JPH07143743A - Insulated type switching power supply - Google Patents

Abstract

PURPOSE:To eliminate the need for a high dielectric-strength component and complicated constitution exclusive for transmitting the output voltage signal of a frequency corresponding to output voltage when the signal is transmitted over the primary winding side of an insulating transformer. CONSTITUTION:In a switching power supply, the DC input of voltage V1 is switched by a transistor Tr1, and changed into an alternating signal S1 by an insulating transistor T1, the signal S1 is rectified and smoothed by a rectifying circuit 5 and a smoothing circuit 6, and the DC output of voltage V2 is generated. A voltage and frequency conversion circuit 4 generates an output voltage signal having a frequency corresponding to the DC output. The output voltage signal is transmitted to a primary winding from the secondary winding of the insulating transformer T1, and restored to a voltage corresponding to voltage V2 by the frequency and a voltage conversion circuit 2. A voltage adjusting circuit 1 responds to the restored voltage, and controls the conductive period of the transistor Tr1 in a negative feedback manner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating type switching power supply in which a DC input side circuit and an output side circuit are insulated by an insulating transformer, and particularly, a high withstand voltage is provided between the input side circuit and the output side circuit. It relates to the required isolated type switching power supply.

[0002]

2. Description of the Related Art In a traveling wave tube or a microwave tube such as a klystron, since a slow wave circuit electrode or a body is used at a ground potential, a high potential of negative tens of thousands of volts is applied to the cathode electrode and the heater electrode. Will be done. Therefore, the heater power supply circuit for these microwave tubes requires an insulated power supply circuit with a high withstand voltage. Further, since the heater voltage corresponds to the cathode temperature of the microwave tube, the heater power supply circuit is also required to have high output voltage stability. In this type of heater power supply circuit, a voltage stabilizing circuit is generally formed on the secondary winding side of an insulation transformer. However, in the heater power supply circuit of this circuit configuration, since the voltage stabilizing circuit is a high-potential circuit, it is necessary to insulate the entire power supply circuit from other circuits, which is not only large in size but also provided on the primary winding side. There is a drawback in that the operation of the output voltage adjustment circuit is dangerous.

One means considered to be suitable for solving the above-mentioned drawback is disclosed in Japanese Patent Laid-Open No. 13565/1989 (Title of Invention: Switching Power Supply). This switching power supply converts the DC output voltage generated in the secondary winding side circuit of the insulation transformer into a signal of a frequency corresponding to this voltage and frequency, and a photocoupler dedicated for this frequency-converted DC output voltage signal. The signal is fed back to the primary winding side circuit of the insulation transformer by an insulation type signal transmission circuit such as an optical fiber or a capacitor couple, and the conduction pulse width of the DC input is controlled based on this feedback signal.

[0004]

However, in the disclosed switching power supply, in a dedicated insulation type signal transmission circuit, a high withstand voltage component of tens of thousands of volts required as a heater power supply for a microwave tube is not used in a photocoupler or a capacitor. The drawback is that it is difficult to achieve.

Further, when an optical fiber is used for the insulation type signal transmission circuit, a light emitting portion for converting the DC output voltage signal into light and a light receiving portion for converting light into an electric signal are required, which complicates the structure. Not only that, it has the drawback of being expensive.

[0006]

The insulated switching power supply of the present invention comprises an insulating transformer for converting electric power into a voltage and transmitting the electric power, and a DC input for switching the DC input in response to a control signal to isolate the switched DC input. A main switch that supplies the primary winding of the transformer, a rectifying / smoothing circuit that rectifies and smoothes the power generated in the secondary winding of the isolation transformer to generate a DC output, and the voltage of the DC output corresponds to this voltage. Voltage / frequency conversion circuit for converting into an output voltage signal of a frequency, an output voltage signal transmission circuit for supplying the output voltage signal to the secondary winding of the isolation transformer, and A frequency / voltage conversion circuit that restores an output voltage signal to a voltage corresponding to the voltage of the DC output, and a negative conduction period of the main switch in response to the restored voltage. And a main switch drive circuit to produce the control signal for controlling.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.
FIG. 2 is a waveform diagram of the main signal in this embodiment.

Referring to FIG. 1 and FIG. 2 together, this insulation type switching power supply has input terminals 101a and 101a.
The DC input of voltage V1 is supplied between
A voltage-stabilized DC output of the voltage V2 is produced between 02a and 102b. The DC input is pulse-width controlled by the switching transistor Tr1 to become a switching signal S2, and this switching signal S2 is supplied to the primary winding of the insulating transformer T1 via the primary side terminals T11 and T12. It should be noted that during the conduction period of the transistor Tr1, the clock signal S3 from the oscillator 3 (cycle 1 / f
The pulse width is controlled to be the pulse width Td by the control signal S6 synchronized with the end time of 1). The insulating transformer T1 insulates the primary winding from the secondary windings connected to the secondary side terminals T21 and T22.

When the switching signal S2 is applied to the primary winding, the insulating transformer T1 outputs the output side terminals T21 and T2.
2 and an alternating signal S1 having a period 1 / f1 is generated. The alternating signal S1 is full-wave rectified by the rectifying circuit 5 including the diodes D51 and D52, and then the choke coil L6.
It is smoothed by a smoothing circuit 6 including 1 and a capacitor C61. The smoothed component of the alternating signal S1 becomes the DC output.

