JPS6227000Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that detects a predetermined charging voltage of a battery to be charged and stops charging.

This type of device is generally designed on the assumption that the charging power supply voltage is approximately constant and that the battery being charged is also normal. However, when using, for example, a lead-acid battery as a charging power source, if the power supply voltage is extremely low, even if the battery to be charged continues to be charged,
The predetermined charging voltage may not be reached and the battery being charged may be overcharged. Also, for example, if the power supply voltage is extremely high, or if the battery to be charged or a portion thereof is short-circuited, a large charging current will continue to flow through the device, potentially damaging the device. The above disadvantages are more likely to occur as the charging rate of the battery to be charged increases.

This invention not only detects a predetermined charging voltage of the battery to be charged and terminates charging, but also protects the battery by stopping charging when the charging current is too large or too small. The purpose is to protect the battery. An embodiment of the present invention will be described below with reference to the drawings. A is a lead-acid battery as a charging power source and is connected to DC power supply terminals 1 and 2. A first relay switch S ₁ and a series circuit 3 of a battery to be charged B, such as a sealed nickel-cadmium battery, are connected to the power supply terminal via current-limiting resistors R ₁ and R ₂ .
The series circuit and current-limiting resistors R ₁ and R ₂ form a battery charging path 4, and one current-limiting resistor R ₂ constitutes charging current detection means. At both ends of the series circuit 3, there is a second relay switch with a start switch _S3 installed in parallel.
A series circuit 5 including S ₂ , a relay coil RY, and a switch transistor T are connected in parallel.

Reference numeral 6 denotes a detection circuit which directly detects a predetermined charging voltage of the battery or its corresponding converted voltage to generate a detection output.

7 is a control circuit, and a switch transistor T
It stops charging the battery through current control, and is constructed with first and second transistors Q ₁ and Q ₂ as main elements. The transistors are connected in a relationship that facilitates conduction, with the base of one transistor interconnecting the collector of the other transistor. In the embodiment, the detection output of the detection circuit 6 is applied to the base of the first transistor _Q1 via the diode _D1 , and the emitter output of the second transistor Q is applied to the base of the switch transistor T via the diode _D4 . be done. 1st
A shorting switch _S4 is provided between the base and emitter of the transistor _Q1 , and this switch is temporarily closed when charging starts in conjunction with the start switch _S3 , and the first and second transistors are closed. If Q ₁ and Q ₂ are conductive, both transistors are cut off.

Next, 8 is a sensing circuit that senses that the charging current flowing through the current-limiting resistor _R2 serving as charging current detection means deviates from a certain current range, and detects a current higher than the current range. It consists of a high current detection circuit 9 that detects a current value, and a low current detection circuit 10 that detects a current value lower than the above-mentioned current range. The high current detection circuit 9 consists of a series circuit 11 consisting of a resistor _R3 and a constant voltage element Z connected across a series circuit consisting of a battery B and a current limiting resistor _R2 , and a resistor connected across a battery B.
It consists of a third transistor Q ₃ whose collector and emitter are connected via R ₄ , and whose base is connected to the intermediate connection point 12 of the series circuit 11 . The high current detection circuit detects that the voltage drop across the current limiting resistor _R2 caused by the flow of charging current is
Constant voltage at intermediate connection point 12 and third transistor Q ₃
When the voltage difference between the base and emitter of the threshold is greater than the threshold voltage difference between the base and emitter of the third transistor, the third transistor is cut off and a high voltage is output from its collector. The output is applied to the base of the first transistor _Q1 via the diode _D2 . The low current detection circuit 10 is connected in parallel with the series circuit 11, and the resistor _R5 connects the series circuit of the charge indicating light emitting diode L and the collector-emitter of the fourth transistor _Q4 , and connects the base-emitter of the fourth transistor. It is connected to both ends of current-limiting resistor _R2 via resistor _R6 . In the low current detection circuit, when the voltage drop across the current limiting resistor _R2 is smaller than the threshold between the base and emitter of the fourth transistor _Q4 , the fourth transistor is cut off and a high voltage is output from its collector. , the output is connected to the first transistor Q ₁ through the diode D ₃
applied to the base of

