JP6416711B2 - Control device for power converter - Google Patents

Description

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

  There is a power supply control device described in Patent Document 1 that outputs power supplied from a DC power source connected to the input side via a transformer. The power supply control device described in Patent Document 1 includes a main power storage device, a capacitive load connected between the power lines of the main power storage device, and a capacitive load between the power lines of the main power storage device via a bidirectional converter. And an auxiliary power storage device connected in parallel. Power transfer between the main power storage device and the auxiliary power storage device is performed using a bidirectional converter. Further, by supplying the power of the auxiliary power storage device to the capacitive load using the bidirectional converter, charging is performed until the voltage of the capacitive load becomes equal to the voltage of the main power storage device.

JP 2007-295699 A

  When the bidirectional converter in the power supply control device described in Patent Document 1 is a forward active clamp type DCDC converter having a choke coil on the auxiliary storage battery side, charging the capacitive load increases the current of the choke coil. It is done by repeating the decrease. Further, the power supply control device described in Patent Document 1 is not provided with a limiting resistor or the like for preventing an inrush current from the viewpoint of cost reduction and miniaturization of the system.

  Here, the condition for reducing the current of the choke coil is that the voltage of the auxiliary storage battery is smaller than the value obtained by dividing the voltage of the capacitive load by the turn ratio of the coils constituting the bidirectional converter. Therefore, when the voltage of the capacitive load is small, such as at the start of charging, the choke coil current continues to increase. As a result, the DCDC converter may be deteriorated or damaged.

  The present invention has been made to solve the above-described problems, and a main object of the present invention is to provide a control device for a power converter that can suppress an excessive current in a circuit.

  The present invention is a power conversion device that supplies power from an input side to which a DC power supply is connected to an output side via a transformer, the first coil provided as an input side of the transformer, the first coil, A switching circuit including a first switching element connected in parallel and a second switching element connected in series with the first coil; a choke coil provided between the switching circuit and the DC power supply; and the transformer A second coil provided on the output side, magnetically coupled to the first coil, and provided as an output side of the transformer; a third switching element and a capacitor connected in parallel or in series with the second coil; A forward active unit that supplies power from the input side to which the DC power supply is connected to the output side via a transformer. A control apparatus for a ramp circuit, wherein the first switching element and the third switching element are turned off and the second switching element is turned on, and the first switching element and the second switching element are turned off. , A first mode for performing control to turn on the third switching element, control for turning on the first switching element and the third switching element, and turning off the second switching element, and the first switching. A control for turning off the element and the third switching element and turning on the second switching element, and a control for turning off the first switching element and the second switching element and turning on the third switching element. A second mode to perform, the first switching element and the third switching; A third mode for performing control to turn on the child and turn off the second switching element, and control to turn off the first switching element and the third switching element and turn on the second switching element; Of these, at least two modes are executed.

  In the above configuration, at least one of the first mode and the second mode is executed. In the first mode and the second mode, since control is performed to turn off both the first switching element and the second switching element, the current flowing through the choke coil can be reduced. Therefore, it can prevent that the electric current which flows into a choke coil continues increasing, and can suppress degradation and failure of a power converter device by extension.

It is a schematic block diagram of a power converter device. It is a time chart which shows the control in a 1st mode. It is a figure which shows the electric current path | route in 1st mode. It is a time chart which shows the control in 2nd mode. It is a figure which shows the electric current path | route in 2nd mode. It is a time chart which shows the control in a 3rd mode. It is a figure which shows the electric current path | route in 3rd mode. It is a flowchart which shows the process which a control part performs. It is a time chart which shows control in the 3rd mode in a 2nd embodiment. It is a control block diagram which shows the process which the control part in 2nd Embodiment performs. It is a time chart which shows control in the 1st mode in a 3rd embodiment. It is a time chart which shows the control in the 2nd mode in 4th Embodiment. It is a time chart which shows the control in the 3rd mode in a 5th embodiment. It is a circuit diagram of the power converter device in 6th Embodiment. It is a figure which shows another example of a power converter device. It is a figure which shows another example of a power converter device.

  Hereinafter, each embodiment will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are denoted by the same reference numerals in the drawings, and the description of the same reference numerals is used.

<First Embodiment>
FIG. 1 is a circuit diagram of the power conversion device according to the present embodiment. The power conversion apparatus according to the present embodiment supplies power supplied from a secondary battery 100 that is a DC power source provided on the input side to the output side via a transformer Tr.

  The first coil L1 provided as the input side of the transformer Tr is connected in series with a second switching element Q2 which is a MOSFET, and the first switching element Q1 which is a MOSFET is connected in parallel to the series connection body. Has been. More specifically, the drain of the first switching element Q1 is connected to one end of the first coil L1, and the drain of the second switching element Q2 is connected to the other end of the first coil L1. The source of the first switching element Q1 and the source of the second switching element Q2 are connected.

  A connection point between the drain of the first switching element Q1 and the first coil L1 is connected to the positive electrode of the secondary battery 100 via the choke coil L3. On the other hand, the connection point between the source of the first switching element Q1 and the source of the second switching element Q2 is connected to the negative electrode of the secondary battery 100. A capacitor 101 is connected in parallel to the secondary battery 100.

  A second coil L2 that is magnetically coupled to the first coil L1 is provided on the output side of the transformer Tr. The turn ratio between the first coil L1 and the second coil is 1: N. On the output side, the third switching element Q3, which is a MOSFET, and the capacitor C3 are connected in series to form a series connection body, and the series connection body and the second coil L2 are connected in parallel to form a parallel connection body. A fourth switching element Q4, which is a MOSFET, is connected in series to the parallel connection body. More specifically, one end of the second coil L2 and one end of the capacitor C3 are connected, the other end of the capacitor C3 and the drain of the third switching element Q3 are connected, and the other end of the second coil L2 and the third switching are connected. The source of the element Q3 is connected. The drain of the fourth switching element Q4 is connected to the connection point between the second coil L2 and the source of the third switching element Q3.

