CN101726638A - Isolation circuit and impedance detection circuit with same - Google Patents

Abstract

An isolation circuit and an impedance detection circuit with the same are provided, wherein a first impedance element, a second impedance element and an impedance element to be detected are sequentially connected in series to form a loop. The selection unit electrically connects at least one of the first connection points of the first impedance element and the second connection points of the first impedance element and the impedance element to be tested to the fourth connection point according to the control of the control unit. The voltage supply unit outputs an input voltage to the second impedance element and the third joint of the impedance element to be tested according to the control of the control unit. The isolation detection unit is connected to the fourth contact point to output an output signal for calculating the resistance value of the impedance element to be detected. The invention can accurately detect the impedance element to be detected; in addition, the online tester applying the isolation circuit and the impedance detection circuit has simple mechanism, and can be compatible with different types of circuit boards to be tested through simple maintenance.

Description

Isolation circuit and impedance detection circuit with isolation circuit

technical field

The present invention relates to a detection circuit for a printed circuit board (PCB), in particular to an isolation circuit and an impedance detection circuit with the isolation circuit.

Background technique

The online tester (in circuit tester; ICT) is a static component tester, and it can accurately and high-speed measure the bad problems of the installed components on the printed circuit board (printed circuit board; PCB), such as: component leakage , wrong welding, reverse installation, empty welding, and poor raw materials, as well as open and short circuits between lines on the printed circuit board. Components that can be measured with an online tester include: most electronic components such as resistors, capacitors, diodes, transistors, inductors, transformers, and integrated circuits (IC).

At present, the online tester is a testing device widely used in the circuit board assembly process. The test method used by the online tester is mainly based on component isolation, that is, when a certain component under test is tested, the component under test is not affected by other components connected to the component under test. In other words, the in-circuit tester has an isolation (guarding) function, which prevents the component under test from being affected by the bypass component during testing.

Moreover, applying the test technology of the online tester to the circuit board test of the server system can greatly improve the test efficiency and coverage of the soldering quality of the circuit board.

Generally speaking, when designing a printed circuit board, some test points will be designed on the circuit of the printed circuit board. Traditionally, when testing, the bed of needles of the in-circuit tester will be pushed against the printed circuit board to be tested, and the circuit of each functional module on the printed circuit board will correspond to a test circuit module of the in-circuit tester. When the printed circuit board to be tested is complex and huge, the corresponding test circuit module on the online tester will have redundant functions, complex mechanism, and is not convenient to be flexibly compatible with other types of printed circuit boards to be tested. Easy maintenance.

Contents of the invention

In view of the above problems, the present invention is to provide an isolation circuit and an impedance detection circuit with the isolation circuit, so as to solve the problems existing in the prior art when the printed circuit board (printed circuit board; PCB) to be tested is complicated and huge. The corresponding test circuit modules on the in-circuit tester (ICT) have redundant functions, complex mechanisms, are difficult to be compatible with other types of printed circuit boards to be tested, and are not easy to maintain.

The isolation circuit disclosed in the present invention is applied to a circuit under test to isolate the bypass impedance element of the circuit under test.

The circuit to be tested has a first contact, a second contact, a third contact, a first impedance element, a second impedance element and an impedance element to be tested.

The first impedance element is connected between the first contact and the second contact. The impedance element to be tested is connected between the second contact and the third contact. And the second impedance element is connected to the first contact and the third contact.

The isolation circuit includes a fourth contact, a voltage supply unit, a selection unit, a control unit and an isolation detection unit.

The voltage supply unit is used for outputting an input voltage to the third contact.

The selection unit is used for electrically connecting at least one of the first contact and the second contact to the fourth contact.

The control unit is connected to the voltage supply unit and the selection unit, and the control unit is used for controlling the supply of the input voltage of the voltage supply unit and controlling the connection switching of the selection unit.

The isolation detection unit is used for outputting an output signal. And this output signal can be used as the calculation of the resistance value of the impedance element to be tested.

Here, the voltage supply unit may include a power supply and a power switch.

The power switch is connected between the third contact and the power supply. The power supply is used to provide the input voltage. The power switch is controlled by the control unit to conduct the third contact and the power supply, thus transmitting the input voltage provided by the power supply to the third contact.

The selection unit may include a first switch and a second switch.

The first switch is connected between the first contact and the fourth contact, and the second switch is connected between the second contact and the fourth contact.

