WO2007123098A1

WO2007123098A1 - Switching power supply circuit and its control method

Info

Publication number: WO2007123098A1
Application number: PCT/JP2007/058307
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: JPWO2007123098A1

Abstract

A switching power supply circuit realizing both reduction of the power consumption and shortening of the reset time and quickly dealing with the change from a stand-by state to an overload state. The switching power supply circuit comprises a transformer having a core containing an amorphous magnetic material, a switching element for flowing current through the primary-side winding of the transformer according to the drive signal, an output circuit for producing an output voltage according to the voltage induced in the secondary-side winding of the transformer, and a control circuit for generating the drive signal according to the current flowing through the primary-side winding of the transformer and the output voltage of the output circuit and switching among a normal operation mode, a normal standby mode, and a complete standby mode according to the output current of the output circuit or a mode switching signal supplied from outside.

Description

Specification

Switching power supply circuit and control method thereof

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 a method for controlling the operation of such a switching power supply circuit.

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. In a switching power supply, a transformer is used when electrical insulation is required between the input side and the output side. On the other hand, when electrical insulation is not required between the input side and the output side, a chopper type switching power supply using a choke coil instead of a transformer may be used.

[0003] Generally, a ferrite having a low loss and high efficiency is used as a magnetic body serving as a core of a transformer or a choke coil. However, since ferrite is easily magnetically saturated, if the core is saturated and the magnetic properties are deteriorated, the winding current wound around the core exceeds the allowable value. To avoid this, it is necessary to form a gap in the core. In that case, leakage of magnetic flux from the gap becomes a problem. In particular, in an impact printer, in order to supply a sufficient current to the solenoid of the plunger that drives the print head, a switching power supply that can output a current even in an overload state is desired.

By the way, as part of energy saving in electronic devices such as impact printers, a standby mode is provided to reduce power consumption. However, if the switching operation is completely stopped in the standby mode, it takes time for the output voltage to rise when returning from the standby mode to the normal operation mode.

[0005] As a related technology, JP-A-8-51774 discloses a switching power source that can obtain a desired optimum frequency at a light load with a simple and low-cost structure. A circuit is disclosed. This switching power supply circuit is a high cycle for heavy loads. Switching means for supplying a DC voltage to the load side using either a low-frequency switching frequency or a low-cycle switching frequency for a light load, and a load signal indicating a light load condition.

Switching frequency switching means for switching the switching frequency of the switching means to the switching frequency for the light load. However, even in this switching power supply circuit, it is difficult to achieve both reduction in power consumption and reduction in recovery time.

[0006] Japanese Patent Application Publication JP-A-9-134096 discloses an image forming apparatus capable of reducing power loss during standby. This image forming apparatus includes a drive system power supply circuit for supplying voltage to a device that operates during image formation, a controller that turns on the drive system power supply circuit, standby during non-image formation, and image formation. And a control system power supply circuit for supplying a voltage to the controller. According to this image forming apparatus, since the control system power supply circuit supplies a voltage to the controller both during standby and during image formation, the controller can turn on and off the drive system power supply circuit. In standby mode when images are not formed, the controller turns off the drive system power supply circuit, eliminating the standby power loss of the drive system power supply circuit and improving the power saving effect. However, JP-A-9-134096 does not mention shortening the recovery time or dealing with overload.

[0007] Sarako, JP-P2002-199729A has disclosed a power source for an image forming apparatus that can reduce power consumption during standby and image formation of the image forming apparatus. The image forming apparatus power supply includes a detection circuit for detecting an output voltage, a comparison circuit for comparing the detected output voltage with a reference voltage, and a constant output voltage based on a comparison result by the comparison circuit. A PWM control circuit that performs PWM control and a transformer that is driven by the output of the PWM control circuit are provided. On the secondary side of the transformer, there are a plurality of control outputs that are output at a constant voltage and drive outputs that are subordinate output. In a power supply for an image forming apparatus configured to have an output, when a predetermined time has elapsed after the end of the image forming operation, the power is output from the reference voltage changing unit based on the energy saving signal from the control unit of the image forming apparatus. The reference voltage change signal is used to change the reference voltage of the control output voltage of the comparison circuit, and the control output voltage and the drive output voltage are output lower than the rated output voltage during the image forming operation. At the time of return, the reference voltage of the comparison circuit is changed by the reference voltage change signal output based on the energy saving signal from the control unit of the image forming apparatus, and the control output voltage and the drive output are changed. The rated output voltage during image forming operation is output as the voltage.

[0008] According to this image forming apparatus power supply, the power consumption can be reduced by making the drive output voltage during standby of the image forming apparatus lower than the drive output voltage during operation of the image forming apparatus. Can do. However, since both the control output voltage and the drive output voltage change based on the energy saving signal, if these output voltages are set to low in the energy saving mode, the control circuit cannot operate. If the output voltage is set to a high value, the energy saving effect will be diminished.

Disclosure of the invention

Problems to be solved by the invention

Accordingly, in view of the above points, the present invention provides a switching power supply circuit that can quickly cope with a change to a standby state force overload state by reducing power consumption and shortening the recovery time. And it aims at providing the method of controlling operation | movement of such a switching power supply circuit.

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 transformer that has an input voltage applied to one end of the primary winding, and is connected to the other end of the primary winding of the transformer, and supplies current to the primary winding of the transformer in accordance with a pulsed drive signal. Switching circuit, an output circuit that generates an output voltage based on the voltage generated on the secondary side of the transformer, and a drive signal based on the current flowing in the primary side of the transformer and the output voltage of the output circuit A normal operation mode in which at least a predetermined power can be supplied to the load based on the output current of the output circuit or in accordance with a mode switching signal to which an external power is also supplied, and a load that is smaller than the predetermined power Can supply to A control circuit for switching between a first standby mode and a second standby mode in which the supplied power is zero; [0011] Further, a control method for 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. The input voltage is applied to one end of the primary winding and the other end of the primary winding of the transformer. The current is applied to the primary winding of the transformer according to the pulsed drive signal. A switching power supply circuit control method including a switching element that flows and an output circuit that generates an output voltage based on a voltage generated on the secondary side of the transformer, in a normal operation mode. Reduce the pulse width or the number of pulses in the drive signal so that the normal operation mode shifts to the first standby mode when the output current is lower than the predetermined value for more than the first predetermined period. Step (a) and the first standby mode In the first standby mode when the output current of the output circuit is smaller than the predetermined value for more than the second predetermined period or according to the mode switching signal to which the external force is also supplied. From the normal operation mode to the second standby mode according to the step (b) of stopping or deactivating the drive signal so as to shift to the second standby mode and the mode switching signal supplied from the outside in the normal operation mode. The drive signal is stopped or deactivated so as to shift to the mode, and in the second standby mode, the mode shifts from the second standby mode to the normal operation mode according to the mode switching signal supplied from the outside. The step (d) of starting or activating the drive signal so that the first standby mode is activated when the output current of the output circuit becomes larger than a predetermined value in the first standby mode. Comprising a step (e) to increase the pulse width or Roh number pulse in the drive signal so as to shift to Luo normal operation mode. The invention's effect

[0012] According to the present invention, in the switching power supply circuit, the transformer or choke coil having the core including the amorphous magnetic material is used to improve the characteristics of the output current supplied to the load, and two different standby modes. By providing a balance between reducing power consumption and shortening recovery time, it is possible to respond quickly even if the standby state force changes to an overload state.

