JP2013021583A - Drive circuit for current drive type semiconductor switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: A conventional drive circuit for current drive type semiconductor switch 8 requires a switch and means of controlling the switch in order to suppress power loss in the drive circuit and hence the number of components used increases.SOLUTION: The present invention comprises: a first variable resistor 10 that has a negative temperature characteristic connected between a power supply 1 and the base or gate terminal of a current drive type semiconductor switch 8, and a heat conductive section 11 overheated by operational loss by a collector or drain current of the current drive type semiconductor switch 8. The first variable resistor 10 is positioned so that heat is supplied by the heat conductive section 11. With such a simple configuration, power loss in the drive circuit can be suppressed without increasing the number of components.

Description

  The present invention relates to a drive circuit for a current drive type semiconductor switch.

  FIG. 11 shows a driving circuit for a conventional current-driven semiconductor switch. A conventional drive circuit for a current-driven semiconductor switch has an energy storage inductor 4 connected between a first switching element 2 connected to a power source 1 and a second switching element 3 grounded. A diode 5 grounded in reverse bias is connected to a connection point between the first switching element 2 and the inductor 4, and a power source 6 is connected to the connection point between the inductor 4 and the second switching element 3. A control electrode (base or gate) of a current-driven semiconductor switch 8 whose emitter or drain is grounded is connected via a load 7, and further, the first switching element 2 and the second switching element 3 are turned on, thereby causing an inductor. Energy stored in the inductor 4 by turning off the first switching element 2 and the second switching element 3. After supplying the current based on the control electrode (base or gate) of the current driven semiconductor switch 8, the second switching element 3 is turned on to ground the inductor 4, and the current based on the energy accumulated in the inductor 4 Is provided with a control unit 9 that outputs a control signal for turning on the first switching element 2.

As described above, the current supplied to the control electrode (base or gate) of the current-driven semiconductor switch 8 is supplied from the power source 1 without the resistor, and the first switching element 2 and the second switching controlled by the control unit 9. It is supplied based on the energy stored in the inductor 4 using the element 3. (See Patent Document 1)
In this way, a current supply to the control electrode (base or gate) of the current driven semiconductor switch 8 can be performed without using a resistor, thereby providing a drive circuit that suppresses power loss.

Japanese Patent Laid-Open No. 5-243943

  In the drive circuit of the current-driven semiconductor switch 8 of the prior art, in order to store the current supplied to the control electrode (base or gate) in the inductor 4, the diode 5, the first switching element 2, and the second switching element 3. Therefore, the control unit 9 for driving the switching element is required, and the number of parts increases. Furthermore, there is a problem that electric power for operating the control unit 9 and electric power for driving the first switching element 2 and the second switching element 3 are required. An object of the present invention is to provide a drive circuit for the current drive type semiconductor switch 8 having a simple configuration with a small number of parts and suppressing power loss.

  In order to solve the above-described problem, a first variable resistor 10 having a negative temperature characteristic connected between the power source 1 and the gate terminal of the current-driven semiconductor switch 8, and the emitter of the current-driven semiconductor switch 8 or The heat conducting unit 11 is overheated due to operation loss due to drain current, and the first variable resistor 10 is arranged to be supplied with heat by the heat conducting unit 11.

  This provides a drive circuit for the current drive type semiconductor switch 8 with a simple configuration with a small number of parts and reduced power loss.

  The drive circuit of the current drive type semiconductor switch 8 of the present invention can perform current drive type semiconductor switch drive with a simple configuration with a small number of parts and reduced power loss.

The figure which shows the drive circuit of the current drive type semiconductor switch of this invention The figure which shows the drive circuit of the current drive type semiconductor switch of this invention The figure which shows the temperature characteristic of the 1st variable resistance in the Example of this invention. The figure which shows the temperature characteristic of the 2nd variable resistance in the Example of this invention. The figure which shows the temperature characteristic of the 3rd variable resistance in the Example of this invention. The figure which shows the electrical property of the current drive type semiconductor switch in the Example of this invention The figure which shows the electrical property of the current drive type semiconductor switch in the Example of this invention Schematic of an air conditioner power converter in an embodiment of the present invention Inverter circuit diagram in an embodiment of the present invention The figure which shows the drive circuit of the current drive type semiconductor switch in the Example of this invention The figure which shows the drive circuit of the current drive type semiconductor switch in a prior art

  The first invention is overheated by a first variable resistor having a negative temperature characteristic connected between a power source and a gate terminal of a current driven semiconductor switch, and an operation loss due to a drain current of the current driven semiconductor switch. The first variable resistor is arranged to be supplied with heat by the heat conducting unit, so that the gate current can be adjusted according to the drain current of the current driven semiconductor switch. Thus, power loss in the drive circuit can be suppressed.

