JPH05336678A - Charge control method and circuitry for charger - Google Patents

Abstract

PURPOSE:To charge a battery accurately with no erroneous operation through a simple constitution by setting the capacitance of a variable capacitive element, representative of voltage information, at a predetermined level when the voltage of secondary battery is within a range lower than the predetermined level. CONSTITUTION:When the voltage of a secondary battery is low, base bias voltage of a transistor Q1 is low and the transistor Q1 is turned OFF. Since an identical potential is applied across a variable capacity diode D1, potential difference goes zero to maximize the capacitance of the diode D1 If the capacitance of the capacitor C1 and the capacitance CD1 of the diode D1 are set such that CD1>>C1, the voltage information capacitance C01 is substantially equal to C1. When the voltage of secondary battery increases to a level sufficient for turning the transistor Q1 ON, the voltage information capacitance C01 becomes equal to the capacitance CD1 of the diode D1. Since the voltage of secondary battery is applied, as it is, onto the diode D1 at that time, the capacitance CD1 decreases as the voltage of secondary battery increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type charger to which a voltage / capacity conversion type secondary battery voltage detection method using a variable capacitance diode whose secondary side circuit configuration is extremely simple is applied. In order to obtain safe operation of the battery, a circuit system for performing control when the secondary battery voltage is lower than the voltage during the normal charge / discharge cycle and equivalently to the case where the secondary battery voltage is higher than the specified voltage, and The present invention relates to a circuit configuration therefor.

[0002]

2. Description of the Related Art In recent years, a primary control system has become common also in chargers in order to reduce the size and cost of devices.
The configuration of the secondary side of the switching charger of the primary control system is generally that shown in FIG. That is, the electric power for charging the secondary electricity 1 is supplied from the primary side through the high frequency output transformer 2, and in the secondary side, this is converted into a direct current by the rectifying / smoothing circuit 3 and then converted into a constant current. Supply to the next battery 1. Further, this current is detected by the current detection unit 4 for controlling the charging current, and the result is transmitted as current information to the control unit (not shown) on the primary side. The simplest means of transmission is an optical coupler (photocoupler) including a light emitting diode and a light receiving element. Further, in order to know the degree of charging of the secondary battery, the voltage of the battery is detected by the voltage detection circuit 5, and this is transmitted to the primary side, and the control unit on the primary side determines whether the battery is present or not, The degree of charging, the end of charging, etc. are detected, and the charging is controlled accordingly.

In the primary side circuit of the transformer T, the DC output is obtained by controlling the passage angle or pulse width of the AC signal supplied to the transformer or by changing the ON-OFF time ratio of switching. Generally, PWM (Puls Width Mo
A control called "duration-pulse width modulation" is performed.

There are various possible means for detecting the voltage of the secondary battery, but a relatively high voltage resolution is required to detect the end of charging. As a means for obtaining such resolution, analog-to-digital conversion is generally used. However, with this means, the circuit configuration on the secondary side becomes complicated, and an auxiliary power supply for supplying the analog-digital conversion circuit is required on the secondary side. Since it requires a means for stabilizing the above, it has been a factor that hinders downsizing and price reduction.

On the other hand, it is effective to use a voltage-capacitance conversion type as the simplest structure for the secondary side voltage detecting section, and the basic structure is generally that shown in FIG. The voltage detection unit in this figure is composed of two elements, a resistor R and a variable capacitance diode D, and applies the voltage of the secondary battery 1 to D via R having a high resistance value and at the same time applies the applied voltage. The secondary radio wave voltage is measured by knowing the capacitance of the dependent diode D on the primary side. The oscillation method is a means for knowing the capacitance of the diode D on the primary side, and measuring the frequency or the cycle of oscillation is effective in increasing the resolution. The coupling between the primary side and the secondary side is generally achieved by using a capacitor having a capacitance value sufficiently larger than the capacitance value of D1 and having a withstand voltage sufficient to obtain the required isolation.

As shown in FIG. 6, the relationship between the secondary battery voltage and the capacitance value of the diode D as the voltage information, that is, the voltage-capacitance conversion characteristic in the configuration of FIG. The relationship between the and output becomes monotonous.

However, the characteristics shown in FIG. 6 are not always desirable in consideration of the secondary voltage and the charge control based on it. Explaining this, when the secondary battery voltage is lower than the voltage during a normal charge / discharge cycle, that is,
Considering the secondary battery voltage state close to zero when the secondary battery is completely discharged, it is not preferable to charge the secondary battery with a normal rapid charging current in this state because it shortens the life of the secondary battery. There are many. Further, in this state, the secondary battery voltage fluctuates greatly, and thus sufficient charging cannot be obtained by the method of completing charging with a voltage drop. In other words, when a secondary battery such as nickel or cadmium has a property that the battery voltage rises once when the charge progresses to a substantially saturated state and then becomes a steady cutoff voltage at a value that decreases slightly, this characteristic is used. It is common to control so that the rapid charging is terminated by detecting the decrease, and this method is usually called the -ΔV _B method. Therefore, in the charger adopting this method, if there is a region where the secondary battery voltage value with extremely small remaining power fluctuates as described above, the voltage drop detection mechanism in the saturation voltage region operates and even if the battery is not charged yet. Regardless, there is a problem that charging is terminated.

Further, when the constant current circuit operates especially when the output voltage value is close to zero, the difference from the supply voltage becomes large, and the heat generation of the charger becomes large accordingly. This is often seen, and it is remarkable when the input voltage of the constant current section has to be set to a relatively large value in order to generate the constant current.

[0009]

SUMMARY OF THE INVENTION The present invention solves the problems in the conventional charging method as described above, and has a simple structure, which is free from malfunctions and can perform accurate charging, and a charging control method and circuit for a charger. Is intended to provide.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the first invention of the present application converts a secondary battery voltage to be charged into a capacitance value as voltage information using a variable capacitance element, and performs a charging operation based on this capacitance. In the control method, when the secondary battery voltage is within a predetermined value or less, the capacity value as the voltage information is kept constant at a predetermined value.

A second aspect of the present invention is a method for converting a voltage of a secondary battery to be charged into a capacitance value by using a variable capacitance element and controlling a charging operation based on the capacitance value. A fixed capacitor is arranged in series with the diode, and the fixed capacitor is short-circuited when the voltage of the secondary battery exceeds a predetermined voltage.

A third aspect of the present invention is a charger for converting a voltage of a secondary battery to be charged into a capacitance value using a variable capacitance element and controlling a charging operation based on the capacitance value. While connecting a fixed capacitive element in series with the capacitive element,
When the battery voltage is below the threshold value, the potential difference across the variable capacitance element does not change, and above the threshold value, it changes with the battery voltage.

A fourth invention of the present application is a charger for converting a voltage of a secondary battery to be charged into a capacitance value as voltage information using a variable capacitance element and controlling a charging operation based on the capacitance value. , A switch means that conducts when the battery voltage of the secondary battery is a predetermined value or more, a variable capacitance element and a fixed capacitance element are connected in series, and a secondary battery voltage is applied to both ends thereof And a means for deriving as information and a means for applying the positive or negative potential of the secondary battery to both ends of the variable capacitance element via two resistance elements, so that the capacitance element is short-circuited by the switch means. It is characterized by being connected.

A fifth aspect of the present invention is a charger for converting a voltage of a secondary battery to be charged into a capacitance value using a variable capacitance element and controlling a charging operation based on the capacitance value. Two thresholds are set to monitor the capacitance value of the element,
When the first threshold value is higher than the second threshold value, when the capacitance value of the variable capacitance element is larger than the first threshold value, rapid charging is performed, and the capacitance value is the first threshold value and the second threshold value. It is characterized in that the trickle charging current is set when the current value is in between, and the charging is stopped when the capacitance value is equal to or less than the second threshold value.

[0015]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a voltage-capacity conversion characteristic diagram adopted in the present invention to achieve the above object. In this figure, when the secondary battery voltage is gradually raised from zero volt, the output capacity is kept small until a certain voltage is reached, and at a voltage higher than a predetermined voltage, a monotonous voltage capacity characteristic is exhibited as in the conventional case. The circuit is configured as follows. If this characteristic is used, excessive heat may be generated when a fully discharged battery is charged by using only one threshold value in the primary side control unit, or as a result, false detection due to fluctuations in battery voltage may occur. Also, no malfunction occurs.

