JP2009027866A - Controller of step-up/step-down converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a step-up/step-down converter, which can stably switch a step-up operation and a step-down operation. <P>SOLUTION: The controller of the step-up/step-down converter is provided with power connection terminals 5 to which a reactor 1, step-up IGBT 2, step-down IGBT 3 and a capacitor 4 being a power accumulation element are connected, output terminals 7 to which a motor 6 performing power running and regeneration running is connected, and a control part (not illustrated in figure 1). The control part 10 switches step-up IGBT 2 and step-down IGBT 3 so that load of the motor 6 or the reactor 1 becomes not more than prescribed load. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for a step-up / down converter that includes a step-up switching element and a step-down switching element and performs control of power supply to a load and control of supply of regenerative power obtained from the load to a storage element .

  Conventionally, in a general buck-boost converter, a DC power supply on the input side is controlled (boosted) to an arbitrary voltage, and electric power is supplied to an electric motor or the like connected to the output side. As a method for controlling the output voltage at this time, voltage control is the mainstream (see, for example, Patent Document 1).

  When a device such as a generator is connected to the output side, the buck-boost converter needs to move (step down) the power from the output side to the input side in order to keep the output side voltage constant. For example, when the device connected to the output side of the converter is an electric motor, the power running operation and the regenerative operation are repeatedly performed depending on the state of the load. For this reason, the step-up / down converter needs to detect the voltage state on the output side, determine whether boosting or step-down is necessary, and switch control.

However, in such a step-up / step-down converter, if a switching element that performs step-up and a switching element that performs step-down are simultaneously turned on, a large current flows and is dangerous. For this reason, when switching between step-up and step-down, a dead time is provided between a switching element that performs step-up and a switching element that performs step-down (see, for example, Patent Document 2).
JP 2006-042536 A JP 2004-120844 A

  However, when performing the voltage step-up operation or the step-down operation by voltage control, the energy transfer during power running operation and regenerative operation becomes large and the current becomes excessive, which may damage the switching element.

  Therefore, an object of the present invention is to provide a control device for a step-up / down converter capable of performing a step-up operation and a step-down operation without damaging a switching element.

  A control device for a buck-boost converter according to one aspect of the present invention includes a first terminal for transferring power to and from an electric motor that performs both power running operation and regenerative operation, a second terminal to which a power source is connected, A step-up switching element for controlling the supply of electric power from the power source to the electric motor, a step-down switching element for controlling the supply of regenerative power obtained from the electric motor to the power source, and the step-up switching element And a step-up / down converter control device having a step-down switching element and a reactor connected between the second terminal and the step-up / down converter so that the terminal voltage value of the first terminal becomes a voltage target value. Voltage control means for driving and controlling the switching element or the step-down switching element, and the value of the current flowing through the reactor becomes a predetermined current threshold, Either the current control means for driving and controlling the step-up switching element or the step-down switching element, and the voltage control means or the current control means so that the load of the first terminal or the reactor is equal to or lower than a predetermined load. Control switching means for selectively switching between.

  The voltage control means for driving and controlling the step-up switching element or the step-down switching element and the value of the current flowing through the reactor are predetermined so that the terminal voltage value of the first terminal becomes a voltage target value. Current control means for driving and controlling the step-up switching element or the step-down switching element so that the current threshold value is equal to or less than the current threshold, the control switching means, wherein the load of the electric motor or the storage element is less than or equal to a predetermined load As described above, when the drive control is performed by the voltage control unit in order to selectively switch either the voltage control unit or the current control unit, the reactor flows through the reactor. When the absolute value of the current to be generated becomes larger than the current threshold, the driving control by the current control means may be switched.

  Further, instead of the above-described case, voltage control means for driving and controlling the step-up switching element or the step-down switching element so that the terminal voltage value of the first terminal becomes a voltage target value, and the reactor are passed. Current control means for driving and controlling the step-up switching element or the step-down switching element so that the value of the flowing current becomes a predetermined current threshold, and the control switching means includes the electric motor or the power storage element. Drive control by the current control means is performed in order to selectively switch either the voltage control means or the current control means so that the load of the current is equal to or less than a predetermined load. In addition, when the terminal voltage value of the first terminal returns to the target voltage value, the driving control by the voltage control unit may be switched.