The first switch is controlled by the control unit to conduct the first contact and the fourth contact, and the second switch is controlled by the control unit to conduct the second contact and the fourth contact.

The isolation detection unit may include an amplifier and a third impedance element.

The amplifier has a positive input, a negative input and an output. The negative input terminal of the amplifier is connected to the fourth contact, and the positive input terminal of the amplifier is grounded. The third impedance element is connected between the negative input terminal of the amplifier and the output terminal of the amplifier.

Here, when the control unit controls the voltage supply unit to output the input voltage and controls the selection unit to electrically connect the first contact and the second contact to the fourth contact respectively, the isolation detection unit will output an output signal with a first voltage value.

When the control unit controls the voltage supply unit to output the input voltage and controls the selection unit to electrically connect the first contact to the fourth contact, the isolation detection unit will output an output signal with a second voltage value.

When the control unit controls the voltage supply unit to output the input voltage and controls the selection unit to electrically connect the second contact to the fourth contact, the isolation detection unit will output an output signal with a third voltage value.

Wherein, with the help of the input voltage, the first voltage value, the second voltage value, the third voltage value, the resistance value of the first impedance element, the resistance value of the second impedance element and the resistance value of the third impedance element, the The resistance value of the impedance element.

The impedance detecting circuit with the isolation circuit disclosed in the present invention is used for detecting the resistance value of the impedance element to be tested.

This impedance detection circuit with isolation circuit includes a first contact, a second contact, a third contact, a first impedance element, a second impedance element, a fourth contact, a voltage supply unit, a selection unit, a control unit, an isolation detection unit and a calculation unit.

The first impedance element is connected between the first contact and the second contact. The impedance element to be tested is connected between the second contact and the third contact. And the second impedance element is connected to the first contact and the third contact.

The voltage supply unit is used for outputting an input voltage to the third contact.

The selection unit is used for electrically connecting at least one of the first contact and the second contact to the fourth contact.

The control unit is connected to the voltage supply unit and the selection unit, and the control unit is used for controlling the supply of the input voltage of the voltage supply unit and controlling the connection switching of the selection unit.

The isolation detection unit is used for outputting an output signal. And this output signal can be used as the calculation of the resistance value of the impedance element to be tested.

The calculation unit is electrically connected to the output of the isolation detection unit. Here, the calculation unit can calculate the resistance value of the impedance element to be tested according to the input voltage, the output signal, the resistance value of the first impedance element, the resistance value of the second impedance element and the resistance value of the isolation detection unit.

Here, the voltage supply unit may include a power supply and a power switch.

The power switch is connected between the third contact and the power supply. The power supply is used to provide the input voltage. The power switch is controlled by the control unit to conduct the third contact and the power supply, thus transmitting the input voltage provided by the power supply to the third contact.

The selection unit may include a first switch and a second switch.

The first switch is connected between the first contact and the fourth contact, and the second switch is connected between the second contact and the fourth contact.

The first switch is controlled by the control unit to conduct the first contact and the fourth contact, and the second switch is controlled by the control unit to conduct the second contact and the fourth contact.

The isolation detection unit may include an amplifier and a third impedance element.

The amplifier has a positive input, a negative input and an output. The negative input terminal of the amplifier is connected to the fourth contact, and the positive input terminal of the amplifier is grounded. The third impedance element is connected between the negative input terminal of the amplifier and the output terminal of the amplifier.

Here, when the control unit controls the voltage supply unit to output the input voltage and controls the selection unit to electrically connect the first contact and the second contact to the fourth contact respectively, the isolation detection unit will output an output signal with a first voltage value.

When the control unit controls the voltage supply unit to output the input voltage and controls the selection unit to electrically connect the first contact to the fourth contact, the isolation detection unit will output an output signal with a second voltage value.

When the control unit controls the voltage supply unit to output the input voltage and controls the selection unit to electrically connect the second contact to the fourth contact, the isolation detection unit will output an output signal with a third voltage value.

Wherein, with the help of the input voltage, the first voltage value, the second voltage value, the third voltage value, the resistance value of the first impedance element, the resistance value of the second impedance element and the resistance value of the third impedance element, the The resistance value of the impedance element.

