Circuit Design of 30W DC-DC Synchronous Rectifier Converter

GW MB10F 0.8A 1000V rectifier bridge

Probe current voltage pin 420*4450 head diameter 5.0 over current current and voltage pin

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

Photocoupler

Summary:

The DPA-Switch greatly simplifies the design compared to designs that use discrete devices. R1 sets the input under/overvoltage points to 33 V and 86 V, respectively, so that the maximum duty cycle decreases linearly with the input voltage to prevent saturation of the core during transient loads. The stringent UV/OV threshold tolerance range defines the gate voltage range of the secondary MOSFET, allowing for low cost self-driven synchronous rectification. R3 sets the internal current limit of the DPA425R to 45% of the nominal value. Larger models of DPA-Switch reduce conduction losses and increase efficiency without affecting design or overload functions.

The gate capacitances of VR1 and Q1 provide clamping and core reset to the drain voltage. The auxiliary winding of inductor L2 provides a bias supply to U1, which provides higher efficiency than adding a winding to T1.

C17 and R15 drive the gate of Q2, and C17 provides DC isolation to prevent overvoltage on the Q1 gate during shutdown. D4 resets the voltage of C17 before the next switching cycle begins. R17 filters out the gate voltage spike of Q1, and D2 prevents the body diode of Q1 from turning on. MOSFETs Q1 and Q2 are connected as a self-driven synchronous rectifier.

design feature

• Very few components
• High efficiency - with synchronous rectification efficiency of 90%
• Precise UV/OV for self-driven synchronous rectification
• No current sense resistor or current transformer requirements
• Output overload, open loop and over temperature protection
• 300 kHz switching frequency—optimized efficiency with simple self-driven synchronous rectification

30W DC-DC synchronous rectifier converter circuit diagram

See the uploading documentation for details (click to download)