JPH01234051A - Controlling method for series resonance converter - Google Patents

Abstract

PURPOSE:To prevent the open phase of an apparatus and to control said apparatus stably, by turning ON first - second main switching elements, when a value obtained by subtraction of an output voltage from the voltage of the ends of said main switching elements goes down to a reference voltage if no output voltage control signal is given. CONSTITUTION:A series resonance converter is composed of first - second main switching elements 1-2 of field-effect transistors, diodes 3-4, resonance capacitors 5-6, a tank circuit 10, a main transformer 11, and a resonance reactor 12 to supply a load 16 with power from a transformer secondary winding via diodes 13-14 and the like. Further, said converter is equipped with a control circuit 20 connecting respective voltage sensors 17-19 of sensing points a-c of the tank circuit 10 and the like to turn ON and OFF said main switching elements 1, 2 from a driver circuit 22 through transformers 23-26 and the like. In this case, when a value obtained by subtraction of an output voltage converted into a primary side value from the both end voltage of both elements 1, 2 goes down to a reference voltage, said elements 1, 2 are turned ON so that open phase of an apparatus is prevented and so on.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention includes a main switch element that is in the on state when the first or second main switch element is in the on state, and an E transformer. a first resonant circuit; A second resonant circuit configured without a second main switch element and a main transformer is provided, and the on/off of the first or second main switch element is controlled by an output type cuff A control signal. hand,
The present invention relates to a method for a series resonant converter to obtain a predetermined DC output.

[Conventional technology]

Series resonant converters are used as one method of converting a DC input voltage to a DC output voltage of a different polarity or voltage value. A series resonant converter is a series resonant circuit of a reactor and a capacitor.

It consists of a main switch element such as a transistor, a field effect transistor, a diode, a transformer, etc.
This is a converter that causes a resonant current to flow by turning the main switch element on and off, rectifies and smoothes the resonant current via a transformer, and obtains a DC voltage again. Resonant current generally has a sinusoidal waveform and naturally extinguishes, so there is no need to forcibly turn off the main switch element, and the main switch element turns off when it naturally extinguishes, so switching loss does not exist in principle. The effects of higher efficiency, lower noise, smaller size, and lighter weight can be expected.

The magnitude of the resonant current in the series resonant converter is determined by the inductance value of the resonant reactor, the capacitance value of the resonant capacitor, the cycle of turning on and off the main switch element, the DC input voltage, and the RI current small output voltage value. Therefore, much research is being conducted on the relationship between these values and the resonant current. Based on these studies, in order to control the output voltage of a series resonant converter at a constant voltage regardless of the value of the output current, the off-period of the main switching element is changed. The magnitude of the output current (
It is said that adjusting the average value of the resonant current is the act of adjusting the average value of the resonant current. However, when a series resonant converter is controlled at constant voltage using frequency control, the output current and operating frequency are in a proportional relationship, so the operating frequency drops to the audible 11 range at light loads (when the output current is small). There is a problem in that it is closed and generates noise.

To solve this problem, a tank circuit consisting of a parallel resonant circuit whose impedance becomes infinite at the resonant frequency is inserted into the series resonant loop, and by increasing the impedance of the resonant loop at light loads, the operating frequency becomes load dependent. A series resonant converter has been proposed to suppress the

[Problem to be solved by the invention] However, by applying negative feedback to this proposed DC resonant converter, the output power! 4.If you wish to do something.

With conventional control methods, during transients such as startup, load fluctuations, and input fluctuations, phase loss may occur or the operating frequency may fall below the parallel resonant frequency of the tank circuit. Since the impedance of the series resonant loop decreases at the parallel resonant frequency of the tank circuit, positive feedback occurs below the parallel resonant frequency, making stable control impossible.

