Spurious-noise-free buck regulator for direct powering of analog/RF loads using PWM control with random frequency hopping and random phase chopping
Spurious-noise-free buck regulator for direct powering of analog/RF loads using PWM control with random frequency hopping and random phase chopping
复制标题
无寄生噪声降压稳压器，使用具有随机跳频和随机相位斩波功能的 PWM 控制直接为模拟/射频负载供电
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
A. Fayed
中科院分区：
文献类型：
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作者：
C. Tao;A. Fayed
Buck稳压器由于其高功率转换效率而广泛应用于便携式设备中。然而，由于它们的伪输出噪声，它们不能直接用于功率敏感的模拟/RF模块，并且需要后续的线性低差稳压器（ldo）来为这些模块生成二次低噪声供电轨。这导致效率降低，尺寸和成本增加。此外，随着开关频率的增加以减少无源元件，ldo在滤波开关噪声方面变得不那么有效，因为它们在1MHz[1]以上的电源抑制（PSR）很差。本文研究了几种通过控制降压稳压器的开关行为来降低其杂散噪声的技术。这包括在控制回路中使用ΔΣ或Δ调制器[2,3]，这虽然减少了杂散，但会导致本底噪声的大幅增加，从而要求后续的LDOs[1]。其他技术使用随机跳频[4]或周期性单调频率步进[5]将每个脉冲的功率重新分配为多个较小的脉冲。然而，由此产生的频谱仍然是假的，并且在最大的杂散中报告的减少被限制在10到12dB。这种有限的减少，加上产生了许多额外的杂散，使负载电路容易受到性能下降的影响。提出了一种基于随机跳频和相位斩波相结合的降压变换器脉宽调制控制方案。该技术完全消除了杂散，消除了瞬变，非常低的本底噪声，并且在面积和功率上的开销很小。
Buck regulators are widely employed in portable devices due to their high power-conversion efficiency. However, due to their spurious output noise, they are not directly used to power sensitive analog/RF modules, and subsequent linear low-dropout regulators (LDOs) are needed to generate secondary low-noise supply rails for these modules. This results in lower efficiency, and increased size and cost. Moreover, as switching frequencies increase to reduce passive components, LDOs become less effective in filtering the switching noise due to their poor power-supply rejection (PSR) beyond 1MHz [1]. Several techniques for reducing the spurious noise of buck regulators by manipulating their switching behavior have been studied. This includes using ΔΣ or Δ modulators in the control loop [2, 3], which although reduce the spurs, result in large increases in the noise floor that mandates subsequent LDOs [1]. Other techniques redistribute the power of each spur into multiple smaller ones using random frequency hopping [4], or periodic monotonic frequency stepping [5]. However, the resulting spectrum continues to be spurious and the reduction reported in the largest spur is limited to 10 to 12dB. This limited reduction, coupled with the fact that many extra spurs are generated, leaves the load circuitry vulnerable to performance degradation. This paper proposes a pulse-width modulation (PWM) control scheme for buck converters based on combining random frequency hopping with phase chopping. The technique results in full elimination of spurs, elimination of hopping transients, very low noise floor, and minimalist implementation with little overhead on area and power.