Control device, switching power supply circuit, and control method

Abstract

To provide a control device capable of suppressing ripple generation on an input voltage at switchover of an operation mode of a switching power supply circuit.SOLUTION: A control device for controlling a switching power supply circuit, when changing over its operation mode, sets a duty ratio in PWM control for a first switching element before the changeover of its operation mode to a first starting point which is the start to change the duty ratio of the PWM control for the first switching element after changeover of its operation mode, then linearly changes the duty ratio of the PWM control for the first switching element from the first starting point, while setting a duty ratio of PWM control for a second switching element before the changeover of its operation mode to a second starting point which is the start to change the duty ratio of the PWM control for the second switching element after changeover of its operation mode, then linearly changes the duty ratio of the PWM control of the second switching element from the second starting point.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a switching power supply circuit, and a control method. [Background technology]

[0002] 2. Description of the Related Art Research and development is being conducted into technology relating to a buck-boost switching power supply circuit that can output an output voltage of a desired magnitude independent of the magnitude of the input voltage.

[0003] In this regard, a switching power supply circuit is known which includes: first switching means consisting of a plurality of switching elements for controlling the conduction state of the input side; second switching means consisting of a plurality of switching elements for controlling the conduction state of the output side; feedback pulse generating means for generating a feedback pulse having a pulse width according to the output potential; first control means for switching between a plurality of operation modes including at least a step-down mode and a step-up mode according to the input potential, providing a feedback pulse to the first switching means in the step-down mode and providing a feedback pulse to the second switching means in the step-up mode; and second control means for controlling the feedback pulse generating means so that the duty ratio of the feedback pulse is constant regardless of the plurality of operation modes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-318662 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the switching power supply circuit described in Patent Document 1, ripples may occur in the input voltage when switching between operating modes, which is undesirable as it places a load on the circuit elements of the switching power supply circuit.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a control device, a switching power supply circuit, and a control method that can suppress the occurrence of ripples in the input voltage when switching the operating mode of the switching power supply circuit. [Means for solving the problem]

[0007] Another aspect of the present disclosure is a control device that controls a switching power supply circuit including a first switching element and a second switching element, and operates the switching power supply circuit in an operating mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operating mode for operating the switching power supply circuit, the control device sets a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operating mode switching as a first starting point from which to start changing the duty ratio in PWM control of the first switching element after the operating mode switching, and linearly changes the duty ratio in PWM control of the first switching element from the first starting point, and sets a duty ratio in PWM control of the second switching element before the operating mode switching as a second starting point from which to start changing the duty ratio in PWM control of the second switching element after the operating mode switching, and linearly changes the duty ratio in PWM control of the second switching element from the second starting point.

[0008] Another aspect of the present disclosure is a switching power supply circuit including a first switching element and a second switching element, wherein the switching power supply circuit is operated in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operation mode for operating the switching power supply circuit, a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching is set as a first starting point at which a change in the duty ratio in PWM control of the first switching element after the operation mode switching begins, and the duty ratio in PWM control of the first switching element is changed linearly from the first starting point, and a duty ratio in PWM control of the second switching element before the operation mode switching is set as a second starting point at which a change in the duty ratio in PWM control of the second switching element after the operation mode switching begins, and the duty ratio in PWM control of the second switching element is changed linearly from the second starting point.

[0009] Another aspect of the present disclosure is a control method for controlling a switching power supply circuit including a first switching element and a second switching element, wherein the switching power supply circuit is operated in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operation mode for operating the switching power supply circuit, a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching is set as a first starting point from which a change in the duty ratio in PWM control of the first switching element after the operation mode switching begins, and the duty ratio in PWM control of the first switching element is changed linearly from the first starting point, and the duty ratio in PWM control of the second switching element before the operation mode switching is set as a second starting point from which a change in the duty ratio in PWM control of the second switching element after the operation mode switching begins, and the duty ratio in PWM control of the second switching element is changed linearly from the second starting point. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to suppress the occurrence of ripples in the input voltage when the operation mode of a switching power supply circuit is switched. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing an example of the configuration of a switching power supply device 1 according to an embodiment. [Figure 2] 10 is a diagram for explaining how the control device 20 changes the duty ratio when the operation mode is switched. FIG. [Figure 3] 10A and 10B are diagrams for explaining temporal changes in input voltage values when the duty ratio is changed nonlinearly when switching between operation modes. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a control device 20. [Figure 5]10 is a diagram showing an example of the flow of processing performed by an operation mode determination unit 21. FIG. [Figure 6] FIG. 2 is a diagram showing an example of a block diagram illustrating feedback control performed by a feedback control unit 22. [Figure 7] FIG. 10 is a diagram showing an example of a processing flow in which a feedback control unit 22 performs I control. [Figure 8] FIG. 10 is a diagram showing an example of the flow of processing performed by a range determination unit 231. [Figure 9] FIG. 10 is a diagram showing an example of the flow of processing performed by a counter unit 232. [Figure 10] 2 is a diagram showing an example of the configuration of each of a first comparing section 25 and a second comparing section 26 that output a PWM signal based on a carrier signal generated by a carrier signal generating section 24. FIG. [Figure 11] 10 is a diagram showing an example of the flow of processing performed by a signal switching unit 27. FIG. [Figure 12] FIG. 10 is a diagram showing a first modified example of the configuration of the control device 20. [Figure 13] 3 is a diagram showing an example of changes over time in the first comparison value and the second comparison value when the input voltage value changes over time as shown in FIG. 2. FIG. [Figure 14] 14 is a diagram showing an example of the flow of processing in which the operation mode determination unit 21 determines the operation mode using seven values x1 to x4 and y1 to y3 shown in FIG. [Figure 15] FIG. 10 is a diagram showing a second modified example of the configuration of the control device 20. [Figure 16] 10 is a diagram showing a modified example of the flow of processing performed by the signal switching unit 27. FIG. [Figure 17] 10 is a diagram for explaining that the operation mode determination unit 21 changes the upper limit voltage value z1 and the lower limit voltage value z2. FIG. [Figure 18] 10 is a diagram showing an example of a flow of processing in which the operation mode determination unit 21 changes the upper limit voltage value and the lower limit voltage value. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Embodiment> Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Herein, in the embodiments, a conductor that transmits an electrical signal corresponding to DC power or an electrical signal corresponding to AC power will be described as a transmission line. The transmission line may be, for example, a conductor printed on a substrate, a conductor formed in a linear shape, or another conductor. Furthermore, in the embodiments, the term "voltage" refers to a potential difference from a predetermined reference potential, and illustrations and descriptions of the reference potential will be omitted. Here, the reference potential may be any potential. In the embodiments, as an example, a case will be described in which the reference potential is ground potential. Furthermore, in the embodiments, the magnitude of a certain voltage will be described as the voltage value. In this case, for example, the magnitude of an input voltage described below will be referred to as the input voltage value.

[0013] <Configuration of a switching power supply unit> The configuration of a switching power supply device 1 according to an embodiment will be described below with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of a switching power supply device 1 according to an embodiment.

[0014] The switching power supply 1 is a device that receives a direct current from a connected power supply and is controlled so that a direct current voltage of a predetermined value is supplied as an input voltage. The switching power supply 1 outputs an output voltage corresponding to a connected load in response to the supplied input voltage. For ease of explanation, the input voltage supplied to the switching power supply 1 will be referred to simply as the input voltage. For ease of explanation, the output voltage output from the switching power supply 1 in response to the load will be referred to simply as the output voltage. The switching power supply 1 includes at least two switching elements. As an example, the following description will be given of a case where the switching power supply 1 includes two switching elements: a first switching element S1 and a second switching element S2.

[0015] The switching power supply device 1 includes a switching power supply circuit 10 and a control device 20. In the switching power supply device 1, the control device 20 may be configured separately from the switching power supply circuit 10 as shown in FIG.

[0016] The switching power supply circuit 10 includes a first side CC1 including a first upper arm AU1 and a first lower arm AD1 of an H-bridge, and a second side CC2 including a second upper arm AU2 and a second lower arm AD2 of the H-bridge. The switching power supply circuit 10 also includes a coil CL connecting a first connection point CN1 between the first upper arm AU1 and the first lower arm AD1 on the first side CC1 and a second connection point CN2 between the second upper arm AU2 and the second lower arm AD2 on the second side CC2 via a transmission line. The switching power supply circuit 10 also includes a first switching element S1 provided in the first upper arm AU1. The switching power supply circuit 10 also includes a first current limiter D1 provided in the first lower arm AD1 to limit the direction of current flow from the first lower arm AD1 side to the first upper arm AU1 side. The switching power supply circuit 10 also includes a second current limiter D2 provided in the second upper arm AU2 to limit the direction of current flow from the second lower arm AD2 side to the second upper arm AU2 side. The switching power supply circuit 10 also includes a second switching element S2 provided in the second lower arm AD2. The switching power supply circuit 10 also includes resistors R11 and R12 connected in series between the first upper arm AU1 and the first lower arm AD1, a capacitor C1 connected between the first upper arm AU1 and the first lower arm AD1, resistors R21 and R22 connected in series between the second upper arm AU2 and the second lower arm AD2, and a capacitor C2 connected between the second upper arm AU2 and the second lower arm AD2. Between the first upper arm AU1 and the first lower arm AD1, the resistors R11 and R12 connected in series are connected in parallel with the capacitor C1. Between the second upper arm AU2 and the second lower arm AD2, the resistors R21 and R22 connected in series are connected in parallel with the capacitor C2. The switching power supply circuit 10 may further include other elements, other members, other devices, etc., as long as the functions of the switching power supply circuit 10 described in the embodiment are not impaired. Furthermore, the switching power supply circuit 10 may be configured with another bridge instead of the H bridge, as long as the functions of the switching power supply circuit 10 described in the embodiment are not impaired.In this case, the number of switching elements included in the switching power supply circuit 10 may be any number as long as it is two or more.

[0017] As shown in FIG. 1, the switching power supply circuit 10 is connected to a DC power supply P, which is an example of the power supply, and a load LD, which is an example of the load.

[0018] The DC power supply P may be any power supply that can input a DC current to the switching power supply circuit 10. The DC power supply P may be, for example, a solar panel, a DC power supply that rectifies and smooths commercial power, a secondary battery, or a switching power supply. The switching power supply may be, for example, a switching converter. In the following, as an example, a case where the DC power supply P is a solar panel will be described. The DC power supply P is connected between the first upper arm AU1 and the first lower arm AD1, and applies a DC voltage as an input voltage between the first upper arm AU1 and the first lower arm AD1. In this way, the DC power supply P supplies (inputs) the input voltage to the switching power supply circuit 10. In the following, as an example, a case will be described in which the DC power supply P applies a DC voltage as an input voltage between the first upper arm AU1 and the first lower arm AD1, with the first upper arm AU1 being the high-potential arm on the first side CC1 and the first lower arm AD1 being the low-potential arm on the first side CC1 (i.e., the arm on the ground potential side in this example). Note that, in the example shown in Fig. 1, the DC power supply P is separate from the switching power supply circuit 10, but it may also be configured integrally with the switching power supply circuit 10.

[0019] Furthermore, the DC power supply P functions as a DC current source and inputs a DC current to the switching power supply circuit 10. The DC current (DC power) input to the switching power supply circuit 10 is controlled by the control device 20 to an input voltage of a target input voltage value. As a result of such control by the control device 20, the DC power supply P supplies an input voltage to the switching power supply circuit 10. For ease of explanation, the target input voltage value, i.e., the target value of the input voltage value, will be referred to simply as the target value in the following description. Here, the target value may be input to the control device 20 by inputting information indicating the target value from an external device, by inputting a reference voltage within the control device 20, or by some other method.

[0020] The load LD is, for example, a rechargeable secondary battery. The secondary battery may be, for example, a lithium ion battery or a lithium polymer battery. Instead of a secondary battery, the load LD may be another device (for example, a motor) that operates in response to a DC voltage. The load LD is detachably connected between the second upper arm AU2 and the second lower arm AD2, and a DC voltage supplied between the second upper arm AU2 and the second lower arm AD2 is supplied as an output voltage. Hereinafter, as an example, a case will be described in which the switching power supply circuit 10 applies a DC voltage between the second upper arm AU2 and the second lower arm AD2 as an output voltage, with the second upper arm AU2 serving as a high-potential arm on the second side CC2 and the second lower arm AD2 serving as a low-potential arm on the second side CC2 (i.e., an arm on the ground potential side in this example). This causes the switching power supply circuit 10 to output an output voltage. Although the load LD is separate from the switching power supply circuit 10 in the example shown in FIG. 1 , it may be integrated with the switching power supply circuit 10. The load LD may be configured to be irremovably connected between the second upper arm AU2 and the second lower arm AD2.

[0021] The first switching element S1 is, for example, a field effect transistor, but may be another switching element such as a bipolar transistor instead of a field effect transistor.

[0022] The first current limiting unit D1 is, for example, a diode. In this case, the anode of the first current limiting unit D1 is connected to the first lower arm AD1 via a transmission line. In addition, in this case, the cathode of the first current limiting unit D1 is connected to the first upper arm AU1 via a transmission line. Note that instead of a diode, the first current limiting unit D1 may be a switching element such as a field effect transistor, or may be another element capable of limiting the direction of current from the first lower arm AD1 side to the first upper arm AU1 side.

[0023] The second switching element S2 is, for example, a field effect transistor. Note that the second switching element S2 may be another switching element such as a bipolar transistor instead of a field effect transistor.

[0024] The second current limiting unit D2 is, for example, a diode. In this case, the anode of the second current limiting unit D2 is connected to the second lower arm AD2 via a transmission line. In addition, in this case, the cathode of the second current limiting unit D2 is connected to the second upper arm AU2 via a transmission line. Note that instead of a diode, the second current limiting unit D2 may be a switching element such as a field effect transistor, or may be another element capable of limiting the direction of current from the second lower arm AD2 side to the second upper arm AU2 side.

[0025] With the above configuration, when an input voltage is input between the first upper arm AU1 and the first lower arm AD1, the switching power supply circuit 10 outputs an output voltage between the second upper arm AU2 and the second lower arm AD2. If the first current limiting unit D1 and the second current limiting unit D2 are each switching elements, the switching power supply circuit 10 can also output an output voltage between the first upper arm AU1 and the first lower arm AD1 by inputting an input voltage between the second upper arm AU2 and the second lower arm AD2. However, if the first current limiting unit D1 and the second current limiting unit D2 are each diodes, the switching power supply circuit 10 can suppress increases in manufacturing costs. This is desirable for mass production of switching power supply circuits 10.

[0026] Furthermore, the switching power supply circuit 10 can operate in three operating modes: a step-up mode, a step-up / step-down mode, and a step-down mode, by controlling the first switching element S1 and the second switching element S2 using the control device 20. The step-up mode is an operating mode in which the input voltage is increased relative to the output voltage. The step-up / step-down mode is an operating mode in which the input voltage is maintained relative to the output voltage. The step-down mode is an operating mode in which the input voltage is decreased relative to the output voltage. Note that the control methods for the first switching element S1 and the second switching element S2 in the switching power supply circuit 10 according to these three operating modes are known methods, and therefore will not be described in the embodiments. In the following description, the operating modes of the switching power supply circuit 10 will be simply referred to as "operation modes."

[0027] The control device 20 detects each of the input voltage value and the output voltage value, and controls the switching power supply circuit 10 based on the detected input voltage value and output voltage value. In the example shown in FIG. 1, the control device 20 detects the voltage value of the voltage at the connection point between the resistive elements R11 and R12 as the input voltage value, and detects the voltage value of the voltage at the connection point between the resistive elements R21 and R22 as the output voltage value. Note that the control device 20 may use other methods to detect each of the input voltage value and the output voltage value. Furthermore, the function of detecting at least one of the input voltage value and the output voltage value may be provided in the switching power supply circuit 10 instead of the control device 20. For convenience of explanation, the function of detecting the input voltage value will be referred to as an input voltage detection unit, and the function of detecting the output voltage value will be referred to as an output voltage detection unit.

[0028] The control device 20 switches the operating mode according to the difference between the detected input voltage value and the detected output voltage value, thereby causing the switching power supply circuit 10 to operate as a constant voltage output source. When switching the operating mode, the control device 20 identifies the duty ratio in PWM (Pulse Width Modulation) control of the first switching element S1 before the operating mode switch as a first starting point from which to start changing the duty ratio in PWM control of the first switching element S1 after the operating mode switch, and identifies the duty ratio in PWM control of the second switching element S2 before the operating mode switch as a second starting point from which to start changing the duty ratio in PWM control of the second switching element S2 after the operating mode switch. The control device 20 then linearly changes the duty ratio in PWM control of the first switching element S1 after the operating mode switch from the identified first starting point, and linearly changes the duty ratio in PWM control of the second switching element S2 after the operating mode switch from the second starting point. This allows the control device 20 to suppress discontinuous changes in the duty ratio in PWM control of the first switching element S1 when the operating mode is switched, and also suppresses discontinuous changes in the duty ratio in PWM control of the second switching element S2 when the operating mode is switched. As a result, the control device 20 can suppress ripples in the input voltage when the operating mode is switched. Hereinafter, for convenience of explanation, the PWM signal input to the gate terminal of the first switching element S1 will be referred to as the “first PWM signal.” Hereinafter, for convenience of explanation, the input of the first PWM signal to the gate terminal of the first switching element S1 will be referred to as the “first PWM signal being input to the first switching element S1.” Hereinafter, for convenience of explanation, the PWM signal input to the gate terminal of the second switching element S2 will be referred to as the “second PWM signal.” Furthermore, for convenience of explanation, the input of the second PWM signal to the gate terminal of the second switching element S2 will be referred to as the input of the second PWM signal to the second switching element S2.For ease of explanation, the duty ratio in the PWM control of the first switching element S1 (i.e., the duty ratio of the first PWM signal) will be referred to as the first duty ratio. For ease of explanation, the duty ratio in the PWM control of the second switching element S2 (i.e., the duty ratio of the second PWM signal) will be referred to as the second duty ratio.

[0029] <How the control device changes the duty ratio when switching between operation modes> Hereinafter, how the control device 20 changes the duty ratio when the operation mode is switched will be described with reference to Fig. 2. Fig. 2 is a diagram for explaining how the control device 20 changes the duty ratio when the operation mode is switched.

[0030] 2 shows four timing charts, timing chart CH1 to timing chart CH4. The horizontal axes of these four timing charts have the same origin and indicate the elapsed time from the origin.

[0031] Timing chart CH1 is a timing chart showing an example of a change in a target value over time. Timing chart CH2 is a timing chart showing an example of a change in an input voltage value and an output voltage value over time. Timing chart CH3 is a timing chart showing an example of a change in a first duty ratio over time. Timing chart CH4 is a timing chart showing an example of a change in a second duty ratio over time.

[0032] In the example shown in FIG. 2, the control device 20 changes the target value as shown in timing chart CH1. A curve F1 plotted on timing chart CH1 shows an example of the change in the target value over time. Therefore, the vertical axis of timing chart CH1 represents the target value. Note that the change in the target value over time shown in FIG. 2 is a change that is experimentally applied by the user operating the control device 20 so that the change in the first duty ratio and the second duty ratio over time becomes clear. Therefore, the control device 20 does not change the target value as shown by curve F1 during normal use of the switching power supply circuit 10.

[0033] In the example shown in FIG. 2, the target value is maintained at a constant voltage value V1 during the period from timing TA to timing T1. In addition, in this example, the target value linearly decreases from voltage value V1 to voltage value V2, which is lower than voltage value V1, during the period from timing T1 to timing T4. In this example, the target value is maintained at a constant voltage value V2 during the period from timing T4 to timing T5. In this example, the target value linearly increases from voltage value V2 to voltage value V1 during the period from timing T5 to timing T7. In this example, the target value is maintained at a constant voltage value V1 during the period from timing T7 onwards.

[0034] 2 is the upper limit of the target value that can be input to the switching power supply circuit 10, and the voltage value V2 is the lower limit of the target value that can be input to the switching power supply circuit 10. In other words, the following describes, as an example, a case where the voltage value V1 is the upper limit of the voltage value of the input voltage that can be input to the switching power supply circuit 10, and the voltage value V2 is the lower limit of the voltage value of the input voltage that can be input to the switching power supply circuit 10.

[0035] When the target value changes as shown in timing chart CH1, control device 20 changes the input voltage value as shown in timing chart CH2. Curve F2 plotted in timing chart CH2 shown in Figure 2 shows an example of the change in the input voltage value over time. Therefore, the vertical axis of timing chart CH2 represents the voltage value.

[0036] In the example shown in FIG. 2, the input voltage value changes to follow the target value, and is therefore kept constant at voltage V1 during the period from timing TA to timing T1. Also, in this example, the input voltage value drops linearly from voltage V1 to voltage V2 during the period from timing T1 to timing T4. Also, in this example, the input voltage value is kept constant at voltage V2 during the period from timing T4 to timing T5. Also, in this example, the input voltage value increases linearly from voltage V2 to voltage V1 during the period from timing T5 to timing T7. And, in this example, the input voltage value is kept constant at voltage V1 during the period from timing T7 onwards.

[0037] Here, the actual output voltage value changes randomly or periodically depending on the remaining charge of the battery (load LD), noise, the load state, etc. However, for simplicity of explanation, the following will be described as an example in which the switching power supply circuit 10 always outputs an output voltage of a predetermined voltage value V3, as shown by the straight line F3 plotted in the timing chart CH2. Also, the following will be described as an example in which the voltage value V3 is smaller than the voltage value V1 and larger than the voltage value V2. Here, the straight line F3 shows an example of the change in the output voltage value over time.

[0038] 2, when the input voltage value changes, the control device 20 changes the operation mode over time in the following order: step-down mode, step-up / step-down mode, step-up mode, step-up / step-down mode, and step-down mode. As a result, the control device 20 operates as an input voltage control device that keeps the input voltage value input to the switching power supply circuit 10 constant with respect to the target value.

[0039] When the operating mode is the step-down mode, the control device 20 changes the first duty ratio through feedback control and the second duty ratio through linear change control. In this embodiment, changing a duty ratio through linear change control means changing the duty ratio linearly, i.e., changing the duty ratio at a predetermined rate of change. However, if the duty ratio is increased to its upper limit during linear change control, the duty ratio is maintained at the upper limit during linear change control. Also, if the duty ratio is decreased to its lower limit during linear change control, the duty ratio is maintained at the lower limit during linear change control. Hereinafter, for convenience of explanation, the predetermined rate of change will be referred to simply as the "predetermined rate of change." On the other hand, when the operation mode is the voltage step-up / step-down mode or the voltage step-up mode, the control device 20 changes the first duty ratio by linear change control and changes the second duty ratio by feedback control.

[0040] In the embodiment, the switching power supply circuit 10 is controlled by the control device 20 to operate in the step-down mode when the input voltage is higher than a predetermined upper limit voltage z1. The upper limit voltage z1 is a threshold determined according to the output voltage, and is, for example, a voltage value obtained by adding 10% of the output voltage to the output voltage, but is not limited to this. In the embodiment, the switching power supply circuit 10 is controlled by the control device 20 to operate in the step-up mode when the input voltage is lower than a predetermined lower limit voltage z2. The lower limit voltage z2 is a threshold determined according to the output voltage, and is, for example, a voltage value obtained by subtracting 10% of the output voltage from the output voltage, but is not limited to this. In the embodiment, the switching power supply circuit 10 is controlled by the control device 20 to operate in the step-up / step-down mode when the input voltage is equal to or lower than the upper limit voltage z1 and equal to or higher than the lower limit voltage z2. Note that both the upper limit voltage z1 and the lower limit voltage z2 may be equal to the output voltage. In this case, the switching power supply circuit 10 is controlled in one of two operation modes, a step-up mode or a step-down mode. Note that the control device 20 may be configured to switch the operation mode of the switching power supply circuit 10 by another method based on the input voltage value and the output voltage value. Note that in Fig. 2, the hierarchical relationship between the voltage value V1, the voltage value V2, the upper limit voltage value z1, the lower limit voltage value z2, and the output voltage value V3 is voltage value V1 > upper limit voltage value z1 > output voltage value V3 > lower limit voltage value z2 > voltage value V2.

[0041] When the control device 20 changes the input voltage value as shown in timing chart CH2, the control device 20 changes the first duty ratio as shown in timing chart CH3 and the second duty ratio as shown in timing chart CH4. Here, curve F4 in timing chart CH3 shows an example of the temporal change in the first duty ratio. Therefore, the vertical axis of timing chart CH3 indicates the duty ratio. Furthermore, in timing chart CH3, the portion of curve F4 that shows the temporal change in the first duty ratio due to feedback control is distinguished by the type of line from the portion of curve F4 that shows the temporal change in the first duty ratio due to linear change control. Meanwhile, curve F5 in timing chart CH4 shows an example of the temporal change in the second duty ratio. Therefore, the vertical axis of timing chart CH4 also indicates the duty ratio. Furthermore, in timing chart CH4, the portion of curve F5 that shows the temporal change in the second duty ratio due to feedback control is distinguished by the type of line from the portion of curve F5 that shows the temporal change in the second duty ratio due to linear change control. In Fig. 2, the hierarchical relationship among duty ratios DH1 to DH3 is duty ratio DH2 > duty ratio DH3 > duty ratio DH1. Also, in Fig. 2, the hierarchical relationship among duty ratios DH4 to DH8 is duty ratio DH7 > duty ratio DH5 > duty ratio DH6 > duty ratio DH4 > duty ratio DH8.

[0042] During the period from timing TA to timing TB, the control device 20 controls the switching power supply circuit 10 in step-down mode because the input voltage value is higher than the upper limit voltage value z1. Therefore, during this period, the first duty ratio is changed by feedback control. More specifically, during the period from timing TA to timing T1, the first duty ratio is maintained at duty ratio DH1 by feedback control. Then, during the period from timing T1 to timing TB, the first duty ratio increases from duty ratio DH1 to duty ratio DH2 by feedback control. Meanwhile, during the period from timing TA to timing TB, the second duty ratio is maintained at 0% by linear change control. Here, in the embodiment, this change in the second duty ratio is treated as a linear change when the predetermined rate of change is 0.

[0043] During the period from timing TB to timing TC, the control device 20 controls the switching power supply circuit 10 in the buck-boost mode because the input voltage value is equal to or lower than the upper limit voltage value z1 and equal to or higher than the lower limit voltage value z2. Therefore, during this period, the first duty ratio changes through linear change control. More specifically, during the period from timing TB to timing T2, the first duty ratio decreases from duty ratio DH2 to duty ratio DH3 through linear change control. Here, duty ratio DH3 is the lower limit of the first duty ratio under linear change control. Therefore, during the period from timing T2 to timing TC, the first duty ratio is maintained at duty ratio DH3 through linear change control. Meanwhile, during the period from timing TB to timing TC, the second duty ratio changes through feedback control. More specifically, during the period from timing TB to timing T2, the second duty ratio increases from 0% to duty ratio DH4. Then, during the period from timing T2 to timing TC, the second duty ratio increases from duty ratio DH4 to duty ratio DH5.

[0044] During the period from timing TC to timing TD, the control device 20 controls the switching power supply circuit 10 in boost mode because the input voltage value is lower than the lower limit voltage value z2. Therefore, during this period, the first duty ratio changes through linear change control. More specifically, during the period from timing TC to timing T3, the first duty ratio increases from duty ratio DH3 to 100% through linear change control. Here, 100% is the upper limit value of the first duty ratio under linear change control. Therefore, during the period from timing T3 to timing TD, the first duty ratio is maintained at 100% through linear change control. Meanwhile, during the period from timing TC to timing TD, the second duty ratio changes through feedback control. More specifically, during the period from timing TC to timing T3, the second duty ratio decreases from duty ratio DH5 to duty ratio DH6. During the period from timing T3 to timing T4, the second duty ratio increases from duty ratio DH6 to duty ratio DH7. During the period from timing T4 to timing T5, the second duty ratio is maintained at duty ratio DH7. Then, during the period from timing T5 to timing TD, the second duty ratio decreases from duty ratio DH7 to duty ratio DH8.

[0045] During the period from timing TD to timing TE, the control device 20 controls the switching power supply circuit 10 in the buck-boost mode because the input voltage value is equal to or lower than the upper limit voltage value z1 and equal to or higher than the lower limit voltage value z2. Therefore, during this period, the first duty ratio is changed by linear change control. More specifically, during the period from timing TD to timing T6, the first duty ratio is decreased from 100% to duty ratio DH3 by linear change control. As described above, duty ratio DH3 is the lower limit of the first duty ratio under linear change control. Therefore, during the period from timing T6 to timing TE, the first duty ratio is maintained at duty ratio DH3 by linear change control. Meanwhile, during the period from timing TD to timing TE, the second duty ratio is changed by feedback control. More specifically, during the period from timing TD to timing T6, the second duty ratio is increased from duty ratio DH8 to duty ratio DH6. Then, during the period from timing T6 to timing TE, the second duty ratio drops from duty ratio DH6 to 0%.

[0046] During the period after timing TE, the control device 20 controls the switching power supply circuit 10 in step-down mode because the input voltage value is higher than the upper limit voltage value z1. Therefore, during this period, the first duty ratio is changed by feedback control. More specifically, during the period from timing TE to timing T7, the first duty ratio is reduced from duty ratio DH3 to duty ratio DH1 by feedback control. Then, during the period after timing T7, the first duty ratio is maintained at duty ratio DH1 by feedback control. Meanwhile, during the period after timing TE, the second duty ratio is maintained at 0% by linear change control.

[0047] As described above, the control device 20 changes the first duty ratio and the second duty ratio while switching the operating mode in response to changes in the input voltage value. In the example shown in FIG. 2 , the operating mode is switched at timings TB, TC, TD, and TE. The control device 20 continuously changes the first duty ratio and the second duty ratio at timings TB, TC, TD, and TE. Specifically, when switching the operating mode at timings TB, TC, TD, and TE, the control device 20 sets the first duty ratio before the operating mode switch as a first starting point and linearly changes the first duty ratio after the operating mode switch from the first starting point. The control device 20 also sets the second duty ratio before the operating mode switch as a second starting point and linearly changes the second duty ratio after the operating mode switch from the second starting point. For example, at timing TB, the first duty ratio before the operating mode switch is duty ratio DH2. Therefore, the control device 20 specifies the duty ratio DH2 as the first start point at timing TB, and linearly changes the first duty ratio after the operation mode is switched from the specified first start point, duty ratio DH2, to duty ratio DH3. For example, at timing TB, the second duty ratio before the operation mode is switched is 0%. Therefore, the control device 20 specifies 0% as the second start point at timing TB, and linearly changes the second duty ratio after the operation mode is switched from the specified second start point, 0%, to duty ratio DH4. This situation is similar for each of timings TC to TE. Therefore, the function that draws the curve F4 indicating the temporal change in the first duty ratio and the function that draws the curve F5 indicating the temporal change in the second duty ratio are both continuous functions. In other words, the first duty ratio and the second duty ratio do not change discontinuously when the operation mode is switched. This allows the control device 20 to suppress the occurrence of ripples in the input voltage when the operation mode is switched, as shown by the curve F2 in FIG.

[0048] FIG. 3 is a diagram illustrating the temporal change in the input voltage value when the duty ratio is changed nonlinearly when switching between operation modes. Similar to FIG. 2, FIG. 3 shows four timing charts, timing chart CH1 to timing chart CH4. The temporal change in the target value in timing chart CH1 shown in FIG. 3 is the same as the temporal change in the target value in timing chart CH1 shown in FIG. 2. Similarly to the example shown in FIG. 2, the timings at which the control device 20 switches between operation modes are timings TB to TE. However, in the example shown in FIG. 3, the second duty ratio changes nonlinearly at timings TB and TE. In other words, in this example, the second duty ratio changes discontinuously at timings TB and TE. In this example, the first duty ratio changes nonlinearly at timings TC and TD. In other words, in this example, the first duty ratio changes discontinuously at timings TC and TD. As a result, in the example shown in Figure 3, ripples occur at timings TB, TC, TD, and TE on curve F2, which shows the change in input voltage over time. This places a load on the circuit elements of switching power supply circuit 10, which is undesirable.

[0049] Output fluctuation suppression is a known method for suppressing ripples in the curve showing temporal changes in the input voltage value. However, it is known that output fluctuation suppression cannot suppress ripples in the curve showing temporal changes in the input voltage value that occur when switching operating modes due to fluctuations in the output voltage value. It is also known that output fluctuation suppression is not suitable for maximum power tracking control of solar panels when the DC power source P is a solar panel, as in this example. Furthermore, when the output fluctuation suppression method is adopted, the switching power supply device 1 must switch the polarity of the difference calculator used for error calculation, which complicates the structure, control, etc., and may hinder practical application of the power supply device for solar panels.

[0050] Therefore, as described above, in the switching power supply device 1, when switching the operating mode, the control device 20 sets the first duty ratio before the switching of the operating mode as a first starting point and linearly changes the first duty ratio after the switching of the operating mode from the first starting point. Also, the control device 20 sets the second duty ratio before the switching of the operating mode as a second starting point and linearly changes the second duty ratio after the switching of the operating mode from the second starting point. This allows the control device 20 to suppress ripples in the input voltage when switching the operating mode. In this example, a solar panel is connected to the switching power supply circuit 10 as the DC power source P. That is, the control method of the first duty ratio and the second duty ratio by the control device 20 described in the embodiment is also suitable for maximum power tracking control of the solar panel. As a result, this control method does not hinder practical application to power supplies for solar panels. Therefore, this control method can provide a switching power supply device with greater versatility than an output fluctuation suppression method.

[0051] In the embodiment, the nonlinear change of the first duty ratio when switching the operation mode means that the first duty ratio changes suddenly before and after the operation mode switching to an extent that the first duty ratio after the operation mode switching can be considered to have started to change from a first starting point that does not match the first duty ratio before the operation mode switching. In the embodiment, the nonlinear change of the second duty ratio when switching the operation mode means that the second duty ratio changes suddenly before and after the operation mode switching to an extent that the second duty ratio after the operation mode switching can be considered to have started to change from a second starting point that does not match the second duty ratio before the operation mode switching. In the embodiment, the first duty ratio before switching the operation mode refers to the first duty ratio at the timing when the control device 20 determines that the operation mode has been switched. In the embodiment, the second duty ratio before switching the operation mode refers to the second duty ratio at the timing when the control device 20 determines that the operation mode has been switched.

[0052] <Control device configuration> The configuration of the control device 20 will be described below with reference to Fig. 4. Fig. 4 is a diagram showing an example of the configuration of the control device 20.

[0053] The control device 20 includes an operation mode determination unit 21, a feedback control unit 22, a linear change control unit 23, a carrier signal generation unit 24, a first comparison unit 25, a second comparison unit 26, a signal switching unit 27, and a memory unit 28. Some or all of the operation mode determination unit 21, the feedback control unit 22, the linear change control unit 23, the carrier signal generation unit 24, the first comparison unit 25, the second comparison unit 26, and the signal switching unit 27 may be software function units executed by various processors, or may be hardware function units configured by various circuits, ASICs (Application Specific Integrated Circuits), etc.

[0054] The operation mode determination unit 21 determines whether the operation mode is a step-up mode, a step-down mode, or a step-down mode. The operation mode determination unit 21 may have any configuration capable of determining whether the operation mode is a step-up mode, a step-down mode, or a step-down mode. For convenience of explanation, determining whether the operation mode is a step-up mode, a step-down mode, or a step-down mode will be referred to as determining the operation mode below. In the example shown in FIG. 4 , the operation mode determination unit 21 determines the operation mode based on the input voltage value and the output voltage value. The operation mode determination unit 21 outputs information indicating the determination result, i.e., operation mode information indicating the determined operation mode, to the feedback control unit 22, the linear change control unit 23, and the signal switching unit 27. The operation mode determination unit 21 also reads out operation mode information previously stored in the storage unit 28 and outputs the read out operation mode information to the feedback control unit 22 and the linear change control unit 23 as previous operation mode information indicating the operation mode previously determined by the operation mode determination unit 21. Then, the operation mode determination unit 21 replaces the operation mode information stored in the storage unit 28 with operation mode information indicating the currently determined operation mode. Note that, when the operation mode determination unit 21 operates for the first time, operation mode information indicating a predetermined operation mode is stored in the storage unit 28. The operation mode determination unit 21 may be configured to determine the operation mode using another method. The operation mode determination unit 21 may be configured to output the operation mode information to the feedback control unit 22, the linear change control unit 23, and the signal switching unit 27 using another method. The operation mode determination unit 21 may be configured to output the previous operation mode information to the feedback control unit 22 and the linear change control unit 23 using another method. For this reason, the operation mode determination unit 21 may be configured not to store the operation mode information in the storage unit 28. Details of the processing performed by the operation mode determination unit 21 will be described later.

[0055] The feedback control unit 22 determines whether the operation mode has been switched based on the operation mode information and previous operation mode information acquired from the operation mode determination unit 21. Then, the feedback control unit 22 outputs a first signal to be compared with a carrier signal to generate a PWM signal through feedback control according to the determination result of whether the operation mode has been switched. More specifically, the feedback control unit 22 outputs a first signal to be compared with a carrier signal to generate a PWM signal in the feedback control for changing the first duty ratio and the feedback control for changing the second duty ratio. The feedback control unit 22 also outputs the first signal through feedback control based on the input voltage value detected by the control device 20, a target value, and a second signal (described later). Here, the voltage value indicated by the first signal is a value corresponding to the difference between the input voltage value and the target value. Therefore, for convenience of explanation, the voltage value indicated by the first signal will be referred to as a first comparison value hereinafter. In other words, the first signal is a signal indicating the voltage of the first comparison value. The input of the input voltage value to the feedback control unit 22 may be performed by inputting information indicating the input voltage value, by inputting a signal indicating the voltage of the input voltage value, or by other methods. The input of the target value to the feedback control unit 22 may be performed by inputting information indicating the target value, by inputting a reference voltage for the voltage value, or by other methods. For convenience of explanation, the carrier signal generated by the carrier signal generation unit 24 will be simply referred to as the carrier signal below. The feedback control unit 22 outputs a first signal to a first comparison unit 25 (described later) and also outputs the first signal to the linear change control unit 23. Details of the processing performed by the feedback control unit 22 will be described later.

[0056] The linear change control unit 23 determines whether the operation mode has been switched based on the operation mode information and previous operation mode information acquired from the operation mode determination unit 21. Then, the linear change control unit 23 outputs a second signal to be compared with the carrier signal to generate a PWM signal by linear change control according to the determination result of whether the operation mode has been switched. More specifically, the linear change control unit 23 outputs the second signal to be compared with the carrier signal to generate a PWM signal in the linear change control that changes the first duty ratio and the linear change control that changes the second duty ratio. The linear change control unit 23 also includes a range determination unit 231 and a counter unit 232. Hereinafter, for convenience of explanation, the voltage value indicated by the second signal will be referred to as a second comparison value. In other words, the second signal is a signal indicating the voltage of the second comparison value.

[0057] The range determination unit 231 determines the range within which the second comparison value of the voltage indicated by the second signal is changed each time the operation mode is switched, based on the operation mode currently determined by the operation mode determination unit 21, the operation mode previously determined by the operation mode determination unit 21, the voltage value of the voltage indicated by the first signal output by the feedback control unit 22, and the second signal previously output. Therefore, the range determination unit 231 does not perform any operation unless the operation mode is switched. However, only during the initial operation, the range determination unit 231 determines the range within which the second signal is changed, based on the operation mode currently determined by the operation mode determination unit 21, the operation mode previously determined by the operation mode determination unit 21, the first signal output by the feedback control unit 22, and the second signal indicating the voltage of the second comparison value when the second comparison value is a predetermined initial value. The initial value may be any value as long as it does not impair the function of the control device 20 described in the embodiment. For ease of explanation, the range determined by the range determination unit 231 will be referred to simply as the target range in the following description. In this example, the range determination unit 231 identifies the operation mode currently determined by the operation mode determination unit 21 based on operation mode information acquired from the operation mode determination unit 21, but may be configured to identify the operation mode using other methods. In this example, the range determination unit 231 identifies the operation mode previously determined by the operation mode determination unit 21 based on previous operation mode information acquired from the operation mode determination unit 21, but may be configured to identify the operation mode using other methods. Every time the range determination unit 231 determines a target range, it outputs information indicating the determined target range to the counter unit 232. Details of the processing performed by the range determination unit 231 will be described later.

