JP2003087959A - Switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching device capable of easily detecting blownout filament of a lamp in response to even a change in the magnitude of watt or number of the lamps. SOLUTION: This switching device is equipped with a main switch Q1 positioned between a DC power supply VB and a plurality of lamps 2, a current detecting means 3 of obtaining a voltage signal with a magnitude proportional to the current passing through the main switch Q1, a reference voltage generating means 4 of generating a reference voltage Vp of a roughly middle value between a load voltage when all of a plurality of lamps 2 are on and a load voltage in case of a blownout filament to one lamp, and a comparator CMP1 which compares the reference voltage Vp generated by the reference voltage generating means 4 with a voltage signal Vn detected by the current detecting means 3 and determines if the lamp 2 has a breakage in the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching device which is arranged between a lamp load and a DC power source to switch the lamp load on and off and to detect a disconnection of the lamp load.

[0002]

2. Description of the Related Art For example, various lamps such as a headlight and a tail lamp mounted on a vehicle are turned on and off by applying a DC voltage output from a battery of the vehicle. Further, a switch using a semiconductor element is used to control lighting and extinction of such a lamp, and by turning on and off the semiconductor switch, lighting and extinction of the lamp are switched.

Further, a switching device has been proposed which has not only an on / off switching operation, but also a function of detecting the disconnection of a lamp and notifying the occupant of a vehicle when the lamp is disconnected. Have been used for.

As a conventional example of such a switching device, for example, one described in Japanese Patent Laid-Open No. 2000-299624 (hereinafter referred to as a conventional example) is known. In the conventional example, a MOS-type switch is provided between the DC power supply and the lamp load for switching the lamp load on and off.
A main switch composed of an FET is provided, and the voltage between the drain and the source of the main switch is measured to detect the occurrence of core disconnection of the lamp load.

That is, when a plurality of lamp loads mounted are all operating normally (normal), the drain-source voltage is disconnected, and when one lamp load is disconnected (when disconnected) Since there is a difference between the drain-source voltage and the drain-source voltage, the occurrence of disconnection is detected by measuring the drain-source voltage.

Therefore, the drain during normal operation and disconnection
In order to detect the difference in the voltage between the sources, the MO
It is necessary to select the on-resistance of the S-FET. Hereinafter, this will be described in detail.

For example, when driving two 21 W (watt) lamps, the current value per lamp is 1.75 A (ampere) when the power supply voltage is 12 V (volts). If a MOS-FET with an on-resistance of 20 mΩ is used, the drain-source voltage per lamp is 35 m.
The voltage difference between the normal state (when two lights are lit) and the disconnection (when one light is lit) is also 35 mV. Therefore, even if the error in the potential difference comparison is ± 15 mV, it is possible to detect the disconnection of one of the two lights without malfunctioning.

Here, when the wattage of the lamp is 5 W, the current per lamp is 0.
42A. Therefore, the on-resistance is 20m as above.
When a MOS-FET of Ω is used, the voltage difference between the normal state and the disconnection is 8.4 mV, and therefore, if a detection error of ± 15 mV exists, erroneous detection will occur.

Therefore, when the wattage of the lamp or the number of lamps is changed, it is necessary to change the ON resistance of the MOS-FET in accordance with this. For example, the ON resistance is 8
If set to 3mΩ, the potential difference will be 35mV, so 5
Even when the W lamp is used, the core disconnection can be detected with high accuracy.

[0010]

As described above, in the conventional switching device, if the wattage of the lamp or the number of lamps changes, it becomes impossible to detect the disconnection of the lamp with high accuracy, which causes a problem. However, if you change the wattage of the lamp or the number of lamps, the MO
The on-resistance of the S-FET must be changed.

Therefore, there is a drawback in that a lot of time and labor are required for changing the design of the circuit, and it becomes a hindrance when integrating the entire circuit.

The present invention has been made in order to solve such a conventional problem, and an object thereof is to easily change the wattage of the lamp load or the number of lights. It is an object of the present invention to provide a switching device capable of detecting disconnection of a lamp load in response to such a work.