  In these cases, the voltage control means calculates a first switching duty by PI control based on a difference between the terminal voltage value of the first terminal and the target voltage value, and The current control means is configured to drive and control the step-down switching element, and the current control means calculates a second switching duty by PI control based on a difference between a current value flowing through the reactor and the current threshold value, and The control switching unit is configured to control driving of the step-up switching element and the step-down switching element. When the control switching unit switches from the voltage control unit to drive control by the current control unit, the current control unit immediately after switching The calculated second switching duty is calculated by the voltage control means immediately before switching. The second switching duty is corrected to be equal to the first switching duty, and the value of the first switching duty calculated by the voltage control means immediately after switching is calculated by the current control means immediately before switching. The first switching duty may be corrected to be equal to the second switching duty.

  In this case, each of the first switching duty and the second switching duty is given a different symbol when driving the step-up switching element and when driving the step-down switching element. Also good.

  Further, in this case, the control switching means causes the current control means to perform drive control of the step-down switching element when the sign of the driving duty is the first sign, and When the code is the second code, the voltage control means may perform drive control of the boosting switching element.

  Further, in this case, the control switching means is configured such that when the drive control of the step-up switching element is performed by the voltage control means, and the sign of the drive duty is the first sign, the voltage If the control means continues driving control of the boosting switching element and the sign of the driving duty is the second sign, the voltage control means may stop driving control of the boosting switching element. .

  Further, in place of the above case, the control switching means may be configured such that when the drive control of the step-down switching element is performed by the current control means, the sign of the driving duty is the first sign. , Causing the current control means to stop driving control of the step-down switching element, and if the sign of the driving duty is a second sign, cause the current control means to continue driving control of the step-down switching element. May be.

  Further, instead of the above-described case, the control switching unit may be configured such that when the drive control by the voltage control unit and the current control unit are both stopped, the drive duty code is the first code. Causes the voltage control means to perform drive control of the step-up switching element, and when the sign of the drive duty is a second sign, performs drive control of the step-down switching element to the current control means. You may let them.

  The switching means may turn off the driving duty during the stop period.

  According to the present invention, it is possible to provide a specific effect that it is possible to provide a control device for a step-up / step-down converter that can stably perform a step-up operation and a step-down operation without damaging a switching element.

  Hereinafter, an embodiment to which a control device for a buck-boost converter according to the present invention is applied will be described.

  FIG. 1 is a diagram schematically showing a circuit configuration of a buck-boost converter that is driven and controlled by the buck-boost converter control device of the present embodiment. This step-up / down converter receives power from a reactor 1, a step-up IGBT (Insulated Gate Bipolar Transistor) 2, a step-down IGBT 3, a power supply connection terminal 5 for connecting a capacitor 4 used as a power supply, and a motor 6. And an output terminal 7 and a capacitor 8 inserted between the output terminals 7. In addition, although the capacitor | condenser 4 is shown here as a power supply, this power supply is not restricted to the capacitor | condenser 4, You may comprise with the secondary battery which can be charged / discharged, Moreover, it is a power supply of the other form which can transmit / receive electric power. There may be. Further, the motor 6 connected to the output terminal 7 may be an electric motor capable of power running operation and regenerative operation.

  The buck-boost converter according to the present embodiment can be applied to, for example, a power supply control unit of a hybrid construction machine. In such an application, for example, the voltage value of the capacitor 4 is about 200 to 350 V, the output rated voltage at the output terminal 7 is about 350 V, the rated output is about 20 kW, the instantaneous maximum output power is ± 80 kW, the rated current is ± 100 A, The instantaneous maximum current is about ± 400A. For this reason, the reactor 1, the step-up IGBT 2, the step-down IGBT 3, the power supply connection terminal 5, the output terminal 7, and the capacitor 8 are required to withstand such applications.

