JP5721137B2 - Short-circuit protection device for semiconductor devices - Google Patents

Description

  The present invention relates to a short circuit protection device for a power semiconductor device, and particularly to provide a power semiconductor device that automatically and quickly protects a semiconductor element from a large current caused by a load short circuit and is less likely to fail. It relates to protective devices.

Power semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors) are widely used mainly in power control devices such as inverters.
When the load connected to the IGBT is short-circuited, a large current of 1000 A or more per 1 cm ^{2 of} the IGBT chip flows, the temperature of the chip rises rapidly by about 300 K in 1 μsec, and the IGBT is destroyed. High speed protection is required to prevent such destruction.

FIG. 18 shows an example of a conventional load short-circuit protection device.
In an IGBT used in a conventional load short-circuit protection device, a sense emitter having a small area obtained by separating the emitter from the main emitter of the IGBT is provided on a chip (see, for example, Patent Document 1). The sense emitter is connected to the main emitter through sense resistor R _S, the voltage drop across the sense resistor R _S is output to the control circuit.

In the conventional load short-circuit protection method, the current is taken out to the sense emitter about 1/1000 from the path through which the IGBT emitter current _IE flows, and the voltage drop is detected by the sense resistor R _S. Since a large current does not flow during the rated operation of the IGBT, the voltage drop at the sense resistor R _S is small and it is not determined that the load is short-circuited. On the other hand, when the load is short-circuited, a large current flows through the IGBT, and as a result, a large current flows in proportion to the sense emitter, and the voltage drop at the sense resistor R _S increases. Therefore, when the increase in the voltage drop is detected by the control circuit and it is determined that the load is short-circuited, the gate voltage of the IGBT is decreased to decrease the emitter current _IE flowing in the IGBT.

The conventional load short-circuit protection method described above has the following problems.
(1) Since a large current of 1000 A or more per 1 cm ² flows when the load is short-circuited, the emitter current I _E tends to cause noise in the current flowing through the sense emitter, and the control circuit determines that the load is short-circuited to prevent malfunction due to noise. It takes time to do. That is, it is necessary to pass through a filter to remove noise, but it takes time to remove noise by the filter (a time delay occurs), so it is difficult to speed up short-circuit protection.
(2) The IGBT has been reduced in size, thickness and capacity, and the current density flowing through the chip will increase while the thermal capacity of the chip will decrease in the future. Along with this, the speed of the temperature rise of the chip at the time of load short-circuiting becomes faster and higher-speed short-circuit protection is required, but it is difficult to increase the speed by the conventional protection method.

FIG. 19 shows changes in the gate charge Q _G when the above-described IGBT is in rated operation and when the load is short-circuited. The result shown in the figure is obtained by using an IGBT having a withstand voltage of 600 V and a collector-emitter voltage V _CE of 100 V.

As shown in the figure, when a load connected to a power semiconductor (power semiconductor device), for example, an IGBT, is short-circuited, the gate charge Q _G is reduced from that during rated operation. This is due to the mirror effect of the MOS gate element and the negative gate capacitance, and the characteristic that the gate charge Q _G decreases when the load is short-circuited is common to all MOS gate elements.

  FIG. 20 shows an outline of the load short-circuit protection device and its operating condition, and FIG. 21 shows details of the load short-circuit protection device of FIG.

  As shown in FIG. 20A, the load short-circuit protection device is configured by functions of a gate driving unit 51, a charge detection unit 52, a reference voltage generation unit 53, a determination unit 54, and the like.

  As shown in FIG. 21, the gate driving means 51 is means for amplifying the voltage and current of the pulse signal generated by the gate control signal (PWM) forming means 55 and transmitting it to the MOS gate of the IGBT. This is a means comprising a gate drive circuit comprising an amplifier AMP and transistors Tr1 and Tr2 for current amplification.

Charge detecting means 52 is a means composed of for example a current mirror circuit consisting of transistors Tr3~Tr6 and resistors R3 to R6, and the integration circuit using a resistor R _QG and capacitor C _M. Current mirror circuit, for the purpose of separating the control circuit for routing and load short decision through which the emitter current I _E of the IGBT, equal to the current I _G flowing through the gate of the IGBT, a current I _G ^* flowing through the charge detection unit Used for output.

