JPH0614108B2 - DC power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] A DC power supply circuit including a battery end detection circuit, in which a voltage Vin between terminals decreases due to a temporary increase in output current, and a warning signal output is a steady output current. If the voltage Vin between terminals rises when returning to the state, the purpose is to realize a DC power supply circuit with a function to be reliably released, and there is a voltage detector that detects the voltage Vin between terminals of the battery. However, in a DC power supply circuit that outputs a warning signal when the inter-terminal voltage Vin becomes lower than a reference value, the output signal is inverted from a high level to a low level in a section in which the current flowing from the battery to the load is larger than the steady state. Load monitoring circuit and the current flowing from the battery to the load returns to the steady state, and the voltage applied to the voltage detector when the output signal of the load monitoring circuit reverses from low level to high level. The voltage Vch is composed of a circuit having a differentiating circuit for temporarily increasing the voltage Vin between the terminals of the battery.

[Industrial application field]

The present invention relates to a battery-driven DC power supply that supplies current to various devices, and more particularly to a DC power supply circuit including a battery end detection circuit.

Battery-powered power supplies have been used for radios and tape recorders, but in recent years, battery-powered power supplies have come to be used in various portable devices such as word processors and personal computers.

Such devices have a minimum power supply voltage required to maintain operation, and the device will not operate when the battery voltage drops below that. This state is called a battery end, and it is necessary to replace the battery or charge the battery before that.

However, if the battery replacement or charging is too early, there is a lot of waste, and if the time is late, it becomes often unusable at an important time. Therefore, there is a demand for realization of a DC power supply circuit that can properly output warning signals before the end of the battery or at which the battery replacement or charging can be instructed.

[Conventional technology]

 FIG. 3 is a block diagram showing a conventional DC power supply circuit.

In FIG. 3, a conventional DC power supply circuit includes a battery 1 and a regulator 2. The terminal voltage Vin of the battery 1 decreases with discharge, but a current flowing through a load 3 connected to the output side of the regulator 2 Is a steady state, a constant voltage is applied to the load 3.

However, the capability of the regulator 2 to keep the output voltage constant is limited, and when the inter-terminal voltage Vin of the battery 1 drops below the limit, the output voltage drops and the load 3 cannot maintain the operating state. This limit is the so-called battery end, and it is necessary to replace or charge the battery before that.

Therefore, as a means for instructing the timing of battery replacement or charging before reaching the battery end, a warning signal is output when the terminal voltage Vin of the battery 1 becomes equal to or lower than the reference value Ve, and the terminal voltage Vin is changed by battery replacement or charging. It has a voltage detector 4 which outputs a release signal for canceling the previous warning signal when the reference value Ve is exceeded.

[Problems to be Solved by the Invention]

FIG. 4 is a time chart for explaining problems in the conventional circuit.

In FIG. 4 (a), when the current flowing through the load is in a steady state, the terminal voltage Vin of the battery gradually decreases with discharge, and then decreases to the reference value Ve or less, and then the reference value V
It does not rise above e (it may be recovered by turning off the power, but in the case of such a phenomenon, it may be ignored because it immediately drops when the power is turned on). Therefore, when the voltage Vin between the terminals of the battery exceeds the reference value Ve, FIG.
As shown in (b), a warning signal indicating the battery end is output from the voltage detector.

On the other hand, even before the inter-terminal voltage Vin of the battery reaches the reference value Ve, when the current flowing through the load temporarily increases, the inter-terminal voltage Vin sharply decreases as shown in FIG. 4 (a). It becomes the reference value Ve or less. As a result, as shown in FIG. 4 (b), the voltage detector outputs a warning signal indicating the battery end. However, the drop in the terminal voltage Vin in this case is due to the temporary increase in the output current, and it rises when the current flowing through the load returns to the steady state and can be continuously used.

Therefore, when the inter-terminal voltage Vin exceeds the reference value Ve and rises, a release signal for canceling the previous warning signal is output from the voltage detector, but the reference value Ve has hysteresis. The reference value Ve when the warning signal is output is different from the reference value Veh when the inter-terminal voltage Vin rises and the warning signal is released. As a result, even if the inter-terminal voltage Vin rises above the reference value Ve, the warning signal is not released as shown in FIG. 4 (b) unless it exceeds the reference value Veh, so it is erroneously recognized as reaching the battery end. There was a problem of being replaced.

An object of the present invention is to provide a device equipped with a battery-powered power source, in which the inter-terminal voltage Vin decreases due to a temporary increase in the output current, and the output warning signal causes the inter-terminal voltage Vin to return when the output power source returns to the steady state. It is intended to realize a DC power supply circuit having a function of being surely released when the voltage rises.

[Means for Solving the Problems]

FIG. 1 is a block diagram showing a DC power supply circuit according to the present invention. Note that the same object is denoted by the same symbol throughout the drawings.

The above object has a battery (1) and the voltage detector for detecting a terminal voltage V _in of the battery (1) to (4), and outputs a and vigilance signal the terminal voltage V _in is equal to or less than the reference value In the DC power supply circuit, in the section where the current flowing from the battery (1) to the load (3) is larger than the steady state, the output signal is inverted from the high level to the low level, and the load current monitoring circuit (5),
When the current flowing from the battery (1) to the load (3) returns to a steady state and the output signal of the load current monitoring circuit (5) is inverted from low level to high level, the voltage detector (4 ), The output of the differentiating circuit (6) is added to the inter-terminal voltage V _in of the battery (1) so as to temporarily increase the voltage V _ch . if the return increases the terminals voltage V _in in to the steady state is achieved by a DC power supply circuit of the present invention it is certainly to be able to cancel the warning signal.

[Action]

In the section where the current flowing from the battery to the load is larger than the steady state in Fig. 1, the load monitoring circuit in which the output signal is inverted from the high level to the low level, and the current flowing from the battery to the load returns to the steady state, By providing a differentiating circuit for temporarily increasing the voltage Vch applied to the voltage detector when the output signal of the monitoring circuit is inverted to a high level with respect to the terminal voltage Vin of the battery, a temporary output current is provided. The warning signal that was output due to a decrease in the inter-terminal voltage Vin due to a sudden increase in the output voltage returns to the steady state of the output current
If the voltage rises, it is possible to realize a DC power supply circuit having a function of being reliably released.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings. 2. FIG. 2 is a time chart showing the operation of the DC power supply circuit according to the present invention.

The DC power supply circuit according to the present invention includes a load monitoring circuit 5 and a differentiating circuit 6, and the output signal of the load monitoring circuit 5 is input to the differentiating circuit 6 including a capacitor 61 and a diode 62, and the terminal voltage Vin of the battery 1 Is applied to the voltage detector 4 via the diode 62.

When the inter-terminal voltage Vin of the battery shown in FIG. 2 (a) decreases due to discharge, the voltage Vch applied to the voltage detector 4 shown in FIG. 2 (b) also decreases, and the voltage Vch is the reference value. V
When it becomes e or less, as shown in FIG. 2 (c), the voltage detector 4 outputs a warning signal indicating the battery end.

However, even before the battery reaches the battery end, if the output current temporarily increases, the inter-terminal voltage Vin drops sharply as shown in FIG. 2 (a), and as shown in FIG. 2 (b). At the same time, the voltage Vch applied to the voltage detector also drops, and as shown in FIG. 2 (c), the voltage detector outputs a warning signal indicating the battery end.

In this case, the decrease in the inter-terminal voltage Vin and the voltage Vch applied to the voltage detector is caused by the temporary increase in the output current. When the output current returns to the steady state, the inter-terminal voltage Vin increases. Along with this, the voltage Vch applied to the voltage detector also becomes higher than the reference value Ve, and the warning signal indicating the battery end, which was output before, must be released at that time.

However, the reference value Ve has hysteresis, and the previous warning signal is not released unless the voltage Vch applied to the voltage detector exceeds the reference value Veh. Therefore, in the DC power supply circuit according to the present invention, when the output current returns to the steady state, a voltage Vch higher than the inter-terminal voltage Vin is applied to the voltage detector to forcibly cancel the warning signal output previously. It is configured.

That is, when the output current of the battery shifts from the steady state to the large current, the load monitoring circuit 5 outputs the output signal as shown in FIG.
As shown in (d), it is configured to invert from a high level to a low level, and when it returns to a steady state, it inverts from a low level to a high level again. This output signal is input to the capacitor 61, and the voltage Vch applied to the voltage detector is the second
When the output current of the battery returns to the steady state as shown in FIG. 7B, it becomes higher than the original terminal voltage Vin of the battery and exceeds the reference value Veh. As a result, as shown in FIG. 2 (c), the warning signal indicating the battery end is released.

In this way, in the section where the current flowing from the battery to the load is larger than the steady state, the load monitoring circuit in which the output signal is inverted from the high level to the low level and the current flowing from the battery to the load returns to the steady state, and the load monitoring is performed. The voltage Vch applied to the voltage detector when the output signal of the circuit is inverted to a high level is provided with a differentiating circuit for temporarily increasing the voltage Vin between the terminals of the battery to temporarily output the output current. If the inter-terminal voltage Vin decreases due to a large increase and the outputted warning signal increases the inter-terminal voltage Vin due to the return of the output current to a steady state, a DC power supply circuit having a function of being reliably released is realized. be able to.

〔The invention's effect〕

As described above, according to the present invention, in a device equipped with a battery-powered power source, the inter-terminal voltage Vin decreases due to the temporary increase of the output current, and the output warning signal is returned to the steady state of the output current. If the inter-terminal voltage Vin rises, it is possible to provide a DC power supply circuit having a function of being reliably released.

[Brief description of drawings]

1 is a block diagram showing a DC power supply circuit according to the present invention, FIG. 2 is a time chart showing an operation of the DC power supply circuit according to the present invention, FIG. 3 is a block diagram showing a conventional DC power supply circuit, and FIG. The figure is a time chart for explaining the problems in the conventional circuit. In the figure, 1 is a battery, 2 is a regulator, 3 is a load, 4 is a voltage detector, 5 is a load monitoring circuit, 6 is a differentiating circuit, 61 is a capacitor, and 62 is a diode.

Claims (1)

[Claims] 1. A has a battery (1) and the voltage detector for detecting a terminal voltage V _in of the battery (1) (4), outputs a warning signal the terminal voltage V _in is equal to or less than the reference value In the section where the current flowing from the battery (1) to the load (3) is larger than the steady state in the direct current power supply circuit, the output signal is inverted from high level to low level and the load current monitoring circuit (5) When the current flowing from the battery (1) to the load (3) returns to a steady state and the output signal of the load current monitoring circuit (5) is inverted from low level to high level, the voltage detector ( In order to temporarily increase the voltage V _ch applied to 4), the output of the differentiating circuit (6) is added to the terminal voltage V _in of the battery (1). if the terminal voltage V _in at the return to steady state is increased, reliably to be able to cancel the warning signal DC power supply circuit characterized in that.