Odd isn't - we still think that CMOS is as cheap-as-chips and MOSFET drivers as being exotic. But CMOS is getting expensive as it is going slowly out of fashion, and everyone's using MOSFET drivers these days.
Some of them have hysteresis on the inputs with relatively accurate thresholds and with a bit of ingenuity you can implement most of the usual 555 circuits with them, but with massive amounts of output drive.

My simulation shows a peak gate current of a little over 400mA with the paralleled CD4050 driver, so that would seem to be comparable to the MCP1402 driver for simulation purposes.
I could find no MCP1402 Spice model.

 

8-Amps Continuous, 30-Amps Peak...............

 

Based upon a rough calculation I came up with about 90%, but the actual will likely be less.
Yes. 86%.

 

Based upon a rough calculation I came up with about 90%, but the actual will likely be less.
Yes. 86%.

I also got that value for the LED power divided by the V1 power.

 

I have been unable to source some components
Yes I can get them from the states but I refuse to pay $US25-30 freight for a few grams
Are there alternatives to these:
FDS6575
CD4050B
MBRB2545CT

Thanks

If you want to roll your own switching regulator with common ICs, below is the LTspice simulation of a simple hysteretic type (bang-bang) constant-current switching regulator that uses a LM339/393 comparator as the controller.
The hysteretic control has the advantages of being very simple and inherently stable, thus requiring no feedback compensation (and thus has no startup overshoot).

The six CD4050 buffers (one IC package) are used in parallel as a poor-man's MOSFET gate driver.
The TL431 provides a stable 2.5V reference voltage.

The efficiency should be in the neighborhood of 80-90%, much higher than a linear regulator or series resistor, thus greatly reducing heat-sink requirements.

There is some ripple in the LED current, but that is not noticeable to the eye at that high a switching frequency.

Edit: Cautionary Note -- The circuit has no short-circuit protection so a prolonged short from the L1 output to ground will likely blow the MOSFET.

View attachment 244588

 

Those numbers are not exclusive to the USA,
you can get them worldwide under the same part number.
.
.
.

 

Multiple problems at this
Those component numbers do not show up on local suppliers sites
Actually not true - RS components have most but are sold in multiples of 25

 

Are there alternatives to these:
FDS6575
CD4050B
MBRB2545CT

The Schottky diode and the P-MOSFET can be just about any that meet the requirements.
5A and ≥30V rating for the diode and MOSFET.
≤10mΩ on-resistance and ≤50nc total gate charge for the MOSFET.

The CD4050 can be replaced by many MOSFET gate drivers, such as the MCP1402.

If you tell me what you can get, I can tell you if they are appropriate.

 

Thanks again
While hunting components I found these devices
Any thoughts on these?

 

Do they meet your current requirements?

 

Sadly no. Only 3 watts

 

My simulation shows a peak gate current of a little over 400mA with the paralleled CD4050 driver, so that would seem to be comparable to the MCP1402 driver for simulation purposes.
I could find no MCP1402 Spice model.

This is the circuit I built a while ago based on the MCP1401. Not quite so efficient as yours as there is more voltage dropped across the sense resistor (approx 0.45V - hysteresis points are 0.3V and 0.6V), but I used 3 or 4 LEDs so that loss was less significant.
It should also be possible to use the MCP1402's own hysteresis, and reduce the number of components even further, although it may need a bit of fiddling with the resistor values to get the right drive current, because the MCP1402 thresholds are not accurately defined (though quite repeatable)
I can't find a Spice model either.

 

Thank you for your assistance
Some questions:
I am a bit confused bout what is going on between R1 and U3
I get U3 sets the current
You state "select R1 to give about 100mV at the LEDs operating current"
I am not sure how to do this??? Just put in a resistor of a higher value eg 0.1 ohm and lower this until I get 100 mV across this resistor??

Is it possible for you to post your Circuit file as I would like to test the circuit at different voltages??
Are there equivalent to these:
I can get these but freight can be exorbitant and/or I must buy a minimum of 25 pieces

TL431a
LM339/393
CD4050B
FDS6575
MBRB2545CT

Thanks again

If you want to roll your own switching regulator with common ICs, below is the LTspice simulation of a simple hysteretic type (bang-bang) constant-current switching regulator that uses a LM339/393 comparator as the controller.
The hysteretic control has the advantages of being very simple and inherently stable, thus requiring no feedback compensation (and thus has no startup overshoot).