[Means to solve the problem]

In order to eliminate the above-mentioned drawbacks, the present invention provides a first or second main switch element that is configured to include a main switch element that is in the on state and a main transformer when the first or second main switch element is in the on state.
a resonant circuit, and a first resonant circuit. It is equipped with a second resonant circuit configured without a second main switch element and a main transformer, and outputs power to turn on and off the first or second main switch element. In the 'MgaM method of a series resonant converter that obtains a predetermined DC output by controlling from the M control signal, if the output power control signal is not generated during transients such as load fluctuations and human power fluctuations, the first or ST converts the output voltage from the voltage applied across the main switch element 2 to the primary side.
When the value obtained by subtracting the value of the voltage decreases to the reference voltage (K), the voltage state detection signal turns on the first or second main switch element.

The present invention provides a control method for a series resonant converter, which is characterized by preventing phase loss and sustaining one oscillation.

[Function] According to such a control method for a series resonant converter, even when an output power control signal is not generated during a transient period, phase loss is prevented, a negative feedback state is maintained, and stable control is possible.

〔Example〕

FIGS. 1 and 2 are diagrams for explaining one embodiment of the present invention.

In FIG. 1, there is shown a circuit in which a first ball switch element 12 which is a field effect transistor, a second king switch element 2 are connected in series in the forward direction, and a Li8 circuit in which a diode 3.4 is connected in series in the forward direction. ] i! A DC input power source 7 is connected between each end of the resonant capacitor 8 and a circuit in which the resonance capacitors 5 and 6 are connected in series. The main switch element 1.2 has a forward polarity with respect to the DC input type a7, but the diode 3.4 has a reverse polarity.

The connection point of the diode 3.4 and the connection point of the resonance capacitor 5.6 are connected to each other, and this connection point and the switch 1
A tank circuit 10 consisting of a parallel circuit of a resonant reactor 8 and a resonant capacitor 9 is connected between the connection point of the children 1 and 2;
The primary winding of the main transformer 11.

A series connection circuit with the resonance reactor 12 is connected.

A diode 13.14 is installed in the secondary winding of the King transformer II.
Output capacitor 15 and load 16 are connected via.

Detection point a of the DC input voltage ■, with reference to the (-) terminal of the DC input power source 7, and detection point of the resonance voltage ■ゎ.

That is, the DC output voltage, which is the voltage across the connection point between the tank circuit 10 and the primary winding of the main transformer 11, and the load 16;
, are connected to the control circuit 20 via voltage detectors 17, 18 and 19, respectively. A current detector 21 is inserted into the current path of the resonance reactor 8 and detects the current of the resonance reactor 8 in the direction of the arrow.

'LQ t111 connected to circuit 20. Drive circuit 22
receives the signal from the control circuit 20 and transforms the transformers 23 and 24.
Sends on and off signals to the main switch element 1 through the terminals.

They are connected to the main switch element 2 via transformers 25 and 26 so as to send on and off signals, respectively. Reference numerals 27 to 30 are switching elements made of transistors, diodes, etc., which are turned on only when the respective signals are sent in synchronization with the respective signals.

As an initial condition, the resonance capacitor 5 is connected to the DC input power source 7.
The operation will be explained with reference to FIG. 2, assuming that the resonant capacitor 6 is charged to a voltage of 0 and the resonance capacitor 6 is discharged to a zero voltage. In this state 7.3, when the output power control signal S1 as shown in FIG. Main switch element l-resonant reactor 12-
The charging current to the resonance capacitor 6 flows through the primary winding of the main transformer 11 - the tank circuit 10, and at the same time the primary winding of the two main switch elements -1'l-resonant reactor +2--1) lance ll- The discharge current of the resonance capacitor 5 flows through the tank circuit 10. This current is a resonant current 11 that discharges the resonance capacitor 5 and charges the resonance capacitor 6. If the direction of the arrow shown in FIG.
The result is as shown in Figure (C). Drain-source voltage of switch element 1■1. Anode voltage of diode 14 (cathode grounded)■. .

The detected voltages V-, Vb, and Vc at detection points a, b, and c, and the detected current 1t of the current detector 21 are respectively shown in FIG.
Shown in (g). Also, for the reference voltage, (v, -V, -
VC) and a voltage waveform showing the calculation result.

