JP2009232514A - Protection circuit, semiconductor device, and electric apparatus - Google Patents

Abstract

The accuracy of an overcurrent protection function is improved.
Based on a detection resistor that detects a current flowing through a protected circuit as a voltage, a set current flowing through the protected circuit, and an actual voltage generated in the detection resistor in response to the set current, A correction circuit that corrects a value of a reference voltage for protecting the protected circuit from an overcurrent, and the measured voltage and the reference voltage are compared to detect whether or not the measured voltage exceeds the reference voltage. A protection circuit comprising: an overcurrent detection circuit; and a control circuit that controls to protect the protected circuit from an overcurrent when the actually measured voltage exceeds the reference voltage in the overcurrent detection circuit.
[Selection] Figure 1

Description

  The present invention relates to a protection circuit, a semiconductor device, and an electric device.

  For example, a power semiconductor device used in an inverter circuit may be destroyed in an extremely short time when an abnormality such as a three-phase motor lock occurs. Therefore, when the current flowing through the power semiconductor device becomes an overcurrent exceeding the reference current, it is necessary to appropriately provide an overcurrent protection function for stopping the operation of the inverter circuit.

  In order to realize an overcurrent protection function by detecting whether or not the current flowing through the power semiconductor device exceeds the reference current, for example, a current detection resistor that detects the current flowing through the power semiconductor device as a voltage Etc. are used. Then, the voltage detected by the current detection resistor and the reference voltage having a magnitude corresponding to the magnitude of the reference current are compared by a differential amplifier or the like, and when the detected voltage exceeds the reference voltage, the operation of the inverter circuit is stopped. Let

For example, a shunt resistor is used as such a current detection resistor.
JP 2003-319546 A

  By the way, a shunt resistor used as a current detection resistor has a relatively small resistance value so that a voltage generated at both ends does not increase even when an overcurrent flows. For this reason, the voltage detected by the shunt resistor is easily affected by the voltage drop of the wiring impedance generated from the wiring pattern of the shunt resistor. When receiving such influences, the magnitude of the voltage detected by the shunt resistor as the current flowing through the power semiconductor device or the like may not correspond to the magnitude of the current actually flowing through the power semiconductor device or the like. In such a case, an error occurs in the detection of the overcurrent, and there is a possibility that the overcurrent protection function cannot be fully exhibited.

  A main invention for solving the problem is a protection circuit, wherein a detection resistor that detects a current flowing through the protected circuit as a voltage, a set current flowing through the protected circuit, and the set current corresponding to the set current A correction circuit for correcting a value of a reference voltage for protecting the protected circuit from an overcurrent based on an actual voltage generated in a detection resistor, and comparing the actual voltage with the reference voltage, An overcurrent detection circuit that detects whether or not a voltage exceeds the reference voltage, and when the measured voltage exceeds the reference voltage in the overcurrent detection circuit, control is performed to protect the protected circuit from overcurrent. A control circuit.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, it is possible to improve the accuracy of the overcurrent protection function.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

<< Device using integrated circuit with overcurrent protection function >>
=== Inverter circuit ===
The inverter apparatus 100 provided with the protection circuit which implement | achieves an overcurrent protection function based on this embodiment is demonstrated with reference to FIG.

  The overcurrent protection function according to the present embodiment is to stop the three-phase motor 130 when the current to be detected exceeds the predetermined current due to the lock of the three-phase motor 130, etc. This function prevents current destruction and failure of the protected object such as the three-phase motor 130.

  The inverter device 100 according to the present embodiment is used in power electronics devices such as an air conditioner, a washing machine, and a refrigerator, and converts AC power into AC power of another magnitude, frequency, and phase according to the inverter load. It is a device for. Specifically, the inverter device 100 converts the AC voltage of the three-phase AC power source 105 including the R-phase coil, the S-phase coil, and the T-phase coil into a DC voltage by the converter circuit 110, and then converts the AC voltage by the inverter circuit 120. An AC voltage for driving an inverter of a three-phase motor 130 (inverter load) having a U-phase coil, a V-phase coil, and a W-phase coil is generated based on the DC voltage.

  In FIG. 1, the inverter device 100 includes an inverter circuit 120, a microcomputer 140 (correction circuit), a three-phase motor 130, a converter circuit 110, and a three-phase AC power source 105. The protection circuit according to the present embodiment includes the microcomputer 140 and the inverter circuit 120.

  The inverter circuit 120 is provided as an integrated circuit including at least a V + terminal, a V− terminal, a U terminal, a V terminal, a W terminal, voltage monitoring terminals Lu, Lv, Lw, and voltage adjustment terminals Mu, Mv, Mw. .

A DC voltage changed by the converter circuit 110 is applied between the V + terminal and the V− terminal. A smoothing capacitor CX is connected between the V + terminal, the V− terminal, and the converter circuit 110, and a DC voltage applied from the converter circuit 110 between the V + terminal and the V− terminal is stabilized by the smoothing capacitor CX. To do.
The U terminal, V terminal, and W terminal are connected to the U phase coil, V phase coil, and W phase coil of the three-phase motor 130, respectively.

  The voltage monitoring terminals Lu, Lv, and Lw are terminals for monitoring the detection voltages of the shunt resistors Ru, Rv, and Rw (detection resistors) by the microcomputer 140 outside the inverter circuit 120.

  The voltage adjustment terminals Mu, Mv, and Mw are terminals for supplying reference voltages Vru, Vrv, and Vrw individually adjusted by the microcomputer 140 toward the overcurrent detection circuit 123, respectively.

  The inverter circuit 120 includes a switching circuit 121, shunt resistors Ru, Rv, and Rw (detection resistors), RC filters 122a, 122b, and 122c, an overcurrent detection circuit 123, and amplification circuits 124a, 124b, and 124c, And a driver circuit 125 (control circuit).

  The switching circuit 121 includes switching elements Q1 to Q6 and regenerative diodes D1 to D6 connected in reverse parallel to the switching elements Q1 to Q6, and supplies a DC voltage applied via the V + terminal and the V− terminal as a power source. Operates as a voltage. As the switching elements Q1 to Q6, power semiconductor devices such as power MOSFETs and IGBTs are employed.

  The switching elements Q1, Q2, and Q3 are provided on the current discharge side (V + terminal side) and are called source transistors. The switching elements Q4, Q5, Q6 are provided on the current suction side (V-terminal side) and are called sink transistors. Switching elements Q1 and Q4 are connected in series, and the connection point of switching elements Q1 and Q4 is connected to the U terminal. The switching elements Q2 and Q5 are connected in series, and the connection point of the switching elements Q2 and Q5 is connected to the V terminal. The switching elements Q3 and Q6 are connected in series, and the connection point of the switching elements Q3 and Q6 is connected to the W terminal.

  The shunt resistors Ru, Rv, and Rw are resistance elements that are provided between the emitters of the switching elements Q4, Q5, and Q6 and the V-terminal, respectively, and are used for overcurrent detection in the overcurrent detection circuit 123. The shunt resistor Ru is a resistance element used for overcurrent detection with respect to a current input from the U terminal via the U-phase coil. The shunt resistor Rv is a resistance element used for overcurrent detection with respect to a current input from the V terminal via the V-phase coil. The shunt resistor Rw is a resistance element used for overcurrent detection for a current input from the W terminal via the W-phase coil.

  The RC filter 122a is a filter that applies a voltage generated at a connection point na between the switching element Q4 and the shunt resistor Ru via the signal line 127a and outputs a smoothed voltage Vu to the overcurrent detection circuit 123. . The RC filter 122b is a filter that applies a voltage generated at a connection point nb between the switching element Q5 and the shunt resistor Rv via the signal line 127b and outputs a voltage Vv obtained by smoothing the voltage to the overcurrent detection circuit 123. . The RC filter 122c is a filter that receives a voltage generated at a connection point nc between the switching element Q6 and the shunt resistor Rw via the signal line 127c and outputs a smoothed voltage Vw to the overcurrent detection circuit 123. .

  The overcurrent detection circuit 123 includes voltages Vu, Vv, Vw supplied via the signal lines 127a to 127c, and reference voltages Vru, vrv, Vrw supplied from a digital / analog converter 405 (to be described later) of the microcomputer 140. Is a circuit that detects whether or not an overcurrent has passed through any of the shunt resistors Ru, Rv, and Rw. The overcurrent detection circuit 123 outputs a low level detection signal DET when an overcurrent in the inverter circuit 120 is detected. Further, when the detection signal DET is high impedance, it represents a case where no overcurrent is detected. A detailed configuration example of the overcurrent detection circuit 123 will be described later.

  The amplifying circuit 124a serves as a voltage follower that applies a voltage generated at a connection point na between the switching element Q4 and the shunt resistor Ru via a signal line 128a and outputs a monitor voltage Vsu obtained by impedance conversion of the voltage to the microcomputer 140. It has a function. The amplifying circuit 124b is a voltage follower that applies a voltage generated at a connection point nb between the switching element Q5 and the shunt resistor Rv via the signal line 128b and outputs a monitor voltage Vsv obtained by impedance conversion of this voltage to the microcomputer 140. It has a function. The amplifying circuit 124c is a voltage follower that applies a voltage generated at a connection point nc between the switching element Q6 and the shunt resistor Rw via the signal line 128c and outputs a monitor voltage Vsw obtained by impedance conversion of this voltage to the microcomputer 140. It has a function.

  The driver circuit 125 (control circuit) outputs a control signal for controlling the rotation speed of the three-phase motor 130 to the switching circuit 121 in accordance with an instruction from the microcomputer 140 or the like. When the driver circuit 125 receives the high-impedance detection signal DET from the overcurrent detection circuit 123, the driver circuit 125 has, for example, a phase difference of 120 degrees, and controls on / off of the switching elements Q1 to Q3. Three pulse width modulated first rectangular waves, and three pulse width modulations that are generally 180 degrees out of phase with respect to the first rectangular waves and control on / off of the switching elements Q4 to Q6 The control signal (each base signal of switching element Q1-Q6) which consists of the 2nd rectangular wave which was made is output.

  Further, when the driver circuit 125 receives the low level detection signal DET from the overcurrent detection circuit 123, the driver circuit 125 outputs a control signal for turning off all the switching elements Q1 to Q6. Thereby, the overcurrent protection function for the switching circuit 121 is executed. The control signal when the high-impedance detection signal DET is output from the overcurrent detection circuit 123 is not limited to turning off all the switching elements Q1 to Q6. Any signal may be used as long as it is instructed to control to such an extent that protection is possible.

=== Overcurrent detection circuit ===
A detailed configuration example of the overcurrent detection circuit 123 according to the present embodiment will be described with reference to FIG. The overcurrent detection circuit 123 includes three open collector output comparators 1233a, 1233b, and 1233c, a capacitor Ca connected between the signal line 129a connected to the positive terminal of the open collector output comparator 1233a and the ground, and an open collector output. A capacitor Cb connected between the signal line 129b connected to the + terminal of the comparator 1233b and the ground, and a capacitor Cc connected between the signal line 129c connected to the + terminal of the open collector output comparator 1233c and the ground. It is comprised by.

  In the open collector output comparator 1233a, the reference voltage Vru is applied to the + terminal from the microcomputer 140 via the signal line 129a, and the voltage Vu output from the RC filter 122a is applied to the − terminal. The open collector output comparator 1233a operates with the power supply voltage Vcc. When the voltage Vu is lower than the reference voltage Vru, the comparison signal UO of the open collector output comparator 1233a is high impedance, and when the voltage Vu is higher than the reference voltage Vru, the comparison signal UO of the open collector output comparator 1233a is at the low level. Become.

  In the open collector output comparator 1233b, the reference voltage Vrv is applied from the microcomputer 140 via the signal line 129b to the + terminal, and the voltage Vv output from the RC filter 122b is applied to the − terminal. The open collector output comparator 1233b operates with the power supply voltage Vcc. When the voltage Vv is lower than the reference voltage Vrv, the comparison signal VO of the open collector output comparator 1233b is high impedance, and when the voltage Vv is higher than the reference voltage Vrv, the comparison signal VO of the open collector output comparator 1233b is low level. Become.

