JP2009038969A - Dc/dc converter, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized, light-weight, highly efficient and inexpensive DC/DC converter. <P>SOLUTION: The DC/DC converter includes a DC power source input part, first and second capacitors connected in series and an output part connected to the first and second capacitors connected in series. The DC/DC converter further includes the power source of the DC power source input part, a switching means for switching the connection configuration of the first and second capacitors with a plurality of incorporated switches, and a switching control means for performing on/off control over each switch in the switching means corresponding to an operation mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a DC / DC converter, and more particularly to a DC / DC converter and a program capable of boosting a DC voltage at a predetermined magnification.

  A DC / DC converter that converts a DC (direct current) voltage into a voltage is used in various devices. For example, a power generation device using a solar cell, a wind power generation device, a fuel cell system, a hybrid vehicle, and the like. In particular, when a DC / DC converter is applied to a technical area where there are strong spatial and weight restrictions such as automobiles, the demand for miniaturization and weight reduction of the DC / DC converter becomes very strong.

FIG. 7 is a circuit configuration diagram of a step-up DC / DC converter that is well known conventionally.
In the circuit shown in FIG. 7, the switches SW are alternately turned on / off. Magnetic energy is stored in the inductor L when the switch SW is turned on, and the magnetic energy stored in the inductor L when the switch SW is turned off is supplied to the output side as electric power. At this time, since the output from the inductor L is added to the power supply voltage, the boosted voltage as a whole is obtained at the output section.

  However, in such a boosting method, in order to perform sufficient boosting while preventing magnetic saturation of the inductor L, the inductor L using a heavy and large core is necessary. This becomes an impediment to reducing the size and weight of the entire DC / DC converter.

  In view of this, a charge pump circuit that uses a capacitor called a flying capacitor has been proposed as a voltage conversion method for devices that are strongly required to be reduced in size and weight, such as mobile phones (see, for example, Patent Document 1). Conventionally, a stabilized power supply circuit using a switched capacitance method has also been proposed (see, for example, Patent Document 2).

  In these systems, a flying capacitor is generally used for power transfer. FIG. 8 is a diagram showing a conventional example of a DC / DC converter using a flange capacitor and its operating state, which are shown in FIGS. 8A and 8B by alternately switching the switches SW11 and SW12. The state is repeated alternately.

  That is, in the state shown in FIG. 8A, SW11 → ON, SW14 → ON, SW12 → OFF, and SW13 → OFF. In the state shown in FIG. 8B, SW11 → OFF, SW14 → OFF, SW12 → ON, SW13 → ON.

  In the state shown in FIG. 8A, a current I1 flows through a route of power source E → SW11 → flying capacitor C11 → SW14 → power source E for a predetermined time, and electric charge is accumulated in the flying capacitor C11. At this time, since the positive charge is accumulated in the positive electrode of the output capacitor C12 at the previous operation timing, this charge is discharged to the output side.

  On the other hand, in the state shown in FIG. 8B, a current I2 flows through a route on the power source E → SW13 → flying capacitor C11 → SW12 → output side for a predetermined time. At this time, the electric charge accumulated in the flying capacitor C11 at the previous operation timing is discharged to the output side, and this amount is added to the power supply voltage E so that a boosted voltage can be taken out on the output side (approximately 2 of the power supply voltage). Times). At the same time, the output capacitor C12 is charged by the current Ic, and thereafter, the state shown in FIG.

  In the DC / DC converter having the configuration shown in FIG. 8, a voltage twice the power supply voltage is required as the withstand voltage characteristic of the output capacitor C12. When an output that is an integral multiple of the desired power supply voltage is obtained, the withstand voltage of the capacitor C12 increases by 2, 3, 4, and so on as the number of flying capacitors increases. The high withstand voltage output capacitor is required to have a large capacity so that current can be supplied while the switch SW12 is OFF. As a result, the output capacitor becomes large, leading to an increase in the size and cost of the DC / DC converter. .

  Further, in the configuration shown in FIG. 8, the current from the power source and the flying capacitor C11 and the discharge current from the output capacitor C12 are alternately supplied to the output side. (Caused by using a high voltage capacitor to increase the amount of heat generated).

