KR20080008948A - Voltage converter - Google Patents

Abstract

A voltage converter is provided to prevent the dynamic loss inside a transistor by providing a moderate rectification condition when a load current is changed. A voltage converter includes power transistors(111,112,121,122), an inverter apparatus(1), an electromagnetic node(2), a rectifier and filter(3). The power transistors are continuously connected as a pair. The inverter apparatus has a first inverter(11) which consists of resonance condensers(115,116,125,126) parallel connected to electrodes of the power transistors. The electromagnetic node has a first transformer(21) which consists of an input winding(212) and an output winding(213), and is connected to the inverter apparatus. The rectifier and filter is connected to an output terminal. The inverter apparatus has a second inverter(12) which has a similar structure to the first inverter, and has additional inductance. The electromagnetic node has a second transformer(22) which has a similar structure to the first transformer.

Description

Voltage converters {VOLTAGE CONVERTER}

1 shows a circuit of the voltage converter of the present invention.

2 shows an equivalent circuit diagram of a first transformer of the electromagnetic node of FIG. 1.

FIG. 3 schematically shows the configuration of the electromagnetic node 2 of FIG. 1.

<Short description of the symbols in the drawings>

Inverter unit 1, electromagnetic node 2.

Rectifier and Filter 3, First Inverter 11.

Auxiliary inductance of the second inverter 12, inverter device 13.

Power transistors 111, 112, power capacitors 113, 114.

Resonant capacitors 115, 116 of the first inverter 11, power transistors 121, 122.

Power capacitors 123, 124, resonant capacitors 125, 126 of the second inverter 12.

First transformer 21 and second transformer 22 of electromagnetic node 2, magnetic core 211.

Input winding 212, two output windings 213 of the first transformer 21.

Magnetic core 221, input winding 222.

Two output windings 223 of the second transformer 22, diodes 31, 32.

Filter (inductance) 33 of rectifier 3, inductance of magnetization circuit 216.

Leakage inductance 217, gap 214 of magnetic core 211 of first transformer 21.

Terminal 225, gap 224 of magnetic core 221 of second transformer 22.

FIELD OF THE INVENTION The present invention relates to a transducer device, which can be used primarily in power supplies for electric arc welding.

See RF Patents 2190926, N03K17 / 082, N02M7 / 538, published April 20, 2005, Bul. No. The transducer known by [11] is manufactured based on a push-pull circuit to which an active-inductive load is applied. The converter is equipped with locking capacitors connected in parallel with the power transistors and a feedback resistor connected between the drain of the collector or power transistor and the blocking inlet of the precursor for the control signal of the transistors. The drawbacks of the converter are the excessive dynamic losses in the power transistor resulting from the persistence and overcharging of the locking capacitor upon activation and interruption of the collector current and the significant losses on the feedback resistors in the power rectifier circuit.

 A.c. 1796082 USSR, N02M 3/335, published 15.02.93, Bul. No. 6] push-pull DC converters are connected in series to form a series of resonant circuits with a resonant capacitor, a diode having a double-wound throttle electromagnetic node. In the form, the secondary windings of the two double winding throttles are connected to the output of the converter via a rectifier diode and a filter.

These throttles alternate in half life. During the first half of the half-life it acts as a transformer to deliver the overcharge current of the capacitor to the load side, and during the second half of the half-life it acts as a throttle to transfer the accumulated energy back to the load as a return (self-clearing) mode.

As a result, the commutation of the power transistor in the zero current state is ensured, whereby the dynamic loss is reduced. The disadvantage of this converter is that it requires an additional throttle with two windings. This degrades the volume-dimension characteristics, increases the current amplitude through transistor resonance, and places stringent demands on the conversion frequency value. This is because deviations in the commutation period violate zero current requirements at the moment of transistor switching.

Family of Phase-Shifting Resonance Controllers / Integrated Circuits: Chips for Pulse Power Sources and Their Application as conventional voltage converters having a resonant configuration for switching to zero voltage. Edition 2.-M .: DODEKA, 2000, Fig. 18, p. 256] is known.

Conventional converters include inverters configured via bridge circuits on successively connected power transistors, resonant capacitors connected in parallel to the power electrodes of each power transistor, and inverter devices with electromagnetic nodes of transformers. In conventional converters the input windings and output winding outlets connected to the AC inverter output circuit via additional inductance are connected to the output terminals via rectifier diodes and filters. The converter's transistor keys are operated with virtually no losses in the run / stop intervals by permanent load currents.

