JP3477029B2 - Synchronous double current power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of power supplies, and more particularly to a double current power supply in which a secondary side rectifier circuit is synchronously controlled with a primary side full bridge circuit.

[0002]

2. Description of the Related Art A power supply is an indispensable circuit for an electronic device. The power supply is installed as a power supply device independently of the electronic device, incorporated in the electronic device, or partly on a printed circuit board with another circuit. A variety of installation methods can be selected according to the amount of power to be supplied, such as being installed in a coexisting state.

Reference numeral 101 in FIG. 10 indicates an AC.
The power supply circuit is suitable for dropping a commercial voltage of 100 V to obtain a large-capacity output current, has a transformer 120, and the primary side and the secondary side are insulated.

On the primary side, a diode bridge circuit 13
0, smoothing capacitor 141, four transistors 111
To 114, the primary winding 121 in the transformer 120 is provided, and each of the transistors 111 to 114 and the primary winding 1 is provided.
21 forms a full bridge circuit 110.

A commercial power supply 142 is connected to the diode bridge circuit 130. The commercial voltage AC100V is full-wave rectified, smoothed by a smoothing capacitor 141, and the generated DC voltage is supplied to the full bridge circuit 110. When the full bridge circuit operates, an alternating current can flow through the primary winding 121.

On the secondary side, a secondary winding 122 in the transformer 120, four diodes 231-234, a smoothing coil 243, and an output capacitor 241 are provided. Magnetically coupled to the primary winding 121,
By the alternating current flowing through the primary winding 121, the secondary winding 1
22 is configured to generate an alternating electromotive force.

Each of the diodes 231 to 234 is diode-bridge connected to form a secondary side rectification circuit 230. The AC voltage induced in the secondary winding 122 is full-wave rectified to obtain a smoothing coil 243 and an output capacitor. It is configured so that the output voltage supplied to the load 241 and converted into a DC voltage by the smoothing coil 243 and the output capacitor 241 can be supplied to the load 200.

In the power supply circuit 101 having such a configuration, when the output voltage is detected and fed back to the primary side by a photo coupler (not shown) or the like, the full bridge circuit 110 of the full bridge circuit 110 is electrically insulated from the primary side and the secondary side. Since the control can be performed, it is possible to safely make the output voltage a constant voltage.

However, in the above-described power supply circuit 101, the current flowing through the secondary winding 122 always flows through the two diodes in the secondary side rectifying circuit 230 during the half cycle period of the switching frequency. There is a problem of large loss and poor efficiency.

Therefore, measures have been taken even in the prior art,
Each diode 231-234 in the secondary side rectifier circuit 230
In addition, although a low V _F diode or a Schottky diode has been used to reduce the loss, it is not sufficient for a low-voltage, large-current output power supply, and a countermeasure against it has been desired.

[0011]

SUMMARY OF THE INVENTION The present invention was created to solve the above-mentioned disadvantages of the prior art, and its object is to provide a highly efficient power source.

Another object of the present invention is to provide a power supply which requires only a small capacity of the secondary side inductance component and a simple smoothing circuit.

[0013]

In order to solve the above-mentioned problems, the invention according to claim 1 has a transformer provided with a primary winding and a secondary winding, and the primary winding is provided on the primary side. A primary side current control means for flowing an AC voltage in the line is provided, and a secondary side rectification circuit configured by connecting in parallel a circuit in which a rectifying element and an inductance element are connected in series is provided on the secondary side, and Both ends of the secondary winding are respectively connected to connection portions of the rectifying element and the inductance element, and a power supply configured to obtain a DC voltage by smoothing the voltage rectified by the secondary side rectifying circuit. A circuit,
The rectifying element is composed of MOSFETs, and each MOSFE
T is synchronously controlled with the primary side current control means, and the induced electromotive force induced in the secondary winding when the primary side current control means causes an alternating current to flow through the primary winding, and the synchronous control, The MOSFET operates in the third quadrant, and the induced current flowing in the secondary winding is
It is characterized in that it is configured to flow through T and the inductance element.

