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.
Feature
- 725V rated MOSFET
- Line compensated overload power - no additional components
- ±5% turn on UV threshold: line voltage sense with single external resistor
- Simple ON/OFF control, no loop compensation needed
- Selectable current limit through BP/M capacitor value
- Tight I2f parameter tolerance reduces system cost
- ON-time extension - extends low-line regulation range/hold-up time to reduce input bulk capacitance
- Self-biased: no bias winding or bias components
- Accurate hysteretic thermal shutdown protection with automatic recovery eliminates need for manual reset
- Auto-restart delivers <3% of maximum power in short-circuit and open loop fault conditions
- Output overvoltage shutdown with optional Zener