The disadvantage of this converter is that if the converter load current slowly or momentarily fluctuates to the rated load or short-circuit duty that occurs when welding power is supplied at idling, the degree of dynamic loss of the inverter transistor is excessive. Is that. At low load currents, the energy accumulated in the additional inductance is not sufficient to recharge the resonant capacitor, which disturbs the transistor's moderate commutation conditions. At high load currents, the recharge time is excessively long and the modulation angle and output voltage are reduced.

In order to solve this problem in the prior art, the present invention seeks to provide a novel voltage converter capable of reducing dynamic losses in a transistor.

In addition, the present invention is to provide a novel voltage converter capable of satisfying moderate rectification conditions with zero voltage switching when the load current changes.

According to an aspect of the present invention, a voltage converter includes an inverter device having a first inverter including a resonant capacitor connected in parallel to an electrode of a transistor, a first transformer including an input winding and an output winding. And an electromagnetic node connected to the inverter device, and a rectifier and a filter connected to the output terminal. Here, the inverter device further includes a second inverter having a configuration similar to that of the first inverter, has an additional inductance, and the electromagnetic node further includes a second transformer having a configuration similar to the first transformer.

The first inverter and the second inverter are each connected in reverse connection to the input windings of the corresponding transformer, and form two pairs of output windings connected in series with each other, thereby being connected in parallel to the power outlet and connected to the AC outlet. Continuously connected and reversely connected to the rectifier and the filter, respectively, to form a semi-bridge circuit.

Each of the magnetic cores of the first transformer and the second transformer is configured to have a gap, and the coupling points of the power transistors of the first inverter and the second inverter are connected to each other through the additional inductance.

The above main features of the invention-that is, the inverter device is equipped with an electromagnetic node equipped with another similar inverter and further inductance, a similar transformer. Here, the two inverters are connected in parallel with the power inlet and are continuously connected to the AC outlet by forming two pairs of output windings connected in series and in a reverse connection to the corresponding transformer input windings and reversed to the corresponding rectifier diode and filter. Configured by connected half-bridge circuits. Here, the magnetic cores of the two transformers are configured as gaps, and the transistor coupling points of the two inverters are connected to each other via auxiliary inductance-which is novel and not known at all, so called protection of novelty. It is thought to meet.

In addition, these features ensure novel rectification as the converter load current changes to achieve a novel technical effect of reducing dynamic losses in the transistor, and in this respect, the present invention provides a so-called progressive level of protection requirements. It is thought to meet.

1 shows a circuit of a voltage converter composed of components corresponding to the following reference numerals.

FIG. 2 shows an equivalent circuit of the first transformer 21 of the electromagnetic node consisting of the components corresponding to the following reference numerals (the equivalent circuit diagram of the second transformer 22 is similar).

3 shows a diagram of an electromagnetic node 2 composed of components corresponding to the following reference numerals.

As a possible variation in FIG. 3, the output windings 213 and 223 pairs may be configured to be shared for transformers 21 and 22 to pass through the inlets of magnetic cores 211 and 221.

The voltage converter (FIG. 1) of the present invention is a series of power capacitors 113, 112, 121, and 122 (a MOSFET transistor with an internal "parasitic" reverse-wiring diode is shown) in series and in series. , Inverter device 1 having two inverters 11 and 12 which are mainly made up of half-bridge circuits on 114, 123 and 124.

Resonant capacitors 115, 116, 125, and 126 are connected in parallel with the respective power transistors 111, 112, 121, 122. If the commutation frequency is high, the parasitic storage capacity of the cross diode and power transistors can be used together with the resonant capacitor.

Electromagnetic node 2 is connected to the AC outlet of inverters 11 and 12 and to the outlet of the electromagnetic node and to rectifier 3 with a filter. Inverters 11 and 12 are connected in parallel by a power supply outlet and are connected to a power source U1. They are continuously connected back to back by the AC outlet with the weight of the output voltage. This achieves the above continuous reverse connection.

An end of the input winding 212 is connected to the coupling point of the transistors 111 and 112 of the first inverter 11, and a start of the input winding 222 is connected to the coupling point of the transistors 121 and 122 of the second inverter 12. The start and end portions of the input windings 212 and 222 are connected to coupling points of the power capacitors 113 and 114 and coupling points of 123 and 124, respectively.

The output windings 213 and 223 are paired by continuous coupling. These winding pairs 213 and 223 are connected in reverse phase. That is, the first part is connected to the diode 32, the end is connected to the diode 31, and the first and the end are connected to the inductance 33.

