JPS63167674A - Flyback type ringing choke converter - Google Patents

Abstract

PURPOSE:To reduce the size and the weight of a flyback type ringing choke converter by using the base-driving winding of a converter transformer as a secondary winding in combination. CONSTITUTION:A ringing choke converter is composed of a constant-voltage controller having first-second switching transistors (Tr) Q1-Q2. a converter transformer TS, its primary winding L1, secondary winding L2, an oscillation time constant regulating resistor R1 and capacitor C2, and a constant voltage control Tr Q3. In this case, positive feedback voltage supplying means including a series circuit of a resistor R1 and a capacitor C2 is provided between one end of the winding L2 of the transformer TS and the Trs Q1, Q2. This means uses the base driving winding L3 of the transformer TS as the secondary winding L2 in combination, and supplies its induced voltage as a positive feedback voltage to the base of the Tr Q1. Thus, as the ON/OFF time ratio of the Trs Q1, Q2 is varied, even if a load current increases at the time of small input voltage, an output voltage does not lower.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flyback type ringing choke converter (single-stone self-excited DC-DC converter).

(Prior art) This type of conventional ringing choke converter has a second
There is a circuit configuration shown in the figure. The circuit configuration of the ringing choke converter shown in FIG. 2 will be explained together with its operation.

In FIG. 2, the positive voltage of the DC power supply is always applied to the DC power supply terminal Vdd. When an on/off switch (not shown) connected to the input terminal IN is turned on in this application state, a starting current flows from the DC power supply terminal Vdd to the base of the first switching transistor Ql via the starting resistor R3, causing the first switching transistor Ql to turn on. switching transistor Q
1 is conductive. Due to this conduction, a base current is supplied to the base of the second switching transistor Q2 via the collector-emitter of the first switching transistor Ql.

This base current makes the second switching transistor Q2 conductive, and the current from the DC power supply terminal Vdd flows to the ground via the primary winding L1 of the converter transformer TS and the collector-emitter of the second switching transistor Q2.

Then, when current flows through the negative winding Ll, the secondary winding L2 and the base drive winding L of the converter transformer TS
A voltage is induced at 3. The voltage induced in the base drive winding L3 is applied to the base of the first switching transistor Ql through the resistor R1 and capacitor C2, which together with the base drive winding L3 constitute elements for adjusting the oscillation time constant of the switching transistor. supplied to In this case, this voltage acts as a positive feedback voltage that further conducts the first switching transistor Ql in the on direction, so the first switching transistor Q1 is rapidly turned on, and at the same time, the second switching transistor Q2 is also turned on. .

In this case, the polarity of the voltage across the secondary winding L2 of the converter transformer TS is the voltage polarity that makes it non-conductive with respect to the rectifier diode D2, that is, the polarity of the voltage across the secondary winding L2 of the converter transformer TS is the voltage polarity that makes it non-conductive with respect to the rectifier diode D2. Since the voltage at one end of the winding L2 becomes positive, the rectifier diode D2 becomes non-conductive and no current flows through the secondary winding L2. Therefore, only the excitation current of the converter transformer TS flows through the negative side winding L1. Since this excitation current increases in proportion to time, the second switching transistor Q
2 collector current increases. In this case, since the base current of the second switching transistor Q2 is supplied from the first switching transistor Ql, the collector current of the first switching transistor Ql tends to increase.

However, since the collector current of the first switching transistor Ql is limited by the base current supplied from the base drive winding L3, if the base current cannot maintain the saturation of the first switching transistor Ql, the collector current of the first switching transistor Ql 1 switching transistor Ql goes out of saturation. Therefore, the base current of the second switching transistor Q2 is also limited, and if it becomes unable to maintain saturation as the current of the second switching transistor Q2 itself increases, the second switching transistor Q2 will also come out of saturation. As a result, the collector-emitter voltage of the second switching transistor Q2 increases.

When the collector-emitter voltage of the second switching transistor Q2 increases and the voltage across the primary winding L1 of the converter transformer TS decreases, the voltage across the base drive winding L3 also decreases. Then, the first. The collector-emitter voltage of the second switching transistors Q1 and Q2 further increases. A collector like this
Since the increase in the emitter voltage is positively fed back, the eleventh and second switching transistors Ql and Q2 are quickly turned off.

At the moment when each switching transistor Ql, Q2 turns from on to off, the diode D2 becomes conductive due to the current flowing through the secondary winding L2, which is determined according to the relationship of the magnetic field between the - secondary winding Ll and the secondary winding L2. do. Then, when diode D2 becomes conductive, the anode side voltage of diode D2,
That is, the output terminal 0UT(-) side layer pressure is a voltage obtained by subtracting the voltage across the diode D2 from the voltage across the secondary winding L2.

Then, when the magnetic energy stored in the converter transformer TS is transferred to the output side, the current in the diode D2 becomes zero, so the diode D2 is turned off. At the moment the diode D2 is turned off, the winding voltages of the primary and secondary windings Ll and L2 of the converter transformer TS become zero, but the voltage of the first switching transistor Ql again flows through the starting resistor R3. It is turned on by current.

Such an eleventh second switching transistor Q1.
Output terminal 0UT(-) due to repeated on/off of Q2
is given a DC voltage.

A constant voltage control transistor Q3 is connected between the output terminal 0UT(-) and the base of the first switching transistor Q1.
, a constant voltage control circuit composed of a constant voltage diode DI and a bias resistor R2 is connected thereto. Since the operation of this constant voltage control circuit is well known, its explanation will be omitted. CI is a capacitor for cutting direct current.

