JP4862616B2 - Power converter - Google Patents

Description

  The present invention eliminates the need to arrange a temperature sensitive element such as a thermocouple near the switching element when measuring the element temperature of a power conversion apparatus including a switching element such as IGBT (Insulated Gate Bipolar Transistor). The present invention relates to a technology for downsizing.

As a power converter, there is generally an inverter device that connects a DC voltage source and a load. The switching element made of a semiconductor provided in the inverter device is vulnerable to high temperatures, and the invention for detecting the temperature of the switching element so as not to destroy the inverter device due to a temperature rise has been conventionally as described in, for example, Patent Document 1 and Patent Document 2 Things are known.
The IGBT gate drive circuit described in Patent Document 1 applies a high-frequency AC voltage between the gate and emitter terminals of the IGBT when the switching element is off, and a current that flows to the gate terminal of the IGBT due to this AC voltage. Based on the above, the capacitance of the IGBT in operation is measured. Since this capacitance has a correlation with temperature, the element temperature of the IGBT is measured by detecting the capacitance.
In the on-chip temperature detection device described in Patent Document 2, when the switching element is turned off, a small constant current that does not turn on the switching element flows through the base, and the forward voltage of the diode between the base and the emitter terminal is detected. The device temperature is detected using the temperature characteristics.
JP-A-5-56553 JP 2002-289856 A

  However, the above-described conventional temperature detecting device has the following problems. That is, the temperature of the switching element can be measured only during a period in which the element is off so as not to affect the normal driving of the switching element. As a result, a sufficient measurement period cannot be ensured at the time of large output of the power conversion device with a long on time and a short off time. Therefore, in the prior art, the temperature of the switching element must be measured at the time of a small output of the power conversion device, and the temperature of the switching element must be relied upon estimation at the time of a large output. As a result, even when the temperature of the switching element is high and the output is high, there is a high need for accurate temperature measurement, but accurate temperature measurement cannot be performed.

  In addition, in a power conversion device such as an inverter device, a switch is operated by applying a measurement signal to a switching element to prevent the power supply from being short-circuited. The arm must be turned off. At this time, a switching loss occurs when the arm is turned on / off.

  An object of this invention is to propose the power converter device which can detect element temperature correctly irrespective of the magnitude of the output of a power converter device.

For this purpose, the power converter according to the invention is as described in claim 1,
A switching element for electrically connecting a DC voltage source and a load; and an element driving circuit for supplying a gate signal for on / off operation to the switching element, and generating a pulsed voltage by turning on and off the switching element. In the power converter that controls the drive current of the load by
When the element driving circuit applies the gate signal to the gate terminal of the switching element to turn on the switching element, the voltage value of the gate signal and the current value of the element current flowing from the switching element to the load are The temperature state of the switching element is determined from a map or a calculation formula that defines the above relationship.

According to the power conversion device of the present invention, accurate temperature measurement is possible regardless of the length of the off period of the switching element. Therefore, the element temperature can be accurately detected even at the time of a large output of the power conversion device having a short off period, and element protection can be appropriately achieved.
Further, it is not necessary to turn off the arm opposite to the arm whose temperature is to be measured, and the switching loss can be reduced.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 is a circuit configuration diagram showing an overall outline of a power converter, a voltage source, and a load according to an embodiment of the present invention. Six switching elements 41 to 46 are electrically connected between the positive terminal and the negative terminal of the DC voltage source 10. The switching elements 21 to 26 are IGBTs, and the connection and arrangement of these switching elements 41 to 46 are the same as those of a known inverter device. A three-phase AC motor 30 as a load is electrically connected to the switching elements 41 to 46.
An element drive circuit 20 for turning on and off the switching elements 41 to 46 is connected to the gate terminals of the switching elements 41 to 46. Switching elements 41 to 46 and element driving circuit 20 constitute a power conversion device.

  The voltage source 10 is a power source for the three-phase AC motor 30. As shown in FIG. 1, the switching elements 41 to 46 electrically connect the voltage source 10 and the three-phase AC motor 30. The element driving circuit 20 gives a gate signal for on / off operation to the gate terminals of the switching elements 41 to 46 to turn on and off the switching elements 41 to 46. As a result, a pulse voltage is generated to control the drive current of the three-phase AC motor 30.

