Line-Frequency Noise Suppressor to Reduce Audible Noise in Induction Heating Systems

Induction heating (IH) technology is widely used in domestic applications due to its high heating efficiency and environmentally friendly operations. As the performance of domestic IH appliances has advanced and user demands have increased, technologies enabling multi-coil operations and high-output power have been introduced. Additionally, heating performance for high-power operations with weakly magnetic-coupled vessels has been developed to enhance user convenience. However, when heating them, the high-power operation induces a large resonant current, resulting in audible noise caused by the line frequency. To reduce audible noises caused by the line frequency, active rectification techniques such as power factor corrections (PFC) circuits can convert the low-frequency AC into DC. However, this approach increases the entire IH system’s costs. This paper proposed a domestic IH system operating with a line-frequency noise suppressor (LNS) circuit to attenuate the audible noise issue. The LNS handles only partial power compared with PFCs, offering a cost advantage while providing an alternative solution to improve user convenience. The proposed IH system employing the LNS is experimentally verified with a 1.8-kW half-bridge IH inverter and LNS circuit prototypes.