JPS6222123A - Power supply circuit of electronic appliance - Google Patents

Abstract

PURPOSE:To reduce the power consumption in the 2nd constant voltage circuit by applying a rectified voltage from the 1st rectifier output terminal to an input circuit of the 2nd constant voltage circuit when the voltage of the input terminal to the 2nd constant voltage circuit drops. CONSTITUTION:The 1st and 2nd rectifier output terminals 11, 12 reach a prescribed voltage at normal operation and the 1st 2nd constant voltage circuit 1, 2 apply a prescribed constant voltage operation. In this case, the 2nd rectified power voltage Vi3 and the 2nd constant voltage output Vo2 are fed respectively to a comparator 9 as a control circuit, no on-voltage is fed to a control terminal 16, an electronic switch 8 keeps the off-state and prescribed voltages Vo1, Vo2 appear at the 1st and 2nd constant voltage terminals 6, 7. On the other hand, when the voltage at the secondary side of a power transformer 4 drops due to any cause, the control signal from the comparator 9 is fed to the terminal 16 to turn on the switch 8 and the 1st rectified output voltage Vi1 is fed to the input of the circuit 2, which is driven by the voltage Vi1.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a power supply circuit for electronic equipment that obtains a stabilized output from a constant voltage circuit by converting unstabilized rectified voltage obtained from an AC power supply through a rectifier circuit. .

(B) Conventional technology In general, power supply circuits for electronic devices rectify and smooth AC voltage from an AC power source, and then apply a constant voltage stabilized in a constant voltage circuit to the load, such as the DC power supply of various ICs. It is configured to be added to the terminal.

As an example of this constant voltage circuit,
No. 1 is raised, and a configuration for obtaining a plurality of stabilizing voltages is shown.

In addition, when simply providing a plurality of first and second constant voltage circuits (IO2), each is separately connected to an AC power source (
3) is connected to the constant voltage circuits (1) and (2) through the power transformer (4) and the rectifier circuit (5), and each is operated independently to provide stable voltage from the output terminals (6) and (7). The converted DC voltage is supplied to the desired load.

(C) Problems to be Solved by the Invention Regarding the prior art example of Japanese Patent Publication No. 4G-23701 mentioned above, if the underlying constant voltage circuit goes from a normal operating state to an abnormal operating state, another Not only does it have the disadvantage that even one voltage is not a constant voltage, but also the setting of one circuit constant is extremely critical, so it is not very suitable as a power supply circuit for electronic equipment.

On the other hand, the power supply circuit shown in FIG. 5 assumes that the first output terminal voltage is V. I, the input voltage is Vi, and the second output voltage is ■.

6. The input voltage is V□, the AC reduced voltage guarantee of the output terminal voltage is -A%, and the saturation voltage Vsa in the constant voltage circuit (2)
t, V□ at the rated AC voltage must be set to .

As an example, V, , = 5 volts, Vsat ==
If 1.5 volts and A=35%, then Vi, ≧10 volts, (Vat - V.,) × E is a constant voltage circuit (2)
Therefore, in the above embodiment, when the AC rated voltage is used, 1/1/2 of the power supplied to the constant voltage circuit (2) is consumed.
2 is wasted.◎Here, ◎ represents the current flowing through the constant voltage circuit (2).

B) Means for Solving the Problems The present invention provides a power supply circuit including a plurality of constant voltage circuits with different high and low voltages, in which first and second constant voltage circuits are connected to the output side of a rectifier circuit. , a switching means is connected to the input sides of the first and second constant voltage circuits, an output terminal of the second constant voltage circuit is connected to a control terminal of the switching means, and the second constant voltage circuit is controlled. When the output voltage decreases, the switching means is turned on, and the first rectified voltage appearing at the input terminal of the first constant voltage circuit is applied as the input voltage of the second constant voltage circuit, thereby increasing the constant voltage at the AC rated voltage. This configuration reduces the power consumption of the circuit.

(e) Effect When the voltage at the input terminal of the second constant voltage circuit in the present invention drops, the switching means is turned on, so that the second constant voltage circuit can be driven by the first rectified voltage, and the voltage decreases due to the decrease in AC voltage. At the time of guarantee, it is possible to reduce power consumption in the second constant voltage circuit.

