No more hard work developing firmware! USB-C PD 3.0 PPS can be achieved with this controller
Latest update time：2023-03-08
Reads：
Larger displays, stronger performance and higher data throughput are trends in 5G smartphones, driving demand for larger battery capacity and fast charging capabilities. How to break through traditional charging methods is a challenge for designers. Because traditional charging methods are inefficient and consumers have increasing expectations for fast charging, excessive heating may occur at power levels that meet this demand. .
The programmable power supply (PPS) feature introduced in USB Type-C
®
(USB-C) Power Delivery (PD) 3.0 enables an effective solution, but the required firmware development still delays product delivery time.
This article will introduce issues related to fast charging of 5G mobile phones, and how USB-C PD 3.0 PPS can help designers efficiently meet the requirements for faster charging of larger-capacity batteries. It will then introduce and demonstrate how developers can use
the
highly integrated
ON
Semiconductor
USB-C controller, which implements USB-C PD 3.0 PPS in a finite state machine (FSM). This eliminates the need to develop firmware, speeding up the fast charging capabilities of next-generation chargers.
More powerful smartphones bring new challenges for fast-charging adapters
According to market analysts, 5G smartphones are expected to account for more than 50% of total smartphone shipments by 2023.
However, in the process of using these mobile phones to obtain 5G services, users will find that existing mobile phone chargers and charging stations can no longer meet the fast charging needs of this new generation of smartphones.
As we've already seen with 5G phones like the Samsung S20 Ultra 5G, these phones are technologically advanced, with larger screens and more processing power than earlier smartphones. In order to cope with their larger screens and correspondingly higher power consumption, existing 5G mobile phones already use larger batteries. For example, the Samsung S20 Ultra 5G has a screen size of 6.9 inches and uses a 5,000 milliamp-hour (mAh) battery with a capacity that is 25% higher than that of the previous generation model.
While consumers expect longer battery life from large-capacity batteries, they also hope that charging time will become shorter, not longer by 25%. For manufacturers hoping to meet the growing demand for charging stations in cars, homes and offices, how to shorten the charging time of high-capacity batteries has become a major problem in the face of battery bottlenecks.
Lithium-ion (Li-ion) battery manufacturers impose strict thresholds on charging current and voltage. A traditional lithium-ion battery with a rated capacity of 1000 mAh has a rated charging rate of 0.7 C, which means the charging current is 700 mA. For a fully depleted 5000mAh battery, it takes about 45 minutes to charge to 50% at a 0.7 C charging rate (or 3500 mA charging current).
More advanced battery technologies can support charge rates greater than 1 C, but both the charger and the device being charged need to accommodate significantly increased power levels. For example, a 5,000 mAh battery charged at the higher 1.5 C rate only takes about 22 minutes to charge from 0% to 50%, but the 7.5 amps (A) charging current will cause the components to charge even in a high-efficiency charging system. Causes stress and creates excessive heat loads. In fact, as USB-C becomes widely accepted as the industry-standard interface for power and other functions, the maximum current that compatible chargers can provide on USB-C cables will be limited. The USB-C cable has a maximum current of 5 A and contains a marker IC that provides cable information to the connected device. (For non-emarker cables, the maximum current is 3 A).
Of course, mobile device manufacturers can overcome this limitation by inserting a charge pump between the power input and the battery charging circuit. For example, to support a 7.5 A charging system, the travel adapter can provide 10 V at 4 A, thus relying on a typical split-in-two charge pump to output 5 V to the charging circuit at approximately 8 A. This approach allows the travel adapter to increase the USB-C voltage (VBUS) while maintaining USB-C compatible current levels.
Increasing charging power requires more effective control
The ability to support VBUS greater than 5 V enables the use of this high voltage, low current approach.
The USB PD 2.0 specification defines a set of fixed Power Delivery Objects (PDOs) that specify fixed combinations of voltage levels (5, 9, 15 and 20 V) and current (3 or 5 A).
Although USB PD 2.0 fixed PDO can achieve higher charging power, setting the charging voltage and current to be fixed, too high or too low will result in low charging efficiency, unacceptable thermal load and stress on components. In fact, the charging circuit operates optimally when its input voltage (provided by USB-C VBUS) is slightly higher than its output voltage (battery voltage). However, since the battery voltage continuously changes during normal operation, how to maintain optimal charging efficiency becomes a big challenge. When the battery is discharged, the difference between the battery voltage and the USB-C charging voltage (VBUS) will become larger, which will reduce the charging efficiency. On the contrary, when the battery is fully charged, the charging circuit needs to reduce the charging current to protect the battery.
