JP4476309B2 - Method for adjusting current sensor device - Google Patents

Description

The present invention relates to adjusting how the current sensor device using a Hall element whose resistance value changes according to the magnetic flux.

FIG. 10 is a diagram illustrating a circuit configuration of a current sensor device that has been generally used conventionally , as disclosed in Patent Document 1 , for example . In this figure, reference numeral 10 denotes a Hall element. The Hall element 10 is connected to a constant voltage power supply VCC between input terminals a and d, and is driven by a constant current through an operational amplifier 11 and a transistor 12. The output terminals b and c of the Hall element 10 are connected to a differential amplifier circuit 13 which is an amplifier circuit that amplifies the output signal of the Hall element 10. The resistor 14 is a resistor for correcting the gain temperature characteristic of the Hall element 10, and the variable resistor 15 is a first trimming resistor for adjusting the driving constant current of the Hall element 10. The variable resistor 16 is a second trimming resistor for adjusting the offset voltage. The Hall element 10 is not limited to constant current driving, and may have a circuit configuration with constant voltage driving.

Next, a gain adjustment method and an offset voltage adjustment method for the current sensor device configured as described above will be described.
In FIG. 11, suppose that the current sensor device characteristic has L1 as a target value. The output voltage when the input current to the Hall element 10 is 0 (A), that is, the offset voltage is Voff (V), the gain width when the input current is supplied + I (A) is + Vg (V), and the output voltage is The characteristics are such that Voff + Vg (V), the gain width when the input current is supplied to −I (A) is −Vg (V), and the output voltage is Voff−Vg (V).

The characteristic before adjusting the current sensor device is , for example , the characteristic of L2 . For the current sensor device having the characteristic of L2, the gain is adjusted by trimming the first trimming resistor 15 shown in FIG. The trimming resistor 16 is trimmed to adjust the offset voltage, thereby adjusting the target value characteristic L1.

  A method of gain adjustment will be described. First, the offset voltage Voff1 (V) when no current is supplied is measured. Next, the first trimming resistor 15 is trimmed to the characteristic of L3 where the output voltage is Voff1 + Vg (V) while supplying the current + I (A) and feeding back the output of the differential amplifier circuit 13. This completes the adjustment of the gain width.

  Next, a method for adjusting the offset voltage will be described with reference to FIG. The adjustment of the offset voltage is performed by trimming the second trimming resistor 16 until the output voltage becomes L4 characteristics where the output voltage becomes Voff while feeding back the output of the differential amplifier circuit 13 in a state where no current is supplied. This completes the adjustment of the current sensor device. However, at this time, the output characteristic of the current sensor device does not coincide with the characteristic L1 as the target value.

  As described above, the conventional adjustment method of the current sensor device has a problem that the gain width does not become + Vg because the offset voltage changes from Voff1 to Voff2 after the gain width is adjusted. This is because, as shown in FIG. 13, the Hall element 10 has a characteristic that the offset voltage changes by changing the drive current.

  For this reason, after the adjustment of the current sensor device is completed, in the step of inspecting the output characteristics, the difference from the target value of L1 is compared, and if the accuracy exceeds the allowable accuracy, the circuit board of the current sensor device is discarded. Or, the adjustment of the Hall element 10 and the first and second trimming resistors 15 and 16 is performed again, and trimming is performed again, resulting in an increase in cost.

By the way , in order to avoid the re-trimming by disposing the current sensor circuit board and replacing the parts, a method of adjusting the offset voltage of the Hall element to zero before adjusting the gain width and then adjusting the gain width Has been proposed (see, for example, Patent Document 2 ).

JP 2004-20560 A (paragraphs 0016 to 0018, FIGS. 1 and 5) JP-A-8-327482 (paragraphs 0014 to 0018, FIG. 3)

According to the method disclosed in Patent Document 2 , the characteristics of the current sensor as the target value can be obtained, but the adjustment process for adjusting the zero offset before the gain adjustment, the subsequent gain adjustment process, and finally the offset An adjustment process and a total of three adjustment processes are required. Therefore, since the time for using an expensive adjuster becomes long, the equipment capacity of the adjuster tends to be insufficient when mass-produced, and it is necessary to purchase a new adjuster, which also increases the cost.

The present invention has been made to solve the above problems, it is not discarded or re-trimming of the substrate, and requires only a adjusting process is small and provide coordination how current sensor device for the purpose of low-cost To do.

  An adjustment method of a current sensor device according to the present invention includes a Hall element whose resistance value changes according to magnetic flux, a constant voltage circuit or a constant current circuit for driving the Hall element, and an output signal from the Hall element. In a method of adjusting a current sensor device that adjusts a current sensor device including an amplifier circuit that amplifies while feeding back an output of the amplifier circuit, a gain adjustment target value for adjusting a gain of the current sensor device is The offset voltage change amount caused by the gain adjustment is adjusted as a corrected gain adjustment target value, and then the offset voltage is adjusted.

According to the present invention, there is no need for disposal or re-trimming of the substrate, and adjusting process requires also less, it is possible to obtain the adjustment how the current sensor device exhibits a low cost-effective.

With reference to the accompanying drawings, illustrating a preferred embodiment with the adjustment how the current sensor apparatus according to the present invention.

Embodiment 1 FIG.
FIG. 1 is a circuit configuration diagram of the current sensor device according to the first embodiment, and lands X and Y are provided at the output terminals b and c of the Hall element 1. The lands X and Y are configured to be opened and closed by the inter-land opening / closing means 2. Further, a first trimming resistor 3 for adjusting the driving constant current of the Hall element 1 is provided. The first trimming resistor 3 has a change in offset voltage caused by gain adjustment, as will be described later. The gain adjustment target value with the amount corrected is input. Further, a second trimming resistor 16 for adjusting the offset voltage is provided. The first trimming resistor 3 functions as a gain adjusting unit of the current sensor device, and the second trimming resistor 16 functions as an offset voltage adjusting unit of the current sensor device. The other parts are the same as those in the conventional circuit configuration diagram described in FIG. 10, and the description is omitted by giving the same reference numerals.

The current sensor device according to the first embodiment is configured as described above. Next, an adjustment method thereof will be described with reference to FIGS.
First, in a state in which no current is supplied, the lands X and Y connected to the output terminals b and c of the Hall element 1 are short-circuited externally by the inter-land opening / closing means 2, and the zero offset voltage Voff3 is measured. The switching means 2 is opened to remove the short circuit between the lands X and Y, and the non-zero offset voltage Voff1 is measured. Next, a current + I (A) is supplied, and the gain width Vg1 before gain adjustment is measured. FIGS. 2 and 3 show how these measurements were performed.

  Here, there is a difference between the values of the non-zero offset voltage Voff1 and the zero offset voltage Voff3 because the Hall element 1 has an offset voltage as described above. The offset voltage of the Hall element 1 is generally proportional to the drive current. The voltage difference between the zero offset voltage Voff3 and the non-zero offset voltage Voff1 is the offset voltage of the Hall element 1 multiplied by the gain of the differential amplifier circuit 13 in the drive current before gain adjustment.

  Here, calculation of the amount of change in the offset voltage by changing the gain by adjusting the first trimming resistor 3 of the current sensor device will be described with reference to FIG.

In the circuit configuration shown in FIG. 1, when the gain is adjusted, the drive current of the Hall element 1 changes, so that the offset voltage of the Hall element 1 changes. The offset voltage of the Hall element 1 and the drive current are in a proportional relationship, and the drive current and the adjustment gain width are also in a proportional relationship. As a result, the adjustment gain width and the offset voltage of the Hall element 1 are also in a proportional relationship. Therefore, the amount of change in the offset voltage of the current sensor device due to the change in the offset voltage of the Hall element 1 after gain adjustment can be calculated by the following equation (1).
Amount of change in offset voltage of current sensor device before and after gain adjustment =
Target gain Vg ÷ pre-adjustment gain Vg1 x (zero offset voltage Voff3-non-zero offset voltage Voff1) (1)
Therefore, the offset voltage Voff2 after gain adjustment is calculated by the following equation (2).
Offset voltage Voff2 after gain adjustment =
Target gain Vg ÷ pre-adjustment gain Vg1 × (zero offset voltage Voff3−nonzero offset voltage Voff1) + nonzero offset voltage Voff1 (2)

Since the offset voltage Voff2 after gain adjustment can be found from the above calculation, the gain adjustment supplies a current of + I (A) and feeds back the output of the differential amplifier circuit 13, while the output voltage is “offset voltage Voff2 + after gain adjustment”. The first trimming resistor 3 may be trimmed until the target gain Vg is reached. This is shown in FIG. If this method is adopted, the characteristic L3 is obtained such that the gain width is accurately the target gain Vg. This completes the gain adjustment.

  Next, the offset voltage is adjusted. The offset voltage is adjusted by trimming the second trimming resistor 16 until the output voltage becomes Voff while feeding back the output of the differential amplifier circuit 13 in a state where no current is supplied. This is shown in FIG. The characteristics for which the gain adjustment and the offset voltage adjustment have been completed coincide with the target characteristic L1.

