This paper proposes a novel synchronous rectifier (SR) driving scheme for resonant converters. It is very suitable for high-frequency, high-efficiency, and high-power-density dc-dc resonant converters with SRs. In this paper, an LLC resonant converter with the proposed synchronous rectification is designed and analyzed. With the proposed driving scheme, the SR body diode conduction is reduced to almost zero. The driving scheme eliminates the reverse-recovery problem of SRs. Both current and voltage stresses are greatly decreased, and the conduction loss and switching loss of SRs are also reduced considerably. The experimental results show that the proposed LLC resonant converter with SRs can achieve low stress, high efficiency, and high power density.

A Novel Driving Scheme for Synchronous Rectifiers in LLC Resonant Converters

Several techniques to mitigate conducted electromagnetic interference (EMI) in switch-mode power supplies (SMPS) have been reported in literature. Of these, this paper reviews those techniques that are primarily meant for ac-dc and dc-dc power converters. The techniques are broadly classified based on two criteria-1) reduction of the noise after generation and 2) reduction of the noise at the generation stage itself. A detailed classification and review of various noise mitigation techniques currently available in literature are presented. It is believed that the classification and review of the conducted EMI mitigation techniques presented in this paper would be useful to SMPS researchers and designers.

Conducted EMI Mitigation Techniques for Switch-Mode Power Converters: A Survey

The matrix converter stands as an alternative in power conversion. It has no energy storage devices, performing the energy conversion by directly connecting input with output phases through bidirectional switches based on power semiconductors, allowing high-frequency operation. For this reason, it is known as the all-silicon power converter, featuring reduced size and weight. Forced commutations of the high number of semiconductors cause switching losses that reduce the efficiency of the system and imply the use of large heat sinks. This paper presents a novel method to reduce switching losses based on predictive control. The idea is to predict switching losses for every valid switching state of the converter, if applied during the next sampling time, and then, select the optimum state based on an evaluation criterion. The proposed strategy was experimentally tested on an 18-kVA matrix converter driving an 11-kW induction machine, reducing energy losses and increasing efficiency up to 3% compared to the basic strategy. As a consequence, the converter misuses less energy and requires smaller heat sinks.

Predictive Approach to Increase Efficiency and Reduce Switching Losses on Matrix Converters

The piecewise linear model has traditionally been used to calculate switching losses in switching mode power supplies due to its simplicity and good performance. However, the use of the latest low voltage power MOSFET generations and the continuously increasing range of switching frequencies have made it necessary to review this model to account for the parasitic inductances that it does not include. This paper presents a complete analytical switching loss model for power MOSFETs in low voltage switching converters that includes the most relevant parasitic elements. It clarifies the switching process, providing information about how these parasitics, especially the inductances, determine switching losses and hence the final converter efficiency. The analysis presented in this paper yields two different types of possible switching situations: capacitance-limited switching and inductance-limited switching. This paper shows that, while the piecewise linear model may be applied in the former, the proposed model is more accurate for the latter. Carefully-obtained experimental results, described in detail, support the analytical results presented.

An Insight into the Switching Process of Power MOSFETs: An Improved Analytical Losses Model

This paper presents an analytical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The limitations of a conventional buck converter in high-current (10 A or more), and high-frequency (HF, 3–30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are highlighted. The series capacitor buck converter exhibits desirable characteristics at HF, including lower switching loss, less inductor current ripple, automatic phase current balancing, duty ratio extension, and soft charging of the energy transfer capacitor. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at HF. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A). Some guidelines for inductor selection are provided, and a switch stress comparison reveals that the maximum converter switch stress is reduced by 30%.

Comparison of a Buck Converter and a Series Capacitor Buck Converter for High-Frequency, High-Conversion-Ratio Voltage Regulators

This paper proposes a new resonant gate drive circuit for driving both the control metal oxide semiconductor field effect transistor (MOSFET) and synchronous MOSFET in a synchronous buck converter. The circuit can recover more than 70% of the conventional gate drive loss. More importantly, the driving circuit can also reduce the switching loss. It charges and discharges the gate of MOSFET at a constant current during switching interval. Other advantages of the proposed circuit include better noise immunity for dv/dt turn on, less sensitive to parasitic track inductance. The experimental prototype shows that the loss reduction is 10% of the output power for 12 V input, 1.5 V/15 A output with switching frequency of 1 MHz.

