Bridge-less power conversion device with power-factor improvement function

Abstract

To provide a power conversion device which makes an AC / DC power conversion device with a function of improving power-factor of AC power inputted lower noise more easily compared with a prior art device.SOLUTION: Bridge-less rectification is performed by a bridge rectification circuit combining a transformer coupling reactor and a switching element, and an AC / DC conversion having a power-factor improving function and with low noise and high efficiency is performed. Further, if a bypass current circuit is provided in parallel to a rectification diode charging a smooth capacitor and ZCS (Zero-Current-Switching) of the switching element is performed, the AC / DC conversion with lower noise and higher efficiency can be performed.SELECTED DRAWING: Figure 1

Description

Detailed Description of the Invention [Technical field]

[0001] The present invention relates to an AC / DC power conversion device having a function for correcting the power factor of input AC power, and in particular to a power conversion device capable of reducing noise compared to conventional devices. [Background technology]

[0002] Devices that run on AC power can reduce the power factor of the AC power source, and in the worst case scenario, can have a negative impact on the power grid. For this reason, power supply devices that are connected to the power grid generally have a function that prevents the power factor from being reduced.

[0003] As in Patent Document 1, an active filter is used that uses a boost circuit to shape the AC input current so that the flowing current approximates the waveform of the input voltage, and reactors are placed on both input lines to suppress the decrease in power factor and reduce noise.

[0004] However, this method cannot sufficiently remove noise, particularly common-mode noise generated by rectifier diodes connected in series to the switching element during recovery, and so a high-speed, high-voltage diode is required, as in conventional measures.Patent Document 2 proposes a switching power supply device using a bridgeless boost converter that removes the common-mode pulse voltage of the switching frequency that is fed back to the input by providing a small input line inductor with three windings and an AC blocking capacitor in the input stage.

[0005] Furthermore, Patent Document 3 discloses a system that includes a coupling reactor that constitutes an in-phase inductor and a boost inductor that is connected to each phase, a rectifier circuit that connects switching elements in a full-bridge configuration and full-wave rectifies AC, a smoothing capacitor having two smoothing capacitors connected in series to the output of the rectifier circuit, and an X capacitor having two across-the-line capacitors connected in series to be used as a noise filter, and that reduces common mode noise by connecting the connection points of the two smoothing capacitors and the connection points of the two X capacitors together.

[0006] Moreover, in Patent Document 4, an AC input and a DC output are connected via a capacitor to reduce the potential fluctuation of the DC output caused by the on / off switching of a switching element, thereby suppressing the generation of noise. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2001-268920 A [Patent Document 2] JP 2013-110829 A [Patent Document 3] JP 2020-145842 A [Patent Document 4] US7215560 publication Summary of the Invention [Problem to be solved by the invention]

[0008] In Patent Document 2, a choke coil with a special structure is required for the noise filter. In addition, it is still necessary to use a high-performance rectifier diode (for example, a Schottky barrier rectifier diode (SBD) or a silicon carbide (SiC) rectifier diode).

[0009] Furthermore, in Patent Document 3, a coupling reactor is used, two across-the-line capacitors are connected in series, and two smoothing capacitors are connected in series, which requires a large mounting space and still requires the use of high-performance rectifier diodes.

[0010] In addition, in Patent Document 4, a capacitor is used to connect the AC input terminal and the DC output terminal to reduce the potential fluctuation of the DC output caused by the on / off of the switching element, but the voltage generated in the reactor is cancelled, so the effect of the reactor is halved. In other words, one reactor does not function due to the effect of the capacitor, and only the other reactor functions effectively.

[0011] Although there are various proposals as described above, there is a need for an even simpler and more effective method, particularly a method that allows the use of rectifier diodes with general characteristics rather than high performance diodes. [Means for solving the problem]

[0012] Therefore, the present invention provides a bridgeless power conversion device with power factor correction, characterized in that it includes a transformer coupled reactor in which a first winding and a second winding are coupled with each other with a predetermined leakage inductance, a first arm in which a first rectifier diode and a first switching element are connected in series, a second arm in which a second rectifier diode and a second switching element are connected in series, one end of an AC power supply connected to a connection point of the first rectifier diode and the first switching element via the first winding, the other end of the AC power supply connected to a connection point of the second rectifier diode and the second switching element via the second winding, a smoothing capacitor charged with the current output by the first arm and the current output by the second arm, and both ends of the AC power supply are connected to both ends of the smoothing capacitor via capacitors, respectively.

[0013] Furthermore, the present invention provides a bridgeless power conversion device with a power factor correction function, in which a third winding and a fourth winding are coupled to the first winding with a predetermined leakage inductance, a fifth winding and a sixth winding are coupled to the second winding with a predetermined leakage inductance, a first current bypass circuit consisting of the third winding, the sixth winding, a first reactor, and a third diode is connected in parallel to the first diode, and a second current bypass circuit consisting of the fourth winding, the fifth winding, a second reactor, and a fourth diode is connected in parallel to the second diode.

[0014] Furthermore, the transformer coupling reactor may include a first core constituting a first closed magnetic path consisting of a first leg, a second leg, and a coupling portion coupling both ends of the first leg and the second leg, a first bypass core having two core materials with a protrusion on one part arranged opposite to each other with a required gap between them and inserted into a space within the first magnetic path, a first winding wound around the first leg, a third winding and a fourth winding wound on the first winding, a second winding wound around the second leg, a fifth winding and a sixth winding wound on the second winding, a second bypass core inserted between the first winding, the third winding, and the fourth winding, and a third bypass core inserted between the second winding, the fifth winding, and the sixth winding, and the leakage inductance may be adjusted by the position of each bypass core. Effect of the Invention

[0015] According to the present invention, the transformer coupling reactor is provided with leakage inductance due to the bypass core, and the leakage inductance in which energy is stored is used to perform boost converter operation, so that the boost operation and power factor correction function can be performed efficiently. Furthermore, in this invention, a current bypass circuit is provided for the rectifier diode, enabling ZCS (Zero Volt Switching) when the switching element is turned on and off. Furthermore, it is possible to prevent a large current from flowing due to a sudden voltage being applied to the rectifier diode, making it possible to achieve high efficiency and low noise without using high performance diodes. [Brief description of the drawings]

[0016] [Figure 1] Block diagram of a bridgeless power conversion device with a power factor correction function according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram of the operation of a transformer coupling reactor used in the first embodiment of the present invention. [Diagram 3] A block diagram of a bridgeless power conversion device having a power factor correction function according to a second embodiment of the present invention. [Figure 4] Pseudo current and voltage waveform diagram of each element in the second embodiment of the present invention [Diagram 5] Principle diagram of a transformer coupling reactor used in the second embodiment of the present invention [Figure 6] Modification of the transformer coupling reactor core used in the second embodiment of the present invention [Figure 7] Structural diagram of a modified example of a transformer coupling reactor used in the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0017] A block diagram of a first embodiment of the present invention is shown in Fig. 1. An AC power source Vac, which is an input, is connected to inputs a1 and b1 of a transformer coupling reactor 10 (details of the structure will be described later). Furthermore, a first arm 12 in which a first diode D1 and a first switching element Q1 are connected in series, a second arm 13 in which a second diode D2 and a second switching element Q2 are connected in series, and a smoothing capacitor C10 are each connected in parallel. Outputs a2 and b2 of the transformer coupling reactor 10 are connected to the connection points of the diodes and switching elements of each arm.

[0018] Furthermore, both ends of the AC power supply Vac are connected to both ends of a smoothing capacitor C10 via capacitors C1 and C2, respectively. Note that the connections from the capacitors C1 and C2 to the smoothing capacitor C10 do not have to be to both ends, as long as they are connected to either one of them.

[0019] The control circuit 11 simultaneously turns on and off the switching elements Q1 and Q2 to keep the voltage generated across the smoothing capacitor C10 constant, and also detects the input voltage Vac and adjusts the on / off duty so that the waveform of the input current Iac becomes similar to that of the input power supply Vac.

[0020] The principle of operation of the transformer coupling reactor is as follows. Figure 2 shows a model of the principle of the transformer coupling reactor. In Figure 2(a), the transformer T1 has a first winding n11 and a first secondary winding n12 wound around a core c100, the transformer T2 has a second winding n101 and a second secondary winding n102 wound around a core c101, and the reactor L1 has a reactor winding n wound around a core c102 having a gap Lg. Here, the first secondary winding n12, the second secondary winding n102, and the reactor winding n are connected in series, respectively. Then, the sum of the magnetic flux φ1 generated by the first winding n11, the magnetic flux φ2 generated by the second winding n101, and the magnetic flux φ3 generated by the reactor winding n becomes zero. In other words, as described in JP 2006-262601 A, the operation is the same as that of the transformer in Figure 2(b). What should be noted here is the presence of inductance L1. Inductance L1 acts equally on transformer T1 or transformer T2. Energy is stored in inductance L1 via the first winding n11 or the second winding n101, and when switching elements Q1 and Q2 are turned off, the energy is released to inductance L1 via the first winding n11 or the second winding n101, so that boost operation can be performed efficiently and reliably.

[0021] Its operation is as follows: First, in Fig. 1, if point a1 of the transformer coupling reactor 10 is at a positive voltage, when switching elements Q1 and Q2 are turned on, a current flows through the path of connection point a1 → first winding n11 → connection point a2 → switching element Q1 → switching element Q2 → connection point b2 → second winding n21 → connection point b1, and energy is stored in inductance L1 via the self-inductance of the first winding n11 and the second winding n21.

[0022] Next, when switching elements Q1 and Q2 are turned off, current flows through the path of connection point a1 → first winding n11 → connection point a2 → first diode D1 → smoothing capacitor C10 → parasitic diode of switching element Q2 → connection point b2 → second winding n101 → connection point b1, and the energy stored in inductance L1 is released via the AC power supply Vac, and the first winding n11 and second winding n101, and the smoothing capacitor C10 is charged with the boosted voltage.

[0023] In addition, a capacitor C1 is connected between a connection point a1 of the transformer coupling reactor 10 and one end of the smoothing capacitor C10, and a capacitor C2 is inserted between a connection point b1 of the transformer coupling reactor 10 and the other end of the smoothing capacitor C10. This makes it possible to suppress a common mode voltage change in the smoothing capacitor C10 that occurs when the switching elements Q1 and Q2 are turned on and off. The voltage generated in the first winding n11 or the second winding n101 becomes small due to the action of the capacitor C1 or the capacitor C2, so that the boost operation decreases, but the stored energy of the inductance L1 is released via the first winding n11 or the second winding n101, so that the decrease in the boost operation can be suppressed. In other words, a reduction in common mode noise can be expected, and the boost operation can be performed efficiently. EXAMPLES

[0024] Next, a second embodiment of the present invention is shown in Fig. 3. The second embodiment aims to make the switching elements Q1 and Q2 of the bridgeless PFC power conversion device of the first embodiment ZCS when they are turned on and off. The difference from the first embodiment is the configuration of the transformer coupling reactor 201. The operation and structure will be described with reference to the circuit block diagram in Fig. 3, the time sequence in Fig. 4, and the structural diagram of the transformer coupling reactor 201 in Fig. 5.

[0025] First, the structure of the transformer coupling reactor 201 will be described based on the circuit block diagram in Fig. 3 and the structural diagram in Fig. 5. The core of the transformer coupling reactor 201 is composed of a first leg A, a second leg B, and a third leg C, and both ends of each leg are connected. The first winding n21 of the transformer T21 is wound around the first leg A, and the third winding n23 and the fourth winding n24 are wound thereon. The second winding n31 of the transformer T32 is wound around the third leg C, and the fifth winding n33 and the sixth winding n34 are wound thereon. Furthermore, a gap Lg is provided in the second leg B.

[0026] 3, the transformer coupling reactor 201 wound in this manner has a first current bypass circuit, which is made up of a series circuit of the third winding n23, the sixth winding n34 with reverse polarity, the reactor L2, and the diode D23, connected in parallel to the diode D1. This first current bypass circuit bypasses the current flowing through the rectifier diode D1, and sets the on / off state of the switching element Q1 to ZCS.

[0027] Furthermore, a second current bypass circuit consisting of a series circuit of the fifth winding n33, the fourth winding n24 with reverse polarity, the reactor L3, and the rectifier diode D24 is connected in parallel to the rectifier diode D2. This second current bypass circuit bypasses the current flowing through the rectifier diode D2, and sets the on / off state of the switching element Q2 to ZCS.

[0028] Incidentally, reactors L2 and L3 may be generated by inserting a bypass core CR2 between the first winding n21 and the third winding n23 to reduce coupling and generating reactor L2 with the generated leakage inductance, as shown in transformer coupled reactor 201 in Fig. 5, or by inserting a bypass core CR3 between the second winding n31 and the fifth winding n33 to generate reactor L3 with the leakage inductance obtained by reducing coupling. The leakage inductance can be easily generated by using bypass cores CR2 and CR3, and can be easily adjusted by changing the position of the bypass cores.

