JPH05122932A - 1-transistor voltage resonance converter - Google Patents

Abstract

PURPOSE:To reduce the switching loss of a semiconductor switching element such as FET by providing a time-constant circuit between the drive winding of a transformer and the semiconductor switching element and by turning ON the semiconductor switching element at the time when the value of drain voltage of the semiconductor switching element becomes zero. CONSTITUTION:When FET1 is turned ON, electric current flowing through the FET1 rises rectilinearly so that magnetic energy is stored in the exciting inductance of the primary winding N1 of a transformer T and the FET is turned OFF. When the FET1 is turned OFF, the exciting inductance of the primary side winding N1 and a capacitor C1 resonate and respective voltages of the primary side winding N1, secondary side winding N2 and drive winding N3 rise so that output current is supplied to a load 70. When the energy of the exciting inductance of the primary side winding N1 moves to the load side, the voltage of the primary side winding N1 changes in the zero direction and a time-constant circuit 60 turns ON the FET1 at the time when the drain current of the FET1 becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates an AC voltage in an output winding of a transformer having a resonance circuit element by turning a DC power supply voltage on and off by a semiconductor switching element, and rectifies and smoothes this AC voltage. The present invention relates to a single-stone voltage resonant converter that obtains a predetermined voltage. Since this converter can obtain high efficiency, it is most suitable for a portable power supply for satellite communication which receives a collector voltage of a traveling wave tube, for example, using a battery of 48V as an input.

[0002]

2. Description of the Related Art A semiconductor switching element turns on and off a direct-current power supply voltage to generate an alternating-current voltage in an output winding of a transformer having a resonance circuit element. The alternating-current voltage is rectified and smoothed to a predetermined voltage. As a resonant converter that can be obtained, a one-stone voltage resonant converter is known.

This conventional one-stone voltage resonant converter is
MOS which is a semiconductor switching element by resonance operation
It reduces the turn-on and turn-off loss of the FET and improves the efficiency.

[0004]

However, in the above-mentioned conventional example, since it is of the separately excited type, it is necessary to detect the zero point of the drain voltage of the MOSFET to determine the turn-on timing thereof, and therefore operate in the resonance mode. There is a problem in that the control circuit for this becomes complicated.

The present invention provides a FE with a simple control circuit.
An object of the present invention is to provide a self-excited one-wheel voltage resonant converter capable of reducing the switching loss of a semiconductor switching element such as T.

[0006]

The present invention comprises a DC power supply,
By having a resonant capacitor that resonates with the exciting inductance of the transformer, a semiconductor switching element, a diode connected in parallel with this semiconductor switching element, and a rectifying / smoothing circuit, by turning on and off the semiconductor switching element, In a resonant converter for generating an AC voltage in the output winding of the transformer and rectifying and smoothing the AC voltage by the rectifying / smoothing circuit to obtain a predetermined voltage, a drive winding of the transformer and a control pole of a semiconductor switching element. A predetermined time constant circuit is provided between and, and this time constant circuit turns on the semiconductor switching element at the timing when the voltage across the semiconductor switching element becomes zero.

[0007]

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

In this embodiment, a DC power source E1, a transformer T having a primary winding N1, a secondary winding N2 and a drive winding N3, a resonance capacitor C1 which resonates with the exciting inductance of the transformer T, and It has FET1 as a semiconductor switching element connected in parallel with the resonance capacitor C1.

Further, the starting circuit 10 is arranged so that when the DC power source E1 is turned on, when the voltage E of the power source E1 reaches a predetermined value, the FE
A circuit for starting T1, which includes transistors T2 and T3
The transistor T3 is turned off and the transistor T2 is turned on when the voltage E does not reach a predetermined value when the DC power source E1 is turned on.

The peak current detection circuit 20 is a circuit for detecting the peak value of the current flowing through the FET1 when the FET1 is on, and the current detection resistor R9, the resistor R10 and the capacitor C3 connected in series with the FET1. And a time constant circuit configured by. This time constant circuit removes noise components such as so-called beard. A current transformer may be used instead of the peak current detection circuit 20.

The drive circuit 30 is a circuit for turning off the FET 1 when the detected peak current value reaches a predetermined value, and is equivalently connected to a thyristor in a PN circuit.
P transistor T4, NPN transistor T5 and resistor R
7 and R8.

