JPH01318577A - Inverter - Google Patents

Abstract

PURPOSE:To improve the power factor of a power source by operating an inverter as a step-down voltage inverter for a voltage higher than a predetermined level and operating the inverter as a step-up current inverter for a voltage lower than the predetermined level. CONSTITUTION:Capacitors 1, 2 for bypassing DC current when one of P-side switching elements Q1, Q3, Q5 or N-side switching elements Q2, Q4, Q6 do not conducting and inductances 3, 4 for suppressing increase of DC current when all of the P-side and N-side switching elements Q1-Q6 conduct provided. The inverter is operated in transition between a step-down mode where one of the P-side or N-side switching elements Q1-Q5, Q2-Q6 are turned ON/OFF to regulate the inverter output voltage and a step-up mode where the P-side and the N-side switching elements Q1-Q6 are kept conductive for a predetermined time. Since current can be fed to a brushless motor 5 even when the source voltage is low because of the induction voltage of the brushless motor 5, the source power factor is improved.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an inverter device.

[Conventional technology]

A device that combines a capacitorless type inverter and an AC motor, such as a brushless motor, is disclosed in Japanese Patent Laid-Open No. 58
As described in Publication No. 212384, by detecting the first winding current and chopping the inverter to keep the peak value of the winding current constant, the pulsation of the winding current is suppressed and the inverter and motor The aim was to improve efficiency.

[Problem to be solved by the invention]

The conventional technology described above has a problem in that the power factor of the power supply is low because current can only be supplied to the motor when the DC voltage is higher than the induced voltage of the motor.

The present invention has been made in view of the above points, and an object of the present invention is to provide an inverter device that can supply current to a motor and improve the power factor of the power supply even when the DC voltage is lower than the induced voltage of the motor. This is the purpose.

[Means to solve the problem]

The above purpose is to provide the device with a capacitor that bypasses the DC current when one of the P-side and N-side switching elements is non-conductive, and an inductance element that suppresses the increase in DC current when both the P-side and N-side switching elements are conductive. A step-up mode in which the inverter output voltage is adjusted by turning on and off one of the P-side and N-side switching elements, and a step-up mode in which both the P-side and N-side switching elements are made conductive for a certain period of time. This can be achieved by driving with

[Effect]

The device is provided with a capacitor that bypasses the DC current when one of the P-side and N-side switching elements is non-conductive, and an inductance element that suppresses an increase in DC current when both the P-side and N-side switching elements are conductive, and the P-side The operation was performed by transitioning between a step-down mode in which the inverter output voltage is adjusted by turning one of the N-side switching elements on and off, and a step-up mode in which both P and N-side switching elements are made conductive for a certain period of time. , it becomes possible to supply current to the motor even when the power supply voltage is lower than the induced voltage of the motor, and the power factor of the power supply can be improved.

In other words, when considering a 50 Hz single-phase AC power supply.

In response to 100Hz DC voltage ripples, the AC input current is sinusoidal even when the DC voltage is small by operating as a voltage source inverter in step-down mode above a certain DC voltage and as a current source inverter in step-up mode below it. Since the motor current can be controlled, an inverter device can be obtained that can be applied even when there is intermittent pulsation in the DC voltage, and the power supply power factor is improved. The present invention will be explained based on an example. An embodiment of the present invention is shown in FIGS. 1-5.

P-side and N-side switching elements Q1 connected in series
In this embodiment, the inverter device is equipped with Q8 and converts direct current into alternating current with a variable frequency.
Side switching element Q1. QB, Qll (P side)
, QZ, QI, QB (N side) are provided with capacitors 1 and 2 that bypass DC current when one is non-conductive, and P side and N side switching elements Ql, QB, Qs, QZ, Q number,
The P-side and N-side switching elements Ql are provided with an inductance of 3°4 to suppress an increase in direct current when both Qe conduct.

QB, QB, QI A step-down mode in which the inverter output voltage is adjusted by turning on or off one of QI, QB, and P-side and N-side switching elements Qt+Qa, Qa+Q2.
It was operated by transitioning between a boost mode in which both QI and Qa were made conductive for a certain period of time. By doing this, even when the power supply voltage is lower than the induced voltage of the motor, for example, the brushless motor 5, it is possible to supply the brushless motor 5L:R voltage, so that the DC voltage is lower than the induced voltage of the motor. In some cases, an inverter device can be used to supply current to the motor and improve the power factor of the power supply.

