JP2696847B2 - Vehicle charging control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control device for a vehicle, and more particularly, to a charge control device that can effectively prevent intermittent noise generated due to intermittent rotor coil excitation current. [Prior Art] FIG. 5 shows a circuit diagram of a conventional charge control device. The charging generator 1 has a rotor coil 11, and the voltage adjustment circuit 2 is provided with a switching transistor 21 for controlling ON / OFF of the current of the rotor coil 11. The transistor 21 is operated by a transistor 23 at the preceding stage, and the transistor 23 is connected to the vehicle-mounted battery 3 via a resistance voltage dividing circuit provided with a Zener diode 26.
Is fed back. A reference voltage is set by the Zener diode 26, and the operation of the switching transistor 21 is controlled such that the feedback voltage matches the reference voltage.
The generated voltage generated in the stator coil 12 is supplied to the battery 3 after being rectified into a direct current by the rectifier 13. Thus, the battery charging voltage is always maintained at a predetermined constant value. By the way, the rotor coil 11 is provided with a flywheel diode 22 in parallel to effectively use the back electromotive force and also to protect the transistor 21, but when the transistor 21 is turned on, the flywheel diode 22 accumulates. The output voltage at the B terminal drops sharply due to the rapid release of electric charges, causing noise. Also, when the transistor 21 is turned off, the output voltage fluctuates due to the back electromotive force, which also causes noise. there were. Therefore, conventionally, as shown in the figure, a capacitor is connected between the base on the input side of the transistor 23 and the collector on the output side.
24 is provided to constitute a Miller integrating circuit, and the switching operation of the switching transistor 21 is moderated to prevent noise. [Problems to be Solved by the Invention] However, in the above-described conventional configuration, although the integration operation is effectively performed when the switching transistor is turned on and noise can be greatly reduced, the integration operation is not sufficiently performed when the switching transistor is turned off and noise is reduced. There was a problem that reduction of the amount was insufficient. In addition, since it is necessary to use a capacitor having a relatively large capacity as a capacitor, there is also a problem that it becomes an external chip capacitor and it is difficult to make a monolithic IC of all circuits. The present invention solves such a problem, and provides a charge control device that can effectively suppress the generation of noise when the switching transistor is intermittently operated and that can make the entire circuit compact and IC. With the goal. [Means for Solving the Problems] The configuration of the present invention will be described with reference to the drawings.
(FIG. 1) has a switching transistor 21 for ON-OFF control of the current of the rotor coil 11, compares the fed-back battery voltage with a reference voltage, activates the switching transistor 21 by a binary output, and sets the battery charging voltage. A charge control device that keeps a constant value inverts the binary output and generates an output that rises to a “1” level with a gradual time for a “0” level input (FIG. 2). And a plurality of emitter follower transistor circuits 27B provided between the output terminal of the delay circuit 27A and the base of the switching transistor 21. [Operation] When the binary output generated by comparing the battery voltage with the reference voltage changes from the “1” level to the “0” level, the output of the delay circuit gradually has the “0” level with time. The level further rises to "1" level, and accordingly, the switching transistor gradually conducts through the emitter follower transistor circuit. In this way, it is possible to avoid a sudden discharge of the accumulated charge of the flywheel diode when the exciting current is applied, thereby preventing the generation of noise. When the binary output changes from "0" level to "1" level, the output of the delay circuit immediately drops from "1" level to "0" level. Output gradually becomes "0" with time due to the contribution of the junction capacitance between the collector and the base of the remaining transistors except the first transistor.
Descend to the level. Thus, the switching transistor is slowly turned off, and a sudden decrease in the exciting current is avoided, thereby preventing the occurrence of noise due to the back electromotive force of the rotor coil. [Effects] As described above, according to the charging control device of the present invention, it is possible to effectively prevent the occurrence of noise in the output of the charging generator in any case of intermittent rotor coil current. Further, since the present invention utilizes the collector-base junction capacitance of the emitter follower transistor, there is no need to externally attach a large-capacity chip capacitor, and the entire circuit can be made compact and monolithic. [Embodiment] In FIG. 1, a charging generator 1 has a rotor coil 11, a stator coil 12, and a rectifier 13, and a voltage adjusting circuit 2 is connected in series to the rotor coil 11 to disconnect and connect its exciting current. A switching transistor 21 is provided, which comprises a pair of Darlington-connected transistors. The rotor coil 11 is provided with a flywheel diode 22 in parallel. The transistor 21 is operated by a binary output of a comparator 28 via a noise prevention circuit 27 whose configuration will be described later. The reference voltage Vc from the reference voltage generation circuit 281 is input to the “−” terminal of the comparator 28.
