【 Weak current College 】 switching power supply technology of the latest and programme 】

Introduction

With energy-saving technologies are growing ever louder, the miniaturization of electronic equipment, environmental protection, higher requirements, switching power supply technology is in rapid development. More efficient, smaller size, fewer electromagnetic pollution, more reliable work of switching power supplies almost every month in innovation. This article is intended for the last two years the switching power supply outstanding technological advances are described, the following areas.

1 synchronous rectification technology

Since the late 1990s was born after the synchronous rectification, it brought the switching power supply efficiency has made important contributions. Current IC control technology for synchronous rectification programme has been generally accepted for research and development engineer, new listing of high mid-range switch power almost no no synchronous rectification technology works, now of synchronous rectification technology are working hard to achieve ZVS and ZCS way of synchronous rectification. In 2002, the company issued United States Galaxy ZVS synchronous rectification technology, has now been widely used. This way of synchronous rectification technology subtly Deputy edge driven synchronous rectification of pulse signal and PWM pulse signal original side, its increased linkage along ahead of original side PWM pulse signal rising edge, falling edge lag method enables synchronous rectification MOSFET of ZVS. The latest available dual-output type PWM control IC almost always within the control logic for realization of Deputy edge ZVS synchronous rectification in the control Terminal. For example: Linear Technology Corporation (Linear-Tech) LTC3722, LTC3723, inter, Sergio (INTERSIL) company ISL6752, IC not only solve the primary-side power MOSFET for soft-switching, and focus on the good side of ZVS, Vice-President of synchronous rectification, use this IC fabrication of DC/DC converters, thetotal conversion efficiency is reached 94%.

In asymmetric of switching power supply circuit topology, particularly for performance good forward converter or forward active clamp circuit, Deputy of synchronous rectification in order to achieve synchronous rectifier ZVS way, eliminate MOSFET body diode conduction losses and reverse recovery time of loss, Texas Instruments ' latest patented technology "pre detection gate drive technology" in the control chip adds a large number of digital control technology, forward converter synchronous rectification of the birth of control chip UCC27228 enables forward converter efficiency reached an unprecedented high efficiency. With good original edges clamped technology, this latest circuit mode is the primary side of soft-switch works, ZVS addresses the core reduction and energy regeneration, reduces the power MOSFET voltage stress, also achieved the best side of ZVS, Vice-President of synchronous rectification, integrated use of both technology and medium power DC/DC converter, its efficiency is 94%, power density also can reach over 200W per cubic inch.

2 best junior PWM control IC

Active clamp technology after ten years of the gods, since 2002 VICOR Corporation this patents expire after the lifting of the ban, companies published new active clamp control IC the birth up like mushrooms, as to the user the best choice. Holders of earlier clamped control technology of TI company, not only to maintain the original UCC3580 series, and new development performance and superior UCC2891-94; it takes the current-controlled manner, with side clamp and low-side clamp two control programme, presents a completely new control techniques. ONSEMI (on) company first introduced low-voltage (100V) clamped by NCP1560 control chip, then launched a high-voltage applications active clamp control chip NCP1280. It not only solved the LCDTV, plasma TV power requirements, and now for the next generation of fanless PC power do masterPWMIC, visible to the technology of the future market prospects of wonderful. United States national of 5000 series dedicated to have an active clamp control IC, LM5025 is the model. Even obscure Semtech Corporation also offers a active clamp control chip, the model is SC4910. So many semiconductor company without capital investment in this kind of control chip, is by no means wealthy, powerful nowhere is everywhere so that it has a huge market behind. Until recently, TI company new active clamp control ICUCC2897, have to be clamped with PWM control done perfect. United States national has just launched an interactive work of can be clamped work of forward-control ICLM5034 that can enter filter capacitors does not increase the output power is doubled, so that active clamp technology reached the level of power 1kW. But businessmen feizhao company gives the cheapest clamped control SD7559 ICSD7558 and greatly reduces the clamped technology use cost.

