JPH11178319A - Gate signal control method for power converter with auxiliary resonance commutation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain simple and positive zero voltage switch by igniting a main switching element in such a condition that the output current of a current transformer with a primary winding connected is a prescribed value or lower after a bidirectional auxiliary switching element is turned on, and peak resonance current of a resonant capacitor and a resonance reactor is elapsed. SOLUTION: The detection signal of a current transformer CT is detected by two resistors R1, R2, and zero current is detected by comparators COMP1, 2. A main switching element is on-gated by conducting synchronization for control signals SG1, 2 controlled by a CPU with the signal of the comparator and D flip-flop DFF1, 2, that is, by conducting synchronization with respective last transition signals of the COMP1, 2 and DFF1, 2 respectively, a GS1 or an SG2 is outputted, which corresponds to any one on-gate signal of the main switching elements. An auxiliary switch is turned on when the input signal SG1 is at an H-level, and another auxiliary switch is turned on when the SG2 signal is at the H-level. It is thus possible to prevent an unnecessary gate signal from entering the main switching element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary resonance transformer comprising a series circuit of a bidirectional auxiliary switch and a resonance reactor between a connection point of a main switch element connected in series and a connection point of a voltage dividing smoothing capacitor connected in series. The present invention relates to a gate signal control method for a power converter with a flow circuit.

[0002]

2. Description of the Related Art A previously filed Japanese Patent Application Laid-Open No. 7-337022
As described in the above, William McMu of the United States
The circuit according to the rray is a method that can be practically used as a large-capacity power converter, and the present invention relates to an improvement thereof. Hereinafter, the related art will be described with reference to the drawings. FIG. 5 is a conventional circuit diagram of a power conversion device using an auxiliary resonance commutation circuit, where E is a DC power supply, CD1 and CD2 are series-connected voltage-smoothing capacitors for dividing the DC power supply, and S1 and S2.
S2 is a main switch element, D1 and D2 are main switch elements S
1 and S2 are antiparallel diodes, C1 and C2 are resonance capacitors connected in parallel to the main switch elements S1 and S2, L is a resonance reactor, and SA1 and SA2 are auxiliary switch elements forming a bidirectional switch. In FIG. 5, Vc denotes a voltage across the resonance capacitor, Ir denotes a current flowing through the resonance reactor, and Io denotes a load current.

A situation in which the load current Io commutates from the state flowing through the diode D2 to the main switch element S1 will be described below. Note that E is a DC power supply voltage, and each current and voltage is positive in the direction of the arrow. FIG. 6 shows waveforms during the commutation operation of the voltage Vc of the resonance capacitor C1 and the current Ir of the resonance reactor L. When the bidirectional auxiliary switch element SA1 is at time t
By turning on at 0, the voltage divided by the voltage dividing and smoothing capacitor connected to the DC power supply is applied to both ends of the resonance reactor L, and the current flowing through the resonance reactor L increases linearly. At time t1 when this current becomes equal to the load current Io, the circulating current flowing through the diode D2 becomes zero, and the diode D2 is turned off. When the diode D2 is turned off, the current flowing in the resonance reactor L flows to the resonance capacitors C1 and C2, and the resonance operation by the resonance capacitors C1 and C2 and the resonance reactor L starts. At time t2 when the voltage Vc of the resonance capacitor C1 becomes zero, the main switch element S1 is turned on. This is zero voltage switching, which is one of the features of this circuit.

[0004]

However, the time from turning on the auxiliary switch element SA1 to turning on the main switch element S1 varies depending on the load current Io and the voltage of the DC power supply E. Since there are elements that change with temperature, such as the reverse recovery time of the antiparallel diode, the time during which this voltage Vc becomes zero cannot be fixed. When the time is fixed, the voltage Vc is not always zero when the main switch element is turned on, so that zero-voltage switching cannot be achieved, causing problems such as an increase in element loss and an increase in EMI noise. Conventionally, knowing that the element loss increases, the method from turning on the auxiliary switch element to turning on the main switch element is fixed, or the time is estimated from the magnitude of the load current and DC voltage. Had been taken.

A method of detecting and controlling the resonance capacitor voltage Vc in order to achieve zero voltage switching is also conceivable, but it is extremely difficult to detect the voltage Vc of the resonance capacitor particularly in a high-voltage circuit, resulting in safety and reliability. Problems arise.
Further, when estimating the switching timing, it is not possible to cope with an element that changes with temperature, such as a reverse recovery time of an anti-parallel diode of a main switch element, and complicated control such as many sensors and a computer capable of high-speed operation is performed. Requires a circuit. In particular, since the commutation period corresponds to the dead time of an ordinary inverter, it is necessary to control the commutation period at a high speed of about several microseconds, and it has been practically difficult to control the zero voltage switching. The present invention has been made to solve such a problem.

