JP7287117B2 - power tools and control circuits - Google Patents

Description

The present invention has a function to prevent driving of a driving source such as a motor when the power is turned on while an operation switch such as a trigger switch instructs driving (hereinafter also referred to as "power-on malfunction prevention function"). The present invention relates to a power tool and a control circuit for controlling a drive source of the power tool.

Patent Document 1 listed below discloses an example of a circuit that realizes a malfunction prevention function when power is turned on. The operation of this circuit is based on the premise that an operation switch is provided in the current path of the motor.

JP-A-2008-62343

There is also a power tool that does not have an operation switch in the current path of the motor. When such a power tool is equipped with a power-on malfunction prevention function, the circuit configuration of Patent Document 1 cannot be applied as it is.

SUMMARY OF THE INVENTION The present invention has been made in recognition of such circumstances, and its object is to provide a power tool and a control circuit in which the versatility of a circuit that realizes a malfunction prevention function at power-on is enhanced.

One aspect of the invention is a power tool. This power tool
a driving source;
a control circuit that controls the drive source;
an operation switch capable of switching between driving and stopping the drive source, the operation switch instructing to drive the drive source when it is on and instructing to stop the drive source when it is off ;
The control circuit is
a power input;
a prevention circuit that prevents the drive source from being driven when a voltage of a predetermined value or more is applied to its detection terminal when power is turned on;
a switching element provided between the power supply input unit and the detection terminal;
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
a third external connection terminal connected to the control terminal of the switching element;
The operation switch is provided between the third external connection terminal and the ground ,
The switching element is on when the operation switch is on when the power is on, and the switching element is off when the operation switch is off when the power is on;
When power is turned on with the operation switch in the ON state, a voltage equal to or higher than the predetermined value is applied to the detection terminal from the power input unit via the switching element.

The drive source may be a motor, and the number of revolutions of the motor may vary according to the amount of operation of the operation switch.

The control circuit comprises a control unit,
A first voltage, which is a voltage on the detection terminal side of the switching element, and a second voltage, which is a voltage on the control terminal side of the switching element, may be input to the control section.

The first voltage has a different level depending on whether the switching element is turned on or off,
The second voltage has a different level depending on whether the operation switch is turned on or off,
The control unit may set a condition for driving the drive source that the first and second voltages are at predetermined levels.

Another aspect of the invention is a power tool. This power tool
a driving source;
a control circuit that controls the drive source;
an operation switch capable of switching between driving and stopping the drive source, the operation switch instructing to drive the drive source when it is on and instructing to stop the drive source when it is off ;
The control circuit is
a power input;
a prevention circuit that prevents the drive source from being driven when a voltage of a predetermined value or more is applied to its detection terminal when power is turned on;
a switching element provided between the power supply input unit and the detection terminal;
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
a third external connection terminal connected to the control terminal of the switching element;
The operation switch is provided in parallel with the switching element between the first external connection terminal and the second external connection terminal ,
When the operation switch is turned on and the power is turned on, from the power supply input section via the first external connection terminal, the second external connection terminal, and the operation switch, to the detection terminal the predetermined A voltage greater than or equal to

Another aspect of the invention is a power tool. This power tool
a driving source;
a control circuit that controls the drive source;
an operation switch capable of switching between driving and stopping the drive source, the operation switch instructing to drive the drive source when it is on and instructing to stop the drive source when it is off ;
The control circuit is
a power input;
a prevention circuit that prevents the drive source from being driven when a voltage of a predetermined value or more is applied to its detection terminal when power is turned on;
a switching element provided between the power supply input unit and the detection terminal;
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
a third external connection terminal connected to the control terminal of the switching element;
The operation switch is provided in a current path of the drive source,
the drive source side of the operation switch and the first external connection terminal connected to the detection terminal side of the switching element are connected to each other ;
When the operating switch is turned on and the power is turned on, a voltage equal to or higher than the predetermined value is applied from the power supply to the detection terminal via the operating switch and the first external connection terminal.

Another aspect of the present invention is a control circuit for controlling a drive source of a power tool,
a power input;
a prevention circuit for preventing driving of the drive source when a voltage equal to or higher than a predetermined value is applied from the power supply input unit to its detection terminal when the power is turned on;
and a switching element provided between the power supply input unit and the detection terminal,
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
and a third external connection terminal connected to the control terminal of the switching element.

