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“Scrolling through boring GOSTs ...” or requirements analysis when developing an LED driver

I have to admit - I like to develop LED drivers. Apparently there is something special in creating light, some kind of magic. Let the debate continue about the harmfulness of the so-called “blue peak”, even if in the store we can still buy horrible LED bulbs with 100% ripple, however, to develop a good LED-driver is an excellent task. However, this is lyrics and it's time to move on to the topic.



I decided to write an article about one of my developments - a compact LED-driver with very interesting characteristics, however, boringperfectionism does not allow this to be done without a preamble, where did the requirements come from that will be applied during development. If you dig a little deeper, there are decent nuances and I think many people share the well-known principle of "the essence in detail" (and this is not only about electronic components).

Such thoughts prompted me to write this article-excursion into the world of GOSTs.

So, if you are interested in the requirements for LED equipment, as well as recommendations for CE certification - welcome to cat.

State Standards List


Here I give a list of all documents with full names in order to use short names in the text in the future.

Decree of the Government of the Russian Federation No. 1356 “On approval of requirements for lighting devices and electric lamps used in alternating current circuits for lighting purposes” , hereinafter referred to as the “Resolution”.

GOST R 55705-2013. Lighting devices with LED light sources. General specifications.

GOST CISPR 15-2014. Standards and methods for measuring the characteristics of radio interference from electric lighting and similar equipment.

GOST IEC 61000-3-2-2017. Emission standards for harmonic current components (equipment with an input current of no more than 16 A in one phase).

GOST R 51514-2013. Resistance of general-purpose lighting equipment to electromagnetic interference.

GOST R IEC 60598-1-2011. Lamps. Part 1. General requirements and test methods.

Classification requirements


  • Power factor
  • Light ripple
  • Coefficient of performance (COP)
  • EMC requirements
  • Safety requirements

Why exactly these requirements are proposed to be considered? These parameters have a significant impact on the choice of structure, and later on the circuitry of the LED driver. In addition, these requirements are very important in product certification.

Power factor


We turn to GOST R 55705-2013 to understand how it is standardized:


But that is not all, in the “Resolution” there are also requirements in this part, as to lamps:

So to the lamps:


The question arises how to link these requirements with the requirements of GOST, because the second stage toughens the requirements given in GOST R 55705-2013, but we will consider that the decision is more important.

Light ripple


In GOSTs, this parameter is not standardized, so we turn to the "Resolution":


By the way, I forgot to mention what the first and second stages are:


It turns out that the second stage has already arrived!

Coefficient of performance (COP)


The question is, what does this parameter do here if it is not standardized in any GOST? In general, I believe that by many developers and customers the value of efficiency is greatly underestimated. There are two aspects, the first one, efficiency is heat dissipation, and it in turn affects the design (measures for heat removal) and reliability.

Secondly, there is an important parameter - light output (lm / W), which, by the way, is very fully normalized by the “Resolution”. Obviously, efficiency has a significant effect on light output.

EMC requirements. Emission


EMC requirements are divided into noise immunity and interference emission. The first is how the product withstands external noise, and the second - how it emits interference.

Emission includes:

  • Conducted interference
  • Radiated interference
  • Harmonic current emission

Conducted interference- this is interference propagating through the wires, in fact - current ripples that the driver "sends" to the network, if we talk about interference on the supply circuits. Measurement is performed using a spectrum analyzer. The product (LED-driver or luminaire) is connected to the mains supply via the “network equivalent” (LISN) and the signal is sent to the spectrum analyzer from the network equivalent. During certification tests, this happens when there is a grounded plane and at a certain position of the test product relative to this plane (as far as I remember, at a distance of 40 cm). When testing in the company's own laboratory (or home laboratory, if it was possible to accumulate on a spectrum analyzer), it is possible to conduct research on the table. But still I recommend creating conditions that are as close as possible to the conditions of the certification lab.

The emission standards are described by GOST CISPR 15-2014. For example, the standards for conducted noise on network (supply) contacts in the frequency range from 9 kHz to 30 MHz look like this:

In general, this GOST also normalizes the level of interference at the output and on the control circuits of the LED driver. However, this is a rather rare case, because usually a lamp with an already installed driver is usually certified and only the power circuits are output. In any case, in my practice, it was never for LED drivers that I had to measure the conducted noise on the output or control circuits.

For example, I will give a scan for conducted noise, it may look like this:


Or so:


Radiated interference is the interference that is being broadcast. The test is carried out in a special anechoic room:


For measurements, a special antenna or a set of antennas is used, measurements are carried out in horizontal and vertical polarization, the signal from the antenna, as well as in the case of conducted noise, is output to the spectrum analyzer. The norms for emitted interference on the network (supply) contacts in the frequency range from 9 kHz to 30 MHz look like this:


Emission of harmonic current components. In essence, these are the amplitudes of the harmonics of the consumed current. Standardized by GOST IEC 61000-3-2-2017. Let me remind you that LED equipment according to this GOST is classified as class C equipment. Harmonic components:


EMC requirements. Noise immunity


Noise immunity is standardized by the standard GOST R 51514-2013 and includes immunity to the following factors:

  • Electrostatic discharge
  • Radio frequency electromagnetic field
  • Industrial frequency magnetic field
  • Nanosecond Pulsed Interference
  • Injected Currents
  • High energy microsecond impulse noise
  • Voltage dips and interruptions

This topic is very extensive and, perhaps, is beyond the scope of this article. From my experience of certification testing, I can say that tests for electrostatic discharges and microsecond pulsed noise of high energy can be especially critical. Of course, nanosecond interference is also a serious test, but usually if "microseconds" have passed, then "nanoseconds" are automatically passed.

Safety requirements


If we talk about safety requirements, these are mainly design requirements, so I propose to leave them to the designer. What nevertheless affects the choice of the structure and circuitry of the LED driver is the electrical safety equipment classes and the corresponding galvanic isolation voltages between the primary and secondary sides. GOST R IEC 60598-1-2011 describes the classes as follows:


Class II:


1 — :

a) , , , , , , , , . II .

b) , , - . II .

c) , ) b) .

2 — II, , .

3 — , II. , , , , , , .

Note 4 - A luminaire with double and / or reinforced insulation having a contact clamp or a grounding terminal is classified as a class I luminaire. However, a protection class II stationary luminaire designed for a loop-type connection method may have an internal grounding terminal clamp to ensure continuity of grounding. wires that do not end in this luminaire, provided that this clamp is isolated from accessible metal parts by insulation of protection class II.

Note 5 - Luminaires of protection class II may have elements in which protection against electric shock is provided by the use of SELV.

Class III:


A little bit about CE certification


Roughly what awaits you:


Some tips:

  • . ;
  • 5-7 , 10. , 1 , , «Fail», 3 , ;
  • – . ;
  • Do not take for test tests products that have already passed any tests for microsecond and nanosecond pulses. These effects can lead to the degradation of protective elements (fuses, fusible resistors, varistors) and the device may burn out at the wrong time.

Conclusion


So, the analysis of requirements in the development of LED driver circuitry is a big and important topic. Especially if you are going to honestly certify your products. Or even more so get a CE certificate and sell for export. Let me remind you that this material is an introduction to my article about the development of LED-drivers, so - see you soon.

Interesting developments and so that when testing was only "Pass"!

Power is cool - deal with it.

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