or it may be sent to controller 10 from a higher-level controller.

[0039] Controller 10 receives the detected voltage V FC (It is applied to the second capacitor C) FC The measured voltage), the detected voltage V FC The voltage is compared with a preset second voltage command value, and the difference between them is calculated. This voltage command value is preset by the upper-level controller and is approximately equal to the first capacitor C. DC Half of the voltage. According to one embodiment of the invention, the controller 10 is based on the actual measured current (i.e., the detected current) of the inductor L and the voltage applied to the second capacitor C. FC The second detection voltage V FC The on / off state of each switch S1 to S4 is controlled by the product of the difference between the second voltage command value and the second voltage command value.

[0040] Figure 2 A block diagram of the controller of a DC-DC converter according to one embodiment of the present invention is shown in more detail.

[0041] refer to Figure 2 According to one embodiment of the present invention, the controller 10 of the DC-DC converter includes a voltage controller 11, a current controller 12, and a flying capacitor voltage controller 13.

[0042] The voltage controller 11 includes a subtractor 111 and a PI controller 112. The subtractor 111 detects the voltage V. DC (This is the actual measured voltage between the first I / O terminal T11 and the second I / O terminal T12) or the detected voltage V DC (This is the actual measured voltage between the third I / O terminal T21 and the fourth I / O terminal T22) and the preset first voltage command value V. DC * Compare and calculate the detection voltage V DC With the first voltage command value V DC The difference between * is calculated by the subtractor 111. The PI controller 112 performs proportional-integral control to reduce the difference calculated by the subtractor 111. By performing proportional-integral control, the PI controller 112 outputs an inductor current command value I representing the target current to flow through the inductor L. L * This reduces the difference calculated by subtractor 111.

[0043] The current controller 12 includes a subtractor 121 and a PI controller 122. The subtractor 121 calculates the inductor current command value I provided by the voltage controller 11. L *The actual detected current I flowing through inductor L L The difference between them. PI controller 122 performs proportional-integral control to generate a first control voltage command value V that can reduce the output value of subtractor 121. DM *. First control voltage command value V DM *Used to determine the on-off duty cycle of switches S1 to S4.

[0044] Figure 2 An example of voltage controller 11 and current controller 12 performing proportional-integral control is shown. However, the control technique is not limited to this. Various techniques known in the art can be utilized.

[0045] The flying capacitor voltage controller 13 includes a subtractor 131, a proportional controller 132, a reciprocal calculator 133, and a multiplier 134. The subtractor 131 receives the voltage applied to the second capacitor C. FC Detection voltage V FC The detection voltage V FC With the preset second voltage command value V FC The subtractor 131 compares the values ​​and calculates the difference. The proportional controller 132 performs proportional control and outputs a control command value that reduces the output value of the subtractor 131. The reciprocal calculator 133 calculates the detected inductor current I. L The multiplier 134 multiplies the output value of the proportional controller 132 with the reciprocal output from the reciprocal calculator 133, and uses the calculated product as the second control voltage command value V. CM * Output.

[0046] Additionally, the controller 10 may further include: an adder 141, a subtractor 142, a second adder 143, a first switch controller 144, and a second switch controller 145; the adder 141 converts the first control voltage command value V output by the current controller 12 into a single value. DM *The second control voltage command value V output by the flying capacitor voltage controller 13 CM *Add them together to generate a first duty cycle command value V1*; the subtractor 142 detects the detection voltage V between the I / O terminals. DC Subtract the first control voltage command value V from the middle DM *; The second adder 143 adds the result value output by the subtractor 142 to the second control voltage command value V. CM*Add; The first switch controller 144 determines the on / off state of each of the first switch S1 and the fourth switch S4 based on the comparison result between the first duty cycle command value V1* and the triangular wave signal with a preset frequency generated by the triangular wave generator 146; The second switch controller 145 determines the on / off state of each of the second switch S2 and the third switch S3 based on the comparison result between the second duty cycle command value V2* and the triangular wave signal with a preset frequency output by the triangular wave generator 146.

[0047] Regarding the above configuration, the first control voltage command value V is used. DM * and second control voltage command value V CM * The first duty cycle command value V1* and the second duty cycle command value V2* are represented by Equation 1.

[0048] [Equation 1]

[0049] V1*=V CM *+V DM *

[0050] V2*=V CM *+(V DC -V DM *).

[0051] Here, the first control voltage command value V DM *Based on the output voltage V of the DC-DC converter DC The generated value, and has an impact on the output, while the second control voltage command value V CM *Based on the voltage V of the flying capacitor FC The generated value, and the voltage V across the flying capacitor. FC Or the output voltage V of the DC-DC converter DC With the voltage V across the capacitor FC The difference V between DC -V FC Yes, it has an impact. Specifically, it affects the first control voltage command value V. DM * Used to control the output voltage of the DC-DC converter, and the second control voltage command value V CM * Used to control the voltage across the flying capacitor.

[0052] Figures 3 to 6 This is a schematic diagram illustrating the flow of current in a DC-DC converter according to one embodiment of the present invention.

[0053] Figure 3 The first state is shown, in which the first switch S1 and the second switch S2 are on, and the third switch S3 and the fourth switch S4 are off. When capacitor C DC voltage V DCWhen the inductor L is fully applied to the connection point between the inductor L and the switch S2 or S3, the first state is established.

[0054] Figure 4 The second state is shown, in which the first switch S1 and the third switch S3 are turned on, and the second switch S2 and the fourth switch S4 are turned off. This corresponds to the capacitor C. DC voltage V DC With flying capacitor C FC voltage V FC When the voltage difference between the two is applied to the connection node between inductor L and switch S2 or S3, the second state is established.

[0055] Figure 5 The third state is shown, in which the second switch S2 and the fourth switch S4 are on, and the first switch S2 and the third switch S3 are off. When the flying capacitor C... FC voltage V FC When applied to the connection node between inductor L and switch S2 or S3, a third state is established.

[0056] Figure 6 The fourth state is shown, in which the first switch S1 and the second switch S2 are off, and the third switch S3 and the fourth switch S4 are on. The fourth state is established when no voltage is applied to the connection point between the inductor L and the switch S2 or S3.

[0057] exist Figures 3 to 6 In the state shown, current flows through what is called the flying capacitor C. FC The second capacitor C FC In the second and third states, the flying capacitor C FC The voltage change. During the total duration of the second and third states, the flying capacitor C is charged. FC In or from the flying capacitor C FC The electrical energy released depends on the current flowing through the inductor L and the ratio of the second state to the third state.

[0058] This can be represented by Equation 2.

[0059] [Equation 2]

[0060] I FC =sC FC V FC

[0061] I FC =D CM ·I L

[0062]

[0063] Among them, “D” CM"This indicates that current flows through the flying capacitor C" FC The duty cycle, which is determined by the proportional control of the flying capacitor voltage controller 13, and is expressed by the third line of Equation 2. The third line of Equation 2 indicates that without utilizing the inductor current I... L The duty cycle in the case of the reciprocal of K. In Equation 2, "K P "" indicates the gain of the proportional controller 132.

[0064] Equation 2 can be reduced to Equation 3, and Equation 4 can be obtained by calculating the transfer function based on Equation 3.

[0065] [Equation 3]

[0066]

[0067] [Equation 4]

[0068]

[0069] In order to control the transfer function of Equation 4 in the closed-loop form of a first-order low-pass filter, the relationship in Equation 5 must be established.

[0070] [Equation 5]

[0071]

[0072] Equation 5 shows that linear control characteristics can only be obtained when the gain of the proportional control is inversely proportional to the inductor current.

[0073] Therefore, in one embodiment of the invention, the flying capacitor voltage controller 13 includes a function for obtaining the inductor current I. L The configuration of the reciprocal calculator 133 enables stable control of the overall current.

[0074] Here, the controller in the flying capacitor voltage controller 13 can be implemented using a proportional-integral (PI) controller instead of the proportional controller 132. However, when using a PI controller, the accumulated value in the integrator may generate a large duty cycle pulsation depending on the direction of the current. This means that in the inductor current I... L Controllability deteriorates significantly when the value approaches zero. Therefore, it is best to use a proportional controller.

[0075] Figures 7 to 9 A graph illustrating the characteristics of the reciprocal of the inductor current used in the control operation of a DC-DC converter according to an embodiment of the present invention.

[0076] As mentioned above, when the inductor current I L The reciprocal of the value is applied in the case of flying capacitor voltage control, such as... Figure 7 As shown, when the inductor current I L When it approaches zero, the inductor current I L The reciprocal of this value tends towards positive infinity or negative infinity. Therefore, depending on the direction of the inductor current, the voltage across the flying capacitor cannot be properly controlled, or the second control voltage command value V... CM * Significant drift. Due to this effect, there may be a problem with controllability deterioration near zero current.

[0077] In various embodiments of the present invention, a technique for limiting inductor current is provided to prevent such degradation of controllability.

[0078] First, such as Figure 8 As shown, when the input inductor current I L When the magnitude is within a preset range A near zero, the reciprocal calculator 133 included in the flying capacitor voltage controller 13 will calculate the inductor current I. L The reciprocal of (i.e., the sense current of the inductor) 1 / I L Limit to a preset constant value ±INV_I L _max. When the inductor current I is limited as described above. L The reciprocal of (1 / I) L When the value of ) is set, it can prevent the gain from tending to infinity when the inductor current approaches zero. Therefore, it can improve controllability near zero current.

[0079] According to one embodiment of the present invention, such as Figure 9 As shown, there is another technique to prevent the controllability degradation of the flying capacitor. That is, when the inductor current I input to the reciprocal calculator 133 included in the flying capacitor voltage controller 13... L When the magnitude is within a preset range A near zero, the reciprocal of the inductor current (i.e., the sense current of the inductor) 1 / I L Set to a linear change. As mentioned above, when the inductor current I... L The reciprocal of (1 / I) L The value of ) is limited to a predetermined range of ±INV_I L When the gain changes linearly within the range of _max, it can prevent the gain from approaching infinity when the inductor current is close to zero. Therefore, it can improve controllability near zero current.

[0080] As per the above reference Figure 8 and Figure 9 As mentioned above, in limiting the inductor current I L The inductor current I when the sensing current of the inductor is close to zero. L The reciprocal of 1 / I LWhen the value is , the system can operate stably when the controller included in the flying capacitor voltage controller 13 is implemented using a proportional-integral controller, and when the controller is implemented using a proportional controller.

[0081] The aforementioned operations / functions performed by the controller can be implemented as computer-readable code / algorithms / software stored on a computer-readable recording medium. A computer-readable recording medium is any data storage device that can store data that can subsequently be read by a computer or processor / microprocessor. Examples of computer-readable recording media include hard disk drives (HDDs), solid-state drives (SSDs), silicon disk drives (SDDs), read-only memory (ROM), random access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, etc.

[0082] The aforementioned controller may include one or more processors / microprocessors. The controller may be implemented using circuitry. The controller may perform the aforementioned operations / functions by executing computer-readable code / algorithms / software stored on a computer-readable recording medium.

[0083] Although the invention has been described with reference to preferred embodiments, these preferred embodiments are presented for illustrative purposes only to describe the technical spirit of the invention, and those skilled in the art will understand that various modifications and changes can be made without departing from the scope and spirit of the invention. Therefore, it should be understood that the scope of protection of the invention is defined by the appended claims rather than the description presented above.

Claims

1. A DC-DC converter, comprising: First capacitor; The first switch, the second switch, the third switch, and the fourth switch are connected in series between the first electrode and the second electrode of the first capacitor; The second capacitor has its first electrode connected to the connection node between the first switch and the second switch, and its second electrode connected to the connection node between the third switch and the fourth switch. An inductor, the first terminal of which is connected to the connection node between the second and third switches; as well as The controller controls the on / off state of each of the first to fourth switches based on the calculation results of the difference between the first detected voltage and the first voltage command value, the difference between the second detected voltage and the second voltage command value, and the reciprocal of the detected current, wherein the detected current is the measured current flowing through the inductor; Wherein, the first detection voltage is the measured voltage between the first electrode and the second electrode of the first capacitor or the measured voltage between the second terminal of the inductor and the connection node of the first capacitor and the fourth switch, and the second detection voltage is the measured voltage between the first electrode and the second electrode of the second capacitor.

2. The DC-DC converter according to claim 1, wherein, The controller controls the on / off state of each of the first to fourth switches based on the value obtained by applying a preset proportional control constant to the difference between the second detection voltage and the second voltage command value, and by multiplying the result of applying the preset proportional control constant by the reciprocal of the detection current.

3. The DC-DC converter according to claim 2, wherein, When the magnitude of the detected current is within a preset range near zero, the controller determines the reciprocal of the detected current as a preset constant value.

4. The DC-DC converter according to claim 2, wherein, When the magnitude of the detected current is within a preset range near zero, the controller determines the reciprocal of the detected current as a preset constant value that changes linearly within the preset range.

5. The DC-DC converter according to claim 1, wherein, The controller includes: A voltage controller that generates a current command value for the current flowing through the inductor based on the difference between a first detected voltage and a first voltage command value; A current controller that generates a first control voltage command value based on the difference between the current command value and the detected current; and The flying capacitor voltage controller generates the second control voltage command value based on the difference between the second detected voltage and the second voltage command value and the reciprocal of the detected current.

6. The DC-DC converter according to claim 5, wherein, The flying capacitor voltage controller includes: A subtractor that calculates the difference between the second detected voltage and the second voltage command value; A proportional controller whose output is a value obtained by applying a proportional control value to the calculation result of the subtractor; A reciprocal calculator that calculates the reciprocal of the detected current; and The multiplier multiplies the value output by the proportional controller by the result calculated by the reciprocal calculator, and outputs the product obtained by multiplication as the second control voltage command value.

7. The DC-DC converter according to claim 6, wherein, When the magnitude of the detected current is within a preset range near zero, the reciprocal calculator determines the reciprocal of the detected current as a preset constant value.

8. The DC-DC converter according to claim 6, wherein, When the magnitude of the detected current is within a preset range near zero, the reciprocal calculator determines the reciprocal of the detected current as a preset constant value that changes linearly within the preset range.

9. The DC-DC converter according to claim 5, wherein, The controller includes: The first adder adds the first control voltage command value and the second control voltage command value to generate the first duty cycle command value; A subtractor that subtracts the first control voltage command value from the first detected voltage; The second adder adds the output value of the subtractor to the second control voltage command value to generate the second duty cycle command value. A first switch controller determines the on / off state of each of the first and fourth switches based on a comparison between a first duty cycle command value and a triangular wave signal having a predetermined frequency; and The second switch controller determines the on / off state of each of the second and third switches based on a comparison between the second duty cycle command value and the triangular wave signal.

10. The DC-DC converter according to claim 1, further comprising: A voltage sensor is used to obtain a measured voltage between the first electrode and the second electrode of the first capacitor or a measured voltage between the second terminal of the inductor and the connection node of the first capacitor and the fourth switch.

11. The DC-DC converter of claim 1, further comprising a current sensor for obtaining a measured current flowing through the inductor.

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