[MUSIC PLAYING] The third topology, pretty close to the SEPIC, is the Zeta Converter. The Zeta converter steps up and steps down the input voltage. So on a first glance, sounds similar to a SEPIC. But it isn't because it's a forward topology. The energy is transferred directly from input to output, so not influenced by a low frequent, Right Half Plane Zero.
Means the Zeta offers better dynamic performance than the SEPIC converter. And we got an LC filter located at the output. We got the continuous current at the output with low ripple.
But there is no free lunch. The SEPIC has a continuous current at the input. The Zeta has a pulse current at the input, so high reflected ripple to the source.
Same for all those topologies. If the inductors are coupled, the windings ratio one by one is mandatory. Here, for the Zeta, we use a buck controller, single driver. Low cost is fully efficient. If we do it with synchronous rectification, we can do it with a synchronous buck device compared to the true buck boost. Same for the other topologies as well. A single FET and a single rectifier only is needed.
We got also compared to a non-isolated flyback. Very clean waveforms, no ringing, low EMI, multiple outputs. Possible, and for bigger rectifier currents, as already stated, a synchronous buck device improves efficiency here to lower losses at our rectifier.
And similar to SEPIC and similar to Cuk, the same thing. If the switch is closed, we got both magnetizing currents across the switch. And if the switch is opened, we got both demagnetizing currents across the rectifier.
So we have a look at the upper picture. We got voltage present across the coupling capacitor C1. And we got the input voltage present at input capacitor CI. If we close the switch, we force the magnetizing current across L2, and we force the magnetizing current across L1.
On the other hand, if we open the switch, we got the demagnetizing currents. Those are forced by L1 across D1, and the coupling capacitor, C1. And on the other side, we got the demagnetizing current forced by L2 across output capacitor and our rectifier.
As we notice, the input current is pulsed, so high reflected ripple. But, as we can see, the output current is continuous. So low EMI, low ripple at the output. [音乐播放] 第三种拓扑为 Zeta 转换器， 与 SEPIC 非常接近。 Zeta 转换器可升高 和降低输入电压。 因此，它初看起来 类似于 SEPIC。 但两者不同，因为 它是一种正向拓扑。 能量直接从输入 传输到输出， 因此不受低频率、 右半平面零点的 影响。 这意味着 Zeta 具有 比 SEPIC 转换器更好的 动态性能。 而且输出端有 一个 LC 滤波器。 我们在输出端得到具有 低纹波的连续电流。 但天下没有免费的午餐。 SEPIC 在输入端 具有连续电流。 Zeta 在输入端 具有脉冲电流， 因此会给电源带来 高的反射纹波。 所有此类拓扑都是如此。 如果耦合了电感器， 则绕组比必须 为 1 比 1。 此处，对于 Zeta，我们使用 降压控制器、单一驱动器。 低成本且充分有效。 与真正的 降压-升压相比， 如果我们对其 使用同步整流， 则可以对其使用同步降压器件。 其他拓扑 也是如此。 只需要单个 FET 和 单个整流器。 与非隔离式反激 相比，我们还可以得到 非常干净的波形、 无振铃、低 EMI、 多路输出。 前面已经说明， 对于较大的 整流器电流， 同步降压器件 可以在此处提高效率， 降低整流器的损失。 与 SEPIC 和 Cuk 相似， 都是一样的。 如果闭合开关， 则两个磁化电流 都会通过该开关。 如果断开开关， 则两个消磁电流都会 通过整流器。 请看一下 上方的图片。 跨耦合电容器 C1 存在电压。 并且输入电容器 CI 上存在输入电压。 如果我们闭合开关， 则会强制磁化电流 通过 L2，并强制 磁化电流通过 L1。 另一方面， 如果我们断开该开关， 则会得到 消磁电流。 这些电流由 L1 强制通过 D1 和耦合电容器 C1。 在另一侧， L2 强制 消磁电流通过输出 电容器和整流器。 我们注意到，输入 电流为脉冲式， 因此具有高的反射纹波。 但我们可以看到， 输出电流是连续的。 因此在输出端 具有低 EMI、低纹波。 This website is under heavy load (queue full) We're sorry, too many people are accessing this website at the same time. We're working on this problem. Please try again later.