[0058] Counter unit 232 changes the second comparison value of the voltage indicated by the second signal at a predetermined rate of change from the start point to the end point of the target range determined by range determination unit 231, and outputs a second signal each time the second comparison value is changed. For example, if the range is 2 volts to 5 volts, the start point is 2 volts, the end point is 5 volts, and the predetermined rate of change is 0.1 volts, counter unit 232 outputs the second signals in the following order: a second signal indicating a voltage of 2 volts, a second signal indicating a voltage of 2.1 volts, a second signal indicating a voltage of 2.2 volts, ..., a second signal indicating a voltage of 4.9 volts, and a second signal indicating a voltage of 5 volts. For example, if the range is 2 volts to 5 volts, the starting point is 5 volts, the ending point is 2 volts, and the predetermined rate of change is 0.1 volts, the counter unit 232 outputs second signals in the following order: a second signal indicating a voltage of 5 volts, a second signal indicating a voltage of 4.9 volts, a second signal indicating a voltage of 4.8 volts, ..., a second signal indicating a voltage of 2.1 volts, and a second signal indicating a voltage of 2 volts. Note that the second comparison values of the voltages of these second signals are shown as examples for ease of understanding and are different from the second comparison values actually used. The counter unit 232 outputs the second signal to the second comparison unit 26 (described later), and also outputs the second signal to each of the range determination unit 231 and the feedback control unit 22. Details of the processing performed by the counter unit 232 will be described later.

[0059] The carrier signal generating unit 24 generates a carrier signal of a predetermined frequency. The method for generating the carrier signal by the carrier signal generating unit 24 may be a known method or a method to be developed in the future. The frequency may be any frequency that can generate a PWM signal. Details of the processing performed by the carrier signal generating unit 24 will be described later.

[0060] The first comparing unit 25 generates a PWM signal corresponding to the comparison between the first signal and the carrier signal as the tenth PWM signal. The method for generating the PWM signal by the first comparing unit 25 may be a known method or a method to be developed in the future. Details of the processing performed by the first comparing unit 25 will be described later.

[0061] The second comparing unit 26 generates a PWM signal corresponding to the comparison between the second signal and the carrier signal as a 20th PWM signal. The method for generating the PWM signal by the second comparing unit 26 may be a known method or a method to be developed in the future. Details of the processing performed by the second comparing unit 26 will be described later.

[0062] Based on the operation mode information acquired from the operation mode determination unit 21, the signal switching unit 27 determines whether the operation mode currently determined by the operation mode determination unit 21 is the buck mode, the buck-boost mode, or the boost mode. If the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the buck mode, it inputs the tenth PWM signal generated by the first comparing unit 25 to the first switching element S1 as the first PWM signal, and inputs the twentieth PWM signal generated by the second comparing unit 26 to the second switching element S1 as the second PWM signal. If the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the buck-boost mode or the boost mode, it inputs the 20th PWM signal generated by the second comparing unit 26 to the first switching element S1 as the first PWM signal, and inputs the tenth PWM signal generated by the first comparing unit 25 to the first switching element S1 as the first PWM signal. That is, signal switching unit 27 switches the output destination of each of the two PWM signals according to the operation mode currently determined by operation mode determination unit 21. Note that signal switching unit 27 may be configured to identify the operation mode currently determined by operation mode determination unit 21 based on operation mode information stored in storage unit 28, or may be configured to identify the operation mode by another method.

[0063] The storage unit 28 stores various types of information used in the control device 20. For example, the storage unit 28 stores operation mode information indicating the operation mode determined by the operation mode determination unit 21 this time.

[0064] With the above configuration, when switching the operation mode for operating the switching power supply circuit 10, the control device 20 linearly changes the first duty ratio after the operation mode is switched from the first start point, and linearly changes the second duty ratio after the operation mode is switched from the second start point. This allows the control device 20 to suppress the occurrence of ripples in the input voltage when switching the operation mode.

[0065] <Processing performed by the operation mode determination unit> The processing performed by the operation mode determination unit 21 will be described below with reference to Fig. 5. Fig. 5 is a diagram showing an example of the flow of processing performed by the operation mode determination unit 21.

[0066] The operation mode determination unit 21 calculates the difference between the input voltage value detected by the input voltage detection unit and the output voltage value detected by the output voltage detection unit as the voltage difference (step S110).

[0067] Next, the operation mode determination unit 21 determines whether or not the voltage difference calculated in step S110 is lower than the lower limit voltage value z2 (step S120). In Fig. 5, the process of step S120 is indicated by "lower than lower limit voltage?"

[0068] If it is determined that the voltage difference calculated in step S110 is lower than the lower limit voltage value z2 (step S120-YES), the operation mode determination unit 21 determines that the operation mode is the voltage step-up mode (step S130). In Fig. 5, the process of step S130 is indicated by "operation mode is voltage step-up mode."

[0069] After the process of step S130 is performed, the operation mode determination unit 21 outputs operation mode information indicating the currently identified operation mode to each of the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27 (step S140). In Fig. 5, the process of step S140 is indicated by "output of operation mode information."

[0070] Next, operation mode determination unit 21 reads out the operation mode information stored in storage unit 28 as previous operation mode information indicating the operation mode determined last time, and outputs the read previous operation mode information to feedback control unit 22 and range determination unit 231 (step S150). In Fig. 5, the process of step S150 is indicated by "output previous operation mode information."

[0071] Next, the operation mode determination unit 21 stores operation mode information indicating the currently specified operation mode in the storage unit 28 (step S160). Then, the operation mode determination unit 21 ends the processing of the flowchart shown in Fig. 5. In Fig. 5, the processing of step S160 is indicated by "storing operation mode information."

[0072] On the other hand, if it is determined that the voltage difference calculated in step S110 is equal to or greater than the lower limit voltage value z2 (step S120-NO), the operation mode determination unit 21 determines whether the voltage difference calculated in step S110 is higher than the upper limit voltage value z1 (step S170). In Fig. 5, the process of step S170 is indicated by "Higher than upper limit voltage?"

[0073] If it is determined that the voltage difference calculated in step S110 is higher than the upper limit voltage value z1 (step S170-YES), the operation mode determination unit 21 determines that the operation mode is the step-down mode (step S180). In Fig. 5, the process of step S180 is indicated by "operation mode is step-down mode".

[0074] After processing of step S180 is performed, the operation mode determination unit 21 transitions to step S140 and outputs operation mode information indicating the operation mode identified this time to each of the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27.

[0075] On the other hand, if the operation mode determination unit 21 determines that the voltage difference calculated in step S110 is equal to or less than the upper limit voltage value z1 (step S170-NO), it determines that the operation mode is the voltage step-up / step-down mode (step S190). In Fig. 5, the process of step S190 is indicated by "operation mode is voltage step-up / step-down mode".

[0076] After processing of step S190 is performed, the operation mode determination unit 21 transitions to step S140 and outputs operation mode information indicating the operation mode identified this time to each of the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27.

[0077] The operation mode determination unit 21 may be configured not to output operation mode information to some or all of the feedback control unit 22, the range determination unit 231, and the signal switching unit 27. In this case, some or all of the feedback control unit 22, the range determination unit 231, and the signal switching unit 27 identify the operation mode currently determined by the operation mode determination unit 21 by reading the operation mode information stored in the storage unit 28 from the storage unit 28. The operation mode determination unit 21 may also be configured not to output previous operation mode information to either or both of the feedback control unit 22 and the range determination unit 231. In this case, either or both of the feedback control unit 22 and the range determination unit 231 identify the operation mode previously determined by the operation mode determination unit 21 by reading the operation mode information stored in the storage unit 28 from the storage unit 28. That is, in this case, the operation mode determination unit 21 stores both the operation mode information and the previous operation mode information in the storage unit 28.

[0078] As described above, the operation mode determination unit 21 determines whether the operation mode is the step-up mode, the step-up / step-down mode, or the step-down mode.

[0079] <Feedback control function> The function of the feedback control unit 22 will be described below with reference to Fig. 6. Fig. 6 is a diagram showing an example of a block diagram illustrating the feedback control performed by the feedback control unit 22.

[0080] The feedback control unit 22 receives the input voltage value, the target value, the operation mode information, the previous operation mode information, and the second signal output from the counter unit 232. The control target of the feedback control unit 22 is the first comparison value of the voltage indicated by the first signal.

[0081] The feedback control unit 22 calculates the difference between the input voltage value detected by the input voltage detection unit and the target value as an error in feedback control. Then, the feedback control unit 22 calculates the first comparison value by adding together a P control output value output by P (proportional) control based on the calculated error and an I control output value output by I (integral) control based on the calculated error. The feedback control unit 22 outputs a first signal indicating the voltage of the calculated first comparison value. Here, the P control performed by the feedback control unit 22 is a known control using a P gain, so a description thereof will be omitted. Furthermore, the I control performed by the feedback control unit 22 is performed by the processing of the flowchart shown in FIG. 7. When performing I control, the feedback control unit 22 uses the input operation mode information and the input previous operation mode information.

[0082] <Processing by which the feedback control section performs I control> Hereinafter, a process in which the feedback control unit 22 performs I control will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example of the flow of a process in which the feedback control unit 22 performs I control.

[0083] The feedback control unit 22 determines whether the operation mode has been switched based on the input operation mode information and the input previous operation mode information (step S210). Specifically, if the operation mode indicated by the operation mode information matches the operation mode indicated by the previous operation mode, the feedback control unit 22 determines that the operation mode has not been switched. On the other hand, if the operation mode indicated by the operation mode information does not match the operation mode indicated by the previous operation mode, the feedback control unit 22 determines that the operation mode has been switched. In FIG. 7, the processing of step S210 is indicated by "Has the operation mode been switched?"

[0084] When it is determined that the operation mode has not been switched (step S210-NO), the feedback control unit 22 outputs a value obtained by adding the previous I control output value to a value obtained by multiplying the error calculated in the previous stage of I control by the I gain as the current I control output value (step S250). Note that, during the initial operation, the feedback control unit 22 uses a value that is predetermined as the initial value of the I control output value as the previous I control output value. Also, in FIG. 7, the error is represented by err, the I gain is represented by Igain, the previous I control output value is represented by Pre_Gierr, the I control output value to be output is represented by Gierr, and the second comparison value of the voltage indicated by the second signal is represented by cmpv2. Also, in FIG. 7, the processing of step S250 is represented by "Gierr = err * Igain + Pre_Gierr".

[0085] Next, the feedback control unit 22 specifies the I control output value output in step S250 as the previous I control output value (step S260). Note that in Fig. 7, the processing of step S260 is indicated by "Pre_Gierr = Gierr". After the processing of step S260 is performed, the feedback control unit 22 ends the processing of the flowchart shown in Fig. 7.

[0086] On the other hand, if it is determined that the operation mode has been switched (step S210-YES), the feedback control unit 22 determines whether the operation mode after the switch is the step-down mode, the step-up / step-down mode, or the step-up mode based on the input operation mode information (step S220). In Fig. 7, the processing of step S220 is indicated by "What is the operation mode?"

[0087] When the feedback control unit 22 determines that the operation mode after switching is the step-down mode (step S220-step-down mode), it specifies the second comparison value of the voltage indicated by the input second signal as the previous I control output value (step S270). In FIG. 7, the process of step S270 is indicated by "Pre_Gierr=cmpv2". The process of step S270 is performed to continuously change each of the first duty ratio and the second duty ratio when the operation mode is switched to the step-down mode. The reason for this will be described later.

[0088] Next, the feedback control unit 22 transitions to step S250 and outputs the I control output value obtained by adding the value obtained by multiplying the error calculated in the previous stage of I control by the I gain and the previous I control output value identified in step S270.

[0089] On the other hand, when the feedback control unit 22 determines that the operation mode after switching is the buck-boost mode (step S220-buck-boost mode), it determines whether the operation mode before switching was the buck mode based on the previous operation mode information (step S230). In Fig. 7, the processing of step S230 is indicated by "Previous operation mode is buck mode?"

[0090] When it is determined that the operating mode before the change was the buck mode (step S230-YES), the feedback control unit 22 specifies the second comparison value of the voltage indicated by the input second signal as the previous I control output value (step S240). In FIG. 7, the process of step S240 is indicated by "Pre_Gierr=cmpv2". The process of step S240 is performed to continuously change each of the first duty ratio and the second duty ratio when the operating mode is changed from the buck mode to the buck-boost mode. The reason for this will be described later.

[0091] Next, the feedback control unit 22 transitions to step S250 and outputs the I control output value obtained by adding the value obtained by multiplying the error calculated in the previous stage of I control by the I gain and the previous I control output value identified in step S270.

[0092] On the other hand, if the feedback control unit 22 determines that the operating mode before switching was not the step-down mode (step S230-NO), it transitions to step S250 and outputs the I control output value obtained by adding the value obtained by multiplying the error calculated in the previous stage of I control by the I gain and the previous I control output value identified in the processing of step S260 executed last time.

[0093] As described above, the feedback control unit 22 outputs the I control output value through I control. In this example, the feedback control unit 22 can calculate a first comparison value through feedback control and output a first signal indicating the voltage of the calculated first comparison value.

[0094] <Processing performed by the range determination unit> The processing performed by range determination section 231 will be described below with reference to Fig. 8. Fig. 8 is a diagram showing an example of the flow of processing performed by range determination section 231.

[0095] The range determination unit 231 determines whether the operation mode has been switched based on the input operation mode information and the input previous operation mode information (step S210). Specifically, if the operation mode indicated by the operation mode information matches the operation mode indicated by the previous operation mode, the range determination unit 231 determines that the operation mode has not been switched. On the other hand, if the operation mode indicated by the operation mode information does not match the operation mode indicated by the previous operation mode, the range determination unit 231 determines that the operation mode has been switched. Note that in FIG. 8, the processing of step S310 is indicated by "Has the operation mode been switched?"

[0096] When it is determined that the operation mode has not been switched (step S310-NO), the range determination unit 231 does nothing and ends the processing of the flowchart shown in FIG.

[0097] On the other hand, if it is determined that the operation mode has been switched (step S310-YES), the range determination unit 231 determines whether the operation mode after the switch is the step-down mode, the step-up / step-down mode, or the step-up mode based on the input operation mode information (step S320). In Fig. 8, the processing of step S320 is indicated by "What is the operation mode?"

