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    About China manufacturing

    What about Vietnam and India as alternatives to China for low cost manufacturing?

    There are pros and cons with any country that you select to manufacture your products. Below are a few points to consider when comparing China to India and Vietnam:

    1. India and Vietnam have underdeveloped logistics infrastructure which causes delays and problems with reliability.

    2. India businesses have a higher incidence of theft amongst its workforce.

    3. India’s total cost of labor is higher than China when you consider productivity, benefits costs and management oversight required (overhead).

    4. Vietnam has lower labor, land and housing costs than China.

    5. India and Vietnam have underdeveloped supply bases when compared to China – especially in electronics,

    electro-mechanical, sheet metal, plastics, etc.

    6. India has less of a cultural and language barrier with western companies.

    7. Vietnam has a greater language barrier with western companies.

    8. India has less intellectual property challenges than China.

    9. India and Vietnam workers are less skilled than China lending themselves to simpler, less complex product manufacturing.

    10. Vietnam is offering attractive government incentives for new business development.

    11. The size of China’s economy as measured by GDP is 2.5X greater than India’s and over 35X greater than Vietnam – important if you are considering selling your products in any of these countries.


    Isn’t doing business with China becoming more costly as wages are increasing, fuel costs to export goods is rising, government VAT taxes on imported goods, etc..?

    The economics of doing business with China is changing that’s for sure. History shows us time and again that as developing countries grow, the cost of doing business in these economies also tends to grow. Some factors to consider are:

    1. Can a large percentage of your product’s parts/materials be sourced within China vs. having to be imported (avoid import duties, freight costs and higher material costs)?

    2. Does your product have a fair amount of manual assembly associated with it so as to leverage China’s relatively low labor costs?

    3. Are the physical attributes of your product(s) well suited for cost effective logistics? This is especially important if a significant % of your product is going to be sold into markets outside of China and needs to be shipped to North America, Europe, etc.

    4. Are you looking at growing your business by selling your product(s) inside of China? If so, having your product(s) manufactured in China is a big plus in not only keeping your costs down, but in being looked upon more “favorably” by China businesses and consumers of your products and services.

    Don’t the cultural, language, time and distance differences make doing business with China more cumbersome and inefficient?

    It depends….
    First and foremost, doing business in China is a long term commitment and company strategy. Leveraging China’s vast resources and growing consumer economy requires patience and the selection of the “right” China partner(s) to work with.
    Secondly, China businesses that are focused on serving Western customers have offices in North America and Europe to act as the primary communication link and perform the much needed project management function on a day-to-day basis. Additionally, these businesses have several English speaking Chinese employees not only at the executive/senior management level, but in such key roles as quality assurance, engineering, project management, manufacturing and customer service.
    Thirdly, with today’s technology (Skype video calling, the internet, file sharing, etc.), and offices in local geographies (e.g., U.S. and Europe), around the clock communications and work are a “given” so that precious time isn’t lost on critical projects.
    Last but not least, getting most products into and out of China is becoming less cumbersome every day. The logistical infrastructure within China such as shipping ports, international airports, highways, etc. continues to grow and expand from the “Gold Coast” in the east to more and more of the central and western rural cities.

    Can “Western” companies doing business with China get a fair hearing in PRC’s legal system?

     China’s commercial laws are changing rapidly to correspond to Western commercial laws, especially since joining the WTO, but the process is not yet complete. Companies need to understand the impact of both their own country’s laws and China’s laws on their business dealings with China.
    One recommendation is to work with China companies that have a “parent” company that is headquartered in Hong Kong which abides by a legal system based on English common law. Business contracts can be made with the “parent” company on behalf of the China partner and administered according to Hong Kong law.

    If having your product manufactured in China, a few obvious things to consider are:

    1. Choose a manufacturing partner that does not directly or indirectly compete with your products with its own branded products.

    2. Ensure that the China manufacturer has a robust document control system and procedures that are audited by an independent, certified party on a periodic basis. Having a registered and up-to-date ISO9001 quality system should be a must.

    3. Sign a Non-Disclosure Agreement (NDA) that legally protects your IP.
    4. Speak with current or past customers of the manufacturer to discuss how their IP has been protected by the manufacturer.

    What can be done to protect my intellectual property and guard against the “copying” of technology?

