Recognize the quality of LED-drivers

Rob Snoek - R&D manager Lumotech B.V. - Heerhugowaard

Elements where LED-driver technology is key

• Safety• Compliance

• Power supply and cabling• High power factor

• Life time• Thermal design• High grade components (Elco’s)• Efficiency

Elements where LED-driver technology is key

• Reliability• Thermal protection• Surge protection

• Quality of light• No flicker• No rippel• (warm) dimming

Type of drivers found in the market:

• What is the difference between Constant Current and Constant Voltage?

• Why/where is CC used? Pro’s and Con’s?

• Why/where is CV used? Pro’s and Con’s?

Safety and Standards

The ECO design directive

From 2016 for drivers the following is applicable:• Max standby power of 0,5W• Max no-load power of 0,5W• Chemical substances in pcb, housing and all components

Safety and Standards

• EN55015 (Limits and methods of measurement of radio

disturbance characteristics of electrical lighting

and similar equipment)

• EN61000-3-2 (Limits for harmonic current emissions, equipment input, current ≤16 A per phase)

• Etc, etc, etc

Standards CE

What is Inrush current and why is this important?

• Lumotech drivers: no input elco inrush current is low. Only X2 filter capacitors minimum inrush peak.

• No standard for measurement of inrush current. Lumotech always uses the HA-1600A from TTI and test on 240Vac, fase 60º

=30W

Power supply and cabling

• For light applications < 25W the PFC is not standardized. These requirements will change soon!

• We recommend to require a PFC > 0,9 at full load.

• The power factor for loads > 25W should be higher than 0,9

What is: Power factor and why is this important?

Power supply and cabling

Tc is the highest temperature point at the surface of the driver at the documented ambient temperature, Ta.

A sales person: high Tc value => excellent driver…….. This is a wrong assumption…

Important is the difference between between Ta and Tc.

A small difference means that there is no heat concentration in the driver, which is the right design.

Tc should always be considered in relation to Ta.

What is: Tc and why is this important?

Life time

Elco’s, temperature and ripple current.

Temperatuur of resistors and ceramic capacitors Voltage over resistors and ceramic capacitors Location of ceramic capacitors on the PCB. Peak currents and di/dt ratinf of film capacitors.

Mosfet in lineaire mode

Varistors

Inrush current limiter

Life time

Electrolytic capacitors:10 degrees temperature reduction double life time

Hence elco with 10.000 hrs @105°C:20.000 hrs at 95°C40.000 hrs at 85°C80.000 hrs at 75°C

Life time

Advertisent of a wellknown EU driver manufacturer:

Life timer: 50’000 h at tc = 75°C

In the datasheet is stated:Ta = 50°CTc = 85°C

35’000 hrs tc = 85°C, 10% failure rate50’000 hrs tc = 75°C, 10% failure rate Refer to

At an ambient temperature of 50°C. This is the temperature of the lamp in which the driver is located, is Tc 85°CHence within 35000 hrs one can expect 10% failure!

Life time

• Low efficiency strong heat generation in driver.

• When measuring the input voltage and current

separate from the output voltage and current the

result will be incorrect due to the phase diffrence

• Often LED-products are sold with efficiency calculations that should convince the customer on the energy savings. But how is that at dimming?

What is: Efficiency and why is this important?Life time

• Shutdown => Light switches of at over temperature.

• Current regulating => limitation of the power output of the driver.

When an airco fails, the light stays on and will dim minimally.(dim effect almost invisable.)

Shutdown: Light switches off at “over temperature” or stays on but the guarantee will not longer be valid. (temperature patern is logged in the driver!)

What is: Thermal protection and why is that important?

Reliability

• Surge protection can be measured two ways.

• Differential. Between phase and zero

• Common mode. Between phase and ground, zero and ground.

• Drivers without ground connection sometimes allow 10kV common mode surge, but when the differential mode surge is 1kV the driver will not surfive the expected life time

• Nevertheless companies advertise with 10kV surge protection.

• Ensure to ask for differential surge protection!

What is: Surge protectie and why is this important?Reliability

• Question from customer: Do Lumotech drivers

generate a 9Hz flickering at the output? => NO!

• Root cause of 9Hz flickering: control loop speed of the primary controller.

• Solution:1) Choose the correct control loop speed

+ sec. buffer elco minimum 100Hz ripple

2) a second stage almost no ripple present

What is: LED-current stability and why is this important?

Quality of light

• 9 – 10 Hz flicker of LEDs is hardly visable and difficult to test.

• Some people are more sensitive to light flicker, allthough the intensity of the deviation is very small.

• In particular in office enviromenments differences in light intensity will become apparent.

• Measurement by portable phones or cameras cannot be done.Due to interference of the phone with the flickering at the output.

What is: LED-current stability and why is this important?

Quality of light

Netspanning en Drivers

• Gelijkspanning op het lichtnet wordt veroorzaakt door asymmetrische belastingen, zoals bijvoorbeeld een goedkope retrofit ledlamp, een haardroger op half vermogen, espressomachines e.d.

• Vele dingen worden getest van een driver, maar heeft u ook wel eens getest of u driver correct functioneert als de netspanning een kleine DC offset heeft?

• Wij hebben een voorbeeld, DEMO

Lichtkwaliteit

Lumotech heeft een breed programma drivers met zero ripple current

Zero ripple current betekent dat de uitgang voor wat betreft stroom en spanning geen PWM of 100Hz ripple bevatten, ook niet tijdens het dimmen.Bij nagenoeg alle Lumotech drivers wordt tijdens het dimmen geen PWM gebruiktZero ripple programma is:

L05011i2,L05011i3 en L05011i4L05031L05025 en L05040 serie

Zero ripple

Lichtkwaliteit

Warm dimming means that aLED, which is suitable for warm dimming functions in accordance with the specificationThe color of the LED changes to a warm color during dimming.

A driver with PWM dimming method connected to a warm-to-dim LED, will not offer the expected result.

DEMO

Warm dimming or dim to warm

Quality of light

Additional points of interest.

• A LED driver is only but one element in a lighting installation. As example

following other components can play a role:

• A presence detector

• A light sensor

• A Dali to 1-10V converter

• A Dali master system

Standardisation ensures that drivers are safe and most drivers are covered by a safety certification mark like ENEC.

However, when including an extern component, ensure that such product is not directly connected to the external power. Check whether a transformer or HF transformer is part of the product or check the double isolation marking on such product.

Conclusion

A responsable choice for a suitable LED driver should be made by hand of following criteria: • Safety• Power supply and cabling• Expected life time• Reliability• Quality of light

Questions?

“Thanks for your attention!”Please consult: www.Lumotech.com and find the white paper

“lifting the lid of LED drivers