JPH0475468A - Inverter - Google Patents

Abstract

PURPOSE:To obtain an inverter in which a voltage across a capacitor as a power source of an upper arm semiconductor switch driving circuit is not lowered by so correcting a switch control signal that a lower arm switch is temporarily closed when the lower arm switch is continuously opened for a predetermined time or longer, and charging it when the arm switch is closed. CONSTITUTION:A counter 40a inputs the output of a voltage comparator 34, counts it when the input is '1', and generates an output signal when it counts for a predetermined period. Further, when an input signal is continued in a '1' state, similar operation is repeated. A one shot pulse generator 40b generates a pulse when the counter 40a outputs. A switching circuit 40c closes a lower arm semiconductor switch 2 while a pulse is output from the generator 40b to charge a capacitor 18. Thus, even if the capacitor having a small capacity is used, an inverter which is normally operated, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter device that converts direct current to alternating current by pulse width modulation.

[Conventional technology]

FIG. 10 is a block diagram showing a conventional inverter device, which is normally used to drive a three-phase induction motor. In Figure 1O, (1) is a DC power supply, (2) is a U-phase lower arm switch in three-phase AC, for example, a U-phase lower arm semiconductor switch, and (5) is a U-phase upper arm switch, for example, U It is a phase upper arm semiconductor switch, and a U phase lower arm semiconductor switch (2) and a U phase upper arm semiconductor switch (
5) are connected in series, with the ten poles of the DC power supply (1) connected to the U-phase upper arm semiconductor switch (5) at both ends connected in series, and the U-phase lower arm semiconductor switch (2)
The negative pole of the DC power supply [1] is connected to the side of A pulse width modulated U-phase AC output is taken out from the connection point (1001) between the lower arm semiconductor switch (2) and the U-phase upper arm semiconductor switch (5). (8
) is a three-phase induction motor connected as a load of an inverter device, (9) is a U-phase lower arm semiconductor switch (2)
(12) is a feedback diode connected in antiparallel to the upper arm semiconductor switch (5) of the U phase, and feedback diode (9), (12) is connected in antiparallel to the U-phase upper arm semiconductor switch (5).
) is provided to prevent abnormal voltage from occurring when the V-phase and W-phase upper-arm semiconductor switches and lower-arm semiconductor switches, which will be described later, are turned off.

(15) is a U-phase lower arm semiconductor switch drive unit that drives the U-phase lower arm semiconductor switch (2), for example, a U-phase lower arm semiconductor switch drive circuit; (16) is a U-phase upper arm semiconductor switch ( 5), for example, a U-phase upper arm semiconductor switch drive circuit, and (17) a DC power supply for a U-phase lower arm semiconductor switch drive circuit (15).

Note that this DC power supply (17) is also used as a DC power supply for a V-phase lower arm semiconductor switch drive circuit (not shown) and a W-phase lower arm semiconductor switch circuit (not shown). (18) is the U-phase capacitor, (19)
When the U-phase lower arm semiconductor switch (2) is on, the DC voltage of the DC power supply (17) is connected to the U-phase capacitor (
18), charges the U-phase capacitor (18), and
When the phase lower arm semiconductor switch (2) is turned off and the voltage at the connection point (1001) between the U phase lower arm semiconductor switch (2) and the U phase upper arm semiconductor switch (5) becomes high, the cutoff occurs. The U-phase capacitor (18) functions as a power source for the U-phase upper arm semiconductor switch drive circuit (16). (30)
is a U-phase voltage command generating means, for example, a U-phase voltage command generating unit, which generates a U-phase voltage command in pulse width modulation that converts a voltage into a pulse width of a predetermined cycle pulse, (33)
is a carrier signal generating means, for example, a carrier signal generating section, which generates a carrier signal as an alternating current wave having the same period as the pulse period in the pulse width modulation described above.

