Power conversion device

Abstract

A power conversion device according to an embodiment of the present invention comprises: an high-side switch and a first diode connected in series; a second diode and a low-side switch connected in series; a first transformer unit connected to a first node between the high-side switch and the first diode and to a second node between the second diode and the low-side switch; a third diode connected in series with an output side of a second transformer unit; and a balancing unit which is connected in parallel with the second diode, and balances a drain-source voltage of the high-side switch and a drain-source voltage of the low-side switch.

Description

power conversion device

[0001] The present invention relates to a power conversion device, and more specifically, to a power conversion device including a voltage balancing circuit between switches.

[0002] Rapid chargers for electric vehicles support high-speed charging at hundreds of kilowatts. They consist of power modules with capacities of tens of kilowatts, connected in parallel, and output a large amount of power. When connected to an electric vehicle, the power modules receive AC power from the grid and output DC power to charge the electric vehicle's battery.

[0003] Power modules can include various types of converters, including flyback converters. Simultaneous operation of the switches in a flyback converter can result in voltage inequality between the switches, leading to concentrated heat generation in one switch, potentially damaging components.

[0004] The technical problem to be solved by the present invention is to provide a power conversion device including a voltage balancing circuit between switches.

[0005] In order to solve the above technical problem, a power conversion device according to an embodiment of the present invention includes an upper switch and a first diode connected in series; a second diode and a lower switch connected in series; a first transformer connected to a first node between the upper switch and the first diode and a second node between the second diode and the lower switch; a third diode connected in series with an output side of the first transformer; and a balancing unit connected in parallel with the second diode and balancing a drain-source voltage of the upper switch and a drain-source voltage of the lower switch.

[0006] Additionally, the balancing unit may include a first capacitor connected in parallel with the second diode.

[0007] In addition, the balancing unit can compensate for a third capacitance value obtained by subtracting a second parasitic capacitance value between one of the two input terminals of the input unit of the first transformer and the ground from a first parasitic capacitance value between the other input terminal and the ground.

[0008] Additionally, the capacity of the first capacitor may correspond to the third capacitance value.

[0009] Additionally, the upper switch and the lower switch can be turned on and off simultaneously.

[0010] In addition, it includes a first heat sink that releases heat of the upper switch to the outside; and a second heat sink that releases heat of the lower switch to the outside, and the ground of the first heat sink and the ground of the second heat sink can correspond to the ground connected to the lower switch.

[0011] In addition, it includes a driving power unit that supplies gate power to the upper switch and the lower switch, and the driving power unit includes: a first gate driver circuit that generates gate power of the upper switch; a second gate driver circuit that generates gate power of the lower switch; and a second transformer connected to the first gate driver circuit and the second gate driver circuit, and the second transformer may include two output sides, the primary side of which is connected to the control unit, and the secondary side of which is connected to the first gate driver circuit and the second gate driver circuit, respectively.

[0012] Additionally, the primary side and the secondary side of the first transformer may be insulated, and the primary side and the secondary side of the second transformer may be insulated.

[0013] Additionally, the first heat sink and the upper switch may be insulated, and the second heat sink and the lower switch may be insulated.

[0014] Additionally, it may include an input-side capacitor connected in parallel with the upper switch and the first diode; and an output-side capacitor connected in parallel with the third diode.

[0015] Additionally, the power conversion device may be a flyback converter.

[0016] In order to solve the above technical problem, a power conversion device according to an embodiment of the present invention includes an upper switch and a first diode connected in series; a second diode and a lower switch connected in series; a first transformer connected to a first node between the upper switch and the first diode and a second node between the second diode and the lower switch; a third diode connected in series with an output side of the second transformer; and a first capacitor connected in parallel with the second diode.

[0017] According to embodiments of the present invention, voltage balancing between switches can be achieved to prevent damage to components.

[0018] FIG. 1 illustrates a power conversion device according to one embodiment of the present invention.

[0019] Figures 2 to 4 are block diagrams of a power conversion device according to an embodiment of the present invention.

[0020] Figure 5 is an example of a circuit implementation of a power conversion device according to an embodiment of the present invention.

[0021] FIG. 6 is a drawing for explaining voltage balancing of a power conversion device according to an embodiment of the present invention.

[0022] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0023] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0024] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0025] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0026] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0027] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and are not intended to limit the nature, order, or sequence of the components.

[0028] And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, it may include not only cases where the component is 'connected', 'coupled', or 'connected' directly to the other component, but also cases where the component is 'connected', 'coupled', or 'connected' by another component between the component and the other component.

[0029] Additionally, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below," the meaning may include not only the upward direction but also the downward direction based on one component.

[0030] Figure 1 illustrates a power conversion device according to one embodiment of the present invention. The power conversion device (100) according to one embodiment of the present invention is composed of a switching unit (110), a transformer unit (120), and a balancing unit (130), and may include a driving power unit (150), a control unit (160), and a heat sink (171, 172).

[0031] A power conversion device (100) according to an embodiment of the present invention may be a power conversion device of an electric vehicle charging device. Here, the power conversion device (100) may be mounted on a power module of the electric vehicle charging device. The power module may receive AC power from the grid (50 / 60 Hz), convert it into DC power for charging an electric vehicle battery, and output it. Alternatively, the power module may receive DC power from an energy storage system (ESS), convert it into DC power for charging a battery, and output it. Power may be received from an external power source, such as a solar power generation module. The power conversion device (100) according to an embodiment of the present invention may be an insulated converter, or a converter that generates auxiliary power for an inverter module.

[0032] Through the switching operation of the switching unit (110), input is input to the transformer unit (120), and the power input to the transformer unit (120) can be converted and output. The switching unit (110) includes a plurality of switches, and in order to resolve voltage imbalance between the plurality of switches, a balancing unit (130) can be connected to the switching unit (110). The balancing unit (130) can compensate for the difference in parasitic capacitance value between the switches of the switching unit (110) to balance the voltage between the switches.

[0033] The switching unit (110) may include an upper switch (111), a lower switch (114), a first diode (112), and a second diode (113).

[0034] The upper switch (111) and the first diode (112) may be connected in series, and the second diode (113) and the lower switch (114) may be connected in series. As shown in Fig. 2, the upper switch (111) and the lower switch (114) may be connected in parallel to the input section where power is input, and may be connected in series with the first diode (112) and the second diode (113), respectively. An input capacitor (142) may be connected in parallel to the input section.

[0035] One end of the upper switch (111) may be connected to the input section, and the other end may be connected to the first diode (112). The first diode (112) may have a cathode connected to the upper switch (111) and an anode connected to the ground. Here, the ground may be the ground of the power conversion device (100), and may be the ground of the device with the lowest potential in the power conversion device (100) or a device in which the power conversion device (100) is mounted.

[0036] The lower switch (114) is connected in parallel with the upper switch (111), but may be connected in series with the second diode (113). The second diode (113) may have a cathode connected to the input section and an anode connected to the lower switch (114). One end of the lower switch (114) may be connected to the anode of the second diode, and the other end may be connected to ground.

[0037] The transformer (120) is connected to the switching unit (110) and can receive power from the switching unit (110). The transformer (120) may include a first transformer (121). The first transformer (121) may be a transformer, and may be an insulating transformer in which the primary and secondary sides of the first transformer (121) are insulated.

[0038] The primary side of the first transformer (121) may be connected to the first node (115) and the second node (116). The first node (115) may be a node between the upper switch (111) and the first diode (112), and the second node (116) may be a node between the second diode (113) and the lower switch (114). The primary side (+) input terminal of the first transformer (121) may be connected to the first node (115), and the primary side (-) input terminal of the first transformer (121) may be connected to the second node (116).

[0039] The secondary side, which is the output side of the first transformer (121), can be connected to a third diode (141). The third diode (141) can be connected in series with the secondary side (+) output terminal of the first transformer (121). An output capacitor (143) can be connected in parallel to the output side.

[0040] The upper switch (111) and the lower switch (114) may overlap at least a portion of the time when they are on or off. The upper switch (111) and the lower switch (114) may be turned on and off simultaneously. The upper switch (111) and the lower switch (114) may include a MOSFET switch, or may be a MOSFET switch including a diode. In addition, they may be various semiconductor switches.

[0041] A power conversion device (100) according to an embodiment of the present invention may be a two-switch flyback converter including an upper switch (111) and a lower switch (114).

[0042] When the upper switch (111) and the lower switch (114) are turned on, a path of the upper switch (111) - the first transformer (121) - the lower switch (114) is formed, so that power can be supplied to the first transformer (121) via the upper switch (111). At this time, the first diode (112) and the second diode (113) are connected in reverse, so that power is not connected to the first diode (112) and the second diode (113).

[0043] When the upper switch (111) and the lower switch (114) are turned off, a path is formed in the direction of the first diode (112) - the first transformer (121) - the second diode (113), so that leakage energy is recycled to the input side through the two diodes, thereby eliminating clamping loss, increasing efficiency, reducing thermal stress, and at the same time clamping the maximum voltage stress of the power MOSFET to the input voltage.

[0044] The driving power unit (150) can control the on / off operation by supplying driving power to the upper switch (111) and the lower switch (114). The upper switch (111) and the lower switch (114) can be MOSFET switches, and the driving power unit (150) can include a gate driver that supplies power to the gate of the MOSFET switch. The upper switch (111) and the lower switch (114) can receive gate power from the driving power unit (150) simultaneously.