  The connection point between the second coil L2 and the capacitor C3 is connected to the positive output terminal 200a, and the source of the fourth switching element Q4 is connected to the negative output terminal 200b. A capacitor 201 is connected in parallel to the positive output terminal 200a and the negative output terminal 200b.

  The power converter detects an input side voltage VL that detects the input side voltage VL that is the voltage of the secondary battery 100, and a reactor current IL that is a current that flows through the choke coil L3 (current that flows through the circuit on the input side). An input current detection unit 103 and an output side voltage detection unit 202 that detects an output side voltage VH that is a voltage on the output side (the voltage of the capacitor 201) are provided. The detected input side voltage VL, output side voltage VH, and reactor current IL are input to the control unit 10.

  The control unit 10 performs a calculation based on the input side voltage VL, the output side voltage VH, and the reactor current IL, and transmits a control signal to the first to fourth switching elements Q1 to Q4. At this time, on the output side, control is performed by selecting one of the first to third modes in accordance with the progress of charging of the capacitor 201. The control unit 10 also controls the supply of power from the output side to the input side. Since this control is well known, the description thereof is omitted.

  The control in the first mode will be described with reference to the time chart of FIG. In the first mode, the control A for turning off the first switching element Q1, the third switching element Q3, and the fourth switching element Q4 and turning on the second switching element Q2, and the first switching element Q1 and the second switching element Q2 , And the control B for turning off the fourth switching element Q4 and turning on the third switching element Q3 are alternately performed. In other words, the first switching element Q1 and the fourth switching element Q4 are always turned off, and the second switching element Q2 and the third switching element Q3 are alternately turned on. The total of the period during which control A is performed and the period during which control B is performed is defined as one control cycle. Further, the ratio of the length of the period in which the control A is performed and the period in which the control B is performed is set to D: (1-D) using D which is a number less than one.

  In the control A, the change amount dIL / dt per unit time of the reactor current IL is expressed by the following equation (1).

また、出力電流ＩＣの単位時間あたりの変化量は、リアクトル電流ＩＬの単位時間あたりの変化量ｄＩＬ／ｄｔをＮで除算した値となる。第２コイルＬ２に印加される電圧である励磁電圧ＶＴは出力側電圧ＶＨと等しい。コンデンサＣ３の電圧であるコンデンサ電圧ＶＣは、制御Ａの期間の長さを制御Ｂの期間の長さで除算した値に、出力側電圧ＶＨを乗算した値となる。励磁電流ＩＭの時間変化量は、励磁電圧ＶＴを励磁インダクタンスで除算したものであるため、直線的に単調増加する。すなわち、制御Ａが行われる期間のうち、前半の期間ａ１では、励磁電流ＩＭは負の値であり、後半の期間ａ２では、励磁電流ＩＭは正の値となる。なお、励磁電流ＩＭについて、コンデンサＣ３側から第２コイルＬ２を経て、第３スイッチング素子Ｑ３のソース側へと流れる向きを正としている。

The change amount per unit time of the output current IC is a value obtained by dividing the change amount dIL / dt per unit time of the reactor current IL by N. An excitation voltage VT, which is a voltage applied to the second coil L2, is equal to the output side voltage VH. The capacitor voltage VC, which is the voltage of the capacitor C3, is a value obtained by multiplying the length of the control A period by the length of the control B period and the output side voltage VH. The time change amount of the excitation current IM is obtained by dividing the excitation voltage VT by the excitation inductance, and therefore increases linearly and monotonously. That is, in the period in which the control A is performed, the excitation current IM has a negative value in the first half period a1, and the excitation current IM has a positive value in the second half period a2. Note that the direction in which the exciting current IM flows from the capacitor C3 side through the second coil L2 to the source side of the third switching element Q3 is positive.

  A current path when the control A is performed will be described with reference to FIG. In FIG. 3A, current paths are indicated by arrows. On the first coil L1 side, the current supplied from the secondary battery 100 takes a path that passes through the choke coil L3, the first coil L1, and the second switching element Q2. On the second coil side, a path passing through the fourth diode D4 and the second coil L2 is taken.

  As described above, since the reactor current IL increases in the control A, the control B is performed to reduce the reactor current IL on condition that the reactor current IL becomes the first command value Iref1 which is a predetermined value. .

  In the control B, the reactor current IL becomes zero, and accordingly, the output current IC also becomes zero. On the other hand, since a closed circuit including the capacitor C3 is formed on the second coil L2 side, the capacitor C3 applies a voltage to the second coil, and the excitation voltage VT becomes a negative value of the capacitor voltage VC. This capacitor voltage VC takes the same value as in control A. The time change amount of the excitation current IM is obtained by dividing the excitation voltage VT by the excitation inductance, and thus linearly and monotonously decreases. That is, among the periods in which the control B is performed, the excitation current IM has a positive value in the first half period b1, and the excitation current IM has a positive value in the second half period b2.

  A current path when the control B is performed will be described with reference to FIGS. 3B and 3C. FIG. 3B shows a current in the period b1. FIG. 3C shows a current in the period b2.

  In the control B, since the first switching element Q1 and the second switching element Q2 are both OFF on the first coil L1 side, the power supply from the secondary battery 100 is not performed.

  On the second coil L2 side, the third switching element Q3 is turned on to include a second coil L2, a capacitor C3, and a parallel connection body of the third switching element Q3 and the third diode D3. A closed circuit is formed. Thereby, when the excitation current IM takes a positive value, that is, in the period b1, the excitation current IM flows in the order of the second coil L2, the third diode D3, the third switching element Q3, and the capacitor C3. On the other hand, when the exciting current IM takes a negative value, that is, in the period b2, the exciting current IM flows in the order of the second coil L2, the capacitor C3, and the third switching element Q3.

