JP2545612B2 - Output voltage control device for portable generator - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output voltage control device for a portable generator, and more particularly to an output voltage control device for a small portable generator that outputs a relatively large capacity DC.

(Prior art and its problems) In a generator that requires a relatively large current output,
The diameter of the output winding also becomes large, and sufficient consideration must be given to the insulation between winding coils in terms of withstand voltage and materials.

Considering this request for a relatively small portable generator, for example, in a generator that outputs a current of 30 to 40 A, a large-diameter coil for output winding is wound in a place where the iron core cannot be made too large. The wire machine requires a lot of tension,
Further, a semiconductor component for controlling the output voltage also needs to have a large capacity and a large size, which becomes a factor of complicating the control circuit unit.

On the other hand, for example, in a welding generator as disclosed in Japanese Utility Model Laid-Open No. 62-142473, two sets of output windings are provided so that the outputs of both sets can be superposed, and only one of them can be output. It is also considered that the welding current can be variably controlled in the range of a small current to a large current by controlling the chopper, but like a normal DC output generator,
It is very difficult to control such that the output voltage is kept at a constant level.

On the other hand, the applicant simultaneously controls a plurality of independent output windings, a plurality of thyristor bridge circuits respectively connected to the output windings, and a gate input voltage of the plurality of thyristor bridge circuits at the same time. We have already proposed an output voltage control device for a portable generator, which is composed of a control circuit (see Japanese Patent Application No. 1-85360).

By the way, when an electronic protector (breaker) using a power MOS FET is installed as a protection device for such an output voltage control device, for example, an output terminal (load)
When a short circuit occurs, the current detection circuit detects an overcurrent (overload) condition due to a large current flowing through the power MOS / FET, and then turns off the power MOS / FET to shut off the output. It is not preferable because a momentary large current may flow in between.

This momentary large current is caused by the rapid discharge current of the electric charge charged in the smoothing capacitor, and in order to withstand this momentary large current, it is necessary to devise the configuration of the detection circuit. In many cases, a large power MOS / FET with a large forward current allowance is required in terms of current and time. However power MO
Since S / FET is expensive when it is large, there are many requests to keep it as small as possible.

On the other hand, when the output terminal is short-circuited as described above, the amount of instantaneous current flowing in the power MOS / FET is reduced, that is, by reducing the smoothing capacitor capacity, a relatively small power MOS / FET can be used. Although it can be used satisfactorily, the capacity of the smoothing capacitor is limited by the charging / discharging current during operation, and simply lowering the capacity will exceed the allowable ripple amount of the capacitor and adversely affect the capacitor itself. Will end up.

In view of the above problems, the present invention enables the capacity of the smoothing capacitor to be reduced by reducing the ripple current supplied from the rectifier circuit to the smoothing capacitor, and the output of the portable generator that addresses the above problems. An object is to provide a voltage control device.

(Means for Solving the Problem) In order to achieve the above object, the present invention is provided with a plurality of output windings independently wound around the same iron core and corresponding to the respective output windings. A rectifier power supply unit that is independent of each other with a plurality of thyristor bridge rectifier circuits, connects the thyristor bridge rectifier circuits of each of these units in parallel, combines their outputs, and smooths them with a smoothing capacitor. It is composed of a power supply circuit and a field effect transistor which is interposed in series between the DC power supply circuit and the output terminal and which is turned off when the voltage drop between the source and the drain due to overcurrent exceeds a predetermined value. Overcurrent protection circuit and detection of the variation amount different for each of the thyristor bridge rectifier circuits according to the variation amount of the voltage of the DC power supply circuit It is characterized in that a voltage control circuit for controlling the gate input voltage at a level is provided.

(Function) The amount of voltage fluctuation of the DC power supply circuit is detected at different detection levels, and the gate input voltage is controlled for each thyristor bridge rectification circuit to automatically control the voltage of the DC power supply circuit to a substantially constant level. To do.

(Embodiment) Hereinafter, an embodiment of an output voltage control device for a portable generator according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an overall configuration diagram of an output voltage control device according to the present invention. In FIG. 1, reference numeral 1 denotes an AC generator driven by an engine, which has two independent output windings L ₁ and L _{2 respectively.}
And an independent control winding (auxiliary winding) L ₃ are wound around the same stator core.

This AC generator 1 has an outer rotor type magnet rotor (not shown) around a multi-pole fixed iron core around which windings are wound.
Are driven by an engine to rotate, and the output winding L ₁ and the output winding L ₂ output three-phase power, and the control winding L ₃ outputs single-phase power.

The output windings L ₁ and L ₂ are connected to three-phase rectifier thyristor bridge circuits 2 and 3 each composed of a thyristor and a diode, and each three-phase output is full-wave rectified and voltage-controlled as described later. To be done. Thyristor bridge circuit 2,
The respective output terminals of 3 are combined and connected to the smoothing capacitor C, and the capacitor C smoothes a combination of the respective full-wave rectifier circuits.

The FET provided on the output side of the smoothing capacitor C is a field effect transistor (power MOS FET) provided as breaker means for shutting off the overcurrent when it is energized, and the drain terminal is the positive terminal of the capacitor C and the source is The terminal is connected to the output terminal 6.

In this embodiment, 12 V DC is output for external load.

On the other hand, the auxiliary winding L ₃ is connected to the rectifier diode 4 and the constant voltage circuit 5. The rectifying diode 4 rectifies the single-phase output from the auxiliary winding L ₃ , and the constant voltage circuit 5 converts this rectified output into a constant voltage. Now, if the voltage across the terminals of capacitor C is 12
V, assuming that the output voltage of the constant voltage circuit 5 itself is 8V, the input / output common terminal 5a of the constant voltage circuit 5 is connected to the positive terminal of the capacitor C, so this terminal 5a exhibits 12V, and the output of the constant voltage circuit 5 Terminal 5b exhibits 20V.

Reference numerals 7 and 8 denote comparators, and the constant voltage output from the constant voltage circuit 5 is connected to the inverting terminals (−) of the comparators 7 and 8 by resistors R ₁ and R 2.
_The reference voltage obtained by dividing by ₂ is supplied to each, and the non-inverting terminal (+) of the comparator 7 is supplied with the potential (20V) of the output terminal 5b of the constant voltage circuit 5 and the potential (0V of the negative terminal of the capacitor C).
The voltage V ₇ obtained by dividing the difference V) by resistors R ₃ , R ₄ , and R ₅ is supplied, and the non-inverting terminal (+) of the comparator 8 is divided by the potential difference V ₈ (V ₇ > V ₈ ) is supplied. Since the potential of the output terminal 5b of the constant voltage circuit 5 is constant, both voltages V ₇ and V ₈ reflect the fluctuation of the voltage across the capacitor C.

The output terminal of the comparator 7 is a thyristor bridge rectifier circuit 2
Is connected to the gate terminal of each thyristor and connected to the output terminal 5b of the constant voltage circuit 5 via a resistor, and the output terminal of the comparator 8 is connected to the gate terminal of each thyristor of the thyristor bridge rectifier circuit 3 It is connected to the output terminal 5b of the constant voltage circuit 5 via a resistor.

9 inputs the voltage between the source and drain terminals of the FET
The gate control circuit outputs the low level signal to the gate terminal to cut off the conduction of the FET when the source-drain voltage rises to a predetermined value.

The operation of the output voltage control circuit configured as above will be described below.

According load current flowing from the output terminal 6, 6 'to an external load increases, the voltage across the capacitor C is lowered, the resistance R ₃ in accordance with this, R _4, R voltage V ₇ of the respective connection points _5, V ₈ is 5a
It will rise from the viewpoint.

First, when neither of the connection point voltages V ₇ and V ₈ reaches the reference voltage supplied to the inverting terminals of the comparators 7 and 8, both of the comparators 7 and 8 send a low level signal to each thyristor bridge rectifier circuit 2, It outputs to each thyristor 3 and neither circuit 2 nor 3 conducts or rectifies.

Next, since the connection point voltages V ₇ and V ₈ have a relationship of V ₇ > V _{8, when} the output voltage decreases, V ₇ exceeds the reference voltage, and when V ₈ does not reach the reference voltage, the comparator 7 Increases the gate input voltage of the thyristor bridge rectifier circuit 2 according to V ₇ ,
Further, in this state, when the output voltage rises due to the reduction of the load, that is, when V ₇ drops, the gate input voltage is lowered accordingly. At this time, the comparator 8
Since V ₈ does not reach the reference voltage, the gate input voltage is not output to the thyristor bridge rectifier circuit 3, so the thyristor bridge rectifier circuit 3 does not conduct or rectify.

Further, when both the connection point voltages V ₇ and V ₈ exceed the reference voltage due to the decrease in the output voltage, both the comparators 7 and 8
The gate input voltage of the thyristor bridge rectifier circuits 2 and 3 is increased according to V ₇ and V _8, and both thyristor bridge rectifier circuits 2 and 3 are turned on to supply the rectified output to the capacitor C.

As described above, the control for maintaining the output voltage substantially constant is performed regardless of the increase or decrease of the load current.

By the way, when two thyristor bridge rectifier circuits are simultaneously controlled by a single comparator output voltage, the relationship between the ripple current and the output voltage with respect to the load current is expressed as shown in FIGS. 2 (a) and 2 (b), for example. That is,
When the maximum supply load current amount is, for example, 30 A, the maximum ripple current exhibits 12.5 A when the load current is 15 A, and 0 A and
The ripple current exhibits the minimum value (0A) when supplying 30A. The output voltage gradually decreases as the load current increases.

