阅读说明：本技术 一种自激式推挽电路 (Self-excitation push-pull circuit ) 是由 王中于 于 2020-03-24 设计创作，主要内容包括：本发明公开了一种自激式推挽电路,包括第一图腾柱电路,包括三极管Q1和三极管Q4,三极管Q1的集电极连接有输入源正端,三极管Q1的发射极与三极管Q4的集电极相连；三极管Q1和三极管Q4的基极均经电阻与电源输入端相连,三极管Q4的发射极连接输入源负端；第二图腾柱电路包括三极管Q2和三极管Q3,三极管Q2的集电极连接输入源正端,三极管Q2的基极与电源输入端相连,三极管Q2的发射极与三极管Q3的集电极相连,三极管Q3的发射极连接输入源负端,三极管Q3的基极与变压器相连；变压器,包括连接变压器的原边绕组N1和N2,原边绕组N1的两端分别与三极管Q1的发射极、三极管Q2的发射极相连,原边绕组N2连接输出电路。本发明可简化变压器绕制工艺和焊接难度。(The invention discloses a self-excited push-pull circuit, which comprises a first totem pole circuit, a second totem pole circuit and a third totem pole circuit, wherein the first totem pole circuit comprises a triode Q1 and a triode Q4, the collector electrode of the triode Q1 is connected with the positive end of an input source, and the emitter electrode of the triode Q1 is connected with the collector electrode of a triode Q4; the base electrodes of the triode Q1 and the triode Q4 are connected with the input end of the power supply through resistors, and the emitting electrode of the triode Q4 is connected with the negative end of the input source; the second totem pole circuit comprises a triode Q2 and a triode Q3, wherein a collector of the triode Q2 is connected with the positive end of an input source, a base of the triode Q2 is connected with the input end of a power supply, an emitter of the triode Q2 is connected with a collector of the triode Q3, an emitter of the triode Q3 is connected with the negative end of the input source, and a base of the triode Q3 is connected with the transformer; the transformer comprises primary windings N1 and N2 connected with the transformer, two ends of the primary winding N1 are respectively connected with an emitter of a triode Q1 and an emitter of a triode Q2, and the primary winding N2 is connected with an output circuit. The invention can simplify the winding process and welding difficulty of the transformer.)

1. A self-excited push-pull circuit, comprising:

the first totem pole circuit comprises a triode Q1 and a triode Q4, wherein the collector electrode of the triode Q1 is connected with the positive input source terminal, and the emitter electrode of the triode Q1 is connected with the collector electrode of the triode Q4; the base electrodes of the triode Q1 and the triode Q4 are connected with the input end of the power supply through resistors, and the emitting electrode of the triode Q4 is connected with the negative end of the input source;

the second totem pole circuit comprises a triode Q2 and a triode Q3, wherein the collector of the triode Q2 is connected with the positive end of the input source, the base of the triode Q2 is connected with the input end of the power supply, the emitter of the triode Q2 is connected with the collector of the triode Q3, the emitter of the triode Q3 is connected with the negative end of the input source, and the base of the triode Q3 is connected with the transformer;

the transformer comprises primary windings N1 and N2 connected with the transformer, two ends of the primary winding N1 are respectively connected with an emitter of a triode Q1 and an emitter of a triode Q2, and the primary winding N2 is connected with an output circuit.

2. A self-excited push-pull circuit as claimed in claim 1, wherein the transistors Q1, Q2, Q3 and Q4 are NPN transistors.

3. A self-excited push-pull circuit according to claim 2, wherein in the first totem pole circuit, the on-off states of transistor Q1 and transistor Q4 are opposite; in the second totem pole circuit, the on/off states of the transistor Q2 and the transistor Q3 are opposite.

4. A self-excited push-pull circuit as claimed in claim 3, wherein the base of the transistor Q1 is connected with a diode D1, the cathode of the diode D1 is connected with the B terminal of the primary winding N1, and the a terminal of the primary winding N1 is connected with the base of the transistor Q4 via a capacitor C2; the emitter of the transistor Q1 is connected with the collector of the transistor Q4 through a diode D3, and the cathode of the diode D3 is connected with the B end of the primary winding N1.