If the charging level provided by the travel adapter cannot be directly reduced, power dissipation will increase, thereby reducing efficiency and causing heating. Therefore, the optimal charging level will continue to change, often in an incremental manner, which requires corresponding incremental control of charging voltage and current to achieve maximum efficiency.
How does USB-C PD 3.0 PPS improve efficiency?
The USB-C PD 3.0 PPS feature is designed to meet the growing demand for higher charging efficiency at higher charging power, allowing the charged device (current sinking device) to request the charger (current sinking device) to enhance the PDO Published mV and mA step values increase or decrease charging voltage and current.
Using this capability, the sinking device can adjust the voltage and current of its sinking device to optimize charging efficiency.
The introduction of PPS has significantly changed the way the charging process works. In the past, the charger simultaneously controlled and executed the charging algorithm. After adopting PPS, the control of the charging algorithm is transferred to the filling device, requiring the charger to execute the algorithm according to the instructions of the filling device.
Through the PPS, a smartphone or other infusion device communicates with the charger to optimize power delivery, resulting in a mutually agreed-upon PD "contract" through a negotiated agreement that includes a brief interaction like the one below.
-
The charger discovers whether the connecting cable has 5 A capability
-
The charger broadcasts its charger voltage and current capabilities described in up to 7 PDOs
-
Inject the device to request one of the broadcast PDOs
-
The charger accepts the requested PDO
-
The charger delivers power at agreed voltage and current levels
Advanced mobile devices, such as the aforementioned Samsung 5G phone, take advantage of this capability to provide fast charging using compatible chargers. For manufacturers designing fast-charging travel adapters and building charging stations into other products, implementing such charging protocols often requires developing controller firmware that can execute the protocol and operate the associated power supply device. However, for mature standards like USB-C PD PPS, FSM solutions provide an effective alternative that eliminates the need for firmware development that can delay final product delivery. ON Semiconductor's
FUSB3307
Adaptive Charger Controller adopts USB-C PD 3.0 FSM implementation including PPS, accelerating charger development to meet the fast charging requirements of next-generation smartphones and other high-capacity battery mobile devices .
Integrated controller for USB-C PD 3.0 compliant fast charger
ON Semiconductor's FUSB3307 is an integrated power controller that enables USB-C PD 3.0 PPS without the need for an external processor.
In addition to cable detection, load gate driver, multiple protection functions, and constant voltage (CV) and constant current (CC) regulation, the device also integrates in hardware a complete PD 3.0 device policy manager, policy engine, protocols and PHY layer.
The FUSB3307 is designed to support AC/DC and DC/DC chargers, providing a full set of responses suitable for PD power supplies. Therefore, designers can implement a USB-C PD 3.0 compliant power supply using the FUSB3307 and a relatively small number of other devices and components.
When connected to a sink device, the FUSB3307 automatically detects the capacity of the sink device and cable and broadcasts its capacity according to the USB-C specification. When the sink device responds with optional PDO support, the FUSB3307 enables VBUS and controls the power circuitry to ensure the requested charging voltage and current levels are delivered to the sink device.
Because the FUSB3307 integrates a full set of control functions, its basic operating principles remain conceptually consistent in AC/DC and DC/DC charger designs. In response to commands from the sinking device, the FUSB3307 in the charger uses its CATH output pin to drive a feedback control signal to the charger power stage. During charging, the FUSB3307 uses the VFB pin to monitor the charging voltage and the IS+/IS- pins to monitor the charging current flowing through the sense resistor. These monitored levels are fed back to internal voltage and current loop error circuits connected to the voltage (VFB) and current (IFB) pins. These signals in turn control the CATH pin for CV and CC control. Additional pins in the FUSB3307's 14-pin small outline integrated circuit (SOIC) package support load gate driver, USB-C connector interface and protection functions.
FUSB3307 charger controller simplifies charger design
Of course, each type of charger design will use a different configuration for the primary CATH output, VFB input, and other pins.
In an AC/DC wall charger or AC/DC adapter, the FUSB3307 monitors the voltage and current on the secondary side and drives control feedback to the primary side (Figure 1).
