JPH0312068Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor converter, particularly a self-limiting transistor converter with overvoltage protection. A conventional transistor converter of this type is illustrated in FIG.

In Figure 1, Q ₁ is the main transistor, T ₁ is the replacement transformer, n ₁ , n ₂ , n ₃ are the primary windings of T ₁ , respectively.
Secondary winding, feedback winding, Ei is DC input power supply, E ₀ is DC output, C ₁ , C ₂ , C ₃ , C ₄ are capacitors, R ₁ ,
R ₂ is a resistor, D ₁ , D ₂ , D ₃ are rectifier diodes, DZ ₁
is a constant voltage diode and _Q2 is a transistor.
When the DC input power source Ei is applied, a starting current flows through the resistor _R1 , turning on the main transistor _Q1 .
As a result, the base current of _Q1 flows through _D1 and _R2 due to the voltage induced in the feedback winding _n2 of the main transformer _T1 , and the current flowing through the primary winding _n1 is determined by the amplification factor of _Q1. The collector current increases to Ic. At this time, the rectifier diode _D3 on the secondary winding _n2 side is in a blocking state, and no current flows to the load connected to the DC output _E0 , and energy is stored in _T1 . then Q ₁
When the current in T1 is turned off, the energy stored in _T1 causes current to flow to the load side. At the same time, a flyback voltage (proportional to the output voltage) with a polarity opposite to that shown in the figure is generated in the feedback winding _n3 , and the flyback voltage is passed through the capacitor _C2 and the diode _D2 .
Charge capacitor _C2 . When the transistor Q ₁ is turned on again, the voltage of the feedback winding n ₃ (with the polarity shown) and the voltage of the capacitor C ₂ are combined and applied to the emitter-base of the transistor Q ₂ and the constant voltage diode DZ ₁ . Therefore the output voltage E ₀
When is high, this weighted voltage quickly reaches the voltage of the constant voltage diode _DZ1 , so the transistor _Q2 is turned on and the transistor _Q1 is turned off to make the DC output _E0 constant voltage.

In FIG. 1, for example, if the emitter of the transistor _Q2 for constant voltage control is opened due to a failure or test, the output becomes an abnormal overvoltage.
Therefore, there were drawbacks such as damage to components such as transistors and adverse effects on load. The present invention eliminates the above-mentioned drawbacks and provides a safe and economical transistor converter that provides effective protection in the event of output overvoltage. The present invention will be explained below with reference to the drawings. FIG. 2 is a circuit diagram showing an embodiment of the present invention, and the same reference numerals as in FIG. 1 represent the same parts. The present invention provides a series circuit of a resistor R ₃ , a three-terminal thyristor Th, and a diode D ₅ at the DC input terminal (between both ends of the capacitor C ₁ ), and also includes an absorption transistor Q ₃ that absorbs the base current of the main transistor Q ₁ . It is connected in parallel relation to the feedback winding n ₃ of T ₁ and its base is connected to the connection point of said thyristor Th and diode D ₅ . In addition, the gate of the thyristor Th is connected to a constant voltage diode _DZ3 and a resistor.
It is connected to one end of capacitor _C2 via _R5 . According to this configuration, when the transistor becomes open, the output voltage becomes excessive, but the flyback voltage of the feedback winding _n3 increases the voltage of the capacitor _C2 , and this voltage is applied to the diode _DD5 → thyristor Th. It is applied to the path of gate → constant voltage diode DZ ₃ → resistor R ₅ and turns on thyristor Th. Therefore, a base current is supplied to the transistor Q ₃ via the resistor R ₃ and the thyristor Th, and in order to turn it on, the base current of the main transistor Q ₁ is bypassed and the main transistor Q ₁ is turned off. As a result, each component such as transistor _Q1 is protected from overvoltage. In addition, DZ ₂ in Fig. 2 is a constant voltage diode for starting the main transistor Q ₁ , and when the DC input Ei reaches a predetermined value, the main transistor
Supply starting current to Q ₁ through resistor R ₁ . or,
R ₄ and C ₅ are resistors and capacitors, D ₄ is a diode, and the capacitor C ₅ is charged to the polarity shown in the figure through the resistors R ₁ and R _4. When the thyristor Th is turned on, the resistor R ₄ → diode D ₄ → Thyristor Th → Transistor Q ₃ It has the function of supplying a large base current to transistor Q ₃ through the base-emitter path of transistor Q 3. Also, the diode D ₄ maintains the stopped state so as not to restart the main transistor Q ₁ in order to bypass the base starting current of the main transistor Q ₁ through the resistor R ₁ and the voltage regulator diode DZ ₂ through the thyristor Th. . To restart, cut off the DC input power supply Ei and set capacitor _C1 to OV, then turn Ei
It will start when you turn it on again. Note that if R ₁ can sufficiently obtain the holding current of the thyristor Th, R ₃ is unnecessary. In FIG. 2, addition of circuits or elements with other functions and equivalent modifications are naturally included in the gist of the present invention. As mentioned above, the present invention provides a safe and economical transistor converter that effectively protects against output overvoltage, eliminates component damage and adverse effects on the load, and has practical effects. It is a big thing.

[Brief explanation of the drawing]

Fig. 1 is a conventional circuit, and Fig. 2 is a circuit diagram showing an embodiment of the present invention, in which Q ₁ is the main transistor, T ₁
is the conversion transformer, n ₁ is the primary winding, n ₂ is the secondary winding, n ₃ is the feedback winding, Ei is the DC input power supply, E ₀ is the DC output, C ₁ , C ₂ , C ₃ , C ₄ , C ₅ is a capacitor, R ₁ ,
R ₂ , R ₃ , R ₄ , R ₅ are resistances, D ₁ , D ₂ , D ₃ , D ₄ , D ₅
is a rectifier diode, DZ ₁ , DZ ₂ , DZ ₃ are constant voltage diodes, Th is a bidirectional three-terminal thyristor, Q ₂
is a transistor, and _Q3 is an absorption transistor.

Claims (1)

[Scope of utility model registration request] A main transistor Q ₁ is connected between the primary winding ni and the input power source Ei of a conversion transformer T ₁ having a primary winding n ₁ , a secondary winding n ₂ and a feedback winding n ₃ , and the secondary winding A main circuit in which a rectifier diode _D3 is connected to the winding _n2 and the feedback winding _n3 is connected to the base of the main transistor _Q1 , and the main circuit is connected between the base and emitter of the main transistor _Q1 . A series circuit of a capacitor C ₂ and a diode D ₂ connected in polarity to be charged by the flyback voltage generated in the feedback winding n ₃ between the feedback winding _{n 3} and the capacitor C ₂ . In the transistor converter, the transistor converter includes a control circuit including a constant voltage diode _Dz1 connected between the connection point of the control transistor _Q2 and the base of the control transistor _Q2 , and a bidirectional three-terminal thyristor connected between the input power supply. A series circuit of Th and diode _D5 ,
a second control transistor Q3 whose base is connected to the connection point between the thyristor Th and the diode _D5 , and whose collector and emitter are connected between the base and emitter of the main transistor Q1; the gate of the thyristor Th and the capacitor C; A transistor converter characterized in that it has an overvoltage protection circuit consisting of a constant voltage diode _DZ3 connected between _one end of the transistor converter.