JPH07336881A - Power supply device and power supply method thereof - Google Patents

Abstract

PURPOSE:To provide a power supply device and a power supply method thereof detecting the lowering of battery residue without depending upon load and capable of properly stopping the power supply. CONSTITUTION:A power supply device has a voltage divider resistor 3 detecting voltage V2 obtained by dividing battery voltage V1, a current detecting resistor 4 detecting load currents I, a limiter diode 5 connected in parallel with the current detecting resistor 4, a differential amplifier 6 amplifying voltage generated at both ends of the current detecting resistor 4, a regulator 7 generating reference voltage Vs, a comparator 8 comparing reference voltage Vs and divided voltage V2, and a control section 9 controlling the supply of power in response to an output from the comparator 9. Battery voltage 1 is reduced by the internal impedance of the power supply device with the increase of load currents I, but divided voltage V2 corresponding to battery voltage 1 is increased and corrected by the differential amplifier 6, thus detecting battery residue in a small quantity, then preventing the stoppage of the supply of power. Over-discharge can be prevented by limiting increase and correction to excess load currents 1.

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 having a battery as a main power supply and a power supply method thereof.

[0002]

2. Description of the Related Art Conventionally, as this type of power supply device, there is known a power supply device which detects a battery voltage and stops power supply when the detected battery voltage falls below a set voltage.

[0003]

However, since the battery has an internal impedance, the battery voltage fluctuates depending on the load current, and the battery voltage decreases if the load current is large regardless of the remaining battery amount. In this case, even if the remaining battery level is sufficient, there is a problem that the power supply is stopped due to the decrease in the battery voltage and the device cannot be used, or the device is interrupted during use.

Further, when using a device whose load current value is known, it is possible to correct the battery voltage according to the load current value only when the device is used.
There was a problem that the load current had to be known in advance.

Further, when the load fluctuates, for example, when the printer is driven, the load current was normally 100 mA, but during the printing operation, the load current is increased to 5 A. At this time, the battery level is sufficient, but the battery level is warned each time printing is performed, and the printing operation is stopped. If such a load variation is large, there is a risk of over-discharging rather than correction.

[0006] Therefore, an object of the present invention is to provide a power supply device and a power supply method thereof, which can detect that the remaining battery level has decreased without being influenced by a load and can appropriately stop the power supply.

[0007]

In order to achieve the above object, a power supply device according to claim 1 of the present invention comprises voltage detection means for detecting a battery voltage, and the detected voltage exceeds a set voltage. When a power supply device that supplies power to the load, current detection means for detecting a current flowing through the load,
Voltage correction means for correcting the voltage detected by the voltage detection means according to the detected current, voltage comparison means for comparing the corrected voltage with a set voltage, and the result of the comparison, the correction Supply stopping means for stopping the power supplied to the load when the applied voltage falls below the set voltage.

According to a second aspect of the power source device of the present invention, in the power source device of the first aspect, the voltage correcting means corrects the detected voltage according to the upper limit value when the current flowing through the load exceeds the upper limit value. Correction limiting means for

According to a third aspect of the present invention, there is provided a power supply method for a power supply device which detects a battery voltage and supplies power to the load when the detected voltage exceeds a set voltage. The flowing current is detected, the voltage detected by the voltage detecting means is corrected according to the detected current, the corrected voltage is compared with a set voltage, and as a result of the comparison, the corrected voltage is corrected. When the voltage falls below the set voltage, the power supplied to the load is stopped.

[0010]

In the power supply device according to the first aspect of the present invention, when power is supplied to the load when the voltage detected by the voltage detecting means exceeds the set voltage, the current detecting means detects the current flowing through the load, The voltage correction means corrects the voltage detected by the voltage detection means according to the detected current, the voltage comparison means compares the corrected voltage with the set voltage, and as a result of the comparison, the supply stopping means. The power supplied to the load is stopped when the corrected voltage falls below the set voltage.

In the power supply device according to the second aspect, when the current flowing through the load exceeds the upper limit value, the correction limiting means provided in the voltage correcting means corrects the detected voltage according to the upper limit value. .

