JP2005318790A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charger capable of securing a charging current as large as possible in a short time even in a battery which is charged by a constant charging current and requires a long charging time. <P>SOLUTION: This charger having a function for supplying charging currents of a plurality of stages to the battery rapidly charges the battery by gradually decreasing the charging current to an allowable current corresponding to the reduction of a charging current which the battery can allow with the progress of charging. Furthermore, the charger includes a function for gradually switching a first charging current to an Nth charging current. This stepwise switching is conducted when it is detected that a battery voltage during a charging current-off period reaches a battery voltage VB (N-1) from a prescribed battery voltage VB1 corresponding to each current switching. During the charge period by the Nth charging current, the battery voltage during the charging current-off period reaches a peak in the ending stage of charging. When it is detected that the battery voltage drops after the peak, the charging is completed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a charging control technique for a charger.

As a conventional charger, charging was performed with a constant current from the start of charging to the completion of charging, and the completion of charging was detected by detecting a voltage drop in the battery voltage at the end of charging. For example, Patent Literature 1 describes, as a conventional technique, continuously charging a constant current-controlled charging current to a charged battery and monitoring a change in battery voltage to detect completion of charging.
JP 2000-324709 A

  However, in the conventional method in which a constant current is supplied from the start of charging to the completion of charging, the charging current is limited to the maximum current that the battery can tolerate at the end of charging, and no more charging current can be supplied. For this reason, with the recent increase in capacity of nickel-metal hydride storage batteries, in batteries where the current that the battery can tolerate at the end of charging is limited to about 0.5 It, the charging time is about 2 hours with a 0.5 It constant current. Was the shortest.

  Note that It is a unit representing the charging current or discharging current of the battery, and the numeric value of the rated capacity of the battery is 1 It. For example, in the case of a battery with a capacity of 2000 mAh, 1 It is 2000 mA and 0.5 It is 1000 mA.

  FIG. 2 shows the time transition of the battery voltage and the charging current according to the conventional example. When a charging current of 0.5 It flows after the start of charging, and about 2 hours have passed after that, the battery voltage reaches its peak when the completion of charging approaches. After that, it descends slowly. The battery voltage drop after this peak is detected, charging is completed, and charging is terminated. In the vicinity of this charging completion, especially in the period from when the charging capacity exceeds about 90% until the charging is completed, the pressure inside the battery rises, so if the charging current exceeds the allowable value of the battery, the safety valve of the battery is activated However, gas may flow out from the inside, which may cause deterioration of battery performance.

  With the recent increase in capacity of batteries, this allowable current value tends to decrease, and some batteries have come to operate when a charging current of 0.5 It or more flows. Therefore, the upper limit of the charging current is limited to a current value that does not activate the safety valve at the end of charging, and when charging with a charging current of 0.5 It from the beginning of charging, the charging time is about 2 hours is the shortest. It was.

  In addition, since only two stages of charging and charging completion are displayed for the charging display, there is no means for telling about what percentage of charging is in progress during charging, which is somewhat inconvenient for the user.

  An object of this invention is to provide the charger which can ensure as much charge amount as possible in a short time compared with the past.

  In order to solve the above-mentioned problems, the charger has a function of supplying charging currents of multiple stages to the battery, and the charging current is allowed according to the reduction of the allowable charging current of the battery as the charging progresses. It is reduced stepwise below the current to enable quick charging in a shorter time.

  In addition, when having a function of switching from the first charging current to the Nth charging current step by step, the stepwise switching of the charging current from the first to the Nth charging is performed by changing the battery voltage during the charging current off period. The battery voltage VB1 is detected when the battery voltage VB (N-1) is reached from the battery voltage VB1 set in advance for the current switching, and the battery voltage in the charging current off period is charged in the Nth charging current charging period. Has a function of detecting that the voltage reaches a peak at the end of charging and then the voltage is dropped to complete charging.

  A function is provided for performing capacity display during charging in accordance with stepwise charging current switching in the middle of charging, and displaying charging completion in response to detection of charging completion.

  Furthermore, by providing a switching element for connecting a plurality of batteries in series and a bypass switching element connected in parallel with each battery, the charging current is duty controlled so that a plurality of batteries can be charged simultaneously. Is also possible.

  The charger according to the present invention has the above-described configuration, and can achieve faster charging even for a battery in which the charging current at the end of charging is limited to be low. Specifically, even a battery whose charging current cannot exceed 0.5 It by constant current charging can be rapidly charged within one hour without deteriorating its battery performance.

