JP2826361B2 - Converter control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter for converting an AC voltage into a DC voltage by rectifying and smoothing the AC voltage and converting the input current waveform into a waveform similar to the input voltage waveform.

[Conventional technology]

5 and 6 are diagrams for explaining a conventional converter control method. FIG. 5 is a circuit diagram, and FIG. 6 is an operation waveform diagram.

In FIG. 5, an AC voltage is subjected to full-wave rectification by a full-wave rectifier circuit 2 via a high-frequency filter 1, and switching elements 4, 5 of a chopper circuit 3 are switched at a frequency sufficiently higher than the frequency of the AC voltage. Chapper circuit 3
To obtain a DC voltage at the output.

The operation of the chopper circuit 3 in FIG. 5 will be described with reference to the operation waveform diagram shown in FIG. First, when the switching elements 4 and 5 are simultaneously turned on, energy is accumulated in the choke coil 6 and the current I ₁ (shown in FIG. 6 (b)) flowing through the choke coil 6 and the current I ₁ flowing through the switching elements 4 and 5
₂ (shown in FIG. 6 (c)) shows that the inductance of the choke coil 6 is L and the voltage full-wave rectified by the full-wave rectifier circuit 2 is E (shown in FIG. 6 (a)). Rise with the slope of. Next, turn off the switching elements 4 and 5 at the same time, the energy accumulated in the choke coil 6, a rectifying diode 7, the current I ₁ flowing through the current (choke coil 6 via the flywheel diode 8 6 Figure (b)
To the current I ₃ flowing through the rectifying diode 7 Figure 6 (d)
) Flows, and charges a large-capacity smoothing capacitor 9, from which a DC output voltage E ₀ is obtained. The current I ₁ flowing through the choke coil 6 is detected by the current transformer 10 and the current detection value obtained by extracting the low-frequency component, the deviation between the output voltage E ₀ and the reference voltage E _ref detected and amplified by the error amplifier 11 The difference between the proportional value of the full-wave rectified waveform of the AC voltage and the voltage detection value obtained by calculating with a voltage-controlled gain amplifier (hereinafter referred to as VCA) 12 is amplified by an operational amplifier 13 and its output is minimized. The drive of the switching elements 4 and 5 is controlled by the pulse width control circuit 14 as described above.

By controlling in this way, the current waveform (shown in FIG. 6 (b)) of the choke coil 6 is made similar to the full-wave rectified voltage waveform (shown in FIG. 6 (a)), and harmonics of the input current are obtained. The components are reduced.

[Problems to be solved by the invention]

However, in such a control method, since the current waveform of the choke coil is similar to the full-wave rectified voltage waveform, harmonics can be reduced as compared with the capacitor input type rectifier circuit, but the input current waveform is different from the input voltage waveform. It is no longer similar. Because, to make the input current waveform similar to the input voltage waveform, the duty ratio of the switching element must be constant regardless of the voltage phase. However, as in this example, the current of the choke coil is changed to a sine wave. Then, the duty ratio of the switching element must be controlled by the voltage phase. As a result, there is a disadvantage that the input power factor is deteriorated. In addition, special current transformers are required to measure DC current.

[Means for solving the problem]

The present invention provides a full-wave rectifier circuit for obtaining a full-wave rectified voltage by full-wave rectifying an AC voltage and a transformer having a primary winding connected to an output of the full-wave rectifier circuit. A switching element connected between the primary winding of the transformer and the output of the full-wave rectifier circuit, the switching element being on / off controlled at a conversion frequency sufficiently higher than the AC voltage, and connected to the secondary winding of the transformer; A series circuit of a diode and a smoothing capacitor is provided. When the switching element is on, energy is stored in the primary winding of the transformer, and when the switching element is off, the energy is stored in the secondary winding of the transformer via the diode to the smoothing capacitor. A method for controlling a converter that releases energy and supplies power to a load from both ends of the capacitor,
The current integral value of each switching of the primary winding current of the transformer is proportional to a value obtained by multiplying an error voltage between the output voltage of the converter and a reference voltage by a proportional value of the full-wave rectified voltage. And a control method of the converter, characterized in that the control method is as follows.

[Action]

According to such a converter control method, the input current waveform can be made similar to the input voltage waveform, and the input power factor can be improved as if a resistor were connected to the input terminal.

〔Example〕

1 and 2 are diagrams for explaining an embodiment of the present invention. FIG. 1 is a circuit diagram, and FIG. 2 is an operation waveform diagram.

In FIG. 1, an AC voltage is connected to an input terminal of a full-wave rectifier circuit 2 via a high-frequency filter 1, and a primary winding N1 of a transformer 15 and a switching element are connected between DC output terminals of the full-wave rectifier circuit 2. 4 are connected. Then, a series circuit of the rectifier diode 7 and the smoothing capacitor 9 is connected to the secondary winding N2 of the transformer 15, and an output is taken out between terminals of the smoothing capacitor 9. The output voltage stabilization control is performed by amplifying an error between a voltage obtained by dividing the output voltage E ₀ by the resistors 16 and 17 and the first reference voltage E _ref by the error amplifier 11 and isolating the error by the photocoupler 18. The obtained value and the full-wave rectified voltage E
A value e _ref obtained by multiplying the value obtained by voltage division at 19.20 with the multiplier 21 is used as a second reference voltage, and the transformer 15
Of the primary winding is detected by the current transformer 22, the current integration value obtained by integration by the current integration circuit 23 is compared by the voltage comparator 24, and the output is sent to the drive circuit 25 to send the switching element 4. By turning on and off.

