JP6406133B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that transforms electric power supplied from a DC power source and supplies it to an output side.

  There exists a power supply control apparatus of patent document 1 as what charges a capacitive load using DC power supply. 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 Literature 1 is a current input type push-pull DCDC converter having a choke coil on the auxiliary battery, the charging to the capacitive load is performed by the current of the choke coil. This is done by repeating the increase and 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 problems, and a main object thereof is to provide a power conversion device capable of suppressing overcurrent.

  The present invention relates to a power converter for supplying power from an input side to which a DC power source is connected to an output side through a transformer, a choke coil having an input terminal connected to a positive electrode of the DC power source, Having a tap, both ends of which are connected to a predetermined connection point via a first switching element and a second switching element, respectively, the center tap is connected to the negative electrode of the DC power supply, and the predetermined connection point is an output of the choke coil A first coil constituting the transformer, connected to an end, or the center tap is connected to an output end of the choke coil and the predetermined connection point is connected to the negative electrode of the DC power supply; A third switching element that switches connection between the DC power source and the choke coil; and when the third switching element is OFF, An energization means for connecting the input end of the yoke coil and the predetermined connection point so as to be energized; a second coil constituting the transformer that is magnetically coupled to the first coil; the first switching element; Each of the switching elements includes a pulse generation unit that transmits one of an ON signal and an OFF signal, and the first switching element, the second switching element, and the third switching element are all ON. And a period in which one of the first switching element and the second switching element is ON, and the other of the first switching element and the second switching element and the third switching element are OFF. .

  In the above configuration, when all of the first switching element, the second switching element, and the third switching element are turned on, the current flowing through the choke coil can be increased. On the other hand, if one of the first switching element and the second switching element is turned ON and the other of the first switching element and the second switching element and the third switching element are turned OFF, the DC power supply is disconnected and Since electric power is supplied from the first coil side to the second coil side, electric power can be supplied while reducing the current flowing through the choke coil regardless of the voltage on the second coil side. Therefore, even when the voltage on the second coil side is low, it is possible to provide a period for reducing the current of the choke coil, and it is possible to suppress an excessive increase in the current of the choke coil.

It is a circuit diagram of the power converter concerning a 1st embodiment. It is a figure which shows the electrical pathway in period (alpha). (A) is a figure which shows the electrical pathway in period (beta), (b) is a figure which shows another electrical pathway in period (beta). (A) is a figure which shows the electrical pathway in period (gamma), (b) is a figure which shows another electrical path in period (gamma). It is a time chart which shows control of the 1st mode. It is a time chart which shows control of the 2nd mode. It is a control block diagram in a 1st embodiment. It is a flowchart which shows the process of 1st Embodiment. It is a time chart which shows control of the 1st mode in a 2nd embodiment. It is a circuit diagram of the power converter device which concerns on 3rd Embodiment.

  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>
The power conversion device according to the present embodiment is mounted on a hybrid car including a secondary battery such as a lead battery having a nominal voltage of 12V and a high voltage storage battery such as a lithium ion battery having a nominal voltage of several hundred volts. .

  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 is a DCDC converter 10, and a positive input terminal 30 a and a negative input terminal 30 b of the DCDC converter 10 are connected to a secondary battery 30 that is a DC power supply, and an output terminal of the DCDC converter 10. A capacitive load 40 (smoothing capacitor) is connected in parallel, and a positive output terminal 50 a and a negative output terminal 50 b are provided at the output terminal of the DCDC converter 10. The electric power stored in the secondary battery 30 is transformed by the DCDC converter 10 and output from the positive electrode side output terminal 50a and the negative electrode side output terminal 50b. The electric power input from the positive electrode side output terminal 50 a and the negative electrode side output terminal 50 b is transformed by the DCDC converter 10 and input to the secondary battery 30. A high voltage storage battery, an electric load, a generator, and the like (not shown) are connected to the positive electrode side output terminal 50a and the negative electrode side output terminal 50b, and power can be exchanged with the secondary battery 30.

  The DCDC converter 10 includes a choke coil 11, a transformer Tr, a bridge circuit 14, a first switching element Q1, and a second switching element Q2.

  The transformer Tr is composed of a first coil L1 and a second coil L2 that are magnetically coupled to each other, and the first coil L1 has a center tap 13. The number of turns of the second coil L2 is N / 2 times the number of turns of the first coil L1. That is, the number of turns of the second coil L2 is N times the number of turns from one end of the first coil L1 to the center tap 13. The second coil L2 is connected to the capacitive load 40 via the bridge circuit 14 and the output terminal of the DCDC converter 10.