     Since China joined the World Trade Organization (WTO), Beijing has strengthened its legal framework to comply with the WTO Agreement on Intellectual Property Rights (IPR). Enforcement of these strengthened IPR laws continues to be a challenge for China’s central and local governments.
    If you are planning on selling your products into the China market, you should file your patents with China’s State Intellectual Property Office (SIPO), promptly register any trademarks, logos, and internet domains, and register copyrights with China’s National Copyright Administration (NCA). For further information on IPR in China, click here.
    Another way of protecting your product IP is to develop any system software and source code outside of China and download the software into a secure microprocessor or other programmable device. Provide these secure devices to your China manufacturing partner for integration into the final product.

    It is a piece of fact that switching mode power supplies (SMPS) are, most of all, manufactured in China, no matter if it is a America, Asia or Europe brand. Why China?

     Work Force:
    Largest in the world. Exceeds U.S., India, Japan and Mexico combined.
    The “World’s Factory”:
    Over 3,000,000 factories with dominance in steel, textiles, and electronics to name a few.
    Logistics:
    China has 32 international airports and 21 shipping ports
    Education:
    1,553 universities offering undergraduate and graduate degrees in every discipline with an emphasis on engineering.
    Economy:
    Predicted to surpass the U.S. economy by 2035 if not sooner and doubling it by 2050.
    Growth:
    GDP expected continued growth into double digits.
    International companies in China:
    Over 280,000 (480 of the top 500)
    Population:
    1.3 Billion people/consumers. China’s major cities will add 350 million people by 2030.
    English Language:
    China’s primary and secondary education system is teaching students to speak, listen to and read English as a second language.
    Don’t ask “IF CHINA?” Ask “WHEN CHINA?”

    DC/DC Converter modules

    I need more than 24V out in my application, but I can’t find anything in your catalog. How can I get this output voltage?

    You can use a dual 15V output converter (+/-15V), omitting the common pin and using only the +Vout pin and –Vout pins. This is true of any dual output converter, so +/-5V = 10V, +/-9V = 18V, +/-12V = 24V and +/-15V = 30V. 

    What’s the difference between unregulated and regulated converters?

    An unregulated converter is a cheaper solution but offers less stability over the output voltage. The output voltage can change depending on both the load and the Input voltage variations. Therefore, the input voltage range is restricted to +/-5% or +/-10% and the output voltage can rise substantially during noload conditions. However, even an unregulated converter offers a low +/-5% output voltage variation over the load range of 20% to 100%. 


    Regulated converters offer a much better load and line voltage regulation, typically less than 1%, so the output voltage is not dependent on the load or input voltage. In addition, the input voltage range is higher (2:1, 4:1 or up to 7:1 with non-isolated converters). 

    What’s the input quiescent current?

    The current drawn by the converter when it is idle (not loaded). All converters contain oscillators that absorb power even if no power is being drawn from the converter.

    Can the converters be cleaned with an ultrasonic cleaner?

    Yes. They can be ultrasonically cleaned as long as the cleaning fluid used is not aggressive and does not attack any of the metal, plastic or epoxy parts.

    Note: We should take into consideration that some converters have empty holes (for optional features, such as control pins), so it’s possible that a small amount of cleaning fluid could wick its way through these holes and work its way under the base plate. This will not damage the converters (underneath the base plate it’s completely encased in epoxy) but be aware that if the board is baked to dry it off, the temperature of the oven should remain bellow 100°C so this trapped liquid doesn’t turn to steam and cause problems.

    I am using a 12V battery as input source. Do I need any extra components?

    The main problem with a 12 battery as a power source is that it can deliver very high inrush currents. Normally with lower power converters (under 20W), this is not a problem, but for the higher power converters the inrush current can damage the converters.

    The other issue with batteries is if the end-user connects the battery the wrong way around. This will instantly destroy any converter.

    To avoid these problems, an external blocking diode or FET can be fitted and either a soft-start circuit or an inrush current filter can be added. Please contact PAIRUI Technical Support for suggested circuits and component values.



    Why do I need a DC/DC converter?

    There are many reasons why you should use a DC/DC converter, but the most common applications are: 

    - To match the loads to the power supply (e.g. to generate higher, lower or dual outputs from a single source, or to invert a supply rail.) 

    - To isolate primary and secondary circuits (e.g. for safety reasons or to protect a sensitive circuit from interference) 

    - To simplify power supplies (e.g. multiple output converters or one converter per rail (point-of-load) can reduce power supply complexity, overall cost and board space requirements while at the same time increasing flexibility, reliability and system efficiency. ) 

    Do all your converters include input surge protection?

    No, not all of our converters include input surge protection, for those who do not state that input surge protection is included on their datasheets we suggest you use a suppression diode and/or an input capacitor as input surge protection.  

    Will your converters operate the above operating temperature range?

    Yes, if they are derated (not used at full power). However, the simpler low cost converters have no over temperature protection. If they are used outside of the temperature specification for a long period of time, they may fail. Our higher power converters are fitted with over temperature protection. If they overheat they will simply shut down.

    Does the isolation apply to both high and low side between the input and output?

    The isolation is tested with the inputs shorted together and the outputs shorted together and then the test voltage is applied between the input and output side. In this way the insulation is tested for all possible pathways between input and output, so the value applies equally for the low side and high side input. 

    Switching Regulators DMV78 series

    What’s the linearity range of the dimming function?

    The linearity outside the 10~90% range of the PWM dimming is not perfect, but still pretty good. The Analog dimming can be used in a 0~100% range. 

    Why should I replace my cheap Linear Regulators for a more expensive Switching Regulator (DMV78 series)?

    The DMV78 series costs more than a linear regulator because it is intelligent. It may look similar to a three-pin linear regulator, but inside is a controller chip that protects the converter against overload, over temperature and short circuits. This makes it very robust and hard-to-kill. 

    Even if the converter itself costs more, the savings that can be made in the primary power supply (because it needs less output current), assembly (because there is no fiddly heatsink, screw, nut and thermal paste to worry about) and inventory (one part rather than 7 parts with the linear regulator + heatsink + mounting + input and output capacitors) mean that the overall power supply cost can be lower with the DMV78 than with the "cheap" linear regulator. 

    Do I need any external converters for the DMV78 family?

    No external components are needed. An input capacitor is recommended only if the input voltage exceeds 26V. An output capacitor helps reduce output ripple further, but the ripple is relatively low anyway. 

    Why do I need an input capacitor?

    The input capacitor is required only if the input voltage can exceed 26VDC, otherwise it can be omitted. 

    Can I use a bigger capacitor in my output circuit?

    Higher capacitance is allowed, but the capacitor may discharge back into the output of the converter if the input supply is suddenly removed. If the power supply input voltage decays gradually when powered down, then even 1000µF is ok. If the input voltage is suddenly disconnected, then the converter could be damaged by the reverse current flowing back into the output. 

    The suggested 220µF maximum output capacitance for the DMV78 series is to help to protect the converter against reverse currents.

    What type of capacitors do you recommend with the DMV78 series? Are ceramics ok, or do you recommend tantalum?

    Type is not critical. Actually, a lower quality, relatively high ESR capacitor on the input is actually an advantage as its internal resistance helps damp down any switch-on surge oscillations, so a ceramic input capacitor is overkill! Tantalum or electrolytic are therefore recommended for both input and output capacitors. 

    Recommended capacitor types are 3.3µF/50V Electrolytic on the input and 100µF/6V Electrolytic on the output. 

    Is there a minimum load requirement for the DMV78 series?

    It is recommended that the DMV78 series of switching converters is used with a minimum load of 6mA to guarantee that the output is stable under all operating conditions.

    How does the enable pin on the DMV78 series work?

    The enable pin has two functions: Below 2.6V, the converter is OFF (the output power stage is switched off, but the converter oscillator is still running). Below 1.6V, the converter is in ultra-low power mode (20µA shutdown mode)

    Can I tie the on/off pin of the DMV78 series to the Vin pin if Vin goes up to 32V?

    The absolute maximum voltage accepted in that pin is 15V, although it's not recommended to go higher than 5V. You cant connect the input directly to the control pin.

    Recent cases of product safety have me concerned about China manufacturers not maintaining the high standards of compliance of the United States and Western Europe. Is my business and my customers at risk if I have my products manufactured in China?

    The majority of the product safety and quality problems with China exports occurred in 2007 and early 2008. Products categories that were affected included: pet food, animal feed, toothpaste, food products, drugs, tires, drywall, and toys. Since then, the China government and responsible agencies have enacted comprehensive inspections of exported products as well as stricter enforcement of penalties to both individuals and businesses for violations of the legal safety and health standards. 

    As for electromechanical and electronic based products (e.g., industrial, medical, energy, computing, data/telecom, etc.), selecting a reputable, trustworthy China manufacturing partner is essential. A good starting point is to get referrals and testimonials from business colleagues that you trust and that have a long history of doing business with China manufacturers. Secondly, it is recommended that the manufacturer you select has a documented and registered quality system (e.g., ISO9000). Third, evidence of a comprehensive supplier quality management program to closely monitor the supply base is essential. Fourth, a quality control system that includes incoming inspection, production inspection and test, and final product inspection is a must to ensure your product is being manufactured to your specifications. And last but not least, conduct an initial audit of the manufacturer to validate conformance of its processes against documented procedures.