The control circuitry may be provided on a single substrate.

Any combination of the above constituent elements, and conversion of expressions of the present invention between methods and systems are also effective as embodiments of the present invention.

According to the present invention, it is possible to provide a power tool and a control circuit in which the versatility of the circuit that realizes the malfunction prevention function at power-on is enhanced.

1 is a side sectional view of a power tool 1 according to an embodiment of the present invention; FIG. 4 is a schematic circuit diagram of the power tool 1 when the trigger switch 7 is provided in the current path of the motor 6; FIG. 4 is a schematic circuit diagram of the power tool 1 when the trigger switch 7 is provided outside the current path of the motor 6 and connected to the controller 21. FIG. 4 is a schematic circuit diagram of the power tool 1 when the trigger switch 7 is a continuously variable trigger switch; FIG. 5 is a time chart of normal operation of the circuit of FIG. 4; FIG. 5 is a time chart when the malfunction prevention function at power-on of the circuit of FIG. 4 operates; 5 is a time chart when a switching element 30 fails during operation of the circuit of FIG. 4; 5 is a flow chart showing the operation of the circuit of FIG. 4;

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. The same or equivalent constituent elements, members, processes, etc. shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. Moreover, the embodiments are illustrative rather than limiting the invention, and not all features and combinations thereof described in the embodiments are necessarily essential to the invention.

This embodiment relates to a power tool 1 and its control circuit 30. FIG. The power tool 1 is a cordless jigsaw that operates with power from a battery pack 9 . Since the mechanical configuration and operation of the power tool 1 are well known, only a brief description will be given below. As shown in FIG. 1 , the power tool 1 has a base 2 and a housing 3 provided above the base 2 . A battery pack 9 is detachably connected to the rear end of the housing 3 . A motor 6 as a driving source, a reduction mechanism 5 , a reciprocating motion conversion mechanism 8 , and a main board (control board) 20 are provided in the housing 3 .

The motor 6 is an inner rotor type brushless motor. The rotation of the motor 6 is decelerated by the deceleration mechanism 5 and converted into reciprocating motion of the plunger 10 by the reciprocating motion converting mechanism 8 . A blade 11 is attached to the lower end of the plunger 10 as a tip tool that reciprocates up and down together with the plunger 10 . The blade 11 projects downward from the bottom surface of the base 2 . A trigger switch 7 is provided on the handle portion 3 a of the housing 3 . The trigger switch 7 is an example of an operation switch that allows an operator to switch between driving and stopping the motor 6 .

The trigger switch 7 may be provided in the current path of the motor 6 as shown in FIG. 2, provided outside the current path of the motor 6 as shown in FIG. As shown, it may be a continuously variable trigger switch with one end connected to ground. The continuously variable trigger switch can change the number of rotations of the motor according to the amount of operation. A signal cannot be sent to the control unit 21 via the The control circuit 30 of the present embodiment realizes a common function of preventing malfunction when the power is turned on, regardless of whether the trigger switch 7 has any configuration or arrangement shown in FIGS. 2 to 4 . The control circuit 30 is provided on the single main board 20 .

As shown in FIGS. 2 to 4, the control circuit 30 includes a control section 21, a power supply circuit (power supply IC) 28, a power-on malfunction prevention circuit 29, a switching element 40, and external connection terminals 31-37. The external connection terminal 37 is a power input section and is connected to the positive terminal of the battery pack 9 . The output voltage of the battery pack 9 is supplied as a power supply voltage to the power supply circuit 28 and the power-on malfunction prevention circuit 29 via the external connection terminal 37 .

A switching element 40 such as a P-channel bipolar transistor or FET (Field effect transistor) is provided between the external connection terminal 37 and the detection terminal 29 a of the power-on malfunction prevention circuit 29 . The switching element 40 is an element that turns on when its own control terminal (gate) is energized with GND and turns off when it is opened. The switching element 40 is used only in the case of FIG. 4, that is, when the trigger switch 7 is a switch with one end connected to ground, such as a continuously variable trigger switch.

