Control circuit

Abstract

To achieve a power-saving mode at low cost.SOLUTION: A control circuit (10) includes: a first DC-DC converter (DDC1) for receiving power from a switching power supply (21); a second DC-DC converter (DDC2) for receiving power from the switching power supply or the first DC-DC converter; a main control circuit (ICc) for receiving power from the second DC-DC converter; and a mode control circuit (ICm) for receiving power from an auxiliary power supply (22).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control circuit for a power supply system using a switching power supply. [Background technology]

[0002] In electrical devices such as printers, power supply systems are used that can reduce the power consumption of the electrical devices by monitoring the usage status of the electrical devices and switching them to a power saving mode during standby periods. Patent Document 1 discloses a power supply system that includes a switching power supply and a control circuit (such as a control device) that includes a mode control circuit (mode control block) that monitors the usage status of the electrical devices and determines the power mode.

[0003] In the conventional technology of Patent Document 1, a mode control circuit instructs a power supply control circuit, which controls a switching element in a switching power supply, to turn on / off a switching operation, thereby switching the power mode. In the power saving mode, the switching operation is stopped, and power consumption inside the switching power supply and in the circuits that receive power from the switching power supply is almost eliminated. In the power saving mode, power is no longer supplied from the switching power supply, which is the main power supply, so that the mode control circuit is supplied with power from a small-capacity power supply circuit, which is a sub-power supply. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-31337 A Summary of the Invention [Problem to be solved by the invention]

[0005] The power supply system of the prior art in Patent Document 1 has a circuit configuration that assumes that the power supply control circuit of the switching power supply, which is commercialized under the name of a power supply control IC (Integrated Circuit) or the like, operates by receiving an external command to turn on / off the switching operation. However, a power supply control IC that can receive such a signal to realize the on / off switching operation of the switching power supply is more expensive than a power supply control IC that does not receive such a signal.

[0006] In addition, the primary side of a switching power supply is usually insulated from other circuits. For this reason, a photocoupler is used to transmit the above signal from the control circuit side to the power supply control IC. However, photocouplers are relatively expensive electronic components, which leads to high costs for the power supply system.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a control circuit that can realize a power saving mode at low cost in a power supply system equipped with a switching power supply. [Means for solving the problem]

[0008] In order to solve the above problems, a control circuit according to a first aspect of the present invention includes a first DC-DC converter that receives power from a switching power supply and outputs power, a second DC-DC converter that receives power from the switching power supply or the first DC-DC converter and outputs power, a main control circuit that operates by receiving power from the second DC-DC converter, and a mode control circuit that operates by receiving power from an auxiliary power supply, wherein the mode control circuit is capable of sending either an enable command or a disable command to a DC-DC converter arranged between the switching power supply and the main control circuit, of the first DC-DC converter and the second DC-DC converter, A DC-DC converter disposed between the switching power supply and the main control circuit, The power supply device includes a configuration for outputting power in accordance with the enable command and for stopping the output of power in accordance with the disable command.

[0009] The control circuit according to a second aspect of the present invention may be configured in such a way that in the first aspect, the disable command is a no-voltage signal.

[0010] The control circuit according to aspect 3 of the present invention is the control circuit of aspect 1 or 2 above, further comprising a first power supply line for supplying power from the auxiliary power supply to the mode control circuit, and a second power supply line for supplying power from the first DC-DC converter to the mode control circuit, and the mode control circuit may be configured to be capable of sending either the enable command or the disable command to the second DC-DC converter disposed between the switching power supply and the main control circuit.

[0011] A control circuit according to a fourth aspect of the present invention may be configured in such a manner that in the third aspect, the second power supply line is connected to the first power supply line.

[0012] A control circuit according to a fifth aspect of the present invention is based on the fourth aspect, and may further include a diode provided in the second power supply line, the cathode of which is connected to the first power supply line.

[0013] A control circuit according to a sixth aspect of the present invention may be configured in any one of the third to fifth aspects above, wherein the second DC-DC converter is capable of receiving power from the first DC-DC converter and outputting power, and the mode control circuit is capable of sending either the enable command or the disable command to the first DC-DC converter arranged between the switching power supply and the second DC-DC converter, and when it is determined that the power supplied from the auxiliary power supply is sufficient, it sends the disable command to the first DC-DC converter, and when it is determined that the power supplied from the auxiliary power supply is insufficient, it sends the enable command to the first DC-DC converter and sends the disable command to the second DC-DC converter.

[0014] A control circuit according to a seventh aspect of the present invention may be configured in accordance with the sixth aspect above, wherein the mode control circuit determines that the power supplied from the auxiliary power source is insufficient by detecting that the voltage supplied from the auxiliary power source through the first power supply line is less than a predetermined value.

[0015] The control circuit according to aspect 8 of the present invention may be configured in such a way that, in aspect 6 or 7 above, when the mode control circuit determines that the power supplied from the auxiliary power supply is sufficient, it further sends the disable command to the second DC-DC converter.

[0016] A control circuit according to a ninth aspect of the present invention may be configured in such a way that, in the above-mentioned first or second aspect, the second DC-DC converter is capable of receiving power from the first DC-DC converter and outputting power, and the mode control circuit is capable of sending either the enable command or the disable command to the first DC-DC converter disposed between the switching power supply and the second DC-DC converter. Effect of the Invention

[0017] According to one embodiment of the present invention, it is possible to provide a control circuit that can realize a power saving mode at low cost in a power supply system including a switching power supply. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram showing the configuration of a control circuit according to a first embodiment of the present invention and a power supply system to which the control circuit is applied. [Diagram 2] FIG. 11 is a circuit diagram showing the configuration of a control circuit according to a second embodiment of the present invention and a power supply system to which the control circuit is applied. [Diagram 3] FIG. 11 is a functional block diagram showing a configuration of a mode control circuit of a control circuit according to a second embodiment of the present invention. [Figure 4] 10 is a flowchart showing a power saving mode transition process performed by a main control circuit of a control circuit according to a second embodiment of the present invention. [Diagram 5] 10 is a flowchart showing a normal mode process performed by a mode control circuit of a control circuit according to a second embodiment of the present invention. [Figure 6] 10 is a flowchart showing a power saving mode process performed by a mode control circuit of a control circuit according to a second embodiment of the present invention. [Figure 7] 10 is a flowchart showing a main control circuit startup process performed by a main control circuit of a control circuit according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a circuit diagram showing the configuration of a control circuit according to a third embodiment of the present invention and a power supply system to which the control circuit is applied. [Figure 9] FIG. 1 is a block diagram showing a schematic configuration of a control circuit of a conventional technology and a power supply system to which the control circuit is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [Embodiment 1] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] <Power supply system> 1 is a block diagram showing the configuration of a control circuit 10 according to the first embodiment and a power supply system 1 to which the control circuit 10 is applied. The power supply system 1 is mounted on an electric device such as a printer.

[0021] The control circuit 10 of the power supply system 1 monitors the state of each part of the electric device, and when it is expected that the required operation of the electric device, for example, printing in the case of a printer, will not be performed for a long time, it switches the electric device to a power saving mode. In the power saving mode, the supply of power to each predetermined part of the electric device is stopped. In the power saving mode, the supply of power to the main control circuit ICc mounted on the control circuit 10 is also stopped.

[0022] For example, when it is determined that the required operation of the electrical device is to be performed, such as when a user operates a switch, the power supply system 1 returns to the normal mode and resumes the supply of power to each component of the electrical device and to the main control circuit ICc. In this way, the power supply system 1 has a function of suppressing power consumption by applying a power saving mode in order to reduce the power consumption of the entire electrical device.

[0023] The power supply system 1 includes a control circuit 10, a switching power supply 21, and a small-capacity power supply 22 (auxiliary power supply). AC power is supplied to each of the switching power supply 21 and the small-capacity power supply 22 from an AC power supply external to the electrical device. As shown in FIG. 1, the switching power supply 21 and the small-capacity power supply 22 may be formed on the same power supply board 20.

[0024] <Switching power supply> The switching power supply 21 is a main power supply that generates DC power to be supplied to each part of the electric device from AC power received from outside the electric device. The switching power supply 21 is equipped with power supply control circuit ICs that control the switching operation of the switching power supply 21. The power supply control circuit ICs having such functions are manufactured as integrated circuits (ICs) under names such as power supply control IC and switching power supply control IC.

[0025] <Small capacity power supply (auxiliary power supply)> The small-capacity power supply 22 is a DC power supply for supplying DC power to the mode control circuit ICm in the control circuit 10 through the first power supply line regardless of whether the power supply system 1 is in the normal mode or the power saving mode.

[0026] The auxiliary power supply for supplying DC power to the mode control circuit ICm is not limited to the above-mentioned small-capacity power supply 22 that receives AC power from an AC power supply and supplies small-capacity DC power. For example, it may be a power supply provided with a storage device such as a secondary battery or a capacitor that is charged during normal mode and supplies DC power to the mode control circuit ICm at least during power saving mode. Alternatively, it may be a power supply provided with a photovoltaic cell or primary battery that supplies small-capacity DC power to the mode control circuit ICm at least during power saving mode.

[0027] <Control circuit> The control circuit 10 includes a first DC-DC converter DDC1, a second DC-DC converter DDC2, a main control circuit ICc, and a mode control circuit ICm. The first DC-DC converter DDC1 can receive power from a switching power supply 21 and output DC power. The second DC-DC converter can receive power from the first DC-DC converter DDC1 and output DC power.

[0028] The main control circuit ICc operates by receiving power from the second DC-DC converter DDC2. The mode control circuit ICm operates by receiving power from the small-capacity power supply 22. Therefore, the mode control circuit ICm can operate regardless of whether the mode is the power saving mode or the normal mode.

[0029] The mode control circuit ICm sends a first operation control signal Se1 indicating either a first enable command or a first disable command to the first DC-DC converter DDC1. The first DC-DC converter DDC1 outputs power in accordance with the first enable command and stops outputting power in accordance with the first disable command.

[0030] The mode control circuit ICm also sends a second operation control signal Se2 indicating either a second enable command or a second disable command to the second DC-DC converter DDC2. The second DC-DC converter DDC2 outputs power in accordance with the second enable command and stops outputting power in accordance with the second disable command.

[0031] The mode control circuit ICm can set the state of the power supply system 1 to the normal mode by sending a first enable command to the first DC-DC converter DDC1 and a first enable command to the second DC-DC converter DDC2. Also, the mode control circuit ICm can set the state of the power supply system 1 to the power saving mode by sending a first disable command to the first DC-DC converter DDC1.

[0032] <Power supply system to which a conventional control circuit is applied> FIG. 9 is a block diagram showing the configuration of a conventional control circuit 10P and a power supply system 1P to which the control circuit 10P is applied, for comparison with the control circuit 10 and power supply system 1 according to the first embodiment.

[0033] Unlike the first embodiment, the power supply control circuit ICsP included in the switching power supply 21P of the prior art follows an operation control signal from a mode control circuit ICmP. In this way, the power supply control circuit ICsP switches between executing and stopping the switching operation of the switching power supply 21P, so that the power supply system 1P of the prior art can realize a normal mode in which the switching power supply 21P performs output, and a power saving mode in which it does not perform output. The power supply control circuit ICsP having such a function is also manufactured as an integrated circuit (IC) under the name of power supply control IC, switching power supply control IC, etc.

[0034] The primary side of a switching power supply is usually insulated from other circuits. For this reason, in the power supply system 1P of the prior art, the control circuit 10P is equipped with a photocoupler PC, and the operation control signal is transmitted to the mode control circuit ICmP in a state insulated from the control circuit 10P.

[0035] <Action and effect> In the power supply system 1P of the prior art, the power supply control circuit ICsP of the switching power supply 21P switches between execution and stop of the switching operation upon receiving an on / off command for the switching operation from the mode control circuit ICmP. However, a power supply control circuit having such a function is expensive compared to a power supply control circuit without such a function.

[0036] Furthermore, the power supply system 1P of the conventional technology requires a photocoupler PC to transmit an on / off command for the switching operation from the control circuit 10P. However, a photocoupler is a relatively expensive electronic component, which leads to an increase in the cost of the power supply system 1P.

[0037] However, in the power supply system 1 according to the first embodiment, inside the control circuit 10, the first DC-DC converter DDC1 on the upstream side (closer to the switching power supply) receives a command from the mode control circuit ICm and switches between outputting and stopping power output. Therefore, switching between normal mode and power saving mode can be achieved at a lower cost than in the prior art.

[0038] Also, inside the control circuit 10, the downstream second DC-DC converter DDC2 can switch between outputting and stopping power by receiving a command from the mode control circuit ICm without stopping the output of the first DC-DC converter DDC1. This makes it possible to realize a power saving mode while supplying power from the first DC-DC converter DDC1 to a required location, for example, a mode control IC.

[0039] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0040] <Power supply system> The second embodiment is a more specific embodiment of the configurations of the control circuit 10 and the power supply system 1 according to the first embodiment. Fig. 2 is a circuit diagram showing the control circuit 10 according to the second embodiment and the power supply system 1 to which the control circuit 10 according to the second embodiment is applied.

[0041] The power supply system 1 includes a control circuit 10, a switching power supply 21, and a small-capacity power supply 22 (auxiliary power supply). The switching power supply 21 and the small-capacity power supply 22 are each supplied with AC power from an AC power supply Vs external to the electrical device. As shown in FIG. 1, the switching power supply 21 and the small-capacity power supply 22 may be formed on the same power supply board 20. The switching power supply 21 is a main power supply that generates DC power to be supplied to each component of the electrical device. The small-capacity power supply 22 is a DC power supply that supplies DC power to a mode control circuit ICm in the control circuit 10 regardless of whether the power supply system 1 is in a normal mode or a power saving mode.

[0042] <Switching power supply> 2, the switching power supply 21 includes a transformer TR, and includes, as a primary circuit of the transformer TR, a diode bridge DB, a capacitor Cs, a switching element Qt, a DC voltage generating circuit 211, and a power supply control circuit ICs. The switching power supply 21 also includes, as a secondary circuit of the transformer TR, a secondary rectifying and smoothing circuit 212 and a voltage detection circuit VD.

[0043] The AC power from the AC power supply Vs is rectified and smoothed by a rectifying and smoothing circuit consisting of a diode bridge DB and a capacitor Cs, and is input to the primary side of the transformer TR via a switching element Qt. The switching element Qt is gate-controlled by a power supply control circuit ICs, and performs a switching operation that turns on and off the input to the primary side of the transformer TR.

[0044] The switching element Qt is a voltage-driven semiconductor element that is turned on / off by a gate voltage and may be a MOS-FET (Metal-Oxide Semiconductor Field Effect Transistor) or another FET.

