KR19990058752A - Switching Control Circuit of Step-up Converter for Low Loss Soft Switching Power Factor Control - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching control circuit of a boost converter for low loss type soft switching power factor control. Conventionally, a product of a voltage and a current generated when a switching element is turned on / off is a switching loss that occurs in each element. The loss of the switching elements and diodes is greatly increased due to the reverse recovery characteristics of the diode during switching, and the efficiency is considerably lowered. In order to dissipate these losses, the use of a large heat sink and a large There is a problem of using a fan of air volume. Therefore, in the present invention, the duty signal determiner 58 changes the duty of the frequency based on the signal output from the power factor controller 57 for controlling each switch of the boost converter, and the output of the duty signal determiner 58. An oscillator 59 for outputting a frequency according to the oscillation unit 59, a switching cycle variable unit 61 for varying a switching cycle by receiving an output signal of the oscillator 59, the oscillator 59 and a switching cycle variable unit 61. Switching cycle selector 60 for determining a drive cycle for driving the switching device by using the output waveform of the; and a switching driver for driving the switching device by receiving the output signal of the switching cycle selector 60 ( 62), by supplying a switching control signal to the boost converter to enable switching under zero voltage or zero current conditions in order to minimize the switching losses of the switch and diode. Reduce the loss due to the reverse recovery characteristics of the diode almost to zero, to one to compactly configure the entire system, to eliminate the use of large fans and air flow of a large heat sink for heat radiation cycle to the switching loss.

Description

Switching Control Circuit of Step-up Converter for Low Loss Soft Switching Power Factor Control

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching control circuit of a boost type converter for soft switching power factor control capable of minimizing switching losses of switches and diodes. The present invention relates to a switching control circuit of a step-up converter for soft switching power factor control, in which a large heat sink for heat dissipation and a large air volume fan can be removed, thereby making the whole system compact.

As shown in FIG. 1, the power supply circuit having no power factor control function includes a rectifying unit 10 for rectifying an input commercial power and outputting the rectified DC voltage, and a DC voltage output from the rectifying unit 10. It is composed of a filter capacitor (C) for filtering the supply to the load (12).

As shown in FIG. 3, the circuit configuration of the conventional power factor control boost converter includes a rectifying unit 10 for rectifying an input commercial power and outputting the rectified DC voltage, and outputting from the rectifying unit 10. Step-up converter section 11 for performing an operation for improving the power factor with respect to the voltage, and a filter capacitor (C) for filtering the voltage output from the step-up converter section 11 to supply to the load 12 ), A current detector 13 for detecting an input current, an input voltage detector 14 for detecting an input voltage, and an output voltage detector 15 for detecting an output voltage generated when the load 12 is operated. And a power factor controller 16 for outputting a switching signal for power factor control to the boost converter 11 using the current and voltage values detected by the detectors 13 to 15.

Looking at the prior art configured in this way in detail as follows.

First, referring to FIG. 1 and FIG. 2 for a power supply circuit without a power factor control function, the commercial power through the power supply stage and the commercial current as shown in FIG. I _AC ) Is supplied to the rectifier 10.

Then, the rectifier 10 rectifies the input commercial power using a bridge diode to make a DC voltage, and outputs the rectified DC voltage to the filter capacitor C.

At this time, the input current I _IN supplied to the filter capacitor C is as shown in FIG.

The filter capacitor C receiving the input current I _IN and the DC voltage as described above is filtered, and the filtered voltage, that is, the output voltage Vo as shown in FIG. ) To operate.

The power factor of a circuit operating as described above usually has a value between 0.4 and 0.7.

In addition, the harmonics component is too large to meet the international standard IEC 1000-3.

When the power factor is low, the effective power is also reduced, which reduces the power available in the home.

Therefore, a power factor control circuit is inserted to reduce power factor and harmonics.

Such a circuit is illustrated in FIG. 3, and will be described below based on FIGS. 3 and 4.

