開關(guān)電源設(shè)計(jì)外文翻譯-其他專業(yè)(已修改)
2025-02-04 11:19 本頁面
【正文】 《功率因數(shù)校正開關(guān)電源的研究與設(shè)計(jì)》外文翻譯 Switching Power Supply Design(開關(guān)電源設(shè)計(jì) ) CHAPTER 3 Half and FullBridge Converter Topologies Introduction Halfbridge and fullbridge topologies stress their transistors to a voltage equal to the DC input voltage not to twice this value, as do the pushpull, singleended, and interleaved forward converter to pologies. Thus the bridge topologies are used mainly in offline converters where supply voltage would be more than the switching transistors could safely tolerate. Bridge topologies are almost always used where the normal AC input voltage is 220 V or higher, and frequently even for 120V AC inputs. An additional valuable feature of the bridge topologies is that primary leakage inductance spikes (Figures and ) are easily clamped to the DC supply bus and the energy stored in the leakage inductance is returned to the input instead of having to be dissipated in a resistive snub ber element. HalfBridge Converter Topology Basic Operation Halfbridge converter topology is shown in Figure . Its major advantage is that, like the doubleended forward converter, it subjects the “off” transistor to only V dc and not twice that value. Thus it is widely used in equipment intended for the European market, where the AC input voltage is 220 V. First consider the input rectifier and filter in Figure . It is used universally when the equipment is to work from either120VACAmerican power or 220V AC European power. The circuit always yields roughly 320V rectified DC voltage, whether the input is 120 or FIGURE Halfbridge converter. One end of the power transformer primary is connected to the junction of filter capacitors C1, C2 via a small DC locking capacitor Cb . The other end is connected to the junction of Q1, Q2, which turn “on” and “off” on alternate half cycles. With S1 in the closed position, the circuit is a voltage doubler 。 in the open position, it is a fullwave rectifier. In either case, the rectified output is about 308 to 336 V dc. 220 V AC. It does this when switch S1 is set to the open position for 220V AC input, or to the closed position for 120V AC input. The S1 ponent is normally not a switch。 more often it is a wire link that is either installed for 120 V AC, or not for 220 V AC. With the switch in the open 220V AC position the circuit is a full wave rectifier, with filter capacitors C1 and C2 in series. It produces a peak rectified DC voltage of about (220) ?2 or 308 V. When the switch is in the closed 120V AC position , the circuit acts as a voltage doubler. One half cycle of the input voltage when A is positive relative to B, C1 is charged positively via D1 to a peak of ( 120) ? 1 or 168 V. On a half cycle when A is negative with respect to B, capacitor C2 is charged positively via D2 to 168 V. The total voltage across C1 and C2 in series is then 336 V. It can be seen in Figure that with either transistor “on,” the “off” transistor is subjected to the maximum DC input voltage and not twice that value. Since the topology subjects the “off” transistor to only V
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