Since the charge is obtained by time integration of the current, the gate charge Q _{G of the} IGBT is obtained by measuring the current I _G ^* flowing through the charge detection means 52. In order to detect the change in the gate charge Q _G of the IGBT, the current I _G ^* is converted into the gate charge voltage V _QG using the fact that the charge accumulated in the capacitor C _M is equal to the gate charge Q _G. Q _G change is detected.

The reference voltage generating means 53 determines the load short-circuit at high speed to the extent that no malfunction occurs with the value between the gate charge voltage V _QG at the rated operation and load short-circuit in consideration of the IGBT characteristics. _Is a means for generating a reference voltage V _REF .

The judging means 54 is a means for judging the load short circuit by comparing the magnitude of the gate charge voltage V _QG and the reference voltage V _REF .

At the rated operation, as shown in FIG. 20B, the gate charge voltage V _QG is larger than the reference voltage V _REF , and the protection signal is not output.

When the load short-circuit, even if the gate charge voltage V _QG with decreasing gate charge Q _G as shown in FIG. 20 (c) decreases, the gate charge voltage V _QG than the reference voltage V _REF becomes smaller. When the magnitudes of the gate charge voltage V _QG and the reference voltage V _REF are reversed, the judging means 54 judges that the load is short-circuited and outputs a protection signal. When the protection signal is output, the ON signal to the gate driving means 51 is cut off, and the input to the IGBT becomes an OFF signal to turn off the IGBT and cut off the emitter current _IE .
Such a protection method is already known and disclosed in, for example, Patent Document 2.

JP 2001-211059 A JP 2003-188382 A

As described above, when the short-circuit protection device disclosed in Patent Document 2 is used, since the change in the gate charge Q _G is detected, the protection speed is faster than the protection using the sense IGBT. On the other hand, it takes time to change parameters such as reference voltage V _REF (values of resistors, capacitors, etc., size and characteristics of transistors used, etc.). There is a problem that the performance of parts changes due to a change in temperature, which affects the judgment condition as to whether or not the load is short-circuited. Moreover, it is necessary to change the design of circuit parameters due to differences in the design of the IGBT to be used, withstand voltage, current capacity, etc., which increases complexity and is not suitable for mass production.

  Therefore, the present invention has been made in consideration of these circumstances, and a short circuit of a semiconductor device in which optimum parameters can be automatically set even if there is a difference in characteristics or a temperature change of a semiconductor element, particularly an IGBT. An object is to provide a protective device.

In order to solve the above problems, a first configuration of the present invention includes a charge detection means for detecting a voltage corresponding to the charge of the input portion of the semiconductor element, and a load short circuit from the charge of the input portion during rated operation of the semiconductor element. A reference voltage generating means for generating a reference voltage for determining whether the voltage detected by the charge detecting means corresponds to a gate charge at a rated operation of the semiconductor element or a gate charge at the time of a load short circuit In the short-circuit protection device for a semiconductor device, the reference voltage generation in a semiconductor device short-circuit protection device having a determination means for determining whether the voltage is a voltage and a semiconductor element driving means for outputting a signal for stopping the operation of the semiconductor element when the determination means detects a load short-circuit the means, characterized in that a reference voltage storage unit for memorize a reference voltage for determining the load short circuit from the charge of the input unit during rated operation during operation of the semiconductor element To.

  According to a second configuration of the present invention, in the first configuration, an analog / digital conversion unit that converts an analog output of the charge detection unit into a digital signal is provided, and the reference voltage generation unit and the determination unit are digitized. The digital-analog converting means converts the digital output signal from the judging means into an analog signal and outputs the analog signal to the semiconductor element driving means.

  According to a third configuration of the present invention, in the second configuration, a second analog / digital conversion unit that converts a gate control signal to the semiconductor element driving unit into a digital signal, and a digital signal from the determination unit when a load is short-circuited. Using an output signal as a trigger, an attenuation waveform forming means for converting a waveform output to the gate drive means into a digital attenuation waveform, an output of the second analog / digital conversion means, and an output of the attenuation waveform forming means are rated operations. And a multiplexer that selects and outputs to the digital-to-analog converting means according to the time and when the load is short-circuited.

