JP3462348B2 - Buck-boost chopper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step-up / step-down chopper used for a power supply of various electronic devices.

[0002]

2. Description of the Related Art In recent years, with the diversification of electronic devices and the diversification of semiconductor devices such as ICs (semiconductor integrated circuits), it has sometimes been necessary to obtain a DC output voltage different from the power supply voltage of a DC power supply. In such a case, a DC-DC converter is used. In the DC-DC converter, a step-down chopper is used to obtain a DC output voltage lower than the DC power supply voltage, and a step-up chopper is used to obtain a DC output voltage higher than the DC power supply voltage. When the DC power supply voltage changes within a certain range, and the DC output voltage is set to a constant value within the range of the change of the power supply voltage, the step-up / step-down chopper having the functions of the step-down chopper and the step-up chopper is used. Used.

[0003]

In a step-up / step-down chopper, as a method of reducing the size of the choke coil and reducing the ripple of the output voltage, it is considered that the switching operation of each transistor of the step-down unit and the step-up unit is accelerated. One example is shown in FIG. In FIG. 2, reference numeral 22 denotes a first transistor.
DC power supply 21 is connected between the emitter on the side and ground.
The collector has a diode 23 with one end grounded.
And one end of the choke coil 24 are connected.
The first transistor 22, the diode 23, the choke
The coil 24 constitutes a step-down unit 26. Also, the second
The collector of the transistor 25 is connected to the choke coil.
A diode 27 is connected to the other end of the
A capacitor 28 is connected between the arm 27 and the ground.
You. The choke coil 24 and the second transistor
The star 25, the diode 27, and the capacitor 28
Make up. 30 is the first transistor 22 and the second transistor
To control the switching operation of the transistor 25
Control circuit via the pre-drive circuits 31 and 32
It is connected to the base of the transistor. Where pre
The drive circuits 31 and 32 are connected to the first transistor 22 and
By increasing the switching speed of the second transistor 25
When the switching loss of the transistor is reduced,
Provided to reduce output voltage ripple
It is. As described above, in the conventional step-up / step-down chopper, when the transistors of the step-down unit and the step-up unit are switched at a high speed, it is necessary to provide a pre-drive circuit in addition to the control circuit . In general, DC-D
Some semiconductor integrated circuits used for C converters, etc.
Some of them incorporate a pre-drive circuit, but they are not suitable for forming a step-up / step-down chopper. The reason is that the functions of the pre-drive circuit built in the semiconductor integrated circuit are limited, so that the use of the semiconductor integrated circuit is also limited. For this reason, a semiconductor integrated circuit without a pre-drive circuit is generally used for the step-up / step-down chopper. Therefore, the pre-drive circuit for each transistor of the step-down unit and the step-up unit must be formed by external components. However, there is a disadvantage that the circuit configuration becomes complicated and the cost increases.

[0004]

SUMMARY OF THE INVENTION According to the present invention, a first and a second transistor and the two transistors are provided in order to eliminate the above-mentioned conventional disadvantages.
And the choke coil connected between the collectors of the transistors.
Comprising , the first transistor and the choke coil ,
A transistor connected between the collector of the first transistor and ground.
A step-down portion is formed with an ion, and the second transistor and
The choke coil is a collector of the second transistor.
A diode connected to the
Step-up / step-down type with a booster formed by connected capacitors
In the chopper, between the bases of the transistors,
Is the feedback winding and capacitor coupled to the choke coil?
Connected to the output of the choke coil
A part of the signal is fed back through the feedback circuit.
And each transistor is connected to each base.
Operation is controlled by one control circuit.
It is. The present invention is configured as described above.
In addition to the control signal at the base of each transistor, the control signal
The feedback voltage synchronized with the frequency of
The rising and falling voltage became steep,
Therefore, switching without a conventional pre-drive circuit
Speed can be increased.

