JP2577656B2 - Rechargeable battery charging method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a secondary battery charging method capable of performing more accurate operations.

[Conventional technology]

Secondary batteries, especially Ni-Cd storage batteries, are often rapidly charged so that they can be used even in an emergency. Even for quick charging, it is necessary to perform constant current charging so as not to damage the battery and to perform control to prevent overcharging. Conventional charge control methods include a -ΔV charge detection method, a voltage detection method, a temperature control method, and a timer method.

The -ΔV charge detection method is often applied to Ni-Cd storage batteries. Since the Ni electrode generates heat when charging is completed, it is detected that the voltage rises to a certain value and then drops by ΔV, and charging is completed at that time. There is a feature that the charge amount can be secured.
FIG. 4 is a block diagram showing a conventional battery charging circuit configuration of the -ΔV charge detection system. In FIG. 4, 1 is a battery, 2 is a charging power supply, 3 is a charge detection switch, 4 is a pulse generator, 5 and 6 are gate circuits, 7 is a voltage comparison circuit, and 8 is a peak value holding circuit. . When charging the battery 1 from the charging power supply 2, the charge detection switch 3 is initially closed to start charging. When charging proceeds according to the battery 1 and the charging current, the gate 5 is closed by a pulse from the pulse generator 4 and the battery voltage at that time is stored in the peak value holding circuit 8.
Hold with. The peak value holding circuit 8 is a known circuit using a diode, a resistance element, and a capacitor, and is a voltage at which the voltage across the capacitor is held. The gate 5
The gate 6 is closed after a lapse of a predetermined time from when the voltage is held by closing the gate. At this time, since the gate 5 is open, the value holding the previous battery voltage and the new voltage are compared by the comparison circuit 7. FIG. 5 shows a temporal change in the voltage of the battery 1 and the like according to FIG. FIG. When charging is started, the change in the voltage across the battery is large. Therefore, the voltage change value per unit time (the unit time is, for example, 1 minute) is extremely large, but the change in the battery voltage will be soon. As it becomes smaller, the voltage change coefficient becomes an extremely small value. Next, charging proceeds. For example, after a lapse of 60 minutes, a change in the battery voltage per unit time increases again. Therefore, the voltage values before and after the time per unit time are compared in the comparison circuit 7 in FIG. When the voltage value at the later time is measured to be larger than the voltage value at the previous time, it is determined that the battery is being charged. As shown in FIG. 5, when the charging is completed, the subsequent voltage value decreases. Therefore, when compared in the comparison circuit 7, the voltage value at a later time is smaller. Therefore, when detecting that the decrease value has changed more than the predetermined value ΔV, the comparison circuit 7 generates an output and controls the charge detection switch 3 to be turned off.
When the switch 3 is turned off, the charging of the battery 1 is completed. ΔV is set in advance based on the battery 1 and the charging current. At this time, the decrease in the battery voltage is based on the generation of heat in the electrodes as described above.

[Problems to be solved by the invention]

In the conventional battery charging circuit shown in FIG. 4, the peak value holding circuit 8 causes the held potential to leak as the capacitor charge leaks over time, causing a potential drop. The other potential to be compared by the comparison circuit 7 is not necessarily the potential before a predetermined time. For this reason, an error occurs in the detection of -ΔV, and there is a disadvantage that switching to trickle charging is not performed accurately.

[Means for solving the problem]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks, accurately maintain the maximum voltage value at the time of completion of charging of a secondary battery by a digital circuit, and accurately switch to trickle charging with high precision timing. An object of the present invention is to provide a secondary battery charging method that can be obtained.

[Means for solving the problem]

A power supply for quick charging of the secondary battery is provided.After the start of the quick charging, the voltage at both ends of the battery is measured, the peak value detection circuit detects the maximum voltage, and then the measured voltage decreases. In the charging method of the secondary battery, which detects that the charging is completed when the decrease value becomes equal to or less than the predetermined value, the peak value detection circuit is constituted by a digital circuit, and the digital circuit comprises (a) one input terminal. Apply the battery voltage during charging to the terminal,
A voltage obtained by dividing the voltage from the constant voltage power supply by resistance and the output voltage of the D / A converter are applied to the other input terminal, and the applied voltages of both input terminals are compared.
A voltage comparison circuit and (b) a clock pulse generator, a pulse counter, and a D / A converter for obtaining an analog value corresponding to the output of the first voltage comparison circuit; and (c) one input terminal is the first voltage comparison circuit. Is connected to one input terminal of the circuit, and applies the output of the D / A converter to the other input terminal by resistance division,
It is characterized by comprising a second voltage comparison circuit that compares the applied voltages of both input terminals and detects the end of charging based on the output of the comparison result.

(Operation)

The circuit for switching and controlling the quick charge and the torcle charge is initially controlled to perform the quick charge. Therefore, initially, the secondary battery is rapidly charged from the charging power supply. When the charging of the battery is substantially completed, the voltage at both ends of the battery is detected and measured by the peak value detecting circuit constituted by the digital circuit having the above configuration. That is, the voltage of the battery being charged is input to one input terminal of the first voltage comparison circuit, the voltage obtained by dividing the voltage from the constant voltage power supply to the other input terminal, and the D / A converter output voltage described later. Is applied for comparison.

For example, when the voltage of one input terminal is higher than the voltage of the other input terminal, the first voltage comparison circuit outputs a signal “H”. If the state is continuing, it is determined that the battery is being charged. The output value of the D / A converter also becomes a large value as an analog value.

One input terminal of the second voltage comparison circuit receives the voltage of one input terminal of the first voltage comparison circuit, and the other input terminal receives the voltage of the other input terminal.
D / A converter output voltage, that is, dV from the voltage of one input terminal
Low voltage is applied. The charging voltage of the battery is applied to one input terminal of each voltage comparison circuit, and when the rapid charging is completed, the voltage drops by dV due to the charging characteristics. Therefore, the voltage of the input terminal of the second voltage comparison circuit may have the same value. When the value becomes the same, the output of the second voltage comparison circuit determines that the charging is completed, and switches to trickle charging as necessary. At this time dV
Is selected to be a predetermined value that is not related to the battery voltage, so that the end of quick charge can be accurately determined.

〔Example〕

FIG. 1 is an overall view showing an embodiment of a charging method for a secondary battery according to the present invention. In FIG. 1, 1 is a secondary battery to be charged, 2 is a power supply for charging, 10 is a quick charge / trickle charge switching control circuit, 11 is a digital / peak value holding circuit / comparison circuit, 12 is a constant voltage source, 13 indicates a control output terminal. The operation is the same as that described in the section of [Action].

Next, FIG. 2 is a block diagram showing in detail the digital holding circuit and comparison circuit 11 in FIG. 1 as an embodiment of the present invention. That is, in FIG. 2, 1 is a secondary battery to be charged, 2 is a charging power source, 10 is a rapid charging / trickle charge switching control circuit, 12 is a constant voltage source, and 13 is a digital / peak holding circuit / comparison. Output terminal of the circuit 11, 14 is a Zener diode, 15 to 19 are resistance elements, 20 is a first voltage comparison circuit, 21 is a second voltage comparison circuit, 22 is a NAND circuit, 23 is a binary counter, and 24 is D / A conversion , 25 is a buffer amplifier, and 26 is a clock generation source.

The non-inverting input terminal (+) of the first voltage comparison circuit 20 has
The voltage of the battery 1 is applied with its level shifted by the zener diode 14. The voltage of the constant voltage source 12 is applied to the inverting input terminal (-) of the first voltage comparison circuit 20.
And the value divided by the ratio of the resistance elements 17 to 19 and the D / A converter 24
Is output. Therefore, if the input terminal (+) is higher than the input terminal (-), the output of the first voltage comparison circuit 20 becomes "H". Its output is one input of the NAND circuit 22, and the other input of the NAND circuit 22 is the clock generation source.
The clock from 26. Therefore, the output of the NAND circuit 22 is generated in response to the clock becoming “H”, and the binary counter 23 performs frequency division counting. The count value is converted by the D / A converter 24, amplified as an analog output by the buffer amplifier 25, and the output is applied to the connection point between the resistance elements 17 and 18.

If the voltage at the inverting input terminal (-) of the first voltage comparing circuit 20 becomes higher than the voltage (corresponding to the battery voltage) of the non-inverting input terminal (+) of the first voltage comparing circuit 20, the first voltage The output of the comparison circuit 20 becomes “L”. Since this operation keeps the output value of the D / A converter 24 constant, the first voltage comparison circuit
The voltage of the inverting input terminal (−) of 20 indicates that the voltage maximum value of the rechargeable battery is maintained.

The resistance elements 17 and 18 operate so as to make the difference between the voltage of the inverting input terminal (−) of the first voltage comparing circuit 20 and the voltage of the inverting input terminal (−) of the second voltage comparing circuit 21 constant. ing. (The operation of the constant value output of the D / A converter 24 is involved). Therefore, the voltage of the inverting input terminal (−) of the second voltage comparison circuit 21 maintains a voltage lower than the maximum value of the battery voltage by a certain voltage. The voltage difference is expressed as “dV”. Since it is considered to correspond to -ΔV for detecting the end of the rapid charging, the same expression is used. (This voltage value can be called the difference value of the comparison voltage for judgment after the end of charging).

