Intelligent Power Sharing for Next-Generation Charger Design

Power adapters with multiport power sharing allow multiple electronic devices to be charged or powered simultaneously. These adapters have multiple output ports, each capable of delivering power to different devices including smartphones, tablets, laptops, or other USB-powered consumer electronics, smart home, IT, and industrial equipment products.

Traditional multiport power adapters have limited/no dynamic power sharing ability and power each device with equal or a pre-set power delivery level. All connected ports will receive the same maximum power output, regardless of the type of device and their battery charge levels (for example, a 40W 2C charger will deliver 20W to each device).

Let’s consider a conventional four-port charger (3 x Type-C, 1 x Type-A, rated 100W total). The power supplied by each port at any time will depend on individual connections and when those connections were made. Ports will have discrete maximum power steps, depending on which ports have a connection. For example,

·      C1 could be 100W or 65W or 45W

·      C2 could be 100W or 30W or 65W

·      C3 could be  30W

·      A1 could be  30W or 18W

However, a new generation of multiport chargers are offering the ability to dynamically allocate power among the different output ports based on actual power requirements. This means that the adapter can intelligently distribute the available power across the connected devices, ensuring that each receives the appropriate amount of power for efficient charging or operation.

Power adapters with multiport power sharing usually come with various charging technologies, such as USB Power Delivery (USB-PD) or Qualcomm Quick Charge, which provide fast charging capabilities for compatible devices. They may also have additional safety features, such as overvoltage protection, overcurrent protection, and short circuit protection, to safeguard the connected devices from potential power-related risks.

The convenience of having multiple output ports in a single power adapter with power sharing capability allows users to reduce clutter and simplify their charging setup, making it ideal for home, office, or travel use. It can also be a cost-effective solution for powering multiple devices simultaneously without the need for individual power adapters for each device.

Delivering Next-Generation Multiport Power Sharing

Developing the latest multi-port chargers is being made much simpler thanks to the emergence of DC/DC converter ICs with integrated, intelligent power sharing functionality, such as the Silanna Semiconductor SZPL3002A. This synchronous buck converter operates with efficiencies up to 98%, has a selectable switching frequency ranging from 667kHz to 2MHz and offers a selectable soft start time and supports communication through an I2C bus. Input voltage range is 7V to 27V and the IC is capable of providing a 3.3V to 21V output at 3.25A, which covers PD (Power Delivery) and PPS (Programmable Power Supply) requirements.

A unique feature of the SZPL3002A is its integrated PD controller, which supports both Type A and C ports. By integrating the buck converter and the PD controller into a single IC package, the SZPL3002A simplifies and speeds the design of 65W fast charger and adapter applications with up to four ports, while ensuring efficient power sharing among connected devices.

The PD controller enables adaptive power sharing across two, three, or four ports with auto power re-balancing and power throttling at elevated temperatures. This means that when multiple devices are connected to the SZPL3002A for charging, the PD controller communicates with each device to establish their power needs and dynamically adjusts the power output accordingly.

Power Re-Balancing

When charging any battery-powered device, the device will need the most power at start, tailing off to a trickle or operating power at the end. For example, a phone may make 20W contract but needs < 5W after full charge, a laptop may make 60W contract but needs < 5W after full charge and a tablet may make 45W contract but needs < 5W after full charge.

Silanna’s SZPL3002 monitors actual charging demand on ports which are measured at regular intervals and if demand is < contract, lower contract negotiated within the charger. In a power sharing environment harvested power is offered back into the available power and is available for some of the other ports that may need power for charging other devices.

As an example, let’s consider a 65W multiport adapter. When a single device is plugged in, the PD Controller communicates with the device to determine its power requirements and if the device has a battery level of 20% or below, it will receive 100% of the available power.

Click image to enlarge

Figure 2: Adaptive Intelligent Power Sharing

When a second device is added, the PD Controller will communicate with the new device to establish its power needs. For instance, if the second device is a smartphone with a battery level of 30%, the PD Controller will reduce the power allocated to the first device to 57.5W and allocate 7.5W to the smartphone.

Similarly, when a third device is added, the communication loop is repeated to establish the new power requirements. The power allocated to the first and second channels may be further adjusted based on the battery levels of all connected devices. This adaptive power sharing algorithm ensures that the maximum output of multiport adapter is shared among the devices that need power the most.

As the battery level of the first device increases, the power IC allows for power rebalancing without establishing a new contract, allowing for efficient redistribution of available power. For example, the power allocated to the first device may be reduced by 10W, and the additional 10W may be redirected to the second device.

Protective Power Throttling

Many charger manufacturers require NTC measurements near Type-C output connectors. Type-C connector contacts can become resistive due to dirt/lint, resulting in the creation of high temperatures at the connector which can lead to scorching or system-wide charging unit shutdown. Using an external NTC thermistor input, the SZPL3002A can measure the case/connector temperature. If the temperature reaches a programmable warning level, the SZPL3002A will re-negotiate a lower power level (lower current) with the connected device. This repeats a number of times throughout the process of charging. If the temperature continues to increase past a programmable critical level, ports will disconnect.

Integrated VCONN Power Supply

Signal lines on Type-C connectors provide VCONN power supply that powers the cable electronics. The lines swap positions depending on which way the cable is inserted. All PD3.0-compliant C-to-C Cables have e-Marker chips that communicate to the port and transmit certain cable specifications and capabilities, for example current handling capacity, manufacturer, resistance and data speed. The e-Marker chip needs a power supply bias voltage of 3.3~5.0V. Most devices either do not have any provision for VCONN or leave it to the designer to supply VCONN and the switching matrix out to the connector pins. The SZPL3002A, however, has an integrated VCONN that not only supplies 100mW to the e-Marker IC but also integrates the switching matrix.

Summary

Figure 3 shows how the combination of the latest active clamp flyback AC/DC controllers with compact and highly integrated semiconductors such as the SZPL3002A can significantly simplify fast charger design.

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Figure 3: 65W 2C1A high-power-density AnyPort™ Schematic

Such a system - which is available as a production-ready reference design from Silanna Semiconductor - deploys multiple SZPL3002 devices to provide a compact, lightweight highly efficient intelligent, adaptive power sharing solution that optimizes power sharing among connected devices based on their actual charging needs.

Silanna Semiconductor