Non-isolated DC / DC converter

Abstract

An object of the present invention is to provide a high-efficiency and low-noise non-insulated DC / DC converter while suppressing an increase in cost and size. 【Means for Solving the Problem】The present invention is an H-bridge type DC / DC converter that connects a primary circuit in which two primary-side devices are connected in series and a secondary circuit in which two secondary-side devices are connected in series with a choke coil L1, and includes a primary-side capacitor Ca connected in parallel to one or each of the primary-side devices, and a secondary-side capacitor Cb connected in parallel to one or each of the secondary-side devices. Each of the primary-side devices and the secondary-side device on the low-potential side is a switching device, the secondary-side device on the high-potential side is a diode D4, and the total capacitance C of the primary circuit in , the total capacitance C of the secondary circuit out , the relationship between the maximum value Vimax of the input DC voltage of the primary circuit and the minimum value Vomin of the output DC voltage of the secondary circuit is Vimax 2 ·C in < Vomin 2 ·C out is characterized by this.

Claims

1. A primary circuit in which two primary-side devices are connected in series between a pair of primary terminals to which DC is input, A secondary circuit in which two secondary devices are connected in series between a pair of secondary terminals that output DC, A choke coil connects the connection point of the two primary devices to the connection point of the two secondary devices, An H-bridge type DC / DC converter comprising, The system further comprises a primary capacitor connected in parallel to one or each of the primary devices, and a secondary capacitor connected in parallel to one or each of the secondary devices. Each of the primary devices and the secondary device on the low-potential side are switching devices composed of a switching element consisting of a parasitic capacitance and a parallel diode with the high-potential side as the cathode. The secondary device on the high-potential side is a diode with the high-potential side as the cathode, and Total capacitance C of the primary circuit ｉｎ and the total capacitance C of the secondary circuit ｏｕｔ Relationship Vimax ２ ・C ｉｎ < Vomin ２ ・C ｏｕｔ Being A DC / DC converter characterized by the following features. However, Vimax is the maximum value of the DC voltage Vi input to the primary terminal pair, and Vomin is the minimum value of the DC voltage Vo output from the secondary terminal pair.

2. The device further comprises a control device that turns the switching device on or off by controlling the switch element, The control device is The switching device of the primary circuit is turned on alternately. After turning off the switching device on the high-potential side of the primary circuit, and after a predetermined time has elapsed, the switching device on the low-potential side of the primary circuit is turned on, thereby reversing the current of the choke coil using the discharge current of the secondary capacitor. By turning off the switching device on the low-potential side of the primary circuit while the current in the choke coil is reversed, charge is discharged from the parasitic capacitance of the switching device on the high-potential side of the primary circuit, and if the primary-side capacitor is connected to the switching device, charge is also discharged from the primary-side capacitor, and Zero-volt switching is achieved by turning off the switching device on the low-potential side of the primary circuit, and then turning on the switching device on the high-potential side of the primary circuit after a predetermined time has elapsed. The DC / DC converter according to claim 1, characterized by the following:

3. The control device is The DC / DC converter according to claim 2, characterized in that the switching device on the low-potential side of the secondary circuit is kept off at all times.

4. The control device is The DC / DC converter according to claim 2, characterized in that the switching device on the low-potential side of the secondary circuit is turned on during the period when the switching device on the low-potential side of the primary circuit is turned on, and is turned off during the period when the switching device on the high-potential side of the primary circuit is turned on.

5. The DC / DC converter according to claim 2, characterized in that the predetermined time is the time calculated by formula 1. [Math 1] Here, Td is the predetermined time (sec), L1 is the inductance of the choke coil (H), C1 is the parasitic capacitance of the switching device on the high-potential side of the primary circuit (F), C2 is the parasitic capacitance of the switching device on the low-potential side of the primary circuit (F), and Ca is the total capacitance of the primary side capacitor (F).

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