control device

Abstract

To provide a control device capable of reducing standby power.SOLUTION: A control device 2 comprises: a rectifier circuit 21 for rectifying an AC voltage: a constant voltage circuit 22 provided with a smoothing capacitor for smoothing a rectified DC voltage, that generates a constant voltage; a control circuit 26 operated at the generated constant voltage; a charging circuit 27 provided with a capacitor for charging the smoothing capacitor, that is connected in series with the rectifier circuit 21; a bypass switch 28 parallelly connected so as to bypass the charging circuit 27; a start switch 29 that is closed to feed energy charged by the smoothing capacitor to the control circuit 26, when being shifted to a normal operation state from a standby state; and another bypass switch 30 parallelly connected so as to bypass the start switch. The control circuit 26 closes the bypass switches 28, 30 with power from the smoothing capacitor, when starting the normal operation state, and opens the bypass switches 28, 30, when starting the standby state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device capable of reducing standby power.

Background Art

[0002] A general electronic device having a control circuit such as a microcomputer (microcontroller) consumes minute power even in a standby state where the load is not being driven, in order to detect an operation from a user or drive a timer. In such an electronic device, when using a dropper type power supply circuit mainly mounted on inexpensive household appliances, since it is a shunt type that divides a constant current between a constant voltage circuit and a control circuit, the power consumption of the control circuit remains constant regardless of whether it is in a normal operating state or a standby state. Therefore, the power consumption in the standby state cannot be reduced.

[0003] FIG. 6 is a block diagram showing an example of the configuration of a conventional electronic device 101. In FIG. 6, the conventional electronic device 101 is connected to a commercial power supply 3, and includes a load 11, a rectifier circuit 21 that rectifies an AC voltage from the commercial power supply 3, a constant voltage circuit 122 connected to the rectifier circuit 21 and generating a constant voltage, a relay contact 23 that opens and closes the supply of AC power to the load 11, a relay drive circuit 24 for driving the relay contact, a reception unit 25 that receives an operation from a user, and a control circuit 126 that operates with the constant voltage generated by the constant voltage circuit 122. Note that the rectifier circuit 21 may be, for example, a half-wave rectifier circuit. Also, the control circuit 126 may control the supply of power to the load 11, etc., by controlling the relay drive circuit 24 according to an operation received by the reception unit 25, for example.

[0004] In conventional electronic devices 101 with this configuration, current flows even in standby mode, as shown by the arrows in Figure 6, and power is consumed accordingly. For example, if a temperature-controlled kettle with a 1300W heater is used 5 times a day for 5 minutes each time, the daily power consumption for the heater would be approximately 541.7 Wh. If the standby power consumption is 1.2W and the device is plugged into a power source all day, the daily power consumption for standby would be 28.8 Wh. Therefore, the proportion of standby power to total power consumption (approximately 570.5 Wh) is about 5%, which contradicts the image of power saving that users expect. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-058916 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Various methods have been used to reduce standby power consumption (see, for example, Patent Document 1). While it is conceivable to use more efficient switching-type isolated or non-isolated AC-DC converters in electronic devices, it is impossible to completely eliminate standby power. Furthermore, using switching-type AC-DC converters presents the problem of high costs. Another option is to insert a mechanical AC switch into the AC line to completely cut off current in standby mode, but this presents problems such as high costs depending on the current during switching, the risk of users forgetting to turn off the switch, and the inability to use it in devices with timer functions.

[0007] The present invention was made to solve at least one of the above problems, and aims to provide a device that can reduce standby power without using a switching type AC-DC converter or AC mechanical switch. [Means for solving the problem]

[0008] To achieve the above objective, a control device according to one aspect of the present invention comprises: a rectifier circuit for rectifying an AC voltage; a constant voltage circuit connected to the rectifier circuit and having a smoothing capacitor for smoothing the DC voltage rectified by the rectifier circuit, and generating a constant voltage; a control circuit that operates using the constant voltage generated by the constant voltage circuit; a charging circuit connected in series with the rectifier circuit and having a capacitor for charging the smoothing capacitor; and a first bypass switch connected in parallel with the charging circuit and for bypassing the charging circuit, wherein the control circuit closes the first bypass switch at the start of the normal operating state and opens the first bypass switch at the start of the standby state. With this configuration, for example, in standby mode, standby power can be reduced by preventing DC current from flowing through the capacitor in the charging circuit.

[0009] Furthermore, in a control device according to one aspect of the present invention, a start switch is closed to supply energy charged in a smoothing capacitor to a control circuit when transitioning from a standby state to a normal operating state, and a second bypass switch is connected in parallel with the start switch to bypass the start switch, wherein the control circuit may, at the start of the normal operating state, be operated by the energy charged in the smoothing capacitor to close the first and second bypass switches, and at the start of the standby state, also open the second bypass switch. This configuration allows the control circuit to be operated by the energy stored in the smoothing capacitor when switching from standby to normal operation. Furthermore, it is possible to virtually eliminate the power consumption of the control circuit in standby mode, significantly reducing standby power. This reduction in standby power can also be achieved without using expensive components such as AC switches.

[0010] Furthermore, a control device according to one aspect of the present invention may further include a resistor connected in parallel with the charging circuit to compensate for the voltage drop of the smoothing capacitor due to leakage current of the circuit in the standby state. This configuration allows the smoothing capacitor to continue storing the charge necessary to start the control circuit, even during long periods of standby.

[0011] Furthermore, in a control device according to one aspect of the present invention, a resistor connected in parallel to the charging circuit is further provided, and the control circuit may have fewer functions operated in the standby state than in the normal operating state, and the operating clock frequency may be lower than in the normal operating state. This configuration reduces the power consumption of the control circuit in standby mode, and as a result, reduces standby power consumption. Furthermore, since at least a portion of the control circuit is operating even in standby mode, it becomes possible to use functions such as timers. [Effects of the Invention]

[0012] According to one aspect of the present invention, a control device can reduce standby power consumption. [Brief explanation of the drawing]

[0013] [Figure 1] Block diagram showing the configuration of the electronic device according to Embodiment 1 of the present invention. [Figure 2] Circuit diagram showing an example of the configuration of the control device according to the same embodiment. [Figure 3] Block diagram showing other configurations of the electronic device according to the same embodiment. [Figure 4] Block diagram showing the configuration of the electronic device according to Embodiment 2 of the present invention. [Figure 5] Circuit diagram showing an example of the configuration of the control device according to the same embodiment. [Figure 6] Block diagram showing the configuration of conventional electronic devices [Modes for carrying out the invention]

[0014] The control device according to the present invention will be described below using embodiments. In the following embodiments, components denoted by the same reference numerals are the same or equivalent, and their further description may be omitted.

[0015] (Embodiment 1) A control device according to Embodiment 1 of the present invention will be described with reference to the drawings. In this embodiment, when transitioning from a standby state to a normal operating state, the control circuit is activated by the energy charged in the smoothing capacitor, and power is supplied for the normal operating state.

[0016] Figure 1 is a block diagram showing the configuration of the electronic device 1 according to this embodiment, and Figure 2 is a circuit diagram showing an example of the configuration of the control device 2 according to this embodiment. Note that some of the configuration of the control device 2 is omitted in Figure 2. The electronic device 1 comprises a load 11 and a control device 2 that controls the supply of power to the load 11. The load 11 is driven by electricity and may be, for example, a heater, motor, or lighting. The load 11 may be driven by, for example, AC power. In this embodiment, the case in which the load 11 is a cooking heater such as a temperature-controlled kettle or electric pot will be mainly described. More specifically, the case in which the electronic device 1 is a temperature-controlled kettle will be mainly described. Note that the electronic device 1 may be connected to the commercial power supply 3 by plugging the plug at the end of the power cord of the electronic device 1 into an outlet, and AC power from the commercial power supply 3 may be supplied to the electronic device 1.

[0017] Referring to FIG. 1, the control device 2 includes a rectifier circuit 21, a constant voltage circuit 22, a relay contact 23, a relay drive circuit 24, a reception unit 25, a control circuit 26, a charging circuit 27, a first bypass switch 28, a start switch 29, and a second bypass switch 30. The control device 2 drives the control circuit 26 by a dropper-type power supply having the rectifier circuit 21 and the constant voltage circuit 22. Also, the control device 2 has a normal operation state and a standby state. The normal operation state is a state in which all functions of the control circuit 26 can operate, for example, a state in which control regarding on / off of power supply to the load 11 can be performed. On the other hand, the standby state is a state in which the operable functions of the control circuit 26 are more restricted than in the normal operation state. In the standby state, usually, power supply to the load 11 is not performed. In the present embodiment, the case where all functions of the control circuit 26 are restricted in the standby state, that is, the case where power supply to the control circuit 26 is stopped, will be described. In Embodiment 2, the case where some functions of the control circuit are restricted in the standby state, that is, the case where less power than in the normal operation state is supplied to the control circuit, will be described.

[0018] The rectifier circuit 21 rectifies the AC voltage from the commercial power supply 3. The rectifier circuit 21 may be a half-wave rectifier circuit. As an example, as shown in FIG. 2, it may have a diode 211 and a resistor 212. A voltage other than the voltage corresponding to the Zener diodes 223, 224 substantially applies to the resistor 212 out of the 100V voltage from the commercial power supply 3. Therefore, the current is determined by the resistance value of the resistor 212. Note that the rectifier circuit 21 may be, for example, a full-wave rectifier circuit.

