JP2013223280A - Power supply control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a stable driving voltage to a control IC while preventing an excessive voltage from being applied to the control IC even at normal time when an over voltage does not occur.SOLUTION: In a power supply control device, a first auxiliary winding 25c and a second auxiliary winding 25d having numbers of turns different from each other are provided in a transformer 25, and a control signal CS on the basis of a power supply voltage required by a printer is input. The power supply control device is provided with a driving voltage output circuit 34 that rectifies a voltage in response to the control signal CS out of AC voltages induced by the first auxiliary winding 25c and the second auxiliary winding 25d and can output a DC voltage smoothed as a driving voltage of a control IC 38. On account of this, the power supply control device outputs the voltage from the second auxiliary winding 25d having the smaller number of turns when a voltage Vout is relatively high and can protect the control IC 38 from an over voltage. The power supply control device outputs the voltage from the first auxiliary winding 25c having the larger number of turns when the voltage Vout is relatively low and can stabilize the driving voltage.

Description

  The present invention relates to a power supply control device that supplies a power supply voltage to an electrical device.

  Conventionally, as this type of power supply control device, a DC voltage obtained by rectifying and smoothing a commercial power supply is converted into an AC voltage by switching a switching circuit and applied to the primary winding of the transformer, and applied to the secondary winding of the transformer. An apparatus has been proposed in which an induced AC voltage is rectified into a DC voltage, smoothed, and supplied to an electrical device (for example, see Patent Document 1). In this apparatus, in order to supply a driving voltage to a control IC that outputs a switching signal to a switching circuit, a first auxiliary winding and a second auxiliary winding having a smaller number of turns than the first auxiliary winding. Winding is provided so that the output can be switched. During normal times when the secondary side voltage is relatively stable, a DC voltage obtained by rectifying and smoothing the AC voltage induced in the first auxiliary winding is supplied to the control IC, and the secondary side voltage suddenly appears. When the overvoltage becomes an overvoltage, the first auxiliary winding is switched to the second auxiliary winding, and the AC voltage induced in the second auxiliary winding is rectified and the smoothed DC voltage is output to the control IC. To do. As a result, the control IC can be protected from overvoltage.

JP 2009-213261 A

  By the way, an electrical device to which a power supply voltage is supplied from such a power supply control device has a sleep mode for suppressing power consumption, and normally requires a high voltage as the supplied power supply voltage. Some require low voltage. In accordance with this, there are some power supply control devices that switch the output voltage on the secondary side into two steps of high and low. However, in the above-described power supply control device, the first auxiliary winding is always used at normal times when no overvoltage occurs, and switching to the second auxiliary winding is not considered. For this reason, when the number of turns of the first auxiliary winding is determined based on when the secondary side is at a low voltage, a drive voltage exceeding the upper limit may be supplied to the control IC when the voltage is switched to a high voltage. It is not preferable from the viewpoint of equipment protection. Conversely, if the number of turns of the first auxiliary winding is determined based on the voltage when the secondary side is at a high voltage, a drive voltage lower than the lower limit may be supplied to the control IC when the voltage is switched to a low voltage. There is a possibility that the driving voltage cannot be sufficiently supplied.

  The main purpose of the power supply control device of the present invention is to supply a stable drive voltage to the control IC while preventing an excessive voltage from acting on the control IC even during normal times when no overvoltage occurs.

  The power supply control device of the present invention employs the following means in order to achieve the main object described above.

The power supply control device of the present invention is
A power supply control device that inputs the control signal from an electrical device that outputs a control signal based on a required power supply voltage and supplies the power supply voltage to the electrical device,
A first rectifying / smoothing circuit that rectifies and smoothes an input power supply and outputs a DC voltage;
A switching circuit that converts the DC voltage output from the first rectifying and smoothing circuit into an AC voltage by switching;
A primary winding wound on the primary side and applied with an AC voltage converted by the switching circuit, a secondary winding wound on the secondary side, and winding on the primary side with different numbers of turns. A transformer having a plurality of rotated auxiliary windings;
A second rectifying / smoothing circuit that rectifies and smoothes the AC voltage induced in the secondary winding of the transformer and outputs the DC voltage to the electrical device;
A feedback signal is generated based on the output voltage so that the output voltage output from the second rectifying / smoothing circuit becomes a constant voltage according to the control signal, and the generated feedback signal is sent to the primary side of the transformer. A constant voltage control circuit for transmission;
A control IC that operates in response to the supply of a driving voltage, inputs the transmitted feedback signal, generates a switching signal of the switching circuit based on the feedback signal, and outputs the switching signal;
As the driving voltage, a driving voltage output circuit capable of outputting a DC voltage obtained by rectifying and smoothing an AC voltage induced in the auxiliary windings according to the control signal;
It is a summary to provide.

  In the power supply control device of the present invention, a plurality of auxiliary windings are wound on the primary side of the transformer with different numbers of turns, and a control signal based on the power supply voltage required by the electrical equipment is input. The constant voltage control circuit generates a feedback signal so as to obtain an output voltage corresponding to the control signal, transmits the feedback signal to the primary side, and a control IC that operates upon receiving the supply of the driving voltage is based on the feedback signal. Generates and outputs a switching signal of the switching circuit, and the driving voltage output circuit generates a DC voltage obtained by rectifying and smoothing an AC voltage induced in a plurality of auxiliary windings of the transformer according to the control signal. And output as a driving voltage. Accordingly, it becomes possible to output a DC voltage from the auxiliary winding having a more appropriate number of turns as a driving voltage in accordance with the control signal, that is, in accordance with the power supply voltage required by the electric equipment. For this reason, when the output voltage is relatively high although no overvoltage has occurred, the control IC can be protected from the overvoltage by outputting the DC voltage from the auxiliary winding having a relatively small number of turns as the driving voltage. When the voltage is relatively low, the driving voltage can be stabilized by outputting a DC voltage from the auxiliary winding having a relatively large number of turns as the driving voltage. As a result, it is possible to supply a stable driving voltage to the control IC while preventing an excessive voltage from acting on the control IC even during normal times when no overvoltage occurs.

