JPH0638539A - Power source - Google Patents

Abstract

PURPOSE:To move the noise of an audible range out of the range and to reduce the noise by providing a circuit for dividing an ON period of a PWM wave signal. CONSTITUTION:A circuit for dividing an ON period of a PWM wave signal is provided between a PWM circuit 48 and a driver 60. A PWM waveform (1) from the circuit 48 is input to an AND gate 12 together with an output (2) of a shift register 11. If no input of the wave (1) exists at the register 11, the output (2) of the register 11 is ON, and hence if the wave (1) is ON, an output (3) becomes ON. If the ON is continued for a predetermined period, QA-QD of the register 11 become ON, and hence the output (2) of the register 11 is turned OFF, and the output (3) is operated by an AND of the waveform (1) and the output (2) of the register by the AND gate 12, and hence the output (3) becomes OFF. Thus, the signal of the output (3) is obtained. That is, the noise is moved out of an audible range to be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device used as a power supply for an electric motor or the like.

[0002]

2. Description of the Related Art FIG. 3 shows a main circuit portion in a conventional inverter power supply device for driving a three-phase induction motor. In FIG. 3, reference numeral 31 is a full-wave rectifier circuit that rectifies alternating current from a commercial three-phase alternating current source 32, 33 is a smoothing capacitor, and 34 to 39 are switching elements. Among the switching elements 34 to 39, the switching elements 34 and 35 correspond to the U phase of the output voltage supplied to the electric motor, the switching elements 36 to 37 correspond to the V phase, and the switching elements 38 and 39 correspond to the W phase. . The switching elements 34 and 35 are connected in series, and further, the smoothing capacitor 33 is connected in parallel. Similarly, the switching elements 36 and 37 and 38 and 39 are connected in series, respectively, and further connected in parallel with the smoothing capacitor 33.
40 to 45 are diodes, the diode 40 is connected in parallel to the switching element 34, and the diode 41 is connected in parallel to the switching element 35. Similarly diode 42
.About.45 are also connected in parallel to the switching elements 36 to 39, respectively.

The three-phase induction motor 46 is driven by a three-phase AC voltage supplied from the U, V, and W phases, and the U phase draws a voltage from the connection point e ₁ of the switching elements 34 and 35, and V
The phases W and W draw the voltage from the connection points e ₂ and e ₃ of the switching elements 36 and 37 and 38 and 39, respectively.

FIG. 4 shows a process of generating a voltage waveform for driving the three-phase induction motor 46. A shown in (1) of FIG.
B and C are the three-phase AC voltage, which is a sine wave signal for setting the motor speed, and the respective phase differences are equal to 120 degrees. Hereinafter, these three sine wave signals are collectively referred to as a motor speed setting signal. Further, T is a triangular wave signal. Both the motor speed setting signals A, B, C and the triangular wave signal T are shown in FIG.
Is input to a comparator 54, which will be described later, and from this comparator, PW
The M wave signal is output. The duty ratio of the PWM wave signal changes depending on the cycle of the motor speed setting signals A, B and C. Then, if the switching elements 34 to 39 are turned on / off in accordance with this PWM wave signal, FIG.
UV, VW, and WU line voltages as shown in (5), (6), and (7) are applied, and the three-phase induction motor 46 can be driven.

BUs shown in (2), (3) and (4) of FIG.
The generation process of each signal of P, BUN, BVP, BVN and BWP, BWN will be described with reference to drive circuits 60, 6 described later in FIG.
Available in 1, 60 ', 61', 60 ", 61".

FIG. 5 shows a control circuit for driving the switching elements 34 to 39 shown in FIG. 3. Reference numeral 48 denotes a pair of switching elements which generate a PWM wave signal and are connected in series (eg, 34, 34 in FIG. 3). 35) also has the function of avoiding the state where it is turned on at the same time, and is called the PWM circuit 48 below.
The PWM circuit 48 includes a delay circuit for delaying a signal composed of 49 and 50 resistors and capacitors, and 51 and 52.
And an inverter circuit 53, and a comparator 54 for comparing the above-mentioned electric motor speed setting signals A, B, C with the triangular wave signal T, and outputs a PWM wave signal from both signals.

A signal delayed by the delay circuit 49 is input to one input terminal of the AND circuit 51, and an undelayed signal is input to the other input terminal. Similarly, the AND circuit 52 also receives the delayed signal from the delay circuit 50 and the undelayed signal. However, an inverter 53 is inserted in the preceding stage of 50 and 52, and an inverted PWM wave signal is output.

Therefore, the P output from the comparator 54 is applied to the signal processing section composed of the delay circuit 49 and the AND circuit 51.
The WM wave signal is sent as it is, and the PWM wave signal inverted by the inverter 53 is sent to the signal processing unit including the delay circuit 50 and the AND circuit 52.

Reference numeral 60 is a drive circuit for driving the switching element 34, and 61 is a drive circuit for driving the switching element 35. The configuration of the drive circuit 61 is similar to that of the drive circuit 60. Therefore, the description thereof is omitted. 62 is a photo coupler, which is used for insulation. 63 and 64 are transistors for output, 63 is an NPN type and 64 is a PNP type. That is, when the base voltages of both transistors become "Hi", the NPN type transistor 63 is turned on and the PNP type transistor 64 is turned off. Reference numeral 65 is a transistor for amplifying the output signal of the photocoupler 62, and the voltage amplified by this transistor 65 is applied to the transistors 63, 64.
Will be applied to the base.

