Two types of diodes commonly used between batteries or inverters and solar panel arrays

- Jan 12, 2019-

Diodes are very important components in the solar panel panel array. The commonly used diodes have the following two types.


1. Anti-back charge (blocking) diode


Between the energy storage battery or the inverter and the solar panel array, a blocking diode is connected in series so that the solar panel is equivalent to a diode with a PN junction to prevent the solar panel from operating at a lower voltage during night or rainy days. When the DC bus voltage is supplied, the battery reversely sends power to the square of the solar panel, thus consuming energy and causing the square to generate heat. It is connected in series in the circuit of the solar panel square array, and acts as a single guide.


Since the blocking diode has a conduction tube voltage drop, the series consumes a certain amount of power when operating in the circuit. The commonly used silicon rectifier diode tube has a voltage drop of 0.6 to 0.8V, and the tube voltage drop of the large-capacity silicon rectifier diode can reach 1 to 2V. If a Schottky diode is used, the tube voltage drop can be reduced to 0.2 to 0.3V, but Xiao The voltage resistance and current capacity of the special diode are relatively small, so pay attention when selecting it.


2. Bypass diode


When there are more solar panel assemblies connected in series to form a solar panel square, it is necessary to connect a single pole in parallel with each solar panel assembly. When one of the components is blocked by a shadow or fails to generate electricity, a forward bias can be formed across the diode to bypass the current, which will not affect the power generation of other normal components, while also protecting the solar panel assembly from Damaged by a higher forward bias or due to "hot spot effect" heating. This type of diode connected in parallel across the component is called a bypass diode.


Silicon rectifier diodes are commonly used in photovoltaic arrays. When selecting models, care should be taken to ensure that their capacity is margined to prevent breakdown damage. Usually, the withstand voltage should be twice the maximum reverse operating voltage, and the current capacity should be twice the expected maximum operating current.


Some controllers have anti-reverse function and can also be connected to the blocking diode. If all of the solar panel components are connected in parallel, the bypass diodes may not be connected. In practical applications, since the bypass diode is added to increase the cost and loss, the bypass diode can be omitted for the case where the number of solar panel components is not connected in series and the field working conditions are good.