Can the Two H-Bridges of L293D be Used to Drive the Same Motor for Higher Current?

When discussing the use of H-bridges to drive motors, one common question that arises is whether it's possible to use two H-bridges in parallel to achieve higher current capabilities. The short answer is that it is possible, but it is not recommended. This article will explore the challenges and risks associated with parallel H-bridge usage, the alternatives that can be employed, and a comparison with more powerful H-Bridge ICs.

Understanding H-Bridges and Motor Current Requirements

H-Bridges, such as the popular L293D, are integral components in the world of motor control. They are designed to switch current flow, allowing the motor to rotate in either direction with varying speeds. Each H-bridge provides a channel for the motor to draw current, and properly designed H-Bridges can handle a range of current requirements.

Challenges in Parallel H-Bridge Usage

While it is technically possible to connect two L293D H-bridges in parallel to drive the same motor and achieve higher current, this approach is fraught with significant risks and inefficiencies:

Risk of Uneven Current Distribution

One of the main hazards of connecting two H-bridges in parallel is the risk of uneven current distribution. During the initial start-up of the motor, the high current required can overload one H-bridge while the other remains underutilized. This can lead to overheating and damage to the H-bridge ICs.

Potential for Short Circuit

Another significant drawback is the likelihood of a short circuit. If the two H-bridges are not synchronized properly, the higher current demand could result in a momentary or sustained overcurrent through one H-bridge. This can cause the IC to switch on before the other, leading to a potential short circuit and damage to the components.

Alternatives to Consider

Given the risks associated with using two H-bridges in parallel, there are several alternative solutions that can be considered:

Relay Control

One solution is to use a relay to switch between H-bridges based on the current demand. This approach ensures that only the necessary H-bridge is active at any given time, reducing the risk of overheating and current imbalance. Relays are well-suited for high-current applications and can handle the transient current spikes that occur during motor start-up.

Power Switching

Another option is to incorporate a power switch in the circuit. A power switch, such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or IGBT (Insulated-Gate Bipolar Transistor), can be used to switch between the H-bridges. This approach ensures that the motor is only drawing current from the active H-bridge, thus reducing the risk of short circuits and uneven current distribution.

Alternative High-Current H-Bridge ICs

For applications that require high currents, it is advisable to consider more robust H-Bridge ICs. Here are a few options that can support higher current requirements:

TB Series ICs

The TB series of H-Bridge ICs is designed for high-powered motor control applications. These ICs provide higher current capabilities and are less prone to the risks associated with parallel H-bridge usage. The TB6560 and TB67R226, for example, are suitable for applications requiring currents ranging from 5A to 20A.

DRV Series ICs

The DRV series, such as the DRV8833, offers high current drive capabilities and is widely used in industrial and robotics applications. These ICs are equipped with advanced protection features and can handle currents up to 3.5A, making them a reliable choice for high-demand applications. Furthermore, the DRV series often has lower heat generation, reducing the need for extensive cooling solutions.

Comparison of L298N, TB6612, and DRV8833

For a detailed comparison of the L298N, TB6612, and DRV8833, you can refer to the following link: L298N vs TB6612 vs DRV8833: High Current Driver Comparison. This comparison will provide you with a comprehensive understanding of the features, current capabilities, and applications of each H-Bridge IC.

Conclusion

In summary, while it is technically possible to use two H-bridges, such as the L293D, in parallel to achieve higher current, it is not recommended due to the risks of uneven current distribution and potential short circuits. Instead, consider alternative solutions such as relays, power switches, and high-current H-Bridge ICs like the TB series and DRV series. These alternatives offer a safer and more reliable way to drive motors with high current demands.