According to the present invention, the reference voltage generating means, by providing the reference voltage storage unit for the reference voltage serial to憶to determine the load short-circuit from the input of the charge during the rated operation of the semiconductor device, the semiconductor device (IGBT) Even if there are differences in characteristics or temperature changes, the optimum parameters can be set automatically. Further, by using digital processing for the determination part, it is possible to increase the speed.

It is the block diagram and waveform diagram which show the basic composition of the short circuit protection apparatus of the semiconductor device of this invention. It is an operation | movement waveform diagram of the rated state in the block shown in FIG. It is an operation | movement waveform diagram of the load short circuit state in the block shown in FIG. It is a time chart of the time taken until short circuit protection. It is explanatory drawing of the outline and operating conditions of the short circuit protection apparatus using the digital circuit which concerns on embodiment of this invention. It is explanatory drawing which shows the outline | summary of the logic element of AND in the embodiment of this invention, and the outline | summary of signal composition. It is a block diagram which shows the outline | summary of the short circuit protection apparatus which incorporated the signal synthesis | combination function in embodiment of this invention in the digital circuit. It is explanatory drawing of the short circuit protection apparatus which mounted the several means based on embodiment of this invention on one semiconductor chip. It is explanatory drawing of the short circuit protection apparatus which mounted the several means based on embodiment of this invention on one semiconductor chip. It is explanatory drawing of the short circuit protection apparatus which mounted the several means based on embodiment of this invention on one semiconductor chip. It is explanatory drawing of the short circuit protection apparatus which mounted the several means based on embodiment of this invention on one semiconductor chip. It is a block diagram which shows the structure of the short circuit protection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the short circuit protection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the short circuit protection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the short circuit protection apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the short circuit protection apparatus which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the short circuit protection apparatus which concerns on embodiment of this invention. It is explanatory drawing of the short circuit protection apparatus using the conventional sense IGBT. It is a related figure of the gate voltage and gate charge in the conventional short circuit protection apparatus. It is a figure which shows the circuit diagram and operating condition of the short circuit protection apparatus using the conventional analog circuit. It is a circuit diagram of the short circuit protection apparatus using the conventional analog circuit.

The present invention is based on the fact that the gate charge Q _{G of the} IGBT is reduced when the load is short-circuited than when the rated operation is performed. That is, the main point of the present invention is to increase the speed of the conventional protection method by detecting the change in the gate charge Q _G of the IGBT.

  FIG. 1 shows an outline of a load short-circuit protection device according to the first embodiment, which was actually tested using a digital circuit, and its operating conditions. In this example, an IGBT is used as a power semiconductor element.

  The load short-circuit protection device 1 includes a gate drive circuit 2, a gate charge measurement circuit 3, an A / D converter 4, a digital filter 5, a peak detector 6, a comparator 7, a pulse generator 8, a gate off voltage 9, a gate controller 10, It is composed of a D / A converter 11.

  The gate drive circuit 2 is a circuit that amplifies the voltage and current of the pulse signal generated by the gate control signal (PWM) forming means and transmits it to the MOS gate of the IGBT, as in the conventional example shown in FIG. This circuit is composed of an amplifier for voltage amplification and a gate drive circuit for current amplification.

As in the circuit of FIG. 21, the gate charge measuring circuit 3 detects the gate charge for the purpose of separating the path through which the emitter current _IE that reaches a value of 1000 A or more when the load is short-circuited and the control circuit for determining the load short-circuit. A function to incorporate the circuit to be incorporated into the gate drive circuit 2. That current I _G flowing through the gate of the IGBT, as a circuit for equal output current I _G ^* flowing through the charge detection unit, a current mirror circuit, and constituted by an integrating circuit that uses a capacitor and a resistor. A circuit for detecting the gate charge is conceivable in addition to this circuit, and is not limited to this circuit system. For example, a circuit in which components that sense current magnetically are integrated on a semiconductor circuit, a circuit in which the gate is driven by electric charge, and the electric charge can be digitally controlled are examples.

