JP2889372B2 - Stabilized power supply circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply circuit used for an electronic device, and more particularly, to a switching method capable of obtaining a stable DC voltage by switching and smoothing a current. It relates to a stabilized power supply circuit.

[Prior Art] A DC voltage is usually used as a power supply voltage in an electronic device. The commercial power supply (AC 100, 50 Hz / 60 Hz) has a waveform as shown in FIG. This commercial power supply is rectified by a diode, and becomes a current having a waveform shown in FIG. 7 (b). By rectifying the rectified current with a capacitor, a DC voltage as shown in FIG. 7 (c) can be obtained.

Referring to FIG. 7 (c), the DC voltage thus obtained includes a ripple component. Further, when another electronic device having a large load is connected to the commercial power supply, the amplitude of the commercial power supply shown in FIG. 7A fluctuates. As a result, the voltage value of the DC voltage as shown in FIG. 7 (c) may fluctuate. Since such fluctuation has an adverse effect on the operation of the electronic device, various methods are used to stabilize the DC voltage. This method is roughly classified into a series regulator and a switching regulator.

The simplest example of a series regulator uses a Zener diode. In this method, a current flows through a resistor and a Zener diode, and a Zener voltage is extracted as an output. However, this method is a drop method, and all excess current is dissipated as heat. Therefore, there is a disadvantage that the efficiency is low and the circuit is adversely affected.

On the other hand, the switching regulator divides the unstable voltage Vin into an ON portion 74 and an OFF portion 72 by using some switching means, as shown in FIG. 9, and obtains a DC voltage by smoothing the divided portions. It is. An arbitrary stable output DC voltage can be obtained by changing the time ratio of the ON and OFF portions. Switching regulators are classified into various names according to the ON / OFF switching method. However, since all of them are based on switching operation, they are collectively called a switching regulator or a switching stabilized power supply.

According to this method, referring again to FIG. 9, when the switching means is OFF, the flowing current becomes 0, and when the switching means is ON, the voltage becomes 0. Since the power consumption P = V × I, the power consumption of the switching stabilized power supply is ideally zero.

However, referring to Fig. 10, the voltage at ON is actually 0.7V
Due to about 1.0 V and the duplication of the voltage waveform and the current waveform, a portion where the voltage waveform and the current waveform intersect occurs as shown by hatching in FIG.
Therefore, even in the switching regulator, heat is generated in this portion, and constant power is consumed. But,
Compared with the above-mentioned series regulator system, the switching regulator system has been widely used at present because it has been designed to be lightweight and high-density and easy to control.

FIG. 8 is a circuit block diagram of a power supply portion of a color television using a conventional switching stabilized power supply circuit. Referring to FIG. 8, a power supply circuit of the color television includes a horizontal oscillation circuit 10 for obtaining a horizontal output (FIG. 11) to be described later.
The horizontal excitation circuit 12, the horizontal output circuit 14, the unstable DC voltage 26 obtained by rectifying and smoothing the commercial power supply, and the horizontal output circuit 14 and the unstable DC voltage 26 A flyback transformer 16 for boosting the output waveform, a diode 18 connected to the flyback transformer 16, and a diode 18 for rectifying the waveform boosted to a high voltage by the flyback transformer 16, and a diode 18 A cathode ray tube 20 having a capacity 22, a diode 66 for rectifying a waveform boosted to a small / medium pressure by the flyback transformer 16, a small / medium voltage device 68 driven by the waveform rectified by the diode 66, The flyback transformer 16 is connected to the unstable DC voltage 26 and converts the unstable DC voltage given from the unstable DC voltage 26 to a stable DC voltage. Iback transformer 16
And a conventional stabilized power supply circuit 62 for supplying power to the primary coil as excitation power.

The horizontal output waveform output from the horizontal output circuit 14 (11th
FIG. 2 shows an output necessary for scanning the cathode ray tube 20 in the horizontal direction. Referring to FIG. 11, horizontal output horizontal pulse
The interval of 78 corresponds to one horizontal scanning period in which the electron beam emitted from the cathode of the cathode ray tube 20 scans on the phosphor screen of the cathode ray tube 20. The period during which the horizontal pulse 78 lasts corresponds to the period required for the baseline of the scan to return to the beginning of the next scan (retrace period).

