η-BalanceTM Current Mode PWM Controller@65KHz
FEATURES
◆ Less than 75mW Standby Power
◆ Programmable OLP Debounce Time
◆ Proprietary η-BalanceTM Control to Boost Light Load Efficiency
◆ Proprietary “Zero OCP/OPP Recovery Gap” Control
◆ Proprietary “Audio Noise Free OCP Compensation”
◆ Dmax up to 80%
◆ Fixed 65KHz Switching Frequency
◆ Built-in Frequency Shuffling
◆ Built-in Soft Start Function
◆ Frequency Reduction and Burst Mode Control for Energy Saving
◆ Built-in Synchronous Slope Compensation
◆ Cycle-by-Cycle Current Limiting
◆ Built-in Leading Edge Blanking (LEB)
◆ Current Mode Control
◆ Pin Floating Protection
◆ Very Low Startup Current
◆ Audio Noise Free Operation
◆ VDD UVLO, OVP
APPLICATIONS
Offline AC/DC Flyback Converter for
◆ AC/DC Adaptors
◆ Open-frame SMPS
◆ Laptop Charger
GENERAL DESCRIPTION
SF5533 is a high performance, high efficiency, highly integrated current mode PWM controller for offline flyback converter applications. The OLP debounce time can be programmed in SF5533.
In SF5533, PWM switching frequency with shuffling is fixed 65KHz and is trimmed to tight range. When the output power demands decrease, the IC decreases switching frequency based on the proprietaryη-BalanceTM control to boost power conversion efficiency at the light load. When output power falls below a given value, the IC enters into burst mode and can achieve less than 75mW no load power.
The IC can achieve “Zero OCP/OPP Recovery Gap” using SiFirst’s proprietary control algorithm. SF5533 also has built in proprietary “Audio Noise Free OCP Compensation”, which can achieve constant power limiting and can achieve audio noise operation at heavy loading when line input is around 90VAC.
SF5533 integrates functions and protections of Under Voltage Lockout (UVLO), VDD Over Voltage Protection (OVP), Cycle-by-cycle Current Limiting (OCP), Pins Floating Protection, Over Load Protection (OLP), Gate Clamping, RT Pin Short-to-GND Protection, Leading Edge Blanking (LEB), Soft Start, etc.
SF5533 is available in SOT23-6 package.