Power Electronics

Digital Power SoC Delivers 92% Efficiency to Isolated Designs

Integrating the company's GreenEdge™ 2-kV isolation technology on silicon, Akros Silicon's AS14x4 family delivers a 92%-efficient, space-saving, and cost-effective solution to isolated system power applications.

Intended for applications such as industrial, datacom, automotive, medical, residential gateway, and display, an isolated quad-output digital-power SoC from Akros Silicon Inc. suits isolated power designs. As shown in Fig. 1, the AS14x4 integrates a 2-kV isolation barrier and a wide-input-range (9 to 72 V) isolated primary converter to enable its use in 12/24-Vdc, 24-Vac distributed, and 48-V distributed-power applications requiring a 36- to 72-V input voltage range.

All internal connections between the primary and secondary power planes are isolated using Akros' proprietary GreenEdgeâ„¢ high-voltage and high-speed isolation technology to eliminate the need for optoisolators in both power-control loops and I2C/GPIO/ADC paths between these power planes. The device integrates the functionality of up to eight separate ICs used in current implementations.

Built-in cross-isolation dc-dc timing management and digital power control delivers 92% dc-dc efficiency (See Fig. 2) with excellent light-load efficiency management for energy-efficient, green-power applications. Power management capabilities include:

  • Hardware-programmable start-up power sequencing
  • Individual output Power-Good management
  • Voltage margining for each output
  • Primary GPIO controlled via secondary GPIO or I2C
  • Isolated ADC for primary-side sensor measurements
  • 5-V microcontroller compatible with interrupt on alarm services
  • Programmable watchdog timer

AS14x4 Features

Typically used in an isolated flyback topology, the AS14x4 includes one primary-to-secondary synchronous PWM controller, two secondary-side synchronous dc-dc buck regulators, and an additional secondary-side dc-dc buck or boost controller.

All four PWM clocks are user programmable for rate and then automatically synchronized and spread-spectrum-modulated to improve clock phase-edge EMI control and power efficiency.

Selectable spread-spectrum clocking on all PWMs reduces power-supply spectral noise by more than 15 dB to lower the EMI signature of the switch-mode power supplies and ease system design for EMC compliance. The AS14x4 meets UL60950 and UL1577 requirements basic isolation to 1,500 VRMS.

Synchronous converters with digital loop and timing control are integrated with digital isolation as part of an advanced power-system architecture for high-efficiency and cost-effective designs. Bi-directional isolated GPIO and isolated A/D conversion ease system-level design in many industrial and medical applications.

SUPPORTING NEXT-GENERATION POWER ARCHITECTURE

The AS14x4 product family allows designers to address energy efficiency and lower cost requirements of next-generation equipment while reducing system-level design complexity and development costs. Thus, the AS14x4 platform allows designers to leverage cutting-edge technology even under challenging budgets and cost targets.

While both hardware (pin-I/O controlled) and software (I2C controlled) operation is available, the I2C register set gives the platform designer several additional advanced device features, including:

  • Enable/disable each power output for system power management
  • Individual-output Power-Good management with interrupt on alarm services
  • Voltage margining for each output
  • Isolated primary-side GPIO controlled via I2C
  • Isolated primary-side A/D converter monitored via I2C
  • Multiple spread-spectrum algorithms on all PWMs and watchdog timers

The AS14x4 product family listed in the Table covers the range of system power and feature requirements. The AS1454/34 devices are I 2C-capable with advanced system diagnostics and programmability features. AS14x4 products are available in footprint-compatible, 64-pin 9x9 QFN, RoHS-compliant packages.

With internal buck-regulator options of 1.25 A (AS1424/34) or 2 A (AS1444/54), the device family provides a scalable platform solution for sub-50-W applications. Hardware-programmable device operation is available on all four devices.

Akros Silicon provides a complete development kit including the hardware evaluation board (EVB) shown in Fig. 2. A software GUI can access AS14x4 software features, and the USB I2C controller simplifies connecting the EVB or end-product to a PC. Also provided are reference design schematics, BOM, layout and application guides.

SURVEILLANCE CAMERA APPLICATION

Fig. 3 shows the implementation of a power subsytem for a surveillance camera. These units are generally powered from a distributed 12-V/24-Vdc or a 24-Vac power bus. Each unit requires an isolated power supply to prevent individual system faults from impacting the distributed power system.

The AS14x4 can be used to generate all the typical rails for camera electronics, including a boost-rail such as 8 to 12 V for pan/tilt/zoom (PTZ) motors. Additional power for an external camera heater can also be supplied via a 12-V output rail as shown.

The input ADC and GPIO are useful for connectivity to devices such as motion sensors, ambient light detectors, and other system alarm contacts. Very similar implementaiton is also required for building-management system/access-system controllers, like in Biometric Access Readers.

INDUSTRIAL DATACOM APPLICATION

The typical power subsystem requirement in industrial datacom applications is shown in Fig. 4. Here, the distributed 48-V power is used to power each piece of equipment.

To prevent ground loops and noise isolation, each unit contains an isolated power supply. A single AS14x4 can be used to generate all the power rails for the unit. Integrated isolated GPIO is very useful for backplane relay or I/O controls. Input A/D conversion can be utilized for input power monitoring as a self-test diagnostics measure.

The AS14x4 family allows scalability of design to cover a wide-range of equipment with common scalable designs. Spread-spectrum clocking provides added EMI reduction for stringent industrial environments.

INFOTAINMENT SYSTEM APPLICATION

A power subsystem requirement for typical infotainment systems (Fig. 5) can be implemented in buildings, hospitals, automotive, and locomotive environments. In bus or train applications, these systems run off of 24-V or 48-V battery supplies, and per-node isolation is needed for noise and ground-loop isolation.

An integrated LED controller on the AS14x4 is particularly useful for driving the LED backlight on infotainment units. Full electronics powering can be supported by the AS14x4, reducing cost and area without sacrificing noise isolation.

High efficiency of the AS14x4 eases thermal design of these units. The input A/D converter can also be used for active power measurements and self diagnostics also.

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