JP2011004557A - Dc/dc power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC/DC power conversion device that executes stable voltage transition operation while suppressing an overcurrent.SOLUTION: The DC/DC power conversion device is configured as follows. High-voltage side switch elements and low-voltage side switch elements of first/second bridge circuits A11, A2 are ON/OFF-controlled. Consequently, a part of energy stored in a smoothing capacitor Cs1 connected to the first bridge circuit A11 is transferred to an LC serial body Lcr1 through the first bridge circuit A11. Further, the energy is transferred to a smoothing capacitor Cs2 connected to the second bridge circuit A2, from the LC serial body Lcr1 through the second bridge circuit A2. The device includes voltage detecting means 31, 32 for detecting voltages of the smoothing capacitors Cs1, Cs2, and an operation-mode determining means 100 for determining the operation mode according to voltage detection values of the smoothing capacitors Cs1, Cs2 and a voltage command value Vref. Gate-signal generating means 1A, 1B change a gate-signal pattern on the basis of the determined operation mode.

Description

  The present invention relates to a DC / DC power converter that converts a DC voltage into a DC voltage that is stepped up or stepped down.

  As a conventional DC / DC power conversion apparatus, an inverter circuit including at least two semiconductor switches including a semiconductor switch connected to a positive potential and a semiconductor switch connected to a negative potential is connected in series. Consists of a multiple voltage rectifier circuit with a plurality of rectifiers and a plurality of capacitors connected in series. The inverter circuit generates an AC voltage, and the multiple voltage rectifier circuit generates a high voltage DC voltage and supplies it to the load. A DC / DC converter is described (for example, see Patent Document 1).

  In addition, as a conventional DC / DC power converter, it is composed of an inverter circuit and a double voltage rectifier circuit, and an inductor is connected in series with the capacitor to increase the charge / discharge current to the capacitor by utilizing the LC resonance phenomenon. There is a switched capacitor converter, which realizes power conversion with little reduction in efficiency even when a large amount of power is transferred (see Non-Patent Document 1, for example).

JP-A-9-191638

Futoshi Itoba et al .: "Control characteristics of resonant switched capacitor converter", IEICE Technical Report, IEICE Technical Report, EE2005-62, pp7-12, 2006

A conventional DC / DC power conversion device includes an inverter circuit and a rectifier circuit, and performs DC / DC power conversion using charging / discharging of a capacitor. In addition, an inductor is connected in series with a capacitor to connect LC. Large power can be transferred with high efficiency by utilizing the resonance phenomenon. However, in the conventional DC / DC power conversion device, when the voltage difference of the smoothing capacitor is large at the time of starting the device or the like, a large current flows through the LC series body of the semiconductor element or the capacitor and the inductor. There was a need.
In addition, in the conventional DC / DC power converter, since the boost ratio can only be a fixed multiple according to the number of circuit stages, when there is a low-voltage side voltage fluctuation, the high-voltage side voltage has a voltage fluctuation that is twice the boost ratio of the low-voltage side voltage. Therefore, it is necessary to use a withstand voltage component that allows for this voltage fluctuation as a component connected to the high-voltage side voltage.

The present invention provides a DC / DC power conversion device that has been made to solve the above-described problems and that can perform a stable voltage transition operation while suppressing overcurrent.
Moreover, the DC / DC power converter device which can vary a step-up ratio in the state which suppressed the overcurrent is provided.

The DC / DC power converter according to the first invention is
A plurality of smoothing capacitors connected in series from the low voltage side to the high voltage side;
A first bridge circuit in which a high-voltage side switch element and a low-voltage side switch element are connected in series between the positive and negative terminals of the low-voltage side smoothing capacitor;
A second bridge circuit in which a high-voltage side switching element and a low-voltage side switching element are connected in series between the positive and negative terminals of the high-voltage side smoothing capacitor;
Gate signal generating means for generating a gate signal for on / off control of the high-voltage side switch element and the low-voltage side switch element,
A first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the first bridge circuit; and a first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the second bridge circuit. An LC series body consisting of an energy transfer capacitor and an inductor is connected between the two intermediate terminals,
A part of the energy stored in the smoothing capacitor connected to one of the first or second bridge circuits by the on / off control of the high-voltage side switch element and the low-voltage side switch element, Transition to the LC serial body connected to the one bridge circuit through a bridge circuit, and further pass through the other bridge circuit of the first or second bridge circuit connected to the LC serial body from the LC serial body. In the DC / DC power converter for shifting to the smoothing capacitor connected to the other bridge circuit,
Voltage detecting means for detecting the voltage of the smoothing capacitor;
An operation mode determining means for determining an operation mode according to the voltage detection value and the voltage command value of the smoothing capacitor;
The gate signal generation means changes the gate signal pattern based on the determined operation mode.

The DC / DC power converter according to the second invention is
A first smoothing capacitor having a reference voltage terminal as a low-voltage side terminal and a first voltage terminal as a high-voltage side terminal, and a k-th smoothing having a (k−1) th voltage terminal as a high-voltage side terminal and a k-th voltage terminal as a low-voltage side terminal. Capacitors (k = 2,..., N; n is an integer of 2 or more) are connected in series,
The first bridge circuit formed by connecting the high-voltage side switch element and the low-voltage side switch element in series between the positive and negative terminals of the first smoothing capacitor is connected in parallel (m is an integer, 1 ≦ m ≦ n−1). And
(N-1) second bridge circuits each having a high-voltage side switch element and a low-voltage side switch element connected in series between the positive and negative terminals of the k-th (k = 2,..., N) smoothing capacitor. Provided,
Gate signal generating means for generating a gate signal for on / off control of the high-voltage side switch element and the low-voltage side switch element,
A first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the first bridge circuit; and a first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the second bridge circuit. An LC series body consisting of an energy transfer capacitor and an inductor is connected between the two intermediate terminals,
A part of the energy stored in the smoothing capacitor connected to one of the first or second bridge circuits by the on / off control of the high-voltage side switch element and the low-voltage side switch element, Transition to the LC serial body connected to the one bridge circuit through a bridge circuit, and further pass through the other bridge circuit of the first or second bridge circuit connected to the LC serial body from the LC serial body. In the DC / DC power converter for shifting to the smoothing capacitor connected to the other bridge circuit,
Voltage detecting means for detecting the voltage of each of the smoothing capacitors;
An operation mode determination means for determining an operation mode according to the voltage detection value and the voltage command value of each of the smoothing capacitors,
The gate signal generation means changes the gate signal pattern based on the determined operation mode.

  According to the DC / DC power converter of the first invention, the gate signal generating means for generating the gate signal for on / off control of the high-voltage side switch element and the low-voltage side switch element, and the voltage for detecting the voltage of the smoothing capacitor A voltage detection unit; and an operation mode determination unit that determines an operation mode according to a voltage detection value and a voltage command value of the smoothing capacitor. The gate signal generation unit is configured to respond to the operation mode determined by the operation mode determination unit. By changing the gate signal pattern, a stable voltage transition operation with suppressed overcurrent becomes possible.

  According to the DC / DC power conversion device of the second invention, it is possible to perform a stable voltage transition operation in which overcurrent is suppressed, and to output a voltage according to the voltage command value. That is, the voltage Vn between the VH terminal and the Vcom terminal can be boosted to about n times, about (n-1) times,... About 1 time the voltage V1 of the V1 terminal-Vcom terminal. In addition, the voltage Vn between the VH and Vcom terminals as the output voltage is stepped down from the state of about n times the voltage V1 between the V1 terminal and the Vcom terminal to a voltage of about (n-1) times, about 1 time. can do.

It is a figure which shows the circuit structure of the DC / DC power converter device by Embodiment 1 of this invention. It is a figure which shows the timing chart of the DC / DC power converter device by Embodiment 1 of this invention. It is a figure which shows the 2nd timing chart of the DC / DC power converter device by Embodiment 1 of this invention. It is operation | movement explanatory drawing when the operation mode of the DC / DC power converter device by Embodiment 1 of this invention is mode 1. FIG. It is operation | movement explanatory drawing when the operation mode of the DC / DC power converter device by Embodiment 1 of this invention is mode 3. FIG. It is operation | movement explanatory drawing when the operation mode of the DC / DC power converter device by Embodiment 1 of this invention is mode 2. FIG. It is a figure which shows the timing chart of the DC / DC power converter device by Embodiment 2 of this invention. It is operation | movement explanatory drawing when the operation mode of the DC / DC power converter device by Embodiment 2 of this invention is mode 4. FIG. It is operation | movement explanatory drawing when the operation mode of the DC / DC power converter device by Embodiment 2 of this invention is mode 4a. It is an output voltage transition diagram of the DC / DC power converter device by Embodiment 2 of this invention. It is a figure which shows the timing chart of the DC / DC power converter device by Embodiment 3 of this invention. It is operation | movement explanatory drawing when the operation mode of the DC / DC power converter device by Embodiment 3 of this invention is mode 5. FIG. It is a figure which shows the circuit structure of the DC / DC power converter device by Embodiment 5 of this invention. It is a figure which shows the circuit structure of the DC / DC power converter device by Embodiment 6 of this invention. It is a figure which shows the control circuit of the DC / DC power converter device by Embodiment 6 of this invention.

Embodiment 1 FIG.
A DC / DC power converter according to Embodiment 1 of the present invention will be described below.
1 is a diagram showing a circuit configuration of a DC / DC power conversion apparatus according to Embodiment 1 of the present invention. In the DC / DC power converter shown in FIG. 1, the voltage V3 between the VH terminal and the Vcom terminal is boosted to about 3 times, about 2 times, or about 1 time the voltage V1 of the VL terminal-Vcom terminal. Has a function to output. The voltage V2 between the VM terminal and the Vcom terminal has a function of outputting a voltage obtained by boosting the voltage V2 between the VL terminal and the Vcom terminal to about twice or about one time the voltage V1 between the VL terminal and the Vcom terminal.

