EPE Association: EPE 2007 - Subtopic 04-3 - DS: Soft switching converters and control

EPE 2007 - Subtopic 04-3 - DS: Soft switching converters and control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 04: 'Soft switching converters and control' > EPE 2007 - Subtopic 04-3 - DS: Soft switching converters and control

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   A Non-Isolated Interleaved ZVT Boost Converter with High Step-Up Conversion Derived from its Isolated Counterpart
By WU Jiande; HE Xiangning; LI Wuhua; XIE Rui [View]
[Download]

Abstract: The loss distribution of the interleaved boost converter is analyzed in high step-up non-isolated applications in this paper. A novel interleaved ZVT boost converter is derived from its isolated counterpart to overcome the disadvantages of the conventional boost converter in high step-up conversion. With the proposed converter, the extreme duty cycle is avoided and the switch voltage stress is reduced. And only one set of clamp circuit composed of an auxiliary switch and a small capacitor is required for the interleaved two phases to recycle the leakage energy and to clamp the turn-off voltage spikes, which simplifies the circuit structure. The output diode turn-off current falling rate is controlled by the leakage inductance to alleviate the reverse -recovery problem and to reduce the reverse-recovery losses. The experimental results show that the derived interleaved ZVT boost converter is suitable for high current, high efficiency and high step-up non-isolated applications.

   An Isolated Interleaved Active-Clamp ZVT Flyback-Boost Converter with Coupled Inductors
By SHI Jianjiang; HU Min; HE Xiangning; LI Wuhua [View]
[Download]

Abstract: The fundamental limitations of interleaved flyback converters for high step-up DC/DC applications are analyzed in this paper. A novel interleaved flyback-boost converter is derived with further modifications on the interleaved flyback converter, which extends the voltage gain and reduces the voltage stress of the switch. The active-clamp circuits are employed to recycle the leakage energy. Both the main and the auxiliary switches can realize ZVT soft switching condition. The turn-off voltage spikes of the main switch are clamped by the active-clamp circuits. Due to the leakage inductance of the coupled inductors, the output diode reverse-recovery problem is alleviated dramatically. A 1 kW prototype with 40V-input-to-380V-output operating at 50 kHz switching frequency built in the lab verifies the effectiveness of the proposed converter. The efficiency of nearly 90\% at full load is achieved. More than 7\% efficiency improvements with active-clamp circuits are achieved compared with the case with RCD snubbers.

   Analysis of Self-Oscillating DC-DC Resonant Power Converters using a Hysteretic Relay
By WILLIAMS David; FOSTER Martin; BINGHAM Chris; STONE Dave; GILBERT Adam [View]
[Download]

Abstract: The paper presents a technique for exciting resonant DC-DC converters in a self-oscillating manner. The analysis necessary to predict the behaviour of such converters is also given. The oscillation is based on the behaviour of a hysteretic relay with a negative hysteresis transition. Self-oscillating converters benefit from higher efficiency/higher power density than their non-self-oscillating counterparts as they can be operated closer to the tank resonant frequency. The self-oscillating mechanism presented here is also simple and cost effective to implement. A prototype converter is presented in order to verify the theoretical claims.

   Control method and snubber selection for a 5 MW wind turbine single active bridge DC/DC converter
By MAX Lena; THIRINGER TorbjÃ¶rn [View]
[Download]

Abstract: In this paper the design and control aspects of the single active bridge DC/DC converter are investigated for the application to be used in a 5 MW wind turbine. The control of the converter is discussed as well as different design considerations as turn-off snubber circuits and leakage inductance of the transformer. It is found that the variable frequency control with a turn-off snubber capacitor gives the lowest losses for the application in a wind turbine. The losses for the single active bridge converter using variable frequency control is 3.2 - 3.8 \% of the input power, depending on the position in the wind farm, compared to 3.8 - 4.1 \% for the converter with constant frequency control.

   Control Model of a Closed Loop Power-Controlled Series-Type Resonant Induction Heating System
By CEGLIA Gerardo; GIMENEZ Maria; GUZMAN Victor; WALTER Julio [View]
[Download]

Abstract: This work presents the mathematical modeling of a power controlled, resonant operated inductive heating system. Experimentally the power is measured over the heating coil and processed to have the real power as a feedback signal that manages a pulse density (delta) modulator topology with a PID compensation network. The results shows that it is possible to directly control the real output power of the inverter, opening the possibility to obtain information about the energy transferred to the load in situations where this is critical, for example, in precise heating processes.

