JPH03253231A - Battery charger - Google Patents

Abstract

PURPOSE:To avoid overcharging without predetermining charging conditions separately by a method wherein a battery voltage detecting means which detects a battery voltage and a maximum peak value detecting means which detects the maximum peak value of the battery voltage and generates a maximum peak signal are provided. CONSTITUTION:A nickel-cadmium battery is employed as a battery. A supply circuit 2 which stabilizes the output current of a rectifier 1 and supply a predetermined charging current to the battery 4 and a protective circuit 3 are provided. As the protective circuit 3 has a battery voltage detecting means 31 which detects the voltage of the battery 4, a maximum peak value detecting means 35 which generates a maximum peak detection signal when the battery voltage shows the maximum peak value and a cut-off timer 36 which starts time counting in accordance with the maximum peak detection signal, the charging current is cut off when it becomes certain that the charging will be completed after a predetermined time passes because the detected battery voltage shows the maximum peak value.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a battery charger having a protection circuit for preventing overcharging of a battery.

[Problems to be Solved by the Prior Art and Invention] Conventionally, in battery chargers, in order to prevent overcharging of the battery, a timer or the like is used to supply charging current only for a set time. A method that limits the charging current to a certain level, or a method that cuts off the charging current when the battery voltage reaches a predetermined voltage is adopted.

However, in conventional methods, the charging time or the voltage at which charging is cut off is set in advance, so only uniform operation is possible.Therefore, if a battery that does not meet the set conditions is used, The function of preventing battery overcharging was not fully achieved. Therefore, when adapting to various batteries, charging time, charging voltage, etc. had to be reset for each individual battery.

Therefore, the present invention provides a puffer battery charger that has a protection function that can effectively prevent overcharging without having to set charging conditions individually in advance, even when the types of batteries to be charged are different or their characteristics vary. Its purpose is to provide.

[Means to solve the problem]

The battery charger of the present invention includes a supply circuit that supplies a predetermined charging current to the battery, and a protection circuit that prevents overcharging of the battery. battery voltage detection means; maximum peak detection means for detecting the maximum peak of the detected battery voltage detected by the battery voltage detection means and generating a maximum peak detection signal; The present invention is characterized in that it includes a cut-off timer that sends out a control signal after the elapse of time, and a cut-off means that cuts off the charging current in response to the cut-off signal.

[Function] When a battery is charged, especially for an N1-cd battery, there is a relationship between battery charging time and battery voltage as shown in FIG. That is, when a charger is connected to the battery and charging is started, the battery voltage increases approximately in proportion to the charging time.

Then, as charging of the battery progresses and charging approaches completion, the amount of increase becomes smaller, and the battery voltage reaches its maximum peak when charging is completed. Thereafter, the battery becomes overcharged, and in this overcharged state, the panteri voltage begins to decline from its maximum peak.

The battery charger of the present invention includes battery voltage detection means for detecting battery voltage, and maximum peak detection means for detecting the maximum peak of the battery voltage to generate a maximum peak signal. For this reason, we focused on the property of the battery charging characteristics mentioned above, that is, the property that the battery voltage shows the highest value (maximum peak) when charging is completed, and decreases as it becomes overcharged, and the battery voltage reaches its maximum value. The maximum peak voltage at the time is used as the voltage value at the end of charging. The battery charger of the present invention includes a maximum peak detection means that generates a maximum peak detection signal when the battery voltage reaches its maximum peak, and a cutoff timer that starts timing based on the detection signal. When the maximum peak is detected and it is certain that charging is completed after a predetermined period of time has elapsed, the charging current is cut off. Such control is automatically operated based on the charging characteristics of a general battery, regardless of the type of battery.

Note that the charging current cut off by the cutoff means is a current for substantially charging the battery, and does not include trickle current or the like for maintaining the charged voltage.

〔Example〕

An embodiment of a battery charger according to the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a block diagram showing the configuration of the battery charger of this embodiment, and FIG. 2 is a flowchart illustrating the operation of the battery charger of this embodiment.