With respect to the primary side current control means, as in the invention described in claim 2, at least 4 parts are provided for the primary winding and the primary winding.
A full-bridge circuit composed of a plurality of transistors is provided, and the MOSFET can be synchronously controlled with two transistors having different phases from the four transistors.

Further, when controlling the amount of the alternating current flowing through the primary winding, the conduction time of the transistor in the full bridge circuit is made constant and the phases are shifted as in the invention of claim 3. It can be carried out.

Incidentally, any one of claims 1 to 3
The power supply circuit described in the paragraph (4) can be provided in the electronic device regardless of whether it is externally mounted or built in like the invention of the fourth aspect.

According to the structure of the power supply of the present invention described above, the transformer has the transformer provided with the primary winding and the secondary winding,
On the primary side, primary side current control means for applying an alternating voltage to the primary winding to flow an alternating current is provided. A circuit in which a rectifying element and an inductance element are connected in series is connected in parallel on the secondary side, and a secondary side rectifying circuit configured by the circuit is provided. And the inductance element are respectively connected.

The rectifying element in the secondary side rectifying circuit is a MOSFE
It is composed of T, and its MOSFET is synchronously controlled by the primary side current control means. The synchronous control is a MOS in which an alternating current flows in the primary winding and a voltage generated in the secondary winding biases the source and drain in the opposite direction from the normal case used as a switching element.
A voltage is applied to the gate terminal of the FET, and its MOS
The FET is configured to operate in the third quadrant.

The third quadrant operation of the MOSFET will be outlined by taking an n-channel MOSFET as an example. Generally, a MOSFET used for supplying power to a power supply circuit or the like has a diffusion structure as shown in FIG. When a positive voltage equal to or higher than the threshold voltage is applied to the gate terminal, a channel is formed near the surface of the back gate region and the source region and the drain region are electrically connected.

In that state, normally, a positive voltage is applied to the drain terminal with respect to the source terminal (V _DS > 0), and a current is passed from the drain terminal to the source terminal to control the voltage of the gate terminal. By doing so, the MOSFET is used as a switch element. In this state, the pn junction formed by the back gate region and the drain region is reverse-biased, so that no current flows in the pn junction.

On the contrary, when a positive voltage is applied to the source terminal with respect to the drain terminal (V _DS <0) while a voltage higher than the threshold voltage is applied to the gate terminal, a current flows from the source terminal to the drain terminal. Flows.

In this state, the pn junction is forward biased, so that the voltage between the drain terminal and the source terminal is p.
When the forward conduction voltage of the n-junction is exceeded, current also flows in the pn-junction.

The vertical axis represents the drain current I _D flowing between the drain and the source, and the horizontal axis represents the voltage V _DS between the drain and the source. The characteristics of the n-channel MOSFET are shown in the graph of FIG. The curve in the first quadrant of the XY plane is used as a switch element with current flowing in the normal direction (when a positive voltage is applied to the drain terminal with respect to the source terminal)
The curve in the third quadrant shows the characteristic when a current flows in a direction opposite to the normal direction (when a positive voltage is applied to the source terminal with respect to the drain terminal).

The curve shown by the broken line in the third quadrant is the characteristic when no voltage is applied to the gate terminal, and shows the diode characteristic of the pn junction.

In the third quadrant of the graph of FIG. 4, if the drain current I _D flowing from the source to the drain is equal to or less than I _MAX , the voltage drop when the voltage is applied to the gate terminal is as follows. Small compared to the voltage drop. Therefore, when a rectifying element utilizing the characteristics of the third quadrant of the MOSFET is used instead of the pn junction diode, there is a great feature that the loss due to the voltage drop of the rectifying element can be reduced. It is called three-quadrant motion.

In the power supply circuit of the present invention, when a voltage in the range of the first quadrant is applied between the source and drain of the MOSFET due to the voltage generated in the secondary winding, it is synchronized with the primary side current control means. By control, no voltage is applied to the gate terminal of the MOSFET, and the MOSFET is in a cutoff state.

