JP2000217351A - Switching power supply unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain low noise by transferring energy stored in a charge storage capacitor to a charge supply transformer, and supplying the energy stored in the charge supply transformer to a power source during turn-off of a switching element. SOLUTION: An auxiliary switching element 13 turns on at turn-off of a switching element 3. During 1/4 of a resonance cycle of the electrostatic capacity of a charge storage capacitor 11 and the inductance of the primary winding of a charge supply transformer 12, the switching unit is turned on to transfer the stored energy of the charge storage capacitor 11 to the charge supply transformer 12. When the auxiliary switching element 13 turns off, the stored energy flows into a power source 1 through a charge supply diode 14, and when the energy stored in the charge storage capacitor 11 at the time of turning-on the switching element 3 is supplied to the power source during the off-period of the switching element. It is thus possible to suppress spike noise at the time of turning-on a reflux diode without increasing the loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply for supplying a stabilized DC voltage to electronic equipment.

[0002]

2. Description of the Related Art In recent years, switching power supplies have been strongly required to be smaller, more efficient, and have lower noise as electronic equipment has become smaller, more sophisticated, and more energy efficient. First, a conventional example of this kind will be described with reference to FIG.

FIG. 5 shows a circuit configuration of a conventional switching power supply device. In FIG. 5, reference numeral 1 denotes a DC output power supply for supplying an input voltage, 2 denotes a transformer, and one end of a primary winding 2a is connected to a negative electrode of the power supply 1 via a switching element 3; The secondary winding 2b is connected to a rectifying circuit composed of a rectifying diode 4 as a rectifying element and a circulating diode 5 as a circulating element. The tertiary winding 2c of the transformer 2 has one end connected to the positive electrode of the power supply 1, the other end connected to the cathode of the reset diode 9, and the anode of the reset diode 9 connected to the negative electrode of the power supply 1. On the other hand, the output of the rectifier circuit is connected to the load 8 via the output terminal 7 after being connected to the smoothing circuit 6.

Next, the operation will be described. The switching element 3 receives the controlled pulse drive signal and turns on / off.
The input of the DC power supply 1 is intermittently applied to the primary winding 2a of the transformer 2 repeatedly. After the AC voltage induced at both ends of the secondary winding 2b by this switching operation is rectified by the rectifier diode 4 and the return diode 5, it is converted into a DC voltage by the smoothing circuit 6, and the load is output via the output terminal 7. 8 to supply the output voltage. Further, a reset current of the transformer 2 flows through the tertiary winding 2c and the reset diode 9 during the off period of the switching element 3, and resets the magnetic flux of the transformer 2.

In the switching power supply device configured as described above, the rectifier diode 4 conducts at turn-on,
When a reverse voltage is applied to the freewheel diode 5, a reverse recovery current of the freewheel diode 5 flows through the transformer 2b, and energy is accumulated in the leakage inductance of the transformer 2, so that a large spike noise occurs at turn-on.

FIG. 6 shows another circuit configuration diagram of a conventional switching power supply device. In FIG. 6, reference numerals 1 to 9 are the same as those in FIG. 10 is a charging diode, 11 is a charge storage capacitor, and 10 and 11
Are connected in parallel to the reflux diode connected in series. Reference numeral 15 denotes a discharging resistor connected in parallel with the charging diode 10.

The basic operation of the switching power supply device configured as described above is exactly the same as that of the switching power supply device shown in FIG. 5, but the charge storage capacitor 11 is connected in parallel with the return diode 5. When the switching element 3 is turned on, the secondary winding 2 of the transformer 2 is turned on.
A voltage is applied to b, and a current flows into the charge storage capacitor 11 via the rectifying diode 4 and the charging diode 10. Therefore, when the switching element 3 is turned on, the rise of the voltage generated at both ends of the freewheel diode 5 becomes gentle, spike noise is reduced, and energy causing the spike noise is transferred to the charge storage capacitor 1.
1 absorbs low noise. However, at the time of turn-off, the energy stored in the charge storage capacitor 11 is discharged through the discharge resistor 15 and consumed by the discharge resistor 15.

[0008]

In the above-described conventional configuration, in the case of the switching power supply shown in FIG. 5, when the rectifier diode 4 is turned on at the time of turn-on and a reverse voltage is applied to the return diode 5, the return current is reduced. The reverse recovery current of the diode 5 flows through the transformer 2b, and the energy stored in the leakage inductance of the transformer 2 generates a large spike noise at the time of turn-on. Therefore, a diode with a high withstand voltage is required, and the noise is prevented. Become.

On the other hand, in the case of the switching power supply device shown in FIG. 6, the rise of the voltage generated at both ends of the freewheeling diode 5 when the switching element 3 is turned on becomes gradual due to the addition of the charge storage capacitor 11, thereby reducing the spike noise. The spike noise is reduced by the charge storage capacitor 11 as compared with the switching power supply device shown in FIG. 5, but the energy stored in the charge storage capacitor 11 is reduced by the discharge resistor. Since the power is consumed at 15, the loss increases.

The present invention has been made in order to solve the above-mentioned problems. The rising of the voltage generated between both ends of the free wheel diode 5 becomes gentle, and the spike noise is reduced. Energy is absorbed by the charge storage capacitor 11 to reduce noise, and the charge storage capacitor 11
It is an object of the present invention to provide a switching power supply device in which the loss is not increased by supplying the energy stored in the switching power supply.

[0011]

According to a first aspect of the present invention, there is provided a switching power supply device comprising: a series circuit of a charging diode and a charge storage capacitor connected in parallel to a free wheel diode;
A series circuit of a charge supply transformer and an auxiliary switching element connected in parallel to the charge storage capacitor, and a charge supply diode connected to the secondary winding of the charge supply transformer and connected in parallel to the power supply, At the time of turn-off, the auxiliary switching element is turned on, the energy charged in the charge storage capacitor is transferred to the charge supply transformer composed of a flyback transformer, and the energy stored in the charge supply transformer is turned off by turning off the auxiliary switching element. Supply to the

A switching power supply according to a second aspect of the present invention provides a series circuit of a charging diode and a charge storage capacitor connected in parallel to a freewheel diode, a charge supply transformer and an auxiliary switching connected in parallel to the charge storage capacitor. A charge supply diode connected in series with the element and a secondary winding of the charge supply transformer, and connected in parallel with the output terminal, turning on the auxiliary switching element at turn-off, and charging the charge storage capacitor. The energy stored in the charge supply transformer is supplied to a load by transferring the stored energy to a charge supply transformer constituted by a flyback transformer and turning off the auxiliary switching element.

The switching power supply according to a third aspect of the present invention provides a series circuit of a charging diode and a charge storage capacitor connected in parallel to a freewheel diode, a charge supply transformer and an auxiliary switching connected in parallel to the charge storage capacitor. A charge supply diode connected in series with the element and a secondary winding of the charge supply transformer and connected in parallel with the return diode, turning on the auxiliary switching element at turn-off, and charging the charge storage capacitor. The energy stored in the charge supply transformer is supplied to a load by transferring the stored energy to a charge supply transformer constituted by a flyback transformer and turning off the auxiliary switching element.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numerals 1 to 11 are the same as those of the conventional apparatus. 12 is a charge supply transformer, 13 is an auxiliary switching element, 14
Is a charge supply diode connected to a power supply.

Next, the operation will be described. When the switching element 3 is turned on, a voltage is applied to the secondary winding 2b of the transformer 2 and the rectifier diode 4 and the charging diode 10
A current flows into the charge storage capacitor 11 via.
Therefore, when the switching element 3 is turned on, the rise of the voltage generated at both ends of the freewheeling diode 5 becomes gentle, spike noise is reduced, and the energy that causes the spike noise is absorbed by the charge storage capacitor 11, thereby reducing the noise. Is possible. When the switching element 3 is turned off, the auxiliary switching element 13
Is turned on, and the auxiliary switching element 13 is 1/1 of the resonance cycle of the capacitance Cc of the charge storage capacitor 11 and the inductance Lc of the primary winding of the charge supply transformer 12.
During 4, the energy stored in the charge storage capacitor 11 is transferred to the charge supply transformer 12. When the auxiliary switching element 13 is turned off, the energy stored in the charge supply transformer 12 flows into the power supply 1 via the charge supply diode 14. Due to this operation, the energy stored in the charge storage capacitor 11 when the switching element 3 is turned on is supplied to the power supply during the off period of the switching element 3, so that the low noise when the switching element 3 is turned on without increasing the loss. Can be achieved. FIG. 4 shows the operation waveform of each part.

Embodiment 2 FIG. 2 shows a second embodiment of the present invention. In FIG. 2, reference numerals 1 to 14 are the same as those in the first embodiment, but the charge supply diode 14 connected to the secondary winding 12b of the charge supply transformer 12 is connected to the output terminal 7. .

Next, the operation will be described. The operation at the time of turning on the switching element 3 is the same as that of the first embodiment, and a detailed description thereof will be omitted. When the switching element 3 is turned off, the auxiliary switching element 13 is turned on. The auxiliary switching element 13 is located between the capacitance Cc of the charge storage capacitor 11 and 共振 of the resonance period of the inductance Lc of the primary winding of the charge supply transformer 12. It turns on and transfers the energy stored in the charge storage capacitor 11 to the charge supply transformer 12. When the auxiliary switching element 13 is turned off, the energy stored in the charge supply transformer 12 flows into the load 8 via the charge supply diode 14 and the output terminal 7. Due to this operation, the energy stored in the charge storage capacitor 11 when the switching element 3 is turned on is supplied to the load 8 during the off period of the switching element 3, so that the energy when the switching element 3 is turned on is reduced without increasing the loss. Noise can be achieved.

Embodiment 3 FIG. 3 shows a third embodiment of the present invention. In FIG. 3, reference numerals 1 to 14 are the same as those in the first embodiment, but the charge supply diode 14 connected to the secondary winding 12 b of the charge supply transformer 12 is connected in parallel to the freewheel diode 5. ing.

Next, the operation will be described. The operation at the time of turning on the switching element 3 is the same as that of the first embodiment, and a detailed description thereof will be omitted. When the switching element 3 is turned off, the auxiliary switching element 13 is turned on. The auxiliary switching element 13 is located between the capacitance Cc of the charge storage capacitor 11 and 共振 of the resonance period of the inductance Lc of the primary winding of the charge supply transformer 12. It turns on and transfers the energy stored in the charge storage capacitor 11 to the charge supply transformer 12. When the auxiliary switching element 13 is turned off, the energy stored in the charge supply transformer 12 flows into the load 8 via the charge supply diode 14, the smoothing circuit 6, and the output terminal 7. With this operation, the energy stored in the charge storage capacitor 11 when the switching element 3 is turned on is changed by the switching element 3
Is supplied to the load 8 during the off period of the switching element 3, it is possible to reduce the noise at the time of turning on the switching element 3 without increasing the loss.

[0020]

According to the first aspect of the invention, when the switching element 3 is turned on, the voltage at both ends of the freewheeling diode 5 rises slowly, so that noise can be reduced, and the energy causing spike noise can be stored in the charge storage capacitor. Since it is stored in the switching element 3 and becomes a part of the DC input power during the OFF period of the switching element 3, it is possible to reduce spike noise at the time of turning on the free wheel diode without increasing loss. As a result, there is an effect that a switching power supply device that can use a diode with high efficiency, low noise, and low withstand voltage can be configured.

According to the second and third aspects of the present invention, when the switching element 3 is turned on, the voltage between both ends of the freewheel diode 5 rises gently, so that noise can be reduced and energy that causes spike noise can be reduced. Since the charge is stored in the charge storage capacitor 11 and becomes a part of the output power during the OFF period of the switching element 3, it is possible to reduce spike noise when the freewheeling diode is turned on without increasing the loss. As a result, there is an effect that a switching power supply device that can use a diode with high efficiency, low noise, and low withstand voltage can be configured.

[Brief description of the drawings]

FIG. 1 is a diagram showing Embodiment 1 of a power supply device according to the present invention.

FIG. 2 is a diagram showing Embodiment 2 of the power supply device according to the present invention.

FIG. 3 is a diagram showing Embodiment 3 of the power supply device according to the present invention.

FIG. 4 is a diagram showing operation waveforms according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a conventional DC power supply device.

FIG. 6 is a diagram showing another conventional DC power supply device.

[Explanation of symbols]

1 power supply, 2 transformers, 3 switching elements, 4
Rectifier diode, 5 reflux diode, 6 smoothing circuit, 7
Output terminal, 8 load, 9 reset diode, 10
Charging diode, 11 charge storage capacitor, 12
Transformer for charge supply, 13 auxiliary switching element, 1
4 Charge supply diode, 15 Discharge resistor.

Claims (3)

[Claims] 1. A power supply for outputting a DC, a switching element for converting the DC output voltage to an AC voltage, and a primary winding, a secondary winding, and a tertiary winding. A transformer for transmitting voltage, a reset diode having one end connected to the other end of the tertiary winding connected to the positive electrode of the power supply, and an anode connected to the negative electrode of the power supply, A rectifying element that is connected and conducts when the switching element is turned on, a rectifying element that is connected in parallel with the secondary winding and the rectifying element and that conducts when the switching element is turned off, the rectifying element and the circulating element A smoothing circuit for smoothing the voltage output from the rectifier circuit, and an output terminal for receiving the power output from the smoothing circuit. In a switching power supply device for supplying power to a load, a series circuit of a charge storage capacitor and a charging diode connected in parallel to the freewheeling diode, a charge supply transformer and an auxiliary switching element connected in parallel to the charge storage capacitor And a charge supply diode connected to a secondary winding of the charge supply transformer and connected in parallel to a power supply that outputs the direct current.When the switching element is turned on, the charge storage capacitor is provided. And supplying the electric charge charged in the charge storage capacitor to the power supply during the off period of the switching element. 2. A power supply for outputting a DC, a switching element for converting the DC output voltage into an AC voltage, and a primary winding, a secondary winding, and a tertiary winding. A transformer for transmitting voltage, a reset diode having one end connected to the other end of the tertiary winding connected to the positive electrode of the power supply, and an anode connected to the negative electrode of the power supply, A rectifying element that is connected and conducts when the switching element is turned on; a reflux element that is connected in parallel with the secondary winding and the rectifying element and conducts when the switching element is turned off; the rectifying element and the reflux element A smoothing circuit for smoothing the voltage output from the rectifier circuit, and an output terminal for receiving the power output from the smoothing circuit. In a switching power supply for supplying power to a load, a series circuit of a charge storage capacitor and a charge diode connected in parallel to the freewheeling diode, a charge supply transformer and an auxiliary switching element connected in parallel to the charge storage capacitor And a charge supply diode connected to the secondary winding of the charge supply transformer and connected to the output terminal.When the switching element is turned on, the charge storage capacitor is charged. A switching power supply device, wherein the charge stored in the charge storage capacitor is supplied to a load during the off period of the switching element. 3. A power supply for outputting a DC, a switching element for converting the DC output voltage to an AC voltage, a primary winding, a secondary winding, and a tertiary winding. A transformer for transmitting voltage, a reset diode having one end connected to the other end of the tertiary winding connected to the positive electrode of the power supply, and an anode connected to the negative electrode of the power supply, A rectifying element that is connected and conducts when the switching element is turned on, a rectifying element that is connected in parallel with the secondary winding and the rectifying element and that conducts when the switching element is turned off, the rectifying element and the circulating element A smoothing circuit for smoothing the voltage output from the rectifier circuit, and an output terminal for receiving the power output from the smoothing circuit. In a switching power supply device for supplying power to a load, a series circuit of a charge storage capacitor and a charging diode connected in parallel to the freewheeling diode, a charge supply transformer and an auxiliary switching element connected in parallel to the charge storage capacitor And a charge supply diode connected to the secondary winding of the charge supply transformer and connected in parallel with the return element.When the switching element is turned on, the charge storage capacitor is charged. A switching power supply device for supplying the charge charged in the charge storage capacitor to a load during an off period of the switching element.