PWM Half-Bridge Resolver Excitation With Lower Power Loss
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Solution Overview
Problem
Conventional excitation of resolver coils results in high power losses due to linear operation of transistors in push-pull output stages, requiring high input voltages and inefficient energy use.
Innovation Solution
The use of half bridges with fully switched semiconductor switching elements and pulse width modulation (PWM) to generate excitation voltage, minimizing losses and allowing efficient use of available supply voltage, along with complementary control of switching elements and optional dead time to prevent short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a push-pull output stage with linear mode transistors is used for power amplification, then the excitation signal can be amplified, but high power losses occur due to linear operation
Solution Approach 1:
The patent changes the operating parameters of the transistors from linear mode to switching mode (fully on or fully off). This parameter change eliminates the high power losses associated with linear operation while maintaining the required power amplification capability through PWM control of the half-bridge circuit.
Solution Approach 2:
The patent employs pulse width modulation (PWM) which uses periodic switching action to control the average output power. The transistors are switched on and off periodically at high frequency, allowing the excitation voltage to be generated with minimal power loss while achieving the required average power level through duty cycle control.
2Power
If a push-pull output stage is used for current amplification, then the excitation signal can be driven, but high input voltage is required compared to output voltage
Solution Approach 1:
The patent changes the voltage utilization parameter by using a half-bridge configuration that can efficiently switch between positive and negative supply voltages. This allows the full supply voltage range to be utilized at the output, eliminating the requirement for input voltage to be twice the output voltage amplitude as in conventional push-pull stages.
Solution Approach 2:
The patent replaces the conventional push-pull output stage with a half-bridge circuit topology. This substitution fundamentally changes how voltage and current are amplified, allowing for more efficient voltage utilization and eliminating the need for high input voltage margins while maintaining current amplification capability.
3Power
If linear mode operation is used in transistors, then power amplification can be achieved, but high power dissipation as thermal energy occurs
Solution Approach 1:
The patent changes the transistor operating state from linear mode to switching mode. In switching mode, transistors operate either fully on (low resistance) or fully off (high resistance), minimizing the time spent in the high-power-dissipation linear region. This parameter change dramatically reduces thermal energy dissipation while maintaining power amplification through PWM control.
Solution Approach 2:
By using periodic switching action at high frequency, the patent minimizes the duration that transistors spend in the linear operating region where power dissipation is highest. The rapid switching between on and off states ensures that thermal energy dissipation is minimized while the average power amplification requirement is met through duty cycle modulation.
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 adjustment of excitation voltage, enabling efficient and effective excitation of resolver coils while avoiding high power dissipation as thermal energy.
Implementation Method 1
Instead, a target output voltage of a half-bridge is generated by pulse width modulation (PWM). The individual switching elements in the half-bridge are fully switched on.
Implementation Method 2
Unlike a push-pull output stage, the switching elements are not operating in a lossy linear mode. This significantly reduces electrical losses and allows for precise adjustment of excitation voltage.
Data Source
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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 (Hl). In this case, the switching elements of the half-bridge (Hl) 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 (Hl) can be additionally increased by means of suitable resonant circuits (LI, CI, C3...).