JP2703293B2 - Engine driven AC generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention rectifies the AC output of an engine-driven AC generator, particularly an AC generator driven by an engine, to DC, and further generates a pulse width modulation (PWM) signal. The present invention relates to an engine-driven AC power generator that converts a predetermined low-frequency AC voltage into a predetermined low-frequency AC voltage using an inverter circuit driven by an AC power generator.

[Conventional technology]

Since the generation frequency of an engine-driven alternator is determined by the number of revolutions of the engine, the alternating-current voltage generated by the alternator must be once generated in order to always generate a constant frequency, for example, a commercial frequency of 50 Hz or 60 Hz. The DC voltage is converted to an AC voltage again by using an inverter circuit, so that an AC voltage having the constant commercial frequency is constantly generated irrespective of the fluctuation of the engine speed.

As a conventional inverter circuit for converting this direct current to alternating current, a circuit having a switching element circuit configuration as shown in FIG. 4 has been used.

FIG. 6 shows a circuit configuration in which switching elements for generating an alternating current are connected in a bridge form by bipolar transistors 1 to 4 for generating a commercial frequency alternating current having a rectangular waveform between output terminals 5 and 6. Has been conventionally used as an effective method.

FIG. 7 shows a switching element for generating an alternating current.
It has a circuit configuration in which FET transistors 7 to 10 are connected in a bridge. It is necessary to drive at a high frequency such as a PWM signal. In place of the above transistors 1 to 4, it is excellent in switching speed by voltage drive and like a bipolar transistor. Since it has no storage time, it is composed of FET transistors that are convenient for driving at high frequencies.

In order to stabilize the AC output of the commercial frequency, a method of stabilizing the DC output when the AC voltage generated from the AC generator is rectified and converted into DC is shown in FIG.
The circuit of FIG. 9 was used. That is, FIG. 8 shows a circuit configuration for stabilizing the DC output by phase control. The thyristor corresponding to the voltage of each phase of the three-phase AC generator 14 by the gate signal from the phase detection circuit 15 is used. It controls 16 to 18 conduction angles and tries to stabilize them.

FIG. 9 shows a circuit configuration in which the DC output is stabilized by the chopper method.
The rectifier circuit 19 converts the AC voltage generated from 14 into DC,
Chopper circuit according to the level of this converted DC voltage
It is intended to make 20 work and to stabilize it.

[Problems to be solved by the invention]

The conventional inverter circuits shown in FIGS. 6 and 7, respectively, and the DC stabilizing circuits shown in FIGS. 8 and 9 have the following problems, respectively. That is, in the inverter circuit shown in FIG. 6, bipolar transistors 1 to 4 are used. Due to the storage time, there is a limit in driving at a high frequency, and when driving at a high frequency such as a PWM signal is desired. , There is a problem that it cannot be used because of its lack of followability.

In the inverter circuit shown in FIG. 7, since a bias voltage must be applied between the gate and the source of each of the FET transistors 7 to 10, a three-system power supply in which the ground points are insulated as shown in FIG. 11 to 13
There is a problem that requires.

In the DC stabilization circuit shown in FIG. 8, the phase control is performed for each phase voltage, so that the phase detection circuit 15 becomes complicated, and when the output of the small-capacity three-phase AC generator 14 is phase-controlled, There is a problem that the output waveform of the three-phase AC generator 14 is distorted and linear control cannot be practically performed.

In the DC stabilizing circuit shown in FIG. 9, when the output capacity becomes large, a large switching element of the chopper circuit 20 must be used, and when it cannot be controlled by one switching element, a plurality of switching elements are connected in parallel. There is a problem that the control is complicated, such as connecting, switching simultaneously, and equally sharing the load.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and a transistor and a FET are provided in an inverter circuit part.
A bridge circuit that performs switching with a pair of transistors is configured, and the transistor is driven by a low-frequency square wave, and a FET transistor that is paired with the transistor is driven by a high-frequency PWM signal during an ON period of the rectangular wave. In this manner, switching can be performed even at a high frequency, and the DC output can be stabilized with a simple circuit configuration to generate a stabilized AC voltage having a sine waveform at a predetermined low frequency, that is, a commercial frequency. It is intended to provide a power generator.