A second variable resistor having a negative temperature characteristic and a second variable resistor having a positive temperature characteristic connected in series between a power source and a gate terminal of the current-driven semiconductor switch;
A heat conduction unit that is overheated due to an operation loss due to a drain current of the current-driven semiconductor switch; wherein the first variable resistor is supplied with heat by the heat conduction unit; and the second variable resistor is the heat conduction unit. The first and second variable resistors are arranged with a negative slope of the resistance value with respect to the temperature of the first variable resistor. By reducing the positive slope of the resistance value with respect to the temperature of the variable resistor 2, it becomes possible to adjust the gate current according to the drain current considering the ambient temperature of the current-driven semiconductor switch, Power loss in the drive circuit can be suppressed.

According to a third aspect of the present invention, there is provided a first variable resistor having a negative temperature characteristic and a second variable resistor having a positive temperature characteristic, which are connected in series between a power source and a gate terminal of a current-driven semiconductor switch, and a positive A third variable resistor having a temperature characteristic; and a heat conduction unit that is overheated due to an operation loss due to a drain current of the current-driven semiconductor switch, wherein the first and third variable resistors are heated by the heat conduction unit. And the second variable resistor is arranged to be supplied with heat from a portion other than the heat conducting portion (for example, a peripheral portion of the current-driven semiconductor switch), and the first and third variable resistors are When the amount of heat supplied by the heat conducting unit is less than a predetermined value, the sum of the first and third variable resistance values has a negative temperature characteristic, and the resistance to the temperature of the sum of the first and third variable resistances From the negative slope of the value to the temperature of the second variable resistor When the positive slope of the resistance value to be performed is small and the amount of heat supplied from the heat conducting unit exceeds a predetermined value, the third variable resistor has a gate current of the current-driven semiconductor switch limited and a drain current Has a temperature characteristic that results in a resistance value that is substantially interrupted, it becomes possible to adjust the gate current according to the drain current in consideration of the ambient temperature of the current-driven semiconductor switch, and the power in the drive circuit Loss can be suppressed, and further load protection by overcurrent suppression can be performed.

  The fourth invention is applied to an air conditioner in which the ambient temperature and the drain current flowing through the current-driven semiconductor switch vary greatly depending on the conditions, so that the gate according to the drain current considering the ambient temperature of the current-driven semiconductor switch. The current can be adjusted, power loss in the drive circuit can be suppressed, and overcurrent suppression can also be performed to protect a load such as a motor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 2 shows a drive circuit of the current drive type semiconductor switch 8 in the embodiment of the present invention.

  A first variable resistor 10 having a negative temperature characteristic and a second variable resistor 12 having a positive temperature characteristic connected in series between the power source 1 and the base terminal or gate terminal of the current-driven semiconductor switch 8; A third variable resistor 13 having a positive temperature characteristic and a heat conducting unit 11 that is overheated due to an operation loss due to a collector or drain current of the current-driven semiconductor switch 8 are provided. The variable resistor 13 is supplied with heat by the heat conducting unit 11, and the second variable resistor 12 is supplied with heat from other than the heat conducting unit 11 (for example, the peripheral part of the current-driven semiconductor switch 8). Placed in.

