JP2011217440A - Discharge control apparatus for power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem, wherein the temperatures of a switching element of a high-potential side and a switching element of a low-potential side is excessively increased, when the charging voltage of a capacitor is controlled at a prescribed voltage or below, by executing processing for short-circuiting both electrodes of the capacitor by bringing both switching elements to an on-state.SOLUTION: In a discharge controller, the switching element Swp of the high-potential side is repeatedly turned on and off a plurality of times in a non-saturation region, while maintaining the switching element Swn of the low-potential side in an on-state in a saturation region, thereby generating a plurality of times of a state where both electrodes of the capacitor 16 are short-circuited to execute discharge control. Here, a gate applied voltage of the switching element Swp of the high-potential side is operated, in order to feedback-control a temperature detected by a temperature-sensitive diode SD.

Description

  The present invention relates to a power conversion circuit for converting the power of a DC power supply to a predetermined value, a capacitor interposed between the power conversion circuit and the DC power supply, and an electric path between the power conversion circuit, the capacitor and the DC power supply. Applied to a power conversion system comprising an opening / closing means for opening and closing the capacitor, and under a situation where the opening / closing means is in an open state, the charging voltage of the capacitor is reduced to a specified voltage or less by performing a process of shorting both electrodes of the capacitor. The present invention relates to a discharge control device for a power conversion system including discharge control means for controlling discharge.

  As this type of discharge control device, for example, as shown in Patent Document 1 below, the switching element on the high potential side and the switching element on the low potential side of the inverter are simultaneously turned on, so that the input terminal of the inverter There has also been proposed one in which both electrodes of a connected capacitor are short-circuited to discharge the capacitor. In this control device, the voltage applied to the gate of the IGBT, which is a switching element, is reduced compared to the normal time during discharge control in order to avoid an excessive increase in current flowing when both electrodes of the capacitor are short-circuited. I am letting.

JP 2009-232620 A

  By the way, during the discharge control, the amount of heat generated per unit time of the switching element tends to be very large. Here, since the amount of heat generation depends on the amount of current flowing through the switching element, it can be limited by reducing the voltage applied to the gate. However, the current that actually flows through the switching element due to variations in device characteristics due to individual differences in switching elements and changes over time, and variations in applied voltage due to individual differences in switching circuit drive circuits and changes over time, etc. Is difficult to control with high accuracy, and as a result, the temperature of the switching element may become excessively high.

  The present invention has been made to solve the above-mentioned problems, and its object is to short-circuit both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element. An object of the present invention is to provide a discharge control device for a power conversion system that can suitably control the temperature of a switching element when controlling the charging voltage of the capacitor to a specified voltage or less by performing the process.

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

  According to a first aspect of the present invention, there is provided a power conversion circuit that includes a series connection body of a high-potential side switching element and a low-potential side switching element and that converts the power of a DC power source into a predetermined power, the power conversion circuit, and the DC The present invention is applied to a power conversion system including a capacitor interposed between power supplies, and an open / close means for opening and closing an electric path between the power conversion circuit and the capacitor and the DC power supply, and the open / close means is opened. The discharge voltage of the capacitor is discharged below a specified voltage by performing a process of shorting both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element. In a discharge control device of a power conversion system comprising a discharge control means for controlling, the switching element on the high potential side and the The potential-side switching element is a voltage-controlled switching element, and the discharge control means is configured such that the current in one of the non-saturation regions of either the high-potential side switching element or the low-potential side switching element is any one. The voltage applied to the conduction control terminal of each one of the switching elements and the switching element of each of the other is set so as to be smaller than the other one, and the temperature of either one of the switching elements is detected And a temperature detection unit, and an operation unit for operating a voltage application mode to the conduction control terminal of any one of the switching elements so as to feedback control the temperature detected by the temperature detection unit.

  In the above invention, heat generation of the switching element on the high potential side and the switching element on the low potential side during the discharge control of the capacitor is more remarkable in either one of the switching elements. For this reason, it can avoid suitably that the temperature of both switching elements becomes high by performing feedback control of this temperature as a control amount.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the operating means uses the value of the voltage applied to the conduction control terminal of one of the switching elements as the operation amount of the feedback control. To do.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the discharge control means switches the switching state of one of the two while the other is in an on state, A process of generating a short-circuited state of the two electrodes a plurality of times is performed by repeating any one of the on state and the off state a plurality of times.

  In the above invention, since the discharge period of the capacitor can be controlled in a time-sharing manner, the amount of heat generated per unit time of the switching element can be reduced, and accordingly, the temperature of the switching element is preferably prevented from excessively rising. be able to. Further, in the above invention, since one of the switching states is switched while the other is in the on state, the switching state of one of the other is switched at the time of switching of one of the switching states. In addition, a situation in which the through current becomes large can be avoided.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the operation means uses the value of the voltage applied to the conduction control terminal of the one of the switching elements as the operation amount of the feedback control. In addition, the detection value of the discharge current of the capacitor is used as an input, and the time for which one of the switching elements is turned on for one cycle of the on state and the off state to control the amount of heat generated by the one of the switching elements. The apparatus further comprises means for operating the time ratio.

  In the above invention, the amount of heat generation is grasped based on the detected value of the discharge current, and by controlling the amount of heat generation, the amount of heat generated due to a decrease in controllability of the amount of discharge current due to specific differences due to individual differences such as switching elements and aging It is possible to suitably compensate for a decrease in controllability. In the above invention, the operation amount for controlling the calorific value grasped from the detected value of the discharge current and the operation amount for temperature feedback control are set as parameters different from each other, so that the hardware means Even when the operating means is constructed, it is easy to simplify the configuration.

  According to a fifth aspect of the present invention, in the first aspect of the invention, the discharge control means switches the switching state of one of the two while the other is in the on state, A process of generating a short-circuit state of the two electrodes a plurality of times by repeating the on-state and off-state of the plurality of times, and the operating means includes the on-state of the one of the switching elements and the The time ratio, which is the ratio of the on-state time to the off-state period, is used as the operation amount of the feedback control.

1 is a system configuration diagram according to a first embodiment. FIG. The circuit diagram which shows the circuit structure of the drive unit concerning the embodiment. The time chart which shows the discharge control at the time of abnormality concerning the embodiment. The figure which shows the relationship between a gate applied voltage and an electric current. The figure which shows the characteristic of the minute electric current of a sense terminal. The circuit diagram which shows the circuit structure of the drive unit concerning 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a discharge control device of a power conversion system 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. The illustrated motor generator 10 is an in-vehicle main machine and is mechanically coupled to drive wheels. Motor generator 10 is connected to high-voltage battery 12 via inverter IV and a parallel connection body of relay SMR2 and resistor 14 and relay SMR1. Here, the high voltage battery 12 has a terminal voltage of, for example, a high voltage of 100 V or higher. Further, among the input terminals of the inverter IV1, the capacitor 16 and the discharge resistor 18 are connected in parallel to the inverter IV side of the relays SMR1 and SMR2.

  The inverter IV is configured by connecting three series connection bodies of a high-potential side switching element Swp and a low-potential side switching element Swn as power elements in parallel. The connection points of the high-potential side switching element Swp and the low-potential side switching element Swn are connected to the respective phases of the motor generator 10.

  Between the input / output terminals (between the collector and the emitter) of the switching element Swp on the high potential side and the switching element Swn on the low potential side, the free wheel diode FDp on the high potential side and the free wheel diode FDn on the low potential side are connected. The cathode and anode are connected. The switching elements Swp and Swn are both formed of insulated gate bipolar transistors (IGBT). The 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.

  The minute current output from the sense terminal St flows through the shunt resistor 19, and the voltage drop due to this flows into the drive unit DU for driving the switching element Sw # (# = p, n). The drive unit DU forcibly turns off the switching element Sw # when it is determined that the current flowing between the input terminal and the output terminal of the switching element Sw # is equal to or greater than the threshold current Ith based on the voltage drop amount in the shunt resistor 19. It has a function to make a state.