  FIG. 2 is a block diagram showing a configuration of the element driving circuit 20. Since the element drive circuit 20 is common to the switching elements 41 to 46, only one of the switching elements 41 to 46 is shown in FIG. 2 as a representative, and only the switching element 41 is representative in order to avoid duplication of explanation. Show.

  The drive signal generator 201 outputs a command signal sig_PWM for pulse width modulation control to the pulse operation gate drive circuit 202, and outputs a command signal sig_test1 for temperature detection of the switching elements 41 to 46 to the temperature detection gate drive circuit. It outputs to 203. The command signal sig_PWM usually realizes the output of the target power converter. However, during the element protection mode described later, the output of the power conversion device is limited to be smaller than the target.

  The drive signal generator 201 defines an element temperature detection period α, which will be described later, and outputs sig_search = 1 to the gate drive circuit selection circuit 204 during the element temperature detection period α, and gates sig_search = 0 during periods other than the period α. Output to the drive circuit selection circuit 204.

  The pulse operation gate drive circuit 202 outputs a drive gate signal to the gate terminal of the switching element 41 based on the command signal sig_PWM. Based on the command signal sig_test1, the temperature detection gate drive circuit 203 outputs a detection gate signal to the gate terminal of the switching element 41 and the element temperature determination unit 208.

  Based on the received signal sig_search, the gate drive circuit selection circuit 204 outputs a signal sig_select for selecting one of the pulse operation gate drive circuit 202 or the temperature detection gate drive circuit 203 to the selector 205. Specifically, when sig_search = 1, the switching signal sig_select = 1 is output. When sig_search = 0, the switching signal sig_select = 0 is output.

The selector 205 switches the gate signal for driving or detection. Specifically, when the received switching signal sig_select = 1, the temperature detection gate drive circuit 203 is connected to the gate terminal of the switching element 41. When the switching signal sig_select = 0, the pulse operation gate drive circuit 202 is connected to the gate terminal of the switching element 41.
While the selector 205 selects the aforementioned pulse operation gate drive circuit 202, the drive gate signal from the pulse operation gate drive circuit 202 is input to the switching element 41. During this time, the switching element 41 generates a pulse voltage for executing the pulse width modulation control. In contrast, while the selector 205 selects the above-described temperature detection gate drive circuit 203, a detection gate signal from the temperature detection gate drive circuit 203 is input to the switching element 41. These pulse operation gate drive circuit 202, temperature detection gate drive circuit 203 and selector 205 constitute a gate drive circuit unit 206.
As described above, since the selector 205 switches the gate signal from the detection gate signal to the drive gate signal, the gate drive circuit unit 206 can continuously output gate signals having different waveforms.

  The element current value detector 207 detects a current flowing from the switching element 41 to the motor 30. Specifically, it is checked whether the element current of the switching element 41 flowing through the collector terminal of the switching element 41 has reached a predetermined value i_sw. If it has reached, the result is output to the element temperature determination unit 208. The predetermined value i_sw is a current value for determining that the collector current is flowing when the switching element is turned on from off. The element temperature determination unit 208 monitors the gate voltage Vg, and reads the gate voltage when the predetermined current value i_sw is reached, thereby measuring the gate-on voltage value Vg1 at which the switching element is turned on. The element temperature determination unit 208 determines the temperature of the switching element 41 from the characteristic that the gate-on voltage value Vg1 varies with the element temperature. If it is determined that the area is in the danger of damage, sig_result = 0 is output to the drive signal generator 201. On the other hand, if it is determined that the element temperature is in the safe region, sig_result = 1 is output to the drive signal generator 201.

While receiving the sig_result = 1 indicating the safety region, the drive signal generator 201 sets the above-described command signal sig_PWM as usual corresponding to the target output of the power converter. Then, the switching element 41 is operated to turn on continuously until the element rating after the end of the element temperature detection period α, which will be described later with reference to FIG.
On the other hand, while receiving sig_result = 0 indicating the damage risk region, the above-described command signal sig_PWM is set to the element protection mode for limiting the output of the power converter. Thereby, the temperature rise of the switching element 41 can be suppressed.