[Means for solving the problem]

In order to achieve the above object, an engine-driven AC generator of the present invention includes an AC generator driven by an engine, a rectifier circuit for rectifying an AC voltage generated by the AC generator into DC, and a rectifier circuit. An inverter circuit unit for converting a DC voltage of a circuit unit to a low-frequency AC voltage, wherein the inverter circuit unit converts the AC voltage to DC and further converts the AC voltage to a predetermined low-frequency AC voltage. And a bridge circuit section in which a transistor alternately driven by a low-frequency signal and an FET transistor driven by a high-frequency signal during an ON period of the transistor are connected in a bridge. Hereinafter, description will be made with reference to the drawings.

〔Example〕

FIG. 1 is a circuit configuration of an embodiment of an engine-driven AC power generator according to the present invention, FIG. 2 is a configuration of an embodiment of an inverter circuit unit using a PWM method, and FIG. 3 is supplied to a switching element of a bridge circuit unit. FIG. 4 shows the configuration of an embodiment of a bridge circuit section, and FIG. 5 shows the configuration of an embodiment of a rectifier circuit section for stabilizing a DC output.

Before explaining the circuit configuration of one embodiment of the engine-driven AC power generator according to the present invention shown in FIG. 1, before the inverter circuit unit and the bridge circuit unit by the PWM method used in FIG.
The rectifier circuit section will be described first.

In FIG. 2, reference numerals 1, 2, 5, and 6 correspond to those in FIG. 6, and 9, 10 correspond to those in FIG.

Reference numeral 22 is a sine wave generation circuit, 23 is a rectangular wave generation circuit, 24 is a triangular wave generation circuit, 25 and 26 are absolute value circuits, 27 is a comparator, 28
Represents a drive signal supply circuit, 29 and 30 represent AND circuits, 31 and 32 represent inverter circuits, and 33 represents a bridge circuit unit.

The sine wave generating circuit 22 has a predetermined low frequency sine wave,
An oscillator that generates a sine wave of a commercial frequency of 50 Hz or 60 Hz, for example, a known circuit such as a Wien bridge oscillator is used. The frequency of the AC output voltage at the output terminals 5 and 6 is determined by the oscillation frequency of the sine wave generation circuit 22. FIG. 3 (I) shows a sine wave waveform output from the sine wave generation circuit 22.

The rectangular wave generating circuit 23 receives the sine wave of the commercial frequency from the sine wave generating circuit 22, and synchronizes with each positive or negative waveform of the sine wave in FIGS. 3 (V) and (VI). Each of the illustrated rectangular waves is output. These two rectangular waves are generated by separating the sine waves from the sine wave generating circuit 22 at the threshold levels L ₁ and L ₂ shown in FIG. 3 (I). It is generated so as not to become H level.

The triangular wave generating circuit 24 is an oscillator for generating a triangular wave shown in FIG. 3 (II), and its oscillation frequency is selected to be higher than the commercial frequency of the sine wave generated from the sine wave generating circuit 22, for example, 10 KHz. Are used.

The absolute value circuits 25 and 26 are full-wave rectifier circuits that turn a negative waveform into a positive waveform based on a zero level with respect to the input signal waveform. The negative waveform is turned back, and the absolute value circuit 26 operates to turn the negative waveform of the triangular wave of the triangular wave generating circuit 24 back. Therefore, from these two absolute value circuits 25 and 26, the third
The waveform of the solid line shown in FIG.

The comparator 27 includes a sine-wave full-wave rectified waveform in which a negative waveform portion is turned back to the positive side in the absolute value circuit 25, and an absolute value circuit 26.
The pulse corresponding to the level of the full-wave rectified sine wave is compared with the full-wave rectified waveform triangular wave whose frequency is about twice that of the original triangular waveform with the negative waveform part turned back to the positive side. This is a circuit that generates a PWM signal having a width. Therefore, the comparator 27 outputs the PWM signal shown in FIG. 3 (IV).

The drive signal supply circuit 28 is a circuit for supplying the drive signal to the switching element of the bridge circuit section 33. The drive signal supply circuit 28 is generated from the rectangular wave generation circuit 23 in synchronization with the positive and negative waveforms of the sine wave generated from the sine wave generation circuit 22. Drive signals Φ ₁ , Φ ₂ , and the drive signal Φ of the square wave
₁ , Φ ₂ and the PWM signal output from the comparator 27 are ANDed by AND circuits 29 and 30, respectively, to obtain drive signals Φ ₃ ,
_Four signals of Φ4 are prepared.

