JP2022045199A - Control device for dc-dc converter - Google Patents

Abstract

To provide a control device for a DC-DC converter capable of suppressing fluctuations in output power of a power source.SOLUTION: A control device 50 is applied to a DC-DC converter including a first half-bridge circuit having an input-side switch, a second half-bridge circuit having an output-side switch, and a reactor connecting the first and second half-bridge circuits. The control device 50 includes a first control unit 60 for performing switching control of the input-side switch based on an input voltage, a second control unit 70 for calculating a second duty ratio Duty2 of the output-side switch for controlling power supplied from a power source to a power supply object to be target power P*, and a reduction factor calculation unit 63 that causes the first control unit 60 to calculate a third duty ratio Duty3 when a target current IL* of the reactor determined based on the target power P* is less than a predetermined current value determined based on a minimum value Duty2min of a range that the second duty ratio Duty2 can take.SELECTED DRAWING: Figure 6

Description

The present invention relates to a control device for a DCDC converter.

Conventionally, for example, as described in Patent Document 1, a DCDC converter that transforms a voltage input from a power source and outputs it to a power supply target is known. The DCDC converter connects a first half-bridge circuit having an input side switch on the upper arm side, a second half bridge circuit having an output side switch on the lower arm side, and a first half bridge circuit and a second half bridge circuit. It is equipped with a reactor.

Japanese Unexamined Patent Publication No. 2018-98973

The DCDC converter performs switching control of the input side switch based on the input voltage from the power supply to the DCDC converter. Further, the DCDC converter calculates the on-time of the output-side switch for controlling the power supplied from the power supply to the power supply target to the target power, and performs switching control of the output-side switch based on the calculated on-time.

The inventor of the present application has found that the following problems occur in the above-mentioned control.

When the output side switch is driven by the minimum value in the range that the on-time can take, the output power of the power supply is set as the predetermined power. Therefore, when the target power is less than the predetermined power, there arises a problem that the output power of the power supply cannot be reduced to the target power only by the control by the on-time.

In order to deal with this problem, it is conceivable to carry out an intermittent operation. In the intermittent operation, the DCDC converter turns on and off the input side switch and the output side switch only in one switching cycle out of a plurality of switching cycles, and the power is supplied from the power supply. The power supplied to the power supply is set to the predetermined power supply. On the other hand, the DCDC converter turns off the input side switch and the output side switch in the remaining switching cycle, and suspends the power output. As a result, the power supplied from the power supply to the power supply target is reduced to the target power. However, in this case, there is a concern that the output power of the power source will fluctuate greatly. When the fluctuation becomes large, for example, during the period when the power supply is temporarily stopped, the power supply becomes a high potential state, and the deterioration of the power supply may be accelerated.

The present invention has been made in view of the above circumstances, and a main object thereof is to provide a control device for a DCDC converter capable of suppressing fluctuations in the output power of a power source.

The present invention comprises a first half-bridge circuit having an input-side switch on the upper arm side, a second half-bridge circuit having an output-side switch on the lower arm side, and the first half-bridge circuit and the second half-bridge circuit. A DCDC converter control device that is applied to a DCDC converter that includes a reactor to be connected and that transforms the input voltage input from the power supply and outputs it to the power supply target by switching and controlling the input side switch and the output side switch. In order to control the first control unit that performs the switching control of the input side switch and the power supplied from the power supply to the power supply target to the target power based on the input voltage from the power supply to the DCDC converter. The on-time of the output-side switch is calculated, and based on the calculated on-time, it is determined based on the second control unit that performs the switching control of the output-side switch and the minimum value in the range in which the on-time can be taken. When the target power is smaller than the predetermined power, the reduction unit is provided to reduce the output power of the power supply without shortening the on-time.

According to the present invention, when the target power is smaller than the predetermined power determined based on the minimum value in the range in which the on-time can be taken, the reduction process is performed without shortening the on-time. As a result, the execution of intermittent operation is suppressed while reducing the power supplied from the power source to the power supply target to the target power. As a result, fluctuations in the output power of the power source can be suppressed.