The first switching element Q1 and the second switching element Q2 are MOSFETs, and both ends of the first coil L1 are connected to the source of the first switching element Q1 and the source of the second switching element Q2, respectively. On the other hand, the drain of the first switching element Q1 and the drain of the second switching element Q2 are both connected to the predetermined connection point 12. A first end of the choke coil 11 is connected to the predetermined connection point 12, and a second end of the choke coil 11 is connected to the positive input side 30a via the third switching element Q3. The center tap 13 of the first coil L1 is connected to the negative electrode of the secondary battery 30 via the negative electrode side input end 30b.
The choke coil 11 and the third switching element Q3 and the center tap 13 and the negative input terminal 30b are connected by a third diode D3. The third diode D3 is an energization unit that enables energization from the negative electrode side to the positive electrode side and interrupts the energization from the positive electrode side to the negative electrode side. The first switching element Q1 and the second switching element Q2 each have a first parasitic diode D1 and a second parasitic diode D2 that are connected in parallel in opposite directions.

  The bridge circuit 14 includes fourth to seventh parasitic diodes connected in parallel in the opposite direction to the fourth to seventh switching elements Q4 to Q7 and the fourth to seventh switching elements Q4 to Q7, which are MOSFETs. It is comprised by D4-D7. One end of the second coil L2 is connected to the source of the fourth switching element Q4 and the drain of the fifth switching element Q5. The other end of the second coil L2 is connected to the source of the sixth switching element Q6 and the drain of the seventh switching element Q7. The drain of the fourth switching element Q4 and the drain of the sixth switching element Q6 are connected to the output terminal on the high voltage side, and the source of the fifth switching element Q5 and the source of the seventh switching element Q7 are the output terminal on the low voltage side. It is connected to the. In this bridge circuit 14, when power is supplied from the first coil L 1 side to the second coil L 2 side, the bridge circuit 14 functions as a rectifier circuit by the fourth to seventh parasitic diodes D 4 to D 7, and from the second coil L 2 side. When power is supplied to the first coil L1 side, the fourth to seventh switching elements Q4 to Q7 function as a switching circuit. In addition, since it is well-known about the control at the time of functioning the bridge circuit 14 as a switching circuit, description is abbreviate | omitted.

  The DCDC converter 10 includes an input voltage detection unit 17, an output voltage detection unit 18, a current detection unit 19, a pulse generation unit 20, and a drive circuit 21. The input voltage detection means 17 is a voltage sensor, for example, and detects the input voltage Vin which is a voltage input from the secondary battery 30 to the choke coil 11. The output voltage detection means 18 is a voltage sensor, for example, and detects the output voltage Vc that is the voltage of the capacitive load 40. The current detection means 19 is a current sensor, for example, and detects a reactor current IL indicating the current of the choke coil 11. The output voltage Vc is a voltage of the capacitive load 40 and may be referred to as a “capacitive load voltage”.

  The input voltage Vin detected by the input voltage detector 17 and the output voltage Vc detected by the output voltage detector 18 are input to the pulse generator 20. Based on the input voltage Vin and output voltage Vc that are input, the pulse generator 20 generates a first PWM signal that is a drive signal for the first switching element Q1 and a second PWM signal that is a drive signal for the second switching element Q2. It is generated and transmitted to the drive circuit 21.

  The drive circuit 21 drives the first switching element Q1 based on the first PWM signal received from the pulse generator 20, and drives the second switching element Q2 based on the second PWM signal.

  In the present embodiment, the capacity load 40 is charged with the electric power stored in the secondary battery 30. At this time, the DCDC converter 10 functions as a current input type push-pull DCDC converter. Charging is started when a charging start command is generated in the ECU mounted on the vehicle when the vehicle is powered on. On the other hand, charging is performed until the voltage close to the voltage of the high voltage storage battery is set as the target voltage and the output voltage Vc reaches the target voltage. In addition, the value memorize | stored in the memory in ECU may be used for a target voltage, and a target voltage may be calculated based on the measured value of the voltage of a high voltage storage battery. It is also possible to adopt means for acquiring the charge start command and the target voltage value from the outside of the vehicle.

  FIG. 2 shows a path of a current flowing through the circuit when all of the first switching element Q1, the second switching element Q2, and the third switching element Q3 are turned on. In this state, since the first coil L1 is in a short circuit state, the voltage of the first coil L1 is zero. Therefore, the input voltage Vin is applied to the choke coil 11, and the reactor current IL increases. At this time, dIL / dt (A / s), which is a change amount of the reactor current IL per time, is expressed by the following equation (1), where L (H) is the self-inductance of the choke coil 11.