The A / D converter 4 converts the gate charge voltage V _{QG into} a digital signal. In this embodiment, the A / D converter 4 is operated at 60 MHz.
The reason is that, as described above, the density of the current flowing through the IGBT is increased, and the speed required for protecting the IGBT is increased, and the protection in 1 μsec or less is required. From this value, the speed required for protection is calculated as 1 MHz or more. However, if protection is actually applied, 10 MHz or more, which is 10 times this value, is required when considering the number of clocks required for A / D conversion. The
For the above reason, in the first embodiment, the A / D converter 4 is operated at 60 MHz in order to obtain a sufficient load short-circuit protection speed.

A digitized signal is input to a digital circuit (using an FPGA (Field-Programmable Gate Array) or the like) to perform signal processing for load short-circuit protection. In the first embodiment, the digital circuit is operated at 32 MHz.
This is because, as with the reason for determining the parameters of the A / D converter 4 described above, program processing capability at a sufficient speed (10 MHz or higher) is required.

  The digital filter 5 realizes high reliability by removing noise of the digitized input signal and reducing signal variations to prevent program malfunction. In the present embodiment, noise removal at a frequency of 150 kHz or more is performed.

  Examples of the digital filter 5 include an FIR (Finite Impulse Response) filter in which a weighting parameter is added to each element of the moving average, or an IIR (Infinite Impulse Response) filter that obtains a desired filter characteristic by incorporating feedback. The IIR filter has a complicated structure, but the number of gates used by the digital circuit is small. On the other hand, the FIR filter has a simple configuration, but the number of gates used by the digital circuit is large.

  In the first embodiment, normally, the number of gates of a digital circuit is sufficiently large (400,000 gates), the number of coefficients required for design is small, and the time required for design can be shortened. A filter (10,000 gates) was used.

The peak detector 6 is used to detect a stable voltage V _PEAK at the high level of the waveform of the gate charge voltage V _QG at the rated operation output from the digital filter 5. A reference voltage V _REF for determining whether or not a load short circuit has occurred is generated from the detected value and stored.

As shown in FIG. 1B, the reference voltage V _REF is generated by automatically subtracting a certain value from the high-level and stable voltage V _PEAK of the detected gate charge voltage V _QG waveform. To do. The value to be subtracted is set to a value that does not cause a malfunction due to noise and can reliably determine a short circuit when the load is short-circuited.

For example, if the mirror charge (change value of the charge value that greatly changes the gate charge amount near the gate threshold voltage) is less than or equal to the value corresponding to the change in the charge amount, It is possible to detect changes and detect short circuits. In particular, if the value is between one-third and two-thirds of the value corresponding to the change in the amount of charge, there are few malfunctions. On the other hand, it is possible to increase the speed by reducing the subtraction value by improving the filter performance or removing the noise component.
For example, when the gate drive circuit 2 and the IGBT are formed on the same chip with an IGBT on a power IC, this value can be reduced, and high-speed protection is possible.

If the setting of V _REF as described above can be performed in a rated operation state that is not a load short-circuit, it can be used to determine a short circuit after the protection circuit is actually installed in the inverter device and the rated operation is performed. it is possible to store the V _REF, it becomes possible to correspond even what IGBT same protection circuit.

Further, even if the IGBT is replaced with a new type for future maintenance or the like, it is possible to protect the IGBT having different characteristics without changing the protection circuit or the gate drive circuit. In addition, it is conceivable that the characteristics of the gate charge change as the temperature of the IGBT changes. However, if the temperature changes, the parameters can be reset, or V _REF can be changed based on the data from the temperature sensor. It is also possible to reconfigure the system.

If a program that analyzes the waveform of the gate charge is set up in a test run before the inverter system is shipped, for example, the current flowing through the IGBT, the condition of the applied voltage, the temperature, and other changes in the gate charge characteristics are memorized, and the accuracy of short circuit detection Can be improved and malfunction can be prevented. In addition, by periodically resetting V _REF , it is possible to detect a short circuit with high accuracy even if the gate charge or the gate threshold characteristic changes due to the aging of the IGBT.

It is desirable that V _REF be equal to or lower than the voltage corresponding to the value of the stepped corner of the mirror charge (see FIG. 19, the corner of the A portion appearing at 11 V and 20 nC in this figure). In this case, malfunction can be prevented even when the gate voltage does not rise to a desired value for some reason.