Note that the carrier signal is a triangular wave or a sawtooth wave, and has a frequency higher than the frequency of the above-mentioned U-phase voltage command.

(34) has the above-mentioned U-phase voltage command inputted to one input, the above-mentioned carrier signal inputted to the other input, and outputs when the above-mentioned U-phase voltage command is larger than the above-mentioned carrier signal. Set it to "1"', and set it to 10" when it is small U
Phase voltage comparison means, for example, a U-phase voltage comparator.

Note that the output of the carrier signal generator (33) is also input to the V-phase and W-phase voltage comparators (35) and (36). (37) inverts the output signal of the U-phase voltage comparator (34), and inverts the U-phase lower arm single conductor switch drive circuit (1
5), and the output of the U-phase voltage comparator (34) is connected to the human power of the 2U-phase upper arm semiconductor switch drive circuit (16).

The lower arm semiconductor switch (2), upper arm semiconductor switch (5), feedback diode f9+,
(12i, lower arm semiconductor switch drive circuit (15)
, upper arm semiconductor switch drive circuit (16), capacitor (18), diode (19), voltage command generator (3
0), voltage comparator (34), and NOT circuit (37) were for the U phase, but for the ■ phase, the lower arm semiconductor switch (3), the upper arm semiconductor switch (6), and the feedback diode ( lO), (13), lower arm semiconductor switch drive circuit (not shown), upper arm semiconductor switch drive circuit (not shown), 2 capacitors (not shown), diode (not shown), voltage command generator [ 31), voltage comparator (
35), NOT circuit (38), and for the W phase, a lower arm semiconductor switch (4), an upper arm semiconductor switch (7), and a feedback diode [11], (14).
, lower arm semiconductor switch drive circuit (not shown), upper arm semiconductor switch drive circuit (not shown), capacitor (not shown), diode (not shown), voltage command generator (32), voltage comparator (36), NOT circuit (39)
There are two types, each of which is constructed in the same way as the U-phase one and functions in the same way.

Next, the operation will be explained with reference to FIGS. 11 to 14.

Figure 11 (lla) shows the voltage command waveforms and carrier signals of the U phase, ■ phase, and W phase.
1011 is a waveform indicating the voltage command of the U phase, (11021 is a waveform indicating the voltage command of the ■ phase, (11031 is a waveform indicating the voltage command of the W phase, and (1104) is the waveform of the carrier signal. Figure titb+ shows the U-phase voltage comparator (
34). In Fig. 11 (lla), when the U-phase voltage command waveform (ttot) is larger than the carrier signal waveform (l104), it is 1"', and when it is smaller, it is 0". When the voltage value of the U-phase voltage command is high, the pulse width is wide (and when it is low, the pulse width is narrow. This shows the output waveform, and shows the waveform in the ■ phase corresponding to the waveform in the U phase (Fig. 11!1lbl).

Next, the output voltage of the DC power supply [1] and the output voltage of three-phase AC pulse width modulated by the inverter device will be explained. If a general commercial three-phase alternating current with an effective line voltage value of 200 cm is rectified and converted to direct current, a direct current of 5 volts x 200 V can be obtained. The output of three-phase AC pulse width modulated by an inverter device based on this DC has a maximum value of phase voltage E
"X 200/2 V = 5" x 1 o o v becomes a three-phase alternating current, and when this is converted into line voltage, the maximum value of line voltage becomes 5 tung x tai x 100 v. This three-phase alternating current is sine In the case of a wave, the effective value of the line voltage is F x t o v
It becomes 4173v.

Therefore, it is not possible to drive a 200V three-phase induction motor as it is, so without changing the voltage amplitude,
In order to increase the power supplied to the three-phase induction motor of the load, it is converted to three-phase alternating current (not a sine wave) but a saturated sine wave.

In FIG. 11, voltage command waveforms (1101) to f
1103) is a sine wave and a 5 carrier signal [1104]
The amplitude of the voltage command waveforms (1101) to (1103) is slightly thicker than that of the voltage command waveforms (1101) to (1103).
3) is made larger than the amplitude of the carrier signal (11041), and equivalently the voltage command waveforms (1101) to (110
3) is not a sine wave, but a saturation voltage waveform with the peak of the sine wave distorted flat, and the voltage command when the power supplied to the three-phase induction motor (8) of the load is increased. FIG. 3 is a diagram showing a waveform and a waveform of a carrier signal. In FIG. 12 (12a), (1201), (1202), [
1203) are the voltage command waveforms of the U phase, ■ phase, and W phase, respectively, and (1205) is the voltage command waveform (120
11 to (12031), (1206) is the amplitude of the carrier signal waveform [1104]. Note that the amplitude of the voltage command (12051 is Q, and the amplitude of the carrier signal (12051) is
When 061 is P, Q/P is called the voltage control rate.

Figure 12 (12b) ~ (12dl is Figure 12 f12
The waveform of the t't 6 N pressure command (12 (I
The output waveforms of the voltage comparators (34) to (36) are shown when ll, (12f]21, f1203) are output from the corresponding voltage command generation units (30) to (32), respectively.

Now, as shown in FIG. 12 (12b) to F12dl, the output waveforms of the voltage comparators (34) to (36) are near the peak of the waveform of the corresponding voltage command, and the carrier signal (1
101), there is a portion that remains unchanged at "1" or -0- for more than one cycle.

In FIG. 10, the U-phase upper arm semiconductor switch drive circuit (16) operates using a capacitor (18) as a power source, and this capacitor (18) is connected to the U-phase lower arm semiconductor switch (2). Since it is configured to be charged when it is on, when the state '1'' shown in (lZbl) in Fig. 12 continues for a long time, the U-phase lower arm semiconductor switch (2) remains off. During this period, the capacitor (18) is not charged and continues to discharge in order to operate the phase upper arm semiconductor switch (5).
The voltage across the capacitor (18) drops.

FIG. 13 is an enlarged view of a part of FIG. 1O to show how the U-phase capacitor (18) is charged.
) is charged.

Figure 14 (1'4a) shows the waveform shown in Figure 11 (ttb+) and the voltage (1401) across the capacitor (18) when this waveform is output from the voltage comparator (34).
FIG. 14 (14b) is a diagram showing the first
FIG. 2 is a diagram showing a comparison between the waveform shown in FIG. 2 (12b) and the voltage f1403) across the capacitor (18) when this waveform is output from the voltage comparator (34).

In (14b) of Figure 14, (14 (14) indicates the minimum value of the voltage (14031) across the capacitor (18), and this value is the voltage across the capacitor (18) at (t4a) in Figure 14. (1401) minimum value (140
2) is a smaller value.

When the voltage across the capacitor (18) decreases, the U-phase upper arm semiconductor switch drive circuit (16) cannot sufficiently drive the U-phase upper arm semiconductor switch (5). ) will not only malfunction, but will also result in destruction of the U-phase upper arm semiconductor switch (5).

To prevent voltage drop across the capacitor (18),
Conventionally, the capacitance of the capacitor (18) has been made very large, but it has become large and expensive. Note that the capacitor (18) and the U-phase lower arm semiconductor switch (2) are for the U-phase;
phase capacitor (not shown), ■ phase lower arm semiconductor switch (3), and W phase capacitor (not shown),
The same applies to the W-phase lower arm semiconductor switch (4).

[Problems to be Solved by the Invention] Since the conventional inverter device that converts direct current to alternating current by pulse width modulation is configured as described above, for example,
When the voltage control rate is made larger than 1, if the period during which the lower arm semiconductor switch is off becomes longer, the voltage across the capacitor that functions as the power supply for the upper arm semiconductor switch drive circuit will decrease, so the above-mentioned The capacitance of the capacitor has been increased to prevent voltage drop, but the problem has been that the capacitor becomes larger and more expensive.

