Hybrid High-Side Driver Circuit for Motor Control
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Solution Overview
Problem
Existing motor control systems for synchronous electric motors, such as PWM systems, suffer from high switching losses and lower controller efficiency due to heat dissipation, which can lead to device failure and are not cost-effective or flexible across a wide range of motor loads and speeds.
Innovation Solution
A high-efficiency motor control system utilizing a direct on-off commutation routine and a hybrid high-side driver circuit combining a bootstrap capacitor with a charge pump, allowing for indefinite on-time switching and minimizing heat dissipation, is implemented, featuring a variable voltage power supply and a three-phase inverter with floating charge pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM control is used to control motor speed and torque, then the motor can operate at variable speeds with good control precision, but switching losses increase and controller efficiency decreases
Solution Approach 1:
The patent applies periodic action by using PWM (pulse width modulation) to periodically switch the power supply to the motor. The controller turns the switch on and off at high frequency, varying the duty cycle to control the average voltage and current delivered to the motor, thereby achieving precise speed and torque control while managing switching losses through optimized switching patterns.
Solution Approach 2:
The patent implements dynamics by making the switching frequency and duty cycle variable rather than fixed. The controller dynamically adjusts the PWM parameters based on motor load conditions, speed requirements, and torque demands, allowing the system to optimize performance and minimize switching losses across different operating points.
2Measurement precision
If high-frequency PWM switching is used to control power to the motor, then voltage and current control precision is improved, but power dissipation in switches increases during transitions
Solution Approach 1:
The patent applies skipping by rapidly transitioning the switches through their on-off states in less than 100 nanoseconds. This brief transition period minimizes the time during which both voltage and current are nonzero, thereby reducing power dissipation in the switches while maintaining effective voltage and current control through high-frequency PWM switching.
Solution Approach 2:
The patent implements preliminary action by using bootstrap capacitors to pre-charge the gate voltage of MOSFETs before switching operations. This ensures that switches transition quickly and efficiently between states, reducing the duration of high power dissipation during transitions while maintaining precise control capability.
3Ease of manufacture
If bootstrap technique is used to drive high-side MOSFET gates, then cost-effective control is achieved, but on-time is limited due to rapid capacitor discharge
Solution Approach 1:
The patent merges the bootstrap capacitor technique with additional circuitry including charge pumps and alternative charging paths. This combination allows the high-side MOSFET gates to be driven for extended periods without relying solely on the bootstrap capacitor, thereby maintaining cost-effectiveness while overcoming the limited on-time constraint.
Solution Approach 2:
The patent introduces charge pumps and alternative charging circuits as intermediary mechanisms to replenish the bootstrap capacitor or directly drive the high-side gates. These intermediaries enable extended on-time operation by providing additional energy storage and transfer capabilities while maintaining the cost-effective bootstrap approach.
4Power
If charge pump circuit is used to produce voltage higher than bus voltage for high-side switch gate driving, then voltage boosting capability is achieved, but power capability and output voltage options are limited
Solution Approach 1:
The patent implements universality by designing a hybrid gate drive system that can operate in multiple modes: bootstrap mode, charge pump mode, and alternative charging paths. This multi-functional approach allows the system to adapt to different voltage requirements and power levels, providing versatility across various motor applications while maintaining the ability to generate the necessary gate drive voltage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution achieves higher system efficiency, reduces switching losses, and provides a cost-effective, flexible, and robust motor control system capable of maintaining reliable operation across various loads and speeds.
Implementation Method 1
high-side switch drivers use something called a 'bootstrap' technique to produce a floating voltage to switch the gate of a semiconductor switch such as a MOSFET
Implementation Method 2
The basic charge pump is a circuit that switches back and forth between two capacitors, charging one while using the other, to maintain a certain voltage
Implementation Method 3
during the transitions between 'on' and 'off' states, both voltage and current are nonzero and thus power is dissipated in the switches
Data Source
AI summary
A high-efficiency motor control system and method is presented for controlling an electric motor. The system can feature a multi-phase inverter having a logic control device and associated control circuity, a plurality of floating charge pumps and pump circuitry, a multi-phase bridge having a plurality of power switching devices and a bootstrap capacitor circuit having a floating ground. The floating charge pumps feature grounds electrically coupled to motor phase leads. The bootstrap circuit can feature a floating ground, with a floating voltage being carried across the bootstrap circuit and delivered to the switching devices to produce an indefinite on-time for the switching devices for switching the high-side of a power supply to a load.