The Panteri charger of this embodiment uses a Nilakad storage battery as a battery, and the charging time is about 1 hour.
As shown in the figure, a DC conversion circuit 1 rectifies and smoothes an AC power source, a supply circuit 2 that stabilizes the output current of the DC conversion circuit 1 and supplies a predetermined charging current to a battery 4, and a battery 4.
The protection circuit 3 prevents overcharging of the battery.

The protection circuit 3 includes a battery voltage detection means 31 for detecting the voltage of the battery 4 , a filter means 32 for removing noise from the Panteli voltage detection signal detected by the Panteli voltage detection means 31 , and a voltage detection signal supplied from the supply circuit 2 to the battery 4 . a first timer 34a and a second timer 34b which are started when the charging current detecting means 33 detects the charging current; A maximum peak detection means 35 that detects the maximum peak; a cutoff timer 36 that starts timing when the maximum peak is detected by the maximum peak detection means 35 and sends out a control signal after a predetermined time; and a control signal from the cutoff timer 36. Alternatively, it has a cutoff means 37 that generates a cutoff signal in response to a signal from the second timer 34b, and puts the supply circuit 2 into a non-supply state in response to the cutoff signal to cut off the supply of charging current to the battery 4. .

The battery charger of this embodiment configured as described above is
It operates as shown in the flowchart of FIG.

First, when the battery 4 is connected in step S-100, the battery 4 is supplied with a charging current that is converted into a direct current of a predetermined voltage by the DC circuit 1 and stabilized by the supply circuit 2. Note that control such as interruption and conduction of the charging current is performed by turning a transistor (not shown) of the supply circuit 2 ON-OFFl as in the case of a conventional battery.

The voltage Ev of the battery 4 is always detected by the battery voltage detection means 31.
Furthermore, the charging current supplied to the battery 4 is detected by the charging current detection means 33 (step S-102).

In step S-104, the charging current detecting means 33 detects the charging current, that is, detects that charging of the battery pack 4 has started, and at the same time, the first timer 34a and the second timer 34b start measuring time. . These timers are each set with a first timer setting time TI and a second timer setting time T2. Setting time T1 and T
2 is appropriately set to comply with the standard specifications of the battery to be charged, and in this embodiment, the set time T1 of the first timer 34a is approximately 5 minutes, and the set time T1 of the second timer 34b is set as appropriate.
2, the charge is 15 times per hour, which is 25% more than when charging for one hour. This set time T1 is, as shown in FIG.
The set time T2 is set to a time that exceeds the time when the first peak P1 that is seen at the beginning when charging the Niracad storage battery occurs, and the set time T2 is set to the time that exceeds the time when the second peak P2 occurs when charging is completed.

In step S-106, it is determined whether the first timer 34a has counted the set time T1.

When the set time T1 is counted, step S-108
Then, the first timer 34a starts the maximum peak detection means 35. The maximum peak detecting means 35 compares the battery voltage detection signal to determine whether it is at the maximum peak or not.

In step S-110, the voltage Ev of the battery 4 is passed through the battery voltage detection means 31, the filter means 32 for removing noise from the detected voltage signal, and then passed through the maximum peak detection means 3.
5, the maximum peak (P2) of the battery voltage is detected and full charge is confirmed.

A maximum peak detection signal is then generated and sent to the cut-off timer 36.

Next, the process moves to step S-112, and the cut-off timer 36 starts timing based on the maximum peak detection signal. That is,
The maximum peak detection means 35 detects the maximum peak of the battery voltage and starts counting the time when full charge is confirmed. In step 114, the elapsed time after the detection of the maximum peak is counted and the counted time is compared with a set time Δt that is set to a predetermined time in advance. If the count exceeds the set time ΔL, the process moves to step S-116. In this embodiment, the set time Δt is set to about 1 minute. The set time Δt is normally set in a range of about 30 seconds to 5 minutes, and an appropriate time is set depending on the type of battery to be charged. When this set time Δt has elapsed, a control signal is sent to the cutoff means 37. In step S-116, the cutoff means 37 generates a cutoff signal based on the control signal from the cutoff timer 36, and the cutoff signal is supplied to the supply circuit 2. Thus, the cutoff signal causes the transistor (not shown) of the supply circuit 2 to turn OFFII.
m, and the supply of charging current is stopped.

