High-Side Low-Side Switch Loss Equalization in Multiphase Converters
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Solution Overview
Problem
Existing power stage designs for motor drives experience unequal losses and heating between high-side and low-side switches due to unequal RMS current, leading to reduced torque capability at lower speeds or duty-cycles, and existing pulse-width modulation techniques do not provide an optimal solution across the operating duty-cycle.
Innovation Solution
A multiphase switching converter system with a controller that generates phase-shifted gate drive signals with complementary duty-cycles for high-side and low-side switches, ensuring equalized losses and heating across switch pairs, thereby improving torque capability and reducing cooling complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pulse-width modulation techniques are used, then the control is simple, but unequal losses and heating occur between high-side and low-side switches
Solution Approach 1:
The patent applies asymmetry by intentionally creating asymmetric duty cycles for high-side and low-side switches. Instead of using symmetric 50% duty cycles, the controller assigns different duty cycle values to equalize the RMS current and power losses in both switches, thereby resolving the unequal heating problem while maintaining simple control architecture
Solution Approach 2:
The patent changes the duty cycle parameter dynamically to achieve loss equalization. By adjusting the duty cycle values of high-side and low-side switches based on their respective power loss characteristics, the system optimizes thermal distribution without increasing control complexity
2Loss of energy
If different switches with different on-state resistances are used, then unequal losses are accounted for, but design complexity increases
Solution Approach 1:
The patent applies local quality by assigning different duty cycle values to high-side and low-side switches based on their specific power loss characteristics. This localized parameter adjustment equalizes losses without requiring different switch components, thereby avoiding increased design complexity while effectively addressing the unequal heating issue
3Temperature
If more cooling is provided for the switch with more losses, then heating is managed, but the system complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by proactively equalizing power losses through asymmetric duty cycle assignment before thermal issues arise. This preventive approach distributes heat generation evenly across both switches, eliminating the need for additional cooling measures and reducing overall system complexity
4Speed
If conventional PWM techniques are used, then the torque capability at high speeds is maintained, but torque capability at lower speeds or duty-cycles is reduced
Solution Approach 1:
The patent applies dynamics by making the duty cycle values adaptive and variable. The controller dynamically adjusts the duty cycles of high-side and low-side switches based on operating conditions, enabling optimal torque capability across the entire speed range while maintaining simple control implementation
Data Source
AI summary
An electrical system includes a motor and a plurality of switch pairs, each switch pair having a high-side switch, a low-side switch, and a switch node coupled to the motor. The electrical system also includes gate driver circuitry coupled to each switch of the plurality of switch pairs. The electrical system also includes a controller coupled to the gate driver circuitry. The controller is configured to direct the gate driver circuitry to provide a first set of gate drive signals together with (i.e., overlapping pulses) a second set of gate drive signals, wherein the first set of gate drive signals is phase-shifted relative to the second set of gate drive signals.