Furthermore, since many switches are provided in the method shown in FIG. 8, it is necessary to perform highly accurate on / off control using a control device or the like.
JP 2003-61339 A JP 2003-111388 A

  The present invention has been made to solve the above-described problems, and the present invention provides a DC / DC converter and a program capable of realizing a reduction in size, weight, efficiency, and price. With the goal.

The present invention has been made to solve the above problems, and a DC / DC converter according to the present invention is connected to a DC power input unit, a plurality of switches, a plurality of capacitors, and the plurality of capacitors. An output unit, and selectively performing the plurality of capacitors by performing on / off control of the plurality of switches according to an operation mode, thereby performing any one of operations of boosting, conduction, and regeneration. And
With such a configuration, a plurality of switches (for example, the switches SW1 to SW4 shown in FIG. 1) are on / off controlled, and a plurality of capacitors (for example, the capacitors C1 and C2 shown in FIG. 1) are controlled by the power supply voltage of the DC power input unit. ) Are individually charged, and a boosted voltage is obtained at the output section connected to the plurality of capacitors (boosting). In the regeneration mode, a plurality of switches (for example, the switches SW1 to SW4 shown in FIG. 1) are turned on / off, and the regenerative power stored in the plurality of capacitors is returned to the power supply side (regeneration). Also, a plurality of switches (for example, the switches SW1 to SW4 shown in FIG. 1) are turned on / off, and the voltage of the DC power supply input unit is directly output to the output unit (conduction).
As a result, the same circuit can be used for any of the booster circuit, the conduction circuit, and the regenerative circuit by simply changing the switch operation.

The DC / DC converter according to the present invention further includes switching means for performing on / off control of the plurality of switches based on the instructed operation mode and the voltages of the DC power supply input unit and the output unit. Features.
With such a configuration, a plurality of switches (for example, the switches SW1 to SW4 shown in FIG. 1) are controlled to be turned on / off in the designated operation mode, and the voltage of the DC power supply input unit is compared with the voltage of the output unit. , ON / OFF control of a plurality of switches.
Thus, for example, when the instructed mode is the boost mode, when the load is a motor and the voltage of the output unit suddenly rises due to the regenerative braking operation, a plurality of such functions are detected and the regenerative function is activated. These switches (for example, the switches SW1 to SW4 shown in FIG. 1) can be on / off controlled.

In addition, a DC / DC converter according to the present invention includes a DC power input unit, first and second capacitors connected in series, and an output unit connected to the first and second capacitors. A first switch that connects a positive side of the DC power input unit to a positive side of the first capacitor and a positive side of the output unit; and a positive side of the DC power input unit. A second switch connected to a negative electrode side of the first capacitor and a positive electrode side of the second capacitor, and a negative electrode side of the power input unit, the negative electrode side of the first capacitor and the second capacitor A third switch connected to the positive electrode side of the power supply, and a fourth switch connecting the negative electrode side of the power input unit to the negative electrode side of the second capacitor and the negative electrode side of the output unit. Depending on the first to the first Each of the switches is turned on or off, by selectively function the first and second capacitors, the boosting, conduction, and performs any of the operations of the regenerative.
With such a configuration, the first to fourth switches (for example, the switches SW1 to SW4 shown in FIG. 1) are turned on / off, and the first capacitor (for example, the capacitor C1 shown in FIG. 1) and the second capacitor are controlled. The capacitors (for example, the capacitor C2 shown in FIG. 1) are alternately charged with the power supply voltage of the DC power supply input section, and the boosted voltage is output from the output section (boost). In addition, the first to fourth switches are turned on / off, and the regenerative power stored in the first capacitor and the second capacitor is alternately returned to the power supply side (regeneration). Further, the first switch and the fourth switch are turned on, the second switch and the third switch are turned off, and the power source of the DC power source input unit is directly conducted to the output unit (conduction).
As a result, the same circuit can be used for any of the booster circuit, the conduction circuit, and the regenerative circuit by simply changing the operation of the switch.