If V _REF is stored in the memory as a function of V _GE , a more reliable setting with less malfunctions is possible. Specifically, set high V _REF is at V _GE is high, is at V _GE is low by setting low V _REF, fewer malfunctions can be reliable and fast protection. In rated operation, even if relatively low frequency noise is applied to the gate voltage or gate charge, if V _GE swings higher, Q _G becomes higher, and if V _GE swings lower, V _QG decreases. Because.

Once the reference voltage V _REF is generated, the value is stored by using a memory (flash memory or nonvolatile memory). Further, by using a large-capacity memory, the waveform of the gate charge Q _G during rated operation can be stored, and the reference voltage V _REF can be stored and generated as a waveform.

The gate charge voltage V _QG and the reference voltage V _REF are compared using a digitally configured comparator 7. When the gate charge voltage V _QG falls below the reference voltage V _REF , it is determined that the load is short-circuited, and a protection signal is output to the gate controller 10 (see FIG. 1C).

  The gate controller 10 directly outputs a TTL pulse from the pulse generator 8 during rated operation. In this embodiment, the TTL pulse output from the pulse generator 8 corresponds to a PWM (Pulse Width Modulation) signal in an actual practical device. When the load is short-circuited, the TTL pulse from the pulse generator 8 is interrupted, and the stored gate-off voltage 9 (in this case, a digital signal corresponding to 0 V) is output.

The D / A converter 11 performs analog signal processing of the signal from the pulse generator 8. In the first embodiment, the D / A converter 11 is operated at 125 MHz.
This is because the IGBT is actually operated at a switching frequency of 5 to 20 kHz, and the turn-on time of the IGBT is usually 500 nsec or less. In order to obtain sufficient time resolution, it is necessary to perform conversion at 20 MHz or more, which is 10 times or more. This is because when a high-performance IGBT is used, the turn-on time is about 100 nsec. Therefore, it is necessary to perform conversion at 100 MHz or more. In the first embodiment, D / A at 125 MHz in order to obtain sufficient time resolution. The converter 11 was operated.

  When the IGBT is rated, the signal from the pulse generator 8 passes through the gate controller 10 as it is, is converted into an analog signal by the D / A converter 11 and is input to the gate drive circuit 2 to drive the IGBT.

  When the load is short-circuited, the ON signal from the pulse generator 8 is cut off by the gate controller 10, and the input to the gate drive circuit 2 becomes the OFF signal. Thereby, the IGBT is turned off, and the main current flowing through the IGBT is cut off.

FIG. 2 shows the operation in the rated state.
As shown in the figure, the gate charge voltage V _QG does not decrease during rated operation. The signal output from the pulse generator 8 passes through the gate controller 10, is converted into an analog signal by the D / A converter 11, and is input to the gate drive circuit 2, thereby driving the IGBT.

FIG. 3 shows the operation in the load short-circuit state.
As shown in the figure, when the load is short-circuited, the gate charge voltage V _QG decreases compared to the rated operation. The decrease is detected by the comparator 7 in the digital circuit to determine that the load is short-circuited, and a signal is output to the gate controller 10. When a signal is input to the gate controller 10, the ON signal from the pulse generator 8 is cut off, and the input to the D / A converter 11 becomes an OFF signal. Thereby, the input to the gate driving circuit 2 becomes an OFF signal, and the IGBT is turned off to cut off the main current.

FIG. 4 shows the time required for load short-circuit protection.
As shown in the figure, it takes 2 μs from turning off the IGBT to cutting off the main current after the load short circuit occurs.

About half of the time from when the load short-circuit occurs until the main current is cut off is dead time for preventing malfunction of the program. If the load short circuit can be detected in real time while the gate charge voltage V _QG is rising while the performance of the digital filter 5 is improved and the dead time is reduced, the short circuit protection time can be shortened to 1 μs or less. It becomes.

FIG. 5 shows an outline and operating conditions of a load short-circuit protection device using a digital circuit according to the second embodiment.
As shown in FIG. 5A, the load short-circuit protection device 20 includes a gate drive unit 21, a charge detection unit 22, an analog / digital conversion unit 23, a filter 24, a reference voltage detection unit 25, a storage unit 26, and a determination unit. 27, gate control signal forming means 28, signal synthesis 29, and the like.

