JPH0526959Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an automatic voltage regulator used in an alternating current generator driven by an internal combustion engine or the like.

(Prior art and its problems) Conventionally, as an automatic voltage regulator that controls the output voltage of an alternator such as a portable engine generator to a substantially constant value regardless of load fluctuations, for example, there is an automatic voltage regulator shown in FIG. something is known.

In FIG. 3, symbol G is a synchronous generator driven by an engine, and on the rotor side of this generator G, a rotor core 1 is attached to the crankshaft of the internal combustion engine directly or through a suitable coupling.
is arranged, and the field winding 2 is wound around it. Furthermore, an excitation winding 3 and an output winding 4 are provided on the stator side, and a part of the output winding 4 serves as a detection winding 4a.

A conventional automatic voltage regulator for such a generator G is configured as follows. That is, this automatic voltage regulator u includes a first rectifying and smoothing circuit 5,
It is composed of a second rectifying and smoothing circuit 6, a detection circuit 7, and a control circuit 8.

The first rectifying and smoothing circuit 5 includes a full-wave rectifier 51 that rectifies the output voltage of the excitation winding 3;
It consists of a capacitor _C1 that smoothes the rectified output of
A field current supply source that sends out a field current If to the output line 9 is formed.

The second rectifying and smoothing circuit 6 includes a full-wave rectifier 61 that rectifies the output voltage of the detection winding 4a, and a smoothing circuit that includes a resistor _R1 and a capacitor _C2 . The voltage waveform of the smoothing capacitor C ₂ is a pulsating waveform as shown in FIG. 6, and this is led to the detection circuit 7.

The detection circuit 7 consists of a resistor R ₂ for deriving the terminal voltage of the capacitor C ₂ to the control circuit 8, and a resistor R ₃ connected between the derived end of the resistor R ₂ and the ground _. The voltage is divided by resistors R ₂ and R ₃ to form a detection voltage of an appropriate level at the output terminal of resistor R ₂ .

The control circuit 8 includes a Zener diode DZ for setting the operating level of the control circuit 8 to a predetermined level, and a switching circuit consisting of an inverted connection of two transistors Q ₁ and Q ₂ as switching elements, The output line 9 is connected via the field winding 2 to the collector terminal of the transistor _Q2 . Note that D is a flywheel diode connected in parallel with the field winding 2. This control circuit 8
In this case, when the detected voltage is lower than the Zener voltage (a set voltage at a predetermined level), the previous stage transistor Q ₁ is turned off and the next stage transistor Q ₂ is turned on, and the above-mentioned field is turned off only during the period when this transistor Q ₂ is turned on. A field current If is supplied to the field winding 2 from a magnetic current supply source.

That is, as shown in FIG. 4, the level of the pulsating waveform portion of the detected voltage Vc is compared with that of the Zener voltage Vz, and in the section t where Vc<Vz periodically occurs, a predetermined field current If is supplied to the field winding 2, thereby adjusting the output voltage of the generator G.

By the way, since this type of automatic voltage regulator is equipped with a flywheel diode D for surge absorption, problems caused by the flywheel diode D may occur. In other words, generators equipped with this type of automatic voltage regulator are used as power sources in locations where commercial frequency power is difficult to obtain, such as civil engineering work sites, and therefore, generators equipped with this type of automatic voltage regulator are used as power sources in places where commercial frequency power is difficult to obtain, such as at civil engineering work sites. Capacitive loads with improvement capacitors are often connected. In this case, in the generator G, as is well known, a positive phase magnetic field and a negative phase magnetic field are generated due to armature reaction, and the positive phase component performs a magnetizing action to strengthen the field of the generator G, and the negative phase magnetic field is 2 interlinks with the field winding at twice the synchronous speed in the opposite direction to the rotor, causing a phenomenon that induces an alternating current voltage of twice the frequency in the field winding.

In response to a rise in output voltage due to such a magnetizing effect, the automatic voltage regulator turns off transistor Q ₂ and cuts off the current supply path to field winding 2 in order to suppress the rise in output voltage. However, since the flywheel diode D is connected in parallel to the field winding 2, the AC voltage of twice the frequency induced in the field winding 2 is rectified by the flywheel diode D. The current flows back into the closed loop of the field winding 2 and the flywheel diode D, causing a self-excitation effect in the generator G. As a result, abnormal voltage is generated out of control of the automatic voltage regulator.

