JP4858253B2 - Transistor drive circuit - Google Patents

Description

  The present invention relates to a circuit for driving a transistor.

  A circuit is known that switches between a state in which power is supplied to a load and a state in which power is not supplied by switching on and off of a transistor connected to the load. For example, the inverter circuit converts DC power into AC power by switching on / off of the transistor, and supplies the AC power to the motor. On / off of a transistor in this type of circuit is controlled by a drive circuit connected to the gate electrode (or base electrode) of the transistor.

FIG. 20 shows an operation waveform diagram when a field effect transistor is used for this type of transistor. The drive circuit switches the transistor on and off by supplying the drive voltage Vin to the gate electrode of the transistor.
First, a transition period in which the transistor is turned on will be described. When the drive voltage Vin changes from low to high, a positive gate current Ig flows toward the gate electrode of the transistor, and charges are accumulated in the gate electrode. When charges are accumulated in the gate electrode, the gate-source voltage Vgs of the transistor increases. When the gate-source voltage Vgs rises, the drain current Id starts to flow from the drain to the source of the transistor, and the drain-source voltage Vds decreases. Through these processes, the transistor shifts from off to on.
Next, the transition period T100 in which the transistor is turned off will be described. When the drive voltage Vin changes from high to low, the charge accumulated in the gate electrode is discharged, a negative gate current Ig flows from the gate electrode to the drive circuit, and the gate-source voltage Vgs decreases. When the gate-source voltage Vgs decreases, the drain current Id also decreases, and the drain-source voltage Vds increases. Through these processes, the transistor shifts from on to off.

As shown in FIG. 20, a surge voltage is generated in the drain-source voltage Vds at the end of the transition period T100 when the transistor is turned off. This surge voltage is caused by a drain current Id that changes sharply and an inductance that is parasitic on the wiring on the drain electrode side in the circuit.
In order to suppress the increase of the surge voltage, the drain current Id may be gradually changed. For example, if the gate resistance of the transistor is increased, the rate at which charges accumulated in the gate electrode are discharged decreases, and the negative gate current Ig flows gently. As a result, the drain current Id also decreases gradually, and an increase in surge voltage can be suppressed. However, when the drain current Id of the transistor is gradually reduced, the time required for the transistor to turn off increases and the turn-off loss increases. In other words, this type of transistor has a trade-off relationship between the surge voltage and the turn-off loss in the turn-off transient period T100.

  In order to break this trade-off relationship, it is desirable that the drain current Id is changed abruptly at the beginning of the turn-off transition period T100, and the drain current Id is changed slowly at the end of the transition period T100. If the drain current Id is abruptly changed at the beginning of the transition period T100, the time required for turn-off can be shortened. As a result, turn-off loss can be kept low. Further, if the drain current Id is slowly changed at the end of the transition period T100, an increase in surge voltage can be suppressed.

  Patent Document 1 discloses a technique for adjusting a resistance value of a gate resistance of a transistor based on a voltage between main electrodes of the transistor (a voltage between a drain electrode and a source electrode, a voltage between a collector electrode and an emitter electrode, and the like). In the technique of Patent Document 1, the resistance value of the gate resistance is increased when the voltage between the main electrodes of the transistor is large, and the resistance value of the gate resistance is adjusted small when the voltage between the main electrodes is small. Specifically, the drive circuit of Patent Document 1 includes variable resistance means connected to the gate electrode of the transistor. The resistance variable means is composed of a semiconductor switching element and a fixed resistor connected in parallel thereto. The semiconductor switching element is turned off when the voltage between the main electrodes of the transistor is larger than a predetermined value, and is turned on when the voltage is smaller than the predetermined value. That is, when the voltage between the main electrodes of the transistor is large, the gate resistance is largely adjusted according to the resistance value of the fixed resistor by turning off the semiconductor switching element. When the voltage between the main electrodes of the transistor is small, the gate resistance is adjusted to be small according to the internal resistance of the semiconductor switching element by turning on the semiconductor switching element.

  If the drive circuit of Patent Document 1 is used, the resistance value of the gate resistance is adjusted to be small by turning on the semiconductor switching element at the beginning of the turn-off transition period (when the voltage between the main electrodes is small), and the gate current is steep. Fluctuates. As a result, the drain current of the transistor can be abruptly changed, and the time required for turn-off can be shortened. Further, at the end of the turn-off transition period (when the voltage between the main electrodes is large), the semiconductor switching element is turned off, so that the resistance value of the gate resistance is greatly adjusted, and the gate current fluctuates slowly. As a result, the drain current of the transistor can be changed slowly, and an increase in surge voltage can be suppressed.

Japanese Patent Laid-Open No. Hei 6-291631

In the drive circuit of Patent Document 1, a high resistance state of the gate resistance is realized by using a high resistance fixed resistor. In order to suppress an increase in surge voltage, it is desirable to set the resistance value of the fixed resistor large. However, a high resistance fixed resistor increases turn-off loss. Therefore, in order to suppress an increase in turn-off loss, the timing for switching to the high-resistance fixed resistor by the on / off operation of the semiconductor switching element must be accurately set at the end of the transient period in which the turn-off is performed. At the end of the turn-off transition period, the transistor main electrode voltage reaches a high state. In the drive circuit of Patent Document 1, the on / off operation of the semiconductor switching element must be controlled by accurately transforming the voltage between the main electrodes of the transistor to the threshold value of the on / off operation of the semiconductor switching element. Therefore, in order to realize such a circuit, the number of necessary parts increases, and an increase in cost is inevitable.
The present invention provides a technique for adjusting a resistance value of a gate resistance of a transistor based on a voltage between main electrodes of the transistor by a method different from that of Patent Document 1. In the above description, the problem of the present invention has been described with a focus on the transition period in which the transistor is turned off. There are many. The present invention provides a technique that can provide useful results during both turn-off and turn-on transitions.

The technology disclosed in this specification can be embodied in a circuit for driving a transistor. The driving circuit disclosed in this specification includes a variable resistor that is electrically connected to a gate electrode of a transistor. The width of the current path of the variable resistor is adjusted by a depletion layer that expands and contracts according to the voltage between the main electrodes of the transistor.
The driving circuit disclosed in this specification does not use the on / off operation of the semiconductor switching element. The drive circuit adjusts the width of the current path of the variable resistor using a depletion layer that expands and contracts according to the voltage between the main electrodes of the transistor. When the depletion layer expands and the width of the current path of the variable resistor becomes narrow, the resistance value of the variable resistor is adjusted to be large. When the depletion layer contracts and the width of the current path of the variable resistor increases, the resistance value of the variable resistor is adjusted to be small. The depletion layer expands and contracts according to the voltage between the main electrodes of the transistor, and the event is continuous with the increase and decrease of the voltage between the main electrodes of the transistor. Unlike the on / off operation of the semiconductor switching element, a circuit for accurately setting the threshold value is not required. The configuration of the driving circuit disclosed in this specification is simplified.

In the driving circuit disclosed in the present specification, it is preferable that the resistance value of the variable resistor is adjusted to be small when the voltage between the main electrodes of the transistor is small, and is adjusted to be large when the voltage between the main electrodes is large.
According to this aspect, the resistance value of the gate resistance is adjusted to be small at the beginning of the transition period in which the transistor is turned off, and the resistance value of the gate resistance is adjusted to be large at the end of the transition period. Therefore, in the driving circuit of the present invention, the resistance value of the gate resistance can be adjusted to be small in the early stage of the turn-off transition period, and the gate current can be rapidly changed. As a result, the drain current of the transistor can be abruptly changed, and the time required for turn-off can be shortened. Furthermore, in the driving circuit of the present invention, the resistance value of the gate resistance can be adjusted greatly at the end of the turn-off transition period, and the gate current can be varied slowly. As a result, the drain current of the transistor can be changed slowly, and an increase in surge voltage can be suppressed. The driving circuit of this aspect can improve the characteristics of the transient period in which the transistor is turned off.

The variable resistor disclosed in this specification may include a p-type semiconductor region and an n-type semiconductor region in contact with the p-type semiconductor region. In this case, the p-type semiconductor region is electrically connected to the gate electrode of the transistor. The n-type semiconductor region is electrically connected to the output electrode of the transistor. Here, examples of the output electrode of the transistor include a drain electrode and a collector electrode.
In this variable resistor, the p-type semiconductor region is a current path. When the voltage between the main electrodes of the transistor increases, the pn junction between the p-type semiconductor region and the n-type semiconductor region is reverse-biased, and a depletion layer extends in the p-type semiconductor region. For this reason, when the voltage between the main electrodes of the transistor increases, the width of the current path is adjusted to be narrow. On the other hand, when the voltage between the main electrodes of the transistor decreases, the depletion layer extending to the p-type semiconductor region contracts. For this reason, when the voltage between the main electrodes of the transistor is reduced, the width of the current path is adjusted to be wide.
The drive circuit having this variable resistor can improve the characteristics of the transient period in which the transistor is turned off.

In the driver circuit disclosed in this specification, a Zener diode is preferably provided between the n-type semiconductor region and the output electrode of the transistor.
When the Zener diode is provided, the voltage between the main electrodes of the transistor is not applied to the n-type semiconductor region of the variable resistor until the Zener diode breaks down. Therefore, the width of the current path of the variable resistor is kept wide until the Zener diode breaks down. As a result, the resistance value of the variable resistor can be kept small and the gate current can be changed abruptly in the early stage of the transition period in which the transistor is turned off. As a result, the drain current of the transistor is abruptly changed, and the time required for turn-off can be further shortened. A plurality of Zener diodes may be connected in series. The voltage applied to the n-type semiconductor region can be adjusted by a plurality of Zener diodes.

