When I've wanted to look at stability, ripple, noise, etc. of various DC power sources, I don't have an obvious load. There are a number of "adjustable DC load" circuits knocking around, based essentially on the principle of using a power transistor / MOSFET as a current limiter, but shorting the output to ground to simulate a load at a given current. From what I've seen, the output stage of the load is usually a high-power MOSFET with a sense resistor and some feedback to control the MOSFET.
However, at least one resource tries/ claims to maintain electrical isolation between the circuit under test, and the load control circuit.
The sense resistor R1 is a 4-terminal Vishay resistor that has an isolation voltage of 100V between its 100 milliOhm sensor, and the voltage it reportes from such sensing. But I cannot see (or don't understand) that the MOSFET in this situation provides similar isolation between the component providing the power, and the component simulating the load.
I see that we do get less-common 4-terminal MOSFETs. Is the motivation to provide for isolation between the MOSFET "control" and the MOSFET "output"? If not, and I did want some electrical isolation between the control circuit and the tested supply (say using a more conventional 3-terminal MOSFET), what might be the suggestions?
Thanks in anticipation...
Peter
However, at least one resource tries/ claims to maintain electrical isolation between the circuit under test, and the load control circuit.
The sense resistor R1 is a 4-terminal Vishay resistor that has an isolation voltage of 100V between its 100 milliOhm sensor, and the voltage it reportes from such sensing. But I cannot see (or don't understand) that the MOSFET in this situation provides similar isolation between the component providing the power, and the component simulating the load.
I see that we do get less-common 4-terminal MOSFETs. Is the motivation to provide for isolation between the MOSFET "control" and the MOSFET "output"? If not, and I did want some electrical isolation between the control circuit and the tested supply (say using a more conventional 3-terminal MOSFET), what might be the suggestions?
Thanks in anticipation...
Peter
Attachments
-
87.7 KB Views: 1