The circuit is a voltage doubler, the diodes are sms7630. The reverse breakdown voltage of sms7630 is 2V. In ADS simulation, the output voltage never exceeds 2V. However, in practice, I can get 4.5 V(10dbm input,915MHz) before impedance matching. After matching(at around -7dbm input, the matching components are L1, L2, as figure shows), the output voltage reaches 6.5V (10dbm input,915MHz). The signal source is a signal generator. The plot shows the simulation result of the output voltage( Red line is before matching).
Problem. Sometimes the circuit suddenly goes strange. Firstly, the output voltage will urgently ripple for a while, then it will behave like broken. For example, normally, the output is 1.6V with a -7dbm input, after the strange ripple, it goes down to 0.5V.
I had tried to change a new diode, it will back to normal for a while, but the same problem will still happen. I had tried to change new capacitors, it will work for a while, again, the same problem will occur after a while.
I guess the problems maybe:
1. Somewhere is poor contact? I had checked the circuit and changed PCB, the same problem still happen.
2. The capacitor breaks. The rated voltage of the capacitor is 50V. It is unlikely the problem.
3. The diode is reversed breakdown. I had checked the diode and its reverse resistance is normal. Besides, only change the capacitor can repair the problem for a while.
Why the output voltage can reach a much higher value than the reverse breakdown voltage?
What might the problem?
Can anyone help me to analyze the problem?
Many thanks
Dear Pengyu,
welcome,
If your voltage increases than the breakdown voltage of the diode then it causes the malfunction of the circuit. You have to use a diode with a breakdown voltage at least double the maximum reverse bias voltage of the diode.
The other notice is that your matched output voltage is smaller than the unmatched voltage. This is not correct. The matched voltage is the largest possible output voltage.
You have to adjust your matching circuit. I think you have to use tapped inductor instead of two separate inductors.
For trouble shooting you have to show us the voltage waveform at all nodes.
Also you operate your circuit with no load. It is required to operate it with load.
Your diode may not be damaged but it may act as a zener diode limiting the voltage across it to 2V.
Please consider my comments and report.
Best wishes
Dear Pengyu,
welcome,
If your voltage increases than the breakdown voltage of the diode then it causes the malfunction of the circuit. You have to use a diode with a breakdown voltage at least double the maximum reverse bias voltage of the diode.
The other notice is that your matched output voltage is smaller than the unmatched voltage. This is not correct. The matched voltage is the largest possible output voltage.
You have to adjust your matching circuit. I think you have to use tapped inductor instead of two separate inductors.
For trouble shooting you have to show us the voltage waveform at all nodes.
Also you operate your circuit with no load. It is required to operate it with load.
Your diode may not be damaged but it may act as a zener diode limiting the voltage across it to 2V.
Please consider my comments and report.
Best wishes
Abdelhalim abdelnaby Zekry I think the plot is not correct, just for reference.
On the printed circuit board, the output voltage after matching can reach 6.9V with a 1M ohm load, compared to around 4.5V before matching.
There is a huge difference between simulation and practice.
Abdelhalim abdelnaby Zekry Thank you sir. After a second thought and experiment. I am pretty sure that the problem is the reverse breakdown voltage. The matched circuit can produce 7V voltage, but the diode can only sustain for a short period(within 1 minute in my experiment). It will enter reverse breakdown state after a while.
- Badges
- Science topic
- Similar topics
- Entomology
- Resistance