KR100407017B1 - The Electronic Power Transformer for conversion of AC to AC/DC - Google Patents

Abstract

The present invention is based on the bidirectional Pulse Phase Modulation (PPM) switching technology to provide a new concept of electronic power transformer that can supply a constant DC voltage as well as supplying a sine voltage capable of polarity inversion and a continuously variable unit power factor. It is about. The device can be operated as an AC-AC converter by applying PPM modulation through high-frequency bidirectional switching, and eliminates the need for tap installation, which was necessary for the existing transformer to supply various load voltages. The weight and weight of the iron core, which occupies most of the weight and volume of the transformer, are reduced to reduce the size and weight. In addition, it is possible to operate as an AC-DC converter with an AC-DC conversion function that can be continuously changed by controlling the switch on the secondary side by using the switch on the primary side of the high frequency electronic power transformer of the device. .

Description

The Electronic Power Transformer for conversion of AC to AC / DC}

The present invention relates to an electronic power transformer capable of AC-AC / DC conversion and a method therefor.

The international technology trend of industrial or household electric and electronic products is smaller and lighter in proportion to the development of devices including semiconductors and the emergence of new concepts, and in order to receive a different power supply for each device to be used due to different voltage standards. It is no exaggeration to say that the use of transformers is a major part of the overall system because use is an essential element. However, because the transformer generally used consists of iron core and coil, it is heavy and bulky, so it is difficult to carry and carry, and it is not possible to manufacture compact size when using the transformer. Although it is difficult to use a transformer because it needs to be attached, research on AC-DC / DC-DC converters, DC-AC inverters and UPS (AC-DC-AC) has been actively conducted in the power electronics field. There is almost no research on the AC-AC converter (electronic power transformer) that can be solved.

On the other hand, the transformer currently being used must take the inconvenience of winding the number of turns or installing a tab in order to vary the voltage required by the load. In addition, in the case of DC load, a power supply device (SMPS, Switching Mode Power Supply) using a separate adapter or switching element is installed and supplied (see FIG. 1). However, power transformers, which will be used in the power electronics field, can supply a wide range of rated voltages, and require a small, lightweight and economical electric power transformer. As described above, the use of transformers is not only necessary for supplying different voltage specifications for different countries and different power supplies for each device, but also a power supply device using an additional power switching element to supply DC voltage. or SMPS). In addition, since the power of the commercial frequency (60Hz) component is boosted or stepped down through the transformer in the whole system, if the total capacity increases, the size or weight of the transformer also increases, resulting in an inefficient configuration of the entire system. To minimize the volume and weight of the

Accordingly, the electronic power transformer according to the present invention supplies various load voltages, eliminates the necessity of tap installation, which is essential for the existing transformer, and reduces the volume and weight of the iron core occupying most of the weight and volume of the transformer. In order to reduce the size and weight of the transformer occupying the entire system, high-frequency switching using PPM (Pulse Phase Modulation) was applied to the bidirectional switches installed on the primary and secondary sides. In addition, in the present invention, by controlling the switching element on the secondary side of the high-frequency electronic power transformer can be operated as an AC-DC converter having a continuously variable AC-DC conversion function, which is essential for a load requiring a DC power supply. This eliminates the need for an adapter or SMPS.

1 is a block diagram of a conventional transformer for obtaining a DC output voltage.

2 is a circuit diagram of an electronic power transformer according to the present invention.

FIG. 3 is a circuit diagram illustrating a configuration of a bidirectional switch in FIG. 2 and including a pair of unidirectional switches.

4 is a voltage waveform at each point in the electronic power transformer according to the present invention.

5 is a voltage and switching control signal waveform at each point by the PPM control applied to the electronic power transformer of the present invention.

FIG. 6 is an enlarged view (5ms to 6ms) in which the switching control signal of FIG. 5 is enlarged.

7 is an input / output voltage waveform (left) and switching signals (right) of the primary and secondary sides according to the signal phase difference through PPM control, and (a, b) to (i, j) are the signal phase differences of the primary and secondary sides, respectively. Is 0 degrees, 45 degrees, 90 degrees, 135 degrees, and 180 degrees.

8 is an input / output voltage waveform and a switching signal of primary and secondary sides for obtaining a DC output.

The configuration of the electronic power transformer capable of AC-AC / DC conversion according to the present invention is as follows. In other words, AC power,

A circuit device connected to the AC power source and connected in series with a first reactance, a first capacitor, a second capacitor, and a second reactance;

First and third bidirectional switches branched between a reactance and a capacitor of the circuit device to modulate an input voltage, connected in series with each other, and alternately switched at times other than dead time;

Second and fourth bidirectional switches connected in parallel with the first and third bidirectional switches and serially connected to each other and alternately switched at times other than a dead time;

With transformer,

Branched between the second and fourth bidirectional switches to form a primary coil of the transformer, and selecting and connecting one of a point between two capacitors in the circuit device or a point between the first and third bidirectional switches. With changeover switch,

It operates every positive and negative half-cycle of the power line frequency to demodulate the voltage induced by the transformer, and is electrically connected to the transformer, in series with each other, and alternates at times other than dead time. Fifth and sixth bidirectional switches switched to;

A third reactance and a load branched from the transformer and the point between the fifth bidirectional switch and the sixth bidirectional switch;

And a capacitor connected in parallel with the load at a rear end of the third reactance.

In this case, the bidirectional switch may be configured by a combination of a pair of unidirectional switch elements.

Meanwhile, the first and third bidirectional switches on the primary side of the electronic power transformer and the second and fourth bidirectional switches are driven at a duty ratio of 50% with a 180 degree phase difference, and the second side of the electronic power transformer The fifth and sixth bidirectional switches are also operated at a duty ratio of 50% with a 180 degree phase difference, and the phases of the output voltage are controlled by synchronizing with the first and fourth bidirectional switches or the second and third bidirectional switches. By varying the magnitude and phase continuously, it is possible to supply commercial frequency power to various loads.

In addition, according to the present invention, the AC-AC / DC convertible electronic power transformer can supply various DC voltages having different polarities and magnitudes, which adjust phases of the fifth bidirectional switch and the sixth bidirectional switch during a half cycle of a commercial frequency. Can be supplied.

At this time, the output DC voltage can be supplied within a range of a positive maximum value to a negative maximum value, and PPM control is performed on the primary and secondary coil sides of the transformer and the first and second The phases of the fifth bidirectional switch and the sixth bidirectional switch which are operated in synchronization with the fourth bidirectional switch or the second and third bidirectional switches can be implemented by inverting the phases of the commercial frequency for half a period.

On the other hand, the AC-AC / DC conversion and power transformer method according to the present invention consists of the following steps.

That is, a circuit device connected to the AC power source and the AC power source and connected in series with the first reactance, the first capacitor, the second capacitor, and the second reactance, and the first and second branches branched between the reactance of the circuit device and the capacitor. A third bidirectional switch, a second bidirectional switch connected in parallel with the first and third bidirectional switches, connected in series with each other, a transformer, and branched between the second bidirectional switch and the second bidirectional switch; A switching switch constituting a primary coil and selecting one of a point between two capacitors in the circuit device or a point between the first and third bidirectional switches; a fifth switch electrically connected to the transformer and connected in series with each other; A sixth bidirectional switch, a third reactance branched from the transformer and a point between the fifth bidirectional switch and the sixth bidirectional switch; In the electronic power transformer consisting of a capacitor that is connected in parallel with the load in the third group and the reactance connected in series with the load, the rear end of the third reactance,

Alternately high frequency switching of the first and third bidirectional switches and the first and third bidirectional switches with each other at a time other than a dead time to modulate an input voltage;

Alternately high frequency switching the fifth and sixth bi-directional switches alternately with each other every half period in time other than dead time to demodulate the voltage induced by the transformer;

Phases of the first and fourth bidirectional switches or the second and third bidirectional switches and phases of the fifth or sixth bidirectional switches to supply power of a commercial frequency capable of continuously varying the magnitude and phase of the output voltage. Varying using PPM control;

In order to supply DC voltages having different polarities and magnitudes, the phases of the fifth bidirectional switch and the sixth bidirectional switch operating in synchronization with the first and fourth bidirectional switches or the second and third bidirectional switches may be set at a commercial frequency. Operating by inverting 180 degrees for half a cycle,

Continuously controlling PPM control on the primary and secondary coil sides of the transformer to control the DC output voltage, including the AC output, from a positive maximum to a negative maximum. .

