Daniel Kramnik's Project Log
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Induction Heater 2.0
Introduction
This is a follow-up project to my first induction heater, which I built for my junior year AP Physics E&M midyear project.
Design
I wanted to have only one circuit board in this project, so I integrated a TL494 VFO, ‘HC14-based PWM generator (for average power control), switching synchronization flop, and IGBT brick driver in one design:
This is the board file for the first prototype control board, it contains several errors that I plan to fix in the next board I etch. For example, I accidentally connected the ‘HC109 flip flop’s supply to +15V instead of +5V in my original schematic, so I was forced to rip up the trace once I’d soldered it and manually wire it. Also, I wired the brick drive MOSFETs to the +15V rail, instead of a separate +24V rail, so the output to too low to drive the brick effectively and there is significant heating of the IGBT half bridge as a result.
The reason I used a giant string of 1uF blocking capacitors instead of one large capacitor is because I just happen to have a bag of small 1uF 50V ceramic capacitors that work well for this application. The space between the control board logic and brick drive is for an intermediate GDT – something I hope to eliminate in my next design by using a totem pole instead of an intermediate bridge:
Daniel Kramnik's Project Log
Menu
Skip to content
Home
Articles
Audio
Code
Electronics
Tesla Coils
The Workshop
Induction Heater 2.0
Introduction
This is a follow-up project to my first induction heater, which I built for my junior year AP Physics E&M midyear project.
Design
I wanted to have only one circuit board in this project, so I integrated a TL494 VFO, ‘HC14-based PWM generator (for average power control), switching synchronization flop, and IGBT brick driver in one design:
This is the board file for the first prototype control board, it contains several errors that I plan to fix in the next board I etch. For example, I accidentally connected the ‘HC109 flip flop’s supply to +15V instead of +5V in my original schematic, so I was forced to rip up the trace once I’d soldered it and manually wire it. Also, I wired the brick drive MOSFETs to the +15V rail, instead of a separate +24V rail, so the output to too low to drive the brick effectively and there is significant heating of the IGBT half bridge as a result.
The reason I used a giant string of 1uF blocking capacitors instead of one large capacitor is because I just happen to have a bag of small 1uF 50V ceramic capacitors that work well for this application. The space between the control board logic and brick drive is for an intermediate GDT – something I hope to eliminate in my next design by using a totem pole instead of an intermediate bridge:
Construction and Testing
The rev. 1 control board is connected to a half bridge brick, which has an 8uF 800V snubber, 2200uF 250V filter, and a pair of 20uF 600V half bridge capacitors. I decided not to use a voltage doubler to reduce parts count and allow the power supply to fit directly on the brick: