JPS6230467Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power converter such as a ringing chain converter.

Figure 1 shows the basic circuit of a conventional power converter, and Figure 2 shows a timing chart of the operation of Figure 1.
is the collector-emitter voltage of transistor _Q1 , b is the voltage of winding N _P of transformer _T2 , and c is the transformer
The collector current I _c of the transistor Q ₁ flowing through the winding N _P of T ₂ , d is the voltage appearing at the winding N _S of the transformer T ₂ , e is the current flowing through the winding N _S of the transformer T ₂ , f
is the voltage appearing at the winding N _B of the transformer T ₂ , and g is the relationship between the magnetic flux Φ of the transformer T ₁ and the ampere line NI.

In the circuit of FIG. 1, when the input power supply V _io is applied, a current flows through the starting resistor R _S to positively bias the base of the transistor Q ₂ and make it conductive.
When transistor Q ₂ becomes conductive, transistor Q ₁ also becomes conductive. (Fig. 2a) If the transistor Q ₁ becomes conductive at all, a voltage is applied to the primary winding N _P of the transformer T ₂ (Fig. 2 b), so that the base winding N _B of the transformer T ₂ is energized (Fig. 2 b). A voltage is generated that positively biases the base of transistor Q ₂ and brings transistors Q ₁ and Q ₂ into saturation. (Period of T _po in Figure 2 a) Transformer T ₂
The current in the winding N _P of and the collector current of the transistor Q ₁ increases linearly due to the inductance of the winding N _P of the transformer T ₂ . (Fig. 2c) At this time, the voltage generated in the secondary output winding N _S of the transformer T ₂ is blocked by the rectifier diode D _REC . The voltage developed in the winding N _P of the transformer T ₂ (FIG. 3d) is also applied to the primary winding N _C1 of the saturable transformer T ₁ . Due to this voltage, the magnetic flux of the saturable transformer T ₁ increases linearly and reaches the final saturation magnetic flux Φ _S. That is, as shown in FIG. 2g, the transistor Q ₁
By turning ON, the magnetic flux Φ of the transformer T ₂ reaches the saturation magnetic flux Φ _S. At this time, the secondary winding N _C of the saturable transformer T _1
2 is made open by diode _D3 . When the magnetic flux of transformer T ₁ reaches Φ _S , winding N _C1 of transformer T ₁
The voltage generated at is applied to the resistor R _C. Then, transistor Q ₃ is brought into conduction via resistor R ₁ and diode D ₂ . When transistor Q ₃ becomes conductive, the current that has been flowing to the base of transistor Q ₂ flows to the collector of transistor Q ₃ and transistors Q ₁ and Q ₂ suddenly become blocked. (Situation shown in Fig. 2 aT _pff ) At this time, a reverse voltage is generated in each winding of the transformer T ₂ (Fig. 2 b, d, f) _.
The generated voltage supplies current to the load R and the smoothing capacitor _C2 via the diode _DREC . Further, at this time, the value of the voltage generated in the winding N _S is clamped to the output voltage V _put . However, at this time, the voltage drop in the forward direction of the diode _DREC is ignored.

At this time, the winding N _P of transformer T ₂ has N _P /N _S・V
_put Also, a reverse voltage of N _B /N _S ·V _put is generated in the winding N _B. The reverse voltage generated in the winding N _B of the transformer T ₂ is applied to the winding N _C1 of the transformer T ₁ excluding the voltage drop across the resistor R _C . At this time, a transistor Q ₄ is connected to the winding N _C2 of the transformer T ₁ via a diode D ₃ .
A current i _C1 determined by the conduction state of flows. The value of this current is controlled by the values of the reference voltage E _ref and the output voltage V _put . Also, this current is converted into the winding N _C1 of the transformer T ₁ by the relationship _{N C1}・i _C1 /N _C2
It becomes ₂ . The voltage applied to the winding N _C1 of the transformer T ₁ is the difference between the voltage generated in the winding N _B of the transformer T ₂ and the voltage drop R _C・i _{C2 .}
The magnetic flux changes from Φ _S up to a certain value Φ. That is,
Depending on the blocking state of transistors Q ₁ and Q ₂ , the transformer
A reverse voltage is generated in the winding N _B of the transformer T ₂ , and this reverse voltage is applied to the winding N _C1 of the transformer T ₁ , which causes it to be reverse excited, and the value of the magnetic flux changes from Φ _S to Φ, as shown in Figure 2g. changes up to. The amount of change in this magnetic flux is the amount of change in transistors Q ₁ and Q ₂
Determine the conduction time. That is, the voltage drop R _C・i _C
By increasing the value of ₂ , the return amount of the magnetic flux Φ shown in FIG. 2g becomes smaller, and the ON/OFF time of the transistor _Q1 shown in FIG. 2a becomes shorter. On the contrary, R
By decreasing the value of _C ·i _C2 , the return amount of the magnetic flux Φ shown in FIG. 2g increases, and the ON/OFF time of the transistor _Q1 shown in FIG. 2a becomes longer.
When transistors Q ₁ and Q ₂ are conducting, the transformer
When the energy stored in the inductance of the winding N _P of T ₂ is completely discharged to the secondary side, the first operation begins and the transistors Q ₁ and Q ₂ conduct and repeat the above operation.

As described above, in the circuit shown in Figure 1, in order to control the output voltage (output current) constant, when the transistors Q ₁ and Q ₂ are in the blocking state, the amount of change in the magnetic flux of the transformer T ₁ (from Φ _S to Φ ) to control the conduction time of transistors Q ₁ and Q ₂ .

The amount of change in magnetic flux is determined by the excitation current flowing through the winding N _C1 of the transformer T ₁ . Therefore, by reducing this excitation current, the time required for transformer _T1 to reach magnetic saturation can be shortened. Furthermore, the excitation current i _C2 is determined by the value of i _C1 and the value of the resistor R _C , but if you try to increase the value of i _C1 , you will need to increase the values of E _ref and U _put , which may cause oscillation. Large and stable output cannot be obtained. Furthermore, the excitation current has large variations, and it is necessary to reduce this in order to prevent malfunctions.

Therefore, in order to reduce the excitation current, conventionally the value of the resistor R _C is increased to reduce the excitation current. However, by increasing the resistor R _C , the voltage drop due to this resistor R _C increases, and there is a risk that the transistor Q ₃ will be erroneously turned on via the diode D ₂ and may also be turned on due to disturbances. It has been difficult to obtain stable switching operation.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, and the purpose is to provide transistors Q ₁ and Q ₂ that turn on and off the power supply, and a transformer T ₂ connected to the collectors of the transistors Q ₁ and Q ₂ . Winding N _P included in
and a winding N _B coupled to the winding by a transformer _T2 ,
a primary side of the saturable transformer T ₁ connected to the winding N _B ; a network of resistors and diodes connected in series to the primary side of the saturable transformer T ₁ ; and the network and the transistor. In a power converter comprising a control transistor _Q3 connected to the emitters of _Q1 and _Q2 and turning off the transistors Q1 _{and Q2} ,
The network consists of a diode D ₁₁ , a low resistance R ₁₁ and a high resistance
When the transistors Q ₁ and Q ₂ are on, the excitation current is supplied to the primary side of the saturable transformer through the low resistance R ₁₁ , and when it is off, the excitation current is supplied through the high resistance _{R 12 .} , is achieved by exciting the saturable transformer by supplying a reverse excitation current to the primary side of the saturable transformer and controlling the control transistor _Q3 .

Embodiments of the power converter according to the present invention will be described in detail below.

