Giving all the challenges and uncertainties the world is still facing at the end of 2023, one thing is certain – we are unified for a greener planet. Under the initialtive of decarbonation, global players in the market and higher efficiency standards such as 80 PLUS Titanium are driving the power industry towards next level of efficient solutions with greater power density. Over the years of technological advancement, designing compact and efficient Power Factor Correction (PFC) power supplies is a complex yet manageble challenge. It has been long since PFC performance has no fundamental break-thorugh until the widespread of third-generation power semiconductor devices (gallium nitride, GaN and silicon carbide, SiC). Thereafter, the beauty of Totem-Pole Bridgeless PFC (TPPFC) is fully unlashed.

Compared to traditional bridged PFC topologies, the TPPFC mainly has three advantages. Firstly it enables higher power density as it has less component counts since the rectifing bridge is not employed in this topology. Moreover, such a simplified circuitry further improves system efficieny, particularly beneficial for situations with low-voltage input. Additionally, the adaptation of GaN FETs not only boosts the efficiency even higher but also empowers Constant Current Mode (CCM) PFC for higher power applications.

However, all these benefits come with a cost. Due to the absence of a bridge rectifier, the input AC voltage is directly applied to the switching transistors in this topology. Thus the TPPFC circuit tends to be vulnerable from unusual scenarios. For instance, surge, temporary missing of AC voltage, PCB noise, to name a few. This is exactly why engineers are hesitate to have their hands on this daunting task.

To harvest benefits without risking the system robustness, Hynetek Semiconductor has launched the HP1010, the very first dedicated PFC controller for Totem-Pole topology applications. A real-time control and hefty reliablity are seemlessly orchestrated by fast state machine and high performance analog front-end. The cycle-by-cycle current limit (CBC) effectively prevents overcurrent issues caused by abnormal power fluctuations. Surge protection can rapidly shutdown slow synchronous rectifiers and this is especially critical for system stability and reliability when strikes occur on opposite polarity of the AC line.  Additionally, the HP1010 offers a rich set of programmable protections, which means more flexibility and unique designs. For examples, overvoltage/undervoltage protections for both input and output, open-circuit protection, and the much more, which can be configured or disabled independently based on your preference.

The HP1010 features intelligent switching modes (CCM, DCM, and Burst Mode) to adapt to different load conditions, achieving good light-load efficiency. Frequency dithering effectively improves the electromagnetic interference (EMI) of TPPFC power systems. And above all, designing with HP1010 has never been simpler. Meeting your design specifics and accelerating time-to-market, a user friendly Graphic User Interface (GUI) software is readily to be downloaded from Hynetek website.

As first in its kind in the industry, the HP1010 is suitable for a wide range of power systems, including cloud computing/data centre, AI, 5G/telecom, industrial, ultra-high-density (UHD) power supplies and so forth.

Figure 1：HP1010 Pin and package

Key feature of HP1010:

· Highly flexible digital PWM, selectable frequencies from 20 kHz to 200 kHz

· 25 MHz ADC situated in high-performance analogue front-end

· Sophisticated digital control loop

· Smooth current at AC zero-crossings

· Frequency dithering for better EMI

· Multimode operations (CCM, DCM, and Burst mode)

· Fast loop response

· High-voltage DC input

· RMS power measurement

· Intelligent relay and inrush current control

· X-capacitor discharge

· Comprehensive fault protections

· Low power consumption, supply current as low as 1 mA in sleep mode

· I2C and UART interfaces through GUI

· 4 mm x 4 mm QFN-24L package, Figure 1

High Integration: simple but not simplistic

The HP1010 is packaged in a 4 mm x 4 mm QFN-24L, consistent of high-speed ADC, comparators, and other analogue front-end components. The peripheral circuitry is streamlined in a compact form factor that occupies a small PCB area, saving circuit board space and lowering BOM cost.

Figure 2: Typical Application Circuit of HP1010

High Efficiency: rejecting waste

HP1010 has demonstrated 99% peak efficiency in the 600-Watt reference design.

Figure 3: Efficiency Curve of 600W Totem Pole PFC Evaluation Board

Hynetek patented techology: expertise of no other

The novel current sense is materialised through a pair of current transformers applied to the fast leg of this topology. Once CBC is triggered on multiple accounts, the HP1010 provides the flexibility to shut down, automatic reset, or power-off then restart the system. Such configurations and real-time debugging can be accomplished through the graphical user interface (GUI) in Figure 4.

Figure 4: HP1010 Graphical User Interface

Programmable open-loop soft start at zero crossings:

Parasitic capacitance of the Power FETs on the slow leg of Totem-Pole topology varies across differenct vendors. The number and width of PWM pulses during zero transitions can be customised so as to optimise the voltage discharge process on the switching node.Similarly, such design flexibility is also available for the unequal delay time of disparate relays, which ultimately yields a safer and more efficient system. 

Figure 5: Smooth AC Zero-Crossing Control

Abstain from reverse current when AC input drops:

Thanks to high-speed AC voltage feedforward, duty cycle tracks real-time changes of AC input. When the drop of input voltage is detected, the HP1010 immediately switches off fast synchronous rectifiers of Totem-Pole PFC, hence effectively preventing reverse current. The measured resuilts are as shown in Figure 6.

Figure 6: (Left): Power Voltage Drops 45° Continuously For 2 Ms; (Right): Power Voltage Drops At 0° Continuously For 10 Ms

Lightning protection:

Lightning strikes stress the system with sharp spikes, either in or out-of phase with AC voltages. Controllers must be able to quickly detect the polarity of the input voltage and adjust accordingly. Otherwise, it's easy to damage the subsequent circuits. The HP1010 has showed a superb performance on this issue, rapid lightning detection followed by instant swit-off of the power FETs, given in Figure 7 and Figure 8.

Figure 7: Positive Half-Cycle Negative Lightning Strike

Figure 8: Negative Half-Cycle Positive Lightning Strike

PF and THD testing:

Respectively, Figure 9 and Figure 10 present PF and THD measurement results of the HP1010 at 110 Vac and 230 Vac inputs. Rather decent performance has been achieved for both parameters.

Figure 9: PF curve of the 600W evaluation board

Figure 10: THD curve of the 600W evaluation board

Detailed information of this 600 W evaluation board are listed below:

· Input voltage range: 90 VAC ~ 264 VAC

· Output voltage: 400 VDC

· Output power: 600 W

· Typical efficiency: 98.7%

Figure 11: 600W Evaluation Board Using HP1010

As a part of total solution, the HP3600 is a dual-channel isolated gate driver from Hynetek HySwitch^® family.  Paired with the HP1010, Totem-Pole system is readily at your reach.

Figure 12: HP3600 Pin Definitions and Package Diagram

The HP3600 features strong driving capability of 4 A/6 A source and sink current. Safe and fast driving performance is secured by 150 kV/μs Common Mode Transient Immunity (CMTI) and 48 ns propagation delay.  VDDA/VDDB supports up to 33 V, and VDDI operates in a wide input range of 3 V to 18 V, suitable for either analogue or digital controller interfaces. All power pins have undervoltage lockout (UVLO) protection with a threshold of 3 V, ideal for isolated applications of GaN MOSFETs.

The total solution (HP1010+HP3600) represents a milestone of innovation here in Hynetek. Building a green future, Henetek believes in IC-Intelligent and IC-Energetic. There will be more energy-saving products from Hynetek in contribution to carbon neutrality and advancement of green economy.