The beneficial effect of the present invention is that the isolation circuit and the impedance detection circuit with the isolation circuit isolate the bypass impedance element in the circuit to be tested by means of the isolation circuit, so as to accurately measure the resistance value of the impedance element to be measured. Applying the isolation circuit and the impedance detection circuit with the isolation circuit of the present invention to an online tester can detect the impedance components to be tested on the printed circuit board. And, when being used for the quality inspection of the printed circuit board, especially the circuit board of the servo (server) system, the mechanism of the online tester applying the isolation circuit and the impedance detection circuit according to the present invention is simplified, and can be obtained by simple maintenance. Compatible with different kinds of circuit boards under test.

The above description of the content of the present invention and the following description of the implementation are used to demonstrate and explain the spirit and principle of the present invention, and to provide further explanation of the patent application scope of the present invention.

Description of drawings

1 is a schematic diagram of an impedance detection circuit with an isolation circuit according to a first embodiment of the present invention;

2 is a schematic diagram of an impedance detection circuit with an isolation circuit according to a second embodiment of the present invention;

3 is a schematic diagram of an impedance detection circuit with an isolation circuit according to a third embodiment of the present invention;

FIG. 4 is a schematic diagram of a computing unit of an embodiment;

FIG. 5 is a schematic diagram of a voltage supply unit according to an embodiment.

Among them, reference signs

100 circuits under test

210 control unit

230 voltage supply unit

232 power supply

2321-232n power supply

250 selection units

270 isolation detection unit

272 amplifier

290 computing units

292 Measurement Department

294 Storage Department

296 Computing Department

So output signal

N1 first contact

N2 second contact

N3 third contact

N4 fourth contact

Z1 the first impedance element

Z2 Second impedance element

Z3 third impedance element

Zx Impedance element to be tested

Rzx Resistance

K0 power switch

K0_1-K0_n power switch

K1 first switch

K2 second switch

C0 control signal

C0_1-C0_n control signal

C1 control signal

C2 control signal

Vin input voltage

+ positive input

- Negative input

Detailed ways

The detailed features and advantages of the present invention are described in detail below in the embodiments, the content of which is sufficient to enable any person skilled in the art to understand the technical content of the present invention and implement it accordingly, and according to the content disclosed in this specification, the scope of the patent application and With the accompanying drawings, anyone skilled in the art can easily understand the related objects and advantages of the present invention. The following examples further illustrate the concept of the present invention in detail, but do not limit the scope of the present invention in any way.

According to the isolation circuit and the impedance detection circuit with the isolation circuit of the present invention, the bypass impedance element in the circuit to be tested is isolated by the isolation circuit, so as to accurately measure the resistance value of the impedance element to be tested.

FIG. 1 is a schematic diagram of an impedance detection circuit with an isolation circuit according to an embodiment of the present invention.

Please refer to FIG. 1 , an impedance detection circuit with an isolation circuit is used to detect a resistance value of an impedance element Zx to be tested.

The circuit under test 100 has a first node N1 , a second node N2 , a third node N3 , a first impedance element Z1 , a second impedance element Z2 and an impedance element under test Zx.

The isolation circuit is applied to the circuit under test 100, and the isolation circuit can be used to isolate the bypass impedance element (ie, the first impedance element Z1 and the second impedance element Z2) in the circuit under test 100, so as to accurately measure the impedance element Zx under test resistance value.

The first impedance element Z1 is connected between the first node N1 and the second node N2. The impedance element Zx to be tested is connected between the second node N2 and the third node N3. The second impedance element Z2 is connected to the first node N1 and the third node N3. In other words, the first impedance element Z1 , the second impedance element Z2 and the impedance element Zx to be tested are sequentially connected in series to form a loop.

Wherein, the impedance element Zx to be tested may include one or more electronic components, such as resistors, capacitors, diodes, triodes, inductors, transformers, and integrated circuits. For example, the impedance element Zx to be tested can be a resistor, or a plurality of resistors connected in parallel, in series or in parallel.

The first impedance element Z1 may include one or more electronic components, such as resistors, capacitors, diodes, triodes, inductors, transformers, and integrated circuits. For example, the first impedance element Z1 can be a resistor, or a plurality of resistors connected in parallel, in series or in parallel.

The second impedance element Z2 may include one or more electronic components, such as resistors, capacitors, diodes, triodes, inductors, transformers, and integrated circuits. For example, the second impedance element Z2 can be a resistor, or a plurality of resistors connected in parallel, in series or in parallel.

