I've read about step up converters working from unbelievably low voltages 20mV , namely the LTC How can circuits even start at those low voltages? I studied the patent that was briefly briefly shown to us by user IgnacioVazquez-Abrams to the extent that I begin to understand the operation of it. The patent doesn't exactly describe the operation of LTC but something very similar to it.
Here's what I made of it. Feel free to offer any corrections. Consider the following picture, taken from the patent :. At the heart of it, there is Q1, a junction FET whose threshold voltage is very near zero volts. So near, in fact, that ambient noise of the current source thermopile or whatever causes changes in the conductivity of Q1. This causes changes in the current through the primary winding of the transformer T1, which transforms the changes in current to changes in voltage at the secondary winding, at the ratio of the windings of the transformer, for example These are then fed back to the gate of the FET, in the case of this schematic at an inverted phase, so that Q1 will further amplify the noise oscillations.
The net effect is that whenever sufficient current is provided by the current source, the circuit formed by Q1, C1 and T1 quickly begins to oscillate at a roughly known rate. As the oscillation starts, an AC voltage is formed at the secondary winding of T1. This will then be rectified, regulated and used to power up the circuitry. In a typical application, a storage capacitor typically a few hundred microfarads is connected to VOUT.
As soon as VAUX exceeds 2. The current available to charge the capacitor will depend on the input voltage and transformer turns ratio, but is limited to about 4. On edit, leaving this up because shows the historical aspect of how the solution was found.
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LTC Material Declaration. Quality And Reliability. Symbols and Footprints. LTC Discussions. All LTC Discussions. Ask your question ». Select a country. Check Inventory. Model Package Pins Temp. Once the output voltage drops below 0. Starting it up again requires the input voltage to rise above the startup voltage threshold. The regulator allows the input voltage to exceed the output voltage without getting damaged while remaining within the absolute maximum ratings.
The output regulation does deteriorate however. If such conditions may occur in your application, make sure the load can handle these higher voltages safely. Our power supply modules are simply awesome because we design them carefully, with you in mind.
Instead we show rather conservative values of what is safely handled. Which means that if you were to push the boundaries, there should be a fair amount of headroom. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Notify me of followup comments via e-mail.
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