Next, the operation will be described. The switching element 4 is turned on at a fixed frequency, and energy is stored in the single winding N1 of the transformer during the ON period. Then, the current of the primary winding N1 of the transformer is detected by the current transformer 22 and integrated by the current integration circuit 23. The integrated current value obtained by dividing the full-wave rectified voltage E of the input voltage by the resistors 19 and 20 is obtained. Multiplier 21 multiplies the proportional value of the voltage obtained by the
When the voltage matches the second reference voltage obtained by multiplying by, the voltage comparator 24 transitions from L to H, sends a signal to the drive circuit 25, and turns off the switching element 4. During the off period of the switching element 4, energy is released from the secondary winding N2 of the transformer 15 to the capacitor 9 via the diode 7, and DC power is extracted from the capacitor 9. Current integration circuit 23
Is periodically reset by the oscillation circuit 26, the voltage comparator 24 transitions from H to L, sends a signal to the drive circuit 25, and turns on the switching element 4.

On the other hand, since all the current flowing to the input flows to the output, if the input current waveform is similar to the voltage waveform, the output voltage pulsates at the fundamental period of the full-wave rectified voltage. Therefore, in the error amplification between the output voltage and the first reference voltage _Eref , the error amplifier
If 11 has an amplification gain in the fundamental frequency component of the full-wave rectified voltage, a signal is sent to reduce the pulsating component of the output, and the second reference voltage e _ref changes during one cycle of the input voltage, and the input current The waveform is no longer similar to the input voltage waveform.
For this reason, the amplification gain of the error amplifier 11 is reduced sufficiently with respect to the fundamental wave component of the full-wave rectified voltage by the resistor 27 and the capacitor 28 so that no response is made. FIG. 2 is an operation waveform diagram of FIG. 1, wherein (a) is a pulsating current, (b) is a current integrated value, (c) is a current flowing through the switching element 4,
(D) is the secondary winding current of the transformer 15, (e) is the oscillation circuit
26 shows an output signal, and (f) shows an output signal of the voltage comparator 24. Assuming that the voltage value at an arbitrary phase of the input voltage is e _i , the current I flowing when the switching element 4 is turned on is L, where the inductance value of the primary winding N1 of the transformer 15 is L, and the initial value is I _0. When the switching cycle is T and the on-time is T _on , the current integrated value I _it is Becomes Then, this current integrated value is used as the switching period T
The value divided by becomes the average current in the switching. Since the current integrated value matches the proportional value of the input voltage waveform, if the switching frequency component is removed with a high frequency filter,
Since the switching cycle T is constant, the input current waveform is similar to the input voltage waveform.

FIG. 3 is a diagram for explaining another embodiment of the present invention, in which a band-pass filter 29 is inserted in the output voltage detector of the circuit of FIG. 1 to remove the fundamental frequency component of the full-wave rectified voltage. After that, the frequency response is input to the error amplifier 11 to speed up the frequency response outside the band and improve the response to load fluctuation.

FIG. 4 is a diagram for explaining another embodiment of the present invention. A high-speed response chopper circuit 30 is connected to the output of the circuit of FIG.
Are connected. In the embodiment shown in FIG. 1, the response is slow, and also in the embodiment shown in FIG. 3, when there is a voltage pulse of the fundamental frequency component of the full-wave rectified voltage and the load is disturbed, the stabilization control is performed at a high speed, and It is configured so that accurate power can be supplied. Note that this chopper circuit 30
Is well known, and the description of the operation is omitted.

〔The invention's effect〕

As described above, according to the present invention, the input current waveform is similar to the input voltage waveform with a simple configuration without using any special circuit for the current detection current transformer for the current waveform control. As a result, as if a resistor was connected to the input terminal, the input power factor could be improved.

[Brief description of the drawings]

FIGS. 1 and 2 are diagrams for explaining an embodiment of the present invention, FIGS. 3 and 4 are diagrams for explaining an embodiment of the present invention, and FIGS. 5 and 6, respectively. Is a diagram for explaining a conventional example. DESCRIPTION OF SYMBOLS 1 ... High frequency filter 2 ... Full-wave rectifier circuit 3 ... Chopper circuit 4,5 ... Switching element 6 ... Choke coil 7 ... Rectifier diode 8 ... Fly wheel diode 9 ... Smoothing Capacitor, 10 Current transformer 11 Error amplifier 12, VCA 13 Differential amplifier 14, Pulse width control circuit 15 Transformer 16, 17, Resistor 18 Photocoupler 19 , 20… resistor 21… multiplier 22… current transformer 23… current integrating circuit 24… voltage comparator 25… drive circuit 26… oscillation circuit 27… resistor 28… capacitor 29 …… Bandpass filter 30 …… High-speed response chopper circuit

Claims (1)

(57) [Claims] 1. A full-wave rectifier circuit for obtaining a full-wave rectified voltage by full-wave rectifying an AC voltage, a transformer having a primary winding connected to an output of the full-wave rectifier circuit, and a primary winding of the transformer. A switching element connected between the line and the output of the full-wave rectifier circuit and controlled to be turned on and off at a conversion frequency sufficiently higher than the AC voltage; and a series of a diode and a smoothing capacitor connected to the secondary winding of the transformer. A circuit for storing energy in the primary winding of the transformer when the switching element is turned on, and discharging energy from the secondary winding of the transformer to the smoothing capacitor via the diode when the switching element is turned off. A method for controlling a converter for supplying power to a load from both ends of a converter, wherein a current integral value of each switching of a primary winding current of the transformer is determined by determining an output voltage of the converter and a reference voltage. And a control method for multiplying the error voltage of the full-wave rectified voltage by a proportional value of the full-wave rectified voltage so as to be proportional to the value obtained.