JP4118496B2 - Power semiconductor device and overcurrent protection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power semiconductor device including a power transistor used as a switching element in a power conversion device such as an inverter device. The present invention relates to a technique for protecting a power transistor by detecting a current.
[0002]
[Prior art]
FIG. 3 is a circuit diagram showing a part of a conventional power semiconductor device including an IGBT overcurrent detection circuit. In the figure, IT is an input terminal of a power semiconductor device connected to a main circuit (not shown), and 101 is a main IGBT having a collector terminal TC connected to the input terminal IT. A current Ico excluding a sense current Is described later from Ic flows from the collector terminal TC of the main IGBT 101 to the emitter terminal TE. Reference numeral 102 denotes an auxiliary IGBT, and a sense current Is, which is a part of the main current Ic, flows from the collector terminal TC of the auxiliary IGBT 102 to the sense terminal TS at the time of turn-on. Since the main IGBT 101 and the auxiliary IGBT 102 are integrally formed in one semiconductor wafer, both 101 and 102 are simply referred to as an IGBT 100.
[0003]
On the other hand, the sense resistor 103, the capacitor 113 connected in parallel to the sense resistor 103, the power supply 111 that generates the reference voltage Vref, and the sense voltage Vs generated in the sense resistor 103 is set to the + side input, and the reference voltage Vref is − The comparator 210 as the side input and the overcurrent detection output terminal 310 constitute an overcurrent detection circuit of the IGBT 100.
[0004]
Next, the operation of the circuit of FIG. 3 will be described. Now, assume that the main IGBT 101 is on and the auxiliary IGBT 102 is also on. At this time, most of the main current Ic flowing from the main circuit to the collector terminal TC of the IGBT 100 flows in the main IGBT 101 as the current Ico, and a part of the main current Ic flows in the auxiliary IGBT 102 as the sense current Is and is sensed by the sense resistor 103. Detected as The comparator 210 compares the sense voltage Vs with the reference voltage Vref, and changes the output from the “L” level to the “H” level when the sense voltage Vs exceeds the reference voltage Vref. As a result, an “H” level signal indicating detection of an overcurrent state is output from the overcurrent detection output terminal 310 to the outside.
[0005]
Another example of the prior art is disclosed in FIG. 1 of JP-A-11-299218. Also in this prior art, the sense current flowing through the auxiliary IGBT is detected by the sense resistor, and the overcurrent state is detected by comparing the obtained sense voltage and the reference voltage with a comparator. 3 is the same as the prior art example 3.
[0006]
[Problems to be solved by the invention]
In a conventional overcurrent detection circuit, the presence or absence of an overcurrent state is detected by comparing a sense voltage obtained by detecting a sense current with a sense resistor and a reference voltage with a comparator. However, when the auxiliary IGBT is turned on, a local change in which the current increase rate (dIs / dt) of the sense current has a maximum and a minimum occurs at the recovery stage. Therefore, the fluctuation amount of the sense current is detected as sense voltage noise by the sense resistor. Usually, since the reference voltage of the comparator is as small as 0.5 V, for example, a state in which the sense voltage exceeds the reference voltage easily occurs due to superposition of noise of the sense voltage. As a result, there is a problem that the comparator is erroneously determined to be in an overcurrent state although it is not actually in an overcurrent state, and erroneous overcurrent protection is activated.
