WO2007123099A1

WO2007123099A1 - Switching power supply circuit

Info

Publication number: WO2007123099A1
Application number: PCT/JP2007/058308
Authority: WO
Inventors: Hideo Sato; Takahiro Kobayashi; Hiroaki Takahashi
Original assignee: Oki Power Tech Co., Ltd.
Priority date: 2006-04-18
Filing date: 2007-04-17
Publication date: 2007-11-01
Also published as: JP2007288951A

Abstract

A switching power supply circuit having an improved ability to supply current to a dynamic load in which the current consumption increases instantaneously and adapted for efficiently and stably supplying electric power to a steady load whose consumption current varies with a small variation width. The switching power supply circuit comprises a first transformer having a core of an amorphous magnetic material, a second transformer having a core of a ferrite magnetic material, a first switching element for flowing a current through the primary-side winding of the first transformer according to a first drive signal, a second switching element for flowing a current through the primary-side winding of the second transformer according to a second drive signal, first and second output circuits for generating first and second output voltages according to the voltages induced in the secondary-side windings of the first and second transformers, respectively, and first and second control circuits for independently generating the first and second drive signals.

Description

Specification

Switching power supply circuit

Technical field

TECHNICAL FIELD [0001] The present invention generally relates to a switching power supply circuit used in an electronic device such as an impact printer, and more particularly to a switching power supply circuit having a plurality of outputs. Background art

In recent years, switching power supplies that are small and light and can efficiently extract electric power are widely used along with the small and light electronic devices. Especially in electronic devices such as impact printers, switching power supplies having multiple outputs are often used.

[0003] For example, in addition to a plunger that electromagnetically drives a print head, a control circuit for controlling transmission / reception of data to / from a personal computer or the like and control of the plunger is incorporated in the impact printer. ing. Generally, the solenoid of the plunger operates at a voltage of about 24V to 42V, and the force control circuit operates at a voltage of about 3.3V to 5V. Under these circumstances, impact power printers use switching power supplies that can extract a plurality of different output voltages.

[0004] Loads such as plungers of impact printers are in milliseconds or seconds! /, And dynamically fluctuates from a no-load state to a state that consumes 2 to 3 times the rated output current of the power circuit. In addition, a load such as a plunger may instantaneously consume about 10 times the rated output current of the power circuit. On the other hand, a load such as a control circuit is relatively stable with a small fluctuation range of current consumption over a long period of time. In this application, a stable load in which the fluctuation range of the current consumption is within about 50% of the rated output current of the power supply circuit is called a steady load, and the fluctuation range of the current consumption is larger than that! Called Mick load.

Conventionally, in a switching power supply circuit, a ferrite magnetic material is often used as a core of a transformer for stepping up or down an input voltage. In switching power supply circuits with multiple outputs, the primary circuit is shared to handle multiple loads. In many cases, multiple secondary circuits are provided.

However, when an output for supplying electric power to a dynamic load and an output for supplying electric power to a steady load are provided in such a configuration, Cross-regulation problems occur. For example, when a current about 10 times the rated current flows instantaneously in a dynamic load, the core of the transformer using the magnetic material of ferrite reaches a saturation state, and as a result, the output voltage for a steady load is greatly increased. It will fluctuate. Although it is conceivable to use a 3-terminal regulator to stabilize the output voltage, the voltage fluctuation range on the input side of the 3-terminal regulator must be set large.

[0007] As a related technique, Japanese Patent Application Publication JP-P2001-333577A discloses a power supply device that can insulate from the primary side of the main transformer and extract many outputs. In this power supply, an output circuit that outputs power via the auxiliary transformer is newly connected to the secondary winding of the main transformer. JP—P2001—333577A has a structural limitation on the number of secondary windings that can be installed in the main transformer. By connecting another auxiliary transformer to the secondary winding of the main transformer, It is described that many output circuits can be easily and inexpensively added. However, JP-P2001-333577A does not describe solving a problem caused by a dynamic load.

Disclosure of the invention

Problems to be solved by the invention

Therefore, in view of the above points, the present invention improves the current supply capability for a dynamic load in which the current consumption increases instantaneously, such as a plunger of an impact printer, and at the same time as a control circuit. An object of the present invention is to provide a switching power supply circuit that efficiently and stably supplies a steady load with a small current fluctuation range.

Means for solving the problem

In order to solve the above-described problem, a switching power supply circuit according to one aspect of the present invention includes a core including an amorphous magnetic body, and a primary side wire and a secondary side wire wound around the core. A first transformer in which an input voltage is applied to one end of the primary side wire, a core including a ferrite magnetic body, and a primary side wire and a secondary side wire wound around the core. Input voltage is 1 The second transformer applied to one end of the secondary winding and the primary side of the first transformer connected to the other end of the primary winding of the first transformer and according to the pulsed first drive signal The first switching element for passing current through the winding and the other end of the primary winding of the second transformer, and the primary winding of the second transformer according to the pulse-shaped second drive signal A second switching element that supplies current to the first transformer, a first output circuit that generates a first output voltage based on a voltage generated on the secondary side of the first transformer, and a second transformer A second output circuit that generates a second output voltage based on the voltage generated on the secondary side winding, and a first and second drive circuit that independently generate the first and second drive signals, respectively. And a second control circuit.

The invention's effect

[0010] According to the present invention, a transformer or a choke coil having a core containing an amorphous metal magnetic body is used to improve saturation characteristics and to improve cross-regulation between outputs of a plurality of systems, thereby preventing dynamic loads. The current supply capability can be improved, while efficient and stable power supply can be performed for a steady load.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of a switching power supply circuit according to a first embodiment of the present invention.

2 is a diagram showing in detail the configuration of a control circuit and the like in the first voltage conversion circuit shown in FIG.

3 is a circuit diagram showing a configuration example of a secondary side voltage detection circuit and a detection voltage generation circuit in the first voltage conversion circuit shown in FIG. 1.

4 is a waveform diagram for explaining the operation of the control circuit in the first voltage conversion circuit shown in FIG. 2 in an overload state.

5 is a waveform diagram for explaining the operation of the control circuit shown in FIG. 2 in a normal state.

6 is a diagram showing a configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG.

FIG. 7 is a diagram showing a configuration of a switching power supply circuit according to a second embodiment of the present invention.

8 is a diagram showing in detail the configuration of a control circuit and the like in the first voltage conversion circuit shown in FIG. FIG. 9 is a diagram showing in detail the configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG.

FIG. 10 is a diagram showing a configuration of a switching power supply circuit according to a third embodiment of the present invention.

11 is a diagram showing a first configuration example of the constant voltage output circuit shown in FIG. 9.

12 is a diagram showing a second configuration example of the constant voltage output circuit shown in FIG.

FIG. 13 is a diagram showing a configuration of a switching power supply circuit according to a fourth embodiment of the present invention.

14 is a diagram showing a configuration example of the PFC circuit shown in FIG. 12.

FIG. 15 is a diagram showing a configuration of a switching power supply circuit according to a fifth embodiment of the present invention. FIG. 16 is a diagram showing a configuration of a switching power supply circuit according to the sixth embodiment of the present invention. Best mode for carrying out

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 1 is a diagram showing a configuration of a switching power supply circuit according to the first embodiment of the present invention. This switching power supply circuit includes a rectifying / smoothing circuit 10 connected to the input terminals 1 and 2 of the AC power supply voltage, a first voltage conversion circuit 11 connected to the output terminal 3 and the output terminal 4, an output terminal 5 and And a second voltage conversion circuit 12 connected to the output terminal 6.

[0014] The rectifying / smoothing circuit 10 includes, for example, a diode bridge and a capacitor. The AC voltage applied between the input terminal 1 and the input terminal 2 is full-wave rectified by the diode bridge and smoothed by the capacitor. .