[0012]

Embodiments of the power supply device and the power supply method thereof according to the present invention will be described below. FIG. 1 is a circuit diagram showing the configuration of the power supply device of this embodiment. In the figure, 1 is a battery as a main power source, 2 is a power switch, 3 is a voltage dividing resistor for dividing a power source voltage, 4 is a current detecting resistor, 5 is a limiter diode for limiting a potential difference generated across the current detecting resistor 4. , 6 are potential differences I × R generated across the current detection resistor 4.
Is a differential amplifier that amplifies. The cathode side of the diode 5 is a regulator 7 that generates a reference voltage Vs, a load RL
And the power supply circuit 10. The load RL is a printing unit of a printer (not shown). 8 is the voltage V2 divided by the voltage dividing resistor 3 and the reference voltage Vs of the regulator 7.
When the divided battery voltage V2 becomes lower than the reference voltage Vs, the output voltage Vc of the comparator 8 becomes L level and notifies the control unit 9 that the remaining battery level is low. The control unit 9 controls the printing operation of the printer, and outputs the output voltage Vc of the comparator 8.
Performs the printing operation at H level and stops the printing operation at L level. Reference numeral 10 is a power supply circuit that supplies a stabilized power supply voltage to the control unit 9.

In the power supply device having the above structure, when the battery voltage is V1, the resistance value R of the current detection resistor 4, the current flowing through the current detection resistor 4 is I, and the voltage divided by the voltage dividing resistor 3 is V2, The voltage V2 is represented by Equation 1.

[0014]

## EQU1 ## V2 = K1 × V1 + K2 × I × R Here, K1 and K2 are positive constants.

The limiter diode 5 limits the potential difference I × R generated across the current detecting resistor 4 to the forward drop voltage VF of the diode, and the current exceeding the forward drop voltage VF flows through the limiter diode 5. . Therefore, I
When xR <VF, the voltage V2 is expressed by Equation 1,
When I × R = VF is reached, no further increase in the potential difference I × R occurs, so the voltage V2 is expressed by Equation 2.

[0016]

## EQU00002 ## V2 = K1.times.V1 + K2.times.VF The operation characteristics of this power supply device will be described. FIG. 2 is a timing chart showing the voltage-current characteristics of the power supply device.
In the figure, a section (A) shows a case where the load current I is held at a constant value and the battery voltage V1 is reduced at a constant rate, and a section (B) holds the battery voltage V1 at a constant value and the load current The case where I is increased at a constant rate is shown.

In the section (A), the voltage V2 of the voltage dividing resistor 3 also decreases in proportion to the decrease of the battery voltage V1, and when the voltage V2 becomes lower than the reference voltage Vs at the time point h, the output voltage Vc of the comparator 8 becomes L level. Becomes It is detected from this L level that the battery level is low.

In the section (B), the potential difference I × R generated across the current detection resistor 4 as the load current I increases.
Will increase. At this time, the battery voltage V1 is constant,
Since the output voltage Vd thereof increases with the increase of the potential difference I × R input to the differential amplifier 6, the voltage V of the voltage dividing resistor 3 is increased.
2 is increased and corrected. The increase-corrected voltage V2 is at time i
Becomes higher than the reference voltage Vs. As a result, the output of the comparator 8 becomes H level. At this time i, the control unit 9 is informed that the remaining battery level is sufficient.

Further, the load current I continues to increase, and the time j
Then, I × R = VF, but even if the load current I is increased thereafter, the increase of the potential difference I × R is suppressed by the limiter diode 5, and the increase correction is limited. Therefore, the voltage V2 of the voltage dividing resistor 3 is held at a constant value and does not change.

As described above, since the voltage V2 of the voltage dividing resistor 3 is corrected to increase as the potential difference I × R increases between the time points i to j, the remaining battery level is not detected to be small, and
Power supply stoppage can be prevented. Further, after the time point j, the potential difference I × R which increases with the increase of the load current I is limited by the limiter diode 5, so the overdischarge of the battery is prevented by suppressing the correction for further increasing the voltage V2 of the voltage dividing resistor 3. it can.

Next, a case where the printer is actually used as a power source for the printing unit will be described. FIG. 3 is a timing chart showing the voltage and current characteristics during the printing operation of the printer. The current I flowing through the current detection resistor 4 is usually 100 mA when printing is not performed, but when printing is performed, the load current sharply increases and may increase to 5 A or more (see D, E and F in the same figure). ). In the cases of D and E in the same figure, when the load current, that is, the load current I flowing through the current detection resistor 4, increases, the voltage V2 of the voltage dividing resistor 3 is increased and corrected, so that the battery voltage V1 decreases due to the internal impedance of the battery. It is possible to suppress a decrease in the voltage V2 of the voltage dividing resistor 3 as compared with the ratio. Therefore, the battery level is not detected so low that the printer stops every time printing is performed.

Further, in the case of FIG. 4F, the load current I is rapidly increased, and the potential difference I × R generated across the current detection resistor 4 is limited by the limiter diode 5, so that the voltage difference is further exceeded. There is no increase correction and it is possible to prevent sudden overdischarge of the battery.

[0023]

According to the power supply device of the first aspect of the present invention, when power is supplied to the load when the voltage detected by the voltage detection means exceeds the set voltage, the current is flown to the load by the current detection means. The current is detected, the voltage detected by the voltage detection unit is corrected by the voltage correction unit according to the detected current, the corrected voltage is compared with the set voltage by the voltage comparison unit, and the As a result, since the electric power supplied to the load is stopped when the corrected voltage is lower than the set voltage by the supply stopping means, it is possible to accurately detect the decrease in the remaining battery level without knowing the load current in advance.
It is possible to prevent the device from stopping during use even though the battery level is sufficient.

According to the power supply device of the second aspect,
When the current flowing through the load exceeds the upper limit value, the detected voltage is corrected according to the upper limit value by the correction limiting unit provided in the voltage correction unit, so that when the load fluctuation is large, over-discharge occurs. You can avoid the risk of becoming.

Further, according to the power supply method of the power supply device of the third aspect, in the power supply method of the power supply device, which detects the battery voltage and supplies power to the load when the detected voltage exceeds the set voltage. A current flowing through the load is detected, the voltage detected by the voltage detecting means is corrected according to the detected current, the corrected voltage is compared with a set voltage, and the result of the comparison is Since the power supplied to the load is stopped when the corrected voltage is lower than the set voltage, it is possible to accurately detect the decrease in the battery remaining amount without knowing the load current in advance, and the battery remaining amount is sufficient. Nevertheless, it is possible to prevent the device from stopping during use.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a power supply device according to an embodiment.

FIG. 2 is a timing chart showing current-voltage characteristics of the power supply device.

FIG. 3 is a timing chart showing voltage and current characteristics during a printing operation of the printer.

[Explanation of symbols]

 1 ... Battery 3 ... Dividing resistance 4 ... Current detection resistance 5 ... Limiter diode 6 ... Differential amplifier 7 ... Regulator 8 ... Comparator 9 ... Control unit 10 ... Power supply circuit

Claims (3)

[Claims] 1. A power supply device comprising voltage detection means for detecting a battery voltage, which supplies power to a load when the detected voltage exceeds a set voltage, and current detection means for detecting a current flowing through the load, Voltage correction means for correcting the voltage detected by the voltage detection means according to the detected current; voltage comparison means for comparing the corrected voltage with a set voltage; and, as a result of the comparison, the correction A power supply device for stopping the power supplied to the load when the applied voltage falls below the set voltage. 2. The voltage correcting means comprises correction limiting means for correcting the detected voltage according to the upper limit value when the current flowing through the load exceeds the upper limit value. 1. The power supply device according to 1. 3. A power supply method for a power supply device which detects a battery voltage and supplies power to a load when the detected voltage exceeds a set voltage, wherein a current flowing through the load is detected, and the detected current is detected. According to the above, the voltage detected by the voltage detecting means is corrected, the corrected voltage is compared with a set voltage, and as a result of the comparison, the load is applied to the load when the corrected voltage is lower than the set voltage. A power supply method for a power supply device, characterized in that the power supply is stopped.