It is very important to understand the difference between product and component standards, and that product and component safety standards have different scopes, tests, and requirements. Optical isolators rely mostly on thickness for internal spacing whereas digital isolators have insulation of less than one-thousandth of an inch and rely on safety testing ( Figure 1 ).įigure 1 Here is a comparison of optical and digital isolators. Digital isolators utilize polyimide/silicone-dioxide for their insulation. The newer generation of digital isolators, magnetic and capacitive, offer advantages in performance, size, and power efficiency. Optos have larger footprints and provide high levels of isolation when a film barrier is used. Optical isolators, also referred to as optocouplers or optos, employ an opaque silicone polymer material as the internal insulation. Capable of high speeds and relatively small package. Uses polyimide or silicone dioxide insulation.Ĭapacitive – Uses a changing electric field to transmit energy by means of capacitance. Magnetic – Inductive coupling transfer using transformer coil design and provides high isolation at high frequencies. Advantage is high electrical isolation values. Optical – Uses light (LED) transfer across a transparent nonconductive insulation barrier. There are three isolator technologies in use today: VDE and UL Certifications (International and North America)ħ-17 (VDE 0884-11) to replace digital isolator standard VDE 0884-10 in the future. Isolation Voltage, V IOTM (test voltage) e.g., 2,500 – 5,000Vac Working Voltage, V IORM (supply voltage) e.g., 150 – 600Vac (210 – 840Vpeak) Reinforced Insulation (tests and spacings) This article will cover important isolator selection parameters, including:Ĭomponent Standards (IEC 6, VDE 0884-10 1 ,UL 1577) The purpose of this article is to highlight the standards, insulation, tests, and ratings for isolators used in hazardous voltage applications where an isolator is used as a safety isolating component. Isolator components are referred to as safety-critical components and require special consideration to ensure that they meet the relevant safety standards and are safe for use in products. They function by transmission of signal coupling from primary-to-secondary circuits through various mediums including optical (light), magnetic (inductive) and capacitance (charge). Isolator components are integrated circuit semiconductor devices (ICs) which provide safety isolation (insulation). Reinforced insulation is required between hazardous voltage and user-touchable circuits. There are several levels of safety insulation: Basic, Double, and Reinforced. Non-hazardous voltage circuits, +/-3.3Vdc, 5Vdc, and 12Vdc, are typically user-touchable and must be isolated from hazardous voltages, > 30Vrms/42.4Vpeak/60Vdc, to protect the user from dangerous voltages! Safety isolation is the separation of a section of non-touchable hazardous voltage circuits (> 30Vrms/42.4Vpeak/60Vdc) from user- touchable circuits (≤ 30Vrms/42.4Vpeak/60Vdc).
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