  The gate driving means 21 is a means for amplifying the voltage and current of the pulse signal generated by the gate control signal (PWM) forming means 28 and transmitting it to the IGBT MOS gate, as in the conventional example. This means is composed of an amplifier for voltage amplification and a gate drive circuit for current amplification.

  The charge detection means 22 is a means constituted by a current mirror circuit and an integration circuit as in the conventional example.

The analog / digital conversion means 23 is a means for converting the gate charge voltage V _{QG into} a digital signal.
A digitized signal is input to a digital circuit (using an FPGA or the like) to perform signal processing for load short-circuit protection.

The filter 24 removes noise from the input digitized signal and reduces signal variation, thereby preventing malfunction of the program and realizing high reliability.
The reference voltage detecting means 25 detects a stable voltage V _PEAK at the high level of the waveform of the gate charge voltage V _QG at the rated operation output from the filter 24, and determines whether or not a load short-circuit state has occurred from this detected value. This is means for generating a reference voltage V _REF for determination.

The storage means 26 is means for storing the reference voltage V _REF .
Once the reference voltage V _REF is generated, the value is stored by using a memory (flash memory or nonvolatile memory). Further, by using a large-capacity memory, the waveform of the gate charge Q _G during rated operation can be stored, and the reference voltage V _REF can be stored and generated as a waveform.

Determination means 27, as shown in FIG. 5 (b), by comparing the gate charge voltage V _QG and the reference voltage V _REF, it is determined that the load short circuit state when the gate charge voltage V _QG falls below the reference voltage V _REF Means.

In the signal synthesis 29, the input signal is processed using a logic circuit.
When the IGBT is in rated operation, the signal output from the determination unit 27 and the PWM signal output from the gate control signal (PWM) formation unit 28 are synthesized by a logic circuit, and the signal is input to the gate drive unit 21. The IGBT is driven.

  On the other hand, when the load is short-circuited, the ON signal output from the determination unit 27 described above is cut off, whereby the input signal to the gate drive unit 21 becomes an OFF signal. Thereby, the IGBT is turned off to cut off the main current.

  For example, as shown in FIG. 6A, signal synthesis is performed using AND logic elements. FIG. 6B shows the contents of the logical operation by the AND element.

  During the rated operation, as shown in FIG. 6C, a high signal is output from the determination means 27. The signal after the signal synthesis is the same as the signal output from the gate control signal (PWM) forming means 28. The IGBT is driven when the signal is input to the gate driving means 21.

  When the load is short-circuited, a low signal is output from the determination unit 27 as shown in FIG. Regardless of the signal output from the gate control signal (PWM) forming means 28, the Low signal is output as the signal after the signal synthesis. As a result, an OFF signal is input to the gate driving means 21 to turn off the IGBT and cut off the main current.

FIG. 7 shows an outline of a short-circuit protection device in which a signal synthesis function for synthesizing a protection signal and an output from a gate control signal (PWM) forming unit is incorporated in a digital circuit.
As shown in the figure, by performing signal synthesis with a digital circuit, it is possible to make it less susceptible to external noise.

FIG. 8 shows an outline of the short circuit protection device in which the digital circuit, the analog / digital conversion means 23, and the digital circuit are mounted on one semiconductor chip.
As shown in the figure, when the semiconductor chips are combined, the wiring length can be shortened and the influence of noise can be reduced. In addition, the circuit scale can be reduced and the cost can be reduced.

FIG. 9 shows an outline of a short-circuit protection device in which the digital circuit, the gate drive means 21 and the charge detection means 22 are mounted on one semiconductor chip.
As shown in the figure, when a single semiconductor chip is used, when the current of several hundreds A or more is passed through the IGBT, the IGBT cannot be driven unless a discrete element is used for the gate driving means 21. An IGBT used for home appliances and the like that flows only about several A to 10 A has a small gate capacity, so that it can be driven by an IC chip, and the number of components can be reduced by placing it on a semiconductor chip.

FIG. 10 shows an outline of a short circuit protection device in which a digital circuit, an IGBT, and a gate control signal (PWM) forming unit 28 are mounted on one semiconductor chip.
As shown in the figure, the number of components can be reduced by combining the gate control (PWM) forming means 28 and the IGBT substrate together with one semiconductor chip as compared with the load short-circuit protection device of FIG. .

