KR20030050276A - Electronic ballast circuit - Google Patents

Abstract

PURPOSE: An electronic stabilizer circuit is provided to be capable of controlling the switches for controlling power factor correction(PFC) and pulse width modulation(PWM) by one chip. CONSTITUTION: A switching transistor(Q2) has a source terminal connected to a ground and a gate terminal controlled by a control circuit(126). A diode(136) has an anode connected to a drain terminal of the switching transistor and a cathode connected to a main power line of a buck converter(118). An inductor(138) has one side connected to the anode of the diode, and a capacitor(140) is connected between another side of the inductor and the main power line of the buck converter.

Description

Electronic ballast circuit {ELECTRONIC BALLAST CIRCUIT}

The present invention relates to an electronic ballast circuit, and more particularly, to an electronic ballast circuit for driving a high intensity discharge lamp (hereinafter referred to as a HID lamp).

The demand for gas discharge lamps, such as fluorescent lamps, for home or office use continues to increase. In order to drive the discharge lamp from the main power line, a ballast is used as the interface between the power line and the lamp.

One important function of the ballast is to drive the discharge lamp with a signal with the appropriate voltage and current levels. Another important function of the ballast is to improve the power factor. The current level required to operate the discharge lamp is determined first of all by the characteristics of the gas contained in the lamp. Power factor correction is necessary to ensure that ballast operation does not generate noise on the power lines. In general, the power factor correction circuit controls the current provided by the ballast to be in phase with the power line waveform.

With the advent of HID lamps, the ballast also needed to ensure that the discharge vessel was driven with a low frequency current signal of 1 kHz or less. It is difficult to drive HID lamps at high frequencies because of arc instability caused by acoustic resonance.

1 is a circuit diagram of a conventional electronic ballast for driving a HID lamp. The ballast includes an upper signal line and a lower signal line, respectively, connected to respective terminals of the main power line. As shown in FIG. 1, the electronic ballast circuit 10 includes an EMI filter 12, a full bridge diode rectifier 14, a boost converter 16, a buck converter 18, a commutator 20, and a HID lamp. 42 is cascaded.

The EMI filter 12 serves to remove electromagnetic interference, and the full bridge diode rectifier 14 serves to rectify the AC voltage signal provided from the main power line.

The boost converter 16 is connected between an inductor 22 along the upper signal line of the electronic ballast 10, a diode 28 connected in series with the inductor 22, an anode of the diode 28 and the lower signal line. And a switching transistor 26 having a gate terminal controlled by a power factor correction control circuit 24, and a capacitor 30 connected between the cathode of the diode 28 and the lower signal line, By adjusting the waveform of the power supply current, the power factor of the electronic ballast 10 is improved, and a stable high dc voltage is output.

The buck converter 18 is a switching transistor 34 having a gate terminal connected to the upper signal line and controlled by a pulse width modulation (PWM) control circuit 32, and an inductor connected in series to the switching transistor 34 ( 38), a diode 36 having a cathode connected to one end of the inductor 38 and an anode connected to the lower signal line, and a capacitor 40 connected between the other end of the inductor 38 and the lower signal line. And generates a dc current for driving the lamp.

The commutator 20 includes four transistor switches that alternately operate to switch the current signal supplied to the lamp 42, and typically changes the polarity of the lamp at low frequencies in the 100 Hz range.

In the conventional ballast circuit shown in FIG. 1, the switching transistor 26 in the boost converter 16 is connected between the upper signal line and the lower signal line and the switching transistor 34 and the inductor 38 in the buck converter 18. ) Is connected to the upper signal line so that one chip includes a PFC control circuit for controlling the switching transistor 26 in the boost converter 16 and a PWM control circuit for controlling the transistor switch 34 in the buck converter 18. It was difficult to implement. In addition, since the switching transistors 26 in the boost converter 16 and the switching transistors 34 in the buck converter 18 are controlled by separate control circuits, it is difficult to control these two transistor switches at the same frequency. It was. Therefore, reducing the noise on the power line was not easy.

An object of the present invention is to provide an electronic ballast circuit capable of controlling a PFC control switch and a PWM control switch with one chip.

Another object of the present invention is to provide an electronic ballast circuit capable of controlling the PFC control switch and the PWM control switch at the same frequency.

It is still another object of the present invention to provide an electronic ballast circuit capable of smoothly performing initial startup of a HID lamp.

1 is a circuit diagram of a conventional electronic ballast for driving a HID lamp.

2 is a circuit diagram of an electronic ballast according to the present invention for driving a HID lamp.

<Description of the symbols for the main parts of the drawings>

12, 112: EMI filter 14, 114: full bridge diode rectifier

16, 116: boost converter 18, 118: buck converter

120: protection circuit and commutator 122: lighting circuit

126: first control circuit 146: second control circuit

152: relay 154: piezoelectric ceramic transformer

162: arrester

The electronic ballast circuit according to the present invention includes a boost converter, a buck converter, a protection circuit and a commutator, and a lighting circuit, and the buck converter includes a source terminal connected to ground and a gate terminal controlled by the first control circuit. A second switching transistor, a diode having an anode connected to the drain terminal of the second switching transistor and a cathode connected to the main power line of the buck converter, an inductor having one end connected to the anode of the diode, and And a capacitor connected between the other end of the inductor and the main power line of the buck converter.

In addition, the electronic ballast circuit according to the present invention includes a boost converter, a buck converter, a protection circuit and a communicator, and a lighting circuit, the lighting circuit comprising: a piezoelectric ceramic transformer; Switching means connected in parallel to the piezoelectric ceramic transformer; A capacitor connected in series with the piezoelectric ceramic transformer; And a primary winding of the second transformer and a variable resistance means for starting a lamp connected in series with both ends of the capacitor, wherein the capacitor is charged by a high voltage generated by the piezoelectric ceramic transformer at the initial start of the lamp. And a voltage charged in the capacitor is applied to the primary winding of the second transformer and a high voltage is induced in the secondary winding of the second transformer to discharge the lamp.

Hereinafter, an electronic ballast circuit according to the present invention will be described with reference to the accompanying drawings.

2 is an electronic ballast circuit according to the present invention for driving an HID lamp, and includes an upper signal line 168 and a lower signal line 170 connected to respective terminals of a main power line. As shown in FIG. 2, the electronic ballast circuit 110 according to the present invention includes an EMI filter 112, a full bridge diode rectifier 114, a boost converter 116, a buck converter 118, a protection circuit and a commutator. 120, a lighting circuit 122, a first power circuit 172, a second power circuit 174, and a lamp 166.

The boost converter 116 includes a primary winding 124-1 of the first transformer having one end connected to the first control circuit 126, the upper signal line 168, and a primary winding 124-1 of the first transformer. Diode 132 having an anode connected to the other end of the circuit), a switching transistor Q1 and a diode 132 connected between the anode of the diode 132 and ground (GND) and controlled by the first control circuit 126. The first voltage distribution circuit 176 is connected between the cathode of the and the ground (GND) and having an output terminal connected to the first control circuit 126, and the cathode (node (N1)) of the diode 132 and ground ( And a capacitor 134 connected between the GNDs.

The buck converter 118 is connected to a switching transistor Q2 having a source terminal connected to ground GND and a gate terminal controlled by the first control circuit 126, and a drain terminal of the switching transistor Q2. A diode 136 having an anode connected to the node N1 and an inductor 138 having one end connected to the anode of the diode 136, and the other end N2 of the inductor 138 and the node ( And a capacitor 140 connected between N1).

The protection circuit and the commutator 120 are connected to the second control circuit 146, the node N1 and the node N2, and having an output terminal connected to the f / b in terminal of the second control circuit 146. 2 voltage distribution circuit 178, resistor R4 having one end connected to node N1 and the other end connected to OCP terminal of second control circuit 146 (node N3), second control circuit 146 A photo coupler 142 and a node having an input port connected between the Vcc terminal and the f / b out terminal of the output terminal and an output port connected between the Vdc terminal and the ground (GND) terminal of the first control circuit 126. Each gate terminal is connected in series between N1 and node N3 and each gate terminal is connected between switching transistors Q3 and Q5 controlled by second control circuit 146 and between node N1 and node N3. Each gate terminal is connected in series and has switching transistors Q4 and Q6 controlled by the second control circuit 146.

The lighting circuit 122 includes a piezoelectric ceramic transformer 154 having one end connected to the drain terminal of the switching transistor Q5, a diode 156 having an anode connected to the other end of the piezoelectric ceramic transformer 154, and a diode ( A resistor R7 having one end connected to the cathode of the capacitor 156, a capacitor 158 having one end connected to the other end of the resistor R7, and a second connected in series with both ends of the capacitor 158 Inductor 160, the other end of the capacitor 158 and the lamp connected between the primary winding 164-1 and the arrester 162 of the transformer, the other end of the capacitor 158 and the drain terminal of the switching transistor Q6 Secondary winding 164-2b of the second transformer connected between 166, secondary winding 164-2a of the second transformer connected between the other end of the piezoelectric ceramic transformer 154 and the lamp 166; ), The cont terminal of the second control circuit 146 and one end of the piezoelectric ceramic transformer 154 A relay 152 having a first port connected thereto and a second port connected between the node N4 and the other end of the piezoelectric ceramic transformer 154, and a cont terminal and a node of the second control circuit 146. The diode 150 is connected between N4.

