JP2005207826A - Voltage detection device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage detection device and its method capable of improving detection accuracy inexpensively. <P>SOLUTION: The both terminal voltage of a battery B is divided by potential dividing resistances R1-R3. An A/D converter 11 compares all both terminal voltages V1-V3 of the plurality of potential dividing resistances R1-R3 with a reference voltage respectively, and converts them into digital data. A CPU 12a to which the digital data are supplied detects the both terminal voltage of the battery B based on the sum of all the digital data acquired by converting all the both terminal voltages V1-V3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a voltage detecting apparatus and method for detecting a detected voltage by converting a divided voltage of the detected voltage into digital data.

  As shown in FIG. 3, when the terminal voltage of the battery B, which is the detected voltage, is larger than the allowable input voltage range of the A / D converter 11, the conventional voltage detecting device divides the voltage by a voltage dividing resistor and D-converted. For example, when the terminal voltage of the battery B of 12 V is detected, the voltage is divided by about 1/3 by the voltage dividing resistors R1 and R2, and the divided voltage is converted by the A / D converter 11.

  However, in the above-described conventional voltage detection device, in order to accurately detect the detected voltage, for example, when dividing the voltage to 1/3, a voltage dividing resistor capable of accurately dividing the detected voltage to 1/3 is required. There is a problem that a high-precision voltage dividing resistor is required. For example, if the voltage is divided by 1/3, the amount of change in the detected voltage is also reduced to 1/3. Therefore, the detection resolution is worse than when A / D conversion is performed without dividing the detected voltage. turn into. For this reason, if the resolution of A / D conversion, that is, the number of bits is increased, the cost is increased.

  Accordingly, the present invention focuses on the above-described problems, and an object of the present invention is to provide a voltage detection apparatus and method that can improve detection accuracy at a low cost.

  According to the first aspect of the present invention, there is provided a voltage dividing resistor for dividing the voltage to be detected, and an A / D conversion means for comparing all the voltages across the plurality of voltage dividing resistors with a reference voltage and converting them into digital data. And a detecting means for detecting the detected voltage based on a sum of all digital data obtained by converting the voltages across the terminals.

  According to the first aspect of the present invention, the voltage to be detected is divided by the voltage dividing resistor. The A / D conversion means compares the voltages across the plurality of voltage dividing resistors with the reference voltages, respectively, and converts them into digital data. The detecting means detects the detected voltage based on the sum of all digital data obtained by converting the voltage across all terminals. Therefore, by detecting the detected voltage based on the sum of all digital data obtained by converting all the voltages across the voltage dividing resistors, the accuracy of the voltage dividing resistors does not affect the voltage detection accuracy. . Moreover, the detection resolution can be increased as compared with the case where the detected voltage is divided and the divided voltage is A / D converted.

  According to a second aspect of the present invention, there is provided the voltage detecting device according to the first aspect, wherein the capacitor, a switching switch for connecting both ends of the plurality of voltage dividing resistors to the capacitor, and the switching switch are controlled. A switching control means for sequentially connecting both ends of the plurality of voltage dividing resistors to the capacitor; a conversion switch provided between the capacitor and the A / D converting means; the voltage dividing resistor; A voltage detection device further comprising: conversion control means for turning on the conversion switch each time the connection with the capacitor is switched and supplying the voltage across the capacitor to the A / D conversion means. .

  According to the second aspect of the present invention, the changeover switch connects both ends of the plurality of voltage dividing resistors to the capacitor. The switching control means controls the switching switch to sequentially connect both ends of the plurality of voltage dividing resistors to the capacitor. A conversion switch is provided between the capacitor and the A / D conversion means. Whenever the switching between the voltage dividing resistor and the capacitor changes, the conversion control means turns on the conversion switch and supplies the voltage across the capacitor to the A / D conversion means for conversion. Accordingly, by supplying the voltage across the voltage dividing resistor to the A / D conversion means via the capacitor, it is easy to insulate the source of the detected voltage from the A / D conversion means and the detection means. The voltage across the voltage dividing resistors can be converted by a single A / D conversion means.

  According to a third aspect of the present invention, the voltage to be detected is divided by a plurality of voltage dividing resistors, all the voltages across the plurality of voltage dividing resistors are respectively compared with a reference voltage, converted into digital data, The voltage detection method is characterized in that the detected voltage is detected based on the sum of all digital data obtained by converting the voltage.

  According to the invention described in claim 3, the detected voltage is divided by the voltage dividing resistor. All the voltages across the plurality of voltage dividing resistors are each compared with a reference voltage and converted into digital data. The detected voltage is detected based on the sum of all digital data obtained by converting the voltage across all terminals. Therefore, by detecting the detected voltage based on the sum of all digital data obtained by converting all the voltages across the voltage dividing resistors, the accuracy of the voltage dividing resistors does not affect the voltage detection accuracy. . In addition, the detection resolution can be increased compared to the case where the detected voltage is divided and the divided voltage is A / D converted.

  As described above, according to the first and third aspects of the invention, by detecting the detected voltage based on the sum of all digital data obtained by converting all the voltages across the voltage dividing resistors, The accuracy of the voltage dividing resistor does not affect the voltage detection accuracy. Moreover, since the detection resolution can be increased as compared with the case where the detected voltage is divided and the divided voltage is A / D converted, the voltage detection apparatus capable of improving the detection accuracy at a low cost and its You can get the method.

  According to the second aspect of the present invention, by supplying the voltage across the voltage dividing resistor to the A / D conversion means via the capacitor, the source of the detected voltage, the A / D conversion means and the detection means It is possible to obtain a voltage detecting device capable of converting the voltages across the plurality of voltage dividing resistors with a single A / D conversion means while being insulated from each other.

  The present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a voltage detection apparatus (hereinafter referred to as apparatus 10) that implements the voltage detection method of the present invention. As shown in the figure, the device 10 includes resistors R1 to R3 that divide the terminal voltage VB of the battery B, one capacitor C for the resistors R1 to R3, and both ends of the resistors R1 to R3 connected to the capacitor. Switching switches SW1 to SW3 for sequentially connecting to both ends of C are provided.

  Further, the device 10 compares the voltage across the conversion switch SW4 provided between the A / D converter 11 as the A / D converter 11 and the capacitor C and the analog capacitor C with a reference voltage by comparing the voltage across the reference voltage. An A / D converter 11 for converting data and a microcomputer 12 (hereinafter referred to as μCOM) 12 to which digital data converted by the A / D converter 11 is supplied are provided. The μCOM 12 is connected to control terminals (not shown) of the switching switches SW1 to SW3 and the conversion switch SW4 described above, and performs on / off control of the switching switches SW1 to SW3 and the conversion switch SW4.

  The above-described μCOM 12 includes a central processing unit (CPU) 12a that performs various processes according to a program, a ROM 12b that is a read-only memory that stores a processing program and the like performed by the CPU 12a, and a work that is used in various processes in the CPU 12a. The RAM 12c is a readable / writable memory having an area and a data storage area for storing various data.

  Next, the operation of the apparatus 10 having the above-described configuration will be described below with reference to a flowchart showing the processing procedure of the CPU 12a in FIG. The CPU 12a starts in response to the detection command for the terminal voltage VB of the battery B, sets the counter formed in the RAM 12c in the first initial step (not shown) to 1, and then proceeds to the first step S1.

  In step S1, the CPU 12a turns on the switching switch SWn corresponding to the count value of the counter, and connects the voltage Vn across the voltage dividing resistor Rn to the capacitor C. With this connection, the voltage across the capacitor C becomes equal to the voltage Vn across the voltage dividing resistor Rn. When the process proceeds to step S1 immediately after the start, since the counter is set to 1 by the initial step, the switching switch SW1 is turned on.

  Thereafter, the CPU 12a turns off the switching switch SWn (step S2), disconnects the connection between the voltage dividing resistor Rn and the capacitor C, and then turns on the conversion switch SW4 to change the voltage across the capacitor C to A. / D converter 11 is supplied (step S3). When both ends of the capacitor C are connected, the A / D converter 11 converts both ends of the capacitor C into digital data based on the comparison with the reference voltage and supplies the digital data to the CPU 12a.