5. The self-excited push-pull circuit as claimed in claim 4, wherein a diode D2 is connected to the base of the transistor Q2, and the cathode of the diode D2 is connected to the a terminal of the primary winding N1; the emitter of the transistor Q2 is connected to the collector of the transistor Q3 through a diode D4, the base of the transistor Q3 is connected to the B terminal of the primary winding N1, and the cathode of the diode D4 is connected to the A terminal of the primary winding N1.

6. The self-excited push-pull circuit of claim 5, wherein the base electrodes of the transistor Q1, the transistor Q2, the transistor Q3 and the transistor Q4 are respectively connected with a resistor R1, a resistor R2, a resistor R3 and a capacitor C1.

7. A self-excited push-pull circuit as claimed in claim 1, wherein the input source negative terminal is connected to ground.

8. The self-excited push-pull circuit according to claim 1, wherein the output circuit comprises a rectifying circuit connected to the primary winding N2, and the rectifying circuit is a bridge rectifying circuit or a half-wave rectifying circuit.

9. A self-excited push-pull circuit as claimed in claim 1, wherein the number of coils connecting the primary windings N1 and N2 of the transformer is the same.

Technical Field

The invention relates to the technical field of transformers, in particular to a self-excitation push-pull circuit.

Background

In the existing communication and power equipment, especially in the low-voltage DC/DC power converter with power within 0.1-2W, the self-excited push-pull circuit is used, the power module in the equipment is required to be small in volume, and the self-excited push-pull circuit is simple in structure and few in elements, and is the first choice for designing the power module; the most common self-excited push-pull circuit is shown in fig. 1 and 2, the transformer shown in fig. 1 has 6 windings, the circuit shown in fig. 2 has 7 windings, and the circuits shown in fig. 1 and 2 are the core of transformer technology.

However, the conventional self-excited push-pull circuit shown in fig. 1 and 2 has the following drawbacks:

(1) because the transformer has 6 or 7 windings, 12 or 14 wire ends in total, the number of the windings is large, and the number of turns of each winding is large, the coil volume of the winding is increased, and the product volume is increased; if a small-sized magnetic ring is used, the winding process becomes very difficult;

(2) the number of the wire ends and the wire tails of the welded winding is as large as 12, so that the welding process difficulty is increased;

(3) because the coil volume of the winding is large, a plurality of coils are stacked together in a disordered manner, so that the inductance and the distributed capacitance among the windings are greatly changed, and the consistency of the performance parameters of the transformer is influenced.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a self-excited push-pull circuit, which simplifies the winding process and the welding difficulty in transformer production and reduces the volume of a transformer.

The purpose of the invention is realized by adopting the following technical scheme:

a self-excited push-pull circuit comprising:

the first totem pole circuit comprises a triode Q1 and a triode Q4, wherein the collector electrode of the triode Q1 is connected with the positive input source terminal, and the emitter electrode of the triode Q1 is connected with the collector electrode of the triode Q4; the base electrodes of the triode Q1 and the triode Q4 are connected with the input end of the power supply through resistors, and the emitting electrode of the triode Q4 is connected with the negative end of the input source;

the second totem pole circuit comprises a triode Q2 and a triode Q3, wherein the collector of the triode Q2 is connected with the positive end of the input source, the base of the triode Q2 is connected with the input end of the power supply, the emitter of the triode Q2 is connected with the collector of the triode Q3, the emitter of the triode Q3 is connected with the negative end of the input source, and the base of the triode Q3 is connected with the transformer;

the transformer comprises primary windings N1 and N2 connected with the transformer, two ends of the primary winding N1 are respectively connected with an emitter of a triode Q1 and an emitter of a triode Q2, and the primary winding N2 is connected with an output circuit.

Further, the transistors Q1, Q2, Q3 and Q4 are NPN transistors.

Further, in the first totem pole circuit, the conduction and cut-off states of the transistor Q1 and the transistor Q4 are opposite; in the second totem pole circuit, the on/off states of the transistor Q2 and the transistor Q3 are opposite.

