JPH0331032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flyback transformer power supply circuit equipped with a multiplier rectifier circuit, and its purpose is to attenuate the ringing voltage that occurs during the on period of a switching circuit for generating flyback pulses. It is.

In general, image pickup tubes and picture tube drive power circuits in video cameras, etc., require various voltages for electron beam acceleration, electron beam control, signal circuits, etc.
From thousands of volts to tens of volts. These voltages are generated by boosting and rectifying the flyback pulse voltage generated during the off period of the flyback pulse generation switching circuit to an arbitrary voltage using a transformer, similar to the high voltage generation circuit of a television receiver. It has gained.

However, the boosted flyback pulse voltage has a waveform in which a ringing voltage is superimposed due to the leakage flux and stray capacitance of the transformer. This ringing voltage causes disturbances such as vertical streaks on the screen during the ON period of the flyback pulse generation switching circuit.

The present invention solves these problems,
By inserting a resistive element into the multi-voltage rectifier circuit, the ringing voltage that conventionally caused interference with the screen can be attenuated.

Hereinafter, one embodiment of the present invention will be described using the drawings of FIGS. 1 to 5. In the embodiment, a case will be described in which a nominal triple pressure Kotscroft circuit is used.

In FIG. 1, 1 is a switching circuit for generating flyback pulses, 2 is a power supply terminal, 3 is a flyback transformer, 4 and 5 are the first and second windings of the flyback transformer 3, 6, 7 is a rectifier diode for the low output voltage, 8 and 9 are smoothing circuits for the low output voltage, 10 and 11 are output terminals for the low output voltage, 12 is a nominal triple voltage Kotscroft circuit, and 13, 14 and 15 are the Kotscrofts. Rectifier diodes of the circuit 12, 16, 17, and 18 are stacking capacitors of the Kotscroft circuit 12, 19 is a load, 20 is an output terminal of the Kotscroft circuit 12, and 21 is a resistor inserted and connected to accomplish the purpose of the present invention. It is element.

From power supply terminal 2 to flyback transformer 3
When power is applied to the switching circuit 1 through the first winding 4, a flyback pulse voltage is generated across the first winding 4 as the switching circuit 1 turns on and off. The flyback pulse voltage generated in the first winding 4 induces a flyback pulse output voltage in the second winding 5 due to transformer action.

FIGS. 2a and 2b show voltage waveforms obtained by the above operation. Fig. 2a shows the flyback pulse voltage generated in the first winding 4, and Fig. 2b shows the flyback pulse voltage generated in the second winding 5.
is the flyback pulse output voltage induced by This flyback pulse output voltage is
The tap terminal provided on the winding 5 is led out to rectifier diodes 6, 7, smoothing circuits 8, 9, and Kotscroft circuit 12 connected to the respective terminals, and a DC voltage corresponding to each flyback pulse output voltage is output. It is obtained at each output terminal 10, 11, 20. The following voltages are charged to each of the stacking capacitors 16, 17, and 18 of the Kotscroft circuit 12. That is, if the input voltage is the value shown in FIG. 2b, the peak-to-peak value of the flyback pulse output voltage V ₀ (=V ₁
+V ₂ ), and the stacking capacitor 17 is charged with the peak value V ₁ of the flyback output voltage.

Here, the off period of the Kotsukucroft circuit 12,
The operation during the on period will be explained using the equivalent circuits shown in FIGS. 3a and 3b. In addition, in FIGS. 3a and 3b, the same parts as in FIG. 1 are given the same numbers.

Figure 3a is an operational equivalent circuit diagram during the off period;
FIG. b is an operational equivalent circuit diagram during the on period.

First of all, let's talk about the operation during the off period in the third section.
To describe using Figure a, the rectifier diodes 13, 1
5 is conductive during the flyback pulse output positive voltage period of the off period. During steady operation, the stacking capacitors 17 and 18 are connected to the peak value V ₁ and peak-to-peak value V ₀ (V ₁ +
V ₂ ). It is assumed that the stacking capacitor 16 is charged in advance to a peak-to-peak value V ₀ in a steady state.

Next, the operation during the on period will be explained using FIG. 3b. The rectifier diode 14 is conductive during the flyback pulse output negative voltage, that is, the trapezoidal wave portion voltage period of the on period. The charging voltage and diode operating current at this time are shown in FIGS. 4a and 4b.

