JPS62141861A - Switching power supply circuit - Google Patents

Abstract

PURPOSE:To exclude the effect of noise when a switching transistor (TR) is turned off by adjusting the phase of a high frequency inverter synchronizing signal. CONSTITUTION:A signal is converted into a signal V2 having a pulse width in response to a time constant depending on a variable resistor R4 and a capacitor C1 in the 1st one-shot multivibrator 62. Then the signal is converted into a pulse V3 rising synchronously with the trailing of an output pulse V2 of the 1st one-shot multivibrator 62 and having a pulse width required to drive a switching TR Q1 of a high frequency inverter 2a, amplified by an amplifier circuit 64 and inputted to the high frequency inverter 2a. That is, a desired delay is given to the phase of the horizontal synchronizing signal detected from a CRT display device by adjusting the variable resistor R4 provided to the 1st one-shot multivibrator 62 and the result is used for a synchronizing signal of the inverter 2a.

Description

[Detailed Description of the Invention] [Summary] In a ringing choke converter type switching power supply circuit that is used as a power supply for a CRT display device and is driven in synchronization with a horizontal synchronization signal, the phase of the horizontal synchronization signal used for synchronization is changed. The adjustable configuration prevents the noise generated during switching from adversely affecting the horizontal deflection circuit.

[Industrial Application Field] The present invention relates to an improvement of a ringing choke converter type (hereinafter referred to as RCC type) switching power supply circuit used as a DC stabilized power source.

A switching power supply circuit is composed of an input rectifier, a high frequency inverter, a control section that controls the output voltage of the high frequency inverter, etc., and is classified into various types mainly depending on the configuration of the high frequency inverter.

Among these, the RCC type switching power supply circuit is also called an on-off type, and uses a high-frequency inverter to convert direct current to multiphase alternating current using a switch-noting transistor, and then converts this to the desired voltage using a transformer. Direct current is obtained through rectification, and energy is stored in the transformer especially when the switching transistor is on.

The structure is such that current flows through the load during the off period. Therefore, the output can be controlled by changing the duty cycle in switching.

In addition, the RCC method uses the least number of parts among high-frequency inverter methods, and has the advantage that there is no need to match characteristics because it uses only one switching transistor, making it suitable for relatively small-capacity stabilized power supplies. It is used.

Note that, particularly in those used for CRT display devices, a method is usually adopted in which the switching period is synchronized with a horizontal synchronizing signal.

At this time, it is desirable that the configuration be such that the influence of noise generated when the switching transistor is turned on and off can be prevented.

[Conventional technology]

FIG. 5 is a configuration diagram of a conventional example of a switching power supply circuit driven in synchronization with a horizontal synchronizing signal of a CRT display device.

1 is an input rectifier that rectifies and smoothes AC input.

2 is an RCC type high frequency inverter consisting of a switching transistor old, a transformer TI, etc.

3 is an output rectifier that rectifies and smoothes the AC output obtained by the high frequency inverter 2.

4 is a flyback transformer (FBT) of a CRT display device.
), a synchronization signal detection section detects a horizontal synchronization signal.

Reference numeral 5 denotes a control unit that starts the high-frequency inverter 2, stabilizes the output voltage Vo, and performs other controls.

Further, FIG. 6 shows a timing chart showing the relationship among the horizontal synchronizing signal Vf, the primary current 1c of the transformer T1, the collector voltage Vc of the old transistor, the output current 1d of the high frequency inverter 2, and the noise appearing in the output voltage.

That is, the high-frequency inverter 2 uses the unstabilized DC obtained by the input rectifier 1 as a power source, and uses the horizontal periodic pulse Vf obtained by the synchronization signal detector 4 to turn on and off the switching transistor OLD and drive the transformer Tl. do.

The control unit 5 controls the base current of the switching transistor Q1 according to the output voltage obtained by the detection coil C of the transformer T1.

The operating pulse width Td is controlled to control the output voltage.

With this configuration, the switching transistor (H) is turned on during the retrace period, that is, during blanking, so that noise when turned on does not appear on the display screen.

