JP2012178934A - Ac/dc adapter and power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC/DC adapter that reduces standby power.SOLUTION: A smoothing electrolytic capacitor C3 has impedance greater than standard impedance for suppressing a ripple voltage below a standard value. With a primary power plug 11 connected to an outlet, a ripple voltage appearing on a voltage line DC+ is greater than the standard value. A comparator 31 lowers an output voltage to a standby voltage when the ripple voltage is greater than a threshold. A capacitor characteristically combined with the electrolytic capacitor C3 to provide impedance not greater than the standard impedance is connected to an input circuit of a load. When a secondary power plug 17 is connected to the load, the ripple voltage is suppressed below the standard value and the comparator 31 returns the output voltage to a rated voltage.

Description

  The present invention relates to a technology for reducing standby power of an AC / DC adapter used for an electric device, and more specifically, reduces standby power not only when the AC / DC adapter is in a single state but also when connected to the electric device. Related to technology.

  In recent years, it has become more important to reduce power consumption due to standby power consumption (hereinafter referred to as standby power) of electrical equipment. Standby power refers to the power consumed when an electrical device is not performing its original utility. For example, the power consumed when a TV, VCR, air conditioner, etc. is waiting for a remote control operation. That is true. Notebook-type portable computers (hereinafter referred to as notebook PCs) receive power from built-in batteries when they are carried, but in offices, power is supplied from AC / DC adapters that convert AC voltage of commercial power into DC voltage. To work.

  The AC / DC adapter is provided as a device separated from the notebook PC for reasons such as a reduction in heat generation, weight reduction, and miniaturization of the notebook PC. The AC / DC adapter has a primary power plug connected to a commercial power outlet and a secondary power plug connected to a power jack of the notebook PC. Since the outlet is in a place that is difficult for the user to access, such as the floor or wall under the desk, the primary power plug should be connected to the outlet even when the secondary power plug is not connected in normal use. Yes.

  The state of the AC / DC adapter in which the primary power plug is connected to the outlet of the commercial power supply and the secondary power plug is not connected to the jack of the notebook PC is called a single state, and the secondary power plug is connected to the jack of the notebook PC This state is called a connection state. Since the AC / DC adapter has an oscillation circuit on the primary side of the AC / DC adapter, the oscillation circuit continues to operate and generates standby power as long as the primary plug is connected to the commercial power supply even in a single state. In general, the AC / DC adapter main body is not provided with a mechanical switch for stopping the oscillation circuit in a single state from the viewpoint of cost, safety and operability.

  Patent Document 1 discloses a technique for reducing standby power by intermittently operating a PWM circuit regardless of whether an AC / DC adapter including a control terminal is a single unit or a connected state. Patent Document 2 discloses a technique for reducing standby power of an AC adapter connected to an electronic device using a two-wire cord. In this technology, a power circuit for no load and a power circuit for rated load with low loss are prepared in the AC adapter, and whether the plug is connected to the electronic device by detecting the magnitude of the output voltage. Is switched to one of the power supply circuits.

  Patent Literature 3 discloses a technique for reducing standby power by completely stopping the operation of an AC adapter in a standby state using two wires. When the switch of the device is turned off and the output voltage decreases, the photocoupler operates to reset the latch circuit and stop the oscillation circuit. When the switch of the device is turned on, the current detection circuit detects the current flowing from the internal battery, and operates the photocoupler to set the latch circuit and operate the oscillation circuit. With such a configuration, even with two electric wires, the operation of the oscillation circuit can be controlled according to the on / off state of the switch on the device side. Furthermore, the oscillation circuit can be stopped when the AC adapter is removed from the device.

Japanese Patent No. 4487748 JP 2003-111418 A JP 2000-308257 A

  In the invention of Patent Document 1, a control terminal is required for the secondary power plug in order to intermittently operate the AC / DC adapter during standby. In a notebook PC, a processor, a display, a hard disk drive, a charger for charging a battery, and the like consume a lot of power. The rated power of the AC / DC adapter may be selected so that the battery cannot be charged when the system operates at the maximum power consumption from the viewpoint of economy. In this case, since the battery is charged using the difference between the power consumption of the system and the rated power of the AC / DC adapter, the system needs to recognize the rated power of the currently connected AC / DC adapter.

  It is convenient if AC / DC adapters with various rated powers can be connected to one notebook PC. For example, if an AC / DC adapter having a large capacity is used in an office, the battery can be always charged. On the other hand, if an AC / DC adapter with a small capacity is used at the destination, the burden of carrying is reduced. At that time, if the AC / DC adapter has an identification terminal on the secondary power plug, the system can recognize the rated power of the AC / DC adapter when the secondary power plug is connected. When the control terminal is used to control the PWM circuit as in the invention of Patent Document 1, an identification terminal is further provided to make the secondary power plug have four terminals, or the identification terminal is not provided and dedicated to the notebook PC. Inconveniences such as using only the AC / DC adapter of this type arise.

  In the invention of Patent Document 2 in which standby power is reduced by a two-wire system, the power circuit for no load is always operating, and it is necessary to prepare two power systems. In the invention of Patent Document 3, it is necessary to provide an internal battery inside the device to supply power to the AC adapter. Therefore, there is a need for a method that uses only two power circuits to detect that the AC / DC adapter is in a standby state where it is not necessary to supply power and to reduce standby power.

  Accordingly, an object of the present invention is to provide an AC / DC adapter capable of reducing standby power in both a single state and a connected state. A further object of the present invention is to provide an AC / DC adapter that can detect the standby state of the AC / DC adapter only by a power circuit and reduce power consumption. A further object of the present invention is to provide a power supply system composed of such an AC / DC adapter and electrical equipment.

