| 摘要 |
A vehicle power-supply unit has chargeable and rechargeable first power supply and second power supply connected to a voltage transducer at input and output terminals, respectively, and a switch element connected between the output terminal of the voltage transducer and the second power supply. By controlling a rector current flown through a reactor connected to at least two switching elements at one end when the voltage transducer is started, a capacitor connected between the other end of the reactor and the ground is charged, and the switch element is brought in a connection state according to a charging voltage of the capacitor and a voltage value of the second power supply. Consequently, a vehicle power-supply unit can protect the elements by preventing a rush current during a backflow and reverse connection and at start-up. |
| 主权项 |
1. A vehicle power-supply unit, comprising:
a DC-to-DC converter with a chargeable and dischargeable first power supply connected to an input terminal and a chargeable and dischargeable second power supply connected to an output terminal and performing DC voltage transformation, wherein the converter includes at least two switching elements connected respectively between the input terminal and one end of a reactor and between the one end of the reactor and a ground and operated to switch by a control circuit; a capacitor connected between the other end of the reactor and the ground; and a switch element connected between the other end of the reactor and the output terminal, and wherein the control circuit performs a sampling to obtain a voltage at the input terminal, a voltage at the output terminal, and a reactor current flown through the reactor every certain number of switching times with a predetermined switching period with which the switching elements are operated; adjusts a duty ratio of the switching elements in synchronization with the sampling; controls the switching elements to operate the certain number of switching times at a first duty ratio determined according to a voltage value at the input terminal, an inductance value of the reactor, a predetermined current value outputted from the converter, the switching period, and the certain number of switching times and then estimates an initial charging voltage value preliminarily charged to the capacitor according to the reactor current value, the voltage value at the input terminal, the first duty ratio, and the inductance value; charges the capacitor while changing a second duty ratio, which is a voltage ratio of the initial charging voltage value and the voltage value at the input terminal, by a predetermined amount at a time and estimates a charging voltage value of the capacitor during charging of the capacitor according to the reactor current value, a capacity value of the capacitor, and the switching period; and applies ON control to the switch element when the charging voltage value of the capacitor reaches a predetermined threshold value. |