  In addition, by displaying the capacity in the middle of charging along with the stepwise charging current switching in the middle of charging, a user-friendly charger is available for users who want to charge as much as possible in a short time without reaching completion of charging. Can be provided.

  Furthermore, by providing a switch element for connecting a plurality of batteries in series and a bypass switch element connected in parallel with each battery, a plurality of batteries having different charge states can be rapidly charged simultaneously.

(Embodiment 1)
A more specific embodiment of the present invention will be described with reference to FIG. 1 as an example in which the charging current is gradually switched. FIG. 1 is a diagram showing the time transition of battery voltage and charging current during charging. After the start of charging, a current of about 3 It is supplied to the battery as the first charging current to perform charging. As a current pattern, a current is supplied for about 1.1 seconds as a current on period, and then a current off period of about 0.1 seconds is provided. The detection voltage VB1 for switching the charging current is detected by detecting the battery voltage during this current off period, that is, when no current flows.

  This is because, in the present embodiment, since a large current of about 7.8 A is used as the first charging current, the battery voltage during the current on period, that is, the battery voltage when the current is flowing is detected. Since the contact resistance between the output terminal of the charger and the battery, the voltage drop generated at the terminal itself, and the voltage drop in the copper foil pattern of the printed circuit board are added to the battery voltage and read, the accurate battery voltage is It becomes very difficult to measure. For this purpose, the battery voltage during the current off period is detected. This is because the voltage drop in the contact resistance or the like does not occur during the current off period, and the accurate voltage of only the battery can be detected without being affected by the voltage drop.

  In addition, the detection voltage VB1 for detecting the current switching point is set to an open circuit voltage at that time by previously setting an electric current value for charging 50% of the rated capacity of the battery charged by charging for 10 minutes by experiment. Further, since the battery voltage has a negative temperature characteristic, a temperature characteristic equivalent to the temperature characteristic of the battery voltage is obtained and set in advance for the detection voltage VB1. Then, after the start of charging, the battery voltage rises as the charging with the first charging current proceeds, and it is detected that the battery voltage during the current off period has reached VB1, and the charging with the first charging current is terminated. The charging time by the first charging current is about 10 minutes in the present embodiment, and the charging capacity is about 50%. Simultaneously with the switching of the charging current, the display indicating the charging state is also switched, so that it is possible to notify the user that charging of about 50% of the battery rated capacity has been completed.

  Next, charging is continued by switching to a current of about 1 It as the second charging current, but the battery voltage once falls to a low voltage at this point, but rises again as the charging by the second charging current proceeds. Similarly to the first charging current period, the charging period by the second charging current is repeated by repeating a current on period of about 1.1 seconds and a current off period of about 0.1 seconds, and the current is turned off. The battery voltage in the period is detected, and the battery voltage VB2 that is the switching voltage to the third charging current is detected. When the charging proceeds and the battery voltage reaches VB2, the charging by the second charging current is terminated. The charging time by the second charging current is about 20 minutes, and the charging capacity is also about 30% of the battery rated capacity. From the beginning of charging, the charging time is about 30 minutes and the total charging capacity is about 80%. However, at this charging capacity of 80%, the battery internal pressure has not started to rise significantly, and about 1 It The safety valve is activated by this current and battery performance is not degraded. In this case, the display indicating the charging state is switched simultaneously with the switching of the charging current, so that the user can be informed that about 80% of the charging has been completed.

  Thereafter, the charging is continued by switching to a current of about 0.5 It as the third charging current. At this time, the battery voltage once decreases and then increases. As with the first charging current and the second charging current, the charging period of the third charging current proceeds by repeating a current on period of about 1.1 seconds and a current off period of about 0.1 seconds. The battery voltage is also detected during the current off period. Charging proceeds, the battery voltage reaches a peak at the end of charging, and then gradually decreases. A voltage drop after the peak of the battery voltage is detected and it is determined that charging is completed, and the display is switched to a charging completion display. The charging time by the third charging current is about 30 minutes, and the charging capacity is about 25% of the battery rated capacity. In the region near the completion of charging, the charging current is 0.5 It, which is an allowable value for the battery, so that the battery performance does not deteriorate due to the operation of the safety valve. The cumulative total from the start of charging is about 1 hour as the charging time and about 105% as the total charging capacity, and the battery has been fully charged.