The variable resistor disclosed in this specification includes a p-type semiconductor region, an insulator region in contact with the p-type semiconductor region, and a conductor region facing the p-type semiconductor region through the insulator region. You may have. In this case, the p-type semiconductor region is electrically connected to the gate electrode of the transistor. The conductor region is electrically connected to the output electrode of the transistor. The p-type semiconductor region, the insulator region, and the conductor region form a MIS structure (Metal Insulator Semiconductor).
In this variable resistor, the p-type semiconductor region is a current path. When the voltage between the main electrodes of the transistor increases, a depletion layer extends in the p-type semiconductor region due to the field effect of the MIS structure. For this reason, when the voltage between the main electrodes of the transistor increases, the width of the current path is adjusted to be narrow. On the other hand, when the voltage between the main electrodes of the transistor decreases, the depletion layer extending to the p-type semiconductor region contracts. For this reason, when the voltage between the main electrodes of the transistor is reduced, the width of the current path is adjusted to be wide.
The drive circuit having this variable resistor can improve the characteristics of the transient period in which the transistor is turned off.

In the driver circuit disclosed in this specification, a Zener diode is preferably provided between the conductor region and the output electrode of the transistor.
When the Zener diode is provided, the voltage between the main electrodes of the transistor is not applied to the conductor region of the variable resistor until the Zener diode breaks down. Therefore, the width of the current path of the variable resistor is kept wide until the Zener diode breaks down. As a result, the resistance value of the variable resistor can be kept small and the gate current can be changed abruptly in the early stage of the transition period in which the transistor is turned off. As a result, the drain current of the transistor is abruptly changed, and the time required for turn-off can be further shortened. A plurality of Zener diodes may be connected in series. The voltage applied to the n-type semiconductor region can be adjusted by a plurality of Zener diodes.

The technology disclosed in this specification can provide a driving circuit in which a transistor and a variable resistor are integrally formed. This drive circuit includes a transistor and a variable resistor electrically connected to the gate electrode of the transistor. The width of the current path of the variable resistor is adjusted by a depletion layer that expands and contracts according to the voltage between the main electrodes of the transistor. The transistor and the variable resistor are provided on the same semiconductor substrate.
When the transistor and the variable resistor are provided on the same semiconductor substrate, it is not necessary to prepare the transistor and the variable resistor as separate components. When the transistor and the variable resistor are provided on the same semiconductor substrate, the drive circuit can be configured with a small number of parts, and the drive circuit can be reduced in size and excellent in practicality.

In order to provide the transistor and the variable resistor on the same semiconductor substrate, for example, the variable resistor preferably has a p-type semiconductor region and an n-type semiconductor region in contact with the p-type semiconductor region. . In this case, the p-type semiconductor region is provided on the semiconductor substrate via an insulating film, and is electrically connected to the gate electrode of the transistor. The n-type semiconductor region is provided on the semiconductor substrate via an insulating film and is electrically connected to the output electrode of the transistor.
According to the embodiment, the variable resistor composed of the p-type semiconductor region and the n-type semiconductor region is provided on the semiconductor substrate. The transistor and the variable resistor are integrally constructed using the same semiconductor substrate.

The material of the p-type semiconductor region and the n-type semiconductor region is preferably polycrystalline silicon.
When polycrystalline silicon is employed, a p-type semiconductor region and an n-type semiconductor region can be easily formed on a semiconductor substrate by using a semiconductor device manufacturing process.

  The drive circuit of the present invention adjusts the width of the current path of the variable resistor using a depletion layer that expands and contracts according to the voltage between the main electrodes of the transistor. The drive circuit of the present invention has a simplified configuration and can be manufactured at a low cost.

Preferred features of the invention are listed.
(First Feature) The drive circuit of the present invention drives a field effect transistor.
(Second Feature) The variable resistor is provided on the same semiconductor substrate as the transistor.
(Third feature) The variable resistor is a pinch resistor. The pinch resistor has a structure in which a p-type semiconductor region is sandwiched between n-type semiconductor regions. The p-type semiconductor region is substantially completely depleted when a DC voltage supplied to the transistor is applied to the n-type semiconductor region.
(Fourth feature) The variable resistor is a MOS resistor (Metal Oxide Semiconductor). The MOS resistor has a stacked structure of a conductor region, an insulator region, and a p-type semiconductor region. The p-type semiconductor region is substantially completely depleted when a DC voltage supplied to the transistor is applied to the n-type semiconductor region.

(First embodiment)
FIG. 1 shows a circuit diagram of a drive circuit 10 for driving a field effect transistor 20 (n-type MOSFET). The transistor 20 is connected between the load 30 and the ground. A parasitic inductance of wiring is connected between the transistor 20 and the load 30. The drive circuit 10 supplies a rectangular-wave drive voltage Vin to the gate electrode G of the transistor 20 and switches the transistor 20 on and off based on the drive voltage Vin. The drive circuit 10 switches between a state where the DC voltage Vdd of the voltage supply source 40 is supplied to the load 30 and a state where it is not supplied by switching the transistor 20 on and off. A protective Zener diode 22 is connected between the source electrode S and the gate electrode G of the transistor 20, so that a voltage exceeding a certain level is not applied to the gate electrode G.

