JP2005033948A - Ac adaptor and charging method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the heat generation of a charge control element in a body. <P>SOLUTION: A ΔV detection circuit (45) arranged at a secondary-side circuit detects the bouncing of an adapter voltage (V<SB>ADP</SB>) that is generated when a charging state shifts to a constant voltage charging region from a constant current charging region, and outputs a detection signal. A variable resistor (R6') is reduced in its resistance value in response to the detected signal. Thereby a reference voltage fed to a constant voltage control circuit (42) is regulated so that the adapter voltage (V<SB>ADP</SB>) is lowered by an amount of the bounced voltage (ΔV'-ΔV). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an AC adapter.

  This type of AC adapter is used to charge a secondary battery built in or attached to a main body such as a mobile phone. The secondary battery may be a lithium ion battery.

FIG. 1 shows a state where the AC adapter 10 is connected to a main body 20 such as a mobile phone. The AC adapter 10 is connected to the main body 20 via a cable having a resistance value. The AC adapter 10 has an anode (cathode) 11 and a cathode (anode) 12 and generates an adapter voltage V _ADP between its terminals.

On the other hand, the main body 20 includes a backflow prevention diode D, a charge control element Q such as a transistor as a charge control element, a secondary battery 21, and a charge control circuit 22. The charging control circuit 22 controls charging of the secondary battery 21 by controlling the charging control element Q. Although not shown, the charging control circuit 22 has a regulator therein. The secondary battery 21 generates a battery voltage (charging voltage) V _BATT .

  As shown in FIG. 2, the VI characteristic of the AC adapter has a constant current / constant voltage characteristic.

When charging control is performed on the secondary battery 21 of the main body 20, as is clear from FIG. 1, as for the constant voltage, between the AC adapter 10 and the secondary battery 21, cable loss, loss due to contact resistance, backflow prevention diode Since there is Vf of D and the like, the accuracy of the charging voltage V _BATT is not obtained. Therefore, as described above, the charging control circuit 22 has a regulator.

Further, the adapter voltage V _ADP of the AC adapter 10 is set to a higher voltage so that a voltage that can be charged can be supplied even if the factor causing the voltage loss varies to the maximum.

  This type of AC adapter includes a primary side circuit that turns on and off a DC voltage applied to the primary winding of the transformer by a switching element, and a secondary output voltage that rectifies and smoothes the current induced in the secondary winding of the transformer. The secondary side circuit which outputs.

  In such an AC adapter, the primary circuit and the secondary circuit need to be electrically insulated and separated in order to prevent accidents such as electric shock. In general, a photocoupler or an insulating transformer is used as means for electrically insulating and separating. In the AC adapter, it is necessary to perform constant current control and constant voltage control. For this reason, it is necessary to return the change in the current flowing in the secondary side circuit as a constant current control signal and the change in the secondary side output voltage as a constant voltage control signal to the primary side circuit. In this case, the constant current control signal and the constant voltage control signal are returned (feedback) from the secondary side circuit to the primary side circuit via the photocoupler.

  Hereinafter, a conventional AC adapter will be described with reference to FIG. The illustrated switching AC adapter includes a rectifying / smoothing circuit 31, a primary winding Np of a transformer T, a switching control circuit 32, and a switching (SW) element 33 as a primary side circuit.

  The input AC voltage supplied from the AC power supply is rectified / smoothed by the rectifying / smoothing circuit 31 and converted to an input DC voltage. This input DC voltage is applied to the primary winding Np of the transformer T and turned on and off by the switching element 33. On / off of the switching element 33 is controlled by an on / off control signal supplied from the switching control circuit 32.

The illustrated AC adapter circuit includes a secondary winding Ns of the transformer T and a rectifying / smoothing circuit 41 as a secondary side circuit. The AC voltage induced in the secondary winding Ns of the transformer T is rectified / smoothed by the rectifying / smoothing circuit 41 and outputs the adapter voltage V _ADP .

The secondary circuit is provided with a constant voltage control circuit 42, a constant current control circuit 43, and a reference voltage generation circuit 44. The constant voltage control circuit 42 detects a change in the adapter voltage V _ADP and outputs a constant voltage control signal. This constant voltage control signal is fed back to the switching control circuit 32 provided in the primary side circuit as a feedback signal via the OR gate G and the photocoupler PC. The constant current control circuit 43 detects a current flowing through the secondary side circuit and outputs a constant current control signal. This constant current control signal is also fed back to the switching control circuit 32 provided in the primary circuit as a feedback signal via the OR gate G and the photocoupler PC. The reference voltage generation circuit 44 is for supplying a reference voltage to the constant voltage control circuit 42 and the constant current control circuit 43.

One end of resistors R 1 and R 2 is connected to the anode 12, and the other end of the resistor R 1 and the other end of the resistor R 2 are connected to a constant current control circuit 43. Further, resistors R3 and R4 for _dividing the adapter voltage V _ADP are connected in series between the cathode 11 and the other end of the resistor R2. A divided voltage of the adapter voltage V _ADP is supplied to the constant voltage control circuit 42 from a connection point between the resistors R3 and R4. The reference voltage generation circuit 44 is connected to the cathode 11, and resistors R5 and R6 for dividing the reference voltage are connected in series between the reference voltage generation circuit 44 and the other end of the resistor R2. Yes. A divided voltage of the reference voltage is supplied to the constant current control circuit 43 from the connection point between the resistors R5 and R6.

Incidentally, the transformer T is wound auxiliary winding N _B, one end of the auxiliary winding N _B, the switching element 33 is connected to the rectifying / smoothing circuit 31 and the switching control circuit 32, the auxiliary winding N _B Are connected to the switching control circuit 32 and the phototransistor collector of the photocoupler PC.

  In any case, the conventional AC adapter 10 performs constant voltage control using a fixed reference voltage.

FIG. 4 shows the charging characteristics of the conventional AC adapter 10. The horizontal axis represents time t [h], and the vertical axis represents voltage V and current I. While the battery voltage V _BATT is low, the battery is charged with a constant charging current Ic. When the battery voltage V _BATT reaches a predetermined voltage, constant voltage charging is performed. As shown in FIG. 4, the adapter voltage V _ADP is always higher than the battery voltage V _BATT .

However, in the configuration of the conventional AC adapter 10, a high voltage difference ΔV ′ is generated between the adapter voltage V _ADP and the battery voltage V _BATT in the constant voltage charging region, and the charge control transistor (charge control element) inside the main body 20 is generated. ) There is a problem of causing Q to generate heat. The jumping voltage (ΔV′−ΔV) is about 0.5 V, although it varies depending on the model / product.

  Next, with reference to FIG. 5, the reason why the voltage jumps when switching from the constant current charging region to the constant voltage charging region will be described. 5A, 5 </ b> B, and 5 </ b> C, the VI characteristic of the AC adapter 10 is indicated by a thick solid line, and the VI characteristic of the charge control circuit 22 is indicated by a thin solid line.

As shown in FIG. 5A, when the battery voltage V _BATT is low, the battery is in a constant current charge state, and the battery voltage V _BATT and the adapter voltage V _ADP gradually increase with a minimum potential difference ΔV. .

As shown in FIG. 5B, charging proceeds and the battery voltage V _BATT is changed to the corner of the VI characteristic of the charge control circuit 22 (the charge control mode is switched from the constant current charge control mode to the constant voltage charge control mode). The battery voltage V _BATT and the adapter voltage V _ADP gradually increase with a minimum necessary potential difference ΔV until the point of change).

_Assume that the battery voltage V _BATT enters the constant voltage portion of the VI characteristic of the charge control circuit 22 as shown in FIG. In this case, since the charging current Ic of the AC adapter 10 and the charging current flowing through the secondary battery 21 are the same, the adapter voltage V _ADP naturally enters the constant voltage charging region of the AC adapter 10 with the VI characteristic. For this reason, the adapter voltage V _ADP jumps from the point of FIG. 5B to the point of FIG. 5C.

This is the reason why a high voltage difference ΔV ′ occurs between the adapter voltage V _ADP and the battery voltage V _BATT in the constant voltage charging region.

  In particular, at point A shown in FIG. 2 (the point at which the constant current charging region is switched to the constant voltage charging region), since the charging current Ic is maximum, the heat generation of the charge control transistor (charge control element) Q is maximum. It is a point.

  Therefore, the subject of this invention is providing the AC adapter which can suppress the heat_generation | fever of the charge control element inside a main body.

According to the present invention, the AC adapter (10A) used for charging the secondary battery (21) built in or attached to the main body (20), the primary winding (Np) of the transformer (T). A primary side circuit that turns on and off the input DC voltage applied by the switching element (33), and an AC voltage induced in the secondary winding (Ns) of the transformer is rectified and smoothed to output an adapter voltage (V _ADP ). A secondary circuit, a constant voltage control circuit (42) for detecting a change in adapter voltage and outputting a constant voltage control signal, and a constant current for detecting a charging current flowing through the secondary circuit and outputting a constant current control signal A control circuit (43), a photocoupler (PC) that feeds back a constant voltage control signal and a constant current control signal to a primary side circuit as feedback signals, and switching that controls on / off of the switching element in response to the feedback signals In the AC adapter provided with the control circuit (32), it is provided in the secondary side circuit to detect and detect a jump in the adapter voltage that occurs when the charging state shifts from the constant current charging region to the constant voltage charging region. An AC adapter comprising: a detection means (45) for outputting a signal; and a voltage adjustment means (44, R5, R6 ′) for reducing the adapter voltage by an amount corresponding to the jumping voltage in response to the detection signal. It is done.

  The AC adapter further includes a reference voltage generation circuit (44) for supplying a reference voltage to the constant voltage control circuit, and the reference voltage generation circuit can vary the reference voltage by a variable resistor (R6 ′). The voltage adjusting means may be configured to reduce the adapter voltage by adjusting the resistance value of the variable resistor. The main body may be a mobile phone, for example.

In addition, according to the present invention, there is provided a method of charging a main battery (20) or a secondary battery (21) incorporated in a mounting with an adapter voltage (V _ADP ), and a) a battery voltage (V _{BATT of the} secondary battery). B) a step of performing constant current charging while b) is low; b) a step of switching the charging state from constant current charging to constant voltage charging when the battery voltage of the secondary battery reaches a predetermined voltage; Is detected (45), and a charging method including the step of lowering the adapter voltage by the amount of the jumping voltage is obtained.

  In addition, the code | symbol in the said parenthesis is attached | subjected in order to make an understanding of this invention easy, and it is only an example, and of course is not limited to these.

  In the present invention, when the adapter voltage jumping that occurs when the state of charge is changed from constant current charging to constant voltage charging is detected, the adapter voltage is lowered by this jumping voltage. The constant voltage charging can be performed while maintaining the minimum necessary voltage which is the potential difference between the battery voltage and the battery voltage. As a result, there is an effect that heat generation of the charge control element inside the main body can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An AC adapter 10A according to an embodiment of the present invention will be described with reference to FIG. The illustrated AC adapter 10A uses a variable resistor R6 ′ instead of the resistor R6, and has the same configuration as the conventional AC adapter 10 shown in FIG. 3 except that a ΔV detection circuit 45 is added. Have Components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

The ΔV detection circuit 45 is connected to the cathode 11. The ΔV detection circuit 45 detects a jump in the adapter voltage V _ADP that occurs when the charging state shifts from the constant current charging region to the constant voltage charging region, and outputs a detection signal. In response to this detection signal, the resistance value of the variable resistor R6 ′ is adjusted to be small.

  Hereinafter, the operation of the AC adapter 10A will be described with reference to FIG. 7 in addition to FIG. FIG. 7 is a diagram showing the charging characteristics of the AC adapter 10A shown in FIG. The horizontal axis represents time t [h], and the vertical axis represents voltage V and current I.

In the constant current charging region, the constant current control circuit 43 constantly monitors the charging current Ic. The constant current control circuit 43 outputs a constant current control signal so that the charging current Ic is constant. This constant current control signal is fed back to the switching control circuit 32 of the primary side circuit as a feedback signal through the OR gate G and the photocoupler PC. That is, constant current charging is performed while the battery voltage V _BATT of the secondary battery 21 is low.

At this time, the adapter voltage V _ADP of the AC adapter 10A has a voltage drop (V _BATT) obtained by adding the voltage drop ΔV to the battery voltage V _BATT since the voltage drop of the charging control circuit 22 in the main body 20 is minimized. + ΔV).

When the battery voltage V _BATT of the secondary battery 21 gradually increases and the battery voltage V _BATT reaches a predetermined voltage, the charging state is switched from constant current charging to constant voltage charging. At the time when this charging state is about to shift from constant current charging to constant voltage charging, as described above, a difference ΔV ′ between the constant voltage value of charging in the main body 20 and the constant voltage value of the AC adapter 10A occurs. The adapter voltage V _ADP jumps up.

When the ΔV detection circuit 45 detects the jump of the adapter voltage V _ADP , the ΔV detection circuit 45 supplies a detection signal to the variable resistor R6 ′. In response to this detection signal, the variable resistor R6 ′ decreases its resistance value. That is, the reference voltage supplied to the constant voltage control circuit 42 is adjusted so that the adapter voltage V _ADP is lowered by the jump voltage (ΔV′−ΔV).

  Thereafter, the reference voltage value is fixed, and the state changes to a fully charged state. Thereby, the minimum potential difference ΔV can be maintained.

Therefore, in the conventional AC adapter 10, the adapter voltage V _ADP has a specified voltage value in the constant voltage charging region (see FIG. 4). However, in the AC adapter 10A according to the present embodiment, from the constant current charging region. Charging is performed while maintaining the minimum potential difference ΔV except for a predetermined short period after switching to the constant voltage charging region. The predetermined short period is, for example, 10 milliseconds. In other words, AC adapter 10A according to the present embodiment maintains the minimum voltage ΔV that is the potential difference (V _ADP −V _BATT ) between adapter voltage V _ADP and battery voltage V _BATT during constant current charging. , Perform constant voltage charging. As a result, the heat generation of the charge control element Q inside the main body 20 can be suppressed.

  As described above, the present invention has been described with reference to the embodiments, but the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, the case where the present invention is applied to an AC adapter for a mobile phone has been described as an example. However, the present invention can be applied to an AC adapter that supplies power to a charging circuit in addition to a mobile phone. It is.

In the embodiment of the present invention, the adapter voltage V _ADP is lowered by reducing the resistance value of the variable resistor R6 ′ connected to the reference voltage generation circuit 44, but is connected to the constant voltage control circuit 42. The reference voltage generating circuit 44 may be a voltage variable reference voltage generating circuit, and the adapter voltage V _ADP may be decreased by lowering the reference voltage of the voltage variable reference voltage generating circuit. In this case, the constant current control circuit 43 requires a reference voltage generation circuit that is supplied with a fixed reference voltage.

It is a block diagram which shows the state by which the AC adapter was connected to the main body which incorporates a secondary battery. It is a characteristic view which shows the VI characteristic of AC adapter. It is a block diagram which shows the structure of the conventional AC adapter. It is a figure which shows the charge characteristic of the conventional AC adapter shown in FIG. FIG. 4 is a diagram for explaining the reason why a voltage jump occurs when the conventional AC adapter shown in FIG. 3 is switched from a constant current charging region to a constant voltage charging region. It is a block diagram which shows the structure of the AC adapter which concerns on one embodiment of this invention. It is a figure which shows the charge characteristic of the AC adapter shown in FIG.

Explanation of symbols

10A AC adapter 20 Main body (mobile phone)
21 Secondary Battery 22 Charge Control Circuit 31 Rectification / Smoothing Circuit 32 Switching Control Circuit 33 SW Element 41 Rectification / Smoothing Circuit 42 Constant Voltage Control Circuit 43 Constant Current Control Circuit 44 Reference Voltage Generation Circuit 45 ΔV Detection Circuit T Transformer Np Primary Winding Ns Secondary winding N _B Auxiliary winding R6 'Variable resistor

Claims (4)

An AC adapter used for charging a secondary battery built in or attached to a main body, a primary side circuit for turning on and off an input DC voltage applied to a primary winding of a transformer by a switching element, and a second side of the transformer A secondary circuit that rectifies and smoothes an AC voltage induced in the secondary winding and outputs an adapter voltage; a constant voltage control circuit that detects a change in the adapter voltage and outputs a constant voltage control signal; and the secondary A constant current control circuit that detects a charging current flowing through the side circuit and outputs a constant current control signal; a photocoupler that feeds back the constant voltage control signal and the constant current control signal to the primary side circuit as a feedback signal; and In an AC adapter comprising a switching control circuit for controlling on / off of the switching element in response to a feedback signal,
Detection means provided in the secondary side circuit for detecting a jump of the adapter voltage that occurs when a charging state shifts from a constant current charging region to a constant voltage charging region, and outputting a detection signal;
An AC adapter comprising: voltage adjusting means for reducing the adapter voltage by an amount corresponding to the rising voltage in response to the detection signal. The voltage regulator further includes a reference voltage generation circuit for supplying a reference voltage to the constant voltage control circuit, and the reference voltage generation circuit is configured so that the reference voltage can be varied by a variable resistor. The AC adapter according to claim 1, wherein the adapter voltage is lowered by adjusting a resistance value of the variable resistor. The AC adapter according to claim 1, wherein the main body is a mobile phone. A method of charging a secondary battery built in or attached to a main body with an adapter voltage,
a) performing constant current charging while the battery voltage of the secondary battery is low;
b) switching the charging state from the constant current charging to the constant voltage charging when the battery voltage of the secondary battery reaches a predetermined voltage;
and c) a step of decreasing the adapter voltage by the amount of the jumping voltage when a jumping of the adapter voltage that occurs when the charging state is shifted from the constant current charging to the constant voltage charging is detected.

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