[0019] The constant voltage circuit 22 is connected to the rectifier circuit 21 and generates a constant voltage. Usually, the connection is in series. In the present embodiment, the case where the constant voltage circuit 22 generates a constant voltage of 24V, a constant voltage of 9V, and generates a constant voltage of 5V for supplying to the control circuit 26 from the 9V constant voltage will be mainly described. As an example, as shown in FIG. 2, the constant voltage circuit 22 may include smoothing capacitors 221 and 222 for smoothing the DC voltage rectified by the rectifier circuit 21, a Zener diode 223 connected in parallel with the smoothing capacitor 221 for generating a voltage of 24V, a Zener diode 224 connected in parallel with the smoothing capacitor 222 for generating a voltage of 9V, a Zener diode 225, a resistor 226, a bipolar transistor 227 for generating a voltage of 5V from the 9V voltage, and a capacitor 228 for stabilizing the generated 5V power.

[0020] As shown in FIG. 2, the constant voltage circuit 22 preferably generates an intermediate voltage which is the voltage corresponding to the smoothing capacitor 222, and generates a target constant voltage (for example, 5V supplied to the control circuit 26, etc.) by stepping down the intermediate voltage. By doing so, more charges can be stored at the intermediate voltage, and as will be described later, when shifting from the standby state to the normal operation state, more power can be supplied when supplying the energy charged in the smoothing capacitor 222 to the control circuit 26. Also, by generating an intermediate voltage, stepping down the intermediate voltage, and generating a target constant voltage, the ripple existing in the DC output from the rectifier circuit 21 can be reduced. Further, the smoothing capacitor 222 preferably has a capacitance capable of storing enough charges to start the control circuit 26 during initial charging or when shifting from the standby state to the normal operation state.

[0021] For example, if the capacitances of smoothing capacitors 221 and 222 are each 220 μF, and the capacitance of capacitor 271 in the charging circuit 27 is 22 μF, then the combined capacitance of the series-connected smoothing capacitors 221 and 222 and capacitor 271 is 55 / 3 μF (= 1 / (1 / 220 μF + 1 / 220 μF + 1 / 22 μF)). Therefore, the charge of each capacitor is 2585 μC (= 141 V × (55 / 3) μF). Consequently, the voltage across smoothing capacitors 221 and 222 after initial charging following connection of the electronic device 1 to the commercial power supply 3 is 11.75 V (= 2585 μC / 220 μF), considering only the voltage division of the capacitors. On the other hand, due to the shunt function of the Zener diode 224 connected in parallel with the smoothing capacitor 222, the voltage across the smoothing capacitor 222 after initial charging is limited to 9V. Therefore, the charge stored in the smoothing capacitor 222 after initial charging is 1980μC (=9V × 220μF). Assuming that the current consumption of the control circuit 26 at startup is 1mA, the charge stored in the smoothing capacitor 222 will allow the control circuit 26 to operate for 1.98 seconds (=1980μC / 1000μA). However, considering that the control circuit 26 will stop operating when the voltage falls below a predetermined threshold voltage, strictly speaking, the control circuit 26 will operate for a slightly shorter time than 1.98 seconds. In this way, the time for which the control circuit 26 can operate due to the charge stored in the smoothing capacitor 222 can be calculated from the capacitance of the smoothing capacitor 222. Preferably, the capacitance of the smoothing capacitor 222 is selected such that this time is longer than the time required for the control circuit 26 to perform the control to close the first and second bypass switches 28 and 30, as will be described later.

[0022] The relay contact 23 is a contact that switches the supply of AC power to the load 11. The relay drive circuit 24 is a circuit for switching the relay contact 23 and is controlled by the control circuit 26. For example, the relay drive circuit 24 may have resistors 241 and 242, a bipolar transistor 243, resistors 244, 245 and 246, and a bipolar transistor 247, as shown in Figure 2. Note that resistor 245 is the resistance of the coil for driving the relay. In the circuit shown in Figure 2, the voltage across wiring L1 is at the reference potential (0V). Therefore, when a -5V control signal is output from the control circuit 26 to resistor 241, the bipolar transistor 243 turns on accordingly, and as a result, the bipolar transistor 247 also turns on. Then, current flows through resistor 245, and the relay contact 23 is closed. On the other hand, when the control signal output from the control circuit 26 to the relay drive circuit 24 becomes 0V, both bipolar transistors 243 and 247 turn off, so no current flows through resistor 245, and the relay contact 23 opens. In this way, the power supply to the load 11 is controlled.

[0023] The reception unit 25 receives operations from the user. The reception unit 25 may receive operations such as setting a timer or setting a temperature. The reception unit 25 passes a signal corresponding to the received operation to the control circuit 26. The reception unit 25 may be an input device such as a switch or input key that receives operations from the user. Although not shown in Figure 1, the control circuit 26 may also receive sensing results from a temperature sensor such as a thermistor or other sensors.

[0024] The control circuit 26 operates using a constant voltage generated by the constant voltage circuit 22. In this embodiment, as an example, the control circuit 26 operates using a constant voltage of 5V generated by the constant voltage circuit 22. The control circuit 26 may be, for example, a microcontroller for an embedded system specifically designed for the electronic device 1, on which a program for controlling the electronic device 1 is written. At the start of normal operation, the control circuit 26 operates using the energy charged in the smoothing capacitor 222 to close the first and second bypass switches 28 and 30. As a result, current flows by bypassing the charging circuit 27 and the start switch 29. Preferably, the control circuit 26 is programmed to first close the first and second bypass switches 28 and 30 at startup, which is the start of normal operation. The control circuit 26 also opens the first and second bypass switches 28 and 30 at the start of standby.

