JP5422909B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that includes a switching element such as an IGBT (Insulated Gate Bipolar Transistor) and converts a voltage from a voltage source to supply power to the load, and when the power conversion device supplies a large output to the load Even so, the present invention relates to a technique for accurately determining the state of the switching element.

As a power converter, there is generally an inverter device that connects a DC voltage source and a load. A switching element made of a semiconductor provided in an inverter device is vulnerable to high temperatures, and an invention for determining the state of a switching element so that the switching element does not break down due to a rise in temperature is conventionally known, for example, as described in Patent Document 1. ing.
The technique described in Patent Document 1 is provided with a high-frequency voltage generation mechanism in a switching element driving circuit that outputs a gate signal for turning on / off a switching element to a control terminal of the switching element. This high-frequency voltage generation mechanism measures the element parasitic capacitance by applying a high-frequency drive signal to the switching element, and estimates the temperature of the switching element from the measurement result.
JP-A-5-56553

  However, the technique described in Patent Document 1 as described above causes problems as described below. That is, since a high-frequency voltage for measurement is applied to the switching element, measurement can be performed only in the off period in which the switching element is idle so as not to affect the normal driving of the switching element. However, sufficient measurement cannot be performed in the off period where the element time is very small, such as during high output in PWM drive. Therefore, it is difficult to measure the switching element temperature when the element temperature is considered to be the highest, and when the power converter has a high output.

  An object of the present invention is to propose a power conversion device that can accurately determine the state of a switching element even when the power conversion device has a large output and that is not accompanied by a switching loss.

For this purpose, the power conversion device according to the present invention comprises:
A switching element for electrically connecting a voltage source and a load; and a switching element operating means 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 for supplying power from the voltage source to the load by
The switching element operating means includes a switching element driving circuit that outputs the gate signal to a control terminal of the switching element;
A switching element state determining means for determining the state of the switching element based on the magnitude of the voltage in the voltage parallel period of the control terminal when the switching element operates from off to on to generate a pulsed voltage is provided. It is a thing.

  According to the power conversion device of the present invention, since the state of the switching element is determined based on the magnitude of the voltage in the voltage parallel period of the control terminal when operating from off to on to generate the pulse voltage, It is possible to accurately grasp the switching element temperature at the time of a large output of the power conversion device in which the temperature becomes the highest. Therefore, the switching element can be effectively protected.

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 41 to 46 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.
The switching element operating means 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 switching element operating means 20 constitute a power converter.

  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 switching element operating means 20 gives a gate signal for on / off operation to the control terminals of the switching elements 41 to 46 to turn on and off the switching elements 41 to 46. Thereby, a pulse voltage is generated and electric power is supplied from the voltage source 10 to the three-phase AC motor 30. The switching element operating unit 20 controls the drive current of the three-phase AC motor 30 by controlling the ratio of the on-time and the off-time, that is, the period (width) of the pulse voltage, for the switching elements 41 to 46. Execute.

  FIG. 2 is a functional block diagram of the switching element operating means 20. Since the switching element operating means 20 is common to the switching elements 41 to 46, only one switching element 41 of the switching elements 41 to 46 is representatively shown in FIG.

  The switching element operation unit 20 outputs a gate signal to the control terminal 411 of the switching element 41 based on the PWM drive signal generation unit 201 that outputs a pulse operation command sig_PWM for pulse width modulation control, and the pulse operation command sig_PWM. The switching element drive circuit 202 for turning on and off the switching element 41 is provided. Further, the switching element operating means 20 includes switching element state determining means 203 for determining the state of the switching element based on the voltage change of the control terminal 411 when the switching element 41 operates from off to on to generate a pulse voltage. Yeah.

  The PWM drive signal generation means 201 generates a pulse operation command sig_PWM by comparing a PWM carrier wave and a voltage command value (not shown), and outputs a switching element on / off command to the switching element drive circuit 202. An element on signal sig_swon = 1 indicating the operation of switching 41 from off to on is output to the switching element state determination means 203. Upon receiving the element ON signal sig_swon = 1, the switching element state determination means 203 samples the voltage Vg of the control terminal 411 output from the switching element drive circuit 202, and determines the state of the switching element 41 from the control terminal voltage change. Then, the switching element state determination unit 203 outputs the determination result sig_result to the PWM drive signal generation unit 201. If the determination result sig_result is 0: the element is normal, the PWM drive signal generation unit 201 performs normal pulse width modulation control. On the other hand, if the determination result sig_result is 1: element abnormality, the PWM drive signal generation unit 201 performs a switching element protection operation that shortens the ON period and lengthens the OFF period to shorten the pulse voltage period. Do.

