• DCM+QR Combined Operating Mode
• Switching Frequency Range: 25kHz–500kHz
• Automatic Valley Lockout from 1 to 6 cycles
• Low Frequency Burst Operation (1kHz)
• Frequency Modulation to Reduce EMI Noise
• Internal Soft-Start  Integrated 700V HV Startup
• Brown-In/Brown-Out Protections
• X Capacitor Discharge Protection (Optional)
• Vcc OVP
• Output UVP
• Current Sense Resistor Short Protection
• Internal and External OTP
• Compact Package: SSOP9

The SQ33020A is a high frequency quasi-resonant (QR) flyback controller designed for power delivery (PD) adaptors and quick battery chargers. It can deliver 240W output power with 25kHz–500kHz switching frequency. The SQ33020A operates using peak current control. It provides a QR mode in which the MOSFET can be turned on at a valley point to reduce switching loss, especially under high input voltages. In conventional QR flyback solutions, the valley number always varies between 1 and 2 or between 3 and 5, which increases VO ripple and creates audible noise. The SQ33020A uses a proprietary circuit to lock the valley number between 1 and 6, which provides more stability than conventional QR solutions. If load decreases, the SQ33020A will enter discontinuous conduction mode (DCM) to reduce the switching frequency for higher efficiency. Under very light loads, the SQ33020A enters burst mode to reduce power loss. The SQ33020A provides multiple mechanisms to ensure reliable operation: HV startup, X capacitor discharge, brown-out protection, VCC overvoltage protection (OVP), output undervoltage protection (UVP), internal and external overtemperature protection (OTP), and openloop protection (OLP). For higher efficiency, use the SQ33239 as a secondary side synchronous rectifier controller in conjunction with the SQ33020A to achieve zero voltage switching (ZVS). The SQ33020A is available in an SSOP9 package.