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This PCB horizontally mounted Horizontal EI57 Power Transformer is an efficient coupling transformer designed specifically for switch mode power supplies (SMPS). Its core adopts classic EI-57 silicon steel sheet, which has excellent magnetic properties and high saturation magnetic flux density. The horizontal structure design enables it to be tightly attached and directly soldered onto the PCB board, greatly saving the vertical space inside the equipment, making it very suitable for use in compact switch mode power supply solutions with limited height.
As a coupling type transformer, it mainly plays a key role in energy transmission, electrical isolation, and voltage conversion in circuits, effectively ensuring the stability and safety of the power supply. This transformer has been carefully designed with the characteristics of low loss, low leakage inductance, and high coupling efficiency, which can significantly improve the overall conversion efficiency and power density of the power supply. It is an ideal choice for engineers when developing high-performance, high reliability AC-DC or DC-DC power modules.
The Five Core Functions of PCB Horizontal EI57 Power Transformer :
1. Energy Transfer&Power Conversion
This is its most fundamental function. Transformers efficiently
transfer the high-frequency pulse energy generated by primary side
switching transistors (such as MOSFETs) to the secondary side
through the principle of electromagnetic induction, thereby
achieving the required DC power output (such as 12V/5V/24V, etc.).
The EI-57 iron core and coil design have been optimized for
high-frequency switching mode, achieving efficient energy
conversion.
2. Electrical Isolation
As a coupled transformer, it establishes a robust electrical
isolation barrier between the primary (high voltage side) and
secondary (low voltage side) circuits while achieving energy
transfer. This can effectively prevent high voltage from entering
the low voltage end, greatly improving the safety and
anti-interference ability of the system, protecting the safety of
backend loads and operators, and is a key component that complies
with safety regulations such as UL and CE.
3. Voltage Transformation
By changing the turns ratio of the primary and secondary coils, the
transformer can flexibly achieve step up or step down functions,
providing the required output voltage for the switching power
supply. Designers can customize winding schemes based on different
input and output specifications, with strong adaptability.
4. Implement Impedance Matching
Transformers can change the equivalent impedance of a circuit. By
designing a reasonable turns ratio, it can "reflect" the load
impedance on the secondary side to the primary side, matching it
with the optimal operating characteristics of the power switching
device, thereby ensuring maximum power transmission to the load,
reducing losses caused by reflected energy, and improving system
efficiency and stability.
5. Core Reset&Energy Reset
In forward switching power supply topologies, transformers must
undergo magnetic reset every working cycle to prevent magnetic core
saturation. The design of the transformer (including possible
reserved reset windings or utilizing its magnetic circuit
characteristics) provides a path for the safe release of magnetic
flux energy, ensuring that the transformer can reliably return to
its initial state during each switching cycle, which is the
foundation for the continuous and stable operation of the power
supply.
Horizontal EI57 Power Transformer Feature Category | Specific Characteristic | Description / Typical Value | Benefit / Implication |
Mechanical | Mounting Style | Horizontal (Low-Profile) PCB Mount | Saves vertical space, enables compact and flat power supply designs. |
Core Type & Size | EI-57 Lamination | Standardized size offering a good balance of power handling, cost, and availability. | |
Termination | PCB Pins | Designed for direct soldering onto a printed circuit board, enabling automated assembly. | |
Isolation Class | Functional Isolation (Typically Reinforced or Basic) | Provides necessary electrical separation between primary and secondary for safety and noise reduction. | |
Electrical - General | Operating Frequency | 20kHz - 250kHz+ (e.g., for Flyback, Forward converters) | Designed for high-frequency switching operation, allowing for smaller magnetics. |
Primary Inductance (Lp) | Value specified by design (e.g., 1.5mH ±10%) | A critical parameter determining the transformer's energy storage capacity in flyback topologies. | |
Coupling Type | Coupling (Galvanic Isolation) | Transfers power and signals between circuits while maintaining electrical isolation. | |
Electrical - Isolation | Isolation Voltage | Hi-Pot Test: ~3kV AC (1-2 sec) between Primary & Secondary | Ensures reliability and safety, protecting users and downstream circuits from high voltage. |
Insulation Resistance | >100 MΩ (e.g., 500VDC test) | Indicates the quality of the insulation materials and construction. | |
Electrical - Losses | Winding Resistance | Low DCR (DCRpri & DCRsec specified, e.g., <1Ω) | Minimizes copper (I²R) losses, improving overall efficiency and thermal performance. |
Core Losses | Optimized for high-frequency operation | Reduced hysteresis and eddy current losses within the core, leading to higher efficiency. | |
Leakage Inductance | Minimized by design and winding technique | Reduces voltage spikes on switching elements, improves energy transfer efficiency, and lowers EMI. | |
Thermal | Operating Temperature | Class A (105°C) or Class B (130°C) | Reliable operation within the temperature range of typical power supply environments. |
Temperature Rise | Low ΔT under full load (e.g., <40°C) | Indicates good efficiency and thermal management, contributing to long-term reliability. | |
Reliability & Standards | Regulatory Compliance | Designed to meet UL / CE / IEC standards (e.g., IEC 61558, UL 506) | Ensures the component meets international safety and performance norms. |
Flammability Rating | Core and bobbin material rated UL94 V-0 | Prevents the propagation of flame, enhancing the safety of the end product. |