JPH0487560A - switching power supply - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a switching power supply device that supplies DC stabilized voltage to various industrial and consumer electronic devices.

Conventional technology In recent years, switching power supplies have been widely used as DC stabilized power supplies for various industrial and consumer electronic devices due to their highly efficient energy conversion characteristics, but there is a strong demand for smaller and more efficient ones. It is being A conventional switching power supply device will be explained below.

As a means to reduce switching loss and increase the switching frequency, which are common technical issues in conventional switching power supply devices, the inventor has already developed a regenerative flyback type switching power supply device as shown in Fig. 3. did. In Figure 3, 1 is the input DC power supply;
It is constructed by rectifying and smoothing alternating current voltage, or by using batteries, etc.

Let this input voltage be El. 2 is a transformer, which has a primary winding 21 and a secondary winding 22. The winding ratio between the primary winding 21 and the secondary winding 22 is n:1. Reference numeral 3 denotes a first switch means, which is composed of a switch element 31 and a diode 32. 4 is a second switch means, which is composed of a switch element 41 and a diode 42. 5.7 is a capacitor, and 8 is a rectifier and smoothing circuit, which is composed of a diode 81 and a capacitor 82, and supplies an output voltage ICo to the load 9. A control drive circuit 1o detects the output voltage xO and outputs a drive pulse with a predetermined on/off ratio to the switch elements 31 and 41 in order to stabilize the output voltage xO. Figure 4 is a waveform diagram of each part of the switching power supply shown in Figure 3.
is the voltage across the primary winding 21, is the primary current flowing in the primary winding 21, is the secondary current flowing in the secondary winding 22, φ
indicates the magnetic flux of transformer 2. The operation of the switching power supply shown in FIG. 3 will be described below with reference to FIG. 4.

When the first switch means 3 is on in period 1, the second
The switch means 4 is off, and the input voltage ]Ei is applied to the primary winding 21, and the 1st amendment flow ■.

increases linearly and stores excitation energy in the transformer 2.

In period 2, when the first switch means 3 is turned off, the capacitor 7 and the excitation inductance of the transformer 2 resonate, and the voltages of each winding of the transformer 2 are reversed. 1
When the next winding voltage V reaches the voltage across the capacitor 6, the second switch means 4 is turned on and the transition to the first period 3 occurs.

During period 3, the excitation energy stored in the transformer 2 is released from the primary winding 21 to the capacitor 5 via the second switch means 4.

The rectifier and smoothing circuit 8 outputs the output voltage xO from the secondary winding 22.
is discharged to the load 9 via. At this time, the primary current I decreases almost linearly with the current value immediately before the first switch means 3 turned off as an initial value, and the secondary current I2 starts flowing from zero and increases. If the capacitance of capacitor 5 is large enough, its voltage will increase the flyback voltage of primary winding 21 by n
It is clamped to 1co, and the generation of surge voltage is almost eliminated. The primary current I1 eventually becomes less than zero and flows in the opposite direction, that is, in the direction of discharging from the capacitor 6 to the primary winding 21.In steady operation, the voltage across the capacitor 6 is stable, so the average charging and discharging current is The value will be zero.

In period 4, when the second switch means 4 is turned off, the capacitor 7 and the leakage inductance of the transformer 2 resonate, and the voltages of each winding of the transformer 2 are reversed. 1
When the next winding voltage V, becomes Xi, the first switch means 3
turns on and shifts to 1 period 6. At this time, the 2 modified constitutional flow 2 continues to flow due to inertia due to the leakage inductance of the transformer 2. Let this final value be "21."

During the period 6, the first switch means 3 and the diode 81 are on.

increases sharply with -technique z+/n as the initial value, and 2-revised construction, on the contrary, decreases. 2 becomes zero, the diode 81 is turned off and the period returns to period 1.

Through the above operations, the following equation approximately holds true, assuming that the on period (period 1 and period 5) of the switch means 3 is Ton, and the off period is Toff.

Ei)<Ton=nHoXToff That is, by adjusting the on/off ratio of the switch means 3, the output voltage zO can be stabilized and controlled. In addition, the energy of voltage reversal in period 4 is stored by demagnetization and reverse excitation in period 3, and zero cross turn-on is possible (
! :fx;b.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, sufficient reverse excitation energy must be stored in period 3 in order to turn on the zero-cross turn. I had to increase the amplitude. As a result, power loss occurs on the primary side, and instead of reducing high-frequency noise by mitigating voltage changes during switching using zero-cross turn-on, there is the problem of increased noise in the low range. Ta.

The present invention solves the above-mentioned problems, and while inheriting the strong voltage clamping ability, zero cross turn-on, and high frequency noise reduction effect that are the advantages of conventional power regenerative switching power supplies, it reduces the excitation inductance more than necessary. It is an object of the present invention to provide a switching power supply device with higher efficiency and lower noise by reducing the amplitude of the primary current without setting it to a smaller value.

Means for Solving the Problems To achieve this object, the switching power supply device of the present invention comprises a DC input power supply, a transformer having at least a primary winding and one or more secondary windings.

a series circuit of an inductance element connected to both ends of the DC input power supply, a primary winding of the transformer, and a first switch means;
A series circuit of a second switch means and a capacitor connected in parallel is connected to both ends of the series circuit of the next winding, and rectifies and smoothes the flyback voltage generated in the secondary winding of the transformer to supply a DC output voltage to the load. a rectifying and smoothing circuit, a control drive circuit that alternately drives the first and second switch means at a predetermined on-off ratio, and both ends of the first switch means, or the inductance element and the transformer connected in series. A capacitor is connected to at least one power point at both ends of the primary winding or at both ends of the second switch means.

This configuration reduces the back excitation energy during the off period,
By utilizing the energy stored in the inductance element, the zero-cross turn-on caused by the leakage inductance of the transformer can increase the amplitude of the resonant voltage and facilitate the condition.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to one drawing.

FIG. 1 is a circuit diagram of a switching power supply device according to an embodiment of the present invention. In FIG.

Reference numeral 1 is an input DC power source, which is configured by rectifying and smoothing an AC voltage, or by a battery or the like. This input voltage is
Let it be i. 2 is a transformer, which has a primary winding 21 and a secondary winding 22. The turn ratio of the primary winding 21 and the secondary winding 220 is n:1. Also, let the excitation inductance of the primary winding 21 be .

3 is a first switch means, which is composed of a switch element 31 and a diode 32. Reference numeral 4 denotes a second switch means, which is composed of a switch element 41 and a diode 42. 6 is a capacitor, 6 is an inductance element,
Let the inductance be L9. 7 is a capacitor, 8
is a rectifier smoothing circuit, diode 81 and capacitor 8
2 and supplies the output voltage Xo to the load 9. 1o
is a control drive circuit which detects the output voltage Ko and outputs a drive pulse 7 with a predetermined on-off ratio to the switch elements 31 and 41 in order to stabilize it. FIG. 2 is an operational waveform diagram of each part of the switching power supply device shown in FIG. Primary current, engineering, is 2
The secondary current flowing through the secondary winding 22 and φ indicate the magnetic flux of the transformer 2. The operation of the switching power supply shown in FIG. 1 will be explained below with reference to FIG.

In period 1, when the first switch means 3 is on, the second
The switch means 4 is off, the input voltage ICzL, / (L, +L') is applied to the primary winding 21, and the input voltage E i L' / (L, +L') is applied to the inductance element 6.
-)-L') is applied, and the voltage increases linearly to store excitation energy in the transformer 2 and the inductance element 6.

In period 2, when the first switch means 3 is turned off, the capacitor 7 and the excitation inductance of the transformer 2 resonate, and the voltages of each winding of the transformer 2 are reversed. 1
When the next winding voltage V reaches the voltage Xc across the capacitor 6, the second switch means 4 is turned on, and the period shifts to period 3.

During period 3, the excitation energy stored in the transformer 2 is released from the primary winding 21 to the capacitor 6 via the second switch means 4.

The rectifier and smoothing circuit 8 outputs the output voltage KO from the secondary winding 22.
is discharged to the load 9 via. At this time, the primary current I, decreases almost linearly with a slope (nxo-Kc)/L" with the current value immediately before the turn-off of the first switching means 3 as the initial value, and the secondary current I2 flows from 0 m. However, if the capacitance of the capacitor 6 is large enough, the voltage of the switching means 3 will be clamped to IC1-1-Ec, and the generation of surge voltage will almost disappear. The current flows in the opposite direction, that is, in the direction of discharging from the capacitor 6 to the primary winding 21. In steady operation, the voltage Ec across the capacitor 6 is stable, so the average value of the charging and discharging current is zero.

In period 4, when the second switch means 4 is turned off, the capacitor 7 and the inductance element 6 resonate, and each winding voltage of the transformer 2 is inverted. When the primary winding voltage V, reaches lC1, the first switch means 3 is turned on and a transition to the first period 6 occurs. At this time, the lacquer 2 continues to flow due to inertia due to the leakage inductance of the transformer 2. Let this final value be 21.

