Since 1996, the architecture of USB (Universal Serial Bus) has been used as a standard for connectors and their related signal and power transmission. During this period, many changes were made to the specifications in order to improve the performance of systems adopting these standards. The latest developments applicable to power design include USB Type-C connectors, USB Power Delivery specifications, and USB Programmable Power Supply specifications. These enhanced features make USB an excellent choice for providing power, whereas in the past, USB was primarily a data and signal provider with limited power capabilities. In this article, we will discuss the relationship between USB Type-C, USB Power Delivery, and USB programmable power supplies, as well as their relationship with power supplies.

USB Type-C: is a standardized USB connector; The benefits include compact, stylish, and reversible design.

USB Power Delivery: is a specification that allows load and power to negotiate multiple standard power delivery levels. USB Power Delivery increases the power supply capacity of USB to 100 W, which is particularly useful when powering multiple devices.

USB Programmable Power Supply: is a supplementary specification for USB Power Delivery, which describes how the load and power supply communicate to achieve an increasing level of Power Delivery. This feature is particularly useful for battery charging.

USB Type-C connector

The USB Type-C (also known as USB-C) connector design is symmetrical, so it can be inserted in any way, which means there is no right or top or bottom inversion. Compared to the USB connector design, this makes the plug faster and easier to insert. When using previous connector designs, users were required to visually inspect the connector to determine the correct direction, or to insert the connector through repeated attempts; Causing slight inconvenience. Another feature of the USB Type-C plug is its rounded edges, which have the advantage of self alignment when inserting the plug.　　

The USB Type-C plug is designed to provide a moderate level of power (less than 100 W), and the specifications related to the small plug allow power to be transmitted to various compact electronic products. One advantage of using USB connectors for power and signal transmission is that it is a complex design with relatively low development costs. This is mainly due to the economies of scale achieved through the widespread adoption of connectors worldwide. Another advantage is that the system has been validated by a large number of users and product designs, which means that the design has proven its reliability and there is very little possibility of unknown operational problems. It is important to note that due to the complexity and speed provided by USB Type-C, the price of USB Type-C is usually higher than that of previous generation USB connectors. However, as USB C-type connectors become increasingly common, it is expected that costs will be adjusted accordingly.

Unqualified USB Type-C applications

Due to its fashionable design, small size, and low cost, designers may choose to use USB Type-C connectors, but have decided not to comply with USB Power Delivery standards. As long as the voltage of the unqualified power supply is 5 V and the maximum load current specification is less than the 5 A rated value of the connector, the possibility of equipment damage caused by using unqualified design is very low. If the output voltage provided by an unqualified power supply is greater than the traditional USB voltage of 5 USB, there is a huge risk of damaging the load.

The relationship between USB Type-C, power supply, and 3.1 Gen 2

The USB Type-C connector is closely related to USB 3.1 Gen 2 and USB Power Delivery. This often confuses people about the relationship between Type-C, 3.1 Gen 2, and USB Power Delivery concepts. It is important to note that although these concepts are interrelated and complementary, they are independent. Devices or power supplies can use USB connectors, but cannot achieve USB 3.1 Gen 2 or USB Power Delivery.

It is important to note that the USB protocol can be implemented using connectors other than the specified USB connector. Customers may choose to utilize USB data and power protocols to leverage the already deployed large-scale development and validation work of USB, but do not use USB standardized connectors to create proprietary systems.

USB powered

One of the goals of USB is to maintain interoperability between old and new versions of the specification. In previous versions of the USB standard, the transmitted voltage was specified as 5V. The USB Power Delivery standard allows transfer of voltages of 5 V, 9 V, 15 V, or 20 V, with a maximum power level of 100W.　　

　　
　　USB Power Delivery has established an operating protocol to ensure that the higher voltage available in the latest USB version does not damage old devices designed for 5 V operation. To prevent such damage, USB Power Delivery requires qualified devices to initially provide a maximum 5 V voltage of 900 mA to the load. The communication between the load and the power supply can establish higher maximum load current and higher working voltage. If there is no communication after connecting the load and power supply, the power supply configuration will maintain a maximum load current capacity of 5 V and 900 mA. If communication between the load and the power supply is lost after establishment, the power supply will be safely restored to 5 V and 900 mA configurations.　　

Power level specified by USB Power Delivery

USB powered application

When the product is complex and expensive, the advantage of USB Power Delivery being able to create a single power supply that can be used to power multiple products will be the greatest benefit. An example of a USB Power Delivery application is a power supply used to charge phones, laptops, tablets, smartwatches, and earplugs. All of these products are complex enough to increase the cost and complexity of communication with power sources. Additionally, users may be in vehicles, rooms, offices, or travel where they expect to provide power, but the mix of different power loads will be difficult to predict. In these cases, the USB Power Delivery power supply will negotiate with each device to provide the correct voltage and current configuration required for the load.

Although the claim that USB Power Delivery can achieve faster battery charging is true, they may be misunderstood. The time required for battery charging is limited by the structure of the battery and the power supply capacity of the power supply. If the charging of the battery is limited by the power transmission capability of the charger rather than the battery structure, implementing USB Power Delivery will shorten the time required for battery charging. When the power output capacity of two power supplies is the same, USB Power Delivery does not reduce charging time compared to a fixed output power supply.

For USB powered products, products that may not be suitable are those that are not too complex, have relatively low prices, and have relatively low power consumption requirements. Cheaper products may not be able to withstand design and manufacturing costs, as the device has built-in USB Power Delivery function for communication with the power supply. In most applications that choose power supply for load power, the power capacity is only selected based on the load demand. If a higher capacity power supply is specified, the excess capacity in the power supply will result in the size and cost of the power supply exceeding the required capacity. The power supply capacity of USB power supply must be designed to provide the maximum rated power of a configurable source. Lightweight systems that can be powered by USB Power Delivery sources or smaller Power Delivery sources will incur cost and size losses in using USB Power Delivery sources.

USB programmable power supply

Compared to traditional protocols and USB Power Delivery protocols, the USB Programmable Power Supply protocol provides better power control. The USB power transmission operation protocol controls how the USB power supply provides discrete voltage levels, while the USB programmable power operation protocol establishes the ability to control the output voltage and current characteristics of the power supply at the granularity level.

USB Programmable Power Application

A common application provided by USB programmable power supplies that requires precise control of voltage and current is battery charging. In a conventional battery charger topology, a voltage source is applied to the battery charging control circuit, and the system's output provides appropriate voltage and current to charge the battery. When standardizing the charging voltage and current characteristics of the battery, this method works well, so the battery charging circuit can become a standard design. For applications that require customized voltage and current charging curves for batteries, a USB programmable power supply may be a better solution. Using a USB programmable power supply, the load will monitor the status of the battery and provide commands to the power supply to charge the battery at the correct voltage and current curve. It should be noted that when configuring a USB programmable power supply for battery charging, the development team needs to design, implement, and test battery charging algorithms and circuits, while when selecting a standard battery charging circuit, it is necessary that the battery supplier's charging circuit has completed most or all of these tasks.

conclusion

The USB type-c connector and USB Power Delivery specification have made significant improvements to the USB standard. Although implementing complete standards will allow for significant system enhancements, implementing only a portion of new standards and protocols can also achieve significant benefits. It is expected that the USB Type-C connector will be used in many traditional 5V power supply applications due to its small size, improved design, and low connector cost, with a load current requirement of 5A or less.