High efficiency green mode switching power supply controller design principle

100V, 250mA, surface mount, high speed switching diode

Probe domestic switch needle KG-300K needle head diameter is 3.0mm normally open switch needle

0805 green 0805 emerald green

Overview:
A high-efficiency green mode step-down switching power supply controller chip design scheme is proposed, which is characterized by PWM/Burst multi-mode control strategy to improve power conversion efficiency under full load conditions. By reducing power consumption in low load and standby conditions, static power consumption of modern portable devices powered by batteries can be reduced, extending device standby time and battery life. The chip also achieves a smooth transition during mode conversion and suppression of overshoot voltage. In addition, a high-precision, high-efficiency on-chip current sensing technology is introduced to further reduce power consumption. The chip is designed and manufactured in a 115μm BCD (bip ola r2CMOS2DMOS) process. The test results show that the chip has achieved the expected performance requirements.

1 Introduction The step-down integrated switching power supply controller is widely used in various portable devices. In recent years, with the improvement of performance and functions of battery-powered portable devices, such as mobile phones, MP3 players, PDAs, higher and higher requirements have been placed on the efficiency of switching power supplies.

To increase efficiency and reduce off-chip components, current Buck converters typically integrate power switches and synchronous rectifier switches. At the same time, in order to reduce the size of the off-chip inductive components to suit the application of portable devices, the switching frequency is often set to the order of several megabits or more. The problem with this is that when the converter is operated under light load conditions, the switching losses become the main power loss. While portable devices work just in standby mode, that is, under light load conditions, light load efficiency is critical to extending battery life. Therefore, the issue of improving light load efficiency has received a lot of attention.

A common way to solve the above problem is to reduce the switching frequency under light load conditions so that the efficiency of the converter remains at a level similar to the heavy load. This technique has PFM/PWM multimode modulation, common gate drive, etc., but they have one common drawback: the switching frequency is modulated with the load, which makes the design of the off-chip filter quite complicated.
The green mode step-down power integrated switching power supply controller chip proposed in this paper adopts Burst/PWM multi-mode modulation technology. The control converter operates in PWM mode at a constant frequency under heavy load, and when the load is reduced to a certain level, it automatically Switch to Burst mode and work at a reduced constant frequency. Its main advantage is to reduce switching losses without increasing the design complexity of the off-chip filter. In addition, Burst mode can be enabled or disabled by user control depending on the needs of the application. And in the mode conversion process, the double reference method is used to achieve smooth transition and load hysteresis of mode conversion. At the same time, the chip introduces on-chip current sensing technology to replace the traditional resistance current detection, which reduces power consumption to some extent. The integration of power switches and synchronous rectification switches also simplifies the design of off-chip application circuits.

2 System Design The green mode step-down switching power supply controller proposed in this paper is a Buck converter with constant frequency operation and peak current control mode. The output voltage is adjusted by the off-chip voltage divider resistor. The power switch and synchronous rectifier switch are all on-chip. integrated. The system principle is shown in Figure 1.

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