JP4350840B2 - 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-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. By extending the off time of the switching element 3 so that the oscillation frequency is lowered at the time of light load power such as standby power, the switching loss of the switching element 3 is reduced to increase the efficiency at light load power. To do. That is, the voltage of the drive system winding 2 of the transformer 1 having inductance is applied to the gate of the switching element 3 to turn on the switching element 3, and the feedback control circuit 21 connected to the output voltage detection circuit 20 on the secondary side. The second NPN-type transistor 22 connected to is turned on to turn off the switching element 3, and a current is passed through the capacitor 24 connected to the secondary winding by the back electromotive force of the transformer to output a stable voltage. in ringing choke converter vibration oscillation, a resistor 7 between the collector of the gate and the first PNP transistor 6 of the switching element 3, also the first PNP-type transistor 6 emitter and drive system winding 2 a capacitor 8 between one end, the emitter and further wherein the first PNP transistor 6 Over scan a resistor 9 and a capacitor 10 connected in parallel between the resistor 15 between the other end of the base and the drive system winding 2 of the first PNP transistor 6, the first PNP transistor 6 and the collector and a resistor 7 between the collector of the second NPN transistor 22, the emitter of the first PNP transistor 6 and the emitter of the third PNP transistor 18 is connected, the third PNP type A resistor 19 and a capacitor 25 are connected in parallel between the emitter and base of the transistor 18, and a parallel circuit of a smoothing capacitor 12 and a resistor 14, a rectifier diode 11 and a resistor 13 are connected between one end and the other end of the drive system winding 2. A resistor 17 and a Zener diode 16 are connected in series between the negative electrode of the smoothing capacitor 12 and the base of the third PNP transistor 18 in series. And, it is a ringing choke converter.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, the flyback voltage (voltage applied to 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, and conversely, the output voltage of the control system winding 5 decreases. When the light load power is reached, the voltage of the capacitor 12 drops. Therefore, when the voltage of the capacitor 12 is detected by the Zener diode 16 and the output power of the winding 5 of the control system is small, the transistor 18 is turned off, and the transistor 6 Since the time during which the switch is turned on is long, the off time of the switching element 3 is lengthened and the oscillation frequency is shortened.
On the contrary, when the output power of the winding 5 is increased, the transistor 18 is turned on and the time during which the transistor 6 is turned on is shortened. Therefore, the off time of the switching element 3 is shortened and the oscillation frequency can be increased. .
[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 (applied voltage to the capacitor 12) of the winding 2 of the drive system is decreased by the Zener diode 16 and the transistor 18 is turned off. By lengthening the time for which the transistor 6 is turned on, the off time of the switching element 3 can be lengthened and the oscillation frequency can be lowered as shown in FIG.
For this reason, since the ratio of the ON time of the switching element 3 to one cycle (reciprocal of the oscillation frequency) becomes small, the efficiency at the time of light load power can be increased as compared with the conventional circuit 2 as shown in FIG. It contributes greatly to energy saving and 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, 18, 22 Transistor 7, 9, 13, 14, 15, 17, 19 Resistance 8, 10, 12, 24, 25 Capacitor 11, 23 Diode 16 Zener Diode 20 Voltage detection circuit 21 Feedback control circuit

Claims (1)

The voltage of the drive system winding (2) of the transformer (1) having inductance is applied to the gate of the switching element (3) to turn on the switching element (3), and the secondary output voltage detection circuit ( The second NPN transistor (22) connected to the feedback control circuit (21) connected to 20) is turned on to turn off the switching element (3), and is connected to the secondary winding by the counter electromotive force of the transformer. In a self-excited oscillation ringing choke converter that passes a current through a capacitor (24) and outputs a stable voltage,
A resistor (7) between the collector of the gate of the first PNP-type transistor of the switching device (3) (6), The emitter and a drive system winding of said first PNP type transistor (6) (2 and a capacitor (8) between one end of), further parallel connected resistor between the emitter and the base (9) and a capacitor (10) of said first PNP type transistor (6), said first collector and second NPN type transistor of the resistance between the other end of the base and the drive system winding of the PNP transistor (6) (2) (15), said first PNP type transistor (6) ( connect a resistor (7) between the collector of 22), the emitters of the third PNP type transistor of the first PNP-type transistor (6) (18) connected, the third PNP transistor ( 18) Emi A parallel connection of a smoothing capacitor (12) and a resistor (14) between one end and the other end of the drive system winding (2). A rectifier diode (11) and a resistor (13) are connected in series, and a resistor (17) and a Zener diode (16) are connected in series between the negative electrode of the smoothing capacitor (12) and the base of the third PNP transistor (18). A ringing choke converter characterized by being connected.

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