  In the open collector output comparator 1233c, the reference voltage Vrw is applied to the + terminal from the microcomputer 140 via the signal line 129c, and the voltage Vw output from the RC filter 122c is applied to the − terminal. The open collector output comparator 1233c operates with the power supply voltage Vcc. When the voltage Vw is lower than the reference voltage Vrw, the comparison signal WO of the open collector output comparator 1233c becomes high impedance, and when the voltage Vw is higher than the reference voltage Vrw, the comparison signal WO of the open collector output comparator 1233c is low level. Become.

  The comparison signals UO, VO, WO of the open collector output comparators 1233a, 1233b, 1233c are connected to the connection point P by wired OR. A combined output signal obtained by combining the comparison signals UO, VO, and WO from the connection point P is input to the driver circuit 125 as the detection signal DET.

=== Microcomputer ===
The configuration of the microcomputer 140 will be described with reference to FIG.
The relationship between the current flowing through the shunt resistor Ru and the voltage generated at the connection point na between the switching element Q4 and the shunt resistor Ru (shunt resistance detection voltage) is, for example, according to Ohm's law as shown by the solid line a in FIG. Based on this, a proportional straight line having a slope corresponding to the resistance value of the shunt resistor Ru is obtained. Therefore, from the value of the voltage generated at the connection point na based on the relationship between the current flowing through the shunt resistance Ru and the voltage generated at the connection point na according to the resistance value of the shunt resistance Ru shown in FIG. The value of the current flowing through the shunt resistor Ru can be detected. In other words, based on the relationship shown in FIG. 3a, the reference current value can be converted into a voltage value to obtain the reference voltage value (initial value). Here, the reference current is a current having a reference magnitude for determining whether or not to execute the overcurrent protection function. That is, the reference current is a current that becomes a threshold for setting an overcurrent when the current flowing through the switching circuit 121 is larger than the reference current.

  However, the actual measurement value of the voltage generated at the connection point na depends on the influence of the voltage drop due to the wiring impedance (broken line b in FIG. 3) and the shunt resistance Ru according to the wiring pattern when the shunt resistor Ru is incorporated in the inverter device 100. When the flowing current is 0 A, there is a case where it is affected by the offset voltage generated by the transmission system or the like (one-dot chain line c in FIG. 3). In this case, the current flowing through the shunt resistor Ru and the actual measurement value of the voltage generated at the connection point na are, for example, the relationship shown by the solid line d in FIG. 3, and therefore do not match the relationship shown by the solid line a in FIG. Therefore, the reference voltage (initial value) set based on the relationship shown by the solid line a in FIG. 3 is a voltage value corresponding to the value of the reference current in the relationship with the measured value of the voltage generated at the connection point na. Not. Therefore, the overcurrent detection circuit 123 detects the overcurrent by comparing the reference voltage (initial value) set based on the relationship shown by the solid line a in FIG. 3 with the actual measurement value of the voltage generated at the connection point na. Then, an error may occur in the detection of the overcurrent. The same applies to the shunt resistors Rv and Rw.

  Therefore, the microcomputer 140 individually supplies a plurality of set currents whose current values are determined in advance to each of the shunt resistors Ru, Rv before the inverter device 100 is shipped, for example, during calibration operation. , Rw, a plurality of voltages generated at a connection point na between the switching element Q4 and the shunt resistor Ru, a connection point nb between the switching element Q5 and the shunt resistor Rv, and a connection point nc between the switching element Q6 and the shunt resistor Rw. Monitor the measured value of. Based on the set current and the monitored voltage, the relationship between the current flowing through the shunt resistor Ru and the actual measured value of the voltage generated at the connection point na, the current flowing through the shunt resistor Rv and the actual measurement of the voltage generated at the connection point nb. The relationship between the value and the current flowing through the shunt resistor Rw and the measured value of the voltage generated at the connection point nc is obtained. Based on the obtained relationships, reference voltages Vru, Vrv, and Vrv corresponding to the magnitude of the reference current are output to the overcurrent detection circuit 123 in relation to the measured values of the voltages generated at the connection points na, nb, and nc. The overcurrent detection error of the overcurrent detection circuit 123 is calibrated.

  Note that processing performed by the protection circuit according to the present embodiment regarding the current input from the terminal U is hereinafter referred to as processing for the U phase. In addition, processing performed by the protection circuit according to the present embodiment regarding the current input from the terminal V is hereinafter referred to as processing for the V phase. In addition, processing performed by the protection circuit according to the present embodiment regarding the current input from the terminal W is hereinafter referred to as processing for the W phase.

  Further, DVs0 (Dvs1) shown in FIG. 2 indicates monitor voltage data DVsu0 (DVsu1) when the protection circuit according to the present embodiment performs the process for the U phase, and monitors when the process for the V phase is performed. The voltage data DVsv0 (DVsv1) is indicated, and when the process for the W phase is performed, the monitor voltage data DVsw0 (DVsvw1) is indicated.

  Further, DVr shown in FIG. 2 indicates reference voltage data DVru when the protection circuit according to the present embodiment performs processing for the U phase, and indicates reference voltage data DVrv when processing for the V phase. When processing for the W phase is performed, reference voltage data DVrw is shown.

  The microcomputer 140 includes an analog / digital converter 401, a memory unit 402, a parameter calculation unit 403 (calculation processing unit), a reference voltage calculation unit 404 (calculation processing unit), and a digital / analog converter 405. The

  The analog-digital converter 401 is connected to the voltage monitoring terminals Lu, Lv, Lw of the inverter circuit 120. The analog-digital converter 401 receives the monitor voltage Vsu0 and the monitor voltage Vsu1 from the voltage monitor terminal Lu. Further, the monitor voltage Vsv0 and the monitor voltage Vsv1 are input from the voltage monitor terminal Lv. Further, the monitor voltage Vsw0 and the monitor voltage Vsw1 are input from the voltage monitor terminal Lw.

