JPH0426334A - Charge control circuit for secondary battery - Google Patents

Abstract

PURPOSE:To perform output control appropriately and reliably through a relatively simple structure by continuously detecting the surface temperature of a secondary battery and stopping the operation of an inverter circuit forcibly through a drive control means when thus detected temperature exceeds a set value. CONSTITUTION:A charge control circuit for secondary battery comprises a temperature detecting means producing a signal when the temperature rises to a predetermined level through charging operation, a capacitor 41 for feeding the temperature detecting mans with driving power, means interlocked with an inverter circuit 22 to control the charging amount of the capacitor 41, and a drive control means interlocked with a signal fed from the temperature detecting mans to stop operation of th inverter circuit 22. When the temperature on the surface of a secondary battery 6 or the vicinity thereof exceeds an upper limit, the temperature detecting means starts to output a signal and sustains output of signal until the temperature drops below a lower limit. Consequently, transition can be made reliably from quick charge to supplementary charge through a relatively simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charging control circuit for a secondary battery, and particularly to one that limits charging when a temperature rise accompanying charging exceeds a set value.

[Prior Art] Conventionally, this type of charging control includes an inverter circuit as a charging means, and by giving temperature characteristics to the circuit elements of this inverter circuit, the output from the inverter circuit is reduced as the temperature rises. Restrictions are common.

Furthermore, it has been proposed that a temperature detecting means is provided separately from the inverter circuit, and when this detecting means detects a temperature rise, the output from the inverter circuit is limited.

[Problems to be Solved by the Invention] However, with the method of imparting temperature characteristics to the circuit elements of the inverter circuit, it is difficult to appropriately respond to the temperature rise of the secondary battery.

On the other hand, the method of controlling the output of the inverter circuit by providing a separate temperature detection means allows the output to be controlled in response to temperature rises at any location, but on the other hand, when trying to perform appropriate control in response to the state of charge, the circuit configuration becomes difficult. ! becomes sloppy, and as a result, −
On the other hand, there was a problem in that proper control operations could not be performed due to malfunctions.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a charging control circuit that has a relatively simple configuration and can reliably perform appropriate output control.

[Means for Solving the Problems] As shown in the schematic configuration of FIG. 1, the charging control circuit according to the present invention includes a temperature detection means that generates a signal when the temperature rise due to charging reaches a predetermined value; A capacitor 41 that supplies driving power to the temperature detection means, and an inverter circuit 2
2, and a drive control means for stopping the operation of the inverter circuit 22 in conjunction with the input of the signal sent from the temperature detection means. ing.

The temperature detecting means described above starts outputting a signal when the temperature on or near the surface of the secondary battery 6 exceeds the upper limit temperature Ta shown in FIG. 2(a), and reaches the lower limit temperature T.

It is possible to maintain the output of the signal until the voltage drops below , and also to change the magnitude of the output signal in accordance with the amount of charge of the capacitor 41.

[Function] With the above-described configuration, when the commercial AC power source 13 is applied to the inverter circuit 22, it is converted to a predetermined charging voltage and charging of the secondary battery 6 is started.

At the same time, the charge amount control means operates, and the capacitor 4
1 to start the temperature detection means.

As charging progresses, for example, the surface temperature of the secondary battery 6 increases accordingly. This temperature rise is continuously detected by the temperature detection means, and when the temperature exceeds a set value, a signal is sent to the drive control means, and the drive control means forcibly stops the operation of the inverter circuit 22.

Then, the charging of the capacitor 41 by the charge amount control means is stopped, the capacitor 41 is discharged, and the magnitude of the output signal of the temperature detection means is reduced or stopped. As a result, the operation of the drive control means is stopped, and the inverter circuit 22 is Resume oscillation. At that moment, the inverter circuit 22 stops oscillating again in substantially the same manner as above, and as a result, the inverter circuit 22 is driven intermittently at time intervals determined by the discharging time constant of the capacitor 41, and as a result, the secondary battery 6 Charging for the battery will then shift to supplementary charging.