すなわち、リアクトル電流ＩＬは、直線的に増加する。なお、第１スイッチング素子Ｑ１、第２スイッチング素子Ｑ２及び第３スイッチング素子Ｑ３をいずれもＯＮとする期間を、期間αとする。

That is, reactor current IL increases linearly. Note that a period during which all of the first switching element Q1, the second switching element Q2, and the third switching element Q3 are ON is defined as a period α.

  FIG. 3A shows a path of a current flowing through the circuit when the first switching element Q1 is turned on and the second switching element Q2 and the third switching element Q3 are turned off. FIG. 3B shows a path of a current flowing through the circuit when the second switching element Q2 is turned on and the first switching element Q1 and the third switching element Q3 are turned off. At this time, dIL / dt (A / s), which is a change amount of reactor current IL per time, is expressed by the following equation (2).

すなわち、リアクトル電流ＩＬは直線的に減少する。なお、第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２の一方をＯＮとし、第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２の他方と、第３スイッチング素子Ｑ３とをＯＦＦとする期間を期間βとする。

That is, reactor current IL decreases linearly. Note that a period during which one of the first switching element Q1 and the second switching element Q2 is turned ON and the other of the first switching element Q1 and the second switching element Q2 and the third switching element Q3 are turned OFF is a period β. .

  FIG. 4A shows a path of current flowing through the circuit when the first switching element Q1 and the third switching element Q3 are turned on and the second switching element Q2 is turned off. FIG. 4B shows a path of current flowing through the circuit when the second switching element Q2 and the third switching element Q3 are turned on and the first switching element Q1 is turned off. At this time, dIL / dt (A / s), which is the amount of change of reactor current IL per time, is expressed by the following equation (3).

すなわち、入力電圧Ｖｉｎが、出力電圧Ｖｃを巻数比Ｎで除算した値より大きければ、ΔＩが正の値をとるため、リアクトル電流ＩＬは増加する。一方、入力電圧Ｖｉｎが、出力電圧Ｖｃを巻数比Ｎで除算した値より小さければ、ΔＩが負の値をとるため、リアクトル電流ＩＬは減少する。なお、第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２の一方及び第３スイッチング素子Ｑ３をＯＮとし、第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２の他方をＯＦＦとする期間を期間γとする。

That is, if the input voltage Vin is greater than the value obtained by dividing the output voltage Vc by the turns ratio N, ΔI takes a positive value, and thus the reactor current IL increases. On the other hand, if the input voltage Vin is smaller than the value obtained by dividing the output voltage Vc by the turns ratio N, ΔI takes a negative value, and thus the reactor current IL decreases. A period γ is a period in which one of the first switching element Q1 and the second switching element Q2 and the third switching element Q3 are turned on and the other of the first switching element Q1 and the second switching element Q2 is turned off.

  In the control during this period γ, the reactor current IL increases when the output voltage Vc is small, such as when charging of the capacitive load 40 is started. Therefore, if the capacitive load 40 is charged using the period α and the period γ, the reactor current IL continues to increase, and the choke coil 11 may be deteriorated.

  Therefore, in the present embodiment, when the output voltage Vc is equal to or lower than the predetermined value V1, the control in the first mode in which the period α and the period β are alternately repeated is performed, and the output voltage Vc is larger than the predetermined value V1. In this case, the second mode control is performed in which the period α and the period γ are alternately repeated. The predetermined value V1 for switching between the first mode and the second mode is a value larger than a value obtained by multiplying the input voltage Vin by the turn ratio N. That is, if the output voltage Vc rises until the reactor current IL decreases in the period γ, the second mode control is performed.

FIG. 5 shows the control state of the first switching element Q1, the second switching element Q2, and the third switching element Q3, the value of the reactor current IL, and the output current Ic when performing the control in the first mode. The first switching element Q1 and the second switching element Q2 have a duty value set to a value larger than 50% so that the ON periods of each other overlap each other.
On the other hand, the third switching element Q3 starts the ON control simultaneously with starting the ON control of the first switching element Q1, and starts the OFF control simultaneously with starting the OFF control of the second switching element Q2. Furthermore, the ON control is started simultaneously with the start of the ON control of the second switching element Q2, and the OFF control is started simultaneously with the start of the OFF control of the first switching element Q1. That is, the timing for starting the ON control of the third switching element Q3 is equal to the timing for starting the ON control of the first switching element Q1 and the timing for starting the ON control of the second switching element Q2, respectively. The timing for starting the OFF control of the first switching element Q1 is equal to the timing for starting the OFF control of the first switching element Q1 and the timing for starting the OFF control of the second switching element Q2.