  The principle of the present invention is that the AC / DC adapter detects the magnitude of the ripple voltage superimposed on the output voltage, and the AC / DC adapter automatically performs standby power reduction operation or normal operation. Here, the standby power reduction operation can be an operation for lowering the output voltage or an operation for extending the switching period. The normal operation may be an operation that can output a rated voltage and supply electric power to the electrical device.

  In the present invention, the AC / DC adapter is in a state in which power supply is required in a connected state connected to an electric device, a state in which power supply is not required even in the connected state, or a single state not connected to the electric device. Is detected by the magnitude of the ripple voltage. Use the difference between the capacitance of the smoothing capacitor that reduces the ripple voltage, the equivalent series resistance, and / or the equivalent series inductance to identify the state that requires power supply and the state that does not require power supply using the ripple voltage. can do. Hereinafter, the total characteristic of the smoothing capacitor's capacitance, equivalent series resistance, and equivalent series inductance is referred to as impedance.

Here, Z is the impedance of the smoothing capacitor, C is the capacitance, R is the equivalent series resistance, and L is the equivalent series inductance.

  The AC / DC adapter according to the present invention converts an AC voltage into a DC voltage and supplies electric power to an electrical device. When the switching circuit causes the main switch to perform a switching operation, a ripple voltage is superimposed on the output voltage. The ripple voltage detection circuit detects a ripple voltage in a connection state with respect to the electric device and a single state disconnected from the electric device. By not providing a sufficient smoothing capacitor in the AC / DC adapter, it is possible to always generate a ripple voltage of a predetermined value or more in a single state.

  The standby power control circuit determines that it is in a single state when the ripple voltage is equal to or higher than a predetermined value, and reduces the standby power of the AC / DC adapter. According to such a configuration, it can be determined only by the two-wire power circuit that the AC / DC adapter is in a single state or a connected state, so that the secondary power plug, the AC / DC adapter main body, and the electric device The configuration can be simplified.

  The AC / DC adapter has a first smoothing capacitor that reduces a ripple voltage superimposed on the output voltage, and the ripple voltage is provided in the first smoothing capacitor and the input circuit of the electrical device when the ripple voltage is connected to the electrical device. The combined impedance of the two smoothing capacitors can be configured to decrease below the standard value of the ripple voltage required for the AC / DC adapter. In this case, the impedance of the first smoothing capacitor can reduce the ripple voltage to such a level that abnormal heat generation and abnormal noise do not occur in a single state and cannot be suppressed to the standard value.

  The impedance obtained by synthesizing the first smoothing capacitor and the second smoothing capacitor can be determined to a value necessary for suppressing the ripple voltage below the standard value. By providing the second smoothing capacitor with an impedance characteristic that supplements the first smoothing capacitor, the ripple voltage can be reliably suppressed to less than the standard value when connected to the electrical device.

  As the impedance of the first smoothing capacitor is increased and the impedance of the second smoothing capacitor is decreased, it becomes easier to distinguish the single state from the connected state by the difference in ripple voltage, but the ripple voltage in the single state increases too much. That is not preferable. When the impedance ratio of the first smoothing capacitor and the second smoothing capacitor is in the range of 1: 1 to 2: 1, the ripple voltage is increased to such an extent that the single state and the connected state can be reliably distinguished, and the single state Occurrence of abnormal heat generation and abnormal noise in the AC / DC adapter due to the increased ripple voltage can be prevented.

  The standby power control circuit controls the switching circuit to reduce the output voltage to a standby voltage lower than the rated voltage when the ripple voltage is higher than the predetermined value, and to return the output voltage to the rated voltage when the ripple voltage is lower than the predetermined value. Can do. By reducing the output voltage, the AC / DC adapter can reduce the standby current by reducing the leakage current generated in the device of the secondary side circuit. In addition, by operating the control circuit without setting the output voltage to zero, it is possible to perform a reduction operation of power consumption and a normal operation by determining whether the control circuit itself is in a single state or a connection state with a simple circuit.

  When the electrical device controls connection and disconnection of the second smoothing capacitor to the input circuit, the second smoothing capacitor may not be connected due to circumstances such as overdischarge or removal of the battery. If the standby voltage control circuit is designed to restore the output voltage from the standby voltage to the rated voltage when the current flowing through the output circuit is greater than or equal to the specified value, the standby voltage control circuit increases the output current using the standby voltage. The power supply can be started after returning.

  When the switching circuit operates the main switch by PWM control, the switching circuit can perform an intermittent oscillation operation that skips a predetermined number of operating cycles of the main switch when the ripple voltage is equal to or higher than a predetermined value. By performing the intermittent oscillation operation, the switching frequency of the main switch can be reduced by lowering the switching frequency even in the case of PWM control with a constant cycle. The standby voltage is preferably as low as possible within a range in which the operations of the ripple voltage detection circuit and the standby power control circuit do not become unstable because more standby power can be reduced. However, in the present invention, the standby voltage is set to 25% or less of the rated voltage. be able to.

  In another aspect of the present invention, a power supply system including a portable computer capable of mounting a battery pack and an AC / DC adapter for supplying power to the portable computer is provided. The AC / DC adapter includes a first smoothing capacitor. The portable computer includes a second smoothing capacitor in the input circuit that reduces the ripple voltage below a standard value required for the AC / DC adapter when the AC / DC adapter is connected. If the portable computer controls the connection and disconnection of the second smoothing capacitor to the input circuit, the connection of the second smoothing capacitor is possible when power supply is unnecessary even when the AC / DC adapter is connected. Can be controlled to reduce standby power. While the portable computer is in a power-off state, the system can be connected when a second smoothing capacitor is connected when charging is required and disconnected when charging is complete.