  The control in the second mode will be described with reference to the time chart of FIG. In the second mode, the control C for turning on the first switching element Q1 and the third switching element Q3 and turning off the second switching element Q2 and the fourth switching element Q4, and the first switching element Q1 and the third switching element Q3. And the control A for turning off the fourth switching element Q4 and turning on the second switching element Q2, the first switching element Q1, the second switching element Q2, and the fourth switching element Q4 are turned off, and the third switching element Q3 is turned on. Control B to be turned ON is performed in order. The total of the period during which control A is performed, the period during which control B is performed, and the period during which control C is performed is defined as one control cycle. The ratio of the sum of the period during which control A is performed, the period during which control B is performed, and the period during which control C is performed, that is, the period during which the second switching element Q2 is turned on and the third switching element The ratio of the length of the period in which Q3 is ON is set to D: (1-D) using D which is a number less than one.

  In the control C, the change amount dIL / dt per unit time of the reactor current IL is expressed by the following equation (2).

すなわち、リアクトル電流ＩＬは、直線的に単調増加する。第１コイルＬ１には通電がなされないため出力電流ＩＣはゼロである。第２コイルＬ２に印加される電圧である励磁電圧ＶＴは、第２コイルＬ２側でコンデンサＣ３を含む閉回路が形成されるため、コンデンサＣ３の電圧であるコンデンサ電圧ＶＣと等しい。コンデンサＣ３の電圧であるコンデンサ電圧ＶＣは、制御Ａの期間の長さを制御Ｂの期間の長さと制御Ｃの期間の長さとの和で除算した値に、出力側電圧ＶＨを乗算した値となる。励磁電流ＩＭの時間変化量は、励磁電圧ＶＴを励磁インダクタンスで除算したものであるため、直線的に単調減少する。

That is, reactor current IL increases monotonously linearly. Since the first coil L1 is not energized, the output current IC is zero. The excitation voltage VT that is the voltage applied to the second coil L2 is equal to the capacitor voltage VC that is the voltage of the capacitor C3 because a closed circuit including the capacitor C3 is formed on the second coil L2 side. The capacitor voltage VC, which is the voltage of the capacitor C3, is obtained by dividing the length of the control A period by the sum of the length of the control B period and the length of the control C period, and a value obtained by multiplying the output side voltage VH. Become. The time change amount of the excitation current IM is obtained by dividing the excitation voltage VT by the excitation inductance, and thus linearly and monotonously decreases.

  A current path when the control C is performed will be described with reference to FIG. On the first coil L1 side, since the first switching element Q1 is ON and the second switching element Q2 is OFF, the current supplied from the secondary battery 100 passes through the choke coil L3 and the first switching element Q1. Will take the path to do. On the second coil side, the third switching element Q3 is turned on to include a second coil L2, a capacitor C3, and a parallel connection body of the third switching element Q3 and the third diode D3. A closed circuit is formed. Thereby, when the exciting current IM takes a negative value, the exciting current IM flows in the order of the second coil L2, the capacitor C3, and the third switching element Q3.

  Thus, since the reactor current IL monotonously increases in the control C, the process shifts from the control C to the control A on condition that the reactor current IL becomes the second command value Iref2, which is a predetermined value.

  In the subsequent control A, as shown in FIG. 5B, the same current path as that of the control A in the first mode is taken, so that the description thereof is omitted. Switching from the control A to the control B may be performed under a condition that a predetermined time elapses from the start of the control C, or may be a condition that a predetermined time elapses from the start of the control A. The time chart of FIG. 4 shows an example in which the reactor current IL is constant in the period A, but the amount of change in the reactor current IL is the input side voltage VB and the output side as shown in the above equation (1). Depending on the relationship of the voltage VH, it may increase monotonously or may decrease monotonously.

  In the control B, as shown in FIG. 5C, since the first switching element Q1 and the second switching element Q2 are both OFF on the first coil L1, the supply of current from the secondary battery 100 is performed. I will not. On the second coil L2 side, the third switching element Q3 is turned on to include a second coil L2, a capacitor C3, and a parallel connection body of the third switching element Q3 and the third diode D3. A closed circuit is formed. Thereby, when the exciting current IM takes a positive value, the exciting current IM flows in the order of the second coil L2, the third diode D3, the third switching element Q3, and the capacitor C3.

  In the present embodiment, for simplification of explanation, in the control B period, the excitation current IM always takes a positive value in the control B, and the excitation current IM always takes a negative value in the control C. The length and the length of the control C period are defined. However, depending on the ratio of the lengths of the control B and the control C, the excitation current IM may shift from positive to negative in the control B, and in the control C, the excitation current IM may always take a negative value. In B, the exciting current IM always takes a positive value, and in the control C, the exciting current IM may shift from positive to negative.

  Next, the control in the third mode will be described with reference to the time chart of FIG. In the third mode, the control C for turning on the first switching element Q1 and the third switching element Q3 and turning off the second switching element Q2 and the fourth switching element Q4, and the first switching element Q1 and the third switching element Q3. And the control A which turns off the fourth switching element Q4 and turns on the second switching element Q2 is alternately performed. The total of the period during which control A is performed and the period during which control C is performed is defined as one control cycle. Further, the ratio of the length of the period in which the control C is performed and the period in which the control C is performed is set to D: (1-D) using D which is a number less than one.

  In the control C, the reactor current IL monotonously increases linearly as in the second mode. Since the first coil L1 is not energized, the output current IC is zero. The excitation voltage VT that is the voltage applied to the second coil L2 is equal to the capacitor voltage VC that is the voltage of the capacitor C3 because a closed circuit including the capacitor C3 is formed on the second coil L2 side. The capacitor voltage VC, which is the voltage of the capacitor C3, is obtained by dividing the length of the control A period by the sum of the length of the control B period and the length of the control C period, and a value obtained by multiplying the output side voltage VH. Become. The time change amount of the excitation current IM is obtained by dividing the excitation voltage VT by the excitation inductance, and thus linearly and monotonously decreases. Therefore, in the first half period c1 of the control C, the exciting current IM takes a positive value, and in the second half period c2 of the control C, the exciting current IM takes a negative value.

