“Electric energy is the energy basis for the operation of modern society. Electric energy is converted into specifications through power supply equipment, and the electric energy that meets the requirements is delivered to electric equipment. In the process of converting electrical energy by a power supply device, energy loss occurs. The power supply is ubiquitous as the interface between electrical energy and electrical equipment, and the loss at any point will be greatly amplified. Whether from the perspective of cost or from the perspective of environmental protection, we cannot ignore these losses, so reducing losses and improving power efficiency become The tireless pursuit of scientific research and engineering personnel.
Electric energy is the energy basis for the operation of modern society. Electric energy is converted into specifications through power supply equipment, and the electric energy that meets the requirements is delivered to electric equipment. In the process of converting electrical energy by a power supply device, energy loss occurs. The power supply is ubiquitous as the interface between electrical energy and electrical equipment, and the loss at any point will be greatly amplified. Whether from the perspective of cost or from the perspective of environmental protection, we cannot ignore these losses, so reducing losses and improving power efficiency become The tireless pursuit of scientific research and engineering personnel.
TDTTP4000W066B adopts non-isolated structure, has power factor correction (PFC) function, adopts totem pole topology, can output 4kW of power, and the efficiency is claimed to reach 99%. The high efficiency of the power board can be achieved, mainly thanks to the core power device GaN FET. The device has low reverse recovery charge. Through the use of GaN FETs, power board power density can be increased, circuit system size and weight can be reduced, and system cost can be reduced.
TDTTP4000W066B out of the box
The outer packaging is a white corrugated box with a product introduction sticker on the surface, which is simple and practical. However, it is quite satisfactory visually. If the packaging is more beautiful, it will definitely improve the impression score.
Open the box, you can see that there are 25mm thick shock-absorbing sponges on the top and bottom of the box. Inside the box is a power supply evaluation board sealed in an anti-static bag, a quick instruction manual, and an auxiliary power supply for the evaluation board.
The main electrical performance parameters of the evaluation board:
Input Voltage: 85VAC ~ 265VAC, 47Hz ~ 63Hz
Input current: 18A (2000W at 115VAC) or (4000W at 230VAC) 10% short-time overload
Output voltage: 387VDC ± 5VDC
PWM frequency: 66kHz
Auxiliary power supply 12VDC
For TDTTP4000W066B, Transphorm provides very detailed information on its official website, including technical documents, design files and BOM (component details) of the power board.
Open the antistatic bag and take out the power board. As a power supply with a power of 4kW, its size really surprised the author. Therefore, the author went to several large Electronic device websites to check related power supply products. There are very few power supply products of the same power level. much bigger. The figure below is a comparison between the power evaluation board and the Redmi 5 PLUS. It can be seen that the power density of the power board is extremely high.
Most of the components of the power board are placed on the front of the circuit board. From the figure below, it can be seen that the components are not very crowded, and the spacing between the components can be clearly seen. Most of the space is occupied by inductors and capacitors. On the back of the circuit board, there are a small number of components, mainly 9 nylon pillars, which are convenient for the placement of the power board.
The auxiliary power supply is 12VDC, which supplies power to the control card and cooling fan.
The control card adopts TI’s TMDSCNCD28335. The control core of this card is based on the TMS320F28335 chip, which can be purchased separately. The control card is inserted into the card slot and clamped with a clip for shock resistance.
As shown in the figure below, the power of 4kW is output through two GaN FETs and two MOSFETs. The GaN FETs and MOSFETs are in contact with a white pad, and the white pad is in contact with the heat sink, and the contact surface is coated with thermal grease. The GaN FETs are fastened by screws and the MOSFETs are clamped by clips. There is no white spacer introduced in the data. The author believes that the white spacer is some kind of heat dissipation material, which is used here to adapt the distance between the FET and the heat sink. Cooling is accomplished by two fans forcing air to cool a small radiator.
It is necessary to focus on GaN FET. As the core power device of the circuit, this power board uses TP65HO35WS 650V, 35 mΩ from Transphorm. The device combines advanced high-voltage GaN HEMT and low-voltage silicon MOSFET technologies for outstanding reliability and performance. The TP65HO35WS improves the efficiency of silicon devices through lower gate charge, lower crossover loss and smaller reverse recovery charge Qrr. The TP65H035WS package is TO-247, the package form and internal structure are shown in the following figure.
The key parameters of TP65H035WS are shown in the following table
The application topology of TP65H035WS is shown in the following table
The power board adopts totem-pole bridgeless PFC topology, which is more efficient and lower cost than traditional Dual-boost. The traditional topology requires 2 MOSFETs, 2 inductors, and 2 SiC diodes (D1, D2). The totem pole bridgeless PFC using GaN FET only needs one Inductor, 2 GaN FETs, and the other D1 and D2 can use diodes or MOSFETs with equivalent internal resistance to achieve higher efficiency.
In the totem-pole bridgeless PFC topology, GaN FETs Q1 and Q2 form a high-frequency branch, which operates at a frequency of 66kHz. MOSFET S1 and S2 form a low-frequency branch and work at the power frequency (50/60Hz). During the positive half cycle of the input voltage, S1 is turned on and S2 is turned off. At this time, the high-frequency branch has two modes: Q1 is turned on, Q2 is turned off, the external power supply charges the inductor L, and the capacitor is responsible for supplying power to the load. The current flow is shown in the figure below. When Q1 is turned off and Q2 is turned on, the external power supply and the inductor together supply power to the load and capacitor. In the negative half cycle of the input voltage, S2 is turned on and S1 is turned off. Similarly, the high-frequency branch also has two modes. During the dead time of Q1, Q2 switching, the inductor current direction does not change and freewheels through the body diode of the GaN FET.
Ultimately, the path of electrical energy in the power strip is shown by the blue arrow in the figure below.
Power Evaluation Board Power-Up Test
Test environment: The input uses a 10KW auto-voltage regulator, the output load uses a pure resistive high-power resistance box, the input and output are monitored by a voltmeter and an ammeter, and the temperature is monitored by a thermal imager.
Note that the control power is turned on first, and then the power power is turned on; the power power is turned off first, and then the control power is turned off.
Before the actual measurement of the power supply board, a non-PFC-corrected voltage and current waveform was cut as a reference. As shown in the figure below, the current waveform is seriously distorted, contains a large number of high-order harmonics, and the power loss is large, which is also a serious pollution to the power grid.
After the PFC correction of the power board, the voltage and current waveforms are shown in the following figure. It can be seen from the figure that the current waveform after PFC correction is basically the same as the voltage waveform. At the zero-crossing point of the transition from the negative half cycle to the positive half cycle, the two waveforms overlap. In one cycle, the current waveform slightly leads the voltage waveform.
Before and after calibration, the waveform contrast is very obvious.
The following are some actual test results, in which the efficiency is as high as 99% when it is loaded at 230V.
230V full load test situation:
230V medium load test situation:
The actual test efficiency of TDTTP4000W066B power board is calculated as follows:
From the above table, we can see that the output voltage is still very stable, and the high-efficiency region is relatively wide. During the test, we found that most of the efficiencies are above 98.5%, and the highest efficiency at the middle-load time of the measured part is close to 99% when the input voltage is 230V. %. At the same time, due to the limitations of the test environment and test conditions, it is a pity that the official maximum efficiency value has not been measured. But even the efficiency measured now is definitely competitive. At present, this power board is the most efficient among the products of the same power level on sale. In the author’s test, the simulated load process is close to the actual working condition, and the measured parameters have strong reference value for end customers.
The significance of high efficiency is not only to save electricity, but also to save electricity expenses. High efficiency also corresponds to low loss and less heat dissipation. The pressure on the thermal design of the overall power supply system will be reduced, the structure will be reduced, and the weight will be reduced, the design and manufacturing costs of the power supply will be reduced, and the products will be more competitive. Transphorm’s TDTTP4000W066B power supply evaluation board is a good example of this. The design is clear and clear, the control part is a Texas DSP, and the main circuit structure is a totem-pole bridgeless PFC. The 4000W power PFC inductor has a diameter of 70mm. The main control tube uses gallium nitride, which has no reverse recovery problem, high efficiency and fast switching speed.
From the voltage input, output and power output of the power supply evaluation board, the author speculates that the design target of the power supply board is most likely to be an electric vehicle charger. As electric vehicles become more and more popular, the high-power and high-efficiency characteristics of the power board will surely produce huge economic and social benefits.