Good afternoon.
I have a backup controller schematic with a supercapacitor charger based on the LTC3350. Its output doesn't use step-up mode. Instead, the output of the LTC7804 boost converter, powered by the supercapacitor bank, is connected in parallel to VOUT. I noticed that when the charging threshold of 4.5V (the step-up controller's turn-on voltage) is exceeded, the LTC7804 attempts to control the transistors, regulating the output voltage. The LTC7804 is configured for 10V, while VOUT is supplied with 12V from a laboratory power supply. Thus, the LTC7804 inadvertently becomes a supercapacitor charger, since current flows through the upper switch toward the "input," i.e., the connection point of the supercapacitors. Is it possible to avoid controlling the power transistors when VOUT is clearly above or equal to the regulation point? Currently my controller is set to skip pulses at low loads, but this does not help.