  A current path when the control C is performed will be described with reference to FIGS. 7 (a) and 7 (b). On the first coil L1 side, since the first switching element Q1 is ON and the second switching element Q2 is OFF, the current supplied from the secondary battery 100 passes through the choke coil L3 and the first switching element Q1. Will take the path to do. On the second coil side, the third switching element Q3 is turned on to include a second coil L2, a capacitor C3, and a parallel connection body of the third switching element Q3 and the third diode D3. A closed circuit is formed. Thereby, when the exciting current IM takes a positive value, the exciting current IM flows in the order of the second coil L2, the third diode D3, the third switching element Q3, and the capacitor C3 as shown in FIG. 7A. It becomes. On the other hand, when the excitation current IM takes a negative value, the excitation current IM flows in the order of the second coil L2, the capacitor C3, and the third switching element Q3 as shown in FIG. 7B.

  In the subsequent control A, the reactor current IL decreases linearly and monotonously based on the above equation (1). The amount of change per unit time of the output current IC is a value obtained by dividing the amount of change dIL / dt per unit time of the reactor current IL by N. An excitation voltage VT, which is a voltage applied to the second coil L2, is equal to the output side voltage VH. The capacitor voltage VC, which is the voltage of the capacitor C3, is a value obtained by multiplying the length of the control A period by the length of the control B period and the output side voltage VH. The time change amount of the excitation current IM is obtained by dividing the excitation voltage VT by the excitation inductance, and therefore increases linearly and monotonously. That is, in the period in which the control A is performed, the excitation current IM has a negative value in the first half period a1, and the excitation current IM has a positive value in the second half period a2.

  A current path when the control A is performed will be described with reference to FIG. On the first coil L1 side, the current supplied from the secondary battery 100 takes a path that passes through the choke coil L3, the first coil L1, and the second switching element Q2. On the second coil side, a path passing through the fourth diode D4 and the second coil L2 is taken.

  These first mode, second mode, and third mode are switched according to the value of the output side voltage VH. When charging of the capacitor 201 is started, control is performed in the first mode. When charging proceeds and the output side voltage VH becomes larger than the first predetermined value V1, control is performed in the second mode. When the charging further proceeds and the output side voltage VH becomes larger than the second predetermined value V2, the control is performed in the third mode.

  As shown in the above equation (1), power can be supplied from the input side to the output side in the first mode control because the value obtained by multiplying the input side voltage VL by the turns ratio N is the output side. This is the case when the voltage is higher than VH. Therefore, assuming that the input side voltage VL is constant, the first predetermined value V1 is set to be at least smaller than a value obtained by multiplying the input side voltage VL, which is a constant, by the turn ratio N. Further, the condition that the reactor current IL decreases in the control A in the third mode is that the value obtained by multiplying the input side voltage VL by the turn ratio N is smaller than the output side voltage VH. Therefore, assuming that the input side voltage VL is constant, the second predetermined value V2 is set to be at least larger than a value obtained by multiplying the input side voltage VL, which is a constant, by the turn ratio N.

  Next, a series of processes executed by the control unit 10 will be described with reference to the flowchart of FIG. The control according to the flowchart of FIG. 8 is executed at a predetermined control cycle.

  First, it is determined whether an activation request has been acquired (S101). The start request command signal is transmitted from, for example, an ECU or the like, which is a host control device. When the activation request has not been acquired (S101: NO), the standby state is continued without performing a series of controls.

  If the activation request is acquired (S101: YES), the output side voltage VH is acquired (S102), and it is determined whether or not the output side voltage VH is equal to or lower than the first predetermined value V1 (S103). If the output side voltage VH is equal to or lower than the first predetermined value V1 (S103: YES), control in the first mode is performed (S104). If the output side voltage VH is not less than or equal to the first predetermined value V1 (S103: NO), it is subsequently determined whether or not the output side voltage VH is less than or equal to the second predetermined value V2 (S105). If the output side voltage VH is less than or equal to the second predetermined value V2 (S105: YES), control is performed in the second mode (S106). On the other hand, if the output side voltage VH is not less than or equal to the second predetermined value V2 (S105: NO), control is performed in the third mode (S107).

  After the control in any one of the first mode, the second mode, and the third mode is performed for a predetermined time, the control end determination is performed (S108). In the process of S108, for example, the output side voltage VH may be acquired again, and it may be determined whether or not the output side voltage VH is equal to or higher than a predetermined upper limit value. The determination as to whether or not the output-side voltage VH has become equal to or higher than a predetermined upper limit value may be made after a negative determination is made in S105. If it is determined that the control is to be terminated (S108: YES), the process is terminated until a start request is made. If it is not determined to end the control (S108: NO), it is determined whether an end request has been acquired (S109). This end request command signal is transmitted from a host control device such as an ECU. If an end request is acquired (S109: YES), a series of processing is ended and the process waits until an activation request is made. If the end request is not acquired (S109: NO), the processing after S102 is executed again.

  Note that, in the flowchart of FIG. 8, only control related to charging control for the capacitor 201 is shown, but the power conversion apparatus performs power conversion other than charging control for the capacitor 201. For example, there is a control in which the power supplied via the positive electrode side output terminal 200a and the negative electrode side output terminal 200b is stepped down to charge the secondary battery 100. Since the control is a well-known control, description thereof is omitted.

  With the above configuration, the power conversion device according to the present embodiment has the following effects.

