The Atmel ATtiny85 microcontroller is a compact, cost-effective solution that can serve as a capable PWM controller for switching power supplies. Its versatility and simplicity make it an appealing choice for a range of power supply applications, including buck, boost, and flyback converters. Here we see how this microcontroller fits into the world of PWM switching power supplies and how it compares to dedicated PWM controllers.
Key Features of the ATtiny85 for Switching Power Supplies
Hardware PWM Capabilities
The ATtiny85 supports hardware PWM generation on multiple pins, which is critical for controlling the power transistors in switching power supplies. For instance, the ATtiny85 can efficiently manage the passive output stage of a power supply, a design often used for off-line applications. For more details, read about passive output stages in SMPS.
Compact and Cost-Effective
The small size and low cost of the ATtiny85 make it ideal for applications where space and budget are constraints. This is particularly beneficial when designing output stages in PWM circuits, where compact design is often a priority.
The circuit diagram below shows how ATtiny85 AVR microcontroller can be used a a PWM controller in the halfwave forward mode converter switching circuit.
Learn more about designing output stages in PWM.
Clock Speed and Flexibility
With a clock speed of up to 20 MHz (using an external crystal), the ATtiny85 can handle moderate switching frequencies required for many power supply applications. While it may not match the performance of dedicated controllers for high-frequency designs, it’s more than sufficient for low to mid-range power supplies.
Low Power Consumption
The energy efficiency of the ATtiny85 is another advantage, especially in applications where minimizing power loss is critical. This feature aligns well with the demands of switching power supplies, which aim for high efficiency by reducing losses in the system.
Applications of ATtiny85 in Power Supplies
Buck Converters
The ATtiny85 can be effectively used in buck converter designs to step down voltage with high efficiency. For a comparison of buck converters and other power supply types, refer to this comprehensive guide on difference between buck converter and forward converter.
Flyback Converters
The microcontroller’s ability to generate precise PWM signals makes it suitable for controlling flyback converters, which are widely used in isolated power supply designs. For selecting the right components for flyback and other PWM switching power supplies, check out this guide on choosing PWM switching power supplies.
Boost Converters
With its programmable nature, the ATtiny85 can also be configured for boost converters, making it a versatile choice for stepping up voltage in applications where size and simplicity are key.
Limitations of ATtiny85 for Switching Power Supplies
Resource Constraints
The ATtiny85 has limited memory (8 KB flash, 512 bytes SRAM), which can restrict its use in complex control algorithms or designs requiring high-resolution PWM.
Lack of Advanced Features
Unlike specialized PWM controllers, the ATtiny85 does not have built-in features such as current sensing, error amplifiers, or protection mechanisms. These features are essential in high-performance power supply designs and must be implemented externally when using the ATtiny85.
Frequency Range
While the ATtiny85 can achieve reasonable PWM frequencies, very high-frequency power supplies may require microcontrollers or controllers with higher clock speeds and dedicated PWM peripherals.
Magnetic Component Design Considerations
The performance of the ATtiny85 in switching power supplies also depends on the design of the magnetic components, such as inductors and transformers. For insights into designing these components, refer to this guide on magnetic component design.
Conclusion
The Atmel ATtiny85 is a strong contender for simple and cost-sensitive switching power supply designs. Its compact size, hardware PWM capabilities, and low power consumption make it ideal for low-power applications. However, for high-power or high-frequency designs, a dedicated PWM controller or a more advanced microcontroller may be a better fit.
If you’re exploring switching power supplies or considering the ATtiny85 for your project, understanding the balance between simplicity and performance is key. Dive deeper into switching power supply designs by learning about passive output stages in SMPS or 555 timer-based buck converter designs.
