Multiphase DC-DC converter

Abstract

To provide a multi-phase DC / DC converter capable of performing a synchronization control so that switching timings are not overlapped with a simple configuration.SOLUTION: A multi-phase DC / DC converter 11 comprises: a master converter 201 that is one of a plurality of DC / DC converters 20 connected in parallel with each other; slave converters 202 and 203 that are the residual DC / DC converters excluding the master converter; and control devices 222 and 223 that control a switching operation of the slave converters using the master converter as a reference. The control device controls the switching operation of each slave converter on the basis of a value of a master current Ich1 as a current flowing through an inductor L1 of the master converter so that switching timings of the plurality of DC / DC converter are not overlapped with each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The disclosure in this specification relates to a multi-phase DCDC converter.

Background Art

[0002] Patent Document 1 discloses a multi-phase DCDC converter including a plurality of DCDC converters connected in parallel. The description of the technical elements in this specification is incorporated herein by reference.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, a PWM signal delayed with respect to the PWM signal output to one of the DCDC converters is generated, and the switching timing of each DCDC converter is made different by outputting the delayed PWM signal to other DCDC converters.

[0005] The control method using a frequency synchronization signal represented by Patent Document 1 has a complicated configuration and high cost. In order to simplify the configuration and reduce the cost, it is preferable to use a control method by current feedback. However, in the case of the current feedback method, there is no PWM signal that can be a reference, and further, there is a problem that the driving frequency varies due to external factors such as an input voltage and an output voltage. From the above viewpoints, or other viewpoints not mentioned, further improvement of the multi-phase DCDC converter is required.

[0006] One of the objectives of the disclosure is to provide a multi-phase DC-DC converter that enables synchronous control to prevent switching timing overlaps with a simple configuration. [Means for solving the problem]

[0007] One of the disclosed items is a multi-phase DC-DC converter. A multiphase DC-DC converter comprising multiple DC-DC converters (20) having inductors and switches, which boost the input voltage and output it by the switching operation of the switches, wherein the multiple DC-DC converters are connected in parallel, The master converter (201), which is one of several DC-DC converters, The slave converters (202, 203) are the remaining DC-DC converters after the master converter, A control device (222, 223) that controls the switching operation of the slave converter with respect to the master converter, Equipped with, The control unit controls the switching operation of the slave converters based on the value of the master current, which is the current flowing through the inductor of the master converter, so that the switching timings of each of the multiple DC-DC converters do not overlap. death, The master converter switch turns off when the master current reaches a predetermined upper limit current value, and turns on again when the master current drops to a predetermined lower limit current value. The control unit switches on the slave converter when the master current rises and reaches a predetermined current threshold that is lower than the upper limit current value. Another disclosure is a multi-phase DC-DC converter. A multiphase DC-DC converter comprising multiple DC-DC converters (20) having inductors and switches, which boost the input voltage and output it by the switching operation of the switches, wherein the multiple DC-DC converters are connected in parallel, The master converter (201), which is one of several DC-DC converters, The slave converters (202, 203) are the remaining DC-DC converters after the master converter, A control device (222, 223) that controls the switching operation of the slave converter with respect to the master converter, Equipped with, The control unit controls the switching operation of the slave converters based on the value of the master current, which is the current flowing through the inductor of the master converter, so that the switching timings of each of the multiple DC-DC converters do not overlap. Multiple DC-DC converters include multiple slave converters. If the master converter fails, the multiple slave converters will switch independently and asynchronously.

[0008] According to the disclosed multi-phase DCDC converter, the switching timing of the slave converter is controlled based on the value of the master current. As a result, even without using a frequency synchronization signal, it is possible to perform synchronization control so that the switching timings of the plurality of DCDC converters do not overlap with each other. Therefore, it is possible to provide a multi-phase DCDC converter capable of performing synchronization control with a simple configuration so that the switching timings do not overlap.

[0009] The plurality of aspects disclosed in this specification adopt different technical means in order to achieve their respective purposes. The scope of claims and the reference numerals in parentheses described in this section exemplarily show the correspondence with the parts of the embodiments described later, and are not intended to limit the technical scope. The objects, features, and effects disclosed in this specification will become clearer by referring to the detailed description that follows and the attached drawings.

Brief Description of Drawings

[0010] [Figure 1] It is a diagram showing an ECU provided with a multi-phase DCDC converter according to the first embodiment. [Figure 2] It is a diagram showing an operation sequence. [Figure 3] It is a diagram for explaining a method of calculating a current threshold value. [Figure 4] It is a diagram showing an operation sequence in a multi-phase DCDC converter according to the second embodiment. [Figure 5] It is a diagram for explaining a method of calculating a current threshold value. [Figure 6] It is a diagram showing a reference example. [Figure 7] It is a diagram showing the configuration of a slave converter in a multi-phase DCDC converter according to the third embodiment. [Figure 8] It is a diagram for explaining a method of correcting a current threshold value. [Figure 9] It is a diagram showing a modification example. [Figure 10]In the multi-phase type DCDC converter according to the fourth embodiment, it is a flowchart showing the processing at the time of a failure. [Figure 11] It is a diagram showing a modification example. [Figure 12] It is a diagram showing a modification example.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, a plurality of embodiments will be described based on the drawings. In each embodiment, the same reference numerals may be given to corresponding components, and redundant explanations may be omitted. When only a part of the configuration is described in each embodiment, the configuration of another embodiment described previously can be applied to other parts of the said configuration. Further, not only the combinations of configurations explicitly shown in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined with each other as long as there is no problem with the combination.

[0012] (First Embodiment) First, based on FIG. 1, the schematic configuration of an ECU including a multi-phase type DCDC converter will be described. ECU is an abbreviation for Electronic Control Unit. The ECU may be referred to as an electronic control device. The

[0013] <ecu> As shown in Figure 1, the ECU 10 is equipped with a multi-phase DC-DC converter 11. The multi-phase DC-DC converter 11 is a boost DC-DC converter. The multi-phase DC-DC converter 11 is equipped with multiple DC-DC converters 20 connected in parallel to each other, as will be described later.