[0015] The first voltage conversion circuit 11 is connected in series with a transformer 20 that steps up or steps down an AC voltage on the primary side and outputs it to the secondary side, and a primary side wire 21 of the transformer. A switching element 30 for passing a current to the primary winding 21 of the transformer in accordance with the drive signal, and a primary current detection circuit 40 for detecting a current flowing to the primary winding 21 of the transformer. .

[0016] Further, the first voltage conversion circuit 11 generates a half-wave voltage generated on the secondary side winding 22 of the transformer. The rectifying diode 51, the capacitor 52 for smoothing the rectified voltage, the secondary side voltage detecting circuit 60 for detecting the smoothed voltage at both ends of the capacitor 52, and the detection result of the primary side current detecting circuit 40 and A control circuit 70 that generates a drive signal based on the detection result of the secondary side voltage detection circuit 60 and limits the period during which current flows through the primary side winding 21 of the transformer. An optical signal transmission element such as a photo force bra is used for a part of the feedback signal path from the secondary side voltage detection circuit 60 to the control circuit 70.

The transformer 20 includes a magnetic core 24, a primary side wire 21, a secondary side wire 22, and an auxiliary wire 23 that are wound around the core 24. Assuming that the number of primary side wires 21 is N1 and the number of secondary side wires 22 is N2, when there is no loss, the step-up ratio between the primary side and the secondary side is N2ZN1. In addition, the auxiliary feeder 23 is used to supply a power supply voltage to the control circuit 70. The dot symbol attached to the transformer 20 indicates the polarity of the winding.

[0018] The second voltage conversion circuit 12 is connected in series to a transformer 90 that boosts or steps down the AC voltage on the primary side and outputs it to the secondary side, and a primary side 91 of the transformer. Switching element 100 that allows current to flow through the primary side 91 of the transformer, a primary current detection circuit 110 that detects current that flows through the primary side 91 of the transformer, and the secondary of the transformer A diode 53 for half-wave rectifying the voltage generated on the side wire 92, a capacitor 54 for smoothing the rectified voltage, a secondary-side voltage detection circuit 115 for detecting the smoothed voltage at both ends of the capacitor 54, And a control circuit 120 that generates a drive signal based on the detection result of the primary side current detection circuit 110 and the detection result of the secondary side voltage detection circuit 115.

The transformer 90 includes a magnetic core 94, a primary side wire 91, a secondary side wire 92, and an auxiliary wire 93 that are wound around the core 94. If the number of primary side wires 91 is N3, and the number of secondary side wires 92 is N4, then if there is no loss, the step-up ratio between the primary side and the secondary side is N4ZN3. The auxiliary feeder 93 is used to supply a power supply voltage to the control circuit 120. Note that the dot symbol attached to the transformer 90 indicates the polarity of the winding.

[0020] Generally, in a switching power supply, as a power transmission system from the primary side to the secondary side of the transformer, a forward system that transmits power from the primary side to the secondary side when the switching element is turned on, and There is a flyback system that transmits power from the primary side to the secondary side when the switching element is turned off. In the present embodiment, the present invention can be applied to both of them. Adopts the flyback method.

In a flyback type switching power supply as shown in FIG. 1, the primary side winding 21 and the secondary side winding 22 of the transformer have a reverse polarity relationship, and the switching element 30 is turned on. During this period, the primary current of the transformer 20 increases. On the secondary side of the transformer 20, the secondary current does not flow because it is reverse-biased by a diode. The transformer 20 stores energy in the core 24 when the switching element 30 is on.

Next, when the switching element 30 is turned off, the magnetic field tries to maintain the current, so that the voltage polarity of the transformer 20 is reversed and a current flows on the secondary side of the transformer 20. The secondary current of the transformer 20 is charged to the capacitor 52 through the diode 51 connected in series to the secondary side feeder 22 of the transformer, so that a DC output is generated between the output terminal 3 and the output terminal 4. Generate voltage. The first voltage conversion circuit 11 has been described above, but the same applies to the second voltage conversion circuit 12.

[0023] The first voltage conversion circuit 11 is used for a limited time in milliseconds or seconds from a no-load state to a state that consumes 2 to 3 times the rated output current. Therefore, the first output voltage is supplied to a dynamic load that fluctuates dynamically until it consumes 10 times the rated output current. On the other hand, the second voltage conversion circuit 12 supplies the second output voltage to a stable steady load in which the fluctuation range of the consumption current falls within about 50% of the rated output current. Here, the rated output current represents the magnitude of the output current at which the MOSFET used as a switching element in each voltage conversion circuit can operate stably and stably. It is determined in advance based on the input voltage and MOSFET specifications.

In the present embodiment, it is assumed that the impact power printer is a load power device of a switching power supply circuit. The first voltage conversion circuit 11 supplies power to the solenoid of the plunger that drives the print head of the impact printer. On the other hand, the second voltage conversion circuit 12 supplies power to a control circuit for controlling transmission / reception of data to / from a personal computer or the like and driving of the plunger.

Therefore, suitable materials are selected for the transformer core 24 in the first voltage conversion circuit 11 and the transformer core 94 in the second voltage conversion circuit 12 according to the load. As the transformer core 24 in the first voltage conversion circuit 11 that supplies power to the dynamic load, an amorphous metal magnetic material having a high saturation magnetic flux density is used. As a specific material, for example, an amorphous alloy Fe—Co (60 to 80 wt%) containing iron (Fe) and conoleto (Co) can be used. As the core type, a Balta type molded by sintering a powder material is suitable. A laminate type in which ribbon-like cores are laminated can also be used.

On the other hand, as the transformer core 94 in the second voltage conversion circuit 12 that supplies power to the steady load, a ferrite magnetic material is used. Ferrite magnetic materials have been characterized by their low loss and high efficiency, and so far have been commonly used as core materials for transformers.

[0027] Amorphous metal magnetic materials have the characteristics that the hysteresis characteristics and the eddy current loss are small and the high frequency characteristics are good because the change in the magnetic characteristics due to the temperature at which the saturation magnetic flux density is higher than that of ferrite. In addition, by using an amorphous metal magnetic body as the core of the transformer, the heat generation amount of the core, which is hard to be saturated magnetically, is small, so that it is possible to supply more than twice as much power as when ferrite is used. Because there is no need to form a gap in the gap, leakage of magnetic flux with gap force is no longer a problem.

[0028] However, when an amorphous metal magnetic material is used, the inductance per power (also referred to as "AL value") is smaller than when ferrite is used. Even if it increases, the inductance of a winding will become small and the electric current which flows into a winding will increase. In addition, since the magnetic material of amorphous metal is difficult to saturate, the peak current flowing in the shoreline can be increased. However, when the peak current increases, there is a problem that the switching element is easily destroyed. Therefore, in this embodiment, the switching element is protected by devising a circuit.

FIG. 2 is a diagram showing in detail the configuration of the control circuit and the like in the first voltage conversion circuit shown in FIG. In the present embodiment, an N-channel MOSFET 31 is used as the switching element 30 shown in FIG. The MOSFET 31 has a drain connected to the primary winding 21 of the transformer, a source connected to the rectifying / smoothing circuit 10, and a gate to which a drive signal is applied from the gate driver 79. [0030] The transformer primary side wire 21 and the drain / source path of the MOSFET 31 are connected in series, and the voltage obtained by rectifying and smoothing the AC power supply voltage in the rectifying and smoothing circuit 10 is the series voltage. Supplied to the circuit. The MOSFET 31 allows a current to flow through the primary side winding 21 of the transformer in accordance with a pulsed drive signal applied to the gate.