FIG. 11 shows an outline of a short-circuit protection device in which the gate control signal (PWM) forming means 28 is incorporated in a digital circuit, and the digital circuit and IGBT are mounted on one semiconductor chip.
As shown in the figure, by simplifying the gate control signal (PWM) forming means 28, control of the gate control signal (PWM) is simplified.

FIG. 12 shows an outline of a practical short-circuit protection device.
As shown in the figure, the basic structure is the same as in FIG. 6, but an analog / digital conversion / modulation means 32, a multiplexer 33, an attenuation waveform forming means 31, a digital / analog conversion means 34, and the like are added as functions.

  The analog / digital conversion / modulation means 32 performs analog / digital conversion on the signal input from the gate control signal (PWM) formation means 28 and converts the number of bits of the signal to the number of bits of the signal output from the attenuation waveform formation means 31. It is a means to match.

  The multiplexer 33 outputs the signal from the analog / digital conversion / modulation means 32 with no input to the selection terminal during rated operation. When the load is short-circuited, a signal is input from the comparator 30 to the selection terminal, and the waveform from the attenuation waveform forming means 31 is output.

  If the IGBT is turned off rapidly when a load short-circuit occurs, a voltage jump due to a parasitic inductor occurs and causes destruction. Therefore, an attenuation waveform is input to the gate of the IGBT by the attenuation waveform forming means 31 and the IGBT is turned off more slowly. Is desirable. For this reason, the attenuation waveform is digitally generated by using a lookup table for generating an attenuation waveform set in advance, an attenuation waveform generation means using a down counter, a function (for example, an exponential function), or a combination thereof. It is desirable to turn it off slowly.

  As shown in the figure, the means and functions enclosed by the broken line can be made to correspond to the signal synthesis shown in FIGS.

FIG. 13A shows an integration means 35 provided in place of the reference voltage detection means 25 in the block diagram of FIG. 12. As shown in FIG. 13B, the IGBT of which noise has been removed by the filter 24 is shown. The voltage V _QG corresponding to the gate charge is integrated. Since the value when the load short-circuit that integration is reduced compared to operation rated Compare time integrated voltage V _SC load short and when the integrated voltage V _NC rated operation in the comparator 30, and is configured to be detected.

FIG. 14A is provided with a differentiating means 36 instead of the reference voltage detecting means 25 in the block diagram of FIG. As shown in FIG. 14B, the differentiating means 36 differentiates the voltage V _QG corresponding to the gate charge of the IGBT from which noise has been removed by the filter 24. Since the differentiated value decreases when the load is short-circuited compared to the rated operation, the comparator 30 is configured to compare and detect the rated operation differential voltage and the load short-circuit differential voltage.

FIG. 15 (a) is provided with an enumeration means 37 instead of the reference voltage detection means 25 in the block diagram of FIG. 12, and as shown in FIG. 15 (b), the IGBT of which noise has been removed by the filter 24 is shown. since the voltage V _QG corresponding to gate charge is shortened during the time the load short circuit to stabilize at a high level, at time t _NC and the load short-circuit until the voltage V _QG at rated operation is stabilized at high level by the comparator 30 The time t _SC until the voltage V _QG is stabilized at a high level is compared and detected.

FIG. 16A is provided with a subtracting means 38 instead of the reference voltage detecting means 25 in the block diagram of FIG. 12, and as shown in FIG. 16B, the gate of the IGBT from which noise has been removed by the filter 24. Since the voltage V _QG corresponding to the charge decreases when the load is short-circuited compared to the rated operation, the difference V _dif between the values is measured, and when this value becomes large, it is determined that the load is short-circuited.

FIG. 17A is a flowchart showing the operation in the embodiment shown in FIG. In step S100, the gate charge voltage V _QG of the IGBT is detected using the charge detection means 22. In step S110, it is determined whether or not the reference voltage V _REF has been stored in the storage means 26. If not yet stored, in step S120, a stable value V _PEAK at a high level of V _QG is stored. In step S130, a value of V _REF is generated, and the process returns to step S100.

If the reference voltage V _REF has already been stored in step S110, the process proceeds to step S140. In step S140, it is determined whether or not V _REF needs to be changed. Specifically, taking into account the change in temperature T of the semiconductor chip in step S142, the change in threshold value V _{TH in} step S144, the change in power supply voltage V _{DC in} step S146, and the change in gate charge voltage V _{QG in} step S148, when there is a change regenerates the V _REF in the program at step S150, the flow returns to step S100.

