JPS6281979A - Transistor dc converter - Google Patents

Abstract

PURPOSE:To improve efficiency by stabilizing output voltage by the control of constant voltage by a voltage control circuit together with oscillation operation and stopping the supply of the collector currents of a discharge control transistor from a tertiary winding at ON time of a switching transistor. CONSTITUTION:A constant-voltage output is obtained at an output terminal 12 by controlling constant voltage by a voltage control circuit 11 together with oscillation operation by a transformer 2 and a transistor 4. When the switching transistor 4 is turned ON, the discharge currents of a capacitor 20 flow by a closed circuit consisting of the capacitor 20, a resistor 10, the switching transistor 4 and a discharge control transistor 22, and the base currents of the switching transistor 4 are fed. The voltage of a tertiary winding 9 works the discharge control transistor 22 in the direction of a reverse bias and a diode 19 is fitted at that time, thus making no collector current flow while using the tertiary winding 9 as a power supply.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transistor DC converter for use in a DC power supply circuit for video equipment, audio equipment, etc.

[Conventional technology]

As shown in Figure 2, a transformer (2) is connected to the DC power supply (l, ;
The primary winding m (, s+ and the switching transistor (4
) and the secondary @ wire of the transformer (2) (
A rectifier circuit consisting of a diode (6) and a capacitor (7) is connected to 5), and a transformer + is connected to drive the base.
Volume 3 on 21 m (9)'! -Setting, this 3rd best & +9
)' Connect to the base of the transistor (4) through the resistor aory, further connect the voltage control circuit UUV to the base of the transistor (4), and apply a constant voltage to the output terminal α power. The available switching regulators are known. Note that Q4) is a commercial AC vL source.

It is connected to a DC power supply (11) consisting of a rectifier circuit.

■ is the starting resistance, the drunken current tS peak and the transistor (4)
is connected between the base of the The voltage control circuit old J is a base current bypass transistor (1) connected between the base and emitter of a switching transistor (4).
5), and a diode and capacitor σ71. to control this Y II. When the transistor (4) is off, the voltage of the tertiary winding (9) (equivalent to the output voltage) is photoelectrically applied to the capacitor an, and the scaling of this voltage and the Zener diode (+8) Based on the comparison with the voltage transistor σ5) 'k Ilf control - f
'Ij4IN' has been set as follows.

In the switching regulator described above, when the supply of DC power starts, a starting current flows through the starting resistor Q4) and one oscillation starts. When the transistor (4) is turned on, a power supply voltage is applied to the primary winding 11Jl (3), and a corresponding voltage is applied to the tertiary @ paddy (9).

A base current is supplied from this winding (9) to the transistor (4). Thereafter, when the flefter current of the transistor (4) is saturated, it is turned off, and during this off period, the busy diode (6) is turned on, and the energy of the transformer [2+ is released to the output side. The output voltage is controlled by allowing a part of the current 1 of the tertiary winding (9) to bypass the transistor 5). Since this type of operation is well known, its explanation will be omitted.

By the way, in this type of device, if the voltage E for the power supply increases, the voltage of J2+ and the voltage and current of the tertiary winding (9) also increase. Since the regulator has a voltage control circuit α]J.

3rd @! The entire current I in (9) is the transistor (
4) and is bypassed to the voltage control transistor u9. Since the bypass current is unrelated to driving the transistor (4), it results in a power loss.

Is this problem one device? For example, the AC power supply voltage to be connected is
It becomes noticeable when changing from OOV to 220V. When using with a 100v AC power supply in Japan and 220v in a foreign country.
It is conceivable to configure the power supply circuit to switch according to changes in the AC illumination voltage, so that it can be used in both cases where it is used with an AC power source of 1.
Not only does the circuit configuration become complicated and the switching operation become troublesome, but there is also a risk of forgetting 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 voltage changes for some reason.

The applicant is 1% of Tanuni who solves the above-mentioned problem.
In 1986-45) No. 87, when the switching transistor +4) is off, the tertiary winding +&! A capacitor that is charged with a nearly constant voltage induced in +9)? Provided.

Is there a way to supply the base current of the switching transistor with the charge of this capacitor? The proposed method can greatly improve the efficiency when the input voltage is high.

[The problem that the invention aims to solve]

However, the circuit shown as an example in the above-mentioned application is limited to the capacitor release 1! The kth switch element forming the circuit kl is configured to be forward biased by the tertiary winding. Therefore, a relatively large current flows through the discharge circuit forming switch element based on the voltage of the tertiary winding.

Therefore, an object of the present invention is to provide an extremely efficient transistor@#L converter by utilizing the invention of the above-mentioned application.

