JPH06233473A - Voltage detector for switching type charging circuit - Google Patents

Abstract

PURPOSE:To obtain high-precision battery voltage-frequency characteristics by using a piezoelectric vibrator in an oscillator circuit. CONSTITUTION:A secondary battery voltage detecting circuit is constituted by connecting a voltage to capacitance converting circuit 11 composed of a variable capacitance diode D1, and an oscillating part 12 with a piezoelectric vibrator Y1 and a capacitor C2. As the piezoelectric vibrator Y1, a quartz vibrator is used, for example. It becomes possible to perform high-stability voltage-frequency conversion by detecting the terminal voltage change of a secondary battery 10 as a change in capacitance of the variable capacitance diode D1, finding the change as a change in oscillation frequency of the oscillating part 12, and using a piezoelectric vibrator Y1. Consequently, it becomes possible to obtain high-precision battery voltage-frequency characteristics.

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, which has a simple secondary side circuit configuration and is capable of detecting the battery voltage of a secondary battery with high accuracy. Regarding the device.

[0002]

2. Description of the Related Art There is an increasing demand for downsizing and cost reduction of equipment, and a primary control system for controlling switching based on a terminal voltage of a battery is generally used in a charger. In the charging circuit that uses the primary control method, the secondary side performs processing such as voltage measurement, presence / absence of battery, charging status, and termination of charging, but by performing these processing on the primary side as much as possible, the secondary side It is preferable to simplify the circuit configuration in order to reduce the cost of the device, reduce the size, and increase the efficiency. FIG. 5 shows a secondary side configuration example of the switching type charger using the primary control system in which the microcomputer having the above-mentioned various processing functions arranged on the primary side. The power for charging the secondary battery is supplied from the primary side via the high frequency output transformer T, and on the secondary side, the output of the transformer T is converted into direct current by the rectifying / smoothing circuit 1 and then via the constant current circuit 2. It is applied to the secondary battery 3. On the other hand, to detect the state of the secondary battery 3, the voltage detection circuit 4 is used to measure the terminal voltage of the secondary battery 3, and this is transmitted to the charging control system provided on the primary side. In the charge control system, the presence / absence of a battery, the state of charge, the end of charging, etc. are determined based on the supplied secondary battery voltage information,
Based on this information, the switching circuit is turned on / off to control the charging current. In such a switching type charger, an IC including a voltage controlled oscillator or the like is used as the voltage detection circuit 4, and the secondary battery voltage value is transmitted to the primary side by performing voltage-frequency conversion to control the switching circuit. There is. However, in the voltage detection method as described above, the voltage detection circuit 4 provided on the secondary side does not
There is a problem that an auxiliary power source for driving C is required, a means for supplying the power source, a means for stabilizing the power source voltage, etc. are required, and the device becomes large and expensive. . Further, as a voltage detection circuit for a secondary battery which does not require a power source for the secondary side circuit, the one shown in FIG. 6 can be considered. The circuit 5 is provided in the secondary side circuit, while the capacitance detection circuit 7 including the oscillator 6 and the coil L1 is provided in the primary side circuit. The voltage / capacitance conversion circuit 5 includes coupling capacitors C1 and C2. Connected to the capacitance detection circuit 7. Coupling capacitor C
1 and C2 have capacitance values sufficiently larger than the capacitance of the varactor diode D1, have a withstand voltage for necessary isolation, and have a commercial frequency (50H).
In the frequency range (z to 60 Hz), a capacitor having a small capacity that can be ignored is used. The capacitance conversion type voltage detection circuit having such a configuration utilizes that the capacitance of the variable capacitance diode D1 depends on the applied voltage, and the voltage of the secondary battery 3 is detected by detecting the capacitance of the variable capacitance diode D1. To measure the coil L1, the capacitor C
1, the oscillator 6 oscillates at the natural frequency of the total inductance of C2 and the diode D1, and the oscillation frequency fluctuates according to the capacitance change of the diode D1, that is, the voltage change of the secondary battery. By measuring, the state of the secondary battery can be detected. Although it is possible to use a switching type circuit such as a 555 type timer integrated circuit which is an industrial standard as the oscillating section 6, since the input impedance of the oscillating section changes significantly depending on the change of the state, the varactor diode D1 is used. The applied voltage fluctuates greatly and it is difficult to perform highly accurate capacitance measurement. Therefore, it is preferable to measure the frequency using a sine wave or substantially sine wave oscillating circuit in which the input impedance does not change.
Since the coil is used, there is a problem that it is difficult to achieve miniaturization and cost reduction from the viewpoints of stability, size and price of the element.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and does not require an auxiliary power source on the secondary side, and can achieve miniaturization and cost reduction with a simple structure. An object of the present invention is to provide a voltage detection device for a switching type charging circuit that can obtain highly accurate battery voltage-frequency characteristics.

[0004]

SUMMARY OF THE INVENTION In order to achieve this object, a voltage detection device according to the present invention converts a secondary battery voltage to be charged into a capacitance using a variable capacitance diode, and detects this as an oscillation frequency on the primary side. In the primary control switching type charger, the variable capacitance diode and the piezoelectric vibrator are provided in the oscillation loop, and one electrode of the piezoelectric vibrator is connected to the primary side and the other electrode is connected to the secondary side. Thus, the voltage-frequency characteristic of the oscillating unit is stabilized with high accuracy, and the number of isolation capacitors used for isolation between the primary side and the secondary side is reduced.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a diagram showing an embodiment for carrying out a voltage detection method for a switching type charging circuit according to the present invention. The secondary battery 10 is a transformer not shown,
It is charged through the rectifying / smoothing circuit and the constant current circuit. On the other hand, the secondary battery voltage detection circuit has a configuration in which the voltage-capacitance conversion circuit 11 including the resistor R1 and the variable-capacitance diode D1 and the oscillation unit 12 are coupled by the piezoelectric vibrator Y1 and the capacitor C2. A crystal oscillator may be used as the piezoelectric oscillator Y1, for example. In the secondary battery voltage detection circuit configured as described above, a change in the terminal voltage of the secondary battery 10 is detected as a change in the capacitance of the variable capacitance diode D1, and the change in capacitance is captured by the oscillator 12 as a change in the oscillation frequency. By using the piezoelectric vibrator Y1 in place of the coil used in the conventional oscillating unit, highly stable voltage-frequency conversion can be performed. Further, the piezoelectric vibrator Y1 is used in place of the conventionally used primary-side and secondary-side isolation capacitor C1, but piezoelectric materials such as quartz and ceramics, which are materials for various piezoelectric vibrators, are used. Originally, it has excellent insulating properties, and in particular, if a piezoelectric vibrator having a small coupling coefficient is used, isolation can be achieved without affecting the AC equivalent circuit. Therefore, by replacing the oscillating inductor and the isolating capacitor with a single crystal oscillator, it is possible to reduce the number of parts of the switching type charging circuit, and to realize the downsizing and cost reduction of the device.

FIG. 2 is a diagram showing another embodiment of the present invention, and is different from the embodiment shown in FIG. 1 in that the resistance of the voltage-capacitance conversion circuit 11 is a variable resistance voltage divider RV1. is there. That is, the secondary battery voltage detection circuit shown in FIG. 1 takes into consideration the fact that the voltage-frequency conversion characteristics fluctuate due to variations in the electrical characteristics of the constituent elements. Although there are variations in the electrical characteristics on the primary side and the secondary side as well, in the normal design, variations in the components on the secondary side are the main cause, and variations in the varactor diode are particularly large, and voltage-frequency conversion sensitivity is high. Is not constant, the variation of the capacitance characteristic of the variable capacitance diode is corrected by using the variable resistance voltage divider VR1. By configuring the secondary battery voltage detection circuit in this manner, the variable resistance voltage divider RV1 has a function of adjusting the sensitivity of frequency conversion, and the battery voltage of the secondary battery is small in size, low in price, and highly accurate. Can be monitored. If a control circuit using a microcomputer or the like is used for the charging circuit, it is possible to interrupt the supply of the charging current when adjusting the sensitivity, and during adjustment of the sensitivity, a reference voltage source is provided across the variable resistance voltage divider RV1. And the variable resistance voltage divider RV1 may be adjusted so that a desired oscillation frequency and a desired frequency change rate can be obtained at a predetermined voltage value.

On the other hand, for variations in the offset term of the voltage-frequency conversion characteristic, the circuit may be configured to adjust the frequency offset as shown in FIG. That is, as shown in the figure, a variable capacitor CV1 and a resistor R2 are provided at one end of a variable capacitance diode D1, a reference voltage source is connected instead of the secondary battery during frequency offset adjustment, and a predetermined voltage is used at a predetermined frequency. The variable capacitor CV1 may be adjusted so that
By using 1 as a variable resistance voltage divider as shown in FIG. 2, it is possible to make the voltage-frequency conversion characteristic a constant value due to variations in the electrical characteristics of the primary side and secondary side constituent elements. The voltage of the secondary battery can be detected with high accuracy.

Further, it is possible to construct a highly accurate secondary battery voltage detection circuit without using the variable capacitor and variable resistance voltage divider as described above. That is, the variable capacitor and the variable resistance voltage divider mechanically change their values,
Since it is unstable with respect to external factors such as vibration, a charging circuit having a memory for calibration in the control unit may be used as shown in FIG. In FIG. 4, 13 is a switching controller, and 14 is a writable read-only memory, such as a RAM backed up by a PROM or a battery. In the charging circuit configured as described above, the control unit 13
When a specified mode, for example, an O volt calibration mode is specified, a set voltage of 0 V is applied across the variable capacitance diode D1 provided on the secondary side to oscillate at that time. The oscillation frequency output from the unit 12 is written in the memory 14. When the V _n calibration mode is designated, V _n is applied as the set voltage, and the oscillation frequency output from the oscillator 12 at that time is written and recorded in the memory 14. When the operation mode signal is input to the control unit 13, the control unit 13 corrects the voltage-frequency conversion characteristic based on the oscillation frequency data recorded in the memory 14 and the signal supplied from the oscillation unit 12, and highly accurately. The secondary battery voltage can be detected, and highly accurate voltage detection can be performed without increasing the number of constituent parts.

[0009]

Since the present invention is constructed and functions as described above, a power source for driving the circuit is not required on the secondary side of the switching type charging circuit, and an inductor (coil) is provided in the oscillation circuit. Since a piezoelectric vibrator is used instead, a highly stable voltage-frequency conversion characteristic can be obtained, and the number of capacitors for the primary side and secondary side isolation that was conventionally required is reduced to one. It is possible to achieve a significant effect in achieving downsizing and cost reduction of the device.

[0010]

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a secondary battery voltage measuring circuit according to the present invention.

FIG. 2 is a diagram showing another embodiment of the secondary battery voltage measuring circuit according to the present invention.

FIG. 3 is a diagram showing another embodiment of the secondary battery voltage measuring circuit according to the present invention.

FIG. 4 is a diagram showing another embodiment of the secondary battery voltage measuring circuit according to the present invention.

FIG. 5 is a diagram showing a circuit configuration on the secondary side of a primary control switching type charger having a conventionally used control function in a primary side circuit.

FIG. 6 is a diagram showing a method of using a capacitor for isolation between a primary side circuit and a secondary side circuit.

[Explanation of symbols]

 1 ... Rectification / smoothing circuit 2 ... Constant current generation circuit 3, 10 ... Secondary battery 4 ... Voltage detection circuit 5, 11 ... Voltage capacity conversion circuit 6, 12 ... Oscillation section 7 ... Capacitance detection circuit 13 ... Control unit 14 ... Writable read-only memory C1, C2, ... Capacitor D1 ... Variable capacitance diode R1, R2 ... Resistor Y1 ... Crystal Resonator RV1 ・ ・ ・ Variable resistance voltage divider CV1 ・ ・ ・ Variable capacitor

Claims (1)

[Claims] 1. A primary control switching type charger, wherein a secondary battery voltage to be charged is converted into a capacity by using a variable capacity diode and is detected as an oscillation frequency on a primary side, wherein the variable capacity is included in an oscillation loop. A secondary battery voltage detection device comprising a diode and a piezoelectric vibrator, wherein one electrode of the piezoelectric vibrator is connected to the primary side and the other electrode is connected to the secondary side.