The isolation circuit includes a fourth node N4 , a control unit 210 , a voltage supply unit 230 , a selection unit 250 and an isolation detection unit 270 .

The control unit 210 is connected to a voltage supply unit 230 and a selection unit 250 .

The circuit under test 100 is connected between the voltage supply unit 230 and the selection unit 250 .

The selection unit 250 and the isolation detection unit 270 are respectively connected to the fourth node N4. In other words, the selection unit 250 is connected to the isolation detection unit 270 via the fourth contact N4.

The voltage supply unit 230 outputs an input voltage to the third node N3 of the circuit under test 100 according to the control of the control unit 210 .

The selection unit electrically connects at least one of the first contact N1 and the second contact N2 to the fourth contact N4 according to the control of the control unit 210 .

That is, the control unit 210 may output a control signal to control the supply of the input voltage of the voltage supply unit 230 and control the connection switching of the selection unit 250 .

The isolation detection unit 270 outputs an output signal So under the input voltage provided by the voltage supply unit 230 and the conducting connection of the selection unit 250 . The output signal So can be used for calculating the resistance value of the impedance element Zx to be tested.

Wherein, when the control unit 210 controls the voltage supply unit 230 to output the input voltage to the third contact N3 of the circuit under test 100, and the control unit 210 controls the selection unit 250 to turn on the first contact N1 and the fourth contact N4 and to turn on the second contact When N2 is at the fourth contact N4, the isolation detection unit 270 will output an output signal So with a first voltage value (V1).

Furthermore, when the control unit 210 controls the voltage supply unit 230 to output the input voltage to the third contact N3 of the circuit under test 100, and the control unit 210 controls the selection unit 250 to turn on the first contact N1 and the fourth contact N4, the isolation detection unit 270 outputs an output signal So having a second voltage value ( V2 ).

Moreover, when the control unit 210 controls the voltage supply unit 230 to output the input voltage to the third contact N3 of the circuit under test 100, and the control unit 210 controls the selection unit 250 to turn on the second contact N2 and the fourth contact N4, the isolation detection unit 270 An output signal So having a third voltage value (V3) is output.

Among them, with the help of the first voltage value (V1), the second voltage value (V2), the third voltage value (V3), the resistance value (Rz1) of the first impedance element Z1, and the resistance value (Rz2) of the second impedance element Z2 and the resistance value (Rz3) of the isolation detection unit 270 can be calculated to obtain the resistance value (Rzx) of the impedance element Zx to be tested. In other words, the impedance element to be tested can be known according to the output signal So, the resistance value (Rz1) of the first impedance element Z1, the resistance value (Rz2) of the second impedance element Z2 and the resistance value (Rz3) of the isolation detection unit 270. Zx resistance (Rzx).

Here, the voltage supply unit 230 may include a power source 232 and a power switch K0. The power switch K0 is connected between the third node N3 and the power source 232 . The power source 232 is connected between the power switch K0 and ground.

The power supply 232 is used to provide an input voltage. The power switch K0 receives a control signal C0 from the control unit 210, and is closed or opened according to the control signal C0. When the power switch K0 is closed according to the control signal C0, the third node N3 and the power source 232 are conducted through the power switch K0, so the input voltage provided by the power source 232 is transmitted to the third node N3 through the power switch K0. In other words, the power switch K0 is controlled by the control unit 210 to connect the third node N3 and the power source 232 , thereby transmitting the input voltage output by the power source 232 to the third node N3 .

The selection unit 250 may include a first switch K1 and a second switch K2. The first switch K1 is connected between the first node N1 and the fourth node N4, and the second switch K2 is connected between the second node N2 and the fourth node N4.

The first switch K1 receives a control signal C1 from the control unit 210, and is closed or opened according to the control signal C1. When the first switch K1 is closed according to the control signal C1, the first contact N1 and the fourth contact N4 are turned on via the first switch K1.

The second switch K2 receives a control signal C2 from the control unit 210 and is closed or opened according to the control signal C2. When the second switch K2 is closed according to the control signal C2, the second contact N2 and the fourth contact N4 are turned on through the second switch K2.

In other words, the first switch K1 is controlled by the control unit 210 to conduct the first contact N1 and the fourth contact N4, and the second switch K2 is controlled by the control unit 210 to conduct the second contact N2 and the fourth contact. N4.

The isolation detection unit 270 may include an amplifier 272 and a third impedance element Z3.

