JPH1123679A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a battery life display from becoming unstable near a threshold due to variation of impedance inside a battery by writing battery life data into a nonvolatile memory when a battery voltage being inputted by an A/D converter has become lower than a first voltage and reading the data at a specific timing. SOLUTION: A control part 5 inputs a battery voltage via an A/D converter 6 when a switch 2 is on, and judges that a battery life ended when the battery voltage has become lower than the assurance value at the lower side of the battery voltage that can be boosted by a regulator 3. Accordingly, a battery life display means 7 reports that the battery life has been reached, thus promoting the replacement of a battery. When the control part 5 judges that the battery life ended, it stores the data in a non-volatile memory 17 and reads the information when a power is turned on, thus preventing the battery life display from flickering due to a value close to a threshold even if the battery voltage becomes unstable due to the impedance inside the battery 1 and current fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly, to a power supply device for an apparatus using a battery such as an ear canal thermometer for obtaining and displaying a body temperature from infrared rays emitted near the human eardrum.

[0002]

2. Description of the Related Art Conventionally, this kind of power supply device is generally as shown in FIG. As a specific example, here, an ear canal thermometer that obtains and displays body temperature from infrared rays emitted near the human eardrum is shown. In FIG. 7, a battery 1 configured by connecting two dry batteries in series supplies 3 V to a regulator 3 through a switch 2. Regulator 3 is DC-D
The C converter boosts the voltage to 5 V, stabilizes the voltage, and supplies power to the load circuit 4.

[0003] The control unit 5 operates while the switch 2 is on.
The battery voltage is input via the / D converter 6, and when the regulator voltage falls below the low voltage side guaranteed value (tentatively, 2.5V) of the battery voltage that can be boosted to 5V, it is determined that the battery life is reached. In response to this, the battery life display means 7 (using an LCD with low power consumption) notifies the user of the battery life and prompts the user to replace the battery.

Since the battery 1 has an internal impedance, the voltage becomes unstable due to current fluctuation. Therefore, a hysteresis is set for the threshold value so that the display does not flicker even when the value fluctuates just before the threshold value.

FIG. 8 is an internal block diagram of the load circuit 4. In the sensor unit 8, the light collecting means 9 formed of a waveguide collects infrared light emitted from the vicinity of the eardrum and collects the infrared light on the pyroelectric sensor 10. The chopper 11 reciprocates between the focusing means 9 and the pyroelectric sensor 10 and periodically blocks infrared rays (the chopper is driven by a piezoelectric element).

The inside of the chopper 11 is a mirror surface,
The pyroelectric sensor 10 outputs an AC signal proportional to the difference between the measurement target and the temperature of the pyroelectric sensor 10 (hereinafter, referred to as self-temperature) by alternately viewing the measurement target and the pyroelectric sensor 10 by the chopper 11. The temperature of the object to be measured can be obtained by back-calculating the difference between the object to be measured and the self-temperature from the AC signal and adding the self-temperature obtained by the thermistor 12.

[0007] The signal processing circuit 13 is an AC amplifier for amplifying a minute AC signal emitted from the pyroelectric sensor 10 to a voltage that can be taken into the microcomputer 14. The load drive circuit 15 needs to output a high-voltage pulse in order to operate the chopper 11 with a piezoelectric element, and is constituted by a booster circuit. The booster circuit operates only at the time of measurement because the efficiency decreases and the current consumption increases in proportion to the boost ratio. The temperature display means 16 is constituted by an LCD like the battery life display means 7.

[0008]

However, the conventional power supply has the following problems.

(1) In general, the internal impedance of a dry battery tends to fluctuate depending on the temperature and the like. In particular, the output voltage of a discharged battery tends to be unstable. Even if flicker does not occur due to the addition of hysteresis, the indication of battery replacement may be turned on or off at every measurement near the threshold, which may lead to misunderstanding of the user.

(2) As means for solving the above problems,
Once the battery life is judged, there is a method of continuing the display, but when the power switch is turned off, the state is released, so near the threshold value, the battery replacement display will be turned on or off every time the power is turned on. This can lead to misunderstanding of the user.