During the period 6, the first switch means 3 and the diode 81 are on, so the primary current I1 is 1.2. /n
The secondary current I2 increases sharply from the initial value, and the secondary current I2 decreases on the contrary. When the secondary current I2 becomes zero, the diode 81 is turned off and the period returns to period 1.

Through the above operations, the switch means 30 turns on (Ton2).
and let the off period be Toff.

Approximately the following formula holds true.

ICi×(Tonl−1−Ton2)=lcxToff
KixTon1xL.

=nlCox(TOn2+Toff)X(Lj+L')
That is, by adjusting the on/off ratio of the switch means 3, the output voltage ICo can be stabilized and controlled.

Now, the reason why the zero-cross turn-on condition of this switching power supply is better than the zero-cross turn-on condition of the conventional switching power supply will be explained. In period 4, when the switch means 4 turns off,
Because it is flowing.

In the conventional example, voltage reversal was caused by resonance between the leakage inductance of the transformer 2 and the capacitor 8. The amplitude of this resonant voltage is determined by the leakage inductance.

The smaller the capacitance of the capacitor 8, the larger the capacitance becomes.

However, increasing the leakage inductance.

This will degrade the regulation characteristics during multiple outputs and the energy conversion efficiency of the transformer, and reducing the capacitance of capacitor 8 will increase the slope of voltage reversal at turn-on and turn-off, which will reduce the effect of reducing high-frequency noise. It will cause deterioration. In contrast, in the embodiment of the present invention, the inductance element 6 is inserted.
The inductance element 6 can be sufficiently excited by the 1 amended flow I flowing in the period 3, and the stored energy is transferred to the switch means 4.
can be used for voltage reversal by turning off. Moreover, since the inductance element 6 is inserted on the primary side, the regulation characteristics will not deteriorate even if multiple outputs are used.

Effects of the Invention As described above, the present invention provides a direct current input power source and at least one
a transformer having a secondary winding and one or more secondary windings; an inductance element connected to both ends of the DC input power source; a series circuit of the primary winding of the transformer and a first switch means; A series circuit of a second switch means and a capacitor connected in parallel is connected across a series circuit of the element and the primary winding of the transformer, and a flyback voltage generated in the secondary winding of the transformer is rectified and smoothed, and a load is applied. A rectifying and smoothing circuit that supplies DC output voltage to. Said first and second
a control drive circuit that alternately drives the switch means at a predetermined on-off ratio, and both ends of the first switch means, or
By providing a configuration in which a capacitor is connected to at least one power point between the series-connected inductance element and both ends of the primary winding of the transformer, or both ends of the second switch means, the conventional power regeneration type While inheriting all the advantages of a switching power supply, the zero-cross turn-on conditions have been improved and the excitation inductance of the transformer can be set to a large value, reducing the amplitude of the primary current, resulting in a switching power supply with higher efficiency and lower noise. It is possible.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a switching power supply according to an embodiment of the present invention, FIG. 2 is a waveform diagram of each part of the embodiment shown in FIG. 1, and FIG. 3 is a circuit diagram of a conventional switching power supply. , FIG. 4 is an operational waveform diagram of each part of the conventional example shown in FIG. 3. 1... Input DC power supply, 2... Transformer, 3... First Nuwitch means, 4...
Second Nuitch means. 6... Capacitor, 6... Inductance element. 7... Capacitor, 8... Rectifier and smoothing circuit, 9... Load, 10... Control drive circuit. Name of agent: Patent attorney Shigetaka Awano and 1 other person 2nd
Directly to Figure 3 7' Steam power transformer 7th power transformer 7th group switching means 2nd class non-contact switching switching inductance element A current *; ft 1 each precious stone 344 meters, 32. 4-2. ,? 1 2 wide line switching element diode

Claims (1)

[Claims] A transformer having a DC input power source, at least a primary winding and one or more secondary windings, an inductance element connected to both ends of the DC input power source, a primary winding of the transformer, and a first switch means. a series circuit of the inductance element and the primary winding of the transformer;
a series circuit of a second switching means and a capacitor connected in parallel; a rectifying and smoothing circuit that rectifies and smoothes the flyback voltage generated in the secondary winding of the transformer and supplies a DC output voltage to the load; a control drive circuit that alternately drives two switch means at a predetermined on-off ratio, and both ends of the first switch means, or both ends of the inductance element and the primary winding of the transformer connected in series, or
A switching power supply device comprising a capacitor connected to at least one location on both ends of the second switch means.