JP6906703B2 - Power converter - Google Patents

Description

The present invention relates to a power conversion device, and more specifically, to a power conversion device that performs DC voltage conversion (DC / DC conversion).

A power conversion device is known that can obtain an arbitrary output voltage obtained by stepping up and down the input DC voltage by controlling the ratio of the accumulated amount and the released amount of magnetic energy of the reactor by operating the switching element on and off. ..

For example, Japanese Patent Application Laid-Open No. 2004-120940 (Patent Document 1) describes a circuit configuration of a so-called H-bridge type switching regulator as a DC-DC converter capable of raising and lowering pressure. Specifically, the first and second switching elements constituting the step-down circuit, the third and fourth switching elements constituting the step-up circuit, the connection points of the first and second switching elements, and the third and third. A circuit configuration including a reactor connected to and from a connection point of a fourth switching element is disclosed.

In the DC-DC converter of Patent Document 1, when the input voltage is boosted and output, the first switching element is always turned on, while the third and fourth switching elements are periodically turned on and off. To obtain an output voltage higher than the input voltage. On the other hand, when the input voltage is stepped down and output, the DC-DC converter has an output voltage lower than the input voltage by a buck-boost operation in which the first to fourth switching elements are periodically turned on and off. To get.

Japanese Unexamined Patent Publication No. 2004-120940

The DC-DC converter of Patent Document 1 fluctuates within a certain range of the input voltage by switching between the step-up operation and the step-up / down operation (for example, 3.0 [V] to 4.2 [V] in a lithium ion battery. Even if it fluctuates), it is possible to stably obtain a substantially constant output voltage (for example, 3.3 [V]).

However, when the input voltage is stepped down, the step-up / down operation must be performed, so that switching loss occurs in both the step-down circuit and the step-up circuit, and there is a concern that the efficiency may decrease.

The present invention has been made to solve such a problem, and an object of the present invention is a power converter that raises and lowers an input voltage during step-down and step-up without destabilizing control operation. It is to improve the efficiency of power conversion (DC / DC conversion) at both times.

In a certain aspect of the present invention, a power conversion device that outputs an output voltage obtained by stepping up and down an input voltage, the step-down circuit including the first switching element, the step-up circuit including the second switching element, and a controller. To be equipped. The controller generates first and second control signals that control the on / off of the first and second switching elements in order to control the output voltage according to the output voltage command value of the power converter. The controller includes an operation mode selection unit and a duty control unit. The operation mode selection unit receives the input of the output voltage command value and outputs the operation mode selection result of the power converter and the control target voltage of the output voltage. The duty control unit controls the on / off duty ratio of each of the first and second switching elements according to the selection result of the operation mode and the control target voltage. The operation mode includes the first and second modes. In the first mode, the output voltage is controlled to a control target voltage lower than the input voltage by the duty ratio of the first switching element while fixing the on / off of the second switching element. In the second mode, the output voltage is controlled to a control target voltage higher than the input voltage by the duty ratio of the second switching element while fixing the on / off of the first switching element. The operation mode selection unit sets the control target voltage of the output voltage while avoiding the boundary voltage range between the first threshold value lower than the input voltage and the second threshold value higher than the input voltage.

According to the present invention, in the first mode, the on / off of the switching element of the step-up circuit is fixed to generate an output voltage whose input voltage is stepped down, and in the second mode, the on / off of the switching element of the step-down circuit is fixed. It is possible to generate an output voltage that boosts the input voltage, and it is possible to set the control target voltage of the output voltage in the first and second modes while avoiding the boundary voltage range that sandwiches the input voltage. Therefore, it is possible to improve the efficiency of power conversion both at the time of step-down and at the time of step-up without destabilizing the control operation.

It is a circuit diagram explaining the structure of the power conversion apparatus which concerns on Embodiment 1. FIG. It is a block diagram explaining the function of the controller shown in FIG. It is a flowchart for demonstrating the operation of the operation mode selection part shown in FIG. It is a conceptual diagram for demonstrating the operation of the operation mode selection part which concerns on the modification 1 of Embodiment 1. FIG. It is a block diagram explaining the function of the controller which concerns on the modification 2 of Embodiment 1. FIG. It is a block diagram explaining the function of the duty calculation part shown in FIG. It is a mode transition diagram of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a conceptual diagram explaining the relationship between the output voltage and the mode in the power conversion apparatus which concerns on Embodiment 2. FIG. It is a circuit diagram explaining the structure of the power conversion apparatus which concerns on Embodiment 2. FIG. It is a block diagram explaining the function of the controller shown in FIG. It is a flowchart for demonstrating the operation of the operation mode selection part shown in FIG. It is a block diagram explaining the function of the controller which concerns on the modification of Embodiment 2. It is a circuit diagram explaining the structure of the power conversion apparatus which concerns on Embodiment 3. FIG. It is a block diagram explaining the function of the controller shown in FIG. It is a block diagram explaining the function of the duty calculation unit shown in FIG. It is a figure explaining the setting example of the feedforward term shown in FIG. It is a simulation waveform diagram at the time of operation mode switching with the increase of the output voltage command value in the power conversion apparatus which concerns on Embodiment 2. FIG. It is a simulation waveform diagram at the time of operation mode switching with the increase of the output voltage command value in the power conversion apparatus which concerns on Embodiment 3. FIG. FIG. 5 is a simulation waveform diagram at the time of operation mode switching due to a decrease in an output voltage command value in the power conversion device according to the second embodiment. FIG. 5 is a simulation waveform diagram at the time of operation mode switching due to a decrease in an output voltage command value in the power conversion device according to the third embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the figure are designated by the same reference numerals, and the explanations are not repeated in principle.

Embodiment 1.
FIG. 1 is a circuit diagram illustrating a configuration of a power conversion device according to a first embodiment.

With reference to FIG. 1, the power conversion device 5a according to the first embodiment includes a step-down circuit 10, a step-up circuit 20, a controller 30a, a reactor L1, and a smoothing capacitor C1. The power conversion device 5a further includes input terminals N11 and N12 connected to the DC power supply 40, and output terminals N21 and N22 connected to the load 41.

The input terminal N11 is connected to the high potential side of the DC power supply 40, and the input terminal N12 is connected to the low potential side of the DC power supply 40. The output terminal N21 is connected to the high potential side of the load 41, and the output terminal N22 is connected to the low potential side of the load 41. The input terminal N12 and the output terminal N22 on the low potential side are connected by a common power line (for example, ground wiring) GL. The power line GL is also connected to the low potential side of the smoothing capacitor C1.

Hereinafter, the DC voltage between the input terminals N11 and N12 input from the DC power supply 40 is referred to as an input voltage Vin. Similarly, the DC voltage between the output terminals N21 and N22 output to the load 41 is also referred to as an output voltage Vout. Both the input voltage Vin and the output voltage Vout are DC voltages. Although not shown, voltage sensors for detecting the input voltage Vin are arranged at the input terminals N11 and N12. Similarly, voltage sensors for detecting the output voltage Vout are arranged at the output terminals N21 and N22. The detected values of the input voltage Vin and the output voltage Vout are input to the controller 30a.

The output voltage command value Vout * is further input to the controller 30. Since the power conversion device 5a has both the step-down circuit 10 and the step-up circuit 20, the output voltage command value Vout * can be set on either the high voltage side or the low voltage side of the input voltage Vin. The controller 30 controls the operation of the step-down circuit 10 and the step-up circuit 20 so that the output voltage Vout can be stably obtained according to the output voltage command value Vout *.

The step-down circuit 10 includes a first switching element Tr1 and a first semiconductor element Di1. The first switching element Tr1 is connected between the node N1 to which one end of the reactor L1 is connected and the input terminal N11. The first semiconductor element Di1 is connected between the node N1 and the input terminal N12.