  First, the main circuit configuration of the DC / DC power conversion device will be described with reference to FIG. Smoothing capacitors Cs1, Cs2, and Cs3 functioning as voltage sources for smoothing the input / output voltage and transferring energy are connected in series, the reference voltage terminal Vcom is connected to the low-voltage side terminal of the smoothing capacitor Cs1, and the high-voltage side of the smoothing capacitor Cs1. The low voltage output terminal VL is connected to the terminal, the medium voltage output terminal VM is connected to the high voltage side terminal of the smoothing capacitor Cs2, and the high voltage output terminal VH is connected to the high voltage side terminal of the smoothing capacitor Cs3. A circuit A11 in which two MOSFETs (S1L, S1H) as a low voltage side switch and a high voltage side switch are connected in series, and a circuit A12 in which MOSFETs (S4L, S4H) as a low voltage side switch and a high voltage side switch are connected in series are a smoothing capacitor The first bridge circuits A11 and A12 are configured by being connected between both terminals of Cs1. A circuit A2 in which MOSFETs (S2L, S2H) as low voltage side switches and high voltage side switches are connected in series is connected between both terminals of the smoothing capacitor Cs2, and MOSFETs (S3L, S3H) as low voltage side switches and high voltage side switches. Are connected between both terminals of the smoothing capacitor Cs3 to constitute second bridge circuits A2 and A3, respectively.

  Further, an intermediate terminal serving as a connection point between the two MOSFETs (S1L, S1H) in the first bridge circuit A11 and an intermediate terminal serving as a connection point between the two MOSFETs (S2L, S2H) in the second bridge circuit A2. The LC series body LCr1, which is configured by a series body of a capacitor Cr1 and an inductor Lr1 and functions as an energy transfer element, is connected between Similarly, an intermediate terminal serving as a connection point between the two MOSFETs (S4L, S4H) in the first bridge circuit A12 and an intermediate point serving as a connection point between the two MOSFETs (S3L, S3H) in the second bridge circuit A3. An LC series body LCr2 which is configured by a series body of a capacitor Cr2 and an inductor Lr2 and functions as an energy transfer element is connected between the terminals.

  Next, the peripheral circuit configuration of the DC / DC power converter will be described. The gate drive circuits 21 to 24 use the low-voltage gate signals (G1L to G4L, G1H to G4H) input from the control circuit 1 as potential reference signals for the MOSFETs (S1L to S4L, S1H to S4H). It has a function of converting the level and a drive function of supplying voltages and currents necessary for on / off control of each MOSFET (S1L to S4L, S1H to S4H). The voltage sensors 31, 32, and 33 are connected to both terminals of the smoothing capacitors Cs 1, Cs 2, and Cs 3, detect the smoothing capacitor voltages Vcs 1, Vcs 2, and Vcs 3 and transmit them to the control circuit 1.

As shown in FIG. 1B, the control circuit 1 includes an operation mode determination unit 100 and gate signal generation units 1A and 1B. The operation mode determination unit 100 has a function of determining the operation mode of the DC / DC power converter according to the voltage command value Vref and the detected voltage values Vcs1, Vcs2, and Vcs3 of the smoothing capacitors Cs1, Cs2, and Cs3. Yes. The first bridge circuit and the second bridge circuit, whose intermediate terminals are connected via the LC serial body, are configured to have the same operation mode. Specifically, the first bridge circuit A11 and the second bridge circuit A2 are operated in the operation mode A, and the first bridge circuit A12 and the second bridge circuit A3 are operated in the operation mode B. The operation mode A and the operation mode B may be the same or different as described later.
The gate signal generation means 1A and 1B have means for generating a gate signal for controlling each MOSFET (S1L to S4L, S1H to S4H) according to the operation mode determined by the operation mode determination means 100. Yes. Specifically, the gate signal generation means 1A generates gate signals G1L, G1H, G2L, G2H for controlling the MOSFETs (S1L, S1H, S2L, S2H) according to the operation mode A, and the gate drive circuit 21 , 22. Similarly, the gate signal generation unit 1B generates gate signals G4L, G4H, G3L, and G3H for controlling the MOSFETs (S4L, S4H, S3L, and S3H) according to the operation mode B, and supplies them to the gate drive circuits 24 and 23. Output.
The control circuit 1 may be composed of one CPU, the operation mode determination means 100 is composed of a CPU such as a microcomputer or DSP, and the gate signal generation means 1A and 1B are composed of logic elements such as FPGA and CPLD. It doesn't matter.

Next, the detailed operation of the operation mode determination unit 100 will be described. FIG. 2 shows a case where the voltage V3 between the VH terminal and the Vcom terminal is stepped up stepwise from a state where the voltage V3 is equal to the voltage V1 between the VL and Vcom terminals to twice the voltage V1 and three times the voltage V1. It is a figure which shows a timing chart.
When the voltage command value Vref is equal to the voltage V1 and the voltage boost command value of the voltage V3 between the VH terminal and the Vcom terminal is 1 time, the operation mode A output to the gate signal generating means 1A and the output to the gate signal generating means 1B The operation mode B to be performed is mode 1. When the voltage command value Vref is V1 × 2 and the boost command value is doubled, only the operation mode A output to the gate signal generating unit 1A is in mode 2, and the voltage target value of the smoothing capacitor Cs2 is V1. When the voltage detection value Vcs2 of the smoothing capacitor Cs2 becomes equal to or higher than the threshold voltage Vth1, the operation mode A shifts to mode 3. Next, when the voltage command value Vref is V1 × 3 and the boost command value is tripled, only the operation mode B output to the gate signal generating unit 1B is in the mode 2, and the voltage target value of the smoothing capacitor Cs3 is V1. Become. When the voltage detection value Vcs3 of the smoothing capacitor Cs3 becomes equal to or higher than the threshold voltage Vth1, the operation mode B shifts to mode 3. Modes 1, 2, and 3 will be described in detail later.
Here, as a criterion for determining that the operation mode shifts from mode 2 to mode 3, the mode shift is performed at the moment when the smoothing capacitor voltages Vcs2 and Vcs3 become equal to or higher than the threshold voltage Vth1, but the smoothing capacitor voltages Vcs2 and Vcs3 are Vth1. The mode may be changed after a predetermined time has elapsed from the time at which the above has occurred.
The threshold voltage Vth1 is set to a value (approximately 0.6 to 0.9 times) slightly smaller than the low voltage side voltage V1. If the threshold voltage Vth1 is extremely small, the value of the current flowing in the resonance circuit increases as described later when switching to mode 2. Conversely, when the threshold voltage Vth1 is equal to or higher than V1, it is not possible to switch to mode 2. Therefore, it is necessary to make the value slightly smaller than V1 in consideration of various error factors.

FIG. 3 is a diagram illustrating a timing chart when the voltage V3 between the VH terminal and the Vcom terminal is increased to a voltage target value that is three times the voltage V1 from a state where the voltage V3 between the VH terminal and the Vcom terminal is equal to the voltage V1 between the VL and Vcom terminals.
When the voltage command value Vref is equal to the voltage V1 and the voltage boost command value of the voltage V3 between the VH terminal and the Vcom terminal is 1 time, the operation mode A output to the gate signal generating means 1A and the output to the gate signal generating means 1B The operation mode B to be performed is mode 1. When the voltage command value Vref is V1 × 3 and the boost command value is tripled, the operation mode A output to the gate signal generation unit 1A and the operation mode B output to the gate signal generation unit 1B are both mode 2. Become. When the smoothing capacitor voltage Vcs2 becomes equal to or higher than the threshold voltage Vth1, the operation mode A shifts to mode 3, and when the smoothing capacitor voltage Vcs3 becomes equal to or higher than the threshold voltage Vth1, the operation mode B shifts to mode 3.

Next, the detailed operation of the gate signal generation means 1A, 1B will be described.
FIG. 4 is a diagram illustrating a gate signal waveform output from the gate signal generation unit when the operation mode input from the operation mode determination unit 100 is mode 1. In FIG. Here, it is assumed that the corresponding MOSFETs (S1L to S4L, S1H to S4H) are turned ON when the gate signal waveforms (G1L to G4L, G1H to G4H) are High.
When the operation mode is mode 1, the gate signals (G1L, G1H, G4L, G4H) of the MOSFETs (S1L, S1H, S4L, S4H) connected to the smoothing capacitor Cs1 are fixed at Low. Conversely, the gate signals (G2L, G2H, G3L, G3H) of the MOSFETs (S2L, S2H, S3L, S3H) connected to the smoothing capacitors (Cs2, Cs3) other than the smoothing capacitor Cs1 are fixed at High.
By outputting such a gate signal waveform, when the operation mode A is mode 1, the voltage detection value Vcs2 of the smoothing capacitor Cs2 becomes zero, and the voltage VM of the intermediate output terminal becomes equal to the voltage VL of the low voltage output terminal. Similarly, when the operation mode B is mode 1, the voltage detection value Vcs3 of the smoothing capacitor Cs3 is zero, and the voltage VH at the high voltage output terminal is equal to the voltage VM at the intermediate output terminal. When both the operation mode A and the operation mode B are mode 1, the voltage detection values Vcs2 and Vcs3 of the smoothing capacitors Cs2 and Cs3 are both zero, so the voltage VH at the high voltage output terminal is equal to the voltage VL at the low voltage output terminal. The boost ratio is 1 time.