  The first variable resistor 10 and the third variable resistor 13 have a sum of the first variable resistor 10 and the third variable resistor 13 when the amount of heat supplied by the heat conducting unit 11 is less than a predetermined value. It has a negative temperature characteristic, and the positive slope of the resistance value with respect to the temperature of the second variable resistor 12 is less than the negative slope of the resistance value with respect to the temperature of the sum of the first variable resistor 10 and the third variable resistor 13. The third variable resistor 13 is configured such that when the amount of heat supplied from the heat conducting unit 11 exceeds a predetermined value, the base or gate current of the current driven semiconductor switch 8 is limited, and the collector or drain current is reduced. It has a temperature characteristic that provides a resistance value that is substantially interrupted.

  The operation and action of the drive circuit of the current drive type semiconductor switch 8 configured as described above will be described below.

  First, the temperature of the heat conducting part 11 corresponding to the package or semiconductor device covering the semiconductor device that is overheated due to the operation loss of the collector or drain current flowing in the current driven semiconductor switch 8 is Tc, and is supplied by the heat conducting part 11. FIG. 3 and FIG. 5 show the temperature characteristics of the first variable resistor 10 and the third variable resistor 13 whose resistance values are changed by the applied heat, respectively.

  As shown in FIG. 3, the first variable resistor 10 has a negative temperature characteristic with respect to the temperature Tc of the heat conducting section 11 in the current driven semiconductor switch 8, and the third variable resistor 13 is shown in FIG. The current drive type semiconductor switch 8 has a positive temperature characteristic with respect to the temperature Tc of the heat conducting portion 11, and particularly when the temperature Tc of the heat conducting portion 11 is equal to or higher than Tclim, the base or gate current is limited to reduce the collector or drain current. Make the resistance value to block. FIG. 4 shows the temperature characteristics of the second variable resistor 12 whose resistance value changes due to the heat supplied from the ambient temperature of the current-driven semiconductor switch 8 or the ambient temperature Ta. As shown in FIG. 4, the second variable resistor 12 has a positive temperature characteristic with respect to the ambient temperature Ta.

  For example, when GaN (gallium nitride), which is a wide bandgap compound semiconductor, is used for the current-driven semiconductor switch 8, the gate current Ig and the drain current Id have electrical characteristics as shown in FIG. When the temperature Tc of the heat conducting unit 11 in the current-driven semiconductor switch 8 is fixed at Tca, the maximum drain current that can flow is given by the relationship between the gate currents Ig_a, Ig_b, and Ig_c: Ig_a> Ig_b> Ig_c It becomes maximum when the gate current Ig is set to Ig_a, and becomes minimum when the gate current Ig is set to Ig_c.

  Further, the temperature Tc and the drain current Id of the heat conducting unit 11 in the current driven semiconductor switch 8 have electrical characteristics as shown in FIG. When the gate current Ig is fixed at Ig_a, if the magnitude relationship among the temperatures Tca, Tcb, and Tcc of the current-driven semiconductor switch 8 is Tca> Tcb> Tcc, the maximum drain current that can flow is the current-driven semiconductor switch 8. It becomes the maximum when the temperature Tc of the heat conducting part 11 is set to Tcc, and becomes the minimum when the temperature Tc of the heat conducting part 11 in the current drive type semiconductor switch 8 is set to Tca.

  Here, the power loss of the drive circuit when the ambient temperature Ta is the same, the temperature rise ΔT due to the drain current Id, and the temperature Tc of the heat conducting section 11 in the current drive type semiconductor switch 8 will be described.

For example, the condition (a) is that the ambient temperature Ta = 20 ° C. and the temperature rise ΔT due to the drain current Id is ΔT = 20 ° C. (Tc = 40 ° C.), and the temperature rise ΔT due to the ambient temperature Ta = 20 ° C. and the drain current Id is ΔT = When the condition (b) is 40 ° C. (Tc = 60 ° C.), the first to third variable resistors (10, 12, 13) in which temperature characteristics are considered in advance so that a necessary gate current flows due to the drain current Id. ), The resistance value of the second variable resistor 12 depending on the ambient temperature Ta is Rg2 (20 ° C.), and the first and third variable resistors (10, 13) depending on the temperature Tc of the heat conducting unit 11 When the resistance values are Rg1 (40 ° C.), Rg3 (40 ° C.), Rg1 (60 ° C.), and Rg3 (60 ° C.), the gate resistances Rg (a) and Rg (b) of the conditions (a) and (b), respectively. ) Is as follows.
Rg (a) = Rg1 (40 ° C.) + Rg2 (20 ° C.) + Rg3 (40 ° C.)
Rg (b) = Rg1 (60 ° C.) + Rg2 (20 ° C.) + Rg3 (60 ° C.)
Here, if the sum of the resistance values of Rg1 and Rg3 is selected in advance so as to have a negative temperature characteristic, the magnitude relationship between Rg (a) and Rg (b) is Rg (a)> Rg (b).
Thus, the gate current of the drive circuit having a large drain current Id is adjusted to be large, and conversely, the gate current of the drive circuit having a small drain current Id is adjusted to be small.