  In the first mode, by controlling in this manner, the control of the period α and the control of the period β are alternately repeated as shown in FIG. Reactor current IL increases in period α and decreases in period β. The output current Ic in FIG. 5 is a current that flows on the second coil L2 side. The output current Ic is zero in the period α and becomes a value corresponding to the reactor current IL in the period β.

  The ON timing and OFF timing of the first to third switching elements Q1 to Q3 in the first mode are controlled such that the average value IL_ave of the reactor current IL becomes the first command value Iref1. The first command value Iref1 is a predetermined value so that the reactor current IL does not become excessive, and is stored in a memory or the like.

  In performing the control in the first mode, if the increase amount of the reactor current IL in the period α is equal to the decrease amount of the reactor current IL in the period β, the reactor current IL does not become excessive. At this time, if the ratio of the lengths of the period α and the period β is D: (1-D), the following expression (4) may be satisfied. The length of the period α is determined by the following expression (5). D shown is obtained.

加えて、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、第１指令値Ｉｒｅｆ１よりも大きい値である第１補正指令値Ｉｒｅｆ１＊となるように、第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２をＯＦＦとするタイミングを制御する。このスロープ電流Ｉｓは、直線的に増加する、仮想的な値である。なお、スロープ電流Ｉｓの時間当たりの増加量をｍ１としている。このとき、第１補正指令値Ｉｒｅｆ１＊は次式（９）で算出することができる。なお、次式（６）では、トランスＴｒによる変圧において電力の損失が無い理想的なものであるとしているが、一般的にはトランスＴｒでは電力の損失がある。この場合には、１未満の値である電力変換効率により、電流の補正項である右辺第２項を補正すればよい。

In addition, in order to suppress subharmonic oscillation, the first switching is performed so that the value obtained by adding the slope current Is to the reactor current IL becomes a first correction command value Iref1 * that is larger than the first command value Iref1. The timing for turning off the element Q1 and the second switching element Q2 is controlled. The slope current Is is a virtual value that increases linearly. In addition, the increase amount per hour of the slope current Is is m1. At this time, the first correction command value Iref1 * can be calculated by the following equation (9). In the following formula (6), it is assumed that there is no power loss in the transformation by the transformer Tr, but generally there is a power loss in the transformer Tr. In this case, the second term on the right side, which is the current correction term, may be corrected by the power conversion efficiency that is a value less than one.

続いて、第２モードの制御を行う際の、第１スイッチング素子Ｑ１、第２スイッチング素子Ｑ２及び第３スイッチング素子Ｑ３の制御状態、リアクトル電流ＩＬの値、及び、出力電流Ｉｃの値を、図６に示す。第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２は、互いのＯＮ期間が重複するように、Ｄｕｔｙ値が５０％よりも大きい値に設定されている。第３スイッチング素子Ｑ３は、常にＯＮ状態とする制御が行われる。

Subsequently, the control state of the first switching element Q1, the second switching element Q2, and the third switching element Q3, the value of the reactor current IL, and the value of the output current Ic when performing the control in the second mode are shown in FIG. It is shown in FIG. The first switching element Q1 and the second switching element Q2 have a duty value set to a value larger than 50% so that the ON periods of each other overlap each other. The third switching element Q3 is controlled to always be in an ON state.

  In the second mode, by controlling in this way, the period α and the period γ are alternately repeated as shown in FIG. As described above, the second mode is performed when the above expression (3) is a negative value. For this reason, reactor current IL increases in period α and decreases in period γ. The output current Ic is zero in the period α, and becomes a value corresponding to the reactor current IL in the period γ.

  The ON timing and OFF timing of the first switching element Q1 and the second switching element Q2 in the second mode are controlled such that the average value IL_ave of the reactor current IL becomes the second command value Iref2. The second command value Iref2 is a predetermined value so that the reactor current IL does not become excessive, and is stored in a memory or the like. Further, the second command value Iref2 may be the same value as the first command value Iref1, or may be a different value.

  Also in the second mode, similarly to the first mode, the increase amount of the reactor current IL in the period α is controlled to be equal to the decrease amount of the reactor current IL in the period γ. At this time, if the ratio of the lengths of the period α and the period γ is D: (1-D), the following expression (7) may be satisfied. The length of the period α is determined by the following expression (8). D shown is obtained.

