JP2000341945A - Ringing choke converter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance efficiency of operation under the light load condition by lowering the oscillation frequency, when an output voltage in the secondary side has a light load. SOLUTION: A zener diode 15 detects that a flyback voltage of the coil 2 of the transformer in the non-control system is varied with variation of an output power of the coil 5 of the transformer in the control system of this circuit. Here, after the transistor 6 is turned off during a light load condition, the off time of the switching element 3 is elongated by as long as the time until for the saturation of a saturable reactor 17. Thereby, the oscillation frequency can be lowered, and the rate occupied in one cycle of the switching loss can be set small for enhancing the efficiency during light load condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ringing choke converter circuit for a DC power supply circuit, which is intended to reduce the oscillation frequency when the output current on the secondary side falls below a certain value, thereby increasing the efficiency of the power supply. .

[0002]

2. Description of the Related Art FIG. 2 shows a conventional DC circuit. When the output current on the secondary side increases, the oscillation frequency decreases, and when the output current decreases, the oscillation frequency increases. Since the output current is inversely proportional to the oscillation frequency, the efficiency at the time of light load with a small output current is deteriorated.

[0003]

As described above, in the ringing choke converter circuit conventionally used, the oscillation frequency at a light load is higher than that at a rated load, so that the ratio of switching loss to the oscillation frequency is small. There is a problem that the efficiency increases at a light load and the high-frequency noise such as a noise terminal voltage and a radiation noise at a light load deteriorates. Therefore, means for reducing the oscillation frequency at a light load has been required.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and utilizes a ringing choke converter circuit in which a flyback voltage of a non-control winding system fluctuates due to output power of a control winding system. By detecting this voltage, the switching element 3 is turned on at light load power so that the oscillation frequency becomes lower at light load power such as standby power.
By extending the off-time and increasing the oscillation frequency, the switching loss of the switching element 3 is reduced, and the efficiency at the time of light load power is increased. That is, using the transformer 1 having inductance,
When the switching element 3 is turned on by applying the voltage of the winding 2 of the transformer 1 to the gate of the switching element 3, a current flows through the primary winding 4 of the transformer 1, and at this time, the secondary winding 5 of the transformer 1 A rectifier diode 19 is connected so that no current flows, and a secondary-side output voltage detection circuit 20
Transistor 1 by feedback control 21 from
8 is turned on and the switching element 3 is turned off, the back electromotive force of the transformer causes the capacitor 2 to pass through the secondary winding 5.
2, a self-oscillating ringing choke converter circuit that outputs a stable voltage by connecting a gate of the switching element 3 and a collector of the PNP transistor 6 via a resistor 7, and connects the emitter of the PNP transistor 6 to the emitter of the PNP transistor 6 The winding 2 is connected via a capacitor 8 and a PNP
A resistor 9 and a capacitor 10 are connected in parallel between the emitter and the base of the type transistor 6, and a rectifying diode 11 and a smoothing capacitor are connected between one end and the other end of the winding 2 so that a flyback voltage is generated when the switching element 3 is off. 12 is connected via a resistor 13, a load resistor is connected across the smoothing capacitor 12, and the negative electrode of the smoothing capacitor 12 and the base of the PNP transistor 6 are connected via a series circuit of a resistor 15 and a Zener diode 16. A ringing choke converter circuit characterized in that a saturable reactor 17 is connected between the collector and the emitter of the PNP transistor 6.

[0005]

In FIG. 1, a flyback voltage (a voltage of a capacitor 12) of a winding 2 which is a drive winding of a switching element 3 fluctuates according to an output power of a winding 5 of a secondary control system. I do. When the output power of the control system winding 5 increases, the voltage of the capacitor 12 increases, and conversely, the output power of the control system winding 5 decreases, and when the load becomes light load, the voltage of the capacitor 12 decreases. 1
2 can be detected by the Zener diode 16. When the output power of the control system winding 5 is large,
Since the time during which the transistor 6 is turned on is shortened and the off time of the switching element 3 is shortened, the oscillation frequency is increased. Conversely, the output power of the winding 5 of the control system is reduced, and the transistor 6 is turned off when the load becomes lighter. Therefore, the off time of the switching element 3 becomes longer by the time until the saturable reactor 17 is saturated. , The oscillation frequency can be lowered.

[0006]

FIG. 1 shows a basic circuit of an embodiment of the present invention.
Data obtained by experiments using this circuit are "control system output power-oscillation frequency" in FIG. 3 and "control system output power-efficiency" in FIG. FIG. 2 shows a conventional circuit having no oscillation frequency control circuit, and experimental data based on the circuit is also shown in FIGS. 3 and 4.

[0007]

According to the present invention, as shown in FIG. 3, when the control system output power becomes light load power, the flyback voltage (voltage of the capacitor 12) of the drive system winding 2 is reduced by the Zener diode 16. By detecting the transistor 6 and turning it off, the off time of the switching element 3 can be lengthened by the time until the saturable reactor 17 is saturated, and the oscillation frequency can be lowered. For this reason, the ratio of the ON time of the switching element 3 to one cycle (the reciprocal of the oscillation frequency) is reduced, so that the efficiency at the time of light load power can be increased as compared with the conventional circuit as shown in FIG. And contribute to energy saving.

[Brief description of the drawings]

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

FIG. 2 is a basic circuit according to a conventional example.

FIG. 3 is a comparison of data of “control system output power—oscillation frequency” obtained in an experiment of an embodiment of the present invention with a conventional example.

FIG. 4 is a comparison of data of “control system output power—efficiency” obtained in an experiment of an embodiment of the present invention with a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Converter transformer 2 Transformer drive system winding 3 Switching element (FET) 4 Transformer primary winding 5 Transformer secondary winding 6 Transistor 7 Resistance 8 Capacitor 9 Resistance 10 Capacitor 11 Diode 12 Capacitor 13 Resistance 14 Resistance 15 Resistance Reference Signs List 16 Zener diode 17 Saturable reactor 18 Transistor 19 Diode 20 Voltage detection circuit 21 Control circuit 22 Capacitor

Claims (1)

[Claims] When a switching element is turned on by applying a voltage of a winding of the transformer to a gate of the switching element using a transformer having an inductance, a current flows through a primary winding of the transformer. A rectifier diode is connected so that current does not flow through the secondary winding, and when the transistor is turned on and the switching element is turned off by feedback control from the output voltage detection circuit on the secondary side, the secondary winding is generated by the back electromotive force of the transformer. In a self-oscillating ringing choke converter circuit that outputs a stable voltage by flowing current through a capacitor through a wire, the gate of the switching element and the collector of the PNP transistor are connected via a resistor, and the emitter and winding of the PNP transistor are connected. Are connected via a capacitor, and a PNP transistor Connect a resistor and a capacitor in parallel between the emitter and base, and connect a rectifier diode and a smoothing capacitor via a resistor between one end and the other end of the winding so that a flyback voltage is generated when the switching element is off. A load resistor is connected to both ends of the capacitor, and the negative electrode of the smoothing capacitor and PNP
A ringing choke converter circuit, wherein a base of a transistor is connected via a series circuit of a resistor and a Zener diode, and a saturable reactor is connected between the collector and the emitter of the PNP transistor.