(3) In the conventional power supply device, the limit point at which performance can be guaranteed is determined from the output voltage of the battery and the input / output characteristics of the regulator obtained in advance through experiments. Since there is a variation, it is necessary to indicate that the battery is to be replaced before the actual limit.

(4) In general, when the battery is energized, the temperature rises due to heat generated by the internal impedance, thereby lowering the internal impedance, so that the voltage increases with the passage of time from the energization. In addition, for a load having a large current variation, the voltage variation of the load itself is also added, so that it has been difficult to accurately detect the battery voltage.

(5) Although the load drive circuit has a built-in booster circuit, the duty ratio is the highest until the secondary voltage reaches the set value, so that a large rush current flows every time the measurement is started. On the other hand, the regulator has a transient characteristic caused by a sudden current fluctuation even within the current supply capacity. Therefore, if a rush current flows through the load drive circuit at the start of the measurement, the power supply voltage of the microcomputer changes suddenly and suddenly with each measurement, which may cause the microcomputer to run away.

(6) The regulator has a current supply capability, and has a characteristic that the voltage drops when a current exceeding the current supply capability is applied. Here, if the inrush current of the load drive circuit flows and exceeds the current supply capability of the regulator, the power supply voltage of the microcomputer temporarily drops, whereby the reset is applied, and the battery may run out prematurely.

The present invention solves the above-mentioned problems, and provides a power supply device that can solve the above-mentioned problems with a simple configuration.

[0016]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a battery, a switch for turning on and off the power supply of the battery, a regulator for supplying power by the switch and maintaining a constant voltage, and a power supply from the regulator. A load circuit, an A / D converter for inputting a battery voltage from the switch, a non-volatile memory for holding data even when the switch is off, and a battery voltage input by the A / D converter for the first voltage. The battery life data is described in the non-volatile memory when it falls short, and the control unit reads the battery life data at a predetermined timing. The battery life display means displays the result of reading the battery life data.

According to the above invention, the battery supplies power to the regulator via the switch, the regulator stabilizes the voltage and supplies power to the load circuit, and the control unit calculates the battery life from the battery voltage input by the A / D converter. Since the determination is made and described in the nonvolatile memory, once the battery life is determined, the determination is retained even after the power is turned off.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a battery, a switch for turning on and off the power supply of the battery, a regulator for supplying power by the switch to keep the voltage constant, a load circuit supplied from the regulator, An A / D converter for inputting a battery voltage from a subsequent stage, a nonvolatile memory for holding data even when the switch is turned off, and a battery life data when the battery voltage input by the A / D converter falls below a first voltage And a controller for reading the battery life data at a predetermined timing and a battery life display means for displaying the result of reading the battery life data.

The battery supplies power to the regulator via a switch, the regulator stabilizes the voltage and supplies power to the load circuit, and the control unit determines the battery life from the battery voltage input by the A / D converter to determine the battery life. Since it is written in memory,
Once the battery life is determined, the determination is retained even after the power is turned off.

Further, when the battery voltage inputted by the A / D converter exceeds a second voltage higher than the first voltage, the control unit erases the battery life data described in the nonvolatile memory. is there.

Then, the control unit inputs the battery voltage by the A / D converter, and determines the life of the battery according to the first invention.
Since the battery life data described in the non-volatile memory is erased when the voltage exceeds the second voltage higher than the second voltage, a stable battery life determination release operation can be obtained by the hysteresis effect.

Further, the A / D converter inputs a power supply voltage from the secondary side of the regulator at the timing when the load circuit is operating.

The control unit inputs the secondary voltage of the regulator at the timing when the load circuit is performing the temperature detecting operation by the A / D converter, and thus directly detects the limit of the current supply capability of the regulator.

Further, the A / D converter inputs the power supply voltage from the primary side of the regulator at a timing immediately after the switch is turned on, and the load circuit does not operate for a predetermined time after the switch is turned on.

