JPH07245949A - Ringing choke converter - Google Patents

Abstract

PURPOSE:To provide a ringing choke converter(RCC) circuit, from which low noises are generated and loss of which is reduced. CONSTITUTION:In a control circuit for a switching transistor, a delay circuit is formed by a resistor 8 connected in series with a control winding 14 and a capacitor 10 connected in parallel with the resistor 8, and an off period is controlled. The delay period is set so that the switching transistor 4 is turned on at the time close to the trough point of a resonance period by a capacitor 9 in series with the primary winding 13 of a transformer 12, thus lowering energy stored in the capacitor 9 when the switching transistor 4 is tuned on, then reducing loss and noises at the time of off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-stone converter, which is a ringing choke converter (RC).
The present invention relates to an improvement of a DC converter called C).

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional circuit, in which 1 is a DC power supply, 2 is an input capacitor, 3 is a starting resistor,
Reference numeral 4 is a transistor, 5 is a second transistor connected to the base of the transistor 4 and the emitter (2), and is controlled by the output voltage control circuit 11. Further, a diode 7, a capacitor 6, and a resistor 8 are connected as a drive circuit for the transistor 4.

In FIG. 3, when the DC power supply 1 is turned on, a base current is supplied to the transistor 4 from the starting resistor 3 and the transistor 4 is turned on. As a result, the voltage of the DC power supply 1 is applied to the primary winding 13. Further, a voltage is generated in the control winding 14 to supply a current to the base of the transistor 4. As a result, the collector current of the transistor 4 increases and energy is stored in the transformer 12. When the collector current increases to a certain value, the control circuit turns on the transistor 5, which turns off the transistor 4. When the transistor 4 turns off, the energy stored in the transformer 12 passes through the diode 16 from the secondary winding. The through capacitor 17 is charged. When the energy is released from the secondary winding, a voltage is generated in the control winding due to the residual energy. With this voltage, the transistor 4 is turned on again and oscillation continues.

[0004]

2. Description of the Related Art In FIG. 3, when the transistor 4 is turned off, a serge voltage is generated in the primary winding 13 of the transformer 12. In order to prevent the transistor 4 from being destroyed by the surge voltage, there is a method of connecting the capacitor 9 in parallel with the transistor 4 and reducing dv / dt to reduce the surge voltage. However, during the off period, the capacitor 9
Has energy stored therein, and when the transistor 4 is turned on, this energy is discharged to increase the loss of the transistor 4, and there is a problem that noise is generated due to a spike current at the time of discharging.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low noise, low loss ringing choke converter (RCC) circuit (3).

[0006]

According to the present invention, the basic circuit configuration is almost the same as the conventional example, but in a control circuit of a switching transistor, a resistor connected in series with a control winding and a resistor connected in parallel to the control winding are provided. The connected capacitor forms a delay circuit to control the off period. By setting this delay period so that the switching transistor turns on near the valley of the resonance cycle due to the capacitor in series with the primary winding of the transformer, the energy stored in the capacitor decreases when the switching transistor turns on. However, it is possible to reduce the loss and noise at the time of turning on.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram thereof. In the figure, 1 is a DC power supply, 2 is an input capacitor, 3 is a starting resistor, 4 is a transistor (main switching element), 5 is a second transistor connected to the base and emitter of the transistor 4, and an output voltage control circuit. It is controlled by 11. Further, as a drive circuit of the transistor 4, a diode 7, a capacitor 6, a resistor 8 and a capacitor 1 for a delay circuit are provided.
0 is connected.