  The portable computer includes a bleeder resistor that causes a current exceeding a predetermined value to flow in the output circuit in response to pressing of the switch when the standby voltage is being output, and the standby power control circuit detects the current flowing through the bleeder resistor. The switching circuit may be controlled so as to return from the standby voltage to the rated voltage. As a result, even when the battery pack of the portable computer is overdischarged and the second smoothing capacitor cannot be connected to the input circuit, the current can be passed through the bleeder resistor to increase the output current and return to the rated voltage. When the bleeder resistance switch is also used as a power button, it does not give a burden on the user to operate, and it is not necessary to add a switch to the casing of the portable computer.

  According to the present invention, it is possible to provide an AC / DC adapter capable of reducing standby power in both a single state and a connected state. Furthermore, according to the present invention, it is possible to provide an AC / DC adapter that can detect a standby state of the AC / DC adapter only by a power circuit and reduce power consumption. Further, according to the present invention, it is possible to provide a power supply system including such an AC / DC adapter and an electric device.

It is a functional block diagram which shows the structure of the outline of an AC / DC adapter. 2 is a functional block diagram showing a schematic configuration of a notebook PC. FIG. It is a flowchart explaining operation | movement of the power supply system comprised by the AC / DC adapter and notebook PC. It is a figure which shows the state of the output voltage in the procedure of FIG. 3, and the ripple voltage superimposed on it.

[Configuration of AC / DC adapter]
FIG. 1 is a functional block diagram showing a schematic configuration of an AC / DC adapter 10 according to the present embodiment. FIG. 2 is a functional block diagram showing a schematic configuration of the notebook PC 100 that operates by receiving power from the AC / DC adapter. The AC / DC adapter 10 includes a primary power plug 11 connected to the outlet of the AC power source and a secondary power plug 17 connected to the power jack 101 of the notebook PC 100. A primary side circuit 13 is connected to the primary power plug 11, and a secondary side circuit 15 is connected to the primary side circuit 13 with an insulating transformer ITR interposed therebetween. The secondary side circuit 15 is connected to the secondary power plug 17 through three lines, ie, a voltage line DC +, an identification line ID, and a ground line GND.

  The primary power plug 11 is connected to a rectifying bridge diode 21 that full-wave rectifies an AC voltage. The output of the rectifier bridge diode 21 is connected to an electrolytic capacitor C1 that smoothes the full-wave rectified DC voltage. The insulation transformer ITR includes a primary winding P, a secondary winding S, and an auxiliary winding A. The positive terminal of the primary winding P is connected to the positive terminal of the rectifier bridge diode 21, and the negative terminal is a field effect transistor (FET) configured as a main switch between the negative terminal of the rectifier bridge diode 21. ) 1 is connected. The gate of the FET 1 is connected to the output terminal OUT of a pulse width modulation IC (PWM-IC) 25.

  The anode of the diode D1 is connected to the plus terminal of the auxiliary winding A, and the cathode of the diode D1 is connected to the power supply terminal Vcc of the PWM-IC 25. As long as the primary power plug 11 is connected to the outlet, the PWM-IC 25 can operate with power supplied from the auxiliary winding A. An electrolytic capacitor C2 is connected between the cathode of the diode D1 and the negative terminal of the auxiliary winding A. The electrolytic capacitor C2 smoothes the DC voltage that is half-wave rectified by the diode D1.

  A starting resistor R1 is connected between the positive terminal of the primary winding P and the cathode of the diode D1. The starting resistor R1 starts operation by applying a voltage to the power supply terminal Vcc of the PWM-IC 25 when the primary power plug 11 is connected to the outlet. The PWM-IC 25 is an IC controller that controls the output voltage output from the voltage line DC + by controlling on / off of the FET 1. The PWM-IC 25 controls the voltage applied to the primary winding P of the insulation transformer ITR by variably controlling the ON period (duty ratio) while keeping the ON / OFF cycle of the FET 1 constant.

  The PWM-IC 25 includes an output terminal OUT, a power supply terminal VCC, and a feedback terminal FB. The output terminal OUT sends a signal for controlling the FET 1 with a duty ratio corresponding to the output voltage to the gate. The power supply terminal VCC receives power for operating the PWM-IC 25. A phototransistor PTR is connected to the feedback terminal FB. The feedback terminal FB receives a signal for controlling the duty ratio from the phototransistor PTR in order to maintain the output voltage of the voltage line DC + at a rated voltage or a standby voltage described later.

  The photo transistor PTR is formed integrally with the photo diode LED of the secondary side circuit 15 to constitute a photo coupler. The photo coupler functions to insulate between the primary side circuit 13 and the secondary side circuit 15 of the isolation transformer ITR. Instead of the photo coupler, a solid state relay or an electromagnetic relay having a similar insulation function may be employed. The primary side circuit 13 can adopt the same structure as the conventional AC / DC adapter. In conventional AC / DC adapters, when the primary power plug is connected to the outlet, the PWM-IC automatically operates to output the rated voltage even when the secondary power plug is not connected to the notebook PC 100. As a result, a large amount of standby power was consumed.

  The anode of the diode D2 is connected to the plus terminal of the secondary winding S, and one terminal of the inductor L is connected to the cathode of the diode D2. The other terminal of the inductor L is connected to the voltage line DC +. An electrolytic capacitor C3 is connected between the voltage line DC + and the ground line GND connected to the negative terminal of the secondary winding S. The inductor L and the electrolytic capacitor C3 constitute a smoothing circuit that removes a ripple component from the voltage half-wave rectified by the diode D2 and smoothes the output voltage.