That is, the output signal BUP is transmitted to the transistor 63.
And 64 at connection point E. BUP shown in FIG. 4 (2)
Is a switching signal to the switching element 34 based on the PWM signal obtained from the comparator 54 of the motor speed signal A and the triangular wave signal T shown in FIG. 4 (1), and the BUP signal extracted from the connection point E is It is sent to the terminal BUP of the switching element 34 of FIG. Moreover, from the drive circuit 61, as shown in FIG.
The BUN signal shown in (2) is input to the switching element 35 of FIG.

The PW provided for the other phases V and W
M circuit 48 ', 48 "and drive circuit 60', 60", 61 ',
The 61 ″ has the same configuration as the PWM circuit 48 and the drive circuits 60 and 61 described above, and the drive circuits shown in FIG.
BVP, BUN signal, BWP, BWN shown in (3) and (4) of
The signal is output.

FIG. 6 shows a triangular wave voltage generating circuit for supplying the triangular wave signal T to the comparator 54. The triangular wave signal T having a frequency determined by the time constants of the resistor 66 and the capacitor 67.
Is generated and sent to the comparator 54 of FIG.

[0013]

In the conventional configuration as described above, the PWM speed signal is obtained by comparing the electric motor speed setting signals A, B and C with the triangular wave signal T by the comparator.
There is a problem that the noise of the wave signal is large because it is in the audible region.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the noise by moving the noise in the audible region to the outside of the audible region.

[0015]

In order to solve the above problems, the present invention divides the ON period of a PWM wave signal by a control circuit using a shift register to move noise in the audible region to outside the audible region. And move.

[0016]

According to the present invention, noise in the audible area can be reduced by moving it outside the audible area.

[0017]

1 is a circuit diagram for dividing an ON period of a PWM wave signal according to an embodiment of the present invention, and FIG. 2 is a time chart thereof. In FIG. 1, 11 is a shift register,
12 is an AND circuit and 13 is an inverter. The circuit of Fig. 1 is connected to the output side of the PWM circuit 48 (48 ', 48 ") of Fig. 5. The PWM circuit 48 (hereinafter, this PWM circuit will be described, but the other 48', 48" are also the same. So it is omitted)
The WM waveform has a long pulse as shown in FIG. 2 (1), and the output of the shift register 11 ((2) in FIG. 2) and A
It is input to the ND circuit 12. When there is no PWM wave input to the shift register 11, the output of the shift register 11 is O
Since it is N, when the PWM wave is turned on, the output shown in FIG. 2 (3) is turned on. If continued a certain period is ON, since the ON until Q _A to Q _D of the shift register 11, the output of the shift register 11 is output to OFF takes an AND of the PWM waveform and the shift register output even AND circuit 12 outputs Turns off. In this way, the output signal is obtained.

That is, by dividing the ON period of the PWM wave signal by the control circuit using the shift register, it is possible to move the noise in the audible region to the outside of the audible region and reduce the noise due to the noise.

[0019]

As described above, the power supply device of the present invention can reduce the noise by moving the noise in the audible region to the outside of the audible region by dividing the ON period of the PWM wave signal. it can.

[Brief description of drawings]

FIG. 1 is a circuit diagram for dividing an ON period of a PWM signal according to an embodiment of the present invention.

FIG. 2 is a timing chart of FIG.

FIG. 3 is a main circuit unit in a conventional inverter power supply device.

FIG. 4 is a diagram showing a process of generating a voltage waveform for driving the three-phase induction motor of FIG.

5 is a control circuit for driving the switching element of FIG.

FIG. 6 is a diagram showing a conventional triangular wave generation circuit.

[Explanation of symbols]

11 ... Shift register, 12, 51, 52 ... AND circuit, 1
3, 53 ... Inverter, 31 ... Full-wave rectification circuit, 32 ... 3-phase AC power supply, 34-39 ... Switching element, 40-45 ... Diode, 46 ... 3-phase induction motor, 48, 48 ', 48 "...
PWM circuit, 49, 50 ... Delay circuit, 54 ... Comparator, 6
0, 61, 60 ', 61', 60 ", 61" ... Drive circuit, 62
… Photo coupler, 63, 64… Output transistor, 65
... transistor.

Claims (1)

[Claims] 1. A first and a second switching device, comprising first and second switching elements connected in series to a DC power source.
From the switch unit configured to supply the voltage at the connection point of the switching element of the load device to the load device, the triangular wave voltage generation unit that generates a triangular wave voltage, the AC voltage generation unit that generates an AC voltage, and the triangular wave voltage generation unit. And a PWM circuit having a comparator for generating a PWM wave signal which is inverted when one exceeds the potential of the other by comparing the triangular wave voltage with the AC voltage from the AC voltage generator, and the PWM wave from the comparator. In a power supply device including a drive circuit that alternately turns on the first and second switching elements by a signal, a circuit that divides an ON period of a PWM wave signal is provided between the PWM circuit and the drive circuit. A power supply device characterized in that noise in a region is moved outside the audible region.