JP2011151911A - Voltage converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage converter 1 including two switching elements 2, 3, wherein when a dead time Td is inserted in a switching signal and as a result, a difference is produced between a command voltage S and an output voltage V<SB>0</SB>and this difference is to be compensated, feedforward control free from a delay time is carried out in place of conventional feedback control. <P>SOLUTION: A control part 9 determines whether voltage is being increased or decreased based on the direction of current passing through the lower arm 6 or the upper arm 7 in the voltage converter 1. It makes correction to eliminate the influence of the dead time from a switching signal in the cycle of the switching signal based on this determination. Feedforward control is carried out to eliminate the influence of a dead time before voltage is output. As a result, voltage correction is enabled without a delay in response. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a voltage converter that performs voltage conversion between an electric motor and a DC power source.

  In recent years, an electric motor such as a motor is used as a drive source for a vehicle such as an automobile, and a chargeable / dischargeable DC power source such as a lithium ion battery is used as a power supply source for the electric motor.

  Between the DC power source and the electric motor, a voltage converter called a bidirectional converter or a two-quadrant chopper circuit is provided. This voltage converter is a step-up converter that boosts the voltage of the DC power source (for example, about 200V) to the voltage required for driving the motor (for example, about 200V to 650V) during powering, that is, when power is supplied from the DC power source to the motor. Function. In addition, when the vehicle is decelerating, the motor operates as a generator, and functions as a step-down converter that reduces the voltage of the motor when regenerating power from the motor to a DC power source.

  Here, the voltage converter will be described with reference to FIG. The voltage converter 1 is connected between the DC power supply 20 and the electric motor 30. The voltage converter 1 includes a first switching element 2 and a second switching element 3 connected in series to the first switching element 2. Further, a first diode 4 is connected in parallel to the first switching element 2, and a second diode 5 is connected in parallel to the second switching element 3. Here, the combination of the switching element and the diode is called an “arm”. In FIG. 24, the combination of the first switching element 2 and the first diode is called a lower arm 6, and the combination of the second switching element 3 and the second diode is called an upper arm 7. A reactor 12 is connected to the wiring connecting the lower arm 6 and the upper arm 7.

  Further, the first switching element 2 and the second switching element 3 are connected to the control unit 9. The control unit 9 includes a signal generation unit 10 and a signal correction unit 11.

  In the configuration described above, the booster circuit that boosts the voltage of the DC power supply 20 during power running is configured by the first switching element 2, the second diode 5, and the reactor 12. On the other hand, a step-down circuit that steps down the voltage of the electric motor 30 during regeneration includes the second switching element 3, the first diode 4, and the reactor 12.

  Here, the rate of boosting the voltage of the DC power supply 20 is determined by the on / off ratio of the first switching element 2. On the other hand, the rate at which the voltage from the motor 30 is stepped down is determined by the on / off ratio of the second switching element 3. The on / off ratio of the first switching element 2 is determined by the switching signal Tr1 generated by the signal generation unit 10 of the control unit 9, and the on / off ratio of the second switching element 3 is generated by the signal generation unit 10. It is determined by the switching signal Tr2. Here, the switching signal is a signal composed of binary values of ON and OFF, and is a signal that defines the ON time and OFF time of the first or second switching element 2 or 3 in an arbitrary period.

A command voltage S is sent to the signal generator 10 from a power management controller (not shown) that makes an output request of the electric motor 30. Known method a first switching signal Tr2 ₀ switching signal Tr1 ₀ and second switching elements 3 of the switching element 2 required to output a command voltage S the signal generator 10 produced by, for example, a triangular wave comparison method To do.

Further, the signal generator 10 generates switching signals Tr1 ₁ and Tr2 _{1 in} which a section called dead time Td is inserted into the switching signals Tr1 ₀ and Tr2 ₀ . This is to prevent a short circuit due to the first switching element 2 and the second switching element 3 being simultaneously turned on, and during the dead time Td period, the first switching element 2 and the second switching element. Both 3 are off. Based on the switching signals Tr1 ₁ and Tr2 ₁ generated as described above, the control unit 9 performs on / off control of the first switching element 2 and the second switching element 3.

Here, based on the switching signals Tr1 ₁ and Tr2 ₁ in which the dead time Td is inserted into the switching signals Tr1 ₀ and Tr2 ₀ generated based on the command voltage S, the first and second switching elements 2 and 3 By performing the on / off control, the output voltage V _O of the voltage converter 1 is different from the command voltage S. Specifically, it is known that during boosting (powering), the degree of boosting is weakened at a predetermined rate, and the output voltage V _O is boosted only to a value lower than the command voltage S. Further, it is known that the degree of step-down is increased at a predetermined rate during step-down (regeneration), and the output voltage V _O is lower than the command voltage S.

Therefore, in Patent Document 1, a signal correction unit 11 is provided in the control unit 9 to reduce the difference between the command voltage S and the output voltage V _O by feedback control. That is, the signal correction unit 11 receives the output voltage V _O of the voltage converter 1, calculates the difference between the output voltage V _O and the command voltage S, and increases or decreases the output voltage S based on this difference.

  JP 2003-309997 A

However, the feedback control is delayed in response to ensure the integration time. For example, a delay of several cycles occurs with respect to the switching cycle. Therefore, for example, when the value of the command voltage S suddenly changes during the delay time, such as when the vehicle slips and suddenly switches from the power running process to the regeneration process, the difference between the command voltage S and the output voltage V _O of the voltage converter. Sometimes increased.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a voltage converter that performs voltage correction by feedforward control that does not generate a delay time, instead of the conventional feedback control.

  The invention according to claim 1 is a voltage converter that is connected between a DC power source and an electric motor and performs step-up and step-down of a voltage. The voltage converter passes a current during an on-time and interrupts the current during an off-time. A lower arm comprising a switching element, a first diode connected in parallel to the first switching element, a second switching element, and a second diode connected in parallel to the second switching element; An upper arm connected in series to the lower arm, a current direction determiner for determining a direction of a current flowing through the upper arm or the lower arm, a voltage command indicating an output voltage, and the current direction A determination signal in the current direction is received from a determination device, and on and off times of the first and second switching elements are determined based on the voltage command and the determination signal. Characterized by comprising a control unit which generates a switching signal for on / off control of the first and second switching elements, and a voltage converter.

  The invention according to claim 2 is the voltage converter according to claim 1, wherein the control unit includes a signal generation unit and a signal correction unit, and the signal generation unit is configured based on the voltage command. A first switching signal in which an on time and an off time of the first switching element are determined and a second switching signal in which an on time and an off time of the second switching element are determined are generated, and the signal correction is performed. The unit corrects the first switching signal and the second switching signal based on the determination signal, and the control unit corrects the first switching signal based on the corrected first switching signal and the second switching signal. The voltage converter performs on / off control of the first and second switching elements.

