JP4646929B2 - Charger - Google Patents

Description

  The present invention relates to a battery charger, and more particularly to a charger that reduces power consumption when a battery is not attached.

  It is important for the charger to be able to reduce the power consumption when no battery is set. This is because the power consumption in this state is not used effectively. In order to reduce useless power consumption of the charger without setting the battery, a switch that physically detects the battery set can be provided. (See Patent Document 1)

  The charger of Patent Document 1 outputs a charging voltage in a state where the battery is set and the plunger of the switch is pushed, and in a state where the plunger of the switch is not pushed by the battery, in other words, in a state where the battery is not set, By switching the switch off, power consumption can be reduced to zero when the battery is not charged. However, a charger that realizes this requires the provision of a switch that physically detects the battery set, resulting in high component costs. Also, a switch with a physically moving part has a short life compared to an electronic circuit, and if the switch fails, the battery cannot be charged normally, or the battery is set and cannot be charged normally. .

  In order to eliminate this drawback, a charger has been developed that electrically detects a no-load condition with no battery connected and significantly lowers the output voltage of the switching power supply in the no-load condition to reduce power consumption. Yes. (See Patent Document 2)

Since the charger of Patent Document 2 significantly reduces the output voltage of the switching power supply in a no-load state, it is necessary to provide a dedicated circuit on the battery side in order to detect that the battery is installed. The charger of patent document 2 is provided with the detection terminal connected to the negative electrode side of a battery via resistance in addition to the positive / negative terminal of a battery. From the change in electrical resistance between the detection terminal and the negative electrode terminal of the battery, a no-load state and a state where the battery is mounted are discriminated. Therefore, this charger needs to provide a dedicated circuit on the battery side, and the circuit configuration becomes complicated. In addition, when a dedicated terminal causes poor contact, it is impossible to determine the battery mounting state, and the battery cannot be charged normally.
JP 2002-199612 A JP 2006-20437 A

  The present invention has been developed for the purpose of solving this drawback. An important object of the present invention is to provide a charger that can electrically detect battery mounting while simplifying the overall circuit configuration, and can significantly reduce wasteful power consumption in a no-load state in which no battery is mounted. is there.

The charger of the present invention has the following configuration in order to achieve the above-described object.
The charger is connected to a switching power source 1 that converts input power into a DC voltage for charging the battery 10, a voltage adjusting circuit 2 that controls the output voltage of the switching power source 1, and an output side of the switching power source 1. The switching element 3 that converts the output voltage of the switching power source 1 into a pulse voltage for detecting the battery 10, and the pulse voltage output from the switching element 3 is supplied to the connection terminal 8 of the battery 10 to determine whether the battery 10 is present. In a no-load state in which the battery 10 is not charged while being detected, the output voltage of the switching power supply 1 is set to a low voltage state in synchronization with the “Low” timing of the pulse voltage via the voltage adjustment circuit 2. A control circuit 4 is provided that holds the output voltage of the switching power supply 1 in a high voltage state in the charged state.

  The charger according to claim 2 of the present invention supplies power to the control circuit 4 from the switching power supply 1 in addition to the configuration of claim 1, and operates the control circuit 4 under the low voltage state of the switching power supply 1. The voltage to be used.

  According to a third aspect of the present invention, in addition to the configuration of the first aspect, a charger control circuit 5 for controlling either or both of the voltage and current for charging the battery 10 is connected to the output side of the switching power supply 1. is doing. The charger further includes a power switch circuit 6 that cuts off the power supply of the charging control circuit 5 when the switching power supply 1 is in a low voltage state.

  The charger of claim 4 of the present invention is the charger of the lithium ion secondary battery 10A in addition to the configuration of claim 3, and the charge control circuit 5 is a constant voltage / constant current circuit.

  The charger of claim 5 of the present invention uses the switching element 3 in combination with the charge switch 7 that controls the charging of the battery 10 in addition to the configuration of claim 1.

  Furthermore, in the charger of claim 6 of the present invention, in addition to the configuration of claim 1, the time width of the pulse voltage “High” is set shorter than the time width of the high voltage state.

