JP7455006B2 - Power supplies and power supplies for medical imaging diagnostic equipment - Google Patents

Description

Embodiments disclosed in this specification and the drawings relate to a power supply device and a power supply device for a medical image diagnostic apparatus.

BACKGROUND ART Conventionally, in a power supply device including an inverter circuit or the like that outputs a large current, an insulated gate bipolar transistor (hereinafter referred to as an IGBT), for example, is used as a power device that is a core component of the inverter circuit. IGBTs control large amounts of energy when performing switching operations in inverter circuits. If the thermal resistance of the IGBT increases due to solder cracks caused by thermal fatigue, the IGBT may be damaged. If the IGBT is damaged, it may have a major impact not only on the power supply device but also on the system using the power supply device. Therefore, it is desired to detect IGBT element damage in advance.

It is difficult to predict element damage in IGBTs, and requires, for example, complicated monitoring such as temperature monitoring to predict damage, and definition of abnormality determination conditions based on circuit operations including IGBTs. For this reason, it is not easy to predict damage to IGBTs because the circuit for detecting abnormalities in IGBTs becomes complicated.

Japanese Patent Application Publication No. 2017-195714

One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to easily predict damage to IGBTs in a power supply device. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. Problems corresponding to the effects of each configuration shown in the embodiments described later can also be positioned as other problems.

The medical image diagnostic apparatus power supply device according to the present embodiment includes an IGBT, a measurement section, a determination section, and a notification section. The IGBT is driven according to a drive signal output from a control unit in a medical image diagnostic apparatus. The measurement unit measures the collector-emitter voltage (hereinafter referred to as Vce-sat value) of the IGBT. The determination unit determines whether the Vce-sat value exceeds a reference value. The notification section outputs a restriction command for limiting driving of the IGBT and a predetermined warning to the control section when the Vce-sat value exceeds the reference value. The determination unit determines a correspondence relationship between a first electrical characteristic of the power device at a predetermined temperature lower than an upper limit temperature regarding damage to the power device and a second electrical characteristic of the power device at the upper limit temperature; A predetermined number of times an initial value set based on the third electrical characteristic of the power device obtained by measurement at the predetermined temperature is used as the reference value.

FIG. 1 is a diagram showing an example of the configuration of functional blocks of a power supply device for a medical image diagnostic apparatus according to an embodiment. FIG. 2 is a diagram showing an example of the hardware configuration of a power supply device for a medical image diagnostic apparatus according to the embodiment. FIG. 3 is a diagram showing an example of sampling timing for a current waveform of a collector current according to the embodiment. FIG. 4 is a diagram showing an example of a representative characteristic curve at a junction temperature of 25° C. and a Vce-sat value corresponding to the first collector current, according to the embodiment. FIG. 5 is a diagram showing an example of a representative characteristic curve at a junction temperature of 25° C. and a plurality of Vce-sat values corresponding to a plurality of collector currents, according to the embodiment. FIG. 6 shows a voltage difference between a Vce-sat value in a representative characteristic curve with a junction temperature of 25° C. and a Vce-sat value in a representative characteristic curve with a junction temperature of 150° C. with respect to the first collector current, according to the embodiment. Diagram showing. FIG. 7 is a diagram showing a plurality of voltage differences depending on the Vce-sat values corresponding to the second to nth collector currents, respectively, according to the embodiment. FIG. 8 is a diagram showing an example of an initial calibration curve, which is a curve showing initial values of a plurality of Vce-sat values corresponding to a plurality of collector currents, according to the embodiment. FIG. 9 is a diagram illustrating an example of a cause of abnormality in an IGBT according to the embodiment. FIG. 10 is a diagram showing an example of a change in Vce-sat value for a predetermined collector current when the junction temperature changes from 25° C. to 150° C. according to the embodiment. FIG. 11 is a flowchart showing an example of an abnormality detection process procedure according to the embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A power supply device used in a medical image diagnosis apparatus (hereinafter referred to as a power supply apparatus for a medical image diagnosis apparatus) will be described below with reference to the drawings. Examples of the medical image diagnostic apparatus include an X-ray computed tomography apparatus, a magnetic resonance imaging apparatus, an X-ray diagnostic apparatus, and a nuclear medicine diagnostic apparatus. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant explanations will be omitted as appropriate.

(Embodiment)
FIG. 1 is a diagram showing an example of the configuration of functional blocks of a power supply device 1 for a medical image diagnostic apparatus according to the present embodiment. The power supply device 1 for a medical image diagnostic apparatus includes a power device 11, a restriction section 13, a generation section 15, a measurement section 17, a storage section 19, a calculation section 21, a determination section 23, and a notification section 25. Be prepared. Referring to FIG. 2, the hardware configuration of the power device 1 for a medical image diagnostic apparatus includes the power device 11, the restriction unit 13, the generation unit 15, the measurement unit 17, the determination unit 23, and the notification unit 25. Explain.

FIG. 2 is a diagram showing an example of the hardware configuration of the power supply device 1 for a medical image diagnostic apparatus. The hardware configuration of the power supply device 1 for a medical image diagnostic apparatus includes a Vce-sat monitoring circuit 10. The Vce-sat monitoring circuit 10 monitors a Vce-sat value indicating a voltage between an emitter 115 and a collector 117 in an IGBT 111 corresponding to a power device.

The power device 11 is realized by, for example, an IGBT 111 as a hardware configuration. The IGBT 111 is used to control power to a power supply destination. The IGBT 111 is driven according to a drive signal output from a control unit in the medical image diagnostic apparatus. A gate 113 of the IGBT 111 is electrically connected to an output terminal of a drive limiting circuit 131.