FIG. 3 shows a control flow for determining the temperature of the switching element 41.
First, in step S1, it is determined whether the element current flowing through the collector terminal has reached a predetermined value i_sw. When the element current reaches a predetermined value i_sw, the process proceeds to the next step S2. In step S2, the gate voltage Vg when the element current reaches the predetermined value i_sw is read, and this read value is used as the gate-on voltage Vg1. In the next step S3, the gate-on voltage Vg1 is compared with a threshold value Vgth for determining whether or not the element temperature is higher than the voltage value in the overtemperature state. As a result of the comparison, if it is determined that Vg1 <Vgth (YES), since the element temperature is high and the device is in a damage risk region, sig_result = 0 is output and this control flow is finished. On the other hand, if it is determined that Vg1 <Vgth is not satisfied (NO), since the element temperature is low and in the safe region, sig_result = 1 is output and this control flow ends. As described above, according to the present embodiment, it is possible to accurately obtain the element temperature from the gate-on voltage value whether it is in the danger of damage region or in the safety region.

In other words, the gate-on voltage Vg1 at which the current value of the element current becomes the predetermined value i_sw varies depending on the temperature of the switching element. That is, there is a map or calculation formula that defines the relationship between the voltage value of the gate signal and the current value of the element current for each temperature. A semiconductor element used for switching such as an IGBT has a characteristic that a current value with respect to a certain gate voltage, for example, a voltage Vg, increases as the temperature rises. From this characteristic, the above map or calculation formula can be obtained.
In the present embodiment, the temperature state of the switching element is determined from the threshold value Vgth obtained by simplifying these maps or calculation formulas. If these maps or calculation formulas are obtained by experiments and stored in the element driving circuit 20, and the maps or calculation formulas are directly referred to, the temperatures of the switching elements 41 to 46 can be obtained.

  FIG. 4 is a graph illustrating a driving gate signal output from the pulse operation gate drive circuit 202 to the gate terminal of the switching element 41. The pulse operation gate drive circuit 202 has a configuration suitable for generating a rectangular wave for pulse operation as shown in FIG. 4 in accordance with a required on / off time.

  FIG. 5 is a graph showing a detection gate signal output from the temperature detection gate drive circuit 203 to the gate terminal of the switching element 41 and the element temperature determination unit 208. As shown in FIG. 5, the temperature detection gate drive circuit 203 has a configuration suitable for creating a waveform that gradually increases from 0 when turned on from off.

  By dividing the gate driving circuit 202 and the gate driving circuit 203 into the gate driving circuit 202 and the gate driving circuit 203 by dividing the means for outputting the gate signal for pulse operation and the means for outputting the gate signal for detection as in this embodiment, different signals are output by the same means. This can be simplified compared to the output configuration.

  The drive signal generator 201 outputs the command signal sig_test1 and the command signal sig_PWM so that the frequency and phase of the detection gate signal shown in FIG. 5 and the drive gate signal shown in FIG. 4 are synchronized. When the detection gate signal shown in FIG. 5 gradually increases and reaches the gate-on voltage Vg1, the signal sig_search is output. For this reason, the gate signal of the switching element 41 is as shown in FIG. 6 in which the gate signals of FIGS. 5 and 4 are made continuous.

FIG. 6 shows the voltage waveform of the gate signal output from the gate drive circuit unit 206. In FIG. 6, α is an element temperature detection period. The gate signal in the element temperature detection period α is a gate signal from the temperature detection gate drive circuit 203, and the gate voltage Vg gradually increases with time. Β is a pulse operation period. The gate signal in the period β is a gate signal from the pulse operation gate drive circuit 202, and the gate voltage Vg is sufficiently high. In the period β, the switching element 41 is turned on, and the switching element 41 performs a pulse operation so as to generate one pulse voltage.
When the pulse operation is completed and the switching element 41 is turned off from on, the switching signal sig_select is output during the off state, and the selector 205 is switched from the pulse operation gate drive circuit 202 to the temperature detection gate drive circuit 203. In preparation for the next element temperature detection.