The coupling points of transistors 111, 112, 121, and 122 are coupled to each other through auxiliary inductance 13. Electromagnetic node 2 (FIGS. 2 and 3) consists of two transformers 21 and 22 in planar form. Their magnetic cores 211 and 221 are made of ferromagnetic material (iron oxide is preferred for high conversion frequencies).

As one method, it is suggested that the output windings 213 and 223 pass through the inlets of the two magnetic cores 211 and 221, whereby the output windings 213 and 223 are shared by the two transformers 21 and 22 so that the production technology of these nodes Can be simplified.

During moderate rectification of these transistors, two parameters of the transformer equivalent circuit are used as the inductance and leakage inductance 217 of the magnetization circuit 216. Their value can be changed by selecting gaps 214 and 224. In other words, as the gap increases, the first and second parameters decrease. The voltage converter itself is built on a serial component base and is therefore considered industrially feasible.

The voltage converter of the present invention operates as follows. Due to the alternating commutation of transistors 111 and 112 of the first inverter 11 (transistors 121 and 122 of the second inverter 12), the input winding 212 (the output winding 222 of the transformer 22) of the transformer 21 has its end part (the beginning thereof). And alternately connect to the positive or negative pole of the power source.

At the coupling point of power capacitors 113 and 114 (123, 124), the voltage value corresponds to one half of the power supply voltage (i.e., 0.5U1). The resulting voltage variables of rectangular inverters 11 and 12 are converted to the same required level and summed algebraically. That is, the signals (polarity display) on the second windings 213 and 223 are taken into consideration.

It is rectified and moderate to get a constant output voltage U2. U2 is regulated and stabilized through a feedback channel through the control unit to control the phase change between the output voltages of inverters 11 and 12. Therefore, when the modulation angle (pulse duty cycle) is small, the bidirectional pulses of the voltages on the output windings 213 and 223 have a long stop time between them and have little width, and the output voltage U2 (low value) becomes low.

As the modulation angle increases, the down time decreases and the output voltage increases. Certain conditions are required to achieve resonant phenomena with one of the resonant capacitors 115, 116, 125, and 126 and additional inductance 13 and / or magnetization circuit 216 with coil inductance and leakage inductance 217 of the transformer to perform moderate rectification.

The magnetizing circuit inductances of the two transformers 21 and 22 have significant values compared to the leakage inductance and determine the nature of the current increase (usually linear to the input) through them when voltage is supplied to the output windings 212 and 222.

In the case of power transistor rectification, a dynamic loss of power occurs, which is related to the finite length of the rectification interval, the presence of voltage on the transistor, and the increase (or decrease) of the current. These losses can be minimized by the use of a resonant capacitor connected in parallel with the transistor, as this ensures a switch rectification process with zero voltage on this capacitor.

If the choice of single-tuned network parameters is inappropriate, dynamic power loss can be expected even at idle. This is because if there is a voltage on the capacitor, the energy accumulated there is proportional to the square of the voltage on that device (W _c = 0.5CU ² ). The energy is dispersed on the transistor where rectification proceeds, and when the conversion frequency is high, this energy causes a relatively large dynamic loss, which corresponds to rough rectification of the transistor.

When a resonant process is formed, moderate commutation requires a sufficient level of energy to accumulate in the inductance in order to fully recharge the resonant capacitor to zero voltage in the transistor switching interval. This energy is proportional to the current flowing through it, equaling W _L = 0.5LI ² .

In addition, the resonance oscillation time T must be in a specific relationship with the rectification time t _k of the transistor, that is, T ≧ 4t _k . At this time, an excessive increase in T results in a decrease in the modulation angle and a decrease in the output converter voltage, which can be quite harmful.

After the resonant capacitor is discharged to zero voltage, time t _k is intentionally introduced into the conversion cycle so that the transistor can be shifted. For this purpose, a parameter selection is required which can be changed during the transfer to other modes (nominal conditions, average load, idle state, short circuit). In the present invention, a resonant capacitor and three types of inductances (inductance of the magnetization circuit and leakage inductance and additional inductance for transformers) are used for this purpose.