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 switching power supply circuit shown in FIG. is there.

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

FIG. 4 is a waveform diagram for explaining the operation of the control 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.

FIG. 6 is a diagram showing an example of a change in output power of the switching power supply circuit according to the first embodiment of the present invention.

FIG. 7 is a waveform diagram of a drain current in the switching power supply circuit according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a switching power supply circuit according to a second embodiment of the present invention.

9 is a diagram showing in detail the configuration of the control circuit and the like shown in FIG.

10 is a diagram showing a configuration of a switching power supply circuit according to a third embodiment of the present invention. FIG. 11 is a diagram showing a configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG. 12] A diagram showing a configuration of a switching power supply circuit according to a fourth embodiment of the present invention. [FIG. 13] A diagram showing a configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG. 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 input terminals 1 and 2 of an AC power supply voltage, a transformer 20 that boosts or steps down an AC voltage on the primary side, and outputs the boosted voltage to the secondary side. Is connected in series to the primary side wire 21 of the A switching element 30 for flowing a current through the primary side winding 21 of the power source, and a primary side current detection circuit 40 for detecting a current flowing through the primary side winding 21 of the transformer.

Furthermore, this switching power supply circuit includes a diode 51 that half-wave rectifies the voltage generated on the secondary side winding 22 of the transformer, a capacitor 52 that smoothes the rectified voltage and generates an output voltage, The detection result of the secondary side voltage detection circuit 60 detecting the output voltage at both ends of the capacitor 52, the secondary side current detection circuit 80 detecting the secondary side output current, and the primary side current detection circuit 40 A control circuit 70 that generates a drive signal based on the detection result of the secondary side voltage detection circuit 60 and switches the mode of the switching power supply circuit based on the detection result of the secondary side current detection circuit 80 is provided. Here, the diode 51 and the capacitor 52 constitute an output circuit. 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 and the secondary side current detection circuit 80 to the control circuit 70.

[0016] 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. .

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] Generally, in a switching power supply, as a power transmission method from the primary side to the secondary side of the transformer, a forward method 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. The present invention can be applied to either of them. In the present embodiment, a flyback method is adopted.

In a flyback 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 the operation, the primary current of the transformer 20 increases. On the secondary side of the transformer 20, Since the diode is reverse-biased, no secondary current flows. 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 current, so that the voltage polarity of the transformer 20 is reversed and 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.

In the present embodiment, it is assumed that the load power of the switching power supply circuit is an impact printer. The switching power supply circuit supplies power to the solenoid of the plunger that drives the print head of the impact printer. For a load such as a plunger of an impact printer, the current consumption fluctuates greatly in a short time in milliseconds or seconds.

[0022] Therefore, an amorphous metal magnetic body having a high saturation magnetic flux density is used as the core 24 of the transformer. As a specific material, for example, amorphous alloy Fe—Co (60 to 80 wt%) containing iron (Fe) and cobalt (Co) can be used. As the core type, a norotype molded by sintering a powder material is suitable. Also, a laminate type in which ribbon-like cores are laminated can be used.

[0023] Amorphous metal magnetic material has the characteristics that the hysteresis characteristic and the eddy current loss are small and the high frequency characteristic is good because the change in the magnetic characteristic 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.

[0024] 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, a circuit device is devised. Thus, the switching element is protected.

[0025] Further, in the present embodiment, three types of modes of a normal operation mode, a normal standby mode, and a complete standby mode are provided. Here, the normal operation mode refers to a mode in which the switching power supply circuit can supply at least predetermined power (rated output power) to the load. The rated output power represents the output power at which the MOSFET 31 can stably operate and is determined in advance based on the AC input voltage of the switching power supply circuit, the standard of the MOSFET 31, and the like. In the normal operation mode, for example, a voltage of 40 V required to drive the print head is supplied to a blanker in an impact printer serving as a load. The output current of the switching power supply circuit varies depending on the load state. For example, it is about 1 A in the normal state, but is about 1 OA in a predetermined period in the overload state.

[0026] The normal standby mode refers to a mode in which a power that is smaller than the rated output power can be supplied to the load in order to save energy. In the normal standby mode, for example, the voltage of 20V required to fix the print head is supplied to the flanger in the impact printer that becomes the load. Alternatively, the switching operation of the MOSFET 31 may be performed intermittently while the output voltage of the switching power supply circuit is the same as that in the normal operation mode. Also, the complete standby mode refers to a mode in which the output power is zero with the output voltage and output current of the switching power supply circuit set to zero for further energy saving.

FIG. 2 is a diagram showing in detail the configuration of a control circuit and the like in the switching power supply 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 primary winding 21 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.

[0028] 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. [0029] 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 element characteristics and the gate and 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 clock signal generation circuit 73, a mode switching circuit 74, a comparator 75, a blanking pulse generation circuit 76, an AND circuit 77, and an OR circuit 72. A pulse 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. Thus, the detection result of the secondary side voltage detection circuit 60 can be transmitted to the primary side detection voltage generation circuit 71 while maintaining isolation between the primary side and the secondary side of the transformer 20. 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 shows the secondary side voltage detection circuit and the detection voltage in the switching power supply circuit shown in FIG. It is a circuit diagram which shows the structural example of a production | generation circuit. 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. Thus, when the output 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 a diode 81 that rectifies the voltage generated on the auxiliary auxiliary wire 23 of the transformer, a 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.

[0036] The light-emitting diode 62 and the phototransistor 83 are usually often configured as a photopower bra. The phototransistor 83 receives the optical signal generated by the light-emitting diode 62 and depends on its intensity. Output current from the emitter. The current from which the emitter power of the phototransistor 83 is also output is input to the inverting input terminal of the operational amplifier 87 via the resistor 84.

[0037] 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 a 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.

Further, 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.