The six CD4050 buffers (one IC package) are used in parallel as a poor-man's MOSFET gate driver.
The TL431 provides a stable 2.5V reference voltage.

The efficiency should be in the neighborhood of 80-90%, much higher than a linear regulator or series resistor, thus greatly reducing heat-sink requirements.

There is some ripple in the LED current, but that is not noticeable to the eye at that high a switching frequency.

Edit: Cautionary Note -- The circuit has no short-circuit protection so a prolonged short from the L1 output to ground will likely blow the MOSFET.

View attachment 244588

 

Thank you for your assistance
Some questions:
I am a bit confused bout what is going on between R1 and U3
I get U3 sets the current
You state "select R1 to give about 100mV at the LEDs operating current"
I am not sure how to do this??? Just put in a resistor of a higher value eg 0.1 ohm and lower this until I get 100 mV across this resistor??

Is it possible for you to post your Circuit file as I would like to test the circuit at different voltages??
Are there equivalent to these:
I can get these but freight can be exorbitant and/or I must buy a minimum of 25 pieces

TL431a
LM339/393
CD4050B
FDS6575
MBRB2545CT

Thanks again

Tayda will ship from Thailand to .Darwin for $10 in 2 to 4 days. Less ($1) if you're willing to wait longer (7 to 30 days). The don't have the complete selection of RS but you can make it work if you want to be cheap.

https://www.taydaelectronics.com/ic...uffers-line-drivers-hex-non-inverting-ic.html

https://www.taydaelectronics.com/ic...39-low-power-quad-voltage-comparators-ic.html

https://www.taydaelectronics.com/ic...tl431acl-tl431-precision-shunt-regulator.html

https://www.taydaelectronics.com/di...5tf6s-super-fast-recovery-diode-10a-600v.html

https://www.taydaelectronics.com/t-...f-irlz44n-power-mosfet-n-channel-47a-55v.html

 

Oops
https://taydaelectronics.com/datasheets/files/a-1683.pdf

 

I am a bit confused bout what is going on between R1 and U3
I get U3 sets the current

U3 adjusts the comparison voltage for comparator U1.
U1 turns on the MOSFET (output goes low) when the voltage from the current resistor R1 drops below U3's wiper voltage, and turns it back off when the voltage goes above U3's voltage (as modified by the hysteresis provided by R6 and R7).

You state "select R1 to give about 100mV at the LEDs operating current"

You just calculate the value of R1 that give 100mV at the desired LED current.
For example, for 2000mA (2A) the resistor value would be 0.1V / 2A = 50mΩ.

Is it possible for you to post your Circuit file

Below

 

Thanks
Never heard of these blokes until now .... I shall Check them out.

Tayda will ship from Thailand to .Darwin for $10 in 2 to 4 days. Less ($1) if you're willing to wait longer (7 to 30 days). The don't have the complete selection of RS but you can make it work if you want to be cheap.

https://www.taydaelectronics.com/ic...uffers-line-drivers-hex-non-inverting-ic.html

https://www.taydaelectronics.com/ic...39-low-power-quad-voltage-comparators-ic.html

https://www.taydaelectronics.com/ic...tl431acl-tl431-precision-shunt-regulator.html

https://www.taydaelectronics.com/di...5tf6s-super-fast-recovery-diode-10a-600v.html

https://www.taydaelectronics.com/t-...f-irlz44n-power-mosfet-n-channel-47a-55v.html

 

Thanks again
"Thanks" seems so cheap and inadequate

GP

U3 adjusts the comparison voltage for comparator U1.
U1 turns on the MOSFET (output goes low) when the voltage from the current resistor R1 drops below U3's wiper voltage, and turns it back off when the voltage goes above U3's voltage (as modified by the hysteresis provided by R6 and R7).
You just calculate the value of R1 that give 100mV at the desired LED current.
For example, for 2000mA (2A) the resistor value would be 0.1V / 2A = 50mΩ.
Below

 

Thanks again
"Thanks" seems so cheap and inadequate

Glad to help.
It's what I enjoy doing.
You can always click on thebutton at the bottom of a post if you want to give a little thumbs-up to someone who helped you.

 

I have been unable to source some components
Yes I can get them from the states but I refuse to pay $US25-30 freight for a few grams
Are there alternatives to these:
FDS6575
CD4050B
MBRB2545CT

Thanks

Why not just use a 555 PWM?
Its cheap and simple.