KR20180065271A - DC/DC Converter circuit using synchronous rectifying switching regulator - Google Patents

Abstract

Disclosed is a DC/DC converter circuit of a synchronous rectifying switching regulator. The DC/DC converter circuit includes: a filter (1) for eliminating conductive noise of an input voltage; an overvoltage protection circuit (4) for detecting an overvoltage of the input voltage and suppressing the overvoltage; a PWM switching controller (6) for PWM switching; an overheat sensing circuit (8) for sensing overheating of the DC/DC converter circuit of the synchronous rectifying switching regulator; a current sensor (7) for sensing the overcurrent of a transformer; an FET (9) for a switching operation; a PWM control circuit (10) for controlling the FET for the switching operation; an LC filter (3) for smoothing an output voltage; and an overvoltage protection circuit (5) for detecting overvoltage of the output voltage and suppressing the overvoltage. A PWM controller and an overheat detector are provided in the DC/DC converter circuit of the synchronous rectifying switching regulator to prevent the DC/DC converter circuit of the synchronous rectifying switching regulator from being malfunctioned caused by external factors such as temperature and the like.

Description

[0001] The present invention relates to a DC / DC converter circuit of a synchronous rectification type switching regulator,

The present invention relates to a DC / DC converter circuit of a synchronous rectification type switching regulator. More specifically, the present invention relates to a DC / DC converter circuit circuit of a synchronous rectification type switching regulator having a thermal stability and an overvoltage protection function of an apparatus for converting a DC voltage into a DC voltage and reducing the influence of temperature.

With the development of the industry and the expansion of the spread of new and renewable energy, the large capacity DC / DC converter (DC power converter) has been actively studied from the viewpoint of small size and light weight, and is being used for broadcasting communication equipment, OA equipment, Power generators, low-voltage / high-current converters, or high-voltage converters in fields such as computers, ozone generators, and the like. In order to achieve high integration and high efficiency of the DC / DC converter technology, a soft switching method is used in which the switching point of the switch is made to be the zero voltage or the zero current of the switch and the switching loss and the switching stress can be reduced. Here, in order to implement the soft switching system, high-frequency resonance characteristics are introduced. In this case, since a resonant reactor and a resonant capacitor for resonance must exist, the cost is increased, which is disadvantageous for high power density.

In Korean Patent No. 10-1031282, the DC / DC converter includes a half-bridge switching unit, a transformer unit, a rectifying unit, and an output unit. The half-bridge switching unit supplies the input DC power to the transformer unit described below. More specifically, the half-bridge switching unit describes the supply of the input DC power so that current flows alternately in both directions of the input side coil of the transformer unit. Also, the half bridge switching unit is described in Korean Patent Registration No. 10-1031278 The DC / DC converter includes a full-bridge switching unit, a transformer unit, a rectifying unit, and an output unit. The full-bridge switching unit supplies the input DC power to the transformer unit. More specifically, the full-bridge switching unit supplies the input DC power so that current flows alternately in both directions of the input coil of the transformer unit. The full-bridge switching unit includes a first switch and a second switch connected in parallel to the input DC power supply and connected in series to each other, a third switch connected in parallel to the input DC power supply and connected in series to each other, And the end of the first switch and the second switch and the end of the third switch and the fourth switch (114) are connected to both ends of the input side coil of the transformer unit, respectively. That is, the full-bridge switching unit bridges the input DC power source and the transformer unit. In addition, the first switch and the fourth switch are simultaneously 'on', and the second switch and the third switch are simultaneously 'on' so as to be alternately closed loop with the input side coil. That is, the first switch and the fourth switch, or the second switch and the third switch are alternately turned on, and the current flows to the input side coil in different directions.

United States Patent Application Publication No. US2008 / 0030178A European Patent Application Publication No. EP 2 110 935 A2 Korean Patent No. 10-1031282 Korean Patent No. 10-1031278

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC / DC converter circuit of a synchronous rectification type switching regulator which includes a PWM controller, an overheat sensor, and the like, There is a problem that the DC / DC converter circuit of the rectifying type switching regulator malfunctions. Therefore, there is a technical problem to solve such a problem.

In order to solve these technical problems, the present invention attempts to solve such a problem by controlling a DC / DC converter circuit of a synchronous rectification type switching regulator by providing a PWM controller and an overheat detector.

Therefore, by providing the PWM controller and the overheat detector according to the present invention, the DC / DC converter circuit of the synchronous rectification type switching regulator is prevented from malfunctioning due to external factors such as overheating.

1 is a DC / DC converter circuit diagram of a conventional synchronous rectification type switching regulator.
2 is a block diagram of a DC / DC converter circuit of a synchronous rectification type switching regulator according to the present invention.
3 is an application example of the PWM controller according to the present invention.
4 is an overheat sensing circuit diagram according to the present invention
5 is a circuit diagram of a PWM controller according to the present invention.
6 is an external circuit diagram for determining the PWM frequency in the PWM controller.
7 is a waveform in which the PWM waveform of the PWM controller is distorted according to the temperature.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention. Hereinafter, the present invention will be described in detail with reference to the drawings.