The first switching element Tr1 cuts off the input current from the DC power supply 40 when it is off. The first semiconductor element Di1 secures a recirculation path of the reactor current IL flowing through the reactor L1 when the first switching element Tr1 cuts off the input current, and the power line GL (input terminal) from the node N1. It is arranged so that no current flows to N12 and the output terminal N22).

The reactor L1 is connected between the step-down circuit 10 and the step-up circuit 20, specifically, between the nodes N1 and N2. The smoothing capacitor C1 is connected between the output terminals N21 and N22 to suppress the AC component of the output voltage Vout by the power conversion device 5a.

The booster circuit 20 has a second switching element Tr2 and a second semiconductor element Di2. The second switching element Tr2 is connected between the node N2 connected to the other end of the reactor L1 and the power line GL. The second semiconductor element Di2 is connected between the node N2 and the output terminal N21 and the high potential side of the smoothing capacitor C1).

The second switching element Tr2 forms a current path for accumulating magnetic energy in the reactor L1 by connecting the node N1 and the power line GL when it is turned on. The second semiconductor element Di2 secures a current path from the step-down circuit 10 and the reactor L1 to the output terminal N21 when the first switching element Tr2 is turned off, and the output terminal N21 (smoothing capacitor C1). ), It is arranged to prevent the backflow of the current to the reactor L1 and the step-down circuit 10.

The first and second switching elements Tr1 and Tr2 can be configured by an IGBT (Insulated Gate Bipolar Transistor) as illustrated in FIG. 1, but any element can be turned on and off according to a control signal. Can be applied. For example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor) can also be used to configure the first and second switching elements Tr1 and Tr2.

The first and second semiconductor elements Di1 and Di2 can be configured by diodes having the connection directions illustrated in FIG. The first semiconductor element Di1 can be composed of a switching element (IGBT, MOSFET, etc.) that is turned on and off complementarily with the first switching element Tr1 instead of a diode. Similarly, the second semiconductor element Di2 can be configured not with a diode but with a switching element (IGBT, MOSFET, etc.) that is turned on and off complementarily with the second switching element Tr2. When the semiconductor elements Di1 and Di2 are configured by the switching element, the conduction loss can be reduced as compared with the diode. In particular, when the second semiconductor element Di2 is composed of a switching element, it is possible to form a current path for regeneration from the load 41 to the DC power supply 40.

Further, the first and second switching elements Tr1 and Tr2 and the first and second semiconductor elements Di1 and Di2 can be made of any semiconductor material, and can be made of any semiconductor material. In addition to Si (silicon), SiC ( Silicon carbide) or GaN (gallium nitride) or the like can also be applied.

In the step-down circuit 10, the first switching element Tr1 may be connected between the input terminal N12 and the semiconductor element Di1 as long as the input current from the DC power supply 40 can be cut off. In this case, the first semiconductor element Di1 can be paraphrased as being connected between the input terminal N11 and the node N1 and the first switching element Tr1 and the output terminal N22.

Similarly, in the booster circuit 20, the second semiconductor element Di2 forms a current path from the step-down circuit 10 or reactor L1 to the smoothing capacitor C1, while blocking the current to the smoothing capacitor C1 step-down circuit 10 or reactor L1. Anything that does. Therefore, the second semiconductor element Di2 may be connected to the power line GL side between the output terminal N22 and the second switching element Tr2. In this case, if the second semiconductor element Di2 is a diode, the second semiconductor element Di2 is connected with the direction from the output terminal N22 toward the input terminal N12 as the forward direction. Further, the second switching element Tr2 is connected between the node N2 and the output terminal N21 (the positive electrode side of the smoothing capacitor C1) and the power line GL.

The controller 30a outputs a control signal S1 for controlling the on / off of the first switching element Tr1 of the step-down circuit 10 and a control signal S2 for controlling the on / off of the second switching element Tr2 of the step-up circuit 20. In the following description, it is assumed that the switching elements Tr1 and Tr2 are in the off state if the on / off state is not specified.

The controller 30a can be configured by, for example, an analog circuit including an operational amplifier or the like, or dedicated hardware such as an ASIC (Application Specific Integrated Circuit). Further, the controller 30a can also operate so as to realize the control function described below by executing the program mounted in the memory (not shown) on the processor (not shown). .. The memory can be configured by DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), ROM (Read Only Memory), etc., and the processor is a CPU (Central Processing Unit), MPU (Micro Processing). It can be configured by a Unit), an MCU (Micro Control Unit), or the like.

FIG. 2 is a block diagram illustrating the function of the controller 30a. The function of each block described in each block diagram including FIG. 2 can be realized by either hardware by a dedicated electronic circuit or software by program processing. Alternatively, the function of the block may be realized by a combination of hardware and software.

With reference to FIG. 2, the controller 30a includes an operation mode selection unit 31, a duty calculation unit 32, a duty selection unit 33, and a PWM (Pulse Width Modulation) signal generation unit 34.

The output voltage command value Vout * and the threshold values V1 and V2 are input to the operation mode selection unit 31. Based on the comparison between the output voltage command value Vout * and the threshold values V1 and V2, the control target voltage Vc * and the mode selection signal Smd for duty control of the first and second switching elements Tr1 and Tr2 are set. The mode selection signal Smd is a signal indicating the selection result of the operation mode of the power conversion device 5a. In the first embodiment, the operation mode includes a step-down mode in which the step-up circuit 20 is stopped and the step-down circuit 10 is operated, and a step-up mode in which the step-down circuit 10 is stopped and the step-up circuit 20 is operated.

The threshold value V1 is set to a voltage value lower than the input voltage Vin. On the other hand, the threshold value V2 is set to a voltage value higher than the input voltage Vin. The threshold values V1 and V2 can be fixed values predetermined based on the characteristics of the DC power supply 40 (for example, the rated output voltage range). Alternatively, the threshold values V1 and V2 may be set as variable values so that the above voltage conditions (V1 <Vin and V2> Vin) are surely satisfied based on the detected value of the input voltage Vin by the voltage sensor (not shown). It is possible.

FIG. 3 shows a flowchart explaining the operation of the operation mode selection unit 31.
With reference to FIG. 3, when the operation mode selection unit 31 inputs the output voltage command value Vout * to the power conversion device 5a in step 110 (hereinafter, simply referred to as “S”) 110, the output voltage command is given by S120. The value Vout * is compared with the thresholds V1 and V2. Specifically, it is determined whether or not it is within the range of V1 <Vout * <V2 (boundary voltage range).

When V1 <Vout * <V2 (when YES is determined in S131), the operation mode selection unit 31 sets the control target voltage Vc * to the threshold value V1 instead of the output voltage command value Vout * by S130 (Vc * = V1). On the other hand, when Vout * ≤ V1 or V2 ≤ Vout (when NO is determined in S131), the output voltage command value Vout * is set as the control target voltage Vc * by S140 (Vc * = Vout *). Further, the operation mode selection unit 31 outputs the control target voltage Vc * set in S130 or S140 to the duty calculation unit 32 (FIG. 2). According to S120 to S140, the control target voltage Vc * is set while avoiding the boundary voltage range of V1 <Vc * <V2.

The operation mode selection unit 31 compares the control target voltage Vc * with the threshold value V2 by S160. Then, when Vc * ≧ V2 (when YES is determined in S160), the boost mode is selected by S180. When the boost mode is selected, the mode selection signal Smd is set to "1" and output to the duty calculation unit 32 and the duty selection unit 33. On the other hand, when Vc * <V2 (when NO is determined in S160), the step-down mode is selected by S190. When the step-down mode is selected, the mode selection signal Smd is set to "0" and output to the duty calculation unit 32 and the duty selection unit 33.

When the operation mode selection unit 31 outputs the control target voltage Vc * (S150) and the mode selection signal Smd (S180, S190) based on the output voltage command value Vout * read in S110, the process ends.