Next, a value obtained by shifting the charging voltage of the battery 1 by the Zener diode 14 is input to the non-inverting input terminal (+) of the second voltage comparison circuit 21. The voltage at the inverting input terminal (-) is maintained at a voltage value dV lower than the maximum charging value of the battery 1 as described above. Therefore, when the voltage of the battery 1 reaches the end of the quick charge, the voltage of the non-inverting input terminal (+) becomes higher than the voltage of the inverting input terminal (-). Until then, the output of the second voltage comparison circuit was "H". However, when the rapid filling was completed, the voltage of the battery dropped, and when the voltage dropped dV below the maximum charging voltage, the second voltage comparison circuit 21 Changes to “L”.

FIG. 3 is a diagram showing a voltage change of the battery and a terminal voltage change in the circuit. A curve A indicates a voltage change of the battery, that is, a voltage change between the non-inverting input terminal (+) of the first voltage comparing circuit 20 and the non-inverting input terminal (+) of the second voltage comparing circuit 21.

A curve B indicates a voltage change at the inverting input terminal (-) of each of the second low voltage circuits 21. The output of the second voltage comparison circuit 21 is "H" when the curve A has a higher voltage than the curve B, and the state is reversed after the time Tc, so that the output changes to "L". Therefore, when the potential of the output terminal 13 changes from “H” to “L”,
The control circuit 10 switches from quick charge to trickle charge.

In FIG. 2, a clock source 26, a NAND circuit 22, and a binary counter 23 perform digital operations, and the D / A converter 2
The maximum value of the battery being charged is accurately maintained within the range of the quantization error based on the resolution of 4.

Further, after the battery voltage is held, the voltage change dV at the terminal (−) until “L” is output from the second voltage comparison circuit 21 is dV = ｛1 regardless of the voltage of the battery being charged. / (1 + k)｝ Vr ｛k / (1 + k)｝ Ve. Here, k = (resistance 16 · resistance 17) = (resistance 19 ·
Resistance 18) Vr = voltage of constant voltage source 12 Ve = quantization error.

〔The invention's effect〕

As described above, according to the present invention, when the battery voltage reaches the maximum value for the end of charging, the value is held by the digital circuit, so that the held voltage is accurate and the comparison for judgment after the end of charging is performed. The difference between the voltage values can be set to a value irrelevant to the voltage of the rechargeable battery, and the value is also accurate, so that switching to trickle charge can be performed properly if necessary after the end of quick charge. The effect that can be done.

[Brief description of the drawings]

FIG. 1 is an overall view showing an embodiment of a charging method for a secondary battery according to the present invention, FIG. 2 is a view showing a detailed configuration of the embodiment, FIG.
FIG. 4 is a diagram showing the voltage change in FIG. 2, FIG. 4 is a diagram showing the configuration of a conventional battery charging circuit, and FIG. 5 is a diagram showing the voltage change in FIG. 1 ... Battery 2 ... Charging power supply 10 ... Quick charge / trickle charge switching control circuit 11 ... Digital peak value holding circuit and comparison circuit 12 ... Constant voltage source 13 ... Control output terminal 20 ... 1st voltage comparison circuit, 21 ... 2nd voltage comparison circuit

Claims (1)

(57) [Claims] A power supply for rapidly charging a secondary battery is provided. After the start of the rapid charging, the voltage across the battery is measured, and a peak value detection circuit detects a maximum voltage value. In a charging method for a secondary battery, which detects that charging has been completed when the measured voltage decreases to a predetermined value or less, the peak value detection circuit is constituted by a digital circuit, and the digital circuit includes ( A) Apply the voltage of the battery being charged to one input terminal, apply the resistance-divided voltage from the constant voltage power supply to the other input terminal, and apply the output voltage of the D / A converter to both input terminals. A first voltage comparison circuit that compares applied voltages and generates an output of the comparison result; and (b) a clock pulse generator, a pulse counter, and a D / D for obtaining an analog value corresponding to the output of the first voltage comparison circuit. A converter and (c) one input terminal are the first voltage The input of the D / A converter is connected to one input terminal of the comparator circuit and the other input terminal is divided by a resistor, and the applied voltage of both input terminals is compared. And a second voltage comparison circuit for detecting.