On the other hand, when a voltage in the range of the third quadrant is applied between the source and drain of the MOSFET, the voltage is applied to the gate terminal by synchronous control, and the MOS is applied.
The FET is configured to operate in the third quadrant. Therefore, the MOSFET has the same rectifying action as the diode.

When the voltage generated in the secondary winding is applied to the inductance element by the MOSFET which operates in the third quadrant and a current flows through the inductance element, energy is accumulated in the inductance element. When the inductance element releases the stored energy,
It operates like a constant current source and tries to maintain the flowing current at a constant value.

Therefore, since the internal impedance of the inductance element that releases energy is very large, the inductance element maintains a constant current even when a voltage such that a current flows in the opposite direction is applied. Therefore, the inductance element operating in constant current has the same rectifying action as the diode.

As described above, since the secondary side rectifier circuit used in the power supply circuit of the present invention has the same rectifying action as the diode bridge circuit, the AC voltage generated in the secondary winding can be rectified, and A DC voltage can be obtained by smoothing the voltage.

Comparing the secondary side rectifying circuit of the present invention and the diode bridge circuit, in the diode bridge circuit, a voltage drop of two diodes occurs due to the current flowing every half cycle of the switching frequency. On the other hand, in the secondary side rectifier circuit of the power supply circuit of the present invention, only the voltage drop of one MOSFET operating in the third quadrant is sufficient.
Therefore, the power supply circuit of the present invention has low loss and high efficiency. Further, since the inductance element functions as a choke coil and the ripple component is smaller than in the case where one choke coil is used, the smoothing circuit can be composed of only the capacitor.

The primary side current control means as described above is provided with a full bridge circuit composed of four transistors and a primary winding, and each transistor is controlled to flow an alternating current through the primary winding. be able to.

In that case, the MOSFE in the secondary side rectifier circuit
It is necessary to control the third quadrant operation of T in synchronization with the operation of the full bridge circuit.
The voltage may be applied to the gate terminal in synchronization with the two transistors of different phases in the full bridge circuit.

In the case of performing such synchronization control, if the conduction time of the transistor is changed to control the amount of alternating current flowing in the primary winding, the synchronization control becomes complicated. Therefore, in the present invention, the conduction time of the transistors in the full-bridge circuit is made constant and the phases are shifted to change the conduction time of two transistors of the same phase, thereby controlling the amount of alternating current flowing in the primary winding. There is.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Reference numeral 1 in FIG. 1 is a synchronous double-current power supply according to an example of the present invention, and has a transformer T provided with a primary winding 21 and a secondary winding 22.

On the primary side of this synchronous double current power supply circuit 1,
Diode bridge circuit (primary side rectifier circuit) 43, smoothing capacitor C ₁ , 4 composed of n-channel MOSFET
The individual transistors Q _{1 to} Q ₄ are provided, and the transistors Q _{1 to} Q ₄ and the primary winding 21 form a full bridge circuit 10.

A commercial power supply 42 is connected to the diode bridge circuit 43, and a commercial voltage AC100 to be applied is supplied.
V is full-wave rectified, smoothed by a smoothing capacitor C ₁ , and a DC voltage is supplied to the full bridge circuit 10.

Of the _four transistors Q _{1 to} Q ₄ , when one set of transistors Q ₁ and Q ₄ is in the A phase and the other set of transistors Q ₂ and Q ₃ is in the B phase, it is in the A phase. When the B-phase and the B-phase are alternately turned on, an alternating current can be passed through the primary winding 21.

On the secondary side, an output capacitor C ₂ , A-phase and B-phase inductance elements L ₁ and L ₂ , and A-phase and B-phase MOSFETs 31 and 32 are provided, and the inductance element L ₁ and A secondary side rectifier circuit 30 is configured by L ₂ and MOSFETs 31 and 32. The secondary winding 22 is magnetically coupled to the primary winding 21, and when a current flows through the primary winding 21, an induced electromotive force is generated at both ends of the secondary winding 22.