The DC / DC converter according to the present invention further includes switching means for performing on / off control of the first to fourth switches based on the instructed operation mode and the voltages of the DC power supply input unit and the output unit. Furthermore, it is characterized by having.
With such a configuration, the first to fourth switches (for example, the switches SW1 to SW4 shown in FIG. 1) are turned on / off in the designated operation mode, and the voltage of the DC power input unit and the voltage of the output unit are controlled. , And a plurality of switches are on / off controlled.
Thus, for example, when the instructed mode is the boost mode, when the load is a motor (including an inverter of an AC motor and a brushless motor) and the voltage of the output unit suddenly increases due to the regenerative braking operation, The first to fourth switches can be on / off controlled to detect and activate the regeneration function.

The DC / DC converter of the present invention is characterized in that the first to fourth switches are transistor switches with flywheel diodes.
With such a configuration, when on / off control of the first to fourth switches (for example, the switches SW1 to SW4 shown in FIG. 1) is performed for each of the operation modes of boosting, regeneration, and conduction, When current flows only in one direction and the current direction is the forward direction of the flywheel diode, the on / off control of the transistor switch is not performed and the switching action (rectification action) of the flywheel diode is used. To do.
Thereby, the number of switches to be turned on / off can be reduced, and the switching control can be simplified.

In the DC / DC converter of the present invention, the transistor switch is an IGBT.
Thereby, high speed, large current, and high voltage switching control is possible.

The DC / DC converter of the present invention is characterized in that the first and second capacitors are film capacitors.
As a result, the charge storage efficiency of the film capacitor (the electrolytic capacitor is about 80% and the film capacitor is about 98%), the advantages of small size, light weight, and low price can be used, and the efficiency of the DC / DC converter can be increased. Miniaturization and low price can be realized.

The DC / DC converter according to the present invention is characterized in that the first and second capacitors are ceramic capacitors.
As a result, the storage efficiency can be further reduced while maintaining the same level as when a film capacitor is used.

In the DC / DC converter of the present invention, in the step-up mode, the first and fourth switches are always turned off, and the second and third switches are alternately turned on / off. When the switch is turned on, the flywheel diodes of the second switch and the fourth switch are turned on; when the third switch is turned on, the flywheel diode of the first switch and the third switch are turned on; In the conduction mode, the first to fourth switches are always off, the flywheel diodes of the first and fourth switches are conducted, and in the regeneration mode, the second and third switches are always off, By alternately turning on / off the first and fourth switches, the first switch and the third switch when the first switch is turned on. To conduct the switch of the flywheel diode, and wherein the to conduct the second flywheel diode and the fourth switch of the switch during on of the fourth switch.
With such a configuration, in the boost mode, the first and fourth switches (for example, the switches SW1 and SW4 shown in FIG. 4) are always turned off, and the second and third switches (for example, the switch SW2 shown in FIG. 4). , SW3) are alternately turned on / off, and when the second switch is turned on, the flywheel diodes of the second switch and the fourth switch (for example, the flywheel diode D4 shown in FIG. 4) are made conductive. 2 capacitors (for example, the capacitor C2 shown in FIG. 4) are charged. Further, when the third switch is turned on, the flywheel diode of the first switch (for example, the flywheel diode D1 shown in FIG. 4) and the third switch are made conductive, and the first capacitor (for example, the capacitor shown in FIG. 4) C1) is charged.
In the conduction mode, the first to fourth switches (for example, SW1 to SW4 shown in FIG. 5) are always turned off, and the flywheel diodes of the first and fourth switches (for example, the flywheel diode shown in FIG. 5). D1 and D4) are turned on, and the voltage of the DC power supply input unit is output to the output unit as it is.
Further, in the regeneration mode, the second switch (for example, SW2 shown in FIG. 6) and the third switch (for example, SW3 shown in FIG. 6) are always turned off, and the first switch (for example, SW1 shown in FIG. 6). ) And the fourth switch (eg, SW4 shown in FIG. 6) are alternately turned on / off, so that when the first switch is turned on, the flywheel diodes (eg, FIG. 6 is turned on, and the regenerative power stored in the first capacitor (for example, the capacitor C1 shown in FIG. 6) is returned to the DC power supply side. Further, when the fourth switch is turned on, the flywheel diode (for example, flywheel diode D2 shown in FIG. 6) of the second switch and the fourth switch are made conductive, and the second capacitor (for example, shown in FIG. 6). The regenerative power stored in the capacitor C2) is returned to the DC power source side.
As a result, the same circuit can be used for any of the booster circuit, the conduction circuit, and the regenerative circuit by simply changing the operation of the switch.