  As shown in FIG. 6, the gate voltage Vg of the gate signal has a waveform that gradually increases in the period α, and is the gate-on voltage Vg1 instantaneously in the period α, and the gate voltage Vg is instantaneously shifted from the period α to the period β. The waveform increases rapidly as a rectangular wave. The above is a series of operations in element temperature detection.

  When the modulation factor is 0.9 in the power conversion device that performs PWM driving with a carrier frequency of 10 [kHz], the period during which the switching element is on is 90 [μs]. Since dead time and the like are added to this, the period during which the switching element is turned off is less than 10 [μs]. With the conventional element temperature detection means shown in Patent Documents 1 and 2, sufficient measurement time cannot be secured.

However, according to the present embodiment, the element temperature can be detected when the switching elements 41 to 46 shift from the off state to the on state, and it is not necessary to provide a sufficient period for temperature measurement as in the conventional example. . Therefore, an accurate temperature measurement can be performed during the high output of the power converter without impairing the normal pulse width modulation control.
Further, it is not necessary to turn off the arm opposite to the arm whose temperature is to be measured, and switching loss can be reduced.

  Although not shown in the figure, the device temperature is detected if the gate voltage value at the start of the device temperature detection period α is larger than the gate 0 and smaller than the gate threshold value Vgth and the gate signal waveform is trapezoidal. The time required for this can be further shortened.

  Although not shown, a characteristic diagram showing the relationship between the element temperature and the gate-on voltage value stored in advance in step S3 in the flowchart of FIG. 3 described above, and the gate-on voltage value Vg1 measured in step S2 , And the accurate element temperature may be detected.

In the power conversion device that performs the pulse width modulation control, as shown in FIG. 7, it is preferable to generate the signal sig_search by defining the element temperature detection period α based on the triangular wave comparison method and the modulation rate.
In FIG. 7, γ of the horizontal straight line intersecting with the triangular wave is a pulse width modulation control (PWM) modulation rate, and is set by known pulse width modulation control. Then, the element temperature detection modulation factor δ is set on the triangular wave having γ by being separated from the PWM modulation factor γ by a predetermined distance.

As shown in FIG. 7, the predetermined distance between γ and δ defines the element temperature detection period α.
In the element temperature detection period α from the modulation factor δ to the modulation factor γ, the signal sig_search = 1 is output to select the temperature detection gate drive circuit 203, and the signal sig_search = 0 is output during the time other than the above. Thus, the pulse operation gate drive circuit 202 is selected.

  According to the above-described triangular wave comparison method and the generation of the signal sig_search based on the modulation rate, the signal sig_search can be easily generated, so the start time of the element temperature detection period α and the length of the period α are preferably realized. This makes it easy to manage the element temperature detection period α.

Although it may be a fixed value, the predetermined distance and the temperature of the switching element in the previous pulse operation may be defined, and the predetermined distance between γ and δ may be feedback controlled. For example, initially, a predetermined distance between γ and δ is set as an initial value. When it is determined in the previous pulse operation that the element temperature is in the risk of damage, when the obtained element temperature increases, the predetermined distance between γ and δ is made shorter than the previous value (initial value). When it is determined that the element temperature obtained in the previous pulse operation has returned to a low state, the predetermined distance between γ and δ is returned to the initial value.

  Thus, by setting the element temperature detection modulation factor by feedback control based on the previously set element temperature detection modulation factor δ and the previously obtained switching element temperature, the previous element temperature detection period α is set to the next period α. Therefore, the time required for measuring the gate-on voltage value Vg1 can be optimized, and the element temperature can be detected appropriately. And it becomes possible to prescribe | regulate the element temperature detection period (alpha) appropriately, can reduce an excess element temperature detection period, and can reduce a power loss.

  Next, another embodiment for determining the element temperature will be described with reference to FIGS. Note that a description of portions common to the above-described embodiments is omitted.

  The configuration of the element driving circuit 20 in this embodiment is the same as the block diagram shown in FIG. 2, but the gate driving circuit unit 206 in FIG. 2 is replaced with a gate driving circuit unit 209 shown in FIG. This embodiment is characterized in that the gate drive circuit unit 209 does not have a selector, and the pulse operation gate drive circuit 202 and the temperature detection gate drive circuit 203 are connected in parallel. A resistor R1 is interposed between the pulse operation gate drive circuit 202 and the switching element. A resistor R2 is interposed between the temperature detection gate drive circuit 203 and the switching element.