The overall block diagram of the power supply system which concerns on 1st Embodiment. A functional block diagram showing switching control in normal mode. A time chart showing an example of switching control in the normal mode. The time chart which shows the switching control of the comparative example 1. The time chart which shows the switching control of the comparative example 2. A functional block diagram showing switching control in low output mode. Correspondence table showing the relationship between the reduction coefficient and each parameter. A time chart showing an example of switching control in a low output mode. A flowchart showing a procedure of processing performed by a control device. The flowchart which shows the processing procedure of the low output mode which concerns on 2nd Embodiment. The overall block diagram of the power supply system which concerns on 3rd Embodiment.

<First Embodiment>
Hereinafter, the first embodiment in which the control device of the DCDC converter according to the present invention is embodied will be described with reference to the drawings.

As shown in FIG. 1, the power supply system 100 includes a DCDC converter 10, a power supply 11, and an electric load 12 as a “power supply target”. The DCDC converter 10 transforms the voltage input from the power supply 11 and supplies it to the electric load 12. In this embodiment, the power source 11 is a fuel cell. The power supply target is not limited to the electric load 12, and may be, for example, a storage battery.

The DCDC converter 10 is a buck-boost chopper circuit, and includes first to fourth switches Q1 to Q4 and a reactor 31. In this embodiment, each switch Q1 to Q4 is an IGBT. Freewheel diodes (hereinafter, simply diodes) are connected in antiparallel to each switch Q1 to Q4.

The emitter, which is the low potential side terminal of the first switch Q1, is connected to the collector, which is the high potential side terminal of the second switch Q2, and the first end of the reactor 31. The emitter of the third switch Q3 and the collector of the fourth switch Q4 are connected to the second end of the reactor 31. The emitter of the second switch Q2 is connected to the emitter of the fourth switch Q4. In the DCDC converter 10, the first switch Q1 and the second switch Q2 form the first half-bridge circuit 32, and the first switch Q1 corresponds to the "input side switch". Further, the third switch Q3 and the fourth switch Q4 form the second half bridge circuit 33, and the fourth switch Q4 corresponds to the "output side switch".

The positive electrode terminal of the power supply 11 and the collector of the first switch Q1 are connected by the first high potential side path 21H, and the negative electrode terminal of the power supply 11 and the emitter of the second switch Q2 are connected by the first low potential side path 21L. Has been done. Further, the positive electrode terminal of the electric load 12 and the collector of the third switch Q3 are connected by the second high potential side path 22H, and the negative electrode terminal of the electric load 12 and the emitter of the fourth switch Q4 are on the second low potential side. It is connected by the path 22L.

The power supply system 100 includes an input voltage sensor 41, an output voltage sensor 42, and a current sensor 43. The input voltage sensor 41 detects the potential difference (specifically, the input voltage from the power supply 11) between the first high potential side path 21H and the first low potential side path 21L. The output voltage sensor 42 detects the potential difference (specifically, the output voltage to the electric load 12) between the second high potential side path 22H and the second low potential side path 22L. The current sensor 43 detects the energizing current of the reactor 31. The detected values of the sensors 41 to 43 are input to the control device 50 included in the power supply system 100.

The control device 50 performs switching control of each switch Q1 to Q4 based on the detected values of the sensors 41 to 43, thereby transforming the input voltage of the power supply 11 and outputting it to the electric load 12. In switching control, one of the first and second switches Q1 and Q2 is turned on and the other is turned off. Further, one of the third and fourth switches Q3 and Q4 is turned on, and the other is turned off. In the present embodiment, the switching cycles of the switches Q1 to Q4 are set to the same switching cycles.

The control device 50 has a target input voltage Vin * of the DCDC converter 10, a target output voltage Vout * of the DCDC converter 10, and a target power P * which is a target value of the power supplied from the power supply 11 to the electric load 12 from the upper ECU 51. Is entered.

The control device 50 sets the target current IL * of the reactor 31 based on the target power P * of the power supply 11. The control device 50 performs switching control in the normal mode or switching control in the low output mode in which the output power P of the power supply 11 is lower than that in the normal mode, depending on the value of the target current IL *.

The function provided by the control device 50 can be provided by, for example, software recorded in a substantive memory device, a computer that implements the software, hardware, or a combination thereof.

