{"id":5380,"date":"2023-06-05T16:19:39","date_gmt":"2023-06-05T08:19:39","guid":{"rendered":"http:\/\/www.dcl-controls.com\/?p=5380"},"modified":"2025-03-31T09:18:37","modified_gmt":"2025-03-31T09:18:37","slug":"why-voltage-signal-oscillate","status":"publish","type":"post","link":"https:\/\/dclactuator.com\/ro_ro\/sprijin\/ta-acutator\/de-ce-oscileaza-semnalul-de-tensiune","title":{"rendered":"De ce oscileaz\u0103 semnalele de ie\u0219ire de tensiune \u00een anumite condi\u021bii?"},"content":{"rendered":"
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\u00a0<\/h3>

1. Calea de transmisie a semnalului de tensiune<\/strong><\/h2>
\"Fig.
Fig. 1 Calea de transmisie a semnalelor sursei de tensiune<\/figcaption><\/figure>

A\u0219a cum se arat\u0103 \u00een Figura 1<\/strong>Un sistem de transmisie a semnalului de tensiune este alc\u0103tuit din trei componente cheie:<\/p>

  1. Circuit de ie\u0219ire a tensiunii cu feedback negativ<\/strong><\/p><\/li>

  2. Cablu de transmisie a semnalului<\/strong><\/p>

    • Include capacitate parazit\u0103 (C1)<\/strong> \u015fi inductan\u021b\u0103 parazit\u0103 (L1)<\/strong>, care depind de lungimea cablului<\/strong> \u015fi schema de cablare<\/strong>.<\/p><\/li><\/ul><\/li>

    • Circuit de achizi\u021bie a semnalului de intrare<\/strong><\/p>

      • Poate include o filtru trece-jos (L2, C2)<\/strong>.<\/p><\/li><\/ul><\/li><\/ol>

        2. De ce apare oscila\u021bia?<\/strong><\/h2>

        \u00centr-un sistem de semnal de tensiune cu feedback negativ, semnalul de intrare se calculeaz\u0103 astfel:<\/p>

        \u2223Xi\u2032\u2223=\u2223Xi\u2223\u2212\u2223Xf\u2223|X_i'| = |X_i| \u2013 |X_f|<\/span><\/p>

        Totu\u0219i, dac\u0103 semnalul de feedback (|Xf|) este defazat cu 180\u00b0<\/strong>, ecua\u021bia se schimb\u0103 \u00een:<\/p>

        \u2223Xi\u2032\u2223=\u2223Xi\u2223+\u2223Xf\u2223|X_i'| = |X_i| + |X_f|<\/span><\/p>

        Aceasta \u00eenseamn\u0103 c\u0103, chiar dac\u0103 f\u0103r\u0103 semnal de intrare<\/strong> se aplic\u0103 (|Xi| = 0<\/strong>), cel\/cea\/cei\/cele semnalul de feedback men\u021bine ie\u0219irea<\/strong>, duc\u00e2nd la oscila\u021bie auto-sus\u021binut\u0103<\/strong>.<\/p>

        Pentru ca oscila\u021bia s\u0103 aib\u0103 loc, trebuie \u00eendeplinite dou\u0103 condi\u021bii:<\/p>

        1. C\u00e2\u0219tigul buclei este mai mare dec\u00e2t 1:<\/strong> |AF| > 1<\/strong><\/p><\/li>

        2. Schimbarea de faz\u0103 satisface:<\/strong> \u03c6A + \u03c6F = (2n+1)\u03c0<\/strong><\/p><\/li><\/ol>

          The schimbare de faz\u0103<\/strong> \u00een bucl\u0103 provine din mai multe surse:
          \u2714 Capacitatea parazit\u0103 (C1) \u0219i inductan\u021ba (L1) \u00een cablul de transmisie<\/strong>
          \u2714 Componentele filtrului trece-jos (L2, C2) \u00een circuitul de intrare<\/strong>
          \u2714 Condensatoare de filtrare \u00een circuitul de ie\u0219ire<\/strong><\/p>

          Dac\u0103 defazajul total atinge 180\u00b0<\/strong>, poate ap\u0103rea autooscila\u021bie.<\/p>

          3. Cum s\u0103 prevenim oscila\u021bia?<\/strong><\/h2>

          Pentru a preveni oscila\u021bia, una dintre cele dou\u0103 condi\u021bii de mai sus nu trebuie \u00eendeplinit\u0103<\/strong> \u00een intervalul de frecven\u021b\u0103 opera\u021bional\u0103.<\/p>

          \"Fig.
          Fig. 2 Starea buclei de feedback negativ f\u0103r\u0103 oscila\u021bie<\/figcaption><\/figure>

          A\u0219a cum se arat\u0103 \u00een Figura 2<\/strong>, sunt luate \u00een considerare dou\u0103 frecven\u021be critice:<\/p>

          • fc:<\/strong> Frecven\u021ba la care c\u00e2\u0219tigul buclei |AF| scade la 0 dB<\/strong>.<\/p><\/li>

          • pentru:<\/strong> Frecven\u021ba la care defazajul buclei dep\u0103\u0219e\u0219te -180\u00b0<\/strong>.<\/p><\/li><\/ul>

            Pentru a men\u021bine stabilitatea, c\u00e2\u0219tigul trebuie s\u0103 fie sub 0 dB<\/strong> c\u00e2nd defazajul ajunge la -180\u00b0.<\/p>

            4. De ce semnalele de ie\u0219ire curente sunt mai stabile<\/strong><\/h2>
            \"Fig.
            Fig. 3 Bucla de feedback a sursei de curent<\/figcaption><\/figure>
            \"Fig.
            Fig. 4 Bucla de feedback a sursei de tensiune<\/figcaption><\/figure>

            Circuite de ie\u0219ire a semnalului de curent<\/strong> sunt mai pu\u021bin predispuse la oscila\u021bii deoarece:
            \u2714 Calea lor de feedback este limitat\u0103 la componentele interne<\/strong> (a\u0219a cum se arat\u0103 \u00een Figura 3<\/strong>).
            \u2714 Varia\u021biile de sarcin\u0103 extern\u0103 au un efect redus asupra schimb\u0103rii de faz\u0103 sau a c\u00e2\u0219tigului<\/strong>.<\/p>

            \u00cen contrast, circuite de ie\u0219ire de tensiune<\/strong> (Figura 4) primi\u021bi feedback de la punct de ie\u0219ire<\/strong>, adic\u0103 cabluri externe \u0219i circuite de e\u0219antionare<\/strong> poate influen\u021ba schimbarea de faz\u0103 \u0219i amplificarea. Dac\u0103 parametrii lor se modific\u0103, sistemul poate \u00eendeplini condi\u021biile de oscila\u021bie<\/strong>, duc\u00e2nd la instabilitate.<\/p>

            5. Concluzie<\/strong><\/h3>

            Semnalele de ie\u0219ire de tip tensiune pot oscila atunci c\u00e2nd:
            \u2714 Componentele parazite introduc o schimbare de faz\u0103 de 180\u00b0.<\/strong>
            \u2714 C\u00e2\u0219tigul buclei r\u0103m\u00e2ne mai mare de 1 la aceast\u0103 schimbare de faz\u0103.<\/strong><\/p>

            Pentru a evita oscila\u021biile:
            \u2714 Asigura\u021bi-v\u0103 c\u0103 amplificarea buclei este redus\u0103 sub 0 dB \u00eenainte ca defazajul s\u0103 ating\u0103 180\u00b0.<\/strong>
            \u2714 Minimizarea capacit\u0103\u021bii\/inductan\u021bei parazitare \u00een cablurile de transmisie.<\/strong>
            \u2714 Folose\u0219te o filtrare adecvat\u0103 pentru a stabiliza bucla de feedback.<\/strong><\/p>

            \u00cen contrast, ie\u0219iri de tip curent<\/strong> sunt mai stabile, deoarece bucla de feedback este mai pu\u021bin afectat\u0103 de condi\u021biile de sarcin\u0103 externe<\/strong>.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"

            \u00a0 1. Calea de transmisie a semnalului de tensiune Dup\u0103 cum se arat\u0103 \u00een Figura 1, un sistem de transmisie a semnalului de tensiune este alc\u0103tuit din trei componente cheie: Circuit de ie\u0219ire a tensiunii cu feedback negativ Cablu de transmisie a semnalului Include capacitate parazit\u0103 (C1) \u0219i inductan\u021b\u0103 parazit\u0103 (L1), care depind de lungimea cablului \u0219i de configura\u021bia cablajului. Circuit de achizi\u021bie a semnalului de intrare Poate include un filtru trece-jos (L2, [\u2026]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"elementor_theme","format":"standard","meta":{"_acf_changed":true,"footnotes":""},"categories":[8],"tags":[49],"class_list":["post-5380","post","type-post","status-publish","format-standard","hentry","category-ta-acutator","tag-input-signal"],"acf":[],"_links":{"self":[{"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/posts\/5380","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/comments?post=5380"}],"version-history":[{"count":0,"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/posts\/5380\/revisions"}],"wp:attachment":[{"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/media?parent=5380"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/categories?post=5380"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dclactuator.com\/ro_ro\/wp-json\/wp\/v2\/tags?post=5380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}