UL 1577 2019-06 PDF

Full title and description

St UL 1577 2019-06 — Standard for Optical Isolators (redline revision published June 11, 2019). This document contains the UL component safety requirements, test methods and insulation criteria for optical isolators (also called optical couplers or photocouplers) used as components in electrical and electronic equipment.

Abstract

UL 1577 specifies safety requirements that verify the dielectric isolation performance and constructional integrity of optical isolators intended to provide unidirectional signal transfer between dielectrically isolated circuits (equipment rated up to 600 V). Tests include dielectric (rated) voltage, insulation and material evaluations, thermal and mechanical checks, and production/routine testing guidance to ensure isolation is maintained in service.

General information

• Status: Active (component standard; edition in active use; revisions available).
• Publication date: Redline revision: June 11, 2019 (commonly referenced as 2019-06). Note: later administrative revision issued July 6, 2023.
• Publisher: Underwriters Laboratories (UL LLC).
• ICS / categories: Electrical and electronic equipment safety; optoelectronics; component insulation and separation requirements (relevant ICS groups include categories for semiconductor/optoelectronic devices and electrical safety).
• Edition / version: Applies to UL 1577 (Edition 5 with redline revisions, including the June 11, 2019 redline).
• Number of pages: Varies by publisher format (PDF/hardcopy and redline packages); typical downloadable UL PDF editions for component standards are usually in the low double-digit to low triple-digit page range depending on included annexes and redline material. (Exact page count depends on the specific UL release package.)

Scope

These requirements cover optical isolators (optocouplers/photocouplers) intended to provide unidirectional signal transfer between dielectrically isolated circuits, for use in equipment with supply voltages not exceeding 600 V AC RMS or DC. The standard addresses the electrical isolation properties of the insulation between isolated circuits and also covers double-protection optical isolators used in circuits rated up to 250 V, 50/60 Hz, where isolator breakdown could create fire or shock hazards. It does not cover the unrelated electrical properties of the separate (non-isolated) circuits.

Key topics and requirements

• Definition and classification of optical isolator types (basic, reinforced, double-protection) and intended applications.
• Dielectric (rated) voltage testing and verification of insulation between isolated circuits (including test voltages and procedures).
• Creepage and clearance / physical spacing requirements appropriate for the rated voltages and insulation class.
• Material evaluations (polymeric material long-term properties and use-in-equipment evaluations referenced via UL 746B / UL 746C).
• Thermal, mechanical, corrosion and environmental testing to confirm insulation integrity under expected use conditions.
• Production and routine test guidance (type testing vs. 100% production-line checks) and marking/labeling expectations for UL recognition.

Typical use and users

Manufacturers of optocouplers/photocouplers, electronic component designers, power-supply and industrial control system designers, safety and compliance engineers, and testing/certification laboratories use UL 1577 to design, test and demonstrate that optoisolator components meet North American safety insulation requirements before integration into end products.

Related standards

Commonly referenced and complementary standards include IEC/EN standards for photocouplers/optocouplers (for example IEC 60747-5-5 and its later editions), and UL polymeric material standards referenced by UL 1577 (UL 746B, UL 746C). Equipment-level safety standards such as IEC 62368-1 / IEC 60601 / IEC 60950 series (and their UL/ANSI counterparts) are also relevant when an isolator is used as a component in end products.

Keywords

UL 1577, optical isolator, optocoupler, photocoupler, dielectric isolation, reinforced insulation, rated voltage, dielectric withstand, creepage, clearance, UL 746B, UL 746C.

FAQ

Q: What is this standard?

A: UL 1577 is an Underwriters Laboratories component safety standard titled "Standard for Optical Isolators" that defines insulation and test requirements for optocouplers/photocouplers used to provide electrical isolation between circuits.

Q: What does it cover?

A: It covers the electrical isolation properties of optical isolators, including dielectric (withstand) testing, material evaluations, spacing (creepage/clearance), environmental and mechanical tests, and special provisions for double-protection devices for use in potentially hazardous end‑product applications.

Q: Who typically uses it?

A: Component manufacturers (optocoupler vendors), electronic designers, compliance engineers, and testing/certification laboratories responsible for demonstrating component-level insulation and safety. Designers of power supplies, industrial drives, medical or telecom equipment that rely on isolation also use it to choose/qualify components.

Q: Is it current or superseded?

A: The June 11, 2019 document is a redline revision of UL 1577 (often referenced as 2019-06). UL 1577 is an active component standard; administrative and redline updates have continued (for example a later administrative update dated July 6, 2023). Users should check the publisher for the latest edition or redline notices before applying the standard.

Q: Is it part of a series?

A: UL 1577 sits within UL's family of component and equipment safety standards. It references UL polymeric material standards (UL 746B, UL 746C) for material testing and is aligned in scope with international optocoupler standards (IEC 60747-5-5 and related semiconductor/optoelectronics clauses).

Q: What are the key keywords?

A: Optical isolator, optocoupler, photocoupler, dielectric strength, isolation, reinforced insulation, creepage, clearance, UL 1577, UL 746B, UL 746C.