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

First, referring to FIG. 2, the electronic power transformer (AC-AC / DC converter) according to the present invention has an advantage of delivering power to a variable DC load as well as a variable AC load of a commercial frequency. The input voltage is modulated by the bidirectional switching elements S1, S2, S3, S4. The basic principle is similar to the ring modulation method in the size modulation method of the communication system. The modulated waveform is a waveform consisting of a product of an input waveform having a system frequency and a switching signal that is alternately turned on and off at a high frequency with a duty ratio of 50%. The ring modulated voltage is applied to the primary side of the high frequency transformer and the voltage induced on the secondary side is demodulated by the bidirectional switches S5 and S6 controlled in synchronization with high frequency.

The operations of switches S5 and S6 are synchronized at high frequency, and operate alternately every half cycle, similar to the conventional synchronous rectification circuit. The internal connection of the bidirectional switching elements of the primary and secondary sides using MOS-FETs or IGBT pairs, which are frequently used as unidirectional switch elements, is shown in FIG. can do.

On the other hand, in the case of an electronic power transformer having a fixed turn ratio, S1, S3, and S5 are driven at a duty ratio of 50%. On the other hand, S2, S4 and S6 are equally driven with a 180 degree phase difference. The operating waveforms at representative points P1, P2, P3 and P4 of the electronic power transformer with a fixed turn ratio are shown in FIG.

Electronic power transformer according to the present invention has the advantage that can be used without the use of a separate adapter (or SMPS) when supplying a DC voltage to the load, which is the primary switch of the electronic power transformer (So) at a point b By switching to the point and inverting the switch on the secondary side for half a period, it can also be operated as an AC-DC converter with a continuously variable AC-DC conversion function.

PWM control method is widely used to control DC-DC converter and DC-AC inverter. The proposed electronic power transformer (AC-AC converter) can apply PWM switching to the 1st and 2nd side of the high frequency transformer, but it is preferable to apply PPM control with simpler control circuit configuration. The basic principle of the PPM control applied to FIG. 2 is shown in FIG. 5. As shown in Fig. 5, the switches S1, S3, S2 and S4 of the primary side circuit are alternately switched except for dead time. The S5 and S6 switches on the secondary side are also switched alternately except for a short dead time. Therefore, the internal impedance of the primary and secondary sides of the high frequency transformer can be kept small through such a switching operation. This property is desirable for maintaining a stable voltage against nonlinear loads.

As can be seen from the enlarged switching control signal of FIG. 6, the power of the commercial frequency that can be continuously varied by controlling the phase difference between the primary switch (S1, S4 or S2, S3) and the secondary switch (S5 or S6). It can be seen that can be supplied. This can be confirmed by comparing the waveforms of the input voltage and the output voltage according to the phase difference of the first and second sides (see FIG. 7). The waveforms on the left of each of FIG. 7 represent input waveforms at the top and variable output waveforms at the bottom, and the relative phase difference can be confirmed. The waveform on the right side of FIG. 7 shows the phase difference and the primary / secondary switching signal corresponding to the input / output voltage waveform on the left side. The condition for obtaining the maximum output voltage of the positive phase is when the signal phase difference between the primary and secondary sides is 0 degrees (Fig. 7 (a, b)). In addition, the phase difference for obtaining the zero output voltage may be implemented at 90 degrees (FIG. 7 (e, f)). In the same way, the condition for obtaining the maximum output voltage of the negative phase or the maximum output voltage of 0.5 times may be implemented by zooming the switching drive signal phase difference 180 degrees and 135 degrees, respectively (Figs. 7 (i, j), ( g, h)).