  According to the configuration of the present embodiment shown in FIGS. 1 and 2 described above, the element states of the switching elements 41 to 46 can be determined from the control terminal voltages of the switching elements 41 to 46. Therefore, it is not necessary to additionally provide a temperature detecting element in the switching elements 41 to 46, and a reduction in cost in detecting the element state can be realized. Moreover, it is not necessary to arrange a thermosensitive element such as a thermocouple in the vicinity of the switching elements 41 to 46, which can contribute to miniaturization of the power conversion device.

  Furthermore, in the prior art that outputs the measurement signal of the element state to the switching elements 41 to 46 in the power conversion device such as an inverter, the switch is opened by applying the measurement signal to the switching element. In order to prevent the voltage source from being short-circuited, it is necessary to turn off the arm opposite to the arm being measured. At this time, a switching loss occurs when the arm is turned on / off. However, according to the configuration of the present embodiment shown in FIGS. 1 and 2 described above, it is not necessary to turn on / off the opposite arm, thereby reducing the switching loss. It becomes possible.

  Moreover, the range where the temperature of the switching element becomes the largest is when the power converter is at a high output, and it is necessary to accurately grasp the element temperature at the time of the high output from the viewpoint of element protection. However, at the time of high output, since the period during which the switching element is turned on becomes longer, the period during which the switching element is turned off becomes relatively shorter. If the modulation factor is 0.9 in a power converter that performs PWM driving with a carrier frequency of 10 kHz, the time for which the switching element is on is 90 μs. Since the dead time is added to this, the time for which the switching element is turned off is 10 μs or less. For this reason, in the conventional technology for detecting the element temperature during the element off period, sufficient measurement time cannot be taken at the time of large output, and as a result, the temperature can be detected in a low output range and the element temperature at the time of large output can be estimated. It was. According to the present embodiment, the above problem can be solved, and the switching element temperature can be detected quickly and accurately regardless of the length of the element off time.

  FIG. 3 is a time-dependent change diagram showing the actual voltage change of the switching element control terminal 411. As shown in FIG. 3, the element-on signal sig_swon = 1 is output at the instant t1, and the generation of the pulse voltage is started. After the output of the element ON signal sig_swon = 1, there is a slight deviation until the switching element is fully turned on at the subsequent instant t2. This shift period is called an element off-on transition period. During this period, the control terminal voltage Vg rises and continues to rise, but the voltage increase rate of the control terminal voltage Vg becomes near zero along the way. This is generally known as the Miller effect, and there is a period M during which the control terminal voltage Vg becomes the Miller effect voltage Vm. This mirror effect voltage Vm is defined as a voltage in the voltage parallel period M. This Miller effect voltage Vm is greatly affected by fluctuations in the control terminal threshold voltage Vgth (not shown), which is a boundary voltage at which the switching element changes from the OFF state to the ON state, and Vm and Vgth have characteristics that change in conjunction with each other. Have. Also, since the control terminal threshold voltage Vgth decreases as the element temperature Tj of the switching element rises, the element temperature that is the state of the switching element is detected by detecting the change in the mirror effect voltage Vm during the element off-on transition period. Can be determined. When the generation of the pulse voltage is finished after the instant t2, the element off signal sig_swon = 1 is output at the following instant t3.

  FIG. 4 is a flowchart showing the switching element state determination executed by the switching element state determination unit 203. When the element on signal sig_swon = 1 is input to the switching element state determination means 203, this flowchart is entered, and the voltage Vg of the control terminal 411 is sampled during the element off / on transition period (t1 to t2) shown in FIG. By detecting the control terminal voltage Vg in the vicinity where the voltage increase rate is near 0, the element state can be detected. First, in step S1, the control terminal voltage Vg is continuously sampled to calculate a voltage change at the control terminal 411.

