車載冰箱單極驅(qū)動(dòng)實(shí)現(xiàn)穩(wěn)定溫度

根據(jù)電流方向，Peltier設(shè)備可以實(shí)現(xiàn)加熱和制冷。
　　
多數(shù)工程師都知道電晶體冰箱被稱為Peltier設(shè)備，或更普通的TECs（熱電冷卻器），也知道怎樣對(duì)溫度敏感的電子器件有效制冷，例如光學(xué)探測(cè)器和電晶體激光器。也許缺少認(rèn)同，但也是共識(shí)，TECs為雙向熱泵，根據(jù)供電電流的方向，可以進(jìn)行加熱和制冷。TECs因此被作為精確微型調(diào)溫裝置的基礎(chǔ)，維持溫度在設(shè)定范圍之間，避免周圍溫度的漂移。
　　
雙向TEC驅(qū)動(dòng)存在不便于設(shè)計(jì)的問(wèn)題。它需要雙重兩極電源供電或相對(duì)復(fù)雜的H橋驅(qū)動(dòng)輸出電路，包括一系列電源晶體管在熱流指示所需的方向上，選擇性的反轉(zhuǎn)TEC激勵(lì)。但另一個(gè)方法提供用消耗效率來(lái)簡(jiǎn)化問(wèn)題的優(yōu)勢(shì)。本設(shè)計(jì)方案提出一個(gè)獨(dú)特的方法實(shí)現(xiàn)雙向TEC溫度控制，避免雙電源供電的不便和雙向驅(qū)動(dòng)的復(fù)雜。它采用所有TECs很少人知道的詞：驅(qū)動(dòng)電流異常高水平下的網(wǎng)絡(luò)熱流內(nèi)在反轉(zhuǎn)。
　　
每個(gè)TEC（包括IMAX）的性能驅(qū)動(dòng)電流，導(dǎo)致最大網(wǎng)絡(luò)冷卻。繪出熱轉(zhuǎn)遞隨相對(duì)IMAX的驅(qū)動(dòng)電流，形成一條典型的拋物線曲線（圖1）。左邊圖中灰色的半邊顯示常用雙極TEC的工作區(qū)域，將驅(qū)動(dòng)電流劃分出–0.5×IMAX 


　　
圖2顯示了高性能PID（比例-積分-微分）反饋環(huán)的執(zhí)行情況。器件數(shù)少于雙極驅(qū)動(dòng)方案的1/4。反饋穩(wěn)定性高，建立時(shí)間短。缺點(diǎn)是電流為常規(guī)雙極驅(qū)動(dòng)器的150%，限制了該技術(shù)應(yīng)用于能量消耗和熱耗散要求不嚴(yán)格和適當(dāng)?shù)男⌒蚑ECs。


　　
英文原文：
　　
Thermoelectric-cooler unipolar drive achieves stable temperatures
　　
Depending on the direction of current flow, Peltier devices can both heat and cool.
　　
W Stephen Woodward, Chapel Hill, NC; Edited by Charles H Small and Fran Granville -- EDN, 12/3/2007
　　
Most engineers know about the solid-state refrigerators called Peltier devices or, more commonly, TECs (thermoelectric coolers) and how they can actively cool temperature-sensitive electronic components, such as optical detectors and solid-state lasers. It’s also common knowledge—although perhaps less so—that TECs are bidirectional heat pumps and can therefore both heat and cool, depending on the direction of the supplied drive current. TECs can therefore serve as the basis for precision microthermostats, maintaining a predetermined temperature against ambient-temperature excursions that range both above and below the setpoint.

The rub is that bidirectional-TEC drive tends to be an inconvenient design problem. It requires either dual bipolar power supplies or relatively complex H-bridge-drive output circuits involving arrays of power transistors that selectively reverse the TEC excitation as the required direction of heat flow dictates. But an alternative method offers advantages whenever si mplicity matters more than efficiency. This Design Idea presents a novel approach to bidirectional-TEC-temperature control that avoids both the inconvenience of dual power supplies and the complexity of bidirectional drive. It works by exploiting a little-known quirk of all TECs: the inherent reversal of net heat flow at unconventionally high levels of drive current.
　　
The specifications of every TEC include IMAX, the drive current that results in maximum net cooling. Plotting heat transfer versus drive current relative to IMAX results in a typical parabolic curve (Figure 1). The left-hand, gray half of the plot in the figure shows the usual bipolar TEC’s operating region, which confines drive current to the range of –0.5×IMAX
　　
Figure 2 shows an implementation of the concept in a high-performance PID (proportional-integral-derivative)-feedback loop. The component count is less than one-fourth that of a comparable bipolar-drive design. Feedback stability is robust, and settling time is short. The downside is a current draw as much as 150% higher than that for a conventional bipolar driver, which limits the technique to applications in which power consumption and heat dissipation aren’t critical priorities and small TECs are adequate.