Which LED driver?......

[HappyHippyDad]

I'm not too sure which LED driver I can use to replace the one in the picture.
It states max 21V, does this mean any thing less than that is ok? It also says DC 24V though, which has confused me.

Would it be a constant current LED driver seeing as though thus one implies the voltage is changeable?

I'll have a read up on LED 'converter' as opposed to driver.

 

[Pretty Mouth]

Would it be a constant current LED driver seeing as though thus one implies the voltage is changeable?

Seems to be constant current, 350mA.

Regarding the data for secondary, my best guess is that 350mA can be maintained with voltages up to 21V, and if the voltage goes above this to 24V, it can only output 300mA.

 

[HappyHippyDad]

Seems to be constant current, 350mA.

Regarding the data for secondary, my best guess is that 350mA can be maintained with voltages up to 21V, and if the voltage goes above this to 24V, it can only output 300mA.

So would this be ok, even though the voltage could be higher?

 

[brianmoooore]

It's designed to put a constant current through a fixed, but unknown, resistance. To do this the output voltage will set itself to that determined by Ohms law.
It's 350mA, so if the circuit resistance is 50 ohms, the output voltage will set itself at 17.5 volts. (E=I x R = 0.35 x 50 = 17.5).
If connected to the same load as the original, and with the same constant current, then the replacement will have the same voltage at its terminals.

 

[Pretty Mouth]

So would this be ok, even though the voltage could be higher?
View attachment 101635View attachment 101635

I would expect so. The driver tries to maintain a 350mA current, by adjusting the voltage, within its limits. Unless the lamp is a fraction of a watt, this should work okay

 

[HappyHippyDad]

Thanks both ................. extra word

 

[Lucien Nunes]

The original unit will operate in either constant-current or constant-voltage mode, according to the connected load.

CV: For loads taking 0-300mA at 24V, the voltage will be constant at 24V.
CC: For loads dropping 0-21V at 350mA, the current will be constant at 350mA.

These regimes occur with two separate ranges of load. We shouldn't really talk about the 'resistance' of LEDs since they don't behave like resistors (their current and voltage don't vary in proportion). Instead, let's consider the load on the driver to be a variable resistor, set initially at say 10 ohms, that we are going to increase steadily.

The driver will output a constant 350mA into the load developing 0.35x10=3.5V, and will continue to do so as the resistance is increased, until it reaches 60 ohms at which point the voltage is 0.35x60=21V. This is the highest voltage at which the current is regulated at 350mA and if it increases further, we leave the constant-current regime and regulation is not guaranteed. The limit of 21V is called the 'voltage compliance' in CC mode.

As the resistance increases further and reaches 80 ohms we enter the constant-voltage regime. The voltage stops rising and becomes regulated at 24V, with a current of 24/80=300mA. As the resistance continues to increase, the voltage remains at 24V as the current drops towards zero.

The new driver does not show a constant-voltage mode officially, but if it does go into constant-voltage mode at low load current, it would deliver 34V (not 24V like the old one) and would over-drive a small 24V CV load. OTOH if the load is a 350mA CC one, then because the 34V compliance is wider than the original 24V, it will work just fine as a replacement.