Brief Introduction to the Performance and Application Circuit of NXP LED Driver IC SSL2101

LEDs have been used in electronic systems for many years, primarily as indicator lights for electronic devices. Driving LED Lighting The key driver of the market is the emergence of high-brightness LEDs and intelligent LED controllers. The main design challenges facing product designers using high-brightness LEDs include thermal management, drive schemes, topology architectures, and existing infrastructure. To replace existing dimmable incandescent or halogen light sources, it is necessary to implement an electronic light driver system that not only works with existing dimmer switches but also replicates the dimming performance of existing light sources.

NXP SSL2101IC can meet the above performance requirements. In addition, it is a highly efficient power converter. This is the first IC in the industry to integrate these capabilities, which enables high-brightness LED lamp designers to integrate electronic circuits in a cost-saving and volume-saving way and benefit from the best thermal trade-off.

Introduction to NXPSSL2101

Existing LED street lights and household general LED lighting solutions are basically divided into two parts, one is the AC-DC power adapter that converts 220V mains power to 24V or 48V, and the other is the LED boost controller that provides drive current to the LED. This discrete solution not only requires many components, but also takes up a considerable space. In order to solve these shortcomings, NXP has developed an integrated single-chip solution SSL2101. It is also the world's first integrated dimmable mains LED driver.

The NXP SSL2101 is a small form factor switch mode power supply (SMPS) controller IC designed specifically for driving LED devices and provides dimming capability to further improve the energy efficiency of LED lighting.

The SSL2101 can drive a variety of lighting systems with different power requirements, including LED retrofit lamps, LED modules, LED spotlights, spotlights, and LED light strings for store displays.

The dimmable capability of the SSL2101 provides lighting system designers with a unique opportunity to design more energy efficient systems. This cost-effective device has a high level of integration, a low total number of electronic components, and minimal board space while allowing designers to take full advantage of the dimmable nature of LEDs.

NXPSSL210X Block Diagram Introduction

●Integrated high-voltage MOSFET to reduce board space

●Integrated dimming circuit, which helps to reduce board space and allows flexible parameter adjustment

The SSL2101 is fully compatible with today's lighting infrastructure and can operate directly from rectified mains power and in conjunction with phase dimmers. The SSL2101 contains a high voltage power switch that can be started directly from the rectified mains voltage, eliminating the need for an external start-up circuit. To support dimming capabilities, the SSL2101 includes two integrated high voltage switches for voltage divider operation, as well as an input for sensing real-time lamp power and activating additional voltage divider operation when required.

The SSL2101 also provides non-isolated (buck) and isolated (flyback) solutions on a single chip. It has an additional input that can be used to detect demagnetization of the inductive component to ensure that the magnetic material is fully utilized and prevent current hard switching. The device's built-in circuit can be used to reduce capacitive turn-on losses and optimize valley switching efficiency, allowing the SSL2101 to perform efficient power conversion at low power levels. The SSL2101 uses on-time mode and frequency mode to control LED brightness. The combination of frequency variation control and on-time control produces a dimming curve similar to that of an incandescent lamp. The use of two control methods also allows designers to reduce peak currents, helping to reduce audible noise from transformers or inductors.

This IC provides a reliable and safe thermal solution through thermally enhanced packaging and built-in over-temperature protection (OTP). It also has short winding protection (SWP) and over-current protection (OTP) functions to meet regulatory requirements for safety and power factor.

NXPSSL2101 main features

The SSL2101 is a multi-chip module (MCM) in an SO16 package that contains a high-efficiency power converter and internal circuitry to achieve mains dimming compatibility. Compared with existing solutions, it has the following advantages:

◆Integrated power switch: This reduces component costs and ensures optimal drive and switch protection.

◆ Valley Detection: This feature reduces converter losses because the switch can be closed at the optimal time.

◆Integrated bleeder switch and comparator: This reduces component count and size.

◆ Intelligent bleeder operation: SSL2101 can detect when bleeder operation is not needed (such as when the LED chain provides sufficient load), which can reduce power consumption and increase system efficiency.

◆ Enhanced heat sink pin design: This increases the life of the SSL2101 and allows it to operate normally at higher ambient temperatures. For alternative solutions, the life of electronic components at higher temperatures is a key parameter.

Duty cycle and converter switching frequency based dimming: This allows the designer greater freedom to define parameter values, which enables the designer to achieve more precise low-brightness dimming and eliminate audio transformer noise by adjusting the parameters that control the dimming system.

◆Logarithmic dimming correction: This allows the LED to dim in the same way as an incandescent or halogen lamp.

◆ Built-in over-temperature protection, over-current protection, short-circuit detection and maximum duty cycle limitation: These features ensure the high reliability of SSL2101 even under extreme working conditions.

LED Characteristics

LEDs require a completely different type of driver than incandescent or halogen lamps. Whereas incandescent lamps behave as pure resistive loads with self-stabilizing characteristics, LEDs require a current source. The luminous flux produced by an LED is approximately proportional to the current flowing through the device. The forward voltage of an LED increases with increasing current, but decreases with increasing temperature. In this respect, LEDs behave like diodes. However, during operation, the forward voltage (VF) of an LED is very large. This voltage is related to the energy (eV) generated when electrons are converted into photons, which in turn is directly related to the color of the light. In addition, VF values ​​can vary greatly between different production batches.

Serial/Parallel Configuration

In most applications where LEDs are used to replace existing light sources, multiple LEDs need to be connected to the driver because a single LED cannot produce enough luminous flux. LEDs can be connected in series or in parallel. If the LEDs are connected in series, the total voltage across the LED chain is equal to the sum of the forward voltages (the current in all LEDs is equal). If the LEDs are connected in parallel, the current will be distributed among the branches. However, since the forward voltage of an LED decreases as the temperature rises, this configuration is inherently unstable. As the temperature rises, more and more current will flow to the branches with lower forward voltages, which will become brighter, while those with higher forward voltages will become dimmer.

However, one reason to use a parallel configuration (or series-parallel combination) is that it allows a large number of LEDs to be connected together at a safe supply voltage, whereas a series connection would require an unacceptably high voltage to achieve the same brightness.

The parallel configuration also provides other advantages. If a problem occurs in one LED or connection in a serially connected LED chain, it will cause a short circuit and all LEDs in the entire chain will not emit light. However, this situation will not happen if a parallel configuration is adopted. When a parallel configuration is adopted, it is recommended to add a current regulation mechanism to each branch to prevent thermal runaway and unequal current or light.

In summary, the efficiency of the power converter is highest when the difference between the output and input voltage is minimal. When the LED driver is powered by mains input, a higher output voltage can be generated, allowing more LEDs to be connected in series.

Mains dimming

Standard industrial and domestic dimmers are designed for use with incandescent lamps, and some more advanced models can be used with transformers connected to halogen lamps. Mains dimmers specifically for LED loads are still rare.

The cost of purchasing and installing a new dedicated dimmer can easily exceed the light source itself, so an LED lighting system that works with existing dimming infrastructure, such as one built around the NXP SSL2101, opens the door to a market with huge potential and potential.

Since existing dimmers are designed for incandescent lamps (approximately resistive loads, power is mostly between 20W and 50W), some additional circuitry is needed to allow them to be used in LED lighting systems. There is no standard for incandescent lamp dimmers on the market, so there are a large number of mains dimmers with different performance and parameter values ​​on the market.

NXPSSL2101DEMO Introduction

At present, we have used this dimming IC to produce a LED dimming bulb DEMO, and used it with a Samsung 2-watt LED light source (a 2-watt LED has a luminous flux of 150LM). It can use the existing dimming system to achieve continuous adjustment of the LED bulb within the range of 0%-100%, with an efficiency of more than 70%. The power supply drives three 2-watt Samsung LEDs, with a total power of 6 watts (input voltage: 220V, output: 0.18A/30V).

NXP SSL2101 accelerated life test exceeds 7,000 hours

The SSL2101 is undergoing one of the longest accelerated life tests in the industry, running with zero failures since December 2008. To date, the test has reached 7,000 hours and is still ongoing. Traditional life test procedures in the semiconductor industry are usually based on 1,000 hours of testing time, which is far exceeded.

A random batch of SSL2101 IC drivers were tested under high stress conditions from standard production, and all test samples remained fully functional after more than 7,000 hours of operation at an IC junction temperature of 150°C. Multiple tests and different settings were used to detect all possible failure modes under several usage conditions, including continuous turn-on, on/off switching cycles, and various usage combinations. Based on the accelerated life model, the extrapolated life of SSL2101 in real lighting applications is estimated as follows:

●Lifespan exceeds 60,000 hours at 105°C

●Lifespan exceeds 35,000 hours at 115°C

●Lifespan exceeds 20,000 hours at 125°C

● Lifespan exceeds 7,000 hours at 150°C

Introduction to NXPSSL2102

It is the latest LED integrated mains dimming driver IC, which can support 25W maximum power, its deep dimming capability can be as low as 1% of full light intensity, and is compatible with a variety of dimmers. The compact, highly integrated, and energy-efficient LED driver IC is an ideal choice for small sealed LED lighting applications.

The SSL2102 is suitable for high-efficiency and high-power factor LED lighting applications, including: 8W to 15W compact applications; 15W to 25W LED modules, such as LED spotlights and downlights; and LED light strings for shopping mall counters with a maximum power of 25W.

Key features of the SSL2102 include:

◆Achieve visually natural dimming through built-in logarithmic dimming curve

◆Support most dimmers on the market (such as thyristor type, transistor type)

◆High integration, few external components required

◆Supports switching power supply design of isolated and non-isolated architectures

◆SO20 wide-body package with enhanced heat dissipation

◆Best energy efficiency valley switch detection

◆Built-in demagnetization detection

◆Built-in over-temperature protection function (OTP)

◆Supports startup from rectified mains voltage As an LED driver IC with integrated dimming controller and switching power supply module, SSL2102 has the same functions as SSL2101, but supports higher power, allowing customers to apply one design to multiple different end products with a wider range of power ratings.

NXPSSL210X Typical Applications

NXPSSL210X secondary side constant current IC application

●Customers who want higher current accuracy can use a dedicated constant current IC

●Constant current ICRT8456 is specially used for LED constant current drive

● Constant current IC is placed on the secondary side, no secondary DC/DC conversion is performed, thus improving efficiency.