[0013]

In order to achieve the above-mentioned object, the invention according to claim 1 of the present application is arranged between a DC power supply and a plurality of lamp loads to turn on the lamp loads.
A switching device having a function of controlling turning-off and detecting a disconnection when the lamp load is disconnected, in a switching device having a function of being interposed between the DC power supply and a plurality of lamp loads. A semiconductor switch, a current detection means for obtaining a voltage signal having a magnitude corresponding to a current value flowing through the main semiconductor switch, a load voltage when all of the plurality of lamp loads are lit, and a single lamp disconnection Of the reference voltage generated by the reference voltage generating means, and the reference voltage generating means for generating a reference voltage that is an approximately intermediate value with the load voltage of And comparing means for determining whether or not the lamp load is broken.

The invention according to claim 2 is arranged between a DC power supply and a plurality of lamp loads to control ON / OFF of the lamp load, and when a disconnection occurs in the lamp load. A switching device having a function of detecting this, comprising: a main semiconductor switch interposed between the DC power supply and a plurality of lamp loads; and a first resistor, wherein the main semiconductor switch A current detecting means for obtaining a voltage signal having a magnitude proportional to a current value flowing through the main semiconductor switch by causing a current having a magnitude proportional to a current value flowing through the first resistor to flow through the first resistor;
And a current source for supplying a predetermined current to the third resistor, the load voltage is divided by the second resistor and the third resistor. Generated by the reference voltage generating means, which generates a substantially intermediate voltage between the load voltage when the lamp loads are all lit and the load voltage when one lamp is disconnected. The reference voltage is compared with the voltage signal detected by the current detection means to determine whether the lamp load is broken or not.

According to a third aspect of the present invention, the current detecting means is turned on / off in conjunction with the main semiconductor switch, and a sense semiconductor switch for supplying a current to the first resistor, and the main semiconductor switch. A first amplifier that outputs a voltage according to a difference value between the output voltage of the switch and the output voltage of the sense semiconductor switch; and the first amplifier that is interposed between the sense semiconductor switch and the first resistor, A transistor that adjusts the value of the current flowing through the first resistor according to the output of the first amplifier.

According to a fourth aspect of the present invention, the current detecting means is a sense semiconductor switch which is turned on / off in conjunction with the main semiconductor switch to flow a current through the first resistor, and the first semiconductor switch. A second amplifier that amplifies the voltage generated across the resistor.

According to a fifth aspect of the present invention, the first resistor is interposed between the DC power source and the main semiconductor switch, and the current detecting means is provided at both ends of the first resistor. It is characterized in that a third amplifier for amplifying the generated voltage is provided.

According to a sixth aspect of the present invention, the main semiconductor switch and the sense semiconductor switch are MOS-F.
It is characterized by being composed of ET.

According to a seventh aspect of the present invention, among the constituent elements of the switching device, the first resistor and the first resistor are provided.
The resistor, the second resistor, and the third resistor are partially or wholly integrated, except for the components.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a switching device according to an embodiment of the present invention. As shown in the figure, the switching device 1 is arranged between a DC power supply VB and a plurality of (two in this example) lamps (lamp loads) 2 to switch the lamps 2 on and off. The main switch (main semiconductor switch) Q1 is provided between the DC power source VB and the lamp 2 and is composed of a MOS-FET. Furthermore,
It is provided with a current detection means 3 for detecting a current flowing through the lamp 2, a reference voltage generation means 4, and a comparator (comparison means) CMP1.

The current detecting means 3 is a sense switch (sense semiconductor switch) Q2 composed of a MOS-FET.
An amplifier (first amplifier) 5, a transistor Q3 arranged on the output side of the amplifier 5, and a resistor R1, and the drain of the sense switch Q2 is a DC power supply V
It is connected to B, and the source is connected to the negative input terminal of the amplifier 5 and the emitter of the transistor Q3. Further, the collector of the transistor Q3 has a resistor R1.
Is connected to ground via. Further, the FET drive voltage is supplied to the gate of the sense switch Q2.

The reference voltage generating means 4 includes a series connection circuit of a resistor (first resistor) R2 and a resistor (second resistor) R3, a current mirror circuit composed of transistors Q4 and Q5, and a current source 6. have. The current source 6 is installed between the collector of the transistor Q5 and the ground.
The series connection circuit of the resistors R2 and R3 is arranged between the source of the main switch Q1 and the ground, and the collector of the transistor Q4 is connected to the connection point of the resistors R2 and R3.

Further, the collector of the transistor Q3 is connected to the negative side input terminal of the comparator CMP1, and the resistance R
The connection point of 2 and R3 is connected to the positive side input terminal of the comparator CMP1. Further, a FET driving voltage is applied to the gate of the main switch Q1, and a Zener diode ZD1 for stabilizing the voltage is provided between the source and the gate of the main switch Q1. .

Further, the main switch Q1 and the sense switch Q2 are formed on the same chip, and the respective FETs are connected in parallel so that the current capacity of the sense switch Q2 is smaller than the current capacity of the main switch Q1. Determines the number of transistors to connect. For example, if the number of transistors forming the FET of the main switch Q1 is 5,
000, and the number of transistors forming the FET of the sense switch Q2 is one.

Next, the operation of this embodiment configured as described above will be described. When the FET drive voltage is supplied to the gates of the main switch Q1 and the sense switch Q2, both the main switch Q1 and the sense switch Q2 are turned on, and the voltage output from the DC power supply VB is supplied to the lamp 2, Lamp 2 lights up.

Further, when the sense switch Q2 is turned on, the source voltage of the sense switch Q2 and the source voltage of the main switch Q1 (that is, the load voltage VL) are supplied to the amplifier 5, so that there is a difference between these voltages. A corresponding voltage signal is output from the amplifier 5. Since this voltage signal is supplied to the gate of the transistor Q3, an amplified current flows between the emitter and collector of the transistor Q3.

That is, DC power source VB, sense switch Q
2, current flows through the path of the transistor Q3 and the resistor R1. At this time, the amplifier 5 outputs a signal according to the difference between the source voltage of the main switch Q1 and the source voltage of the sense switch Q2, so that the resistor R1 has a magnitude proportional to the current flowing through the main switch Q1. The voltage signal is generated.

The voltage generated in the resistor R1 is supplied to the negative side input terminal of the comparator CMP1. Also,
The reference voltage Vp (resistors R2 and R3) generated by the reference voltage generating means 4 is applied to the positive input terminal of the comparator CMP1.
The voltage generated at the connection point is supplied, and the two are compared.

The reference voltage generated by the reference voltage generating means 4 will be described below. When the voltage generated in the resistor R1 is Vn, the voltage Vn can be expressed by the following equation (1).

Vn = (IL / n) * R1 (1) where IL is the load current and n is the area ratio of the MOS-FET.

The area ratio means the FET constituting the main switch Q1 and the FE constituting the sense switch Q2.
It is the ratio of the number to T and is, for example, 5000.

Therefore, the voltage Vn represented by the equation (1) is applied to the negative side input terminal of the comparator CMP1. Further, when one of the two lamps 2 is disconnected, the load current IL decreases, so the load voltage VL decreases, and the voltage Vn becomes the reference voltage Vp (the voltage at the connection point between the resistors R2 and R3). When it falls below, the output of the comparator CMP1 becomes H level, and the disconnection signal is output.

At this time, the reference voltage Vp supplied to the plus side input terminal of the comparator CMP1 is the voltage Vn when the two lamps 2 are both normal and the voltage when only one lamp 2 is disconnected. If it is set in the middle of Vn, the disconnection of the lamp 2 can be detected.

The current flowing through the lamp 2 changes non-linearly with respect to the power supply voltage VB, but can be approximated by a straight line in a certain voltage range. When the current value when one lamp 2 is lit at the lower limit of the core detection voltage range is ILL and the current value at the upper limit is ILH, the reference voltage VpL at the lower limit load voltage of the core detection is
The reference voltage VpH at the core breaking detection upper limit load voltage may be set by the following equations (2) and (3).

[0035]   VpL = {(m-1 / 2) * ILL / n} * R1 (2)   VpH = {(m-1 / 2) * ILH / n} * R1 (3) However, m is the number of lamps.

On the other hand, according to the circuit shown in FIG.
Can be expressed by the following equation (4).

Vp = (R3 * VL + R2 * R3 * Icc) / (R2 + R3) (4) where VL is the load voltage and Icc is the current value of the current source 6.

Here, assuming that the core breaking detection lower limit load voltage is VLL and the core breaking detection upper limit load voltage is VLH, the following expressions (5) and (6) can be obtained from the expressions (2) to (4). it can.

(R3 * VLL + R2 * R3 * Icc) / (R2 + R3) = {(m-1 / 2) * ILL / n} * R1 (5) (R3 * VLH + R2 * R3 * Icc) / (R2 + R3) ) = {(M-1 / 2) * ILH / n} * R1 (6) Then, the resistances R2 and R3 can be determined from the equations (5) and (6), and will be obtained by this. Can be obtained.

