The TOPSwitch-FX series MCU power integrated circuit can be widely used in various switch power modules. This article introduces the circuit design of a 12V, 30W high-efficiency switch power supply.
This document introduces the TOP FX series microcontroller switching power supply, which can be used in general and specialized power supplies, standby supplies, and power modules. It explains the external current‑limiting design, voltage‑feedforward technique, and the use of LT817A linear optocoupler feedback for stable regulation.
The manual details a multi‑output configuration with five rails (+30 V, +18 V, +5 V, +3.3 V, –5 V) and a standby power stage providing 5 V/2 A and 3.3 V/2 A outputs. Features such as soft‑start, dummy‑load‑free standby operation, and EMI mitigation are also covered. This manual is written in Chinese.
| Input AC voltage range | 85‑265 V |
|---|---|
| Output power (single‑rail) | 30 W |
| Maximum efficiency (full load) | 80 % |
| Primary output voltage | +12 V, 2.5 A |
| Output rail +30 V | 100 mA |
| Output rail +18 V | 550 mA |
| Output rail +5 V | 2.5 A |
| Output rail +3.3 V | 3 A |
| Output rail –5 V | 100 mA |
| Standby output 5 V | 2 A |
| Standby output 3.3 V | 2 A |
| DC input voltage range (standby circuit) | 200‑375 V |
| Soft‑start total time | 14 ms |
The supply accepts an AC input voltage from 85 V to 265 V.
It can deliver up to 30 W of output power with a full‑load efficiency of about 80 %.
No, the TOP FX can skip its switching cycle in idle mode, eliminating the need for a dummy load.