  In FIG. 1, a control unit that drives the step-up IGBT 2 and the step-down IGBT 3 by PWM (Pulse Width Modulation) is omitted. Such a control unit can be realized by either an electronic circuit or an arithmetic processing unit. In the present embodiment, a control unit realized by an arithmetic processing device will be described with reference to FIG.

  FIG. 2 is a diagram showing a circuit configuration of the control device for the buck-boost converter according to the present embodiment in a control block. As shown in the figure, the control unit 10 of the buck-boost converter according to the present embodiment includes a voltage control unit 11, a current control unit 12, a control switching unit 13, and a buck-boost switching unit 14.

  The control unit 10 is connected to a power connection terminal 5, an output terminal 7, a boosting PM (Power Module) 15, and a step-down PM 16. These are connected so that the hardware configuration shown in FIG. 1 can be realized. That is, the booster IGBT 2 and the step-down IGBT 3 included in the step-up PM 15 and the step-down PM 16 are PWM-driven by the control unit 10, and as a result, the power supply voltage Vbat and the power supply current Ibat are output from the power supply terminal 5. Are connected to output the output voltage Vout.

  The voltage control unit 11 drives and controls the boosting IBGT 2 and the step-down IGBT 3 by performing PI (Proportional Integral) control based on the difference between the target voltage value Vout_ref and the output voltage Vout output from the output terminal 7. For this purpose, the first switching duty duty_v is calculated. In the calculation process of the first switching duty duty_v, the control unit 13 corrects the voltage integral value Vout_I. This correction method will be described later.

  The current control unit 12 performs the PI control based on the difference between the current threshold value Ibat_ref and the power supply current Ibat output from the power supply connection terminal 5, thereby driving and controlling the boosting IBGT2 and the step-down IGBT3. 2 Calculate the switching duty duty_i. In the calculation process of the second switching duty duty_i, the control unit 13 corrects the current integrated value Ibat_I. This correction method will be described later.

  Here, in the step-up / step-down converter according to the present embodiment, the switching duty for driving the step-up IGBT 2 and the switching duty for driving the step-down IGBT 3 are distinguished from each other by using different signs. Therefore, each of the first switching duty and the second switching duty described above is given a positive sign for driving the boosting IGBT 2 and given a negative sign for driving the step-down IGBT 3.

  The control switching unit 13 selectively switches either the voltage control unit 11 or the current control unit 12 so that the load of the reactor 1 or the motor 6 (output terminal 7) is equal to or lower than a predetermined load. Specifically, when the drive control by the voltage control unit 11 is performed, if the absolute value of the current flowing through the reactor 1 becomes larger than the current threshold value, the drive control is switched to the current control unit 12. Further, when drive control by the current control unit 12 is being performed, when the terminal voltage value of the output terminal 7 becomes higher than the target voltage value, switching to drive control by the voltage control unit 11 is performed.

  Such switching between voltage control and current control is performed by the switching unit 13 </ b> A of the control switching unit 13. If the switching unit 13A is connected to plus (+), voltage control is performed, and if it is connected to minus (−), current control is performed.

  Further, as described above, the control switching unit 13 corrects the voltage integral value calculated by the voltage control unit 11 using the second switching duty, and also changes the current integration value calculated by the current control unit 12 to the first switching duty. Use to correct.

  The correction method will be described below. During voltage control, the switching units 13B and 13C of the control switching unit 13 are connected to the plus (+) side, and during current control, the switching units 13B and 13C are minus ( -) Connected to the side.

Here, correction of the voltage integral value Vout_I and the current integral value Ibat_I will be described. When the voltage control unit 11 and the current control unit 12 calculate the first switching duty for voltage control and the second switching duty for current control, normally, the voltage command and the current command do not match. The duty supplied to the step-up IGBT 2 or the step-down IGBT 3 becomes discontinuous when the control is switched. In the buck-boost converter according to the present embodiment, when switching the voltage control unit 11 and the current control unit 12, the following conditions are satisfied. The initial value of the switching duty is corrected using (1) and (2).
(1) Set Vout_I to (duty_i-Vout_P).
(2) Set Ibat_I to (duty_v-Ibat_P).

