Power switch tube, PWM controller and high-frequency transformer is an indispensable part of the switch power supply。 The traditional switch power supply is normally made by using high frequency power switch tube pision and the pins, such as using PWM integrated controller UC3842 + MOSFET is domestic small power switch power supply, the design method of a more popularity。 

  Since the 1970s, emerged in many function complete integrated control circuit, switch power supply circuit increasingly simplified, working frequency enhances unceasingly, improving efficiency, and for power miniaturization provides the broad prospect。 Three end off-line pulse width modulation monolithic integrated circuit TOP (Three switch Line) will Terminal Off with power switch MOSFET PWM controller one package together, has become the mainstream of switch power IC development。 Adopt TOP switch IC design switch power, can make the circuit simplified, volume further narrowing, cost also is decreased obviously  Monolithic switching power supply has the monolithic integrated, the minimalist peripheral circuit, best performance index, no work frequency transformer can constitute a significant advantage switching power supply, etc。 American PI (with) company in Power in the mid 1990s first launched the new high frequency switching Power supply chip, known as the "top switch Power", with low cost, simple circuit, higher efficiency。 The first generation of products launched in 1994 represented TOP100/200 series, the second generation product is the TOPSwitch - debuted in 1997 Ⅱ。 The above products once appeared showed strong vitality and he greatly simplifies the design of 150W following switching power supply and the development of new products for the new job, also, high efficiency and low cost switch power supply promotion and popularization created good condition, which can be widely used in instrumentation, notebook computers, mobile phones, TV, VCD and DVD, perturbation VCR, mobile phone battery chargers, power amplifier and other fields, and form various miniaturization, density, on price can compete with the linear manostat AC/DC power transformation module。 

  Switching power supply to integrated direction of future development will be the main trend, power density will more and more big, to process requirements will increasingly high。 In semiconductor devices and magnetic materials, no new breakthrough technology progress before major might find it hard to achieve, technology innovation will focus on how to improve the efficiency and focus on reducing weight。 Therefore, craft level will be in the position of power supply manufacturing higher in。 In addition, the application of digital control IC is the future direction of the development of a switch power。 This trust in DSP for speed and anti-interference technology unceasing enhancement。 As for advanced control method, now the inpidual feels haven't seen practicability of the method appears particularly strong,perhaps with the popularity of digital control, and there are some new control theory into switching power supply。

 （1）The technology: with high frequency switching frequencies increase, switch converter 

volume also decrease, power density has also been boosted, dynamic response improved。 Small power DC - DC converter switch frequency will rise to MHz。 But as the switch frequency unceasing enhancement, switch components and passive components loss increases, high-frequency parasitic parameters and high-frequency EMI and so on the new issues will also be caused。

  （2）Soft switching technologies: in order to improve the efficiency of non-linearity of various soft switch, commutation technical application and hygiene, representative of soft switch technology is passive and active soft switch technology, mainly including zero voltage switch/zero current switch (ZVS/ZCS) resonance, quasi resonant, zero voltage/zero current pulse width modulation technology (ZVS/ZCS - PWM) and zero voltage transition/zero current transition pulse width modulation (PWM) ZVT/ZCT - technical, etc。 By means of soft switch technology can effectively reduce switch loss and switch stress, help converter transformation efficiency