JP2009303386A - Resonant switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resonant switching power supply that reduces noise while achieving simplification of a circuit configuration for noise reduction. <P>SOLUTION: The resonant switching power supply is composed of a capacitor and a primary winding of a transformer, which are connected to switching elements controlled by an oscillator, a secondary winding of the transformer, and a rectifier smoothing circuit. The switching elements are driven by a sine wave while a conduction angle of the sine wave is controlled. Switching elements Q1-Q4 are driven by a sine wave by a sine-wave oscillator 13 and a phase controller 15 while a conduction angle of the sine wave is controlled by a feedback signal from output on the secondary side so as to adjust input power to a prescribed value, thereby maintaining output on the secondary side at a constant level. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a circuit configuration of a power supply device, particularly a resonant switching power supply, and a driving method using the circuit configuration.

FIG. 2 is a circuit diagram showing a low position of a resonant switching power supply that utilizes a resonance phenomenon by connecting a capacitor to a winding of a transformer. The input voltage Vin is adjusted to a predetermined value by the DC / DC converter 21 and connected to the switching elements Q1 to Q4. The bases of the switching elements Q1 to Q4 are connected to the rectangular wave oscillator 23, and the switching elements Q1, Q2 and Q3, Q4 are driven to be in reverse phase. A connection point of the switching elements Q1 and Q2 and a connection point of the switching elements Q3 and Q4 are connected to a series circuit of the capacitor C and the primary winding Lp of the transformer T.

The energizing direction of the primary winding of the transformer T is switched by the rectangular wave oscillator 23, and accordingly, an AC output voltage corresponding to the secondary side of the transformer T is obtained. This can be rectified by a diode and smoothed by a capacitor to obtain a predetermined DC output voltage. Of course, the AC output can be used as it is.

In the above circuit, a rectangular wave is used to drive a resonant circuit including the capacitor C and the primary winding Lp. Since there is a limit to the Q of the resonance circuit, there is a problem that the harmonics of the rectangular wave cannot be completely removed and remain as a noise source.
Japanese Utility Model Publication No. 58-121186 Japanese Patent No. 3547837

The present invention provides a resonant switching power supply that reduces noise that has been a problem in the related art and enables simplification of the circuit configuration.

The present invention solves the above problem by using a sine wave as a signal for driving a resonance circuit and controlling the conduction angle of the sine wave. That is, in a resonance type switching power source composed of a capacitor connected to a switching element controlled by an oscillator, a primary winding of the transformer, a secondary winding of the transformer, and a rectifying / smoothing circuit, the switching element is driven by a sine wave. In addition, the sine wave conduction angle is controlled to keep the output constant.

Operationally, a drive signal is generated from an input voltage by a capacitor connected to a switching element controlled by an oscillation circuit and a primary winding of the transformer, and a DC output is generated by a secondary winding of the transformer and a rectifying and smoothing circuit. In the resonant switching power supply to be obtained, the switching element is sine-wave driven by the sine wave oscillator and the phase controller, and the energization angle of the sine wave is controlled by the feedback signal from the secondary side output so that the input power is predetermined It is characterized in that the output on the secondary side is kept constant by adjusting to the value of.

According to the present invention, the energization time of the switching element is controlled by chopping the sine wave into an appropriate waveform using the phase controller, thereby controlling the energy input to the resonance circuit. Thereby, the output voltage can be maintained at a desired value. Although the slope on one side of the control waveform is steep, the other slope remains a sine wave, so that switching noise can be reduced to ½.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. The basic configuration of the resonant switching power supply is the same as that in the above example, and the input (drive) voltage Vin is connected to the switching elements Q1 to Q4. The bases of the switching elements Q1 to Q4 are connected to the sine wave oscillator 13 via the phase controller 15, and the switching elements Q1, Q2 and Q3, Q4 are driven so as to be in reverse phase. A connection point of the switching elements Q1 and Q2 and a connection point of the switching elements Q3 and Q4 are connected to a series circuit of the capacitor C and the primary winding Lp of the transformer T.

The configuration of the secondary side of the transformer T is the same as that of the above-described blue, but a detection winding Ld is provided, and the detection signal is fed back to the phase controller 15 as a feedback signal (FB). In response to this detection output, when the output voltage becomes higher than a predetermined value, the energization angle of the sine wave that is the output of the phase controller 15 is narrowed to reduce the energy supplied to the tons. Conversely, when it becomes low, the conduction angle of the sine wave is widened to increase energy. As a result, the output on the secondary side can be kept constant.

The signal applied to the bases of the switching elements Q1 to Q4 can arbitrarily set the width of the ON time from a full wave sine wave to near zero amplitude. That is, as shown in FIG. 3, the time when the sine wave output is present and the limitation are to control the on-time of the switching element by arbitrarily setting the width of the time when the output does not exist. The feedback of the detection signal on the secondary side may be the AC output of the winding or may be converted to DC.

The present invention can be widely used not only for a resonance type switching power supply but also for a power supply circuit of a discharge tube driving device.

Circuit diagram showing an embodiment of the present invention Circuit diagram showing a conventional resonant switching power supply Explanatory diagram of operation waveforms of the present invention

Explanation of symbols

13: Sine wave oscillator
15: Phase controller
Q1-Q4: Switching element
C: Capacitor T: Transformer
Lp: Primary winding
Ls: Secondary winding Ld: Detection winding

Claims (3)

In a resonant switching power supply configured by a capacitor connected to a switching element controlled by an oscillator, a primary winding of the transformer, a secondary winding of the transformer, and a rectifying and smoothing circuit,
A resonant switching power supply characterized in that the switching element is driven in a sine wave and the output angle is kept constant by controlling the conduction angle of the sine wave. In a resonant switching power supply configured by a capacitor connected to a switching element controlled by an oscillator, a primary winding of the transformer, a secondary winding of the transformer, and a rectifying and smoothing circuit,
The switching element is driven by a sine wave by a sine wave oscillator and a phase controller, and the conduction angle of the sine wave is controlled by a feedback signal from the secondary side output to keep the output constant. Type switching power supply. A resonant switching power supply that generates a drive signal from an input voltage by a capacitor connected to a switching element controlled by an oscillation circuit and a primary winding of the transformer, and obtains a DC output by a secondary winding of the transformer and a rectifying and smoothing circuit In
The switching element is driven by a sine wave by the sine wave oscillator and the phase controller, and the conduction angle of the sine wave is controlled by the feedback signal from the secondary output to adjust the input power to a predetermined value. A resonant switching power supply characterized in that the output on the secondary side is kept constant.

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