  FIG. 9 is a graph showing the voltage waveform of the gate signal output from the gate drive circuit unit 209. Because of the parallel connection as shown in FIG. 8, the element temperature detection period α and the pulse operation period β are realized by superimposing the drive gate signal and the temperature detection gate signal.

  According to this embodiment, the number of selectors can be reduced and the gate drive circuit unit can be simplified.

  Next, another embodiment for determining the element temperature will be described with reference to FIG. Yet another embodiment is characterized in that one component is 205 instead of the two components 202 and 203 described above. Note that a description of portions common to the above-described embodiments is omitted.

  The configuration of the element driving circuit 20 in this embodiment is the same as that of the block diagram shown in FIG. 2, but the gate driving circuit unit 206 in FIG. 2 is replaced with a gate driving circuit unit 210 shown in FIG. The gate drive circuit unit 210 includes a gate drive circuit 211 that receives the command signal sig_PWM and outputs a gate signal, and a selector 212 that receives the switching signal sig_select = 0 and selects the resistor R3 or the resistor R4. .

The gate drive circuit 211 outputs a driving gate signal to the selector 212 in the same manner as the pulse operation gate driving circuit 202 described above.
The selector 212 includes a resistor R3 and a resistor R4 connected in parallel. The resistance value of the resistor R3 is larger than the resistance value of the resistor R4. The received driving gate signal is output to the gate terminal of the switching element 41 via the resistor R3 or the resistor R4.

  The speed at which the voltage value of the gate signal acts on the switching element has a characteristic that it has a time constant determined by the capacitance of the switching element and the gate resistance value. As shown in FIG. 10, by selecting two resistors R3 and R4 having different resistance values and connecting them to the gate resistance value of the switching element 41, the resistors R3 and R4 are elements that can change the speed of the gate signal. Works. Then, two states having different gate resistance values can be realized, and a function similar to that of the gate drive circuit unit 206 shown in FIG. 2 can be obtained.

  According to the present embodiment, it becomes possible to output a gate signal for driving and a gate signal for temperature detection by one gate driving circuit, thereby further simplifying the gate driving circuit unit and reducing the cost. it can.

  Next, still another embodiment for determining the element temperature will be described with reference to FIG. Note that a description of portions common to the above-described embodiments is omitted.

  The configuration of the element driving circuit 20 in this embodiment is shown in the block diagram of FIG. This basic configuration is common to the block diagram shown in FIG. A function for outputting an end signal sig_end to the gate drive circuit 204 when the element temperature determination is completed is added to the element temperature determination unit 204 in FIG. Even when sig_search = 1 is received, the gate drive circuit 204 outputs a switching signal sig_select = 0 on condition that the end signal sig_end is received.

  According to the present embodiment, when the time required for the determination of the element temperature is short, it is possible to reduce the element temperature detection period α that is excessive after the element determination is completed, thereby preventing power loss during the excess time. can do. In particular, this embodiment is useful in defining the element temperature detection period α based on the above-described triangular wave comparison method and modulation factor.

  Next, another embodiment for determining the element temperature will be described with reference to FIGS. Note that description of parts common to the above-described embodiment, such as the configuration of the element driving circuit 20 and the waveform of the driving gate signal, is omitted.

FIG. 12 shows a control flow for determining the temperature of the switching element 41, which replaces the control flow shown in FIG.
First, in step S11, the temperature detection gate drive circuit 203 (see FIG. 2) outputs the determination gate voltage Vth to the gate terminal of the switching element 41. This determination gate voltage Vth is a rectangular wave as shown in FIG. 13, and one rectangular wave is an extremely short time. The determination gate voltage Vth is a value for determining whether the element temperature is in a damage risk area or a safety area. The determination gate voltage Vth replaces the waveform gradually increasing from 0 shown in FIG.

