JPS596593B2 - Inverter control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter control circuit that reduces power loss of main circuit transistors in an inverter device.

A specific example of a conventional inverter device is shown in FIG.
1 is a DC power supply, TR1 to TR6 are power transistors,
D1 to D6 are feedback diodes, DTI is a main circuit current detector, M is a motor, B and C are base control circuits, Li is a reactor, and each phase is magnetically coupled.

The control circuit of the conventional inverter device described above will be explained with reference to FIG. 2. This figure shows an analog-to-digital conversion circuit A
In the specific example of /D1, V1 is the power supply, Al is the amplifier, and R
1, R2 is a resistance.

Further, FIG. 3 shows a concrete example of the base control circuit 6.
C is a hexadecimal ring counter, and 1C1 to 1C12 are digital gate ICs. Since it has the above-mentioned configuration, the analog-to-digital conversion circuit shown in FIG. The output terminal B becomes L if the ←) terminal potential of amplifier Al is higher than the terminal potential, and vice versa.

Further, the logic is configured such that when the output of the amplifier Al is H, the main circuit power transistor D1 is conductive, and when the output is L, the main circuit power transistor D is non-conductive. Fourth
The figure shows the output waveform of terminal B, and FIG. 5 shows the waveform of each terminal output from terminals 1a to 1f of the base control circuit shown in FIG. 3. Figure 6 shows the output waveforms of terminals 2a to 2f in Figure 2.
Each of the main circuit transistors TR1 to TR6 is driven by each signal waveform shown in FIG. An isolation amplifier may also be used if the circuit requires it. Part of the motor phase current when the main circuit transistors TR, -TR6 are driven by the control signals described above is shown in waveforms in FIG.
When an enlarged view of this Fig. 7 is shown in Fig. 8, t is
0N power transistor conduction time, TOFF is power transistor non-conduction time, IO is average current, and ΔI is ripple current.

In this conventional control scheme, the two power transistors are always operated in two switching modes: conducting or non-conducting. The equivalent circuits of these two switching modes are shown in FIGS. 9A and 9B. In the figure, 2L is the inductance of reactor L1, 2t and r
is the motor internal impedance, and e is the voltage generated inside the motor. Here, assuming that the motor internal impedance is small compared to the reactor inductance,
If omitted, T and t are obtained as follows. (H
, -e) Since t = 2L・2ΔI, 8XT and FIG. 9BJ. V) t + t The minimum value is when e=o, 0N0F
F-1! The maximum switching frequency f is M as shown in equation (3) below.
I'm going to be ax.

That is, the circuit constants can be determined from the switching frequency given by equation (3).

In the conventional control system, the main circuit switching frequency is determined by equation (3), which has the disadvantage of not being sufficient in terms of cost and performance, such as increasing the reactor L1 or increasing the ripple current ΔI. . If the reactor has the same current ripple ΔI, the switching frequency of the main circuit is reduced to 1/2, thereby reducing the power loss of the main circuit transistor and improving reliability.

In other words, the purpose is to reduce the capacity of the reactor L, and to provide a control circuit for an impert device with good cost performance. The configuration of the present invention will be explained below.The present invention adds yet another control method to the conventional control method.

That is, in the conventional control method, the two power transistors were in only two modes: conducting and non-conducting at the same time, but the present invention further allows one of the two power transistors to be conducting and the other to be non-conducting. This is an additional control system. Therefore, the principle of the present invention will be explained with reference to FIG. 10 along with the operation of one embodiment. In the figure, A, b, and c are the switching modes of the three main circuits.

If we call a the power running, mode b the recirculation, and mode c the regeneration, the above three modes vary depending on the load power factor, but in the case of a lagging power factor due to the motor load, a→b -+c→b→a→b-+c...or a→b→a→b...The state is repeated. a-? The switching frequency of the main circuit transistor when repeating the mode b→c-+b→a→b→c . . . is determined as follows. That is,
In the case of mode a, 2L/2Δ mode b is the same as the conventional method.
If t -?・・・・・・・・・(4) NRP-
In the case of c mode c, t otsu b● otsu a1?・・・・・・・・・(2) E ・・・・・・・・・(5) However, when e='', L (however, e=-'' → ・・・・・・(6) That is, a →b→c
0N- of each power transistor per cycle of
0FF repetition minimum 16L●Δ1 hour? Tonashi P. The highest switching is Fmax=Ichitomoe U-・・・・・・(
7) 1C8T, that is, the switching frequency is halved compared to the conventional control system.

Explaining FIG. 11, this conversion circuit compares a command signal and a detection signal A to create a main circuit power transistor control signal, and R3 to RlO are resistors and V
Rl is a variable resistor, A2 to A5 are amplifiers, and D7 to D8 are diodes.

A2 and A3 have amplification degrees of R7/R3 and R8/R4, respectively, and A4 and A operate as comparators that compare the command signal and the detection signal. R, , R, and O are positive feedback resistors that determine the hysteresis width, and form a dead zone determined within the actual usage range to prevent the switching frequency from becoming unnecessarily high. VR is a variable resistor that provides a level difference between the freewheeling signal and the regenerative signal. In this FIG. 11, the output e of the amplifier A4 is the regenerative signal, and the output D of the amplifier A5 is
is a reflux signal, and the input potential of the detection signal A becomes more negative as the main circuit current becomes larger. The output potentials of amplifiers A2 and A3 are also negative. For example, A4 (
d) If the input terminal potential of A4 (g) input terminal potential) is also high, the output c of amplifier A4 is L level, that is, the main circuit current 0FF signal, and in the opposite case, the output c of A4 is H level, that is, the main circuit current 0FF signal. The circuit current becomes a 0N signal. Amplifier A3,A
5 operates similarly. Next, when a combination with a ring counter is shown in FIG. 12, the output waveforms of 3a to 3f are as shown in FIG. 13. FIG. 14 shows output waveforms 4a to 4f, and it is understood that the one-arm main circuit transistor performs switching in the three modes of power running, circulation, and regeneration described above. The reason why the reflux signal is given to the first half 600 of the conductive signals 120 in FIG. 12 is necessary to make only one transistor conductive and the other transistor non-conductive in the reflux state. Although the present invention described above is sufficiently practical, it is applicable to various digital gate ICs.
Because it is combined, the timing of the six signals is
There may be slight fluctuations.

Therefore, the main circuit current control signal, that is, C in FIG.
, using the output signal of the monostable multivibrator 0SM operated by the ring counter input signal as the D signal,
When combined as shown in FIG. 15 in addition to FIG. 12, stable frequency control characteristics can be obtained in synchronization with the command frequency of the power control device. In other words, this forces the transistor ON signal to such an extent that it does not adversely affect the main circuit. Although a motor is used as the load in one embodiment of the present invention, similar effects can be achieved with other load devices.

As described above, by using the control method and control circuit according to the present invention, the switching frequency of the main circuit power transition can be reduced to 1/4 compared to the conventional control method. For example, the capacitance of the reactor used in the circuit can be reduced, which improves cost performance, and improves the frequency stability of the main circuit during switching control, resulting in high reliability. There is.

[Brief explanation of the drawing]

Figure 1 is the main circuit diagram of the inverter device, Figure 2 is a conventional current control analog-to-digital conversion circuit diagram, Figure 3 is a conventional base control circuit diagram, Figure 4 is an A/D output waveform diagram, Figures 5 and 6 are output waveform diagrams of the base control circuit in Figure 3, Figure 7 is a main circuit current waveform diagram, Figure 8 is an enlarged view of Figure 7, and Figure 9 is based on the conventional control method. Main circuit equivalent circuit diagram,
FIG. 10 is an equivalent circuit diagram of the main circuit of the control method according to the present invention,
Fig. 11 is an analog-to-digital conversion circuit diagram according to the present invention, Fig. 12 is a base control circuit according to the present invention, Fig. 13 is an intermediate output waveform diagram of Fig. 12, and Fig. 14 is an output waveform diagram of the base control circuit according to the present invention. , 1st g1; is a main circuit frequency stabilization control circuit diagram according to another example of Tomiaki Mkeki. E,...DC power supply, TR, ~TR6...power transistor, D1-D8...diode, DTl...
Detector, M...Motor, L1...Reactor, B,
C, . . . base control circuit, A/D, . . . analog-digital converter) VcO. ．． ．． Power supply) Al5A5゜8
゜Amplifier) R1~RlO...Resistance, VR,...Variable resistor, R, C,...Ring counter, ICl-~I
C27... Digital gate IClOSM... Monostable multivibrator, 2L... Inductance of reactor L1, 2t, r... Motor internal impedance, e... Motor internally generated voltage, Note that the same symbols in the diagram are the same. , or a significant portion.

Claims (1)

[Claims] 1. A DC reactor with a center tap, a first main transistor having an emitter terminal connected in series to one terminal of the DC reactor, and a collector connected in series to the other terminal of the DC reactor. A circuit comprising a second main transistor with terminals connected to it, a DC power supply connected in parallel to the three sets of the circuit, and a feedback diode connected in antiparallel from the emitter connection terminal of the DC reactor to the negative terminal of the DC power supply. , an inverter circuit comprising a feedback diode connected in antiparallel from a collector connection terminal of the DC reactor to a positive terminal of the DC power supply, and a center tap of the DC reactor connected to a load;
This circuit is equipped with two comparison circuits that compare the main circuit current detection signal and the command signal with a level difference, respectively, to obtain the power mode, circulation mode, and regeneration mode control signals. An inverter control circuit characterized in that the switching frequency of the main circuit transistors is controlled by obtaining an AND between the control signal and the base control signal of each of the transistors. 2. The inverter control circuit according to claim 1, further comprising a monostable multivibrator added thereto as an inverter circuit.