Overview: For this test the voltage input of the Filament Supply was connect to the output of the HV Pulser. In this test the HV Pulser was tested at multiple operating Frequencies: 1kHz, 10kHz,100kHz, 1MHz, 10MHz, and 100MHz. The operating frequency was adjusted by flipping switches tied to clocking cycles on the FPGA.

Measurements: The ON, POS, and NEG control signals were measured directly from the PMOD connector on the BASYS 3 FPGA. The same system for measurements on the filament supply was used as Filament Supply RevA 2/7/20.

Results: As expected the system operates near ideal at frequencies of 1kHz, 10kHz, and 100kHz. At a switching frequency the system begins to deviate from an ideal model. However, the performance at 1Mhz is good. The system has a fall time of about 100ns and an even faster rise time of about 200ns. There is about a only about a 50ns prorogation delay between the signals on the PMOD connector of the FPGA and the full response from the Filament Supply. The Filament supply maintains a current through the load without any measurable delay.
Special Note on Drift:
It's important to note that this system is meant to drive a filament load. This filament has some ambient current as electrons drift. To counteract this behavior the HV Pulser has a fixed current sink and a current source controlled by the ON signal. Because there is no ambient current in the load used for lab testing the current source was fixed on (ON signal fixed at logic HIGH) to cancel the draw of the current sink. In a test run with the current source off (ON signal fixed at logic LOW), the current sink slowly drags the output towards the negative supply voltage during inactivity between the NEG and POS signals. When driving a load with an ambient current the effects of these currents should cancel and the output shouldn't drift to this degree. Finding the proper balance between the ambient load current, current sink, and current source will be essential to getting the desired output. Details of how to adjust these values is provided in this SETUP page.

Last modified 4 years ago Last modified on Feb 28, 2020, 1:29:48 PM