JPH11299090A - Power supply adapter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a non-load state and to make the loss extremely small. SOLUTION: An AC1 switch circuit SW1 and a capacitor becoming high impedance are installed on the primary side of a transformer 12 in parallel. The AC12 switch circuit SW1 is controlled by a control circuit 16. One secondary side of the transformer 12 is connected to the anode of a diode 13 and a capacitor 14 is inserted between the cathode of the diode 13 and the other secondary side of the transformer 12. An AC2 switching circuit SW2 is inserted between the cathode of the diode 13 and a terminal T3. A load detection circuit 15 is connected to both ends of an AC2 switching circuit SW2. The load detection circuit 15 supplies a signal to the control circuit 16 for controlling the AC1 switching circuit SW1 and controls the AC2 switching circuit SW2. The control circuit 16 controls the on/off operation of the AC1 switching circuit SW1, in accordance with the supplied signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply adapter capable of substantially eliminating loss when no load is applied.

[0002]

2. Description of the Related Art A power supply adapter (hereinafter, referred to as an AC adapter) capable of both supplying and charging power to a set of electronic devices having a secondary battery therein (hereinafter, referred to as a set) has been known. ing. The AC adapter is connected to the set when charging the secondary battery of the set, operating the set independently of charging, or operating the set while charging. Immediately after performing these operations,
There is not much disconnection between the adapter and the set.

FIG. 20 is a block diagram of a conventional AC adapter.
Shown in Between the terminal T1 and one of the primary sides of the transformer 163, an AC switch circuit 161 and a capacitor 162 having high impedance are inserted in parallel. The other primary side of the transformer 163 is connected to the terminal T2.

[0004] One of the secondary sides of the transformer 163 is connected to the anode of the diode 164, and between the cathode of the diode 164 and the other side of the secondary side of the transformer 163.
Capacitor 165 and detection circuit 169 are inserted in parallel. The collector of the transistor 166 is a diode 1
64, the emitter of which is connected to terminal T3
Connected to A resistor 167 is inserted between the collector and the emitter of the transistor 166. The cathode of Zener diode 168 is connected to the base of transistor 166, and its anode is connected to terminal T4. Terminal T4 is connected to the other secondary side of transformer 163.
When the detection circuit 169 detects a load, a signal is transmitted to the control circuit 170. The control circuit 170 controls the ON / OFF operation of the AC switch circuit 161 according to the signal. The set load 171 is connected to the terminal T
3, T5 and terminals T4, T6.

[0005]

At this time, when the AC switch circuit 161 is turned off, the supply of the voltage power to the set is completely stopped, so that the signal transmitted from the set cannot be output. . For this reason, the AC switch circuit 161 is always turned on, and power is supplied to the secondary side. That is, as shown in FIG. 21, it is not possible to eliminate a loss portion (shaded portion in FIG. 21) irrespective of the load state unless the device is completely stopped. That is, there is a problem that power cannot be completely saved because a loss has occurred regardless of the state of the load.

Further, when the AC switch circuit 161 is turned off to have a high impedance state, the detection circuit 169 for detecting a load cannot be operated.

Further, when the AC switch circuit 161 is turned off, the voltage drops.
There was a problem that it was not possible to turn on the 61.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to detect a no-load state, minimize the loss, detect connection of a load, and output a predetermined power supply in view of these problems. It is to provide a power supply adapter which can be used.

[0009]

According to a first aspect of the present invention, there is provided a power supply adapter which is connected to a commercial power supply and outputs a predetermined power, a power supply circuit for generating an output power,
A load detecting means for detecting the presence or absence of a load, and an output power generation operation of the power supply circuit is stopped when no load is detected by the load detecting means, and a necessary power is supplied to the load detecting means to connect the load. And a power supply switching means for starting an output power generation operation of the power supply circuit when detecting that the power supply is being performed.

