JP4303358B2 - Ringing choke converter circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ringing choke converter circuit for a DC power supply circuit, and aims to increase the efficiency of the power supply by lowering the oscillation frequency when the output current on the secondary side falls below a certain value.
[0002]
[Prior art]
FIG. 2 shows a DC circuit that has been used conventionally. When the output current on the secondary side increases, the oscillation frequency decreases, and when the output current decreases, the oscillation frequency increases. The switching loss of the switching element 3 is inversely proportional to the oscillation frequency. Therefore, the efficiency at the time of a light load with a small output current deteriorates.
[0003]
[Problems to be solved by the invention]
As described above, the ringing choke converter circuit used in the past has a higher oscillation frequency at light load than at rated load, so the ratio of switching loss to the oscillation frequency increases and the efficiency at light load deteriorates. In addition, there is a problem that high-frequency noise such as noise terminal voltage and radiation noise at the time of light load deteriorates, and means for reducing the oscillation frequency at light load has been demanded.
[0004]
[Means for Solving the Problems]
The present invention solves the above-mentioned problem, and detects the voltage by using the ringing choke converter circuit that the flyback voltage of the non-control winding system fluctuates due to the output power of the control winding system. In order to reduce the oscillation frequency at the time of light load power such as standby power, the switching element 3 is turned off and the oscillation frequency is increased at light load power, thereby reducing the switching loss of the switching element 3 and reducing the oscillation frequency. It is intended to increase the efficiency during load power. That is, by applying the voltage of the winding 2 of the transformer 1 to the gate of the switching element 3 using the transformer 1 having inductance, when the switching element 3 is turned on, a current flows through the primary winding 4 of the transformer 1, At this time, a rectifier diode 19 is connected so that current does not flow through the secondary winding 5 of the transformer 1, the transistor 18 is turned on by the feedback control 21 from the output voltage detection circuit 20 on the secondary side, and the switching element 3 is turned off. Then, in the self-excited oscillation ringing choke converter circuit in which a current flows to the capacitor 22 through the secondary winding 5 due to the counter electromotive force of the transformer and outputs a stable voltage, the gate of the switching element 3 and the collector of the PNP transistor 6 are connected. via a resistor 7 connected, emitter and switch of the PNP transistor 6 The drive winding 2 of ring element 3 is connected via a capacitor 8, connected in parallel a resistor 9 and a capacitor 10 between the emitter and base of the PNP transistor 6, between the one end and the other end of the drive winding 2 A rectifier diode 11 and a smoothing capacitor 12 are connected via a resistor 13 so that a flyback voltage is generated when the switching element 3 is off, a load resistor is connected to both ends of the smoothing capacitor 12, and the negative electrode of the smoothing capacitor 12 and a PNP transistor 6 is connected through a series circuit of a resistor 15 and a Zener diode 16, a saturable reactor 17 is connected between the collector and emitter of the PNP transistor 6, and the output power on the transformer secondary side becomes light load power. The flyback voltage generated in the drive winding 2 is detected by the Zener diode 16 and the PNP A ringing choke converter circuit for causing only time period until the saturable reactor 17 to turn off the transistor 6 is saturated by increasing the off time of the switching element 3 decreases the oscillation frequency of the switching element 3.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, the flyback voltage (voltage of the capacitor 12) of the winding 2 that is the drive winding of the switching element 3 varies depending on the output power of the winding 5 of the secondary control system. When the output power of the control system winding 5 increases, the voltage of the capacitor 12 increases. Conversely, the output power of the control system winding 5 decreases, and when the load becomes light load power, the voltage of the capacitor 12 decreases. Twelve voltages can be detected by the Zener diode 16.
When the output power of the winding 5 of the control system is large, the time during which the transistor 6 is turned on is shortened and the off time of the switching element 3 is shortened, so that the oscillation frequency is increased. On the contrary, when the output power of the winding 5 of the control system decreases and the light load power is reached, the transistor 6 is turned off. Therefore, the off time of the switching element 3 is increased by the time until the saturable reactor 17 is saturated. The oscillation frequency can be lowered.
[0006]
【Example】
FIG. 1 is 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 that does not have the above-described oscillation frequency control circuit, and experimental data obtained therefrom are also shown in FIGS.
[0007]
【The invention's effect】
In the present invention, when the control system output power becomes light load power, the flyback voltage (voltage of the capacitor 12) of the winding 2 of the drive system decreases as shown in FIG. The off-time of the switching element 3 can be lengthened and the oscillation frequency can be lowered by the amount of time until the saturable reactor 17 is saturated after turning off.
For this reason, since the ratio of the ON time of the switching element 3 to one cycle (the reciprocal of the oscillation frequency) is reduced, the efficiency at the time of light load power can be increased as compared with the conventional circuit as shown in FIG. It is a great place to 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 “control system output power—oscillation frequency” data obtained in an experiment of an embodiment of the present invention with a conventional example.
FIG. 4 is a comparison of “control system output power—efficiency” data obtained in an experiment of an embodiment of the present invention with a conventional example.
[Explanation of symbols]
1 Converter transformer 2 Transformer drive winding 3 Switching element (FET)
4 Transformer primary winding 5 Transformer secondary winding 6 Transistor 7 Resistor 8 Capacitor 9 Resistor 10 Capacitor 11 Diode 12 Capacitor 13 Resistor 14 Resistor 15 Resistor 16 Zener diode 17 Saturable reactor 18 Transistor 19 Diode 20 Voltage detection circuit 21 Control circuit 22 Capacitor

Claims (1)

Using a transformer having inductance, the voltage of the winding of the transformer is applied to the gate of the switching element. When the switching element is turned on, a current flows through the primary winding of the transformer, and at this time, the secondary winding of the transformer When a rectifier diode is connected so that no current flows, and 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 current flows to the capacitor through the secondary winding by the back electromotive force of the transformer. In the ringing choke converter circuit of self-oscillation that outputs a stable voltage,
The gate of the switching element and the collector of the PNP transistor are connected via a resistor,
Connecting the emitter of the PNP transistor and the drive winding of the switching element via a capacitor;
Connect a resistor and capacitor in parallel between the emitter and base of the PNP transistor,
A rectifier diode and a smoothing capacitor are connected via a resistor so that a flyback voltage is generated when the switching element is turned off between one end and the other end of the drive winding.
Connect a load resistor across the smoothing capacitor,
Connect the negative electrode of the smoothing capacitor and the base of the PNP transistor through a series circuit of a resistor and a Zener diode,
Connect a saturable reactor between the collector and emitter of a PNP transistor ,
When the output power on the secondary side of the transformer becomes light load power, the Zener diode detects that the flyback voltage generated in the drive winding decreases, and the PNP transistor is turned off to saturate the saturable reactor. A ringing choke converter circuit characterized in that the switching element's off time is lengthened by the amount of time until the oscillation frequency of the switching element is lowered .

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