JP2001238365A - Secondary battery charge control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a secondary cell charging control circuit, capable of freely setting a charging current by the control by a high voltage switch in a battery pack. SOLUTION: A switch circuit 2 is connected to a secondary cell 3 in the battery pack 19. The circuit 2 is connected to the output of an AC-DC converter 1 in an adapter power source 18. The output of a clock signal generator 6 variable at a duty factor by a duty factor variable terminal 4 is connected to the input terminal 16P of a level shifter 16. Thus, a on/off of the switch circuit 2 is controlled by the output signal of the shifter 16. The drain of a high breakdown voltage P-channel MOS transistor 9 of a reset circuit 17 is connected to the drain of an N-channel MOS transistor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery charging control circuit for charging a secondary battery in a battery pack incorporated in a portable device, a personal computer, or the like.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional example of a secondary battery charging control circuit. In FIG. 2, the adapter power supply 1b includes an AC / DC converter 2b and a charging current control circuit 3b.
When charging the secondary battery 4b in the battery pack 5b, charging is performed by the charging current control circuit 3b of the adapter power supply 1b.

[0003]

Conventionally, a secondary battery in a battery pack such as a portable device or a personal computer has been charged by using a charging current control circuit built in an adapter power supply. When the type of the battery, the charging current, and the charging time change, the adapter power supply itself needs to be changed. Therefore, there is a problem that it is difficult to respond to the change in the charging condition.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide a secondary battery charge control circuit which can set a charge current value by a customer's will by controlling a high voltage switch in a battery pack. It is intended for.

[0005]

According to a first aspect of the present invention, there is provided a secondary battery charging control circuit for changing a duty factor when charging a secondary battery, generating a clock signal having the duty factor, and A level shift circuit that inputs a signal and converts a signal of the potential of the first power supply and the ground potential into a potential of the second power supply and the ground potential, and outputs the output of the level shift circuit when the first power supply is at the ground potential. It comprises means for fixing the potential of the second power supply or the ground potential, and a switch circuit connected in series to the secondary battery and controlled to be turned on and off by an output of the level shift circuit.

According to the secondary battery charging control circuit, the charging current and the charging time can be freely set according to the type and the charging state of the secondary battery by changing the duty factor of the clock signal. . Therefore, it is possible to realize a secondary battery charge control circuit that can set a charge current value at the will of the customer by controlling a high voltage switch in the battery pack.

According to a second aspect of the present invention, there is provided a secondary battery charging control circuit,
2. The level shift circuit according to claim 1, wherein the gate of the first conductivity type field effect transistor is connected to the output of the inverting amplifier which is the potential of the first power supply. A signal input terminal (16P) which is a potential of the first power supply and an input terminal of the inverting amplifier (14) are connected to a gate of 11), and a drain of the first conductivity type field effect transistor (10) and a second conductivity type are connected. The gate of the field effect transistor (13) and the drain of the second conductivity type field effect transistor (12) are connected, and the drain of the first conductivity type field effect transistor (11) and the second conductivity type field effect transistor (12) Is connected to the drain of the second conductivity type field effect transistor (13), and the second conductivity type field effect transistor (13) and The source of the second conductivity type field effect transistor (12) is connected to the second power source, and the means for fixing the output of the level shift circuit (16) to the second power source or the ground potential is a first conductivity type electric field effect transistor. The first power supply is connected to the gate of the effect transistor (8), and the resistor (7) connected to the gate of the first conductivity type field effect transistor (9) and the second power supply is connected to the first conductivity type field effect transistor ( 8), wherein the drain of the first conductivity type field effect transistor (9) and the drain of the first conductivity type field effect transistor (11) are connected.

According to the secondary battery charging control circuit of the second aspect, the same effect as that of the first aspect is obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a secondary battery charging control circuit according to an embodiment of the present invention. The switch circuit 2 is connected to the lithium ion secondary battery 3 in the battery pack 19.
And the switch circuit 2 is connected to the output of the AC / DC converter 1 inside the adapter power supply 18. An output of a clock signal generation circuit 6 whose duty factor can be varied by a duty factor variable terminal 4;
The input terminal 16P of the level shift circuit 16 is connected, and the output signal of the level shift circuit 16 controls the conduction state and the release state of the switch circuit 2. The clock signal generation circuit 6 is, for example, a product number MN101C249 manufactured by Matsushita.
(8-bit microcomputer). The level shift circuit 16 includes high-breakdown-voltage Nch-MOS transistors 10 and 11 of the first conductivity type and a high-breakdown-voltage Pch of the second conductivity type.
-MOS transistors 12 and 13, reference voltage generation circuit 5
And a high-voltage inverter (inverting amplifier) 15 which is a potential of a second power source which uses the output of the AC / DC converter 1 as a power source. And high breakdown voltage Nc
The drain of the h-MOS transistor 11 has a high breakdown voltage Nc
A high-withstand-voltage Pch-MOS output from a reset circuit 17 composed of h-MOS transistors 8 and 9 and a high-withstand-voltage Pch-MOS transistor 7 used as a high-resistance element
The drain of the transistor 9 is connected. The reset circuit 17 serves as means for fixing the potential of the second power supply or the ground potential.

The operation of the secondary battery charging control circuit configured as described above will be described. For example, the duty coefficient variable terminal 4 is adjusted, and the clock signal is generated from the clock signal generation circuit 6 so that the duty coefficient becomes 50%. The amplitude level of the signal generated at this time is such that the low level is the ground potential and the high level is the potential of the reference voltage generating circuit 5 (hereinafter referred to as VCC).
Is set to This clock signal is applied to the input terminal 16p of the level shift circuit 16, and when the high level of the clock signal is VCC, the high voltage Nch-MOS transistor 11 is turned on, and the output of the low voltage inverter 14 becomes the ground potential and the high voltage Nch -The MOS transistor 10 is turned off. As a result, the high voltage Pch-MOS transistor 12 is turned on and the high voltage Pch-MOS transistor 13 is turned off, and the output of the high voltage inverter 15 becomes A
It becomes the potential of the C / DC converter 1 (hereinafter referred to as VA). As a result, the switch circuit 2 composed of Pch-MOS transistors is released by the output of the high-voltage inverter 15. Similarly, when a low-level signal is output from the clock signal generation circuit 6, the output of the high-voltage inverter 15 becomes low level, and as a result, the switch circuit 2 becomes conductive. When the potential of the secondary battery 3 becomes extremely low due to overdischarge or the like and the output potential of the reference voltage generating circuit 5 drops to the ground potential, the reset circuit 1
7 is turned on, the output potential of high-voltage inverter 15 becomes V
Since the switch circuit 2 is fixed to A, the switch circuit 2 is fixed to the open state without being uncertain. As described above, according to the voltage level state output from the clock signal generation circuit 6, the switching state of the switch circuit 2 is changed to the duty state by the duty factor of 50.
%, And the secondary battery 3 is charged by the AC / DC converter 1. By changing the duty coefficient depending on the type of the secondary battery 3 or the state of charge, the average value of the charging current per unit time can be freely changed.

As described above, according to one embodiment of the present invention, means for varying a duty factor when charging a secondary battery, means for generating a clock signal having a varied duty factor, and a clock signal And a level shift circuit that converts the signal of the potential of the first power supply and the ground potential to the potential of the second power supply and the ground potential, and the output of the level shift circuit when the first power supply is the ground potential, for example, the normal output or Means for fixing the inverted output to the potential of the second power supply or the ground potential, and a switch circuit connected in series to the secondary battery and controlled on and off by the output of the level shift circuit, It is possible to freely set the charging current and the charging time according to the type and the charging state.

In the present embodiment, the level shift circuit 16 and the reset circuit 17 are connected so that the switch circuit 2 is fixed to the open state when the output potential of the reference voltage generation circuit 5 drops to the ground potential. , Reset circuit 17
By connecting the drain of the high-withstand voltage Pch-MOS transistor 9 to the drain of the high-withstand voltage Nch-MOS transistor 10 of the level shift circuit 16, when the output potential of the reference voltage generating circuit 5 drops to the ground potential, It is also possible to fix it in a conductive state.

[0014]

According to the secondary battery charging control circuit of the present invention, by changing the duty factor of the clock signal, the charging current and the charging time can be freely set according to the type and the charging state of the secondary battery. Can be set. Therefore, it is possible to realize a secondary battery charge control circuit that can set a charge current value at the will of the customer by controlling a high voltage switch in the battery pack.

According to the secondary battery charging control circuit of the second aspect, the same effect as that of the first aspect is obtained.

[Brief description of the drawings]

FIG. 1 is a charge control circuit diagram of a secondary battery according to an embodiment of the present invention.

FIG. 2 is a conventional secondary battery charging control circuit diagram.

[Explanation of symbols]

1, 2b AC / DC converter 2 Switch circuit 3, 4b Secondary battery 3b Charging current control circuit 4 Duty coefficient variable terminal 5 Reference voltage generation circuit 6 Clock signal generation circuit 7, 12, 13 High voltage Pch-MOS transistor 8, 9 , 10, 11 High voltage Nch-MOS transistor 14 Low voltage inverter 15 High voltage inverter 16 Level shift circuit 16P Input terminal of level shift circuit 16 Reset circuit 18, 1b Adapter power supply 19, 5b Battery pack

Claims (2)

[Claims] 1. A means for varying a duty factor when a secondary battery is charged, a means for generating a clock signal having the duty factor, and receiving the clock signal to generate a signal of a potential of a first power supply and a signal of a ground potential. A level shift circuit for converting the potential of the two power supplies to a ground potential, means for fixing the output of the level shift circuit to the potential of the second power supply or the ground potential when the first power supply is at the ground potential, A switch circuit connected in series to the battery and controlled to be turned on and off by an output of the level shift circuit. 2. The level shift circuit according to claim 1, wherein the gate of the first conductivity type field effect transistor is connected to the output of the inverting amplifier which is the potential of the first power supply, and further connected to the first conductivity type field effect transistor. A signal input terminal (16P) which is a potential of the first power supply and an input terminal of the inverting amplifier (14) are connected to a gate of 11), and a drain of the first conductivity type field effect transistor (10) and a second conductivity type are connected. The gate of the field effect transistor (13) and the drain of the second conductivity type field effect transistor (12) are connected, and the drain of the first conductivity type field effect transistor (11) and the second conductivity type field effect transistor (12) Is connected to the drain of the second conductivity type field effect transistor (13), and the second conductivity type field effect transistor (13) and the second Two conductivity type field effect transistor (1
The source of (2) is connected to a second power supply, and the means for fixing the output of the level shift circuit (16) to the second power supply or the ground potential is connected to the gate of the first conductivity type field effect transistor (8). One power supply is connected, a gate of the first conductivity type field effect transistor (9) and a resistor (7) connected to the second power supply are connected to a drain of the first conductivity type field effect transistor (8), The secondary battery charging control circuit according to claim 1, wherein a drain of the first conductivity type field effect transistor (9) is connected to a drain of the first conductivity type field effect transistor (11).