KR19990058750A - Switching control circuit of boost converter for 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 soft switching power factor control. Conventionally, a product of voltage and current generated when switching elements are turned on and off is a switching loss generated in each element. Many of these overlapping parts cause a large loss. In particular, diodes have a low efficiency due to loss due to reverse recovery characteristics, and in order to dissipate these losses, a large heat sink and a large fan must be used. Therefore, in the present invention, the duty signal determiner 20, the oscillator 30, and the switching cycle selector 40 are configured to switch the voltage of the boost converter including the rectifier, the boost converter and the soft switch at zero voltage. And generating a switching control signal using the switching driver 50 to switch each switch at zero voltage to minimize switching losses of the switch and the diode, thereby reducing the loss due to the reverse recovery characteristic of the diode to almost zero. The use of a large heat sink to dissipate the losses and the elimination of large airflow fans allows for compact system construction.

Description

Switching control circuit of boost converter for 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, which is described below with reference to FIG. 3.

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 12, 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.

Therefore, an object of the present invention for solving the conventional problems as described above is to switch the soft converter power factor converter for soft switching power factor control to prevent the loss of efficiency by reducing the loss by always soft switching at each switching In providing a control circuit.

Another object of the present invention is to reduce the switching losses of the switch and diode to almost zero, the switching control circuit of the step-up converter for soft switching power factor control to remove the heat sink for heat dissipation, etc. to compactly configure the whole system In providing.

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 the boost converter for soft switching power factor control of the present invention.

6 is an operating waveform diagram of an output voltage and an input current of FIG. 5.

FIG. 7 is a detailed circuit diagram of a duty signal determiner, an oscillator, and a switching cycle selector in FIG. 5; FIG.

8 is a waveform diagram of input and output signals in FIG.

Explanation of symbols on the main parts of the drawings

10: power factor controller 20: duty signal determiner

21: rectifier 22: soft switching unit

23: load 24: current detector

25: input voltage detector 26: output voltage detector

30: oscillator 40: switching cycle selector

50: 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, a switching cycle selector configured to receive an output signal of the duty signal determiner, and determine a driving cycle of the switching element, and an output signal of the switching cycle selector Characterized in that consisting of a switching drive unit for driving the switching element .

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

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 21 rectifies an input commercial power and outputs the rectified DC voltage, and the rectifying unit 21. Step-up converter unit 22 performing an operation to improve 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 22 A filter 23 for filtering the voltage output from the boost converter unit 22 and supplying it to a load and a current flowing through the inductor of the boost converter unit 22 are detected. An input voltage detector 25 for detecting a voltage supplied from the current detector 24, the rectifier 21 to the boost converter 22, and an output for detecting an output voltage generated during the load operation. By using the voltage detector 26 and the current and voltage values detected by the detectors 24 to 26, a switching signal for power factor control is switched to the boost converter 22 and the soft switch 23. Outputting the output power of the power factor controller 10, the duty signal determiner 20 that changes the duty of the frequency based on the signal output from the power factor controller 10, and the duty signal determiner 20, respectively. A switching cycle selector 40 which receives the input and determines the driving cycle of the switching element, and a switching driver 50 which receives the output signal of the switching cycle selector 40 to drive the switching element.

As shown in FIG. 7, the duty signal determiner 20 integrates the input pulses using resistors R1 (R8) and capacitors (C1) and C3 through the integrator and through the integrator. Operational amplifier (OP1) that inputs the integrated voltage to the non-inverting terminal and receives the reference voltage adjusted by the resistors R3 and R4 (R10 and R11) as the inverting terminal and compares the two values to determine the duty of the signal. OP2).

In addition, as shown in FIG. 7, the switching period selector 40 performs an AND-combination of predetermined pulses set by signal duty to generate a signal for driving a switch Sa of the soft switching unit. ), A first NOR gate NOR1 for noring two pulses input to the AND gate ADD, and a pulse output from the AND gate ADD, an output pulse of the first NOR gate NOR1, A second NOR gate NOR2 for generating a signal for driving the switch of the boost type converter unit by generating the output pulse of the AND gate ADD.

Referring to the operation and effect of the present invention configured as described in detail as follows.

In FIG. 5, when commercial power is supplied, the rectifier 21 is rectified by the rectifier 21, and the rectified DC voltage and a current proportional to the voltage are supplied to the boost converter 22.

Then, the current detector 24 detects the current flowing through the inductor L of the boost converter 22 through the detection resistor Rs and outputs it to the power factor controller 10, and the input voltage detector 25 receives the inductor ( Detects an input voltage supplied to L) and outputs it to the power factor controller 10, and the output voltage detector 26 detects an output voltage generated at the time when the load operates and outputs it to the power factor controller 10. .

Accordingly, the power factor control unit 10 switches the switch S1 of the boost type converter unit 22 and the auxiliary switch Sa of the soft switching unit 23 by using currents and voltages supplied from the respective detection units 24 to 26. Outputs a switching control signal for switching under zero current and zero voltage conditions.

At this time, as shown in FIG. 6A, in the initial state, the switch S1 of the boost type converter unit 22 is turned off, so that the current of the inductor L ( I _L Is supplied to the filter capacitor C and the load 23 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 22 ( V _S1 ) Is the output voltage Vo as shown in FIG.

At this time, in order to turn on the switch S1 of the boost type converter unit 22 in the power factor control unit 10, the auxiliary switch Sa of the soft switching unit 23 is switched as shown in FIG. Output at zero current condition and turn it on. (T0)

Then, the resonant inductor Lr of the soft switching unit 23 receives the output voltage Vo 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 FIG. 6 (h), and resonates in the pass of the auxiliary resonance capacitor Cr1 and Cr1-Lr-Sa, so that the voltage of the switch S1 of the boost converter unit 22 ( V _S1 ) Drops to zero as in (e) of FIG. 6 (t1-t2 section).

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

From the t2 section, the current of the resonant inductor (L) i _Lr ) Is freewheeling to D1-Lr-Sa path and Da2-Da1-Lr-Sa path (t2 ~ t3).

After a certain time, when the auxiliary switch Sa of the soft switching unit 23 is turned off and the switch S1 of the boost type converter unit 22 is turned on as shown in FIGS. 6B and 6A, the resonance inductor is turned on. (L) current ( i _Lr ) Resonates with the pass of Lr-Cr2-Da1 and drops to zero.

The switching of the two switches S1 and Sa at t3 switches at zero voltage, resulting in little loss.

Current of the resonant inductor (L) i _Lr ) Becomes zero and this time it continues to resonate in the path of Lr-S1-Da2-Cr2 and the current of resonant inductor (L) ( i _Lr ) Increases as in Fig. 6 (c) due to resonance in the opposite direction.

Voltage of resonant capacitor Cr2 ( V _Cr2 ) Becomes zero as shown in (d) of FIG. 6 (t5 section), the current of the resonant inductor L ( i _Lr ) Continues to freewheeling while the switch S1 of the boost type converter section 22 is turned on in the path Lr-S1-Da.

When the switch S1 of the boost type converter unit 22 is turned off (section t6) by the power factor controller 10, the voltage of the switch S1, which is the voltage of the resonant capacitor Cr1, is resonated in the Lr-Cr1-Da pass. As shown in FIG. 6E, the output voltage Vo rises to increase the voltage of the diode D ( V _D ) Drops to zero as in (g) of FIG. 6.

At this time as well, the switch S1 is turned off at zero voltage so that there is almost no loss.

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 _Lr ) Is applied to the load, and at this time, the resonant inductor Lr is applied with the output voltage Vo, thereby providing the resonant inductor current ( i _Lr ) Decreases linearly to zero as shown in FIG.

After this, the state is maintained until the power factor control unit 10 turns on the switch S1 again, thereby ending one cycle. In this way, switching is always done with soft switching to minimize losses.

The switching control signal for turning on or off the switch of the boost converter 22 and the soft switching unit 23 operating as described above is transferred from the power factor controller 10 to the duty signal determination unit 20 through its A and B terminals. Output

Then, the first duty determiner 20a of the duty signal determiner 20 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 values according to the voltage control terminal of the first timer 30a of the oscillator 30 ( Vcon).

Then, the first timer 30a outputs a pulse (a dot waveform) in the form as shown in FIG.

At this time, the second duty determiner 20b of the duty signal determiner 20 and the second timer 30b of the oscillator 30 also have the same pulse as in FIG. b point waveform) is output.

Therefore, the AND gate AND of the switching period selector 40 is turned on only when the high point of the a- and b-point waveforms is turned on, and the first gate NOR1 receives a pulse (point C waveform) as shown in FIG. )

Then, the first NOR gate NOR1 receives the a point, the b point, and the c point waveforms, respectively. In this case, the first NOR gate NOR1 is turned on only when the a, b, and c point waveforms are all low. ) And outputs a pulse (d dot waveform) as shown in FIG. 8D to the second NOR gate NOR2.

In this case, the second NOR gate NOR2 receives the c-point and d-point waveforms and noarses. In this case, the second NOR gate NOR2 outputs a high signal by turning on only when the c- and d-point waveforms are in a low section. Outputs the same pulse (e point waveform) as in (e).

At this time, the voltages input to the switch Sa of the soft switching unit 23 and the switch S1 of the boost type converter unit 22 are respectively a c-dot waveform and a second NOR gate NOR2 output through the AND gate ADD. ) Becomes the e-dot waveform output through

The c-point waveform and the e-point waveform drive the corresponding switch through the switching driver 50.

As described above, by using a switching control circuit for controlling the switch of the boost type converter for minimizing the loss by the soft switching operation, a corresponding switching control signal is supplied to switch under the condition of zero voltage or zero current.

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 (4)

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 cycle signal determiner for varying the duty of the frequency, a switching cycle selector configured to receive an output signal of the duty signal determiner, and determine a driving cycle of the switching device; Characterized in that it comprises a switching drive for driving A switching control circuit of a boost converter for soft switching power factor control. The reference voltage control unit of claim 1, wherein the duty signal determining unit receives two integrators integrated with a resistor and a capacitor with respect to an input pulse, and a reference voltage adjusted by a resistor receiving a voltage integrated through the integrator as a non-inverting terminal, respectively. The switching control circuit of the step-up converter for soft switching power factor control, characterized in that consisting of two operational amplifiers to receive the inverting terminal to compare the two values to determine the duty of the signal. The switching control circuit of claim 1, wherein the oscillator comprises two timers respectively outputting pulses having different periods according to input voltage control signals. The switching gate selector of claim 1, wherein the switching period selector generates and outputs a signal for driving a switch of a soft switching unit by AND-combining predetermined pulses respectively set by signal duty, a pulse input to the AND gate, and the AND gate. A first noble gate for releasing the output pulse, a second noble gate for generating a signal for driving a switch of the boost type converter by releasing the output pulse of the first noble gate and the output pulse of the AND gate. A switching control circuit of a boost converter for soft switching power factor control, characterized in that.