Systems and Methods to Provide Enhanced Diode Bypass Paths

• US 20120199172A1
• Filed: 09/16/2011
• Published: 08/09/2012
• Est. Priority Date: 03/15/2010
• Status: Active Grant

• Current Assignee: Tigo Energy, Inc
• Original Assignee: Tigo Energy, Inc
• Inventors: Avrutsky, Mordechay
• Granted Patent: US 9,425,783 B2
• Time in Patent Office: Days
• US Class Current: 136/244
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 2207/10 Control circuit supply, e.g. means for supplying power to the control circuit
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 3/04 by static converters
• CPC Class Codes: H03K 17/082 by feedback from the output to the control circuit
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

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.

Claims

1. A solar panel, comprising:

a set of solar cells; and

a bypass switch circuit connected to the set of solar cells and configured to allow a bypass current to bypass the set of solar cells, the bypass switch circuit comprising;

a bypass transistor connected in parallel with an output of the set of solar cells, wherein when activated the bypass transistor provides a path for the bypass current, the bypass transistor having a parasitic diode;

a first diode connected to receive the output and configured to be conductive when the parasitic diode of the bypass transistor is conductive; and

a control circuit coupled with the bypass transistor and the first diode to activate the bypass transistor in response to the parasitic diode of the bypass transistor becoming conductive.

2. The solar panel of claim 1, wherein the control circuit comprises:

an energy storage device connected to the first diode to be charged when the parasitic diode is conductive, the energy storage device to provide a first voltage;

a voltage converter connected to the energy storage device to generate a second voltage from the first voltage; and

a controller connected to the voltage converter and the bypass transistor to use the second voltage to control the bypass transistor.

3. The solar panel of claim 2, wherein the voltage converter is a single cell converter.

4. The solar panel of claim 2, wherein the energy storage device is a capacitor connected to be charged using a voltage drop difference between the parasitic diode and the first diode.

5. The solar panel of claim 4, wherein after the bypass transistor is activated, the controller is configured to deactivate the bypass transistor after a predetermined time period has elapsed.

6. The solar panel of claim 5, wherein a ratio of a time period in which the parasitic diode of the bypass transistor is in a conductive state, to a subsequent time period in which the controller keeps the bypass transistor in an activated state, is less than 1:

100.

7. The solar panel of claim 2, wherein the bypass transistor is a power MOSFET.

8. The solar panel of claim 2, further comprising a low dropout regulator connected to receive the output from the set of solar cells and configured to supply power to the controller when the parasitic diode is not conductive.

9. The solar panel of claim 2, wherein the controller is configured to control a gate of the bypass transistor for activation of the bypass transistor, based at least in part on a voltage on the energy storage device.

10. 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.

11. The bypass switch circuit of claim 10, 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.

12. The bypass switch circuit of claim 11, wherein the voltage regulator is a low dropout regulator.

13. The bypass switch circuit of claim 10, wherein time periods to charge and discharge the first and second capacitors determine a duty cycle of the bypass transistor.

14. The bypass switch circuit of claim 13, 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.

15. The bypass switch system of claim 10, 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.

16. The bypass switch system of claim 10, 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.

17. 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.

18. The method of claim 17, wherein the first diode is not conductive when the transistor is activated.

19. The method of claim 18, further comprising:

discharging the first capacitor and the second capacitor after the voltage drop across the transistor is reduced.

20. The method of claim 19, further comprising:

deactivating the transistor after the first capacitor and the second capacitor are discharged to a predetermined level.