JPH0410304B2 - - Google Patents

Description

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

[Background technology]

The conventional charging circuit (Japanese Unexamined Patent Publication No. 57-34740)
A backflow prevention diode is provided to prevent current from flowing backwards from the battery to the charger after charging is complete, but since the diode is installed in series with the battery, a large current flows, resulting in loss. The problem was that it was large. If the charging current is I [A] and the voltage across the diode is V _F [V], then the loss P
is expressed by the following equation.

PI×V _F [Watt] and 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, and the inside of the IC8 are connected from the terminal 2b through the resistors _R1 to _R3 . A reverse current tries to flow to the negative terminal 2c of the battery 2 via the terminal of the IC 8, but in order to prevent this, a reverse current prevention diode _D4 is connected to the battery in series with the negative terminal 2c of the battery 2. However, during charging, the main charging circuit consisting of the transformer 3, diode D ₁ D ₂ , battery 2, diode D ₄ transistor Tr ₁ connected in series,
A large charging current was flowing, and the loss occurred in diode _D4 as described above.

A charging circuit designed to prevent loss and heat generation during charging is shown in FIG.
1 is a battery to be charged, and the charging control circuit 1 controls charging of this battery 2. As shown in FIG. 3
is a transformer that steps down the voltage of the AC power supply AC to the required voltage, and the secondary output of this transformer 3 is full-wave rectified and smoothed by a rectifier and smoothing circuit 5 consisting of a diode _D1D2 , a capacitor _{C1 ,} etc. Ru. 6 is a voltage detection circuit that detects the voltage of battery 2, and a resistor
It is composed of R ₁ to R ₃ . 6a is an output terminal of the voltage detection circuit 6. Plus of rectifier smoothing circuit 5,
A main charging circuit is constructed by connecting the battery 2 and a series circuit of a transistor _Tr1 , which is a charging current control element, between the negative terminal and the negative terminal. 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 an IC 8 to control charging of the battery 2.
is connected to the terminal. 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, a thermistor R ₄ , and a resistor R ₆ R ₆ are connected to the terminal, respectively. The other end of the component is a rectifier smoothing circuit 5
connected to the negative side of the The output terminal of IC8 is connected to the base of the transistor _Tr1 via a resistor _R8 . Also, transistor Tr ₁
A resistor _R7 is connected between the collector and emitter of. Reference numeral 9 denotes a lighting diode constituting a charging display means, which lights up to display an indication during charging. A rectifying and smoothing circuit consisting of a diode D ₄ and a capacitor C ₄ between the secondary side of the transformer 3 and the diode D ₁ ;
An NPN type transistor Tr ₂ serving as a switching element is connected via a resistor R ₉ . The collector of this transistor Tr ₃ is the anode terminal 2b of the battery 2.
The emitters are respectively connected to the voltage detection circuit 6 and the power terminal on the anode side of the charging control circuit 1 which serves as a power source. In addition, the above diode D ₄ , the sondenser C ₄ ,
A drive circuit is made up of resistor _R9 , etc.

FIG. 3 shows the functional block diagram of FIG. 2,
The IC8 mainly consists of a voltage switch VI converter and the like. The capacitor timer in the figure consists of a capacitor C ₂ , a thermistor R ₄ , and a resistor R ₅ R ₆ , and the current control section consists of a transistor Tr ₁ and a resistor R ₇ . 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. Further, as will be described later, when the battery 2 is charged and the voltage of the voltage detection circuit 6 becomes medium than the Zener voltage, the electric charge of the capacitor _C2 is discharged, and V-
The output current from the I converter 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 IC 8 is charged, current is output from the terminal 〓, the transistor Tr ₁ is turned on, and the battery 2 is Charging will start. As this charging progresses, the battery voltage V rises, and this battery voltage V becomes the set voltage.
When the voltage reaches V ₁ or higher, the charging current no longer flows to the capacitor C ₂ due to the operation of IC 8. 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. In addition, due to the function of IC8, the output current of the terminal _〓 and the transistor _Tr1
The base current of will gradually decrease, resulting in
Transistor Tr ₁ also changes from saturated state to unsaturated state. Then, when the discharge of the capacitor _C2 progresses and its voltage becomes zero, the output current at the terminal 〓 of IC8 becomes zero, and the transistor _Tr1 is turned off. However, a low current, determined by the resistor R ₇ connected in parallel to the transistor Tr ₁ , flows, causing a supplementary charging current to the battery 2 . Note that, as shown in FIG. 4, the time t ₁ when the battery voltage V reaches the set voltage V ₁ or higher
The time from t ₂ to the point in time when the charging current becomes a constant minute current is determined by the capacitor C ₂ , thermistor R ₄ , and resistor
It is determined by the specific number of R ₅ R ₆ , and these can be set arbitrarily and 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 source is turned off when charging is complete. In this way, the conventional example shown in Fig. 2 has the effect of preventing loss and heat generation during charging, but on the other hand, when connecting an AC power source,
When battery 2 is not connected to current control circuit 1,
The current flows through diode D ₄ , resistor R ₉ , and transistor
The current flows through the base emitter of Tr ₂ , the resistor R ₁₀ , and the light emitting diode 9, causing the problem that the battery 2 lights up even though it is not being charged, and does not perform its original function of indicating charging.

