1. Introduction
Recently, with the development of industrialization, the use of the renewable resources—photovoltaic arrays, fuel cells, etc.—have been a most effective solution. However, they are DC sources with low voltage, low current, and instability. To link them to loads or grid applications, the power conversion generation in
Figure 1 was developed. To convert the low voltage of the renewable sources into 200 V or 400 V DC voltage, a high step-up DC-DC stage [
1,
2,
3] is set up as the first stage in the power-conversion system. The second-stage DC-AC converter can provide 110 Vrms or 220 Vrms AC volts for the grid-connected application.
Since the components have an equivalent series resistance (ESR), the traditional boost converter is difficult to step up a large gain voltage. When the high boost voltage is required, the boost converter needs to have a large duty cycle, which leads to high conduction loss and reducing efficiency [
4,
5,
6]. Moreover, in order to achieve the high boost voltage gain, the various DC-DC converters have been presented, including isolated and non-isolated topologies. The isolated topology [
7,
8,
9,
10] can provide the isolation between input and output terminals, which is based on a high-frequency transformer. Since the isolated topologies include a DC-AC stage and an AC-DC stage, they required a number of components, which increase the circuit’s size. If the leakage inductances are designed carelessly, the switches appear as a voltage spike. The non-isolated topologies [
11,
12,
13,
14,
15,
16,
17,
18,
19] can achieve a high efficiency with a simple circuit because of the lack of a transformer. In the non-isolated topologies, the high step-up voltage gain can be achieved by using the following techniques: cascade boost, switched-capacitor, switched-inductor, coupled inductor, and a mixture of them. The coupled-inductor-based converters [
12,
13,
14] have a large voltage conversion ratio with increasing efficiency and reduces the voltage/current stress on switches and diodes. However, the circuits are complex to design and the leakage problem of the coupled inductor causes a high voltage spike on semiconductor components. The dual-switch-based converters [
15,
16,
17] present a high voltage gain with high input current ripple. In these topologies, an additional active switch is required with the increasing gate drive. The SC structure was proposed in [
18]. By charging the capacitors in parallel and discharging them in series the SC-based converter produces a high voltage at the output side. In [
19], an interleaved DC-DC multilevel converter was proposed by combining a multilevel boost structure and a single inductor multiplier Cuk converter to achieve a minimum input current ripple. A non-isolated high step-up DC-DC converter with single-inductor-energy-storage cell-based SCs (SIESC-SCs) was introduced in [
20]. By changing the SC cell connection, various converter topologies are obtained.
To decrease the converter’s size and obtain a high voltage gain, the cascade boost converter, the voltage multiplier cells (VMC) boost converter, and the dual boost converter were proposed, as shown in
Figure 2. The cascade boost converter, as shown in
Figure 2a, can provide a high ratio, but the circuit is complex, and the size and cost of the converter are increased. The cascade converter can reduce switch
S1 and diode
D1 voltage stress, high flexibility, and suitability for high power applications. However, the switch
S2 and diode
D2 voltage stress are high. The VMC boost converter were presented in [
5] and is shown in
Figure 2b. The voltage ratio of the VMC boost converter can achieve a larger gain voltage by increasing the N cell of the VMC. The switches’ and diodes’ voltage stresses are decreased, and the diodes are turned off with ZCS. However, the duty cycle is limited and the switches’ current stress is large, and the voltage stress is dependent on the number of VMC. The dual converter was quoted from [
6], as shown in
Figure 2c. Similarly, the dual boost converter decreases the voltage stress on the switches, the inductor current is rated roughly at half of the total input current, and the isolated gate driver is needed for the dual boost converter.
This paper proposes a new boost converter based on a switched-capacitor structure. The proposed SC converter has a large step-up gain with continuous input current. The operating principles and circuit analysis in continuous conduction mode (CCM) and discontinuous mode (DCM) are presented. The parameters selection of the proposed SC converter and a comparison with conventional converters are shown. Simulation and experiment verifications prove the correctness of the operating analysis.
4. Comparison with Other High Voltage Gain Converters
The comparison between the proposed SC converter and other converters, including the dual boost converter (DBC) [
3], the cascade boost converter (CBC) [
5], the boost voltage multiplier cell (B-VMC) (
n = 2) [
6], the single inductor multiplier Cuk converter (SLMC) [
19], and the converter with the SIESC-SCs [
20], are shown in
Table 3 and
Table 4. In the comparison to DBC [
3], B-VMC [
6], and CBC [
5], the proposed SC converter saves one inductor. Moreover, the voltage stress on diodes and switches of the proposed SC converter is small. Similar to the CBC [
5] and B-VMC [
6], the proposed SC converter uses one active switch. Compared to the DBC [
3], B-VMC [
6], CBC [
5], and SIESC-SCs [
20], the proposed SC converter uses two more diodes and capacitors, but the voltage gain of the proposed SC converter is higher. When the gain and voltage stress of active components are considered, the SLMC [
19] is an interesting topology. However, the proposed SC converter has the same advantages with SLMC [
19] and uses one less capacitor and one less diode.
Figure 8 shows the voltage gain comparison between the proposed SC converter and the other non-isolated converters in the CCM. The voltage gain of the proposed SC converter is the same as that of SLMC [
19] and is highest when
D < 2/3. Therefore, the proposed configuration is more profitable than other non-isolated configurations of the boost coefficient.