You don't tend to convert patch formats.
Most will apply the one format and then regenerate it using another format.
That said a search pchtxt as I had not heard of it before landed me on
https://github.com/3096/ipswitch/tree/master/example which apparently can convert.
I will note however IPS is limited to slightly under 16 megabytes, in place patching (basically anything PS1 or newer, or DS or newer is out unless you want large patches)/won't relocate data if you move it, ( struggles to expand files (usually same lists as before but can include others) and has no verification (sometimes good, sometimes bad, generally good if you want to ensure you are patching the right file and not using the wrong version of a game). This is why people moved away from it.