  When the digital data is supplied from the A / D converter 11 (Y in step S4), the CPU 12a stores the supplied digital data in the RAM 12c (step S5), and then turns off the switch SW4 for switching (step S5). Step S6), disconnecting the connection between the capacitor C and the A / D converter 11. Thereafter, the CPU 12a determines whether or not the counter value has reached the number 3 of the voltage dividing resistors R1 to R3 (step S7).

  When the count value is not 3 (N in step S7), the CPU 12a must supply the voltage across all the voltage dividing resistors R1 to R3 to the A / D converter 11 via the capacitor C. to decide. Then, in order to supply the voltage across the voltage dividing resistor R (n + 1) to the A / D converter 11, the count value stored in the RAM 12c is incremented (step S8), and the process returns to step S1.

  On the other hand, if the count value is 3 (Y in step S7), the CPU 12a determines that the voltage across all the voltage dividing resistors R1 to R3 has been supplied to the A / D converter 11 via the capacitor C. To do. Then, the CPU 12a obtains the sum of digital data corresponding to all the voltage dividing resistors R1 to R3 supplied in the RAM 12c, and performs a detection process using the obtained sum as the terminal voltage VB of the battery B (step S9). The process is terminated. As is apparent from the above operation, it can be seen that the CPU 12a functions as detection means, switching control means, and conversion control means.

The voltages V1 to V3 across the voltage dividing resistors R1 to R3 and the terminal voltage VB of the battery B have the following relationship.
V1 = {R1 / (R1 + R2 + R3)} × VB
V2 = {R2 / (R1 + R2 + R3)} × VB
V3 = {R3 / (R1 + R2 + R3)} × VB
From this, the following equation can be derived.
V1 + V2 + V3 = (R1 + R2 + R3) / (R1 + R2 + R3) × V = V

  That is, by detecting the voltage across the battery B, which is the detected voltage, based on the sum of all digital data obtained by converting the voltage across all the voltage dividing resistors R1 to R3, the voltage dividing resistors R1 to R1 are detected. The accuracy of R3 does not affect the voltage detection accuracy. Moreover, the detection resolution can be increased as compared with the case where the detected voltage is divided by the same number of bits and the divided voltage is A / D converted.

  In addition, by supplying the voltage V1 to V3 across the voltage dividing resistors R1 to R3 to the A / D converter 11 via the capacitor C, the battery B that is the source of the terminal voltage VB that is the detected voltage; The two end voltages V1 to V3 of the plurality of voltage dividing resistors R1 to R3 can be easily converted by one A / D converter 11 while being insulated from the A / D converter 11.

1 is a circuit diagram showing an embodiment of a voltage detection apparatus 10 that implements a voltage detection method of the present invention. It is a flowchart which shows the process sequence of CPU12a which comprises the voltage detection apparatus 10 of FIG. It is a circuit diagram which shows an example of the conventional voltage detection apparatus.

Explanation of symbols

11 A / D converter (A / D conversion means)
12a CPU (detection means, switching control means, conversion control means)
R1 to R3 Voltage dividing resistor C Capacitor SW1 to SW3 Switching switch SW4 Conversion switch

Claims (3)

A voltage dividing resistor that divides the voltage to be detected;
A / D conversion means for comparing all the voltages across the plurality of voltage dividing resistors with each reference voltage and converting them into digital data;
A voltage detection apparatus comprising: a detection unit configured to detect the detected voltage based on a sum of all digital data obtained by converting the voltage across all terminals. The voltage detection device according to claim 1,
A capacitor,
A switch for connecting both ends of the plurality of voltage dividing resistors to the capacitor;
Switching control means for controlling the switching switch and sequentially connecting both ends of the plurality of voltage dividing resistors to the capacitor;
A conversion switch provided between the capacitor and the A / D conversion means;
Conversion control means for turning on the conversion switch and supplying the voltage across the capacitor to the A / D conversion means each time the connection between the voltage dividing resistor and the capacitor is switched. Voltage detector. Divide the voltage to be detected by multiple voltage dividing resistors,
All the voltages across the plurality of voltage dividing resistors are each compared with a reference voltage and converted into digital data,
A voltage detection method, comprising: detecting the detected voltage based on a sum of all digital data obtained by converting the voltage across all terminals.

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