A high-precision offline switching power supply circuit, applied to low-power AC/DC chargers and adapters.

The SP5715F is a high-precision offline switching power supply circuit used in low-power AC/DC chargers and adapters. The SP5715F uses primary-side sensing for precise constant current and constant voltage control, eliminating the need for optocouplers and TL431 typically used in such applications.

In constant current mode, the output power is set by the sampling resistor Rs connected to the CS pin. In constant voltage mode, the chip's various operating modes ensure high overall conversion efficiency. Additionally, the chip incorporates line voltage drop compensation, resulting in good load regulation. The SP5715F operates in PFM mode under constant current and PWM mode under constant voltage, reducing frequency at light loads.

The SP5715F provides power-on soft-start and various self-recoverable protection functions, including cycle-by-cycle current limiting (OCP), VDD overvoltage protection (OVP), VDD overvoltage clamping, undervoltage protection (UVLO), and overtemperature protection. The SP5715F's spread-spectrum function provides better EMI performance.

Typical Application Diagram

Features

• Constant voltage accuracy of 5% and constant current accuracy of 5% across the full voltage range

• Uses primary-side feedback control, eliminating the need for optocouplers and TL431

• Externally adjustable constant current value and output power

• Built-in primary-side feedback constant current control

• Built-in adaptive peak current control

• Built-in primary inductance compensation

• Enhanced line voltage drop compensation, externally adjustable

• Power-on soft start

• Built-in leading edge blanking (LEB) function

• Cycle-by-cycle current limiting protection (OCP)

• Undervoltage protection (UVLO), overvoltage protection (OVP), VDD voltage clamping protection

Applications

• Mobile phone chargers

• PDA and digital camera chargers

• Auxiliary power supplies for televisions and personal computers

• Replacement for linear regulators and RCC power supplies