KR100426801B1 - Electronic ballasts for hid-lamp - Google Patents

Abstract

The present invention generates a quasi-spherical wave giving a proper time difference at turn-on and turn-off time, and through the quasi-square wave so that the switching element is zero voltage switching (ZVS) and zero current switching (ZCS). To minimize the switching loss, control the oscillation frequency of the switching signal (square wave) by detecting the lamp output voltage, and adjust the duty of the switching signal to detect the zero crossing of the lamp output current. An electronic ballast for a high-intensity discharge (HID) lamp.

Description

Electronic ballast for high pressure lamp {ELECTRONIC BALLASTS FOR HID-LAMP}

The present invention relates to an electronic ballast (HID: High Intensity Discharge) electronic ballast, and more particularly, to generate a quasi-square wave giving a proper time difference between the turn-on and turn-off time, the switching element is zero voltage Minimize switching loss by switching (ZVS) and zero current switching (ZCS), control the oscillation frequency of switching signal (square wave) by detecting lamp output voltage, and simultaneously detect zero crossing of lamp output current. The present invention relates to an electronic ballast for a high-pressure lamp in which the lamp output is stabilized by adjusting the duty of the switching signal.

At present, the main technical issues of the electronic ballast for high voltage lamps (HID) are as follows: (1) a technique for eliminating acoustic resonance, (2) a technique for minimizing losses due to heat generation of the switching element, and (3 The technique of stably (constantly) controlling the output of a lamp having a variable negative resistance characteristic and an ignition technique.

First, (1) a technique for removing the acoustic resonance phenomenon is a method of mixing a low frequency of several hundred hertz (Hz) with a high frequency voltage and current of several tens of kilohertz (KHz), and varying the voltage and current of the high frequency in time. And a method of adding and superimposing them (shaking high frequencies), and a method of avoiding a frequency band causing acoustic resonance.

Techniques for reducing the heat generation of the switching element (2) include a method of adding a snubber circuit and a method of using a zero voltage or current switching control circuit.

In addition, the technique (3) of controlling the output of the lamp having the variable negative resistance characteristic and the ignition technology in general are not easy to obtain a constant output due to the complicated electrical characteristics of the high-pressure lamp, so the tube current control method is generally adopted. And the tube voltage may be used to implement a protection circuit.

Under this background, the conventional ballast technology of high voltage lamps (HID) has a large switching loss when it is used mostly at frequencies above the resonant frequency band, thereby reducing the loss by 10% to 20% of high frequency at low frequencies. It adopts the circuit structure to include to a degree.

Prior art US Pat. No. 6,020,691 uses a zero current switching method to avoid resonance and reduce switching losses by containing 10-20% of high frequency of 20-50KHz in a spherical low frequency of 80-200Hz. Due to the large number of passive components such as and capacitors, the circuit configuration is complicated and the durability of the capacitor is reduced.

In addition, Japanese Patent No. O341596, which is a prior art, has a problem in which a frequency is fixed in a full bridge and a duty ratio of a square wave is adjusted according to an output power, but in the case of a high output lamp, a problem of heat generation of a switching element has to be solved.

In addition, although the prior art domestic patent (application number: No. 195-0005284) controls the output power of the lamp through the frequency control, the high-pressure lamp, because the current control by the current control only by the frequency control is insufficient, especially switching The use of passive elements such as capacitors, resistors, and diodes in parallel with the switch elements in order to eliminate heat generation of the elements has caused a problem of deterioration in efficiency.

On the other hand, the conventional circuits related to the ignition circuit are very diverse, the generation of high pressure for the initial lamp is easy to be ignited, but the technology for shortening the life of the lamp is low due to the low technology to apply the appropriate voltage to the lamp after ignition This resulted in a problem that the end of the life of the lamp easily breaks up to the ballast.

The present invention has been made to solve the above problems, an object of the present invention is to apply a switching signal using a full bridge inverter, the two switching elements have a driving frequency due to the combination of the lamp output voltage and current By applying a switching signal (square wave) and detecting the phase of the lamp output current to determine the turn-on and turn-off times of the other two switching elements, the driving frequency and duty of the lamp output can be adjusted simultaneously. It is to provide an electronic ballast for a high-pressure lamp that can maintain the output of the stably.