  In the next step S2, whether or not the control terminal voltage change rate ΔVg / Δt, which is the voltage change of the control terminal 411, is significantly reduced compared to ΔVg / Δt in the Vg rising period (element on / off transition period t1 to t2). Judging. If the control terminal voltage change rate ΔVg / Δt is significantly reduced compared to ΔVg / Δt during the Vg increase period (Yes), it is determined that the control terminal voltage change rate ΔVg / Δt is close to 0, and the next step S3 Proceed to On the other hand, if not significantly decreased (No), the process returns to step S1 to continue the continuous sampling of the control terminal voltage Vg.

In step S3, the control terminal voltage Vg sampled immediately before is set as the mirror effect voltage Vm shown in FIG.
In the next step S4, it is determined whether or not the mirror effect voltage Vm is less than the element abnormality determination value Vj. If the element abnormality determination value Vj is equal to or greater than (No), it is determined that the switching element 41 is in a temperature range in which it can operate normally, and the process proceeds to step S5. In step S <b> 5, it is assumed that the switching element 41 is in the normal range, and the determination result sig_result = 0 (element normal) is output to the PWM drive signal generation unit 201. And this flow is exited. The PWM drive signal generation unit 201 outputs a pulse operation command sig_PWM related to normal pulse width modulation control. This is the waveform indicated by I in FIG.

  On the other hand, if it is less than the element abnormality determination value Vj (Yes), it is determined that the switching element 41 is so hot that it cannot operate normally and is in the abnormal range, and the process proceeds to step S6. In step S 6, the determination result sig_result = 1 (element abnormality) is output to the PWM drive signal generation means 201. And this flow is exited. The PWM drive signal generation unit 201 enters the switching element protection mode and outputs a pulse operation command sig_PWM having a waveform indicated by II in FIG. Since the element on period II is shorter than the normal element on period I, the temperature rise of the switching elements 41 to 46 is avoided to protect them.

  According to the above-described embodiment, the state of the switching element 41 is determined based on the voltage value of the control terminal 411 when the voltage change rate ΔVg / Δt of the control terminal 411 is close to 0. It is possible to accurately grasp the switching element temperature without affecting the voltage generation. Further, it is not necessary to turn on or off the switching element of the reverse arm for measuring the switching element state of the arm, and the switching loss can be reduced.

  Further, according to the above-described embodiment, when the state of the switching elements 41 to 46 determined by the switching element state determination unit 203 is out of the normal range (sig_result = 1), the PWM drive signal generation of the switching element operation unit 20 is performed. Since the means 201 shifts to the switching element protection mode after the next operation from OFF to ON (II in FIG. 5), the switching elements 41 to 46 can be effectively protected.

  As a modification of the present embodiment, the PWM drive signal generation unit 201 may output a pulse operation command sig_PWM having a waveform shown in FIGS. 6 and 7. This consists of a switching element state determination command I that is weak enough not to turn on, and an on operation command II that is continuous with the I. As soon as the determination of the switched element state is completed, switching from the command I to the command II is immediately performed. Thereby, the time loss required for the determination of the switch-on element state can be suppressed to a level that does not cause a problem.

  The switching element drive circuit 202 that outputs a gate signal linked to the pulse operation command sig_PWM composed of the command I and the command II also performs the ON operation before the gate signal is switched from OFF to ON and the ON operation gate signal is output. A switching element state determination gate signal continuous with the gate signal is output to the control terminal 411. As a result, the switching elements 41 to 46 gradually shift from the off state to the on state rather than the instantaneous transition between off and on as shown in FIG.

  The switching element state determination gate signal corresponding to the switching element state determination command I shown in FIG. 7 is substantially equal to the mirror effect voltage Vm of the control terminal 411 in the element on / off periods t1 to t2 described above with reference to FIG. Thereby, the states of the switching elements 41 to 46 can be determined based on the voltage change of the control terminal 411 by the switching element state determination gate signal.

According to the switching element state determination command I shown in FIGS. 6 and 7, when the mirror effect voltage becomes less than the element abnormality determination value Vj, the switching to the command II can be quickly stopped. Can be increased.
The above-described state determination of the switching elements 41 to 46 by the switching element state determination gate signal is useful when the power conversion device has a short output period shorter than the element off period, and the switching element shown in FIG. Use protected mode.

  Note that the states of the switching elements 41 to 46 may be determined based on a change in current flowing through the control terminal 411 or a current value based on the switching element state determination gate signal. The current Ig flowing through the control terminal 411 will be described later.

  According to the above-described modification, it is possible to suppress the control terminal voltage sampling rate required for element state determination. In particular, it is possible to prevent an excessive load on the element state determination means 203 at the time of a small output. For this reason, the thermal countermeasure of the switching element operating means 20 becomes easy. Further, when the output is large, the element state determination gate signal interlocked with FIGS. 6 and 7 is not used, and the state determination in the off-on immediate switching operation described above with reference to FIG. It becomes possible to accurately determine the state of the switching element at the time of large output.

  Next, the power converter device which becomes 2nd Example of this invention is demonstrated. The basic configuration of the second embodiment is the same as that shown in FIGS.

  FIG. 8 is a flowchart showing the switching element state determination executed by the switching element state determination unit 203 of the second embodiment. When the element ON signal sig_swon = 1 is input to the switching element state determination means 203, this flowchart is entered. First, in step S21, the timer Ttimer starts to count down.

  In the next step S22, it is determined whether or not the timer Ttimer has reached a predetermined time Ts. If not reached yet (No), the timer Ttimer continues to count down until a predetermined time Ts elapses after the element on signal sig_swon = 1 is output. When the elapsed time after outputting the element ON signal sig_swon = 1 reaches the predetermined time Ts (Yes), the process proceeds to step S23.

  In step S23, the control terminal voltage Vg is sampled when a predetermined time Ts elapses after the element on signal sig_swon = 1 is output, and this Vg is set as the mirror effect voltage Vm. And it progresses after step S4 mentioned above in FIG.

According to the present embodiment, as shown in the control flow of FIG. 8, the switching element state determination unit 203 obtains the elapsed time Ttimer from the instant t1 when the gate signal is switched from OFF to ON, and the elapsed time Ttimer has a voltage change of 0. Since the control terminal voltage value Vg when the predetermined time Ts required for the neighboring period M has been reached is detected and the state of the switching element 41 is determined using the control terminal voltage value Vg as the mirror effect voltage Vm, the following effects are obtained. can get.
In other words, when the load characteristic of the three-phase AC motor 30 is clear or the like, the time required for the control terminal voltage Vg to rise and the subsequent period during which the control terminal voltage increase rate is close to 0 are known in advance. An optimal control terminal acquisition timing can be obtained by calculating or storing the control terminal voltage rise time and setting it as the predetermined time Ts.
Further, by detecting the control terminal voltage after a predetermined time Ts after the switching elements 41 to 46 are switched from OFF to ON, it is possible to avoid excessive voltage sampling and simplify the system required for element state detection.

  Next, the power converter device which becomes 3rd Example of this invention is demonstrated. In this embodiment, the control terminal voltage acquisition timing near the control terminal voltage change rate 0 in the first embodiment is determined using the control terminal current. The basic configuration of the third embodiment is the same as that shown in FIG.

FIG. 9 is a functional block diagram of the switching element operating means 20. Since the switching element operating means 20 is common to the switching element 41 to 46, in FIG. 9 to avoid duplicate description representatively shown per only one switching element 41 of the switching elements 41 to 46.

  The switching element operation means 20 includes the PWM drive signal generation means 201, the switching element drive circuit 202, and the switching element state determination means 203 described above with reference to FIG. Further, the switching element operating unit 20 includes an element control terminal current detecting / determining unit 204 having a function of detecting the current flowing through the control terminal 411 and determining the Vg acquisition timing.

  The element driving circuit 202 and the control terminal 411 of the element 41 are connected via the resistance element 412. The element control terminal current detection / determination means 204 is configured to calculate the element control terminal current value by acquiring a voltage drop generated in the resistance element 412. This resistance element 412 is generally used to adjust the switching element on / off speed, and is particularly known by the name of gate resistance. For this reason, the resistance element 412 is not a component newly added in order to implement | achieve this structure.

  The element control terminal current detection / determination means 204 is electrically connected to both ends of the resistance element 412, and detects the control terminal current Ig. Then, the detection / non-detection command sig_search is output to the PWM drive signal generation unit 201.

  FIG. 10 shows the actual current change and voltage change of the switching element control terminal 411. As shown in FIG. 10, the control terminal voltage change rate becomes close to 0 in the element off-on transition period from the output of the element on command sig_swon = 1 at the instant t1 until the switching element is fully turned on at the subsequent instant t2. In the vicinity, the control terminal current Ig rapidly increases and rises, and then suddenly decreases and falls, thus showing a remarkable change.

