JPS5850878A - Power supply for dc-to-dc converter - Google Patents

Abstract

PURPOSE:To obtain a DC-DC converter of low power consumption added with an efficient preheating circuit, by switching the inductor of a line filter during preheating operation, and supplying its output to a heater circuit. CONSTITUTION:When changeover switches S1 and S2 are set (on side PH) for preheating operation, a switching transistor 4 switches an inductance 12 as a load. A voltage is induced on the secondary side of the inductance 12 to supply electric power to a heater circuit 8. Then, the heater voltage is detected by a lead wire 11 and fed back to a control circuit 5, so a reted voltage is applied to the heater circuit 8. In the figure, 14 is a filter and 15 is a rectifying and smoothing circuit.

Description

[Detailed description of the invention] The present invention is a television receiver, TV Josca 2.

This invention relates to a DC-DO converter device that can be used in cameras, etc., and aims to provide an In-DC converter device with a low power consumption and efficient preheat circuit.

FIG. 1 shows an example of a conventional l11-DC converter device. In FIG. 1, 1 is a DC power supply, 3 is a converter transformer, 4 is a switching transistor, 6 is a control circuit,
6 is a group of output terminals of the converter transformer 3, 7 is an image pickup tube,
8 is a heater, 9 is a resistor, 10 is a load, and 11 is a feedback lead wire. Now, in order to supply power from the same DC power supply 1 to the converter power supply circuit and load 10,
In order to prevent interference from the converter power source from affecting the load 10, it is necessary to connect a line filter 2 consisting of an inductance L and a capacitor C between the DC power source 1 and the converter transformer 3.

Furthermore, as shown in Figure 1, the heater voltage is connected to the control circuit 6 by the lead wire 11 to stabilize each output circuit 6 of the converter transformer.The changeover switches S1 and S2 are interlocked. During normal operation of the converter power supply, the selector switch is on the N side.
A voltage is generated at the output terminal group 6 of the converter transformer 3, and power is supplied to the heater 8. Next, heater 8
When only ゛ lights up (when in so-called preheat state)
The input winding of the converter transformer 30 is released and the changeover switch S1 and ≦2 are switched to the P and H sides in order to disable the converter power supply. In this case (during preheating), the converter power supply is in an inactive state,
Preheating power is supplied to the heater 8 through a resistor 9. In addition to the drawback that the power loss corresponding to the voltage drop of the resistor 9 deteriorates the efficiency during preheating, the effect of this on the heater voltage in particular becomes greater as the input voltage becomes higher.

For example, when using a heater with a voltage of 2.8 V and a rating of 0.3 W, Doff, the voltage of the source 1, and the power loss of the resistor 9 are shown in Table 1.

Table 1 The present invention takes the above-mentioned drawbacks into consideration and attempts to reduce power loss during preheating as much as possible, and is an nc-DC converter power supply consisting of a converter transformer, a switching transistor, a control circuit, a rectifier and smoothing circuit, etc. It consists of a line filter consisting of an inductor with an output winding and a capacitor, a heater circuit for the image pickup tube, etc., and a changeover switch.
The converter transformer is opened, and the switching transistor connects the line filter's output winding inductor L.
The output winding of the inductor L supplies power to a heater circuit such as an image pickup tube.

- Examples of the present invention will be described below with reference to the drawings. An embodiment of the present invention is shown in FIG. In FIG. 2, the same numbers and symbols as in FIG. 1 represent the same components or have the same functions, and their explanations will be omitted.

12 is an inductor with an output winding, and 13 is a diode. A changeover switch S1 is provided between the inductor 12 of the filter 14 and the capacitor C, and a diode 13 is provided between the capacitor C and the primary winding of the converter transformer 3. Further, a changeover switch S2 is provided between the input terminal of the rectifier smoothing circuit 16 and the separate winding wave 16 of the converter transformer 3 and the output winding of the inductor 12, and is connected to the output terminal heater 8 of the rectifier smoothing circuit 15. The switch 510P-H side is connected to the collector of the transistor 4.

When the DC-DC converter power supply 3 normally supplies power to other circuits, the heater circuit 8, etc. through the output terminal group 6, the changeover switches S and S2 are on the N side. In this case, the inductor L12 switches the quintic selector switch S and S2, which function as a part of a normal line filter, at the time of preheating (: P, H side). In this case, since the switching transistor 4 continues its switching operation, when the inductor L12 is connected to the collector of the switching transistor 4, the inductor L12 is switched. One end of the output winding of this inductor L12 is grounded, and the other end is connected to the heater circuit 8 to supply power. In this case, the power for the control circuit is supplied from the DC power supply 1, and the control circuit operates even during preheating.

Furthermore, since the heater voltage is detected by the lead wire 11 and fed back to the control circuit 6, the rated voltage is applied to the heater circuit 8.

Note that a diode 13 is inserted between the line filter 2 and the input winding of the converter transformer 3, and the function of this diode 13 is to pass through the input winding of the converter transformer 30 during the operation of the switching transistor 4 during preheating. The function of this function is to stop the operation of the converter transformer so that the collector pulse voltage does not appear on the secondary side.

In this way, unlike the circuit shown in FIG. 1, which supplies power to the heater 8 through the resistor 9, this circuit supplies the heater voltage itself to the heater circuit 8, resulting in extremely low power consumption. Good efficiency.

FIG. 3 shows another embodiment of the present invention. The embodiment shown in FIG. 2 is for a separately excited type DC-DC converter.
The figure shows the case of a self-excited DC-DCC set.
The same numbers and symbols as in FIG. 2 indicate the same items or the same functions. In FIG. 3, 17 is a base winding provided on the DC-In converter 3, 18 is a base winding provided on the inductor 12, and switch S3 is interlocked with S and S2, and switches the base windings 17 and 18. To explain the operation below 0 which is a changeover switch, it is usually SL,
The changeover switches S2 and S5 are on the N side, and the inductor 12 works as a line filter, and a base current flows through the control circuit 5 to the base of the switching transistor 4 by the base winding 17 of the inductor meter transformer 30. Next, changeover switch S1. Switch S2 and S3 to the preheat FfKP-H side). In this case, an inductor 12 is connected to the base of the switching transistor 4.
A base current flows from the base winding 18 provided in the control circuit through the control circuit. Therefore switching transistor 4
continues the switching operation, and also detects the heater voltage on the lead wire 11 and feeds it back to the control circuit 6, so the heater voltage is stable even during preheating, and there is no need to use a dummy resistor like in the conventional example. , In-DC
It is efficient because it supplies power using a converter method.

In addition, an embodiment in which the circuit shown in FIG. 2 and the circuit shown in FIG. etc.) is also possible.

Generally, the converter circuit operation tends to become unstable due to line filter inductance (converter transformer primary winding inductance) and light load during preheating, but if the frequency control type is used as the control method for the output voltage, the above Phenomena such as this will be resolved.

, 9 In addition, since the inductor of line/filter 2 must be used for switching operation during preheating, the effect of the line filter is lost and noise is likely to be generated, but the power during preheating is extremely low (for example, o, 5W). -0
, 51), the maximum current value flowing through the switching transistor 4 is also reduced, and as a result, noise is extremely reduced. Therefore, line filling is not required during preheating.
lk6'l! In the power supply circuit, the inductor L of the line/filter is switched during preheating, and its output is supplied to the heater circuit, so there is no need to add any special circuits, low power consumption, and extremely high efficiency. It can provide a preheat circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional DC-NC controller 1 and a power supply device; FIG. 2 is a circuit diagram of a Q-DC controller power supply according to an embodiment of the present invention; FIG. 3 is a circuit diagram of the DC-DC=+y overnight power supply device in the embodiment of the same site. . . . Switching transistor, 8 . . . Heater, S4. S2.
S3...Switching switch, 1...DC power supply, 3...Converter transformer, 12...
...Inductor 0 agent's name Patent attorney Nakao
Toshio and 1 other person Figure 1 @ 2 [1,4 Figure 3

Claims (1)

[Claims] A converter transformer, a switching transistor, and a rectifying and smoothing circuit D (consisting of an inductor and a capacitor with an output winding connected between the DC converter power supply and the NC power supply of the input winding of the converter transformer) The converter transformer is made to open the converter transformer by the changeover switch during preheating, and the inductor of the line filter is switched by the switching transistor. A DC-DC converter power supply device characterized in that the output winding of the inductor supplies power to a heater circuit of the cathode ray tube or the like.