(Problem to be Solved by the Invention) In recent years, there has been a strong demand for smaller and lighter ringing choke converters, and with this, there is also a desire to reduce product costs without deteriorating operating performance. However, in the conventional ringing choke converter, the base drive winding L is used to supply a positive feedback voltage to the base of the first switching transistor Q1.
3 is required. This base drive winding L3
Therefore, in conventional ringing choke converters, the converter transformer is not only heavy and large, but also the product cost is high, and it has been pointed out that there is a problem that it cannot meet the above requests and requests. Ta.

In addition, in the ringing choke converter with the conventional structure, when the output is increased (load current is increased) while the power supply voltage (input voltage) input manually from the power supply terminal Vdd is kept constant, the output voltage increases at a certain load current value. However, the degree of the decrease was particularly noticeable when the input voltage was low, and as a result, the output voltage characteristics were not very good.

Therefore, in order to solve the above problem, the present invention makes the secondary winding of the converter transformer also serve as the base drive winding, thereby creating a base drive winding separate from the primary winding and the secondary winding. This eliminates the need to provide a power supply, making the product smaller and lighter, and lowering product costs.It also maintains good output voltage characteristics by preventing the output voltage from dropping too much even when the input terminal is low and the load current increases. The present invention aims to provide a ringing choke converter that can be obtained.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides for a voltage induced in the secondary winding between one end of the secondary winding of the converter transformer and the base of the switching transistor. A positive feedback voltage supply means is provided for supplying a positive feedback voltage to the base of the switching transistor, and the base driving color wire for supplying the positive feedback voltage to the base of the switching transistor is also used as the secondary winding, and the secondary winding The invention is characterized in that the voltage induced in the side winding is supplied as the positive feedback voltage to the base of the switching transistor via the positive feedback voltage supply means.

(Function) By providing the secondary winding that also serves as the base drive winding, there is no need to provide a separate base drive winding.

In addition, since the voltage across the secondary winding is the positive feedback voltage to the base of the switching transistor, in the input/output voltage equation of the switching transistor expressed by the following equation, the length of TI with respect to T2 of the present invention is longer than the conventional one.

Vo = A-Vi ''-(Tl'/(Tl+72)] where A is a constant, Vo is the output voltage, Vi is the input voltage, T
1 is the on period of the switching transistor, and T2 is the off period of the switching transistor.

In other words, when the input terminal is low, the load current increases and the output voltage does not drop significantly as in the conventional case.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram of a flyback type ringing choke converter according to an embodiment of the present invention. In FIG. 1, parts corresponding to those in FIG. 2 are given the same reference numerals.

In the ringing choke converter of the embodiment, the second
Portions with the same reference numerals as those in the conventional example in the figures have the same configuration unless otherwise specified.

The configurations of the embodiment that differ from the conventional example are as follows.

That is, between one end of the secondary winding L2 of the converter transformer TS and the bases of the eleventh second switching transistors Ql and Q2 (however, the second switching transistor Q
In the case of 2, it is passed through the DC cut capacitor CI. )
A positive feedback voltage supply means including a series circuit of a resistor R1 and a capacitor C2 is provided.

This positive feedback voltage supply means doubles the base drive winding L3 of the converter transformer TS as the secondary winding L2, and supplies the induced voltage in the secondary winding L2 to the first switching as the positive feedback voltage. It is designed to be supplied to the base of transistor Ql.

A description of the basic operation of the converter L ringing choke converter will be omitted since it is the same as that shown in FIG. 2.

In the ringing choke converter of this embodiment, when a voltage is applied to the primary winding Ll of the converter transformer TS, a voltage is simultaneously induced in the secondary winding L2, which also serves as the base drive winding Ll. . The voltage induced in the secondary winding L2 is applied in the opposite direction to the rectifier diode D2.

Therefore, the induced voltage in the secondary winding L2 is applied as a positive feedback voltage to the base of the first switching transistor Q1.

This positive feedback voltage causes each switching transistor Ql to
, Q2 turns on and off.

(Effects) As is clear from the above explanation, according to the present invention,
Since the base drive winding of the converter transformer is also used as the secondary winding, there is no need to provide a separate base drive winding.As a result, not only can the converter transformer be made smaller and lighter, but the base drive Since no winding is required, it is possible to obtain a converter with a low product cost.

Furthermore, in the present invention, since the base drive voltage of the switching transistor is the voltage generated between both ends of the secondary winding, as described in the above (effects) section, as the on/off time ratio of the switching transistor changes, Even if the load current increases when the input voltage is small, the output voltage does not drop as much as in the past, and as a result, good output characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional example. Q11Q2 are switching transistors, TS is a converter transformer, Ll is a primary winding, and L2 is a secondary winding.

Claims (1)

[Claims] (1) A switching transistor that is driven to oscillate at a predetermined oscillation frequency by a positive feedback voltage applied to the base, and a primary winding whose one end is connected to a DC power supply terminal and whose other end is connected to the collector of the switching transistor. a converter transformer including a base drive winding that supplies the positive feedback voltage to the base of the switching transistor, and a secondary winding whose one end is connected to one pole of the rectifier diode; a constant voltage control circuit connected between the pole part and the base of the switching transistor; one output terminal connected to the other pole part of the rectifier diode; and the other output terminal connected to the DC power supply terminal. and a pair of output terminals, the flyback ringing choke converter comprising: one end of the secondary winding connected to one pole of the rectifier diode and a base of the switching transistor; A positive feedback voltage supply means is provided between the secondary winding and the base to supply the voltage induced in the secondary winding to the base as a positive feedback voltage, and the base drive winding is also used as the secondary winding. A flyback type ringing choke converter, characterized in that the voltage induced in the secondary winding is supplied as the positive feedback voltage to the base of the switching transistor via the positive feedback voltage supply means.