JPH1127871A - Charging equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the voltage drop in a semiconductor device for voltage drop more than previously, in charging equipment which charges a secondary battery, receiving the supply of an AC magnetic force line. SOLUTION: A charger on the secondary side possesses a secondary coil 3 that an AC magnetic force line should pierce, a resonance control circuit 11 which is capable of adjustment of a Q-value, constituting a resonance system together with the secondary coil 3, a rectifying circuit 5 which rectifies an AC obtained from the secondary coil 3, a transistor 8 for voltage drop which is interposed between the output end of the rectifying circuit 5 and a secondary battery 10, the first charge control circuit 4 which controls the Q-value of the resonance control circuit 11, according to the deviation between the output voltage of the rectifying circuit 5 and the specified voltage, the second charge control circuit 4 which controls the operation of the transistor 8, according to the charge current and the charge voltage supplied to the secondary batter 10, and also controls the Q-value of the resonance control circuit 11. Then, the output voltage of the rectifying circuit 5 is controlled by adjusting the Q value of the resonance control circuit 11, when the battery voltage is low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a secondary battery provided in a portable telephone or the like.

[0002]

2. Description of the Related Art As this type of charging apparatus, FIG.
2. Description of the Related Art A non-contact charging device as shown in FIG. The charging device includes a primary charger A and a secondary charger B. The primary charger A is, for example, a commercial AC power source (AC10).
0V) and an AC current generating circuit (21) for generating an AC current, and a primary coil through which the AC current flows from the circuit.
(22). On the other hand, the secondary-side charger B includes a secondary coil (23) through which the magnetic field lines generated from the primary coil (22) pass, and a rectifier circuit (rectifying an alternating current obtained from the secondary coil (23)). 28), a transistor (24) for reducing the output voltage of the rectifier circuit (28) and supplying the same to the secondary battery (27), and a constant current / constant voltage control circuit (25) for controlling the operation of the transistor (24). ) And a resistor (26) for detecting a charging current.

[0003] In the above charging device, the secondary charger B
Is arranged close to the primary coil (22) of the primary charger A, so that the alternating magnetic field lines generated from the primary coil (22) pass through the secondary coil (23). Then, energy is transmitted to the secondary charger B, and the secondary battery (27) is charged. Here, the constant current / constant voltage control circuit (25) includes:
Output voltage of rectifier circuit (28) is constant current / constant voltage control circuit (25)
Is supplied as a power supply voltage of the secondary battery (27), and information of a charging current and a charging voltage for the secondary battery (27) is supplied. When the charging voltage is lower than a predetermined threshold voltage, the charging current approaches a predetermined target value. After the charging current reaches a predetermined voltage, the charging voltage is reduced to a predetermined target value V.
The constant voltage control is executed to maintain the voltage at b.

FIGS. 3 (a) and 3 (b) show current and voltage changes by the constant current control and the constant voltage control.
As shown in (a), the charging current Ia is set to the target value by the constant current control.
(For example, 100 mA), and the charging voltage Vo is maintained at a target value (for example, 4.1 V) as shown in FIG. In this process, the output voltage (rectified output) V 'of the rectifier circuit (28) shown in FIG. 2 gradually increases as shown by a two-dot chain line in FIG. 3 (b) to control the voltage drop of the transistor (24). As a result, the above-described constant current control and constant voltage control are realized, and a change in the charging voltage Vo indicated by a solid line is obtained.

[0005]

However, in the conventional charging device shown in FIG. 2, as shown in FIG.
In particular, the difference between the rectified output Vs' at the start of charging and the charging voltage Va is large, and the transistor (24) which is a semiconductor device for voltage drop is used.
, A large heat loss is caused by the voltage drop. Therefore, especially when a secondary charger is built in a small device such as a mobile phone, it is difficult to reduce the size of the transistor (24) package due to heat generation, which hinders miniaturization of the device. I was

An object of the present invention is to provide a charging device capable of reducing a voltage drop in a voltage drop semiconductor device as compared with a conventional device.