Referring again to FIG. 2, the mode switching circuit 74 measures the time by counting the clock signal supplied from the clock signal generation circuit 73 and from the secondary side current detection circuit 80. Switching between the normal operation mode, the normal standby mode, and the complete standby mode is performed based on the output optical signal or the mode switching signal to which an external force is also supplied. For example, in the normal operation mode, the mode switching circuit 74, when the state where the output current detected by the secondary side current detection circuit 80 is smaller than a predetermined value continues beyond the first predetermined period, Transition from the normal operation mode to the normal standby mode, and in the normal standby mode, the state where the output current detected by the secondary-side current detection circuit 80 is smaller than the predetermined value continues beyond the second predetermined period. Or from the normal standby mode to the complete standby mode according to the mode switching signal supplied from the outside, and in the normal operation mode, the normal operation mode is completely switched from the normal operation mode according to the mode switching signal supplied by the external force. Enter standby mode.

[0040] Further, the mode switching circuit 74 shifts from the complete standby mode to the normal operation mode in accordance with the mode switching signal supplied from the outside in the complete standby mode. When the output current detected by the detection circuit 80 becomes larger than a predetermined value, the normal standby mode is shifted to the normal operation mode. The mode switching signal shall be low level in the normal operation mode or normal standby mode and high level in the complete standby mode. For example, by detecting the temperature of the print head of the printer, the mode switching signal may be generated so that when the temperature of the print head falls below a predetermined value, the mode shifts to the complete standby mode.

[0041] The mode switching circuit 74 switches the value of the control voltage V supplied to the detection voltage generation circuit 71 between the normal operation mode, the normal standby mode, and the complete standby mode.

C

The output voltage of the switching power supply circuit can be changed. Alternatively, the mode switching circuit 74 can reduce the number of pulses by thinning out pulses in the drive signal by periodically activating the forced reset signal in the normal standby mode, or in the complete standby mode. By activating the forcible reset signal, the drive signal may be deactivated to stop the switching operation of the MOS FET 31. Alternatively, the mode switching circuit 74 may stop the oscillation operation in the clock signal generation circuit 73 in the complete standby mode.

[0042] In the normal operation mode, the mode switching circuit 74 outputs from the secondary side current detection circuit 80. The load state on the secondary side is detected based on the optical signal to protect the MOSFET 31. In other words, the mode switching circuit 74 generates a drive signal so as to supply power greater than the rated output power to the load in accordance with the magnitude of the output current detected by the secondary-side current detection circuit 80. Set the first period and the second period for generating the drive signal so that the power within the rated output power is supplied to the load, and in the second period, the output power will be within the rated output power. The forced reset signal is periodically activated.

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 AND circuit 77 calculates a logical product of the comparison signal output from the comparator 75 and the blanking pulse signal output from the blanking pulse generation circuit 76. The OR circuit 72 calculates the logical sum of the output signal of the AND circuit 77 and the forced reset signal output from the mode switching circuit 74.

[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. In the pulse width setting circuit 78, the reset signal has priority over the set signal. The clock signal generated by the clock signal generation circuit 73 is supplied to the set terminal S of the pulse width setting circuit 78. Also supplied to the reset terminal R of the comparison signal power pulse width setting circuit 78 generated by the comparator 75 during the period when the forced reset signal is at low level and the blanking pulse signal is at high level. Is done.

[0045] The pulse width setting circuit 78 sets the output signal in synchronization with the clock signal, and resets the output signal in synchronization with the comparison signal output from the comparator 75, whereby the pulse width in the drive signal is set. Set. When the forced reset signal becomes high level, the pulse width setting circuit 78 is always reset, and the drive signal becomes low level. 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. FIG. 4 is a waveform diagram for explaining the operation of the control circuit shown in FIG. 2 in an overload state. Fig. 4 (a) shows the clock signal V generated by the clock signal generation circuit 73.

CK

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

Η Η

Yes.

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.

[0048] If the primary current of the transformer increases, the speed at which energy is stored in the core 24 increases. Furthermore, when the current consumption increases momentarily in the load, it can be dealt with by increasing the period during which the drain current I flows. That

D at the time of drain current I

If an upper limit is set for the period during which D is passed, the power consumption is restored before the temperature of the MOSFET 31 rises abnormally, so there is no possibility of the MOSFET 31 being instantly 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 MOSF ET31 is turned off at the point A shown in FIG. 4 (b).

[0049] 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

Here, the comparison signal V output from the comparator 75 is supplied from the primary side current detection circuit 40.

COMP

Detected based on the output first detection voltage and the detection result of the secondary voltage detection circuit 60 This is obtained by comparing with the second detection voltage generated by the voltage generation circuit 71. 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

[0051] 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 1S Secondary 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, the gate voltage of the MOSFET 31 becomes V level, and the drain current I at point A shown in FIG.

G

Stops.

D

In this manner, the control circuit 70 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 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

[0054] In the normal state! Since the load on the secondary side is light compared to the overload state, the output voltage on the secondary side rises, and the detection result of the secondary side voltage detection circuit 60 is Based on this, the second detection voltage generated by the detection voltage generation circuit 71 is decreasing. Therefore, in Fig. 5 (c) As shown, 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

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 illustrating an example of a change in output power of the switching power supply circuit according to the first embodiment of the present invention. In Fig. 6, the horizontal axis represents the elapsed time, and the vertical axis represents the output power of the switching power supply circuit.

[0057] During the period (a) in which the power supply switch of the printer is turned on and the output voltage of the switching power supply circuit rises, the mode switching circuit 74 sets the mode of the switching power supply circuit to the normal operation mode. In the period (b), the switching power supply circuit is in the normal operation mode, and the mode switching circuit 74 sets the control voltage V so that the output voltage becomes, for example, 40V. At this time, a current of 1A flows through the load, and the output power is 40V X

C

1A = 40W. This output power shall correspond to the rated output power of the switching power supply circuit. The normal operation mode continues from period (b) to period (i).

[0058] In period (c), if the output current suddenly increases due to load fluctuations and the output power is overloaded, which is greater than the rated output power, the current flowing in the primary primary wire 21 of the transformer also increases. Add. In this embodiment, since an amorphous metal magnetic material is used for the core of the transformer, even if the output power increases momentarily, it can be dealt with by increasing the drain current I of the MOSFET 31. As explained above, the drain current I Since there is an upper limit, the MOSFET 31 is protected against instantaneous destructive force. This limits the output current to 10A, for example.

[0059] Further, the mode switching circuit 74 has a time T for supplying electric power larger than the rated output power to the load based on the value of the output current detected by the secondary-side current detection circuit 80, and the rated current.

Set the time T to supply power within 1A output power to the load. This allows for period (c)

1B

, The pulse width of the drive signal is set by the comparison signal generated by the comparator 75, and in the subsequent period (d), the mode switching circuit 74 forcibly resets the output power to be within the rated output power. Activate the signal periodically to limit the pulse width in the drive signal. In period (d), the output voltage and output current of the switching power supply circuit decrease, but the output current is maintained, so that the operation of the plunger driving the print head in the impact printer is continued. Is called.

[0060] The operations in the periods (e) and (f) and the periods (g) and (h) are the same as the operations in the periods (c) and (d). Depending on the value of the output current detected by the side current detection circuit 80, the time T to T for supplying the load with power greater than the rated output power and the time for supplying the power within the rated output power to the load Τ to Τ Different from

1A 3Α IB 3Β. In other words, the mode switching circuit 74 sets a shorter time for supplying power larger than the rated output power to the load as the output current increases in order to protect the MOSFET 31.

[0061] In the period (i), when the printing operation by the printer is interrupted and the state in which the output current is smaller than a predetermined value continues for a predetermined period (for example, 5 minutes), the mode switching circuit 74 In the period (j), the mode of the switching power supply circuit is set to the normal standby mode to save energy. In the normal standby mode, the mode switching circuit 74 reduces the reference voltage V supplied to the detection voltage generation circuit 71. As a result, the comparator 75

C

The detection voltage supplied to the inverting input terminal is lowered, the reset timing in the pulse width setting circuit 78 is advanced, the pulse width in the drive signal is shortened, and the output voltage of the switching power supply circuit is lowered. For example, the mode switching circuit 74 sets the control voltage V so that the output voltage becomes 20V. Alternatively, the mode switching circuit 74 is a switching power supply circuit.

C

The number of pulses in the drive signal is reduced by periodically activating the forced reset signal while maintaining the same output voltage as in normal operation mode. 31 switching operations may be performed intermittently!

When the printing operation of the printer is resumed at the end of the period (j), the switching power supply circuit again shifts to the normal operation mode in the period (k). During period (j), MOS FET 31 is performing switching operation, so that the output voltage of the switching power supply circuit can be quickly raised when the normal operation mode is entered.

[0063] In the period (k), when the printing operation by the printer is interrupted and the state in which the output current is smaller than the predetermined value continues for a predetermined period (for example, 5 minutes), the mode switching circuit 74 In period (1), the mode of the switching power supply circuit is set to the normal standby mode.

[0064] Furthermore, when the mode switching signal changes to a high level indicating the complete standby mode at the end of the period (1), the mode switching circuit 74 changes the mode of the switching power supply circuit to the complete standby mode in the period (m). To further save energy. Alternatively, if the output current remains lowered for a predetermined period (for example, 30 minutes) due to the interruption of the printing operation by the printer, the mode switching circuit 74 sets the mode of the switching power supply circuit to the complete standby mode. Anyway, okay.

[0065] In the complete standby mode, when the mode switching circuit 74 sets the forced reset signal to the noise level, the output of the OR circuit 72 becomes high level, the noise width setting circuit 78 is reset, and the drive signal is Deactivated. As a result, the MOSFET 31 stops the switching operation, so that the output power becomes zero and a great energy saving is achieved.

[0066] When the mode switching signal changes to the low level representing the normal operation mode at the end of the period (m), the mode switching circuit 74 sets the forced reset signal to the low level in the period (n). As a result, the drive signal is activated, and the MOSFET 31 starts the switching operation. However, it takes a certain time for the output voltage to rise. Thereafter, in the period (o), the normal operation mode is continued.

[0067] Thus, in the switching power supply circuit according to the present embodiment, there are two types of standby modes, the normal standby mode and the complete standby mode. In the complete standby mode, the switching element can be turned off to completely reduce the output power to zero, but the disadvantage is that the time until the output voltage rises is increased. There However, the output power cannot be completely reduced to zero, but a normal standby mode is provided that can shorten the time until the output voltage rises.When the load current decreases for a short period, the normal standby mode is entered. As a result, a rapid rise in output voltage can be realized while saving energy.

FIG. 7 is a waveform diagram of the drain current in the switching power supply circuit according to the first embodiment of the present invention. In Fig. 7, the horizontal axis represents the elapsed time, and the vertical axis represents the drain current value. Periods (b) to (j) shown in Fig. 7 correspond to periods (b) to (1) shown in Fig. 6, respectively.

[0069] In the period (b), the pulse width in the drive signal is set so that the switching power supply circuit supplies the rated output power to the load. During the period (c), the current flowing through the load suddenly increases, so the mode switching circuit 74 supplies output power exceeding the rated output power to the load according to the output current detected by the secondary current detection circuit 80. Time period T

Output power within the rated output power for time T in the subsequent period (d)

1B

Limit the pulse width in the drive signal to supply force to the load.

[0070] In the period (e), the mode switching circuit 74 sets a period during which the output power exceeding the rated output power is supplied to the load according to the output current detected by the secondary current detection circuit 80 at time T. Within the rated output power for time T during the subsequent period (f)

2A 2B

The pulse width in the drive signal is limited so that output power is supplied to the load.

[0071] In the period (g), the mode switching circuit 74 sets a period during which the output power exceeding the rated output power is supplied to the load according to the output current detected by the secondary side current detection circuit 80 at time T. Within the rated output power for time T during the subsequent period (h)

3A 3B

[0072] Further, when the state in which the output current is smaller than the predetermined value continues for a period exceeding the predetermined period in period (i), mode switching circuit 74 sets the switching power supply circuit in the normal standby mode in period (j). To reduce the control voltage V.

C

Reduce the output pulse voltage of the switching power supply circuit to 20V.

In the present embodiment, the secondary side current detection circuit 80 shown in FIG. 1 detects the output current (secondary side current) of the output circuit, and the control circuit 70 determines the load of the output circuit based on the output current. Condition Although an example of switching between the first standby mode (normal standby mode) and the second standby mode (complete standby mode) by judging the situation has been described, the present invention is not limited to this. Since it is a well-known fact that the output current of the output circuit is also reflected in the primary side current of the transformer, the primary side voltage waveform, and the voltage waveform of the third side wire provided separately in the transformer. It is also possible to indirectly determine the load status of the output circuit by measuring the current on the primary side of the transformer.

[0074] Next, a second embodiment of the present invention will be described.

FIG. 8 is a diagram showing a configuration of a switching power supply circuit according to the second embodiment of the present invention. In the second embodiment, a description will be given by taking as an example a Chietsuba boost type switching power supply circuit.

[0075] This switching power supply circuit includes a rectifying / smoothing circuit 10 connected to AC voltage input terminals 1 and 2, and one end connected to the rectifying / smoothing circuit 10, and cores magnetic energy generated by a current flowing in the winding. Is connected to the other end of the choke coil 100, the switching element 110 is configured to flow current through the choke coil 100 in accordance with the Norse drive signal, and the switching current detection circuit 120 is configured to detect the current flowing through the switching element 110. And have. Here, when the primary side of the transformer is used as the choke coil 100, the secondary side of the transformer can be used for generating an internal power source.

Further, this switching power supply circuit includes a diode 51 that half-wave rectifies the voltage generated at the other end of the choke coil 100, a capacitor 52 that generates an output voltage by smoothing the rectified voltage, and an output terminal Output voltage detection circuit 130 that detects the output voltage at 3 and 4; output current detection circuit 140 that is inserted between the capacitor 52 and output terminal 4 to detect the output current; and the detection result of the switching current detection circuit 120 And a control circuit 150 that generates a drive signal based on the detection result of the output voltage detection circuit 130 and switches the mode of the switching power supply circuit based on the detection result of the output current detection circuit 140. Here, the diode 51 and the capacitor 52 constitute an output circuit.

The choke coil 100 stores energy in the core when the switching element 110 is on. Next, when switching element 110 is turned off, the magnetic field attempts to maintain the current. Therefore, the current of the choke coil 100 flows to the capacitor 52 via the diode 51, and the capacitor 52 is charged, so that a DC output voltage is generated between the output terminal 3 and the output terminal 4.

In the present invention, an amorphous metal magnetic material having a high saturation magnetic flux density is used as the core of the choke coil 100. As a specific material, for example, an amorphous alloy Fe—Co (60 to 80 wt%) containing iron (Fe) and connort (Co) can be used. As the core type, a norotype molded by sintering a powder material is suitable. A laminate type in which ribbon-like cores are laminated can also be used.

[0079] Amorphous metal magnetic material is easy to mold even when performing E-shaped core molding, which has a higher saturation magnetic flux density than ferrite, and hysteresis loss and magnetic property change with temperature are small. It has the characteristics of low eddy current loss and good high frequency characteristics. In addition, by using an amorphous metal magnetic material as the core of the choke coil, the core is less likely to be saturated magnetically and the amount of heat generated is small. Since there is no need to form a gap, leakage of magnetic flux with gap force is no longer a problem.

[0080] 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. 9 is a diagram showing in detail the configuration of the control circuit and the like shown in FIG. In the present embodiment, an N-channel MOSFET 111 is used as the switching element 110 shown in FIG. MOSFET 111 has a drain connected to the other end of choke coil 100, a source connected to rectifying and smoothing circuit 10 via switching current detection circuit 120, and a gate to which a drive signal is applied from gate driver 159. is doing.

[0082] Drain of choke coil 100 and MOSFET 111 'source path and switching current detection The voltage power 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 111 passes current through the choke coil 100 in accordance with a pulsed drive signal applied to the gate.

The control circuit 150 includes a mode switching circuit 151, a clock signal generation circuit 152, a comparator 154, a blanking pulse generation circuit 155, an AND circuit 156, an OR circuit 157, and a pulse width setting circuit 158. And a gate driver 159.

The mode switching circuit 151 measures the time by powering the clock signal supplied from the clock signal generation circuit 152, and the detection voltage output from the output current detection circuit 140 or an external force is also supplied. Switching between the normal operation mode, normal standby mode, and complete standby mode is performed based on the mode switching signal. For example, in the normal operation mode, the mode switching circuit 151 operates when the state in which the output current detected by the output current detection circuit 140 is smaller than a predetermined value continues beyond the first predetermined period. To the normal standby mode, and in the normal standby mode, when the state where the output current detected by the output current detection circuit 140 is smaller than the predetermined value continues beyond the second predetermined period, Or, transition from the normal standby mode to the complete standby mode according to the mode switching signal to which an external force is also supplied, and shift from the normal operation mode to the complete standby mode according to the mode switching signal supplied from the outside in the normal operation mode. .

[0085] Further, in the complete standby mode, the mode switching circuit 151 shifts from the complete standby mode to the normal operation mode in accordance with the mode switching signal supplied from the outside. In the normal standby mode, the output current detection circuit 140 When the detected output current becomes larger than the predetermined value, the normal standby mode is shifted to the normal operation mode.

[0086] The mode switching circuit 151 switches the value of the control voltage V supplied to the output voltage detection circuit 130 between the normal operation mode, the normal standby mode, and the complete standby mode.

C

The output voltage of the switching power supply circuit can be changed. Alternatively, the mode switching circuit 151 periodically activates the forced reset signal in the normal standby mode, thereby reducing the number of pulses in the drive signal and reducing the number of pulses in the complete standby mode. By deactivating the forced reset signal, the drive signal is deactivated and M The switching operation of the OSFET 111 may be stopped. Alternatively, the mode switching circuit 151 may stop the oscillation operation in the clock signal generation circuit 152 in the complete standby mode.

In the normal operation mode, mode switching circuit 151 detects the load state on the secondary side based on the detection voltage output from output current detection circuit 140, and protects MOSFET 111. That is, the mode switching circuit 151 generates a drive signal so as to supply a power larger than the rated output power to the load according to the magnitude of the output current detected by the output current detection circuit 140. Set a second period for generating a drive signal so that power within the rated output power is supplied to the load, and forcibly reset signal so that the output power is within the rated output power in the second period. Is activated periodically.

[0088] The clock signal generation circuit 152 generates a clock signal. Further, the detection voltage output from the switching current detection circuit 120 is input to the non-inverting input terminal of the comparator 154, and the detection voltage output from the output voltage detection circuit 130 shown in FIG. Input to the power terminal. In the output voltage detection circuit 130, 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 130 by the limiter circuit.

Comparator 154 compares the detection voltage output from switching current detection circuit 120 with the detection voltage output from output voltage detection circuit 130, and outputs a comparison signal representing the comparison result. The blanking pulse generation circuit 155 is a blanking pulse 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 111 is turned off while the primary current of the transformer is small. Generate a signal. The AND circuit 156 obtains a logical product of the comparison signal output from the comparator 154 and the blanking pulse signal output from the blanking pulse generation circuit 155. The OR circuit 157 obtains the logical sum of the output signal of the AND circuit 156 and the forced reset signal output from the mode switching circuit 151. [0090] The pulse width setting circuit 158 is configured by, for example, an RS flip-flop having a set terminal S, a reset terminal R, and an output terminal Q. In the pulse width setting circuit 158, the reset signal has priority over the set signal. The clock signal generated by the clock signal generation circuit 152 is supplied to the set terminal S of the pulse width setting circuit 158. Further, the comparison signal generated by the comparator 154 is supplied to the reset terminal R of the noise width setting circuit 158 during the period when the forced reset signal is at the low level and the blanking pulse signal is at the high level. .

[0091] The pulse width setting circuit 158 sets the output signal in synchronization with the clock signal and resets the output signal in synchronization with the comparison signal output from the comparator 154. Set. When the forced reset signal becomes high level, the pulse width setting circuit 158 is always reset and the drive signal becomes low level. The gate driver 159 drives the gate of the MOSFET 111 based on the drive signal output from the pulse width setting circuit 158.

Since the operation of the control circuit shown in FIG. 9 is substantially the same as that shown in FIGS. 4 to 7, the operation of the control circuit 150 will be described in detail with reference to FIGS. 4 and 6.

Referring to FIG. 4, the clock signal V generated by the clock signal generation circuit 152

CK

The output signal of the pulse width setting circuit 158 is set in synchronization with the rising edge, and the gate voltage V ((e) in Fig. 4) goes high.

G

The comparison signal output from the comparator 154 compares the first detection voltage output from the switching current detection circuit 120 and the second detection voltage output from the output voltage detection circuit 130. It is obtained. In an overload condition, the drain current I of the MOSFET 111 increases and the first detection voltage increases, and the output voltage decreases and the second detection voltage

D

However, an upper limit is set in the output voltage detection circuit 130 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 154 becomes high level. As a result, the output signal of the pulse width setting circuit 158 is reset, and the gate voltage V of the MOSFET 111 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 150 turns on the MOSFET 111 at a constant period and The MOSFET 111 is turned off in synchronization with the rising edge of the comparison signal. In Fig. 4 (e), the period during which the MOSFET 111 is turned on is represented by T, and the MOSFET 111 is turned off.

ON

The period is represented by T.

OFF

[0095] Referring to FIG. 6, in the period (a) when the output voltage of the switching power supply circuit rises when the power supply switch of the printer device is turned on, the mode switching circuit 151 changes the mode of the switching power supply circuit to the normal operation mode. Set. In the period (b), the switching power supply circuit is in the normal operation mode, and the mode switching circuit 151 has an output voltage of, for example, 4

Set the control voltage V to be 0V. At this time, a current of 1A flows through the load,

c

The output power is 40V X 1A = 40W. This output power corresponds to the rated output power of the switching power supply circuit. The normal operation mode continues from period (b) to period (i).

[0096] In the period (c), when the output current suddenly increases due to the load fluctuation and the output power becomes an overload state larger than the rated output power, the current flowing through the choke coil 110 also increases. In the present embodiment, since the amorphous metal magnetic material is used for the core of the choke coil, even when the output power increases momentarily, it can be coped with by increasing the drain current I of the MOSFET 111. As explained above, the drain

D

Since there is an upper limit on current I, MOSFET 111 is protected against instantaneous breakdown force

D

. This limits the output current to 10A, for example.

[0097] Further, the mode switching circuit 151, based on the value of the output current detected by the output current detection circuit 140, and the time T for supplying power larger than the rated output power to the load

Set the time T to supply power within 1A rated output power to the load. This allows the period (c

1B

), The pulse width of the drive signal is set by the comparison signal generated by the comparator 154, and in the subsequent period (d), the mode switching circuit 151 forces the output power to be within the rated output power. Periodically activate the reset signal to limit the pulse width in the drive signal. In the period (d), although the output voltage and output current of the switching power supply circuit are reduced, the output current is maintained, so that the plunger drives the print head continuously in the impact printer.

[0098] The operations in periods (e) and (f) and periods (g) and (h) are also performed in periods (c) and (d). Although the operation is the same, the mode switching circuit 151 has a time T to T for supplying power larger than the rated output power to the load according to the value of the output current detected by the output current detection circuit 140 and the rated current. The time to supply power within the output power to the load is different from Τ to Τ

1A 3Α IB 3Β That is, in order to protect MOSFET 111, mode switching circuit 151 sets a shorter time for supplying power larger than the rated output power to the load as the output current increases.

[0099] In the period (i), when the printing operation by the printer is interrupted, and the state where the output current is smaller than the predetermined value continues for a predetermined period (for example, 5 minutes), the mode switching circuit 151 In the period (j), the switching power supply circuit mode is set to the normal standby mode to save energy. In the normal standby mode, the mode switching circuit 151 reduces the reference voltage V supplied to the output voltage detection circuit 130. This makes the comparator 1

C

The detection voltage supplied to the inverting input terminal of 54 decreases, the reset timing in the pulse width setting circuit 158 is advanced, the pulse width in the drive signal is shortened, and the output voltage of the switching power supply circuit decreases. . For example, the mode switching circuit 151 sets the control voltage V so that the output voltage becomes 2 OV. Alternatively, the mode switching circuit 151 may be a switch

C

The number of pulses in the drive signal is reduced by periodically activating the forced reset signal while keeping the output voltage of the power supply circuit the same as in the normal operation mode.

It is also possible to cause the MOSFET111 to switch intermittently! ,.

[0100] When the printing operation of the printer is resumed at the end of the period (j), the switching power supply circuit again shifts to the normal operation mode in the period (k). In the period (j), the MOSFET 111 performs the switching operation, so that the output voltage of the switching power supply circuit can be quickly raised when shifting to the normal operation mode.

[0101] In the period (k), when the printing operation by the printer is interrupted and the state where the output current is smaller than the predetermined value continues for a predetermined period (for example, 5 minutes), the mode switching circuit 151 In period (1), the mode of the switching power supply circuit is set to normal standby mode.

[0102] Furthermore, when the mode switching signal changes to a high level indicating the complete standby mode at the end of the period (1), the mode switching circuit 151 switches the switching power supply circuit during the period (m). The road mode is set to the complete standby mode to further save energy. Alternatively, if the output current remains reduced for a predetermined period (for example, 30 minutes) due to the interruption of the printing operation by the printer, the mode switching circuit 151 sets the mode of the switching power supply circuit to the complete standby mode. It ’s okay.

[0103] In the complete standby mode, when the mode switching circuit 151 sets the forced reset signal to the noise level, the output of the OR circuit 157 becomes high level, the pulse width setting circuit 158 force S is reset, and the drive signal is not turned on. Activated. As a result, the MOSFET 111 stops the switching operation, so that the output power becomes zero and a great energy saving is achieved.

[0104] When the mode switching signal changes to a low level indicating the normal operation mode at the end of the period (m), the mode switching circuit 151 sets the forced reset signal to a low level in the period (n). As a result, the drive signal is activated, and the MOSFET 111 starts the switching operation. However, it takes a certain time for the output voltage to rise. Thereafter, in the period (o), the normal operation mode is continued.

[0105] Next, a third embodiment 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 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.

The configurations of the rectifying / smoothing circuit 10 and the first voltage conversion circuit 11 are the same as the configuration of the switching power supply circuit according to the first embodiment shown in FIG. The second voltage conversion circuit 12 is connected in series to a transformer 160 that boosts or steps down the AC voltage on the primary side and outputs it to the secondary side, and a primary side wire 161 of the transformer. A switching element 170 that allows current to flow through the primary winding 161 of the transformer according to the drive signal, a primary current detection circuit 180 that detects current flowing through the primary winding 161 of the transformer, and a secondary winding of the transformer 16 Diode 53 that half-wave rectifies the voltage generated at 2; capacitor 54 that smoothes the rectified voltage; secondary voltage detection circuit 190 that detects the smoothed voltage across capacitor 54; and primary Side current detection circuit 180 detection result and secondary side voltage detection circuit 190 And a control circuit 200 that generates a drive signal based on the detection result. The configuration of secondary side voltage detection circuit 190 is the same as the configuration of secondary side voltage detection circuit 60 shown in FIG.