[0045] A switching operation is performed by the switching element Qt under the control of the power supply control circuit ICs, and AC power is generated on the secondary side of the transformer TR. The AC power generated on the secondary side is rectified and smoothed by the secondary side rectifying and smoothing circuit 212, and is output as DC power from the switching power supply 21. A voltage detection circuit VD provided at the output stage of the switching power supply 21 monitors the output voltage of the switching power supply 21, and sends a voltage monitor signal as the output of the built-in photocoupler PC1 to the power supply control circuit ICs.

[0046] The DC voltage generating circuit 211 is a circuit that supplies DC power for operating the power supply control circuit ICs. The DC voltage generating circuit 211 is configured by a primary side secondary winding of the transformer TR and a rectifying and smoothing circuit connected thereto.

[0047] The power supply control circuit ICs, which controls the switching element Qt, is a circuit having the following functions: It receives power for the operation of the power supply control circuit ICs from the DC voltage generation circuit 211 via port Vcc. It outputs a gate control signal to the switching element Qt from port OUT. It receives a voltage monitor signal from the voltage detection circuit VD at port FB. The power supply control circuit ICs performs feedback control of the switching operation so that the output voltage of the switching power supply 21 becomes a predetermined value (24V in this specific example).

[0048] When AC input from the AC power supply Vs begins at port VH, it receives power to start up the power supply control circuit ICs. Power supply control circuit ICs with such functions are manufactured as integrated circuits (ICs) under names such as power supply control IC and switching power supply control IC.

[0049] In the switching power supply 21, a voltage monitor signal for the primary-side power supply control circuit ICs to feedback-control the output voltage of the switching power supply 21 is generated by the output of the photocoupler PC1 of the secondary-side voltage detection circuit VD. Therefore, the primary-side circuit and the secondary-side circuit of the transformer TR are configured to be insulated from each other.

[0050] <Small capacity power supply> The small-capacity power supply 22 (auxiliary power supply) is a power supply for supplying DC power to the mode control circuit ICm. The small-capacity power supply 22 includes an input capacitor C1, an input capacitor C2, an AC-DC converter ADC, and a charging capacitor Cc. The ground Vgd on the output side of the small-capacity power supply 22 is shared with the control circuit 10.

[0051] The AC input from the AC power supply Vs to the switching power supply 21 is branched and input to the AC-DC converter ADC through the input capacitors C1 and C2 connected to the input terminals of the AC-DC converter ADC. Therefore, the small-capacity power supply 22 can supply DC power to the mode control circuit ICm regardless of whether the power supply system 1 is in the normal mode or the power saving mode. A charging capacitor Cc is connected between the output terminals of the AC-DC converter ADC, which is also the output of the small-capacity power supply 22. As shown in FIG. 2, in the specific example of the first embodiment, the output voltage of the small-capacity power supply 22 is DC 3.3V.

[0052] <Control circuit> The control circuit 10 includes a first DC-DC converter DDC1, a second DC-DC converter DDC2, a main control circuit ICc, and a mode control circuit ICm. The first DC-DC converter DDC1 receives power from a switching power supply 21 and outputs power obtained by converting the voltage. The second DC-DC converter DDC2 receives power from the first DC-DC converter DDC1 and outputs power obtained by converting the voltage.

[0053] The first DC-DC converter DDC1 supplies DC power of a required voltage (5V as a specific example) to each part of the electric device. The second DC-DC converter DDC1 also supplies DC power of a required voltage (3.3V as a specific example) to each part of the electric device. As shown in Fig. 2, the control circuit 10 may further include a third DC-DC converter DDC3, a fourth DC-DC converter DDC4, etc. that supply DC power of the required voltages.

[0054] The main control circuit ICc is a circuit that operates by receiving power from the second DC-DC converter DDC2 in the normal mode and controls each part of an electrical device such as a printer. Therefore, the main control circuit ICc consumes a relatively large amount of power during operation. The mode control circuit ICm is a circuit that can operate by receiving power from the small-capacity power source 22 through the first power supply line Ln1 even in the power saving mode.

[0055] Furthermore, even if the power supply from the small-capacity power supply 22 becomes insufficient, the mode control circuit ICm can operate by receiving power from the first DC-DC converter DDC1 through the second power supply line Ln2. For this reason, as shown in FIG. 2, the second power supply line Ln2 is connected to the middle of the first power supply line Ln1. Also, a diode D is arranged in the second power supply line Ln2 so that the first power supply line Ln1 side is the cathode and the first DC-DC converter DDC1 side is the anode. By arranging the diode D, DC power is not supplied from the small-capacity power supply 22 to the first DC-DC converter DDC1 side, i.e., to each part of the electric device to which the first DC-DC converter DDC1 supplies power.

[0056] The mode control circuit ICm sends a first operation control signal Se1 to the first DC-DC converter DDC1. The first operation control signal Se1 is a signal that represents either a first enable command or a first disable command. The initial state of the first operation control signal Se1 is the first enable command.

[0057] If sufficient power is supplied to the first DC-DC converter DDC1, when the first operation control signal Se1 is the first enable command, the first DC-DC converter DDC1 performs a voltage conversion operation and outputs power. On the other hand, when the first operation control signal Se1 is the first disable command, the first DC-DC converter DDC1 stops the voltage conversion operation and does not output power.

[0058] Moreover, the mode control circuit ICm sends a second operation control signal Se2 to the second DC-DC converter DDC2. The second operation control signal Se2 is a signal representing either a second enable command or a second disable command. The initial state of the second operation control signal Se2 is the second enable command.

[0059] If sufficient power is supplied to the second DC-DC converter DDC2, when the second operation control signal Se2 is the second enable command, the second DC-DC converter DDC2 performs voltage conversion operation and outputs power. On the other hand, when the second operation control signal Se2 is the second disable command, the second DC-DC converter DDC2 stops voltage conversion operation and does not output power.

[0060] It is preferable that the first operation control signal Se1 is set so that the first disable command is a no-voltage signal. This is to further reduce power consumption of the entire control circuit 10 when the operation of the first DC-DC converter DDC1 is stopped. It is also preferable that the second operation control signal Se2 is set so that the second disable command is a no-voltage signal. This is to further reduce power consumption of the entire control circuit 10 when the operation of the second DC-DC converter DDC2 is stopped.

[0061] The first operation control signal Se1 sent by the mode control circuit ICm indicates a first enable command in the initial state. Also, the second operation control signal Se2 sent by the mode control circuit ICm indicates a second enable command in the initial state. In the normal mode, the main control circuit ICc receives power through the switching power supply 21, the first DC-DC converter DDC1, and the second DC-DC converter DDC2, in that order, and operates.

[0062] If the control circuit 10 is provided with a line (output terminal OUT1 in FIG. 2) that outputs the output voltage from the switching power supply 21 as is, a relay that is turned on / off in synchronization with the operation of the second DC-DC converter may be provided on the line. This makes it possible to synchronize the output / non-output of the line that outputs the output voltage from the switching power supply 21 as is with the output / non-output from the second DC-DC converter. In other words, it becomes possible to stop the output from the output terminal OUT1 in the energy saving mode.

[0063] The main control circuit ICc may be configured to include one or more central processing units (CPUs) or one or more integrated circuits (ICs) such as application specific integrated circuits (ASICs). The main control circuit ICc may also be configured to include one or more CPUs and one or more ICs such as ASICs.

[0064] The mode control circuit ICm may be configured to include one or more CPUs or one or more ICs such as ASICs. The main control circuit ICc may be configured to include one or more CPUs and one or more ICs such as ASICs. Furthermore, at least a part of the main control circuit ICc and at least a part of the mode control circuit ICm may be configured as a common IC.

[0065] When the main control circuit ICc or the main control circuit ICc includes a CPU, the CPU executes instructions of a program, which is software that realizes each function. In this case, the main control circuit ICc or the main control circuit ICc includes a readable recording medium that stores the program. The object of the present invention is achieved by having the CPU read and execute the program from the recording medium.

[0066] <Mode control circuit> Next, the configuration of the mode control circuit ICm of the control circuit 10 will be described. Fig. 3 is a block diagram showing a schematic configuration of the mode control circuit ICm. The mode control circuit ICm has the following functional blocks: a power receiving unit 111, a switch operation detection unit 112, a voltage detection unit 113, a first operation instruction unit 114, and a second operation instruction unit 115. The mode control circuit ICm also has the following functional blocks: a communication unit 116, a control unit 117, and a recording unit 118.

[0067] The power receiving unit 111 receives DC power from the small-capacity power supply 22 or the first DC-DC converter DDC1 through a port P1 connected to the first power supply line Ln1, and supplies the power to each unit of the mode control circuit ICm.

[0068] The switch operation detection unit 112 monitors the voltage of the port P2 to which the switch SW is connected, and monitors the state of the operation of the switch SW by the user. When the user performs a predetermined switch operation indicating an instruction to transition from the power saving mode to the normal mode during the power saving mode, the switch operation detection unit 112 notifies the control unit 117. Furthermore, the switch operation detection unit 112 may notify the control unit 117 when the user performs a predetermined switch operation indicating an instruction to transition from the normal mode to the power saving mode during the normal mode.

[0069] The voltage detection unit 113 is a functional block that detects the voltage through a port P3. The port P3 is connected to the first power supply line Ln1. The control unit 117 judges the voltage state from the voltage detected by the voltage detection unit 113. That is, if the detected voltage is equal to or higher than a predetermined value, it is judged that the power supply from the small-capacity power source 22 to the mode control circuit ICm is sufficient and the voltage state is normal, and if the detected voltage is less than the predetermined value, it is judged that the power supply is insufficient and the voltage state is abnormal.

[0070] The first operation instruction unit 114 is a functional block that outputs a first operation control signal Se1 through a port P4. The first operation control signal Se1 is sent to the first DC-DC converter DDC1. The second operation instruction unit 115 is a functional block that outputs a second operation control signal Se2 through a port P5.

[0071] The second operation control signal Se2 is sent to the second DC-DC converter DDC2, the third DC-DC converter DDC3, and the fourth DC-DC converter DDC4. Therefore, the third DC-DC converter DDC3 and the fourth DC-DC converter DDC4 switch between output / output stop in synchronization with the second DC-DC converter DDC2, but the operation of the third DC-DC converter DDC3, etc. will not necessarily be explicitly described below.

[0072] The communication unit 116 is a functional block that communicates with the main control circuit ICc through the port P6. The control unit 117 is a functional block that controls each part of the mode control circuit ICm and performs various calculations and judgments. The recording unit 118 is a functional block that records information.

[0073] <Power saving mode transition processing by the main control circuit> When the power supply system 1 is started, that is, when the electric device is started, the output of power from the switching power supply 21 and the small-capacity power supply 22 is started. The mode control circuit ICm is started, and a first enable command in an initial state is sent as a first operation control signal Se1 to the first DC-DC converter DDC1, and the first DC-DC converter DDC starts output. Also, a second enable command in an initial state is sent as a second operation control signal Se2 to the second DC-DC converter DDC2, and the second DC-DC converter DDC starts output.

[0074] In this way, power is supplied to the main control circuit ICc, and the main control circuit ICc starts up. Then, the state of the power supply system 1 becomes the normal mode state. The main control circuit ICc executes the power saving mode transition process shown in the flowchart of Fig. 4. The power saving mode transition process will be described below with reference to Fig. 4.

[0075] Step S11: The main control circuit ICc judges whether or not to transition to the power saving mode. If the main control circuit ICc judges to transition to the power saving mode (YES in S11), the flow proceeds to step S12. Otherwise (YES in S11), the flow repeats step S11.

[0076] The conditions for the judgment by the main control circuit ICc may be set appropriately depending on the electric device. For example, if a predetermined operation in the electric device, for example printing in the case of a printer, has not been performed for a certain period of time, the main control circuit ICc may determine to transition to the power saving mode. Alternatively, the switch operation detection unit 112 in the mode control circuit ICm may detect the operation of the switch SW by the user, and the main control circuit ICc may determine to transition to the power saving mode when it receives a notification to that effect from the mode control circuit ICm.

[0077] Step S12: The main control circuit ICc obtains the voltage state from the mode control circuit ICm.

[0078] Step S13: The main control circuit ICc then judges whether the voltage state acquired from the mode control circuit ICm is normal or not. If it is judged to be normal (YES in S13), the flow proceeds to step S14. Otherwise (NO in S13), the flow proceeds to step S15.

[0079] Step S14: The main control circuit ICc instructs the mode control circuit ICm to send a first disable command as the first operation control signal Se1. Then, the flow of the power saving mode transition process ends. In this case, the first DC-DC converter DDC1 is in a state where it does not output power, power is no longer supplied to the second DC-DC converter DDC2, and the main control circuit ICc stops. Similarly, power is no longer supplied to the third DC-DC converter DDC3 and the fourth DC-DC converter DDC4. The power supply system 1 transitions to the power saving mode.

[0080] Step S15: The main control circuit ICc instructs the mode control circuit ICm to send a second disable command as the second operation control signal Se2. Then, the flow of the power saving mode transition process ends. In this case, the second DC-DC converter DDC2 is in a state where it does not output power, and the main control circuit ICc stops. The third DC-DC converter DDC3 and the fourth DC-DC converter DDC4 are also in a state where they do not output power.

[0081] The power supply system 1 transitions to a power saving mode different from that in the case where step S14 is reached. Also, since the power supply from the small-capacity power supply 22 to the mode control circuit ICm is insufficient, by not stopping the operation of the first DC-DC converter DDC1, power is supplied from the DC-DC converter DDC1 to the mode control circuit ICm.

[0082] <Normal mode processing by the mode control circuit> When the power supply system 1 is started up or when the power supply system 1 transitions to the normal mode (when the mode flag is set to the normal mode), the mode control circuit ICm executes normal mode processing shown in the flowchart of Fig. 5. The normal mode processing will be described below with reference to Fig. 5.

[0083] Step S21: The control unit 117 judges whether or not an instruction to send a first disable command as the first operation control signal Se1 is received from the main control circuit ICc via the communication unit 116. If it is judged that the instruction has been received (YES in S21), the flow proceeds to step S23. Otherwise (NO in S21), the flow proceeds to step S22.

[0084] Step S22: The control unit 117 judges whether or not an instruction to send a second disable command is received as the second operation control signal Se2 from the main control circuit ICc through the communication unit 116. If it is judged that the instruction is received (YES in S22), the flow proceeds to step S24. Otherwise (NO in S21), the flow returns to step S21.

[0085] Step S23: The control unit 117 causes the first operation instruction unit 114 to send a first disable command as the first operation control signal Se1. Next, the flow proceeds to step S25.

[0086] Step S24: The control unit 117 causes the second operation instruction unit 115 to send a second disable command as the second operation control signal Se2. Next, the flow proceeds to step S25.

[0087] Step S25: The control unit 117 sets the mode flag to the power saving mode, and then the flow of the normal mode process ends.

[0088] <Power saving mode processing by the mode control circuit> When the mode control circuit ICm transitions to the power saving mode (when the mode flag is set to the power saving mode), it executes the power saving mode process shown in the flowchart of Fig. 6. The power saving mode process will be described below with reference to Fig. 6.

[0089] Step S31: The control unit 117 judges whether the voltage state has changed to an abnormal state. That is, it judges whether the voltage detected by the voltage detection unit 113 has changed from a state equal to or greater than a predetermined value to a state below the predetermined value. If it is judged that the state has changed to an abnormal state (YES in S31), the flow proceeds to step S33. Otherwise (NO in S31), the flow proceeds to step S32.

[0090] Step S32: If the voltage state has not changed to an abnormal state, the control unit 117 further judges whether or not another factor for transitioning to the normal mode has occurred. If it is judged that the factor has occurred (YES in S32), the flow proceeds to step S33. Otherwise (NO in S32), the flow returns to step S31. Here, the other factor for transitioning to the normal mode may be, for example, the switch operation detection unit 112 detecting the operation of the switch SW.

[0091] Step S33: The control unit 117 initializes the first operation control signal Se1 and the second operation control signal Se2. That is, the first operation instruction unit 114 sends an enable command as the first operation control signal Se1, and the second operation instruction unit 115 sends an enable command as the second operation control signal Se2. Then, the first DC-DC converter DDC1 and the second DC-DC converter DDC2 start output. Power is supplied to the main control circuit ICc, and the main control circuit ICc starts up. Power supply to each part of the electric device also starts, and the mode transitions to the normal mode.

[0092] Step S34: The control unit 117 sets the mode flag to the normal mode, and then the flow of the power saving mode process ends.

[0093] <Main control circuit startup process by the main control circuit> When the main control circuit ICc transitions from the power saving mode to the normal mode and power supply is started to start, it executes the main control circuit startup process shown in the flowchart of Fig. 7, and if the startup state continues, it subsequently executes the power saving mode transition process shown in the flowchart of Fig. 4. The main control circuit startup process will be described below with reference to Fig. 7.

[0094] Step S41: The main control circuit ICc acquires startup information from the mode control circuit ICm. Here, the startup information is information on whether the first and second operation control signals Se1 and Se2 have been initialized due to a change in the voltage state, or whether the first and second operation control signals Se1 and Se2 have been initialized due to the occurrence of another normal mode transition factor.

[0095] That is, this is information on whether the path leading to step S33 of initialization of the first operation control signal Se1 and the second operation control signal Se2 in the power saving mode processing was YES in step S31 or YES in step S32.

[0096] Step S42: The main control circuit ICc judges whether the startup information acquired from the mode control circuit ICm is information indicating that the voltage state has changed. If it is judged that the information indicates that the voltage state has changed (YES in S42), the flow proceeds to step S43. Otherwise (NO in S42), the flow ends. In this case, since the mode has been changed to the normal mode due to a factor such as the operation of the switch SW, the main control circuit ICc continues in the startup state, and the power supply system 1 continues in the normal mode.

[0097] Step S43: The main control circuit ICc judges whether the voltage state acquired from the mode control circuit ICm is normal or not. If it is judged to be normal (YES in S43), the flow proceeds to step S44. Otherwise (NO in S43), the flow proceeds to step S45.

[0098] Step S44: The main control circuit ICc instructs the mode control circuit ICm to send a first disable command as the first operation control signal Se1. Then, the flow of the main control circuit startup process ends. In this case, although the startup information indicates that there has been a change in the voltage state, the voltage state has returned to normal, so the first DC-DC converter DDC1 does not supply power to the mode control circuit ICm, and the mode transitions to the power saving mode again. The supply of power to the main control circuit ICc stops, and the main control circuit ICc stops operating.

[0099] Step S15: The main control circuit ICc instructs the mode control circuit ICm to send a second disable command as the second operation control signal Se2. Then, the flow of the main control circuit startup process ends. In this case, since the voltage state is abnormal, the first DC-DC converter DDC1 supplies power to the mode control circuit ICm, and the mode is shifted to the power saving mode again. The supply of power to the main control circuit ICc is stopped, and the main control circuit ICc stops operating.

[0100] <Actions and Effects> Similarly to the first embodiment, the power supply system 1 to which the control circuit 10 according to the second embodiment is applied can realize the power supply system 1 capable of switching between normal mode and power saving mode at low cost compared to the conventional technology.

[0101] According to the second embodiment, the control circuit 10 includes a first DC-DC converter DDC1 that operates according to a first operation control signal Se1, and a second DC-DC converter DDC2 that operates according to a second operation control signal Se2. When the power supply from the small-capacity power supply 22 to the mode control circuit ICm is sufficient, the control circuit 10 stops the operation of the first DC-DC converter DDC1. As a result, the control circuit 10 stops the power supply to the main control circuit ICc via the second DC-DC converter DDC2, and executes the power saving mode.

[0102] On the other hand, when the power supply from the small-capacity power supply 22 to the mode control circuit ICm is insufficient, the control circuit 10 stops the operation of the second DC-DC converter DDC2 without stopping the operation of the first DC-DC converter DDC1. As a result, the control circuit 10 stops the power supply from the second DC-DC converter DDC2 to the main control circuit ICc and executes the power saving mode. Then, power is supplied from the first DC-DC converter DDC1 to the mode control circuit ICm through the first power supply line Ln1.

[0103] Therefore, according to the second embodiment, even if the power supply from the auxiliary power supply becomes insufficient, the power supply to the mode control circuit ICm can be maintained, and a situation in which the electrical equipment cannot return to the normal mode and cannot perform normal operation is prevented.

[0104] [Embodiment 3] The third embodiment is a modification of the second embodiment. In the control circuit 10 according to the second embodiment, the first DC-DC converter DDC1 capable of supplying power to the small-capacity power supply 22 and the second DC-DC converter DDC2 supplying power to the main control circuit ICc are connected in series. In the control circuit 10A according to the third embodiment, the first DC-DC converter DDC1 capable of supplying power to the small-capacity power supply 22 and the second DC-DC converter DDC2 supplying power to the main control circuit ICc are connected in parallel.

[0105] 8 is a circuit diagram showing a control circuit 10A according to embodiment 3 and a power supply system 1A to which the control circuit 10A is applied. In embodiment 3, the second DC-DC converter DDC2 is connected to the output of the switching power supply 21. Like the second DC-DC converter, the third to fifth DC-DC converters DDC3 to DDC5 are also connected to the output of the switching power supply 21, and operate or stop according to the second operation control signal Se2. In a specific example of embodiment 3, the DC voltage output by the first DC-DC converter DDC1 is 5V.

[0106] The control circuit 10A operates in the same manner as the flows shown in the flowcharts of Figures 4 to 7, except for the following changes. In step S14 of the power saving mode transition process and in step S44 of the main control circuit startup process, the main control circuit IC instructs the mode control circuit ICm to send a second disable command as the second operation control signal Se2. In addition, in step S23 of the normal mode process, the mode control circuit ICm sends a second disable command as the second operation control signal Se2.

[0107] In the second embodiment, when the first DC-DC converter DDC1 stops outputting power, the second DC-DC converter DDC2 also stops outputting power. In the third embodiment, the operation is changed so that the second DC-DC converter DDC2 stops outputting power when it receives a second disable command. The third embodiment also provides the same effects as the second embodiment.

[0108] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The embodiments obtained by appropriately combining the disclosed technical means are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in the embodiments.

[0109] In the above-described embodiments, a printer has been given as an example of an electrical device to which the control circuit of the present invention is applied. However, the control circuit of the present invention is not limited to a printer, and may be applied to a copying machine, a multifunction machine having a printer or copying machine function, a communication device, a video device such as a television, or other electrical devices. [Explanation of symbols]

[0110] 1, 1A power system 10, 10A control circuit ICc Main control circuit ICm mode control circuit P1~P6 ports DDC1 First DC-DC converter DDC2 Second DC-DC converter DDC3~DDC5 3rd DC-DC converter~5th DC-DC converter Ln1 1st feeder line Ln2 2nd feeder line D Diode Se1 First operation control signal (enable command or disable command) Se2 Second operation control signal (enable command or disable command) 20 Power supply board 21, 21A switching power supply DB Diode Bridge ICs Power supply control circuits TR Transformer VD voltage detection circuit 211 DC voltage generator circuit 212 Secondary rectifier smoothing circuit 22 Small capacity power supply (auxiliary power supply) ADC AC-DC Converter

Claims

1. a first DC-DC converter that receives power from a switching power supply and outputs power; a second DC-DC converter that receives power from the first DC-DC converter and outputs power; a main control circuit that operates by receiving power from the second DC-DC converter; a mode control circuit that operates by receiving power from an auxiliary power supply; a first power supply line for supplying power from the auxiliary power supply to the mode control circuit; a second power supply line for supplying power from the first DC-DC converter to the mode control circuit; The mode control circuit includes: a control circuit for controlling the switching power supply from the first DC-DC converter to the second DC-DC converter disposed between the switching power supply and the main control circuit, and a control circuit for controlling the first DC-DC converter from the first DC-DC converter to the second DC-DC converter; When it is determined that the power supplied from the auxiliary power source is sufficient, the disable command is sent to the first DC-DC converter; when it is determined that the power supplied from the auxiliary power source is insufficient, the enable command is sent to the first DC-DC converter and the disable command is sent to the second DC-DC converter; a control circuit for controlling the first DC-DC converter and the second DC-DC converter to output power in accordance with the enable command and to stop outputting power in accordance with the disable command.

2. 2. The control circuit according to claim 1, wherein the disable command is a no-voltage signal.

3. The mode control circuit includes: determining that the power supplied from the auxiliary power source is insufficient; 3. The control circuit according to claim 1, wherein the step of detecting the voltage supplied from the auxiliary power source through the first power supply line is less than a predetermined value.

4. The mode control circuit includes:

4. The control circuit according to claim 3, further comprising, when it is determined that the power supplied from said auxiliary power supply is sufficient, sending said disable command to said second DC-DC converter.

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