In S130, it is also possible to set Vc * = V2. Even if Vc * = V2, the control target voltage Vc * can be set while avoiding the boundary voltage range of V1 <Vc * <V2. Further, in S160, the control target voltage Vc * and the threshold value V1 may be compared. In this case, the step-down mode (Smd = “1”) can be selected when Vc *> V1, while the step-down mode (Smd = “0”) can be selected when Vc * ≦ V1.

With reference to FIG. 2 again, the duty calculation unit 32 calculates the duty ratio Dc for controlling the output voltage Vout to the control target voltage Vc *. The duty calculation unit 32 switches the control calculation of the duty ratio Dc between the step-down mode and the step-up mode according to the mode selection signal Smd. Hereinafter, for each of the first switching element Tr1 and the second switching element Tr2, the ratio (Ton / Tc) of the on-period Ton to the switching period Tc when it is turned on and off is defined as the duty ratio.

In the step-down mode in which the step-down circuit 10 operates, the following equation (1) is established between the output voltage Vout and the input voltage Vin by using the duty ratio D1 of the first switching element Tr1.

Vout = D1 · Vin ... (1)
Therefore, in the step-down mode, it can be calculated by the following equation (2) using the detected value of the input voltage Vin and the control target voltage Vc *.

Dc = Vc * / Vin ... (2)
Alternatively, the duty ratio Dc can be calculated by feedback control (typically, PI control) using the voltage deviation ΔVout (ΔVout = Vc * −Vout) of the output voltage. Alternatively, the duty ratio Dc in the step-down mode can be obtained by adding the feedforward term (Equation (2)) based on Vin and the feedback term based on the output voltage deviation ΔVout.

In the boost mode in which the boost circuit 20 operates, the following equation (3) is established between the output voltage Vout and the input voltage Vin by using the duty ratio D2 of the second switching element Tr2.

Vout = 1 / (1-D2) ・ Vin ... (3)
Therefore, in the boost mode, it can be calculated by the following equation (4) using the detected value of the input voltage Vin and the control target voltage Vc *.

Dc = 1- (Vin / Vc *) ... (4)
Even in the boost mode, the duty ratio Dc can be calculated by the feedback control based on the output voltage deviation ΔVout described above, or the feedforward term (Equation (3)) and the feedback term based on the output voltage deviation ΔVout It is also possible to obtain the duty ratio Dc in the step-down mode by adding.

The duty selection unit 33 uses the duty ratio Dc calculated by the duty calculation unit 32 to form a duty ratio D1 of the first switching element Tr1 (step-down circuit 10) and a second switching element Tr2 (boost circuit 20). The duty ratio D2 is set. The duty selection unit 33 outputs the duty ratios D1 and D2 in the step-down mode and the step-up mode, respectively, according to the mode selection signal Smd.

In the step-down mode of the mode selection signal Smd = "0", D2 = 0 is set in order to fix the second switching element Tr2 (boost circuit 20) to off. On the other hand, the duty ratio D1 of the step-down circuit 10 is set to the duty ratio Dc calculated to control the output voltage Vout to the control target voltage Vc * (D1 = Dc). For example, D1 is set to a duty ratio Dc according to the equation (2).

On the other hand, in the step-up mode of the mode selection signal Smd = "1", D1 = 1 is set in order to fix the first switching element (step-down circuit 10) on. On the other hand, the duty ratio D2 of the booster circuit 20 is set to the duty ratio Dc calculated to control the output voltage Vout to the control target voltage Vc * (D2 = Dc). For example, D2 is set to a duty ratio Dc according to equation (4).

The PWM signal generation unit 34 outputs a control signal S1 for turning on / off the switching element Tr1 according to the duty ratio D1 and a control signal S2 for turning on / off the switching element Tr2 according to the duty ratio D2. The control signals S1 and S2 are input to the switching elements Tr1 and Tr2 as shown in FIG.

In the PWM signal generation unit 34, the voltage Vcw of a periodic carrier wave (for example, a sawtooth wave or a triangular wave) is compared with the voltages VD1 and VD2 proportional to the duty ratios D1 and D2. , S2 are generated. Specifically, assuming that the amplitude of the carrier wave is equivalent to the voltage VD1 (VD2) when the duty ratio is 1.0, S1 (S2) is used to turn on the switching element Tr1 (Tr2) in the period of Vcw ≦ VD1 (VD2). ) = "1", while S1 = "0" can be set to turn off the switching element Tr1 (Tr2) in the period of Vcw> VD1 (VD2).

As a result, the switching elements Tr1 and Tr2 are turned on and off at the switching period Tc corresponding to the carrier wave period, and the ratio of the on period during the switching period Tc is the duty ratios D1 and D2 output from the duty selection unit 33. It is controlled according to. In the step-down mode, by setting D2 = 0, the control signal S2 = "0" is fixed, and the second switching element (boost circuit 20) is fixed off. Further, in the step-up mode, by setting D1 = 0, the control signal S1 = "0" is fixed, and the first switching element (step-down circuit 10) is fixed on.

As described above, according to the power conversion device 5a according to the first embodiment, when the output voltage Vout is controlled according to the output voltage command value Vout * that can be set for both step-down and step-up of the input voltage Vin. In the step-down mode, the switching of the second switching element (boost circuit 20) is stopped (fixed off), and in the step-up mode, the switching of the first switching element (step-down circuit 10) is stopped (fixed on). This makes it possible to perform highly efficient DC / DC conversion while avoiding the occurrence of switching loss in both the step-down circuit 10 and the step-up circuit 20.

Further, it is avoided that the control target voltage Vc * is set within the boundary voltage range of V1 <Vc * <V2 (V1 <Vin, V2> Vin), which is the boundary region between the step-up mode and the step-down mode. The step-down circuit 10 and the step-up circuit 20 can be controlled. Therefore, even if the input voltage Vin fluctuates, it is possible to avoid frequent switching between the step-down mode and the step-up mode, and stabilize the control operation of the power conversion device 5a.

Modification example of the first embodiment 1.
In the first modification of the first embodiment, different setting examples of the control target voltage Vc * in the operation mode selection unit 31 in the first embodiment will be described. In the first modification of the first embodiment, only the method for setting the control target voltage Vc * at the time of switching between the step-up mode and the step-down mode by the operation mode selection unit 31 is different from that of the first embodiment. Since the configuration and control of the above are the same as those in the first embodiment, the detailed description will not be repeated.

FIG. 4 is a conceptual diagram illustrating the operation of the operation mode selection unit 31 according to the first modification of the first embodiment. The horizontal axis of FIG. 4 is the time axis, and the vertical axis is the voltage.

With reference to FIG. 4, the control target voltage Vc * set by the operation mode selection unit 31 when the output voltage command value Vout * drops from the boost mode region (Vout * ≧ V2) with the passage of time. Behavior is indicated by reference numerals 304-306.

Reference numeral 304 indicates the behavior of the control target voltage Vc * according to the first embodiment. That is, when the output voltage command value Vout * enters the boundary voltage range (V1 <Vout * <V2) from the boost mode region (Vout * ≧ V2), Vc * = V1 is immediately set. As a result, the control target voltage Vc * input to the duty calculation unit 32 momentarily changes from V2 to V1. As a result, there is a concern that the control of the power conversion device 5a becomes unstable due to the sudden change in the calculated duty ratio Dc.

Therefore, in the first modification of the first embodiment, the operation mode selection unit 31 sets the control target voltage Vc * after limiting the temporal change of the control target voltage Vc * as shown by reference numerals 305 and 306. Change from V2 to V1. At reference numeral 305, the control target voltage Vc * changes from V2 to V1 so as to decrease monotonically according to the ramp function at a constant rate. Further, at reference numeral 306, the control target voltage Vc * changes from V2 to V1 so as to decrease monotonically according to the quadratic function. As a result, it is possible to prevent the control of the power conversion device 5a from becoming unstable by slowing down the temporal change of the control target voltage Vc *. The control target voltage Vc * can be monotonically reduced according to any function without being limited to the ramp function and the quadratic function indicated by reference numerals 305 and 306.