The drive circuit 10 includes a drive voltage generation circuit 11, a fixed resistor R10, a first diode D10, a second diode D12, and a variable resistor R12. The second diode D12 may be deleted as necessary. The fixed resistor R10, the first diode D10, the variable resistor R12, and the protection Zener diode 22 are provided on the same semiconductor substrate as the transistor 20. A specific form will be described in an example described later.
A series circuit of the fixed resistor R10 and the first diode D10 is connected between the gate electrode G and the gate terminal G10. A series circuit of the variable resistor R12 and the second diode D12 is connected between the gate electrode G and the gate terminal G10. The drive voltage generation circuit 11 is electrically connected to the gate terminal G10. That is, the series circuit of the fixed resistor R10 and the first diode D10 and the series circuit of the variable resistor R12 and the second diode D12 constitute a parallel circuit between the drive voltage generation circuit 11 and the transistor 20. The anode of the first diode D10 is connected to the gate terminal G10 via the fixed resistor R10, and the cathode of the first diode D10 is connected to the gate electrode G of the transistor 20. The anode of the second diode D12 is connected to the gate electrode G of the transistor 20 via the variable resistor R12, and the cathode of the second diode D12 is connected to the gate terminal G10.

  The resistance value of the variable resistor R12 is adjusted based on the drain-source voltage Vds of the transistor 20 measured by the drain voltage detecting means 50. The resistance value of the variable resistor R12 is adjusted to be small when the drain-source voltage Vds of the transistor 20 is small, and is adjusted to be large when the drain-source voltage Vds is large.

FIG. 2 shows an operation waveform diagram of the transistor 20.
First, a transition period in which the transistor 20 is turned on will be described. The drive voltage Vin is supplied to the wiring on the fixed resistor R10 side because the second diode D12 is provided in the reverse direction. When the drive voltage Vin changes from low to high, the drive voltage Vin is converted into a positive gate current Ig (+) by the fixed resistor R10 and supplied to the gate electrode G of the transistor 20. When a positive gate current Ig (+) is supplied to the gate electrode G of the transistor 20, charges are accumulated in the gate electrode G. When charges are accumulated in the gate electrode G, the gate-source voltage Vgs of the transistor 20 increases. When the gate-source voltage Vgs rises, the drain current Id starts to flow from the drain electrode D to the source electrode S of the transistor 20, and the drain-source voltage Vds decreases. Through these processes, the transistor 20 shifts from off to on.

  Next, the transition period T10 in which the transistor 20 is turned off will be described. When the drive voltage Vin changes from high to low, the charge accumulated in the gate electrode G is discharged. The negative gate current Ig (−) accompanying the discharge of the charge flows toward the wiring on the variable resistor R12 side because the first diode D10 is provided in the reverse direction. In the early stage when the transistor 20 is turned off, since the drain-source voltage Vds is small, the resistance value of the variable resistor R12 is adjusted to a small value. For this reason, the negative gate current Ig (−) can fluctuate sharply in the early stage of the transient period T10 in which it is turned off. For this reason, the charge accumulated in the gate electrode G of the transistor 20 can be quickly discharged in the early stage of the turn-off transient period T10. As a result, the time required for turn-off can be shortened at the beginning of the turn-off transition period T10. In some cases, as shown in FIG. 2, the time of the transition period T10 required for the transistor 20 to be turned off can be shortened as compared to the transition period T100 of the conventional driving circuit.

At the end of the turn-off transient period T10, the drain-source voltage Vds rises. The resistance value of the variable resistor R12 is greatly adjusted as the drain-source voltage Vds increases. For this reason, the negative gate current Ig (−) can change slowly at the end of the turn-off transient period T10. Therefore, the charge accumulated in the gate electrode G of the transistor 20 can be slowly discharged at the end of the turn-off transient period T10. As a result, the drain current Id of the transistor 30 flows slowly, and an increase in surge voltage can be suppressed.
According to the drive circuit 10, the trade-off relationship existing between the surge voltage and the turn-off loss can be broken in the transition period T10 in which the transistor 30 is turned off.

A specific circuit configuration will be described below. In addition, the same code | symbol is attached | subjected about the same component and the description is abbreviate | omitted.
FIG. 3 shows an example in which the variable resistor R12 and the drain voltage detection means 50 of FIG. The pinch resistor 60 includes an n-type first semiconductor region 62 of polycrystalline silicon containing n-type impurities, a p-type semiconductor region 64 of polycrystalline silicon containing p-type impurities, and a polycrystal containing n-type impurities. A silicon n-type second semiconductor region 65 is provided. The n-type first semiconductor region 62 and the n-type second semiconductor region 65 are separated by a p-type semiconductor region 64. The n-type first semiconductor region 62 is electrically connected to the drain electrode D of the transistor 20 through the first electrode 61. The n-type second semiconductor region 65 is electrically connected to the drain electrode D of the transistor 20 through the second electrode 66. One end of the p-type semiconductor region 64 is electrically connected to the gate electrode G of the transistor through the third electrode 67. The other end of the p-type semiconductor region 64 is electrically connected to the gate terminal G10 through the fourth electrode 63.

