CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2020-0179563, filed on Dec. 21, 2020, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

1. Field of the Invention

The present disclosure relates to a large-capacity bidirectional electrically-isolated low voltage DC-DC converter (LDC) in which bidirectional LDC circuits are packaged in consideration of a flow of electric power and cooling efficiency at the time of boosting and bucking, and a cooling structure applied thereto.

2. Description of the Related Art

A low voltage DC-DC converter (LDC), which is a direct current electric power supplier that is applied to eco-friendly vehicles (HEV, PHEV, EV, FCV, etc.) by replacing an alternator of an internal combustion engine, is an essential device that receives high voltage battery electric power (for example, 180V to 450V) from a vehicle and charges a low voltage battery (for example, 12V) or that supplies necessary electric power to an electronic device. The LDC is used to increase fuel efficiency and cope with increasing electric loads by reducing a burden on an engine.

Components of the LDC are mainly composed of a high voltage electric power conversion component, a low voltage electric power conversion component, and a magnetic component that performs the functions of electric power transfers and electrical insulation between high voltage stage and low voltage stage.

A conventional LDC has a unidirectional function of receiving electric power from a high voltage battery (HVB) mounted in a vehicle and outputting electric power at a level of low voltage (for example, 12V) through an internal electric power conversion process.

Vehicles' electric loads have been recently increasing in response to user demand (4 kW class), and there is a need for a bidirectional LDC capable of transferring electric power from an electric power source of the low voltage battery (for example, 12V) to the high voltage stage. That is, there is a demand for a bidirectional LDC capable of not only electric power transfer from the high voltage stage to the low voltage stage (buck mode), which is the unidirectional function of the conventional LDC, but also electric power transfer from the low voltage stage to the high voltage stage (boost mode).

When applying the bidirectional LDC to a vehicle, a method for mounting a boost type LDC and a buck type LDC on the vehicle separately from each other may be used; however, there is another general method having a stacked structure of using only a cooling passage in common. In this case, the vehicle requires a space for mounting two devices and various interface components. Even when the components are implemented as a single package, it is difficult to utilize an internal dead space.

SUMMARY

As described above, in response to an increase in an amount of vehicle electric load caused by a recent request of a user, it is required to increase a capacity of a conventional isolated unidirectional (buck type) low voltage DC-DC converter (LDC) and to further include a (boost type) LDC having a boost function of transmitting low voltage electric power (for example, 12V) to a high voltage stage. When an LDC having both the boosting function and the buck function is applied to a vehicle, a package technology with high electric power density is required in the same manner as an electronic device for an electrically powered vehicle.

It is an object of the present disclosure to provide a high electric power density bidirectional isolated LDC assembly, in which a large-capacity bidirectional isolated LDC circuit is packaged in consideration of a flow of electric power so as to use components in common and minimize an internal dead space.

It is another object of the present disclosure to provide a high electric power density bidirectional isolated LDC assembly with a cooling structure optimized for cooling efficiency applied to packaging of a large-capacity bidirectional isolated LDC circuit.

According to an aspect of the present disclosure, there is provided a bidirectional isolated LDC assembly packaged with a high voltage stage, a low voltage stage, and a bidirectional isolated LDC circuit including a buck circuit and a boost circuit connected in parallel between the high voltage stage and the low voltage stage. The LDC assembly may include a power board subassembly including the high voltage stage, a part of the buck circuit, and the boost circuit; a transformer subassembly including a transformer of the buck circuit; an output power board subassembly including a part of the buck circuit; and an EMC filter subassembly including an EMC filter included in the low voltage stage.

According to another aspect of the present disclosure, there is provided a cooling structure of the bidirectional isolated LDC assembly. The cooling structure may include a first cooling passage through which coolant flows to cool a BtB switch of the buck circuit of the output power board subassembly; a second cooling passage through which the coolant discharged from the first cooling passage flows to cool the transformer of the buck circuit of the transformer subassembly; a third cooling passage through which the coolant discharged from the second cooling passage flows to cool the buck circuit of the power board subassembly; a fourth cooling passage through which the coolant discharged from the third cooling passage flows to cool the boost circuit of the power board subassembly; and a fifth cooling passage through which the coolant discharged from the fourth cooling passage flows to cool a switching device of the buck circuit of the output power board subassembly.

Configurations and operations of the present invention will become more apparent through specific embodiments to be described later with reference to the drawings.