[0006]

SUMMARY OF THE INVENTION The present invention provides a DC power supply, a series-connected body comprising two sets of main switch elements connected in parallel to the DC power supply and having an antiparallel diode and a resonance capacitor in parallel. A voltage dividing / smoothing capacitor for dividing the voltage into two, an auxiliary resonance commutation circuit having one end connected to a voltage dividing point of the voltage dividing / smoothing capacitor and comprising a series circuit of a bidirectional auxiliary switch element and a resonance reactor; A current transformer having a primary winding connected between the other end of the resonant commutation circuit and an intermediate point of the series-connected body, at a connection point between the primary winding of the current transformer and the auxiliary resonance commutation circuit; In a power conversion device including a load having one end connected thereto, after the auxiliary switch element is turned on, after a peak value of a resonance current due to the resonance capacitor and the resonance reactor has passed, and the output current of the current transformer is a predetermined current, It realizes the zero voltage switching by firing the main switching element at a value less state.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram of a power converter with an auxiliary resonance commutation circuit according to the present invention, wherein CT is a current transformer,
GA1 and GA2 indicate the gate circuits of the main switch elements, GAA1 and GAA2 indicate the gate circuits of the auxiliary switch elements, and Is indicates the current flowing through the current transformer.
Note that the portions denoted by the same reference numerals as those in FIG. 5 have the same function and the same configuration.

FIG. 3 is a conceptual diagram of the main circuit element firing timing control circuit in FIG. 1, where R1 and R2 are resistors, CO
MP1 and COMP2 are comparators, DFF1 and DFF
2 is a D flip-flop. Control signals SG1, SG
Reference numeral 2 denotes a signal controlled by a CPU or the like, which gives a condition for turning on S1 when SG1 is at level H, and gives a signal for turning off S1 at level L. Similarly, SG2 is at level H
The condition for turning on S2 is given by
Off signal command.

That is, the detection signal of the current transformer CT is detected by the resistors R1 and R2,
Zero current is detected by COMP2. After that, the control signal SG
1 and SG2, the detection signals of the comparator are synchronized with D flip-flops DFF1 and DFF2, and an on-gate is output to the main switch element. Specifically, COM
The falling edge of the output signal SCOMP2 of P2 and CO
The falling of the output signal SCOMP1 of MP1 synchronizes with the D flip-flops DFF1 and DFF2, respectively, and outputs GS1 or GS2 corresponding to the on-gate signal of the main switch element S1 or S2. Since the input signal SG1 is simultaneously supplied to the gate circuit GAA1 of the auxiliary switch element SA1, the auxiliary switch element SA1 is turned on when the SG1 signal goes to level H. Similarly, the input signal SG2 is simultaneously input to the auxiliary switch element SA1. Element SA2
When the SG2 signal goes to level H, the auxiliary switch element SA2 is turned on.

FIG. 2 shows the current / voltage waveforms of each part shown in FIGS. 1 and 3 and the signal waveforms of each part of the main circuit element firing timing control circuit for each direction of load current and commutation direction. In the figure, the S1 gate signal is a gate signal to the main switch element S1 in FIG. 1, the S2 gate signal is a gate signal to the main switch element S2 in FIG. 1, and the SA1 gate signal is a gate to the auxiliary switch element SA1 in FIG. Signal and SA2 gate signal are the main switch element S in FIG.
This is a gate signal to A2. These four gate signals are on-gate signals at level H and off-gate signals at level L.

State 1 in FIG. 2 shows a state when the auxiliary switch element SA1 is turned on at the same timing as in FIG. 6, that is, when the anti-parallel diode D2 is turned on. At which time the current transformer current Is reaches 0 A, and therefore Vc = 0 V
In S2, the S1 gate signal goes high in synchronization with the fall of SCOMP2, and the zero voltage switching of the main switch element S1 is performed. Similarly, state 4 shows a state in which the auxiliary switching element SA2 is turned on while the anti-parallel diode D1 is on, and after the resonance current reaches the maximum value and the current transformer current Is Is 0A,
Therefore, at time t2 when Vc = 0V, SCOMP
In synchronization with the fall of 1, the S2 gate signal goes to level H, and the zero voltage switching of the main switch element S2 is performed.