When supplying commercial power to the rectifier 10, the rectifier 10 rectifies the input voltage and outputs the rectified voltage (V _IN ) to the boost converter 11, the rectified voltage (V _IN ) is A voltage with twice the frequency of the input supply frequency (50/60 Hz) comes out.

When this voltage (V _IN ) is input and output to the boost converter 11, a current in phase with the input voltage (V _IN ) flows through the inductor (L). The in-phase sine wave current flows and the power factor is nearly 1.0.

At this time, the output voltage Vo that is filtered through the diode D and the filter capacitor C and supplied to the load 12 becomes a voltage larger than the peak value of the input voltage V _IN .

When the output voltage Vo is detected by the output voltage detector 15 and output to the power factor controller 16, the power factor controller 16 controls the output voltage to operate stably.

The power factor controller 16 controls the current of the inductor L to follow the input voltage V _IN , which is an input voltage detected by the input voltage detector 14 and an input current detected by the current detector 13. Control by using.

Since the switching element S1 operates at a high frequency of 50 KHz or more, the current of the inductor L serves as a current source during each switching.

When the switching element S1 of the boost converter 11 is turned on by the power factor controller 16 by the operation as described above, the inductor L receives the voltage V _IN rectified through the rectifier 10, The inductor current I _L rises linearly.

At this time, the energy charged in the filter capacitor C is supplied to the load, and the diode D is turned off because of a reverse voltage applied thereto.

When the switching element S1 of the boost converter 11 is turned off by the power factor controller 16, the diode D is turned on so that the inductor L receives the (Vo-V _IN ) voltage and the inductor current I _L ) decreases linearly.

In this case, power is supplied from the input to the output to charge the filter capacitor C and supply energy to the load 12.

By repeating the above operation, the inductor current I _L follows the shape of the input voltage and improves the power factor on the power supply side.

However, in the prior art as described above, the product of voltage and current generated when switching devices are turned on and off is a switching loss generated in each device. During the reverse recovery period of (D), a current flows in the diode D through the path of the diode D → switching element S1 → filter capacitor C, which is the switching element S1 and diode D. ) Significantly increases the loss. Therefore, the efficiency is considerably lowered, and in order to dissipate these losses, there is a problem of using a large heat sink and a fan of a large air volume.

Accordingly, an object of the present invention to solve the conventional problems as described above is to provide a boost converter for soft switching power factor control to minimize the loss by always soft switching at each switching.

1 is a power supply circuit diagram without a conventional power factor control.

2 is an operating waveform diagram of an output voltage and an input current of FIG. 1.

3 is a circuit diagram of a conventional power factor-type boost converter.

4 is a voltage and current waveform diagram at the time of switching in FIG.

5 is a switching control circuit diagram of a boost converter for a low loss type soft switching power factor control of the present invention.

FIG. 6 is a diagram showing switching states and current voltage waveforms during one switching cycle in FIG. 5; FIG.

FIG. 7 is a detailed circuit diagram of a switching period selecting part and a switching period variable part in FIG. 5; FIG.

8 is an input / output signal waveform diagram of each part in FIG. 7.