The first power supply circuit 172 is connected to the other end of the secondary winding 124-2a and the first transformer secondary winding 124-2a of the first transformer having one end connected to the ground GND. Diode 128 having an anode present therein, a capacitor 130 connected between the cathode of diode 128 and ground, and a resistor R1 connected between the upper signal line 168 and the cathode of diode 128. Equipped with. The cathode of the diode 128 is also connected to the Vcc terminal of the first control circuit 126.

The second power supply circuit 174 is the secondary winding 124-2b of the first transformer having one end connected to the ground GNDB of the second control circuit 146, and the first transformer secondary winding 124-. A diode 148 having an anode connected to the other end of 2b), and a capacitor 144 connected between the cathode of the diode 148 and the ground GNDB of the second control circuit 146. .

Hereinafter, the operation of the electronic ballast according to the present invention shown in FIG.

The EMI filter 112 serves to remove electromagnetic interference, and the full bridge diode rectifier 114 serves to full-wave rectify the AC voltage signal provided from the main power line.

The boost converter 116 improves the power factor of the electronic ballast 110 by adjusting the waveform of the power supply current and outputs a stable high dc voltage. The first control circuit 126 functions to control the power factor improvement of the boost converter 116 and the pulse width modulation (PWM) of the buck converter 118, and already has one chip for a switch mode power supply (SMPS). It is commercially available. When the switching transistor Q1 is turned on, energy is accumulated in the primary winding 124-1 of the first transformer. When the switching transistor Q1 is turned off, this energy is accumulated in the capacitor 134 through the diode 132. . When an AC voltage of 85 to 264 V is applied, a DC voltage of about 400 V is accumulated in the capacitor 134. The voltage accumulated in the capacitor 134 is distributed by the first voltage distribution circuit 176 and input to the Vfb terminal of the first control circuit 126 to be used to adjust the switching frequency of the switching transistor Q1. In addition, the voltage accumulated in the capacitor is used as the main power source of the buck converter 118, the protection circuit and the communicator 120.

Buck converter 118 generates a dc current to drive the lamp. When the switching transistor Q2 is turned on, current energy is accumulated in the inductor 138. When the switching transistor Q2 is turned off, current flowing in the inductor 138 flows through the diode 136 to the main power line of the buck converter 18. Flows into.

In the protection circuit and the communicator 120, the switching transistors Q3, Q4, Q5, and Q6 alternately turn on / off the driving circuit 122, and detect and feed back the overvoltage and overcurrent on the line. . The switching transistors Q3, Q4, Q5, and Q6 are controlled by the second control circuit 146 for one period of the switching transistors Q3 and Q6, and the other period for the switching transistors Q4 and Q5. On to drive the lighting circuit 122 and the lamp 166. During the period in which the switching transistors Q3 and Q6 are turned on, the switching transistor Q3, the secondary winding 164-2a of the second transformer, the lamp 166, the secondary winding 164-2b of the second transformer, Current flows through the inductor 160, the switching transistor Q6, the resistor R4, and the inductor 138. This current flows to ground (GND) through switching transistor (Q2) when switching transistor (Q2) is on, and buck converter (118) through diode (136) when switching transistor (Q2) is off. Flow to the power line. The overcurrent flowing in the line is detected as a voltage by the resistor R4 and input to the OCP terminal of the second control circuit 146. The voltage on the main power line of the buck converter 118, that is, the voltage across the capacitor 140, is distributed by the second voltage divider 178 and input to the f / b in terminal of the second control circuit 146. The second control circuit 146 performs data processing based on the overcurrent data input to the OCP terminal and the overvoltage data input to the f / b in terminal, and then outputs the data to the f / b out terminal. When an overcurrent or overvoltage condition occurs, the f / b out terminal is turned low, the photo coupler 142 is turned on, and the Vdc terminal of the first control circuit 126 to which the output terminal of the photo coupler 142 is connected is turned low. It becomes a state. The first control circuit 126 adjusts the duty ratio of the signal output to the PWMout terminal based on the signal received from the Vdc terminal. When an overcurrent or overvoltage condition occurs, the Vdc terminal goes low and the duty ratio of the signal output to the PWMout terminal decreases. As a result, the off period is longer than the on period of the switching transistor Q2, so that the current flowing along the line is reduced, and the voltage on the main power supply is lowered.

The lighting circuit 122 receives the output of the commutator composed of the switching transistors Q3, Q4, Q5, and Q6 to light the lamp 166, and at the initial ignition, high voltage across the lamp 166. Induces to discharge the lamp 166. At initial startup, the relay 152 is off and current flows through the piezoelectric ceramic transformer 154. The piezoelectric ceramic transformer 154 receives the output of a commutator which is full bridge driven at several tens of kHz by the second control circuit 146 and generates a voltage of several kV. As a result, current flows through the diode 156 and the resistor R7, which charges the capacitor 158. The arrestor 162 is a device having a property that a current flows rapidly when it is normally turned off and a constant voltage is applied to both ends. When the voltage charged in the capacitor 158 is greater than or equal to a certain value, the arrester 162 becomes conductive, and the voltage is applied to the primary winding 164-1 of the second transformer. As a result, a high voltage is induced to the secondary windings 164-2a and 164-2b of the second transformer, and the lamp 166 is discharged and current starts to flow. Even though current starts to flow in the lamp 166, the relay 152 is turned off for a predetermined time to heat the lamp 166 with a low current at several kV. After the heating of the lamp 166 is completed, the second control circuit 146 converts the switching frequency of the commutator to tens to hundreds of Hz, and turns on the relay 152 through the cont terminal. When the cont terminal is low, the relay 152 is turned on and the piezoelectric ceramic transformer 154 stops operating. The diode 150 connected in parallel with the relay 152 has the effect of mitigating surge voltage that may occur at the cont terminal.

High current now begins to flow in the lamp 166, which is detected by the overcurrent detecting resistor R4. When an overcurrent occurs, the current detected by the resistor R4 is input to the OCP terminal of the second control circuit 146 and a signal which is low through the signal processing is output to the f / b out terminal. When the f / b out terminal goes low, the output of the photo coupler 142 goes low and is applied to the Vdc terminal of the first control circuit. Accordingly, the duty ratio of the signal output to the PWMout terminal of the first control circuit is reduced, and the on-in section of the switching transistor Q2 is shorter than the off-in section. As a result, the voltage applied to the lamp 166 is reduced. When the current flowing in the lamp 166 falls below the limited value, the voltage applied to the lamp 166 returns to its original state.

The first power supply circuit 172 is a circuit for supplying a power supply voltage to the first control circuit 126. When power is first supplied to the electronic ballast system, the first power supply circuit 172 controls the first power through the resistor R1 from the upper signal line 168. Power is supplied to the Vcc terminal of the circuit 126, and after the current begins to flow in the primary winding 124-1 of the first transformer, it is charged by the current flowing in the secondary winding 124-2a of the first transformer. The power is supplied to the Vcc terminal of the first control circuit 126 by the capacitor 130 voltage.

The second power supply circuit 174 is a circuit required to supply a power supply voltage to the second control circuit 146 and to switch the relay 152. The second power supply circuit 174 is a current flowing through the secondary winding 124-2b of the first transformer. Power is supplied to the Vcc terminal of the second control circuit 146 by the charged capacitor 144 voltage.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

As described above, according to the electronic ballast circuit according to the present invention, it is possible to control the switch for PFC control and the switch for PWM control at the same frequency in one chip. In addition, according to the electronic ballast circuit according to the present invention, it is possible to smoothly start up the HID lamp by using a piezoelectric ceramic transformer in the lighting circuit.

Claims (6)

In an electronic ballast circuit having a boost converter, a buck converter, a protection circuit and a commutator, and a lighting circuit, the buck converter A second switching transistor having a source terminal connected to ground and a gate terminal controlled by the first control circuit; A diode having an anode connected to the drain terminal of the second switching transistor and a cathode connected to the main power line of the buck converter; An inductor having one end connected to an anode of the diode; And And a capacitor connected between the other end of the inductor and the main power line of the buck converter. The method of claim 1, wherein the first control circuit of the buck converter And control the first switching transistor together to improve the power factor of the boost converter. The method of claim 2, wherein the second switching transistor And an electronic ballast circuit operating at the same frequency as said first switching transistor. In an electronic ballast circuit comprising a boost converter, a buck converter, a protection circuit and a commutator, and a lighting circuit, the lighting circuit includes: Piezoelectric ceramic transformer; Switching means connected in parallel to the piezoelectric ceramic transformer; A capacitor connected in series with the piezoelectric ceramic transformer; And A primary winding and a variable resistance means of a second transformer for starting a lamp connected in series with both ends of said capacitor, The capacitor is charged by the high voltage generated by the piezoelectric ceramic transformer at the initial startup of the lamp and the voltage charged on the capacitor is applied to the primary winding of the second transformer and to the secondary winding of the second transformer. Electronic ballast circuit, characterized in that the high voltage is induced to discharge the lamp. The method of claim 4, wherein the variable resistance means An electronic ballast circuit, which is an arrester. The method of claim 4, wherein And a diode and a resistor connected in series between the piezoelectric ceramic transformer and the capacitor.