JPS58175973A - Switching controlled type power source circuit - Google Patents

Abstract

PURPOSE:To enable to use a control transistor which has low reverse withstand voltage by reducing a reverse bias applied between the base and the emitter of the transistor during the OFF period of a switching transistor. CONSTITUTION:Since both control transistors TR2, TR3 are OFF during the OFF period of a switching transistor TR4, the reverse voltage of a feedback coil N is not applied to a point (M), and the point (M) accordingly becomes a voltage which is lower in the amount of a voltage between both terminals of a condenser C5 to a line L2. Therefore, the reverse bias voltage applied between the base and the emitter of the transistor TR2 in this state becomes low. In this manner, an inexpensive transistor which has relatively small reverse withstand voltage can be used for the control transistor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching control type power supply circuit, particularly to a turn-off timing control type power supply circuit.

Switching control type power supply (Secondly, the bronching oscillation type has been realized because it does not require an external drive circuit or drive transformer.This blocking oscillation type can be further divided into various types depending on the control method. One of the classifications is that the present applicant previously filed a patent application in 1985-485.
There is a circuit as shown in Figure IJIJ1 proposed in No. 50 (see Japanese Patent Laid-Open No. 145775/1983).

First, a brief explanation will be given of the power supply circuit shown in FIG. 1, and the problems to be solved by the present invention will be presented.

The power supply circuit shown in Figure 11111 can be roughly divided into Heka! 1st stream section (
1), blocking oscillation section (2), converter transformer (3), error detection section (4), and control circuit section (5)
It consists of the Deba IM flow part (6), and the basic (
- performs the following operation, D, power switch (BY)
When turning on, the starting current rs is supplied from the input rectifier +IJ to the base of the switching transistor (TR4) to start the blocking oscillator (2), and in the steady state after starting, the control circuit part (51+'': The turn-off timing of the switching transistor (TR4) is controlled according to the output C: of the error detection section (4).
) is turned off as follows.

In other words, when the switching transistor (TR4) is on, the current flowing between its collector and emitter [11C
Therefore, a negative voltage (L I Y & quasi-U line) is generated on the upper end side of the current detection resistor (R11) (a negative voltage that increases over two hours), and this voltage is applied to B via the resistor (R14) and capacitor (07) fL-. On the other hand, the voltage generated at the 0 point is compared and amplified with the voltage of the Zener diode (D! By combining the voltages, point B (
A voltage that decreases as the clock strikes the 2nd hour is obtained. When this voltage drops below the positive voltage obtained at point D (-) by the turn-off capacitor (05) charged in advance to the polarity shown in the figure, the control transistor (TR2) (TRI)
are turned on (=) in sequence, and this causes the above capacitor (C
5), a reverse bias current a flows between the base and emitter of the switching transistor (TR4), turning off the transistor (TR4). At that time, the voltage at the 0 point changes depending on the input power supply voltage and the load condition C of the output rectifier (6), so the positive bias level at the point B changes as a result, which causes switching The turn-off timing of the transistor (TR4) is changed to perform constant voltage control.

In addition, in the above operation, the voltage at the 0 point is when the switching transistor (TR4) is off (the second detection winding (N(1
) is obtained by rectifying and smoothing the rectangular wave voltage generated by a diode (D6) and a capacitor (03). Further, the capacitor (05) is charged by the current aIr flowing from the feedback winding (Nl1) through the diode (D7) when the switching transistor (TR4) is off.

The operation of the circuit shown in Figure 1 at turn-off is generally as described above, but this circuit has the following drawbacks.

First, during the off period of the switching transistor (TR4), the pressure C generated in the feedback winding (Nl) between the base and emitter of the transistor is reverse biased, and at this time, the turn-off capacitor (C5 ) is slightly lower than that voltage 4i! (-indicated polarity) (double ν゛ro/) Point D, that is, the emitter of the control transistor (TR2) is at almost the same potential as the reference fin (Ll) ( On the other hand, in this state, no negative voltage is led from point A to point B, so point B has a sufficiently higher positive potential than the above-mentioned quasi-fin (Ll).For this reason, the above-mentioned control The base and emitter of the transistor f (TR2) are strongly reverse biased (2), so a reverse withstand voltage between this transistor (TRz) and the base and emitter must be used.

Next (-1 feedback winding (NB) and detection winding (N'c) are provided separately, and the charging path of the turn-off capacitor (05) (see lr in the figure) is connected from the reference line (Ll) mentioned above. Since it is in an electrically floating state, sufficient insulation must be provided between the two windings (NB) and (No) in order to meet safety standards. Therefore, the converter transformer (3) is large , and the manufacturing process is also complicated.

In addition, a current limiting resistor (R
14) and a DC blocking capacitor (07) are essential.

Therefore, the present invention provides a switching control type 1 that eliminates all of these drawbacks! The proposed source circuit will be described in detail below.

#! Figure 12 shows an embodiment of the power supply circuit of the present invention.
Parts corresponding to those in FIG. 1 are marked with the same rotation. In this embodiment ζ2, an input rectifier (1) and an output rectifier (6
)teeth! It is the same as FIG. J1 and there are no special points to note, and what is featured here is the following configuration of the blocking oscillator (2)-control circuit 5 (5). l! The first characteristic of r' is that the converter transformer (31 (= feedback winding (Nl
) and the detection winding (NO) are connected in series so that the bridge property ζ shown in the figure is 2, and one end (1) of the feedback winding (Nl) is connected to a switching transistor (TR4) via a resistor (R14).
) is connected to the emitter of the switching transistor (TR4) through the positive feedback current limiting circuit (SC), and the middle point (, 31) of the connection between the two windings (Nl) (No) is connected to the base C of the switching transistor (TR4) through the positive feedback current limiting circuit (SC). .

Next, the second feature is that the connection midpoint peak and the current detection resistor (
A turn-off capacitor (Os) is connected between point M on the upper end side of R11) via a diode (D7), and the midpoint [F] of the connection between the capacitor and the diode is reversely conductive to that of the @1 cause. Type! = configured control transistor (TR
2) One end of the (TRI) pair (M)g! 41: This is a point directly connected to the base 4 of the other end of this transistor pair (GISV switching transistor (TR4)).

Furthermore, the third feature is that the both ends (kl (between 11 and 6: detection voltage extraction diode (D6) and capacitor (CI) are connected, and this
Resistance (Ri) - two obtained direct fi'il pressure
(vR) (R4) to provide the base (-) of the error detection transistor (TRI) of the conductivity type opposite to that shown in FIG.

In addition, the collector f (04) and the resistor (RIS) connected to the collector C of the switching transistor (TR4)
is for shaping the waveform of the voltage generated by the input winding (Nl) &2 when this TR4 is turned off.

It is also on the emitter side of the transistor (TR4).

Now, in this embodiment, the operation from activation to turn-on of the switching transistor (TR4) is the same as in the case of FIG. 1, so the explanation will be omitted. I will mainly explain.

First, in a steady state (2), when the switching transistor (TR4) is turned on (the principle of operation will be explained later), a current Ii (Fig. 6 (c)) flows through this transistor, and the current A negative voltage that increases with time is generated at the point.Here, during the off-period of the switching transistor (TR4), the current Ir flowing from the feedback winding (NB) (:Therefore, the turn-off capacitor (aS) is charged to the polarity shown in the figure.The emitter of the control transistor (TRI), that is, point M, is the sum (two equivalent Since this is a negative potential (V iris in Fig. 6 (9)), this potential VC decreases (the negative value increases) by one time C during the ON period of the switching transistor ('I'R4). I'm going to go.

On the other hand, the midpoint of the voltage division (Nl) between the collector of the error detection transistor (TR1) and the line (C between L; connected resistor (R7) (Rs) is the capacitor (Nl) with respect to the line (L wall). f) It is a negative potential (V in FIG. 6 (9)) corresponding to the voltage across both ends of I).

For this reason, the potential of the previous M point is lower than the potential of the N point C=
, the control transistor (TRI) is turned on and (TR
1) is also turned on, which causes the turn-off capacitor (06) → detection resistor (R11) → resistor (R14) →
Between emitsuda base of switching transistor (TR4) → control transistor (TR1) → resistor (R1 (1) →
A reverse bias current flows in the path of the capacitor (C5) and turns off the switching transistor (TI(4). Then this transistor (TRY) is connected to the feedback winding (Nlcr) until it is turned on again.
llEEE (Fig. 6 (e) l: Therefore, the off state 62 is maintained.

Here, during the off period of the switching transistor (TR4), the control transistors (τR2) ('I'R1) are both off, so the aforementioned reverse voltage of the feedback winding (Nl) is applied to the M point. Therefore, this point M has a potential that is lower by the magnetic pressure between both ends of the capacitor (05) with respect to 1 m of the line (L2) (see Figure 6).
Therefore, in this state, the reverse bias voltage applied between the base and emitter of the control transistor (TRY) is
[vM■ of J(!J), which is sufficiently lower than that in the case of FIG.

Note that the switching transistor ('
1" R4) turn-on is off period! 'i'li + two-person resonance'4! Waterfall is 1! Ryuukou 1 direction (2 reversals C
This is accomplished by two things. Further, when the switching transistor (TRY) is turned on, the positive return current RIf that splits into two flows along the illustrated thread path. All of these are the same as in the case of FIG. Further, the electron and current waveforms of each part are as shown in FIG.

FIG. 6 shows another embodiment of the invention. In the same figure, the corresponding parts in Figure 2 are all the same symbols! (However, the point where one end of the positive feedback current limiting circuit (EIK) is connected to the end of the winding (No), and the capacitor for taking out the detection voltage (Oi
) is connected in series with the turn-off Bunden fcOs (different from the case in the 1iIZ diagram in that the two are connected. In other words, in this example, both of the windings ('Nm) (Ha) are connected in series with the turn-off Bunden fcOs. By using it for detection, we are able to supply sufficient positive feedback current to the switching transistor (TR4) (2. The capacitor (oi) for outputting the detection 11EEEff described earlier can be of small capacity, but The operation is basically the same as in the case of FIG.

FIG. 4 also shows another embodiment of the present invention. In this embodiment, a single winding (810) is used for both feedback and detection;
D7ζ in Figure 3: The corresponding diode is deleted and the charging voltage of the turn-off capacitor (OS) is obtained by dividing the capacitance with the smoothing capacitor (OS). This is the same as the circuit shown in Figure 5.

Figure 5 is j! (: This shows another embodiment, which differs from the circuit in FIG. 4 in the following points. That is, the charging of the turn-off capacitor (05) is
yIa ) from the end through the resistor (R17) and the diode (D7). The magnitude of the current is adjusted so that the voltage across this capacitor f-(05) is lower than the voltage across capacitor (C5).

In the circuits shown in FIGS. 1 to 5, when the switching transistor (TR4) is turned off, C2, which supplies sufficient reverse bias current between the base and emitter of the switching transistor (TR4), is the capacitor (O5) ( However, in the embodiment shown in Fig. 4, the capacity is divided by the condenser f(ON)(0!i), so in that case, the aS The capacity must also be large, but in such a case the capacitor (O
f) (0@) are connected in series (: Despite this, the combined capacity of the two eventually becomes large, and as a result, the response of the error detection section (4) to fluctuations in the detection voltage is poor. Therefore, the embodiment shown in FIG. 5 eliminates this drawback.

In the switching control type power supply circuit of the present invention as described above, compared to the conventional circuit shown in FIG.
Since the reverse bias voltage applied between the base and emitter of R2) can be made as small as possible, an inexpensive transistor with a relatively low reverse breakdown voltage can be used as the control transistor.

(2) Since the same winding is used for both feedback and detection, or because the feedback winding and the detection winding are provided consecutively, the converter transformer can be miniaturized and its manufacture becomes easy.

(c) Current detection resistor 1 of Sui7dengue transistor:
There is no need to provide a separate resistor or capacitor for the transistor ζ to control the generated voltage, and the number of parts can therefore be reduced.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the voltage and current waveforms of various parts of a conventional switching control type power supply circuit. (1)...Input rectification section, (21...Blocking oscillation section, (3)...Converter transformer, (4)...
Error detection section, (5)...Control circuit section, (6)...-Output rectification section, (TRz) (TRi)...Control transistor, (TR4)...Switching transistor, (R
11) -1Efi detection resistor, (01s)...Bun dench for turn-off. Procedural amendment (self-motivated) June 4, 1980, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 58647, filed in 1982,2, Name of the invention: Switching control type '11m circuit 6, Patent of the person making the amendment Applicant Address: 2-18 Keihan Hondori, Moriguchi City Name (188) Sanyo Electric Co., Ltd. Representative: Kaoru Iue 4, Agent Address: 2-18 Keihan Hondori, Moriguchi City Contact Information: Telephone (Tokyo) 835-1111 Patent Center Resident - Kamata 5, "Detailed Description of the Invention" column 6 of the specification to be amended, each part of the specification of the contents of the amendment has been amended as follows. Delete ``For the purpose of begging.'' Page 9, line 18: ``(Figure 6 pNJ)''
Supplementary E. Page 10, lines 16 and 17 are corrected as follows. ``For this reason, when the potential at point M becomes lower than the potential at point N by the base-emitter voltage (vBE) of the control transistor (TR2), TR2 turns on.''

Claims (1)

[Claims] (1) For DC input, the input winding of the converter transformer, the collector-emitter of the switching transistor, and the current detection resistor are connected in series, and the feedback winding of the transformer and the switching transistor are connected in series. between the base and emitter (-) of the feedback winding to form a blocking oscillation circuit, and between one end or intermediate tap of the feedback winding connected to the base side of the feedback winding and the connection point of the detection resistor and the DC input. (= A diode and a turn-off capacitor f are connected in this order, and the capacitor is charged by the voltage generated when the switching transistor is turned off. The emitter and collector of the control transistor are connected between the sensing resistor (one end of which is connected to the other end of the capacitor and the base of the switching transistor), and the base of the transistor (: a variable DC voltage is connected to the other end of the capacitor). When the voltage generated by the detection resistor is a predetermined value determined by the variable DC voltage (= a predetermined value determined by the variable DC voltage), the control transistor becomes conductive and the charging voltage of the capacitor changes to the switching voltage. The variable DC voltage is applied between the base and emitter of the transistor, and the voltage is applied to the feedback winding or the chain winding. L[l1 obtained from the continuously wound detection winding
llK' is a voltage obtained by comparing and amplifying the high voltage with a constant reference voltage, and the voltage 4: the quick cut timing of the switching transistor is changed accordingly (from the second point).
2. The switching control type power supply circuit according to claim 1, wherein the DC voltage taken out from the output winding of the converter transformer is stabilized.