JP3633353B2 - Charger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charger for charging a secondary battery.
[0002]
[Prior art]
A circuit diagram of a conventional charger is shown in FIG. In this circuit, an inverter circuit 1 that generates an AC voltage of a predetermined voltage, a transformer T1 in which a primary winding n1 is connected between output terminals of the inverter circuit 1, and a voltage generated in a secondary winding n2 of the transformer T1. A charging power supply circuit 2 that generates a DC voltage of a predetermined voltage by rectification and smoothing, a charging circuit 3 that charges the secondary battery B with the DC voltage generated by the charging power supply circuit 2, and a secondary winding of the transformer T1 The control power circuit 4 that rectifies and smoothes the voltage generated at n3 to generate a DC voltage of a constant voltage (for example, about 5 V), and is supplied with power from the control power circuit 4 to control the charging operation of the charging circuit 3 And a control circuit 5.
[0003]
Here, the charging power supply circuit 2 is connected between a diode D1 having an anode connected to one end of the secondary winding n2 of the transformer T1, and a cathode of the diode D1 and the other end of the secondary winding n2. The capacitor C1 is configured to rectify the voltage generated in the secondary winding n2 by the diode D1, and then smoothes the voltage by the capacitor C1 to generate a predetermined DC voltage.
[0004]
The charging circuit 3 includes an NPN transistor Q1 having a collector connected to a connection point between the diode D1 and the capacitor C1, and a charging terminal to which an anode is connected to the emitter of the transistor Q1 and a positive electrode of the secondary battery B is connected. a charging terminal t2 to which a negative electrode of the secondary battery B is connected is connected to a negative electrode side terminal of the capacitor C1 through a current detection resistor R4. It is connected. The base of the transistor Q1 is connected to an output terminal of a CPU 6 to be described later via a resistor, and is turned on / off according to the high / low of the output signal S1 from the CPU 6.
[0005]
The control power supply circuit 4 includes a diode D3 having an anode connected to one end of the secondary winding n3 of the transformer T1, and a capacitor C2 connected between the cathode of the diode D3 and the other end of the secondary winding n3. And a three-terminal regulator IC1 having a capacitor C2 connected between the input terminals, the voltage generated in the secondary winding n3 is rectified by the diode D3, smoothed by the capacitor C2, and further fixed by the three-terminal regulator IC1. The power is supplied to the control circuit 5 after being stabilized at (about 5V).
[0006]
The control circuit 5 includes a CPU 6 that controls the charging operation of the charging circuit 3, and a constant current constant voltage control circuit that detects the battery voltage VB and the charging current Ib of the secondary battery B and performs constant current charging control and constant voltage charging control. And have. Here, a series circuit of voltage dividing resistors R1, R2 for battery voltage detection is connected between the charging terminals t1, t2, and the connection point of the voltage dividing resistors R1, R2 is connected to the A / D input terminal of the CPU 6. Has been. Further, a series circuit of resistors R5 and R6 is provided between the output terminal of the three-terminal regulator IC1 and one output terminal of the battery detection switch SW1 that conducts between the output terminals when the secondary battery B is attached to the charger. The other output terminal of the battery detection switch SW1 is connected to the ground terminal of the three-terminal regulator IC1, and the connection point of the resistors R5 and R6 is connected to the input terminal of the CPU 6. The anode of the light emitting diode LED1 is connected to the output terminal of the three-terminal regulator IC1, and the cathode of the light emitting diode LED1 is connected to the output terminal of the CPU 6.
[0007]
The collector terminals and emitter terminals of an NPN transistor Q2 are connected to the charging terminals t1 and t2 via a current limiting resistor R7, respectively, and the base of the transistor Q2 is a three-terminal regulator described later via a resistor R8. It is connected to the output terminal of IC1. Thus, when energized, the transistor Q2 is turned on, and a minute dummy current that allows the backflow prevention diode D2 to be conducted through the resistor R7 flows, so that there is a gap between the positive electrode and the negative electrode of the secondary battery B. Even in the open state, a dummy current flows through the resistor R7 and the transistor Q2, and the diode D2 becomes conductive. Note that the transistor Q2 is turned on only when energized in order to prevent the charged secondary battery B from being discharged with the circuit comprising the resistor R7 and the transistor Q2 as a load.
[0008]
Next, the operation of this circuit will be briefly described. When the secondary battery B is attached to the charger, the output terminals of the battery detection SW1 are electrically connected, and a series circuit of resistors R5 and R6 is connected between the output terminals of the three-terminal regulator IC1, and the resistors R5 and R6 are connected. The voltage Va at the connection point drops from 5V to a predetermined voltage. The CPU 6 monitors the voltage Va at the connection point of the resistors R5 and R6, and determines that the secondary battery B is attached to the charger when the voltage Va drops to a predetermined voltage. At this time, the battery voltage VB of the secondary battery B is divided by the voltage dividing resistors R1 and R2, and the divided voltage Vb is input to the A / D input terminal of the CPU 6. The CPU 6 detects the battery voltage VB of the secondary battery B from the divided voltage Vb, and in accordance with the voltage value of the battery voltage VB, the quick charge mode for rapidly charging the secondary battery B, the charge standby mode for waiting for charging, or The charging circuit 3 is operated in a charging end mode for forcibly ending the charging operation.
[0009]
Here, when the battery voltage VB is within a voltage range in which quick charging is performed (that is, when a normal secondary battery B is charged), the CPU 6 sets the quick charging mode based on the battery voltage VB detected from the divided voltage Vb. Judgment is made and a high-level output signal S1 is output to the base of the transistor Q1 to turn on the transistor Q1. When the transistor Q1 is turned on, a substantially constant charging current Ib flows through the transistor Q1 and the diode D2, and the secondary battery B is charged.
[0010]
On the other hand, the constant current / constant voltage detection circuit 7 detects the charging current Ib from the voltage across the resistor R4 and also detects the battery voltage VB. As shown in FIG. 3, the charging current Ib is reduced according to the battery voltage VB. The output of the inverter circuit 1 is controlled so as to perform constant current charging control to be constant and constant voltage charging control to make the battery voltage (charging voltage) VB substantially constant. That is, when the battery voltage VB is lower than the voltage V1 at the time of constant voltage charge control, the constant current constant voltage control circuit 7 outputs a control signal to the inverter circuit 1 through, for example, a photocoupler (not shown), The output of the inverter circuit 1 is controlled so that the charging current is prevented from flowing excessively and the charging current becomes substantially constant (constant current charging control). On the other hand, when the charging of the secondary battery B proceeds and the battery voltage VB rises and reaches the voltage V1 at the time of constant voltage charging control, the constant current constant voltage control circuit 7 outputs a control signal to the inverter circuit 1, The output of the inverter circuit 1 is controlled so that the charging current is gradually decreased and the battery voltage VB becomes the voltage V1. When the charging current Ib decreases to a predetermined current value I1, the constant current / constant voltage control circuit 7 outputs a charging completion signal to the CPU 7, and the CPU 6 turns off the transistor Q1 and ends the charging operation.
[0011]
By the way, in the secondary battery B, a protective element (not shown) for protecting the cell when an abnormality occurs is incorporated in addition to one or a plurality of cells constituting the secondary battery B, which adversely affects the secondary battery. Occurs (for example, overcharge, abnormal rise in battery temperature, etc.), the protective element performs a protective operation to open the positive and negative electrodes of the secondary battery B.
[0012]
[Problems to be solved by the invention]
In the above charger, the divided voltage Vb obtained by dividing the battery voltage VB by the dividing resistors R1 and R2 is input to the CPU 6, and the CPU 6 discriminates the abnormal state of the secondary battery B from the divided voltage Vb. Yes.
[0013]
Here, when the normal secondary battery B is attached to the charger, the battery voltage VB when charging the normal secondary battery B is in a voltage range of, for example, about 5V to about 8.5V. Based on the battery voltage VB detected from the divided voltage Vb, it is determined that the secondary battery B is normal, and the charging circuit 3 is operated in the quick charge mode.
[0014]
Further, when the secondary battery B in which the two electrodes are short-circuited is attached to the charger, the battery voltage VB of the secondary battery B is approximately 0 V, so the CPU 6 detects the battery voltage detected from the divided voltage Vb. Based on VB, it is determined that the secondary battery B is in a short-circuit state, the transistor Q2 is turned off, and the charging operation is forcibly stopped (charging end mode).