FIG. 2 is a functional block diagram showing switching control in a normal mode. The control device 50 includes a first control unit 60 and a second control unit 70. In the normal mode, the first control unit 60 performs voltage control for controlling the first and second switches Q1 and Q2 based on the target input voltage Vin * and the detection voltage Voutr of the output voltage sensor 42. On the other hand, the second control unit 70 implements power control for controlling the third and fourth switches Q3 and Q4 in order to control the power P supplied from the power source 11 to the electric load 12 to the target power P *. Hereinafter, the operation of stepping down the input voltage of the DCDC converter 10 by the first half-bridge circuit 32, boosting the stepped-down voltage by the second half-bridge circuit 33, and outputting the step-down voltage to the electric load 12 will be described.

The first control unit 60 includes a voltage ratio calculation unit 61 and a first on-time calculation unit 62. The voltage ratio calculation unit 61 outputs the voltage ratio (step-down ratio) obtained by dividing the detection voltage Voutr of the output voltage sensor 42 by the target input voltage Vin * to the first on-time calculation unit 62. The first on-time calculation unit 62 calculates the first duty ratio duty 1 by multiplying the voltage ratio calculated by the voltage ratio calculation unit 61 by a predetermined coefficient K. Here, the coefficient K is a real number from 0 to 1, and in the present embodiment, it is set to a value larger than 0.5 and less than 1 (for example, 0.95). The first duty ratio Duty1 is a value that determines the ratio of the on-time of the first switch Q1 and the ratio of the off-time of the second switch Q2 in one switching cycle Tsw.

The second control unit 70 includes a deviation calculation unit 71 and a feedback control unit 72. The target current IL * of the reactor 31 is input to the deviation calculation unit 71. Here, the target current IL * is calculated by dividing the target power P * by the voltage applied to the reactor 31 (for example, Vin ** × Duty1). The deviation calculation unit 71 calculates the current deviation ΔIL by subtracting the detected current ILr of the current sensor 43 from the target current IL * of the reactor 31. The feedback control unit 72 calculates the second duty ratio Duty 2 as an operation amount for feeding back the current deviation ΔIL calculated by the deviation calculation unit 71 to 0. Here, the second duty ratio Duty2 is a value that determines the ratio of the on-time of the fourth switch Q4 and the ratio of the off-time of the third switch Q3 in one switching cycle Tsw.

FIG. 3 shows an example of switching control in the normal mode. In FIG. 3, (a) shows the operating state of the first switch Q1, (b) shows the operating state of the fourth switch Q4, and (c) shows the transition of the detected current ILr of the current sensor 43. The state in which the operating state of the first switch Q1 is reversed is the operating state of the second switch Q2. The state in which the operating state of the fourth switch Q4 is reversed is the operating state of the third switch Q3.

In the normal mode, the first switch Q1 is turned on and the second switch Q2 is turned off for a period determined by the first duty ratio Duty1 in one switching cycle Tsw. Further, the fourth switch Q4 is turned on and the third switch Q3 is turned off for a period determined by the second duty ratio Duty2 in one switching cycle Tsw. As a result, the first period T1 to the third period T3 appear in one switching cycle Tsw.

In the first period T1, the first and fourth switches Q1 and Q4 are turned on, and the second and third switches Q2 and Q3 are turned off. As a result, current is applied to the path including the positive electrode terminal of the power supply 11, the first high potential side path 21H, the first switch Q1, the reactor 31, the fourth switch Q4, the second low potential side path 22L, and the negative electrode terminal of the electric load 12. It flows. In this case, the detected current ILr of the current sensor 43 gradually increases.

In the second period T2, the first and third switches Q1 and Q3 are turned on, and the second and fourth switches Q2 and Q4 are turned off. As a result, the path including the positive electrode terminal of the power supply 11, the first high potential side path 21H, the first switch Q1, the reactor 31, the diode of the third switch Q3, the second high potential side path 22H, and the positive electrode terminal of the electric load 12 Current flows. In this case, the detected current ILr of the current sensor 43 gradually increases.

Here, the rate of increase of the detected current ILr of the current sensor 43 in the second period T2 is smaller than the rate of increase of the detected current ILr of the current sensor 43 in the first period T1. This is because the voltage difference across the reactor 31 in the second period T2 is smaller than the voltage difference across the reactor 31 in the first period T1. In the present embodiment, the first and second periods T1 and T2 correspond to the "first on time", and the second period T2 corresponds to the "second on time".

In the third period T3, the second and third switches Q2 and Q3 are turned on, and the first and fourth switches Q1 and Q4 are turned off. As a result, current is applied to the path including the negative electrode terminal of the power supply 11, the first low potential side path 21L, the second switch Q2, the reactor 31, the third switch Q3, the second high potential side path 22H, and the positive electrode terminal of the electric load 12. It flows. In this case, the detected current ILr of the current sensor 43 gradually decreases.

By adjusting the second duty ratio Duty2 of the second control unit 70, the average current Iave flowing through the reactor 31 in one switching cycle Tsw is controlled by the target current IL *. As a result, the electric power P supplied from the power source 11 to the electric load 12 is also controlled to the target electric power P *.

Here, only the process shown in FIG. 2 causes the problem described below. This problem will be described with reference to FIGS. 4 and 5.

FIG. 4 shows Comparative Example 1 of switching control in a light load state in which the target current IL * is set to be less than a predetermined current value Imin. In Comparative Example 1, control in the normal mode is performed. FIGS. 4 (a) to 4 (c) correspond to FIGS. 3 (a) to 3 (c) above.

When the lower limit value Duty2min in the range where the second duty ratio Duty2 can be taken is set, the average current Iave of the reactor 31 is set to the predetermined current value Imin. In the light load state, a target current IL * smaller than the predetermined current value Imin is set. In this embodiment, the value obtained by multiplying the predetermined current value Imin by Vin ** Duty1 corresponds to the "predetermined power".

The second control unit 70 reduces the second duty ratio Duty 2 to the lower limit value Duty 2 min in order to reduce the average current Iave of the reactor 31 to the target current IL *. However, since the average current Iave of the reactor 31 is reduced only to a predetermined current value Imin, there arises a problem that the average current IL * cannot be reduced to a target current IL * smaller than the predetermined current value Imin.

FIG. 5 shows Comparative Example 2 of switching control in a light load state. In Comparative Example 2, an intermittent operation is performed in order to deal with the above-mentioned problem. FIGS. 5 (a) to 5 (c) correspond to FIGS. 3 (a) to 3 (c) above.

In the intermittent operation of Comparative Example 2, in one switching cycle Tsw out of three switching cycles 3Tsw, a period in which the first switch Q1 is turned on and the second switch Q2 is turned off, and a period in which the fourth switch Q4 is turned on and the third switch Q3 is turned on. There is a period to turn off. During this period, predetermined power is supplied from the power supply 11. On the other hand, in the remaining switching cycle, the first to fourth switches Q1 to Q4 are turned off. During this period, the power supply from the power source 11 is temporarily stopped. As a result, the average current Iave of the reactor 31 is reduced to the target current IL * smaller than the predetermined current value Imin. However, in this case, there is a concern that the fluctuation of the output power P of the power supply 11 becomes large. When the fluctuation of the output power P of the power supply 11 becomes large, the power supply 11 may be in a high potential state during the period when the first to fourth switches Q1 to Q4 are turned off. This may accelerate the deterioration of the power supply 11.

Therefore, in the present embodiment, in the light load state, the switching control in the low output mode shown in FIG. 6 is implemented instead of the control shown in FIG. In the low output mode, in addition to the power control performed by the second control unit 70, the power control is also performed by the first control unit 60.

FIG. 6 is a functional block diagram showing switching control in the low output mode. In FIG. 6, the configurations shown in FIG. 2 above are designated by the same reference numerals for convenience.

The control performed by the second control unit 70 in the low output mode is the same as the control performed by the second control unit 70 in the normal mode. Therefore, in the light load state, the second duty ratio Duty2 is set to the lower limit value Duty2min.

The first control unit 60 includes a reduction coefficient calculation unit 63. The reduction coefficient calculation unit 63 calculates the reduction coefficient f based on the target power P *, the target output voltage Vout *, and the target input voltage Vin * of the power supply 11. Here, the reduction coefficient f is a real number from 0 to 1, and is calculated to be smaller than the coefficient K shown in FIG. The reduction coefficient f is related to at least one of the target power P *, the target output voltage Vout *, and the target input voltage Vin * of the power supply 11, and is based on the map information or mathematical formula information in which the reduction coefficient f is defined. It may be calculated. In the present embodiment, the reduction coefficient f is calculated based on the target power P *, the target output voltage Vout *, and the target input voltage Vin * of the power supply 11.

Specifically, the reduction coefficient f is a value calculated to reduce the energizing current of the reactor 31 from the predetermined current value Imin to the target current IL *, and as shown in FIG. 7, the target power P * of the power supply 11 and the target. It has a correspondence relationship with the output voltage Vout * and the target input voltage Vin *. The larger the target power P * of the power source 11, the larger the reduction coefficient f is calculated. This is because the larger the target power P * is, the larger the target current IL * is set. The larger the target output voltage Vout *, the larger the reduction coefficient f is calculated. This is because the larger the target output voltage Vout * is, the smaller the predetermined current value Imin is. The larger the target input voltage Vin *, the smaller the reduction coefficient f is calculated. This is because the larger the target input voltage Vin *, the larger the predetermined current value Imin.

The first on-time calculation unit 62 calculates the third duty ratio Duty 3 by multiplying the voltage ratio calculated by the voltage ratio calculation unit 61 by the reduction coefficient f. The third duty ratio Duty3 is a value that determines the ratio of the on-time of the first switch Q1 and the ratio of the off-time of the second switch Q2 in one switching cycle Tsw, similarly to the first duty ratio Duty1. In the present embodiment, the first on-time calculation unit 62 and the reduction coefficient calculation unit 63 correspond to the “reduction unit”, and multiplying the voltage ratio by the reduction coefficient f corresponds to the “reduction process”.

FIG. 8 shows an example of switching control in the low output mode. 8 (a) to 8 (c) correspond to FIGS. 3 (a) to 3 (c) above. In FIG. 8, the configurations shown in FIG. 3 above are designated by the same reference numerals for convenience.

In the low output mode, the first switch Q1 is turned on and the second switch Q2 is turned off for a period determined by the third duty ratio Duty3 in one switching cycle Tsw. Since the reduction coefficient f is smaller than the coefficient K, the period determined by the third duty ratio Duty3 in one switching period Tsw is shorter than the period determined by the first duty ratio Duty1. Therefore, the first and second periods T1 and T2, which are the periods in which the energizing current of the reactor 31 gradually increases, are reduced as compared with the normal mode. As a result, the average current Iave of the reactor 31 can be reduced to a target current IL * smaller than the predetermined current value Imin. Therefore, the output power P of the power supply 11 is also reduced to the target power P *.

FIG. 9 shows a procedure of processing performed by the control device 50. This process is repeatedly executed at a predetermined cycle.

In step S10, it is determined whether or not the target current IL * of the reactor 31 is less than the predetermined current value Imin.

If a negative determination is made in step S10, it is determined that the load is not light, and the process proceeds to step S11. In step S11, switching control in the normal mode is performed. In the normal mode, voltage control by the first control unit 60 and power control by the second control unit 70 are performed.

On the other hand, if an affirmative determination is made in step S10, it is determined that the load is light, and the process proceeds to step S12. In step S12, the low output mode is set. In the low output mode, in addition to the power control performed by the second control unit 70, the first control unit 60 also performs power control by controlling the third duty ratio Duty 3.

According to the present embodiment described in detail above, the following effects can be obtained.

When it is determined that the load is light, switching control in the low output mode is performed. As a result, the average current Iave of the reactor 31 can be reduced to the target current IL * without performing the intermittent operation. Therefore, it is possible to suppress fluctuations in the output power P of the power source 11 while reducing the output power P of the power source 11, and thus it is possible to suppress deterioration of the power source 11.

In the low output mode, a reduction coefficient f smaller than the coefficient K in the normal mode is calculated. As a result, the period during which the energization current of the reactor 31 gradually increases is reduced as compared with the normal mode. Therefore, the average current Iave of the reactor 31 can be accurately reduced to the target current IL *, which is less than the predetermined current value Imin. As a result, the output power P of the power supply 11 can be accurately reduced.

