A new tracking method with FPGA chip for ultrasonic welding system
A new feedback control method of using field-programmable gate array (FPGA) chip for ultrasound welding system is appeared in this article. This feedback control circuits of ultrasound welding system consists of microprocessor control unit, signal generator, power amplifier, the feedback of voltage detector and current detector, etc. The experimental results exhibited this feedback control method can effectively and automatically catch frequency and rack a proper frequency for the ultrasound welding system.
Frequency control of MOSFET full bridge power inverter for maximizing output power to megasonic transducer at 3 MHz
The frequency of the MOSFET DC-to-RF power inverter is precisely set at the series resonant frequency of a megasonic transducer by controlling the oscillation frequency of the PLL when the MOSFET DC-to-RF power inverter is used to drive the megasonic transducer having an impedance of as low as 5 to 6 ohms or less. The frequency control system features a current sensor having an effective internal impedance of as low as 0.25 ohm which is negligible compared with the impedance of the megasonic transducer at the series resonant frequency. The impedance of the inverter load composed of the output transducer, matching capacitor, coaxial cable, megasonic transducer, and current sensor is calculated to determine the frequency control range of the PLL. In accordance with the result of calculation, the performance of the phase-frequency comparator, low pass filter, and VCO is decided. When the RF output power of the MOSFET power inverter was 60 W with a power conversion efficiency of 95%, the frequency control range was 2.8 MHz to 3.2 MHz. The PLL covers the range of frequency shifts and variations in the megasonic transducer and VCO.
Compact 600 W DC-to-RF MOSFET inverter for ultrasonic transducer at 1 MHz
Described is a compact single-ended MOSFET inverter with a switching snubber operating at a frequency of 1 MHz, which generates an RF power of 600 W when an ultrasonic transducer with a characteristic impedance of 1 ohm is connected to the inverter. The inverter has a power conversion efficiency of 67% at 1 MHz when a DC voltage of 70 V is supplied to the inverter. The inverter is 22 cm/spl times/l7 cm/spl times/9 cm in dimensions and 2 kg in weight.<<ETX>>