Zener Diode Selection

It is not necessary to limit the DC-DC converter to a voltage below 40V. It will maintain regulation at high efficiency.

Typically, a TVS (Transient Voltage Suppressor) is used to limit voltage to safe values. TVS are only intended for transient and fault conditions, not for limiting voltages under continuous duty. A series resistor is not usually used with a TVS in power applications.

Tim

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DC to DC Converter:

Zener Diode:

The DC to DC converter can handle input voltage upto 40V. DC to DC converter is configured to output 5V. I do not want the input voltage to exceed 33 Volts. That is why I am using a 33V Zener. But I think that DC to DC converter will work fine if I use 6 to 7 volt and 1A Zener. Since the goal is to keep the output of the DC to DC converter stays at 5V. Am I right?

DC to DC converter is driving a Load of 15 ohms. As shown in the following link

Figure 1 showing a resistor in series with the voltage source of value 17.4 V, Zener does not draw any current and output of the DC to DC converter is desirable. Though if I reduce the value of the resistor to 30 ohm than the voltage at the input of the DC to DC converter will raise to 13.2V.

Figure 3 shows that the Zener will burn and it did.

Questions:

1. Do I need a Zener that can activate at 33V and can handle 2A? OR should I get a 6 volt Zener that can handle 1 02 2 amps? I do want to keep the size of the Zener and resistor small.

1. I measured 62mA series current through 50ohm resistor but measured 300mA at the output of the DC to DC converter. Can someone explain how did this work?

Thanks jess

is configured to output 5V. I do not want the input voltage to exceed 33 Volts. That is why I am using a 33V Zener. But I think that DC to DC converter will work fine if I use 6 to 7 volt and 1A Zener. Since the goal is to keep the output of the DC to DC converter stays at 5V. Am I right?

Zener does not draw any current and output of the DC to DC converter is desirable. Though if I reduce the value of the resistor to 30 ohm than the voltage at the input of the DC to DC converter will raise to 13.2V.

get a 6 volt Zener that can handle 1 02 2 amps? I do want to keep the size of the Zener and resistor small.

the output of the DC to DC converter. Can someone explain how did this work?

Don't do that. Get rid of the series resistor.

Use an emitter follower series pass transistor with the 33V zener attached to the base and a resistor from base to collector to limit the voltage inut to the converter to less than 40V.

Or a source follower NMOS. There are better ways to do this at the expense of a couple of components.

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33 Volts. That is why I am using a 33V Zener. But I think that DC to DC con= verter will work fine if I use 6 to 7 volt and 1A Zener. Since the goal is= to keep the output of the DC to DC converter stays at 5V. Am I right?=20

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.4 V, Zener does not draw any current and output of the DC to DC converter = is desirable. Though if I reduce the value of the resistor to 30 ohm than t= he voltage at the input of the DC to DC converter will raise to 13.2V.=20

d I get a 6 volt Zener that can handle 1 02 2 amps? I do want to keep the s= ize of the Zener and resistor small.=20

mA at the output of the DC to DC converter. Can someone explain how did thi= s work?=20

Haven't you been posting this same question for the past 6 months? If you h= aven't caught on by now, you never will. Time to move on, this project is b= eyond you.