    AC/DC Switching Power Supplies

    Do the AC/DC converters need any external components?

    All AC/DC converters contain built-in mains filters, so no external components are necessary. However, some uses require an input fuse, which must be added externally. The –ST option (converters pre-mounted on an insulated PCB with screw terminal input and output connections) also contain an input fuse as standard. 

    Does the AC/DC family have a thermal protection?

    The controller IC has an internal thermal shutdown at 135°C (-10°/+15°C). Once in thermal protection, the controller IC must cool down below 65°C before it will restart. 

    How do I interface a dual supply (AC and DC inputs)?

    A simple solution is to automatically switch inputs using a mains-powered relay. The AC/DC converter does not mind having a DC voltage on its output when it is not powered up (this is a useful feature that enables, for example, a board to be powered up and tested on a bench using a safe DC supply and then only plugged into the mains when the unit has been reassembled into its case). 




    Products in General

    I can’t find any product that meets my requirements. Can you supply a customized converter for me?

    In addition to the standard ranges shown in this data book, PAIRUI has the capability to produce custom DC/DC converters designed to your specific requirements. In general, the parts can be quickly designed to meet any input or output voltage requirements within the ranges of PAIRUI standards products (i.e. up to 48V at either input or output). Prototype samples can also be produced in short timescales. See our application notes for more information or contact PAIRUI Technical Support.

    Why does the On/Off function not work?

    Different converters have different on/off control voltages. Please check the datasheets carefully before connecting the on/off pin to ground or +Vin as this can damage the converter. Some on/off pins may require additional external components if driven with a TTL level signal. 

    Since your products are RoHS compliant, can I assume that they are Lead Free (Pb free)?

    RoHS restricts the use of six hazardous materials. One of the restricted materials is Pb (Lead). Lead-free is often used (or misused) to describe RoHS compliant products. However, RoHS compliant products are not completely Pb free as impurities up to 1000ppm (0.1%) are permitted and there is an exemption allowing the use of lead in high melting point solders required for SMD converters (a suitable lead-free high melting point solder did not exist when the regulations were drafted).

    A revision of the RoHS regulations is planned in 2010, when it is expected that many of the exemptions will be removed. 

    Are PAIRUI parts burn-in during production?

    All PAIRUI parts are burn-in tested in our factory before being shipped to the customer. 

    What material is used in the metal case package?

    Nickel plated copper. 

    How can I clean these parts included in my board?

    As with all electronic devices, strongly reactive agents in hostile environments can attack the encapsulating material and the pins, hence cleaning is recommended with inert solutions (e.g. alcohol or water based solvents) suitable for electronic components and at the temperatures recommended by the cleanser manufacturer.

    What is Isolation?

    Isolation refers to the electrical separation (galvanic isolation) between the input and the output of the converter. This means that the output of an isolated converter is not linked to the input and any electrical interference, voltage differences and fault currents are blocked. This is extremely important in applications where the output circuit is connected to the “real” world and the main circuit must be separated from anything that happens to the output circuit. 

    Is required any input or output capacitor?

    For normal function, no external capacitor is needed. For EMI filtering, consult our recommendations in our Application Notes. 

    Do PAIRUI products include EMI filtering?

    EMI filtering is not included inside the converters. However, an external EMI filter is suggested in our Application Notes. 

    Can I use the Common Mode Choke used in my EMI filter to limit the Inrush current as well?

    The inrush current is dependent on the converter, the load (especially the capacitive load) and the impedance of the primary power supply. Therefore, there is no recommended value for the inrush limiting inductor as this need to be individually worked out for each application. Having said that, usually 22µH~100µH works ok.

    A CMC is a good inrush current limiter because the core does not go into saturation with high currents (the +ve inrush current is balanced out by the -ve inrush current), so it has a dual purpose: EMC filter and inrush limiting. However, for high power converters it is sometimes better to use a low inductance, high current, choke that is selected to reduce inrush rather than a high inductance choke selected for the best EMC filtering because otherwise too much power could be lost through the choke's resistance during normal operation. 

    I have temperature problems. Can I use a heat sink to increase the temperature range?

    The converters have a derating curve that starts usually between 70°C and 85°C. From that temperature point the power is reduced linearly. You can use a heat sink to move this temperature point up a few degrees. If your application doesn’t have a adequate ventilation system, even a large heat sink may not be effective. The solution would be to use a higher power converter instead.