JPH04205012A - Portable electronic appliance - Google Patents

Abstract

PURPOSE:To prevent the sudden drop of voltage caused by a rush current generating at the time of connecting an option appliance to an electronic appliance by providing a current limiting circuit on a power supply section for supplying the option appliance with power. CONSTITUTION:When an option appliance 11 is connected to a handy terminal 10, in order to charge a capacitor C, a large amount of current tries to flow from a battery to the option appliance 11. Then, a potential occurs at both ends of a resistor R1, and a large amount of collector current flows from transistor TRQ2 in a t3 direction. Thus, a current flowing in option appliance 11 is temporarily limited. When capacitor C of option appliance 11 is fully charged, a current tries usually to flow to operate option appliance 11. Then, in the voltages of connecting points t1, t2, t3 and t4 the relation of Vt1>Vt2>Vt3>Vt4 is generated and a collector current flows from transistor TRQ1, thereby supplying the current to the option equipment 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a portable electronic device such as a small handy terminal to which an optional device such as a barcode reader can be connected.

Taking the terminal as an example, the small handy terminal body is equipped with a battery, a control CPU, memory, a liquid crystal display, a keyboard, etc., and can also be connected to a touch scanner and barcode reader as optional equipment. . This small handheld terminal operates with a built-in battery, and displays information entered by the user through the keyboard or read using a touch scanner etc. on the LCD display via the CPU. It can be stored in memory.

Further, a voltage detection circuit that detects a decrease in battery voltage is connected to the battery, and the CPU monitors the state of charge of the battery based on information from this voltage detection circuit.

When using an optional device connected to this small handy terminal, the optional device is equipped with a capacitor for current stabilization, so the moment the optional device is connected to the small handy terminal, the In order to fill the capacitor with charge, a large amount of current temporarily flows from the battery to the optional equipment (rush current), causing the battery voltage to temporarily drop sharply.

In conventional small handheld terminals, the above-mentioned voltage detection circuit detects this temporary voltage drop and sends information to the CPU that the voltage has dropped. There is a risk of malfunctions such as performing a reset or determining that the battery is insufficiently charged and displaying a battery low message even though there is sufficient battery charge remaining.

(Problems to be Solved by the Invention) As described above, in conventional portable electronic devices, when an optional device is connected, the CPU may malfunction due to a temporary voltage drop caused by rush current flowing from the battery to the optional device. There was a problem in that there was a risk that this could happen.

In order to solve the above problems, it is an object of the present invention to provide a portable battery device that limits the rush current that occurs when an optional device is connected and that does not cause a sudden voltage drop.

[Configuration of the Invention (Means for Solving the Problem) In order to achieve the above object, the portable electronic device of the present invention includes a battery and a power supply section that supplies power from the battery to optional equipment. The power feeding unit is provided with a current limiting circuit that limits the amount of current flowing from the battery to the optional equipment.

(Function) A current limiting circuit is provided in the power supply unit that supplies power to the optional equipment, and the current flowing to the optional equipment is always limited to a predetermined value or less. Therefore, no rush current is generated even when an optional device is connected, so there is no possibility that the voltage of the main body of the portable electronic device will suddenly drop.

(Example) Hereinafter, an example in which the portable electronic device of the present invention is applied to a day terminal will be described in detail with reference to the drawings.

First, FIG. 2 shows a block diagram of the handy terminal 0. The non-day terminal of this embodiment includes a CPU as a control means, a memory 2 consisting of a non-volatile memory such as EEFROM as a storage means, an LCD 3 as a display means, a keyboard 4 as an input means, and a battery as a power source. 5, a voltage detection circuit 6 for detecting the voltage of the battery 5, and an external interface 7 for connection to an optional device 11. As equipment connected to this external interface 7, a barcode reader, scanner, etc. (not shown) are prepared as optional equipment.

The information read by this barcode reader etc.
Information input from the keyboard 4 is stored in the memory 2 via the CPUI. Then, the CPUI performs predetermined arithmetic processing based on the data stored in the memory 2, and displays the results on the LCDB. Further, a printer (not shown) is connected to the handy terminal 10, and the calculation results can be outputted by the printer. The battery 5 is made of, for example, a NiCd battery, and supplies power to various electronic components and optional equipment that make up the handy terminal 10. A voltage detection circuit 6 is connected to this battery 5, and when it detects that the voltage of the battery 5 has dropped, the CPU
Warnings are now issued.

Next, FIG. 1 shows a circuit diagram of the power supply section of the handy terminal to explain the flow of current from the battery 5 to the optional device 11 when the optional device is connected to the handy terminal 10. A power supply section of the handy terminal 10 is provided with a current control circuit composed of resistors R1 and R2 and transistors Q1 and Q2. A resistor R1 is connected to the connection point t1 on the + side of the battery 5.
or connected. The other end of this resistor R1 is connected to the emitter of the transistor Q1 at a connection point t2. The collector of the transistor Q1 is connected to a power supply terminal t4 for the optional equipment 11. Also, transistor Q
The base of 1 is connected to resistor R2 at connection point t3.

Further, the other end of the resistor R2 is connected to a switching means (not shown) provided inside the circuit. This switching means has a high potential when the optional device 11 is not connected, so that no current flows to the power supply section, and has a low potential when the optional device 11 is connected, so that current flows to the power supply section. It is something to do. The emitter of the transistor Q2 is connected to the connection point t1 on the child terminal side of the resistor R1 described above. Further, the collector of the transistor Q2 is connected to a connection point t3 between the collector of the transistor Q1 and the resistor R2. Further, the base of the transistor Q2 is connected to the connection point t2 between the resistor R1 and the transistor Q1.

Next, the operation of the current control circuit when the optional device 11 is connected will be explained. When the optional device 11 is connected, the operation of the switching means allows current to flow through the power supply section.

Here, assume that the current that flows when the optional device 11 is normally operating is, for example, 50 to 100 mV.

The optional equipment 11 is provided with a capacitor C of a predetermined capacity for current stabilization.
When connected, a large amount of current (rush current) tries to flow from the battery 5 to the optional device 1 in order to fill the charge of this capacitor C. This rush current is, for example, 150 to 300 mV. At this time, since a large amount of current flows through the resistor R1, a potential difference is generated between both ends of the resistor R, and the voltages at the connection points t1, t2, and t3 have a relationship of Vtl>>Vt2>Vt3. At this time,
A large amount of collector current flows from the transistor Q2 in the direction t3. As a result, the current flowing through the optional device 11 is temporarily limited.

When the capacitor C of the optional device 11 is filled with charge, the battery 4 supplies the optional device 11 with a charge of 50 to 10
A current of 0 mV is about to flow. At this time, each connection point t
1, t2, t3, and t4 voltages: Vtl>Vt2>>
I wonder if there is a relationship of Vt3>Vt4. At this time, collector current flows from transistor Q1, and optional device 1
1 is supplied with current.

As detailed above, the handy terminal 1 of this embodiment
When using the optional device 11 connected to the handy terminal 1, the moment the optional device 11 is connected, the handy terminal 1
Rush current can be prevented from flowing from zero to the optional equipment 11.

Thereby, there is no possibility that the voltage of the battery 5 will suddenly drop as soon as the optional device 11 is connected. Therefore, it is possible to prevent the voltage detection circuit 6 from detecting a voltage drop caused by a rush current and issuing a battery low warning to the CPU even though the battery 5 is sufficiently charged. This eliminates the risk of the CPU malfunctioning.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a portable electronic device that does not cause a sudden voltage drop due to rush current generated when an optional device is connected.

[Brief explanation of the drawing]

Figures 1 and 2 are for explaining this embodiment.
FIG. 1 is a circuit diagram of a power supply section for optional equipment of a handy terminal, and FIG. 2 is a block diagram of the handy terminal. 1...CPU 5...Battery 6...
・Voltage detection circuit 10...Handy terminal 11...Optional equipment agent Patent attorney Nori Chika Nobuoki Yamashita -■ ++++ +++++-++-++-1 The first is Figure 2

Claims (1)

[Claims] The power supply unit includes a battery and a power supply unit that supplies power from the battery to the optional equipment, and the power supply unit is provided with a current limiting circuit that limits the amount of current flowing from the battery to the optional equipment. A portable electronic device characterized by: