Power management design advantage analysis of multi-phase power solutions

There are many applications that can benefit from multi-phase power, such as ASIC or processor core power, car audio power, or server memory applications. Almost any power supply can give full play to the advantages of multi-phase solutions. The advantages of multi-phase power supply include thermal performance, size, output ripple, and transient response. This scheme is suitable for simple buck converters, boost converters, and more complex designs such as active clamp forward or reverse converters.

There are many applications that can benefit from multi-phase power, such as ASIC or processor core power, car audio power, or server memory applications. Almost any power supply can give full play to the advantages of multi-phase solutions. The advantages of multi-phase power supply include thermal performance, size, output ripple, and transient response. This scheme is suitable for simple buck converters, boost converters, and more complex designs such as active clamp forward or reverse converters.

The thermal performance of the power supply related to conduction loss is proportional to the square of the current. The use of multi-phase methods can reduce these losses. For example, using dual-phase, the power supply related to conduction loss can be halved.

●Single phase conduction loss =
●Double phase conduction loss=
●Four-phase conduction loss=

The conduction loss is only a part of the total loss of the power supply, but these losses will be very significant at higher currents.

Reduce the size of the power supply by adopting a multi-phase solution. Although more components need to be used, the size of the components is generally smaller. Magnetic components will occupy most of the power supply space. Although more components are required, the overall volume will be reduced. The size factor is not only related to a true high-current power supply, sometimes a lower-current design will also benefit, and the size can be reduced.

One of the biggest advantages of the multi-phase scheme is the elimination of ripple current. This ripple current cancellation is beneficial to the input and output Capacitors. The figure below is an example of how ripple current cancellation reduces the rms current in the input or output Capacitor.

Power management design advantage analysis of multi-phase power solutions
Figure 1: Buck input capacitor, boost output capacitor

Power management design advantage analysis of multi-phase power solutions
Figure 2: Buck output capacitor, boost input capacitor

Fig. 1 Fig. 2 After being normalized, it can show the reduction of the root mean square current under different phases and the number of duty cycles. Figure 1 is for the input capacitor in a buck converter or the output capacitor in a boost converter. Figure 2 is for the output capacitor in a buck converter or the input capacitor in a boost converter.

Multiple power levels can be used to improve the transient response of the power supply. The main reason for the increase is to reduce the magnetic inductance and make the current rise faster. Smaller magnetic devices will result in greater ripple current, but due to the elimination of ripple current, the ripple performance can remain unchanged. In addition, smaller magnetic components also help increase the converter bandwidth.

To illustrate the advantages of multi-phase converters, the following power supply specifications must be involved:
●Vin=12V
●Vout=1V
●Iout=40A
●Output ripple frequency=500KHz

Comparison of single-phase design and dual-phase design

Power management design advantage analysis of multi-phase power solutions

In short, compared to single-phase solutions, multi-phase power supplies can provide many advantages. Using a multi-phase solution, thermal performance, input and output ripple current, size, and transient response can all be improved. The only disadvantage is that the design is slightly more complicated and has more components than the traditional single-phase solution. The good news is that we can use Texas Instruments (TI) controllers designed specifically for multi-phase design solutions to simplify multi-phase power supply design through the following tested PowerLab design solutions.

Multi-phase step-down converter power supply design:

●PMP2277——Use TPS40180 to realize 3-phase 60A synchronous power supply
●PMP3054——Use TPS40140 to realize 4-phase 80A synchronous power supply
●PMP5621——Use TPS40140 and CSD87350 to realize 4-phase 80A synchronous power supply
●PMP7328——Use TPS40422 and CSD87350 to realize dual-phase 60A synchronous PMBUS power supply

Multi-phase boost converter power supply design:

●PMP2445-Use TPS40090 to achieve 300W4 phase boost for car audio applications
●PMP4538-Use TPS40090 to achieve 500W4 phase boost for car audio applications
●PMP7850-Use LM5122 to achieve dual-phase synchronous boost

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