JP2588032B2 - Battery quick charger - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pulse width control battery quick charger having a protection function.

[Conventional technology]

Conventionally, many types of battery chargers for charging a battery are known. Various types of quick chargers that can charge a battery in a short time are also known. In many quick chargers, the charging and discharging of the charging current must be appropriately controlled in order to prevent the transistor of the stabilizing circuit that maintains the charging current supplied to the battery at a predetermined level from being damaged by heat generated by the large current. Repeat.

[Problems to be solved by the invention]

In most of the battery quick chargers described above, the charging current is supplied or cut off by a pulse generated by a pulse generator. The duty ratio of the pulse width changes in accordance with the fluctuation of the output terminal voltage connected to the battery, and the output terminal voltage controls the time ratio of energization and cutoff of the charging current.

However, since the voltage fluctuation at the output terminal of the supply circuit connected to the battery is quite small, a detection amplifier for amplifying the fluctuation has conventionally been particularly required.

In view of the above, an object of the present invention is to provide a battery quick charger that does not require a detection amplifier for amplifying the above-described voltage fluctuation, and can reduce the number of components and cost.

[Means for solving the problem]

The battery quick charger of the present invention is configured such that an AC power supply is input, a rectifying circuit that performs rectification and smoothing, a supply circuit that stabilizes an output current of the DC circuit and supplies a predetermined charging current to the battery, A pulse generating means in which the duty ratio of the pulse width of the generated pulse changes only by the output voltage of the DC conversion circuit; and controlling the supply circuit in accordance with the pulse output of the pulse generating means to supply and cut off the charging current. And a protection circuit for detecting a charging current supplied to the battery from the supply circuit and stopping the operation of the pulse generation means due to an overcurrent exceeding a predetermined current.

[Action]

In the battery quick charger according to the present invention, the charging current is supplied or cut off by the pulse generated by the pulse generating means. Then, the duty ratio of the pulse width is configured to change according to the fluctuation of the output voltage of the DC conversion circuit.

Generally, the fluctuation of the output voltage of the DC conversion circuit is considerably larger than the fluctuation of the output terminal voltage after passing through the stabilizing circuit. Therefore, it is possible to directly change the duty ratio of the pulse width generated by the pulse generating means without using the detection amplifier by using the output voltage of the DC conversion circuit.

〔Example〕

The battery quick charger of the embodiment according to the present invention
This will be described with reference to FIGS. FIG. 1 is a circuit diagram of a battery quick charger according to the present embodiment, and FIG. 2 is an operation explanatory diagram for explaining the operation thereof.

As shown in FIG. 1, the battery quick charger according to the present embodiment has a DC conversion circuit 1 to which an AC power is input and performs rectification and smoothing, and a stabilization of an output current of the DC conversion circuit 1 to provide a predetermined charging current. Supply circuit 2 for supplying power to battery 5, pulse generating means 3 for changing the duty ratio of the pulse width of the generated pulse according to the output voltage of DC conversion circuit 1, and pulse generating means 3
And a control means 4 for controlling the supply circuit 2 by the pulse output of (1) to supply and cut off the charging current.

The DC conversion circuit 1 includes a transformer 11 for converting an AC output from the AC power supply into a predetermined voltage, a pair of diodes 12a and 12b for full-wave rectifying the AC output of the transformer 11, and diodes 12a and 12a.
And an electrolytic capacitor 13 for smoothing the output of 2b.

The supply circuit 2 includes a first transistor 21 for stabilizing the DC current input from the DC conversion circuit 1 to a predetermined charging current, an eleventh resistor 22 connected to the base of the first transistor 21 to generate a bias, and an eleventh resistor First transistor 21 in parallel with 22
12th resistor for starting current to be connected to the base
23, and a pair of output terminals 24 connected to the battery 5.
a, 24b. A first capacitor 25, which is an electrolytic capacitor, is connected between the output terminals 24a and 24b to prevent ripples and the like.

The pulse generating means 3 includes a first operational amplifier 31 acting as an oscillator, and a second operational amplifier which is connected to a positive input of the first operational amplifier 31 via a first resistor 33 to control ON / OFF of oscillation of the first operational amplifier 31. A transistor 32, a second resistor 34 connected between the base of the second transistor 32 and a reference potential and setting an operating voltage of the second transistor 32;
A third resistor 35 for applying a base voltage to the base of the second transistor 32 in accordance with an output terminal voltage of the supply circuit 2, and a fourth resistor 3 for setting an amplification factor and oscillation conditions of the first operational amplifier 31;
6, a fifth resistor 37, a sixth resistor 38, and a second capacitor 39.

The control means 4 includes the first operational amplifier 31 of the pulse generation means 3.
A third transistor 41 connected to the base of the third transistor 41 via a seventh resistor 42, an eighth resistor 43 for biasing connected between the base of the third transistor 41 and the reference potential,
A third transistor connected between the collector and the base of the transistor 41
A light emitting diode (LED) 45 having a capacitor 44 and indicating that power is being supplied is connected between the collector of the third transistor 41 and the eleventh resistor 22 of the supply circuit 2.

Furthermore, in the present embodiment, a protection circuit 6 for overcurrent is provided. The protection circuit 6 includes a ninth resistor 51 for detecting overcurrent, a second operational amplifier 52 for amplifying the detection signal, and
A fourth transistor 53 for stopping the first operational amplifier 31 of the pulse generating means 3 when an overcurrent occurs, and a tenth transistor connected between the output of the second operational amplifier 52 and the base of the fourth transistor 53.
And a resistor 54.

Next, the operation of the battery quick charger of this embodiment will be described. In the battery quick charger of the present embodiment, when the supply voltage is reduced by 10% from the rated voltage (hereinafter, referred to as an operating voltage), a necessary charging current is obtained.
The secondary voltage of the transformer 11 of the DC conversion circuit 1 is set. Then, the value of the second resistor 34 of the pulse generating means 3 is set so that the ON / OFF control of the charging current by the pulse width control is performed when the operating voltage is exceeded.

First, when the supply voltage is equal to or lower than the operating voltage, the second transistor 32 of the pulse generating means 3 determines that the voltage applied to the base by the output terminal voltage indicated by B in the drawing reaches a predetermined value. Because it is not, it is OFF. Therefore, the first operational amplifier 31 does not operate as an oscillator. At this time, a predetermined voltage is constantly applied to the voltage at the point C in the figure, and the third transistor 41 of the control means 4 is turned on. Then, the first transistor 21 of the supply circuit 2 is turned ON, and a predetermined charging current is continuously supplied to the battery 5 (I in FIG. 2).

Next, when the supply voltage rises and exceeds the operating voltage,
The second transistor 32 of the pulse generating means 3 operates to be turned ON, and the first operational amplifier 31 starts operating as an oscillator. At this time, the duty ratio of the pulse width is mainly determined by the magnitude of the positive input bias resistor of the first operational amplifier 31. This bias resistance is the sum of the resistance between the first resistor 33 and the emitter-collector of the second transistor 32. As a result, the collector current changes according to the voltage applied to the base of the second transistor 32, and the resistance between the emitter and the collector changes, so that the duty ratio of the pulse oscillation of the first operational amplifier 31 changes.

When the supply voltage exceeds the operating voltage and the pulse generating means 3 operates (II in FIG. 2), the pulse width duty ratio of the pulse is changed by the voltage at point A in FIG. By defining the base voltage of the second transistor 32, the resistance between the emitter and the collector of the second transistor 32 is obtained and determined by the resistance.

Thereafter, when the supply voltage further rises (II in FIG. 2).
I), the voltage at point A in FIG. 1 also increases,
The base voltage of the second transistor 32 increases. Then, the collector current increases, and the resistance between the emitter and the collector decreases. As a result, the duty ratio of the pulse width of the first operational amplifier 31 decreases. As shown in FIG. 2 (III), as the supply voltage increases, the duty ratio of the pulse width decreases, and when the voltage exceeds the set voltage, the charging current is cut off.

At this time, the change of the duty ratio of the pulse width
At point A in the figure, that is, the output voltage of the DC conversion circuit is used. Since this voltage fluctuation is sufficiently larger than the fluctuation of the output terminal voltage at point B, the voltage of point A is directly pulsed without using the detection amplifier. Introduced to means 3.

Further, in this embodiment, when the supply current is detected and an overcurrent of a predetermined current or more flows, the ninth resistor 51 for overcurrent detection connected between the output terminal 24b and the reference potential is connected. A potential difference is generated at both ends due to the overcurrent flowing. The potential difference between both ends of the ninth resistor 51 is greatly amplified by the second operational amplifier 52, and its output turns on the fourth transistor 53 via the tenth resistor 54. As a result, the positive input terminal of the first operational amplifier 31 of the pulse generating means 3 is grounded to the reference potential, and the first operational amplifier 31 is turned off. Then, the third transistor 41 of the control means 4 is turned off.
F, the first transistor 21 of the supply circuit 2 is also turned off, and the charging current is cut off. At this time, since the gain of the second operational amplifier 51 is set as high as about 100 db, the input voltage is several m.
Since it operates at about V, the value of the ninth resistor 51 is about several mΩ. Therefore, it is not necessary to use a resistor exclusively, and the resistor 51 can be configured by a pattern or a wire directly on the substrate.

The operational amplifier of the pulse oscillation means used in the present invention is a general-purpose operational amplifier, and an IC for a switching regulator is not particularly required. Also, there is no need to use a coil or the like.

〔The invention's effect〕

The battery quick charger of the present invention performs pulse width control during rapid charging to prevent damage to the supply transistor due to heat generation. Since the duty ratio of the pulse width is changed by directly controlling the pulse oscillating means by the output voltage of the DC conversion circuit, a detection amplifier for detecting a change in the supply voltage is not required, and The number of parts and the cost can be reduced. In addition, when an overcurrent occurs in the charging current, the charging current can be cut off by the protection circuit, so that damage to the battery due to the overcurrent does not occur. As a result, it has become possible to provide a battery quick charger having a protection function that is compact and economical.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a battery quick charger of an embodiment according to the present invention, and FIG. 2 is an operation explanatory diagram for explaining the operation. DESCRIPTION OF SYMBOLS 1 ... DC conversion circuit 2 ... Supply circuit 3 ... Pulse generation means 4 ... Control means

Claims (1)

(57) [Claims] 1. A DC conversion circuit that receives an AC power supply and performs rectification and smoothing, a supply circuit that stabilizes an output current of the DC conversion circuit and supplies a predetermined charging current to a battery, and an output of the DC conversion circuit. A pulse generation unit that changes a duty ratio of a pulse width of a generated pulse only by a voltage; a control unit that controls the supply circuit in accordance with a pulse output of the pulse generation unit to supply and cut off the charging current; A protection circuit for detecting a charging current supplied from the supply circuit to the battery and stopping the operation of the pulse generation means due to an overcurrent exceeding a predetermined current.