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This paper proposes a Bang-Bang Charge Control (BBCC) method for LLC resonant converters. Instead of switching frequency control, the BBCC method utilizes the series resonant capacitor voltage level to trigger the MOSFETs' switching actions. Advantages of the proposed method include fast dynamic performance and simple implementations. Small-signal analysis shows that the loop bandwidth can achieve around 1/6 of the switching frequency in all operating conditions. Experimental results show that 5 to 25 A load step transients are completed within only seven switching cycles at both 400- and 300-V input-voltage conditions. Practical considerations are also discussed in detail. [ABSTRACT FROM AUTHOR]

LLC converters face challenges in high-current applications, where the high conduction loss limits the maximum load capacity and reduces efficiency. Interleaving technique can be used to solve this problem, but the component tolerances of the resonant tanks will cause severe load sharing problem. The SCC-LLC converter was proposed to solve the load sharing problem. However, due to its constant switching frequency operation, it has some limitations over complete line and load variation compared to conventional LLC converters. In this paper, a new control strategy is proposed for the SCC-LLC converter, which enables variable switching frequency operation; thus, it provides uncompromised performance while achieving interleaved operation. Analyses and a design method are provided, and a 600-W two-phase interleaved SCC-LLC prototype is built to verify the feasibility. [ABSTRACT FROM AUTHOR]

In this paper, the concept of the adaptive current source drivers (CSDs) is proposed for the high-frequency synchronous buck converters. Compared to the previous CSD circuits, the adaptive CSD can achieve adjustable drive current and drive voltage according to different load condition. The benefit is that higher drive current and voltage lead to lower switching loss and conduction loss when the load current increases. Therefore, the adaptive CSD is able to realize optimal design to reduce the switching loss, the gate drive loss, and the conduction loss in a wide load range. It should be noted that the adaptive concept is suitable for both the continuous and discontinuous CSDs regardless the drive circuit topologies. Through investigating the CSD circuits, one simple method to achieve the adaptive drive current based on the adaptive voltage is proposed. A 12 V input, 1.3 V output, and 1-MHz synchronous buck converter with the continuous and discontinuous CSDs was built, respectively, to verify the advantages of the proposed adaptive concept and efficiency improvement. [ABSTRACT FROM AUTHOR]

This paper proposes a new current-source driver (CSD) with discontinuous inductor current. Compared to other CSDs proposed in the previous work, the most important advantage of the proposed CSD is the small inductance (typically, 20 nH at 1 MHz switching frequency). This translates into the footprint reduction of as much as 90% compared with the continuous CSDs. Other features of the proposed CSD includes: 1) fast switching speed and reduced switching loss; 2) discontinuous inductor current with low circulating loss; 3) gate energy recovery; and 4) wide range of duty cycle and switching frequency. The experimental results verified the functionality of the proposed CSD. At 12 V input, 1.3 V output, and 1 MHz switching frequency, the new CSD improves the efficiency from 80.7% using a conventional driver to 85.7% at 25 A output, and at 30 A output, from 77.9% to 84.4%. [ABSTRACT FROM AUTHOR]

In this paper, a new self-driven zero-voltage-switching (ZVS) nonisolated full-bridge converter is presented for 12-V input VRM applications. The advantages of the new circuit are: 1) duty cycle extension; 2) ZVS of all the control MOSFETs; 3) lower voltage stress and reduced reverse recovery loss of the synchronous rectifier (SR) MOSFETs; 4) high-drive voltage to reduce RDS(ON) and the conduction loss of the SRs due to gate energy recovery capability; and 5) reduced body-diode conduction and no external drive IC chips with dead time control needed for SRs. Existing multiphase buck controllers and buck drivers can be directly used in the proposed converter. The experimental results verify the principle of operation and significant efficiency improvement. At 12 V input, 1.3 V output voltage, and 1 MHz switching frequency, the proposed converter improves the efficiency, using the buck converter from 80.7% to 83.6% at 50 A, and from 77.9% to 80.5% at 60 A.With two parallel SRs, the efficiency is further improved from 83.6% (single SR) to 84.7% (two SRs) and at 60 A, the efficiency is improved from 80.5% (single SR) to 83.2% (two SRs). [ABSTRACT FROM AUTHOR]

