JP2814091B2 - Charge voltage control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage adjusting circuit for an AC generator for a vehicle such as an automobile, and more particularly to a battery charging pressure control device.

Generally, this type of conventional device rectifies the output of the alternator through a rectifier, charges the battery and compares the battery voltage detection signal with a reference voltage, thereby connecting the battery in series with the excitation coil of the alternator. A method is employed in which a semiconductor switch such as a transistor is turned on and off to adjust an AC output voltage to maintain a battery charging voltage at a predetermined value. However, such a conventional device is maintained at a substantially constant voltage value irrespective of the ambient temperature and the like, and thus has a problem that the battery is overloaded and the life of the battery is shortened, especially at a high temperature. SUMMARY OF THE INVENTION It is an object of the present invention to provide a voltage control device that always keeps a battery voltage at an appropriate value with respect to an ambient temperature, thereby preventing overcharging and overdischarging of a battery and extending the life of the battery.

FIGS. 1 (a) and 1 (b) are a circuit diagram and an output (charging) characteristic diagram of an embodiment of the present invention. In the drawing, reference numeral 27 denotes an AC three-phase generator which generates electric power by rotation of an engine, and 28 denotes a three-phase generator. Wave rectifier, 29 is an exciting 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 driving power supply, and 26 is a main part of the present invention. A reference voltage generating circuit, 36 is a battery, and SW is a switch. The operation of this circuit is as follows.
, And inputs it to one (+) of the comparator 32. The reference voltage generation circuit 26 generates a reference voltage Vf having characteristics shown in FIG. 3B, which will be described later, and inputs it to the other (-) 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,
Output L ₀ becomes the control transistor 31 of comparator 32 is OFF
doing. Therefore, the main transistor 30 is turned on by a current flowing from the battery 36 via the resistor 37, and a current flows through the exciting winding 29, so that the generator 27 generates power. On the other hand, when the battery voltage is higher than the reference voltage, the output of the comparator 32 becomes Hi level, and the control transistor 31 is turned on. Therefore the main transistor 30
Turns off, and the current in the exciting winding 29 disappears to stop power generation.
And keeping the battery voltage V _B to a predetermined value by repeating this operation. Next, the operation of the reference voltage generation circuit 26 will be described.

FIGS. 2 and 3 are circuit diagrams of a reference voltage generating circuit applied to the present invention and operation explanatory diagrams thereof.
4 is an adder.

This operation will be described below. Temperature detecting diode 1 with increasing ambient temperature from the characteristic of the diode, (referred to hereinafter as V _F) forward voltage drop voltage is Tayca his role -2 mV / ° C..
V _F is the resistance 5, the output voltage V ₂ is the resistor 7 and the resistor 8 of becomes smaller than the reference voltages V _1, which is set by the resistor 6 differential amplifier 2, if the resistance 9 and the resistor 10 are equal, respectively The voltage is represented by The differential amplifier 3 has a reference voltage
Resistor 11 so as to operate in V ₁ and a different voltage, the resistor 12 is set. Next, the output voltages V ₂ , V ₃ ,
(FIG. 3a) is applied to the in-phase summing amplifier 4 via resistors 17,18. Equal the resistance 17 becomes the voltage V ₄ is amplified by an amplification factor determined by resistors 19 and 20. This voltage
V ₄ is changed to a maximum saturation voltage V _OH from the minimum saturation voltage V _OL, as shown in FIG. 3 (a), accompanied not resist this change 21,2
When the voltage V ₅ to be divided by 2,23,24 each resistance value of the resistors 21,22,23,24 R21, R22, R23, R24 and to the power supply voltage and V _CC, Range. Therefore, the output voltage Vout of the buffer 25
Changes as shown in FIG. 3 (b). Therefore, when the present invention is applied to the reference voltage generator 26 in which the reference voltage Vout changes as shown in FIG. 3B depending on the temperature, the battery voltage can be changed according to the ambient temperature as shown in FIG. 1B. In FIG. 2, one inflection point is set using two differential amplifiers.
If n differential amplifiers are used, a reference voltage having n-1 inflection points can be created. Also, if a subtractor is used instead of an adder, the amplification factor can be reduced from a certain temperature,
When these are combined, it is possible to set even a reference voltage having a multifold linear temperature characteristic.

As is apparent from the above description, according to the present invention, the battery voltage can be maintained at a predetermined value in accordance with the change in the ambient temperature, so that the battery life is prolonged and the practical effect is great.

[Brief description of the drawings]

1 (a) and 1 (b) are circuit diagrams of an embodiment of the present invention and output (charging) characteristics thereof, and FIGS. 2 and 3 are diagrams of a reference voltage generating circuit applied to the present invention and an explanation of the operation thereof. FIG. In the figure, 26 is a reference voltage generation circuit, 27 is an AC generator, 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)

(57) [Claims] The battery is charged by rectifying the output of the alternator, the battery voltage detection signal is compared with a reference voltage, and the battery voltage is maintained at a predetermined value via a semiconductor switch element. In the charging voltage control device, a plurality of differential amplifier circuits having different temperature characteristics are used, output voltages of the plurality of differential amplifier circuits are added, and the voltage signal is used as the reference voltage, so that the reference voltage is set to the surroundings. A charging voltage control device, wherein a reference voltage generating circuit that operates so as to change the temperature in a linear manner is provided to maintain the battery in accordance with the ambient temperature.