As an example, a lamp 2 with a load of 21 W is used.
A case where two lights are connected will be described. Load voltage range is 10V to 16V, current value of one lamp 2 is 1.578A at 10V, 2.024A at 16V, FET area ratio n = 5
000, resistance R1 = 2.5 KΩ, current value of current source 6 Icc =
If it is 100 μA, the following expressions (7) and (8) are established.

(R3 * 10L + R2 * R3 * 0.0001) / (R2 + R3) = {(2-1 / 2) * 1.578 / 5000} * 2500 (7) (R3 * 16 + R2 * R3 * 0) .0001) / (R2 + R3) = {(2-1 / 2) * 2.024 / 5000} * 2500 (8) By solving the above equations (7) and (8), R2 = 11
It is possible to obtain 0 KΩ and R3 = 6.57 KΩ. FIG. 2 shows changes in the reference voltage Vp when the resistors R2 and R3 are set in this way. A curve S1 shown in the figure is a load voltage V
A curve S2 shows a change of the reference voltage Vp with respect to L
Vn when the lamp is lit, and the curve S3 shows Vn when the one lamp is disconnected (that is, when one lamp is lit). As can be seen from the figure, the reference voltage Vp is set to be an intermediate voltage between the voltage Vn when two lamps are lit and the voltage Vn when one lamp is disconnected. There is. Therefore, even if the load voltage VL fluctuates, the disconnection of the lamp 2 can be reliably detected.

Next, the case of changing the wattage of the lamp 2 will be described. The wattage of the lamp 2 is 5W,
The FET area ratio n = 5000 and Icc = 100 μA are the same as above, and the current value of one lamp is 0.38 A at 10 V, 0.478 A at 16 V, and the resistance R1 is 10
If KΩ, then R2
= 132 KΩ and R3 = 6.82 KΩ can be obtained.

FIG. 3 shows changes in the reference voltage Vp at this time. A curve S11 shown in the figure shows a change in the reference voltage Vp with respect to a change in the load voltage VL, a curve S12 shows Vn when two lights are lit, and a curve S13 shows Vn when one light is disconnected. Then, as in the case of FIG. 2, the reference voltage Vp is set to be an intermediate voltage between the voltage Vn when two lamps are lit and the voltage Vn when one lamp is disconnected. ing. Therefore, even if the load voltage VL fluctuates, the lamp 2 can be reliably operated.
It is possible to detect disconnection.

From the above results, by properly setting the resistance values of the resistors R1, R2 and R3 regardless of the on resistance of the main switch Q1, it is possible to reliably detect the disconnection of the lamps having different wattages. can do.

In this way, in the switching device 1 according to the present embodiment, even when the wattage of the lamp 2 is changed, the reference voltage Vp can be set by appropriately setting the resistance values of the resistors R1 to R3. The value of is a suitable value, that is,
Since it is possible to set an intermediate value between the voltage Vn when two lamps are lit and the voltage Vn when one lamp is disconnected, it is possible to detect the disconnection of the lamp 2 with high accuracy. Will be able to.

Therefore, if the circuit components other than the resistors R1 to R3 are integrated and the resistors R1 to R3 are external parts, the lamps can be easily changed by changing the resistance values of the resistors R1 to R3. Two wattage changes can be accommodated. Further, it is possible to deal with the case where the number of the lamps 2 is changed by the same method.

Next, a second embodiment of the present invention will be described. FIG. 4 is a circuit diagram showing the configuration of the switching device according to the second embodiment of the present invention. As shown in the figure, the switching device 11 includes a DC power source VB.
And a lamp (lamp load) 2 are disposed between the lamp 2 and the lamp 2 to switch between ON and OFF of the lamp 2 and to detect when the lamp 2 is disconnected.
It has a main switch Q1 arranged between the DC power supply VB and the lamp 2.

Further, the current detecting means 13 for generating the voltage signal Vn having a magnitude proportional to the load current flowing through the lamp 2.
And a reference voltage generating means 4 and a comparator CMP1. The main switch Q1, the load 2, the reference voltage generation means 4, and the comparator CMP1 are the same as those shown in FIG.

