Chayant Koompai

An Improved

This paper proposes a modified LLC resonant load configuration of a full-bridge inverter for induction-heating applications. The LLC load configuration is a combination of a series inductor, a matching transformer, and an inductor and a capacitor connected in parallel. The output power is controlled using the asymmetrical voltage-cancellation technique. With the use of a phase-locked loop control, the operating frequency is automatically adjusted to maintain a small constant lagging phase angle under load-parameter variation during the heating process. The proposed configuration has the benefit of smaller inductance and inherent short-circuit protection capability in case a short circuit occurs at the induction coil or from transformer saturation. The validity of the proposed method is verified through computer simulation and hardware experiment at an operating frequency range of 108.7-110.6 kHz.

LLC

The paper describes a full-bridge current-fed inverter for forging applications. Inverter is implemented by using IGBT in series with diodes as its switching devices. The operating frequency is automatically tracked to maintain a small constant leading phase angle when load parameters change. The load voltage is controlled to protect the switches. The output power can be adjusted by varying the input current from phase controlled rectifiers which is a part of current source. The system has been operated at 15.5-16.8 kHz. The output power transferred to the load is 1,595 watts. It can heat the steel work pieces with 15 mm diameter and 120 mm long from room temperature to approximately 1100/spl deg/C within 30 seconds with 0.97 leading power factors on the input side.

Resonant Inverter for Induction-Heating Applications With Asymmetrical Control

This paper presents an asymmetrical control with phase lock loop for series resonant inverters. This control strategy is used in full-bridge topologies for induction cookers. The operating frequency is automatically tracked to maintain a small constant lagging phase angle when load parameters change. The switching loss is minimized by operating the IGBT in the zero voltage resonance modes. The output power can be adjusted by using asymmetrical voltage cancellation control which is regulated with a PWM duty cycle control strategy.

Full-bridge current-fed inverter with automatic frequency control for forging application

The variable-frequency asymmetrical voltage-cancellation (VFAVC) control is proposed in this paper to control the output power for a series resonant load with a full-bridge inverter for home appliance as induction cooking. The asymmetrical voltage-cancellation is used for controlling the output power. With the low quality factor loads, a fixed-frequency control might lead to non-zero-voltage-switching (NON-ZVS) operation. The proposed control strategy ensures the ZVS operation for switching loss reduction by varying the switching frequency slightly higher than the resonant frequency. By using the ZVS constant, the new control strategy is proposed by varying the switching frequency according to the output power. Moreover, this proposed control can improve the overall efficiency of inverter system. The experimental results are given in this paper to verify the proposed control method.

Asymmetrical control with phase lock loop for induction cooking appliances

This paper presents a dual output full-bridge series resonant inverter with improved asymmetrical voltage-cancellation control for induction cooking appliance. The proposed control scheme can adjust the output power separately, and achieves the zero-voltage switching (ZVS) condition with improved efficiency. A laboratory prototype has been implemented on a DSPIC2010 controller. The experimental results are presented to validate the proposed control scheme.

A variable-frequency asymmetrical voltage-cancellation control of series resonant inverters in domestic induction cooking

This paper proposes a high efficiency LLC resonant inverter for induction heating applications by using asymmetrical voltage cancellation control. The proposed control method is implemented in a full-bridge topology for induction heating application. The operating frequency is automatically adjusted to maintain a small constant lagging phase angle under load parameter variation. The output power is controlled using the asymmetrical voltage cancellation technique. The LLC resonant tank is designed without the use of output transformer. This results in an increase of the net efficiency of the induction heating system. The validity of the proposed method is verified through computer simulation and hardware experiment at the operating frequency of 93 to 96 kHz.

A dual output series resonant inverter with improved asymmetrical voltage-cancellation control for induction cooking appliance

A class D current source resonant inverter (CSRI) for induction heating power supplies for ferromagnetic load is proposed in this paper. The converter operates in zero-current switching mode. The switching devices are connected through the common ground and need only a single dc power supply for the gate driver circuitry. A small input inductor (500 µH) is used for shaping the line current with the aim of unity power factor operation on the line input. The operating frequency of the CSRI is automatically adjusted to maintain a small constant leading phase angle under load parameter variation. The maximum output power transferred to the load for this prototype is 1.26 kW. It can heat a 30-mm diameter and 150-mm long steel work-piece from room temperature to approximately 680ºC within 10 minutes.

LLC resonant inverter for induction heating with asymmetrical voltage-cancellation control

This paper presents a high efficiency LCCL series resonant inverter for ultrasonic dispersion system with resonant frequency tracking and asymmetrical voltage cancellation control. With the proposed control, the operating frequency of the inverter is automatically adjusted to track the resonant frequency under load parameter variation due to surrounding condition. The zero-voltage switching (ZVS) is maintained throughout the operation. The output power is controlled using the asymmetrical voltage cancellation (AVC) technique. A full-bridge hardware prototype is constructed and the control algorithm is implemented using an STM32F4 microcontroller. Computer simulation and hardware experiment are provided at an operating frequency range of 37-42 kHz and the output power of 30-125 W.

A soft switching class D current source inverter for induction heating with ferromagnetic load

This paper describes quasi-resonant converter for induction heating in high temperature application. Converter is implemented by using IGBT as its switching. The switching loss is minimized by operating the IGBT in the zero voltage resonance modes. The output power can be adjust by varying the switching frequency of converter. The prototype is tested under load-parameter variation during the heating process and it is rated at approximately 1000W, with operating frequency ranging from 5-7 kHz. The operation principles of quasi-resonant are investigated and validity is verified by simulation and experimental results.

LCCL series resonant inverter for ultrasonic dispersion system with resonant frequency tracking and asymmetrical voltage cancellation control

This paper presents a design of a 1.5kW half-bridge resonant inverter system for induction heating applications. The inverter operates at a switching frequency range of 20–40 kHz where the zero voltage condition operation is maintained. The rectifier circuit employs a pulse-width modulation (PWM) operating at the switching frequency of 10 kHz. With the proposed system, the output power can be controlled by both the inverter frequency and the dc bus voltage. This provides sufficiently fast response to alleviate the switchs current under no load situation (i.e. no work-piece in the induction coil). The advantages of the proposed control system are small size of filter circuitry, low switching loss and faster response at a no load condition.