In the areas of people familiar and widely used ZVS full-bridge phase soft switch technology in solving high power switching power supply efficiency credit on 10 years, this has been a great development. From TI company UC3875 to UCC3895, from linear technology company LTC1922 to Adaptive LTC3722 increased detection power MOSFET work status, thus more accurately adjust switch time do ZVS State of technology, so that the entire bridge phase technology has reached the peak. In particular, the dramatically LTC3722 control IC that narrows the resonant inductance inductance and volume, reduces non-ZVS working state boundary conditions, reduce the duty cycle of loss, etc. However, in a synchronous rectification technology widely applied today, it is not optimal, because synchronous rectification ZVS full-bridge phase-shift circuit is essentially belong to non-symmetric, so it could not achieve full ZVS synchronous rectification. Although TI company engineers have done a great deal of effort, it gives the synchronous rectifier circuit scheme, turn on and off course always half hard switchThus efficiency always behind symmetric circuit topology of ZVS way of synchronous rectification.

In the production area of high power switching power supply, the latest scientific achievements should be INTERSIL Corporation's newest full-bridge PWM symmetric ZVS control IC, its type is the ISL6752. It is a good solution to control both original side MOSFET switch of 4 to ZVS working status and can accurately control the Deputy side synchronous rectifier to ZVS work status of drive signals. In this we can take some interplay: ISL6752 control a symmetrical full bridge circuit. 4-leg in the upper-left and upper right two switches to the 50% duty cycle, pulse width is not supported by the modem. The bottom left and right two switches use pulse width modulation method to adjust the width for the control of the output voltage. It can accurately control the associated pulse power up, shutdown and its latency, thus neatly using parasitic parameters to achieve full bridge 4 only the power MOSFET, ZVS soft switch maintains the original boundary of the highest conversion efficiency. In addition, it also gives the Deputy side synchronous rectifier driver signal. This driver signal in the original side control IC in adjust their relative to the PWM pulse in advance or delay, thereby overcoming transmission signal sent to the Deputy side latency, so that the Deputy of synchronous rectification in any duty in the circumstances to maintain absolute ZVS switching status, ensuring high efficiency synchronous rectification. But such a low price, the IC has maintained almost better than any of the entire bridge phase shift control IC are cheap. Use the IC fabrication of 400W DC/DC converter coupled with excellent power MOSFET, conversion efficiency reaches 95%.

For low-power switching power supply is still a flyback converter with PWM control IC, however it must be a good solution to the Deputy of synchronous rectification of the control. ONSEMI company NCP1207 and NCP1377 is still in the field of high-voltage AC/DC. If longer with TI company flyback converter ICUCC27226 synchronous rectifier control, you can enable them to become almost flawless high efficiency power supply. Low voltage DC/DC area flyback converter control IC, Linear-Tech company LTC3806 is excellent. LTC3806 not only control the PWM, also gives the exact pair of synchronous rectifier driver signal edge, is the low-voltage low-power power control IC masterpiece.

To sum up, we can give out today's switching power supply design time to select the best control mode and best circuit topology. High-power ZVS full-bridge should be combined with a pair of side ZVS synchronous rectification, typical control IC is the ISL6752; secondary power to low power should be clamped forward converter ZVS soft switch with a pair of preflight side gate driver technology for synchronous rectification; and small power should be equipped with good synchronous rectification of quasi-resonant flyback converter circuits.

Recently, in LCDTV's power supply, the more used is the asymmetrical half bridge ZVS technology. Television systems, analog circuits and signal processing circuit, hope that the power of dv/dt and di/dt as small as possible. And asymmetrical half-bridge circuit switching elements just work in this State, this is about 200W television system is the best price-performance. Current control IC have ST company L6598, Philips, ONSEMI of TEA1610 NCP1395 company. Their performance, specific features, there are some subtle differences.

Of course, there is no absolute limit, just different conditions should have the best choice.

3VICOR's latest technology

VICOR Corporation new MHz operating frequency, level per cubic inch power density of 1000W ultra-high PRM (pre-voltage module) and VTM (voltage transformation module) DC/DC power technology is still in the area of the peak. For thefirst time the module power supply power density of up to 1000 watt per cubic inch, really let level power supply product with the miniaturization of significance. However at present VICOR Corporation PRM technology and product is still not complete clearance to market, only the VTM cannot bulk access to the market, but their technology direction. In fact, PRM with VTM combination into a set of regulated power supply, essence is the United States Patent SYNQOR company — the cascade technology; its first level for regulators, the second level is used to isolate and variable pressure.

I have recently put this PRM mindset improved a bit, the PRM Buck-Boost to separate in, or select choose Buck or Boost. Choose Buck, use the preflight 1MHz frequency side gate driver control technology, the input voltage drops to an intermediate voltage, and then add VTM is a high power density of power. Select a Boost, 1MHz operating frequency synchronization Boost control technology, the input voltage up to a higher intermediate values, plus the VTM also form a set of high power density power.

