Series Pass Device Research Articles

Conducted EMI Suppression Using Power Semiconductor Filter With Dynamic Ramp Modulation to Regulate Series Pass Device Voltage

The concept of the power semiconductor filter (PSF) is based on utilizing a series pass device (SPD) operated in linear mode to regulate the input current of switching converters. In order to avoid input current oscillation, a fixed-frequency dynamic ramp modulator has been proposed. It is based on operating the converter at a fixed switching frequency and setting the switching frequency away from the grid-side resonant frequency. Regardless of the input variation, the voltage across the SPD is also maintained at a low level by a dynamic ramp, resulting in low power dissipation in the SPD. An optimized fast-current regulation circuit is designed to achieve high conducted electromagnetic interference (EMI) suppression. A method to predict the EMI suppression performance of the PSF has been proposed in this article. Furthermore, the ground loop inductance in the fast-current regulation circuit has been analyzed, and PCB layout guidelines have been given to mitigate the performance degradation of the PSF caused by this inductance. A 100-W, 90-264 Vac/200 Vdc buck-boost PFC prototype has been built and evaluated; the prototype with the PSF satisfies EMC standard EE55015 class B in the whole range of 150 kHz to 30 MHz.

1-kW Boost-type PFC Using a Low-Voltage Series Pass Module for Input Current Shaping

A power factor corrector extended from a previously proposed boost-type structure with power semiconductor filter (PSF) is presented. The concept of the PSF is based on using a series pass device (SPD) to profile the input current and regulate the output voltage, and an input capacitor to circulate the ripple current generated by the boost converter. However, the input capacitor is charged up slowly with small input current around the zero crossings, causing high voltage stress on the SPD. Then, a high-voltage device for the SPD is needed. However, high-voltage devices have large channel length modulation effect, high leakage current, large voltage drop, and slow response. To accelerate the capacitor charging and thus reduce the voltage stress, this article proposes to replace the output diode with a controllable switch. The converter is temporarily operated as a buck converter during the zero crossings with the input capacitor charged up swiftly by the output capacitor. The voltage across the SPD can be kept low over the line cycle, resulting in improved input current waveform and reduced power dissipation. A series pass module constructed by multiple parallel-connected low-voltage devices is used to increase current rating. The devices are regulated to operate around the knee point of the output characteristics to reduce power loss. A 1 kW, 85-265 Vac/400 Vdc prototype has been built and evaluated.

Modeling and Experimental Assessment of the EMI Characteristics of Switching Converters With Power Semiconductor Filters

An input filtering technology named “power semiconductor filter (PSF)” has been proposed recently. Its operating principle is based on using a series pass device (SPD) to profile the wave shape and magnitude of the input current of converters. The voltage across the SPD is regulated around the “knee point” of the current–voltage characteristic of the SPD to minimize the power dissipation of the SPD. This paper reports the conducted electromagnetic interference (EMI) performance of the converters with the PSF. To suppress differential-mode (DM) EMI, a fast current regulation circuit is proposed to tightly regulate the current through the SPD. To suppress common-mode (CM) EMI, a single CM noise bypass capacitor is proposed. Detailed mathematical models for describing the frequency response of the SPD and main components in the driving network are formulated. A set of selection guidelines for the components will be given. The derived models will be validated by comparing the theoretical prediction with the measurement results of a 100 W, 90–264 Vac LED driver using a buck–boost converter. Results reveal that the PSF reduces the DM noise level by 47.47 dBμV. The CM noise level is reduced by 21.4 dBμV with the bypass capacitor. An integrated circuit for the controller is illustrated to demonstrate the feasibility of reducing the form factor of the filtering section.

Flyback PFC With a Series-Pass Module in Cascode Structure for Input Current Shaping

A flyback power factor corrector (PFC) using a series-pass module (SPM) to shape its input current is presented. The input current is profiled by the SPM with its waveform controlled to be in the same wave shape and phase with the supply voltage and its magnitude controlled to regulate the output voltage. The SPM is constructed by two series-connected power semiconductor devices in a cascode structure. One of them is a high-voltage device of low on -state resistance for sharing major voltage stress, while the other one is a low-voltage device with high-output impedance for profiling the current through the SPM. The SPM has a local control for clamping the voltage across the low-voltage device. Such arrangement allows the PFC to exhibit lower total input current harmonic distortion than that using a single high-voltage series-pass device. To minimize power loss, the operating point of the low-voltage device is regulated around the boundary between its high-gain and fully turn- on operating region by adjusting the duty cycle of the main switch in the flyback converter. A 100-W 85–265-Vac/36-Vdc prototype has been built and evaluated. The conducted electromagnetic interference under different supply voltages will also be given.

Bifurcation Phenomena and Stabilization With Compensation Ramp in Converter With Power Semiconductor Filter

A concept, named as power semiconductor filter, has been demonstrated to be an alternative to perform input harmonic filtering in switched-mode power converters. It utilizes a series pass device (SPD) to profile the wave shape of the supply current, while the voltage across the SPD is regulated at a threshold voltage between the linear and saturation regions of the SPD to minimize its power dissipation. Bulky passive components for input harmonic filtering can then be eliminated or shrunk with such active supply current control. For the sake of circuit elegancy, regulation of the SPD voltage is realized by a bang-bang (peak-voltage) controller to vary the input characteristics of the power conversion stage through adjusting some control parameters, such as duty cycle and switching frequency. Experiments reveal that the entire system might exhibit bifurcation phenomena under some supply and load conditions. This paper will derive a sampled-data model to characterize such system behaviors and to identify the onset of bifurcation and chaos. A compensation ramp will be proposed to introduce into the bang-bang controller to stabilize the system operation. Moreover, the slow-scale dynamics will be studied with small-signal models. The investigations will be exemplified on a 48 W, 40–140 V/24 V buck dc–dc converter prototype.

Boost-Type Power Factor Corrector With Power Semiconductor Filter for Input Current Shaping

This paper extends the application of a solid-state input current harmonic filtering technique, named as power semiconductor filter (PSF), for boost-type power factor corrector (PFC). The filtering technique is based on connecting an active device, namely, series pass device (SPD), in series with the input of the boost converter. By adjusting the control signal to the SPD, the input current of the PFC is profiled to be in phase with the supply voltage and regulate the output voltage. The power dissipation of the SPD is maintained at a low level by operating the SPD at the boundary between the linear and saturation regions. Modeling of the static and dynamical characteristics, design, and analysis of the entire system will be given. A 100 W, 85–265 Vac/400 Vdc PFC with the boost converter operating in discontinuous conduction mode has been built and evaluated. Experimental results reveal that the PSF can reduce the input current harmonics and improve the input power factor. They are in close agreement with the theoretical predictions. Finally, the conducted electromagnetic interference under different supply voltages will also be reported.

Power Semiconductor Filter: Use of Series-Pass Device in Switching Converters for Filtering Input Current Harmonics

An investigation into the use of series-pass device (SPD) to filter out input current harmonics of switching converters is presented. The idea is based on connecting a SPD in series with the input of the switching converter so that the input current of the entire system can be profiled by adjusting the biasing condition of the SPD. To minimize the power dissipation of the SPD, the input impedance of the switching converter is controlled to make the SPD operate at the boundary between the linear and saturation modes. Modeling, design, and analysis of the system architecture will be given. Selection guide for the SPD will also be given. The concept has been applied to a 75-W 90–140-V/24-V classical dc–dc buck converter. Investigations reveal that the proposed architecture allows a substantial reduction in the size of the filter section and gives comparable efficiency as the conventional passive-type LC filter. More importantly, the idea makes the input filter amenable to monolithic integration. These investigations lay the foundation for applying the proposed concept for other power electronic converter systems.

Integration of a series-pass device into switched-mode power converters for input harmonics filtering

A concept called the power semiconductor filter (PSF) is presented in this paper. It is used to perform input harmonics filtering for switched-mode power converters. The realisation of this concept is based on connecting a series-pass device (SPD) in series with the input of the converter, so that the input current of the entire system can be programmed by the SPD. The power dissipation of the SPD is maintained at a low level through a feedback mechanism that adjusts the input impedance of the converter and makes the voltage across the SPD small. The proposed concept has been applied to two applications: a 75 W, 90 V to 140 V/24 V classical buck converter and a 100 W, 90 V to 265 V/400 V power factor corrector (PFC). The results show that the PSF concept can significantly reduce the input current harmonics and improve the power factor with a conversion efficiency comparable to traditional passive filters. The major advantages of the PSF are that the filter section is amenable to monolithic integration and...