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RCC switching power adapter designed combat

Author:Roadsunny Date:2013-12-29 23:10:52
RCC switching power adapter designed combat
RCC its circuit is simple, less components, low-cost advantage, until the 2014's today, RCC in a small
power supply, and still a lot of markets. RCC is called self-oscillating flyback converter is one of the most commonly used medium power switching power supply design approach. But RCC switching power supply design, the result of mutual influence of each parameter to make the calculation, debugging complex. In the design of switching power transformer design is the key, the most important reference transformer design capacity is the operating frequency. RCC designed to focus on the design of its frequency, the frequency of the design as much as possible early in 35K basis to design, but the actual commissioning, RCC operating frequency is likely to reach 100KHZ, are more likely to reach more than 200 KHZ at light loads. 

RCC switching power adapter

RCC (Ringing Choke Convertor) switching power supply with the necessary devices, low cost, no external clock control, continuous work in critical condition, can easily achieve current-mode control, the structure is a single-pole system, easy to get fast and stable In response, automatic power restrictions, etc.. RCC circuit is simple in principle, by the switching transformer and the main switch resonant oscillation, vice-switch duty cycle can be adjusted in order to regulate the output voltage. But the RCC power duty cycle, frequency change with changes in the environment and the use of internal parameters, making the switch to control the current drive waveform extremely difficult to determine, to the selected device parameters, especially the design of the transformer difficult. There are traditional designs nomogram method and core area product AP calculate the checksum method. Both of these methods more practical in a given frequency calculation, but if the unknown frequency, will not be designed with the above two ways. The traditional method is to preset a frequency RCC power, and then design a transformer. But due to the power transformer parameters directly affect the operating frequency, the operating frequency transformer design is often much difference with the default frequency was not working properly; supply design parameters to be repeated, resulting in the initial design of large amount of calculation, and the "patchwork Law "in the late commissioning, the actual frequency is difficult to agree with the theoretical value, resulting in power can not work in the best state of the design.
1.1 RCC principle
RCC schematic diagram shown in Figure 1. After power-up, C3 voltage across a current through the start-up resistor R1, R2, driven by the main switch Q1 is turned on, with the Q1 turns on, to strengthen the inductor T1 Q1 via a feedback control feedback signal pole forward drive, so Q1 rapid conduction. Because the current is proportional to the rate of change of the induced electromotive force, when the maximum (saturated conduction) of the primary current transformer, T1 'the voltage across 0, Q1 starts off from saturation. In this case, T1 'induced back electromotive force, acceleration Q1 off, while the saturation voltage across R4 Q2 driven open, short circuit and the control electrode of Q1, Q1 is turned off so that, after start-up resistors R1, R2 again turns on Q1 pass, and so the cycle. RCC circuit always operates in critical conduction mode flyback conversion does not occur in a continuous mode of energy transfer, the primary current is always a serrated triangular waveform, and will not appear trapezoidal wave. RCC circuit adjusts the input voltage by controlling the primary peak current to achieve.

RCC circuit through the transformer primary winding and switch resonant oscillation generated from the input voltage and the load is constant, the oscillation frequency by the early impact of the secondary inductance is large, especially in the secondary inductance greater impact frequency. RCC work due to variable frequency, and low frequency magnetic saturation of the core will result, so the design must be left when the RCC gap transformer to increase the reluctance to prevent core saturation. Do not work with ordinary transformer early RCC transformer secondary winding is equivalent to the energy storage inductor, coupled transformer core assembly and set aside buffer leakage losses arising from the gap caused by the network, not simply by pressing the primary turns ratio seek times Class turns. Because the RCC's a lot of time with the switch transistor, the pressure is only 400V of VCE, so when the election turns ratio to take into account the flyback voltage and the operating voltage of the transistor and can not exceed the required pressure.

RCC adjustable frequency times the transformer primary inductance, frequency is not allowed for the more reasonable than 100KHZ another experiment, the attention light load test temperature, because of the high frequency of light load, the switch may cause the temperature is too high

RCC reasonable design good power, can design a good RCC, is really to understand the power of the....