Drive signals Φ ₃ and Φ from drive signal supply circuit 28
₄ is configured to drive the FET transistors 9 and 10 in the bridge circuit unit 33 via the inverter circuits 31 and 32, respectively, so that the sine wave generation circuit 22
Transistor 1 for every positive half cycle of the sine wave
And the FET transistor 9 are driven respectively, and the transistor 2 and the FET transistor 10 are driven respectively for each negative half cycle of the sine wave, so that the switching elements of the bridge circuit unit 33 are always driven in an orderly manner. Become. Therefore, an AC voltage having a frequency corresponding to the frequency generated by the sine wave generating circuit 22 is generated between the output terminals 5 and 6.

FIG. 4 shows an embodiment of the bridge circuit unit, and the bridge circuit unit forms the pair described in FIG.
That is, a bridge circuit is constituted by one set of the bipolar transistor 1 and the FET transistor 9 driven at the same time and one set of the bipolar transistor 2 and the FET transistor 10 forming a pair.

The transistors 1 and 2 are provided with Darlington-connected transistors 34 and 35, respectively, and the transistors 34 and 35 are driven by driving transistors 36 and 37, respectively. Drive signals Φ ₁ , Φ _{2 of} rectangular waves are input to these driving transistors 36, 37, respectively, in an orderly manner every positive or negative half cycle of the sine wave generated by the sine wave generating circuit 22.

On the other hand, the FET transistors 9 and 10
Transistors 1 and 2, which are paired with transistors 9 and 10, respectively, provide high-frequency PWM signal drive signals Φ ₃ and Φ ₄
Are respectively input.

In this way, a bipolar transistor is operated for a low-frequency drive signal such as a commercial frequency, and an FE having a high switching speed is used for a high-frequency drive signal such as a PWM signal.
Because it operates with a T-transistor, the harmful effects of storage etc. are eliminated and the transistor
Since the drive signals Φ ₁ and Φ ₂ given to 36 and 37 may be pulses with respect to the ground potential, the power supply circuit of the bridge circuit can be completed by one system, and the circuit is simplified.

FIG. 5 shows an embodiment of a rectifier circuit for stabilizing a DC output. Reference numeral 14 corresponds to that of FIG. 8, reference numeral 38 denotes a rectifier, reference numeral 39 denotes an output voltage detection circuit, and reference numeral 40 denotes a gate. Drive circuit, 41 to 43 are photothyristor couplers, 44 to 46
Represents a thyristor, 47 to 49 represent gate circuits, 50 represents a comparator, and 51 represents a variable resistor.

The three-phase AC voltage generated by the three-phase AC generator 14 is rectified to DC by a thyristor-type rectifier 38 connected in a three-phase bridge.

Now, assuming that the DC output is zero or lower than a predetermined voltage, the detection voltage of the output voltage detection circuit 39 input to the non-inverting input terminal of the comparator 50 is the variable voltage input to the inverting input terminal of the comparator 50. The voltage is lower than the reference voltage of the resistor 51, and the output of the comparator 50 becomes L level. As a result, each LED in the photothyristor couplers 41 to 43 connected in series is turned on, and the photothyristor in each photothyristor coupler is turned on. Of the three thyristors 44 or 46,
The photothyristor of the photothyristor / coupler corresponding to the thyristor having the phase voltage in the ON-enabled state is turned on, and the thyristor having the ON-enabled phase voltage is turned on by turning on the photothyristor. Therefore, the DC output increases. When the DC output becomes higher than a predetermined voltage, the detection voltage of the output voltage detection circuit 39 input to the non-inverting input terminal of the comparator 50 is applied to the variable resistor input to the inverting input terminal of the comparator 50.
The voltage becomes higher than the reference voltage of 51, and the output of the comparator 50 becomes H level. This enables photo thyristors and couplers
Each LED in 41 to 43 goes out, and gate circuits 47 to 49
, And all the thyristors 44 to 46 are turned off. Thereafter, the on / off control is repeated in the same manner, so that the DC output is kept constant and stabilized.

As described above, the gate circuits 47 to 49 are simultaneously made operable, and the thyristors of the phases that can be turned on among the thyristors 44 to 46 are controlled to be turned on. Since the rectifier 38 side and the gate drive circuit 40 side are insulated, the gate drive circuit
The ground line on the side 40 can be shared with the side on the rectifier 38, and only one system is required. Therefore, an effective connection can be made in combination with the next-stage inverter circuit section.

In the embodiment of the engine-driven AC power generator according to the present invention shown in FIG. 1, reference numerals 1, 2, 5, and 6 correspond to those in FIG. 6, and 9, 10 correspond to those in FIG. , 14 correspond to those in Fig. 8, 22 to 28, 31 to 33 correspond to those in Fig. 2, 35 to 37 correspond to those in Fig. 4, and 38, 40 to 50.
Corresponds to that of FIG.

Reference numeral 53 denotes a DC power supply circuit, 54 denotes a voltage supply circuit, 55 denotes an AC output detection circuit, 56 denotes a current detection circuit, 57 denotes an instantaneous peak current detection circuit, 58 denotes an overload detection circuit, 59 denotes a load compensation circuit, and 60 denotes a gate. Drive circuit, 61 and 62 are inductors, 63 is a capacitor, 64 is a dummy resistor, 65 is a thyristor, 66 to 69 are NAND circuits, 70
To 72 are inverter circuits, 73 to 76 are diodes, 7
7,78 represents a resistance.

The voltage supply circuit 54 activates the inverter circuit unit via the drive signal supply circuit 28 when the three-phase AC generator 14 is driven by an engine (not shown) and the number of rotations exceeds a predetermined number of revolutions. When the number of revolutions becomes lower than the set value, the inverter circuit section is deactivated and a stable AC voltage is supplied. Hysteresis is provided between the number of rotations at which the inverter circuit section operates and the number of rotations at which the inverter circuit section is made inoperative to ensure the stability of the device.

The AC output detection circuit 55 is a detection circuit for converting the AC voltage generated at the output terminals 5 and 6 into a constant voltage, and a comparator in the gate drive circuit 40 based on the detection voltage detected by the AC output detection circuit 55. 50 output is changed to H level or L level. Therefore, as described with reference to FIG.
Of the thyristors 44 to 46 is controlled to conduct, and the AC output is made constant through the DC output being made constant.

The current detection circuit 56, the instantaneous peak current detection circuit 57, and the overload detection circuit 58 are provided to protect the device from the occurrence of an abnormality in the device or from an overload state. By not lighting the LEDs of the photothyristor couplers 41 to 43 via 40, the DC output of the rectifier 38 is suppressed, and the generation of AC output is suppressed.

When the instantaneous peak current detection circuit 57 detects a peak current equal to or more than a predetermined value, the switching operation of the FET transistors 9 and 10 is further stopped via the drive signal supply circuit 28 to protect the device.

When the load connected between the output terminals 5 and 6 is light or no load, the load compensation circuit 59
That is, the gate drive circuit 60 is operated by the detection current detected by the voltage drop of the resistors 77 and 78, and the thyristor 65 is turned on, so that the dummy resistor 64 is connected between the output terminals 5 and 6. , Inductor 6
The waveform distortion rate is improved by the filter circuit including the capacitors 1 and 62 and the capacitor 63.

When the load connected to the output terminals 5 and 6 becomes heavier than a predetermined value, the gate drive circuit 60 stops outputting a signal to the gate of the thyristor (triac) 65 due to the detection current of the current detection circuit 56, and the dummy resistor It operates to remove 64 from outputs 5 and 6.

The drive signal supply circuit 28 has four NAND circuits 66 or
Although it is composed of 69 and two inverter circuits 70 and 71, it is basically equivalent to that of FIG. In the case of FIG. 1, when the instantaneous peak current detection circuit 57 detects an abnormal peak current, the three-phase AC generator 14 rises to a predetermined speed or more, and the device can be controlled stably. The configuration is exactly the same as that of FIG. 2 except that the supply of the drive signal to the inverter circuit section, especially the FET transistors 9 and 10 is cut off. Accordingly, the operations of the sine wave generating circuit 22 and the comparator 27 for generating a signal to be input to the drive signal supply circuit 28 are completely the same, and the description thereof will be omitted.

The method of stabilizing the DC voltage of the rectifier 38 and the gate drive circuit 40 is the same as that of FIG.

However, the gate drive circuit 40 is configured to stop the rectifier function of the rectifier 38 when an abnormality occurs to protect the device safety.
Or 76 is provided to activate the stop function.

〔The invention's effect〕

As described above, according to the present invention, a high-frequency PWM signal is shared by FET transistors with a high operation speed, and a low-frequency commercial frequency signal is shared by bipolar transistors. With this configuration, it can operate following a high-frequency PWM signal.
In addition, a single power supply is required.

Further, the thyristor in the rectifier uses a photo thyristor coupler so that the thyristor can be simultaneously turned on to stabilize the DC output, thereby simplifying the circuit configuration.

Since the connection and removal of the dummy resistor are performed according to the connected load, the distortion of the sine wave waveform at the time of light load is improved.

Furthermore, an orderly drive signal can be given to the switching elements constituting the bridge circuit, and the switching elements do not fail to roll.

[Brief description of the drawings]

FIG. 1 is a circuit configuration of an embodiment of an engine-driven AC power generator according to the present invention, FIG. 2 is a configuration of an embodiment of an inverter circuit unit using a PWM method, and FIG. 3 is supplied to a switching element of a bridge circuit unit. FIG. 4 is an explanatory diagram of a signal generation waveform of a drive signal, FIG. 4 is a configuration of an embodiment of a bridge circuit unit, FIG. 5 is a configuration of an embodiment of a rectifier circuit unit for stabilizing a DC output, and FIG.
FIGS. 7 and 8 show the configuration of a conventional switching element in a bridge circuit, and FIGS. 8 and 9 show the configuration of a conventional rectifier circuit for stabilizing a DC output. In the figure, 1 to 4 are transistors, 7 to 10 are FET transistors, 11 to 13 are power supplies, 14 is a three-phase AC generator, 15 is a phase detection circuit, 16 to 18 are thyristors, 19 is a rectifier circuit, 20
Is a chopper circuit, 22 is a sine wave generation circuit, 23 is a rectangular wave generation circuit, 24 is a triangular wave generation circuit, 25 and 26 are absolute value circuits, 27 is a comparator, 28 is a drive signal supply circuit, 33 is a bridge circuit section, 34 Or 37 is a transistor, 38 is a rectifier, 39 is an output voltage detection circuit, 40 is a gate drive circuit, 41 to 43 are photothyristor couplers, 44 to 46 are thyristors, 47 to 49
Is a gate circuit, 50 is a comparator, 53 is a DC power supply circuit, 54
Is a voltage supply circuit, 55 is an AC output detection circuit, 56 is a current detection circuit, 57 is an instantaneous peak current detection circuit, 58 is an overload detection circuit, 5
9 is a load compensation circuit, 60 is a gate drive circuit, 61 and 62 are inductors, 63 is a capacitor, 64 is a dummy resistor, and 65 is a thyristor.

Claims (2)

(57) [Claims] An AC generator driven by an engine, a rectifier circuit for rectifying an AC voltage generated by the AC generator to DC, and a DC voltage of the rectifier circuit converted to a low-frequency AC voltage. An AC circuit for converting an AC voltage into a DC voltage and further converting the AC voltage into a predetermined low-frequency AC voltage, wherein the inverter circuit section includes a transistor alternately driven by a low-frequency signal. And FE driven by a high-frequency signal during the ON period of the transistor
A bridge circuit in which a T transistor is connected in a bridge shape; a filter circuit for making the output waveform of the bridge circuit a sine waveform; a sine wave generating circuit for generating a low frequency sine wave; and a high frequency triangular wave. A triangular wave generating circuit to generate, a comparator that outputs a PWM signal having a pulse width corresponding to a sine wave comparison level based on the sine wave of the sine wave generating circuit and the triangular wave of the triangular wave generating circuit; For each half cycle of the sine wave generated from the circuit, a pair of the pair of transistors in the bridge circuit section and the FET transistor are alternately applied to the low-frequency signal of the rectangular wave and the high-frequency signal of the PWM signal output from the comparator. Drive signal that supplies a drive signal synchronized with the above to the paired transistor and FET transistor of the bridge circuit section, respectively. Engine-driven AC generator apparatus characterized by comprising a supply circuit. 2. A rectifier circuit comprising: a rectifier for rectifying an AC voltage with a set of thyristors, a diode forming a pair with the thyristors, and a photothyristor coupler for controlling conduction of each thyristor. An output voltage detection circuit for stabilizing the voltage, a protection detection circuit for detecting an overload current, an instantaneous peak current, and an overload of a load connected to the output terminal, respectively, and a detection signal and protection for the output voltage detection circuit. A gate drive circuit for inputting each protection detection signal of the detection circuit to the photothyristor / coupler to stabilize the AC output voltage, and to stop the rectifier function of the rectifier in the event of an abnormality; The engine-driven AC generator according to claim 1, wherein the engine-driven AC generator is protected.