  On the other hand, the control device 30 is an electronic control device that uses the low-voltage battery 20 as a power source. The control device 30 operates the inverter IV in order to control the control amount of the motor generator 10 as a control target. Specifically, the control device 30 operates based on detection values of various sensors (not shown) and the like, operation signals gup, gvp, gwp for operating the switching elements Swp for the U phase, the V phase, and the W phase of the inverter IV, Operation signals gun, gvn, and gwn for operating the switching element Swn are generated and output. Thereby, the switching elements Swp and Swn are operated by the control device 30 via the drive unit DU connected to their conduction control terminals (gates). Further, the control device 30 detects a vehicle collision based on the detection value of the acceleration detection means (G sensor 22) that detects acceleration based on the force acting on the device, and forcibly forces the capacitor 16 when a collision is detected. In order to perform the discharge process automatically, the abnormal-time discharge command dis is output to the drive units DU of the U-phase switching elements Swp and Swn, respectively.

  Incidentally, the high voltage system including the inverter IV and the low voltage system including the control device 30 are insulated by an insulating means such as a photocoupler (not shown), and the operation signal g * # (* = u, v, w , # = P, n) and the abnormal-time discharge command dis are output to the high voltage system via the insulating means.

  FIG. 2 shows a configuration of a drive circuit unit for turning on / off switching element Sw # in particular among drive units DU of U-phase switching element Sw #.

  As shown in the figure, each U-phase upper arm and lower arm drive unit DU includes a power supply 40 having a terminal voltage VH, and the voltage of the power supply 40 is switched via a charging switching element 42 and a gate resistor 44. Applied to the conduction control terminal (gate) of Sw #. The gate of the switching element Sw # is connected to the output terminal (emitter) of the switching element via the gate resistor 44 and the discharge switching element 46, and this becomes a gate discharge path. The charging switching element 42 and the discharging switching element 46 are turned on / off by the normal time drive control unit 48 in accordance with the operation signal gu #. As a result, the switching element Sw # is turned on / off by the normal-time drive control unit 48.

  The U-phase drive unit DU further includes a dedicated circuit for turning on / off the switching element Sw # in response to the abnormal-time discharge command dis.

  Here, in the drive unit DU of the U-phase lower arm, the voltage of the power supply 50 having the terminal voltage VH is applied to the gate of the switching element Swn via the charging switching element 52 and the gate resistor 44. The gate is connected to the emitter of the switching element Swn via the gate resistor 44 and the discharging switching element 54. Then, the charging switching element 52 and the discharging switching element 54 are turned on / off by the abnormal-time drive control unit 56 according to the abnormal-time discharge command dis. Thus, the switching element Swn on the low potential side is turned on / off according to the abnormal-time discharge command dis.

  On the other hand, the voltage drop amount of the shunt resistor 19 due to the minute current output from the sense terminal St of the switching element Swn on the low potential side is applied to the non-inverting input terminal of the comparator 62 via the latch 60. An output signal (carrier) of an oscillator 64 that outputs a signal having a predetermined frequency is applied to the inverting input terminal of the comparator 62. As a result, the comparator 62 outputs a signal that is logic “H” when the voltage drop amount is larger than the carrier. Incidentally, the latch 60 holds the value of the input voltage (the voltage drop amount) triggered by the comparator 62 becoming a logic “H”.

  On the other hand, the drive unit DU of the U-phase upper arm includes, in addition to the charging switching element 52, the discharging switching element 54, and the abnormal time drive control unit 56, between the charging switching element 52 and the power supply 50. A regulator 58 that steps down the terminal voltage VH of the power supply 50 and a power supply switching element 71 that opens and closes between the regulator 58 and the power supply 50 are further provided. Here, the switching element 71 for power supply assumes the normally open type which will be in a closed state by inputting the abnormal time discharge command dis. The output signal of the comparator 62 is output as a heat generation control operation amount Mh to the primary side (photodiode) of the switching element Swp on the high potential side via the photocoupler 70. The output terminal on the secondary side (phototransistor) of the photocoupler 70 is connected to the emitter of the switching element Swp, and the input terminal is connected to the power supply 50 via a resistor. Then, the output signal of the photocoupler 70 is input to the abnormality drive control unit 56 for the upper arm. Thereby, the switching element Swp on the high potential side is turned on while the photocoupler 70 is turned off.