[0005]

Embodiments of the present invention will be described below. In FIG. 1, 1 is a DC power supply, 2 is a first transistor having an emitter as an input side and a collector as an output side, and a DC power supply 1 is connected to the input side and one end is grounded to the output side. One end of the choke coil 4 is connected to the diode 3, and the other end of the choke coil 4 is connected to the collector of the second transistor 5 whose emitter is grounded and one end of the diode 7. The other end of the diode 7 is connected to a capacitor 8 having one grounded. 10 is the first
A control circuit for controlling the switching operation of the transistor 2 and the second transistor 5 is connected to the base of each transistor. Reference numeral 13 denotes a feedback circuit formed by a feedback winding 11 electromagnetically coupled to the choke coil 4 and a capacitor 12 connected in series with the feedback winding. Each terminal of the feedback circuit 13 is connected to the first transistor 2 respectively. Second
Are connected to the respective bases of the transistors 5. Here, the first transistor 2, the diode 3, and the choke coil 4 constitute a step-down unit 6, and the choke coil 4, the second transistor 5, the diode 7, and the capacitor 8 constitute a step-up unit 9. ing.

Next, the operation of the above configuration will be described.
Now, when an input voltage is supplied from the DC power supply 1, the step-down unit 6 or the step-up unit 9 operates according to the magnitude Vi of the voltage, and the output voltage Vo generated at both ends of the capacitor 8 is set to a predetermined reference voltage. It acts so as to approach Vs. Here, a high-frequency control signal is given to each base of the first transistor 2 and the second transistor 5 by the control circuit 10, and an electromotive force having a frequency equal to the control signal is applied to both ends of the choke coil 4. Occurs. Electromotive force generated in the choke coil 4 is induced in the feedback winding 11 coupled the choke coil and the electromagnetic, the capacitor 12 is repeated thus charging and discharging the oscillation period of the control signal. Return time
Both ends of the path 13 are connected to the first transistor 2 and the second transistor 2, respectively.
Connected to the base of transistor 5
The base of Njisuta 2,5, control from the control circuit 10
The signal voltage and the terminal voltage of the feedback circuit 13 are added and given.
Can be The terminal voltage of the feedback circuit 13 is the frequency of the control signal.
As a result, each transistor 2,5
The voltage applied to the base is large and steep.
You. As a result, the first transistor 2 and the second transistor
The rise or fall time of register 5,
The switching speed can be increased.

[0007]

According to the present invention, as described above, the first transistor
A choke between the star and the base of the second transistor
A feedback circuit consisting of a feedback winding and a capacitor
Connected, and the output signal of the choke coil is
A part of the first transistor and the second transistor.
Feedback to the base of the
The voltage applied to the base can be large and steep.
Thus, the switching speed can be increased. Sa
Luo, since it is not necessary to provide a special drive circuit circuit
The configuration is simple, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of a buck-boost chopper according to the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional buck-boost chopper.

[Explanation of symbols]

1 DC power supply 2 first transistor 3
7 ... Diode, 4 ... Choke coil, 5 ...
..The second transistor, 6,... The step-down unit, 8, 12,.
・ Capacitor, 9 ・ ・ ・ Step-up unit, 10 ・ ・ ・ Control circuit,
11 ... feedback winding, 13 ... feedback circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 3/155 H03K 5/12 H03K 17/04 H03K 17/64

Claims (1)

(57) [Claims] A first transistor, a second transistor, and the two transistors;
A choke coil connected between the collectors of the transistor
Wherein the choke coil and the first transistor
Is connected between the collector of the first transistor and ground.
Diode The step-down unit is formed with, said second transistor
And the choke coil are connected to the core of the second transistor.
A diode connected between the
A booster is formed by the capacitor connected between the diode and ground.
In the step-up / step-down chopper, the choke coil is provided between bases of the transistors.
A feedback circuit consisting of a feedback winding and a capacitor
Subsequently, part of the output signal of the choke coil is
Return via the return circuit
Transistor in one control circuit connected to each base
The lifting and lowering characterized by the fact that the operation is controlled.
Pressure chopper.