[0014] The ECU 10 supplies power to the load 50. The ECU 10 has the function of boosting the input voltage and supplying it to the load 50. The ECU 10 may have only the function of supplying power, or it may have the power supply function as one of several functions. The load 50 is used in mobile objects such as vehicles, aircraft, ships, construction machinery, agricultural machinery, factories, homes, etc. The ECU 10 can be installed in the above-mentioned mobile objects, factories, homes, etc. In Figure 1, for convenience, only one load 50 is shown, but the number of loads 50 to which power is supplied by the ECU 10 is not limited to one. There may be multiple loads. As an example, the ECU 10 of this embodiment is installed in a vehicle and supplies power for driving a fuel injector, which is a load 50. The fuel injected by the fuel injector may be a liquid fuel such as gasoline, or a gaseous fuel such as hydrogen.

[0015] The ECU 10 of this embodiment includes a microcontroller 12 in addition to a multi-phase DC-DC converter 11. The microcontroller 12 is a microcomputer equipped with a CPU, ROM, RAM, input / output interface, and a bus connecting them. CPU is an abbreviation for Central Processing Unit. ROM is an abbreviation for Read Only Memory. RAM is an abbreviation for Random Access Memory. ROM is a rewritable non-volatile memory that stores various programs and data. ROM is, for example, flash memory. The CPU constructs multiple functional units by executing various programs stored in ROM while utilizing the temporary storage function of RAM.

[0016] The microcontroller 12 outputs instructions for boost operation to the multiphase DC-DC converter 11. For example, the microcontroller 12 specifies a target value for the output voltage, i.e., a target voltage. The microcontroller 12 specifies a current profile, specifically an upper limit current value (peak current value). The microcontroller 12 may also specify a lower limit current value in addition to the upper limit current value as part of the current profile. In addition to the upper limit current value, the microcontroller 12 may also specify an off time between reaching the upper limit current value and the next on-time as part of the current profile. The microcontroller 12 may also specify the start, stop, or pause of the boost operation based on, for example, the vehicle status or the load status. The microcontroller 12 may also switch the number of DC-DC converters 20 to drive, i.e., the number of channels, depending on, for example, the vehicle status or the load status 50. The microcontroller 12 may also specify a channel number.

[0017] <Multiphase DC-DC converter> Next, the multiphase DC-DC converter 11 will be described based on Figure 1. The multiphase DC-DC converter 11 comprises multiple DC-DC converters 20 and a capacitor C0. The multiple DC-DC converters 20 are connected in parallel to each other. The multiple DC-DC converters 20 (boost circuits 21) are connected in parallel to each other with respect to the load 50.

[0018] As an example, the multi-phase DC-DC converter 11 shown in Figure 1 is equipped with three DC-DC converters 20. The multi-phase DC-DC converter 11 consists of one master converter 201 and two slave converters 202 and 203. The master converter 201 serves as the reference for boost control in the multiple DC-DC converters 20. The slave converters 202 and 203 perform boost control based on the master converter 201. The number of DC-DC converters 20 is sometimes referred to as the number of channels (ch) or the number of phases. In Figure 1, the master converter 201 is shown as the master (ch1), the slave converter 202 as the slave (ch2), and the slave converter 203 as the slave (ch3).

[0019] Each of the DC-DC converters 20 includes a boost circuit 21 that increases the input voltage, which is the battery voltage Vbatt, and a control device 22. The master converter 201 includes a boost circuit 211 and a control device 221. The slave converter 202 includes a boost circuit 212 and a control device 222. The slave converter 203 includes a boost circuit 213 and a control device 223.

[0020] The boost circuit 211 includes an inductor L1, a switch Q1, and a diode D1. As an example, the switch Q1 in this embodiment is an n-channel MOSFET. MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor. The switch Q1 is positioned between the power supply terminal to which the battery voltage Vbatt is input and ground. The source of the switch Q1 is connected to ground.

[0021] One terminal of inductor L1 is connected to the power supply terminal, and the other terminal is electrically connected to the drain of switch Q1 via the shunt resistor R1 described later. In other words, inductor L1 and switch Q1 are connected in series between the power supply terminal and ground, with inductor L1 as the high-side. The anode of diode D1 is connected to the drain of switch Q1, and its cathode is connected to the output terminal of master converter 201.

[0022] The boost circuit 211 also has a shunt resistor R1. The shunt resistor R1 is a resistor for detecting the master current Ich1, which is the current flowing through the inductor L1. One terminal of the shunt resistor R1 is connected to the inductor L1, and the other terminal is connected to the drain of the switch Q1. The anode of the diode D1 is connected to the connection point between the shunt resistor R1 and the switch Q1.

[0023] Boost circuits 212 and 213 have a similar configuration to boost circuit 211. Boost circuit 212 includes an inductor L2, a switch Q2, a diode D2, and a shunt resistor R2. The shunt resistor R2 is a resistor for detecting the slave current Ich2, which is the current flowing through the inductor L2. Switch Q2 is located between the power supply terminal, to which the battery voltage Vbatt is input, and ground. The source of switch Q2 is connected to ground. One terminal of inductor L2 is connected to the power supply terminal, and the other terminal is electrically connected to the drain of switch Q2 via the shunt resistor R2. The anode of diode D2 is connected to the connection point between the shunt resistor R2 and switch Q2, and its cathode is connected to the output terminal of slave converter 202.

[0024] The boost circuit 213 includes an inductor L3, a switch Q3, a diode D3, and a shunt resistor R3. The shunt resistor R3 is a resistor for detecting the slave current Ich3, which is the current flowing through the inductor L3. The switch Q3 is located between the power supply terminal, to which the battery voltage Vbatt is input, and ground. The source of the switch Q3 is connected to ground. One of the terminals of the inductor L3 is connected to the power supply terminal, and the other terminal is electrically connected to the drain of the switch Q3 via the shunt resistor R3. The anode of the diode D3 is connected to the connection point between the shunt resistor R3 and the switch Q3, and its cathode is connected to the output terminal of the slave converter 203.

[0025] Thus, each DC-DC converter 20 is equipped with a boost circuit 21 that has a common configuration. The circuit configuration of the boost circuit 21 is not limited to the example described above. For example, switches may be used instead of diodes D1, D2, and D3.

[0026] The control device 22 controls the drive of the boost circuit 21. The control device 22 controls the boost operation by controlling the drive (on drive, off drive) of switches Q1, Q2, and Q3 provided on the boost circuit 21. The control device 22 may be referred to as a control circuit, drive circuit, boost control unit, etc. As an example, the control device 22 in this embodiment controls the drive of the corresponding boost circuit 21 according to instructions from the microcontroller 12. The control device 22 obtains the target voltage of the boosted voltage Vboost and a current profile including the upper limit current value from the microcontroller 12, and controls the drive of the corresponding boost circuit 21.

