Quasi Resonant Inverter Load Recognition Method

Abstract

Induction heating (IH) technology is very popular in domestic applications because of its efficiency and safe operating properties. Resonant inverter circuits are widely used in IH systems owing to their high efficiency and soft-switching capability. Among the resonant inverters used in IH systems, the single-switch quasi-resonant inverter topology is generally preferred for low-cost and low-output-power applications. Despite the low-cost advantage of the quasi-resonant inverter, the soft-switching range is quite narrow, and it is not stable depending on the electrical parameters of the load that is desired to be heated. In other words, there is a critical relationship between the electrical characteristics of the pan, turn-on, and turnoff times, which are the control parameters of the semiconductor switch, and the safe working conditions. In addition, when the importance of closed-loop control methods is evaluated together with the selection of resonant circuit elements, it is essential to determine whether the load is suitable for heating, and to determine the electrical properties of the load to provide both reliable and efficient operating conditions. This study focuses on a new load-detection method based on circuit analysis for quasi-resonant induction hobs. After determining the load parameters, the turn-on and turn-off times of the semiconductor switch were determined to obtain the lowest possible switching loss. Therefore, the boundary conditions of the semiconductor switch are maintained within these limits. The proposed method and its advantages for the switch safe operating area were theoretically examined and proved through simulations and prototype circuits.INDEX TERMS Home appliances, induction cooking systems, induction cookers, load detection methods, resonant converters, single switch quasi resonant inverter. I. INTRODUCTIONInduction heating systems are mainly used in industrial, domestic, and medical applications owing to their user safety, efficient heating, easy cleaning, and fast heating features [1]-[3]. Domestic induction cooking apparatuses comprise at least one induction coil placed beneath the in vitro ceramic glass surface to heat up pans placed on top of the surface [4]- [9]. To heat the pan, the induction coil is supplied with an alternating current that generates a magnetic field at the same frequency as the coil current. This induces eddy currents that cause heating through the pan disposed on the induction surface [4], [6], [10]. The main components of induction heating systems are the rectifier unit, which is used for AC-DC conversion, and resonant inverter units [1], [11], [12]. A general power-transfer loop for domestic appliances is shown in Fig. 1.Depending on the balance between cost and performance, which must be evaluated for each application, different resonant inverter topologies have been proposed [13], [14]. FIGURE 1. General power transfer loop.

Study of half‐bridge series‐resonant induction cooker powered by line rectified DC with less filtering

“…C r (20) This set of ( 19) and ( 20) describes the state of the IH circuit over another T s /2 < t < T s . Since the two states of Figures 3b and 3c are dual antiphase, equations of ( 16)-( 17) and ( 18)-( 19) can form a complete differential equation to describe the IH circuit in a switching period, given by:…”

“…Techniques for online identification of pot materials using inductors as heating elements and sensors by spectral estimation and machine learning [18] or putting the sensing element into a built‐in system‐on‐chip [19] were proposed, respectively. The method presented for determining the loaded material is carried out by using circuit analysis and quasi‐resonance in [20]. In [21], least mean squares based on fuzzy c‐means clustering were used for load identification.…”

“…However, in terms of power estimation and stability, there are very few research and discussions about the familiar half-bridge cooking utensils. Even the latest studies, such as [20,21], the analysis is still based on driving with a near constant DC source. Ref.…”

Modelling and Simulation of Quasi-Resonant Inverter for Induction Heating under Variable Load

“…Single-switch inverters must be specifically designed for each single application because their main drawback is their scarce flexibility, as shown in [12,13]. Due to the single switch and its lack of control inputs, it has a quite narrow control window.…”

A double single-ended resonant inverter for low harmonic line frequency applications

“…The switching frequency was 70K Hz and the duty cycle is 35.7%. For safe operation, Ozturk et al, [17]proved that one-switch resonant topology can be implemented to detect the existence of a load.…”