The present invention relates to a charging generator control apparatus, and particularly to a charging generator control apparatus which is provided with a switching circuit, a diagnostic circuit and a start-up detecting circuit, with which abnormal conditions can be detected and indicated without interfering with or degrading the normal functions of a conventional control circuit.
Control apparatus for a charging generator is the subject of two U.S. patent application, Ser. Nos. 478,000 and 478,126 filed by the present inventors on Mar. 23, 1983.
Referring to FIG. 1, a conventional charging generator control circuit will be described first. In FIG. 1, a three-phase AC generator 1, which may be mounted on a vehicle (not shown) and driven by an engine (not shown) has a three-phase star-connected armature coil 101 and a field coil 102. A full-wave rectifier 2 for full-wave rectifying an AC output of the AC generator 1 is provided with a first rectifier output terminal 201, a second rectifier output terminal 202 and a ground terminal 203. A voltage regulating circuit 3 serves to control the field current flowing through the field coil 102 so as to control the output voltage of the AC generator 1 to maintain it at a first predetermined value.
The voltage regulating circuit 3 is composed of a surge absorbing diode 301 connected across the field coil 102, a pair of power transistors 302 and 303 connected in a Darlington configuration for intermittently interrupting the current flow through the field coil 102, a resistor 304 constituting a base circuit of the transistors 302 and 303, a zener diode 306 used for detecting the output voltage of the AC generator 1 at the sound rectifier output terminal 202 with the diode 306 becoming conductive when this output voltage has reached a first predetermined value, a pair of resistors 307 and 308 connected in series to constitute a voltage dividing circuit, and an initial exciting resistor 309 connected across a charge indicator lamp 6 for supplying the AC generator 1 with an initial exciting current, even when the indicator lamp is broken. Reference numerals 4 and 5 denote a battery and a key switch, respectively.
Next, the operation of the thus-arranged conventional AC generator control apparatus will be described. First, when the key switch 5 is turned on for starting the engine, a base current flows into the transistors 302 and 303 from the battery 4 through the key switch 5 and the resistor 304 making the transistors 302 and 303 conductive. When the transistors 302 and 303 become conductive, a field current flows into the field coil 102 from the battery 4 through the key switch 5, the parallel connection of the charge indicator lamp 6 and the resistor 309, the field coil 2, and the transistors 302 and 303, causing the generation of a field magnetomotive force.
Under this condition, when the engine is started and the AC generator 1 is driven, an AC output induced in the armature coil 101 is full-wave rectified by the full-wave rectifier 2. If the rectified output is lower than the first predetermined value, the dividing-point voltage of the voltage divider constituted by the resistors 307 and 308 is still too low to make the zener diode 306 conductive, and hence the supply of field current is maintained so that the output voltage of the AC generator 1 increases as the rate of rotation increases. Thereafter, as the rate of rotation of the AC generator 1 further increases, the output voltage also increases until it exceeds the first predetermined value and, correspondingly, the dividing point voltage increases to cause the zener diode 306 to conduct, whereupon a base current is supplied to the transistor 305 through the zener diode 306 making the transistor 305 conductive. When the transistor 305 becomes conductive, the transistors 302 and 303 are turned off, cutting off the current flowing through the field coil 102, whereupon the output voltage of the AC generator 1 is lowered.
When the output voltage drops again to the first predetermined value, the zener diode 306 and the transistor 305 once more become non-conductive, causing the transistors 302 and 303 to conduct and energizing the field coil 102 to cause the output of the AC generator 1 to then increase.
The above-mentioned operation is carried out continuously to maintain the output of the AC generator 1 at the first predetermined value and hence to charge the battery 4 with the thus controlled output voltage. When the battery has become fully charged, the output voltage at the second rectifier output terminal 202 becomes substantially equal to the first predetermined value, and hence the charge indicator lamp 6 is extinguished to indicate the charged state.
In the conventional apparatus as described above, in case of a partial failure such as an open circuit in the field exciting circuit, the charge indicator lamp 6 will not light even if the AC generator 1 is in a non-generating state. Thus, the conventional apparatus has a disadvantage that the non-generating state cannot be detected and hence no indication produced of a discharged battery. Moreover, a break in a connection at the first rectifier output terminal 201 cannot be detected.
Accordingly, it is an object of the present invention to provide an AC charging generator control apparatus in which abnormal states or conditions, such as the non-generating stage, the uncontrolled state and the state in which there is a break in connection at the first rectifier output terminal can be detected and indicated.