[0027] The control unit 221 of the master converter 201 includes a voltage monitor unit 23, a master current monitor unit 24, and a drive unit 25. The voltage monitor unit 23 monitors the input voltage, which is the battery voltage Vbatt, and the output voltage, which is the boost voltage Vboost. The master current monitor unit 24 monitors the current flowing through the inductor L1 of the corresponding boost circuit 211, i.e., the master current Ich1. The drive unit 25 drives the switch Q1 on or off based on the instruction value from the microcontroller 12 and the monitoring results.

[0028] The control unit 222 of the slave converter 202, like the control unit 221, includes a voltage monitor unit 23, a master current monitor unit 24, and a drive unit 25. Furthermore, the control unit 222 includes a slave current monitor unit 26 and a calculation unit 27. The voltage monitor unit 23 monitors the battery voltage Vbatt and the boost voltage Vboost, respectively. The master current monitor unit 24 monitors the master current Ich1 flowing through inductor L1. The slave current monitor unit 26 monitors the slave current Ich2 flowing through inductor L2 of the corresponding boost circuit 212. The calculation unit 27 calculates a current threshold for turning on switch Q2 based on the master current Ich1 using a method described later. The drive unit 25 drives switch Q2 on or off based on the instruction value from the microcontroller 12, the monitoring results, and the calculation results.

[0029] The control unit 223 of the slave converter 203 has the same configuration as the control unit 222. In other words, the slave converters 202 and 203 have a common configuration with each other. The control unit 223 includes a voltage monitor unit 23, a master current monitor unit 24, a drive unit 25, a slave current monitor unit 26, and a calculation unit 27. The voltage monitor unit 23 monitors the battery voltage Vbatt and the boost voltage Vboost, respectively. The master current monitor unit 24 monitors the master current Ich1 flowing through the inductor L1. The slave current monitor unit 26 monitors the slave current Ich3 flowing through the inductor L3 of the corresponding boost circuit 213. The calculation unit 27 calculates a current threshold for turning on the switch Q3 based on the master current Ich1 using a method described later. The drive unit 25 drives the switch Q3 on or off based on the instruction value from the microcontroller 12, the monitoring result, and the calculation result.

[0030] Thus, the control device 221 of the master converter 201 monitors only the current (master current) flowing through the inductor of the corresponding boost circuit 21. The control devices 222 and 223 of the slave converters 202 and 203 monitor the current (slave current) flowing through the inductor L1 of the master converter 201 in addition to the current (slave current) flowing through the inductor of the corresponding boost circuit 21. The current flowing through the inductor is sometimes referred to as the boost current or charging current. An example has been shown in which the voltage monitoring unit 23 monitors the battery voltage Vbatt and the boost voltage Vboost, but it is also possible to provide separate monitoring units for the battery voltage Vbatt and the boost voltage Vboost.

[0031] Capacitor C0 is provided between the output terminals of the multiple DC-DC converters 20 and ground. Capacitor C0 stores energy to be applied to the load 50. As an example, in this embodiment, capacitor C0 stores energy to be applied to the solenoid of the fuel injector when the valve is opened. Capacitor C0 supplies a boosted voltage Vboost to the load 50. For example, an electrolytic capacitor can be used as capacitor C0. The output terminals of the boost circuits 21 of each DC-DC converter 20 are commonly connected to the positive terminal of capacitor C0. The cathodes of diodes D1, D2, and D3 are connected to the positive terminal. The negative terminal of capacitor C0 is connected to ground.

[0032] The number of DC-DC converters 20 is not particularly limited. One of the DC-DC converters 20 functions as a master converter, and the remaining ones function as slave converters. The multi-phase DC-DC converter 11 may have, for example, two DC-DC converters 20. In this case, one of the DC-DC converters 20 functions as a master converter, and the other functions as a slave converter. The multi-phase DC-DC converter 11 may have four or more DC-DC converters 20. The number of DC-DC converters 20 in the multi-phase DC-DC converter 11 can be increased or decreased depending on the load 50. For example, DC-DC converters 20 can be added later.

[0033] <Operation Sequence> Next, an example of the operation sequence of the multiphase DC-DC converter 11 will be described based on Figure 2. Figure 2 shows an example of a multiphase DC-DC converter 11 with a master converter 201 and a slave converter 202, i.e., a two-channel configuration. In this embodiment, as an example, the battery voltage Vbatt is set to 12V and the target voltage (threshold voltage) of the boost voltage Vboost is set to 65V.

[0034] The control unit 221 of the master converter 201 turns on switch Q1 when the boosted voltage Vboost falls below the target voltage (65V). In other words, the boost circuit 211 (switch Q1) starts boosting the voltage. The master current Ich1 flowing through inductor L1 rises from 0A (zero amperes) when switch Q1 is turned on. When the master current Ich1 reaches the upper limit current value Ipeak, the control unit 221 turns off switch Q1. With switch Q1 turned off, the master current Ich1 decreases. When the master current Ich1 becomes 0A, the control unit 221 turns switch Q1 on again. In this way, the master converter 201 repeatedly turns switch Q1 on and off until the boosted voltage Vboost exceeds the target voltage.

[0035] The control device 222 of the slave converter 202 calculates the current threshold Ith using the method described later at the timing of turning on switch Q1. As described later, the control device 222 acquires the battery voltage Vbatt and boost voltage Vboost at the timing of turning on switch Q1 and calculates the current threshold Ith. The current threshold Ith is a predetermined value lower than the upper limit current value Ipeak. When the master current Ich1 rises and reaches the current threshold Ith, the control device 222 turns on switch Q2. That is, the boost circuit 212 (switch Q2) starts boosting operation. Switch Q2 turns on with a delay compared to switch Q1, equal to the time it takes for the master current Ich1 to rise from 0A to the current threshold Ith.

[0036] The slave current Ich2 flowing through inductor L2 rises from 0A when switch Q2 is turned on. When the slave current Ich2 reaches the upper limit current value Ipeak, the control device 222 turns off switch Q2. With switch Q2 turned off, the slave current Ich2 decreases. At the timing to turn switch Q1 on again, the control device 222 calculates the current threshold Ith. When the master current Ich1 rises and reaches the current threshold Ith, the control device 222 turns switch Q2 on again. The slave converter 202 repeats turning switch Q2 on and off as described above until the boosted voltage Vboost exceeds the target voltage. The control device 222 calculates the current threshold Ith each time switch Q1 is turned on.

[0037] <Method for calculating current threshold> Next, the calculation method for the current threshold Ith will be explained based on Figure 3. As with Figure 2, Figure 3 describes a 2-channel multi-phase DC-DC converter 11. The upper panel of Figure 3 shows the operating waveform when the battery voltage Vbatt = 12V and the boost voltage Vboost = 12V, specifically the waveforms of the master current Ich1 and the slave current Ich2. The lower panel shows the operating waveform when the battery voltage Vbatt = 12V and the boost voltage Vboost = 60V.

[0038] As described above, the control device 222 (calculation unit 27) of the slave converter 202 calculates the current threshold Ith at the ON timing of switch Q1. The boost circuits 211 and 212 have a common configuration and the same circuit constants. The calculation unit 27 of the control device 222 calculates the current threshold Ith such that the OFF timing of switch Q2 is in opposite phase to the OFF timing of switch Q1, that is, the phase is shifted by 180 degrees.

[0039] It is known that if TPeak is the time it takes for the master current Ich1 to reach its upper limit current value Ipeak from the time the switch is turned on, and Tfall is the time it takes for the switch to return to 0A from the time it is turned off, then the relationship shown in Equation 1 holds true.

number

[0040] To set the off timing of switch Q2 to be in the opposite phase, the delay time Tdelay from when switch Q1 turns on until switch Q2 turns on is obtained by adding time Tpeak to time Tfall and dividing by 2. Rearranging using Equation 1, the delay time Tdelay can be expressed by Equation 2.

number

[0041] Here, if we linearly approximate the boost current, the relationship Tdelay:Tpeak = Idelay:Ipeak holds. Therefore, the current threshold Ith at the delay time Tdelay can be expressed by equation 3.

number

[0042] Thus, the current threshold Ith of the slave converter 202 can be calculated using the upper limit current value Ipeak, the battery voltage Vbatt during boost control, and the boost voltage Vboost. In other words, the current threshold Ith can be calculated by monitoring the battery voltage Vbatt and the boost voltage Vboost.

[0043] When the battery voltage Vbatt = 12V and the boost voltage Vboost = 12V, using the current threshold Ith calculated by equation 3, the off-timing of switch Q2 becomes out of phase with respect to the off-timing of switch Q1, as shown in the upper part of Figure 3. During the period from the off-timing to 11 of switch Q1 to the next off-timing to 12, that is, the period equal to the sum of Tpeak and Tfall, the interval between the off-timing to 2 and off-timing to 11 of switch Q2 is equal to the interval between the off-timing to 2 and off-timing to 12.

[0044] When the battery voltage Vbatt = 12V and the boost voltage Vboost = 60V, using the current threshold Ith calculated by equation 3, the off-timing of switch Q2 becomes out of phase with the off-timing of switch Q1, as shown in the lower part of Figure 3. As shown in the figure, the interval between off-timing to 2 and off-timing to 11 is equal to the interval between off-timing to 2 and off-timing to 12.

[0045] Although the operation sequence and current threshold calculation method were explained using a 2-channel multi-phase DC-DC converter 11 as an example, the method is not limited to this. It can also be applied to multi-phase DC-DC converters 11 with 3 or more channels. The control device of the slave converter calculates the current threshold Ith so that the intervals between the off-times of the multiple DC-DC converters 20 are equal during the period from when the switch Q1 of the master converter 201 is turned off until it is turned off again.

[0046] Specifically, by dividing Equation 3 by the number of DCDC converters 20 capable of driving Ipeak, i.e., the number of channels, a current threshold Ith that is evenly spaced according to the number of DCDC converters 20 can be calculated. For example, in the case of a 3-channel configuration with two slave converters 202 and 203 as shown in Figure 1, the denominator of Equation 3 should be changed from 2 to 3. For example, the control device of a slave converter may further multiply by (n-1), where n is the channel number. In other words, by multiplying (1+Vbatt / Vboost)×Ipeak by (n-1) / number of channels, a current threshold Ith corresponding to the channel number can be calculated.

[0047] For example, in a 3-channel configuration, the current threshold Ith of slave converter 202 (ch2) is (1 + Vbatt / Vboost) × Ipeak × 1 / 3. The current threshold Ith of slave converter 203 (ch3) is (1 + Vbatt / Vboost) × Ipeak × 2 / 3. In a 2-channel configuration, the current threshold Ith of slave converter 202 (ch2) is (1 + Vbatt / Vboost) × Ipeak × 1 / 2, which is shown in equation 3.

[0048] <Summary of the First Embodiment> The multi-phase DC-DC converter 11 of this embodiment employs a current feedback method as the control method. Therefore, compared to a control method using a frequency synchronization signal, it is possible to simplify the configuration and reduce costs.

[0049] In the current feedback method, there is no reference signal, such as a PWM signal, for multiple DC-DC converters. Furthermore, the drive frequency fluctuates due to external factors such as input and output voltages. In this embodiment, the switching timing of slave converters 202 and 203 is controlled based on the value of the master current Ich1 flowing through the inductor L1 of the master converter 201. This allows for synchronous control so that the switching timings of multiple DC-DC converters 20 do not overlap, even without using a frequency synchronization signal. Therefore, a multi-phase DC-DC converter 11 is provided that allows for synchronous control to prevent switching timing overlap with a simple configuration. The multi-phase DC-DC converter 11 is inexpensive and offers high output power.

[0050] Switch Q1 turns off when the master current Ich1 reaches its upper limit current value Ipeak, and turns on again when the master current Ich1 drops to a predetermined lower limit current value of 0A. In other words, switch Q1 is controlled in the same way as general current feedback. In this embodiment, the ON timing of switches Q2 and Q3 is controlled based on the value of the master current Ich1, not the values ​​of the corresponding slave currents Ich2 and Ich3. Switches Q2 and Q3 turn on when the master current Ich1 rises and reaches the corresponding current threshold Ith. Synchronous control is possible to prevent switching timing from overlapping with a simple configuration that compares the value of the master current Ich1 with the current threshold Ith. Even if the drive frequency changes due to external factors such as the battery voltage Vbatt or boost voltage Vboost, the switching timing can be controlled to prevent overlapping.

