R. Vazquez

The fast response double buck DC-DC converter (FRDB): operation and output filter influence

The fast response double buck (FRDB) dc-dc converter was presented like a low output voltage dc-dc converter with fast transient response, in order to feed devices such as microprocessors and digital signal processors (DSPs). The topology of the FRDB is composed of two buck converters connected in parallel, each one of them with different features and aims, and controlled by means of the novel linear-non-linear (LnL) control. In this paper, the topology, the control strategy and the operation principle are shown. Finally, experimental results in different prototypes are presented to show both, the transient response and the recovery time when these prototypes are subjected to load current steps, and the influence of the output filter on these parameters.

Theoretical study and implementation of a fast transient response hybrid power supply

This paper presents a theoretical and experimental study of the hybrid sources capabilities to improve both the dynamic response and the stability of switching power supplies. The hybrid sources are composed by both, a linear and a switching source connected in parallel. The reached improvements have been possible without affecting, significantly, the efficiency of the whole circuit. This solution is checked in low voltage sources. The obtained experimental results show that these power supplies present high dynamical performance, and therefore they can be used to feed digital signal processors and microprocessors.

Linear-non-linear control (LnLc) for DC-DC buck converters: stability and transient response analysis

Power supplies for last generation of microprocessors and DSPs must present low output voltage and fast transient response. The linear-non-linear control (LnLc control) was presented as a solution to improve the transient response in DC-DC buck converters. However, once the LnLc control has been analyzed, other important performances have been found such as, improving the stability of the system, improving the efficiency, reducing of the recovery time, making independent the bandwidth and the switching frequency; reaching all these performances with an easy implementation. In this paper, the features of the linear-non-linear control are described. It will be shown, how the LnLc improves the stability of a DC-DC buck converter modifying the open loop gain and phase as a function of the load current steps. To show this behavior the control transfer function (G/sub LnLc/) has been deduced. Several experimental results have been obtained in a synchronous rectifier buck converter to check its behavior. Thus, the novel LnLc control has been compared with the conventional voltage control under different conditions. Finally, the control transfer function has been obtained experimentally.

Fast transient response with combined linear-non-linear control applied to buck converters

Nowadays, one of the main challenges for power supplies designers is to feed the latest generation of microprocessors and DSPs, since they require high current slew rates together with low output voltage. In this paper, a novel control technique is presented to help the designers to comply with the current requirements. The proposed combined linear-nonlinear control (LnLC) scheme increases significantly the capability of conventional linear control to reduce the recovery time of the output voltage drop produced when a load current step occurs. Experimental results have been obtained for two cases: a synchronous rectifier buck converter, with a conventional voltage loop and the same converter with the novel LnLC. The comparison of these experimental results shows that, with the new control, the recovery time of the output voltage is reduced.

New DC/DC converter with low output voltage and fast transient response

A new alternative to get fast transient response DC/DC switching converters is presented in order to feed devices such as microprocessors and DSPs. The topology of the switching power supply is composed of two buck converters connected in parallel, each one of them with different aims, controlled by means of the linear-nonlinear control. In this paper, the LNL control is reviewed and applied to the proposed power supply (fast response double buck, FRDB). Also, experimental results are obtained to show the main features of the proposed converter and to compare them with the features of some other solution.

PWM-PD multiple output DC/DC converters: operation and control-loop modeling

In this paper, PWM-PD multiple output dc/dc converters are presented. Operation analysis and power block design are shown. Furthermore, a small-signal model is developed for the PWM-PD multiple output dc/dc converters working in continuous conduction mode. The control-block is presented and the closed-loop circuit performances, such as the line, load and cross regulation, are obtained analytically. Finally, experimental results for a PWM-PD converter, with three fully regulated outputs and with transformer, are shown.

Multiple output DC/DC converters based on PWM-pulse delay control (PWM-PD)

Multiple output DC/DC converters are commonly used in electronics equipment. These converters have typical problems such as line, load and cross regulations. The family of converters presented in this paper works at fixed switching frequency and it is characterized by using a combination between pulse width modulation and pulse delay control (PWM-PD), in order to reduce the number of regulator components in the converters. This control technique allows a bigger number of control parameters to be obtained than the number of controlled components. Finally, experimental results in a converter with three insulated outputs are presented.

Theoretical study and implementation of a high dynamic performance, high efficiency and low voltage hybrid power supply

This paper presents a theoretical and experimental study of the hybrid sources capabilities to improve both the dynamic response and the stability of switching power supplies. The hybrid sources are composed by the parallel connection of a linear source and a switching one. The reached improvements are possible without affecting, significantly, the efficiency of the whole circuit. This solution is checked in low voltage sources. The obtained experimental results show these power supplies present high dynamical performance, and therefore they can be used to feed DSPs and microprocessors.

Fast transient response in hybrid sources with combined linear-non-linear control

A new type of hybrid source based on a combined linear-non-linear control (HS-LnL) is presented in this paper. The hybrid sources are composed by both a linear and a switching source connected in parallel. The linear-nonlinear control allows reducing the current provided by the linear source under a load current step. Consequently the efficiency of the hybrid source is improved. Three different prototypes have been built to show the actual operation and to compare the experimental results. These results prove that using the HS-LnL the output voltage variation is limited, the efficiency with respect to the conventional buck converter is almost unaffected by including a linear source, and fast transient response is improved. The experimental results show that the HS-LnL power supplies can be a good solution to feed DSPs and microprocessors.

Modulation Technique for Low Frequency Harmonic Cancellation in Auxiliary Railway Power Supplies

The auxiliary railway power supply (ARPS) is needed in order to provide low and medium voltages to the onboard systems from the catenary high voltage. The outputs of the ARPS can be dc (24 Vdc ÷100 Vdc) or ac (400 Vac). In the case of ac voltage generation, the ac output voltage is under very restrictive total harmonic distortion specifications even in the presence of nonlinear loads which draw low-frequency current harmonics. Along the present paper, a new modulation technique is proposed under the name of harmonic cancellation technique. It is based on the proper pre-distortion of the inverter output voltage in order to generate a controlled fundamental harmonic as well as a set of low-frequency harmonics which cancel out the harmonic pollution due to the nonlinear load performance. The theoretical background needed to implement the modulation technique is provided as well as the experimental validation of the proposed modulation technique through a scale-down prototype.