I am having an issue with the circuits that I am working on in Multisim. The first one is supposed to convert 24VDC into 27VDC/200mA. And it is working just fine. When I substitute VDC source with 220VAC and a transformer the result is almost the same.
The second circuit that gives 12VDC/50mA output also works with this configuration. But when I attach it to the same 220VAC source it gives rather strange results. During the first few milliseconds of simulation Iin shows value of ~-2A. My questions are as follows:
- How do I fix the negative Iin current in beginning in the fourth scheme?
- Is there a simpler way to connect MC34063 to the transformer?
- How can I connect both step-up and step-down converters to the same 24VDC source?