Resolver Excitation Half-Bridge PWM for Low-Loss Coil Driving
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional excitation of a resolver's field coil requires power amplification using push-pull output stages, resulting in high power losses and inefficient use of supply voltage, as transistors operate in a linear mode and require an input voltage twice the output voltage.
Innovation Solution
The use of half-bridges with fully turned-on switching elements for pulse-width modulation (PWM) to generate the excitation voltage, avoiding high-loss linear modes and allowing efficient use of the available supply voltage, with complementary control of switching elements and optional low-pass filters and series capacitors to enhance voltage and protect components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a push-pull output stage is used for power amplification, then the excitation signal can be provided with adequate driver power, but high power losses occur due to transistors operating in linear mode
Solution Approach 1:
The patent changes the operating parameters of the transistors from linear mode to switching mode (fully on or fully off states). This parameter change eliminates the high power loss associated with linear operation while maintaining the ability to provide adequate driver power through PWM control of the half-bridge circuit
Solution Approach 2:
The patent replaces the conventional linear amplification mechanism with a switching mechanism using half-bridge circuitry. The mechanical analogy would be replacing a continuously adjustable valve (linear control) with an on/off switch (switching control), achieving the same power delivery function with much lower losses
2Power
If a push-pull output stage is used, then current amplification can be achieved, but the input voltage must be at least twice as great as the desired output signal amplitude
Solution Approach 1:
The patent changes the voltage utilization parameter by using a half-bridge configuration that can swing the output voltage between VCC and ground (0V). This allows the full supply voltage range to be utilized for the output signal, eliminating the requirement for an input voltage twice as great as the desired output amplitude
Solution Approach 2:
The half-bridge circuit acts as an intermediary between the single-supply voltage source and the resolver field coil. It mediates the voltage delivery by creating a virtual ground reference and enabling bidirectional voltage swings relative to this reference, thereby achieving efficient voltage utilization without requiring excessive input voltage
3Ease of operation
If transistors operate in linear mode, then continuous control of the excitation signal is possible, but high power losses must be dissipated as thermal energy
Solution Approach 1:
The patent employs periodic pulse-width modulation to control the excitation signal. Instead of continuous linear control, the system uses periodic switching actions with variable duty cycles to achieve the desired average output voltage. This periodic action maintains control capability while eliminating continuous power dissipation and associated thermal issues
Solution Approach 2:
The patent substitutes the continuous linear control mechanism with a pulsed switching mechanism. The mechanical analogy would be replacing a continuously adjustable throttle with a series of rapid on/off actions that achieve the same average flow control. This substitution eliminates the continuous energy dissipation inherent in linear mode operation
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 approach significantly reduces electrical losses and allows for precise control of the excitation voltage, enabling efficient and low-loss excitation of the resolver field coil, even with component variations and thermal changes.
Implementation Method 1
The switching elements are therefore not in a high-loss linear mode, in contrast to a push-pull output stage. Instead, a desired output voltage of a half-bridge is produced by means of pulse width modulation (PWM).
Data Source
AI summary
The present invention relates to providing an electrical voltage for exciting an excitation coil of a resolver (2). In this case, the electrical voltage for exciting the excitation coil of the resolver (2) can be generated by means of pulse-width-modulated driving of at least one half-bridge (H1). In this case, the switching elements of the half-bridge (H1) are fully turned on, with the result that losses such as occur during linear operation of semiconductor switches, for example, can be avoided. If appropriate, the voltage (U_e) provided by the half-bridge (H1) can be additionally increased by means of suitable resonant circuits (L1, C1, C3 . . . ).