FIG. 4A shows an embodiment of the present invention. In the figure, R ₁₁ is a low resistance, R ₁₂ is a high resistance, and D ₁₁ is a diode. By connecting the resistors R ₁₁ and R ₁₂ and the diode D ₁₁ as shown in Figure 4A, when the main transistors Q ₁ and Q ₂ are off, the rated output power is transmitted through the resistor R ₁₂ and the saturable transformer T ₁ . Make the resistor R ₁₂ as large as possible and transformer T ₁
A highly stable output voltage is obtained by reducing the excitation current. Furthermore, when the main transistors Q ₁ and Q ₂ are on, the voltage is passed through the saturable transformer T ₁ , the diode D ₁₁ , and the resistor R ₁₁ to prevent malfunctions in the switching operation due to fluctuations in the excitation current of the transformer T ₁ or disturbances. resistance
Highly stable switching operation can be achieved by minimizing the value of _R11 .

Figures 5 and 6 are examples of specific characteristics of the circuit in Figure 4A, and in Figure 3, the voltage ( _Vput ) and current applied to the load when the resistance value of the load is changed. shows the relationship between FIG. 5 shows a comparison of drooping characteristics between a conventional circuit and a circuit according to the present invention, in which the vertical axis represents voltage and the horizontal axis represents current.
In the figure, curves A ₁ and A ₂ show the characteristics of the conventional circuit, where A ₁ is for R _C = 20 Ω and A ₂ is for R _C = 100 Ω.
The case is shown below. Curves B ₁ , B ₂ , and B ₃ are shown in Figure 4 A.
B ₁ is R ₁₁ = 20
Ω, R ₁₂ = 47 Ω, B ₂ is R ₁₁ = 20 Ω, R ₁₂ = 100
In the case of Ω, B ₃ shows the case where R ₁₁ = 20Ω and R ₁₂ = 200Ω, indicating that the drooping characteristic can be obtained by inserting the resistor R ₁₂ . Further, Fig. 6 shows the case where the resistances R ₁₁ and R ₁₂ are changed in the circuit according to the present invention, and the curves C ₁ , C ₂ , ..., C ₇ are in the case where R ₁₁ = 10Ω, and further C ₁ , C ₂ , C ₃ , C ₄ , C ₅ , C ₆ , C ₇ are respectively
_R12 = 30Ω, 50Ω. 67.5Ω, 100Ω, 133Ω, 150
Ω, 205Ω, the curves D ₁ , D ₂ , D ₃ , D ₄ are R ₁₁ =
In the case of 100Ω, D ₁ , D ₂ , D ₃ , and D ₄ are each
The cases where R ₁₂ = 50Ω, 71.5Ω, 100Ω, and 133Ω are shown. In either case, it is shown that the drooping characteristic can be obtained by inserting the resistor _R12 .

Figure 4, B, C, D, and E are all application examples of Figure 4 A, and the resistors R ₁₁ and R ₁₂ are respectively Figure 4 A.
It is clear that it has the same effect as in the case of .

As explained in detail above, the circuit according to the present invention solves the instability of switching operation, which is one of the drawbacks of conventional circuits, by reducing the resistance R ₁₁ and reducing resistance when there are large variations in excitation current or due to disturbances. In order to reduce the voltage applied to R ₁₁ so that transistor Q ₃ does not easily conduct, and to eliminate the low stability of the output voltage, the value of resistor R ₁₂ is made as large as possible within the range that allows the rated output power to be delivered. This reduces the amount of change in the excitation current of the transformer _T1 , thereby achieving high stability of the output voltage. Furthermore, since the amount of change in the excitation current can be kept small, a drooping characteristic can be obtained in the output current when the output terminal is short-circuited.

[Brief explanation of the drawing]

Figure 1 shows an example of the basic circuit of a power conversion circuit;
The figure is a timing chart showing the waveforms of each part of the circuit in Figure 1, Figure 3 is an example of a conventional power conversion circuit, Figure 4 is an example of the power conversion circuit according to the present invention, and Figures 5 and 6. 4 are diagrams showing the operating characteristics of the circuit shown in FIG. 4, respectively. In the figure, R ₁₁ is a low resistance, R ₁₂ is a high resistance, and D ₁₁ and D ₁₂ are diodes.

Claims (1)

[Scope of claims for utility model registration] 1 Transistors Q ₁ and Q ₂ that turn on and off the power supply
, a winding N _P included in the transformer T ₂ connected to the collectors of the transistors Q ₁ and Q ₂ , a winding N _B coupled to the winding by the transformer T ₂ , and the winding N
the primary side of the saturable transformer T ₁ connected to _B , a network of resistors and diodes connected in series to the primary side of the saturable transformer T ₁ , and the circuit network and the transistors Q ₁ , Q In the power converter, the circuit network is composed of a control transistor _Q3 connected to the emitter of No. ₂ and turns off the transistors Q1 and _Q2 , and the circuit network is composed of a diode _D11 , a low resistance _R11 , and _a high resistance _R12 , the transistor
When Q ₁ and Q ₂ are on, the excitation current is supplied to the primary side of the saturable transformer via the low resistance R ₁₁ , and when it is off, the exciting current is supplied to the primary side of the saturable transformer via the high resistance R ₁₂ . A power converter characterized in that the saturable transformer is excited by supplying a reverse excitation current to the side thereof, and the control transistor _Q3 is controlled. 2. The anode of the diode D ₁₁ is connected to the primary side of the saturable transformer, the low resistance R ₁₁ is connected between the cathode of the diode D ₁ and the emitters of the transistors Q ₁ and Q ₂ , and the high resistance _R12 is connected between the anode of the diode _D11 and the emitters of the transistors _Q1 and _Q2 , and a connection point between the diode _D11 and the low resistance _R11 is connected to the control transistor _Q3 . A power converter according to claim 1, characterized in that: 3 The anode of the diode D ₁₁ is connected to the primary side of the saturable transformer T ₁ and the low resistance R ₁₁
is connected between the cathode of the diode _D11 and the emitters of the transistors _{Q1 and Q2} , the high resistance _R12 is connected between the cathode of the diode _D11 and the emitters of the transistors Q1 and Q2, and the high resistance R12 is connected between the cathode of the diode _D11 and the emitters of the transistors Q1 and _Q2 . 2. The power converter according to claim 1, wherein a connection point between the primary side of the saturable transformer _T1 and the diode _D11 is connected to the control transistor. 4 The anode of the diode D ₁₁ is connected to the primary side of the saturable transformer T ₁ and the high resistance R ₁₂
is connected in parallel to the diode _D11 , the low resistance _R11 is connected between the cathode of the diode _D11 and the transistors _Q1 and _Q2 , and the connection point between the diode _D11 and the low resistance is connected to the low resistance R11. The power converter according to claim 1, characterized in that the power converter is connected to a control transistor. 5 the anode of the diode D ₁₁ is connected to the primary side of the saturable transformer T ₁ and the low resistance R ₁₁
is connected between the cathode of the diode D ₁₁ and the transistors Q ₁ and Q ₂ , and the diode
The cathode of _D12 is connected to the anode of the diode _D11 , and the high resistance _R12 is connected to the anode of the diode D11.
Claims for registration of a utility model characterized in that the anode of _D12 is connected between the transistors _Q1 and _Q2 , and a connection point between the diode _D11 and the low resistance _R11 is connected to the control transistor. The power converter according to item 1. 6 the anode of the diode D ₁₁ is connected to the primary side of the saturable transformer T ₁ and the low resistance R ₁₁
is connected between the cathode of the diode _D11 and the emitters of the transistors _Q1 and _Q2 , and the cathode of the diode _D12 is connected to the diode _D11.
The high resistance R ₁₂ is connected to the anode of the diode D ₁₂ and the transistor
A utility model registration claim characterized in that the emitters of Q ₁ and Q ₂ are connected to each other, and a connection point between the primary side of the saturable transformer T ₁ and the diode D ₁₁ is connected to the control transistor. The power converter according to item 1.