[0015]
On the other hand, when the secondary battery B in which the two electrodes are opened by the protection operation of the protective element is attached to the charger, the charging terminal t1, t2 is open, but the transistor Q2 is turned on when energized. The voltage V1 at the time of constant voltage charging control substantially the same as when charging of the normal secondary battery B is completed is generated at the positive charging terminal t1, and the voltage is divided by the voltage dividing resistors R1 and R2. A voltage is input to the CPU 6. Therefore, the CPU 6 has a problem that the secondary battery B in an open state cannot be distinguished from a normal secondary battery B.
[0016]
Thus, it is conceivable to determine the abnormal state of the secondary battery B with the transistor Q1 turned off and the charging current Ib not flowing, but the CPU 6 detects the divided voltage Vb with the transistor Q1 turned off. Then, in the case of the secondary battery B in the open state, the voltage generated at the charging terminal t1 on the positive electrode side is approximately 0V, so the voltage Vb divided by the voltage dividing resistors R1 and R2 is also approximately 0V, and the open state Therefore, there is a problem that the secondary battery B that has become short-circuited and the secondary battery B that has become short-circuited cannot be distinguished.
[0017]
In addition, when the secondary battery B in a short state is attached to the charger, it is necessary to forcibly terminate the charging operation. For example, the protection element operates because the temperature of the secondary battery B has become high. When the secondary battery B that is in the open state is attached to the charger, it waits for charging until the temperature of the secondary battery B decreases and the protection operation of the protection element is released, and then quick charging is performed. The secondary battery B in the open state and the secondary battery B in the short state need to be clearly distinguished from each other.
[0018]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a charger that can accurately determine an abnormal state of a secondary battery.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, in a charger for supplying a charging current from a DC power source to a secondary battery, the charger has a voltage detection means for detecting the battery voltage of the secondary battery. An abnormality detection unit that detects an abnormality of the secondary battery from the detected value of the battery, a charge control unit that controls the charging operation to the secondary battery based on the detection result of the abnormality detection unit, and when charging a normal secondary battery A predetermined detection that is lower than the voltage generated between the two electrodes of the secondary battery and higher than the voltage generated between the two electrodes of the secondary battery when a secondary battery in which the two electrodes are short-circuited is installed. And a detection voltage applying unit that applies a detection voltage between both electrodes of the secondary battery, and the detection voltage applying unit applies a detection voltage between both electrodes of the secondary battery. The detection voltage is applied to both the secondary batteries when charging a normal secondary battery. A normal secondary battery is attached to the charger because the voltage is lower than the voltage generated between them and higher than the voltage generated between both electrodes of the secondary battery when a short-circuited secondary battery is installed. And when a secondary battery in a short state is attached to the charger, and when a secondary battery that is open between the two poles is attached to the charger Since the voltages are different, the abnormality detection unit can accurately detect the state of the secondary battery from the detection result of the voltage detection means.
[0020]
According to a second aspect of the invention, in the first aspect of the invention, a control power supply unit that generates an operating voltage of the charge control unit is provided, and the detection voltage application unit includes an output terminal of the control power supply unit and a secondary battery. Comprising a series circuit of an impedance element connected between the connection terminal to which the positive electrode is connected and a backflow prevention element for preventing current from flowing to the control power supply unit side, and an open state When the secondary battery is attached to the charger, the detection voltage obtained by subtracting the voltage drop of the impedance element and the backflow prevention element from the output voltage of the control power supply is applied across the secondary battery. The detection unit can detect from the detection result of the voltage detection means that the secondary battery is in an open state, and when charging a normal secondary battery, it is more than the voltage generated between both electrodes of the secondary battery. Detection voltage It is low, it can be current to the control power supply unit side by the back current prevention elements to prevent backflow.
[0021]
According to a third aspect of the present invention, in the second aspect of the present invention, the backflow prevention element comprises a plurality of diodes connected in series, and the forward voltage of the diode is obtained by connecting the plurality of diodes in series. The voltage drop due to the voltage of the secondary battery can be reduced, and the voltage value of the detection voltage applied between the two electrodes of the secondary battery can be reduced. When charging a normal secondary battery, the voltage generated between the two electrodes of the secondary battery The potential difference from the detection voltage can be increased to prevent erroneous detection.
