JPH0145265Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a drive circuit for a transistor converter, and in particular, an effective drive circuit that supplies a stable bias current to the main switching transistor that is driven regardless of input/output fluctuations and reduces switching loss. It provides: Figure 1 shows this type of conventional circuit. In the figure, A is the main circuit that forms the converter, B is the control circuit, and in the main circuit, V ₁ is the DC power supply, C is the power supply capacitor, and T ₁
is an output transformer, n ₁ and n ₂ are its primary (input) and secondary (output) windings, Q ₁ is a switching main transistor connected in series to the primary winding n ₁ ,
R ₂ and R ₃ are resistors, C ₂ is a capacitor, D is a rectifier diode, then in control circuit B, V ₂ is an auxiliary power supply that supplies power to the control circuit, T ₂ is a pulse transformer,
n ₁₁ and n ₁₂ are the primary windings, n ₂₀ is the secondary (output) winding,
R ₁ and C ₁ are resistors and capacitors that form a charging circuit from the auxiliary power supply V ₂ , Q ₂ and Q ₃ are control transistors that are turned on and off alternately by the controller IC 1 (control IC), and the transistor Q ₂ is the resistance R ₄
The transistor Q3 is connected in series with the pulse transformer primary winding _n12 and connected between the auxiliary power supply _V2 , and the transistor _Q3 is connected in series with the primary winding _n11 through a capacitor _C1 and a resistor R1 _. connection point and the other end of the power supply _V2 . Next, the operation of this circuit will be explained with reference to FIG. First, the main transistor
When the control transistor Q ₂ is on, a forward bias current is supplied to Q ₁ through the pulse transformer T ₂ to turn it on, and when the control transistor Q ₃ is on, a reverse bias current is supplied to it and it turns it off. It is set like this. In addition, the control transistors Q ₂ and Q ₃ are set to be turned on alternately by the power of the controller IC ₁ which detects the output of the converter and not to be turned on at the same time. _Figures 2b, c and 2d show ideal base current waveforms that can reduce switching loss during the on/off and switching operations _of the main transistor _Q1 . When I did
It is the total current of R ₂ , C ₂ and R ₃ , and IB ₂ is the current flowing through the same resistance R ₃ . Also, when IB ₃ discharges the charge charged in C 1 through R ₁ when transistor Q ₃ is off (when Q ₂ is on ₎ , the charges of R ₂ , C ₂ and R ₃ are discharged at the same time as transistor Q ₃ is on. is the total current (reverse bias current). Here, capacitor _C1 is charged only while the on signal is applied to transistor _Q1 , so
Only between %. In other words, if the ON signal of the transistor _Q1 becomes short when the load is light, the capacitor _C1 will not be charged with a sufficient amount of charge, as shown by VC' in FIG _. (Figure 2 e-
IB3') This leads to an increase in the loss when the transistor Q ₁ is turned off, and if the storage of the transistor R ₁ is long, the charge of the capacitor C ₁ alone will not be enough, and the off time cannot be shortened, resulting in an increase in the loss when the transistor Q 1 is turned off. The disadvantage is that it increases the amount of (Note that the on-time of the transistor _Q3 is 50% to 100% of the switching period of the resistor _R1 , so the resistance value cannot be made too small.) The present invention is simple, using the auxiliary winding of the output transformer. By adding a charging circuit, the above-mentioned drawbacks can be solved at once, and a drive circuit can be provided that can supply the required stable bias current regardless of the input/output conditions and according to the storage time of the main transistor. a main circuit formed by a DC power supply, a switching main transistor connected in series between the primary winding of the output transformer, and a rectifying diode connected to the secondary winding of the output transformer; an auxiliary power supply that supplies power to the control circuit; a pulse transformer having first and second primary windings and a secondary winding; a series circuit of a resistor and a capacitor connected between the auxiliary power supply; and a series circuit between the auxiliary power supply. a first control transistor connected to the first primary winding of the pulse transformer through the first primary winding of the pulse transformer; A second control transistor connected via a winding, and a controller that alternately provides on and off signals to the first and second control transistors, and the main turn on the transistor,
In a drive circuit for a transistor converter having a control circuit for off-control, the output transformer is provided with an auxiliary winding having the same polarity as the primary winding, and
The present invention is characterized in that a circuit is provided that charges the capacitor directly or by an amplified current using the voltage of the auxiliary winding. 3, 4, and 5 are circuit diagrams and operation explanatory diagrams showing one embodiment of the present invention, and the same reference numerals as in the conventional example indicate equivalent parts. In the figure, Ns is an auxiliary winding provided in the output transformer T ₁ with the same polarity as the primary winding n ₁ , and the voltage generated in the auxiliary winding ns is used to charge the capacitor C ₁ . That is, in FIG. 3, there is also a charging transistor Q ₄
This base is controlled by the voltage of the auxiliary winding ns via the diode _D1 , and the amplified current rapidly charges the battery through the path of the auxiliary power supply _V2 →transistor _Q4 →capacitor _C1 . (Figure 5 a-VC)
Further, in FIG. 4, the voltage of the auxiliary winding ns is directly charged via the diode _D1 . With this configuration, the main transistor
Capacitor _C1 is always charged to a normal value even during light loads or high inputs when the on period of _Q1 , that is, the on period of control transistor _Q2 is short, so that sufficient reverse bias is required as shown in Figure 5b. Even if the current IB ₃ can be supplied and the storage time of the main transistor Q ₁ is long, the ON operation of the control transistor Q ₃ generates a voltage in the auxiliary winding ns together with the discharge current of the capacitor C ₁ . transistor
Sufficient reverse bias current is supplied through Q ₄ or diode D ₁ and its off time can be shortened. As is clear from the above explanation, according to the present invention, it is possible to shorten the off-time of the main transistor by simply adding a simple circuit, and it is also possible to control the off-characteristic stably over a wide range, making it particularly suitable for driving converters, etc. The practical effects are significant.