In order to emit an electron beam from the cathode of the cathode ray tube 20 and reach the phosphor screen of the cathode ray tube 20, a high voltage is required. This voltage is, for example, about 25 KV for a 21-inch cathode ray tube. This high pressure is obtained using a horizontal output. As shown in FIG. 11, the waveform obtained from the horizontal output circuit 14 is a pulse having a peak value of about 900V. This pulse is boosted by the flyback transformer 16 and a signal having a higher peak value is obtained in the secondary coil. This output is connected to a diode 18 and a distributed capacitor 22 having a cathode ray tube 20.
By the rectification, a high voltage of several tens of KV can be obtained.

The horizontal output is also used for horizontal scanning of the cathode ray tube 20 by the electron beam. In this case, the horizontal output is supplied to a deflection coil (not shown) in addition to the flyback transformer 16. Due to the resonance action between the coil and the capacitor, a deflection current required for horizontal scanning is obtained.

Referring again to FIG. 8, the flyback transformer 16
One end is the output of the horizontal output circuit 14, and the other end is the stabilized power supply circuit.
A primary winding 28 for exciting a secondary winding of the flyback transformer 16 by a horizontal output using a DC voltage supplied from the stabilized power supply circuit 62 as a power supply, and a secondary winding provided on the secondary side. A high-voltage secondary winding 30 for outputting a high voltage, which is electromagnetically coupled to the primary winding 28, and also electromagnetically coupled to the primary winding 28, and a predetermined A secondary winding 58 for supplying small and medium voltage for supplying a voltage signal, one end is connected to the unstable DC voltage 26, and the other end is connected to the stabilized power supply circuit 62, respectively. And a secondary winding 32 for limiting the rate of increase of the current flowing through the circuit 62 to a rate corresponding to the inductance.

The stabilized power supply circuit 62 has an anode connected to the secondary winding 32 and a cathode connected to the primary winding 28, and interrupts the conduction of current from the anode to the cathode in response to a pulse applied to the gate. SCR (Silicon Controlled Re
ctifier) 64, connected between the cathode of SCR64 and ground, and used for smoothing capacitor 42 for smoothing the output voltage of SCR64, the output of SCR64, the gate of SCR64, and the secondary coil for small and medium voltage 58, and in response to the output voltage of the SCR 64 and the voltage obtained from the small / medium voltage secondary winding 58,
The control circuit 90 includes an SCR 64 and a control circuit 90 that generates a control signal for turning on and off such that the output thereof has a constant voltage.

The SCR 64 has the property of a diode in which current flows from the anode to the cathode. The SCR 64 is turned on by applying a pulse to its gate terminal even if the anode voltage is equal to or lower than a certain voltage required for turning on. Also, SCR6
4 has a property (self-holding action) of continuing conduction as it is once conducted. To stop the conduction of the SCR 64, a reverse voltage may be applied to the anode and the cathode.

The SCR 64 has a switching function as described above. The role of the stabilized power supply circuit 62 is to use this switching function to open and close the voltage (approximately 130 V) provided from the unstable DC voltage 26 to generate a constant power supply of 110 V. SCR6
An error between the voltage output from 4 and smoothed by the smoothing capacitor 42 and the specified 110 V is detected, and the timing of applying a pulse to the gate terminal of the SCR 64 is controlled in accordance with the error, thereby stabilizing the voltage. A constant voltage is obtained as the output of the power supply circuit 62.

Referring to FIG. 12, the control circuit 90 is connected to the cathode of the SCR 64, output from the SCR 64, and
2, an error detection circuit 80 for detecting an error between the voltage smoothed by step 2 and a predetermined voltage (110 V) and outputting an error signal, a small / medium voltage secondary winding 58 and an error detection circuit 80 An integration circuit 84 for integrating the flyback pulse excited by the horizontal output to the small / medium voltage secondary winding 58, further superimposing and outputting the error signal from the error detection circuit 80, An integrator circuit 84 is connected to the error detection circuit 80, and slices a voltage value given from the integrator circuit 84 by a predetermined voltage value to generate a gate pulse applied to the gate of the SCR 64. And

The error detection circuit 80 includes a resistor and a variable resistor VR connected in series between the cathode of the SCR 64 and the ground potential, a base coupled to the variable resistor VR, and a voltage between the output voltage of the SCR 64 and a predetermined voltage. A transistor Q1 for detecting an error,
And a transistor Q2 having a base connected to the collector of transistor Q1 and amplifying the output of transistor Q1.

