JP2551567B2 - Charge control circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control circuit of a charging current in a charger for charging a battery to be charged.

(Prior Art) As a charging current control circuit for a charger, one shown in FIG. 1 is known. That is, in FIG. 1, 1
Is a transistor inverter, and this inverter 1 is connected between both output terminals of a rectifying power source 2 for rectifying an input voltage via a battery 3 to be charged. The output winding 6 wound around the same core as the wire 5 is connected in parallel, and the output winding 6, diode 7, battery 3,
The output winding 6 constitutes a closed circuit. A charge completion indicating element 8 such as a light emitting diode or a lamp is connected in parallel to the output winding 6. Further, the rectifying power source 2 has a current limiting resistor 9
And a rectifying diode 10 and a capacitor 11.

A is a charge control circuit, and the charge control circuit A connects a series circuit of a resistor 12 and a zener diode 13 between both output terminals of the rectifying power source 2 to make the rectified voltage a constant voltage, and connects the zener diode 13 in parallel. The voltage divided into a constant voltage by the voltage dividing circuit of the resistors 14 and 15 and the diode groups 16 and 17 is divided, and the divided voltage is used as a reference voltage Vs for comparison with the voltage of the battery 3. Resistance 14
The collector of the first transistor 18 is connected to one end of the series circuit of the diode group 16 via the resistor 19, and the base of the transistor 18 is connected to the other end.

The emitter of the transistor 18 is connected to the positive electrode of the battery 3 via the series circuit of the resistor 20 and the resistor 21.
The collector of is connected to the base of the second transistor 23 via a diode 22. The emitter of the second transistor 23 connects the resistor 20 to the connection point of the resistor 21, and the collector of the second transistor 23 is connected to the base of the output transistor 24 of the transistor inverter 1. In addition, 25 is a starting resistor, 26 is a speed-up capacitor, 27 is a base current limiting resistor, and 28 and 29 are spike voltage absorbing circuit capacitors and resistors.

Now, when the transistor inverter 1 is operated by the direct current obtained from the rectification power source 2, the transistor inverter 1 causes blocking oscillation and generates a high frequency voltage in the output winding 6. The voltage generated in the output winding 6 is rectified by the diode 7 to charge the battery 3, and the charge completion display element 8 is turned on to indicate that the battery is being charged. When the terminal voltage of the battery 3 at the beginning of charging is low, the charge control circuit A compares the reference voltage Vs with the battery voltage to turn on the transistor 18, and thus turn off the transistor 23.

Therefore, the transistor inverter 1 is normally biased and operates. When the charging progresses and the terminal voltage of the terminal battery 3 becomes higher, the reference voltage Vs is compared with the battery voltage, the transistor 18 is turned off, the transistor 23 is turned on, and the base current of the transistor inverter 1 is bypassed by the transistor 23. The operation of the transistor inverter 1 is stopped and charging is stopped. Therefore, the charging completion display element 8 is also turned off and the charging completion is displayed.

When the voltage of the battery 3 drops in this charging stopped state, the transistor 18 is turned on again and the transistor 23 is turned off. By repeating this, the average value of the end-of-charge current is reduced, and the charge completion display element 8 blinks to display the completion of charge.

FIG. 2 is a charging characteristic diagram. In the figure, the part surrounded by a circle shows the part at the end of charging, and at the end of charging,
The operation shown in the figure is performed.

Here, the battery voltage V when the transistor 18 is turned off
_{If THH} and the battery voltage at the time of turning on are V _THL , the end-of-charge current is determined by the voltage characteristics and V _THH , V _{THL in} which the voltage of the battery _rises and falls depending on the turning on and off of the charging current. Battery voltage V _THH , V to turn on / off transistor 18
_THL can be determined by the constants of each part belonging to the charge control circuit A, but the characteristics of the battery cannot be adjusted.

