JPH1075536A - Starting circuit for power source monitor ic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To define the initial state of charge starting time and prevent generation of malfunction, by delaying the rise of a base voltage of a first transistor constituting a differential pair, from the rise of a base voltage of a second transistor. SOLUTION: A constant current source CC1 is connected with a resistor R3 via a switching circuit SW1. The base of a transistor Q1 is connected with the connection point of the switching circuit SW1 and the resistor R3. A constant current source CC2 is connected with a resistor R1 via a switching circuit SW2. The base of a transistor Q2 is connected with the connection point of the switching circuit SW2 and the resistor R1. Switching circuits SW0, SW2 are turned ON by a control signal A. The control signal A is inputted in a switching circuit SW1 via a delay circuit D. The switching circuit SW1 is turned ON later than the other switching circuits SW0, SW2 by a specified time. Thereby the initial state is always ensured and generation of malfunction can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activation circuit for a power supply monitoring IC which is added to an overcharge detection circuit or an overdischarge detection circuit of a power supply such as a lithium ion power supply.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional power supply monitoring IC starter circuit. In the figure, CC0, CC1, and CC2 are constant current sources that output currents I0, I1, and I2, respectively, and Q1 and Q2.
2, Q6 are PNP transistors, Q3, Q4, Q5 are NPN transistors, SW0 is a switch circuit, R1,
R2 and R3 are resistors, and T is an external input terminal.

The transistors Q1 and Q2 form a differential pair. The base of the transistor Q1 is connected to the connection point between the constant current source CC1 and the resistor R3.
2 is connected to a connection point between the constant current source CC2 and the resistor R1. A constant current source CC0 is connected to the emitters of the transistors Q1 and Q2 via a switch circuit SW0, and the transistors Q3 and Q2 are connected to the collectors.
The input side (collector of the transistor Q3) and the output side (collector of the transistor Q4) of the current mirror circuit constituted by 4 are connected to each other.

The base of the transistor Q5 is connected to a connection point between the collectors of the transistors Q2 and Q4, and the collector is connected to a resistor R2 as a load. The base of the transistor Q6 is connected to a connection point between the resistor R2 and the collector of the transistor Q5, and the emitter is connected to the constant voltage source CV.

The switch circuit SW0 outputs a control signal A
Is turned on when the state changes from an overdischarge state to a standby state (a state in which overcharge or overdischarge can be detected).
When the control signal B indicating that overcharge or overdischarge has been detected is input to the external input terminal T after the predetermined voltage is set, the base voltage of the transistor Q1 becomes higher than the base voltage of the transistor Q2. , Transistor Q
5 turns ON, and an output appears from the collector of the transistor Q6. Note that the overdischarge state refers to a state in which power is not supplied due to overdischarge, and the standby state refers to a state in which an overdischarged battery pack is attached to a charging device or the like and can be charged.

[0006]

In the starting circuit for the power supply IC, regardless of the presence or absence of the control signal A, that is, an overcharge or overdischarge abnormality has occurred and the power cannot be supplied as a battery. Even if there is a constant current source CC
1, currents I1 and I2 of several μA or more are supplied from CC2, the current consumption is large, the overdischarge state progresses, and the characteristics of the lithium ion battery pack deteriorate.

To prevent this, the constant current sources CC1 and CC
C2 may be supplied with a current in accordance with the control signal A in the same manner as the constant current source CC0. In spite of this, an output appears at the time of startup (when a control signal is input) (see FIG. 6), which leads to malfunction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power-supply monitoring IC start-up circuit which does not cause a malfunction and reduces current consumption.

[0009]

According to a first aspect of the present invention, there is provided a starting circuit for a power supply monitoring IC, wherein first and second transistors forming a differential pair and a collector of the first transistor are provided. A current mirror circuit having an input side connected to the output side and a collector of the second transistor, a first constant current source and a first load connected in series, a second constant current source and a second load connected in series. Means for supplying a current from the first constant current source to the first load after a lapse of a predetermined time when a control signal is input; means for supplying a current from the second constant current source to the second load when a control signal is input; Output means connected to the collector of the second transistor;
A base of the first transistor is connected to a connection point between the first constant current source and the first load, and a base of the second transistor is connected to a connection point between the second constant current source and the second load. I have.

According to a second aspect of the present invention, the input side is connected to the first and second transistors forming a differential pair and the collector of the first transistor.
A current mirror circuit having an output connected to the collector of the second transistor; a first constant current source and a capacitor connected in series; a second constant current source and a load connected in series; A means for supplying a current from the constant current source to the capacitor and a means for supplying a current from the second constant current source to the load; and output means connected to the collector of the second transistor. The second transistor is connected to a connection point between the first constant current source and a capacitor, and the base of the second transistor is connected to a connection point between the second constant current source and a load.

With the above configuration, although the current is not supplied in advance as in the prior art, the rise of the base voltage of the first transistor is slower than the rise of the base voltage of the second transistor. An initial state can be determined (output is not generated at the time of startup).

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a power supply monitoring IC starter circuit according to a first embodiment of the present invention.
Is a switch circuit, and D is a delay circuit. The same parts as those of the prior art in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The constant current source CC1 and the resistor R3 are connected via a switch circuit SW1, and the base of the transistor Q1 is connected to a connection point between the switch circuit SW1 and the resistor R3. Similarly, the constant current source CC2 and the resistor R1 are connected via a switch circuit SW2, and the base of the transistor Q2 is connected to a connection point between the switch circuit SW2 and the resistor R1.

The switching circuits SW0, SW1, S
W2 is turned on by the control signal A, but SW1 is turned on.
Receives the control signal A via the delay circuit D, and is turned ON by a predetermined time later than the other switch circuits SW0 and SW2.

Therefore, the rise of the base voltage of each of the transistors Q1 and Q2 becomes as shown in FIG. 2 if the delay time in the delay circuit D is set appropriately.
Even if no current is supplied in advance, the initial state is always ensured, and no malfunction is caused.

FIG. 3 shows a starting circuit for a power supply monitoring IC according to a second embodiment of the present invention, wherein CC is a constant current source for outputting a current I, Q7, Q8, Q9 and Q10 are PNP transistors, and C is It is a capacitor. The same parts as those of the prior art in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

The transistors Q8, Q9, and Q10 form a current mirror circuit with the transistor Q7, respectively.
9, Q10 is the output side. The capacitor C is connected to the collector of the transistor Q8.
The connection point is connected to the base of the transistor Q1. A resistor R is connected to the collector of the transistor Q10.
1 is connected to the transistor Q2 at this connection point.
The base is connected. Also, the transistors Q1,
The emitter of Q2 is connected to the collector of transistor Q9.

The constant current source CC is turned on by a control signal B indicating that overcharge or overdischarge has been detected, and draws a current I from the input side of the current mirror circuit. I flows simultaneously, and the base voltages of the transistors Q1 and Q2 rise. When the capacitance of the capacitor C is C, the base voltage of the transistor Q1 rises with a slope I / C.

Therefore, the relationship between the rise of the base voltage of each of the transistors Q1 and Q2 is determined by the capacitor C
If the capacity of is appropriately selected, it becomes as shown in FIG.
Even if no current is supplied in advance, the initial state is always ensured, and no malfunction is caused.

Although the base voltage of the transistor Q1 keeps increasing with the passage of time, the time until the base voltage of the transistor Q2 exceeds the base voltage is the delay time of the power supply monitoring IC starter circuit.

In the above two embodiments, instead of externally inputting, the current value of the constant current source CC1 is changed so that the transistors Q1, Q2
May be reversed.

[0022]

As described above, according to the starting circuit for a power supply monitoring IC of the present invention, the initial state at the start of charging is determined by delaying the rise of the base voltage instead of supplying current in advance. Therefore, a malfunction does not occur, and the current consumption in the overdischarge state is reduced to about the leak current (1 μA or less), so that the characteristics of the lithium ion battery pack can be prevented from deteriorating.

[Brief description of the drawings]

FIG. 1 is a block diagram of a start-up circuit for a power supply monitoring IC according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between base voltages of transistors Q1 and Q2 in a power supply monitoring IC starter circuit according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a startup circuit for a power supply monitoring IC according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between base voltages of transistors Q1 and Q2 in the power supply monitoring IC starter circuit according to the first embodiment of the present invention.

FIG. 5 is a block diagram of a conventional power supply monitoring IC starter circuit.

FIG. 6 is a diagram illustrating a problem that occurs when a current is simultaneously supplied to each circuit by a control signal A in a conventional power supply monitoring IC starter circuit.

[Description of Signs] Q1, Q2 PNP transistors Q3, Q4, Q5 NPN transistors Q6, Q7, Q8, Q9, Q10 PNP transistors SW0, SW1, SW2 Switch circuits CC, CC0, CC1, CC2 Constant current source CV constant Voltage source R1, R2, R3 Resistance D Delay circuit C Capacitor T External input terminal

Claims (2)

[Claims] In an activation circuit for a power supply monitoring IC added to an overcharge detection circuit or an overdischarge detection circuit, an input side is connected to first and second transistors forming a differential pair and a collector of the first transistor. A current mirror circuit having an output connected to the collector of the second transistor;
A first constant current source and a first load connected in series, a second constant current source and a second load connected in series, and a control signal is input, and after a predetermined time, a current flows from the first constant current source to the first load. And a means for supplying a current from a second constant current source to a second load when a control signal is input; and an output means connected to a collector of the second transistor. A base is connected to a connection point between the first constant current source and the first load, and a base of the second transistor is connected to a connection point between the second constant current source and the second load. A starting circuit for a power supply monitoring IC. 2. A power supply monitoring IC starting circuit added to an overcharge detection circuit or an overdischarge detection circuit, wherein an input side is connected to first and second transistors forming a differential pair and a collector of the first transistor. A current mirror circuit having an output connected to the collector of the second transistor;
A first constant current source and a capacitor connected in series, a second constant current source and a load connected in series, and when a control signal is input, the first constant current source to the capacitor and the second constant current source to the capacitor. Means for supplying current to the load, respectively;
Output means connected to a collector of the second transistor, a base of the first transistor is connected to a connection point between the first constant current source and a capacitor, and a base of the second transistor is A power supply monitor connected to a connection point between the second constant current source and the load;
Start circuit for C.