  Here, the monitor voltage Vsu0 (Vsu1) is a setting current As0 (As1) whose current value is predetermined by turning on the switching elements Q4 and Q2 of the switching circuit 121 or the switching elements Q4 and Q3. The voltage generated at the connection point na when flowing to Ru is a monitor voltage output via the amplifier circuit 124a. Further, the monitor voltage Vsv0 (Vsv1) means that the set current As0 (As1) whose current value is predetermined by turning on the switching elements Q5 and Q1 of the switching circuit 121 or the switching elements Q5 and Q3 is the shunt resistor Rv. The voltage generated at the connection point nb when the current flows through is the monitor voltage output via the amplifier circuit 124b. Further, the monitor voltage Vsw0 (Vsw1) means that the set current As0 (As1) whose current value is determined in advance by turning on the switching elements Q6 and Q1 of the switching circuit 121 or the switching elements Q6 and Q3 is the shunt resistor Rw. Is a monitor voltage that is output via the amplifier circuit 124c when the voltage generated at the connection point nc.

  The analog-to-digital converter 401 converts the input monitor voltages Vsu0, Vsu1, Vsv0, Vsv1, Vsw0, Vsw1 into digital values, and monitors the monitor voltage data DVsu0, Dvsu1, DVsv0, DVsv1, DVsw0, DVsw1 as a memory unit. Stored in 402.

  In this embodiment, the set current As0 is set to 0A, and the monitor voltage data DVsu0, DVsv0, DVsw0 are stored in the memory unit 402 as offset voltages, respectively.

  The memory unit 402 includes monitor voltage data DVsu0, DVsu1, DVsv0, DVsv1, DVsw0, DVsw1 input from the analog-digital converter 401, set current data DAs0, DAs1 corresponding to digital values of the set currents As0, As1, and parameters. The parameters Su, Sv, Sw output from the calculation unit 403 and the reference current data ISD that is a digital value of the reference current value and is input from the outside of the microcomputer 140 are stored. Note that the memory unit 402 can be configured by, for example, a nonvolatile flash memory that can be electrically erased and written and read out at once, or a nonvolatile EEPROM that can be electrically written and read out in units of 1 byte.

  The parameter calculation unit 403 is based on the set current data DAs0, DAs1 and the monitor voltage data DVsu0, DVsu1 among the data stored in the memory unit 402, and the monitor voltage with respect to the change in the set current value (DAs1-DAs0). The ratio of the value change (DVsu1-DVsu0) is calculated as the parameter Su and stored in the memory unit 402. Similarly, the parameter Sv is calculated based on the set current data DAs0 and DAs1 and the monitor voltage data DVsv0 and DVsv1, and stored in the memory unit 402. Similarly, the parameter Sw is calculated based on the set current data DAs0 and DAs1 and the monitor voltage data DVsw0 and DVsw1, and stored in the memory unit 402.

  The reference voltage calculation unit 404 includes a shunt resistor based on the reference current data ISD, parameters Su, Sv, Sw, and monitor voltage data DVs0, DVv0, DVw0 (offset voltage) among the data stored in the memory unit 402. A relationship between currents flowing through Ru, Rv, and Rw and measured values of voltages generated at the connection points na, nb, and nc is obtained, and a reference that is a voltage value corresponding to the reference current data ISD is obtained based on the relationship. Voltage data DVru, DVrv, DVrw is output.

  The digital-to-analog converter 405 converts the reference voltage data DVru, DVrv, Dvrw calculated by the reference voltage calculation unit 404 into analog reference voltages Vru, Vrv, Vrw and outputs them to the voltage adjustment terminals Mu, Mv, Mw, respectively. To do.

  For example, under the control of the microcomputer 140 (not shown), the driver circuit 125 allows the setting current As0 (As1) to flow between the source and sink electrodes of the switching elements Q1 to Q6 of the switching circuit 121. A current I0 (I1) is supplied to the base electrodes of Q1 to Q6. As a result, the set current As0 (As1) flows through the shunt resistors Ru, Rv, and Rw via the switching circuit 121, and the voltages at the connection points na, nb, and nc become voltages corresponding to the set current As0 (As1).

=== Arithmetic Processing Operation of Inverter Device ===
For the correction operation according to the present embodiment, for example, an arithmetic processing operation of the inverter device 100 that is performed in advance before the product of the inverter device 100 is shipped will be described with reference to FIG.

  In FIG. 4, S103 to S104, S108 to S109, and S111 to S112 surrounded by broken lines indicate processing on the microcomputer 140 side, and S114 indicates processing set to the microprocessor 140 from the outside of the microprocessor 140. The other steps show processing on the inverter circuit 120 side.

  In addition, the base electrode of the switching element shown in S101 and S107 of FIG. 4 indicates the switching element Q4 and Q2 of the switching circuit 121 or the base electrode of the switching element Q4 and Q3 in the case of processing for the U phase, and V In the case of processing for the phase, the switching elements Q5 and Q1 of the switching circuit 121 or the base electrodes of the switching elements Q5 and Q3 are shown. In the case of processing for the W phase, the switching elements Q6 and Q2 of the switching circuit 121, or The base electrode of switching element Q6 and Q1 is shown.

  Also, the monitor voltage Vs0 (Vs1) shown in S103 (S108) of FIG. 4 indicates the monitor voltage Vsu0 (Vsu1) in the case of processing for the U phase, and the monitor voltage Vsv0 (Vsv1) in the case of processing for the V phase. In the case of processing for the W phase, the monitor voltage Vsw0 (Vsvw1) is indicated.

  Also, the monitor voltage data DVs0 (Dvs1) shown in S104 and S111 (S109, S111) of FIG. 4 indicates the monitor voltage data DVsu0 (DVsu1) in the case of the U phase process, and the case of the V phase process. Indicates monitor voltage data DVsv0 (Dvsv1), and in the case of processing for the W phase, indicates monitor voltage data DVsw0 (DVsw1).