With reference to FIG. 4, the expansion and contraction of the depletion layer formed in the pinch resistor 60 will be described. The impurity concentration and width of each semiconductor region constituting the pinch resistor 60 are substantially equal when a voltage corresponding to the DC voltage Vdd of the voltage supply source 40 is applied to the first electrode 61 and the second electrode 66. It is formed so as to be completely depleted. Alternatively, as will be described later, when the Zener diode Dz is provided between the pinch resistor 60 and the drain electrode D of the transistor 20, the impurity concentration and width of each semiconductor region constituting the pinch resistor 60 are as follows: When a voltage obtained by subtracting the breakdown voltage of the Zener diode Dz from the DC voltage Vdd is applied to the first electrode 61 and the second electrode 66, the first electrode 61 and the second electrode 66 are depleted and a desired resistance value is obtained.
When the drain-source voltage Vds is 0 V, a depletion layer based on the diffusion potential difference between the p-type semiconductor region 64 and the n-type semiconductor regions 62 and 66 is formed. The width of this depletion layer is small, and the width of the current path of the p-type semiconductor region 64 is secured wide.
When the drain-source voltage Vds is 20 V, the pn junction between the p-type semiconductor region 64 and the n-type semiconductor regions 62 and 66 is reverse-biased, and a depletion layer extends in the p-type semiconductor region 64. For this reason, the width of the current path of the p-type semiconductor region 64 is narrowed.
When the drain-source voltage Vds is 75 V, the pn junction between the p-type semiconductor region 64 and the n-type semiconductor regions 62 and 66 is further reverse-biased, and a depletion layer further extends in the p-type semiconductor region 64. For this reason, the width of the current path of the p-type semiconductor region 64 is extremely narrow, resulting in a high resistance.

FIG. 5 shows the relationship between the voltage V applied to the first electrode 61 and the second electrode 66 of the pinch resistor 60 and the resistance value R of the pinch resistor 60. As shown in FIG. 5, the resistance value R of the pinch resistor 60 continuously increases according to the applied voltage V.
From this result, the resistance value R of the pinch resistor 60 is adjusted to be small when the drain-source voltage Vds is small, and is adjusted to be large when the drain-source voltage Vds is large.

FIG. 6 shows a simulation result of the drive circuit 10 using the pinch resistor 60 having the above characteristics. The resistance value of the fixed resistor R10 was set to 3Ω. Moreover, the simulation result in case the pinch resistor 60 is not provided in FIG. 7 is shown as a comparative example.
As shown in FIG. 6, it was confirmed that the surge voltage was significantly suppressed in the drive circuit 10 using the pinch resistor 60.

FIG. 8 shows a trade-off curve existing between the surge voltage and the turn-off loss.
“No countermeasure” is a result of the drive circuit in which the pinch resistor 60 is not provided. “With countermeasures” is a result of the drive circuit 10 in which the pinch resistor 60 is provided.
In the case of “with countermeasures”, the surge voltage is remarkably reduced without substantially increasing the turn-off loss as compared with the case of “without countermeasures”. The result of “with countermeasures” can be evaluated as being greatly improved from the trade-off curve.

FIG. 9 shows an example of a modification of the drive circuit 10. The drive circuit 10 is characterized in that a Zener diode Dz is provided between the electrodes 61 and 66 of the pinch resistor 60 and the drain electrode D of the transistor 20. The anode of the Zener diode Dz is connected to the electrodes 61 and 66 side of the pinch resistor 60, and the cathode is connected to the drain electrode D side of the transistor 20.
When the Zener diode Dz is provided, the drain-source voltage Vds of the transistor 20 is not applied to the n-type semiconductor regions 62 and 65 of the pinch resistor 60 until the Zener diode Dz breaks down. Therefore, the current path of the pinch resistor 60 is widely maintained until the Zener diode Dz breaks down. As a result, in the early stage of the transition period in which the transistor 20 is turned off, the resistance value of the pinch resistor 60 can be kept small, and the negative gate current Ig (−) can be rapidly changed. As a result, the drain current Id of the transistor 20 can be sharply changed, and the time required for turn-off can be further shortened.
A plurality of Zener diodes Dz may be provided in series. The voltage applied to the n-type semiconductor regions 62 and 65 can be adjusted to a small value by the plurality of Zener diodes Dz. When the voltage applied to the n-type semiconductor regions 62 and 65 is adjusted to a small value, the impurity concentration of the p-type semiconductor region 64 is reduced and / or the p-type interposed between the n-type semiconductor regions 62 and 65. The width of the semiconductor region 64 can be reduced. Therefore, the variation of the depletion layer width when a voltage is applied to the n-type semiconductor regions 62 and 65 increases, and the resistance change of the p-type semiconductor region 64 increases. As a result, the resistance value of the pinch resistor 60 is kept small at the beginning of the transition period when the transistor 20 is turned off, and the resistance value of the pinch resistor 60 is increased at the end of the transition period when the transistor 20 is turned off. Obtainable.

