CN201274416Y - Charging protection circuit for rechargeable accumulator - Google Patents

Abstract

The utility model relates to a protection circuit, in particular to a charging temperature protection circuit for a rechargeable battery. The rechargeable battery charging protection circuit of the present utility model at least includes a first variable resistor, a second variable resistor, and a voltage comparator; The variable resistor is connected in series with the voltage dividing resistor and then connected to the reverse input terminal of the voltage comparator. The first variable resistor detects the ambient temperature, and the second variable resistor detects the battery temperature. The output end of the voltage comparator drives the control pole of the electronic switch, and the electronic switch turns on or off the charging circuit, thereby automatically protecting the temperature of the rechargeable battery. Therefore, the charging protection circuit of the rechargeable battery of the present invention can adjust the protection temperature according to the environment, so the rechargeable battery can obtain effective temperature protection and ensure normal full charge no matter what the environment is.

Description

Rechargeable Battery Charging Protection Circuit

technical field

The utility model relates to a protection circuit, in particular to a charging temperature protection circuit for a rechargeable battery.

Background technique

When charging a rechargeable battery, the battery body generates heat. Especially with fast charging with high current, the heating phenomenon of rechargeable batteries is more obvious. Therefore, it is necessary to protect the rechargeable battery from overheating to prevent the battery from being damaged due to overheating during fast charging.

At present, a common temperature protection method for fast charging of rechargeable batteries is to use a bimetallic temperature switch as protection. Most of the set protection temperature is 45°C, but due to the change of ambient temperature in four seasons, there is a big difference. For example, in winter, if the ambient temperature is assumed to be 0°C, even if the battery uses the fast charging mode, the internal temperature will hardly rise to 45°C, so it is easy to cause the battery to be overcharged. In summer, the ambient temperature is assumed to be 38°C. When the battery is charged quickly, its internal temperature can easily rise to 45°C. The protection circuit works to cut off the charging circuit, so that the rechargeable battery is not fully charged, and the power will be cut off for protection. For nickel-cadmium batteries, it is easy to cause the battery storage capacity to decline due to the memory effect.

Utility model content

In order to solve the above problems, the utility model adopts a thermistor instead of a bimetallic temperature switch, and uses the thermistor installed inside the charging base to monitor the ambient temperature, and adjusts the corresponding protection temperature according to the change of the ambient temperature.

In order to achieve the above object, the utility model adopts the following technical solutions:

The rechargeable battery charging protection circuit of the present utility model includes at least a first variable resistor, a second variable resistor, and a voltage comparator; The variable resistor is connected in series with the voltage dividing resistor and then connected to the reverse input terminal of the voltage comparator.

Further, the first variable resistor and the second variable resistor are thermistors. The resistance of a thermistor can change with temperature. The first thermistor is placed at the base of the charger, and the second thermistor is placed close to the rechargeable battery.

Further, the output terminal of the voltage comparator drives the control electrode of the electronic switch.

Further, the driving method is that the output terminal of the voltage comparator is electrically connected to a constant current circuit composed of two operational amplifiers, and then drives the control pole of the electronic switch.

The electronic switch is a thyristor, the input end of the thyristor is connected to the output end of the DC voltage stabilizing circuit, and the output end of the thyristor is connected to the positive pole of the rechargeable battery.

The utility model adopts two thermistors to replace the bimetal temperature control switch, that is, one of the thermistors detects the ambient temperature, and the other thermistor detects the battery temperature, and the voltage comparator compares the output to control charging. Therefore, the rechargeable battery charging protection circuit of the present utility model can adjust the protection temperature according to the environment, so the rechargeable battery can obtain effective temperature protection and ensure normal full charge no matter what the environment is.

Description of drawings

Fig. 1 is the schematic circuit diagram of the preferred embodiment of the utility model.

Detailed ways

The utility model is further described now in conjunction with the accompanying drawings.

As shown in Figure 1, the rechargeable battery charging protection circuit of the present invention at least includes a first variable resistor (RT), a second variable resistor (RT2), and a voltage comparator (U1C). The first variable resistor (RT) is connected in series with the voltage dividing resistor (R9) to the positive input of the voltage comparator (U1C), and the second variable resistor (RT2) is connected in series with the voltage dividing resistor (R21) to the voltage comparator (U1C). ) reverse input.