Four transistors Q _{1 to} Q ₄ , A phase, B
The phase MOSFETs 31 and 32 are each composed of an impairment type n-channel MOSFET,
One end of each of the A-phase and B-phase inductance elements L ₁ and L ₂ is
They are connected to the drain terminals of the A-phase and B-phase MOSFETs 31 and 32, respectively, and the other ends thereof are connected to each other and to the high voltage side terminal of the output capacitor C ₂ . On the other hand, the source terminals of the A-phase and B-phase MOSFETs 31 and 32 are connected to each other and to the low voltage side terminal of the output capacitor C ₂ .

On the primary side of the synchronous double current power supply circuit 1,
An error signal generator 81, a PI adjuster 82, and a phase shift circuit 83 are provided, and together with the full bridge circuit 10,
Primary side current control means is configured.

The phase shift circuit 83 includes a PI adjuster 82.
The error signal V _PI outputted by the above and the clock signal having a frequency of 50 kHz are inputted, and in the phase shift circuit 83, a sawtooth wave of 100 kHz is generated from the inputted clock signal.

The conduction time and the cut-off period of the _four transistors Q _{1 to} Q ₄ are set so as to be a fixed time of a predetermined number of sawtooth waves (here, two), and each transistor Q ₁ of to Q _4, transistor Q ₃ of the low voltage side of the transistor Q _1, B-phase high-voltage side of the a-phase, begin to conduct by the rising sawtooth, the low voltage side of the a-phase transistor Q ₄ The B-phase high-voltage side transistor Q ₂ is configured to start conduction when the sawtooth wave and the error signal V _PI match.

Between two A-phase transistors Q ₁ and Q ₄ ,
The conduction state between the two B-phase transistors Q ₂ and Q ₃ will be described. When the error signal V _PI becomes larger than the amplitude range of the sawtooth wave, the conduction periods coincide and fall below the amplitude range. , The conduction start timing of the transistors Q ₄ and Q ₃ is advanced by one sawtooth wave.

In this case, when the error signal V _PI is within the amplitude range of the sawtooth wave, the error signal V _PI and the transistor Q ₄ on the low voltage side of the A phase are connected to each other for a period of time smaller than the peak voltage of the sawtooth wave. The B-phase high-voltage side transistor Q ₂ is configured so that the conduction start time is advanced.

Therefore, the two A-phase transistors Q ₁ ,
Between Q ₄ and the two B-phase transistors Q ₂ and Q ₃ ,
The conduction phase can be changed from the matched state (phase shift is zero) to the state shifted by π / 4 of the phase of one triangular wave (the sum of the A phase and the B phase indicates the maximum shift phase amount). π / 2).

On the A phase side, two transistors Q ₁ and Q ₄
Becomes conductive when both of the
When a voltage is applied to the B-phase side, both transistors Q ₂ and Q ₃ become conductive on the B-phase side, and the primary winding 21 has a voltage of the opposite polarity to that when the A-phase becomes conductive. Therefore, during the A-phase conduction period and the B-phase conduction period, that is, the period in which the voltage is applied to the primary winding by each phase, the maximum A duty and the minimum B duty are 1 / min and 1 / min, respectively. It becomes 4 duty.

When the phase A becomes conductive,
Since the voltage V _{T of the} opposite polarity is applied to the primary winding 21 when the phases are in the conducting state, the currents flowing through the primary winding 21 are in opposite directions, and an alternating current flows through the primary winding 21. It will flow.

Now, assuming that the commercial power supply 142 is turned on, the phase A is in a conducting state, and the primary side current J _A has flown into the primary winding 21, as shown in FIG. 5, the terminals of the primary winding 21. A positive voltage is induced at the terminal C of the secondary winding 22 having the same polarity as A, and a negative voltage is induced at the terminal D of the secondary winding having the same polarity as the terminal B of the primary winding 21.