加えて、第２モードにおいても、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、第２指令値Ｉｒｅｆ２よりも大きい値である第２補正指令値Ｉｒｅｆ２＊となるように、第１スイッチング素子Ｑ１及び第２スイッチング素子Ｑ２をＯＦＦとするタイミングを制御する。なお、スロープ電流Ｉｓの時間当たりの増加量をｍ２としている。このとき、第２補正指令値Ｉｒｅｆ２＊は次式（９）で算出することができる。なお、次式（９）においても、１未満の値である電力変換効率により、電流の補正項である右辺第２項を補正してもよい。

In addition, also in the second mode, the value obtained by adding the slope current Is to the reactor current IL to suppress subharmonic oscillation is the second correction command value Iref2 *, which is a value larger than the second command value Iref2. Thus, the timing which turns OFF the 1st switching element Q1 and the 2nd switching element Q2 is controlled. In addition, the increase amount per hour of the slope current Is is m2. At this time, the second correction command value Iref2 * can be calculated by the following equation (9). In the following equation (9), the second term on the right side, which is the current correction term, may be corrected by the power conversion efficiency that is a value less than one.

続いて、パルス生成部２０が実行する処理を、図７の制御ブロック図により説明する。定電流制御部５０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とを、メモリから読み出して制御に用いる。

Next, processing executed by the pulse generation unit 20 will be described with reference to the control block diagram of FIG. The constant current control unit 50 reads from the memory a first command value Iref1 that is a command value of the reactor current IL in the first mode and a second command value Iref2 that is a command value of the reactor current IL in the second mode. Used for control.

  In the constant current control unit 50, the first command value Iref 1 is input to the addition unit 52. The addition unit 52 receives the current correction term calculated by the current correction unit 51. The current correction term calculated by the current correction unit 51 is the second term on the right side of the above equation (6). On the other hand, the second command value Iref2 is input to the adder 54. The addition unit 52 receives the current correction term calculated by the current correction unit 53. The current correction term calculated by the current correction unit 53 is the second term on the right side of the above equation (9).

  The first correction command value Iref1 * and the second correction command value Iref2 * output from the constant current control unit 50 are input to the mode selection unit 60. The mode selection unit 60 further receives an output voltage Vc, and compares the output voltage Vc with a predetermined value V1. Then, it determines and outputs which of the first correction command value Iref1 * and the second correction command value Iref2 * is to be output.

  One of the first correction command value Iref1 * and the second correction command value Iref2 * output from the mode selection unit 60 is input to the peak current control unit 70 and converted into an analog value by the DA converter 71. Input to the negative terminal.

  On the other hand, the slope compensator 73 of the peak current controller 70 generates the value of the slope current Is obtained from the register value as a signal and inputs the signal to the DA converter 74. 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 into an analog waveform by the DA converter 74 are added by the adder 75 and input to the plus terminal of the comparator 72. The slope compensator 73 may directly generate an analog waveform and input it to the comparator 72 without going through the DA converter 74.

  The slope compensator 73 has different m1 and m2 which are the increase amounts of the slope current Is per time in the first mode and the second mode. Specifically, m1 which is the increase amount per time in the first mode is set to be larger than m2 which is the increase amount per time in the second mode. Note that m1 and m2 may be equal.

  The comparator 72 includes one of the first correction command value Iref1 * and the second correction command value Iref2 * input to the minus terminal, and a value obtained by adding the slope current Is to the reactor current IL input to the plus terminal. Make a comparison. 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 77, 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 77. A clock signal from the clock 76 is input to the R terminal of the RS flip-flop 77.

  In the first mode, the RS flip-flop 77 transmits a signal that turns on both the first to third switching elements Q1 to Q3 if the input signal is a high state signal. On the other hand, if the input signal is a low-level signal, one of the first switching element Q1 and the second switching element Q2 is turned on, the other of the first switching element Q1 and the second switching element Q2 and the third switching element. A signal for turning off the element Q3 is transmitted.

  In the second mode, the RS flip-flop 77 transmits a signal that turns on the first to third switching elements Q1 to Q3 if the input signal is a high-level signal. On the other hand, if the input signal is a low signal, one of the first switching element Q1 and the second switching element Q2 and the third switching element Q3 are turned on, and the first switching element Q1 and the second switching element Q2 are turned on. A signal for turning the other off is output.

  The output of the RS flip-flop 77 is output to the drive circuit 21 that drives the first switching element Q1 and the second switching element Q2 after the upper limit value and the lower limit value of the Duty value are set by the Duty limiter 78. Specifically, in the first mode and the second mode, the duty value is larger than 50% so that the ON period of the first switching element Q1 and the ON period of the second switching element Q2 overlap. To control.

