JP2011130600A - Drive device for power conversion circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a scope determined to be a reflux mode is small, wherein, when the reflux mode at which a current flows to a free wheel diode is determined on the basis of the output current of a micro-electrode formed on a semiconductor substrate configuring a power switching element forming an inverter, and the power switching element is turned off when a mode is determined to be the reflux mode. <P>SOLUTION: It is determined whether U, V, W phases are each a reflux mode on the basis of a current sensor for detecting a current iu flowing through the U phase and a current sensor for detecting a current iv flowing through the V phase. As for the W phase, it is determined whether the mode is the reflux mode on the basis of comparison in the magnitude between the currents iu and "-iv". <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a high-potential side switching element for connecting each phase of a three-phase rotating machine to a positive electrode of a DC power source, a low-potential side switching element for connecting each phase to a negative electrode of the DC power source, and these high potentials. A recirculation mode determination applied to a power conversion circuit including a freewheeling diode connected in parallel to at least one of the switching element on the side and the low potential side, and determining whether or not the recirculation mode in which a current flows through the freewheeling diode The present invention relates to a drive device for a power conversion circuit comprising: means and prohibiting means for prohibiting an ON operation of a switching element connected in parallel to the freewheel diode determined to be in the reflux mode.

  2. Description of the Related Art A power conversion circuit (inverter) including a series connection body of a high-potential side switching element and a low-potential side switching element that connects each terminal of a DC power supply and a terminal of a rotating machine is well known. The inverter includes a free wheel diode connected in parallel to the input / output terminal of the switching element. Here, when operating the high-potential side switching element and the low-potential side switching element to flow a sinusoidal current to the rotating machine, the high-potential side switching element and the low-potential side switching element are alternately switched. Generally, a method of driving the pair of switching elements in a complementary manner by turning them on and off is generally used.

  On the other hand, an insulated gate bipolar transistor (IGBT) may be used as the switching element of the inverter. In recent years, a so-called diode built-in IGBT in which a free wheel diode is provided on the same substrate as the IGBT has been proposed as a semiconductor element constituting such an inverter.

  Since the IGBT has a forward direction from the collector to the emitter, no current flows on the reverse side. For this reason, when a pair of switching elements of the inverter are driven in a complementary manner, depending on the flow direction of the sine wave current, the current may not flow to the switching element that is in the on state. And in this case, it becomes a recirculation mode in which an electric current flows into the freewheel diode connected to this in antiparallel.

  By the way, in the diode built-in IGBT, it is known that the amount of voltage drop when a forward current flows through the freewheeling diode increases when a voltage is applied to the gate of the IGBT. For this reason, when the switching elements are operated in a complementary manner, the power loss due to the freewheeling diode when the forward current flows through the freewheeling diode increases, and as a result, the amount of heat generated by the diode built-in IGBT may increase. .

  Therefore, conventionally, for example, as can be seen in Patent Document 1 below, when detecting that a current flows through a freewheel diode, the switching element is forcibly turned off regardless of the on-operation command by the complementary operation. It has also been proposed. Specifically, a minute electrode is provided on the same semiconductor substrate as the free wheel diode, and a minute current of about one thousandth to one tenth of the current flowing through the freewheel diode is taken out from the electrode. Then, when it is determined that a current flows through the free wheel diode based on the minute current, the switching element is forcibly turned off. Thereby, an increase in power loss can be suppressed.

JP 2008-72848 A

  By the way, when detecting the current flowing through the free wheel diode based on the minute current, it is difficult to increase the detection accuracy. For this reason, it becomes difficult to forcibly turn off the switching element unless the current flowing through the freewheeling diode increases.

  It is not limited to the diode built-in IGBT that makes it difficult to turn on the switching element connected in parallel to the freewheeling diode determined to be in the reflux mode.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power conversion circuit that can more appropriately inhibit an on-operation of a switching element connected in parallel to a freewheel diode that is in a reflux mode. It is in providing the drive device of.

  Hereinafter, means for solving the above-described problems and the operation and effect thereof will be described.

  The invention described in claim 1 is a high-potential side switching element that connects each phase of the three-phase rotating machine to the positive electrode of the DC power supply, and a low-potential side switching element that connects each phase to the negative electrode of the DC power supply. Applied to a power conversion circuit including a freewheel diode connected in parallel to at least one of the high-potential side and low-potential side switching elements to determine whether or not it is a reflux mode in which a current flows through the freewheel diode. In the driving device of the power conversion circuit, the recirculation mode determination unit includes: a recirculation mode determination unit configured to perform, and a prohibition unit that prohibits an on operation of the switching element connected in parallel to the freewheel diode determined to be the recirculation mode. The output of the first detection means for detecting the current flowing through the first phase of the three-phase rotating machine and the current flowing through the second phase are detected. A first phase determining means for making a determination based on an output of the two detecting means, and for determining whether the first phase is in a reflux mode based on a current flowing through the first phase; Based on the current flowing through the second phase, second phase determining means for determining whether the second phase is in the reflux mode, the current flowing through the first phase, and the sign of the current flowing through the second phase And third phase determining means for determining whether or not the third phase is in the reflux mode based on a comparison with the inverted one.

  When the presence or absence of the reflux mode is determined using the first detection unit or the second detection unit and the prohibition process is performed by the prohibition unit, a delay occurs until these processes are actually performed. For this reason, it is considered that a handicap due to delay occurs as compared with a case where an electrode is formed on the same substrate as the free wheel diode and a minute current output from this electrode is used. On the other hand, the inventors have found that the decrease in the determination accuracy of the return mode due to the accuracy of the minute current is likely to be greater than the decrease in the determination accuracy of the return mode due to the delay. This means that it is more advantageous to use the first detection means and the second detection means for appropriately performing the prohibition process. In view of this point, the first invention uses the first detection means and the second detection means.

  By the way, the sum of the currents flowing through the respective phases of the three-phase rotating machine is zero. For this reason, the current flowing through the third phase is obtained by inverting the sign of the sum of the current flowing through the first phase and the current flowing through the second phase. For this reason, the inversion timing of the current flowing through the third phase is the timing at which the magnitude relationship between the current flowing through the first phase and the sign of the current flowing through the second phase is inverted. In the above invention, in view of this point, it is possible to suitably determine whether or not the third phase is also in the reflux mode without providing means for detecting the current flowing through the third phase.

  The invention according to claim 2 is the invention according to claim 1, wherein at least one of the switching element on the high potential side and the switching element on the low potential side and the freewheel diode connected in parallel to the at least one are: They are provided on the same semiconductor substrate.

  The freewheeling diode has a higher conduction loss when the switching element is in the on state than when the switching element is in the off state. For this reason, the utility value of the prohibition means is particularly great.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the third phase determination means is configured to determine whether the current flowing through the second phase is inverted from the current flowing through the first phase. When comparing these, by correcting at least one of these, the boundary between the region that is determined to be the reflux mode and the region that is not determined is the side where the forward current flows to the freewheel diode that is the target of determination of the reflux mode. It is characterized by being offset.

  Processing time is required to determine whether or not the return mode is present based on the detection of the phase current and to perform the processing for prohibiting the ON operation of the switching element based on this. For this reason, the actual prohibition process may be delayed by this processing time. Here, when transitioning from the reflux mode to the non-reflux mode state, if the process for canceling the prohibition based on the determination of the transition is delayed, the switching element is turned off by the prohibiting means, so that a current is supplied to the switching element. It falls into a situation where it is not possible to pass current when it should flow. In this regard, in the above invention, the boundary is offset to the side where the forward current flows in the free wheel diode, so that the release of the prohibition by the prohibiting means shifts from the state in the reflux mode to the state not in the reflux mode. It is possible to avoid delays.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the third phase determining means switches from the state where the free wheel diode is not in the reflux mode to the reflux mode, and from the reflux mode to the reflux mode. It is characterized in that the magnitude of the offset is different between the case of shifting to a non-existing state.

  In the above-described invention, it is possible to avoid the hunting phenomenon in which the determination that the current mode is the reflux mode and the determination that the current mode is not the current mode are frequently switched. For this reason, the situation where the prohibition process by the prohibition means and the cancellation thereof are repeated at a high frequency can be suitably avoided.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the first detection means generates a current traveling from one of the power conversion circuit and the three-phase rotating machine to the other. The second detection means is positive and the current traveling from the other to the one is positive.

  In the said invention, what reverse | inverted the code | symbol of the electric current which flows through a 2nd phase can be acquired without performing inversion calculation.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the driving device includes an operation signal for the high-potential side switching element and an operation signal for the low-potential side switching element. And the operation signal of the switching element on the high potential side and the operation signal of the switching element on the low potential side are complementary signals in which the on state and the off state are alternately switched, The prohibiting unit inputs the operation signal, and corrects the operation signal to an off operation command when the operation signal indicates an on operation command of the switching element based on a determination result by the reflux mode determination unit, and outputs it It is the hardware means to do.