[0007]
The present invention has been made to overcome such problems, and its purpose is to cause erroneous determination even if noise occurs in a sense voltage obtained by detecting a sense current with a sense resistor. In other words, it is necessary to establish a technique that can reliably detect that an overcurrent state has occurred and can reliably protect the power transistor from the overcurrent state.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 is a power semiconductor device comprising a first main electrode terminal connected to a main circuit, a second main electrode terminal, a control electrode terminal, and a sense terminal, the control electrode When a control voltage applied to the terminal is equal to or higher than a threshold voltage, a current is passed between the first main electrode terminal and the second main electrode terminal and between the first main electrode terminal and the sense terminal A drive transistor for generating a control voltage and outputting the control voltage from the output terminal, and a power circuit for supplying a sense current to the power transistor, an output terminal connected to the control electrode terminal of the power transistor, and a control terminal. A first and second input terminal connected to the first main electrode terminal and the sense terminal of the transistor, respectively, and an output terminal connected to the control terminal of the drive circuit; With the voltage of The sense voltage of each sense terminal is monitored, and the power transistor is in an overcurrent state only when the sense voltage exceeds the first reference voltage and the monitoring result of the first main electrode terminal voltage also exceeds the second reference voltage. An overcurrent protection circuit that outputs an output signal indicating the overcurrent state to the control terminal, and the drive circuit receives the output signal indicating the overcurrent state in response to receiving the output signal. Is set to be less than the threshold voltage to turn off the power transistor.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
1 is a circuit diagram showing a main part of a power semiconductor device according to Embodiment 1 of the present invention. In the figure, the same symbols and symbols shown in FIG. 3 indicate the same circuit components.
[0012]
The power semiconductor device is roughly composed of a power transistor 100 with a sense terminal, an overcurrent protection circuit 200, and a drive circuit 213. Among these, the power transistor 100 is composed of an IGBT here, but is not limited thereto, and may be composed of another power semiconductor switching element such as a vertical power MOSFET. good.
[0013]
First, a power transistor or IGBT 100 with a sense terminal includes a main IGBT 101 and an auxiliary IGBT 102 that are integrally formed in the same semiconductor substrate. That is, the input terminal IT of the power semiconductor device is connected to a main circuit (not shown) and connected to a drive power supply (not shown: power supply potential Vcc) via a freewheel diode (not shown). Is also connected. Further, the main IGBT 101 has a collector terminal (corresponding to the first main electrode terminal) TC into which the main current Ic flows from the main circuit via the input terminal IT when turned on, and a gate terminal (corresponding to the control electrode terminal) to which a control voltage is applied. ) TG and a grounded emitter terminal (corresponding to the second main electrode terminal) TE. The auxiliary IGBT 102 includes a collector terminal TC and a gate terminal TG shared with the main IGBT 101, and a sense terminal TS that outputs a sense current Is. When the IGBT 100 is turned on after the turn-on in normal operation (when the control voltage V _GE is equal to or higher than the threshold voltage of the IGBT 100), the collector-emitter current Ico obtained by removing the sense current Is from the main current Ic is the main IGBT 101. Current from the collector terminal TC to the emitter terminal TE, and a sense current Is that is a part of the main current Ic flows from the collector terminal TC of the auxiliary IGBT 102 to the sense terminal TS. Reference numeral 110 denotes a free wheel diode.
[0014]
Next, the overcurrent protection circuit 200 includes (A) a first monitor circuit unit or sense voltage monitor circuit unit (103, 113, 111, 210) and (B) a second monitor circuit unit or collector voltage (first main circuit). Electrode terminal voltage) monitor circuit section (104, 106, 107, 105, 108, 211) and (C) overcurrent determination circuit 212 are roughly divided. That is, the overcurrent protection circuit 200 includes a first input terminal (corresponding to one end of the voltage dividing resistor 104) connected to the collector terminal TC of the IGBT 100, and a second input terminal (of the sense resistor 103) connected to the sense terminal TS. And an output terminal (corresponding to an output terminal of the AND circuit 212) connected to a control terminal (not shown) of the drive circuit 213, and a collector voltage _VCE and a sense voltage Vs, respectively. monitored, along with the sense voltage Vs exceeds the first reference voltage Vref1, the main current Ic or IGBT100 is in an overcurrent state only when the even monitoring results or monitor voltage V _CS of the collector voltage V _CE exceeds the second reference voltage Vref2 determined to a has a function of outputting an output signal V _T which indicates the overcurrent state to the control terminal.