[0031] Normally, in order to detect the current flowing through the primary side wire 21 of the transformer, a resistor is inserted in series with the primary side wire 21 and the voltage across this resistor is measured. In that case, power loss occurs due to resistance. Therefore, in the present embodiment, the primary side current detection circuit 40 detects the primary side current based on the drain-source voltage of the MOSFET 31.

The primary-side current detection circuit 40 includes a PNP bipolar transistor 41 and a current source 42 that supplies a current to the emitter of the transistor 41. The transistor 41 has a base to which the potential of the drain force of the MOSFET 31 is applied, and outputs a detection voltage from the emitter by performing an emitter follower operation. In FIG. 2, the base of the transistor 41 may be indirectly connected to the drain of the MOS FET 31 via a force resistor or transistor directly connected to the drain of the MOSFET 31.

When the MOSFET 31 is turned on, the on-resistance between the drain and the source of the MOSFET 31 becomes a value determined by the characteristics of the element and the gate and the source-to-source voltage. However, since the primary winding 21 of the transformer, which is the load of MOSFE T31, contains an inductance component! /, The drain current gradually increases from zero. The product of this drain current and the on-resistance of MOSFET 31 is the drain-source voltage of MOSFET 31. Therefore, if the voltage between the drain and source of MOSFE T31 is measured, a detection voltage proportional to the magnitude of the current flowing through the primary side winding 21 of the transformer can be obtained.

The control circuit 70 includes a detection voltage generation circuit 71, a comparator 72, a clock signal generation circuit 73, an AND circuit 74, a comparator 75, a blanking pulse generation circuit 76, an AND circuit 77, It includes a noise width setting circuit 78 and a gate driver 79.

The detection result of the secondary side voltage detection circuit 60 shown in FIG. 1 is transmitted as an optical signal to the detection voltage generation circuit 71 by using an optical signal transmission element such as a photopower bra. This allows secondary voltage detection while maintaining isolation between the primary and secondary sides of transformer 20. The detection result of the circuit 60 can be transmitted to the detection voltage generation circuit 71 on the primary side. The detection voltage generation circuit 71 generates a detection voltage based on the detection result of the secondary side voltage detection circuit 60.

FIG. 3 is a circuit diagram showing a configuration example of a secondary side voltage detection circuit and a detection voltage generation circuit in the first voltage conversion circuit shown in FIG. In this example, the secondary side voltage detection circuit 60 includes a resistor 61, a light emitting diode 62, and a shunt regulator 63 connected between both terminals of the capacitor 52, and a voltage generated between both terminals of the capacitor 52. And resistors 64 and 65 for dividing the voltage. The voltage divided by the resistors 64 and 65 is applied to the control terminal of the shunt regulator 63. Thereby, when the secondary side voltage exceeds a predetermined voltage, a current flows through the light emitting diode 62, and the light emitting diode 62 emits light with an intensity corresponding to the magnitude of the current to generate an optical signal.

The detection voltage generation circuit 71 is smoothed by the diode 81 that rectifies the voltage generated in the auxiliary auxiliary wire 23 of the transformer, the capacitor 82 that smoothes the voltage rectified by the diode 81, and the capacitor 82. It has a phototransistor 83 to which a voltage is applied to the collector, resistors 84 to 86, an operational amplifier 87, and a diode 88 for limiter.

[0038] The phototransistor 83 receives the optical signal generated by the light emitting diode 62, and outputs a current corresponding to the intensity from the emitter. The current output from the emitter of the phototransistor 83 is input to the inverting input terminal of the operational amplifier 87 via the resistor 84.

[0039] In addition, resistors 85 and 86 are connected to the inverting input terminal of the operational amplifier 87 to form a negative feedback loop, and the control voltage V is applied to the non-inverting input terminal.

C

Thus, a detection voltage corresponding to the output current of the phototransistor 83 is generated. When the load on the secondary side is light, the detection voltage decreases because the voltage on the secondary side increases, and when the load on the secondary side is heavy, the detection voltage increases because the voltage on the secondary side decreases. To do.

Furthermore, a limiter diode 88 is connected between the output terminal and the inverting input terminal of the operational amplifier 87. The limiter diode 88 sets an upper limit on the detection voltage output from the operational amplifier 87. In FIG. 3, a force indicating one diode A plurality of diodes may be connected in series. The upper limit of the detection voltage can be changed depending on the number of diodes. [0041] Referring to FIG. 2 again, the comparator 72 has a Schmitt trigger characteristic, and compares the detection voltage generated by the detection voltage generation circuit 71 with the reference voltage V to determine the state of the load on the secondary side.

REF

And a load state signal indicating whether or not the light load state is present is output as a determination result. The clock signal generation circuit 73 generates a clock signal. The AND circuit 74 obtains a logical product of the load state signal and the clock signal.

[0042] In the light load state, since the detection voltage decreases, the load state signal becomes low level, and the output signal of the AND circuit 74 is also fixed at low level, so the pulse width setting circuit 78 does not generate a pulse. . On the other hand, when the output voltage on the secondary side decreases, the detection voltage increases, so that the load state signal becomes high level, and the clock signal generated by the clock signal generation circuit 73 is supplied to the AND circuit 74 force pulse width setting circuit 78. Therefore, the pulse width setting circuit 78 generates a plurality of pulses in synchronization with the clock signal. In this way, when the control circuit 70 determines that the secondary side is in a light load state, the control circuit 70 can cause the switching element 30 to operate intermittently by reducing the number of pulses in the drive signal.

The comparator 75 compares the detection voltage output from the primary side current detection circuit 40 and the detection voltage generated by the detection voltage generation circuit 71 based on the detection result of the secondary side output voltage. In comparison, a comparison signal representing the comparison result is generated. In addition, the blanking pulse generation circuit 76 is a high level only in a predetermined period synchronized with the clock signal in order to prevent a malfunction in which the MOSFET 31 is turned off while the primary current of the transformer is small. Generate ranking noise signal. The comparison signal generated by the comparator 75 is output from the AND circuit 77 during the period when the blanking pulse signal is at a high level.

[0044] The pulse width setting circuit 78 is configured by, for example, an RS flip-flop having a set terminal S, a reset terminal R, and an output terminal Q. The pulse width setting circuit 78 sets the output signal in synchronization with the clock signal generated by the clock signal generation circuit 73 when the load state signal is at the high level, and at the blanking pulse signal level at the high level. At some point, the pulse width in the drive signal is set by resetting the output signal in synchronization with the comparison signal generated by the comparator 75. The gate driver 79 drives the gate of the MOSFET 31 based on the drive signal output from the pulse width setting circuit 78. Next, the operation of the control circuit shown in FIG. 2 will be described with reference to FIGS. 4 and 5. FIG. 4 is a waveform diagram for explaining the operation of the control circuit in the first voltage conversion circuit shown in FIG. 2 in an overload state.

(A) of FIG. 4 shows the clock signal V generated by the clock signal generation circuit 73.

CK

Yes. The period of the pulse included in the clock signal is T, and the pulse width (period of noise level) is T. Here, the duty (T ZT) of the clock signal is 50%

H H

In this embodiment, since an amorphous metal magnetic material is used for the core 24 of the transformer, the impedance of the primary side wire is reduced when the number of power is the same as compared with the case of using ferrite. The dance is getting smaller. Therefore, as shown in Fig. 4 (b), compared to the case where ferrite is used, the current flowing through the primary side wire 21 of the transformer, that is, the drain current I of the MOSFET 31, becomes larger. MOSFET31 may be destroyed by heat generation

D

. On the other hand, in order to increase the impedance of the wire, the number of wires must be increased, and the transformer becomes large. Therefore, in this embodiment, this problem is solved by the following method.