Amplifier 272 has a positive input +, a negative input - and an output. The negative input terminal − of the amplifier 272 is connected to the fourth node N4, and the positive input terminal + of the amplifier 272 is grounded. The third impedance element Z3 is connected between the negative input terminal of the amplifier 272 and the output terminal of the amplifier 272 .

Wherein, the third impedance element Z3 can be a resistor.

In addition, the output of the isolation detection unit 270 may be connected to a calculation unit 290 as shown in FIG. 3 .

The calculation unit 290 is used to calculate the impedance to be measured according to the output signal So, the resistance value (Rz1) of the first impedance element Z1, the resistance value (Rz2) of the second impedance element Z2 and the resistance value (Rz3) of the isolation detection unit 270 The resistance value (Rzx) of the element Zx.

Referring to FIG. 4 , the calculation unit 290 may include a measurement unit 292 , a storage unit 294 and a calculation unit 296 .

The measurement unit 292 is connected to the isolation detection unit 270 . The calculation unit 296 is connected to the measurement unit 292 and the storage unit 294 .

The measurement part 292 measures the voltage level of the output signal So of the isolation detection unit 270 to obtain a voltage value. The voltage value can be temporarily stored in the storage unit 294 , or can be directly sent to the calculation unit 296 to calculate the resistance value (Rzx) of the impedance element Zx to be tested by the calculation unit 296 .

In addition to temporarily storing the measurement results of the measurement unit 292 (that is, the voltage level of the output signal So), the storage unit 294 can also store calculation programs, the resistance value (Rz1) of the first impedance element Z1, the second impedance Parameter values such as the resistance value (Rz2) of the element Z2 and the resistance value (Rz3) of the isolation detection unit 270.

The calculation unit 296 reads calculation programs, various parameter values, and temporarily stored measurement results stored in the storage unit 294 . Moreover, the calculation unit 296 executes calculation programs based on the measurement results of the calculation unit 296 and various parameter values to obtain the resistance value Rzx of the impedance element Zx to be tested.

Wherein, the storage unit 294 may be realized by one or more memories. The computing unit 296 can be realized by a processor.

The calculation principle of the calculation unit 296 will be described below with reference to FIGS. 2 and 4 . Here, assuming that the input voltage is Vi, the resistance of the first impedance element Z1 is Rz1, the resistance of the second impedance element Z2 is Rz2, and the resistance of the third impedance element Z3 is Rz3.

After the control unit 210 receives the instruction to start the test, the control unit 210 will execute three test modes. For the convenience of description, the three test modes are respectively referred to as the first test mode, the second test mode and the third test mode below. Here, the first test mode, the second test mode and the third test mode are only used to distinguish different test modes, and do not limit that they need to be performed in sequence.

In the first test mode, the control unit 210 outputs control signals C0, C1, and C2 to close the power switch K0, the first switch K1, and the second switch K2, that is, the power switch K0, the first switch K1, and the second switch K2. On state (on). The measuring unit 292 can measure the voltage level of the output signal So as the first voltage value Vo1.

At this time, the current of the first impedance element Z1 corresponds to the current of the third impedance element Z3, that is, the following formula 1:

V1/Rz1＝-Vo1/Rz3 Formula 1

Moreover, the shunt impedance element will produce a voltage divider effect on the resistance value Rzx of the impedance element Zx to be measured, and the following formula 2 can be obtained accordingly:

Rz1＝Rzx//Rz2＝Rzx×Rz2/(Rzx+Rz2) Formula 2

The following formula 3 can be obtained from formula 1 and formula 2.

Rzx×Rz2/(Rzx+Rz2)＝-V1×Rz3/Vo1 Formula 3

In the second test mode, the control unit 210 outputs control signals C0 , C1 , C2 to close the power switch K0 and the first switch K1 , and open the second switch K2 . That is, the power switch K0 and the first switch K1 are in a conduction state (on), and the second switch K2 is in a non-conduction state (off). The measuring unit 292 can measure the voltage level of the output signal So as the second voltage value Vo2.

At this time, the current of the second impedance element Z2 corresponds to the current of the third impedance element Z3, that is, the following formula 4:

V1/Rz2＝-Vo2/Rz3 Formula 4

Moreover, the shunt impedance element will produce a voltage division effect on the resistance value Rzx of the impedance element Zx to be measured, and the following formula 5 can be obtained accordingly:

Rz2＝Rzx//(Rz1+Rz2)＝Rzx×(Rz1+Rz2)/(Rzx+Rz1+Rz2) Formula 5

The following formula 6 can be obtained from formula 4 and formula 5:

Rzx×(Rz1+Rz2)/(Rzx+Rz1+Rz2)＝-V1×Rz3/Vo2 Formula 6

In the third test mode, the control unit 210 outputs control signals C0 , C1 , C2 to close the power switch K0 and the second switch K2 , and open the first switch K1 . That is, the power switch K0 and the second switch K2 are in a conduction state (on), while the first switch K1 is in a non-conduction state (off). The measurement unit 292 can measure the voltage level of the output signal So as the third voltage value Vo3.

At this time, the current of the second impedance element Z2 corresponds to the current of the third impedance element Z3, that is, the following formula 7:

V1/Rz2＝-Vo3/Rz3 Formula 7

Moreover, the shunt impedance element will produce a voltage division effect on the resistance value Rzx of the impedance element Zx to be measured, and the following formula 8 can be obtained accordingly:

Rz2＝(Rzx+Rz1)//Rz2＝(Rzx+Rz1)×Rz2/(Rzx+Rz1+Rz2) Formula 8

The following formula 9 can be obtained from formula 7 and formula 8:

(Rzx+Rz1)×Rz2/(Rzx+Rz1+Rz2)＝-V1×Rz3/Vo3 Formula 9

After completing the three test modes, the calculation unit 296 can calculate the resistance value Rzx of the impedance element Zx to be tested according to the above formula 3, formula 6 and formula 9.

The resistance value Rzx of the impedance element Zx to be tested generated by the computing unit 296 can be output to a display unit (not shown in the figure) for display.

In addition, in order to be suitable for impedance detection of various electronic components, the voltage supply unit 230 can provide different input voltages by multiple power sources 2321-232n and multiple power switches K0_1-K0_n, as shown in FIG. 5 . Wherein, n is a positive integer greater than 1.

These power sources 2321-232n may have the same supply voltage or different supply voltages. The control unit 210 provides a control signal C0_1-C0_n for each of these power switches K0_1-K0_n to determine the closing of one or more power switches in these power switches K0_1-K0_n, so that the input voltage Vin provided to the third contact N3 has the desired Voltage value.

In the isolation circuit and impedance detection circuit of the present invention, the isolation circuit isolates the bypass impedance elements (ie, the first impedance element and the second impedance element) in the circuit to be tested, so as to accurately measure the resistance value of the impedance element to be tested. Applying the isolation circuit and the impedance detection circuit of the present invention to an online tester can detect the impedance element to be tested on the printed circuit board. And, when being used for the quality inspection of the printed circuit board, especially the circuit board of the servo (server) system, the mechanism of the online tester applying the isolation circuit and the impedance detection circuit according to the present invention is simplified, and can be obtained by simple maintenance. Compatible with different kinds of circuit boards under test.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (10)

1. buffer circuit, be applied to a circuit under test, described circuit under test comprises one first contact, one second contact, one the 3rd contact, be connected in one first impedor between described first contact and described second contact, be connected in the impedor to be measured between described second contact and described the 3rd contact and be connected in described first contact and described the 3rd contact between one second impedor, it is characterized in that described buffer circuit comprises:

One the 4th contact;

One voltage feeding unit is in order to provide an input voltage to described the 3rd contact;

One selected cell is in order to at least one is electrically connected to described the 4th contact in described first contact and described second contact;

One control module is connected to described voltage feeding unit and described selected cell, switches with the connection that provides and control described selected cell of the described input voltage of controlling described voltage feeding unit; And

One isolation detection unit, in order to export an output signal, wherein said output signal is used in order to the calculating as described impedor resistance to be measured.

2. buffer circuit according to claim 1 is characterized in that, described voltage feeding unit comprises:

One power supply is in order to provide described input voltage; And

One power switch is connected between described the 3rd contact and the described power supply, in order to according to described the 3rd contact of the control conducting of described control module and described power supply.

3. buffer circuit according to claim 2 is characterized in that, described selected cell comprises:

One first switch is connected between described first contact and described the 4th contact, in order to according to described first contact of the control conducting of described control module and described the 4th contact; And

One second switch is connected between described second contact and described the 4th contact, in order to according to described second contact of the control conducting of described control module and described the 4th contact.

