JPH0683573B2 - Resonant converter and control method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention turns on and off a DC input power supply voltage with a semiconductor switch to obtain an AC voltage in an output winding of a transformer having a resonant circuit element. The present invention relates to a resonance converter that obtains a predetermined DC output voltage from an AC voltage through a rectifying / smoothing circuit and a control method thereof.

[Conventional technology]

In recent years, switching regulators are small and highly efficient, so they are used as power sources for communication equipment and general industrial equipment.
Widely used. In particular, for power supplies for information terminals, there is a strong demand for smaller size, lower price, and lower noise, and circuit systems and parts are being actively developed.

However, the rectangular wave switching mode method, which occupies the mainstream of current switching regulators, has been technically established as a result of many years of research and development, and improvement in performance has come to depend on the development of component parts. .

Therefore, in the high-frequency electrode amplification stage, a class E amplifier circuit has been proposed in order to obtain high power efficiency. this is,
The current i flowing through the semiconductor switch and the voltage V applied to both ends of the semiconductor switch are prevented from existing at the same time by selecting the configuration and constant of the LC circuit, and the rising initial value and falling end of the voltage waveform are set. It tries to make the slope of both values zero.

However, since the class E operation cannot be expected in a switching rectifier with input voltage fluctuations and load fluctuations, the voltage is set to zero when the current of the semiconductor switch rises and drops. Furthermore, the critical point in the operation of this system is at the time when the slope of the final value of the voltage drop becomes zero, and using this vicinity is an economical design for the component parts. Such a voltage resonant converter that performs a switching operation called quasi-resonant switching is used.

[Problems to be Solved by the Invention]

However, at the time of transient changes such as start-up and load changes,
The semiconductor switch may be turned on in the state where the voltage is charged in the resonance capacitor connected in parallel with the semiconductor switch. In this case, the discharge current from the resonance capacitor causes the semiconductor switch to turn on. Since it flows, there is a problem that the semiconductor switch is destroyed, the efficiency is lowered, and the semiconductor switch is disturbed.

A first object of the present invention is to obtain a control method for reliably switching a semiconductor switch of a resonance converter to zero voltage. The second object is to obtain a specific configuration of the resonant converter to which this control method is applied.

[Means for Solving the Problems]

In order to solve the first problem, the present invention turns on and off a DC input power supply voltage with a semiconductor switch, obtains an AC voltage in an output winding of a transformer having a resonance circuit element, and rectifies this AC voltage.・ In the control method of the resonant converter that rectifies and smoothes by the smoothing circuit to obtain a predetermined voltage, the time when the voltage between the main electrodes of the semiconductor switch reaches the set value is detected, and the energy is supplied from the drive winding of the transformer. It is supplied to the control electrode of the semiconductor switch to turn on the semiconductor switch, and when the output voltage reaches the set value, the AVR
The signal forcibly turns off the semiconductor switch,
The present invention proposes a control method for a resonant converter, which is characterized by obtaining a constant voltage output.

In order to solve the second problem, a semiconductor switch having a resonance electrode, a main electrode and a control electrode, and a transformer having at least a primary winding and a secondary winding are provided, and a DC input power source and this transformer are provided. Is a resonant converter that obtains a DC output voltage from a rectifying / smoothing circuit connected to the secondary winding of this transformer, in which the primary winding of this transformer and the main electrode and common electrode of this semiconductor switch are connected in series. One end of the tertiary winding is connected to the resonance electrode of the semiconductor switch, and the other end of the tertiary winding of the transformer is connected to the control electrode of the semiconductor switch via the on-timing circuit. It conducts when the voltage between the main electrode and common electrode of the semiconductor switch reaches a set value. The DC output voltage is detected by the output voltage detection circuit and compared with the reference voltage to detect the AVR signal. The obtained, the AVR signal is intended to propose a resonant converter characterized by short-circuiting between the common electrode and the control electrode of the semiconductor switch by the off circuit.

Incidentally, it is also proposed to connect a capacitor between the main electrode and the resonance electrode of the above semiconductor switch as needed.

〔Example〕

FIG. 1 is a circuit diagram for explaining one embodiment of the present invention, and FIG. 2 is a waveform diagram of each part for explaining the operation.

In FIG. 1, 1 is a DC input power supply, 2 is a semiconductor switch such as a FET, 3 is a transformer having an input winding N ₁ , an output winding N ₂ , and a drive winding N ₃ , and 4 is a diode D ₁ and a capacitor. A rectifying / smoothing circuit consisting of C ₁ , 5 is a load, and 6 is a starting circuit consisting of transistors Q ₁ and Q ₂ and resistors R _{1 to} R ₅ .

7 is an on-diming circuit, which includes a diode D ₂ and a resistor
R ₆ is connected in series to connect the base of the transistor Q ₃ and the drain which is one end of the main electrode of the semiconductor switch 2. The emitter of transistor Q ₃ is capacitor C ₆
Is connected to one end of the winding N ₃ of the transformer 3 via
When the drain voltage of the semiconductor switch 2 reaches the set value of almost zero, the voltage generated from the winding N ₃ of the transformer 3 causes the emitter of the transistor Q ₃ ⇒ base ⇒ resistor R ₆ diode D ₂ ⇒ semiconductor switch ₂ ⇒ starting current flows in the closed circuit of the winding N _3, the transistor Q ₃ is turned on, shorting the resistor R ₇ of the relatively high resistance of the parallel. By turning on the transistor Q _3, the winding gate voltage generated N ₃ is a control electrode of the semiconductor switch 2 via the resistor R ₁₄ of relatively low resistance and a capacitor C _6, is required for the ON voltage application To be done. In this way, the on-timing circuit 7 detects when the voltage between the main terminals of the semiconductor switch 2 is changing due to resonance and when the value becomes a set value close to zero, the semiconductor switch 2
Is to start turning on.

8 is the peak current detection circuit comprising a capacitor C ₃ and resistor R ₉ to R _12. 9 is a transistor Q ₄ , Q ₅ , diode
It is an off circuit consisting of D ₃ , capacitor C ₄ and resistors R _{13 to} R ₁₆ . 10 is an integrated circuit IC, a capacitor C ₅ and resistors R _{17 to} R ₂₂
Is an output voltage detection circuit. C ₀ is a resonance capacitor, D ₀ is a clamp diode, D ₄ is a diode, and ZD ₁
Is a Zener diode, C ₆ and C ₇ are capacitors, and R ₂₃ is a resistor.

As an initial condition, the current and voltage of the resonance capacitor C ₀ are set to zero and the voltage V of the capacitor C ₁ of the rectifying / smoothing circuit 4 is set to V.
_C1 is the assumption that you are charged to the output voltage E _5, illustrating the operation by the second view. In this state, when the control voltage V _GS as shown in FIG. 2 (e) is applied to the control pole of the semiconductor switch 2 at this time t ₁ and the semiconductor switch 2 is turned on, as shown in FIG. 2 (a). Thus, the current I ₂ flowing through the semiconductor switch 2, that is, the input winding current I of the transformer 3
_N1 rises linearly with time.

Next, when the semiconductor switch 2 is turned on at time t ₂ , as shown in FIG. 2 (a), when the semiconductor switch is turned off, the voltage V _C0 of the resonance capacitor C ₀ becomes as shown in FIG. ), The voltage E ₁ of the DC input power source I and the current of the open inductance L ₁ of the input winding N ₁ of the transformer 3 gradually increase.

At time t ₃ , V _C0 = E ₁ , and as shown in FIG. 2 (c),
The current I _C0 of the resonance capacitor C ₀ reaches a peak. After that, the voltage V _C0 of the resonance capacitor C ₀ continues to rise due to resonance with the open inductance L ₁ of the input winding N ₁ of the transformer 3, and at time t ₄ , V _CO = E ₁ + (N ₁ / N ₂ ) · E ₅ next,
The rectifying diode D ₁ of the rectifying and smoothing circuit 4 becomes conductive. As a result, the output winding N ₂ of the transformer 3 is clamped to the output voltage E ₅ via the smoothing capacitor C ₁ of the rectifying and smoothing circuit 4, and the voltage V _C0 of the resonance capacitor C ₀ is at time t ₅ . The resonance waveform of the resonance capacitor C ₀ and the leakage inductance L ₂ of the transformer 3 has a peak _value .

As shown in FIG. 2 (d), the output winding current I _N2 of the transformer 3 is such that the voltage V _C0 of the resonance capacitor C ₀ is again V _C0 = E ₁ +
(N ₁ / N ₂ ) ・ Ascends until time t ₆ when E ₅ . Further, the output winding current I _N2 of the transformer 3 continues to flow due to the energy stored in the leakage inductance L ₂ of the transformer 3, and the output winding N ₂ of the transformer 3 continues to be clamped to the output voltage E ₅ . The voltage V _C0 of the resonance capacitor C ₀ is
At time t ₇ , the voltage E ₁ of the DC input power supply 1 is reached, but due to resonance with the leakage inductance L ₂ of the transformer 3, it continues to decrease and becomes zero at time t ₈ . Clamp diode D ₀ becomes conductive at time t _8, the current of the resonant capacitor C ₀
The clamp diode D ₀ takes over I _C0, and the voltage V _C0 of the resonance capacitor C ₀ is clamped to the forward drop voltage (−V _F0 ) of the clamp diode D ₀ . When the output winding current I _N2 of the transformer 3 becomes zero at time t ₉ , the rectifying diode D ₁ of the rectifying and smoothing circuit 4 becomes non-conducting, and the input winding current I _N1 of the transformer 3 returns to FIG. 2 (a). As shown, it rises linearly with time and returns to zero at time t ₁₀ .

With the above, one cycle of the operation is completed, and the same operation is repeated thereafter. If the semiconductor switch is an FET, the clamp diode D ₀ can be replaced with a parasitic diode inside the FET. Also, during high frequency operation, the resonance capacitor C ₀ can be replaced by the output capacitance of the FET.

By the way, in such a steady operation state, the voltage V of the resonance capacitor C ₀ is controlled by the on-timing circuit 7.
_{Although C0} is detected and the above operation is performed, for example, when the voltage V _C0 of the resonance capacitor C _O does not drop to the set value of the on-timing circuit 7 due to load fluctuation or the like, and the voltage value is high, Is the diode D ₂ of the on-timing circuit 7.
Is reverse-biased and transistor Q ₃ does not turn on, but the control pole of semiconductor switch 2 has a relatively high resistance R ₇
Since the voltage is applied via the semiconductor switch 2, the semiconductor switch 2 gradually becomes conductive, and the voltage V _C0 of the resonance capacitor C ₀ gradually drops. Then, the voltage V of the resonance capacitor C _{0
When CO} reaches the set value, the transistor Q ₃ turns on, the resistor R ₇ is short-circuited, the semiconductor switch 2 turns on rapidly, its current I ₂ increases, oscillation starts, and a steady state is entered. To do. In this way, if the steady operation state is deviated for some reason, the on-diming circuit 7 can detect this and perform an efficient operation while safely correcting it.

Further, at the time of starting, the starting circuit 6 operates. At start-up, a voltage is applied to the control pole of the semiconductor switch 2 via the resistor R ₁ , but if the voltage E ₁ of the DC input power supply ₁ is still low, normal oscillation cannot be performed and the semiconductor There is a problem that heat is generated because the switch 2 cannot be turned on completely. In this embodiment, the transistor Q ₁ is kept on until the voltage E ₁ of the DC input power supply 1 becomes a voltage at which the semiconductor switch 2 can operate, and the voltage E ₁ of the DC input power supply ₁ becomes a certain voltage value. By the way, since the transistor Q ₁ is turned off and the voltage is applied to the control electrode of the semiconductor switch 2 via the resistor R ₁ , the semiconductor switch 2 does not generate heat. In this way, when the voltage of the resonance capacitor C ₀ reaches the set value, the operation is shifted to the steady operation state together with the operation of the on-timing circuit 7 described above.