  Also, the parameter S shown in S111 and S112 of FIG. 4 indicates the parameter Su in the case of processing for the U phase, indicates the parameter Sv in the case of processing for the V phase, and indicates the parameter in the case of processing for the W phase. Sw is shown.

  Further, in FIG. 4, the processing for each of the U phase, the V phase, and the W phase is performed in the order of the U phase, the V phase, and the W phase, but the processing may be performed from any phase.

First, when the arithmetic processing operation of the inverter device 100 is started, an instruction to supply the current I0 to the base electrodes of the switching elements Q1 to Q6 is sent from the microcomputer 140 to the driver circuit 125 (S101).
Next, the current I0 is supplied from the driver circuit 125 to the base electrode of the switching element of the switching circuit 121 corresponding to the process for the U phase (S102).
Next, the monitor voltage Vs0 monitored by the microcomputer 140 is converted into digital value monitor voltage data DVs0 by the analog-digital converter 401 (S103).
Next, the monitor voltage data DVs0 obtained in S103 is stored in the memory unit 402 as an offset voltage (S104).

Next, when the monitor voltage DVs0 for the V phase is not stored in the memory unit 402 as an offset voltage (S105: NO), the processing of S102 to S104 is performed for the V phase.
Next, when the monitor voltage DVs0 for the W phase is not stored in the memory unit 402 as an offset voltage (S105: NO), the processing of S102 to S104 is performed for the W phase.
When the monitor voltage DVs0 for each of the U-phase, V-phase, and W-phase is stored in the memory unit 402 (S105: YES), a current is supplied from the microcomputer 140 to the driver circuit 125 to the base electrodes of the switching elements Q1 to Q6. An instruction to supply I1 is sent (S106).
Next, the current I1 is supplied from the driver circuit 125 to the base electrode of the switching element of the switching circuit 121 corresponding to the process for the U phase (S107).

Next, the monitor voltage Vs1 monitored by the microcomputer 140 is converted into monitor voltage data DVs1 having a digital value by the analog-digital converter 401 (S108).
Next, the monitor voltage data DVs1 obtained in S108 is stored in the memory unit 402 (S109).
Next, when the monitor voltage DVs1 for the V phase is not stored in the memory unit 402 (S110: NO), the processing of S107 to S109 is performed for the V phase.
Next, when the monitor voltage DVs1 for the W phase is not stored in the memory unit 402 (S110: NO), the processing of S107 to S109 is performed for the W phase.

When the monitor voltage DVs1 for each of the U phase, V phase, and W phase is stored in the memory unit 402 (S110: YES), the parameter calculation unit 403 uses the data stored in the memory unit 402 for the U phase. Then, the following arithmetic expression (1) is performed, and the parameter S is calculated (S111).
S = (DVs1-DVs0) / As1 (1)
Then, the parameter S obtained in S111 is stored in the memory unit 402 (S112).

Next, when the parameter S for the V phase is not stored in the memory unit 402 (S113: NO), the processing of S111 to S112 is performed for the V phase.
Next, when the parameter S for the W phase is not stored in the memory unit 402 (S113: NO), the processing of S111 to S112 is performed for the W phase.

  When the parameters S for the U-phase, V-phase, and W-phase are stored in the memory unit 402 (S113: YES), a reference current arbitrarily set from the outside of the microcomputer 140 is stored in the memory unit 402. Reference current data ISD, which is a digital value, is input (S114). The reference current data ISD input in S114 is stored in the memory unit 402 (S115), and the inverter device 100 arithmetic processing operation is terminated.

=== Correcting Operation of Inverter Device ===
The reference voltage correction operation of the inverter device 100 according to the present embodiment will be described with reference to FIGS.

  In FIG. 5, S201 to S205 surrounded by a broken line are processes indicating an initializing operation before the normal drive control of the motor 130 by the inverter device 100 is performed. In the inverter device 100 according to the present embodiment, the reference voltages Vru, Vrv, and Vrw corrected by the microcomputer 140 are respectively supplied to the overcurrent detection circuit 123 during the initialization operation immediately after the set power is turned on.

  Further, the reference voltage data DVr shown in S202 and S203 of FIG. 5 indicates the reference voltage data DVru in the case of the process for the U phase, indicates the reference voltage data DVrv in the case of the process for the V phase, and for the W phase. In the case of the above process, the reference voltage data DVrw is shown.

  Further, the parameter S shown in S202 of FIG. 5 indicates the parameter Su in the case of the process for the U phase, indicates the parameter Sv in the case of the process for the V phase, and indicates the parameter Sw in the case of the process for the W phase. Show.

  Further, DVs0 shown in S202 of FIG. 5 indicates DVsu0 in the case of processing for the U phase, DVsv0 in the case of processing for the V phase, and DVsw0 in the case of processing for the W phase.

  Further, the voltage adjustment terminal M shown in S203 of FIG. 5 indicates the voltage adjustment terminal Mu in the case of the process for the U phase, indicates the voltage adjustment terminal Mv in the case of the process for the V phase, and the W phase. In the case of the process, the voltage adjustment terminal Mw is shown.

  In FIG. 5, the processing for each of the U phase, the V phase, and the W phase is performed in the order of the U phase, the V phase, and the W phase, but the processing may be performed from any phase.

First, the set power source of the microcomputer 140 is turned on when the drive of the inverter device 100 is started (S201). Next, the reference voltage data DVr is obtained from the data stored in the memory unit 402 by the above-described calibration operation corresponding to the process for the U phase by the reference voltage calculation unit 404 based on the following calculation formula (2). Calculated (S202).
DVr = ISD × S + DVs0 (2)
Then, the reference voltage data DVr obtained in S202 is converted to an analog reference voltage Vr by the digital-analog converter 405 of the microcomputer 140 and output to the terminal M (S203).

Next, when the reference voltage Vr for the V phase is not output to the terminal M (S204: NO), the processing of S202 to S203 is performed for the V phase.
Next, when the reference voltage Vr for the W phase is not output to the terminal M (S204: NO), the processes of S202 to S203 are performed for the W phase.