[0047] If the primary current of the transformer increases, the speed at which energy is stored in the core 24 increases. Furthermore, if the current consumption increases momentarily in a dynamic load, the drain current I

This can be dealt with by increasing the period of flowing D. At this time, if an upper limit is set for the period during which the drain current I flows, the temperature of the MOSFET 31 varies.

D

Since the power consumption returns to the original level before it always rises, there is no possibility that the MOSFET 31 is destroyed. In order to perform such an operation, the control circuit 70 sets the upper limit of the pulse width in the drive signal so that the MOSFET 31 is turned off at the point A shown in FIG. 4B.

[0048] The operation of the control circuit 70 will be described in detail. The output signal of the pulse width setting circuit 78 is synchronized with the rising edge of the clock signal V generated by the clock signal generation circuit 73.

CK

Is set and the gate voltage V ((e) in Fig. 4) goes high. This makes the comparator 75

G

The output comparison signal V ((d) in Figure 4) shifts from high level to low level.

COMP

The [0049] Here, the comparison signal V output from the comparator 75 is supplied from the primary-side current detection circuit 40.

COMP

This is obtained by comparing the output first detection voltage with the second detection voltage generated by the detection voltage generation circuit 71 based on the detection result of the secondary side voltage detection circuit 60. In an overload condition, the drain current I of the MOSFET 31 increases and the first detection current

D

As the voltage increases, the output voltage on the secondary side of the transformer decreases and the second detection voltage also increases. However, the detection voltage generation circuit 71 has an upper limit for the second detection voltage. Therefore, when the second detection voltage reaches the upper limit, if the first detection voltage exceeds the upper limit, the comparison signal V output from the comparator 75 becomes a high level.

COMP

The primary-side current detection circuit 40 detects the detection voltage based on the drain voltage V of the MOSFET 31.

D

The above operation will be described based on the drain voltage V ((c) in FIG. 4). Get

D

The drain current V begins to flow when the gate voltage V becomes high.

G D D

The comparison signal V force S high level force output from the comparator 75

COMP

Move to one level. After that, the drain current I gradually increases and the drain voltage V also increases.

D D

Rises second. Drain voltage V force Secondary side voltage detection at point B shown in Fig. 4 (c)

D

The threshold voltage V determined based on the detection result of the circuit 60 (in this case, the second detection voltage)

TH

The comparison signal V force S high level output from the comparator 75 is exceeded.

COMP

Become a bell. As a result, the output signal of the pulse width setting circuit 78 is reset, and the MOSFET 31 gate voltage V power

G becomes one level, and the drain current I stops at the point A shown in Fig. 4 (b).

D

In this way, the control circuit 70 turns on the MOSFET 31 at a constant cycle and turns off the MOSFET 31 in synchronization with the rising edge of the comparison signal V. Figure 4 (e

COMP

) !, and the period during which the MOSFET 31 is turned on is represented by T, and the MOSFET 31 is turned off.

ON

The period is represented by T.

OFF

FIG. 5 is a waveform diagram for explaining the operation of the control circuit shown in FIG. 2 in a normal state. Figure 5 (a) shows the clock signal V generated by the clock signal generation circuit 73.

CK

is doing. 5 (b) shows the drain current I of the MOSFET 31, and FIG.

D

) Indicates the drain voltage V of the MOSFET 31.

D

[0053] In the normal state, the load on the secondary side is light compared to the overload state. The output voltage increases, and the second detection voltage generated by the detection voltage generation circuit 71 based on the detection result of the secondary side voltage detection circuit 60 is low. Therefore, as shown in (c) of FIG. 5, the threshold voltage V determined based on the detection result of the secondary side voltage detection circuit 60 is also

TH

It is getting lower. As a result, after drain current I begins to flow, drain voltage V force

D D s threshold The period until the voltage V is exceeded is also shortened. At point D shown in Fig. 5 (c), the drain current

TH

When the voltage V force S threshold voltage V is exceeded, the comparison signal V (Fig. 5

D TH COMP

(d)) goes high. As a result, the output signal of the pulse width setting circuit 78 is reset, the gate voltage V of the MOSFET 31 ((e) in FIG. 5) becomes a low level, and C shown in FIG. 5 (b).

G

The drain current I stops at the point. Thus, in normal conditions, MOSFE

D

The period during which the drain current I flows through T31 is reduced.

D

Further, when the light load state is entered, the comparator 72 of the control circuit 70 determines that the secondary side is in the light load state based on the detection voltage generated by the detection voltage generation circuit 71. The comparison signal is set to a low level. As a result, the output signal of the AND circuit 74 also becomes low level, the clock signal is not supplied to the pulse width setting circuit 78, and the number of pulses in the drive signal decreases.

In the present embodiment, as shown in FIG. 2, the AND circuit 77 obtains the logical product of the comparison signal output from the comparator 75 and the blanking pulse signal generated by the blanking pulse generation circuit 76. The power of the primary side current detection circuit 40 may be turned on and off by the blanking pulse signal generated by the force blanking pulse generation circuit 76. In that case, the AND circuit 77 can be omitted.

FIG. 6 is a diagram showing a configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG. In the second voltage conversion circuit 12, as in the first voltage conversion circuit 11, an N-channel MOSFET 101 is used as the switching element 100. MOSFET 101 has a drain connected to primary winding 91 of the transformer, a source connected to rectifying and smoothing circuit 10, and a gate to which a drive signal is applied from gate driver 79.

[0057] The transformer primary 91 and the drain / source path of the MOSFET 101 are connected in series, and the voltage obtained by rectifying and smoothing the AC power supply voltage in the rectifying and smoothing circuit 10 is connected to the series. Supplied to the circuit. MOSFET 101 has a voltage applied to the gate. A current is passed through the transformer primary 91 according to the driving signal in the form of a pulse.

The control circuit 120 includes a clock signal generation circuit 73 that generates a clock signal, a detection voltage generation circuit 121 that generates a detection voltage based on the detection result of the secondary side voltage detection circuit 115 shown in FIG. A comparator 75 that generates a comparison signal by comparing the detection voltage output from the secondary current detection circuit 110 and the detection voltage output from the detection voltage generation circuit 121, and a blanking pulse that generates a blanking pulse. A generation circuit 76, an AND circuit 77 that obtains a logical product of the comparison signal and the blanking pulse, a pulse width setting circuit 78 that sets a pulse width in the drive signal based on the output signal of the AND circuit 77, and a pulse width A gate driver 79 that drives the gate of the MOSFET 101 based on the drive signal output from the setting circuit 78 is included.

The configuration of secondary side voltage detection circuit 115 shown in FIG. 1 is the same as the configuration of secondary side voltage detection circuit 60 shown in FIG. The detection result of the secondary side voltage detection circuit 115 is transmitted to the detection voltage generation circuit 121 as an optical signal by using an optical signal transmission element such as a photopower bra. As a result, the detection result of the secondary side voltage detection circuit 115 can be transmitted to the primary side detection voltage generation circuit 121 while maintaining isolation between the primary side and the secondary side of the transformer 90. The detection voltage generation circuit 121 generates a detection voltage based on the detection result of the secondary side voltage detection circuit 115.

The configuration of the detection voltage generation circuit 121 shown in FIG. 6 is the same as the configuration of the detection voltage generation circuit 71 shown in FIG. 3 except for the diode 88 for limiter. Since the second voltage conversion circuit 12 supplies power to a stable steady load, a ferrite magnetic material is used for the core 94 of the transformer. In this case, since there is no possibility of an overcurrent flowing through the primary winding 91 of the transformer, the limiter diode 88 for controlling the drain current is omitted.

