JPS60237822A - Charging circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a charging circuit, and particularly to a charging circuit applicable to a portable wireless device.

[Prior art]

Conventionally, this type of charging circuit has a configuration in which a resistor is connected between the charging power source and the secondary battery, and the charging current is passed using the potential difference between the charging power source voltage and the secondary battery voltage. However, the charging current had to be set to an extremely low value to prevent overcharging of the secondary battery.

However, operating the transmitter of a portable wireless device consumes a large amount of current, so if it is transmitted while charging, the amount of discharge will outweigh the amount of charge, and the voltage of the secondary battery will drop, eventually making the portable wireless device unable to operate. It had the following drawback.

Furthermore, when a secondary battery whose voltage has significantly decreased is charged, an excessive charging current flows through the resistor due to the large potential difference between the charging power supply voltage and the secondary battery voltage, resulting in burnout of the resistor. To prevent this, a fuse is required, and it also has the disadvantage that it takes time and effort to replace the fuse as necessary.

(Object of the Invention) The object of the present invention is to solve the above-mentioned drawbacks, to enable the supply of current to the load at the same time as charging the secondary battery, and furthermore, when charging the secondary battery whose voltage has considerably decreased, An object of the present invention is to provide a charging circuit capable of preventing burnout of a resistor due to excessive current flowing therein.

[Structure of the invention]

A charging circuit according to the present invention includes a first resistor connected between a charging power source and a secondary battery, a series circuit including a second resistor and a transistor connected in parallel with the resistor, and a series circuit including a second resistor and a transistor. a third resistor is connected between the pace or gate of the transistor and the charging power source, a fourth resistor is connected between the pace or gate of the transistor and the secondary battery,
While supplying current to a load directly connected to the secondary battery,
When the voltage of the secondary battery is above a certain value, the transistor is operated in the saturation region, and when the voltage of the secondary battery is below the certain value while supplying current to the load, or when the voltage of the secondary battery is below the certain value, the transistor is operated in the saturation region. The transistor is characterized in that the transistor is configured to operate in a non-saturation region when it is not supplied.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. A charging circuit for a portable wireless device according to an embodiment of the present invention is provided in a first embodiment of the present invention.
The configuration is as shown in the figure.

That is, three transistors Qt, Qs, Q
s, connect the pace of transistor Q and the collector of transistor Q2 through a resistor R1 that adjusts the pace current of transistor Q, connect the emitter of transistor Q and the collector of transistor Q3, and connect the emitter of transistor Q3 to the collector of transistor Q3. Ground.

Furthermore, the emitter of the transistor Q is connected to a charging power supply via a resistor R2, and this is used as an input terminal Pl.
The collector of the transistor Q1 is connected to the internal circuit of the portable wireless device and the built-in secondary battery, and serves as an output terminal P. A resistor R1 is connected as a bypass of a series circuit consisting of a transistor Q1 and a resistor R, and the resistors Ra and Rs are connected to the pace of the transistor Q1, the charging power supply, and the transistor Q!, respectively. is connected between the collector of the transistor Q1 and the bias circuit of the transistor Q1.

On the other hand, transistor Q! A resistor R6 is connected to the pace of the transistor Q1, and a control signal output when the transmitter of the mobile radio device operates is connected from here.The pace of the transistor Q1 is connected to the secondary battery through the resistor. The potential is connected to the voltage of the secondary battery. Further, the paces of transistors Q, , Q, are grounded through resistors R8 and Re, respectively, and are configured to bias transistors Ql and Qs.

Here, the operating states of transistors Q, Q, Q, and Qs will be explained. When transistors Q, , and Qs are both turned on and the pace current of Ql flows,
Alternatively, when the voltage of the secondary battery decreases and a bias voltage is applied to the transistor Q1 from the bias circuit, the transistor Qs is turned on. Note that the transistor Q2 is in the ON state only when a certain control signal is input during transmission from the transmitter, and the transistor Qs is turned on when the voltage of the secondary battery exceeds a certain value determined by the resistor 4 and R@l2. It is turned on only when

Now, if the voltage of the secondary battery has not decreased so much and is above a certain value, current flows through the bypass resistor Ri to charge it.

However, when charging and operating the transmitter at the same time, a control signal is input from the transmitter, so transistor Q! turns on. Moreover, since the voltage of the secondary battery is above a certain value, the transistor Qs is also turned on, and the transistor Q1. A grounding circuit is formed by connecting Q21QI in series. Therefore, the transistor Q operates to the saturation region by flowing a large pace current force through the transistor 79. Therefore, a parallel circuit is formed by resistors R2 and R3, and the resistor Q is set to a value smaller than that of resistor R3 in advance. The main current flows through the resistor R2 and is used to supply current to the transmitter and charge the secondary battery.

Next, when the voltage of the secondary battery drops below a certain value, a bias voltage is applied to the transistor Q by the bias circuit consisting of resistors R4 and R8, so that the transistor Q is turned on and the resistor A current flows through the device Rs. However, since the transistor Qs is in the off state at this time, a large base current does not flow through the transistor Q1, preventing the transistor Q1 from entering the saturation region. That is, an excessive current does not flow through the resistor R3, and burning out of the resistor R can be prevented without using a fuse.

Although the above embodiment describes a charging circuit applied to a portable wireless device, it goes without saying that the present invention is not limited to this and can be applied to various charging devices.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to charge a secondary battery while supplying current to a load, and this invention is particularly useful in frequently used portable radio devices.

Furthermore, even if a secondary battery whose voltage has dropped considerably is charged, an excessive current will not flow, so the resistor will not burn out. Therefore, it is possible to charge the secondary battery without using a fuse, regardless of the degree of depletion of the voltage of the secondary battery.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a charging circuit according to an embodiment of the present invention. Q1 to Q,...Transistors R1 to R9...Resistor Pl...Input terminal P2...Output terminal P3...Control signal input terminal. Patent applicant: NEC Corporation

Claims (1)

[Claims] A first resistor is connected between a charging power source and a secondary battery,
A series circuit consisting of a second resistor and a transistor is connected in parallel with the resistor, a third resistor is connected between the pace or gate of the transistor and the charging power source, and the resistor is connected in parallel with the transistor. and the secondary battery, a fourth resistor is connected between the secondary battery and the second battery while supplying current to a load directly connected to the secondary battery.
When the voltage of the secondary battery is above a certain value, the transistor is operated in the saturation region, and when the voltage of the secondary battery is below the certain value while supplying current to the load, or when the voltage of the secondary battery is below the certain value, the transistor is operated in the saturation region. A charging circuit characterized in that the transistor is configured to operate in a non-saturation region when not supplied.