JPH0326025B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention accurately detects the terminal voltage that matches the amount of discharged electricity of the battery to be charged, and controls the charging time based on this detected voltage to perform complete and reliable charging. This invention relates to a charging device.

Conventional charging devices include (a) one that detects the terminal voltage of the battery being charged and switches from normal charging to supplementary charging when this detected voltage reaches the end-of-charge voltage, and (b) a timer. Some were designed to charge for a preset charging time, while others combined (c), (b), and (b). Of these, (a) and (c)
In devices such as those that control charging time based on the terminal voltage during charging, due to the charging characteristics, the terminal voltage changes slowly with respect to the charging time, making it difficult and inaccurate to detect the end-of-charging voltage, resulting in overcharging. The drawback was that it was easy to run out of charge. Particularly when overcharging occurs, the battery life is shortened. Furthermore, when using the timer (b), it is difficult to determine the charging time to be set, so a similar drawback occurs. In addition to (a), (b), and (c) above, by focusing on the fact that the temperature of the battery to be charged rises when it approaches the end-of-charge voltage, this temperature rise is detected and the supplementary charge is switched from the original charge. Although some devices have been designed to switch to the same mode, the drawback is that it is difficult to adjust the device.

The present invention has been made to eliminate the above-mentioned drawbacks, and for a certain period of time immediately before charging, a discharge current is passed from the battery to be charged to a discharge resistor connected in parallel to the battery to be charged, and the discharge resistor The terminal voltage corresponding to the amount of discharged electricity of the battery to be charged is detected based on the terminal voltage, and the charging time is controlled based on this detected voltage.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing an electric circuit of a charging device using the present invention. In the figure, 1 is a DC power supply for supplying charging power, and this DC power supply 1 is connected to the emitter-collector of a PNP transistor 2 as a switching element, a resistor 3 for limiting charging current, and a diode 4 for blocking reverse current. The battery to be charged 5 is connected via the first switching circuit 16 . A resistor 6 for limiting the supplementary charging current is connected in parallel to the series circuit of the transistor 2 and the resistor 3. A series circuit including a second switching circuit 7 and a discharging resistor 8 is connected in parallel to the battery 5 to be charged. The discharging resistor 8 is set, for example, so that a discharge current of 2 to 3 times the ampere-hour capacity of the battery 5 to be charged flows when the battery is fully charged. A start switch 9 is provided in the first switching circuit 16 and the second switching circuit 7.
for a certain period of time t _s (for example, several tens of seconds) by turning on the
The second switching circuit 7 outputs a control signal.
is turned on and the first switching circuit 1 is turned on.
A first timer circuit 10 is coupled to turn off the timer circuit 6. A clock circuit 11 is coupled to the first timer circuit 10 for detecting just before the end of the output control signal and outputting a trigger signal. Said second
A sampling circuit 12 is connected to a connection point A between the switching circuit 7 and the discharge resistor 8, and this sampling circuit 12 detects the terminal voltage V of the discharge resistor 8 at the connection point A based on the trigger signal from the clock circuit 11. It is configured to extract and output. The output side of the sampling circuit 12 converts the terminal voltage V into a digital signal.
An AD conversion circuit 13 is connected to the output side of the AD conversion circuit 13, and a logic circuit 14 that discriminates an input digital signal and outputs a selection signal is coupled to the output side of the AD conversion circuit 13. A second timer circuit 15 is coupled to the output side of this logic circuit 14, which outputs a control signal for a predetermined time T (corresponding to charging time) corresponding to the terminal voltage V based on the input selection signal. 2
The output side of the timer circuit 15 is connected to the base of the transistor 2.

Next, the operation of the above embodiment will be explained. FIG. 2 shows the discharge characteristics representing the relationship between the terminal voltage V and the discharge time _t of the battery ₅ to _be charged.
It is assumed that the charging time T for completely and reliably charging the battery is T ₁ , T ₂ , T _{3 ,} . . . Tn. next,
As an example, a case will be described in which the battery 5 to be charged is charged at the discharge time _tl . At this time, the terminal voltage V of the charged battery 5 becomes a voltage _Vl higher than the voltage corresponding to the amount of discharged electricity due to the recovery phenomenon.
When the start switch 9 is turned on for charging, the first timer circuit 10 is activated, and the second switching circuit 7 is turned on for the set time _ts (several tens of seconds), and the first switching circuit 16 is turned on. turn off. Then, a discharge current (800 mA to 1200 mA) that is two to three times the ampere-hour capacity C (for example, 400 mAHr) flows from the battery 5 to be charged to the discharging resistor 8, so that the potential at the connection point A (i.e., the terminal voltage V)
As shown by the dotted line b in FIG. 2, the voltage rapidly decreases within the ts time and reaches the discharge curve a, resulting in a terminal voltage that corresponds to the amount of discharged electricity. When time ts elapses from time t _l , the first
When the control signal of the timer circuit 10 disappears, the second switching circuit 7 turns off (the first switching circuit 16 turns on at the same time), and the discharge current stops flowing, but just before the ts period elapses, the clock circuit 11 turns off.
A trigger signal is output from. Therefore, the sampling circuit 12 extracts the terminal voltage V between V ₁ and V ₂ via the connection point A and outputs it to the AD conversion circuit 13 . Then, a digital signal corresponding to the terminal voltage _V2 is output from the AD conversion circuit 13, and this becomes a selection signal in the logic circuit 14 and is sent to the second timer circuit 15.
Therefore, a predetermined control signal is applied from the second timer circuit 15 to the base of the transistor 2. As a result, this transistor 2 has a terminal voltage of
Charging time corresponding to V ₂ T ₂ continues on state.
Therefore, during this charging time T ₂ , the battery 5 to be charged is charged from the DC power supply 1 via the transistor 2 and the diode 4 . In this way, complete and reliable charging is achieved. and,
When T ₂ elapses during charging, the output control signal from the second timer circuit 15 disappears and the transistor 2 is turned off, so switching is made to supplementary charging via the resistor 6 and diode 4 for limiting supplementary charging current.

In the embodiment described above, the case where the battery 5 to be charged is charged at the discharge time t _l has been described, but the present invention is not limited to this. For example, when it is tm time, the second
Like the dotted line c in the figure, when it is at tn, the dotted line d in the figure
The terminal voltage V changes as follows, and the sampling circuit measures the voltage between V ₂ and V ₃ in the former case and
The voltages between Vn _-1 and Vn are respectively taken out and output to the AD conversion circuit 13. Therefore, in the same manner as described above, the second timer circuit 15 outputs the _T3 time and Tn time control signals, and the charging time of the battery 5 to be charged becomes _T3 time and Tn time.

As described above, the present invention allows a discharging current to flow from the battery to be charged to a discharging resistor connected in parallel to the battery to be charged for a certain period of time immediately before charging, and the voltage at the terminals of the resistor for discharging is applied to the battery to be charged. Since the terminal voltage corresponding to the amount of discharged electricity is detected, it is possible to accurately detect the terminal voltage corresponding to the amount of discharged electricity of the battery to be charged. Since the charging time is controlled based on this terminal voltage, complete and reliable charging is possible. Therefore, there is no overcharging or undercharging as in the conventional case, and the life of the battery to be charged is not shortened. Furthermore, since the terminal voltage is detected and the charging time is automatically controlled, there is no need for troublesome adjustments during charging.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an electric circuit in an embodiment of the charging device according to the present invention, and FIG. 2 is a characteristic diagram. DESCRIPTION OF SYMBOLS 1... DC power supply for supplying charging power, 2... Transistor for switching, 3... Resistor for limiting charging current, 4... Diode, 5... Battery to be charged, 6...
...Auxiliary charging current limiting resistor, 7, 16... Switching circuit, 8... Discharging resistor, 9... Start switch, 10... First timer circuit, 11... Clock circuit, 12... Sampling circuit, 13 ……
AD conversion circuit, 14... logic circuit, 15... second
timer circuit.

Claims (1)

[Claims] 1. A charging device that charges a battery to be charged from a charging power supply power supply via a switching element,
A first switching circuit inserted in a charging line from the charging power supply power source to the battery to be charged, a series circuit of a second switching circuit and a discharging resistor connected in parallel to the battery to be charged, and a start switch. a first timer circuit that turns off the first switching circuit and turns on the second switching circuit for a certain period of time based on the on-state, and extracts the terminal voltage of the discharge resistor immediately before the on-time of the second switching circuit ends; an AD conversion circuit that converts the output voltage of this sampling circuit into a digital signal, a logic circuit that discriminates the output signal of this AD conversion circuit and outputs a selection signal, and an output voltage of this logic circuit. A charging device comprising: a second timer circuit that turns on the switching element for a corresponding time based on a selection signal. 2. The charging device according to claim 1, wherein the discharging resistor is set to flow a discharging current that is 2 to 3 times the ampere-hour capacity of the battery to be charged.