  In the next step S12, the element current value detector 207 (see FIG. 2) measures the current i_c at the collector terminal of the switching element 41. In the next step S13, the measured value i_c is compared with a threshold value ith for determining whether or not the element temperature is high. As a result of the comparison, if it is determined that i_c> ith (YES), the element temperature is high and the device is in a damage risk area, so sig_result = 0 is output and this control flow is finished. On the other hand, if it is determined that i_c> ith is not satisfied (NO), since the element temperature is low and is in the safe region, sig_result = 1 is output and this control flow is finished.

  The current value i_c of the device current when the gate signal is fixed to a certain voltage value Vth varies depending on the temperature of the switching device. That is, as described above with reference to FIG. 3, there is a map or calculation formula that defines the relationship between the voltage value of the gate signal and the current value of the element current for each temperature. In the present embodiment, the temperature state of the switching element is determined from a threshold value ith obtained by simplifying these maps or calculation formulas. By directly referring to these maps or calculation formulas, the temperatures themselves of the switching elements 41 to 46 can be obtained.

If the gate voltage of the switching element is constant, according to the present embodiment, which focuses on the temperature characteristic that the current of the collector terminal changes according to the temperature of the switching element, it is in a damage risk area or in a safety area. Alternatively, the element temperature can be accurately obtained based on the temperature characteristics of the collector terminal current i_c.
Further, according to the present embodiment, the current i_c at the collector terminal is very small, and the time required to detect the element temperature is extremely short, so that power loss due to measurement does not become a problem.

  This embodiment can also be implemented in a configuration in which the gate drive circuits described above with reference to FIG. 8 are connected in parallel.

By the way, according to each of the embodiments described above, when the element driving circuit 20 gives a gate signal to turn on the switching elements 41 to 46 from the OFF state, the voltage value Vg of the gate signal and the switching elements 41 to 46 are changed by the load. The temperature state of the switching element is determined from the relationship with the current value i_sw of the element current flowing to a certain motor 30. That is, the element drive circuit 20 uses the element current value detector 207 that detects the current flowing from the switching elements 41 to 46 to the motor 30 and the voltage value Vg of the gate signal when the switching elements 41 to 46 are turned on. And an element temperature determination unit 208 that sets the gate signal voltage value Vg as the gate-on voltage value Vg1 when the element current value detector 207 detects the element current i_sw. The element temperature determination unit 208 includes a gate-on voltage value. Since the temperatures of the switching elements 41 to 46 are obtained based on Vg1,
Regardless of the length of the OFF period of the switching element, accurate temperature measurement is possible. Therefore, the element temperature can be accurately detected even at the time of a large output of the power conversion device having a short off period, and element protection can be appropriately achieved.

Further, as shown in FIG. 6, the element driving circuit 20 gradually increases the voltage value of the gate signal when the switching element 41 is turned on, and rapidly increases the voltage value of the gate signal after the switching element is turned on.
The element temperature can be measured at the time of normal pulse voltage generation that is turned on from off, and the generation of the pulse voltage is not hindered. Further, it is not necessary to turn off the switching element once after detecting the element temperature, and the time required for detecting the element temperature can be minimized.

  In addition, if the waveform of the voltage value of the gate signal in the gradual increase is made trapezoidal, the time until the voltage value Vg of the gate signal reaches the gate-on voltage value Vg1 can be shortened, which is necessary for detecting the element temperature. Time can be further shortened.

In this embodiment, the element driving circuit 20 includes a temperature detection gate driving circuit 203 that gradually increases the voltage value of the gate signal, and a pulse operation gate driving circuit 202 that rapidly increases the voltage value of the gate signal with a rectangular wave. Because it contains
The method for controlling the gate signal can be simplified as compared with the configuration in which two different gate signals are output by the same gate driving circuit.

In this embodiment, the element drive circuit 20 includes a selector 205 that switches the gate signal from one of the temperature detection gate drive circuit 203 and the pulse operation gate drive circuit 202 to the other. The selector 205 generates the drive signal. Since the temperature detection gate drive circuit 203 is selected during the element temperature detection period α defined by the device 201,
A configuration having the two drive circuits 202 and 203 as described above can be suitably realized.

