JPS6057227A - Electronic body temperature measurement temperature circuit - Google Patents

Abstract

PURPOSE:To curtail an average power consumption in the course of measuring a temperature by reducing an electricity conductive ratio of a CR oscillator whose power consumption is the largest. CONSTITUTION:Signals (d), (e) for instructing a selective driving of an oscillation by a thermistor and an oscillation by a reference resistance are generated to a CR oscillator 5 by an oscillation controlling circuit 6. An output of the CR oscillator 5 is counted by a counting circuit 7, and when a count value becomes a prescribed value, an NR signal is outputted to the circuit 6. When an RSTOP signal (i) is made in a FF circuit by the NR signal, etc., and an CR oscillation by a reference oscillator is stopped by this (i) signal, the duty of the (d) signal becomes about 1/2. As a result, an electricity conductive ratio of the CR oscillator whose power consumption is large becomes small, therefore, an average power consumption can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electronic thermometer using a temperature-sensitive element.

[Background of the invention]

Compact electronic thermometers that integrate a temperature measuring part, a circulating part, a display part, a power supply part, and a switch part have become commercially available, but with conventional electronic thermometers, emphasis has been placed on miniaturization.
Many had short battery life. What is a thermometer?
At home, items such as wristwatches are not used every day, but are generally kept in first aid kits for long periods of time and used irregularly in emergencies such as when a person has a fever. Therefore,
It is not desirable for a thermometer to be able to check the battery consumption every day and not be able to use it until it is needed due to insufficient voltage. In order to minimize the possibility of being unable to use the device due to insufficient voltage in an emergency, there are methods to increase the battery capacity and methods to reduce the power consumption, but the battery capacity cannot be increased due to miniaturization. First, electronic thermometers require circuits that consume as little power as possible.

[Purpose of the invention]

The present invention has been made in view of the above requirements, and aims to reduce power consumption. 4. [Summary of the Invention] In the electronic body temperature measurement circuit of the present invention, the linear oscillator with the largest power consumption By energizing at approximately 1/2 full duty, the average power consumption during temperature measurement is reduced.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an overall circuit block diagram of the electronic thermometer, and 1 is a reference clock generator that is turned on and off by a POWI switch. A counter 2 receives the reference clock oscillator as an input, and divides the output of the reference clock generator to produce a signal (b) having a period of about 1.5 seconds. 3 is a register that stores the data of the counter 2, and 4 is a coincidence determination circuit that outputs a signal (EQ)' when the data of the counter 2 and the data of the register 3 match. 5 is a thermistor RTH, a reference resistor) 1 is also a CR oscillator having an EF, a resistor R, and a charging/discharging capacitor C as external components. 6 is the oscillation by the thermistor for the CR oscillator 5,
Signal (d) that commands selective driving of oscillation by the reference resistor
, (e). Oscillation control circuit 6
inputs the output (j) of the coincidence determination circuit 4 and outputs a capture strobe signal (h) to the register 3fC. 7 is a counting circuit that counts the output of the CR oscillator 5, and outputs the output to the NR multiplied signal oscillation control circuit 6 when the counted value reaches a predetermined value. The oscillation control circuit 6 receives the (b) signal from the counter 2 as other input/output, and
A reset signal (C) for the counting circuit 7 and a signal (f) t- for reading the counting result are output. 8 is a maximum value holding circuit that stores all the data of the counting circuit 7; 9 is a circuit that compares the data of the counting circuit 7 and the maximum value holding circuit 8, and when the data of the counting circuit 7 is larger, outputs a signal i)' This is the magnitude comparison circuit COMP that is generated. 10 is a two-person AND gate which receives signals (1) and (f) as inputs. The register 3 stores the data of the counter 2 in response to the signal (h) from the oscillation control circuit 6, and the highest value holding circuit 8 takes in the data of the counting circuit 7 when receiving the output of the AND gate 10. 11 is
12 is a display drive circuit for decoding the binary temperature measurement result stored in the maximum value holding circuit 8 into 7-segment numerical information and driving a liquid crystal display;
It is a 3i digit LCD numeric display.

Next, the operation of the circuit will be explained using a time chart. (
A) is an oscillation ON signal caused by the negative source switch V. When a switch (not shown) is pressed at the start of temperature measurement, the signal becomes "H" and the oscillation of MCK starts.

(b) is a counter output signal that counts all the pulses of the reference clock oscillator 1, and the f'0WER (a) is 6H.
'', at a period of about 1.5 seconds, L n.

The signal (C) is a reset signal for the counting circuit 7, which has the reference clock oscillator 1 amplitude at both the rising and falling edges of the counter output signal.The oscillation by the reference resistor is caused by the signal (d) When the signal is "H", the current is turned on, but this signal rises when the output of the counter 2 is "H".CR oscillator 5
(b) Upon receiving the signal H”k, PL4B, EF・and 几,
C circuit generates sound and outputs the signal (g) to the counting circuit 7.

If we set the time equal to the time when the oscillation curve l for the resistance of the thermistor RTH becomes 20 times the temperature value, and how many pulses it will be for the RREF resistor, and make this eN oscillations, then the oscillation by the reference resistor will be N oscillations. When I counted, NI(,
A signal is output from the counting circuit 7.

Rs'rop is set by the (h) signal, which is the AND output of the NR multiplied signal and (b) signal, and is reset by the A and 8T signals (C). If the C oscillation by the reference oscillator is stopped with this (i) signal, the duty of the d) signal will be approximately 1/2 for the H'' section of the (b) signal.MCK 1 and CR Oscillator 5, ゛15 each ±40% due to source voltage, ambient temperature, external component variation, and IC characteristic variation.
, contains a frequency variation of ±30 cycles, but if the tuning time of the (d) signal is set to 1/2 of that of the (b) signal, the oscillation period of the reference tally clock oscillator 1 becomes faster due to temperature changes and element variations, and C Even if the oscillator 5 becomes the slowest in the same way, the problem that the counting circuit 7 is cleared by A, R8T Shinzuki (C) when the counting circuit 7 counts N oscillations does not occur. (kl) signal, the count number of the counter 2 is taken into the register 3 for a predetermined time, that is, the time until the count of the CR oscillation circuit 5 by the reference resistor REF reaches N. When the counter 2 further counts up and overflows, and the data becomes 0'', the data 'k' of the counting circuit 7
(C) At the same time, the thermistor-on signal TON(e), which causes the CR oscillation circuit including thermistor 1 (, Tl-[, to oscillate instead of the reference grinding resistor RREF (l/j), is activated. stand up

The counting circuit 7 counts the oscillating sound corresponding to the temperature of the thermistor. The counter 2 is counted and amplified until the value stored in the register 3 is reached by the signal (b), and when the data in the counter 2 matches the data in the register 3, an EQ multiplied signal is output from the match determination circuit 4. Ru. The signal (b), which is the output of the EQ multiplication signal counter 2, is gated in the oscillation control circuit 6, and the signal T in FIG.
This becomes a SET signal. The T S T OI) signal (k) that stops the oscillation of the CIt oscillation circuit including the thermistor is '1'.

SET signal (j), A, ) is also sent with ST signal (C
) is made with a frimbufron circuit that is reset.

The current consumption of the reference clock oscillator 1 is 0μA1, and the current consumption of the LCD driver is 1()μA, whereas the bias current of the CR oscillator is at most 300μA. By doing so, the average current consumption can be reduced.

In the embodiment of the present invention, the signals EQ (j) and NR (h) necessary for the temperature measurement sequence are used as energization termination signals, so there is no need for a new circuit for determining a special energization duty. This has the effect of simplifying the circuit configuration.

In the embodiment of the present invention, the energization duty is set to about 1/2, so even if the oscillation frequency of each oscillator ranges from 30 to 40 degrees, there will be no logical problem.

In the embodiment of the present invention, since the sampling time is about 1.5 seconds, there is no problem in practical accuracy as a thermometer, and it is possible to provide all power-saving electronic thermometers. ′
In other words, the skin surface temperature under normal conditions at the measurement location reaches a value close to body temperature approximately 2 to 3 minutes after the start of temperature measurement.
The rate of temperature rise at this time is 0.1°C for 710 seconds, which is sufficiently fast even if the sampling time is about 1.5 seconds (1°rl), and the temperature rise immediately after sampling can be read.

In the electronic body temperature measurement circuit of the present invention, the CIL oscillator, which consumes a large amount of power, is not continuously operated.
Since there is a non-energizing period shown in the shaded area of ale), the average power consumption can be completely reduced. Therefore, the battery life can be extended, and an electronic thermometer with the following effects can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the electronic body temperature measurement circuit of the present invention, and FIG.
The figure is a timing chart of each signal.

Claims (1)

[Claims] 1. In an electronic thermometer that switches and uses a reference time setting resistor and a thermistor as elements of a CR oscillator, and converts the thermistor temperature kA/D by counting the number of oscillations of the CR oscillator. , the CR oscillator is started by the counter output of the reference clock oscillator provided for each oscillation metal, and when the CR oscillator finishes oscillating the circuit including gold in the reference time setting resistor once and oscillating the circuit including the thermistor once, the CR oscillator An electronic body temperature measurement circuit characterized by completely stopping the supply of electricity to the oscillator. 2. During the oscillation period by the reference resistor, when the number of oscillations of the electronic body temperature sensor matches a predetermined value, it is used as an oscillation stop signal and the energization is stopped. circuit. 3. The electronic body temperature measurement circuit according to claim 1, wherein during the period of oscillation by the thermistor, energization is stopped according to the count value of a reference Cronk oscillator provided separately. 4. The electronic body temperature measurement circuit according to claim 1, characterized in that the temperature measurement period per time is about 1.5 seconds, and the energization date of the CR oscillator is set to 1.