[0025] The charging circuit 27 is connected in series with the rectifier circuit 21. For example, the charging circuit 27 may include a capacitor 271 for charging the smoothing capacitor 222 and a resistor 272, as shown in Figure 2. The capacitance of the capacitor 271 in the charging circuit 27 is preferably set to appropriately charge the smoothing capacitors 221 and 222. During initial charging when the electronic device 1 is connected to the commercial power supply 3, the smoothing capacitors 221 and 222 can be charged via this charging circuit 27. In other words, the capacitor 271 can be considered a capacitor for the initial charging of the smoothing capacitors 221 and 222. Furthermore, the presence of the capacitor 271 in the charging circuit 27 prevents current flow in the standby state, thereby reducing standby power to zero.

[0026] The first bypass switch 28 is connected in parallel with the charging circuit 27 and is a switch for bypassing the charging circuit 27. When the first bypass switch 28 is closed, the charging circuit 27 is bypassed, and when the first bypass switch 28 is opened, the charging circuit 27 is not bypassed. An example of the circuit of the first bypass switch 28 will be described later.

[0027] The activation switch 29 is a switch that is closed to supply the energy charged in the smoothing capacitor 222 to the control circuit 26 when transitioning from the standby state to the normal operating state. Therefore, it is preferable that the activation switch 29 is located in part of the current path for supplying the charge stored in the smoothing capacitor 222 to the control circuit 26 when transitioning from the standby state to the normal operating state. As an example, the activation switch 29 may have a switch 291, a diode 292, and resistors 293, 294, and 295, as shown in Figure 2. The switch 291 may be, for example, a normally open momentary switch. When the control device 2 is in the standby state, if the user closes the switch 291, the energy charged in the smoothing capacitor 222 is supplied to the control circuit 26, as shown by arrow A2 in Figure 2. Normally, the time from when the switch 291 is closed until the control circuit 26 is activated is several milliseconds to tens of milliseconds, so the user does not need to keep the switch 291 closed. Switch 291 only needs to be closed for the time between the activation of control circuit 26 and the closing of the first and second bypass switches 28 and 30 immediately afterward.

[0028] When switch 291 is closed during normal operation, the voltage across wiring L3 becomes -5V, which is obtained by dividing 0V and -9V using resistors 294 and 295. This voltage signal is then input to control circuit 26. When control circuit 26 detects this signal input during normal operation, it determines that it is transitioning from normal operation to standby mode and opens the first and second bypass switches 28 and 30. In this way, the system transitions from normal operation to standby mode. Even in this case, the user only needs to keep switch 291 closed for a short time, that is, for a sufficient amount of time for the signal from wiring L3 to be input to control circuit 26. For example, if control circuit 26 detects the voltage of wiring L3 every few tens of milliseconds, the user does not need to keep switch 291 closed.

[0029] The second bypass switch 30 is connected in parallel with the start switch 29 and is a switch for bypassing the start switch 29. When the second bypass switch 30 is closed, the start switch 29 is bypassed, and when the second bypass switch 30 is opened, the start switch 29 is not bypassed.

[0030] The first bypass switch 28 may, for example, have a bipolar transistor 281 and resistors 282 and 283, as shown in Figure 2. The second bypass switch 30 may, for example, have a bipolar transistor 301, a diode 302, and resistors 303 and 304, as shown in Figure 2. Control signals from the control circuit 26 may also be input to the first and second bypass switches 28 and 30 via an auxiliary switch circuit 31, as shown in Figure 2. The auxiliary switch circuit 31 may have a bipolar transistor 311 and resistors 312 and 313. In this case, the first and second bypass switches 28 and 30 may each be considered to also have the auxiliary switch circuit 31. Since the emitter voltages of the bipolar transistors 281 and 301 of the first and second bypass switches 28 and 30 are lower than the -5V to 0V output range of the control circuit 26, the first and second bypass switches 28 and 30 are controlled via the auxiliary switch circuit 31 in this manner.

[0031] When a -5V control signal is output from the control circuit 26 to the resistor 313 of the auxiliary switch circuit 31, the bipolar transistor 311 turns on, and a 0V signal is input to the resistor 282 of the first bypass switch 28 and the diode 302 of the second bypass switch 30. As a result, bipolar transistors 281 and 301 turn on, respectively. In other words, the first and second bypass switches 28 and 30 are closed. On the other hand, when the control signal output from the control circuit 26 to the auxiliary switch circuit 31 becomes 0V, the bipolar transistor 311 turns off, and accordingly, bipolar transistors 281 and 301 also turn off, respectively. In other words, the first and second bypass switches 28 and 30 are opened. In this way, the control circuit 26 can open and close the first and second bypass switches 28 and 30 by switching the control signal output to the auxiliary switch circuit 31.

