In April 2016 Helvar launched four DALI dimmable LED drivers built around hybrid dimming: two compact SELV drivers, the LC1x25-DA and LC1x35-DA, and two high efficiency linear drivers, the LL1x23-80-DA and LL1x80-DA-350-700. The point of all four was steady, good quality light at the bottom of the dimming range, where many LED drivers of the time started to flicker or step.
What hybrid dimming does
A driver can dim LEDs in two ways. Constant current reduction (CCR) lowers the DC current, which gives a flicker-free output but becomes hard to control accurately at very low currents, where colour and output can drift between modules. Pulse width modulation (PWM) switches the full current on and off and varies the duty cycle, which stays precise at low levels but adds a modulation frequency to the light.
Hybrid dimming uses each where it works best: CCR across the upper part of the range, then PWM below a set threshold, down to 1 %. Helvar published the split for each model:
| Driver | CCR range | PWM range | PWM frequency |
|---|---|---|---|
| LC1x25-DA | 40 to 100 % | 1 to 40 % | 800 Hz |
| LC1x35-DA | 30 to 100 % | 1 to 30 % | 800 Hz |
| LL1x23-80-DA | 20 to 100 % | 1 to 20 % | 1 to 8 kHz |
| LL1x80-DA-350-700 | 20 to 100 % | 1 to 20 % | 1 to 8 kHz |
Compact drivers with SELV below 60 V
The LC1x25-DA (25.2 W, 350 to 700 mA) and LC1x35-DA (35.7 W, 700 to 1050 mA) were designed never to put out more than 60 V in any circumstance. That keeps the LED side within SELV, which makes them simpler and safer to design into luminaires where the LED board is touchable or the insulation is minimal. Both measure 106 x 67 x 28 mm and accept DALI or Switch-Control.
Linear drivers with up to 95 % efficiency
The two linear drivers, both 280 x 30 x 21 mm, targeted long luminaires and high efficiency. The LL1x23-80-DA covers 23 W to 80 W at 150 to 350 mA with efficiency up to 95 %. The LL1x80-DA-350-700 delivers 80 W at 350 to 700 mA with efficiency up to 94 %. Both are non-isolated, which is part of how they reach those figures.
Where these drivers stand now
All four have since been retired. Helvar Components lists the LC1x25-DA, LL1x23-80-DA and LL1x80-DA-350-700 as discontinued and the LC1x35-DA as phasing out. Helvar names the LC43MN22-DA-300-1050 as the replacement for the LC1x35-DA and the LL80HE-DA-100-800 for both linear models.
The archived data is still on Helvar Components, for example the LC1x35-DA page. If you are maintaining luminaires fitted with any of these drivers, send us the model numbers and we will suggest the closest current match.