  When the reference voltage Vr for each of the U-phase, V-phase, and W-phase is output to the terminal M (S204: YES), other initialization processing of the inverter device 100 is performed (S205). When the initialization process of S205 is completed, the inverter device 100 performs normal drive control of the motor 130 based on the corrected reference voltage Vr (S206). Thereafter, the power source of the microcomputer 140 is turned off (S207), and the normal drive control of the motor 130 of the inverter device 100 is finished.

  Here, for example, when the value of the set current As0 is 0A, the value of the set current As1 is 15A, and the value of the reference current is 35A, the current flowing through the shunt resistors Ru, Rv, Rw, and the monitor voltage Vsu, An example of the relationship with Vsv and Vsw is shown by straight lines U, V, and W in FIG.

Based on the parameters Su, Sv, and Sw calculated by the parameter calculation unit 403, values corresponding to the slopes of the straight lines U, V, and W are obtained in consideration of the influence of the wiring impedance component.
Further, by setting the current flowing through the inverter circuit 120 to 0 A, an offset voltage can be obtained from the monitor voltages Vsu0, Vsv0, and Vsw0.

  Therefore, functions indicating the straight lines U, V, and W can be calculated from the parameters Su, Sv, and Sw and the monitor voltage data DVsu0, DVsv0, and DVsw0. Since the reference voltage data DVru, DVrv, Dvrw corresponding to the reference current data ISD is obtained based on the functions indicating the straight lines U, V, W, the voltages generated at the connection points na, nb, nc are measured. In relation to the value, the reference voltages Vru, Vrv, Vrv corresponding to the value of the reference current can be obtained. The overcurrent detection circuit 123 compares the voltages Vu, Vv, and Vw generated at the connection points na, nb, and nc through the RC filters 122a, 122b, and 122c with the reference voltages Vru, Vrv, and Vrv, respectively. Thus, the overcurrent detection error can be corrected.

  As described above, in the inverter device 100 including the protection circuit according to the present embodiment, the microcomputer 140 uses the switching circuit 121 and the shunt resistors Ru, Rv, and the reference voltage as the reference for the overcurrent detection of the overcurrent detection circuit 123. In relation to the measured values of the voltages generated at the connection points na, nb, and nc of Rw, correction is performed so that the voltage value indicates the value of the reference current. Therefore, the overcurrent detection error of the overcurrent detection circuit 123 can be calibrated, and the accuracy of the overcurrent protection function can be improved.

  Further, the inverter device 100 including the protection circuit according to the present embodiment is configured so that the current flowing through the plurality of shunt resistors is detected even when the overcurrent detection of each of the currents of the plurality of phases is performed using the plurality of shunt resistors. It is possible to individually obtain the relationship with the actually measured values of the voltages detected by the plurality of shunt resistors, and to individually correct the reference voltage for each phase. Therefore, it is possible to improve the accuracy of the overcurrent protection function without causing a shift in timing for executing the overcurrent protection function among a plurality of phases.

  Further, the overcurrent detection circuit 123 according to the present embodiment includes an open collector output comparator 1233, and the overcurrent protection function is realized by inputting the detection signal DET to the driver circuit 125. As described above, in the inverter device 100 according to the present embodiment, the overcurrent protection operation can be performed directly when the overcurrent is detected by the detection signal DET regardless of the software processing via the arithmetic processing. The speed of current protection operation can be increased.

<< Semiconductor device using insulated metal substrate technology >>
=== Semiconductor Device ===
FIG. 7 is a diagram showing the structure of the semiconductor device 10 using the insulated metal substrate technology. 7A is a cross-sectional view of the semiconductor device 10, and FIG. 7B is a front view of the semiconductor device 10. FIG. 8 is a perspective view of the semiconductor device 10 shown in FIG.

  The case material 3 is formed with a square cylinder surrounded by four side walls 3A, 3B, 3C, 3D, and has an opening 20 on the lower side (in the direction toward C ′ of the paper surface CC ′ axis) and an upper side (paper surface). An opening 21 in the direction of C-C ′ axis toward C) is provided.

  On the inside of the side walls 3 </ b> C and 3 </ b> D of the case material 3, a convex portion 22 facing the inside of the case material 3 is provided at a position slightly elevated from the opening 20. Further, on the inner side of the side walls 3C, 3D of the case material 3, the back surface on the side surface side of the second substrate 2 (surface in the direction toward the C ′ of the paper surface CC ′ axis) at a position slightly lowered from the opening 21. The contact part 23 which contacts is provided.

  On the other hand, in order to secure the screw holes 24 inside the side walls 3A and 3B of the case material 3, they are brought into contact with the back surface of the second substrate 2 (the surface in the direction toward the C ′ of the paper surface CC ′ axis). A contact portion 25 and a separation portion 26 that separates in the direction of the paper surface BB ′ axis of the second substrate 2 are provided. The heat generated in the space between the second substrate 2 and the first substrate 1A is released to the outside through the separation portion 26. In order to obtain a circulating action, it is preferable that at least two spacing portions 26 are formed.

  The base substrate 1B and the first substrate 1A are made of a conductive material such as a material mainly composed of Cu, Al, or Fe, or an alloy thereof. Further, it is made of a material having excellent thermal conductivity, and may be an insulating material such as aluminum nitride or boron nitride. In general, Cu and Al are adopted from the viewpoint of cost, and both are conductive, and therefore, an insulation treatment is required. In the following description, it is assumed that the base substrate 1B and the first substrate 1A employ Al.

  A first substrate 1A having a size smaller than that of the base substrate 1B is fixed to the surface of the base substrate 1B (surface in the direction toward the C of the paper surface C-C ′ axis) by an insulating adhesive 27. The base substrate 1B and the front and back surfaces of the first substrate 1A are provided with an anodized film for preventing scratches.

