Push-pull converter

The duty ratio of each transistor in a push-pull converter (Fig. 10.85(a)) is less than 0.5. Some of the advantages are the transformer flux swings fully and the size of transformer is much smaller (typically half the size) than single-ended converters, and the output ripple is twice the switching frequency of transistors therefore, smaller filters are needed. 

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

Fig. 12 shows a push-pull based DC/AC converter (Jin and Enjeti, 2004), which consists of a front-end boost converter to regulate the DC voltage. A battery is connected to the intermediate DC bus to provide fast dynamic response during load-transients. The push-pull converter operates with a 50% duty ratio and provides rectangular voltage pulses at the secondary of the high-frequency transformer. The cycloconverter is sinusoidally modulated to produce a 60 Hz line-frequency voltage at the output. The push-pull converter... 

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

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. 

The cleavage of the 0-0 bond of the hydroperoxide is promoted by the push-pull mechanism shown in Fig. 4, in which the native HRP reacts with the unionized form of the hydroperoxide. Thus, the latter is converted into a much better nucleophile upon transfer of its proton to the distal basic group (His 42). 

Resin-bound amines can be converted into imines [710,711] or enamines by reaction with carbonyl compounds (Entries 6 and 7, Table 3.39). Resin-bound enamines have also been prepared by Michael addition of resin-bound secondary amines to acceptor-substituted alkynes [712], by Hg(II)-catalyzed addition of resin-bound secondary amines to unactivated alkynes [713], by addition of C-nucleophiles to resin-bound imino ethers [714], and by chemical modification of other resin-bound enamines [712,713,715], Acceptor-substituted enamines ( push-pull alkenes) are not always susceptible to hydrolytic cleavage by TFA alone and might require aqueous acids to undergo hydrolysis [716]. 

Fats and carbohydrates are metabolized down to carbon dioxide via an acetyl unit, CH3C=0, which is attached to a coenzyme, HSCoA, as a thioester called acetyl CoA. Acetyl CoA enters the citric acid cycle and eventually is converted to two molecules of carbon dioxide. The first step in the citric acid cycle is the aldol of acetyl CoA with oxaloacetate (Fig. 8.6). What is so elegant about this aldol is that the acidic and basic groups within the enzyme s active site provide a route that avoids any strongly acidic or basic intermediates. The enzyme accomplishes an aldol reaction at neutral pH, without an acidic protonated carbonyl or basic enolate intermediate via push-pull catalysis (Section 7.4.3). 

Usually, for power levels above 300 W, double-ended converters are used. Full-wave rectifiers are used in the double-ended converters and the ripple frequency of the output voltage is twice the switching frequency. Three important double-ended PWM converter configurations are push-pull (Fig. 10.85(a)), half-bridge... 

Only one smoothing capacitor is required at the input for this configuration (Fig. 10.85(c)) and for the same transistor type as that of half-bridge, output power can be doubled. Usually used for power levels above 1 kW, the design is more costly due to increased number of components (uses four transistors compared to two in push-pull and half-bridge converters.)... 

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