  The charger according to the present invention can electrically determine whether or not a battery is mounted by simplifying the entire circuit configuration. This is because a pulse voltage is output to the connection terminal of the battery to determine whether or not the battery is installed. The pulse voltage is “High” and “Low” when the battery is not loaded, and the “High” voltage is lowered or “Low” when the battery is loaded. The voltage rises to the battery voltage. Accordingly, it is possible to electrically detect that the battery is mounted by detecting a change in voltage of “High” and “Low” of the output pulse voltage “High”. Since the mounting of the battery is electrically detected, it is not necessary to provide a switch for physically detecting the mounting of the battery, and the component cost can be reduced. Further, since the battery mounting is electrically detected, the reliability is higher than that of a switch or the like, and the battery mounting can be reliably detected. Further, in a no-load state where no battery is attached, the output voltage of the switching power supply is set to a low voltage state in synchronization with the pulse voltage “Low”, so that wasteful power consumption in this state can be reduced. By the way, by using the technology of the present invention, it is possible to reduce the wasteful power consumption of the charger without mounting the battery from 800 mW to 280 mW or less.

  Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a charger for embodying the technical idea of the present invention, and the present invention does not specify the charger as follows.

  Further, in this specification, in order to facilitate understanding of the scope of claims, numbers corresponding to the members shown in the examples are indicated in the “claims” and “means for solving problems” sections. It is added to the members. However, the members shown in the claims are not limited to the members in the embodiments.

  The charger shown in the block diagram of FIG. 1 includes a switching power supply 1 that converts a commercial power supply 9 as input power into a DC voltage suitable for charging a battery 10, and a voltage adjustment circuit 2 that controls the output voltage of the switching power supply 1. A switching element 3 connected to the output side of the switching power supply 1 to convert the output voltage of the switching power supply 1 into a pulse voltage for detecting the battery 10, and a pulse voltage output from the switching element 3 to the battery 10 In the no-load state in which the battery 10 is detected by supplying to the connection terminal 8 and the battery 10 is not charged, the output of the switching power supply 1 is synchronized with the OFF timing of the pulse voltage via the voltage adjustment circuit 2. A control circuit 4 is provided that maintains the output voltage of the switching power supply 1 in a high voltage state when the voltage is set to a low voltage state and the battery 10 is charged. That.

  The switching power supply 1 converts the alternating current of the commercial power supply 9 (100 V alternating current in Japan) into direct current of the output voltage of the battery 10. Although not shown, the switching power supply 1 converts alternating current into direct current using a diode bridge and a smoothing circuit, and supplies this direct current to the primary side of the switching transformer via a semiconductor switch. The switching transformer outputs an alternating voltage or a pulsating current that charges the battery 10 on the secondary side. The alternating voltage or pulsating current is converted into direct current by a smoothing circuit composed of a diode and an electrolytic capacitor, and becomes a direct current output. Although the switching power supply 1 switches the semiconductor switch on and off at a predetermined cycle, it can adjust the output voltage on the secondary side of the switching transformer by changing the on-time for turning off, in other words, the duty for switching the semiconductor switch. The charger of FIG. 1 controls the output voltage of the switching power supply 1 with a voltage adjustment circuit 2 via an insulating signal transmitter 11 such as a photocoupler. The switching power supply 1 switches the output voltage between a low voltage state and a high voltage state by a control signal input from the voltage adjustment circuit 2. When the battery 10 is set in the charger and the battery 10 is charged, the output voltage of the switching power supply 1 is maintained in a high voltage state. When the battery 10 is not set in the charger and the switching power supply 1 is in a no-load state, the switching power supply 1 switches the output voltage between a high voltage state and a low voltage state by a control signal input from the voltage adjustment circuit 2.

  The charger shown in the figure charges a battery pack in which three lithium ion secondary batteries 10A are connected in series. This charger can drive the switching power supply 1 with a high voltage output voltage of 15 V and a low voltage output voltage of about 3 to 10 V (the control circuit 4 can be driven with about 3.3 V, but other peripheral circuits (If not shown), the voltage may be about 3.3 V or higher.) The output voltage in the low voltage state is stabilized by the constant voltage IC 17 and determined to be the lowest voltage at which the control circuit 4 can operate. Although the output voltage in the low voltage state can be lowered to reduce wasteful power consumption when the battery 10 is not attached, it is necessary to determine whether or not the battery 10 is attached even in this state. Therefore, in the charger that operates the control circuit 4 that detects the mounting of the battery 10 with the output of the switching power supply 1, the voltage in the low voltage state of the switching power supply 1 is a voltage that allows the control circuit 4 to operate. However, the control circuit 4 is not necessarily operated by the output of the switching power supply 1. For example, a dedicated power supply circuit can be provided separately from the switching power supply, and an operating voltage can be supplied from the power supply circuit to the control circuit. . In this charger, the output voltage in the low voltage state of the switching power supply can be lowered to 0V or close to 0V.