The integration circuit 84 includes a capacitor C1 and a resistor R1. One end of the resistor R1 is connected to a contact point between the secondary winding 58 and the diode 66 (FIG. 8). The capacitance C1 is connected between the other end of the resistor R1 and the ground potential. The contact between the resistor R1 and the capacitor C1 is connected to the emitter of the transistor Q2 via the resistor.

The slice pulse shaping circuit 82 includes a Zener diode 88 provided between the emitter of the transistor Q1 and the ground.
And a transistor whose base is connected to the contacts of the resistor R1 and the capacitor C1, and a diode whose forward direction is connected from the emitter of the transistor Q3 to the emitter of the transistor Q1.
Including 86. The slice / pulse shaping circuit 82 further includes:
The transistor Q4 includes a transistor Q4 having a base connected to the collector of the transistor Q3, and a resistor R3 and a capacitor C2 connected in series between the emitter of the transistor Q4 and the gate of the SCR 64.

Referring to FIGS. 7 to 14, the power supply circuit of a color television using the conventional stabilized power supply circuit operates as follows. Horizontal oscillation circuit 10, Horizontal excitation circuit 12, Horizontal output circuit 14
Gives the primary winding 28 a horizontal output as shown in FIG. Since the small / medium voltage secondary winding 58 is electromagnetically coupled with the primary winding 28, in response to this horizontal output, a flyback pulse as shown in FIG. The signal is supplied to an integrating circuit 84 of 90. The reason why the flyback pulse shown in FIG. 13 (a) has the polarity inverted from the horizontal output shown in FIG. 11 is that the winding direction of the small / medium voltage secondary winding 58 is selected in such a direction. It is because it is.

The transistor Q1 of the error detection circuit 80 detects an error between the cathode voltage of the SCR 64, that is, the output voltage of the stabilized power supply circuit 62 and a predetermined voltage (110V), and outputs a signal corresponding to the error to the base of the transistor Q2. give. Transistor Q2 amplifies this error signal and provides it to integrating circuit 84.

The integrating circuit 84 integrates the flyback pulse supplied from the secondary winding 58 (FIG. 13 (b)) and superimposes it on the DC component of the error amplification output from the transistor Q2 (13th embodiment).
(See the solid line in FIG. (C)). The output of the integrating circuit 84 is applied to the base of the transistor Q3 of the slice pulse shaping circuit 82.

The waveform input to the base of the transistor Q3 is sliced by the voltage Vz determined by the Zener diode 88,
The waveform shown by the solid line in FIG. 13 (d) is obtained at the collector of the transistor Q3. This signal is amplified by a transistor Q4 and then differentiated by a differentiating circuit including a capacitor C2 and a resistor R3. As a result, a gate pulse having the waveform shown in FIG. 13 (e) is obtained.

This gate pulse is input to the gate of SCR64. When this pulse is input, the SCR 64 turns on and increases the current until a negative voltage is input to the anode. The negative voltage applied to the anode is given in response to the horizontal output by the electromagnetic coupling between the primary side winding 28 and the secondary side winding 32.

Consider a case where the output voltage of the stabilized power supply circuit 62 fluctuates. When the output voltage increases, the base voltage of the transistor Q1 increases. Therefore, the collector current of transistor Q1 increases, and as a result, the collector voltage of transistor Q1 decreases. Since the voltage superimposed in the integration circuit 84 decreases, the integration waveform falls as shown by the broken line in FIG. 13 (c). Therefore, Zener diode 88
The point sliced by moves on the time axis. The period during which the collector voltage of the transistor Q3 decreases is also shortened. Therefore, as shown by the dotted line in FIG. 13 (e), the point at which the SCR 64 is turned on moves later. The time at which the SCR64 is turned off is determined by the horizontal output, so the anode current of the SCR64 decreases. As a result, the smoothing capacitor 42
Is controlled so that the output voltage of the stabilized power supply circuit 62 becomes constant.