  In the vicinity of the switching element Swp on the high potential side, a temperature sensitive diode SD for detecting the temperature is provided. Specifically, the cathode side of the temperature-sensitive diode SD is connected to the emitter of the switching element Swp, and the anode side is connected to the output terminal of a constant current circuit 74 using the power supply 50 as a power supply means. Then, the voltage on the anode side is taken into the voltage comparison circuit 76, and the output signal of the voltage comparison circuit 76 is taken into the regulator 58. The regulator 58 variably sets the output voltage VL (<VH) according to the temperature detected by the temperature sensitive diode SD. Incidentally, the output voltage of the temperature sensitive diode SD and the temperature of the detection target have a negative correlation.

  FIG. 3 shows an aspect of discharge control based on the abnormal-time discharge command dis. Specifically, FIG. 3A shows the transition of the abnormal-time discharge command dis, and FIG. 3B shows the transition of the output signal (one-dot chain line) of the latch 60 and the carrier output from the oscillator 64. 3 (c) shows the transition of the state of the switching element Swp on the U-phase high potential side, and FIG. 3 (d) shows the transition of the state of the switching element Swn on the low potential side of the U-phase. As illustrated, in this embodiment, the switching element Swp on the high potential side is periodically switched between the on state and the off state while the switching element Swn on the low potential side of the U phase is maintained in the on state. As a result, there is a period in which both the high-potential side switching element Swp and the low-potential side switching element Swn are turned on at the same time. During this period, the two electrodes of the capacitor 16 are connected via the switching elements Swp and Swn. As a result, the capacitor 16 is discharged.

  At this time, because of the configuration of the drive unit DU shown in FIG. 2, the gate applied voltage of the switching element Swp on the high potential side is on the low potential side as shown in FIGS. 3 (e) and 3 (f). It becomes lower than the gate applied voltage of the switching element Swn. Here, FIG. 3E shows the transition of the gate-emitter voltage Vge of the high-potential side switching element Swp, and FIG. 3F shows the transition of the gate-emitter voltage Vge of the low-potential side switching element Swn. Shows the transition.

  According to such a configuration, the switching element Swp on the high potential side is driven in the non-saturation region, and the switching element Swn on the low potential side is driven in the saturation region. Here, as shown in FIG. 4, the saturation region is a region where the voltage between the input terminal and the output terminal of the switching element (collector-emitter voltage Vce) increases in accordance with the output current (collector current Ic). is there. On the other hand, the non-saturated region is a region where the collector-emitter voltage Vce increases without increasing the collector current. The collector current Ic that becomes the non-saturated region increases as the gate applied voltage (gate-emitter voltage Vge) increases.

  For this reason, by lowering the gate applied voltage of the switching element Swp on the high potential side than the switching element Swn on the low potential side, the switching element Swp on the high potential side is less saturated than the switching element Swn on the low potential side. The current in the region is reduced. As a result, the current flowing through the switching element Swp on the high potential side and the switching element Swn on the low potential side by the discharge control is limited to the current in the non-saturated region of the switching element Swp on the high potential side. Note that it is desirable that the current in the non-saturation region of the switching element Swp on the high potential side is set to be less than the threshold current Ith defined by the drive unit DU. Incidentally, the terminal voltage VH is such that the threshold current Ith is in the saturation region. That is, when controlling the control amount of motor generator 10, switching elements Swp and Swn are driven in the saturation region.

  By the way, in the discharge control triggered by the abnormal-time discharge command dis, the amount of heat generated by the U-phase high-potential side switching element Swp and the low-potential side switching element Swn becomes excessive, and the reliability of the switching elements Swp, Swn is increased. It is desirable to set so that the value does not decrease. Here, the amount of heat generated per unit time of the switching elements Swp and Swn depends on the current flowing therethrough and the on-time and off-time of each switching element Swp. On the other hand, the current flowing through the switching elements Swp and Swn can be controlled by the voltage applied to the gate of the switching element Swp, but it is difficult to increase the controllability. This may result in variations in applied voltage due to individual differences in the drive units DU and changes over time, or variations in current in the non-saturated region due to individual differences in the switching elements Swp themselves and changes over time. Because.

