DCDC converter control device and program

Abstract

A control device (50) for a DC-DC converter (10, 100) is provided with: a current calculation unit (60) for calculating an average current value, which is an average time value in one switching cycle of a current flowing through an inductor (30), on the basis of a current detection value of a current detection unit (42) for detecting the current flowing through the inductor (30); a duty ratio calculation unit that calculates the duty ratio of the current discontinuous pattern on the basis of the command value of the average current value; and a switching control unit (52, 63) that performs switching control of the switch (31) on the basis of the calculated duty ratio. The duty ratio calculation unit calculates relationship information (alpha, beta) between the average current value and the duty ratio on the basis of the average current value and the duty ratio calculated in a plurality of past switching periods, and calculates the duty ratio in the next switching period on the basis of the calculated relationship information and the command value.

Description

Citation of Related Applications

[0001] This application is based on Japanese Patent Application No. 2022-195216 filed on December 6, 2022, the content of which is incorporated herein by reference. Technical Field

[0002] The present disclosure relates to a control device and a program for a DC-DC converter. Background Art Conventionally, a DC-DC converter having a switch and an inductor has been known. As a control device for such a converter, as described in Patent Document 1, a device that calculates a duty ratio in a current discontinuous mode in the next switching cycle based on a current detection value of a current detection unit that detects a current value flowing through the inductor and a presumed inductance value of the inductor is known.

[0004] In view of the possibility of an error between the presumed inductance value of the inductor used for calculating the duty ratio and the actual inductance value of the inductor, the control device calculates a correction value for the duty ratio. Thereby, it is possible to suppress the influence of the above error on the calculation accuracy of the duty ratio. Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-19448 Summary of the Invention

[0006] There may be an error between the current detection value of the current detection unit and the actual current value flowing through the inductor. Due to this current detection error, the duty ratio for the switching control of the switch may deviate from an appropriate value.

[0007] A main object of the present disclosure is to provide a control device and a program for a DC-DC converter that can improve the calculation accuracy of the duty ratio for the switching control of the switch.

[0008] The present disclosure is a control device for a DC-DC converter, applicable to a DC-DC converter including a switch and an inductor, The control device for the DC-DC converter described above repeatedly accumulates magnetic energy in the inductor and releases magnetic energy from the inductor by using the switching control of the switch described above, steps up or steps down the input voltage, and outputs it. The control device for the DC-DC converter described above includes: A current calculation unit that calculates an average current value, which is a time average value of the current flowing through the inductor in one switching cycle of the current flowing through the inductor, based on a current detection value of a current detection unit that detects the current flowing through the inductor; A duty ratio calculation unit that calculates the duty ratio in the current discontinuous mode based on the average current value command value; and A switch control unit that performs switch control of the switch based on the calculated duty ratio, The duty ratio calculation unit calculates relationship information between the average current value and the duty ratio based on the duty ratio and the average current value calculated in a plurality of past switching cycles, Based on the calculated relationship information and the command value, the duty ratio in the next switching cycle is calculated.

[0009] Based on the duty ratio and the average current value calculated in a plurality of past switching cycles, the relationship between the average current value including the current detection error and the duty ratio can be grasped. In view of this, the present disclosure includes the duty ratio calculation unit. Thereby, even when the current detection value of the current detection unit includes a current detection error, the calculation accuracy of the duty ratio in the current discontinuous mode can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] With reference to the accompanying drawings and the following detailed description, the above objects, other objects, features, and advantages of the present disclosure can be made more apparent. The accompanying drawings are as follows. Figure 1 It is a diagram showing the overall structure of a control system including a DCDC converter according to the first embodiment. Figure 2 It is a timing chart showing the switching method and the change of the inductor current value in the current discontinuous mode. Figure 3 It is a timing chart showing the switching method and the change of the inductor current value in the current critical mode. Figure 4 It is a timing chart showing the switching method and the change of the inductor current value in the current continuous mode. Figure 5 It is a diagram showing the relationship between the average inductor current value and the duty ratio, etc. Figure 6 It is a block diagram of the processing in the current discontinuous mode executed by the control device. Figure 7 It is a flowchart showing the control process of the DCDC converter. Figure 8 It is a diagram showing the effect of the first embodiment. Figure 9 It is a diagram showing the effect of the first embodiment. Figure 10 It is a diagram showing the effect of the first embodiment. Figure 11 It is a diagram showing the effect of the first embodiment. Figure 12 is a flowchart showing the control process of the DCDC converter of the second embodiment. Figure 13 is a flowchart showing the control process of the DCDC converter of the third embodiment. Figure 14 is a diagram showing the overall structure of the control system of other embodiments. Detailed Embodiments

[0011] Hereinafter, a plurality of embodiments will be described with reference to the drawings. In a plurality of embodiments, parts and / or related parts that are functionally and / or structurally corresponding may sometimes be marked with the same reference numerals or reference numerals with more than one hundred different digits. For corresponding parts and / or related parts, the description of other embodiments may be referred to.