  Here, Vout_I is a voltage integral value calculated by the voltage control unit 11, duty_i is a second switching duty calculated by the current control unit 12, and Vout_P is a voltage proportional value calculated by the voltage control unit 11.

  Ibat_I is a current integral value calculated by the current control unit 12, duty_v is a first switching duty calculated by the voltage control unit 11, and Ibat_P is a current proportional value calculated by the current control unit 12.

  As shown in the condition (1), the control switching unit 13 corrects the voltage integration value Vout_I calculated by the voltage control unit 11 using the second switching duty duty_i and the voltage proportional value Vout_P. Further, as shown in the condition (2), the control switching unit 13 corrects the current integral value Ibat_I calculated by the current control unit 12 using the first switching duty duty_v and the current proportional value Ibat_P.

  That is, when the current control is switched to the voltage control, all of the switching units 13A to 13C of the control switching unit 13 are switched from the minus (−) side to the plus (+) side. Accordingly, in the switching unit 13B, the voltage integrated value Vout_I immediately after switching from the minus (−) side to the plus (+) side is set to (duty_i−Vout_P). Since this voltage integral value Vout_I (= duty_i−Vout_P) is added to the voltage proportional value Vout_P, the first switching duty duty_v is equal to the second switching duty duty_i obtained at the end of the current control.

  Thus, even when the switching unit 13A is switched from the minus (−) to the plus (+) side when switching from the current control to the voltage control, the duty on the plus (+) side and the minus (−) side of the switching unit 13A is changed. Since the value is the second switching duty duty_i obtained at the end of the current control, the discontinuity at the time of switching to the voltage control can be eliminated.

  Similarly, when switching from voltage control to current control, the switching unit 13C sets the current integrated value Ibat_I immediately after switching from the plus (+) side to the minus (−) side to (duty_v−Ibat_P). Is done. Since this current integral value Ibat_I (= duty_v−Ibat_P) is added to the current proportional value Ibat_P, the second switching duty duty_i is equal to the first switching duty duty_v obtained at the end of the voltage control.

  Thus, even when the switching unit 13A is switched from the plus (+) side to the minus (−) side when switching from the voltage control to the current control, the switching unit 13A has a positive (+) side and a minus (−) side. Since the value of the duty is the first switching duty duty_v obtained at the end of the voltage control, the discontinuity at the time of switching to the current control can be eliminated.

  The control switching unit 13 switches the switching unit 13A as described above to change either the first switching duty obtained from the voltage control unit 11 or the second switching duty obtained from the current control unit 12 to PM15 for boosting. And a driving duty duty_ref for driving the step-down PM 16. When the power supply current Ibat exceeds the power supply current threshold Ibat_ref, the selection is switched to drive control by the current control unit 12 (that is, the second switching duty), and when the output voltage Vout returns to the output target voltage value Vout_ref, This is realized by returning to the drive control unit by the control unit 11 (that is, the first switching duty).

  The selected driving duty duty_ref is transmitted to the step-up / step-down switching unit 14. Since this driving duty duty_ref is either the first switching duty or the second switching duty, a positive sign is attached to the driving duty for boost driving, and the driving duty for step-up / down driving. Is given a negative sign.

  Based on the sign of the driving duty duty_ref transmitted from the control switching unit 13, the step-up / step-down switching unit 14 determines the power module driven by this driving duty duty_ref as either the boosting PM 15 or the step-down PM 16.

  A boosting PM (Power Module) 15 is a power module that incorporates the boosting IGBT 2 described above, a drive circuit for driving the boosting IGBT 2, and a self-protection function.

  Similarly, the step-down PM 16 is a power module that incorporates the above-described step-down IGBT 3, a drive circuit for driving the step-down IGBT 3, and a self-protection function.

  Although the reactor is not shown in FIG. 2, the power supply current Ibat output from the power supply terminal 5 is a current that flows through the reactor.