1, the DC / DC converter circuit of the synchronous rectification type switching regulator includes a half bridge switching unit 11, a transformer unit 12, a rectifying unit 13, and an output unit 14. The half-bridge switching unit 11 supplies the input DC power supply Vin to the transformer unit 12 to be described below. More specifically, the half-bridge switching unit 11 supplies the input DC power supply Vin so that current flows alternately in both directions of the input side coil 121 of the transformer unit 12. The half bridge switching unit 11 includes a first input capacitor 111 connected in parallel to the input DC power supply Vin and connected in series to each other for dividing and storing the input DC power supply Vin, And a second input capacitor 112 and a first input capacitor 111 and a second input capacitor 112. The first input capacitor 111 and the second input capacitor 112 are connected in series, A switch 113 and a second switch 114. [

The first switch 113 is connected to the first input capacitor 111 and the input coil 121 in a closed loop when the first switch 113 is turned on, The second input capacitor 112 and the input coil 121 form another closed loop. That is, the switches 113 and 114 are alternately 'on' so that current flows in different directions to the input side coil. The transformer unit 12 boosts the power stored in each of the input capacitors 111 and 112 and includes an input side coil 121 and an output side coil 122 having a winding ratio a.

In addition, the transformer unit 12 serves to insulate the input DC power supply Vin from the output DC power supply Vout described below. Also, in the embodiment of the present invention, the transformer unit 12 is provided as a high-frequency transformer. The rectifying unit 13 is connected to the output side coil 122 of the transformer unit 12 and rectifies the step-up power supplied from the transformer unit 12. The rectifying unit 13 includes a first diode 131 having an anode connected to one end of the output side coil 122 and a second diode 132 having a cathode connected to one end of the output side coil. The output unit 14 charges the step-up power source rectified by the rectifying unit 13 to form an output DC power source. The output unit 14 has one end connected to the cathode of the first diode 131 and the other end connected to the output side coil 122 And a second output capacitor 142 having a first output capacitor 141 connected to the other end and a second output capacitor 142 having one end connected to the other end of the first diode 131 and the other end connected to the anode of the second diode 132 . That is, the rectifying unit 13 and the output unit 14 output the boosted power outputted from the transformer unit 12 and output the DC / DC converter 100 according to the embodiment of the present invention, There are advantageous advantages. An LC filter unit 15 for smoothing the output DC power may be connected to the output unit 14. One end of the LC filter unit 15 is connected to one end of the first output capacitor 141 And a smoothing capacitor 152 having a smoothing inductor 151 and one end connected to the smoothing inductor 151 and the other end connected to the other end of the second output capacitor. Also, since the smoothing capacitor 152 smoothes the output DC power together with the output capacitors 141 and 142, the capacity is reduced. First, the first switch 113 is turned on and the input DC power source Vin, the first switch 113, the input side coil 121, And the second input capacitor 112 form a closed loop, and the input DC power supply Vin is divided and charged to the first input capacitor 111. [

Next, a current flows in one direction to the input side coil 121 by a power source charged in the first input capacitor 111.

However, it is needless to say that the second switch 114 is first turned on so that the second input capacitor 112 can be charged first. Next, a current is induced in the output side coil 122, and the output side coil 122, the first diode 131, and the first output capacitor 141 form a closed loop, The capacitor 141 charges the step-up power supply stepped up by the transformer unit 12. At this time, the DC / DC converter 100 according to an embodiment of the present invention resonates by the leakage reactance Ll of the transformer unit 12 and the capacitance Cs of the first output capacitor 141 , A series resonance equivalent circuit as shown in Fig.

In addition, the value of the leakage reactance Ll can be calculated by the following equation (1)

The leakage reactance Ll2 of the output side coil 122 may be reduced to the input side by the sum of the sum of the reactance Ll1 and the leakage reactance Ll2 of the output side coil 122. [

수학식(1)

Equation (1)

Here, a is the winding ratio of the transformer unit 12.

Also, the capacitance Cs of the first output capacitor 141 may be expressed by the following equation (2) To the input side of the transformer section (12).

수학식(2)

Equation (2)

수학식(3)Here, a is the winding ratio of the transformer unit 12. In the series resonance equivalent circuit, the resonance frequency fo is expressed by the following equation (3).

Equation (3)

If the resonance frequency fo is larger than the switching frequency of the first switch 113, the inductor current Il becomes discontinuous, and the instant the inductor current < RTI ID = 0.0 > Il starts at 0 [A] and becomes zero current switching (ZCS) operation. When the resonance ends before the first switch 113 is turned off and the first switch 113 is turned on The current is 0 [A], so that the first switch 113 is soft-switched when both the 'on' and the 'off' are selected, so that there is no switching loss.

