JPS61218365A - Switching regulator - Google Patents

Abstract

PURPOSE:To supply a sufficient base current with a simple circuit configuration by supplying a base current of an output stabilizing control bipolar transistor provided at the secondary side of a converter transformer from the transformer. CONSTITUTION:When two types of more DC outputs are generated at the secondary sides of a converter transformer 4 and at least one of them is stabilized by the pulse width control of a bipolar transistor 11, another secondary winding 8 is further provided at the secondary side of the transformer 4. The base current of the transistor 11 is supplied from the winding 8. Thus, since a sufficient base current can be supplied and another power source is not necessary, the size and the weight of the entirety can be reduced.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a switching regulator that can obtain two or more types of stabilized direct current flow, particularly in the secondary winding of a transformer for DC-DC conversion. This invention relates to a switching regulator configured to supply base current to a DC stabilization control polar transistor provided on the secondary side of a transformer.

[Background of the invention]

Conventionally, in switching regulators capable of obtaining two or more types of DC output, the output voltage is usually controlled as shown in FIG. That is, in a switching regulator, generally a DC voltage is obtained from a commercial power supply 1 that is smoothed by a rectifier circuit 2 and a capacitor 3, but this is converted into a high-frequency voltage by a DC-DC conversion transformer (hereinafter simply referred to as a converter transformer) 4. If the voltage is converted into a voltage and further rectified and smoothed by a rectifier/smoothing circuit (equipped with an output stabilization function) 27 or a rectifier/smoothing circuit 27, a DC output voltage can be obtained from the rectifier/smoothing circuits 27 and 28. If the switching transistor 7 (Ql) inserted in series with the primary winding 5 of the converter transformer 4 is controlled on and off at a constant cycle, a high frequency voltage is applied to each of the secondary windings 6 and 19. However, these high-frequency voltages are smoothed by rectifying and smoothing them. ------------A DC output voltage that is higher than that is obtained. In this case, the DC output voltage obtained from the rectifier/smoothing circuit 28 is controlled by making the duty ratio of the on/off state of the switching transistor 7 variable. If the deviation between the DC output voltage and the reference voltage from the reference voltage source 25 is determined using error ann 7°24, and if the switching transistor 7 is controlled to have a variable on state via the bus pulse width control circuit 9, the DC output The voltage is controlled so that its magnitude always matches that of the reference voltage. Therefore, it is clear that the DC output voltage obtained from the rectifier/smoothing circuit 28 can be stabilized and controlled. However, even if this DC output voltage is stabilized, it does not necessarily mean that the voltage obtained by the rectifier-smoothing circuit 27 is also stabilized, so the rectifier-smoothing circuit 27 separately performs stabilization control. It is necessary to do this.

FIG. 4 shows the switching regulator shown in FIG. 3 in more detail. As you can see from this, rectification and
Smoothing circuits 27 and 28 include diodes 10°20, diodes (for flywheel) 14 and 21, and choke coil 1.
5.22 and a capacitor 16.23, which are basically the same structure. The difference is that the rectifier/smoothing circuit 27 further includes a reference voltage source 26, error amplifiers f17, and 9 in order to stabilize its DC output voltage.
pulse width control circuit 18 and switching transistor 1
1 (Q2) is added as shown.

The stabilization principle in this case is the same as in the previous case. If the duty ratio of the on/off state of the switching transistor 11 is controlled as variable, assuming that the switching transistor 7j11 transitions from the on state to the off state synchronously, the rectifier φ smoothing circuit 2
7 provides a stabilized DC output voltage. FIG. 5 shows the a-b voltage Vab, c in FIG.
This shows the voltage waveform of the voltage Vad between d and DC output voltage V obtained from the rectifier/smoothing circuit 27.
OO will be calculated as follows.

Page 1-5- However, Vl is the peak value of the CD-to-CD voltage Vcd, TON,
T oyy indicates the on-state time and off-state time of the switching transistor Qll, respectively.

Therefore, with TON + TOFF constant, TON and TOF vary according to the deviation voltage from the error amplifier 17.
! If ' is simultaneously variably controlled, stabilization control of the DC output voltage VDO becomes possible.

However, when a bipolar transistor is used as the switching transistor (Q2) and the load current is large, it may be necessary to flow several amperes as the base current. As shown in Fig. 4, this base current flows through the base pulse width control circuit 8, so the commercial frequency transformer 29 serves as its power source.
The auxiliary power supply section consisting of the rectifier circuit 30 and the smoothing capacitor 31 must have a sufficiently large capacity. Usually, as this auxiliary power supply, in addition to such a method, a self-excited device such as a ringing choke converter is used.
It has been considered to use a 100-type switching regulator, but in any case, if you are trying to secure an output current of several amperes, the parts used will be large and this will cause practical problems. be. Incidentally, as a publicly known document regarding this type of power supply device, Japanese Patent Application Laid-open No. 116068/1984 can be cited.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a switching regulator that can supply a sufficient base current to a bipolar transistor for output stabilization control provided on the secondary side of a converter with a simple circuit configuration.

[Summary of the invention]

For this purpose, the present invention removes the secondary winding newly provided on the secondary side of the converter transformer so as to supply the base current to the bipolar transistor.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 1 and 2.

FIG. 1 shows a switching regulator according to the present invention.
FIG. 7 shows an example configuration on page 7. As shown in the diagram, the third
What is substantially different from that shown in the figure or Fig. 4 is that the secondary winding of the converter transformer 40 is (2n+1').
(n is an integer of 1 or more; in this example, n=1), and n is used for supplying base current. That is, the secondary windings 6, 19 function similarly to those in FIG. 3 or 4, but the secondary winding 8
is adapted to supply a base current to the switching transistor 11 via a resistor 12. Therefore, it is not necessary to directly supply the 4-Sumi current as the bus width control circuit 18, and the small capacity switching transistor 13 connected to the secondary winding 8 is connected to the error amplifier 7.
It is sufficient to simply perform on/off control using the duty ratio according to the voltage deviation from '17.

In this case, even if the load current is large and several amperes are required as the base current of the switching transistor 11, the current is supplied from the converter transformer 4. Hit bl-do 16
．． (5) The width control circuit 18 only needs to bear the base current of the switching transistor 13 (usually several tens of mA). In other words, the power supply circuit (not shown) for the pulse width control circuits 9 and 18 and the error amplifier f17.24 can be much smaller and have a smaller capacity than the conventional circuits.

Note that the increase in the current flowing through the switching transistor 7 is calculated by increasing the number of turns of the primary winding 5 and the secondary winding 8 by N.
, , N. Also, the base current of the switching transistor 110 is set to 1. It is determined as (N8/N, ) In. Since the value of N, /N is usually less than o,i, this increase in current poses almost no problem in terms of the current capacity of the switching transistor 7.

This is because a current of approximately several amperes normally flows through the switching transistor 7.

Although the present invention has been described above using an example of a forward type switching regulator, the present invention is also applicable to a flyback type switching regulator. FIG. 2 shows a flybank type switching regulator to which the present invention is applied, but no particular explanation is required regarding this page.

〔Effect of the invention〕

As explained above, according to the present invention, the base current to the bipolar transistor for output stabilization control provided on the secondary side of the converter transformer is supplied from the converter transformer, so that the switching regulator can be made smaller and lighter. It has the effect of being able to

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the circuit configuration of an example of a switching regulator according to the present invention, and Figures 3 and 4 are general outlines of a switching regulator that can obtain two or more types of DC output. FIG. 5, which is a diagram showing the configuration and its specific configuration, is a diagram showing voltage waveforms for explaining the circuit operation. 4...Converter transformer, 6,8.19...Secondary side winding M, 7111.13...Switching transistor, 9.18...Riguru width control circuit, 17.24...
・Error amplifier, 25.26...Reference voltage source. Figure 1 Figure 2 B Figure 3 Figure 4 Figure $5

Claims (1)

[Claims] At least one of two or more types of DC outputs obtained from the secondary winding of a DC-DC conversion transformer controls the pulse width using a bipolar transistor connected in series to the transformer secondary winding as a switching transistor. What is claimed is: 1. A switching regulator that is designed to be stabilized by a switching regulator, characterized in that a base current to a bipolar transistor is supplied via a secondary winding newly provided in a DC-DC conversion transformer.