[0015]
(A) In particular, the sense voltage monitor circuit unit includes (1) a sense voltage detection unit that detects the sense voltage Vs using the sense terminal TS as an input terminal, and (2) a first comparator 210. Among these, (1) the sense voltage detection unit is composed of a sense resistor 103 and a capacitor 113 connected in parallel to each other, and (2) the first comparator 210 is one of the ones to which the sense voltage Vs is applied. The input terminal and the other input terminal to which the first reference voltage Vref1 generated by the power supply 111 is applied are compared. The sense voltage Vs is compared with the first reference voltage Vref1, and the sense voltage Vs is compared with the first reference voltage Vref1. The output signal Vcom1 of the first level (eg, “L” level signal) is output in the following cases, and the output signal of the second level (eg, “H” level signal) when the sense voltage Vs exceeds the first reference voltage Vref1. A function of outputting Vcom1 is provided.
[0016]
Note that the resistance value of the sense resistor 103 is set with respect to the first reference voltage Vref1 so that the sense voltage Vs during the abnormal operation is actually larger than the first reference voltage Vref1.
[0017]
(B) In addition, the collector voltage monitor circuit section (1) uses the collector terminal TC as its input terminal, detects an increase in the collector voltage V _CE when the IGBT 100 is turned on, and detects the detection result as the monitor voltage V _CS And (2) a second comparator 211. Among these, (1) the collector voltage monitor section is i) the first and second components arranged in parallel with the IGBT 100 between the collector terminal TC and the emitter terminal TE and sequentially connected in series from the collector terminal TC side. And ii) a capacitor 107 having one end connected to a node between the first voltage dividing resistor 104 and the second voltage dividing resistor 106, and a resistor 105 disposed between the other end of the capacitor 107 and the emitter terminal TE. And iii) a protective diode 108 for avoiding a negative voltage drop caused by the resistor 105. On the other hand, (2) the second comparator 211 has one input terminal to which the monitor voltage V _CS is applied and the other input terminal to which the second reference voltage Vref2 generated by the power source 112 is applied, and the monitor voltage V _CS is compared with the second reference voltage Vref2, and when the monitor voltage V _CS is equal to or lower than the second reference voltage Vref2, an output signal Vcom2 of the first level (eg, “L” level signal) is output, and the monitor voltage V _{When CS} exceeds the second reference voltage Vref2, the output signal Vcom2 of the second level (eg, “H” level signal) is output.
[0018]
The resistance value ratio of the first and second voltage dividing resistors 104 and 106 is such that the peak value of the monitor voltage V _CS that is the output value of the differentiation circuit (107, 106) of ii) is actually higher than the second reference voltage Vref2. Is set to be larger.
[0019]
In addition, the time constant determined by the capacitance value of the capacitor 107 and the resistance value of the resistor 105 forming the differentiating circuit of ii) is the amount of increase in the collector voltage V _CE when the IGBT 100 is turned off and when the IGBT 100 is turned on during abnormal operation. It is set so that the frequency component contained in (dV _CE / dt) or the rising change in the node voltage between the resistors 104 and 106 is surely differentiated by the differentiating circuit.
[0020]
(C) Further, the overcurrent determination circuit 212 has one input terminal to which the output signal Vcom1 of the first comparator 210 is applied and the other input terminal to which the output signal Vcom2 of the second comparator 211 is applied. have, it has a function of outputting an output signal V _T which indicates the overcurrent state observed when the output signal Vcom1 and output signal Vcom2 are both the second level signal to the control terminal of the drive circuit 213. Here, since the first level is set to the “L” level and the second level is set to the “H” level, the overcurrent determination circuit 212 is configured as an AND circuit. Of course, the first level and the second level may be set in reverse, and in that case, the logic circuit configuration of the overcurrent determination circuit 212 may be changed according to the setting.
[0021]
Next, the drive circuit 213 has the control terminal and an output terminal connected to the gate terminal TG of the IGBT 100 via the resistor 109, generates the control voltage V _GE and outputs it from the output terminal. It has a function. In particular, the circuit 213, in response to receipt of the output signal V _T which indicates the occurrence of an overcurrent condition, can the control voltage V _GE turning off IGBT100 set below the threshold voltage.
[0022]
In the following, based on the description of the configuration described above, the operation of the power semiconductor device will be described with reference to FIG.
[0023]
(I) During normal operation, when the IGBT 100 or the main IGBT 101 is turned on (period from turn-on to turn-off), a sense current Is that is a part of the main current Ic flows to the auxiliary IGBT 102 side, and a sense resistor for detecting a sense voltage A sense voltage Vs is generated at both ends of 103. However, since the sense voltage Vs is smaller than the first reference voltage Vref1 during normal operation, the output signal Vcom1 remains at the “L” level.
[0024]
On the other hand, during the ON operation of the main IGBT 101, since the collector voltage V _CE is at the ground potential, no current flows through the collector voltage monitoring path formed by the first and second voltage dividing resistors 104 and 106. Therefore, the monitor voltage Vcs Is also equal to the ground potential, and the output signal Vcom2 remains at "L" level.
[0025]
As a result, during the turn-on operation of the main IGBT 101, the output signal V _T of the overcurrent determination circuit 212 is at the “L” level, and the overcurrent protection function of the main IGBT 101 does not work.
[0026]
When the main IGBT 101 is turned off, the collector voltage V _CE rises from the ground potential to the power supply potential Vcc (since the positive voltage gradient dV _CE / dt is applied to the collector terminal TC), the collector voltage monitor As a result of the current Ica flowing through the working path and the capacitor 107 starting the charging operation, the node voltage between the voltage dividing resistors 104 and 106 is differentiated. For this reason, the peak value of the monitor voltage V _CS showing the differential waveform instantaneously becomes larger than the second reference voltage Vref2, and the output signal Vcom2 becomes “H” level. However, since the output signal Vcom1 remains at the “L” level, and the output signal V _T of the overcurrent determination circuit 212 is still at the “L” level, the overcurrent protection function of the main IGBT 101 does not work in this case as well. .
[0027]
When the next main IGBT 101 is turned on, the capacitor 107 discharges the electric charge to the ground side via the second voltage dividing resistor 106.
[0028]
(II) At the time of abnormal operation When the main current Ic is in an overcurrent state due to an abnormal operation when the main IGBT 101 is turned on, the sense voltage Vs generated at both ends of the sense resistor 103 becomes larger than the first reference voltage Vref1. The output signal Vcom1 becomes “H” level.
[0029]
In addition, at this time, the current Ica also flows through the collector voltage monitoring path. That is, the collector voltage V _CE decreases (negative voltage gradient dV _CE / dt) as in the normal operation for an instant at the start of turn-on, but immediately after that, the collector voltage V _CE increases (positive) exceeding the power supply potential Vcc. Since a voltage gradient dV _CE / dt) is generated, the current Ica flows and the node voltage between the voltage dividing resistors 104 and 106 is differentiated. For this reason, a peak value of the monitor voltage V _CS exceeding the second reference voltage Vref2 is generated, and the output signal Vcom2 becomes “H” level. As a result, the output signal V _T of the overcurrent determination circuit 212 becomes “H” level, the overcurrent protection function of the main IGBT 101 operates, and the drive circuit 213 reduces the gate voltage of the main IGBT 101 to turn off the operation of the main IGBT 101. Control (protect).
[0030]
As described above, the overcurrent determination circuit 212 of this apparatus receives not only the monitor result of the sense voltage but also the monitor result of the current Ica flowing through the collector side path, and whether or not an abnormality has occurred in both the results. Since the occurrence of the overcurrent state of the main current Ic is detected from the viewpoint, it is possible to effectively prevent the situation where the overcurrent protection operation is erroneously activated due to noise generated in the sense voltage, and a true overcurrent state occurs. The overcurrent protection operation can be functioned effectively by accurately detecting the current.
[0031]
(Modification of Embodiment 1)
The configuration described in the first embodiment can also be applied to an overcurrent protection circuit for an IGBT on the high potential side in an inverter circuit or the like.
[0032]
【The invention's effect】
According to the first aspect of the present invention, even if the sense voltage exceeds the first reference voltage due to noise generated in the sense voltage, the monitor voltage of the first main electrode terminal voltage also exceeds the second reference voltage. As long as the state does not occur, the overcurrent protection circuit does not determine that the power transistor is in the overcurrent state, so that it is possible to prevent a malfunction of detecting the overcurrent state due to the noise of the sense voltage.
[0033]
According to the invention of claim 2, when the current flowing into the power transistor (main current) is an overcurrent, the detection of the phenomenon that the first main electrode terminal voltage rises when the power transistor is turned on is detected. Therefore, it is possible to reliably identify whether the main current is in the normal current state within the rating or in the overcurrent state, and the power transistor can be reliably protected from the overcurrent state.
[0034]
According to the third aspect of the present invention, since it is determined whether or not the overcurrent state exists according to both monitoring results, it is possible to effectively prevent the occurrence of erroneous determination due to noise in the sense voltage.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a main part of a power semiconductor device according to a first embodiment of the present invention.
FIG. 2 is a timing chart showing the operation of the power semiconductor device according to the first embodiment of the present invention.
FIG. 3 is a circuit diagram showing a conventional power semiconductor device.
[Explanation of symbols]
100 IGBT, 101 Main IGBT, 102 Auxiliary IGBT, 103 Sense resistor, 107 Capacitor, 105 Resistance, 200 Overcurrent protection circuit, 210 First comparator, 211 Second comparator, 212 Overcurrent determination circuit, 213 Drive circuit

Claims (3)

A first main electrode terminal connected to the main circuit; a second main electrode terminal; a control electrode terminal; and a sense terminal, wherein a control voltage applied to the control electrode terminal is equal to or higher than a threshold voltage A power transistor for passing a current between the first main electrode terminal and the second main electrode terminal and for passing a sense current between the first main electrode terminal and the sense terminal;
An output terminal connected to the control electrode terminal of the power transistor; and a control terminal; a drive circuit that generates the control voltage and outputs the control voltage from the output terminal;
And a first input terminal connected to the first main electrode terminal and the sense terminal of the power transistor, respectively, and an output terminal connected to the control terminal of the drive circuit. The voltage of the electrode terminal and the sense voltage of the sense terminal are monitored, respectively, and the power only when the sense voltage exceeds the first reference voltage and the monitoring result of the first main electrode terminal voltage also exceeds the second reference voltage. An overcurrent protection circuit that determines that the transistor is in an overcurrent state and outputs an output signal indicating the overcurrent state to the control terminal;
The drive circuit sets the control voltage below the threshold voltage in response to receiving an output signal indicating the overcurrent state, and turns off the power transistor.
Power semiconductor device. The power semiconductor device according to claim 1,
The overcurrent protection circuit is
A sense voltage detector configured to detect the sense voltage using the second input terminal as its input terminal;
The sense voltage output from the sense voltage detector is received, the sense voltage is compared with the first reference voltage, and a first level output signal is output when the sense voltage is lower than the first reference voltage. A first comparator that outputs a second level output signal when the sense voltage exceeds the first reference voltage;
A first main electrode terminal voltage monitor that uses the first input terminal as an input terminal, detects an increase in the first main electrode terminal voltage when the power transistor is turned on, and outputs the detection result as the monitor voltage. And
The monitor voltage is received, the monitor voltage is compared with the second reference voltage, and when the monitor voltage is less than or equal to the second reference voltage, the first level output signal is output, and the monitor voltage is the first voltage. A second comparator that outputs the second level output signal when exceeding two reference voltages;
The output signal of the first comparator and the output signal of the second comparator are received, and the output signal of the first comparator and the output signal of the second comparator are both signals of the second level. And an overcurrent determination circuit that outputs an output signal indicating the overcurrent state to the control terminal of the drive circuit only when
Power semiconductor device. An overcurrent protection circuit for protecting a power transistor with a sense terminal connected to a main circuit from an overcurrent state,
The overcurrent protection circuit corresponds to the overcurrent protection circuit according to claim 1 or 2,
Overcurrent protection circuit.

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