[0029] Since the switching elements Q1 and Q2 are turned on and off at a frequency much higher than that of the AC power supply Vac, the voltage change due to the frequency of the AC power supply Vac can be regarded as almost no voltage change for each switching element. Therefore, assume that the AC power supply Vac is such that the transformer T21 of the transformer coupling reactor 201, i.e., the connection point a100, is at a positive potential, and the transformer T32, i.e., the connection point b100, is at a negative potential. First, when the switching elements Q1 and Q2 are off, a current flows through the path of the connection point a100 → the first winding n21 → the third winding n23 → the sixth winding n34 → the reactor L2 → the rectifier diode D23, and charges the smoothing capacitor C10. If the switching elements Q1 and Q2 are turned on at this point, the switching element Q1 cannot make a sudden current change due to the action of the reactor L2, and as the current of the reactor L2 gradually decreases, the current of the switching element Q1 increases, and eventually reaches a steady state. The current and voltage waveforms of each component at this time are from period t1 to period t2 in Figure 4. That is, the switching element Q1 is ZCS because it gradually changes from zero when it is on. When the polarity of the input power supply Vac is reversed, the switching element Q2 also becomes ZCS when switching.

[0030] Next, when the switching element Q1 is turned off, the smoothing capacitor C10 is charged via the rectifier diode D1 by the voltage obtained by adding the energy stored in the inductance L1 due to the self-inductance and / or leakage inductance of the transformer T21 and the input power supply Vac. The current path is the connection points a100→n21→D1→C10→Q2→n31→b100. At this time, current flows through the first winding n21 and the second winding n31, so voltage is generated in the third winding n23 and the sixth winding n34, and the current flows through the path of a100 → n21 → first current bypass circuit (n23 → n34 → L2 → D23) → C10 → Q2 → n31 → b100, and the current flowing through the rectifier diode D1 gradually decreases as shown after time t3 in Figure 4, while the current through the diode D23 increases, and the charging current of the capacitor C10 gradually switches from the rectifier diode D1 to the rectifier diode D23, and then the switching element Q1 is turned from off to on. Then, as in the period from t1 to t2 described above, the on / off state of the switching element Q1 becomes ZCS.

[0031] Similarly, even if the connection point b100 of the transformer coupling reactor 201 is at a positive potential, the ZCS is performed when the switching element Q2 is on due to the action of the reactor L3. When the switching element Q2 is turned off, the current that flowed through the rectifier diode D2 flows to the diode D24 due to the action of the second current bypass circuit (the series circuit of n33, n24, L3, and D24), and the on / off of the switching element Q2 can then be turned on as the ZCS.

[0032] The number of turns of the third winding n23, the fifth winding n33, the sixth winding n34, and the fourth winding n24 should be about 2 to 4% of the number of turns of the first winding n21, and the reactors L2 and L3 should be about 1% of the number of turns of the reactor L1. In this way, the current of the reactor L2 or L3 is continuous, and the current that flows at the moment when the switching element Q1 or Q2 is turned on gradually increases from zero, making ZCS possible. The energy stored in the reactor L2 or L3 is stored in the reactor L1 via the third winding n23, the fifth winding n33, the sixth winding n34, and the fourth winding n24, and is effectively used in the subsequent operation.

[0033] The reactor L2 may utilize the leakage inductance between the first winding n21 and the third winding n23. The reactor L3 may utilize the leakage inductance between the second winding n31 and the fifth winding n33. This allows the component mounting space to be reduced.

[0034] [Example of a transformer coupling reactor] Using a bypass core for a core without a center leg to achieve equivalent performance is known from JP 2017-192206 A. Using this structure, the transformer coupling reactor in Fig. 5 can be made to have the same performance as shown in Fig. 7. The structure is explained below with reference to Figs. 6 and 7. As shown in Fig. 6(a), the reactor core is made up of four cores, core B101, core B102, core D101, and core D102, which form a closed magnetic circuit A100. As shown in Fig. 7(a), the first winding n21 is wound around the core B101, a bypass core CR2 is inserted thereon, and the third winding n23 and the fourth winding n24 are wound thereon in the same layer. The second winding n31 is wound around the core B102, a bypass core CR3 is inserted thereon, and the third winding n33 and the fourth winding n34 are wound thereon in the same layer. That is, the first winding n21 is further inserted so that the convex part of the bypass core CR101 and the convex part of the bypass core CR102 sandwich the closed magnetic circuit A100. With this structure, when the core constituting the closed magnetic circuit A100 is made of laminated thin magnetic material, such as electromagnetic steel sheets, the magnetic flux passes through the bypass cores CR101 and CR102, so that the magnetic flux generated in the first winding n21 passes through the second winding n31 less, and leakage magnetic flux can be easily created. Furthermore, since the magnetic flux generated in the first winding n21 passes through the bypass cores CR101 and CR102 without reaching the second winding n21, the magnetic flux generated by the first winding n21 passes through the bypass core, and a bypass circuit for the magnetic flux is formed. Furthermore, non-magnetic material S101 is inserted between the core D101 and the bypass core CR101, and between the core D101 and the bypass core CR102, so that the magnetic path through which the magnetic flux φ101 passes does not pass through the electromagnetic steel sheets of the core.

[0035] The magnetic flux generated by the second winding n31 and reaching the first winding n21 also passes through the bypass cores CR101 and CR102, forming a leakage inductance. This structure provides the same performance as in Fig. 5, so a high-performance transformer-coupled reactor can be made with any core, regardless of the material or shape of the core. Note that the bypass cores CR101 and CR102 do not have to be made of the core material that constitutes the closed magnetic circuit A100, and may be made of a core material that is less prone to magnetic flux saturation, such as a dust core. [Explanation of symbols]

[0036] Vac AC power supply 100, 200 Power converter 10, 201 Transformer coupling reactor D1, D2, D23, D24 Diodes Q1, Q2 switching elements 11 Control circuit C1, C2, C10 capacitors A, B, C, B101, B102, D101, D102 Core legs c100, c101, c102 core CR101, CR102, CR2, CR3 Bypass Core Lg Gap S101 Non-magnetic material T1, T2 Transformer components in transformer coupling reactor T21, T32 Transformer components in transformer coupling reactor n21, n23, n24 Windings in transformer coupling reactor n31, n33, n34 Windings in transformer coupling reactor

Claims

1. a transformer coupling reactor in which a first winding and a second winding are coupled with each other with a predetermined leakage inductance; a first arm in which a first rectifier diode and a first switching element are connected in series; a second arm in which a second rectifier diode and a second switching element are connected in series; one end of an AC power source connected to a connection point between the first rectifier diode and the first switching element via the first winding; the other end of the AC power supply connected to a connection point between the second rectifier diode and the second switching element via the second winding; a smoothing capacitor that is charged by a current output from the first arm and a current output from the second arm; 1. A bridgeless power conversion device with a power factor correction function, comprising: a leakage reactor connected to both ends of the smoothing capacitor via respective capacitors from both ends of an AC power supply, storing energy from the first winding and the second winding, and discharging energy via the first winding and / or the second winding.

2. a third winding and a fourth winding coupled to the first winding; a fifth winding and a sixth winding coupled to the second winding; a first current bypass circuit including a series connection of the third winding, the sixth winding, a first reactor, and a third diode is connected in parallel to the first rectifier diode; 2. The bridgeless power conversion device with a power factor correction function according to claim 1, wherein a second current bypass circuit consisting of a series connection of the fourth winding, the fifth winding, a second reactor, and a fourth diode is connected in parallel to the second rectifier diode.

3. a first core constituting a first closed magnetic circuit including a first leg, a second leg, and a coupling portion coupling both ends of the first leg and the second leg; a first bypass core, which is formed by arranging two core members each having a protrusion on one portion thereof so that the protrusions face each other with a required gap therebetween and inserting the core members into the space within the first magnetic path; a first winding wound around the first leg; a third winding and a fourth winding wound on the first winding; a second winding wound around the second leg; a fifth winding and a sixth winding wound on the second winding; a second bypass core is inserted between the first winding and the third winding and the fourth winding, and a third bypass core is inserted between the second winding and the fifth winding and the sixth winding; A transformer coupling reactor for a bridgeless power conversion device with a power factor correction function, characterized in that leakage inductance is adjusted by the position of each bypass core.

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