VTM's advantage is that the breakthrough technology thinking mode, this mindset of comprehensive dissemination in present China is difficult, but also quite a long time of development. This should have sufficient venture capital mechanism, but also from Government to business and have a long-term view, do not put a little hope immediate grants. VICOR's VTM has 3 patents, we all know that the more patents many projects the easier breakthroughs, many patent technologies who thought he mastered, we had to wait ten years after using this technology.

4 non-isolated DC/DC technology for rapid development

In recent years, non-isolated DC/DC technology has developed rapidly. As an electronic device or electronic system due to load different, will require a power supply system provides multiple voltage block level. For instance: desktop PC will require + 12V,+ 5V, + 12V,-3.3Vfour voltage and voltage of + 5V standby. The host Board requires 2.5V, 1.8V, 1.5V even 1V, etc. To this end, a set of AC/DC is not possible to give out so much voltage output, but most of the low voltage power supply current is huge. Therefore developed many non-isolated DC/DC converter, which is basically divided into two categories. A class that contains a power switch devices called DC/DC converters. Another type of non-power switching devices require external power MOSFET's called DC/DC controller. Follow the circuit function partition, Buck's Buck; step-up of Boost; there are also able to step-up and step-down SEPIC for Buck-Boost or; there are also positive pressure into negative pressure of INVERTOR, etc. Among the many items, the fastest or Buck's Buck. According to the size of the output current, single phase, two-phase and multiphase; control mode to PWM-based, small to PFM.

In non-isolated DC/DC conversion technology, excellent technology with TI's preflight side gate driver technology, which uses digital technology to control synchronous Buck, the use of this technology for DC/DC converter converts most efficient can achieve 97%, which is his representative TPS40071 products. Boost boost mode also appeared with MOSFET instead of synchronous Boost diode. In the area of low pressure, increasing the efficiency of widely, and are seeking to further eliminate the body diode of the MOSFET conduction and reverse recovery loss problems.

Buck-Boost circuit in the monolithic IC only Liner-tech company LTC3443 is ideal for products, and VICOR Corporation of PRM is the most similar, the conversion efficiency is relatively high, reaching 95% just working voltage is still relatively low, only 6V. With the IC manufacturing and technological progress, this circuit voltage will gradually increase to 20V, 40V, 60V, 100V. At this point, the full-chip IC manufactures "PRM" reached perfection.

5PFC technology breakthrough

In March 2006 at the APEC meeting convened by the United States and China Shanghai held PICM meeting, the engineers made no rectifier bridge of PFC circuit technology, and has been rapidly applied. It takes the two inductors, power MOSFET, two fast recovery diodes form PFC boost circuit, working in all 50% of the half-cycle, thereby dispense the power consumption of bridge rectifier caused, especially at the low end of the input voltage, i.e. AC90V input efficiency as high as 1.5 percentage points. Because of this circuit of input and output, which is not a total site to input voltage detection trouble, United States of using IR company ONESYCLE patent technology design and manufacturing of PFC control ICIR1150S just dispense with the detection of the input voltage, so this session into production without IR1150S rectifier bridge PFC IC most convenient control, this method of working efficiency PFC circuit will be raised to a multiple percentage points. On the technology of interest to engineers can monitor the relevant reports.

TI company the latest interactive technology to PFC PFC brought significant progress in technology. Two-phase interactive PFC circuit takes two boost inductance, two power MOSFET to 180 ° phase alternating work. Output the same power, only half the average input current, thus reducing input EMI filter for power consumption, reducing the intensity of the EMI, thereby increasing the efficiency of simplifying EMI high-power PFC processing difficult. Interactive PFC circuit, the EMI's strength for the price of a single half power strength. In addition, the output voltage ripple also reduce by half, if not require 11.040T maintain time, output of large BULK capacitor can also be reduced by half. At present the company recommended TI system composed by UCC28528 and UCC28221. New independent control IC is about to come out. This technology will undoubtedly make the power supply of PFC section in the conversion efficiency and EMI deal with remarkable progress.
r>6 digital switching power supply

Currently in the entire electronic analog circuit system, digital TV systems, digital newsletter, no communication is today of the digital mobile phone brings easy extremely wonderful life, as for networks is the exclusive realm of digital. And finally a digital fortress is power fields. In recent years, digital power of momentum grows, more and more. In the power of digital connection at the front of the company have TI and Microchip that Texas instruments company and chipscreen international companies. TI company has both a digital signal processing (DSP) technology, and acquired specialized manufacturer PWMIC top UNITRODE Corporation, they merged with the most technical strength. TI DSP companies already use TMS320C28F10 made 48V output of communications power supply module. Which part of the complete PFC and PWM control for digital. Now, the company has developed TI a variety of Digital PWM controller chip. At present mainly UCD7000 series, UCD8000 series and UCD9000 series, they will become the next generation of digital power of toread.