Although the operation when switching from the step-up mode to the step-down mode has been described with reference to FIG. 4, the operation mode selection unit 31 also performs the temporal control target voltage Vc * when switching from the step-down mode to the step-up mode. Limit change. That is, the control target voltage Vc * can be changed according to a ramp function, a quadratic function, or an arbitrary function so that the control target voltage Vc * increases monotonically from V1 to V2.

As described above, in the power conversion device 5a according to the first embodiment, since the control target voltage Vc * is set while avoiding the boundary voltage range (V1 <Vc * <V2), the step-up mode and the step-down mode are switched. , The control target voltage Vc * changes from the voltage range of V2 or more to the voltage range of V1 or less (from step-up mode to step-down mode) or from the voltage range of V1 or less to the voltage range of V2 or more (step-down mode to step-up mode). At that time, the control of the power converter 5a can be stabilized by limiting the temporal change of the control target voltage Vc *.

Modification example of the first embodiment 2.
The second modification of the first embodiment is different in that the controller 30x shown in FIG. 5 is arranged in place of the controller 30a in the first embodiment.

FIG. 5 is a block diagram illustrating the function of the controller 30x according to the second modification of the second embodiment.

Comparing FIGS. 5 and 2, the controller 30x is different from the controller 30a in that it includes a duty calculation unit 32x instead of the duty calculation unit 32. Since the configuration and operation of the other parts of the controller 30x are the same as those of the controller 30a, the detailed description will not be repeated. The duty calculation unit 32x has a function of controlling the reactor current IL flowing through the reactor L1. In the second modification of the first embodiment, in the power conversion device 5a, a current sensor (not shown) for detecting the reactor current IL is arranged between the nodes N1 and N2. The value detected by the current sensor is input to the controller 30x (duty calculation unit 32x).

FIG. 6 shows a block diagram illustrating the function of the duty calculation unit 32x.
With reference to FIG. 6, the duty calculation unit 32x includes a subtraction unit 321 and 323, a voltage control unit 322, and a current control unit 324.

The subtraction unit 321 calculates the output voltage deviation ΔVout by subtracting the output voltage Vout from the control target voltage Vc *. The voltage control unit 382 generates a current target value IL * of the reactor current IL by a feedback control calculation (for example, PI control calculation or PID control calculation) using the output voltage deviation ΔVout.

The subtraction unit 323 calculates the current deviation ΔIL by subtracting the reactor current IL from the current target value IL *. The current control unit 324 calculates the duty ratio Dc by a feedback control calculation (for example, PI control or PID control) for setting the current deviation ΔIL = 0.

When the output voltage Vout is lower than the control target voltage Vc *, the current target value IL * is increased by the voltage control unit 322. On the other hand, when the output voltage Vout is higher than the control target voltage Vc *, the current target value IL * is lowered by the voltage control unit 322. The current control unit 324 calculates the duty ratio Dc so that the current target value IL * adjusted by the voltage control unit 322 to eliminate the output voltage deviation ΔVout and the reactor current IL match. In the duty calculation unit 32x, unlike the duty calculation unit 32, the control calculation of the duty ratio Dc is common between the operation modes (boost mode / step-down mode).

The duty ratio Dc is used for the duty ratio D1 of the first switching element (step-down circuit 10) in the step-down mode, and is used for the duty ratio D2 of the second switching element (boost circuit 20) in the step-up mode.

As a result, according to the second modification of the first embodiment, in addition to the effect of the first embodiment, the output voltage Vout can be controlled to the output voltage command value Vout * while stabilizing the reactor current IL. ..

Embodiment 2.
In the second embodiment, in addition to the step-up mode (step-down circuit 10 stop) and step-down mode (step-up circuit 20 stop) described in the first embodiment, the step-down circuit 10 and step-up are performed in a transient state for switching between the step-up mode and the step-down mode. A control that further introduces a buck-boost mode that operates both of the circuits 20 will be described.

FIG. 7 is a mode transition diagram of the power conversion device according to the second embodiment, and FIG. 8 is a conceptual diagram illustrating the relationship between the output voltage and the mode in the power conversion device according to the second embodiment.

With reference to FIG. 7, in the second embodiment, when shifting from the step-up mode (step-down circuit 10 stop) to the step-down mode (step-up circuit 20 stop) due to a decrease in the output voltage command value Vout *, the step-up mode is started. After the transition to the buck-boost mode, the mode transition is controlled so as to transition from the buck-boost mode to the buck-boost mode.

Similarly, when shifting from the step-down mode (step-up circuit 20 stop) to the step-up mode (step-down circuit 10 stop) due to an increase in the output voltage command value Vout *, the step-down pressure is changed after the step-down mode is changed to the step-up / down pressure mode. The mode transition is controlled so as to transition from the mode to the boost mode.

With reference to FIG. 8, in the second embodiment, the mode is selected based on the output voltage Vout controlled according to the output voltage command value Vout *. In the example of FIG. 8, as the output voltage command value Vout * rises from the step-down mode region (Vout * ≦ V1) to the step-up mode region (Vout * ≧ V2), the output voltage Vout also rises in the step-down mode. It rises from the region (Vout ≦ V1) to the boost mode region (Vout ≧ V2). At this time, it rises to Vout = V1 at time t1, rises to Vout = Vin at time t2, and rises to Vout = V2 at time t3.

In the example of FIG. 8, the step-down mode is selected in the period T1 up to the time t1, the step-up mode is selected in the period T3 after the time t3, and the period T2 at times t1 to t2 and the period T3 at times t2 to t3 , The buck-boost mode is selected. Since the operations of the step-down circuit 10 and the step-up circuit 20 in the step-down mode and the step-up mode are the same as those in the first embodiment, detailed description thereof will not be repeated.

In the buck-boost mode, by turning on and off both the first switching element (step-down circuit 10) and the second switching element (boosting circuit 20), there is a period in which both the switching elements Tr1 and Tr2 stop the on / off operation. Prevents instability of control operation due to this. It is understood that the buck-boost mode has a period (T2) in which the output voltage Vout is lower than the input voltage Vin and a period (T3) in which the output voltage Vout is higher than the input voltage Vin.

When the control target voltage Vc * and the operation mode in the boundary voltage range (V1 to V2) are set according to the first embodiment, in the period T3, the step-down mode is selected even though Vin <Vout, or the period T4. In some cases, the boost mode is selected even though Vin> Vout. In such a case, both the first switching element (step-down circuit 10) and the second switching element (boosting circuit 20) are fixed on or off to stop the on-off operation, so that the voltage and the voltage and Since the current is in an uncontrolled state, there is a concern that the control operation may become unstable.

Therefore, in the second embodiment, when the output voltage Vout is in the boundary voltage range (V1 to V2), the control operation is performed by applying the buck-boost mode in which both the step-down circuit 10 and the step-up circuit 20 operate. To stabilize.

FIG. 9 is a circuit diagram illustrating the configuration of the power conversion device according to the second embodiment.
With reference to FIG. 9, the power conversion device 5b according to the second embodiment includes a controller 30b instead of the controller 30a as compared with the power conversion device 5a (FIG. 1) according to the first embodiment. Is different. Since the configuration and operation of other parts of the power conversion device 5b are the same as those of the power conversion device 5a, the detailed description will not be repeated.

FIG. 10 is a block diagram illustrating the function of the controller 30b.
With reference to FIG. 10, the controller 30b includes an operation mode selection unit 35, a duty calculation unit 32, a duty selection unit 36, and a PWM signal generation unit 34. The duty calculation unit 32 and the PWM generation unit 34 are the same as those in the first embodiment.

In addition to the output voltage command value Vout * and the threshold values V1 and V2, the output voltage Vout is input to the operation mode selection unit 35. The operation mode selection unit 35 outputs the control target voltage Vc * and the mode selection signal Smd.

FIG. 11 is a flowchart illustrating the operation of the operation mode selection unit 35.
With reference to FIG. 11, when the output voltage Vout and the output voltage command value Vout * of the power conversion device 5a are input by S210, the operation mode selection unit 35 uses S220 to S240 similar to S120 to S140 (FIG. 3). , The control target voltage Vc * is set by comparing the output voltage command value Vout * with the threshold voltages V1 and V2. The operation mode selection unit 35 outputs the control target voltage Vc * set in S230 or S240 to the duty calculation unit 32 (32x) by S250 similar to S150 (FIG. 3).

For example, as in the example of FIG. 3, when the output voltage command value Vout * is in the boundary voltage range (V1 <Vout * <V2), Vc * = V1 is set, while in other cases, Vc * = Vout *. Set. That is, also in the second embodiment, the control target voltage Vc * is set while avoiding the boundary voltage range of V1 <Vc * <V2, as in the first embodiment.

In the second embodiment, the operation mode selection unit 35 selects the operation mode by comparing the output voltage Vout with the threshold values V1 and V2. The operation mode selection unit 31 compares the output voltage Vout with the threshold value V2 by S260. Then, when Vout ≧ V2 (when YES is determined in S260), the boost mode is selected by S280. When the boost mode is selected, the mode selection signal Smd is set to "1" as in the first embodiment. On the other hand, when Vc * <V2 (NO determination in S260), the operation mode selection unit 35 further compares the output voltage Vout with the threshold value V1 by S270. Then, when Vout ≦ V1 (when NO is determined in S270), the step-down mode is selected by S300. When the step-down mode is selected, the mode selection signal Smd is set to "0" as in the first embodiment.

On the other hand, when Vout> V1 (NO determination in S270), that is, when V1 <Vout <V2, the buck-boost mode is selected by S290. When the buck-boost mode is selected, the mode selection signal Smd is set to "2".

The mode selection signal Smd is set to any of "0", "1", and "2" by any of S280 to S300, and is output to the duty calculation unit 32 and the duty selection unit 33.

With reference to FIG. 10 again, the duty calculation unit 32 will be described in the first embodiment based on the input voltage Vin and the output voltage Vout, the control target voltage Vc * from the operation mode selection unit 35, and the mode selection signal Smd. As described above, the duty ratio Dc for the step-down mode is calculated when the mode selection signal Smd = “0”, and the duty ratio Dc for the step-down mode is calculated when the mode selection signal Smd = “1”. Further, the duty calculation unit 32 calculates the duty ratio Dc so as to be used for the duty ratio D2 of the booster circuit 20 in the buck-boost mode (Smd = “2”).

The duty selection unit 36 has a duty ratio D1 of the step-down circuit 10 (switching element Tr1) and a step-up circuit 20 (switching element) in each of the step-down mode, the step-up mode, and the step-up / down mode according to the mode selection signal Smd. The duty ratio D2 of Tr2) is set. The duty ratios D1 and D2 in each of the step-down mode (Smd = "0") and the step-up mode (Smd = "1") are set in the same manner as in the first embodiment.

In the buck-boost mode (Smd = “2”), the duty selection unit 36 fixes the duty ratio D1 of the step-down circuit 10 (switching element Tr1) to the determined duty ratio Ds regardless of the control target voltage Vc *. .. On the other hand, the duty ratio D2 of the booster circuit 20 (switching element Tr2) is set to the duty ratio Dc from the duty calculation unit 32 (D1 = Ds, D2 = Dc).

The duty ratio Ds in the step-down circuit 10 may be a predetermined fixed value or a value variably set for each selection of the buck-boost mode. In particular, since the input voltage to the booster circuit 20 is lower than the threshold value V1 to prevent the switching element Tr2 from being fixed off, Ds <(V1 / Vin) is guaranteed according to the input voltage Vin. It is also possible to set Ds variably according to Vin.

In the step-up / down mode, it is understood that the input voltage to the booster circuit 20 is Ds · Vin from the equation (1). Therefore, by substituting Vin in the equation (4) with (Ds · Vin), the duty ratio Dc in the buck-boost mode by the duty calculation unit 32 can be calculated according to the following equation (5).

Dc = 1- (Ds · Vin / Vc *)… (5)
In each operation mode, the PWM signal generation unit 34 generates control signals S1 and S2 according to the duty ratios D1 and D2 set by the duty selection unit 36, as in the first embodiment. The first switching element (step-down circuit 10) and the second switching element (boosting circuit 20) are turned on or off according to the control signals S1 and S2 output from the PWM signal generation unit 34.

Therefore, according to the power conversion device according to the second embodiment, in the step-up mode and the step-down mode, as in the first embodiment, the switching of one of the step-down circuit 10 and the step-up circuit 20 is stopped, so that the DC The efficiency of / DC conversion is improved.

Further, as in the first embodiment, the control target voltage Vc * is set while avoiding the boundary voltage range (V1 to V2), and the step-down voltage mode is introduced corresponding to the boundary voltage range to reduce the voltage. It is avoided that both the switching elements Tr1 and Tr2 stop the on / off operation in both the circuit 10 and the booster circuit 20. Thereby, it is possible to prevent the control operation from becoming unstable in the region.

In the second embodiment, as in the first embodiment, the control target voltage Vc * is set by avoiding the boundary voltage range (V1 to V2) with respect to the output voltage command value Vout * that can be arbitrarily set. By doing so, the application of the buck-boost mode is limited to the case where the output voltage command value Vout * changes beyond the boundary voltage range (V1 to V2), and the buck-boost mode is constantly applied. Can be prevented. As a result, the efficiency of DC / DC conversion can be improved by increasing the application period of the step-up mode and the step-down mode in which switching of one of the step-down circuit 10 and the step-up circuit 20 is stopped.

A modified example of the second embodiment.
The modified example of the second embodiment is different in that the controller 30y shown in FIG. 12 is arranged in place of the controller 30b in the second embodiment.

FIG. 12 is a block diagram illustrating the function of the controller 30y according to the modified example of the second embodiment.

Comparing FIGS. 5 and 2, the controller 30y is different from the controller 30a in that it includes a duty selection unit 37 instead of the duty selection unit 36. Since the configuration and operation of the other parts of the controller 30y are the same as those of the controller 30b, the detailed description will not be repeated.

Similar to the duty selection unit 36, the duty selection unit 37 has a duty ratio D1 of the step-down circuit 10 (switching element Tr1) in each of the step-down mode, the step-up mode, and the step-up / down mode according to the mode selection signal Smd. And the duty ratio D2 of the booster circuit 20 (switching element Tr2) are set.

The duty selection unit 37 is different from the duty selection unit 36 in that the duty ratios D1 and D2 are set in the buck-boost mode. That is, the duty ratios D1 and D2 in each of the step-down mode (Smd = "0") and the step-up mode (Smd = "1") are set in the same manner as in the first embodiment.

In the buck-boost mode (Smd = “2”), the duty selection unit 37 fixes the duty ratio D2 of the booster circuit 20 (switching element Tr2) to the determined duty ratio Ds regardless of the control target voltage Vc *. .. On the other hand, the duty ratio D1 of the step-down circuit 10 (switching element Tr2) is set to the duty ratio Dc from the duty calculation unit 32 (D1 = Dc, D2 = Ds). The duty ratio Ds in the booster circuit 20 may also be a predetermined fixed value or a value variably set for each selection of the buck-boost mode.

In the step-up / down mode, the step-up ratio in the step-up circuit 20 is fixed, so that the product of the output voltage of the step-down circuit 10 and the step-up ratio must be equal to the control target voltage Vc *. Therefore, in the formula (3), the duty ratio Dc is calculated according to the following formula (7) by modifying the following formula (6) obtained by D2 = Ds and Vin = Vin · Dc. Can be done.

