JPH0777495B2 - Power supply device with discharge control circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power supply device that uses, as a power source, a plurality of rechargeable batteries connected in series, and in particular, a plurality of rechargeable batteries have different discharge voltages. Therefore, the present invention relates to a discharge control circuit provided in the power supply device in order to prevent deterioration of the battery and the like.

[Conventional technology and problems to be solved]

As a power source for a mobile phone or the like, there is known a power supply device including a power source configured by connecting a plurality of rechargeable batteries in series.

This power supply device has the following problems. That is, the charge-discharge characteristics of rechargeable batteries often differ due to variations in the physical or chemical characteristics of their constituent materials or structural variations due to various factors in the manufacturing process. When using rechargeable batteries with such characteristic differences connected in series, especially when there is a difference in discharge voltage, among the batteries connected in series, the battery with the lower discharge voltage has a deeper discharge depth. Part of the battery is over-discharged, and when the difference in discharge voltage between the batteries is significantly different, the battery is forcibly discharged, which causes the battery life to decrease and liquid leakage.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a discharge control circuit capable of stopping discharge when the discharge voltages of rechargeable batteries connected in series are significantly different. An object of the present invention is to provide a provided power supply device.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, in the present invention, in a power supply device equipped with a plurality of rechargeable batteries connected in series as a power source, voltage detection means for detecting the discharge voltage of the rechargeable batteries, and this voltage detection. Based on the output of the means, a potential difference detecting means for detecting a potential difference between the rechargeable batteries, a comparing means for comparing the detected potential difference with a reference voltage, and a potential difference detected by the comparing means is the reference voltage. And a cutoff unit for cutting off the power supply path from the power source to the load side.

[Action]

In the present invention, each discharge voltage of the plurality of rechargeable batteries connected in series is detected by the voltage detecting means. The difference between the detected respective values is detected by the potential difference detection means. Each detected difference is compared with a preset reference voltage by the comparison means. Then, when the detected voltage difference is larger than the reference voltage, the power supply path is shut off by the shutoff means. Therefore, when the discharge voltage of each rechargeable battery greatly differs in this way, the discharge operation of the battery is stopped.

〔Example〕

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

FIG. 1 is a schematic block diagram of the power supply device of this example. As shown in this figure, the device 1 of this example includes three rechargeable batteries A, B, and C connected in series as a power source, and the positive terminal of the battery A, which is the positive terminal of the device 1, supplies power. It is connected to the positive side output terminal 15 of the device via a lead wire l1 forming a path and a switch 14 interposed there. Further, the negative terminal of the battery C, which is the negative terminal thereof, is connected to the negative output terminal 16 of the device via the lead wire 12 that constitutes the power supply path.

A differential amplifier 2 is connected in parallel to the rechargeable battery A,
The positive input terminal of the amplifier is connected to the positive side of the battery A, and the negative input terminal is connected to the negative side of the battery A. Similarly, the differential amplifier 3 is connected in parallel to the rechargeable battery B, and the positive side input terminal of the amplifier is the battery B.
Of the battery B, and its negative input terminal is connected to the negative side of the battery B, respectively.

The output side of the differential amplifier 2 is connected to the positive side input terminal of the differential amplifier 4 in the next stage and the negative side input terminal of the differential amplifier 5,
Each is connected. On the other hand, the other input terminal of each differential amplifier 4, 5 is connected to the negative input terminal of the preceding differential amplifier 3. Similarly, the output side of the differential amplifier 3 in the preceding stage is connected to the positive side input terminal of the differential amplifier 6 in the next stage and the negative side input terminal of the differential amplifier 7, respectively. The other input terminals of the differential amplifiers 6 and 7 are connected to the negative input terminal of the differential amplifier 3 at the preceding stage.

Next, the output sides of the differential amplifiers 4 to 7 are respectively connected to the diodes 8 to 11 in the forward direction, and the other side of these diodes is connected to the positive side input terminal of the comparator 13. ing. The reference voltage Vc output from the potential setting unit 12 is applied to the negative input terminal of this comparator. The output side of the comparator 13 is connected to the input side of the switch 14 described above. The switch 14 is in a closed state while a low logic level signal is input, and, on the contrary, is in an open state while a high logic level signal is input.