  Therefore, in the present embodiment, the heat generation amount grasped from the discharge current by the discharge control is set as a direct control amount so that it is not excessively increased. That is, by performing the discharge control in the manner shown in FIG. 3, the higher the value of the output signal of the latch 60 (the greater the discharge current), the higher or lower switching element Swp is turned on / off. Control is performed so that the time ratio of the on-time to the cycle becomes small. As a result, when the discharge current is large, control is performed to reduce the amount of heat generated within a unit time (for example, one cycle of the carrier), thereby avoiding an excessive increase in the amount of heat generated per unit time. it can.

  Here, the current as a parameter for grasping the amount of generated heat is the minute current output from the sense terminal St of the switching element Swn on the low potential side. The output of the sense terminal St of the switching element Swp on the high potential side is This is in view of the fact that the accuracy is higher than that when a minute current is used. FIG. 5 shows a voltage drop amount (sense voltage) in the shunt resistor 19 based on a minute current output from the sense terminal St for each of the switching element Swn driven in the saturation region and the switching element Swp driven in the non-saturation region. The relationship of the dispersion | variation (maximum value MAX, minimum value MIN) is shown. As shown in the figure, the variation in the sense voltage driven in the non-saturation region is very large, and the current detection accuracy is low.

  In the present embodiment, the temperature of the switching element Swp on the high potential side is set as a control amount, which is detected by the temperature sensitive diode SD, and feedback control is performed so that the detected value does not become excessively high. Here, the feedback control amount is set to the temperature of the switching element Swp on the high potential side because the majority of the heat generated by the discharge control is due to the switching element Swp on the high potential side driven in the non-saturation region. It is in view of becoming.

  Note that evenly dividing the amount of heat generated by driving both the high-potential side switching element Swp and the low-potential side switching element Swn in the non-saturation region means that individual differences in the switching elements Swp and Swn and the drive unit DU, It is very difficult because of change. That is, due to the individual differences and changes over time, it is difficult to match the current in one of the non-saturated regions with that in the other. When a difference occurs, the amount of heat generation increases as the current value in the unsaturated region decreases. Incidentally, setting the control amount to the temperature of both the switching elements Swp and Swn makes the feedback controller very complicated. For this reason, in this embodiment, the direction in which the amount of heat generation is increased is specified in advance by setting the gate application voltage of the high-potential side switching element Swp to be lower than that of the low-potential side switching element Swn.

  As shown in FIG. 2, the voltage applied to the gate of the switching element Swp is adopted as the operation amount of the temperature feedback control in this embodiment. As a result, as shown in FIG. 3E, when the output voltage of the temperature sensitive diode SD decreases (when the temperature detected by the temperature sensitive diode SD increases), the applied voltage is decreased. As a result, the current in the non-saturated region of the switching element Swp on the high potential side can be reduced, so that the discharge current can be reduced.

  Note that, as shown in FIG. 3, the high potential side switching element Swp is turned on / off a plurality of times while the low potential side switching element Swn is kept on. This is a setting for avoiding a decrease in current controllability such as an excessively large current flowing through the element Swp and the switching element Swn on the low potential side. That is, when the switching element Swn on the low potential side is turned on / off a plurality of times while the switching element Swp on the high potential side is kept on, the switching state of the switching element Swn on the low potential side is switched from the off state to the on state. The inventors have found that during the transition to the state, a phenomenon occurs in which the controllability of the current is lowered, for example, the gate applied voltage of the switching element Swp on the high potential side rises above the voltage VL. . In FIG. 3, after the abnormal-time discharge command dis is output, the low-potential side switching element Swn is turned on and then the high-potential side switching element Swp is turned on. This is a setting for avoiding the problem reliably.

  By the way, when the discharge control is to repeat the simultaneous ON state and the simultaneous OFF state of the high potential side switching element Swp and the low potential side switching element Swn a plurality of times, the ON time for one cycle of the ON / OFF period Inconvenience is likely to occur by variably setting this time ratio as the operation amount. That is, in this case, if the duty ratio is operated independently between the upper arm and the lower arm, the controllability of the heat generation amount is lowered. Further, if the on / off operation is not performed while communicating between the upper arm and the lower arm, the switching state of the high potential side switching element Swp is switched while the low potential side switching element Swn is in the on state. Setting is also difficult.

  In addition, the reason why the operation amount for controlling the heat generation amount grasped from the discharge current and the operation amount for temperature feedback control are set as different operation amounts is to simplify the controller.

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

  (1) In order to feedback control the temperature of the switching element Swp on the high potential side driven in the non-saturation region, the gate applied voltage was manipulated. Thereby, it can avoid suitably that the temperature of switching element Swp, Swn becomes high too much by discharge control.

  (2) By repeating the ON state and the OFF state of the high potential side switching element Swp driven in the non-saturation region a plurality of times while maintaining the low potential side switching device Swn driven in the saturation region in the ON state. The process which produces | generates the short circuit state of the both electrodes of the capacitor | condenser 16 in multiple times was performed. Thus, by performing the time ratio control, the amount of heat generated per unit time can be reduced. Also, by controlling the time ratio of the switching element Swp on the high potential side, it is possible to avoid a situation where the through current becomes large as in the case of controlling the ratio of the switching element Swn on the low potential side.

  (3) In order to control the heat generation amount of the switching element Swp on the high potential side, the time ratio of the on state with respect to one cycle of the on state and the off state was manipulated. Thereby, it is possible to reduce a margin in the feedback control. That is, in the feedback control, since a parameter for preventing the reliability of the switching elements Swp and Swn from being directly reduced is set as a direct control amount, a margin amount is required in order to ensure certainty of avoiding a decrease in reliability. It is easy to be demanded to enlarge. On the other hand, in the present embodiment, a unit based on basic control (open loop control) that is triggered by the abnormal-time discharge command dis by focusing on the current as the cause, not the temperature as a result of heat generation. When the calorific value per hour deviates from what is assumed, this can be dealt with quickly.

  Furthermore, the operation means is constructed by hardware means by setting the operation amount for controlling the amount of heat generated from the detected value of the discharge current and the operation amount for temperature feedback control to be different parameters. Even in this case, it is easy to simplify the configuration.

  (4) Without directly propagating the amount of discharge current detected as the emitter reference voltage of the switching element Swn on the low potential side to the switching element Swp side on the high potential side, the operation signal (heat generation) of the switching element Swp on the high potential side After generating the control operation amount Mh), it was output to the switching element Swp side on the high potential side. As a result, it is possible to perform continuous variable control of the on-time according to the amount of discharge current using a means for propagating a binary signal as the insulating means.

(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, the operation amount for controlling the heat generation amount grasped from the detected value of the discharge current and the operation amount for temperature feedback control are replaced with those in the first embodiment.

  FIG. 6 shows the configuration of the drive unit DU of the U-phase upper arm according to the present embodiment. In FIG. 6, members corresponding to those shown in FIG. 2 are given the same reference numerals for convenience.

  As shown, the output voltage of the temperature sensitive diode SD is applied to the non-inverting input terminal of the comparator 80. The carrier output from the oscillator 82 is applied to the inverting input terminal of the comparator 80. Thereby, the lower the output voltage of the temperature sensing diode SD (the higher the temperature detected by the temperature sensing diode SD), the smaller the on-time ratio of the on-off period of the switching element Swp.

  The discharge current is detected by a current sensor 84 configured to include a Hall element or the like, and the peak value of the current detected by the current sensor 84 is held by a peak hold circuit 86. The regulator 58 variably sets the gate application voltage in accordance with the voltage output from the peak hold circuit 86. Thereby, the applied voltage can be lowered as the discharge current detected by the current sensor 84 is larger.

(Other embodiments)
Each of the above embodiments may be modified as follows.
<About operation means>
The operation means is not limited to one in which the temperature feedback manipulated variable and the manipulated variable for controlling the calorific value obtained from the discharge current value are different parameters. For example, both operation amounts may be applied voltages. For example, the relationship between the detected temperature value and the applied voltage and the relationship between the discharge current value and the applied voltage are set, and the current in the non-saturation region is reduced among the pair of applied voltages determined from these relationships. It can be done by adopting the one to do.

