Analysis of line-scan output/e.h.t. generator circuit for c.r.t. displays

The operation of a typical line-scan output/e.h.t. generator circuit is analysed in detail. The results are given as a set of equations which are solved by an APL program, details of which are included. The analysis demonstrates how the various voltages, currents and time intervals in the circuit vary with e.h.t. load current. An important characteristic of the circuit is e.h.t. voltage regulation; this is found to depend significantly on the transformer leakage inductance, and on the charge storage and forward resistance of the e.h.t. rectifier. Over a range of load current depending on the leakage inductance, regulation is substantially better than if the leakage inductance were zero. Another characteristic that shows a similar dependence on leakage inductance is the flyback time. Performance of a test circuit has been computed and compared with measurements. The computed output voltage is found to be about 5.5 to 7% high and the incremental internal resistance about 33% low; probably the result of ignoring transfomer losses.