Power Supply Basics

What you need to know when transitioning from the CSS65 to the new CSS65A

Posted by Dulcie on August 30, 2017
Posted in: Power Supply Basics

The TDK-Lambda CSS65 series of 65W 2”x4” power supplies was first launched in 2009 and now, in 2017, the newly developed CSS65A is replacing the older series.

Since 2009, new energy saving regulations have been introduced in the EU (Code of Conduct Tier 2) and the US (DOE Level VI), reducing allowable off-load power consumption and increasing average efficiency targets. Although these standards are primarily for external power supplies, many customers require their internal power supply to conform to these new requirements. Power supply manufacturers have had to modify their power supply designs to include new techniques and components to reduce waste energy. Additionally, operation at higher altitudes is now being demanded (driven primarily by China) and medical equipment for home healthcare is required to meet tougher immunity and voltage dip testing.

Below is a comparison showing the main changes between the CSS65 and CSS65A:

Earth leakage current<250µA<100µA
Average efficiencyNot specified>89% (>86% for 5V model)
Off-load power consumptionNot specified<75mW
AltitudeITE: 2,000m, Medical: 3,000mITE: 5,000m, Medical: 3,000m
to Ground isolation
500Vdc1,500Vac (1 x MoPP)
ImmunityIEC 61000-4EN60601-1-2,
12V & 15V output rating60W65W
Output ripple and noise5V: 50mV
15V: 150mV
19V: 190mV
24V: 240mV
48V: 480mV
5V: 100mV (200mV*)
15V: 120mV (300mV*)
19V: 120mV (300mV*)
24V: 200mV (300mV*)
48V: 200mV (480mV*)

* Measured with < 30% load. Due to pulse skipping techniques for energy saving.

Existing features (like remote sense) and interconnections remain the same, although the CSS65A now has the option to be supplied with JST connectors.

With the exception of a slight increase in light-load ripple voltage which, if the end load has some electrolytic capacitor filtering, should not cause any issues, the product performance has been enhanced to meet the changing standards.

If you have any questions, please contact your local TDK-Lambda sales office.