Strengthen the transient response of digital buck switching power supply load

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Overview:
With the advancement of technology, power management plays a very important role in various electronic products. Among them, general household computers and portable computers are particularly cautious about CPU power management, even in the nanosecond time (ns). With dozens of Ampere-level changes, the output voltage remains stable. The CPU power management system uses the popular buck switching power supply. This article is to discuss how to enhance the load transient response of the digital buck switching power supply.
Generally, the regulator is shown in Figure 1. The input power (Input Power, VIN) is converted to the desired output voltage (Output Power, VOUT) through the negative feedback (VFB) system to meet the user's required full load (ILoad). The output and maintains the voltage regulation function. When the load current changes stepwise and exceeds the response speed of the voltage regulator system, the output voltage will change, which is called the load transient response of the voltage regulator system.

Figure 1: Schematic diagram of the general regulated power supply system First, we must understand how the output voltage changes when the load transient reaction occurs. This article will take the example of output current from light load to heavy load. As shown in Figure 1 above, when discussing the transient response, the output capacitor (COUT) must be considered for its equivalent series resistance (ESR) and equivalent series inductance (ESL); the output voltage changes as shown in Figure 2, when the output current From the light load (ILoad1) to the heavy load (ILoad2) in a stepwise manner, in addition to the capacitor discharge supply output when the current changes instantaneously, the equivalent series resistance causes a pressure drop (Dropout Voltage) and an equivalent series inductance to cause a voltage drop surge ( Spike), then the negative feedback system starts to react and charges the output capacitor, and finally the system is gradually regulated, and how to charge the output capacitor in real time to avoid excessive voltage drop and quickly stabilize the voltage becomes a major issue in the power supply system.
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