Vc * = 1 / (1-Ds) · (Vin · Dc) ... (6)
Dc = (Vc * / Vin) · (1-Ds) ... (7)
In each operation mode, the PWM signal generation unit 34 generates control signals S1 and S2 in the same manner as in the first and second embodiments according to the duty ratios D1 and D2 set by the duty selection unit 37.

Therefore, the step-down circuit 10 and the step-up circuit 20 can be obtained by applying the buck-boost mode in the boundary voltage range (V1 to V2) by the power conversion device according to the modified example of the second embodiment and in the same way as in the first embodiment. It is avoided that both the switching elements Tr1 and Tr2 stop the on / off operation in both of them. As a result, as in the second embodiment, it is possible to improve the efficiency of DC / DC conversion and prevent the control operation from becoming unstable in the boundary voltage range.

Further, in the second embodiment and the modified example, in the step-up / down mode, one of the step-down circuit 10 and the step-up circuit 20 can set the duty ratio Ds without performing arithmetic processing according to the control target voltage Vc *. That is, the calculation load can be reduced.

In each of the second embodiment and the modified example, in each of the controller 30 (FIG. 10) and the controller 30y (FIG. 12), the duty calculation unit 32 is replaced with the modified example 2 of the first embodiment. It is also possible to calculate the duty ratio Dc by the duty calculation unit 32x. In this case, in the duty calculation unit 32x, as described above, the control calculation of the duty ratio Dc is common between the operation modes. Therefore, in the buck-boost mode, as in the duty calculation unit 32, for the step-down circuit 10 or It is not necessary to change the calculation formula of the duty ratio Dc for the booster circuit 20 between the booster mode and the step-down mode.

Further, the control target voltage Vc * is changed from V2 to V1 (step-up mode to step-down mode) or from V1 to V2 (step-down) by combining the modification 1 of the first embodiment with the second embodiment and the modified example. It is also possible to limit the temporal change of the control target voltage Vc * when changing from the mode to the step-up mode). By doing so, the control operation can be further stabilized by gradual change of the control target voltage Vc * in the calculation of the duty ratio Dc in the buck-boost mode.

Embodiment 3.
In the third embodiment, the control at the time of switching between the buck-boost mode described in the second embodiment and each of the step-down mode and the step-up mode will be described.

FIG. 13 is a circuit diagram illustrating the configuration of the power conversion device according to the third embodiment.
With reference to FIG. 13, the power conversion device 5c according to the third embodiment includes a controller 30c instead of the controller 30b as compared with the power conversion device 5b (FIG. 9) according to the second embodiment. Is different. Further, in the power conversion device 5c, a current sensor (not shown) is arranged between the nodes N1 and N2 as in the modification 2 of the first embodiment, and the detected value of the reactor current IL is sent to the controller 30c. Entered. Since the configuration and operation of other parts of the power conversion device 5c according to the third embodiment are the same as those of the power conversion devices 5a and 5b, detailed description thereof will not be repeated.

FIG. 14 is a block diagram illustrating the function of the controller 30c.
With reference to FIG. 14, the controller 30c includes an operation mode selection unit 35, a duty calculation unit 38, a duty selection unit 36, and a PWM signal generation unit 34. The operation mode selection unit 35, the duty selection unit 36, and the PWM generation unit 34 are the same as those in the second embodiment. Therefore, also in the controller 30c, the operation mode is selected by the operation mode selection unit 35 to be one of the step-down mode, the step-up mode, and the step-up / down mode, and the mode selection signal Smd is set to “0”. It is set to either "1" or "2".

FIG. 15 is a block diagram illustrating the function of the duty calculation unit 38.
With reference to FIG. 15, the duty calculation unit 38 includes a subtraction unit 381, 383, a voltage control unit 382, and a current control unit 384. The duty calculation unit 38 has a function of controlling the reactor current IL in addition to the output voltage Vout, as in the duty calculation unit 32x according to the second modification of the first embodiment.

Similar to the subtraction unit 321 (FIG. 6), the subtraction unit 381 calculates the output voltage deviation ΔVout by subtracting the output voltage Vout from the control target voltage Vc *. Similar to the voltage control unit 322 (FIG. 6), the voltage control unit 382 performs a feedback control calculation using the output voltage deviation ΔVout (for example, a control calculation by PI control or PID control) to perform a current target value IL of the reactor current IL. Generate a feedback term of *.

In the voltage control unit 382, when the operation mode is switched, the current target value IL * is generated by adding the current feedforward (FF) term Iff, which will be described later, to the feedback term. On the other hand, when the operation mode is maintained, the feedback term is set to the current target value IL * as it is without adding the current FF term If.

Similar to the subtraction unit 323 (FIG. 6), the subtraction unit 383 calculates the current deviation ΔIL by subtracting the reactor current IL from the current target value IL *.

The subtraction unit 383 calculates the current deviation ΔIL by subtracting the reactor current IL from the current target value IL *. The current control unit 384 calculates the duty ratio Dc by a feedback control calculation (for example, a control calculation by PI control or PID control) for setting the current deviation ΔIL = 0. In the current control unit 384, when the operation mode is switched, the duty ratio Dc is generated by adding the duty feedforward (FF) term Dff, which will be described later, to the feedback term. On the other hand, when the operation mode is maintained, the feedback term is set to the duty ratio Dc as it is without adding the duty FF term Dff. In the voltage control unit 382 and the current control unit 384, it is possible to determine whether or not the operation mode is switched by the transition of the value of the mode selection signal Smd.

As described above, in the third embodiment, the current FF term and the duty FF term are added at the time of switching the operation mode in the voltage control unit 382 and the current control unit 384 in which the control calculation is common between the operation modes. The current FF term and the duty FF term are calculated so as to be reflected in the feedback term by I (integral) control with respect to the current target value IL * and the duty ratio Dc. That is, these feed-forward terms once added are reflected in the voltage control unit 382 and the current so as to be continuously reflected in the calculation result (current target value IL * and duty ratio Dc) after the operation mode is switched. The control calculation in the control unit 384 is configured.

FIG. 16 shows a chart illustrating a setting example of the current FF term and the duty FF term.
With reference to FIG. 16, the transition of the operation mode is changed from the step-up mode to the buck-boost mode, from the buck-boost mode to the step-up mode, and from the step-down mode to the buck-boost mode, and There are four types, from the buck-boost mode to the buck-boost mode. The calculation formulas for the current FF term and the duty FF term are individually predetermined for each of the above four types of operation mode switching.

When the operation mode is switched from the boost mode to the buck-boost mode, the duty FF term (Dff) is calculated based on the voltage applied to the reactor L1 in the boost mode and the buck-boost mode. Further, the current FF term (Iff) is calculated based on the current flowing through the capacitor C1 in the step-up mode and the buck-boost mode. Specifically, the duty FF term (Dff) is calculated according to the following formula (8), and the current FF term (Iff) is calculated according to the following formula (9).

Dff = Vin / Vout ・ (1-Ds)… (8)
If = (1 / Ds-1) ・ IL… (9)
When the operation mode is switched from the step-up / down mode to the step-up mode, the duty FF term (Dff) is calculated based on the voltage applied to the reactor L1 in the step-up / down mode and the step-up mode. Further, the current FF term (Iff) is calculated based on the current flowing through the capacitor C1 in the step-up / down mode and the step-up mode. Specifically, the duty FF term (Dff) is calculated according to the following formula (10), and the current FF term (Iff) is calculated according to the following formula (11).

Dff = (Vin / Vout) · (Ds-1) ... (10)
If = (Ds-1) ・ IL… (11)
When switching the operation mode from the step-down mode to the step-up / down mode, the duty FF term (Dff) is calculated based on the voltage applied to the reactor L1 in the step-down mode and the step-up / down mode. The current FF term (Iff) is calculated based on the current flowing through the capacitor C1 in the step-down mode and the buck-boost mode. Specifically, the duty FF term (Dff) is calculated according to the following formula (12), and the current FF term (Iff) is calculated according to the following formula (13).