Note that when the drive limiting circuit 131 is omitted, the gate 113 is electrically connected to a control section in the medical image diagnostic apparatus. The emitter 115 in the IGBT 111 is electrically connected to a power input terminal of a power supply destination (for example, a gradient magnetic field power supply in a magnetic resonance imaging apparatus, a high voltage generator in an X-ray computed tomography apparatus or an X-ray diagnostic apparatus, etc.). be done. A collector 117 in the IGBT 111 is electrically connected to a power supply source (for example, AC power supplied from a commercial power source, DC power obtained by rectifying the AC power, etc.). Since the IGBT 111 is an existing semiconductor element, a description thereof will be omitted. Note that the power device 11 can be implemented as hardware without being limited to the IGBT 111, and may be implemented using other power transistors or the like.

The restriction unit 13 restricts the driving of the power device 11 by adjusting the drive signal output from the control unit in the medical image diagnostic apparatus. The restriction unit 13 is realized by a drive restriction circuit 131 as a hardware configuration. The drive limit circuit 131 is realized by, for example, a microprocessor such as a digital signal processor (hereinafter referred to as DSP). Note that the drive limit circuit 131 may be applied to an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or another complex programmable logic device (Complex). Programmable Logic Device: CPLD), simple programmable logic device (SPLD), or the like.

The drive restriction circuit 131 adjusts the drive signal output from the control unit based on the restriction command output from the notification unit 25. The adjustment of the drive signal is a restriction on the drive of the power device 11, and specifically corresponds to the degenerate operation of the IGBT 111. The degenerate operation of the IGBT 111 relates to, for example, fail software for a medical image diagnostic apparatus, and corresponds to driving the IGBT 111 while reducing the load on the IGBT 111. Note that the drive restriction circuit 131 may adjust the drive signal so as to stop driving the IGBT 111 upon reception of the restriction command.

Specifically, upon receiving the restriction command output from the abnormality notification circuit 251, the drive restriction circuit 131, for example, reduces the duty ratio of the drive signal (that is, reduces the ON time) and reduces the ON time of the drive signal. and reducing the amplitude. The drive limiting circuit 131 outputs a drive signal adjusted by at least one of reducing the duty ratio and reducing the amplitude of the drive signal to the gate 113 of the IGBT 111. Note that the function executed by the drive restriction circuit 131 may be executed by a circuit that generates a drive signal for the IGBT 111 in a control unit in a medical image diagnostic apparatus. At this time, the limiting section 13 shown in FIG. 1, that is, the drive limiting circuit 131 shown in FIG. 2 may be omitted.

The generation unit 15 is realized by a sampling timing generation circuit 151 as a hardware configuration. For example, the sampling timing generation circuit 151 is realized by a DSP, ASIC, FPGA, CPLD, SPLD, or the like. The sampling timing generation circuit 151 generates a sampling timing related to the measurement of the Vce-sat value by the measurement unit 17 based on the output command of the collector current Ic in the collector 117 of the IGBT 111.

FIG. 3 is a diagram showing an example of sampling timing for the current waveform of collector current Ic. As shown in FIG. 3, the sampling timing corresponds to a period (sampling window) during which the collector current Ic is constant at 300 A, for example. As shown in FIG. 3, the sampling window corresponds to, for example, a period in which the collector current Ic is constant over several milliseconds to several tens of milliseconds. As a result, the Vce-sat value is measured during a period in which the collector current Ic is constant.

The measurement unit 17 is realized by a Vce-sat measurement circuit 171 as a hardware configuration. For example, the Vce-sat measurement circuit 171 is realized by a DSP, ASIC, FPGA, CPLD, SPLD, or the like. The Vce-sat measurement circuit 171 monitors the electrical characteristics of the IGBT 111. The electrical characteristics are, for example, the relationship among collector current Ic, collector voltage Vc, and emitter voltage Ve, and depend on the temperature of IGBT 111. The Vce-sat measurement circuit 171 measures the Vce-sat value between the collector 117 and emitter 115 in the IGBT 111.

Specifically, the Vce-sat measuring circuit 171 calculates the Vce-sat corresponding to the collector current Ic at the sampling timing according to the sampling command output from the sampling timing generation circuit 151, that is, the sampling timing at which the collector current Ic becomes constant. Measure the value. More specifically, the Vce-sat measurement circuit 171 measures the collector voltage Vc in the IGBT 111 at the sampling timing. Further, the Vce-sat measurement circuit 171 measures the emitter voltage Ve in the IGBT 111 at the sampling timing. The Vce-sat measurement circuit 171 measures the Vce-sat value by calculating the difference between the collector voltage Vc and the emitter voltage Ve. The Vce-sat measurement circuit 171 outputs the measured Vce-sat value to the storage section 19 and the determination section 23.

The storage unit 19 is realized as a hardware configuration by a memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory) that stores various information. Note that the hardware configuration of the storage unit 19 is not limited to these memories, and may be realized by other storage devices. The storage unit 19 stores at least one reference value (that is, a threshold value or an initial value). Note that the reference value may be set in advance according to each of the plurality of collector currents in the collector 117 and stored in the storage unit 19. The storage unit 19 stores a plurality of reference values for a plurality of collector currents in a correspondence table, for example, a look-up table format. Furthermore, the storage unit 19 stores a plurality of Vce-sat values that have been continuously measured since the start of use of the IGBT 111, together with the measurement date and time, as a log. The storage unit 19 stores a predetermined period preset by the user.