The operation of the SCR 64 will be described with reference to FIGS. 8 and 14. As described above, the waveform at the output point A of the horizontal output circuit 14 in FIG. 8 is a waveform as shown in FIG. 14 (a). The waveform at the output B point of the secondary winding 58 is
As shown in FIG. 13 (a), the waveform of FIG. 14 (a) is inverted.

When a gate pulse as shown in FIG. 14B is applied to the gate of the SCR 64, the SCR 64 turns on as described above. The anode current starts to flow in SCR64. However, the secondary winding 32 is connected between the unstable DC voltage 26 and the SCR 64.
Are connected in series, the increasing speed of the anode current is limited to a speed corresponding to the inductance, and gradually increases.

When the rise of the horizontal pulse shown in FIG. 14 (a) reaches the point in time, the anode current starts to decrease. Then, when the anode voltage reaches a negative peak as shown in FIG. 14 (c), the SCR 64 is turned off.

As described above, the anode voltage on which the inverted sliback pulse of the horizontal pulse is superimposed is turned on by the gate pulse shown in FIG. 14B and turned off by the negative pulse of the anode voltage itself. As a result, SCR6
In FIG. 4, an anode current as shown in FIG. 14 (d) flows, and a voltage portion shown as “output voltage” in FIG. 14 (c) is taken out, smoothed by a smoothing capacitor 42, and Voltage can be obtained.

[Problems to be Solved by the Invention] A conventional stabilized power supply circuit uses an SCR. The SCR is driven by a pulse applied to the gate. for that reason,
There is a problem in that erroneous operation is likely to occur when pulse noise is applied to the gate. In addition, SCR
Is replaced with another semiconductor active element, there is a problem that spike noise occurs when switching from ON to fOF, and the element is destroyed.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a stabilized power supply circuit which is unlikely to cause a malfunction with respect to pulse noise and which is unlikely to be damaged by spike noise.

[Means for Solving the Problems] A stabilized power supply circuit according to the present invention includes an input terminal (source), an output terminal (drain), and a control terminal (gate).
Wherein the input terminal (source) is connected to an unstable DC power supply (26), and the input terminal (source) is responsive to a control signal input to the connection terminal (gate). A transistor (34) for continuing a current between the transistor (34) and the output terminal (drain); and a transistor (34) connected between the DC power supply (26) and the transistor (34). 34) The secondary winding (32) of the flyback transformer (16), which limits the rate of increase of the current with respect to the input voltage to the speed corresponding to the inductance during conduction, and the secondary winding of the flyback transformer. In response to the horizontal output from the horizontal output circuit (14), it is electromagnetically coupled to the line (32) to have the opposite polarity,
A primary winding (28) of a flyback transformer (16) for reducing a current flowing through the transistor (34), and a current output from the output terminal (drain) of the transistor (34), In response to the DC voltage smoothed by the smoothing means (42), and according to the magnitude of a predetermined voltage and the smoothed DC voltage, The transistor (3
4) a control means (36) for providing a control signal for controlling the control terminal (gate) to an intermediate point between a secondary winding (32) of the flyback transformer (16) and the control terminal (Gate), and in response to the horizontal output, the control signal is instantaneously interrupted for a predetermined period including at least when the control means (36) shuts off the transistor (34). And means (40) for preventing the above.

[Operation] In the above-described stabilized power supply circuit, a period in which the current passing through the transistor (34) is reduced by the operation of the primary winding (28) of the flyback transformer (16) is provided. During this time, when a control signal for turning off the transistor (34) is output from the control means (36), the control signal is relaxed. Therefore, the current flowing through the transistor (34) is not instantaneously cut off.