Note that after the charging current is cut off, a small predetermined current can be supplied to the pantry 4 as a trickle current, as in the case of rapid charging.

Further, in step S-104, the second timer 34b
starts, the process advances to step S-118, and step S
-118, it is determined whether the count has reached a set predetermined time T2. Second timer 34
When the count of b reaches the set time T2, step S-
Regardless of the determination at step S-110, the process moves to step S-116 and the charging current is cut off in the same manner as described above. This means that when the charging current is not cut off even after the set time T2 is reached,
This function is a safety measure that detects the maximum peak of the charging voltage and assumes that the protection circuit has not operated properly, and forcibly cuts off the charging current to reliably protect the battery, charger, etc. from overcharging. .

In addition, in step S-106, it is determined whether the count of the first timer 34a exceeds the set time T1, and if the count exceeds the set time T1, the maximum peak detection means 35 is started in step S-108. This is to avoid malfunctions caused by the battery voltage peak phenomenon (PL) observed in the initial stage of charging in the charging characteristics of the Niracad storage battery shown in FIG. In this way, the set values T1 and T2 of the first timer 34a and the second timer 34b are set to appropriate values to prevent malfunctions caused by charging characteristics and to operate as a backup.

Note that the control by the first timer 34a and the second timer 34b is not limited to the above-mentioned method, but may be a method in which the first timer 34a and the second timer 34b both control the maximum peak detection means 35, for example.

In this way, this embodiment has functions for preventing malfunctions and backing up in addition to the basic configuration according to the present invention.

Further, a protection function may be added to the above embodiment to cut off charging when the battery voltage drops by a predetermined value from the maximum peak value.

Note that although this embodiment is used by connecting to a household power source, a car battery or the like may be used as the power source, and the present invention is not particularly limited to the embodiment shown above. As long as the battery charger has the basic configuration of the invention, it is possible to add predetermined functions as necessary, and this naturally falls within the scope of the invention.

Further, each means can be applied in either an analog system or a digital system, and - in boat fishing, a microcomputer plays the main function.

〔Effect of the invention〕

As is clear from the above description, the battery charger of the present invention focuses on and utilizes the charging characteristics of the battery, and includes a battery voltage detection means for detecting the battery voltage, and a battery charger that detects the maximum peak of the battery voltage. The protection circuit includes a maximum peak detection means for detecting full charge by detecting the maximum peak, a cutoff timer for counting a predetermined time after the detection of the maximum peak, and a cutoff means for cutting off the charging current based on a control signal of the cutoff timer.

Therefore, the battery charger of the present invention can automatically detect the completion of charging and cut off the charging current according to the charging characteristics of the battery being charged.

As a result, it is possible to accurately prevent overcharging regardless of differences in charging characteristics of batteries, and the usability of the battery charger is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a battery charger according to an embodiment of the present invention, and FIG. 2 is a flowchart showing the operating procedure thereof. FIG. 3 is a characteristic diagram showing an example of battery charging characteristics. 2... Supply circuit 3... Protection circuit 4... Battery 31... Battery voltage detection means 35... Maximum peak detection means 36 ・ 37 ・

Claims (1)

[Claims] 1. A supply circuit that supplies a predetermined charging current to a battery;
A battery charger comprising a protection circuit for preventing overcharging of a battery, the protection circuit comprising: battery voltage detection means for detecting the voltage of the battery; and a maximum battery voltage detected by the battery voltage detection means. a maximum peak detection means that detects a peak and generates a maximum peak detection signal; a cutoff timer that starts timing based on the maximum peak detection signal and sends out a control signal after a predetermined time elapses; and a cutoff timer that cuts off the charging current according to the control signal. A battery charger characterized in that it has a cutoff means.