Then, the control unit inputs the voltage on the primary side of the regulator at the timing when the battery cools down and the power consumption is low immediately after the switch is turned on by the A / D converter. On the other hand, the load circuit does not operate during this time. , Input the lowest battery voltage stably.

Also, a battery, a regulator supplied from the battery and maintaining a constant voltage, a constant current circuit supplied from the regulator to limit the current to a predetermined value or less, and a load drive circuit supplied from a subsequent stage of the constant current circuit And a microcomputer supplied with power from a stage preceding the constant current circuit.

The chopper intermittently blocks infrared rays, the signal processing circuit amplifies the electric signal output from the pyroelectric sensor, and the constant current circuit limits the power supply from the regulator to a predetermined current or less. The load drive circuit supplies power from the constant current circuit to drive the chopper, and the temperature calculation unit supplies power from the regulator to calculate the output values of the signal processing circuit and the thermistor and convert them to temperature. It is less susceptible to a voltage drop due to an inrush current when turned on, and operates stably.

Further, the current set value of the constant current circuit is set lower than the current that can be supplied by the regulator and higher than the current when the load drive circuit is stable.

Since the constant current circuit limits the current at a current value lower than the current that can be supplied by the regulator when the load driving circuit is turned on, the temperature calculation unit is affected by the voltage drop due to the rush current when the load driving unit is turned on. However, when the load driving section is stable, it supplies a current higher than the current required by the load driving section.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of a power supply device according to Embodiment 1 of the present invention. In FIG.
The batteries 1 connected in series are supplied with 3 V to the regulator 3 via the switch 2. Regulator 3 is DC
A DC converter, which boosts the voltage to 5 V, stabilizes the voltage, and supplies power to the load circuit 4;

While the switch 2 is on, the control unit 5
The battery voltage is input via the / D converter 6, and when the regulator 3 falls below the low-side guaranteed value of the battery voltage that can be boosted to 5V (assuming it is 2.5V), it is determined that the battery life has expired. In response to this, the battery life display means 7 (using an LCD with low power consumption) notifies the user of the battery life and prompts the user to replace the battery. The above is the same as the conventional example.

Once the control unit 5 determines that the battery life has expired, it stores it in the nonvolatile memory 17 and reads out the information when the power is turned on. As a result, even if the battery voltage becomes unstable due to the internal impedance and the current fluctuation of the battery 1, the battery life display does not flicker just below the threshold value.

(Embodiment 2) FIG. 2 is a flowchart of the control unit 5 of the power supply unit according to Embodiment 2 of the present invention. Example 1
, The predetermined voltage (0.
When the voltage exceeds the voltage V2 which is higher by 2 to 0.3 V), the battery life data described in the nonvolatile memory 17 is erased.

As a result, the battery life data held while the power is turned off in the first embodiment is released when the battery is replaced with a new battery. Further, a hysteresis effect caused by providing a voltage difference between V1 and V2 provides A stable operation can be obtained.

(Embodiment 3) FIG. 3 is a block diagram of a power supply device according to Embodiment 3 of the present invention. In FIG. 3, the control unit 5 detects the secondary voltage of the regulator 3 via the A / D converter 6 at the timing when the temperature of the load circuit 4 is detecting the temperature, and determines that the battery life is reached when the voltage falls below a predetermined voltage. . The regulator 3 is a DC-DC converter. When the voltage of the battery 1 falls below a predetermined voltage, the regulator 3 cannot be boosted, and the secondary voltage drops. Generally, the current consumption of the load circuit 4 increases during the temperature measurement, so that the boosting condition of the regulator 3 at that time is the strictest.
If the voltage on the secondary side of the regulator 3 is stable, the detection accuracy will not be reduced. Therefore, observing the voltage drop at this point will most accurately grasp the life of the system.

(Embodiment 4) FIG. 4 is a timing chart showing the relationship between the time elapsed since the switch 2 was turned on and the battery voltage of the power supply unit according to Embodiment 4 of the present invention. The primary-side voltage of the regulator 3 that rises when the switch 2 shown in FIG. 3 is turned on enters a Tb period in which the internal impedance decreases due to heat generation and a voltage rises through a stable Ta period. When the temperature of the battery becomes stable, the voltage starts rising during the Tc period, but when the load is operated during the Td period, the current temporarily increases and the voltage drops.

