JPH0496696A - Voltage controller for vehicle alternator - Google Patents

Abstract

PURPOSE:To suppress noise, occurring upon turn ON of an exciting coil, through a simple circuitry and to reduce provability of failure by providing a generator incorporating an exciting coil and an armature coil for generating an electromotive force corresponding to the variation of field and a semiconductor element for supplying and interrupting current to/from the exciting coil. CONSTITUTION:When the battery voltage exceeds a regulation voltage, a comparator 14 produces a Hi output signal. Consequently, output of an inverter 25 in a charge pump circuit 11 is inverted to (to) and a transistor 24 is turned OFF thus interrupting power supply to the gate. On the other hand, a transistor 34 in a gate discharge circuit 12 receives Hi output from the comparator 14 and turned ON thus blocking the current 12 of a constant current circuit 36 from being fed to a transistor 33. Furthermore, a transistor 35 is turned OFF and current 13 is fed from a constant current circuit 37 to the transistor 33. Consequently, the current 13 of the constant current circuit 37 is fed to a transistor 32 thus discharging the gate thereof. As a result, a semiconductor element 8 is turned OFF and the exciting current of an exciting coil 4 decreases thus reducing the power to be produced by a generator 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage control device for a vehicle alternator that controls energization of an excitation coil of a generator using a semiconductor element.

[Prior Art] A technique disclosed in Japanese Patent Application Laid-Open No. 64-20000 is known as a conventional technique.

This technology reduces the noise generated when an excitation coil is turned on (or off) by a semiconductor element. The semiconductor device consists of a current detection circuit that detects the current of the semiconductor element, and an arithmetic circuit that controls the current of the semiconductor element so that it rises (or falls) according to the slope of the slope signal.

[Problem to be solved by the invention] The above-mentioned technology can be applied to slope circuits, current detection circuits,
The circuit configuration of the arithmetic circuit becomes complicated. For this reason, the voltage control device for a vehicle alternator shown in the prior art has a problem of high potential failure probability and high manufacturing cost.

The present invention provides a voltage control device for a vehicle alternator that can reduce noise generated when an excitation coil is turned on with a simple circuit configuration, reduce failure probability, and reduce manufacturing costs.

A generator includes an armature coil that generates an electromotive force by changes in the magnetic field generated by the excitation coil, and a semiconductor element that intermittents the current flowing through the excitation coil, and a driving signal is given to the semiconductor element to drive the semiconductor element. and a control circuit that turns on the excitation coil and supplies current to the excitation coil.

Then, when the control circuit turns on the semiconductor element,
A voltage between the terminals of the semiconductor element is detected, and a preliminary drive signal having a smaller driving force for the semiconductor element than the drive signal is applied to the semiconductor element until the voltage between the terminals drops to a predetermined value. Thereafter, when the voltage between the terminals drops to a predetermined value, the drive signal is applied to the semiconductor element.

[Means for Solving the Problems] In order to achieve the above object, the voltage control device for a vehicle alternator of the present invention employs the following technical means.

A voltage control device for a vehicle alternator includes an excitation coil that is energized to form a magnetic field, and the excitation 31 action] When turning on a semiconductor element, the control circuit provides a preliminary drive signal to the semiconductor element. The preliminary drive signal has a smaller driving force for the semiconductor element than the drive signal.

This prevents a sudden large current from being supplied to the excitation coil when the semiconductor element is turned on, thereby suppressing the generation of spike voltage in the armature coil. As a result,
Switching noise caused by spike voltage can be suppressed.

Alternatively, in the case where a flywheel diode is provided in parallel with the excitation coil, when the semiconductor element is turned on, a large current is prevented from flowing through the semiconductor element, and a large current is not supplied to the excitation coil. Therefore, the charges accumulated in the flywheel diode are discharged, and the flywheel diode is prevented from being short-circuited by the recovery current when the semiconductor element is turned on. As a result, it is possible to suppress the occurrence of switching noise caused by short-circuiting of the flywheel diode.

Thereafter, the voltage between the terminals of the semiconductor element decreases to a predetermined value. Then, the control circuit provides a drive signal to the semiconductor element. Since the drive signal has a larger driving force for the semiconductor element than the preliminary drive signal, a large current is supplied to the excitation coil and a large magnetic field is generated in the excitation coil.

[Effects of the Invention] The present invention provides a circuit configuration that applies a preliminary drive signal with a small driving force to a semiconductor element when turning on the semiconductor element, and a circuit configuration that applies a preliminary drive signal with a small driving force to the semiconductor element when the voltage between the terminals of the semiconductor element decreases to a predetermined value. The circuit configuration for switching to the drive signal can be easily realized compared to the conventional technology.