[Purpose of the invention]

The present invention has been provided in view of the above-mentioned points, and provides a charging circuit whose purpose is to display a light-emitting diode constituting a charging display means only when a battery is being charged.

[Display of invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A specific circuit diagram is shown in FIG. 5, and the circuit is configured almost the same as the conventional one. In this circuit, as a switching element between charging control circuit 1 and battery 2.
A PNP type transistor Tr ₃ is inserted and connected.
That is, the emitter of the transistor _Tr3 is connected to the battery 2, and the collector is connected to the light emitting diode 9 constituting the charging display means via the resistor _R10 .
In addition, the base of the transistor Tr ₃ is connected to the transformer 3 and the rectifying diode D ₄ so that the potential is lower than that of the main charging circuit, and the anode of the diode D ₄ and the main charging circuit are connected to the capacitor C ₄ for smoothing. is connected to the cathode of In addition, diode D ₄
The direction is opposite to that in FIG. Further, a series circuit of a diode _D4 , a Zener diode _D5 having a Zener potential higher than the voltage of the battery 2 to be charged, and a resistor _R9 is connected to the base of the transistor _Tr3 . In addition, the battery 2 and the charging control circuit 1
It is connected to the charging main circuit through terminals 2a, 2b, and 2c, respectively, which are detachable via plug blades.

Next, the operation will be explained. Note that the operation when charging the battery 2 is the same as the conventional one, so a description thereof will be omitted.

First, when the AC power source AC is connected and the battery to be charged 2 is not connected, the transistor
Since Tr ₃ is a PNP type transistor, no current flows through the emitter through the terminal 2a of the battery 2, so naturally no current flows through the collector either. Therefore, no current flows through the light emitting diode 9, which uses the collector current of the transistor _Tr3 as its power source, and does not turn on.

Battery to be charged 2 is connected and AC power supply
When AC is not connected, transistor Tr ₃
The battery voltage is applied through the emitter, base, resistor R ₉ , Zener diode D ₅ , diode D ₄ , transformer 3, and resistor R ₇ , but if the Zener voltage of Zener diode D ₅ is set higher than the battery voltage, Since the Zener diode D ₅ is not energized, no base current flows through the transistor Tr ₃ and the transistor Tr ₃ is not turned on, so no current flows through the light emitting diode 9 and it does not light up.

Next, when the AC power source AC is connected and the battery to be charged 2 is connected, the diode D ₄
Through half-wave rectification, a power supply with a voltage opposite to that of the power supply by diodes D ₁ , D ₂ and capacitor C ₁ is formed in capacitor C ₄ . As a result, when the battery 2 is connected, a voltage between the battery voltage and the cobalt _C4 is applied to the Zener diode _D5 , and the applied voltage becomes a voltage higher than the Zener voltage, and the Zener diode _D5 is energized, causing the transistor Base current flows through Tr ₃ , transistor Tr ₃ is turned on, current flows through light emitting diode 9, and it lights up. That is, since a voltage higher than the Zener voltage is applied to the Zener diode _D5 , the transistor _Tr3 is turned on, and the current flows through the anode of the main charging circuit, terminals 2a and 1b of the battery 2, the transistor _Tr3 , the resistor _R10 , and the light emitting The light flows through the diode 9 to the cathode of the main charging circuit, and the light emitting diode 9 lights up.

After charging is completed, the light emitting diode 9 is turned off by the display control circuit in the IC 8 when the charging current becomes less than a certain current.

〔Effect of the invention〕

As described above, the present invention provides a first,
A second terminal is provided, and a rectifier path and the first terminal are provided in the AC power supply.
A main charging circuit is formed by connecting a series circuit of a battery to be charged and a charging current control element for controlling the charging current of the battery through the terminal of A charging control circuit that controls charging of the battery by controlling the charging current control element is connected in parallel with the battery via a second terminal, and the anode side of the battery and the anode side of the charging control circuit are connected via the second terminal. A switching element is inserted and connected between the AC power supply and the switching element is turned on when the charge control circuit is driven by the AC power supply to charge the battery, and the switching element is turned off when the AC power supply is turned off. In the charging circuit, the charging control circuit is provided with a charging display means for displaying a lighting display when the battery is being charged by a current flowing through the switching element when the switching element is on, wherein the driving circuit is a rectifier circuit. A diode and a capacitor that generate a negative voltage from the output of Connect a capacitor, connect the anode of the diode and the anode of the Zener diode above, and connect it to the switching element.
A PNP transistor is used, the base of the PNP transistor is connected to the cathode of the Zener diode, the emitter is connected to the anode side of the battery via the second terminal, and the collector of the transistor is connected to the charging control circuit. Since it is connected to the anode side of the battery, when the battery is not connected, a PNP type transistor is inserted between the AC power source and the charging display means of the charging control circuit.
Since the charging display means and the collector of the transistor are connected and the Zener voltage of the Zener diode is higher than the above negative voltage, the Zener diode does not turn on, so the current flows through the collector and base of the PNP transistor. Therefore, when the battery is connected and the battery is charged, the negative voltage of the drive circuit and the battery voltage are is applied to the Zener diode, and the Zener diode is turned on, thereby driving the transistor and causing a current to flow through the transistor to the charging display means, thereby displaying charging.

[Brief explanation of drawings]

Fig. 1 is a specific circuit diagram of the conventional example, Fig. 2 is a specific circuit diagram of another conventional example, Fig. 3 is a functional block diagram of the same, Fig. 4 is an explanatory diagram of the same as the above, and Fig. 5 is the invention of the present invention. FIG. 2 is a specific circuit diagram of the embodiment. 1 is a charging control circuit, 2 is a battery, Tr ₃ is a transistor, and AC is an alternating current power source.

Claims (1)

[Claims] 1. First and second terminals are provided on the anode side of the battery, and the battery to be charged and the charging current control element for controlling the charging current of this battery are connected in series via the rectifier circuit and the first terminal to the AC power source. A charging main circuit is formed by connecting the circuits, and a charging control circuit that detects the voltage of the battery and controls charging of the battery by controlling the charging current control element according to the voltage value is connected via a second terminal. Connected in parallel with the battery, a switching element is inserted and connected between the anode side of the battery and the anode side of the charging control circuit via the second terminal, and is driven by the AC power source to drive the charging control circuit and charge the battery. A driving circuit is provided that turns on the switching element when charging the battery, and turns off the switching element when the AC power supply is turned off, and when the switching element is on, the current flowing through the switching element lights up the display when the battery is being charged. In the charging circuit, the charging control circuit is provided with a charging display means for performing the following:
The anode of the diode is composed of a diode and a capacitor that generate a negative voltage from the output of the rectifier circuit, and a Zener diode that has a Zener voltage higher than the battery voltage and the negative voltage, and the cathode is connected to the rectifier circuit side. and the above capacitor, connect the anode of the diode and the anode of the above Zener diode, use a PNP transistor as the switching element, and connect the above capacitor to the cathode of the Zener diode.
Connect the base of the PNP transistor and
A charging circuit characterized in that an emitter is connected to the anode side of the battery via a second terminal, and a collector of the transistor is connected to the anode side of the charging control circuit.