Further, the operation means is not limited to the control amount that is the amount of heat generated from the discharge current value.
<Discharge current detection means for determining the amount of heat generated>
The discharge current detection means for grasping the heat generation amount is not limited to those exemplified in the above embodiments. For example, it may be a means for detecting the amount of voltage drop due to the shunt resistance of the current output from the output terminal of the switching element Swp.
<Discharge control means>
As the discharge control means, the short-circuit state of both electrodes of the capacitor 16 is repeated a plurality of times by repeating the ON state and the OFF state of the high potential side switching element Swp a plurality of times while maintaining the low potential side switching element Swn in the on state. The process is not limited to the process of generating. For example, a process of generating a short circuit state of both electrodes of the capacitor 16 a plurality of times by repeating the ON state and the OFF state of the low potential side switching element Swn a plurality of times while maintaining the switching element Swp on the high potential side in an on state. It may be what you do. However, even in this case, the gate applied voltage on the side where the ON state and the OFF state are repeated a plurality of times is set lower, and the operation is performed in the non-saturated region. Further, for example, a process of generating a short-circuit state of both electrodes of the capacitor 16 a plurality of times by repeating a simultaneous on state and a simultaneous off state of the high potential side switching element Swp and the low potential side switching element Swn a plurality of times. It may be what you do. Again, the gate applied voltage is adjusted so that one of the high-potential side switching element Swp and the low-potential side switching element Swn is operated in the non-saturation region, and the temperature of either one is set as the feedback control amount. Is desirable. However, at this time, it is desirable to switch the switching state of the operation in the non-saturation region while the operation in the saturation region is in the on state. Further, both the high-potential side switching element Swp and the low-potential side switching element Swn may be turned on only once in the discharge control period. Again, by adjusting the gate applied voltage to operate one of the high-potential side switching element Swp and the low-potential side switching element Swn in the non-saturated region, the temperature of one of the switching elements Swp and the low-potential side switching element Swn is set as the feedback control amount. To do.

  Further, the discharge control is not limited to using only the combination of the switching element Swp on the high potential side and the switching element Swn on the low potential side that applies a voltage to one phase of the motor generator 10. For example, the switching element Swp on the high potential side and the switching element Swn on the low potential side of each phase may be switched so as to be sequentially turned on.

  In addition, it is not restricted to what uses the discharge command dis at the time of abnormality produced | generated by the control apparatus 30 as a trigger. For example, a dedicated means for generating an abnormal-time discharge command dis in a high-voltage system may be provided and used as a trigger.

In addition, the discharge control performed by turning on both the high-potential side switching element Swp and the low-potential side switching element Swn is not limited to the time of abnormality, but is performed every time the relay SMR1 is switched to the open state. May be.
<About drive unit DU>
The U-phase drive unit DU is not limited to one provided with the charging switching element 42 and the discharging switching element 46 in a normal state, and the charging switching element 52 and the discharging switching element 54 in an abnormal state. For example, instead of sharing these, for the upper arm, the means for applying a voltage to the input terminal of the charging switching element may be different between the normal time and the abnormal time.

In addition, the switching element Sw # may not be provided with a function for forcibly turning off the switching element Sw # by exceeding the threshold current Ith.
<About DC / AC converter circuit>
As a DC / AC converter circuit (inverter IV) in which both the high-potential side switching element and the low-potential side switching element are turned on during the discharge control, the circuit between the rotating machine as the in-vehicle main unit and the high-voltage battery 12 is used. It is not limited to mediating power transfer. For example, the transfer of electric power between the high voltage battery 12 and a rotary machine other than the main machine such as a rotary machine provided in the air conditioner may be used.

<Other>
In each of the above embodiments, once the voltage drop amount of the shunt resistor 19 is held by the latch 60 in one discharge control period, it is fixed, but this is not a limitation. It is desirable that the latch holds the peak value (maximum value) of the voltage drop amount of the shunt resistor 19 and updates the holding value with each ON operation in repetition of the ON state and the OFF state.

  The high-potential side switching element Swp and the low-potential side switching element Swn used for discharge control are not limited to IGBTs, and may be field effect transistors such as power MOS field effect transistors.

  -It is not restricted to the structure by which the high voltage battery 12 is directly connected to the input terminal of the inverter IV. For example, a boost converter including a reactor, a switching element connected in parallel to the capacitor 16 via the reactor, a free wheel diode, and a capacitor connected to a series connection body of the switching element and the free wheel diode is connected to an inverter IV. May be connected to the input terminal. In this case, the capacitor connected to the output terminal of the boost converter and the capacitor 16 are subject to discharge control, and the voltage of the capacitor 16 is discharged through the freewheel diode as the voltage of the capacitor of the boost converter decreases. The Rukoto. Incidentally, when a switching element on the high potential side is connected in parallel to the freewheel diode, discharge control is performed by turning on both of the pair of switching elements connected between the output terminals of the boost converter. You can also.

  The vehicle is not limited to a hybrid vehicle, and may be, for example, an electric vehicle in which the energy resource stored for the in-vehicle main engine is only electric energy.

  The discharge control means is not limited to that mounted on the vehicle, but may be applied to, for example, a power conversion system that converts power from a DC power source provided in a house into AC. In this case, the abnormal time may be a case where an earthquake or the like is detected.

  DESCRIPTION OF SYMBOLS 10 ... Motor generator, 12 ... High voltage battery (one embodiment of DC power supply), 16 ... Capacitor, 30 ... Control device, Swp ... High potential side switching element, Swn ... Low potential side switching element Swn, DU ... Drive unit .

Claims (5)

A power conversion circuit comprising a series connection body of a switching element on the high potential side and a switching element on the low potential side and converting the power of the DC power supply to a predetermined value; a capacitor interposed between the power conversion circuit and the DC power supply; Applied to a power conversion system comprising an opening / closing means for opening / closing an electric path between the power conversion circuit and the capacitor and the DC power source, and switching on the high potential side under a situation where the opening / closing means is opened. Electric power provided with a discharge control means for controlling the discharge voltage of the capacitor to a specified voltage or less by performing a process of short-circuiting both electrodes of the capacitor by turning on both the element and the switching element on the low potential side In the discharge control device of the conversion system,
The high-potential side switching element and the low-potential side switching element are voltage-controlled switching elements,
The discharge control means is configured to detect either one of the high-potential side switching element and the low-potential side switching element so that a current in a non-saturated region is smaller than the other one. The voltage applied to the conduction control terminal of each of the other switching elements is set,
Temperature detecting means for detecting the temperature of any one of the switching elements;
Discharge control for a power conversion system comprising: operating means for operating a voltage application mode to a conduction control terminal of any one of the switching elements so as to feedback control the temperature detected by the temperature detecting means. apparatus.   2. The discharge control device for a power conversion system according to claim 1, wherein the operation unit sets a value of a voltage applied to a conduction control terminal of one of the switching elements as an operation amount of the feedback control.   The discharge control means switches either one of the switching states while the other is in the on state, and repeats both the on state and the off state a plurality of times. The discharge control device for a power conversion system according to claim 1 or 2, wherein a process of generating a short circuit state of the electrode a plurality of times is performed.   The operation means uses the value of the voltage applied to the conduction control terminal of one of the switching elements as the operation amount of the feedback control, and receives the detected value of the discharge current of the capacitor as an input. The apparatus further comprises means for manipulating a time ratio of the on-state of one of the switching elements to the on-state for one cycle in order to control the heat generation amount of the one of the switching elements. Item 5. A discharge control device for a power conversion system according to Item 3. The discharge control means switches either one of the switching states while the other is in the on state, and repeats both the on state and the off state a plurality of times. The process of generating the short circuit state of the electrode multiple times,
The operation means uses a time ratio, which is a ratio of time of the on-state to the cycle of the on-state and the off-state of any one of the switching elements, as the operation amount of the feedback control. The discharge control apparatus of the power conversion system of description.

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