[0098] When the range determination unit 231 determines that the operating mode after switching is the step-down mode (step S320—step-down mode), it identifies the first comparison value of the voltage indicated by the input first signal as the start point of the target range (step S360). Here, in FIG. 8, the first comparison value is indicated by cmpv1, and the start point of the target range is indicated by start_val. Therefore, in FIG. 8, the processing of step S360 is indicated by "start_val=cmpv1." The processing of step S360 is performed to continuously change each of the first duty ratio and the second duty ratio when the operating mode is switched to the step-down mode. The reason for this will be described later.

[0099] Next, range determination unit 231 specifies 0.0 as the end point of the target range (step S370). Here, 0.0 is a value predetermined as the end point of the target range when the operating mode is the step-down mode. Also, in FIG. 8, the end point of the target range is indicated by end_val. Therefore, in FIG. 8, the processing of step S370 is indicated by "end_val=0.0". After the processing of step S370 is performed, range determination unit 231 outputs information indicating the start point and end point of the target range to counter unit 232, and ends the processing of the flowchart shown in FIG. 8.

[0100] On the other hand, if the range determination unit 231 determines that the operation mode after switching is the buck-boost mode (step S320-buck-boost mode), it determines whether the operation mode before switching was the buck mode based on the previous operation mode information (step S330). In Fig. 8, the processing of step S330 is indicated by "Is the previous operation mode the buck mode?"

[0101] When it is determined that the operating mode before the switch was the buck mode (step S330-YES), the range determination unit 231 identifies the first comparison value of the voltage indicated by the input first signal as the start point of the target range (step S340). Here, in FIG. 8, the processing of step S340 is indicated by "start_val=cmpv1". The processing of step S340 is performed to continuously change each of the first duty ratio and the second duty ratio when the operating mode is switched from the buck mode to the buck-boost mode. The reason for this will be described later.

[0102] Next, range determination unit 231 specifies 0.7 as the end point of the target range (step S350). Here, 0.7 is a value predetermined as the end point of the target range when the operating mode is the step-up / step-down mode. Also, in FIG. 8, the processing of step S350 is indicated by "end_val=0.7". After the processing of step S350 is performed, range determination unit 231 outputs information indicating the start point and end point of the target range to counter unit 232, and ends the processing of the flowchart shown in FIG. 8.

[0103] On the other hand, if range determination unit 231 determines that the operating mode before the switch was not the step-down mode (step S330-NO), it identifies the second comparison value of the voltage indicated by the input second signal as the start point of the target range (step S380). Here, in FIG. 8, the second comparison value is indicated by cmpv2. Therefore, in FIG. 8, the processing of step S380 is indicated by "start_val=cmpv2".

[0104] Next, range determination unit 231 proceeds to step S350 and specifies 0.7 as the end point of the target range. After the processing of step S350 is performed, range determination unit 231 outputs information indicating each of the start point and end point of the target range to counter unit 232, and ends the processing of the flowchart shown in FIG.

[0105] On the other hand, if the range determination unit 231 determines that the operation mode after the change is the boost mode (step S320—boost mode), it specifies the second comparison value of the voltage indicated by the input second signal as the start point of the target range (step S390). Here, in FIG. 8, the processing of step S390 is indicated by “start_val=cmpv2.”

[0106] Next, range determination unit 231 specifies 1.0 as the end point of the target range (step S400). Here, 1.0 is a value predetermined as the end point of the target range when the operating mode is the boost mode. Also, in FIG. 8, the processing of step S400 is indicated by "end_val=1.0". After the processing of step S400 is performed, range determination unit 231 outputs information indicating the start point and end point of the target range to counter unit 232, and ends the processing of the flowchart shown in FIG. 8.

[0107] As described above, the range determination unit 231 identifies the start and end points of the target range each time the operating mode is switched and outputs information indicating the identified start and end points of the target range to the counter unit 232. Because the start and end points of the target range are identified in this manner, when switching the operating mode, the control device 20 can set the first duty ratio before the operating mode switch as the first start point from which the first duty ratio after the operating mode switch begins to change, and linearly change the first duty ratio from the first start point, and set the second duty ratio before the operating mode switch as the second start point from which the second duty ratio after the operating mode switch begins to change, and linearly change the second duty ratio from the second start point. The reason for this can be understood by understanding the processing performed by the counter unit 232 (described later) and the processing performed by the signal switching unit 27 (described later). Note that, for ease of explanation, the information output by the range determination unit 231 to the counter unit 232 will be referred to as target range information hereinafter. That is, the target range information is information that indicates both the start point and the end point of the target range.

[0108] <Processing performed by the counter> The processing performed by counter unit 232 will be described below with reference to Fig. 9. Fig. 9 is a diagram showing an example of the flow of processing performed by counter unit 232. For ease of explanation, the following description will refer to the end point of the start point and end point indicated by the target range information currently acquired from range determination unit 231 as the current end point.

[0109] The counter unit 232 specifies, as the second comparison value specified this time, the start point among the start point and the end point indicated by the target range information acquired this time from the range determination unit 231 (step S410). Here, in FIG. 9, the start point among the start point and the end point indicated by the target range information acquired this time from the range determination unit 231 is indicated by start_val, and the second comparison value is indicated by cmpv2. Therefore, in FIG. 9, the process of step S410 is indicated by "cmpv2 = start_val".

[0110] Next, the counter unit 232 determines whether or not the second comparison value specified in step S410 matches the end point this time (step S420). Here, in FIG. 9, the end point this time is indicated by "end_val". Therefore, in FIG. 9, the process of step S420 is indicated by "cmpv2 = end_val?". In the determination of step S420, whether or not the second comparison value matches the end point this time may allow a slight difference determined in advance, or may not allow the difference. That is, in the determination of step S420, the counter unit 232 determines that the second comparison value matches the end point this time when the difference between the second comparison value and the end point this time is less than or equal to the difference, and determines that the second comparison value does not match the end point this time when the difference between the second comparison value and the end point this time exceeds the difference.

[0111] When the counter unit 232 determines that the second comparison value specified in step S410 matches the end point this time (step S420 - YES), the process of the flowchart shown in FIG. 9 ends.

[0112] On the other hand, when the counter unit 232 determines that the second comparison value specified in step S410 does not match the end point this time (step S420 - NO), it determines whether or not the second comparison value is smaller than the end point this time (step S430). In FIG. 9, the process of step S430 is indicated by "cmpv2 < end_val?".

[0113] If the counter unit 232 determines in step S410 that the second comparison value is smaller than the current end point (YES in step S430), it increases the second comparison value by a predetermined change value (step S440). Then, in step S440, the counter unit 232 outputs a second signal indicating the voltage of the second comparison value after being increased by the change value to the second comparator 26. Hereinafter, for convenience of explanation, the change value will be referred to as the "predetermined change value." Note that in FIG. 9, the process of step S440 is indicated by "count up cmpv2." The predetermined change value is, for example, 0.001, but is not limited thereto. By performing the process of step S440, the control device 20 can linearly increase the first duty ratio and the second duty ratio at a predetermined change rate in linear change control. Therefore, the predetermined change value is determined according to the predetermined change rate.

[0114] After the process of step S440 is performed, the counter unit 232 transitions to step S420, and determines whether the second comparison value after being increased by the predetermined change value in step S440 matches the current end point.

[0115] On the other hand, if counter unit 232 determines that the second comparison value identified in step S410 is equal to or greater than the current end point (step S430-NO), counter unit 232 decreases the second comparison value by a predetermined change value (step S450). Then, counter unit 232 outputs a second signal indicating the voltage of the second comparison value after being decreased by the change value to second comparator 26. Note that in FIG. 9, the processing of step S450 is indicated by "count down cmpv2." By performing such processing of step S450, control device 20 can linearly decrease the first duty ratio and the second duty ratio at a predetermined change rate under linear change control.

[0116] After the process of step S450 is performed, the counter unit 232 proceeds to step S420 and determines whether the second comparison value after being decreased by the predetermined change value in step S450 matches the current end point.

[0117] Through the above-described processing, counter unit 232 can linearly change the second comparison value from the start point toward the end point of the target range determined by range determination unit 231. As a result, control device 20 can linearly change the first duty ratio and the second duty ratio at a predetermined rate of change in linear change control.

[0118] <Operations of the Carrier Signal Generator, First Comparator, and Second Comparator> The operations of the carrier signal generating unit 24, the first comparing unit 25, and the second comparing unit 26 will be described below with reference to Fig. 10. Fig. 10 is a diagram showing an example configuration of the first comparing unit 25 and the second comparing unit 26, which output a PWM signal based on the carrier signal generated by the carrier signal generating unit 24.

[0119] 10, the first comparing section 25 and the second comparing section 26 are, for example, comparators. In order to simplify the drawing, the positive and negative power supply terminals of the comparators are omitted from FIG.

[0120] As described above, the first comparison unit 25 compares the carrier signal obtained from the carrier signal generation unit 24 with the first signal obtained from the feedback control unit 22, and outputs the tenth PWM signal to the signal switching unit 27.

[0121] On the other hand, as described above, the second comparison unit 26 outputs the 20th PWM signal to the signal switching unit 27 by comparing the carrier signal obtained from the carrier signal generation unit 24 with the second signal obtained from the counter unit 232 of the linear change control unit 23.

[0122] As described above, the control device 20 can generate the tenth PWM signal based on the first signal and the twentieth PWM signal based on the second signal. The control device 20 can then switch the output destinations of the tenth PWM signal and the twentieth PWM signal according to the operation mode using the signal switching unit 27 described below.

[0123] <Processing performed by the signal switching unit> The processing performed by the signal switching unit 27 will be described below with reference to Fig. 11. Fig. 11 is a diagram showing an example of the flow of processing performed by the signal switching unit 27.

[0124] Based on the operation mode information acquired from the operation mode determination unit 21, the signal switching unit 27 determines whether the operation mode currently determined by the operation mode determination unit 21 is the step-down mode (step S510). In Fig. 11, the processing of step S510 is indicated by "Is the operation mode the step-down mode?"

[0125] When the signal switching unit 27 determines that the current operation mode determined by the operation mode determination unit 21 is the step-down mode (step S510-YES), it outputs the tenth PWM signal acquired from the first comparison unit 25 to the first switching element S1 as the first PWM signal (step S520). In FIG. 11, the tenth PWM signal is indicated by PWM10, and the first PWM signal is indicated by PWM1. Therefore, in FIG. 11, the process of step S520 is indicated by "PWM1=PWM10."

[0126] Next, the signal switching unit 27 outputs the 20th PWM signal acquired from the second comparing unit 26 to the second switching element S2 as the second PWM signal (step S530). In FIG. 11, the 20th PWM signal is indicated by PWM20, and the second PWM signal is indicated by PWM2. Therefore, in FIG. 11, the processing of step S530 is indicated by "PWM2=PWM20." Note that in the flowchart shown in FIG. 11, the processing of step S520 and the processing of step S530 may be performed in reverse order or in parallel. After the processing of step S530 is performed, the signal switching unit 27 ends the processing of the flowchart shown in FIG. 11.

[0127] On the other hand, if the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the step-up / step-down mode or the step-up mode (step S510-NO), it outputs the 20th PWM signal acquired from the second comparison unit 26 to the first switching element S1 as the first PWM signal (step S540). In Fig. 11, the process of step S540 is indicated by "PWM1=PWM20".

[0128] Next, the signal switching unit 27 outputs the tenth PWM signal acquired from the first comparing unit 25 to the second switching element S2 as the second PWM signal (step S550). In FIG. 11, the processing of step S550 is indicated by "PWM2=PWM10." Note that in the flowchart shown in FIG. 11, the processing of step S540 and the processing of step S550 may be performed in reverse order or may be performed in parallel. After the processing of step S550 is performed, the signal switching unit 27 ends the processing of the flowchart shown in FIG. 11.

[0129] Through the above-described processing, signal switching unit 27 switches the output destination of each of the two PWM signals according to the operation mode currently determined by operation mode determination unit 21. This allows control device 20 to change one of the first duty ratio and the second duty ratio by feedback control and change the other of the first duty ratio and the second duty ratio by linear change control according to the operation mode.

[0130] In this way, control device 20 can change one of the first duty ratio and the second duty ratio by feedback control, and can change the other of the first duty ratio and the second duty ratio by linear change control. Furthermore, control device 20 can continuously change each of the first duty ratio and the second duty ratio when switching the operation mode by using feedback control by feedback control unit 22 and linear change control by linear change control unit 23. As a result, control device 20 can suppress the occurrence of ripples in the input voltage when switching the operation mode of the switching power supply circuit.

[0131] As described above, signal switching unit 27 switches the output destination of each of the two PWM signals depending on the operation mode currently determined by operation mode determination unit 21. When the PWM signal output as the first PWM signal switches from the tenth PWM signal to the twentieth PWM signal during operation mode switching, in order for the first duty ratio to change continuously, the first comparison value of the voltage indicated by the first signal after the operation mode switching must be equal to the second comparison value of the voltage indicated by the second signal before the operation mode switching. Also, when the PWM signal output as the first PWM signal switches from the twentieth PWM signal to the tenth PWM signal during operation mode switching, in order for the first duty ratio to change continuously, the second comparison value of the voltage indicated by the second signal after the operation mode switching must be equal to the first comparison value of the voltage indicated by the first signal before the operation mode switching. On the other hand, when the PWM signal output as the second PWM signal switches from the 10th PWM signal to the 20th PWM signal upon switching the operating mode, in order for the second duty ratio to change continuously, the first comparison value of the voltage indicated by the first signal after switching the operating mode must be equal to the second comparison value of the voltage indicated by the second signal before switching the operating mode. Also, when the PWM signal output as the second PWM signal switches from the 20th PWM signal to the 10th PWM signal upon switching the operating mode, in order for the second duty ratio to change continuously, the second comparison value of the voltage indicated by the second signal after switching the operating mode must be equal to the first comparison value of the voltage indicated by the first signal before switching the operating mode. The processes of steps S240 and S270 performed by the feedback control unit 22 and steps S340 and S360 performed by the linear change control unit 23 are processes for achieving these. These processes enable the first duty ratio and the second duty ratio to change continuously upon switching the operating mode. However, this means that discontinuous changes occur in the temporal changes of the first comparison value and the second comparison value (see FIG. 13). That is, the control device 20 imposes discontinuous changes on the first comparison value and the second comparison value, thereby suppressing the occurrence of ripples in the input voltage when the operation mode is switched.The processing of steps S240 and S270 performed by the feedback control unit 22 and the processing of steps S340 and S360 performed by the linear change control unit 23 correspond to the processing of identifying the first starting point and the second starting point, respectively, as described above.