The voltage V2 between the output terminals 102a and 102b is divided by the voltage detection circuit 7 which is a voltage divider composed of resistors R71 and R72. The divided voltage of the voltage V2 is supplied to the voltage / frequency conversion circuit (V / F) 4. The voltage / frequency conversion circuit 4 includes a voltage / frequency converter 4
2 generates an output voltage signal having a frequency f2 proportional to the divided voltage, and further outputs this output voltage signal to the amplifier 41.
Amplify by. The output voltage signal from the amplifier 41 is applied to the secondary side terminal S21 of the insulating transformer T1 via the capacitor C2.

When the output voltage signal is applied to the secondary side terminal T21 of the insulating transformer T1, the output voltage signal is transmitted between the primary side terminals T11 and T12 of the insulating transformer T1. The alternating signal S1 and the switching signal S2 described above actually include the output voltage signal component of the frequency f2 in addition to the switching signal component of the period 1 / f1. Switching signal S appearing at the primary side terminal T12
Of the two, the component of the output voltage signal is the capacitor C1.
Via the timing circuit 22 of the frequency / voltage conversion circuit 2
Is supplied to. The timing circuit 22 is composed of an analog switch, samples the component of the output voltage signal in synchronization with the clock signal S3, and generates the output voltage signal S4 in which the switching frequency component is less mixed. The output voltage signal S4 is a frequency / voltage converter (F /
V) 21 restores the voltage S5 proportional to the voltage V2. The voltage / frequency converter 42 and the frequency / voltage converter 21 are commercially available as semiconductor integrated circuits.

The voltage S5 is supplied to the voltage adjusting circuit 1,
The voltage hold circuit 12 holds the clock signal S3 for each period. The control circuit 11 of the voltage adjusting circuit 1 outputs the output terminals 102a and 1a based on the held voltage S5.
Pulse width T so that the voltage V2 between
A control signal S6 is generated by controlling d in a negative feedback manner. This control signal S6 drives the transistor Tr1 which is the main switch, as described above. Here, the control circuit 11 includes an output voltage adjusting circuit for setting the voltage V2, and the reference voltage and the voltage S5 generated by the output voltage adjusting circuit.
And the pulse width T of the control signal S6 based on the result of comparing
Determine d.

FIG. 3 shows an insulating transformer T1 used in this embodiment.
It is a figure which shows the frequency characteristic of the signal transmission efficiency of.

Signal transmission efficiency from the primary (input side) winding to the secondary (output side) winding of the isolation transformer T1 or the signal transmission efficiency from the secondary winding to the primary winding which is in a reciprocal relation with this. Is below the lower limit frequency f _L due to magnetic saturation of the core,
When the upper limit frequency f _H or more is caused by the skin effect of the winding and the increase of the core loss, the decrease is remarkable, and a frequency between the frequencies f _L and f _H is generally set as the operating frequency. In this embodiment, both the switching signal S2 and the output voltage signal need to be transmitted by the insulating transformer T1. Since the output voltage signal needs to be sampled by the timing circuit 22, the frequency f2 of the output voltage signal is the switching frequency f of the switching signal S2.
It is higher than 1. That is, the frequency f2 is the frequency f1.
And the frequency f _H.

[0016]

As described above, according to the present invention, since the output voltage signal of the frequency corresponding to the output voltage is transmitted to the primary winding of this isolation transformer through the isolation transformer, it is dedicated to the transmission of the above-mentioned output voltage signal. There is an effect that it does not require high withstand voltage parts and a complicated structure, and is excellent in operability and economy.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a waveform diagram of main signals in the present embodiment.

FIG. 3 is a diagram showing frequency characteristics of signal transmission efficiency of an insulating transformer T1 used in this embodiment.

[Explanation of symbols]

 1 voltage adjustment circuit 2 frequency / voltage conversion circuit 3 oscillator 4 voltage / frequency conversion circuit 5 rectifier circuit 6 smoothing circuit 7 voltage detection circuit 11 control circuit 12 voltage hold circuit 21 frequency / voltage converter (F / V) 22 timing circuit 41 amplifier 42 voltage / frequency converter (V / F) 101a, 101b input terminal 102a, 102b output terminal C1, C2, C61 capacitor D51, D52 diode L61 choke coil R72, R72 resistor T1 insulation transformer T11, T12 input side terminal T21, T22 output side terminal Tr1 transistor

Claims (3)

[Claims] 1. An insulation transformer for converting electric power into voltage and transmitting it, a main switch for switching a DC input in response to a control signal and supplying the switched DC input to a primary winding of the insulation transformer, A rectifying / smoothing circuit that rectifies and smoothes the power generated in the secondary winding of the isolation transformer to generate a DC output, and a voltage / frequency conversion that converts the voltage of the DC output into an output voltage signal having a frequency corresponding to this voltage. Circuit, an output voltage signal transmission circuit for supplying the output voltage signal to the secondary winding of the isolation transformer, and the output voltage signal generated in the primary winding of the isolation transformer to a voltage corresponding to the voltage of the DC output. And a frequency / voltage conversion circuit for restoring the main switch drive circuit for generating the control signal for negatively controlling the conduction period of the main switch in response to the restored voltage. And an isolated switching power supply. 2. A timing circuit, wherein the frequency / voltage conversion circuit samples the output voltage signal generated in the primary winding of the isolation transformer at a timing immediately before switching of the DC input, and the sampled output signal. The insulated switching power supply according to claim 1, further comprising a frequency / voltage converter that restores a voltage corresponding to the voltage of the DC output. 3. The frequency range of the output voltage signal generated by the voltage / frequency conversion circuit is set to be higher than the switching frequency.
Insulated switching power supply described.