JP3052950B1 - Power supply circuit - Google Patents

Abstract

An object of the present invention is to provide a power supply circuit in which both rising characteristics and dynamic characteristics are simultaneously improved. SOLUTION: A capacitor group 40 in which a first capacitor 38 and a second capacitor 39 are connected in series, and a resistor group 43 in which a first resistor 41 and a second resistor 42 are connected in series, are connected at an intermediate point 37. And a ground between the first capacitor 38 and the second capacitor 39.
And the second midpoint 4 between the first resistor 41 and the second resistor 42
5 and the third capacitor 51, and the second
And the PWM control circuit 35 is connected to the middle point 45.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit used for various electronic devices and communication devices, which generates a voltage pulse by a primary side resonance operation of a transformer, boosts the voltage pulse, and outputs the voltage pulse from a secondary side. Things.

[0002]

2. Description of the Related Art A conventional power supply circuit will be described below with reference to the drawings.

FIG. 3 is a circuit diagram of a conventional power supply circuit, and FIG. 4 is a waveform diagram showing a waveform of a high output voltage of a transformer section in the power supply circuit.

Referring to FIG. 3, a conventional power supply circuit has a primary coil 1 and a secondary coil 2 and a flyback transformer including a transformer section 4 for supplying an anode voltage to a cathode ray tube 3 such as a display device, and the like. It includes a PWM control circuit 5 for controlling a low output voltage output from the coil 1 and a high voltage detection circuit 6 for detecting a difference between the anode voltage and the high output voltage output from the secondary coil 2 as a detection voltage.

The PWM control circuit 5 controls the low output voltage based on the detected voltage.
Is provided between the PWM control circuit 5 and the halfway point 7 connecting the secondary coil 2 and the cathode ray tube 3, and a capacitor group 10 in which a first capacitor 8 and a second capacitor 9 are connected in series.
And a resistor group 13 in which the first resistor 11 and the second resistor 12 are connected in series, are connected in parallel between the halfway point 7 and the ground, and the first capacitor 8 and the second capacitor 9 Is connected to the second middle point 15 of the first resistor 11 and the second resistor 12, and the second middle point 15 is connected to the PWM.
The control circuit 5 is connected.

Further, the switching element 16, the damper diode 17, the resonance capacitor 18, the diode 19 for canceling the reverse recovery time of the switching element 16, and the drive power supply 20 are connected to the primary coil 1 of the transformer section 4. .

At this time, the capacitance value (C1) of the first capacitor 8, the capacitance value (C2) of the second capacitor 9, and the first
The relationship between the resistance value (R1) of the resistor 11 and the resistance value (R2) of the second resistor 12 is (C1) * (R1) = (C2) *
(R2).

FIG. 4 is a waveform diagram showing the waveform of the high output voltage of the transformer section. In this waveform diagram, the range A indicates the rising characteristics when the power supply circuit is powered on, and the range B indicates the dynamic characteristics.

In general, the rising characteristics are better as the voltage becomes higher in a short time, and the dynamic characteristics are better as the voltage is smoothed.

[0010]

In the above-mentioned conventional configuration,
To improve the rising characteristics, the second capacitor 9
May be increased, but the dynamic characteristic deteriorates, as shown in FIG. 5, and
In order to improve the dynamic characteristics, the capacitance value (C2) of the second capacitor 9 may be reduced. However, the rising characteristics are deteriorated, as shown in FIG. There was a problem that it could not be improved.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a power supply circuit in which both the rising characteristic and the dynamic characteristic are improved at the same time.

[0012]

According to the present invention, there is provided a transformer having a primary coil and a secondary coil for supplying an anode voltage to a cathode ray tube, and a low power output from the primary coil. A control circuit that controls a voltage, and a high voltage detection circuit that detects a difference between the anode voltage and a high output voltage output from the secondary coil as a detection voltage, wherein the control circuit is based on the detection voltage. Controlling the low output voltage, the high voltage detection circuit is provided between the control circuit and a halfway point connecting the secondary coil and the cathode ray tube, and a first capacitor and a second A capacitor group in which a capacitor is connected in series and a resistor group in which a first resistor and a second resistor are connected in series are connected in parallel between the halfway point and ground, and the first capacitor and the second capacitor are connected in parallel.
A third midpoint between the first midpoint with the capacitor and a second midpoint between the first resistor and the second resistor, and a second midpoint with the control circuit. Is connected.

With the above configuration, the first capacitor and the second capacitor
Since the first middle point of the first capacitor and the second middle point of the first resistor and the second resistor are connected by the third capacitor, the rising characteristics and the dynamic characteristics can be improved at the same time. .

This is because, when the power of the power supply circuit is turned on, the capacitance value of the first capacitor (C1), the capacitance value of the second capacitor (C2), and the capacitance value of the third capacitor ( In both C3), no electric charge is stored, and the respective capacitance values are 0. Therefore, at the moment when the power is turned on, the capacitance value (C2) of the second capacitor is:
The capacitance value is obtained by adding the capacitance value (C3) of the third capacitor, and the relationship between the resistance value (R1) of the first resistor and the resistance value (R2) of the second resistor is (C1) * (R1 ) <(C2)
* (R2).

Regarding the improvement of the dynamic characteristics, the capacitance value of the first capacitor (C1) and the capacitance value of the second capacitor (C
2) Since the charge is accumulated in both the capacitance value (C3) of the third capacitor, the capacitance value (C3) of the second capacitor
2) is reduced by the combined capacity, and (C1) * (R1)
> (C2) * (R2).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION
A transformer having a primary coil and a secondary coil and supplying an anode voltage to the cathode ray tube; a control circuit for controlling a low output voltage output from the primary coil; and a control circuit for controlling the anode voltage and the high voltage output from the secondary coil. A high voltage detection circuit for detecting a difference from an output voltage as a detection voltage, wherein the control circuit controls the low output voltage based on the detection voltage, and the high voltage detection circuit A capacitor group in which a first capacitor and a second capacitor are connected in series between a halfway point for connecting a secondary coil and the cathode ray tube and the control circuit; a first resistor and a second resistor; Are connected in parallel between the halfway point and ground, a first midpoint between the first capacitor and the second capacitor, the first resistor and the second resistor are connected in series. The second midpoint of the resistance While connected third capacitors, a configuration that is connected to the second middle point and said control circuit.

With the above configuration, the first capacitor and the second capacitor
Since the first middle point of the first capacitor and the second middle point of the first resistor and the second resistor are connected by the third capacitor, the rising characteristics and the dynamic characteristics can be improved at the same time. .

(Embodiment) Hereinafter, a power supply circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of a power supply circuit according to an embodiment of the present invention, and FIG. 2 is a waveform diagram showing a waveform of a high output voltage of a transformer section in the power supply circuit.

Referring to FIG. 1, a power supply circuit according to an embodiment of the present invention has a primary coil 31 and a secondary coil 32 and a flywheel comprising a transformer section 34 for supplying an anode voltage to a cathode ray tube 33 such as a display device. A back transformer, a PWM control circuit 35 for controlling a low output voltage output from the primary coil 31, and a high voltage detection circuit 36 for detecting a difference between an anode voltage and a high output voltage output from the secondary coil 32 as a detection voltage. And

The PWM control circuit 35 controls the low output voltage based on the detected voltage, and the high voltage detection circuit 36 controls the intermediate point 37 connecting the secondary coil 32 and the cathode ray tube 33 to a PWM signal. A capacitor group 40 provided between the control circuit 35 and a first capacitor 38 and a second capacitor 39 connected in series; a first resistor 41 and a second resistor 42;
Are connected in parallel between the midpoint 37 and the ground, and a first midpoint 44 between the first capacitor 38 and the second capacitor 39, a first resistor 41 and the first resistor 41 are connected in series. 2
Of the resistor 42 and the second midpoint 45 with the third capacitor 5
1 and the second midpoint 45 and the PWM control circuit 35 are connected.

Further, the primary coil 31 of the transformer section 34
Are connected to a switch element 46, a damper diode 47, a resonance capacitor 48, a diode 49 for canceling the reverse recovery time of the switch element 46, and a drive power supply 50.