Means for Solving Problem C] The present invention, which achieves the above object, will be explained with reference to the reference numerals in the drawings showing the embodiment. A series circuit of a wire (3) and a switching transistor (4), a secondary winding (5) electromagnetically coupled to the primary winding (3), and a 1 mJ What is the diode (6) that turns on when the switching transistor (switching transistor) turns off? Rectifier circuit containing (
8) and the said primary volume 116! +3) and the secondary winding f
5+ 1c 3 electromagnetically coupled and grounded to the base and emitter curve of the switching transistor (4)
Next winding (9)? In the DC converter provided, the above 3
A switching transistor mb capacitor (20) connected between the next winding (9) and the switching transistor (ijJ) and the tertiary winding (9) when the switching transistor (4) is turned off. a diode OCJ connected between one end of the tertiary winding (9) and one end of the capacitor (20) with a polarity turned on at a voltage of ffIJ; is turned on by the voltage induced in the tertiary winding (9) when the tertiary winding (9) is turned off, and is connected to the other end of the tertiary winding (9) and the other end of the continuum winding (0). The second diode IJII and E+ are connected to the capacitor 20.
) is connected between one end of the switching transistor (4) and the emitter of the switching transistor (4), and is oriented in such a way that a one-dimensional voltage is applied between the emitter and the collector by the voltage across the capacitor when the switching transistor (4) is turned on. When the discharge control transistor (22) and the pre-fix switching transistor (4) are off, an on-drive base current is supplied to the FF7 control transistor 2z.

When the switching transistor (4) is turned on, the discharge control transistor [22 is connected to the on-drive base tlr[
With the base control circuit that supplies Kaoru? It is recommended that you have a transistor directly connected to the converter.

[For production]

Since the above invention utilizes the invention of the earlier application, the basic operation is the same as that of the earlier application. Shieta・shi, release? [1
1ll transistor (221 is connected in the forward direction with respect to the capacitor [phase]! 7.3?: is connected in the opposite direction with respect to the winding (9), so when the switching transistor is turned on, 3 The collector current of the control transistor is not supplied from the next winding.

When it is on, almost no current flows through the tertiary winding 1IIl (9),
Power loss t1 is significantly reduced.

〔Example〕

Next, a switching regulator according to an embodiment of the present invention will be described with reference to FIG. However, in the code ~a
8) is substantially the same as the one indicated by the symbol Ll- in FIG. 2, so its explanation will be omitted. In this embodiment, a first diode 09 is connected between one end of the tertiary winding mm (9) and the base of the switching transistor (4).
and resistor aO) and capacitor (21J 7)'-
It is connected. The first diode H is the third best Iv3!
It is connected between one end of (9) and one end (right end) of capacitor I, and is turned on by the voltage induced in the tertiary winding (9) when the switching transistor (4) is turned off. have.

To configure the capacitor 40 photoelectric circuit, the tertiary winding m
A second diode (7III) is connected between the other end (lower end) of +9 and the other end (left end) of the capacitor.

This second diode (2D) has a polarity that turns on when the switching transistor (4) is off.

Discharge 11 for capacitor (2ω discharge circuit)
The J*l transistor Q21 is connected between one end (right end) of the capacitor (20) and the emitter of the switching transistor (4), and is connected to the voltage of the tertiary winding (9) when the switching transistor (4) is off. It has a reverse biased polarity. This discharge control transistor 2z is turned on only when the switching transistor (4) is turned on, and its base is connected to the tertiary winding (9) through a resistor (23).
) is connected to one end of the

Note that the capacitor connected between one end of the tertiary winding (9) and the base of the switching transistor (4) is for quickly starting up.

〔motion〕

In the circuit of FIG. 1, when the electronic switch (not shown) is turned on, the base current of the switching transistor (4) is supplied through the starting resistor [14], and the switching transistor (4) is turned on. After that, when the switching transistor (4) is saturated and turned off, the diode (6) is turned on, and the energy stored in the transformer (2) is released when the switching transistor (4) is turned on, causing the flip switching. The transistor (4) turns on.In addition to the above-mentioned oscillation operation, a constant voltage output is obtained at the output terminal a due to the constant voltage control by the voltage control circuit ulJ.By the way, the on period of the switching transistor (4) In this case, the power supply voltage EI is applied to the tertiary winding (9).
A nearly constant voltage independent of N is generated. This voltage is
Since the voltage is opposite to the voltage when the switching transistor (4) is turned on, the second diode Gll is turned on, and the tertiary winding (9), the second diode Qυ, the capacitor (20), and the second diode Gll are turned on. A closed circuit consisting of 1 diode Q'JE'' is formed, and the capacitor 2 is photoelectronized at a constant voltage.In this off state, the voltage of the 3rd best Ivil (9) is directed to forward bias the discharge control transistor by 1. However, the base of the discharge control transistor is connected to the resistor (23
Since it is connected to the upper end of the third-order transistor (9) with a valve I, no base current flows and the discharge 117 control transistor is kept in an off state.

