JPH058764Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a charging circuit that is incorporated into a small electric appliance such as a rechargeable electric shaver.

[Background technology] Figure 6 is from Japanese Patent Application No. 57-134509 (Japanese Patent Application No.
25533) shows a specific circuit diagram of a conventional quick charging circuit. The circuit shown in FIG. 6 uses a power conversion circuit called an on-off type, and first, the circuit operation of this on-off type will be explained. Diode Bridge Ref
By switching the commercial power supply rectified by the transistor Q and smoothed by the capacitor Csu through the coil L1, the magnetic energy stored in _the coil _L1 is transferred to the secondary coil _L2 during the off period of the transistor Q. The diode _D0 is used to rectify the current and charge the battery Ba. here,
Furthermore, the base of transistor Q is charged by charging control circuit A.
The output current is controlled by controlling the output of the The charging control circuit A is composed of a frequency fixing circuit, a pulse width modulation circuit, etc., and is composed of a comparator Cp ₁ , resistors Rf ₁ to Rf ₉ , a capacitor Cf, transistors Qf ₁ and Qf ₂ , and a Zener diode Zf. frequency fixed circuit _A1 ,
It consists of a pulse width modulation circuit A ₂ composed of a comparator Cp ₂ , resistors Rf ₁₀ to Rf ₁₂ and a resistor _RE .
The frequency fixing circuit A ₁ includes a charging circuit for a capacitor Cf consisting of a resistor Rf ₁ and a capacitor Cf, and a resistor Rf ₂ ,
Comparator with reference voltage obtained by voltage division with Rf ₄
Input to Cp ₁ , discharge the capacitor Cf from resistor Rf ₃ through transistor Qf ₁ , and calculate the discharge characteristics of capacitor Cf with respect to the reference voltage obtained from the combined resistance of resistor Rf ₄ , resistor Rf ₅ , transistor Qf ₂ , and resistor Rf ₂ . By keeping constant, the discharge time is made constant, and thereby a pulse waveform with a constant period can be obtained as the output of the comparator _Cp1 .
Thus, this pulse is stabilized by the Zener diode Zf, and the reference voltage obtained by dividing it with the resistors Rf ₁₀ and Rf ₁₁ and the voltage obtained by detecting the secondary current flowing through the coil L ₂ with the resistor R _E are obtained. are compared by comparator Cp ₂ to control the output current.

The second detection sensor _S2 for detecting charge capacity (for overcharge control), which is an output current control means, includes transistors Q _B1 and Q _B2 , a Zener diode Z _B , and a resistor R _B1 ~
It consists of R _B5 . In other words, the voltage stabilized by the Zener diode Z _B is connected to the resistor R _B2 ,
The voltage is divided by R _B3 , and the base of transistor Q _B2
The emitter is compared with the battery voltage through resistor R _B4 , and when the battery voltage rises and the base current of transistor Q _B2 stops flowing, transistor Q _B2 switches from on to off, and transistor Q _B1 switches from off to on. The base of transistor Q is then clamped to stop oscillation and the output charging current to zero. As the charging current becomes zero, the battery voltage drops, and transistors Q _B1 and Q _B2 are inverted again and begin oscillation. This repetition is repeated as intermittent oscillation using the time constant of battery Ba, and the output current is reduced. Next, the operation of the timer circuit shown in the circuit of FIG. 6, which is the detection sensor _S1 for detecting the first charge capacity, will be explained. This timer circuit is composed of a timer IC 11', resistors Rt ₁ to Rt ₃ , a capacitor Ct, and a transistor Qt'. Reference power supply terminal Vref to stabilize reference oscillation for timer from voltage, capacitor Ct and resistance for oscillation
It has a terminal t for connecting Rt ₃ and an output terminal Out. In addition, this timer circuit and charging control circuit A
The charging part is composed of the Thus this timer
The operation of IC11' is as soon as the charger is powered on, it clears the internal frequency divider circuit, divides the reference oscillation set by resistor Rt ₃ and capacitor Ct, and outputs after counting a predetermined number. Terminal Out is H
It changes from level to L level. When the output terminal Out changes from the H level to the L level, the transistor Qt' becomes conductive, and the resistor Rt ₁ is inserted in parallel with the resistor Rf ₁₁ of the charging control circuit A, so that the + terminal of the comparator Cp ₂ This will lower the reference voltage. This allows the comparator
The detection level of Cp ₂ is lowered and the output charging current can be switched. Here, the time limit of the timer circuit is set to, for example, about 1 minute,
This ensures that the required charging capacity can be quickly obtained.

