The real development of the switching power supply began in the 70s. During this period, the establishment of the system's power electronics theory provided a good and necessary basis for the development of switching power supplies. However, at the initial stage of product application, there are disadvantages such as low switching frequency, low power density, and poor reliability. Therefore, the main development direction of the switching power supply is to continuously improve the above disadvantages.
The appearance of devices such as high-power FETs and insulated gate transistors provides extremely favorable conditions for high-frequency and high-power converters. The emergence of new devices and new topology theories make switching power supplies increasingly reliable, mature, economical and applicable.
The current development of switching power supply can be summarized as the following aspects:
With the increase of the switching frequency, the frequency of the switching converter is also reduced, the power density is also greatly improved, and the dynamic response is improved. The switching frequency of the low-power DC/DC converter will rise to MHz. However, as the switching frequency continues to increase, new problems such as increased loss of switching elements and passive components, high-frequency parasitic parameters, and high-frequency EMI will also arise.
Digital Technology In traditional power electronics, the control section is designed and operated on analog signals. At present, in the entire electronic analog circuit system, television, audio equipment, photo processing, communications, and networks have gradually been digitized, and the last fortress without digitization is the power supply field. In recent years, research on digital power has continued unabated, and more and more results have been achieved. The leading companies in power digitalization are TI and Microchip.
The soft-switching technology is used to improve the conversion efficiency of the converter and various soft-switching technologies are applied. The representative passive soft-switching technology and active soft-switching technology mainly include zero-voltage switching/zero-current switching (ZVS/ZCS). Resonance, quasi-resonant, zero voltage/zero current pulse width modulation (ZVS/ZCS-PWM) and zero voltage transition/zero current transition pulse width modulation (ZVT/ZCT-PWM) techniques. The use of soft-switching technology can effectively reduce the switching loss and the switching stress, which contributes to the improvement of converter conversion efficiency.
Power Factor Correction (PFC)
Since the AC/DC conversion circuit has rectifying elements and filter capacitors at the input, when the sinusoidal voltage is input, the power factor of the single-phase rectified power-supplying electronic equipment on the grid side (AC input) is only 0.6 to 0.65. With a PFC (Power Factor Correction) converter, the power factor at the grid side can be increased to 0.95 to 0.99, and the input current THD is less than 20%. It not only controls the harmonic pollution of the power grid, but also improves the overall efficiency of the power supply. This technology is called Active Power Factor Correction (APFC) single-phase. The development of APFC at home and abroad is relatively early and the technology is mature. At present, the PFC technology is mainly divided into two major categories: active PFC technology and passive PFC technology. Using PFC technology can improve the power factor at the input of the AC/DC converter and reduce the harmonic pollution to the power grid. However, it needs to continue research and development.
The modularization of modular technology has two meanings. One is the modularization of power devices and the other is the modularization of power supply units. In recent years, some companies have installed the drive protection circuit of the switching power supply into the power module to form an “intelligent†power module (IPM), which not only reduces the size of the entire machine, but also facilitates the design and manufacture of the entire machine. In fact, due to the increasing frequency, the influence of the parasitic inductance and parasitic capacitance of the lead wire becomes increasingly serious, causing greater electrical stress on the device (expressed as overvoltage, overcurrent, and burr). In order to improve the reliability of the system, some manufacturers have developed a “user-specific†power module (ASPM) that installs all the hardware of a complete machine into a module in the form of a chip. Such a module undergoes strict and reasonable heat. , electrical, mechanical design, to achieve the perfect situation of optimization. It can be seen that the purpose of modularization is not only to facilitate the use, to reduce the size of the whole machine, but more importantly to eliminate the traditional connection and minimize the parasitic parameters so as to minimize the electrical stress on the device and improve the reliability of the system. .
The appearance of devices such as high-power FETs and insulated gate transistors provides extremely favorable conditions for high-frequency and high-power converters. The emergence of new devices and new topology theories make switching power supplies increasingly reliable, mature, economical and applicable.
The current development of switching power supply can be summarized as the following aspects:
With the increase of the switching frequency, the frequency of the switching converter is also reduced, the power density is also greatly improved, and the dynamic response is improved. The switching frequency of the low-power DC/DC converter will rise to MHz. However, as the switching frequency continues to increase, new problems such as increased loss of switching elements and passive components, high-frequency parasitic parameters, and high-frequency EMI will also arise.
Digital Technology In traditional power electronics, the control section is designed and operated on analog signals. At present, in the entire electronic analog circuit system, television, audio equipment, photo processing, communications, and networks have gradually been digitized, and the last fortress without digitization is the power supply field. In recent years, research on digital power has continued unabated, and more and more results have been achieved. The leading companies in power digitalization are TI and Microchip.
The soft-switching technology is used to improve the conversion efficiency of the converter and various soft-switching technologies are applied. The representative passive soft-switching technology and active soft-switching technology mainly include zero-voltage switching/zero-current switching (ZVS/ZCS). Resonance, quasi-resonant, zero voltage/zero current pulse width modulation (ZVS/ZCS-PWM) and zero voltage transition/zero current transition pulse width modulation (ZVT/ZCT-PWM) techniques. The use of soft-switching technology can effectively reduce the switching loss and the switching stress, which contributes to the improvement of converter conversion efficiency.
Power Factor Correction (PFC)
Since the AC/DC conversion circuit has rectifying elements and filter capacitors at the input, when the sinusoidal voltage is input, the power factor of the single-phase rectified power-supplying electronic equipment on the grid side (AC input) is only 0.6 to 0.65. With a PFC (Power Factor Correction) converter, the power factor at the grid side can be increased to 0.95 to 0.99, and the input current THD is less than 20%. It not only controls the harmonic pollution of the power grid, but also improves the overall efficiency of the power supply. This technology is called Active Power Factor Correction (APFC) single-phase. The development of APFC at home and abroad is relatively early and the technology is mature. At present, the PFC technology is mainly divided into two major categories: active PFC technology and passive PFC technology. Using PFC technology can improve the power factor at the input of the AC/DC converter and reduce the harmonic pollution to the power grid. However, it needs to continue research and development.
The modularization of modular technology has two meanings. One is the modularization of power devices and the other is the modularization of power supply units. In recent years, some companies have installed the drive protection circuit of the switching power supply into the power module to form an “intelligent†power module (IPM), which not only reduces the size of the entire machine, but also facilitates the design and manufacture of the entire machine. In fact, due to the increasing frequency, the influence of the parasitic inductance and parasitic capacitance of the lead wire becomes increasingly serious, causing greater electrical stress on the device (expressed as overvoltage, overcurrent, and burr). In order to improve the reliability of the system, some manufacturers have developed a “user-specific†power module (ASPM) that installs all the hardware of a complete machine into a module in the form of a chip. Such a module undergoes strict and reasonable heat. , electrical, mechanical design, to achieve the perfect situation of optimization. It can be seen that the purpose of modularization is not only to facilitate the use, to reduce the size of the whole machine, but more importantly to eliminate the traditional connection and minimize the parasitic parameters so as to minimize the electrical stress on the device and improve the reliability of the system. .
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