  Next, a series of processes executed by the pulse generator 20 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 voltage Vc is acquired (S102), and it is determined whether or not the output voltage Vc is equal to or lower than the predetermined value V1 (S103). If the output voltage Vc is less than or equal to the predetermined value V1 (S103: YES), control in the first mode is performed (S104). If the output voltage Vc is not less than or equal to the predetermined value V1 (S103: NO), control is performed in the second mode (S105).

  After one of the control in the first mode and the second mode is performed for a predetermined time, the control end determination is performed (S106). In the process of S106, for example, the output voltage Vc may be acquired and it may be determined whether or not the output voltage Vc is equal to or higher than a predetermined upper limit. Note that the determination of whether or not the output voltage Vc is equal to or greater than a predetermined upper limit value may be made after a negative determination is made in S103. When it is determined that the control is to be ended (S106: YES), a series of processing is ended, and the process waits until an activation request is made. If it is not determined to end the control (S106: NO), it is determined whether an end request has been acquired (S107). This end request command signal is transmitted from a host control device such as an ECU. If an end request is acquired (S107: YES), a series of processes are ended and the process waits until an activation request is made. If the end request is not acquired (S107: NO), the processing after S102 is executed again.

  In the flowchart of FIG. 8, only control related to charging control to the capacitive load 40 is shown, but the DCDC converter 10 performs power conversion other than charging control to the capacitive load 40. For example, there is a control in which the power supplied via the connection terminals 40a and 40b is stepped down to charge the secondary battery 30. 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 voltage Vc is smaller than the predetermined value V1, by performing the control in the first mode, one of the first switching element Q1 and the second switching element Q2 is ON, and the first switching element Q1 and the second switching element Q2 A period β in which the other switching element Q2 and the third switching element Q3 are OFF is provided. During this period β, the reactor current IL can be reduced regardless of the value of the output voltage Vc. Therefore, it is possible to prevent the reactor current IL from continuing to increase, and as a result, it is possible to suppress deterioration and failure of the DCDC converter 10.

  When the output voltage Vc becomes larger than the predetermined value V1, such as when charging of the capacitive load 40 has progressed, the first to third switching elements Q1 to Q3 are controlled by performing the second mode control. Is also ON, a period in which one of the first switching element Q1 and the second switching element Q2 and the third switching element Q3 are ON, and the other of the first switching element Q1 and the second switching element Q2 is OFF. γ is provided. Therefore, the reactor current IL can be increased in the period α. By reducing the reactor current IL in the period γ, the reactor load IL can be quickly charged while the reactor current IL is excessively charged. Increase can be suppressed.

  The peak current control unit 70 performs constant current control using the first correction command value Iref1 * and the second correction command value Iref2 * input from the constant current control unit 50. Thereby, in the case where a change occurs in the input voltage Vin, the robustness against overcurrent can be improved. In addition, in calculating the first correction command value Iref1 *, the increase amount of the reactor current IL in the period α is equal to the decrease amount of the reactor current IL in the period β, and the second correction command value Iref2 *. Is calculated such that the increase amount of the reactor current IL in the period α is equal to the decrease amount of the reactor current IL in the period γ. Therefore, an excessive increase and an excessive decrease in the reactor current IL can be suppressed, and both rapid charging and circuit protection can be achieved.

Second Embodiment
The power converter according to the present embodiment has a circuit configuration common to that of the first embodiment, and a part of the control in the first mode is different. Specifically, in the present embodiment, the ON timing and OFF timing of the third switching element Q3 are not synchronized with the ON timing and OFF timing of the first switching element Q1 and the second switching element Q2. FIG. 9 shows the control states of the first to third switching elements Q1 to Q3 and the reactor current IL at that time in the power conversion device according to the present embodiment.

  During the period α, the first to third switching elements Q1 to Q3 are all ON. During the period β, one of the first switching element Q1 and the second switching element Q2 is ON, and the other of the first switching element Q1 and the second switching element Q2 and the third switching element Q3 are OFF. During the period γ, one of the first switching element Q1 and the second switching element Q2 and the third switching element Q3 are ON, and the other of the first switching element Q1 and the second switching element Q2 is OFF. During the period δ, both the first switching element Q1 and the second switching element Q2 are ON, and the third switching element Q3 is OFF.

  In the present embodiment, the OFF timing of the first switching element Q1 and the second switching element Q2 is made constant, and the OFF timing of the third switching element Q3 is made variable so that the increase amount and the decrease amount of the reactor current IL are reduced. It should just be equal. Further, the OFF timing of the third switching element Q3 is fixed, and the OFF timing of the first switching element Q1 and the second switching element Q2 is made variable so that the increase amount and the decrease amount of the reactor current IL are equal. It is good.

  Thus, by providing at least the period α and the period γ, it is possible to obtain a period during which the reactor current IL can be increased and a period during which the reactor current IL can be decreased.

  In the present embodiment, the control in the second mode is the same as that in the first embodiment, and the description thereof is omitted.

  With the above configuration, the power conversion device according to the present embodiment has an effect similar to that of the first embodiment.

<Third Embodiment>
The power converter according to the present embodiment is partially different from the first embodiment in circuit configuration. FIG. 10 is a circuit diagram of the power converter according to this embodiment.

  The power conversion apparatus according to the present embodiment is a DCDC converter 10, and a positive input terminal 30 a and a negative input terminal 30 b of the DCDC converter 10 are connected to a secondary battery 30 that is a DC power supply, and an output terminal of the DCDC converter 10. A capacitive load 40 (smoothing capacitor) is connected in parallel, and a positive output terminal 50 a and a negative output terminal 50 b are provided at the output terminal of the DCDC converter 10.

  The DCDC converter 10 includes a choke coil 11, a transformer Tr, a bridge circuit 14, a first switching element Q1, and a second switching element Q2.

  The transformer Tr is composed of a first coil L1 and a second coil L2 that are magnetically coupled to each other, and the first coil L1 has a center tap 13. The number of turns of the second coil L2 is N / 2 times the number of turns of the first coil L1. That is, the number of turns of the second coil L2 is N times the number of turns from one end of the first coil L1 to the center tap 13. The second coil L2 is connected to the capacitive load 40 via the bridge circuit 14 and the output terminal of the DCDC converter 10.

  The first switching element Q1 and the second switching element Q2 are MOSFETs, and both ends of the first coil L1 are connected to the drain of the first switching element Q1 and the drain of the second switching element Q2, respectively. The first end of the choke coil 11 is connected to the center tap 13 of the first coil L1, and the second end of the choke coil 11 is connected to the positive-side input end 30a via the third switching element Q3. On the other hand, the predetermined connection point 12 is connected to the negative electrode of the secondary battery 30 through the negative electrode side input end 30b. The choke coil 11 and the third switching element Q3 and the predetermined connection point 12 and the negative input side 30b are connected by a third diode D3. The third diode D3 is an energization unit that enables energization from the negative electrode side to the positive electrode side and interrupts the energization from the positive electrode side to the negative electrode side. The first switching element Q1 and the second switching element Q2 each have a first parasitic diode D1 and a second parasitic diode D2 that are connected in parallel in opposite directions.

  Since the bridge circuit 14 is the same as that of the first embodiment, the description thereof is omitted.

  The DCDC converter 10 includes an input voltage detection unit 17, an output voltage detection unit 18, a current detection unit 19, a pulse generation unit 20, and a drive circuit 21. The input voltage detection means 17 is a voltage sensor, for example, and detects the input voltage Vin which is a voltage input from the secondary battery 30 to the choke coil 11. The output voltage detection means 18 is a voltage sensor, for example, and detects the output voltage Vc that is the voltage of the capacitive load 40. The current detection means 19 is a current sensor, for example, and detects a reactor current IL indicating the current of the choke coil 11.

  The input voltage Vin detected by the input voltage detector 17 and the output voltage Vc detected by the output voltage detector 18 are input to the pulse generator 20. Based on the input voltage Vin and output voltage Vc that are input, the pulse generator 20 generates a first PWM signal that is a drive signal for the first switching element Q1 and a second PWM signal that is a drive signal for the second switching element Q2. It is generated and transmitted to the drive circuit 21.

  The drive circuit 21 drives the first switching element Q1 based on the first PWM signal received from the pulse generator 20, and drives the second switching element Q2 based on the second PWM signal.

  In the present embodiment, the same control as in the first embodiment or the second embodiment is performed for the control of the first to third switching elements Q1 to Q3.

  With the above configuration, the power conversion device according to the present embodiment has an effect similar to that of the first embodiment.

<Modification>
In each embodiment, the third diode D3 is used as the energization means that enables energization from the negative electrode side to the positive electrode side and cuts off the energization from the positive electrode side to the negative electrode side, but instead of the third diode D3 It is also possible to provide a switching element and drive the switching element in synchronization with the third switching element Q3.

