JPS6028006B2 - Stabilized power supply circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A stabilized power supply circuit using a switching method is constructed as shown in FIG.

In the figure, 1 indicates a power transformer, and a DC power source 2 and a switching transistor Q are connected to the primary coil la.

The oscillation output Po (see FIG. 2A) obtained from the oscillator 4 is supplied to the pulse modulator 5 to undergo pulse width modulation, and then supplied to the transistor Q as a switching pulse. As is well known, a rectifier circuit 6 is connected to the secondary coil lb of the transformer 1, so that a predetermined output voltage can be obtained from a terminal 6a. In order to stabilize this world voltage, a voltage detection circuit 7 is usually connected to the terminal 6a, and the above-mentioned pulse width modulator 5 is controlled (pulse width control) according to the detected voltage, thereby stabilizing the output voltage. I'm trying.
For example, if the pulse width modulated switching pulse PM has a pulse width of 7 as shown in Figure 2B, the collector current ic of the transistor Q will be as shown in Figure 2C, and the base current iB will be as shown in Figure 2B. It becomes like this.

When the output voltage is higher than the predetermined voltage, the pulse width is controlled to a pulse width of 2 as shown in Fig. 2E, and as a result, the collector current iB also becomes as shown in Fig. 2F, thereby suppressing the rise in the output voltage. ing. By the way, when stabilizing the output voltage by controlling the pulse width in this way, although the pulse width of the switching pulse PM can be controlled according to the output voltage, it is not possible to control the pulse width up to the peak value of the pulse current.

That is, the peak value of the pulse current is constant regardless of the pulse width. Therefore, when the pulse width is narrow, the base current iB of transistor Q becomes excessive, and therefore a large current is required to turn off transistor Q. In the case of Fig. 2 F, transistor Q is completely turned off. Therefore, the switching characteristics deteriorate.
In order to improve the switching characteristics, it is sufficient to control the peak value at the same time as controlling the pulse width. For example, when the pulse width becomes 2, the base current i
It is possible to reduce the peak value of B, but if the peak value is controlled in this way, the circuit becomes complicated, so the switching characteristics are currently sacrificed. The present invention takes these points into consideration, and is designed to ensure that the switching state is not affected by the pulse width, especially in a device that attempts to keep the output voltage constant through pulse width control.

The stabilized power supply circuit according to the present invention will be explained in detail with reference to FIG. 3 and subsequent figures. FIG. 3 shows an example of the present invention, in which a resonant circuit 10 including a switching transistor Q (first switching element) is connected to the primary coil la side of the transformer 1.

In this example, a resonant circuit has a primary coil la as a resonant element, and a resonant capacitor 1 is connected in parallel with the primary coil la.
1 is connected, and a damper diode 12 is also connected. The switching transistor Q is therefore connected in parallel with these resonant circuits. Also, between the primary coil la and the capacitor 11, there is a power source (first
A charging capacitor 13, which acts as a power source (power source), is connected in series. In the present invention, a second power supply 2 is further provided in the current path between the damper diode 12 and the transistor Q.
, the second switching element 21, and an inductance element are further connected in series.

In this example, the inductance element is 1 of the transformer 20.
This is a case where the secondary coil 20a is used, and the above-mentioned DC power supply 2 is used as the second power supply. Second
In this example, an SCR is used as the switching element 21. A diode 22 is connected in series between the connection points P, , P2 with the groove characteristics shown.

This diode 22 is connected to the second switching element 21,
The second power supply 2 is connected through the switching transistor Q.
It is used to form a current loop so that the current is supplied, and the current loop between the connection points P and P2 is interrupted. Also,
Due to the presence of this diode 22, a current loop can be formed between the capacitor 13, which is the first power source, and the transistor Q. With this configuration, the power supply path to the second switching element 21 is cut off when the transistor Q is turned off, and this element 21 can be controlled.

If the diode 22 is not provided, the second power source 2 will be directly connected and control of the element 22 will be impossible. On the other hand, the second coil 20b of the transformer 20 is connected to both ends of the capacitor 13 through a diode 23 for a reverse current element. Due to this closed loop, the electromotive force generated in the secondary coil 20b is charged to the capacitor 13 through the diode 23.
Transistor Q receives oscillation output P obtained from oscillator 4.

is directly supplied to the second switching element 21, and its switching phase is controlled according to the detected output of the output voltage. In this example, the pulse width modulator 5 is used in the same way as explained in FIG. The differential pulse is the trigger pulse P
It is used as T. Next, the operation of the stabilized power supply circuit configured as described above will be explained with reference to FIG.