[0132] Note that instead of the configuration described above, the control device 20 may be configured to continuously change the first duty ratio and the second duty ratio when switching between operations by using another configuration. For example, the control device 20 may be configured to include a processor, and the processor outputs the first duty ratio and the second duty ratio according to the operation mode, thereby continuously changing the first duty ratio and the second duty ratio when switching between operations.

[0133] As described above, when switching the operating mode, the control device 20 linearly changes the first duty ratio after switching the operating mode from the first starting point and linearly changes the second duty ratio after switching the operating mode from the second starting point. This allows the control device 20 to suppress ripples in the input voltage when switching the operating mode. As a result, the control device 20 can seamlessly switch the operating mode. Furthermore, since the control device 20 can suppress ripples in the input voltage when switching the operating mode, it can reduce fluctuations in the input voltage when switching the operating mode, and as a result, it can also suppress fluctuations in the output voltage. This is useful because it leads to improved efficiency in extracting power from the solar panel, which is the DC power source P in this example. This is because the control device 20 can suppress fluctuations in the input voltage when switching the operating mode, with respect to fluctuations in the target value due to illuminance fluctuations when the DC power source P is a solar panel (i.e., maximum power tracking). Furthermore, the control device 20 can suppress the occurrence of ripples in the input voltage when the operation mode is switched, and therefore can suppress the application of loads to the circuit elements of the switching power supply circuit 10.

[0134] <First Modification of the Embodiment> In the first modification of the embodiment, the operation mode determination unit 21 determines the operation mode based on a first signal and a second signal, instead of the configuration in which the operation mode is determined based on the input voltage value and the output voltage value.

[0135] FIG. 12 is a diagram showing a first modified example of the configuration of the control device 20. Unlike the example shown in FIG. 4, the example shown in FIG. 12 does not input the input voltage and the output voltage to the operation mode determination unit 21, but instead inputs a first signal from the feedback control unit 22 and a second signal from the counter unit 232. Therefore, the switching power supply circuit 10 and the control device 20 may be configured without the function of an output voltage detection unit. The configuration of the control device 20 shown in FIG. 12 is the same as the configuration of the control device 20 shown in FIG. 4, except for the difference in the input and output to the operation mode determination unit 21. Therefore, further detailed description of the configuration of the control device 20 shown in FIG. 12 will be omitted.

[0136] In the first modification of the embodiment, the operation mode determination unit 21 determines the operation mode based on a first signal input from the feedback control unit 22 and a second signal input from the counter unit 232. Then, the operation mode determination unit 21 outputs operation mode information indicating the currently determined operation mode to each of the feedback control unit 22, the range determination unit 231, and the signal switching unit 27. Furthermore, the operation mode determination unit 21 reads out operation mode information previously stored in the storage unit 28, and outputs the read operation mode information to each of the feedback control unit 22 and the linear change control unit 23 as previous operation mode information indicating the operation mode previously determined by the operation mode determination unit 21. Then, the operation mode determination unit 21 replaces the operation mode information stored in the storage unit 28 with operation mode information indicating the currently determined operation mode.

[0137] Here, when the input voltage value changes over time as shown in Fig. 2, the first comparison value and the second comparison value change over time as shown in Fig. 13. Fig. 13 is a diagram showing an example of the changes over time of the first comparison value and the second comparison value when the input voltage value changes over time as shown in Fig. 2.

[0138] The timing chart CH2 shown in FIG. 13 is the same as the timing chart CH2 shown in FIG. 2. That is, in the example shown in FIG. 13, the input voltage value changes over time as in the example shown in FIG. 2. Here, when the first duty ratio and the second duty ratio each change over time as shown in FIG. 2, the first comparison value changes over time as shown by the curve F6 of the timing chart CH5 shown in FIG. 13. The curve F6 plotted in the timing chart CH5 indicates the change over time of the first comparison value in this case. Also, in this case, the second comparison value changes over time as shown by the curve F7 of the timing chart CH6 shown in FIG. 13. The curve F7 plotted in the timing chart CH6 indicates the change over time of the second comparison value in this case. Note that the horizontal axes of the timing charts CH5 and CH6 are the same as the horizontal axis of the timing chart CH2. Also, the vertical axis of the timing chart CH5 indicates the first comparison value. Also, the vertical axis of the timing chart CH6 indicates the second comparison value.

[0139] Here, when the operation mode determination unit 21 determines the operation mode based on the first comparison value and the second comparison value that change over time as shown in Fig. 13, the operation mode determination unit 21 determines the operation mode using the first comparison value and the second comparison value at each of timings TB, TC, TD, and TE. That is, the operation mode determination unit 21 can determine the operation mode based on the first comparison value and the second comparison value by using seven values x1 to x4 and y1 to y3 shown in Fig. 13. Note that these seven values are, for example, x1 = 0.9, x2 = 0.5, x3 = 0.2, x4 = 0.0, y1 = 0.0, y2 = 0.7, and y3 = 1.0, but are not limited to these.

[0140] Fig. 14 is a diagram showing an example of the flow of a process in which the operation mode determination unit 21 determines the operation mode using the seven values x1 to x4 and y1 to y3 shown in Fig. 13. Note that, hereinafter, as an example, a case will be described in which information indicating each of these seven values is stored in advance in the storage unit 28.

[0141] The operation mode determination unit 21 reads out the operation mode information previously stored in the storage unit 28, and determines whether the previously determined operation mode is the step-down mode, the step-up / step-down mode, or the step-up mode based on the read operation mode information (step S610). In Fig. 14, the process of step S610 is indicated by "What was the previous operation mode?"

[0142] When the operation mode determination unit 21 determines that the previously determined operation mode is the step-down mode (step S610—step-down mode), it determines whether the first comparison value of the voltage indicated by the input first signal is greater than x1 and whether the second comparison value of the voltage indicated by the input second signal matches y1 (step S690). In FIG. 14, the first comparison value is indicated by cmpv1 and the second comparison ratio is indicated by cmpv2. Therefore, in FIG. 14, the processing of step S690 is indicated by "cmpv1>x1 & cmpv2=y1".

[0143] When the operation mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is greater than x1 and that the second comparison value of the voltage indicated by the input second signal matches y1 (step S690-YES), it determines that the operation mode is the buck-boost mode (step S700). In this way, by the processes of steps S690 and S700, the operation mode determination unit 21 can determine that the operation mode has switched from the buck mode to the buck-boost mode at timing TB. In FIG. 14, the process of step S700 is indicated by "operation mode is buck-boost mode."

[0144] After the process of step S700 is performed, the operation mode determination unit 21 outputs operation mode information indicating the currently identified operation mode to each of the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27 (step S660). In Fig. 14, the process of step S660 is indicated by "output of operation mode information."

[0145] Next, operation mode determination unit 21 reads out the operation mode information stored in storage unit 28 as previous operation mode information indicating the operation mode determined last time, and outputs the read previous operation mode information to feedback control unit 22 and range determination unit 231 (step S670). In Fig. 14, the process of step S670 is indicated by "output previous operation mode information."

[0146] Next, the operation mode determination unit 21 stores operation mode information indicating the currently specified operation mode in the storage unit 28 (step S680). Then, the operation mode determination unit 21 ends the processing of the flowchart shown in Fig. 14. In Fig. 14, the processing of step S680 is indicated by "storing operation mode information."

[0147] On the other hand, if operating mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is equal to or less than x1 and / or that the second comparison value of the voltage indicated by the input second signal does not match y1 (step S690-NO), it determines that the operating mode has not been switched, proceeds to step S660, reads out the operating mode information stored in storage unit 28 as operating mode information indicating the currently determined operating mode, and outputs the read-out operating mode information to feedback control unit 22, range determination unit 231, and signal switching unit 27. After the process of step S660 is performed, operating mode determination unit 21 proceeds to step S670, reads out the operating mode information stored in storage unit 28 as previous operating mode information indicating the previously determined operating mode, and outputs the read-out previous operating mode information to feedback control unit 22 and range determination unit 231. After the process of step S670 is performed, operation mode determination unit 21 proceeds to step S680, where it stores operation mode information indicating the currently identified operation mode in storage unit 28. Note that the process of step S680 in this case does not change the operation mode information stored in storage unit 28. Therefore, the process of step S680 in this case may be omitted. After the process of step S680 is performed, operation mode determination unit 21 ends the process of the flowchart shown in FIG. 14.

[0148] On the other hand, when the operation mode determination unit 21 determines that the previously determined operation mode is the step-up / step-down mode (step S610-step-up / step-down mode), it determines whether or not the first comparison value of the voltage indicated by the input first signal is greater than x2 and the second comparison value of the voltage indicated by the input second signal matches y2 (step S620). In Fig. 14, the process of step S620 is indicated by "cmpv1>x2 & cmpv2=y2".

[0149] When the operation mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is greater than x2 and that the second comparison value of the voltage indicated by the input second signal matches y2 (step S620-YES), it determines that the operation mode is the voltage step-up mode (step S630). In this way, by the processes of steps S620 and S630, the operation mode determination unit 21 can determine that the operation mode has switched from the voltage step-up / buck mode to the voltage step-up mode at timing TC. Note that in FIG. 14, the process of step S630 is indicated by "operation mode is voltage step-up mode."

[0150] After the process of step S630 is performed, the operation mode determination unit 21 determines whether the first comparison value of the voltage indicated by the input first signal is equal to or less than x4 and whether the second comparison value of the voltage indicated by the input second signal matches y2 (step S640). In Fig. 14, the process of step S640 is indicated by "cmpv1<=x4 & cmpv2=y2".

[0151] If the operation mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is equal to or less than x4 and that the second comparison value of the voltage indicated by the input second signal matches y2 (YES in step S640), it determines that the operation mode is the step-down mode (step S650). In FIG. 14, the process of step S630 is indicated by "operation mode is step-down mode." In this way, the operation mode determination unit 21 can determine that the operation mode has switched from the step-up / step-down mode to the step-down mode at timing TE through the processes of steps S640 and S650. Note that if the operation mode determination unit 21 determines that the operation mode is the step-up mode in steps S620 and S630, it determines in the process of step S640 that the first comparison value of the voltage indicated by the input first signal is greater than x4 and / or that the second comparison value of the voltage indicated by the input second signal does not match y2. For this reason, the operation mode determination unit 21 is configured so as not to simultaneously perform the process of step S630 and the process of step S650 in each operation.

[0152] Next, the operation mode determination unit 21 proceeds to step S660, where it outputs operation mode information indicating the operation mode currently identified in step S650 to the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27. After the process of step S660, the operation mode determination unit 21 proceeds to step S670, where it reads out the operation mode information stored in the storage unit 28 as previous operation mode information indicating the previously determined operation mode, and outputs the read previous operation mode information to the feedback control unit 22 and the range determination unit 231. After the process of step S670, the operation mode determination unit 21 proceeds to step S680, where it stores the operation mode information indicating the currently identified operation mode in the storage unit 28. Then, the operation mode determination unit 21 ends the process of the flowchart shown in FIG. 14.

[0153] On the other hand, if the operation mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is greater than x4 and / or that the second comparison value of the voltage indicated by the input second signal does not match y2 (NO in step S640), the operation mode determination unit 21 transitions to step S660 and outputs operation mode information indicating the operation mode currently identified in step S630 to each of the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27. After the process of step S660 is performed, the operation mode determination unit 21 transitions to step S670 and reads out the operation mode information stored in the storage unit 28 as previous operation mode information indicating the previously determined operation mode, and outputs the read previous operation mode information to each of the feedback control unit 22 and the range determination unit 231. After the process of step S670 is performed, the operation mode determination unit 21 transitions to step S680 and stores the operation mode information indicating the currently identified operation mode in the storage unit 28. Then, the operation mode determination unit 21 ends the processing of the flowchart shown in FIG.

[0154] On the other hand, when the operation mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is less than or equal to x2 and / or the second comparison value of the voltage indicated by the input second signal does not match y2 (step S620 - NO), it transitions to step S640 and determines whether the first comparison value of the voltage indicated by the input first signal is less than or equal to x4 and the second comparison value of the voltage indicated by the input second signal matches y2.

[0155] On the other hand, when the operation mode determination unit 21 determines that the previously determined operation mode is the boost mode (step S610 - boost mode), it determines whether the first comparison value of the voltage indicated by the input first signal is greater than x3 and the second comparison value of the voltage indicated by the input second signal matches y3 (step S710). In FIG. 14, the first comparison value is indicated by cmpv1 and the second comparison ratio is indicated by cmpv2. Therefore, in FIG. 14, the process of step S690 is indicated by "cmpv1 < x3 & cmpv2 = y3".

[0156] When the operation mode determination unit 21 determines that the first comparison value of the voltage indicated by the input first signal is greater than x3 and the second comparison value of the voltage indicated by the input second signal matches y3 (step S710 - YES), it specifies that the operation mode is the buck - boost mode (step S720). Thus, the operation mode determination unit 21 can specify that the operation mode has switched from the boost mode to the buck - boost mode at timing TD through the processes of step S710 and step S720. In FIG. 14, the process of step S720 is indicated by "the operation mode is the buck - boost mode".

[0157] After the process of step S720, the operation mode determination unit 21 transitions to step S660 and outputs operation mode information indicating the operation mode currently identified in step S720 to the feedback control unit 22, the range determination unit 231 of the linear change control unit 23, and the signal switching unit 27. After the process of step S660, the operation mode determination unit 21 transitions to step S670 and reads out the operation mode information stored in the storage unit 28 as previous operation mode information indicating the previously determined operation mode, and outputs the read previous operation mode information to the feedback control unit 22 and the range determination unit 231. After the process of step S670, the operation mode determination unit 21 transitions to step S680 and stores the operation mode information indicating the currently identified operation mode in the storage unit 28. Then, the operation mode determination unit 21 ends the process of the flowchart shown in FIG. 14.

[0158] On the other hand, if it is determined that the first comparison value of the voltage indicated by the input first signal is equal to or less than x3 and / or that the second comparison value of the voltage indicated by the input second signal does not match y3 (step S710-NO), it determines that the operation mode has not been switched, and proceeds to step S660, where it reads out the operation mode information stored in storage unit 28 as operation mode information indicating the currently determined operation mode, and outputs the read operation mode information to feedback control unit 22, range determination unit 231, and signal switching unit 27. After performing the process of step S660, operation mode determination unit 21 proceeds to step S670, where it reads out the operation mode information stored in storage unit 28 as previous operation mode information indicating the previously determined operation mode, and outputs the read previous operation mode information to feedback control unit 22 and range determination unit 231. After performing the process of step S670, operation mode determination unit 21 proceeds to step S680, where it stores the operation mode information indicating the currently determined operation mode in storage unit 28. In this case, the processing of step S680 does not change the operation mode information stored in storage unit 28. Therefore, the processing of step S680 in this case may be omitted. After the processing of step S680 is performed, operation mode determination unit 21 ends the processing of the flowchart shown in FIG.

[0159] As described above, the operating mode determination unit 21 can determine the operating mode based on the first and second signals, instead of determining the operating mode based on the input voltage value and the output voltage value. In this case, the control device 20 can cause the switching power supply circuit 10 to operate in each operating mode using the maximum or minimum duty ratio set as the first duty ratio and the second duty ratio, regardless of changes in the input voltage value and the output voltage value, respectively. This is useful because it leads to stable operation of the switching power supply circuit 10 over a wider range than when the operating mode determination unit 21 determines the operating mode based on the input voltage value and the output voltage value. However, when the operating mode determination unit 21 determines the operating mode based on the input voltage value and the output voltage value, the control device 20 can respond more quickly than when the operating mode determination unit 21 determines the operating mode based on the first and second signals.

[0160] The operation mode determination unit 21 may be configured to switch between determining the operation mode based on the input voltage value and the output voltage value and determining the operation mode based on the first signal and the second signal depending on the situation. For example, the operation mode determination unit 21 may be configured to determine the operation mode based on the input voltage value and the output voltage value during the first operation, and to determine the operation mode based on the first signal and the second signal during the second or subsequent operations. This allows the control device 20 to operate the switching power supply circuit 10 more stably.

[0161] <Modification 2 of the embodiment> FIG. 15 is a diagram illustrating a second modified example of the configuration of the control device 20. In the second modified example of the embodiment, as shown in FIG. 15, the signal switching unit 27 is provided between the feedback control unit 22 and the first comparing unit 25, and between the linear change control unit 23 and the second comparing unit 26. In other words, in the second modified example of the embodiment, the signal switching unit 27 is provided before the first comparing unit 25 and the second comparing unit 26. Therefore, in the second modified example of the embodiment, the feedback control unit 22 outputs a first signal to the signal switching unit 27. Furthermore, in the second modified example of the embodiment, the counter unit 232 outputs a second signal to the signal switching unit 27.

[0162] When the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the buck mode, it outputs the first signal acquired from the feedback control unit 22 as a tenth signal to the first comparing unit 25, and outputs the second signal acquired from the linear change control unit 23 as a twentieth signal to the second comparing unit 26. When the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the buck-boost mode or the boost mode, it outputs the first signal acquired from the feedback control unit 22 as a tenth signal to the second comparing unit 26, and outputs the second signal acquired from the linear change control unit 23 as a twentieth signal to the first comparing unit 25.

[0163] When the first comparing unit 25 receives a tenth signal from the signal switching unit 27, it generates a PWM signal corresponding to a comparison between the received tenth signal and the carrier signal as a first PWM signal and inputs the generated first PWM signal to the first switching element S1. On the other hand, when the first comparing unit 25 receives a twentieth signal from the signal switching unit 27, it generates a PWM signal corresponding to a comparison between the received twentieth signal and the carrier signal as a first PWM signal and inputs the generated first PWM signal to the first switching element S1.

[0164] When the second comparing unit 26 receives the tenth signal from the signal switching unit 27, it generates a PWM signal corresponding to a comparison between the received tenth signal and the carrier signal as a second PWM signal and inputs the generated second PWM signal to the second switching element S2. On the other hand, when the second comparing unit 26 receives the twentieth signal from the signal switching unit 27, it generates a PWM signal corresponding to a comparison between the received twentieth signal and the carrier signal as a second PWM signal and inputs the generated second PWM signal to the second switching element S2.

[0165] In the second modification of the embodiment, the configuration of the control device 20 is the same as the configuration of the control device 20 shown in Fig. 5, except for the matters described above. Therefore, further detailed description of the configuration of the control device 20 shown in Fig. 15 will be omitted.

[0166] FIG. 16 is a diagram showing a modified example of the flow of processing performed by the signal switching unit 27.

[0167] Based on the operation mode information acquired from the operation mode determination unit 21, the signal switching unit 27 determines whether the operation mode currently determined by the operation mode determination unit 21 is the step-down mode (step S810). In Fig. 16, the processing of step S810 is indicated by "Is the operation mode the step-down mode?"

[0168] When the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the step-down mode (step S810-YES), it outputs the first signal acquired from the feedback control unit 22 to the first comparing unit 25 as a tenth signal (step S820). In FIG. 16, the first signal is indicated by SIG1, and the tenth signal is indicated by SIG10. Therefore, in FIG. 16, the processing of step S820 is indicated by "SIG10=SIG1".

[0169] Next, the signal switching unit 27 outputs the second signal acquired from the counter unit 232 to the second comparing unit 26 as the 20th signal (step S830). In FIG. 16, the second signal is indicated by SIG2, and the 20th signal is indicated by SIG20. Therefore, in FIG. 16, the processing of step S830 is indicated by "SIG20=SIG2." Note that in the flowchart shown in FIG. 16, the processing of step S820 and the processing of step S830 may be performed in the reverse order or may be performed in parallel. After the processing of step S830 is performed, the signal switching unit 27 ends the processing of the flowchart shown in FIG. 16.

[0170] On the other hand, when the signal switching unit 27 determines that the operation mode currently determined by the operation mode determination unit 21 is the step-up / step-down mode or the step-up mode (step S810-NO), it outputs the second signal acquired from the counter unit 232 to the first comparing unit 25 as the tenth signal (step S840). In Fig. 16, the processing of step S840 is indicated by "SIG10=SIG2".

[0171] Next, the signal switching unit 27 outputs the first signal acquired from the feedback control unit 22 to the second comparing unit 26 as the 20th signal (step S850). In FIG. 16, the processing of step S850 is indicated by "SIG20=SIG1." In the flowchart shown in FIG. 16, the processing of step S840 and the processing of step S850 may be performed in the reverse order or may be performed in parallel. After the processing of step S850 is performed, the signal switching unit 27 ends the processing of the flowchart shown in FIG. 16.

[0172] As described above, even if the signal switching unit 27 is provided in front of the first comparing unit 25 and the second comparing unit 26, the control device 20 can switch the output destination of each of the two PWM signals in accordance with the operation mode currently determined by the operation mode determining unit 21. This allows the control device 20 to change one of the first duty ratio and the second duty ratio by feedback control and change the other of the first duty ratio and the second duty ratio by linear change control in accordance with the operation mode.

[0173] <Modification 3 of the embodiment> In the third modification of the embodiment, the operation mode determination unit 21 determines the operation mode based on the input voltage value and the output voltage value, as in the embodiment. However, unlike the embodiment, the operation mode determination unit 21 in the third modification of the embodiment has hysteresis. In other words, in the third modification of the embodiment, the operation mode determination unit 21 changes at least one of the upper limit voltage value z1 and the lower limit voltage value z2 when switching the operation mode. This enables the control device 20 to improve the stability of the operation of the switching power supply circuit 10 when switching the operation mode. Below, as an example, a case will be described in which the operation mode determination unit 21 changes either the upper limit voltage value z1 or the lower limit voltage value z2 when switching the operation mode.

[0174] For example, as shown in FIG. 17, the operation mode determination unit 21 changes each of the upper limit voltage value z1 and the lower limit voltage value z2. FIG. 17 is a diagram for explaining how the operation mode determination unit 21 changes each of the upper limit voltage value z1 and the lower limit voltage value z2. FIG. 17 shows timing charts CH2 to CH4 shown in FIG. 2. As shown in FIG. 17, the operation mode determination unit 21 uses the upper limit voltage value z1 as the upper limit voltage value in the step-up / step-down mode and the step-up mode. On the other hand, the operation mode determination unit 21 uses the upper limit voltage value z1-a as the upper limit voltage value in the step-down mode. Here, a may be any value, for example, a value that is 10% of the upper limit voltage value z1, but is not limited to this. Furthermore, the operation mode determination unit 21 uses the lower limit voltage value z2 as the lower limit voltage value in the step-up mode. On the other hand, the operation mode determination unit 21 uses a lower limit voltage value z2-b as the lower limit voltage value in the step-down mode and the step-up / step-down mode, where b may be any value, such as, but not limited to, 10% of the lower limit voltage value z2.

[0175] In this way, the operation mode determination unit 21 changes either the upper limit voltage value or the lower limit voltage value when switching the operation mode. More specifically, the operation mode determination unit 21 changes either the upper limit voltage value or the lower limit voltage value when switching the operation mode by the processing of the flowchart shown in FIG.

[0176] 18 is a diagram showing an example of the flow of processing in which the operation mode determination unit 21 changes the upper limit voltage value and the lower limit voltage value. Note that, as an example, the following describes a case in which the upper limit voltage value is the upper limit voltage value z1 and the lower limit voltage value is the lower limit voltage value z2 during the initial operation of the operation mode determination unit 21. However, the upper limit voltage value and the lower limit voltage value during the initial operation of the operation mode determination unit 21 may be other values.

[0177] The operation mode determination unit 21 determines whether the operation mode has been switched based on the input operation mode information and the input previous operation mode information (step S910). Specifically, if the operation mode indicated by the operation mode information matches the operation mode indicated by the previous operation mode, the operation mode determination unit 21 determines that the operation mode has not been switched. On the other hand, if the operation mode indicated by the operation mode information does not match the operation mode indicated by the previous operation mode, the operation mode determination unit 21 determines that the operation mode has been switched. In FIG. 18, the processing of step S910 is indicated by "Has the operation mode been switched?"

[0178] When the operation mode determination unit 21 determines that the operation mode has not been switched (step S910-NO), it does nothing and ends the processing of the flowchart shown in FIG.

[0179] On the other hand, if it is determined that the operation mode has been switched (step S910-YES), the operation mode determination unit 21 determines whether the operation mode after the switch is the step-down mode, the step-up / step-down mode, or the step-up mode based on the input operation mode information (step S920). In Fig. 18, the processing of step S920 is indicated by "What is the operation mode?"

[0180] When the operation mode determination unit 21 determines that the operation mode after switching is the step-down mode (step S920-step-down mode), it sets the lower limit voltage value to the lower limit voltage value z2 (step S950) and ends the processing of the flowchart shown in Fig. 18. In Fig. 18, the processing of step S950 is indicated by "lower limit voltage value=z2".

[0181] Furthermore, when the operation mode determination unit 21 determines that the operation mode after switching is the buck-boost mode (step S920-buck-boost mode), it determines whether the operation mode before switching was the buck mode or not based on the previous operation mode information (step S930). In Fig. 18, the processing of step S930 is indicated by "Previous operation mode is buck mode?"

[0182] If it is determined that the operation mode before the switch was the step-down mode (step S930-YES), the operation mode determination unit 21 sets the lower limit voltage value to lower limit voltage value z2-b (step S940) and ends the processing of the flowchart shown in Fig. 18. In Fig. 18, the processing of step S940 is indicated by "lower limit voltage value=z2-b".

[0183] On the other hand, if the operation mode determination unit 21 determines that the operation mode before the switch was not the step-down mode (step S930-NO), it sets the upper limit voltage value to upper limit voltage value z1 (step S960) and ends the processing of the flowchart shown in Fig. 18. In Fig. 18, the processing of step S960 is indicated by "upper limit voltage value=z1".

[0184] Furthermore, when the operation mode determination unit 21 determines that the operation mode after switching is the boost mode (step S920-boost mode), it sets the upper limit voltage value to the upper limit voltage value z1-a (step S970) and ends the processing of the flowchart shown in Fig. 18. In Fig. 18, the processing of step S970 is indicated by "upper limit voltage value=z1-a".

[0185] As described above, the operation mode determination unit 21 changes either the upper limit voltage value or the lower limit voltage value when switching the operation mode. That is, the operation mode determination unit 21 has hysteresis. This allows the control device 20 to improve the stability of the operation of the switching power supply circuit 10 when switching the operation mode.

[0186] The above-described items may be combined in any manner.