  In the above invention, the processing of the prohibiting means can be executed without increasing the calculation load of the means for generating the complementary signal.

  The invention according to claim 7 is the invention according to any one of claims 1 to 5, wherein the operation signal of the switching element on the high potential side and the low potential are controlled in order to control the control amount of the three-phase rotating machine. Software processing means for performing processing for generating and outputting an operation signal of the switching element on the side as software processing, wherein the reflux mode determination means and the prohibition means are configured by the software processing means. Features.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the three-phase rotating machine is an in-vehicle main machine, and the prohibiting means and the reflux mode determining means are the main machine. A low-voltage system that is insulated from a high-voltage system that is provided is configured.

  The phase current detection means is normally insulated from the electrical path connecting the three-phase rotating machine and the power conversion circuit. For this reason, in the above invention, for example, when the invention has the matters specified in claim 6, if the means for generating the complementary signal constitutes a low voltage system, the output signals of the first detecting means and the second detecting means are propagated. There is no need to provide an insulating means in the path.

1 is a system configuration diagram according to a first embodiment. FIG. Sectional drawing which shows the cross-sectional structure of IGBT and freewheel diode concerning the embodiment. The time chart which shows the judgment method of the recirculation | reflux mode concerning the embodiment. The figure which shows the structure of the interruption | blocking circuit concerning the embodiment. The time chart which shows the judgment method of the recirculation | reflux mode of W phase concerning the embodiment. The perspective view which shows arrangement | positioning of the current sensor concerning 2nd Embodiment. The system block diagram concerning 3rd Embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a control device for a power conversion circuit according to the present invention is applied to a hybrid vehicle will be described with reference to the drawings.

  FIG. 1 shows the system configuration of this embodiment. As shown in the figure, a motor generator 10 as an in-vehicle main machine is connected to a high voltage battery 12 via an inverter IV. The inverter IV is configured by connecting three series-connected bodies of a power switching element Swp on the high potential side and a power switching element Swn on the low potential side in parallel. A connection point between each power switching element Swp and power switching element Swn is connected to each phase of motor generator 10. A high-potential-side freewheel diode FDp and a low-potential-side freewheel are provided between the input / output terminals (between the collector and the emitter) of the high-potential-side power switching element Swp and the low-potential-side power switching element Swn. The cathode and anode of the diode FDn are connected.

  On the other hand, the control device 16 uses the low-voltage battery 14 as a power source, and operates the inverter IV to control the control amount of the motor generator 10 as a control target. Specifically, the control device 16 operates the operation signals gup, gvp, gwp for operating the power switching elements Swp for the U phase, V phase, and W phase of the inverter IV based on the detection values of the current sensors 52, 54, and the like. And operation signals gun, gvn, and gwn for operating the power switching element Swn are generated and output. Thereby, the power switching elements Swp and Swn are operated by the control device 16 via the drive unit DU connected to their conduction control terminals (gates). Incidentally, the high voltage system including the inverter IV and the low voltage system including the control device 16 are insulated by an insulating means such as a photocoupler (not shown), and the operation signal is transmitted to the high voltage system via the insulating means. Is output. The current sensors 52 and 54 are means capable of detecting not only the size but also the direction of current flow. In the figure, it is described that the current sensors 52 and 54 are on the low voltage system side, but this is because the current sensors 52 and 54 do not contact the electric path between the motor generator 10 and the inverter IV. This is because it is connected to the control device 16 without an insulating means.

  Each of the power switching elements Swp and Swn is a switching element that has an input terminal and an output terminal that are uniquely defined and prevents current from flowing from the output terminal to the input terminal. Specifically, these are constituted by insulated gate bipolar transistors (IGBT). The power switching elements Swp and Swn include a sense terminal ST that outputs a minute current having a correlation with a current flowing between the input terminal and the output terminal and a current flowing through the freewheel diodes FDp and FDn. This function of the sense terminal ST is made possible by using a diode built-in type IGBT. That is, in the present embodiment, the high-potential side power switching element Swp and the high-potential side freewheel diode FDp are formed adjacent to each other on the same semiconductor substrate. The free wheel diodes FDn on the side are formed adjacent to the same semiconductor substrate.

  FIG. 2A shows a cross-sectional configuration of the power switching element Swp (Swn) and the free wheel diode FDp (FDn) according to the present embodiment. In the following description, the power switching elements Swp and Swn are collectively referred to as the power switching element Sw, and the free wheel diodes FDp and FDn are collectively referred to as the free wheel diode FD.

  As illustrated, the semiconductor substrate 20 is formed with an IGBT region and a diode region. A region extending from the main surface side to the back surface side of the semiconductor substrate 20 is an N-type region 22 whose conductivity type is N-type. A P-type region 24 having a P-type conductivity is formed in the surface layer portion on the main surface side of the semiconductor substrate 20, and the N-type having a concentration higher than that of the N-type region 22 in the P-type region 24. An N-type region 26 having the conductivity type is formed. The P-type region 24 and the N-type region 26 are connected to an IGBT emitter terminal E and a diode anode terminal. A gate electrode 30 is formed on the P-type region 24 and the N-type region 26 via a gate oxide film 28.

  On the other hand, an N-type region 36 and a P-type region 34 having a concentration higher than that of the N-type region 22 are provided side by side on the back surface side of the semiconductor substrate 20. Here, the P-type region 34 constitutes a collector region of the IGBT, and the N-type region 36 constitutes a cathode region of the diode. An N-type region 32 having a concentration lower than that of the N-type region 22 is formed between the P-type region 34 and the N-type region 36 and the N-type region 22.

  FIG. 2B is a plan view schematically showing the main surface side of the semiconductor substrate 20. As shown in the drawing, most of the main surface side is an emitter region, and a gate region and a sense electrode 38 are formed as a region smaller than this. Here, the actual area of the sense electrode 38 is about one thousandth of the area of the emitter region, so that a very small current is correlated with the current flowing through the IGBT and the free wheel diode. Can be output.

  The drive unit DU not only has a function of turning on / off the power switching element Sw in accordance with an operation signal g (general notation of the operation signals gup, gvp, gwp, gun, gvn, gwn), but also inputs the power switching element Sw. When the detected value of the current flowing between the terminal and the output terminal (collector and emitter) is determined to be excessively large, the power switching element Sw is also forcibly turned off. Specifically, when it is determined that the current flowing between the input terminal and the output terminal of the power switching element Sw is greater than or equal to the threshold current Ith based on the minute current output from the sense terminal ST of the power switching element Sw, the power switching element It has a function of forcibly turning off Sw. Specifically, as illustrated in the drive unit DU corresponding to the W-phase upper arm in the drawing, this is the amount of voltage drop in the resistor 40 due to the minute current output from the sense terminal ST, and the threshold value. This is performed by means (comparator 42) for comparing the magnitude with the threshold voltage Vth corresponding to the current Ith. That is, the result of the comparison by the comparator 42 is taken into the drive circuit 44 that charges and discharges the gate of the power switching element Sw in accordance with the operation signal g. In the drive circuit 44, when it is determined that the current flowing through the power switching element Sw exceeds the threshold current Ith, the power switching element Sw is turned off regardless of the instruction of the operation signal g.

  By the way, the control device 16 includes a CPU 16a and generates an operation signal g by software processing. For this reason, if the operation signal g is generated by determining whether or not it is a reflux mode in which no current flows in the power switching element Sw and current flows in the free wheel diode FD connected in parallel thereto, the calculation load of the CPU 16a Becomes excessive. For this reason, the control device 16 operates the operation signal g as a complementary signal for alternately turning on and off the high-potential side power switching element Swp and the low-potential side power switching element Swn regardless of whether or not the return mode is set. Is generated.

  However, in the case where the diode built-in type IGBT is used as the power switching element Sw as described above, when the power switching element Sw connected in parallel to the freewheeling diode FD is turned on in the reflux mode, the power loss is reduced. To increase. For this reason, when it is judged that it is in recirculation mode, it is desirable to mount the function which cancels the ON operation command of operation signal g. Here, in order to quickly perform the process of turning off the power switching element Sw in the reflux mode, it is effective to use the output of the sense terminal ST and cancel the ON operation command of the operation signal g in the drive unit DU. You might also say that. This is because if the outputs of the current sensors 52 and 54 are used, a delay occurs until the ON operation command of the operation signal g is canceled. However, the minute current output from the sense terminal ST has low accuracy in expressing the current flowing between the input terminal and the output terminal of the power switching element Sw. For this reason, it is not possible to determine that the current mode is the reflux mode immediately after the transition to the reflux mode in which the amount of current flowing through the freewheel diode FD is small.