In FIG. 1, when the DC power supply 1 is turned on,
A base current is supplied from the starting resistor 3 to the transistor 4 to turn on the transistor 4. As a result, the voltage of the DC power supply 1 is applied to the primary winding 13. Further control winding 14
A voltage is generated on the transistor 4 and a current is supplied to the base of the transistor 4. As a result, the collector current of the transistor 4 increases and energy is stored in the transformer 12. When the collector current increases to a certain value, the control circuit turns on the transistor 5, which turns off the transistor 4.
When the transistor 4 is turned off, the energy stored in the transformer 12 passes through the diode 16 from the secondary winding and charges the capacitor 17. (4) When the energy is released from the secondary winding, a voltage is generated in the control winding due to the residual energy. This voltage passes through the delay circuit formed by the resistor 8 and the capacitor 10 and the transistor 4 is turned on after a certain time delay.

At this time, at the same time when the secondary winding is turned off, 1
Resonance by the next winding and the capacitor 9 starts. The delay time is set by the values of the resistor 8 and the capacitor 10 so that the transistor 4 is turned on when the resonance voltage of the capacitor 9 is near the valley point. As a result, when the transistor 4 is turned on, the energy stored in the capacitor 9 is reduced. Therefore, the discharge current flowing from the capacitor 9 to the collector of the transistor 4 is reduced when turned on, and the loss of the transistor 4 and noise due to switching are reduced. It can be reduced.

That is, FIG. 2 shows the voltage waveform of the capacitor 9. In the figure, Vin is an input voltage, and when the transistor 4 is off (TOFF), the voltage VS level in which the flyback voltage is superimposed on the power supply voltage is held. When the energy of the secondary winding 15 is released, the primary winding 13 and the capacitor 9 start to resonate while the transistor 4 is turned on (TD1). However, in the conventional circuit, the transistor 4 is turned on when the voltage of the capacitor 9 is near the power supply voltage (Vin), so that this energy is released as described above.

On the other hand, in the present invention, the above effect is obtained by continuing the resonance and delaying the on-start of the transistor 4 until the voltage of the capacitor 9 reaches the valley point of the resonance voltage (time TD2). . By the way, capacitor 9
The series resonance cycle (Tr) between the primary winding 12 and Tr is Tr = 2π × (L · C) 1/2 (1) where C: capacitance of the capacitor 9 L: primary winding It is represented by the inductance of line 12. Therefore, the time when the resonance voltage becomes the valley point is ¼ of the period Tr. (5) For this time setting, the capacitance of the capacitor 9 and the time constants of the resistor 8 and the capacitor 10 may be adjusted according to the input and output conditions of the converter.

[0012]

In the conventional circuit, as a countermeasure against the switching noise generated by the transistor, an expensive noise countermeasure component and a great deal of development time are required, and the loss is increased due to the noise countermeasure and the efficiency is sacrificed. It was The present invention is low noise, with the addition and modification of a few components of the conventional circuit.
A low loss ringing choke converter can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of a circuit according to an embodiment of the present invention.

FIG. 3 Conventional circuit diagram

[Explanation of symbols]

 1, DC power supply 2, input capacitor 3, starting resistor 4, transistor 5, control transistor 6, capacitor 7, diode 8, resistor 9, capacitor 10, capacitor 11, output voltage control circuit (6) 12, transformer 13 Primary winding 14, control winding 15, secondary winding 16, output diode 17, output smoothing capacitor

Claims (4)

[Claims] 1. A DC power supply, a transformer having a primary winding, a secondary winding, and a control winding, a main switching element connected in series with the primary winding, and a rectifier connected to the secondary winding. In a ringing choke converter including a smoothing circuit and a control circuit for the main switching element, a surge voltage suppressing capacitor is connected in parallel with the main switching element, and a resistor and a capacitor are provided between the control windings. A ringing choke converter characterized in that a delay circuit is provided to control an off period during operation of the main switching element. 2. The delay time of the delay circuit is set such that when the main switching element is turned off, the series resonance period (Tr) formed by the main switching element and the inductance of the primary winding is approximately one.
4. The ringing choke converter according to claim 1, wherein the ringing choke converter is set to / 4. 3. A ring choke converter according to claim 1, wherein a bipolar transistor is used as the main switching element. 4. A MOSFET as a main switching element
The ringing choke converter according to claim 1, wherein: