JP5568898B2 - Lithium-ion battery charge control method - Google Patents

Description

  The present invention relates to a charge control method for a lithium ion battery that can be charged from an external power source and charged from a motor while the vehicle is running.

  Voltage detection accuracy is important for charging lithium-ion batteries, so the output voltage of the charger is converted to a constant DC voltage, and a structure that converts from a DC sine wave (pulsating flow) is required. (For example, see Patent Document 1).

Japanese Patent Laid-Open No. 10-295076 (see FIG. 1)

  In the charger disclosed in FIG. 1 of Patent Document 1, it is conceivable to further reduce the size without using the backflow preventing diode D5 and the capacitor C4. In this case, the terminal voltage of the lithium ion battery is also a sine wave. It becomes. Therefore, if it is attempted to control charging when the terminal voltage of the lithium ion battery is equal to or higher than a predetermined voltage, there is a problem that charging is stopped before full charging and the battery cannot be fully charged.

  The present invention has been made in view of such a conventional problem, and an object thereof is to provide a charge control method for a lithium ion battery that correctly detects a median voltage during charging from an external power source. .

  A feature of the present invention is a lithium ion battery mounted on a vehicle, and in the charge control method for a lithium ion battery that can be charged from an external power source and charged from a motor running on the vehicle, the external power source is a charger. It is determined whether or not the battery is connected in a chargeable state, and when the external power supply is connected to the charger in a chargeable state, the frequency of the external power supply is detected, and according to the detected frequency Determining the sampling rate of the charging voltage applied to the lithium ion battery, measuring the charging voltage according to the determined sampling rate, and calculating the average value of the measured charging voltages at the center of the voltage when charging from an external power source. As a value.

  According to the feature of the present invention, it is possible to correctly detect the median value of the output voltage of the charger in which the output voltage fluctuates in a sine wave, so that charging is stopped before the full charge is reached. It can be suppressed and the battery can be fully charged. That is, by using the median value of the output voltage, it is possible to prevent the charging of the lithium ion battery from being terminated at an early stage at the maximum voltage value. Further, it is possible to use an inexpensive charger while preventing adverse effects on the lithium ion battery.

In the feature of the present invention, whether or not charging from the external power source is performed by detecting whether or not the external power source is connected to the charger in a chargeable state, or charging from the motor while the vehicle is running is performed. The charging voltage applied to the lithium ion battery may be detected by a method that is different depending on whether charging is performed from an external power source or charging from a motor while the vehicle is running. Thereby, the change of the charging voltage by the difference in the voltage waveform input into a lithium ion battery can be monitored correctly.

  As described above, according to the present invention, it is possible to provide a charging control method for a lithium ion battery that correctly detects the median voltage during charging from an external power supply.

It is a flowchart which shows an example of the method of calculating the median value of an output waveform about the DC voltage of the sine wave waveform output from the charger shown in FIG. It is a circuit diagram which shows an example of the charger used when implementing the charge control method of the lithium ion battery concerning embodiment of this invention. It is a graph which shows the example of the reading timing with respect to the charging voltage which consists of a sine wave waveform.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are denoted by the same reference numerals.

  With reference to FIG. 2, an example of the charger used when implementing the charge control method of the lithium ion battery concerning embodiment of this invention is demonstrated. A rectifier circuit 12 using a diode bridge composed of four diodes D1 to D4 is connected to an output terminal of an external power source 11 composed of an AC power source. Both electrodes of the smoothing capacitor C are connected to the output terminal of the rectifier circuit 12. Further, an inductance Lr and semiconductor switch elements Q1 to Q4 are connected to the output terminal of the rectifier circuit 12. Specifically, the element Q1 and the element Q2 are connected in series, the element Q3 and the element Q4 are connected in series, and these two sets are connected in parallel.

  A primary winding L1 of the transformer T is connected between the emitter electrode of the element Q1 and the collector electrode of the element Q4. By connecting the lithium ion battery to both terminals of the secondary winding L2 of the transformer T, the lithium ion battery is connected to the charger in a chargeable state. Although not shown, the charger includes a controller for controlling on / off of each of the semiconductor switch elements Q1 to Q4.

  The charger shown in FIG. 2 does not have the function of converting the AC voltage input from the external power supply 11 into a constant DC voltage and outputting it, and therefore outputs from both terminals of the secondary winding L2 of the transformer T. The applied voltage (output voltage) is a sine wave waveform (pulsating current) as shown in FIG.

  The charge control method for a lithium ion battery according to the embodiment of the present invention is a method of calculating the median value of the output waveform for the DC voltage of the sine waveform output from the charger shown in FIG.

  With reference to FIG. 1, an example of a method for calculating the median value of the output waveform for the DC voltage of the sinusoidal waveform output from the charger shown in FIG. 2 will be described. Here, it demonstrates as operation | movement of the controller (not shown) with which a charger is provided.