The DC / DC converter according to the present invention further has a regeneration prevention mode in which the first and fourth switches are always turned off to prevent the regeneration operation.
Thereby, when it is desired to prevent unnecessary regeneration, the regeneration prevention mode can be realized.

  The computer program according to the present invention controls the plurality of switches in a DC / DC converter having a DC power input unit, a plurality of switches, a plurality of capacitors, and an output unit connected to the plurality of capacitors. A program for causing a computer to execute the process of controlling on / off of the plurality of switches according to any of the operation modes of step-up, conduction, and regeneration, and selectively causing the plurality of capacitors to function It is made to perform.

  Further, the computer program according to the present invention is based on the instructed operation mode and the voltage of the output unit detected by the DC power input unit and the output voltage detector detected by the input voltage detector. It is characterized by causing a computer to execute a switch on / off control process.

  The computer program of the present invention includes a DC power input unit, a first switch that connects a positive side of the DC power input unit to a positive side of a first capacitor and a positive side of the output unit, and the DC power source. A second switch for connecting a positive side of the input unit to a negative side of the first capacitor and a positive side of the second capacitor; and a negative side of the DC power input unit to a negative side of the first capacitor. And a third switch connected to the positive side of the second capacitor, and a fourth switch connecting the negative side of the DC power input part to the negative side of the second capacitor and the negative side of the output part A program for causing a computer to control the first to fourth switches, wherein the first to fourth switches according to one of the operation modes of step-up, conduction, and regeneration. Controls to fourth on / off switch, characterized in that to execute a process for selectively function the plurality of capacitors to the computer.

  Further, the computer program of the present invention is based on the instructed operation mode and the voltage of the output unit detected by the DC power supply human power unit and the output voltage detection unit detected by the input voltage detection unit. It is characterized by causing a computer to execute a switch on / off control process.

  The DC / DC converter of the present invention can be used for any of a booster circuit, a conduction circuit, and a regenerative circuit by simply changing the switching operation in the same circuit. In addition, since an inductor for accumulating magnetic energy is not required as in the conventional example, the DC / DC converter can be reduced in size, weight, and cost. In addition, two capacitors having a breakdown voltage comparable to the power supply voltage can be used, and a high breakdown voltage output capacitor is not required.

  Further, the number of switches to be switched is always two, and switching control is easy. Regardless of the size of the load, boosting (including 1-fold boosting) and regeneration can be performed with the same switching duty ratio over time.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an example of the basic configuration of a DC / DC converter according to the present invention. The DC / DC converter of the present invention has a double boosting (outputs a voltage that is approximately twice the power supply voltage of the DC power supply input unit), a single boosting (outputs the power supply voltage as it is), a step-down (power regeneration). ) Has a function.

  The DC / DC converter shown in FIG. 1 includes a switching unit 1 including a power source E, a first switch SW1, a second switch SW2, a third switch SW3, and a fourth switch SW4, a first capacitor C1, 2 capacitors C2 and an output section. The first capacitor C1 and the second capacitor C2 are connected in series, and it is desirable to use a film capacitor or the like.

  In addition, the control circuit unit 2 has a function of controlling on / off of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 in the switching unit 1. The input voltage detection unit 3 in the control circuit unit 2 has a function of detecting an input voltage supplied from the power supply voltage E, and the output voltage detection unit 4 has a function of detecting an output voltage of the output unit. . The voltage comparison unit 5 has a function of comparing the power supply voltage detected by the input voltage detection unit 3 with the output voltage detected by the output voltage detection unit 4.

  Further, the regenerative load detection unit 6 is based on the comparison result of the power supply voltage and the output voltage in the voltage comparison unit 5, for example, in the case of “output voltage> 2 × power supply voltage” during the double boosting operation, It is determined that a load that is generating electric power, such as a motor during regenerative braking, is connected. The switching control unit 10 is means for performing on / off control of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4. The switching control unit 10 also has a function of controlling the on / off time (duty ratio) of the switches SW1 to SW4 in the switching unit 1.

