“The trend towards larger capacity batteries requiring the same or faster charging times is accelerating the adoption of USB-C PD. When designing USB PD adapters and chargers, it is necessary to meet the latest energy efficiency standards such as COC V5 Tier2, and consider the miniaturization design to match the trend of thin, short but feature-rich such as mobile portable devices.

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The trend towards larger capacity batteries requiring the same or faster charging times is accelerating the adoption of USB-C PD. When designing USB PD adapters and chargers, it is necessary to meet the latest energy efficiency standards such as COC V5 Tier2, and consider the miniaturization design to match the trend of thin, short but feature-rich such as mobile portable devices.

Onsemi’s recently launched 65 W high frequency quasi-resonant (QR) USB PD adapter and fast charging reference design supports PD 3.0, PPS, BC 1.2 and other fast charging protocols, with an average energy efficiency of nearly 92%, far exceeding COC V5 Tier2 standard, and only 50 mm x 50 mm x 28 mm in size, it is an ideal choice for applications such as smartphone fast charging and laptop adapters.

Figure 1: 65 W high frequency QR USB PD adapter and fast charging solution

The design integrates ON semiconductor‘s NCP1345 high frequency QR flyback pulse width modulation (PWM) controller, superjunction MOSFET, NCP4307 synchronous rectifier controller and FUSB15101 PD controller, supporting an input voltage range of 90 VAC to 264 VAC and an output voltage of 3.3 V to 21 V.

Figure 2: Circuit schematic diagram of 65 W high frequency QR USB PD adapter and fast charging solution

Increasing the operating frequency can reduce the size of the power supply, the design can reach 190 KHz at 264 VAC, full load, and built-in Gallium Nitride (GaN) to further increase the switching frequency and reduce losses. The NCP1345 QR flyback topology uses a proprietary valley lockout circuit to ensure stable valley switching until the 6th valley, as the load is further reduced, at no load and light load, the NCP1345 enters Quiet Skip and flyback Discontinuous Conduction Mode (DCM), and then transition to frequency flyback mode to reduce switching losses and improve no-load and light-load efficiency.

Valley Lock and Quiet Skip achieve market-leading noise performance and improved electromagnetic interference (EMI) performance due to the reduced harmonic content of the waveform, which reduces the need for EMI filters and thus lowers cost. The built-in adaptive drive circuit can effectively reduce the voltage stress of the secondary. Coupled with the NCP4307 synchronous rectifier controller, it can not only replace the diode rectifier with MOSFET, thereby reducing the voltage drop and conduction loss across the rectifier, and achieve higher system energy efficiency, but also reduce parasitic ringing and system noise and improve reliability.

The FUSB15101 USB Type-C and PD controller integrates a high-efficiency Arm® Cortex®-M0+ processor and custom-designed peripherals to seamlessly support USB PD 3.0 applications, integrating all the requirements of a power port to provide an optimal system The solution can be easily customized according to specific application requirements, and the complete embedded firmware solution includes advanced power sharing algorithms to effectively optimize the total system power consumption.

Energy efficiency test

We tested the average energy efficiency and light load (10% load) energy efficiency of the 65 W high frequency QR USB PD adapter reference design at 115 VAC (blue curve) and 230 VAC (red curve) input voltage, as can be seen from the graph below It is far higher than the COC V5 Tier 2 average energy efficiency standard and the COC V5 Tier 2 light-load energy efficiency standard. The standby power consumption when outputting 5 V voltage is less than 45 mW, which is far better than the energy efficiency standard.

Figure 3: Energy Efficiency Curve

Safety protection functions and limited power supply (LPS) testing

The 65 W high frequency QR USB PD solution integrates a wealth of safety and protection functions, including: precise over-voltage protection (OVP), over-current protection (OCP), short-circuit protection (SCP), open-loop protection, X2 capacitor discharge, etc.

Moreover, the 65 W USB PD solution meets the LPS requirements under both the PDO and PPS protocols, and the test results are shown in the table below. The PDO supports five fixed voltage levels: 5 V 3 A, 9 V 3 A, 12 V 3 A, 15 V 3 A, 20 V 3.25 A, and the LPS standard requires output 5 V 3 A, 9 V 3 A, 12 V The maximum short-circuit current is 8 A at 3 A, 6.67 A at 15 V 3 A output, and 5 A at 20 V 3.25 A output. The output voltage, output current and output power delivered by the LPS standard power supply to the load are all within the requirements, so as to avoid hazards such as electric shock and fire.

Performance Testing

After testing, the 65 W high frequency QR USB PD adapter reference design has less than 80 mV ripple and noise under various load conditions, stable dynamic performance, and excellent EMI and thermal performance.

Figure 4: Ripple at 90 VAC for the 65 W High Frequency QR USB PD Adapter Reference Design

Figure 5: 65 W High Frequency QR USB PD Adapter Reference Design Thermal Imaging