[Problem that the invention seeks to solve]

In the conventional example with the above configuration, when the voltage fluctuation range of the AC input power supply is widened, the on-period Td of the switching transistor changes due to changes in load or variations in circuit constants. Therefore, noise generated when the switching transistor 01 is turned off may have an adverse effect on the deflection circuit system on the load side.

For example, if the voltage fluctuation range of the AC input power supply is 85 to 132
In the case of volts, when the on-period Td of the switching transistor reaches a certain value, when it turns off, jitter occurs in the driving pulse of the horizontal deflection circuit, which causes a problem in that the displayed image shakes. be.

That is, an object of the present invention is to eliminate the influence of noise when the switching transistor is turned off.

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention.

6 is a phase adjustment unit that adjusts the phase of the horizontal synchronization signal detected from the CRT display device.

2a is a ringing choke converter-type 17-frequency inverter that oscillates in synchronization with the horizontal synchronizing signal whose phase is adjusted by the 1-phase adjustment section 6.

[Effect]

That is, by adjusting the phase of the horizontal synchronization signal used for synchronizing the high-frequency inverter 2a in the phase adjustment section 6, the noise generated when the high-frequency inverter 2a is turned off is adjusted to a point where it does not affect the deflection circuit system. This is to prevent an adverse effect from occurring on the second display surface by shifting the display surface.

〔Example〕

FIG. 2 is a block diagram of the embodiment, and the same reference numerals as those in FIG. 1, which is a principle diagram, and FIG. 5, a conventional example, refer to the same objects, and the explanation thereof will be omitted.

In addition, 7 is a protective transformer provided to protect the switching transistor Q1 in the high-frequency inverter 2a. A specific configuration example of the 1-phase adjustment section 6 is shown in FIG. 3, and a timing chart of the waveforms of each section is shown in FIG. Shown in Figure 4.

The horizontal synchronizing signal νf detected by the fly-high transformer (FBT) is sent to the switching transistor circuit 6.
1, the signal is converted into a signal ν2 having a pulse width according to a time constant determined by a variable resistor R4 and a capacitor C1 in a first one-shot multi-by-break 62.

Subsequently, the second one-shot multi-high break 63 rises in synchronization with the fall of the output pulse v2 of the first one-shot multi-high break 62, and generates a pulse necessary for driving the switching transistor 01 of the high-frequency inverter 2a. The signal is converted into a pulse v3 of width V3, amplified by the amplifier circuit 64, and then input to the high frequency inverter 2a.

That is, the first one-shot multi-bye break 62
By adjusting variable resistor R4 provided in .

A desired delay is given to the phase of the horizontal synchronizing signal detected from the CRT display device, and this is used as the synchronizing signal for the high frequency inverter 2a.

〔Effect of the invention〕

As explained above, according to the present invention, the phase of the high-frequency inverter synchronization signal can be adjusted, so that the noise generated when the high-frequency inverter is turned off can be shifted to a point where it does not affect the deflection circuit system. 1. It is possible to prevent any adverse effects from occurring on the display screen.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention. FIG. 2 is a configuration diagram of the embodiment. FIG. 3 shows a specific example of the phase adjustment section. FIG. 4 is a timing chart of the embodiment. FIG. 5 is a configuration diagram of a conventional example. FIG. 6 shows an explanatory diagram of a conventional example. In the figure. ■ is the input rectifier, 2a is the high frequency inverter. 3 is an output rectifier, and 4 is a horizontal period detector. 5 is a control section, and 6 is a phase adjustment section. a P / 1st picture of the dragonfly from Travelogue 1 ``'6'''
4 Fig. 2 Fig. 3 Timing chart of visit-1 Fig. 4 Fig. 5 O Explanatory diagram of cousin auction Fig. 6

Claims (1)

[Claims] A switching power supply circuit for a CRT display device, comprising: a phase adjustment section (6) that adjusts the phase of a horizontal synchronization signal detected from the CRT display device; A ringing choke converter type high-frequency inverter that oscillates with
2a) A switching power supply circuit comprising: