What is class 2, class II and LPS? What is the difference between class I and class II?

Date：2016-07-17

Explanation:

 “CLASSI, II ,III” : Mainly consider the insulation system of product, derived from the IEC system, simple explanation is as follows:

1,From appearance: 
Class I power supply: (3pin AC plug) 
Class II power supply :(2pin AC plug)， 
2. From current leakage:
Class I power supply :0.75mA(Max) 
Class II power supply:0.25mA(Max) 
3.HI-POT 
Class I power supply :1500VAC 60SEC 10mA 
Class II power supply :3000VAC 60SEC 10mA
4. From Nameplates :
Class I power supply  no“回” double insulation symbol 
Class II power supply  with“回” double insulation symbol 

5. Earth ground connection resistance test
Class I power supply no need
Class II power supply necessary

 Class 2 mainly Consider the current and energy capacity,derived from(Canadian Electrical Code Part I) / US regulations. The circuit voltage can be divided into 0-20 V, 20-30 V, 30-60 V and 60 -150 V four ranges. They have specific requirements for each size range to current and energy capacity. If confirmed as CLASS 2 circuit, you can reduce the number of parts required on this circuit, on purpose of saving cost .To specific the product standard, CAN / CSA C22.2 No.223 (ELV, cLASS 2 output power adapter) and UL1310 and CAN / CSA C22.2 No.950 (computer information products) and UL1950 are applied. in order to achieve CLASS2 circuit requirements, you can use the following ways to limit the current circuit: 1. Make use of transformer’s impedance itself to limit (one minute after the short-circuit current drops to the required value or less) 2. Use the overcurrent protection device to limit (using the appropriate specifications of the fuse to cut off the circuit) 3. Use Electronic circuit protection to limit (under normal and abnormal conditions can automatically limit the current to a predetermined value or less)

UL Class 2 LED Power Supplies meet the US power supply safety standards used to regulate low power sources, has limitation voltage,power,current.

The maximum output voltage under any load condition (including no load) between any two output terminations of a unit shall not be more than the peak voltages

42.4V peak for sinusoidal or nonsinusoidal AC

60V for continuous DC (if apply US UL and CA UL at the same time, empty load can not over 42.4VDC  )

The UL Class 2 standard limits the output power to be less than 100W, output current to 5A, output voltage to 60VDC and leakage current to be less than 0.75mA

LPS: When an electronic circuit is powered by a limit power source, its output current and power are under the limitation shown in Table 3.4, and the risk of fire can be reduced significantly. So, the safety distances and flammability rating of components can be much lower. In this way, the design cost for SPS compliant with LPS can be reduced as compared with non LPS SPS. 

References[edit]

• IEC 61140: Protection against electric shock — Common aspects for installation and equipment. International Electrotechnical Commission. 2001. (formerly: IEC 536-2: Classification of electrical and electronic equipment with regard to protection against electric shock, 1992)
• BS 2754 : 1976 (1999): Memorandum. Construction of electrical equipment for protection against electric shock.
• Wikipedia:https://en.wikipedia.org/wiki/Appliance_classes

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