[0187] <Additional Notes> [1] 1. A control device that controls a switching power supply circuit including a first switching element and a second switching element, wherein the control device operates the switching power supply circuit in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operation mode for operating the switching power supply circuit, the control device sets a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching as a first start point from which to start changing the duty ratio in PWM control of the first switching element after the operation mode switching, and linearly changes the duty ratio in PWM control of the first switching element from the first start point, and sets a duty ratio in PWM control of the second switching element before the operation mode switching as a second start point from which to start changing the duty ratio in PWM control of the second switching element after the operation mode switching, and linearly changes the duty ratio in PWM control of the second switching element from the second start point. [2] the switching power supply circuit includes: a first side including a first upper arm and a first lower arm of an H-bridge; a second side including a second upper arm and a second lower arm of the H-bridge; a coil connecting a first connection point between the first upper arm and the first lower arm on the first side and a second connection point between the second upper arm and the second lower arm on the second side; the first switching element provided in the first upper arm; a first current limiting unit provided in the first lower arm and limiting a direction of current from the first lower arm side to the first upper arm side; a second current limiting unit provided in the second upper arm and limiting a direction of current from the second lower arm side to the second upper arm side; and the second switching element provided in the second lower arm. [3] The control device according to [2], wherein, when switching the operation mode from a first mode to a second mode, the control device changes the duty ratio of the first switching element after the operation mode switching from the first starting point by feedback control, and changes the duty ratio of the second switching element after the operation mode switching from the second starting point by linear change control; when switching the operation mode from the second mode to the first mode, the control device changes the duty ratio of the first switching element after the operation mode switching from the first starting point by linear change control, and changes the duty ratio of the second switching element after the operation mode switching from the second starting point by feedback control, and the linear change control is control that changes the duty ratio linearly. [4] The switching power supply circuit or the control device includes an input voltage detection unit that detects a voltage value of an input voltage input between the first upper arm and the first lower arm, and an output voltage detection unit that detects a voltage value of an output voltage output between the second upper arm and the second lower arm, and the control device includes an operation mode determination unit that determines the operation mode, a carrier signal generation unit that generates a carrier signal of a PWM signal, a feedback control unit that outputs a first signal to be compared with the carrier signal to generate PWM signals for feedback control of a duty ratio in PWM control of the first switching element and feedback control of the duty ratio in PWM control of the second switching element, a linear change control unit that outputs a second signal to be compared with the carrier signal to generate PWM signals for the linear change control of the duty ratio in PWM control of the first switching element and the linear change control of the duty ratio in PWM control of the second switching element, and a linear change control unit that generates a PWM signal in accordance with a comparison of the first signal and the carrier signal as a tenth PWM signal. a second comparing unit that generates a PWM signal corresponding to a comparison between the second signal and the carrier signal as a 20th PWM signal; and a signal switching unit that, when the operation mode determination unit determines that the operation mode is the first mode, inputs the 10th PWM signal generated by the first comparing unit to the first switching element as a first PWM signal and inputs the 20th PWM signal generated by the second comparing unit to the second switching element as a second PWM signal, when the operation mode determination unit determines that the operation mode is the second mode, and inputs the 20th PWM signal generated by the second comparing unit to the first switching element as the first PWM signal and inputs the 10th PWM signal generated by the first comparing unit to the first switching element as the first PWM signal, when the operation mode determination unit determines that the operation mode is the second mode, wherein the feedback control unit outputs the first signal by feedback control based on the voltage value of the input voltage detected by the input voltage detection unit, a target value of the voltage value of the input voltage, and the second signal output by the linear change control unit, and the linear change control unitThe control device according to [3], further comprising: a range determination unit that determines a range in which the second signal is changed based on the operation mode determined by the operation mode determination unit, the first signal output by the feedback control unit, and the second signal output previously, each time the operation mode is switched; and a counter unit that outputs the second signal each time the voltage value of the voltage indicated by the second signal is changed at a predetermined rate of change from the start point to the end point of the range determined by the range determination unit. [5] The control device described in [4], wherein the operation mode determination unit determines whether the operation mode is the first mode or the second mode based on the voltage value of the input voltage detected by the input voltage detection unit and the voltage value of the output voltage detected by the output voltage detection unit. [6] The control device described in [4], wherein the operating mode determination unit determines whether the operating mode is the first mode or the second mode based on the first signal output from the feedback control unit and the second signal output from the linear change control unit. [7] The control device described in [4], wherein the operation mode determination unit determines whether the operation mode is the first mode or the second mode based on the voltage value of the input voltage detected by the input voltage detection unit and the voltage value of the output voltage detected by the output voltage detection unit during the initial operation of the control device, and then determines whether the operation mode is the first mode or the second mode based on the first signal output from the feedback control unit and the second signal output from the linear change control unit. [8] The control device according to [4], further comprising a memory unit that stores information indicating the operation mode currently determined by the operation mode determination unit and the operation mode previously determined by the operation mode determination unit. [9] The control device according to any one of [3] to [8], wherein the first mode is a step-down mode, and the second mode is a step-up / step-down mode or a step-up mode.

[10] The control device according to [5], wherein the operation mode determination unit has hysteresis.

[11] The control device according to any one of [2] to

[10] , wherein the power source that inputs the input voltage between the first upper arm and the first lower arm is a solar panel.

[12] 1. A switching power supply circuit comprising a first switching element and a second switching element, wherein the switching power supply circuit is operated in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and wherein, when switching the operation mode for operating the switching power supply circuit, a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching is set as a first starting point from which a change in the duty ratio in PWM control of the first switching element after the operation mode switching begins, and the duty ratio in PWM control of the first switching element is changed linearly from the first starting point, and a duty ratio in PWM control of the second switching element before the operation mode switching is set as a second starting point from which a change in the duty ratio in PWM control of the second switching element after the operation mode switching begins, and the duty ratio in PWM control of the second switching element is changed linearly from the second starting point.

[13] A control method for controlling a switching power supply circuit including a first switching element and a second switching element, wherein the switching power supply circuit is operated in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operation mode for operating the switching power supply circuit, the method comprises: setting a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching as a first starting point from which to start changing the duty ratio in PWM control of the first switching element after the operation mode switching; and linearly changing the duty ratio in PWM control of the first switching element from the first starting point; setting a duty ratio in PWM control of the second switching element before the operation mode switching as a second starting point from which to start changing the duty ratio in PWM control of the second switching element after the operation mode switching; and linearly changing the duty ratio in PWM control of the second switching element from the second starting point.

[0188] The embodiments of this disclosure have been described in detail above with reference to the drawings, but the specific configuration is not limited to this embodiment, and may be changed, substituted, deleted, etc. as long as it does not deviate from the gist of this disclosure. [Explanation of symbols]

[0189] 1...switching power supply device, 10...switching power supply circuit, 20...controller, 21...operation mode determination unit, 22...feedback control unit, 23...linear change control unit, 24...carrier signal generation unit, 25...first comparison unit, 26...second comparison unit, 27...signal switching unit, 28...storage unit, 231...range determination unit, 232...counter unit, AD1...first lower arm, AD2...second lower arm, AU1...first upper arm, AU2...second upper arm, C1...capacitor, C2...capacitor, CL...coil, CN1...first connection point, CN2...second connection point, D1...first current limiting unit, D2...second current limiting unit, LD...load, P...DC power supply, R11...resistance element, R12...resistance element, R21...resistance element, R22...resistance element, S1...first switching element, S2...second switching element

Claims

1. A control device that controls a switching power supply circuit including a first switching element and a second switching element, The switching power supply circuit is operated in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operation mode for operating the switching power supply circuit, a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching is set as a first start point at which a change in the duty ratio in PWM control of the first switching element after the operation mode switching starts, and the duty ratio in PWM control of the first switching element is changed linearly from the first start point, and a duty ratio in PWM control of the second switching element before the operation mode switching is set as a second start point at which a change in the duty ratio in PWM control of the second switching element after the operation mode switching starts, and the duty ratio in PWM control of the second switching element is changed linearly from the second start point. Control device.

2. The switching power supply circuit comprises: a first side including a first upper arm and a first lower arm of an H-bridge; a second side including a second upper arm and a second lower arm of the H-bridge; a coil connecting a first connection point between the first upper arm and the first lower arm on the first side and a second connection point between the second upper arm and the second lower arm on the second side; the first switching element provided in the first upper arm; a first current limiting unit provided in the first lower arm and configured to limit a direction of current flow from the first lower arm side to the first upper arm side; a second current limiting unit provided in the second upper arm and configured to limit a direction of current flow from the second lower arm side to the second upper arm side; the second switching element provided in the second lower arm; Equipped with The control device according to claim 1 .

3. When switching the operation mode from a first mode to a second mode, the control device changes the duty ratio of the first switching element after the operation mode switching from the first start point by feedback control, and changes the duty ratio of the second switching element after the operation mode switching from the second start point by linear change control; when switching the operation mode from the second mode to the first mode, the control device changes the duty ratio of the first switching element after the operation mode switching from the first start point by linear change control, and changes the duty ratio of the second switching element after the operation mode switching from the second start point by feedback control; The linear change control is a control that changes the duty ratio linearly. The control device according to claim 2 .

4. The switching power supply circuit or the control device is an input voltage detection unit that detects a voltage value of an input voltage input between the first upper arm and the first lower arm; an output voltage detection unit that detects a voltage value of an output voltage output between the second upper arm and the second lower arm; Equipped with The control device an operation mode determination unit that determines the operation mode; a carrier signal generating unit that generates a carrier signal for a PWM signal; a feedback control unit that outputs a first signal to be compared with the carrier signal to generate a PWM signal in feedback control of a duty ratio in PWM control of the first switching element and in feedback control of a duty ratio in PWM control of the second switching element; a linear change control unit that outputs a second signal to be compared with the carrier signal to generate a PWM signal in the linear change control of a duty ratio in the PWM control of the first switching element and the linear change control of a duty ratio in the PWM control of the second switching element; a first comparison unit that generates a PWM signal corresponding to a comparison between the first signal and the carrier signal as a tenth PWM signal; a second comparison unit that generates a PWM signal corresponding to a comparison between the second signal and the carrier signal as a 20th PWM signal; a signal switching unit that, when the operation mode determination unit determines that the operation mode is the first mode, inputs the tenth PWM signal generated by the first comparison unit as a first PWM signal to the first switching element and inputs the twentieth PWM signal generated by the second comparison unit as a second PWM signal to the second switching element, and, when the operation mode determination unit determines that the operation mode is the second mode, inputs the twentieth PWM signal generated by the second comparison unit as the first PWM signal to the first switching element and inputs the tenth PWM signal generated by the first comparison unit as the first PWM signal to the first switching element; Equipped with the feedback control unit outputs the first signal by feedback control based on a voltage value of the input voltage detected by the input voltage detection unit, a target value of the voltage value of the input voltage, and the second signal output by the linear change control unit; The linear change control unit a range determination unit that determines, each time the operation mode is switched, a range in which the second signal is changed based on the operation mode determined by the operation mode determination unit, the first signal output by the feedback control unit, and the second signal previously output; a counter unit that outputs the second signal each time a voltage value indicated by the second signal is changed at a predetermined rate of change from the start point to the end point of the range determined by the range determination unit; Equipped with The control device according to claim 3 .

5. the operation mode determination unit determines whether the operation mode is the first mode or the second mode based on the voltage value of the input voltage detected by the input voltage detection unit and the voltage value of the output voltage detected by the output voltage detection unit. The control device according to claim 4.

6. the operation mode determination unit determines whether the operation mode is the first mode or the second mode based on the first signal output from the feedback control unit and the second signal output from the linear change control unit. The control device according to claim 4.

7. the operation mode determination unit determines whether the operation mode is the first mode or the second mode based on the voltage value of the input voltage detected by the input voltage detection unit and the voltage value of the output voltage detected by the output voltage detection unit during an initial operation of the control device, and then determines whether the operation mode is the first mode or the second mode based on the first signal output from the feedback control unit and the second signal output from the linear change control unit. The control device according to claim 4.

8. a storage unit that stores information indicating the operation mode currently determined by the operation mode determination unit and the operation mode previously determined by the operation mode determination unit, The control device according to claim 4.

9. the first mode is a step-down mode, The second mode is a step-up / step-down mode or a step-up mode. The control device according to claim 3 .

10. The operation mode determination unit has hysteresis. The control device according to claim 5 .

11. a power source that inputs the input voltage between the first upper arm and the first lower arm is a solar panel; The control device according to claim 2 .

12. A switching power supply circuit including a first switching element and a second switching element, The switching power supply circuit is operated in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit, and when switching the operation mode for operating the switching power supply circuit, a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching is set as a first start point at which a change in the duty ratio in PWM control of the first switching element after the operation mode switching starts, and the duty ratio in PWM control of the first switching element is changed linearly from the first start point, and a duty ratio in PWM control of the second switching element before the operation mode switching is set as a second start point at which a change in the duty ratio in PWM control of the second switching element after the operation mode switching starts, and the duty ratio in PWM control of the second switching element is changed linearly from the second start point. Switching power supply circuit.

13. A control method for controlling a switching power supply circuit including a first switching element and a second switching element, comprising: operating the switching power supply circuit in an operation mode corresponding to a difference between a voltage value of an input voltage to the switching power supply circuit and a voltage value of an output voltage from the switching power supply circuit; When switching the operation mode for operating the switching power supply circuit, a duty ratio in PWM (Pulse Width Modulation) control of the first switching element before the operation mode switching is set as a first start point at which a change in the duty ratio in PWM control of the first switching element after the operation mode switching starts, and the duty ratio in PWM control of the first switching element is changed linearly from the first start point, and a duty ratio in PWM control of the second switching element before the operation mode switching is set as a second start point at which a change in the duty ratio in PWM control of the second switching element after the operation mode switching starts, and the duty ratio in PWM control of the second switching element is changed linearly from the second start point. Control method.

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