JPS62173981A - Transistor dc converter - Google Patents

Abstract

PURPOSE:To inhibit overcurrents, sharing a transistor for controlling discharge by OFF-controlling the transistor for controlling discharge and suppressing the base currents of a switching transistor when the voltage of a transformer drops by a load short-circuit, etc. CONSTITUTION:A constant-voltage output is acquired at an output terminal 36 by oscillation operation by a switching transistor 6 as well as constant- voltage control by a voltage control circuit 26. When the output terminal 36 is brought to a short-circuit state and the voltage of each winding for a transformer 4 largely drops, a Zener diode 23 cannot be turned ON by the voltage of a tertiary winding 11, a transistor 20 for controlling discharge is not turned ON, and a discharge circuit for a capacitor 16 is not formed. Accordingly, the base currents of the switching transistor 6 largely lower, thus inhibiting the collector currents of the transistor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transistor direct current converter for using direct current in a valve circuit of video equipment, audio equipment, etc.

[Conventional technology]

The primary, secondary, and tertiary windings of the transformer are coated, and the switching transistors connected to the primary winding in a series of peaks are driven on and off by the voltage of the tertiary winding, and the output stage of the secondary winding is An on/off type switching regulator, generally called a CC, which obtains a regulated output voltage is well known.

In this switching regulator of sustenance! As the voltage increases, the voltage in the primary winding and the voltage and current in the tertiary winding also increase. To maintain constant voltage characteristics, 3
All of the current in the next winding must be bypassed to the voltage control transistor instead of being supplied to all switching transistors. Since the bypass tfi is related to the driving of the switching transistor, it results in power loss.

This problem is caused by the AC 11 that connects the equipment! This becomes noticeable when the voltage is changed from 100 to 220, for example. When using 100V AC t@ in Japan and 22V in foreign countries.
In order to be able to cope with the problems when using a 0V AC power supply, it may be possible to configure the power supply circuit by switching it according to changes in AC iamt pressure, but instead of using one circuit. Not only is the configuration complicated and the switching operation troublesome, but there are also cases where people forget to switch. Such a problem occurs not only when the AC power supply voltage changes, but also in any case where the DC power supply terminal changes for some reason.

In order to solve all the problems mentioned above, the applicant has filed Japanese Patent Application No. 60-45) 87 and % Application No. 60-22167.
0e, we proposed a method in which a capacitor is provided that is exposed to the almost constant voltage obtained in the transformer when the switching transistor is off, and the base current of the switching transistor is supplied by the charge of this capacitor. According to this method, it is possible to significantly improve the efficiency when the input voltage is high.

[Problem that the invention seeks to solve]

However, the above-mentioned application does not explain overcurrent protection.Therefore, an object of the present invention is to provide both overcurrent protection against load short circuits and prevention of efficiency decline due to input voltage fluctuations using a common circuit. Our aim is to provide DC converters that can be used.

[Means to solve problems]

To achieve the above object, the present invention will be described with reference to the reference numerals in the drawings showing the embodiments.
5), a switching transistor (6) whose collector is connected to the other end of the primary winding (5), and whose emitter is connected to the other end of the pair of DC power supply terminals; A secondary winding (7) electromagnetically coupled to the wire (5) and a rectifier connected to the secondary 9 wire (7) with a polarity that turns on at 7r7 of the switching transistor (6). , an n* smoothing capacitor (9) connected between a pair of output lines on the output side of the diode (8), the primary winding (5; and the secondary winding (71)
1 to 1! && coupled tertiary winding (old), a base driving capacitor ub+ for supplying base current to the switching transistor (6), and a base driving capacitor ub+ for supplying base current to the switching transistor (6), and a ) voltage to charge the base driving capacitor u6), and a charging circuit that charges the base driving capacitor u6) with the switching transistor (6) voltage, and supplies a discharge current of the base driving capacitor (output) as the base current of the switching transistor (6) during the ON period of the switching transistor (6). A discharge control circuit selectively connects the base driving capacitor 06) between the base and emitter of the switching transistor (6), and a discharge control circuit that selectively connects the base driving capacitor 06) to the switching transistor (9) to keep the output voltage constant. The base of (6) has a constant voltage control circuit section that controls the current and performs DC-DC conversion.7? (
16+ 'a' The switching transistor (6)
A discharge control transistor (to) for selectively connecting between the base and the emitter and a voltage of 2 (°C) obtained from the transformer (4) during the ON period of the switching transistor (6). If the value is within the normal range, the discharge control transistor is turned on by the voltage Vc of the transformer (4), and the voltage obtained from the transformer (4) is lower than the normal range. The present invention relates to a transistor DC converter characterized in that the transistor control circuit for controlling the discharge control turns off the discharge control transistor when the voltage is low (.p).

