JP2002315309A - Electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce standby power consumption in an electronic device. SOLUTION: For achieving the purpose, a voltage-detecting circuit 15 is connected between a choke coil 8 and an output terminal 2. To this voltage- detecting circuit 15, a switching control circuit 13 is connected via a standby state detecting circuit 18 and a control circuit 19 in a standby state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device such as a rice cooker.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional electronic device of this kind.
That is, as shown in FIG. 5, the electronic device has a configuration including a power supply circuit 3 having an input terminal 1 and an output terminal 2, and a load 4 connected to the output terminal 2 of the power supply circuit 3. I was

The power supply circuit 3 includes a diode 5 and a capacitor 6 provided in order from the input terminal 1 to the output terminal 2.
And a switching element 7 and a choke coil 8. Further, a voltage detection circuit composed of a series body of a Zener diode 9 and a resistor 10 is connected between the choke coil 8 and the output terminal 2.

A connection point between the Zener diode 9 and the resistor 10 is connected to a transistor 12 via a resistor 11, and a collector of the transistor 12 is connected to a base of the switching element 7 via a switching control circuit 13. Have been.

That is, the input terminal 1 is connected to a home power supply 1.
4 is connected, and it is smoothed by a smoothing circuit including a diode 5 and a capacitor 6, and the voltage is changed by changing the ON / OFF duty of the switching element 7.
For example, an output of 12 V is output to the output terminal 2. The load 4 is in this case like a control circuit activated at 12V.

In FIG. 5, the output terminal 2 is connected to a Zener diode 9 in order to maintain 12V.
When the voltage is lower than 12 V, the Zener diode 9 is turned on and the transistor 12 is turned on to transmit this to the switching control circuit 13, and the switching control circuit 13 is turned on.
Is a switching element based on the transmitted information.
The voltage at the output terminal 2 can be maintained at 12 V by varying the ON and OFF duties of.

[0007]

A problem with the above prior art is that it is not possible to reduce the standby power.

That is, in the conventional example, the Zener diode 9 in FIG. 5 operates depending on whether the output terminal 2 drops below 12 V or not, thereby turning the switching control circuit 13 on and off. However, such control is performed by determining whether the load 4 is large or small. For example, when the load 4 requires less power than the light load, for example, during standby, like,
In the case where only a small amount of power that can simply secure operation is consumed, power consumption cannot be suppressed by such a rough control.

Accordingly, an object of the present invention is to reduce standby power.

[0010]

According to the present invention, a voltage detecting circuit is connected between a choke coil and an output terminal, and a standby state detecting circuit is connected to the voltage detecting circuit. A switching control circuit is connected to the standby state detection circuit via a standby control circuit.

That is, in the voltage detection circuit,
By connecting the standby state detection circuit, it is detected that the load is in the standby state, thereby controlling the operation of the switching control circuit through the standby state control circuit, so that the power consumption in the standby state is small. Can be none.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a power supply circuit having an input terminal and an output terminal, and a load connected to the output terminal of the power supply circuit, wherein the power supply circuit has In order from the input terminal to the output terminal, connect the rectifier circuit, the switching element, and the choke coil,
A voltage detection circuit is connected between the choke coil and the output terminal, and the voltage detection circuit is connected to the switching element via a switching control circuit, and the voltage detection circuit is connected to a standby state detection circuit, The standby state detection circuit is an electronic device to which the switching control circuit is connected via a standby state control circuit, and that a voltage detection circuit is connected between the choke coil and the output terminal, and the voltage detection circuit By connecting the standby state detection circuit, it is detected that the load is in the standby state, and when this state is detected, by controlling the switching control circuit from the standby state detection circuit via the standby control circuit, This makes it possible to perform the most appropriate power control during standby.

Next, according to a second aspect of the present invention, first and second voltage detection circuits are connected between a choke coil and an output terminal, and a switching control circuit is connected to the first voltage detection circuit. 2. The electronic apparatus according to claim 1, wherein a standby state detection circuit is connected to the second voltage detection circuit, wherein a voltage for making the voltage of the output terminal constant between the choke coil and the output terminal is detected. By separately providing the first voltage detection circuit and the second voltage detection circuit for detecting the standby state, appropriate power control can be performed.

According to a third aspect of the present invention, there is provided the electronic apparatus according to the second aspect, wherein the first voltage detecting circuit is constituted by a series body of a Zener diode and a resistor. By configuring the detection circuit with a series body of a Zener diode and a resistor, the circuit configuration can be simplified.

According to a fourth aspect of the present invention, the second voltage detecting circuit comprises a series body of a plurality of resistors, and a connecting point of these resistors is connected in series with a Zener diode and a resistor. 3. The electronic device according to claim 2, wherein a standby state detection circuit comprising a body is connected, wherein the second voltage detection circuit is configured by a series body of a plurality of resistors to simplify the configuration,
Further, in this state, a standby state detection circuit composed of a series body of a Zener diode and a resistor is formed at a connection point of the resistors, so that the configuration can be further simplified.

