JP3274025B2 - Power supply device and power supply method thereof - Google Patents

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 using a battery as a main power supply and a power supply method therefor.

[0002]

2. Description of the Related Art Heretofore, as this type of power supply device, there has been 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 due to the load current, and the battery voltage drops when the load current is large regardless of the remaining battery level. In this case, even if the remaining battery power is sufficient, there is a problem that the power supply is stopped due to a decrease in the battery voltage and the device cannot be used, or the device is interrupted during use.

When using a device whose load current value is known, it is conceivable to correct the battery voltage according to the load current value only when using the device.
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 is normally 100 mA, but during a printing operation, the load current is increased to 5 A. At this time, the remaining battery level is sufficient, but a warning of the remaining battery level is issued every time printing is performed, and the printing operation is stopped. When such a load fluctuation is large, there is a danger of overdischarging by correction.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a power supply device capable of detecting that the remaining battery level has decreased without being influenced by a load and appropriately stopping the power supply, and a power supply method thereof.

[0007]

In order to achieve the above object, a power supply device according to a first aspect of the present invention includes voltage detecting means for detecting a battery voltage, and the detected voltage is lower than a set voltage. When the power supply to stop the power to the load, current detection means for detecting the current flowing to the load,
Depending on the detected current, and a voltage correction means for correcting the detected voltage by said voltage detecting means, said load
When the flowing current exceeds the set upper limit, the voltage
A voltage that sets the voltage corrected by the correction means to a predetermined voltage
Correction limiter, the voltage corrector, and the voltage corrector.
Voltage comparing means for comparing the voltage corrected by the control means with the set voltage, and supply stopping means for stopping power supplied to the load when the corrected voltage falls below the set voltage as a result of the comparison. Prepare.

[0008]

According to a second aspect of the present invention, there is provided a power supply method for a power supply device, comprising detecting a battery voltage, and detecting the set voltage with the detected voltage.
In a power supply method of a power supply device for stopping power to a load when the power falls below , a current flowing to the load is detected, and if the detected current does not exceed an upper limit value, the current is detected according to the detected current. , corrected before dangerous out voltage, is the detection
If the detected current exceeds the upper limit, the detected voltage
Was corrected to a predetermined voltage, is compared with the setting voltage and the corrected voltage, the result of the comparison, the corrected voltage to stop the power supplied to the load when below the set voltage.

[0010]

[0011]

[0012]

Next, an embodiment of a power supply device and a power supply method of the present invention will be described. FIG. 1 is a circuit diagram showing a configuration of the power supply device of the present embodiment. In the figure, 1 is a battery which is a main power supply, 2 is a power switch, 3 is a voltage dividing resistor for dividing a power supply voltage, 4 is a current detecting resistor, 5 is a limiter diode for limiting a potential difference generated between both ends of the current detecting resistor 4. , 6 represent a potential difference I × R generated at both ends of the current detection resistor 4.
Is a differential amplifier that amplifies the current. The cathode side of the diode 5 has a regulator 7 for generating a reference voltage Vs and a load RL.
And the power supply circuit 10. The load RL is a printing unit of a printer (not shown). Reference numeral 8 denotes a voltage V2 divided by the voltage dividing resistor 3 and a 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 controller 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 the H level, and stops the printing operation at the L level. A power supply circuit 10 supplies a stabilized power supply voltage to the control unit 9.

In the power supply device having the above configuration, if 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 Expression 1.

[0014]

V1 = K1 × V1 + K2 × I × R where K1 and K2 are positive constants.

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

[0016]

V2 = K1.times.V1 + K2.times.VF The operating characteristics of this power supply 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 kept at a constant value and the battery voltage V1 is reduced at a constant rate, and a section (B) shows that the battery voltage V1 is kept at a constant value and the load current is kept constant. This shows a case where I is increased at a constant rate.

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 remaining battery level is low.

In the section (B), a potential difference I × R generated at both ends of the current detection resistor 4 as the load current I increases.
Increases. At this time, although the battery voltage V1 is constant,
Since the output voltage Vd increases in accordance with the increase in the potential difference I × R input to the differential amplifier 6, the voltage Vd of the voltage dividing resistor 3 is increased.
2 is corrected for increase. The voltage V2 corrected for increase is at the time point i.
Becomes higher than the reference voltage Vs. As a result, the output of the comparator 8 becomes H level. At this time point i, the controller 9 is informed that the remaining battery level is sufficient.

Further, the load current I continues to increase, and the time j
Then, 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 maintained at a constant value and does not change.

As described above, between the time points i and j, the voltage V2 of the voltage dividing resistor 3 is corrected to increase as the potential difference I × R increases.
Stop of power supply can be prevented. Further, after time j, the potential difference I × R that increases with the increase of the load current I is limited by the limiter diode 5, so that the overdischarge of the battery is prevented by suppressing the correction that further increases 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 section of the printer will be described. FIG. 3 is a timing chart showing voltage and current characteristics during a printing operation of the printer. The current I flowing through the current detection resistor 4 when printing is not performed is usually 100 mA, but when printing is performed, the load current rapidly increases and may increase to 5 A or more (see FIGS. D, E, and F). ). In the case of FIGS. 3D and 3E, 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 corrected to increase. The reduction in the voltage V2 of the voltage dividing resistor 3 can be suppressed as compared with the ratio. Therefore, it is not detected that the remaining battery level is low, and the disadvantage that the printer is stopped every time printing is performed is avoided.

In the case of FIG. 2F, there is a sudden increase in the load current I, and the potential difference I × R generated at both ends of the current detection resistor 4 is limited by the limiter diode 5, so that a further increase is caused. There is no increase correction, and it is possible to prevent sudden overdischarge of the battery.

[0023]

According to the present onset light according to the present invention, the current flowing through the load
Accordingly, when correcting the voltage detected by the voltage detecting means,
If the current flowing through the load exceeds the upper limit, the correction value is fixed
By doing so, it is possible to accurately detect a decrease in the remaining battery level without knowing the load current in advance , and to prevent the device from stopping during use even though the remaining battery level is sufficient , If the load fluctuates greatly,
Risk can be avoided.

[0024]

[0025]

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating 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]

 DESCRIPTION OF SYMBOLS 1 ... Battery 3 ... Divider resistance 4 ... Current detection resistor 5 ... Limiter diode 6 ... Differential amplifier 7 ... Regulator 8 ... Comparator 9 ... Control part 10 ... Power supply circuit

Claims (2)

(57) [Claims] 1. A power supply device, comprising: voltage detecting means for detecting a battery voltage; and stopping power to a load when the detected voltage falls below a set voltage, wherein a current flowing through the load is detected. Current detection means, voltage correction means for correcting the voltage detected by the voltage detection means according to the detected current, and when the current flowing through the load exceeds a set upper limit value
The voltage corrected by the voltage correction means is a predetermined voltage.
Voltage correction limiting means for adjusting the voltage , voltage comparison means for comparing the voltage corrected by the voltage correction means and the voltage correction control means with a set voltage, and as a result of the comparison, the corrected voltage is the set voltage And a supply stopping means for stopping the power supplied to the load when the power supply voltage falls below the threshold value. 2. A power supply method for a power supply device for detecting a battery voltage and stopping power to a load when the detected voltage is lower than a set voltage, wherein a current flowing through the load is detected. If the current does not exceed the upper limit,
Depending on the current, correct the pre danger out voltage, said analyzing
If the output current exceeds the upper limit, the detected
The voltage is corrected to a predetermined voltage, is compared with the setting voltage and the corrected voltage, the result of the comparison, the corrected voltage to stop the power supplied to the load when below the set voltage A power supply method for a power supply device, comprising: