Use of current injected control in solenoid focusing coil power supplies

The use of current-injected control in the design of solenoid power supplies is discussed. Such a supply is required to provide a constant current to a large inductive load. The control to output (power stage) transfer characteristics are worked out for a generalized load. The location of the poles and zeros and the effect of load inductance on the inner current loop are investigated. This control technique is seen to have inherent feedforward capability, and therefore to have better line rejection than the standard voltage-mode converter. This is also investigated for a solenoid converter using current-mode control. The results are verified and compared using a SPICE computer simulation