Magnetic Saturation Characteristics of High-Frequency Transformers and Their Impacts & Solutions

I. Magnetic Saturation Characteristics of High-Frequency Transformers

    During the magnetization of ferromagnetic materials, the Magnetic Flux Density (B) increases with the rising external Magnetic Field Strength (H). However, when H exceeds a certain threshold, B tends to stabilize at a constant value, entering the magnetic saturation state. This magnetization curve exhibits a typical characteristic: in the critical saturation zone, B approximately equals Bp upon entering saturation, and when B approximately equals Bo, it reaches the saturated region. For switching power supplies, the state where the magnetic flux (Φ = B * S) within the high-frequency transformer no longer changes significantly with the external H is defined as magnetic saturation. As the change in B becomes very small relative to changes in H, the permeability (μ = ΔB/ΔH, the slope of the curve) decreases significantly, leading to a pronounced reduction in the inductance (Lp) of the primary winding.

II. Hazards of Magnetic Saturation

    Magnetic saturation severely impacts switching power supplies. It can cause component overheating and even damage. Under saturation, the primary winding inductance (Lp) drops significantly. This leads to a rapid increase in the power dissipation of both the primary winding's DC resistance (copper resistance) and the power switching transistor, causing a sharp rise in the primary side current. If the control chip's current limiting circuit cannot protect in time, the switching transistor may be damaged immediately. Key manifestations of magnetic saturation failure include:

1. Overheating of the high-frequency transformer.

2. Overheating of the switching transistor.

3. Rapid drop in output voltage under increased load, failing to achieve the designed output power.

III. Methods to Counteract Magnetic Saturation

1. Appropriately reduce the number of primary winding turns (Np): Reducing Np decreases the inductance, thereby increasing the critical saturation current. This is because the Magnetic Field Strength (H) is proportional to the product of Np and the primary peak current (Ip). If Ip remains constant, reducing Np lowers H, reducing the likelihood of core saturation.

2. Select a larger core size and increase the air gap width.

IV. Measuring Magnetic Saturation

    Detecting magnetic saturation is primarily done by observing the current waveform of the primary winding. Under normal conditions, the primary winding acts as an inductor, with its current rising and falling in a triangular waveform over time. When the core begins to saturate, the current rise rate suddenly accelerates, forming a sharp peak.

    Why Does Golden Eagle High-Frequency Transformer Earn Customer Recognition?

1. Lean Production Line (One-Piece Flow): Eliminates work-in-progress (WIP) pile-up.

2. Full Automation: From winding and assembly to comprehensive testing.

3. 100% Certified Materials from Renowned Suppliers: Ensures quality from the source.