  When the output side voltage VH is small, such as at the start of charging (precharging) of the capacitor 201, the first switching element Q1, the third switching element Q3, and the fourth switching element Q4 are turned off by the control in the first mode. And control A for turning on the second switching element Q2, and control B for turning off the first switching element Q1, the second switching element Q2, and the fourth switching element Q4 and turning on the third switching element Q3. It is supposed to be done alternately. Therefore, the current of the choke coil L3 increased in the control A can be reduced in the control B. Therefore, it can prevent that the electric current which flows into the choke coil L3 continues increasing, and can suppress deterioration and failure of a power converter device by extension.

  When the output side voltage VH becomes larger than the first predetermined value V1, the mode is shifted to the second mode, the first switching element Q1 and the third switching element Q3 are turned on, and the second switching element Q2 and the fourth switching Control C for turning off the element Q4, Control A for turning off the first switching element Q1, the third switching element Q3 and the fourth switching element Q4, and turning on the second switching element Q2, the first switching element Q1, It is assumed that the control B in which the second switching element Q2 and the fourth switching element Q4 are turned off and the third switching element Q3 is turned on is sequentially performed. Therefore, the current flowing through the choke coil L3 can be increased by the control C, and the power supply speed to the output side can be improved. Further, the current of the choke coil L3 can be reduced by the control B. Therefore, it can prevent that the electric current which flows into the choke coil L3 continues increasing, and can suppress deterioration and failure of a power converter device by extension.

  When the output side voltage VH becomes larger than the second predetermined value V2, such as when the precharge to the capacitor 201 further proceeds, the mode shifts to the third mode, and the first switching element Q1 and the third switching element Control C for turning on Q3 and turning off the second switching element Q2 and the fourth switching element Q4, and turning off the first switching element Q1, the third switching element Q3 and the fourth switching element Q4, and the second switching element Q2 The control A is turned on alternately. Therefore, the current flowing through the choke coil L3 can be increased by the control C, the current flowing through the choke coil L3 can be decreased by the subsequent control A, and the capacitor 201 that has been charged can be further quickly charged. Can do.

  The third command value Iref3 is larger than the first command value Iref1 and the second command value Iref2. Thereby, the reactor current IL does not become excessive in the first mode and the second mode. Therefore, when both the first switching element Q1 and the second switching element Q2 are turned off, the avalanche current generated based on the reactor current IL is not excessively increased, and the first switching element Q1 and the second switching element Q2 fail. And deterioration can be suppressed. In addition, in the third mode, the charging time on the output side can be shortened by setting the third command value Iref3 to a larger value.

Second Embodiment
In the present embodiment, the control in the third mode is partially different from the first embodiment. FIG. 9 shows the open / closed states of the first to fourth switching elements Q1 to Q4 in the third mode in this embodiment, and the reactor current IL at that time. In the present embodiment, the sum of the period during which control C is performed and the period during which control A is performed is defined as one control cycle Ts. That is, the period from when the ON control of the first switching element Q1 and the third switching element Q3 is started to when the ON control of the second switching element Q2 ends is one control cycle Ts. In performing the series of controls in the third mode, the first switching element Q1 and the third switching element Q3 are turned off, and the timing for starting the ON control of the second switching element Q2 is made variable, whereby the reactor current IL The average value IL_ave is controlled to be the third command value Iref3.

  In the third mode, if the increase amount of reactor current IL in control C is equal to the decrease amount of reactor current IL in control A, an excessive increase in reactor current IL can be suppressed. When the ratio of the length of the period in which the control C is performed and the period in which the control A is performed is D: (1-D) using D which is a number less than 1, the following expression (3) is established: D is obtained by the following equation (4).

加えて、第３モードでは、低調波発振を抑制すべく、リアクトル電流ＩＬにスロープ電流Ｉｓを加算した値が補正指令値Ｉｒｅｆ３＊となるように、制御Ｃから制御Ａへと切り替えるタイミングを制御する。このスロープ電流Ｉｓについて、図９を用いて説明する。スロープ電流Ｉｓは、直線的に増加する仮想的な値であり、スロープ電流Ｉｓの時間当たりの増加量はｍである。制御Ｃにおけるリアクトル電流ＩＬの増加量をΔＩＬとし、スロープ電流Ｉｓの増加量をΔＩｓとすれば、補正指令値Ｉｒｅｆ３＊は次式（５）で算出することができる。なお、次式（５）において、トランスＴｒの電力変換効率をηとしており、トランスＴｒが損失の無い理想的なものであれば、ηは１である。

In addition, in the third mode, the timing for switching from the control C to the control A is controlled so that the value obtained by adding the slope current Is to the reactor current IL becomes the correction command value Iref3 * in order to suppress subharmonic oscillation. . The slope current Is will be described with reference to FIG. The slope current Is is a virtual value that increases linearly, and the amount of increase of the slope current Is per time is m. If the increase amount of the reactor current IL in the control C is ΔIL and the increase amount of the slope current Is is ΔIs, the correction command value Iref3 * can be calculated by the following equation (5). In the following equation (5), the power conversion efficiency of the transformer Tr is η, and η is 1 if the transformer Tr is ideal without loss.

続いて、制御部１０が実行する処理を、図１０の制御ブロック図により説明する。定電流制御部２０では、第１モードにおけるリアクトル電流ＩＬの指令値である第１指令値Ｉｒｅｆ１と、第２モードにおけるリアクトル電流ＩＬの指令値である第２指令値Ｉｒｅｆ２、及び、第３モードにおけるリアクトル電流ＩＬの指令値である第３指令値Ｉｒｅｆ３とを、メモリから読み出して制御に用いる。

Next, processing executed by the control unit 10 will be described with reference to the control block diagram of FIG. In the constant current control unit 20, the first command value Iref1 that is the command value of the reactor current IL in the first mode, the second command value Iref2 that is the command value of the reactor current IL in the second mode, and the third mode A third command value Iref3, which is a command value of the reactor current IL, is read from the memory and used for control.