The voltage V _{THL at} which the transistor 18 turns on is lowered, that is,
If the difference between V _THH and V _THL is set to a large value, the period during which the transistor inverter 1 stops, that is, the period when the charging current is zero, becomes long, and the light-off time of the charging completion element 8 also becomes long, and it does not light easily. I don't know if the charger is working properly. On the other hand, increase V _THL , that is, V
_When the difference between _THH and V _THL is set to be small, the cycle of lighting and extinguishing is accelerated, the charging completion element 8 blinks quickly, the completion of charging is not clearly known, and it becomes difficult to set the end-of-charge current.

Even if the battery keeps the charging current at a safe current,
As shown in the figure, when the battery voltage peak is exceeded, the battery voltage gradually decreases, so it becomes difficult for the battery voltage to rise to V _THH , and finally, the battery voltage does not rise to V _THH and recharge occurs. The charging current becomes the current value before the charging control is applied, which causes a problem that the battery to be charged deteriorates due to overcharging.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and outputs a reference oscillation signal in response to a signal from a voltage detection unit that detects a terminal voltage of a battery to be charged. It is possible to obtain a stable end-of-charge current by controlling the current, and to provide a charge control circuit that resets the full charge state when the load is driven in this state to drive the load appropriately. To aim.

(Structure of the Invention) A charging control circuit according to the present invention is a charging control circuit in which a battery to be charged is connected in series with a switching element, and charging is performed by switching the switching element. A voltage detecting means for detecting the voltage of the battery, and a reference oscillating circuit for intermittently turning on / off the switching operation of the switching element when a detection signal indicating that the detected voltage by the voltage detecting means has reached a predetermined voltage is received. A switch provided between the battery to be charged and a load connected in parallel, and a reset circuit that stops the operation of the reference oscillation circuit in conjunction with the switch are provided.

(Example) This invention is demonstrated along an Example.

In FIG. 5, 1 is a transistor inverter circuit,
Reference numeral 2 is a rectifying power source, and B is a pre-pressure detection circuit that detects the voltage of the battery 3 to be charged. Here, the charged battery 3 is 1
Although cells are taken as an example, any number of cells may be used as long as they are voltage detection circuits matching the number of cells to be charged. Explaining the voltage detection circuit B of this embodiment, T1 is a power supply terminal of the voltage detection circuit B, T2 is an input terminal for reading the voltage of the battery 3 to be charged, T3 is an output terminal, and T4 is a GND terminal.

C is a reference oscillation circuit, which is composed of a latch circuit D and an astable multivibrator E that produces a reference oscillation signal. In the latch circuit D, T5 is a power supply terminal, T6 is an input terminal from the voltage detection circuit B, and T7 is an output. Terminal, T8 is GND terminal. T9 is an output terminal of the astable multivibrator E. F is a power supply for the voltage detection circuit B and the reference oscillation circuit C, and the power supplies for the four NAND elements 30, 31, 32, 33 are also terminals T
Got from 5.

Now, when an input voltage is applied to the rectified power supply 2, the transistor inverter 1 operates and the battery 3 to be charged is charged. When charging progresses and the terminal voltage of the battery 3 at the end of charging rises, the reference voltage Vs of the voltage detection circuit B is compared with the battery voltage. If the battery voltage is high, the output terminal T3 of the voltage detection circuit B outputs the signal H ( High) → L (low) is issued.

The H → L signal is input to the input terminal T6 of the latch circuit D. In the latch circuit D, the output terminal T7 first outputs the H signal, but once the H → L signal is input to the input terminal T6, the output terminal T7 becomes H → L and the input of the input terminal T6 becomes
After that, regardless of whether it becomes H or L, the output terminal
T7 uses a circuit that remains L. The base of a transistor 35 is connected to the output terminal T7 of the latch circuit D via a resistor 34, and the emitter of this transistor 35 is GND.
In addition, the collector is connected to the base of the control transistor 36. The base of the transistor 36 is connected to the output terminal T9 of the unstable multivibrator E via the resistor 37, the emitter of the transistor 36 is connected to GND, and the collector is connected to the base of the output transistor 24 of the transistor inverter 1. ing.

