JP2654103B2 - Charging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a charging device for charging a secondary battery.

[Prior Art] FIG. 2 shows a circuit configuration of a conventional charging device. In this charging apparatus, a rectified output obtained by rectifying an AC power supply E by a diode bridge DB is converted into an AC output by an inverter 1, and the output of the inverter 1 is rectified and smoothed by an output unit 2 to recharge the secondary battery B.
And a charging current detecting unit 3 which detects a charging current with a charging current detecting resistor R ₀ connected in series with the secondary battery B and feeds it back to a control circuit 4. . In the present embodiment uses a one as an inverter 1 of the separately excited, on the primary winding L ₁ and the switching element Q ₀ which is connected to the output of the series to the diode bridge DB of the oscillation transformer T ₁ in control circuit 4, Off and oscillating transformer T ₁
The primary winding L ₁ and by resonating the resonant circuit of the capacitor C ₁ of those for obtaining an AC output to the secondary winding L _2. Incidentally, as the switching element Q ₀ in the charging device they are using MOSFET. The control circuit 4 of the inverter 1 is operating a voltage obtained by rectifying and smoothing the voltage induced in the tertiary winding L ₃ of the oscillation transformer T ₁ a diode D ₁ and capacitor C ₁ as a power source. The output unit 2 includes a diode D _01, D ₀₂ for rectifying an AC voltage induced in the secondary winding L ₂ of the oscillation transformer T _1, the choke coil L ₀ and capacitor C ₀ smoothes the rectified output
It consists of. The charging current detection unit 3 is provided with the secondary battery B
The voltage across the resistor R ₀ inserted in series with the
Amplified by a non-inverting amplifier circuit 5 composed of P ₁ and resistors R _{2 to} R ₄ ,
The amplified output to output to the control circuit 4 through the photocoupler PC _1, the voltage induced in the 4 winding L ₄ is a flyback winding of the oscillating transformer T ₁ a diode D ₂ and capacitor C ₃ It operates using the rectified and smoothed voltage as a power supply. The charging current detection unit 3 is provided with a trickle charging circuit 9 that uses the output of the charging current detection unit 3 to trickle charge the secondary battery B when charging is completed. This trickle charging circuit 9
A timer circuit 6 in which a charging time is set, a transistor Q ₂ and resistors R ₁ , R ₂ for increasing the amplification factor of the non-inverting amplifier circuit 5 by an output when the time counted by the timer circuit 6 reaches the charging time.
₅ and an amplification factor switching circuit 10. The amplification factor switching circuit 10 by turning the transistor Q ₁ in the output of the timer circuit 6 at the time of completion of charging, and a resistor R ₅ in parallel to the resistor R _4, during charging At the time of completion of charging, To increase the amplification factor of the non-inverting amplification factor circuit 5.

The operation of the control circuit 4 of the inverter 1 to which the output of the charging current detector 3 is fed back will be described. In the control circuit 4, increases the charging current during charging, the output of non-inverting amplifier circuit 5 is increased, it operates to shorten the ON period of the switching element Q _0. By thus shorten the ON period of the switching element Q _0, the voltage induced in the secondary winding L ₂ and the output of the inverter 1 by reducing, decreasing the charging current of the secondary battery B. Further, when a reverse charging current decreases, the control circuit 4 by lengthening the ON period of the switching element Q _0, increase the charging current. That is, the control circuit 4 has a function of keeping the charging current constant in response to the feedback signal from the charging current detection unit 3.

Thus charging is performed, set in the timer circuit 6 is charging time comes are the (charging is completed), the transistor to Q ₁ amplification factor switching circuit 10 is turned on, the noninverting as described above The amplified output of the amplifier circuit 5 increases. At this time, the charging current is controlled to be small by the control circuit 4 in the same manner as when the charging current is increased.
In this case, the charging current is set to such a small current that the secondary battery B is not overcharged. That is, the trickle charging circuit 9 controls the amplified output of the non-inverting amplifier circuit 5 to be an output for trickle charging the secondary battery B, so that the secondary battery B is not overcharged when charging is completed. It is.

By the way, the charging current of the secondary battery B after the completion of the charging needs to be set as small as possible in order to prevent the deterioration of the secondary battery B. However, reducing too the charging current, the lower the output voltage extractable from 4 winding L _4, Accordingly the charging current detection unit 3 does not operate normally. Therefore, in this conventional charging device, the amplification factor of the non-inverting amplifier circuit 5 is set (the resistances R _{3 to} R ₃₎ so that the charging current becomes the minimum charging current that can normally operate the charging current detecting unit 3. ₅ ). But op amp
OP _1, photocoupler PC _1, characteristic of the resistance R ₃ to R ₅ are changed by the surrounding environment such as temperature. Therefore, if when the properties such as the operational amplifier OP ₁ to the charging current during the charging completion smaller varies, the charging current detector 3 will not work properly.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and an object of the present invention is to allow a charging current detection unit to operate normally due to a change in characteristics of components at the time of completion of charging. An object of the present invention is to provide a charging device that does not disappear.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, an output holding circuit that keeps the output of the charging current detection unit constant when charging is completed is provided in the charging current detection unit.

(Function) As described above, the present invention provides an output holding circuit for keeping the output of the charging current detection unit constant at the time of completion of charging in the charging current detection unit. The output of the charging current detection unit at the time of completion of charging can be kept constant, thereby preventing the output voltage of the power supply circuit from dropping to a voltage at which the charging current detection unit does not operate normally at the time of completion of charging. It was done.

(Embodiment) FIG. 1 shows an embodiment of the present invention. The basic structure of this embodiment similar to the FIG. 2 circuit of the conventional example described above, a series circuit of the present embodiment and the transistor Q ₂ and a resistor R _6, the light emitting output and the photocoupler PC ₁ of the power supply circuit 7 connected between the diodes LD _1, in that the output of non-inverting amplifier circuit 5 are to be applied to the light emitting diode LD ₁ through the transistor Q ₂ is different from the embodiment described above. That is, when you trickle charge the secondary battery B with a charging device during charging is completed, the output holding circuit 8 to keep the output of the charging current detection unit 3 constant are constituted by the transistors Q ₂ and resistor R _6. Incidentally, the transistor Q ₂ are intended to operate as an emitter follower, the output output of the transistor Q ₂ of the non-inverting amplifier circuit 5 the resistance of the charging completion of the resistor R ₆ has been set to saturate. Therefore, when the output voltage of the power supply circuit 7 is varied when charging is completed, it is adapted to vary the current flowing through the transistor Q ₂ accordingly. The resistance R ₂ of the present embodiment since it is enough to supply the base current to the transistor Q _2, is made larger than the resistance value of the resistance R ₂ of the conventional example.

When charging is completed, operational amplifier OP ₁ , photocoupler PC ₁ , resistor R ₃
Description will be given of a case where the characteristics change of the to R ₅ has occurred. In addition,
The following description will be described for the case where the resistor R ₃ to R ₅ or charging current detector 3 at the output of the power supply circuit 7 by either or both of the variation of the operational amplifier OP ₁ can not operate properly. The state in which the output voltage of the power supply circuit 7 decreases until the charging current detection unit 3 cannot operate normally occurs when the output of the non-inverting amplifier circuit 5 increases beyond the set output at the time of completion of charging. However, in the present embodiment, since the output holding circuit 8 is provided, the output of the non-inverting amplifier circuit 5 does not increase, and the output voltage of the power supply circuit 7 decreases until the charging current detection unit 3 cannot operate normally. Nothing. That is, the output of the non-inverting amplifier circuit 5 increases, and the power supply circuit 7
If the output voltage of the drops, the current flowing through the transistor Q ₂ is reduced, increase in the output of the inverting amplifier circuit 5 is suppressed. Therefore, the output voltage of the power supply circuit 7 does not decrease until the charging current detection unit 3 cannot operate normally. On the other hand, when the output of the non-inverting amplifier circuit 5 decreases, the output of the power supply circuit 7 increases, so that the output of the non-inverting amplifier circuit 5 increases in the output holding circuit 8 and the charging current increases. It operates so as not to become larger than the trickle current for overcharging B. That is, by maintaining the output voltage of the power supply circuit 8 when fully charged by the output holding circuit 8 constant, that variations in the characteristics such as the operational amplifier OP ₁ is to work properly charging current detector 3 even if You can. For this reason, the charging current after the completion of charging can be set as small as possible, and the setting range of the charging current for trickle charging the secondary battery B can be widened.
Incidentally, since the time of completion of charging as described above transistor Q ₂ is in the saturated state, but according to the fluctuation of the output voltage of the power supply circuit 7 output current of the transistor Q ₂ is to change,
When the output voltage of the power supply circuit 7 as during charge is sufficiently high, the transistor Q ₂ is are to avoid saturation, it current corresponding to the output of non-inverting amplifier circuit 5 of emitting photocoupler PC ₁ Flow to diode LD ₁ and secondary battery B
At the time of charging, the operation is the same as in the conventional example. That is, the output holding circuit 8 does not adversely affect during charging. Further, in the same manner when the characteristics of the photocoupler PC ₁ is changed, and the output voltage of the power supply circuit 7 to be constant, the charging current detector 3 can be prevented from not operate properly.

[Effect of the Invention] As described above, according to the present invention, the output holding circuit that keeps the output of the charging current detection unit constant when charging is completed is provided in the charging current detection unit. The output of the charging current detection unit at the time of completion of charging can be kept constant by the holding circuit, so that the output voltage of the power supply circuit does not drop to a voltage at which the charging current detection unit does not operate normally at the time of completion of charging. is there.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional example. 1 is an inverter, 2 is an output unit, 3 is a charging current detection unit, 4
The control circuit has a non-inverting amplifier circuit 5, the power supply circuit 7, the output holding circuit 8, the trickle charge circuit, B is a secondary battery 9, Q ₀ is a switching element, T ₁ is oscillating transformer, L ₁ is 1 Next winding,
L ₂ is a secondary winding, L ₄ is a quaternary winding, R ₀ is resistance.

Claims (1)

(57) [Claims] 1. An inverter in which a primary winding of an oscillation transformer and a switching element are connected in series to a DC power supply, and the switching element is turned on and off to obtain an AC output from a secondary winding of the oscillation transformer. An output unit for charging a secondary battery with a voltage obtained by rectifying and smoothing the AC output of an inverter, and a power supply circuit for obtaining power from a voltage induced in a flyback winding of an oscillation transformer, are inserted in series with the secondary battery. A charging current detecting section for detecting a charging current with a resistor and amplifying and outputting a voltage between both ends of the resistor; turning on and off the switching element; and charging the charging current in accordance with an output of the charging current detecting section. The inverter includes a control circuit that makes the output of the charging current detection unit trickle-charge the secondary battery when charging is completed; And an output holding circuit to maintain a constant output of DENDEN current detecting unit charger apparatus characterized by comprising provided in the charging current detector.