On the other hand, in the device of the present invention in which the two thyristor bridge rectifier circuits 2 and 3 are controlled by different output voltages respectively output from the corresponding comparators, the relation between the ripple current and the output voltage with respect to the load current is Is represented, for example, as shown in FIGS. 2 (c) and 2 (d).
That is, when the maximum supply load current amount is 30A, the load current is supplied only from the rectifying bridge circuit 2 while the load current is 0 to 15A, so that the maximum ripple current 6A is supplied when the load current 7.5A is supplied. , 0A and 15A supply, ripple current shows minimum value. Next, since the thyristor bridge rectifier circuit 2 always supplies a three-phase rectified output during the load current of 15 to 30 A, there is almost no ripple current from the circuit, and the rectifier bridge circuit 3 outputs according to the increase of the load current Generates electric current. Therefore, the ripple current reaches the maximum value of 6A when the load current of 22.5A is supplied, and becomes the minimum when the load current of 15A and 30A is supplied.

As described above, the maximum value of the ripple current can be significantly reduced in the device having the configuration of the present invention, and for example, in the present embodiment, it is reduced by about 6.5A. Therefore, it is possible to use a low-capacity capacitor having a small ripple tolerance.

By the way, the power MOS that constitutes the overcurrent protection circuit
The FET gate control circuit 9 detects the source-drain terminal voltage corresponding to the FET source-drain terminal current, and supplies an off signal to the FET gate terminal when this voltage rises and reaches a predetermined value. The current between the source and drain terminals of the FET, that is, the flow of the supply current to the external load, is cut off. However, as described above, the capacitance of the capacitor C in the device of the present invention is smaller than that of the conventional device. Therefore, even if the output terminals 6 and 6 ′ are short-circuited, the amount of capacitor discharge current flowing through the FET is small, and therefore it is possible to use a FET having a relatively small withstand current capacity.

Incidentally, two output windings L ₁ in the above embodiment, L ₂ and the output winding L _1, L ₂ two rectifier bridge circuits 2 and 3 which are respectively connected to, the two thyristor bridge rectifier circuit 2 ,
Although it is composed of two comparators 7 and 8 for controlling the gate inputs of 3 with different voltages, the invention is not limited to the structure of this embodiment, and the output winding and the corresponding thyristor bridge rectifier circuit, Even if a large number of comparators are provided, the output voltage can be controlled with the same idea.

(Effects of the Invention) As described in detail above, the present invention provides a plurality of output windings independently wound around the same iron core, and a plurality of thyristor bridges provided corresponding to the respective output windings. A DC power supply circuit that forms a plurality of independent rectification power supply units with a rectification circuit, connects the thyristor bridge rectification circuits of the respective units in parallel, combines the outputs, and smooths this with a smoothing capacitor, An overcurrent protection circuit composed of a field effect transistor that is inserted in series between this DC power supply circuit and the output terminal and turns off when the voltage drop between the source and drain due to overcurrent exceeds a predetermined value. And a gate input with a detection level having a different fluctuation amount for each of the thyristor bridge rectifier circuits according to the fluctuation amount of the voltage of the DC power supply circuit. Since the voltage control circuit for controlling the voltage is provided, the maximum ripple current value can be reduced by shifting the peak value of the ripple current of the thyristor bridge rectifier circuit. Can be used, and FET with a small forward current allowable value can also be used.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the device of the present invention, and FIG. 2 is a characteristic diagram showing a relationship between a ripple current and an output voltage with respect to a load current, comparing a conventional device and the device of the present invention. 1 ... AC generator, 2, 3 ... Thyristor bridge rectifier circuit, C ... Smoothing capacitor, FET ... Field effect transistor, 9 ... Field effect transistor gate control circuit, 7, 8 ... Comparator.

Claims (1)

(57) [Claims] 1. A plurality of rectifying power sources, which are independent of each other by a plurality of output windings which are independently wound around the same iron core, and a plurality of thyristor bridge rectifying circuits which are provided corresponding to the respective output windings. A DC power supply circuit that forms a unit, connects the respective thyristor bridge rectifier circuits of these respective units in parallel, combines the outputs, and smooths this with a smoothing capacitor, and between this DC power supply circuit and the output terminal. An overcurrent protection circuit that is interposed in series and that is configured to include a field effect transistor that is turned off when the voltage drop between the source and drain due to overcurrent exceeds a predetermined value, and the amount of voltage fluctuation of the DC power supply circuit. According to the above, each thyristor bridge rectifier circuit is provided with a voltage control circuit that controls a gate input voltage at a detection level with a different variation amount. The output voltage control apparatus for a portable power generator, characterized in that.