A New Control Scheme for a Class-D Inverter with Induction Heating Jar Application by Constant Switching Frequency
ABSTRACT
In this paper, a simple power control scheme for a constant frequency Class-D inverter with a variable duty cycle isproposed. It is more suitable and acceptable for high- frequency induction heating (IH) jar applications. The proposedcontrol scheme has the advantages of not only wide power regulation range but also ease of control output power. Also itcan achieve a stable and efficient Zero-Voltage-Switching (ZVS) in a whole load range. The control principles of theproposed method are described in detail and its validity is verified through simulated and experimental results on 42.8kHzIGBT for induction heating rated on 1.6kW with constant frequency variable power.
Keywords: IH-Jar(Induction Heating-Jar), PFM(Pulse Frequency Modulation), PWM(Power Width Modulation),Class-D Inverter, ZVS(Zero-Voltage-Switching)
1. Introduction
Recently with the development of power semiconductordevices, new circuit techniques and control schemes,research on high frequency circuits and advanced powerdevices such as MOSFETs and IGBTs etc. have beenmany performed for high power applications [1]-[15]. Thevarious resonant inverters using power devices such asMOSFETs and IGBTs offer reduced switching loss byusing soft-switching technique and offer attractivepossibilities in developing higher frequencies of operation,higher efficiency, a smaller size and lighter weight.Induction heating (IH) has been a part of high powerapplications and widely used in industrial fields, office automation fields and electric home appliances. Inparticular, IH-Jar, which is an application of IH is used inhome appliances such as cookers [3]-[5].The requirements for IH applications are as follows:- High frequency switching - High efficiency- Power factor close to unity - Low cost- Wide load range - ReliabilityHigh-frequency Class-D inverters have become verypopular and become more and more widely used invarious applications. It must be effectively selectedaccording to the application in order to meet the inverterrequirements under a high frequency switching operationdue to load specifications. An important goal of powercontrol is to achieve an efficient and useful product.Generally, most induction heating applications use avariable frequency scheme to control output power [5]-[6].The frequency modulation control is a basic method that isapplied against the variation of load or line frequency.


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