An embodiment of the present invention will be described below with reference to the accompanying drawings. The same parts as those in the conventional example are denoted by the same reference numerals, and the description thereof will be simplified.

In FIG. 1, reference numeral 15 denotes a voltage detection circuit provided between the choke coil 8 and the output terminal 2. The voltage detection circuit 15 is constituted by a series body of resistors 16 and 17. A standby state detection circuit 18 is connected to a connection point between the resistors 16 and 17, and the standby state detection circuit 18
Is connected to the switching control circuit 13 via the standby control circuit 19.

The standby state detection circuit 18 is described in detail in FIG.
As shown in FIG. 2, the standby control circuit 19 is composed of a series body of a Zener diode 20 and a resistor 21.
2 and transistors 23 and 24 and resistors 25 and 26. The resistor 21 is connected to a connection point between the Zener diode 20 and the resistor 22.

FIG. 3 is a diagram showing four of A, B, C and D in FIG.
The operation waveform at the point is shown. First, when the power consumption in the load 4 basically consumes only the standby power, the potential at the connection point between the resistor 16 and the output terminal 2 in FIG. 2 has a ripple as shown in FIG. The voltage increases.

The reason is that basically, the system for stabilizing the voltage of the output terminal 2 becomes difficult to operate. More specifically, if the power consumption in the standby state is detected as described above, the power consumption is immediately detected, and the zener diode 9 operates, so that the switching control circuit 13
A circuit for stabilizing the operation in which the switching element 7 is turned on and off does not frequently operate. Therefore, the potential of the output terminal 2 is in a state including a ripple as shown in FIG. become.

At this time, the voltage detected between the resistors 16 and 17 is the threshold voltage level 2 shown in FIG.
If it exceeds 7, the standby state detecting circuit 18 will detect that the standby state has been entered at that time. At this time, the Zener diode 20 conducts, whereby the transistor 23 conducts, and the transistor 24 is turned off. As a result, at the point C in FIG. 2, as shown in FIG. 3C, an H signal is output during a period in which the threshold voltage level 27 is exceeded.

Then, the switching control circuit, which has been subjected to frequent duty control as shown in FIG. 3 (a) under light load conditions, adds a waveform as shown in FIG. 3 (c). As a result, no pulse is generated at the point D in FIG. 2 during the H level in FIG. 3C, as shown in FIG. 3D. That is, during this time, the power of the output terminal 2 is controlled so that the transistor 7 does not operate and the load 4 consumes only the standby power.

FIG. 4 is for reference, and shows a state when the load 4 is consuming a large amount of power. In this case, as shown in FIG. 4D, the duty control of ON and OFF is performed from the switching control circuit 13 at the point D in FIG.

During this time, as described above, since the switching control circuit 13 is normally controlled to be frequently turned on, the waveform at the output terminal 2 portion, that is, the portion (b) of FIG. 4 is shown in FIG. Unlike a light load, the threshold voltage level 27 does not exceed. In this case, as shown in FIG. 4 (c), there is no H pulse in the C portion.

FIG. 4A shows a control waveform from the transistor 12 to the switching control circuit 13.

In FIGS. 1 to 5, reference numeral 28 denotes a smoothing capacitor, which is an electrolytic capacitor because it has a capacity as large as possible.

[0027]

As described above, according to the present invention, a voltage detecting circuit is connected between a choke coil and an output terminal, and a standby state detecting circuit is connected to the voltage detecting circuit. Since the switching control circuit is connected via the time control circuit, when the load is in the standby state, it can be detected and the appropriate power consumption can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is an operation waveform diagram at points A to D in FIG. 2;

FIG. 4 is an operation waveform diagram at points A to D in FIG. 2;

FIG. 5 is a circuit diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 input terminal 2 output terminal 3 power supply circuit 4 load 7 switching element 8 choke coil 13 switching control circuit 15 voltage detection circuit 18 standby state detection circuit 19 standby control circuit

Claims (4)

[Claims] 1. A power supply circuit having an input terminal and an output terminal, and a load connected to the output terminal of the power supply circuit, wherein the power supply circuit includes a rectifier circuit in order from an input terminal to an output terminal; A switching element is connected to a choke coil, a voltage detection circuit is connected between the choke coil and an output terminal, and the voltage detection circuit is connected to the switching element via a switching control circuit. An electronic device in which a standby state detection circuit is connected to the circuit, and the switching control circuit is connected to the standby state detection circuit via a standby control circuit. 2. The method according to claim 1, further comprising:
The electronic device according to claim 1, wherein a second voltage detection circuit is connected, a switching control circuit is connected to the first voltage detection circuit, and a standby state detection circuit is connected to the second voltage detection circuit. 3. The electronic device according to claim 2, wherein the first voltage detection circuit is configured by a series body of a Zener diode and a resistor. 4. A second voltage detection circuit comprising a series body of a plurality of resistors, and a connection point between these resistors is connected to a standby state detection circuit comprising a series body of a Zener diode and a resistor. 3. The electronic device according to 2.