[0012] <First Embodiment> Hereinafter, a first embodiment in which the control device of the present disclosure is embodied will be described with reference to the drawings.

[0013] As Figure 1 shown, the DCDC converter 10 is a non-insulated boost converter that boosts the voltage input from the high-potential side input terminal THi and the low-potential side input terminal TLi and outputs it from the high-potential side output terminal THo and the low-potential side output terminal TLO. The DCDC converter 10 includes an inductor 30, a switch 31, a diode 32, and a capacitor 33. In the present embodiment, the switch 31 is an N-channel MOSFET. In addition, the switch 31 is not limited to an N-channel MOSFET, and for example, an IGBT with a freewheeling diode connected in reverse parallel may also be used.

[0014] The first end of the inductor 30 is connected to the positive terminal of the DC power supply 20 via the high-potential side input terminal Thi. The second end of the inductor 30 is connected to the drain of the switch 31 and the anode of the diode 32. The negative terminal of the DC power supply 20 is connected to the source of the switch 31 via the low-potential side input terminal TLi. The DC power supply 20 is a storage battery or a fuel cell, etc.

[0015] The cathode of the diode 32 is connected to the first end of the capacitor 33 and the high-potential side output terminal THo. The second end of the capacitor 33 is connected to the source of the switch 31, the low-potential side input terminal TLi, and the low-potential side output terminal TLO. The high-potential side output terminal THo is connected to the positive terminal of the storage battery 21, and the negative terminal of the storage battery 21 is connected to the low-potential side output terminal TLO. The storage battery 21 is a rechargeable secondary battery, for example, a lithium-ion storage battery or a nickel-metal hydride storage battery.

[0016] The DCDC converter 10 includes an input voltage sensor 40 as an input voltage detection unit, an output voltage sensor 41 as an output voltage detection unit, and a current sensor 42 as a current detection unit. The input voltage sensor 40 detects the input voltage of the DCDC converter 10, and the output voltage sensor 41 detects the output voltage of the DCDC converter 10. The current sensor 42 detects the current value flowing through the inductor 30. The detection values of the respective sensors 40 to 42 are input to a control device 50 included in the DCDC converter 10.

[0017] The control device 50 is mainly constituted by a microcomputer 51, and the microcomputer 51 includes a CPU. The functions provided by the microcomputer 51 can be provided by software recorded in a physical memory device and a computer that executes the software, software only, hardware only, or a combination thereof. For example, when the microcomputer 51 is provided by an electronic circuit as hardware, it can be provided by a digital circuit or an analog circuit including a plurality of logic circuits. For example, the microcomputer 51 executes a program stored in a non-transitory tangible storage medium serving as a storage unit included in itself. The program includes, for example, a program for processing such as those shown later Figure 7 and so on. A method corresponding to the program is executed by executing the program. The storage unit is, for example, a non-volatile memory. In addition, the program stored in the storage unit can be updated through a communication network such as the Internet by OTA (Over The Air).

[0018] The control device 50 selects a control mode from among a current discontinuous mode and a current continuous mode, and performs switching control of the switch 31.

[0019] As Figure 2As shown, the discontinuous current mode is a control mode in which a period during which the current value flowing through the inductor 30 becomes 0 is generated in one switching cycle Ts of the switch 31. The control device 50 calculates the duty ratio Duty of the discontinuous current mode and performs switching control of the switch 31 based on the calculated duty ratio Duty. The duty ratio Duty is a value that determines the ratio of the on-period Ton of the switch 31 in one switching cycle Ts (Ton / Ts = Duty). The control device 50 turns on the switch 31 during the period of "Duty×Ts" in one switching cycle Ts and turns off the switch 31 during the period of "(1 - Duty)×Ts". During the on-period of the switch 31, the current value flowing through the inductor 30 gradually increases, and magnetic energy is stored in the inductor 30. During the off-period of the switch 31, the magnetic energy stored in the inductor 30 is released, and the current value flowing through the inductor 30 decreases to 0. Thus, in one switching cycle Ts, the time-varying waveform of the current value flowing through the inductor 30 is ideally a waveform that becomes triangular-wave-shaped and then remains 0.

[0020] As Figure 4 shown, the continuous current mode is a control mode in which current continuously flows from the first end side to the second end side of the inductor 30 in one switching cycle Ts of the switch 31. The control device 50 calculates the duty ratio Duty of the continuous current mode and performs switching control of the switch 31 based on the calculated duty ratio Duty. In addition, the duty ratio Duty of the continuous current mode can be calculated, for example, based on the following equation (eq1).

[0021] [Equation 1] In the above equation (eq1), VLmes is the input voltage detection value detected by the input voltage sensor 40 in the current switching cycle, VHmes is the output voltage detection value detected by the output voltage sensor 41 in the current switching cycle, and Kp is the proportional gain of the feedback term. In addition, Iref represents the command value of the average current value flowing through the inductor 30. The average current value is the time average in one switching cycle Ts of the current flowing through the inductor 30. The command value Iref input to the control device 50 is updated, for example, every other switching cycle Ts. In addition, Imes is the average current value flowing through the inductor 30 (hereinafter referred to as the average current detection value) calculated based on the current value flowing through the inductor 30 detected by the current sensor 42 (hereinafter referred to as the current detection value ILmes). Incidentally, the feedback term on the right side in the above equation (eq1) is not essential.

[0022] In addition, the boundary between the discontinuous current mode and the continuous current mode becomes Figure 3The current critical mode shown. The current critical mode is a control mode in which the switch 31 is switched on at the moment when the current value flowing through the inductor 30 decreases to 0.

[0023] In addition, the current detection value ILmes is used to calculate the duty ratio Duty in the current discontinuous mode. The current detection value ILmes includes a current detection error. In order to suppress the influence of this current detection error on the control of the DCDC converter 10, the control device 50 calculates the duty ratio Duty in the current discontinuous mode. Hereinafter, the calculation method of this duty ratio Duty will be described.

[0024] The basic calculation formula of the duty ratio Duty in the current discontinuous mode is expressed by the following formula (eq2). In the following formula (eq2), Ls represents the inductance value of the inductor 30, and fsw represents the switching frequency of the switch 31 (=1 / Ts).

[0025] [Mathematical formula 2] Here, when solving the above formula (eq2) for the current value and considering the existence of a current detection error, the following formula (eq3) is derived. In the following formula (eq3), as shown in the relationship between the average current value and the duty ratio Duty, Ierr is the offset current error between the average current detection value Imes and the command value Iref when the duty ratio Duty is 0. Figure 5 The relationship between the average current value and the duty ratio Duty shows that Ierr is the offset current error between the average current detection value Imes and the command value Iref when the duty ratio Duty is 0.

[0026] [Mathematical formula 3] On the right side of the above formula (eq3), the coefficients multiplied by the duty ratio Duty include VHre, VLre, and Lsre. VHre represents the actual output voltage, VLre represents the actual input voltage, and Lsre represents the actual inductance value of the inductor 30.

[0027] Figure 5 Shows the relationship between the command value Iref and the average current detection value when the command value Iref is gradually increased at a constant speed. In the Figure 5 example shown, the rising speed of the command value Iref is different from the rising speed of the average current detection value. Specifically, the rising speed of the average current detection value is higher than the rising speed of the command value Iref. This is because the current detection value ILmes used to calculate the average current detection value contains a gain error.

[0028] The above formula (eq3) is expressed as the following formula (eq4). The following formula (eq4) is the relationship information with the duty ratio Duty as the independent variable and the average current detection value Imes as the dependent variable. In the following formula (eq4), α as the coefficient information of the independent variable is a correction coefficient, and β as the intercept information is an offset correction value.

[0029] [Equation 4] I mes = α·Duty 2 + β…(eq4) As Figure 5 shown, based on the relationship between the average current detection value Imes_a and the duty ratio Dutya in the first period of a certain switching cycle, the average current detection value Imes_b and the duty ratio Dutyb in the second period of a switching cycle different from the first period, and the above formula (eq4), the following formula (eq5) is derived. Additionally, in Figure 5 , the command value corresponding to the duty ratio Dutya is represented by Iref_a, and the command value corresponding to the duty ratio Dutyb is represented by Iref_b.

[0030] [Equation 5] When solving the above formula (eq5) for the correction coefficient α and the offset correction value β, the following formula (eq6) is derived.

[0031] [Equation 6] That is, the correction coefficient α and the offset correction value β can be calculated based on the average current detection values and duty ratios in two different first and second periods.

