JPH0227897B2 - - 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. In addition, a heat sink was also required to effectively dissipate this heat, which caused 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, via the terminal of IC8, battery 2
A backflow prevention diode _D7 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, the charging circuit configured by connecting the transformer 3, diode D ₁ D ₂ , battery 2, diode D ₇ and transistor Tr ₁ 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 Tr ₁ as a charging current control element for controlling the charging current of the battery 2 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 the anode side of the battery 2.
is connected to the terminal of IC8 to control charging of battery 2. In addition, a Zener diode _D3 for reference voltage generation is connected to the terminal of IC8.
The terminal has a capacitor for setting the constant of the timer circuit.
C ₂ , thermistor R ₄ and resistor R ₅ R ₆ are connected respectively,
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 resistor _R3
is connected to the base of the transistor _Tr1 via the transistor Tr1. Also, the collector of transistor Tr ₁
A resistor _R7 is connected between the emitters. Reference numeral 9 represents a light emitting diode, which lights up to display an indication during charging. 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. 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 ₁ , which is a switching element, turning on transistor Tr ₁ , 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,
No charging current flows through capacitor _C2 . As a result, capacitor C ₂ is replaced by thermistor R ₄ , resistor
Discharge begins through R ₅ R ₆ , and the voltage of capacitor C ₂ gradually decreases due to this discharge.
Also, due to the action of IC8, the terminal output current and the base current of transistor Tr 1 gradually decrease in accordance with the drop in the voltage of capacitor C ₂ , and as a result, transistor Tr _{1 also} changes from the saturated state to the unsaturated state. become. 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 supply 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, the battery 2 is not connected to the charging control circuit 1 when the AC power supply AC is connected. When not, the current flows through diode D ₄ , resistor R ₉ , and transistor Tr ₂
The current flows through the base emitter, the resistor _R10 , and the light emitting diode 9.Therefore, there was a problem in that the battery 2 was turned on even though it was not being charged, and did 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 by lighting only when a battery is being charged.

[Disclosure of the 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 substantially the same as the conventional one, except that a transistor Tr ₃ as a switching element and resistors R ₁₂ and R ₁₃ are added to the light emitting diode 9. That is, the collector and emitter of the transistor Tr ₃ are connected in parallel to both ends of the light emitting diode 9, and a series circuit of resistors R ₁₂ and R ₁₃ is connected between the anode and cathode of the main charging circuit to adjust the voltage of the main charging circuit. The connection between both resistors _{R12 and R13} is connected to the base of transistor _Tr3 .

Next, the operation will be explained. Note that the operation during charging of the battery 2 is the same as the conventional one, so a description thereof will be omitted. resistance
R ₁₂ R ₁₃ divides the voltage between the anode and cathode of the main charging circuit and connects it to the base of transistor Tr ₃ , resistor R ₁₂ R ₁₃
A voltage divided by the constant is given. Here, when the charger (charging circuit) is connected to an AC power source AC and battery 2 is not connected, the voltage between the anode and cathode of the main charging circuit is V _A , and battery 2 is connected. If the voltage at the time is V _B , then V _A > V _B
Otherwise, it cannot be charged. Therefore, this V _A and V _B
Since there is always a voltage difference between
If the voltage applied to the base of transistor Tr ₃ when V _A is V′ _A and the voltage applied to the base of transistor Tr ₃ when voltage V _B is V′ _B , transistor Tr ₃ is turned on at V′ _A , and V _B ′ The constant of the resistor R ₁₂ R ₁₃ and the transistor Tr ₃ so that the transistor Tr ₃ is turned off at
If the constant is set, the transistor Tr ₃ will be turned on when the voltage is V _A , that is, when the charger is connected to the AC power source and the battery 2 is not connected. When transistor Tr ₃ turns on, the diode
A current flows through D ₄ , resistor R ₉ , base-emitter of transistor Tr ₂ , resistor R ₁₀ and collector-emitter of transistor Tr ₃ . Therefore, since no current flows through the light emitting diode 9, the light emitting diode 9 does not light up. Furthermore, when the voltage between the anode and cathode of the main charging circuit is V _B , that is, when battery 2 is connected, transistor Tr ₃ is off, so diode D ₄ , resistor R ₉ , and transistor Tr Current flows through the base emitter of ₂ , the resistor ₁₀ and the light emitting diode 9, so that the light emitting diode 9 lights up to indicate charging.

