{"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:\/\/dclcontrols.com\/ko_kr\/%ec%a7%80%ec%9b%90\/%ec%95%84%ed%81%90%ed%85%8c%ec%9d%b4%ed%84%b0\/why-voltage-signal-oscillate","title":{"rendered":"\ud2b9\uc815 \uc870\uac74\uc5d0\uc11c \uc804\uc555 \ucd9c\ub825 \uc2e0\ud638\uac00 \uc9c4\ub3d9\ud558\ub294 \uc774\uc720\ub294 \ubb34\uc5c7\uc77c\uae4c\uc694?"},"content":{"rendered":"
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\u00a0<\/h3>

1. Voltage Signal Transmission Path<\/strong><\/h2>
\"Fig.
Fig. 1 Transmission path of voltage source signals<\/figcaption><\/figure>

As shown in Figure 1<\/strong>, a voltage signal transmission system consists of three key components:<\/p>

  1. Negative feedback voltage output circuit<\/strong><\/p><\/li>

  2. Signal transmission cable<\/strong><\/p>

    • Includes parasitic capacitance (C1)<\/strong> \uadf8\ub9ac\uace0 parasitic inductance (L1)<\/strong>, which depend on cable length<\/strong> \uadf8\ub9ac\uace0 wiring layout<\/strong>.<\/p><\/li><\/ul><\/li>

    • Input signal acquisition circuit<\/strong><\/p>

      • May include a low-pass filter (L2, C2)<\/strong>.<\/p><\/li><\/ul><\/li><\/ol>

        2. Why Does Oscillation Occur?<\/strong><\/h2>

        In a negative feedback voltage signal system, the input signal is calculated as:<\/p>

        \u2223Xi\u2032\u2223=\u2223Xi\u2223\u2212\u2223Xf\u2223|X_i’| = |X_i| – |X_f|<\/span><\/p>

        However, if the feedback signal (|Xf|) is phase-shifted by 180\u00b0<\/strong>, the equation changes to:<\/p>

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

        This means that even if no input signal<\/strong> is applied (|Xi| = 0<\/strong>), the feedback signal sustains the output<\/strong>\uadf8 \uacb0\uacfc self-sustaining oscillation<\/strong>.<\/p>

        For oscillation to occur, two conditions must be met:<\/p>

        1. Loop gain is greater than 1:<\/strong> |AF| > 1<\/strong><\/p><\/li>

        2. Phase shift satisfies:<\/strong> \u03c6A + \u03c6F = (2n+1)\u03c0<\/strong><\/p><\/li><\/ol>

          \uadf8\ub9ac\uace0 phase shift<\/strong> in the loop comes from multiple sources:
          \u2714 Parasitic capacitance (C1) and inductance (L1) in the transmission cable<\/strong>
          \u2714 Low-pass filter components (L2, C2) in the input circuit<\/strong>
          \u2714 Filter capacitors in the output circuit<\/strong><\/p>

          \ub9cc\uc57d total phase shift reaches 180\u00b0<\/strong>, self-oscillation can occur.<\/p>

          3. How to Prevent Oscillation?<\/strong><\/h2>

          To prevent oscillation, one of the two conditions above must not be met<\/strong> within the operational frequency range.<\/p>

          \"Fig.
          Fig. 2 Condition of negative feedback loop without oscillation<\/figcaption><\/figure>

          As shown in Figure 2<\/strong>, two critical frequencies are considered:<\/p>

          • fc:<\/strong> The frequency where loop gain |AF| drops to 0 dB<\/strong>.<\/p><\/li>

          • fo:<\/strong> The frequency where loop phase shift exceeds -180\u00b0<\/strong>.<\/p><\/li><\/ul>

            To maintain stability, the gain should be below 0 dB<\/strong> when the phase shift reaches -180\u00b0.<\/p>

            4. Why Current Output Signals Are More Stable<\/strong><\/h2>
            \"Fig.
            Fig. 3 Current source feedback loop<\/figcaption><\/figure>
            \"Fig.
            Fig. 4 Voltage source feedback loop<\/figcaption><\/figure>

            Current signal output circuits<\/strong> are less prone to oscillation because:
            \u2714 Their feedback path is confined to internal components<\/strong> (as shown in Figure 3<\/strong>).
            \u2714 External load variations have little effect on phase shift or gain<\/strong>.<\/p>

            In contrast, voltage output circuits<\/strong> (Figure 4) take feedback from the output point<\/strong>, meaning that external cables and sampling circuits<\/strong> can influence phase shift and gain. If their parameters change, the system may meet the oscillation conditions<\/strong>, leading to instability.<\/p>

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

            Voltage-type output signals can oscillate when:
            \u2714 Parasitic components introduce a 180\u00b0 phase shift.<\/strong>
            \u2714 Loop gain remains greater than 1 at this phase shift.<\/strong><\/p>

            To avoid oscillation:
            \u2714 Ensure loop gain is reduced below 0 dB before phase shift reaches 180\u00b0.<\/strong>
            \u2714 Minimize parasitic capacitance\/inductance in transmission cables.<\/strong>
            \u2714 Use appropriate filtering to stabilize the feedback loop.<\/strong><\/p>

            In contrast, current-type outputs<\/strong> are more stable since their feedback loop is less affected by external load conditions<\/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. \uc804\uc555 \uc2e0\ud638 \uc804\uc1a1 \uacbd\ub85c \uadf8\ub9bc 1\uc5d0\uc11c \ubcf4\ub294 \ubc14\uc640 \uac19\uc774, \uc804\uc555 \uc2e0\ud638 \uc804\uc1a1 \uc2dc\uc2a4\ud15c\uc740 \uc138 \uac00\uc9c0 \uc8fc\uc694 \uad6c\uc131 \uc694\uc18c\ub85c \uc774\ub8e8\uc5b4\uc838 \uc788\uc2b5\ub2c8\ub2e4. \ub124\uac70\ud2f0\ube0c \ud53c\ub4dc\ubc31 \uc804\uc555 \ucd9c\ub825 \ud68c\ub85c, \uc2e0\ud638 \uc804\uc1a1 \ucf00\uc774\ube14(\ucf00\uc774\ube14 \uae38\uc774 \ubc0f \ubc30\uc120 \ubc30\uce58\uc5d0 \ub530\ub77c \ub2ec\ub77c\uc9c0\ub294 \uae30\uc0dd \uc815\uc804 \uc6a9\ub7c9(C1) \ubc0f \uae30\uc0dd \uc778\ub355\ud134\uc2a4(L1) \ud3ec\ud568), \uc785\ub825 \uc2e0\ud638 \ud68d\ub4dd \ud68c\ub85c(\uc800\uc5ed \ud1b5\uacfc \ud544\ud130(L2, [\u2026]) \ud3ec\ud568 \uac00\ub2a5)<\/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:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/posts\/5380","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/comments?post=5380"}],"version-history":[{"count":0,"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/posts\/5380\/revisions"}],"wp:attachment":[{"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/media?parent=5380"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/categories?post=5380"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dclcontrols.com\/ko_kr\/wp-json\/wp\/v2\/tags?post=5380"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}