Explanation of symbols on the main parts of the drawings

51 rectifier 52 booster type converter

53 soft switching unit 54 current detection unit

55: input voltage detector 56: output voltage detector

57: power factor controller 58: duty signal determiner

59: oscillator 60: switching cycle selector

61: switching cycle variable portion 62: switching driver

The present invention for achieving the above object is to boost the converter to perform the power factor control function to receive the output of the rectifier rectifying the commercial power source, and to reduce the loss by performing a soft switching operation to improve the power factor of the boost converter portion. A soft switching unit, a detection unit for detecting a voltage and a current for the switching operation, a power factor control unit for receiving the output of the detection unit and controlling the switches of the boost converter unit and the soft switching unit, respectively; A duty signal determiner for varying the duty of the frequency based on the signal, an oscillator for outputting a frequency according to the output of the duty signal determiner, a switching cycle variable unit for varying a switching cycle by receiving an output signal of the oscillator; Switching element using the output waveform of the oscillator and the switching period variable portion Receiving the switching period selection unit, and the switching period selection unit output signal for determining the driving period for driving is characterized in that consisting of the switching driving unit that drives the switching element.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 5 is a switching control circuit diagram of a boost converter for soft switching power factor control according to the present invention. As shown therein, a rectifying unit 51 rectifies an input commercial power and outputs the rectified DC voltage, and the rectifying unit 51. Step-up converter unit 52 that performs an operation for improving the power factor with respect to the voltage output from the step, and soft switching to reduce the loss by performing a soft switching operation to improve the power factor of the step-up converter unit 52 A filter 53 for filtering the voltage output from the boost converter unit 52 and supplying it to a load and a current flowing through the inductor of the boost converter unit 52. An input voltage detector 55 for detecting a voltage supplied from the current detector 54, the rectifier 51 to the boost converter 52, and an output for detecting an output voltage generated during the load operation. The switching signal for controlling the power factor using the voltage detector 56 and the current and voltage values detected by the detectors 54 to 56 are switched to the boost converter 52 and the soft switch 53. A power factor controller 57 for outputting each of them, a duty signal determiner 58 for varying the duty of the frequency based on the signal output from the power factor controller 57, and a frequency corresponding to the output of the duty signal determiner; Using the oscillation unit 59, the switching period variable unit 61 for varying the switching period by receiving the output signal of the oscillation unit 59, and the output waveform of the oscillation unit 59 and the switching period variable unit 61 is used The switching period selector 60 determines a driving cycle for driving the switching element, and the switching driver 62 receives the output signal of the switching period selector 60 to drive the switching element.

As shown in FIG. 7, the switching period variable part 61 includes a capacitor C5 and a variable resistor R14 that change the switching period by a time constant, and the capacitor C5 and a variable resistor R14. Inverter I for inverting and outputting a switching cycle varied by).

In addition, as shown in FIG. 7, the switching period selecting unit 60 uses the pulses output from the first timer 59a of the oscillation unit 59 and the output pulses of the switching period variable unit 61 as soft inputs. A first and gate AND1 for generating a signal for driving the first auxiliary switch Sa2 of the unit 53, two output pulses output from the oscillator 59, and the first and gate AND1. To drive the switch of the boost type converter unit 52 by inputting the first NOR gate NOR1 for releasing the output pulse of the output pulse and the outputs of the first AND gate AND1 and the first NOR gate NOR1. A soft switching unit using the second NOR gate NOR2 for generating a signal for outputting, the output pulse of the oscillation unit 59 input to the first and gate AND1 and the output pulse of the switching period variable unit 61 as inputs. A third NOR gate NOR3 for generating a signal for driving the second auxiliary switch Sa2 of 53. Sung.

When described in detail with respect to the operation and the effect of the present configuration as described above.

In FIG. 5, when commercial power is supplied, the rectifier 51 is rectified by the rectifier 51, and the rectified DC voltage and a current proportional to the voltage are supplied to the boost converter 52.

Then, the current detector 54 detects the current flowing through the inductor L of the boost converter 52 through the detection resistor Rs and outputs it to the power factor controller 57, and the input voltage detector 55 is an inductor ( The input voltage supplied to L) is detected and output to the power factor controller 57, and the output voltage detector 56 detects the output voltage generated at the time when the load operates and outputs the output voltage to the power factor controller 57. .

Accordingly, the power factor controller 57 uses the current and voltage supplied from each of the detection units 54 to 56 to switch S1 of the boost type converter unit 52 and the first auxiliary switch Sa1 of the soft switching unit 53. ) Outputs a switching control signal for switching under zero current and zero voltage conditions.

At this time, as shown in (a) of FIG. 6, in the initial state, the switch S1 of the boost type converter unit 52 is turned off, so that the current of the inductor L ( I _L Are supplied to the filter capacitor C and the load through the diode D, respectively.

Then, the current flowing through the diode D ( I _D Is the current of the inductor L as shown in FIG. I _L ) And the voltage applied to the switch S1 of the boost type converter section 52 ( V _S1 Denotes an output voltage Vo as shown in FIG.