  The invention according to claim 3 is the voltage converter according to claim 2, wherein the signal correction unit supplies a current from a contact point connecting the upper arm and the lower arm toward the lower arm or the upper arm. , The first switching signal ON time and the second switching signal OFF time are corrected to extend by a predetermined time, and a current flows from the lower arm or the upper arm toward the contact. When the current is flowing, the voltage converter performs a correction to shorten the ON time of the first switching signal and the OFF time of the second switching signal by a predetermined time.

  Further, the invention according to claim 4 is the voltage converter according to claim 3, wherein the voltage converter includes detection means for detecting a differential value of the current flowing through the wiring connecting the upper arm and the lower arm, and the current direction The determiner receives the differential value of the current detected by the detection means, receives the first and second switching signals from the signal generator, and turns on the received first and second switching signals. The voltage converter detects a direction of a current flowing through the upper arm or the lower arm on the basis of switching between / off and a differential value of the current.

  Further, the invention according to claim 5 is the voltage converter according to claim 3, wherein the voltage converter according to claim 3 is provided with detection means for detecting a differential value of the current flowing through the wiring connecting the contact and the lower arm, and the current direction determination A detector receives a differential value of the current detected by the detection means, receives the first switching signal from the signal generation unit, and switches the on / off of the received first switching signal and the current The voltage converter detects a direction of a current flowing through the lower arm based on a differential value of the voltage.

  Due to the effect of dead time, the degree of boosting is weakened at a predetermined rate at the time of boosting, and the degree of stepping down is strengthened at a predetermined rate at the time of stepping down. Can be performed. The inventors of the present application can determine whether the current is flowing up or down from the direction of the current flowing through the upper or lower arm of the voltage converter, and further, this determination and the correction of the switching signal based on the determination. Found that can be done before the voltage is output. As a result, feedforward control that outputs a voltage in a state in which the influence of the dead time is removed in advance can be performed. Therefore, a response delay unlike the conventional feedback control does not occur, and a sudden voltage change can be dealt with.

It is a figure which illustrates the voltage converter and peripheral circuit which concern on embodiment of this invention. It is a figure which illustrates the process in which the switching signal sent to a voltage converter is produced | generated. It is a figure which illustrates the flow of the electric current of a voltage converter and a peripheral circuit at the time of regeneration. It is a figure which illustrates the flow of the electric current of a voltage converter and a peripheral circuit at the time of regeneration. It is a figure which illustrates the flow of the electric current of a voltage converter and a peripheral circuit at the time of power running. It is a figure which illustrates the flow of the electric current of a voltage converter and a peripheral circuit at the time of power running. It is a figure explaining correction | amendment of the switching signal at the time of regeneration. It is a figure explaining correction | amendment of the switching signal at the time of power running. It is a figure explaining correction | amendment of the switching signal at the time of regeneration. It is a figure explaining correction | amendment of the switching signal at the time of power running. It is a figure which illustrates the voltage converter and peripheral circuit which concern on another embodiment. It is a figure explaining the change of the voltage of the coil provided in the switching signal, the lower arm electric current, and the wiring connected to a lower arm at the time of power running. It is a figure explaining the change of the voltage of the coil provided in the wiring connected to a switching signal, a lower arm electric current, and a lower arm at the time of regeneration. It is a figure which shows the flowchart for producing | generating a current direction determination signal. It is a figure explaining the production | generation of a current direction determination signal. It is a figure explaining the production | generation of a current direction determination signal. It is a figure which illustrates the result when the voltage correction concerning embodiment of this invention is implemented. It is a figure which illustrates the waveform of the electric current which flows through a reactor. It is a figure explaining the production | generation of a current direction determination signal. It is a figure explaining the output of the correction value of a switching signal. It is a figure explaining the output of the correction value of a switching signal. It is a figure explaining the output of the correction value of a switching signal. It is a figure explaining the output of the correction value of a switching signal. It is a figure which illustrates the conventional voltage converter and a peripheral circuit.

  FIG. 1 shows a voltage converter and its peripheral circuits according to this embodiment. First, the peripheral circuit configuration of the voltage converter 1 will be described. The voltage converter 1 is connected between the DC power supply 20 and the electric motor 30. The DC power source 20 is composed of a rechargeable secondary battery such as a lithium ion battery. The electric motor 30 is composed of a motor such as a permanent magnet motor.

  Further, a power supply side capacitor 21 is connected in parallel with the voltage converter 1 when viewed from the DC power supply 20 between the voltage converter 1 and the DC power supply 20.

  Further, between the voltage converter 1 and the electric motor 30, an inverter 25 and a load side capacitor 22 are respectively connected in parallel with the voltage converter 1 when viewed from the electric motor 30.

  Next, the configuration of the voltage converter 1 will be described. The voltage converter 1 includes a first switching element 2 and a second switching element 3 connected in series to the first switching element 2. The first switching element 2 and the second switching element 3 are composed of a voltage control type transistor such as an IGBT (insulated gate bipolar transistor), and a current flows between the collector and the emitter during the on-time and Current flow is interrupted.

  Further, the first switching element 2 and the second switching element 3 are connected to the control unit 9. The control unit 9 includes a signal generation unit 10 and a signal correction unit 11.

  The first diode 4 is connected in parallel to the first switching element 2 in parallel so that the direction from the emitter side to the collector side of the first switching element 2 is the forward direction of the diode, Similarly, a second diode 5 is connected to the second switching element 3 in antiparallel. The combination of the first switching element 2 and the first diode 4 is called a lower arm 6, and the combination of the second switching element 3 and the second diode 5 is called an upper arm 7.

  A reactor 12 made of a coil or the like is connected to a contact (node) 13 connecting the upper arm 7 and the lower arm 6.

  Further, among the wires connecting the upper arm 7 and the lower arm 6, a current detector 14 including an ammeter or the like is provided on the wire closer to the lower arm 6 than the contact 13. The current detector 14 can transmit a determination signal indicating a current direction to the signal correction unit 11 of the control unit 9.

  The voltage converter 1 and the peripheral circuit configuration have been described above. Next, a generation process of the switching signal that determines the on / off time of the first switching element 2 and the second switching element 3 will be described, and further, the boost operation and the step-down operation of the voltage converter 1 based on the generated switching signal Will be described.