  Note that the voltage comparison unit 5 and the switching control unit 10 in the control circuit unit 2 may be realized by dedicated hardware, and the control circuit unit 2 includes a computer such as a memory and a CP U. A system may be provided, and a program (not shown) for realizing the functions of the voltage comparison unit 5 and the switching control unit 10 may be loaded into a memory and executed to implement the functions.

  In the DC / DC converter shown in FIG. 1, by performing on / off control of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4, Three types of operation modes, a 1 × step-up mode and a step-down (power regeneration) mode, can be realized arbitrarily. The selection of the operation mode is determined by the application or the like. When the present invention is employed in an electric vehicle, for example, the double boost mode is used during high-speed driving, and the single boost mode is used during low-speed driving.

  First, the most basic double boost mode will be described. The double boost mode is a mode in which the output voltage is approximately twice the voltage of the power supply voltage E (approximately 2E voltage).

  2 and 3 are diagrams for explaining the double boosting mode. In the double boost mode, the switch circuit shown in FIG. 2A is equivalent to FIG. That is, the switch SW1 and the switch SW4 in the circuit shown in FIG. 2A can be replaced with the diode D1 and the diode D4, respectively. The reason for this will be described with reference to FIG.

  FIG. 3 is a diagram for explaining the operation in the double boost mode. In FIG. 3, as shown in FIG. 3A, when SW3 is turned on and switch SW2 is turned off, current I1 flows through the route of power supply E → diode D1 → capacitor C1 → switch SW3 → power supply E. . At this time, the capacitor C1 is charged according to the power supply voltage E.

Next, as shown in FIG. 3B, when the switch SW2 is turned on and the switch SW3 is turned off, a current I3 flows through a route of power supply E → switch SW2 → capacitor C2 → diode D4 → power supply E. At this time, the capacitor C2 is charged to the power supply voltage E. This switching control is repeated alternately. Thereby, each of the capacitor C1 and the capacitor C2 is charged to the voltage E, and the capacitor C1 and the capacitor C2 are connected in series, so that a voltage output of about 2E can be obtained at the output unit. Then, a discharge current I2 is output from C1 and C2 to the output side.

  In the double boost mode shown in FIG. 3, the current flows through a branch (branch circuit) provided with a diode D1 (corresponding to the switch SW1 in FIG. 2A) and a diode D4 (corresponding to the switch SW4 in FIG. 2A). Since the direction of the current is only a fixed direction, it is only necessary that the switches SW1 and SW4 are normally closed and only the diode switching action (rectification action) can be realized.

  Thus, in the DC / DC converter of the present invention, when the diode switching action (the action of flowing the current in one direction) can be used, the diode is actively used instead of the switch, and the number of switches to be controlled is controlled. Devised to reduce. Specific examples will be described in the Examples section.

  Next, an embodiment of the DC / DC converter of the present invention will be described. FIG. 4A is a diagram showing an embodiment of the DC / DC converter according to the present invention, and is a diagram for explaining the operation in the double boost mode. FIG. 4B is a diagram illustrating the operation timing of the switches SW1 and SW2 and the charging current waveform to the capacitors C1 and C2.

  The DC / DC converter shown in FIG. 4 includes a power supply E, a smoothing capacitor (electrolytic capacitor) C4 on the input side, an IGBT unit 1 and an IGBT unit 2 composed of two (a pair) IGBT elements, an inductor L, a capacitor C1, C2 and C3. The capacitors C1, C2, and C3 are film capacitors in this embodiment.

  Compared with the operation explanatory diagram of double boosting in FIG. 3, the flywheel diode D1 of the IGBT element (SW1) on the upper side of the IGBT section 1 in FIG. 4 corresponds to the diode D1 in FIG. The lower IGBT element corresponds to the switch SW2. Further, the IGBT element on the upper side of the IGBT section 2 in FIG. 4 corresponds to SW3 in FIG. 3, and the flywheel diode D4 of the IGBT element (SW4) on the lower side in the IGBT section 2 corresponds to diode D4 in FIG.