At this time, in order to turn on the switch S1 of the boost type converter 52 in the power factor controller 57, the auxiliary control Sa of the soft switching unit 53 is switched as shown in FIG. Output at zero current condition and turn it on. (T0)

Then, the resonant inductor Lr receives the output voltage V0 and the current ( i _Lr ) Increases linearly as in FIG.

This current ( i _Lr Is the current in the inductor (L) I _L Equal to), the current in diode (D) I _D ) Becomes zero as shown in (i) of FIG. 6, and resonates with the auxiliary resonant capacitor Cr1 and the Cr1-Sa1-Lr path, thereby reducing the voltage of the switch S1 ( V _S1 ) Drops to zero as shown in (f) of FIG. 6 (t1-t2 section).

At this time, the voltage of the diode (D) V _D ) Rises from zero to the output voltage Vo as shown in FIG.

From t2, the current of the resonant inductor Lr ( i _Lr ) Is fed back into the D1-Sa1-Lr pass.

After a certain time, as shown in FIGS. 6B and 6A, when the first auxiliary switch Sa1 is turned off and the switch S1 is turned on, the resonance inductor Lr current ( i _Lr ) Resonates in the Lr-Da2-Cr2 pass and drops to zero.

The switching of the two switches S1 and Sa at t3 switches at zero voltage and there is almost no loss.

Current of resonant inductor (Lr) i _Lr Is zero, the switch-on procedure is complete.

In order to turn off the switch S1 of the boost type converter 52 by the switching control signal of the power factor controller 57, the second auxiliary switch Sa2 is first turned on as shown in FIG. (t5)

Then, the energy stored in the auxiliary resonance capacitor Cr2 is resonated in the Cr2-Sa2-Lr path, and the energy of the auxiliary resonance capacitor Cr2 is converted into the current of the resonance inductor Lr. i _Lr In the form of).

Voltage of the auxiliary resonance capacitor Cr2 V _Cr2 ) Becomes zero as shown in FIG. 6E, the current of the resonant inductor Lr i _Lr ) Resonates in the path Lr-Da1-Cr1 so that the voltage of the switch S1, which is the voltage of the auxiliary resonance capacitor Cr1, rises to the output voltage Vo, and the voltage of the diode D drops to zero.

When the voltage of the switch S1 is equal to the output voltage Vo, the diode D conducts and the current of the inductor L ( I _L ) Is transmitted to the load, and the resonant inductor Lr is applied with an output voltage Vo to give the resonant inductor current ( i _Lr ) Decreases linearly to zero as shown in FIG.

After this, the state is maintained until the power factor controller 57 again signals the switch S1 to be turned on, thereby ending one cycle.

As such, each switching always switches at zero voltage or zero current to minimize the loss of each switch and diode of FIG. 5.

As such, the power factor controller 57 outputs the duty signal determiner 58 through the A and B terminals thereof as a boost type converter that minimizes losses of switches and diodes.

Then, the first duty decider 58a of the duty signal determiner 58 is integrated by the resistor R1 and the condenser C1 and then transferred to the non-inverting terminal (+) of the first operational amplifier OP1.

The reference voltage adjusted by the resistors R3 and R4 is input to the inverting terminal (−) of the first operational amplifier OP1.

Accordingly, the first operational amplifier OP1 compares two values input to the non-inverting terminal (+) and the inverting terminal (-), and compares the corresponding values to the voltage control terminal (1) of the first timer 59a of the oscillator 59. Vcon).

Then, the first timer 59a outputs a pulse (a dot waveform) to the switching period selector 60 in the form as shown in FIG.

At this time, the second duty determiner 58b of the duty signal determiner 58 and the second timer 59b of the oscillator 59 also have the same pulse as shown in FIG. b point waveform) is outputted to the switching period variable part 61.

Accordingly, the switching period variable part 61 receives the output pulse (b point waveform) of the oscillator 59 and outputs the b point waveform to the time constant of the time constant C5 and the variable resistor R14 and the inverter I. The period is controlled to output a pulse in a low state for a certain time.