[0007]

The charging device according to the present invention comprises:
As a secondary charger, a secondary coil (3) through which AC magnetic field lines supplied from the primary charger should pass, and a secondary coil (3)
And a resonance control circuit (11) capable of adjusting the Q value, a rectifier circuit (5) for rectifying an alternating current obtained from the secondary coil (3), and a rectifier circuit (5). The Q value of the resonance control circuit (11) is changed according to the voltage drop semiconductor element interposed between the output terminal and the secondary battery (10) and the deviation between the output voltage of the rectifier circuit (5) and a predetermined reference voltage. First charging control circuit for controlling (4)
And a second charge control circuit for controlling the operation of the voltage drop semiconductor element and controlling the Q value of the resonance control circuit (11) according to the charge current and the charge voltage supplied to the secondary battery (10). (7). When the charge voltage is lower than the reference voltage, the first charge control circuit (4)
(5) controlling the Q value of the resonance control circuit (11) so as to maintain the output voltage at the reference voltage;
(7) controls the voltage drop of the voltage-dropping semiconductor element to bring the charging current or the charging voltage closer to the target value. On the other hand, when the charging voltage is higher than the reference voltage, the second charging control circuit (7) The Q value of the resonance control circuit (11) is controlled so that the charging current or the charging voltage approaches the target value, and the voltage dropping semiconductor element is controlled so that the voltage drop by the voltage dropping semiconductor element approaches zero.

Here, when the charging voltage is lower than a predetermined threshold voltage, the second charging control circuit (7) performs constant current control so that the charging current approaches a predetermined target value. After reaching the voltage, the charging voltage is reduced to a predetermined target value V
The constant voltage control for maintaining the voltage at b is performed.

[0009] On the other hand, the primary charger includes an AC current generating circuit.
(1) and a primary coil (2) that receives an alternating current supplied from the circuit and generates an alternating magnetic field line, and the secondary coil (3) is arranged close to the primary coil (2). By 1
The line of alternating magnetic force generated from the secondary coil (2) is the secondary coil (3)
Penetrate through.

When charging the discharged secondary battery (10) by the charging device of the present invention, first, constant current control is executed by the second charging control circuit (7). Here, the first
The charge control circuit (4) controls the Q value of the resonance control circuit (11) to maintain the output voltage of the rectifier circuit (5) at a reference voltage (for example, 3V). In this state, the second charge control circuit (7) moves the semiconductor device for voltage drop to the active area, and adjusts the voltage drop to create a charge voltage, and the secondary battery (10)
Is applied. As a result, the battery voltage gradually increases and reaches the reference voltage.

At this time, the second charge control circuit (7) sets the semiconductor device for voltage drop to an ON state (short-circuit state), and sets the voltage drop to zero. On the other hand, the second charge control circuit (7)
Adjusts the Q value of the resonance control circuit (11), and adjusts the rectifier circuit (5).
Is gradually increased from the reference voltage to maintain the charging current at the target value. This further increases the battery voltage and reaches a predetermined threshold voltage.

At this point, the second charge control circuit (7) switches from the constant current control to the constant voltage control, and adjusts the Q value of the resonance control circuit (11) to maintain the charge voltage at the target value Vb. And the output voltage of the rectifier circuit (5). Here, since the voltage drop of the voltage drop semiconductor element is zero, the output voltage of the rectifier circuit (5) is directly applied to the secondary battery (10) as a charging voltage. As a result, the secondary battery (10) is further charged, and reaches a fully charged state.

In a specific configuration, the second charge control circuit
In (7), the output voltage of the rectifier circuit is supplied as a power supply voltage. In the specific configuration, immediately after the start of charging as described above, even during a period in which the charging voltage is not sufficiently increased,
Regardless of the charging voltage, the output voltage (rectified output) of the rectifier circuit (5) is maintained at a predetermined reference voltage (for example, 3 V).
A sufficient power supply voltage can always be ensured.

[0014]

According to the charging device of the present invention, the rectified output at the start of charging is smaller than in the prior art, so that the difference between the rectified output and the charging voltage, that is, the voltage drop due to the voltage drop semiconductor element is reduced. Heat loss is reduced. Therefore, when the charging device is incorporated in a device such as a mobile phone, the problem of heat generation does not occur, and the device can be downsized.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A non-contact charging device to be equipped in a portable telephone according to the present invention will be described below in detail with reference to the drawings. The charging device according to the present invention,
As shown in FIG. 1, it comprises a primary charger A and a secondary charger B. As the secondary battery (10), for example, a lithium ion battery is used.