Fig. 7 shows the charging current waveform over time of the circuit shown in Fig. 6. In Fig. 7, the shaded area is the charging portion due to the first average charging current, and T ₁ is the charging portion due to the first average charging current. Time to reach capacity, T ₂ is the battery
This is the detection time of full charge using the second average charging current, which takes a relatively long time to charge at least 80% of the rated charging capacity of Ba.

However, in such a conventional example, since a current several times the normal charging current flows through the _T1 portion, the battery voltage increases even if the battery Ba is empty due to the influence of the internal impedance of the battery Ba. Sometimes I put it away. Therefore, depending on the settings of the detection sensor S ₂ for overcharging prevention, the detection sensor S ₂ may be activated before the battery capacity is reached, that is, before the battery Ba is charged.
may operate and oscillation may stop. Conversely, if the detection voltage of detection sensor S ₂ is increased, there is a risk that even if the battery capacity is full, it will not reach that voltage after switching to the normal charging current, resulting in overcharging. Ta. This state is shown in FIG.
That is, in Fig. 8, the horizontal axis is time and the vertical axis is the battery voltage _VB , and the voltage (reference voltage) at which the detection sensor _S2 for overcharging prevention operates is shown.
When Vth is assumed, under normal conditions, as shown by the solid line, it is not controlled even in the T ₁ portion, but when the internal impedance of the battery Ba is high, as shown by the dashed-dotted line, the control region may be reached.

[Purpose of the invention] The present invention has been provided in view of the above-mentioned points, and by controlling charging by switching the apparent battery voltage, it is possible to ensure the required battery capacity for one or several times. This provides a charging circuit that aims to ensure that the

[Disclosure of the invention] (Example 1) An example of the invention will be described below with reference to the drawings. FIG. 1 shows the first embodiment, and the overall basic configuration is almost the same as that in FIG. The present invention is characterized in that a voltage switching means is provided for switching the battery voltage between the apparent battery voltage and the actual battery voltage in correspondence with the first average charging current and the second average charging current, respectively. be. The voltage switching means is constructed as follows. That is, a transistor Qo is provided between the output terminal Out of the timer IC 11' and the transistor Qt, and the output terminal Out is connected to the base of the transistor Qs via the resistor _Rt4 , and the collector of the transistor Qs is connected to the battery Ba. Connected to the emitter of transistor Q _B2 that detects voltage.

Since the overall basic operation is the same as the conventional one, the explanation will be omitted, and the gist of the present invention will be described. When the power is turned on, the output terminal Out of the timer IC 11', which is the first detection sensor _S1 , is at the H level, so the transistors Qo and Qs are turned on. At this time, the second detection sensor S ₂ for overcharge control
The battery voltage is detected by detecting the voltage Vcut divided by resistors R _B4 and R _B6 . That is, the resistance R _B2 and
The reference voltage Vth divided by R _B3 and the above voltage
Vcut is compared, and when Vth≧Vcut, the transistor
Q _B2 is on and transistor Q _B1 is off, but
When Vth<Vcut, transistor Q _B2 turns off.
Transistor Q _B1 turns on and stops the inverter's oscillation. When the timer IC 11' counts up, the output terminal Out goes to L level, transistors Qo and Qs turn off, and transistor Qt turns on, so the reference voltage of comparator Cp ₂ decreases, the charging current is throttled, and the transistor Since Qs is turned off, the battery voltage V _B remains at the detection terminal (emitter of transistors Q _B2 and Q _B1 )
given to. In other words, Vcut=V _B. In this way, by changing the apparent voltage when looking at the battery Ba side of the detection sensor S ₂ for overcharge control during 1-minute charging and normal charging, the influence on the battery voltage due to the internal impedance of battery Ba can be covered. It is something that can be done. Note that this method is useful because the temperature of the battery Ba is also detected at the same time, so if the detection sensor _S2 , which is the overcharge control circuit, is integrated into an IC, the reference voltage cannot be changed internally.