Dff = (Vin / Vout) · (Db-Ds) -Db ... (12)
If = ((1 / Ds) ・ (Vout / Vin) -1) ・ IL… (13)
When the operation mode is switched from the step-up / down mode to the step-down mode, the duty FF term (Dff) is calculated based on the voltage applied to the reactor L1 in the step-up / down mode and the step-down mode. Further, the current FF term (Iff) is calculated based on the current flowing through the capacitor C1 in the buck-boost mode and the buck-boost mode. Specifically, the duty FF term (Dff) is calculated according to the following formula (14), and the current FF term (Iff) is calculated according to the following formula (15).

Dff = Ds + Db · ((Vin / Vout) -1) ... (14)
If = (Ds · (Vin / Vout) -1) · IL ... (15)
In the equations (8) to (15), Vin, Vout, and IL are the input voltage Vin, the output voltage Vout, and the reactor current IL at the time of calculating the current FF term and the duty FF term according to the operation mode switching. Is the detected value of. Further, Ds indicates a fixed duty ratio Ds of one of the step-down circuit 10 (switching element Tr1) and the step-up circuit 20 (switching element Tr2) used in the buck-boost mode before or after the operation mode switching. Db corresponds to the duty ratio Dc of the other of the step-down circuit 10 and the step-up circuit 20 determined by the formula (5) or (7) using the fixed duty ratio Ds in the buck-boost mode.

The calculation formula shown in FIG. 16 is an example, and it is also possible to calculate the current FF term and the duty FF term by using other calculation formulas.

Next, the effect of feedforward control at the time of switching the operation mode according to the third embodiment will be described using the simulation waveforms of FIGS. 17 to 20. The horizontal axis of FIGS. 17 to 20 is the time axis, and the vertical axis shows the output voltage Vout, the reactor current IL, and the transition of the duty ratio.

FIG. 17 is a simulation waveform diagram at the time of operation mode switching due to an increase in the output voltage command value in the power conversion device 5b according to the second embodiment. FIG. 17 shows a simulation result when the power conversion device 5b is controlled by using the duty calculation unit 32x (FIG. 6) instead of the duty calculation unit 32 in the configuration of FIG.

With reference to FIG. 17A, as the output voltage command value Vout * rises from the step-down mode, the control target voltage Vc * rises while avoiding the boundary voltage range (V1 to V2) after the time ta. As a result, the output voltage Vout is higher than the output voltage command value Vout * and rises to the threshold value V2. With the introduction of the buck-boost mode, the operation mode is switched from the step-down mode to the buck-boost mode at time ta, and the operation mode is switched from the buck-boost mode to the boost mode at time tb.

17 (b) shows an enlarged view before and after the time ta in FIG. 17 (a), and FIG. 17 (c) shows an enlarged view before and after the time tb in FIG. 17 (a).

With reference to FIGS. 17 (b) and 17 (c), in the power conversion device 5b according to the second embodiment, since the predetermined duty ratio Ds is used in the buck-boost mode, when switching to the buck-boost mode and When switching from the buck-boost mode, the duty ratio changes relatively significantly. As a result, the output voltage Vout fluctuates and the convergence of the reactor current IL is slowed down in each of the operation mode switching at the time ta and tb.

FIG. 18 is a simulation waveform diagram at the time of operation mode switching due to an increase in the output voltage command value in the power conversion device 5c according to the third embodiment. FIG. 18 shows a simulation result when the output voltage command value Vout * changes under the same conditions as in FIG.

In FIG. 18A, the operation mode is switched from the step-down mode to the step-up / down mode at the same time ta as in FIG. 17A, and the operation mode is switched from the step-up / down mode to the step-up mode at time tb. Occurs. Further, FIG. 18 (b) shows an enlarged view of FIG. 18 (a) before and after the time ta, and FIG. 18 (c) shows an enlarged view of FIG. 18 (a) before and after the time tb. Is done.

Comparing FIG. 18 (b) with FIG. 17 (b), when switching from the step-down mode to the buck-boost mode at time ta, the power conversion device 5c according to the third embodiment has a current FF term and a duty FF term. By the addition of, the amount of change to the predetermined duty ratio Ds described above is relaxed. As a result, it is understood that the fluctuation of the output voltage Vout hardly fluctuates, and the reactor current IL converges quickly.

Similarly, from the comparison of FIGS. 18 (c) and 17 (c), even when the buck-boost mode is switched to the step-down mode at time tb, the power conversion device 5c according to the third embodiment has a current FF term. It is understood that the fluctuation of the output voltage Vout hardly fluctuates and the reactor current IL converges quickly due to the addition of the duty FF term.

FIG. 19 is a simulation waveform diagram at the time of operation mode switching due to a decrease in the output voltage command value in the power conversion device 5b according to the second embodiment. In FIG. 19, similarly to FIG. 17, the simulation result when the power conversion device 5b is controlled by using the duty calculation unit 32x (FIG. 6) in the controller 30b (FIG. 12) is shown.

With reference to FIG. 19A, as the output voltage command value Vout * decreases from the step-down mode, the control target voltage Vc * decreases while avoiding the boundary voltage range (V1 to V2) after the time ct. As a result, the output voltage Vout is lower than the output voltage command value Vout *, and drops to the threshold value V1. With the introduction of the buck-boost mode, the operation mode is switched from the step-up mode to the buck-boost mode at the time tk, and the operation mode is switched from the buck-boost mode to the buck-boost mode at the time dt.

19 (b) shows an enlarged view of FIG. 19 (a) before and after the time tk, and FIG. 19 (c) shows an enlarged view of FIG. 19 (a) before and after the time tk.

With reference to FIGS. 19 (b) and 19 (c), in the power conversion device 5b according to the second embodiment, the current FF term and the duty FF term are added when the operation mode is switched at the time tk and td. The duty ratios D1 and D2 are calculated without any problem. In the power conversion device 5b according to the second embodiment, the output voltage Vout fluctuates at each of the time tc and td, and the convergence of the reactor current IL is also delayed.

FIG. 20 is a simulation waveform diagram at the time of operation mode switching due to an increase in the output voltage command value in the power conversion device 5c according to the third embodiment. FIG. 20 shows a simulation result when the output voltage command value Vout * changes under the same conditions as in FIG.

Also in FIG. 20 (a), the operation mode switching from the step-up mode to the buck-boost mode occurs at the same time tc as in FIG. 19 (a), and the operation mode switching from the buck-boost mode to the buck-boost mode occurs at the time td. Occurs. Further, FIG. 20 (b) shows an enlarged view of FIG. 20 (a) before and after the time tk, and FIG. 20 (c) shows an enlarged view of FIG. 20 (a) before and after the time tk. Is done.

Comparing FIG. 20 (b) with FIG. 19 (b), the current FF term and the duty FF term in the power conversion device 5c according to the third embodiment at the time of switching from the step-up mode to the buck-boost mode at time tk. It is understood that the fluctuation of the output voltage Vout hardly fluctuates and the reactor current IL converges quickly by the addition of.

Similarly, from the comparison of FIGS. 20 (c) and 19 (c), even when switching from the buck-boost mode to the step-down mode at time dt, the power conversion device 5c according to the third embodiment has a current FF term. It is understood that the fluctuation of the output voltage Vout hardly fluctuates and the reactor current IL converges quickly due to the addition of the duty FF term.

As described above, according to the power conversion device according to the third embodiment, it is possible to prevent the control operation in the boundary voltage range (V1 to V2) from becoming unstable due to the introduction of the buck-boost mode described in the second embodiment. , The behavior of the output voltage Vout and the reactor current IL at the time of switching the operation mode between each of the step-up mode and the step-down mode and the step-up / down mode can be stabilized.

