Current Mode PWM Controller 25mA 7-Pin SOIC Tube

The UCC28740 isolated-flyback power-supply controller provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. Constant-Current (CC) regulation is accomplished through Primary-Side Regulation (PSR) techniques. This device processes information from opto-coupled feedback and an auxiliary flyback winding for precise high-performance control of output voltage and current.An internal 700-V startup switch, dynamically controlled operating states, and a tailored modulation profile support ultra-low standby power without sacrificing startup time or output transient response.Control algorithms in the UCC28740 allow operating efficiencies to meet or exceed applicable standards. The drive output interfaces to a MOSFET power switch. Discontinuous conduction mode (DCM) with valley-switching reduces switching losses. Modulation of switching frequency and primary current-peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.The controller has a maximum switching frequency of 100 kHz and always maintains control of the peak-primary current in the transformer. Protection features keep primary and secondary component stresses in check. A minimum switching frequency of 170 Hz facilitates the achievement of less than 10-mW no-load power.

Less than 10-mW No-Load Power Capability

Opto-Coupled Feedback for CV, and
Primary-Side Regulation (PSR) for CC

Enables ±1% Voltage Regulation and ±5%
Current Regulation Across Line and Load

700-V Startup Switch

100-kHz Maximum Switching Frequency Enables
High-Power-Density Charger Designs

Resonant-Ring Valley-Switching Operation
for Highest Overall Efficiency

Frequency Dithering to Ease EMI Compliance

Clamped Gate-Drive Output for MOSFET

Overvoltage, Low-Line, and Overcurrent
Protection Functions

SOIC-7 Package