[0032] Next, the operation of the electronic device 1 according to this embodiment will be described. First, when the electronic device 1 is connected to the commercial power supply 3, current flows as shown by arrow A1 in Figure 2, and the smoothing capacitors 221 and 222 of the constant voltage circuit 22 are charged by the capacitor 271 of the charging circuit 27. At this point, the control device 2 is in standby mode. Once charging is complete, the current stops flowing, so the standby power consumption in standby mode can be reduced to zero.

[0033] Next, when the user temporarily closes switch 291 of the start switch 29, the charge stored in the smoothing capacitor 222 flows as current, as shown by arrow A2 in Figure 2. This current starts the control circuit 26, and the system transitions from standby to normal operation. Immediately after starting, the control circuit 26 changes the control signal output to the auxiliary switch circuit 31 from 0V to -5V. This control signal closes the auxiliary switch circuit 31, and a 0V signal is input to the first and second bypass switches 28 and 30. In response, the first and second bypass switches 28 and 30 close, and current flows as shown by arrow A3 in Figure 2. In other words, power is supplied to the control circuit 26 via a path that bypasses the charging circuit 27 and the start switch 29. In this way, once the system is in normal operation, all the charge stored in the capacitor 271 of the charging circuit 27 is discharged via the bipolar transistor 281, and the charging circuit 27 is refreshed. In normal operation, for example, user operations may be received by the reception unit 25, and power supply to the load 11 may be started accordingly, thereby performing operations such as water boiling. Alternatively, the control circuit 26 may start supplying power to the load 11 when, for example, the system transitions from standby to normal operation. Furthermore, the control circuit 26 may stop supplying power to the load 11 when, for example, it detects the completion of water boiling based on sensing results from the temperature sensor, or when it detects the elapsed of the warming time set by the user.

[0034] To forcibly terminate the power supply to load 11, for example, to forcibly terminate the water heating operation, the user temporarily closes switch 291 of the start switch 29. The voltage across wiring L3 is then input to control circuit 26, which determines that it is transitioning from normal operation to standby mode and changes the control signal output to auxiliary switch circuit 31 from -5V to 0V. This control signal opens auxiliary switch circuit 31. In response to the opening of auxiliary switch circuit 31, the first and second bypass switches 28 and 30 are also opened, and the charge stored in the 5V capacitor 228 of the constant voltage circuit 22 is consumed by control circuit 26 and surrounding circuits. As a result, the voltage of the 5V power supply circuit becomes lower than the reset voltage, and control circuit 26 stops operating. At this point, the smoothing capacitors 221 and 222 of the constant voltage circuit 22 are already charged to 24V and 9V respectively. Therefore, the capacitor 271 of the charging circuit 27 is charged to 108V (=141V-24V-9V) by the current flowing through the Zener diodes 223 and 224. Once charging is complete, the current stops flowing, and the system enters a standby state. When the system enters a standby state, the operation of the control circuit 26 stops, and the control signal output from the control circuit 26 to the relay drive circuit 24 also becomes 0V. Therefore, even if power was being supplied to the load 11 just before transitioning from the normal operating state to the standby state, the power supply to the load 11 will be stopped. Note that if power is being supplied to the load 11 when transitioning from the normal operating state to the standby state, the control circuit 26 may control the relay drive circuit 24 so that the power supply to the load 11 is stopped before outputting the control signal to open the first and second bypass switches 28 and 30. Furthermore, when the completion of water heating is detected, or when the user-set keep-warm time has elapsed, the control circuit 26 may stop supplying power to the load 11 and control the system to switch from the normal operating state to a standby state. In other words, the control circuit 26 may control the system to open the first and second bypass switches 28 and 30.

[0035] As described above, the control device 2 according to this embodiment makes it possible to prevent power from being supplied to the control circuit 26 in the standby state. Therefore, standby power can be reduced to zero. Furthermore, when returning from the standby state to the normal operating state, the control circuit 26 can be started using the energy charged in the smoothing capacitor 222, allowing for a quick return to the normal operating state. Therefore, compared to switching the AC power on and off with an AC mechanical switch, it becomes possible to transition to the normal operating state more quickly. In addition, in the normal operating state, the first and second bypass switches 28 and 30 can be used to bypass the charging circuit 27 and the start switch 29, thereby supplying power to the control circuit 26. Furthermore, since the switching from the standby state to the normal operating state can be done using the DC switch 291, costs can be reduced compared to using an AC mechanical switch. In addition, the transition from the normal operating state to the standby state can be performed by the control circuit 26. Therefore, user operation is not necessarily required to transition to the standby state. For example, in a temperature-controlled kettle, when the water temperature reaches the set temperature, the power supply to the load 11 can be stopped and the device can automatically transition to the standby state. Furthermore, since it does not perform high-frequency operations, an EMI filter is not required.