The calculation unit 21 is realized by, for example, a DSP, ASIC, FPGA, CPLD, SPLD, etc. as a hardware configuration. The calculation unit 21 calculates the change over time in the Vce-sat value using the plurality of Vce-sat values stored together with the measurement date and time. The calculation unit 21 calculates a prediction of damage to the IGBT 111 based on the calculated change over time. For example, the calculation unit 21 calculates a prediction of damage to the IGBT 111 over a longer period by combining the increasing trend of the Vce-sat value and the power cycle data of the IGBT 111. The calculation unit 21 outputs the calculated damage prediction and changes over time to the notification unit 25. Note that the calculated damage prediction may be stored in the storage unit 19 together with the calculation date and time of the damage prediction. The calculated damage prediction is used as information for preventive maintenance during maintenance of the power supply device 1 for the medical image diagnostic apparatus. Note that in the present power supply device 1 for a medical image diagnostic apparatus, if preventive maintenance based on the calculated damage prediction of the IGBT 111 is not required, the main calculation unit 21 and various processes related to the damage prediction of the IGBT 111 can be omitted.

The determination unit 23 is realized by an abnormality determination circuit 231 as a hardware configuration. For example, the abnormality determination circuit 231 is realized by a DSP, ASIC, FPGA, CPLD, SPLD, or the like. The abnormality determination circuit 231 determines whether the IGBT 111 is abnormal using a reference value stored in its own memory (not shown) and the Vce-sat value measured by the measurement unit 17. For example, the abnormality determination circuit 231 determines whether the measured Vce-sat value exceeds a reference value. Note that the reference value may be stored in the storage unit 19. The reference value is a value indicating a reference value regarding the Vce-sat value for the collector current Ic. The reference value corresponds to at least one of a threshold value and an initial value.

The threshold value (abnormality determination threshold value) is a limit value indicating a limit regarding damage to the IGBT 111, and is, for example, Vce corresponding to the current rating (collector current) under the rated upper limit temperature condition (for example, junction temperature Tj = 150°C) in the IGBT 111. -corresponds to the sat value. That is, the threshold value corresponds to the voltage between the collector 117 and the emitter 115 that corresponds to the current rating at the upper limit temperature for damage of the power device 11. Hereinafter, the initial value will be explained first, and then the determination of abnormality of the IGBT 111 by the abnormality determination circuit 231 will be described.

(initial value)
The electrical characteristics of an IGBT depend on temperature and are represented by a curve (device characteristic curve) such as a Vce-sat characteristic that shows the correlation between voltage and current. The electrical characteristics (data sheet) of the IGBT are provided by the manufacturer that manufactures the IGBT. The electrical characteristics provided by the manufacturer indicate representative values of a plurality of IGBTs manufactured by the manufacturer. That is, the electrical characteristics of IGBTs vary from one individual to another. Therefore, the initial value is the one obtained by calibrating the electrical characteristics (hereinafter referred to as the representative characteristic curve) indicating the representative value in accordance with the IGBT 111 installed in the power supply device 1 for medical image diagnostic equipment (hereinafter referred to as the “representative characteristic curve”). , the initial calibration curve). The initial value corresponds to a value indicating a standard for aging deterioration of the IGBT 111. The initial value is derived by measuring the correlation between the voltage, current, and temperature in the IGBT 111 mounted in the manufacturing stage of the power supply device 1 for the medical image diagnostic apparatus. The procedure for deriving the initial value will be described below.

With respect to the temperature (junction temperature) related to the representative characteristic curve, the Vce-sat value is measured under constant current output conditions. The current output condition corresponds to, for example, the value of the collector current Ic in the IGBT 111. In measuring the Vce-sat value, the case temperature Tc of the IGBT 111 is also measured. Based on the measured case temperature Tc, the current output condition, and the measured Vce-sat value (or the collector voltage Vc and emitter voltage Ve), the junction temperature Tj is calculated using a predetermined calculation formula. As the calculation formula for calculating the junction temperature Tj from the case temperature Tc, an existing calculation formula can be used as appropriate. Hereinafter, in order to make the explanation more concrete, the junction temperature Tj related to the measurement of the Vce-sat value will be explained as 25° C. in deriving the initial value, but it is not limited to this.

If the calculated junction temperature and the temperature related to the representative characteristic curve are dissociated, the current output condition may be maintained, the temperature of the IGBT 111 may be controlled separately using an external heat source, and the Vce-sat value may be measured again. good.

FIG. 4 is a diagram showing an example of a representative characteristic curve 25CC at a junction temperature Tj of 25° C. and a Vce-sat value Vce-sat1 corresponding to the first collector current Ic1. As shown in FIG. 4, the first collector current Ic1 is, for example, 100 A, and when the junction temperature Tj is 25° C., the Vce-sat value is measured based on the sampling timing. Vce-sat (representative value) in FIG. 4 indicates the Vce-sat value when the first collector current Ic1 is 100A in the representative characteristic curve 25CC. The representative characteristic curve 25CC when the junction temperature Tj is 25° C. corresponds to the first electrical characteristic of the IGBT 111 at a predetermined temperature lower than the upper limit temperature for damage of the IGBT 111.

By changing the current output condition, that is, the collector current Ic in the IGBT 111, n Vce-sat values (n is a natural number of 2 or more) at a junction temperature Tj of 25° C. are measured. FIG. 5 is a diagram showing an example of a representative characteristic curve 25CC at a junction temperature Tj of 25° C. and a plurality of Vce-sat values Vce-sat1 to Vce-satn corresponding to a plurality of collector currents Ic1 to Icn. As shown in FIG. 5, from the plot of the plurality of Vce-sat values Vce-sat1 to Vce-satn corresponding to the first to n-th collector currents Ic1 to Icn, the electrical characteristics peculiar to the IGBT 111 with respect to the junction temperature of 25° C. A curve (hereinafter referred to as a unique curve) 25UC is obtained.