  The first command value Iref1 and the second command value Iref2 become the values of the first command value Iref1 and the second command value Iref2 when the second switching element Q2 transitions from the ON state to the OFF state. The avalanche current generated based on this is set so as not to be excessive. The first command value Iref1 and the second command value Iref2 are output from the constant current control unit 20 as they are. Note that the first command value Iref1 and the second command value Iref2 may be the same value or different values.

  The third command value Iref3 is larger than the first command value Iref1 and the second command value Iref2 because it is not restricted by the avalanche current. The third command value Iref3 is input to the feedback control unit 21. In addition, the feedback control unit 21 acquires an average value IL_ave that is the actual current of the reactor current IL. The average value IL_ave is obtained by accumulating the reactor current IL detected by the current detection unit for a predetermined period and averaging the values. The third command value Iref3 and the average value IL_ave are input to the addition unit 22, and the addition unit 22 takes the difference between the third command value Iref3 and the average value IL_ave. This difference is input to the PI controller 23 and input to the limiter 24. In the limiter 24, if the output value of the PI controller 23 is larger than the upper limit value, the output value is limited to the upper limit value. The output value from the limiter 24 is added to the third command value Iref3 in the adder 25, and is output from the feedback control unit 21.

  On the other hand, the current correction unit 27 receives the input side voltage VL and the output side voltage VH, and outputs the correction amount of the third command value Iref3. This correction value is based on the above equation (3), and is added to the sum of the third command value Iref3 and the output value of the feedback control unit 21 by the adder 26, whereby the correction command value Iref3 * is obtained. .

  The first command value Iref1, the second command value Iref2, and the correction command value Iref3 * output from the constant current control unit 20 are input to the mode selection unit 30. Further, the output side voltage VH is also input to the mode selection unit 30, and the output side voltage VH is compared with the first predetermined value V1 and the second predetermined value V2. Then, one of the first command value Iref1, the second command value Iref2, and the correction command value Iref3 * is determined and output.

  One of the first command value Iref1, the second command value Iref2, and the correction command value Iref3 * output from the mode selection unit 30 is input to the peak current control unit 40, converted into an analog value by the DA converter 41, Input to the negative terminal of the comparator 42.

  On the other hand, the slope compensator 43 of the peak current controller 40 generates a value of the slope current Is obtained from the register value as a signal and inputs the signal to the DA converter 44. As described above, the slope current Is is a sawtooth wave signal that monotonously increases linearly from 0 A in each control cycle. Then, the slope current Is and the reactor current IL that have been converted to an analog waveform by the DA converter 44 are added by the adder 45 and input to the plus terminal of the comparator 42. The slope compensator 43 may directly generate an analog waveform and input the analog waveform to the comparator 42 without going through the DA converter 44.

  The slope compensator 43 sets the value of the slope current Is to zero in the first mode and the second mode, and outputs the above-described sawtooth wave slope current Is in the third mode. This is because the first mode has a period in which both the first switching element Q1 and the second switching element Q2 are OFF, and the reactor current IL becomes zero during that period, and as a result, the subharmonic oscillation phenomenon occurs. This is because it does not occur.

  The comparator 42 adds the slope current Is to any one of the first command value Iref1, the second command value Iref2, and the correction command value Iref3 * input to the minus terminal, and the reactor current IL input to the plus terminal. Compare with the value. Then, in a period in which the input value of the plus terminal is smaller than the input value of the minus terminal, a signal in a high state is input to the S terminal of the RS flip-flop 47, and the period in which the input value of the plus terminal is larger than the input value of the minus terminal , A low signal is input to the S terminal of the RS flip-flop 47. A clock signal is input from the clock 46 to the R terminal of the RS flip-flop 47.

  In the first mode, if the input signal is a low signal, it means that the reactor current IL has exceeded the first command value Iref1. Therefore, the RS flip-flop 47 transmits a signal for turning on the third switching element Q3 and turning off the first switching element Q1, the second switching element Q2, and the fourth switching element Q4, thereby controlling the control B from the control A. Switch to. When one control cycle elapses, from the control B, the second switching element Q2 is turned on and the first switching element Q1, the third switching element Q3, and the fourth switching element Q4 are sent off. Switch to control A.

  In the second mode, if the input signal is a low signal, it means that the reactor current IL has exceeded the second command value Iref2. For this reason, the RS flip-flop 47 transmits a signal for turning on the second switching element Q2 and turning off the first switching element Q1, the third switching element Q3, and the fourth switching element Q4. Switch to. Subsequently, when a predetermined time less than one control cycle elapses from the start of the control C, the RS flip-flop 47 turns on the third switching element Q3, and the first switching element Q1, the second switching element Q2, and the fourth switching element. The control A is switched to the control B by transmitting a signal for turning off the element Q4. When one control cycle elapses, from the control B, the second switching element Q2 is turned on and the first switching element Q1, the third switching element Q3, and the fourth switching element Q4 are sent off. Switch to control C.

  In the third mode, if the input signal becomes a low signal, it means that the value obtained by adding the slope current Is to the reactor current IL exceeds the correction command value Iref3 *. For this reason, the RS flip-flop 47 transmits a signal for turning on the second switching element Q2 and turning off the first switching element Q1, the third switching element Q3, and the fourth switching element Q4. Switch to. When one control cycle elapses, from the control A, the second switching element Q2 is turned on, and the first switching element Q1, the third switching element Q3, and the fourth switching element Q4 are sent off. Switch to control C.

  The output of the RS flip-flop 47 is input to the duty limiting unit 48. In the duty limiting unit 48, if the length of each control period exceeds the upper limit value, the upper limit value is set. If the length of each control period is lower than the lower limit value, the lower limit value is set. And a control signal is transmitted to the 1st-4th switching elements Q1-Q4.

  With the configuration described above, the power conversion device according to the present embodiment has the following effects in addition to the effects exhibited by the power conversion device according to the first embodiment.

  The peak current control unit 40 performs constant current control using each command value input from the constant current control unit 20. As a result, when the input side voltage VL changes, the robustness against overcurrent can be improved.

  The slope current is added when the peak current control is performed for the reactor current IL in the third mode. Thereby, subharmonic oscillation of reactor current IL can be suppressed.

<Third Embodiment>
In the present embodiment, the control in the first mode is partly different from the power converter according to the first embodiment. FIG. 11 is a time chart showing processing executed by the control unit 10 in the power conversion apparatus according to the present embodiment.

  In the present embodiment, when switching from the control A to the control B, the control AB for turning off all of the first to fourth switching elements Q1 to Q4 is performed, and a dead time is provided.

  When switching the switching element from ON to OFF, the recovery is not performed immediately, but recovery is performed. Therefore, if the third switching element Q3 is turned ON at the timing when the second switching element Q2 is turned OFF, There is a possibility that the ON period overlaps. That is, when switching from the control A to the control B, if the ON period of the second switching element Q2 and the ON period of the third switching element Q3 overlap, a short circuit occurs in the circuit on the output side. In the present embodiment, when switching from the control A to the control B, the control AB is performed to turn off the first to fourth switching elements Q1 to Q4, so that the second switching element Q2 can be recovered. Necessary time can be secured, and a short circuit in the output-side circuit can be suppressed.

  In addition, when switching from the control B to the control A, a dead time in which all of the first to fourth switching elements Q1 to Q4 are turned off may be provided.

<Fourth embodiment>
In the present embodiment, the control in the second mode is partly different from the power converter according to the first embodiment. FIG. 12 is a time chart showing processing executed by the control unit 10 in the power conversion device according to the present embodiment.

  In the present embodiment, when switching from the control C to the control A, the control CA is performed in which the first to third switching elements Q1 to Q3 are all turned on and the fourth switching element Q4 is turned off. Is supposed to be provided. In addition, similar to the third embodiment, when switching from the control A to the control B, the control AB is performed to turn off the first to fourth switching elements Q1 to Q4. AB is the same as that in the third embodiment, and a description thereof will be omitted.

  When switching the switching element from OFF to ON, the switching element does not immediately turn ON. Therefore, if the second switching element Q2 is turned ON at the timing when the first switching element Q1 is turned OFF, the first switching element Q1 and the second switching element There is a possibility that a period in which both the elements Q2 are OFF occurs. That is, a period corresponding to the period in which the control B is performed occurs, and there is a possibility that an avalanche current is generated.

  In the present embodiment, when switching from the control C to the control A, the control CA is performed in which all of the first to third switching elements Q1 to Q3 are turned on and the fourth switching element Q4 is turned off. Thereby, when switching from the control C to the control A, both the first switching element Q1 and the second switching element Q2 are not turned off, and the generation of the avalanche current can be suppressed.

  In the control CA, both the first switching element Q1 and the second switching element Q2 may be turned on, and the third switching element Q3 and the fourth switching element Q4 may be turned off.

<Fifth Embodiment>
In the present embodiment, the control in the third mode is partially different from that of the power converter according to the first embodiment. FIG. 13 is a time chart showing processing executed by the control unit 10 in the power conversion apparatus according to the present embodiment.

  In this embodiment, when switching from the control A to the control C, a control AC is performed in which the first switching element Q1 is turned on and the second to fourth switching elements Q2 to Q4 are turned off, and a dead time is provided. It is supposed to be. In addition, when switching from control C to control A, control CA is performed in which all of the first to third switching elements Q1 to Q3 are turned on and the fourth switching element Q4 is turned off, and an overlap time is provided. It is supposed to be. Since this control CA is the same as that in the fourth embodiment, a description thereof will be omitted.

  When switching the switching element from ON to OFF, the recovery is not performed immediately, but recovery is performed. Therefore, if the third switching element Q3 is turned ON at the timing when the second switching element Q2 is turned OFF, There is a possibility that the ON period overlaps. That is, when switching from the control A to the control C, if the ON period of the second switching element Q2 overlaps with the ON period of the third switching element Q3, a short circuit occurs in the circuit on the output side. In this embodiment, when switching from the control A to the control C, the control AC is performed in which the first switching element Q1 is turned on and the second to fourth switching elements Q2 to Q4 are turned off. The time required for the recovery of the two switching elements Q2 can be secured, and a short circuit in the output side circuit can be suppressed.

<Sixth Embodiment>
In the present embodiment, the circuit on the output side is different from the power conversion device according to the first embodiment. FIG. 14 is a circuit diagram of the power converter according to the present embodiment.

  One end of the second coil L2 constituting the output side of the transformer Tr is connected to the positive output terminal 200a, and the other end is connected to the drain of the fourth switching element Q4. The connection point between the second coil L2 and the drain of the fourth switching element Q4 is connected to the source of the third switching element Q3 via the capacitor C3a, and the source of the fourth switching element Q4 is connected to the third switching element Q3. Connected to the drain. The connection point between the source of the fourth switching element Q4 and the third switching element Q3 is connected to the negative output terminal. A third diode D3a is connected in parallel in the reverse direction to the third switching element Q3, and a fourth diode D4 is connected in parallel in the reverse direction to the fourth switching element Q4.

  Note that the processing executed by the control unit 10 is the same as that in the first embodiment, and the processing in the second to fifth embodiments may be added to the processing in the first embodiment.

<Modification>
In each embodiment, the choke coil L3 is provided on the positive electrode side of the secondary battery 100. However, as shown in FIGS. 15 and 16, the choke coil L3a includes the first switching element Q1 and the second switching element Q2. May be provided between the connection point and the negative electrode of the secondary battery 100.

