JP4350839B2 - Ringing choke converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ringing choke converter for a DC power supply circuit, and aims to increase the efficiency of a 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 that has been 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-described problem, and applies the voltage of the drive system winding 2 of the transformer 1 having inductance to the gate of the switching element 3 to turn on the switching element 3. The second NPN transistor 20 connected to the feedback control circuit 19 connected to the output voltage detection circuit 18 is turned on to turn off the switching element 3, and the capacitor 15 connected to the secondary winding 5 by the counter electromotive force of the transformer. current flows, in the self-oscillating ringing choke converter and outputs a stable voltage, a resistor 7 between the gate of the switching device 3 and the collector of the first PNP transistor 6, also, the first PNP a capacitor 8 between one end of the emitter and the drive system winding 2 of the type transistors 6, further said first P P-type transistor 6 and the resistor 9 and the capacitor 10 between the emitter and base are connected in parallel, a resistor is interposed between the other end of the base and the drive system winding 2 of the first PNP transistor 6, the A series circuit of another resistor 11 and a phototransistor of the photocoupler 12 is connected in parallel to the resistor 13, and a switch 16, a resistor 17 and a photodiode of the photocoupler 12 are connected in series to both ends of the secondary output. This is a ringing choke converter.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, when the switch 16 is turned on by a control signal at the rated load, the phototransistor of the photocoupler 12 is turned on to form a parallel circuit of the resistor 11 and the resistor 13, so that the base resistance value of the transistor 6 is reduced. 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.
On the contrary, when the switch 16 is turned off at light load, the phototransistor of the photocoupler 12 is turned off and only the resistor 13 is provided, so that the base resistance value of the transistor 6 is increased and the time for which the transistor 6 is turned on is increased. Since the switching element 3 becomes longer and the OFF time becomes longer, 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】
According to the present invention, when the control system output power becomes light load power, as shown in FIG. 3, the switch 16 is turned off by the control signal to increase the base resistance value of the transistor 6 and extend the time for turning on the transistor 6. As a result, the off-time of the switching element 3 can be lengthened to lower the oscillation frequency.
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 conventional basic circuit.
FIG. 3 is a characteristic diagram of “control system output power—oscillation frequency”.
FIG. 4 is a characteristic diagram of “control system output power-efficiency”.
[Explanation of symbols]
1 Converter transformer 2 Transformer drive winding 3 Switching element (FET)
4 Primary winding of transformer 5 Secondary winding of transformer 6, 20, 22 Transistors 7, 9, 11, 13, 17 Resistors 8, 10, 15 Capacitor 12 Photocoupler 14 Diode 16 Switch 18 Voltage detection circuit 19 Feedback control circuit

Claims (1)

The voltage of the drive system winding of the transformer having inductance is applied to the gate of the switching element to turn on the switching element, and the second NPN connected to the feedback control circuit connected to the output voltage detection circuit on the secondary side In the self-oscillating ringing choke converter that turns on the type transistor and turns off the switching element, flows current to the capacitor connected to the secondary winding by the back electromotive force of the transformer, and outputs a stable voltage.
The resistance between the collector of the gate of the first PNP-type transistor of the switching element, also connect a capacitor between one end of the emitter and the drive system winding of said first PNP type transistor, further wherein the a resistor and a capacitor connected in parallel between the emitter and the base of the first PNP-type transistor, a resistor is interposed between the other end of the base and the drive system winding of said first PNP type transistor, in parallel with the resistor A ringing choke converter characterized by connecting a series circuit of a resistor and a phototransistor of a photocoupler to each other, and further connecting a switch, a resistor and a photocoupler photodiode in series at both ends of the secondary output.

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