How to Select a Rectifier Diode for Power Supply or LED Driver

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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.

Scope This application note compares fast recovery rectifiers and Schottky barrier rectifiers, using four Suntan parts (ES2J, RS3M, SS310, SS510). We focus on reverse voltage rating (VRRM), average forward current (IF(AV)), forward voltage drop (VF), reverse recovery behavior (trr), surge capability (IFSM), and thermal resistance (RθJL). The goal is to help you select an efficient fast switching diode / low VF Schottky rectifier for SMPS, LED lighting, telecom DC power rails, and industrial control systems.

1. Identify Your Circuit Type

Match application stress before you open a datasheet

Different circuits impose different electrical stresses on diodes. Before you even shortlist parts, clarify where the diode sits:

Common diode use cases Typical ranges

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)

Schottky diodes are ideal for low-voltage, high-efficiency rails. Fast recovery and super fast types survive high-voltage / inductive stress.

2. Evaluate Key Parameters

VRRM, IF(AV), VF, trr, thermal path

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.

3. Comparing Suntan Rectifier Diodes

ES2J / RS3M / SS310 / SS510

Rectifier performance summary (SMD packages) Typical values

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

Data source: Suntan datasheets for ES2J, RS3M, SS310, SS510.

4. Practical Selection Workflow

Step-by-step decision path

1. Define input / output voltage → determines VRRM.
2. Estimate average current → pick IF(AV) with ≥20% margin.
3. Check power efficiency goals → prefer lower VF to cut heat.
4. Confirm switching frequency → Schottky for MHz-level, fast recovery for high-voltage kHz stages.
5. Assess temperature / cooling → lower RθJL and solid PCB copper for thermal safety.

5. Typical Use Cases

Where each diode family fits best

• 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.

6. FAQ

Design notes for SMPS, telecom power, LED drivers

Q1. Why not use Schottky diodes everywhere?

Because they have lower reverse voltage ratings (≤100 V). High-voltage rails still require fast recovery / super fast parts like ES2J or RS3M.

Q2. What causes diode overheating?

Excessive forward current or a high VF part in a high-load rail. You solve it by choosing proper IF(AV) headroom and good thermal resistance.

Q3. Can I replace RS3M with SS510 for better efficiency?

Not 1:1. RS3M is rated 1000 V. SS510 is only 100 V. Always confirm your voltage margin and snubber network before substitution.

7. Conclusion

Picking the right rectifier for 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.

8. Contact, Datasheets & Media

Samples, cross-reference, application review

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.

Request Engineering Support Get a Quote / Sample

Figure 1. Rectifier overview (video)

Overview of Suntan ES2J / RS3M fast recovery rectifiers and SS310 / SS510 Schottky barrier rectifiers. Typical usage: switch-mode power supplies (SMPS), LED driver output, telecom DC rails, and industrial control modules where low forward voltage and thermal stability matter.

Figure 2. Package / application reference

ES2J (super fast recovery), RS3M (fast switching), SS310 / SS510 (Schottky, low VF). These DO-214AA / DO-214AB SMD rectifier diodes are widely used in AC/DC front ends, DC/DC converters, LED lighting drivers, and telecom / industrial power modules where surge capability and thermal margin are critical.

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