The transformer 160 includes a magnetic core 164, a primary side wire 161, a secondary side wire 162, and an auxiliary wire 163 wound around the core 164. If the number of primary side wires 161 is N3 and the number of secondary side wires 162 is N4, and there is no loss, the step-up ratio between the primary side and secondary side is N4ZN3. The auxiliary feeder 163 is used to supply a power supply voltage to the control circuit 200. The dot symbol attached to the transformer 160 indicates the polarity of the winding.

[0108] The first voltage conversion circuit 11 can be used until the no-load state power consumes 2 to 3 times the rated output current for a short time in milliseconds or seconds, or in some cases rated. The first output voltage is supplied to a dynamic load that fluctuates dynamically until it consumes 10 times the 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 is within about 50% of the rated output current. Here, the rated output current represents the magnitude of the output current that can stably operate the MOSFET used as a switching element in each voltage conversion circuit. It is determined in advance based on the input voltage and MOSF ET standards.

In the present embodiment, it is assumed that the load power of the switching power supply circuit is an impact printer. 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, an appropriate material is selected for the transformer core 24 in the first voltage conversion circuit 11 and the transformer core 164 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. On the other hand, as the transformer core 164 in the second voltage conversion circuit 12 that supplies power to the steady load, a ferrite magnetic material is used. Ferrite magnetic material is low Since it has characteristics of loss and efficiency, it has been generally used as a core material for transformers.

FIG. 11 is a diagram showing a configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG. The basic configuration of the control circuit in the second voltage conversion circuit is the same as that of the control circuit 70 shown in FIG. 2 except that there is no component for limiting the drain current and no mode switching circuit.

In the second voltage conversion circuit 12, similarly to the first voltage conversion circuit 11, an N-channel MOSFET 171 is used as the switching element 170. MOSFET 171 has a drain connected to primary winding 161 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.

[0113] The primary side wire 161 of the transformer and the drain 'source path of the MOSFET 171 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 171 causes a current to flow through the primary side winding 161 of the transformer in accordance with a pulsed drive signal applied to the gate.

The control circuit 200 includes a detection voltage generation circuit 201 that generates a detection voltage based on the detection result of the secondary side voltage detection circuit 190 shown in FIG. 10, and a clock signal generation circuit 73 that generates a clock signal. The comparator 75 that compares the detection voltage output from the primary-side current detection circuit 40 and the detection voltage generated by the detection voltage generation circuit 201 to generate a comparison signal that represents a comparison result, and the clock signal A blanking pulse generation circuit 76 that generates a blanking pulse signal that becomes a high level only during a predetermined period, an AND circuit 77, an output signal that is set in synchronization with the clock signal, and a comparison signal that is output from the comparator 75. The pulse width setting circuit 78 sets the pulse width in the drive signal by resetting the output signal in synchronization with the signal, and the drive signal output from the pulse width setting circuit 78 And a gate driver 79 for driving the gate of MOSFET171 Te.

Here, the configuration of the detection voltage generation circuit 201 is the same as the configuration of the detection voltage generation circuit 71 shown in FIG. 3 except for the diode 88 for the limiter. Since the second voltage conversion circuit 12 is for supplying power to a stable steady load, a magnetic material of ferrite is used for the core 164 of the transformer. In that case, an overcurrent is generated in the primary primary wire 161 of the transformer. Since there is no possibility of flowing, the limiter diode 88 for limiting the drain current is omitted.

[0116] 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.

In the third embodiment, by applying a predetermined voltage to the inverting input terminal of the comparator 75 instead of the detection voltage generated by the detection voltage generation circuit 201, the primary-side current detection circuit 40 The drive signal may be generated based on the detection result. Even in that case, if the detection voltage output from the primary current detection circuit 40 exceeds the predetermined voltage, the output signal of the pulse width setting circuit 78 is reset, so the upper limit of the pulse width in the drive signal is set. be able to.

[0118] Next, a fourth embodiment of the present invention will be described.

FIG. 12 is a diagram showing a configuration of a switching power supply circuit according to the fourth embodiment of the present invention. In the switching power supply circuit according to the fourth 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.

The configurations of the rectifying / smoothing circuit 10 and the first voltage conversion circuit 11 are the same as the configuration of the switching power supply circuit according to the second embodiment shown in FIG. The second voltage conversion circuit 12 has one end connected to the rectifying / smoothing circuit 10 and connected to the choke coil 210 that stores magnetic energy generated by the current flowing in the winding in the core, and the other end of the choke coil 210. Switching element 220 for passing current to choke coil 210 in accordance with the driving signal, switching current detection circuit 230 for detecting current flowing to switching element 220, and half-wave rectification of the voltage generated at the other end of choke coil 210 Detection of the diode 53, the capacitor 54 that generates the output voltage by smoothing the rectified voltage, the output voltage detection circuit 240 that detects the output voltage at the output terminals 5 and 6, and the switching current detection circuit 230 And a control circuit 250 that generates a drive signal V based on the result and the detection result of the output voltage detection circuit 240. Also in the present embodiment, an appropriate material for the core of the choke coil 100 in the first voltage conversion circuit 11 and the core of the choke coil 210 in the second voltage conversion circuit 12 is used depending on the load. Selected. As the core of the choke coil 100 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. On the other hand, a ferrite magnetic material is used as the core of the choke coil 210 in the second voltage conversion circuit 12 that supplies power to a steady load.

FIG. 13 is a diagram showing a configuration of a control circuit and the like in the second voltage conversion circuit shown in FIG. The basic configuration of the control circuit in the second voltage conversion circuit is the same as that of the control circuit 150 shown in FIG. 9 except that there is no function for limiting the drain current and no mode switching circuit.

In the second voltage conversion circuit 12, as in the first voltage conversion circuit 11, an N-channel MOSFET 221 is used as the switching element 220. MOSFET 221 has a drain connected to choke coil 210, a source connected to rectifying and smoothing circuit 10, and a gate to which a drive signal is applied from gate driver 159.

The choke coil 210 and the drain / source path of the MOSFET 221 are connected in series, and the voltage 1S 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 221 causes a current to flow through the choke coil 210 in accordance with a pulsed drive signal applied to the gate.