This invention was made to solve the above-mentioned problems, and even when the voltage control rate is made larger than 1,
An object of the present invention is to obtain an inverter device in which the voltage across a capacitor functioning as a power source for an upper arm semiconductor switch drive circuit (14) does not drop.

[Means for Solving the Problems] An inverter device according to an eighth aspect of the present invention has a plurality of switch series bodies in which an upper arm switch and a lower arm switch are connected in series, and the upper arm switch and the above-mentioned upper arm switch of each switch series body are connected in series. The lower arm switch is turned on and off in a complementary manner based on the switch control signal given to each series switch, and pulse width modulated alternating current is generated from the connection point of each upper arm switch and lower arm switch of the multiple switch series. The switch circuit from which the output is taken out, one of the switch series bodies among the plurality of switch series bodies,
An upper arm switch drive section and a lower arm switch drive section drive the first and second switches as the upper arm switch and the lower arm switch, respectively, based on the switch control signal.When the second switch is on, it is charged and the upper arm switch A voltage that compares the magnitude of a voltage command with the same frequency as the AC output taken from the connection point between the capacitor, the first switch, and the second switch, which operates as a power source for the drive unit, and a carrier signal with a higher frequency than the voltage command. Comparing means, based on the output of the voltage comparing means, outputs a signal that turns on the second switch when the carrier signal is larger than the voltage command and turns it off when it is smaller than the voltage command as a switch control signal; The switch operation correction means corrects the switch control signal so that the second switch is temporarily turned on when the second switch remains off for a predetermined period of time or more.

In addition, the upper arm switch and the lower arm switch have Fj number of switch bodies in which the upper arm switch and the lower arm switch are connected in series, and the upper arm switch and lower arm switch of each switch series body are as follows:
A switch that is turned on and off in a complementary manner based on a switch control signal given to each switch series, and a pulse width modulated AC output is taken out from the connection point of each upper arm switch and lower arm switch of a plurality of switch series. An upper arm switch drive unit that drives a first switch and a second switch as an upper arm switch and a lower arm switch of any one of the plurality of switch series bodies based on a switch control signal; Lower arm switch drive unit, a capacitor that is charged when the second switch is on and operates as a power source for the upper arm switch drive unit, a voltage command and voltage with the same frequency as the AC output taken out from the connection point of the first and second switches. The signal is compared in magnitude with a carrier signal having a higher frequency than the voltage command, and when the carrier signal is higher than the voltage command, the second switch is turned on, and when it is smaller than the voltage command, the second switch is turned off. Voltage comparison means outputs to the driving lower arm switch drive section; if there is a portion where the voltage command is larger than a predetermined value smaller than the amplitude of the carrier signal, this large portion is limited to a predetermined value and the voltage command is made into a saturated waveform. The voltage command limiting means is provided.

[Function] In the inverter device configured as described above, the switch operation correction means generates a signal that turns on the lower arm switch when the carrier signal is larger than the voltage command and turns it off when the carrier signal is smaller than the voltage command based on the output of the voltage comparison means. 8 as a switch control signal, and when the lower arm switch is turned off for more than a predetermined period of time due to the switch control signal, the switch control signal is corrected so that the lower arm switch is temporarily turned on, and the lower arm switch is turned on. This prevents the voltage between the terminals of the capacitor, which operates as a power source for the upper arm switch drive section, from dropping.

