The Bridge Rectifier

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Cassandra Blair
7 years ago
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1 9/4/004 The Brdge ectfer.doc 1/9 The Brdge ectfer Now consder ths juncton dode rectfer crcut: 1 Lne (t) - O (t) _ 4 3 We call ths crcut the brdge rectfer. Let s analyze t and see what t does! Frst, we replace the juncton dodes wth the CV model: Lne (t) 1 - O (t) 4 _ 3 Jm tles The Un. of Kansas ept. of EEC

2 9/4/004 The Brdge ectfer.doc /9 Q: Four gul-durn deal dodes! That means 16 sets of dad-gum assumptons! A: True! Howeer, there are only three of these sets of assumptons are actually possble! Consder the current flowng through the rectfer. Ths current of course can be poste, negate, or zero. It turns out that there s only one set of dode assumptons that would result n poste current, one set of dode assumptons that would lead to negate current, and one set that would lead to zero current. Q: But what about the remanng 13 sets of dog gone dode assumptons? A: egardless of the alue of source, the remanng 13 sets of dode assumptons smply cannot occur for ths partcular crcut desgn! Jm tles The Un. of Kansas ept. of EEC

It turns out that there s only one set of dode assumptons that would result n poste current, one set of dode assumptons that would lead to negate current, and one set that would

3 9/4/004 The Brdge ectfer.doc 3/9 Let s look at the three possble sets of assumptons: >0 The rectfer current can be poste only f these assumptons are true: 1 and 3 are reerse based. and 4 are forward based. Lne (t) _ >0 1 >0 4 - O (t) 3 Analyzng ths crcut, we fnd that the output oltage s: = 14V. O and the f.b. deal dode currents are: 14. = = Jm tles The Un. of Kansas ept. of EEC

poste only f these assumptons are true: 1 and 3 are reerse based. and 4 are forward based.

4 9/4/004 The Brdge ectfer.doc 4/9 and, fnally the r.b. deal dode oltages are: = Thus, > 0 when: and < 0 when: 14. > > 0 > 14. V < 0 > 0 Therefore, we fnd that for ths crcut: = 14V. when > 14V. O <0 The rectfer current can be negate only f these assumptons are true: 1 and 3 are forward based. and 4 are reerse based. Jm tles The Un. of Kansas ept. of EEC

V < 0 > 0 Therefore, we fnd that for ths crcut: = 14V. when > 14V.

5 9/4/004 The Brdge ectfer.doc 5/9 Lne (t) _ <0 < O (t) 3 Analyzng ths crcut, we fnd that the output oltage s: = 14V. O whle the f.b. deal dode currents are both : 14. = = and the r.b. deal dode oltages are both: = Jm tles The Un. of Kansas ept. of EEC

6 9/4/004 The Brdge ectfer.doc 6/9 Thus, > 0 when: and, < 0 when: 14. > > 0 > 14. V <14. V < 0 Therefore, we lkewse fnd for ths crcut: = 14V. when < 14V. O =0 The rectfer current can be zero only f these assumptons are true: All deal dodes are reerse based! Lne (t) = O (t) _ =0 3 3 Jm tles The Un. of Kansas ept. of EEC

O =0 The rectfer current can be zero only f these assumptons are true: All deal

7 9/4/004 The Brdge ectfer.doc 7/9 Analyzng ths crcut, we fnd that the output oltage s: O = = 0 whle the deal dode oltages of and 4 are each: 14. = = 4 and the deal dode oltages of 1 and 3 are each: 14. = = 1 3 Thus, < 0 when: and, 1 < 0 when: 14. < < 0 < < < 0 < 14. >14. Therefore, we also fnd for ths crcut that: = 0 when both < 14V. and > 14V. (-1.4< < 14V). O Jm tles The Un. of Kansas ept. of EEC

are each: 14. = = 4 and the deal dode oltages of 1 and 3 are each: 14.

8 9/4/004 The Brdge ectfer.doc 8/9 Q: You know, that dang Mzzou grad sad we only needed to consder these three sets of dode assumptons, yet I am stll concerned about the other 13. How can we be sure that we hae analyzed eery possble set of ald dode assumptons? A: We know that we hae consdered eery possble case, because when we combne the three results we fnd that we hae a pece-wse lnear functon! I.E.,: 14V. f < 14V. O = 0 f -1.4 < < 1 4V. 14V. f > 14V. O Jm tles The Un. of Kansas ept. of EEC

concerned about the other 13. How can we be sure that we hae analyzed eery possble set of ald dode assumptons?

9 9/4/004 The Brdge ectfer.doc 9/9 Note that the brdge rectfer s a full-wae rectfer! If the nput to ths rectfer s a sne wae, we fnd that the output s approxmately that of an deal full-wae rectfer: A O (t) 1.4 t A (t) We see that the juncton dode brdge rectfer output s ery close to deal. In fact, f A>>1.4 V, the C component of ths juncton dode brdge rectfer s approxmately: A V O 14V. π Just 1.4 V less than the deal full-wae rectfer C component! Jm tles The Un. of Kansas ept. of EEC

4 t -1.4 -A (t) We see that the juncton dode brdge rectfer output s ery close to deal. In fact, f A>>1.

The Full-Wave Rectifier

The Full-Wave Rectifier 9/3/2005 The Full Wae ectfer.doc /0 The Full-Wae ectfer Consder the followng juncton dode crcut: s (t) Power Lne s (t) 2 Note that we are usng a transformer n ths crcut. The job of ths transformer s to