LIGHTECH TRAILING EDGE DIMMING DRIVER

For a trailing-edge dimmer if insufficient current is drawn to force a zero-crossing before the next half-line cycle, the dimmer may misfire, causing shimmer or flicker. A Buck-boost converter continues switching provides a low impedance to the input when the input voltage has fallen below output voltage, making this topology more suitable for trailing-edge dimmers. Prior to joining PI, Andrew spent 11 years as a power supply design engineer before transitioning to a sales and marketing role at Advance Power, then Vishay Siliconix. The designer trades off efficiency in order to achieve best possible dimmer compatibility but is not able to guarantee performance due to the variability of dimmer component values. This blog highlights how dimmer type determines both the selection of damper and bleeder circuits in LED drivers, and the switching topology needed to optimize operation. Aug 18, 8: That-being-said, it is unlikely that the average consumer will know whether their fixture is controlled by a leading-edge or a trailing-edge dimmer, and so it is important that LED replacement bulbs work with both types.

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Compact fluorescent bulbs also known as CFL or stick shape should be taken as non-dimmable unless stated on the bulbs packaging. With no capacitive or inductive elements, the incandescent bulb does oscillate when presented with the voltage step of a dimmed AC sine wave.

Simplified schematic of a trailing-edge, phase-cut dimmer. Phase-cut dimmers, either leading-edge or trailing-edge, make up the bulk of the dimmer market. Sign Up for Our Newsletter: Minimum and maximum loads for dimmer switches All dimmer switches have an operational range or load that they can work within, a w dimmer can have 10 x 40 w lamps on it8 x 50w lamps on it or any combination that adds up to a maximum of w.

These two types of phase cutting dimmer get their names from the part of the AC wave that they cut off. That-being-said, it is unlikely that the average consumer will know whether their fixture is controlled by a leading-edge or a trailing-edge dimmer, and so it is important that LED replacement bulbs work with both types.

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Practical designs usually accommodate trailing-edge dimmers.

Leading-Edge vs. Trailing-Edge Dimmers | LED Journal

If this is the case then you are using standard mains dimming. Dimming LEDs – The difference between leading and trailing edge. For a buck topology, when the input voltage falls below the output voltage, the switching circuit cannot draw any power from the AC rail and is therefore unable to bleed down the switch voltage.

Most phase dimmer compromise its performance in order to comply with LED lighting design. There are two types of mains dimmer; leading edge and trailing edge collectively known as phase cutting dimmers. A w Incandescent or Halogen dimmer may have a w loading when used in conjunction with an LED light source.

Typical input current waveform for a power-factor-corrected dimmable bulb showing the oscillation caused by input current dropping below IH. Our range of LED dimmers are changeable between trailing edge and leading edge modes but are set to trailing edge mode by default. You can browse the range here.

The national grid supplies AC alternating current Electricity to our homes, offices, restaurants, pubs and clubs. The designer trades off efficiency in order to achieve best possible dimmer compatibility but is not able to guarantee performance due to the variability of dimmer component values. LED bulbs are produced in dimmable and non-dimmable versions.

Why shimmering and tdailing occurs in leading-edge dimmers and why leading-edge and trailing-edge dimmers respond differently In leading-edge phase-cut dimmers, the switching element is typically a TRIAC.

If you are in doubt about the compatibility of any products or how to make changes to your electrical circuits then we advise using a qualified electrician.

There are other types of dimming such as Dali, DMX, and Zigbee but these are more commonly used in larger buildings with more complex lighting needs.

Lightech NDL Phase dim.

An LED lamp load does not exhibit incandescent-like pure resistance, and so, when presented with a step voltage the EMI filter and the bulk capacitance of the switching stage will cause an oscillation in the input current I F see figure 3.

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For this reason, buck-boost converters and tapped-buck drivers with ICs, which switch through the whole line cycle as the LYTSwitch-4 from Power Integrations, can pull down the dimmer voltage after it turns off and are therefore better able to support trailing-edge dimmers. Trailing edge switches work best ximming LEDs.

Trailing-edge dimmers require the input voltage of the LED driver to fall to zero each half-cycle to enable the dimmer controller to energize its own supply rails. A Buck-boost converter continues switching provides a low impedance to the input when the input voltage has fallen below output voltage, making this topology more suitable for trailing-edge dimmers.

Research both the lamps and the dimmer switch before buying so that you know you have a combination that works. This ensures that the zero-crossing detector will turn on the switch at the beginning of the next voltage half-line cycle.

If there is insufficient impedance to bleed down the dimmers output voltage eddge the next AC cycle begins, then the dimmer may edeg causing shimmer and flicker. This blog highlights how dimmer type determines both the selection of damper and bleeder circuits in LED drivers, and the switching topology needed to optimize operation.

Prior to joining PI, Andrew spent 11 years as a power supply design engineer before transitioning to a sales and marketing role at Advance Power, then Vishay Siliconix.

Leading-Edge vs. Trailing-Edge Dimmers

These devices are increasingly called upon to support LED replacement lamps, which offer challenges unanticipated by the designers of the dimmer systems, such as low current draw and very fast luminous response to minor power fluctuations.

It works either way, trailing edge and leading edge. To further enhance damping, a bleeder is needed to compensate for, or mask the ringing below, the holding current.