BPSemi (晶丰明源) DC/DC Converters

Select buck converters when output voltage is lower than input voltage (step-down). Select boost converters when output voltage is higher than input voltage (step-up). For applications where input voltage can be above or below output voltage, use buck-boost converters. Buck converters are generally more efficient and less complex than boost converters. Consider the input voltage range, output voltage, output current, and efficiency requirements when selecting converter topology.

Use buck for step-down, boost for step-up, buck-boost for variable input. Contact LiTong for topology selection guidance.

Synchronous rectification replaces the output diode with a MOSFET to reduce conduction losses. In traditional buck converters, the freewheeling diode has a forward voltage drop of 0.3-0.7V, causing significant power loss at high currents. Synchronous rectification using a low-Rds(on) MOSFET reduces this voltage drop to millivolts, dramatically improving efficiency especially at low output voltages and high currents. The efficiency improvement can be 5-15% depending on operating conditions. All modern high-efficiency DC/DC converters use synchronous rectification.

Choose synchronous buck converters for high-current or low-voltage applications. Contact LiTong for efficiency optimization.

Loop stability considerations: 1) Follow manufacturer recommendations for output capacitor selection (type, value, ESR), 2) Use ceramic capacitors with adequate capacitance at DC bias, 3) Add external compensation if required for your specific application, 4) Minimize output capacitor ESR to avoid double-pole issues, 5) Keep switching frequency and crossover frequency properly separated. BPSemi converters with internal compensation simplify design but still require proper output capacitor selection. For critical applications, perform loop gain measurements to verify stability margins.

Follow BPSemi capacitor selection guides or contact LiTong for loop stability analysis and compensation design.

DC/DC converter EMI considerations: 1) Input filtering - use ceramic capacitors close to the IC input pins, 2) Switching node - minimize copper area to reduce radiation, 3) Grounding - use star grounding and minimize ground loops, 4) Layout - place input capacitor, inductor, and output capacitor close together, 5) Snubbers - add RC snubbers if needed to suppress ringing, 6) Shielding - use shielded inductors for noise-sensitive applications. Good layout is the most important factor for EMI performance. Follow manufacturer layout guidelines closely.

Follow BPSemi layout guidelines or contact LiTong for EMI troubleshooting and filter design.

DC/DC converter power dissipation calculation: Ploss = Pout × (1/η - 1), where Pout is output power and η is efficiency. For example, with 5V output at 2A (10W) and 90% efficiency: Ploss = 10W × (1/0.9 - 1) = 1.11W. Calculate junction temperature: Tj = Ta + (Ploss × Rthja). Ensure Tj stays below maximum rating (typically 125°C or 150°C). For thermal design: 1) Use adequate copper area for heat sinking, 2) Add thermal vias under the IC, 3) Consider airflow for high-power applications, 4) Use thermal simulation for critical designs.

Calculate power dissipation and verify junction temperature. Contact LiTong for thermal design support.