In addition, the voltage comparison means compares the magnitude of a voltage command having the same frequency as the AC output taken out from the connection point of the lower arm switch and the upper arm switch with a carrier signal having a higher frequency than this voltage command, and then outputs the carrier signal. When is greater than the voltage command, turn on the lower arm switch,
When the voltage is small, a signal to turn it off is output as a switch control signal to the lower arm switch drive section, and the voltage command limiter controls the voltage command so that the part where the voltage command is large compared to a predetermined value smaller than the amplitude of the carrier signal is The lower arm switch is turned on at the cycle of the carrier signal, and a drop in the voltage between the terminals of a capacitor that is charged when the lower arm switch is turned on and operates as a power source for the upper arm switch driving section is prevented.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a block diagram of an inverter device according to an embodiment of the present invention. In the figure, (40) is inserted between the output of the U-phase voltage comparator (34) and the input of the U-phase N07 circuit (37) and the U-phase upper arm semiconductor switch-over circuit (16). The unit 1 for correcting the change-in-phase operation is, for example, a U-phase change-in operation correction unit.

FIG. 2 is a block diagram showing details of the U-phase switch operation correction section (40). In the figure, (40al is a counter that inputs the output of the U-phase voltage comparator (34), counts when the input is 1'', and generates a pressure signal after counting for a predetermined period, and (40bl is a counter that generates a pressure signal. The one-shot pulse generator (40c) which outputs a predetermined pulse width signal using the output signal as a trigger sets its output to ``0'' while the one-shot pulse is being output from the one-shot pulse generator (40b), and normally outputs a predetermined pulse width signal. is a switching circuit that outputs the U-phase voltage comparator (34).

Next, according to FIG. 3, the U-phase switch operation correction section (40)
The operation will be explained in detail. Counter (4 (Ia)
is reset when the input is 10'' and counts when the input is 'l''.

(3a) in FIG. 3 is the input signal of the counter (40al), and (3b) shows the state of the counter (40a).The content of the counter (40al) is the maximum value (3b
1), the counter (40a) outputs 8 pulses and at the same time the counter (40a) outputs 8 pulses as shown in (3C).
The contents of a) are reset to 0.

Furthermore, if the input signal of the counter (40a) continues to be at -1-, the same operation is repeated.

The one-sea l-/tbal pulse generator f40b) is triggered by the above-mentioned pulse outputted by the counter (40a), and generates (
A pulse having a predetermined pulse width is generated as shown in 3d). The switching circuit (40cl is a one-shot pulse generator (40bl) is “0” while the pulse is being output)
The U-phase lower arm switch drive unit, for example, U
The input of the phase lower arm semiconductor switch drive circuit (15) is set to '1''', the U phase lower arm semiconductor switch (2) is turned on, and the U phase capacitor (18) is charged.The U phase capacitor ( 18) is the U-phase upper arm switch drive unit (1) while the IJ phase lower arm semiconductor switch (2) is off.
6), and the terminal voltage decreases over time. (3e) is a diagram showing the change in the voltage between the terminals of the U-phase capacitor (18), (3all is the voltage between the terminals of the U-phase capacitor (18), and (3e2) is a diagram showing the change in the voltage between the terminals of the U-phase capacitor (18).
(3e3) shows the drop in voltage between the terminals of the U-phase capacitor (18) when the pulse shown in (3d) is not applied, and (3e3) shows the voltage drop between the terminals of the U-phase capacitor (18) when the pulse shown in (3d) is applied. It shows the decrease in electrical work between terminals.

As shown in (3e), the U-phase switch operation correction section (
40) reduces the drop in voltage between the terminals of the U-phase capacitor (18).

Regarding the ■ phase and the W phase, the ■ phase switch operation correction section (41) and the W phase switch operation correction section (
42) is provided in the same manner as for the U phase, and operates in the same manner.

Note that FIG. 1 is the same as the conventional example except that a U-phase switch operation correction section (40), a V-phase switch operation correction section (41), and a W-phase switch operation correction section (42) are provided. It is the same as FIG. 1O shown in FIG.

Next, regarding another embodiment of the present invention, FIGS.
This will be explained using figures. FIG. 4 is a block diagram of the entire inverter device. In the figure, (60) indicates the U-phase voltage command output from the U-phase voltage command generator (30) and the carrier signal generator (33). A voltage (401) indicating the amplitude of the carrier signal is input, and the voltage of the above-mentioned phase voltage command and the voltage [401] indicating the amplitude of the above-mentioned carrier signal are input.
4011, the above-mentioned U-phase voltage command is larger because it is a U-phase saturation pulse generator that generates a predetermined period of ``1''1'' every time a preset certain period of time is exceeded. , (50) is the U-phase saturation pulse generator (60
), when a level of ``1'' is output, the output is set to ``0''.
” and is normally a U-phase switching unit that switches to output the output signal of the voltage comparator (34). Note that the U-phase saturation pulse generation unit (60) and the U-phase switching unit (50) A U-phase switch operation correction section (90) is configured.

FIG. 5 is a diagram showing the operation of FIG. 4, and in FIG. The signal (11041) is shown, (sb) is the output waveform of the U-phase voltage comparator (34), and (5c) is the output waveform of the U-phase voltage command when the voltage of the U-phase voltage command is larger than the amplitude of the carrier signal [11041-
(5d) outputs a signal of "1" for a predetermined time every time the signal of (5C) exceeds a preset fixed time f5dl). Output waveform, [Se) U phase switching section (50)
The output waveform of is shown.

(6a) of FIG. 6 is a diagram comparing the voltage between the terminals of the U-phase capacitor (18) and the output waveform of the U-phase voltage comparator (34), and (6aO) is a diagram showing a comparison between the voltage between the terminals of the U-phase capacitor (18) and the output waveform of the U-phase voltage comparator (34). Voltage comparator (3
4) output waveform, [6al] is the U-phase capacitor (18
), (6a21 is the U-phase capacitor (18
) shows the decrease in the voltage between the terminals.

In addition, (6b) in FIG. 6 is a diagram comparing the terminal voltage of the U-phase capacitor (18) and the output waveform of the U-phase switching unit (50) in FIG. 4, and (6bO) is The output waveform of the U-phase switching unit (50), f6bll indicates the voltage between the terminals of the U-phase capacitor (18), and [6b2] indicates the drop in the voltage between the terminals of the U-phase capacitor (18). In the inverter device shown in FIG. 6 and shown in FIG. 4, the drop in voltage between the terminals of the U-phase capacitor ([8)] is reduced.

Figure 7 shows the waveform of (5C) in Figure 5.
” saturation pulse generation part of U phase when the state continues for a long time (
60), and (7c) in FIG. 7 shows that the output voltage of the U-phase voltage command unit (30) is the carrier signal (1104).
) signal that becomes 1" when the amplitude is larger than that of (7d)
For example, the output waveform of the U-phase saturation pulse generator (60) is shown.

Regarding the inverter device shown in FIG. 4, the U phase has been described above, but the ■ phase and W phase are also similar to the U phase. In FIG. 4, (51) is a V-phase switching section;
(52) is a W-phase switching unit, (61) is a phase saturation pulse generation unit, and (62) is a W-phase saturation pulse generation unit, which are connected in the same way as in the U-phase. ■It operates in the same way as in the phase. Note that the ■ phase switch operation correction section (91) is configured by the ■ phase saturation pulse generation section (61) and the ■ phase switching section (51), and the W phase saturation pulse generation section (62) and the W phase switching section (51) W by the switching part (52)
A phase switch operation correction section (92) is configured.

Furthermore, in the inverter devices shown in FIGS. 1 and 4, the explanation has been made assuming that only the lower arm semiconductor switches (2) to (4) are turned on for a predetermined time every time the off time exceeds a predetermined time. If you want to reduce the positive/negative asymmetry of the current flowing through the load, you can forcibly turn on the upper arm semiconductor switches (5) to (7) for a predetermined time every time the off time exceeds a predetermined time. good.

Next, as another embodiment of the present invention, an inverter device shown in Section 8 will be described. In the figure, (7
0) is the part of the output waveform of the U-phase voltage command generation section (30) that is larger than the voltage upper limit value, which is set to be smaller than the maximum value of the carrier signal output from the two-carrier signal generation section (33), as described above. The voltage command limiting means for the second phase, for example, the U-phase This is the voltage command limiter.

