JPS5959078A - Power source control system for switching type power source - Google Patents

Abstract

PURPOSE:To effectively prevent the abnormal rise of an output power source voltage when the circuit becomes abnormal by controlling the transistor current of a photocoupler in response to the output power source voltage. CONSTITUTION:When a switch S is closed so that a transistor Q1 becomes ON, a condenser C4 starts charging by a coil N5. A transistor Q3 is turned ON at this time point, the transistor current of a photocoupler PC increases, and the transistor Q2 is not turned ON until the current flowed to the resistor R3 becomes considerably large. Accordingly, the conversion energy through the transformer T is large. Thereafter, when the output gradually increases, the current of the transistor Q3 decreases, the transistor current of the photocoupler PC thus decreases, thereby early turning the transistor Q2 ON and reducing the switching power.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of ≦6 Ming] The present invention relates to a resource control method for a switching type %I source device using a photocoupler.

[Technical background of the invention and its focus]

A conventional switching power supply using a photocoupler is constructed as shown in FIG. 1, and its operation is as follows. First, when the switch S closes, the base current flows to the transistor Q+ through the resistor R1, and the transistor Q is turned on. When the transistor Q is turned on, a direct current is applied to the winding NIζ of the transformer T, = It nE E, and a voltage is induced across the winding N21 of the transformer T, and the diode D.

Sufficient base current is supplied to transistor Q1 through resistor R2. After this, Transistor Q! The collector air 1/li increases with a slope determined by the tar pressure E and the inductance of the winding N1.The voltage generated across the resistor R3 due to the current'θ force 11 turns on the transistor Q2. voltage (VLI)
If the delay is delayed to E), the normal current supplied to the base of the transistor Q+ is bypassed through the diode Din and the resistor R2, and the current flowing to the collector of the transistor Q1 is reduced.

Once the collector current of transistor Q1 begins to decrease, the voltage across winding N2 drops due to transformer action, which causes the base current of transistor Q to increase (
This decreases, and the 1-range nut Q suddenly shifts to the off state O, and a reverse voltage is induced in each @ line. At this time, since the voltage of the colored line 1q is in the 111 direction of the diode D2, a current flows through the diode D2, charging the capacitor → NO CI, and a current flows through the load L1.

4. While this condition continues, the snow pressure in the winding N is:
The base of transistor Q+ is reverse biased through capacitor C2 and resistor R2.

Furthermore, the capacitor L-C is also charged through the diode 1]3 by the Uto of the -8 line N1. In this state, the transistor RI Q1 on I (l bow 1 - lance °l ゛ stored λ
Until the J energy released is released M: <.

After this discharge, the lower pressure of each winding becomes 0, but at this time, the charge l of the capacitor C2 causes the transistor Rq+4 to move to the on-state state J''. The operation of the output voltage VO11T, that is, the capacitor C
Both fP and F pressures of 1 go up. This is the operation of the rising history.3, This is the operation of the rise history.
'r rises, resistance R4, I? , 5 and town resistance vB
The base voltage of the transistor Qs divided by
The sum of the Zener voltage VZ of the Zener diode ZD and the base-emitter voltage vnE of the transistor Q, that is, (V
When it becomes higher than Z + VBz<'), the transistor Q
3 is turned on, and current flows through the light emitting diode of the photocoupler PC. At this time, a current proportional to the current flowing through the light emitting diode flows through the phototransistor of the photocoupler PC, and the base potential (bias) of the transistor Q2 is applied through the resistor R6. increases and the voltage across R3 increases, the transistor Q
2 is turned on, and transistor Q1 is turned off. Therefore, when the transistor Q1 is on, the energy stored in the transformer T is proportional to the magnitude of the bias, i'm It acts in the direction of lowering the output voltage VOUT, and the output voltage VOUT
When T becomes lower, the current of the photocoupler PC decreases and the bias becomes smaller, which acts in the direction of increasing the output voltage and voltage VOUT. In this way, the output type F:EVOU is kept constant. Similarly, the resistor R7 is for resisting the bias '11 style of the Zener diode ZD.

Given the above circuit numbers, when considering the failure modes of the llt control circuit, the transistor current of the photocoupler PC decreases or becomes O? This is the most common case, and in that case, the output voltage VOUT rises rapidly, causing problems such as damage to the load. In order to prevent this, conventional methods such as adding an over-output prevention circuit have been used. Measures are needed,
This results in an increase in the number of components to be mounted and the complexity of the circuit, which poses a problem in terms of cost reduction, miniaturization, etc.

[Purpose of the invention]

The present invention is based on the above-mentioned Mc' actual situation, and in a switching power supply device using a photocoupler in one stabilization control circuit, a simple and inexpensive α circuit configuration reduces the transistor current of the photocoupler. To provide a power supply control method for a switching power supply device that can secure a highly safe power supply by actually preventing an abnormal increase in output power supply voltage when a circuit abnormality occurs. With the goal.