[0032] In the present embodiment, the control device 50 calculates the correction coefficient α and the offset correction value based on the average current detection value Imes1 and the duty ratio Duty1 calculated in a switching cycle one switching cycle earlier than the current switching cycle (hereinafter, the previous switching cycle. Corresponding to the "first period"), the average current detection value Imes2 and the duty ratio Duty2 calculated in a switching cycle two switching cycles earlier than the current switching cycle (hereinafter, the penultimate switching cycle. Corresponding to the "second period"), and the above formula (eq6). The average current detection value Imes1 is calculated based on a plurality of current detection values ILmes detected in the previous switching cycle, and the average current detection value Imes2 is calculated based on a plurality of current detection values ILmes detected in the penultimate switching cycle.

[0033] Here, as shown in the above formula (eq3), the correction coefficient α depends on the output voltage VHre, the input voltage VLre, and the inductance value Lsre. If the voltages VHre, VLre, and the inductance value Lsre change from the previous switching cycle to the current switching cycle, the calculation accuracy of the correction coefficient α may decrease. The inductance value Lsre may change according to the current value flowing through the inductor 30.

[0034] Therefore, in order to suppress the influence of variations in the voltages VHre, VLre, and the inductor value Lsre on the calculation accuracy of the correction factor α, the correction parameter γ in the current switching period shown in the following formula (eq7) and the correction parameter γ1 in the previous switching period shown in the following formula (eq8) are calculated. The correction factor shown as "γ / γ1" is a parameter for suppressing the influence of variations in the voltages VHre, VLre, and the inductor value Lsre on the calculation accuracy of the correction factor α. Then, based on the correction factor α, the offset correction value β, the correction factor "γ / γ1", and the following formula (eq9), the duty ratio Duty in the current discontinuous mode is calculated.

[0035] In the following formula (eq7), VHmes is the output voltage detection value in the current switching period, VLmes is the input voltage detection value in the current switching period, and Ls is the estimated inductance value of the inductor 30 in the current switching period. In the following formula (eq8), VHmes1 is the output voltage detection value in the previous switching period, VLmes1 is the input voltage detection value in the previous switching period, and Ls1 is the estimated inductance value of the inductor 30 in the previous switching period.

[0036] [Equation 7]

[0037] [Equation 8]

[0038] [Equation 9] Figure 6 The control block diagram of the current discontinuous mode executed by the control device 50 is shown.

[0039] In the control device 50, the average current calculation unit 60 calculates the average current detection value Imes in the current switching period Ts based on the current detection value ILmes. The current value flowing through the inductor 30 is sampled multiple times (for example, more than ten times) by the current sensor 42 in one switching period Ts. The average current detection value Imes is calculated for each switching period and stored in the storage unit (memory) included in the control device 50.

[0040] The correction value calculation unit 61 calculates the correction factor α and the offset correction value β based on the average current detection value Imes 1 and the duty ratio Duty1 calculated in the previous switching period, the average current detection value Imes2 and the duty ratio Duty2 calculated in the period before the previous switching period, and the following formula (eq6). The correction factor α and the offset correction value β are calculated and updated for each switching period.

[0041] The calculation unit 62 calculates a correction parameter γ based on the detected output voltage value VHmes and the detected input voltage value VLmes in the current switching cycle, the estimated inductance value Ls of the inductor 30 in the current switching cycle, and the above formula (eq7). Here, the estimated inductance value Ls in the current switching cycle can be calculated, for example, based on inductance mapping information or mathematical formula information associating the average current detection value and the estimated inductance value, and the average current detection value Imes in the current switching cycle.

[0042] The calculation unit 62 calculates a correction parameter γ1 based on the detected output voltage value VHmes1 and the detected input voltage value VLmes1 in the previous switching cycle, the estimated inductance value Ls1 of the inductor 30 in the previous switching cycle, and the above formula (eq8). Here, the estimated inductance value Ls1 in the previous switching cycle can be calculated, for example, based on the above inductance mapping information or mathematical formula information and the average current detection value Imes1 in the previous switching cycle.

[0043] The calculation unit 62 calculates the duty ratio Duty in the current switching cycle based on the calculated γ, γ1, the calculated correction coefficient α and the offset correction value β, the command value Iref, and the above formula (eq9). This duty ratio Duty is a value that determines the on period of the switch 31 in the next switching cycle.

[0044] The current control unit 63 calculates a drive command Sg for the switch 31 based on the calculated duty ratio Duty, and outputs the calculated drive command Sg to the drive circuit 52. The drive command Sg consists of an on command and an off command for the switch 31. The drive circuit 52 performs switching control of the switch 31 based on the drive command Sg.

[0045] In addition, in the present embodiment, the drive circuit 52 and the current control unit 63 correspond to the "switching control unit", and the correction value calculation unit 61 and the calculation unit 62 correspond to the "duty ratio calculation unit".