Next, the operation of mode 3 as the steady boost mode will be described.
FIG. 5 shows the gate signal waveforms (G1L to G4L, G1H to G4H) output from the gate signal generation means 1A and 1B when the operation mode input from the operation mode determination means 100 is mode 3, and the LC serial body LCr1, It is a figure which shows the electric current which flows through the LCr2, and each MOSFET (S1L-S4L, S1H-S4H). Regarding the polarity of the current, the direction in which the MOSFET flows from the drain to the source is positive, and the direction in which the LC series body flows from the high potential side bridge circuit to the low potential side bridge circuit is positive.
The gate signals G1L, G1H, G4L, and G4H are ON / OFF signals having a cycle Ts0 that is slightly larger than the resonance cycle Tr determined by the LC series circuit of Lr1 and Cr1 and a duty of about 50%, and the MOSFET is turned on when the gate signal is High. It becomes.
When the gate signals G1L and G4L become High and S1L and S4L are turned on, a part of energy stored in the smoothing capacitors Cs1 and Cs2 is transferred to the capacitors Cr1 and Cr2 through the following paths.
Cs1⇒S2L⇒Lr1⇒Cr1⇒S1L
Cs1⇒Cs2⇒S3L⇒Lr2⇒Cr2⇒S4L
Next, when the gate signals G1H and G4H become High and S1H and S4H are turned on, the energy charged in the capacitors Cr1 and Cr2 is transferred to the smoothing capacitors Cs2 and Cs3 through the following paths.
S1H⇒Cr1⇒Lr1⇒S2H⇒Cs2
S4H⇒Cr2⇒Lr2⇒S3H⇒Cs3⇒Cs2

As described above, energy is transferred from the smoothing capacitors Cs1 and Cs2 to the smoothing capacitors Cs2 and Cs3 by charging and discharging the capacitors Cr1 and Cr2. Then, the voltage V1 input between the voltage terminals VL and Vcom is set to a voltage V2 boosted about twice, and is output between the voltage terminals VM and Vcom, and the voltage V3 is boosted about three times to the voltage terminal. Output between VH and Vcom. Here, since each of the capacitors Cr1 and Cr2 constitutes an LC series circuit in which the inductors Lr1 and Lr2 are connected in series, the energy transfer uses a resonance phenomenon, and a large amount of energy can be transferred efficiently. In addition, since switching is performed in a state where the energization current of the MOSFET is zero (zero current switching), a highly efficient DC / DC power conversion operation can be performed.
Since each MOSFET has a parasitic diode, the gate control signals G2L, G2H, G3L, and G3H of the MOSFETs (S2L, S2H, S3L, and S3H) are not necessary in principle. However, as shown in FIG. 5, if a gate control signal is used to turn on each MOSFET when the parasitic diode is turned on by utilizing the synchronous rectification action of the MOSFET, the MOSFET on-voltage is reduced. Is possible.
In FIG. 5, Td is a dead time for preventing a short circuit due to simultaneous conduction of MOSFETs (S1L, S1H). Td2 is an operation delay time for preventing energy backflow. Although basically not occurring, if the voltage of the capacitor Cr1 is higher than the voltage of the capacitor Cs1, if S2L is turned ON before S1L, an energy reverse flow phenomenon may occur. The current path in this case is as follows.
Cr1 → Lr1 → S2L → Cs1 → S1L (diode)

The reason why the switching period Ts0 is set to a value slightly larger than the resonance period Tr determined by the LC series circuit including the inductor Lr and the capacitor Cr in the operation mode 3 will be described.
If the switching period Ts0 is smaller than the resonance period Tr, the MOSFET is turned off before the current flowing through the LC series circuit becomes zero, so that a turn-off loss and a switching surge voltage are generated in the MOSFET. Further, since the MOSFET is turned on while the excitation energy of the inductor Lr remains, a turn-on loss and a switching surge voltage are generated in the MOSFET. The turn-on loss and the turn-off loss not only deteriorate the efficiency of the DC / DC power converter, but also increase the cost due to the increase in the size of the heat sink and fan for cooling the MOSFET.
In the operation mode 3, a demerit when the switching period Ts0 becomes sufficiently larger than the resonance period Tr will be described. When the switching period Ts0 is increased, the number of times power is transferred per unit time is decreased. Therefore, when compared under a constant power transmission condition, a current value flowing through the LC series circuit or MOSFET increases. Specifically, when the switching period Ts0 is k times, the effective current value flowing through the LC series circuit or the MOSFET is √ (k) times under the condition of transmitting constant power, and the MOSFET or the LC series circuit is The conduction loss is k times. The increase in conduction loss not only deteriorates the efficiency of the DC / DC power converter, but also increases the cost due to the increase in the size of the heat sink and fan for cooling the MOSFET.
As described above, even if the switching cycle Ts0 is smaller than the resonance cycle Tr or the switching cycle Ts0 is too larger than the resonance cycle Tr, the efficiency of the DC / DC power converter is deteriorated. A value slightly larger than the resonance period Tr (about 1 to 1.5 times) is the optimum condition.

The operation mode 3 as the steady operation has been described so far, but the operation mode 3 as the transient operation will be described below. In the steady operation, the voltages Vcs2 and Vcs3 of the smoothing capacitors Cs2 and Cs3 are substantially equal to the voltage Vcs1 of the smoothing capacitor Cs1, so that a high-efficiency step-up operation by zero current switching can be performed by performing the mode 3 operation. . However, if mode 3 operation is performed in a state where the smoothing capacitor voltage Vcs2 or Vcs3 is extremely lower than Vcs1, an excessive current flows through the LC series body functioning as a MOSFET or energy transfer element. The phenomenon will be described below.
Here, in order to simplify the description, a description will be given immediately after the boost command value changes from 1 to 2 times. Under this condition, since the operation mode B is always mode 1, the voltage Vcs3 of the smoothing capacitor Cs3 changes to zero, and the operation mode A changes from mode 1 to mode 3, so the initial voltage of the smoothing capacitor Cs2 becomes almost zero. In addition, it is assumed that the resonance period Tr and the switching period Ts0 determined by the LC series circuit coincide with each other, and the capacity of the smoothing capacitor Cs2 is sufficiently larger than the capacity of the energy transfer capacitor Cr1.

When the gate signal G1L becomes High and the MOSFET (S1L) is turned on, the current Icr (t) flowing from the smoothing capacitor Cs1 to the capacitor Cr1 can be expressed by Expressions 1 and 2.
Equation 1 and Equation 2 are differential equations Ri + L (di / dt) + q / when the DC voltage V is instantaneously applied to the RLC series circuit composed of the MOSFET (S2L), the inductor Lr1, the capacitor Cr1, and the MOSFET (S1L). c = E is the solution,
i = E / (ωL) × e ^−αt sin (ωt).
However, R ² <4L / C, and α = R / (2L), ω = √ {1 / (LC) − (R / (2L) ² )}.

  In the above formulas 1 and 2, R is the total resistance component of the capacitor Cs1, MOSFET (S2L), inductor Lr1, capacitor Cr1, MOSFET (S1L), and Vcr0 is the initial voltage of the capacitor Cr1 just before the mode 3 is shifted. The sign of the capacitor current Icr (t) is positive in the direction flowing from the inductor Lr1 to the capacitor Cr1 in FIG. The voltage Vcra of the capacitor Cr1 immediately after the energy is transferred from the smoothing capacitor Cs1 to the energy transfer capacitor Cr1 can be expressed by Equations 3 and 4.

  When the voltage Vcs2 of the smoothing capacitor Cs2 is zero, the initial voltage Vcr0 of the energy transfer capacitor Cr1 is also zero, so the voltage Vcra of the capacitor Cr1 is expressed by Equation 5.

Next, when S1L is turned off and S1H is turned on, the energy stored in the capacitor Cr1 is transferred to the upper smoothing capacitor Cs2. At this time, the current Icr ^* (t) flowing from the energy transfer capacitor Cr1 to the smoothing capacitor Cs2 is expressed by Equation 6, and the voltage Vcrb of the capacitor Cr1 immediately after the energy transfer from the energy transfer capacitor Cr1 to the smoothing capacitor Cr2 is , Represented by Equation 7.

  When the voltage Vcs2 of the smoothing capacitor Cs2 is substantially zero, V2 = V1. Therefore, the voltage Vcrb of the capacitor Cr1 immediately after the energy transfer operation is performed once is expressed by Equation 8.

  From Equation 3, Equation 5, and Equation 8, the voltage VcrN of the capacitor Cr1 immediately after the energy transfer operation is performed N times can be expressed by Equation 9.

Since A is a positive value (0 <A <1), Equation 9 means that the voltage amplitude of the capacitor Cr1 increases every time the energy transfer operation is repeated. When the voltage amplitude of the capacitor Cr1 increases, the current Icr flowing through the capacitor Cr1 increases from Equation 1, and therefore the current increases each time the energy transfer operation is repeated.
Thus, when the smoothing capacitor voltage Vcs2 is extremely lower than Vcs1, when the operation mode A is set to mode 3, the LC series body LCr1 functioning as a MOSFET (S1L, S1H, S2L, S2H) or an energy transfer element is obtained. An excessive current flows, and there is a possibility that the element is destroyed due to the overcurrent. Similarly, when the smoothing capacitor voltage Vcs3 is extremely lower than Vcs1 and the operation mode B is set to mode 3, the LC series body LCr2 functioning as a MOSFET (S4L, S4H, S3L, S3H) or an energy transfer element is excessive. There is a possibility that current flows and element destruction occurs due to overcurrent.

In the present embodiment, when the smoothing capacitor voltages Vcs2 and Vcs3 are sufficiently smaller than the input voltage Vcs1, the operation mode is set to mode 2 in order to prevent element destruction due to overcurrent. Hereinafter, the operation of mode 2 will be described.
6 shows the gate signal waveforms (G1L to G4L, G1H to G4H) output from the gate signal generation means 1A and 1B when the operation mode input from the operation mode determination means 100 is mode 2, and the LC serial body LCr1, It is a figure which shows the electric current which flows through the LCr2, and each MOSFET (S1L-S4L, S1H-S4H). The difference between mode 2 and mode 3 is that the switching period Ts1 in mode 2 is made larger than the switching period Ts0 in mode 3.

The operation in mode 2 will be described with a current path. Here, in order to simplify the description, a description will be given immediately after the boost command value changes from 1 to 2 times. Under this condition, since the operation mode B is always mode 1, the voltage Vcs3 of the smoothing capacitor Cs3 changes to zero, and the operation mode A changes from mode 1 to mode 2. Therefore, the initial voltage of the smoothing capacitor Cs2 becomes almost zero.
When the gate signal G1L becomes High and S1L is turned on, a part of energy stored in the smoothing capacitor Cs1 is transferred to the capacitor Cr1 through the following path.
Cs1⇒S2L⇒Lr1⇒Cr1⇒S1L
The voltage Vcra of the capacitor Cr1 immediately after the energy is transferred from the smoothing capacitor Cs1 to the energy transfer capacitor Cr1 is expressed by the above-described equation 5, and V2 <Vcra. Therefore, the energy stored in the capacitor Cr1 is MOSFET (S1L , S2H) through the parasitic diodes to the smoothing capacitors Cs1 and Cs2 through the following path.
Cr1⇒Lr1⇒S2H⇒Cs2⇒Cs1⇒S1L

  The voltage Vcrc of the capacitor Cr1 immediately after the energy is transferred from the energy transfer capacitor Cr1 to the smoothing capacitors Cs1 and Cs2 is expressed by Expression 10.