  Therefore, in this embodiment, instead of using the output of the sense terminal ST, it is determined whether the current mode is the reflux mode using the outputs of the current sensors 52, 54, and the operation signal g is turned on according to the determination result. Correct the operation command. Specifically, a cutoff circuit 50 as dedicated hardware means for performing such processing is provided, and an operation signal g of the control device 16 is once input to the cutoff circuit 50 and then output from the cutoff circuit 50 to the drive unit DU.

  FIG. 3 shows a process performed by the cutoff circuit 50.

  As shown in the figure, in the present embodiment, the direction of traveling from the inverter IV side to the motor generator 10 side is positive, and the current of one phase flowing through the motor generator 10 is greater than or equal to the threshold current IHn (> 0). The lower arm of the phase is determined to be in the reflux mode, and when the current of one phase is equal to or less than the threshold current IHp (<0), it is determined that the upper arm of the phase is in the reflux mode. Further, when the current of one phase flowing through the motor generator 10 is equal to or less than the threshold current ILn (> 0), it is determined that the lower arm of the phase has shifted to a state other than the reflux mode, and the current of the one phase is When the threshold current ILp (<0) or more is reached, it is determined that the upper arm of the phase has shifted to a state other than the reflux mode. Here, the threshold currents ILn and ILp are generated from when it is determined that they are not in the reflux mode based on the outputs of the current sensors 52 and 54 until the canceling process of the ON operation command of the operation signal g is actually canceled. The delay time is set in consideration. On the other hand, when the threshold currents ILn and ILp are set to zero, there is a possibility that the on-operation command is canceled due to the delay even though the return mode is not set.

  Further, as described above, the threshold current IHn for determining that the lower arm shifts to the reflux mode is different from the threshold current ILn for determining that the lower arm shifts to the non-reflux mode, and the upper arm is set to the reflux mode. The threshold current IHp for determining the shift to the state is different from the threshold current ILp for determining the shift to the non-return mode. This is intended to increase resistance to noise. That is, when the phase current is very small and the determination that the current mode is the reflux mode and the determination that the current mode is not the current mode are frequently repeated due to noise or the like, the power switching element Sw is turned on / off at a high frequency. In this case, heat generation increases.

  FIG. 4 shows a configuration of the cutoff circuit 50 according to the present embodiment. Here, first, correction processing of the U-phase operation signals gup, gun based on the current sensor 52 that detects the current flowing through the U-phase, and the V-phase operation signal gvp, based on the current sensor 54 that detects the current flowing through the V-phase, A configuration for realizing gvn correction processing will be described.

  As illustrated, the U-phase current iu (actually a voltage signal) detected by the current sensor 52 and the reference voltage Vthp of the reference power supply 63 are taken into the hysteresis comparator 62. Then, the output signal of the hysteresis comparator 62 and the operation signal gup for the U-phase upper arm are input to the AND circuit 61, and these logical product signals are output from the AND circuit 61 as the final operation signal gup. Here, the hysteresis comparator 62 generates threshold values VHp and VLp shown in the lower part of the figure. Here, the threshold value VHp corresponds to the threshold current IHp shown in FIG. 3, and the threshold value VLp corresponds to the threshold current ILp.

  On the other hand, the U-phase current iu detected by the current sensor 52 and the reference voltage Vthn of the reference power supply 68 are taken into the hysteresis comparator 67. Then, the output signal of the hysteresis comparator 67 and the operation signal gun of the U-phase lower arm are input to the AND circuit 66, and these AND signals are output from the AND circuit 66 as the final operation signal gun. Here, the hysteresis comparator 67 generates threshold values VHn and VLn shown in the lower part of the figure. Here, the threshold value VHn corresponds to the threshold current IHn shown in FIG. 3, and the threshold value VLn corresponds to the threshold current ILn.

  Similarly, the V-phase current iv (actually a voltage signal) detected by the current sensor 54 and the reference voltage Vthp of the reference power supply 73 are taken into the hysteresis comparator 72. Then, the output signal of the hysteresis comparator 72 and the operation signal gvp for the V-phase upper arm are input to the AND circuit 71, and these AND signals are output from the AND circuit 71 as the final operation signal gvp. Further, the V-phase current iv and the reference voltage Vthn of the reference power supply 78 are taken into the hysteresis comparator 77. Then, the output signal of the hysteresis comparator 77 and the operation signal gvn of the V-phase lower arm are input to the AND circuit 76, and these AND signals are output from the AND circuit 76 as the final operation signal gvn.