Figure 1: In an AC/DC design for a wall charger or adapter, the FUSB3307 controls the PWM controller via an isolated optocoupler to respond to different charging voltage commands from the sinking device. (Image source: ON Semiconductor)
In this charging design, the FUSB3307 CATH output pin is typically connected to the secondary-side optocoupler cathode to provide a feedback control signal to the primary-side pulse-width modulation (PWM) controller (ON Semiconductor's
NCP1568
). On the secondary side, the voltage and current sense inputs of the FUSB3307 will monitor the output from a synchronous rectifier controller, such as ON Semiconductor's
NCP4308
.
For example, in DC/DC charger designs used in automotive applications, the FUSB3307 directly controls the DC/DC controller. Here, the FUSB3307 CATH feedback signal is connected to a DC/DC controller such as ON Semiconductor's
NCV81599
compensation (COMP) pin (Figure 2).
Figure 2: In a car charger DC/DC charger design, the FUSB3307 directly controls the voltage output of the DC/DC controller, increasing or decreasing the output based on instructions fed into the device such as a 5G phone or other mobile device. (Image source: ON Semiconductor)
ON Semiconductor
implements this special DC/DC charger design for the FUSB3307 in its
FUSB3307MX-PPS-GEVB
evaluation board. Designed to operate from a single DC supply, the board provides a complete charger that complies with USB PD 3.0 and PPS requirements, delivering up to 5 A at VBUS levels from the standard minimum of 3.3 V to a maximum of 21 V.
Using this evaluation board, developers can explore the interaction of the FUSB3307 with USB PD 3.0 standard-compliant devices as well as legacy USB PD 2.0 devices. Developers can immediately begin exploring the fast charging process by monitoring the VBUS voltage and current delivered by the evaluation board to USB-C PD-enabled devices. Similar devices such as laptops or smartphones, etc.
This approach provides special implications for the FUSB3307's ability to interact with off-the-shelf USB PD 3.0 5G phones, and for the phones to use the USB PD 3.0 PPS protocol to optimize their charging voltage and current. In a demonstration of this capability [1], an off-the-shelf Samsung S20 Ultra 5G phone was found to issue a series of instructions to the FUSB3307MX-PPS-GEVB evaluation board to modify the charging voltage and current (Figure 3).
Figure 3: ON Semiconductor’s FUSB3307MX-PPS-GEVB evaluation board demonstrates the FUSB3307’s ability to respond to off-the-shelf 5G phone commands to fine-tune its charging voltage and current. (Image source: ON Semiconductor)
In this demonstration, after the evaluation board and mobile phone are connected, the 5G mobile phone selects the baseline PDO (5.00 V, 5.00 A maximum), as shown in the first 10 seconds of the figure.
At this stage, the charging voltage (VBUS) is 5 V, and the charging current (IBUS) of the 5G mobile phone is about 2 A.
The 5G phone then requests a higher PDO, stating that the charger is capable of delivering 8 V at 4 A.
FUSB3307 responds to the request and changes immediately:
VBUS jumps to 8 V as requested, and IBUS appears to gradually increase because the 5G phone increases the IBUS current.
After a sharp jump in VBUS, the possible increase in charging power due to PPS becomes apparent. A 5G phone will request an increase of 40 millivolts (mV) in VBUS approximately every 210 milliseconds (ms), gradually raising VBUS to higher levels. When the IBUS reaches 4 A (dashed green line in the figure), the FUSB3307 uses the standard PPS protocol to send an alarm message to notify the 5G phone that the requested current limit has been reached. The 5G phone continues to make requests, further increasing VBUS in 40 mV increments, eventually reaching 9.8 V. In daily use, the charging capabilities of this adaptive charger can achieve the maximum charging efficiency required for fast charging without overheating or other conditions that affect the charging device.
ON Semiconductor's FUSB3307MX-PPS-GEVB evaluation board allows developers to immediately explore USB-C PD applications in existing devices and extend the board's associated reference design to enable fast implementation in USB PD 3.0-compliant devices. Full customization. Best of all, no firmware development is required for implementation. With the FUSB3307 device, developers use familiar power technology to build an adapter that can take full advantage of fast charging for next-generation 5G phones and other compatible devices.
Conclusion:
Although 5G mobile phones bring a rich new feature and functional experience to users, the larger capacity batteries required to support these devices have become a challenge for designers. In particular, they need to make sure travel adapters and charging stations provide fast charging but don't overheat the phone.
ON Semiconductor's FUSB3307 adaptive charge controller is fully USB PD 3.0 PPS compliant - providing a straightforward design solution without the need for firmware development. By combining this controller with common power devices and components, developers can quickly implement an adapter to support the rapidly expanding number of USB PD 3.0-enabled 5G phones and other mobile devices.
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