Systems and methods to provide enhanced diode bypass paths
Systems and methods are herein disclosed for efficiently allowing current to bypass a group of solar cells having one or more malfunctioning or shaded solar cells without overwhelming a bypass diode. This can be done using a switch (e.g., a MOSFET) connected in parallel with the bypass diode. By turning the switch on and off, a majority of the bypass current can be routed through the switch, which is configured to handle larger currents than the bypass diode is designed for, leaving only a minority of the current to pass through the bypass diode.
1. A bypass switch circuit, comprising:
a bypass transistor having a parasitic diode, the bypass transistor to be connected in parallel with an output of a group of solar cells;
a first diode;
a first capacitor connected in series with the first diode, wherein a path formed by the first diode and the first capacitor is connected in parallel with the bypass transistor;
a single cell converter connected to the first capacitor to receive an input, the single cell converter to generate an output;
a second diode connected to receive the output of the single cell converter;
a second capacitor connected in series with the second diode; and
a controller connected to the second capacitor and configured to activate the bypass transistor in response to the parasitic diode being conductive.
2. The bypass switch circuit of claim 1 , further comprising:
a voltage regulator configured to use the output of the group of solar cells to power the controller when the parasitic diode is not conductive.
3. The bypass switch circuit of claim 2 , wherein the voltage regulator is a low dropout regulator.
4. The bypass switch circuit of claim 1 , wherein time periods to charge and discharge the first and second capacitors determine a duty cycle of the bypass transistor.
5. The bypass switch circuit of claim 4 , wherein after a first time period in which the parasitic diode of the bypass transistor is conductive, the controller activates the bypass transistor for a second time period, and a ratio between the first time period and the second time period is less than 1:100.
6. The bypass switch circuit of claim 1 , further comprising:
a timer coupled with the controller to control a length of a time period during which the controller keeps the bypass transistor activated.
7. The bypass switch circuit of claim 1 , wherein the first diode is configured to be conductive when the parasitic diode of the bypass transistor is conductive; and when the parasitic diode of the bypass transistor is reverse biased, the first diode is reverse biased.
8. A method for controlling electric currents in a photovoltaic system, the method comprising:
charging a first capacitor, in response to a bypass current passing through a parasitic diode of a transistor connected in parallel to an output of a group of solar cells, using a first diode powered by a voltage drop across the parasitic diode;
converting a first voltage across the first capacitor to generate a second voltage;
charging a second capacitor using the second voltage;
powering a controller using the second capacitor; and
activating the transistor using the controller to reduce a voltage drop across the transistor, after the first capacitor and the second capacitor are charged to a predetermined level.
9. The method of claim 8 , wherein the first diode is not conductive when the transistor is activated.
10. The method of claim 9 , further comprising:
discharging the first capacitor and the second capacitor after the voltage drop across the transistor is reduced.
11. The method of claim 10 , further comprising:
deactivating the transistor after the first capacitor and the second capacitor are discharged to a predetermined level.
12. A method comprising:
charging a first capacitor, in response to a bypass current passing through a parasitic diode of a transistor connected in parallel to an output of a group of solar cells, using a first diode, wherein a first terminal of the first diode is connected to a terminal of the transistor, and a second terminal of the first diode is connected to a terminal of the first capacitor, and wherein the first diode is not conductive when the transistor is activated;
converting a first voltage across the first capacitor to generate a second voltage;
charging a second capacitor using the second voltage;
powering a controller using the second capacitor; and
after the first capacitor and the second capacitor are charged to a predetermined level, activating the transistor using the controller.
13. The method of claim 12 , further comprising:
discharging the first capacitor and the second capacitor after the voltage drop across the transistor is reduced.
14. The method of claim 13 , further comprising:
deactivating the transistor after the first capacitor and the second capacitor are discharged to a predetermined level.