Abstract: A direct-current (DC) voltage conversion device includes an energy providing circuit, a first transistor switch, a second transistor switch, a third transistor switch, a fourth transistor switch, and an output capacitor. The first transistor switch is turned on. The second transistor switch and the fourth transistor switch are turned off. The energy providing circuit charges the parasitic capacitance of the second transistor switch. When the third transistor switch is turned on, the parasitic capacitance discharges the output capacitor to establish the same voltage drops across the parasitic capacitance and the output capacitor. After establishing the same voltage drops across the parasitic capacitance and the output capacitor, the parasitic capacitance of the second transistor switch charges the parasitic capacitance of the fourth transistor switch, thereby establishing a zero voltage drop across the fourth transistor switch and achieving zero voltage switching.

Abstract: A universal charging device and a universal charging method thereof is disclosed. An AC voltage is converted into a DC charging voltage. At least two first charging processes are sequentially performed. In each first charging process, the DC charging voltage is adjusted to be larger than the terminal voltage of a battery based on the terminal voltage and the DC charging voltage charges the battery. The DC charging voltage generates a DC charging current and a pulse current to flow through the battery until the terminal voltage is equal to the DC charging voltage. A voltage across the battery established by the pulse current satisfies a charged condition. When the terminal voltage is equal to the DC charging voltage, the DC charging current is converted into a decreasing trickle current until the value of the trickle current is decreased to a triggered current value.

Abstract: A direct-current (DC) voltage conversion device includes a resonate driving device, at least two second transformers, at least two second transformers, at least two third transformers, and a rectifying device. The primary sides of the second transformers are connected in series via a first conductive wire and coupled to the resonate driving device via a second conductive wire. The primary sides of the second transformers are connected in series via a third conductive wire and coupled to the resonate driving device via a fourth conductive wire. The primary sides of the third transformers are connected in series via a fifth conductive wire and coupled to the resonate driving device via a sixth conductive wire. The rectifying device is coupled to the secondary sides of the transformers.

Abstract: A power conversion device includes a transformer, a first electrical switch, a second electrical switch, at least one balanced capacitor, at least one voltage-stabilizing capacitor, and a power-providing circuit. The first electrical switch, the second electrical switch, the balanced capacitor, and the voltage-stabilizing capacitor are connected to the primary side of the transformer, and the secondary side of the transformer is connected to the power-providing circuit. The primary side has a first terminal, a second terminal, and a third terminal therebetween. The first electrical switch and the second electrical switch are respectively connected to a high-voltage terminal and a low-voltage terminal, and the voltage-stabilizing capacitor is connected between the two voltage terminals. One end of the balanced capacitor is connected to the third terminal, and another end of the balanced capacitor is connected to the voltage-stabilizing capacitor or the voltage terminals.