TinySwitch-4 combines a high-voltage power MOSFET switch with a power supply controller in one device. Unlike conventional PWM (pulse width modulator) controllers, it uses a simple ON/OFF control to regulate the output voltage. The controller consists of an oscillator, enable circuit (sense and logic), current limit state machine, 5.85V regulator, BYPASS/MULTIFUNCTION pin undervoltage, overvoltage circuit, and current limit selection circuitry, over-temperature protection, current limit circuit, leading edge blanking, and a 725V power MOSFET. TinySwitch-4 incorporates additional circuitry for line undervoltage sense, auto-restart, adaptive switching cycle on-time extension, and frequency jitter. Figure 3 shows the functional block diagram with the most important features.