In the above configuration, the discharged battery B is connected to terminal 1.
3 and 14 and temporarily closes the start switch _S3 , the first and second transistors _Q1 and _Q2 are in the cut-off state due to the temporary closing of the short-circuit switch _S4 , and the switch transistor T conducts.
Therefore, the relay coil RY is energized and closes the first and second relay switches S ₁ and S ₂ , and the relay coil RY is self-held by closing the second relay switch S ₂ . Therefore, the start switch S ₃ is then opened, but in this case also each relay switch S ₁ ,
S ₂ is closed and battery B begins to be charged at a charging rate of, for example, 4C. In this case, if the voltage of lead-acid battery A is within the normal range and battery B is also normal, the voltage drop across current-limiting resistor R ₂ due to the charging current of the battery is equal to the constant voltage at intermediate connection point 12 and the voltage across third transistor Q ₃ . Since it is smaller than the base-emitter threshold voltage difference, the third transistor becomes conductive and the output of the high current detection circuit 9 does not appear. In addition, since the voltage drop across the current limiting resistor _R2 is greater than the threshold between the base and emitter of the fourth transistor _Q4 , the fourth transistor becomes conductive and the output of the low current detection circuit 10 does not appear, causing the light emitting diode L to light up. to display charging status.

Battery B is charged in this state, and when the detection circuit 6 detects a predetermined charging voltage of battery B,
The detection output is applied to the base of the first transistor Q ₁ and the first and second transistors Q ₁ and Q ₂
becomes conductive, and the collector voltage of the second transistor _Q2 decreases. Therefore, the switch transistor T
is cut off and the relay coil RY is no longer energized, so the first and second relay switches S ₁ and S ₂ are opened and charging of the battery B is stopped and completed.

If the charging current flowing through the current limiting resistor R ₂ during charging deviates from the constant charging current range, the following will occur. First, when the actual charging current value is larger than the value in this fixed current range,
Since the voltage drop across the current limiting resistor _R2 due to the charging current is greater than the voltage difference between the constant voltage at the intermediate connection point 12 and the base-emitter threshold of the third transistor _Q3 , the third transistor cuts off and A high voltage is output from the collector. Since the output is applied to the base of the first transistor _Q1 , the first and second transistors _Q1 and _Q2 become conductive, and the collector voltage of the second transistor _Q2 , that is, the base voltage of the switch transistor T, decreases. The switch transistor shuts off and stops charging as described above. Further, when the actual charging current is smaller than the value in the certain current range, the voltage drop across the current limiting resistor _R2 is smaller than the threshold between the base and emitter of the fourth transistor _Q4 , so the fourth transistor is cut off. A high voltage is output from its collector. The output is the first
Since it is applied to the base of transistor _Q1 , charging is stopped as described above. The open circuit voltage of a nickel cadmium battery when fully charged is about 1.25V, but there is a voltage drop due to internal resistance when charging.
In the case of 1C charging (charging with a current equivalent to the amount of electricity discharged by the battery per unit time), charging ends when the voltage reaches approximately 1.5V (however, the set voltage at the end of charging depends on the rated charge). (different). However, when the charging current is small, the voltage drop due to the internal resistance is small, so even when fully charged, the voltage is only about 1.3V, and the detection circuit 6 does not operate. As a result, charging may continue indefinitely and become overcharged, so charging is stopped when the current is low.

In an embodiment, the range of the constant charging current is:
The voltage drop across current-limiting resistor _R2 due to the charging current is
greater than the base-emitter threshold of the fourth transistor _Q4 , and the constant voltage at the intermediate connection point 12 and the third
This corresponds to a range smaller than the voltage difference between the base and emitter of transistor _Q3 and the threshold.

As described above, according to the present invention, a charging current detecting means is provided in the charging path of the battery to be charged, and a sensing circuit is also provided for sensing that the charging current detected by the means is a value that deviates from a certain current range. Since charging of the battery is stopped based on the output of the sensing circuit, the sensing circuit produces an output when such a small charging current flows that the sensing circuit cannot detect the predetermined charging voltage of the battery. It is possible to prevent overcharging of the battery caused by the charging current being too high, and also to prevent damage to the device due to the charging current being too large. That is, when the voltage of the power source battery is low and the charging current is small, charging is stopped, so the power source battery is not over-discharged, and is particularly suitable for charging from an automobile battery.

[Brief explanation of the drawing]

The drawing is an electrical circuit diagram showing an embodiment of the device according to the present invention. B...Battery, 6...Detection circuit, 7...Control circuit, 4...Charging path, _R2 ...Charging current detection means,
8...Sensing circuit.

Claims (1)

[Scope of utility model registration request] The device is equipped with a detection circuit that detects a predetermined charging voltage of a battery to be charged that is charged by a power source battery, and a control circuit that stops charging the battery based on the detection output of the circuit, and the device includes a charging current in a charging path of the battery. A detection means is provided, and a sensing circuit is provided for sensing that the charging current detected by the means deviates from a certain current range, and the control circuit is actuated based on the output of the sensing circuit. A battery charging device characterized by: