Can a 1-10V dimmer dim the load down to OFF?

A lot of clients come across wondering why the 1-10V dimmer they have bought can't dim the light down to OFF. The answer that they usually get is that because the dimmer they are using is 1-10V dimmer which can dim the light down to only 10%. Alternatively, they are advised to get a 0-10V dimmer to be able to dim their lights down to OFF.

Unfortunately, the previous answer is inaccurate.

Which circuit element that defines the dimming level?

In fact, the dimmer whether it's 1-10V or 0-10V dimmer is not the circuit element that defines to which level the light can be dimmed down. The dimmer only sends a dimming signal to the driver, which is different from the driving current that drives the LED chips in the luminaire. The driver in its turn maps the dimming signal from the dimmer to the dimming range that it's capable of operating within. In other words, the driver is the circuit element that defines to which level the light can be dimmed down.

Then what's the difference between 1-10V and 0-10V dimmers?

A very common misconception is that the difference between 1-10V dimmer and 0-10V dimmer is that the first can dim the load down to 10% while the latter can dim the load down to 0% (dim to OFF). This is incorrect!

The main difference between 1-10V and 0-10V dimmers is the current direction, not the dimming level. Both of 1-10V dimmer and 0-10V dimmer are capable of dimming the load down to 0%.

• The 1-10V dimmer is a current sink as defined in IEC60929 Annex E2.1 which means that the current flows from the driver to the dimmer. The standard mentioned nothing about to which level the load can be dimmed using that dimmer. This dimming protocol is mainly used for general lighting. This means the dimmer is a simple 2-wire device that receives the 10V signal from the driver on one of its two terminals and reshapes it to reflect the required dimming level and resends it back to the driver through its other terminal. (You can check the wiring diagram of any of the 1-10V dimmers in the market)

• The 0-10V dimmer is a current source as defined in ESTA Annex E1.3, which means that the current flows from the dimmer towards the driver. This dimming protocol is mainly used for entertainment lighting such as theatrical lighting. That definition means that the standard 0-10V dimmer is a 4-wire device that receives an AC 220V power signal on one side (input side) then reshapes it to be a DC 0-10V dimming signal on the output side based on the user input. Then the signal is sent to the driver to map it on its dimming range to dim up/down the load. (You can check the wiring diagram of Philips Sunrise - SR1200ZTUNV 0-10V dimmer)

So, how can a load be dimmed down to OFF?

As I mentioned above, the driver is the circuit element that's responsible for defining the dimming level of the load. Every dimmable driver has a dimming curve which describes the dimming journey from the minimum allowed dimming value up to 100% output. Most of the drivers have a linear dimming curve which means the load lumen output corresponds linearly to the dimming signal from the dimmer. One of the driver's important specifications is the minimum dimming value. Most of the drivers in the market have a minimum dimming value of 10% of the max output, which corresponds to 1V in case of 1-10V dimmer and corresponds to 0V in case of a 0-10V dimmer. This means 10% is the minimum output that the driver can deliver to the load regardless of what type of dimmer controlling the driver. In order to dim the load down to OFF, the driver needs to be able to deliver as low as 0.1% of the max output.

In Conclusion, if you need to dim your load down to OFF, you need to check the driver connected to the load, not the dimmer connected to the driver. If the driver is able to deliver as low as 0.1% of the max output, this means the load can be dimmed down to OFF regardless of the dimmer type connected to it.

Thanks for your time and I will meet you in the next article!