  In the first substrate 1A, an insulating film 28 is coated on the anodized film on the surface, and the first conductive pattern 7 made of Cu is formed thereon. The first conductive pattern 7 includes an island, a wiring, an electrode pad, and the like. For example, an inverter circuit 120 including switching elements Q <b> 1 to Q <b> 6 as the power semiconductor device 4 is electrically connected to the island of the first conductive pattern 7. In addition, a diode, a resistor, a capacitor, and the like are mounted on the first substrate 1A.

  A lead fixing pad is provided on the side surface of the first substrate 1A (the surface on the A, A 'side of the paper surface A-A' axis), and the external lead 29 is fixed by a brazing material. The external lead 29 is inserted into the through hole 32 of the mounting board so as to protrude from the head of the case material 3.

  The first substrate 1A fixed to the surface of the base substrate 1B is fitted into the opening 29 on the lower side of the case material 3 (the direction toward the C ′ of the paper surface C-C ′ axis). An L-shaped step is provided on the inside of the side walls 3A, 3B, 3C, and 3D of the case material 3, and the side surface of the base substrate 1B (the surface on the A, A ′ side of the paper surface AA ′ axis and the paper surface B) -The surface on the B, B 'side of the B' axis) and the surface (the surface in the direction toward the C on the paper surface CC 'axis) come into contact with each other and are fixed. Therefore, the opening 29 is sealed by the first substrate 1A fitted to the case material 3. As described above, since the second substrate 2 is held on the side walls 3C and 3D of the case material 3, the first substrate 1A and the second substrate 2 are arranged in parallel in parallel.

  The 2nd board | substrate 2 consists of resin-made boards, for example, the glass epoxy board | substrate called a printed circuit board is preferable. At least one or more second conductive patterns 30 are formed on the surface of the second substrate 2 (the surface in the direction toward the C of the paper surface C-C ′ axis). Similar to the first conductive pattern 7, the second conductive pattern 30 includes islands, wirings, electrode pads, and the like. For example, an integrated circuit 31 such as a microcomputer 140 or a DSP (Digital Signal Processor) for controlling the operation of the inverter circuit 120 is electrically connected to one island of the second conductive pattern 30. Since the integrated circuit 31 such as the microcomputer 140 or the DSP desirably avoids the influence of heat, it can be accurately operated by being disposed on a substrate different from the substrate on which the inverter circuit 120 is disposed. In addition, a transistor, a diode, a resistor, a capacitor, and the like are mounted on the second substrate 2.

  Before the second substrate 2 is provided on the case material 2, a resin that completely seals the circuit components mounted on the first substrate 1A is provided by potting or the like. Moreover, resin which completely seals the circuit components mounted on the second substrate 2 is provided as necessary. A through hole 32 for inserting the external lead 29 is provided in the vicinity of the side of the second substrate 2. Through the through hole 32, the circuit mounted on the first substrate 1A and the circuit mounted on the second substrate 2 are electrically connected.

  The inverter circuit 120 shown in FIG. 1 can be realized as the semiconductor device 10 using the insulated metal substrate technology shown in FIGS. FIG. 9 is a diagram illustrating a mounting example of main circuit components of the semiconductor device 10. 9A is a diagram showing an example of mounting the first substrate 1A, and FIG. 9B is a diagram showing an example of mounting the second substrate 2. As shown in FIG. In the mounting example, the first board 1A is a metal board, and the second board 2 is a printed board.

  As shown in FIG. 9A, at least an inverter circuit 120 is mounted on the first substrate 1A. The voltage monitoring terminals Lu, Lv, Lw, the voltage adjustment terminals Mu, Mv, Mw, etc. are realized as the external leads 29 shown in FIG. Since the first substrate 1A is a metal substrate with good thermal conductivity, it is less necessary to consider variations in the temperature characteristics of the shunt resistors Ru, Rv, and Rw, and overcurrent protection can be performed appropriately. .

  Further, as shown in FIG. 9B, a control circuit 200 is mounted on the second substrate 2 as an integrated circuit 31 such as a microcomputer 140 or a DSP. As described above, the control circuit 200 is the most important circuit component that governs overall control of the semiconductor device 10, and therefore the second substrate 2 different from the circuit component mounted on the first substrate 1 </ b> A. It is preferable to mount on the side. As a result, the control circuit 200 is not affected by the temperature rise of the switching circuit 121 and the driver circuit 125 mounted on the first substrate 1A. The case material 3 does not necessarily have to hold the second substrate 2 on which the control circuit 200 is arranged together with the first substrate 1A. The control circuit 200 may be held by a case material (not shown) different from the case material 3.

  Further, in consideration of deformation of the case material 3 due to thermal expansion of the first substrate 1A and deformation of the second substrate 2 due to heat generated from the circuit components mounted on the first substrate 1A, the first substrate 1A. It is preferable to mount the circuit components by shifting from the center position where the second substrate 2 is most curved.

=== Application Example of Semiconductor Device ===
The semiconductor device 10 (hereinafter referred to as an inverter circuit module 60) is attached to, for example, an air conditioner outdoor unit 50 (housing) shown in FIG. FIG. 10 is a diagram showing the internal structure of the air conditioner outdoor unit 50 using the inverter circuit module 60.
The air conditioner outdoor unit 50 includes a fan 51, a frame 52, a compressor 53, a heat radiation fin 55, and an inverter circuit module 60.

  The fan 51 circulates air and has a heat exchanger on the back side (negative direction of the paper surface Y axis). The frame 52 is arranged adjacent to the fan 51 in parallel in the positive direction of the paper surface X axis. A compressor 53 is provided below the insole plate 52A of the frame 52 (the negative direction of the paper surface Z axis), and circuit components are mounted above the insole plate 52A of the frame 52 (the positive direction of the paper surface Z axis). A printed circuit board or the like is attached.

  Furthermore, the inverter circuit module 60 is mounted on the side wall plate 54 on the negative direction side of the X axis of the frame 52. The inverter circuit module 60 is attached so that the second substrate 2 side faces the side wall plate 54 of the frame 52. In addition, the radiation fins 55 are attached to the base circuit board 1B side of the inverter circuit module 60.

  The code | symbol 56 shown in FIG. 10 has shown air flow path AB produced | generated because air warms and raises. The grooves of the radiating fins 55 are provided in the direction along the air flow paths A to B (the Z-axis direction on the paper surface). Therefore, if the notch portions along the air flow paths A to B shown in FIG. 8 are also provided on the inverter circuit module 60, the heat dissipation is further improved. In addition, the codes | symbols 70-73 shown by FIG. 8 have shown an example of the notch part along the air flow paths AB shown in FIG.

  Although the present embodiment has been described above, the above-described examples are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed / improved without departing from the spirit thereof, and the present invention includes equivalents thereof.

  For example, in the above-described embodiment, the case of the inverter circuit 120 and the inverter circuit module 60 is given as an example of the circuit and circuit module having the overcurrent protection function. Any circuit or circuit module that needs to have an overcurrent protection function, such as a signal processing circuit and its circuit module, or a display drive circuit for the plasma display and its circuit module, may be used.

  In addition, as an application example of the inverter circuit module 60, the air conditioner outdoor unit 50 is given as an example, but in various industries such as washing machines, refrigerators, automobiles, robots, FA (Frequency Automation), NC (Numerical Control) machine tools It can be applied to electrical equipment that requires inverter control.

It is a figure which shows the structural example of the inverter apparatus containing the protection circuit which concerns on this embodiment. It is a figure which shows the structural example of the microcomputer shown in FIG. It is a figure which shows the relationship between the electric current which flows into shunt resistance, and the voltage which shunt resistance detects. It is a figure which shows the example of arithmetic processing operation | movement of the inverter apparatus which concerns on this embodiment. It is a figure which shows the correction | amendment operation example of the inverter apparatus which concerns on this embodiment. It is a figure which shows the relationship between the electric current which flows into the inverter circuit which concerns on this embodiment, and a monitor voltage. (A) is sectional drawing of the semiconductor device which concerns on this embodiment, (b) is a surface view of the semiconductor device which concerns on this embodiment. FIG. 8 is a perspective view of the semiconductor device shown in FIG. 7. (A) is the figure which showed the example of mounting of the 1st board | substrate of the semiconductor device shown in FIG. 7, (b) is the figure which showed the example of mounting of the 2nd board | substrate of the semiconductor device shown in FIG. It is the figure which showed the internal structure of the air-conditioner outdoor unit using the inverter circuit module which concerns on this embodiment.

Explanation of symbols

Ru, Rv, Rw Shunt resistor 123 Overcurrent detection circuit 125 Driver circuit 140 Microcomputer 1A First substrate 2 Second substrate 3 Case material 10 Semiconductor device 31 Integrated circuit 60 Inverter circuit module 50 Air conditioner outdoor unit

Claims (6)

A detection resistor for detecting the current flowing through the protected circuit as a voltage;
A reference voltage value for protecting the protected circuit from an overcurrent is corrected based on a set current flowing through the protected circuit and an actual voltage generated in the detection resistor corresponding to the set current. A correction circuit;
An overcurrent detection circuit that compares the measured voltage with the reference voltage and detects whether the measured voltage exceeds the reference voltage;
A control circuit that controls to protect the protected circuit from an overcurrent when the measured voltage exceeds the reference voltage in the overcurrent detection circuit;
A protection circuit comprising: The correction circuit includes:
Based on a plurality of set currents individually flowing in the protected circuit and a plurality of actually measured voltages generated individually in the detection resistors corresponding to the plurality of set currents, the current flowing in the detection resistors and the detection Obtaining a relationship of voltages generated in the resistors, and correcting the reference voltage based on the relationship;
The protection circuit according to claim 1. The correction circuit includes:
Based on the relationship, the reference voltage prepared as an initial value is corrected.
The protection circuit according to claim 2. A plurality of detection resistors for detecting a plurality of currents flowing through the protected circuit as a plurality of voltages;
In order to protect the protected circuit from an overcurrent based on a plurality of set currents flowing through the protected circuit and a plurality of actually measured voltages generated in the plurality of detection resistors corresponding to the plurality of set currents. A correction circuit that individually corrects the plurality of reference voltages,
An overcurrent detection circuit that compares the plurality of actually measured voltages with the plurality of reference voltages, respectively, and detects whether one or more of the actually measured voltages exceed the corresponding reference voltage;
A control circuit that controls to protect the protected circuit from overcurrent when one or more of the actually measured voltages exceed the corresponding reference voltage in the overcurrent detection circuit;
A protection circuit comprising: A substrate having a conductive pattern on the surface;
One or more integrated circuits electrically connected to the conductive pattern and disposed on the substrate;
A case for holding the substrate,
The integrated circuit comprises:
A protected circuit;
A detection resistor that detects a current flowing through the protected circuit as a voltage;
A reference voltage value for protecting the protected circuit from an overcurrent is corrected based on a set current flowing through the protected circuit and an actual voltage generated in the detection resistor corresponding to the set current. A correction circuit;
An overcurrent detection circuit that compares the measured voltage with the reference voltage and detects whether the measured voltage exceeds the reference voltage;
A control circuit that controls to protect the protected circuit from overcurrent when the measured voltage exceeds the reference voltage in the overcurrent detection circuit;
A semiconductor device. A substrate having a conductive pattern on the surface;
One or more integrated circuits electrically connected to the conductive pattern and disposed on the substrate;
A case for holding the substrate;
A case in which the case is disposed, and
The integrated circuit comprises:
A protected circuit;
A detection resistor for detecting the current flowing through the protected circuit as a voltage;
A reference voltage value for protecting the protected circuit from an overcurrent is corrected based on a set current flowing through the protected circuit and an actual voltage generated in the detection resistor corresponding to the set current. A correction circuit;
An overcurrent detection circuit that compares the measured voltage with the reference voltage and detects whether the measured voltage exceeds the reference voltage;
A control circuit that controls to protect the protected circuit from overcurrent when the measured voltage exceeds the reference voltage in the overcurrent detection circuit;
Electrical equipment characterized by that.

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