[0010] The AC in the primary side of the transformer in the AC adapter
1 switch circuit, and a high impedance element such as a capacitor, a resistor,
A coil or the like is provided. Furthermore, an AC2 switch circuit is provided on the secondary side of the transformer, and a load detection circuit inserted in parallel with the AC2 switch circuit can detect the presence or absence of a load. AC1 switch circuit and AC
The two-switch circuits are both turned on when a load is connected, and are both turned off when there is no load. When the AC1 switch circuit is turned off at the time of no load, the input becomes a high impedance state,
Loss can be reduced. With this high-impedance input, power enough to operate the load detection circuit is output from the secondary side of the transformer.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. An AC1 switch circuit SW1 and a high impedance capacitor 11 are inserted in parallel between the terminal T1 and one of the primary sides of the transformer 12. The other primary side of the transformer 12 is connected to the terminal T2. A
The C1 switch circuit SW1 is controlled by the control circuit 16.

One of the secondary sides of the transformer 12 is connected to the anode of the diode 13, and a capacitor 14 is inserted between the cathode of the diode 13 and the other of the secondary side of the transformer 12. A voltage power supply is generated from the diode 13 and the capacitor 14. An AC2 switch circuit SW2 is connected between the cathode of the diode 13 and the terminal T3.
Is inserted. The load detection circuit 15 is connected to both ends of the AC2 switch circuit SW2, and detects whether a load is connected. In accordance with the detection result, a signal is supplied to the control circuit 16 to control the AC1 switch circuit SW1, and the ON / OFF operation of the AC2 switch circuit SW2 is controlled. The control circuit 16 controls the ON / OFF operation of the AC1 switch circuit SW1 according to the supplied signal.

The set comprises terminals T3, T5 and T4, T
6 are connected. A set switch circuit SW3 is inserted between the terminal T5 and the set load 17, and the load 1
7 and the terminal T6 are connected.

In the embodiment shown in FIG. 1, the capacitor 11 is inserted in parallel with the AC1 switch circuit SW1, but is not limited to the capacitor 11, but may be any other type having a high impedance at the frequency of the commercial power supply. Alternatively, for example, a resistor or a coil having high impedance may be used.

FIG. 2 shows a second embodiment of the present invention.
FIG. 2 is an example of an AC adapter in which an AC2 switch circuit SW2 is removed by using a transformer having a secondary winding and a tertiary winding having a different winding ratio on the secondary side. AC1 is connected between the terminal T1 and _one of the transformers 22 _1.
A switch circuit SW1 and a high-impedance section 21 composed of a high-impedance capacitor, resistor or coil are inserted in parallel. Other transformer 22 ₁ is connected to the terminal T2.

[0016] The transformer 22 _2, diode bridge 2
3 input. A capacitor 24 is inserted between one of the outputs of the diode bridge 23 and the terminal T4, and a constant voltage circuit 25 that outputs a constant voltage and a constant current is inserted between one of the outputs of the diode bridge 23 and the terminal T3. You. Trans 22 ₃ is connected to the input of the diode bridge 26. A capacitor 27 is inserted between one of the outputs of the diode bridge 26 and the terminal T4, and a detection circuit 28 is inserted between one of the outputs of the diode bridge 26 and the terminal T3. Diode bridge 2
The other output of each of 3 and 26 is connected to terminal T4.

The detection circuit 28 detects the current output from the terminal T3. Based on the detected current, AC
In order to control the ON / OFF operation of the one-switch circuit SW1, a switch ON / OFF signal circuit 2
9 is supplied with a signal. In the switch ON / OFF signal circuit 29, a signal for performing the ON / OFF operation of the AC1 switch circuit SW1 is generated based on the supplied signal. The generated signal is supplied from the switch ON / OFF signal circuit 29 to the control circuit 30. Control circuit 30
Is an AC1 switch circuit SW based on the supplied signal.
1 on / off operation.

Here, the transformer 22 of the embodiment described above is used.
₁ turns (primary winding) and N _1, transformer 22 ₂ turns (secondary winding) and N _2, when the transformer 22 ₃ turns the (tertiary winding) and N _3, the relationship is, N a _{1 »N 2, N 2 <N} 3 and N ₁ »N _3.