   DC-reactor-less hybrid DC-DC converter with a core composed of four legs
By MATSUDA Yoshiaki; WAKATSUKI Yoshimasa; UNNO Hiroshi; SAITO Tadashi; SAOTOME Hideo; KIKUCHI Yoshihiko; YUKAWA Tadashi; YOSHIAKI Matsuda [View]
[Download]

Abstract: Efficiency improvement and cost reduction are important requirements for the design of DC-DC converters. Zero voltage switching is one good solution for increasing efficiency, and an active clamp circuit is useful for implementing it effectively. A cost reduction could be achieved by devising a new transformer that functions not only as a conventional transformer but also as a DC reactor that reduces the switching device peak current. The magnetic core of the new transformer is composed of four legs. A novel hybrid DC-DC converter in which forward and fly-back converters are combined by using the transformer was developed. However, no design methodology for such a transformer has yet been established. Therefore, the modeling of the excitation circuit of the transformer is required. This paper proposes a novel method that simulates the operations of the DC-DC converter and estimates the magnetic flux distribution in the new transformer. The magnetic circuit of the transformer is transformed into its equivalent electric circuit with two ideal transformers. The performance of the DC-DC converter was examined by circuit simulations including the magnetic circuit of the transformer. Circuit simulation results agree fairly well with experimental ones.

   Feed-forward control of non-linear inductors providing soft-switching of dc-dc-converters
By STADLER Michael; PFORR Johannes [View]
[Download]

Abstract: A novel auxiliary circuit with a current controlled non-linear inductor has been developed to achieve soft-switching for different converter topologies. This paper outlines the operation principle of the auxiliary circuit and gives details about the control of the non-linear inductor. A model has been developed that allows the calculation of the control current dependent on the operating point of the converter. This model has been implemented into a digital controller. A prototype converter has been built and tested to verify theoretical predictions. Measurements have shown that the efficiency of the prototype converter is greatly improved by the auxiliary circuit. Experimental results are in good correlation with theoretical prediction.

   High Efficiency Control Methods for Class-E Resonant Converter for Step-Down Applications Using Piezoelectric Transformers (PT)
By NITTAYARUMPHONG Sadachai [View]
[Download]

Abstract: An array of solutions to handle the losses in switching mode power supplies such as zero-voltage-switching (ZVS), or as zero-current-switching (ZCS), have been developed and applied. There is still a limitation to eliminate the losses in the switching devices to be near to zero. The loss characteristics of a switching IGBT, such as turn-off switching loss due to the tail current under either ZVS or ZCS condition is defined as an important factor that limits the efficiency of the converter, especially in small size power supplies used at high operation switching frequency. In this work the dissipative energy of a resonant converter using PT is not reduced only by ZVS condition, but also by non-switched intervals during the operation, called burst mode. The system is classified to represent two cases of output load, called full load and light load. In the light load situation, the converter can optimize the transferred energy without losing the constant output regulation behaviour, which is done by burst mode control. Different burst mode classification methods between full load and light load have been investigated for different control techniques. The frequency based burst mode classification was evaluated to be most advantageous over phase-angle or switch current time interval observation, perspectively independent of the resonant converter topology. An active burst mode technique has been derived for output voltage feed-back. The work has been proved for a Class-E topology, fulfilling the "Code of conduct on efficiency of external power supplies" in a 3 Watts off-line power supply application.

   ZVS-ZCS Full-Bridge DC-DC Converter for Voltage Step-Up in Fuel Cell Distributed Generation Systems
By BOJOI Radu; GRIVA Giovanni; TENCONI Alberto; KOVACEVIC Goran [View]
[Download]

Abstract: This paper proposes a ZVS-ZCS full-bridge converter for voltage step-up applications, where only a few solutions have been proposed in the literature. A new auxiliary circuit is used on the high-voltage side of the proposed converter to achieve Zero Current Switching (ZCS) for one converter leg, while Zero Voltage Switching (ZVS) is achieved for the other leg by means of snubber capacitors. The principle of operation has been analyzed and verified on a 20 kW, 50 kHz prototype converter. The proposed converter can be a viable solution for fuel cell distributed generation systems, where voltage boost and efficiency are key issues.