In addition, since soft switching can be implemented without providing a separate resonant reactor, the addition of passive elements can be reduced. Next, the first switch 113 is turned off, the second switch 114 is turned on, and the input DC power source Vin, the second switch 114, the input coil 121, And the first input capacitor 111 form one closed loop and the input DC power supply Vin is charged and charged to the second input capacitor 112. The second input capacitor 112 The current flows to the input side coil 121 in the other direction. Next, a current is induced in the output side coil 121, and the output side coil 121, the second diode 132, and the second output side capacitor 142 form a closed loop, The capacitor 142 charges the step-up power supply stepped up by the transformer unit 12. In addition, the operation of switching the zero current of the second switch 114 is the same as the operation of switching the zero current of the first switch 113, so the description is omitted. Therefore, the switches 113 and 114 are all capable of soft switching.

However, the DC / DC converter circuit of such a synchronous rectification type switching regulator has a phenomenon that the PWM frequency is distorted as shown in Fig. 7 due to external factors such as overheating, and there is no input / output overvoltage protector or overheat detection circuit, Therefore, a circuit is constructed as shown in Fig. 2 to solve this problem.

2, when the input voltage is inputted, the voltage is passed through the filter 1, which is removed by the input OVP 4, and the overvoltage is removed by the PWM controller, And the voltage is boosted through the transformer 2, or the voltage is lowered.

The signal switched by the PWM frequency is switched by the FET device, which also senses the current of the drain former 2 and inputs the PWM control signal. The signal boosted by the transformer is filtered by an LC filter, which is a low-pass filter, to become an output voltage. An overvoltage protector (5) is provided at the output voltage terminal to suppress the occurrence of an overvoltage.

The PWM controller 6 is a PWM input frequency generating circuit for dividing the input voltage, and the PWM controller 6 is connected to the overheat protection circuit 8.

The overheat protection circuit 8 detects overheating of the DC / DC converter circuit of the synchronous rectification type switching regulator and transmits an overheat detection signal to the control unit. In addition, the transformer 2 amplifies or drops the input voltage, and the voltage is usually determined in proportion to the ratio of the number of windings of the primary side and the secondary side of the transformer 2. In order to measure the current of the transformer 2, a current sensor 7 is provided. In general, a current sensor using a Hall effect and a current sensor using a current loop are used as a current sensor. If the current value of the current detector is more than a certain voltage, the control circuit senses it and sends an overcurrent message and cut off the power if necessary. The switching device of AC voltage in the DC / DC converter circuit of the synchronous rectification type switching regulator usually uses the FET and applies the voltage to the gate terminal of the FET to turn on and off the FET.

The LC filter connected to the output voltage stage is a low-pass filter and is used to smooth the voltage. The PWM controller is capable of remote monitoring by transmitting communication signals remotely.

The PWM controller circuit is shown in Fig. 3, and the overheat protection circuit is shown in Fig. Fig. 5 is a PWM controller circuit, in which the PWM output frequency is determined by R3, C2, C34 in Fig. When the temperature of the PWM output frequency increases due to overheating of the DC / DC converter, frequency distortion occurs as shown in FIG. To prevent this, the stability of the capacitance value is increased by changing the capacitance value of the conventional Tantalum capacitor to the stable MLCC capacitor even when the temperature rises, thereby preventing the frequency distortion according to the temperature.

1 filter
2 transformer
3 LC filter
4 Input Overvoltage Protector (Input OVP)
5 Output Overvoltage Protector (Output OVP)
6 PWM controller
7 current detector
8 Overheat protection circuit
9 FET circuit
10 PWM control circuit
11 half-bridge switching section
12 Transformer section
13 rectification part
14 Output
15 Low frequency filter (LC filter)

Claims (4)

A DC / DC converter circuit of a synchronous rectification type switching regulator which converts an input voltage inputted to an input terminal into a predetermined constant voltage and outputs the constant voltage,
A filter (1) for eliminating conductive noise of an input voltage;
An overvoltage protection circuit (4) for detecting an overvoltage of the input voltage and suppressing it;
A PWM switching controller (6) for PWM switching;
An overheat sensing circuit (8) for sensing overheating of the DC / DC converter circuit of the synchronous rectification type switching regulator;
A current sensor (7) for sensing the overcurrent of the transformer;
FET 9 for switching;
A PWM control circuit (10) for controlling the FET for switching;
An LC filter (3) for smoothing an output voltage;
And an overvoltage protection circuit (5) for detecting an overvoltage of the output voltage and suppressing the overvoltage of the output voltage. The DC / DC converter circuit of the synchronous rectification type switching regulator
Claim 1
Wherein the PWM control circuit (10) has a frequency determined by a resistor (R3) and a capacitor (C2) connected to the outside of the DC / DC converter circuit (10) of the synchronous rectification type switching regulator
Claim 1
The PWM control circuit 10 uses the second and fourth terminals in the following drawing and has a circuit as follows. A capacitor c4, a capacitor C3 and a resistor R4 And the capacitor C2 and the capacitor C34 are connected in parallel as shown in FIG. 6, and the resistor R3, the resistor R26, R66, R32, R27, R45 and R24 are connected, The DC / DC converter circuit of the synchronous rectification type switching regulator
The method of claim 2,
DC converter circuit of the synchronous rectification type switching regulator, wherein the resistor R3 of the PWM controller is 47k ohms, and the capacitors C2, C3, C4, and C34 are MLCC capacitors.

Images