Transformer Heating and 5V Output Drop

The behavior your are describing (transformer heating, output voltage drop above ~0.45A, and audible noise) strongly indicates that the transformer is being operated outside its intended magnetic limits—most likely approaching core saturation.

In a forward converter using the MAX17599, the transformer must be specifically designed for the operating conditions (input voltage range, duty cycle, switching frequency, and active-clamp reset). If parameters such as turns ratio, magnetizing inductance, or core size are not properly matched, excessive magnetic flux can occur. This leads to:

• Increased magnetizing current and losses → heating

• Loss of efficient energy transfer → output voltage droop

• Mechanical vibration of the core/windings → audible noise

Based on these symptoms, it is very likely that the selected transformer is not suitable for this application or operating point. A transformer designed specifically for this topology and power level (such as the one used in the evaluation board) is recommended to ensure proper performance and reliability.

The behavior your are describing (transformer heating, output voltage drop above ~0.45A, and audible noise) strongly indicates that the transformer is being operated outside its intended magnetic limits—most likely approaching core saturation.

In a forward converter using the MAX17599, the transformer must be specifically designed for the operating conditions (input voltage range, duty cycle, switching frequency, and active-clamp reset). If parameters such as turns ratio, magnetizing inductance, or core size are not properly matched, excessive magnetic flux can occur. This leads to:

• Increased magnetizing current and losses → heating

• Loss of efficient energy transfer → output voltage droop

• Mechanical vibration of the core/windings → audible noise

Based on these symptoms, it is very likely that the selected transformer is not suitable for this application or operating point. A transformer designed specifically for this topology and power level (such as the one used in the evaluation board) is recommended to ensure proper performance and reliability.