[0051] The current threshold may be stored in memory beforehand. As an example, the calculation unit 27 of the control devices 222 and 223 in this embodiment calculates the current threshold Ith based on the upper limit current value Ipeak, the battery voltage Vbatt, and the boost voltage Vboost. In this way, by shifting the phase of the switching timing, i.e., the on-timing and off-timing, in multiple DC-DC converters 20, fluctuations in the boost voltage Vboost can be suppressed compared to a configuration that controls them in phase. For example, component stress can be reduced.

[0052] The current threshold calculation may be performed only once during the boost operation period, for example, at the initial ON timing of switch Q1. As an example, the control devices 222 and 223 of this embodiment calculate the current threshold Ith each time switch Q1 of the master converter 201 is turned ON. The control devices 222 and 223 acquire the battery voltage Vbatt and boost voltage Vboost each time switch Q1 is turned ON and calculate the current threshold Ith. Therefore, even if the battery voltage Vbatt or boost voltage Vboost fluctuates, the current threshold Ith can be set according to the fluctuation. In other words, robustness can be improved.

[0053] The switching timings of each of the multiple DC-DC converters 20 do not need to be different from one another. For example, the control devices 222 and 223 in this embodiment calculate a current threshold Ith such that the intervals between the off-timings of the multiple DC-DC converters 20 are equal during the period from when the switch Q1 of the master converter 201 is turned off until it is turned off again. This further suppresses fluctuations in the boosted voltage Vboost.

[0054] <Variation> In multiple DC-DC converters 20, the control devices 22 may be connected to each other in a way that allows communication. For example, instructions from the microcontroller 12 may be transmitted to other control devices 222, 223 via the control device 221 of the master converter 201. The multi-phase DC-DC converter 11 may include a microcontroller 12. The control device 22 may provide at least some of the functions of the microcontroller 12.

[0055] The example shown includes a control device 221 for the master converter 201 comprising a voltage monitor unit 23, a master current monitor unit 24, and a drive unit 25, but is not limited to this. For example, it may further include a slave current monitor unit 26 and a calculation unit 27. In other words, the configuration of the control device 22, and consequently the configuration of the DC-DC converter 20, may be common to the master converter 201 and the slave converters 202 and 203.

[0056] (Second Embodiment) This embodiment is a modification based on the prior embodiment, and the description of the prior embodiment can be referenced. In the prior embodiment, switch Q1 was turned off when the value of the master current Ich1 became 0A (zero amperes). In other words, the lower limit current value was set to 0A. Alternatively, a lower limit current value other than 0A may be set, and switch Q1 may be turned off when the value of the master current Ich1 falls to the lower limit current value.

[0057] The configuration of the multiphase DC-DC converter 11 and ECU 10 according to this embodiment is the same as the configuration described in the prior embodiment.

[0058] <Operation Sequence> In this embodiment, as an example, the operation sequence of a 2-channel multi-phase DC-DC converter 11 will be described. Figure 4 corresponds to Figure 2.

[0059] The control unit 221 of the master converter 201 turns on switch Q1 when the boosted voltage Vboost falls below the target voltage (65V). In other words, it starts the boost operation. The master current Ich1 rises from 0A when switch Q1 is turned on. When the master current Ich1 reaches the upper limit current value Ipeak, the control unit 221 turns off switch Q1. When switch Q1 is turned off, the master current Ich1 falls. When the master current Ich1 falls to the lower limit current value Ibottom, the control unit 221 turns switch Q1 on again. The slave converter 202 repeatedly turns switch Q1 on and off until the boosted voltage Vboost exceeds the target voltage. The lower limit current value Ibottom is set between 0A and the upper limit current value Ipeak.

[0060] The control device 222 of the slave converter 202 calculates the current threshold Ith using the method described below when the switch Q1 is turned on. The current threshold Ith is current threshold Ith1 for the first time the switch is turned on, and current threshold Ith2 for the second time and beyond. The control device 222 obtains the battery voltage Vbatt and boost voltage Vboost at the time the switch Q1 is turned on and calculates the current threshold Ith. The current threshold Ith is a predetermined value lower than the upper limit current value Ipeak.

[0061] At the initial ON timing of switch Q1, the control device 222 calculates the current threshold Ith1. When the master current Ich1 rises to the current threshold Ith1 due to the ON of switch Q1, the control device 222 turns on switch Q2. When the slave current Ich2 reaches the upper limit current value Ipeak, the control device 222 turns off switch Q2. When switch Q2 is turned off, the slave current Ich2 falls. At the timing of turning switch Q1 on again, the control device 222 calculates the current threshold Ith2. When the master current Ich1 rises to the current threshold Ith2, the control device 222 turns switch Q2 on again. The slave converter 202 repeatedly turns switch Q2 on and off until the boost voltage Vboost exceeds the target voltage. The control device 222 calculates the current threshold Ith each time switch Q1 is turned on.

[0062] <Method for calculating current threshold> Next, the method for calculating the current threshold in the above-described operation sequence will be explained based on Figure 5. Here again, a 2-channel multi-phase DC-DC converter 11 will be used as an example. Figure 5 corresponds to the lower part of Figure 3. Figure 5 shows the operating waveform when the battery voltage Vbatt = 12V and the boost voltage Vboost = 60V. Similar to the previous embodiment, the boost circuits 211 and 212 have a common configuration and the same circuit constants. The calculation unit 27 of the control device 222 calculates the current threshold Ith such that the off timing of switch Q2 is in opposite phase to the off timing of switch Q1.

[0063] Here, TPeak0 is the time it takes for the master current Ich1 to rise from 0A to the upper limit current value Ipeak, and Tpeak1 is the time it takes for the current to rise from the lower limit current value Ibottom to the upper limit current value Ipeak. The time Tfall, which is the time it takes for the current to fall from the upper limit current value Ipeak to the lower limit current value Ibottom when switch Q1 is turned off, can be shown by equation 4.

number

[0064] In order to set the off timing of switch Q2 to be in the opposite phase, the delay time Tdelay from when switch Q1 turns on until switch Q2 turns on can be expressed by equation 5.

number

[0065] Here, if we linearly approximate the boost current, the current threshold Ith at the delay time Tdelay can be expressed by equation 6.

number

[0066] As shown in Figure 5, during the first switching (1st time), the master current Ich1 rises from 0A to the upper limit current value Ipeak, whereas from the second time onward, it rises from the lower limit current value Ibottom to the upper limit current value Ipeak. Therefore, in control using the upper limit current value Ipeak and the lower limit current value Ibottom, it is necessary to change the current threshold Ith between the first time and from the second time onward. The current threshold Ith1 for the first time is the value calculated by equation 6. The current threshold Ith2 for the second time onward is the value obtained by adding the lower limit current value Ibottom to the current threshold obtained by equation 6.