  Further, in the power supply control apparatus of the present invention for supplying a power supply voltage to the electrical equipment that selectively requires either a high power supply voltage or a low power supply voltage, the transformer is configured as a plurality of auxiliary windings. 1 auxiliary winding and a second auxiliary winding having a smaller number of turns than the first auxiliary winding, and the drive voltage output circuit is an alternating current induced in the first auxiliary winding. A first output line for rectifying the voltage and outputting a smoothed DC voltage; a second output line for rectifying the AC voltage induced in the second auxiliary winding and outputting a smoothed DC voltage; A switch for switching between conduction and interruption of one output line, and turning off the switch so that the first output line is interrupted in a signal state where the control signal requires the high power supply voltage, The control signal requires the low power supply voltage. The first output line could also be made to turn on the switch to be conducting while. In this way, when a two-stage power supply voltage, that is, a high power supply voltage and a low power supply voltage, is selectively output to an electrical device, a stable driving voltage can be supplied to the control IC with a simple configuration.

  In this aspect of the power supply control apparatus of the present invention, the drive voltage output circuit outputs a high output voltage from the second rectifying and smoothing circuit in a signal state in which the control signal requires the high power supply voltage. When the switch is turned off by a high voltage on the first output line, and the low output voltage is output from the second rectifying and smoothing circuit in a signal state in which the control signal requires the low power supply voltage The switch may be turned on by a low voltage of the first output line. By so doing, it is possible to supply an appropriate driving voltage to the control IC using the change in voltage output from the first auxiliary winding to the first output line.

  Furthermore, in the power supply control device of the present invention of this aspect, the driving voltage output circuit is configured to turn on the first semiconductor switch as the switch and turn on the first semiconductor switch when turned on, and turn off the first semiconductor switch. A second semiconductor switch that turns off the first semiconductor switch; and the second semiconductor switch that outputs a high output voltage from the second rectifying and smoothing circuit in a signal state in which the control signal requires the high power supply voltage. When the second semiconductor switch is turned off by a high voltage of one output line, and a low output voltage is output from the second rectifying and smoothing circuit in a signal state in which the control signal requires the low power supply voltage And a third semiconductor switch that turns on the second semiconductor switch by a low voltage of the first output line.

  Furthermore, in the power supply control device of the present invention according to this aspect, the first semiconductor switch is a MOSFET having a source and a drain connected to the first output line, and the second semiconductor switch 1 transistor, the third semiconductor switch is a second transistor, and the drive voltage output circuit includes a first resistor, a second resistor, and the first resistor on the first output line. A collector and an emitter of the transistor are connected in series with each other, a third resistor and a collector and an emitter of the second transistor are connected in series with each other in the first output line, and a fourth output is connected with the first output line. A resistor and a fifth resistor are connected in series, and a connection point between the first resistor and the second resistor is connected to the gate of the MOSFET. The connection point between the third resistor and the collector of the second transistor is connected to the base of the first transistor, and the connection point between the fourth resistor and the fifth resistor is the connection point of the second transistor. It can also be connected to the base. In this way, a relatively compact circuit configuration can be achieved using MOSFETs, transistors, and resistors. Further, the resistance value (resistance value) of the fourth resistor and the fifth resistor is turned on so that the second transistor is turned on while the output voltage from the second rectifying / smoothing circuit is switched from the low output voltage to the high output voltage. If the ratio is determined, a stable driving voltage can be supplied to the control IC while protecting from overvoltage even during switching from the low output voltage to the high output voltage.

  Alternatively, in the power supply control device according to the aspect of the invention, the drive voltage output circuit emits light in response to the first semiconductor switch as the switch and the signal requiring the high power supply voltage as the control signal. A light emitting element that stops emitting light upon receiving a signal that requires the low power supply voltage as the control signal; and the first semiconductor switch is turned off when receiving light emitted from the light emitting element, and the light emission And a light receiving element that turns on the first semiconductor switch when light emission from the element is not received.

  Furthermore, in the power supply control device according to the aspect of the present invention, the first semiconductor switch is a MOSFET having a source and a drain connected to the first output line, and the light emitting element has an anode side of the control signal. A photodiode connected to an input line and having a cathode side grounded to a ground; the light receiving element is a phototransistor; and the driving voltage output circuit includes a first resistor and a second resistor on the first output line. A resistor and a collector and an emitter of the phototransistor may be connected in series with each other, and a connection point between the first resistor and the second resistor may be connected to the gate of the MOSFET. In this way, it is possible to reduce the number of necessary parts and to make a simpler circuit configuration.

FIG. 2 is a schematic configuration diagram of a printer 60 supplied with power from an AC adapter. 2 is a circuit configuration diagram of a power supply circuit 20 of the AC adapter 10. FIG. The circuit block diagram of the power supply circuit 20B of the AC adapter 10 of a modification.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a printer 60 supplied with power from an AC adapter 10 according to an embodiment of the present invention, and FIG. 2 is a circuit configuration diagram of a power circuit 20 of the AC adapter 10. The AC adapter 10 receives a commercial power supply (AC 100 V or the like), converts it into either a high voltage DC voltage (DC 40 V or the like) or a low voltage DC voltage (DC 10 V or the like), and supplies it to the printer 60. In addition, the printer 60 operates by receiving a DC voltage from the AC adapter 10 as a power supply voltage. The printer 60 is in a normal state in which various parts such as printing can be performed by supplying power to each part, and the power supply to each part is stopped in a normal state. It is configured to be able to switch between a sleep state with less power consumption. As shown in FIG. 2, the AC adapter 10 has three lines including a power line Vout, a GND line, and a control signal CS line (a control signal CS (Control Signal) is a signal input from the printer 60). Thus, the printer 60 is connected. Note that the voltage output to the voltage line Vout is also referred to as voltage Vout.

