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Zener Diode Power Rating Calculation




Output of Zener Diode Power Rating Calculation

Zener Diode Power Rating Calculator is an online electronic tool to measure the values of Power Rating, Resistance Value and Resistance Power Rating. When the normal PN junction diode operates in reverse breakdown voltage, the current through the junction and the power dissipated at the junction will be high. The normal diode will get damaged in such reverse biasing. Whereas, the Zener Diode is a special type of PN junction diode with adequate power dissipation capabilities to operate in the breakdown region. Zenor doide normally used under reverse bias conditions. Zener Diode is heavily doped than ordinary diodes. The breakdown voltage depends upon the doping level. If the diode is heavily doped the breakdown occurs under reverse biasing at the lower breakdown voltage and vice versa. The sharp current increasing under breakdown conditions is due to Avalanche Breakdown and Zenor Breakdown. The diode can be widely used as a voltage regulator. To designing the electronic circuits along with Zenor diodes, the resistance and power rating calculation is necessary. By using this Online Zener Diode Power Rating Calculator, one can easily calculate the resistor value, power rating and resistor power rating based on the input values of Source Voltage, Output Voltage and Maximum Current

稳压二极管功耗计算器

首页 › 电子电路 › 稳压二极管功耗计算器
最后更新: · 公式与示例已人工校对

稳压管长期工作在反向击穿区,功耗等于稳压值乘电流,超过额定值就会热失效。很多电路在设计时只算了负载电流,忘了空载时全部电流都灌进稳压管。这个工具专门核算最坏工况下的管耗与结温,帮你判断要不要加散热或改方案。

使用方法

  1. 填入稳压值、输入电压与限流电阻
  2. 填入负载电流的最小值与最大值
  3. 读取空载与满载时的稳压管电流、功耗与结温估算

计算公式

总电流 Itotal = (Vin − Vz) / Rs 由限流电阻决定
稳压管电流 Iz = Itotal − IL 空载时 Iz 最大,这是最坏工况
管耗 Pz = Vz · Iz 必须小于额定功耗并留 50% 余量
结温 Tj = Ta + Pz · Rth(j-a) Rth 见手册,玻封约 300 ℃/W

计算示例

Vin = 12 V,Vz = 5.1 V,Rs = 220 Ω,负载 0~30 mA
  1. Itotal = (12 − 5.1) / 220 ≈ 31.4 mA
  2. 空载时 Iz = 31.4 mA,Pz = 5.1 × 0.0314 ≈ 0.16 W
  3. 满载 30 mA 时 Iz 仅 1.4 mA,接近截止,稳压效果变差
结果:空载管耗 160 mW,已接近 1/2 W 器件上限,需换 1 W 型号

要点与常见误区

  • 最坏工况永远是负载开路,核算时必须按 IL = 0 检查。
  • 玻封 1/2 W 稳压管在常温下的实际可持续功耗常低于标称值,建议按 60% 使用。
  • 需要长期稳定工作时,稳压管方案不如三端稳压器或 TL431,后者精度与热稳定性都好得多。

常见问题

稳压管发烫正常吗?
温热正常,烫手说明管耗接近上限。用 Pz = Vz·Iz 核算,若超过额定的 60% 就该换大功率型号或改电路。
为什么满载后电压掉下来了?
负载吃掉大部分电流后,稳压管电流低于最小稳压电流,进入曲线拐点以下,稳压失效。
1N4733 能过多大电流?
1N4733 是 5.1 V/1 W 稳压管,理论最大电流约 196 mA,但实际要按散热条件大幅降额。

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