JPH0731070A - Pulse charger - Google Patents

Abstract

PURPOSE:To improve the reliability of charging and to reduce the cost by detecting a voltage level of a pulsating current obtained by rectifying the AC voltage from the commercial power source and intermittently controlling the charge current in response to its detecting result. CONSTITUTION:A secondary cell 49 which is chargeable by the AC voltage supplied from the commercial power source 20 is charged by an intermittent pulse current. That is, the AC voltage supplied from the power source 20 is rectified by rectifying means (full-wave rectifier) 14, a pulsating voltage level obtained by the means 24 is detected by pulsating voltage detecting means (Zener diode) 26, and the charging current is intermittently controlled by current control means (constant-current controller) 32 in response to the detection result. Thus, the reliability is improved, and the cost can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse charger, and more particularly to a pulse charger which charges a rechargeable secondary battery with intermittent pulse current by an AC voltage supplied from a commercial power source.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, in a pulse charger of this type, an AC voltage obtained from a commercial power source 50 is stepped down by a transformer 52, rectified by a rectifying element 54 and then smoothed by a capacitor 56. The smoothed voltage is supplied to the constant current controller 58. On the other hand, this pulse charger is provided with a pulse generator 62 so that it can generate intermittent pulses. Also, in response to the pulse, the transistor 64
Can be turned on and off. The output of the transistor 64 controls the constant current control unit 58 to be turned on and off intermittently, and the charging current flowing through the rechargeable secondary battery 60 is an intermittent pulse current.

[0003]

However, since the conventional pulse charger as described above is configured to be smoothed after the AC voltage obtained from the commercial power source is rectified, it has a large capacity. Because a capacitor is needed,
The reliability was reduced and the cost was increased. Further, a separate pulse generator is provided so that the charging current becomes an intermittent pulse current, which is also a factor of high cost.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a pulse charger having high reliability and low cost.

[0005]

To achieve this object, the battery charger of the present invention charges a rechargeable secondary battery with intermittent pulse current using a commercial power source.
Further, the rectifying means for rectifying the AC voltage supplied from the commercial power source, the pulsating voltage detecting means for detecting the voltage level of the pulsating current obtained by rectifying by the rectifying means, and the pulsating voltage detecting means. And a current control unit for intermittently controlling the charging current according to the detection result.

[0006]

The pulse charger of the present invention having the above structure is
The AC voltage supplied from the commercial power source is rectified by the rectifying means, the voltage level of the pulsating current obtained thereby is detected by the pulsating voltage detecting means, and the current control means determines the charging current according to the detection result. Control intermittently.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, the structure of the pulse charger will be described with reference to FIG.
Transformer 22 for stepping down the AC voltage from the device, full-wave rectifying element 24 as rectifying means, Zener diode 26 as pulsating current voltage detecting means, resistors 28, 30, and constant current control section 32 as current controlling means. And transistors 38 and 39 for transmitting a detection signal from the pulsating current voltage detection means to the constant current control unit 32, and a charging terminal 34.

More specifically, the commercial power source 20 is the transformer 2
2 is connected to the primary side. The secondary side of the transformer 22 is connected to the AC input terminal of the full-wave rectifying element 24. The plus side 24a of the DC output terminal of the full-wave rectifying element 24 is connected to the collector of the transistor 42 in the constant current controller 32. The negative side 24b of the DC output terminal of the full-wave rectifying element 24 is connected to the negative side 34b of the charging terminal 34 and constitutes a ground potential. Zener diode 2
6. The resistors 28 and 30 are connected in series, and the full-wave rectifying element 2
It is connected between the positive side 24a of the DC output terminal 4 and the ground. The connection point A between the resistors 28 and 30 is connected to the base of the transistor 39.

The emitter of the transistor 39 is connected to the ground, the collector thereof is connected to the base of the transistor 38, and at the same time, the full-wave rectifying element 24 is connected via the resistor 37.
Is connected to the positive side 24a of the DC output terminal. The emitter of the transistor 38 is connected to the ground, and the collector of the transistor 38 is connected to the base of the transistor 42 in the constant current controller 32 via the resistor 36. Transistor 4
A resistor 40 is connected between the two collectors and bases. The emitter of the transistor 42 is a current detection resistor 44.
It is connected to the plus side 34a of the charging terminal 34 via.

One terminal of the current detecting resistor 44 (the emitter side of the transistor 42) is connected to the negative input of the operational amplifier 46, and the other terminal of the current detecting resistor 44 (the charging terminal 34 side) is a zener diode 48. Is connected to the plus input of the operational amplifier 46 via the. The output of the operational amplifier 46 is connected to the base of the transistor 42 and at the same time connected to the positive power supply side of the operational amplifier 46.

Next, the operation of the pulse charger of this embodiment will be described with reference to FIGS. 1 and 2.

First, the AC voltage from the commercial power source 20 is stepped down by the transformer 22, becomes the AC voltage shown in FIG. 1 (a), and is generated between the ground and the point B. This voltage is rectified by the full-wave rectifying element 24 and becomes the pulsating current voltage shown in FIG. 1B, which is generated between the ground and the point C.