By providing a hysteresis characteristic to the temperature detection described above, once the surface temperature of the secondary battery 6 reaches the upper limit value Ta, the input of the commercial AC power supply 13 is stopped and the drive of the inverter circuit 22 is completely stopped. The supplementary charging state can be maintained until the temperature drops below the lower limit value Tb.

[Example] The present invention will be described below based on an example in which the present invention is implemented in an electric shaver, but the present invention is not limited to this, but the present invention can be applied in substantially the same way to various small electric devices that are equipped with a charging device alone or a charging means in a power source part. Of course, it can be implemented.

As shown in FIG. 3, an electric shaver 1 embodying the present invention has an outer cutter 2 removably attached to the upper part of a main body case 3, and a spiral inner cutter 4 disposed inside the outer cutter 2. are placed in sliding contact. Furthermore, inside the main body case 3, there is a motor 5 that rotationally drives the inner cutter 4, a secondary battery 6 that supplies rotational driving power to the motor 5, and a charging control for the secondary battery 6 or a motor 5. It houses an electric circuit 7 that performs various controls such as rotation control. Further, in the center of the front of the main body case 3, there is provided a knob 9 of a sliding switch 8 that regulates the timing of energization of the motor 5, and below the switch knob 9, a motor rotation display section 10 that displays the rotation control status of the motor 5. and a battery capacity display section 11 that displays changes in battery capacity. Furthermore, at the bottom of the main body case 3, there is a power cord 1 with a power plug at the tip.
2 can be inserted and removed freely, and in addition to charging the secondary battery 6, the motor 5 can be directly driven by the commercial AC power source 13.

FIG. 4 shows the electrical circuit 7 built into the main body case 3 mentioned above.
It is a block diagram showing the overall schematic configuration, and includes a charging circuit 14 for the secondary battery 6, a drive circuit 15 for the motor 5, and a detection circuit 16 that performs various detection operations for the charging circuit 14 and the motor drive circuit 15. , a control circuit 17 that generates a predetermined signal in response to a detection signal input from the detection circuit 16, and a display circuit 18 that displays a display corresponding to the states of the charging circuit 14 and the motor drive circuit 15.

The charging circuit 14 performs full-wave rectification of the commercial AC power supply 13 in a rectifier 20, then applies the voltage to an inverter circuit 22 via a temperature fuse 21, and after the inverter circuit 22 steps down the input voltage to a predetermined charging voltage, A charging current is supplied to a secondary battery 6 such as a Ni-Cd battery.

The inverter circuit 22 includes an FET 23 as shown in FIG.
is used as a neutral switching element in the main circuit, and the current flowing through the switching transistor 24 provided in parallel with the gate terminal of this FET 23 and the resistor 25 provided on the base side of the transistor 24 is set to a predetermined value. The off timing of the FET 23 is regulated by turning the FET 23 on in response to a period in which the FET 23 is exceeded, and by bypassing the gate voltage with the transistor 24. That is, from the rectifier 20 side, FET2
In conjunction with the application of gate voltage to the gate terminal of FET 3, FET 23 is turned on, and the current flowing through resistor 25 connected in series with the main circuit gradually increases. When this current exceeds a predetermined value, the transistor 24 turns on and the FET 23
As a result, no current flows through the resistor 25 through the FET 23, but a pulse-like voltage is output from the output coil 26 of the inverter circuit 22, and this voltage causes the Zener diode 27 to conduct, causing current to flow through the resistor 25. As a result, the on state of the transistor 24 is further maintained.

When the output voltage from the output coil 26 is removed, the transistor 24 is turned off again, repeating the operation described above.

The motor drive circuit 15 applies the output voltage from the secondary battery 6 side described above to the motor rotation control section 28 via the switch 8, and performs rotation control to maintain the rotation speed of the motor 5 constant, while displaying the In the drought-sun rotation display section 10 of the circuit 18, the state in which rotation control is being performed is displayed by flashing light emitting diodes.

The detection circuit 16 includes a detection section 2 that detects the presence or absence of AC input.
9 and a load drive timing detection unit 30 to constantly detect the charging/discharging state of the secondary battery 6, and the control circuit 17 integrates changes in charging capacity using a timer.
The current capacity of the secondary battery 6 is displayed on the battery capacity display section 11.
Relative display is performed by increasing or decreasing the number of blinking light emitting diodes. Furthermore, the load amount detection section 31 detects the magnitude of the load current and corrects the rate of increase/decrease at the time of relative display of the current capacity, and the battery voltage detection section 32 detects the lower limit voltage and upper limit voltage of the secondary battery 6. The pressure is measured and the displayed value of battery capacity is corrected to account for the difference.

On the other hand, when the secondary battery 6 is rapidly charged, after the battery voltage detection unit 32 detects that the terminal voltage of the secondary battery 6 has reached the set value, the control circuit 17 further detects that a certain period of time has elapsed. When it is determined that a preset condition has been reached by software such as The battery is stopped intermittently to transition from rapid charging to supplementary charging. Furthermore, in the ambient temperature detection section 34,
For example, when it is detected that charging is being performed at a low temperature such as 0°C or lower, the charging current is narrowed down more rapidly than when controlling by normal battery voltage, and the internal gas pressure of the secondary battery 6 is reduced. Prevent abnormal rise. Furthermore, the battery temperature detection unit 35 constantly detects the surface temperature of the secondary battery 6, and when the control circuit 17 determines that the temperature has risen above the set temperature, the control circuit 17 detects the temperature as described above. A control signal is immediately sent to the switching transistor 33, and the charging operation by the inverter circuit 22 is configured to shift from rapid charging to supplementary charging.

In addition to the charging control operation by software in the control circuit 17 described above, the present invention separately includes a charging control section 40 configured with hardware shown in FIG. Even if there is a charge current, the feature is that the charging current can be directly narrowed down.

The charging control unit 40 includes a capacitor 41 provided as a power source.
In contrast, the secondary battery 6 is connected via the switching element 42, and the inverter circuit 22 is activated to turn on the switching element 42 corresponding to the charging period from the output coil 26 to the secondary battery 6. 41 is charged to the terminal voltage of the secondary battery 6. The charging voltage of the capacitor 41 is stabilized by the voltage regulator diode 43, and then the voltage is stabilized by the resistor 44.4.
5 to form a reference voltage, and a thermistor 46 and a resistor 47 placed in contact with the peripheral surface of the secondary battery 6 to divide the voltage to form a detection voltage, each of which is used as the input voltage of a comparator 48. There is.

The comparator 48 uses an operational amplifier, inputs the above-mentioned reference voltage to the positive terminal, inputs the detection voltage to the negative terminal, and connects the control transistor 4 to the output terminal.
9, the surface temperature of the secondary battery 6 rises, the resistance of the thermistor 46 decreases, and when the detected voltage falls below the reference voltage, the output of the comparator 48 becomes rJ, J
From rH.

The oscillation of the inverter circuit 22 can be forcibly stopped by turning on the transistor 49 and grounding the gate terminal of the FET 23 provided in the inverter circuit 22.

Further, the comparator 48 is of an oven collector type, and the charging voltage of the capacitor 41 is applied to the output terminal via a resistor 50, and positive feedback is applied via the resistor 51 to maintain a predetermined hysteresis characteristic. It is configured to have

With the above configuration, the inverter circuit 2
Immediately after connecting the commercial AC power supply 13 to 2, the capacitor 41
There is no charging, the transistor 49 is in an off state because the base voltage is low, and the inverter circuit 22 starts normal oscillation. Immediately after that, the switching element 42 is turned on, the capacitor 41 is rapidly charged by the secondary battery 6, and the comparator 48 starts a predetermined comparison operation. When charging of the secondary battery 6 progresses and the temperature of the battery surface rises to reach the upper limit temperature Ta at time t1, the comparison voltage across the thermistor 46 becomes lower than the reference voltage and the output is reversed. Then, the transistor 49 is turned on and the oscillation of the inverter circuit 22 is forcibly stopped, and accordingly the switching element 42 is turned off, charging of the capacitor 41 is stopped, and discharging is started. When the voltage across the capacitor 41 decreases to below the on-voltage of the transistor 49, the transistor 49 is turned off and the inverter circuit 22 resumes oscillation, but at that moment the switching element 42 is turned on and the capacitor 41 is turned off. The battery is charged to the voltage, and the inverter circuit 22 is turned off again. The above-mentioned on/off cycle is determined by the discharge time constant of the capacitor 41, and by intermittent driving the inverter circuit 22 at a rate of, for example, about a few tenths of the time of rapid charging, the secondary battery 6 can be switched from the rapid charging state to the auxiliary charging state. They are forced to move into the state. Since the comparison Wg 48 is provided with hysteresis, the intermittent oscillation state described above continues even when the surface temperature of the secondary battery 6 falls below the upper limit temperature Ta shown in FIG. 2(a), and the inverter circuit 2
It is reset when the input of the commercial AC power supply 13 to the battery 2 is cut off and the surface temperature of the secondary battery 6 falls below the lower limit temperature Tb.

Note that the power source for charging the capacitor 41 is not limited to the secondary battery 6, and can also be supplied from the power source voltage side. Moreover, instead of using the output from the output coil 26 for charging as the signal for turning on the switching element 42, it is also possible to provide a separate coil exclusively for detection and use its output signal. By supplying the above-mentioned ON signal from the power supply voltage side, it is possible to completely stop the inverter circuit 22 instead of causing it to oscillate intermittently.

[Effects of the Invention] As described above, the present invention supplies the driving power for the temperature detection means from the capacitor 41, and the capacitor 41
Since the amount of charge is controlled in conjunction with the operation of the inverter circuit 22, it is possible to reliably transition from quick charging to supplementary charging with a relatively simple configuration.

Furthermore, by providing hysteresis characteristics during temperature detection, once the temperature detection is activated, the supplementary charging state can be maintained until the charging is completely stopped by unplugging the outlet, thereby suppressing overcharging of the secondary battery as much as possible. be done.

[Brief explanation of drawings]

Figure 1 is a schematic diagram explaining the basic configuration of the present invention, Figure 2 is a schematic diagram explaining the basic configuration of the present invention.
Figures (a) to (C) are waveform diagrams showing control states. Figures 3 to 6 show an example of an electric shaver in which the present invention is implemented, Figure 3 is a partially cutaway front view showing the external appearance, and Figure 4 shows the schematic configuration of the entire electric circuit. FIG. 5 is an electric circuit diagram showing the configuration of the inverter circuit, and FIG. 6 is an electric circuit diagram showing the specific configuration of the main part of the present invention. 6 ・ ・ ]-3 ・ 16 ・ 22 ・ 40 ・ 41 ・ 46 ・ 48 ・ ・Secondary battery, ・Commercial AC power supply, ・Detection circuit, ・Inverter circuit, ・Charge control section, ・Capacitor, ・Thermistor, ・Comparison vessel. Inventor Tomiyasu Mizota 1/Co

Claims (1)

[Scope of Claims] 1. A charging control circuit that controls the operation of an inverter circuit (22) to regulate the end time of rapid charging of a secondary battery (6), which controls the temperature rise due to charging to a predetermined value. A temperature detection means that generates a signal when the temperature reaches the temperature, and a capacitor 41 that supplies driving power to this temperature detection means.
In conjunction with the operation of the inverter circuit (22), means for controlling the amount of charge in the capacitor (41) described above, and in conjunction with the input of the signal sent from the temperature detection means described above, the operation of the inverter circuit (22) is performed. A charging control circuit for a secondary battery, comprising a drive control means for stopping operation. 2. The above-mentioned temperature detection means is configured such that the temperature on or near the surface of the secondary battery (6) is the upper limit temperature T.
When the temperature exceeds _a, the output of the signal is started, and the output of the signal can be maintained until the temperature falls below the lower limit temperature T_b, and the magnitude of the output signal changes in accordance with the amount of charge of the capacitor (41). The charging control circuit according to claim 1.