In addition, after charging is completed, the light emitting diode 9
The internal display control circuit turns off the light when the charging current drops below a certain level. Also, AC power supply
When AC is not connected to the charger and the battery 2 is not connected, the transistor Tr ₂ is turned off, so the light emitting diode 9 does not light up.

〔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 having a light emitting diode that detects the voltage and controls charging of the battery according to the voltage value and displays a lighting indication of battery charging is installed in parallel with the main charging circuit, and connects the anode side of the battery and the charging control circuit. A first switching element is inserted between the anode side and the anode side, and when the battery is charged by driving the charge control circuit driven by the AC power source, the first switching element is turned on and the AC power source is turned on. A drive circuit is provided to turn off the first switching element when it is off, an NPN transistor is used for the first switching element, the base is connected to the drive circuit side, and the collector is connected to the anode side of the battery, In a charging circuit in which the emitter of the transistor is connected to the anode side of the charge control circuit, and the light emitting diode is connected to the emitter of the transistor, a second transistor is connected in parallel with the light emitting diode, and a battery is connected to the charge control circuit. A voltage dividing resistor is connected to the base of the second transistor, which turns off the second transistor when the battery is connected and turns on the second transistor when the battery is not connected, so when no AC power is applied. In this case, the drive circuit turns off the first switching element, the transistor, so that the battery is not discharged even if the battery is connected, and the second transistor is connected in parallel with the light emitting diode. By connecting a voltage dividing resistor to the base of the second transistor, which turns off the second transistor when the battery is connected to the charge control circuit and turns on the second transistor when the battery is not connected, When the battery is not connected to the charging control circuit, the second transistor is turned on by the divided voltage of the voltage dividing resistor, bypassing the current flowing to the light emitting diode and preventing the light emitting diode from lighting up. This has the effect that the charging display does not display when the battery is not connected, unlike in the past.
Further, when a battery is connected and the battery is to be charged, the second transistor is turned off and a current is allowed to flow through the light emitting diode to provide a lighting indication of charging. Furthermore, a second light-emitting diode connected in parallel to the light-emitting diode can be configured to turn off the light-emitting diode when the battery is not connected, and turn on the light-emitting diode when the battery is connected and charging. Since it is composed of a transistor and a voltage dividing resistor connected to the base of this second transistor, it can be constructed with a small number of parts and a simple circuit, and therefore the increase in cost can be kept to an extremely low level. This has the effect of making it possible.

[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, 9 is a light emitting diode, Tr ₂ is a transistor which is a first switching element, Tr ₃ is a second transistor, AC is an alternating current power supply, and R ₁₂ and R ₁₃ are resistors.

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 detects the voltage of the battery and converts it into a voltage value. A charging control circuit having a light emitting diode that controls charging of the battery according to the battery charge and displays a lighting indication of battery charging is provided in parallel with the main charging circuit, and a charging control circuit is provided between the anode side of the battery and the anode side of the charging control circuit. When the first switching element is inserted and connected, and the charging control circuit is driven by the AC power source to charge the battery, the first switching element is turned on, and when the AC power source is turned off, the first switching element is turned on. A drive circuit is provided to turn off the battery, an NPN type transistor is used as the first switching element, the base is connected to the drive circuit side, the collector is connected to the anode side of the battery, and the emitter of the transistor is connected to the charging circuit. In a charging circuit that is connected to the anode side of the control circuit and the light emitting diode is connected to the emitter of the transistor, when a second transistor is connected in parallel with the light emitting diode and a battery is connected to the charging control circuit, the second transistor is connected to the emitter of the transistor. A charging circuit characterized in that a voltage dividing resistor is connected to the base of the second transistor to turn off the transistor and turn on the second transistor when a battery is not connected.