When there is no change in V _REF in step S140, the process proceeds to step S160, and the magnitudes of V _REF and V _QG are compared. When the detected V _QG is larger than V _REF, no protection signal is output from the comparator 30 in step S170. When V _QG is smaller than V _REF , the process proceeds to step S180, and the comparator 30 outputs a protection signal. In step S190, the attenuation waveform forming means 31 outputs an attenuation waveform, and in step S200, the IGBT is turned off.

  As described above, according to the embodiment of the present invention, since a stable value at a high level of the voltage corresponding to the gate charge in the rated operation state is stored and converted to the reference voltage, a circuit necessary for protecting the IGBT Parameters can be easily changed, set and detected automatically, and can be automatically handled even if IGBTs having different characteristics are used. In addition, a change in characteristics due to the temperature of the IGBT and a change in characteristics due to a secular change can be dealt with, and it is possible to easily realize a multi-function.

  INDUSTRIAL APPLICABILITY The present invention is suitably used in the field of power control devices such as inverters as a short-circuit protection device for semiconductor devices that can automatically set optimal parameters even when there are differences in IGBT characteristics or temperature changes. be able to.

DESCRIPTION OF SYMBOLS 1 Load short circuit protection device 2 Gate drive circuit 3 Gate charge measurement circuit 4 A / D converter 5 Digital filter 6 Peak detector 7 Comparator 8 Pulse generator 9 Gate off voltage 10 Gate controller 11 D / A converter 20 Load short circuit protection device 21 Gate Drive means 22 Charge detection means 23 Analog / digital conversion means 24 Filter 25 Reference voltage detection means 26 Storage means 27 Judgment means 28 Gate control signal formation means 29 Signal synthesis 30 Comparator 31 Gate voltage attenuation waveform formation means when short circuit occurs 32 digital conversion and modulation unit 33 multiplexers 34 digital-to-analog converter 35 the integrating means 36 differential means 37 listed means 38 subtraction means Q _G IGBT gate charge V _QG gate charge voltage V _CE collector-emitter Stable value V _P digital high level of pressure V _GE gate-emitter voltage I _G current flows to the gate of the IGBT I _G ^* current flows to the charge detecting unit V _REF reference voltage V _peak nominal operating time of the gate charge voltage V _QG Output from circuit High High level (“1”) signal Low Low level (“0”) signal

Claims (3)

Charge detection means for detecting a voltage corresponding to the charge of the input part of the semiconductor element, and a reference for generating a reference voltage for judging whether a load short circuit has occurred from the charge of the input part during rated operation of the semiconductor element Determining means for determining whether the voltage detected by the charge detecting means is a voltage corresponding to the gate charge at the rated operation of the semiconductor element or a voltage corresponding to the gate charge at the time of a load short circuit; In a short circuit protection device for a semiconductor device having semiconductor element driving means for outputting a signal for stopping the operation of the semiconductor element when the determination means detects a load short circuit,
Said reference voltage generating means, and wherein a provided with a storage means for memorize a reference voltage for determining whether the load short-circuit from the input of the charge during the rated operation of the semiconductor device occurs Short circuit protection device.   An analog-to-digital conversion unit that converts an analog output of the charge detection unit into a digital signal is provided, the reference voltage generation unit and the determination unit are digitized, and a digital output signal from the determination unit is converted into an analog signal to be converted into the analog signal. 2. The short-circuit protection device for a semiconductor device according to claim 1, further comprising a digital / analog conversion means for outputting to the semiconductor element driving means.   A second analog-to-digital conversion means for converting an analog control signal to the semiconductor element driving means into a digital signal, and a digital output waveform to the gate driving means triggered by a digital output signal from the judgment means when the load is short-circuited Attenuation waveform forming means for converting into a proper attenuation waveform, and the digital / analog conversion means by selecting the output of the second analog / digital conversion means and the output of the attenuation waveform forming means during rated operation and during load short-circuiting The short-circuit protection device for a semiconductor device according to claim 2, further comprising a multiplexer for outputting to the semiconductor device.

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