The external connection terminal (first external connection terminal) 31 is connected to one end of the switching element 40 , the detection terminal 29 a of the power-on malfunction prevention circuit 29 , and the first voltage input terminal of the control section 21 . The external connection terminal (second external connection terminal) 32 is connected to the other end of the switching element 40 and the external connection terminal 37 . The external connection terminal (third external connection terminal) 33 is connected to the control terminal of the switching element 40 and the second voltage input terminal of the control section 21 . The external connection terminal 34 is connected to a power line to which the output voltage (control system power supply voltage) Vcc of the power supply circuit 28 is supplied (hereinafter also simply referred to as "power line"). The external connection terminal 35 is connected to the speed adjustment signal input terminal of the control section 21 . The external connection terminal 36 is connected to the ground.

In the case of FIG. 2 , one end of the trigger switch 7 is connected to the positive terminal of the battery pack 9 . The other end of the trigger switch 7 is connected to the motor 6 via the inverter circuit 47 and to the external connection terminal 31 . In the case of FIG. 3 , one end of the trigger switch 7 is connected to the external connection terminal 31 and the other end is connected to the external connection terminal 32 . That is, the trigger switch 7 is provided in parallel with the switching element 40 between the external connection terminals 31 and 32 .

In the case of FIG. 4, the trigger switch 7 is provided between the external connection terminals 33 and 36 . The trigger switch 7 includes a volume (variable resistor) provided between the external connection terminals 34 and 36, and externally connects a voltage (speed control signal) corresponding to the operation amount (pull amount) of the trigger switch 7 by the operator. Output to terminal 35 . When the trigger switch 7 is turned on, the voltage of the control terminal of the switching element 40 becomes low level, the switching element 40 is turned on, and the output voltage Vbt of the battery pack 9 is applied to the power-on malfunction prevention circuit 29 via the switching element 40 . is applied to the detection terminal 29a.

2 and 3, when the trigger switch 7 is turned on, the output voltage Vbt of the battery pack 9 is applied to the detection terminal 29a of the power-on malfunction prevention circuit 29 via the trigger switch 7. FIG. 4, one end of the trigger switch 7 must be grounded, so that voltage cannot be applied to the detection terminal 29a of the power-on malfunction prevention circuit 29 via the trigger switch 7. FIG. Since the control circuit 30 of the present embodiment has the switching element 40, even when one end of the trigger switch 7 is grounded as shown in FIG. The output voltage Vbt of the battery pack 9 can be applied to the detection terminal 29a of the power-on malfunction prevention circuit 29 via the .

The voltage of the external connection terminal 31 is input to the first voltage input terminal of the controller 21 as the first switch detection voltage Va. The voltage of the external connection terminal 33 is input to the second voltage input terminal of the control section 21 as the second switch detection voltage Vb. The voltage of the external connection terminal 35 is input to the speed adjustment signal input terminal of the controller 21 as a speed adjustment signal. The external connection terminals 33 to 36, like the switching element 40, are used only in the case of FIG. 4, that is, when the trigger switch 7 is a switch with one end connected to the ground, such as a continuously variable trigger switch. Therefore, the control unit 21 is set in advance so as to ignore the voltages of the external connection terminals 33 and 35 except in the case of FIG.

The power supply circuit 28 steps down the output voltage Vbt of the battery pack 9 to obtain a control system power supply voltage Vcc, which is supplied to the control unit 21 and the like as an operating voltage. When the trigger switch 7 is turned on and the battery pack 9 is connected (when the power is turned on), the power-on malfunction prevention circuit 29 detects a voltage of a predetermined value or higher at the detection terminal 29a (here, when the power is turned on). When a voltage approximately equal to the power supply voltage Vbt) is applied, an operation prohibition signal is output to the power supply circuit 28 before the power supply circuit 28 is started, and the activation of the power supply circuit 28 is prevented, thereby preventing the motor 6 from being driven. Prevent, ie prevent the power tool 1 from being driven. As a method for preventing the motor 6 from being driven, it is also possible to prevent the turn-on of a switching element provided in the current path of the motor 6 instead of preventing the start of the power supply circuit 28, or to send a drive prohibition signal to the control unit 21. It may be sent out to prohibit drive control of the motor 6 . The power supply circuit 28 is configured to generate the control system power supply voltage Vcc only when the trigger switch 7 is operated in the correct order after the power is turned on.