In the low output mode, the reduction coefficient f is calculated based on the target power P *, the target output voltage Vout *, and the target input voltage Vin *. As a result, in a state where the second duty ratio Duty2 is controlled to its lower limit value Duty2min, the third duty ratio Duty3 required to reduce the average current Iave of the reactor 31 to the target current IL * can be accurately calculated. can.

<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In the first embodiment, the reduction coefficient f is calculated by the reduction coefficient calculation unit 63 in the low output mode, but in the present embodiment, the reduction coefficient f is calculated by the process shown in FIG. 10 in the low output mode.

FIG. 10 shows a processing procedure of the low output mode corresponding to step S12 of FIG. In step S20, it is determined whether or not the output power P of the power supply 11 is larger than the target power P *. If an affirmative determination is made in step S20, the process proceeds to step S21.

In step S21, the reduction coefficient f is reduced by a predetermined value. In the following step S22, the third duty ratio Duty 3 is calculated using the reduced reduction coefficient f. In the first half-bridge circuit 32, switching control is performed by the reduced third duty ratio Duty3. After that, the process returns to step S20 again. Therefore, the reduction coefficient f is gradually reduced in step S21 until the output power P of the power supply 11 becomes equal to or less than the target power P * in step S20. In the present embodiment, step S21 and the first on-time calculation unit 62 correspond to the “reduction unit”, and step S22 corresponds to the “reduction process”.

Also in this embodiment, the same effect as that of the first embodiment can be obtained.

<Third Embodiment>
Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In the third embodiment, as shown in FIG. 11, the power supply system 100 includes an oxygen supply unit 80, and as a reduction process, the oxygen supply amount is replaced with the process of multiplying the voltage ratio in FIG. 6 by the reduction coefficient f. A process for reducing M is performed.

The oxygen supply unit 80 supplies oxygen to the power source 11 which is a fuel cell. The power source 11 generates electricity by reacting oxygen supplied from the oxygen supply unit 80 with a fuel such as hydrogen gas. Therefore, the more oxygen supplied from the oxygen supply unit 80, the larger the output power P of the power supply 11.

The control device 50 is connected to the oxygen supply unit 80, and controls the oxygen supply amount M supplied by the oxygen supply unit 80 to the power supply 11.

In the present embodiment, the process shown in FIG. 2 is executed in each of the normal mode and the low output mode, and the process shown in FIG. 6 is not executed. Of the processes shown in FIG. 9 that are executed by the control device 50, the process in step S12 has been changed. Specifically, in step S12, as the low output mode process, a process of reducing the oxygen supply amount M from the oxygen supply amount M in the normal mode is performed. As a result, the output power P of the power supply 11 can be accurately reduced without performing the intermittent operation. Therefore, the fluctuation of the output power P of the power supply 11 can be suppressed, and eventually the deterioration of the power supply 11 can be suppressed. In the present embodiment, step S12 corresponds to the "reduction unit" and the "reduction process".

<Other embodiments>
In addition, each of the above-mentioned embodiments may be changed and carried out as follows.

-The power source 11 is not limited to a fuel cell, but may be, for example, a storage battery (specifically, a secondary battery).

The switch constituting the DCDC converter 10 is not limited to the IGBT, and may be, for example, an N-channel MOSFET having a body diode.

In the first to third embodiments, instead of the configuration in which the upper and lower arms of the first half bridge circuit 32 are provided with switches, a configuration in which a switch is provided on the upper arm side and a rectifying element may be provided on the lower arm side may be used. Here, the rectifying element may be any as long as it allows the flow of current in the direction from the first low potential side path 21L toward the first end of the reactor 31, and is, for example, a diode.

In the first to third embodiments, instead of the configuration in which the upper and lower arms of the second half bridge circuit 33 are provided with switches, a configuration in which a rectifying element is provided on the upper arm side and a switch is provided on the lower arm side may be used.

In the first to third embodiments, when it is determined that the load is light, an intermittent operation may be performed in addition to the reduction process. Even in this case, the number of times the intermittent operation is performed can be reduced by performing the reduction process during several switching cycles. Therefore, the fluctuation of the output power P of the power supply 11 can be suppressed, and eventually the deterioration of the power supply 11 can be suppressed.

-In step S10 of the first embodiment, it is determined whether or not the target current IL * of the reactor 31 is less than the predetermined current value Imin, but the determination as to whether or not it is in a light load state is not limited to this. For example, it may be determined whether or not the target power P * is less than the predetermined power Pmin. Here, the predetermined power Pmin is, for example, a value obtained by multiplying the predetermined current value Imin by Vin ** Duty1.

-In step S20 of the second embodiment, instead of determining whether the output power P of the power supply 11 is larger than the target power P *, the difference between the output power P of the power supply 11 and the target power P * is greater than a predetermined value. It may be determined whether it is large or not. If the difference between the output power P of the power source 11 and the target power P * is larger than a predetermined value, the process proceeds to step S21. On the other hand, when the difference between the output power P of the power source 11 and the target power P * is equal to or less than a predetermined value, this process ends. As a result, the reduction coefficient f is gradually reduced until the difference between the output power P of the power source 11 and the target power P * becomes a predetermined value or less.

• In FIGS. 2 and 6 above, the target power P * may be input to the deviation calculation unit 71 in place of the target current IL * of the reactor 31. The deviation calculation unit 71 calculates the power deviation ΔP by subtracting the power P supplied from the power source 11 to the electric load 12 from the target power P *. The feedback control unit 72 calculates the second duty ratio Duty 2 as an operation amount for feeding back the power deviation ΔP calculated by the deviation calculation unit 71 to 0.

-In FIGS. 2 and 6, the detection voltage Vinr of the input voltage sensor 41 may be input to the voltage ratio calculation unit 61 instead of the target input voltage Vin *.

In FIGS. 2 and 6, the target output voltage Vout * may be input to the voltage ratio calculation unit 61 instead of the detection voltage Voutr of the output voltage sensor 42.

10 ... DCDC converter, 32, 33 ... 1st and 2nd half bridge circuits, 50 ... control device, 60, 70 ... 1st and 2nd control units, 63 ... reduction coefficient calculation unit, Q1, Q4 ... 1st and 1st 4 switches.

Claims (5)

The first half-bridge circuit (32) having an input side switch (Q1) on the upper arm side,
A second half-bridge circuit (33) having an output side switch (Q4) on the lower arm side,
It is applied to a DCDC converter (10) including a reactor (31) for connecting the first half-bridge circuit and the second half-bridge circuit, and power is supplied by switching and controlling the input side switch and the output side switch. In the DCDC converter control device (50) that transforms the input voltage input from (11) and outputs it to the power supply target (12).
A first control unit (60) that performs the switching control of the input side switch based on the input voltage from the power supply to the DCDC converter.
A second that calculates the on-time of the output-side switch for controlling the power supplied from the power supply to the power supply target to the target power, and performs the switching control of the output-side switch based on the calculated on-time. Control unit (70) and
When the target power is smaller than the predetermined power determined based on the minimum value in the range in which the on-time can be taken, the reduction unit (62, 63) that reduces the output power of the power supply without shortening the on-time. ), And a DCDC converter control device. The on-time is the second on-time.
The first control unit calculates the first on time of the input side switch for stepping down the voltage input from the power supply and supplying it to the reactor based on the input voltage, and calculates the first on. The switching control of the input side switch is performed based on the time.
The DCDC converter control device according to claim 1, wherein the reduction unit performs, as the reduction process, a process of shortening the first on-time as compared with the case where the target power is equal to or more than the predetermined power. The first control unit calculates the first on-time based on the input voltage and the output voltage supplied from the DCDC converter to the power supply target.
The DCDC converter control device according to claim 2, wherein the reduction unit shortens the first on-time based on at least one of the input voltage, the output voltage, and the target power. When the target power shifts from a state in which the target power is equal to or higher than the predetermined power to a state in which the target power is smaller than the predetermined power, the reduction unit waits until the power supplied from the power supply to the power supply target becomes the target power. The control device for a DCDC converter according to claim 2, wherein the first on-time is gradually reduced to shorten the first on-time. The power source is a fuel cell.
According to claim 1, the reduction unit performs, as a reduction process, a process of reducing the oxygen supply amount of the oxygen supply unit (80) that supplies oxygen to the fuel cell as compared with the case where the target power is equal to or higher than the predetermined power. The DCDC converter controller described.

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