{"id":19580,"date":"2026-10-19T11:45:56","date_gmt":"2026-10-19T03:45:56","guid":{"rendered":"https:\/\/www.wehopower.com\/news\/led-driver-output-voltage-constant-current-window\/"},"modified":"2026-10-19T11:45:56","modified_gmt":"2026-10-19T03:45:56","slug":"led-driver-output-voltage-constant-current-window","status":"publish","type":"news","link":"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/","title":{"rendered":"LED Driver Output Voltage: Check the Full Constant-Current Window"},"content":{"rendered":"<div class=\"weho-blog-content\" id=\"weho-article-19\" data-weho-article-id=\"19\">\n<p class=\"direct-answer\"><strong>An LED driver&#8217;s output voltage depends on its output mode and operating state. For a constant-current driver, the LED string determines the required working voltage; that voltage must stay inside the driver&#8217;s documented constant-current window at the selected current.<\/strong> Check both ends of the window across LED variation, temperature, current tolerance, and connection losses. The advertised wattage, nominal output voltage, and maximum open-circuit voltage cannot replace this check.<\/p>\n<figure class=\"cover release-hero\"><picture><source media=\"(max-width:640px)\" type=\"image\/webp\" srcset=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/cover-19-mobile.webp\" width=\"780\" height=\"600\"><source type=\"image\/webp\" srcset=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/19-cover-960.webp 960w, https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/19-cover.webp 1200w\" sizes=\"(max-width:760px) calc(100vw - 34px), 760px\"><img fetchpriority=\"high\" src=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2026\/10\/19-cover.webp\" width=\"1200\" height=\"675\" alt=\"LED Driver Output Voltage: Check the Full Constant-Current Window  title=\" loading=\"eager\" decoding=\"async\" led driver output voltage: check the full constant-current window title =\"\"><\/picture><figcaption>Conceptual voltage-window illustration; the actual operating limits must come from the exact driver and LED documents.<\/figcaption><\/figure>\n<details class=\"article-toc\" open>\n<summary>\ubaa9\ucc28<\/summary>\n<nav class=\"toc-links\" aria-label=\"Article sections\"><a href=\"#voltage-meanings\">Separate four output-voltage meanings<\/a><a href=\"#led-inputs\">Collect the LED and driver boundaries<\/a><a href=\"#string-corners\">Calculate the complete string window<\/a><a href=\"#outside-window\">Interpret an out-of-window condition<\/a><a href=\"#operating-states\">Check startup, dimming, and disconnection<\/a><a href=\"#qualification-record\">Keep a useful qualification record<\/a><a href=\"#voltage-inquiry\">Request the exact operating limits<\/a><\/nav>\n<\/details>\n<p>This guide gives luminaire OEM engineers a repeatable voltage-window screen. It concerns directly driven constant-current LED strings. LED strips with their own current-setting circuitry require a different <a href=\"https:\/\/www.wehopower.com\/ko\/news\/constant-current-vs-constant-voltage-led-driver-how-to-choose-for-your-project\/\" data-weho-link-kind=\"guide\">constant-voltage or constant-current interface review<\/a>.<\/p>\n<section id=\"voltage-meanings\">\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">\ubaa9\ucc28<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"\ubaa9\ucc28 \ud1a0\uae00\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">\ube44\ub140\uc7a5<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewbox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewbox=\"0 0 24 24\" version=\"1.2\" baseprofile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Separate_four_output-voltage_meanings\" >Separate four output-voltage meanings<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Collect_the_LED_and_driver_boundaries\" >Collect the LED and driver boundaries<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Calculate_the_complete_string_window\" >Calculate the complete string window<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Interpret_an_out-of-window_condition\" >Interpret an out-of-window condition<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Check_startup_dimming_and_disconnection\" >Check startup, dimming, and disconnection<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Keep_a_useful_qualification_record\" >Keep a useful qualification record<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-voltage-constant-current-window\/#Request_the_exact_operating_limits\" >Request the exact operating limits<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Separate_four_output-voltage_meanings\"><\/span>Separate four output-voltage meanings<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>A constant-current driver adjusts its output voltage to establish the specified current through a compatible LED load. Its usable regulation range is bounded. A constant-voltage supply instead regulates a voltage while the connected circuit determines current within the supply&#8217;s limits. Some products have combined or programmable operating regions, so inspect the actual output characteristic.