Warpspeed
Solar Wizard
I looked at a few prospective pwm voltage mode control chips for this, and all had an excellent error amplifier for battery voltage regulation, but the current limit part needed for solar regulation was usually difficult to use in this application.
One notable exception, was the Texas Instruments TL494. This is becoming a fairly old chip, but it does have two excellent easy to use error amplifiers, and works very well in this application.
Error amplifier one is used for solar voltage regulation, and is connected the opposite way around to conventional. The inverting input becomes the solar voltage input, and the non inverting input the fixed +5v reference. As solar voltage rises, the duty cycle is increased to act as a shunt voltage regulator.
Error amplifier two regulates battery voltage in the normal way. The non inverting input comes from battery, the inverting input from the +5v reference. This holds a constant voltage regulated battery voltage, once bulk charging is completed.
Each error amplifier can be over compensated with a very simple type one integrator. We do not need to have super fast optimally damped transient response ! Just complete stability, and error corrections can be comparatively qute slow, and it will still be much faster than a perturb and observe algorithm.
This just drives a conventional buck converter in the usual way. It could not be any simpler.
One notable exception, was the Texas Instruments TL494. This is becoming a fairly old chip, but it does have two excellent easy to use error amplifiers, and works very well in this application.
Error amplifier one is used for solar voltage regulation, and is connected the opposite way around to conventional. The inverting input becomes the solar voltage input, and the non inverting input the fixed +5v reference. As solar voltage rises, the duty cycle is increased to act as a shunt voltage regulator.
Error amplifier two regulates battery voltage in the normal way. The non inverting input comes from battery, the inverting input from the +5v reference. This holds a constant voltage regulated battery voltage, once bulk charging is completed.
Each error amplifier can be over compensated with a very simple type one integrator. We do not need to have super fast optimally damped transient response ! Just complete stability, and error corrections can be comparatively qute slow, and it will still be much faster than a perturb and observe algorithm.
This just drives a conventional buck converter in the usual way. It could not be any simpler.