This phenomenon appears more remarkably when the room temperature is low than when it is high. This is because the temperature rise due to heat generation is large, and the internal impedance changes accordingly.

On the other hand, since the load circuit 4 does not operate during the Te period from the time when the switch 2 is turned on, the battery life can be determined very stably by taking the battery voltage during the Ta period.

(Embodiment 5) FIG. 5 is a block diagram of a power supply device according to Embodiment 5 of the present invention. In the sensor unit 8 shown in FIG. 5, the light collecting means 9 composed of a waveguide collects infrared rays emitted from the vicinity of the eardrum and focuses the infrared rays on the pyroelectric sensor 10.
The chopper 11 reciprocates between the focusing means 9 and the pyroelectric sensor 10 and periodically blocks infrared rays (the chopper is driven by a piezoelectric element).

The inside of the chopper 11 is a mirror surface,
The pyroelectric sensor 10 outputs an AC signal proportional to the difference between the temperature of the measurement target and the temperature of the pyroelectric sensor 10 by alternately viewing the measurement target and itself by the chopper 11. The difference between the object to be measured and the self temperature is calculated back from the AC signal, and the thermistor 12
By adding the self-temperature obtained in the above, the temperature of the measurement target can be obtained.

The signal processing circuit 13 is an AC amplifier for amplifying a minute AC signal emitted from the pyroelectric sensor 10 to a voltage that can be taken into the microcomputer 14. The load drive circuit 15 needs to output a high-voltage pulse in order to operate the chopper 11 with a piezoelectric element, and is constituted by a booster circuit. Since the efficiency of the booster circuit decreases and the current consumption increases in proportion to the boost ratio, the booster circuit is operated only during measurement. The temperature display means 16 is constituted by an LCD like the battery life display means 7. The above is the same as the conventional example.

In the load drive circuit 15, an inrush current flows at the start of the operation of the chopper 11, and if it is left as it is, the entire secondary voltage of the regulator 3 drops.
Supply current via With this configuration, the load driving circuit 15
When turned on, the secondary side voltage of the constant current circuit 18 decreases, but the primary side hardly decreases. Therefore, the signal processing circuit 13 and the microcomputer 14 which require a stable power supply are configured to take power from this.

(Embodiment 6) FIG. 6 is a graph showing output characteristics of a power supply device according to Embodiment 6 of the present invention, and is a graph of the output voltage and output current (VI characteristics) of the regulator 3 shown in FIG.

If the voltage on the secondary side is equal to or less than the predetermined current, feedback control is applied and a constant voltage can be maintained. However, the voltage starts decreasing at a certain point. The current at this time is represented by I
1 and the current consumption during stable operation of the load drive circuit 15 is I3
, The set value I2 of the constant current circuit 18 is I1> I2
> I3 is set.

In the battery life of such a system, since the power supply voltage of the microcomputer is reduced due to the rush current when the load drive circuit 15 is turned on and the system is reset, the rush current is suppressed to suppress the reduction of the power supply voltage. The service life can be further extended.

[0047]

As described above, the present invention has the following advantageous effects.

(1) Since the fact that the battery voltage has decreased and the battery life has expired is stored in the non-volatile memory, the battery life is maintained even if the power is turned off once. The life determination is not switched every time the power is turned on even at the threshold. Further, even when the battery voltage becomes unstable due to the internal impedance and the current fluctuation of the battery, the life determination is not switched every time the power is turned on.

(2) When a predetermined voltage higher than the voltage determined as the battery life is detected, the battery life data in the non-volatile memory is erased. Therefore, the battery life data that can be retained even when the power is turned off is replaced with a new battery. Can be canceled when. In addition, a stable determination operation can be obtained by the hysteresis effect in which the voltage to be released is set higher than the voltage for determining the battery life.

