source:Industry News Popular:adapter release time:2021-09-09 10:58:04 Article author:sznbone
The basic composition of the power adapter
There are two types of contemporary power adapters: one is DC power adapter; the other is communication AC power adapter. The key to the detailed introduction here is only the DC power adapter, its function is to convert the pure natural switching power supply (crude power) with weak power quality, such as voltage switching power supply or battery switching power supply, into a higher quality DC voltage considering the provisions of machinery and equipment. (Jidian).
1. The basic composition of the power adapter
The basic composition of the power adapter is shown in the figure below. UI is the DC voltage after the voltage rectifier filter, UO is the converted DC output voltage. The DC-DC converter is used for output power conversion. It is a key part of the power adapter. In addition, there are also starting, overcurrent and/or overcurrent. Voltage protection, noise filter and other components.
Opinion feedback control loop checks the output voltage and compares it with the standard voltage. According to the deviation amplifier becomes larger, the single pulse width adjustment circuit and the controller manipulate the on-off time ratio of the semiconductor material to adjust the size of the output voltage or current.
DC/DC converters have a variety of circuit modes. Commonly used are PWM converters whose working wave is a square wave and series resonant converters whose working wave is a standard sine wave.
For series-connected regulated power supply, the output has no response to the keyed transient. The key is the unit step response decision of the regulator tube. However, the series resonant converter with standard sinusoidal waveform is for the switch-type adjustable regulated power supply. There are more transient transitions at the output end. In addition to increasing the switching frequency, the unit step response of the feedback amplifier has been improved, and the transient response of the power adapter can be improved without the problem of transient response. The load transition transient has no key to response The decision is made by the characteristics of the LC filter at the output, so it is possible to improve the transient non-response characteristics by increasing the switching frequency and reducing the multiplication of the output filter LC.
2. Classification of power adapters
The power adapter can be divided into two types: AC/DC and DC/DC. As a secondary switching power supply, the DC/DC converter has maintained a modular design, and the technical design and production process have been perfected and standardized in all countries in the world, and It has been recognized by customers. However, once the switching power supply AC/DC, with its own characteristics, it has encountered more complicated technical problems and manufacturing problems in the process of modular design. The following two types of power supplies The structure and characteristics of the adapter are discussed in many aspects.
1. Self-excited
The self-excited power adapter uses a regulator tube and a switching transformer auxiliary winding to form a feedback regulation loop to maintain the resonance circuit and stabilize the voltage output. Because the regulating tube of the self-excited power adapter doubles as an oscillating tube, there is no need for an oscillator. The differential signal is generated by a resonant circuit, which is a differential signal with a non-fixed frequency, which changes with the input voltage and load. The frequency is higher at light load, the frequency is lower at light load, and intermittent oscillation occurs at full load.
The self-excited power adapter itself has a certain self-maintenance function. Once the load is too heavy, the feedback standard will be destroyed and the shock will be terminated, thereby maintaining the power adapter. Because of its high maximum current value and large harmonic distortion current, especially when working with high power and large current, the reliability is poor, so it is mostly used in places with low output power below 60W.
2. He is aggressive
The regulating tube of the other-excited power adapter circuit does not participate in the whole process of encouraging the single pulse oscillation, and the provided oscillator causes the single pulse to operate the regulating tube. For example, the common integrated circuit UC3842, NCP1200, TL494 and other integrated control boards can output PWM single pulse with adjustable duty cycle. Nowadays, many integrated control panels can be based on the light and heavy automatic elevator switching frequency of the output output power, so that it can maintain high-quality switching power supply conversion and high efficiency under different load conditions.
Because the integrated control board integrates the maintenance circuit, the control circuit, the oscillation circuit and the opinion feedback data signal inspection circuit on the same integrated IC, its anti-interference ability is good, the circuit is simple, the function is complete, and it can be oscillated and stabilized. , Over-current, over-voltage and under-voltage protection and other maintenance functions are unmatched by discrete power adapters, so the use of them has become more and more common in recent years.
