JPH0588052B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a charging circuit for charging a plurality of batteries.

[Background Art] Conventionally, this type of charging circuit has been shown in FIG. 4. This is done by rectifying the AC power supply Vs with a rectifier bridge Rec as a rectifier circuit, smoothing it with a smoothing capacitor _C1 , and applying the created DC voltage to the base of the switching transistor _Q1 with a starting resistor _R1 . The voltage induced in the feedback winding _L3 by the collector current of the switching transistor _Q1 flowing into the primary winding _L1 of the oscillation transformer _T is switched to the base of the switching transistor _Q1. By applying positive feedback to the switching transistor Q ₁ , the switching transistor Q ₁ is caused to oscillate by blocking, and this switching transistor Q ₁
During the ON period of the switching transistor Q1, the charging battery _B1 is charged, and even during the off period of the switching transistor _Q1 , the charging batteries _B1 and _B2 are charged by the back electromotive force induced in the secondary winding _L2 in the oscillation transformer T. It was meant to charge the battery. Here, rechargeable battery B ₁ is the main battery, and rechargeable battery B ₂
is the auxiliary battery, and the diodes D ₁ and D ₂ are used when back electromotive force is generated in the secondary winding L ₂ of the oscillation transformer T.
Insert to charge rechargeable batteries B ₁ and B ₂ ,
Resistor _R2 is inserted to reduce the charging current of rechargeable battery _B2 . However, the above-mentioned charging circuit is useful when charging the sub-battery _B2 when the charging current is small, such as at an 8-hour rate or a 16-hour rate, relative to the battery capacity, and has the advantage of not requiring overcurrent control. Yes, but it cannot be quickly charged. Furthermore, if a product with an integrated charging circuit is plugged into an outlet and your hand slips and drops it into water, there is a risk of getting an electric shock if you try to pick it up. Several types of accidents have been reported. This is also because the primary and secondary sides are not insulated, and as mentioned above, the above circuit is not suitable for devices used in places with moisture, such as shavers used in bathtubs and electric toothbrushes. It had the following drawback.

Therefore, a charging circuit capable of rapid charging is provided in which the primary side and the secondary side are insulated. In this charging circuit, as shown in Fig. 5, the DC voltage created by rectifying and smoothing the AC power supply Vs with the rectifier bridge Rec and the smoothing capacitor _C1 is converted into AC by the blocking oscillation of the switching transistor _Q1 . However, the point that the rechargeable batteries B ₁ and B ₂ are charged using the induced voltage induced in the secondary winding L ₂ of the oscillation transformer T is almost the same as the above conventional example, but the switching transistor Q ₁ is When on, the oscillating transformer T
The voltage induced in the secondary winding L ₂ of the charged battery B ₁ ,
A so-called on-off method (feed-forward method) is used to charge _B2 , and therefore the circuit configuration is different. In this conventional example, the rechargeable batteries B ₁ and B ₂ are connected to the charging circuit by an adapter A, and the oscillation transformer T has a reset winding L ₄ and an auxiliary winding L ₅ . _B1 ,
The control means includes a determination circuit 1 that detects the state of charge with _B2 , and a charging control circuit 2 that controls switching of the switching transistor _Q1 using the output of the determination circuit 1. The determination circuit 1 includes transistors Q ₆ and Q ₇ , diodes D ₁ to D ₆ , resistors R ₃ to R ₇ , and Zener diodes ZD ₁ and ZD ₂ , and the charging control circuit 2 includes transistors Q ₂ to _{Q 4} , It consists of a light emitting diode LD, a photocoupler PC, etc. Here, the significance of equipping the rechargeable battery _B2 as an auxiliary battery in addition to the rechargeable battery _B1 is due to the following reason. For example, charge battery B ₁ in a bathtub, etc.
If the battery runs out, you may get an electric shock if you accidentally try to insert _the device plug into a commercial power outlet with wet hands. This is because the risk of electric shock can be prevented by switching the battery B ₁ to the rechargeable battery B ₂ .

The operation of this conventional example will be explained below. A switching transistor is constructed in the same way as the conventional example above.
When Q ₁ performs blocking oscillation, a voltage is induced in the secondary winding L ₂ of the oscillation transformer T, and this voltage is transmitted via the diode D ₀₁ and the choke coil L ₀ to the charging battery B ₁ and the resistor R ₂ . Rechargeable battery B ₂
is applied to Here, the choke coil L ₀ allows the energy stored when the switching transistor Q ₁ is on to flow through the diode D ₀₂ so that the charging batteries B ₁ and B ₂ are charged even when the switching transistor Q ₁ is off. Rechargeable batteries B ₁ , B ₂
It is used to charge the battery. Here, the reset winding
_L4 is a diode D that transfers the energy stored in the secondary winding _L2 when the switching transistor _Q1 is on so as to suppress the flyback voltage of the secondary winding _L2 that occurs when the switching transistor _Q1 is off. ₇ to the smoothing capacitor _C1 , which improves the energy efficiency of the entire circuit. Further, the auxiliary winding _L5 is used as a power source for the control means by rectifying and smoothing the induced voltage generated when the switching transistor _Q1 is turned on using the diode _D03 and the capacitor _C0 . The determination circuit 1 then detects the state of charge of the rechargeable batteries B ₁ and B ₂ via the resistor R ₀ . The voltage applied to the determination circuit 1 via this resistor R ₀ is applied to the emitter of the transistor Q 7 via the resistor R ₄ , and this voltage is applied to the emitter of the transistor Q ₇ through the transistor Q ₇ and the diodes D ₁ to D ₅ and the resistors R ₆ and R It is compared with the base potential determined by ₇ . And the base potential is higher, i.e. the rechargeable battery
When B ₁ and B ₂ are not sufficiently charged, transistor Q ₇ is turned on and transistor Q ₆ is turned off. Then, transistor Q ₄ of charging control circuit 2
turns on, current flows through the light emitting diode LD and emits light, and the photocoupler PC turns on. Therefore transistor Q ₂ is on, transistor
Without Q ₃ turning off and controlling the base of switching transistor Q ₁ , the charging circuit can be used to charge the battery.
Charge B ₁ and B ₂ . and rechargeable battery B ₁ ,
When B ₂ is charged, the transistor
_Q4 is turned off and the light emitting diode LD does not emit light, and the transistor _Q3 is turned on and the base potential of the switching transistor _Q1 is lowered below the Zener voltage of the Zener diode _ZD3 , and the rechargeable batteries _B1 , _B2
It is set so that almost no charging is performed. So-called overcurrent control is performed. Here, the Zener diode ZD ₁ stabilizes the power supply voltage of the determination circuit 1 in order to stabilize the operation of the determination circuit 1, and the Zener diode ZD ₂ is a protection diode. Further, the resistor R ₂ inserted in series with the rechargeable battery B ₂ of this embodiment has the following function. For example, if rechargeable batteries B ₁ and B ₂ are charged in parallel without using resistor R ₂ , rechargeable battery B ₂ will be sufficiently charged, and rechargeable battery B ₁ will be charged in parallel.
When the battery is empty, the potential difference will be about 1.2 to 1.3V and an instantaneous current will flow from the rechargeable battery _B2 to the rechargeable battery _B1 , which is extremely dangerous. Therefore, a resistor _R2 is inserted to prevent this instantaneous current. Also, by inserting resistor R ₂ as described above,
When rechargeable batteries B ₁ and B ₂ are connected to the charger body,
Current can flow in the other direction through resistor _R2 so that the battery voltages of rechargeable battery _B1 and rechargeable battery _B2 are always balanced, and by controlling overcurrent of rechargeable battery _B1 , charging can be performed simultaneously. Overcurrent control of battery _B2 can also be performed.

By the way, if only the above-mentioned resistor R ₂ is present, the rechargeable battery B _{2 is sufficiently charged and the rechargeable battery B 2} is fully charged.
When _B1 is insufficiently charged, rechargeable battery B1 is charged from rechargeable battery _{B2 ,} and rechargeable battery _B2 passes too much charging current to rechargeable battery _B1 , causing rechargeable battery _B2 to charge. There will be a shortage.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to provide a charging circuit that can prevent a rechargeable battery from becoming insufficiently charged as an auxiliary battery. .

[Disclosure of the Invention] Example 1 An example of the present invention is shown in FIGS. 1 to 3.
In this embodiment, a transistor _Q5 is inserted between the resistor _R2 and the charging battery _B2 . The circuit operates by turning on the transistor _Q5 using the voltage generated in the auxiliary winding _L5 so as to connect the sub battery _B2 only when the main battery _B1 is being charged. By inserting this _{transistor Q5} , as _{shown in FIG} .
(sat) (where _I2 is the current flowing through transistor _Q5 , and Vce(sat) is the saturation voltage of transistor _Q5 ). For this reason, there is a possibility that the capacity of the rechargeable battery B ₂ will be insufficient, but if the resistor R ₂ is set so that the rechargeable battery B ₂ can be sufficiently charged after one or two or several uses, it can be used normally. does not pose a problem. As shown in Figure 3, the charging current between the rechargeable batteries B ₁ and B ₂ is such that at first, the rechargeable battery B ₁ is rapidly charged, and as the charging current of the rechargeable battery B _{1 decreases, the rechargeable battery B 1} is rapidly charged.
The charging current of _B2 is increasing. In other words, by inserting transistor _Q5 ,
If you only connect rechargeable batteries B ₁ and B ₂ and the charging circuit with adapter A, the battery will change from rechargeable battery B ₁ to rechargeable battery B _2.
The capacity of rechargeable battery _B1 is ensured, and no current flows from rechargeable battery _B2 to rechargeable battery _B1.
Since no current flows through the rechargeable battery B ₂
capacity can be secured and prepared for emergencies.

[Effects of the Invention] As described above, the present invention connects one rechargeable battery to another rechargeable battery in parallel via a switching means, and when the switching transistor is turned on or
Since the above-mentioned switching means is turned on when the above-mentioned charging current is outputted after being turned off, the other charging battery as the auxiliary battery is connected only when the above-mentioned one charging battery as the main battery is being charged. When one rechargeable battery is insufficiently charged and another rechargeable battery is sufficiently charged, the above one rechargeable battery is charged by another rechargeable battery, and the other rechargeable battery is insufficiently charged. This produces an effect that does not result in

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention;
2 and 3 are explanatory diagrams of the same operation as above, FIG. 4 is a circuit configuration diagram showing a conventional example, and FIG. 5 is a circuit configuration diagram showing another conventional example. 1 is a judgment circuit, 2 is a charging control circuit, _Q1 is a switching transistor, Rec is a rectifier bridge, T
is a transformer, L ₁ and L ₂ are windings, B ₁ and B ₂ are charging batteries, and Q ₅ is a transistor.

Claims (1)

[Claims] 1. Connect the primary winding of an oscillation transformer to the output of a rectifier circuit connected to an AC power source via the collector and emitter of a switching transistor, and send a part of the oscillation output of this oscillation transformer to the base of the switching transistor. In a charging circuit that is provided with an inverter circuit having a feedback winding that provides positive feedback, and that charges a plurality of rechargeable batteries with different battery capacities using the rectified output of this inverter circuit, one rechargeable battery is connected to another rechargeable battery. are connected in parallel via a switching means, and the switching means is turned on when the switching transistor is turned on and off to output a charging current.