Further, the first variable resistor (RT) and the second variable resistor (RT2) are thermistors. The resistance of a thermistor can change with temperature. The first thermistor (RT) is placed at the base of the charger to detect the ambient temperature. The second thermistor (RT2) is placed close to the rechargeable battery to detect the battery temperature.

In the preferred embodiment of the present utility model, both the first thermistor (RT) and the second thermistor (RT2) are 10K ohm thermistors. As shown in Figure 1, the first thermistor (RT) is connected in series with a 15K ohm voltage divider resistor (R9) and then connected to the positive input terminal of the voltage comparator (U1C), and the voltage divider resistor (R9) is connected in series with a 22K ohm resistor ( R8) and a 2.2K ohm current limiting resistor (R3) divide the positive voltage from the DC voltage regulator circuit to the output terminal. Similarly, the second thermistor (RT2) is connected in series with a 1K ohm voltage divider resistor (R21) and then connected to the reverse input terminal of the voltage comparator (U1C), and the voltage divider resistor (R21) is connected in series with a 5.6K ohm resistor (R6) And the 2.2K ohm current limiting resistor (R3) divides the voltage from the DC voltage regulator circuit to the output terminal.

After the two comparison voltages are input to the voltage comparator (U1C), its output terminal outputs the comparison voltage to drive the control pole of the electronic switch. As shown in FIG. 1 , the driving method is that the output terminal of the voltage comparator (U1C) is electrically connected to a constant current circuit composed of two operational amplifiers (U1A, U1D), and then drives the control pole of the electronic switch. Among them, the operational amplifier (U1D) forms a constant current source circuit, and the output terminal of the constant current source is connected to the output terminal of the voltage comparator (U1C) and then connected to the inverting input terminal of the operational amplifier (U1A) to drive the control pole of the electronic switch. In addition, it also drives a red LED to indicate the charging status indicator. A green LED is driven by a zero-crossing comparator (U1B) to indicate a full state indicator.

The electronic switch can be a thyristor, a high-power triode, or other switching circuits with a control terminal. The best implementation mode of the utility model adopts thyristor (Q1), the input terminal of thyristor (Q1) is connected to the output end of DC voltage stabilizing circuit, and the output terminal of thyristor (Q1) is connected to the positive pole of rechargeable battery. The control electrode of the thyristor (Q1) controls whether it is turned on or not, so as to conduct temperature protection for the charging circuit to be turned on and off.

In the best implementation mode of the utility model, when the ambient temperature is 0°C, the circuit temperature protection is set to 20°C protection, and when the ambient temperature is 38°C, the circuit temperature protection is set to 50°C protection. Therefore, it can properly protect the rechargeable battery in a large temperature range.

Claims (6)

1, rechargeable battery charge protector is characterized in that: comprise first variable resistor (RT), the second adjustable resistance (RT2), voltage comparator (U1C) at least; First variable resistor (RT) series connection divider resistance (R9) back connects voltage comparator (U1C) positive input, and the second adjustable resistance (RT2) series connection divider resistance (R21) back connects voltage comparator (U1C) reverse input end.

2, rechargeable battery charge protector as claimed in claim 1 is characterized in that: described first variable resistor (RT) and the second adjustable resistance (RT2) are thermistor.

3, rechargeable battery charge protector as claimed in claim 1 or 2 is characterized in that: described first variable resistor (RT) is positioned over the charger base place, and the second adjustable resistance (RT2) is positioned near the rechargeable battery place.

4, rechargeable battery charge protector as claimed in claim 1 is characterized in that: described voltage comparator (U1C) output drives the control utmost point of electronic switch.

5, rechargeable battery charge protector as claimed in claim 4 is characterized in that: described type of drive is the control utmost point that voltage comparator (U1C) output electrically connects the constant-current circuit rear drive electronic switch of being made up of two operational amplifiers (U1A, U1D).

6, as claim 4 or 5 described rechargeable battery charge protectors; it is characterized in that: described electronic switch is controllable silicon (Q1); the input termination direct current regulation circuit output of controllable silicon (Q1), the output termination rechargeable battery positive pole of controllable silicon (Q1).

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