[Brief explanation of the drawing]

FIGS. 1 and 2 are conventional circuit diagrams and illustrations of their operation, and FIGS. 3, 4, and 5 are circuit diagrams of one embodiment of the present invention and illustrations of its operation. A...Main circuit, B...Control circuit, _T1 ...Main transistor,
n ₁ ...Primary winding, n ₂ ...Secondary winding, ns ...Auxiliary winding, T ₂ ...Pulse transformer, n ₁₁ , n ₁₂ ...Primary winding, n ₂₀ ...Secondary Winding, IC ₁ ... Controller, Q ₁ ... Main transistor, Q ₂ , Q ₃ ... Control transistor,
Q ₄ ... Charging transistor, D ₁ ... Charging diode, C ₁ , C ₂ , C ... Capacitor, R ₁ ... Charging resistor, R ₂ , R ₃ ... Bias resistor.

Claims (1)

[Scope of utility model registration request] A switching main transistor connected in series between a DC power supply and a primary winding of an output transformer;
It has a main circuit formed by a rectifying diode connected to the secondary winding side of the output transformer, an auxiliary power supply that supplies power to the control circuit, and first and second primary windings and secondary windings. a pulse transformer, a series circuit of a resistor and a capacitor connected between the auxiliary power source, and a first control transistor connected between the auxiliary power source via a first primary winding of the pulse transformer; , a second control transistor connected between the connection point of the resistor and the capacitor and one end of the auxiliary power supply via the second primary winding of the pulse transformer; and the first and second control transistors. In a drive circuit for a transistor converter, the transistor converter has a controller that alternately applies on and off signals to the transistors, and has a control circuit that controls on and off of the main transistor through a secondary winding of the pulse transformer. 1. A drive circuit for a transistor converter, comprising: an auxiliary winding having the same polarity as the winding; and a circuit that charges the capacitor directly or by an amplified current using the voltage of the auxiliary winding.