SM72445_15 Datasheet, PDF (7/20 Pages) Texas Instruments – SM72445 Programmable Maximum Power Point Tracking Controller With Adjustable PWM Frequency

SM72445
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OPERATION DESCRIPTION
SNVS795 – MARCH 2012
OVERVIEW
The SM72445 is a programmable MPPT controller capable of outputting four PWM gate drive signals for a 4
switch buck-boost converter with an independent Panel Mode. The typical application circuit is shown in Figure 2.
The SM72445 does not require a dedicated switch to implement Panel Mode. The four buck-boost switches can
be controlled to implement PM. A dedicated switch may be used for higher efficiency. Setting the voltage on pin
A2 selects between the options.
The SM72445 uses an advanced digital controller to generate its PWM signals. A maximum power point tracking
(MPPT) algorithm monitors the input current and voltage and controls the PWM duty cycle to maximize energy
harvested from the photovoltaic module. MPPT performance is very fast. Convergence to the maximum power
point of the module typically occurs within 0.01s. This enables the controller to maintain optimum performance
under fast-changing irradiance conditions.
Transitions between buck, boost, and Panel Mode are smoothed. Output voltage and current limiting functionality
are integrated into the digital control logic. The controller is capable of handling both shorted and no-load
conditions and will recover smoothly from both conditions.
ƒ RST pin is pulled low
RESET
ƒ RST pin is pulled low
SOFT-START
ƒ Iout < Iout_th
PM_STARTUP
ƒ Iout < Iout_th
ƒ Iout >= Iout_th
ƒ Iout > Iout_th
AND
Starting time
elapsed
PM
ƒ PM pin is pulled low
ƒ In Buck-Boost mode for x seconds where x can be set on
ADC Ch 2
MPPT
ƒ Every 60 seconds after going into Panel Mode,
MPPT mode will be entered for a maximum of 4
seconds time to check whether or not the converter
is operating at maximum power point
OR
ƒ There is an x% change in power from the power
when panel mode was engaged. This percentage
can be set on ADC Ch 2
Figure 8. High Level State Diagram for Startup
STARTUP
SM72445 has a soft start feature that will ramp its output voltage for a time of 250ms if the bridge is configured to
run at 215kHz and up to 500ms if the bridge is configured for 110kHz.
If no output current is detected during soft-start time, the device will then enter Panel Mode for 60 seconds. A
counter will start once the minimum output current threshold is met (set by ADC input channel 4, pin A4). During
these 60 seconds, any variation on the output power will not cause the chip to enter MPPT mode. Once 60
seconds have elapsed, the unit will enter operational PM mode and the pre-determined power level variation at
the output will engage the chip in MPPT mode.
Copyright © 2012, Texas Instruments Incorporated
Product Folder Links: SM72445
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