When the voltage Vcs2 of the smoothing capacitor Cs2 is substantially zero, V2 = V1 and A has a positive value (0 <A <1), so the voltage Vcrc of the energy transfer capacitor Cr1 has a positive value. At this time, by turning off the gate signal G1L of the MOSFET (S1L), the current of the LC series body LCr1 becomes zero.
Next, when the gate signal G1H becomes High and S1H is turned on, the energy charged in the capacitor Cr1 is transferred to the smoothing capacitor Cs2 through the following path.
Cr1⇒Lr1⇒S2H⇒Cs2⇒S1H
When the voltage Vcrd of the capacitor Cr1 immediately after the energy is transferred from the energy transfer capacitor Cr1 to the smoothing capacitor Cs1, the current of the LC series LCr1 becomes zero. When the voltage Vcrd becomes a negative value, current flows through the parasitic diode of the MOSFET (S1H, S2L) to the capacitor Cr1 through the following path, and the voltage of the energy transfer capacitor Cr1 is finally positive. It becomes the value of.
Cr1⇒S1H⇒S2L⇒Lr1

As described above, in the operation mode 2, the voltage Vcr1 of the energy transfer capacitor Cr1 is lowered by setting the switching cycle Ts1 to be twice or more the resonance cycle Tr and operating the LC resonance for one cycle every switching half cycle. In this state, the switching operation of the MOSFETs (S1L, S1H) can be performed. As a result, the voltage amplitude of the energy transfer capacitor Cr1 can be suppressed, and even when the smoothing capacitor voltage Vcs2 is extremely lower than the smoothing capacitor voltage Vcs1, an increase in the capacitor current Icr1 that is a problem in mode 3 is prevented. It becomes possible to do. Further, since switching can be performed when the energization current of the MOSFETs (S1L, S1H) is zero, zero current switching is possible, and highly efficient DC / DC power conversion operation is possible.
The operation when the operation mode A is the mode 2 has been described so far, but the operation when the operation mode B is the mode 2 is the same. The stable operation by preventing the increase of the energy transfer capacitor current Icr2 and the MOSFET (S4L , S4H), high-efficiency operation by zero current switching becomes possible.

  As described above, in the first embodiment, the gate signal generating means (1A, 1B) for generating the gate signal for on / off control of the semiconductor switching elements (S1L to S4L, S1H to S4H), and the voltage of the smoothing capacitor Voltage detection means (31-33) for detecting the voltage, and an operation mode determination means 100 for determining an operation mode according to the voltage detection value of the smoothing capacitor and the voltage command value, and gate signal generation means (1A, 1B) ) Can stably output the voltage V3 corresponding to the voltage command value Vref by changing the gate signal pattern according to the operation mode determined by the operation mode determination means 100.

Embodiment 2. FIG.
A DC / DC power converter according to Embodiment 2 of the present invention will be described below.
The circuit configuration of the DC / DC power converter according to Embodiment 2 of the present invention is the same as that of Embodiment 1 (FIG. 1) of the present invention, and the control method is different. FIG. 7 is a timing chart when the voltage V3 between the VH and Vcom terminals as the output voltage is increased from the state equal to the voltage V1 between the VL and Vcom terminals to a voltage twice as high as the voltage V1 and three times as high as the voltage V1. FIG. The difference from the first embodiment is that the operation mode in which the voltage detection value Vcs2 or Vcs3 of the smoothing capacitor Cs2 or Cs3 is lower than the voltage target value V1 is not the mode 2 described in the first embodiment but the following mode. The mode 4 described below is used.

The operation in mode 4 of the second embodiment will be described below.
8 shows gate signal waveforms (G1L to G4L, G1H to G4H) output from the gate signal generation means 1A and 1B when the operation mode input from the operation mode determination means 100 is mode 4, LC serial body LCr1, It is a figure which shows the electric current which flows through LCr2, and the electric current which flows through each MOSFET (S1L-S4L, S1H-S4H). Ts2 in the figure is the switching period of mode 4, and, like mode 2, has a value that is at least twice the resonance period Tr determined by the LC series circuit of inductor Lr and capacitor Cr. In addition, Ton2 in the figure is the ON time of the MOSFETs (S1L, S4L), and is a value that is half or less of the resonance period Tr determined by the LC series circuit.

The operation of mode 4 will be described with a current path. Here, in order to simplify the description, a description will be given immediately after the boost command value changes from 1 to 2 times. Under this condition, since the operation mode B is always mode 1, the voltage Vcs3 of the smoothing capacitor Cs3 changes to zero, and the operation mode A changes from mode 1 to mode 4, so the initial voltage of the smoothing capacitor Cs2 becomes almost zero.
When the gate signal G1L becomes High and the MOSFET (S1L) is turned on, a part of energy stored in the smoothing capacitor Cs1 is transferred to the capacitor Cr1 through the following path.
Cs1⇒S2L⇒Lr1⇒Cr1⇒S1L

In mode 4, the MOSFET (S1L) is turned off before the current flowing through the LC series circuit becomes zero. At this time, since the MOSFET is turned off in a current-energized state, a turn-off loss and a switching surge voltage are generated in the MOSFET (S1L). Immediately after the MOSFET (S1L) is turned off, the excitation energy of the inductor Lr1 is present. Therefore, the excitation energy of the inductor Lr1 passes through the parasitic diode of the MOSFET (S1H, S2L) and transfers to the capacitor Cr1 through the following path.
Lr1⇒Cr1⇒S1H⇒S2L
At this time, by setting the ON time Ton2 of the MOSFETs (S1L, S4L) so that the voltage of the energy transfer capacitor Cr1 is equal to or lower than the voltage V2 between the VM terminal and the Vcom terminal, the current flowing through the LC series circuit Becomes zero.

Next, when the MOSFET (S1H) is turned on, the energy stored in the capacitor Cr1 is transferred to the capacitor Cs2 through the following path.
Cr1⇒Lr1⇒S2H⇒Cs2⇒S1H
When the voltage of the capacitor Cr1 immediately after the energy transfer from the energy transfer capacitor Cr1 to the smoothing capacitor Cs2 becomes a positive value, the current of the LC series body LCr1 becomes zero. When the voltage of the capacitor Cr1 becomes a negative value, a current flows through the parasitic diode of the MOSFET (S1H, S2L) to the capacitor Cr1 through the following path, and the voltage of the energy transfer capacitor Cr1 finally becomes Is a positive value.
Cr1⇒S1H⇒S2L⇒Lr1

  As described above, in the operation mode 4, the switching period Ts2 is set to be longer than the resonance period Tr determined by the LC series circuit (preferably set to be twice or more of Tr), and the on-time Ton2 of the MOSFET (S1L) is set to the LC series circuit. Therefore, the voltage amplitude of the energy transfer capacitor Cr1 can be suppressed, and even when the smoothing capacitor voltage Vcs2 is extremely lower than Vcs1, stable DC / DC power conversion operation is possible.

In the operation mode 4, since the turn-off operation is performed while the MOSFET (S1L) is energized, a turn-off loss occurs in the MOSFET (S1L) and a switching surge voltage at the turn-off occurs in the MOSFET (S1L). In response to this, the on-time Ton2 of the MOSFET (S1L) may be set so that both the turn-off loss and the switching surge voltage are acceptable.
Regarding the turn-on operation, all MOSFETs always perform the turn-on operation in a zero current state, so that the turn-on loss and the switching surge voltage are almost zero. This is because the switching period Ts2 is set to be twice or more the resonance period Tr determined by the LC series circuit, so that the current flowing through the LC series circuit LCr1 is always zero before the MOSFET is turned on.

  Next, as another pattern of the operation mode 4, an operation explanatory diagram of the operation mode 4a is shown in FIG. FIG. 9 shows gate signal waveforms (G1L to G4L, G1H to G4H) output from the gate signal generation means 1A and 1B, currents flowing through the LC series bodies LCr1 and LCr2, and MOSFETs (S1L to S4L, S1H to S4H). The flowing current is shown. In the figure, Ts3 is a switching period of the operation mode 4a, and has a value larger than a resonance period Tr determined by an LC series circuit including an inductor Lr and a capacitor Cr. Ton2 is the ON time of the MOSFETs (S1L, S4L), and is set to a value equal to or less than half of the resonance period Tr determined by the LC series circuit, as in the operation mode 4. Ton3 is the on time of the MOSFETs (S1H, S4H), which is the same as or slightly longer than the on time Ton of mode 2 or mode 3.

The main difference between the operation mode 4a and the operation mode 4 is that the high-side MOSFETs (S1H, S4H) are turned on immediately after the low-side MOSFETs (S1L, S4L) are turned off. There are mainly two merits in this operation.
The first merit is that by turning on the MOSFETs (S1H, S4H) during the energy transition period from the inductor Lr to the capacitor Cr, the on-voltage of the MOSFET (S1H) is reduced due to the synchronous rectification action and the loss. It is possible to reduce.
A second merit is that the transmission period per unit time increases because the switching period Ts3 of the operation mode 4a can be shorter than the switching period Ts2 of the operation mode 4. When the amount of transmitted power per unit time increases, the voltage transition time of the VH-Vcom terminal voltage V3 as the output voltage is shortened, so that the responsiveness as a DC / DC power converter is improved.

  Next, a method of changing the on-time Ton2 of the MOSFETs (S1L, S4L) according to the smoothing capacitor voltages (Vcs1, Vcs2, Vcs3) in order to further increase the transmission power amount per unit time will be described. As before, for the sake of simplicity of explanation, the case where the boost command value is 1 to 2 times, the operation mode A is mode 1 to mode 4, and the operation mode B is mode 1 will be described.

  When the gate signal G1L becomes High and S1L is turned on, the current Icr (t) flowing from the smoothing capacitor Cs1 to the capacitor Cr1 is expressed by the above-described Expressions 1 and 2. Here, if the on-time of the MOSFET (S1L) is sufficiently shorter than the resonance period Tr determined by the LC series circuit, the voltage amplitude of the energy transfer capacitor Cr1 is small, and the capacitor voltage Vcr1 after the energy transfer operation is completed. Is considered to be substantially the same value as the voltage Vcs2 of the smoothing capacitor Cs2. As a result, the peak current Icr (max) flowing through the MOSFET (S1L) can be approximately expressed by Expression 11.

  Here, Lr is the inductance value of the inductor Lr1, Vcs1 is the voltage of the smoothing capacitor Cs1, Vcs2 is the voltage of the smoothing capacitor Cs2, and Ton2 is the ON time of the MOSFET (S1L). Expression 11 shows that the peak current Icr (max) of the MOSFET (S1L) depends on the smoothing capacitor voltage Vcs2, and when the on-time is constant, as the smoothing capacitor voltage Vcs2 increases, the peak current Icr ( max) decreases. When the peak current decreases, the amount of transmitted power decreases, so the voltage transition time of the VH-Vcom terminal voltage V3 as the output voltage increases, and the responsiveness as a DC / DC power converter decreases.

  In order not to reduce the transmission power amount, it is necessary to change the on-time Ton2 of the MOSFET (S1L) so that the peak current Icr (max) becomes constant. Equation 12 shows the on-time Ton2 of the MOSFET (S1L) for making the peak current of the MOSFET (S1L) constant.

Here, Vcs2 (ref) is a target voltage of the smoothing capacitor Cs2, and in the operation mode 4, Vcs2 (ref) = Vcs1. As shown in Equation 12, the peak current Icr (max) of the MOSFET (S1L) can be made substantially constant by increasing the on-time Ton2 of the MOSFET (S1L) as the smoothing capacitor voltage Vcs2 increases. It becomes.
The operation when the operation mode B is the mode 4 is the same, and as the smoothing capacitor voltage Vcs3 increases, the on-time Ton2 of the MOSFET (S4L) is increased to increase the peak current Icr (max of the MOSFET (S4L)). ) Can be made almost constant.

  FIG. 10 shows a transition image of the voltage command value Vref and the output voltage V3 when the on time Ton2 of the MOSFET (S1L) is made constant and when the on time Ton2 is varied according to the smoothing capacitor voltage. When Ton2 is constant, the voltage increase rate decreases as the output voltage V3 increases, so that the time until the target voltage is reached becomes longer. When Ton2 is variable, the rate of voltage increase is substantially constant even when the output voltage V3 increases, so that it is possible to shorten the time until the target voltage is reached.

  As described above, in the second embodiment, the ON time Ton2 of the MOSFETs (S1L, S4L) is determined by the LC series circuit as an operation mode when the smoothing capacitor voltages Vcs2, Vcs3 are sufficiently smaller than the input voltage Vcs1. By operating at half or less of the resonance period Tr, the voltage amplitude of the energy transfer capacitor Cr1 can be suppressed, and a stable operation can be achieved by preventing an increase in the energy transfer capacitor current Icr2. Further, the peak current of the MOSFETs (S1L, S4L) is not increased by changing the ON time Ton2 of the MOSFETs (S1L, S4L) according to the difference between the voltage command value Vref of the smoothing capacitor and the smoothing capacitor voltages Vcs2, Vcs3. In addition, since the amount of transmission power per unit time can be increased, the responsiveness as a DC / DC power converter can be improved.

Embodiment 3 FIG.
A DC / DC power conversion apparatus according to Embodiment 3 of the present invention will be described below.
The circuit configuration of the DC / DC power converter according to Embodiment 3 of the present invention is the same as that of Embodiment 1 of the present invention (FIG. 1), and the control method is different. FIG. 11 is a timing chart when the voltage V3 between the VH and Vcom terminals as an output voltage is lowered from three times the voltage V1 between the VL and Vcom terminals to twice the voltage V1 and the same voltage as V1. FIG.

When the voltage command value Vref is V1 × 3 and the step-up command value of the voltage V3 between the VH terminal and the Vcom terminal is three times, the operation mode A output to the gate signal generation unit 1A and the output to the gate signal generation unit 1B The operation mode B to be performed is mode 3. When the voltage command value Vref becomes V1 × 2 and the boost command value is doubled, only the operation mode B output to the gate signal generating unit 1B is in mode 5, and the voltage target value of the smoothing capacitor Cs3 becomes zero. When the voltage detection value Vcs3 of the smoothing capacitor Cs3 becomes equal to or lower than the threshold voltage Vth2, the operation mode B shifts to mode 1. Next, when the voltage command value Vref becomes V1 and the boost command value becomes 1 time, only the operation mode A output to the gate signal generating means 1A becomes the mode 5, and the voltage target value of the smoothing capacitor Cs2 becomes zero. . When the voltage detection value Vcs2 of the smoothing capacitor Cs2 becomes equal to or lower than the threshold voltage Vth2, the operation mode A shifts to mode 1.
Here, as a criterion for transitioning the operation mode from mode 5 to mode 1, the mode transition is illustrated at the moment when the smoothing capacitor voltages Vcs2 and Vcs3 become equal to or lower than the threshold voltage Vth2, but the smoothing capacitor voltage is Vth2. The mode may be changed after a predetermined time has elapsed from the time point below.

The operation in mode 5 of the third embodiment will be described below.
12 shows the gate signal waveforms (G1L to G4L, G1H to G4H) output from the gate signal generating means 1A and 1B when the operation mode input from the operation mode determining means 100 is mode 5, and the LC serial body LCr1, It is a figure which shows the electric current which flows through the LCr2, and each MOSFET (S1L-S4L, S1H-S4H). Ts4 in the figure is the switching period of mode 5, and is a value that is at least twice the resonance period Tr determined by the LC series circuit composed of the inductor Lr and the capacitor Cr. In addition, Ton4 in the figure is the ON time of the MOSFETs (S1L, S4L), and is a value that is half or less of the resonance period Tr determined by the LC series circuit.

  The operation in mode 5 will be described with a current path. Here, in order to simplify the description, a case where the boost command value changes from 2 times to 1 time will be described. Under this condition, since the operation mode B is always mode 1, the voltage Vcs3 of the smoothing capacitor Cs3 is zero, and the operation mode A changes from mode 3 to mode 5. Therefore, the initial voltage of the smoothing capacitor Cs2 is V1, and the energy transfer capacitor The initial voltage of Cr1 is almost equal to V1.

When the gate signal G2H becomes High and the MOSFET (S2H) is turned on, the energy stored in the smoothing capacitor Cs2 is transferred to the capacitor Cr1 through the following path.
Cs2⇒S2H⇒Lr1⇒Cr1⇒S1H
When half the time of the resonance period Tr determined by the LC series circuit has elapsed, the current flowing through the LC series circuit LCr1 becomes zero. After the current flowing through the LC series circuit LCr1 becomes zero, when the gate signal G1L is set to High and the MOSFET (S1L) is turned on, the energy stored in the smoothing capacitor Cs1 and the smoothing capacitor Cs2 is expressed by the following path. Transition to capacitor Cr1.
Cs1⇒Cs2⇒S2H⇒Lr1⇒Cr1⇒S1L

In mode 5, the MOSFET (S1L) is turned off before the current flowing through the LC series circuit becomes zero. At this time, since the MOSFET is turned off in a current-energized state, a turn-off loss and a switching surge voltage are generated in the MOSFET (S1L). Immediately after the MOSFET (S1L) is turned off, the excitation energy of the inductor Lr1 is present, so the energy stored in the smoothing capacitor Cs2 and the excitation energy of the inductor Lr1 pass through the parasitic diode of the MOSFET (S1H) and pass through the capacitor shown in the following path. Transition to Cr1.
Cs2⇒S2H⇒Lr1⇒Cr1⇒S1H
At this time, by setting the ON time Ton4 of the MOSFET (S1L) so that the voltage of the energy transfer capacitor Cr1 is equal to or lower than the voltage V2 between the VM terminal and the Vcom terminal, the current flowing through the LC series circuit is zero. It becomes.

Next, when the MOSFET (S2L) is turned on, the energy stored in the capacitor Cr1 shifts to the smoothing capacitor Cs1 through the following path.
Cr1⇒Lr1⇒S2L⇒Cs1⇒S1L
At this time, since a parasitic diode is formed in the MOSFET (S1L), the gate control signal G1L is not necessary in principle. However, if a gate control signal G1L that is turned on when the parasitic diode is turned on is input, the synchronous rectification action of the MOSFET The loss of the MOSFET (S1L) can be reduced by the decrease of the on-voltage. When the voltage of the capacitor Cr1 immediately after the energy transfer from the energy transfer capacitor Cr1 to the smoothing capacitor Cs2 becomes a positive value, the current of the LC series body LCr1 becomes zero. When the voltage of the capacitor Cr1 becomes a negative value, a current flows through the parasitic diode of the MOSFET (S1H, S2L) to the capacitor Cr1 through the following path, and the voltage of the energy transfer capacitor Cr1 finally becomes Is a positive value.
Cr1⇒S1H⇒S2L⇒Lr1

  In this way, by operating the operation mode A in mode 5, energy can be transferred from the smoothing capacitor Cs2 arranged on the high potential side to the smoothing capacitor Cs1 arranged on the low potential side, so that VH− The Vcom terminal voltage V3 can be lowered from V1 × 2 times to V1 × 1 times. Similarly, by operating the operation mode B in mode 5, energy can be transferred from the smoothing capacitor Cs3 arranged on the high potential side to the smoothing capacitor Cs1 arranged on the low potential side, so that VH-Vcom as the output voltage The terminal voltage V3 can be lowered from V1 × 3 times to V1 × 2 times.

  In the operation mode 5, since the turn-off operation is performed with the current conduction of the MOSFETs (S1L, S4L), a turn-off loss and a switching surge voltage at the turn-off are generated in the MOSFETs (S1L, S4L). For this, the on-time Ton4 of the MOSFETs (S1L, S4L) may be set so that both the turn-off loss and the switching surge voltage are acceptable. Regarding the turn-on operation, all MOSFETs always perform the turn-on operation in a zero current state, so that the turn-on loss and the switching surge voltage are almost zero.

  Next, a method of changing the on-time Ton4 of the MOSFETs (S1L, S4L) according to the smoothing capacitor voltages (Vcs1, Vcs2, Vcs3) in order to further increase the transmission power amount per unit time will be described. Here, in order to simplify the description, a case where the boost command value is doubled to 1 time, the operation mode A is mode 3 to mode 5, and the operation mode B is mode 1 will be described.

  When the gate signal G1L becomes High and the MOSFET (S1L) is turned on, the current Icr (t) flowing from the smoothing capacitor Cs1 to the capacitor Cr1 is expressed by Expression 13 and Expression 2 described above.

  Here, R is a total resistance component of Cs1, Cs2, S2H, Lr1, Cr1, and S1L, and Vcr0 is an initial voltage of the capacitor Cr1 immediately before the MOSFET (S1L) is turned on. The sign of the capacitor current Icr (t) is positive in the direction flowing from the inductor Lr1 to the capacitor Cr1 in FIG. If the ON time of the MOSFET (S1L) is sufficiently shorter than the resonance period Tr determined by the LC series circuit, the voltage amplitude of the energy transfer capacitor Cr1 is small, and the capacitor voltage Vcr0 immediately before the MOSFET (S1L) is turned on is It is considered that the value is substantially the same as the voltage Vcs1 of the smoothing capacitor Cs1. As a result, the peak current Icr (max) flowing through the MOSFET (S1L) can be approximately expressed by Expression 14.

  Here, Lr is the inductance value of the inductor Lr1, Vcs2 is the voltage of the smoothing capacitor Cs2, and Ton4 is the ON time of the MOSFET (S1L). Expression 14 shows that the peak current Icr (max) of the MOSFET (S1L) is proportional to the smoothing capacitor voltage Vcs2, and when the on-time is constant, as the smoothing capacitor voltage Vcs2 decreases, the peak current Icr ( max) decreases. When the peak current decreases, the amount of transmitted power decreases, so the voltage transition time of the VH-Vcom terminal voltage V3 as the output voltage increases, and the responsiveness as a DC / DC power converter decreases.

  By changing the ON time Ton4 of the MOSFET (S1L) according to the smoothing capacitor voltage Vcs2, the peak current Icr (max) can be made constant, and the reduction in the transmission power amount can be suppressed. Equation 15 shows the on time Ton4 of the MOSFET (S1L) for making the peak current of the MOSFET (S1L) constant.

Here, Vcs2 (ref) is a target voltage of the smoothing capacitor Cs2, and in the operation mode 5, Vcs2 (ref) is zero. As shown in Expression 15, the peak current Icr (max) of the MOSFET (S1L) can be made substantially constant by making the on-time Ton4 of the MOSFET (S1L) inversely proportional to the smoothing capacitor voltage Vcs2. The operation when the operation mode B is mode 5 is the same, and by making the on-time Ton4 of the MOSFET (S4L) inversely proportional to the smoothing capacitor voltage Vcs3, the peak current Icr (max) of the MOSFET (S4L) becomes substantially constant. It becomes possible to do.
By making the peak current Icr (max) of the MOSFETs (S1L, S4L) substantially constant, it is possible to suppress a decrease in the transmission power amount, and to shorten the time until the target voltage is reached.

  As described above, in the third embodiment, as a transient operation mode when the step-up ratio is lowered, the MOSFETs (S1L, S4L) are used in the LC series circuit during the period in which the MOSFETs (2H, 3H) are on. By turning on for a time that is half or less of the determined resonance period Tr, it is possible to transfer energy from the smoothing capacitor arranged on the high potential side to the smoothing capacitor arranged on the low potential side. Further, by changing the ON time Ton4 of the MOSFET (S1L, S4L) according to the difference between the voltage command value Vref of the smoothing capacitor and the smoothing capacitor voltage Vcs2 or Vcs3, the amount of transmission power per unit time can be increased. As a result, the responsiveness as a DC power converter can be improved.

Embodiment 4 FIG.
In the present embodiment, in a device having the same configuration and operation mode as the DC / DC power conversion device (FIG. 1) described in the above embodiment, the low-voltage side voltage (VL-Vcom voltage) varies greatly. A control method will be described.

As a first case, in the initial state, the voltage detection value Vcs1 between the VL and Vcom terminals is 150V, and the voltage command value Vref is 300V. The operation mode determination unit 100 determines that the boost command value is double based on the voltage command value Vref and the voltage detection value Vcs1, and the operation mode A output to the gate signal generation unit 1A is mode 3, and the gate signal generation unit 1B. The operation mode B output to is assumed to be mode 1.
Here, when the voltage detection value Vcs1 between the VL and Vcom terminals decreases from 150V to 100V, the operation mode determination unit 100 changes the boost command value from 2 times to 3 times, and is output to the gate signal generation unit 1A. The operation mode A maintains mode 3, and the operation mode B output to the gate signal generation means 1B shifts from mode 1 to mode 3 via mode 2 (or mode 4 or mode 4a). As a result, the voltage between the VH and Vcom terminals becomes 300 V, and the decrease in the high voltage side voltage (the voltage between the VH and Vcom terminals) due to the decrease in the low voltage side voltage (the voltage between the VL and Vcom terminals) can be reduced. Become. By preventing the high voltage side voltage from decreasing abnormally, it is possible to reduce the influence on the equipment connected to the high voltage side voltage.
As described above, the operation mode determination unit 100 determines the boost command value according to the voltage command value Vref and the voltage detection value Vcs1, so that even when the low-voltage side voltage (voltage between VL and Vcom) is extremely lowered. Therefore, it is possible to reduce fluctuations in the high-voltage side voltage (voltage between VH and Vcom) and maintain a desired value.

As a second case, in the initial state, the voltage detection value Vcs1 between the VL and Vcom terminals is 100V, and the voltage command value Vref is 300V. The operation mode determination unit 100 determines that the boost command value is tripled from the voltage command value Vref and the voltage detection value Vcs1, and outputs the operation mode A to the gate signal generation unit 1A and the gate signal generation unit 1B. Both operation modes B are mode 3.
Here, when the voltage detection value Vcs1 between the VL-Vcom terminals increases from 100V to 150V, the operation mode determination means 100 changes the boost command value from 3 times to 2 times and outputs it to the gate signal generation means 1A. The operation mode A maintains mode 3, and the operation mode B output to the gate signal generation means 1B shifts from mode 3 to mode 1 via mode 5. As a result, the voltage between the VH and Vcom terminals becomes 300 V, and the increase in the high voltage side voltage (voltage between the VH and Vcom terminals) due to the increase in the low voltage side voltage (voltage between the VL and Vcom terminals) can be reduced. . By preventing the high-voltage side voltage from rising abnormally, it is possible to reduce the withstand voltage of the components connected to the high-voltage side voltage.
As described above, the operation mode determination unit 100 determines the boost command value according to the voltage command value Vref and the voltage detection value Vcs1, so that even when the low-voltage side voltage (voltage between VL and Vcom) rises abnormally. The fluctuation of the high-voltage side voltage (voltage between VH and Vcom) can be reduced and maintained at a desired value.

Embodiment 5 FIG.
FIG. 13 is a diagram showing a circuit configuration of a DC / DC power conversion apparatus according to Embodiment 5 of the present invention. The circuit configuration of the DC / DC power conversion device in FIG. 13 is different from the circuit configuration of the DC / DC power conversion device in FIG. 1 between the intermediate terminal of the first bridge circuit and the intermediate terminal of the second bridge circuit. The connection mode of the LC series body is different.

  That is, an intermediate terminal serving as a connection point between the two MOSFETs (S1L, S1H) in the first bridge circuit A11 and an intermediate terminal serving as a connection point between the two MOSFETs (S2L, S2H) in the second bridge circuit A2. The LC series body LCr1 composed of the series body of the capacitor Cr1 and the inductor Lr1 is connected between the capacitor and the inductor Lr1. An intermediate terminal serving as a connection point between the two MOSFETs (S1L, S1H) in the first bridge circuit A11 and an intermediate terminal serving as a connection point between the two MOSFETs (S3L, S3H) in the second bridge circuit A3. The LC series body LCr2 composed of a series body of the capacitor Cr2 and the inductor Lr2 is connected between the capacitor and the inductor Lr2.

As shown in FIG. 13B, the control circuit 1 includes an operation mode determination unit 100 and a gate signal generation unit 1A. The operation mode determination unit 100 includes a voltage command value Vref, a smoothing capacitor, and the like. It has a function of determining the operation mode of the DC / DC power converter according to the voltage detection values Vcs1, Vcs2, and Vcs3 of Cs1, Cs2, and Cs3. Here, since the first bridge circuit and the second bridge circuit, whose intermediate terminals are connected via the LC serial body, are configured to have the same operation mode, the first bridge circuit A11 and the second bridge circuit are connected to each other. The second bridge circuits A2 and A3 are operated in the operation mode A.
Then, the gate signal generation unit 1A generates gate signals G1L, G1H, G2L, G2H, G3L, and G3H for controlling the MOSFETs (S1L, S1H, S2L, S2H, S3L, and S3H) according to the operation mode A. , Output to the gate drive circuits 21, 22, 23.

Next, the operation of the operation mode determination unit 100 will be described.
First, a case where the voltage V3 between the VH terminal and the Vcom terminal is boosted to a voltage three times V1 from a state where the voltage V3 between the VH terminal and the Vcom terminal is equal to the voltage V1 between the VL and Vcom terminals is described.
When the voltage command value Vref is equal to V1 and the step-up command value of the voltage V3 between the VH terminal and the Vcom terminal is 1 time, the operation mode A output to the gate signal generating means 1A is mode 1. When the voltage command value Vref is V1 × 3 and the boost command value is tripled, the operation mode A output to the gate signal generating unit 1A is mode 2, 4 or 4a, and the smoothing capacitor voltage Vcs2 is equal to or higher than the threshold voltage Vth1. Then, the operation mode A shifts to mode 3. Modes 1, 2, 4, 4a and 3 are as described in the above embodiment.
Next, the case where the voltage V3 between the VH and Vcom terminals as the output voltage is stepped down from the state of three times the voltage V1 between the VL and Vcom terminals to the same voltage as V1 will be described.
When the voltage command value Vref is V1 × 3 and the voltage command value V3 between the VH terminal and the Vcom terminal is triple, the operation mode A output to the gate signal generating unit 1A is mode 3. When the voltage command value Vref becomes V1 and the boost command value becomes 1 time, the operation mode A output to the gate signal generating means 1A becomes mode 5, and when the smoothing capacitor voltage Vcs2 becomes the threshold voltage Vth2 or less, the operation mode A Shifts to mode 1. Mode 5 is as described in the above embodiment.

