Can Schottky diodes be used in parallel?

Schottky Diode is widely used in various power supplies and rectifier circuits because of its low direct voltage and fast recovery time. Many engineers will consider whether Schottky diodes can be used in parallel when designing high current power supply or load.

Principle of Schottky Diodes in Parallel

Schottky diode is different from conventional PN junction diode, and its schottky junction formed by the contact between metal and semiconductor material has lower direct voltage drop and very fast switching speed. Using multiple Schottky diodes in parallel is usually to increase the current carrying capacity, thus improving the overall performance of the circuit. Compared with conventional diodes, the design of Schottky diodes in parallel is more difficult, mainly because the characteristics and working mode of Schottky diodes have higher requirements for parallel design.

Advantages of Schottky Diodes in Parallel

Improve current carrying capacity: Schottky diode has low direct voltage drop and fast recovery characteristics, but its current carrying capacity is relatively small. By connecting multiple Schottky diodes in parallel, the current can be shared with each diode, thus improving the current handling capacity of the circuit and avoiding the overload of a single diode.

Reduce power consumption: The low direct voltage drop of Schottky diodes makes them generate lower power consumption when working. By connecting a plurality of diodes in parallel, the power loss of each diode is small, thus reducing the energy loss of the whole system and improving the efficiency.

Improve the reliability of the system: If one Schottky diode fails due to overload or fault, other diodes can still work, thus improving the fault tolerance and reliability of the system.

Challenge of Schottky Diodes Parallel Connection

Although the use of Schottky diodes in parallel can bring many advantages, there are still some challenges in actual design. Due to the characteristics of Schottky diodes, especially the slight difference in direct voltage, they may face the following problems when used in parallel:

Direct voltage is inconsistent: direct voltage of Schottky diodes is usually low, but there may be slight differences in direct voltage between Schottky diodes of different batches, brands and even the same model. Direct voltage difference will lead to uneven distribution of current between parallel diodes, which may cause some diodes to bear too much current, resulting in overheating and damage.

Thermal runaway problem: The direct voltage of Schottky diode increases with the increase of temperature. When the temperature of a diode rises, its direct voltage will increase slightly, which may cause the diode to share less current, thus causing the temperature to rise further, resulting in the phenomenon of thermal runaway. If one of the diodes in parallel goes into a thermal runaway state, it will heat up faster and fail, which will affect the stability of the whole circuit.

Uneven current distribution: Even Schottky diodes of the same model have slightly different direct voltage due to process differences. The current will flow more through the diode with lower direct voltage, while the diode with higher direct voltage will share less current, which may lead to uneven current distribution and affect the performance and stability of the circuit.

How to optimize the parallel design of Schottky diodes

In order to ensure that Schottky diodes can share current evenly when connected in parallel, and avoid uneven current distribution and thermal runaway, the following are some suggestions for optimal design:

Choose diodes of the same model and batch: In order to ensure the same direct voltage of diodes, it is best to choose Schottky diodes of the same model and batch. This ensures that the characteristics of diodes are as consistent as possible, thus avoiding uneven current distribution.

Use current-sharing resistor: To ensure even current distribution, a small resistor can be connected in series between each parallel Schottky diode and the load. These resistors can balance the current, make the current borne by each diode more uniform, and reduce the risk of overheating of individual diodes.

Choose an appropriate heat dissipation scheme: Schottky diode's low direct voltage and fast recovery make it generate less heat when it works, but with the increase of current, the heat dissipation problem still needs to be considered. In order to avoid diode failure caused by excessive temperature, we should ensure that the circuit has sufficient heat dissipation measures, such as using a radiator, increasing the heat dissipation area, or using a package with better heat dissipation performance.

Use protection circuit: Adding protection circuit (such as overcurrent protection and thermal protection) to the circuit can avoid causing more serious problems when a diode fails. The protection circuit can detect the abnormality in time and cut off the current, so as to prevent the whole power supply system from being damaged.

It is an effective method to use Schottky diodes in parallel to improve current carrying capacity, reduce power consumption and improve system reliability. However, due to the direct voltage and temperature characteristics of Schottky diodes, the current distribution may be uneven, so special attention should be paid to these problems in design.