JP4284580B2 - Switching power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to improvement of control characteristics when a coupled inductor means for power factor improvement is introduced in a DC / DC converter type switching power supply of current mode control.
[0002]
[Prior art]
FIG. 3 is a circuit configuration diagram showing a flyback type switching power supply including a current mode control DC / DC converter.
Reference numeral 1 denotes an AC power source, and 2 denotes a full-wave rectifier circuit that rectifies an input from the AC power source. The output voltage Vi of this full-wave rectifier circuit is supplied to the smoothing capacitor 4 through the coupled inductor means 3 for power factor improvement.
[0003]
5 is a transformer means, N1 is the primary winding, N2 is the secondary winding. Reference numeral 6 denotes a switching element constituted by a MOS FET. The output voltage VB of the smoothing capacitor 4, the primary winding N1, the switching element 6 source and drain are connected in series, and the output voltage VB of the smoothing capacitor 4 It is configured to be applied to the primary winding N1 of the transformer means 5 via.
[0004]
The AC voltage generated in the secondary winding N2 of the transformer means 5 is converted to a DC output voltage VO through a rectifying / smoothing circuit including a diode 7 and a capacitor 8, and supplied to the load 9.
[0005]
A switching control circuit 10 receives a DC output voltage VO and a voltage signal Vs proportional to the current Id flowing through the switching element 6, compares the voltage related to VO with its own reference voltage, and amplifies the error. The switching control signal Vg is supplied to the gate of the switching element 6 so that the signal becomes equal to the peak value of Vs, and the switching duty of the switching element 6 is controlled. Reference numeral 11 denotes a switch current detection resistor inserted in the source circuit of the switching element 6 and generates a voltage signal Vs proportional to the current Id.
[0006]
In such a configuration, when the input voltage Vi applied to the smoothing capacitor 4 is an output obtained by full-wave rectification of an AC power supply, the current flowing to the smoothing capacitor 4 side in the half-cycle period of the full-wave rectification signal is short. A large pulse current results in a decrease in power factor and disturbance to the external environment.
[0007]
Therefore, the applicant as a technique for power factor correction, disclosed a coupled inductor means for inserting technique for power factor improvement between the primary winding rectifier circuit output and the transformer means Hei 11-37334 0.
[0008]
The element indicated by 3 in FIG. 3 is the coupled inductor means disclosed in the prior application. One ends of the first winding n1 and the second winding n2 of the coupled inductor means are connected in common and connected to the rectifier circuit output Vi, and the other end of the first winding n1 is connected to the transformer means 5 via the first diode 12. The primary winding N1 is connected to a tertiary winding N3 formed to extend. Furthermore, the other end of the second winding n2 is connected to the smoothing capacitor 4 via the second diode 13.
[0009]
Since the operation of the coupled inductor means is described in detail in the specification of the prior application, description thereof is omitted in the present application. FIG. 4 is an image diagram of the power factor improvement by introducing the coupled inductor means, and is represented by the sum of the current In1 of the first winding n1 and the current In2 of the second winding n2 during the half cycle period of the rectifier circuit output Vi. The average value of the input current is corrected from a large pulse signal to a smooth signal waveform, the conduction angle α is expanded, and the power factor is improved.
[0010]
5 and 6 show the waveforms of the respective parts during the conduction period and the non-conduction period of the input current, in which (A) shows the connection voltage VN3 between the first diode 12 and the tertiary winding N3 (B ) Is the input current In1 of the first winding n1 of the coupled inductor means, (C) is the input current In2 of the second winding n2 of the coupled inductor means, and (D) is the drain current Id of the switching element 6. (E) shows the current IN2 of the secondary winding N2 of the transformer means 5.
[0011]
Each waveform of (A) to (E) shows one cycle of the switching element 6 that is controlled to be opened and closed. When the period is T and the opening and closing duty is D, the switching element 6 is turned on in the first half DT and the second half ( 1-D) At T, the switching element 6 is off.
[0012]
The connection voltage VN3 between the first diode 12 and the tertiary winding N3 shown in FIG. 5 and FIG. 6A is VB (VB (V) when the voltage of the smoothing capacitor 4 is VB while the switching element 6 is on. 1−N3 / N1), and VB + (N3 / N2) VO when the switching element 6 is off.
[0013]
The input current In1 of the first winding n1 of the coupled inductor means shown in (B) rises to the peak value In1p with a constant gradient during the ON period of the input current in FIG. Becomes a triangular wave. When the switching element 6 is in the off period, the input current In2 of the second winding n2 of the coupled inductor means becomes a triangular wave that descends with a constant gradient from the peak value (n1 / n2) In1p toward zero. On the other hand, In1 and In2 are zero in the non-conduction period of the input current of FIG.
[0014]
[Problems to be solved by the invention]
Here, in the ON period of the switching element 6 in the conduction period of the input current shown in FIG. 5D, the peak value of the drain current Id is (N3 / N1) In1p than the input current Id ′ related to the original control. Only a large current. As shown in FIG. 5E, the output current IN2 during the OFF period of the switching element 6 is a triangular wave that drops from (N1 / N2) Id ′ to zero, and no error occurs.
[0015]
Thus, in the conduction period of the input current, since the drain current Id ′ larger than the input current In1p related to the original control flows, the switching element 6 flows. Therefore, when controlled in the current mode, the switch including the current that does not contribute to the output power In order to control the current, there is a problem that voltage fluctuation (commercial ripple) occurs in the DC output voltage VO in synchronization with the cycle of the AC power supply.
[0016]
An object of the present invention is to provide a switching power supply in which a DC / DC converter type switching power supply of current mode control eliminates the above-described problems when a coupled inductor means for power factor improvement is introduced.
[0017]
[Means for Solving the Problems]
In order to achieve such a problem, the feature of claim 1 of the present invention is that a rectifier circuit that rectifies an input from an AC power supply, a smoothing capacitor that smoothes the output of the rectifier circuit, and a The output voltage is received by the primary winding of the transformer means via the switching element, and the AC voltage generated in the secondary winding of the transformer means is converted to the DC output voltage via the rectifying and smoothing circuit, and the DC output A switching control circuit that controls opening and closing of the switching element so that an error-amplified signal is equal to a peak value of a current flowing through the switching element; in the switching power supply; and a coupled inductor means which is inserted between the primary winding, an auxiliary of the coupled inductor means Supplying a correction signal based on the voltage generated on line to the switching control circuit lies in that to correct the peak value of the current flowing through the switching element.
[0018]
Further, the present invention is characterized in that the coupled inductor means has one end of the first winding and the second winding connected in common and connected to the rectifier circuit output, and the other end of the first winding connected to the first winding. The other end of the second winding is connected to the smoothing capacitor via the second diode, and is connected to the tertiary winding formed by extending to the primary winding of the transformer means via the one diode. It is in the point.
[0019]
Further, the present invention is characterized in that a primary delay circuit comprising a series circuit of a resistor and a capacitor is connected to the auxiliary winding, and the correction signal is obtained via the primary delay circuit.
[0020]
In addition, the present invention is characterized in that it includes addition means for adding the correction signal and a voltage signal proportional to the current flowing through the switching element and supplying the correction signal to the switching control circuit.
[0021]
Features of the embodiments of the present invention, the addition means is in that is realized by the resistor means.
[0022]
Features of the embodiments of the present invention is that the switching element is constituted by a MOS-type FET.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing a flyback type switching power supply in which the present invention is applied to a current mode control DC / DC converter having a coupled inductor means for power factor improvement.
The same elements as those in the conventional circuit described with reference to FIG.
[0024]
A dotted line block 14 is a correction circuit which is a feature of the present invention. In this correction circuit, n3 is an auxiliary winding added to the coupled inductor means 3. The voltage induced in the winding is converted into a correction signal voltage -Ve through a first-order lag circuit composed of a series circuit of a resistor 15 and a capacitor 16.
[0025]
The resistors 17 and 18 constitute an adder circuit, and supply a signal (Vs−Ve) obtained by adding the voltage Vs proportional to the drain current Id of the switching element 6 and the correction signal voltage −Ve to the switching control circuit 10. This added signal corresponds to the apparent drain current Id corrected with −Ve.
[0026]
FIG. 2 is a waveform diagram of each part of the ON and OFF periods of the switching element in the conduction period. (A) shows the voltage Vn3 of the auxiliary winding n3, and (B) shows the first winding n1 of the coupled inductor means. The input current In1, (C) shows the correction signal voltage -Ve, and (D) shows the drain current Id of the switching element 6.
[0027]
The current of the n1 winding when the switching element 6 is in the on period (ton) is (Vi−Vn1) ton / Ln1, where the inductance of the n1 winding is L, whereby the voltage Vn3 of the auxiliary winding n3 is As shown in (A), when the output side voltage of the first winding of the coupled inductor means 3 is Vn1, and the output side voltage of the second winding is Vn2, the switching element 6 is a negative voltage ( Vi−Vn1) n3 / n1, and when the switching element 6 is off, the positive voltage (VB−Vn2) n3 / n2.
[0028]
The input current In1 of the first winding n1 of the coupled inductor means shown in (B) becomes a triangular wave that rises to a peak value In1p with a constant gradient and becomes zero while the switching element 6 is on. In1p is zero when the switching element 6 is off.
[0029]
The correction signal voltage -Ve of (C) is a signal obtained by obtaining the voltage Vn3 of (A) through a first-order lag circuit, and the switching element 6 increases from zero to a predetermined negative voltage during the ON period. Is a triangular wave signal that increases to a positive predetermined value during the off period.
[0030]
Here, by appropriately setting the time constant of the first-order lag circuit, the correction signal voltage −Ve approximates the waveform of the n1 winding current In1 when the switching element 6 shown in FIG. The voltage signal waveform can be reversed in polarity.
[0031]
Accordingly, a signal (Vs−Ve) obtained by adding the correction signal voltage −Ve to the detection signal voltage Vs of the drain current Id of the switching element 6 is guided to the switching control circuit 10 as an apparent drain current Id detection signal. As shown in (D), the peak value of Id during the ON period of the switching element 6 is the original control target current Id in which the error (N3 / N1) In1p explained in FIG. '.
[0032]
In the embodiment of the present invention, the simplest series circuit of a resistor and a capacitor is shown as the first-order lag circuit circuit, but the present invention is not limited to this, and an appropriate calculation means can be arbitrarily selected.
Further, although the flyback type is shown as the topology of the DC / DC converter, the present invention is not limited to this, and the present invention can be effectively applied to a switching power supply having a DC / DC converter having another topology. it can.
【The invention's effect】
As is apparent from the above description, according to the present invention, when a coupled inductor means for power factor improvement is introduced in a DC / DC converter type switching power supply of current mode control, the output power from the switch current. The value excluding the inductor current component that does not contribute to the current can be controlled in the current mode, and the output ripple voltage of the commercial frequency component can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing a flyback type switching power supply including a current mode control DC / DC converter to which the present invention is applied.
FIG. 2 is a waveform diagram of each part for explaining the operation of the present invention.
FIG. 3 is a circuit configuration diagram showing a conventional flyback switching power supply including a current mode control DC / DC converter.
FIG. 4 is an image diagram of power factor improvement by introducing a coupled inductor means.
FIG. 5 is a waveform diagram of each part during a conduction period of an input current.
FIG. 6 is a waveform diagram of each part during a non-conduction period of input current.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Rectifier circuit 3 Coupled inductor means 4 Smoothing capacitor 5 Transformer means 6 Switching element 7 Diode 8 Capacitor 9 Load 10 Switching control circuit 11 Switch current detection resistance 12 First diode 13 Second diode 14 Correction circuit 15 Resistance 16 Capacitor 17 Addition resistor 18 Addition resistor n1 Coupled inductor first winding n2 Coupled inductor second winding n3 Coupled inductor auxiliary winding

Claims (3)

A rectifier circuit for rectifying the input from the AC power source, a smoothing capacitor for smoothing the output of the rectifier circuit, and the output voltage of the smoothing capacitor is received by the primary winding of the transformer means via the switching element, and the transformer means 2 The AC voltage generated in the next winding is converted into a DC output voltage through a rectifying and smoothing circuit, and the DC output voltage is detected and compared with a reference voltage. In a switching power supply comprising a switching control circuit for controlling opening and closing of the switching element so as to be equal to a peak value, and a coupled inductor means inserted between the rectifier circuit output and a primary winding of a transformer means,
Supplying a correction signal based on the voltage generated in the auxiliary winding of the coupled inductor means to the switching control circuit, correcting the peak value of the current flowing through the switching element ;
The coupled inductor means has one end of a first winding and a second winding connected in common and connected to the output of the rectifier circuit, and the other end of the first winding is connected to the transformer means via a first diode. And the other end of the second winding is connected to the smoothing capacitor via a second diode.
Switching power supply you wherein a. 2. The switching power supply according to claim 1 , wherein a first-order lag circuit comprising a series circuit of a resistor and a capacitor is connected to the auxiliary winding, and the correction signal is obtained through the first-order lag circuit. 2. The switching power supply according to claim 1 , further comprising adding means for adding the correction signal and a voltage signal proportional to the current flowing through the switching element and supplying the correction signal to a switching control circuit.

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