At this time, the capacitance value (C1) of the first capacitor 38, the capacitance value (C2) of the second capacitor 39, the resistance value (R1) of the first resistor 41, and the resistance value of the second resistor 42 The relationship with (R2) is (C1) * (R1) = (C2)
* (R2), and the capacitance value (C3) of the third capacitor 51 is made to contribute to this, whereby the second
The capacitance value of the capacitance value (C2) of the capacitor 39 of
(C1) * (R1) = (C2) * (R2)
(C1) * (R1)> (C2) * (R2),
(C1) * (R1) <(C2) * (R2).

FIG. 2 is a waveform diagram showing the waveform of the high output voltage of the transformer section. In this waveform diagram, the range A indicates the rising characteristics when the power supply circuit is powered on, and the range B indicates the dynamic characteristics.

The operation of the power supply circuit having the above configuration will be described below.

With the above configuration, the first midpoint 44 between the first capacitor 38 and the second capacitor 39 and the second midpoint 45 between the first resistor 41 and the second resistor 42 are connected to the second 3, first, when the power of the power supply circuit is turned on, the capacitance value (C1) of the first capacitor 38,
Both the capacitance value (C2) of the second capacitor 39 and the capacitance value (C3) of the third capacitor 51 have no accumulated electric charge, and their respective capacitance values are 0. The capacitance value (C2) of the capacitor 39 is a capacitance value obtained by adding the capacitance value (C3) of the third capacitor 51, and the resistance value (R1) of the first resistor 41 and the resistance value of the second resistor 42 The relationship with (R2) is (C1) * (R1)
<(C2) * (R2).

In a normal state after the power is turned on, the capacitance value (C1) of the first capacitor 38, the capacitance value (C2) of the second capacitor 39, and the capacitance value (C3) of the third capacitor 51 are In both cases, since electric charges are accumulated, the capacitance value (C2) of the second capacitor 39 is reduced by the combined capacitance, and becomes (C1) * (R1)> (C2) * (R2).

Therefore, the rising characteristics and the dynamic characteristics can be improved at the same time.

As described above, according to the embodiment of the present invention,
The first capacitor 38 and the second capacitor 39
Is connected to the second middle point 45 of the first resistor 41 and the second resistor 42 by the third capacitor 51, so that the rising characteristic and the dynamic characteristic can be simultaneously improved.

[0030]

As described above, according to the present invention, the first middle point between the first capacitor and the second capacitor, and the second middle point between the first resistor and the second resistor. Are connected by the third capacitor, it is possible to provide a power supply circuit having improved rising characteristics and dynamic characteristics simultaneously.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a power supply circuit according to one embodiment of the present invention.

FIG. 2 is a waveform diagram showing a waveform of a high output voltage of a transformer unit in the power supply circuit.

FIG. 3 is a circuit diagram showing a conventional power supply circuit.

FIG. 4 is a waveform diagram showing a waveform of a high output voltage of a transformer unit in the power supply circuit.

FIG. 5 is a characteristic diagram showing rising characteristics and dynamic characteristics when the capacitance value of a second capacitor is increased.

FIG. 6 is a characteristic diagram showing rising characteristics and dynamic characteristics when the capacitance value of the second capacitor is reduced.

[Explanation of symbols]

 31 primary coil 32 secondary coil 33 cathode ray tube 34 transformer unit 35 PWM control circuit 36 high voltage detection circuit 37 midway point 38 first capacitor 39 second capacitor 40 capacitor group 41 first resistor 42 second resistor 43 resistor Group 44 First midpoint 45 Second midpoint 46 Switch element 47 Diode 48 Resonant capacitor 49 Diode 50 Drive power supply 51 Third capacitor

Claims (1)

(57) [Claims] A transformer having a primary coil and a secondary coil for supplying an anode voltage to a cathode ray tube; a control circuit for controlling a low output voltage output from the primary coil; A high-voltage detection circuit that detects a difference from a high output voltage output from the coil as a detection voltage, wherein the control circuit controls the low output voltage based on the detection voltage; A circuit is provided between the control circuit and a halfway point connecting the secondary coil and the cathode ray tube, and a capacitor group in which a first capacitor and a second capacitor are connected in series; a first resistor; A resistor group in which a second resistor is connected in series is connected in parallel between the halfway point and ground, and a first middle point between the first capacitor and the second capacitor, and the first resistor And the second resistor A power supply circuit in which the second midpoint is connected with a third capacitor and the second midpoint is connected with the control circuit.