On the other hand, when comparing the input and output voltage waveforms in Figs. 7 (a, b) and 7 (i, j), it can be seen that the phases of the switches S5 and S6 are inverted. Therefore, it can be seen that when the switch S5 and S6 signals are changed during the half cycle of the commercial frequency, a DC voltage of positive or negative polarity can be obtained (FIG. 8). Therefore, by applying the PPM control continuously like the method of acquiring the variable AC output voltage, the DC output voltage can be controlled from the maximum value of (+) to the maximum value of (-).

The application of AC-AC converter with sinusoidal input and output is expected to be applied to all power electronics in the future as the existing power transformer is widely used. As described above, it is possible to solve the trouble of using a transformer with a tap to receive a different voltage standard and a different power supply for each device to be used. In order to step up or step down, the inefficiency of the transformer increases in size and weight when the total capacity is increased.However, when the proposed electronic power transformer is used, the volume of the transformer occupies most of the volume or weight of the entire system. The weight can be minimized. In addition, it can solve the burden of installing a separate adapter to supply a DC voltage from a commercial power supply can provide a more economical transformer.

Claims (4)

AC power supply; A circuit device connected to the AC power source and connected in series with a first reactance, a first capacitor, a second capacitor, and a second reactance; First and third bidirectional switches branched between a reactance of the circuit device and a capacitor to modulate an input voltage, and connected in series with each other and alternately switched at times other than a dead time; Second and fourth bidirectional switches connected in parallel with the first and third bidirectional switches and connected in series with each other and alternately switched at times other than dead time; Transformers; Branching between the second and fourth bidirectional switches to form a primary coil of the transformer, and selecting and connecting one of a point between two capacitors in the circuit device or a point between the first and third bidirectional switches. Changeover switch; Fifth and sixth bidirectional switches electrically connected to the transformer and serially connected to each other and alternately switched to each other at a time other than dead time to demodulate the voltage induced by the transformer; A third reactance and a load branched from the transformer and a point between the fifth bidirectional switch and the sixth bidirectional switch; And a capacitor connected in parallel with the load at a rear end of the third reactance. 2. An electronic power transformer capable of AC-AC / DC conversion. The electronic power transformer of claim 1, wherein the bidirectional switch is a combination of a pair of unidirectional switch elements. 3. The method according to claim 1 or 2, wherein the phases of the first and fourth bidirectional switches or the second and third bidirectional switches and the fifth or sixth bidirectional are provided to supply power of a commercial frequency which is continuously variable. An electronic power transformer capable of AC-AC / DC conversion, characterized in that the phase of the switch is controlled. Circuit devices connected in series in order of AC power, first reactance, first capacitor, second capacitor, and second reactance connected to AC power, and first and third bidirectional branches branched between reactance and capacitor of circuit device A primary side of the transformer branched between a switch, second and fourth bidirectional switches connected in parallel with the first and third bidirectional switches, and connected in series with each other, a transformer, and the second and fourth bidirectional switches A switching switch that forms a coil and selects and connects one of a point between two capacitors in the circuit device or a point between the first and third bidirectional switches, and fifth and sixth electrically connected to the transformer and connected in series to each other; A bidirectional switch, a third reactance branched from the transformer and a point between the fifth bidirectional switch and the sixth bidirectional switch; In the third and the reactance connected in series with the load, the electronic power transformer consisting of a capacitor is parallel connected to the load from the rear end of the third reactance, Alternately switching the first and third bidirectional switches and the first and third bidirectional switches with each other at a time other than a dead time to modulate an input voltage; and Alternately switching the fifth and sixth bidirectional switches every half period of a high frequency within a time other than a dead time to demodulate the voltage induced by the transformer; Controlling the phases of the first and fourth bidirectional switches or the second and third bidirectional switches and the phases of the fifth or sixth bidirectional switch to supply power of a commercially variable commercial frequency; Varying phases of the fifth bidirectional switch and the sixth bidirectional switch during a half cycle of a commercial frequency to supply DC voltages having different polarities; Continuously controlling PPM control on the primary and secondary coil sides of the transformer to control the output DC voltage from a positive maximum to a negative maximum; When the turn number of the transformer is fixed, the first, third and fifth bidirectional switches are driven at a duty ratio of 50%, and the second, fourth and sixth bidirectional switches are 180 And driving the same with the phase difference; AC-AC / DC conversion and power transformation method.