Therefore, when the gate drive power supply voltage Ec is used, the power loss of the drive circuit when the drain current is large (condition (b)) is Ec ² / Rg (b), and the drive circuit when the drain current is small (condition (a)). Is Ec ² / Rg (a) (<Ec ² / Rg (b)), and it is possible to suppress the power loss in the drive circuit by supplying the gate current according to the necessity of the drain current Id.

  Next, the power loss of the drive circuit when the temperature Tc of the heat conducting unit 11 in the current drive type semiconductor switch 8 is equal, the ambient temperature Ta, and the drain current Id are different will be described.

For example, the condition (c) is that the temperature Tc = 80 ° C. of the heat conducting unit 11 in the current drive semiconductor switch 8, the ambient temperature Ta = 20 ° C., and the temperature rise ΔT = 60 ° C. due to the drain current Id. When the temperature Tc = 80 ° C. of the heat conducting unit 11, the ambient temperature Ta = 60 ° C., and the temperature increase ΔT = 20 ° C. due to the drain current Id are set as the condition (d), the necessary gate current flows beforehand by the drain current Id. Resistance values of the first and third variable resistors (10, 13) depending on the temperature Tc of the heat conducting unit 11 using the first to third variable resistors (10, 12, 13) in consideration of the temperature characteristics. Are Rg1 (80 ° C.), Rg3 (80 ° C.), and the resistance value of the second variable resistor 12 depending on the ambient temperature Ta is Rg2 (20 ° C.) and Rg2 (60 ° C.), the conditions (c) and (d ) The respective gate resistances Rg (c) and Rg (d) are as follows.
Rg (c) = Rg1 (80 ° C.) + Rg2 (20 ° C.) + Rg3 (80 ° C.)
Rg (d) = Rg1 (80 ° C.) + Rg2 (60 ° C.) + Rg3 (80 ° C.)
Here, since the resistance value of Rg2 has a positive temperature characteristic, the magnitude relationship between Rg (c) and Rg (d) is Rg (c) <Rg (d).
Thus, the gate current of the drive circuit having a large drain current Id is adjusted to be large, and conversely, the gate current of the drive circuit having a small drain current Id is adjusted to be small.

Therefore, when the gate drive power supply voltage Ec is used, the power loss of the drive circuit when the drain current is large (condition (c)) is Ec ² / Rg (c), and the drive circuit when the drain current is small (condition (d)). Is Ec ² / Rg (d) (<Ec ² / Rg (c)). By supplying a gate current according to the necessity of the drain current Id, the power loss in the drive circuit can be suppressed.

  Next, the power loss of the drive circuit when the temperature rise ΔT due to the drain current Id is equal, the ambient temperature Ta, and the temperature Tc of the heat conducting part 11 in the current drive type semiconductor switch 8 will be described.

