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大功率二极管晶闸管知识连载——热特性

<p>文章来源：&nbsp;<a href="https://mp.weixin.qq.com/s/gKcVo4-_P_rIBxJjb9515w">英飞凌工业半导体</a></p&gt;

<p>功率二极管晶闸管广泛应用于AC/DC变换器，UPS，交流静态开关，SVC和电解氢等场合，但大多数工程师对这类双极性器件的了解不及对IGBT的了解，为此我们组织了6篇连载，包括正向特性，动态特性，控制特性，保护以及损耗与热特性。内容摘来自英飞凌《双极性半导体技术信息》。</p>

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<p><strong>4.热性质</strong></p>
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<p>为了维持热平衡，必须排出半导体中转化为热的电能损耗。为此，我们提供了具有明确冷却性质的散热器。通过类比电气电路来描述热等效电路，如图32所示。</p>

<p><img alt="二极管和晶闸管的热等效电路" data-entity-type="file" data-entity-uuid="766c3023-c91d-4c0a-b49b-c787c7050544" src="/sites/default/files/inline-images/1_238.png" /></p>

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<p>图32.二极管和晶闸管的热等效电路</p>
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<p>Rth JC=结-壳稳态热阻</p>

<p>Rth CH=壳-散热器稳态热阻</p>

<p>Rth HA=散热器稳态热阻</p>

<p>a–单面冷却</p>

<p>b–双面冷却</p>

<p><strong>4.1&nbsp;温度</strong></p>

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<p><strong>4.1.1&nbsp; 结温Tvj,Tvj max</strong></p>
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<p>对于所有基本电气性能而言，结温是最重要的参照。它代表半导体系统内的平均空间温度，因此更准确地称为等效结温或虚拟结温。</p>
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<p>最高允许结温Tvj max对器件的功能和可靠性十分重要。如果超过Tvj max，半导体性能可能发生不可逆变化，并可能损坏。</p>
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<p><strong>4.1.2&nbsp; 壳温TC</strong></p>
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<p>Tc是平板型晶闸管或二极管的壳或PowerBLOCK模块的基板的接触区域的最高温度。</p>
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<p><strong>4.1.3&nbsp; 散热器温度TH</strong></p>
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<p>TH是指半导体通过散热器接触区域及其周围的冷却介质与散热器发生热交换而使散热器达到的温度。</p>

<p>英飞凌提供的散热器已在装好元器件的情况下进行了测试和规定。因此，给出的散热器数据包含了器件和散热器之间的热阻RthCH。计算时可以不考虑此值。</p>
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<p><strong>4.1.4&nbsp; 冷却介质温度TA</strong></p>
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<p>Ta是冷却介质进入散热器之前的温度。对于空气冷却，在散热器进风口侧确定此温度。对于液体冷却，则在散热器冷却液进口处确定此温度。</p>
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<p><strong>4.1.5&nbsp; 壳温范围Tcop</strong></p>
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<p>Tcop是可以使功率半导体工作的壳温范围。</p>
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<p><strong>4.1.6&nbsp; 储存温度范围Tstg</strong></p>
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<p>Tstg是功率半导体在不带电情况下可以存储的温度范围。最高允许储存温度与没有时间限制的最高允许结温无关，根据DIN IEC 60747-1，环氧树脂平板型器件和PowerBLOCK模块的最高允许储存温度为Tstg= 150℃，时间限制为672h。</p>
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<p><strong>4.2&nbsp;&nbsp;热阻</strong></p>
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<p><strong>4.2.1&nbsp; 内热阻RthJC</strong></p>
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<p>RthJC是结温Tvj和壳温TC之差与总耗散功率Ptot的比值：</p>

<p><img alt="Ptot的比值" data-entity-type="file" data-entity-uuid="af054332-8731-489f-90d1-acc9833af81f" src="/sites/default/files/inline-images/2_237.png" /></p>
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<p>该值取决于器件的内部设计以及通态电流的波形和频率。</p>

<p>由于热阻的并联，双面冷却的热阻比单面冷却的低（见图32）。</p>

<p>热阻取决于半导体的类型和形状，因此不会100% 测量，但可以在最初的型式认证试验中确定。</p>

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<p><strong>4.2.2&nbsp; 传热热阻RthCH</strong></p>
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<p>RthCH是器件和散热器接触区域的温度差TC-TH与总耗散功率Ptot的比值：</p>