EPE 2007 - Subtopic 04-3 - DS: Soft switching converters and control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 04: 'Soft switching converters and control' > EPE 2007 - Subtopic 04-3 - DS: Soft switching converters and control
	[return to parent folder]

	A Non-Isolated Interleaved ZVT Boost Converter with High Step-Up Conversion Derived from its Isolated Counterpart By WU Jiande; HE Xiangning; LI Wuhua; XIE Rui	[View] [Download]
Abstract: The loss distribution of the interleaved boost converter is analyzed in high step-up non-isolated applications in this paper. A novel interleaved ZVT boost converter is derived from its isolated counterpart to overcome the disadvantages of the conventional boost converter in high step-up conversion. With the proposed converter, the extreme duty cycle is avoided and the switch voltage stress is reduced. And only one set of clamp circuit composed of an auxiliary switch and a small capacitor is required for the interleaved two phases to recycle the leakage energy and to clamp the turn-off voltage spikes, which simplifies the circuit structure. The output diode turn-off current falling rate is controlled by the leakage inductance to alleviate the reverse -recovery problem and to reduce the reverse-recovery losses. The experimental results show that the derived interleaved ZVT boost converter is suitable for high current, high efficiency and high step-up non-isolated applications.

	An Isolated Interleaved Active-Clamp ZVT Flyback-Boost Converter with Coupled Inductors By SHI Jianjiang; HU Min; HE Xiangning; LI Wuhua	[View] [Download]
Abstract: The fundamental limitations of interleaved flyback converters for high step-up DC/DC applications are analyzed in this paper. A novel interleaved flyback-boost converter is derived with further modifications on the interleaved flyback converter, which extends the voltage gain and reduces the voltage stress of the switch. The active-clamp circuits are employed to recycle the leakage energy. Both the main and the auxiliary switches can realize ZVT soft switching condition. The turn-off voltage spikes of the main switch are clamped by the active-clamp circuits. Due to the leakage inductance of the coupled inductors, the output diode reverse-recovery problem is alleviated dramatically. A 1 kW prototype with 40V-input-to-380V-output operating at 50 kHz switching frequency built in the lab verifies the effectiveness of the proposed converter. The efficiency of nearly 90\% at full load is achieved. More than 7\% efficiency improvements with active-clamp circuits are achieved compared with the case with RCD snubbers.

	Analysis of Self-Oscillating DC-DC Resonant Power Converters using a Hysteretic Relay By WILLIAMS David; FOSTER Martin; BINGHAM Chris; STONE Dave; GILBERT Adam	[View] [Download]
Abstract: The paper presents a technique for exciting resonant DC-DC converters in a self-oscillating manner. The analysis necessary to predict the behaviour of such converters is also given. The oscillation is based on the behaviour of a hysteretic relay with a negative hysteresis transition. Self-oscillating converters benefit from higher efficiency/higher power density than their non-self-oscillating counterparts as they can be operated closer to the tank resonant frequency. The self-oscillating mechanism presented here is also simple and cost effective to implement. A prototype converter is presented in order to verify the theoretical claims.

	Control method and snubber selection for a 5 MW wind turbine single active bridge DC/DC converter By MAX Lena; THIRINGER TorbjÃ¶rn	[View] [Download]
Abstract: In this paper the design and control aspects of the single active bridge DC/DC converter are investigated for the application to be used in a 5 MW wind turbine. The control of the converter is discussed as well as different design considerations as turn-off snubber circuits and leakage inductance of the transformer. It is found that the variable frequency control with a turn-off snubber capacitor gives the lowest losses for the application in a wind turbine. The losses for the single active bridge converter using variable frequency control is 3.2 - 3.8 \% of the input power, depending on the position in the wind farm, compared to 3.8 - 4.1 \% for the converter with constant frequency control.

	Control Model of a Closed Loop Power-Controlled Series-Type Resonant Induction Heating System By CEGLIA Gerardo; GIMENEZ Maria; GUZMAN Victor; WALTER Julio	[View] [Download]
Abstract: This work presents the mathematical modeling of a power controlled, resonant operated inductive heating system. Experimentally the power is measured over the heating coil and processed to have the real power as a feedback signal that manages a pulse density (delta) modulator topology with a PID compensation network. The results shows that it is possible to directly control the real output power of the inverter, opening the possibility to obtain information about the energy transferred to the load in situations where this is critical, for example, in precise heating processes.

	DC-reactor-less hybrid DC-DC converter with a core composed of four legs By MATSUDA Yoshiaki; WAKATSUKI Yoshimasa; UNNO Hiroshi; SAITO Tadashi; SAOTOME Hideo; KIKUCHI Yoshihiko; YUKAWA Tadashi; YOSHIAKI Matsuda	[View] [Download]
Abstract: Efficiency improvement and cost reduction are important requirements for the design of DC-DC converters. Zero voltage switching is one good solution for increasing efficiency, and an active clamp circuit is useful for implementing it effectively. A cost reduction could be achieved by devising a new transformer that functions not only as a conventional transformer but also as a DC reactor that reduces the switching device peak current. The magnetic core of the new transformer is composed of four legs. A novel hybrid DC-DC converter in which forward and fly-back converters are combined by using the transformer was developed. However, no design methodology for such a transformer has yet been established. Therefore, the modeling of the excitation circuit of the transformer is required. This paper proposes a novel method that simulates the operations of the DC-DC converter and estimates the magnetic flux distribution in the new transformer. The magnetic circuit of the transformer is transformed into its equivalent electric circuit with two ideal transformers. The performance of the DC-DC converter was examined by circuit simulations including the magnetic circuit of the transformer. Circuit simulation results agree fairly well with experimental ones.

	Feed-forward control of non-linear inductors providing soft-switching of dc-dc-converters By STADLER Michael; PFORR Johannes	[View] [Download]
Abstract: A novel auxiliary circuit with a current controlled non-linear inductor has been developed to achieve soft-switching for different converter topologies. This paper outlines the operation principle of the auxiliary circuit and gives details about the control of the non-linear inductor. A model has been developed that allows the calculation of the control current dependent on the operating point of the converter. This model has been implemented into a digital controller. A prototype converter has been built and tested to verify theoretical predictions. Measurements have shown that the efficiency of the prototype converter is greatly improved by the auxiliary circuit. Experimental results are in good correlation with theoretical prediction.

	High Efficiency Control Methods for Class-E Resonant Converter for Step-Down Applications Using Piezoelectric Transformers (PT) By NITTAYARUMPHONG Sadachai	[View] [Download]
Abstract: An array of solutions to handle the losses in switching mode power supplies such as zero-voltage-switching (ZVS), or as zero-current-switching (ZCS), have been developed and applied. There is still a limitation to eliminate the losses in the switching devices to be near to zero. The loss characteristics of a switching IGBT, such as turn-off switching loss due to the tail current under either ZVS or ZCS condition is defined as an important factor that limits the efficiency of the converter, especially in small size power supplies used at high operation switching frequency. In this work the dissipative energy of a resonant converter using PT is not reduced only by ZVS condition, but also by non-switched intervals during the operation, called burst mode. The system is classified to represent two cases of output load, called full load and light load. In the light load situation, the converter can optimize the transferred energy without losing the constant output regulation behaviour, which is done by burst mode control. Different burst mode classification methods between full load and light load have been investigated for different control techniques. The frequency based burst mode classification was evaluated to be most advantageous over phase-angle or switch current time interval observation, perspectively independent of the resonant converter topology. An active burst mode technique has been derived for output voltage feed-back. The work has been proved for a Class-E topology, fulfilling the "Code of conduct on efficiency of external power supplies" in a 3 Watts off-line power supply application.

	ZVS-ZCS Full-Bridge DC-DC Converter for Voltage Step-Up in Fuel Cell Distributed Generation Systems By BOJOI Radu; GRIVA Giovanni; TENCONI Alberto; KOVACEVIC Goran	[View] [Download]
Abstract: This paper proposes a ZVS-ZCS full-bridge converter for voltage step-up applications, where only a few solutions have been proposed in the literature. A new auxiliary circuit is used on the high-voltage side of the proposed converter to achieve Zero Current Switching (ZCS) for one converter leg, while Zero Voltage Switching (ZVS) is achieved for the other leg by means of snubber capacitors. The principle of operation has been analyzed and verified on a 20 kW, 50 kHz prototype converter. The proposed converter can be a viable solution for fuel cell distributed generation systems, where voltage boost and efficiency are key issues.