FIG. 1 shows a stabilized power supply circuit 24 according to an embodiment of the present invention.
FIG. 2 is a block diagram of a power supply circuit of a color television including
In FIG. 1, the small / medium voltage secondary winding 58 shown in FIG. 8 is omitted for simplicity.
The circuit shown in FIG. 1 differs from the circuit shown in FIG. 8 in that a stabilized power supply circuit 24 according to the present invention is included in place of the conventional stabilized power supply circuit 64. In FIGS. 1 and 8, the same parts are given the same reference numerals and names. Their functions are the same. Therefore, detailed description thereof will not be repeated here.

Referring to FIG. 1, the stabilized power supply circuit 24 has a secondary winding
A power MOSFET in which a source is coupled to one end of 32 through a diode 44 and a drain is connected to one end of the primary winding 28
34, connected between the drain of the power MOSFET 34 and the ground potential, and a smoothing capacitor 42 for smoothing the voltage output from the power MOSFET 34, and connected to the drain of the power MOSFET 34 and smoothed by the smoothing capacitor 42. A switching drive circuit 36 for detecting an error between the applied DC voltage and a predetermined constant voltage (for example, 110 V) and supplying a control signal for controlling the power MOSFET 34 to the gate of the power MOSFET 34 in response to the error. Including.

A diode 38 is connected between the power MOSFET 34 and the switching drive circuit 36 in this direction. power
Between the gate of the MOSFET 34 and the midpoint of the secondary winding 32,
The negative pulse generated by the secondary winding 32 is
Diode for applying voltage to the gate of SFET34 for a certain period
40 are connected.

As shown in FIG. 2, the power MOSFET 34 of FIG. 1 can be replaced by a transistor 34a. Referring to FIG. 2, the emitter of this transistor 34a is a diode 4
Connected to 4. The collector is connected to one end of the primary winding 28. The base is connected to a switching drive circuit 36 via a diode 38 and to an intermediate point of the secondary winding 32 via a diode 40.

The stabilized power supply circuit 24 shown in FIG. 1 and the stabilized power supply circuit 24a shown in FIG. 2 operate in exactly the same manner. Hereinafter, the operation of this stabilized power supply circuit will be described with reference to FIG. 2 for simplification of the description. The transistor 34a is a PNP transistor. Transistor 34a is therefore
Conduction occurs when the emitter voltage is higher than the base voltage, and current flows from the emitter to the collector. This current is called a collector current.

Referring to FIG. 3, the horizontal output (a) and the emitter voltage (b) of the transistor 34a correspond to the horizontal pulse (FIG. 14 (a)) and the anode voltage (FIG. 14) already described with reference to FIG. It is the same as FIG. 14 (c)). The base control voltage (FIG. 3 (d)) applied from the switching drive circuit 36 to the base of the transistor 34a is used to obtain the collector voltage of the transistor Q3 of the conventional device shown in FIG. 13 (d). Can be obtained by a circuit similar to the above circuit.

This base control voltage causes the transistor 34a to
By turning N and OFF, a collector current having a waveform shown in FIG. 3E flows through the transistor 34a.
This operation is almost the same as that using the conventional SCR shown in FIG. However, the stabilized power supply circuit 24a according to the present invention has the following features.

In the transistor 34a, the base is connected to the middle point of the secondary winding 32 via the diode 40. The potential of this portion falls below the emitter voltage at the portion where the collector current decreases as shown in FIG. 3 (e), as shown in FIG. 3 (c). Therefore, even if the switching drive circuit 36 tries to cut off the transistor 34a by the base control voltage shown in FIG. 3D during this section, the current is reduced by the voltage drop portion shown in FIG. 3C. 34a emitter, base,
The current flows through a path connected to the secondary winding 32 via the diode 40. Therefore, even when the switching drive circuit 36 turns off the transistor 34a, the current is not instantaneously cut off. There is no risk of spike noise occurring at the collector of the transistor 34a.

As is well known, spike noise is changed from OFF to O
Switching from ON to OFF is larger than switching to N. This is because even if the applied voltage is cut off instantaneously, the circuit has a transient response characteristic, so that a phenomenon occurs in which the output converges to 0 while vibrating largely. Therefore, as described above, the current from the emitter is promptly supplied to the other at the time of switching from ON to OFF, so that the possibility that spike noise is generated in the collector is reduced.

Since the base control voltage output from the switching drive circuit 36 has the property that the transistor 34a is driven by a constant voltage applied to the base, FIG.
May be a rectangular wave as shown in FIG. In this case, the switching drive circuit 36 may be any circuit as long as current can flow from the base of the transistor 34a.

Thus, the transistor 34a is used as a switching element.
(Or the power MOSFET 34), the signal for driving the switching element may be a rectangular wave as described above. Unlike the case where a conventional SCR is used, even if pulse noise is applied to the base of the transistor, there is no possibility that the transistor 34a malfunctions. Therefore, a stabilized power supply circuit that can operate stably can be provided.

FIG. 4 is a circuit block diagram of a power supply circuit of a color television using a stabilized power supply circuit 46 according to a second embodiment of the present invention. The circuit shown in FIG. 4 is different from the circuit shown in FIG. 1 in that the stabilized power supply circuit 24 is replaced with one end and a middle point of a primary winding 28 and a secondary winding 32. A stabilized power supply circuit 46 connected to the unstable DC voltage 26 and supplying a stable DC voltage to the primary winding 28 is included. In FIGS. 1 and 4, the same components are given the same reference numerals and names. Their functions are the same. Therefore, detailed description thereof will not be repeated here.

Referring to FIG. 4, the stabilized power supply circuit 46 comprises a power MOSFET 52 having a source connected to one end of the primary winding 28, a drain connected to one end of the secondary winding 32 through a diode 44, A smoothing capacitor 42 connected between the source of the MOSFET 52 and the ground potential for smoothing the source voltage of the power MOSFET 52, and a DC voltage connected to the source of the power MOSFET 52 and smoothed by the smoothing capacitor 42. In response to an error from a predetermined voltage (for example, 110 V), the power
Switching drive circuit 48 for applying a control voltage for switching to the gate of MOSFET 52 via diode 50
Is connected between the gate of the power MOSFET 52 and the middle point of the primary winding 28, and applies a positive voltage to the gate of the power MOSFET 52 for a certain period in response to a horizontal pulse applied to the primary winding 28. And a bias circuit 54 for performing the operation.

The bias circuit 54 is connected between the middle point of the primary winding 28 and the power MOSF.
Includes a diode 60 and a resistor 56 connected in series between the gate of the ET 52.

FIG. 5 shows the power MOSFET 52 shown in FIG.
24 shows a stabilized power supply circuit 46a in place of the type transistor 52a.
4 and 5, the same components are given the same reference numerals and the same names. Their functions are the same. Therefore, the operation of the device shown in FIG. 5 will be described below for the sake of simplicity.

The horizontal output applied from the horizontal output circuit 14 to the current decreasing winding 28 has the waveform shown in FIG. 6A similarly to the first embodiment. The collector voltage of the transistor 52a is the sixth
The result is as shown in FIG. This is the same waveform as the emitter voltage (FIG. 3 (b)) in the first embodiment.

Since the transistor 52 (a) is of the NPN type, the base drive voltage output from the switching drive circuit 48 is opposite to the base drive voltage in the first embodiment, as shown in FIG. 6 (d). Having the polarity shown in FIG. This base drive voltage is controlled by the switching drive circuit 48 so as to respond to an error between the DC voltage smoothed by the smoothing capacitor 42 and the predetermined voltage (110 V), so that the output voltage approaches 110 V.

When the horizontal output shown in FIG. 6A is applied to the primary winding 28, the transistor 52a
A bias voltage as shown in FIG. 6 (c) is applied to the base of FIG. Therefore, when the base drive voltage is switched from ON to OFF during this period, similar to the first embodiment,
The current is not interrupted instantaneously. Therefore, there is no possibility that spike noise is generated in the emitter.

Also in this stabilized power supply circuit 46a (46), the drive voltage output from the switching drive circuit 48 is a rectangular wave. Therefore, the pulse noise is
Even if it is input to the base (or gate) of (power MOSFET 52), there is no possibility that the stabilized power supply circuit malfunctions. Therefore, it is possible to provide a stabilized power supply circuit capable of obtaining a stable DC voltage.