[0019] Then, the voltage output from the transformer 22 _2, indicated by a solid line in FIG. 3A, the voltage output from the transformer 22 _3, indicated by a dotted line in FIG. 3A. FIG. 3B shows this AC
Indicates the loss that occurs in the adapter. 3A and FIG.
The time point a in B is the time point when the AC1 switch circuit SW1 changes from the on state to the off state. That is, AC
When the first switch circuit SW1 to an off state, it becomes a high impedance is connected, the loss of the output voltage and the AC adapter from the transformer 22 ₂ decreases. However, the detection circuit 28, since the operated by the output voltage from the transformer 22 _3, AC2 switch circuit SW2
, The load connection on the secondary side can be detected.

FIG. 4 shows a third embodiment of the present invention.
An AC1 switch circuit SW is connected between terminals T1 and T2.
1 and the primary side of the transformer 31 are inserted in series. A grounded center tap is provided on the secondary side of the transformer 31, one of the secondary sides is connected to the anode of the diode 32, and the other of the secondary side is connected to the anode of the diode 33. The cathode of diode 32 and the cathode of diode 33 are connected to terminal T3.
The capacitor 34 is inserted between the terminal T3 and the ground. This diode 32 or 33 and the capacitor 3
4 generates a voltage power supply.

The primary side of the transformer 35 having high impedance is inserted between the terminals T1 and T2.
One of the secondary sides of the transformer 35 is connected to the anode of the diode 36, and the other of the secondary side is grounded. The cathode of the diode 36 is connected to the terminal T7, and a capacitor 37 is inserted between the terminal T7 and the ground. A voltage power supply is generated from the diode 36 and the capacitor 37. A high impedance capacitor, resistor, coil, or the like may be provided between the terminal T1 and the transformer 35. The output relationship between the transformers 31 and 35 is as follows: transformer 31≫transformer 35.

The transformer 35 of this embodiment has a high impedance (small size and low power type), and operates in the same manner as the transformer 31 provided with a tertiary winding. That is, when the transformers 31 and 35 are considered as one transformer, the primary side of the transformer 31 and the transformer 3
The primary side of the transformer 5 is a primary winding, the secondary side of the transformer 31 is a secondary winding, and the secondary side of the transformer 35 is a tertiary winding.
In this case, it is advantageous that the output voltage of the transformer 35 is not changed.

FIG. 5 shows the output and loss characteristics of the transformers 31 and 35, respectively. A shown in the figure is a characteristic when the secondary side of the transformer 31 is not loaded.
b is a characteristic when a load is connected to the secondary side of the transformer 31. Further, c shown in the figure is a characteristic when the secondary side of the transformer 35 is not loaded, and b is a characteristic when a load is connected to the secondary side of the transformer 35. Transformer 3
1 and 35 are equivalent including the load dependency, and the operation is also equivalent.

FIG. 6 shows a fourth embodiment of the present invention.
An AC1 switch circuit SW1 and a high-impedance capacitor 41 are inserted in parallel between the terminal T1 and _one of the transformers 441. Other transformer 44 _1,
Connected to terminal T2. The emitter of the photocoupler 43r is connected to the terminal T2, and its collector is connected to the control circuit 4
2 is connected. The control circuit 42 controls the on / off operation of the AC1 switch circuit SW1.

[0025] trans 44 ₂ is provided is a center tap which is grounded, one of the transformer 44 ₂ diodes 4
5 is connected to the anode, and the other is connected to the anode of the diode 46. The cathode of diode 45 and the cathode of diode 46 are connected. Diode 4
A capacitor 47 is inserted between the cathode of No. 5 and the ground. A voltage power supply is generated from the diode 45 or 46 and the capacitor 47. A constant voltage circuit 48 is inserted between the cathode of the diode 45 and the terminal T3.

[0026] One of the transformer 44 ₃ is connected to the anode of the diode 49, the other of which is grounded. A capacitor 50 is inserted between the cathode of the diode 49 and the ground. A voltage power supply is generated from the diode 49 and the capacitor 50. The cathode of diode 49 is connected to current detection circuit 51. Current detection circuit 51
In, the current value output from the tertiary winding is detected. The detected current value is supplied to the stop circuit 54 and the signal transmission circuit 55. The current detection circuit 51 is connected to the terminal T3 via a constant current circuit 52 and a constant voltage circuit 53. The constant current circuit 52 generates a constant current, and the constant voltage circuit 53 generates a constant voltage higher by ΔV than the constant voltage circuit 48, and outputs the same from the terminal T3.

