Soheil Taraghinia1, Volkan Acikel2, Reza Babaloo1,3, and Ergin Atalar1,3
1UMRAM, Bilkent University, Ankara, Turkey, 2Aselsan A.S., Ankara, Turkey, 3Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
1UMRAM, Bilkent University, Ankara, Turkey, 2Aselsan A.S., Ankara, Turkey, 3Electrical and Electronics Engineering, Bilkent University, Ankara, Turkey
A single stage H-bridge
gradient amplifier utilizing eGaN devices with 150 V/ 50 A voltage/ current ratings and 1 MHz switching frequency is implemented for an insert gradient array system. A single stage LC low pass filter with 50 kHz cut-off frequency is designed to attenuate the ripple current.
Figure 4.
(a) Measured trapezoidal current waveform with 50 A flat top amplitude and 0.25
A/us slew-rate with filter. (b) Temperature
of eGaN transistors to 45° C from room
temperature for the current on (a) with 10% duty cycle and five
minutes of operation. Zoomed version of the current is shown in Fig. 5.
Figure 5.
(a) Zoomed current (top) and voltage (bottom) applied to the coil in Fig. 4
without (a) and with (b) filter. Peak-to-peak ripple current is reduced more
than twelve times by using the LC filter. Small resistance of the coil (about
200 mΩ) requires small voltage levels and PWM duty cycle.
