Zener Diode Series Resistor
Design the series resistor for a Zener shunt regulator from the input range, Zener voltage, and load current, and check Zener current, power, and light-load / full-load / maximum-input conditions.
Key points
Zener Diode Series Resistor: Design the series resistor for a Zener shunt regulator from the input range, Zener voltage, and load current, and check Zener current, power, and light-load / full-load / maximum-input conditions. Formula: R = (Vin − Vz)/(Iz + Iload) ｜ P_R = (Vin − Vz)²/R ｜ Pz = Vz·Iz. Enter parameters on the DD-CAT IDE online tool page to get results instantly, with a calculation-model diagram that updates with the inputs. The Zener must be reverse-biased. The series resistor carries both load current and minimum Zener current, so a larger load needs a smaller resistor and higher dissipation. Check regulation at minimum input and Zener dissipation at maximum input; both boundaries matter.
Inputs
R = (Vin − Vz)/(Iz + Iload) ｜ P_R = (Vin − Vz)²/R ｜ Pz = Vz·IzCalculation model (updates with parameters)
| Recommended series resistor R | 470 Ω | idealValue 460 Ω, by E24 nearest value |
| Resistor current at nominal input | 14.68 mA | R 上current = 稳压管current + loadcurrent |
| Zener current at nominal input | 4.681 mA | 设计target 5 mA |
| Zener current at minimum input | 2.128 mA | needs ≥ 拐点current 1 mA |
| Zener current at maximum input | 7.234 mA | 最坏dissipation工况 |
| Resistor dissipation at maximum input | 139.6 mW | 按最高Input voltageCalculate，选Resistance留 2 ×裕量 |
| Zener dissipation at maximum input | 36.89 mW | 额定 0.50 W |
| Suggested Zener power rating | 0.25 W | 按 2 ×dissipation裕量选取 |
| Zener power margin | 13.55 × | recommend ≥2× |
Engineering notes
- The Zener must be reverse-biased. The series resistor carries both load current and minimum Zener current, so a larger load needs a smaller resistor and higher dissipation.
- Check regulation at minimum input and Zener dissipation at maximum input; both boundaries matter.
- Zener regulators suit low-current, low-cost, low-precision rails; use an LDO or switching supply for higher current or efficiency.
FAQ
- What is Zener Diode Series Resistor for?
- Design the series resistor for a Zener shunt regulator from the input range, Zener voltage, and load current, and check Zener current, power, and light-load / full-load / maximum-input conditions.
- What is the formula for Zener Diode Series Resistor?
- Core formula: R = (Vin − Vz)/(Iz + Iload) ｜ P_R = (Vin − Vz)²/R ｜ Pz = Vz·Iz. The tool returns results instantly using this formula and the selected parameters.
- What engineering notes should I keep in mind when using Zener Diode Series Resistor?
- The Zener must be reverse-biased. The series resistor carries both load current and minimum Zener current, so a larger load needs a smaller resistor and higher dissipation. Check regulation at minimum input and Zener dissipation at maximum input; both boundaries matter. Zener regulators suit low-current, low-cost, low-precision rails; use an LDO or switching supply for higher current or efficiency.