(A) First, in step S01, it is determined whether or not the external power supply 11 is connected to the charger in a state where it can be charged, that is, whether or not the external power supply 11 is connected to the charger in the state shown in FIG. . When it is detected that the external power source 11 is connected to the charger in a state where it can be charged, the process proceeds to step S02, and the detection timing of the DC voltage of the sine wave waveform output from the charger is switched. The detection timing includes at least a detection timing at the time of charging from the external power source 11 and a detection timing at the time of charging from the motor while the vehicle is running.
When confirming the connection of the external power source 11 is 01, switching to the detection timing at the time of charging from the external power source 11.

  (B) Proceeding to step S03, the frequency of the external power source 11 comprising an AC power source is detected. Proceeding to step S05, the sampling rate of the charging voltage applied to the lithium ion battery, that is, the output voltage from the charger, is determined according to the detected frequency. Here, a frequency 2N times the frequency of the external power supply 11 is set as the sampling rate. Then, it progresses to S09 stage and starts charge to a lithium ion battery.

  (C) After starting charging, the process proceeds to step S11, and the charging voltage is measured in accordance with a predetermined sampling rate. Specifically, the instantaneous value of the charging voltage is read at a frequency 2N times that of the external power supply 11. After performing the predetermined number of measurements, the process proceeds to step S13, and an average value of the measured charging voltages is obtained as a median voltage value when charging from the external power source 11.

  (D) Proceed to step S15, compare the calculated median voltage with the end-of-charge voltage, proceed to step S17, terminate the charging if the obtained median voltage reaches the end-of-charge voltage, and if necessary Change the end-of-charge voltage.

  FIG. 3 is a graph showing an example of the reading timing with respect to the charging voltage having a sine wave waveform. The timings T1, T3, T4, and T6 indicated by solid lines among the vertical lines in FIG. 3 are N = 2, that is, the reading timing when reading at a frequency (4f) that is four times the frequency (f) of the external power supply 11, The timings T2 and T5 indicated by the broken lines are N = 1, that is, the reading timing when reading is performed at a frequency (2f) twice the frequency (f) of the external power supply 11.

  Since the read timing is determined according to the frequency of the charging voltage, the average value can be accurately obtained as the median value of the charging voltage even with a small number of samplings.

  The above-described charging voltage reading timing is set only when charging by the external power supply 11. Although the detection timing at the time of charging from the motor while the vehicle is running is not fixed, it is desirable to make the reading interval narrower in detail than when charging by the external power source 11, that is, the reading interval.

  As described above, according to the embodiment of the present invention, the following effects can be obtained.

  It is determined whether the external power source 11 is connected to the charger of FIG. 2 in a chargeable state (S01), and when the external power source 11 is connected to the charger in a chargeable state, the external power source 11 The frequency is detected (S03), the sampling rate of the charging voltage applied to the lithium ion battery is determined according to the detected frequency (S05), the charging voltage is measured according to the determined sampling rate (S11), and measured. The average value of the plurality of charging voltages is obtained as the median voltage value when charging from the external power supply 11 (S13).

  As a result, since the median value of the output voltage of the charger whose output voltage fluctuates in a sine wave can be detected correctly, it is possible to suppress the charging from being stopped before the battery is fully charged. Can be fully charged. That is, by using the median value of the output voltage, it is possible to prevent the charging of the lithium ion battery from being terminated at an early stage at the maximum voltage value. Further, it is possible to use an inexpensive charger while preventing adverse effects on the lithium ion battery.

By detecting whether or not the external power supply 11 is connected to the charger in a chargeable state, charging from the external power supply 11 is performed, or charging from a motor that is running on the vehicle is performed. The charging voltage applied to the lithium ion battery is detected by a method different between charging from the external power source 11 and charging from the motor while the vehicle is running (S02). Thereby, the change of the charging voltage by the difference in the voltage waveform input into a lithium ion battery can be monitored correctly.

  As described above, the present invention has been described by way of one embodiment, but it should not be understood that the discussion and drawings that form part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

DESCRIPTION OF SYMBOLS 11 External power supply 12 Rectifier circuit C Smoothing capacitor D1-D4 Diode T Transformer Q1-Q4 Semiconductor switch element L1 Primary side winding L2 Secondary side winding

Claims (2)

In a lithium-ion battery mounted on a vehicle, the charging control method for a lithium-ion battery capable of charging from an external power source and charging from a motor running on the vehicle,
And determining whether the external power source is connected with the chargeable state to the charger,
When the external power supply is connected to a charger in a chargeable state, the frequency of the external power supply is detected,
Depending on the detected frequency, set to the frequency of 2N times the frequency of the sampling rate of the external power supply of the charging voltage applied to the lithium ion battery (where N is an integer),
The charging voltage determined in accordance with the sampling rate defined,
The average value of the measured plurality of the charging voltage, the charging control method for a lithium ion battery and finding a voltage median during charging from the external power supply. By detecting whether the external power source is connected with a rechargeable state to the charger,
Whether charging from the external power supply is being performed, it is determined whether the charging from the motor while the vehicle is traveling is being performed,
According to the detection timing at the time of charging from the motor running the vehicle or charging from the external power supply, the charging voltage applied to the lithium ion battery is detected,
The charging control method for a lithium ion battery according to claim 1 , wherein the detection timing at the time of charging from the motor while the vehicle is running is shorter than the detection timing at the time of charging from the external power source .

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