4. buffer circuit according to claim 3 is characterized in that, described isolation detection unit comprises:

One amplifier has a positive input terminal, a negative input end and an output terminal, and the described negative input end of wherein said amplifier connects described the 4th contact, and the described positive input terminal ground connection of described amplifier; And

One the 3rd impedor, cross-over connection is between the described output terminal of the described negative input end of described amplifier and described amplifier.

5. buffer circuit according to claim 4, it is characterized in that, control described voltage feeding unit when described control module and export described input voltage and control described selected cell when described first contact and described second contact are electrically connected to described the 4th contact respectively, the output of described isolation detection unit has the described output signal of one first magnitude of voltage; Wherein control described voltage feeding unit when described control module and export described input voltage and control described selected cell when described first contact is electrically connected to described the 4th contact, the output of described isolation detection unit has the described output signal of one second magnitude of voltage; And wherein control described voltage feeding unit and export described input voltage and control described selected cell when described second contact is electrically connected to described the 4th contact when described control module, the output of described isolation detection unit has the described output signal of a tertiary voltage value, so as to learning described impedor resistance to be measured by described input voltage, described first magnitude of voltage, described second magnitude of voltage, described tertiary voltage value, the described first impedor resistance, the described second impedor resistance and the described the 3rd impedor resistance.

6. the impedance detection circuit with buffer circuit in order to detect an impedor resistance to be measured, is characterized in that, comprising:

One first contact;

One second contact is in order to electrically connect a described impedor end to be measured;

One the 3rd contact is in order to electrically connect the described impedor other end to be measured;

One first impedor is connected between described first contact and described second contact;

One second impedor is connected between described first contact and described the 3rd contact;

One voltage feeding unit is in order to provide an input voltage to described the 3rd contact;

One the 4th contact;

One selected cell is in order to at least one is electrically connected to described the 4th contact in described first contact and described second contact;

One control module is connected to described voltage feeding unit and described selected cell, switches with the connection that provides and control described selected cell of the described input voltage of controlling described voltage feeding unit;

One isolation detection unit is in order to export an output signal; And

One computing unit, electrically connect the output of described isolation detection unit, calculate described impedor resistance to be measured in order to resistance according to described input voltage, described output signal, the described first impedor resistance, the described second impedor resistance and described isolation detection unit.

7. the impedance detection circuit with buffer circuit according to claim 6 is characterized in that, described voltage feeding unit comprises:

One power supply is in order to provide described input voltage; And

One power switch is connected between described the 3rd contact and the described power supply, in order to according to described the 3rd contact of the control conducting of described control module and described power supply.

8. the impedance detection circuit with buffer circuit according to claim 7 is characterized in that, described selected cell comprises:

One first switch is connected between described first contact and described the 4th contact, in order to according to described first contact of the control conducting of described control module and described the 4th contact; And

One second switch is connected between described second contact and described the 4th contact, in order to according to described second contact of the control conducting of described control module and described the 4th contact.

9. the impedance detection circuit with buffer circuit according to claim 8 is characterized in that, described isolation detection unit comprises:

One amplifier has a positive input terminal, a negative input end and an output terminal, and the described negative input end of wherein said amplifier connects described the 4th contact, and described positive input terminal ground connection; And

One the 3rd impedor, cross-over connection is between the described output terminal of the described negative input end of described amplifier and described amplifier.

10. the impedance detection circuit with buffer circuit according to claim 9, it is characterized in that, control described voltage feeding unit when described control module and export described input voltage and control described selected cell when described first contact and described second contact are electrically connected to described the 4th contact respectively, the output of described isolation detection unit has the described output signal of one first magnitude of voltage; Wherein control described voltage feeding unit when described control module and export described input voltage and control described selected cell when described first contact is electrically connected to described the 4th contact, the output of described isolation detection unit has the described output signal of one second magnitude of voltage; Wherein control described voltage feeding unit when described control module and export described input voltage and control described selected cell when described second contact is electrically connected to described the 4th contact, the output of described isolation detection unit has the described output signal of a tertiary voltage value; And wherein said computing unit calculates described impedor resistance to be measured by described input voltage, described first magnitude of voltage, described second magnitude of voltage, described tertiary voltage value, the described first impedor resistance, the described second impedor resistance and the described the 3rd impedor resistance.

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