The switching signal is generated by the control unit 9. A command voltage S for driving the electric motor 30 is sent from a power management controller (not shown) to the signal generation unit 10 of the control unit 9. Signal generator 10 generates switching signals Tr1 ₀ that defines the first ON / OFF time of the switching element 2 by a known triangular wave comparison method and the like based on the command voltage S. Furthermore inverse signal of the switching signal Tr1 _0, i.e. generates a signal reversed the on-time and off-time, to do this the second switching signal Tr2 ₀ of the switching element 3. Here, since the switching signal Tr2 ₀ is an inverse signal of the switching signal Tr1 ₀ , the period T _{0 of} both signals becomes equal.

Further, as shown in FIG. 2, the signal generation unit 10 generates switching signals Tr1 ₁ and Tr2 ₁ in which two dead times Td are inserted in the period T ₀ of the switching signals Tr1 ₀ and Tr2 ₀ . Due to the insertion of the dead time Td, the cycle T ₁ of the switching signals Tr1 ₁ and Tr2 ₁ becomes 2Td longer than the cycle T ₀ of the switching signals Tr1 ₀ and Tr2 ₀ .

Here, in the case of performing a first on / off control switching device 2 on the basis of the switching signal Tr1 _1, also was on / off control of the second switching element 3 on the basis of the switching signal Tr2 _1, the voltage The step-up operation or step-down operation of the converter 1 will be described. First, the operation of the voltage converter 1 during step-down (regeneration) will be described. During regeneration, that is, when electric power is sent from the electric motor 30 to the DC power supply 20, the voltage converter 1 acts as a step-down converter. The step-down circuit includes a second switching element 3, a first diode 4, and a reactor 12.

  In the step-down circuit, a current flows from the electric motor 30 during the on-time of the second switching element 3, and this current is, as shown in FIG. 3, the electric motor 30 → second switching element 3 → contact 13 → reactor 12 → DC power supply 20. → Flows along the path of the motor 30. At this time, electromagnetic energy is accumulated in the reactor 12. Next, during the off time (including the dead time) of the second switching element 3, the supply of current from the electric motor 30 is interrupted and an electromotive force is generated in the reactor 12, so that the reactor 12 → Current flows through the path of the DC power source 20 → the first diode 4 → the current detector 14 → the contact 13 → the reactor 12.

It is known that the step-down ratio in the step-down circuit can be expressed by the ratio of the ON time T _2ON of the second switching element 3 to the switching period T ₁ . That is, the voltage of the electric motor 30 is V _H , the dead time, that is, the time when both the first switching element 2 and the second switching element 3 are turned off, Td, and the time when only the second switching element is turned off. the When _{T 2off,} from FIG. 2, the voltage _{V L} applied to the DC power source 20 is obtained by equation 1 below.

Referring to Equation 1, it can be understood that there is a term of dead time Td in the denominator, and the degree of step-down is increased accordingly, that is, the voltage _VL applied to the DC power supply 20 is lower than the command voltage S.

  Next, the operation of the voltage converter 1 during boosting will be described. During power running, that is, when electric power is sent from the DC power supply 20 to the motor 30, the voltage converter 1 acts as a boost converter. The booster circuit includes a first switching element 2, a second diode 5, and a reactor 12.

  In the step-up circuit, during the ON time of the first switching element 2, as shown in FIG. 5, the path of DC power supply 20 → reactor 12 → contact 13 → current detector 14 → first switching element 2 → DC power supply 20. Current flows. At this time, electromagnetic energy is accumulated in the reactor 12. Next, during the off time (including the dead time) of the first switching element 3, the second diode as shown in FIG. 6 with the electromagnetic energy accumulated in the reactor 12 being added to the voltage of the DC power supply 20. 5 is sent to the electric motor 30.

Ratio of the step-up of the booster circuit, the switching period T _1, is known to be determined by the ratio to the first off-time of the switching element 2. That is, when the ON time of the first switching element 2 is T _1ON and the time when only the first switching element 2 is OFF is T _1OFF , the voltage V _H applied to the motor 30 is as follows from FIG. It can be obtained from Equation 2.

Here, for the rightmost side, T _1ON + T _1OFF > T _1OFF ,

That is, as shown in the above equation 3, the ratio of boosting is weakened by the amount of insertion of the dead time Td, and the voltage V _H applied to the electric motor 30 becomes lower than the command voltage S.

As described above, when the on / off control of the first and second switching elements 2 and 3 is performed in a state in which the switching signals Tr1 ₁ and Tr2 ₁ are not corrected, the voltage converter 1 causes the step-down process (during regeneration). ) And the boosting process (during powering) are affected by the dead time Td. Therefore, the signal correction unit 11 of the control unit 9 corrects the switching signals Tr1 ₁ and Tr2 ₁ to remove the dead time influence Td. Hereinafter, correction of the switching signals Tr1 ₁ and Tr2 ₁ will be described.

  As shown in FIG. 3, the current flow of the voltage converter 1 at the time of step-down (regeneration) is as follows. When the second switching element 3 is on, the current flows from the electric motor 30 to the second switching element 3 to the contact 13. → Reactor 12 → DC power supply 20 → Motor 30 As shown in FIG. 4, when the second switching element 3 is off (including dead time), the current is reactor 12 → DC power supply 20 → first diode 4 → current detector 14 → contact 13 → reactor 12. Flowing through the path.

Here, attention is focused on the current flowing through the current detector 14, that is, the flow of the current I ₁ flowing from the contact 13 to which the reactor 12 is connected to the lower arm 6 (hereinafter, the current I ₁ is referred to as “lower arm current”). . When the flow direction of the lower arm 6 is positive from the contact 13, (becomes 0) lower arm current I ₁ is either flows in the negative direction (lower arm 6 → contact 13), or the flow is lost during regenerative Kano either It is understood that it does not flow in the positive direction.

On the other hand, the current flow of the voltage converter 1 during boosting (powering) is as shown in FIG. 5 when the first switching element 2 is on, the current is DC power supply 20 → reactor 12 → contact 13 → current. It flows through the path of the detector 14 → the first switching element 2 → the DC power supply 20. As shown in FIG. 6, when the first switching element 2 is off (including the dead time), the current is DC power supply 20 → reactor 12 → contact 13 → second diode 5 → motor 30 → DC power supply 20. Flowing the route. At this time, it is understood that the lower arm current I ₁ flows either in the positive direction (contact point 13 → lower arm 6) or no longer flows (becomes 0), and does not flow in the negative direction. The

From the above, the lower arm current I ₁ is at the boost it flows through the forward direction (during power running), it is understood that the time of buck when flows through the negative direction (during regeneration). Current detector 14, the signal correction unit in the control unit 9 a determination signal indicating whether a negative or the flow direction of the lower arm current I ₁ is the positive direction by measuring the current value of the lower arm current I ₁ 11 to send. The signal correction unit 11 receives the determination signal from the current detector 14 and determines whether the electric motor 30 is at the time of step-up or step-down. Further, the switching signals Tr1 ₁ and Tr2 ₁ are corrected based on the determination result. Hereinafter, correction of the switching signals Tr1 ₁ and Tr2 ₁ performed by the signal correction unit 11 will be described.

When the signal correction unit 11 receives a signal notifying the flow direction of the lower arm current I ₁ from the current detector 14, the signal correction unit 11 determines whether the electric motor 30 is at the time of step-up or step-down. After this determination, the signal correction unit 11 performs correction on the switching signals Tr1 ₁ and Tr2 ₁ to increase the degree of boosting when boosting and to reduce the degree of bucking when decreasing.

That is, the signal correction unit 11 based on the equation 1 described above at the time of step-down (during regeneration), performs predetermined time shortened to correct the off-time T _2off switching signals Tr2 _1. Further performs predetermined time reduction is corrected switching signal Tr1 ₁ ON time T _1ON in accordance with the correction. Switching signals Tr1 ₁ and Tr2 ₁ before correction are shown in the upper part of FIG. 7, and switching signals Tr1 ₂ and Tr2 ₂ after correction are shown in the lower part.

For example, the signal correction unit 11 performs correction to reduce the OFF time T _2OFF of the switching signal Tr2 ₁ and the ON time T _1ON of the switching signal Tr1 ₁ by 2Td. This correction is expressed by the following mathematical formula 4.

  As shown in Expression 4, it is understood that the influence of the dead time Td is removed by the correction.

The signal correcting unit 11 based on the equation 2 described above during the boosting (power running), the predetermined time extension corrects the switching signal Tr1 ₁ on-time T _1ON. Further performing the predetermined time extension to correct the off-time T _2off switching signals Tr2 ₁ in accordance with the correction. Switching signals Tr1 ₁ and Tr2 ₁ before correction are shown in the upper part of FIG. 8, and switching signals Tr1 ₂ and Tr2 ₂ after correction are shown in the lower part.

For example, the signal correcting unit 11, the switching signal Tr1 ₁ on-time _{T 1ON,} added _{(2Td × T 1ON) / T} 1OFF. This correction is shown in Equation 5 below. Also added to the switching signal Tr2 ₁ the off-time _{T 2off} the _{(2Td × T 2OFF) / T} 2ON in accordance with the correction.

  As shown in Equation 5, it is understood that the influence of the dead time Td is removed by the correction.

Here, the correction timing of the switching signals Tr1 ₁ and Tr2 ₁ will be described. Signal correcting unit 11 corrects the switching signal _Tr1 1, Tr2 ₁ during the period _{T 1} of the switching signal _Tr1 1, Tr2 _1. In other words, and corrects the switching signal _Tr1 1, Tr2 ₁ during which the on / off control of the first and second switching elements 2 and 3 on the basis of the switching signal _Tr1 1, Tr2 _1.

FIG. 9 shows an outline of the correction operation of the switching signals Tr1 ₁ and Tr2 ₁ at the time of step-down (regeneration). As mentioned above, during the step-down switching from the lower arm current _{I 1} if the switching signal Tr2 ₁ is switched from the on-time _{T 2on} off time _{T 2off} is 0 to a negative value. Current detector 14 sends a decision signal indicating that the lower arm current I ₁ flows in the negative direction when the lower arm current I ₁ is changed from 0 to minus signal correcting unit 11. Alternatively, a negative current value is sent to the signal correction unit 11 as it is as a determination signal. The transmissions from the current detector 14 to the signal correcting unit 11 is performed during the off-time of the switching signal Tr2 _{1 T 2Off.} Further, the signal correction unit 11 determines that the voltage is stepped down based on the flow direction of the lower arm current I ₁ or a negative current value, and the off time T _2off and the switching signal Tr1 during the off time T _2Off of the switching signal Tr2 _{1. 1} ON time T _1On is reduced by a predetermined amount. As a result, the switching signals Tr1 ₁ and Tr2 ₁ are corrected during the switching period T ₁ .

FIG. 10 shows an outline of the correction operation of the switching signals Tr1 ₁ and Tr2 ₁ during boosting (powering). As described above, the lower arm current _{I 1} if the switching signal Tr1 ₁ during the boost is switched from OFF time _{T 1Off} ON time _{T 1ON} switches from 0 to a positive value. Current detector 14 sends a determination signal indicating that the lower arm current I ₁ when the lower arm current I ₁ is changed from 0 to a positive flows in the positive direction to a signal correcting unit 11. Alternatively, the current value is sent to the signal correction unit 11 as it is as a determination signal. The transmissions from the current detector 14 to the signal correcting unit 11 is performed during switching signal Tr1 ₁ on-time _{T 1ON.} Determines that further a time of signal correcting unit 11, based on the flow direction the lower arm current _{I 1} boost, the on-time during a switching signal Tr1 ₁ on-time _{T 1ON T 1on} and switching signals Tr2 ₁ the off-time T _{Increase 2Off} by a predetermined amount. As a result, the switching signals Tr1 ₁ and Tr2 ₁ are corrected during the switching period T ₁ .

When the switching signals Tr1 ₁ and Tr2 ₁ are corrected as described above, the control unit 9 turns on / off the first switching element 2 and the second switching element 3 based on the corrected switching signals Tr1 ₂ and Tr2 _2. Controls off operation. Since step-up and step-down are performed based on the corrected switching signals Tr1 ₂ and Tr2 ₂ from which the influence of the dead time Td has been removed, the difference between the output voltage V _O of the voltage converter 1 and the command voltage S is reduced.

Thus, it is determined whether the time of step-down or a voltage step-up based on the flow direction the lower arm current I ₁ in this embodiment, to correct the switching signal Tr1 _1, Tr2 ₁ based on the determination result ing. Since this correction is performed during the period T ₁ of the switching signals Tr1 ₁ and Tr2 ₁ , that is, before the voltage is output, the voltage is output with the influence of the dead time Td removed. As described above, in this embodiment, voltage correction is performed by feedforward control that outputs a voltage in a state in which the influence of the dead time Td is removed in advance, so that in principle there is no response delay that occurs during feedback control. Therefore, in the present embodiment, it is possible to quickly cope with a sudden change in voltage that cannot be corrected in time due to a response delay.

In the embodiment of FIG. 1, the current detector 14 detects the direction of the lower arm current I _1. However, the current detector 14 is provided between the contact 13 and the upper arm 7, and the upper arm 7 is connected to the contact 13. it may be the flow directed to detect the direction of the arm current I ₂ on the positive. At this time, it can be seen from FIG. 4 that the upper arm current I ₂ is either in the negative direction or no longer flows (becomes 0) at the time of step-down (regeneration) and does not flow in the positive direction. Understood. Further, from FIG. 5, at the time of boosting (powering), the upper arm current I ₂ either flows in the positive direction or no longer flows (becomes 0), and does not flow in the negative direction. Understood. That is the upper arm current I ₂ are voltage step-up if flows through the positive direction, a voltage step-down if flows through the negative direction. Based on the tendency of this flow, the signal correction unit 11 corrects the switching signals Tr1 ₁ and Tr2 ₁ .

The voltage correction in the voltage converter according to the present embodiment has been described above. Incidentally, using an ammeter as a current detector 14 in the embodiment described above has been detected the flow direction of the lower arm current I ₁ or the upper arm current I ₂ directly, the lower arm and the contact 13 in place of this the coil 32 is provided in the wiring between the 6 or upper arm 7, and the change of the voltage V _R of the coil 32, the switching signal Tr1 _1, Tr2 ₁ on / off switch and indirectly lower arm current based on the flow direction of I ₁ or the upper arm current I ₂ may be detected. Hereinafter, this detection method will be described.

In the voltage converter 1 shown in FIG. 11, instead of the current detector 14 shown in FIG. 1, the wiring 31 using the induced electromotive voltage around the wiring 31 between the contact 13 and the lower arm 6 is used. Detection means for detecting the differential value of the current flowing through The coil 32 such as Rogowski coil as the detection means is provided in FIG. 11, further coil 32 receives a voltage value _{V R} from the current direction determining unit 33 for receiving the switching signal _Tr1 1, Tr2 ₁ further from the signal generator 10 Is provided.

As described above, the switching signal Tr1 ₁ at the time of boosting (power running) is switched from OFF to ON (rising) the lower arm current I ₁ is changed from 0 to a positive value when. At this time, rising from 0 according to the voltage V _R is the change in the lower arm current I ₁ of the coil 32 provided around the wiring through which the lower arm current I ₁ (differential value) to a positive value, then also 0 Return to. In other words, the lower arm current I ₁ to flow in the positive direction is understood when switched from 0 voltage V _R of the switching signal switching signal Tr1 ₁ rise and the coil 32 to a positive value occurred simultaneously. Thus it is possible to know the direction of flow of the lower arm current I ₁ indirectly by measuring the change in switching the coil voltage V _R of the switching signal Tr1 ₁ ON / OFF.

In general, when capturing changes that occur at the same time, there is the complexity of setting a simultaneous definition (arbitrary grace time is set and changes within the grace time are regarded as simultaneous). Therefore, it is simpler as a determination process to catch the sequentially occurring changes than to catch the simultaneously occurring changes. Therefore, it may be measured changes falling and the coil voltage V _R of the switching signal Tr2 ₁ instead of measuring the change in switching the coil voltage V _R of the switching signal Tr1 ₁ on / off.

Figure shows 12 during boosting and switching of the switching signal _Tr1 1, Tr1 ₁ of (power running), the timing charts of the coil voltage _{V R.} Switching signals Tr2 ₁ (changed from on to off) is falling (switching from OFF to ON) the switching signal Tr1 ₁ rises after the dead time Td has elapsed, this positive value of the lower arm current I ₁ from 0 at the same time Stand up to the value of. Therefore, the lower arm current I ₁ as it flows in the positive direction, the change of the switching signal Tr2 ₁ falling → dead time Td → coil voltage V _R rise is understood that are sequentially observed during the boosting (power running) . It may indirectly detect the flow direction of the lower arm current I ₁ at the booster by track changes to this sequence occurs.

Further, as at the time of step-down (during regeneration) illustrated in FIG. 13, the flow in the negative direction of the switching signal Tr2 ₁ rises when the lower arm current I ₁ at the same time becomes zero. At this time under the influence of a stream of the lower arm current I ₁ varies, the voltage V _R of the coil 32 is returned to also 0 after rising from 0 to a positive value. That coil voltage _{V R} rises simultaneously with the rise of the switching signal Tr2 _1.

In other words a change in the above with reference to the timing of the falling edge of the switching signal Tr1 _1, first falls switching signal Tr1 _first switching element 2, a switching signal Tr2 ₁ rises after the dead time has elapsed, the same lower time the value of the arm current I ₁ is changed to 0 from a negative. Coil voltage V _R at the time of this switching rises. Therefore, the lower arm current I ₁ at the time of buck (during regeneration) is as it flows in the negative direction, the change of the switching signal Tr1 ₁ falling → dead time Td → coil voltage V _R rise is understood that are sequentially observed. It may indirectly detect the flow direction of the lower arm current I ₁ at the time of buck by track changes to this sequence occurs.

The timing of the switching signal _Tr1 1, Tr2 ₁ fall, the flow determines the flow direction of the lower arm current _{I 1} based on the rise timing of the coil voltage _{V R} shown in Figure 14. The current direction determination unit 33 determines the current direction in accordance with this flow chart, to produce a current direction determination signal SGN indicating the flow direction of the lower arm current I ₁ as the determination result. In the present embodiment, as one the value of the current direction determination signal SGN when it is determined that the lower arm current I ₁ is the positive direction flow, was also determined that the lower arm current I ₁ is flowing in the negative direction Sometimes, the value of the current direction determination signal SGN is set to -1. The current direction determination signal SGN generated in this way is transmitted to the signal correction unit 11.

The flowchart of FIG. 14 will be described first at the time of boosting (powering). The current direction determination unit 33 detects the falling edge of the switching signal (S1), and determines whether the falling signal is the switching signal Tr1 ₁ or Tr2 ₁ (S2). If fallen signal is Tr2 _1, it determines whether the coil voltage V _r rises to a positive value after the dead time Td (S4). When the coil voltage V _r rises from 0 to a positive value, the lower arm current I ₁ is flowing in the positive direction as described above, so the current direction determination unit 33 sets the value of the current direction determination signal SGN to 1. (S5). The coil voltage V _r after dead time if not rise to a positive value sets the value of a current direction determination signal SGN to 0 (S6). The waveform of the current direction determination signal SGN generated in this way is shown in FIG. 15 together with the waveforms of the switching signals Tr1 ₁ , Tr2 ₁ , coil voltage V _r , and lower arm current I ₁ .

Next, a description will be given of when the pressure is lowered (during regeneration). Current direction judgment unit 33, whether to detect the falling edge of the switching signal (S1), when fallen signal is a Tr1 ₁ (S2), the coil voltage V _r after the dead time Td rises to a positive value Is determined (S7). When the coil voltage V _r rises, since the lower arm current I ₁ as described above so that the flow in the negative direction, the current direction determining unit 33 sets the value of the current direction determination signal SGN to -1 (S8 ). The coil voltage V _r after dead time if not rise to a positive value sets the value of a current direction determination signal SGN to 0 (S6). The waveform of the current direction determination signal SGN thus generated is shown in FIG. 16 together with the waveforms of the switching signals Tr1 ₁ , Tr2 ₁ , coil voltage V _r , and lower arm current I ₁ .

