The SG3524 is a classic Pulse Width Modulation (PWM) regulator IC, widely used in DC-DC converters, inverters, and switch-mode power supplies. If you're simulating such circuits in Proteus, you might find that this specific model isn't always present in the default library.
If you absolutely need SG3524 for legacy design verification, download the library from (they provide a verified .DSN example), and always scan before extracting. Have you successfully simulated SG3524 in Proteus? Share your experience or errors below – I help debug library issues.