Yuri Panov

Adaptive off-time control for variable-frequency, soft-switched flyback converter at light loads

The soft switching of a flyback converter can be achieved by operating the circuit in the critical conduction mode. However, the critical-mode operation at light loads cannot be maintained due to a very high switching frequency and the loss of the output voltage regulation. A control which regulates the output down to the zero load and maintains soft switching at light loads is proposed. The proposed control scheme was implemented in the 380 V/19 V, 65 W flyback DC/DC converter.

Design considerations for 12-V/1.5-V, 50-A voltage regulator modules

The paper presents design considerations for a 12 V/1.5 V, 50 A voltage regulator module (VRM) for the next generation of microprocessors. The module has stringent power-density and transient-response specifications, which are hard to meet with traditional design techniques. The proposed design solutions increase the VRM efficiency, as well as achieve the desired transient response with a minimum amount of the output capacitance.

Design and performance evaluation of low-voltage/high-current DC/DC on-board modules

The topology selection, design, and performance evaluation of an on-board DC/DC converter, which delivers power from a 48 V input to a 1.2-1.65 V/70 A microprocessor load, are presented. It was shown that the symmetrical half-bridge topology with the current doubler and synchronous rectifiers is a suitable approach for this application. The measured full-load efficiency of a 200 kHz experimental half-bridge converter was higher than 82% in the entire output and input voltage range.

Multiphase buck converters with extended duty cycle

A family of multiphase, pulse-width-modulated (PWM) step-down converters that exhibit high input-to-output voltage conversion ratios is introduced. The proposed converters operate with larger duty cycles and lower voltage stresses on the switches than their conventional converter counterparts making them suitable for applications in high-frequency, nonisolated point-of-load converters employed in powering todays microprocessors

Small-signal analysis and control design of isolated power supplies with optocoupler feedback

Optocouplers are widely used in isolated power supplies to transfer the feedback signal from the secondary to the primary side. In many power supplies, the feedback amplifier is supplied from the output voltage that creates additional feedback path which should be taken into account in the control design. The paper presents a detailed analysis and control design for each of the two possible feedback loops that can be identified. In addition, dynamic limitations of the TL431 shunt regulator and of the optocoupler are discussed. Practical guidelines for the error amplifier design and a design example are presented for both voltage-mode and current-mode controls.

Stability and dynamic performance of current-sharing control for paralleled voltage regulator modules

The parallel operation of voltage regulator modules (VRMs) for high-end microprocessors requires a current-sharing (CS) circuit to provide a uniform load distribution among the modules. A good dynamic performance of the CS circuit is very important since the microprocessors present highly dynamic loads to the VRMs. Stability and dynamic performance of the CS control are considered. To assess these issues, a comprehensive small-signal model of the paralleled VRMs was developed and experimentally verified.

Practical issues of input/output impedance measurements in switching power supplies and application of measured data to stability analysis

Measurements of converter input and output impedances are conducted to verify that the power system has been correctly modeled and designed. Many impedance measurement setups presented in the past are useful for tutorial purposes, but in practice their application is limited to low-power supplies. This paper presents practical impedance measurement circuits, which provide reliable measurements for a wide class of power supplies. The measured impedance data was applied to stability analysis of the computer distributed power system

Performance evaluation of 70-W two-stage adapters for notebook computers

The paper presents the design and performance evaluation of two-stage AC power adapters for notebook computers which deliver 70 W from the universal line. Three versions of the flyback power converter, as well as the PWM and resonant half-bridge power converter were evaluated and compared with respect to their efficiency, component stress, output filter size and complexity.

Loop Gain Measurement of Paralleled DC–DC Converters With Average-Current-Sharing Control

Paralleled operation of dc-dc converters is widely used in todays distributed power systems. Special control circuitry is usually necessary to ensure current sharing among the paralleled modules. The average-current-sharing control method is very popular due to its simple implementation and good performance. Although the analysis and design of the average-current-sharing control were presented in the past, a loop gain measurement technique has not been published. This paper presents a practical loop gain measurement technique that uses two excitation sources. Measured and theoretical data are compared to verify the proposed technique.

Loop gain measurement of paralleled dc-dc converters with average-current-sharing control

Paralleled operation of dc-dc converters is widely used in todays distributed power systems. Special control circuitry is usually necessary to ensure current sharing among the paralleled modules. The average-current-sharing control method is very popular due to its simple implementation and good performance. Although the analysis and design of the average current-sharing control were presented in the past, a loop gain measurement technique has not been published. This paper presents a practical loop gain measurement technique which uses two excitation sources. Measured and theoretical data are compared to verify the proposed technique.