[0036] In principle, standby power can be reduced to zero by selecting a capacitor with the optimal capacitance. However, since actual electronic components such as capacitors and transistors have leakage current, the capacitors will discharge, and for example, the voltages of the smoothing capacitors 221 and 222, 24V and 9V respectively, will drop. If the leakage current of the smoothing capacitors 221 and 222 is greater than the leakage current of the charging circuit 27, the difference will be stored in the charging circuit 27. As time passes, the amount of charge stored in the 9V smoothing capacitor 222 will become insufficient to start the control circuit 26, and there is a risk that the control circuit 26 will not start even if the start switch 29 is closed. For this reason, for example, it is necessary to supply a current greater than the leakage current of the smoothing capacitors 221 and 222, and the Zener diodes 223 and 224, even in the standby state. Accordingly, the control device 2 may further include a resistor 41 connected in parallel with the charging circuit 27, as shown in Figure 3. This resistor 41 is a bypass resistor to compensate for the voltage drop caused by the leakage current of the smoothing capacitors 221 and 222 in the standby state.

[0037] When resistor 41 is present, the standby power will not be zero, but since only enough current to compensate for the leakage current needs to flow through resistor 41, the increase in standby power will not be significant. For example, if the leakage current of the circuit is 10 μA, the current flowing through resistor 41 should be set to 20 μA to allow for a margin. When smoothing capacitors 221 and 222 are charged to 24 V and 9 V respectively, the voltage across capacitor 271 in standby mode will be 108 V (= 141 V - 9 V - 24 V). Therefore, the resistance value of resistor 41 will be 5.4 MΩ (= 108 V / 20 μA). Here, let's assume that a commercially available resistor with a resistance value smaller than 5.4 MΩ, specifically a resistor with a resistance value of 4.7 MΩ, is selected as resistor 41. Furthermore, assuming that the capacitances of smoothing capacitors 221 and 222 are 220 μF each, and the capacitance of capacitor 271 is 22 μF, as described above, the voltage across smoothing capacitor 221 after initial charging following the connection of electronic device 1 to commercial power supply 3 will be 11.75 V. On the other hand, since the voltage across smoothing capacitor 222 is limited to 9 V, the voltage across capacitor 271 will be approximately 120 V (= 141 V - 9 V - 11.75 V), and the maximum current flowing after the initial charging of capacitor 271 will be approximately 26 μA (= 120 V / 4.7 MΩ). The power consumption when this maximum current flows will be 3.7 mW (= 141 V × 26 μA). For example, according to the Japan Electrical Manufacturers' Association's voluntary standards, values ​​are rounded to two decimal places, so a power consumption of 3.7 mW becomes 0.0 W. Thus, even with the addition of resistor 41, the standby power can be reduced to a negligible value that can be considered virtually zero.

[0038] Furthermore, in this embodiment, the case in which a signal instructing the system to transition to the standby state is output to the control circuit 26 when switch 291 of the start switch 29 is closed, and the system transitions from the normal operating state to the standby state, has been described, but this is not required. The control circuit 26 may, for example, perform control to transition from the normal operating state to the standby state in response to an operation received by the reception unit 25. In this case, the start switch 29 does not need to have resistors 294 and 295.

[0039] (Embodiment 2) An electronic device according to Embodiment 2 of the present invention will be described with reference to the drawings. In this embodiment, the power supplied to the control circuit in the standby state is reduced, and some functions of the control circuit are operational even in the standby state.

[0040] Figure 4 is a block diagram showing the configuration of the electronic device 1a according to this embodiment, and Figure 5 is a circuit diagram showing an example of the configuration of the control device 2a according to this embodiment. Note that some of the configuration of the control device 2a is omitted in Figure 5. The electronic device 1a is the same as the electronic device 1 of Embodiment 1, except that it is equipped with control device 2a instead of control device 2, so redundant explanations are omitted.

[0041] The control device 2a is the same as the control device 2 of Embodiment 1, except that it does not have a start switch 29 and a second bypass switch 30, and instead of a constant voltage circuit 22 and a control circuit 26, it has a constant voltage circuit 22a and a control circuit 26a, and further includes a resistor 42, so redundant explanations are omitted.

[0042] The constant voltage circuit 22a is connected to the rectifier circuit 21 and generates a constant voltage. In this embodiment, as an example, we will mainly describe the case in which the constant voltage circuit 22a generates a constant voltage of 24V and a constant voltage of 9V, and generates a constant voltage of 5V to supply to the control circuit 26a from the constant voltage of 9V. As an example, the constant voltage circuit 22a may have smoothing capacitors 221 and 222, a Zener diode 223 for generating a voltage of 24V, a Zener diode 224 for generating a voltage of 9V, and a 5V constant voltage circuit 229 for generating a voltage of 5V from the voltage of 9V, as shown in Figure 5. The configuration other than the 5V constant voltage circuit 229 is the same as that of the constant voltage circuit 22 in Embodiment 1, and its description will be omitted.