[Written by Kawa]

The above invention Kky is a discharge control transistor C.
Since Al+ is turned on in the normal voltage range, supplying the base current of the ℃ switching transistor (6) by the base driving capacitor kills the voltage. Since the base driving capacitor is charged with a controlled voltage during the off period, it is possible to drive the switching transistor (6) with low loss regardless of fluctuations in the power supply voltage. When the transformer (
4; voltage decreases.

Therefore, the discharge control transistor +2[11 is turned off, and the supply of base current from the base drive capacitor (16I) is stopped.Conclusion 1: An excessive current does not flow through the switching transistor (6).

[Example of actual gallery]

Next, a DC converter according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. This DC converter is a ringing choke converter (,: ni) type, and AC 1
! Connected to source terminal +f I f21 t-L DC current - (
A switching transistor (6) is connected between one end and the other end of (3) via a transformer (4) (i+5). The secondary winding (7) of the transformer +4) is
Rectifier diode (81) and smoothing capacitor (91)
The rectifying and smoothing circuit (101 is connected to the transformer (4) and the tertiary winding σ1) is connected to one end of the base driving Ml capacitor u and the resistor [31 and t of the switching transistor (6). It is connected to the base, and the other end is connected to the emitter.
3) It is connected between one end and the base of the switching transistor (6).

11b+ is a second capacitor for driving the t base, which is provided at °C according to the present invention. This second capacitor ubl'
As a charging circuit for charging the tertiary winding with a voltage during the off-period of the switching transistor (6), a reverse current is created between one end of the capacitor σ (to) and one end of the tertiary winding (11). A blocking diode (171) is connected.

Moreover, a die γ-de uQ and a resistor (+91) are connected between the other end of the tertiary winding [1] and the other end of the second capacitor (field).

In order to divert the emitted TaX current of the second capacitor t16) as the base current of the switching transistor +6) during the ON period of the switching transistor (6), one end of the second capacitor +16) is connected to the discharge control transistor ■ and the resistor VcαII. and the switching transistor (6
), and the other end of the second capacitor (1b) is connected to the resistor U and the switching transistor (6
) is connected to the base of n.

In order to turn on the discharge control transistor (201?) only when the voltage of the transformer (4) is within the normal range (pJr constant value or higher), a resistor 122 is connected between this base and one end of the tertiary winding (1N+). A Zener diode is connected through n'''C. The Zener diode serves as a control circuit for selectively turning on the discharge control transistor 4.

′ during the on period of the switching transistor (6)
In order to obtain a transformer voltage corresponding to the voltage, a quaternary winding 12 is provided, and this voltage is
Resistance cl! It is connected in parallel with H. 2. The series (b) path between the capacitor (IZ) and the resistor is the plane series (b) of the diode u71, the second capacitor, and the resistor (191).
b) Connected in parallel to the road.

C26) is one circuit on the constant a pressure side, and the base FM of the switching transistor (6) is connected between this base and emitter to control the flow rate. l
! tR bypass river transistor 127) and this transistor! To explain in more detail, a transformer 5th winding (7+9 is provided) as an output voltage detection winding, and a group of diodes is connected to this 5th winding #i!. The polarity of the second and fifth lines and the diode (7) are connected to the switching transistor (6).
It is set to charge the capacitor 3υ when the power is turned off. Therefore, the voltage across capacitor CD is approximately proportional to the output voltage. A capacitor C31) is connected across the resistor C3, and this voltage dividing point is connected to the base of the transistor ℃(・ru.The emitter of the transistor □□□ is
Connected across the capacitor C (II) and connected to the voltage dividing point between the resistor C and the Zener diode 35. Therefore, the transistor θ is connected to the Zener diode 35
) given by constant voltage t and resistor 3
This error signal is applied to the base of the bypass transistor surface.

As a result, for example, when the output voltage is too high, the resistance value of the bypass transistor becomes small, the bypass amount of the base current increases, and the base current of the switching transistor (6) decreases. (6) The on period becomes shorter and the output voltage returns to a constant value. If the output voltage is too low, the opposite behavior will occur.

〔motion〕

In the circuit shown in Figure 1, when the '\L source switch (shown) is turned on, the base current of the °C switching transistor (6) is supplied through the starting resistor (u5), and the switching transistor (6) is turned on. . After the switching transistor (6) is saturated and turned off,
When the diode (81) is turned on and the switching transistor +6 is turned on, the energy stored in the transformer (4) is released, and when this release ends, the switching transistor (6) is turned on.

Along with the generation operation as described above, a constant voltage is outputted to the output terminal mark by constant voltage control by the voltage control circuit section.

By the way, during the off period of the switching transistor (6), a substantially constant voltage is generated in the tertiary winding "till" in relation to changes in the power supply voltage. Since this voltage is opposite to the voltage when the switching transistor (6) is turned on, the diode α[71 is turned on and the tertiary winding port 1
1. Diode α~, resistor a9, second capacitor αυ
, and a diode lη, a charging closed circuit is formed,
The capacitor is charged with constant voltage.

At 7 o'clock hv, a voltage of 3rd order f/Mllll is generated in the direction of forward biasing the discharge control transistor, but the base of the discharge control transistor is a resistor and the zener diode is closed. Since it is connected to the upper end of the tertiary winding (old), the base current flows, and the discharge control transistor 4 is kept in the f7 state.

When the switching transistor (6) is turned on after the capacitor ub+ is charged, the capacitor (16), the resistor α9), the switching transistor (6), the resistor 2υ, and the discharge? A discharge current flows through the capacitor (16)0 through the discharge closed circuit consisting of the I7 control transistor (4),
The base current of the switching transistor (6) is supplied. At this time, the tertiary winding (1110) voltage is applied to the Zener diode +231 and the base of the transistor C0 for controlling the cable discharge tti of the resistor.

Figure 2 shows the switching transistor (
6) The waveform to the base current is shown below. When the on-period occurs at tl, an upward voltage is generated in the tertiary winding aυ, and a large base current is momentarily supplied by the base current supply circuit consisting of the capacitor q and the resistor a. At the same time, since the discharge control transistor (2 (J) is turned on, the second
A second base current supply circuit consisting of a capacitor (16I discharge (g4 path) also supplies a base 1! current.
After a little more than n), the base current supply through the capacitor Q decreases, but the supply of base current through the capacitor Q decreases;
The supply of base current by I continues.

By the way, a resistor 7 is installed in the discharge circuit of the second capacitor ubl.
11 is connected, and the voltage of the fifth winding is applied here. Therefore, when the 11L source voltage increases, the resistance of the discharge circuit of the second capacitor u6) increases,
The current supplied from the second capacitor L1b decreases. This restricts the supply of excessive drive current.
, efficiency improves. The current flowing through the capacitor 02 increases as the 711 voltage increases (although it is instantaneous, so it does not affect the power loss much).

When the output terminal marks become short-circuited, the voltage of each winding of the transformer (4) drops significantly. As a result, it becomes impossible to turn on the Zener diode with the voltage of the tertiary winding till divided into the on period, and the discharge control transistor 4 does not turn on, forming a discharge circuit for the second capacitor ubl. Not done. Due to this, the base current of the switching transistor (6) is:

No.) Capacitor aZ and resistor a3! As shown in FIG. 3, the current is supplied through the circuit and is significantly reduced, suppressing the collector current of the switching transistor (6).

Note that when the voltage of the DC power supply (3) is in the range of 0 to 60V, the Zener diode is kept off during the on period of the switching transistor (6).

The base current is only supplied via the capacitor α2. When the power supply voltage exceeds 60V'Y.