[0046] Figure 7 Steps of inductor current control executed by the control device 50 are shown. In step S10, the command value Iref in the current switching cycle is acquired. In step S11, the average current calculation unit 60 calculates the average current detection value Imes in the current switching cycle Ts based on a plurality of current detection values ILmes acquired in one switching cycle Ts. In addition, the detected output voltage value VHmes and the detected input voltage value VLmes in the current switching cycle are acquired.

[0049] In step S12, it is determined whether the control mode in the next switching cycle is the current discontinuous mode or the current continuous mode. Specifically, for example, when it is determined that the average current detection value Imes in the current switching cycle is equal to or less than the determination value, it is determined that it is the current discontinuous mode, and when it is determined that the average current detection value Imes exceeds the determination value, it may be determined that it is the current continuous mode.

[0050] When it is determined in step S12 that it is the current continuous mode, proceed to step S13 to calculate the duty ratio Duty of the current continuous mode. For example, it is sufficient to calculate the duty ratio Duty of the current continuous mode based on the output voltage detection value VHmes, the input voltage detection value VLmes, and the above equation (eq1) in the current switching cycle.

[0051] In step S14, based on the duty ratio Duty calculated in step S13, calculate the drive instruction Sg and output it to the drive circuit 52. Thus, based on the duty ratio Duty calculated in step S13, perform the switching control of the switch 31 so that the control mode becomes the current continuous mode.

[0052] In step S15, it is determined whether a drive stop instruction for the DCDC converter 10 has been issued. When it is determined that no drive stop instruction has been issued, proceed to step S10.

[0053] When it is determined in step S12 that it is the current discontinuous mode, proceed to step S16 to calculate the estimated inductance value Ls in the current switching cycle. In addition, calculate the correction parameters γ and γ1 in the current switching cycle.

[0054] In step S17, it is determined whether both the first condition and the second condition are satisfied. The first condition is the condition that the duty ratio Duty1 calculated in the previous switching cycle or the duty ratio Duty2 calculated in the cycle before the previous one is not 0. The first condition is for avoiding the denominator of the determinant on the right side of the above equation (eq6) from being 0 and being unable to calculate the correction coefficient α and the offset correction value β.

[0056] The second condition is the condition that the correction parameter γ1 in the previous switching cycle is a positive value. The second condition is for avoiding the square root on the right side of the above equation (eq9) from being a negative value and being unable to calculate the duty ratio Duty.

[0057] When it is determined in step S17 that both the first condition and the second condition are satisfied, proceed to step S18, and the correction coefficient α and the offset correction value β are calculated and updated by the correction value calculation unit 61.

[0058] In step S19, it is determined whether both the third condition and the fourth condition are satisfied. The third condition is that the command value Iref obtained in step S10 is greater than the offset correction value β calculated in step S18. The fourth condition is that the correction coefficient α calculated in step S18 is greater than 0. The third condition and the fourth condition are conditions for avoiding a negative square root on the right side of the above formula (eq9) and making it impossible to calculate the duty ratio Duty.

[0060] If it is determined in step S19 that both the third condition and the fourth condition are satisfied, the process proceeds to step S20, and the calculation unit 62 calculates the duty ratio Duty of the current discontinuous mode. In the next step S21, based on the duty ratio Duty calculated in step S20, the drive command Sg is calculated and output to the drive circuit 52. Thus, based on the duty ratio Duty calculated in step S20, the switching control of the switch 31 is performed to make the control mode the current discontinuous mode.

[0061] If it is determined in step S17 that at least one of the first condition and the second condition is not satisfied, the process proceeds to step S22, and it is determined whether the offset correction value β1 calculated in the previous switching cycle is equal to or greater than the command value Iref obtained in step S10.

[0062] If it is determined in step S22 that the command value Iref is greater than the offset correction value β1, or if it is determined in step S19 that at least one of the third condition and the fourth condition is not satisfied, the process proceeds to step S23. In step S23, the calculation unit 62 uses the correction coefficient α1 and the offset correction value β1 calculated in the previous switching cycle for the calculation of the duty ratio Duty. In the next step S21, based on the duty ratio Duty calculated in step S23, the drive command Sg is calculated and output to the drive circuit 52. Thus, based on the duty ratio Duty calculated in step S23, the switching control of the switch 31 is performed to make the control mode the current discontinuous mode.

[0063] If it is determined in step S22 that the offset correction value β1 is equal to or greater than the command value Iref, the process proceeds to step S24, and the duty ratio Duty of the current discontinuous mode is set to 0. Therefore, in the next step S21, the drive command Sg is maintained as an off command. Thus, the switch 31 is maintained off in the next switching cycle.

