The basic constant current source circuit is primarily composed of the input stage and the output stage. The input stage provides a reference current, while the output stage delivers the required constant current. Aviation Power Supply
The constant current source circuit is designed to provide a stable current to ensure the stable operation of other circuits. This requires the constant current source circuit to output a constant current, hence the device used as the output stage should have a voltage-current characteristic with saturated output current. This can be achieved by using a BJT or MOSFET operating in a saturated output current state. The AC constant current source employs SPWM (Sine Wave Pulse Width Modulation) at high frequencies, followed by inversion through an IGBT module and isolation output via a transformer.
To ensure stable current output of the transistor, two conditions must be met:
a) The input voltage must be stable – the input stage needs to be a constant voltage source; b) The output transistor's output resistance should be as high as possible (ideally infinite) – the output stage needs to be a constant current source. Basic constant current source circuits, depending on the main components, can be categorized into three types: transistor constant current sources, FET constant current sources, and op-amp constant current sources, etc. 400Hz power supply