Furthermore, the base of the triode Q1 is connected with a diode D1, the cathode of the diode D1 is connected with the B end of the primary winding N1, and the a end of the primary winding N1 is connected with the base of the triode Q4 through a capacitor C2; the emitter of the transistor Q1 is connected with the collector of the transistor Q4 through a diode D3, and the cathode of the diode D3 is connected with the B end of the primary winding N1.

Further, the base of the triode Q2 is connected with a diode D2, and the cathode of the diode D2 is connected with the a end of the primary winding N1; the emitter of the transistor Q2 is connected to the collector of the transistor Q3 through a diode D4, the base of the transistor Q3 is connected to the B terminal of the primary winding N1, and the cathode of the diode D4 is connected to the A terminal of the primary winding N1.

Further, the base electrodes of the triode Q1, the triode Q2, the triode Q3 and the triode Q4 are respectively and correspondingly connected with a resistor R1, a resistor R2, a resistor R3 and a capacitor C1.

Further, the input source negative terminal is grounded.

Further, the output circuit comprises a rectifying circuit connected with the primary winding N2, and the rectifying circuit is a bridge rectifying circuit or a half-wave rectifying circuit.

Further, the number of coils connecting the primary windings N1 and N2 of the transformer is the same.

Compared with the prior art, the invention has the beneficial effects that:

the number of windings of the transformer is reduced to two, so that the volume of the transformer is reduced; and secondly, the number of the transformer windings is reduced, and meanwhile, welding points are reduced, so that the difficulty of winding the windings on a magnetic ring with a small size is simplified, meanwhile, the winding of the windings becomes regular, the distributed capacitance is reduced, the electrical performance is improved, and the winding space is greatly saved.

Drawings

FIG. 1 is a schematic diagram of a conventional self-excited push-pull circuit in the background art;

FIG. 2 is a second schematic diagram of a conventional self-excited push-pull circuit in the prior art;

fig. 3 is a circuit schematic diagram of the self-excited push-pull circuit of the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

Referring to fig. 3, a self-excited push-pull circuit includes a first totem-pole circuit, a second totem-pole circuit, and a winding connected to a transformer.

The first totem-pole circuit comprises two NPN type triodes with the same characteristics, which are named as a triode Q1 and a triode Q4 respectively, and the output waveform of the totem-pole circuit adopting the two NPN type triodes is more stable in a high-temperature environment; in addition, the first totem-pole circuit further comprises two diodes D1, D3.

The collector of the triode Q1 is connected with an input source positive terminal, the base of the triode Q1 is connected with the input source positive terminal through a resistor R1, the emitter of the triode Q1 is connected with the anode of a diode D3, and the cathode of the diode D3 is connected with the collector of a triode Q4; the base electrode of the triode Q1 is connected with the anode of the diode D1, and the cathode of the diode D1 is connected with the collector electrode of the triode Q4; the base electrode of the triode Q4 is connected with the power supply input end through a resistor R3, the emitter electrode of the triode Q4 is connected with the negative end of an input source, and the negative end of the input source is grounded; and a driving output terminal of the first totem-pole circuit is connected to cathodes of the diode D1 and the diode D3.

The second totem pole circuit also comprises an NPN type triode Q2 and a triode Q3 which have the same characteristics, wherein the collector of the triode Q2 is connected with the positive end of the input source, the base of the triode Q2 is connected with the input end of the power supply through a resistor R2, and the base of the triode Q2 is also connected with the anode of a diode D2; the emitter of the transistor Q2 is connected with the anode of the diode D4, and the cathode of the diode D4 is connected with the collector of the transistor Q3; an emitter of the triode Q3 is connected with the negative end of the input source, a base of the triode Q3 is connected with one end of the driving output end of the second totem-pole circuit through a capacitor C1, and a cathode of the diode D2 and a cathode of the diode D4 are connected with the other end of the driving output end of the second totem-pole circuit.

The working principle of the first totem-pole circuit is the same as that of the second totem-pole circuit, wherein the working principle of the first totem-pole circuit is as follows:

if the positive end of the input source inputs direct current voltage + Vin to bias the base of the triode Q4 through the resistor R3, the triode Q4 is turned on, the collector of the triode Q4 is at a low level, and the cathode of the diode D3 connected with the collector of the triode Q4 is also at a low level, so that the diode D3 is turned on, at this time, the voltage between the base and the emitter of the triode Q1 is at a negative voltage, so the triode Q1 is in a cut-off state, and at this time, the output of the first totem-pole circuit is at a low level.

Conversely, if the input voltage + Vin provides a bias current to the base of the transistor Q1 through the resistor R1, the transistor Q1 is turned on, the diode D3 is turned on, the collector of the transistor Q4 is at a high level, the transistor Q4 is turned off, and the cathode of the diode D1 connected to the collector of the transistor Q4 is also at a high level, so that the diode D1 is in an off state; at this time, the input voltage + Vin flows through the diode D3 via the collector and emitter of the NPN transistor Q1, and is output at a high level from the driving output terminal.

It can be seen that in the first totem pole circuit, if the transistor Q1 is turned on, the transistor Q4 must be turned off; if the transistor Q4 is turned on, the transistor Q1 is turned off.

Similarly, in the second totem pole circuit, if the transistor Q2 is on, the transistor Q3 is off; if transistor Q2 is off, then transistor Q3 is on.

In the embodiment, the driving output ends of the first totem-pole circuit and the second totem-pole circuit are connected with primary windings N1 and N2 connected with the transformer, and the primary windings N1 and N2 have the same number of coils; two ends of the primary winding N1 are respectively connected with an emitter of the triode Q1 and an emitter of the triode Q2, two ends of the primary winding N2 are connected with a rectifying circuit, and the rectifying circuit can be a bridge rectifying circuit or a half-wave rectifying circuit.

Specifically, in the first totem-pole circuit, the cathode of the diode D1 is connected with the B end of the primary winding N1, and the a end of the primary winding N1 is connected with the base of the triode Q4 through the capacitor C2; the cathode of the diode D3 is connected to the B terminal of the primary winding N1. In the second totem-pole circuit, the cathode of the diode D2 is connected to the a terminal of the primary winding N1; the base of the transistor Q3 is connected to the B terminal of the primary winding N1 through the capacitor C1, and the cathode of the diode D4 is connected to the A terminal of the primary winding N1.

The operation of the self-excited push-pull circuit of the present embodiment is as follows:

when the power is on, because of the existence of the resistor R3, the triode Q4 is necessarily switched on earlier than the triode Q3, namely, the direct current voltage + Vin is input to the positive end of the input source to provide the base bias current for the triode Q4 through the resistor R3, the triode Q4 is switched on, the triode Q1 is switched off, the triode Q2 is switched on, the triode Q3 is switched off, and the input direct current voltage + Vin sequentially flows through the triode Q2 and the diode D4 and then sequentially flows to the negative end-Vin of the input source through the point A and the point B of the transformer winding N1 and the triode Q4.

At this time, the primary winding N1 generates an induced voltage, i.e., a positive voltage at the a terminal and a negative voltage at the B terminal, so that the transistor Q4 obtains a driving current to accelerate conduction to saturation, and the transistor Q3 is deeply cut off due to reverse bias.

Thereafter, after the transformer is saturated, the polarity of the primary winding N1 of the transformer begins to reverse, i.e., the terminal a is a negative voltage and the terminal B is a positive voltage, at this time, the transistor Q4 is turned off, the transistor Q1 is turned on, the transistor Q3 is turned on, and the transistor Q2 is turned off. At this time, the input dc voltage + Vin sequentially flows through the transistor Q1 and the diode D3, and then sequentially flows through the point B and the point a of the transformer winding N1 and the transistor Q3 to the input source negative terminal-Vin.

When the transformer is saturated again, the polarity is reversed again, and the process is repeated.

Through the improvement, the number of the original 6 windings of the transformer is reduced to 2, 2/3 is compressed, and the number of the welding points is reduced to 4 from the original 12 windings, so that the winding of the winding on the magnetic ring with the outer diameter of only 5 mm is very easy, and meanwhile, the winding of the winding becomes regular, the distributed capacitance is reduced, the electrical performance is improved, and the winding space is greatly saved.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.