  In the double boosting mode of the DC / DC converter shown in FIG. 4, the switch SW1 and the switch SW4 are always off, and as shown in FIG. 4B, the switch SW2 of the IGBT unit 1 and the switch of the IGBT T unit 2 A gate voltage is applied from the switching control unit 10 so as to alternately turn on / off the SW3. In the double boost mode, the switch SW1 of the IGBT unit 1 and the switch SW4 of the IGBT unit 2 function only the flywheel diodes D1 and D4.

  In FIG. 4, when the switch SW2 is on and the switch SW3 is off, the current I1 flows through the route of the power source E → the switch SW2, the inductor L, the capacitor C2, the flywheel diode D4, and the power source E. At this time, the capacitor C2 is charged by the power source E. FIG. 4B shows a waveform of I1 (C2 charging current). Actually, at this time, the current I1 not only charges the capacitor C2, but also a discharge current flows to the load R.

  That is, since the capacitors C1 and C2 are simultaneously connected to the capacitor C3 and the load R, the capacitor C3 is charged and a current I3 flows through the load R as an output current.

  On the other hand, when the switch SW2 is off and the switch SW3 is on, the current I2 flows through the route of the power source E → the flywheel diode D1 → the capacitor C1 → the inductor L → the switch SW3 → the power source E. At this time, the capacitor C1 is charged by the power supply voltage E. At the same time, the capacitors C1 and C2 are also connected to the output side, so that the capacitor C3 is charged and a current I3 flows through the load R as an output current.

  The inductor L is for suppressing the inrush current to the IGBT units 1 and 2 and the capacitors C1 and C2 when the switch is ON, and has a capacity of 1/10 or less of the inductor L of the conventional circuit shown in FIG. Is sufficient (for example, 4 μH to 10 μH at a switching frequency of 10 kHz, although depending on time sensitivity). Therefore, the purpose of use is different from that of the conventional large-sized inductor L shown in FIG. 7, which has been used to store magnetic energy. That is, the inductor L is not an essential component of the present invention.

  The capacitor C3 is provided to smooth the ripple of the output voltage, and is not an essential component of the present invention. Further, the input side 100 μF electrolytic capacitor C4 is provided to lower the impedance of the power source (for example, when the power source is separated from the circuit unit and the power source wiring becomes longer, the power source impedance increases, and the control malfunctions. The electrolytic capacitor C4 prevents this). Therefore, the electrolytic capacitor C4 is not an essential component of the present invention.

  Although the switches SW2 and SW3 are alternately turned on / off (the ideal duty ratio is 50%), the actual switch is not ideal, and a finite transient time is required for ON / OFF. The duty is about 45%. This duty ratio may be set so that the circuit performs the boosting operation most efficiently in accordance with the characteristics of the switches SW1, SW2, capacitors C1, C2, and the like.

  In the DC / DC converter according to the present invention, it is possible to perform double boosting with a slight voltage drop while fixing the duty ratio regardless of the load impedance / resistance value. Can also be controlled by the control circuit unit 2 shown in FIG.

  That is, the voltage E of the DC power supply input unit is detected by the input voltage detection unit 3, the voltage of the output unit is detected by the output voltage detection unit 4, the input voltage value detected by the input voltage detection unit 3, and the output voltage detection The voltage comparison unit 5 compares the output voltage value detected by the unit 4, and based on this comparison value, the switching control unit 10 performs duty control of the on / off times of the switches SW2 and SW3. For example, if the duty ratio at which the circuit performs the boosting operation most efficiently is 45% according to the characteristics of the switches SW1, SW2, capacitors C1, C2, etc., control is performed so as to approach this value.

  In the DC / DC converter of the present invention, since the output voltage is divided by two capacitors, it is not necessary to use a high withstand voltage capacitor on the output side, and it can be sufficiently realized by a light and inexpensive film capacitor. As a result, the amount of heat generated in the capacitor is reduced, and the efficiency of power conversion can be increased.

  The DC / DC converter of the present invention can function not only as a booster circuit but also as a normal rectifier circuit (single booster circuit). FIG. 5 shows an example in which the switch SW1, the switch SW2, the switch SW3, and the switch SW4 are always turned off to operate as a normal rectifier circuit (single boosting mode).

