convert 0 - 5v to 0 - 10v supply - Page 1
Forum section: electronics / projects

author: brownt
author_rank: Regular Contributor
timestamp: March 21, 2018, 12:26:58 am
content: Hi,what type of circuit could be used to convert a 0 - 5v DC supply to a 0 - 10v supply. I have an application where 0 - 5 volts is required most of the time, but sometimes 0 - 10 volts is required. With the 5v application, 5v cannot be exceeded, and so I am looking for some type of inline conversion circuit that can be inserted and removed as required. About 2mA is all that is requiredthanks

author: Zero999
author_rank: Super Contributor
timestamp: March 21, 2018, 10:07:57 am
content: Quote from: blueskull on March 21, 2018, 09:35:10 amUnfortunately the LM2660 is only specified to work down to 1.5V.Quote from: brownt on March 21, 2018, 12:26:58 amYou need a permanent power supply to do this. There is no component capable of converting 0V to 5VDC to 0V to 10VDC, with no other power source. If there is no external power supply, a small battery could be used to power an amplifier or charge pump.

author: brownt
author_rank: Regular Contributor
timestamp: March 22, 2018, 07:33:05 am
content: I see. So, if I drive the LM2660 with say 2.6 volts, there will be 5.2 out, and driven with 5 volts there will be 10 volts out etc. I mean is it a direct linear conversion?

author: Zero999
author_rank: Super Contributor
timestamp: March 22, 2018, 09:40:41 am
content: Quote from: brownt on March 22, 2018, 07:33:05 amYes, that's correct. The output of the LM2660 is equivalent to double the input voltage, in series with a resistor. The data sheet specifies a typical output resistance of 6.5Ohm, at a supply voltage of 5V, but it will be higher, at lower supply voltages, because the internal switching MOSFETs won't have quite as much gate drive.If the input voltage is reduced below 1.5V, it might not work properly. It's possible it will work below 1.5V, but there is no guarantee, one IC might and another might not. There is likely to be some hysteresis, i.e. it might start working when the voltage is ramped up to 1.4V, but not stop working, until its reduced below 1.2V. Temperature could also be a factor too with it working below 1.5V at room temperature, but failing when it's very hot or cold.

author: brownt
author_rank: Regular Contributor
timestamp: March 23, 2018, 04:06:57 am
content: I see. thanks. Not working over the full range is a problem. Using an external power supply is fine, but what type of circuit is required?

author: brownt
author_rank: Regular Contributor
timestamp: March 23, 2018, 05:01:24 am
content: can you provide some detail?

author: brownt
author_rank: Regular Contributor
timestamp: March 23, 2018, 05:54:53 am
content: I see. A non-inverting op-amp configuration with two resistors with a 1:2 ratio. So perhaps 100k and 220k. How does the size of the values relate. For example 1M:2.2M; 100k:220K; 10k:22k etc.Also, how do you get exactly double?

author: brownt
author_rank: Regular Contributor
timestamp: March 23, 2018, 09:49:53 am
content: I see. I'll give it a go. thanks

author: Zero999
author_rank: Super Contributor
timestamp: March 23, 2018, 10:49:28 am
content: Note that the op-amp can't boost the voltage, above the supply voltage. It will need to be powered from at least 10V, if it has a rail-to-rail output or at least 12V if not.The simplest power supply is a couple of 9V batteries in series, for a single supply op-amp, such as the LM358 or LM321. A small 12V battery such as the A23 battery could be used with a low power, rail-to-rail OPA705 op-amp is probably the most compact solution, but the resistor values should be high, to keep power consumption to a minimum. Another option is running the LM358 or LM321 from a charge pump, such as the ICL7660 and 9V battery.