The hardware structure of a typical mobile phone charger, based on the Qualcomm Quick Charge 2.0 protocol using the Dialog IC scheme, is illustrated in Figure 1. The iW626, acting as the QC2.0 protocol controller, negotiates power supply with the device via the D+/D- signals of the USB port and the application processor (AP) on the phone side. It then adjusts the output voltage by controlling the primary AC/DC controller, iW1780, through an optocoupler. This setup enables efficient and controlled power delivery.
In contrast, a charger designed for the USB Power Delivery (PD) protocol retains the same AC/DC circuitry but replaces the QC protocol controller with a PD controller such as Cypress’s CCG2. As one of the earliest USB-IF-certified PD controllers, CCG2 integrates an ARM Cortex-M0 processor and a complete PD protocol transceiver. It supports various devices including chargers, mainframes, accessories, and EMAC cables. The Type-C port has been widely adopted by leading brands like Apple, Lenovo, HP, Dell, Xiaomi, and LeTV, demonstrating its market acceptance.
Figure 2 shows the schematic of a charger using the CCG2 PD controller paired with the Dialog AC/DC controller. CCG2 communicates with the device via the CC signal of the Type-C port and the AP, then controls the output voltage and current through PWM control and an optocoupler. It also samples VBUS to ensure reliable operation of the PD state machine and manages VBUS switching via a MOSFET. Additionally, CCG2 can support QC3.0 through D+/D-, allowing both PD and QC to coexist on a single Type-C port—though they cannot operate simultaneously due to priority settings. Beyond voltage regulation, PD also enables current control for precise charging or high-current fast charging.
CCG2 features internal ADC for voltage and current sampling, closed-loop control, and protection mechanisms such as OVP, OCP, and UVP. However, these protections are software-based and not real-time enough to serve as a backup for the AC/DC controller. Cypress's third-generation PD controller, CCG3, improves on this by integrating hardware-based OCP and OVP, enhancing ADC accuracy and offering an optimized solution for high-current direct charging. Many mobile phone manufacturers have started evaluating this design.
What is the PD Charging Protocol?
The PD charging protocol, developed by the USB-IF organization, allows for significantly higher power delivery than traditional USB standards. While the standard 5V/2A Type-C interface is limited to 10W, PD can increase this to up to 100W. Google has mandated that all Android 7.0+ devices must support PD, aiming to unify the fast-charging market and reduce fragmentation.
What Does the PD Protocol Fast Charge Mean?
USB-PowerDelivery (USB PD) is a key fast-charging standard developed by the USB-IF. It enables higher voltages and currents over USB cables, supporting up to 100W of power delivery. Unlike Type-C, which is a physical connector, PD is a communication protocol that defines how power is negotiated between devices. Type-C supports up to 5V/3A by default, but when combined with PD, it can deliver up to 100W. This makes it ideal for laptops, smartphones, and other power-hungry devices.
The Future of USB PD
USB PD has evolved to version 3.0, and under Google’s influence, it has begun to replace Qualcomm’s QC protocol. It has received support from China’s Ministry of Industry and Information Technology and is expected to bring more consistency to the fast-charging market in the near future.
Advantages of PD Fast Charging
PD focuses on multi-device power delivery, enabling bidirectional and even networked charging. In contrast, QC is limited to unidirectional charging and lacks networking capabilities. While PD adoption is still growing, especially among high-end devices like Apple’s MacBook, Meizu, HTC, and Google Pixel notebooks, domestic manufacturers are increasingly adopting PD-compatible chargers, such as the ORICO TSM-1U, which features a sleek design and improved user experience.
How USB PD Fast Charging Works
USB PD communication involves modulating protocol messages into a 24 MHz FSK signal, which is then coupled onto the VBUS line. This signal is detected by the device and decoded to negotiate power delivery. A low-pass filter, consisting of an isolation inductor, is used to prevent interference with the DC voltage. The communication process includes detecting PD support, negotiating voltage and current, and dynamically adjusting power during charging. This ensures efficient and flexible power delivery across a wide range of devices.
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