The main steps of transistor rectification at steady state for modulation angles and rated loads near their maximum are: In this embodiment, when no energy is transferred to the load side through transformers 21 and 22, it is assumed that the voltage transformation cycle ends. Transistor 111 of the first inverter 11 and transistor 121 of the second inverter 12 are activated. Voltage + 0.5U ₁ is supplied from capacitors 113 and 123 to the end of input winding 212 and the beginning of input winding 222. Because of the subtractive polarity of these windings, the sum of the voltages on the winding pairs 212 and 222 becomes zero, and the load current is supplied to the energy accumulated by the inductance 33. Equilibrant current in input windings 212 and 222 circulates freely through transistors 111 and 121, but in reverse mode (from power to drain) through the reverse diode. Capacitors 115 and 125 are fully discharged, and capacitors 116 and 126 are charged to the level of 0.5U ₁ . The current in the additional inductance 13 is zero.

From the control device, a signal is emitted to lock the transistor 111. This stops without causing any loss in the zero voltage state on capacitor 115, after which it is charged to a level of 0.5U ₁ as part of the equilibrium current. In capacitor 116 the opposite process takes place, discharging to zero level at 0.5U ₁ with another part of the same current, preparing the conditions for operating transistor 112 after time t _k has elapsed.

In response to the signal from the control device, transistor 112 is operated with zero voltage on capacitor 116 and the end of input winding 212 connected to the negative pole of the power supply is stopped. The rate of current increase from the negative level to the specific load current is then determined by the applied voltage and leakage inductance of 0.5U ₁ .

Because of the positive polarity of the total voltage on the pair of output windings 213 and 223, diode 32 is not blocked and a blocking voltage is supplied to diode 31. The inductance 33 of the filter accumulates energy. Power in this section is transmitted to the load side. Swelling current flows through the additional inductance 13.

Until the interval in which the angle of relative modulation (pulse duty factor) is determined is completed, the current in input windings 212 and 222 increases to the value determined by the load current and magnetization current inductance 216 of transformers 21 and 22. The currents flow along the oblique lines of both inverters 11 and 12, where a rather large amount of energy accumulates within the leakage inductance 217 of both transformers 21 and 22.

Capacitors 116 and 125 are fully discharged, and capacitors 115 and 126 are charged to the level of 0.5U ₁ . In accordance with the signal from the control device, transistor 121 is cut off and the voltage on capacitor 125 is zero. During the period in which play an important role in the expression of the resonant process, since the energy accumulated by the leakage inductance 217, the primary winding inductance and an additional current in the 13 continues, the capacitor 125 is charged to a _first level and 0.5U 0.5U only flow ₁ Voltage Through capacitor 126, which discharges to zero voltage at the level.

After the time t _k has elapsed since the transistor 121 was shut off, the control device issues a signal to unblock the transistor 122. The process of operating this takes place with zero voltage on capacitor 126. The voltage polarity on the input windings 212 and 222 is reversed, and the total voltage of the output windings 213 and 223 pairs is zero. The current on the load side is maintained by the energy accumulated in the inductance 33 of the filter.

A free circulation process of the balanced current through transistors 112 and 122 and their reverse diodes is initiated, and the transistor is converted to reverse mode. Capacitors 116 and 126 are fully discharged, and capacitors 115 and 125 are charged to the level of 0.5U ₁ . The control device transmits a signal for shutting off the transistor 112. At this time, transistor 112 is stopped without loss to zero voltage on capacitor 116.

This capacitor is charged to the level of 0.5U ₁ and transmits part of the balanced current. The opposite process occurs in capacitor 115, so that the remainder of the current is discharged from the 0.5U ₁ level to the 0 level.

In accordance with the signal from the control device, transistor 111 is activated and the voltage on capacitor 115 becomes zero. The end of the input winding 212 is observed to be connected to the positive pole of the power supply. Diode 31 is cut off and inductance 33 accumulates energy. In other words, power is transferred to the load side. Energy accumulates in the leakage inductance of both transformers 21 and 22. Capacitors 115 and 126 are fully discharged, and capacitors 116 and 125 are charged to the 0.5U ₁ level.

In accordance with the signal from the control device, transistor 122 is cut off and the voltage on capacitor 126 is zero. Leakage inductance 127 causes current in the primary winding to flow through capacitor 126, which is charged to 0.5U ₁ level. Leakage inductance 127 also causes current in the primary winding to flow through capacitor 125, which discharges from 0.5U ₁ to zero.

The control device transmits a signal for blocking the transistor 121. This activation process occurs with zero voltage on capacitor 126. After that, all processes are similarly repeated.