[0022]
According to a fourth aspect of the invention, in the first aspect of the invention, an abnormal state display unit for displaying an abnormal state of the secondary battery is provided, and the abnormal state of the secondary battery can be easily displayed from the display of the abnormal state display unit. Can grasp.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit diagram of the charger of this embodiment. In this circuit, an inverter circuit 1 that generates an AC voltage of a predetermined voltage, a transformer T1 in which a primary winding n1 is connected between output terminals of the inverter circuit 1, and a voltage generated in a secondary winding n2 of the transformer T1. A charging power supply circuit 2 that generates a DC voltage of a predetermined voltage by rectification and smoothing, a charging circuit 3 that charges the secondary battery B with the DC voltage generated by the charging power supply circuit 2, and a secondary winding of the transformer T1 The control power supply circuit (control power supply unit) 4 generates a constant voltage (for example, about 5 V) by rectifying and smoothing the voltage generated at n3, and the charging circuit 3 supplied with power from the control power supply circuit 4 And a control circuit 5 for controlling the charging operation. In this circuit, instead of the circuit comprising the transistor Q2 and the resistors R7 and R8 in the circuit shown in FIG. 2, the resistor R3 as an impedance element having one end connected to the charging terminal t1 on the positive electrode side and the resistor R3 A circuit comprising a series circuit of diodes D4 and D5 as backflow prevention elements connected between the other end and the output terminal of the three-terminal regulator IC1 is provided, and the diodes D4 and D5 have their anodes connected to the three-terminal regulator. The output terminal side of the IC 1 and the cathode are connected with the resistor R3 side to prevent the current from flowing from the charging circuit 3 to the control power supply circuit 4 side. Here, the CPU 6 of the control circuit 5 constitutes an abnormality detection unit and a charge control unit, and the voltage dividing resistors R1 and R2 constitute voltage detection means. Since the configuration other than the circuit composed of the resistor R3 and the diodes D4 and D5 is the same as that of the circuit shown in FIG. 2, the description thereof is omitted.
[0024]
Here, the voltage generated when the normal secondary battery B is charged at the charging terminal t1 on the positive electrode side by the detection voltage application circuit (detection voltage application unit) 3a including the resistor R3 and the diodes D4 and D5. A predetermined detection voltage lower than (for example, about 5 V to about 8.5 V) and higher than the voltage range (for example, about 3 V or less) of the battery voltage VB of the secondary battery B that has become short-circuited is given. The detection voltage is a voltage (about 3.5 V) obtained by subtracting the sum (about 1.5 V) of the forward voltages of the diodes D4 and D5 from the output voltage (about 5 V) of the three-terminal regulator IC1. In the present embodiment, two diodes D4 and D5 are connected in series, the voltage drop due to the forward voltage of the diodes D4 and D5 is increased, and the detection voltage generated by the detection voltage application circuit 3a is: Although the erroneous detection of the CPU 6 is prevented by increasing the potential difference from the lower limit value (about 5 V) of the voltage generated when charging the normal secondary battery B, there is no problem even if only one diode is used.
[0025]
Therefore, when the normal secondary battery B is attached to the charger, the voltage (battery voltage VB) generated between both ends of the secondary battery B when charging the normal secondary battery B is about 5V to about 8 .5V, which is higher than the output voltage (about 5V) of the three-terminal regulator IC1, so that the diodes D4 and D5 are turned off. Thus, the CPU 6 detects that the battery voltage VB is within the voltage range of about 5 V to about 8.5 V from the divided voltage Vb, determines that the secondary battery B is normal, and determines that the secondary battery B is normal. Perform the charging operation.
[0026]
In addition, when the secondary battery B that has become short-circuited is attached to the charger, the voltage generated between both electrodes of the secondary battery B is about 3 V or less. Therefore, in the CPU 6, the battery voltage VB is changed from the divided voltage Vb. It is detected that the secondary battery B is in a short state by detecting that the voltage is 3V or less, and the charging operation is forcibly terminated, and the light emitting diode LED1 as an abnormal state display unit is lit, The abnormal state of the secondary battery B is notified.