As shown in FIG. 6, in the unstable multivibrator E, the output of the output terminal T9 repeats H and L.
The frequency of the H signal is determined by the capacitor 38 and the resistor 39, and the frequency of the L signal is determined by the capacitor 38 and the resistor 40. Since the output terminal T7 of the latch circuit D is initially H, the transistor 35 is turned on and the transistor 36 is turned off, so that the output transistor 24 of the transistor inverter 1 normally oscillates.

When the output terminal T7 of the latch circuit D goes from H to L, the transistor 35 is turned off, the transistor 36 is repeatedly turned on and off by the output of the unstable multivibrator E, and when the transistor 36 is on, the transistor inverter 1 Since the base of the output transistor 246 is biased, the output transistor 24 stops oscillating and does not charge the battery 3 to be charged.

Therefore, once the voltage detection circuit B detects the control voltage, the end-of-charge current after charging control and the blinking cycle of the display element 8 for completion of charging are controlled by the capacitor 38 regardless of the voltage characteristics of the battery.
Since the resistance can be adjusted with the resistors 39 and 40, the end-of-charge current can be set to a safe current of the battery, and there is no concern about recharging.

When charge control is performed by the voltage detection method as described above,
During charge control, the battery capacity of the battery 3 to be charged is about 80%.

On the other hand, the resistor 41 and the capacitor 42 in the charge detection circuit B are provided with a time constant, and a zener diode 44 is shown in FIG. 7 between the connection point of the resistor 41 and the capacitor 42 and the base of the transistor 43. In the case of the voltage detection circuit B inserted as described above, the circuit can secure a larger capacity. That is, this circuit compares the reference voltage Vs with the end-of-charge voltage,
When the end-of-charge voltage reaches the reference voltage Vs, the transistor 18
Is turned off, the transistor 23 is turned on, the transistor 45 is turned off, and since the resistor 41 and the capacitor 42 have time constants, it takes a certain time until the transistor 43 turns on. , The charging current is the original charging current that is not controlled as shown in FIG.
Since the charging is continued for a certain period of time determined by the RC timer circuit, more capacity can be secured.

Further, as another means for securing a larger charging capacity, the resistances 39 and 40 of the non-stable multivibrator E may be given temperature characteristics. That is, the transistor inverter 1 generates heat as shown in FIG. 9 when charging the battery 3 to be charged. Immediately before charging control is the peak temperature rises,
After the charge control, the transistor inverter 1 oscillates intermittently by the basic oscillation circuit C, so that the temperature gradually decreases.

Taking advantage of the above temperature characteristics, the resistors 39 and 40 are given temperature characteristics, the duty of the on time of the output transistor 24 is increased immediately after the charging control, and if the temperature of the transistor inverter 1 gradually decreases, the output transistor 24 turns on. It suffices to gradually reduce the duty of time and drop the charging average current to the safe current of the battery 3 to be charged when the temperature of the transistor inverter 1 becomes stable.

In the non-stable multivibrator E, the resistor 39 determines the H signal at the output terminal T10, and the resistor 40 determines the frequency of the L signal at the output terminal T10. When the temperature is high as shown in FIG. , When the L signal is lengthened and the temperature is lowered, it is preferable to lengthen the H signal and shorten the L signal. Therefore, the resistance 39 has a small resistance value when the temperature is high, and a resistance value that increases when the temperature is low, that is, a thermistor resistance having a negative characteristic is used.
On the contrary, a positive characteristic thermistor resistance may be used for the resistor 40. Further, at this time, only one of the resistor 39 and the resistor 40 may be used as the resistor having the temperature characteristic.

The shaded portion of the average charging current in FIG. 10 corresponds to the increase in the charging capacity of the battery 3 to be charged utilizing the temperature characteristic of the transistor inverter 1.

