JPH0227898B2 - JUDENKAIRO - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a charging circuit.

[Background technology]

Traditional charging circuits prevent current from flowing back into the charger from the battery after charging is complete.
A backflow prevention diode is provided, but the diode is connected in series with the battery, so
The problem was that a large current flowed and the loss was large. The charging current is I [A], and the voltage across the diode is
Assuming V _F [V], the loss P is expressed by the following equation.

P=I×V _F [Watt], and it is released as heat. Further, in order to efficiently release this heat, a heat sink is also required, which poses a problem.

Figure 1 shows a conventional specific circuit diagram.
Transformer 3, step down by rectifier diodes D ₁ D ₂ ,
A rectified power source was applied to the battery 2 through the charging control circuit 1 to charge the battery 2. At this point, when charging is completed, the AC power is turned off, and the battery 2 is left connected to the charging control circuit ₁ , the terminals of the IC8, the inside of the _IC8 , Furthermore, the battery 2 is connected via the IC8 terminal.
A backflow prevention diode _D4 is connected in series with the negative terminal 2c of the battery 2 to prevent a reverse current from flowing through the negative terminal 2c of the battery 2. However, during charging, a large charging current flows through the main charging circuit consisting of the transformer 3, diode D ₁ D ₂ , battery 2, diode D ₄ and transistor Tr ₁ connected in series, and the diode D ₄ has the above-mentioned current. There were losses as in

[Purpose of the invention]

The present invention has been provided in view of the above-mentioned points, and provides a charging circuit for the purpose of preventing loss and heat generation during charging.

[Disclosure of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Figure 2 shows a specific circuit diagram, and in the figure, 2
is a battery to be charged, and charging of this battery 2 is controlled by a charging control circuit 1. 3 is AC power supply AC
This is _a transformer that steps down _the voltage _of
It is full-wave rectified and smoothed. A voltage detection circuit 6 detects the voltage of the battery 2, and is composed of resistors _R1 to _R3 . 6a is an output terminal of the voltage detection circuit 6. Between the positive and negative terminals of the rectifying and smoothing circuit 5,
A main charging circuit is constructed by connecting a series circuit of a battery 2 and a transistor Tr ₁ , which is a charging current control element. A voltage detection circuit 6 is connected to the anode side of the battery 2, and an output terminal 6a of the voltage detection circuit 6 is connected to a terminal of an IC 8 to control charging of the battery 2. In addition, a Zener diode D ₃ for generating a reference voltage is connected to the terminal of IC8, and a capacitor C ₂ for setting the constant of the timer circuit is connected to the terminal.
A thermistor R ₄ and a resistor R ₅ R ₆ are connected to each other, and the other end of each of the above components is connected to the negative side of the rectifying and smoothing circuit 5. The output terminal of IC8 is connected to the base of the transistor _Tr1 via a resistor _R8 . Further, a resistor _R7 is connected between the collector and emitter of the transistor _Tr1 . 9 is a charging indicator lamp. A transistor Tr ₂ serving as a switching element is connected between the secondary side of the transformer 3 and a diode D ₁ through a rectifying and smoothing circuit consisting of a diode D ₄ and a capacitor C ₄ and a resistor R ₉ . The collector of this transistor Tr ₂ is connected to the anode terminal 2b of the battery 2, and the emitter is connected to the voltage detection circuit 6 and the anode side power terminal of the charging control circuit 1 serving as a power source. In FIG. 2, a transistor _Tr2 is used as the switching element, but a relay or a thyristor may also be used. Incidentally, a drive circuit is constituted by the diode D ₄ , capacitor C ₄ , resistor R ₉ and the like.

FIG. 3 shows the functional block diagram of FIG. 2,
IC8 mainly consists of a voltage switch, a V-I converter, etc. The capacitor timer in the figure consists of a capacitor C ₂ , a thermistor R ₄ , and a resistor R ₅ R ₆ .
The current control section consists of a transistor _Tr1 and a resistor _R7 . The voltage switch compares the output voltage of the voltage detection circuit 6 and the Zener voltage of the Zener diode _D3 . If the Zener voltage is higher, the voltage switch charges the capacitor _C2 and charges the V-I converter. A current signal proportional to the charging voltage of the capacitor _C2 is outputted to the transistor _Tr1 of the current control section. Furthermore, as will be described later, when the battery 2 is charged and the voltage of the voltage detection circuit 6 becomes higher than the Zener voltage, the electric charge of the capacitor _C2 is discharged, and the output from the V-I converter is proportional to that. The current decreases.

Next, the operation will be explained. AC power transformer 3
through diode D ₄ and resistor R ₉ ,
Current flows into the base of transistor Tr ₂ , which is a switching element, and transistor Tr ₂ is turned on. Current flows from anode terminal 2b of battery 2 to IC 8, and IC
8 works. When IC8 operates and starts charging battery 2, the voltage V of battery 2 becomes higher than the voltage _V1 set by the Zener voltage of Zener diode _D3 connected to the terminal of IC8, as shown in Figure 4. , when the voltage V detected by the voltage detection circuit 6 is smaller, the capacitor C ₂ connected to the terminal of the IC 8 is charged, current is output from the terminal, the transistor Tr ₁ is turned on, and the voltage is supplied to the battery 2. Charging will start. As this charging progresses, the battery voltage V increases, and when the battery voltage V reaches the set voltage _V1 or higher, the charging current no longer flows to the capacitor _C2 due to the operation of the IC8. the result,
Capacitor C ₂ starts discharging through thermistor R ₄ and resistor R ₅ R ₆ , and due to this discharge, the voltage of capacitor C ₂ gradually decreases. Also, due to the function of IC8, the output current of the _terminal and the transistor
The base current of Tr ₁ will gradually decrease, and as a result, transistor Tr ₁ will also go from saturated to unsaturated. Then, the discharge of capacitor _C2 progresses,
When the voltage becomes zero, the output current at the terminal of IC9 becomes zero, and the transistor _Tr1 is turned off.
However, since a low current flows, determined by the resistor R ₇ connected in parallel with the transistor Tr ₁ ,
Supplementary charging current is supplied to battery 2. As shown in FIG. 4, the time from time t ₁ when the battery voltage V reaches the set voltage V ₁ or higher to time t ₂ when the charging current becomes a constant minute current is the time when the capacitor C ₂ and the thermistor
It is determined by the time constants of R ₄ and resistor R ₅ R ₆ , and by setting these arbitrarily, the time can be changed as appropriate. Incidentally, I shown in FIG. 4 indicates the charging current to the battery 2.

At this point, charging of battery 2 is completed and the AC power supply
When turned off, the secondary side potential of the transformer 3 becomes zero and no base current flows through the transistor Tr ₂ , so the transistor Tr ₂ is turned off and no current from the battery 2 flows through the IC 8 . In other words, since the transistors Tr ₂ , etc. are connected in parallel with the main charging circuit (anode circuit) in a bypass manner, a large charging current does not flow, only a small current flows through IC8, and the loss is almost zero. , it does not generate heat and can charge the battery efficiently. In addition, a diode is connected between terminals 2a and 2c of battery 2.
Since D _{1 and} D ₂ are connected, no reverse current will flow from battery 2 even if the AC power is turned off when charging is complete.
Therefore, in this embodiment, the rectifier diode
D ₁ D ₂ will also serve as a diode for backflow prevention.

〔Effect of the invention〕

As described above, the present invention connects an AC power supply with a series circuit of a rectifying circuit, a battery to be charged, and a charging current control element for controlling the charging current of this battery to form a main charging circuit, and A charging control circuit that detects the voltage and controls charging of the battery according to the voltage value is provided in parallel with the main charging circuit, and a switching element is inserted and connected between the anode side of the battery and the anode side of the charging control circuit, When the charging control circuit is driven by an AC power source to charge the battery, the switching element is turned on, and when the AC power source is turned off, the switching element is turned off. When charging, the charging current control element is driven by the charging control circuit to charge the battery, and the large current that charges the battery only flows through the main charging circuit. Only a small current flows, and when the AC power supply is turned off and the battery is not being charged, the switching element is turned off and does not work, so it operates as a backflow prevention device. Since only a small amount of current flows, there is an effect that there is less loss and less heat generation, and the battery can be charged efficiently.

[Brief explanation of drawings]

FIG. 1 is a specific circuit diagram of a conventional example, FIG. 2 is a specific circuit diagram of an embodiment of the present invention, FIG. 3 is a functional block diagram of the same, and FIG. 4 is an explanatory diagram of the same. 1 is a charging control circuit, 2 is a battery, Tr ₂ is a transistor, and AC is an alternating current power source.

Claims (1)

[Claims] 1. A main charging circuit is formed by connecting a rectifier circuit, a series circuit of a battery to be charged, and a charging current control element for controlling the charging current of this battery to an AC power source, and the voltage of the battery is adjusted. A charging control circuit that detects and controls charging of the battery according to the voltage value is installed in parallel with the above-mentioned main charging circuit, and a switching element is inserted and connected between the anode side of the battery and the anode side of the charging control circuit, and the AC A charging circuit comprising a driving circuit that is driven by a power source to drive the charging control circuit to turn on the switching element when charging the battery, and to turn off the switching element when the AC power source is turned off. 2. The charging circuit according to claim 1, wherein the switching element is a transistor.