That is, as shown in FIG. 1, which shows the circuit configuration for speed control of the brushless dryer 5, an AC power source 6 is converted to DC via a full-wave rectifier circuit 7 consisting of diodes D1 to D4. , the positive side of the full-wave rectifier circuit 7 is connected to the P-side switching element Qsp Qsp Qs (Da, De,
Dto is connected to a feedback diode). The negative side of the aftereffect rectifier circuit 7 is connected to the N-side switching elements Q21 Q41 QB (D14
+ Dts and Dte are connected to return diodes). Diode D5. A capacitor 1 (C
t.

Ca, Cs) are provided, and the diode Dtt+Dtzt
Capacitors 2 (C2, C4, C8) are provided between each of the anode terminals of Dlg and the full-wave rectifier circuit 7 side terminal of the inductance 3 to bypass the DC current Inc. The output side of the N-side switching element Q2104, QB, which is connected in series with the P-side switching element Qi, Q3゜QB, is the armature winding of the brushless motor 5, which consists of a rotor 5a and an armature winding 5b, which are made up of permanent magnets, etc. line 5b
It is connected to the.

A control circuit for controlling the speed of the brushless motor 5 includes a microcomputer 8, a position detection circuit 10 for detecting the magnetic pole position of the rotor 5a of the brushless motor 5 from the output of a Hall element 9, etc., and a P-side and N-side switching element. The microcomputer 8 includes a voltage drop across a resistor R1 and a speed command Nl from a speed command circuit 12 in order to detect the DC current Ioc.

Microcomputer 8 has CPU, ROM and RAM
It takes in various programs necessary to drive the brushless motor 5, such as the position detection signal 1oS, the DC current Inc that is the voltage drop of the resistor R1, or the speed command N*, and performs speed control processing and the P-side switching element. Q1. QspQ5 and N-side switching element Qz,
Q4. It performs processing such as outputting the drive signal 13 to the QB.

FIG. 2 is a block diagram of an analog circuit representing various processes within the microcomputer 8. For example, a speed detector represents speed detection processing. The operation of the microcomputer 8 will be described below based on the figure.

First, the speed command N is compared with the actual speed N of the brushless motor, which is transmitted from the position detection signal 10S via the speed detector, and the current command i is determined from the deviation (N-N) via ASR.
*, and calculate current command i* and DC current Ioc (resistance R1
(voltage drop (see Figure 1)) and the DC current i through the A/D converter, and from the deviation (it-i), A
Obtain voltage command chapter v via CR. PWM is performed by comparing the voltage command V* and the signal from the triangular wave generator using a comparator.
Obtain a signal and input it to the lower arm distributor (for N-side switching element) in step-down mode. In addition, add the seven voltage commands and the bias voltage v1, and calculate the deviation (v umbrella - vl)
and the signal from the triangular wave generator are compared in a comparator by 2, and P
Obtain the WM signal and input it to the lower arm distributor in boost mode. The rain arm distributor receives the position detection signal 10S and outputs N.
A 120 degree energizing pulse is generated for the side switching element, but the PWM signals from the comparators Kz and Kg are ANDed, and the output signal of the rain arm distributor is added to become the ignition signal for the N side switching element. . The upper arm distributor (for the P-side switching element) receives the position detection signal 10S and generates a 120-degree energization pulse for the P-side switching element. The 120-degree energization pulse from the lower arm distributor and the upper arm distributor becomes a drive signal 13 to the P-side and N-side switching elements, and becomes an input signal to the driver 11.

FIG. 3 shows two PWM signal generation methods for the comparator Kl. Figure (A) shows a method for generating a PWM signal in the comparator. As is clear from the figure, a PWM signal serving as an ignition signal is generated by comparing the voltage command v rate and a triangular wave, but when the bias voltage vt is reached, only an ON signal is generated. The figure (b) shows the second PWM signal generation method for the comparator. As is clear from the figure, a PWM signal serving as an ignition signal is generated by comparing the deviation (v* vz) between the voltage command V and bias voltage v1 with a triangular wave. It is set so that an on signal is not generated unless the value becomes greater than 1.

FIG. 4 shows the ignition signals to the P-side and N-side switching elements. The figure (A) shows the position detection signal 10S (
(see Figure 1), and the a phase, b phase and C phase are all 120
The signal will be off by a certain degree. Figure (b) shows the firing signals to the switching elements Q1 to QB in the step-down mode, and uses a 120-degree conduction type inverter as an example, so the P-side switching elements Qi, Qa, and Qs of the upper arm are 120 degrees. Only the main energization signal is available, and the N side switching element Q of the lower arm
For x, Qa, and QB, the 120 degree conduction signal is the comparator Kl.
(See Figure 2). The same figure (c) shows the switching element Q1~ in boost mode.
It shows the ignition signal to Q6, the P side switching elements Qt+ QB, Qs of the upper arm only have a 120 degree energization signal, and the N side switching elements Q2.Q6 of the lower arm. Qa,
For QB, a 120 degree energization signal is input from the comparator to the comparator, and 2 is input to the comparator in boost mode (see Figure 2 for both).
The PWM signal from the P side switching element and the N
The side switching elements are both turned on (for example, switching elements Ql and QZ, QB and Qa, or Qs and QB are both turned on, resulting in a power short circuit).

FIG. 5 shows the operation of the main circuit in step-down mode and step-up mode. FIG. 4(a) shows a state in which switching elements Q1 and Qa are turned on in the step-down mode shown in FIG. 4(b). That is, when the single-phase AC power supply 6 is on the positive side, c from the DC current flows from the AC power supply 6 to the diode DI of the full-wave rectifier circuit 7, the inductance 3, the diode D5 . Switching element Q1. It flows through the armature winding 5b, the switching element Qa, the diode D1z, the inductance 4, the resistor R1, and the diode D4. When switching element No. 0 turns off as shown in FIG.
The current flowing through the armature winding 5b is bypassed to the capacitor C3 via the return diode D9 of the switching element Q3. Then, the DC current Inc passing through the inductance 4 flows through the resistor R1, diode D4. Bypassed to Czy C4, CB of capacitor 2 via D3.

FIG. 4(c) shows a state in which switching elements Ql and 02 are turned on in the boost mode shown in FIG. 4(c) above. That is, when the single-phase AC type 'tA6 is on the positive side, the DC current Ioc flows from the AC power supply 6 to the diode D1. It flows through the inductance 4, the resistor R1, and the diode D4 via the inductance 3, the diode Ds, the switching elements Ql, QZ, and the diode Dll. At this time, a DC short circuit occurs, so the DC current Inc increases, but this DC current I
The sudden increase in DC is suppressed by the inductances 3 and 4.

A discharge current from the capacitor Ct also occurs, but its rapid increase is suppressed by the inductance 4. Furthermore, when the switching element Q2 is turned off as shown in FIG.
c is connected to the armature winding 5 via switching elements Qt and Q4.
This is a movement of being pushed into b.

From the above, the operation of the inverter device of this embodiment will be described as follows. A current command i* is determined based on the speed command N*, and a voltage command v is determined based on the current command i*. On the other hand, the DC voltage has a waveform that is simply rectified single-phase AC, and its pulsation increases. When the inverter device of this embodiment is operated under such DC voltage,
When the DC voltage is large, it operates in the step-down mode, and when the DC voltage becomes small and the voltage command v becomes larger than the bias voltage v1, it operates in the step-up mode, and the inductance 3, 4
The current of the brushless motor 5 is controlled using this energy. Therefore, the inverter device of this embodiment can satisfactorily control the motor current even if there is large pulsation in the DC voltage. As a result, the smoothing capacitor can be omitted, and only six small capacitors 01 to CB are required to bypass the direct current. Furthermore, since the boost mode allows power supply current to flow even in a region where the DC voltage is low, the power factor of the power supply improves.

As described above, according to this embodiment, it is possible to downsize the smoothing capacitor and obtain an inverter device that can satisfactorily control the motor current even if there is large pulsation in the DC voltage. Furthermore, the power supply current is controlled using boost mode (DC short circuit mode).

The power factor of the power supply is improved.

In this embodiment, a brushless motor is used as the motor, but other alternating current machines may be used. Further, although a 120-degree energizing type is adopted as the inverter, a 180-degree energizing type may be used.

Further, although the AC power source is single-phase, it may be three-phase.

Furthermore, a transistor was used as a switching element, but
It may be FET or IGBT.

Furthermore, this embodiment can be applied to household appliances such as vacuum cleaners, power tools, and air conditioners.

Another embodiment of the invention is shown in FIG.

In this embodiment, the DC voltage waveform Voc is detected via the resistors R2 and Ra, and the output VD of the A/D converter and the current command i* are detected.
A new current command IO umbrella is obtained by multiplying by .

By doing so, the power supply current can be made closer to a sine wave than in the above case. In this embodiment, the DC voltage is detected from the output voltage of the full-wave rectifier circuit 7, but it goes without saying that it may also be detected from the AC power source 6 via an isolation transformer and a full-wave rectifier circuit.

FIG. 7 shows yet another embodiment of the invention. In this embodiment, capacitors C4 and C5 are provided to bypass the direct current of inductances 3 and 4, and bypass capacitors 01 to Cδ are provided at the terminals of the armature winding 5b. Even if the main circuit is configured in this way, the same effects as in the case described above can be achieved. Note that the diode D5. DB, D7
．． The insertion positions of DIl and D12°Dss are not limited to those in this embodiment, and may be the same as in the embodiment shown in FIG. 1 described above.

〔Effect of the invention〕

As described above, the present invention supplies current to the motor even when the DC voltage is lower than the induced voltage of the motor, improving the power factor of the power supply, and supplying current to the motor even when the DC voltage is lower than the induced voltage of the motor. supply.

An inverter device that can improve the power factor of the power source can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the device configuration of an embodiment of the inverter device of the present invention, FIG. 2 is an analog block diagram of various processes of a microcomputer according to the embodiment, and FIG.
A) and (B) also show PWM signal generation in buck mode and boost mode in one embodiment. (A) is a PWM signal generation diagram in buck mode, and (b) is a PWM signal generation diagram in boost mode.
The M signal generation diagram, Figures 4 (a), (b), and (c) also show the firing signals of the P side and N side switching elements of one embodiment, and (a) is the position detection signal diagram, ( B) is a firing signal diagram in buck mode, (c) is a firing signal diagram in boost mode, and Figures 5 (a) to (d) are the main circuits in buck mode and boost mode of one embodiment. (a) is the main circuit diagram showing the operation in buck mode, (b) is the main circuit diagram also showing the operation in buck mode, and (c) is the main circuit diagram showing the operation in boost mode. Circuit diagram (d) is a main circuit diagram also showing operation in boost mode, FIG. 6 is an analog block diagram of various processes of the microcomputer of another embodiment of the inverter device of the present invention, and FIG. It is a circuit diagram showing the device configuration of still another example of the inverter device of the invention. 1.2... Capacitor (for bypass), 3.4...
Inductance (inductance element), 5... Brushless motor, 5a... Rotor, 5b... Armature winding, 6... AC power supply, 7... Full wave rectifier circuit, 8...
・Microcomputer, Qs, Qδ+Qi...P
Side switching element, Q2t Q4, Q+...N
side switching element. Akira 3rd figure (in (Rono 4th figure (a) C4th Q. G

Claims (1)

[Claims] 1. In an inverter device that includes P-side and N-side switching elements connected in series and converts direct current into variable frequency alternating current, the device includes one of the P-side and N-side switching elements. A capacitor is provided to bypass direct current when non-conducting, an inductance element is provided to suppress an increase in direct current when both the P-side and N-side switching elements are conducting, and one of the P-side and N-side switching elements is turned on or off. An inverter device characterized in that it is operated by transitioning between a step-down mode in which the inverter output voltage is adjusted by adjusting the inverter output voltage, and a step-up mode in which both the P-side and N-side switching elements are made conductive for a certain period of time. 2. The conduction time width in the buck mode in which the output voltage and current of the inverter conducts only one of the P-side and N-side switching elements, and the conduction time in the boost mode in which both the P-side and N-side switching elements conduct. The time width and
The inverter device according to claim 1, wherein the inverter device is configured to change and control the direct current according to a control deviation of the direct current. 3. The conduction time width in the buck mode in which the output voltage and current of the inverter conducts only one of the P-side and N-side switching elements, and the conduction time in the boost mode in which both the P-side and N-side switching elements conduct. The time width and
The inverter device according to claim 1, wherein when the DC voltage fluctuates, the inverter device modulates and controls according to the voltage fluctuation.