In FIG. 4, TD is the damper period, TT is the conduction period,
And TF is the pulse generation period. Therefore, now, the same figure A
When the oscillation output Fo shown in is supplied to the transistor Q, a pulse voltage Vc shown in FIG. Collector current ic shown by the dashed line in Figure C
flows, and furthermore, a damper current iD (indicated by a broken line) shown by D in the figure flows through the damper diode 12. However, in reality, since the operation of the second switching element 21, which will be described later, is involved, collector current io and damper current iDQ as shown by solid lines flow, respectively. During the pulse generation period TF, resonance occurs between the primary coil la and the capacitor 1, so that a coil current iL as shown by E in the figure flows through the primary coil la.

Here, if the modulated output PM is pulse-width modulated by the output of the detection circuit 7 as shown in F in the same figure, the trigger pulse PT shown in G in the same figure is generated. Switching element 21 is turned on.

As a result, the power supply 2 - the primary coil 20a of the transformer 20 -
A current loop is formed through the damper diode 12, the transistor Q, and the second switching element 21, and a current is flows through the second switching element 21 as shown by the date in the figure. As a result, the coil current iP shown in FIG. 1 flows through the primary coil 20a of the transformer 20. When the transistor Q is turned off, the second switching element 21 is turned off at this point, so the pulse voltage Ps generated in the primary coil 20a at this time is a pulse voltage proportional to the coil current iP as shown in J of the figure.

As a result, a similar pulse voltage is induced in the secondary coil 20b, and this pulse voltage is charged to the capacitor 13 through the diode 23 with the polarity shown in the figure while the switching element 21 is off. The magnitude of the charging voltage is determined by the switching phase in the second switching element 21.
That is, the charging voltage is proportional to the on period of the second switching element 21, and the longer the on period, the larger the back electromotive force generated in the primary coil 20a of the transformer 20, and the sufficient DC voltage is applied to the capacitor 13. is stored. Naturally, if the on period is short, the back electromotive force generated in the primary coil 20a will also be proportionally smaller, so that less voltage will be stored in the capacitor 3. Therefore, as shown in Fig. 5, the charging voltage of the capacitor 3 is different when the pulse width of the modulated output PM is controlled to W, (B in the figure) or W2 as shown in E in the figure. Therefore, the pulse voltage Vc generated in the primary coil la of the transformer is different. Since the rectifier circuit 6 is a peak value rectifier, the output voltage changes according to fluctuations in the pulse voltage Vc, so if the pulse width is controlled so that this output voltage is constant, the DC voltage can be stabilized. . According to the configuration of the present invention described above, a stabilized DC voltage can be obtained by simply controlling the switching phase of the second switching element 21 for controlling the transistor Q.

In this case, transistor Q always has a constant oscillation output Po.
is supplied as the switching signal to control only the switching phase in the second switching element 21, regardless of the magnitude of the pulse width.
Transistor Q can always be completely turned off.
Furthermore, since the present invention controls the switching of the second switching element 21, it has effects such as low power consumption. 6 to 8 show other embodiments of the invention. FIG. 6 shows a case where it is applied to a horizontal deflection circuit, and in this case, a series circuit of a horizontal deflection coil 26 and an S-shaped correction capacitor 27 may be connected in parallel to both ends of the resonance capacitor 11 as shown in the figure. . Further, the same effect can be achieved even if the diode 22 is connected in the position shown in the figure. That is, this is because even with this configuration, a current loop is formed in which the desired DC voltage is supplied to the second switching element 21 through the transistor Q. Horizontal deflection coil 2
6, a sawtooth wave deflection current flows as is well known. 7th
The illustrated embodiment includes a transformer 20 and a second switching element 2.
The only difference is the connection position of 1.

Incidentally, all of the embodiments so far have used the primary coil 20a of the transformer 20 as an inductance element, but as shown in FIG. 8, an ordinary inductance element 30 is used without using a transformer. However, the same effect can be obtained. However, in this example, the idea is not to use back electromotive force, but the current loop passing through the inductance element 30, the charging capacitor 13, and the damper diode 12 is controlled by the second switching element 21. Of course, even with this configuration, the same effects as described above can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of the conventional circuit, Fig. 2 is a waveform diagram for explaining its operation, Fig. 3 is a connection diagram showing an example of the stabilized power supply circuit according to the present invention, and Figs. 4 and 5 are its operation. Waveform diagrams for explanation and FIGS. 6 to 8 are connection diagrams showing other embodiments of the present invention. Q is a transistor which is a first switching element, 21 is a second switching element, 10 is a resonant circuit, 20a, 3
0 is an inductor Sos element. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1 has a parallel resonant circuit including a first power supply and a first switching element, a diode is connected between a damper diode provided in this parallel resonant circuit and the first switching element, and a diode is connected between both ends of this diode. A second power supply, a second switching element, and an inductance element are respectively connected directly to or via the first power supply, and the second
A stabilizing power supply circuit configured to control a switching element according to an output voltage to keep the back electromotive force generated in the inductance element constant and supply it to the first power supply.