As a result, it is possible to reduce the failure probability of a voltage control device for a vehicle alternator that reduces noise generated when the excitation coil is turned on, and to keep manufacturing costs low.

[Example] Next, a voltage control device for a vehicle alternator according to the present invention will be described based on an example shown in the drawings.

(Configuration of Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention.
The figure shows an electrical circuit diagram of a voltage control device for a vehicle alternator.

The vehicle includes a battery 2 that supplies power to an electrical load 1 mounted on the vehicle. This battery 2 is charged by a generator 3 driven by an engine (not shown).

The generator 3 consists of an excitation coil 4 that is energized to form a magnetic field, and an armature coil 5 that generates an electromotive force by changes in the magnetic field generated by the excitation coil 4. One of the two is rotationally driven. Note that the alternating current generated in the armature coil 5 is passed through the rectifier circuit 6.
After being converted to DC by
Output to.

The amount of power generated by the generator 3, that is, the amount of power generated by the armature coil 5, is
It is determined by the driving speed of the generator 3 and the energization state of the exciting coil 4. The energization state of the excitation coil 4 is controlled by a control circuit 7, which will be explained next.

The control circuit 7 includes a semiconductor element 8 that cuts on and off the current supplied to the excitation coil 4 . The semiconductor element 8 of this embodiment is N
The channel power MOS FET controls the current value supplied to the excitation coil 4 according to the control state of the voltage value applied to the gate.

Note that the excitation coil 4 is provided with a flywheel diode 9 in parallel.

The gate voltage of the semiconductor element 8 is determined by the battery state determination circuit 1.
0, charge pump circuit 11, and gate discharge circuit 12
It is composed of.

The battery state determination circuit 10 is a circuit that detects the voltage of the battery 2 and determines whether to increase or decrease the amount of power generated by the generator 3, that is, a circuit that determines whether to turn on or turn off the semiconductor element 8. be.

This battery state determination circuit 10 compares the divided voltage value of the battery voltage with the reference voltage obtained by the constant voltage circuit 13 using a comparator 14 . Then, when the battery voltage is higher than the regulated voltage, the comparator 14 outputs the old signal to turn off the semiconductor element 8. Conversely, when the battery voltage is lower than the regulated voltage, the comparator 14 outputs a Lo signal when the semiconductor element 8 is turned on. Note that the divided voltage value of the battery voltage is obtained by the resistors 15 and 16.

Further, the constant voltage circuit 13 is a circuit that generates a constant voltage from the battery voltage supplied via the key switch 17.

The charge pump circuit 11 is connected to the battery state determination circuit 10.
This circuit controls the gate voltage of the semiconductor element 8 according to the output of the constant current supply section 18 and the pump section 19. The constant current supply unit 18 includes transistors 20, 21, and 22 that constitute a current mirror circuit.

This current mirror circuit is controlled by transistor 23. This transistor 23 is further controlled by a transistor 24. This transistor 24 is connected to the comparator 1 of the battery state determination circuit 10.
It is controlled by a signal obtained by inverting the output of 4 by an inverter 25. Note that a constant current circuit 26 is provided in series with the transistor 24, and the current value applied to the gate of the semiconductor element 8 is controlled by the current mirror circuit. In addition, the pump unit 19 is connected to an oscillation circuit 27 that always generates an old -LO double signal, and is operated by this oscillation circuit 27
- It consists of a transistor 28 that is turned OFF, and two capacitors that store the charge applied to the gate of the semiconductor element 8 when the transistor 28 is turned OFF. Note that numerals 30 and 31 shown in the figure are diodes that prevent reverse current flow.

The gate discharge circuit 12 of this embodiment discharges the voltage applied to the gate and reduces the voltage applied to the gate until the voltage between the terminals (drain and source) of the semiconductor element 8 reaches a predetermined value. , forming a preliminary drive signal.

This preliminary drive signal has a much smaller driving force for the semiconductor element 8 than a drive signal that does not discharge the gate charge. A transistor 32 is connected to the gate to discharge the charge on the gate. This transistor 32 constitutes a current mirror circuit with a transistor 33, and by controlling this transistor 33, the transistor 32 is controlled, and the gate voltage is controlled. And the transistor 33 is composed of two transistors 34, 35
controlled by This transistor 34.35 is
Two constant current circuits 3 to be supplied to the transistor 33
The transistor 34 controls the comparator 1 of the battery state determination circuit 10.
4 is turned on when the output is old (when the semiconductor element 8 is turned off), and prevents the current of the constant current circuit 36 from being supplied to the transistor 33. Further, when the output of the comparator 14 of the battery state determination circuit 10 is [0 (
It turns on when the semiconductor element 8 is turned on) and when the voltage value between the terminals of the semiconductor element 8 drops to a predetermined value, and prevents the current of the constant current circuit 37 from being supplied to the transistor 33.

Note that the reference numeral 38 is a diode that guides the current of the constant current circuit 36 to the transistor 35.

In this embodiment, the voltage between the terminals of the semiconductor element 8 is detected by the voltage applied to the excitation coil 4 as a means for detecting the voltage between the terminals of the semiconductor element 8.

Specifically, the voltage between the semiconductor element 8 and the exciting coil 4 is detected by the inverter 39. That is, when the voltage applied to the excitation coil 4 is lower than a predetermined value (when the voltage between the terminals of the semiconductor element 8 does not reach the predetermined value), the inverter 39 outputs the old signal.

Then, when the voltage applied to the excitation coil 4 becomes higher than a predetermined value (when the voltage between the terminals of the semiconductor element 8 reaches a predetermined value)
, the inverter 39 outputs a 0 signal. In this embodiment, a NOR circuit 40 is employed as a circuit for turning on the semiconductor element 8 and determining whether the voltage value between the terminals of the semiconductor element 8 has reached a predetermined value. This NOR circuit 40 is connected to the battery state determination circuit 10.
outputs a signal that turns on the semiconductor element 8, and when the voltage between the terminals reaches a predetermined value due to the output of the inverter 39, the old signal is output to the transistor 35.

(Operation of the embodiment) Next, the operation of the above embodiment will be briefly explained.

b) When the battery voltage becomes higher than the regulated voltage, the comparator 14 of the battery state determination circuit 10 generates an H output signal. Then, the output of the inverter 25 of the charge pump circuit 11 is inverted to LO, the transistor 24 is turned off, and as a result, the transistors 20, 21, 22, 23
is turned off, and power to the gate is stopped.

On the other hand, the transistor 34 of the gate discharge circuit 12 turns on in response to the old output of the comparator 14, and the constant current circuit 3
6 is prevented from being conducted to the transistor 33. Further, since the NOR circuit 40 outputs a signal of OFF, the transistor 35 is turned off and the current of the constant current circuit 37 is 1.
3 flows into transistor 33.

Then, a current 3 equal to that of the constant current circuit 37 flows through the transistor 32, discharging the charge at the gate.

As a result, the semiconductor element 8 is turned off, the excitation current of the excitation coil 4 decreases, and the amount of power generated by the generator 3 decreases.

(1) The operation when the battery voltage is lower than the regulated voltage will be explained using the time chart of FIG. 2.

When the battery voltage becomes lower than the regulated voltage),
The comparator 14 of the battery state determination circuit 10 is [0
generates an output signal. Then, charge pump circuit 1
The output of inverter 25 of No. 1 is inverted to Hl, transistor 24 is turned on, and as a result, transistors 20.21.2
2.23 is turned on, and a current 11 equal to that of the constant current circuit 26 flows through the transistor 20.21. Here, oscillation circuit 2
7 repeats ON-OFF, so the charge pump circuit 11 supplies a current expressed by the following equation to the gate.

Supply current 1=Il±(XVXf) Note that C is the capacitance of the capacitor 29, ■ is the power supply voltage supplied to the charge pump circuit 11, and f is the pumping frequency by the oscillation circuit 27.

On the other hand, the transistor 34 of the gate discharge circuit 12 is turned off in response to the output of the comparator 14 and does not prevent the current I2 of the constant current circuit 36 from being led to the transistor 33. Further, at the initial stage when the battery voltage becomes lower than the adjustment voltage, the voltage applied to the excitation coil 4 is low, and the inverter 39 generates the old signal. Then, Noah circuit 4
0 outputs a LO signal and also turns off the transistor 35. As a result, the current of constant current circuit 36.37 is 2±1
3 flows into the transistor 33, and as a result, the gate current is equal to the pre-drive signal, the supply current I-(current I2 + I3
).

When the gate voltage increases and exceeds the threshold value of the semiconductor element 8 (time t2), the impedance between the terminals of the semiconductor element 8 gradually decreases, and the voltage applied to the excitation coil 4 increases. At this time, the charge stored in the flywheel diode 9 is discharged. Then, as the voltage applied to the excitation coil 4 increases, the inverter 39 switches to LO (
At time t3), the output of the NOR circuit 40 is inverted to the old one. Then, the transistor 35 is turned on, and the transistor 32 whose gate was discharging is also turned off. As a result, the charge pump circuit 11 supplies the supply current ■, which is a drive signal, to the gate. At this time, the charge stored in the flywheel diode 9 has already been discharged, so even if a large current (supply current ■) is supplied to the gate from the charge pump circuit 11, the flywheel diode 9
is not shorted. Further, by supplying a large current (supply current) to the gate, the switching time after time t3 is shortened.

Then, at time t4, the semiconductor element 8 is completely turned on, the excitation current of the excitation coil 4 increases, and the amount of power generated by the generator 3 increases.

(Effects of Example) As shown during the above operation, when the semiconductor element 8 is turned on, a preliminary drive signal is applied to the gate to discharge the charge of the flywheel diode 9, and then a drive signal is applied to the gate. This prevents short-circuiting of the flywheel diode 9 and suppresses the generation of switching noise. Further, by applying the preliminary drive signal to the gate and then applying the drive signal to the gate, the magnetic force of the excitation coil 4 can be prevented from changing suddenly. This prevents the generation of back electromotive force in the armature coil 5, and also suppresses the generation of switching noise due to the back electromotive force of the armature coil 5.

The control circuit 7 of this embodiment has a simpler circuit configuration than the conventional one. As a result, the failure probability of the M-return circuit 7 can be reduced as compared to the conventional art, and manufacturing costs can be kept low.

(Second Embodiment) FIG. 3 shows an electric circuit diagram of a voltage control device for a vehicle alternator according to a second embodiment. Note that the same reference numerals as in the first embodiment indicate the same functional objects.

In this embodiment, a P-channel power MOSFET is used as the semiconductor element 8. Therefore, in this embodiment, the charge pump circuit shown in the first embodiment is not necessary.

The operation when turning on the semiconductor element 8 will be briefly explained.

When the battery voltage becomes lower than the regulated voltage, the comparator 14 of the battery condition determination circuit 10 generates a Lo output signal. Then, transistors 20 and 24 are turned off, and the supply of current to the gate is stopped.

On the other hand, initially when the battery voltage is lower than the adjustment voltage, the voltage applied to the excitation coil 4 is low and the inverter 3
9 generates the old signal. Then, the gate discharge circuit 12
The transistor 34 turns on in response to the old output of the inverter 39, and prevents the current 2 of the constant current circuit 36 from being led to the transistor 33.

Therefore, only the current 3 of the constant current circuit 37 flows through the transistor 33, and as a result, the gate is discharged by the current I3, and the semiconductor element 8 starts to turn on.

Then, the gate voltage increases and the inverter 39's [0
, the transistor 34 is turned off and the current I2. of the constant current circuit 36.37 is reversed. I3 is led to transistor 33. As a result, the gate is discharged by the current I2+I3, the semiconductor element 8 is rapidly turned on, and the excitation coil 4 is energized.

Note that when the battery voltage becomes higher than the regulated voltage, the comparator 14 of the battery condition determination circuit 10 generates the old output signal, turning on the transistor 20.24 and supplying current to the gate. Further, the transistor 35 is turned on, and the discharge of the gate by the gate discharge circuit 12 is stopped. As a result, the gate is charged, the semi-conducting shut-off valve 8 is turned off, and the excitation coil 4 is de-energized.

(Modification) Although an example has been shown in which the preliminary drive signal is formed by partially discharging the drive signal applied to the semiconductor element, the voltage value and current value supplied to the semiconductor element may be switched and applied.

Although an example is shown in which an FET is used as a semiconductor element, the electric circuit is not limited to the circuit configuration of this embodiment, and other elements such as bipolar transistors may be used. Other circuit configurations may be used, such as controlling drive signals.

Figure 2

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention, FIG. 1 is an electric circuit diagram of a voltage control device for a vehicle alternator, and FIG. 2 is a time chart for explaining the operation. be. FIG. 3 is an electric circuit diagram of a voltage control device for a vehicle alternator according to a second embodiment of the present invention. In the figure 3... Generator 4... Excitation coil 5.
... Armature coil 7 ... Control circuit 8 ... Semiconductor element comparator output t2t3 t4 time

Claims (1)

[Scope of Claims] 1) A generator including an excitation coil that is energized to form a magnetic field, and an armature coil that generates an electromotive force by changes in the magnetic field generated by the excitation coil, and a current that flows through the excitation coil. In the voltage control device for a vehicle alternator, the voltage control device includes a semiconductor element that turns on and off, and a control circuit that applies a drive signal to the semiconductor element to turn on the semiconductor element and supply current to the excitation coil. The control circuit detects the voltage between the terminals of the semiconductor element when turning on the semiconductor element, and generates a preliminary drive signal having a smaller driving force for the semiconductor element than the drive signal until the voltage between the terminals decreases to a predetermined value. A voltage control device for an alternator for a vehicle, characterized in that the driving signal is applied to the semiconductor element, and the drive signal is applied to the semiconductor element when the voltage between the terminals decreases to a predetermined value.