jedd999
Newbie level 5
I have a circuit I am treating as a "black box" but it involves a switching regulator. I am trying to "inject current" into the feedback loop of the regulator in order to change the output voltage, but I find that when I do so, it throws both the circuit involving the regulator, and the current source I have created into an unstable state. The current source I used is basically the howland current source (with no zener diode because current must flow in both directions) **broken link removed**
I find that when I greatly increase the output resistance of the current source, then the circuit with the regulator doesnt break down, but the power dissipation of the current source is just way too high (in the range of over 100W). What I need is a design of a current source where the source generation and the load are ISOLATED from one another, so that the feedback loop of the regulator circuit will not affect the current source in any way!
The reason I want to do this is because just using eepots to change resistor values is not stable / accurate enough... the current source i need has to be in the range of -20 to 20 mA, so stability / low noise is a MUST.
Also, any good information about switching regulators, and IF I CAN actually change the output voltage of the switching regulator by injecting current would be awesome!
Any help would be greatly appreciated!
I find that when I greatly increase the output resistance of the current source, then the circuit with the regulator doesnt break down, but the power dissipation of the current source is just way too high (in the range of over 100W). What I need is a design of a current source where the source generation and the load are ISOLATED from one another, so that the feedback loop of the regulator circuit will not affect the current source in any way!
The reason I want to do this is because just using eepots to change resistor values is not stable / accurate enough... the current source i need has to be in the range of -20 to 20 mA, so stability / low noise is a MUST.
Also, any good information about switching regulators, and IF I CAN actually change the output voltage of the switching regulator by injecting current would be awesome!
Any help would be greatly appreciated!