The inverter circuit 47 includes six switching elements such as IGBTs and FETs connected in a three-phase bridge. Each switching element performs a switching operation according to the control of the control unit 21 , for example, PWM control, and supplies a drive current to the stator coil of the motor 6 . The control unit 21 includes a calculation unit such as an MCU (Micro Controller Unit). When the control unit 21 detects that the trigger switch 7 is turned on, the control unit 21 controls the driving of the motor 6 by controlling the switching elements that constitute the inverter circuit 47 . In the case of FIG. 4 , the control unit 21 controls (changes) the rotation speed (number of rotations) of the motor 6 using a speed adjustment signal corresponding to the amount of operation of the trigger switch 7 .

In the case of FIGS. 2 and 3, the control unit 21 detects on/off of the trigger switch 7 from the first switch detection voltage Va. A high level of the first switch detection voltage Va indicates that the trigger switch 7 is on, and a low level indicates that the trigger switch 7 is off. In the case of FIG. 4, the control unit 21 detects on/off of the trigger switch 7 using the second switch detection voltage Vb instead of or in addition to the first switch detection voltage Va. A low level of the second switch detection voltage Vb indicates that the trigger switch 7 is on, and a high level indicates that the trigger switch 7 is off.

In FIG. 4 , the use of the second switch detection voltage Vb by the control unit 21 to detect the on/off state of the trigger switch 7 is a countermeasure against a short-circuit failure (on-failure) of the switching element 40 . When the switching element 40 has a short-circuit failure, the first switch detection voltage Va becomes a high level indicating that the trigger switch 7 is on regardless of whether the trigger switch 7 is on or off. However, even if the switching element 40 is short-circuited, the second switch detection voltage Vb becomes a high level indicating that the trigger switch 7 is off if the trigger switch 7 is off. Therefore, in the case of FIG. 4, the control unit 21 can reliably detect whether the trigger switch 7 is on or off using the second switch detection voltage Vb regardless of whether the switching element 40 is faulty. Further, when the first switch detection voltage Va is at a high level indicating that the trigger switch 7 is on although the second switch detection voltage Vb is at a high level indicating that the trigger switch 7 is off, the control unit 21 controls switching. It is possible to determine that the element 40 is out of order and notify the operator by an alarm or light emission (lighting or blinking of LED).

FIG. 5 is a time chart of normal operation of the circuit of FIG. At time t1, when the battery pack 9 is connected to the power tool 1 with the trigger switch 7 turned off (when the power is turned on), the voltage (power supply voltage Vbt) of the external connection terminal 37, which is the power input section, rises. rises, and the second switch detection voltage Vb becomes high level. When the trigger switch 7 is turned on at time t2, the first switch detection voltage Va becomes high level and the second switch detection voltage Vb becomes low level. At time t3, the start-up of the power supply circuit 28 is completed, and the control system power supply Vcc rises. At time t<b>4 , activation of the control unit 21 is completed, and the control unit 21 starts driving the motor 6 . When the trigger switch 7 is turned off at time t6, the first switch detection voltage Va becomes low level and the second switch detection voltage Vb becomes high level. The controller 21 stops the motor 6 at time t7. If the second switch detection voltage Vb is removed from FIG. 5, the timing chart of the operation of the circuits of FIGS. 2 and 3 is obtained.

FIG. 6 is a time chart when the power-on malfunction prevention function of the circuit of FIG. 4 operates. At time t11 before the battery pack 9 is connected to the power tool 1, the trigger switch 7 is turned on. When the battery pack 9 is connected to the power tool 1 at time t12, the power supply voltage Vbt rises and the first switch detection voltage Va becomes high level. At time t<b>13 , the power-on malfunction prevention circuit 29 operates and transmits an operation prohibition signal to the power supply circuit 28 . When the trigger switch 7 is turned off at time t14, the first switch detection voltage Va becomes low level and the second switch detection voltage Vb becomes high level. At time t<b>15 , the malfunction prevention circuit 29 stops sending the operation prohibition signal to the power supply circuit 28 . When the trigger switch 7 is turned on at time t16, the first switch detection voltage Va becomes high level and the second switch detection voltage Vb becomes low level. At time t17, the start-up of the power supply circuit 28 is completed, and the control system power supply Vcc rises. At time t<b>18 , activation of the control unit 21 is completed, and the control unit 21 starts driving the motor 6 . If the second switch detection voltage Vb is removed from FIG. 6, it becomes a time chart of the operation of the circuits of FIGS.