[0064] Use Figures 8 - 11 The calculation results shown are compared with the comparative example and the structure of the present embodiment is described. In Figures 8 - 11In the illustrated calculation example, the transition of the average current detection value is shown when the command value Iref gradually increases at a constant speed. Figures 8 - 11 The illustrated comparative example is the result of the current discontinuous mode when using the method described in Patent Document 1.

[0065] Figure 8 A case is shown where the actual inductance value of the inductor 30 is smaller than the inductance value used in the control, and the current detection value ILmes is larger than the current value actually flowing through the inductor 30.

[0066] As Figure 8 shown, according to the present embodiment, the average current detection value Imes quickly follows the gradually increasing command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very small. In contrast, in the comparative example, the average current detection value Imes cannot quickly follow the command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very large at the beginning of current control. Additionally, in Figure 8 the example of the present embodiment shown, the average current detection value Imes is a constant value at the start of current control because the switch 31 is turned off when the current detection value ILmes including the offset error Ierr is equal to or greater than the command value Iref.

[0067] Figure 9 The calculation conditions of the calculation result shown in Figure 8 are different from the calculation conditions of the calculation result shown in that the current detection value ILmes is smaller than the current value actually flowing through the inductor 30.

[0068] As Figure 9 shown, according to the present embodiment, the average current detection value Imes quickly follows the gradually increasing command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very small. In contrast, in the comparative example, the average current detection value Imes cannot quickly follow the command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very large.

[0069] Figure 10 A case is shown where the actual inductance value of the inductor 30 is larger than the inductance value used in the control, and the current detection value ILmes is larger than the current value actually flowing through the inductor 30.

[0070] As Figure 10As shown, according to this embodiment, the average current detection value Imes rapidly follows the gradually increasing command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very small. In contrast, in the comparative example, the average current detection value Imes cannot rapidly follow the command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very large.

[0071] Figure 11 The calculation conditions of the calculation results shown in Figure 10 differ from the calculation conditions of the calculation results shown in that the current detection value ILmes is smaller than the current value actually flowing through the inductor 30.

[0072] As Figure 11 shown, according to this embodiment, the average current detection value Imes rapidly follows the gradually increasing command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very small. In contrast, in the comparative example, the average current detection value Imes cannot rapidly follow the command value Iref, and the error between the command value Iref and the average current detection value Imes becomes very large.

[0073] As described above, according to this embodiment, even when the current detection error is included in the current detection value ILmes, the calculation accuracy of the duty ratio Duty in the current discontinuous mode can be improved. As a result, the average current detection value Imes can rapidly follow the command value Iref, and the current controllability in the current discontinuous mode can be improved.

[0074] <Second Embodiment> Hereinafter, with reference to the drawings, the second embodiment will be described centering on the differences from the first embodiment. In this embodiment, the determination method of which one of the current discontinuous mode and the current continuous mode is the control mode in the next switching cycle is changed.

[0075] Figure 12 The steps of inductor current control executed by the control device 50 are shown. In addition, in Figure 12 for convenience, the same symbols are assigned to the processes that are the same as the processes shown in the previous Figure 7 shown.

[0076] After the process of step S11 ends, proceed to step S16.

[0077] After the processing in step S20, S23, or S24 ends, proceed to step S30 to calculate the duty cycle threshold Dth. The duty cycle threshold Dth is a threshold for determining whether the control mode is the current discontinuous mode or the current continuous mode. For example, the duty cycle threshold Dth can be calculated as the upper limit value of the duty cycle Duty that can be obtained in the current discontinuous mode.

[0078] In the next step S31, it is determined whether the duty cycle Duty calculated in step S20, S23, or S24 is greater than the duty cycle threshold Dth. When it is determined in step S31 that the duty cycle Duty is below the duty cycle threshold Dth, it is determined that the control mode in the next switching cycle is the current discontinuous mode, and proceed to step S21. On the other hand, when it is determined in step S31 that the duty cycle Duty is greater than the duty cycle threshold Dth, it is determined that the control mode in the next switching cycle is the current continuous mode, and proceed to step S13. In this case, in the switching determination from the current discontinuous mode to the current continuous mode, the duty cycle of the current discontinuous mode is used.

[0079] <Third Embodiment> Hereinafter, with reference to the drawings, the third embodiment will be described centering on the differences from the first embodiment. In this embodiment, in the current discontinuous mode, when the duty cycle Duty calculated in the current switching cycle changes significantly with respect to the Duty1 calculated in the previous switching cycle, a process for suppressing this change is executed.

[0080] Figure 13 Shows the steps of inductor current control executed by the control device 50. Additionally, in Figure 13 For convenience, the same symbols are used for the same processes as those shown in the previous Figure 7 shown.