(Embodiment 2) FIG. 2 shows a specific circuit diagram of the second embodiment. By the way, in a general push-pull type inverter, two windings are required in the oscillation transformer in order to drive the two transistors Q ₃ and Q ₄ , but this makes the structure of the transformer complicated. Ta. In this embodiment, the battery is charged by a self-excited oscillation circuit having one base winding. The alternating current power supply AC is rectified by the diode bridge Ref and supplies power to the oscillation circuit 8. The base resistor R ₂ is connected to the base winding L ₃ of the transformer T ₃ ,
An oscillation circuit 8 is constituted by this base resistor R ₂ , transistors Q ₃ and Q ₄ , transformer T ₃ and the like. Also,
A control circuit 5 is composed of transistors Q ₅ and Q ₆ ,
The phototransistor PT and photodiode PD of the photocoupler PC form a non-contact connection to separate the input side and output side of the signal system.

When the alternating current power supply AC is turned on, the base resistor R ₂ for starting oscillation turns on either transistor Q ₃ or Q ₄ . transistor Q ₃
When is on, the base current of transistor _Q3 is
It flows through winding L ₃ , resistor R ₂ , transistor Q ₃ , transistor Q ₆ , and when transistor Q ₄ is on, it flows through winding L ₃ , transistor Q ₄ , transistor
Q ₅ flows through resistor R ₂ and turns on alternately.
The main purpose of transistors Q ₅ and Q ₆ of control circuit 5 is to
The purpose is to bypass the base current of transistors Q ₃ and Q ₄ , and the emitter current of transistors Q ₃ and Q ₄ is detected by resistor R ₃ , and the voltage drop across resistor R ₃ is detected between the base and emitter currents of transistors Q ₅ and Q ₆ . This bypasses the base currents of the transistors Q 3 and Q 4 when the voltage exceeds the voltage between the transistors Q ₃ and Q ₄ . Therefore, the resistance R ₃
The output current of the oscillation circuit 8 can be varied by the value of .
The photo coupler PC is connected in parallel with the resistor _R3 , and operates when the photo coupler PC is turned on so as to substantially reduce the resistance value of the resistor _R3 .

Here, the configuration and operation of the inverter control IC 12 will be explained. The equivalent circuit of the inverter control IC 12 is shown in FIG. 3, where the power supply voltage Vcc input from the terminal is stabilized by the transistor _Z1 , diodes _D5 , _D6 , resistor _R10 , resistor _R11 ,
A reference voltage Vref is provided which is divided by diodes D ₇ , D ₈ and D ₉ . By comparing this reference voltage Vref and the battery voltage V _B input from the terminal,
Battery When battery V _B is higher than reference voltage Vref, transistor Tr ₂ operates and the output terminal becomes low level. Therefore, it draws a current through resistor B ₁₂ in FIG. Therefore, transistor _Q9 is turned off, and since no current is applied to photodiode PD, phototransistor PT is also turned off. Then transistor _Q8 is also turned off and the battery
The charging current to Ba is cut off. However, if the oscillation circuit 8 stops oscillating at all, no voltage will be generated in the auxiliary winding L ₆ and no power will be given to the inverter control IC 12. Therefore, by connecting the resistor R ₁₃ , even when the charging current is cut off, no voltage is generated in the auxiliary winding L 6. It is configured to constantly oscillate and obtain power from the auxiliary winding _L6 .
In this way, by providing the auxiliary winding L ₆ and keeping the oscillation circuit 8 constantly oscillating, the voltage of the battery Ba can always be detected when the battery voltage drops or when the battery Ba is unplugged from the adapter plug. It is possible to stably supply power to the circuit (inverter control IC 12) and the timer circuit (timer IC 11). Note that while the battery Ba is being charged, a current flows through the light emitting diode LED ₁ because the transistor Q ₉ is on, and the LED 1 lights up.

