JP3435708B2 - Voltage control device for vehicle alternator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage control device for an alternator for a vehicle which keeps the output voltage of the generator constant.

[0002]

2. Description of the Related Art A vehicle alternator in which a constant current device is provided between a field coil and a voltage control device to keep the output voltage constant is disclosed in Japanese Utility Model Laid-Open No. 59-63700.

[0003]

However, the constant current device for the vehicle alternator requires a shunt resistor for current detection. For this reason, there are problems that the power generation efficiency is reduced and the heat generation is increased due to the loss of the exciting current in the current detection resistor section. Furthermore, since it has a current detection resistor unit, the entire device is integrated into one integrated circuit (hereinafter referred to as IC).
There is a problem that the device cannot be downsized by the above configuration. The present invention has been made to solve the above problems, and an object thereof is to provide a voltage control device for a vehicle alternator having a circuit configuration that does not require a shunt resistor for current detection. is there.

[0004]

As a concrete means for achieving the above object, as a specific means for achieving the above object, the exciting current is limited and the output voltage is kept constant by turning on / off a bipolar transistor interposed in the exciting circuit of the field coil. in the voltage controller for an automotive alternator to, base of the bipolar transistor
Enter the voltage over scan, comparing means for comparing a reference voltage set in advance as the base voltage, the base voltage
And a control means for outputting to the base a control signal for turning off the bipolar transistor based on the output of the comparison means when the voltage becomes equal to or higher than the reference voltage. A device is provided. Further, the bipolar transistor, the comparison means and the control means can be formed on one integrated circuit.

[0005]

[Action] Voltage control apparatus for an AC generator for a vehicle having the above-base of the bipolar transistor to limit the excitation current
The control means outputs a control signal for turning off the bipolar transistor to the base on the basis of the output of the comparison means when the voltage of the output voltage exceeds a preset reference voltage.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram of a voltage control device for a vehicle AC generator. In FIG. 1, 1 is a stator coil of a three-phase AC generator, 2 is a three-phase full-wave rectifier, 3 is a battery charged by the three-phase AC generator, 4 is an electric load, 5 is a field coil, and 6 is It is an ignition switch, and the voltage control device 7 operates when the switch is turned on.

The voltage control device 7 includes a generator output terminal (hereinafter referred to as B terminal) 8, an excitation current control terminal (hereinafter referred to as F terminal) 9, a ground terminal (hereinafter referred to as E terminal) 10, and a power supply terminal (hereinafter referred to as IG terminal). ) 11. F terminal 9 and E
A bipolar transistor (hereinafter referred to as an excitation drive transistor) 12 for controlling an exciting current is provided between the terminals 10, and a field coil 5 is connected to an F terminal 9 to form an exciting circuit 13. Further, the F-terminal 9 and the B-terminal 8 are connected to an exciting current circulating circuit 15 having a flywheel diode 14 interposed therebetween.

A voltage dividing / smoothing circuit 19 composed of voltage dividing resistors 16 and 17 and a smoothing capacitor 18 is connected to the B terminal 8. The divided / smoothed output voltage of the output voltage of the three-phase AC generator is input to the (+) terminal of the voltage control comparator 20.
Further, the divided voltage output of the reference voltage circuit 23 including the resistors 21 and 22 is input to the (−) terminal of the voltage control comparator 20. The comparison output of the voltage control comparator 20 is input to the input terminal 24a of the delay circuit 24. Then, the output terminal 24b of the delay circuit 24 and the excitation drive transistor 12
The control signal circuit 25 connects the base, which is the on / off control terminal of the.

The control signal circuit 25 includes a base bias circuit 2 for the excitation drive transistor 12 which supplies a constant current.
Connect 6 Further, the control signal circuit 25 and the exciting current limiting comparator (hereinafter referred to as current limiting comparator)
Connect to the (+) terminal of 27. Current limit comparator 2
The (-) terminal of 7 has an exciting current limiting reference voltage circuit 31 including constant current circuits 28 and 29 and a transistor 30.
To connect. The comparison output of the current limiting comparator 27 is input to the input terminal 24c of the delay circuit 24.

FIG. 2 is a circuit diagram of the delay circuit 24. The delay circuit 24 is turned on by a reference voltage circuit 104 including voltage dividing resistors 101 and 102 and a capacitor 103, a comparator 105, a transistor 106 which is turned on / off by a comparison output of the voltage control comparator 20, and a comparison output of the current limiting comparator 27. It is composed of a transistor 107 that is turned off.

In the voltage control device 7 of the above embodiment, since the exciting current is small in the case of a light load, the operating state (voltage control mode) is maintained in which the output voltage of the generator is constantly controlled. Further, in the case of heavy load, when the exciting current exceeds the set limiting current, the exciting current is limited and the output voltage of the generator decreases (current limiting mode). The operation of this embodiment will be described below for each of the modes.

(1) Voltage control mode When the ignition switch 6 is turned on, the IG terminal 1
1, the voltage of the battery 3 is applied, and the voltage control device 7 operates. The voltage of the B terminal 8 is divided by the voltage dividing / smoothing circuit 19.
It is smoothed and input to the (+) terminal of the voltage control comparator 20. The resistors 21 and 2 of the reference voltage circuit 23 are connected to the (-) terminal.
The reference voltage divided by 2 is input and both are compared. When the B terminal voltage which is the generator output is lower than the reference voltage, the output of the voltage control comparator 20 becomes “Lo” and is input to the input terminal 24 a of the delay circuit 24.

Therefore, in the delay circuit 24, the transistor 1
06 is turned off and the capacitor 103 is charged. Therefore, as shown in FIG. 3, the input voltage of the (+) terminal of the comparator 105 gradually increases. When the voltage rises above the reference voltage input to the (-) terminal, the comparator 10
The output of 5 is switched from "Lo" to "Hi". Therefore, the excitation drive transistor 12 is turned on, the excitation current flowing through the excitation circuit 13 increases, and the generator output rises. When the generator output rises above the reference voltage set by the reference voltage circuit 23, the output of the voltage control comparator 20 switches from “Lo” to “Hi”. Then, the transistor 106 of the delay circuit 24 is turned on, the output of the comparator 105 is instantly inverted and becomes “Lo”, which is applied to the base of the excitation drive transistor 12 by the control signal circuit 25, and the excitation drive transistor 12 is turned off. Therefore, the exciting current flowing through the exciting circuit 13 decreases, and the generator output decreases. By repeating the above operation, the generator output is controlled to a constant value.

(2) Current limiting mode When the temperature of the field coil 5 is low at the time of starting or low temperature,
Exciting current increases. Further, as the electric load 4 increases, the exciting current also increases. Since the base potential of the transistor depends on the collector current, the base potential V _BE of the excitation drive transistor 12 rises as shown in FIG. The base potential of the excitation drive transistor 12 is input to the (+) terminal of the current limit comparator 27, and the excitation drive when the control current value I _CO is passed to the (-) terminal by the excitation current limit reference voltage circuit 31. Base potential V of transistor 12
A voltage equivalent to _BEO is applied. Therefore, when the exciting current becomes equal to or higher than the control current value I _CO , the output of the current limiting comparator 27 is inverted and becomes “H” as shown in FIG.
i ”and is input to the input terminal 24c of the delay circuit 24.

Therefore, in the delay circuit 24, the transistor 107 is turned on, the output of the comparator 105 is instantly inverted and becomes “Lo”, which is applied to the base of the excitation drive transistor 12 by the control signal circuit 25, and the excitation drive transistor 12 is applied. Turns off. Therefore, the exciting current flowing through the exciting circuit 13 decreases, and the generator output decreases. On the other hand, the output of the current limiting comparator 27 is switched from “Hi” to “Lo” in about several microseconds because the base potential V _BE of the excitation drive transistor 12 is instantly lowered. Therefore, the transistor 107 of the delay circuit 24 is turned off, and the capacitor 103 starts charging again. Comparator 10
When the input voltage of the (+) terminal of No. 5 gradually rises and exceeds the reference voltage input to the (-) terminal, the comparator 1
The output of 05 is switched from "Lo" to "Hi". Therefore,
The excitation drive transistor 12 is turned on, the excitation current flowing through the excitation circuit 13 increases, and the generator output rises. By repeating the above-mentioned operation, the peak value of the exciting current becomes the limiting current value I.
Controlled by _CO .

In the above embodiment, the excitation drive transistor 1
The excitation current limiting reference voltage to be compared with the base potential V _{BE of} 2 is generated by using the excitation current limiting reference voltage circuit 31 using the base voltage V _BE of the transistor 30 in Darlington connection, so that the base of the excitation driving transistor 12 is generated. The electric current is matched with the temperature characteristic of the electric potential, and the limiting current value is made constant regardless of the temperature of the voltage control device 7.

Further, as shown in FIG. 6, the voltage control device 7 including the excitation drive transistor 12 is formed on one monolithic IC 110, and the excitation drive transistor 12 is formed.
By reducing the temperature difference between the excitation current limiting reference voltage circuit 31 and the excitation current limiting reference voltage circuit 31, the temperature dependence of the control current value can be avoided.

[0018]

The voltage control device for an automotive alternator according to the present invention has the above-mentioned structure, and the base voltage of the bipolar transistor for limiting the exciting current is a preset reference voltage.
Based on the output of the comparing means when it becomes more, before the control signal the control means turns off the bipolar transistor
Since the current is output to the base , the current detection shunt resistor is unnecessary, and the generation efficiency is not reduced and heat is not generated due to the excitation current loss. Further, since the shunt resistor for current detection is not used, the voltage control circuit can be formed on the IC, so that there are excellent effects such as miniaturization and improved reliability.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a voltage control device for a vehicle AC generator according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a delay circuit.

FIG. 3 is a time chart showing the operation of the delay circuit in the voltage control mode.

FIG. 4 is a characteristic diagram showing a correlation between a base potential and a collector current of a transistor.

FIG. 5 is a time chart showing the operation of the delay circuit in the current matching mode.

FIG. 6 is a schematic diagram showing a state in which the voltage control device is configured on a monolithic IC.

[Explanation of symbols]

1 ... Stator coil 5 ... Field coil 7 ... Voltage control device 12 ... Excitation drive transistor 13 ... Excitation circuit 24 ... Delay circuit 25 ... Control signal circuit 27 .. .Current limit comparator 28, 29 ... Constant current circuit 3
0 ... Transistor 31 ... Excitation current limit reference voltage circuit 110 ... Monolithic IC

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-328800 (JP, A) JP-A-3-239129 (JP, A) JP-A-4-197045 (JP, A) JP-A-4- 31171 (JP, A) JP-A 2-131362 (JP, A) JP-A 61-293124 (JP, A) JP-A 61-46134 (JP, A) JP-A 64-83156 (JP, A) JP-A-58-43106 (JP, A) JP-A-63-92231 (JP, A) JP-A-5-316667 (JP, A) JP-A-5-122864 (JP, A) Actual Kaihei 3-26299 (JP, U) Actual development Sho 59-63700 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02J 7/24 H02P 9/30

Claims (2)

(57) [Claims] 1. A voltage control device for a vehicle alternator for limiting an exciting current to keep an output voltage constant by turning on / off a bipolar transistor interposed in an exciting circuit of a field coil. enter the base voltage, and comparing means for comparing a reference voltage set in advance as the base voltage, prior to when the base voltage is equal to or greater than the reference voltage
The bipolar transistor based on the output of the comparing means.
And a control means for outputting a control signal for turning off the power supply to the base, the voltage control device for the vehicle alternator. 2. The voltage control device for a vehicle alternator according to claim 1, wherein the bipolar transistor, the comparison means and the control means are formed on one integrated circuit.