The stop circuit 54 controls to stop the operation of the constant voltage circuit 48 based on the supplied current. The anode of the photocoupler 43t is connected to the signal transmission circuit 55, and the cathode is grounded. The signal transmission circuit 55 turns on / off the AC1 switch circuit SW1 with respect to the photocoupler 43t based on the supplied current.
A signal for controlling the off operation is supplied. Terminal T3, T5
The load 56 is connected via terminals T4 and T6.
Terminal T4 is grounded.

At a current value a in FIG. 7, the AC1 switch circuit SW1 is turned off, and at a current value b, the AC1 switch circuit SW1 is turned on. Thus, the current value a, higher ΔV than the output voltage of the constant voltage circuit 48 which is the power output from the transformer 44 ₃ constant voltage circuit 53
From the transformer 44 ₂ at the current value b.
An output voltage is obtained from a constant voltage circuit 48, which is a power supply output from.

FIG. 8 shows a flowchart of an example of this embodiment. In step S1, the AC1 switch circuit SW
1 is turned off, and input power is turned on. In step S2, a voltage is generated in the transformer 44 ₂ and 44 _3. In step S3, the constant current circuit 52 and the constant voltage circuit 53 are operated, and the constant voltage circuit 48 is stopped. In step S4, the constant current detection circuit 51 detects a current. In step S5, it is determined whether or not the detected current is equal to or more than the reference current. If it is determined that the detected current is equal to or more than the reference current, the control proceeds to step S6, and if it is determined that the detected current is smaller than the reference current, Control returns to step S4. In step S6, the constant voltage circuit 48 operates.

In step S7, the AC1 switch circuit S
W1 is turned on. In step S8, this AC
All circuits of the adapter operate. In step S9, the current is detected by the current detection circuit 51. Step S
In 10, it is determined whether or not the detected current is equal to or less than the reference current, and if it is determined that the detected current is equal to or less than the reference current,
The control proceeds to step S11, and if it is determined that the current is larger than the reference current, the control returns to step S9. Step S1
At 1, the operation of the constant voltage circuit 48 is stopped. In step S12, a signal for turning off the AC1 switch circuit SW1 is transmitted via the signal transmission circuit 55 and the photocoupler 43.

FIG. 9 shows a fifth embodiment of the present invention.
FIG. 9 is an example using a switching power supply. A diode bridge 61 is inserted between the terminals T1 and T2. Resistors 62 and 64 are inserted in series between terminal T1 and ground. A resistor 63 is inserted between a connection point between the resistors 62 and 64 and the terminal T2. The connection point between the resistors 62 and 64 is connected to the pulse generation circuit 65. In the pulse generation circuit 65, as will be described later from the input commercial power supply shown in FIG.
10E or a pulse as shown in FIG. 10F is generated, and the pulse is supplied to the switch drive circuit 69.

A capacitor 66 is inserted between one of the outputs of the diode bridge 61 and the ground, and the other of the outputs is grounded. One of the outputs of the diode bridge 61 is connected to an OSC (oscillator) / PWM (pulse width modulation) circuit 6 via a resistor 67 and an AC1 switch circuit SW1.
8 is connected. The OSC / PWM circuit 68 has the FET7
0 is connected to the gate. A diode 71 is connected between the source and the drain of the FET 70. Diode 71
Anode is grounded, and its cathode is
Connected to the other of ₁ . One of the transformer 73 ₁ is connected to one output of the diode bridge 61.

The connection point between the resistor 67 and the AC1 switching circuit SW1 is connected to the cathode of the diode 72, the anode of the diode 72 is connected to one of the transformer 73 _3. Other transformer 73 ₃ is grounded.

One of the transformers 73 ₂ includes a diode 74
And a capacitor 75 is inserted between the other end and the cathode of the diode 74. Other transformer 73 ₂ is connected to the terminal T4. A current detection circuit 76 is provided between the cathode of the diode 74 and the terminal T3.
And AC2 switch circuit SW2 are inserted in series.
The current output from the terminal T3 is detected by the current detection circuit 76, and the detected current is supplied to the control circuit 77 and the operation signal circuit 81. The load detection circuit 79 is connected to the cathode of the diode 74 and the terminal T3. The load detection circuit 79 detects the presence or absence of a load, and the detection result is supplied to the time constant circuit 80 and the operation signal circuit 81.

In the time constant circuit 80, a signal is transmitted to the control circuit 77 after a predetermined time so that the ON / OFF operation of the AC2 switch circuit SW2 is performed in accordance with the supplied detection result. The control circuit 77 controls the on / off operation of the AC2 switch circuit SW2 according to the current from the current detection circuit 76 and / or the signal from the time constant circuit 80. The operation signal circuit 81 supplies a signal to the switch drive circuit 69 to control the on / off operation of the AC1 switch circuit SW1 according to the current from the current detection circuit 76 and / or the signal from the load detection circuit 79. . The switch driving circuit 69 responds to a pulse from the pulse generation circuit 65 and / or a signal from the operation signal 81 to output A
The on / off operation of the C1 switch circuit SW1 is controlled.

A detection circuit 7 is provided between terminals T3 and T4.
8 is inserted. The detection circuit 78 detects the voltage,
It is determined from the voltage whether or not a load is connected. When it is determined that a load is connected, the photocouplers 82t and 82r are turned on, a signal is transmitted to the OSC / PWM circuit 68, and the switching power supply is operated.

In the above-described pulse generation circuit 65, FIG.
A, a single-phase AC commercial power supply is supplied. As an example, assume that the frequency of the waveform shown in FIG. 10A is 50 Hz. FIG. 10B shows a waveform obtained by shifting the phase of the single-phase AC commercial power supply in FIG. 10A by 180 degrees, adding the frequency to the supplied commercial power supply, and performing half-wave rectification. The frequency of the waveform shown in FIG. 10B is 100 Hz. Then, as shown in FIG. 10C, a pulse is generated in accordance with the rise of the half wave shown in FIG. 10B.

FIG. 10D shows a waveform obtained by half-wave rectification of the commercial power supply shown in FIG. 10A as it is. The frequency of the waveform shown in FIG. 10D is 25 Hz. Then, as shown in FIG. 10E, a pulse is generated in accordance with the rise of the half-wave shown in FIG. 10D. Also, as shown in FIG. 10F,
A pulse may be generated at the falling edge of the half-wave shown in FIG. 10D.

As described above, the pulse generation circuit 65 can generate a pulse waveform using the AC signal of the commercial power supply. That is, a pulse power supply may be equivalently generated from a commercial power supply, and operation may be performed using only the pulse portion, thereby increasing the impedance of the circuit under no load. Further, in this example, the description has been made using a commercial power supply of 50 Hz, but a frequency of 60 Hz or any other frequency can be used similarly.

FIG. 11 shows a flowchart of an example of this embodiment. In step S21, the AC adapter operates. In step S22, the current is detected by the current detection circuit. In step S23, it is determined whether or not the detected current is equal to or less than the reference current. If it is determined that the current is equal to or less than the reference current, the control proceeds to step S24. If it is determined that the detected current is greater than the reference current, the control proceeds to step S22. Return.
In step S24, the AC2 switch circuit SW2 is turned off. In step S25, an off signal for turning off the AC1 switch circuit SW1 is generated.
In step S26, a pulse is generated using the input AC signal of the commercial power supply. In step S27, the generated pulse controls the AC1 switch circuit SW1.

In step S28, the load detection circuit operates. In step 92, it is determined whether or not a load is connected. If it is determined that the load is connected, the control proceeds to step S30. If it is determined that there is no load, the control proceeds to step S28. Return. In step S30, the operation of the AC1 switch circuit SW1 controlled by the pulse is stopped. In step S31, AC
One switch circuit SW1 is turned on. Step S
At 32, the AC2 switch circuit SW2 is turned on.

