Hi
I'm using capacitor power supply to Msp430.In this power supply using three phase,two and single phase supply.In this three and two phase are properly working but in single phase was not properly working.
Input:
240V/50Hz
Output:
5v/30mA is required.
In this i'm now using 100ohm resistance,1.4uF capacitor and 5.6V zener diode with 3.3v regulator need 5v input supply.
Only getting upto voltage of 3.8v for input to regulator.
Wat can i do for getting 5V supply to the regulator.
I already refereed the document(SLAA024) for design process, from this i cant get the proper solution.
The circuit shown is simply a half wave rectifier. The 100 Ohms and 1.4uF limit the current flow and the zener clamps the voltage to 5.6V max. The large cap (C21) is used to keep the voltage up during the periods of the AC cycle where the voltage is less than 5.6V. Since this is a half wave rectification on a single phase, there is a minimum of 10ms (half cycle of 50Hz) where there is no voltage charging C21. You can calculate the value of capacitance needed using I = C (dv/dt). The I is the load current or the current used by the system. dV is the allowable change in voltage on the capacitor 5.6V - 3.6V = 2V (this assumes you need at least 0.3V across the LDO to maintain regulation. dt is the time between AC cycles which is 20ms. If I assume a load current of 100mA then the capacitor would need to be 1000uF.
It is hard to diagnose without schematics and scope shots. I assume you used the circuit on page 3-65 of the app note SLAA024. I am guessing that the ripple voltage is too high and the regulator drops out every cycle. The fewer the phases, the higher the ripple voltage will be. You can check this with a scope on the input of the LDO. If the voltage is dropping out once an AC cycle then you will need to increase the size of Cch that is shown on page 3-65.
Thank u scot
Circuit used for supply was from SLAA391 figure2(capacitor power supply) of page 3.
In this I have used the capacitor value of Cm=1.4uF and Rm=100ohm/6W and Breaking voltage of Zener is 5.6V and charging capacitor value was 220uF.
In slaa024 document formula provided to calculate Cchmin Value.In this what is the T and Del Vch?
I'm new to this field.If there is any mistakes or very basic things to applied plz
apologies me. I searched lot in internet but i not get the answer.Plz reply
Thank u scot lester
You have given a clear explanation on my question.Once again thank u scot, we need ur support to continuously ..
regards
kanakNPK
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