JPH06189465A - Charging apparatus - Google Patents

Abstract

PURPOSE:To make it possible to accurately measure the difference in voltage between input and output of a breaking switch and improve the accuracy of detecting the amount of charge. CONSTITUTION:This charging apparatus is controlled as follows: A secondary battery 9 is established. The charging apparatus charges the secondary battery 9 on a constant current when the voltage of the battery is below a specified value; the charger charges the secondary battery 9 on a constant voltage after its terminal voltage has reached the specified value. The charging apparatus is constituted as follows: The charging current to the secondary battery 9 is periodically broken by a switching element 8, and a first voltage V1, the voltage of the section precedent to the switching element 8, before or after the charging current breaking, and a second voltage V2, the voltage of the section on the secondary battery side subsequent to the switching element 8, after the charging current breaking, are detected. The charging apparatus is provided with a means 62 for detecting the difference DELTAV between the first voltage V1 and the second V2; and voltage shifting element ZD for shifting the first voltage V1 and the second V2. The element ZD for shifting voltage is provided with a constant-current circuit 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a secondary battery, and more particularly to a charging device capable of measuring the input-output voltage of a current cutoff switch with high accuracy.

[0002]

2. Description of the Related Art A general charging device of this type is used to charge a secondary battery 103 such as a lead secondary battery.
The constant current charging and the constant voltage charging shown in FIG. 11 are generally performed. 10 shows the relationship between the charging current and the output voltage (output characteristic of the charging device), and FIG. 11 shows the relationship between the charging voltage / current and the charging time (charging characteristic curve).

A charging device using such a charging system is
The configuration is as shown in FIG. This charging device interrupts the charging current by the switch element SE in a constant cycle or in an arbitrary cycle, and detects the voltage difference between the input and output of the switch element SE before and after the current interruption to detect the secondary battery 103.
It is designed to detect the amount of charge and full charge. This charging device uses an A / D converter 101 and a CPU 102.

As described above, in the charging device, the switch SE for cutting off the charging current is provided in order to detect and control / display the charging amount during charging and the end of charging, and the charging current is switched by the switch SE. The voltage is cut off, and the voltage difference or potential difference ΔV between the A1 point voltage and the A2 point voltage before (or after) the cutoff is detected. FIG. 13 shows an example of the charging curve of the secondary battery which is going to be charged in this way. In this charging curve example, it is shown that the charging voltage of the secondary battery changes from about 5V to 10V, for example.

[0005]

However, the voltage difference ΔV
The IC drive voltage of the A / D converter 101 for detecting A is 5V, and the voltage that can be input to the A / D converter 1 is 0V to 5V. Therefore, since the charging voltage of the secondary battery, which changes from about 5V to 10V, cannot be directly input to the A / D converter 101 as it is, the voltage shift is performed before the A / D converter 101.
Need to enter.

In the charging device shown in FIG. 12, the resistors 104 and 105 or the zener diodes 106 and 107 are used to shift the voltage. For example, the resistors 104 and 105 divide the voltage V1 at the point A1 and the voltage V2 at the point A2, respectively, and then
It is input to the / D converter 101.

However, in the voltage shift by the voltage dividing method, for example, the resistance values of the resistors 104 and 105 vary by plus or minus 5%.
The voltage V1 at the point and the voltage V2 at the point A2 are connected to the resistors 104 and 105.
When the input voltage difference ΔV for the A / D converter 101 is divided by, the variation will occur. Similarly, when the Zener diodes 106 and 107 are used instead of the resistors 104 and 105, the voltages V1 and V2 are changed to the Zener diode 10 due to the variation in the voltage of the Zener diodes 106 and 107.
When the voltage is divided by 6 and 107 to obtain the input voltage difference ΔV for the A / D converter 101, the voltage variation will occur.

Due to the occurrence of such variations, the voltage V
If there is a voltage difference between 1 and V2, the currents I1 and I2 become unbalanced, resulting in a different voltage shift amount. Therefore, the input-output voltage (voltage V
It is not possible to accurately measure the difference ΔV of the voltage between 1 and V2).