<\/p>\n<div class=\"weho-table-wrap\" tabindex=\"0\" role=\"region\" aria-label=\"Scrollable engineering table\">\n<table>\n<caption>Voltage entries that answer different questions<\/caption>\n<thead>\n<tr>\n<th scope=\"col\">Entry<\/th>\n<th scope=\"col\">What it tells the engineer<\/th>\n<th scope=\"col\">\uadf8\uac83\uc774 \ub9cc\ub4e4\uc5b4\uc9c0\uc9c0 \uc54a\ub294 \uac83\uc740<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Nominal or rated output voltage<\/td>\n<td>A specified operating point or voltage setting<\/td>\n<td>The complete constant-current range<\/td>\n<\/tr>\n<tr>\n<td>Constant-current window<\/td>\n<td>Voltage range where the stated current regulation applies<\/td>\n<td>Every startup or dimming condition<\/td>\n<\/tr>\n<tr>\n<td>Open-circuit maximum<\/td>\n<td>A specified unloaded-output boundary<\/td>\n<td>Available continuous LED operating voltage<\/td>\n<\/tr>\n<tr>\n<td>Overvoltage protection level<\/td>\n<td>A protection threshold under defined conditions<\/td>\n<td>A normal design target<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>MEAN WELL&#8217;s <a href=\"https:\/\/led.meanwell.com\/productPre.aspx\" target=\"_blank\" rel=\"noopener noreferrer\">LED drive-method explanation<\/a> identifies LED forward-voltage variation and a model-dependent constant-current region. Its numerical examples describe its own products; they are not specifications for a WEHO driver.<\/p>\n<\/section>\n<section id=\"led-inputs\">\n<h2><span class=\"ez-toc-section\" id=\"Collect_the_LED_and_driver_boundaries\"><\/span>Collect the LED and driver boundaries<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Start with the LED module&#8217;s permitted current and forward-voltage limits, including the relevant temperature and manufacturing tolerances. Record how many devices are in series. Typical forward voltage at room temperature is insufficient for an enclosure that must start cold and operate hot.<\/p>\n<p>Obtain the driver&#8217;s current accuracy, applicable constant-current window, input range, temperature limits, and any relationship between current setting and operating region. A selectable-current table may provide a different maximum voltage at each current. Keep voltage adjustment, current adjustment, and dimming commands separate in the review. Check the <a href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-dimming-compatibility\/\" data-weho-link-kind=\"guide\">complete LED dimming control path<\/a> separately.<\/p>\n<p>Use connection resistance at the stated design condition. For a remote-driver layout, also complete the <a href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-output-cable-extension-validation\/\" data-weho-link-kind=\"guide\">output-cable extension review<\/a>. Include both conductors and connectors. When current varies within tolerance, use the appropriate current bound for each corner calculation. The LED voltage limits must themselves be valid at those currents; do not combine unrelated typical figures into a supposed worst case. MEAN WELL&#8217;s <a href=\"https:\/\/led.meanwell.com\/qa.aspx?c=9\" target=\"_blank\" rel=\"noopener noreferrer\">LED selection FAQ, question 3<\/a> similarly calls for checking both ends of the combined LED forward-voltage range.<\/p>\n<\/section>\n<aside class=\"product-documentation\" aria-label=\"Specific product documentation example\" id=\"model-documentation-19\">\n<p><strong>Specific product documentation example<\/strong><\/p>\n<p>Check what a family table actually specifies. The <a href=\"https:\/\/www.wehopower.com\/ko\/product\/ac-dc-12v-24v-36v-48v-led-driver-100w-constant-voltage-waterproof-ip67-switching-power-supply\/\" data-weho-link-kind=\"product_detail\">XLG-100 product page: XLG-100-24 variant<\/a> \uadf8\ub9ac\uace0 <a href=\"https:\/\/www.wehopower.com\/wp-content\/uploads\/2025\/07\/XLG-100.pdf\" target=\"_blank\" rel=\"noopener noreferrer\" data-weho-link-kind=\"datasheet\">XLG-100 datasheet (PDF): XLG-100-24 column<\/a> identify nominal output voltage and rated current, but the linked sheet does not publish the 30\u201342 V \/ 700 mA constant-current operating window assumed below. A rated-current or overcurrent-protection entry is not a substitute for that window. For a direct-driven string, obtain the exact proposed CC model\u2019s published operating-region limits and current tolerance; do not transfer values from a 24 V variant or family headline.<\/p>\n<\/aside>\n<section id=\"string-corners\">\n<h2><span class=\"ez-toc-section\" id=\"Calculate_the_complete_string_window\"><\/span>Calculate the complete string window<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>Original hypothetical example, not a WEHO specification:<\/strong> consider a 700 mA driver with assumed current accuracy of \u00b13% and an assumed 30.0\u201342.0 V constant-current window throughout the conditions being reviewed. Each LED is specified, for this example, between 2.90 and 3.45 V over the complete current, temperature, and production range. The output circuit has 0.80 \u03a9 total loop resistance at the chosen calculation condition.<\/p>\n<p>The current limits are 0.700 \u00d7 0.97 = <strong>0.679 A<\/strong> and 0.700 \u00d7 1.03 = <strong>0.721 A<\/strong>. Corresponding connection drops are 0.5432 V and 0.5768 V. Required driver voltage is the sum of LED forward voltage and connection drop.<\/p>\n<div class=\"weho-table-wrap\" tabindex=\"0\" role=\"region\" aria-label=\"Scrollable engineering table\">\n<table>\n<caption>Hypothetical series-count screen against a 30.0\u201342.0 V window<\/caption>\n<thead>\n<tr>\n<th scope=\"col\">LEDs in series<\/th>\n<th scope=\"col\">Minimum required voltage<\/th>\n<th scope=\"col\">Maximum required voltage<\/th>\n<th scope=\"col\">Arithmetic screen<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>10<\/td>\n<td>29.5432 V<\/td>\n<td>35.0768 V<\/td>\n<td>Below lower window at minimum corner<\/td>\n<\/tr>\n<tr>\n<td>11<\/td>\n<td>32.4432 V<\/td>\n<td>38.5268 V<\/td>\n<td>Within assumed window<\/td>\n<\/tr>\n<tr>\n<td>12<\/td>\n<td>35.3432 V<\/td>\n<td>41.9768 V<\/td>\n<td>Only 0.0232 V below upper boundary<\/td>\n<\/tr>\n<tr>\n<td>13<\/td>\n<td>38.2432 V<\/td>\n<td>45.4268 V<\/td>\n<td>Exceeds upper window<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>The 12-LED maximum is 12 \u00d7 3.45 + 0.721 \u00d7 0.80 = <strong>41.9768 V<\/strong>. Rounding it to 42 V hides a nearly exhausted allowance. If the resistance assumption rises to 0.90 \u03a9, the result becomes 42.0489 V and exceeds the assumed window. A headline power rating cannot resolve this voltage limitation.<\/p>\n<p>The 11-LED option passes this calculation under the stated assumptions. It has not been approved for startup, dimming, fault behavior, thermal performance, or production tolerance beyond those assumptions. Resolve those separately before selecting a driver or changing the string.<\/p>\n<\/section>\n<section id=\"outside-window\">\n<h2><span class=\"ez-toc-section\" id=\"Interpret_an_out-of-window_condition\"><\/span>Interpret an out-of-window condition<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Below the minimum constant-current voltage, the driver may no longer maintain its specified regulation. Above the maximum, it may be unable to deliver the required current. The resulting behavior could involve reduced current, cycling, shutdown, or another documented mode; do not predict it from the window alone.<\/p>\n<p>Likewise, a successful room-temperature sample does not prove the limiting corner. The sample may have lower forward voltage than the production maximum, a shorter harness, or a different case temperature. Record the actual configuration rather than treating visible illumination as a complete pass.<\/p>\n<\/section>\n<section id=\"operating-states\">\n<h2><span class=\"ez-toc-section\" id=\"Check_startup_dimming_and_disconnection\"><\/span>Check startup, dimming, and disconnection<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Review starting conditions separately from steady operation. Ask for the permitted load arrangement, startup behavior, dimming operating area, and output-disconnection instructions. An unloaded meter reading can reflect a protection or restart sequence and is not a reliable substitute for the specified constant-current window.<\/p>\n<p>Ask specifically whether the proposed output connector may be disconnected or reconnected while energized. Depending on the driver design, open-load behavior and charge retained in the output stage can make reconnection a separate current-transient event. The open-circuit maximum alone does not predict the actual voltage trajectory, discharge time or protection response. <a href=\"https:\/\/led.meanwell.com\/qa.aspx\" target=\"_blank\" rel=\"noopener noreferrer\">MEAN WELL\u2019s LED assembly guidance<\/a> gives a manufacturer-specific example of possible surge damage when the LED load is connected after power is applied. Follow the selected driver\u2019s own switching and discharge instructions rather than treating a secondary plug as a load switch.<\/p>\n<p>Evaluate <a href=\"https:\/\/www.wehopower.com\/ko\/news\/led-driver-relay-contact-inrush-rating\/\" data-weho-link-kind=\"guide\">AC-side LED driver inrush current<\/a> separately when switching upstream power. A steady output-voltage-window calculation establishes neither output hot-plug permission nor input-switch compatibility.<\/p>\n<\/section>\n<section id=\"qualification-record\">\n<h2><span class=\"ez-toc-section\" id=\"Keep_a_useful_qualification_record\"><\/span>Keep a useful qualification record<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Retain the exact driver model, suffix, document revision, current setting, LED bin or module specification, series count, harness revision, and temperature conditions. Link each boundary in the calculation to its source. Where the manufacturer gives only a typical value, identify the missing limit and obtain clarification instead of silently treating it as guaranteed.<\/p>\n<p>Define acceptance criteria before testing the assembly. Separate output-current accuracy, successful startup, dimming behavior, electrical output limits, and relevant temperatures. Qualified personnel should use the manufacturer&#8217;s test and isolation instructions. A generic multimeter procedure cannot establish every dynamic or unloaded-output condition.<\/p>\n<\/section>\n<section id=\"voltage-inquiry\">\n<h2><span class=\"ez-toc-section\" id=\"Request_the_exact_operating_limits\"><\/span>Request the exact operating limits<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><a href=\"https:\/\/www.wehopower.com\/ko\/contact\/\" data-weho-link-kind=\"inquiry\">Contact WEHO about an LED-string driver<\/a> through the contact form with permitted current, minimum and maximum string forward voltage, series count and connection losses, plus the input and temperature conditions. Request the corresponding operating-region and startup documentation so the candidate can be evaluated against the actual load.<\/p>\n<\/section>\n<div class=\"sources-note\"><strong>Technical references<\/strong><\/p>\n<ul>\n<li><a href=\"https:\/\/led.meanwell.com\/productPre.aspx\" target=\"_blank\" rel=\"noopener noreferrer\">MEAN WELL LED Driver Power Supply Solution, LED drive methods<\/a><\/li>\n<li><a href=\"https:\/\/led.meanwell.com\/qa.aspx?c=9\" target=\"_blank\" rel=\"noopener noreferrer\">MEAN WELL LED Functionality FAQ, questions 3 and 12<\/a><\/li>\n<\/ul>\n<\/div>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Check the full LED-string voltage range against the driver\u2019s constant-current window. A series-count example exposes a nominal fit with almost no remaining allowance.<\/p>","protected":false},"author":2,"featured_media":19396,"parent":0,"menu_order":32,"comment_status":"","ping_status":"","template":"","format":"standard","meta":{"_acf_changed":false,"_joinchat":[],"footnotes":""},"news_category":[284],"class_list":["post-19580","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","news_category-product-articles","entry"],"acf":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/news\/19580","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/types\/news"}],"author":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/comments?post=19580"}],"version-history":[{"count":0,"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/news\/19580\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/media\/19396"}],"wp:attachment":[{"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/media?parent=19580"}],"wp:term":[{"taxonomy":"news_category","embeddable":true,"href":"https:\/\/www.wehopower.com\/ko\/wp-json\/wp\/v2\/news_category?post=19580"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}