  Next, correction processing of the operation signals gwp and gwn for the W phase in which the phase current is not directly detected by the current sensor will be described. In this embodiment, since the current sensor for detecting the W-phase current is not provided, the magnitude comparison between the current iu detected by the current sensor 52 and the current iv detected by the current sensor 54 is reversed. The sign of the W-phase current iw is determined based on, and based on this, it is determined whether or not the W-phase is in the reflux mode. That is, according to Kirchhoff's law, since “iu + iv + iw = 0”, “iw = − (iu + iv) = − {iu − (− iv)}”, and the U-phase current iu and the V-phase current iv The sign of the W-phase current iw is reversed at the time when the magnitude of “−iv” is reversed. FIG. 5 visually shows this relationship.

  In order to realize such processing, the inverting amplifier circuit 83 inverts the U-phase current iu detected by the current sensor 52 and the V-phase current iv detected by the current sensor 54 as shown in FIG. The offset is input to the hysteresis comparator 82. Here, the inverting amplifier circuit 83 converts the increase in the current iv into a decrease, converts the decrease into an increase, and provides an offset. On the other hand, the hysteresis comparator 82 logically outputs an output signal when the U-phase current iu is larger than a value “−iv” obtained by inverting the sign of the V-phase current iv (corresponding to “−VHp”). Inverted to “H”, and then the U-phase current iu becomes equal to or less than a value obtained by adding a predetermined value (corresponding to “−VLp”) to “−iv” obtained by inverting the above sign. Invert to “L”. In addition, the inverting amplifier circuit 83 not only inverts the V-phase current iv but also offsets it in order to make both the pair of threshold values of the hysteresis comparator 82 larger than the current iv. The AND circuit 81 generates a logical product signal of the output signal of the hysteresis comparator 82 and the operation signal gwp, and outputs it as the final operation signal gwp.

  The U-phase current iu detected by the current sensor 52 and the V-phase current iv detected by the current sensor 54 are inverted and offset by the inverting amplifier circuit 88 and input to the hysteresis comparator 87. Here, the inverting amplifier circuit 88 converts an increase in the current iv into a decrease, converts the decrease into an increase, and provides an offset. On the other hand, the hysteresis comparator 87 reduces the output signal to a logical value by making the U-phase current iu smaller than a value “−iv” obtained by inverting the sign of the V-phase current iv by a predetermined amount or more (corresponding to “VHn”). Inverted to “H”, and then the U-phase current iu becomes equal to or higher than a value obtained by adding a predetermined value (corresponding to “VLn”) to “−iv” obtained by inverting the above sign. ”. In addition, the inverting amplifier circuit 88 not only inverts the V-phase current iv but also offsets it in order to make both the pair of thresholds of the hysteresis comparator 87 smaller than the current iv. Then, the AND circuit 86 generates a logical product signal of the output signal of the hysteresis comparator 87 and the operation signal gwp and outputs it as a final operation signal gwp.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) “−iv” obtained by inverting the signs of the U-phase current iu detected by the current sensor 52 and the V-phase current iv detected by the current sensor 54 for the W phase in which no current is detected by the current sensor Whether or not the reflux mode is selected was determined based on the comparison with the size. Thereby, it can be suitably determined whether or not the W phase is also in the reflux mode.

  (2) The high-potential side power switching element Swp and the free wheel diode FDp and the low potential side power switching element Swn and the free wheel diode FDn are formed on the same semiconductor substrate. Thereby, since the conduction loss is increased by turning on the power switching element Sw in the reflux mode, the utility value of the processing for canceling the ON operation command of the power switching element Sw is particularly great in the reflux mode.

  (3) The boundary (threshold currents ILp, ILn) between the region that is determined to be the return mode and the region that is not determined is offset to the side where the forward current flows in the free wheel diode FD that is the target of the return mode. Accordingly, it is possible to avoid delaying the cancellation of the ON-operation command cancel process from the timing of shifting from the state in the reflux mode to the state not in the reflux mode.

  (4) Threshold currents IHp and IHn for determining that the freewheeling diode FD shifts from the state not in the return mode to the return mode, and threshold currents ILp and ILn for determining the shift from the return mode to the state not in the return mode And was made different. Thereby, the situation where the cancellation process of the ON operation command and the cancellation thereof are repeated at a high frequency can be suitably avoided.