The current detecting means 13 includes an amplifier (second amplifier) 15 and a sense switch Q2 composed of an FET.
And resistors R11 to R15. A resistor R11 is provided between the source of the sense switch Q2 and the lamp 2, and the connection point between the resistor R11 and the sense switch Q2 is connected to the negative side input terminal of the amplifier 15 via the resistor R13.

Further, the connection point between the resistor R11 and the lamp 2 is
It is connected to the positive side input terminal of the amplifier 15 via the resistor R14. In addition, this positive side input terminal is
The negative side input terminal is connected to the ground via 15 and the output terminal of the amplifier 15 via the resistor R12.

When both the main switch Q1 and the sense switch Q2 are turned on, a current proportional to the load current flows through the sense switch Q2 and the resistor R11.
A voltage having a magnitude proportional to the load current is generated across the resistor R11. And this voltage is amplifier 1
Amplified by 5, and supplied as a voltage Vn to the negative side input terminal of the comparator CMP1. Therefore, the voltage Vn is
It can be obtained by the following equation (9).

Vn = Av * (IL / n) * R11 (9) where Av is the gain of the amplifier 15, IL is the load current, and n is
Is the area ratio of the MOS-FET.

Then, using this voltage Vn, the core of the lamp 2 is disconnected in the same procedure as that of the first embodiment described above (that is, the formula (9) is used instead of the formula (1) described above). Can be detected. Then, also in the switching device 11 configured as above, the same effect as that of the switching device 1 shown in the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing the configuration of the switching device according to the third embodiment. As shown in the figure,
The switching device 21 includes a DC power supply VB, a main switch Q1, a lamp (lamp load) 2, a current detection means 23, a reference voltage generation means 4, and a comparator CMP1.
It is equipped with. Main switch Q1, lamp 2
1, the reference voltage generating means 4 and the comparator CMP1 are shown in FIG.
Since the configuration is the same as that shown in FIG. 3, the same reference numerals are given and the description of the configuration is omitted.

The current detecting means 23 comprises an amplifier (third amplifier) 25 and resistors R21 to R25.
The resistor R21 is provided between the DC power source VB and the main switch Q1, and the connection point between the resistor 21 and the DC power source VB is connected to the minus side input terminal of the amplifier 25 via the resistor R23. The connection point between the resistor R21 and the main switch Q1 is connected to the plus side input terminal of the amplifier 25 via the resistor R24.

Further, this plus side input terminal is connected to the resistor R2.
5 is connected to the ground, and the negative side input terminal and the output terminal of the amplifier 25 are connected via a resistor R22.

When the main switch Q1 is turned on, the load current flows through the resistor R21.
A voltage having a magnitude proportional to the load current is generated at both ends of. Then, this voltage is amplified by the amplifier 15 and supplied to the negative side input terminal of the comparator CMP1 as the voltage Vn. Therefore, the voltage Vn is
It can be obtained by the equation (0).

Vn = Av * IL * R21 (10) where Av is the gain of the amplifier 25 and IL is the load current.

Then, using this voltage Vn, the core of the lamp 2 is disconnected in the same procedure as in the first embodiment described above (that is, by using the formula (10) instead of the formula (1) described above). Can be detected. Then, also in the switching device 21 configured as described above, the same effects as those of the switching devices 1 and 11 shown in the first embodiment and the second embodiment can be obtained.

In each of the above embodiments, the lamp 2
Although an example having two lamps has been described, the present invention is not limited to this and can be applied to the case of three or more.

[0061]

As described above, in the switching device of the present invention, the current detecting means generates a voltage having a magnitude proportional to the current flowing through the main semiconductor switch, and the reference voltage generating means generates the lamp. By generating a reference voltage that is intermediate between when all the lights are lit and when one lamp is disconnected, by comparing this reference voltage with the voltage output from the current detection means, It is determined whether the lamp is broken. Therefore, even when the wattage of the lamp load or the number of lamps is changed, this can be dealt with flexibly.

If the first resistor of the voltage detecting means and the second and third resistors of the reference voltage generating means are externally attached and other circuit components are integrated,
The integration becomes easy, and by changing the resistance values of the first to third resistors, it is possible to easily cope with the change in the wattage of the lamp load and the number of lights.

Further, since it is possible to detect the disconnection of the lamp load simply by changing the resistance values of the first to third resistors, it is possible to reduce the size and cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a switching device according to a first embodiment of the present invention.