  In the first embodiment, the third switching element Q3 is provided between the choke coil 11 and the positive input terminal 30a. However, the third switching element Q3 is provided between the center tap 13 and the negative input terminal 30b. It is good also as what provides. In addition, the third switching element Q3 is provided between the choke coil 11 and the positive side input end 30a and between the center tap 13 and the negative side input end 30b, and is controlled in synchronization. Also good.

  In the third embodiment, the third switching element Q3 is provided between the choke coil 11 and the positive input terminal 30a. However, the third switching element is provided between the predetermined connection point 12 and the negative input terminal 30b. Q3 may be provided. The third switching element Q3 is provided between the choke coil 11 and the positive input end 30a and between the predetermined connection point 12 and the negative input end 30b, and is controlled in synchronization. It is good.

  In each embodiment, the peak current control is performed. However, the peak current control may not be performed, and the control may be performed based on a duty value set in advance in association with the output voltage Vc.

  In each embodiment, the peak current control is performed by adding the slope current Is, but the slope current Is is not added and the value of the reactor current IL is the first correction command value Iref1 *, the second correction command value. You may control so that it may become Iref2 *. In this case, in calculating the first correction command value Iref1 * and the second correction command value Iref2 * by the above formula (6) and the above formula (9), it is an increment of the slope current Is in the period α. It is sufficient that ΔIs is not added.

  In each of the above embodiments, the power conversion device is provided in the hybrid car, but the invention can also be applied to other than the hybrid car. In addition, although the DCDC converter 10 can transmit and receive power bidirectionally, it may be configured to be capable of only supplying power from the first coil L1 side to the second coil L2 side. The bridge circuit 14 may be a diode bridge circuit.

  DESCRIPTION OF SYMBOLS 11 ... Choke coil, 12 ... Predetermined connection point, 13 ... Center tap, 18 ... Output voltage detection means, 19 ... Current detection means, 20 ... Pulse generation part, 30 ... Secondary battery, 73 ... Slope compensation part, L1 ... 1 coil, L2 ... 2nd coil, Q1 ... 1st switching element, Q2 ... 2nd switching element, Q3 ... 3rd switching element, Tr ... transformer.

Claims (5)

A power converter that supplies power from an input side to which a DC power supply (30) is connected to an output side via a transformer (Tr),
A choke coil (11) having an input terminal connected to the positive electrode of the DC power supply;
The center tap (13) has both ends connected to a predetermined connection point (12) via the first switching element (Q1) and the second switching element (Q2), respectively, and the center tap is connected to the negative electrode of the DC power source. And the predetermined connection point is connected to the output end of the choke coil, or the center tap is connected to the output end of the choke coil and the predetermined connection point is connected to the negative electrode of the DC power supply. A first coil (L1) constituting the transformer,
A third switching element (Q3) for switching the connection between the DC power supply and the choke coil;
Energization means (D3) for connecting the input end of the choke coil and the predetermined connection point so that energization is possible when the third switching element is OFF;
A second coil (L2) constituting the transformer and magnetically coupled to the first coil;
A pulse generator (20) for transmitting one of an ON signal and an OFF signal to each of the first switching element and the second switching element;
Voltage detection means (18) for detecting an output voltage which is a voltage on the second coil side,
Control for turning on all of the first switching element, the second switching element, and the third switching element; turning on one of the first switching element and the second switching element; The control of turning off the other of the two switching elements and the third switching element is alternately repeated,
When the output voltage is smaller than a predetermined value, the first switching element, the second switching element, and the third switching element are all turned on, and the first switching element and the second switching element A first mode in which one is turned on and the other switching of the first switching element and the second switching element and the third switching element are turned off alternately;
When the output voltage is greater than a predetermined value, both the first switching element and the second switching element are turned on, and one of the first switching element and the second switching element is turned on and the other is turned on. The power conversion device , wherein the second mode in which the control to turn off is alternately repeated and the ON state of the third switching element is continued is set . A current detecting means (19) for detecting a current value of the choke coil;
As the current value becomes the command value is a predetermined value, and controls the first switching element, the second switching element, and the third switching element, according to claim 1 Power converter. The power converter according to claim 2 , wherein peak current control is performed so that the current value becomes the command value. The power conversion apparatus according to claim 2 or 3 , wherein the command value is different between the first mode and the second mode. A slope compensator (73) for adding a slope signal that is a sawtooth wave to the current value;
Wherein a in the first mode and the second mode, characterized in that the slope of the slope signal are different, the power conversion device according to any one of claims 2-4.

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