  (5) The on-operation command of the operation signal g as a complementary signal generated by software processing in the control device 16 is canceled by the cutoff circuit 50 which is hardware means. Thereby, the cancellation process can be executed without increasing the calculation load of the control device 16.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, instead of inverting the output of the current sensor 54, the current sensor 52 and the current sensor 54 are configured such that the positive current direction is reversed. This can be realized by the arrangement shown in FIG. That is, the current sensors 52 and 54 both include Hall elements 52b and 54b in the gaps of the cores 52a and 54a, and a magnetic field generated by a current flowing through the axes of the cores 52a and 54a is generated by the Hall elements 52b and 54b. It is to detect. For this reason, when the current flows from the inverter IV to the motor generator 10, the current sensors 52 and 54 are arranged so that the directions of the magnetic fields sensed by the Hall elements 54a and 54b are opposite to each other. The output is obtained by inverting the sign of that in the first embodiment.

  For this reason, in this embodiment, a circuit for inverting the sign of the output of the current sensor 54 is not provided. However, the output of the current sensor 54 is offset.

  According to this embodiment described above, in addition to the effects (1) to (5) of the first embodiment, the following effects can be obtained.

  (6) The forward direction of the current is reversed between the current sensor 52 and the current sensor 54. This makes it possible to compare the magnitude of the U-phase current iu and “−iv” obtained by inverting the sign of the V-phase current iv without performing the process of inverting the output of the current sensor 54.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 7 shows a system configuration according to the present embodiment. In FIG. 7, members corresponding to those shown in FIG. 1 are given the same reference numerals for the sake of convenience.

  As shown in the figure, this embodiment does not include the cutoff circuit 50 as hardware means. Instead, the function of the cutoff circuit 50 is realized by software processing of the control device 16.

(Other embodiments)
The above embodiments may be implemented with the following modifications.

<About reflux mode judgment means>
In the first embodiment, the detection value (voltage signal) of the current iv flowing through the V phase is inverted and offset by the inverting amplifier circuits 83 and 88, but the present invention is not limited to this. For example, for either one of the high potential side hysteresis comparator 82 and the low potential side hysteresis comparator 87, an offset may be provided by adjusting the outputs of the current sensors 52 and 56 themselves. This method can also be applied to the second embodiment.

  A threshold current for determining whether the high-potential-side freewheel diode FDp is in the reflux mode and a threshold current for determining whether the low-potential-side freewheel diode FDn is in the reflux mode The difference is not limited to the setting on the side for determining the threshold value among the input signals of the hysteresis comparators 62, 67, 72, 77, 82, 87. For example, the setting may be performed on the current side to be compared with the threshold value. This can be done by correcting the current value or adjusting the output of the current sensor that outputs this current value.

  The threshold current is not limited to the case where one free wheel diode FD shifts from the state not in the return mode to the return mode and the case where the free wheel diode FD shifts from the return mode to the state not in the return mode. Even without such setting, the effect (1) of the first embodiment can be obtained.

  A threshold current for determining whether or not the high-potential-side freewheel diode FDp is in the reflux mode and a threshold current for determining whether or not the low-potential-side freewheel diode FDn is in the reflux mode It is not limited to the difference. Even without such setting, the effect (1) of the first embodiment can be obtained.

<About switching elements>
The IGBT is not limited to one in which free wheel diodes are provided on the same semiconductor substrate. Even if this is not the case, the power consumption can be reduced by not turning on the power switching element Swp when a current flows through the freewheeling diode FD.

  The power switching element Sw is not limited to the IGBT, and may be a power MOS field effect transistor, for example. In this case, since the on-resistance of the power MOS field effect transistor is usually smaller than that of the free wheel diode FD, it is considered that a current flows through the power MOS field effect transistor except during the dead time period. However, when the temperature of the transistor becomes high, it is conceivable that the freewheel diode FD is set to the reflux mode. Therefore, the present invention can be applied to such a case.

  When a power switching element Sw that can flow a current bidirectionally by switching the functions of the input terminal and the output terminal, such as a MOS field effect transistor, is used as the power switching element Sw. It is also possible to apply the present invention to a device in which either one of the free potential diode FDn on the low potential side is deleted. By the way, if a dead time period is provided in the on / off operation of the high-potential side power switching element Swp and the low-potential side power switching element Swn, a free wheel diode connected in parallel to each other is required. For example, some power conversion circuits described in US Pat. No. 7,130,205 do not require a dead time period.