  In the conventional AC / DC adapter, the impedance of the electrolytic capacitor C3 is set to a value small enough to suppress the ripple voltage superimposed on the output voltage below the standard value. The impedance required by the electrolytic capacitor C3 in order to suppress the ripple voltage superimposed on the output voltage below the standard value required for the AC / DC adapter is referred to as the standard impedance. In the AC / DC adapter 10, the impedance of the electrolytic capacitor C3 is set to a value larger than the standard impedance.

  However, by connecting the multilayer ceramic capacitor C5 connected to the input circuit of the notebook PC 100, a parallel circuit with the electrolytic capacitor C3 is formed, and the impedance of the electrolytic capacitor C3 of the AC / DC adapter 10 is compensated. Yes. By making the combined impedance sufficiently small, the ripple voltage is suppressed to less than the standard value when power is supplied to the notebook PC 100. Therefore, in the AC / DC adapter 10, when the secondary power plug 17 is not connected to the power jack 101 of the notebook PC 100, a ripple voltage higher than the standard value is superimposed on the output voltage.

  Voltage dividing resistors R2 and R3 connected in series are connected between the voltage line DC + and the ground line GND. A connection portion between the voltage dividing resistor R2 and the voltage dividing resistor R3 generates a control voltage V1 for the PWM-IC 25 to control the output voltage. Further, a light emitting diode LED, a current limiting resistor R4, and a shunt regulator SR connected in series are connected between the voltage line DC + and the ground line GND. A connection point between the voltage dividing resistor R2 and the voltage dividing resistor R3 is connected to a reference voltage (REF) terminal of the shunt regulator SR, and a control voltage V1 is supplied to the REF terminal.

  The voltage dividing resistors R2 and R3, the current limiting resistor R4, the light emitting diode LED, and the shunt regulator SR constitute a feedback circuit that controls the output voltage of the AC / DC adapter 10. Here, the operation when the feedback circuit controls the output voltage on the assumption that the secondary power plug 17 is connected to the notebook PC 100 will be described. The PWM-IC 25 controls the FET 1 with a predetermined duty ratio and outputs a rated voltage to the voltage line DC +. When the power consumption of the notebook PC 100 increases and the voltage of the output circuit decreases, the control voltage V1 also decreases.

  The shunt regulator SR decreases the control current I1 flowing through the light emitting diode LED by decreasing the internal base current and the collector current when the control voltage V1 is decreased. The shunt regulator SR increases the control current I1 when the control voltage V1 rises. The photo diode LED emits light with an intensity corresponding to the magnitude of the control current I1. The output as the light emission amount from the photo diode LED is supplied to the feedback terminal FB of the PWM-IC 25 through the photo transistor PTR.

  The PWM-IC 25 outputs a signal with a small duty ratio from the output terminal OUT when the control current I1 flowing through the photodiode LED increases, and outputs a signal with a large duty ratio when the control current I1 decreases. The output voltage is increased to maintain the output voltage at a constant value. The identification resistor R8 is connected between the identification line ID and the ground line GND. The identification resistor R8 is used for the notebook PC 100 to recognize the rated capacity of the AC / DC adapter 10 from the resistance value when the secondary power plug 17 is connected.

  The AC / DC adapter 10 further includes a comparator 31 that detects a ripple voltage superimposed on the output voltage and controls the output voltage between the rated voltage and the standby voltage. When the output voltage decreases to the standby voltage, the operational amplifier and the comparator connected to the secondary circuit 15 reduce the current leaking to the ground, thereby reducing standby power. In order to reduce the standby power, the standby voltage should be as low as possible, but the limit can be selected within the range in which the transistor connected to the secondary circuit 15 operates normally. The standby voltage can be 25% or less of the rated voltage. As an example, the standby voltage can be 5 V when the rated voltage is 20 V.

  One input terminal of the comparator 31 is connected to the voltage line DC + through the capacitor C4, and the other input terminal is connected to the reference voltage REF. The output terminal of the comparator 31 is connected to the cathode of the light emitting diode LED through the resistor R5. If the multilayer ceramic capacitor C5 cannot be used as a smoothing capacitor because the secondary power plug 17 is not connected to the power jack 101, a ripple voltage of about 5 V (between peaks) is generated on the voltage line DC + as an example. When the secondary power plug 17 is connected to the power jack 101, the impedance of the synthesized smoothing capacitors C3 and C5 becomes below the standard value, so that the ripple voltage drops to about 250 mV as an example.

  The output of the comparator 31 is low at the ground level when the ripple voltage is equal to or higher than a predetermined value. When the comparator 31 outputs low, it is determined that the FET 3 connected in series with the electrolytic capacitor C2 is in an off state as will be described later even when the AC / DC adapter 10 is in a single state or in a connected state. It can be said that. At this time, the resistance value of the resistor R5 is determined such that a control current I1 corresponding to a value for reducing the output voltage to the standby voltage flows to the light emitting diode LED.

  The comparator 31 does not affect the control current I1 flowing in the light emitting diode LED because the output becomes high impedance high when the ripple voltage is less than a predetermined value. Therefore, when the output of the comparator 31 is high, the control current I1 is controlled by the shunt regulator SR, and the output voltage is maintained at the rated voltage. Note that the magnitude of the ripple voltage detected by the comparator 31 is not limited to the peak-to-peak voltage, and may be an average voltage or an effective value.

