DC-DC Converter

Abstract

A DC-DC converter includes an output-side storage capacitor arrangement which has a parallel circuit formed of an electrolytic capacitor, a ceramic capacitor and a circuit arrangement. The circuit arrangement has a series circuit formed of a hybrid electrolytic capacitor and a suppressor diode as well as a resistance connected in parallel with the hybrid electrolytic capacitor.

Claims

1-3. (canceled)

4. A DC-DC converter, comprising: an output-side storage capacitor arrangement having a parallel circuit formed of: an electrolytic capacitor, a ceramic capacitor, and a circuit arrangement, said circuit arrangement including: a series circuit formed of a hybrid electrolytic capacitor and a suppressor diode, and a resistance connected in parallel with said hybrid electrolytic capacitor.

5. The DC-DC converter according to claim 4, wherein said electrolytic capacitor has a rated voltage of 50 V to 70 V.

6. The DC-DC converter according to claim 4, wherein said hybrid electrolytic capacitor has a rated voltage of 30 V to 40 V.

7. The DC-DC converter according to claim 5, wherein said hybrid electrolytic capacitor has a rated voltage of 30 V to 40 V.

Description

[0014] The invention is explained in more detail below on the basis of an exemplary embodiment with the aid of a FIGURE. Here,

[0015] FIG. 1 shows the storage capacitor arrangement of a DC-DC converter according to the invention.

[0016] ADC-DC converter usually provide at its output the energy from an input energy source, via intermediate storage as magnetic energy in a coil, as electrical energy stored in an output capacitor, wherein the voltage at the output capacitor is controlled by means of clocked energization of the coil to prescribed value. The DC-DC converter can in this case be in the form of a step-down, step-up or inverting converter, a primary-clocked or secondary-clocked converter.

[0017] The output capacitor serves as a storage capacitor and, in the storage capacitor arrangement of FIG. 1 according to the invention, is formed having an electrolytic capacitor 1, having a ceramic capacitor 2 connected in parallel therewith and the series circuit, connected in parallel therewith, composed of a hybrid electrolytic capacitor 3 and a suppressor diode 4 and also a resistance 5 connected in parallel with the hybrid electrolytic capacitor 3. The storage capacitor arrangement is to be connected to the DC-DC converter via a reverse-biased diode 6. The suppressor diode 4 is changed to an on state by means of the resistance 5; here, a current of approximately 1 mA flows. The suppressor diode 4 has a clamping voltage of approximately 40 V at a current of 1 mA. The cathode terminal of the diode 6 is also the output terminal of the DC-DC converter to which an, in particular inductive, load can be connected.

[0018] For the case of feedback of energy from an inductive load into the storage capacitor arrangement, the hybrid electrolytic capacitor 3 takes on the greatest proportion on account of its series resistance that is lower compared to the electrolytic capacitor 1 and capacitance that is greater compared to the ceramic capacitor 2, with the result that the voltage at the output terminal cannot increase to a value that could destroy other component parts connected thereto.

[0019] The suppressor diode 4 is to be designed so that the dynamic internal resistance thereof (change in the reverse voltage in the case of a Current change) is as low as possible. In addition, the suppressor diode 4 must be able to absorb a high pulse energy. The reverse current (leakage current) through the suppressor diode 4 must be lower than the current through the parallel resistance 5 by at least a factor of 10 so that no voltage peaks above the rated voltage can occur at the hybrid electrolytic capacitor 3 connected in series. Typical reverse currents of suppressor diodes are at values of up to 25 A in the temperature range up to 125 C.

[0020] Typical can sizes for hybrid electrolytic capacitors are 88 mm with a height of 6 mm (100 F/35 V) or 1010 mm with a height of 1.0 mm (220 F/35 V).

[0021] The peak power loss of the suppressor diode 4 must be greater than the maximum value of the peak feedback current multiplied by the clamping voltage of the suppressor diode 4.