Selecting the right rectifier diode is a critical step in designing a switch-mode power supply (SMPS) or LED driver circuit. A mismatch between voltage, current, and recovery characteristics can lead to higher thermal loss, unstable operation, or even device failure.
This guide explains how to choose a rectifier diode based on reverse voltage rating (VRRM), average forward current (IF(AV)), forward voltage drop (VF), reverse leakage current, and thermal resistance (RθJL) — using Suntan ES2J, RS3M, SS310, and SS510 as real examples.
Different circuits impose different electrical stresses on diodes. Before you even shortlist parts, clarify where the diode sits:
| Circuit Application | Common Voltage Range | Recommended Type |
|---|---|---|
| SMPS Output Stage | 5–48 V | Schottky Diode (SS310 / SS510) |
| AC/DC Converter (Primary) | 85–265 V AC | Fast Recovery Diode (ES2J / RS3M) |
| LED Driver (Constant Current) | 12–48 V | Low-VF Schottky Diode |
| Motor Control / Inverter | 400–1000 V | Super Fast Rectifier (RS3M) |
Reverse Voltage (VRRM)
VRRM defines the maximum reverse bias the diode can withstand.
- For 24 V or 48 V rails, pick diodes rated at least 2× the working voltage.
- Example: SS310 (100 V) or SS510 (100 V) for 24–48 V DC rails.
Average Forward Current (IF(AV))
The diode must handle continuous load current.
- Small rails / LED drivers: 2–3 A class (ES2J / SS310)
- SMPS secondary / power modules: 5 A class (SS510)
Forward Voltage Drop (VF)
Lower VF = lower conduction loss.
- Schottky diodes: ~0.55–0.85 V typical
- Fast recovery diodes: ~1.0–1.3 V typical. Dropping VF from ~1.3 V to ~0.7 V can improve conversion efficiency by about 2–3% in compact supplies.
Reverse Recovery Time (trr)
Important for fast recovery parts.
- ES2J: 35 ns (super fast switching)
- RS3M: 150–500 ns (high-voltage class). For high-frequency SMPS (>100 kHz), you want shorter trr.
Thermal Resistance (RθJL)
Lower RθJL means better heat flow into the PCB copper. Suntan SMC-class rectifiers typically specify ≤15 °C/W, supporting stable operation under load.
| Model | Type | Voltage (VRRM) | Current (IF(AV)) | VF (V) | trr (ns) | Typical Use |
|---|---|---|---|---|---|---|
| ES2J | Super Fast | 600 V | 2 A | 1.25 | 35 | SMPS PFC, inverter |
| RS3M | Fast Recovery | 1000 V | 3 A | 1.30 | 150–500 | Industrial control |
| SS310 | Schottky | 100 V | 3 A | 0.85 | — | LED driver, DC/DC |
| SS510 | Schottky | 100 V | 5 A | 0.85 | — | High-current SMPS output |
- Define input / output voltage → determines VRRM.
- Estimate average current → pick IF(AV) with ≥20% margin.
- Check power efficiency goals → prefer lower VF to cut heat.
- Confirm switching frequency → Schottky for MHz-level, fast recovery for high-voltage kHz stages.
- Assess temperature / cooling → lower RθJL and solid PCB copper for thermal safety.
- SMPS Secondary Rectification: SS510 for low VF and 5 A surge capability.
- Inverter Feedback Path: ES2J for fast recovery and voltage robustness.
- LED Driver Output: SS310 for compact, efficient low-loss operation.
- Industrial Controller: RS3M for 1000 V blocking voltage and surge reliability.
Choosing the correct rectifier diode depends on a balance between voltage, current, VF, and thermal resistance.
For low-voltage SMPS or LED driver applications, Schottky rectifiers like SS310 / SS510 deliver low forward loss and high efficiency. For high-voltage conversion or industrial control, ES2J / RS3M remain reliable fast recovery options with strong surge behavior.
Matching datasheet limits to real circuit stress is what protects thermal margin, prevents runaway heat, and keeps field reliability high.
For full electrical characteristics and rectifier diode datasheets (fast recovery, fast switching, Schottky barrier / low VF), please contact Suntan. Our engineering team supports part selection, thermal evaluation, and form-fit-function replacement for SMPS, LED lighting, telecom power rails, and industrial control.

