JPS61269673A - Frequency control method of ringing choke converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a frequency control method for a ringing choke converter used in a power supply device of an electronic device or the like.

(Prior art) Power supplies for electronic devices require a constant voltage and stable DC power supply, but in general, a self-oscillation type ringing choke converter (hereinafter referred to as RCC), which has a simple circuit and can be constructed at low cost, is used. ) is widely used.

As shown in FIG. 1, this RCC includes a transformer T equipped with a primary coil N1 and a control coil Nc on the input side, and a secondary coil N2 on one or two sides on the other output side, and this secondary coil N1. and a bias circuit 2 connected to the control coil Nc, a main switching transistor 3 having a collector connected to one end of the secondary coil N1, an emitter connected to one end of the control coil Nc, and a heath connected to the circuit 2. and configure it. And -th coil N1
If a DC input is applied to one end of the control coil Nc connected to the other end and the emitter, a pulse wave output with a frequency that changes depending on the size of the load etc. is obtained on the output side, and this output By passing the voltage through the rectifying and smoothing circuit 4, a stabilized and transformed DC voltage is obtained. Incidentally, a suitable RCC having such a function is, for example, disclosed in Utility Model Application Publication No. 55-162.
The conventional circuit described in Japanese Patent No. 385 is well known.

(Problems to be Solved by the Invention) However, since the above-mentioned conventional RCC uses a self-oscillation method, the frequency of the pulse wave output, that is, the automatic oscillation frequency, varies from tens of KHz to hundreds of kilohertz depending on input voltage fluctuations or load fluctuations. Varies between KHz. Therefore, in this type of RCC, switching noise having the relevant frequency occurs (occurs at the rise and fall of the pulse), and currently the noise standards of each country (
For example, in compliance with the FCC standard, VDE standard, etc., a noise filter that removes noise at the above-mentioned oscillation frequency is inserted into the power supply line to reduce the noise level.

However, if the change in the oscillation frequency is small, there is no problem, but if the frequency changes significantly and falls outside the cutoff frequency of the noise filter, the noise filter will no longer function.
A problem arises in that noise cannot be removed.

In addition, in RCCs used in power supplies built into CRT display devices, etc., fluctuations in oscillation frequency interfere with the frequency of signals used in other circuits, causing screen shake, striped patterns, and other problems that affect image quality. This can lead to harmful effects that can cause significant deterioration.

Therefore, the present invention aims to provide an RCC frequency control method that eliminates these problems.

(Means for Solving the Problems) The present invention relates to a frequency control method for an RCC used particularly in a power supply device, etc., and its characteristics include, as shown in FIG. The oscillation frequency of the RCC 1 is synchronized with the frequency of the pulse control signal Sp by applying a pulse control signal SP having a predetermined frequency from the reference oscillator 5, for example, and controlling the switching state of the element 3. That's the point.

(effect) Next, the operation of the present invention will be explained.

When the pulse control signal Sp is not applied, the collector-emitter voltage of the main switch-noting element 3, which is a transistor, for example, is a pulse wave So as shown in FIG. 3(a).
becomes. This pulse wave So corresponds to the on or off state of the main switching element 3, and therefore, the pulse control signal sp having a pulse S1 at the base of the element 3 that can turn on this element 3 ((b) in the same figure) When the pulse S1 is applied, the element 3 is forcibly turned on at the time when the pulse S1 is applied. As a result, due to the function of RCC1, the pulse wave output S becomes zero level when the pulse S1 is applied.
2 ((e) in the same figure) is obtained. That is, the pulse wave output S2 synchronized with the pulse control signal Sp is obtained as the output of RCCl.

(Embodiments) Below, preferred embodiments of the present invention will be described based on the drawings.

First, a specific circuit to which the method of the present invention can be applied will be explained with reference to FIG. The figure illustrates part of a power supply device in a CRT display device.

10 in the figure is RCC. This RCC 10 includes a transformer T having a primary coil NIO wound on the input side and a secondary coil N20 wound on the output side. One end of the -secondary coil NIO and control coil Nco is a DC input, the other end of the -secondary coil NIO is connected to the collector of the main switching transistor (NPN type) Qo, and the other end of the control coil Nco is connected to a predetermined circuit element. It is connected to the base of the transistor QO through. Further, the emitter of the transistor Qo is the control coil Nc.