<Others>
In the second embodiment, the current sensors 52 and 54 illustrated in FIG. 6 are exemplified, but the present invention is not limited to this. For example, an MRE (magnetoresistive element) sensor or the like may be used.

  Even if the cutoff circuit 50 is provided in a high voltage system, the effect (1) of the first embodiment can be obtained.

  -As a three-phase rotary machine, not only a synchronous machine but an induction machine may be used, for example.

  -As a power converter circuit, not only what is mounted in a hybrid vehicle, For example, you may mount in an electric vehicle.

  DESCRIPTION OF SYMBOLS 10 ... Motor generator (one embodiment of a three-phase rotary machine), 16 ... Control apparatus (one embodiment of software processing means), 50 ... Shut-off circuit (One embodiment of reflux mode judgment means and prohibition means), Swp, Swn ... power switching elements, FDp, FDn ... freewheeling diodes.

Claims (8)

A switching element on the high potential side for connecting each phase of the three-phase rotating machine to the positive electrode of the DC power supply, a switching element on the low potential side for connecting each phase to the negative electrode of the DC power supply, the high potential side and the low potential A freewheeling mode determination means for determining whether or not the freewheeling diode is in a freewheeling mode applied to a power conversion circuit including a freewheeling diode connected in parallel to at least one of the switching elements on the side; In a drive device for a power conversion circuit, including a prohibiting unit that prohibits an on operation of a switching element connected in parallel to a freewheeling diode determined to be a reflux mode.
The reflux mode determination means makes the determination based on the output of the first detection means for detecting the current flowing through the first phase of the three-phase rotating machine and the output of the second detection means for detecting the current flowing in the second phase. And
First phase determination means for determining whether the first phase is in a reflux mode based on a current flowing through the first phase;
Second phase determination means for determining whether the second phase is in a reflux mode based on a current flowing through the second phase;
A third phase determining means for determining whether or not the third phase is in the reflux mode based on a magnitude comparison between the current flowing through the first phase and the inverted value of the current flowing through the second phase; A drive device for a power conversion circuit comprising:   2. The at least one of the high-potential side switching element and the low-potential side switching element and a free wheel diode connected in parallel to at least one of the switching elements are provided on the same semiconductor substrate. The drive device of the power converter circuit as described.   The third phase determining means corrects at least one of these when the magnitude of the current flowing through the second phase is inverted with respect to the current flowing through the first phase. 3. The power conversion circuit according to claim 1, wherein a boundary between a region that is determined as the return mode and a region that is not determined as the return mode is offset to a side in which a forward current flows in the free wheel diode that is determined as the return mode. Drive device.   The third phase determining means differs in the magnitude of the offset between a case where the freewheeling diode shifts from the state not in the reflux mode to the reflux mode and a case where the free wheel diode shifts from the reflux mode to the state not in the reflux mode. The drive device for a power conversion circuit according to claim 3, wherein:   The first detection means makes positive the current traveling from one of the power conversion circuit and the three-phase rotating machine to the other, and the second detection means proceeds from the other to the one. The drive device for a power conversion circuit according to any one of claims 1 to 4, wherein the current is positive. The drive device inputs the operation signal of the switching element on the high potential side and the operation signal of the switching element on the low potential side, and drives them,
The operation signal for the high-potential side switching element and the operation signal for the low-potential side switching element are complementary signals that are alternately switched between an on state and an off state,
The prohibiting unit inputs the operation signal, and corrects the operation signal to an off operation command when the operation signal indicates an on operation command of the switching element based on a determination result by the reflux mode determination unit, and outputs it The power conversion circuit driving device according to claim 1, wherein the power conversion circuit driving device is a hardware unit that performs the above operation. Software processing means for performing, as software processing, processing for generating and outputting an operation signal for the high-potential side switching element and an operation signal for the low-potential side switching element to control the control amount of the three-phase rotating machine Prepared,
6. The power conversion circuit drive device according to claim 1, wherein the reflux mode determination unit and the prohibition unit are configured by the software processing unit. The three-phase rotating machine is an in-vehicle main machine,
The said prohibition means and the said recirculation | reflux mode judgment means comprise the low voltage system insulated with respect to the high voltage system comprised with the said main machine, The any one of Claims 1-7 characterized by the above-mentioned. The drive device of the power converter circuit as described.

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