It is another object of the present invention to form a quasi-square wave at the lamp output terminal of a full bridge inverter by using a switching signal due to a lamp driving frequency and a switching signal due to an output current phase. ) And zero current switching (ZCS) to provide an electronic ballast for a high-pressure lamp that prevents the efficiency of switching elements from being deteriorated due to heat generation.

The present invention for achieving the above object is an EMI elimination filter circuit for removing noise causing electromagnetic interference generated when the input power is applied; A full-wave rectification and filter circuit receiving the output voltage of the EMI elimination filter circuit to full-wave rectification to form a predetermined DC voltage and removing noise; A power factor improvement circuit for outputting the power factor by receiving the output voltage of the full-wave rectification and filter circuits; A voltage controlled oscillation circuit receiving the output voltage of the power factor improving circuit and outputting a switching signal to the first switching driving circuit at a frequency according to the output voltage and current of the fed-in lamp; A first switching driving circuit for applying a switching signal (square wave) according to the frequency to two switching elements formed in a full bridge inverter according to the output frequency switching signal of the voltage controlled oscillation circuit; A second switching driving circuit for driving two other switching elements formed in the full bridge inverter at turn-on and turn-off times determined according to the phase of the lamp output current fed back; A full bridge inverter configured to switch by a ramp output driving frequency switching signal of the first switching driver circuit and a switching signal according to an output current phase of the second switch driving circuit and to generate a quasi-square wave to output a lamp driving signal; A lamp driving circuit which lights the lamp by receiving the output voltage of the full bridge inverter; The lamp output voltage and current of the lamp driving circuit are detected and rectified to a DC voltage, and the rectified control signal is applied to the voltage control oscillation circuit as a driving frequency switching signal according to the lamp output, and at the same time, the overvoltage and overcurrent of the lamp output. A voltage detection and protection circuit which protects the circuit by cutting off the output to the voltage controlled oscillation circuit during operation; And detecting the lamp output current of the lamp driving circuit to detect the phase of the output current, and determining the turn on and turn off times of the two switching elements of the full bridge inverter so as to be caused by the detected output current phase. A current phase detection circuit for outputting a control signal to the second switching driving circuit; It has a feature consisting of.

In addition, the full bridge inverter according to the present invention is driven by a switching signal caused by the ramp output drive frequency input from the first switching drive and a switching signal caused by the output current phase input from the second switching drive circuit to generate a quasi-square wave. By outputting, the switching element is set to zero voltage switching (ZVS) and zero current switching (ZCS) at the time of zero crossing of the output current.

In addition, the full bridge inverter according to the present invention is a switching signal determined according to the ramp output driving frequency input from the voltage controlled oscillation circuit and the first switching drive, and the output current phase input from the current phase detection circuit and the second switching drive circuit. It is driven in accordance with the switching signal by the turn on and off time of the, has another feature to adjust the operating frequency and duty of the output lamp.

1 is a circuit block diagram of an electronic ballast for a high pressure lamp according to the present invention,

2 is a diagram illustrating a full bridge inverter, a lamp driving circuit, a voltage detection and protection circuit, and a current phase detection circuit of FIG. 1;

3 is a timing diagram of each part of the switching drive circuit and the full bridge inverter output stage according to the present invention;

4 is a current waveform diagram of the full bridge inverter output stage of FIG.

* Description of the symbols for the main parts of the drawings *

10: EMI elimination filter circuit 20: full wave rectification and filter circuit

30: power factor improvement circuit 40: voltage controlled oscillation circuit

50: first switching drive circuit 60: second switching drive circuit

70: full bridge inverter 80: lamp drive circuit

90: voltage detection and protection circuit 100: current detection circuit

Q1 to Q4: switching elements D1 to D4: diode

R1 to R6: Resistor C1: Capacitor

L1: Inductor T1: Current Transformer

LP: Lamp OP: Calculator

91: lamp voltage detection unit

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

1 is a circuit block diagram of an electronic ballast for a high pressure lamp according to the present invention.

As shown, the electronic ballast for the high voltage lamp according to the present invention is the EMI elimination filter circuit 10 for removing the noise causing electromagnetic interference generated when the input power (AC) and the EMI elimination filter circuit 10 The power factor corrected and outputted by applying the output voltage to the full wave rectification and filter circuit 20 to form a predetermined DC voltage and remove noise, and the output voltage of the full wave rectification and filter circuit 20 is applied. The improvement circuit 30 and the output voltage of the power factor improving circuit 30 are applied and fed back to the first switching driving circuit 50 at a frequency according to the output voltage and the current value of the lamp. A voltage control oscillation circuit 40 for outputting a switching signal and two switching elements formed in the full bridge inverter 70 according to the output frequency switching signal of the voltage control oscillation circuit 40. ) A first switching driving circuit 50 for applying a second switching device for driving two other switching elements formed in the full bridge inverter 70 at turn-on and turn-off times determined according to the phase of the lamp output current fed back. Switching operation is performed by the driving circuit 60, the ramp output driving frequency switching signal of the first switching driving circuit 50 and the switching signal according to the output current phase of the second switch driving circuit 60, and generates a quasi-square wave. A full bridge inverter 70 for outputting a lamp driving signal, a lamp driving circuit 80 for turning on a lamp by applying an output voltage of the full bridge inverter 70, and a lamp output of the lamp driving circuit 80 Voltage and current are detected and rectified to DC voltage, and the rectified control signal is applied to the voltage controlled oscillation circuit 40 as a driving frequency switching signal according to the lamp output, and at the same time, overvoltage and overcurrent of the lamp output. Detects the phase of the output current by detecting a voltage detection and protection circuit 90 to protect the circuit by cutting the output to the voltage controlled oscillation circuit 40 and a lamp output current of the lamp driving circuit 80, Current phase for determining the turn-on and turn-off time of the two switching elements of the full bridge inverter 70 so as to be due to the phase of the detected output current, and outputs the switching control signal to the second switching drive circuit 60 accordingly. It consists of a detection circuit 100.

FIG. 2 is a diagram illustrating a full bridge inverter 70, a lamp driving circuit 80, a voltage detection and protection circuit 90, and a current phase detection circuit 100 of FIG. 1.

As shown, the output terminal of the first switching driver circuit 50 is connected to the gate terminal of the switching elements Q1 and Q2 of the full bridge inverter 70, and the output terminal of the second switching driver circuit 60 is switched. It is connected to the gate terminal of elements Q3 and Q4. In addition, the drain terminal of the switching element Q1 is connected to the drain terminal of the switching element Q3 and at the same time a predetermined DC voltage Vcc is applied, and the source terminal of the switching element Q2 and the switching element Q4 is They are connected to each other and grounded at the same time.

Further, a lamp driving circuit is provided at the drain-source output terminal A of the switching element Q1 and the switching element Q2 and the drain-source output terminal B of the switching element Q3 and the switching element Q4. 80 is connected, and the lamp driving circuit 80 is composed of a lamp LP, an LC resonant circuit 81 composed of a capacitor C1 and an inductor L1.

The voltage detection and protection circuit 90 detects an output voltage and a current applied to both ends of the lamp driving circuit 80 through the voltage divider R1 and R2, and the voltage divider R1 and R2. And a ramp voltage detector 91 for feeding back and outputting a predetermined DC signal generated by rectifying the DC voltage and current to the voltage controlled oscillation circuit 40, wherein the switching driving frequency is changed according to the output voltage and the current level. It is variable.

The current detection circuit 100 is connected in series with the primary side of the current transformer T1 to the lamp LP of the lamp driving circuit 80, and one end of the secondary side is the inverting end of the comparator COM through the resistor R3. It is connected to (-) and at the same time is connected to the output terminal of the comparator COM through the resistor (R4), the other end of the secondary side of the current transformer (T1) through the resistor (R5) of the non-inverting terminal (+) ) And at the same time configured to be connected to the output terminal of the comparator (COM) through a resistor (R6), to detect the phase of the output current.

The operation of the present invention configured as described above will be described below.

First, when the power source AC is input, the input power source AC is supplied to the voltage controlled oscillation circuit 40 through the EMI elimination filter circuit 10, the full-wave rectification and filter circuit 20, and the power factor correction circuit 30. Is approved.

The voltage controlled oscillation circuit 40 receives a DC level signal input from the voltage detection and protection circuit 90 to the first switching driving circuit 50 to pulse at a variable frequency according to the lamp output voltage and current (square wave). Output a switching signal. Here, when the impedance of the lamp LP is large, the driving frequency is decreased, and when the impedance of the lamp LP is small, the driving frequency is increased.

The first switching driving circuit 50 receiving the square wave switching signal according to the variable driving frequency from the voltage controlled oscillation circuit 40 is a gate of the switching element Q1 and the switching element Q2 of the full bridge inverter 70. However, high and low signals are output from the time point t1 as shown in FIG. 3, respectively.

At the same time, the second switching driving circuit 60 receiving the phase switching signal according to the lamp output current input from the current phase detection circuit 100 is the switching element Q3 and the switching element Q4 of the full bridge inverter 70. The low and high signals are output from the time point t2 to the gate terminal of the circuit as shown in FIG.

Therefore, the switching element Q1 and the switching element Q4 of the full bridge inverter 70 are simultaneously turned on at the time points t2 to t3, and the switching element Q2 and the switching element Q3 are the time points t4 to t5. At the same time to turn on at the same time repeatedly, the output terminal (between AB) of the full bridge inverter 70 generates a quasi-square wave output as shown in FIG. In this quasi-square wave, the current flows even in the section t _D where the voltage is "0", and adjusting the section t _D eventually adjusts the duty.

As shown in FIG. 4, the quasi-square wave has a waveform of a current i of each section t1 to t6. At the time point t1, the switching element Q2 is turned off but the zero current switching ZCS is performed. The switching element Q1 turned on at the time point t2 becomes the zero voltage switching ZVS, and the switching element Q3 turned off has a ZCS function. In addition, the switching element Q1 turning off at the time point t3 does not have a ZCS action, and the switching element Q3 turning off at the time point t4 has a ZCS action, and the switching element Q4 turning on at the time point t4 is ZVS. It works.

Therefore, the switching loss occurs only at the switching element Q2 at the time t1 and at the switching element Q1 at the time t3, but no switching loss occurs at the switching element Q3 and the switching element Q4. In particular, the diode D1 and the diode D2 connected in parallel with the switching element Q1 and the switching element Q2 are required to have a fast recovery time, but the diodes D3 and D4 are only for protection and are used for recovery time. There is no big relationship.

In addition, in the present invention, when the lamp LP is turned on by the output of the full bridge inverter 70, a burner effect is used as a method of reducing switching loss, which is a capacitor connected in parallel to the lamp LP ( A resonant circuit 81 composed of C1) and an inductor L1 is constructed.

To explain this, if the capacitor (C1 = C), the inductor (L1 = L) and the lamp (LP = R) are composed of equivalent circuits and the impedance Z between _AB is obtained, then Z _AB = [R + jwL] / [ (1-w ² LC) + jwRC], and the condition of pure water resistance is f (driving frequency) = (1 / 2π) [(LR ² C) / L ² C]. At the driving frequency f, the voltage and the current are in phase with each other. As a result, the switching elements Q1 to Q4 can perform zero voltage switching (ZVS) and zero current switching (ZVC), thereby reducing switching losses. For example, if R = 40Ω, L = 200, C = 22Ω, f There is little switching loss at 69KHz.

In addition, the output voltage and current applied to the lamp LP are divided by the voltage dividing resistors R1 and R2 of the voltage detection and protection circuit 90 and applied to the lamp voltage detection unit 91. The lamp voltage detection unit 91 detects the voltage and current input through the voltage divider R1 and R2 to rectify the AC component to DC, and inputs the rectified signal to the voltage controlled oscillation circuit 40. The driving frequency is outputted, and at the same time, when an overvoltage (including overcurrent) is detected, the circuit is protected by blocking the output to the voltage controlled oscillation circuit 40.

In addition, the output current flowing through the lamp LP is applied to the primary side of the current transformer T1 of the current phase detection circuit 100, and the voltage induced on the secondary side is the resistor R3 and the resistor R5. Are applied to the inverting (-) and non-inverting (+) terminals of the comparator COM, respectively, and the comparator COM outputs high and low signals based on the positive and negative periods of the current waveform. And, through this it is detected the exact phase of the output current, by applying a switching signal according to this phase to the second switching drive circuit 60, the phase of the current flowing through the lamp LP and is applied to the lamp LP The phases of the voltages can be matched, resulting in an accurate capture of zero crossing of the current.

As described above, the present invention firstly generates a quasi-square wave in order to drive the ballast in the high frequency band in which no acoustic resonance occurs, thereby realizing zero voltage, zero current switching, and at the same time has a snubber function By configuring the switching loss can be minimized.

Second, in order to keep the output of the lamp constant at the nominal value, it detects the voltage and current of the lamp and uses the rectified value as the input value of the oscillator to adjust the drive frequency of the inverter in the LC resonance circuit of the output stage connected to the lamp. The current and voltage of the lamp are configured to be added or subtracted, and the output of the lamp is controlled within ± 5% of the nominal value by adjusting the duty of the square wave by the output terminal current.

Claims (6)

EMI elimination filter circuit for removing noise causing electromagnetic interference generated when the input power is applied; A full-wave rectification and filter circuit receiving the output voltage of the EMI elimination filter circuit to full-wave rectification to form a predetermined DC voltage and removing noise; A power factor improvement circuit for outputting the power factor by receiving the output voltage of the full-wave rectification and filter circuits; A voltage controlled oscillation circuit receiving the output voltage of the power factor improving circuit and outputting a switching signal to the first switching driving circuit at a frequency according to the output voltage and current of the fed-in lamp; A first switching driving circuit for applying a switching signal (square wave) according to the frequency to two switching elements formed in a full bridge inverter according to the output frequency switching signal of the voltage controlled oscillation circuit; A second switching driving circuit for driving two other switching elements formed in the full bridge inverter at turn-on and turn-off times determined according to the phase of the lamp output current fed back; A full bridge inverter configured to switch by a ramp output driving frequency switching signal of the first switching driver circuit and a switching signal according to an output current phase of the second switch driving circuit and to generate a quasi-square wave to output a lamp driving signal; A lamp driving circuit which lights the lamp by receiving the output voltage of the full bridge inverter; The lamp output voltage and current of the lamp driving circuit are detected and rectified to a DC voltage, and the rectified control signal is applied to the voltage control oscillation circuit as a driving frequency switching signal according to the lamp output, and at the same time, the overvoltage and overcurrent of the lamp output. A voltage detection and protection circuit which protects the circuit by cutting off the output to the voltage controlled oscillation circuit during operation; And detecting the lamp output current of the lamp driving circuit to detect the phase of the output current, and determining the turn on and turn off times of the two switching elements of the full bridge inverter so as to be caused by the detected output current phase. A current phase detection circuit for outputting a control signal to the second switching driving circuit; Electronic ballast for high pressure lamp, characterized in that consisting of. The method of claim 1, The full bridge inverter is driven by a switching signal resulting from a ramp output driving frequency input from the first switching drive and a switching signal resulting from an output current phase input from the second switching driving circuit, thereby outputting a quasi-square wave, thereby zeroing the output current. An electronic ballast for a high voltage lamp, characterized in that the switching element is set to zero voltage switching (ZVS) and zero current switching (ZCS) at the time of crossing. The method of claim 1, The full bridge inverter has a turn-on and turn-off time of a switching signal determined according to a ramp output driving frequency input from a voltage controlled oscillation circuit and a first switching drive, and an output current phase input from a current phase detection circuit and a second switching drive circuit. The electronic ballast for a high-pressure lamp, characterized in that the drive is driven in accordance with the switching signal, thereby adjusting the operating frequency and duty of the output lamp. The method of claim 1, The lamp driving circuit further includes an LC resonant circuit including a capacitor C1 and an inductor L1 connected in parallel, and minimizes the phase difference between the voltage and the current applied to the output terminal of the full bridge inverter. . The method of claim 1, The voltage detection and protection circuit is generated by rectifying a voltage dividing resistor (R1) (R2) for dividing the output voltage across the lamp driving circuit, and the voltage detected by the voltage dividing resistor (R1) (R2) by direct current. An electronic ballast for a high-pressure lamp, characterized in that it comprises a lamp voltage detection unit for outputting a predetermined signal as a voltage control signal generation. The method of claim 1, The current detection circuit connects the primary side of the current transformer T1 in series with the lamp, and one end of the secondary side is connected to the inverting terminal (-) of the comparator COM through the resistor R3 and at the same time the resistor R4. Is connected to the output terminal of the comparator COM, and the other end of the secondary side of the current transformer T1 is connected to the non-inverting terminal (+) of the comparator COM through the resistor R5 and at the same time through the resistor R6. Electronic ballast for a high-pressure lamp, characterized in that configured to be connected to the output terminal of the comparator (COM).