How to Use a Multiphase Boost Converter
When the required system voltage exceeds the available supply voltage, a boost converter is typically an ideal solution. However, conventional standard boost topologies are not the only option. In certain application scenarios, phase-shifted multiphase boost converters can deliver superior performance: these converters achieve higher efficiency under heavy-load conditions while significantly reducing the required capacitance values for both the input and output stages.
Switch-mode power supplies based on the boost principle can step up a lower input voltage to a higher output voltage. This function can be implemented as shown in the figure. 1 The standard boost topology is shown. This configuration allows the output to receive pulsed current from the inductor. However, since the voltage converter requires a stable output voltage, an output capacitor is needed. C₂ Its role is crucial. —— It must convert the pulsed current into a smooth and constant output voltage. To accomplish this, the output capacitor of a boost regulator typically needs to have a large capacitance value, while its equivalent series resistance should be minimized as much as possible ( ESR ）、 parasitic resistance, equivalent series inductance ( ESL ) and parasitic inductance.
To reduce the stringent requirements on the output capacitor, a multiphase boost converter can be used. In a multiphase architecture, two boost regulators operate in parallel and are connected to the same output capacitor. The two channels operate at 180° Phase-shifted interleaved control (as shown in the figure) 2 as shown). At this point, the output capacitor C₂ Energy is harvested twice during each switching cycle. ， Separately from the inductor L₁ and L₂ . Therefore, upon obtaining the diagram 1 Under the condition of similar voltage ripple in the circuits, C₂ The capacitance only needs to be about half of the original. 。
The advantages of multiphase boost regulators are not limited to the output capacitor; they also extend to the input capacitor. At the input, because the inductor limits the rate of current rise and fall, the boost regulator does not generate pulsed current. Furthermore, as shown in the figure 2 As shown, the two-phase phase-shift inductor can further suppress fluctuations in the input current, thereby allowing the input capacitor to be reduced. C₁ the size.
Multiphase boost converters can also improve conversion efficiency. By distributing the power across multiple branches, the peak current through each component is reduced, thereby enhancing overall efficiency.
Figure 3 Demonstrates the use of an integrated circuit. LT8349 practical application solution. This device is a two-phase synchronous boost converter specifically designed to step up or regulate battery voltage. When the battery delivers a high current for a short period, its terminal voltage will temporarily drop; a two-phase boost converter is ideally suited for such operating conditions, as its phase-shifted operation enables it to draw a more continuous current from the battery side.
Adopt LT8349 Another advantage of the scheme is that it can still achieve extremely high efficiency even under light-load current conditions. To optimize energy efficiency in this mode, one phase can be switched off when the load is light. Under light-load conditions, the battery itself does not experience excessive stress, and the circuit can operate in single-phase mode; however, when a heavy load current of several amperes is required, the second phase automatically turns on, fully leveraging all the benefits of two-phase operation. This feature of shutting off one phase during light-load operation is known as “ Phase cancellation ”。
Figure 3 The example circuit shown can convert 2.5 V The power supply voltage is converted to 6 V the output voltage. In 3 A Under load current, the conversion efficiency can reach 92% ; even when the load current drops as low as 2 mA At that time, the measured efficiency could still reach 90%。
Boost converters exhibit several unique operating modes. The two-phase architecture offers significant efficiency advantages. —— This holds true under both heavy-load and light-load conditions. Moreover, specially tailored integrated circuits make the implementation of this unique operating mode remarkably straightforward.
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How to Use a Multiphase Boost Converter
When the required system voltage exceeds the available supply voltage, a boost converter is typically an ideal solution. However, conventional standard boost topologies are not the only option. In certain application scenarios, phase-shifted multiphase boost converters can deliver superior performance: these converters achieve higher efficiency under heavy-load conditions while significantly reducing the required capacitance values for both the input and output stages.