The USB-C interface is revolutionizing the way electronic devices are charged. The USB-C cable can be connected to either a smartphone or a superbook at either end. Physically, the C-type connector is bi-directional (no matter which end of the cable can be inserted into both ends of the device), it is also non-polar (the connector can be inserted face up or vice versa). During the negotiation process, the connection system can electronically distinguish the polarity. In addition to data transmission, USB-C can support bi-directional power transfer at higher power levels. The default voltage is 5V, and the USB-C port can negotiate with the inserted device to increase the port voltage to 20V at the agreed current level, or other voltage values ​​agreed by both parties. The maximum power provided by the USB-C port is 100W (20V/5A), which is more than enough to charge the laptop. The advantages are so obvious that it is not difficult to understand why electronic device manufacturers are adopting USB-C in their next generation products.
With the increasing adoption of USB PD and USB-C, the computer industry has placed significantly higher demands on the performance of the regulator. Compared to traditional USB-A and USB-B ports with fixed voltage values, the USB-C port is bidirectional and accepts variable input voltages with an output voltage range of 5V to 20V. Its adjustable output voltage allows laptops and other mobile devices to replace traditional AC/DC power adapters and USB-A and B terminals with USB-C ports. With these advantages in mind, some customers have designed two or more USB-C ports in their systems.
However, the current system architecture with two or more USB-C ports is complex and cannot meet the requirements of many customers. This white paper presents a new system architecture that uses Intersil's ISL95338 buck-boost regulator and the ISL95521A combo battery charger. We will discuss how this architecture simplifies design and fully supports all USB-C features. We will also show how this architecture can be applied to the adapter side to implement a programmable power supply (PPS) that can output an adjustable voltage to match the variable input voltage of the USB-C.
A new USB-C architecture
Figure 1 shows a new USB-C architecture consisting of the ISL95338 bidirectional buck-boost regulator and the ISL95521A combined battery charger or the ISL9238 buck-boost battery charger. This new architecture allows the system to charge the battery through the USB-C port, and also supports fast charging when the two PD chargers are plugged into USB-C_1 and USB-C_2. No additional complex port control logic or ICs are required, and the two ports of the architecture fully support USB 3.1 On-The-Go (OTG).
figure 1. Intersil Battery Charger Architecture – Dual USB-C Port with Two Buck-Boost Regulators and One Buck Charger
USB-Type-C: USB-C port
Bi-directional: two-way
2 & 3-cell Li-ion: 2- or 3-cell lithium-ion battery
Comparing Figures 1 and 2, it is easy to see that to achieve the same level of functionality and performance as the Intersil battery charger architecture, the existing battery charger architecture on the market requires more devices and complex external circuitry. Obviously, with the existing battery charging system, each charger channel requires a USB-PD controller to control the two ASGATEs and perform the charging function, which increases the system cost of the design. In order to implement a 5V step-down OTG, the OTG gate also requires a PD controller. Note that existing buck converters can only output a single fixed voltage. Figure 2 shows that if a 5V buck converter is used, the designer can only output a fixed 5V, which does not match the adjustable 5V-20V OTG output voltage required by many USB-C applications.
figure 2. Existing Battery Charger Architecture - Single Buck-Boost Charger + Complex External Logic
USB-Type-C 1: USB-C port 1
5V OTG only: only 5V OTG
Charging battery & Support system: rechargeable battery and support system
External input power selection logic circuitry: logic circuit for selecting an external input power supply
BB charger: buck-boost charger
5V Buck: 5V Buck Converter
The Intersil architecture presented in this paper overcomes all of these shortcomings. Figure 1 shows two ISL95338s in parallel, connecting two USB-C ports to the ISL95521A battery charger. Simplified system architecture, saving customers a lot of cost, because a lot of components have been removed, including various PD controllers, ASGATE and OTG GATE. Most importantly, fewer components were used but performance was not degraded. For example, if the battery needs to be charged, then power the ISL95521A directly from the USB-C input. In addition, the parallel connection of the two ISL95338s provides more options for customer applications.
For example, two USB-C inputs with different power ratings can be used to achieve high power battery charging, which means that the battery charging power is higher than a single USB-C input power. Figure 1 illustrates how this is done by placing an ISL95338 (USB-C set to a higher power rating) in the voltage loop to provide a constant voltage (V0) for the ISL95521A input and an ISL95338 in the current loop. The USB-C), which is rated at a lower power rating, automatically supplies the ISL95521A with maximum power. In other words, there is no need to add additional circuitry or logic to determine the different power ratings of the two parallel ISL95338 buck-boost regulators.
The ISL95338's internal control loop can be automatically selected based on different power ratings to take full advantage of the input power. For the OTG function, the battery power can be supplied via a diode and the power is transmitted to the USB-C output using the ISL95338. This eliminates the need for a 5V buck and OTG gate, as shown in Figure 2. In addition, by using SMBus communication between the two ISL95338, ISL95521A, and PD controllers, the OTG voltage can be adjusted instead of using a fixed value. Figure 3 shows a high-power fast-charging application in which the new Intersil battery charging architecture can be extended to connect four ISL95338s in parallel with an ISL95521A or ISL9238 battery charger. Each USB-C port can operate independently as a sink or source. The architecture also allows traditional adapters to be incorporated into the system as a power source without increasing material costs.
image 3. Intersil Battery Charger Architecture with 4 USB-C Ports - 4 Buck-Boost Regulators + 1 Buck Charger
USB-Type-C 1: USB-C port 1
Normal adaptor: normal adapter
2 & 3-cell Li-ion: 2- or 3-cell lithium-ion battery
Programmable power solution
In traditional USB-A and USB-B applications, the input voltage is fixed, which poses new challenges for USB-C applications because the USB-C port can also accept variable input voltages. The solution is the Programmable Power Supply (PPS) feature, which allows the output voltage and current of the power supply to be programmed and regulated in 20mV/50mA steps to optimize the power path. As shown in Figure 4, the ISL95338 buck-boost regulator is ideal for implementing PPS because it uses the SMBus communication of the USB-PD controller to output an adjustable bidirectional voltage.
Figure 4. New Intersil PPS Architecture
USB-PD Controller: USB-PD Controller
Buck-Boost VR: Buck-Boost Regulator
USB-C Port: USB-C port
in conclusion
Using the ISL95338 in a multi-port USB-C battery charging system enables a new, easy-to-use charging architecture. Compared to existing charging architectures, Intersil's new architecture enables lower cost and higher performance, faster charging and longer battery life. In addition, all USB-C port requirements are fully met, including the ability to implement PPS, which is one of the key USB features that need to be added in future applications.
Easy Electronic Technology Co.,Ltd , https://www.yxpcelectronicgroups.com