FIG. 2 is a diagram showing an example of control using the capacitance detection characteristic shown in FIG. 1. In the example shown in FIG. 2, two threshold values S ₁ and S ₂ are set, but it is simple. S for charger
Method of only ₁ may also be present.

Hereinafter, FIG. 2 will be described. It is assumed that V ₀ is a voltage below which no rapid charging current flows. First, the threshold value S ₁ is a threshold value for determining whether or not to supply the rapid charging current, and the voltage value for this capacity is V ₁ .
This voltage V ₁ is determined based on the charging characteristics of the secondary battery in a predetermined temperature range. If the converted voltage-capacity value exceeds the threshold value S ₁ , the control unit on the primary side performs a normal quick charging operation and monitors the secondary battery voltage while charging the secondary battery with a quick charging current. To do. If the secondary battery voltage is saturated for a predetermined time, or if a predetermined voltage drop is recognized as described above, trickle charging, that is, charging with a small current that does not adversely affect the secondary battery due to overcharge, is started, or Or stop the charging current.

On the other hand, when the capacity value is S ₁ or less and S ₂ or more, the controller on the primary side supplies the trickle charging current to the secondary battery. According to this method, even if the battery is completely discharged, it is possible to suppress the heat generation of the charger and reduce the influence on the secondary battery.

Further, the threshold value S ₂ is a threshold value for stopping the supply of current to the secondary battery, and is the charge end voltage V
It is set according to ₂ , and it is effective to prevent the deterioration of battery performance due to overcharge to the secondary battery, and also functions as protection when the secondary battery is not connected. .. That is, the control unit on the primary side controls so that the charging current is not supplied when the capacitance value is S ₂ or less.

As described above, according to the present invention, it is possible to realize a necessary charging operation from the time of complete discharge by a simple operation of the control unit on the primary side.

FIG. 3 is a diagram showing an example of a circuit in which the diode of FIG. 5 responds to the battery voltage change and the capacity change shown in FIG. 1 is obtained as described above.

The circuit shown in this figure, a capacitor C ₁ in parallel between the collector and the emitter with by applying the base resistor R ₁ and R ₂ of the transistor Q1 min and a voltage of the secondary battery 1. Further, a variable capacitance diode D ₁ for detecting a secondary battery voltage is connected in series to the capacitor C ₁ , and a positive electrode potential of the secondary battery 1 is applied to both ends thereof via resistors R ₃ and R ₄ to obtain the capacitor. The series combined capacitance value of the series circuit including C ₁ and the variable capacitance diode D ₁ is transmitted to the primary side control circuit of the charger as voltage information of the secondary battery. In this circuit, the transistor Q1 is turned on and off depending on the terminal voltage of the secondary battery 1, and as a result, the capacitance change as shown in FIG. 1 can be obtained.

That is, when the secondary battery voltage is low, the base bias voltage of the transistor Q1 is low and the transistor Q1 is low.
1 is turned off. As a result, since the same potential is applied to both ends of the diode D ₁ , the potential difference becomes zero and the capacitance value of the variable capacitance diode becomes the maximum value.
Therefore, the capacitance value is detected as voltage information becomes series combined capacitance of the capacitance C ₁ of the capacitor C _D1 and a capacitor C ₁ of the diode D _1.

Here, the relationship between the value of the capacitor C ₁ and the capacitance C _D1 of the diode D _{1 when} the potential difference is zero is expressed as C _D1 >> C ₁
Then, the voltage information capacity C _D1 is approximately C ₁ .

Since this value remains unchanged as long as the transistor Q1 is in the OFF state, if the capacitor C ₁ is set to a value between S ₁ and S ₂ in FIG.
It can be set as shown in.

On the other hand, the secondary battery voltage rises and a sufficient voltage value V ₀ to ON the transistor Q _1, from a state where the capacitor C ₁ is shortened between the collector and the emitter of the transistor Q _1, The voltage information C _{01 at} a voltage equal to or higher than V ₀ becomes the capacitance value C _D1 of the variable capacitance diode D ₁ .

When the transistor Q1 is turned on, one end of the resistor R ₄ , that is, the cathode side of the diode is grounded. As a result, the secondary battery voltage is directly applied to the variable capacitance diode, and the battery voltage The capacity value decreases as it rises. Therefore, the voltage-capacitance characteristic shown in FIG. 2 is obtained.

As described above, according to the circuit shown in FIG. 3, the voltage detecting method for the charger of the present invention can be realized. However, the realization of the present invention is not limited to this circuit, and various modifications can be made. .. For example, it is provided with two switch means for performing a switching operation in each of two different secondary battery voltages, and as described above, it is necessary to selectively perform trickle charging or quick charging operation in each voltage range. It is also possible to configure that a fixed or variable capacitance of value is connected.

Further, although the case where the applied charger system is the switching type charger has been shown, the present invention is not limited to this example, and is widely applied to the system of converting the secondary battery voltage into a capacity value and monitoring. Applicable.

[0030]

INDUSTRIAL APPLICABILITY As described above, the present invention converts the voltage of the secondary battery into a capacity value and monitors it, and switches to trickle charging or quick charging, or controls the charging as soon as the charging is completed. Since the capacity change as information shows a special change based on the arbitrarily set threshold, it becomes possible to selectively perform trickle charge or quick charge depending on the remaining capacity of the secondary battery. In addition, it is possible to avoid a remarkably overloaded state of the charger and further prevent the charging operation in the completely discharged state, and to have a remarkable effect in constructing an extremely highly reliable charger.

[Brief description of drawings]

FIG. 1 is a diagram showing a voltage capacity conversion characteristic used in a charging method according to the present invention.

FIG. 2 is a diagram showing a relationship between voltage-capacity conversion characteristics and threshold setting according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a voltage-capacitance conversion circuit for implementing the present invention.

FIG. 4 is a configuration diagram showing a secondary side of a general primary control type switching charger.

FIG. 5 is a diagram showing a conventional secondary battery voltage capacity conversion circuit.

FIG. 6 is a conventional voltage-capacity conversion characteristic diagram.

[Explanation of symbols]

1 secondary battery, 2 transformer, 3 rectifying and smoothing circuit, 4
Current detection circuit, 5 voltage detection circuit, R, R ₁ , R ₂ , R
₃ , R ₄ resistance, D, D ₁ variable capacitance diode,

Claims (5)

[Claims] 1. A method of converting a secondary battery voltage to be charged into a capacitance value as voltage information using a variable capacitance element and controlling a charging operation based on the capacitance, wherein the secondary battery voltage is a predetermined value. In the following range, the battery voltage detection method for a charger is characterized in that the capacity value as the voltage information is kept constant at a predetermined value. 2. A method for converting a voltage of a secondary battery to be charged into a capacitance value using a variable capacitance element and controlling a charging operation based on the capacitance value, wherein the variable capacitance diode is fixed in series. A charging control circuit voltage detection method for a charger, wherein a capacitor is arranged and the fixed capacitor is short-circuited when the voltage of the secondary battery exceeds a predetermined voltage. 3. A charger that converts the voltage of a secondary battery to be charged into a capacitance value using a variable capacitance element and controls the charging operation based on this capacitance value, in series with the variable capacitance element. A fixed capacitance element is connected, and when the battery voltage is below the threshold value, the potential difference across the variable capacitance element does not change, and above the threshold value, it changes with the battery voltage. A charging control circuit for a charger characterized by the above. 4. A charger for converting the voltage of a secondary battery to be charged into a capacitance value as voltage information using a variable capacitance element and controlling the charging operation based on this capacitance value. Means for connecting the variable voltage element and the fixed capacitance element in series with the switch means that conducts when the battery voltage is equal to or higher than a predetermined value, and a secondary battery voltage is applied to both ends of the variable capacitance element and the fixed capacitance element to derive the combined capacity as the voltage information And a means for applying a positive or negative electric potential of the secondary battery to both ends of the variable capacitance element via two resistance elements, and the capacitance element is connected so as to be short-circuited by the switch means. The charging control circuit for the charger. 5. A charger for converting a voltage of a secondary battery to be charged into a capacitance value by using a variable capacitance element and controlling a charging operation based on the capacitance value. Two thresholds are set for monitoring, and the first threshold is the second
If the capacitance value of the variable capacitance element is larger than the first threshold value, the fast charging is performed, and if the capacitance value is between the first threshold value and the second threshold value, trickle charging is performed. A charging control method for a charger, characterized in that a current is used and charging is stopped when the capacitance value is equal to or less than a second threshold value.