How to Connect LED in Minus Voltage

Simplified LED Connection in Telecommunication Environment as Signaling Indicator for Power Distribution Unit

with -48VDC 

by : Rifky Cahyadi & Yogi Cahyadi 

1.  Abstract

This invention describes the novelty of connecting a built in LED inside the Circuit Breaker for Equipment (CBE) system in the Telecommunication Field, operating in -48VDC Power Supply. Furthermore, the solution could be also used to connect an external LED signaling to the built in auxiliary contact of a CBE.

The purpose of this invention uses the existing infrastructure available in the Telecommunication Power Distribution system to first indicate the presence of Failure, following by a trip of related Circuit Breaker instantly to provide the visual indication in the Power Distribution Unit, via LED light. This invention includes the method of connecting the LED and the CBE with built in LED, and an external alarming LED through the built in auxiliary contact of a CBE in a -48VDC environment.

1. E-T-A CBE type 3120-F series      b. internal wiring

Figure 1 Circuit Breaker for Equipment (CBE) with built in LED

2.  Abreviations and Acronyms

LED	Light Emitting Diode
CBE	Circuit Breaker for Equipment
DC	Direct Current

 

3.  Existing Implementation

There are many ways in existing implementations of performing an indication / alarming when failure happens in the system. One of the ways by visual indication using DC light bulb that is applicable for DC Power Supply, specifically -48VDC in Telecommunication environment. Plenty of DC light bulbs can be used; the widely known of DC bulb has a bulky size. Thus, it may need quite a space on the Power Distribution Rack itself.  

In case of CBE with built in LED, that is widely used recently, this can be a problem. Applying a minus voltage (-48VDC) in these type of CBEs is almost not efficient. Without additional relay to shift the polarity of the Power Supply, the LED may break. Adding relays and the supporting components into the system would means an additional cost, however with this invention, connecting CBEs with built in LED for visual indication in such environment has no longer limitation.

 

4.  Invention

The invention method describes in this report is meant to provide a solution by making a room for CBE with internal LED to be used in Telecommunication environment with -48VDC, and giving a chance to the LED, the less expensive and compact size of visual indication, to play its role as an indicator / alarming system in the Telecommunication Power Distribution System.

The circuit to connect the LED into a -48VDC power supply is simplified with only using a resistors instead of using a complex voltage shifter relay. The philosophy behind the concept lays on the characteristic operational of the diode, hence the LED itself.

The cathode, abbreviated “K”, sometimes “C” is located at the line perpendicular to the point of the arrowhead. The Anode is on the opposite end and is abbreviated “A”.

Figure 2 Light Emitting Diode symbol

The diode passes current when it is forward biased, which means that the potential at the cathode is more negative than it is at the anode.

Based on this philosophy, we use resistors as a divider of the negative power supply and connect the most negative side of the power supply to cathode of the LED.

Figure 3. LED connection on -48VDC Supply with resistor divider

Figure 4. CBE with internal LED connection on -48VDC Supply

As a summary with this solution we could optimize:

a.  Space when space is premium in the system

b.  Cost efficient with only resistor divider circuit

c.  Make use of the internal LED in the CBE in the Telecommunication voltage environment

5.  Focus of invention

The focus of this invention builds on the following existing concepts.

1)      Power Distribution Unit for Telecommunication application whom require a CBE with built in LED as an indicator

2)      Power Distribution Unit for Telecommunication application whom require an LED as the signaling indicator

The major inventive steps in this claim include as such,

a)  A simple resistor divider circuit to connect LED in the CBE, for CBE with built in LED, into minus power supply source, specifically -48VDC in a Telecommunication environment

b)  Furthermore to connect an external LED as a signaling indicator, into minus power supply source, specifically -48VDC in a Telecommunication environment

  

6.  Example of invention

The example is a Power Distribution Unit System panel for the Telecommunication field, with operating voltage of -48VDC. The panel is to control and protect loads of telecommunication equipment, consist of 2 x 5 circuit breakers as a main breaker and 2 x 1 Circuit breaker as a supporting breaker with built in LED to control and protect the Fans.

The product is called as a Power Distribution Unit (PDU), with general specification as below (See Figure 5):

·         Compact 19 inch Power Distribution Unit, Powder Coated Metal, 2U

·         Design with 2 power source (A and B): with 2 x 5 hot swap Main circuit breaker, type : 8335 and 2 x 1 non-hot swap circuit breaker with illumination, type : 3120

·         Pre-Installed circuit breaker; Nominal current : 10 x 50A, 2 x 3A

·         Off/On Indicator for the Fan switching control and Protection

·         Group Signaling with 2 x 1 LED for Main Circuit Breaker alarming

                                      

Figure 5. PDU Illustration

The PDU signaling alarm is mainly for the Main Circuit Breaker with Collected Tripped Breaker signal (Group Signaling) for each Power Source (A and B).

As for the supporting Circuit Breaker, with the usage of illuminated Type of breaker, CBE with built in LED, it acts as an indication during operating, when there is no faulty occurs.