[0045] The driving power supply unit (150) may include a second transformer unit (151), a first gate driver circuit (152), and a second gate driver circuit (153). The second transformer unit (151) may receive a gate driving signal from the control unit (160), and the second transformer unit (151) may provide the corresponding signal to the first gate driver circuit (152) and the second gate driver circuit (153), respectively. The first gate driver circuit (152) and the second gate driver circuit (153) may generate and supply gate power to the upper switch (111) and the lower switch (114), respectively. At this time, the second transformer unit (151) may be an insulating transformer, and may be an insulating transformer whose secondary side has two output sections. The second transformer unit (151) may be an insulating transformer in which the primary and secondary sides are insulated.

[0046] The heat sink may include a first heat sink (171) and a second heat sink (172). As shown in FIG. 4, the first heat sink (171) may dissipate heat of the upper switch (111) to the outside, and the second heat sink (172) may dissipate heat of the lower switch (114) to the outside. The upper switch (111) and the lower switch (114) may be MOSFET switches, and may generate a lot of heat during operation. In order to dissipate the heat generated from the switches, they may be arranged to be in contact with the first heat sink (171) and the second heat sink (172), respectively. At this time, the first heat sink (171) and the upper switch (111) may be insulated, and the second heat sink (172) and the lower switch (114) may be insulated. The heat sink may be formed of a metal having high thermal conductivity, and may be insulated to prevent short circuiting with the upper switch (111) or the lower switch (114). The first heat sink (171) and the second heat sink (172) may be connected to ground, and the ground of each heat sink may correspond to the ground connected to the lower switch (114). This enables safe operation.

[0047] When the upper switch (111) and the lower switch (114) are turned on and off simultaneously, and the upper switch (111) and the lower switch (114) are turned off due to parasitic components of the insulating components, a voltage inequality may occur between the drain-source voltage of the upper switch (111) and the drain-source voltage of the lower switch (114). The parasitic component may occur due to the insulation of the first transformer (121) and the second transformer (151), the first heat sink (171), and the second heat sink (172), and the lower switch (114) is connected to the ground, but the upper switch (111) is not directly connected to the ground, so a voltage inequality may occur between the drain-source voltage of the upper switch (111) and the drain-source voltage of the lower switch (114). Since the upper switch (111) is not connected to the ground, the potential difference increases depending on whether it is turned on or off. As a result, even if the upper switch (111) and the lower switch (114) are turned off at the same time, the drain-source voltage of the upper switch (111) may be greater than the drain-source voltage of the lower switch (114), and the change in the drain-source voltage of the upper switch (111) may be greater than the change in the drain-source voltage of the lower switch (114). This voltage inequality may cause switching loss, and heat generation in the upper switch may cause damage to components.

[0048] The balancing unit (130) is connected to the switching unit (110) and can balance the voltage between the switches of the switching unit (110). The balancing unit (130) can balance the drain-source voltage of the upper switch (111) and the drain-source voltage of the lower switch (114). For this purpose, the balancing unit (130) can be connected in parallel with the second diode (113).

[0049] The balancing unit (130) may include a first capacitor (131). The first capacitor (131) may be connected in parallel with a second diode (113). As shown in Fig. 2, the first capacitor (131) is connected in parallel with the second diode (113), and compensates for a parasitic capacitor generated on the side of the upper switch (111) connected in parallel with the second diode (113), thereby balancing the voltage between the upper switch (111) and the lower switch (114). Here, the balanced voltage may be the drain-source voltage of the upper switch (111) and the drain-source voltage of the lower switch (114).

[0050] The balancing unit (130) can compensate for a third capacitance value obtained by subtracting a second parasitic capacitance value between one of the two input terminals of the input unit of the first transformer (121) and the ground from a first parasitic capacitance value between the other input terminal and the ground. The sum of the parasitic capacitances of the upper switch (111) may be equal to the first parasitic capacitance value between the (+) input terminal of the input side of the first transformer (121) and the ground, and the sum of the parasitic capacitances of the lower switch (114) may be equal to the second parasitic capacitance value between the (-) input terminal of the input side of the first transformer (121) and the ground. That is, the difference between the parasitic capacitance of the upper switch (111) and the parasitic capacitance of the lower switch (114) is equal to the third capacitance value obtained by subtracting the second parasitic capacitance value from the first parasitic capacitance value. (C_3 = C_eq_HS - C_eq_LS)

[0051] The balancing unit (130) can perform balancing by compensating for the third capacitance value. The balancing unit (130) can perform balancing by setting the capacity of the first capacitor (131) to the third capacitance value. The first capacitor (131) is connected in parallel with the second diode (113) connected to the lower switch (114), so that the parasitic capacitance value of the lower switch (114) can be compensated for so that it is equal to the parasitic capacitance value of the upper switch (111), thereby performing balancing.

[0052] A power conversion device (100) according to an embodiment of the present invention can be implemented as shown in FIG. 5. It may include an upper switch (Q1) and a first diode (D1) connected in series, a second diode (D1) and a lower switch (Q2) connected in series, a first transformer (T1) connected to a first node between the upper switch (Q1) and the first diode (D1) and a second node between the second diode (D2) and the lower switch (Q2), a third diode (D3) connected in series with an output side of the first transformer (T1), and a first capacitor (C3) connected in parallel with the second diode (D2). It may include an input capacitor (C1) and an output capacitor (C2), and may include a second transformer (T2) that transmits a gate signal to each gate driver circuit to drive the upper switch (Q1) and the lower switch (Q2).

[0053] At this time, parasitic capacitance may occur due to insulation. The location where parasitic capacitance occurs may be as shown in Fig. 6. C_para1 may occur in the second transformer (T2), which is an insulating transformer, C_para2 between the first heat sink (HS1) and the upper switch (Q1), C_para3 between the second heat sink (HS2) and the lower switch (Q2), and C_para4 and C_para5 may occur in the first transformer (T1). The sum (C_eq_HS) of the parasitic capacitances of the upper switch (Q1) may be equal to the first parasitic capacitance value between the (+) input terminal of the input side of the first transformer (T1) and the ground, and the sum (C_eq_LS) of the parasitic capacitances of the lower switch (Q2) may be equal to the second parasitic capacitance value between the (-) input terminal of the input side of the first transformer (T1) and the ground.

[0054] In order to balance the upper switch (Q1) and the lower switch (Q2), a third capacitance value is compensated by subtracting the second parasitic capacitance value from the first parasitic capacitance value, and for this purpose, the capacitance value of the first capacitor (C3) connected in parallel with the second diode (113) can be set to the third capacitance value. Through this, the difference between the drain-source voltage of the upper switch (Q1) and the drain-source voltage of the lower switch (Q2) can be reduced.

[0055] When the first capacitor (C3) is not connected in parallel to the second diode (D2), the difference between the drain-source voltage of the upper switch (Q1) and the drain-source voltage of the lower switch (Q2) is 63.23 V based on 600 V, which is a 10.5% difference. However, by connecting the first capacitor (C3) in parallel to the second diode (D2), it was confirmed that the difference was reduced to 18.48 V, a 3.08% difference.

[0056] Reducing the drain-source voltage difference between the switches in a two-switch flyback converter can reduce switching loss variations and heat dissipation differences. This reduces per-component loss, enabling optimized heat dissipation design and component ratings, while ensuring reliable switching operation.

[0057] Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from the essential characteristics of the above-described description. Therefore, the disclosed methods should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. Upper switch and first diode connected in series; A second diode and a low-side switch connected in series; A first transformer connected to a first node between the upper switch and the first diode and a second node between the second diode and the lower switch; A third diode connected in series with the output side of the first transformer; and A power conversion device including a balancing unit connected in parallel with the second diode and balancing the drain-source voltage of the upper switch and the drain-source voltage of the lower switch.

2. In paragraph 1, The above balancing part, A power conversion device comprising a first capacitor connected in parallel with the second diode.

3. In paragraph 2, The above balancing part, A power conversion device that compensates for a third capacitance value obtained by subtracting a second parasitic capacitance value between one of the two input terminals of the input terminal of the first transformer and ground from a first parasitic capacitance value between the other input terminal and ground.

4. In paragraph 3, A power conversion device in which the capacity of the first capacitor corresponds to the third capacitance value.

5. In paragraph 1, A power conversion device in which the upper switch and the lower switch are turned on and off simultaneously.

6. In paragraph 1, A first heat sink that dissipates heat from the upper switch to the outside; and Including a second heat sink that dissipates heat of the lower switch to the outside, A power conversion device in which the ground of the first heat sink and the ground of the second heat sink correspond to the ground connected to the lower switch.

7. In paragraph 1, Includes a driving power unit that supplies gate power to the upper switch and the lower switch, The above driving power unit is, A first gate driver circuit for generating gate power of the upper switch; A second gate driver circuit for generating gate power of the lower switch; and A second transformer connected to the first gate driver circuit and the second gate driver circuit is included, The above second transformer, A power conversion device comprising two output sides, the primary side of which is connected to a control unit and the secondary side of which is connected to the first gate driver circuit and the second gate driver circuit, respectively.

8. In paragraph 7, The primary and secondary sides of the above first transformer are insulated, A power conversion device in which the primary side and the secondary side of the second transformer are insulated.

9. In paragraph 8, The above first heat sink and the upper switch are insulated, A power conversion device in which the second heat sink and the lower switch are insulated.

10. In paragraph 1, An input side capacitor connected in parallel with the upper switch and the first diode; and A power conversion device including an output-side capacitor connected in parallel with the third diode.

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