JPH0117610B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a drive circuit for driving a DC-DC transistor converter, and more particularly to a drive circuit that reduces the size of a drive transformer and increases the speed of a switching transistor.

(b) Background of the Invention In recent years, in communication devices and other devices, it has been desired to simplify circuits in order to improve reliability and reduce costs. In fact, there is a demand for improved performance.

(c) Prior Art and Problems FIG. 1 is a diagram showing an example of the configuration of a conventional drive circuit. In the figure, E ₁ and E ₂ are DC input power supplies, Q ₁ to Q ₃ are transistors, R ₁ is a resistor, T ₁ is a drive transformer (hereinafter referred to as a transformer), and N ₁ to
N ₄ is the winding of transformer T ₁ , RL ₁ is the load, a and b
is a signal input terminal (hereinafter referred to as input terminal).

FIG. 2 is an explanatory diagram of the operation of FIG. 1. In the figure, a is the voltage waveform input to input terminal a, b is the voltage waveform input to input terminal b, and c is the transistor
A diagram showing the output waveform of Q ₁ , d is a diagram showing the output waveform of transistor Q ₂ , e is the waveform of current I ₁ , f is the current
The waveform of _I2 , g is a diagram showing on and off of transistor _Q3 .

FIG. 1 shows a circuit that controls the on/off state of the transistor _Q3 , where the transistor _Q1 controls the on state of the transistor _Q3 , and the transistor _Q1 controls the off state of the transistor _Q3 .

When a signal is input to input terminal a to turn on transistor Q ₁ and to input terminal b to turn off transistor Q ₂ , from input power supply E ₁ , resistor R ₁ - transformer T ₁
Winding N ₁ - transformer T ₁ in the path of transistor Q ₁
A current flows to excite the transformer _T1 , and a voltage is generated in the transformer T1 that forward biases the transistor _Q3 ,
Turn on transistor _Q3 . transistor Q ₃
The current flowing through is fed back to the base of transistor _Q3 by winding _N4 , keeping transistor _Q3 on. After a certain period of time has elapsed, when a signal opposite to the above signal, that is, a signal that turns off transistor Q ₁ and turns on transistor Q ₂ , is input to input terminal a and input terminal b, transistor Q ₁ excites transformer T ₁ . stops, and winding N ₂ of transformer T ₁
By short-circuiting by transistor Q ₂ ,
The current fed back by winding N ₄ is absorbed by winding N ₂ and transistor Q ₃ is turned off. However, there is a storage time in transistor Q ₁ and transistor Q ₂ , there is a period when transistor Q ₁ and transistor Q ₂ are turned on simultaneously, and transistor Q ₁ causes the excitation current of transformer T ₁ to pass through winding N ₂ . There was a problem that the power consumption of the drive circuit increased as it was absorbed by the transformer _Q2 . Also, since the turn-on winding _N1 of transistor _Q3 (for excitation of transformer _T1 ) and the turn-off winding _N2 of transistor _Q3 are separate, the insulation between winding _N1 and winding _N2 is In order to put an insulating layer between winding N ₁ and winding N ₂ , it is necessary to remove winding N ₁ or winding N ₂ and other windings.
The magnetic coupling between N ₃ or winding N ₄ deteriorates and leakage inductance increases, making it easier to generate surge voltages, which may cause problems with circuit stability and impair the high-speed operation of transistor Q ₃ . It becomes a problem.

(d) Object of the invention In order to eliminate such conventional drawbacks, the present invention has the following features:
A drive that improves the magnetic coupling characteristics by reducing the number of windings in the transformer, makes the transformer inexpensive, and speeds up the switching operation of the transistor in the DC-DC transistor converter by using a speed-up capacitor. The purpose is to provide a circuit.

(e) Structure of the invention It has a current feedback transformer T2, and a first transistor Q4 connected to the input winding of the current feedback transformer T2 and a first transistor Q4 connected to the output winding of the current feedback transformer T2. The second transistor Q5 is connected to the input winding of the current feedback transformer T2.
In the drive circuit that turns off the third transistor Q6 connected to the output side of the current feedback transformer and drives the DC-DC converter, the current feedback transformer T2 has an intermediate tap on the input side winding. The collector of the first transistor Q4 is connected to the intermediate tap of the input winding of the current feedback transformer T2, and the emitter is connected to the first tap.
The emitter and collector of the second transistor Q5 are connected to both ends of the input winding of the current feedback transformer T2, and are connected in parallel with the first resistor R2. A second resistor R4 is provided between the speed-up capacitor C1 and the base of the first transistor Q4, and the speed-up capacitor C1 is charged when the first transistor Q4 is turned on. This charging current speeds up the rise of the third transistor Q6 connected to the output side of the current feedback transformer T2, and also causes discharge through the second resistor when the first transistor Q4 is turned off. By doing this, the first transistor Q4 is reverse biased and the first transistor Q4 is reverse biased.
This is characterized by speeding up the off operation of No. 4.

(f) Embodiment of the Invention An embodiment of the present invention will be explained in detail with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing an example of the configuration of the drive circuit of the present invention. In the figure, E ₃ and E ₄ are DC input power supplies, Q ₄ to Q ₆ are transistors, R ₂ to R ₄ are resistors, T ₂ is a drive transformer (hereinafter referred to as a transformer),
N ₅ , N ₅ , N ₆ , N ₇ are the windings of transformer T ₂ , C ₁ is the capacitor, RL ₂ is the load, c and d are the input terminals (hereinafter referred to as input terminals), and e is the intermediate tap of N ₅ . be.

FIG. 4 is an explanatory diagram of the operation of FIG. 3. In the figure, a is the voltage waveform input to input terminal c, b is the voltage waveform to input terminal d, and c is the transistor
Diagram showing on and off of _Q4 , d is transistor
Diagram showing on and off of Q ₅ , e is the waveform of current I ₃ ,
f is a waveform of current I ₄ and g is a diagram showing on and off states of transistor Q ₆ .

Transistors Q ₄ , Q ₅ , and Q ₆ in FIG. 3 correspond to transistors Q ₁ , Q ₂ , and Q ₃ in the conventional circuit example in FIG. 1, respectively, and operate in substantially the same way.

The output of transistor _Q4 is on at input terminal C,
When a signal that turns off the output of transistor Q ₅ is input to input terminal d, resistor R ₂ is connected to input terminal E ₃ .
- Transistor Q ₄ - Winding N of transformer T ₂ Excite transformer T ₂ through the path N ₅ . At this time, a charging current flows into _{C 1 of} the series circuit of resistor R ₃ and capacitor C 1 connected in parallel with resistor R ₂ , E ₃ - Resistor R ₃ - Capacitor C ₁ - Transistor Q ₄ - Winding N' ₅ −E ₃ and overdrives the transistor Q ₆ , so the rise of the transistor Q ₆ becomes faster. The current flowing through transistor Q ₆ is fed back to the base of transistor Q ₆ by winding N ₇ to maintain the on state.

After a certain period of time has elapsed, a signal opposite to the above signal is applied to input terminal F and input terminal D, that is, transistor _Q4 is turned off.
The signal that turns transistor _Q5 on is input, turning transistor _Q4 off and transistor _Q5 on.

The capacitor _C1 is charged when the transistor _Q4 is on, and when the off signal of the transistor _Q4 is input to the input terminal C, the capacitor _C1 reverse biases the transistor _Q4 through the resistor _R4 . Faster off-time, transistors Q ₄ and Q ₅
As a result, wasteful excitation energy consumption is reduced. transistor
When Q ₄ turns off, the excitation of transformer T ₂ by transistor Q ₄ stops, and when transistor Q ₅ turns on, it shorts both ends of winding N ₅ , and the feedback current through winding N ₇ is absorbed by winding N ₅ . and transistor _Q6 is turned off. Since the transistor Q ₅ is turned on and off by one winding N ₅ , T ₂ reduces the number of windings and the insulation layer, which improves the magnetic coupling characteristics and reduces the surge voltage. This increases the stability of transistor Q ₆ operation and enables higher speeds.

(g) Effects of the Invention As is clear from the above description, according to the present invention, by using a common transformer control winding and providing an intermediate tap, it is possible to achieve better results than the conventional circuit in which a drive winding and a stop winding are provided. The number of windings is reduced. Also,
By reducing the number of windings, there are fewer insulation points, which improves the characteristics of the transformer and allows faster switching of the transistor. Furthermore, the fewer the number of insulating points, the easier the transformer can be manufactured. Further, by providing the speed-up capacitor, the switching operation of the transistor of the DC-DC transistor converter can be speeded up, and at the same time, the power consumption of the drive circuit can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a conventional drive circuit, FIG. 2 is an explanatory diagram of the operation of FIG. 1, FIG. 3 is a diagram showing an example of the configuration of the drive circuit of the present invention, and FIG. FIG. 3 is an explanatory diagram of the operation of FIG. 3; In the figure, E1 _{to E4} are DC input power supplies, _Q1 to _Q6 are transistors, _R1 to _R4 are resistors, _T1 and _T2 are drive transformers, and _N1 to _N4 are drive transformers T. ₁
windings of N ₅ , N′ ₅ , N ₆ , N ₇ , T ₂ windings, RL ₁ and RL ₂ are loads, C ₁ is a capacitor, a to d are input terminals, e is a transformer T ₂ This is an intermediate tap.

Claims (1)

[Claims] 1. A first circuit having a current feedback transformer T2 and connected to the input winding of the current feedback transformer T2.
A third transistor Q6 connected to the output winding of the current feedback transformer with a transistor Q4 of
The second transistor Q is connected to the input winding of the current feedback transformer T2.
5, in the drive circuit that turns off the third transistor Q6 connected to the output side of the current feedback transformer and drives the DC-DC converter, the current feedback transformer T2 has an intermediate winding on the input side. The collector of the first transistor Q4 is connected to the intermediate tap of the input winding of the current feedback transformer T2, the emitter is connected to the power supply via the first resistor R2, and the second The emitter and collector of the transistor Q5 are connected to both ends of the input winding of the current feedback transformer T2, and a speed-up capacitor C1 is connected in parallel with the first resistor R2; A second resistor R4 is provided between the bases of the first transistor Q4, and the speed-up capacitor C1 is charged when the first transistor Q4 is turned on, and with this charging current, the output side of the current feedback transformer T2 is The rising speed of the third transistor Q6 connected to
A drive circuit characterized in that the first transistor Q4 is reverse-biased by discharging through the second resistor when the first transistor Q4 is turned off, thereby speeding up the off operation of the first transistor Q4.