The primary charger A is composed of an AC current generating circuit (1) connected to AC 100V to generate an AC current, and a primary coil (2) to which the AC current is supplied from the circuit. On the other hand, the secondary side charger B includes a secondary coil (3) through which the magnetic field lines generated from the primary coil (2) pass, and a resonance control circuit (11) which forms a resonance system together with the secondary coil (3). And 2
Rectifier circuit that rectifies the alternating current obtained from the secondary coil (3)
(5) and the output voltage of the rectifier circuit (5) is reduced to make the secondary battery
A voltage drop transistor (8) to be supplied to (10), a resistor (9) for detecting a charging current, and a first charging control circuit (4) for controlling a Q value of a resonance control circuit (11). , Transistor
A second charge control circuit (7) for controlling the on / off and drop voltage of (8) and controlling the Q value of the resonance control circuit (11).

The resonance control circuit (11) is configured by connecting an FET (13) and a capacitor (12) in series, and by controlling the gate voltage of the FET (13), the resistance of the FET (13) is controlled. Can be changed to adjust the Q value. For example, it is possible to increase the Q value by decreasing the resistance component of the FET (13), thereby increasing the charging voltage or charging current.

The first charge control circuit (4) has an operational amplifier (14), a non-inverting input terminal of the operational amplifier (14) receives a reference voltage Vs (3V), and an inverting input terminal has a rectifier circuit. The output voltage V1 of (5) is input, and a voltage signal corresponding to the difference between the two inputs is applied to the base of the FET (13) of the resonance control circuit (11).

The second charge control circuit (7) comprises a constant current / constant voltage control circuit (16) and a transistor (17). The constant current / constant voltage control circuit (16) operates by receiving supply of a power supply voltage from the output terminal of the rectifier circuit (5), and outputs voltage information obtained from the output terminal of the transistor (8) and a charge current detecting resistor. vessel
The base voltage of the transistor (17) is controlled based on current information obtained from the input terminal of (9). or,
The output voltage of the constant current / constant voltage control circuit (16) is a diode (1
5) is applied to the base of the FET (13) of the resonance control circuit (11).

In the above charging device, the secondary charger B
The secondary coil (3) is placed close to the primary coil (2) of the primary charger A, so that the lines of alternating magnetic force generated from the primary coil (2) pass through the secondary coil (3). Then, energy is transmitted to the secondary charger B, and the secondary battery (10) is charged by constant current control and constant voltage control described later.

FIGS. 3 (a) and 3 (b) show changes in current and voltage by constant current control and constant voltage control, respectively.
Until time t1, the charging current I is controlled by the constant current control.
a is maintained at a predetermined value (100 mA), and the charging voltage Vo is changed to a predetermined value (4.
1V).

In this process, while the charging voltage Vo is lower than the reference voltage Vs (3 V), the first charging control circuit 4 shown in FIG. 1 uses the output voltage of the rectifier circuit 5 and the reference voltage Vs. A voltage signal corresponding to the deviation is created, and the signal is used as a resonance control circuit.
(11) applied to the base of the FET (13), the resonance control circuit (11)
, The output voltage of the rectifier circuit (5) is maintained at the reference voltage Vs as shown by the dashed line in FIG. 3 (b). On the other hand, the constant current / constant voltage control circuit (16) creates a control signal necessary to maintain the charging current at the target value Ia based on the current information at that time, and outputs the control signal to the transistor (17). Apply to base. As a result, a collector current flows through the transistor (17), and the base voltage of the transistor (8) changes. As a result, the potential difference between the collector and the emitter of the transistor (8), that is, the voltage drop is controlled, and the charging voltage Vo shown by the solid line in FIG.
Applied to the secondary battery (10). As a result, the battery voltage (charging voltage Vo) gradually increases and reaches the reference voltage Vs.

When the charging voltage Vo exceeds the reference voltage Vs, the constant current / constant voltage control circuit (16) further increases the control signal to increase the base voltage of the transistor (17), and the transistor (8) Is set to the ON state (short-circuit state). The control signal output from the constant current / constant voltage control circuit (16) is supplied to the resonance control circuit (11) through a diode (15).
It is applied to ET (13) as a base voltage. At this time, the control signal input via the diode (15)
The potential becomes higher than the voltage signal obtained from (14), the resistance component of the FET (13) is adjusted according to the control signal, and the Q value of the resonance control circuit (11) is controlled. As a result, the output voltage of the rectifier circuit (5) becomes equal to the reference voltage V as shown in FIG.
s, the output voltage is higher than the on-state transistor
In (8), the charging current is applied to the secondary battery (10) without a voltage drop, and the charging current is maintained at the target value Ia. As a result, the charging voltage Vo further increases and reaches a predetermined threshold voltage (for example, 4.1 V).

At this point, the constant current / constant voltage control circuit (16)
Is switched from constant current control to constant voltage control, and the charging voltage V
A control signal for maintaining o at the target value Vb is created.
The signal is applied to the base of the transistor (17), the transistor (8) is kept on, and the signal is applied to the FET (13) of the resonance control circuit (11) via the diode (15). And the Q value of the resonance control circuit (11) is controlled. Thus, the output voltage of the rectifier circuit (5) is maintained at the target value Vb as shown in FIG. The output voltage is applied to the secondary battery (10) without causing a voltage drop at the transistor (8) in the ON state. As a result, the secondary battery (10) is further charged and reaches a fully charged state. Then, as shown in FIG. 3A, when the charging current falls below a predetermined threshold, the charging operation is stopped.

In the above charging device, when the battery voltage is lower than the reference voltage Vs (3 V), as shown in FIG. 3B, the output voltage (rectified output) V1 of the rectifier circuit (5) is equal to the reference value. V
Since the voltage is maintained at s (3V) and becomes lower than the conventional rectified output, the voltage drop in the transistor (8) is reduced, and the heat loss in the transistor (8) is reduced. If the battery voltage is higher than the reference voltage Vs (3 V), the transistor
Since the transistor (8) is turned on, the heat loss due to the transistor (8) becomes almost zero. Therefore, regardless of the battery voltage,
The heat loss in the transistor (8) is smaller than before,
As a result, the transistor (8) in a small package can be adopted, and the size of the mobile phone can be reduced.

When the second charge control circuit (7) is integrated into an IC, the minimum value of the power supply voltage is guaranteed by using the output voltage of the rectifier circuit (5) as the power supply voltage of the IC as shown in FIG. Therefore, the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a charging device according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a conventional charging device.

FIG. 3 is a graph showing changes in current and voltage in the charging device.

[Explanation of symbols]

 (1) AC current generating circuit (2) Primary coil (3) Secondary coil (4) First charge control circuit (5) Rectifier circuit (7) Second charge control circuit (8) Voltage drop transistor (10) Secondary battery (11) Resonance control circuit (16) Constant current / constant voltage control circuit

Claims (4)

[Claims] 1. A charging device for charging a secondary battery by receiving a supply of alternating magnetic field lines, comprising: a secondary coil (3) through which the alternating magnetic field lines are to penetrate; and a resonance system together with the secondary coil (3). A resonance control circuit (11) capable of adjusting the Q value; a rectifier circuit (5) for rectifying an alternating current obtained from the secondary coil (3); an output terminal of the rectifier circuit (5) and a secondary battery (10 And a first charge control circuit (Q) for controlling the Q value of the resonance control circuit (11) in accordance with a deviation between the output voltage of the rectifier circuit (5) and a predetermined reference voltage. 4) and the second charging for controlling the operation of the voltage drop semiconductor element and controlling the Q value of the resonance control circuit (11) according to the charging current and the charging voltage supplied to the secondary battery (10). Control circuit (7)
When the charging voltage is lower than the reference voltage,
The first charge control circuit (4) controls the Q value of the resonance control circuit (11) so as to maintain the output voltage of the rectifier circuit (5) at the reference voltage, and the second charge control circuit (7) controls the charge current. Alternatively, while controlling the voltage drop of the voltage dropping semiconductor element to bring the charging voltage closer to the target value, when the charging voltage is higher than the reference voltage, the second charging control circuit (7) changes the charging current or the charging voltage. Q of the resonance control circuit (11) to approach the target value
A charging apparatus characterized by controlling a value and controlling the voltage drop semiconductor element so that a voltage drop by the voltage drop semiconductor element approaches zero. A second charging control circuit that performs constant current control to bring the charging current closer to a predetermined target value when the charging voltage is lower than a predetermined threshold voltage; 2. The charging device according to claim 1, wherein after reaching the predetermined value, constant voltage control is performed to maintain the charging voltage at a predetermined target value. The output voltage of the rectifier circuit is controlled by a charge control circuit.
The charging device according to claim 1, wherein the charging device is supplied as a power supply voltage to the charging device. 4. An AC current generating circuit (1), and a primary coil (2) receiving an AC current from the circuit to generate an AC magnetic field line, the secondary coil (3) being a primary coil. Coil (2)
The charging device according to any one of claims 1 to 3, wherein an AC magnetic field line generated from the primary coil (2) is supplied to the secondary coil (3) by being arranged close to the secondary coil.