JPH0446559A - Control circuit - Google Patents

Abstract

PURPOSE:To omit protective circuits 14, 15 by installing a second control section composed of a diode and a resistor in parallel with a first control section, through which control current flows from a control IC. CONSTITUTION:Diodes 4, 6 and resistors 3, 5 constituting first and second control circuits are connected in parallel, and the two control circuits are set up. When either of the diodes 4, 6 is short-circuited, either of the first and second control circuits is operated normally. Accordingly, a protective circuit need not be provided on the secondary side.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention -! This invention relates to a control circuit used in a switching regulator power supply circuit used in television receivers and the like.

Conventional Technology Generally, to control a Swissching Regulator power supply circuit, a power supply control IC 11° diode 1 is connected as shown in Fig. 2.
2. A control circuit composed of a resistor 13 controls the load change #J on the secondary side.

The power supply control unit G11 has the configuration shown in Figure 3.
When the secondary winding is short-circuited, an excessive current flows through the primary main winding, increasing the collector current of TR1, increasing the voltage across resistor H, and increasing the voltage between both ends of resistor R (terminal 4 and terminal 6).
j) TR3 becomes conductive, and as TR3 conducts m, TR2
conducts. By conducting between TR2 and TR3, T
The pace tJI E V 1 of R1 decreases and operates to reduce the collector current of TR1. When the collector current of TR1 is developed, the switching transformer 1
Excessive current in the primary and secondary windings of 6 can be limited. Note that the diode 12. A pace voltage v1 of TR1 is set by a resistor 13.

Problem to be Solved by the Invention However, in such a control circuit, if the diode 12 is short-circuited or open-circuited, the voltage on the secondary side increases considerably. zener diode 16
It becomes necessary to provide a protection circuit consisting of the following components to prevent the voltage from rising.

The present invention solves these problems and provides protection circuits 1a, t.
The present invention provides a control circuit that can eliminate s.

Means for Solving the Problems In order to solve the above problems, the control circuit of the present invention
A second control section composed of a diode and a resistor is provided in parallel with the first control section through which the control current from C flows.

Effect: With the above-described configuration, even if the first control circuit shuts down or there is an open failure, the voltage on the secondary side of the transformer will not rise, and it is not necessary to provide a protection circuit on the secondary side. It is something that will disappear.

Embodiment Hereinafter, a control circuit according to an embodiment of the present invention will be explained with reference to the drawings.

As shown in Figure 1, 1 is a switching transformer, 2 is a power supply control RC, 3 is a resistor that constitutes the first control circuit through which the control current flows, 4 is a diode, and 6 is a second control circuit. The resistor 6 is also a diode. It is assumed that the voltage control LC2 is the same as the conventional example and is configured as shown in FIG.

According to this embodiment, the first. By providing two control circuits by providing diodes 4, 6 and resistors 3, 5 in parallel, which constitute the second control circuit, even if either of the diodes 4, 6 is switched off, the first. If any one of the second control circuits operates normally, the voltage on the secondary side of the switching transformer 1 will not rise abnormally.

In addition, in Chapter 1, so-called open operation test to check whether the control circuit operates normally during product manufacture, even if any of the diodes 4. Second
Since one of the control circuits operates normally, products whose shipments were previously stopped due to open failures can now be shipped as is.

In addition, since it is no longer necessary to provide a protection circuit that was conventionally provided on the secondary side, there is no longer a need for a Zener diode that constitutes a protection circuit, and since Zener diodes are much more expensive than ordinary diodes, it is less costly. Its practical effects are also high.

Furthermore, since the Zener diode is no longer required,
Conventional Zener diode abnormalities (when open failure occurs,
It is also possible to prevent an abnormal rise in the secondary voltage due to the Zener diode (which always short-circuits).

Effects of the Invention As described above, the present invention provides a protection circuit on the secondary side, since even if the diode through which the control current of the switching regulator power supply flows is open or disconnected, the voltage on the secondary side will not rise. Since there is no need to provide a , it is extremely advantageous in practice.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a Suino Chinda regulator power supply circuit including an embodiment of the control circuit of the present invention, Figure 2 is a circuit diagram of a conventional Suino Chinda regulator power supply circuit, and Figure 3 is a power supply control ICi. FIG. 1...Switching transformer, 2...
Power control IC, 3, 5... Resistor, 4.6...
...-diode. Name of agent Patent attorney Shigetaka Awano and 1 other person Switching transformer 1 Paragraph 1 [IIc Vol.

Claims (1)

[Scope of Claims] A control IC that controls a primary side control winding; a first control section including a diode and a resistor through which a control current flows; and a first control section including a diode and a resistor in parallel with the first control section. A control circuit characterized by comprising two control sections.