  Further, as shown in FIG. 7, in this embodiment, the drive signal generator 201 of the element drive circuit 20 executes the pulse width modulation control based on the pulse width modulation control modulation factor γ and the triangular wave comparison method, and this drive signal generator 201 sets the element temperature detection modulation factor δ, defines the element temperature detection period α based on the element temperature detection modulation factor δ, the pulse width modulation control modulation factor γ, and the triangular wave comparison method, and the signal sig_search = 1 Therefore, the element temperature detection period α can be suitably defined.

In the embodiment shown in FIG. 7, as a means for setting the element temperature detection modulation factor δ, the element temperature detection is performed based on the predetermined distance between γ and δ corresponding to the previous element temperature detection period α and the previously obtained switching element temperature. From setting the modulation factor δ for
It is possible to appropriately define the element temperature detection period α, and it is possible to quickly switch to the pulse operation gate drive circuit 202 to reduce an excessive element temperature detection period and reduce power loss.

In the embodiment shown in FIG. 8, the temperature detection gate drive circuit 203 and the pulse operation gate drive circuit 202 are connected in parallel to the gate terminals of the switching elements 41 to 46.
The means for separating and outputting the gate signal for temperature detection and the gate signal for pulse operation, such as the detector 205, can be omitted, and the cost can be reduced.

Further, the embodiment shown in FIG. 10 includes one gate drive circuit 211 that outputs a gate signal, and a selector 212 that selects one of the two paths and transmits the output gate signal. Since each has a resistance R3 and a resistance R4, which are elements that make the speed of the gate signal different from each other,
A gate signal as shown in FIG. 6 can be generated only by adding an element to one gate driving circuit, and further simplification and cost reduction of the element driving circuit can be achieved.

  In the embodiment shown in FIG. 11, when the element temperature determination unit 208, which is a means for measuring the gate-on voltage value, detects the element current, the element temperature detection end signal sig_end is selected via the gate drive circuit selection circuit 204. 205, the selector 205 switches the gate signal from the temperature detection gate drive circuit 203 to the pulse operation gate drive circuit 202 after receiving the end signal sig_end even in the element temperature detection period α. It is possible to reduce the element temperature detection period α that becomes excessive after the element determination is completed, and to prevent power loss during the excess time.

12 and 13, the element drive circuit 20 includes a temperature detection gate drive circuit 203 that sets a gate signal when the switching elements 41 to 46 are turned on from a predetermined voltage value Vth, An element current value detector 207 for detecting a current value i_c flowing from the switching elements 41 to 46 to the motor 30 at a predetermined voltage value Vth;
Since an element temperature determination unit 208 for determining the temperature of the switching elements 41 to 46 based on the current value i_c is provided,
Regardless of the length of the off period of the switching elements 41 to 46, accurate temperature measurement is possible. Therefore, the element temperature can be accurately detected even at the time of a large output of the power conversion device having a short off period, and element protection can be appropriately achieved.
Further, it is not necessary to turn off the arm opposite to the arm whose temperature is to be measured, and the switching loss can be reduced.

  The above description is merely an example of the present invention, and the present invention can be variously modified without departing from the spirit of the present invention. The claimed switching elements include semiconductor elements such as GTO thyristors and MOS FETs in addition to IGBTs.

1 is a circuit configuration diagram showing an overall outline of a power conversion device, a voltage source, and a load according to an embodiment of the present invention. It is a block diagram which shows the structure of the element drive circuit of the Example. The control flow which judges the temperature of the switching element of the Example is shown. It is a graph which shows the gate signal for a drive which the gate drive circuit for pulse operation outputs to the gate terminal of a switching element. It is a graph which shows the gate signal for a detection which a gate drive circuit for temperature detection outputs to the gate terminal of a switching element, and an element temperature judgment device. It is a graph which shows the voltage waveform of the gate signal which a gate drive circuit part outputs. It is explanatory drawing which shows the function which prescribes | regulates an element temperature detection period based on a triangular wave comparison method and a modulation factor. It is a block diagram which shows the structure of the element drive circuit which becomes another Example. It is a graph which shows the voltage value of the gate signal in the Example. It is a block diagram which shows the structure of the element drive circuit which becomes another Example. It is a block diagram which shows the structure of the element drive circuit which becomes another Example. The control flow which judges the temperature of the switching element which becomes another Example is shown. It is a graph which shows the voltage waveform of the gate signal which the gate drive circuit part of the Example outputs.

Explanation of symbols

10 DC voltage source
20 element drive circuit
201 Drive signal generator
202 Gate drive circuit for pulse operation
203 Gate drive circuit for temperature detection
204 Gate drive circuit selection circuit
205 selector
206 Gate drive circuit
207 Element current detector
208 Element temperature detector
209 210 Gate drive circuit
211 Gate drive circuit
212 selector
30 motor
41 42 43 44 45 46 Switching element

Claims (12)

A switching element for electrically connecting a DC voltage source and a load; and an element driving circuit for supplying a gate signal for on / off operation to the switching element, and generating a pulsed voltage by turning on and off the switching element. In the power converter that controls the drive current of the load by
When the element driving circuit applies the gate signal to the gate terminal of the switching element to turn on the switching element, the voltage value of the gate signal and the current value of the element current flowing from the switching element to the load are A power conversion device configured to determine a temperature state of the switching element from a map or a calculation formula that defines the relationship. The power conversion device according to claim 1,
An element current value detecting means for detecting an element current flowing from the switching element to the load;
The gate-on voltage is monitored by monitoring the voltage value of the gate signal when the switching element is turned on from off, and the gate-current voltage value when the element current value detecting means detects the element current. A value measuring means;
A power conversion device comprising element temperature determination means for determining the temperature of the switching element based on the gate-on voltage value. The power conversion device according to claim 2,
The element drive circuit gradually increases the voltage value of the gate signal when the switching element is turned on from off, and rapidly increases the voltage value of the gate signal after the switching element is turned on. The power conversion device according to claim 3,
The power converter according to claim 1, wherein the waveform of the voltage value of the gate signal in the gradual increase is trapezoidal. In the power converter device according to claim 3 or 4,
The element drive circuit includes a temperature detection gate drive circuit that gradually increases the voltage value of the gate signal, and a pulse operation gate drive circuit that rapidly increases the voltage value of the gate signal with a rectangular wave. Power conversion device. The power conversion device according to claim 5,
The element driving circuit defines an element temperature detection period that is a period for gradually increasing the voltage value of the gate signal,
A selector that switches a gate signal from one of the temperature detection gate drive circuit and the pulse operation gate drive circuit to the other;
The selector selects the temperature detection gate drive circuit during the element temperature detection period. The power conversion device according to claim 6, wherein
The element driving circuit comprises pulse width modulation control means for controlling the pulse voltage based on a modulation factor for pulse width modulation control and a triangular wave comparison method to execute pulse width modulation control,
The pulse width modulation control means comprises element temperature detection modulation factor setting means for setting the element temperature detection modulation factor,
A power conversion apparatus characterized in that the element temperature detection period is defined based on the modulation factor for element temperature detection, the modulation factor for pulse width modulation control, and the triangular wave comparison method. The power conversion device according to claim 7,
The element temperature detection modulation factor setting means sets the element temperature detection modulation factor by feedback control based on the previously set element temperature detection modulation factor and the previously determined switching element temperature. The power conversion device according to claim 6, wherein
The power conversion apparatus, wherein the temperature detection gate drive circuit and the pulse operation gate drive circuit are connected in parallel to a gate terminal of the switching element. In the power converter device according to claim 3 or 4,
The element driving circuit includes a gate driving circuit that outputs a gate signal, and a selector that selects one of two paths and transmits the output gate signal.
An element for changing the speed of the gate signal from each other is provided in each of the paths. The power conversion device according to claim 6, wherein
The gate-on voltage value measuring means outputs an element temperature detection end signal to the selector when detecting the element current,
The power converter according to claim 1, wherein the selector switches the gate signal from the temperature detection gate drive circuit to the pulse operation gate drive circuit after receiving the end signal even in the element temperature detection period. The power conversion device according to claim 1,
Temperature detection gate driving means for turning the switching element on from the off state using the gate signal as a predetermined voltage value;
Element current value detecting means for detecting a current value of an element current flowing from the switching element to the load at a gate voltage of the predetermined voltage value;
A power conversion device comprising element temperature determination means for determining the temperature of the switching element based on the current value.

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