A New Resonant Gate Drive Circuit for Synchronous Buck Converter

This work introduces an improved and simplified method to design electromagnetic interference (EMI) filters for both dc-dc and ac-dc switching power supplies. This method uses the practical approach of measuring the power supply noise spectrum and using the data to calculate the maximum possible magnitude and minimum possible magnitude of the differential mode and common mode noise impedances. The noise impedance magnitude information aids the design of the EMI filter. Phase information for the noise impedance is not required. In addition, information about the topology and control method of the power supply is not needed. This method solves the limitations of existing EMI filter design methods, which are either too complicated to use, or are based on ideal cases that neglect the noise impedance. The analysis and experimental results show that this method can guarantee that the required attenuation can be achieved, especially at low frequencies.

A novel EMI filter design method for switching power supplies

At high-frequency applications, the gate drive loss of the power metal oxide semiconductor field-effect transistor (MOSFET) becomes quite significant. A new dual-channel low side resonant gate drive circuit is proposed in this paper. The proposed drive circuit can provide two symmetrical drive signals for driving two MOSFETs. It charges and discharges the MOSFET gate capacitor with a constant current source. Both gate drive loss and, more importantly, switching loss can be reduced significantly. The proposed resonant gate drive circuit can be used to drive the synchronous MOSFETs in a current doubler or full-wave rectifier configuration. It can also be used to drive the primary MOSFETs in push-pull converters. Analysis, computer simulation, and experimental results show that significant power loss reduction is achieved by the proposed circuit.

A New Dual-Channel Resonant Gate Drive Circuit for Low Gate Drive Loss and Low Switching Loss

At high frequency applications, the gate drive loss of the power MOSFET becomes quite significant. A new dual channel low side resonant gate drive circuit is proposed in this paper. The proposed drive circuit can provide two symmetrical drive signals for driving two MOSFETs. It can recover most of the driving energy and clamp the gate and source voltage of the driven MOSFETs to either drive voltage or ground via a low impedance path. The circuit can also alleviate the dv/dt issue. The proposed circuit consists of four switches and a single winding inductor. The proposed resonant gate drive circuit can be used to drive the synchronous MOSFETs in a current doubler or full-wave rectifier. It can also be used to drive the primary MOSFETs in push-pull converters.

A New Dual Channel Resonant Gate Drive Circuit for

In this paper, a new non-isolated full bridge (NFB) topology is introduced to solve the narrow duty cycle and hard switching problems of the buck converter in low output voltage, high output current applications. In comparison to the Buck converter, it operates at a significantly wider duty cycle and can achieve zero voltage switching for the high side MOSFETs. The NFB significantly reduces the input peak current and transfers a portion of the primary side energy directly to the load thereby reducing the stress on the synchronous rectifiers and filter inductors. Using self-driven synchronous rectifiers, the body diode conduction loss is reduced since no dead time is required between the primary side MOSFETs and the synchronous rectifiers. Given these significant advantages, the NFB can achieve higher efficiency than a two and three phase interleaved buck at the same power level. The efficiency gain enables the NFB to operate at a high switching frequency thereby enabling smaller output inductors to be used to achieve improved dynamic performance. Experimental results and analysis demonstrate that the new NFB can significantly improve the performance of a voltage regulator. The prototype built operated at 500 kHz, 12 V input, 1 V output, up to 30 A load and achieved an efficiency of 84.4% at 30 A load. A 1 MHz prototype achieved a full load efficiency of 82.1%. In comparison, the efficiency of a two and three phase Buck prototype was 79.7% and 82.6% at 30 A load and at 500kHz switching frequency.

Sheng Ye

Papers

A New Resonant Gate Drive Circuit for Synchronous Buck Converter

A novel EMI filter design method for switching power supplies

A New Dual-Channel Resonant Gate Drive Circuit for Low Gate Drive Loss and Low Switching Loss

A New Dual Channel Resonant Gate Drive Circuit for

A Novel Non-Isolated Full Bridge Topology for VRM Applications