* Product Parameters
Operating frequency:10kHz-500KHz Operating temperature:-40℃ to +125℃ Storage temperature:-25℃ to +85℃ Storage humidity:30 to 95%
* Features
The ER7.5 transformer is a small, round, center-pillar transformer with the lowest leakage inductance, best high-frequency performance, and most suitable for miniature isolated power supplies in its size. * Typical application areas
ER7.5 transformers are in the 1W to 1.8W range.Miniature isolation transformers with small size, low leakage inductance, high frequency, and high isolation are the preferred choice.Covering consumer, industrial, and telecommunications sectorsIoTIt can be used in almost all low-power isolated power supply scenarios, such as vehicle-mounted applications.
* Product Standards UL, RoHS, 3C,CQC * Size Specifications 
Type | Structure
Tурe | Dimension（mm） | Pin Row （mm） | Row Pitch（mm） | OD Pin
（mm） | note | A | B | C | Pin | E | F | ER7.5-001 | Vertical | 9.5 | 7.5 | 5.5 | 4+4 | 1.8 | 9.0 | SQ0.25*0.6 | SMD |
*The above are commonly used skeleton styles for the company.,Other styles are not included.,Inquiries are welcome. Our company can customize high-frequency transformers of various specifications according to customer requirements.
ER7.5 Transformer is a high-frequency, low-power surface-mount transformer with the following key performance characteristics: I. Core Electrical Performance Power and Frequency Range Minimum power of 1.0W (ER7.5/5 specification), operating frequency range of 20–200 kHz, suitable for small to medium-power AC-DC and DC-DC power conversion applications. Loss and Efficiency Features “low loss” combined with a “low temperature rise” design, enabling stable energy conversion efficiency during high-frequency operation and minimizing heat impact on equipment. II. Structural and Application Advantages Compact Size and Mounting Compatibility As an SMD (surface-mount device) transformer, it has a “low overall profile height,” making it suitable for precision instruments, computer terminals, program-controlled switches, modular power supplies, and other space-constrained devices. Some specifications offer both SMD and through-hole pin configurations to accommodate different assembly requirements. Performance Stability The overall design emphasizes “stable performance,” maintaining consistent output power and electrical parameters across a wide frequency range (20–200 kHz), meeting the reliability demands of industrial-grade equipment.
The ER7.5 Transformer is a miniature transformer with a circular center post. Within its volume class, it offers the lowest leakage inductance, superior high-frequency performance, and is best suited for compact isolated power supplies. Its key characteristics are as follows:
1. Physical and Structural Features
Utilizes an ultra-compact ER core structure.
The circular center post ensures uniform winding and consistent coil characteristics.
Extremely small footprint: Typical dimensions are approximately 9.5mm × 8.0mm × 6.0mm (L×W×H).
The bobbin typically features a 4+4 pin configuration in an SMD (surface-mount) package.
Ideal for high-density PCBs, ultra-thin designs, and space-constrained power supplies.
2. Electrical Performance Characteristics① Exceptionally Low Leakage Inductance (Primary Advantage)
The combination of a circular center post and layered winding enhances coupling efficiency.
Typical leakage inductance is ≤3.5μH, significantly outperforming many EE/EI-type transformers of similar size.
Benefits: Reduced voltage spikes, improved EMI performance, simplified RCD snubber design, and higher overall efficiency.
② Excellent High-Frequency Performance
Operating frequency range: 20 kHz to 350 kHz.
Typical operating range: 50 kHz to 200 kHz.
Core material is typically PC40/PC44 power ferrite, offering low losses at high frequencies.
③ High Power Density
Despite its minimal size, the rated power reaches 1.0 W to 1.8 W, with a typical value of 1.5 W.
Suitable for low-power isolated supplies, auxiliary power modules, and instrumentation power sources.
④ Reliable Insulation and Withstanding Voltage
Standard input–output isolation withstand voltage: 2 kV AC for 1 minute (can be designed for up to 3 kV).
Compliant with safety standards: UL 60950, IEC 61558, EN 60335.
Insulation class: Class B (130 °C) or Class F (155 °C).
⑤ Stable Inductance and High Consistency
The circular center post ensures uniform air gaps, resulting in minimal inductance (L) tolerance.
Batch-to-batch consistency is superior to square-center-post designs.
Well-suited for automated winding and stable mass production.
3. Thermal and Reliability Features
Temperature rise under natural convection: ≤58 K at full load.
Operating temperature range: -40 °C to +125 °C.
The core is resistant to saturation and offers strong capability to withstand inrush currents.
High long-term operational stability, making it suitable for industrial, automotive, and consumer applications.
4. Winding and Manufacturing Advantages
The circular center post facilitates easier winding, reduces wire breakage, and improves production yield.
High slot fill factor allows for multiple windings (supporting multiple outputs).
Compatible with automated winding equipment, enabling cost-effective production and shorter lead times.
High-Frequency Transformer ER7.5: Detailed Industry Application Scenarios
1. Consumer Electronics (Highest Volume Applications)① Chargers / Power Adapters
Low-power phone chargers, small home appliance power supplies, auxiliary power under 5V/1A, protocol-based power delivery.
Features: Compact size, adequate insulation, EMI-friendly design.
② Network Equipment
Auxiliary power for routers, optical modems, set-top boxes, switches; isolated driver power for PoE modules.
Features: Low leakage inductance avoids interference with network signals.
③ LED Drivers
Low-power LED constant-current drivers, LED strip drivers, auxiliary power for downlights and panel lights.
Features: Slim profile fits narrow lamp housings.
④ Small Home Appliances
Power for electric toothbrushes, shavers, beauty devices, aroma diffusers, small fans, humidifiers, smart locks.
Features: Safe isolation, small size, low cost.
2. Industrial Control & Instrumentation① Industrial Sensor Power Supplies
Power for temperature, humidity, pressure, current, and optical sensors; 4–20mA loop power; isolated sampling.
Features: High isolation, noise immunity, low temperature rise.
② PLC & Industrial Control Modules
Auxiliary power inside PLCs, I/O isolation power, auxiliary start-up power for servo drives and inverters.
Features: Wide operating temperature range, long-term stability.
③ Meters & Measurement Devices
Multimeters, energy meters, temperature controllers, flow meters.
Features: Consistent core performance, stable inductance.
3. Communication & Networking Equipment
Auxiliary power for optical modules, optical modems, 5G small cells, communication modules, NB‑IoT, and Cat.1 modules.
Features: Ultra-compact size, low noise, high isolation.
4. Automotive Electronics (Can Meet Automotive Grade)
Power for in-vehicle sensors, lighting control, BCM auxiliary power, low-power isolated drives.
Compliance: Operates from -40℃ to 125℃.
5. Smart Home & IoT Devices
Smart switches, sockets, curtain motors, security cameras, battery management, power for wireless communication modules.
Features: Ultra-thin, compatible with SMD or through-hole mounting, suitable for high-density PCBs.
6. Core Advantages of ER7.5 (Why Choose It?)
First choice for space-constrained PCBs – saves more space than EE8.3 or EE10.
Circular center post = extremely low leakage inductance – reduces flyback voltage spikes, eases EMI certification.
Excellent high-frequency performance – ideal for mainstream ~100 kHz designs, enabling very small transformer size.
Reliable isolation – standard 2 kV AC isolation, can be designed for 3 kV.
Complies with safety standards – UL 60950, IEC 61558, EN 60335.
Suitable for automated mass production – consistent performance, high yield, and controllable cost.
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