  As described above, the step-down IGBT 3 included in the step-down PM 16 is configured to invert (-1 times) the sign because the negative drive duty duty_ref is transmitted from the step-up / step-down switching unit 14. ing.

  FIG. 3 is a diagram conceptually showing state transition when the step-up / step-down operation is switched by the step-up / step-down switching unit 14. Table 1 shows the relationship between the state transition and the driving duty shown in FIG. Here, for convenience of explanation, mode 0 (Mode = 0) is stopped before starting operation, mode 1 (Mode = 1) is being boosted, mode 2 (Mode = 2) is being stepped down, mode 3 (Mode = 3 ) Is inactive (during stoppage during step-up / down switching).

図３及び表１に示すように、昇降圧コンバータの運転開始時（モード０）に、駆動用デューティが０以上である場合は、昇降圧切替部１４は、昇圧用ＰＭ１５の駆動制御を実行させる。一方、駆動用デューティが負の値である場合は、昇降圧切替部１４は、電圧制御部１１に降圧用ＰＭ１６の駆動制御を実行させる。

As shown in FIG. 3 and Table 1, when the drive duty is 0 or more at the start of operation of the buck-boost converter (mode 0), the buck-boost switching unit 14 causes the boost PM 15 to perform drive control. . On the other hand, when the drive duty is a negative value, the step-up / step-down switching unit 14 causes the voltage control unit 11 to perform drive control of the step-down PM 16.

  When the drive control of the boosting PM 15 is being performed (mode 1), if the drive duty is 0 or more, the step-up / step-down switching unit 14 continues the drive control of the boost PM 15. On the other hand, when the driving duty is a negative value, the step-up / step-down switching unit 14 stops the drive control of the boosting PM 15.

  When the drive control of the step-down PM 16 is being performed (mode 2), if the drive duty is 0 or more, the step-up / step-down switching unit 14 stops the drive control of the step-down PM 16. On the other hand, when the drive duty is a negative value, the step-up / step-down switching unit 14 continues the drive control of the step-down PM 16.

  Further, when the drive control by the voltage control unit 11 and the current control unit 12 is both stopped during the switching of the step-up / step-down (mode 3), when the driving duty is 0 or more, the step-up / step-down switching unit 14 Causes drive control of the boosting PM 15 to be performed. On the other hand, when the drive duty is a negative value, the step-up / step-down switching unit 14 performs drive control of the step-down PM 16.

  The step-up / step-down switching unit 14 turns off the driving duty during the stop period in mode 3.

  FIG. 4 is an operation explanatory diagram showing the state transition shown in FIG. 3 in time series.

  FIG. 4A shows an operation example when the step-up operation is changed to the step-down operation through no operation. As described above, a period of no operation (mode 3 described above) in which the driving duty is turned off is provided between the step-up operation and the step-down operation. For example, when the step-up / step-down control is performed every 200 μs, a non-operation stop period is provided for 200 μs during the transition from the step-up operation to the step-down operation. Thereby, a stable operation can be realized at the time of step-up / down switching.

  Similarly, FIG. 4B shows an operation example when the step-down operation is changed to the step-up operation through no operation. FIG. 4C shows an example of the case where the step-up operation is changed to the step-down operation through no operation, and the state is changed again to the step-up operation through no operation. These are the same as the case shown in FIG. 4A, and show various cases in which a non-operation state is passed when the step-up operation is changed to the step-down operation.

  FIG. 4D shows an operation example when switching between the step-up operation and the step-down operation is frequently performed. As described above, when switching of the step-up / step-down is frequently performed, in addition to the switching operation between the step-up operation and the step-down operation, the case where the step-up operation is changed from the step-up operation to the step-up operation again is included. Thus, even when returning to the same operation, since the non-operation time is as short as one control cycle (200 μsec), stable buck-boost control can be realized.

  FIG. 5 is a diagram conceptually showing switching conditions between voltage control and current control. FIG. 6 is a diagram illustrating an operation example for explaining the switching operation between the voltage control and the current control during the boosting operation. FIG. 7 is a diagram illustrating an operation example for explaining the switching operation between the voltage control and the current control during the step-down operation. Such switching operation between voltage control and current control is executed by the switching control unit 13.