  Therefore, in FIG. 10, the control terminal voltage Vg at the time when the control terminal current Ig becomes equal to the control terminal voltage detection determination current value Ij in the falling period in which the current change rate is negative in the element off-on transition period. By detecting it, it becomes possible to reliably detect the control terminal voltage Vm in the period M in FIG.

  FIG. 11 is a flowchart showing switching element state determination executed by the switching element state determination unit 203 in cooperation with the element control terminal current detection / determination unit 204. When the element ON signal sig_swon = 1 is input to the element control terminal current detection / determination means 204, this flow chart is entered. First, in step S31, the non-detection command of sig_search = 0 that does not acquire the control terminal voltage and the switching element is normal. And a detection result of sig_result = 0 is output.

  In the next step S32, the control terminal current Ig is sampled to monitor whether or not the control terminal current Ig has reached the control terminal current detection start value Is. If not reached yet (No), the monitoring in step S32 is continued until the control terminal current detection start value Is is reached. When the control terminal current detection start value Is is reached (Yes), the process proceeds to step S33. In step S32, it may be monitored whether or not Is is exceeded, and whether or not Is is exceeded. Refer to FIG. 10 for this state.

  In step S33, the control terminal current Ig is sampled, and it is monitored whether or not the control terminal current Ig is equal to or less than the control terminal voltage detection current value Ij. If not yet below (No), the monitoring in step S33 is continued until the control terminal voltage detection current value Ij or less. When the current value is equal to or less than the control terminal voltage detection current value Ij (Yes), the process proceeds to step S34. In step S33, it may be monitored whether it is less than Ij and less than Ij. Refer to FIG. 10 for this state.

  In step S34, a detection command of sig_search = 1 is output to the switching element state determination unit 203 so as to acquire the control terminal voltage. In the next step S35, the control terminal voltage Vg at the time of detection command sig_search = 1 output is sampled, and this Vg is set as the mirror effect voltage Vm. And it progresses after step S4 mentioned above in FIG.

  According to this embodiment, the switching element operating unit 20 includes an element control terminal current detecting / determining unit 204 that detects a current change of the control terminal 411. The switching element state determination unit 203 obtains a voltage change at the control terminal 411 based on the current change. As a result, accurate control terminal voltage sampling timing sig_search = 1 can be secured, unnecessary control terminal voltage sampling can be avoided, and the system required for element state detection can be simplified.

  Further, in this embodiment, since a change in current flowing through the resistance element 412 provided at the connection portion between the connection terminal 411 of the switching elements 41 to 46 and the switching element drive circuit 202 is detected, it is conventionally provided. The control terminal current of the switching elements 41 to 46 can be calculated from the voltage drop using the resistance element 412. Therefore, it is not necessary to provide a new current detection means for detecting the control terminal current, and it is possible to detect a current having a large change rate that cannot be responded by the conventional current detection means.

  Furthermore, in this embodiment, as shown in the control flow of FIG. 11, the element control terminal current detection / determination means 204 detects the current value Ig of the control terminal 411, and the switching element state determination means 203 determines that the current change rate of Ig is The state of the switching elements 41 to 46 is determined based on the voltage value Vg of the control terminal 411 when the current value Ig in the negative falling period becomes equal to or less than the predetermined value Ij. That is, the control terminal voltage Vg is detected when the switching elements 41 to 46 are equal to or less than the predetermined value Ij in the current falling period when the switching elements 41 to 46 are switched from the off state to the on state (step S34), and the switching element state is detected. As a result, it is possible to reliably detect the control terminal voltage Vm that is optimal for determining the switching element state.

  Next, a power converter according to a fourth embodiment of the present invention will be described. In this embodiment, the control terminal voltage Vg acquisition timing based on the change of the control terminal current in the third embodiment is determined by referring to the Ig change rate from the determination based on the Ig / Ij comparison. Accordingly, in the fourth embodiment, FIG. 11 showing the operation flowchart of the element state determination means 203 and the element control terminal current detection / determination means 204 in the third embodiment is changed as shown in FIG. The basic configuration of the fourth embodiment is the same as that shown in FIGS.