In the third embodiment, in the configuration of the controller 30c (FIG. 14), the duty selection unit 37 (FIG. 12) according to the modified example of the second embodiment is replaced with the duty selection unit 36 according to the second embodiment. The same effect can be obtained by applying. Further, by combining the third embodiment with the first modification of the first embodiment, the control target voltage Vc * is changed from V2 to V1 (from step-up mode to step-down mode) or from V1 to V2 (from step-down mode to step-up mode). It is also possible to limit the temporal change of the control target voltage Vc * when changing. By doing so, the control operation can be further stabilized by gradual change of the control target voltage Vc * in the calculation of the duty ratio Dc in the buck-boost mode.

In the present embodiment, the step-down mode corresponds to the "first mode", the step-up mode corresponds to the "second mode", and the buck-boost mode corresponds to the "third mode". Further, the threshold value V1 corresponds to the "first threshold value", the threshold value V2 corresponds to the "second threshold value", the control signal S1 corresponds to the "first control signal", and the control signal S2 corresponds to the "second". Corresponds to "control signal". The feedback control calculation for calculating the current target value IL * from the output voltage deviation ΔVout by the voltage control unit 382 corresponds to the “first feedback control calculation”, and the feedback by the current control unit 384 for calculating the duty ratio Dc from the current deviation ΔIL. The control calculation corresponds to the "second feedback control calculation". Further, in the controllers 30a, 30x, 30b, 30y, 30c (FIGS. 2, FIG. 5, FIG. 10, FIG. 12, FIG. 14), the duty calculation unit (32, 32x, 38) and the duty selection unit (33, 36) , 37) and the "duty control unit" can be configured.

Further, in the power converters 5a to 5c (FIGS. 1, 9, and 13), the DC voltage source is illustrated as the DC power supply 40, but the DC power supply 40 that obtains the DC voltage by the AC power supply and the rectifying circuit is arranged. It is also possible to do. In this case, it is preferable to set the threshold values V1 and V2 according to the characteristics of the AC power supply and the rectifier circuit in order to avoid frequent switching between the step-up mode and the step-down mode. Specifically, the threshold value V1 is set lower than the minimum value of the AC fluctuation (ripple component) of the input voltage Vin output from the rectifier circuit, and the threshold value V2 is set higher than the maximum value of the AC fluctuation (ripple component). Can be set high.

Further, the duty calculation unit 32 (FIGS. 2, 10, and 12) switches between the duty ratio calculation function for the step-down circuit 10 and the duty ratio calculation function for the step-up circuit 20 according to the mode selection signal Smd. However, it is also possible to configure the duty ratio for the step-down circuit 10 and the duty ratio for the step-up circuit 20 to be calculated at all times. In this case, both the duty ratio for the step-down circuit 10 and the duty ratio for the booster circuit 20 are input to the duty selection units 33, 36, 37, but the duty selection unit 33, according to the mode selection signal Smd, 36, 37 have the same duty as in each of the above-described embodiments by selecting from the default duty ratio of 1,0 (or 1,0, Ds) and the duty ratio calculated by the duty calculation unit 32. The ratios D1 and D2 can be output.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

5a, 5b, 5c power converter, 10 step-down circuit, 20 step-up circuit, 30, 30a, 30b, 30c, 30x, 30y controller, 31,35 operation mode selection unit, 32, 32x, 38 duty calculation unit, 33, 36, 37 Duty selection unit, 34 PWM signal generation unit, 40 DC power supply, 41 load, 321, 323, 381, 383 subtraction unit, 322, 382 voltage control unit, 324, 384 current control unit, C1 smoothing capacitor, Di1 No. 1 semiconductor element (step-down circuit), Di1 2nd semiconductor element (boost circuit), GL power line, IL reactor current, IL * current target value, L1 reactor, N1, N2 nodes, N11, N12 input terminals, N21, N22 Output terminal, S1, S2 control signal (switching element), Smd mode selection signal, Tr1 first switching element (step-down circuit), Tr2 second switching element (boost circuit), V1, V2 threshold, Vc * control target voltage , Vout output voltage, Vout * Output voltage command value.

Claims (9)

A power converter that generates an output voltage that is obtained by raising or lowering the input voltage.
A step-down circuit including a first switching element and
A booster circuit including a second switching element and
A controller for generating first and second control signals for controlling the on / off of the first and second switching elements in order to control the output voltage according to the output voltage command value of the power converter is provided.
The controller
An operation mode selection unit that receives an input of the output voltage command value and outputs an operation mode selection result and a control target voltage of the power conversion device.
It includes a duty control unit that controls the on / off duty ratio of each of the first and second switching elements according to the operation mode and the control target voltage.
The operation mode is
A first mode in which the on / off of the second switching element is fixed while the output voltage is controlled to the control target voltage lower than the input voltage by the duty ratio of the first switching element.
It includes a second mode in which the on / off of the first switching element is fixed while the output voltage is controlled to the control target voltage higher than the input voltage by the duty ratio of the second switching element.
The operation mode selection unit sets the control target voltage of the output voltage while avoiding the boundary voltage range between the first threshold value lower than the input voltage and the second threshold value higher than the input voltage. Power converter. When the output voltage command value is within the boundary voltage range, the operation mode selection unit sets one of the first and second threshold values to the control target voltage, while the output When the voltage command value is out of the boundary voltage range, the output voltage command value is set to the control target voltage, and the voltage command value is set to the control target voltage.
The operation mode selection unit is
The first mode is selected when the control target voltage is lower than the other threshold of the first and second thresholds, while the second mode is selected when the control target voltage is higher than the other threshold. The power conversion device according to claim 1, wherein the mode of the above is selected. The operation mode is
It further includes a third mode in which the output voltage is controlled to the control target voltage by turning on and off both the first and second switching elements.
The operation mode selection unit selects the first mode when the output voltage is lower than the first threshold value, and selects the second mode when the output voltage is higher than the second threshold value. The power conversion device according to claim 1 or 2, which is selected and the third mode is selected when the output voltage is between the first and second threshold values. In the third mode, the duty control unit fixes the duty ratio of the first switching element, while controlling the duty ratio of the second switching element to the output voltage to the control target voltage. The power conversion device according to claim 3, which is set to. In the third mode, the duty control unit fixes the duty ratio of the second switching element, while controlling the duty ratio of the first switching element to the output voltage to the control target voltage. The power conversion device according to claim 3, which is set to. The power converter
A reactor connected between the step-down circuit and the step-up circuit is further provided.
In each of the first and second modes, the duty control unit calculates the current target value of the reactor current flowing through the reactor by the first feedback control calculation based on the voltage deviation of the output voltage with respect to the control target voltage. At the same time, the duty ratio of the first or second switching element is calculated by the second feedback control calculation based on the current deviation of the reactor current with respect to the current target value, and
The duty control unit uses a first calculation formula predetermined for the first feedback control calculation when the operation mode is switched between the first or second mode and the third mode. Any of claims 3 to 5, in which the first feedforward term according to the above is added and the second feedforward term according to the second calculation formula determined in advance is added to the second feedback control operation. The power conversion device according to item 1. The power converter
A reactor connected between the step-down circuit and the step-up circuit is further provided.
In each of the first and second modes, the duty control unit calculates the current target value of the reactor current flowing through the reactor by the first feedback control calculation based on the voltage deviation of the output voltage with respect to the control target voltage. Any one of claims 1 to 3, wherein the duty ratio of the first or second switching element is calculated by the second feedback control calculation based on the current deviation of the reactor current with respect to the current target value. The power converter described in. In the first mode, the duty control unit calculates the duty ratio for converting the input voltage into the control target voltage by the step-down circuit, while in the second mode, the booster circuit calculates the duty ratio. The power conversion device according to any one of claims 1 to 3, wherein the duty ratio for converting the input voltage into the control target voltage is calculated. In order to avoid the boundary voltage range and set the control target voltage, the operation mode selection unit is one of a voltage region below the first threshold value and a voltage region above the second threshold value. The power conversion device according to any one of claims 1 to 8, which limits the temporal change of the control target voltage when the control target voltage is changed from one to the other voltage region.

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