OB2273
Quasi-resonant flyback controller with valley switching technology for high-efficiency power supplies up to 75W with...
Product Overview
Description
The OB2273 is a quasi-resonant (QR) flyback controller that achieves high efficiency and low EMI through valley switching operation. It switches the MOSFET at the minimum drain voltage point, reducing switching losses and EMI generation.
The controller features frequency foldback at light loads to maintain high efficiency across the entire load range. Built-in protections include OVP, OCP, OTP, and brown-out protection for reliable operation under all conditions.
OB2273 is well-suited for high-efficiency adapter applications, LED drivers, and auxiliary power supplies where efficiency and EMI performance are critical requirements.
Product Series
OB
Primary Application
High-efficiency adapters
Key Features
- Quasi-resonant valley switching
- Frequency foldback at light load
- Built-in high-voltage startup
- Brown-out protection
- Over-voltage protection
- Over-temperature protection
- Soft-start function
Specifications
| Input Voltage | 85V - 265V AC |
|---|---|
| Output Power | Up to 75W |
| Switching Frequency | Variable (QR mode) |
| Standby Power | < 0.1W |
| Operating Temperature | -40°C to +85°C |
| Package | SOP-8, DIP-8 |
Applications
High-efficiency adapters
Electronic system design
LED lighting drivers
Motor drive and control systems
LCD TV power supplies
Electronic system design
Notebook adapters
Electronic system design
Industrial power supplies
Industrial automation and control
FAE Expert Insights
"The OB2273's quasi-resonant operation is a game-changer for efficiency. Valley switching really works - I've measured 2-3% efficiency improvement over traditional PWM controllers at full load, and even more at light loads due to frequency foldback. EMI is noticeably lower, often passing Class B with minimal filtering. The brown-out protection is well-implemented and prevents nuisance trips. One consideration: QR operation requires careful transformer design for proper valley detection. Make sure the auxiliary winding provides clean voltage feedback. For high-efficiency adapters up to 75W, this is my go-to recommendation."
— Principal FAE - High Efficiency Power, BeiLuo
Frequently Asked Questions
What is quasi-resonant operation in OB2273?
Quasi-resonant operation means the controller switches the MOSFET at the minimum drain voltage point (valley) after the transformer demagnetizes. This reduces switching losses and EMI by switching when voltage and current are at minimum levels.
Use QR operation for high-efficiency applications; standard PWM may be sufficient for cost-sensitive designs.
How does frequency foldback work in OB2273?
At light loads, OB2273 reduces switching frequency to minimize switching losses while maintaining output regulation. This extends the high-efficiency operating range down to very light loads, important for meeting efficiency standards.
Frequency foldback helps meet DoE and CoC efficiency requirements; verify audible noise at very light loads.
What is the difference between OB2263 and OB2273?
OB2263 is a standard PWM controller with fixed frequency operation. OB2273 uses quasi-resonant valley switching for higher efficiency and lower EMI. OB2273 is better for high-efficiency applications; OB2263 is more cost-effective for standard designs.
Choose OB2273 for high-efficiency requirements; OB2263 for cost-sensitive standard applications.
How do I design the transformer for QR operation?
QR transformer design is similar to standard flyback but with attention to leakage inductance and auxiliary winding coupling. Lower leakage inductance provides cleaner valley detection. The transformer should be designed for the desired switching frequency range in QR mode.
Follow On-Bright transformer design guidelines; pay attention to leakage inductance and winding coupling.
Can OB2273 be used for LED driver applications?
Yes, OB2273 is well-suited for LED driver applications due to its high efficiency and excellent EMI performance. The constant voltage output can be converted to constant current using external circuitry, or combined with On-Bright's dedicated LED driver ICs.
Consider OB2273 for high-power LED drivers; dedicated LED drivers may be simpler for basic applications.