AOS Introduces its First Buck Regulator Module
Aimed at industrial applications, the new device from Alpha and Omega Semiconductor delivers output voltages of up to 5.5 V.
Looking to aid engineers in simplifying their designs, Alpha and Omega Semiconductor (AOS) in late June released its first buck regulator module, the AOZ29303QI.
The company touts the device as an easy-to-use power module integrating a buck converter, inductor, and passive components into a compact 9 x 6 x 3.7 mm QFN package. Thanks to its highly integrated nature, the fresh device should allow for quick implementation and thus a faster time to market for OEM products.
The AOZ29303QI. Screenshot used courtesy of Alpha and Omega Semiconductor
The AOZ29303QI works from input voltages ranging from 4.5 to 30 V, and provides adjustable outputs ranging from 0.8 to 5.5 V. The caveat here is that for this unit, as well as for all buck converters, the output voltages possible are always less than that of the device’s input.
The Internal Workings of a Buck Converter
A buck converter is an electronic component that efficiently converts a higher voltage into a lower voltage. Its operation is described by the figure below.
The most basic buck converter. Image [modified] used courtesy of Toshiba
When a signal applied to its gate turns the MOSFET ON and allows positive voltage Vi to pass, that voltage flows through the inductor to the capacitor and load (Vo). An inductor impedes current flow, so the voltage at the load is not allowed to make it to Vi. Note that the diode is reverse biased, so at this point it does not conduct.
When the FET turns OFF, current collapses in the inductor and an opposite voltage is generated. Now the diode is forward biased, so current flows through it to the load. When that voltage begins to fall off, the load relies on energy stored in the capacitor.
The duty cycle of pulsating DC signal is defined as the time it remains at logic level 1, as opposed to logic level 0. The AOZ29303QI’s MOSFET is controlled by a pulsating DC signal to its gate, and can accommodate a duty cycle of up to 87%.
In its simple form, the output voltage of a buck regulator is controlled by the duty cycle. For those who dare, our own Anushree Ramanath explained these concepts in greater detail in a technical article last week.
A Complete Modular Solution
Per Peter Cheng, AOS’ power IC senior marketing director, the AOZ29303QI is based on the company’s AOZ128x family of regulators. The device includes a separate controller IC, eliminating the need for designers to undertake the otherwise difficult, and quite specialized, task of mating separate units. It also cuts down on the bill of materials (BOM) and saves precious board space.
A functional block diagram of the AOZ29303QI. Image used courtesy of Alpha and Omega Semiconductor
“By offering a module option, AOS’ intention is to offer system designers an even simpler implementation, speeding time to market and improving solution size,” said Cheng.
Modes of Operation
The AOZ29303QI can achieve an efficiency level of 93%.
When the power supplied by the controller’s load is low, though, the device switches to what AOS' proprietary pulse energy mode (PEM), described in detail in the unit’s data sheet. Even here, efficiency remains at a solid 85%.
When more power is drawn, the device switches to the more conventional continuous conduction mode (CCM). In this methodology, the current in the inductor is never allowed to reach zero.
The AOZ29303QI’s PWM signal sports an adjustable switching frequency, which users can manipulate via an external capacitor to cover a range extending between 200 kHz and 1 MHz. Output voltage is selected via an external resistor divider.
The unit’s controller includes a soft-start feature that serves to limit in-rush current, ensuring the output voltage will ramp up smoothly to regulation voltage. This feature, too, is controlled via an external capacitor.
The AOZ29303QI targets industrial applications such as factory automation, general-purpose point of load (POL) power, and networking.
Environmental and Physical Notes
The unit is RoHS-compliant and operates over a temperature range of -40 to +85 ℃.