  As shown in FIG. 5A, when the current value of the power supply current Ibat becomes larger than the power supply current threshold Ibat_ref during voltage control by the voltage control unit 11 during the boost operation, the reactor 1 In order to prevent an excessive current flowing in the direction toward the output terminal 7 from flowing through, the switching control unit 13 switches to drive control by the current control unit 12. This corresponds to the case where the first voltage control is changed to the current control in the time series shown in FIG.

  For example, when the power running amount of the motor 6 is large or when the amount of regenerative energy generated by power generation is large, circuit elements such as the reactor 1 are damaged by passing an overcurrent larger than the allowable current value through the circuit elements including the reactor 1. May receive. For this reason, when the current value of the power supply current Ibat flowing through the reactor 1 becomes larger than the power supply current threshold Ibat_ref, the driving control by the current control unit 12 is switched.

  Further, when switching to drive control by the current control unit 12, as shown in FIG. 6, the output voltage Vout greatly decreases from the output target voltage value Vout_ref and does not change unless the load state of the motor 6 is changed.

  When the drive control by the current control unit 12 is performed, when the output voltage Vout returns to the output target voltage value Vout_ref due to a decrease in the power running amount or the regenerative energy amount of the motor 6, the switching control unit 13 Switching to drive control by the control unit 11 is performed. This corresponds to the case where the current control shown in FIG. 6 is changed to the last voltage control in time series.

  Further, as shown in FIG. 5B, when the power supply current Ibat is equal to or lower than the power supply current threshold Ibat_ref during the step-down operation and the voltage control by the voltage control unit 11, the power is supplied to the reactor 1. In order to prevent an excessive current flowing in the direction toward the terminal 5 from flowing, the switching control unit 13 switches to drive control by the current control unit 12. This corresponds to a case where a transition is made from the first voltage control to the current control in the time series shown in FIG.

  When the output control Vout returns to the output target voltage value Vout_ref while the drive control by the current control unit 12 is being performed, the switching control unit 13 switches to the drive control by the voltage control unit 11. This corresponds to the case where the current control shown in FIG. 7 is changed to the last voltage control in time series.

  As described above, according to the buck-boost converter control device of the present embodiment, the voltage control unit 11 calculates the voltage integral value using the second switching duty calculated by the current control unit 12, and the voltage The current control unit 12 calculates the current integral value using the first switching duty calculated by the control unit 11. In addition, when the power supply current Ibat exceeds the power supply current threshold Ibat_ref, switching to drive control by the current control unit 12 is performed, and when the output voltage Vout returns to the output target voltage value Vout_ref, the drive control unit by the voltage control unit 11 is switched. Return.

  As described above, when the power supply current Ibat becomes excessive while using voltage control as a basis, switching to current control is performed to protect the circuit. Since the stop period (no operation) for stopping both the step-up IGBT 2 and the step-down IGBT 3 is provided at the time of switching, the step-up operation and the step-down operation can be performed without damaging the step-up IGBT 2 and the step-down IGBT 3. A control device for a buck-boost converter that can be switched stably can be provided.

  In the above description, the DC drive motor 6 is directly connected to the output terminal 7, but instead, an AC drive motor may be connected to the output terminal 7 via an inverter.

  The control device for the buck-boost converter according to the exemplary embodiment of the present invention has been described above, but the present invention is not limited to the specifically disclosed embodiment, and deviates from the scope of the claims. Various modifications and changes can be made without this.