  The voltage adjustment circuit 2 is a signal input from the control circuit 4 and outputs a control signal for controlling the output voltage of the switching power supply 1 to the switching power supply 1. The voltage adjustment circuit 2 in FIG. 2 includes a comparator 12, and a photocoupler that is an insulating signal transmitter 11 is connected to the output side of the comparator 12. The comparator 12 divides and inputs the output voltage of the switching power supply 1 via the first voltage dividing resistor 13 on one input side, and inputs the reference voltage on the other input side. The voltage adjustment circuit 2 changes the voltage of the switching power supply 1 by changing the reference voltage. As the reference voltage, the voltage output from the constant voltage IC 17 is divided by the second voltage dividing resistor 14 and input. The second voltage dividing resistor 14 is connected in parallel with a ground circuit 14A in parallel with a series circuit in which a control switch 16 is connected in series with a voltage drop resistor 15. The control switch 16 is switched on and off by the control circuit 4 to change the reference voltage input to the comparator 12. When the control circuit 4 turns on the control switch 16, the voltage drop resistor 15 is connected in parallel with the ground-side resistor 14 </ b> A of the second voltage dividing resistor 14. In this state, the second voltage dividing resistor 14 increases the voltage dividing ratio, lowers the voltage output from the constant voltage IC 17, and decreases the reference voltage input to the comparator 12. When the control switch 16 is turned off, the voltage drop resistor 15 is not connected in parallel with the ground-side resistor 14A of the second voltage dividing resistor 14, and the reference voltage of the comparator 12 becomes high. The voltage adjustment circuit 2 outputs a control signal to the switching power supply 1 via the insulated signal transmitter 11 so that the output voltage of the switching power supply 1 becomes a voltage corresponding to the reference voltage of the comparator 12. When the reference voltage of the comparator 12 increases, the output voltage of the switching power supply 1 enters a high voltage state, and when the reference voltage of the comparator 12 decreases, the output voltage of the switching power supply 1 enters a low voltage state.

  The switching element 3 is controlled by the control circuit 4 and switched on and off at a predetermined cycle, and the DC output of the switching power supply 1 is used as a pulse voltage. The pulse voltage is “High” when the switching element 3 is turned on, and “Low” when the switching element 3 is turned off. The charger in FIG. 1 uses the switching element 3 together with a charge switch 7 that controls the charging of the battery 10. The switching element 3 is turned on when the battery 10 is charged, and turned off when the battery 10 is fully charged to stop charging the battery 10.

  The control circuit 4 determines whether or not the battery 10 is attached with the pulse voltage output to the connection terminal 8. When the battery 10 is connected to the connection terminal 8, when the pulse voltage is “High” (about 12.6V), the pulse voltage “High” decreases to the battery voltage, and the pulse voltage is “Low” (about 0V). ), The pulse voltage “Low” rises to the battery voltage. The battery connected to the connection terminal may be a battery pack with a built-in protection circuit, and the switch of the discharge circuit may be turned off. For example, a battery pack with a low remaining battery capacity and overdischarged has its discharge switch (FET) turned off. When this battery is connected to the connection terminal, it cannot be discharged but can be charged (the charging FET switch is in the ON state). Therefore, when the pulse voltage is “High”, the pulse voltage “High” is the battery voltage. When the pulse voltage is in the “Low” state, the discharge cannot be performed and the pulse voltage is kept in the “Low” state. Therefore, the control circuit 4 detects that the pulse voltage “High” has dropped to the battery voltage, and determines that the battery 10 is attached. In addition, when a battery pack is fully charged and a battery pack that turns off the charging switch (charging FET switch) is connected to the connection terminal, the pulse voltage “High” is the voltage when the pulse voltage is “High”. When the pulse voltage is “Low” without changing, the pulse voltage “Low” rises to the battery voltage. Therefore, the control circuit 4 determines that the battery 10 is mounted by detecting that the voltage “Low” of the pulse voltage has increased. When the control circuit 4 detects that the battery 10 is mounted, the control circuit 4 sets the output voltage of the switching power supply 1 to a high voltage state, and further holds the switching element 3 on to charge the battery 10. When the control circuit 4 detects that the battery 10 is not attached, it switches the switching element 3 on and off to output a pulse voltage, and further controls the switching power supply 1 via the voltage adjustment circuit 2 to switch the switching power supply 1. The output voltage is switched between a high voltage state and a low voltage state in synchronization with the pulse voltage (see FIG. 3).

  The control circuit 4 is held in an operating state even when the switching power supply 1 is in a low voltage state. The charger in FIG. 1 connects a constant voltage IC 17 to the output of the switching power supply 1 and supplies power to the control circuit 4 from the constant voltage IC 17. The output voltage of the constant voltage IC 17 is set to an optimum voltage that allows the control circuit 4 to operate. For example, in a battery pack charger that connects three lithium ion secondary batteries to a direct current, the switching power supply 1 has a high voltage state of 15 V, a low voltage output voltage of about 3 to 10 V, and a low voltage Even in the state, a voltage capable of operating the control circuit 4 is supplied from the constant voltage IC 17. The constant voltage IC 17 supplies power supply power and a reference voltage to the comparator 12 of the voltage adjustment circuit 2.

  Further, the charger of FIG. 1 has a charge control circuit 5 connected to the output side of the switching power supply 1. The charge control circuit 5 is a constant voltage / constant current circuit in a charger for charging a lithium ion secondary battery. In a charger for charging a nickel metal hydride battery or a nickel cadmium battery, it is a constant current circuit. Therefore, the charge control circuit 5 is a circuit that controls either or both of the voltage and current for charging the battery depending on the battery to be charged. The charge control circuit 5 includes a power switch circuit 6 that cuts off the power supply of the charge control circuit 5 when the switching circuit 1 is in a low voltage state in order to prevent useless power consumption in a no-load state. The power switch circuit 6 is controlled on and off by the control circuit 4. The power switch circuit 6 is switched off at the timing when the output of the switching power supply 1 is set to a low voltage state in a state where the battery 10 is not attached. At this timing, the charging control circuit 5 does not need to operate, and wasteful power consumption can be eliminated. The charge control circuit 5 of FIG. 1 includes a control IC 18 and a control FET 19 that is a charge switch 7 controlled by the control IC 18. The power supply circuit of the control IC 18 is connected to the output of the switching power supply 1 through the power supply switch circuit 6. When the power switch circuit 6 is turned off, the control IC 18 does not operate. When the power switch circuit 6 is turned on, the control IC 18 operates so that the control FET 19 can be controlled.

The charger of FIG. 1 is controlled to a state in which useless power is not consumed when the battery 10 is not attached by performing the following operation.
[Battery installed]
When the battery 10 is attached, the control circuit 4 detects the voltage of the connection terminal 8 to detect that the battery 10 is attached. When the battery 10 is attached, the voltage at the connection terminal 8 becomes the battery voltage, so the control circuit 4 detects that the battery 10 is attached from the voltage at the connection terminal 8. When a battery pack with a protection circuit that cuts off the discharge current is set, the battery voltage is detected in a state in which the voltage is supplied to the connection terminal. Therefore, the battery voltage can be detected to determine that the battery has been installed. . Further, when a battery pack provided with a protection circuit that cuts off the charging current is set, the battery voltage is detected in a state where no voltage is supplied to the connection terminal. Therefore, it is possible to detect battery attachment by detecting this battery voltage. However, since the battery pack provided with a protection circuit that cuts off the charging current is overcharged when it is further charged, the charging control circuit 5 cuts off the charging current or controls even if the battery installation is detected and charging starts. The circuit 4 detects the full charge of the battery 10 and turns off the charge switch 7 so that the battery 10 is not charged.

