JPH0142168Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stabilized power supply circuit having a power saving function, and particularly to reducing current consumption during power saving.

Stabilized power supply circuits are provided in power supply units of various electronic devices to supply stabilized power to each part, and are an important part of electronic devices. This stabilized power supply circuit tends to be integrated with the development of semiconductor technology, and currently consists of one control semiconductor integrated element and a control semiconductor integrated element connected in series to the power supply line. It consists of a controlled power transistor and external components such as an external resistor and capacitor that detect the output level of the power transistor and control the setting of a reference level.

In the stabilized power supply circuit configured in this manner, the control semiconductor integrated element controls the power transistor so that the output level of the power supply always matches a predetermined set value.

FIG. 1 is a circuit diagram showing one embodiment of a stabilized power supply circuit commonly used in the past. In the figure, reference numeral 1 denotes a semiconductor integrated device for control, which has terminals P ₁ to _{P 8} for external connection. 2 is a power transistor connected in series to the power line between the input terminal 3 of the DC power supply and the output terminal 4 of the stabilized power supply;
5 and 6 are smoothing capacitors connected between the input terminal 3 and output terminal 4 and the ground, respectively; 7,
8 is a resistor that divides the output level of the power transistor 2, and its divided voltage output is supplied to the terminal _P5 of the control semiconductor integrated device 1 as a bias voltage. 9 to 11 are resistors and variable resistors connected in series between the output terminal 4 and the ground, variable resistor 1
The variable voltage generated from the sliding piece 0 is used as an output voltage setting signal to the terminal P ₇ of the control semiconductor integrated device 1.
is supplied to Then, the control semiconductor integrated device 1
, terminal P ₂ is the base of power transistor 2,
Further, the terminal _P3 is connected to the input terminal 3 to control the power transistor. Further, a power save switch 12, which is normally open, is connected between the emitter and base of the power transistor 2.

The stabilized power supply circuit configured in this manner takes the divided voltage value of the output level by the resistors 7 and 8 into the terminal P ₇ of the control semiconductor integrated device 1 as a bias voltage. A control signal is supplied from the terminal _P2 to the power transistor 2 to perform feedback control so that the reference level specified by the variable resistor 10 matches the set value specified by the variable resistor 10. Next, when the power save switch 12 is closed, the emitter and base of the power transistor 2 are shot, so that the power transistor 2 is turned off and enters the power save mode.

However, in the stabilized power supply circuit having the above-described configuration, the connection between the terminals P ₂ and P ₃ of the control semiconductor integrated device 1 is closed by the power save switch 12 in the power save mode, as indicated by arrow A. Current i will flow through the route. In this case, the current i reaches, for example, 30 mA, resulting in a problem that the current consumption during power saving becomes quite large.

Therefore, the purpose of the present invention is to prevent, in a stabilized power supply circuit having a power save function, the output of the power save switch during power save mode from occurring and flowing through external components. Therefore, it is an object of the present invention to provide a stabilized power supply circuit that reduces current consumption during power saving. Hereinafter, the stabilized power supply circuit according to the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a circuit diagram showing an embodiment of the stabilized power supply circuit according to the present invention, and the same parts as in FIG. 1 are indicated using the same symbols. In the figure, 13 is the terminal _P5 of the control semiconductor integrated device 1 and the resistors 7 and 8.
is a switching element connected between the voltage dividing point of the power transistor 2 and the resistor 14.
It is turned on by making it a base input via . The difference from FIG. 1 is that a switching element 13, which is turned on by the output of the power transistor 2 and turned off during power saving, is interposed in series in the leakage current path due to the wraparound.

In the stabilized power supply circuit configured in this way, when DC power is supplied to the input terminal 3 with the power save switch 12 open, this DC power is supplied to the output terminal 4 via the power transistor 2. will be done. In this case, when the output of the power transistor 2 increases, the switching element 13 is turned on, and the output terminal _P5 of the control semiconductor integrated element 1 is connected to the voltage dividing point of the resistors 7 and 8, and the emitter bias of the switching element 13 is is set. On the other hand, the control semiconductor integrated device 1 determines the output level of the power transistor 2 based on the value indicated by the variable resistor 10, and this output level is set to a reference value formed inside the semiconductor integrated device 1. The power transistor 2 is controlled to make the output level constant so that the output level matches the output level.

Next, when the power save switch 12 is closed,
The power transistor 2 is turned off, and the output level accordingly becomes zero. As a result, switching element 1, which had been turned on depending on the output level,
3 is turned off, and the terminal of the control semiconductor integrated device 1
The connection between P ₅ and the voltage dividing point formed by resistors 7 and 8 is opened. Therefore, as shown in Fig. 1, the leakage current i caused by the loop in the power save mode
is cut off, and as a result, the current consumption during the power save mode can be significantly reduced.

In the above embodiment, a case has been described in which the switching element 13 for interrupting leakage current is connected in series between the terminal _P5 of the control semiconductor integrated device 1 and the connection point of the resistors 7 and 8. The invention is not limited to this, and any portion may be used as long as it is a portion through which leakage current flows during the power save mode.

As explained above, the stabilized power supply circuit according to the present invention has a switching element that is turned on by the output of the power transistor in series with the leakage current path in the power save mode. It has the excellent effect of significantly reducing current consumption during mode.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional stabilized power supply circuit, and FIG. 2 is a circuit diagram showing an embodiment of the stabilized power supply circuit according to the present invention. 1... Control semiconductor integrated element, 2... Power transistor, 3... Input terminal, 4... Output terminal,
5, 6... Capacitor, 7, 8, 9, 11, 14
...Resistor, 10...Variable resistor, 12...Power save switch, 13...Switching element.

Claims (1)

[Scope of utility model registration request] a power transistor connected in series to a power supply line; a control semiconductor integrated element that monitors the output level of the power transistor and controls the power transistor so that the output level matches a reference value; and an emitter of the power transistor. A power save switch is connected in series to the leakage current path that occurs in the power save mode, and is turned on only by the output of the power transistor to prevent leakage. A stabilized power supply circuit characterized by being provided with a switching element that interrupts current.