The present invention has been made to solve the above problems, and the present invention is directed to input / output of a current cutoff switch.
It is an object of the present invention to provide a charging device capable of measuring a voltage difference between outputs with high accuracy and improving detection accuracy of a charge amount.

[0010]

According to the present invention, a secondary battery is set, and the secondary battery is charged at a constant voltage or less with a constant current to obtain a terminal of the secondary battery. When the voltage rises to a predetermined voltage, it is controlled so that charging is performed at a constant voltage, and the switching element shuts off the charging current to the secondary battery in a certain cycle. The charging device is configured to detect a first voltage and a second voltage on the secondary battery side of the switch element after the charging current is cut off, and a voltage difference between the first voltage and the second voltage is detected. This is achieved by a charging device in which the detecting means for detecting is provided with a voltage shifting element for shifting the first voltage and the second voltage, and a constant current circuit is provided for the voltage shifting element. Preferably, the voltage shifting element is a resistor. Also, preferably,
The voltage shifting element is a Zener diode.

[0011]

According to the above construction, since the constant current circuit is provided,
Detecting means for detecting a voltage difference between the first voltage and the second voltage (for example, in the embodiment, the A / D converter 62 and the CPU
63), when the voltage applied to the detecting means by the voltage shift element (for example, the Zener diode ZD in the embodiment) is applied to the first voltage and the second voltage, the voltage shift element is applied. A constant current can be passed through. Therefore, the voltage difference between the first voltage and the second voltage is correctly measured without being affected by the electrical variation of the voltage shifting element and the other elements connected to the detecting means. be able to. In the following description, and in the illustrated embodiment, the first voltage detection before the switching element will be described as before the cutoff of the charging current.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The examples described below are preferred specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows a preferred embodiment 1 of the charging device of the present invention, which is an example in which a so-called flyback converter system is adopted. In the first embodiment, the first voltage detection in the stage before the switch element will be mainly described as before the cutoff of the charging current. In FIG. 1, reference numeral 1 denotes an AC connector, which is connected to an AC power source (for example, AC 100V). AC
The AC power source (AC input) from the connector 1 is supplied to the rectification / smoothing circuit 3 via the input filter 2, where it is rectified (for example, pulsating current), smoothed, and then supplied to the primary side of the transformer 4. It is switched by the power MOSFET 5.

The power MOSFET (active element) 5 performs a switching operation by being driven by applying a PWM pulse from a PWM (Pulse Width Modulation) control circuit 6 to its gate. This makes the transformer 4
The secondary output of is controlled.

The primary side of the transformer 4 is a power MOSFET.
By being switched by T5, a predetermined output voltage is generated on the secondary side of the transformer 4, the secondary side output is supplied to the rectifying / smoothing circuit 7, rectified and smoothed to direct current, and then the switch unit 8 Through a secondary battery 9 such as a lead battery or a lithium battery.

A charging current detection resistor 10 is inserted on the negative electrode side of the secondary battery 9, and the potential at this point is input to the output control circuit 11 as an output current signal. Further, the voltage at the A1 point on the input side of the switch unit 8 (hereinafter referred to as the A1 point voltage)
Is input to one terminal of the output control circuit 11 and the selection switch 61 as an output voltage signal.

The selection switch 61 alternately picks up the A1 point voltage on the input side of the switch section 8 and the A2 point voltage on the output side of the switch section 8 and selectively outputs it to the voltage detection circuit 12.

Power supply voltage detection circuit (voltage detection means) 12
Is for controlling the charging control circuit 13 by detecting the potential coming from the selection switch 61 to determine the end of charging. The charge control circuit 13 controls the operation of the switch unit 8 in accordance with the state of charge of the secondary battery 9, has an AC / DC converter and a digital calculator (not shown), and cuts off the charge current. In the vicinity of the switch unit 8 (point A1) and the secondary battery 9 than the switch unit 8 after this interruption.
It has a comparison means for comparing the potential difference or the voltage difference with the voltage at the side position (point A2) with the reference voltage value.