FIG. 11 shows another embodiment of the present invention. In this embodiment, a load 47 such as a motor is connected to both ends of the battery 3 to be charged through the switch 46 in the embodiment shown in FIG. 5, and the load 47 is driven by turning the switch 46 on and off. It is the one. By the way, in this case, when the voltage of the battery 3 to be charged rises, the output transistor 24 of the transistor inverter 1 is controlled and the output transistor 24 of the transistor inverter 1 is controlled and the switch 46 is turned on when the output transistor 24 is oscillated intermittently.
It is expected that the motor of the load 47 will have uneven rotation in synchronization with the intermittent oscillation cycle of 24.

Therefore, in the embodiment of FIG. 11, the load side of the switch 46 is connected to the base of the transistor 49 via the resistor 48, and the collector of the transistor 49 is connected to the connection point of the resistance of the power source F and the Zener diode, that is, the terminal T5. A reset circuit is provided in which the emitter is connected to GND.

With this configuration, the transistor 49 is turned on when the switch 46 is turned on when the load 47 is driven regardless of whether the charge control is performed before or after the charge control, and the power sources of the voltage detection circuit B and the reference oscillation circuit C are set to "L". Then, the charging control is not applied, and the rotation of the motor of the load 47 is prevented. When the switch 46 is turned off again, the power source F of the voltage detection circuit B and the reference oscillation circuit C returns to normal, and the return voltage detection circuit B compares the charged battery 3 with the reference voltage Vs.
Perform normal charge control.

As described above, according to the present invention, the voltage detection means for detecting the voltage of the battery to be charged, and the detection signal when the detection voltage by the voltage detection means reaches a predetermined voltage Switching operation of the switching element is turned on intermittently.
Since a configuration with a reference oscillation circuit for off control is adopted, it is possible to prevent recharging exceeding the peak of the battery voltage as in the past, and to keep the charging current within the safe current range of the battery to be charged. Since it can be controlled, stable charging can be completed. Moreover, since the switch provided between the battery to be charged and the load connected in parallel and the reset circuit that stops the operation of the reference oscillation circuit in association with the switch are provided, the load driving can be performed. Since the state in which the charging control is applied is restored to the state in which the charging control is not applied in association with the operation of the instructing switch, the load driving can be appropriately performed.

[Brief description of drawings]

FIG. 1 is a conventional charge control circuit and circuit diagram, FIG. 2 is a characteristic diagram of charge capacity and battery voltage of a battery to be charged, and FIGS. 3 and 4 are explanatory diagrams of operation by the circuit of FIG. FIG. 5 is a circuit diagram of a charge control circuit according to an embodiment of the present invention, FIG. 6 is an explanatory diagram of an operation by the circuit, FIG. 7 is a partial circuit diagram according to another embodiment, and FIG. 8 is an operation by the circuit. FIG. 9, FIG. 9 is a temperature characteristic diagram of a battery voltage and a transistor inverter, FIG. 10 is an operation explanatory diagram in the case of another embodiment, and FIG. 11 is a circuit diagram of a charge control circuit according to still another embodiment. is there. 1 ... Transistor inverter, 3 ... Battery to be charged,
24: Transistor (switching element), B: Voltage detection circuit, C: Reference oscillation circuit, E: Astable multivibrator, 39, 40, 41 ... Resistor, 42 ... Capacitor, 46
...... Switch, 47 …… Load, 49 …… Transistor (reset circuit).

Claims (1)

(57) [Claims] 1. A charging control circuit in which a battery to be charged is connected in series with a switching element and charging is performed by switching the switching element, and voltage detection means for detecting the voltage of the battery to be charged. A reference oscillating circuit for intermittently turning on and off the switching operation of the switching element when a detection signal indicating that the voltage detected by the voltage detecting means has reached a predetermined voltage is received, and in parallel with the battery to be charged. A charge control circuit comprising: a switch provided between a connected load and a reset circuit that stops the operation of the reference oscillation circuit in conjunction with the switch.