M.H. Pong

A novel high frequency current-driven synchronous rectifier applicable to most switching topologies

A novel current-driven synchronous rectifier is presented in this paper. With the help of a current sensing energy recovery circuit, the proposed current-driven synchronous rectifier can operate at high switching frequency with high efficiency. Compared with those voltage-driven synchronous rectification solutions, this current-driven synchronous rectifier has several outstanding characteristics. It can be easily applied to most switching topologies like an ideal diode. Constant gate drive voltage can be obtained regardless of line and load fluctuation. This makes it desirable in high input range application. Power converters designed with this synchronous rectifier are also capable of being connected in parallel without taking the risk of reverse power sinking. Their principle of operation is given in the paper. A series of experiments verify the analysis and demonstrate the merits.

A low cost DC-DC stepping inductance voltage regulator with fast transient loading response

A fast transient converter modified from a buck converter is proposed. It employs a stepping inductance method by which the output inductor of a buck converter is replaced by two inductors connecting in series. One has large inductance and the other has small inductance. An inductor with small inductance will take over the output inductor during transient load change and speed up dynamic response. In steady state, the large inductance takes over and keeps substantially small ripple current and minimizes RMS loss. An experiment of a 2 V DC-DC converter put under a 20 A transient load change demonstrates the merit of this approach. It is a low cost method applicable to converters with an output inductor.

EMI due to electric field coupling on PCB

In switching power converter circuits, EM noise can couple between PCB traces through the effect of electric field coupling. An experiment using a flyback power converter verifies the severity of this effect. Further experiments and field plots confirm that a good PCB layout can significantly reduce conducted EMI due to unintentional E-field coupling.

Analysis of buck-boost converter inductor loss using a simple online B-H curve tracer

A simple method to plot online B-H curves and calculate the core loss of the inductor in a conventional buck-boost power converter is developed. In order to obtain a reliable loss data, measurement error and phase shift error are analyzed and then quantified. A new method to minimize measurement error is given. A new core loss model in terms of switching duty cycle is presented. This model predicts variation of core loss of an inductor operating in various conditions in a switching converter. This inductor model can be generalized to inductors in other switching converter topologies.

Comparison of three topologies for VRM fast transient application

This paper compares three topologies for voltage regulator modules (VRMs) for fast transient applications. The topologies are the most popular multi-phase converter, a synchronous rectifier buck converter topology and a recently introduced new stepping inductor converter. Analysis and simulation show that the stepping inductor topology gives the fastest response with minimal amount of output filter capacitance.

A fast response full bridge power factor corrector

A fast response full-bridge power factor corrector (FBPFC) is presented in this paper. The power converter is combined by two interleaved boost cells and a conventional full bridge power converter. As the interleaving technique is applied, the input ripple current of the FBPFC is reduced. Experimental result shows that the maximum power factor is 0.98, even without an input filter.

Current-driven synchronous rectification technique for flyback topology

For low voltage, high current application, synchronous rectification technique can help improve efficiency in a flyback converter. This paper investigates some technical challenges within a synchronous rectification flyback converter. One of the major problems is that the discontinuous current mode (DCM) operation is not achievable with a control-driven or self-driven synchronous rectifier. Continuous current mode operation may introduce excessive RMS current and circulation energy at light load or high line condition. To solve this problem, we propose to use an energy recovery current-driven synchronous rectifier for flyback topology. Analysis and experiments demonstrate the performance of this approach.

Effect of switching frequency and number of winding layers on copper loss of an inductor

Power inductor operating in a high frequency switching power converter experiences both core loss and copper loss. It is a common belief that the higher the switching frequency is, the higher will be the inductor loss. In this paper, we demonstrate that this is not the case. In fact the higher the switching frequency, the lower the inductor copper loss. This applies to an inductor with centre-gapped, side-gapped and spacer configurations. In the loss analysis, an optimum number of inductor turns is derived analytically to minimize copper loss incurred by an inductor with side-gapped configuration.

A Diagrammatic Approach to Search for Minimum Sampling Frequency and Quantization Resolution for Digital Control of Power Converters

A diagrammatic approach to find out the minimum sampling frequency and quantization resolution for digital control of power converters is proposed. The proposed solution algorithm combines consideration on both time sampling and quantization resolution axes to search for the minimum required digital controller settings. Experiments results are presented to justify the proposed algorithm.

General impedance synthesizer using minimal configuration of switching converters

A general impedance synthesizer using a minimum number of switching converters is studied in this paper. We begin with showing that any impedance can be synthesized by a circuit consisting of only two simple power converters, one storage element (e.g., capacitor), and one dissipative element (e.g., resistor) or power source. The implementation of such a circuit for synthesizing any desired impedance can be performed by: (i) programming the input current given the input voltage such that the desired impedance function is achieved; and (ii) controlling the amount of power dissipation (generation) in the dissipative element (source) so as to match the required active power of the impedance to be synthesized. Then, the instantaneous power will automatically be balanced by the storage element. Such impedance synthesizers find a lot of applications in power electronics. For instance, a resistance synthesizer can be used for power factor correction (PFC), a programmable capacitor or inductor synthesizer (comprising of small high-frequency converters) can be used for control applications.