Charging is controlled according to the comparison result of the comparing means. Specifically, for example, when the secondary battery 9 is not attached (non-charging state), the switch section 8 for charging is turned off. Alternatively, the switch unit 8 is turned on / off with a pulse having a predetermined cycle to supply a charging current to the secondary battery 9.
Then, the control of the charge state by the charge control circuit 13 is displayed on the display unit 14.

The output control circuit (output control means) 11 is mainly composed of an error lamp or the like, compares the rectified and smoothed secondary side output voltage and output current with a reference value, and outputs the error output to a photocoupler. PW via circuit 15
Output to the M control circuit 6. As a result, the rectified and smoothed secondary side output information is fed back to the primary side of the transformer 4 for PWM control (current feedback), and the constant voltage / constant current charging output characteristics shown in FIG. 10 are obtained. To be

According to such charge output characteristics, for example, a state in which the uncharged secondary battery 9 is mounted in the charging device is point a in the constant current region of the charge output characteristics shown in FIG. When the terminal voltage of the secondary battery 9 rises, it then moves to point b, the charging current gradually decreases, and the battery is fully charged at point c.

Next, FIG. 2 shows a detailed configuration of a circuit portion including the battery voltage detection circuit 12 and the charge control circuit 13. In this example, the A / D converter 62 and the CPU 63
Is an example using. In FIG. 2, an A1 point voltage V1 which is a voltage on the input side of the switch section 8 and an A2 point voltage V2 which is a voltage on the output side of the switch section 8 are the selection switch 61.
Are alternately switched by and input to the A / D converter 62 via the Zener diode ZD for voltage shift, and A / D converted. After this conversion, CPU
It is output to 63. The CPU 63 controls ON / OFF of the switch unit 8 at a constant cycle or an arbitrary cycle according to a stored program (not shown) to turn on / off the charging current. Further, the content of the charging control by the CPU 63 is displayed outside by the charging display unit 23.

The internal voltage of the secondary battery 9 is represented by Vc, the internal resistance is represented by Rb, and the contact resistance of each terminal is represented by Ra. Further, the AC power from the AC connector 1 is input to rectify and smooth the power, and the power MOSFET is provided on the primary side of the transformer 4.
The series of parts that switch by 5 to generate a charging output on the secondary side is represented in FIG. 2 as a charger 30.

Next, FIG. 3 shows a characteristic part of the present invention, and shows a circuit including the voltage detection circuit 29, the secondary battery 9, and the charger 30. This detection circuit 2
Reference numeral 9 is a Zener diode ZD for voltage shift, a constant current circuit 100, a switch 8, an A / D converter 62,
And CPU 63. The secondary battery 9 is shown in a simplified manner in FIG. The detection circuit 29, which is also referred to as the measurement circuit in FIG. 3, shifts the voltage of the secondary battery 9 from 5 V to 10 V into the input voltage range of the A / D converter 62, and also has A1 point voltage V1 and A2 point. The voltage difference ΔV between the voltages V2 can be detected with high accuracy.

In FIG. 3, the selection switch 61 includes a Zener diode ZD for voltage shift and a constant current circuit 1.
00 is connected. Between the Zener diode ZD and the constant current circuit 100, A /
The D converter 62 is connected. This constant current circuit 1
00 has a resistor 200 and a current source 230.

The Zener diode ZD is
Shift the voltage to at least 5V (drop) A1
The voltage difference ΔV between the point voltage V1 and the A2 point voltage V2 is
Direct input to A / D converter 62 as the amount of change and CP
It can be detected by U63. Further, the constant current circuit 100 is added so that the current value flowing through the Zener diode ZD is always a constant current. That is, FIG. 4 shows the static characteristics of the Zener diode ZD. To make the zener voltages Vz1 and Vz2 when the Zener diode ZD is connected to the A1 point side and to the A2 point side constant, the constant currents Iz1 and Iz2 are passed as zener currents. It is clear that the voltage should be shifted.

The voltage difference ΔV between the voltage V1 at the point A1 and the voltage V2 at the point A2 handles a very small voltage such as several tens of mV. Moreover, in consideration of the discharge current from the secondary battery 9, the current flowing through the Zener diode ZD is made small and set to a minute current value.

Description of Operation Next, the operation of the above configuration will be described. As shown in FIG. 1, when the secondary battery 9 is attached to the charging device of this embodiment and AC input is performed, the charging control circuit 13 controls the switch unit 8 to turn on / off, and the charging current is supplied to the secondary battery 9. It is supplied and charging is started. Then, the secondary side output voltage and the output current are compared with the reference value during the charging process. As a result, the error output is output to the PWM control circuit 6 via the photo coupler circuit 15. As a result, the rectified and smoothed secondary side output information is fed back to the primary side of the transformer 4, current feedback control is performed, and the secondary battery 9 is charged under the above-described constant voltage and constant current charging characteristics.
Is charged.

FIG. 5 is a flow chart showing a charge control program executed by the CPU 63 when the secondary battery 9 is rapidly charged. When the charging is started, the rapid charging is started in step S1. this is,
This means that the charging control circuit 13 controls the switch unit 8 to be turned on / off so that the charging current is supplied to the secondary battery 9 to start charging.

Next, in step S2, a CC timer for counting the charging time is started. As a result, the elapsed time from the start of charging is counted. Next, in step S3, it is determined whether or not the CC timer has counted a certain period of time and ended (timed up). If not ended, the process remains in step S3, and when ended, the process proceeds to step S4.

Next, in step S21, the charge control circuit 1
3 switches the selection switch 61 of FIG. 3 to the input side of the switch section 8 to measure the A1 point voltage V1. Then, in step S22, the quick charge is turned off. That is, after the switch section 8 is turned off, next, in step S23, the selection switch 61 is switched to the output side of the switch section 8 to measure the A2 point voltage V2. Then, in step S24, the voltage difference ΔV on the input / output side of the switch unit 8 is set as the difference between the A1 point voltage V1 and the A2 point voltage V2, and the following equation 1
Ask in.

[0032]

[Equation 1]

After that, the process proceeds to step S8, and the voltage difference ΔV
Set voltage value (data V) stored in the CPU 63
Compared with the above, it is detected that the voltage difference ΔV is smaller than the data V. When the relation that the voltage difference ΔV is smaller than the data V is not established, the cutoff state of termination of charging is released, the process returns to step S1, the same processing is repeated, and the charging is restarted for a certain period of time. This period is counted by the timer setting of the CPU 63, the charging current is cut off again at the end of the timer, and the aforementioned voltage difference ΔV is measured again.

Then, when the relationship that the voltage difference ΔV is smaller than the data V is established, the process is performed as the charging end detection point or the full charge detection display, and the charging is ended. Here, consider the constant voltage charging period of the charging curve of the secondary battery 9 shown in FIG. The voltage at the A1 point before the interruption (the terminal voltage of the secondary battery 9 being charged) is constantly controlled by the output control circuit 11 (FIG. 1) of the charger 30 shown in FIG. That is, it can be considered that a constant voltage value = reference voltage. Therefore, the measured value V1 of the voltage at the A1 point before the interruption is a fixed voltage value, and it can be set as the measured value V1 = K (fixed voltage value, for example, 10V), and the voltage difference ΔV can be expressed as a modification of Equation 2. it can.

[0035]

[Equation 2]

On the other hand, the voltage V2 at the A2 point during the interruption of the charging current
Is measuring the battery open-circuit voltage, so V
The voltage difference ΔV between 1 and V2 results in measurement of the battery open circuit voltage. Therefore, the battery open-circuit voltage Vc can be obtained as in Expression 3.

