Bidirectional insulated low voltage DC-DC converter assembly and bidirectional insulated LDC assembly cooling structure

Abstract

The present disclosure relates to a high power density bidirectional insulated low voltage DC-DC converter (LDC) component and a bidirectional insulated LDC component cooling structure, wherein a large capacity bidirectional insulated LDC circuit is packaged in consideration of the flow of power so as to share components and minimize internal dead space. The LDC component comprises: a power board subassembly (100) comprising a high voltage stage, a portion of a step-down circuit and a step-up circuit; a transformer subassembly (200) comprising a transformer of the step-down circuit; an output power board subassembly (300) comprising a portion of the step-down circuit; and an EMC filter subassembly (400) comprising an EMC filter contained in the low voltage stage.

Description

Technical Field

[0001] The present disclosure relates to a large-capacity bidirectional electrically-insulated low-voltage DC-DC converter (LDC) and a cooling structure applied thereto, in which a bidirectional LDC circuit is packaged in consideration of power flow and cooling efficiency when stepping up and down. Background Art

[0002] A low voltage DC-DC converter is a basic device that receives high voltage battery power (e.g. 180V to 450V) from a vehicle and charges a low voltage battery (e.g. 12V) or provides necessary power to electronic devices. This low voltage DC-DC converter (LDC) is a DC power supplier applied to eco-friendly vehicles (HEV, PHEV, EV, FCV, etc.) by replacing the alternator of the internal combustion engine. LDC is used to improve fuel efficiency by reducing the burden on the engine and to cope with the increasing power load.

[0003] The components of the LDC are mainly composed of a high voltage power conversion component, a low voltage power conversion component, and a magnetic component that performs the functions of power transmission and electrical insulation between the high voltage level and the low voltage level.

[0004] A conventional LDC has a unidirectional function of receiving power from a high voltage battery (HVB) installed in a vehicle and outputting power at a low voltage (eg, 12V) level through an internal power conversion process.

[0005] In response to user demand (4kW class), the power load of vehicles has recently increased, and a bidirectional LDC capable of transmitting power from a power source of a low-voltage battery (e.g., 12V) to a high-voltage level is required. That is, there is a demand for a bidirectional LDC capable of transmitting power not only from a high-voltage level to a low-voltage level (buck mode), which is a unidirectional function of a conventional LDC, but also from a low-voltage level to a high-voltage level (boost mode).

[0006] When a bidirectional LDC is applied to a vehicle, a method of installing a boost-type LDC and a buck-type LDC separately from each other on the vehicle can be used; however, there is another general method with a stacked structure, which generally uses only cooling channels. In this case, the vehicle requires space to install two devices and various interface components. Even if the components are implemented as a single package, it is difficult to utilize the internal dead space. Summary of the invention

[0007] As described above, in response to the increase in the amount of electrical load of vehicles caused by recent demands of users, it is necessary to increase the capacity of conventional insulated unidirectional (buck type) low voltage DC-DC converters (LDCs), and also include (boost type) LDCs having a boost function for transmitting low voltage power (e.g., 12V) to a high voltage level. When an LDC having a boost function and a buck function is applied to a vehicle, a packaging technology having a high power density is required in the same manner as electronic devices for electric vehicles.

[0008] An object of the present disclosure is to provide a high power density bidirectional insulated LDC assembly in which a large capacity bidirectional insulated LDC circuit is packaged in consideration of the flow of power so as to co-use components and minimize internal dead space.

[0009] Another object of the present disclosure is to provide a high power density bidirectional insulated LDC component having a cooling structure optimized for cooling efficiency, the cooling structure being applied to packaging of a large capacity bidirectional insulated LDC circuit.

[0010] According to aspects of the present disclosure, a bidirectional insulated LDC component encapsulated with a high voltage stage, a low voltage stage, and a bidirectional insulated LDC circuit including a buck circuit and a boost circuit connected in parallel between the high voltage stage and the low voltage stage are provided. The LDC component may include: a power board subassembly including the high voltage stage, a portion of the buck circuit, and a boost circuit; a transformer subassembly including a transformer of the buck circuit; an output power board subassembly including a portion of the buck circuit; and an EMC filter subassembly including an EMC filter included in the low voltage stage.

[0011] According to another aspect of the present disclosure, a cooling structure of a bidirectional insulating LDC assembly is provided. The cooling structure may include: a first cooling channel through which a coolant flows to cool a BtB switch of a step-down circuit of an output power board subassembly; a second cooling channel through which a coolant discharged from the first cooling channel flows to cool a transformer of a step-down circuit of a transformer subassembly; a third cooling channel through which a coolant discharged from the second cooling channel flows to cool the step-down circuit of a power board subassembly; a fourth cooling channel through which a coolant discharged from the third cooling channel flows to cool a step-up circuit of a power board subassembly; and a fifth cooling channel through which a coolant discharged from the fourth cooling channel flows to cool a switch device of a step-down circuit of an output power board subassembly.

[0012] The configuration and operation of the present invention will become more apparent from specific embodiments which will be described later with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1is a circuit diagram of a large-capacity bidirectional insulated low-voltage DC-DC converter (LDC) according to an embodiment of the present disclosure;

[0014] Figure 2 yes Figure 1 A block diagram of the subcomponents of the LDC circuit;

[0015] Figure 3 An LDC assembly is shown, wherein the subassemblies are assembled and packaged;

[0016] Figure 4 Show Figure 3 The positions of the step-down circuit (10), the step-up circuit (20), the high voltage stage (30) and the low voltage stage (40) in the assembly;

[0017] Figure 5 shows the power flow in buck mode of the LDC assembly according to the present disclosure;

[0018] Figure 6 shows the power flow in boost mode of the LDC assembly according to the present disclosure;

[0019] Figure 7 is an appearance diagram of an LDC module manufactured by embedding an LDC component into a housing;

[0020] Figure 8 A cooling channel for illustrating the cooling structure of the LDC module is shown;

[0021] Fig. 9 showing cooling channels on the upper surface of the LDC module; and

[0022] Fig.10 The cooling channels of the lower surface of the LDC module are shown. DETAILED DESCRIPTION

[0023] With reference to the preferred embodiments described in detail with reference to the accompanying drawings, the advantages and features of the present disclosure and the methods for achieving them will become apparent. However, the present disclosure is not limited to the embodiments described below and may be implemented in various other forms. These embodiments are provided only to fully disclose the present disclosure and fully inform the technical personnel in the field to which the present disclosure belongs of the scope of the present disclosure, and the present disclosure is defined by the attached claims. In addition, the terms used in the specification are only descriptive in nature and not for the purpose of limitation.

[0024] The terms used herein are used only for the purpose of describing a specific embodiment and are not intended to be limited. It must be noted that, as used herein and in the appended claims, unless the context clearly indicates otherwise, the singular forms of "one", "an" and "the" include plural forms. The terms "include", "includes", "includes", "has", "has" or their other variants are inclusive, and therefore specify the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or their combinations. In addition, terms such as "first", "second" and other numerical terms are only used to distinguish one element from another element. These terms are usually only used to distinguish one element from another element.

[0025] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the embodiments of the present disclosure, detailed description of well-known related structures or functions will be omitted when it is considered that such description will make the description of the present disclosure vague.

[0026] Figure 1 is a circuit diagram of a large-capacity bidirectional electrically isolated low-voltage DC-DC converter (LDC) according to an embodiment of the present disclosure. Figure 1 In the circuit diagram of , the main functional unit can be divided into four blocks 10, 20, 30 and 40 (ie, functional division).

[0027] First, a general circuit configuration will be described. A high voltage applied from a high voltage stage 30 including a high voltage battery HV for a vehicle can be stepped down (reduced) by a step-down circuit 10 to be supplied to a low voltage battery LV (e.g., 12V) of a low voltage stage 40 indicated on the right side of the circuit diagram. Conversely, a low voltage applied from a battery LV of a low voltage stage 40 can be stepped up (increased) by a step-up circuit 20 to be supplied to a battery HV of a high voltage stage 30.

[0028] The LDC according to the present embodiment may include: a high voltage stage 30 and a low voltage stage 40 configured as a common circuit; and two independent circuits provided in parallel between the high voltage stage 30 and the low voltage stage 40; that is, a buck circuit 10 and a boost circuit 20. The buck circuit 10 may be an active clamp forward converter circuit (hereinafter referred to as a forward converter circuit), and the boost circuit 20 may be an active clamp flyback converter circuit (hereinafter referred to as a flyback converter circuit).

[0029] First, the main circuit components used in common are as follows.

[0030] -High voltage level 30

[0031] HV: High voltage battery for vehicles (e.g. 180V to 450V)

[0032] CY1, CY2: High voltage level Y-CAP (capacitors connected between each power line and ground for noise filtering)

[0033] CM: High voltage level CM filter (inductor)

[0034] Ci: High voltage level DC filter (capacitor)

[0035] CS1: High voltage level current sensor (using Hall sensor)

[0036] -Low voltage level 40

[0037] LV: Low voltage battery for vehicles (e.g. 12V)

[0038] Co: Low voltage level DC filter (capacitor)

[0039] CS2: Low voltage level current sensor (using Hall sensor). CS2 with high voltage level current sensor CS1 can monitor current in both boost and buck modes and can generate a fault signal when overcurrent occurs to determine operation stop. CS2 can also be used to keep the current at a constant level in the low voltage level.

[0040] BtB: Bidirectional back-to-back switch for isolating low voltage levels

[0041] EMC filter: A low-voltage EMC filter (electromagnetic wave filter) through which a large current flows

[0042] Next, main components of the step-down circuit 10 and the step-up circuit 20 are as follows.

[0043] - Buck circuit 10

[0044] CT: Current sensor, used to sense current and convert the current into a voltage value for current control of the high voltage stage, which is an input unit of the step-down circuit 10. The CT can be implemented as a current transformer.

[0045] CL1: Capacitor used to limit transformer voltage (clamping capacitor)

[0046] Q_HSMN, Q_HSCL: High voltage level switching devices

[0047] TR1: An isolation transformer with one high voltage input (primary side) and two low voltage outputs (secondary and tertiary sides)

[0048] Q_ST, Q_SB: Low voltage level high current type switching devices

[0049] Lo: Inductor used to filter the output current

[0050] -Boost circuit (20)

[0051] CL2: Capacitor used to limit transformer voltage (clamping capacitor)

[0052] Q_LSMN, Q_LSCL: Low voltage level switching devices

[0053] TR2: Isolation transformer with one input (primary side) and one output (secondary side) D1: Diode for rectifying the output power

[0054] As described above, the buck circuit 10 can be configured as a forward converter circuit. A forward converter using HV as input and LV as output can transfer the electrical energy of HV to LV while alternately switching high voltage level switching devices Q_HSCL and Q_HSMN. Since the voltage difference between HV and LV is very large, there are limitations in obtaining the required output voltage by adjusting the duty cycle (=time period of switching on) in the same way as a normal DC-DC converter. Transformer TR1 can be a required element for overcoming this significant difference between input voltage and output voltage and for electrical insulation. Transformer TR1 can determine the ratio of the primary winding to the secondary winding and the tertiary winding (tertiary winding) in consideration of the HV-LV voltage difference and duty cycle variable limitations. When the high voltage level switching devices Q_HSMN and Q_HSCL are working, the second terminal and the third terminal of the transformer can output an AC square wave. The square wave can be rectified by low voltage level high current switching devices Q_ST and Q_SB. By replacing the existing rectifying diode used in the forward converter with a semiconductor device such as MOSFET, the switching devices Q_ST and Q_SB can be used to reduce the decrease in efficiency even when the output current is high. Therefore, high efficiency, which is an important factor for eco-friendly vehicles, can be met. After that, the rectified output voltage can be kept constant and stable through the filtering operation of the output inductor Lo and the output capacitor Co.

[0055] As described above, the boost circuit 20 can be configured as a flyback converter circuit. The flyback converter using LV as input and HV as output can transfer the electric energy of LV to HV while alternately switching the low voltage level switching devices Q_LSCL and Q_LSMN. Since the voltage difference between LV and HV is very large, a transformer TR2 in the same manner as the step-down circuit may be required, and the winding ratio of the transformer TR2 may need to be pre-designed. When the switching devices Q_LSCL and Q_LSMN of the low voltage level are working, the secondary winding of the transformer TR2 can output an AC square wave. The square wave can be rectified by a diode D1, which is a rectifying device connected between the transformer TR2 and the high voltage level. Thereafter, the output capacitor Ci can keep the output voltage constant and stable by filtering the output voltage.

[0056] Figure 2 Shown in Figure 1 The physically divided components in the circuit, so as to Figure 1 The configuration of the package (component) of the large-capacity bidirectional insulated LDC circuit is to arrange these components in consideration of the flow of power and cooling efficiency when stepping up and down. In addition, Figure 3 Assemble and package as shown Figure 2 The LDC component is obtained by physically dividing the sub-components shown.

[0057] Each physically divided sub-assembly may include: a power board sub-assembly 100, which includes a high voltage stage 30, a portion of the step-down circuit 10 (a current sensor CT on the primary side of the transformer TR1, a clamping capacitor CL1, and high voltage stage switching devices Q_HSMN and Q_HSCL) and a boost circuit 20; a transformer sub-assembly 200, which includes a transformer TR1 and an inductor Lo of the step-down circuit 10; an output power board sub-assembly 300, which includes high current switching devices Q_ST and Q_SB of an output unit (low voltage stage) located on the secondary side of the transformer TR1 of the step-down circuit 10, and a DC filter capacitor Co and a BtB switch of the low voltage stage; and an EMC filter sub-assembly 400, which includes an EMC filter that performs a function of noise filtering for the output unit (low voltage stage) in a step-down mode, and performs a function of blocking switching noise for the low voltage stage as an input unit in a step-up mode.

[0058] Here, the current sensor (including the high voltage level current sensor CS1 and the low voltage level current sensor CS2) may be included in the EMC filter subassembly 400, or the current sensor subassembly 500 may be configured as a separate unit, which is a sensor that monitors the current in each boost mode and buck mode and generates a fault signal to determine that the operation is stopped when an overcurrent occurs.

[0059] By assembling the various subcomponents, Figure 3 The configuration shown is a large capacity bidirectional insulated LDC assembly. Figure 3 , the subassemblies 100, 200, 300 and 400 or 500 assembled in the form of a plate or a single unit can be connected by using some means (e.g., screws, rivets, bus bars, etc.), and wire welding can be performed on the subassemblies 100, 200, 300 and 400 or 500 to manufacture the LDC assembly. Therefore, efficient power flow and excellent cooling performance can be obtained when the LDC is stepped up and down.

[0060] Figure 4 Shown in Figure 3 The positions of the step-down circuit 10, the step-up circuit 20, the high voltage stage 30 and the low voltage stage 40 in the components are Figure 1 The functional blocks shown.

[0061] The buck circuit 10 may be divided into a power board subassembly 100, a transformer subassembly 200, and an output power board subassembly 300. Specifically, the switch unit and the boost circuit on the primary side of the transformer TR1 of the buck circuit 10 may be disposed in the power board subassembly 100, and the transformer TR1 and the inductor Lo may be disposed in the transformer subassembly 200, and the output switch unit on the secondary side of the transformer TR1 may be disposed in the output power board subassembly 300.

[0062] The boost circuit 20 may be provided in the power board subassembly 100 ( Figure 4 ).

[0063] The high voltage stage 30 may be completely disposed in the power board subassembly 100 ( Figure 4 In this way, a single high voltage stage 30 circuit is constructed in a step-up / step-down (bidirectional) LDC for common use. That is, one power board subassembly 100 can be used with LDC modules of various specifications (the same applies to other subassemblies).

[0064] The DC filter capacitor Co and BtB switch of the low voltage stage 40 may be provided in the output power board subassembly 300, and the EMC filter may be provided in the EMC filter subassembly 400 (along with related components). In addition, the current sensors CS1 and CS2 may be provided in the current sensor subassembly 500 (along with related components).

[0065] Figure 5The power flow in the buck mode of the LDC assembly according to the present disclosure is shown. The voltage of the high voltage battery HV can be applied to the CM filter of the high voltage stage of the power board subassembly 100 (here, filters such as the CM filter, DC filter and Y-CAP of the high voltage stage can play the role of blocking the introduction of the high voltage stage or the noise released from the high voltage stage), and can be rectified by the transformer and inductor of the transformer subassembly 200 and the synchronous rectifier circuit in the output power board subassembly 300 (the secondary side of the buck circuit) along the arrow direction through the active clamp forward converter (the primary side of the buck circuit) to convert to low voltage. The converted low voltage can be output as a low voltage (LVOUT) through the BtB switch and EMC filter subassembly 400.

[0066] Figure 6 1 shows the power flow in the boost mode of the LDC assembly according to the present disclosure. The voltage of the low voltage battery LV can be input to the EMC filter subassembly 400 for filtering so that the switching noise of the low voltage level does not leak. Thereafter, the filtered voltage can be converted by the BtB switch of the output power board subassembly 300 through the switching device, transformer and rectifier diode of the boost circuit 20 (active clamp flyback converter), and the converted voltage can be output as a high voltage HV OUT through the high voltage level of the power board subassembly 100.

[0067] Figure 7 The appearance of an LDC module manufactured by embedding the above-mentioned LDC assembly in a housing is shown. The LDC module may include a plurality of heat-generating components; a coolant (cooling water, refrigerant, etc.) may be injected into an inlet installed in the housing to allow the coolant to flow through a cooling channel provided in a predetermined path in the housing so as to cool the LDC assembly and discharge the coolant through an outlet. In the above, the configuration of the package (assembly) of the large-capacity bidirectional insulated LDC circuit according to the present disclosure has been described with the motivation of considering cooling efficiency and effective power flow when the LDC is stepped up and down.

[0068] Figure 8 A cooling structure of an LDC module manufactured by embedding the LDC assembly according to the present disclosure into a housing is shown. Fig. 9 shows the bottom surface of the LDC module, Fig.10 The top surface of the LDC module is shown.

[0069] The cooling channels can be Figure 8The design shown is used to cool the LDC module of the present disclosure. ① The coolant introduced through the inlet can flow through the cooling channel to cool the BtB (Back to Back) switch (a bidirectional back-to-back switch for separating the low voltage level), which is a heat-generating component of the output power board subassembly 300. ② The coolant can then pass through the cooling channel through the transformer subassembly 200 to cool the transformer (and inverter) (see Fig.10 ), ③ then the buck circuit (shown in the lower part) and ④ the boost circuit (shown in the upper part) of the power board subassembly 100 can be cooled, and continuously, then ⑤ the low voltage level high current type switching device of the buck circuit in the output power board subassembly 300 can be cooled through the cooling channel located on the bottom surface of the LDC module housing, and then ⑥ can be discharged through the outlet. Through this cooling channel configuration, the circuit components of the boost / buck type bidirectional LDC can be sequentially cooled, thereby achieving an excellent cooling effect.

[0070] According to the present disclosure, the effect of reducing the number of component types and material costs can be obtained by using components in common and reducing the size. Specifically, the high voltage level, the low voltage level, the cooling channel, the housing and the control circuit can be used in common, so the space for installing the product in the vehicle (mainly the engine room) can be ensured, and the weight of the product can be reduced. In addition, the wires (for high voltage, low voltage and signals) used to connect the vehicle and the product to each other can be reduced, and the control variables can also be reduced, so many advantages in the vehicle can be obtained. In addition, the cost and space can be reduced by using filters, PCBs, etc. of high voltage and low voltage levels in common.

[0071] The above description is only an example of the technical concept of the embodiments of the present disclosure, and it should be obvious to those skilled in the art that various modifications, combinations and substitutions can be made without departing from the spirit and scope of the embodiments of the present disclosure. Therefore, the embodiments of the present disclosure should be considered only as descriptive and not for the purpose of limitation. Therefore, the present disclosure is not limited to the above-mentioned embodiments, but is intended to include the following claims and all modifications, equivalents and alternative forms that fall within the spirit and scope of the appended claims.

Claims

1. A bidirectional insulated low-voltage DC-DC converter assembly, wherein the low-voltage DC-DC converter assembly is packaged with a high voltage level and a low voltage level, and the bidirectional insulated DC-DC converter includes a buck circuit and a boost circuit connected in parallel between the high voltage level and the low voltage level, and the low voltage DC-DC converter assembly includes: A power board subassembly, comprising the high voltage stage, a portion of the step-down circuit and the step-up circuit, wherein: a portion of the step-down circuit included in the power board subassembly including a high voltage level switching device located on a primary side of a transformer, a current transformer, and a clamping capacitor located on the primary side of the transformer; a transformer subassembly, including a transformer of the step-down circuit; An output power board subassembly, comprising a portion of the step-down circuit, wherein a portion of the step-down circuit included in the output power board subassembly including a switching device and a back-to-back switch located on a secondary side of the transformer; and An EMC filter subassembly comprises an EMC filter contained in the low voltage stage.

2. The bidirectional insulated low voltage DC-DC converter assembly according to claim 1, wherein: The transformer subassembly also includes an inductor of the buck circuit.

3. The bidirectional insulated low voltage DC-DC converter assembly according to claim 1, further comprising: The current sensor subassembly includes a high voltage level current sensor and a low voltage level current sensor.

4. The bidirectional insulated low voltage DC-DC converter assembly according to claim 1, wherein: The EMC filter subassembly includes a high voltage level current sensor and a low voltage level current sensor.

5. The bidirectional insulated low voltage DC-DC converter assembly according to claim 1, wherein: The buck circuit is an active clamp forward converter circuit, and The boost circuit is an active clamp flyback converter circuit.

6. A bidirectional insulated low-voltage DC-DC converter assembly cooling structure, the cooling structure being used to cool the low-voltage DC-DC converter assembly according to claim 1, comprising: a first cooling channel through which a coolant flows to cool back-to-back switches of a buck circuit of the output power board subassembly; a second cooling channel through which the coolant discharged from the first cooling channel flows to cool the transformer of the step-down circuit of the transformer subassembly; a third cooling channel through which the coolant discharged from the second cooling channel flows to cool the step-down circuit of the power board subassembly; a fourth cooling channel through which the coolant discharged from the third cooling channel flows to cool the boost circuit of the power board subassembly; as well as A fifth cooling channel through which the coolant exhausted from the fourth cooling channel flows to cool the switch device of the step-down circuit of the output power board subassembly.

7. The bidirectional insulated low voltage DC-DC converter assembly cooling structure according to claim 6, wherein: The coolant flowing through the second cooling channel also cools the inductor of the buck circuit.

8. The bidirectional insulated low voltage DC-DC converter assembly cooling structure according to claim 6, wherein: The fifth cooling channel penetrates through the bottom surface of the output power board subassembly.

9. The bidirectional insulated low voltage DC-DC converter assembly cooling structure according to claim 6, further comprising: an inlet through which coolant is introduced into the first cooling channel; as well as An outlet through which coolant is discharged from the fifth cooling passage.

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