JP2005079630A - Floating power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a floating power supply whereby a load side needs not to eliminate noise potential. <P>SOLUTION: The floating power supply 1 is configured with: a power supply 2; a differential amplifier 6; output terminals 7, 8; a resistor R1 for connecting the power supply to an inverting input terminal of the differential amplifier; a resistor R3 for connecting the power supply to a noninverting input terminal of the differential amplifier; a feedback resistor R2 for connecting one of the output terminals to the inverting input terminal of the differential amplifier; and a resistor R4 for connecting the other of the output terminals to the noninverting input terminal of the differential amplifier. Thus, an output potential VS 1 including only a component of the power supply 2 can be obtained as an output signal VS2 independently of floating of ground potential levels GND 1 and GND 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a floating power supply that outputs a signal with a floating ground potential.

One example of a floating power supply is a sensor simulation device. The sensor simulation device is configured to pseudo-output signals similar to the signals output from various sensors mounted on the vehicle to the ECU when performing a function test of the vehicle ECU.
The sensor simulation apparatus will be described with reference to FIG.
In the sensor simulation device 1, the power source 2 outputs a signal VS1 that simulates the sensor output. In the ECU 3, the signal VS1 is amplified to the signal VS2 by the differential amplifier 4.

The positive electrode of the power supply 2 is connected to the non-inverting input terminal (+) of the differential amplifier 4, and the negative electrode of the power supply 2 is grounded to the ground GND 1 in the sensor simulation device 1. Further, the inverting input terminal (−) of the differential amplifier 4 is grounded to the ground GND 2 in the ECU 3.
Here, the differential amplifier 4 is used mainly for removing common-mode noise superimposed on the signal VS1.

The principle that common-mode noise is removed by the differential amplifier 4 will be described with reference to FIG.
The differential amplifier 4 has a property of excluding signals included in both the inverting and non-inverting input terminals from the output signal. Therefore, as shown in FIG. 2, the original signal Vin1 is input to the non-inverting input terminal and the inverting input terminal of the differential amplifier 4 in reverse phase, and the noise component Vin2 is input to the inverting input terminal and the non-inverting input terminal. Input in phase.

  The differential amplifier 4 amplifies the original signal Vin1 input to the inverting and non-inverting input terminals in the opposite phase with a predetermined amplification factor, but the noise component Vin2 input in the same phase is The amplification factor becomes extremely low. Therefore, even when the noise component Vin2 is superimposed on the original signal Vin1, it is possible to eliminate the influence of noise and obtain the output signal Vout that depends only on the original signal Vin1.

However, in the circuit shown in FIG. 1, when a potential difference is generated between the grounds GND1 and GND2 due to noise or the like, a current due to this potential difference flows superimposed on the original signal VS1. For this reason, even if the differential amplifier 4 is used, the influence of noise or the like cannot be eliminated, and the output signal VS2 includes a noise component.
In order to eliminate this influence, it is conceivable to draw a dedicated ground line 5 between the negative electrode of the power supply 2 and the inverting input terminal of the differential amplifier. However, in this case, since currents other than the original signal circulate, it is not realistic.

  Usually, the ground GND1 of the sensor simulation device 1 is often grounded at a location different from the ground GND2 of the ECU 3. For this reason, a potential difference is likely to occur between the grounds, and even if the differential amplifier 4 is used, the influence of noise and the like cannot be eliminated. Recently, in order to detect that the power source of the sensor is grounded, a getter of about 1 to 3 v may be put on the sensor ground. As described above, since the power supply of the sensor is floating, it is difficult to distinguish between the sensor getter and the external noise.

Various techniques for eliminating the influence of the potential difference generated between the ground of the power source and the ground of the differential amplifier have been proposed.
For example, in the measurement sensor signal processing circuit device described in Patent Document 1, the influence is eliminated by providing a reference potential compensation line. Further, in the reference potential difference compensation circuit described in Patent Document 2, the ground potential of the sensor is corrected by the receiving circuit.

JP-A-7-198658 JP 2000-74828 A

In the techniques described in Patent Documents 1 and 2, the potential difference between the ground of the power source and the ground on the load (reception) side is removed on the load side. However, when it is not preferable to add new means on the load side, it is difficult to apply each of the conventional techniques.
An object of the present invention is to eliminate the need to remove the influence of noise or the like on the load side in a floating power supply.

  The present invention relates to a floating power supply that amplifies a power supply output by a differential amplifier and outputs the amplified output to an output terminal, and a first resistor connected to one end of the power supply and an inverting input terminal of the differential amplifier A second resistor connected to the other end of the power supply and the non-inverting input terminal of the differential amplifier; a third resistor connected to one of the output terminals and the inverting input terminal of the differential amplifier; A floating power supply is constituted by a fourth resistor connected to the other of the output terminals and the non-inverting input terminal of the differential amplifier.

  The differential amplifier operates so as to cancel the potential difference between the non-inverting input terminal and the inverting input terminal. This is called an imaginary short. By appropriately selecting the values of the first to fourth resistors, the power supply potential is transferred to the output terminal as the output potential for the imaginary short point. The power supply potential and the output potential are transferred based on the ground potential of the power supply and the ground potential of the output terminal (load), respectively.

  According to the present invention, since the floating power supply side outputs a signal that takes in the ground potential on the load (reception) side, it is not necessary to take measures on the load side to remove the influence of its own ground potential.

  An example in which the present invention is applied to a sensor simulation apparatus will be described with reference to the drawings.

A first embodiment of the sensor simulation device will be described with reference to FIG.
The negative side of the power supply 2 that outputs the signal VS1 is connected to the inverting input terminal (−) of the differential amplifier (op-amp) 6 through the resistor R1.
A connection point between the power supply 2 and the resistor R1 is grounded to the ground GND1. As described above, the potential of the ground GND1 may be floating, for example, by setting a getter of about 1 to 3v in order to detect the sensor power supply ground.

The positive side of the power source 2 is connected to the non-inverting input terminal (+) of the differential amplifier 6 through the resistor R3.
The output of the differential amplifier 6 is connected to the output terminal 7 of the sensor simulation device 1 and is connected to the inverting input terminal (−) through the feedback resistor R2.
A connection point between the resistor R3 and the non-inverting input terminal (+) is connected to the other output terminal 8 through the resistor R4.

The output terminal 7 and the output terminal 8 of the sensor simulation device 1 are connected to the input terminals 11 and 12 of the ECU 3, respectively.
In the ECU 3, the signal from the sensor simulation device 1 is input to the inverting input terminal (−) and the non-inverting input terminal (+) of the differential amplifier 4. The differential amplifier 4 outputs a signal VS2. Note that the ground GND2 of the differential amplifier 4 may be floating due to noise or the like.

The operation principle of the present invention will be described with reference to FIGS.
FIG. 4 is a diagram for explaining the principle of the present invention in association with the conventional operation principle of FIG.
The relationship between the original signal Vin1 and the differential amplifier 6 is the same as in FIG. A noise component (GND2 in FIG. 1) generated on the reception side is applied as Vin2 to the non-inverting input terminal (+) of the differential amplifier 4 via the resistor R4. As a result, the noise component generated on the reception side is superimposed on the output-side signal Vout in the opposite phase, and the reception side can receive the original signal without the noise component.

FIG. 5 conceptually shows the potential of each part in the circuit of FIG.
The differential amplifier 6 operates so as to cancel the potential difference between the inverting input terminal and the non-inverting input terminal. This is called an imaginary short. Therefore, the connection point between the resistors R1 and R2 and the connection point between the resistors R3 and R4 are at the same potential (imaginary short point 13).

  Here, when the ratio of the resistors R1 and R2 and the ratio of the resistors R3 and R4 are selected to be equal (R1 / R2 = R3 / R4), the difference from the power supply potential VS1 is symmetrical with respect to the imaginary short point 13 of the differential amplifier 6. The output potential VS2 of the dynamic amplifier is output at different ground potentials GND1 and GND2. Therefore, the potential VS2 on the ECU 3 side includes only the component of the power source 2 regardless of the floating of the ground potentials GND1 and GND2.

  According to this example, the floating of the ground GND2 generated on the load side is taken in and the signal Vout from the power supply 2 is output. Therefore, it is possible to capture the noise (floating) on the receiving side and send its own signal to the reference point of the other party.

In the first embodiment, the polarity of the signal of the power source 2 is reversed by the differential amplifier 6 of the sensor simulation device 1. In this example, this reversal is canceled.
The circuit of FIG. 6 will be described mainly with respect to differences from FIG.
A differential amplifier 14 is further provided between the power supply 2 and the differential amplifier 6. Since the differential amplifier 14 reverses the polarity of the power supply 2 and inputs a signal to the differential amplifier 6, a signal whose polarity with respect to the ground matches the polarity of the power supply 2 is output from the output terminal 7 and the output terminal 8.

  The floating power supply of the present invention can be applied not only to the sensor simulation apparatus but also to all circuits in which a differential amplifier exists on the load side and a ground floating exists on the power supply side.

It is a figure for demonstrating the conventional sensor simulation apparatus. It is a figure for demonstrating the principle of operation of a differential amplifier. It is a figure which shows the structure of Example 1 of this invention. FIG. 4 is a diagram (part 1) illustrating an operation principle of the circuit of FIG. 3; FIG. 4 is a diagram (part 2) illustrating an operation principle of the circuit of FIG. It is a figure which shows the structure of Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sensor simulation apparatus 2 ... Power supply 3 ... ECU
4 ... differential amplifier 5 ... ground line 6 ... differential amplifier 7 ... output terminal 8 ... output terminal 11, 12 ... input terminal 13 ... imaginary short point 14 ... differential amplifiers GND1, GND2 ... ground

Claims (3)

In a floating power supply that amplifies the power supply output with a differential amplifier and outputs it to the output terminal,
A first resistor connected to one end of the power supply and an inverting input terminal of the differential amplifier;
A second resistor connected to the other end of the power source and a non-inverting input terminal of the differential amplifier;
A third resistor connected to one of the output terminals and an inverting input terminal of the differential amplifier;
A fourth resistor connected to the other of the output terminals and a non-inverting input terminal of the differential amplifier;
Floating power supply characterized by comprising.   The floating power supply according to claim 1, wherein a ratio between the first resistor and the second resistor is equal to a ratio between the third resistor and the fourth resistor.   The floating power supply according to claim 1 or 2, further comprising means inserted between the power supply and the differential amplifier to invert the polarity of the power supply.

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