<p><img alt="传热热阻RthCH" data-entity-type="file" data-entity-uuid="f8b72b67-8a01-4a72-a55c-112c5f22f7b4" src="/sites/default/files/inline-images/3_219.png" /></p>
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<p>规定值仅在器件正确安装时有效（见第8章）</p>
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<p><strong>4.2.3 散热器热阻RthCA</strong></p>
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<p>RthCA是壳温TC和冷却介质温度TA之差与总耗散功率 Ptot的比值：</p>

<p><img alt="散热器热阻RthCA" data-entity-type="file" data-entity-uuid="f95443fc-b56b-437f-8c7c-ae691db8986d" src="/sites/default/files/inline-images/4_193.png" /></p>
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<p><strong>4.2.4&nbsp; 总热阻RthJA</strong></p>
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<p>RthJA是等效结温Tvj和冷却介质温度TA之差与总耗散功率Ptot的比值：</p>

<p><img alt="总热阻RthJA" data-entity-type="file" data-entity-uuid="a3f540d9-cf7e-4655-9bf4-9120424e974b" src="/sites/default/files/inline-images/5_159.png" /></p>

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<p><strong>4.2.5 瞬态内热阻ZthJC</strong></p>
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<p>ZthJC描述了元件热阻随时间的逐渐变化。在数据手册中，ZthJC是用恒定直流规定的，还有一部用脉冲电流规定。此外，部分热阻Rthn和时间常数tn被作为解析函数编在表中。</p>

<p><img alt="ZthJA是以下两项的和" data-entity-type="file" data-entity-uuid="60ac7bdc-db38-44e1-8ac7-d359511c2639" src="/sites/default/files/inline-images/6_145.png" /></p>

<p><strong>4.2.6&nbsp; 散热器瞬态热阻ZthCA</strong></p>

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<p>ZthCA描述了散热器热阻随时间的逐渐变化。ZthCA在单独数据手册中有定义。此外，热阻解析函数的 RthCAn和tn值被列于表格中。散热器通常没有一般定义的瞬态热阻。一方面，瞬态热阻取决于功率半导体和散热器的接触区域。另一方面，冷却方法（自然冷却/强制冷却）和冷却介质的流动也有很大的影响。</p>
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<p>对于自然冷却和油冷，冷却介质的流动是由空气或油的对流造成的。功率耗散限定了对流，因此实际功率耗散是针对自然冷却和油冷确定的。必须注意散热器的正确方向和位置。</p>

<p>对于强制冷却和水冷，冷却介质的流量是指定的。</p>

<p>因脉冲电流造成的短期温度变化与这些参数无关。它们被散热器的大热容量均衡了。</p>

<p>英飞凌提供的散热器已在装好元器件的情况下进行了测试和规定。这些给定的散热器数据包含了器件和散热器之间的传热热阻RthCH。因此，不必考虑此值。</p>
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<p><strong>4.2.7&nbsp; 总瞬态热阻ZthJA</strong></p>
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<p>ZthJA描述了总热阻随时间的逐渐变化。根据瞬态总热阻计算短时负载结温。ZthJA是以下两项的和：</p>

<p><img alt="ZthJA是以下两项的和" data-entity-type="file" data-entity-uuid="6918a9e8-bcec-4cdf-bbbe-5c6d55a1e8df" src="/sites/default/files/inline-images/7_125.png" /></p>
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<p><strong>4.3&nbsp; &nbsp;冷却</strong></p>
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<p><strong>4.3.1&nbsp; 自然空气冷却</strong></p>
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<p>在自然空气冷却（空气对流冷却）过程中，通过空气自然对流排出功率损耗。功率半导体的载流能力通常是在环境温度TA=45°C的条件下确定的。</p>
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<p><strong>4.3.2&nbsp; 强制空气冷却</strong></p>
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<p>在强制空气冷却过程中，通过风扇使冷空气强制通过散热器叶片。功率半导体的载流能力通常是在环境温度TA=35°C的条件下确定的。</p>
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<p><strong>4.3.3&nbsp; 水冷</strong></p>
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<p>在水冷过程中，通过水排出功率损耗。功率半导体的载流能力通常是在进口水温TA=25°C的条件下确定的。</p>
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<p><strong>4.3.4&nbsp; 水冷</strong></p>
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<p>在油冷过程中，通过油排出功率损耗。功率半导体的载流能力通常是在进口油温TA=70°C的条件下确定的。</p>
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