[Summary of the invention]

The present invention lowers the output power supply voltage by reducing the transistor current of the photocoupler provided in the control circuit when the output power supply voltage increases, and increases the DC current of the transistor of the photocoupler when the output power voltage decreases. Then output city source′
It has a circuit configuration that works to make the F1 switch more effective, and because of this Q, even if a circuit abnormality such as a reduction in the photocoupler transistor's current occurs, the output will always be in a highly safe direction. to control the output power ei (, 1F-
This system is designed to reliably prevent an abnormal rise in ζ.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The parts of this embodiment 11 shown in FIG. 2 are as follows. SuC3
, a negative t[
E and its negative 'Fly, i line N
A photocoupler P is connected between L and the base of transistor Q2.
The transistor Q2 is connected to bypass the base current of the transistor Q2. On the other hand, the secondary side transistor Q3 has its base connected to the Zener diode ZDi law, and its emitter connected to the variable resistor VR side. Further, a diode D4 and a capacitor C4 are connected, and a diode of an autocoupler PC is connected between this connection point P and the collector of the transistor Q3 so as to form a positive voltage when the transistor 01 is turned on. f, -1, and resistor R7 is connected between the connection point P and the base of transistor Q3.

Here, the operation of the 1% 1m example shown in FIG. 2 will be explained. When switch S is closed and transistor Q1 is turned on, windings N- and h start charging capacitor C4.

At that point, the voltage on capacitor C1 is still 0, so transistor Q3 is turned on and transistor 03 is turned on.
A large current flows through ρ. Therefore] 1st Nonopura
) The transistor current in C is large and transistor Q2 will not turn on until the current flowing through resistor R3 is quite large. Saddle up and rise to the poem's sweet tink bower, that is,
Reproduction energy through the transformer T is large. After that, when the output increases to J, the weight of transistor Q3 decreases, the transistor current of this O (accordingly to the photocoupler) C decreases, and transistor Q2 turns on earlier. Therefore, the sweet tinkubanau becomes smaller.

In this way, when the output πC pressure VOIJT increases, the transistor 'l'f'+ current of the photocoupler PC decreases,
By turning on the transistor Q2 early, it acts in the direction of lowering the output surface LfZVOUT, and the output voltage VOU
When T decreases, the transistor current of the first coupler PC increases, which delays the turn-on of transistor Q2 and reduces the output pressure V.
It acts in the direction of raising OUT.

In this way, the output pressure V OUT is maintained at -jQl.

After hitting the above, the output pressure VOIJ'l' is 1j lj
When it comes to photocoupler PC transistor fii:
By decreasing fAt, the output voltage V (l U T ”;
When the output pressure V OUT becomes lower, the transistor current of the photocoupler PC is reduced and the output pressure V OUT becomes lower.
Since it acts to reduce u'r, the photocoupler P Accidents such as UT becoming abnormally high and destroying the load can be prevented.Also, capacitor C
The voltage of 3 is proportional to the voltage of capacitor CI.
When it comes to con? il) pressure of sensor C3 also becomes approximately 0,
The pace of transistor Q * I5 photo ・Since the transistor of the coupler PC is no longer able to pull the voltage sufficiently, transistor Q2 turns on earlier, reducing the output power and causing a short circuit■↓7 Reduce the flow. That is, since the current when the load is short-circuited is reduced, protection against the load short-circuit can be easily achieved.

Helmet, the fruit 7ji mentioned above! In f.11, I used a linking type power supply as an example, but f! if 11th
It is also possible to easily realize another lightning source device Cζ using a single-circuit photocoupler.

[Effects of the Invention] - As detailed above, according to the present invention, in a switching power supply device having one photocoupler in the stabilization control circuit, the photocoupler is ′f so that the transistor if if decreases.
A switching type that can securely stop the high-t output power supply outside the PC when a circuit malfunction has occurred, and ensure a highly safe supply of power at all times. A single control system can be provided in the air of the power supply unit F.

4 Figure 1 F of envy? C Simple 4 (a) Figure 1 shows the conventional circuit JF+ circuit 1.21, 2.
The figure is a circuit diagram showing a practical cell 11 of the present invention.

pc...Photocoupler, Q+, Q2-Os
Transistor, D+, D2, D3, D4・
・・Quiode, ZD・・Zener diode, 'r・
...Transformer, N,, N2, N3, N=...Winding (N,, N2...Primary winding; (2), N3, N5...
...secondary volume, gland), VR...variable resistance, R1, R2,
...R7...Resistance, C1゜C2, C3, C,...
capacitor.

Claims (1)

[Claims] In a switching power supply device that uses a photocoupler as a circuit for stabilizing output control, the circuit reduces the transistor current of the photocoupler to lower the output power supply voltage when the output power supply voltage increases, and the output power supply voltage increases. When the voltage of the power source 111 becomes low, the photocoupler transshifts,
In the evening, increase the canister flow and increase the output r11 pressure (
・A power supply control method for a switching power supply device, which is characterized by: 1.