High Performance Current Mode PWM Controller

FEATURES

◆   Proprietary “Zero OCP/OPP Recovery Gap” Control

◆   Built-in Soft Start Function

◆   Pins Floating Protection

◆   Very Low Startup Current

◆   High Voltage CMOS Process with Excellent ESD Protection

◆   Frequency Reduction and Burst Mode Control for Energy Saving

◆   Current Mode Control

◆   Built-in Frequency Shuffling

◆   Programmable Switching Frequency

◆   Built-in Synchronous Slope Compensation

◆   Cycle-by-Cycle Current Limiting

◆   Built-in Leading Edge Blanking (LEB)

◆   Constant Power Limiting

◆   Built-in Leading Edge Blanking (LEB)

◆   Constant Power Limiting

◆   Audio Noise Free Operation

◆   VDD OVP & Clamp

◆  VDD Under Voltage Lockout (UVLO)

APPLICATIONS

Offline AC/DC Flyback Converter for

◆   AC/DC Adaptors

◆   Open-frame SMPS

◆   Set-Top Box Power Supplies

◆   ATX Standby Power

GENERAL DESCRIPTION

SF1530 is a high performance, low cost, highly integrated current mode PWM controller for offline flyback converter applications.

PWM switching frequency with shuffling is externally programmable, which can reduce conduction EMI emission of a power supply. When the output power demands decrease, the IC automatically decreases switching frequency for high power conversion efficiency. When the current set-point falls below a given value, e.g. the output power demand diminishes, the IC enters into burst mode and provides excellent efficiency without audio noise.

The IC can achieve “Zero OCP/OPP Recovery Gap” using SiFirst’s proprietary control algorithm. Meanwhile, the OCP/OPP variation versus universal line input is compensated.

The IC has built-in synchronized slope compensation to prevent sub-harmonic oscillation at high PWM duty output. The IC also has built-in soft start function to soften the stress on the MOSFET during power on period.

SF1530 integrates functions and protections of Under Voltage Lockout (UVLO), VCC Over Voltage Protection (OVP), Cycle-by-cycle Current Limiting (OCP), Pins Floating Protection, Over Load Protection (OLP), RT Pin Short-to-GND Protection, Gate Clamping, VCC Clamping, Leading Edge Blanking (LEB).

SF1530 is available in SOT23-6, DIP-8 packages.