  A current sense resistor R7 is connected to the ground line GND. The AC / DC converter 10 further includes a differential amplifier 33 and a comparator 35 for detecting that the output current I2 is equal to or greater than a predetermined value when the output voltage DC + is a standby voltage and returning the output voltage DC + to the rated voltage. Including. Two input terminals of the differential amplifier 33 are connected to both ends of the current sense resistor R 7, and an output is connected to one input terminal of the comparator 35.

  A reference voltage REF is connected to the other input terminal of the comparator 35. The differential amplifier 33 amplifies and outputs a voltage proportional to the current I2 flowing through the sense resistor R7. The reference voltage REF is set to a voltage corresponding to about 1 to 2 A of the output current I2 flowing through the current sense resistor R7. The output of the comparator 35 is connected to the REF terminal of the shunt regulator SR through the resistor 6.

  When the comparator 35 detects that the output current I2 of about 1 to 2 A flows in the output circuit by the output of the differential amplifier 33 when the output voltage is the standby voltage, the output becomes the low level of the ground level. When the output of the comparator 35 becomes low, the reference voltage V1 decreases and the control current I1 decreases, so the output voltage increases. At this time, the comparator 31 outputs low, but the resistance value of the resistor R6 is set to a value that maintains the control voltage V1 so that the control current I1 corresponding to a value that raises the output voltage to the rated voltage flows to the light emitting diode LED. Has been. In the comparator 35, when the output current I2 is less than the predetermined value, the output becomes high impedance high and does not affect the control voltage V1 determined by the output voltage and the voltage dividing resistors R2 and R3.

  Note that FIG. 1 is merely a simplified description of the main hardware configuration and connection relationships related to the present embodiment in order to describe the present embodiment. In addition to those mentioned in the above description, many devices are used to configure the AC / DC adapter 10. However, they are well known to those skilled in the art and will not be described in detail here. A person skilled in the art arbitrarily selects a plurality of blocks described in FIG. 1 as one integrated circuit or device or conversely divides one block into a plurality of integrated circuits or devices. To the extent possible, it is included in the scope of the present invention.

[Configuration of notebook PC]
Next, the configuration of the notebook PC 100 will be described. The power jack 101 is provided on the casing of the notebook PC 100 and is connected to the secondary power plug 17. The power jack 101 is connected to an input circuit composed of a voltage line DC +, an identification line ID, and a ground line GND corresponding to the output circuit of the AC / DC adapter 10. A multilayer ceramic capacitor C5 and an FET 3 connected in series are connected between the voltage line DC + and the ground line GND. The FET 3 corresponds to a switch that controls the magnitude of the ripple voltage superimposed on the output voltage of the AC / DC adapter 10.

  By connecting the multilayer ceramic capacitor C5, a parallel circuit with the electrolytic capacitor C3 is formed, and the impedance of the electrolytic capacitor C3 of the AC / DC adapter 10 is compensated. Therefore, by reducing the combined impedance sufficiently, when the AC / DC adapter 10 is connected to the notebook PC 100, the impedances of the electrolytic capacitor C3 and the multilayer ceramic capacitor C5 are combined, and the voltage line DC + of the notebook PC 100 is combined. The ripple voltage superimposed on is kept below the standard value.

  The magnitude of the impedance of the electrolytic capacitor C3 is lower than the range in which the ripple voltage generated in the output circuit with the secondary power plug 17 pulled out does not cause abnormal heat generation, noise or noise to the AC / DC adapter 10. In addition, the range in which the comparator 31 can detect whether the secondary power plug 17 is connected to the power jack 101 or pulled out by the ripple voltage can be determined as an upper limit. In one example, the impedance ratio of the electrolytic capacitor C3 and the multilayer ceramic capacitor C5 can be in the range of about 1: 1 to 2: 1.

  The notebook PC 100 is generally provided with a capacitor for removing noise mixed in the input circuit, but its capacitance is much smaller than that of the multilayer ceramic capacitor C5. Further, when the AC / DC adapter 10 is mounted with a smoothing capacitor of standard impedance, the ripple voltage superimposed on the output voltage is sufficiently suppressed to less than the standard value. Even if a smoothing capacitor is added to the notebook PC 100, it is difficult to detect the insertion / extraction of the secondary power plug 17 because the difference in ripple voltage cannot be secured sufficiently.

  A bleeder resistor R9 and a power button PB connected in series are further connected between the voltage line DC + and the ground line GND. When the notebook PC 100 is in a power-off state and the AC / DC adapter 10 outputs a standby voltage, the bleeder resistor R9 applies an output current I2 of a predetermined value or more to the current sense resistor R7 when the power button PB is pressed. Play a role.

  The reference voltage REF of the comparator 35 mounted on the AC / DC adapter 10 outputs high because the output current I2 is small when the notebook PC 100 is in the power-off state, and the bleeder with the standby voltage by pressing the power button PB. It can be determined to output low when a current flows through the resistor R9. The identification line ID is connected to the power controller 103, and the EC 107 performs power management of the notebook PC 100 using the resistance value of the identification resistor R8 read from the power controller 103.

  An FET 2 and a diode D 3 are connected in series to the voltage line DC +, and the cathode of the diode D 3 is connected to the switching circuit 109. The FET 2 is turned off while the connected AC / DC adapter 10 outputs a standby voltage, so that a ripple voltage exceeding the standard value does not enter the inside. The charger 105 can charge the battery pack 111 with the power of the AC / DC adapter 10 when the rated power of the AC / DC adapter 10 has a margin for the power consumption of the system.

  The AC / DC adapter 10 can charge the battery pack 111 by supplying power to the charger 105 when the power supplied to the DC / DC converter 113 is less than a predetermined value. The power terminal of the charger 105 has a primary side connected to the drain of the FET 2 and a secondary side connected to the switching circuit 109. A control terminal of the charger 105 is connected to an embedded controller (EC) 107.

