At present, government organs, environmental groups from all parts of the world, industry's alliance is all promoting the technical development of new power of the high-efficient low consumption in each link of leading from the market access, consumer behavior actively etc.. Among them AC-DC adapter, the awaiting the opportune moment of the charger or no-load power consumption question of the consumption electronic product receive the increasingly many concern. Therefore has produced a lot of new technical standards. According to the incomplete statistics, has already issued and implemented at present, this kind of standard suitable for different trades and area has the amount of kind nearly 20. For example, " star of the energy " of U.S.A. ( Energy star) , the China one " Authorize in Tyre " And charger star sign,etc. which some big mobile phone manufacturers put forward. These standards have mostly made the clear rigorous requirement to no-load losses and operating efficiency. When the products are in conformity with standard, the production firm can add and stick the relevant label on its products, such as " Energy star " ," TLC" ,5 stars,etc.. Not only has shown the technological characteristic of this product ocularly but also guiding the purchase behavior of influencing consumers effectively.
At present, consumers from all parts of the world of ground cover understand and approve gradually for these standards, mandatory technical regulation of making the associated trade or area that the increasingly many trade administrative organ begins to consult and quote these standards too at the same time herein. This not only innovation and challenge technically, have also improved the threshold of the market access greatly. So there are multi-terminal manufacturers more and more and relevant and upper and lower to visit the related supplier to begin to adopt the new method on a large scale, new technology, new material, in order to tackle the challenge to that the new-standard puts forward. BCD has introduced the AP376X series primary side PFM switch power control unit in right time as the professional design manufacturers in integrated circuit of power management, help the power engineer to deal with the new-standard, new challenge easily.
This charger that this text introduces, it is power consumption and efficient design of awaiting the opportune moment ultralowly realized with AP3765 of BCD. AP3765 is BCD newest PFM modal switching power supply primary side control device - -One kind of series AP376X. It has extended the primary side control pattern that BCD is most good at, while guaranteeing global design is succinct and reliable, have " zero " The electric current starts and low the characteristic of the working current. Also exactly " Zero " Electric current start and low working current characteristic make, adopt charger that AP3765 design can meet five-star requirement and star of the energy to await the opportune moment 30mW of charger at present The latest standard.
AP3765 still possesses the systematic open loop to protect, short circuit protection, very practical functions such as soft turn on and frequency jitter,etc.. Characteristic these make the intersection of AP3765 and low-powered charger, adapter, LED the intersection of person who light and application have prominent advantages. Anti exciting power that this circuit is a typical IC controls. The work pattern of the overall system is controlled by IC-AP3765, the whole complete voltage supports section and is in DCM. Among them can be divided into an input section the circuit, start the part, feedback (the voltage of electric current) Some, power conversion fraction and exporting and commutating the part. The input section is commutated D1-D4, and EC1, EC2, L1, L2 make up. Input and adopt " ∏ " Type circuits filtering,it is all right let's dampen different mode noise interference effectively. R1, R6, EC5, D6, R18 make up systematic start and power supply line, it is a key area to adjust power consumption of awaiting the opportune moment. Generally choose 4M- 20M starting resistance, match the starting capacitance of 2.2uF- 10uF. R8, R9, R10 are feedback lines of voltage, among them the reference voltage of FB foot is 4V. R2, R4, R11 make up the electric current and measure the cycle, it is 500mV that the electric current measures the voltage. Then we can receive the output voltage through the following formula, and the electric current exported. Define the ratio to output winding of the first rear axle winding as N1 at first, the turns ratio of output winding and feedback winding is N2, the output voltage is Vo, the output current is Io, the crest current Ipk of primary side. Fig. 2 is AP3765 voltage current characteristic of producing 5V700mA charger.
The power conversion fraction is made up of the triode Q1 that AP3765 drives, T1,etc.. When Q1 turn on, IC drive to be high level, energy storage reach voltage transformer T1, and measure the electric current of primary side. When Q1 shuts off, the low level that IC drives to be, energy is released on the rear end through the voltage transformer T1, and measure the primary side feedback voltage. The output is made up of D8, C5, R14, EC3, R13. Through to each some constituent brief illustration, can find out and it is very simple to use AP3765 to carry on system design, even if can finish to the beginner more easily.
It explains the method to reduce power consumption of awaiting the opportune moment that we come especially, the main loss when the system awaits the opportune moment is checked: Start the circuit part (R1, R6, R11) , IC( AP3765) Work and driving part ( Q1) , energy conversion fraction T1, exporting and commutating some (D8, C5, R14) , output dummy load ( R13) . Look like capacitive loss while being other, loss of sample resistance have loss of absorbing circuit in in most instances may neglect. In the actual design, the starting resistance, probably about 20M, the dummy load outputted uses 10K (5V export) . The working voltage of IC is probably designed about 20V, then under the input voltage condition of 230Vac/50Hz, we can estimate first that await the opportune moment to loss it probably:
Can see the fixed loss of the system, probably about 14mW, and the loss of triode and output diode from the above. Because while awaiting the opportune moment, the operating frequency of IC is very low, probably there is only dozens of Hz, so the switching loss of the triode can be ignored, only consider lossing on-stately. The output diode basically has no passing of current, its loss can be neglected too.
So all loss and add up, in theory probably about 17mW. Consider voltage transformer, diode loss etc., it basically should be about 20mW, can control within 30mW that the charger requires. The result of using the dynamometer WT210 to test actually, about 24mW.
The mentality of designing and skill that case adopt have certain typicality and universality, suitable for most regular application. But direct against some special application, must fully consider the loss of each link in the circuit, the overall equilibrium of compromising, could achieve maximum efficacy. For example, in order to cooperate with the special application of a certain ultra low power consumption one-chip computer, did we once design a section of no load current to 20? AC-DC power of A. We have made overall analysis in producing all components and parts of the no-load losses while designing, test is adjusted, has reduced the no-load power consumption to the maximum extent one by one.
" reduce and loss and raise the efficiency " It is the eternal in trade theme of the power, it is an eternal goal too. This text takes typical circuit of AP3765 as examples, has recommended how to reduce some experiences and methods of the no-load losses effectively. It is not merely the application which is for AP3765, these thinkings, these methods and skills are suitable for the design of other small-scale low power consumption chargers.