  As shown in FIG. 1, the printer 60 includes an inkjet printer unit 62, a main controller 66 that controls the entire apparatus, and a power management unit 70 that controls the supply of power to each unit of the printer 60. These are configured so that various control signals and data can be exchanged with each other via a bus. The printer unit 62 includes a printer mechanism 63 that performs printing by ejecting ink droplets while reciprocating a print head on a sheet conveyed by driving a paper feed roller, and printing included in a print job received from a computer (not shown). And a printer ASIC 64 that controls the printer mechanism 63 to perform printing based on target image data. The main controller 66 is configured as a microprocessor centered on the CPU 67, and includes a flash memory 68 for storing various processing programs and a RAM 69 for temporarily storing data.

  The power management unit 70 supplies and shuts off the high voltage Vout (40 V) to a drive system such as the printer mechanism 63 (motor for driving the paper feed roller, motor for reciprocating the print head, and print head). In addition to being configured to be switchable, a DC / DC converter 72 is provided. The DC / DC converter 72 steps down the voltage Vout (40 V or 10 V) to a predetermined control system voltage (for example, 3.3 V) by switching the switching element, and supplies it to a control system such as the printer ASIC 64 or the main controller 66. To do. In addition, the power management unit 70 mainly cuts off the supply of power to the high voltage system when the printer unit 62 is not operating for a predetermined time in the normal state (no print job is received from the computer). Then, the printer 60 is shifted to the sleep state. In this sleep state, the power management unit 70 continues to output the control signal CS described above to the AC adapter 10 as a signal for indicating that the power supply voltage required by the printer 60 is the low power supply voltage (10 V). On the other hand, when the power management unit 70 receives a print job from the computer in the sleep state, it indicates that the power supply voltage required by the printer 60 is a high power supply voltage (40V). 10 is stopped, the supply of power that has been cut off is resumed, and the printer 60 is returned to the normal state. That is, the printer 60 of the present embodiment indicates that the printer 60 is in a sleep state that requires a low power supply voltage by outputting the control signal CS, and requires a high power supply voltage by stopping the output of the control signal CS. It shows that it is in the normal state.

  As shown in FIG. 2, the power supply circuit 20 of the AC adapter 10 includes, as main components, a first rectifying / smoothing circuit 21, a switching circuit 23, a transformer 25, a second rectifying / smoothing circuit 27, and a constant rectifying / smoothing circuit 27. A voltage control circuit 32, a drive voltage output circuit 34, and a control IC 38 are provided. The first rectifying and smoothing circuit 21 rectifies and smoothes the commercial power supply and outputs a DC voltage. The switching circuit 23 converts the DC voltage output from the first rectifying and smoothing circuit 21 into an AC voltage by switching. The transformer 25 transforms the AC voltage converted by the switching circuit 23, and the second rectifying and smoothing circuit 27 outputs the DC voltage obtained by rectifying and smoothing the AC voltage transformed by the transformer 25 to the power line Vout as an output voltage (voltage). Vout). The constant voltage control circuit 32 receives the control signal CS output from the power management unit 70 of the printer 60 and stabilizes the voltage Vout to a constant voltage according to the state of the printer 60. The driving voltage output circuit 34 outputs a DC voltage generated by using the AC voltage transformed by the transformer 25 as a driving voltage, and the control IC 38 is driven by the driving voltage from the driving voltage output circuit 34. Then, a signal for switching control to the switching circuit 23 is generated and output. Note that the side where the first rectifying / smoothing circuit 21, the switching circuit 23, the driving voltage output circuit 34, and the control IC 38 are disposed across the transformer 25 is referred to as a primary side, and the second rectifying / smoothing circuit 27 or The side on which the voltage control circuit 32 (excluding the phototransistor PT1 of the photocoupler PC1 described later) is disposed is referred to as a secondary side.

  The first rectifying and smoothing circuit 21 includes a diode bridge DB1 in which four diodes connected to a commercial power supply are combined, and a smoothing capacitor C1 connected to the diode bridge DB1. In the first rectifying / smoothing circuit 21, a commercial power supply is full-wave rectified by the diode bridge DB1, and a DC voltage smoothed by the smoothing capacitor C1 is output.

  The switching circuit 23 includes a switching element (MOSFET) QF1 having a gate connected to a DRV terminal (described later) of the control IC 38, a drain connected to the transformer 25, and a source grounded to the ground, and a resistor (not shown). In the switching circuit 23, the DC voltage output from the first rectifying / smoothing circuit 21 is converted into an AC voltage by the switching operation of the switching element QF1.

  The transformer 25 includes a primary winding 25 a connected to the output side of the first rectifying and smoothing circuit 21 and the drain of the switching element QF 1 of the switching circuit 23, and a secondary winding connected to the second rectifying and smoothing circuit 27. The line 25b includes a first auxiliary winding 25c and a second auxiliary winding 25d connected to the driving voltage output circuit 34. In the transformer 25, when an AC voltage converted by the switching operation of the switching element QF1 is applied to the primary winding 25a, an AC voltage corresponding to the turn ratio between the primary winding 25a and the secondary winding 25b. Is induced in the secondary winding 25b. An AC voltage corresponding to the turn ratio between the secondary winding 25b, the first auxiliary winding 25c, and the second auxiliary winding 25d is also applied to the first auxiliary winding 25c and the second auxiliary winding 25d. Each is induced. Here, one end of the first auxiliary winding 25c is grounded and the other end is connected to an anode side of a diode D2 (described later) of the driving voltage output circuit 34, and one end of the second auxiliary winding 25d is connected to the anode side. The other end of the driving voltage output circuit 34 is connected to the anode side of a diode D3 described later. Further, the number of turns of the first auxiliary winding 25c is configured to be larger than the number of turns of the second auxiliary winding 25d. For this reason, the AC voltage induced in the first auxiliary winding 25c is higher than the AC voltage induced in the second auxiliary winding 25d.