[0124] The control circuit 250 compares the clock signal generation circuit 152 that generates the clock signal, the detection voltage output from the switching current detection circuit 230, and the detection voltage generated by the output voltage detection circuit 240. A comparator 154 that generates a comparison signal that represents a comparison result, a blanking pulse generation circuit 155 that generates a blanking pulse signal that is high only during a predetermined period synchronized with the clock signal, an AND circuit 156, a clock The pulse width setting circuit 158 sets the pulse width in the drive signal by setting the output signal in synchronization with the signal and resetting the output signal in synchronization with the comparison signal output from the comparator 154, and the pulse width setting A gate driver 159 that drives the gate of the MOSFET 221 based on the drive signal output from the circuit 158. The configuration of the output voltage detection circuit 240 shown in FIG. 12 is the same as that of the output voltage detection circuit 130 shown in FIG. 8 except for the limiter diode. Since the second voltage conversion circuit 12 is for supplying electric power to a stable steady load, a ferrite magnetic body is used for the core of the choke coil 210. In this case, since there is no possibility that an overcurrent flows through the winding of the choke coil 210, the limiter diode for limiting the drain current is omitted.

[0126] According to the present embodiment, the first voltage conversion circuit 11 and the second voltage conversion circuit 12 use separate choke coils suitable for respective loads, and the primary side 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.

In the fourth embodiment, by applying a predetermined voltage to the inverting input terminal of the comparator 154 instead of the detection voltage generated by the output voltage detection circuit 240, the switching current detection circuit 230 A drive signal may be generated based on the detection result! Even in this case, if the detection voltage output from the switching current detection circuit 230 exceeds a predetermined voltage, the output signal of the pulse width setting circuit 158 is reset, so the upper limit of the pulse width in the drive signal must be set. Can do.

Industrial applicability

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

Claims

The scope of the claims

[1] a core including an amorphous magnetic material, a primary winding and a secondary winding wound around the core, and an input voltage applied to one end of the primary 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 an output voltage based on a voltage generated on the secondary side of the transformer;

The drive signal is generated based on the current flowing through the primary side of the transformer and the output voltage of the output circuit, and the mode switching signal supplied from the outside based on the output current of the output circuit In accordance with the normal operation mode in which at least predetermined power can be supplied to the load, the first standby mode in which power smaller than the predetermined power can be supplied to the load, and the second standby mode in which the supplied power becomes zero And a switching power supply circuit comprising:

[2] a second transformer having a core including a ferrite magnetic body and a primary side wire and a secondary side wire wound around the core, and an input voltage is applied to one end of the primary side wire When,

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

A second control circuit for generating the second drive signal based on at least a current flowing through the primary side winding of the second transformer;

The switching power supply circuit according to claim 1, further comprising:

[3] 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 switching element connected to the other end of the winding of the choke coil, and for causing a current to flow through the winding of the choke coil according to a pulsed drive signal;

An output circuit that generates an output voltage based on a voltage generated at a connection point between the choke coil and the switching element; The drive signal is generated based on the current flowing through the winding of the choke coil and the output voltage of the output circuit, and based on the output current of the output circuit or in accordance with a mode switching signal supplied from the outside. A normal operation mode in which at least predetermined power can be supplied to the load, a first standby mode in which power smaller than the predetermined power can be supplied to the load, and a second standby mode in which the supplied power is zero. A switching power supply circuit comprising: a switching control circuit;

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

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

A second control circuit for generating the second drive signal based on at least a current flowing through the winding of the second choke coil;

The switching power supply circuit according to claim 3, further comprising:

[5] In the normal operation mode, when the state in which the output current of the output circuit is smaller than a predetermined value continues for a period exceeding the first predetermined period, the control circuit switches from the normal operation mode to the first The pulse width or number of pulses in the drive signal is reduced so as to shift to the standby mode, and the state in which the output current of the output circuit is smaller than a predetermined value in the first standby mode exceeds the second predetermined period. The drive signal is stopped or deactivated so as to shift from the first standby mode to the second standby mode in accordance with a mode switching signal supplied from the outside. The drive signal is stopped or deactivated so as to shift from the normal operation mode to the second standby mode in accordance with the mode switching signal supplied from the The drive signal is activated so as to shift from the second standby mode to the normal operation mode in accordance with the mode switching signal supplied from the second standby mode, and in the first standby mode, the output current of the output circuit is larger than a predetermined value. The pulse width or number of pulses in the drive signal is increased so as to shift from the first standby mode to the normal operation mode when The switching power supply circuit according to item 1.

[6] A first period in which the control circuit generates a drive signal so as to supply power greater than the predetermined power to the load according to the magnitude of the output current of the output circuit in the normal operation mode. The switching power supply circuit according to any one of claims 1 to 5, wherein a second period for generating a drive signal is set so as to supply power within the predetermined power to a load.

[7] A transformer including a core including an amorphous magnetic material, a primary winding and a secondary winding wound around the core, and an input voltage applied to one end of the primary winding, A switching element that is connected to the other end of the primary side of the transformer and flows current to the primary side of the transformer in accordance with a pulsed drive signal, and a voltage generated on the secondary side of the transformer. And a control method for a switching power supply circuit including an output circuit for generating an output voltage, wherein a state in which the output current of the output circuit is smaller than a predetermined value exceeds a first predetermined period in a normal operation mode. (A) reducing the pulse width or the number of pulses in the drive signal so as to shift from the normal operation mode to the first standby mode when the operation continues.

In the first standby mode, when the state in which the output current of the output circuit is smaller than a predetermined value continues beyond the second predetermined period, or according to a mode switching signal to which an external force is also supplied (B) stopping or deactivating the drive signal so as to shift from the first standby mode to the second standby mode;

(C) stopping or deactivating the drive signal so as to shift from the normal operation mode to the second standby mode in accordance with a mode switching signal supplied from the outside in the normal operation mode;

(D) starting or activating the drive signal so as to shift from the second standby mode to the normal operation mode in accordance with the mode switching signal to which external force is also supplied in the second standby mode;

In the first standby mode, when the output current of the output circuit becomes larger than a predetermined value, the drive signal is switched to the normal operation mode from the first standby mode. Increasing the pulse width or number of pulses (e),

A control method comprising:

[8] 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, and connected to the other end of the winding of the choke coil. A switching element for passing a current through the winding of the choke coil in accordance with a pulsed drive signal, and an output circuit for generating an output voltage based on a voltage generated at a connection point between the choke coil and the switching element. A switching power supply circuit control method including

In the normal operation mode, when the state in which the output current of the output circuit is smaller than a predetermined value continues beyond the first predetermined period, the driving is performed so that the normal operation mode is shifted to the first standby mode. Reducing the pulse width or number of pulses in the signal (a);

In the first standby mode, when the output current of the output circuit becomes larger than a predetermined value, the pulse width or the number of pulses in the drive signal so as to shift from the first standby mode to the normal operation mode. Step (e) to increase

A control method comprising:

[9] In a normal operation mode, a first period for generating a drive signal so as to supply power greater than the predetermined power to the load according to the magnitude of the output current of the output circuit; 9. The control method according to claim 7, further comprising a step (e) of setting a second period for generating a drive signal so as to supply power within the predetermined power to the load.