The embodiment shown in FIG. 2 also includes a circuit that can switch the charging current to the battery Ba using a timer. The timer IC11 is the one, and Figure 4 shows the block diagram of the timer IC11 (TA7326P).
Timebase TB that generates reference clock pulses
It consists of a multi-stage flip-flop FF ₁ , FF ₂ . . . for frequency-dividing the clock pulse of the time base TB, a flip-flop FF for reset and set, and an output transistor.

When the power is turned on, the timer IC11 operates.
Since the terminal of the timer IC11 is at the L level, no current is supplied to the photodiode _PD2 , so the phototransistor _PT2 is off and the transistor _Q7 is on. Also, when the battery voltage _VB is low, the inverter control IC12 has a terminal H
Because of this level, transistor _Q9 turns on, current is supplied to photodiode PD, and phototransistor PT turns on.
When the resistor _R3 is turned on, the transistor _Q8 is also turned on.
and _R16 are in parallel, and the collector current of transistors _Q3 and _Q4 flows. As a result, the charging current to battery Ba becomes large. When timer IC11 counts up, the terminal of timer IC11 goes to H level, current is supplied to photodiode _PD2 , and phototransistor _PT2 turns on. When phototransistor _PT2 turns on, transistor _Q7 turns off, and when only transistor _Q8 turns on, the collector current of transistors _{Q3 and Q4} flows only through resistor R3, so the impedance becomes high, and the collector current is limited by transistors _Q5 and _Q6 , reducing the charging current.
When the output terminal of 1 is at H level, the transistor
Turn on Q ₁₀ to light up the light emitting diode LED ₂ .

The internal circuit of the inverter control IC 12 is equivalent to the circuit of the detection sensor S ₂ for overcharge control shown in Fig. 1. In this circuit configuration, the battery Ba body and the circuit are separated, so when connected Since a contact resistance occurs in the contact resistance, and the voltage drop due to this contact resistance changes greatly depending on the charging current, as shown in FIG _.
The collector of this transistor Qo is connected to the power supply through a resistor Ro ₂ , and the emitter is grounded. Also, the collector of transistor Qo is a transistor
The collector of the transistor Qs is connected to the base of the transistor Qs, and the resistor Rx ₂ is connected to the terminal of the inverter control IC12.
The emitter is connected through and grounded. These transistors Qo, Qs, resistor Ro ₁ . . . constitute a voltage switching means, and the operation is as follows. In other words, when the power is turned on, the timer IC
The output terminal of No. 11 is at L level, transistor Qo is off, and transistor Qs is on.
Therefore, the battery voltage V _B is divided between the resistors Rx and Rx ₂ , and this divided voltage is used as the apparent voltage of the battery Ba, which is lower than the actual battery voltage Ba and is applied to the terminals of the inverter control IC 12. giving. Next, after the timer IC11 counts up, the output terminal of the timer IC11 becomes H level.
Since the transistor Qo is turned on and the transistor Qs is turned off, the battery voltage V _B is applied as is to the terminal of the inverter control IC 12.
By doing this, the inverter control IC
Charging control can be performed without changing the internal reference voltage of the battery Ba, and the influence of internal impedance and contact resistance of the battery Ba can also be reduced.