First, considering the case where there is no resistance element 21,
The rectifier diode 14 begins to conduct from the beginning of the on period of the flyback pulse output negative voltage waveform and continues to conduct until the peak value _V2 . As shown in FIG. 4b, this voltage waveform gradually decreases during the on period and eventually reaches zero. This diode operating current charges the stacking capacitor 16 to the sum voltage of the flyback pulse output positive voltage _V1 and the flyback pulse output negative voltage _V2 , which is a superimposed sine waveform ringing voltage. The flyback pulse output voltage waveform at this time is shown in FIG. 5a. It is assumed that the stacking capacitors 17 and 18 are charged in advance to a peak value V ₁ and a peak-to-peak value V ₀ as in the off period. In this way, when the resistive element 21 is not present, the input voltage during the on period is not affected by the conduction current of the rectifier diode 14.

Next, considering the case where the resistance element 21 is inserted, the rectifier diode 14 starts conducting from the start point of the on period as in the case without the resistance element 21, but the diode operating current is as shown in FIG. 4b. It increases and decreases with a gentler curve compared to the case where the resistance element 21 is not provided. This diode operating current curve is the stacking capacitor 16, 17.
It is determined by the time constant of the resistance element 21 and the resistance element 21. Here, if the time constant is set so that the diode operating current flows during the on period, the power P expressed by the following equation is consumed during the on period.

P=Iv ² (t)・R Iv(t) = Current function of the rectifier diode 14 R = Resistance value of the resistive element 21 This consumption of power P is the attenuation of the flyback pulse output negative voltage V ₂ superimposed on the ringing voltage. It appears. On the other hand, the voltage component during the on period is the sum of the trapezoidal wave and the ringing voltage, and the effective value of the trapezoidal wave component is larger than the effective value of the ringing voltage. Further, the maximum value of power loss occurs at the peak value of the ringing voltage. Therefore, the trapezoidal wave portion is hardly attenuated, but the ringing voltage is greatly attenuated at the peak of the sine waveform. The flyback pulse output voltage waveform at this time is shown in FIG. 5b.

As shown in FIG. 5b, since the ringing voltage component is greatly attenuated by the resistive element 21, the ringing voltage component superimposed on the on-period voltage of the flyback pulse output voltage is significantly reduced. . Note that the effect on the output voltage due to the insertion of the resistive element 21 is only the attenuation effect of the ringing voltage section and has no effect on the voltage during the on period, so there is almost no decrease in the output voltage.

In addition, in the above explanation, the nominal voltage 3 is used as a multiplier circuit.
Although the voltage doubler circuit has been taken up, the effects of implementing the present invention are as follows.
Even if the number of voltage doubler stages increases to 4x or 5x, the same effect can be obtained by connecting a resistive element in series with a rectifier diode that conducts at a negative voltage during the on period, that is, a trapezoidal wave voltage. Needless to say.

As explained above, according to the present invention, the ringing voltage that occurs during the on period can be easily attenuated by simply inserting and connecting a resistive element, and moreover, it has almost no effect on the generated voltage. A flyback transformer power supply circuit is obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a flyback transformer power supply circuit according to an embodiment of the present invention, FIGS. 2a and 2b are characteristic diagrams showing voltage waveforms of the flyback transformer in the circuit of FIG. 1, and FIGS. 4b is an equivalent circuit diagram for explaining the operation of the present invention, FIGS. 4a and 4b are characteristic diagrams showing the charging voltage and diode operating current of the circuit in FIG. 3, and FIGS. FIG. 3 is an output voltage waveform diagram of a flyback transformer power supply circuit according to the present invention. DESCRIPTION OF SYMBOLS 1... Switching circuit, 3... Flyback transformer, 4... First winding, 5... Second winding, 6... Rectifier diode, 8... Smoothing capacitor, 12... Kotscroft circuit, 14... Rectifier diode, 21... Resistance element.

Claims (1)

[Claims] 1. A flyback transformer comprising a first winding whose one end is connected to a power supply terminal and whose other end is connected to a flyback pulse generation switching circuit, and a second winding having a plurality of tap terminals; It comprises a rectifier circuit and a multivoltage rectifier circuit connected to each of the plurality of tap terminals of the second winding, and conducts during the ON period of the flyback pulse generation switching circuit to charge the capacitor. A flyback transformer power supply circuit characterized in that a resistive element is connected in series with the rectifying element of the multi-voltage rectifying circuit arranged as shown in FIG.