[0067] Thus, the current threshold Ith (Ith1, Ith2) of the slave converter 202 can be calculated using the upper limit current value Ipeak, the lower limit current value Ibottom, the battery voltage Vbatt during boost control, and the boost voltage Vboost. In other words, the current threshold Ith can be calculated by monitoring the battery voltage Vbatt and the boost voltage Vboost. As shown in Figure 5, the off-timing of switch Q2 is in opposite phase to the off-timing of switch Q1. The interval between off-timing to2 and off-timing to11 is equal to the interval between off-timing to2 and off-timing to12.

[0068] Control using an upper limit current value Ipeak and a lower limit current value Ibottom is not limited to 2 channels. It can also be applied to multi-phase DC-DC converters 11 with 3 or more channels. The control device of the slave converter calculates the current threshold Ith so that the off-timing intervals of the multiple DC-DC converters 20 are equal during the period from when the switch Q1 of the master converter 201 is turned off until it is turned off again. Similar to the configuration described in the prior embodiment, the upper limit current value Ipeak in equation 6 should be divided by the number of DC-DC converters 20, i.e., the number of channels. If there are multiple slave converters, it is good to multiply by (n-1) further, where n is the channel number. For example, by multiplying (1+Vbatt / Vboost)×Ipeak by (n-1) / number of channels, the current threshold Ith corresponding to the channel number can be calculated.

[0069] <Summary of the second embodiment> The multi-phase DC-DC converter 11 of this embodiment can achieve the same effects as the configuration described in the prior embodiment. For example, in this embodiment as well, the switching timing of the slave converters 202 and 203 is controlled based on the value of the master current Ich1. Therefore, a multi-phase DC-DC converter 11 can be provided that enables synchronous control so that the switching timings do not overlap, with a simple configuration.

[0070] Switch Q1 turns off when the master current Ich1 reaches its upper limit current value Ipeak, and turns on again when it drops to a predetermined lower limit current value that is not 0A. Switch Q1 is controlled by so-called constant current control. In this embodiment as well, the ON timing of switches Q2 and Q3 is controlled based on the value of the master current Ich1. Synchronous control is possible to prevent the switching timings from overlapping with a simple configuration that compares the value of the master current Ich1 with the current threshold Ith.

[0071] In this embodiment, the current threshold Ith is calculated based on the upper limit current value Ipeak, the lower limit current value Ibottom, the battery voltage Vbatt, and the boost voltage Vboost. By shifting the phase of the switching timings in the multiple DC-DC converters 20, fluctuations in the boost voltage Vboost can be suppressed. In this embodiment as well, the current threshold Ith is calculated each time switch Q1 is turned on. Therefore, even if the battery voltage Vbatt or boost voltage Vboost fluctuates, the current threshold Ith can be set according to the fluctuations. In this embodiment as well, the current threshold Ith is calculated so that the intervals between the off timings of the multiple DC-DC converters 20 are equal during the period from when switch Q1 is turned off until it is turned off again. This further suppresses fluctuations in the boost voltage Vboost.

[0072] (Third embodiment) This embodiment is a modification based on a prior embodiment, and the description of the prior embodiment can be referenced. In the prior embodiment, circuit variations were not considered. Instead, a configuration that can compensate for the shift in off-timing due to circuit variations may be used.

[0073] In the following explanation, we will use a 2-channel multi-phase DC-DC converter as an example. Figure 6 shows a reference example. In Figure 6, the current gradients of the master converter and the slave converter differ due to circuit variations. The slope of the slave current Ich2, shown by the dashed line in Figure 6, is the same as the slope of the master current Ich1. As an example, the slope of the slave current Ich2, shown by the solid line, is steeper than that of the dashed line. Even with the same design objective, the current gradients of the master current Ich1 and the slave current Ich2 may differ due to circuit variations, such as manufacturing variations.

[0074] When the current gradients differ in this way, the off-timing to2 of switch Q2 is shifted from a timing that is in the opposite phase to the off-timing of switch Q1. In the example shown in Figure 6, the off-timing to12 is shifted towards the off-timing to11 side between the off-timings to11 and to12 of switch Q1. The period T1 from off-timing to11 to off-timing to12 is longer than twice the period T2 from off-timing to11 to off-timing to2.

[0075] The multi-phase DC-DC converter 11 according to this embodiment is configured to correct the off-timing deviation caused by the circuit variations described above. Figure 7 shows the configuration of one of the slave converters in the multi-phase DC-DC converter 11, specifically the slave converter 202. The control device 222 of the slave converter 202 has a correction unit 28 in addition to the configuration described in the prior embodiment. The other configurations are the same as those described in the prior embodiment.

[0076] The correction unit 28 monitors whether the off-timing of the slave converters is evenly spaced during the period from when the master converter 201's switch Q1 turns off until it turns off again. The correction unit 28 determines each time whether there is a deviation in the off-timing. If there is a deviation in the off-timing of switch Q2, the correction unit 28 corrects the current threshold Ith so that the intervals become even. In this embodiment, if the above-mentioned period T1 is deviated from twice the value of period T2, the correction unit 28 corrects the current threshold Ith so that T1 = T2 × 2.

[0077] Figure 8 shows the correction result by the correction unit 28. The dashed line in Figure 8 shows the current waveform of the slave current Ich2 when there is no circuit variation. As shown in the reference example in Figure 6, if the slope of the slave current Ich2 is large and the off timing to2 is shifted to the earlier side, the correction unit 28 corrects the current threshold Ith to the side closer to the upper limit current value Ipeak, i.e., to the higher side. As a result the on timing of switch Q2 is delayed, and the off timing to2 is also delayed by the same amount. Therefore, the off timing of switch Q2 is in opposite phase to the off timing of switch Q1. In other words, the off timing intervals become uniform.

[0078] Furthermore, if the off-timing to2 is shifted to the late side due to a small slope in the slave current Ich2, the correction unit 28 corrects the current threshold Ith to move away from the upper limit current value Ipeak, i.e., to the lower side. If there are multiple slave converters, the slave converters other than slave converter 202 have the same configuration as slave converter 202.

[0079] <Summary of the third embodiment> The multi-phase DC-DC converter 11 of this embodiment can achieve the same effects as the configuration described in the prior embodiment. Furthermore, if the current gradient differs due to circuit variations and the off-timing deviates from the equal intervals, it is possible to adjust it to the equal intervals without changing the upper limit current value Ipeak. Since the upper limit current value Ipeak is not changed, component selection for the current path is easy.

[0080] <Variation> An example of correcting the current threshold Ith when there is a discrepancy in the off-timing has been shown, but it is not limited to this. For example, the upper limit current value Ipeak or the lower limit current value Ibottom may also be corrected.

[0081] The correction unit 28 corrects the upper limit current value Ipeak or the lower limit current value Ibottom so that T1 = T2 × 2 if the period T1 described above is shifted from twice the value of period T2. Figure 9 corresponds to Figure 8. The dashed line shown in Figure 9 shows the current waveform of the slave current Ich2 when there is no circuit variation. If the off timing to2 is shifted to the earlier side due to a large slope of the slave current Ich2 as shown in the reference example in Figure 6, the correction unit 28 corrects the upper limit current value Ipeak for the slave current Ich2 to the higher side. As a result, the off timing to2 of switch Q2 is delayed, and the off timing of switch Q2 is in opposite phase to the off timing of switch Q1. In other words, the off timing intervals become uniform.

[0082] Furthermore, if the slope of the slave current Ich2 is small, causing the off-timing to2 to be delayed, the correction unit 28 corrects the upper limit current value Ipeak to a lower value. This advances the off-timing to2 of switch Q2. When using the lower limit current value Ibottom for control, correcting the lower limit current value Ibottom to a higher value advances the off-timing to2, while correcting it to a lower value delays the off-timing to2.

[0083] In a configuration that corrects the current threshold Ith, if the current threshold Ith is corrected to be lower when the current gradient is small, the on-timing current value will increase. Therefore, there is a concern that switching losses will increase. In contrast, in a configuration that corrects the upper limit current value Ipeak or the lower limit current value Ibottom, the on-timing current value can be kept constant.

[0084] (Fourth Embodiment) This embodiment is a modification based on the prior embodiment, and the description of the prior embodiment can be referenced. In the prior embodiment, there was no particular mention of the case where a failure occurs in the DC-DC converter. Instead, the configuration may be such that a predetermined process is executed when a failure occurs in some of the multiple DC-DC converters.

[0085] Figure 10 is a flowchart of the boost control performed by the multiphase DC-DC converter 11 according to this embodiment. As an example, the multiphase DC-DC converter 11 has a 3-channel configuration.

[0086] As described in the prior embodiment, when the boost voltage Vboost falls below the target voltage, the multiphase DC-DC converter 11 starts boost control. First, the multiphase DC-DC converter 11 performs synchronous control using a current threshold Ith (step S101). The control devices 222 and 223 of the slave converters 202 and 203 calculate the current threshold Ith using the method shown in the prior embodiment, for example, the upper limit current value Ipeak, the battery voltage Vbatt, and the boost voltage Vboost. The control devices 222 and 223 can calculate the current threshold Ith corresponding to the channel number by multiplying (1 + Vbatt / Vboost) × Ipeak by (n-1) / number of channels. When the master current Ich1 reaches the corresponding current threshold Ith, the control devices 222 and 223 turn on switches Q2 and Q3.

[0087] Next, the multi-phase DC-DC converter 11 determines whether the boosted voltage Vboost has reached the target voltage, that is, whether the boost control has ended (step S102). If it determines that the boost control has ended, it terminates the series of processes.

[0088] If it is determined that the boost control is not yet complete, the multi-phase DC-DC converter 11 then determines whether or not a failure has occurred in one of the slave converters (step S103). Each of the control devices 22 may have a function to detect failures in the corresponding boost circuit 21, or the microcontroller 12 may have a failure detection function for each DC-DC converter 20. The microcontroller 12 may collect the failure information of the DC-DC converters 20 and transmit it to the control device 22. In a configuration where mutual communication is possible, failure information may be shared through communication between the control devices 22.

[0089] If no failure occurs in the slave converters, the multiphase DC-DC converter 11 executes the process in step S101 again. If a failure occurs in one of the slave converters, the multiphase DC-DC converter 11 reduces the number of drivable channels by 1 (step S104) and executes the process in step S101 again.

[0090] If a failure occurs in some of the multiple slave converters during the boosting period, the control device 22 of the slave converters that are not faulty calculates a current threshold Ith so that the intervals between off-timings are equal, according to the number of master converters 201 and the number of slave converters that are not faulty. For example, if slave converter 203 fails, the control device 222 of slave converter 202 determines that there are two channels of DC-DC converters 20 that can operate normally and calculates a current threshold Ith using the formula 3 described above.

[0091] <Summary of the fourth embodiment> According to the multi-phase DC-DC converter 11 of this embodiment, if one of the slave converters fails, the system switches from 3-channel drive to 2-channel drive. At this time, the current threshold Ith is also switched from the threshold for 3 channels to the threshold for 2 channels. Therefore, even if a failure occurs in some of the slave converters, the effects described in the previous embodiment can be achieved. Although a 3-channel example has been shown, the same effects can be achieved in configurations with 4 or more channels.

[0092] <Variation> The example shown involves executing a predetermined process when the slave converter fails, but the configuration may also be such that the predetermined process is executed when the master converter fails.

[0093] For example, as shown in Figure 11, if the master converter 201 fails, one of the slave converters may function as the master converter. The processes in steps S201 and S202 shown in Figure 11 are the same as the processes in steps S101 and S102 shown in Figure 10. If it is determined in step S202 that the boost control is not yet complete, the multiphase DC-DC converter 11 determines whether or not a failure has occurred in the master converter 201 (step S203). If the master converter 201 has not failed, the multiphase DC-DC converter 11 executes the process in step S101 again. If the master converter 201 has failed, the multiphase DC-DC converter 11 makes one of the slave converters function as the master converter and executes a process to reduce the number of drivable channels by 1 (step S204), and then executes the process in step S101 again.

[0094] As a result of the processing in step S204, in a 3-channel configuration, for example, the slave converter 202 functions as the master converter. The control device 223 of the slave converter 203 determines that there are 2 channels of DC-DC converter 20 that can operate normally, and controls the drive of switch Q3 using the current threshold Ith calculated by equation 3.

[0095] For example, as shown in Figure 12, if the master converter 201 fails, the control may be switched to asynchronous control. The processes in steps S301, S302, and S303 shown in Figure 12 are the same as the processes in steps S201, S202, and S203 shown in Figure 11. If it is determined in step S203 that there is no failure in the master converter 201, the multiphase DC-DC converter 11 executes the process in step S101 again. If the master converter 201 fails, the multiphase DC-DC converter 11 switches from synchronous control using the current threshold Ith to asynchronous control and executes (step S304). As a result, each of the multiple slave converters switches individually as a single-phase DC-DC converter 20.

[0096] After step S304, it is determined whether the boost control has finished (step S305). If the boost control has finished, the series of processes is terminated. If the boost control has not finished, the process in step S304 is executed again.

[0097] (Other embodiments) The disclosures in this specification and drawings are not limited to the exemplary embodiments. The disclosures include the exemplary embodiments and variations thereof by those skilled in the art. For example, the disclosures are not limited to combinations of parts and / or elements shown in the embodiments. The disclosures are implementable in a variety of combinations. The disclosures may have additional parts that can be added to the embodiments. The disclosures include those in which parts and / or elements of the embodiments have been omitted. The disclosures include substitutions or combinations of parts and / or elements between one embodiment and another. The scope of the disclosed technical areas is not limited to the descriptions of the embodiments. Some of the scope of the disclosed technical areas are indicated by the claims and should be understood to include all modifications within the meaning and scope equivalent to the claims.

[0098] The disclosures in the specification and drawings are not limited by the claims. The disclosures in the specification and drawings encompass the technical ideas described in the claims and extend to a wider and more diverse range of technical ideas than those described in the claims. Therefore, a variety of technical ideas can be extracted from the disclosures in the specification and drawings without being bound by the claims.

[0099] When an element or layer is referred to as “on top of,” “connected to,” “connected to,” or “joined,” it may be directly on top of, connected to, connected to, or joined to another element or layer, and there may also be an intervening element or layer. In contrast, when an element is referred to as “directly on top of,” “directly connected to,” “directly connected to,” or “directly joined to” another element or layer, there is no intervening element or layer. Other words used to describe relationships between elements should be interpreted in a similar manner (e.g., “between” vs. “directly between,” “adjacent” vs. “directly adjacent,” etc.). As used in this specification, the term “and / or” includes any combination with respect to one or more of the enumerated items relating to the relationship, and all combinations thereof. [Explanation of Symbols]

[0100] 10…ECU, 11…Multiphase DC-DC converter, 12…Microcontroller, 20…DC-DC converter, 201…Master converter, 202,203…Slave converter, 21,211,212,213…Boost circuit, 22,221,222,223…Control device, 23…Voltage monitor unit, 24…Master current monitor unit, 25…Drive unit, 26…Slave current monitor unit, 27…Calculation unit, 28…Correction unit, 50…Load, C0…Capacitor, D1,D2,D3…Diode, L1,L2,L3…Inductor, Q1,Q2,Q3…Switch, R1,R2,R3…Shunt resistor< / ecu>

Claims

1. A multiphase DC-DC converter comprising a plurality of DC-DC converters (20) having inductors and switches, which boost the input voltage and output it by the switching operation of the switches, wherein the plurality of DC-DC converters are connected in parallel, A master converter (201), which is one of the multiple DCDC converters, The slave converters (202, 203), which are the remaining DCDC converters after removing the master converter, A control device (222, 223) controls the switching operation of the slave converter with respect to the master converter, Equipped with, The control device controls the switching operation of the slave converters based on the value of the master current, which is the current flowing through the inductor of the master converter, so that the switching timings of each of the multiple DCDC converters do not overlap. The switch of the master converter turns off when the master current reaches a predetermined upper limit current value, and turns on again when the master current drops to a predetermined lower limit current value. The control device is a multi-phase DC-DC converter that turns on the switch of the slave converter when the master current rises and reaches a predetermined current threshold that is lower than the upper limit current value.

2. The control device includes a voltage monitor unit (23) that monitors the input voltage and output voltage, a master current monitor unit (24) that monitors the master current, a calculation unit (27) that calculates the switching timing of the slave converter, and a drive unit (25) that drives the switch of the slave converter. The calculation unit calculates the current threshold value based on the upper limit current value, or the upper limit current value and the lower limit current value, the input voltage, and the output voltage. The multiphase DC-DC converter according to claim 1, wherein the drive unit turns on the switch of the slave converter when the master current reaches the current threshold.

3. The multiphase DC-DC converter according to claim 2, wherein the control device calculates the current threshold each time the switch of the master converter is turned on.

4. The multiphase DC-DC converter according to claim 2 or 3, wherein the control device calculates the current threshold so that the intervals between the off timings of the multiple DC-DC converters are equal during the period from when the switch of the master converter is turned off until it is turned off again.

5. The multiphase DC-DC converter according to claim 4, further comprising a correction unit (28) that monitors whether the off timings of the slave converters are evenly spaced during the period from when the switch of the master converter is turned off until it is turned off again, and corrects the current threshold to make the timings even if a deviation occurs.

6. The multiphase DC-DC converter according to claim 4, further comprising a correction unit (28) that monitors whether the off timing of the slave converter is evenly spaced during the period from when the switch of the master converter is turned off until it is turned off again, and corrects the upper limit current value or the lower limit current value to make the timing even if a deviation occurs.

7. The multiple DCDC converters include the multiple slave converters, If some of the multiple slave converters fail, the control device calculates the current threshold so that the intervals between off-timings are equal according to the number of master converters and the number of slave converters that have not failed, according to claim 1, a multi-phase DC-DC converter.

8. A multiphase DC-DC converter comprising a plurality of DC-DC converters (20) having inductors and switches, which boost the input voltage and output it by the switching operation of the switches, wherein the plurality of DC-DC converters are connected in parallel, A master converter (201), which is one of the multiple DCDC converters, The slave converters (202, 203), which are the remaining DCDC converters after removing the master converter, A control device (222, 223) controls the switching operation of the slave converter with respect to the master converter, Equipped with, The control device controls the switching operation of the slave converters based on the value of the master current, which is the current flowing through the inductor of the master converter, so that the switching timings of each of the multiple DCDC converters do not overlap. The multiple DCDC converters include the multiple slave converters, A multi-phase DC-DC converter in which, if the master converter fails, the multiple slave converters switch independently and asynchronously.

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