u/Elegant_Back9525

Hi everyone,
My partner and I (both control and systems engineers) recently finished developing the power section of a smart home switch for a local merchant.
Technical Details:
The board takes 220V AC mains and steps it down to 12V DC and 3.3V DC.

It includes 4 relays for switching.

We did all the schematic design and PCB layout using KiCad.

The prototype was successfully manufactured in China and tested.

Total R&D and design time took us a little over 2 months.

I have attached a 3D render of the board for reference.

The Dilemma:
We have no prior experience in pricing our hardware design services. This was built for a merchant who plans to mass-produce and sell it. We are trying to figure out the fairest compensation model:

1. Should we charge a one-time flat fee for the design? If so, what is a reasonable price range for 2 months of R&D for this type of board?
2. Should we ask for a partnership/royalty model (a percentage of sales/profit)?
3. How should handing over the source files (KiCad) vs. just the Gerbers affect the pricing?

Any advice on industry standards for hardware freelance pricing or personal experiences would be highly appreciated. Thanks!

Hello everyone,

I am currently designing a non-isolated Buck converter power supply that will be integrated into a smart home wall switch. Due to the very constrained space inside the standard junction box, keeping the footprint and BOM count as small as possible is a major priority.

Additionally, the local electrical grid here in my country is highly unstable. The AC input can fluctuate anywhere from 90V up to 270V AC (and sometimes spikes up to 290V).

Here are my core design requirements:

Topology: Non-isolated Buck (High-side)

Input: 90V - 270VAC (needs to survive harsh 290V transients)

Output: 12V DC

Load Current: 220mA continuous (Targeting a 300mA capable IC for thermal headroom and stability)

Cost: Must be extremely cheap for mass production via Chinese PCBA houses (JLCPCB, etc.).

My Current Progress & Dilemma:

I built a prototype on a perfboard using the classic VIPer22A. It works, but I have some concerns. Its switching frequency is around 60kHz. I am wondering if 60kHz is ideal for this kind of compact application, or if I should move to a higher frequency IC to reduce the inductor size (since smaller size is a huge plus for me).

I also evaluated the LNK306 (and a few other LinkSwitch ICs). They are absolutely fantastic, and the low BOM count is exactly what I need. However, when pricing them out for mass production, the IC alone costs around $0.80 - $1.00+, which completely kills the profit margin for a cheap smart switch.

I know ICs like the PN801x or BP2525 are often used in cheap Chinese smart plugs. However, these specific ICs are completely unavailable in my local electronics market for building and testing the initial physical prototypes.

My Questions for the Community:

Is the VIPer22A at 60kHz still a viable and reliable option for commercial smart switches today, or is the required inductor size going to be a bottleneck for a wall box?

If I want to minimize the inductor size (higher frequency) but keep the mass production IC cost down to pennies, what are the best alternatives? How do you guys handle prototyping when your target mass-production IC isn't available locally?

Could you recommend any reliable simulation software or online tools specifically for offline AC-DC non-isolated buck converters? Most tools I find focus heavily on DC-DC.

How do you accurately estimate the wholesale/mass-production BOM cost for components from Chinese suppliers (e.g., LCSC) to calculate the final product cost before committing to a run?

I appreciate any IC recommendations or design insights you can share. Thanks!

Hello everyone,

I am currently designing a non-isolated Buck converter power supply that will be integrated into a smart home wall switch. Due to the very constrained space inside the standard junction box, keeping the footprint and BOM count as small as possible is a major priority.

Additionally, the local electrical grid here in my country is highly unstable. The AC input can fluctuate anywhere from 90V up to 270V AC (and sometimes spikes up to 290V).

Here are my core design requirements:

Topology: Non-isolated Buck (High-side)

Input: 90V - 270VAC (needs to survive harsh 290V transients)

Output: 12V DC

Load Current: 220mA continuous (Targeting a 300mA capable IC for thermal headroom and stability)

Cost: Must be extremely cheap for mass production via Chinese PCBA houses (JLCPCB, etc.).

My Current Progress & Dilemma:

I built a prototype on a perfboard using the classic VIPer22A. It works, but I have some concerns. Its switching frequency is around 60kHz. I am wondering if 60kHz is ideal for this kind of compact application, or if I should move to a higher frequency IC to reduce the inductor size (since smaller size is a huge plus for me).

I also evaluated the LNK306 (and a few other LinkSwitch ICs). They are absolutely fantastic, and the low BOM count is exactly what I need. However, when pricing them out for mass production, the IC alone costs around $0.80 - $1.00+, which completely kills the profit margin for a cheap smart switch.

I know ICs like the PN801x or BP2525 are often used in cheap Chinese smart plugs. However, these specific ICs are completely unavailable in my local electronics market for building and testing the initial physical prototypes.

My Questions for the Community:

Is the VIPer22A at 60kHz still a viable and reliable option for commercial smart switches today, or is the required inductor size going to be a bottleneck for a wall box?

If I want to minimize the inductor size (higher frequency) but keep the mass production IC cost down to pennies, what are the best alternatives? How do you guys handle prototyping when your target mass-production IC isn't available locally?

Could you recommend any reliable simulation software or online tools specifically for offline AC-DC non-isolated buck converters? Most tools I find focus heavily on DC-DC.

How do you accurately estimate the wholesale/mass-production BOM cost for components from Chinese suppliers (e.g., LCSC) to calculate the final product cost before committing to a run?

I appreciate any IC recommendations or design insights you can share. Thanks!

Hello everyone,

I am currently designing a non-isolated Buck converter power supply that will be integrated into a smart home wall switch. Due to the very constrained space inside the standard junction box, keeping the footprint and BOM count as small as possible is a major priority.

Additionally, the local electrical grid here in my country is highly unstable. The AC input can fluctuate anywhere from 90V up to 270V AC (and sometimes spikes up to 290V).

Here are my core design requirements:

Topology: Non-isolated Buck (High-side)

Input: 90V - 270VAC (needs to survive harsh 290V transients)

Output: 12V DC

Load Current: 220mA continuous (Targeting a 300mA capable IC for thermal headroom and stability)

Cost: Must be extremely cheap for mass production via Chinese PCBA houses (JLCPCB, etc.).

My Current Progress & Dilemma:

I built a prototype on a perfboard using the classic VIPer22A. It works, but I have some concerns. Its switching frequency is around 60kHz. I am wondering if 60kHz is ideal for this kind of compact application, or if I should move to a higher frequency IC to reduce the inductor size (since smaller size is a huge plus for me).

I also evaluated the LNK306 (and a few other LinkSwitch ICs). They are absolutely fantastic, and the low BOM count is exactly what I need. However, when pricing them out for mass production, the IC alone costs around $0.80 - $1.00+, which completely kills the profit margin for a cheap smart switch.

I know ICs like the PN801x or BP2525 are often used in cheap Chinese smart plugs. However, these specific ICs are completely unavailable in my local electronics market for building and testing the initial physical prototypes.

My Questions for the Community:

Is the VIPer22A at 60kHz still a viable and reliable option for commercial smart switches today, or is the required inductor size going to be a bottleneck for a wall box?

If I want to minimize the inductor size (higher frequency) but keep the mass production IC cost down to pennies, what are the best alternatives? How do you guys handle prototyping when your target mass-production IC isn't available locally?

Could you recommend any reliable simulation software or online tools specifically for offline AC-DC non-isolated buck converters? Most tools I find focus heavily on DC-DC.

How do you accurately estimate the wholesale/mass-production BOM cost for components from Chinese suppliers (e.g., LCSC) to calculate the final product cost before committing to a run?

I appreciate any IC recommendations or design insights you can share. Thanks!