UCD7000 series mainly digital control of power-driven, have driven forward converter, have driven push-pull and half-bridge circuit. It requires a micro-controller (μ C) or DSP gives the PWM signal can control constitutes a complete digital power. The products have been launched, UCD7100 UCD7201, UCD7230 UCD7440, etc. Among them, the respective control forward converter, half-bridge circuit as well as non-isolated BucK circuit.

UCD8000 series mainly Digital PWM and drive parts. Use it to design digital power simply plus μ C or DSP. For example, you can mix UCD9110 UCD8620 formed a CNC half-bridge circuit.

UCD9000 series mainly including DSP and Digital PWM sections, it requires cooperation with UCD7000 series consist of digital power.

In short, they generally must include hardware parts, but also do software programming. Hardware section includes logical parts, PWM clock, amplifier loop ADC, DAC, and digital signal processing, driven, synchronous rectification in the detection and treatment, etc.

Discussion on digital power, the United States is going iWatt company innovation, it developed the iW digital controller, distinct from the simulation controller, not using PWM technology, but rather on the chip built-in optimization algorithm logic programming, you do not have a user in addition, you can directly apply the controller's internal pulse optimization technology, digital control of switching power supply. IW series have not brought PFC iW2201 and with PFC iW2202. It applies a "pulseTrain" patented technology, including a "power pulse generator" (for the strong electric control) and a "detect pulse generator" (for weak digital signal processing). Controller detection input voltage and load status, without external programming, optimization by chip inside, a "logical algorithm power cycle" and "sensing cycle" and "smart jump cycle" and other control modes, decided to switch-off of. IW series chip uses simple, has achieved a 200W power output.

In the current competitive power in the area of main performance price competition, digital power is still a long way to go; but the power fields of digital Horn is sounded.

7 in the power industry and power in the market of new policy

This is not a technology-related topics, but our current energy shortage, and the power industry is another closely related with the energy consumption of industry, Government and Association of groups should be given the power to guide the direction of development. We have talked about a few examples.

Example 1: the power of no-load power consumption of color TV. In the city, many families in the evening after watching television, using the remote control to turn off method to shut down. When color television's no-load loss more than the European standard 3.5W is less than 1W, Japan is less than 0.6W. At present40% of the domestic family TV evening with remote control methods, the shutdown to estimate million families of useless loss is more than 4 × 108W, gorges of several units of electricity consumption so freely.

Example 2: domestic various home appliances manufacturers for power efficiency is not high, only require low prices. For example, a leading DVD producers, with the power adapter, prefer conversion efficiency of less than 80%, no-load loss 1.5W $ 49 one adapter, but not willing to select a conversion efficiency of 90% or more, no-load loss is less than the $ 59 0.6W one adapter. Why sell-price product good, competitive? as DVD sold out after the user how much electricity, more than how much electricity, it is the user, not the manufacturers. If the Government does not go to the tube, then had to go to build more power stations, the country's energy will always be inadequate. Recently Japan SONY Corporation's notebook adapter is required to give it the necessary power supply manufacturers design no-load power consumption less than 0.1W adapter.

At present, our country's oil imports have more than 50% of the total, still is the lack of oil powers, if the private car and then some more, we go there to find oil? our coal only long enough to be used for 40 years, what is the Government not to use legal and policy to encourage enterprises and engineers more development and production of high-efficiency power? is it not the formulation of policies and laws to restrict those low-efficiency power supply manufacturer's product, you must not enter the market? objectively speaking, at this point we should learn the Western developed countries.

These policies our power technology will have a greater development, China's manufacturing of switch power accounted for more than 80% of the world market, but the high-end market almost did not we share, this is a Chinese engineers and entrepreneurs in a big regret is worthy of serious consideration. Thereforeit would like to take this opportunity to urge and encourage high level switching power supply's research and development and manufacturing, called upon the Government to develop a new energy policy in order to change the structure of our national power products, enhance the level of power products.