That is, the pulse (c point waveform) as shown in Fig. 8C is output.

In this case, the first and gate AND1 of the switching period selecting unit 40 may output an output pulse (a point waveform) of the first timer 59a of the oscillation unit 59 and an output pulse of the switching period variable part 61 (c point). And a signal for driving the first auxiliary switch Sa1 of the soft switching unit 53 is generated (d-dot wave form) as shown in FIG. 8 (d) and output to the switching driver 62. .

In addition, the first NOR gate NOR1 of the switching period selector 60 receives a, b, d point waveforms and outputs a high signal only when the low period is received. A pulse (e-point waveform) is generated and output to the second NOR gate NOR2.

Therefore, the second NOR gate NOR2 only receives a high signal when the output pulse of the first NOR gate NOR1 (e point waveform) and the output pulse of the first and gate AND1 (a point waveform) are low. A signal (f-point waveform) for driving the switch S1 of the boost type converter unit 52 is generated as shown in FIG. 8 (f) by the output noaring process, and outputs the signal to the switching driver 62. .

In addition, the third NOR gate NOR3 of the switching period selecting unit 60 may output an output pulse (a point waveform) of the first timer 59a of the oscillation unit 59 and an output pulse c of the switching period variable unit 61. A signal (g dot waveform) for driving the second auxiliary switch Sa2 of the soft switching unit 53 through the noaring process of outputting a high signal only in a low section of the dot waveform) is shown in FIG. Produced as shown in the output to the switching driver 60.

Accordingly, the switching driver 60 switches the switch S1 of the boost converter 52 and the first and second auxiliary switches Sa1 and Sa2 of the soft switching unit 53 according to an input signal.

Each switch then switches at zero voltage to minimize losses.

Therefore, the present invention provides a switching control signal for switching under zero voltage or zero current to a boost converter in order to minimize the switching loss of the switch and the diode, thereby reducing the loss due to the reverse recovery characteristic of the diode during switching. It has the effect of making the entire system compact, by reducing it to nearly zero, using large heat sinks to eliminate this switching loss, and removing large airflow fans.

Claims (3)

A boost converter that receives the output of a rectifier for rectifying commercial power and performs a power factor control function; a soft switching unit that performs a soft switching operation to reduce power loss to improve the power factor of the boost converter; In the boost converter comprising a detection unit for detecting a voltage and a current for the control and a power factor control unit for receiving the output of the detection unit and controlling the switch of the boost converter unit and the soft switching unit, based on the signal output from the power factor controller. A duty signal determiner for varying the duty of the frequency, an oscillator for outputting a frequency according to the output of the duty signal determiner, a switching period variable for varying a switching cycle by receiving an output signal of the oscillator, and the oscillator And drive the switching element using the output waveform of the variable switching period Switching control circuit of the step-up converter for low-loss type soft switching power factor control, characterized in that it comprises a switching period selector for determining a drive cycle for driving and a switching driver for driving the switching element by receiving the output signal of the switching period selector. . The low loss type soft switching power factor according to claim 1, wherein the switching period variable part comprises a capacitor and a variable resistor for varying the switching period by a time constant, and an inverter for inverting and outputting the switching period by the capacitor and the variable resistor. Switching control circuit of a control boost converter. The switching period selector of claim 1, wherein the switching period selector is configured to generate a signal for driving a first auxiliary switch of the soft switching part by inputting an output pulse of the oscillation part and an output pulse of the switching period variable part, and an output from the oscillator. A signal for driving a switch of a boost type converter by inputting two output pulses and a first noaring gate for outputting the output pulses of the first and gates, and an output of the first and gates And a third quinoa to generate a signal for driving a second auxiliary switch of the soft switching unit by inputting a second noble gate to generate a signal, an output pulse of the oscillation unit and an output pulse of the switching period variable input to the first and gate. A switching control circuit of a step-up converter for low loss type soft switching power factor control, characterized in that consisting of a gate.