[0027]
On the other hand, when the secondary battery B that has been opened by the protection operation of the protective element is attached to the charger, the charging terminals t1 and t2 are open, so that the diodes D4 and D5 are conductive, A detection voltage (about 3.5V) obtained by subtracting the sum of forward voltages of diodes D4 and D5 (about 1.5V) from the output voltage (about 5V) of the three-terminal regulator IC1 is applied between both electrodes of the secondary battery B. Is done. Here, the CPU 6 detects the battery voltage VB from the divided voltage Vb, and the detected value is lower than the voltage (about 5V to about 8.5V) generated when the normal secondary battery B is attached. In addition, since the voltage is higher than the voltage (about 3 V or less) generated when the secondary battery B in a short state is attached, the secondary battery B is determined to be in an open state, and the charging circuit 3 is made to stand by and the light emitting diode LED1 is turned on to notify the user of the abnormal state of the secondary battery B. Thereafter, when the protection operation by the protection element is released, the voltage generated at the positive-side charging terminal t1 is the voltage generated when the normal secondary battery B is attached to the charger (about 5V to about 8. Therefore, the CPU 6 detects the battery voltage VB from the divided voltage Vb, determines that the secondary battery B is normal, turns on the transistor Q1, and operates the charging circuit 3 in the quick charge mode. .
[0028]
As described above, in this circuit, the detection voltage application circuit 3a including the resistor R3 and the diodes D4 and D5 applies a detection voltage of about 3.5 V between both electrodes of the secondary battery B, and charging on the positive electrode side. The terminal t1 has a voltage when the secondary battery B in an open state is attached to the charger, a voltage when a normal secondary battery B is attached to the charger, and a secondary battery in a short state. Since different voltages are generated when B is attached to the charger, whether the secondary battery B is normal or short-circuited by detecting the voltage generated at the charging terminal t1 on the positive electrode side. Alternatively, it is possible to clearly determine whether or not it is in an open state. Therefore, in the CPU 1, depending on the state of the secondary battery B, when the normal secondary battery B is attached to the charger, the charging circuit 3 is operated in the quick charge mode, and the secondary battery B in the short state is operated. When attached to the charger, the charging operation of the charging circuit 3 is forcibly terminated, and when the secondary battery B in an open state is attached to the charger, the charging operation of the charging circuit 3 may be put on standby. it can.
[0029]
In addition, when the charging terminals t1 and t2 are deformed or foreign matter adheres to the charging terminals t1 and t2, contact failure between the terminals of the secondary battery B and the charging terminals t1 and t2 occurs. Since the charging terminals t1 and t2 are in an open state, a voltage of about 3.5 V is generated at the positive charging terminal t1 by the detection voltage applying circuit 3a including the resistor R3 and the diodes D4 and D5. It can be detected from the divided voltage Vb that the charging terminals t1 and t2 are open.
[0030]
Moreover, in the conventional charging circuit, even when the secondary battery B is not connected, a dummy current flows when power is supplied by the circuit constituted by the resistors R7 and R8 and the transistor Q2, so that the resistor R7 generates heat and is lost. However, in the charging circuit of the present embodiment, the path through which current flows through the resistor R7 and the transistor Q2 is eliminated, so that loss (standby power) that occurs at times other than charging (standby) is reduced. Can do.
[0031]
【The invention's effect】
As described above, the invention of claim 1 is a charger for supplying a charging current from a DC power source to a secondary battery, and has a voltage detection means for detecting a battery voltage of the secondary battery, and a detected value of the voltage detection means. An abnormality detection unit for detecting abnormality of the secondary battery from the battery, a charge control unit for controlling the charging operation to the secondary battery based on the detection result of the abnormality detection unit, and a secondary battery when charging a normal secondary battery A predetermined detection voltage lower than the voltage generated between both electrodes of the battery and higher than the voltage generated between both electrodes of the secondary battery when a secondary battery in which the two electrodes are short-circuited is attached. A detection voltage applying unit that is applied between both electrodes of the secondary battery, and the detection voltage applying unit applies a detection voltage between both electrodes of the secondary battery. Occurs between both electrodes of a rechargeable battery when charging a normal rechargeable battery The voltage is higher than the voltage generated between the two electrodes of the secondary battery when a secondary battery in a short state is installed. The voltage generated between the two electrodes of the secondary battery is different between when the secondary battery in the state is attached to the charger and when the secondary battery with both electrodes open is attached to the charger. The abnormality detection unit can accurately detect the state of the secondary battery from the detection result of the voltage detection means, and the charging control unit can control the charging operation of the secondary battery according to the detection result of the abnormality detection unit There is. Furthermore, even if a secondary battery is not connected in the conventional charging circuit, a dummy current flows between the charging terminals when commercial AC power is supplied, and loss occurs. However, in the charging circuit of the present invention, the dummy current Therefore, there is an effect that loss (standby power) that occurs when the secondary battery is not connected (standby) can be reduced.
[0032]
According to a second aspect of the present invention, in the first aspect of the invention, the control power source unit for generating the operating voltage of the charge control unit is provided, and the detection voltage applying unit includes an output terminal of the control power source unit and a secondary battery. Comprising a series circuit of an impedance element connected between the connection terminal to which the positive electrode is connected and a backflow prevention element for preventing current from flowing to the control power supply unit side, and an open state When the secondary battery is attached to the charger, the detection voltage obtained by subtracting the voltage drop of the impedance element and the backflow prevention element from the output voltage of the control power supply is applied across the secondary battery. The detection unit can detect from the detection result of the voltage detection means that the secondary battery is in an open state, and when charging a normal secondary battery, it is more than the voltage generated between both electrodes of the secondary battery. Detection voltage Although low, the current to the control power supply unit side by the back current prevention elements has the effect of being able to prevent backflow.
[0033]
According to a third aspect of the present invention, in the second aspect of the present invention, the backflow prevention element comprises a plurality of diodes connected in series, and the forward voltage of the diode is obtained by connecting the plurality of diodes in series. The voltage drop due to the voltage of the secondary battery can be reduced, and the voltage value of the detection voltage applied between the two electrodes of the secondary battery can be reduced. When charging a normal secondary battery, the voltage generated between the two electrodes of the secondary battery There is an effect that the potential difference from the detection voltage can be increased to prevent erroneous detection.
[0034]
The invention of claim 4 is characterized in that, in the invention of claim 1, an abnormal state display unit for displaying an abnormal state of the secondary battery is provided, and the abnormal state of the secondary battery is easily displayed from the display of the abnormal state display unit. There is an effect that can be grasped.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a charger according to an embodiment.
FIG. 2 is a circuit diagram of a conventional charger.
FIG. 3 is an explanatory diagram illustrating a charging operation of the charger.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 Charge circuit 3a Detection voltage application circuit 4 Control power supply circuit 5 Charge control circuit 6 CPU
B Secondary batteries D4, D5 Diodes R1, R2 Voltage dividing resistor R3 Resistance t1 Charging terminal VB Battery voltage Vb Voltage dividing voltage

Claims (4)

In a charger for supplying a charging current from a DC power supply to a secondary battery, an abnormality detection unit having voltage detection means for detecting a battery voltage of the secondary battery and detecting an abnormality of the secondary battery from a detection value of the voltage detection means And a charge control unit that controls the charging operation to the secondary battery based on the detection result of the abnormality detection unit, and lower than the voltage generated between both electrodes of the secondary battery when charging a normal secondary battery, And the detection voltage which applies the predetermined detection voltage higher than the voltage which generate | occur | produces between the both poles of a secondary battery when the secondary battery in which both electrodes became a short-circuited state is attached A charger comprising: an application unit. A power supply unit for control that generates an operating voltage of the charge control unit, and the detection voltage application unit is connected between an output terminal of the control power supply unit and a connection terminal to which a positive electrode of the secondary battery is connected. 2. The charger according to claim 1, wherein the charger comprises a series circuit of an impedance element and a backflow prevention element for preventing current from flowing to the control power supply unit side. 3. The charger according to claim 2, wherein the backflow prevention element comprises a plurality of diodes connected in series. 2. The charger according to claim 1, further comprising an abnormal state display unit that displays an abnormal state of the secondary battery.

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