JP2000197360A - Ringing choke converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance efficiency under minimum load by employing a ringing choke converter connected with a delay circuit for prolonging the off time of an inverter toward minimum load as a transformer having an uneven core gap. SOLUTION: A ringing choke converter comprises a transformer 2 in which efficiency under minimum load is enhanced by partially decreasing the core gap thereby making gentle the gradient of current flowing through an inverter 6 under minimum load. Furthermore, a circuit 15 for delaying the turn on time of the inverter 6 as the load current decreases, e.g. a ringing choke converter, is connected with a winding 4 for driving the inverter 6. Since the off time of the inverter 6 is prolonged, switching loss ΔP1 per unit time is reduced and the efficiency can be enhanced significantly under minimum load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ringing choke converter utilizing a back electromotive force generated in an output winding 5 when an inverter 6 is turned off. It is intended to save energy by minimizing the input power during standby.

[0002]

2. Description of the Related Art FIG. 3 shows a transformer in which a conventional core is provided with a uniform gap. The inductance characteristic with respect to current is flat as shown in FIG. Since the slope of the current flowing through the inverter 6 is constant, the oscillation frequency of the ringing choke converter increases as the load approaches the minimum load, and the switching loss per time at the minimum load increases, thereby deteriorating the efficiency. FIG. 5 shows a conventional transformer having a structure in which the core gap is made unequal, a part is narrowed, and the other part is widened. The characteristic of the inductance with respect to the current is as shown in FIG. When the current is small, the inductance is large, and when the current is large, the inductance is small. Therefore, the gradient of the current flowing through the inverter 6 at the minimum load is smaller than the gradient of the current at the maximum load. Therefore, the efficiency at the minimum load is improved by the decrease in the slope.
Used in conventional ringing choke converters,
When the output current of the circuit is small, the oscillation frequency increases, and the ratio of the switching loss of the inverter 6 to the time increases, so that the degree of improvement in efficiency at the minimum load is low.

[0003]

As described above, when the gap of the transformer core of the ringing choke converter is as shown in the conventional example of FIG. 3, the gradient of the current of the inverter 6 at the minimum load cannot be reduced. , FIG. 2
When used in the conventional ringing converter, the efficiency at the minimum load is poor as in the conventional example 1 of the experimental data in FIG. When the gap of the transformer core is partially narrowed as shown in FIG. 5, the ringing choke converter has a small gradient of the current of the inverter 6 at the time of the minimum load.
Although the efficiency at the minimum load can be improved as in the conventional example 2 of the experimental data of FIG. 2, if the conventional ringing choke converter of FIG. .

[0004]

The present invention solves the above-mentioned problems. As shown in FIG. 5, the gap of the transformer core is partially narrowed as shown in FIG.
A transformer whose current gradient is reduced to improve the efficiency at the minimum load is used, and the time during which the inverter 6 is turned on is delayed as the load current decreases as in the ringing choke converter of FIG. By connecting the delay circuit 15 to the winding 4 driving the inverter 6, the switching loss ΔP per time of the inverter 6 at the time of the minimum load is reduced, and the efficiency at the time of the minimum load is greatly improved. . That is, a transformer having a core having an unequal gap width and a delay circuit 15 connected to the winding 4 for driving the inverter 6 and delaying the ON time of the inverter 6 in accordance with a decrease in the load current are provided. A ringing choke converter characterized by the following.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A winding 4 for driving an inverter 6
Is connected to the delay circuit 15. The transformer having a core having an unequal gap width reduces the current gradient of the inverter 6 and the switching loss ΔP ₁ when the inverter 6 is turned on. Is extended, the switching loss ΔP per time is further reduced, so that the efficiency at the minimum load can be greatly increased.

[0006]

FIG. 7 shows the temporal change of the current and the voltage when the inverter 6 connected to the inductance of the winding 3 of the transformer is turned on, as shown in FIG. 7. The larger the inductance, the smaller the gradient θ of the current. Furthermore, switching loss [Delta] P ₁ at the time of ON of the inverter 6 is represented by the number 1, as θ becomes small inductance is large, switching loss [Delta] P ₁ at the time on the inverter 6 can be seen that smaller.

[0007]

ΔP ₁ = θ × i (t) × V (t) where θ: slope of current i (t): equation representing current V (t): equation representing voltage

In addition, when the inverter 6 is turned on /
When the off-time (T) is lengthened and the oscillation frequency (f) is lowered, the switching loss ΔP per unit time of the inverter 6 is also reduced, and the relationship is expressed by Expression 2. This ΔP and T
The relation with (= 1 / f) is 3 as shown in FIG. 8, and when T is increased, the effect of Equation 1 and the effect of Equation 2 are combined.
It can be seen that the efficiency at minimum load of the present invention is greatly improved.

[0009]

(Equation 2)

The results of an experiment using the transformer of FIG. 5 for the ringing choke converter of FIG. 1 of the present invention are compared with those of the ringing converter of FIG. 2 using the transformer of FIG. 5 or FIG. Shown in experimental data. In FIG. 9, the efficiency at an output power of 2.1 kW is compared as shown in Table 1.

[0011]

[Table 1]

As a result, the efficiency of the embodiment in which the core of the transformer of FIG. 5 is used for the ringing choke converter of FIG. 1 is higher than that of the conventional example, and the transformer and the delay circuit having the cores with unequal gap widths And are connected in series,
It has been found that the efficiency at minimum load is greatly improved by the present invention.

[0013]

The present invention minimizes the use of a transformer having an unequal core gap in a ringing choke converter to which a delay circuit 15 is connected so that the off time of the inverter 6 becomes longer as the minimum load is approached. The efficiency under load can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a basic circuit diagram of a ringing choke converter according to the present invention.

FIG. 2 is a basic circuit diagram of a conventional ringing choke converter.

FIG. 3 is a cross-sectional view of a transformer core having a uniform gap structure.

FIG. 4 is a current-inductance characteristic of the transformer of FIG. 3;

5 is a cross-sectional view of a transformer core used in the ringing choke converter of FIG. 1 according to the present invention and having a structure in which gaps are made unequal.

FIG. 6 is a graph showing current versus inductance characteristics of the transformer of FIG.

FIG. 7 is a diagram showing a relationship between a difference in inductance between a current and a voltage when the inverter is turned on.

FIG. 8 shows the switching loss of the inverter 6 and T (= 1 /
It is a relation figure with f).

FIG. 9 is an experimental result of output power versus efficiency.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 12 Electrolytic capacitor 2 Transformer 3, 4, 5 Winding 6 Inverter 7 Transistor 8 Control circuit 9 Resistor 10 Capacitor 11 Diode 13 Output voltage error detection circuit 14 Photocoupler 15 Delay circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H730 AA14 AS01 BB43 BB52 DD04 DD26 EE02 EE07 FD01 FF19 FG04 FG07 FG22 ZZ16

Claims (1)

[Claims] 1. A transformer having a core having an unequal gap width and a winding (4) for driving an inverter (6), and delays an on-time of the inverter (6) according to a decrease in load current. A ringing choke converter comprising a delay circuit (15).