  The second rectifying / smoothing circuit 27 includes a diode D4 having an anode connected to the secondary winding 25b of the transformer 25 and a smoothing capacitor C4 connected to the cathode of the diode D4. In the second rectifying / smoothing circuit 27, a DC voltage obtained by half-wave rectifying the AC voltage induced in the secondary winding 25b of the transformer 25 by the diode D4 and smoothing by the smoothing capacitor C4 is output between the power line Vout and the GND line. Output as voltage (voltage Vout).

  The constant voltage control circuit 32 includes a photocoupler PC1, two Zener diodes ZD1 and ZD2, and a transistor Q3. The photocoupler PC1 includes a light emitting diode PD1 whose anode side is connected to the power line Vout, and a phototransistor PT1 whose collector is connected to an FB terminal described later of the control IC 38 and whose emitter is grounded. The Zener diode ZD1 has an anode side grounded to the ground (GND line) and a cathode side connected to the cathode side of the light emitting diode PD1 of the photocoupler PC1. The Zener diode ZD2 has an anode side connected to the collector of the transistor Q3 (grounded to the ground (GND line) via the transistor Q3), and a cathode side connected to a connection point between the light emitting diode PD1 and the Zener diode ZD1 of the photocoupler PC1. ing. The transistor Q3 has an emitter grounded to the ground (GND line) and a base connected to the control signal CS line, and is turned on when the control signal CS is input, and is turned off when the control signal CS is not input. .

  The Zener diode ZD1 and the Zener diode ZD2 of the constant voltage control circuit 32 have different Zener voltages (breakdown voltages), and the Zener voltage of the Zener diode ZD1 is higher than the Zener voltage of the Zener diode ZD2. Here, as described above, when the printer 60 is in the sleep state, since the control signal CS is input from the printer 60 and the transistor Q3 is turned on, a reverse current can be passed through the Zener diode ZD2 having a low Zener voltage. it can. For this reason, even when the voltage Vout is relatively low, a current flows through the light emitting diode PD1 of the photocoupler PC1 to emit light, and a current also flows through the phototransistor PT1 that has received the light emission. A constant voltage control signal (hereinafter referred to as a feedback signal) is input. At this time, the light emission amount of the light emitting diode PD1 changes according to the current flowing through the light emitting diode PD1, that is, the voltage Vout, and the current flowing through the phototransistor PT1 changes according to the light emission amount of the light emitting diode PD1. Is input to the control IC 38 as a signal corresponding to the voltage Vout. On the other hand, when the printer 60 is in the normal state, the control signal CS is not input from the printer 60 and the transistor Q3 is turned off, so that a reverse current cannot flow through the Zener diode ZD2. For this reason, when the voltage Vout is low (the voltage Vout is lower than the Zener voltage of the Zener diode ZD1), no current flows through the light emitting diode PD1 of the photocoupler PC1, and no feedback signal is input to the control IC 38. When the voltage Vout is high (the voltage Vout is higher than the Zener voltage of the Zener diode ZD1), a reverse current can flow through the Zener diode ZD1, so that a current flows through the light emitting diode PD1 of the photocoupler PC1. A feedback signal is input to the control IC 38. Also in this case, the feedback signal is input to the control IC 38 as a signal corresponding to the voltage Vout. As described above, when the printer 60 is in the sleep state and the control signal CS is input, a feedback signal corresponding to the voltage Vout is input to the control IC 38 from the low output voltage state where the voltage Vout is relatively low, and the printer 60 is normally operated. When the control signal CS is not input, the feedback signal corresponding to the voltage Vout is input to the control IC 38 from the high output voltage state where the voltage Vout is relatively high.

  The drive voltage output circuit 34 includes a first output line 35a capable of outputting to the control IC 38 a voltage V1 obtained by rectifying and smoothing the AC voltage induced in the first auxiliary winding 25c by the diode D2 and the smoothing capacitor C3. And a second output line 35b capable of outputting to the control IC 38 a voltage V2 obtained by rectifying and smoothing the AC voltage induced in the second auxiliary winding 25d by the diode D3 and the smoothing capacitor C2. In addition, the driving voltage output circuit 34 includes a switching element (MOSFET) QF2 as a switch whose drain and source are connected to the first output line 35a and switches between conduction and interruption of the first output line 35a, and this switching. And a switch switching circuit 36 for switching on / off of the element QF2. The switch switching circuit 36 includes resistors R1 to R5 and transistors (bipolar transistors) Q1 and Q2. The resistor R1 is connected in parallel between the gate and source of the switching element QF2. The transistor Q1 has a collector connected to the gate of the switching element QF2 via a resistor R2, an emitter grounded to the ground, and a base connected to the first output line 35a via a resistor R3. The resistors R4 and R5 are connected in series between the first output line 35a and the ground, and divide the voltage V1 of the first output line 35a. In the transistor Q2, the collector is connected to the base of the transistor Q1, the emitter is grounded, and the base is connected to the connection point of the resistors R4 and R5. Further, the drain of the switching element QF2 of the first output line 35a and the cathode side of the diode D3 of the second output line 35b are connected, and the control IC 38 side from the connection point is the control IC 38 as a common line. Connected to a VCC terminal described later. In the following description, the voltage V1 of the first output line 35a may be referred to as the voltage V1 from the first auxiliary winding 25c, and the voltage V2 of the second output line 35b may be referred to as the second voltage V2. May be referred to as a voltage V2 from the auxiliary winding 25d.

  The control IC 38 is configured as an IC chip for controlling the switching of the switching element QF1, and includes an HV terminal, an FB terminal, a GND terminal, a DRV terminal, and a VCC terminal. The HV terminal is connected to the input side of the first rectifying and smoothing circuit 21 via the diode D1, and a voltage for starting the control IC 38 is input thereto. The FB terminal is connected to the collector of the phototransistor PT1 of the photocoupler PC1, and receives the feedback signal of the constant voltage control circuit 32 described above. The GND terminal is grounded, and the DRV terminal outputs a switching signal (hereinafter referred to as a switching signal) to the gate of the switching element QF1 of the switching circuit 23. The VCC terminal is connected to the first output line 35a and the second output line 35b of the drive voltage output circuit 34, and receives the drive voltage. The control IC 38 is driven by the voltage input from the HV terminal while the switching control is not being performed, and the first output line 35a or the second output of the driving voltage output circuit 34 while the switching control is being performed. It is driven by the driving voltage output from the line 35b and input from the VCC terminal.

  The control IC 38 generates a switching signal based on the feedback signal from the constant voltage control circuit 32, and outputs the generated switching signal from the DRV terminal to the switching circuit 23 (switching element QF1). As described above, the printer 60 switches the presence / absence of the output of the control signal CS according to the required power supply voltage. In the constant voltage control circuit 32, the voltage Vout is a low output voltage depending on the presence / absence of the input of the control signal CS. The feedback signal is input to the control IC 38 from the state, or the feedback signal is input to the control IC 38 from the state where the voltage Vout is a high output voltage. Therefore, although details are omitted, the control IC 38 performs feedback control so that the voltage Vout becomes high (for example, 40 V) according to the high power supply voltage required by the printer 60 when the control signal CS is not input. When the control signal CS is input, feedback control is performed so that the voltage Vout is lowered (for example, 10 V) according to the low power supply voltage required by the printer 60.

  Next, the operation of the thus configured AC adapter 10 of the present embodiment, in particular, the change in the driving voltage from the driving voltage output circuit 34 based on the control signal CS will be described. First, a case where the printer 60 is in a normal state and the control signal CS is not input will be described. When the control signal CS is not input, as described above, the control IC 38 feedback-controls the switching circuit 23 (switching element QF1) so that the voltage Vout becomes high, so that the voltage Vout becomes a high output voltage. In this case, the AC voltage induced in the first auxiliary winding 25c and the second auxiliary winding 25d exceeds the predetermined voltage and becomes relatively high. Here, when the AC voltage induced in the first auxiliary winding 25c exceeds a predetermined voltage and becomes relatively high, a voltage (voltage V1 divided by the resistors R4 and R5) acting on the base of the transistor Q2 is generated. It goes high and transistor Q2 is turned on. When the transistor Q2 is turned on, the voltage acting on the base of the transistor Q1 is lowered, the transistor Q1 is turned off, the potential difference between the gate and the source of the switching element QF2 is eliminated, and the switching element QF2 is turned off. That is, when the AC voltage induced in the first auxiliary winding 25c is higher than a predetermined voltage, the switching element QF2 is turned off by the switch switching circuit 36, and the first output line 35a is cut off. For this reason, the voltage V2 from the second auxiliary winding 25d is output from the driving voltage output circuit 34 instead of the voltage V1 from the first auxiliary winding 25c. Therefore, when the voltage Vout is a high output voltage, the voltage V2 from the second auxiliary winding 25d having a small number of turns can be supplied to the control IC 38. That is, when the voltage Vout is a high output voltage, the high voltage V1 from the first auxiliary winding 25c having a large number of turns is supplied to the control IC 38, for example, a high voltage exceeding the maximum rating of the control IC 38. Inconveniences such as supply of a driving voltage can be prevented.

  Next, a case where the printer 60 is in the sleep state and the control signal CS is input will be described. When the control signal is input, as described above, the control IC 38 feedback-controls the switching circuit 23 (switching element QF1) so that the voltage Vout becomes low, so that the voltage Vout becomes a low output voltage. In this case, since the voltage induced in the first auxiliary winding 25c is lower than the predetermined voltage and becomes relatively low, the voltage acting on the base of the transistor Q2 becomes low and the transistor Q2 is turned off. When the transistor Q2 is turned off, the transistor Q1 is turned on, a potential difference corresponding to the ratio of the resistors R1 and R2 is generated between the gate and source of the switching element QF2, and the switching element QF2 is turned on. That is, when the AC voltage induced in the first auxiliary winding 25c is lower than a predetermined voltage, the switching element QF2 is turned on by the switch switching circuit 36, and the first output line 35a is turned on. Therefore, the driving voltage output circuit 34 outputs the voltage V1 from the first auxiliary winding 25c. Therefore, when the voltage Vout is a low output voltage, the voltage V1 from the first auxiliary winding 25c having a large number of turns can be supplied to the control IC 38. That is, when the voltage Vout is a low output voltage, the voltage V2 from the second auxiliary winding 25d having a small number of turns is supplied to the control IC 38, for example, the minimum operating voltage of the control IC 38 cannot be secured. Inconvenience can be prevented. Accordingly, a stable driving voltage can be supplied to the control IC 38 in accordance with the control signal CS.

  Here, the number of turns (number of turns) of the secondary winding 25b is Nb [T], the number of turns of the first auxiliary winding 25c is Nc [T], and the number of turns of the second auxiliary winding 25d is Nd [T], An example of Nc, Nd, R4, and R5 will be described assuming that the resistor R4 is R4 [kΩ] and the resistor R5 is R5 [kΩ]. First, the voltage V1 from the first auxiliary winding 25c and the voltage V2 from the second auxiliary winding 25d need to be within the range between the minimum operating voltage VL and the maximum rated VH of the control IC 38. Expressions (1) and (2) are established. Further, from the relationship between the number of turns and the voltage, the following expressions (3) and (4) are established. Furthermore, since the voltage Vbe applied between the base and emitter of the transistor Q2 is the voltage V1 divided by the resistors R4 and R5, the following equation (5) is established.

VL <V1 <VH (1)
VL <V2 <VH (2)
Nc × Vout = Nb × V1 (3)
Nd × Vout = Nb × V2 (4)
Vbe = V1 × R5 / (R4 + R5) (5)

  At this time, the high output voltage of the voltage Vout is 40 [V], the low output voltage is 10 [V], the number of turns Nb is 20 [T], the minimum operating voltage VL of the control IC 38 is 10 [V], and the maximum rated VH is 30. [V], and the voltage Vbe required for the operation (ON) of the transistor Q2 is 0.6 [V]. In the present embodiment, when the voltage Vout is 10 V, the voltage V1 from the first auxiliary winding 25c is supplied to the control IC 38, so that the number of turns of the first auxiliary winding 25c is obtained from the equations (1) and (3). Nc may satisfy the following expression (6). In addition, when the voltage Vout is 40 V, the voltage V2 from the second auxiliary winding 25d is supplied to the control IC 38. From the equations (2) and (4), the number of turns Nd of the second auxiliary winding 25d is The following equation (7) should be satisfied. For this reason, for example, the number of turns Nc of the first auxiliary winding 25c is set to 40 [T], and the number of turns Nd of the second auxiliary winding 25d is set to 10 [T]. In this case, when the voltage Vout is a low output voltage of 10 [V], the voltage V1 from the first auxiliary winding 25c becomes 20 [V] and is output as a driving voltage. In addition, when the voltage Vout is a high output voltage of 40 [V], the voltage V1 from the first auxiliary winding 25c is 80 [V], but the transistor Q2 is turned on and the switching element QF2 is turned off. The voltage V2 from the second auxiliary winding 25d is 20 [V] and is not output as a driving voltage, but is output as a driving voltage. Furthermore, it is necessary that the voltage V1 does not exceed 30 [V], which is the maximum rated VH, even during the transition of the voltage Vout from the low voltage to the high voltage. For this reason, for example, consider resistors R4 and R5 that turn on the transistor Q2 when the voltage V1 becomes 25 [V]. In this case, the value 25 can be substituted into the voltage V1 in the equation (5) and the value 0.6 can be substituted into the voltage Vbe to derive the following equation (8). Therefore, as an example, the resistor R4 is set to 200 [kΩ], The resistor R5 can be set to 5 [kΩ] or the like. By defining in this way, not only when the voltage Vout is a low output voltage or a high output voltage, but also during the switching from the low output voltage to the high output voltage, a stable drive voltage while protecting from overvoltage Can be supplied to the control IC 36.

20 <Nc <60 (6)
5 <Nd <15 (7)
r4≈40 × r5 (8)

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The first rectifying / smoothing circuit 21 of the present embodiment corresponds to the “first rectifying / smoothing circuit” of the present invention, the switching circuit 23 corresponds to the “switching circuit”, the transformer 25 corresponds to the “transformer”, the first The second rectifying / smoothing circuit 27 corresponds to a “second rectifying / smoothing circuit”, the constant voltage control circuit 32 corresponds to a “constant voltage control circuit”, the control IC 38 corresponds to a “control IC”, and outputs a driving voltage. The circuit 34 corresponds to a “driving voltage output circuit”. Further, the first output line 35a corresponds to a “first output line”, the second output line 35b corresponds to a “second output line”, and the switching element QF2 (MOSFET) corresponds to a “switch”. To do.

  According to the AC adapter 10 of the present embodiment described in detail above, the control signal CS based on the power supply voltage required by the printer 60 is input, and the control IC 38 has a constant voltage according to the control signal CS. The switching circuit 23 is feedback-controlled based on the feedback signal. Also, a first auxiliary winding 25c and a second auxiliary winding 25d wound on the primary side with different numbers of turns are provided in the transformer 25, and the first auxiliary winding 25c and the second auxiliary winding are provided. A driving voltage output circuit 34 capable of outputting a voltage corresponding to the control signal CS among the AC voltage induced in 25d as a driving voltage for the control IC 38 is provided. For this reason, when the voltage Vout is high, the voltage V2 from the second auxiliary winding 25d having a small number of turns can be output as a driving voltage to protect the control IC 38 from an overvoltage. When the voltage Vout is low, The driving voltage can be stabilized by outputting the voltage V1 from the first auxiliary winding 25c having a large number of turns as the driving voltage. As a result, it is possible to supply a stable drive voltage to the control IC 38 while preventing an excessive voltage from acting on the control IC 38 in a normal time when no overvoltage is generated on the secondary side.

  The drive voltage output circuit 34 also outputs a first output line 35a that outputs the voltage V1 from the first auxiliary winding 25c and a second output that outputs the voltage V2 from the second auxiliary winding 25d. Line 35b and a switching element QF2 as a switch for switching between conduction and interruption of the first output line 35a, and switching on and off of the switching element QF2 depending on whether or not the control signal CS is input. When a two-stage voltage, ie, a low power supply voltage, is selectively output to the printer 60, a stable driving voltage can be supplied to the control IC 38 with a simple configuration. Further, the switching element QF2 is turned off by the voltage V1 when the voltage Vout is a high output voltage and is turned on by the voltage V1 when the voltage Vout is a low output voltage. A more appropriate driving voltage can be output using the change in the voltage V1 from the line 25c. The driving voltage output circuit 34 can have a relatively compact circuit configuration using MOSFETs, transistors, and resistors.

  In addition, this invention is not limited to the embodiment mentioned above at all, and it cannot be overemphasized that it can implement with a various aspect, as long as it belongs to the technical scope of this invention.

  In the above-described embodiment, the level of the voltage Vout is switched by feedback control according to the presence or absence of the input of the control signal CS, and the switching element QF2 is switched on and off using the change in the voltage V1 from the first auxiliary winding 25c. In other words, the switching element QF2 is turned on / off indirectly using the presence or absence of the input of the control signal CS. However, the present invention is not limited to this. For example, the on / off state of the switching element QF2 may be switched by directly using the presence / absence of the input of the control signal CS. A modified example in this case will be described. FIG. 3 is a circuit configuration diagram of the power supply circuit 20B of the AC adapter 10 according to the modification.

  As shown in FIG. 3, the power supply circuit 20B includes a drive voltage output circuit 34B instead of the drive voltage output circuit 34 of FIG. 2 of the present embodiment (more specifically, a switch instead of the switch switching circuit 36). 2) has the same configuration as each configuration of the power supply circuit 20 in FIG. 2, the same configuration is denoted by the same reference numeral, and the description thereof is omitted. The driving voltage output circuit 34B switches the first output line 35a, the second output line 35b, the switching element QF2 for switching between conduction and interruption of the first output line 35a, and switching on / off of the switching element QF2. A switch switching circuit 36B. The switch switching circuit 36B includes a resistor R1 connected between the gate and source of the switching element QF2, a resistor R2 connected to the gate of the switching element QF2, and a photocoupler PC2. This photocoupler PC2 has a light emitting diode PD2 whose anode side is connected to the control signal CS line and whose cathode side is grounded to the ground GND, a collector which is connected to the gate of the switching element QF2 via a resistor R2, and an emitter which is grounded. It comprises a phototransistor PT2.

  In the drive voltage output circuit 34B configured as described above, when the control signal CS is input from the printer 60, a current flows through the light emitting diode PD2 of the photocoupler PC2, the light emitting diode PD2 emits light, and the light emission is performed. Since a current flows through the received phototransistor PT2, a potential difference is generated between the gate and the source of the switching element QF2, and the switching element QF2 is turned on. Thus, when the control signal CS is input, the first output line 35a is turned on, and the voltage V1 from the first auxiliary winding 25c is supplied to the control IC 38. On the other hand, when the control signal CS is not input from the printer 60, no current flows through the light emitting diode PD2 of the photocoupler PC2, so the light emitting diode PD2 does not emit light, and no current flows through the phototransistor PT2, so the switching element QF2 Is turned off. Thereby, when the control signal CS is not input, the first output line 35a is cut off, and the voltage V2 from the second auxiliary winding 25d having a small number of turns is supplied to the control IC 38. As described above, also in the power supply circuit 20B of the modified example, when the printer 60 is in the sleep state and the control signal CS is input as in the present embodiment, the first auxiliary winding 25c having a large number of turns is output from the first auxiliary winding 25c. The high voltage V1 can be supplied to the control IC 38, and when the printer 60 is in a normal state and the control signal CS is not input, the low voltage V2 from the second auxiliary winding 25d having a small number of turns is supplied to the control IC 38. Therefore, the same effect as that of the present embodiment can be obtained. Further, the number of components necessary for the driving voltage output circuit 38B (switch switching circuit 36B) can be reduced, and a simpler circuit configuration can be achieved.

  In the above-described embodiment, the control signal CS from the printer 60 is not input in the normal state but is input in the sleep state. However, the present invention is not limited to this, and the control signal CS is input in the normal state and not input in the sleep state. It may be a thing. In that case, the switching voltage element QF2 that switches between conduction and interruption of the first output line 35a is turned off when the control signal CS is input, and the drive voltage output circuit 38 is turned on when the control signal CS is not input. (Switch switching circuit 36) may be configured.

  In the embodiment described above, the transformer 25 includes two auxiliary windings, the first auxiliary winding 25c and the second auxiliary winding 25d. However, the present invention is not limited to this, and three or more auxiliary windings are provided. A line may be provided. In this case, the printer 60 requires a plurality of stages of power supply voltages of three or more stages, and a signal indicating that any one of the three or more stages of power supply voltages is required as the control signal CS is input. The output line from each auxiliary winding may be switched between conduction and interruption according to the signal.

  In the above-described embodiment, the conduction and interruption of the first output line 35a are switched by turning on and off the switching element QF2. However, the present invention is not limited to this, and may be switched by another semiconductor switch such as a transistor. Alternatively, any switch may be used as long as it switches between conduction and interruption of the first output line 35a based on the control signal CS.

  In the above-described embodiment, one of the AC voltages induced in the first auxiliary winding 25c and the second auxiliary winding 25d is output by switching between conduction and interruption of the first output line 35a. However, the present invention is not limited to this, and any configuration can be used as long as it can output a DC voltage obtained by rectifying and smoothing an AC voltage induced in one of the auxiliary windings according to the control signal CS as a driving voltage. It is good also as what to do.

  In the above-described embodiment, the voltage Vout is set to 10 V as a low output voltage. However, the voltage Vout is not limited to this, and may be the lowest voltage required by the printer 60 (3.3 V in this embodiment). Even in this case, the minimum operating voltage of the control IC 38 can be secured by adjusting the number Nc of turns of the first auxiliary winding 25c. In this way, 3.3V can be directly supplied to the low voltage system of the printer 60 without going down by the DC / DC converter 72 of the printer 60 during sleep. Conversion loss of the converter 72 can be reduced.

  In the above-described embodiment, the AC adapter 10 according to the present invention has been described as supplying the power supply voltage to the printer 60. However, the present invention is not limited to this, and the AC adapter 10 operates when the power supply voltage is supplied from the AC adapter. Any device that outputs a control signal may supply power to any other electrical device such as a portable personal computer, a video camera, a music player, or a portable information terminal. In addition, the power supply is not limited to the one that inputs a commercial power supply, and any power supply may be input as long as the power supply voltage is supplied from the input power supply to the electric device.