Connect to the DC input terminal above. Note that in the circuit formed on the input side of the transformer TO, R1, R2, R3, R
4 is a resistor, C1 and C2 are capacitors, Dl, D2, D3
is a diode, and D4 is a Zener diode, which are connected as shown. Also, Trance T.

The winding direction is also as shown in the figure.

On the other hand, the secondary side of the transformer To is connected to the load side via a rectifying and smoothing circuit 12 consisting of a diode D5 and a capacitor C3.

On the other hand, the secondary side of the coupling transformer T1 is connected to the base and emitter of the main switching transistor Qo via a series circuit of a resistor R5 and a diode D6. Further, a horizontal synchronizing signal VD is applied to the primary side of the transformer Tl via an amplifier circuit 13. In addition, in the amplifier circuit 13, Ql and C2 are NPN transistors, and C3 is a PN transistor.
P-type transistors, R6, R7, and R8 are resistors, C4 is a capacitor, and D7 is a diode, which are connected as shown in the figure.

Next, a frequency control method of the RCCIO having such a configuration will be explained together with circuit operation with reference to FIGS. 2 and 3. Incidentally, FIG. 3 is a timing chart diagram in the content section of FIG. 2.

First, the operating principle of RCCIO will be described.

When the main switching transistor QO is on, the resistor R
1 and the control coil Nco, a bias current flows through the base, and energy is stored in the primary coil NIO during this on (conduction) period. On the other hand, when the collector current of the transistor QO reaches a certain level, the transistor Qo becomes off (non-conducting) and the
The stored energy of IO is supplied to the secondary coil N20 which is the output side.

When the stored energy has been released, the transistor Qo is again controlled by the action of the resistor R1 and the control coil Neo.
is turned on, and energy is stored in the -order coil. That is, the transistor Qo is repeatedly turned on and off, and automatic oscillation is performed to obtain a pulse wave output of a predetermined frequency at the output side secondary coil N20. In this case, transistor Qo
The collector-emitter voltage of is as shown in Figure 3(a), and the current flowing through the negative coil NIO is as shown in Figure 3(c).
) as shown in the dotted line waveform S3 (in addition, such RCCI
Regarding the specific configuration and operation of O, see Utility Model Application Publication No. 55-162.
(Please refer to the conventional circuit described in Publication No. 385).

Incidentally, in such an RCC 10, a pulse control signal Sp is applied to the main switching transistor Qo according to the present invention. This control signal Sp is a signal as shown in FIG. 3(b), and specifically, a horizontal synchronizing signal HD used in a CRT display device is obtained through the amplifier circuit 13. In the design of the RCC 10, the self-oscillation frequency is set so that the frequency variation range is lower than the frequency of the control signal Sp. This will be explained in detail later. Now, assume that the main switching transistor Qo of the RCC 10 is in the off state. In this state, when the pulse S1 of the control signal Sp is applied to the base of the transistor Qo, the transistor Qo is driven and forcibly turned on. On the other hand, a current S4 having a waveform as shown by the solid line in FIG. 3(c) flows through the secondary coil NIO. In this case, the transistor Qo is turned off corresponding to the storage state of the stored energy, and the next control signal Sp is turned off. The transistor Qo is turned on again by the arrival of the pulse S1. As a result, the current S flowing through the secondary coil N20
The waveform of No. 5 is as shown in Fig. 3(d), and the secondary coil N2
The terminal voltage of 0 is as shown in the same figure (e).

That is, the oscillation frequency of RCC1 is synchronized with the frequency of the pulse control signal Sp.

Therefore, in the above embodiment, the self-oscillation frequency of the RCCIO can be synchronized with the horizontal synchronization signal HD (frequency is 15.75 KHz). This means that the oscillation frequency of the RCC can be fixed at a frequency that is not affected by load fluctuations, etc. As a result, by adjusting the phase etc. in the circuit that actually uses the horizontal synchronization signal HD, such as the horizontal deflection circuit, It is possible to prevent the CRT screen from shaking, striped patterns, etc.

Next, a frequency setting method for carrying out the method of the present invention will be explained in more detail with reference to FIG. The figure shows an output current (load current) vs. operating frequency characteristic diagram in RCCIO. In the same figure, the range indicated by △Io is R
It shows the variation range of the output current of the CCIO, and the range indicated by ΔE shows the variation range of the input voltage of the RCCIO. By the way, as is clear from the figure, due to the characteristics of the RCCIO, as the output current increases, the operating frequency decreases, and on the other hand, as the input voltage increases, the operating frequency increases. Therefore, R
The operating frequency of CClo varies within the shaded area S.

As a result, if the operating frequency of the RCCIO is set in advance, the maximum frequency f1 of the fluctuation point of the operating frequency
For example, the frequency of the pulse control signal Sp from an external oscillator (FIG. 1) may be set so that the frequency f2 is slightly higher than the frequency f2. On the other hand, when the horizontal synchronization signal HD is used as the pulse control signal Sp as in the above embodiment, the frequency f2 is determined, so the operation is performed so that the maximum fluctuation frequency f1 of RCCIO is slightly smaller than the frequency f2. All you have to do is design the frequency. In other words, f
It is necessary to satisfy the condition 1≦f2. Note that the operating frequency characteristics of the RCCIO synchronized by the method of the present invention are fsyc
Indicated by

Furthermore, fixing the RCC oscillation frequency to a constant value means that it can always be fixed within the cutoff frequency of the nozzle filter inserted into the power supply line, and such noise removal measures can also function effectively. .

Note that even if the oscillation frequency of the RCC is forcibly fixed, the energy supplied to the output side (load side) is controlled by changing the pulse width, so the output voltage is stabilized.
The original function of IO itself is not affected.

The circuit in Figure 2 is, so to speak, between the ground on the RCC side and the reference generator mB (
The ground of II+ was made separate and independent by a coupling transformer, but without using such a coupling transformer,
As shown in the figure, the reference oscillator side and the RCC may be directly connected to provide a common ground.

Although the embodiments have been described above, the present invention is not limited to these embodiments. For example, the RCC can be applied not only to the illustrated circuit but also to any configuration of RCC. Furthermore, as shown in Fig. 2, the pulse control signal may be used directly or after being shaped into a signal used in an existing circuit, etc. Also, although a transistor is used as an example of the main switching element, PET, etc. Any switching element can be used. Other changes may be made in the detailed structure, method, etc., without departing from the spirit of the present invention.

(Effects of the Invention) As described above, the RCC frequency control method according to the present invention has the following effects:
The oscillation frequency of the converter is synchronized with the frequency of the pulse control signal by applying a pulse control signal having a predetermined frequency from the outside to the main switching element of the RCC and controlling the switching state of the element. The following significant effects can be obtained without sacrificing the advantages of the RCC oscillation system, which is a low-cost circuit configuration.

■Since the oscillation frequency of the RCC is fixed at a constant level without being affected by input voltage fluctuations, load fluctuations, etc., noise reduction measures such as selecting a noise filter to be inserted into the power supply line become easy.

Moreover, since there is no fluctuation in the oscillation frequency, noise can always be reliably removed.

(2) Also, since the oscillation frequency is fixed, it is easy to take countermeasures against equipment that is disturbed by the generated noise. For example, when the noise frequency fluctuates, in CRT display devices, etc., screen shakes and striped patterns occur, degrading the image quality, but if the noise frequency is fixed, it is easy to design a circuit that can best avoid the noise frequency. becomes.

(2) Furthermore, the method of the present invention can be carried out very easily. In particular, if signals in existing circuits are used, the circuit configuration can be dramatically simplified and can be implemented in a small size and at low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram that can implement the method of the present invention, and FIG.
The figure is a specific circuit diagram showing a part of the power supply device in a CRT display device that implements the method of the present invention.
The figure is a timing chart of current/voltage waveforms in the capacitor section, and FIG. 4 is a diagram of RCC output current versus operating frequency characteristics. In the drawing, 1, 10...RCC. 3, Qo...main switching element, 5...
Reference oscillator, Sp...Pulse control signal, HD.
...Horizontal synchronization signal.

Claims (1)

[Scope of Claims] 1. A pulse control signal having a predetermined frequency is externally applied to the main switching element of the ringing choke converter, and the oscillation frequency of the converter is controlled by the pulse control signal by controlling the switching state of the element. A method for controlling the frequency of a ringing choke converter, characterized in that the frequency is synchronized to the frequency of the ringing choke converter. 2. Claim 1, characterized in that the frequency of the pulse control signal is set higher than the fluctuation range of the oscillation frequency.
Frequency control method for ringing choke converter described in Section 2.