When the switching transistor (4) is turned on after the capacitor 4 is photoelectrically charged, the capacitor and the resistor (101,
Through the closed circuit consisting of the switching transistor (4) and the control transistor (2a, S), the direct current of the capacitor (20) flows, supplying the base current of the switching transistor (4).At this time, The voltage of tertiary best k (9) is in the direction of reverse biasing between the emitter and collector of the discharge control transistor Q3, and since the first diode a is provided with 1., S, the voltage of tertiary The collector current of the transistor 321 does not flow. However, the base current of the transistor 321 is supplied from the tertiary winding (9) by releasing the resistor from the tertiary winding (9). And it's on! II will be controlled. As a result, a capacitor-like discharge circuit is established, and a base current is supplied to the switching transistor (4).

In this circuit, the AC power supply voltage ranges from 100V to 220V, for example.
When VIC changes, switching transistor (4)
When the tertiary winding (9) is turned on, the voltage of the tertiary winding (9) is also low, but the voltage of the tertiary winding (9) is the same as that of the switching transistor (4) and the capacitor. It becomes virtually unrelated to the photoelectric current of (2).Therefore, the switching transistor (4) has an AC?IV source voltage of 0.
It is controlled in the same way as when it is 0V, and a constant voltage is obtained at the output terminal (1'/!J) regardless of fluctuations in the input voltage.

As is clear from the above ρλ and X, in the circuit of Figure 1, the formula is;
Since fluctuations in input voltage are not absorbed by the voltage III control transistor (15), power loss is reduced. Further, the dynamic range of the constant voltage control transistor (15) may be narrow. In addition, if the output terminal uz is short-circuited, the voltage of the capacitor gull will drop, so the switching transistor (4)
The ON period is short, and a fold-back drooping characteristic can be obtained. Furthermore, when the switching transistor (4) is on, the tertiary winding (9) supplies the base current of the discharge control transistor and the capacitor c! 4) to supply the starting current of 1, and discharge I control transistor 2
Since no collector current is supplied, power losses are significantly reduced, and efficiency is greatly improved, especially when the input voltage is low.

The present invention is not limited to the above embodiments, but may be modified. For example, as shown in FIG. 3, in order to control the constant voltage IU control transistor (15!), the voltage at the output terminal A is detected, and the constant voltage control circuit T271 is controlled by I11 to keep this voltage constant. Alternatively, the constant voltage regulator transistor U may be omitted in the circuit shown in FIG. 1, and the cathode of the Zener diode (18) may be connected to the base of the switching transistor (4). It can also be applied when the foot voltage control circuit TIUV is not provided.-1:T, as shown in FIG.
A suboptimal line mark may be provided on the transformer +21, and the base current of the discharge control transistor may be supplied by the voltage of the fourth winding (to) when the switching transistor (4) is on. Also, a speed-up capacitor may be connected in parallel with the resistor 0ω. Alternatively, the capacitor (2) may be connected in series with the lower part of the third-order H(9). Alternatively, the starting current may be supplied by the starting resistor (2) with a current of 9K (starting current).

[gjj fruit of invention]

As is clear from the above, according to the present invention, fluctuations in the output voltage corresponding to fluctuations in the input power supply voltage can be prevented by the robust circuit configuration consisting of a capacitor, this photodischarge control circuit, and the like. : I can do things. Further, it is possible to suppress a decrease in efficiency when the input power supply voltage is high.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a switching regulator according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional switching regulator, and FIG. 3 is a circuit diagram showing a part of a modified switching regulator. (11...1! Source, (21...Trans, (3)・
...Primary winding, (4)...Switching transistor, (5)...Secondary winding, (8)...Rectifier circuit, (9
:...Tertiary winding, a(...first diode, (2
1 node... capacitor, C'll... second diode,... discharge i1J II) transistor.

Claims (1)

[Claims] (1) The transformer primary winding (
3) and a switching transistor (4), and a secondary winding (5) electromagnetically coupled to the primary winding (3).
and a diode () connected to the secondary winding (5) and turned on when the switching transistor (4) is turned off.
a rectifier circuit (8) containing the primary winding (3);
) and a tertiary winding (9) electromagnetically coupled to the secondary winding (5) and connected between the base and emitter of the switching transistor (4), The tertiary winding (9) and the switching transistor (
A switching transistor driving capacitor (20) connected between the switching transistor (4) and the switching transistor (3) when the switching transistor (4) is turned off.
A first diode ( 19 )and,
When the switching transistor (4) is off, the 3
The other end of the tertiary winding (9) and the capacitor (20) have a polarity that is turned on by a voltage induced in the secondary winding (19).
a second diode (21) connected between one end of the capacitor (20) and the emitter of the switching transistor (4); A discharge control transistor (22) is oriented so that a forward voltage is applied between the emitter and collector depending on the voltage of the capacitor (20) at times, and when the switching transistor (4) is turned off, the control transistor (22) 22) and a base control circuit that does not supply an on-drive base current to the switching transistor (4) and supplies an on-drive base current to the discharge control transistor (22) when the switching transistor (4) is on. DC converter.