  In the first embodiment, the configuration in which the lands X and Y provided at the output terminals b and c of the Hall element 1 are opened and closed by the inter-land opening / closing means 2 is illustrated and described. Even if the inter-land opening / closing means 2 is not used, it may be opened / closed by other means, for example, by human operation, and the design can be changed.

As described above, according to the adjustment how the current sensor apparatus according to the first embodiment, to adjust the properties after the adjustment to the characteristic L1 to the target value, it is not necessary to deviate from the target characteristic. Therefore, there is no need to dispose of the current sensor board or re-adjustment by replacing parts, and there is no adjustment step for setting the zero offset voltage as compared with the method according to Patent Document 1. The same two adjustments can be used, and the equipment capacity can be greatly increased, which contributes to cost reduction.

Embodiment 2. FIG.
Will now be described with reference to FIGS about the adjustment how the current sensor apparatus according to the second embodiment. FIG. 7 is a circuit configuration diagram of the current sensor device according to the second embodiment. Instead of using the first and second trimming resistors described in the first embodiment, an EEPROM and an 8-bit R-2R ladder resistor are used. This is a digital trimming configuration used.

  Reference numeral 70 denotes an EEPROM, and reference numeral 71 denotes a gain trimming unit. The gain trimming unit 71 includes a first 8-bit R-2R ladder resistor 72 and an operational amplifier 73. Reference numeral 74 denotes an offset trimming unit. The offset trimming unit 74 includes a second 8-bit R-2R ladder resistor 75 and an operational amplifier 76.

  The thin film resistors Ri and Ro whose resistance values are fixed are used in places where the first and second trimming resistors are mounted in the first embodiment. The resistor 14 is a resistor for correcting the gain temperature characteristic of the Hall element 1 as in the first embodiment, and the other components are the same as those in the first embodiment. Is omitted.

The current sensor device according to the second embodiment is configured as described above, and the mounted Hall element 1 is obtained by previously obtaining the relationship between the drive current and the offset voltage as shown in FIG. Yes. The drive current when measuring the offset voltage with the Hall element alone is the Hall element drive current before gain adjustment in the circuit configuration shown in FIG. The Hall element drive current before gain adjustment can be obtained by the calculation of the following equation (3), assuming that the 8-bit initial data of the gain trimming unit 71 is FFh, for example.
Drive current before gain adjustment =
Vcc × 255 ÷ 256 × (R2 + Rr) ÷ (R1 + R2 + Rr) ÷ Ri (3)
Here, since the resistance values R1, R2, and Ri have good resistance value accuracy by using thin film resistors having fixed resistance values, it is possible to calculate the driving current with high accuracy. The laser trimming resistor has a large initial resistance value variation, and the drive current cannot be calculated with high accuracy. Therefore, the digital trimming configuration is desirable.

Next, a method for adjusting the current sensor device will be described. The target characteristic is the same characteristic L1 in FIGS. 2 and 3 as in the first embodiment.
First, the offset voltage Voff1 is measured in a state where no current is supplied. Next, a current of + I (A) is supplied, and the gain width Vg1 before gain adjustment is measured.

Here, the amount of change in the offset voltage after gain adjustment is calculated. In the circuit configuration of FIG. 7, when the gain is adjusted, the Hall element drive current changes, so that the offset voltage of the Hall element 1 changes. Since the adjustment gain width and the offset voltage of the Hall element 1 are in a proportional relationship as described above, the offset voltage Vhoff2 of the Hall element 1 after gain adjustment can be calculated by the following equation (4).
The offset voltage Vhoff2 of the Hall element 1 after gain adjustment =
Vhoff1 × Vg ÷ Vg1 (4)
Here, Vhoff1 is an offset voltage measured with the Hall element alone in the drive current before gain adjustment.

If the gain of the differential amplifier circuit 14 is G, the offset voltage Voff2 after gain adjustment can be calculated by the following equation (5).
Voff2 = Voff1−Vhoff1 × G + Vhoff1 × G (5)

  Since the offset voltage Voff2 after gain adjustment is found from the above calculation, the gain adjustment supplies the current of + I (A) and feeds back the output of the differential amplifier circuit 13 until the output voltage becomes Voff2 + Vg. The data of the gain trimming unit 71 to be written may be lowered from the initial FFh. This is shown in FIG. In this way, the characteristic L3 has a gain width of exactly Vg. This completes the gain adjustment.

