JPH05268731A - Battery protective circuit - Google Patents

Abstract

PURPOSE:To elongate the life by arranging the constitution such that a ripple current above an allowable value does not flow to a battery. CONSTITUTION:When charging a battery by letting the current to flow from a power source, which is rectified by a rectifier 2, to the battery 5, a shunt 4 detects the current flowing to the battery 5, and an AC ingredient detecting circuit 8 takes out only those of AC, and further an effective value converting circuit 7 seeks its effective value, and a comparator 9 compares it with ripple allowable value, and when the effective value of those of AC gets over this allowable value, it issues an alarm, and expedites the cut off of loads 6A and 6B, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery protection circuit for charging a battery with a power source obtained by rectifying an AC power source.

[0002]

2. Description of the Related Art Conventionally, in a battery charging circuit, the sum of the ripple current effective value flowing by the ripple voltage after AC power supply rectification and the ripple current effective value flowing by the load circuit is the allowable ripple current effective value of the battery (usually 0. 2x
In general, the main circuit constant is determined (for example, by increasing the smoothing reactor) so as not to exceed the battery capacity).

[0003]

However, if the above is done, there is no problem as long as the load is constant, but even if the load fluctuates and a ripple current exceeding the allowable value flows, this cannot be detected. However, there is a problem that the ripple current exceeding the allowable value flows in the battery and the battery life is shortened. Therefore, an object of the present invention is to prevent a ripple current exceeding a permissible value from flowing.

[0004]

In order to solve such a problem, according to the present invention, a detecting means for detecting a ripple current flowing in the battery for a battery charging circuit for charging the battery with a power source obtained by rectifying an AC power source. And a judging means for comparing the detected ripple current with an allowable value and outputting an alarm signal when the ripple current exceeds the allowable value.

[0005]

By detecting the ripple current flowing through the battery, the ripple current exceeding the allowable value is prevented from flowing through the battery, thereby preventing the battery life from being shortened.

[0006]

1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is an AC power supply, 2 is a rectifier composed of a combination of a thyristor and a diode, 3 is a DC smoothing reactor, 4 is a shunt, 5 is a battery, 6, 6A, 6
B is a load, 7 is an effective value conversion circuit, 8 is an AC component detection circuit, 9 is a comparator, 10 is a relay (RY), CA is its contact, SW1 and SW2 are switches for turning on or off the loads 6A and 6B. Is. The rectifier 2 rectifies the alternating current from the power supply 1, the smoothing reactor 3 smoothes the current, and the battery 5 is charged with this smoothed current. Since the shunt 4 is connected to the battery 5, the shunt 4 detects the current flowing through the battery 5.

The AC component detecting circuit 8 is composed of a diode rectifying circuit, a capacitor, an amplifier, etc., and cuts the DC component of the detected current from the shunt 4 which contains the AC component in the DC component by the capacitor to obtain the AC component. Only detect. The effective value conversion circuit 7 is composed of, for example, an IC circuit that calculates the square root of the root mean square of the AC voltage, converts the AC component detected by the AC component detection circuit 8 into its effective value, and inputs it to the comparator 9. .. Comparator 9
Then, the output from the effective value conversion circuit 7 is compared with the battery allowable ripple current setting value, and a predetermined output is output when the former exceeds the latter. This output excites the relay 10,
At the contact CA, an alarm device such as a buzzer (not shown) is activated and an alarm is issued.

FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 1. The left half of FIG. 2 shows only the load 6, and the right half shows the case where the loads 6A and 6B are added to the load 6. Shown respectively. It is to be noted that FIG. 9A shows a current Ib flowing through the battery 5, and FIG. 8B shows an output voltage V of the AC component detection circuit 8.
a, (c) are output voltages Ve of the effective value conversion circuit 7, (d)
Is the reference voltage Vs of the comparator 9, and (e) is the relay 10
Shows the ON and OFF states, respectively. That is, in the case of only the load 6, in this case, the AC component is small as shown on the left side (B) and therefore becomes equal to or lower than the reference voltage (battery allowable value) Vs, so that the relay remains off and the alarm is issued as shown in (E). I can't. On the other hand, load 6 to load 6A
Alternatively, when 6B is added to increase the AC component as shown in the right side (b) and becomes equal to or higher than the reference voltage Vs, the relay is turned on and an alarm is issued as shown in (e). In addition,
When the alarm is issued, the switch SW1 or SW2 is turned off to disconnect the loads 6A and 6B from the system.

[0009]

According to the present invention, since the ripple current flowing in the battery is constantly monitored, the increase / decrease of the ripple current is detected when the load condition changes, and an alarm is issued when the ripple current exceeds the allowable ripple current of the battery. By taking measures such as disconnecting the load based on this, it is possible to avoid the inconvenience of continuing the ripple current to the battery and shortening its life.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of FIG.

[Explanation of symbols]

1 ... AC power supply, 2 ... rectifier, 3 ... DC smoothing reactor,
4 ... shunt, 5 ... battery, 6, 6A, 6B ... load, 7
... RMS conversion circuit, 8 ... AC component detection circuit, 9 ... Comparator, 10 ... Relay (RY), CA ... Relay contact, S
W1, SW2 ... Switch.

Claims (1)

[Claims] 1. A battery charging circuit for charging a battery with a power source obtained by rectifying an AC power source, wherein a detecting means for detecting a ripple current flowing in the battery and a detected ripple current are compared with an allowable value, and this is more than an allowable value. And a determination means for outputting an alarm signal when the battery protection circuit is activated.