JPS5939989B2 - DC↓-DC conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC-DC conversion circuit having a soft switch function to smooth the rise of rush current and the rise of output voltage at the time of startup of a power supply circuit.

In a conventional DC-DC conversion circuit, at startup, an inrush current flows to charge a capacitor of a smoothing circuit connected to the output. If the current capacity of the primary power supply to which the DC-DC conversion circuit is connected is small, such as onboard storage batteries for satellites, the inrush current to the DC-DC conversion circuit causes the primary power supply voltage to drop instantaneously, causing the primary power supply to Connected and operating devices may malfunction or become inoperable. Further, in the conventional DC-DC conversion circuit, the output voltage rises sharply, and in some cases, ringing occurs due to resonance of the smoothing circuit at the rise. Depending on the load connected to this DC-DC conversion circuit, it may be damaged by the sudden rise of the output voltage. An object of the present invention is to provide a DC-DC conversion circuit in which the rise of the rush current at the input end and the rise of the output voltage at the output end are smoothed.

FIG. 1 is a circuit diagram of an embodiment of the present invention, in which 1 is a DC input terminal and 2 is a DC return terminal.

This human power starts and stops the present DC-DC conversion circuit using the switch 3. This input DC voltage is converted into AC by a push-pull inverter circuit consisting of transistors 4, 5 and a transformer 6,
8 and a capacitor 9, and is output to a DC output terminal 10 and a DC return terminal 11. On the other hand, the output signal of the oscillation circuit 12 that outputs a rectangular wave is transmitted to the resistor 13
, 14 to switch and drive transistors 15 and 16. The switching signals of the transistors 15 and 16 drive the transistors 4 and 5 via a transformer 18 and resistors 19 and 20. Further, the resistor 21 allows current to flow through the base of the transistor 17, and the base potential of the transistor IT rises with a time constant determined by the resistor 21 and the capacitor 22. This rising voltage drives the transformer 18 by the transistor IT and controls the switching signal.
The resistor 23 is for discharging the capacitor 22. The operation of this circuit is as follows. When switch 3 is turned on at startup, the emitter potential of transistor IT rises with a time constant determined by resistor 21 and capacitor 22, and transformer 1
The waveform on the output side of transistor 8 also gradually rises, and therefore the drive voltage of transistors 4 and 5 also gradually rises. Therefore, the transistors 4 and 5 switch in the active region at the rise of the drive voltage, so the output waveform of the transformer 6 gradually rises as shown in the waveform of FIG. Further, the voltage between the DC output terminal 10 and the DC output return terminal 11 also rises as shown in the waveform diagram of FIG. In this way, charge is gradually accumulated in the smoothing capacitor 9, so that the rising waveform of the input current at the DC input terminal 1 rises slowly as shown in the waveform diagram of FIG. At the interface point, the respective current and voltage waveforms will rise softly. The rise time of the input voltage varies depending on the components such as the transformer used, but it should operate stably with a voltage of 20V or 10V and a load of about 1A with a slope of about 1A/Ms. has been confirmed.

Further, the oscillation frequency used in this case is 7.5 KHz. As explained above, the DC-DC conversion circuit with the soft switch function according to the present invention reduces the drop in the primary power supply voltage due to the rush current when starting the DC-DC conversion circuit, even when the current capacity of the primary power supply is small. can be done.

Further, by using the DC-DC converter circuit of the present invention in equipment mounted on a satellite, there is an advantage that the bus power supply can be made considerably smaller and lighter.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is a transformer output waveform diagram of Fig. 1, Fig. 3 is an output end voltage waveform diagram of Fig. 1, and Fig. 4 is an input terminal diagram of Fig. 1. It is a terminal current waveform diagram.

Claims (1)

[Claims] 1. Two switching transistors that alternately switch and output DC input voltage using switching signals, a transformer that connects the outputs of these transistors to input terminals, and a rectifier circuit that rectifies the output of this transformer to obtain a DC output voltage. , in a DC-DC conversion circuit comprising an oscillation circuit that generates the switching signal and an oscillation drive circuit that is driven by the DC input voltage and alternately supplies the output of the oscillation circuit to the transistor, when the DC input voltage is activated; D characterized in that it includes a power supply circuit that gently supplies the DC input voltage to the oscillation drive circuit so that the switching transistor operates in a linear region.
C-DC conversion circuit.