Inverter Pulse Shaping for Ultrasonic Tool Harmonic Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power tool inverters generate significant harmonic components in the supply voltage for ultrasonic devices, requiring large filters to attenuate these harmonics, which can be cumbersome and inefficient.
Innovation Solution
The method involves controlling the inverter to emit at least two voltage pulses during half a period of the supply voltage, with the number of pulses adjusted based on the electrical power delivered, using a digital pulse signal generator to optimize the control signal and reduce harmonic components, potentially omitting the need for harmonic filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the inverter emits a conventional single voltage pulse per half period, then the control is simple, but the harmonic components in the supply voltage are significant
Solution Approach 1:
The voltage pulse per half period is segmented into multiple individual pulses (at least two). By dividing a single pulse into multiple segments, the harmonic content of the overall waveform is reduced while maintaining the fundamental frequency output, thus resolving the contradiction between control simplicity and harmonic reduction.
Solution Approach 2:
The inverter employs periodic voltage pulses within each half period, where pulses are repeated at specific intervals. This periodic action pattern allows for harmonic cancellation while maintaining the required output frequency, addressing the contradiction between simple control and harmonic suppression.
2Object-generated harmful factors
If filters are used to attenuate harmonic components, then the harmonics are suppressed, but the filter size and complexity increase
Solution Approach 1:
Harmonic suppression is achieved through preliminary action by shaping the voltage pulses before they reach the output. By pre-configuring multiple pulses with specific timing and duration within each half period, the harmonics are attenuated at the source, eliminating the need for large downstream filters.
Solution Approach 2:
The invention converts the potential harm of multiple switching operations into a benefit by strategically positioning multiple voltage pulses to cancel harmonics. The switching actions that could generate harmonics are instead used constructively to suppress them through interference cancellation, eliminating the need for additional filtering components.
3Object-generated harmful factors
If the number of voltage pulses per half period is increased, then the harmonic components are reduced, but the switching frequency and losses increase
Solution Approach 1:
The pulse configuration is made dynamic and adaptive based on operating conditions. The control system adjusts the number, duration, and spacing of voltage pulses according to the electrical power delivered and load conditions, optimizing the balance between harmonic suppression and switching losses in real-time.
Solution Approach 2:
The invention changes key parameters of the voltage pulses including duration, spacing, and number of pulses based on the electrical power being delivered. By dynamically adjusting these parameters, the system achieves harmonic reduction while minimizing switching losses through optimized pulse widths and intervals.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to power electronics and to a method for actuating an inverter for outputting an AC voltage to an ultrasound device, wherein, depending on the current and/or the voltage, an actual variable is determined, wherein the actual variable is compared with a setpoint variable and a controlled variable is determined for actuating the inverter, wherein, depending on the controlled variable, a control signal for actuating the inverter is generated in such a way that the inverter emits at least two voltage pulses during a half-cycle of the AC voltage to be generated.