As a modification of the present embodiment, in the first voltage conversion circuit 11, a predetermined voltage is applied to the inverting input terminal of the comparator 75 instead of the detection voltage generated by the detection voltage generation circuit 71. Thus, the drive signal may be generated based on the detection result of the primary side current detection circuit 40. Even in this case, the output signal of the pulse width setting circuit 78 is reset when the detection voltage output from the primary side current detection circuit 40 exceeds a predetermined voltage. Thus, the upper limit of the pulse width in the drive signal can be set. On the other hand, the drive signal may be generated based on the detection result of the secondary side voltage detection circuit 60. The same applies to the second voltage conversion circuit 12.

[0062] According to the present embodiment, the first voltage conversion circuit 11 and the second voltage conversion circuit 12 use separate transformers suitable for respective loads, and the primary circuit is independent. Therefore, it is possible to improve the cross regulation with respect to the dynamic load which is a problem in the power supply circuit having outputs of a plurality of systems.

[0063] Next, a second embodiment of the present invention will be described.

FIG. 7 is a diagram showing a configuration of a switching power supply circuit according to the second embodiment of the present invention. In the switching power supply circuit according to the second embodiment, each of the first and second voltage conversion circuits 11 and 12 uses a step-up type chopper circuit including a choke coil instead of a transformer.

[0064] One end of the first voltage conversion circuit 11 is connected to the rectifying and smoothing circuit 10, and the choke coil 130 that stores magnetic energy generated by the current flowing in the winding in the core and the other end of the choke coil 130 are connected. The switching element 30 is connected and flows current through the choke coil 130 in accordance with the pulsed drive signal, and the switching current detection circuit 140 detects current flowing through the switching element 30. Here, when the primary side winding of the transformer is used as the choke coil 130, the secondary side winding of the transformer can be used for generating an internal power source.

[0065] Further, the first voltage conversion circuit 11 includes a diode 51 for half-wave rectifying the voltage generated at the other end of the choke coil 130, and an output terminal by generating an output voltage by smoothing the rectified voltage. Driven based on the capacitor 52 supplied to 3 and 4, the output voltage detection circuit 150 that detects the output voltage at the output terminals 3 and 4, the detection result of the switching current detection circuit 140, and the detection result of the output voltage detection circuit 150 And a control circuit 160 for generating a signal.

[0066] Choke coil 130 stores energy in the core when switching element 30 is on. Next, when the switching element 30 is turned off, the magnetic field tries to maintain the current, so that the current of the choke coil 130 flows to the capacitor 52 via the diode 51, and the capacitor When the sensor 52 is charged, a DC output voltage is generated between the output terminals 3 and 4.

[0067] The second voltage conversion circuit 12 has one end connected to the rectifying and smoothing circuit 10, and stores the magnetic energy generated by the current flowing in the winding in the core, and the other end of the choke coil 170. Switching element 100 that is connected and flows current through choke coil 170 according to a pulsed drive signal, switching current detection circuit 180 that detects the current flowing through switching element 100, and the voltage generated at the other end of choke coil 170 Diode 53 that performs half-wave rectification, capacitor 54 that generates an output voltage by smoothing the rectified voltage and supplies it to output terminals 5 and 6, and an output that detects the output voltage at output terminals 5 and 6 Based on the detection signal generated by the voltage detection circuit 190 and the switching current detection circuit 180 and the detection signal generated by the output voltage detection circuit 190 And a control circuit 200 for generating a signal, Ru.

In the present embodiment, an amorphous metal magnetic material having a high saturation magnetic flux density is used as the core of the choke coil 130 in the first voltage conversion circuit 11 that supplies power to the dynamic load. As a specific material, for example, an amorphous alloy Fe—Co (60 to 80 wt%) containing iron (Fe) and cobalt (Co) can be used. As the core type, a Balta type formed by sintering a powder material or a laminate type in which ribbon-like cores are laminated can be used.

On the other hand, a ferrite magnetic body is used as the core of the choke coil 170 in the second voltage conversion circuit 12 that supplies power to the steady load. Ferrite magnetic materials have been characterized by their low loss and high efficiency, and so far have been commonly used as core materials for transformers.

FIG. 8 is a diagram showing in detail the configuration of the control circuit and the like in the first voltage conversion circuit shown in FIG. In the present embodiment, an N-channel MOSFET 31 is used as the switching element 30 shown in FIG. MOSFET 31 has a drain connected to the other end of choke coil 130, a source connected to rectifying and smoothing circuit 10 via switching current detection circuit 140, and a gate to which a drive signal is applied from gate driver 169. ing.

[0071] Drain of choke coil 130 and MOSFET 31 'source path and switching current detection circuit The voltage obtained by rectifying and smoothing the AC power supply voltage in the rectifying and smoothing circuit 10 is supplied to these series circuits. The MOSFET 31 causes a current to flow through the choke coil 130 in accordance with a pulsed drive signal applied to the gate.

The control circuit 160 includes a clock signal generation circuit 163, a comparator 165, a blanking pulse generation circuit 166, an AND circuit 167, a pulse width setting circuit 168, and a gate driver 169.

The clock signal generation circuit 163 generates a clock signal. Also, the detection voltage output from the switching current detection circuit 140 is input to the non-inverting input terminal of the comparator 165, and the detection voltage output from the output voltage detection circuit 150 shown in FIG. Input to the power terminal. In the output voltage detection circuit 150, when the load of the switching power supply circuit is light, the detection voltage decreases as the output voltage of the switching power supply circuit increases, and when the load of the switching power supply circuit is heavy, the switching power supply The detection voltage increases as the output voltage of the circuit decreases. Furthermore, an upper limit is set for the detection voltage output from the output voltage detection circuit 150 by the limiter circuit.

The comparator 165 compares the detection voltage output from the switching current detection circuit 140 with the detection voltage output from the output voltage detection circuit 150, and outputs a comparison signal representing the comparison result. The blanking pulse generation circuit 166 is a blanking pulse signal that becomes a high level only during a predetermined period synchronized with the clock signal in order to prevent a malfunction in which the MOSFET 31 is turned off while the current of the choke coil is small. Is generated. The A ND circuit 167 obtains a logical product of the comparison signal output from the comparator 165 and the blanking pulse signal output from the blanking pulse generation circuit 166. During the period when the blanking pulse signal is at the high level, the comparison signal is generated from the comparison signal output AND circuit 167 generated by the comparator 165.

[0075] The pulse width setting circuit 168 is configured by, for example, an RS flip-flop having a set terminal S, a reset terminal R, and an output terminal Q. The pulse width setting circuit 168 sets the output signal in synchronization with the clock signal generated by the clock signal generation circuit 163. In addition, the pulse width in the drive signal is set by resetting the output signal in synchronization with the comparison signal generated by the comparator 165 when the blanking pulse signal is at a high level. The gate driver 169 drives the gate of the MOSFET 31 based on the drive signal output from the pulse width setting circuit 168.

Since the operation of the control circuit shown in FIG. 8 is substantially the same as that shown in FIGS. 4 and 5, the operation of the control circuit 160 will be described in detail with reference to FIG.

Rising edge of clock signal V generated by clock signal generation circuit 163

CK

The output signal of the pulse width setting circuit 168 is set in synchronization with the gate voltage V ((e

G

)) Becomes high level.

The comparison signal output from the comparator 165 compares the first detection voltage output from the switching current detection circuit 140 with the second detection voltage output from the output voltage detection circuit 150. It is obtained. In overload condition, MOSFET 31 drain current I

D

Increases, the first detection voltage increases, the output voltage decreases, and the second detection voltage also increases. However, the output voltage detection circuit 150 has an upper limit for the second detection voltage. Therefore, when the second detection voltage reaches the upper limit and the first detection voltage exceeds the upper limit, the comparison signal output from the comparator 165 becomes high level. As a result, the output signal of the pulse width setting circuit 168 is reset, and the gate voltage V of the MOSFET 31 becomes the input.

G

The drain current I stops at the point A shown in Fig. 4 (b).