This paper presents a new nonisolated asymmetrical buck voltage regulator module. A transformer is used to extend the extremely low duty cycle of a conventional buck converter. Turn-off losses can be significantly reduced due to the extension of duty cycle, and there are no turn-on losses owing to the zero-voltage turn-on condition. At the same time, the voltage stress over the synchronous rectifier MOSFETs is also reduced. There- fore, the reverse-recovery losses of the body diode can be reduced. Furthermore, the MOSFETs with lower voltage rating and lower RDS(on) can be used to reduce the conduction losses. In order to reduce the turn-off losses above the switching frequency of 1 MHz further, a new current-source driver is also proposed, which is suitable to this new topology. A 12-V input prototype with the switching frequency of 1 MHz was implemented. Simulation and experimental results verify the functionality and benefits of the proposed topology. [ABSTRACT FROM AUTHOR]

This paper proposes a new current-source gate drive circuit for a synchronous buck converter. The proposed driver can drive two MOSFETs independently with different drive currents for optimal design. For the control MOSFET, the optimal design involves a tradeoff between switching loss reduction and drive circuit loss; while for the synchronous-rectifier MOSFET, the optimal design involves a tradeoff between body diode conduction loss and drive circuit loss. Furthermore, the new drive circuit can achieve: 1) significant switching loss reduction; 2) gate energy recovery and high gate drive voltage to reduce RDS(ON) conduction losses; 3) reduced conduction loss and reverse recovery loss of the body diode; and 4) zero-voltage switching of all the drive switches. The improved driver using integrated inductors is presented with multiphase buck voltage regulators (VRs) to reduce the number of magnetic cores and the core loss. The experimental results prove that a significant efficiency improvement has been achieved. At 1.5 output, the new driver improves the efficiency from 84% using a conventional driver to 87.3% at 20 A, and at 30 A, from 79.4% to 82.8%. Overall, the new driver approach is attractive from the standpoints of both performance and cost-effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, a new resonant gate-drive circuit is proposed to recover a portion of the power-MOSFET-gate energy that is typically dissipated in high-frequency converters. The proposed circuit consists of four control switches and a small resonant inductance. The current through the resonant inductance is discontinuous in order to minimize circulating-current conduction loss that is present in other methods. The proposed circuit also achieves quick turn-on and turn-off transition times to reduce switching and conduction losses in power MOSFETs. An analysis, a design procedure, and experimental results are presented for the proposed circuit. Experimental results demonstrate that the proposed driver can recover 51% of the gate energy at 5-V gate-drive voltage. [ABSTRACT FROM AUTHOR]

Resonant inverters are connected to a high-frequency ac (HFAC) bus, where power is delivered to different locations for points-of-use power management. Such a power distribution system subjects to more perturbations and load uncertainties than inverters operating with single load. A novel voltage control method is proposed in this paper for a high-frequency full-bridge resonant inverter with series-parallel resonant tank. A modified one-cycle controlled phase-shift modulation is proposed to effectively compensate the input line variations. The uncertainty model of the high frequency resonant inverter is developed and analyzed with the resonant circuit component tolerance, input line and load variations taken into design considerations. The voltage feedback controller is designed based on the H∞ robust control theory and is implemented with analog discrete devices. The proposed control scheme has the advantages of fast response for both input line and load perturbations. It also ensures a wide range of system stability and guarantees robustness of the power converter. Both simulations and experimental results are provided to verify with the theoretical analysis through an experimental prototype of a full-bridge resonant inverter with an output power of 150-W operating at 1 MHz and an output voltage of 28 V (rms). [ABSTRACT FROM AUTHOR]

Resistance spot welding is used to join two or more metal objects, and the technique is widely used in, for example, the automotive and electrical industries. This paper introduces the use of the κ-nearest-neighbor (κnn) method to identify similar welding processes. The two main benefits achieved from knowing the most similar process are the following: 1) The time needed for the setup of a new process can be substantially reduced by restoring the process parameters leading to high-quality joints, and 2) the quality of new welding spots can be predicted and improved using the stored information of a similar process. In this paper, the basic κnn method was found to be inadequate, and an extension of the κnn method, which is called similarity measure, was developed. The similarity measure provides information of how similar the new process is by using the distance to the κnns. Based on the results, processes can be classified, and the similarity measure proved to be a valuable addition to the existing methodology. Furthermore, process information can provide a major benefit to welding industry. [ABSTRACT FROM AUTHOR]

A high-efficiency two-stage resonant inverter with effective control of both the magnitude and phase angle of the output voltage was proposed in this paper for high-frequency ac (HFAC) power-distribution applications, where a number of resonant inverters need to be paralleled. In order to parallel multiple resonant inverters of the same operation frequency, each inverter module needs independent control of the phase angle and magnitude of the output voltage. It is also desirable that the output voltage has very low total harmonics distortion, as well as high efficiency over wide input and load ranges. The proposed resonant inverter consists of two stages. The first stage is a two-switch dc/dc converter with zero-voltage transition, and the second stage is a half-bridge resonant dc/ac inverter with fixed duty ratio. A series-parallel resonant tank is used to achieve high waveform quality of the output voltage. The magnitude of the output voltage is regulated through the duty-ratio control of the first stage with pulsewidth modulation. The phase angle of the output voltage is regulated through a pulse-phase-modulation control of the second stage. The proposed resonant inverter has the advantages of better waveform quality, wide range of input and load variations for soft-switching, and independent control of the phase angle and magnitude of the output voltage, making it an attractive candidate for applications where a number of resonant inverters need to be placed in parallel to the HFAC bus and a number of distributed loads are connected to the HFAC bus. The performance is verified with both simulation and experiments. [ABSTRACT FROM AUTHOR]

The control issue of multiple inverter modules operated in parallel is investigated for high-frequency alternative current (HFAC) power distribution architectures, where multiple high-frequency resonant inverters are connected in parallel to the high-frequency high-voltage low-current (HVLC) ac bus, to feed a number of point-of-use power supplies. The circulating current in the multiple inverter system is analyzed first. A novel control scheme is proposed based on, the active and reactive current decomposition concept. In the proposed control, there are two loops: 1) the current sharing control loop and 2) the voltage feedback control loop. For the current sharing loop, the active current and reactive current are controlled separately. It is shown that the minimization of the circulating current can be achieved if both the active current and reactive current of the equivalent load are evenly distributed among activated inverter modules. This control method is superior to the scalar control where only the magnitudes of the currents are controlled. Performance is verified with both simulations and experiments on a prototype HFAC power distribution system where two two-stage resonant inverter modules of 500 kHz and 100 W are connected in parallel through small connection inductors to the 500-kHz 28-V rms HFAC bus. [ABSTRACT FROM AUTHOR]

A new soft-switching technique for buck, boost, and buck-boost converters using coupled inductors is proposed in this paper. The principles of operation of these converters are analyzed in detail. An additional winding is added on the same core of the main inductor for the purpose of commutation. By using hysteresis current control, zero-voltage switching conditions are ensured over a wide load range. The main inductor current is kept in continuous conduction mode with small ripple, which allows high output power and small filter parameters. Also, the switching frequency can be kept constant when the load changes. Prototypes of buck, boost, and buck-boost converters have been built to verify the proposed concept. The experimental results are presented and they verify the analysis. [ABSTRACT FROM AUTHOR]

Presents a study that developed a dynamically robust current control technique for the boost type power factor preregulator. Background on the principle behind the proposed control technique; Analysis of small signal stability; Examination of large-signal stability using computer simulation.

Presents a study which proposed a novel power factor correction technique for single-phase boost type alternating current-to-direct current converters in continuous conduction mode. Principle of the diode current sensing; Design and compensation in voltage feedback loop to achieve fast response and minimize input current harmonics; Experimental results and conclusions.