A PCB transformer is an electrical device that uses mutual inductance to provide isolation, protection, and current transfer. These electronic components offer several advantages, including small size, lightweight design, and seamless integration into circuit layouts, saving valuable space within electronic devices. Mounted directly onto the circuit board, these transformers are commonly used for voltage transformation, signal isolation, impedance matching, noise reduction, and other critical functions in electronic systems.

　　 Working Principle of Transformers in Circuits

　　The internal structure of a transformer consists of different components working together as a whole, each with a distinct function. For example, the primary and secondary windings determine the transformer's turns ratio. The core enhances the magnetic coupling effect, while the pins are used to connect to other components in the circuit. Insulation measures prevent short circuits and other potential problems.

　　Transformers utilize mutual inductance in a circuit to transfer energy or information between two separate circuits via inductive coupling. This method relies on the magnetic field generated by alternating current in one coil inducing a voltage in another adjacent coil. This phenomenon is common in transformers where the primary coil induces a voltage in the secondary coil.

　　When a circuit is energized and current flows through a conductor, a magnetic field is produced. Changes in current cause fluctuations in the magnetic field. According to Faraday's law of electromagnetic induction, placing two conductors within this changing magnetic field induces a voltage in both conductors. This induced voltage facilitates energy transfer from one circuit to another.

　　A transformer consists of two coils, namely the primary and secondary windings, wound around a shared core. When AC current flows through the primary winding, it generates an alternating magnetic field. This field, in turn, induces a voltage in the secondary winding. The voltage ratio between the primary and secondary windings is determined by the turns ratio (number of turns in each coil).

　 　Types of PCB Transformers

　　When your project requires transformers to be mounted on a PCB, you may face challenges in selecting the right components. FS Technology can provide you with cost-effective component alternatives and procurement services. To facilitate the smooth progress of your project, here are some common transformer types:

　　Isolation Transformers: These transformers provide electrical isolation between the primary and secondary windings. They are used to transfer power while ensuring no direct electrical connection exists between the input and output circuits. This is crucial for safety and noise reduction.

　　Autotransformers: Autotransformers have a single winding that serves as both the primary and secondary windings. They are used for voltage transformation, where a portion of the winding acts as the primary and another portion as the secondary. Autotransformers are more compact and efficient than traditional isolation transformers but do not provide complete electrical isolation.

　　Flyback Transformers: This type of transformer is commonly used in switching power supplies. They store energy in the magnetic field during the switch-on period and release it to the secondary winding when the switch is off. This is used to generate an isolated output voltage level.

　　Forward Transformers: Also used in switching power supplies, forward transformers transfer energy directly from the primary winding to the secondary winding while the switching transistor is conducting. They are efficient and suitable for medium-power applications.

　　Push-Pull Transformers: Used in push-pull converter circuits, where the primary winding is driven by two transistors that conduct alternately. This configuration provides efficient energy transfer and is typically used in high-power applications.

　 　Key Issues and Solutions for PCB Transformers

　　Leakage Inductance

　　Leakage inductance is a critical electrical parameter that characterizes the lack of mutual inductance between the inductive portions of a transformer and adjacent coils. Leakage inductance occurs when the magnetic flux generated by the primary winding of the transformer does not fully couple with the secondary winding. This phenomenon causes energy to be stored in the leakage inductance instead of being efficiently transferred to the secondary winding, leading to losses and reduced efficiency.

　　 How to Solve:

　　Wind the primary and secondary coils closer together to maximize magnetic coupling. This proximity improves energy transfer efficiency and reduces the impact of leakage inductance.

　　Incorporate magnetic materials or shielding between the windings to alter the magnetic flux path and reduce leakage. This method helps confine the magnetic field to the desired path.

　　Consider interleaving winding layers to enhance coupling and minimize leakage. This technique ensures more efficient energy transfer between the coils, improving the overall performance of the transformer.

　　 Electromagnetic Interference

　　In transformers, EMI issues typically manifest as electromagnetic radiation and interference with surrounding circuits. The primary causes are the use of high-frequency currents or signals that switch rapidly during operation. Additionally, the layout of transformer windings and wires, as well as current paths, can also contribute to these problems.

　　 How to Solve:

　　Enclose the PCB transformer using shielding materials or enclosures to reduce the propagation of electromagnetic radiation.

　　Integrate ferrite beads into the circuit to absorb high-frequency noise and prevent its propagation.

　　Proper grounding and component placement can minimize EMI by controlling current paths and reducing loop areas.

　　 Noise

　　Noise problems typically manifest as high-frequency oscillations or spurious signals. These issues can stem from unstable or high-frequency components, unstable supply voltages, electromagnetic coupling between coils, or improper component selection.

　 　How to Solve:

　　Incorporate power supply filters as part of the PCB design process.

　　Optimize the circuit by selecting more stable transformer components.

　　Consider lowering the operating frequency if feasible.

　　Utilize simulation tools and testing equipment to assess the noise characteristics of the circuit. Through this assessment, you can fine-tune the design and minimize noise-related challenges.

　 　Thermal Management

　　PCB transformers, like all components, generate heat during operation. If not managed properly, overheating can lead to performance degradation, reliability issues, and even component failure.

　　 How to Solve:

　　Mount a heatsink to the transformer or adjacent components to dissipate heat.

　　Ensure adequate spacing around the transformer to allow for heat dissipation.

　　Use thermal vias in the PCB to transfer heat from the component side to the other side of the circuit board.

　　Select materials with good thermal conductivity for the PCB and other nearby components.