At this time, a voltage is applied to the gate terminal of the A-phase MOSFET 31 by the phase shift circuit 83 in synchronization with the transistor Q _1, and the voltage induced across the secondary winding 22 is applied. As a result, the potential of the source terminal is higher than the potential of the drain terminal, so that the A-phase MOSFET 31 operates in the third quadrant, and the voltage induced in the secondary winding 22 causes the inductance of the terminal C → A-phase. Element L ₁ → load side (parallel circuit of output capacitor C ₂ and load 90) → A-phase MOSFET 31 → terminal D,
The secondary-side current I _A flows through the path, and energy is stored in the A-phase inductance element L ₁ .

In that state, when the transistor Q ₄ is cut off, the transistor Q ₁ and the transistor Q ₂ are provided on the primary side.
When a current flows in a closed loop formed by a diode (here, a pn junction in the transistor Q ₂ ) connected in anti-parallel to the transistor, and then the transistor Q ₁ is also cut off, the current that has been flowing is regenerated.

[0052] their current, indicated by symbol J _'A in FIG. 6 (a). In this state, the gate voltage is not applied to the B-phase MOSFET 32, the B-phase MOSFET 32 is cut off, and no current flows. On the other hand, the A-phase inductance element L ₁ releases the accumulated energy and becomes a constant current source to maintain the secondary side current I _A.

From that state, as shown in FIG.
When the phase transistors Q ₂ and Q ₃ are turned on, the primary winding 21
, A primary-side current J _B flows in the opposite direction to that when the phase A was in a conducting state, and a positive voltage is induced at the terminal D of the secondary winding 22 and a negative voltage is induced at the terminal C.

At this time, a voltage is applied to the gate terminal of the B-phase MOSFET 32 in synchronization with the transistor Q _3, and the voltage induced in the secondary winding 22 causes the potential of the source terminal to rise. Since it is higher than the potential of the drain terminal, the B-phase MOSFET 32 operates in the third quadrant, and the voltage induced across the secondary winding 22 causes the terminal D → B-phase inductance element L ₂ → load. The secondary side current I _B flows through the path of side → B-phase MOSFET 32 → terminal C, and energy is stored in the B-phase inductance element L ₂ .

When energy is stored in the B-phase inductance element L ₂ , a voltage is applied to the A-phase inductance element L ₁ in the direction opposite to the direction in which the secondary side current I _A due to energy emission flows. However, the A-phase inductance element L ₁ has a high internal impedance because it is performing a constant current operation, and maintains the secondary current I _A that flows. Therefore, the secondary side currents I _A and I _B are supplied to the load side from the two inductance elements L ₁ and L ₂ of the A phase and the B phase, respectively.

At this time, since the gate voltage is not applied to the A-phase MOSFET 31 and the potential of the drain terminal is higher than the potential of the source terminal, it is in the cutoff state and no current flows.

From that state, the B-phase transistor Q ₂ ,
When Q ₃ is cut off in this order, a current J ′ _B flows on the primary side. On the secondary side, two inductance elements L ₁ and L
₂ operates as a constant current source by the accumulated energy, and continues to supply the secondary side currents I _A and I _B to the load side, respectively, as shown in FIG. 7 (c).

Next, when the phase A becomes conductive and the primary side current J _A flows through the primary winding 21 again as shown in FIG. 7 (d), it is the same as the state shown in FIG. 6 (a). Then, a positive voltage is induced at the terminal C and a negative voltage is induced at the terminal D of the secondary winding 22. Due to the voltage induced in the secondary winding 22, the terminal C, the A-phase inductance element L ₁ , the load side, the A-phase MOSFET 31,
The secondary current I _A flows through the path of the terminal D, and energy is stored in the A-phase inductance element L ₁ . At this time,
The B-phase inductance element L ₂ operates as a constant current source and maintains the flowing secondary current I _B. B-phase MOSF
The ET32 is in a cutoff state and no current flows.

Thus, the two inductance elements L
Energy is stored in ₁ and L ₂ during the period in which the A-phase and B-phase are in the conducting state, respectively, and secondary currents I _A and I _B are supplied by the stored energy during the other periods. ,
Each of the inductance elements L ₁ and L ₂ has a secondary current I
_A, supplied to the load side together I _B. Secondary side current I _A , I _B
Since the phases of the two are different and the peak of the ripple is located at a different time, the smoothing circuit is connected to the output capacitor C ₂
The ripple can be easily removed even if it is composed of. Therefore, the output voltage V _{out in} a smoothed and DC voltage state is supplied to the load 90.

The output voltage V _out is detected by a voltage detection circuit (not shown), and is output as a voltage signal V _{L to} the error signal generator 81 on the primary side in a state of being electrically insulated by a photo coupler. The error signal generator 81 has
And the command value V _L ^* along with the voltage signal V _L is input, the difference between the voltage signal V _L command value V _L ^* is taken and output to PI regulator 82 as an error signal V _PI. The PI adjuster 82 is
The phase shift circuit 8 is arranged so that the value of the error signal V _PI becomes small.
3 is controlled to change the phase difference between the transistors Q _{1 to} Q ₄ , and the output voltage V _{out is} thus made constant.

As described above, since the secondary side currents I _A and I _B are always flowing through the two inductance elements L ₁ and L ₂ , one inductance element is used on the load side. It is possible to supply twice as much current as in the case where it is in use. Therefore, the synchronous double current power supply circuit 1 of the present invention is suitable for low voltage large current output.

In the above synchronous double current power supply circuit 1,
On the A-phase side, the high-voltage side transistor Q ₁ conducts before the low-voltage side transistor Q ₄ , and on the B-phase side, the low-voltage side transistor Q ₃ precedes the high-voltage side transistor Q _2. However, the order may be reversed. Also, one cycle is made up of four triangular waves, but one cycle is made up of two triangular waves.
If it is a cycle, the phase shift amount is 0 for A phase and B phase, respectively.
It can be ~ π.

In this synchronous double current power supply circuit 1, the winding ratio of the primary winding to the secondary winding is set to 15: 1 (primary: secondary),
A one-turn coil (0.69 μH) was used for the A-phase and B-phase inductance elements L ₁ and L ₂ , and the output voltage was set to 3V. A variable resistor was used as a load, and the output current I _out was changed to measure the characteristics. The relationship between the output capacity (V _out × I _out ) and the efficiency / output voltage was measured. The primary commercial power supply 42 is an AC
It is 100V.

The measurement results are shown on the abscissa with the output capacity (W).
The efficiency (%) is plotted on the left vertical axis and the output voltage (V) is plotted on the right vertical axis, which is shown in the graph of FIG. When the load is light or heavy, the efficiency is decreased, and the efficiency is highest between 250 and 350W. The maximum efficiency is 78.1% at 340 (W). The output voltage fluctuation was 7.3%.

FIG. 3 shows operation waveforms when the on-duty of each of the transistors Q _{1 to} Q ₄ is smaller than 1/2, the voltage V _T of the primary winding 21, the A-phase and B-phase inductance elements L ₁ and L. Current I _L1 , I _L2 flowing through ₂ and output capacitor C ₂
The respective waveforms of the current I _C flowing through are shown in a timing chart (the operating waveforms of the transistors Q _{1 to} Q ₄ represent ON in the high state and OFF in the low state).

Since the two inductance elements L ₁ and L ₂ are used, it can be seen that the ripple current to the output capacitor is small. The current I _C flowing into the output capacitor is the sum of the currents I _L1 and I _L2 flowing through the inductance elements L ₁ and L ₂ .

As described above, by using the synchronous double-current power supply circuit 1 of the present invention, it is possible to obtain a low-loss, high-output power supply with a small capacity inductance element.

In the above synchronous double current power supply circuit 1, n
Although the full bridge circuit is configured by the channel MOSFET, the high voltage side can be a p-channel MOSFET and the low voltage side can be an n-channel MOSFET. Also,
It may be constituted by a bipolar transistor having a flyback diode provided between the emitter and the collector.

In the synchronous double current power supply circuit 1 described above, the photocoupler is used for the insulation between the primary side and the secondary side, but other means,
For example, a pulse transformer or the like can be used.

Although the power supply circuit has been described above, the present invention broadly includes not only the power supply circuit but also electronic devices such as a power supply device, a measuring device, and a manufacturing device having the power supply circuit.

[0071]

The large current can be efficiently taken out by the small-capacity inductance element. Since the rectifying action of the inductance element is used, the number of rectifying elements can be small. A highly efficient power supply can be obtained simply by operating the secondary side rectification circuit in synchronization with the primary side full bridge circuit. Since the loss is small, the power supply device can be downsized.

[Brief description of drawings]

FIG. 1 is an example of a power supply circuit of the present invention

FIG. 2 is a timing chart for explaining a control method of a full bridge circuit in the power supply circuit.

FIG. 3 is a timing chart for explaining an operating state.

FIG. 4 is a graph for explaining the third quadrant operation of MOSFET.

FIG. 5 is a diagram for explaining a current path that flows when a full bridge circuit starts operating.

6A is a diagram for explaining a current path that flows when the A-phase side that started operation is cut off. FIG. 6B is a diagram for explaining a current path that flows when the B-phase side is conductive from that state. Figure

FIG. 7 (c): A diagram for explaining a current path that flows when the B-phase side is subsequently cut off. (D): A diagram for explaining a current path that flows when the A-phase side is conducted again.

FIG. 8 is a graph showing the relationship between output capacity, efficiency, and output voltage.

FIG. 9 is a sectional view for explaining a diffusion structure of an n-channel MOSFET.

FIG. 10 shows an example of a conventional power supply circuit.

[Explanation of symbols]

1 …… Synchronous double current power supply circuit 10 …… Full bridge circuit 21 …… Primary winding 22 …… Secondary winding 30 …… Secondary side rectifier circuit 3
1, 32 ... Two rectifying elements (MOSFETs) 43 ...
… Primary side rectifier circuit (diode bridge circuit) T …… Transformer Q _{1 to} Q ₄ … 4 transistors
L ₁ , L ₂ ... 2 inductance elements

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-149635 (JP, A) JP-A-8-317508 (JP, A) JP-A-8-317575 (JP, A) JP-A-6- 54528 (JP, a) United States Patent 5179512 (US, a) WO 98/033267 (WO, A1) (58 ) investigated the field (Int.Cl. ^7, DB name) H02M 3/28 H02M 3/335 H02M 7 /twenty one

Claims (4)

(57) [Claims] 1. A transformer having a primary winding and a secondary winding, wherein primary side is provided with primary side current control means for flowing an AC voltage through the primary winding, and secondary side is provided. A secondary side rectification circuit is provided in which a circuit in which a rectification element and an inductance element are connected in series is connected in parallel, and both ends of the secondary winding are connected to the rectification element and the inductance element. A power supply circuit configured to obtain a direct-current voltage by smoothing a voltage connected to each other and rectified by the secondary side rectification circuit, wherein the rectification element is formed of a MOSFET and each MOSFE
T is synchronously controlled with the primary side current control means, and by the synchronous control with the induced electromotive force induced in the secondary winding when an AC current is passed through the primary winding by the primary side current control means, The MOSFET operates in the third quadrant, and the induced current flowing in the secondary winding is
A synchronous double current power supply circuit characterized in that it is configured to flow through an SFET and the inductance element. 2. The primary side current control means has a full bridge circuit composed of the primary winding and at least four transistors, and the MOSFET is the
2. The synchronous double current power supply circuit according to claim 1, wherein the synchronous double current power supply circuit is configured so as to be synchronously controlled with two transistors having different phases among the individual transistors. 3. When controlling the current amount of the alternating current flowing through the primary winding, the conduction time of a transistor in the full bridge circuit is made constant and the phase is shifted. The synchronous double current power supply circuit according to claim 2. 4. An electronic device comprising the synchronous double current power supply circuit according to claim 1. Description: