JP2751153B2 - Voltage regulator for vehicle charging generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage regulator for a vehicle charging generator, and more particularly, to a circuit configuration of a voltage regulator capable of making the entire charging generator compact and inexpensive. [Background Art] A charging generator of a vehicle is provided with a voltage regulator, which controls a field winding current of the charging generator to adjust the amount of power generation. The AC generated voltage is converted into a DC voltage by a full-wave rectifier provided in the charging generator and supplied to a vehicle-mounted battery or the like. When the output terminal of the full-wave rectifier is disconnected, for example, a high voltage (hereinafter referred to as G pulse) generated in the armature winding of the charging generator appears at the terminal, and the connection of the on-vehicle battery is made. In the case where the voltage is disconnected, an external surge from the igniter reaches the output terminal and a high voltage appears. Then, the current of the field winding connected between the output terminals of the full-wave rectifier is reduced by the G pulse and the external surge.
The semiconductor switch that is turned on and off may be damaged. In order to prevent this, there is a type in which the full-wave rectifier is configured by a power Zener diode having a predetermined Zener voltage. Particularly, for the purpose of absorbing an external surge, the positive and negative electrodes of the full-wave rectifier are used. It is known that a zener diode is provided on each side (Japanese Patent Publication No. 54-5083). [Problems to be Solved by the Invention] However, for an external surge, the Zener diodes on the positive electrode side and the negative electrode side are connected in series. A field-effect transistor (FET) that is required for semiconductor switches and has the characteristic of low resistance when conducting
Is difficult to use as a semiconductor switch.
The reason is that the smaller the resistance of the FET during conduction, the lower the breakdown voltage. The present invention has been made by paying attention to the fact that the external surge has a high voltage but a small energy, and can absorb the external surge satisfactorily even if the number of the power zener diodes is reduced, whereby the charging generator It is an object of the present invention to provide a voltage regulator for a vehicle charging generator that can reduce the size and cost of the vehicle, and that can use an FET having a small conduction resistance as a semiconductor switch and can also increase the output of the charging generator. . [Means for Solving the Problems] The configuration of the present invention will be described with reference to FIG.
Is the field winding of the vehicle charging generator with the full-wave rectifier 2 installed inside
The current of 32 is controlled to keep the output voltage of the charging generator constant. All of the positive-side diodes or all of the negative-side diodes of the full-wave rectifier 2 are composed of power Zener diodes 21A, 21B, and 21C.
Turn on the current of the field winding 32 connected between 3 and the negative output terminal 24
A semiconductor switch 11 for performing -OFF control is provided. Further, a voltage detection circuit 12 is provided, which is provided when the voltage of the positive output terminal 23 exceeds a predetermined value.
Is made conductive. Here, the predetermined value V1 is set to a value satisfying Vz ≦ V1 ≦ 2Vz, where the zener voltage of the power zener diodes 21A, 21B, 21C is Vz. [Operation] In the voltage regulator of the present invention, when the connection of the positive output terminal 23 is disconnected, a high voltage is generated in the armature winding 31, but this is generated on the positive or negative side of the full-wave rectifier 2. The zener diodes 21A, 21B, 21C provided limit the voltage to a low constant voltage. Therefore, a voltage higher than the breakdown voltage is not applied to the semiconductor switch 11. On the other hand, when the vehicle-mounted battery is disconnected, a high voltage due to an external surge appears at the positive output terminal 23, which is detected by the voltage detection circuit 12, and the semiconductor switch 11 is turned on. As a result, the high voltage is instantaneously eliminated,
Also in this case, no high voltage is applied to the semiconductor switch 11. Therefore, a semiconductor switch having a low withstand voltage can be used. [Embodiment] In FIG. 1, a voltage adjusting device 1 includes resistors 13a, 13b, 13
a P-type MOS which is a semiconductor switch having a voltage feedback circuit in which c is connected in series, a Zener diode 14 for setting a reference voltage, and control transistors 15 and 16 and connected to a field winding 32 of a charging generator -It has FET11. The full-wave rectifier 2 is provided on the output side of the three-phase armature winding 31 of the charging generator. The positive-side diode of the rectifier 2 is replaced with ordinary rectifier diodes 22A, 22B, and 22C. Zener diodes 21A, 21B, 21
There is as C. The positive output terminal 23 of the full-wave rectifier 2 is connected to the vehicle-mounted battery 4 and the electric load 5 via a charging line, and is also connected to the source of the FET 11.
The negative output terminal 24 is connected to the field winding 32,
Grounded. The flywheel diode 17 is provided in parallel with the field winding 32, and the collector of the control transistor 15 is connected to the vehicle battery 4 via the ignition switch 6. Furthermore, the gate of FET11 and the negative output terminal 2
A Zener diode 12 as a voltage detection circuit is provided between the four. Note that the Zener voltage Vz of the power Zener diodes 21A to 21C is set to be lower than the battery voltage and within a range that does not adversely affect the battery charging, in consideration of the ripple and the voltage drop of the charging line current. Then FET11
The voltage of the positive output terminal 23, at which conduction of the
Assuming that the breakdown voltage is VBs, Vz <V1 <BVs. As an example, the Zener voltage Vz of the power Zener diodes 21A to 21C is set to about 30 V, and the Zener voltage of the Zener diode 12 is set to a voltage not more than twice the Zener voltage Vz of the power Zener diodes 21A to 21C, that is, about 30V. About 25V so that FET11 conducts when it exceeds 30V
And In the voltage regulator having the above configuration, when the feedback voltage VF of the charging voltage exceeds the Zener voltage of the Zener diode 14, the transistor 16
Is turned off, the FET 11 becomes non-conductive, and the field winding current stops. As a result, the power generation stops, and the charging voltage decreases. The feedback voltage VF is a Zener diode 14
When the voltage drops below the Zener voltage of the transistor, the transistor 16 turns on, the FET 11 conducts, power generation starts, and the charging voltage increases. In this way, the charging voltage is kept constant. Now, when the connection of the positive output terminal 23 is disconnected, the armature winding 31
Becomes no load, and the generated voltage rises sharply. Here, when the power generation voltage is close to 30 V, the Zener diodes 21A to 21C are short-circuited between the phases to suppress the power generation voltage. Thus, the G pulse appearing at the positive output 23 is limited to a value less than 30V. When the vehicle-mounted battery 4 is disconnected, the positive output terminal 23
Is subject to extraneous surges. In this case, if the external surge exceeds 30 V, the source-gate of the FET 11 is biased and the FET 11 becomes conductive. As a result, the extraneous surge is quickly eliminated. At this time, the extraneous surge flows through the FET 11, but since the time is extremely short, there is no problem such as heat generation. Only one of the positive-side diode and the negative-side diode is a power Zener diode 21A.
Since the temperature is set to 2121 C, the number of power zener diodes to be installed is reduced, thereby making it possible to reduce the size and cost of the entire charging generator. In the above embodiment, all the negative-side diodes of the full-wave rectifier are Zener diodes, but all of the positive-side diodes may be Zener diodes. Alternatively, all of the diodes on both the positive electrode side and the negative electrode side may be Zener diodes. When the exciter diodes 25 and 26 are provided from the neutral point of the armature winding 31 as shown in FIG. 2, one of the exciter diodes 25 and 26 is a power Zener diode. By the way, the rectifier diode 22 in each of the above embodiments is used.
A, 22B and 22C are preferably Schottky diodes. This is because a Schottky diode has a smaller forward voltage drop of about 0.5 V than a general diode, and thus has less loss. Therefore, the Schottky diode generates a small amount of heat during operation, and does not require a heat dissipation structure or a heat insulation structure, so that it is possible to reduce the size of the charging generator. The above Schottky diode is usually a reverse breakdown voltage BVR
Is about 60 V (current 30 A), but there is no problem because BVR <Vz for the Zener voltage Vz of the power Zener diodes 21 A, 21 B, and 21 C (about 30 V in each of the above embodiments). Also,
The leakage current is as large as several tens mA to several hundred mA, but this is not a problem because each Schottky diode is connected in series with the power Zener diode. [Effects] As described above, according to the present invention, all of the positive-side diodes or all of the negative-side diodes of the full-wave rectifier are used as power Zener diodes, and the semiconductor switch is turned on when the voltage at the positive output terminal exceeds a predetermined value. Is provided, and the predetermined value V1 is set to Vz ≦ V1 ≦ 2Vz (Vz:
By setting to satisfy the Zener voltage of the power Zener diode), the breakdown voltage of the Zener diode connected in series is not required for the semiconductor switch as in the past, so a MOS-FET with sufficiently low conduction resistance is used as the semiconductor switch. can do. Therefore, it is possible to increase the field winding current without causing the problem of heat generation, and it is possible to increase the output of the charging generator.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are circuit diagrams showing different embodiments of the present invention. DESCRIPTION OF SYMBOLS 1 ... Voltage regulator 11 ... MOS field effect transistor (semiconductor switch) 12 ... Zener diode (voltage detection circuit) 2 ... Full-wave rectifier 21A, 21B, 21C ... Power Zener diode 22A, 22B, 22C ... Rectifier diode 23 ... Positive output Terminal 24: negative output terminal 31: armature winding 32: field winding

Claims (1)

(57) [Claims] In a voltage regulator for controlling a current of a field winding of a vehicle charging generator having a full-wave rectifier therein to maintain a constant output voltage of the charging generator, all of the positive-side diodes of the full-wave rectifier are provided. Or, all of the negative-side diodes are composed of power Zener diodes, and a semiconductor switch is provided for ON-OFF controlling the current of the field winding connected between the positive output terminal and the negative output terminal of the full-wave rectifier,
A voltage detection circuit is provided for turning on the semiconductor switch when the voltage at the positive output terminal exceeds a predetermined value, and the predetermined value V1 is a value that satisfies Vz ≦ V1 ≦ 2Vz where the Zener voltage of the power Zener diode is Vz. A voltage adjusting device for a vehicle charging generator, wherein the voltage adjusting device is set to: 2. 2. The voltage regulator for a vehicle charging generator according to claim 1, wherein a diode other than the power Zener diode among the diodes constituting the full-wave rectifier is a Schottky diode.