Full-bridge converter

Figure 4-18 Phase modulation of a PWM full-bridge converter.

There are control ICs presently in the market. This is one technique to increase the frequency of full-bridge converters and gain three to five percent in efficiency over the normal PWM full-bridge converters. The cost of the supply does increase since more gate drive transformers are required. 

Figure 3.5 Rectifier voltage waveforms of a 2 kW silicon full-bridge converter (a) without and (b) with active snubber circuitry. (From [6], 1991 IEEE. Reprinted with permission.)...

FIGURE 10.85 (a) Push-pull converter, (b) half-bridge converter, (c) full-bridge converter. Coupling capacitor Cc is... 

Using a proper control technique, a full-bridge converter can be operated in a zero-voltage switching (ZVS) mode (Dalai, 1990). This type of operation results in negligible switching losses. At reduced load currents, however, the ZVS property is lost. There has been much effort to overcome this problem, but the converter requires additional components to maintain the ZVS. 

Any Buck-derived topology (e.g., the Forward converter, the Half-Bridge, the Push-Pull, the Full-Bridge, etc.) needs an output choke. Otherwise it is akin to running a Buck without its inductor—you can thereby create a dead short cross the input supply rails. 

Sabate, J. A., et al., High-Voltage, High-Power, ZVS, Full-Bridge PWM Converter Employing an Active Snubber, Proc. 6th IEEE Applied Power Electronics Conference and Exposition 1991, March 10-15, 1991, pp. 158-163. 

Figure 36.9 Equivalent circuits of different DC-DC converters. (a) Step-down (b) step-up (c) step-down/step-up (d) full bridge. Reproduced from [25].

Fig. 12 Push-pull converter based DC/AC converter followed by a full-bridge cycloconverter.

Figure 3-28 Output stages for forward and boost-mode converters (a) balf-wave forwardmode (b) center-tapped forward-mode (c) full-wave bridge forward-mode (d) boost-mode.

The exciter is an AC generator with a stator-mounted field. Direct cur rent for the exciter field is provided from an external source, typically u small variable voltage rectifier mounted at the motor starter. Exciter oui put is converted to DC through a three-phase, full-wave, silicon-diode bridge rectifier. Thyristors (silicon-controlled rectifiers) switch the cur rent to the motor field and the motor-starting, field-discharge resistors These semiconductor elements are mounted on heat sinks and assembled on a drum bolted to the rotor or shaft. 

A frequency converter can also be used as a starting aid and also does not have to be configured for full power. However, since it often cannot be operated at motor voltage, both an inverter-transformer for voltage reduction in front of the frequency converter, as well as a motor transformer for voltage increase after the frequency converter have to be used. All three components are bridged after starting, to run at full power. 

Many assays that have been bead-captured and gel-based have been converted to 96-well polystyrene microtiter plates to standardize the format for automation and higher throughput. In many ways, plate formats are a bridge to the higher-density microarray formats and remain quite useful until full conversion to microarray or microfluidic formats can be made. Microtiter plate assays or activated microbeads (i.e., Luminex) for panels of cytokines are widely available because of their use in clinical medicine. 

The most desirable recorder is one which has a 1-mv span, a full-scale deflection time of about 1 sec, and a chart speed of 15 in. per hour. These recorders are, however, quite expensive. A small 10-mv recorder is available, and this is quite satisfactory for most purposes. It may be converted to a fairly satisfactory 1-mv recorder with the scale-change kit which is available. Another recorder is available at one-fifth the price of the latter instrument, but since this is basically a 0-to-l milliammeter, it requires an amplifier between the bridge and itself. 

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