(Example 3) FIG. 5 shows a third example. In each of the embodiments described above, the battery voltage was switched between the apparent battery voltage and the actual battery voltage in correspondence with the first average charging current and the second average charging current, respectively. The same results as switching the battery voltage can be obtained by switching the reference voltage. Therefore, in this embodiment, the reference voltage of the output current control means is switched to a voltage that switches the reference voltage of the output current control means to an apparent reference voltage and an actual reference voltage corresponding to the first average charging current and the second average charging current. A switching means is provided. In other words, inverter control
Insert a diode Ds into the GND terminal of IC12,
By connecting a transistor Qs in parallel to this diode Ds, the reference voltage inside the inverter control IC 12 is increased. In other words, when the power is turned on, transistor Qs is off and the inverter control IC
The reference voltage 12 becomes higher by the forward drop voltage of the diode Ds, and when the timer IC 11 counts up, the transistor Qs turns on.
The reference voltage will be lowered. Therefore, charging control of the battery Ba becomes possible in the same manner as described above. Also,
This diode Ds may be replaced with a resistor.

[Effects of the invention] As described above, the present invention provides a first average charging current that charges energy equivalent to N times of use of an electrical device (N is a number of 1 or more) in a relatively short time, and a battery rating. a charging unit that sequentially and selectively supplies a second average charging current that charges at least 80% of the charging capacity over a relatively long period of time; and a charging unit that compares the battery voltage with a reference voltage and charges the battery with a charging current. and a timer that controls the charging section with its output to switch the charging current from the first average charging current to the second average charging current when the timer expires after a predetermined time from the start of charging. In the charging circuit, when the timer times out, the battery voltage detected at the same time as the charging current is changed so that the detected battery voltage changes from an apparent battery voltage that is lower than the actual battery voltage to the actual battery voltage. or switching the reference voltage of the output current control means from an apparent reference voltage higher than the actual reference voltage corresponding to the second average charging current to an actual reference voltage. Since the voltage switching means switches the battery voltage or the reference voltage of the output current control means in accordance with the first average charging current and the second average charging current, the internal impedance of the battery and Compared to conventional configurations in which contact resistance causes the battery to not be charged or is overcharged due to changes in voltage drop caused by the charging current, these effects can be reduced, and the capacity during short-term charging can be reduced. It can reduce overcharging of the battery due to insufficient voltage or incorrect setting of the reference voltage.Furthermore, since the voltage switching means is switched by a timer, there is no need for a resistor to detect the charging current of the battery, which reduces the loss and heat generated by this resistance. The advantage is that there are no problems.

[Brief explanation of drawings]

Figure 1 is a specific circuit diagram of one embodiment of the present invention, Figure 2 is a specific circuit diagram of an embodiment of the present invention.
The figure is a specific circuit diagram of another embodiment of the same as above, Figure 3 is an internal circuit diagram of the inverter control IC of the same as the above, Figure 4 is an internal circuit diagram of the timer IC of the same as the above, and Figure 5 is a further embodiment of the same as the above. A specific circuit diagram of the example, FIG. 6 is a specific circuit diagram of a conventional example, and FIGS. 7 and 8 are explanatory diagrams of the same. Ba is a battery, Qo and Qs are transistors, Ds is a diode, R _B6 and R _X2 are resistors, 11 is a timer IC,
12 indicates an inverter control IC.

Claims (1)

[Scope of utility model registration request] A first average charging current that charges energy equivalent to N uses of the electrical device (N is a number of 1 or more) in a relatively short time, and a first average charging current that charges at least 80% of the rated charging capacity of the battery for a relatively long time. 2nd time to charge
a charging unit that sequentially and selectively supplies an average charging current of In a charging circuit equipped with a timer that controls the charging section and switches the charging current from the first average charging current to the second average charging current, when the timer times out, it is detected at the same time as the charging current is switched. Either the battery voltage is switched so that the detected battery voltage changes from an apparent battery voltage lower than the actual battery voltage to the actual battery voltage, or the reference voltage of the output current control means is changed to a second average charging current. 1. A charging circuit comprising a voltage switching means for switching from an apparent reference voltage higher than an actual reference voltage corresponding to the actual reference voltage to an actual reference voltage.