The Zener diode is turned on, allowing the second capacitor to supply base current.

The blood flow transducer of this example is used at 100-220V.
Therefore, unless an abnormality such as a load short circuit occurs, the base current I# is supplied by the second capacitor t16).

[Modified example]

The invention is not limited to the embodiments described above.

For example, the following hand shapes are possible.

^1 As shown in factor 4, instead of the first constant voltage control circuit Miya, a control circuit tv) Y is provided to form an error signal between the voltage at the output terminal ω and the base S voltage, and the error output is used for bypass. It is also good to control the transistor @.

(8) As shown in Figure 15, the pressure control circuit has a four-diode C effect, a capacitor field, and a Zener diode (4) 1
It is also possible to form a with a bypass transistor digit (1° (C1 As shown in Fig. 6, a charging winding (4) 1 is provided in the transformer (4) separately from the tertiary winding 111I, and this is connected to the second capacitor σ8 through the diode (4 pins),
It is also possible to emit light using the voltage during the off period.

〔Effect of the invention〕

As is clear from the above υ), when the voltage of the transformer decreases due to a load short circuit, etc., the discharge control transistor is turned off.
(As a result, the base current of the switching transistor is suppressed. Therefore, the overcurrent due to load short circuits, etc. is suppressed by sharing the discharge control transistor, and the N1 circuit formation is simplified. 1 sudden power loss is reduced. It becomes less.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an RJ 4-flow current transformer according to an embodiment of the present invention. The second figure is a waveform diagram of the base current of the switching transistor when the voltage of the transformer is normal. Figure 3 is a waveform diagram of the base current of the switching transistor when the voltage of the transformer is low, Figures 4, 5, and 6.
The figures are circuit diagrams each showing a part of a blood flow transducer of a modified example. (5)...Primary winding [16)...Switching transistor. mouth υ...tertiary winding, aZ...th) capacitor, le...
...2nd C capacitor, rigid...discharge control transistor, 1231...T 1932 Patent Application No. 153282, Title of Invention Transistor DC Converter 3, Pi
Ii Relationship with the case of the person making the correction Applicant 4, Agent 5, Date of amendment order Voluntary 6, Number of inventions increased by amendment 7, Subject of amendment (1) Negative line 9, line 12 of the specification “And the enemy (11 and)”
Delete. (2) Figure 1 of the drawing shall be amended to the attached drawing.

Claims (1)

[Claims] (1) A primary winding (5) of a transformer (4) whose one end is connected to one of a pair of DC power supply terminals, and
5) a switching transistor (6) whose collector is connected to the other end and whose emitter is connected to the other of the pair of DC power supply terminals; and a secondary winding that is electromagnetically coupled to the primary winding (5). a rectifying diode (8) connected to the secondary winding (7) and having a polarity that turns on when the switching transistor (6) is turned off; A smoothing capacitor (9) connected between a pair of output lines on the output side and the primary winding (
5) and a tertiary winding (11) electromagnetically coupled to the secondary winding (7); a base drive capacitor (16) for supplying base current to the switching transistor (6); During the OFF period of the transistor (6), the voltage of the tertiary winding (11) is applied to the base driving capacitor (16).
); and a charging circuit configured to charge the base driving capacitor (16) so as to supply a discharge current of the base driving capacitor (16) as a base current of the switching transistor (6) during the ON period of the switching transistor (6). 16), a discharge control circuit that selectively connects the base and emitter of the switching transistor (6), and a base current of the switching transistor (6) so as to keep the output voltage of the smoothing capacitor (9) constant. and a constant voltage control circuit (26) for controlling DC-DC conversion, and the discharge control circuit connects the base driving capacitor (16) between the base and emitter of the switching transistor (6). a discharge control transistor (20) for selectively connecting to the discharge control transistor (20); and if the voltage obtained from the transformer (4) during the ON period of the switching transistor (6) has a value within a normal range, the discharge control Transistor (20)
is controlled to be turned on based on the voltage of the transformer (4), and the discharge control transistor (20) is controlled to be turned off when the voltage obtained from the transformer (4) has a value lower than the normal range. A transistor direct current converter comprising a control transistor control circuit.