[Fig. 2] Load voltage VL when driving a 21 W lamp
5 is a characteristic diagram showing a change in reference voltage Vp with respect to FIG.

FIG. 3 is a characteristic diagram showing changes in a reference voltage Vp with respect to a load voltage VL when driving a 5 W lamp.

FIG. 4 is a circuit diagram showing a configuration of a switching device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a switching device according to a third embodiment of the present invention.

[Explanation of symbols]

1,11,22 Switching device 2 lamps (lamp load) 3,13,23 Current detection means 4 Reference voltage generating means 5 amplifiers (first amplifier) 6 current source 15 amplifier (second amplifier) 25 amps (3rd amp) CMP1 comparator (comparison means) Q1 main switch (main semiconductor switch) Q2 Sense switch (sense semiconductor switch) ZD1 Zener diode VB DC power supply

Continued front page    F term (reference) 3K073 AA75 AA93 AB01 BA09 CF10                       CF18 CG02 CJ21                 5G004 AA04 AB03 BA05 DA04 DC03                       DC05                 5J055 AX37 AX49 AX55 AX65 BX16                       CX22 CX28 DX22 DX42 DX53                       DX73 DX83 EX01 EX02 EX07                       EY01 EY13 EY17 EY21 EY30                       EZ03 EZ10 EZ57 FX05 FX07                       FX13 FX17 FX38 GX01 GX06

Claims (7)

[Claims] 1. A function arranged between a DC power supply and a plurality of lamp loads to control ON / OFF of the lamp load and to detect when a disconnection occurs in the lamp load. A switching device comprising: a DC power supply; a main semiconductor switch interposed between a plurality of lamp loads; and a current detector for obtaining a voltage signal having a magnitude corresponding to a current value flowing through the main semiconductor switch. Means, a reference voltage generating means for generating a reference voltage that is a substantially intermediate value between the load voltage when all of the plurality of lamp loads are on, and the load voltage when one lamp is disconnected, and the reference voltage Comparing means for comparing the reference voltage generated by the generating means with the voltage signal detected by the current detecting means to determine whether the lamp load is disconnected. Switching device according to claim. 2. A function arranged between a DC power supply and a plurality of lamp loads to control ON / OFF of the lamp load and to detect when a disconnection occurs in the lamp load. A switching device including: a main semiconductor switch interposed between the DC power supply and a plurality of lamp loads; and a first resistor, which is proportional to a current value flowing in the main semiconductor switch. A current detection unit that obtains a voltage signal having a magnitude proportional to the value of the current flowing through the main semiconductor switch by causing a current having a magnitude to flow through the first resistor, and a second resistor and a third resistor. A series connection circuit and a current source for supplying a predetermined current to the third resistor are provided, and the load voltage is divided by the second resistor and the third resistor,
The load voltage when all the lamp loads are lit,
A reference voltage generation unit that generates a substantially intermediate voltage between the load voltage when one lamp is disconnected, a reference voltage generated by the reference voltage generation unit, and a voltage signal detected by the current detection unit are compared. And a comparing means for determining whether or not the lamp load is disconnected. 3. The current detecting means is a sense semiconductor switch which is turned on and off in cooperation with the main semiconductor switch to flow a current through the first resistor, an output voltage of the main semiconductor switch and the sense semiconductor switch. A first amplifier that outputs a voltage according to a difference value from the output voltage of the semiconductor switch, and a first amplifier that is interposed between the sense semiconductor switch and the first resistor and that corresponds to the output of the first amplifier. The switching device according to claim 2, further comprising: a transistor that adjusts a current value flowing through the first resistor. 4. The current detection means is a sense semiconductor switch which is turned on and off in conjunction with the main semiconductor switch to flow a current through the first resistor, and is generated at both ends of the first resistor. The switching device according to claim 2, further comprising: a second amplifier that amplifies the voltage to be applied. 5. The first resistor is interposed between the DC power source and the main semiconductor switch, and the current detection means amplifies a voltage generated across the first resistor. The switching device according to claim 2, wherein the switching device comprises three amplifiers. 6. The switching device according to claim 2, wherein the main semiconductor switch and the sense semiconductor switch are composed of MOS-FETs. 7. A part or all of the constituent elements of the switching device except the first resistor, the first resistor, the second resistor, and the third resistor. 7. The integrated circuit according to claim 2, wherein the integrated circuit is integrated.
The switching device according to claim 1.