Replacing 48 MLCCs with 4 LKZ Capacitors for Compact, Cost-Effective Robot Joint Motor Controllers
1. Robot Joint Miniaturization Puts Greater Design Pressure on DC-Link Capacitors
High-performance robots, including quadruped robots, are increasingly moving toward higher integration, lower weight, and more compact mechanical designs. As a result, the space available for power components inside robot joint motor controllers is becoming increasingly constrained.
In a joint drive system, the DC-Link capacitor is positioned at the input of the drive bus, close to the power MOSFET bridge. Its primary functions are to absorb DC-bus voltage ripple and provide support for transient high-current demands during motor acceleration and deceleration. Its performance can therefore directly affect power stability and the accuracy of motor-control operation.
For DC-Link capacitor design in robot joint motor controllers, several requirements must be addressed simultaneously: sufficient capacitance, high ripple-current capability, limited PCB space, and overall bill-of-materials (BOM) cost.
In an actual quadruped robot joint motor project, a conventional solution using multiple MLCCs in parallel had become increasingly difficult to meet all of these requirements at the same time.
2. 48 Parallel MLCCs Increase Component Count—and Add New Engineering Challenges
The customer’s original design used 48 × 100 V, 10 μF MLCCs in a 1210 package, connected in parallel.
Using a large number of parallel ceramic capacitors consumed a significant amount of PCB real estate, making it more difficult to further reduce the size of the drive unit for a compact robot joint module. At the same time, the high component count increased the overall bill-of-materials (BOM) cost.
Another limitation was the capacitance available from each individual MLCC. The overall solution struggled to handle high-current load conditions. During actual operation, the capacitors exhibited noticeable thermal buildup, accompanied by increased operating noise.
As power stability and dynamic response were affected, the motor-control system also failed to achieve the required level of control accuracy expected by the project.
For robot manufacturers, however, the resulting cost goes beyond the purchase price of the capacitors themselves. When a large number of components consume valuable PCB space, designing a more compact joint structure becomes more challenging. Insufficient high-current capability can lead to increased heat generation and noise, which may further affect overall robot performance. And when the dynamic response of the power supply begins to affect control accuracy, DC-Link capacitor selection becomes an integral part of the system-level performance.
3. YMIN LKZ Series: Reconfiguring DC-Link Energy Storage with Four 150 μF Capacitors
To address the requirements described above, YMIN replaced the original MLCC configuration with its LKZ series liquid aluminum electrolytic capacitors.
The LKZ series uses high-density materials and advanced vibration-resistant construction to provide high capacitance in a compact package.
For the 100 V, 150 μF LKZ specification used in this project:
- Capacitance: 150 μF per capacitor
- ESR: As low as 200 mΩ
- Ripple current: 0.9 A per capacitor
- Dimensions: 8 × 25 mm
The actual solution uses four 100 V, 150 μF LKZ capacitors in parallel, each measuring 8 × 25 mm.
This configuration provides a total capacitance of 600 μF.
Compared with the original configuration of 48 × 100 V, 10 μF MLCCs, the LKZ solution significantly reduces the number of components required to provide the DC-Link energy-storage function by increasing the capacitance available from each individual capacitor.
This change in architecture addresses capacitance, PCB layout, and component count simultaneously, providing a simpler and more compact implementation for robot joint designs.
4. Replacement Results: Improvements in Space, Cost, and Operating Performance
In this project, the original configuration of 48 × 100 V, 10 μF MLCCs was replaced with four 100 V, 150 μF LKZ capacitors in an 8 × 25 mm package.
For the customer, the approximately 20% reduction in occupied space and more than 60% reduction in overall cost delivered direct and quantifiable project value.
At the same time, the increased high-current capability—nearly doubling that of the original solution—resolved the previous issues of excessive heat generation and operating noise, while enabling the motor-control system to achieve the required control accuracy.
With a single capacitor configuration change, the design addressed multiple objectives simultaneously, including hardware miniaturization, BOM cost reduction, operating stability, and control performance.
5. Reducing More Than Component Count: Simplifying Design and Production
Reducing the number of capacitors from 48 to four creates a fundamental difference in the system-level design approach between the LKZ solution and the original MLCC configuration.
The original design required a large number of parallel components to achieve the required capacitance, meaning the PCB had to reserve installation space for dozens of capacitors.
By contrast, the LKZ solution uses four 150 μF capacitors in parallel to achieve a total capacitance of 600 μF, significantly reducing the number of components required in the DC-Link section.
For a robot joint module, this translates into approximately 20% savings in physical space, leaving greater layout flexibility for other circuits and mechanical structures.
From a cost perspective, the overall project cost was reduced by more than 60%.
This value does not come from a single parameter improvement. Instead, it results from a more efficient combination of component count, capacitance configuration, PCB footprint, and high-current capability.
6. The 100 V LKZ Series Offers Multiple Capacitance Options
To accommodate different capacitance requirements, the 100 V LKZ series is available in a range of coated aluminum-can configurations. Depending on the specific design requirements, individual capacitors can be used alone or connected in parallel to achieve the required capacitance and current-handling capability.
The 100 V LKZ configuration used in this quadruped robot joint motor controller is 4 × LKZ 100 V, 150 μF, 8 × 25 mm, providing a total capacitance of 600 μF.
Because operating conditions and capacitance requirements vary across applications, the actual capacitor configuration should be selected and validated based on the specific system requirements.
7. Making Capacitor Selection Serve System-Level Value, Not Just Individual Specifications
In this application, the value of the LKZ solution extends beyond improvements in any single electrical parameter. Instead, it lies in improving the overall efficiency of the DC-Link design.
By reducing the number of parallel components and optimizing the capacitance configuration, the customer achieved a more compact capacitor solution within the available PCB space, while maintaining the power-handling capability required under highly dynamic loads, operating stability, and cost control.
For robot joint motor controllers, this type of design optimization can further reduce the constraints that capacitor selection places on mechanical layout, thermal management, and control performance. In this way, the capacitor configuration can better support the overall goals of robot miniaturization and reliable operation.
YMIN can provide LKZ series datasheets, internal test reports, samples, and technical selection support. For further information, please contact our technical support team at ymin-sale@ymin.com.
Note: The data presented in this article are based on YMIN internal testing and feedback from actual customer applications. Typical values are provided for reference only. Actual performance should be verified against the applicable datasheet.
Learn More About YMIN LKZ Series Capacitors
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