  The power controller 103 is a semiconductor logic circuit that controls the FET 2, FET 3, the switching circuit 109, and the DC / DC converter 113. A power button PB is connected to the power controller 103. The power button PB is provided on the surface of the casing of the notebook PC 100 and is used to turn on the notebook PC 100. The terminal connected to the bleeder resistor R9 of the power button PB, the control terminal of the FET 3, and the terminal connected to the power controller 103 operate in conjunction so as to be turned on only when pressed.

  The EC 107 is a microcomputer that manages the power and temperature of the notebook PC 100. The EC 107 instructs the power controller 103 to control the power of the notebook PC 100. The battery pack 111 is compatible with a smart battery system, and the EC 107 acquires battery information from the battery pack 111 and controls the charger 105. The switching circuit 109 switches the system when the power source for the DC / DC converter 113 is switched to either the AC / DC adapter 10 or the battery pack 111 and when the battery pack 111 is charged.

  The notebook PC 100 conforms to the ACPI standard, and transitions to a power state of one of a power-on state (S0), a suspend state (S3), a hibernation state (S4), and a soft-off state (S5). To do. In the hibernation state and the soft-off state, power is supplied to the power controller 103 and the EC 107, but power is not supplied to most other devices, and the notebook PC 100 consumes the lowest power.

  In this specification, the hibernation state and the soft-off state are collectively referred to as a power-off state. The DC / DC converter 113 is composed of a plurality of blocks, and supplies power to devices in a range corresponding to the power state of the notebook PC 100. The system component 115 includes hardware such as a CPU, main memory, disk drive, and network controller, and a program executed by the CPU. The EC 107 is also a part of the system component 115.

  The EC 107 switches on / off states of the FET 2 and FET 3 via the power controller 103 based on data or information received from the battery pack 111 or the system component 115. The EC 107 normally controls the FET 2 and FET 3 to be on when the notebook PC 100 is in a power-on state. At this time, the notebook PC 100 can receive power from the AC / DC adapter 10 at the rated voltage.

  When the EC 107 receives a signal for stopping the power supply from the AC / DC adapter 10 from the system component 115 or the battery pack 111, the EC 107 turns off the FET 3 to increase the ripple voltage of the voltage line DC +, and the output voltage becomes the standby voltage. The standby power of the AC / DC adapter 10 can be reduced. The EC 107 prevents the standby voltage with a large ripple voltage from being supplied to the notebook PC 100 by turning off the FET 2 when turning off the FET 3.

  Specifically, when the battery pack 111 requests charging when the EC 107 is in a power-off state, the FET 3 is turned on so that the AC / DC adapter 10 outputs a rated voltage, and the battery pack 111 does not request charging. At this time, or when charging is completed, the FET 3 can be turned off and the AC / DC adapter 10 can be controlled to output a standby voltage.

  In buildings where a large number of notebook PCs 100 are introduced, peak-cut operation may be performed to reduce the power consumption of the entire building during a specific summer time. The system component 115 recognizes that the peak cut operation is performed through the network. The EC 107 switches the switching circuit 109 so as to supply power from the battery pack 111 for a predetermined time when receiving a notification to execute the peak cut operation from the system component 115 in the power-on state. .

  The EC 107 can reduce standby power of the AC / DC adapter 10 by turning off the FET 2 and FET 3 at that time. Thus, even when the notebook PC 100 is in the connected state where the secondary power plug 17 is connected to the power jack 101, the FET 3 is turned off when the power supply is not required, thereby turning off the AC / DC adapter 10. Standby power can be reduced. Furthermore, the power controller 103 can turn on the FET 3 when the power button PB is pressed to start the notebook PC 10. In this way, when the notebook PC 100 is activated when the secondary power plug 17 is connected, the AC / DC adapter 10 is initially controlled to be a power source, and the battery pack 111 is Electricity can be secured. Alternatively, the opening / closing of the FET 3 may be directly linked to the pressing of the power button PB.

[Power system operation]
Next, the operation of the power supply system including the AC / DC adapter 10 and the notebook PC 100 will be described. FIG. 3 is a flowchart showing operations of the AC / DC adapter 10 and the notebook PC 100. FIG. 4 is a diagram illustrating the state of the output voltage and the ripple voltage superimposed thereon in the procedure of FIG. In block 201, the primary power plug 11 is connected to the outlet of the commercial power source. The PWM-IC 25 automatically starts oscillation and generates an output voltage. Since the impedance of the electrolytic capacitor C3 is less than the standard impedance, a ripple voltage exceeding the threshold Th1 is superimposed on the output voltage, and the comparator 31 outputs low in block 203.

  As a result, in block 205, the control current I1 flowing through the light emitting diode LED increases, and the PWM-IC 25 decreases the output voltage to the standby voltage (time t1). At this time, since the output current I2 is zero, the comparator 35 outputs high and does not affect the control voltage V1. As a result, the AC / DC adapter 10 reduces standby power in a single state. In block 207, the secondary power plug 17 is connected to the power jack 101.

  The comparator 31 monitors the magnitude of the ripple voltage superimposed on the output voltage while the primary power plug 11 is connected to the outlet. In block 209, if FET3 is turned on in the notebook PC 100, the ripple voltage is reduced to less than the threshold Th2 by connecting the multilayer ceramic capacitor C5 to the output circuit of the AC / DC adapter 10 (time t2), and the comparator The output of 31 goes high. At this time, the control current I1 corresponding to the control voltage V1 in which the standby voltage is divided by the voltage dividing resistors R2 and R3 flows to the light emitting diode LED, and in block 211, the PWM-IC 25 controls the output voltage to the rated voltage ( Time t3). At this time, since the output of the comparator 31 is high, the control current I1 is not affected.

  The differential amplifier 33 and the comparator 35 monitor the magnitude of the output current I2 while the primary power plug 11 is connected to the outlet. At this time, the control current I1 is influenced by the magnitude of the output current I2. I do not receive it. When the output current I2 is larger than the threshold value, the comparator 35 makes the output low so that the control voltage V1 is lowered to a predetermined value, and the PWM-IC 25 raises the output voltage to the rated voltage. When the output current I2 is smaller than the threshold value, the output of the comparator 35 becomes high, and the control voltage V1 becomes a value obtained by dividing the standby voltage. Since the output of the comparator 31 is high, the PWM-IC 25 increases the output voltage so that the control current I1 increases to a value corresponding to the rated voltage.

  In block 213, in the notebook PC 100, the EC 107 detects whether there is a charge stop request from the battery pack 111 in the power-off state or a peak cut request from the system component 115 in the power-on state. When requested, the EC 107 turns off the FETs 2 and 3 at block 215 (time t4). As a result, in block 217, since the multilayer ceramic capacitor C5 is released from the output circuit of the AC / DC adapter 10, the ripple voltage superimposed on the output voltage increases to a threshold Th1 or more.

  In block 217, the output of the comparator 31 becomes low, the control current I1 increases, and the PWM-IC 25 decreases the output voltage to the standby voltage (time t5). At this time, if it is after the charge stop request or the peak cut request, the FETs 2 and 3 are turned off, so the output current I2 is sufficiently smaller than the threshold value of the comparator 35, and the comparator 35 outputs high and the control voltage V1. The output voltage is maintained at a value at which the standby voltage is reached.

  Therefore, even if the AC / DC adapter 10 is connected to the notebook PC 100, the standby power can be reduced by outputting the standby voltage when the notebook PC 100 does not require power. In block 219, the EC 107 determines whether or not there is a request to restore the output voltage from the battery pack 111 or the system component 115 to the rated voltage.

  When there is a return request, the power controller 103 turns on FETs 2 and 3 in block 221. As a result, the ripple voltage superimposed on the output voltage falls below the threshold Th2, and the output voltage rises to the rated voltage in block 211. Here, it is assumed that the FET 3 is turned off and the FET 2 is turned on when power is not supplied to the power controller 103. When the battery pack 111 is overdischarged or the battery pack 111 is removed while the output voltage is outputting the standby voltage in the power-off state, the power of the power controller 103 is stopped and the FET 3 is turned on. It is expected that it will not be possible.

  When the user recognizes that power is not supplied from the AC / DC adapter 10 with the indicator of the notebook PC 10, the user presses the power button PB to activate the notebook PC 100 in block 223. As a result, a current flows through the bleeder resistor R9 and the output current I2 rises above the threshold value of the comparator 35. The output of the comparator 35 becomes low and the resistor R6 controls the control voltage V1 so that the shunt regulator SR sets the control current I1 to a value corresponding to the rated voltage. At this time, since the ripple voltage is large, the output of the comparator 31 is low, but the shunt regulator SR increases the control current I1, and the output voltage rises to the rated voltage in block 225.

  At this time, since a ripple voltage higher than a specified value is superimposed on the output voltage, the EC 107 immediately turns on the FET 3 through the power controller 103 to suppress the ripple voltage to less than the standard value when power is supplied. In block 227, when the secondary power plug 17 is pulled out to use the notebook PC 100 for mobile, the process proceeds to block 203, and the AC / DC adapter 10 again performs standby power reduction operation in a single state.

  Up to now, the standby power reduction operation of the AC / DC adapter 10 has been described with reference only to reducing the standby voltage in the secondary circuit 15 by lowering the output voltage to the standby voltage. The PWM-IC 25 can also control the FET 1 in an intermittent oscillation mode called a burst mode (registered trademark). The intermittent oscillation mode is normally used for the purpose of reducing standby power by substantially reducing the operating frequency by skipping a predetermined number of PWM oscillation periods at light load.

  In the present invention, when operating with the standby voltage when the ripple voltage is equal to or higher than the predetermined value, the standby power of the primary circuit 13 including the switching loss of the FET 1 is simultaneously reduced by shifting the PWM-IC 25 to the intermittent oscillation mode. can do. Instead of the PWM-IC 25, a pulse frequency modulation IC (PFM-IC) that variably controls the off period while keeping the on period of the FET 1 constant may be employed.

  Although the present invention has been described with the specific embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and is known so far as long as the effects of the present invention are achieved. It goes without saying that any configuration can be adopted.

DESCRIPTION OF SYMBOLS 10 ... AC / DC adapter 11 ... Primary power plug 13 ... Primary side circuit 15 ... Secondary side circuit 17 ... Secondary power plug 25 ... PWM-IC
ITR ... Insulation transformer

Claims (20)