FIG. 9 is a diagram showing the operation of the inverter shown in FIG. 8. In the figure, (9a) is the carrier signal [1104], ), (1902) is the 8-power waveform of the ■ phase voltage generator (31), f1903) is the W phase voltage command generator (32) (7) output waveform, (901) is the voltage upper limit value, f902+ indicates the voltage lower limit value. (9b) shows the output waveform of the voltage comparator (34), in (9c), (9cl) is the voltage between the terminals of the U-phase capacitor (18), (9cLl is the voltage between the terminals of the U-phase capacitor (18) The voltage drop (C9C3) in Figure 8 is the U-phase capacitor (
18) shows the drop between the terminals. As shown in (9c), compared to the conventional example, the drop in voltage between the terminals of the U-phase capacitor (18) is significantly reduced.

Note that what prevents the voltage between the terminals of the U-phase capacitor (18) from decreasing is that the part of the output waveform of the U-phase voltage command generator (30) that is greater than the voltage minus upper limit value (9011) is set to the voltage upper limit value. This is because the voltage is limited to the lower limit value (901), and the portion smaller than the lower voltage limit value (902) is set to the lower voltage limit value (902).
902), the voltage lower limit value (9021) may not be used.

Further, although the above explanation regarding FIGS. 8 and 9 is only about the U phase, as shown in FIG. 8, the voltage command limiting section (71) of the ,
There is a W-phase voltage command restriction section (72), which has the same function as the U-phase voltage command restriction section (70) and operates in the same manner.

Furthermore, the lower arm semiconductor switches (2), (3), (4) shown in FIGS. 1, 4, and 8
) The upper arm semiconductor switches (5) and (61, n) may be any switch element including a GBT or a barwa MO5FET.

Further, although the DC power supply (17) shown in FIGS. 1, 4, and 8 is a common power supply for U-phase, ■-phase, and W-phase, it may be provided separately.

Furthermore, the carrier signal (
1104) is illustrated as a triangular AC waveform in FIG. 5 (5a) and FIG. 9 (9a), but it may be a fixed-tooth AC waveform.

In addition, voltage command generation units (3o), +31), (3
2), U-phase, ■-phase, and W-phase voltage comparators (34)
, +351, (36), U phase, ■ phase, and W
Phase switch operation correction section (40), (41), (42
), (90), (911, (92), U-phase, ■-phase, and W-phase voltage command limiter (70).

(711, (72), and Kya'J7 signal generator (
33) may be configured on software using a CPU and memory.

Furthermore, although the inverter devices shown in FIGS. 1, 4, and 8 are three-phase AC inverters, they may be single-phase AC inverters. In addition, in a single-phase AC inverter device, in a three-phase AC inverter device, the circuit related to the W phase is removed, the U-phase voltage command generation section (3o) is replaced with a single-phase voltage command generation section, and the voltage of the ■ phase is changed. The command generating section (31) is configured to generate a voltage command having a phase difference of 180 degrees from the voltage command generated by the above-mentioned single-phase voltage command generating section.