A feedback voltage VF obtained by dividing the voltage of the battery 3 by the resistors 29A and 29B is input to the “+” terminal. In the figure, 4
Is a key switch. FIG. 2 shows the configuration of the noise prevention circuit 27. The circuit
27 is delay circuit 27A and emitter follower transistor circuit 2
7B, the delay circuit 27A includes a transistor 271 receiving the binary output of the comparator 28, a transistor 274 forming a Miller integrating circuit, a capacitor 272, a diode 273, and a charging current source 275. The emitter follower transistor circuit 27B has two transistors 276 and 277 connected in an emitter follower connection, collector resistors 278A and 278B, and a discharge current source 279. The emitter of the transistor 277 is connected to the base of the switching transistor 21. In the charge control device having the above configuration, when VF <Vc, the comparator output becomes “0” level, and the transistor 271 is turned off. The base potential of the transistor 276 does not rise immediately because the capacitor 272 is in a discharging state, and the current amount of the charging current source 275 and the capacitor 272
Gradually becomes the “1” level in the time determined by the capacity of As a result, the conduction of the switching transistor 21 is gradually reduced over time, the rapid release of the accumulated charge of the flywheel diode is prevented, and the generation of noise when the rotor coil excitation current is applied is prevented. When VF> Vc, the comparator output becomes "1" level, and the transistor 271 is turned on. Transistor 276
Is immediately turned off when its base potential goes to "0" level, while transistor 277 has its collector
It does not become completely non-conductive until the charge stored in the junction capacitance C between the bases is discharged. Therefore, the switching transistor 21 becomes gradually non-conductive over time, the generation of the back electromotive force of the rotor coil 11 is suppressed, and the generation of noise when the excitation current is stopped is prevented. According to such a configuration, generation of noise can be effectively suppressed in any case of intermittent rotor coil current.
Further, since the collector-base junction capacitance C is used, or the capacitor 272 can be made as small as the charging current source 275, a monolithic IC of the entire circuit can be realized without providing an external capacitor. FIG. 3 shows another embodiment of the present invention, in which a transistor
A capacitor 280 may be provided between the collector and base in addition to the junction capacitance of 277. In this case, the capacitance of the capacitor is small enough to be realized by a monolithic IC (about several tens of pF).
Things are good. FIG. 4 shows still another embodiment of the present invention, in which the emitter follower transistors 276 and 277 can be Darlington-connected. The emitter follower transistor is not limited to the two-stage connection as in the above embodiment, but may be three or more stages in order to obtain a necessary delay time. Further, the discharge current source 279 is not always necessary.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall circuit diagram of a charge control device, FIG. 2 is a circuit diagram of a noise prevention circuit, and FIGS. 3 and 4 each show another embodiment of the present invention. FIG. 5 is an overall circuit diagram of a charge control device showing a conventional example. 1 ... Charging generator 11 ... Rotor coil 2 ... Voltage adjusting circuit 21 ... Switching transistor 22 ... Fly wheel diode 27 ... Noise prevention circuit 27A ... Delay circuit 27B ... Emitter follower transistor circuit 281 ... Reference Voltage generation circuit 3 ... Battery

Claims (1)

(57) [Claims] It has a switching transistor for ON-OFF control of the rotor coil current of the vehicle charging generator, compares the fed-back battery voltage with a reference voltage, activates the switching transistor by a binary output, and keeps the battery charging voltage constant. In the charge control device, a delay circuit is provided for inverting the binary output and for generating an output that rises to a “1” level with a gradual time for a “0” level input, and an output terminal of the delay circuit. A charge control device for a vehicle, wherein a plurality of emitter follower transistor circuits are provided between the bases of the switching transistors.