(Embodiment 2)
A more specific embodiment when the present invention is used in a charger capable of producing a plurality of batteries will be described with reference to FIGS. FIG. 3 is a circuit block diagram of a DC input type charger capable of charging four batteries.

  B1 to B4 are nickel metal hydride batteries to be charged. SW1 to SW4 are switch elements provided to connect four batteries in series, and SW5 to SW8 are bypass switch elements provided in parallel with the batteries. SW9 is a switch element that constitutes a circuit for detecting the battery voltage in the charge controller. R1 is a resistance for detecting a charging current, and LEDs 1 to LED3 are LEDs for displaying a charging state. As other circuit blocks, a DC / DC converter section, a constant current control section, a 5V power supply section, and a charge control section are provided.

  In the above configuration, when a DC power source is applied to the input and the battery is connected, the DC / DC converter starts oscillating, and the charging current that is made constant by the current detection resistor R1 and the constant current control unit is supplied to the battery. Is done. When all four batteries B1 to B4 are connected, the charging current flows through the path of DC / DC converter → SW1 → B1 → SW2 → B2 → SW3 → B3 → SW4 → B4. When three batteries are connected to B2, B3, and B4, the charging current passes through the bypass switch SW5 in the path of DC / DC converter → SW5 → SW2 → B2 → SW3 → B3 → SW4 → B4. Flows. When only one battery is connected to B4, the charging current flows through the bypass switches SW5, SW6, and SW7 along the path of DC / DC converter → SW5 → SW6 → SW7 → SW4 → B4. Thus, a charging circuit is formed by combining opening and closing of the switch elements SW1 to SW4 for series connection and the switch elements SW5 to SW8 for bypass according to the number of batteries, and a plurality of batteries are charged.

  The battery voltage of each battery is detected during the charging current OFF period set at an arbitrary time. FIG. 4 shows the waveform of the charging current. In this embodiment, the charging current ON period of 1.1 seconds and the charging current OFF period of 0.1 seconds are alternately repeated. The battery voltage of each battery is detected for 0.1 seconds during this charging current OFF period. When this battery voltage is detected, the DC / DC converter unit is first stopped to stop the charging current. Thereafter, the switch element SW9 is closed, and the battery voltage of each battery is detected by a combination of opening and closing of SW1 to SW9. For example, when the battery voltage of B1 is detected, the voltage of the battery B1 is detected by forming a circuit of charge control unit → SW9 → SW1 → B1 → SW6 → SW7 → SW8. At this time, SW5, SW2, SW3, and SW4 are in the “open” state.

  In addition, during the charging current ON period of 1.1 seconds, duty control of the charging current is performed so that an appropriate charging current flows through each of the plurality of batteries. In the present embodiment, the charging current has two charging current peak values, and duty control is performed on the two charging current peak values to form three charging current average values, and each battery according to the charging progress state. An appropriate charging current is made to flow every time. FIG. 4 shows a configuration of the first charging current, FIG. 5 shows a configuration of the second charging current, and FIG. 6 shows a charging current waveform in the case of the configuration of the third charging current.

  In FIG. 4, the average value of the first charging current is 7.2 A. This 7.2 A is configured by controlling the charging current peak value 7.8 A to a duty ratio of 92%. In FIG. 5, the average value of the second charging current is 2.3A, but this 2.3A is a means for controlling the charging current peak value 7.8A to 29%, and 2.5A to 92%. It comprises two types of means for duty control. Also in FIG. 6, the average value of the third charging current is 1.2 A, but this 1.2 A is a means for duty-controlling the charging current peak value 7.8 A to 15%, and 2.5 A is 48%. It is composed of two types of means for duty control.