[0081] After the processing in step S20, S23, or S24 ends, proceed to step S40 to calculate the allowable change value ΔD. The allowable change value ΔD is determined based on the change amount of the duty cycle starting from the previous switching cycle determined by the above formula (eq2). Specifically, for example, the allowable change value ΔD can be calculated by the following formula (eq10). The coefficient Kc (>0) in the following formula (eq10) can be set to a value between 3 and 5, for example. Additionally, on the right side of the following formula (eq10), Iref1 is the command value Iref in the previous switching cycle.

[0082] [Equation 10] In the next step S41, it is determined whether the absolute value of the difference between the duty ratio Duty calculated in the current switching cycle and the duty ratio Duty1 calculated in the previous switching cycle is greater than the allowable variation value ΔD.

[0083] In the case where a negative determination is made in step S41, the process proceeds to step S21. On the other hand, in the case where an affirmative determination is made in step S41, the process proceeds to step S421, and the value obtained by adding the duty ratio Duty1 calculated in the previous switching cycle and the allowable variation value ΔD is regarded as the duty ratio Duty calculated in the current switching cycle. After that, the process proceeds to step S21. According to the present embodiment described above, it is possible to suppress the influence of improper effects such as noise on the calculation accuracy of the duty ratio Duty in the current discontinuous mode.

[0085] <Other Embodiments> In addition, the above-described embodiments can also be implemented with the following modifications.

[0086] · In the above formula (eq9), the correction coefficient “γ / γ1” may not be used. In this case, the control device may calculate the duty ratio Duty based on the following formula (eq11).

[0087] [Mathematical Formula 11] · In Figure 1 In the shown structure, instead of the storage battery 21, an electrical load may also be connected to the output terminals THo and TLO. In this case, instead of the current-controlled DCDC converter, the DCDC converter may also be a voltage-controlled DCDC converter in which a current negative feedback loop control (Japanese: current minor loop control) is added to the current control of the control device.

[0088] · As the control system, it is not limited to Figure 1 the shown structure. For example, it may also be Figure 14 the shown structure. Figure 14 The shown structure is a motor drive system of an electric vehicle including a fuel cell 90. The system includes a boost converter 100, a storage battery 91, an inverter 110, and a motor 120. The boost converter 100 boosts the output voltage of the fuel cell 90 and supplies it to the inverter 110. The inverter 110 converts the DC power supplied from at least one of the boost converter 100 or the storage battery 91 into AC power and supplies it to the armature winding of the motor 120. In this structure, the present disclosure can also be applied to the current control of the boost converter 100.

[0089] · In the calculation process based on the above formula (eq6), the duty ratio and the average current detection value used are the values in the previous switching cycle and the value in the cycle before the previous one, but it is not limited to this. For example, the values in two past switching cycles selected from the switching cycles from ten switching cycles earlier than the current switching cycle to the previous switching cycle can also be used. For example, the value in the previous switching cycle and the values in the previous three switching cycles can be used, or the value in the cycle before the previous one and the values in the previous five switching cycles can be used. However, it is desirable to select two past switching cycles such that the length between the two past switching cycles is a length where the relationship between the average current value and the duty ratio in the first past switching cycle is not significantly different from the relationship between the average current value and the duty ratio in the second past switching cycle.

[0090] · As the DCDC converter to which the present disclosure is applied, it is not limited to a boost converter, and can also be a buck converter that steps down the input voltage and outputs, or a buck-boost converter having a boost function and a buck function. Even in this case, as in the above formula (eq4) corresponding to the boost converter, for the buck converter or the buck-boost converter, it is also possible to determine the coefficient information (specifically, the correction coefficient) of the independent variable and the intercept information (specifically, the offset correction value) in the mathematical formula with the duty ratio as the independent variable and the average current value as the dependent variable. Therefore, even in the buck converter or the buck-boost converter, it is possible to calculate the coefficient information and the intercept information based on the duty ratio and the average current detection values in the two past switching cycles.

[0091] In addition, as the DCDC converter to which the present disclosure is applied, it is not limited to a non-insulated converter, and can also be an insulated converter including a transformer. The transformer has a primary inductor on the input side and a secondary inductor on the output side. The insulated DCDC converter is, for example, a flyback converter, a forward converter, a push-pull converter, or a full-bridge converter, and has a switch on the primary side.