(Purpose of the invention) This invention provides an automatic voltage regulator that can effectively suppress the self-excitation effect caused by the armature reaction when a capacitive load is connected using a simple circuit and improve the stabilization performance of the output voltage. The purpose is to

(Structure of the invention) In order to achieve the above object, according to this invention, the output voltage of a generator equipped with a field winding in which flywheel diodes are connected in parallel is detected, and the field winding is adjusted based on the detected output voltage. Automatic voltage adjustment that stabilizes the output voltage of the generator by controlling on/off the field current supplied to the field winding by controlling the first transistor connected in series to the winding. In the device, a second transistor to which the flywheel diode is connected in parallel;
a third transistor for enabling the second transistor to be turned on when the supply field current is turned off by the first transistor; and the first transistor provided between the base and collector of the third transistor. a capacitor for turning on the third transistor and turning off the second transistor when the supplied field current is controlled to be turned on by the transistor; and a capacitor for turning on the third transistor and turning off the second transistor when the supplied field current is controlled to be turned off by the first transistor. a diode connected in a reverse direction between the base and emitter of the third transistor to form a discharge path of the capacitor; and a diode provided between the capacitor and the base of the third transistor to turn on the third transistor. and a residual voltage regulation circuit that regulates the residual voltage of the capacitor in order to set the start timing of the capacitor, and the voltage applied to the second transistor is slightly increased in the on-enabled state of the second transistor. An automatic voltage regulator is provided, characterized in that the automatic voltage regulator is configured to turn on at certain times.

(Examples) Hereinafter, each example of this invention will be described with reference to the accompanying drawings. Components that are the same as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted.

FIG. 1 shows an automatic voltage regulator according to an embodiment of this invention. This automatic voltage regulator 10 is provided with a self-excitation prevention circuit 11 after a control circuit 8 to prevent self-excitation when a capacitive load is connected. This is something we have tried to deal with.

The self-excitation prevention circuit 11 includes a first transistor Q ₄ connected between the collector of the subsequent transistor Q ₂ in the control circuit 8 and the output line 9, and connected in parallel to the field winding 2 and the flywheel diode D, respectively.
and a second transistor connected in parallel to the first transistor _Q4 to control on/off of the first transistor Q4.
between the transistor Q ₃ , the voltage divider circuit consisting of the resistors R ₅ and R ₆ connected between the base of the second transistor Q ₃ and the ground, and the connection point A of the resistors R ₅ and R ₆ and the output line 9. and a diode D1 connected in reverse direction between the base and emitter of the second transistor _Q3 , and connected in series between the front stage transistor _Q1 of the control circuit 8 and the output line 9. A diode D2 is connected in the forward direction between the connection point of the resistors R ₃ and R ₄ and the connection point A.

In the above configuration, when the detection voltage is smaller than the Zener voltage, transistor Q ₁ is turned off, transistor Q ₂ is turned on, and the field current If
flows through transistor _Q2 . At this time, in the self-excitation prevention circuit 11, the base current of the second transistor Q3 is supplied via the diode _D2 , and the terminal voltage of the field winding 2 increases due to an increase in the field current If. The capacitor _C3 is charged according to
Supplied on the base of Q ₃ . As a result, the second transistor Q ₃ is turned on, which turns off the first transistor Q ₄ .

On the other hand, if the detected voltage is larger than the Zener voltage, transistor _Q1 turns on and the transistor
Q ₂ turns off. In the self-excitation prevention circuit 11, the capacitor _C3 is discharged through the path of the output line 9, the field lines 2, the diode D1 and the resistor _R6 . As a result, the base of the second transistor _Q3 becomes reverse biased, so it turns off, and the first transistor Q3 turns off.
Turn Q ₄ on and ready.

Therefore, when a capacitive load is connected, when the output voltage increases due to the magnetizing effect and transistor _Q2 turns off, the alternating current based on the alternating voltage induced in the field winding 2 by the armature reaction will be During the half cycle, via the flywheel diode D,
In the other half cycle, the current flows through the field windings 2 through the first transistor _Q4 , so the average current value (DC component) in the field windings 2 becomes zero, greatly reducing the self-excitation effect and making it stable. voltage adjustment operations can be performed.

Next, the role of diode D1 will be explained.
If the self-excitation prevention effect is performed without diode D1, the discharging capacitor
Since a half-wave rectified voltage is applied to C ₃ via the flywheel diode D, a voltage determined by the voltage division ratio of resistors R ₅ and R ₆ remains in the capacitor C ₃ without being able to be discharged. This residual voltage determines the operating point of the second transistor _Q3 , but how it is set has a significant impact on the stability and reliability of the self-excitation prevention circuit 11.

That is, if we consider the case where there is no voltage divider circuit of diode D1 and resistors R ₅ and R ₆ , the residual voltage is first defined by the emitter-base voltage V _EB of the second transistor Q ₃ , but this V _EB The variation is quite large, and when the residual voltage is large, the operating point of the second transistor Q ₃ becomes high, so the transistor Q ₂
Even if the first transistor Q4 turns on and starts supplying the field current If, the first transistor _Q4 does not turn off and the transistor
Both Q ₂ and Q ₄ are turned on. Since this short-circuits the output of the rectifying and smoothing circuit 5, an excessive current flows through both transistors Q ₂ and Q ₄ and is likely to lead to element destruction. In addition, when the residual voltage is low, the operating point of the second transistor _Q3 becomes low, so
The first transistor when transistor Q ₂ is off
Since it is not possible to reliably set Q ₄ to the on state and the second transistor Q ₃ to the off state, stable operation of the self-excitation prevention circuit 11 cannot be guaranteed. That is, if the second transistor Q ₃ turns on before the first transistor Q ₄ , the first transistor Q ₄ cannot turn on. The pulsating current flowing through the flywheel diode D causes the field winding 2 to
As the terminal voltage of the second transistor increases,
Q ₃ is fixed in the on state and the first transistor Q ₄ is fixed in the off state, which results in an increase in the self-excitation effect. Furthermore, even if the first transistor Q ₄ is turned on first, the collector current of the first transistor Q ₄ increases.
When the emitter voltage V _CE increases, the second transistor Q ₃ may turn on, and depending on the size of the capacitive load, self-excitation may not be prevented as described above.

Therefore, in this idea, the second transistor
A diode D1 is connected in the reverse direction between the base and emitter of _Q3 so that the residual voltage of the capacitor _C3 is independent of the _VEB of the second transistor _Q3 ,
Moreover, the residual voltage is set to a desired value determined by the voltage division ratio of the resistors R ₅ and R ₆ , thereby solving the above-mentioned problems related to the residual voltage.

Note that the residual voltage can be generated by the Zener diode ZD2 installed between _the capacitor _C3 and the base of _the second transistor _Q3 , as shown in FIG. It may also be specified by Zener voltage.

(Effects of the invention) As detailed above, according to the automatic voltage regulator according to the invention, the first transistor to which the flywheel diode is connected in parallel, and the first transistor to which the flywheel diode is connected in parallel, a second transistor for turning on the transistor; and a second transistor provided between the base and collector of the second transistor, and driving the second transistor on when controlling the supply field current to turn on the first transistor. a capacitor for turning off the second transistor; a diode connected in a reverse direction between the base and emitter of the second transistor to form a discharge path for the capacitor when controlling the supply field current to turn off; and a residual voltage regulation circuit that is provided between the bases of the second transistor and regulates the residual voltage of the capacitor in order to set the start timing of turning on the second transistor.
The transistor can form a current path in one half cycle of the alternating current flowing through the field winding when a capacitive load is connected. Therefore, when a capacitive load is connected, the average value of the alternating current flowing through the field winding can be reduced to zero, the self-excitation effect can be greatly suppressed, and the generation of abnormal voltage can be prevented. At this time, the residual voltage of the capacitor is made independent of the emitter-base voltage of the second transistor by the diode, and can be set to a desired value by the residual voltage regulating circuit. On/off control of the first transistor by the second transistor can be performed reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an automatic voltage regulator according to one embodiment of this invention, FIG. 2 is a block diagram showing an automatic voltage regulator according to another embodiment of this invention, and FIG.
The figure is a configuration diagram showing a conventional automatic voltage regulator.
The figure is a characteristic diagram showing the relationship between the detected voltage and the set voltage and the supply timing of the field current in a general voltage regulating operation of the automatic voltage regulating device. 2... Field winding, 3... Excitation winding, 4... Output winding, 4a... Detection winding, 5, 6... Rectification and smoothing circuit, 7... Detection circuit, 8... Control circuit, 10,2
0...Automatic voltage regulator, 11, 21...Self-excitation prevention circuit, _Q4 ...First transistor, _Q3 ...Second transistor, _C3 ...Capacitor, D1...
...Diode, R ₅ , R ₆ ... Resistor, ZD1 ... Zener diode.

Claims (1)

[Claims for Utility Model Registration] 1. Detecting the output voltage of a generator equipped with a field winding in which flywheel diodes are connected in parallel; In an automatic voltage regulator that controls on/off the field current supplied to the field winding by controlling on/off the transistor, and stabilizes the output voltage of the generator, the flywheel diodes are connected in parallel. a third transistor for enabling the second transistor to be turned on when the first transistor turns off the supplied field current; and a base of the third transistor. When the first transistor provided between the collectors turns on the supplied field current, the third transistor is turned on and the second transistor is turned on.
a capacitor for turning off the transistor, and a base-emitter connection of the third transistor that is to form a discharge path for the capacitor when the first transistor turns on the supplied field current. a diode, and a residual voltage regulating circuit provided between the capacitor and the base of the third transistor and regulating the residual voltage of the capacitor in order to set the start timing of turning on the third transistor, An automatic voltage regulator characterized in that the second transistor is configured to turn on when the voltage applied to the second transistor slightly increases in the on-enabled state. 2. The automatic voltage regulator according to claim 1, wherein the residual voltage regulating circuit is a voltage dividing circuit that divides the terminal voltage of the capacitor and forms a discharge path on one side. 3. The automatic voltage regulator according to claim 1, wherein the residual voltage regulation circuit is comprised of a Zener diode that sets the charging/discharging start voltage of the capacitor.