[0043] The 5V constant voltage circuit 229 is preferably a low-power constant voltage circuit. For example, in the configuration that generates a 5V voltage in Embodiment 1, i.e., to stably operate the Zener diode 225, resistor 226, and bipolar transistor 227, a current is required that keeps the Zener voltage constant. On the other hand, low-power constant voltage circuits that can generate a 5V voltage and operate with approximately 100 μA are also known. For example, such a low-power constant voltage circuit may be used as the 5V constant voltage circuit 229.

[0044] Control circuit 26a is the same as control circuit 26 of Embodiment 1, except that in the standby state, it operates fewer functions than in the normal operating state, the operating clock frequency is lower than in the normal operating state, and it does not control the start switch 29 and the second bypass switch 30, so its description is omitted. The operating clock frequency of control circuit 26a may be 8MHz in the normal operating state and 32kHz in the standby state, for example. In the standby state, for example, only the timer function may be operated, or only the function of receiving control signals from the reception unit 25 may be operated. In any case, the number of operable functions will be fewer in the standby state than in the normal operating state.

[0045] Resistor 42 is connected in parallel to the charging circuit 27 and is a resistor that supplies power to the control circuit 26a in standby mode. The resistance value of resistor 42 is preferably large enough to supply the minimum necessary power to the control circuit 26a in standby mode, in order to reduce standby power consumption.

[0046] Next, the operation of the electronic device 1a according to this embodiment will be described. First, when the electronic device 1a is connected to the commercial power supply 3, the smoothing capacitors 221 and 222 of the constant voltage circuit 22 are charged by the capacitor 271 of the charging circuit 27, and current flows as shown by arrow A4 in Figure 5. The control circuit 26a is started up by the power supplied in this way. Note that the smoothing capacitors 221 and 222 are charged in a shorter time by the capacitor 271 of the charging circuit 27. Therefore, the time until the control circuit 26a starts up can be shortened. After starting up, the control circuit 26a changes the control signal output to the auxiliary switch circuit 31 from 0V to -5V. The auxiliary switch circuit 31 is closed by this control signal, and the first bypass switch 28 is also closed accordingly, and current flows as shown by arrow A5 in Figure 5. In other words, power is supplied to the control circuit 26a via a path that bypasses the charging circuit 27. Therefore, sufficient power is supplied to the control circuit 26a. In this normal operating state, the control circuit 26a operates in normal power consumption mode. That is, the control circuit 26a operates with an operating clock frequency higher than that of the standby state, and all functions are capable of operating.

[0047] Here, the reception unit 25 is assumed to have a first mechanical switch that receives instructions to transition from the normal operating state to the standby state, and a second mechanical switch that receives instructions to transition from the standby state to the normal operating state. When the user presses the first mechanical switch to transition to the standby state, the control circuit 26a receives a signal corresponding to the press. In response to this signal, the control circuit 26a opens the auxiliary switch circuit 31 and the first bypass switch 28 by setting the control signal output to the auxiliary switch circuit 31 to 0V. When the first bypass switch 28 is opened, charging of the capacitor 271 of the charging circuit 27 begins accordingly, and after the charging is completed, current flows as shown by arrow A4 in Figure 5, and the device enters the standby state. At the same time as opening the first bypass switch 28, the control circuit 26a transitions to a low power consumption mode. In this low power consumption mode, the control circuit 26a lowers the frequency of the operating clock and limits the functions that are operated. For example, if only the timer function is to be operated in standby mode, the control circuit 26a may only perform a count-up for the timer function, and when the count value reaches the set value, it may be controlled to transition to the normal operation state.

[0048] Furthermore, for example, if only the function for receiving user instructions to transition to the normal operating state is activated in the standby state, when the user presses the second mechanical switch to transition to the normal operating state in the standby state, the control circuit 26a receives a signal corresponding to that press. In response to this signal, the control circuit 26a closes the auxiliary switch circuit 31 and the first bypass switch 28 by setting the control signal output to the auxiliary switch circuit 31 to -5V. When the first bypass switch 28 is closed, current flows as shown by arrow A5 in Figure 5. The control circuit 26a also transitions from low power consumption mode to normal power consumption mode. That is, the control circuit 26a increases the frequency of the operating clock and makes all functions operational. For example, the control circuit 26a may start supplying power to the load 11 in response to user operation.

[0049] Next, we will explain how to determine the resistance value of resistor 42. First, we estimate the current consumption in the standby state. For example, if the current consumption of the 5V constant voltage circuit 229 in the standby state is 100μA and the current consumption of the control circuit 26a is 20μA, then their total is 120μA. If we set the circuit current of resistor 42 to 200μA, taking into account variations in components, then in the standby state, if the smoothing capacitor 221 is charged to 24V, the voltage across the capacitor 271 in the charging circuit 27 will be 108V, so the resistance value of resistor 42 will be 540kΩ (=108V / 200μA). Also, since the resistance value of resistor 42 is usually greater than the resistance value of resistor 272, resistor 42 will also be responsible for the discharge characteristics of capacitor 271 during a power outage in the standby state. Therefore, by setting the discharge time constant of capacitor 271 to a constant that decays faster than the discharge characteristics of capacitor 222, the startup time of the control circuit 26a when power is restored after a power outage can be shortened. The time it takes for the voltage of capacitor 222 to drop by 63.2% due to discharge is 10.428 seconds (= (0.632 × 9V × 220μF) / (120μA)). Therefore, by setting the resistance value of resistor 42 to 474kΩ (= 10.428 seconds / 22μF) or less, the discharge time of capacitor 271 can be shortened compared to capacitor 222. For this reason, a commercially available resistor with a resistance value of 470kΩ may be used as resistor 42. For example, if the resistance value of resistor 42 is set to 470kΩ and the capacitances of smoothing capacitors 221 and 222 are each set to 220μF If the capacitance of capacitor 271 is 22 μF, as explained in Embodiment 1, the voltage across capacitor 271 when the initial charging of smoothing capacitors 221 and 222 is complete is approximately 120 V, so the maximum current is approximately 255 μA (≒ 120 V / 470 kΩ). As a result, the standby power is approximately 36 mW (≒ 141 V × 255 μA). In this case as well, if rounded to the second decimal place according to the voluntary standards of the Japan Electrical Manufacturers' Association, the power consumption of 36 mW becomes 0.0 W, and the standby power can be reduced to a minuscule value that can be considered virtually zero.

[0050] As described above, the control device 2a according to this embodiment can reduce standby power by reducing the power supplied to the control circuit 26a in the standby state. Such a reduction in standby power can be achieved relatively easily by providing a charging circuit 27 for initial charging, a resistor 42 for supplying power to the control circuit 26a in the standby state, and a first bypass switch 28 connected in parallel to the charging circuit 27 in a resistor dropper type power supply circuit. Furthermore, in the standby state, the control circuit 26a can reduce power consumption by reducing the number of functions it operates and by lowering the frequency of its operating clock. In addition, during initial charging, the smoothing capacitors 221 and 222 are charged using the charging circuit 27 which has a capacitor 271, so the charging time can be shortened compared to the case where the smoothing capacitors 221 and 222 are charged via the resistor 42. This is because the resistor 42 has a large resistance value in order to reduce standby power.

[0051] In Embodiments 1 and 2, examples were described in which the relay drive circuit 24, the first and second bypass switches 28 and 30, and the auxiliary switch circuit 31 are switched on and off by bipolar transistors. However, the circuits may be switched on and off using MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) instead of bipolar transistors, or other switching elements may be used.

[0052] Furthermore, the resistance values ​​of the resistors and capacitances of the capacitors included in the circuit diagrams of Figures 2 and 5 are preferably selected appropriately so that the above-described process is executed. It also goes without saying that the circuits in Figures 2 and 5 are examples, and the same configuration and functions as the control device 2 according to Embodiment 1 and the control device 2a according to Embodiment 2 can be achieved with other circuit configurations.

[0053] Furthermore, the embodiments described above are illustrative examples for specifically carrying out the present invention and do not limit the technical scope of the present invention. The technical scope of the present invention is indicated by the claims rather than by the description of the embodiments, and modifications within the literal scope and equivalent meaning of the claims are intended. [Explanation of Symbols]

[0054] 1, 1a Electronic equipment 2, 2a Control device 21 Rectifier circuit 22, 22a, Constant voltage circuit 26, 26a Control circuits 27 Charging circuit 28 First bypass switch 29. Start switch 30 Second bypass switch 221, 222 Smoothing Capacitors 228, 271 Capacitors

Claims

1. A rectifier circuit that rectifies AC voltage, A constant voltage circuit is connected to the rectifier circuit and has a smoothing capacitor for smoothing the DC voltage rectified by the rectifier circuit, and generates a constant voltage. A control circuit that operates using a constant voltage generated by the constant voltage circuit, A charging circuit connected in series with the rectifier circuit and having a capacitor for charging the smoothing capacitor, The system comprises a first bypass switch connected in parallel with the charging circuit for bypassing the charging circuit, The control circuit is a control device that closes the first bypass switch when the normal operating state starts and opens the first bypass switch when the standby state starts.

2. A start switch that is closed to supply the energy charged by the smoothing capacitor to the control circuit when transitioning from standby to normal operation, The system further comprises a second bypass switch connected in parallel with the aforementioned start switch for bypassing the start switch, The control device according to claim 1, wherein the control circuit operates using the energy charged in the smoothing capacitor to close the first and second bypass switches at the start of the normal operating state, and opens the second bypass switch at the start of the standby state.

3. The control device according to claim 2, further comprising a resistor connected in parallel to the charging circuit for compensating for the voltage drop of the smoothing capacitor due to leakage current of the circuit in standby mode.

4. The charging circuit further comprises a resistor connected in parallel, The control device according to claim 1, wherein the control circuit, in standby mode, has fewer functions to operate than in normal operating mode, and the operating clock frequency is lower than in normal operating mode.

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