The present invention has been described based on the embodiment in which the present invention is applied to a power supply circuit of a color television. However, the present invention is not limited to the embodiments described above, and can be applied to other electronic devices.

[Effects of the Invention] As described above, according to the present invention, when a control signal for turning off a transistor is output, the control signal is relaxed. Therefore, the current flowing through the transistor is not instantaneously interrupted. There is no possibility that spike noise is generated from the transistor, and there is no possibility that the element is destroyed, and a stable DC voltage can be obtained. further,
Since a transistor is used, a rectangular wave is used as a control signal. Unlike a conventional stabilized power supply circuit using an SCR, a pulse is not used to control a switching element. Therefore, the stabilized power supply circuit according to the present invention is strong against pulse noise and can generate a stable DC voltage.

As a result, it is possible to provide a stabilized power supply circuit which does not easily malfunction due to pulse noise and does not damage elements due to spike noise.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply circuit of a color television using a stabilized power supply circuit according to the present invention, FIG. 2 is a circuit block diagram of a main part of a modification of FIG. 1, and FIG. FIG. 4 is a waveform diagram for explaining the operation of the first embodiment of the present invention. FIG. 4 is a block diagram of a power supply circuit of a color television using the stabilized power supply circuit according to the second embodiment of the present invention. FIG. 5 is a block diagram of a main part of a modified example of the circuit shown in FIG. 4, FIG. 6 is a waveform diagram for explaining the operation of the second embodiment, and FIG. FIG. 8 is a waveform diagram showing conversion from a commercial power supply to a DC voltage, FIG. 8 is a circuit block diagram of a color television using a conventional stabilized power supply circuit, and FIG. 9 is a conventional switching stabilized power supply circuit. FIG. 10 is a schematic waveform diagram showing the operation of the switching stabilizing power supply. FIG. 11 is a schematic waveform diagram showing power consumption of the circuit, FIG. 11 is a waveform diagram of a horizontal output, FIG. 12 is a block diagram of a circuit for controlling the SCR of the conventional stabilized power supply circuit, FIG. 13 and FIG. 14 are waveform diagrams showing the operation of the conventional stabilized power supply circuit. In the figure, 16 is a flyback transformer, 24, 24a, 46, and 46a are stabilized power supply circuits, 26 is an unstable DC voltage, 28 is a current reducing winding, 32 is a current limiting winding, and 34 and 52 are power. MOSFET, 34
a and 52a are transistors, 36 and 48 are switching drive circuits, 40 is a bias diode, 42 is a smoothing capacitor, and 54 is a bias circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-56-125164 (JP, A) JP-A-57-11580 (JP, A) JP-A-63-171070 (JP, A)

Claims (1)

(57) [Claims] 1. An input terminal (source), an output terminal (drain), and a control terminal (gate), wherein the input terminal (source) is connected to an unstable DC power supply (26). A transistor (34) for continuing a current between the input terminal (source) and the output terminal (drain) in response to a control signal input to the connection terminal (gate); A flyback that is connected between the transistor (26) and the transistor (34) and limits a rate of current increase with respect to an input voltage to a rate corresponding to the inductance when the transistor (34) is turned on. The secondary winding (32) of the transformer (16) and the secondary winding (32) of the flyback transformer are electromagnetically coupled so as to have opposite polarities, and are output from the horizontal output circuit (14). In response to the horizontal output of A primary winding (28) for reducing a current flowing through the transistor (34) and a current output from the output terminal (drain) of the transistor (34); A smoothing means (42) for converting the DC voltage into a voltage, and responding to the DC voltage smoothed by the smoothing means (42), according to the magnitude of a predetermined voltage and the smoothed DC voltage, A control means (36) for providing a control signal for controlling the transistor (34) to the control terminal (gate); an intermediate point of a secondary winding (32) of the flyback transformer (16); The control signal is instantaneously shut off for a predetermined period including at least when the control means (36) shuts off the transistor (34) in response to the horizontal output in response to the horizontal output. Be done Characterized in that a means (40) for preventing the occurrence of the power supply is provided.