FIG. 12 shows a sixth embodiment of the present invention. FIG. 12 shows an example of the secondary side of the transformer of the AC adapter. Transformer 9 is connected between terminals T1 and T2.
One primary is inserted. One of the secondary sides of the transformer 91 is connected to the anode of the diode 92, and a capacitor 93 is inserted between the other side of the secondary side and the cathode of the diode 92. A voltage power supply is generated from the diode 92 and the capacitor 93. The anode of diode 94 is connected to the cathode of diode 92, and a capacitor 95 is inserted between the cathode and terminal T4. The circuit section 96 is inserted between the cathode of the diode 92 and the terminal T3. An AC2 switch circuit SW2 is inserted between the circuit section 96 and the terminal T4. A voltage detection circuit 97 is inserted between terminals T3 and T4.

The voltage detection circuit 97 determines whether or not a load is connected based on the detected voltage, and the result of the determination is supplied to the OSC / PWM circuit. The load detection circuit 98 is connected to the cathode of the diode 94 and the terminal T3. The load detection circuit 98 detects whether a load is connected or not, and supplies the result of the determination to the signal generation circuit 99. In the signal transmission circuit 99, a signal is transmitted so as to control the on / off operation of the AC1 switch circuit SW1 according to the supplied signal.

FIG. 13 shows a seventh embodiment of the present invention. FIG. 13 is an example in which the AC2 switch circuit SW2 is removed much more than in FIG. Therefore, the same portions are denoted by the same reference numerals, and description thereof will be omitted.
A resistor 1 is connected between the cathode of the diode 92 and the terminal T3.
01 and the current detection circuit 102 are inserted in parallel.

As described above, although the AC2 switch circuit SW2 may be removed, a current flows to the load of the circuit section 96.
In order to eliminate this, it is better to provide an AC2 switch circuit SW2 as shown in FIG. This A
Since the C2 switch circuit SW2 can perform a switching operation, the circuit section 96 can be stopped. Further, even if the AC2 switch circuit SW2 does not operate as a switch circuit, the load detection circuit 98 can be operated by the voltage power supply generated from the diode 94 and the capacitor 95.

FIG. 14 shows an eighth embodiment of the present invention. FIG. 14 is an example in which a triac is used for the AC1 switch circuit SW1. Terminal T1 is connected to one of the inputs of diode bridge 111, and triac 116 is inserted between the other input of diode bridge 111 and terminal T2. Terminal T1 and diode 11
2 is connected between the anode of the diode 112 and the terminal T2.
4 is inserted. A resistor 115 is inserted between the resistor 113 and the terminal T2. The emitter of the photocoupler 127r is connected to the connection point between the resistors 113 and 115, and the collector is connected to the gate terminal of the triac.

One of the outputs of the diode bridge 111 is connected to _one of the transformers 125 ₁ and
5 ₁ of the other is connected to the collector of the transistor 122. Resistors 117 and 118 are inserted in series between the other input of diode bridge 111 and the other output. A capacitor 119 is inserted between the outputs of the diode bridge 111. Diode bridge 11
The resistor 120 and the OSC / PWM circuit 121 are inserted in series between the outputs of the first and second outputs. The base of the transistor 122 is connected to the OSC / PWM circuit 121, and the emitter is connected to the other output of the diode bridge 111. One of the transformers 125 ₃ is a diode 124
, And a capacitor 123 is inserted between the other end and the cathode of the diode 124. The other output of the transformer 125 ₃ of the other and the diode bridge 111 are connected. The cathode of the diode 124 is
It is connected to a connection point between the resistor 120 and the OSC / PWM circuit 121.

The connection point between resistors 117 and 118 is connected to timer circuit 126 to which photocoupler 127t is coupled. This timer circuit 126 includes a transformer 125
The on / off operation of the photocoupler 127 is performed based on the signal supplied from the secondary-side signal generation circuit.