Based on the current direction determination signal SGN generated as described above, the signal correction unit 11 determines whether the motor 30 is at the time of step-up or step-down, and the switching signals Tr1 ₁ , Tr2 ₁ are based on the determination result. Perform the correction. Since the current direction determination signal SGN switching signal _Tr1 1 generates a trigger, Tr2 ₁ falling appears every half cycle of the switching signal _{Tr1 1,} Tr2 1, lower in period _{T 1} unit of the switching signal _Tr1 1, Tr2 ₁ it is possible to detect the flow direction of the arm current I _1. Thus, the correction switching signal _Tr1 1, Tr2 ₁ it is possible to perform a switching signal _Tr1 1, Tr2 ₁ of within the period _{T 1,} be carried out feedforward control to remove the influence of the dead time Td before the output voltage it can.

In the above-described embodiment, attention is paid to the change in the lower arm current I _1. However, the coil 32 is arranged in the wiring between the contact 13 and the upper arm 7, and the change in the upper arm current I ₂ is noted. Voltage correction may be performed.

  Here, the result of the voltage correction performed using the current direction determiner 33 is shown in FIG. FIG. 17 shows a comparison between the voltage correction according to the conventional feedback control and the voltage correction according to the present embodiment when the electric motor 30 is suddenly switched from the power running process to the regenerative process during the response delay time in the feedback control due to vehicle slip or the like. It is what.

In FIG. 17, the left side shows voltage correction by conventional feedback control, and the right side shows voltage correction by this embodiment. The electric power change of the electric motor 30 is shown in the uppermost stage, and the electric power value is rapidly switched from positive (power running) to negative (regeneration). Furthermore, the second stage shows whether or not the switching signals Tr1 ₁ and Tr2 ₁ have been corrected. Further, the graph of the third-stage change in the reactor current I _L flowing through the reactor 12 is shown, the graph at the fourth stage are shown voltage variation of the load-side capacitor 22.

It will now be described reactor current _{I L.} Since the flow and the lower arm current I ₁ and the upper arm current I ₂ in the reactor 12, the reactor current I _L represents the sum of the lower arm current I ₁ and the upper arm current I _2. Specifically, as shown in FIGS. 3 and 4, at the time of step-down (regeneration), the upper arm current I ₂ flows through the reactor 12 when the second switching element 3 is on, and the lower arm current when it is off. I ₁ flows. The 5, as shown in FIG. 6, step-up time in the (power running) of the lower arm current I ₁ flows in the reactor 12 when the first switching element 2 is turned on, the upper arm current I ₂ is in the off Flowing.

By the way, in the above-described FIGS. 15 and 16 and the like, the waveform of the lower arm current I _{1 is} a pulse that takes only a predetermined negative binary value of 0 and a predetermined positive binary value during power running, and 0 and a predetermined negative value during regeneration. However, there is a slight increase / decrease in value. Specifically, the boost at the lower arm current I ₁ flows when the switching signal Tr1 ₁ is ON (the power running), the electromagnetic energy is accumulated in the reactor 12 at this time, the lower arm current I ₁ values Tends to rise. The upper arm current I ₂ flows when the switching signal Tr1 ₁ is turned off, the electromagnetic energy is emitted from the reactor 12 at this time, the value of the upper arm current I ₂ becomes a downward trend. Thus, the reactor current I _L which the lower arm current I ₁ and the upper arm current I ₂ is synthesized, a sawtooth waveform as shown in FIG. 18.

Since the upper arm current I ₂ flows, electromagnetic energy is accumulated in the reactor 12 at this time when the switching signal Tr2 ₁ at the time of step-down (during regeneration) is on, the value of the upper arm current I ₂ is the upward trend Become. Switching signals Tr2 ₁ is to flow the lower arm current I ₁ becomes off, the electromagnetic energy is released in the reactor 12 at this time, the value of the lower arm current I ₁ becomes a downward trend. Thus, the reactor current I _L in this case is sawtooth-like waveform.

Returning to FIG. 17, the conventional feedback control will be described. Since the power change shown in FIG. 17 occurs during the response delay period, the conventional feedback control cannot correct the switching signal. Therefore, the output voltage V _O is lower than the command voltage S both during power running and during regeneration. Reactor current I _L affected by this electric motor 30 stagnates around 0A when switching to the regeneration of power running. Further, since there is a difference between the command voltage S and the output voltage V _O , charges are accumulated in the load side capacitor 22 in order to smooth this difference.

On the other hand, the voltage correction according to the present embodiment will be described. The signal correction unit 11 corrects the switching signals Tr1 ₁ and Tr2 ₁ according to the power change of the electric motor 30. As shown in the second graph on the right side of FIG. 17, during power running, it is detected that the lower arm current I ₁ is in the positive direction, and a correction for increasing the degree of boosting is applied to the switching signals Tr _{1 1} and Tr 2 _1. and it performs, also performs correction to reduce the degree of the detected step-down the lower arm current I ₁ is negative direction when a regenerative the switching signal Tr1 _1, Tr2 _1. As a result, the reactor current I _L as is along the power change of the electric motor 30 changes to a slope shape, stagnation near 0A is not observed. Also, entrapment requires only a small amount of the switching signal Tr1 _1, Tr2 ₁ correction charge of the load-side capacitor 22 so the difference is reduced between the output voltage V _O and the command voltage S by being performed.

As described above, it is possible to quickly correct the switching signals Tr1 ₁ and Tr2 ₁ by performing voltage correction in the present embodiment. In particular, in the present embodiment, since a small amount of charge is stored in the load side capacitor 22, a capacitor having a smaller capacity than that of the conventional capacitor can be used. As a result, the cost of the capacitor can be reduced.

Note that the graph of the right second-stage switching signal correction of FIG. 17, when the value of the reactor current I _L is near 0 (hence the value of the upper arm current I ₂ the values of the lower arm current I ₁ in the vicinity of 0 In other words, the current direction determiner 33 pauses the determination of the current direction. This is because the current direction determining unit 33 are continuously outputs 0 as a current direction determination signal when the value of the reactor current I _L is near 0.

When the reactor current I _L is near 0, as shown in FIG. 18, the reactor current I vertices positive value of the mountain of the waveform of the _L, root apex of takes a negative value, the vertex of the vertex of the peaks and valleys The current value becomes zero. On the other hand, when the reactor current _{I L} is not near zero, 15, as shown in FIG. 16, the switching signal _Tr1 1, Tr2 ₁ of switches (i.e. the apex or vertex of the valley of the mountain) simultaneously with the lower arm current _{I 1} And the value of the upper arm current I ₂ becomes zero. That is, as the timing of the current value becomes zero differs between absence and when the reactor current I _L is near 0. In response to this, it is assumed that the timing is different between the absence and when rising even reactor current I _L of the coil voltage V _r is around 0.

As a result, when the reactor current I _L is near 0, the coil voltage V _r rises at a timing different from the timing in the flowchart shown in FIG. 14. That does not rise in the coil voltage _{V r} after the dead time after the switching signal Tr1 ₁ or Tr2 ₁ falls, it is 0 as a current direction determination signal SGN output (S6). By continuously outputting 0 as the determination signal in the current direction, the signal correction unit 11 stops correcting the switching signals Tr1 ₁ and Tr2 ₁ .

Note that every aspect to pause the determination of the current direction when in the vicinity of a value 0 of the reactor current I _L, it is possible to perform the same operation in the embodiment with a current detector 14 in Figure 1. That is, it is possible to pause the determination of the current direction by setting a threshold value in the current detector 14 in advance and performing a process such as not determining the current direction when the current value is within the threshold value.

Above, the switching of the switching signal Tr1 _1, Tr2 ₁ ON / OFF has been described indirect method of determining the flow direction of the lower arm current I ₁ or the upper arm current I ₂ by the change in the coil voltage V _R. In the above-described embodiment, the falling edges of both the switching signals Tr1 ₁ and Tr2 ₁ are detected. However, the detection of the falling edge of the switching signal Tr2 ₁ is omitted, and only the falling edge of the switching signal Tr1 ₁ is detected. May be detected. At this time, the lower arm current I ₁ when the sequentially changed switching signal Tr1 ₁ falling → dead time Td → coil voltage V _R rise with reference to Figure 13 is flowing in the negative direction, i.e. at the time of step-down (during regeneration) there a determination, the lower arm current I ₁ with reference to Figure 12 when there is no rise of V _R of the coil voltage in the dead time after Td is flowing in the positive direction, that is, when is a voltage step-up (power running) judge.

Incidentally, in this embodiment, the (see FIG. 18) when the lower arm current I ₁ is near 0, because there is no rise of the coil voltage V _R after the dead time Td elapses, as described above, the lower arm current I It is determined that ₁ is flowing in the positive direction. Thus, in a case of detecting only the falling edge of the switching signal Tr1 _1, when the lower arm current I ₁ as compared with the case of detecting the falling edge of both of the switching signals Tr1 ₁ and Tr2 ₁ is near 0 However, both can perform feedforward control and can perform voltage correction without a response delay. Furthermore former determining process is simple since it is only necessary to detect the fall of only the switching signals Tr1 _1.

Meanwhile, when the switching signal _Tr1 1, Tr2 ₁ of the frequency becomes higher, the waveform of the coil voltage _{V R} is affected by the parasitic inductance of the first and second switching elements 2 and 3. For example, as shown in FIG. 19, the waveform of the coil voltage V _R superimposed vibration waveform called ringing waveform. This ringing wave is attenuated to zero in a period shorter than the dead time Td.

If normal power running (see FIG. 15), first by but never coil voltage V _R rises after the first falling switching signal Tr1 _1, this ringing wave is superimposed on the coil voltage V _R 1 of the coil voltage V _R even after the fall of the switching signal Tr1 ₁ would rise to rapid positive value after the fall once negative value. Then, in the determination flow of FIG. 14, the value of 1 (S5) is output where the value of the current direction determination signal SGN should be 0 (S6).

Therefore, in this embodiment, instead of detecting the falling timings of the switching signals Tr1 ₁ and Tr2 ₁ , the flow direction of the lower arm current I ₁ is determined based on the rising and falling timings of the switching signal Tr1 ₁ .

As shown in FIG. 19, the ringing wave is generated simultaneously with the switching of the lower arm current I ₁ . The switching of the lower arm current I ₁ is caused by switching of the gate voltages of the first switching element 2 and the second switching element 3. The gate voltages of the first switching element 2 and the second switching element 3 are switched by switching signals Tr1 ₁ and Tr2 ₁ . Switching signals Tr1 ₁ and Tr2 ₁ are sent from the control unit 9 to the first switching element 2 and the second switching element 3. At this time, the switching signals Tr1 ₁ and Tr2 ₁ arrive from the control unit 9 to the first switching element 2 and the second switching element 3 until the gate voltages of the first switching element 2 and the second switching element 3 are switched. There is a slight delay time. Therefore, a ringing wave is generated after a delay time has elapsed since the switching signals Tr1 ₁ and Tr2 ₁ were switched in the control unit 9.

Utilizing this phenomenon, after the time of power running has risen switching signal Tr1 _1, the lower arm current I ₁ flows in the positive direction from zero after the lapse of a delay time, which the coil voltage V _R rises at the same time. Therefore, it is possible to detect the positive direction of the flow of the lower arm current I ₁ by sequentially detecting a change of the switching signal Tr1 ₁ rise → coil voltage V _R rise.

Further, after the fall of the switching signal Tr1 ₁ is, the flow of the lower arm current I ₁ is interrupted after a lapse of a delay time, which the coil voltage V _R falls simultaneously. Therefore, it is possible to detect that the positive direction of flow of the lower arm current I ₁ becomes 0 by sequentially detecting a change of the switching signal Tr1 ₁ falling → coil voltage V _R falling.

On the other hand, during regeneration, falling switching signal Tr1 ₁ is, the switching signal Tr2 ₁ rises after the lapse dead time Td, is more negative direction of flow of the lower arm current I ₁ after a lapse of the delay time is cut off. At the coil voltage V _R rises at the same time. Accordingly, by sequentially detecting a change in the switching signal Tr1 ₁ falling → coil voltage V _R rise, it is possible to detect that a negative direction of flow of the lower arm current I ₁ becomes 0.

Also, after the switching signal Tr2 ₁ falls, the flow from the lower arm current I ₁ 0 after a lapse of a delay time in the negative direction, which a ringing waveform generated in the coil voltage V _R at the same time. Then the switching signal Tr1 ₁ rises through the dead time Td. At this time, the ringing wave of the coil voltage V _R so is attenuated during the dead time Td, the coil voltage V _R when the switching signal Tr1 ₁ rises is 0. Therefore, it is possible to detect the negative direction of the flow of the lower arm current I ₁ by a sequence of no switching signal Tr1 ₁ rise → coil voltage V _R changes (maintaining 0).

Further, instead of the method for determining the current direction described above, the flow direction of the lower arm current I ₁ can also be obtained by using the coil 32 having an accuracy capable of detecting the rising edge of the switching signal Tr1 ₁ and the recovery current of the first diode 4. Can be detected.