(f) Example The power supply circuit of an electronic device of the present invention will be explained according to the drawings. Fig. 1 is a basic configuration diagram showing the same circuit of the present invention, Fig. 2 is an implementation circuit diagram of the same circuit, and Fig. 3 is a basic configuration diagram showing the same circuit of the present invention. The figure shows a waveform diagram of each part in FIG. 2, and FIG. 4 shows a characteristic diagram of FIG. 2.

In the drawings, the same elements as in Fig. 5 are given the same figure numbers, (8) is an electronic switch as a switching means, (9) is a comparator as a control circuit, and (9) is a switching device for preventing backflow. diode, (b) (6) are the first and second rectified output terminals, (to) α4 is a potential difference detection transistor constituting the comparator (9), (to) is a switching transistor as a switching means, and (2) ) indicates a smoothing capacitor.

Next, to explain the operation of the present invention, first in FIG. 1, when 100V as a commercial power source is applied to the power transformer (4) from the AC power source (3), the power transformer (4) adjusts the voltage to a predetermined voltage. The voltage is stepped down from the secondary side of the power transformer (4) through a bridge-connected rectifier circuit (5) for single-wave rectification, and Vll from the first rectifier output terminal (b), and the second rectifier output. A rectified voltage vi appears from the terminal (2). (Set as Vcs > Vzt.) Here, during normal operation, the first rectified output terminal (6) and the second
The rectifier output terminal has reached a predetermined voltage, and the first constant voltage circuit (1) and the second constant voltage circuit (2) perform a predetermined constant voltage operation. (The switching diode (2) is in the on state.) Therefore, at this time, the second rectified output voltage
4. and a second constant voltage output v,,2 are applied to the output, that is, the control terminal (to) trap, no on voltage is applied, the electronic switch (8) remains off, and the first constant voltage terminal (6) and A predetermined voltage ■ is applied to each of the second constant voltage terminals (7). , and■. appears, and a constant voltage is supplied to various ICs and the like as loads connected to the next stage.

On the other hand, if the voltage on the secondary side of the power transformer (4) drops for some reason, the comparator (9) is connected to the control terminal (to).
, the electronic switch (8) is turned on and the first rectified output voltage (vL, ) is applied as an input to the second constant voltage circuit (2), and the second constant voltage The circuit (2) is driven by said first rectified voltage. Here, the diode structure is a switching diode in which the first rectified output VL flows back to the second rectified output V when the electronic switch (8) is turned on.

Here, a case where the AC power supply in FIG. 2 is at the rated voltage and a case where the voltage is lowered will be explained.

First, when the AC power supply is at the rated voltage, Vu = Vot + vsat + 'd--'' (2
) is applied to the second constant voltage circuit (2).

The potential difference between the voltage V and VOR is monitored by the potential difference detection transistor (to) serving as the comparator.

Next, as the voltage of the AC power supply (3) decreases, when (2) and (2) enter the region shown in the following equation (3), the potential difference detection transistor (2) α4 turns on and off, respectively, and the switching transistor al19 turns on.

Vi,≦(■.t+Usat”vd)
...""...' (3) In equations (2) and (3), Usat represents the voltage drop in the second constant voltage circuit (2), and vd represents the forward rising voltage of the switching diode αO.

The second rectified voltage Vi is the second constant voltage circuit (2)
At the AC reduced voltage guaranteed limit point (-A%).

Vi, ≧(Vox + Usat) --
” (4).

This allows the second constant voltage circuit (2
) power consumption P is P=υsat X I...
...(5). (■ is the second constant voltage circuit (2)
) shows the current flowing through. ) In the above configuration, Vl), = 5 ports, ν,
If 8t=1.5 volts, the second constant voltage circuit (2)
The power supplied to the second constant voltage circuit (2) is 6.5XI, and the power consumption in the second constant voltage circuit (2) is 5XI.

Therefore, for the said supply power 6.5XI.

1.5XI/6.5XI=0.23 That is, only 23% of the power is wasted. In the example shown in FIG.
1 is set so that the potential difference detection transistor (to) is turned off when it satisfies equation (3), and the resistance Q value R8 is set to set the loop gain of the transistor (2) α4 (2) to At the same time, the on/off operation of the transistor has hysteresis characteristics.

It is set to speed up the switching operation of the transistor (2) and suppress the switching transient power consumption of the transistor (2).

These values are shown below.