FIG. 7 is a time chart when switching element 30 fails during operation of the circuit of FIG. In FIG. 7, the operation up to time t4 is the same as in FIG. At time t5, the switching element 40 is short-circuited. When the trigger switch 7 is turned off at time t6, the first switch detection voltage Va remains at high level because the switching element 40 is turned on, and the second switch detection voltage Vb becomes high level. The controller 21 stops the motor 6 at time t7.

FIG. 8 is a flow chart showing the operation of the circuit of FIG. When the battery pack 9 is connected to the power tool 1 (Yes in S1), if the trigger switch 7 is not off (No in S2), the power-on malfunction prevention circuit 29 is activated (S3). If the trigger switch 7 is off (Yes in S2) and the power-on malfunction prevention circuit 29 is activated (S4: Yes), the power-on malfunction prevention circuit 29 stops (S5). The motor 6 is stopped (S7). When the first switch detection voltage Va is substantially equal to the power supply voltage Vbt (Yes in S8), if the control unit 21 has not started (No in S8a), the control unit 21 starts up (S8b). If the second switch detection voltage Vb is normal, that is, at a low level (ground level) (Yes in S9) and if a failure of the switching element 40 is not detected (No in S10), the control unit 21 operates the motor 6. Drive (S11). In step S9, if the second switch detection voltage Vb is abnormal, that is, it is not low level (No in S9), and if this state continues for a certain period of time or longer (Yes in S12), the control unit 21 detects the failure of the switching element 40. is detected (S13), and the motor 6 is stopped (S7). If the switching element 40 fails in step S10 (Yes in S10), the control unit 21 stops the motor 6 (S7). When the first switch detection voltage Va is low level in step S8 (No in S8), the control unit 21 stops the motor 6 (S7).

According to this embodiment, the following effects can be obtained.

(1) Since the control circuit 30 has the switching element 40, even if one end of the trigger switch 7 is grounded as shown in FIG. Thus, the output voltage Vbt of the battery pack 9 can be applied to the detection terminal 29a of the power-on malfunction prevention circuit 29. FIG. Therefore, the control circuit 30 can commonly implement the malfunction prevention function when the power is turned on regardless of the configuration and arrangement of the trigger switch 7 in any of FIGS. 2 to 4 . Therefore, it is not necessary to design a circuit that realizes the function of preventing malfunction at the time of power-on according to the configuration and arrangement of the trigger switch 7, thereby reducing design effort and cost.

(2) The control unit 21 sets the condition for driving the motor 6 that the voltage (second switch detection voltage Vb) of the external connection terminal 33 to which the other end of the trigger switch 7 is connected is low level. Even if the element 40 is short-circuited, the motor 6 will not be driven if the trigger switch 7 is off. Therefore, when the switching element 40 is short-circuited, the malfunction of driving the motor 6 even though the trigger switch 7 is off is suppressed.

(3) When the first switch detection voltage Va is at a high level indicating that the trigger switch 7 is on although the second switch detection voltage Vb is at a high level indicating that the trigger switch 7 is off, the control unit 21 It is possible to determine that the switching element 40 is out of order and notify the operator by an alarm or light emission.

Although the present invention has been described above with reference to the embodiments, it will be understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiments within the scope of the claims. By the way. Modifications will be discussed below.

The power tool of the present invention is not limited to the jigsaw exemplified in the embodiment, and may be other types of power tools having a function of preventing malfunction when the power is turned on. The motor may be a brushed motor. The power tool of the present invention is not limited to a cordless type that operates on power from a battery pack, and may be a corded type that operates on power from an external power source. In this case, the output voltage of the rectifying/smoothing circuit to which the AC voltage is input corresponds to the power supply voltage Vbt. Also, connecting the power cord to the external power supply corresponds to turning on the power.

REFERENCE SIGNS LIST 1 power tool, 2 base, 3 housing, 3a handle portion, 5 speed reduction mechanism, 6 motor, 7 trigger switch (operation unit), 9 battery pack, 10 plunger, 11 blade (tip tool), 20 main board (control board) , 21 arithmetic unit (control unit), 28 power supply circuit (power supply IC), 29 malfunction prevention circuit at power-on, 29a detection terminal, 30 control circuit, 31 to 36 sixth external connection terminal, 40 switching element, 47 inverter circuit

Claims (8)

a driving source;
a control circuit that controls the drive source;
an operation switch capable of switching between driving and stopping the drive source, the operation switch instructing to drive the drive source when it is on and instructing to stop the drive source when it is off ;
The control circuit is
a power input;
a prevention circuit that prevents the drive source from being driven when a voltage of a predetermined value or more is applied to its detection terminal when power is turned on;
a switching element provided between the power supply input unit and the detection terminal;
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
a third external connection terminal connected to the control terminal of the switching element;
The operation switch is provided between the third external connection terminal and the ground ,
The switching element is on when the operation switch is on when the power is on, and the switching element is off when the operation switch is off when the power is on;
A power tool, wherein when power is turned on with the operation switch in the ON state, a voltage equal to or greater than the predetermined value is applied to the detection terminal from the power supply input unit via the switching element. 2. The power tool according to claim 1 , wherein said drive source is a motor, and the rotation speed of said motor changes according to the amount of operation of said operation switch. The control circuit comprises a control unit,
3. The power according to claim 1 , wherein a first voltage that is the voltage on the detection terminal side of the switching element and a second voltage that is the voltage on the control terminal side of the switching element are input to the control unit. tool. The first voltage has a different level depending on whether the switching element is turned on or off,
The second voltage has a different level depending on whether the operation switch is turned on or off,
4. The power tool according to claim 3 , wherein said control unit sets a condition for driving said drive source that said first and second voltages are at predetermined levels. a driving source;
a control circuit that controls the drive source;
an operation switch capable of switching between driving and stopping the drive source, the operation switch instructing to drive the drive source when it is on and instructing to stop the drive source when it is off ;
The control circuit is
a power input;
a prevention circuit that prevents the drive source from being driven when a voltage of a predetermined value or more is applied to its detection terminal when power is turned on;
a switching element provided between the power supply input unit and the detection terminal;
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
a third external connection terminal connected to the control terminal of the switching element;
The operation switch is provided in parallel with the switching element between the first external connection terminal and the second external connection terminal ,
When the operation switch is turned on and the power is turned on, from the power supply input section via the first external connection terminal, the second external connection terminal, and the operation switch, to the detection terminal the predetermined A power tool to which a voltage greater than or equal to a value is applied . a driving source;
a control circuit that controls the drive source;
an operation switch capable of switching between driving and stopping the drive source, the operation switch instructing to drive the drive source when it is on and instructing to stop the drive source when it is off ;
The control circuit is
a power input;
a prevention circuit that prevents the drive source from being driven when a voltage of a predetermined value or more is applied to its detection terminal when power is turned on;
a switching element provided between the power supply input unit and the detection terminal;
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
a third external connection terminal connected to the control terminal of the switching element;
The operation switch is provided in a current path of the drive source,
the drive source side of the operation switch and the first external connection terminal connected to the detection terminal side of the switching element are connected to each other ;
When the power is turned on with the operation switch turned on, a voltage equal to or higher than the predetermined value is applied from the power supply to the detection terminal via the operation switch and the first external connection terminal. tool. A control circuit for controlling a drive source of a power tool,
a power input;
a prevention circuit for preventing driving of the drive source when a voltage equal to or higher than a predetermined value is applied from the power supply input unit to its detection terminal when the power is turned on;
and a switching element provided between the power supply input unit and the detection terminal,
a first external connection terminal connected to one end of the switching element;
a second external connection terminal connected to the other end of the switching element;
and a third external connection terminal connected to the control terminal of the switching element. 8. The control circuit of claim 7 , provided on a single substrate.

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