The relationship with the voltage waveform showing the calculation result of (V, -VC) is shown in the second view (h). Next, at time t2, the voltage (V, -V,
-V, > falls to the reference voltage K, the control circuit 20 issues a voltage state detection signal S2 that attempts to turn on the main switch element 1.
Ignored due to prohibition of continuous firing of the main switch element. At time t:l, when the voltage of the resonance capacitor 5 reaches the voltage of the DC input power supply 7, the diode 3 becomes conductive at this moment, and the current 11 flowing through the resonance reactor 12 becomes Resonance reactor 12-ball transformer 11
flows through the primary winding of - tank circuit 10 - diode 3 - L switch element I. This current (1) is consumed by the load 16 via the diode 14.

The time becomes zero. Time L4 when this current 11 becomes zero
Then, an off signal S is applied to the ball switch element 1. At the time when the detected value of the current detector 21 becomes a zero current value from 5 negative to positive, a current state detection signal S4 that turns on the king switch 1 is generated, but at the same time within the same period Ignored due to IL between successive firings of the main switch element. When the half cycle of operation is completed and the output power control signal S'+ as shown in FIG. 2(b) is applied to the king switch element 2 at time t, the king switch element 2 turns on and resonates. Capacitor 5 charges and resonance capacitor 6 discharges.

The first-order I (cycle ends) with the same operation as described above.

In this case, at time L7, the voltage (Vb Vc) is
When the voltage falls to the reference voltage K, the voltage state detection signal S't that turns on the main switch element 2 is output to the control circuit 2.
0, but it is ignored due to the prohibition of continuous firing of the same main switch element within the same cycle. Also, current detection 2
Time t, when the detected value in S21 becomes the zero-voltage tIL value from positive to negative. Then, a current state detection signal S'a that turns on the main switch element 2 is generated, but in this case as well, it is ignored because continuous firing of the same main switch element within the same period is prohibited. In such a steady operating state, the operating frequency is automatically adjusted by repeating the above operation of detecting the output voltage and applying the output power control signals s, , s', to the main switch element 1.2. control to keep the output voltage constant. Also, as is clear from the above explanation, the output power control signals s, s'.

, voltage state detection signals s, , s', and current state detection signals s, , s', the priorities of the signals are such that the signal emitted first is given priority.

By the way, in such a steady state of operation.

For example, if a load fluctuation occurs and the load becomes light (output current decreases), it becomes necessary to lower the operating frequency, and the generation of the output power control signals St, S'+ is temporarily stopped. However, as explained above, in this embodiment,
In such a case, at time t2 when (vll-V, -VC) has fallen to the reference voltage K, voltage state detection signal S2 is applied to the main switch element l to turn on the main switch element l, and (VbVe ) falls to the reference voltage K
At 7.

Since the main switch element 1.2 is operated by applying the voltage state detection signal S''2 to the main switch knob 2 and turning on the main switch 1 switch 2, the output power control signal s,...
Even during a transient period in which s' does not occur, phase loss is prevented, a negative feedback state is maintained, and stable control is possible.

Here, K, which is a constant voltage value, is the voltage state detection signal s,
, s', is the value obtained by subtracting the value obtained by converting the output voltage into a linear example from the voltage applied to the main switching element 1.2 immediately before the main switching element 1.2 is turned on. , main switch element 1. When 2 is turned on, the potential must be such that a current flows, so it must be a positive value.

Further, within the range where seven oscillations can be sustained, the smaller the value, the closer the operating frequency is to the w-row resonance frequency of the tank circuit IO, which makes it possible to reduce the heavy load, which is desirable.

In normal transient fluctuations, the voltage state detection signal S
The oscillation is sustained by the operation of t, S's, and the output power control signals s, , s', eventually come into operation.
It is possible to return to a steady state of operation. However, 9, for example, from a heavy load to a light load (from a state where the output current is high to a state where the output current is low).

When there is a large load change, the amplitude voltage of the tank circuit 10 itself is small, so fa pressure (V, -V.

-Vc), the amplitude of the voltage (V, -Vゎ) is small.

There are cases where the voltage does not drop to the reference voltage, and in this case, the output power control signals S+, S'+ and the voltage state detection signal s2. s', both of which do not occur.

As is clear from FIG. 2, at times 11, 1, . . Then, the current state detection signal s4. is applied to the main switch element 1.2. s', and operates to turn on the main switch element 1.2. At this time, the vibration frequency of the tank circuit 10 decreases toward the parallel resonance frequency.

The operating frequency also decreases, and along with the decrease, the amplitude voltage of the tank circuit IO itself increases, and the voltage state detection signal St + S
'Z operates with priority over the output power control signals s, , s', and eventually the output power fi control signals S+, S'+ start operating, and the normal operating state is restored.

In this way, even during a transient period in which neither the output power control signals S+, S'+ nor the voltage state detection signals St, S'z occur, phase loss is prevented and the negative feedback state is maintained.
Stable control can be performed.

[Below] The second embodiment describes the case of a constant voltage regulator, but
Constant current control can also be implemented in the same way.

The third section is a jump for explaining another embodiment of the present invention. In the same figure, the resonance capacitor 5.6 is the first
It has a circuit configuration that also serves as the resonance capacitor 9 explained in the figure.

The input capacitors 31 and 32 divide the voltage of the DC input power supply 7. The method of controlling the series resonant converter of this embodiment is almost the same as that described in the embodiment of FIG. 1, and the same effects can be obtained.

FIG. 4 is a diagram for explaining another embodiment of the present invention. In the figure, diodes 33 and 34 are connected in parallel with the upper switching elements 1 and 2, respectively, and with polarities opposite to those of the upper switching elements 1 and 2. The 'tlIyrJ method of the series resonant converter of this embodiment is almost the same as that explained in the embodiment of Fig.
A similar effect can be obtained.

FIG. 5 is a diagram for explaining another embodiment of the present invention. This embodiment has a circuit configuration that is a combination of the embodiment shown in FIG. 3 and the embodiment shown in FIG. Regarding the control method of the series resonant converter of this embodiment, the first
This is almost the same as that described in the embodiment shown in the figure, and similar effects can be obtained.

[Effects of the Invention] As described above, the present invention includes a one-L switch element and a main transformer that are in the on state when the first or second main switch element is in the on state. a first resonant circuit; A second resonant circuit configured without a second main switch element and a ball transformer is provided, and the on/off of the first or second main switch element is controlled by an output power control signal. , in a control method of a series resonant converter that obtains a predetermined DC output, if the output power allocation signal described in 1-1 is not generated during transients such as load fluctuations and input fluctuations, the L2 first or second main switch element is When the value obtained by subtracting the value of the output voltage converted to the primary side from the voltage applied to both ends falls to the reference voltage (K), the voltage state detection signal causes the first or second main switch 1 to be activated. This is a control method for a series resonant converter characterized by turning on the converter to prevent phase loss and sustain seven oscillations. Since the present invention has such characteristics, even during a transient period in which no output power control signal is generated, phase loss can be prevented, a negative feedback state can be maintained, and stable control can be performed.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining one embodiment of the present invention, and FIGS. 3 to 5 are diagrams for explaining other embodiments of the present invention, respectively. l...First main switch 1 element 2...Second main switch element 3, 4.13. +4.33.34... Diode 5.6.9... Resonance capacitor 7... DC input power supply 8.12... Resonance reactor 10... Tank circuit 11... Main transformer 15. ...Output capacitor 15...Load +7.18.19...Voltage detector 20...Control circuit 21...Current detector 22...Drive circuit 23-26...Transformer 27-30 ...Switch elements 31, 32...Human power capacitor patent applicant Origin Electric Co., Ltd. Kishi 1 Mouth'! +4 figure

Claims (1)

[Claims] When the first or second main switch element is in the on state, a first resonant circuit configured to include the main switch element in the on state and the main transformer; a second resonant circuit configured without the second main switch element and the main transformer; In a method for controlling a series resonant converter that obtains a DC output of When the value obtained by subtracting the value obtained by converting the output voltage to the primary side from the current voltage drops to the reference voltage (K), the voltage state detection signal turns on the first or second main switch element and detects a phase loss. A method for controlling a series resonant converter, characterized by preventing oscillation and sustaining oscillation.