I built the 100kHz triangle wave generator to use with the 100W flyback converter circuit. This is used as one input to the comparator in the feedback loop.

Here's an example in a DC-DC buck converter for where the ramp function is used in the feedback. A very similar method is used in the flyback converter.

Below is the schematic. The design uses high-voltage input LDOs for power to the comparator and operational amplifier; this is not an isolated power supply for this reason.

The main reason for implementing with an LDO instead of a secondary winding is the ease of implementation, and I will be winding the flyback coil manually.

The design uses the TLV3501 and OPA365 for creating the triangle wave. These parts were selected for their high slew rates and were chosen from the TI application note on creating a triangle wave generator.

The voltage reference used is a REF3425 to give the midpoint reference for the OPA and TLV components.

Testing results were good; the triangle wave was clean with very little curve in the slope.