1. Introduction
Ultrasound imaging is a technique widely used for diagnostic purposes as it is a non-ionizing, real-time, non-invasive and inexpensive imaging modality [1,2,3]. In particular, point-of-care ultrasound systems have been used to bring modern medical imaging technology to remote areas such as rural areas, allowing for faster diagnosis. These systems utilize the capabilities and resources of the phone/tablet to process, display, and transmit ultrasound images. This small device is usually powered by a lithium-ion battery or USB power supply.However, the performance of point-of-care ultrasound systems is hampered by the limited number of ultrasound array transducer elements, overheating, and battery issues that impact the sensitivity and resolution of such ultrasound systems [4,5].To overcome overheating and battery issues, manufacturers need to use cooling systems such as fans and aluminum heat pipe structures, although the internal structures of field ultrasound systems are much smaller than traditional desktop ultrasound machines. [4].
The entire architecture is shown in Figure 1 and mainly consists of piezoelectric sensors, high voltage (HV) switches, controllers, imaging systems and power supplies.The basic principle of the ultrasound imaging system is to transmit ultrasound burst signals to the area of interest of the organ, receive the echo, and perform imaging processing [6].The piezoelectric element is ceramic and has the property of converting electrical signals into ultrasonic pressure waves and vice versa, so it can be used as both a transmitter and a receiver [7]. To excite these elements, ultrasonic sensors typically consist of many piezoelectric elements and use DC-DC converters to control logic inputs from low voltage (up to 80 V) and high frequency (2 –20 MHz) [8].Many researchers have developed portable ultrasound scanner prototypes that provide variable symmetrical bipolar voltages to the probe [9,10,11]. Voltages up to ±80 V can be obtained from low-voltage sources in a single conventional bipolar converter stage. Unfortunately, the supply voltage level is low and for high voltage applications the voltage gain should be higher. In addition, the input current ripple of the converter should be low to reduce output power fluctuations and extend the life of the power supply.Chipmakers are also an important source of knowledge and expertise [12,13], as they are the primary producers of design notes. They also provide system design guidance, but component integration can be difficult. For example, the datasheet may be incomplete or the source code may not be available (e.g., Texas Instruments swroop-smartprobe reference design files).However, most of the power consumption and overheating issues come from the DC-DC converter, reducing the efficiency of the system [14]. To optimize high-voltage designs for low power consumption, Rathod et al. [15] Electrical impedance matching is advocated to increase the level of energy transferred to the transducer. Therefore, in order to improve the voltage gain, efficiency, and lifetime of the system, a high-voltage bipolar DC-DC converter with high efficiency and low input current ripple should be used.
Basically, traditional bipolar non-isolated DC-DC converters are widely used in high-voltage bipolar DC-DC converters due to their simplicity, easy control, and continuous input current.They also have lower component count compared to isolated converter topologies [16]. However, this high duty cycle creates high conduction losses in the active switch and diode reverse recovery losses.In addition, the switching voltage stress is also high, equal to the output voltage [12,13,17]. Isolated converters, such as forward, flyback, half-bridge, full-bridge, and push-pull, can provide high voltage gain by increasing the turns ratio of the transformer. However, it also has some significant issues such as leakage inductance, core saturation, thermal effects, high voltage spikes on the switches, large number of switching devices and transformers, more isolated sensors, complex control schemes, and huge size.Higher cost compared to non-isolated converters [18,19,20,21,22,23]. As a result, power consumption is high, increasing switching losses and noise, further reducing system performance.Therefore, consider the requirements of a smart ultrasound scanner [24,25,26]non-isolated converters are preferred.
While many topologies can meet high gain requirements, most have long duty cycles, creating a risk of inductor current saturation and degrading converter performance [27,28,29,30,31,32,33]. A lot of research has been done to develop bipolar high-gain converters to overcome the shortcomings of ordinary bipolar converters. As a simple technique to enhance the voltage gain of conventional bipolar converters, switched capacitor/switched inductor voltage multiplier cells (VMCs) are used [17]. However, in these topologies, a metal-oxide-semiconductor field-effect transistor (MOSFET) is connected in series with the power supply at the input, which inevitably results in pulsed input current and higher conduction losses. Some of the more competitive programs are surveyed here.exist [34]In , the analysis and control of a boost converter using a winding cross-coupled inductor approach for DC microgrid applications is presented. This converter has extremely high gain and low voltage loading on the semiconductor. The leakage energy is recovered through the passive clamp circuit. The large number of power diodes and capacitors is the main disadvantage of this structure. A single-switch ultra-high boost DC-DC converter is proposed using a three-winding coupled inductor and VMC. [35]. Low diode reverse recovery, low duty cycle and high efficiency are the main advantages of this topology. However, it has the problem of high input current ripple, and to solve this problem, an RC low-pass filter is used.A novel bipolar output converter is proposed [36]. The converter has a very simple circuit configuration and can achieve high boost voltage gain by employing an active switched inductor network. A DC-DC converter topology is proposed by reducing the ripple of the input current. [37] Bipolar output voltages are provided in secondary form with the same and different voltage levels and a common ground. The disadvantage is that it uses two power switches to operate simultaneously.Symmetrical multilevel DC-DC boost converter with ripple reduction structure is also analyzed [38]. The advantages of this topology are high voltage gain, low switching stress, and the ability to reduce input current ripple and capacitor voltage ripple. To further improve the output voltage at low duty cycle, the coupled inductor is combined with VMC: [39]. Continuous input current with low ripple, common ground between output and input ports, low voltage stress on the semiconductor, low component count, high voltage gain and high efficiency are the main advantages of the proposed converter.exist [40], the proposed structure can achieve higher voltage gain by using magnetic coupling and VMC. Use low resistance power MOSFETs to reduce conduction losses.
This article focuses on the design and analysis of a compact, non-isolated symmetric high-voltage gain power supply for powering smart ultrasound scanner transmitters. The design generates programmable bipolar power up to ±80V from a single stage of very low input voltage. The converter is designed to provide continuous input current using only a single active switch and allows relatively reduced voltage stress on all power semiconductors of the DC-DC converter. Therefore, this paper makes the following contributions:
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Symmetry error minimization;
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Wide voltage level range and high accuracy;
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Optimize energy transportation;
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Continuity of Service.
The remainder of this paper is organized as follows: Section 2 describes the research system and introduces the novel DC-DC converter that constitutes the originality of this study. Section 3 presents design considerations. Section 4 provides a theoretical comparative analysis of the proposed converter, focusing on efficiency and voltage gain. Section 5 presents the simulation and experimental results. Finally, Section 6 concludes the paper.