JPS6338694Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is an electronic device that has a stabilized power supply circuit and a rechargeable battery such as a storage battery. The present invention relates to a charging device for charging.

Conventional configuration and its problems One of the methods for charging a storage battery is a constant voltage charging method.

Although various charging characteristics of this constant voltage method can be considered, a typical characteristic is shown in FIG. Charging characteristics A are those when there are no current-limiting resistors before and after the stabilized power supply circuit, and have the advantage of short charging times, but on the other hand, excessive current may occur when the storage battery voltage is low or there is a short circuit. This has the drawback of causing deterioration of storage battery characteristics, equipment failure, etc.

Characteristic B has a current limiting resistor inserted on the output side of the stabilized power supply circuit, and although the charging current is limited, there is a problem in that the charging time becomes longer.

The characteristic of C is that a current limiting resistor is inserted on the input side of the stabilized power supply circuit, and the voltage is constant until a certain current value D, and after that, the current limiting effect is performed. This characteristic shows satisfactory characteristics in terms of charging current limitation and charging time.

In order to achieve this C characteristic, the power switch is usually used to switch the load side (load - built-in storage battery) and to switch the current limiting resistor (short circuit when the power switch is on - current limit when the power switch is off). A switch with at least two circuits and two contacts is required.

Purpose of the invention In view of these points, the present invention provides a charging device that has a simple circuit configuration using a switch with one circuit and two contacts, and that does not cause excessive current to flow as in C above and can shorten charging time. The purpose is to

Structure of the invention In the invention, the first and second terminals to which an external DC power source is connected are in contact with the second terminal when the external DC power source is not connected, and when connected, the first and second terminals are connected to the second terminal. An external DC power input terminal having a third terminal that is open is used. and,
The input terminal of the stabilized power supply circuit including the reference voltage element is connected to the first terminal, the reference point of the reference voltage terminal is connected to the third terminal, and the output terminal of the stabilized power supply circuit and the third terminal are connected. A series circuit consisting of a rechargeable battery and a diode for backflow prevention is connected in between. In addition, the common terminal of the switch is connected to the output terminal of the stabilized power supply circuit, the first fixed terminal of this switch is connected to the connection point between the battery and the diode, and the second fixed terminal of the switch is connected to the output terminal of the stabilized power supply circuit.
Connect a load between the fixed terminal and the second terminal of
A resistor is connected in series with the reference voltage element between the second terminal and the third terminal.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the figure, 1 is an external DC power supply input terminal, which has first and second terminals a, c and a third terminal b to which an external DC power supply is connected. (not shown) is in a short circuit state when it is not connected, and is in an open state when it is connected. 2 is a fuse, and 3 is a smoothing capacitor, which is inserted between terminals a and c via fuse 2.
4 is a control transistor, 5 is a bleeder resistor, 6
7 is a reference voltage Zener diode inserted into the base of the control transistor 4, and 7 is a smoothing capacitor. These elements 3 to 7 constitute a stabilized power supply circuit. 8 is a power switch whose common terminal a is connected to the emitter of the control transistor 4; 9 is a backflow prevention diode, 10 is a storage battery connected in series with this backflow prevention diode 9, and this series circuit is inserted between the emitter of the control transistor 4 and the terminal b. 11 is a current limiting resistor which is a feature of the present invention, and terminals b and c
inserted in between. A load 12 is inserted between one fixed terminal C of the power switch 8 and the terminal c. The other fixed terminal b of the power switch 8 is connected to the connection point between the backflow prevention diode 9 and the storage battery 10.

In the above configuration, the external DC power supply is connected to input terminal 1.
When applied to terminals b and c, terminals b and c are opened, and terminal a
The positive electrode is connected to terminal c, and the negative electrode is connected to terminal c. The external power supply voltage is applied to a smoothing capacitor 3, and this voltage is applied to a Zener diode 6 via a series stabilizing resistor 5.
, and provides a base bias for the control transistor 4.

Here, when the power switch 8 is on, that is, when the terminals a and c are short-circuited, the stabilized output voltage of the stabilized power supply circuit is applied to the load 12. At this time, the resistor 11 is a Zener diode 6
It only operates as a series resistor.

Furthermore, the storage battery 10 is not charged because the diode 9 enters in the opposite direction.

On the other hand, when the power switch 8 is off, that is, when the terminals a and b are short-circuited, the load 12
is disconnected from the stabilized power supply circuit, and the storage battery 10 is charged via the power switch 8 and the current limiting resistor 11. That is, the resistor 11 is inserted on the input side of the stabilized power supply circuit only during charging, and provides the characteristic c shown in FIG. 2.

Normally, the resistor 11 may be a small resistance in terms of charging current limiting characteristics, and even if it is inserted in series with the Zener diode 6 during normal operation of the device, it will not significantly deteriorate the stabilization characteristics of the device.

In addition, when operating the load 12 with the built-in storage battery 10, the connection between the external DC power source and the input terminal 1 is released, and the common terminal a of the power switch 8 is connected to the fixed terminal c.
All you have to do is connect to . At this time, the above embodiment shows a case where the load 12 is driven without passing through the stabilizing power supply circuit in order to avoid voltage drop of the storage battery 10 as much as possible. Furthermore, since the resistor 11 is short-circuited between the terminals b and c of the input terminal 1 at this time, it does not adversely affect the operation.

Although FIG. 1 shows a stabilized power supply circuit consisting of a control transistor 4, smoothing capacitors 3 and 7, and a Zener diode 6, as shown in FIG. It is also effective when applied to a stabilized power supply circuit consisting of elements, etc.

Here, 20 is a series control transistor, 21 is a starting resistor, 22 is an error detection transistor, 23,
24 and 25 are voltage dividing resistors and variable resistors;
26 is a reference voltage element, 27 is a bleeder resistor, 28
is a discharge prevention diode.

Effects of the Invention As explained above, according to the present invention, when charging the built-in storage battery using the stabilization power supply circuit in an electronic device having a stabilized power supply circuit and a built-in storage battery, the charging current limiting resistor is stabilized. Insert it into the power supply side of the power supply circuit to limit the charging current.
During normal operation, the load current does not flow through this charging current limiting resistor, and by configuring the resistor to operate as a series resistor of the reference voltage element, a constant voltage charging circuit with current limiting characteristics is realized at low cost. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a charging device according to an embodiment of the present invention, FIG. 2 is a diagram showing various charging characteristics, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. 1... External DC power supply input terminal, 3, 7... Smoothing capacitor, 4... Control transistor, 5...
...Resistor, 6...Reference voltage element, 8...Power switch, 9...Reverse current prevention diode, 10...Storage battery, 11...Resistor, 12...Load.

Claims (1)

[Scope of utility model registration request] The first and second terminals to which an external DC power source is connected are in contact with the second terminal when the external DC power source is not connected, and when the external DC power source is connected, the first and second terminals are connected to the second terminal.
An external DC power input terminal is provided having a third terminal opened from the terminal, an input terminal of a stabilized power supply circuit including a reference voltage element is connected to the first terminal, and a reference point of the reference voltage terminal is provided. is connected to the third terminal, and a series circuit of a rechargeable battery and a diode for preventing backflow is connected between the output terminal of the stabilized power supply circuit and the third terminal, and the stabilized power supply is connected to the third terminal. The common terminal of the switch is connected to the output terminal of the circuit, the first fixed terminal of the switch is connected to the connection point between the battery and the diode, and the second fixed terminal of the switch is connected to the second terminal. A charging device, wherein a load is connected between the charging device and a resistor connected in series with the reference voltage element between the second terminal and the third terminal.