# [Buck boost converters] Nixie tube clock project

#### Diogo Ferreira 2

Joined Mar 16, 2017
20
Hello, I'm trying to make a nixie tube clock project and i am very unsure about the power delivery solutions.

1st problem - Currently in my schematic have a LM7805 ic (with 12v Vin) to power the Ic's, but from my calculations i would be using 236mA from it thus having (12v-5v)*236mA wich results in about 1.65W of dissipation, since i dont want to have a big bulky heat sink im looking for a buck converter that would do the job.

2nd problem - After looking on the internet i found a cool page and schematic of a boost converter (using the IC MC34063A) from 12vdc to 180vdc which is exactly what i needed to power the nixie tubes. the problem is that i dont have enough knowledge to check if that circuit would do what i want.

3rd and final problem - Can someone help me check if the boost circuit works and help me design a buck converter with the same type of ic used in the boost converter?

My project with schematic is the following link:
https://easyeda.com/diogoferreira889/nixie-clock

Diogo Ferreira

#### Diogo Ferreira 2

Joined Mar 16, 2017
20
Another question this one came from a weird brainstorm while watching some youtube videos
Can i use a voltage divider at the input of the LM7805 to reduce Vin thus reducing the power dissipation?

#### Marley

Joined Apr 4, 2016
499
That boost circuit probably works OK. Though to be honest I don't like the choice of IC used because it doesn't drive the MOSFET properly.
Don't use a voltage divider on the input to the LM7805. For lowest power dissipation replace with a simple buck converter like the attached.

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#### KeithWalker

Joined Jul 10, 2017
2,803
Hello, I'm trying to make a nixie tube clock project and i am very unsure about the power delivery solutions.

1st problem - Currently in my schematic have a LM7805 ic (with 12v Vin) to power the Ic's, but from my calculations i would be using 236mA from it thus having (12v-5v)*236mA wich results in about 1.65W of dissipation, since i dont want to have a big bulky heat sink im looking for a buck converter that would do the job.

2nd problem - After looking on the internet i found a cool page and schematic of a boost converter (using the IC MC34063A) from 12vdc to 180vdc which is exactly what i needed to power the nixie tubes. the problem is that i dont have enough knowledge to check if that circuit would do what i want.

3rd and final problem - Can someone help me check if the boost circuit works and help me design a buck converter with the same type of ic used in the boost converter?

My project with schematic is the following link:
https://easyeda.com/diogoferreira889/nixie-clock

Diogo Ferreira
Here is a buck circuit. It is for a car USB charger that will do just what you want.
https://dmohankumar.wordpress.com/2016/10/04/car-usb-charger-using-mc-34063-start-up-project-40/

#### mvas

Joined Jun 19, 2017
539
1st problem - Currently in my schematic have a LM7805 ic (with 12v Vin) to power the Ic's, but from my calculations i would be using 236mA from it thus having (12v-5v)*236mA wich results in about 1.65W of dissipation, since i dont want to have a big bulky heat sink im looking for a buck converter that would do the job.
They make a 3-Terminal 5 Volt Switching Regulator that directly replaces the 7805.