  When the element ON signal sig_swon = 1 is input to the element control terminal current detection / determination means 204, the flowchart shown in FIG. 12 is entered. First, in step S41, a non-detection command of sig_search = 0 that does not acquire the control terminal voltage and a detection result of sig_result = 0 in which the switching element is normal are output.

  In the next step S42, the control terminal current Ig is continuously sampled to calculate the current change rate ΔIg / Δt per time.

As shown in FIG. 10, the current change rate ΔIg / Δt rapidly increases immediately after sig_swon = 1 and rises, and then suddenly decreases and falls.
In the next step S43, after the current change rate ΔIg / Δt starts to decrease, when ΔIg / Δt becomes significantly smaller than ΔIg / Δt in the falling period, that is, when the decrease becomes moderate. N is determined as the optimum timing for detecting the control terminal voltage Vg. Further, a threshold value for identifying that the rate of change has decreased may be set in the current rate of change.
In the next step S44, a detection command sig_search = 1 is output so as to acquire the control terminal voltage.

  In the next step S45, the control terminal voltage Vg at the time of detection command sig_search = 1 output is sampled, and this Vg is set as the mirror effect voltage Vm. And it progresses after step S4 mentioned above in FIG.

According to this embodiment, as shown in the control flow of FIG. 12, the switching element state determination unit 203 calculates the current change rate ΔIg / Δt when the control terminal current Ig changes from rising to decreasing (step S42). When the current change rate ΔIg / Δt becomes significantly smaller than the current change rate during the falling period of the current value (step S43), the voltage value Vg of the control terminal at the time of detection is determined as the mirror effect voltage Vm. To determine the state of the switching element. Referring to the actual current change and voltage change (see FIG. 10), it will be understood that the control terminal current Ig becomes the Miller effect voltage Vm at the point N when the current change rate during the falling period becomes significantly smaller. .
As a result, it is possible to absorb the deviation of the optimum timing in the detection of the control terminal voltage due to manufacturing variations of the switching elements 41 to 46 and to reliably detect the optimum control terminal voltage Vm for the element state determination.

  Next, a power converter according to a fifth embodiment of the present invention will be described. In this embodiment, the Vg detection timing in the third embodiment is determined using the control terminal current after a predetermined time has elapsed after sig_swon = 1 output. Accordingly, the operation flow of the switching element state determination means 203 and the element control terminal current detection / determination means 204 in the third embodiment is changed as shown in FIG. 13 instead of FIG. The basic configuration of the fifth embodiment is the same as that shown in FIGS.

  When the element ON signal sig_swon = 1 is input to the element control terminal current detection / determination means 204, the flowchart shown in FIG. 13 is entered. First, in step S51, a non-detection command of sig_search = 0 that does not acquire the control terminal voltage and a detection result of sig_result = 0 in which the switching element is normal are output. Then, the timer Ttimer starts to count down.

  In the next step S52, it is determined whether or not the timer Ttimer has reached a predetermined time Ts. If not reached yet (No), the timer Ttimer continues to count down until a predetermined time Ts elapses after the element on signal sig_swon = 1 is output. When the elapsed time after outputting the element ON signal sig_swon = 1 reaches the predetermined time Ts (Yes), the process proceeds to step S53.

  In step S53, the control terminal current Ig is sampled, and it is monitored whether or not the control terminal current Ig is equal to or less than the control terminal voltage detection current value Ij. If it is not yet lower than Ij (No), the monitoring in step S53 is continued until the current value Ij for detecting the control terminal voltage is lower than Ij. When the current value is equal to or less than the control terminal voltage detection current value Ij (Yes), the process proceeds to step S54. In step S53, it may be monitored whether it is less than Ij and less than Ij. Refer to FIG. 10 for this state.

  In step S54, a detection command of sig_search = 1 is output to the switching element state determination unit 203 so as to acquire the control terminal voltage. In the next step S35, the control terminal voltage Vg at the time of detection command sig_search = 1 output is sampled, and this Vg is set as the mirror effect voltage Vm. And it progresses after step S4 mentioned above in FIG.

  According to the present embodiment, as shown in the control flow of FIG. 13, the element control terminal current detection / determination means 204 obtains an elapsed time Ttimer from the instant t1 when the gate signal is switched from OFF to ON, and the elapsed time Ttimer is The current value Ig from when the predetermined time Ts is reached is detected, and the state of the switching element is determined based on the control terminal voltage value Vm when the current value Ig is equal to or less than the predetermined value Ij. Therefore, unnecessary current value sampling can be eliminated, and the control terminal voltage Vg necessary for determining the state of the switching elements 41 to 46 can be reliably detected.

