Tool/software:
I tried to generate -20V DC output voltage with +5V input with LM2611 EVM and LM 2611 with similar circuit design.
When i use a power supply with current limit setting more than 1.5A. It can generate -20V well with very small current.
However, when i use a power supply with current limit setting less than 1A. it can not generate output voltage well.
In addition, power supply just generate input voltage as 1.5~2.5V with C.C.
I already read the datasheet and checked belows
- Using the desired output voltage, calculate the value of the feedback resistors. The reference voltage is 1.23 V. Resistors of 50 kΩ or less must be used due to the leakage at the NFB pin.
--> So i does not handle the RFB1 and changed RFB2 as 2kΩ to make a resistor less than 50kΩ.
- 8.2.7.2.1 High Duty Cycle and Load Current Operation
The circuit in Figure 35 is used for high duty cycles (D > 0.5) and high load currents. The duty cycle begins to increase beyond 50% as the input voltage drops below the absolute magnitude of the output voltage. RFB3 and CFF2 are added to the feedback network to introduce a low frequency lag compensation (pole-zero pair) necessary to stabilize the circuit under the combination of high duty cycle and high load currents.
--> I also added RFB3,1kΩ, and CFF2, 1uF, but it can not help.
There are only -5V regulation examples in the datasheet.
in Summary,
For the -20V DC regulating circuit with LM2611,
With power supply 5V, 1A setting --> it does not operate well with C.C
With power supply 5V, 2A setting --> it operate well with small current, less than 10mA
I want to apply this circuit to the mobile robot system so that it does not have an enough capability for the current.
I appreciate your attention for this problem, i wish i can get a hint to resolve it.
Thanks