FIG. 15 shows a ninth embodiment of the present invention. FIG. 15 is an example in which a thyristor is used for the AC1 switch circuit SW1. Terminals T1 and T2 are connected to the input of diode bridge 131, and one of the outputs of diode bridge 131 is connected to the anode of thyristor 132. A resistor 133 is inserted between the cathode and the gate terminal of the thyristor 132, and a resistor 134 is inserted between the anode and the gate terminal of the thyristor 132. A resistor 135 is inserted between the gate terminal of the thyristor 132 and the collector of the transistor 136. The emitter of transistor 136 is connected to the other output of diode bridge 131, and the gate is connected to timer circuit 144.

A resistor 138 and a PWM circuit 142 are inserted between the cathode of the thyristor 132 and the emitter of the transistor 136 in parallel with the capacitor 137.
One of the transformers 143 ₁ is connected to the cathode of the thyristor 132, the other of is connected to the collector of the transistor 141. The emitter of the transistor 141 is
Transistor 136 is connected to the emitter, and its base is connected to PWM circuit 142. One of the transformer 143 ₃ is connected to the anode of the diode 140, the other of is connected to the emitter of the transistor 141.
A capacitor 139 is inserted between the cathode of diode 140 and the emitter of transistor 141. The cathode of diode 140 is connected to a connection point between resistor 138 and PWM circuit 142.

A signal is supplied to the timer circuit 144 from the secondary side of the transformer 143, and the transistor 136 is turned on in accordance with the supplied signal. Transistor 136
Is turned on, the thyristor 132 is turned on, and the input power is supplied to the transformer 143.

FIG. 16 shows a flowchart of an example of this embodiment. In step S41, a current is detected.
In step S42, it is determined whether or not the detected current is equal to or less than the reference current. If the detected current is determined to be equal to or less than the reference current, the control proceeds to step S43. Control returns to step S41.
In step S43, a signal for operating the timer circuit is generated. In step S44, the timer circuit operates according to the generated signal. In step S45,
The presence or absence of a load is detected. In step S46, it is determined whether or not a load is connected. If it is determined that a load is connected, the control proceeds to step S47, and if it is determined that there is no load, step S45 returns to control. In step S47, an ON signal for turning on the switch element of the AC1 switch circuit SW1 is transmitted. Step S48
In step S41, the switch element is turned on.
The control returns to.

At this time, if it is determined in step S46 that the load is connected, the control is shifted to step S47, but the control may be shifted to step S49. In step S49, the operating timer circuit is stopped, and the control moves to step S43.

FIG. 17 is a flowchart showing an example of the operation of the timer circuit in step S44 described above. Step S
At 51, the operation of the timer circuit is performed. Step S5
At 2, it is determined whether or not the time Δt has elapsed.
If it is determined that the predetermined time has elapsed, step S53
When it is determined that the predetermined time Δt has not elapsed, the control returns to step S51. Step S5
In 3, the switch element of the AC1 switch circuit SW1 is turned on for a predetermined time Δt. In step S54, it is determined whether or not the frequency is 1 Hz. If it is determined that the frequency is 1 Hz, the control proceeds to step S55. If it is determined that the frequency is not 1 Hz, the control returns to step S53. Step S
At 55, the switch element is turned off, and step S
Control returns to 51.

FIG. 18 shows an equivalent block diagram of the present invention. Between the power supply unit 151 and the load 155,
AC1 switch circuit SW1, AC2 switch circuit SW
2. Terminals T3 and T5 and set switch circuit SW3 are inserted in series. The resistor 152 is connected in parallel with the AC1 switch circuit SW1, and the resistor 153 is connected in parallel with the AC2 switch circuit SW2. Also, the resistor 153
Is inserted between the inputs of the comparison amplifier 154. The presence or absence of a load is detected based on the output result output from the comparison amplifier 154. As described above, in the present invention, at least two switches are equivalently used in series.
As a result, the load connection of the set can be detected.

Further, comparing the conventional equivalent block diagram shown in FIG. 19 with the block diagram of the present invention shown in FIG. 18, FIG. 19 shows a configuration in which the AC2 switch circuit SW2 is removed. Thus, the AC2 switch circuit SW
When the AC1 switch circuit SW1 is turned on when there is no 2, a large current flows through the resistor 153.
Must select a resistor with a small value. Therefore, the condition of the value of the resistor 152 and the value of the resistor 153 is as follows.
Since “the value of the resistor 152 ≫the value of the resistor 153”, it is difficult for the comparison amplifier 154 to perform load detection with low power. On the other hand, in the present invention, by providing the AC2 switch circuit SW2, the value of the resistor 153 can be selected to be large, so that load detection can be performed with low power.

[0057]

According to the present invention, since the AC1 switch circuit SW1 is turned off to increase the impedance, the loss at the time of load is reduced by a factor of 1 to 1 as compared with the prior art.
/ 10 or less.

According to the present invention, the fact that the load has been removed is detected from the output current, the AC1 switch circuit SW1 is turned off, and the input becomes a high impedance, so that the loss can be controlled to be small. When a load is connected to the AC adapter, input power can be automatically supplied.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment to which the present invention is applied.

FIG. 2 is a block diagram showing a second embodiment to which the present invention is applied.

FIG. 3 is a schematic diagram used for describing output characteristics applied to the present invention.

FIG. 4 is a block diagram showing a third embodiment to which the present invention is applied.

FIG. 5 is a schematic diagram used for describing output characteristics applied to the present invention.

FIG. 6 is a block diagram showing a fourth embodiment to which the present invention is applied.

FIG. 7 is a schematic diagram used for describing output characteristics applied to the present invention.

FIG. 8 is a flowchart of an example of the present invention.

FIG. 9 is a block diagram showing a fifth embodiment to which the present invention is applied.

FIG. 10 is a schematic diagram of an example of a signal applied to the present invention.

FIG. 11 is a flowchart of an example of the present invention.

FIG. 12 is a block diagram showing a sixth embodiment to which the present invention is applied.

FIG. 13 is a block diagram showing a seventh embodiment to which the present invention is applied.

FIG. 14 is a block diagram showing an eighth embodiment to which the present invention is applied.

FIG. 15 is a block diagram showing a ninth embodiment to which the present invention is applied;

FIG. 16 is a flowchart of an example of the present invention.

FIG. 17 is a flowchart of an example of the present invention.

FIG. 18 is an equivalent circuit diagram of an example of the present invention.

FIG. 19 is an equivalent circuit diagram of a conventional example.

FIG. 20 is a block diagram of an example of a conventional AC adapter and a set.

FIG. 21 is a schematic diagram used for describing power consumption loss.

[Explanation of symbols]

SW1 ... AC1 switch circuit, SW2 ... AC2
Switch circuit, SW3 ... Set switch circuit, 1
1, 14 ... condenser, 12 ... transformer, 13
... Diode, 15 ... Load detection circuit, 16 ...
.Control circuit, 17 ... load

Claims (5)

[Claims] 1. A power supply adapter connected to a commercial power supply and outputting a predetermined power supply, a power supply circuit for generating an output power supply, a load detection means for detecting the presence or absence of a load, and a no load by the load detection means. The output power generation operation of the power supply circuit is stopped at the time of detection, the necessary power is supplied to the load detection means, and the output power generation of the power supply circuit is detected at the time of detecting that the load is connected. A power supply adapter characterized by comprising a power switching means for starting an operation. 2. The power supply adapter according to claim 1, further comprising a switching unit that is turned off when there is no load between the power switching unit and the output terminal. 3. The power supply switching means according to claim 1, wherein the power supply switching means includes a transformer having switching means connected between a commercial power supply and a primary side thereof, and a power supply circuit connected to a secondary side thereof. And power supply adapter. 4. The power supply switching means according to claim 1, further comprising: switch means connected between a commercial power supply and a primary side thereof; a power supply circuit connected to a secondary side thereof; A power supply adapter comprising a transformer to which the load detecting means is connected. 5. The first transformer according to claim 1, wherein a first transformer connected to the power supply circuit on a secondary side thereof, and current detecting means for detecting an output current is connected to the secondary side thereof. And a second transformer connected in parallel, wherein the winding ratio of the first and second transformers is different.