  Next, the offset voltage is adjusted. The adjustment of the offset voltage may be performed by changing the data of the offset trimming unit 74 written in the EEPROM 70 until the output voltage becomes Voff while feeding back the output of the differential amplifier circuit 13 in a state where current is not supplied. This is shown in FIG. The characteristic for which the gain adjustment and the offset adjustment are completed is a characteristic L1 that is a target value.

As described above, according to the adjustment how the current sensor apparatus according to the second embodiment, since the possible characteristic after adjustment to the characteristic L1 to the target value, as in the conventional example, when the off-target properties There is no need to dispose of the current sensor substrate or re-adjusting the parts, and the adjustment process is only twice as compared with the method according to Patent Document 1, so that the cost can be reduced.

This invention can be utilized to adjust how the current sensor device for the purpose of low cost.

It is a circuit block diagram of the current sensor apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the zero offset voltage and nonzero offset voltage of the current sensor apparatus which concern on Embodiment 1 of this invention. It is a figure which shows the gain width before gain adjustment of the current sensor apparatus which concerns on Embodiment 1 and Embodiment 2 of this invention. It is a figure explaining calculation of the amount of change of offset voltage by gain adjustment of the current sensor apparatus concerning Embodiment 1 of this invention. It is explanatory drawing of the target voltage at the time of gain adjustment of the current sensor apparatus which concerns on Embodiment 1 of this invention, and the characteristic after gain adjustment. It is explanatory drawing of offset adjustment of the current sensor apparatus which concerns on Embodiment 1 and Embodiment 2 of this invention. It is a circuit block diagram of the current sensor apparatus which concerns on Embodiment 2 of this invention. It is explanatory drawing of calculation of the offset voltage variation | change_quantity by the gain adjustment of the current sensor apparatus which concerns on Embodiment 2 of this invention. It is explanatory drawing of the target voltage at the time of gain adjustment of the current sensor apparatus which concerns on Embodiment 2 of this invention, and the characteristic after gain adjustment. It is a figure which shows the circuit structure of the current sensor apparatus currently used conventionally. It is explanatory drawing of the characteristic after the target voltage and gain adjustment at the time of the conventional gain adjustment. It is explanatory drawing of the characteristic after the conventional offset adjustment and adjustment completion. It is a figure which shows the relationship between the offset voltage of a Hall element, and a drive current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Hall element 2 Land switching means 3,15 1st trimming resistor 11 Operational amplifier 12 Transistor 13 Differential amplifier circuit 14 Resistor 16 2nd trimming resistor VCC Constant voltage power supply X, Y Land L1 Target characteristic L2 Gain Characteristic L3 before adjustment Characteristic L4 after gain adjustment Characteristic Voff after gain / offset adjustment Offset voltage Voff1 of target characteristic Offset voltage before gain adjustment (non-zero offset voltage)
Voff2 Offset voltage after gain adjustment Voff3 Offset voltage when Hall element output is short (zero offset voltage)
Vg Gain width Vg1 when + I (A) is supplied as a target characteristic Gain width Vhoff1 when + I (A) is supplied before gain adjustment Offset voltage Vhoff2 of Hall element at drive current before gain adjustment Drive current after gain adjustment Hall element offset voltage at

Claims (6)

A current sensor device comprising: a Hall element whose resistance value changes according to magnetic flux; a constant voltage circuit or a constant current circuit for driving the Hall element; and an amplifier circuit for amplifying an output signal from the Hall element. In the adjustment method of the current sensor device that adjusts while feeding back the output of the amplifier circuit,
The gain adjustment target value when adjusting the gain of the current sensor device is adjusted as a gain adjustment target value obtained by correcting the amount of change in the offset voltage caused by the gain adjustment, and then the offset voltage is adjusted. A method for adjusting the current sensor device.   The amount of change in the offset voltage caused by adjusting the gain is a zero offset voltage measured by short-circuiting between the output terminals of the Hall element, and a non-zero offset voltage measured without short-circuiting between the output terminals of the Hall element, 2. The method of adjusting a current sensor device according to claim 1, wherein the adjustment is performed using an unadjusted gain width measured before the gain adjustment and a target gain width.   3. The method of adjusting a current sensor device according to claim 2, wherein the calculation is target gain width / unadjusted gain width × (zero offset voltage−non-zero offset voltage).   2. The method of adjusting a current sensor device according to claim 1, wherein a value obtained by previously measuring the Hall element alone is used as the amount of change in the offset voltage caused by the gain adjustment. (Delete) (Delete)

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