  As described above, also in the circuit configuration of the DC / DC power converter shown in FIG. 13, the gate signal for generating the gate signal for on / off control of the high-voltage side switch element and the low-voltage side switch element is the same as in the above embodiment. Operation mode for determining the operation mode according to the generation means 1A, voltage detection means 31, 32, 33 for detecting the voltage of the smoothing capacitor, and the voltage command value Vref and the voltage detection values Vcs1, Vcs2, Vcs3 of the smoothing capacitor The gate signal generation unit 1A includes a determination unit 100. The gate signal generation unit 1A can perform a stable voltage transition operation with suppressed overcurrent by changing the gate signal pattern according to the operation mode determined by the operation mode determination unit 100. It becomes.

Embodiment 6 FIG.
Hereinafter, a DC / DC power converter according to Embodiment 6 of the present invention will be described.
14 is a diagram showing a circuit configuration of a DC / DC power converter according to Embodiment 6 of the present invention, and FIG. 15 is a diagram showing a controller of the DC / DC power converter of FIG. In the DC / DC power converter shown in FIG. 14, the voltage Vn between the VH terminal and the Vcom terminal is approximately n times, approximately (n−1) times, approximately approximately 1 time the voltage V1 between the V1 terminal and the Vcom terminal. Has a function of outputting a boosted voltage. Similarly, it has a function of outputting a voltage obtained by boosting the voltage Vk between the Vk terminal and the Vcom terminal to about k times, about (k-1) times, about 1 time the voltage V1 of the V1 terminal to the Vcom terminal. . However, k = 2,..., N, and n is an integer of 2 or more.

In FIG. 14, the main circuit configuration of the DC / DC power conversion apparatus includes a first smoothing capacitor Cs1, a second smoothing capacitor Cs2,..., Which function as a voltage source for smoothing input / output voltages and transferring energy. k smoothing capacitors Csk,..., nth smoothing capacitor Csn are connected in series. The reference voltage terminal Vcom is connected to the low voltage side terminal of the first smoothing capacitor Cs1, the first output terminal V1 is connected to the high voltage side terminal of the first smoothing capacitor Cs1, the second output terminal V2 is connected to the high voltage side terminal of the second smoothing capacitor Cs2. ..., the high voltage output terminal Vn (VH) is connected to the high voltage side terminal of the nth smoothing capacitor Csn.
A circuit A11 in which two MOSFETs (S11L, S11H) as a low voltage side switch and a high voltage side switch are connected in series, and a circuit A1m in which MOSFETs (S1mL, S1mH) as a low voltage side switch and a high voltage side switch are connected in series are The first bridge circuits A11,..., A1m are configured by being connected between both terminals of the first smoothing capacitor Cs1. However, m is an integer satisfying 1 ≦ m ≦ n−1.
Further, a circuit A2 in which MOSFETs (S2L, S2H) as a low-voltage side switch and a high-voltage side switch are connected in series is connected between both terminals of the second smoothing capacitor Cs2, and so on. A circuit An in which MOSFETs (SnL, SnH) are connected in series is connected between both terminals of the nth smoothing capacitor Csn, thereby constituting a second bridge circuit A2,.

  An intermediate terminal serving as a connection point between the two MOSFETs (S11L and S11H) in the first bridge circuit A11 and an intermediate terminal serving as a connection point between the two MOSFETs (S2L and S2H) in the second bridge circuit A2. An LC series body LCr1 that is configured by a series body of a capacitor Cr1 and an inductor Lr1 and functions as an energy transfer element is connected between them. Similarly, an intermediate terminal that is a connection point of two MOSFETs (S1mL, S1mH) in the first bridge circuit A1m and an intermediate point that is a connection point of two MOSFETs (SnL, SnH) in the second bridge circuit An. An LC series body LCrm, which is constituted by a series body of a capacitor Crm and an inductor Lrm and functions as an energy transfer element, is connected between the terminals. In this manner, a capacitor Cr and an inductor Lr are connected in series between the intermediate terminal of the two MOSFETs in the first bridge circuit and the intermediate terminal that is the connection point of the two MOSFETs in the second bridge circuit. The LC serial body which is comprised by this and functions as an energy transfer element is connected. Here, as in the configuration of FIG. 1, an LC series body composed of a capacitor and an inductor is connected in a one-to-one correspondence from the intermediate terminal in the first bridge circuit to the intermediate terminal in the second bridge circuit. (In this case, m = n), and as described in the fifth embodiment, from the intermediate terminal in one first bridge circuit to the intermediate terminals in a plurality of second bridge circuits. A configuration in which a plurality of LC series bodies including capacitors and inductors are connected is also possible. Therefore, m is an integer that satisfies 1 ≦ m ≦ n−1.

  Next, the peripheral circuit configuration of the DC / DC power conversion device of FIG. 14 will be described. The gate drive circuits 211 to 21m receive low-voltage gate signals (G11L to G1mL, G11H to G1mH) input from the control circuit 1 to the MOSFETs (S11L to S1mL, S11H to S1mH) in the first bridge circuit. It has a function of converting a potential level into a source potential reference signal and a drive function of supplying a voltage and a current necessary for on / off control of each MOSFET (S11L to S1mL, S11H to S1mH). Similarly, the gate drive circuits 22-2n receive the low-voltage gate signals (G2L-GnL, G2H-GnH) input from the control circuit 1 and the MOSFETs (S2L-SnL, S2H--) in the second bridge circuit. SnH) has a function of converting a potential level to a source potential reference signal and a drive function of supplying a voltage and a current necessary for on / off control of each MOSFET (S2L to SnL, S2H to SnH). Yes. The voltage sensors 31, 32, ..., 3n are connected to both terminals of the smoothing capacitors Cs1, Cs2, ..., Csn, respectively, and detect and control the smoothing capacitor voltages Vcs1, Vcs2, ..., Vcsn. Is transmitted to the circuit 1.

As shown in FIG. 15, the control circuit 1 includes an operation mode determination unit 100 and gate signal generation units 1A,. The operation mode determination means 100 determines the operation mode of the DC / DC power converter according to the voltage command value Vref and the detection voltages Vcs1, Vcs2,..., Vcsn of the smoothing capacitors Cs1, Cs2,. It has a function to judge. The first bridge circuit and the second bridge circuit, whose intermediate terminals are connected via the LC serial body, are configured to have the same operation mode. Specifically, the first bridge circuit A11 and the second bridge circuit A2 are operated in the operation mode A11,..., And the first bridge circuit A1m and the second bridge circuit An are operated in the operation mode A1m.
The gate signal generating means 1A,..., 1M are for controlling each MOSFET (S11L to S1mL, S11H to S1mH) of the first bridge circuit according to the operation mode determined by the operation mode determination means 100. Means for generating a gate signal and a gate signal for controlling each MOSFET (S2L to SnL, S2H to SnH) of the second bridge circuit are provided. Specifically, the gate signal generation unit 1A generates gate signals G11L, G11H, G2L, and G2H for controlling the MOSFETs (S11L, S11H, S2L, and S2H) according to the operation mode A11, and the gate drive circuit 211. , 22. Similarly, the gate signal generation unit 1M generates gate signals G1mL, G1mH, GnL, and GnH for controlling the MOSFETs (S1mL, S1mH, SnL, SnH) according to the operation mode A1m, and the gate drive circuits 21m, 2n Output to.

  The operation of the operation mode determination unit 100 is the same as that of the above embodiment, and the same mode as the mode described in the above embodiment can be applied to the operation mode.

As described above, in the present embodiment, the voltage Vn between the VH terminal and the Vcom terminal is about n times, about (n-1) times, about 1 time the voltage V1 between the V1 terminal and the Vcom terminal. The voltage can be boosted. Similarly, the voltage Vk between the Vk terminal and the Vcom terminal can be boosted to about k times, about (k-1) times,... About 1 times the voltage V1 of the V1 terminal to Vcom terminal.
In addition, the voltage Vn between the VH and Vcom terminals as the output voltage is stepped down from the state of about n times the voltage V1 between the V1 terminal and the Vcom terminal to a voltage of about (n-1) times, about 1 time. can do. Similarly, the voltage Vk between the Vk terminal and the Vcom terminal can be stepped down from about k times the voltage V1 at the V1 terminal to the Vcom terminal to about (k−1) times,.

Embodiment 7 FIG.
In the present embodiment, in the configuration of the DC / DC power converter shown in FIG. 1 or FIG. 14, it operates as a step-down circuit that steps down the voltage input between the VH terminal and the Vcom terminal to the voltage of the VL terminal and the Vcom terminal. The case where it does is demonstrated.
Here, the step-down operation of the DC / DC power converter of FIG. 1 will be described. When operating as a step-down circuit, the second bridge circuits A2 and A3 are driving inverters that send the voltages of the smoothing capacitors Cs2 and Cs3 to the low voltage side by the on / off operation of the MOSFETs (S2L, S2H, S3L, S3H). Operates as a circuit. The first bridge circuits A11 and A12 are used as a rectifier circuit that rectifies the current driven by the second bridge circuits A2 and A3 and shifts the energy to the low voltage side.

Next, energy transfer when the DC / DC power converter of FIG. 1 operates as a step-down circuit will be described.
When the MOSFETs (S1H, S2H) are turned on by the gate signals G1H, G2H, a part of energy stored in the smoothing capacitor Cs2 is transferred to the capacitor Cr1 through the following path.
Cs2->S2H->Lr1->Cr1-> S1H
Next, when the MOSFETs (S1L, S2L) are turned on by the gate signals G1L, G2L, a part of energy stored in the capacitor Cr1 is transferred to the smoothing capacitor Cs1 through the following path.
Cr1 → Lr1 → S2L → Cs1 → S1L
In addition, when the MOSFETs (S4H, S3H) are turned on by the gate signals G4H, G3H, a part of energy stored in the smoothing capacitors Cs2, Cs3 is transferred to the capacitor Cr2 through the following path.
Cs2->Cs3->S3H->Lr2->Cr2-> S4H
Next, when the MOSFETs (S4L, S3L) are turned on by the gate signals G4L, G3L, a part of energy stored in the capacitor Cr2 is transferred to the smoothing capacitors Cs1, Cs2 through the following path.
Cr2 → Lr2 → S3L → Cs2 → Cs1 → S4L

  As described above, in the configuration of the DC / DC power converter illustrated in FIG. 1 or FIG. 14, the voltage input between the VH terminal and the Vcom terminal can be stepped down to the voltage of the VL terminal and the Vcom terminal.

G1L to G4L, G1H to G4H gate signals,
G11L to G1mL, G11H to G1mH gate signal,
G2L to GnL, G2H to GnH gate signals,
S1L to S4L, S1H to S4H MOSFETs,
S11L-S1mL, S11H-S1mH MOSFET,
S2L to SnL, S2H to SnH MOSFETs,
Cs1, Cs2, Cs3,..., Csn smoothing capacitor,
Cr1, Cr2, ..., Crm Energy transfer capacitors,
Lr1, Lr2, ..., Lrm inductors,
LCr1, LCr2, ..., LCrm LC series body, VH high voltage terminal,
VM medium voltage terminal, VL low voltage terminal, Vcom reference voltage terminal, 1 control circuit,
1A, 1B,... 1M gate signal generating means, 100 operation mode determining means,
A11, A12,..., A1m first bridge circuit,
A2, A3,..., An second bridge circuit,
211, ..., 21m, 22, 23, ..., 2n gate drive circuit,
31, 32, 33, ..., 3n Voltage sensor.

Claims (19)

A plurality of smoothing capacitors connected in series from the low voltage side to the high voltage side;
A first bridge circuit in which a high-voltage side switch element and a low-voltage side switch element are connected in series between the positive and negative terminals of the low-voltage side smoothing capacitor;
A second bridge circuit in which a high-voltage side switching element and a low-voltage side switching element are connected in series between the positive and negative terminals of the high-voltage side smoothing capacitor;
Gate signal generating means for generating a gate signal for on / off control of the high-voltage side switch element and the low-voltage side switch element,
A first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the first bridge circuit; and a first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the second bridge circuit. An LC series body consisting of an energy transfer capacitor and an inductor is connected between the two intermediate terminals,
A part of the energy stored in the smoothing capacitor connected to one of the first or second bridge circuits by the on / off control of the high-voltage side switch element and the low-voltage side switch element, Transition to the LC serial body connected to the one bridge circuit through a bridge circuit, and further pass through the other bridge circuit of the first or second bridge circuit connected to the LC serial body from the LC serial body. In the DC / DC power converter for shifting to the smoothing capacitor connected to the other bridge circuit,
Voltage detecting means for detecting the voltage of the smoothing capacitor;
An operation mode determining means for determining an operation mode according to the voltage detection value and the voltage command value of the smoothing capacitor;
The DC / DC power conversion apparatus wherein the gate signal generation means changes a gate signal pattern based on the determined operation mode. A first smoothing capacitor having a reference voltage terminal as a low-voltage side terminal and a first voltage terminal as a high-voltage side terminal, and a k-th smoothing having a (k−1) th voltage terminal as a high-voltage side terminal and a k-th voltage terminal as a low-voltage side terminal. Capacitors (k = 2,..., N; n is an integer of 2 or more) are connected in series,
The first bridge circuit formed by connecting the high-voltage side switch element and the low-voltage side switch element in series between the positive and negative terminals of the first smoothing capacitor is connected in parallel (m is an integer, 1 ≦ m ≦ n−1). And
(N-1) second bridge circuits each having a high-voltage side switch element and a low-voltage side switch element connected in series between the positive and negative terminals of the k-th (k = 2,..., N) smoothing capacitor. Provided,
Gate signal generating means for generating a gate signal for on / off control of the high-voltage side switch element and the low-voltage side switch element,
A first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the first bridge circuit; and a first intermediate terminal serving as a connection point between the high voltage side switch element and the low voltage side switch element of the second bridge circuit. An LC series body consisting of an energy transfer capacitor and an inductor is connected between the two intermediate terminals,
A part of the energy stored in the smoothing capacitor connected to one of the first or second bridge circuits by the on / off control of the high-voltage side switch element and the low-voltage side switch element, Transition to the LC serial body connected to the one bridge circuit through a bridge circuit, and further pass through the other bridge circuit of the first or second bridge circuit connected to the LC serial body from the LC serial body. In the DC / DC power converter for shifting to the smoothing capacitor connected to the other bridge circuit,
Voltage detecting means for detecting the voltage of each of the smoothing capacitors;
An operation mode determination means for determining an operation mode according to the voltage detection value and the voltage command value of each of the smoothing capacitors,
The DC / DC power conversion apparatus wherein the gate signal generation means changes a gate signal pattern based on the determined operation mode. When the voltage between the reference voltage terminal and the first voltage terminal becomes low, the operation mode determination means determines an operation mode by increasing the boost command value based on the voltage command value and the voltage detection value. When a predetermined voltage is output between the reference voltage terminal and the nth voltage terminal and the voltage between the reference voltage terminal and the first voltage terminal becomes high, based on the voltage command value and the voltage detection value 3. The DC / DC power converter according to claim 2, wherein a step-up command value is lowered to determine an operation mode, and a predetermined voltage is output between the reference voltage terminal and the nth voltage terminal. When the difference between the voltage detection value of the smoothing capacitor and the voltage target value is large, the switching frequency of the high-voltage side switch element and the low-voltage side switch element is lowered. The DC / DC power converter according to any one of claims 1 to 3, wherein the frequency is increased. When the difference between the voltage detection value of the smoothing capacitor and the voltage target value is smaller than a predetermined value, the switching frequency of the high-voltage side switch element and the low-voltage side switch element is set to one half or more of the resonance frequency of the LC series body. The switching frequency of the high-voltage side switching element and the low-voltage side switching element is set to a half or less of the resonance frequency of the LC series body when greater than a predetermined value. The DC / DC power converter device described in 1. When the difference between the voltage detection value and the voltage target value of the smoothing capacitor connected to the second bridge circuit is smaller than a predetermined value, the second bridge circuit connected to the second bridge circuit via the LC serial body. 3. The DC / DC switch according to claim 1, wherein the high-voltage side switch element and the low-voltage side switch element in one bridge circuit are alternately turned on / off at a switching period Ts0 slightly larger than the resonance period Tr of the LC series body. DC power converter. When the voltage of the smoothing capacitor connected to the second bridge circuit is boosted and the difference between the voltage detection value of the smoothing capacitor and the voltage target value is larger than a predetermined value, the second bridge circuit The high-voltage side switch element and the low-voltage side switch element in the first bridge circuit connected to each other through the LC series body are alternately turned on and off at a switching cycle that is at least twice the resonance cycle Tr of the LC series body. The DC / DC power converter according to claim 1 or 2 to be controlled. 8. The on-time of the high-voltage side switch element and the low-voltage side switch element in the first bridge circuit is set to be slightly larger than one half of the resonance period Tr of the LC series body. DC / DC power converter. 8. The DC / DC power converter according to claim 7, wherein an on-time of the low-voltage side switch element in the first bridge circuit is set to a half or less of a resonance cycle Tr of the LC series body. 10. The DC / DC power converter according to claim 9, wherein the high-voltage side switch element in the first bridge circuit is turned on immediately after the low-voltage side switch element is turned off. 10. The DC / DC power converter according to claim 9, wherein an ON time of the low-voltage side switch element in the first bridge circuit is changed according to a difference between a voltage detection value of the smoothing capacitor and a voltage target value. When the difference between the voltage detection value of the smoothing capacitor and the voltage target value is large, the ON time of the low-voltage side switch element in the first bridge circuit is shortened, and the difference between the voltage detection value of the smoothing capacitor and the voltage target value is reduced. The DC / DC power converter according to claim 11, wherein when the voltage is small, the on-time of the low-voltage side switch element in the first bridge circuit is lengthened. When the voltage of the smoothing capacitor connected to the second bridge circuit is stepped down, and the difference between the voltage detection value of the smoothing capacitor and the voltage target value is larger than a predetermined value, the second bridge circuit The high-voltage side switch element and the low-voltage side switch element are alternately turned on and off at a switching cycle that is at least twice the resonance cycle Tr of the LC series body connected to the second bridge circuit. 2. The DC / DC power converter according to 2. The high-voltage side switch element in the second bridge circuit and the low-voltage side switch element in the first bridge circuit connected to the second bridge circuit via the LC serial body are simultaneously turned on. The DC / DC power converter device according to claim 13, wherein a time for performing is provided. After the high-voltage side switch element in the second bridge circuit is turned on, after a time more than one half of the resonance period Tr of the LC series body connected to the second bridge circuit has elapsed, The DC / DC power converter according to claim 14, wherein the low-voltage side switch element in the first bridge circuit is turned on. The DC / DC power converter according to claim 13 or 14, wherein an on-time of the low-voltage side switch element in the first bridge circuit is set to a half or less of a resonance period Tr of the LC series body. . The DC / DC power converter according to claim 16, wherein an on-time of the low-voltage side switch element in the first bridge circuit is changed according to a difference between a voltage detection value of the smoothing capacitor and a voltage target value. When the difference between the voltage detection value of the smoothing capacitor and the voltage target value is large, the ON time of the low-voltage side switch element in the first bridge circuit is shortened, and the difference between the voltage detection value of the smoothing capacitor and the voltage target value is reduced. The DC / DC power converter device according to claim 17, wherein the ON time of the low-voltage side switch element in the first bridge circuit is lengthened when the voltage is small. 19. The high-voltage side switch element and the low-voltage side switch element are power MOSFETs having a parasitic diode between a source and a drain, or semiconductor switching elements in which diodes are connected in antiparallel. The DC / DC power conversion device described.

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