This article is part of the能源管理系列：How to Easily Design Power Supplies
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您将学到什么：
- 其他拓扑用于smp超出了three most common types?
- 常见和先进的孤立拓扑。
- What is the switched capacitor converter?
Beyond the three basic, nonisolated switch-mode power-supply topologies discussed inPart 1，还有更多拓扑。但是，它们都需要额外的电源组件，这通常使它们更高的成本并降低其电源转换效率。除某些例外，在电动路径中添加其他组件通常会增加损失。
Some of the most popular topologies are SEPIC, Zeta, Ćuk, and the four-switch buck-boost. They each offer features not available with the three basic topologies. The most important features of each topology include:
- Sepic：The SEPIC can generate a positive output voltage out of a positive input voltage that may be higher or lower than the output voltage. Boost regulator ICs may be used to design a SEPIC power supply. The drawback of this topology is the need for a second inductor or one coupled inductor and a SEPIC capacitor.
- Zeta:The Zeta converter is similar to the SEPIC, but it’s capable of generating a positive or negative output voltage. In addition, it doesn’t have a right-half-plane zero (RHPZ), thereby simplifying the regulation loop. A buck-converter IC can be used for such a topology.
- ®：The Ćuk converter offers an inversion of a positive input voltage into a negative output voltage. It uses two inductors, one on the input side and one on the output side, making it quite low noise on the input and output sides. The drawback is that only a few switch-mode power-conversion ICs support this topology, since a negative voltage-feedback pin is required for the regulation loop.
- Four-switch buck-boost:近年来，这种转换器类型变得非常流行。它从正输入电压提供了正输出电压。输入电压可能高或低于调整后的输出电压。该转换器取代了许多SEPIC设计，因为它具有更高的功率转换效率，并且仅需要一个电感器。
最常见的孤立拓扑
Besides nonisolated topologies, some applications require galvanically isolated power converters. The reasons may be safety concerns, the need to have floating grounds in larger systems where different circuits are interconnected, or the prevention of ground current loops in noise-sensitive applications. The most common isolated converter topologies are the flyback and forward converters.
反式转换器通常用于高达60 W的功率水平。电路以按时将能量存储在变压器中的方式。在禁止时间，该能量将释放到转换器的次级，从而为输出提供动力。
该转换器易于构建，但是它需要相对较大的变压器来存储适当操作所需的所有能量。这方面将拓扑限制为较低的功率水平。Figure 1在顶部显示一个飞回转换器，底部显示一个前向转换器。
除了飞回转换器外，前进转换器也非常受欢迎。它使用变压器的方式不同于反式飞回。在按时，当电流流过主要侧绕组时，电流也流经次级绕组。
能量不应存储在变压器的核心中。在每个切换周期之后，我们必须确保所有核心的磁化都释放到零，以使变压器在许多切换循环后不会饱和。通过一些不同的技术可以实现这种能量释放。一种流行的方法是使用带有小的额外开关和电容器的活动夹。
Figure 2显示了使用该ltspice仿真环境的前向活动夹具设计的示意图ADP1074。In the forward converter, there’s an additional inductor in the output path compared to the flyback（图1，再次）。尽管它是具有相关空间和成本含义的另一个组件，但与反式转换器相比，它有助于产生低噪声输出电压。同样，向前转换器在与飞回相同的功率水平上所需的变压器尺寸可能要小得多。
先进的孤立拓扑
除了飞回和前向拓扑外，还有许多基于变压器的循环隔离转换器概念。以下列表提供了有关这些转换器中最常见的基本解释：
- Push-pull:The push-pull topology is similar to the forward converter. However, instead of one low-side switch, this topology requires two active low-side switches. Also, it requires a primary transformer winding with a center tap. The advantage of the push-pull is an operation with generally lower noise compared to a forward converter. In addition, it needs a smaller transformer. The hysteresis of the BH curve of a transformer is utilized in two quadrants rather than just one.
- Half-bridge/Full-bridge:These two topologies are typically used for higher power designs from a few hundred watts up to a few kilowatts. They require high-side switches in addition to low-side switches but enable very high power transfer with relatively small transformers.
- ZVS：The term zero voltage switching (ZVS) comes up often when discussing high-power isolated converters. Another term for such converters is LLC (inductor-inductor-capacitor) converters. These architectures aim for very high efficiency conversion. They generate a resonance circuit and switch the power switches while the voltage or current across the switches is close to zero, thus minimizing the switching losses. However, such designs may be difficult to design and the switching frequency isn’t fixed, sometimes yielding EMI problems.
Switched Capacitor Converters
In addition to linear regulators and switch-mode power supplies, there’s a third group of power converters—switched capacitor converters. They’re also referred to as charge pumps. Switched capacitor converters, which use switches and capacitors to multiply or invert voltages, offer the big advantage of not needing any inductor.
Typically, such converters are employed for low power levels of below 5 W. However, recent advances have allowed for much higher power switched capacitor converters.Figure 3显示LTC7820in a 120-W design at 98.5% efficiency, converting 48 V to 24 V.
第3部分本系列将涵盖数字电源，EMI注意事项，过滤和无声切换器。
