Mark E. Jacobs

Optimal Feedback Control of Switch-Mode Power Converters

A new controller-filter structure for a switch-mode power converter is described. The controller produces a minimum-time control signal for step changes in output voltage or in load current by partitioning the state-vector plane for the converters output filter with a simple curve. A companion filter estimates the state vector of the power converter by modeling the response of the power converter to the control signal. The controller, abandoning the traditional approach of producing duty cycle using a sawtooth waveform with an adjustable threshold, avoids the performance limitations ordinarily encountered with a linear feedback approach

Worth of a Watt - Implications for Systems and Device Designers

The capital equivalent cost of consuming ac or dc power in a central office is determined as a function of service life, electric rate and energy inflation rate. The results are used to compute life-cycle equipment costs and to determine the most economical operating point of non-linear power processing devices.

Distributed Power Architecture Concepts

For critical electronic equipment applications such as PBXs (Private Branch Exchanges), system reliability is as important an index of performance as equipment first cost. To minimize the effects of power failures on overall reliability, duplicate systems may be used to power the same loads. However, in todays tight economy, such redundant configurations are often not a cost-effective alternative. Distributed power architectures are designed to meet this dual challenge of low cost and high reliability. A distributed powering arrangement divides the system load into several groups, each powered by its own power conversion unit, to limit the effect of isolated power component failures on total system operation. The result is an economical fault-tolerant system. This paper discusses cost and reliability factors for distributed power architectures.

The practical limits of forced-air cooling of electronic equipment

Cooling with forced air is analyzed from a general perspective. It is demonstrated that there are physical processes that limit the maximum dissipation of heat from a frame or shelf of electronic equipment. These constraints are shown to arise from the limitations on allowable acoustic noise. Some results from fluid mechanics are used to construct a pressure-flow model of heat removal. Two problems of determining maximum heat dissipation are then described. In the first, the maximum dissipation in a fan-cooled shelf is derived subject to an acoustic noise constraint. In the second problem, a shelf of circuit cards is examined for which the pressure drop is already given. For this case the maximum dissipation is derived and shown to be proportional to the square-root of pressure and to the top area of the shelf. It is noted that both of these results are essential in designing new system and in specifying high-dissipation elements such as power supplies.<<ETX>>

Active snubbers to eliminate diode reverse recovery and achieve zero-current turn-off in DC-DC converters

This paper presents a new active snubber topology for bridge-type converters. The snubber circuit reduces the turn-off current of the primary switches to zero prior to their turn-off, and thus significantly reduces their turnoff loss. The snubber circuit also clamps all secondary diodes at their turn-off and recovers all the diode reverse recovery energy. There is no duty cycle loss associated with the soft commutation, and the power loss of the auxiliary circuit is kept low even at extreme operating points (e.g. full duty cycle, short-circuit, or light load DCM operation).

An improved high-efficiency rectifier for telecom applications

A rectifier circuit architecture for achieving a power train conversion efficiency greater than 92% for a 12 kW rectifier for telecom applications is described for a design for a 380/480 V three phase AC input utilizing semiconductor devices with commonly available breakdown voltages is presented, including predicted and laboratory measurements of power train efficiency. An averaged model of the power train is developed in conjunction with a description of the control strategy.

A Distributed Power Architecture for the System 75 Digital Communications System

The distributed power architecture for the System 75 Digital Communications System offers performance that would be difficult to achieve with conventional power architectures. With distributed power, each circuit-card shelf is powered by its own off-line switcher (OLS) power units. This limits the effects of a power-unit failure and contributes to increased system reliability. An optional battery reserve system ensures uninterrupted power without an external uninterruptible power system. The result is that System 75 is a low-cost, easy-to-repair digital communications system.

Critical Issues in Powering Emerging Telecommunications Systems

This paper describes the impact of the rapidly evolving telecommunications network on power and powering arrangements, paying close attention to the confluence of telecommunications and computer systems. Fundamental features of powering strategies are addressed, including reserve energy systems, interconnect, thermal, and distributed architectures.

A New, Low-Cost Common Mode RFI Suppression Technique for Switch Mode Power Supplies

This paper presents a new method to attenuate common-mode conducted radio frequency interference (RFI) fed back onto the ac power input leads of a high-frequency switching power supply. The technique uses a circuit to cancel the effect of the noise-generating sources. This method is also effective for reducing common mode noise on the output leads. The benefits and effectiveness of this low-cost RFI suppression technique are discussed.

Worth of a watt: The new economics and technologies

In a study presented at INTELEC in 1978 and updated in 1981 , the capital-equivalent cost of continuously dissipating a watt in a Bell System central office was examined. It was estimated that the worth of an ac watt in 1977 was