D

In this manner, the control circuit 160 turns on the MOSFET 31 at a constant period and turns off the MOSFET 31 in synchronization with the rising edge of the comparison signal. In Fig. 4 (e), the period during which V and MOSFET 31 are turned on is represented by T and the period during which MOSFET 31 is turned off.

ON

Is represented by T.

OFF

FIG. 9 is a diagram showing in detail the configuration of the control circuit and the like in the second voltage conversion circuit shown in FIG. In the second voltage conversion circuit 12, as in the first voltage conversion circuit 11, an N-channel MOSFET 101 is used as the switching element 100. MOSFET 101 has a drain connected to the winding of choke coil 170, a source connected to rectifying and smoothing circuit 10, and a gate to which a drive signal is applied from gate driver 169.

[0080] The winding of choke coil 170 and the drain 'source path of MOSFET 101 are connected in series. Then, the voltage obtained by rectifying and smoothing the AC power supply voltage in the rectifying and smoothing circuit 10 is supplied to these series circuits. The MOSFET 101 causes a current to flow through the winding of the choke coil 170 in accordance with a pulsed drive signal applied to the gate.

The control circuit 200 includes a clock signal generation circuit 163 that generates a clock signal, a detection voltage output from the switching current detection circuit 180, and a detection voltage output from the output voltage detection circuit 190 shown in FIG. Comparator 165 that generates a comparison signal by comparison, blanking pulse generation circuit 166 that generates a blanking pulse, AND circuit 167 that obtains a logical product of the comparison signal and the blanking pulse, and an output of AND circuit 167 A pulse width setting circuit 168 for setting the pulse width in the drive signal based on the signal and a gate driver 169 for driving the gate of the MOSFET 101 based on the drive signal output from the pulse width setting circuit 168. It is out.

The configuration of the output voltage detection circuit 190 shown in FIG. 7 is the same as that of the output voltage detection circuit 150 except for the limiter circuit. Since the second voltage conversion circuit 12 is for supplying electric power to a stable steady load, a ferrite magnetic material is used for the core of the choke coil 170. In that case, the limiter circuit is omitted because there is no possibility of overcurrent flowing through the primary primary wire 91 of the transformer.

As a modification of the present embodiment, in the first voltage conversion circuit 11, a predetermined voltage is applied to the inverting input terminal of the comparator 165 instead of the detection voltage output from the output voltage detection circuit 150. Thus, the drive signal may be generated based on the detection result of the switching current detection circuit 140. Even in that case, if the detection voltage output from the switching current detection circuit 140 exceeds the predetermined voltage, the output signal of the pulse width setting circuit 168 is reset, so the upper limit of the pulse width in the drive signal must be set. Can do. On the other hand, the drive signal may be generated based on the detection result of the output voltage detection circuit 190. The same applies to the second voltage conversion circuit 12.

[0084] Next, a third embodiment of the present invention will be described.

FIG. 10 is a diagram showing a configuration of a switching power supply circuit according to the third embodiment of the present invention. This switching power supply circuit includes a transformer core, a primary side wire, and a primary side between the first voltage conversion circuit 11 and the second voltage conversion circuit 12 in the first embodiment shown in FIG. The side circuit is used in common. According to this, it is possible to reduce the cost of the switching power supply circuit having a plurality of outputs.

In the switching power supply circuit in FIG. 10, the transformer 20 includes a magnetic core 24, a primary side wire 21, a secondary side wire 22, a secondary side wire 25, which are wound around the core 24, And an auxiliary feeder 23. Also in this embodiment, an amorphous metal magnetic material is used as the core 24 of the transformer. If the number of primary side wires 21 is N1, the number of secondary side wires 22 is N 2 and the number of secondary side wires 25 is N5, 2 The induced voltage generated in the secondary winding 22 is determined by the ratio of the power N1 and the power N2, and the induced voltage generated in the secondary winding 25 is determined by the ratio of the power N1 and the power N5.

In this embodiment, the voltage force diode 51 and the capacitor 52 obtained from the secondary side wire 22 of the transformer 20 are rectified and smoothed, respectively, and the smoothed voltage is output to the output terminal 3 as the first output voltage. And 4 supplied. On the other hand, the secondary side winding 25 of the transformer 20 is also rectified and smoothed by the voltage force diode 53 and the capacitor 54, respectively, and the smoothed voltage is stabilized by the constant voltage output circuit 210 to obtain the second output voltage. To the output terminals 5 and 6. The configurations of the primary side current detection circuit 40, the secondary side voltage detection circuit 60, and the control circuit 70 are the same as those in the first embodiment.

Also in the present embodiment, the first output voltage is supplied to a dynamic load such as a plunger that drives the print head in the impact printer. Therefore, the effect obtained by using an amorphous magnetic material for the transformer core 24 is the same as that in the first embodiment. The second output voltage is supplied to a steady load such as a control circuit for controlling transmission / reception of data with a personal computer or the like and driving of the plunger.

[0088] It is desirable that the second output voltage is stable at a low voltage that does not need to be a high voltage like the first output voltage. Generally, 3.3V to 5V is often used as the power supply voltage for the control circuit, so a steady voltage of 3.3V to 5V is desired as the second output voltage. However, the induced voltage generated in the secondary winding 25 varies depending on the state of the dynamic load to which the first output voltage is supplied. Assuming such a state, this embodiment In this case, a constant voltage output circuit 210 is provided after the diode 53 and the capacitor 54.

FIG. 11 is a diagram showing a first configuration example of the constant voltage output circuit shown in FIG. The constant voltage output circuit 210 includes a step-down chopper circuit 220, a chopper control circuit 230 for controlling the step-down chopper circuit 220, and a voltage detection signal detected by detecting the voltage across the capacitor 54. A voltage monitoring circuit 240 that outputs to The input / output of the step-down chitoclover circuit 220 is not isolated, but is isolated from the primary circuit and other secondary circuits by the transformer 20 shown in FIG.

The step-down chopper circuit 220 includes an N-channel MOSFET 221 as a switching element, a diode 222, a choke coil 223, and a capacitor 224. As the core of the choke coil 223, a magnetic material of farite is used. The drain of the MOSFET 221 is connected to one end (high potential side) of the capacitor 54, the source is connected to the force sword of the diode 222 and one end of the choke coil 223, and the gate is connected from the chopper control circuit 230. A pulsed drive signal is supplied. The other end of the choke coil 223 is connected to one end (high potential side) of the capacitor 224. The anode of the diode 222 is connected to the other end (low potential side) of the capacitor 54 and the other end (low potential side) of the capacitor 224!

[0091] Based on the voltage detection signal output from voltage monitoring circuit 240, chitsuba control circuit 230 generates a drive signal for causing MOSFET 221 to perform a switching operation. When the MOS FET 221 performs a switching operation, an alternating current flows through the choke coil 223, and the alternating voltage generated across the choke coil 223 is rectified by the diode 222. As a result, the voltage across the capacitor 54 is stepped down and supplied to the output terminals 5 and 6 as the second output voltage.

Here, when the voltage between both ends of the capacitor 54 becomes higher than a predetermined value, the chopper control circuit 230 decreases the duty of the drive signal so that the ON period of the MOSFET 221 is decreased from the predetermined period, When the voltage across the capacitor 54 becomes lower than a predetermined value, the duty of the drive signal is increased so that the ON period of the MOSFET 221 is longer than the predetermined period. FIG. 12 is a diagram showing a second configuration example of the constant voltage output circuit in FIG. In this example, a boosting chiba circuit is used instead of the step-down chiba circuit. The constant voltage output circuit 210 detects the voltage across the capacitor 54 by detecting the voltage across the step-up chopper circuit 250, the chopper control circuit 260 for controlling the step-up chopper circuit 250, and the chopper control circuit 260. Output voltage monitoring circuit 240.

The step-up chopper circuit 250 includes a choke coil 251, an N-channel MOSFET 252 as a switching element, a diode 253, and a capacitor 254. As the core of the choke coil 251, a ferrite magnetic material is used. One end of the choke coil 251 is connected to one end (high potential side) of the capacitor 54, and the other end of the choke coil 251 is connected to the drain of the MOSFET 252 and the anode of the diode 253. The force sword of the diode 253 is connected to one end (high potential side) of the capacitor 254. The source of the MOSFE T252 is connected to the other end (low potential side) of the capacitor 54 and the other end (low potential side) of the capacitor 254. A pulsed drive signal is sent from the chopper control circuit 260 to the gate of the MOSFET 252. Supplied.

Based on the voltage detection signal output from voltage monitoring circuit 240, chitsuba control circuit 260 generates a drive signal for causing MOSFET 252 to perform a switching operation. When the MOS FET 252 performs a switching operation, an alternating current flows through the choke coil 251, and the alternating voltage generated across the choke coil 251 is rectified by the diode 253. As a result, the voltage across the capacitor 54 is boosted and supplied to the output terminal 5 as the second output voltage.

Here, when the voltage across the capacitor 54 becomes higher than a predetermined value, the chopper control circuit 260 reduces the duty of the drive signal so that the ON period of the MOSFET 252 is reduced from the predetermined period, When the voltage across the capacitor 54 becomes lower than a predetermined value, the duty of the drive signal is increased so that the ON period of the MOSFET 221 is longer than the predetermined period.

[0097] Next, a fourth embodiment of the present invention will be described.

FIG. 13 is a diagram showing a configuration of a switching power supply circuit according to the fourth embodiment of the present invention. In this switching power supply circuit, the adjustment in the first embodiment shown in FIG. Instead of the flow smoothing circuit 10, a PFC (power factor controller) circuit 15 is used. The PFC circuit converts the voltage obtained by rectifying the AC voltage into an AC voltage by switching, and when converting the obtained AC voltage into a DC voltage again, the waveform and phase of the voltage and current are changed. In addition, this circuit improves the power factor. In addition, an output system (output terminals 7 and 8) for supplying a third output signal to the load through a constant voltage output circuit 210 similar to that shown in FIG. 10 is connected to the second voltage conversion circuit 12. Yes.

FIG. 14 is a diagram showing a configuration example of the PFC circuit shown in FIG. The PFC circuit 15 includes a rectifier circuit 18 connected to the input terminals 1 and 2 of the AC voltage, a choke coil 270 connected to the rectifier circuit 18 and storing magnetic energy generated by current flowing in the winding in the core. The switching element 30 is connected to the other end of the choke coil 270 and flows a current through the choke coil 270 in accordance with a pulsed drive signal, and a switching current detection circuit 280 detects the current flowing through the switching element 30. Here, when the transformer primary side winding is used as the choke coil 270, the transformer secondary side winding can be used for generating the internal power supply.

Furthermore, the PFC circuit 15 includes a diode 51 that half-wave rectifies the voltage generated at the other end of the choke coil 270, and generates a PFC output voltage by smoothing the rectified voltage to generate a PFC output terminal 16 and 17 includes a capacitor 52 supplied to 17, an output voltage detection circuit 290 that detects the PFC output voltage at the PFC output terminals 16 and 17, and a control circuit 300 that sets the pulse width of the drive signal.

[0100] The rectifier circuit 18 is configured by, for example, a diode bridge, and full-wave rectifies the AC voltage applied between the input terminal 1 and the input terminal 2. The choke coil 270 stores energy in the core when the switching element is on. Next, when the switching element is turned off, the magnetic field tries to maintain the current, so that the current in the choke coil 270 flows to the capacitor 52 through the diode 51, and the capacitor 52 is charged. DC output voltage is generated between

[0101] The core of the choke coil 270 in the PFC circuit 15 is made of an amorphous metal magnetic material, like the transformer core 24 in the first voltage conversion circuit 11 at the subsequent stage. Improves resistance to overcurrent due to dynamic load. Further, a switching current detection circuit 280 and an output voltage detection circuit 290 are provided in order not to destroy the switching element 30 due to overcurrent. The configuration and operation of the output voltage detection circuit 290 are the same as those of the secondary side voltage detection circuit 60 shown in FIG.

Control circuit 300 performs pulse width control for overcurrent based on the detection signal generated by switching current detection circuit 280. Further, the detection signal force generated by the output voltage detection circuit 290 is fed back to the control circuit 300. The configuration and operation of the control circuit 300 are the same as those of the control circuit 160 shown in FIG.

Referring again to FIG. 13, the first voltage conversion circuit 11 supplies power to a dynamic load such as a plunger that drives a head in the printer. Therefore, the effect obtained by using an amorphous magnetic material for the core 24 of the transformer is the same as that in the first embodiment. The second voltage conversion circuit 12 supplies power to a steady load such as a control circuit for controlling transmission / reception of data with a personal computer or the like and driving of the plunger. Furthermore, the constant voltage output circuit 210 supplies power to a small-capacity dynamic load.

[0104] Next, a fifth embodiment of the present invention will be described.

FIG. 15 is a diagram showing a configuration of a switching power supply circuit according to the fifth embodiment of the present invention. In this switching power supply circuit, by adding an inverter circuit to the first embodiment shown in FIG. 1, the first voltage conversion circuit 11 outputs an AC voltage.

In the present embodiment, an NPN bipolar transistor 331 is used as a switching element. Also, the voltage force rectified and smoothed by the voltage force diode 51 and the capacitor 52 obtained from the secondary side winding 22 of the transformer 20, respectively, is constituted by the NPN bipolar transistors 371 to 374, the coil 375 and the capacitor 376. Input to the inverter circuit. The control circuit 360 is a drive signal for driving the transistors 331 and 371 to 374 based on the detection signal output from the primary side current detection circuit 40 and the detection signal output from the secondary side voltage detection circuit 60. Is generated.

In the first voltage conversion circuit 11, the collector of the transistor 371 is connected to the force sword of the diode 51, and the emitter is connected to the output terminal 4. Also, transistor 372 The Kuta is connected to the output terminal 4, and the emitter is connected to the polarity side of the transformer where the dot of the secondary side winding 22 is attached. On the other hand, the collector of the transistor 373 is connected to the force sword of the diode 51, and the emitter is connected to one end of the coil 375. The collector of the transistor 374 is connected to one end of the coil 375, and the emitter is connected to the polarity side of the transformer where the dot of the secondary winding 22 is attached. The other end of the coil 375 is connected to the output terminal 3. A capacitor 376 is connected between the output terminals 3 and 4.

A plurality of control signals output from the control circuit 360 are supplied to the bases of the transistors 331 and 371 to 374, and perform switching control of each transistor. As a result, it is output from the secondary side winding 22 of the transformer 20 and converted into a DC voltage force AC voltage rectified by the diode 51. Further, the second voltage conversion circuit 12 may be the same as the second voltage conversion circuit 12 shown in FIG. 1 or outputs an AC voltage in the same way as the first voltage conversion circuit 11 shown in FIG. It may be what you do.

[0108] Next, a sixth embodiment of the present invention will be described.

FIG. 16 is a diagram showing a configuration of a switching power supply circuit according to the sixth embodiment of the present invention. In this switching power supply circuit, the first voltage conversion circuit 11 outputs an alternating voltage by adding an inverter circuit to the second embodiment shown in FIG.