Next, the off circuit 9 will be described. The capacitor C ₄ combines the signal detected by the peak current detection circuit 8 with the input current and the signal detected by the output voltage detection circuit 10 with the output voltage.
The integrated voltage is applied to the base of the transistor Q ₅ to turn it on, and then the transistor Q ₄ turns on to forcibly turn off the semiconductor switch 2 at high speed by positive feedback. When the black dot mark side inverts the voltage generated in the drive winding N ₃ of the transformer 3 becomes negative electrode, by applying a current flowing through the negative extreme pressure to the transistor Q _4, Q ₅ transistor
Q _4, Q ₅ forcibly turned off at high speed. In this way,
The semiconductor switch 2 can be driven at high speed.

Next, the peak current detection circuit 8 will be described. The input current through resistor R ₉ and detected via the resistor R _10, are superimposed on the AVR signal. In this way, the peak value of the input current is detected and limited during startup and overload.
Further, the voltage fluctuation of the DC power supply 1 can be corrected via the resistor R ₁₁ .

〔The invention's effect〕

Since the present invention has the characteristics as described above, it is possible to prevent the semiconductor switch from being turned on rapidly in the state where the resonance capacitor is charged with a voltage, and to prevent a decrease in the destruction efficiency of the semiconductor switch. it can. Further, the semiconductor switch can be driven at high speed in the steady state.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining one embodiment of the present invention, and FIG. 2 is a waveform diagram of each part for explaining the operation. 1 ... DC input power source, 2 ... Semiconductor switch, 3 ... Transformer, 4 ... Rectifying / smoothing circuit, 5 ... Load, 6 ... Start-up circuit, 7
On-timing circuit 8 Peak current detection circuit 9 Off circuit 10 Output voltage detection circuit C ₀ Resonance capacitor D ₀ Clamp diode

Claims (3)

[Claims] 1. A semiconductor switch is used to turn on and off a DC input power supply voltage to obtain an AC voltage at an output winding of a transformer having a resonance circuit element, and the AC voltage is rectified and smoothed by a rectifying / smoothing circuit. In a method of controlling a resonance converter that obtains a predetermined voltage, a time point when the voltage between the main electrodes of the semiconductor switch reaches a set value is detected, and energy is applied from the drive winding of the transformer to the control electrode of the semiconductor switch. A method for controlling a resonant converter, wherein the semiconductor switch is supplied to turn on the semiconductor switch, and when the output voltage reaches a set value, the semiconductor switch is forcibly turned off by an AVR signal to obtain a constant voltage output. . 2. A DC input power source and a transformer for the same, comprising a semiconductor switch having a common electrode, a main electrode and a control electrode, and a transformer having at least a primary winding, a secondary winding and a tertiary winding. A resonant converter in which a primary winding, a main electrode and a common electrode of the semiconductor switch are connected in series, and a DC output voltage is obtained from a rectifying / smoothing circuit connected to a secondary winding of the transformer, One end of the tertiary winding is connected to the common electrode of the semiconductor switch, and the other end of the tertiary winding of the transformer is connected to the control electrode of the semiconductor switch via an on-timing circuit. The circuit conducts when the voltage between the main electrode and the common electrode of the semiconductor switch reaches a set value, and detects the DC output voltage through the output voltage detection circuit,
A resonance converter characterized in that an AVR signal is obtained by comparison with a reference voltage, and this AVR signal short-circuits the control electrode and the common electrode of the semiconductor switch by an off circuit. 3. The resonance converter according to claim 2, wherein a capacitor is connected between the main electrode and the common electrode of the semiconductor switch.