R, = 4.7 to Ω* Rt = l OK Ω, R, = 1
Figure 3 shows the waveforms of each part in Figure 2, and the potential of the second rectified output terminal @ of the rectifier circuit (5) is the same as the AC power supply (3).
Contains ripples peculiar to the rectified output,
As the AC voltage decreases, the potential difference detection transistor (to) is turned on at the bottom of the ripple, α4 is turned off, and 1
The electric potential of the point person is v2 only at that moment. It was raised to ■.

2, the occurrence of ripples is suppressed. When the AC voltage further decreases, a ripple component appears in vOI, but no ripple component appears in V, as long as equation (4) is satisfied.Therefore, the base voltage of the potential difference detection transistor is V, (Fig. 3 ( stomach)).

As shown in the collector voltage Vct (FIG. 3(b)), the voltage has a sawtooth waveform and a pulse waveform.

On the other hand, the collector voltage VC of 4 to the potential difference detection transistor!
is the collector voltage ve of the potential difference detection transistor U
1 (FIG. 3 (c)).

When the AC voltage further decreases, the conduction angle of the switching transistor (to) gradually increases, and the upper end of the ripple of the first rectified output terminal (b) becomes (■.t + vact
+υd), the switching transistor (to) is always on, and the input voltage of the second constant voltage circuit (2) is always vL, and when the AC voltage becomes even lower, the input voltage of the first constant voltage circuit (1 ), a ripple component appears, but
No ripple appears in the constant voltage output of the second constant voltage circuit (2) as long as formula (4) is satisfied. FIG. 3) shows the waveform at the input terminal (black) of the 2' constant voltage circuit (2). FIG. 4 shows the characteristics of the output voltages (Vol and 2) of each constant voltage circuit (1) and (2), input power, and power consumption with respect to the AC voltage of the AC power supply (3).

(G) Effects of the Invention According to the present invention, a power supply circuit includes a constant voltage circuit that derives a plurality of constant voltages (high and low constant voltages).

The voltage of the AC power supply is lower than that of conventional power supplies.The configuration is such that rectified output is supplied from the input terminal on the high voltage side to the input terminal on the low voltage side, and the power consumption in the constant voltage circuit on the low voltage side is equal to that of the conventional power supply circuit. It can be reduced to 1/2 or less compared to . Furthermore, since the output voltage of the constant voltage circuit is used as the reference potential for voltage drop monitoring, the voltage drop monitoring range is automatically corrected according to variations in the output voltage of the constant voltage circuit itself, so extremely stable operation can be guaranteed.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a power supply circuit for an electronic device according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the same circuit. 3 shows a waveform diagram of each part in FIG. 2, FIG. 4 shows a characteristic diagram of FIG. 2, and FIG. 5 shows a basic configuration diagram of the conventional circuit. Explanation of main drawing numbers (1)-1, first constant voltage circuit, (2)...second constant voltage circuit, (3)...AC power supply, (4)...power transformer, (5)... Rectifier circuit, (6)... First
constant voltage terminal, (7)...second constant voltage terminal, (9
)...Comparator% 顛...Switching diode,
(b)...First rectified output terminal. (2)...Second rectified output terminal, (2)α◆...
Potential difference detection transistor, 06... switching transistor. (2)...Control terminal. Applicant Sanyo Electric Co., Ltd. and one other representative Patent attorney Shizuo Sano txi Figure 5 Figure 2 Figure 2 1B3 Figure 4 (400X)

Claims (1)

[Claims] (1) A rectifier circuit connected to an AC power supply, a first constant voltage circuit connected to a first rectifier output terminal of the first rectifier circuit, and a voltage lower than the voltage of the first rectifier output terminal. A switching means is connected between a second constant voltage circuit connected to a second rectified output terminal having a rectifier output terminal, and the first constant voltage circuit and the second constant voltage circuit, and a switching means is connected to a control terminal of the switching means. , connects the output side of the control circuit connected to the output terminal of the second constant voltage circuit, and connects the output side of the control circuit to which the output terminal of the second constant voltage circuit is connected;
A switching diode for reverse current blocking is connected between the rectifier output terminals of the second constant voltage circuit, and when the voltage at the input terminal of the second constant voltage circuit decreases, the switching means is turned on and the switching diode is turned off. A power supply circuit for electronic equipment, characterized in that a rectified voltage is supplied from the first rectified output terminal to an input terminal of the circuit.