RU2807665C1 - Power factor corrector - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to AC to DC voltage converters that can be used in secondary power supply systems for power factor correction, converting, regulating and stabilizing a DC output voltage. The device contains the primary winding 1 of the power transformer 3, connected through a regulating switch 2 implemented in the form (MOSFET), the control electrode of which is connected to the pulse-duration controller 11 and the terminals of the rectifier bridge, the secondary windings 4, 9 of which are connected through rectifier diodes 5, 8 to series-connected filter capacitors 6, 7, in parallel with which load 10 is connected. In the proposed power factor corrector, the beginning of the primary winding 1 of the power transformer 3 is connected to the positive pole of the rectifier bridge, the second pole of which is connected through the regulating switch 2 to the negative pole of the rectifier bridge. The anode of the rectifying diode 5 is connected to the beginning of the secondary winding 4 of the power transformer 3, the cathode of which is connected to one of the terminals of the capacitor 6. The second terminal of capacitor 6 is connected to the end of winding 4. The end of winding 4 is connected to one of the terminals of capacitor 7, the second terminal of which is connected to the anode of the rectifying diode 8, the cathode of which is connected to the beginning of winding 9, the end of which is connected to the end of winding 4. Load 10 is connected in parallel to the series-connected capacitors 6 and 7. The control electrode of the regulating key 2 is connected to the pulse-width controller 11.

EFFECT: formation of a constant output voltage from an alternating input voltage using one voltage converter that combines the functions of a Boost Converter and a DC-to-DC Converter, which performs electrical isolation and obtains the required level of constant output voltage, ensuring the current is in phase with alternating voltage, simplifying the control circuit of the voltage converter, improving the performance of the power factor corrector.

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Description

The invention relates to electrical engineering, in particular to AC-to-DC voltage converters, and can be used in secondary power supply systems for power factor correction, conversion and regulation of DC output voltage.

Power factor correctors are known [Robert W. Erickson Fundamentals of Power Electronics page 603 FIG. 17.11].

The disadvantage of the known power factor correctors is the use of two-stage devices that include a boost regulator (Boost Converter), to the output of which a DC-DC Converter is connected, which performs electrical isolation and obtains the required level of output voltage.

The second disadvantage of known power factor correctors is the complexity of controlling such a power factor corrector.

The closest in technical essence to the proposed device is the power factor corrector given in the book [Robert W. Erickson Fundamentals of Power Electronics p. 603 FIG. 17.11], in which a power factor corrector is connected to the AC voltage source through a rectifier bridge, which includes a boost regulator (Boost Converter) with its own control circuit, to the output of which a DC-DC Converter is connected, providing electrical isolation and obtaining the required level of constant output voltage, to which the load with its control circuit is connected.

The disadvantages of this power factor corrector are the use of two stages for converting electrical energy, including a boost regulator (Boost Converter) and a DC-to-DC Converter (DC-DC Converter), which performs electrical isolation and obtains the required level of DC output voltage, as well as the need to use two control devices for a boost regulator (Boost Converter) and a DC-DC Converter, which makes it difficult to control such a power factor corrector.

The purpose of the invention is to generate a constant output voltage from an alternating input voltage using a single voltage converter that combines the functions of a boost regulator (Boost Converter) and a DC-to-DC Converter (DC-DC Converter), which performs electrical isolation and obtains the required level of constant output voltage , ensuring the current is in phase with alternating voltage, simplifying the control circuit of the voltage converter, improving the performance of the power factor corrector.

This goal is achieved by the fact that instead of a boost regulator (Boost Converter), the primary winding of a transformer with a series-connected regulating switch is connected to the output terminals of the rectifier bridge, the secondary windings of which are connected through rectifier diodes to capacitive filters and the load, and the control electrode of the regulating key is connected to the device management.

In fig. 1, 2, 3 and 4 show schematic electrical diagrams of embodiments of the proposed power factor corrector. In fig. 1 shows a schematic diagram of the power factor corrector; in fig. Figure 2 shows a schematic electrical diagram of a power factor corrector with the introduction of additional linear inductance in series with one of the secondary windings of the transformer; in fig. 3 shows a schematic electrical diagram of a power factor corrector with the introduction of an additional linear inductance connected in parallel with one of the windings of the transformer, for example, the secondary winding; in fig. Figure 4 shows a schematic electrical diagram of a power factor corrector with the introduction of an additional multi-section filter.

In it (Fig. 1), the beginning of the primary winding 1 of the power transformer 3 is connected to the positive pole of the rectifier bridge, the second pole of which is connected to the negative pole of the rectifier bridge through the regulating key 2. Connected to the beginning of the secondary winding 4 of the power transformer 3 is the anode of the rectifying diode 5, the cathode of which is connected to one of the terminals of the capacitor 6. The second terminal of the capacitor 6 is connected to the end of the winding 4. The end of the winding 4 is connected to one of the terminals of the capacitor 7, the second terminal of which is connected to the anode of the rectifying diode 8, the cathode of which is connected to the beginning of winding 9, the end of which is connected to the end of winding 4. A load 10 is connected in parallel to the series-connected capacitors 6 and 7. The control electrode of the regulating key 2 is connected to the pulse-width controller 11.

In fig. 2, linear inductance 12 is connected in series with the beginning of the secondary winding 4.

In fig. 3, an additionally introduced linear inductance 13 is connected in parallel to the secondary winding 4 of the power transformer 3.

In fig. 4, in parallel with the series-connected capacitors 6 and 7, an additionally introduced filter is included, consisting of a series-connected L-shaped LC filter 14, a parallel resonant circuit 15, the number of which can be more than one, and a capacitor 16, in parallel with which the load 10 is connected.

Let us consider the principle of operation of the proposed power factor corrector based on the assumption of the ideality of the key elements, the steady state of operation and the continuity of change in the magnetic flux in the core of transformer 3. Let us denote by D the duration of the on state of switch 2 relative to period T.

Let us assume that at the moment of considering the operation of the power factor corrector, a positive half-wave of sinusoidal voltage arrives from an alternating voltage source, which is rectified by a rectifier bridge. In this case, at the stage of the closed state DT of switch 2, two processes occur simultaneously, one of which is associated with the accumulation of energy in the magnetizing inductance of transformer 3, connected in series with switch 2 and a source of rectified alternating voltage, and the second process is associated with the direct transfer of energy to the load through forward biased rectifier diode 5 and secondary winding 4.

The magnitude of the current through the rectifier diode 7 is determined by the balance of charges of the capacitor 6 at the time intervals DT and (1-D)T , i.e. at time intervals of switched on and off states of key 2.

After turning off key 2 during the time interval (1-D)T, the voltage on the windings of transformer 3 changes sign. As a result, the rectifying diode 5 closes, and the diode 8 opens, and the accumulated energy during the time interval DT in the magnetizing inductance of the power transformer 3 is output through the secondary winding 9 of the transformer 3 into the capacitor 7, which leads to the restoration of the transformer 3.

Separation of the functions of the secondary windings of transformer 3, operating at time intervals DT and (1-D)T, allows more efficient control of the electromagnetic processes of the voltage converter.

When the polarity of the input voltage source changes, all the processes described above are repeated.

The sum of the voltages on capacitors 6 and 7 is the output voltage on load 10.

The introduction of an additional linear inductance 12 in series with the secondary winding 4 of the transformer 3 (Fig. 2) makes it possible to effectively limit the maximum current through the diode 7 and ensure that the control switch 2 is turned on to zero current value.

The introduction of an additional linear inductance 13 connected in parallel with the secondary winding 4 of the power transformer 3 (Fig. 3) makes it possible to weaken the rigid connection of the magnetizing inductance of the power transformer 3 with the number of its turns, geometry and gap.

A low-frequency source of alternating input voltage introduces additional low-frequency ripple into the output direct voltage, which is undesirable for a number of loads, for example, LED lighting devices, which is eliminated by introducing an additional multi-stage filter (Fig. 4), composed of an L-shaped LC filter 14, one or several sections of parallel resonant filters 15 and a capacitive filter 16.

Thus, the proposed power factor corrector allows, in comparison with the known device, to electrically decouple the DC output voltage from the AC input voltage in one power unit, ensure that the current and AC input voltage are in phase, ensure that the control switch is turned on to zero current, and weaken or eliminate low-frequency ripples in DC output voltage and simplify control of the power factor corrector.

Claims (3)

1. A power factor corrector containing a choke, the winding of which is connected through a regulating switch to the output terminals of a rectifier bridge, the input of which is connected to a source of input alternating voltage; a circuit consisting of a series-connected capacitor and the primary winding of a transformer is connected in parallel with the regulating key, characterized in that two diodes and two series-connected filter capacitors are introduced, the transformer contains two back-to-back secondary windings connected in series, the first of which is connected in series to the first filter capacitor through the first diode, and the second secondary winding of the transformer is connected through the second diode to the second filter capacitor, the outermost terminals of the circuit are in series connected filter capacitors are connected to opposite poles of the corresponding diodes and are terminals for connecting the load, and a control pulse-width controller is connected to the control electrode of the regulating switch. 2. The power factor corrector according to claim 1, characterized in that an additional linear inductance is introduced, connected in series with the secondary winding of the transformer, operating during the time interval when the control switch is on. 3. The power factor corrector according to claim 1, characterized in that between the extreme terminals of the circuit of series-connected filter capacitors and the terminals for connecting the load, an additional multi-link filter is introduced, made of a series-connected L-shaped LC filter, a parallel resonant circuit consisting of one or more links, and an additional capacitor, in parallel with which the load is connected.