  When the switching of the switches SW1 to SW4 is stopped, the current I1 flows from the power source E to the load R as it is through the flywheel diode D1 of the IGBT unit 1 and the flywheel diode D4 of the IGBT unit 2. That is, the current I1 flows through the route of the power supply E → the flywheel diode D1 of the IBGT1 → the load R → the flywheel diode D4 of the IBGT2 → the power supply E. At this time, the capacitors C1 and C2 do not particularly contribute to boosting, and the output voltage is about one time the input voltage.

  The DC / DC converter of the present invention has a step-down (power regeneration) function (step-down mode). For example, when a motor or the like is used as the load on the output side and the rotation speed is decelerated (regenerative braking operation, etc.) and the voltage on the output (load) side increases, the output (load) side is input (power supply) The battery can be charged to a power source such as a battery on the input side (returning energy to the input side) so that the voltage on the output (load) side is stepped down until it becomes twice the voltage on the input side. Is not necessarily required to be twice the voltage on the input side on the load side, and may be regenerated to an intermediate value as appropriate depending on the load characteristics, such as 2.1 times or 2.5 times.

  FIG. 6 is a diagram for explaining the power regeneration operation. For example, this operation mode can be used when “output voltage> 2 × power supply voltage” in the double boosting operation. In this power regeneration mode, the gate voltage is set so that the switch SW2 of the IGBT unit 1 and the switch SW3 of the IGBT unit 2 are always OFF, and the switch SW1 of the IGBT unit 1 and the switch SW4 of the IGBT unit 2 are alternately turned on / off. Is applied (see FIG. 6B).

  When the switch SW1 is on and the switch SW4 is off, the current I1 flows through the route of the capacitor C1, the switch SW1, the power source E, the flywheel diode D3, the inductor L, and the capacitor C1. At this time, the power source E is charged by the capacitor C1.

  When the switch SW1 is off and the switch SW4 is on, a current I2 flows through the route of the capacitor C2, the inductor L, the flywheel diode D2, the power source E, the switch SW4, and the capacitor C2. At this time, the power source E is charged by the capacitor C2.

  In this way, by alternately discharging the capacitors C1 and C2, it is possible to transfer surplus power to the input side until the voltage becomes approximately ½ times the voltage on the output side. Even if the output voltage rises and the power to return in the reverse direction (= output → input) increases, the current waveform increases, and the operation can always be performed with the same duty ratio.

FIG. 9 is a diagram showing a waveform measurement example of each part in an actual circuit using the present invention, and shows waveforms at an input voltage of 199.8 V, an output voltage of 393.3 V, and an output of 5.75 kW. This waveform is for the double boost mode.

  In FIG. 9, symbol a1 is a gate waveform for turning on / off the switch SW2, a2 is a current waveform of the switch SW2, a3 is a gate waveform for turning on / off the switch SW3, a4 is a current waveform of the switch SW3, a5 is a current waveform on the negative side of the capacitor C2, a6 is a current waveform on the negative side of the capacitor C1, a7 is a current waveform flowing from the power source E and the capacitor C4 to the IGBT unit 1, and a8 is a current waveform flowing to the capacitor C3 and the load side. Is shown.

  As described above, in the DC / DC converter according to the present invention, if the switch SW1, the switch SW2, the switch SW3, the switch SW4, the IGBT unit 1, and the IGBT unit 2 are formed of the same element, FIG. Each operation described in FIG. 6 can be realized by the same circuit. As in the present invention, SW1 and SW2 are formed by one IGBT portion 1, and SW3 and SW4 are formed by one IGBT portion 2, thereby realizing circuit miniaturization and wiring simplification.

In addition, since the output voltage is divided by two capacitors, a high voltage capacitor is not required, and a low-cost one can be used. When capacitors are used in series in a normal circuit, a bleeder resistor for preventing voltage bias is required. However, in the present invention, this is also unnecessary, and the power conversion efficiency is improved accordingly.
Further, the number of switches to be switched is always 2 or less, and switching control is easy. In addition, boosting (including 1-fold boosting) and regeneration are possible with the same switching duty ratio over time, regardless of the size of the load. Further, in the blocking mode in which the same circuit is switched, it can be used for any of a booster circuit, a conduction circuit, and a regenerative circuit by simply changing the switch SW1SW2.
In the embodiment, the first and second capacitors are film capacitors. However, other capacitors such as ceramic capacitors may be used. When a ceramic capacitor is used, the storage efficiency can be further reduced while maintaining the same level as the film capacitor. Further, according to the present invention, the regeneration prevention mode can be realized when it is desired to prevent unnecessary regeneration. In this regeneration prevention mode, the switches SW1 and SW4 are always turned off and the respective flywheel diodes are allowed to function.

  Although the embodiment of the present invention has been described above, the DC / DC converter of the present invention is not limited to the above illustrated example, and various modifications can be made without departing from the gist of the present invention. Of course. For example, the principle of the present invention can be applied to a booster circuit of three times or more.

  According to the present invention, the DC / DC converter can be reduced in size, weight, and cost, and the power conversion can be realized with high efficiency. In addition, input to the inverter that raises the generated voltage to the grid voltage level (FC (fuel cell), wind power generation, etc.), boosting the motor drive voltage of the automatic hybrid system, and a voltage higher than the general battery voltage are required. It can be used for a system using a load, a moving body such as an automobile, and a home electric appliance having a small installation place.

The figure which shows the example of a fundamental structure of the DC / DC converter by this invention. FIG. 1 is a diagram for explaining the principle of double boosting. FIG. 2 for explaining the principle of double boosting. The figure for demonstrating the operation | movement at the time of 2 times pressure | voltage rise mode. The figure which shows the example in the case of making it operate | move as a normal rectifier circuit. The figure for demonstrating power supply regeneration operation | movement. The figure which shows the example of the conventional pressure | voltage rise type DC / DC converter. The figure which shows the example of the DC / DC converter using the conventional flying capacitor. The figure which shows the example of a measurement waveform of each part in an actual circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switching part 2 Control circuit part 3 Input voltage detection part 4 Output voltage detection part 5 Voltage comparison part 6 Regenerative load detection part 10 Switching control part C1 Capacitor C2 Capacitor C3 Capacitor D1 Diode D2 Diode D3 Diode D4 Diode SW1 Switch SW2 Switch SW3 Switch SW4 switch

Claims (2)

A DC / DC converter comprising a DC power input unit, first and second capacitors connected in series, and an output unit connected to the first and second capacitors,
A first switch for connecting a positive side of the DC power input unit to a positive side of the first capacitor and a positive side of the output unit;
A second switch for connecting a positive side of the DC power input unit to a negative side of the first capacitor and a positive side of the second capacitor;
A third switch connecting the negative side of the power input unit to the negative side of the first capacitor and the positive side of the second capacitor;
A fourth switch connecting the negative side of the power input unit to the negative side of the second capacitor and the negative side of the output unit;
An inductor connected between a connection point of the second switch and the third switch, and a connection point of a negative electrode of the first capacitor and a positive electrode of the second capacitor;
Depending on the operation mode, each of the first to fourth switches is turned on or off, and the first and second capacitors are selectively functioned to perform any operation of boosting, conducting or regenerating. A DC / DC converter characterized by the above. A DC / DC converter comprising a DC power input unit, first and second capacitors connected in series, and an output unit connected to the first and second capacitors,
A first switch for connecting a positive side of the DC power input unit to a positive side of the first capacitor and a positive side of the output unit;
A second switch for connecting a positive side of the DC power input unit to a negative side of the first capacitor and a positive side of the second capacitor;
A third switch connecting the negative side of the power input unit to the negative side of the first capacitor and the positive side of the second capacitor;
A fourth switch connecting the negative side of the power input unit to the negative side of the second capacitor and the negative side of the output unit;
DC / having a connection point between the second switch and the third switch, and an inductor connected between a connection point between the negative electrode of the first capacitor and the positive electrode of the second capacitor. A program for causing a computer to control the plurality of switches in the DC converter,
A program for controlling the on / off of the plurality of switches according to any one of the operation modes of step-up, conduction, and regeneration, and causing a computer to execute processing for selectively functioning the plurality of capacitors.

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