Power supply circuit and field emission electron source

A power supply circuit, comprising:

• field effect transistors Si coupled in series via drains and sources in sequence, wherein 1≤i≤n, i and n are natural numbers, n≥2, and wherein a source of S1 is coupled to a negative electrode of a voltage source, and a drain of Sn is used as an output terminal of the power supply circuit to couple to a load;
• a first group of diodes D1i coupled in series, wherein 1≤i≤n, i and n are natural numbers, n≥2, and wherein D11 is coupled in parallel between a gate of S2 and the negative electrode of the voltage source, D11 is not coupled to a gate of the field effect transistor S1, and D1n is coupled in parallel between a gate of the Sn and the drain of the Sn, the remaining D1i are coupled in parallel between gates of the Si and gates of Si+1 when n>2;
• a first group of resistors R1j, 2≤j≤n, wherein R1j are coupled in parallel between the gates of the Si and the sources of the Si, and wherein a value of j corresponds to a value of i, and i and j are natural numbers;
• and
• a current feedback module configured to adjust an internal resistance of the field effect transistors Si, 1≤i≤n, coupled in series in sequence, so as to cause a current passing through the load to be constant;
• wherein the field effect transistors Si, 1≤i≤n, operate in a constant current region,
• wherein the current feedback module comprises:
• a detection unit coupled in series with the load and configured to detect the current passing through the load, wherein the load is coupled to the output terminal of the power supply circuit;
• a control signal generation unit configured to generate a control signal according to the current passing through the load, and apply the control signal to the gate of the field effect transistor S1.