JPH02168823A - Charging voltage controller - Google Patents

Abstract

PURPOSE:To prevent overcharge and over-discharge of a battery and to lengthen the service life of the battery by providing a reference voltage generating circuit for varying the reference voltage in zigzag with respect to the ambient temperature thereby maintaining the battery voltage continuously at a proper level regardless of the ambient temperature. CONSTITUTION:Battery voltage is divided through resistors 33, 34 then the divided voltage is fed to + side of a comparator 32. Since the temperature detecting diode 1 in a reference voltage generating circuit 26 has such characteristic that the voltage drops forward as the ambient temperature rises, reference voltage Vout of a buffer 25 varies in zigzag. A comparator 32 compares the reference voltage Vout with the battery voltage, and if the battery voltage is lower than the reference voltage a transistor 30 turns ON to feed current through an exciting winding 29 thus generating power from a generator 27. If the battery voltage is higher than the reference voltage, the transistor 30 is turned OFF to interrupt current supply to the exciting winding 29 thus stopping generation of power. Battery voltage is maintained at a predetermined level by repeating the operation. By such arrangement, service life of the battery is lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage regulating circuit for an alternator for a vehicle such as an automobile, and particularly to a variable charging voltage control device.

Generally, this type of conventional device rectifies the output of the alternator through a rectifier to charge the battery and compares the battery voltage detection signal with a reference voltage, which is connected in series to the excitation coil of the alternator. A method has been adopted in which a semiconductor switch such as a transistor is controlled on and off to adjust the AC output voltage and maintain the battery charging voltage at a predetermined value. However, such conventional devices, regardless of the ambient temperature etc.
Since the voltage is maintained at a nearly constant voltage value, there is a problem that the battery becomes overloaded, particularly at high temperatures, and the battery life is shortened. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a voltage control device that prevents overcharging and overdischarging of a battery and prolonging the life of the battery by always maintaining the battery voltage at an appropriate value with respect to the ambient temperature.

Figures 1 (a) and (b) are a circuit diagram of an embodiment of the present invention and its output (charging) characteristics. 29 is an excitation winding, 30 is a main transistor, 31 is a control transistor, 32 is a comparator, 33 and 34 are battery voltage detection resistors, 35 is a stabilized power source for driving, and 26 is a main part of the present invention. The reference voltage generating circuit 36 is a battery, and SW is a switch. The operation of this circuit is as follows: First, the battery voltage is detected (divided) by resistors 33 and 34, and this is input to one side (+) of the comparator 32. Further, the reference voltage generation circuit 26 generates a reference voltage Vf having characteristics shown in FIG. 3(b), which will be described later.
is generated and input manually to the other side () of the comparator. Then, the comparator 32 compares the reference voltage Vf with the battery voltage, and when the battery voltage is lower than the reference voltage, the output of the comparator 32 is 11.

Therefore, the main transistor 30 is turned on by the current flowing from the battery 36 through the resistor 37, and the excitation winding 29 is turned on.
A current flows through the generator 27, and the generator 27 generates electricity.

On the other hand, when the battery voltage is higher than the reference voltage, the comparator 32
The output of is 11 levels, and the control transistor 3]
Turn on. Therefore, Runcissister 30 is OF F
L, the current in the excitation winding 29 disappears and power generation is stopped. By repeating this operation, the battery voltage V11 is maintained at a predetermined value. Next, the operation of the reference voltage generation circuit 2G will be explained.

2 and 3 are circuit diagrams of a reference voltage generation circuit applied to the present invention and explanatory diagrams of its operation, in which 2.3 is a differential amplifier, 4 is a differential amplifier;
is an adder.

This operation will be explained next. Temperature detection diode] Due to the characteristics of the diode, as the ambient temperature increases by 1, the forward voltage drop voltage (hereinafter referred to as V1) will be approximately -2rn V /
'C becomes lower. When Vl becomes smaller than the reference voltage (1) set by the resistors 5, 6, the output voltage V of the differential amplifier 2 becomes the voltage represented by the resistors 7, 8, and 9. The resistor 11 and the resistor 12 are set so that the differential amplifier 3 operates at a reference voltage different from (1). Next, the output voltage of the differential amplifier 2.3 ■2, ■, (Figure 3 a)
is applied to the in-phase summing amplifier 4 via resistors 17 and 18.

If the resistances 7.18 and 19.18 are equal, the voltage V will be amplified by the amplification factor determined by the resistance 19.20.

As shown in Fig. 3(a), this voltage 1 is a small saturation pressure V. , some saturation voltage from ■. 11, and as a result of this change, the voltage divided by the resistors 21, 22, 23, 24 ■1. is the resistance value of resistor 21, 22, 23, 24 as R
21, R22, R23, R2/] and set the power supply voltage to ■1.
In this case, the battery voltage can be maintained at a predetermined value according to changes in the ambient temperature, so the battery life can be extended, which has a great practical effect.

(However, ■, +l≦V4≦V n u ). Therefore, the output voltage Vout of the buffer y-25 changes as shown in FIG. 3(b). Therefore, the present invention provides a reference voltage Vou
When used in a reference voltage generator 26 in which t changes with temperature as shown in FIG. 3 (l), the battery voltage can be changed as shown in FIG. 1 with ambient temperature. In Figure 2, two differential amplifiers are used to set one inflection point, but by shifting the number of differential amplifiers to n, it is possible to create a reference voltage with n-1 inflection points. . Furthermore, if a subtracter is used instead of an adder, the amplification factor can be reduced from a certain temperature, and by combining these, it is possible to set a reference voltage that has temperature characteristics in the form of multiple polygonal lines.

As is clear from the above explanation, according to the present invention,

[Brief explanation of the drawing]

Figures 1 (a) and (b) are circuit diagrams of one embodiment of the present invention and their output (charging) characteristics diagrams, Figures 2 and 3 are reference voltage generation circuit diagrams and their operation explanations applied to the present invention. It is a diagram. In the figure, 26 is a reference voltage generation circuit, 27 is an alternator, 28 is a rectifier, 29 is an excitation winding, 30 is a main transistor, 31 is a control transistor, 32 is a comparator, and 36 is a battery.

Claims (1)

[Claims] In a charging voltage control device that rectifies the output of an alternator to charge a battery, and also compares the battery voltage detection signal with a reference voltage to maintain the battery voltage at a predetermined value via a semiconductor switch element, A charging pressure control device characterized in that a reference voltage generating circuit is provided to vary the reference voltage in a polygonal manner with respect to ambient temperature, and the battery is maintained in accordance with ambient temperature.