3. DC/DC power adapter
The DC/DC type power adapter converts a fixed DC voltage into a variable DC voltage, also known as a DC chopper. Chopping L. There are two methods for the work of the DCDC type power adapter: one is The pulse width modulation method T will not change, change the frequency adjustment method t (universal); second, the frequency adjustment method t will not change but change T (easy to cause an impact). The actual circuits are as follows
①Buck circuit-blood pressure lowering chopper, its output average voltage Uo is lower than the key-in voltage UD, and the optical rotation is the same;
②Boost circuit—transformer chopper, whose average output voltage Uo exceeds the key-in voltage UD, and the optical rotation is the same;
③Buck-Boost circuit step-down or transformer chopper, its output average voltage Uo exceeds or falls below the key-in voltage
④ Cuk circuit-blood pressure lowering or transformer chopper, its output average voltage Uo exceeds or falls below the key-in voltage UD, the optical rotation in and out in turn, the inductor transmits.
Nowadays, the technical nature of soft-switching has led to a qualitative leapfrogging of DC/DC converters. British VICOR power adapter business design plans are in and out. In turn, capacitors transmit a variety of ECI soft-switching DC/DC converters manufactured and manufactured, and their output is larger. The power is 300W, 600W, 800W, etc., the relative power is 6.2W/cm3, 10W/cm3, 17W/cm3, and the efficiency rate is 80%~90%. A kind of soft switch technology released by the latest news of the Japanese NemicLambda company High-frequency power adapter control module RM series products, its switching frequency is 200~300kHz, the power has exceeded 27W/cm3, and the same ballast (mos-fet instead of Schottky diode) is used to increase the high efficiency of all circuits to 90 %
4. Power adapter AC/DC converter
The AC/DC converter converts the communication alternating current into direct current, and its output power current flow can be doubled. The conversion of the output power current flow into the load is called a "rectifier", and the output power current is transferred from the load back to the switching power supply. It is called "active inverter power supply". The AC/DC converter is entered as 50/60Hz alternating current, which must be passed through the rectifier and filter. Relatively speaking, the electrolytic capacitor of the filter with a large volume is indispensable. In addition. , Due to potential safety hazards, such as UL, CCEE and other specifications and EMC command restrictions (such as IEC, FCC, CSA), communication and AC input must add EMC filters and use components that meet the testing standards, so that AC is limited The volume of /DC switching power supply is further practical. In addition, because of the internal high frequency, high pressure, and large current switching posture, the difficulty factor of dealing with EMC electromagnetic compatibility testing problems has increased, and the design of the internal high-density installation circuit The plan clearly puts forward very high regulations. For the same reason, high voltage and high current switching promotes the loss of switching power supply during operation, which limits the system process of the modular design of AC/DC converters. Therefore, it is necessary to select a reliable electrical system Sexual design can make its work efficiency exceed a certain satisfactory level
AC/DC converters can be divided into half-wave circuits and full-wave circuits according to the wiring method of the circuit; according to the operating characteristics of the circuit, they can be divided into three types: uncontrollable, half-controlled and full-controlled; according to the number of switching power supply phases, they can be divided into single-phase circuits. 、Three-phase and multi-phase; according to the quadrant in circuit work, it can be divided into one quadrant, two quadrants, three quadrants and four quadrants
5. Power adapter circuit structure
The circuit structure of the switch-type adjustable regulated power supply has many kinds:
①According to the driver method, there are self-encouragement and other incentives
②According to the working method of the DC/DC converter, someone orders a positive excitation type and a reverse excitation type, push-pull type, semi-productive chain, full-productive chain, blood pressure lowering type, variable voltage type and elevator pressure type, etc.;
③According to the circuit composition, there are series resonance type and non-series resonance type
④According to the operation method, there are pulse width modulation (PWM) type, single pulse frequency modulation (PFM) type and PWM and PFM mixed teaching
⑤Is the switching power supply protection and feedback adjustment data signal coupling method
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