“World’s First” Buck Converter IC With Intelligent Power Sharing
Silanna Semiconductor unveiled a high-efficiency, single-chip USB port power supply solution that claims to reduce component count and simplify the power-sharing design in multi-port fast chargers.
Thanks to newer semiconductor technologies like gallium nitride (GaN), fast chargers' power density, efficiency, and compactness have increased significantly. A standard charger delivers around 5 W to the connected device, while modern fast chargers can give up to 100 W power. With that in mind, many major flagship phones in the market offer fast charging, which delivers high power to your smartphone for quick charging.
The continued demand for more powerful smartphones with better displays and 5G features has created a demand for next-generation AC adapters to charge larger lithium-ion batteries quickly. Moreover, consumers need more power but don't need bulky adapters. Therefore, charger manufacturers are trying to make faster chargers with a higher power density and smaller, lightweight form factor.
A fast charger usually consists of a highly efficient DC-DC buck converter and a power delivery (PD) controller that manages the power sent to the devices.
Silanna Semiconductor's latest power IC. Image [modified] used courtesy of Silanna Semiconductor
Hoping to take on the challenge of fast charger designs, Silanna Semiconductor announced a new power IC, SZPL3002A, which combines a high-efficiency synchronous buck converter and an advanced power delivery controller in a single QFN packaging measuring only 5 mm x 5 mm. The new IC claims to significantly reduce the components needed to implement a 65 W charger with up to 4 ports.
In this article, we'll look at the importance of PD controllers concerning fast charging and then look a bit more into Silanna's power IC.
Importance of PD Controllers
When considering portable devices, the high-power capability of USB cables is essential for the battery to be charged faster. If we deliver 15 W power through a USB type-C cable, the battery won't get 15 W because power will dissipate across the resistance of the cable and connectors (around 300 milliohms). As a result, there will also be a voltage drop across these undesired resistances.
An example USB PD block diagram ecosystem. Image used courtesy of STMicroelectronics
The losses, in this case, seem to be negligible. However, consider a battery charged by a 15 W 5 V USB supply in the constant voltage phase supplying 4.4 V. Here, a maximum 0.6 V voltage drop is allowed across the resistances, which translates to only 8.8 W of transferrable power.
For designers to overcome these limitations, a USB PD controller is used to increase the supply's output voltage and power up to 20 V and 100 W, respectively. The PD controller also allows charging 2.5 W or lower power cellphones by adjusting the output accordingly.
Silanna's Integrated Charging Solution
Silanna's new integrated solution is built around a wide-voltage range, high-frequency point-of-load DC-DC converter operating at an efficiency of around 98%. It states to offer extremely low power dissipation at no load and forms a temporary feedback path to allow for well-controlled startup operation until the USB PD controller biases itself and takes over the output voltage control.
The converter integrates a low resistive upper FET (field effect transistor) and lower FET of 41 milliohms and 38 milliohms, respectively. Additionally, it features a selectable switching frequency from 667 kHz to 2 MHz and a wide output voltage range of 3.3 V–21 V. Moreover, it also comes with security features such as over-current protection, over-voltage protection, and an I2C bus for communication.
A single chip solution combining a power ASIC, digital ASIC, Microcontroller, low Rds(on) upper and lower FET, and OTP memory all in one package. Image used courtesy of Silanna
This USB PD controller offers USB PD V 3.0 Type C interfaces and QC 2.0/3.0/4.0/5.0 support for Type A/C connections and it intelligently adapts and shares power across 2, 3, or 4 ports. Its power rebalancing feature allocates unused power on previously connected ports, while another feature, called power throttling, lowers the current when the temperature thresholds are reached.
The PD controller integrates five power profiles. It offers one fully programmable power profile and four pre-programmed sets that designers can choose with an external resistor value. This feature helps OEMs to use this powerful solution for their targeted charging applications.
The port controller also comes with Silanna's CO2 Smart Power feature, which offers high efficiency and area savings. For the port controller, the feature means that it demonstrated a high-power density with excellent low-line (90 V AC) and high-line (230 V AC) efficiencies while using lower-cost components. The products in the CO2 smart power also reduce the standby power drain and hence, contribute less to harmful CO2 emissions.