First, the recovery current will be described. When a reverse voltage is applied suddenly after a forward current is passed through the diode, electrons injected into the p-type region of the diode move to the n-type region, or positive electrons that have been injected into the n-type region. The hole moves to the p-type region, and current flows in the direction opposite to the forward direction. This current is called a recovery current, and is generated when the first switching element 2 is switched from OFF to ON during powering. The waveform of the lower arm current I ₁ at this time is shown in the second stage on the left side of FIG. Under the influence of the recovery current, the first switching element 2 after it is turned on, the value of the lower arm current I ₁ falls after rises temporarily large, a stable positive value. In response to this current change, the value of the coil voltage V _R changes immediately negative value after rises exactly 0, then shows the value of 0. In other words, the switching signal Tr1 ₁ and the coil 32 change in the order of switching signal Tr1 ₁ rising → coil voltage V _R : 0 → positive → negative. By detecting this change, it can be determined that the lower arm current I ₁ is flowing in the positive direction.

On the other hand, it shows a lower arm current I ₁ of the waveform at the time of regeneration to the second stage the right side of FIG. 20. As shown in the waveform, the recovery current when during regeneration which has risen switching signal Tr1 ₁ is not generated, the recovery current is generated when the switching signal Tr1 ₁ falls. That is, in the case of the switching signal Tr1 ₁ rise → coil voltage V _R no change can be determined that the lower arm current I ₁ flows in the negative direction.

Next, a process in which the signal correction unit 11 outputs the correction value DIR for correcting the switching signals Tr1 ₁ and Tr2 ₁ based on the current direction determination signal SGN sent from the current direction determiner 33 will be described.

In addition to the current direction determination signal SGN sent from the current direction determiner 33, the signal correction unit 11 also receives a triangular wave (carrier signal) used by the signal generation unit 10 to generate the switching signals Tr1 ₀ and Tr2 _0. Will be sent. The signal correction unit 11 determines the peak value of the trough and the peak value of the triangular wave and the instantaneous value of the current determination signal SGN.
(1) If the instantaneous value of the current direction determination signal SGN is positive at the apex of the valley of the triangular wave, a correction value that increases the on time T _1ON of the switching signal Tr1 ₁ and the off time T _2OFF of the switching signal Tr2 ₁ by a predetermined amount. DIR is output.
(2) If the instantaneous value of the current direction determination signal SGN is 0 at the apex of the valley of the triangular wave, the correction value DIR is set to 0.
(3) If the instantaneous value of the current direction determination signal SGN is negative at the top of the peak of the triangular wave, a correction value for reducing the OFF time T _2OFF of the switching signal Tr2 ₁ and the ON time T _1ON of the switching signal Tr1 ₁ by a predetermined amount. DIR is output.
(4) If the instantaneous value of the current direction determination signal SGN is 0 at the peak of the triangular wave peak, the correction value DIR is compared to 0. The result is shown in FIG. The upper row shows the triangular wave, the middle row shows the current direction determination signal SGN, and the lower row shows the waveform of the correction signal DIR. The period of the triangular wave is equal to the period T ₁ of the switching signal, and correction can be performed during the period T _t of the switching signals Tr1 ₁ and Tr2 ₁ by outputting the correction value DIR according to the peak and valley of the triangular wave. .

  Furthermore, as shown in FIG. 22, the maximum point in one period of the correction signal DIR may be sampled to perform a calculation as a representative value in the switching period. Further, instead of sampling the maximum value, an averaging process may be performed as shown in FIG.

  In the above-described embodiment, the pressure is increased in the power running process and the pressure is decreased in the regeneration process. However, the present invention is not limited to this aspect. For example, when the power supply voltage is higher than the voltage of a load such as an electric motor, the voltage is lowered during the power running process, and the voltage is raised during the regeneration process. The present invention can also be applied to such a circuit.

DESCRIPTION OF SYMBOLS 1 Voltage converter, 1st switching element, 2nd switching element, 4th 1st diode, 5th 2nd diode, 6 lower arm, 7 upper arm, 9 control part, 10 signal generation part, 11 signal Correction unit, 12 reactors, 13 contacts, 14 current detector, 20 DC power supply, 21 power supply side capacitor, 22 load side capacitor, 25 inverter, 30 electric motor, 32 coil, 33 current direction determiner.

Claims (5)

A voltage converter that is connected between a DC power source and an electric motor and performs voltage step-up and step-down.
A lower arm comprising: a first switching element that passes current during on-time and interrupts current during off-time; and a first diode connected in parallel to the first switching element;
An upper arm consisting of a second switching element and a second diode connected in parallel to the second switching element, and connected in series to the lower arm;
A current direction determiner for determining a direction of a current flowing through the upper arm or the lower arm;
While receiving the voltage command which shows output voltage, the determination signal of the said current direction is received from the said current direction determination device, and the ON time of the said 1st and 2nd switching element based on the said voltage command and the said determination signal And a controller for generating on / off control of the first and second switching elements by generating a switching signal defining an off time;
A voltage converter characterized by comprising: The voltage converter according to claim 1,
The control unit includes a signal generation unit and a signal correction unit,
In the signal generator, a first switching signal in which an on time and an off time of the first switching element are determined based on the voltage command, and an on time and an off time of the second switching element are determined. A second switching signal is generated;
The signal correction unit corrects the first switching signal and the second switching signal based on the determination signal,
The control unit performs on / off control of the first and second switching elements based on the corrected first switching signal and second switching signal;
A voltage converter characterized by that. The voltage converter according to claim 2, wherein
When the current is flowing from the contact connecting the upper arm and the lower arm toward the lower arm or the upper arm, the signal correction unit is configured to turn on the first switching signal and the second switching signal. When the current is flowing from the lower arm or the upper arm toward the contact point, the ON time of the first switching signal and the second switching signal are A voltage converter characterized by performing a correction to shorten the off time by a predetermined time. The voltage converter according to claim 3, wherein
A detecting means for detecting a differential value of a current flowing through a wiring connecting the upper arm and the lower arm;
The current direction determiner is
While receiving the differential value of the current detected by the detection means, receiving the first and second switching signals from the signal generation unit,
The voltage conversion characterized by detecting the direction of the current flowing through the upper arm or the lower arm based on the ON / OFF switching of the first and second switching signals received and the differential value of the current. vessel. The voltage converter according to claim 3, wherein
A detecting means for detecting a differential value of a current flowing through a wiring connecting the contact and the lower arm;
The current direction determiner is
While receiving the differential value of the current detected by the detection means, receiving the first switching signal from the signal generation unit,
A voltage converter for detecting a direction of a current flowing through the lower arm based on on / off switching of the received first switching signal and a differential value of the current.

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