[Effect of the invention] As described above, there is a plurality of switch series bodies in which the upper arm switch and the lower arm switch are connected in series, and the upper arm switch and the lower arm switch are complementary to each other in a predetermined manner. The lower arm switch in the switch circuit, which turns on and off at the timing of By turning on and off, the voltage between the terminals of the capacitor, which is charged when the lower arm switch is turned on and operates as a power source for the upper arm switch driving section that drives the upper arm switch connected in series with the lower arm switch, is reduced. Since this is prevented, it is possible to obtain an inverter device that operates normally even if the above-mentioned capacitor has a small capacitance of 4°.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an inverter device showing an embodiment of the present invention, FIG. 2 is a block diagram showing details of the U-phase switch operation correction section in FIG. 1, and FIG. 3 is similar to FIG. 1. FIG. 4 is a block diagram of an inverter device showing another embodiment of the present invention;
5 to 7 are explanatory diagrams of the operation of the inverter device shown in FIG. 4, FIG. 8 is a block diagram of the inverter device showing yet another embodiment of the present invention, and FIG. 9 is the same as that shown in FIG. FIG. 3 is an explanatory diagram of the operation of the shown inverter device. Figure 1O is a block diagram of a conventional inverter device;
1 to 12 are explanatory views of the operation of the inverter device shown in FIG. , FIG. 14 is an explanatory diagram of the operation of the inverter device shown in FIG. 10. In the figure, (1) is the direct ft, power supply, (2) to (4) are lower arm semiconductor switches for U phase, ■ phase, and W phase, respectively, and (5) to (7) are U phase, ■ phase, respectively. , and W-phase upper arm semiconductor switch, (16) is a U-phase upper arm semiconductor switch drive circuit, (18) is a U-phase capacitor, (34) to (36) are U-phase, ■-phase, and W-phase, respectively. Phase voltage comparators, (40) and (90) are U-phase switch operation correction sections, (41) and (91) are V-phase switch operation correction sections, (42) and (92) are W-phase switches. The operation correction sections (70) to (72) are voltage command limiting sections for the U phase, ■ phase, and W phase, respectively. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) There is a plurality of switch series bodies in which an upper arm switch and a lower arm switch are connected in series, and the upper arm switch and lower arm switch of each of the switch series bodies are provided for each switch series body. a switch circuit that is turned on and off in a complementary manner based on a switch control signal sent to the plurality of switches in series, and a pulse width modulated AC output is taken out from a connection point between the upper arm switch and the lower arm switch of each of the plurality of switches in series, the plurality of switches; An upper arm switch drive unit and a lower arm that respectively drive first and second switches as the upper arm switch and the lower arm switch of any one of the switch series bodies in the series body based on the switch control signal. a switch driver; a capacitor that is charged when the second switch is turned on and operates as a power source for the upper arm switch driver; a voltage having the same frequency as the AC output taken out from a connection point between the first switch and the second switch; Voltage comparison means for comparing the magnitude of the command and a carrier signal having a higher frequency than the voltage command, and turning on the second switch when the carrier signal is higher than the voltage command based on the output of the voltage comparison means. , outputs a signal to turn it off as the switch control signal when it is small, and
An inverter device comprising: switch operation correction means for correcting the switch control signal so as to temporarily turn on the second switch when the second switch is turned off for a predetermined period of time or more due to the switch control signal. (2) It has a plurality of switch series bodies in which an upper arm switch and a lower arm switch are connected in series, and the upper arm switch and lower arm switch of each of the above switch series bodies are provided for each switch series body. a switch circuit that is turned on and off in a complementary manner based on a switch control signal sent to the plurality of switches in series, and a pulse width modulated AC output is taken out from a connection point between the upper arm switch and the lower arm switch of each of the plurality of switches in series, the plurality of switches; an upper arm switch drive unit that drives first and second switches, as the upper arm switch and the lower arm switch, of any one of the switch series bodies in the series body, based on the switch control signal; a lower arm switch drive unit, a capacitor that is charged when the second switch is turned on and operates as a power source for the upper arm switch drive unit, and a frequency that is the same as the AC output taken out from the connection point between the first switch and the second switch; The voltage command is compared in magnitude with a carrier signal having a higher frequency than the voltage command, and when the carrier signal is higher than the voltage command, a signal is generated to turn on the second switch, and when it is smaller, to turn it off. Voltage comparison means outputs the switch control signal to the lower arm switch driving section that drives the second switch; An inverter device comprising: voltage command limiting means that limits the voltage command to the predetermined value and makes the voltage command a saturated waveform.