(3) The voltage on the secondary side of the power supply regulator (the voltage supplied to the load circuit) is measured during the temperature measurement to determine the battery life. Therefore, the internal impedance of the battery and the boosting capability of the power supply regulator are determined. Regardless of the variation, the battery life can be accurately detected.

(4) Since the voltage on the primary side of the power regulator is measured immediately after the switch is turned on and the operation of the load circuit is prohibited during that period, the detection of the battery voltage is affected by the internal impedance of the battery and the room temperature. I will not receive it.
Further, the detection of the battery voltage is not affected by the load fluctuation.

(5) The load driving circuit for driving the chopper is supplied with power from the power supply regulator via the constant current circuit, and the microcomputer and the signal processing circuit are supplied with power directly from the power supply regulator. The inrush current at the time is suppressed by a constant current circuit so that the power supply voltage of the microcomputer is hardly reduced, and the life of the battery can be extended. Also,
Since the power supply voltage of the sensor signal processing circuit is stabilized, the accuracy is improved.

(6) Since the setting of the constant current circuit is set to be equal to or less than the current supply capability of the power supply regulator, the inrush current during the operation of the load drive circuit is suppressed by the constant current circuit, so that the power supply voltage of the microcomputer can be reduced. So that the battery life can be further extended. Further, since the power supply voltage of the sensor signal processing circuit is extremely stable, further improvement in accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply device according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a control unit of a power supply device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a power supply device according to a third embodiment of the present invention.

FIG. 4 is a timing chart of a power supply device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a power supply device according to a fifth embodiment of the present invention.

FIG. 6 is an output characteristic diagram of a constant current circuit of a power supply device according to a sixth embodiment of the present invention.

FIG. 7 is a block diagram of a conventional power supply device.

FIG. 8 is a block diagram of a load circuit of a conventional power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 2 Switch 3 Regulator 4 Load circuit 5 Control part 6 A / D converter 7 Battery life display part 17 Non-volatile memory

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiyuki Tanaka 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A battery, a switch for turning on and off the power supply of the battery, a regulator for supplying power by the switch and maintaining a constant voltage, a load circuit supplied from the regulator, and a battery voltage input from a subsequent stage of the switch. A
An A / D converter, a non-volatile memory that retains data even when the switch is off, and a battery life data described in the non-volatile memory when the battery voltage input by the A / D converter falls below a first voltage. And a power supply device comprising: a control unit that reads the battery life data at a predetermined timing; and a battery life display unit that displays a result of reading the battery life data. 2. The control section, when the battery voltage input to the A / D converter exceeds a second voltage higher than the first voltage,
The power supply device according to claim 1, wherein the battery life data described in the nonvolatile memory is erased. 3. The power supply device according to claim 1, wherein the A / D converter inputs a power supply voltage from a secondary side of the regulator at a timing when the load circuit is operating. 4. The A / D converter receives a power supply voltage from a primary side of a regulator at a timing immediately after a switch is turned on, and a load circuit does not operate for a predetermined time after the switch is turned on. Item 7. The power supply according to Item 1. 5. A battery, a regulator supplied from the battery and maintaining a constant voltage, a constant current circuit supplied from the regulator to limit the current to a predetermined value or less, and a load driving circuit supplied from a subsequent stage of the constant current circuit. And a power supply device comprising a microcomputer to which power is supplied from a stage preceding the constant current circuit. 6. The power supply device according to claim 5, wherein a current set value of the constant current circuit is set lower than a current that can be supplied by the regulator and higher than a current when the load drive circuit is stable. 7. A load circuit comprising: a light collecting means for collecting infrared light; a pyroelectric sensor disposed on an optical axis of the light collecting means for converting the infrared light into an electric signal; A chopper intermittently intercepting the infrared light between the electric sensors, a thermistor thermally coupled to the pyroelectric sensor, a signal processing circuit for amplifying an output signal of the pyroelectric sensor, and a load driving circuit for driving the chopper The power supply device according to any one of claims 1 to 6, further comprising: a microcomputer that calculates a temperature from the signal processing circuit and an output signal of the thermistor; and a temperature display unit that displays a calculation result of the microcomputer.