[0092] For example, in the case of a forward converter, an inductor different from the secondary inductor of the transformer (hereinafter referred to as a specific inductor) is provided on the secondary side. In the forward converter, during the ON period of the switch on the primary side, the current value flowing through the specific inductor on the secondary side gradually increases, and magnetic energy is stored in the specific inductor. In addition, during the OFF period of the switch on the primary side, the current value flowing through the specific inductor gradually decreases to 0. Thus, in one switching cycle, the time-lapse waveform of the current value flowing through the specific inductor becomes a triangular wave-like waveform and then becomes a waveform maintained at 0.

[0093] In addition, for example, in the case of a flyback converter, during the ON period of the switch on the primary side, the current value flowing through the inductor constituting the primary side of the transformer gradually increases, and magnetic energy is accumulated in the primary side inductor and the iron core of the transformer. Further, during the OFF period of the switch on the primary side, the accumulated energy is released, and the current value flowing through the primary side inductor gradually decreases to 0. Thus, in one switching cycle, the time-varying waveform of the current value flowing through the primary side inductor becomes a triangular-wave-shaped waveform and then becomes a waveform that is maintained at 0.

[0094] · The control unit and its method described in the present disclosure can also be implemented by a dedicated computer provided by configuring a processor and a memory, and the above processor is programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit described in the present disclosure and the method of this control unit can be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit described in the present disclosure and the method of this control unit can be implemented by one or more dedicated computers, and the dedicated computers are configured by a combination of a processor programmed to execute one or more functions and a memory and a processor constituted by one or more hardware logic circuits. In addition, the computer program can also be stored in a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer. Although the present disclosure has been described based on the embodiments, it should be understood that the present disclosure is not limited to the above embodiments and configurations. The present disclosure also includes various modifications and modifications within the equivalent scope. In addition, various combinations and modes, and further combinations and modes including only one element, more than one element or less than one element thereof also belong to the scope and ideological scope of the present disclosure.

Claims

1. A control device for a DCDC converter, wherein the control device (50) for the DCDC converter is applicable to a DCDC converter comprising a switch (31) and an inductor (30), The control device of the DCDC converter repeatedly stores magnetic energy in the inductor and releases magnetic energy from the inductor by switching control of the switch, thereby transforming and outputting an input voltage. The control device of the DCDC converter comprises: a current calculation unit (60) for calculating an average current value, which is a time average value of the current flowing through the inductor in one switching cycle, based on a current detection value of a current detection unit (42) for detecting the current flowing through the inductor; a duty ratio calculation unit that calculates a duty ratio of a current discontinuous mode based on a command value of the average current value; as well as a switch control unit (52, 63) for performing switch control of the switch based on the calculated duty ratio, The duty ratio calculation unit calculates relationship information (α, β) between the average current value and the duty ratio based on the duty ratio and the average current value calculated in a plurality of past switching cycles, Based on the calculated relationship information and the command value, the duty ratio in the next switching cycle is calculated.

2. The control device for a DCDC converter according to claim 1, characterized in that: The duty ratio calculation unit calculates the relationship information based on the duty ratio and the average current value calculated in a first cycle as a past switching cycle and the duty ratio and the average current value calculated in a second cycle as a past switching cycle and earlier than the first cycle, The relationship information is coefficient information (α) of the independent variable in a mathematical expression that takes the duty ratio as an independent variable and takes the average current value as a dependent variable, and intercept information (β) in the mathematical expression.

3. The control device of the DCDC converter according to claim 2, characterized in that: The duty ratio calculation unit acquires an input voltage detection value and an output voltage detection value of a voltage detection unit that detects an input voltage and an output voltage of the DCDC converter. calculating an estimated inductance value of the inductor based on the current detection value, The duty ratio in the next switching cycle is corrected based on the input voltage detection value, the output voltage detection value and the estimated inductance value in the current switching cycle and the input voltage detection value, the output voltage detection value and the estimated inductance value in the first cycle.

4. A program, the program being applicable to a DCDC converter (10, 100) comprising a switch (31), an inductor (30) and a computer (51), The program repeatedly performs storage of magnetic energy in the inductor and release of magnetic energy from the inductor by switching control of the switch, thereby transforming and outputting an input voltage of the DCDC converter. The program causes the computer to execute the following processing: A process of calculating an average current value, which is the time average of the current flowing through the inductor in one switching cycle of the current flowing through the inductor, based on the current detection value of a current detection unit (42) that detects the current flowing through the inductor; A duty ratio calculation process of calculating the duty ratio of the current discontinuous mode based on the command value of the average current value; And A process of performing switching control of the switch based on the calculated duty ratio, The duty ratio calculation process calculates relationship information (α, β) between the average current value and the duty ratio based on the duty ratio and the average current value calculated in a plurality of past switching cycles, Based on the calculated relationship information and the command value, calculate the duty ratio in the next switching cycle.

Images