An AC / DC adapter that converts AC voltage to DC voltage and supplies electric power to an electrical device,
A switching circuit that controls the output voltage by controlling the main switch;
A ripple voltage detection circuit for detecting the ripple voltage in a connected state connected to the electrical device and in a single state disconnected from the electrical device;
An AC / DC adapter comprising: a standby power control circuit that determines that the state is the single state when the ripple voltage is equal to or higher than a predetermined value and reduces standby power of the AC / DC adapter.   The AC / DC adapter includes a first smoothing capacitor that reduces a ripple voltage superimposed on the output voltage, and the first smoothing capacitor and the electric device when the ripple voltage is connected to the electric device. The AC / DC adapter according to claim 1, wherein the impedance is reduced to a value less than a standard value of a ripple voltage required for the AC / DC adapter due to a combined impedance of a second smoothing capacitor included in the input circuit.   The impedance of the first smoothing capacitor is larger than the standard impedance satisfying the standard value of the ripple voltage, and the impedance of the second smoothing capacitor is a value equal to or less than the difference between the standard impedance and the impedance of the first smoothing capacitor. The AC / DC adapter according to claim 2.   The AC / DC adapter according to claim 2 or 3, wherein an impedance ratio between the first smoothing capacitor and the second smoothing capacitor is in a range of 1: 1 to 2: 1.   The standby power control circuit reduces the output voltage to a standby voltage lower than a rated voltage when the ripple voltage is equal to or higher than the predetermined value, and returns the output voltage to the rated voltage when the ripple voltage is lower than the predetermined value. The AC / DC adapter according to claim 1, wherein the switching circuit is controlled.   The standby power control circuit returns the output voltage from the standby voltage to the rated voltage when a current flowing through the output circuit becomes a predetermined value or more while the standby voltage is being output. AC / DC adapter.   The switching circuit causes the main switch to operate by PWM control, and the switching circuit performs an intermittent oscillation operation that skips a predetermined number of switching cycles of the main switch when the ripple voltage is a predetermined value or more. The AC / DC adapter according to claim 6. A power supply system including an electric device and an AC / DC adapter for supplying electric power to the electric device,
The AC / DC adapter is
A switching circuit that controls the output voltage by controlling the main switch;
A ripple voltage detection circuit for detecting the ripple voltage in a connected state connected to the electrical device and in a single state disconnected from the electrical device;
A standby power control circuit that determines that the ripple voltage is equal to or greater than a predetermined value and reduces the standby power of the AC / DC adapter,
The electrical device is an input circuit,
A power supply system comprising a smoothing capacitor that reduces the ripple voltage below a standard value required for the AC / DC adapter when the AC / DC adapter is connected.   The power supply system according to claim 8, wherein the electrical device controls connection and disconnection of the smoothing capacitor with respect to the input circuit. A power supply system comprising a portable computer capable of mounting a battery pack and an AC / DC adapter for supplying power to the portable computer,
The AC / DC adapter is
A switching circuit that controls the output voltage by controlling the main switch;
A first smoothing capacitor that reduces a ripple voltage superimposed on the output voltage;
A ripple voltage detection circuit for detecting the ripple voltage in a connected state connected to the portable computer and a single state disconnected from the portable computer;
A standby power control circuit that determines that the ripple voltage is equal to or greater than a predetermined value and reduces the standby power of the AC / DC adapter,
The portable computer is an input circuit,
A power supply having a second smoothing capacitor that reduces the ripple voltage below a standard value required for the AC / DC adapter with an impedance combined with the first smoothing capacitor when the AC / DC adapter is connected. system.   The power supply system according to claim 10, wherein the portable computer controls connection and disconnection of the second smoothing capacitor to the input circuit in response to an instruction from the system.   The power supply system according to claim 11, wherein the instruction from the system is an instruction to start or end charging of the battery pack that is generated in a power-off state. The portable computer has a bleeder resistor that causes a current of a predetermined value or more to flow to an output circuit of the AC / DC adapter in response to pressing of a switch when the AC / DC adapter supplies the standby voltage;
The power supply system according to any one of claims 10 to 12, wherein the standby power control circuit controls the switching circuit to detect a current flowing through the bleeder resistor and to restore the standby voltage to the rated voltage. . An AC / DC adapter that can be connected to an electrical device is a method for reducing standby power,
Starting a switching operation when the primary power plug is connected to a commercial power source;
The AC / DC adapter detecting a ripple voltage superimposed on an output voltage;
Generating an output voltage on which a ripple voltage of a predetermined value or more is superimposed when the AC / DC adapter is not connected to the electrical device;
A method in which the AC / DC adapter performs a standby power reduction operation when the ripple voltage is equal to or higher than the predetermined value. Outputting a voltage on which a ripple voltage less than a predetermined value is superimposed when the AC / DC adapter is connected to the electrical device;
The method according to claim 14, further comprising the step of normal operation of the AC / DC adapter when the ripple voltage is less than the predetermined value. A method for reducing standby power of an AC / DC adapter that includes a primary power plug and a secondary power plug and can be connected to a portable computer equipped with a battery pack,
Providing the input circuit with a smoothing capacitor that reduces the ripple voltage superimposed on the output voltage of the AC / DC adapter by the portable computer;
Starting a switching operation when the primary power plug is connected to a commercial power source;
The portable computer disconnecting the smoothing capacitor from the input circuit to increase the ripple voltage while the secondary power plug is connected to the portable computer;
Detecting the increase of the ripple voltage and causing the AC / DC adapter to reduce the standby power. The portable computer connecting the smoothing capacitor to the input circuit to reduce the ripple voltage while the secondary power plug is connected to the portable computer;
The method according to claim 16, further comprising the step of detecting that the ripple voltage has dropped and causing the AC / DC adapter to perform normal operation.   The method according to claim 16 or 17, wherein the standby power reduction operation is an operation in which the AC / DC adapter reduces an output voltage to a standby voltage.   The method according to claim 18, wherein the smoothing capacitor is connected to the input circuit when the battery pack is requested to be charged while the portable computer is in a power-off state.   The method according to any one of claims 16 to 19, wherein the standby power reduction operation is an operation of extending a period of the switching operation.

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