In the present embodiment, the control circuit 380 drives the transistors 331 and 371 to 374 based on the detection signal output from the switching current detection circuit 140 and the detection signal output from the output voltage detection circuit 150. A drive signal for generating the signal is generated. A plurality of control signals output from the control circuit 360 are supplied to the bases of the transistors 331 and 371 to 374 to perform switching control of each transistor. As a result, it is output from the choke coil 130 and converted into a DC voltage force AC voltage rectified by the transistor 331. Further, the second voltage conversion circuit 12 may be the same as the second voltage conversion circuit 12 shown in FIG. 7, or, like the first voltage conversion circuit 11 shown in FIG. 16, outputs an AC voltage. It may be something that helps.

Industrial applicability

[0110] The present invention can be used in a switching power supply used in an electronic device.

Claims

The scope of the claims

[1] A first transformer having a core including an amorphous magnetic material, a primary side winding and a secondary side winding wound around the core, and an input voltage applied to one end of the primary side winding. When,

A second transformer having a core including a ferrite magnetic body, a primary winding and a secondary winding wound around the core, and the input voltage is applied to one end of the primary winding;

A first switching element connected to the other end of the primary winding of the first transformer, and causing a current to flow through the primary winding of the first transformer in accordance with a pulsed first drive signal; A second switching element connected to the other end of the primary winding of the second transformer and for passing a current through the primary winding of the second transformer in accordance with a pulsed second drive signal; A first output circuit for generating a first output voltage based on a voltage generated in the secondary side winding of the first transformer;

A second output circuit for generating a second output voltage based on a voltage generated in the secondary side winding of the second transformer;

First and second control circuits for independently generating the first and second drive signals, respectively

A switching power supply circuit comprising:

[2] The first control circuit generates the first drive signal based on the current flowing through the primary side of the first transformer or the first output voltage,

The second control circuit generates the second drive signal based on a current flowing in a primary side wire of the second transformer or the second output voltage;

The switching power supply circuit according to claim 1.

[3] A primary-side current detection circuit that detects a current flowing in a primary-side winding of the first transformer, a secondary-side voltage detection circuit that detects the first output voltage,

And the first control circuit generates the first drive signal based on the detection result of the primary-side current detection circuit and the detection result of the secondary-side voltage detection circuit, and the 2 3. The switching power supply circuit according to claim 2, wherein an upper limit of a pulse width in the first drive signal is set based on a detection result of the secondary voltage detection circuit.

[4] The first control circuit includes: A detection voltage generation circuit that generates a detection voltage with an upper limit set based on a detection result of the secondary side voltage detection circuit;

A comparator that compares a detection voltage generated by the primary-side current detection circuit with a detection voltage generated by the detection voltage generation circuit to generate a signal representing a comparison result; and a clock signal that generates a clock signal A generation circuit;

By setting the output signal in synchronization with the clock signal generated by the clock signal generation circuit and resetting the output signal in synchronization with the signal generated by the comparator, the pulse width in the first drive signal is set. The switching power supply circuit according to claim 3, further comprising: a pulse width setting circuit for setting

[5] a first choke coil having a core including an amorphous magnetic material and a winding wound around the core, and an input voltage applied to one end of the winding;

A second choke coil having a core including a ferrite magnetic body and a winding wound around the core, wherein the input voltage is applied to one end of the winding;

A first switching element connected to the other end of the winding of the first choke coil and passing a current through the winding of the first choke coil according to a pulsed first drive signal; A second switching element that is connected to the other end of the winding of the choke coil, and causes a current to flow through the winding of the second choke coil in accordance with a pulsed second drive signal; the first choke coil; A first output circuit for generating a first output voltage based on a voltage generated at a connection point with the first switching element;

A second output circuit for generating a second output voltage based on a voltage generated at a connection point between the second choke coil and the second switching element;

A switching power supply circuit comprising:

[6] The first control circuit generates the first drive signal based on the current flowing in the primary side winding of the first transformer or the first output voltage,

The second control circuit generates the second drive signal based on a current flowing in a primary side wire of the second transformer or the second output voltage; The switching power supply circuit according to claim 5.

[7] a switching current detection circuit that detects a current of the first switching element; an output voltage detection circuit that detects the first output voltage;

The first control circuit generates the first drive signal based on the detection result of the switching current detection circuit and the detection result of the output voltage detection circuit, and the output voltage detection circuit 7. The switching power supply circuit according to claim 6, wherein an upper limit of a pulse width in the first drive signal is set based on the detection result.

[8] The first control circuit includes:

A detection voltage generation circuit for generating a detection voltage with an upper limit set based on a detection result of the output voltage detection circuit;

A comparator that compares the detection voltage generated by the switching current detection circuit with the detection voltage generated by the detection voltage generation circuit to generate a signal representing a comparison result;

A clock signal generation circuit for generating a clock signal;

By setting the output signal in synchronization with the clock signal generated by the clock signal generation circuit and resetting the output signal in synchronization with the signal generated by the comparator, the pulse width in the first drive signal is set. The switching power supply circuit according to claim 7, further comprising: a pulse width setting circuit that sets

[9] A core including an amorphous magnetic material, a primary side winding wound around the core, a first secondary side winding and a second secondary side winding, and the input voltage is the primary side A transformer applied to one end of the winding;

A switching element connected to the other end of the primary side of the transformer, and for passing a current to the primary side of the transformer according to a pulsed drive signal;

An output circuit for generating a first output voltage based on a voltage generated in the first secondary side wire of the transformer;

A choke coil having a core containing a magnetic material of ferrite and a winding wound around the core, and a second secondary side winding force of the transformer is turned on. A chitotsuba circuit that generates a second output voltage by controlling; A control circuit for generating the drive signal;

A switching power supply circuit comprising:

[10] A primary-side current detection circuit that detects a current flowing in the primary side of the transformer,

A secondary side voltage detection circuit for detecting the first output voltage;

And the control circuit generates the drive signal based on the detection result of the primary-side current detection circuit and the detection result of the secondary-side voltage detection circuit, and the control circuit of the secondary-side voltage detection circuit The switching power supply circuit according to claim 9, wherein an upper limit of a pulse width in the drive signal is set based on a detection result.

[11] a choke coil having a core including an amorphous magnetic body and a winding wound around the core, and an input voltage is applied to one end of the winding;

A first switching element connected to the other end of the winding of the choke coil, and causing a current to flow through the winding of the choke coil in accordance with a pulsed first drive signal;

A voltage generating circuit for generating a second voltage based on a first voltage generated at a connection point between the choke coil and the first switching element;

A core including an amorphous magnetic material, and a primary winding and a secondary winding wound around the core, and a second voltage generated by the voltage generation circuit is applied to one end of the primary winding. Mark with the first trance,

A core including a magnetic body of ferrite, and a primary side wire and a secondary side wire wound around the core, and the second voltage generated by the voltage generation circuit is connected to one end of the primary side wire With a second trance carved in,

A second switching element connected to the other end of the primary winding of the first transformer, and causing a current to flow through the primary winding of the first transformer in accordance with a pulsed second drive signal; A third switching element connected to the other end of the primary winding of the second transformer, and for passing a current through the primary winding of the second transformer in accordance with a pulsed third drive signal; A first output circuit for generating a first output voltage based on a voltage generated on a secondary side winding of the first transformer;

A second output circuit for generating a second output voltage based on a voltage generated in the secondary side winding of the second transformer; First and second control circuits for independently generating the first and second drive signals, respectively

A switching power supply circuit comprising:

A primary-side current detection circuit that detects a current flowing through a primary-side winding of the first transformer; a secondary-side voltage detection circuit that detects the first output voltage;

And the first control circuit generates the second drive signal based on the detection result of the primary-side current detection circuit and the detection result of the secondary-side voltage detection circuit, and the 2 12. The switching power supply circuit according to claim 11, wherein an upper limit of a pulse width in the second drive signal is set based on a detection result of the secondary side voltage detection circuit.