When this pulsating voltage is lower than the Zener voltage 27 of the Zener diode 26, no current flows through the resistors 28 and 30, and the voltage at the point A becomes 0 V as shown in FIG. 1 (c). ing. Therefore, the transistor 39
Has a base potential of 0, the transistor 39 is turned off, a base current flows through the transistor 38 through the resistor 37, and the transistor 38 is turned on.

Further, the pulsating voltage is the Zener diode 2
When the voltage is higher than the Zener voltage 27 of 6, the current flows through the Zener diode 26 and the resistors 28 and 30, and a part of the current flows as the base current of the transistor 39. At this time, the voltage at the point A is the voltage between the base and emitter of the transistor 39, as shown in FIG. Since the base current flows through the transistor 39, the collector current flows through the transistor 39 through the resistor 37, and the collector potential of the transistor 39 becomes almost 0 volt. Therefore, the base potential of the transistor 38 is almost zero.
Volts and transistor 38 is turned off.

As described above, when the pulsating current voltage is lower than the Zener voltage 27 of the Zener diode 26, the transistor 38 is turned on, and when the pulsating voltage is higher than the Zener voltage 27, the transistor 38 is OF.
It becomes F.

Next, the constant current operation will be described. Most of the current flowing through point C is the collector of the transistor 42.
It flows between the emitters and flows into the rechargeable secondary battery 49 via the current detection resistor 44 and the charging terminal 34. At this time,
When a voltage proportional to the charging current appears at both ends of the current detection resistor 44 and becomes higher than the Zener voltage of the Zener diode 48, the output voltage of the operational amplifier 46 becomes low, so that the base potential of the transistor 42 becomes low and the transistor 42 becomes low. The current flowing between the collector and emitter of 42 is reduced. On the contrary, when the voltage across the current detection resistor 44 becomes lower than the Zener voltage of the Zener diode 48, the output voltage of the operational amplifier 46 becomes higher, so that the base potential of the transistor 42 becomes higher and the collector-emitter of the transistor 42 becomes higher. The flowing current is large.

As described above, the constant current control section 32 has a function of making the current flowing into the rechargeable secondary battery 49 constant.

On the other hand, when the transistor 38 is turned on, the base potential of the transistor 42 becomes sufficiently low, and no current flows between the collector and emitter of the transistor 42. When the transistor 38 is OFF, the base potential of the transistor 42 is determined based on the constant current operation described above, and a constant current flows between the collector and the emitter of the transistor 42.

As described above, the transistor 38 is turned on.
Since OFF is determined by the level of the pulsating voltage at the point C, the current flowing through the rechargeable secondary battery 49 is as shown in FIG. 1 (d).

Therefore, in this embodiment, it is possible to perform pulse constant current charging with a frequency twice that of the commercial power source 20.

In this embodiment, the analog type constant current control unit is used as the current control means, but it is also possible to use a switching type constant current control unit. At that time, the detection signal from the pulsating current voltage detection means,
It is also useful to use the switching transistor to turn on / off a circuit that oscillates at high frequency.

Further, by replacing the resistor 28 and the like with a variable resistor, it is possible to control the duty of ON / OFF of the charging pulse.

[0024]

As is apparent from the above description, the pulse charger of the present invention rectifies the AC voltage supplied from the commercial power source and the pulsating current obtained by rectifying the AC voltage. A pulsating current voltage detecting means for detecting the voltage level and a current controlling means for intermittently controlling the charging current according to the detection result of the pulsating current voltage detecting means are provided, and the rechargeable secondary battery is charged. Since the charging current can be a pulsed constant current, it does not require a large-capacity capacitor for smoothing and a pulse generator as compared to conventional devices, has high reliability, and can keep costs low. Becomes

[Brief description of drawings]

1A is a diagram showing an AC voltage obtained by stepping down an AC from a commercial power source, FIG. 1B is a diagram showing a pulsating voltage after rectification,
FIG. 3C is a diagram showing a voltage at a point A in FIG. 2, and FIG. 3D is a diagram showing a charging current flowing in a rechargeable secondary battery.

FIG. 2 is a circuit diagram showing an embodiment embodying the configuration of a pulse charger of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a conventional pulse charger.

[Explanation of symbols]

 20 Commercial Power Supply 24 Full Wave Rectifier 26 Zener Diode 28 Resistor 30 Resistor 32 Constant Current Controller 49 Secondary Battery

Claims (1)

[Claims] 1. A pulse charger for charging a chargeable / dischargeable secondary battery with an intermittent pulse current using a commercial power source, comprising: rectifying means for rectifying an AC voltage supplied from the commercial power source; Means for rectifying the pulsating voltage obtained by rectifying the AC voltage by means, and current control means for intermittently controlling the charging current according to the detection result of the pulsating voltage detecting means. And a pulse charger characterized by having.