JPH05184079A - Charging current switching circuit for battery - Google Patents

Abstract

PURPOSE:To provide a charging current switching circuit for a charger which can select the charging current appropriately depending on the type of secondary battery having different capacity. CONSTITUTION:A selection switch SW selects a charging current and a voltage reference supply circuit 1 supplies a voltage reference Vs of plus potential which is fed, as an input voltage, to a PWM control integrated circuit IC 1 in order to control a switching element on the primary, i.e., a FET Q3, thus controlling the secondary charging current Io. Since the voltage drop across the resistor R1 due to the charging current is equalized to the voltage reference Vs, a constant charging current Io can be obtained. According to the invention, charging current can be fed to each type of secondary battery without replacing the charger by selecting the charging current through the selection switch SW.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charging double current switching circuit used for charging batteries having different charging double currents.

[0002]

2. Description of the Related Art A conventional charger charges a battery with one type of charging current.

[0003]

However, recently, various types of secondary batteries having different capacities have been widely used,
There is an increasing demand for a charger that can select an appropriate charging stream.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a battery charging double current switching circuit which should be provided in a charger capable of charging various secondary batteries having different charging double currents. To aim.

[0005]

In order to solve the above-mentioned problems, a battery charge-two-current switching circuit of the present invention comprises a selection switch SW for selecting charge current and a selection switch SW in a charging circuit for charging a battery. The reference voltage supply circuit 1 that supplies different reference voltages Vs depending on the selection of SW, and the charging current I
A PWM (pulse width modulation) control integrated circuit IC1 which outputs a pulse width control signal pw from an input by a combined voltage Ve of a voltage drop R1 × Io generated in a resistor R1 by o and the reference voltage Vs, and this PWM control integrated circuit A switching element FET Q3 for controlling the current width of the pulse current flowing from the DC power supply Es to the primary side by the pulse width control signal pw from the IC1 and a converter transformer T1 for electromagnetically coupling the primary side and the secondary side. And a rectifier circuit 2 for rectifying the secondary side output to supply a charging double current Io to the battery E as a load, each of which is a constant current charging double current adapted to a secondary battery having a different charging double current. It is characterized by charging batteries.

[0006]

Operation: For each battery having different charging flow, the charging flow is selected by the selection switch SW. The selection of the selection switch SW causes the reference voltage supply circuit 1 to supply the reference voltage Vs having a predetermined positive potential. Initially this reference voltage V
s becomes the input voltage of the PWM control integrated circuit IC1. PW
The M control integrated circuit IC1 outputs a pulse width control signal pw for widening the primary side pulse current width to the FET Q3 which is the primary side switching element. In accordance with the operation of the primary side FET Q3, the converter transformer T
The electric power on the secondary side increases via 1 and the charging flow Io increases. The charge current Io, the voltage drop R1 × Io of the negative potential due to the resistor R1 and the reference voltage Vs are connected via a resistor, and the combined voltage Ve becomes the input voltage of the PWM control integrated circuit IC1. The charging stream Io continues to increase until the combined voltage Ve becomes zero, and when it becomes zero, the charging stream Io becomes a constant charging current Io. In this way, by selecting the charge stream from the selection switch SW, each charge stream can be supplied to various secondary batteries without replacing the charger. ..

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a switching circuit for switching between charging and discharging of a battery. First, the circuit configuration will be described. The selection switch SW is a switch for selecting the charge flow for charging various batteries having different capacities with the charge flow. The reference voltage supply circuit 1 is a circuit that supplies the reference voltage Vs determined by the selection of the selection switch SW, and includes transistors Q1 and Q2 and a resistor. The resistor R1 is a charging current I for charging the battery E.
It is a power type resistor that detects o and converts it into a voltage. PWM
The control integrated circuit IC1 is composed of an amplifier 4 and a PWM control circuit 3. The non-inverting input terminal + of the amplifier 4 is connected to the ground via the resistor 3 and amplifies the input voltage applied to the inverting input terminal −.

The PWM control circuit 3 compares the output from the amplifier 4 with the triangular wave of a carrier having a constant frequency and outputs a pulse width control signal pw. The FET Q3 is a switching element that switches the voltage from the DC power supply Es on the primary side, and is a field effect transistor. The converter transformer T1 electromagnetically couples the primary side and the secondary side, and the rectifier circuit 2 is composed of a rectifier D1 and a smoothing capacitor C1.
The secondary output is rectified to supply the charging stream Io to the load battery E. The symbol R represents resistance.

Next, the operation of the battery charge-two-current switching circuit will be described. For each battery having a different charging flow, the charging flow is selected by the selection switch SW. For example, when the selection switch SW is opened as shown in the figure, a current flows from the power supply voltage Vref of the reference voltage supply circuit 1 to the base of the transistor Q2 through the resistors R10 and R9, and the transistor Q2 is turned on.
Turns on. The base of the transistor Q1 is pulled to the minus side, the base current flows in the order of the power supply voltage Vref → the emitter of the transistor Q1 → the base → the transistor Q2, and the transistor Q1 is turned on. Therefore, the resistance R
4 and the resistor R5 are in parallel, and the parallel resistor Rp is R4 / R5.
It becomes equivalent to / (R4 + R5).