(Second embodiment)
FIG. 10 shows the drive circuit 10 of the second embodiment. The drive circuit 10 includes a MOS resistor 160 having a MOS structure.
The MOS resistor 160 includes a first insulator region 162 made of silicon oxide, a p-type semiconductor region 164 made of single crystal silicon containing a p-type impurity, and a second insulator region 165 made of silicon oxide. The first insulator region 162 and the second insulator region 165 are separated by a p-type semiconductor region 164. The first electrode 161 is opposed to the p-type semiconductor region 164 with the first insulator region 162 interposed therebetween. The second electrode 166 is opposed to the p-type semiconductor region 164 with the second insulator region 165 interposed therebetween. The first electrode 161 and the second electrode 166 are electrically connected to the drain electrode D of the transistor 20. One end of the p-type semiconductor region 164 is electrically connected to the gate electrode G of the transistor through the third electrode 167. The other end of the p-type semiconductor region 164 is electrically connected to the gate terminal G10 through the fourth electrode 163.

The MOS resistor 160 can adjust the width of the depletion layer that expands and contracts in the p-type semiconductor region 64 due to the electric field effect.
FIG. 11 shows the relationship between the voltage V applied to the first electrode 161 and the second electrode 166 of the MOS resistor 160 and the resistance value R of the MOS resistor 160. As shown in FIG. 11, the resistance value R of the MOS resistor 160 increases substantially continuously according to the applied voltage V.
From this result, the resistance value R of the MOS resistor 160 is adjusted to be small when the drain-source voltage Vds is small, and is adjusted to be large when the drain-source voltage Vds is large.

FIG. 12 shows a simulation result of the drive circuit 10 using the MOS resistor 160 having the above characteristics. The resistance value of the fixed resistor R10 was set to 3Ω. FIG. 7 shows a simulation result when the MOS resistor 160 is not provided as a comparative example.
As shown in FIG. 12, it was confirmed that the surge voltage was significantly suppressed in the drive circuit 10 using the MOS resistor 160.

FIG. 13 shows a trade-off curve existing between the surge voltage and the turn-off loss.
“No countermeasure” is a result of the drive circuit in which the MOS resistor 160 is not provided. “With countermeasures” is a result of the drive circuit 10 in which the MOS resistor 160 is provided.
In the case of “with countermeasures”, the surge voltage is remarkably reduced without substantially increasing the turn-off loss as compared with the case of “without countermeasures”. The result of “with countermeasures” can be evaluated as being greatly improved from the trade-off curve.

(Third embodiment)
14 to 17, the circuit elements of the pinch resistor 60, the Zener diode Dz, the diode D 10, the fixed resistor R 10, and the protective Zener diode 22 in the drive circuit 10 shown in FIG. The example provided in the board | substrate is shown. All of these circuit elements are provided on a semiconductor substrate. The transistor 20 and these circuit elements are integrated using a semiconductor substrate, and are configured by one chip.
In the present embodiment, the second diode D12 in the drive circuit 10 shown in FIG. 9 is omitted. If the second diode D12 is eliminated, the positive gate current Ig (+) can be changed slowly at the beginning of turn-on, and the gate current Ig (+) can be changed rapidly at the end of turn-on. it can.

  FIG. 14 schematically shows a perspective view of a main part of the pinch resistor 60 provided on the semiconductor substrate. In addition, each code | symbol attached | subjected to FIG. 14 respond | corresponds to the code | symbol of each component of the pinch resistor 60 of FIG. As will be described later, the pinch resistor 60 is provided on the semiconductor substrate via an oxide film. Polycrystalline silicon is used as the material of the pinch resistor 60. Phosphorus is introduced into the n-type first semiconductor region 62 and the n-type second semiconductor region 65, and boron is introduced into the p-type semiconductor region 64.

FIG. 15 shows a surface layout of a semiconductor substrate on which circuit elements such as the transistor 20 and the pinch resistor 60 are integrally provided. A portion indicated by a broken line is a portion where an aluminum wiring is formed. Hereinafter, the surface layout of FIG. 15 will be described with reference to the circuit shown in FIG.
The source electrode S of the transistor 20 is disposed on most of the surface of the semiconductor substrate. In the semiconductor substrate below the source electrode S, a semiconductor region required for the transistor 20 is formed. A gate electrode G extends from the periphery of the source electrode S toward the inside while being electrically insulated from the source electrode S. The source electrode S and the gate electrode G of the transistor 20 are connected via a protective Zener diode 22 at the upper left corner. Polycrystalline silicon is used as the material of the protective Zener diode 22. The protective Zener diode 22 is provided on the semiconductor substrate via an oxide film.

  In the upper right corner of the surface layout, a Zener diode Dz, a pinch resistor 60, a diode D10, and a fixed resistor R10 are arranged. FIG. 16 is a longitudinal sectional view corresponding to the line XVI-XVI in FIG. FIG. 17 is a longitudinal sectional view corresponding to the line XVII-XVII in FIG.

  As shown in FIG. 16, the pinch-off resistor 60 is provided on the semiconductor substrate via an oxide film 72. An aluminum wiring extends above the pinch-off resistor 60, and the aluminum wiring is electrically connected to both the n-type first semiconductor region 62 and the n-type second semiconductor region 65 of the pinch-off resistor 60. . This aluminum wiring is electrically insulated from the p-type semiconductor region 64 of the pinch-off resistor 60. A portion where the aluminum wiring and the n-type first semiconductor region 62 are connected is called a first electrode 61 and corresponds to the first electrode 61 of FIG. A portion where the aluminum wiring and the n-type second semiconductor region 65 are connected is called a second electrode 66 and corresponds to the second electrode 66 of FIG. One end of the aluminum wiring is electrically connected to the cathode of the Zener diode Dz as shown in FIG. The anode of the Zener diode Dz is connected to an equipotential ring electrode (EQR) that makes a circuit around the semiconductor substrate. The equipotential ring electrode (EQR) is electrically connected to the drain electrode D of the transistor 20. Therefore, the anode of the Zener diode Dz is electrically connected to the drain electrode D of the transistor 20 via the equipotential ring electrode (EQR).

  As shown in FIG. 17, the p-type semiconductor region 64 of the pinch-off resistor 60 is electrically connected to two aluminum wirings at both ends thereof. One aluminum wiring extends from the gate terminal G10 as shown in FIG. One aluminum wiring is electrically connected to one end of the p-type semiconductor region 64 through the third electrode 63. The other aluminum wiring extends from the gate electrode G as shown in FIG. The other aluminum wiring is electrically connected to the other end of the p-type semiconductor region 64 through the fourth electrode 67. The third electrode 63 and the fourth electrode 67 correspond to the third electrode 63 and the fourth electrode 67 of FIG.

  As shown in FIG. 15, a series circuit of a diode D10 and a fixed resistor R10 is connected between the gate electrode G and the gate terminal G10. Polycrystalline silicon is used as a material for the diode D10 and the fixed resistor R10. The resistance value of the fixed resistor R10 is adjusted by the concentration of the introduced impurity.

  By adopting such a configuration, the circuit elements of the pinch resistor 60, the Zener diode Dz, the diode D10, the fixed resistor R10, and the protective Zener diode 22 are integrally constructed on the same semiconductor substrate as the transistor 20. Can do. By adopting such a configuration, it is not necessary to prepare each of the circuit elements separately. For this reason, the chip for the drive circuit disclosed in this specification can be constructed without increasing the number of parts. When the transistor and the circuit element are provided on the same semiconductor substrate, the drive circuit can be configured with a small number of components, and the drive circuit can be reduced in size and excellent in practicality.

(Fourth embodiment)
18 and 19 show an example of a Zener diode Dz connected between the drain D of the transistor 20 and the pinch resistor 60. FIG.
In the example shown in FIG. 18, a plurality of Zener diodes Dz are connected between the n-type first semiconductor region 62 of the pinch resistor 60 and the drain D of the transistor 20. Further, a plurality of Zener diodes Dz are also connected between the n-type second semiconductor region 65 of the pinch resistor 60 and the drain D of the transistor 20. That is, a parallel circuit of a plurality of zener diodes Dz and a plurality of zener diodes Dz is connected between the drain D of the transistor 20 and the pinch resistor 60. In this example, the number of Zener diodes Dz between the n-type first semiconductor region 62 and the drain D is equal to the number of Zener diodes Dz between the n-type second semiconductor region 65 and the drain D. Further, as shown in FIG. 19, the n-type first semiconductor region 62 and the n-type second semiconductor region 65 are short-circuited, and a plurality of Zener diodes Dz are formed between the n-type first semiconductor region 62 and the drain D. A series circuit may be connected. Instead of this example, a series circuit composed of a plurality of Zener diodes Dz may be connected between the n-type second semiconductor region 65 and the drain D. In addition, the n-type first semiconductor region 62 and the n-type second semiconductor region 65 may be short-circuited with a metal wiring or the like.

  When a plurality of Zener diodes Dz are provided, the voltage applied to the n-type semiconductor regions 62 and 65 can be adjusted to a small value. That is, the voltage applied to the n-type semiconductor regions 62 and 65 is adjusted to a value obtained by subtracting the total breakdown voltage of the plurality of Zener diodes Dz from the drain-source voltage Vds of the transistor 20. Therefore, the voltage applied to the n-type semiconductor regions 62 and 65 can be adjusted according to the number of Zener diodes Dz. When the voltage applied to the n-type semiconductor regions 62 and 65 is adjusted to a small value, the impurity concentration of the p-type semiconductor region 64 is reduced and / or the p-type interposed between the n-type semiconductor regions 62 and 65. The width of the semiconductor region 64 can be reduced. Therefore, the variation of the depletion layer width when a voltage is applied to the n-type semiconductor regions 62 and 65 increases, and the resistance change of the p-type semiconductor region 64 increases. As a result, the resistance value of the pinch resistor 60 is kept small at the beginning of the transition period when the transistor 20 is turned off, and the resistance value of the pinch resistor 60 is increased at the end of the transition period when the transistor 20 is turned off. Obtainable.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

The basic structure of the drive circuit of an Example is shown. The operation waveform figure of the drive circuit of an Example is shown. The specific structure of the drive circuit of an Example is shown. The mode of the depletion layer which expands and contracts to the pinch resistor of an Example is shown. The relationship between the voltage applied to the pinch resistor of an Example and the resistance value of a pinch resistor is shown. The simulation result of the drive circuit of an Example is shown. The simulation result of the drive circuit of a comparative example is shown. The relationship of the surge voltage and turn-off loss of the drive circuit of an Example is shown. The concrete structure of one modification of the drive circuit of an Example is shown. A specific configuration of another modification of the driving circuit of the embodiment will be described. The relationship between the voltage applied to the pinch resistor of a modification and the resistance value of a pinch resistor is shown. The simulation result of the drive circuit of a modification is shown. The relationship of the surge voltage and turn-off loss of the drive circuit of a modification is shown. The perspective view of a pinch resistor is shown. The surface layout of a semiconductor substrate is shown. The longitudinal cross-sectional view corresponding to the XVI-XVI line of FIG. 15 is shown. The longitudinal cross-sectional view corresponding to the XVII-XVII line of FIG. 15 is shown. An example of a Zener diode is shown. Another example of a Zener diode is shown. The operation | movement waveform diagram of the drive circuit of a prior art example is shown.

Explanation of symbols

10: drive circuit 11: drive voltage generation circuit 20: transistor 30: load 40: voltage supply source 40
50: drain voltage detecting means 60: pinch resistors 61, 62, 161, 162: electrodes 62, 65: n-type semiconductor region 64, 164: p-type semiconductor region 160: MOS resistors 162, 165: insulator region R10: Fixed resistor R12: Variable resistor

Claims (10)

A circuit for driving a transistor,
A variable resistor electrically connected to the gate electrode of the transistor;
A drive circuit characterized in that the width of the current path of the variable resistor is adjusted by a depletion layer that expands and contracts according to the voltage between the main electrodes of the transistor.   2. The drive circuit according to claim 1, wherein the resistance value of the variable resistor is adjusted to be small when the voltage between the main electrodes of the transistor is small, and is adjusted to be large when the voltage between the main electrodes is large. The variable resistor has a p-type semiconductor region and an n-type semiconductor region in contact with the p-type semiconductor region.
the p-type semiconductor region is electrically connected to the gate electrode of the transistor;
3. The driving circuit according to claim 2, wherein the n-type semiconductor region is electrically connected to the output electrode of the transistor.   4. The drive circuit according to claim 3, wherein a Zener diode is provided between the n-type semiconductor region and the output electrode of the transistor. The variable resistor has a p-type semiconductor region, an insulator region in contact with the p-type semiconductor region, and a conductor region facing the p-type semiconductor region through the insulator region,
the p-type semiconductor region is electrically connected to the gate electrode of the transistor;
3. The drive circuit according to claim 2, wherein the conductor region is electrically connected to the output electrode of the transistor.   6. The drive circuit according to claim 5, wherein a Zener diode is provided between the conductor region and the output electrode of the transistor. A drive circuit,
A transistor,
A variable resistor electrically connected to the gate electrode of the transistor;
The width of the current path of the variable resistor is adjusted by a depletion layer that expands and contracts according to the voltage between the main electrodes of the transistor,
A driving circuit, wherein a transistor and a variable resistor are provided on the same semiconductor substrate. The variable resistor has a p-type semiconductor region and an n-type semiconductor region in contact with the p-type semiconductor region.
The p-type semiconductor region is provided on the semiconductor substrate via an insulating film, and is electrically connected to the gate electrode of the transistor,
8. The drive circuit according to claim 7, wherein the n-type semiconductor region is provided on the semiconductor substrate via an insulating film and is electrically connected to the output electrode of the transistor.   9. The semiconductor device according to claim 8, wherein the material of the p-type semiconductor region and the n-type semiconductor region is polycrystalline silicon. 10. The drive circuit according to claim 8, wherein a Zener diode is provided between the n-type semiconductor region and the output electrode of the transistor.

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