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Comprising automotive manufacturers, Tier-1 automotive electrical suppliers and audio-video manufacturers, the industry standards body introduced the resultant MOST (Media Oriented Systems Transport) standard.

band stop filter

Comprising automotive manufacturers, Tier-1 automotive electrical suppliers and audio-video manufacturers, the industry standards body introduced the resultant MOST (Media Oriented Systems Transport) standard.

The flyback topology seems like the obvious choice for this application. The power level is consistent with a flyback. Multiple high-voltage outputs are easy to generate with a flyback, and the flyback is well understood.

However, there are challenges with the flyback: the topology includes unclamped power switch voltages that can ring excessively; it usually needs a two-stage output filter; and cross regulation over zero to full load will not be three percent.

band stop filter

Figure 1 shows an alternate approach. Do you recognize the topology? Let's look at some of this topology's good aspects, assuming that all the loading is only the –27 volt output.

Turning off the switch causes the C16 to clamp the power switch (Q1). The output rectifier (D2) is clamped by C16 when the power switch is on. Therefore, the ringing typically associated with the flyback is not present. Also, the input and output currents through the coupled inductor can be continuous, which greatly simplifies both input and output filters.

band stop filter

This topology is a C'uk converter. The challenge with implementing this topology is that the typical engineer does not understand it well. This is primarily because the C'uk only finds occasional use or the engineer does not even consider it most of the time.

A power supply for VOIP phones is extremely cost-sensitive, power-loss sensitive, and needs reasonable (5%) cross regulation. These are high-volume systems with large price pressures, and are typically battery backed-up where every watt is at a premium. Each output needs to be well-controlled for cross loading and to protect downstream amplifiers. This combination of requirements is a challenge for a flyback due to the ringing, and requires either pre-loads or additional power regulation circuits. The C'uk converter excels in this application as shown in Table 1 .

band stop filter

Efficiency was two percent better than a flyback, even assuming the flyback had no preload. This was made possible by the use of lower voltage switches and diodes, due to the lack of ringing in the circuit.

Besides the speed control section, the inverter plays a crucial role in enabling the power conversion process in a wind power system. In the case of wind turbines, variable-speed generation devices, an inverter is essential for the devices to connect to the grid and supply code-compliant power. Inverters can be either single (commercial) or three-phase (industrial) discrete components or modules and are controlled by a DSP to provide high-efficiency power conversion. High-performance inverter systems require precision timing control of power devices as well as safety isolation to prevent hazardous high voltage switching transients from damaging the controller and operator.

As an example, in a 30kW power conversion system, a simple AC-DC-AC converter and modular control strategy for grid-connected wind system was implemented.

The figure below shows a similar block diagram of the power converter. As the voltage and frequency of generator output vary along with the wind speed change, a DC-DC boosting chopper is utilized to maintain constant DC link voltage. The input DC current is regulated to follow the optimized, predetermined current reference for maximum power point operation of the turbine system. On connecting to the grid, PWM signals control the IGBTs through ACPL-332J gate drivers to supply currents into the utility line by regulating the DC link voltage of the inverter.

In order to achieve optimum system efficiency, the converter illustrated in Figure 2, and many others show that important current and voltage information must be fed back to the DSP for calculation and effective control. This information may include DC link current, generator phase currents, inverter output phase currents, and DC link voltages. This need poses opportunities for current/voltage sensors with requirements of not only sufficient accuracy, response speed, but also high switching noise rejection and safety insulation, at a competitive cost.

Iso-amp measures current and voltage


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