The discharge control operation of the device 1 having this configuration will be described.

First, on the output side of the differential amplifier 2, the discharge voltage V1 of the battery A is
Appears. The discharge voltage V1 of the rechargeable battery B appears on the output side of the differential amplifier 3. On the other hand, the discharge voltage V3 of the rechargeable battery C appears at the negative side input terminal of the differential amplifier 3. Therefore, the voltage V1 which is the output of the differential amplifier 2 appears at the positive side input terminals of the differential amplifiers 4 and 5 in the next stage, and the potential V2 which is the output of the differential amplifier 3 is in the differential amplifiers 6 and 7 in the next stage. Appears at the positive input terminal of. Further, the voltage V3 appears at the negative side terminals of the differential amplifiers 4 and 6 and the positive side terminals of the differential amplifiers 5 and 7, respectively.

As a result, the voltages V1 and V3 are applied to the output side of the differential amplifiers 4 and 5.
And the voltage difference between the voltages V2 and V3 appears on the output side of the differential amplifiers 6 and 7. Therefore, these outputs are connected to the positive side input of the comparator 13 obtained by wired OR via the diode, and the larger voltage difference of the absolute difference between the voltages V1 and V2 and the absolute difference between the voltages V2 and V3. Is applied.

This voltage difference is compared with the reference voltage in the comparator 13, and when the voltage difference is smaller, the low logic level signal is output from here, and in the opposite field, the high logic level signal is output. This output signal is output by switch 14 (eg,
p-channel MOSFET), and when this output signal is inverted from the low logic level to the high logic level, the switch 14 is opened and the power supply path 11 is cut off.

As described above, in the power supply device 1 of this example, when the voltage difference between the rechargeable batteries A and C or the voltage difference between the batteries B and C connected in series exceeds the reference voltage value, The power supply path is automatically cut off to stop the discharge of the rechargeable battery. Therefore, since it is possible to avoid the discharging operation under the condition of such a large voltage difference, it is possible to prevent the adverse effects such as the shortening of the life of each rechargeable battery and the leakage of the liquid, which are caused by performing the discharging operation. be able to.

In this example, between batteries A and C, and battery B,
Only the voltage difference between C is detected, and the discharge control is performed based on this. In addition to this, the voltage difference between the batteries A and B is detected, and the discharge is performed even when this difference exceeds a certain level. By prohibiting, undesired discharge can be more surely avoided. In addition, in this example, a power source in which three batteries are connected in series is used. However, the number of the batteries is increased, and in response to the increase in the number of batteries, the differential amplifier on the front stage side and the next stage If the number of differential amplifiers on the side is increased and circuit connections similar to those in this example are formed, the present invention can be applied to a power supply circuit having a large number of batteries.

〔The invention's effect〕

As described above, the present invention, in a power supply device in which a plurality of rechargeable batteries are connected in series, detects the difference in the discharge voltage of each battery, and supplies the power when the difference is equal to or greater than a predetermined value. Since the discharge control circuit for stopping is provided, it is possible to prevent the battery life from decreasing and the liquid leakage from occurring due to the discharge voltage difference of the rechargeable battery.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a power supply device according to an embodiment of the present invention. [Description of symbols] 1 ... Power supply device 2,3,4,5,6,7 ... Differential amplifier 8,9,10,11 ... Diode 12 ... Potential setting unit 13 ... Comparator 14 ... Switches 15,16 …… Output terminals A, B, C …… Rechargeable batteries. l1, l2 ... Lead wire (power supply path).

Claims (1)

[Claims] 1. A power supply device using a plurality of rechargeable batteries connected in series as a power source, wherein voltage detection means for detecting a discharge voltage of the rechargeable batteries and output based on the voltage detection means A potential difference detection means for detecting a potential difference between the rechargeable batteries, a comparison means for comparing the detected potential difference with a reference voltage, and a potential difference detected by the comparison means when the potential difference is larger than the reference voltage. A power supply device having a discharge control circuit, comprising: a cutoff unit that cuts off a power supply path from a power source to a load side.