JPS5827216A - Switching regulator - Google Patents

Abstract

PURPOSE:To reduce losses of a snubber circuit by providing a separate winding in the secondary winding of a conversion transformer and connecting a rectifying/smoothing circuit that works when a switching transistor is off on the separate winding. CONSTITUTION:A DC power source 1 is supplied to a main transformer 3 through a switching transistor 2, and at the same time, energy is supplied from a smoothing choke 13 connected to the secondary winding of the main transformer 3 to load 15. A snubber circuit consisting of aondenser 7, a resistance 8 and a diode 9 is connected to the collector of the switching transistor 2. A separate winding 21 is provided in the secondary side of the main transformer, and rectifying/smoothing circuits 22, 23 that a diode 22 conducts when the transistor 2 is off are connected. By this way, the fly-back power of the main transformer 3 is supplied to a load 24, and the power consumption of the snubber circuit can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forward type switching regulator.

In a forward switching regulator, the main transformer is provided with a feedback winding and a snubber circuit in order to dissipate the flyback voltage and excitation energy of the main transformer that occurs when the main transistor is off. A conventional example is shown in FIG. In the figure, when the main transistor 2 is turned on, a current flows from the DC power supply 1, a voltage is generated in the primary winding 4 of the main transformer 30, a voltage is induced in the secondary winding 6, and the diode 11 is turned on in the forward direction. biased,
Energy is supplied to the load 16. At the same time, excitation energy is accumulated in the choke transformer 13. Next, when the main transistor 2 is turned off, a reverse voltage is induced in each winding of the main transformer 3, and the diode 10 is biased in the j@ force direction.

A part of the excitation energy is fed back to the power supply 1g40.

A charging current also flows through the capacitor 7 through the diode 9 . This charging current absorbs the spike voltage that occurs when transistor 2 is off, but the energy charged in capacitor 7 needs to be dissipated during the off period of transistor 2, so it is currently consumed as a loss through resistor 8. This resulted in a decrease in efficiency, and it was still necessary to use a power type resistor as the resistor 8.

The present invention is intended to solve the problems in the conventional circuits described above. Hereinafter, one embodiment of the present invention will be explained based on an illustrated embodiment, and parts similar to those explained in FIG. 1 are denoted by the same reference numerals. FIG. 2 is a circuit diagram of a first embodiment of the present invention. In this embodiment, the main transformer 3 is provided with a separate winding 21 and connected so that the diode 22 is biased in the forward direction when the transistor 2 is off. By choosing the ratio appropriately, a separate output with the desired voltage can be obtained across the capacitor 23.

Note that 24 in the figure represents a load. The above output is different.

A conventional snubber circuit, namely a capacitor and a resistor 8, is used to supply the flyback power of the main transformer 3.
In addition, the power consumed by the diode 9 can be reduced.

As described above, in this first embodiment, by using the flyback power of the main transformer, another output can be easily obtained and the loss of the snubber circuit can be reduced.

FIG. 3 shows a second embodiment of the invention. This second embodiment has a separate winding 21, a diode 22 and a capacitor 2.
The flyback voltage obtained in step 3 is stabilized using a transistor 31 and a capacitor 32, and power is supplied to a load 24. That is, this second
An example of this is.

This output is more stable than the separate output obtained by the first embodiment shown in FIG.

FIG. 4 shows two third embodiments of the present invention. In FIG. 4, the flyback power of the main transformer 3 is supplied to a capacitor 41, a capacitor 46, and a load 24 by a separate winding 21 and a diode 22. Further, by driving the transistor 43 with the base voltage shown in FIG. 6(b), the electric charge of the capacitor 41 is discharged, and the resistor 42
Consume with.

In this discharge circuit, the diode 44 does not affect the discharge of the charge in the capacitor 46, and the capacitor 41 only needs to have the capacity necessary to absorb only the spike voltage when the transistor 2 is turned off. A sufficiently small capacity is sufficient in comparison. Therefore, less power is consumed by the resistor 42 than in the conventional example shown in FIG.

As described above, according to the third embodiment shown in FIG. 4, the primary side snubber circuit in the conventional circuit becomes unnecessary by using the low power consumption snubber circuit provided on the secondary side.
Efficiency will be improved.

As described above, according to the present invention, power consumption in a snubber circuit can be reduced, circuit efficiency can be improved,
Further, the obtained separate output can be used as a bias power source for a control circuit or the like. Furthermore, by combining the second embodiment shown in FIG. 3 and the third embodiment shown in FIG.
A fourth embodiment as shown in FIG. 6 is also possible, and it is possible to obtain a separate output that is more efficient and stable than the second and third embodiments. Note that it is also possible to obtain a single output that combines the two.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional forward type switching regulator, and FIGS. 2, 3, and 4 are a circuit diagram of a conventional forward switching regulator. Second. Circuit diagram of the third embodiment, FIG. 6(a)
*(b) is an operating waveform diagram of the transistor shown in FIG. 4, and FIG. 6 is a circuit diagram of a fourth embodiment of the present invention. 1... DC power supply, 2... Main transistor, 3... Main transformer, 4... Primary winding of main transformer, 6...・Feedback winding of main transformer,
6... Secondary winding of main transformer, 7.14, 23
, 41, 45... Capacitor, 8, 42...
...Resistance, 9,10°11.12,22,44.・
... Diode, 13 ... Choke transformer, 21 ... Separate winding of main transformer, 15, 24
...Load, 31, 43, 51...Transistor. Name of agent: Patent attorney Toshio Nakao and 1 other person
3rIII Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] a main transformer having a primary winding, a secondary winding, a feedback winding and a separate winding; a main transistor having a collector-emitter path connected to the DC power source in series with the primary winding; a first diode connected to the power supply in series with the feedback winding so as to be reverse biased; a parallel circuit of a capacitor and a resistor connected in parallel to the primary winding; and a second diode. a first power supply circuit that rectifies and smoothes the output obtained from the secondary winding and supplies it to the first load; and a second power supply circuit that rectifies and smoothes the output obtained from the separate winding. A switching regulator comprising a second power supply circuit that supplies the load to the load.