The potential at the connection point between the resistors R4 and R5, that is, the reference voltage Vs supplied by the reference voltage supply circuit 1 is expressed by the following equation. Vs = Vref (R1 + R2) / (Rp + R1 + R2) (Equation 1) That is, the reference voltage supply circuit 1 supplies the reference voltage Vs having a predetermined positive potential. Initially, the reference voltage Vs of the equation 1 is applied to the inverting input terminal − of the amplifier circuit 4 of the PWM control integrated circuit IC1. P of the PWM control integrated circuit IC1
The WM control circuit 3 outputs a pulse width control signal pw that widens the primary side pulse current width. FET Q on the primary side
3 performs switching so that the pulse width is widened by the pulse width control signal pw. Converter transformer T
The converted electric power is increased on the secondary side via 1 and the direct current rectified by the rectifier D1 of the rectifier circuit 2 is charged by the charging current Io.
As a result, the battery E is charged. This charging current Io flows through the resistor R1 arranged in series with the battery E and causes a voltage drop R1 × Io.
Generate. Since the connection point between the resistor R1 and the battery E is grounded to the ground, the above voltage drop R1 × Io has a negative value. This negative voltage drop R1 × I
o and the reference voltage Vs of Equation 1 are connected via a resistor 2,
The charging current Io continues to increase until the combined voltage Ve becomes zero, and when it reaches zero, the charging current Io having a constant current is constant.
Becomes

When the selection switch SW is closed, the base of the transistor Q2 is grounded to the ground via the resistor R9, so that the base current does not flow and the transistor Q2 is turned off. The transistor Q1 is also turned off. That is, the reference voltage Vs supplied by the reference voltage supply circuit 1 is expressed by the following equation. Vs = Vref · (R1 + R2) / (R4 + R1 + R2) (Equation 2) That is, since Rp <R4, Vs of Equation 2 <Vs of Equation 1 is satisfied. Voltage drop R1 × Io and reference voltage Vs of Equation 2
Are connected via a resistor 2, and the charging current Io continues to increase until this combined voltage Ve becomes zero, and when it becomes zero, the charging current Io becomes a constant constant current Io. As described above, by selecting the charging stream with the selection switch SW, it is possible to supply the charging stream with a constant constant current to each battery without replacing the charger.

The selection by the selection switch SW has been described above in the case of two types of large and small charging currents. However, for example, transistors Q1 and Q2 are provided with a multi-stage transistor and the selection switch SW selects this. It is also possible to set three or more types of constant current charging flow. The DC power supply Es may be a rectified AC or a battery.

FIG. 2 is a characteristic diagram of charging pressure and charging flow. In the figure, the horizontal axis represents the charge flow rate Io, and the vertical axis represents the charge flow rate Vo. The characteristic curve A is obtained by increasing the charging current Io by opening the selection switch SW in FIG. Characteristic curve B is obtained by closing the selection switch SW to reduce the charging current Io. Both the characteristic curve A and the characteristic curve B are vertical, which clearly shows that the charging current Io is a constant current.

[0014]

As described above, the battery charge switching circuit according to the present invention includes the selection switch SW for selecting the charge current and the reference voltage for supplying the different reference voltage Vs depending on the selection of the selection switch SW. The voltage drop R1 × I generated in the resistor R1 by the supply circuit 1 and the charging double current Io.
PWM control integrated circuit I for outputting a pulse width control signal pw from an input of a combined voltage Ve of o and the reference voltage Vs
FE of the switching element that controls the current width of the pulse current flowing from the DC power supply Es to the primary side by C1 and the pulse width control signal pw from the PWM control integrated circuit IC1.
T Q3, a converter transformer T1 that electromagnetically couples the primary side and the secondary side, and a rectifier circuit 2 that rectifies the output of the secondary side and supplies a charging stream Io to the battery E of the load, Since each battery is configured to be charged by a constant-current charging current which is adapted to each secondary battery having a different current, the charging current can be selected with a selection switch for each secondary battery having a different current. Just select and you can easily charge properly. Therefore,
There is no need to prepare many chargers with different charging flows,
The effect is great both economically and in terms of space.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a switching circuit for charging and discharging a battery according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of charging voltage and charging current in one embodiment of the present invention.

[Explanation of symbols]

 1 Reference Voltage Supply Circuit 2 Rectifier Circuit 3 PWM Control Circuit 4 Amplifier C1 Electrolytic Capacitor D1 Rectifier E Battery Es DC Power Supply IC1 PWM Control Integrated Circuit Q1, Q2 Transistor Q3 FET R1 Power Source Resistor R2-R10 Resistor SW Select Switch T1 Converter Trance

Claims (1)

[Claims] 1. In a charging circuit for charging a battery, a selection switch (SW) for selecting a charging flow and a reference voltage supply circuit (1) for supplying a different reference voltage (Vs) depending on the selection of the selection switch (SW). ), And the pulse width control signal (pw) is output from the input of the combined voltage (Ve) of the voltage drop (R1 × Io) generated in the resistor (R1) due to the charging double current (Io) and the reference voltage (Vs). And a switching element for controlling the current width of the pulse current flowing from the DC power supply (Es) to the primary side by the PWM control integrated circuit (IC1) and the pulse width control signal (pw) from the PWM control integrated circuit (IC1). FET (Q3), a converter transformer (T1) that electromagnetically couples the primary side and the secondary side, and rectifies the output of the secondary side to charge the battery (E) of the load with a continuous charge (I
and a rectifying circuit (2) for supplying the same, and charging each of the batteries with a constant-current charging double current adapted to a different secondary battery having different charging double current. circuit.