Development Trend Of DoB High Voltage Linear Drive IC
- Dec 29, 2018 -

What is the DoB IC ("de" power supply) scheme?


DoB (Driver on Board) or Driverless, which is commonly referred to as "de" power supply, is not without power supply, but a new driving mode different from traditional switching power supply. It is a new driving mode derived from the characteristics of LED.


DoB IC has many pioneers in the industry. There are mainly Seoul Semiconductor, British Lynk Labs, Texas Instruments, Exclara in the United States, and Taiwan's Industrial Technology Research Institute, Interlight and other giants. However, China started late because of its insufficient R&D reserves and slow response. However, the domestic development is rapid, and now a number of enterprises have kept pace with the pace of research and development of DoB IC. But the industry, especially the traditional power suppliers, rejected or even suppressed the "no power" products, which hindered the development of this innovative new technology to a certain extent.


DoB IC Solution is the Future Road of LED Lighting Drive Development


This paper focuses on three aspects:


Standardization, Scale and Automation


Traditional power supply devices are many, large volume and complex processing bring inconvenience to standardization, automation and large-scale production. According to incomplete statistics, there are currently more than 20,000 LED lamps manufacturers in China. I believe that in the next 5-10 years, there will be more than thousands of enterprises. In order to survive in this cruel competition, improving production efficiency and accelerating automation will be the only way. If we still rely on traditional power supply, we will face great challenges.


stability


Because there are many components in traditional power supply, the bad factor increases naturally. Especially, the life of electrolytic capacitor directly increases the probability of LED lamp failure. Although capacitors are used in filling valley in order to eliminate 100HZ stroboscopic in DoB IC driver, they are essentially different from traditional power supply capacitors in specific applications. On the other hand, capacitance failure in linear valley filling will not cause dead light. The capacitance failure in traditional power supply directly leads to dead light.


Intelligent lighting


As far as intelligent lighting is concerned, linear IC driver has its inherent advantages over traditional switching power supply driver. Traditional power supply can also realize intelligent lighting, but the cost or cost of system integration is far more than linear.


Considering the above, this table shows that DoB linear IC is a cost-effective LED driver, regardless of its stability, safety, performance parameters and high cost.


Current problems in DoB IC


1) Low utilization and efficiency of lamp beads


2) The problems of narrow working voltage range, difficult heat dissipation and voltage flashover caused by the difference of linear adjustment rate


3) 100HZ power stroboscopic


4) Single IC drive power is small, up to 9W


If the core problem mentioned above can not be solved fundamentally, it is difficult to say that the DoB IC driver scheme is the future of LED driver.


How to solve the problems of DoB IC?


(1) To improve the efficiency of power supply by high-order subsection. The core of high-order segmenting is to achieve 23-order segmented driving by NMOS and PMOS hybrid control. Here, the 23-order piecewise 23-segment refers not to the traditional physical segment of the LED lamp string, but to the logical 23 states.


DOB技术LED驱动IC

Comparing the common voltage waveforms of four segments and high-order segments, we can see that the voltage waveforms of 23 segments are almost sinusoidal, which improves the power efficiency by more than 90%, so that our IC can drive 25W.


(2) Dynamic configuration, in fact, can be summarized in a simple sentence: when the voltage is low, each sub-series is in parallel, and when the voltage is high, each sub-series is in series. This sentence sounds simple, but it took nearly half a year. We call it "dynamic configuration". The substring beads are continuously lit in each voltage section, thus improving the light efficiency and the utilization ratio of the beads by 10%-15%.


(3) To solve the problem of 100HZ stroboflash, we need to adopt active valley filling technology: when the voltage rises, the capacitor is charged, and when the voltage crosses zero, the capacitor supplies power to the lamp string. Completely overcome 100%, 100HZ stroboscopic. On the basis of these, the utilization rate and light efficiency of 10%-15% lamp beads were also increased.


(4) The difference of linear adjustment rate and narrow working voltage are the important factors hindering the development of linear drive. The lamp power increases with the increase of voltage, which is a poor user experience. Through the so-called "dynamic configuration" and "active Valley filling", the output power remains basically unchanged under different voltage states, which solves the problem of linear adjustment rate difference well.


(5) Voltage flicker is the change of light output under the condition of large-scale voltage instability fluctuation. For the pressure flashover problem still exists, it has not been solved. Here, the line voltage compensation technology is used. When the voltage fluctuates in a large range, if the DoB IC detects the change of peak voltage, it can automatically compensate for the change of light output, which can suppress the flashing of lamps caused by voltage fluctuation.


(6) Improve efficiency, heat dissipation technology, single drive power to 25W.


The Inborn Advantage of DoB IC Scheme in Intelligent Lighting


Intelligent lighting is indispensable to the realization of smart home, but without intelligent driving, it is difficult to be called intelligent lighting.


Dimming can be divided into built-in dimming and external dimming.


The so-called built-in dimming is that IC has integrated subsection dimming function to achieve fast switching dimming without increasing any power cost and reducing power performance indicators. Through the switch, 100% - 50% - 10% three-stage switch dimming can be realized, and the function of color temperature can also be realized.


So-called external dimming, you can see this framework: various external sensors such as radar/infrared/voice control module or WIFI/Bluetooth/zigbee module transmit instructions to MCU main control chip (which may be included in wireless communication module), MCU sends instructions to linear constant current driver chip through SDQ single-line protocol, so as to realize the dynamic change of luminance of lamps. With the lowest system cost and the greatest flexibility, various complex intelligent dimming can be realized.


Reasons for DoB IC Scheme's Market Share Not High


Firstly, from the perspective of time and development process, DoB IC scheme has developed rapidly in recent years. Compared with the traditional drive which has developed for decades, it is a new direction and innovation. To replace the traditional switching power supply, it needs an industrial verification process.


Secondly, more importantly, the core problem of linear IC driver has not been solved, and there is still a certain distance between performance and switching power supply ratio. These are the reasons that hinder the development of linear drive and are not widely recognized.


If the problem can not be solved, linear IC driver will always be a trend. It will not replace the traditional power drive, and it will not become the so-called mainstream of the future.