  -In each embodiment, although the 1st-3rd mode shall be performed, what is necessary is just to perform at least 2 mode among 1st-3rd modes. That is, power supply may be started in the first mode, and if the first predetermined value V1 is reached, the third mode may be performed without passing through the second mode. Further, the third mode may be performed if the supply of power is started in the second mode and the first predetermined value or the second predetermined value V2 is reached.

  In each embodiment, in the second mode, the control C is switched to the control A on condition that the reactor current IL becomes the second command value Iref2. However, whether the reactor current IL increases or decreases in the control A is determined by the relationship between the input side voltage VL and the output side voltage VH. That is, depending on the relationship between the input side voltage VL and the output side voltage VH, the reactor current IL when switching from the control A to the control B may be larger or smaller than the second command value Iref2. is there. If the reactor current IL becomes smaller than the second command value Iref2, the time required for precharging the capacitor 201 increases, and if the reactor current IL becomes larger than the second command value Iref2, the avalanche current increases. Therefore, the second command value Iref2 used for switching from the control C to the control A is corrected using the input side voltage VL and the output side voltage VH, and the reactor current IL is changed to the second value when switching from the control A to the control B. It is good also as what controls so that it may become command value Iref2. By doing so, it is possible to suppress both an increase in charging time and an increase in avalanche current.

  In performing the control in the first to third modes, the peak current control for switching the control on condition that the reactor current IL becomes the command value is performed. In this regard, in each mode, the length of the period for performing each control may be determined in advance, and the control may be performed regardless of the value of the reactor current IL. By doing so, the control can be simplified. In this case, the length of each control period may be variably set according to the values of the input side voltage VL and the output side voltage VH.

  In performing the control in the first to third modes, the fourth switching element Q4 is always OFF, so the fourth switching element Q4 may not be provided.

  In each embodiment, the switching element is a MOSFET, but other switching elements may be employed.

  DESCRIPTION OF SYMBOLS 10 ... Control part, 43 ... Slope compensation part, 103 ... Input current detection part, 202 ... Output side voltage detection part, C3 ... Capacitor, C3a ... Capacitor, L1 ... 1st coil, L2 ... 2nd coil, L3 ... Choke coil , L3a ... choke coil, Q1 ... first switching element, Q2 ... second switching element, Q3 ... third switching element, Tr ... transformer.

Claims (12)

A first coil (L1) provided as an input side of a transformer (Tr);
A switching circuit comprising a first switching element (Q1) connected in parallel with the first coil, and a second switching element (Q2) connected in series with the first coil;
A choke coil (L3) provided between the switching circuit and the DC power source (100);
First binds the coil and magnetically pre-SL, a second coil provided as the output side of the transformer and (L2),
A series connection body of a third switching element (Q3) and a capacitor (C3) connected in parallel or in series with the second coil;
From the input side of the DC power source (100) is connected, said a transformer control device for the forward active clamp circuit for supplying power to the output side via the (Tr) (10),
Control for turning off the first switching element and the third switching element and turning on the second switching element, turning off the first switching element and the second switching element, and turning on the third switching element A first mode for performing control, and
Control for turning on the first switching element and the third switching element and turning off the second switching element, turning off the first switching element and the third switching element, and turning on the second switching element And a second mode for performing control to turn off the first switching element and the second switching element and to turn on the third switching element;
Control for turning on the first switching element and the third switching element and turning off the second switching element, turning off the first switching element and the third switching element, and turning on the second switching element A control device that executes at least two modes of the third mode in which control is performed. An output side voltage detector (202) for detecting the output side voltage as an output side voltage;
When the output side voltage is smaller than a first predetermined value, the first mode is executed,
When the output side voltage is larger than the first predetermined value and smaller than a second predetermined value larger than the first predetermined value, the second mode is executed,
The control device according to claim 1, wherein the third mode is executed when the output-side voltage is larger than the second predetermined value. An output-side voltage detector that detects the output-side voltage as an output-side voltage;
When the output side voltage is smaller than a predetermined value, the first mode is executed,
The control device according to claim 1, wherein the third mode is executed when the output-side voltage is larger than the predetermined value. An output-side voltage detector that detects the output-side voltage as an output-side voltage;
When the output side voltage is smaller than a predetermined value, the second mode is executed,
The control device according to claim 1, wherein the third mode is executed when the output-side voltage is larger than the predetermined value. In at least one of the first mode and the second mode, the first switching element and the second switching element are controlled by turning off the first switching element and the third switching element and turning on the second switching element. the switching element is turned OFF, when switching to the control to oN the third switching element performs the first switching element, any control to OFF said second switching element and the third switching element, wherein Item 5. The control device according to any one of Items 1 to 4.   In at least one of the second mode and the third mode, from the control of turning on the first switching element and the third switching element and turning off the second switching element, the first switching element and the third mode The control for turning on all of the first switching element, the second switching element, and the third switching element is performed when switching to the control of turning off the switching element and turning on the second switching element. Item 5. The control device according to any one of Items 1 to 4.   In the third mode, from the control of turning off the first switching element and the third switching element and turning on the second switching element, the first switching element and the third switching element are turned on, and the first switching element is turned on. 5. When switching to control for turning off two switching elements, control is performed to turn on the first switching element and turn off the second switching element and the third switching element. The control device according to item 1. A current detector (103) for detecting a current value flowing through the choke coil;
The control device according to any one of claims 1 to 7, wherein in each of the modes, each of the switching elements is controlled such that the current value becomes a predetermined command value.   The control device according to claim 8, wherein the command value in the third mode is larger than the command value in another mode.   The control device according to claim 8 or 9, wherein each of the switching elements is controlled such that a peak value of the current value becomes the command value. A slope compensator (43) for adding a slope signal that is a sawtooth wave to the current value;
As a value obtained by adding the slope signal to the current value becomes the command value, and controls the respective switching elements, the control device according to any one of claims 8-10.   The control device according to claim 11, wherein the slope compensator does not add the slope signal in the first mode and the second mode, and adds the slope signal in the third mode.

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