[0037]

[Equation 3]

FIG. 6 is a charging characteristic curve when the charging current is periodically interrupted. Further, FIG. 7 shows X in FIG.
It is the curve which expanded the part. As is clear from FIG. 6 and FIG. 7, it can be seen that the voltage difference ΔV caused by the interruption of the charging current decreases as the voltage of the secondary battery 9 increases. Therefore, by calculating the voltage difference ΔV and estimating the voltage of the secondary battery 9 from the value, it can be accurately determined whether or not the charging is completed.

Since the constant current circuit 100 of FIG. 3 is provided when detecting the voltage difference ΔV in this way, the current Iz flowing through the Zener diode ZD is the same as that of the selection switch 6.
Even if 1 is on the A1 point side or A2 point side, the same current can be obtained. That is, as mentioned above,
With the static characteristics of the Zener diode ZD shown in FIG. 4, the same Zener current Iz (Iz1 = Iz2 = Iz),
Therefore, the same Zener voltage Vz (Vz1 = Vz2 = V
z).

As described above, the voltage difference between the voltage at the A1 point and the voltage at the A2 point is irrespective of the variation of the parts which has been generated conventionally.
It is possible to perform the measurement that is not affected by the change in the voltage of the secondary battery 9. That is, it can be said that the charging device of this embodiment of the present invention is the detection circuit 29 in which the impedance of the voltage detection circuit is constant. by the way,
Even if a resistance element is used at this Zener diode ZD, a constant voltage drop amount can be obtained if the current value flowing through the resistance is made constant.

Next, another preferred second embodiment of the present invention will be described. The second embodiment will be described with reference to FIG. The second embodiment is shown in correspondence with the first embodiment shown in FIG. In the second embodiment, the voltage detection circuit 329
have. The detection circuit 329 includes a transistor T1,
Includes T2, diodes D1, D2 and resistor Z, as well as a constant current circuit 300.

A transistor T1 and a diode D1 are connected to the point A1. A transistor T2 and a diode D2 are connected to the point A2. The transistors T1 and T2 switch the voltage V1 at the A1 point and the voltage V2 at the A2 point, and replace the selection switch 61 of the first embodiment shown in FIG. Also, the diodes D1 and D2
Is a diode for preventing reverse breakdown voltage of these transistors T1 and T2.

The transistors T1 and T2 are surrounded by a dotted line 170. Also, the diode D
1 and D2 are also surrounded by a dotted line 180. These dotted lines 17
0 and 180 are arranged side by side on the same chip. Therefore, variations in the on-resistance of these elements can be almost ignored. The output sides of the diodes D1 and D2 are connected to a voltage shifting resistor Z. The resistor Z is provided with a constant current circuit 300. In addition,
The voltage shift resistor Z is a Zener diode ZD.
Can be changed.

This constant current circuit 300 includes a transistor T
s, a reference voltage E1, a resistor Rs, and a capacitor C1. The transistor Ts has a reference voltage E1 at its base.
Can be input to make the current Is flowing through the resistor Rs constant. The current Is flowing through the resistor Rs is as shown in Expression 4.

[0045]

[Equation 4]

Here, the Vbe voltage is the base-emitter voltage of the transistor Ts. By interposing this constant current circuit 300, the currents I1 and I2 flowing through the diodes D1 and D2 become equal currents. Next, the A1 point voltage V1 and the A2 point voltage V2 are switched, and the A / D converter 362
The timing of input to will be described with reference to FIG. First,
The voltage shift voltage V11 of the A1 point voltage V1 is the same as that of the equation (5).

[0047]

[Equation 5]

In addition, the voltage shift voltage V of the A2 point voltage V2
21 is the end of the equation 6.

[0049]

[Equation 6]

Here, as shown in FIG. 8, Vr is the voltage across the resistor Z, and Vce1 and Vce2 are
The respective collector-emitter voltages of the transistors T1 and T2 are shown. As described above, the transistor T
Since ON resistances in 1, T2 and the diodes D1 and D2 can be almost ignored, Vce1 = Vce
2, and the on-voltage of the diode D1 and the on-voltage of the diode D2 are equal.

On the other hand, due to the existence of the constant current circuit 300, the current I1 = the current I2, so that the voltage Vr of the voltage shifting resistor Z becomes a constant voltage. These conditions are given in Equation 5
By applying the above to Equation 6, Equations 7 and 8 relating to the voltage V11 and the voltage V21 are obtained. Here, the constant K is represented by Expression 9.

[0052]

[Equation 7]

[0053]

[Equation 8]

[0054]

[Equation 9]

That is, because of the presence of the constant current circuit 300, even if the A2 point voltage V2 (the voltage of the secondary battery 9) changes with respect to the A1 point voltage V1, the impedance of the detection circuit 329 is constant, Highly accurate A1 point voltage V1 and A2
The voltage difference ΔV between the point voltages V2 can be detected. By the way, the present invention is not limited to the above embodiment. For example, unlike the embodiment described above, as shown in FIG.
V1 voltage measurement after interruption of charging current (after quick charge off)
You may make it to. That is, the detection of the first V1 voltage at the stage before the switch element is performed after the cutoff of the charging current.

[0056]

As described above, according to the present invention, even if the voltage between the input and the output of the current cutoff switch is switched and the voltage difference is changed, the first voltage and the second voltage are changed. The impedance of a circuit (detection circuit also called a measurement circuit) including detection means for detecting a voltage difference can be made constant,
The voltage between the input and output of the current cutoff switch or the voltage difference can be measured with high accuracy, and the detection accuracy of the charge amount can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first preferred embodiment of a charging device of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a circuit portion including a battery voltage detection circuit and a charge control circuit in the first embodiment shown in FIG.

3 is a diagram showing a voltage difference detection circuit in the circuit shown in FIG.

FIG. 4 is a diagram showing voltage-current characteristics of a Zener diode.

FIG. 5 is a diagram for explaining a procedure of rapid charging of a secondary battery and measurement of V1 voltage and V2 voltage.

FIG. 6 is a diagram showing charging characteristics of a secondary battery.

FIG. 7 shows the X portion of FIG. 6 in detail.

FIG. 8 is a diagram showing a second preferred embodiment of the charging device of the present invention, corresponding to the first embodiment of FIG.

FIG. 9 is a diagram showing the operation timing of the detection circuit in the second embodiment of FIG. 9;

FIG. 10 is a graph showing the V different from the rapid charging of the secondary battery in the present invention
The figure for demonstrating the procedure of measurement of 1 voltage and V2 voltage.

FIG. 11 is a diagram showing constant voltage and constant current characteristics in a conventional charging device.

FIG. 12 is a diagram showing a charging mode in a conventional charging device.

FIG. 13 is a diagram showing a conventional charging device.

FIG. 14 is a diagram showing charging characteristics of a normal secondary battery.

[Explanation of symbols]

V1 A1 point voltage V2 A2 point voltage ZD Zener diode (voltage shift element) 200 Resistor (voltage shift element) 230 Constant current source 8 Switch section (switch element) 9 Secondary battery 29 Voltage detection circuit 61 Selection switch 62 A / D converter (voltage difference detection means) 63 CPU (voltage difference detection means) 100 constant current circuit

Claims (3)

[Claims] 1. A secondary battery is set, the secondary battery is charged at a constant voltage or less with a constant current, and when the terminal voltage of the secondary battery rises to a predetermined voltage, the secondary battery is charged with the constant voltage. By controlling and shutting off the charging current to the secondary battery by the switching element at a certain cycle, the first voltage before the switching element before or after the interruption of the charging current and the switching element after the interruption of the charging current. A charging device configured to detect a second voltage on the secondary battery side, wherein the detection means for detecting a voltage difference between the first voltage and the second voltage includes a first voltage and a second voltage. A charging device comprising: a voltage shift element for shifting the voltage, and a constant current circuit for the voltage shift element. 2. The charging device according to claim 1, wherein the voltage shifting element is a resistor. 3. The charging device according to claim 1, wherein the voltage shifting element is a Zener diode.