In sum, in the nominal load mode, most of the energy is accumulated by the leakage inductance, and the minimum energy is accumulated by the inductance of the magnetization circuit, which leads to moderate rectification of the transistor. During the short stop period (maximum modulation angle), within the additional inductance 13, the role of the current in the resonant process becomes less important, since it is not possible to have enough time margin to rise to the dominant level. If a short circuit occurs on the load side, the leakage inductance in the resonant process may increase further, and as the commutation time increases, the modulation angle and average load current decrease. This increases the reliability of the transducer and the dynamic losses remain at almost zero levels.

Suppose there is a mode near idle with a low load current state. In this case, the energy accumulated in the leakage inductance 217 and the inductance of the magnetization circuit 216 is not only insufficient to charge the resonant capacitors 115 and 116, but also insufficient to secure the moderate rectification of the power transistors 111 and 112, Significant dynamic loss occurs.

Since the inductance of the magnetizing circuit 216 exceeds the leakage inductance 217 several times, when idle, there is no current increase determined by the inductance of the magnetizing circuit 216. The energy accumulated in the resonant capacitor and dispersed in the transistor is proportional to (0.5U ₁ ) ² . In other words, when the supply voltage is high, such a factor of dynamic loss is still important. This situation proves the validity of the transmission for the half-bridge inverter circuit. The energy accumulated in the resonant capacitor is reduced by four times.

In addition, in the voltage converter of the present invention, the additional inductance 13 is adopted to improve the resonant process progress condition when resonating the resonant capacitor. This is possible by connecting additional inductance 13, thereby affecting the dependence of the energy accumulated on the inductance at the modulation angle (stop time).

Thanks to the feedback to the low load current, the stop time increases (decrease in modulation), which increases the charging time of the additional inductance 13, increasing the amount of the current at the end of the interval, and consequently the energy accumulation. This ensures moderate rectification of the transistor and reduces the dynamic loss of power.

When the load current is large, the down time is reduced, thereby reducing the influence of the additional inductance 13, and strengthening the role of leakage inductance and magnetizing circuit inductance. At the average load current value, the effect of the additional inductance is less than the idle state, but the role of the magnetization circuit 216 inductance and leakage inductance increases to ensure the resonant process of the transistor and the conditions that allow for moderate rectification. By selecting the gap sizes of the magnetic cores 211 and 221, the ratio of such parameters is selected, which ensures the conditions for moderate rectification of the transistor.

Thus, the voltage converter of the present invention ensures a moderate rectification condition when the load current changes, including in the case of pulse characteristics, thereby ensuring a reduction in dynamic losses in the transistor.

This technical effect is achieved as follows. Each transformer in the electromagnetic node provides three components: a transformer to achieve the required output voltage level, an inductance (magnetization circuit inductance) connected in parallel to the output winding, and a continuous inductance (leakage inductance) to the input winding.

The relationship between these inductances is chosen by changing the gap. These two inductances accumulate energy not only for the short circuit but also for the average and rated currents, and this accumulated energy is sufficient to proceed the resonant process for recharging the capacitor. This ensures moderate rectification of the power transistors.

Additional inductance is connected between the two inverters to provide enough resonant process and enough energy to cause moderate commutation of the transistor when the load current is low and the stopping period between the voltage impulses supplied through the transformer is long. This process cannot be achieved using only the magnetizing and leakage inductances of the transformer.

When the load current changes, the roles of the three inductances are also automatically redistributed, and the required moderate commutation is provided with low dynamic losses. In addition, the application of a half-bridge inverter reduced the energy accumulated in the resonant capacitor four times, and consequently the dynamic losses associated with recharging these resonant capacitors.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and implementations are possible, and it is obvious that the present invention falls within the scope of the present invention.

Claims (3)

An inverter device having a first inverter comprising a power transistor continuously connected in pairs, and a resonant capacitor connected in parallel to the electrodes of the respective power transistors, the first transformer comprising an input winding and an output winding, An electromagnetic node connected to the inverter device, and a rectifier and a filter connected to the output terminal, The inverter device further comprises a second inverter having a configuration similar to that of the first inverter, and having an additional inductance, The electromagnetic node further comprises a second transformer of a similar configuration to the first transformer. The method of claim 1, The first inverter and the second inverter are each connected in reverse connection to the input windings of the corresponding transformer, and form two pairs of output windings connected in series with each other, thereby being connected in parallel to the power outlet and connected to the AC outlet. Said voltage converter being connected in series and reversely connected to said rectifier and filter, respectively, to form a semi-bridge circuit. The method of claim 1, Each of the magnetic cores of the first transformer and the second transformer is configured to have a gap, and the coupling points of the power transistors of the first inverter and the second inverter are connected to each other through the additional inductance. The voltage converter.

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