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All colleagues unite and focus their efforts to write a new chapter of developmentSwitching power adapters have four modulation methods.
所属分类： Industry News
发布时间：2020-04-13
Nowadays, electricity is used in virtually every field. Today, I’ll walk you through four modulation methods commonly employed in switch-mode power adapters—topics that many people may not be familiar with. Let’s take a look at these four modulation techniques:
1. Pulse Density Modulation Type
Abbreviated as PDM, or Pulse Density Modulation, this technique is characterized by a constant pulse width, with voltage regulation achieved by adjusting the pulse count. It employs zero-voltage switching, which can significantly reduce losses in power switching devices.
2. Pulse Width Modulation Type
Abbreviated as PWM, or pulse-width modulation, this technique is characterized by a constant switching period; the duty cycle is adjusted by varying the pulse width to achieve voltage regulation. At its core lies the PWM controller. Pulse‑width‑modulated switching power supplies are among the most widely used, offering a broad range of duty‑cycle adjustment, and PWM can also be synchronized with the main system’s clock.
3. Hybrid Modulation Type
It is a combination of methods ⑴ and ⑵. Both the switching period and the pulse width are variable and adjustable. It incorporates both a PWM controller and a PFM controller.
4. Pulse Frequency Modulation Type
Abbreviated as PFM, or pulse‑frequency modulation, this technique features a constant pulse width and adjusts the duty cycle by varying the switching frequency to achieve voltage regulation. At its core is the PFM controller. Pulse‑frequency‑modulated switching power supplies are particularly well suited for portable devices, as they can reduce the control IC’s quiescent current even under low‑duty‑cycle, low‑frequency conditions.
From the above four modulation methods, we can see that, Switching power supply There are two main types of modulation: pulse-width modulation (PWM) and frequency modulation. Pulse-width modulation adjusts the output voltage (or power) by varying the duty cycle—the ratio of the on-time (Ton) to the waveform period. It should be noted that PWM controllers can be implemented as standalone integrated circuits or integrated into switch-mode regulators or monolithic switching power supplies. Switch-mode regulators belong to the category of DC–DC converters, whereas switching power supplies typically fall under AC–DC converters.