Application and Development of Monolithic Switching Power Supply
At present, medium and small power switching power supplies are developing in the direction of monolithic integration. In this paper, the performance characteristics and typical applications of various monolithic switching power supplies that have been introduced in recent years are described in detail.
The monolithic switching power supply integrated circuit has the advantages of high integration, high-cost performance, the simplest peripheral circuit, the best performance index, and can form an isolated switching power supply with high efficiency and no power frequency transformer. After it came out in the mid and late 1990s, it showed strong vitality. At present, it has become the preferred integrated circuit for the development of medium and low power switching power supplies, precision switching power supplies and power modules in the world. The switching power supply formed by it is equivalent to the linear regulated power supply of the same power in cost, and the power supply efficiency is significantly improved, and the volume and weight are greatly reduced. This creates favorable conditions for the promotion and popularization of new switching power supplies.
Switching power supply is known as high-efficiency and energy-saving power supply, it represents the development direction of regulated power supply, and has now become the mainstream product of regulated power supply. Over the past 20 years, integrated switching power supplies have been developing in the following two directions.
The first direction is to integrate the control circuit, the core unit of the switching power supply. In 1997, Pulse Width Modulation (PWM) controller integrated circuits were first developed abroad. Motorola, SiliconGeneral, Unitrode, etc. successively launched a number of PWM chips. Typical products include MC3520 and SG3524. , UC3842. Since the 1990s, high-speed PWM and PFM (pulse frequency modulation) chips with a switching frequency of 1MHz have been developed abroad, such as UC1825 and UC1864.
The second direction is centering, and the low-power switching power supply realizes monolithic integration. This is roughly divided into two stages: In the early 1980s, Italian-French Semiconductor Co., Ltd. (SGS-Thomson) took the lead in introducing the L4960 series of monolithic switching regulators. The company introduced the L4970A series in the 1990s. Its characteristics are that the pulse width modulator, power output stage, protection circuit, etc. are integrated into one chip. When using, it needs to be equipped with a power frequency transformer to isolate it from the power grid. ), high current (1.5A ~ 10A), high efficiency (over 90%) switching power supply. But in essence, it is still a DC/DC power converter.
In 1994, Power Corporation of the United States first successfully developed a three-terminal isolated pulse width modulation monolithic switching power supply in the world, which was hailed as a "top switching power supply". The first generation of products is the TOPSwitch series, and the second generation is the TOPSwitch-II series that came out in 1997. In 1998, the company launched the TinySwitch series of high-efficiency, low-power, low-cost four-terminal single-chip switching power supplies. After that, Motorola introduced MC33370 series five-terminal single-chip switching power supply in 1999, also known as High Voltage Power Switching Regulator. At present, the single-chip switching power supply has formed four series and nearly 70 types of products.