  10 AC adapter, 20, 20B power supply circuit, 21 first rectifying / smoothing circuit, 23 switching circuit, 25 transformer, 25a primary winding, 25b secondary winding, 25c first auxiliary winding, 25d second auxiliary Winding, 27 Second rectifying / smoothing circuit, 32 Constant voltage control circuit, 34, 34B Driving voltage output circuit, 35a First output line, 35b Second output line, 36, 36B Switch switching circuit, 38 Control IC , 60 printer, 62 printer unit, 63 printer mechanism, 64 printer ASIC, 66 main controller, 67 CPU, 68 flash memory, 69 RAM, 70 power management unit, 72 DC / DC converter, C1, C2, C3, C4 smoothing capacitor D1, D2, D3, D4 diode, DB1 Diode bridge, PC1, PC2 photocoupler, PD1, PD2 light emitting diode, PT1, PT2 phototransistor, Q1, Q2, Q3 transistor, QF1, QF2 switching element (MOS type FET), R1, R2, R3, R4, R5 resistance, ZD1, ZD2 Zener diode.

Claims (7)

A power supply control device that inputs the control signal from an electrical device that outputs a control signal based on a required power supply voltage and supplies the power supply voltage to the electrical device,
A first rectifying / smoothing circuit that rectifies and smoothes an input power supply and outputs a DC voltage;
A switching circuit that converts the DC voltage output from the first rectifying and smoothing circuit into an AC voltage by switching;
A primary winding wound on the primary side and applied with an AC voltage converted by the switching circuit, a secondary winding wound on the secondary side, and winding on the primary side with different numbers of turns. A transformer having a plurality of rotated auxiliary windings;
A second rectifying / smoothing circuit that rectifies and smoothes the AC voltage induced in the secondary winding of the transformer and outputs the DC voltage to the electrical device;
A feedback signal is generated based on the output voltage so that the output voltage output from the second rectifying / smoothing circuit becomes a constant voltage according to the control signal, and the generated feedback signal is sent to the primary side of the transformer. A constant voltage control circuit for transmission;
A control IC that operates in response to the supply of a driving voltage, inputs the transmitted feedback signal, generates a switching signal of the switching circuit based on the feedback signal, and outputs the switching signal;
A driving voltage output circuit capable of outputting, as the driving voltage, a DC voltage obtained by rectifying and smoothing an AC voltage induced in the plurality of auxiliary windings according to the control signal;
A power supply control device comprising: The power supply control device according to claim 1,
The power supply control device according to claim 1, wherein the power supply voltage is supplied to the electrical equipment that selectively requires either a high power supply voltage or a low power supply voltage.
The transformer has, as the plurality of auxiliary windings, a first auxiliary winding and a second auxiliary winding having a smaller number of turns than the first auxiliary winding,
The driving voltage output circuit includes:
A first output line that outputs a smoothed DC voltage by rectifying the AC voltage induced in the first auxiliary winding, and a DC voltage that rectifies and smoothes the AC voltage induced in the second auxiliary winding. A second output line that outputs and a switch that switches between conduction and interruption of the first output line,
The switch is turned off so that the first output line is cut off when the control signal requires the high power supply voltage, and the first signal when the control signal requires the low power supply voltage. The power supply control device is characterized in that the switch is turned on so that the output line is turned on. The power supply control device according to claim 2,
The driving voltage output circuit includes a high voltage of the first output line when a high output voltage is output from the second rectifying and smoothing circuit in a signal state in which the control signal requires the high power supply voltage. The switch is turned off by the low voltage of the first output line when the control signal is in a signal state requiring the low power supply voltage and the low output voltage is output from the second rectifying and smoothing circuit. The power supply control device, wherein the switch is turned on. The power supply control device according to claim 3,
The driving voltage output circuit includes:
A first semiconductor switch as the switch;
A second semiconductor switch that turns on the first semiconductor switch when turned on and turns off the first semiconductor switch when turned off;
When the high output voltage is output from the second rectifying / smoothing circuit in a signal state where the control signal requires the high power supply voltage, the second semiconductor switch is turned on by the high voltage of the first output line. The second output is caused by the low voltage of the first output line when the low output voltage is output from the second rectifying and smoothing circuit in a signal state in which the control signal requires the low power supply voltage. A third semiconductor switch for turning on the semiconductor switch;
A power supply control device comprising: The power supply control device according to claim 4,
The first semiconductor switch is a MOSFET having a source and a drain connected to the first output line,
The second semiconductor switch is a first transistor;
The third semiconductor switch is a second transistor;
In the driving voltage output circuit, a first resistor, a second resistor, and a collector and an emitter of the first transistor are connected in series to the first output line, and a third resistor is connected to the first output line. And a collector and an emitter of the second transistor are connected in series with each other, and a fourth resistor and a fifth resistor are connected in series with the first output line, so that the first resistor and the second resistor are connected. A connection point of the second resistor is connected to the gate of the MOSFET, a connection point of the third resistor and the collector of the second transistor is connected to a base of the first transistor, and the fourth resistor And the fifth resistor is connected to the base of the second transistor. A power supply control device, comprising: The power supply control device according to claim 2,
The driving voltage output circuit includes:
A first semiconductor switch as the switch;
A light emitting element that emits light upon receiving a signal that requires the high power supply voltage as the control signal, and that stops light emission upon receipt of a signal that requires the low power supply voltage as the control signal;
A light receiving element that turns off the first semiconductor switch when receiving light emitted from the light emitting element and turns on the first semiconductor switch when not receiving light emitted from the light emitting element;
A power supply control device comprising: The power supply control device according to claim 6,
The first semiconductor switch is a MOSFET having a source and a drain connected to the first output line,
The light emitting element is a photodiode whose anode side is connected to the input line of the control signal and whose cathode side is grounded.
The light receiving element is a phototransistor,
In the driving voltage output circuit, a first resistor, a second resistor, and a collector and an emitter of the phototransistor are connected in series to the first output line, and the first resistor and the second resistor are connected to each other in series. A connection point with a resistor is connected to the gate of the MOSFET.

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