eddie_matos
New Member
Hi all,
This is my first "non-Arduino" electronics project. I'm a mechanical engineer and this is my first go at trying to build a more efficient, economic and compact circuit then what you end up with when using an Arduino.
I'm trying to build a DC-DC step-down converter circuit that will output 5V (0.5A) to a USB socket (for connecting low-power appliances such as mobile phones). The power supply is a 15V solar panel. I know there are tons of example circuits all over the place, and I have already racked up a few hours playing around with a step-down converter using the MC34063(ACN).
My main difficulty is when the available power from the solar panel dips below the load power demand (e.g. when a cloud comes along). When this happens the step-down converter forces the solar panel operating voltage way below the maximum power point voltage (into the variable-voltage zone), and it gets stuck there even after the cloud has passed. I know this is only a problem because I'm choosing to spec my panel operating voltage at 15V instead of 7V. I tried using a 7V panel very successfully: when a cloud came along the resulting decrease in the panel voltage also decreased the output voltage, thereby decreasing the power demand and preventing the input voltage from falling any lower. Unfortunately however, the 15V panel is a must.
I've looked into several maximum power point tracking solutions but none of them seem cheap enough for my needs. My favourite so far is the LT3652 from Linear Tech. You can use it to set a minimum input voltage (e.g. set at the maximum power voltage of the solar panel). So when a cloud comes along and the input voltage drops and hits this set minimum, the output voltage is decreased to lower the power demand and prevent the input voltage from dropping lower.
The problem is that the LT3652 is still pretty expensive and overkill for my needs (it does stuff like temperature compensation and is rated at 2A output), and I really want to try and keep the cost down. So I was basically hoping that someone knew of a cheap and cheerful way to trick the MC34063 into doing something similar. It doesn't need to track the optimum panel voltage to the nearest mV, it just has to prevent the panel voltage from going so low that it gets stuck over there and doesn't come back!
I'd be very grateful for any links to another post, or a website, that describes such a solution. Though if my problem is more than simply not knowing the right search terms, then feel free to tell me go back to my sodding Arduino or something
Cheers,
Ed
This is my first "non-Arduino" electronics project. I'm a mechanical engineer and this is my first go at trying to build a more efficient, economic and compact circuit then what you end up with when using an Arduino.
I'm trying to build a DC-DC step-down converter circuit that will output 5V (0.5A) to a USB socket (for connecting low-power appliances such as mobile phones). The power supply is a 15V solar panel. I know there are tons of example circuits all over the place, and I have already racked up a few hours playing around with a step-down converter using the MC34063(ACN).
My main difficulty is when the available power from the solar panel dips below the load power demand (e.g. when a cloud comes along). When this happens the step-down converter forces the solar panel operating voltage way below the maximum power point voltage (into the variable-voltage zone), and it gets stuck there even after the cloud has passed. I know this is only a problem because I'm choosing to spec my panel operating voltage at 15V instead of 7V. I tried using a 7V panel very successfully: when a cloud came along the resulting decrease in the panel voltage also decreased the output voltage, thereby decreasing the power demand and preventing the input voltage from falling any lower. Unfortunately however, the 15V panel is a must.
I've looked into several maximum power point tracking solutions but none of them seem cheap enough for my needs. My favourite so far is the LT3652 from Linear Tech. You can use it to set a minimum input voltage (e.g. set at the maximum power voltage of the solar panel). So when a cloud comes along and the input voltage drops and hits this set minimum, the output voltage is decreased to lower the power demand and prevent the input voltage from dropping lower.
The problem is that the LT3652 is still pretty expensive and overkill for my needs (it does stuff like temperature compensation and is rated at 2A output), and I really want to try and keep the cost down. So I was basically hoping that someone knew of a cheap and cheerful way to trick the MC34063 into doing something similar. It doesn't need to track the optimum panel voltage to the nearest mV, it just has to prevent the panel voltage from going so low that it gets stuck over there and doesn't come back!
I'd be very grateful for any links to another post, or a website, that describes such a solution. Though if my problem is more than simply not knowing the right search terms, then feel free to tell me go back to my sodding Arduino or something
Cheers,
Ed