In the above description, each circuit element is an ideal case and may actually have a slight voltage due to circuit loss. In any case, the resonance capacitor is set at time t2 when the current Is becomes zero. The voltage Vc of C1 becomes a minimum value.
That is, utilizing the complementarity of the voltage Vc and the current Is, the current Ic
s is sensed to control the on-gate timing of the main switch element. According to the embodiment in which the main circuit element firing timing control circuit is configured as described above, the main switch elements S1 and S2 can be almost reliably set even if the load current Io changes and the load current or the DC power supply changes. Can be switched at zero voltage.

By configuring the main circuit element firing timing control circuit as shown in FIG. 3, when the load current flows to the diode D2 in the state 2 of FIG. 2, the main switch element S2
In addition, in state 3, control can be performed so that a gate signal is not output to the main switch element S1, so that unnecessary gate signals to the main switch element can be prevented. FIG. 4 shows a current waveform of the current Is and a time chart of each part of the main switch element firing timing control circuit when the load current in the state 2 and the state 3 in FIG. 2 is small. In FIG. 4, even when the current Is becomes zero at the time point 3 when the load current reverses the polarity, the comparator COMP2 in the state 2 changes from H to L in the state 2, and the signals GS2 and GS2 respectively.
Since GS1 becomes high level, the main switch element can be turned on.

According to the present invention, by obtaining a signal transformed to the secondary winding by using the current transformer, the insulation from the main circuit is easily performed and the propagation of the noise is small, so that the primary current waveform is formed. A faithful secondary current can be safely extracted, and furthermore, control is performed by detecting zero current, so that it is hardly affected by circuit drift due to temperature and the like, so that zero voltage switching control becomes easy. Zero voltage switching allows for a reduction in element loss and EMI noise of the main switch element. Further, since the load current is also detected at the same time, the anti-parallel diode of one of the main switch elements also has the effect of preventing unnecessary pulse signals during circulation.

[0015]

As is apparent from the above description, the present invention has the following advantages. That is, simple and reliable zero-voltage switching can be realized by a current transformer and a simple control circuit for current detection, and the loss of the main switch element is reduced.
I noise can be reduced. Also, unnecessary gate signals to the main switch element can be prevented. The control circuit shown in the embodiment is conceptual only, and the present invention relates to a power converter using an auxiliary resonance commutation circuit, a transformer provided between a connection point where the main switch elements are connected in series and an output terminal. The present invention relates to a gate control method for controlling a main switch element when a current flowing through a current transformer becomes zero during a commutation period.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a main part of a power conversion circuit and an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG. 1 and a timing chart of a control circuit.

FIG. 3 is a circuit diagram showing a main configuration of a main circuit firing timing element control circuit.

FIG. 4 is a timing chart of a control circuit and waveforms for explaining the operation of FIG. 1;

FIG. 5 is a circuit diagram showing a basic circuit of a power converter having an auxiliary resonance commutation circuit.

FIG. 6 is a waveform chart for explaining the operation of the circuit in FIG. 5;

[Explanation of symbols]

E DC power supply CD1, CD2 Voltage dividing smoothing capacitor S1, S2 Main switch element D1, D2 Anti-parallel diode C1, C2 Resonant capacitor L Resonant reactor SA1, SA2 Auxiliary switch element CT Current transformer Vc Resonant capacitor voltage Ir Resonant reactor current Io Load Current Is Current transformer current GA1, GA2 Main switch element gate circuit GAA1, GAA2 Auxiliary switch element gate circuit SG1 S1 gate signal command (G
AA1 input signal) SG2 S2 gate signal command (G
AA2 input signal) SCOMP1, SCOMP2 Comparator output signal GS1, GS2 Firing timing control circuit output signal R1, R2 Resistor COMP1, COMP2 Comparator DFF1, DFF2 D flip-flop

Claims (1)

[Claims] 1. A DC power supply, connected in parallel to the DC power supply,
A series connection body composed of two sets of main switch elements each having an anti-parallel diode and a resonance capacitor in parallel, a voltage division smoothing capacitor for dividing the voltage of the DC power supply into two, and one end at a voltage division point of the voltage division smoothing capacitor. Is connected, an auxiliary resonance commutation circuit comprising a series circuit of a bidirectional auxiliary switch element and a resonance reactor, and a primary winding is provided between another end of the auxiliary resonance commutation circuit and an intermediate point of the series connection body. In the power converter including a current transformer connected, a primary winding of the current transformer, and a load having one end connected to a connection point of the auxiliary resonance commutation circuit, after the auxiliary switch element conducts, the resonance capacitor and the An auxiliary resonance commutation circuit characterized in that the main switch element is fired after a peak value of a resonance current by the resonance reactor has passed and in a state where the current transformer output current is equal to or less than a predetermined current value. Gate signal control method with the power converter.