HF920A Fixed Frequency Offline Regulator SOIC8

HF920A Fixed Frequency Offline Regulator SOIC8

The HF920A is a flyback regulator with a monolithic 900V MOSFET.

Key Specifications

Features

• Monolithic 900V/15Ω MOSFET and High Voltage Current Source
• Fixed Switching Frequency, Programmable up to 150kHz
• Current-Mode Control Scheme
• Frequency Jittering
• Low Standby Power Consumption via Active Burst Mode.
• <30mW No-Load Consumption
• Internal Leading-Edge Blanking (LEB)
• Built-In Soft-Start (SS) Function
• Internal Slope Compensation
• Over Voltage and Under Voltage Protections programmable through the PRO Pin

Typical Application Circuit

Applications

• E-Meters
• Industrial Controls
• The maximum output power is limited by junction temperature.
• Test is done under TA = 50°C. The test board is placed into a box about 20cm*15cm*10cm.
• To reduce VDS, the turns ratio is set to 5.
• Single output, VOUT = 12.5V.
• GND of the SOIC8-7A package is connected to a 3cm2 copper area with exposed copper strips. GND of the SOIC14-11 package is connected to a 2.5cm2 copper area.

Design Notes

• The PFC inductor must support the maximum duty cycle at the lowest line voltage, which is where saturation risk peaks.
• High-voltage startup and X-capacitor discharge paths dominate no-load standby loss; verify them against the efficiency target.
• Leakage inductance and the RCD clamp set the turn-off loss — snubber values are a thermal trade-off, not a fixed recipe.
• Synchronous rectification timing must track the primary switching; a mistimed SR FET conducts through its body diode and fails hot.

Common Questions