[Battery not installed]
The control circuit 4 detects a no-load state in which the battery 10 is not mounted from the voltage at the connection terminal 8. The control circuit 4 that has detected this state switches the switching element 3 on and off at a predetermined cycle, and uses the voltage supplied to the connection terminal 8 as a pulse voltage. Further, the control circuit 4 controls the switching power supply 1 via the voltage adjustment circuit 2 to bring the output voltage of the switching power supply 1 into a low voltage state in synchronization with the “Low” timing of the pulse voltage. FIG. 3 shows the pulse voltage supplied to the connection terminal 8 and the timing for switching the switching power supply 1 between the high voltage state and the low voltage state when the battery 10 is not attached. In this figure, the switching power supply 1 takes about 50 msec (possible at about 30 to 150 msec) for the output voltage to be in a high voltage state, and about 450 msec (possible at about 300 to 1000 msec) for the output voltage to be in a low voltage state. As shown, the high voltage state and the low voltage state are switched at a cycle of about 500 msec. As shown in this figure, the charger of the present invention can reduce wasteful power consumption in a no-load state in which no battery is mounted by switching the output voltage of the switching power supply 1 between a high voltage state and a low voltage state. Furthermore, the charger can adjust the duty for switching the switching power supply 1 between the high voltage state and the low voltage state to adjust the power consumption of the charger in the no-load state where no battery is attached to an optimum value.

  Further, in the charger controlled at the timing shown in FIG. 3, the time width of the pulse voltage “High” is set shorter than the time width in which the output voltage of the switching power supply 1 is in the high voltage state. In order to control the pulse voltage and the output voltage of the switching power supply 1 at this timing, the control circuit 4 switches off the switching element 3 in a state where the battery 10 is not mounted, and a predetermined time elapses. The output voltage can be controlled to be in a low voltage state. As shown in this figure, the charger of the present invention needs to completely match the timing for switching the pulse voltage between “High” and “Low” with the timing for switching the switching power supply 1 between the high voltage state and the low voltage state. There is no. This is because the power consumption can be reduced by setting the output voltage of the switching power supply 1 to a low voltage state during the whole or a part of the time period of the pulse voltage “Low”.

It is a block diagram of the charger concerning one Example of this invention. It is a block diagram which shows an example of a voltage adjustment circuit. It is a figure which shows the timing which switches the pulse voltage supplied to a connection terminal, and the output voltage of switching power supply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Switching power supply 2 ... Voltage adjustment circuit 3 ... Switching element 4 ... Control circuit 5 ... Charge control circuit 6 ... Power supply switch circuit 7 ... Charge switch 8 ... Connection terminal 9 ... Commercial power supply 10 ... Battery 10A ... Lithium ion secondary battery 11 ... Insulation type signal transmitter 12 ... Comparator 13 ... First voltage dividing resistor 14 ... Second voltage dividing resistor 14A ... Earth side resistance 15 ... Voltage drop resistance 16 ... Control switch 17 ... Constant voltage IC
18 ... Control IC
19 ... Control FET

Claims (6)

  A switching power supply (1) that converts input power into a DC voltage that charges the battery (10), a voltage adjustment circuit (2) that controls the output voltage of the switching power supply (1), and an output of the switching power supply (1) Connected to the switching element (3) for converting the output voltage of the switching power supply (1) into a pulse voltage for detecting the battery (10), and the pulse voltage output from the switching element (3) to the battery ( 10) is supplied to the connection terminal (8) to detect the presence of the battery (10), and in the no-load state where the battery (10) is not charged, the voltage voltage is adjusted via the voltage adjustment circuit (2). In synchronization with the “Low” timing, the output voltage of the switching power supply (1) is set to a low voltage state, and the output voltage of the switching power supply (1) is held in a high voltage state when the battery (10) is charged ( 4) Charger with.   The charging according to claim 1, wherein the switching power supply (1) supplies power to the control circuit (4), and the low voltage state of the switching power supply (1) is a voltage for operating the control circuit (4). vessel.   Connected to the output side of the switching power supply (1) is a charge control circuit (5) for controlling either or both of the voltage and current for charging the battery (10), and when the switching circuit (1) is in a low voltage state, The charger according to claim 1, further comprising a power switch circuit (6) for cutting off the power supply of the charge control circuit (5).   The charger according to claim 3, wherein the charger is a lithium ion secondary battery (10A), and the charge control circuit (5) is a constant voltage / constant current circuit.   The charger according to claim 1, wherein the switching element (3) is used in combination with a charge switch (7) for controlling charging of the battery (10).   The charger according to claim 1, wherein the time width of “High” of the pulse voltage is set shorter than the time width of the high voltage state.

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