JP3399782B2 - Automotive charging voltage control circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging voltage control circuit for an automobile. 2. Description of the Related Art There is an electric circuit for automobiles in which a battery is charged by an ACG (alternating current generator) linked to an engine, and various loads are driven by using the battery as a power source. In a two-wheeled vehicle using such a circuit, it is desirable that the vehicle be operable even when the battery is completely discharged or disconnected for some reason. FIG. 3 shows a conventional charge voltage control circuit for a two-wheeled vehicle in which the above-mentioned measures against battery detachment are taken. In the circuit of FIG. 3, the ACG 1 is provided so as to be linked with an engine (not shown), and the voltage generation terminal of the ACG 1 is connected to the charging terminal CH of the charging voltage control circuit 12. A battery terminal BT, which is a voltage supply terminal of the charging voltage control circuit 12, has a flasher relay 3 as a load, a battery 4, a stop lamp SL as one of the loads, and an ignition control circuit CDI. It is connected. The right and left flasher lamps LL and RL are connected to the flasher relay 3, and the flasher lamp selected by the selection switch SW1 blinks. The stop lamp SL is also turned on via the switch SW2. [0005] In the charging voltage control circuit 12, a thyristor SCR is connected in series between the terminals CH and BT. A node between the charging terminal CH and the anode of the thyristor SCR is grounded via the resistor R1, the diode D5, and the transistor Q1 in this order. Its resistance R1
The node between the thyristor SCR and the diode D5 is connected to the gate of the thyristor SCR via the diode D2 in the forward direction, and further, the thyristor SCR is connected via the resistor R2.
And the battery terminal BT. A node between the cathode of the thyristor SCR and the battery terminal BT is connected to a forward diode D3.
The resistor R3 and the capacitor C1 are grounded in this order. The node between the diode D3 and the resistor R3 is connected to the transistor Q1 via the Zener diode ZD.
Connected to the base. In the charging voltage control circuit 12 configured as described above, when the battery 4 is in the normal state of charge, the battery 4 is charged by the half-wave waveform of the positive voltage generated at the battery terminal BT, Zener diode ZD
If the battery voltage becomes higher than the withstand voltage of
The transistor Q1 is turned on to prevent the gate current from flowing, thereby inhibiting the thyristor SCR from being turned on to prevent overcharging. Thus, the turn-on prohibition means is configured. Next, the case where the battery 4 is deteriorated or disconnected is described below with reference to FIG. In this case, the capacitor C1 has a half-wave waveform of a positive voltage generated at the battery terminal BT by the ACG1.
Is charged, and when the voltage exceeds the withstand voltage value of the Zener diode ZD, the transistor Q1 is turned on. The ON time of the transistor Q1 is determined by the time constant of the capacitor C1 and the resistor R3.
As shown by the solid line. That is, while the transistor Q1 is on, the thyristor SCR remains off even if a positive voltage waveform is generated at the charging terminal CH, and no voltage is generated at the battery terminal BT. However, when the flasher lamps LL and RL are turned on when the battery is disconnected or the like, the battery terminal BT becomes a negative voltage due to the influence of the internal inductance as shown in the waveform of the flasher lamp operation in FIG. Even if the transistor Q1 is turned on and the node A is grounded, the cathode terminal of the thyristor SCR has a negative potential, so that a current flows through the gate of the thyristor SCR via the resistor R1 and the diode D2. Therefore, the thyristor SCR cannot be turned on (i.e., an imaginary line in the drawing), and the voltage of the battery terminal BT cannot be adjusted, so that an excessive voltage may be applied to the load connected to the battery terminal BT. In order to solve such a problem and realize a vehicle charging voltage control circuit capable of performing appropriate voltage adjustment even when the battery is disconnected or the like, the present invention has been developed. A vehicle charging voltage control circuit provided between a generator and a battery linked to an engine, comprising: a charging terminal connected to the generator; and a battery terminal connected to the battery and a load. A thyristor having an anode connected to the charging terminal and a cathode connected to the battery terminal, and an overvoltage for detecting the voltage of the battery terminal and prohibiting the thyristor from being turned on when the detected voltage reaches an overvoltage value. Preventing the gate current from flowing through the thyristor when the overvoltage prevention means operates and the battery terminal becomes a negative voltage. In order to stop the operation, a circuit for bypassing the gate current to the battery terminal is provided. Here, the case where the battery terminal becomes a negative voltage is, specifically, when the battery is disconnected or the battery is completely discharged, and the negative voltage is caused by the influence of the inductance of a load having an L component. Means when it occurs. Further, the battery overvoltage prevention means for prohibiting the thyristor from being turned on can be achieved by a circuit configuration that detects an overvoltage generated at the battery terminal, turns off the thyristor, and turns off the thyristor for a predetermined time. Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings. FIG. 1 shows a vehicle charging voltage control circuit 2 to which the present invention is applied. The same parts as those in the conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted. In the conventional example, a diode D is connected to the collector of the transistor Q1.
1, the diode D1 is provided on the emitter side of the transistor Q1 in the circuit of FIG. 1 according to the present invention. The node between the emitter of the transistor Q1 and the diode D1 is connected to the battery terminal BT via the diode D4 in the forward direction. Transistor Q
When the battery terminal BT is in a negative state while the thyristor SCR1 is on, the gate current of the thyristor SCR is bypassed to the battery terminal BT via the transistor Q1 and the diode D4.
Is prohibited. When the battery 4 is disconnected in the circuit of FIG. 1, the transistor Q1 is turned on when the battery terminal BT voltage exceeds the withstand voltage of the Zener diode ZD, as in the conventional example, and the capacitor C1 and the resistor R3 are turned on.
, The transistor Q1 repeats on / off in accordance with the time constant. When the transistor Q1 is turned on when the battery 4 is disconnected or the like, the gate of the thyristor SCR is grounded, so that the gate current can be prevented from flowing. It depends on the ON time of Q1. Therefore, ACG1
By setting the off time of the thyristor to some extent so that the positive voltage waveform does not occur at the battery terminal BT every time, it is possible to prevent an overvoltage of the battery terminal BT when the battery is disconnected. Thus, the turn-off means is configured. The case where the flasher relay 3 operates when the battery is disconnected will be described below. In this case, a negative voltage is generated at the battery terminal BT due to the influence of the inductance of the flasher relay 3. According to the present invention, when the transistor Q1 is turned on, the gate of the thyristor SCR is connected to the battery terminal BT.
1 on the anode side shown in FIG.
The potential at the point relative to the cathode changes as shown at the bottom of FIG. That is, while the negative voltage is being generated at the battery terminal BT, when the transistor Q1 is on, the potential at the point A (the anode side of the thyristor SCR) is not at the ground level but at the battery terminal B
Since the negative voltage of T pulls the thyristor S
There is no current that can turn on the CR, and FIG.
The thyristor SCR is turned off as shown in the fourth row. When the transistor Q1 is turned on, the voltage drop of the line passing through the diode D4 is reduced by the threshold voltage Vth of the thyristor SCR as shown at the bottom of FIG.
The thyristor SCR does not turn on when a negative voltage is generated at the battery terminal BT due to the influence of the inductance of the flasher relay 3. As described above, according to the present invention, when the battery is disconnected or the battery is completely discharged, a negative voltage is generated at the battery terminal due to the influence of the inductance of the load having the L component. Can also prevent the thyristor from turning on by bypassing the gate current of the thyristor to the battery terminal, and by controlling the normal turn-on inhibiting means,
It is possible to prevent the voltage of the battery terminal from abnormally increasing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a main part circuit diagram showing a vehicle charging voltage control circuit according to the present invention. FIG. 2 is a diagram showing a control waveform based on the present invention. FIG. 3 is a main part circuit diagram showing a conventional vehicle charging voltage control circuit. FIG. 4 is a diagram showing control waveforms in a conventional circuit. [Description of Signs] 1 ACG 2 charging voltage control circuit 3 flasher relay 4 battery 12 charging voltage control circuit D4 bypass diode

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-159933 (JP, A) JP-A-9-285035 (JP, A) JP-A-2-88432 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) H02J 7/14 H02P 9/00-9/48

Claims (1)

(57) [Claim 1] A vehicle charging voltage control circuit provided between a battery and a generator linked to an engine, comprising: a charging terminal connected to the generator; A battery terminal connected to the battery and the load; a thyristor having an anode connected to the charging terminal and a cathode connected to the battery terminal; and a voltage detected at the battery terminal, and the detected voltage becomes an overvoltage value. Overvoltage prevention means for prohibiting the thyristor from being turned on, wherein when the overvoltage prevention means operates and the battery terminal becomes a negative voltage, a gate current is prevented from flowing through the thyristor. A charging voltage control circuit for an automobile, comprising a circuit for bypassing a gate current to the battery terminal.