It is a figure which shows schematically the circuit structure of the buck-boost converter driven and controlled by the control apparatus of the buck-boost converter of this Embodiment. It is a figure which shows the circuit structure of the control apparatus of the buck-boost converter of this Embodiment with a control block. It is a figure which shows notionally the state transition at the time of a step-up / step-down operation | movement switching by a step-up / step-down switching part. It is operation | movement explanatory drawing which shows the state transition shown in FIG. 3 in time series. It is a figure which shows notionally the switching conditions of voltage control and electric current control. It is a figure which shows the operation example for demonstrating the switching operation | movement of the voltage control and electric current control during a pressure | voltage rise operation. It is a figure which shows the operation example for demonstrating the switching operation | movement of voltage control and electric current control in step-down operation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Reactor 1, 2 step-up IGBT, 3 step-down IGBT, 4 capacitor, 5 power supply connection terminal, 6 motor, 7 output terminal, 8 capacitor, 10 control part, 11 voltage control part, 12 current control part, 13 control switching part , 14 Step-up / down switching unit, 15 PM for boosting, 16 PM for step-down.

Claims (10)

A first terminal for transferring power to and from an electric motor that performs both power running and regenerative operation;
A second terminal to which a power supply is connected;
A step-up switching element for controlling the supply of electric power from the power source to the electric motor;
A step-down switching element for controlling supply of regenerative power obtained from the electric motor to the power source;
In a control device for a step-up / down converter having the step-up switching element, the step-down switching element, and a reactor connected between the second terminal,
Voltage control means for driving and controlling the step-up switching element or the step-down switching element so that the terminal voltage value of the first terminal becomes a voltage target value;
Current control means for driving and controlling the step-up switching element or the step-down switching element so that the value of the current flowing through the reactor becomes a predetermined current threshold;
A control device for a buck-boost converter, comprising: control switching means for selectively switching either the voltage control means or the current control means so that the load of the first terminal or the reactor is equal to or less than a predetermined load.   The control switching means switches to drive control by the current control means when the absolute value of the current flowing through the reactor becomes larger than the current threshold when drive control by the voltage control means is performed. The control device of the step-up / step-down converter according to claim 1.   The control switching means switches to drive control by the voltage control means when the terminal voltage value of the first terminal returns to the target voltage value when drive control by the current control means is being performed. The control device of the step-up / down converter according to 1. The voltage control means calculates the first switching duty by PI control based on the difference between the terminal voltage value of the first terminal and the target voltage value, and drives and controls the step-up switching element and the step-down switching element. Configured to
The current control means calculates the second switching duty and performs drive control of the step-up switching element and the step-down switching element by PI control based on a difference between a current value flowing through the reactor and the current threshold value. Configured to
When the control switching means switches from the voltage control means to the drive control by the current control means, the value of the second switching duty calculated by the current control means immediately after switching is changed by the voltage control means immediately before switching. The second switching duty is corrected to be equal to the calculated first switching duty, and is calculated by the voltage control means immediately after switching when switching from the current control means to drive control by the voltage control means. The control of the step-up / down converter according to claim 2 or 3, wherein the first switching duty is corrected so that a value of the first switching duty is equal to a second switching duty calculated by the current control means immediately before switching. apparatus.   5. Each of the first switching duty and the second switching duty is given a different symbol when driving the step-up switching element and when driving the step-down switching element. 6. Control device for step-up / down converter.   The control switching means performs drive control of the step-up switching element when the sign of the drive duty is the first sign, and when the sign of the drive duty is the second sign, The control device for a step-up / down converter according to claim 5, wherein drive control of the step-down switching element is performed.   When the drive switching of the boosting switching element is being performed and the sign of the driving duty is the first sign, the control switching means continues the drive control of the boosting switching element, The step-up / down converter control device according to claim 5, wherein when the drive duty code is the second code, drive control of the boosting switching element is stopped.   The control switching means stops the drive control of the step-down switching element when the drive duty of the step-down switching element is being performed and the sign of the drive duty is the first sign, The step-up / down converter control device according to claim 5, wherein when the drive duty code is the second code, drive control of the step-down switching element is continued.   When the drive switching of the step-up switching element and the step-down switching element is in a stopped state, the control switching means, when the sign of the driving duty is the first sign, the step-up switching element 6. The step-up / down converter control device according to claim 5, wherein when the drive duty is a second sign, the step-down switching element is driven.   The control device for a buck-boost converter according to any one of claims 4 to 9, wherein the switching unit turns off the driving duty during the stop period.

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