Based on the representative characteristic curve 25CC among the multiple representative characteristic curves corresponding to multiple junction temperatures provided by the manufacturer regarding IGBT111 and the representative characteristic curve of the IGBT111's service limit junction temperature (hereinafter referred to as upper limit temperature). Then, the difference in Vce-sat values for each of the plurality of collector currents (hereinafter referred to as voltage difference) is calculated. The representative characteristic curve of the upper limit temperature corresponds to the second electrical characteristic of the IGBT 111 at the upper limit temperature. Hereinafter, in order to make the explanation concrete, it is assumed that the upper limit temperature is 150°C. That is, the difference in Vce-sat value for the same collector current Ic in two representative characteristic curves showing the electrical characteristics of the IGBT 111 at an upper limit temperature of 150° C. and a predetermined temperature of 25° C. is calculated according to each of a plurality of collector currents. be done.

FIG. 6 is a diagram showing the voltage difference ΔVce-sat1 between the Vce-sat value @25CC in the representative characteristic curve 25CC and the Vce-sat value @150CC in the representative characteristic curve 150CC with respect to the first collector current Ic1. FIG. 7 is a diagram showing voltage differences ΔVce-sat2 to ΔVce-satn corresponding to the second to nth collector currents Ic2 to Icn, respectively. As shown in FIGS. 6 and 7, the voltage difference ΔVce-sat is calculated for each of the plurality of collector currents.

Next, we will examine the correspondence between the first electrical characteristic 25CC and the second electrical characteristic 150CC, and the third electrical characteristic (specific curve 25UC) of the IGBT 111 obtained by measurement at a predetermined temperature before using the IGBT 111. ), and the initial value is set based on. Specifically, the plurality of collector currents (Vce-sat1 to Vce-satn) corresponding to the plurality of collector currents (first to nth collector currents Ic1 to Icn) in the characteristic curve 25UC are By respectively adding a plurality of voltage differences ΔVce-sat1 to ΔVce-satn corresponding to the current, a Vce-sat value corresponding to each current output condition at the upper limit temperature, that is, each collector current is obtained. The correspondence between the first electrical characteristic 25CC and the second electrical characteristic 150CC corresponds to voltage differences ΔVce-sat1 to ΔVce-satn. The collector-emitter voltage obtained above corresponds to the initial value. In other words, the obtained plurality of initial values are Vce-sat values corresponding to each of the plurality of collector currents at the upper limit temperature with respect to the IGBT 111 mounted in the power supply device 1 for medical image diagnostic apparatus.

FIG. 8 is a diagram showing an example of an initial calibration curve 150UC, which is a curve showing a plurality of initial values corresponding to a plurality of collector currents. As shown in FIG. 8, the first initial value IVce-sat1 corresponding to the first collector current Ic1 is different from the collector-emitter voltage Vce-sat1 corresponding to the first collector current Ic1 in the characteristic curve 25UC by a voltage difference ΔVce. -obtained by adding sat1. Further, the second initial value IVce-sat2 corresponding to the second collector current Ic2 is obtained by adding the voltage difference ΔVce-sat2 to the collector-emitter voltage Vce-sat2 corresponding to the second collector current Ic2 in the characteristic curve 25UC. It can be obtained with The third initial value IVce-sat3 corresponding to the third collector current Ic3 can be obtained by adding the voltage difference ΔVce-sat3 to the collector-emitter voltage Vce-sat3 corresponding to the third collector current Ic3 in the characteristic curve 25UC. It will be done. Similarly, the n-th initial value IVce-satn corresponding to the n-th collector current Icn is determined by the voltage difference ΔVce-satn from the collector-emitter voltage Vce-satn corresponding to the n-th collector current Icn in the characteristic curve 25UC. It can be obtained by adding

The initial calibration curve 150UC shown in FIG. 8 corresponds to a curve in which the individual differences of each IGBT are reflected in the representative characteristic curve 150CC for the IGBT 111 installed in the power supply device 1 for a medical image diagnostic apparatus. In other words, the initial calibration curve 150UC corresponds to a curve obtained by calibrating the representative characteristic curve 150CC based on actual measurements of the IGBT 111 installed in the power supply device 1 for medical image diagnostic apparatus. In the above explanation, the initial calibration curve 150UC was generated using characteristic curves plotted under different current output conditions (collector current), but when calculating the initial value limited to one current output condition, It is possible to omit the process of changing the current output condition (collector current) and performing measurement and plotting. Hereinafter, determination of abnormality of the IGBT 111 will be explained.

The abnormality determination circuit 231 determines whether the Vce-sat value measured by the Vce-sat measurement circuit 171 exceeds a reference value. If the Vce-sat value exceeds the reference value, the abnormality determination circuit 231 determines that an abnormality has occurred in the IGBT 111 related to measurement. At this time, the abnormality determination circuit 231 outputs the detection of abnormality to the IGBT 111 (hereinafter referred to as abnormality detection) to the notification unit 25.

For example, the abnormality determination circuit 231 uses the threshold value as a reference value, and determines that an abnormality has occurred in the IGBT 111 related to measurement when the Vce-sat value exceeds the threshold value. Further, the abnormality determination circuit 231 uses a predetermined number of times the initial value as a reference value, and determines that an abnormality has occurred in the IGBT 111 related to measurement when the Vce-sat value exceeds a predetermined number of times the initial value. do. The predetermined number of times is, for example, about 2 to 3 times to 10 times. An abnormality related to the IGBT 111 will be explained below.

FIG. 9 is a diagram illustrating an example of a cause of abnormality in the IGBT 111. Here, in order to simplify the explanation, the insulating substrate and the like on the base plate are omitted. As shown in FIG. 9, each input/output to the IGBT 111 is electrically connected to an external metal layer 120 or the like via a bonding wire 119 shown in FIG. 9, for example. IGBT 111 is installed on base plate 124 via solder 122, for example. Heat generated in the IGBT 111 is transferred to the base plate 124 via the solder 122. The base plate 124 has a function as a heat sink that radiates heat generated by the IGBT 111.