The output voltage error detection circuit 40 detects the error voltage of the output voltage by comparing the DC voltage (output voltage) rectified and smoothed by the voltage doubler rectifier circuit 50 with the voltage of the reference voltage source E2. A circuit for applying the detected error as a bias to the drive circuit 30, resistors R11 and R12 for dividing the output voltage, a reference voltage source E2, and a differential amplifier A.
With MP. The differential amplifier AMP includes resistors R11 and R
It is an amplifier that outputs the difference (error in output voltage) between the divided voltage value by 12 and the value of the reference voltage source E2.

Further, the time constant circuit 60 is provided between the drive winding N3 of the transformer T and the gate of the FET1, and is composed of a resistor Rg and a gate input capacitance Cg of the FET1.
The FET1 is set to turn on at the timing when the drain voltage (voltage across both ends) of the FET1 is zero.
In practice, the time constant circuit 60 is composed of a resistor Rg, a gate input capacitance Cg, and a DC cut capacitor C2. The Zener diode ZD connected in parallel with the gate input capacitance Cg forms a loop for discharging the reverse current generated in the drive winding N3, and
It protects the gate of the FET1. Drive winding N3
A normal diode may be used instead of the Zener diode ZD only for discharging the reverse current generated in the above.

Further, since FET1 has a diode component inside, it is not necessary to connect a diode in parallel with FET1, but a semiconductor switching element (transistor, static induction transistor, etc.) having no diode component inside is provided. Element), it is necessary to connect a diode in parallel with the semiconductor switching element.

Further, in the above embodiment, Vo> n
The winding ratio n, which is the ratio between the secondary winding number and the primary winding number of the transformer T, is set so as to be 2.E. Note that Vo indicates the output voltage, and E indicates the voltage of the power supply E1.

Next, the operation of the above embodiment will be described.

FIG. 2 is a time chart in the above embodiment.

First, at startup, if the voltage of the power source E1 is low, the transistor T3 is turned off and the transistor T2 is turned on.
Is on and FET1 is off. From this state, when the voltage of the power source E1 gradually rises and reaches a predetermined value, the transistor T3 is turned on, the transistor T2 is turned off, the gate of the FET1 is charged through the starting resistor R1, and the FE
T1 begins to turn on. The resistor R5 is a resistor for performing positive feedback from the collector of the transistor T2 to the base of the transistor T3 to speed up on / off operation.

When the FET1 starts to turn on, the primary winding N1
The voltage of the power source E1 is applied to the primary winding N1 with the black dot side of + as +, and a voltage with + on the black dot side is also generated in the drive winding N3, and is applied to the gate of FET1 via the capacitor C2 and the resistor Rg. Positive feedback is applied and FET1 is completely turned on. At this time, the current flowing through the FET1 rises almost linearly from zero. While FET1 is on (between t0 and t1), a voltage of approximately nE is generated in the secondary winding N2 with the black dot as +, and the capacitor C4 is charged to nE with the polarity shown. At the same time, magnetic energy is stored in the exciting inductance of the primary winding N1. The current of this FET1 is
It is detected by the current detection resistor R9, and if this current increases,
The current flowing to the base of the transistor T5 via the resistor R10 increases, and the transistor T5 turns on.

When the transistor T5 is turned on, the transistor T4 is also turned on, the transistors T5 and T4 are kept in the on state with each other, the gate charge of the FET1 is discharged, and F
ET1 turns off at high speed. When the FET1 is turned off, the voltage of the drive winding N3 is inverted, so that the capacitor C
2. Transistors T5 and T4 via resistors Rg and R9
Is reverse-biased, the transistors T5 and T4 are turned off, and the next turn-on of the FET1 is prepared.

When the FET1 is turned off, the exciting inductance of the primary winding N1 and the capacitor C1 resonate, and each voltage of the primary winding N1, the secondary winding N2 and the drive winding N3 shows a non-black dot. When the voltage rises as a positive value and the sum of the voltage of the secondary winding N2 and the voltage of the capacitor C4 exceeds the output voltage V0, the diode D2 turns on and supplies the output current. Therefore, the voltage of the secondary winding N2 at this time is V0-n · E,
The voltage of the primary winding N1 is (Vo / n) -E, and
The drain voltage of T1 is Vo / n because it is the sum of the voltage E of the power supply E1 and the voltage of the primary winding N1.

When the energy of the exciting inductance of the primary winding N1 moves to the load side and the diode D2 is turned off, the voltage of the primary winding N1 changes in the zero direction. When the resonance voltage of the primary winding N1 becomes equal to the voltage E of the power source E1 with the black dot side as +, the drain voltage of the FET1 becomes zero. In addition, the time constant circuit 60 uses the FE as described above.
The gate voltage is applied to the FET1 at the timing when the drain voltage of T1 becomes zero, so that the FET1 turns on after the drain voltage of the FET1 becomes zero. Thus, since the FET1 is turned on at the timing when the drain voltage of the FET1 becomes zero, theoretically, the FET1
No turn-on loss occurs.

At time t2, the voltage of the primary winding N1 becomes larger than the voltage E of the power source E1. At this time, F
The voltage of ET1 should be negative, but since the diode component exists in FET1, the voltage of FET1 is almost 0V.
(Forward voltage of diode is -0.6 V). Thus, when the voltage of the FET1 is almost 0V, the time constant circuit 60 is set so that the gate voltage of the FET1 exceeds the threshold value.
By setting the time constant of, resonant operation without turn-on loss is performed. In FIG. 2, the negative component of the current of the FET1 indicates the current flowing through the diode in the FET1.

By the way, the output voltage also changes in accordance with the change of the load 70, and the error detection circuit 40 outputs the change of the output voltage as an error, and the bias current flows through the transistor T5 of the drive circuit 30. That is, when the output voltage becomes higher than the set value, the bias current increases in accordance with the increase, the timing at which the transistors T5 and T4 turn on becomes earlier, and the timing at which the FET1 turns off also becomes earlier. Therefore, the ON time of the FET1 is shortened, and the output voltage is controlled to decrease. On the contrary, when the output voltage becomes lower than the set value, the bias current decreases according to the lowering value, the timing of turning on the transistors T5 and T4 is delayed, and the FET1
Will turn off later. Therefore,
The on-time of the FET1 becomes longer and the output voltage is controlled to increase. In this way, the output voltage value is automatically controlled to the set value.

In order to increase the set value of the output voltage,
The voltage value of the reference power supply E2 in the error detection circuit 40 may be increased. On the contrary, in order to lower the set value of the output voltage, the voltage value of the reference power source E2 may be decreased.

When the number of stages of the voltage doubler rectifier circuit is m, the winding ratio n is adjusted so that Vo> n · m · 2 · E.
By setting, the resonance mode is guaranteed. Further, instead of the voltage doubler rectifier circuit 50, a half-wave rectifier circuit or a double-wave rectifier circuit may be used. If a half-wave rectifier circuit is used, Vo
The winding ratio n may be set so that> n · E, and when the double-wave rectifier circuit is used, the winding ratio n may be set so that Vo> 2 · n · E ( Vo is the output voltage, and E is the voltage of the DC power supply E1). In an actual power supply, since the power supply voltage fluctuates, it is necessary to select the lowest input voltage as the voltage E of the power supply E1.

Next, FIG. 3 shows another embodiment in which the drive circuit 30 is directly connected to the gate of the FET 1 so that the turn-off of the FET 1 can be accelerated as compared with the embodiment of FIG.

In the above embodiment, the resonance capacitor C1
Is connected in parallel to the FET1, but instead of providing the capacitor C1, the capacitor C1a may be connected in parallel with the primary winding N1 as shown by the broken lines in FIGS. 1 and 3 in principle. Are the same.

[0029]

According to the present invention, in the resonance converter, when the turn-on loss of the semiconductor switching element such as the FET is reduced, the control circuit for operating in the resonance mode can be simplified.

[Brief description of drawings]

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

FIG. 2 is a time chart in the above embodiment.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

[Explanation of symbols]

 C1 ... Resonance capacitor T ... Transformer E1 ... DC power supply 1 ... FET 10 ... Start-up circuit 20 ... Peak current detection circuit 30 ... Drive circuit 40 ... Output voltage error detection circuit 50 ... Double voltage rectification circuit 60 ... Time constant circuit

Claims (1)

[Claims] 1. A semiconductor switching device comprising a DC power supply, a resonance capacitor that resonates with an exciting inductance of a transformer, a semiconductor switching device connected in series with an input winding of the transformer, and a rectifying / smoothing circuit. By turning on and off, an AC voltage is generated in the output winding of the transformer, the AC converter is rectified and smoothed to obtain a predetermined voltage. In the resonant converter, the semiconductor switching element is an input winding of the transformer. And the transformer has a drive winding, and a predetermined time constant circuit is provided between the drive winding and the control pole of the semiconductor switching element. The time constant circuit is the semiconductor switching element. It is characterized in that the semiconductor switching element is turned on at the timing when the voltage across both ends becomes almost zero. And compression common vibration converter.