JPH033464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a chopper type switching power supply circuit.

[Background Art] Fig. 1 shows a perspective view of the entire main body of a chopper type switching power supply circuit, in which a heat sink 3 for heat radiation is formed around the outer shape, and a heat sink plate 3 for heat radiation is formed on the upper part of one side for AC power input and DC voltage input. A terminal board 4 for output is arranged, and mounting holes 5 for mounting to a casing or the like are bored in the four corners of the lower part. Figure 2 shows a specific circuit diagram of a conventional switching power supply circuit.
In the figure, 6 is a rectifier circuit, which is composed of a step-down transformer T ₁ , a rectifier diode bridge DB ₁ , and smoothing electrolytic capacitors C ₁ and C ₂ . 1
is a voltage control circuit that can arbitrarily convert the DC output voltage from the rectifier circuit 6 to the average value of the load voltage supplied to the load using a chopper type, and uses Darlington-connected control transistors as switching elements.
It consists of a transistor Tr ₁ , a transistor Tr ₃ that turns on and off the transistor Tr ₁ , a transistor L ₁ L ₂ , and the like. 2 is a switching control circuit for switching the control transistor Tr ₁ by driving the transistor Tr ₃ , and is composed of an IC 7 for switching the transistor Tr ₁ at an arbitrary cycle, a power supply section 8 of this IC 7, etc. has been done. By externally attaching a resistor and a capacitor of appropriate values to IC7, the average value of the load voltage can be set appropriately, and the transistor _Tr1 performs a switching operation along the period. A DC stabilized voltage is applied to the power input terminal 9 of the IC 7, and the stabilized voltage is generated by the power supply unit 8. The power supply section 8 is composed of a Zener diode ZD for setting a reference voltage, a control transistor _Tr2, and the like. The power supply section 8 receives power from a rectifier circuit 6, and the rectifier circuit 6 supplies power to both control circuits 1 and 2.

In addition, a light emitting diode LED serving as a display element and a resistor R ₁ are connected to the input side or output side of the voltage control circuit 1.
A long string of circuits is connected in parallel to indicate the power supply. However, in such conventional examples, since the light emitting diode LED is connected to the above location, the transistor that performs the switching operation is
Due to the influence of Tr ₁ , the current flowing through the light emitting diode LED fluctuates greatly, making the brightness unstable, and the fluctuations due to load are large.
There was a problem with large current consumption.

[Object of the Invention] The present invention has been provided in view of the above-mentioned points, and provides stable display of brightness of a display element, and
The present invention provides a switching power supply circuit aimed at reducing power consumption.

[Disclosure of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 3 shows a specific circuit diagram of this embodiment. The difference from the conventional circuit is the emitter (input side) of the transistor Tr ₁ of the voltage control circuit 1 and the input side of the power supply section 8 of the switching control circuit 2. A light emitting diode LED is inserted and connected in series between the collector of the main transistor _Tr2 . Therefore, the light emitting diode LED is separated from the input side of the transistor Tr ₁ and connected to both control circuits 1 and 2 without being connected in parallel.
Since it is inserted in series between the power supply terminals of the transistor Tr1, it is not directly affected by the switching operation of the transistor _Tr1 , and the lighting of the light emitting diode LED can be stably displayed.

[Effects of the Invention] As described above, the present invention has a display element inserted and connected in series to the power input terminal side of the switching control circuit, so the display element can be connected in parallel to the input side or output side of the switching element. Compared to the conventional method, the display is no longer directly affected by the switching operation of the switching element, so there is no change in load or brightness due to the type of display element.
The display element can be stably lit and displayed,
Moreover, it has the effect of reducing current consumption.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the entire switching power supply circuit, FIG. 2 is a specific circuit diagram of a conventional example, and FIG. 3 is a specific circuit diagram of an embodiment of the present invention. 1 is a voltage control circuit, 2 is a switching control circuit, and 9 is a power input terminal.

Claims (1)

[Claims] 1. A voltage control circuit that controls the conversion of a constant DC voltage into an appropriate load voltage through switching operation by a switching element, and a switching control circuit that switches the switching element of the voltage control circuit at predetermined intervals are provided, and both control circuits are provided. A switching power supply circuit characterized in that a display element is inserted and connected in series to the power input terminal side of a switching control circuit in a switching power supply circuit in which power supplies of the circuit are connected in parallel.