  The above are only examples of the present invention, and the present invention can be variously modified without departing from the spirit of the present invention.

FIG. 1 is a circuit configuration diagram showing an overall outline of a power converter, a voltage source, and a load according to a first embodiment of the present invention. It is a functional block diagram of the element drive circuit of the same Example. It is a time-dependent change figure which showed the actual voltage change of the switching element control terminal. The control flow of switching element state judgment of the same Example is shown. It is a figure which shows the pulse operation command of the Example by a waveform. It is a figure which shows the pulse operation command used as the modification of the Example with a waveform. It is a figure which shows the pulse operation command used as the modification of the Example with a waveform. The control flow of switching element state judgment which becomes a 2nd example is shown. It is a functional block diagram of the element drive circuit of 3rd Example. It is a time-dependent change figure which showed the actual voltage change of the switching element control terminal. The control flow of switching element state judgment of the same Example is shown. The control flow of switching element state judgment which becomes a 4th example is shown. The control flow of the switching element state judgment which becomes 5th Example is shown.

Explanation of symbols

10 Voltage source 20 Switching element operating means 30 Motor (load)
41 42 43 44 45 46 Switching element 201 PWM drive signal generation means 202 Switching element drive circuit 203 Switching element state determination means 204 Element control terminal current detection / determination means 411 Control terminal 412 Resistance element

Claims (8)

A switching element for electrically connecting a voltage source and a load; and a switching element operating means 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 for supplying power from the voltage source to the load by
The switching element operating means includes a switching element driving circuit that outputs the gate signal to a control terminal of the switching element;
Switching elements example immediately a switching element state determining means for determining the state of the switching element based on the magnitude of the voltage of the voltage parallel period of the control terminal in generating the pulse voltage operating from OFF to ON,
The switching element driving circuit outputs a switching element state determination gate signal continuous with the on operation gate signal before the gate signal is switched from off to on and outputs the on operation gate signal.
The switching element state determination means includes
Determine the state of the switching element based on the voltage change or current change of the control terminal by the switching element state determination gate signal,
When the state of the switching element determined by the switching element state determination means is out of the normal range, the switching element operation means shifts to the switching element protection mode after the next operation from OFF to ON, The power conversion apparatus according to claim 1, wherein a pulse operation command having an on period shorter than an on period of the switching element is output to the switching element driving circuit . The power conversion device according to claim 1,
The switching element state determining means determines the state of the switching element based on a control terminal voltage value when the voltage change rate of the control terminal is close to zero. The power conversion device according to claim 2,
The switching element state determining means obtains an elapsed time from when the gate signal is switched from off to on, detects a control terminal voltage value when the elapsed time reaches a predetermined time, and controls the control terminal voltage value The state of a switching element is judged based on this, The power converter device characterized by the above-mentioned. In the power converter device according to claim 1 or 2,
The switching element operation means comprises element control terminal current detection / determination means for detecting a current change of the control terminal,
The switching element state determining means obtains a voltage change of the control terminal based on the current change. The power conversion device according to claim 4, wherein a resistance element is provided at a connection portion between the control terminal and the switching element drive circuit.
The element control terminal current detection / determination means detects a current change of a current flowing through the resistance element. The power conversion device according to claim 4 or 5,
The element control terminal current detection / determination means detects a current value of the control terminal,
The switching element state determining means determines the state of the switching element based on a voltage change of the control terminal when the current value in a falling period in which the current change rate of the current value is negative becomes a predetermined value or less. A power conversion device. The power conversion device according to claim 4 or 5,
The element control terminal current detection / judgment means calculates a current change rate when the current change starts to decrease, and the current change rate is significantly smaller than the current change rate during the falling period of the current value. Detect when
The switching element state determining means determines the state of the switching element based on a voltage change of the control terminal at the time of detection. The power conversion device according to claim 4 or 5,
The element control terminal current detection / judgment means obtains an elapsed time from when the gate signal is switched from OFF to ON, detects the current value from when the elapsed time reaches a predetermined time,
The switching element state determining means determines the state of the switching element based on a voltage change of the control terminal when the detected current value becomes a predetermined value or less.

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