  FIG. 7 shows the transition of the charging current average value in an example in which two batteries are charged using the above three charging current average values. The transition of the charging current average value of the battery B1 having a remaining capacity of 0% due to discharge in the upper stage and the transition of the charging current average value of the battery B2 having a remaining capacity of about 30% in the lower stage are shown. In the period A after the start of charging, the charging current average value 7.2A flows to both the battery B1 and the battery B2. Next, charging proceeds, the charge control unit detects the first stage of the battery B2, only the charging current of the battery B2 is switched to the average value 2.3A, and the average charging current value of the batteries B1 and B2 is It becomes a different period B. FIG. 8 shows a charging current waveform in which the duty control is performed in this period B. During the period B-1, the charging current peak value 7.8A flows for both the batteries B1 and B2, and the circuit connection is DC / DC converter → SW1 → B1 → SW2 → B2 → SW7 → SW8. Next, in the period B-2, SW2 is “open”, SW6 is “closed”, the circuit connection is DC / DC converter → SW1 → B1 → SW6 → SW7 → SW8, and the charging current peak value 7.8A is Only the battery B1 flows. Period B-3 is the above-described battery voltage detection period. The DC / DC converter stops to stop charging, and the battery voltage is detected by the charge control unit. Based on the ratio of the charging current ON time and the OFF time from the period B-1 to the period B-3, as described above, the charging current peak value 7.8A is duty controlled to 92% for the battery B1, thereby charging current. An average value of 7.2A is obtained, and for battery B2, a charge current average value of 2.3A is obtained by duty-controlling the charge current peak value of 7.8A to 29%.

  Next, when charging progresses and the charging current of the battery B1 is also switched, the period shifts to a period C in FIG. In period C, the charging current peak value is changed to 2.5 A, and the charging current average value 2.3 A is obtained by duty-controlling the charging current peak value 2.5 A to 92%. For the battery B2, the charging current average value in the period B and the period C is the same as 2.3A, but the configuration is the charging current peak value of 2.5A from the 29% duty ratio of the charging current peak value of 7.8A. The duty ratio is changed to 92%.

  In each subsequent period, the switching time of the switch element is similarly controlled so that an appropriate charging current average value flows in each battery. In addition, when the number of batteries increases to 3 or 4, similarly, by controlling the switching time of the switch element, an appropriate charging current can be supplied to each battery, and multiple batteries can be charged. It is what.

  In order to inform the user of the progress of charging, for example, using LEDs 1 to 3 shown in FIG. 3, when LED 1 is lit red in the state where the first charging current is flowing and switched to the second charging current. LED1 is switched to green lighting, LED2 is lighted red, and so on, and when charging is completed, LEDs 1 to 3 may all be green.

  The charger of the present invention is a useful technique for rapid charging of a nickel metal hydride storage battery or the like. In particular, with a recent increase in capacity, even a battery that cannot accept a large current as an overcharge performance of the battery can be rapidly charged without causing performance deterioration.

  In addition, charging capacity is displayed along with stepwise current switching during charging, and a plurality of batteries are connected in series by switching elements, and charging current is duty controlled to charge multiple batteries. The user-friendliness is remarkably improved.

The figure which shows transition of the battery voltage and charging current by one embodiment of this invention The figure which shows transition of the battery voltage and charging current by the form of a prior art example The circuit block diagram of one Example of this invention State diagram of the first charging current Second charging current state diagram State diagram of the third charging current Figure showing the transition of the average charging current The figure which shows the charging current waveform in the period B

Explanation of symbols

VB1 Battery voltage for detecting the end of the first charging current VB2 Battery voltage for detecting the end of the second charging current Vb Battery voltage I Charging current SW1 to SW4 Switch elements SW5 to SW8 for connecting batteries in series SW9 Switch element constituting battery voltage detection circuit R1 Current detection resistor LED1-LED3 Light-emitting diode for charging state display

Claims (4)

Rechargeable battery charger has the function of supplying multiple levels of charging current to the battery, and the charging current can be reduced below the allowable current as the battery's allowable charging current decreases with the progress of charging. The battery charger is characterized in that it has been reduced to a faster charge. When the first to Nth charging currents have a function of switching from the first charging current to the Nth charging current step by step, the first to Nth charging currents are switched by changing the battery voltage during the charging current off period. On the other hand, it is detected that the battery voltage VB1 reaches the battery voltage VB (N-1) from the preset battery voltage VB1, and during the charging period with the Nth charging current, the battery voltage in the charging current off period is at the end of charging. The charger according to claim 1, which has a function of detecting a voltage drop after reaching a peak and completing charging. The charger according to claim 1 or 2, wherein a charge capacity display is performed in accordance with switching of a stepwise charge current during charging, and a charge completion display is performed in accordance with detection of charge completion. A switch element for connecting a plurality of batteries in series and a bypass switch element connected in parallel with each battery are provided, and a plurality of batteries can be charged by duty-controlling the charging current. The charger according to any one of claims 1 to 3.

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