JP2001339936A - Power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize display of an operating mode at low cost in a power supply that operates in a constant-voltage control mode and a constant-current control mode. SOLUTION: In the power supply operating in the constant-voltage control mode and the constant-current control mode, provided are a first amplifying circuit 20 that outputs a signal corresponding to the error between a first detection level that is proportional to the output current and a first reference level, a second amplifying circuit 30 that outputs a signal corresponding to the error between a second detection level that is proportional to the output current and a second reference level, a control-level generating circuit 40 that generates a control level based on a signal from the first amplifying circuit 20 and a signal from the second amplifying circuit 30, a power circuit 10 that generates a voltage that is proportional to the control level as the output voltage, a comparison circuit 51 wherein its one-side input is connected to an output of the first amplifying circuit 20 and its another-side input is connected to an output of the second amplifying circuit 30, and an information means 52 connected to the output of the comparison circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device that can selectively operate in a constant voltage control mode and a constant current control mode.

[0002]

2. Description of the Related Art In a power supply device, it is necessary to control a voltage or a current supplied to a load to a constant value in accordance with the type of a load connected to the power supply device and its operation state. By providing both functions of a constant voltage control mode for controlling the voltage supplied to the load at a constant level and a constant current control mode for controlling the current supplied to the load at a constant level, various types of loads can be realized with one power supply device. Can be handled.

[0003] Further, for example, in the case of rapidly charging a Li-based secondary battery, it is necessary to perform charging by combining constant-current charging and constant-voltage charging. A power supply device that can be selectively operated in the control mode is required.

[0004]

When using a power supply having a constant voltage control mode and a constant current control mode, it is necessary to confirm that the power supply is operating normally in a desired operation mode. For example, when the secondary battery should be charged while supplying a constant current in the constant current mode, an excessive current flows through the secondary battery when the power supply device is operating in the constant voltage mode due to a failure or the like. In addition, abnormal heat generation may occur in the secondary battery, or rupture may occur in an extreme case.

However, in a general power supply device, the internal operation state cannot be grasped from the outside. Therefore, this type of power supply device needs to have a function of externally displaying whether the power supply device is operating in the constant voltage control mode or the constant current control mode. In order to realize such a display function, it is necessary to add a circuit having a relatively complicated configuration,
This leads to an increase in the manufacturing cost of the power supply device.

SUMMARY OF THE INVENTION It is an object of the present invention to realize a display function of an operation mode at low cost in a power supply device which can selectively operate in a constant voltage control mode and a constant current control mode.

[0007]

According to a first aspect of the present invention, there is provided a power supply device comprising:
In a power supply device selectively operable in a constant voltage control mode and a constant current control mode, a signal corresponding to an error between a first detection level and a first reference level proportional to an output voltage supplied to a load is output. A first amplifier circuit that outputs a signal corresponding to an error between a second detection level proportional to an output current supplied to a load and a second reference level; A control level generating circuit for generating a control level based on a signal output from the amplifier circuit and a signal output from the second amplifier circuit; and a voltage proportional to the control level output from the control level generating circuit, A comparison circuit having one input terminal connected to the output of the first amplification circuit and the other input terminal connected to the output of the second amplification circuit, and an output of the comparison circuit. Connected to Characterized by providing the notifying means.

[0008] In the power supply device of the first aspect, the first amplifier circuit outputs a signal corresponding to an error between the first detection level and the first reference level, which is proportional to the output voltage supplied to the load. The second amplifier circuit outputs a signal corresponding to an error between a second detection level proportional to an output current supplied to the load and a second reference level. The control level generation circuit generates a control level based on a signal output from the first amplifier circuit and a signal output from the second amplifier circuit. The power supply circuit generates a voltage proportional to the control level output from the control level generation circuit as the output voltage.

When the control level generating circuit generates a control level corresponding to the signal output from the first amplifier circuit (in the case of the constant voltage control mode), the first level is proportional to the output voltage.
The operation is performed so as to cancel the error between the first detection level and the first detection level, so that the output voltage is kept constant.
Further, when the control level generation circuit generates a control level corresponding to the signal output from the second amplifier circuit (in the case of the constant current control mode), the second detection level proportional to the output current and the second detection level , The output current is kept constant.

When operating in the constant current control mode, the error detected by the first amplifier circuit increases, and when operating in the constant voltage control mode, the error detected by the second amplifier circuit increases. . Since the first amplifier circuit and the second amplifier circuit have a relatively large amplification degree, the level of a signal output from the first amplifier circuit and the second amplifier circuit greatly changes between the constant current control mode and the constant voltage control mode.

Since the comparison circuit compares the output level of the first amplifier circuit with the output level of the second amplifier circuit, the power supply operates in either the constant current control mode or the constant voltage control mode. The comparison result changes depending on whether the The notifying unit notifies the comparison result of the comparison circuit to the outside by, for example, lighting display of a lamp. According to a second aspect of the present invention, in the power supply device of the first aspect, the control level generating circuit includes a resistor circuit for dividing a third reference level, and an output between the resistor circuit and the output of the first amplifier circuit. And a second backflow prevention element connected between the output of the resistor circuit and the output of the second amplifier circuit, and one input of the comparison circuit. A terminal is connected between the output of the first amplifier circuit and the first backflow prevention element, and the other input terminal of the comparison circuit is connected to the output of the second amplifier circuit and the second backflow prevention element. And connected between them.

According to a second aspect, the control level is generated based on a third reference level. When operating in the constant voltage control mode, the control level is determined according to the current flowing through the resistor circuit and the first amplifier circuit via the first backflow prevention element, and when operating in the constant current control mode, The control level is determined according to the current flowing through the resistor circuit and the second amplifier circuit via the second backflow prevention element.

[0013] The first backflow prevention element and the second backflow prevention element function to operate the first backflow prevention element and the second backflow prevention element according to the level of the output between the first amplifier circuit and the second amplifier circuit.
Since the current flows through one of the backflow prevention elements, the device operates in one of the constant current control mode and the constant voltage control mode. By connecting the input terminal of the comparison circuit between the output of the first amplification circuit and the first backflow prevention element and between the output of the second amplification circuit and the second backflow prevention element,
The operation mode can be easily identified.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a power supply device according to the present invention will be described with reference to FIGS. This embodiment corresponds to claims 1 and 2. FIG. 1 is a block diagram showing the configuration of the power supply device of this embodiment. FIG. 2 is a time chart showing an operation example of the power supply device of this embodiment. FIG. 3 is a graph showing the relationship between Vref and Vo of the power supply body.

In this embodiment, the first amplifier circuit, the second amplifier circuit, the control level generation circuit, the power supply circuit,
The comparing circuit and the notifying means are a constant voltage error amplifier circuit 20, a constant current error amplifier circuit 30, and a reference level generation circuit 4 respectively.
0, power supply main body 10, operational amplifier 51, and light emitting diode 52. The resistor circuit of claim 2 corresponds to the resistors R5 and R6. The first backflow prevention element and the second backflow prevention element in claim 2 correspond to the diodes D1 and D2, respectively.

Referring to FIG. 1, this power supply device includes a power supply body 10, a constant voltage error amplifier circuit 20, a constant current error amplifier circuit 30, a reference level generation circuit 40, and an operation mode display circuit 50. The output terminal 12 of the power supply body 10,
An optional load 60 is connected to 13. The power supply main body 10 is a DC power supply. DC power appearing at the output terminals 12 and 13 of the power supply body 10 is supplied to the load 60. The voltage applied between the terminals of the load 60 is the output voltage Vo,
Is an output current Io.

The input terminal of the constant voltage error amplifier 20 has
A signal Vv output from the power supply body 10 is applied. A voltage proportional to the level of the output voltage Vo appears in the signal Vv. A signal Vi output from the power supply main body 10 is applied to an input terminal of the constant current error amplifier circuit 30. A voltage proportional to the level of the output current Io appears in the signal Vi.

The constant voltage error amplifier 20 includes a resistor R
1, R2, an operational amplifier 21 and a constant voltage source 22 are provided. The constant voltage source 22 outputs a constant DC voltage used for constant voltage control as a reference voltage Vr1. When the reference voltage Vr1 is changed, the set value of the output voltage Vo in the constant voltage control mode changes. The signal Vv is connected to the resistors R1,
The voltage is divided by R2 and applied to the minus input terminal of the operational amplifier 21 as the voltage Vv1. The reference voltage Vr1 is applied to the positive input terminal of the operational amplifier 21. The operational amplifier 21 amplifies the difference between the reference voltage Vr1 and the voltage Vv1 as a voltage error. The amplified voltage error is the voltage Vx
At the output of the operational amplifier 21.

The constant current error amplifier 30 includes a resistor R
3, R4, an operational amplifier 31 and a constant voltage source 32 are provided. The constant voltage source 32 outputs a constant DC voltage used in constant current control as a reference voltage Vr2. When the reference voltage Vr2 is changed, the set value of the output current Io in the constant current control mode changes. The signal Vi is connected to the resistors R3 and R3.
The voltage is divided by R4 and applied as a voltage Vi1 to the minus input terminal of the operational amplifier 31. The reference voltage Vr2 is applied to the positive input terminal of the operational amplifier 31. The operational amplifier 31 amplifies the difference between the reference voltage Vr2 and the voltage Vi1 as a current error. The amplified current error is the voltage Vy
At the output of the operational amplifier 31.

The reference level generation circuit 40 includes a constant voltage source 4
1, diodes D1 and D2, and resistors R5 and R6. The constant voltage source 41 converts a constant DC voltage to a reference voltage Vr.
Output as 3. The reference voltage Vr3 is connected to the resistors R5 and R6.
Are controlled by the voltage Vx output from the constant voltage error amplifier 20 and the voltage Vy output from the constant current error amplifier 30.

When the voltage Vx is smaller than the reference voltage Vref, the current Ix flows through the diode D1 in the direction indicated by the arrow in FIG.
It is almost equal to x. When the voltage Vy is smaller than the reference voltage Vref, the current Iy flows through the diode D2 in the direction indicated by the arrow in FIG.
ref becomes substantially equal to the voltage Vy.

The reference voltage Vref generated by the reference level generation circuit 40 is applied to the reference voltage input terminal 11 of the power supply body 10. The power supply body 10 controls the output voltage Vo so as to be proportional to the level of the input reference voltage Vref. That is, the input / output characteristics (Vref,
Vo) is as shown in FIG. 1 operates in one of the constant voltage control mode and the constant current control mode. First, the operation in the constant voltage control mode will be described.

When the output voltage Vo is higher than the set value, (Vv1> Vr1) at the input of the operational amplifier 21 of the constant voltage error amplifier 20, so that the voltage Vx decreases and the reference voltage Vref also decreases. Become. As a result, the power supply body 10 lowers the output voltage Vo. Also, the output voltage Vo
Is lower than the set value, (Vv1 <Vr) at the input of the operational amplifier 21 of the constant voltage error amplifier 20.
1), the voltage Vx increases and the reference voltage Vref
Will also be higher. As a result, the power supply body 10 increases the output voltage Vo.

That is, the constant voltage error amplifying circuit 20 controls the diode D1 so that the output voltage Vo is maintained at the set value.
To control the reference voltage Vref. Next, the operation in the constant current control mode will be described. When the output current Io is larger than the set value, the constant current error amplifier 30
(Vi1> Vr2) at the input of the operational amplifier 31
, The voltage Vy decreases and the reference voltage Vref also decreases. As a result, the power supply body 10 lowers the output voltage Vo, so that the output current Io decreases.

When the output current Io is smaller than the set value, the operational amplifier 3 of the constant current error amplifier 30
At the input of 1, since (Vi1 <Vr2), the voltage Vy increases and the reference voltage Vref also increases. As a result, the power supply body 10 increases the output voltage Vo, so that the output current Io increases. That is, the constant current error amplifier circuit 30 controls the reference voltage Vref via the diode D2 so that the output current Io is maintained at the set value.

When the power supply of FIG. 1 is used as a charger for a secondary battery, the power supply operates as shown in FIG. That is, it operates in the constant current control mode at first, and automatically shifts to the constant voltage control mode at a certain point. When operating in the constant current control mode, the voltage across the terminals of the secondary battery serving as the load 60 increases with the progress of charging, so that the output voltage Vo increases with time. In this case, since the output voltage Vo is lower than the set value, the constant voltage error amplifying circuit 2
At 0, (Vv1 <Vr1), and the voltage Vx increases, so that (Vx> Vy). That is, since the constant current error amplifier circuit 30 controls the reference voltage Vref, constant current control is performed.

When the output voltage Vo rises with the progress of charging and the output voltage Vo reaches a set value, the voltage Vx output from the constant voltage error amplifier circuit 20 decreases, and the reference voltage Vref changes to the voltage Vx. Will change accordingly. That is, the constant voltage error amplifier 20 controls the reference voltage Vref so that the output voltage Vo is maintained at the set value. Further, since the rise of the output voltage Vo is limited by the constant voltage control of the constant voltage error amplification circuit 20, the output current Io decreases. When the output current Io decreases (becomes smaller than the set value), the constant current error amplifier circuit 30 becomes (Vi1 <Vr2) and the voltage Vy rises (Vx <Vy). That is, the mode is automatically switched from the constant current control mode to the constant voltage control mode.

The operation mode display circuit 50 shown in FIG. 1 comprises an operational amplifier 51, a light emitting diode 52, resistors R7, R
8, R9. The operational amplifier 51 operates as an analog comparator. A voltage Vx extracted from between the output of the operational amplifier 21 and the diode D1 is applied to one input terminal of the operation mode display circuit 50. The voltage Vy extracted from between the output of the operational amplifier 31 and the diode D2 is applied to the other input terminal of the operation mode display circuit 50.

That is, the operational amplifier 51 compares the voltage Vx appearing at the output of the constant voltage error amplifier 20 with the voltage Vy appearing at the output of the constant current error amplifier 30 in a binary manner. Light emitting diode 52 connected to the output of operational amplifier 51
Turns on or off according to the comparison result of the operational amplifier 51. That is, when operating in the constant current control mode, since (Vx> Vy), the output of the operational amplifier 51 becomes low and the light emitting diode 52 is turned on. When operating in the constant voltage control mode, since (Vx <Vy), the output of the operational amplifier 51 becomes high level and the light emitting diode 52 is turned off. Therefore, the light emitting diode 52 is turned on only in the constant current control mode, and indicates the operation mode.

Although the operation mode is displayed by using the light emitting diode 52 in the example of FIG. 1, other notification means may be used. For example, the operation mode may be notified by sound output, or a special notification signal may be output to the outside.

[0031]

As described above, according to the present invention, a power supply device having a function of informing of a constant current / constant voltage operation mode can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a power supply device according to an embodiment.

FIG. 2 is a time chart illustrating an operation example of the power supply device according to the embodiment;

FIG. 3 is a graph showing a relationship between Vref and Vo of the power supply body.

[Description of Signs] 10 Power supply body 11 Reference voltage input terminal 12, 13 Output terminal 20 Constant voltage error amplifier circuit 21, 31 Operational amplifier 22, 32 Constant voltage source 30 Constant current error amplifier circuit 40 Reference level generation circuit 41 Constant voltage source Reference Signs List 50 operation mode display circuit 51 operational amplifier 52 light emitting diode 60 load R1 to R9 resistor D1, D2 diode

Claims (2)

[Claims] In a power supply device selectively operable in a constant voltage control mode and a constant current control mode, an error between a first detection level proportional to an output voltage supplied to a load and a first reference level is reduced. A first amplifier circuit for outputting a signal corresponding to the output signal; a second amplifier circuit for outputting a signal corresponding to an error between a second detection level proportional to an output current supplied to the load and a second reference level; A control level generation circuit that generates a control level based on a signal output by the first amplification circuit and a signal output by the second amplification circuit; and a control level that is proportional to the control level output by the control level generation circuit. A power supply circuit for generating a voltage as the output voltage; a comparison circuit having one input terminal connected to the output of the first amplifier circuit and the other input terminal connected to the output of the second amplifier circuit; The comparison circuit And a notification means connected to the output of the power supply. 2. The power supply device according to claim 1, wherein the control level generating circuit includes a resistor circuit for dividing a third reference level, and an output between the resistor circuit and an output of the first amplifier circuit. A first backflow prevention element connected to
A second backflow prevention element connected between the output of the resistor circuit and the output of the second amplifier circuit, wherein one input terminal of the comparison circuit is connected to the output of the first amplifier circuit and A power supply connected between the first backflow prevention element and the other input terminal of the comparison circuit between the output of the second amplifier circuit and the second backflow prevention element; apparatus.