For example, the temperature rise ΔT = 20 ° C. due to the drain current Id, the ambient temperature Ta = 20 ° C., and the temperature Tc = 40 ° C. of the heat conducting unit 11 in the current drive type semiconductor switch 8 are set as the condition (e). Assuming that the condition (f) is 20 ° C., the ambient temperature Ta = 60 ° C., and the temperature Tc = 80 ° C. of the heat conducting section 11, the temperature characteristics are considered in advance so that the necessary gate current flows due to the drain current Id. The first to third variable resistors (10, 12, 13) are used, and the resistance values of the first and third variable resistors (10, 13) depending on the temperature Tc of the heat conducting section 11 are Rg1 (40 ° C.), respectively. , Rg3 (40 ° C.), Rg1 (80 ° C.), Rg3 (80 ° C.), and the resistance value of the second variable resistor 12 depending on the ambient temperature Ta are Rg2 (20 ° C.) and Rg2 (60 ° C.), respectively. ( c) and gate resistances Rg (c) and Rg (d) of condition (d) are as follows.
Rg (e) = Rg1 (40 ° C.) + Rg2 (20 ° C.) + Rg3 (40 ° C.)
Rg (f) = Rg1 (80 ° C.) + Rg2 (60 ° C.) + Rg3 (80 ° C.)
Here, the sum of the resistance values of Rg1 and Rg3 has a negative temperature characteristic, and the positive slope of the resistance value with respect to the temperature of the resistance value of Rg2 is smaller than the negative slope with respect to the temperature of the sum of the resistance values of Rg1 and Rg3. If preselected so that the relationship between Rg (e) and Rg (f) is Rg (e)> Rg (f)
When the drain current Id is equal, the gate temperature of the drive circuit is increased so that the ambient temperature Ta and the temperature Tc of the heat conducting unit 11 are increased. Conversely, the ambient temperature Ta and the temperature Tc of the heat conducting unit 11 are Adjustment is made so that the gate current of the driving circuit to be lowered becomes small.

Therefore, when the gate drive power supply voltage Ec is used, the power loss of the drive circuit when the ambient temperature Ta and the temperature Tc of the heat conducting unit 11 are high (condition (f)) is Ec ² / Rg (f), the ambient temperature Ta, When the temperature Tc of the heat conducting unit 11 is low (condition (e)), the power loss of the drive circuit is Ec ² / Rg (e) (<Ec ² / Rg (f)), and the drain current Id is required as required. By supplying the gate current, power loss in the drive circuit can be suppressed.

Further, a case where the temperature Tc of the heat conducting unit 11 of the current drive type semiconductor switch 8 is equal to or higher than Tclim will be described. When the gate current Ig at which the drain current Id is substantially cut off is equal to or less than Iglim, the temperature of the heat conducting unit 11 when the drain current exceeding the maximum allowable current of the current drive type semiconductor switch 8 or the load 7 flows is Tclim, The resistance value of the third variable resistor 13 is Rg3 (Tcrim), and the third variable resistor 13 is set in advance so as to satisfy the following relationship.
Ec <{Iglim × Rg3 (Tclim)}
As a result, the current-driven semiconductor switch 8 or the load 7 becomes a protection means that eliminates the need for a mechanical device against overcurrent, and higher reliability can be realized by combining with other protection devices.

Moreover, the case where the drive circuit shown in FIG. 2 is applied to an inverter circuit for driving a compressor such as an air conditioner will be described. FIG. 8 is a schematic diagram of an air conditioner power converter, and FIG. 9 shows an inverter circuit. The AC power supply 14 is input rectified to the diode bridge 16 via the reactor 15, and the rectified voltage is smoothed by the capacitor 17. The smoothed voltage is input to the inverter circuit 18, converted into AC power, and transmitted to the compressor motor 19 that is the load 7. Here, the inverter circuit 18 is composed of six (Q _UH , Q _UL , Q _VH , Q _VL , Q _WH , Q _WL ) current-driven semiconductor switches 8 as GaN semiconductor switches as power semiconductors.

In general, an inverter circuit for driving a compressor such as an air conditioner has a configuration in which six power semiconductors are arranged in one module 20. Figure 10 shows a drive circuit of a power semiconductor switch _{(Q UH,} Q _UL) of the upper and lower arm and a power semiconductor switch is a current-driven semiconductor switch 8 on the upper arm side _{(Q UH)} of the U-phase in the module 20.

  If the module 20 is considered as the heat conducting unit 11, the first and third variable resistors (10, 13) are arranged inside the module 20, and the second variable resistor 12 is arranged outside the module 20. For example, as described above, the gate current is adjusted in accordance with the change in the drain current flowing through the current-driven semiconductor switch 8 (power semiconductor) and the ambient temperature of the power semiconductor, thereby suppressing the operation loss in the drive circuit.

  Especially when the environmental temperature and the ambient temperature where the inverter circuit 18 is installed, such as an inverter air conditioner, vary greatly depending on the season (summer winter) or time zone (day and night), and the inverter operating current varies greatly due to the inverter operation. By supplying the gate current adjusted to the required current value according to the drain current and temperature, it is not necessary to set the gate current assuming the maximum drain current value or the condition (temperature) where the drain current is most difficult to flow. Operation loss in the drive circuit can be suppressed.

  Note that the third variable resistor 13 may be omitted.

  Further, the application to the inverter circuit for an air conditioner has been described, but the same effect can be expected in various inverter circuits such as a refrigerator, a washing machine, and a vacuum cleaner that vary in temperature and current value.

  As described above, by using the variable resistor whose resistance value varies depending on the temperature, the gate current is changed according to the temperature Tc (device case temperature) of the heat conducting portion 11 of the current-driven semiconductor switch 8, the ambient temperature Ta, and the drain current Id. By adjusting the power loss, the power loss in the drive circuit can be suppressed.

As described above, the present invention has a simple configuration with a small number of parts and a low power consumption in the drive circuit, particularly in an inverter device having a large change in environmental temperature and operating current, as compared with the drive circuit of the conventional current-driven semiconductor switch 8. Since loss can be suppressed, it can be applied to various inverter devices such as air conditioners, refrigerators, and washing machines.

1 Power supply (control side)
2 First switching element 3 Second switching element 4 Inductor 5 Diode 6 Power supply (load side)
DESCRIPTION OF SYMBOLS 7 Load 8 Current drive type semiconductor switch 9 Control part 10 1st variable resistance 11 Heat conduction part 12 2nd variable resistance 13 3rd variable resistance 14 AC power supply 15 Reactor 16 Diode bridge 17 Capacitor 18 Inverter circuit 19 Motor 20 Module

Claims (4)

A first variable resistor having a negative temperature characteristic connected between a power supply and a gate terminal of the current-driven semiconductor switch; and a heat conducting portion that is overheated due to an operation loss due to a drain current of the current-driven semiconductor switch. ,
The drive circuit of the current drive type semiconductor switch, wherein the first variable resistor is arranged to be supplied with heat by the heat conducting unit. A first variable resistor having a negative temperature characteristic and a second variable resistor having a positive temperature characteristic connected in series between the power supply and the gate terminal of the current-driven semiconductor switch;
A heat conduction part that is overheated due to operation loss due to drain current of the current-driven semiconductor switch;
The first variable resistor is arranged to be supplied with heat by the heat conducting part, and the second variable resistor is arranged to be supplied with heat from other than the heat conducting part (for example, the peripheral part of the current driven semiconductor switch). And the first and second variable resistors have a positive slope of the resistance value with respect to the temperature of the second variable resistor smaller than a negative slope of the resistance value with respect to the temperature of the first variable resistor. Drive circuit for drive semiconductor switch. A first variable resistor having a negative temperature characteristic, a second variable resistor having a positive temperature characteristic, and a third having a positive temperature characteristic are connected in series between the power supply and the gate terminal of the current-driven semiconductor switch. Variable resistance,
A heat conduction part that is overheated due to operation loss due to drain current of the current-driven semiconductor switch;
The first and third variable resistors are supplied with heat from the heat conducting unit, and the second variable resistor is supplied with heat from other than the heat conducting unit (for example, the peripheral portion of the current-driven semiconductor switch). The first and third variable resistors have a temperature characteristic in which the sum of the first and third variable resistance values is negative when the amount of heat supplied by the heat conducting unit is less than a predetermined value. The positive slope of the resistance value with respect to the temperature of the second variable resistor is smaller than the negative slope of the resistance value with respect to the temperature of the sum of the first and third variable resistors, and the third variable resistor has the thermal resistance When the amount of heat supplied from the conduction unit exceeds a predetermined value, the gate current of the current-driven semiconductor switch is limited, and the temperature characteristic is such that the drain current has a resistance value that is substantially cut off. Drive circuit for current-driven semiconductor switch. 4. The drive circuit for a current driven semiconductor switch according to claim 1, wherein the drive circuit is applied to an output variable type air conditioner.