The materials on the heat transfer path between the IGBT 111 and the base plate 124 generally have different coefficients of linear expansion. Therefore, cracks 126 as shown in FIG. 9 may occur in the solder 122 corresponding to the joint between the IGBT 111 and the base plate 124 due to thermal fatigue (metal fatigue) accompanying the operation of the IGBT 111. The crack 126 increases the thermal resistance between the IGBT 111 and the base plate 124. As the thermal resistance increases due to the occurrence of the crack 126, the temperature of the IGBT 111, such as the junction temperature Tj, increases.

FIG. 10 is a diagram showing an example of a change in the Vce-sat value with respect to a predetermined collector current Icp when the junction temperature Tj changes from 25°C to 150°C. That is, FIG. 10 shows a change in the characteristics of the Vce-sat value due to an increase in thermal resistance regarding the IGBT 111. As shown in FIG. 10 and the like, the electrical characteristics of the IGBT 111 (representative characteristic curve 25CC and representative characteristic curve 150CC) depend on the temperature of the IGBT 111, for example, the junction temperature Tj. That is, the relationship between the Vce-sat value and the current output (collector current Ic) differs depending on the temperature conditions of the IGBT 111. Therefore, when the IGBT 111 operates under the same current output condition, that is, the same collector current Ic, if the relationship between the collector current Ic, which is the current output, and the Vce-sat value changes (collapses) due to changes in the IGBT 111 over time, This means that a change has occurred in the temperature conditions of the IGBT 111.

When comparing the Vce-sat value measured by the measurement unit 17 with the representative characteristic curve provided by the manufacturer, for example, the relationship between the collector current Ic and the Vce-sat value is assumed in the design of the operating conditions of the IGBT 111. There is no problem in using the IGBT 111 as long as it matches the representative characteristic curve corresponding to the junction temperature Tj=80°C. However, if the Vce-sat value is located on the representative characteristic curve corresponding to a junction temperature Tj = 150°C that deviates from the design assumption due to changes in the IGBT 111 over time, the abnormality determination circuit 231 determines that some kind of temperature increase has occurred in the IGBT 111. It can be determined that it did. In other words, since there is a correlation between voltage, current, and temperature in the representative characteristic curve as described above, the temperature rise of IGBT 111 due to an increase in thermal resistance due to the occurrence of cracks 126 in solder 122, etc. will affect the electrical characteristics. This appears as a direction of performance deterioration. Therefore, by monitoring the electrical characteristics of the IGBT 111, it is possible to detect signs of abnormality in the IGBT 111 or deterioration of the characteristics of the IGBT 111, triggered by a change in the relationship between voltage, current, and junction temperature.

For these reasons, when the temperature of the IGBT 111 increases from 25° C. to 150° C., the Vce-sat value increases from Vce-sat p1 to Vce-sat p2, as shown in FIG. Therefore, the abnormality determination circuit 231 can detect an abnormality in the IGBT 111 by comparing the Vce-sat value and the reference value (threshold value and initial value) for a constant collector current Ic. Note that the determination in the abnormality determination circuit 231 in FIG. 2 will be described in detail later.

Note that the abnormality of the IGBT 111 is not limited to one related to thermal damage caused by the crack 126, but may also be caused by, for example, a malfunction in a heat dissipation circuit connected to a heat dissipation plate such as the base plate 124. The heat dissipation circuit is installed, for example, in a cooler such as an air-cooled device or a water-cooled device. An example of a malfunction in an air cooling device is damage to a bearing related to a cooling fan. Furthermore, problems with water cooling equipment include, for example, clogging of piping related to the circulation of refrigerant liquid. Furthermore, defects in TIM (Thermal Interface Material) used to connect a heat sink and a heat sink circuit include, for example, deterioration due to separation of heat sink grease. According to this embodiment, it is also possible to detect a malfunction in the cooling device as an abnormality in the IGBT 111.

The abnormality determination circuit 231 determines whether the Vce-sat value stored in the storage unit 19 increases over a predetermined period. For the same collector current Ic, the fact that the Vce-sat value continues to increase over a predetermined period indicates that the IGBT 111 continues to deteriorate at least over a predetermined period. Therefore, the abnormality determination circuit 231 detects an abnormality in the IGBT 111 when the Vce-sat value continues to increase over a predetermined period.

When the measured Vce-sat value exceeds the reference value, that is, when an abnormality detection is received from the determination unit 23, the notification unit 25 issues a restriction command to limit the drive of the power device 11 and a predetermined warning. Output to control unit. The notification unit 25 is realized by an abnormality notification circuit 251 as a hardware configuration. The abnormality notification circuit 251 is realized by, for example, a DSP, ASIC, FPGA, CPLD, SPLD, or the like. The abnormality notification circuit 251 outputs a restriction command to the drive restriction circuit 131 when the measured Vce-sat value exceeds the reference value.

Further, the abnormality notification circuit 251 may output a restriction command and a warning to the control unit when the Vce-sat value stored in the storage unit 19 increases over a predetermined period. The abnormality notification circuit 251 may output the damage prediction calculated by the calculation unit 21 to the control unit. The abnormality notification circuit 251 may display warnings, damage predictions, etc. on the display of the medical image diagnostic apparatus in which the present medical image diagnostic apparatus power supply device 1 is installed, or may indicate maintenance of the medical image diagnostic apparatus. You may also send it to a service center that will perform the repair.

The above is a general description of the power supply device 1 for a medical image diagnostic apparatus according to the present embodiment. Hereinafter, a procedure for detecting an abnormality in the IGBT 111 (hereinafter referred to as an abnormality detection process) executed in the power supply device 1 for a medical image diagnostic apparatus will be described. FIG. 11 is a flowchart illustrating an example of the procedure of abnormality detection processing. It is assumed that prior to execution of the abnormality detection process shown in FIG. 11, calibration of the representative characteristic curve regarding the IGBT 111, that is, derivation of the initial value and the initial calibration curve 150UC, has been executed in advance. The abnormality detection process is executed when a medical image diagnostic apparatus equipped with the medical image diagnostic apparatus power supply device 1 is started up or when the state of the IGBT 111 is monitored while the medical image diagnostic apparatus is in operation.

(Anomaly detection processing)
(Step S111)
When a collector current output command regarding the initial value and initial calibration curve 150UC is output from the control unit of the medical image diagnostic apparatus, the sampling timing generation circuit 151 generates a sampling window, that is, a sampling timing, based on the collector current Ic output command. Set. The sampling timing generation circuit 151 outputs the set sampling timing to the Vce-sat measurement circuit 171.

(Step S112)
The Vce-sat measurement circuit 171 measures the Vce-sat value at the set sampling timing. The Vce-sat measurement circuit 171 outputs the measured Vce-sat value to the storage section 19 and the abnormality determination circuit 231. At this time, the abnormality determination circuit 231 reads the reference value (threshold value and initial value) from the storage unit 19. Note that reading of the reference value may be executed at any timing before step S113 below. Note that in this step, the calculation unit 21 may calculate a damage prediction of the IGBT 111 from the increasing tendency of the Vce-sat value, and the calculated failure prediction may be outputted to the control unit etc. by the abnormality notification circuit 251.

(Step S113)
The abnormality determination circuit 231 compares the measured Vce-sat value with a threshold value corresponding to the collector current value in the output command. If the measured Vce-sat value is equal to or greater than the threshold (YES in step S113), the abnormality determination circuit 231 outputs abnormality detection to the abnormality notification circuit 251 as shown in FIG. If the measured Vce-sat value is less than the threshold (NO in step S113), the process in step S114 is executed.

(Step S114)
The abnormality determination circuit 231 compares the measured Vce-sat value with a predetermined number times the initial value corresponding to the collector current value in the output command. If the measured Vce-sat value is sufficiently larger than the initial value, that is, if the measured Vce-sat value is larger than the predetermined number of times the initial value (YES in step S114), the abnormality determination circuit 231 detects the abnormality. It is output to the abnormality notification circuit 251 as shown in FIG. If the measured Vce-sat value is not sufficiently larger than the initial value, that is, if the measured Vce-sat value is smaller than a predetermined number of times the initial value (NO in step S114), the process of step S115 is executed.

(Step S115)
The abnormality determination circuit 231 determines whether the Vce-sat value increases over a predetermined period. In other words, the abnormality determination circuit 231 performs self-diagnosis of the IGBT 111 using the log of the Vce-sat value. The self-diagnosis by the abnormality determination circuit 231 corresponds to detecting a continued change (increase) in the Vce-sat value as a sign of an abnormality in the IGBT 111. The determination process in this step corresponds to determining whether the IGBT 111 has deteriorated over time. If the Vce-sat value increases over a predetermined period (YES in step S115), the process in step S116 is executed.

If the Vce-sat value has not increased over the predetermined period (NO in step S115), the process in step S111 is executed. That is, if the determination results in steps S113 to S115 are all NO, the process in step S111 is repeated. Thereby, the state (abnormal or normal) of the IGBT 111 is constantly monitored. Note that the process of this step may be executed before the process of step S113 or step S114.

(Step S116)
If YES in steps S113 to S115, that is, if abnormality detection is output from the abnormality determination circuit 231, the abnormality notification circuit 251 outputs a restriction command to the drive restriction circuit 131 and the control section. In addition, the abnormality notification circuit 251 outputs a predetermined warning to the control unit.

(Step S117)
The drive restriction circuit 131 drives the IGBT 111 in degenerate operation. Note that the degenerate operation may be executed by the control unit of the medical image diagnostic apparatus in which the present medical image diagnostic apparatus power supply device 1 is mounted. Further, in this step S117, it is also possible to stop driving the IGBT 111.

As a modification of the technical concept of the present embodiment, when the sampling window condition is not satisfied and the sampling timing cannot be set during operation of the medical image diagnostic apparatus equipped with the power supply device 1 for the medical image diagnostic apparatus, the step In S112, the Vce-sat value may be constantly measured. At this time, according to this modification, at least one process from step S113 to step S115 can be executed at all times regardless of the current output condition. Furthermore, as another modification of the technical idea of the present embodiment, at least one of the processes from step S113 to step S115 for determining whether the IGBT 111 is abnormal may be executed.

According to the power supply device 1 for a medical image diagnostic apparatus according to the embodiment described above, the power device 11 is driven according to the drive signal output from the control unit in the medical image diagnostic apparatus, and the collector 117 and emitter 115 of the power device 11 are , and determines whether the Vce-sat value exceeds a reference value regarding the Vce-sat value for the collector current Ic in the collector 117, and determines whether the Vce-sat value exceeds the reference value. In this case, a restriction command for restricting the drive of the power device 11 and a predetermined warning are output to the control unit of the medical image diagnostic apparatus. Further, according to the present power supply device 1 for a medical image diagnostic apparatus, a voltage value (threshold value) corresponding to the current rating at the upper limit temperature regarding damage to the power device 11 is used as a reference value in accordance with each of the plurality of collector currents.

As a result, according to the power supply device 1 for a medical image diagnostic apparatus, the thermal dependence and reference value of the electrical characteristics of the IGBT 111, which is a power device used in the inverter circuit, are used to detect abnormalities in the IGBT 111 due to heat. The presence or absence of the IGBT 111 is determined from the viewpoint of a change in the electrical characteristics of the IGBT 111. That is, according to the power supply device 1 for a medical image diagnostic apparatus, the thermal resistance increases due to cracks 126 of the solder 122 due to thermal fatigue of the IGBT 111, and the electrical resistance of the IGBT 111 due to the temperature rise of the IGBT 111 due to the increase in thermal resistance. By detecting changes in characteristics, it is possible to predict damage to the IGBT 111.

For these reasons, according to the present power supply device 1 for medical image diagnostic equipment, by using the element characteristic curve provided by the manufacturer, only the electrical characteristics such as voltage and current are monitored, and the temperature of the IGBT 111 is monitored. etc. are no longer necessary. As a result, according to the present power supply device 1 for a medical image diagnostic apparatus, a temperature sensor for measuring the temperature of the IGBT 111, temperature monitoring of the IGBT 111, definition of abnormality judgment conditions based on circuit operation, etc. are not required, and the circuit configuration is simple. Since the electrical characteristics of the IGBT 111 are monitored, signs of damage to the IGBT 111, which is the main focus, can be detected. In addition, according to the power supply device 1 for a medical image diagnostic apparatus, the IGBT 111 can be passively degenerated and stopped in response to a new command from a host that has received an abnormality warning.

From the above, according to the power supply device 1 for a medical image diagnostic apparatus, damage to the power supply device 1 for a medical image diagnostic apparatus 1 due to sudden breakage can be avoided by predicting damage to the IGBT 111. The impact on the system related to equipment can be reduced or avoided, and overall reliability can be improved. Furthermore, according to the present power supply device 1 for medical image diagnostic equipment, abnormality detection processing can be realized with a simple circuit configuration with a small number of parts without complicating the circuit configuration. Reliability can be improved by increasing the mean time between failures (MTBF).

Further, according to the present power supply device 1 for a medical image diagnostic apparatus, the correspondence relationship (voltage difference ) and the third electrical characteristic of the power device 11 obtained by measurement at a predetermined temperature before use of the power device 11, and a predetermined number times the initial value set based on this is used as the reference value.

The device characteristic curves (first electrical characteristics and second electrical characteristics) provided by the manufacturer used for abnormality determination indicate representative values of IGBTs, and it is known that the characteristics of IGBTs vary from individual to individual. Therefore, the initial calibration of the element characteristic curve and abnormality determination threshold is performed by measuring the correlation between the voltage, current, and temperature of the individual IGBT 111 at the manufacturing stage of the power supply device 1 for the medical image diagnostic apparatus. As a result, according to the present power supply device 1 for a medical image diagnostic apparatus, the accuracy of abnormality detection of the IGBT 111 can be improved. In addition, during normal use after shipment of the power supply device 1 for medical image diagnostic equipment, a temperature measurement circuit etc. for initial calibration is not required, so it is possible to predict damage to the power device 11 without complicating the abnormality detection circuit. can be done easily.

Further, according to the power supply device 1 for a medical image diagnostic apparatus, the sampling timing regarding the measurement of the Vce-sat value by the measurement unit 17 is generated based on the output command of the collector current Ic in the collector 117 of the IGBT 111. Measure the Vce-sat value according to the sampling timing. As a result, according to the power supply device 1 for a medical image diagnostic apparatus, the Vce-sat value can be measured under the condition that the same collector current Ic is always output, further improving the accuracy of abnormality detection of the IGBT 111. can be done.

Further, according to the power supply device 1 for a medical image diagnostic apparatus, when the measured Vce-sat value exceeds the reference value, a restriction command is issued to the restriction unit 13 that can restrict the drive of the power device 11 by adjusting the drive signal. output and adjust the drive signal based on the limit command. At this time, the restriction on the drive of the power device 11 is a degenerate operation of the power device 11, and is at least one of a reduction in the duty ratio of the drive signal and a reduction in the amplitude of the drive signal.

For these reasons, according to the present power supply device 1 for a medical image diagnostic apparatus, when the electrical characteristics (voltage/current) monitored in the IGBT 111 exceed a preset threshold value in comparison with the representative characteristic curve, , as a sign of damage to the IGBT 111, an abnormality warning is notified to the upper host side (for example, a control unit in a medical image diagnostic apparatus), and further, the operation (output) of the power supply device 1 for the medical image diagnostic apparatus is reduced or stopped, etc. on the safety side. It is possible to perform control that operates on In addition, according to the present power supply device 1 for a medical image diagnostic apparatus, the restriction unit 13 actively performs degeneration and stop control without waiting for a new command from a host that has received an abnormality warning, and the operation can be performed more quickly. You can also deal with abnormalities.

Further, according to the power supply device 1 for a medical image diagnostic apparatus, it is determined whether or not a plurality of stored Vce-sat values increase over a predetermined period, and a plurality of Vce-sat values increase over a predetermined period. If the number increases over , a limit command and a warning are output to the control unit. As a result, according to the present power supply device 1 for a medical image diagnostic apparatus, signs of abnormality in the IGBT 111 can be used for self-diagnosis, and degenerate operation of the IGBT 111 can be performed.

Further, according to the power supply device 1 for a medical image diagnostic apparatus, a damage prediction regarding use of the power device 11 is calculated based on the change in the Vce-sat value over time, and the calculated damage prediction is output to the control unit. As a result, according to the power supply device 1 for a medical image diagnostic apparatus, prediction of damage to the IGBT 111 based on the increasing trend of the Vce-sat value can be used for maintenance as preventive maintenance.

If an increase in thermal resistance occurs due to cracks 126 or the like in the solder 122 due to thermal fatigue of the IGBT 111, the abnormality in the IGBT 111 will not self-recover. Therefore, when the abnormality progresses, the output of other power supplies automatically stops, or the drive of IGBT 111 shifts to degenerate operation. By checking notifications (warning), maintenance logs, etc., it is possible to determine whether or not the damage prediction function related to the abnormality detection processing according to this embodiment is implemented in another power supply device, that is, whether or not the damage prediction function related to the abnormality detection processing according to this embodiment is implemented in another power supply device. It can be determined whether the technical features in the power supply device 1 are implemented.

In addition, in this embodiment, the function to detect an abnormality in the IGBT 111 is described in the manual of the other power supply device as part of the self-diagnosis function of the other power supply device, along with information on how to read error notifications, maintenance logs, etc. There may be cases where this is the case. For this reason, for example, if an error notification indicates that the system will automatically stop or transition to degraded operation due to "damage prediction," if you check the abnormality detection algorithm of IGBT 111 in other power supplies, you can use this medical image diagnosis. It can be determined whether the technical features of the device power supply device 1 are implemented.

Moreover, as an application example of the technical idea in this embodiment, the present power supply device 1 for medical image diagnosis apparatus is not limited to being used in a medical image diagnosis apparatus, but may be used in other apparatuses. For example, the present power supply device 1 for a medical image diagnostic apparatus may be used as a power supply device in an electric vehicle, an electric device having a power device, or the like. At this time, the power device 11 is driven in accordance with a drive signal output from a host computer in an electric vehicle or electric device. Furthermore, when the measured Vce-sat value exceeds the reference value, the notification unit 25 outputs a restriction command for restricting the drive of the power device 11 and a predetermined warning to the host computer. The operations and effects in this application example are the same as those in the power supply device 1 for medical image diagnostic apparatus in this embodiment, so the explanation will be omitted.

According to at least the embodiments, modifications, applications, etc. described above, it is possible to easily predict damage to the power device 11 in the power supply device. This makes it possible to provide a low-cost power supply device with improved reliability without complicating the circuit.

Although several embodiments have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, and combinations of embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

1 Power supply device for medical image diagnostic equipment 10 Vce-sat monitoring circuit 11 Power device 13 Restriction unit 15 Generation unit 17 Measurement unit 19 Storage unit 21 Calculation unit 23 Judgment unit 25 Notification unit 111 Insulated gate bipolar transistor (IGBT)
113 Gate 115 Emitter 117 Collector 131 Drive restriction circuit 151 Sampling timing generation circuit 171 Vce-sat measurement circuit 231 Abnormality determination circuit 251 Abnormality notification circuit

Claims (10)

A power device that is driven according to a drive signal output from a control unit in a medical image diagnostic apparatus;
a measurement unit that measures a Vce-sat value corresponding to the collector-emitter voltage of the power device;
a determination unit that determines whether the Vce-sat value exceeds a reference value;
a notification unit that outputs a restriction command to limit driving of the power device and a predetermined warning to the control unit when the Vce-sat value exceeds the reference value;
Equipped with
The determination unit determines a correspondence relationship between a first electrical characteristic of the power device at a predetermined temperature lower than an upper limit temperature regarding damage to the power device and a second electrical characteristic of the power device at the upper limit temperature; and a third electrical characteristic of the power device obtained by measurement at the predetermined temperature, and using a predetermined number of times the initial value set based on the reference value.
Power supply device for medical image diagnostic equipment. The determination unit uses, as the reference value, a voltage value corresponding to a current rating at an upper limit temperature regarding damage to the power device.
The power supply device for a medical image diagnostic apparatus according to claim 1. further comprising a generation unit that generates sampling timing regarding measurement of the Vce-sat value based on a collector current output command in the power device,
The measurement unit measures the Vce-sat value according to the sampling timing.
The power supply device for a medical image diagnostic apparatus according to claim 1 or 2 . further comprising a limiting section capable of limiting driving of the power device by adjusting the drive signal,
The notification unit outputs the restriction command to the restriction unit when the Vce-sat value exceeds the reference value,
the limiting unit adjusts the drive signal based on the limiting command;
A power supply device for a medical image diagnostic apparatus according to any one of claims 1 to 3 . The drive limitation is a degenerate operation of the power device, and is at least one of a reduction in the duty ratio of the drive signal and a reduction in the amplitude of the drive signal.
A power supply device for a medical image diagnostic apparatus according to any one of claims 1 to 4 . The reference value is set according to each of a plurality of collector currents in the power device,
A power supply device for a medical image diagnostic apparatus according to any one of claims 1 to 5 . further comprising a storage unit that stores the Vce-sat value,
The determination unit determines whether the stored Vce-sat value increases over a predetermined period,
The notification unit outputs the restriction command and the warning to the control unit when the stored Vce-sat value increases over a predetermined period.
A power supply device for a medical image diagnostic apparatus according to any one of claims 1 to 6 . further comprising a calculation unit that calculates a damage prediction regarding use of the power device based on a change in the Vce-sat value over time,
The notification unit outputs the damage prediction to the control unit.
The power supply device for a medical image diagnostic apparatus according to claim 7 . The power device is realized by an insulated gate bipolar transistor,
A power supply device for a medical image diagnostic apparatus according to any one of claims 1 to 8 . A power device that drives according to a drive signal output from a host computer;
a measurement unit that measures a Vce-sat value corresponding to the collector-emitter voltage of the power device;
a determination unit that determines whether the Vce-sat value exceeds a reference value;
a notification unit that outputs a restriction command to limit driving of the power device and a predetermined warning to the host computer when the Vce-sat value exceeds the reference value;
Equipped with
The determination unit determines a correspondence relationship between a first electrical characteristic of the power device at a predetermined temperature lower than an upper limit temperature regarding damage to the power device and a second electrical characteristic of the power device at the upper limit temperature; and a third electrical characteristic of the power device obtained by measurement at the predetermined temperature, and using a predetermined number of times the initial value set based on the reference value.
power supply.

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