KR200178692Y1 - Electronic ballast for gas discharge lamp - Google Patents

Abstract

The present invention relates to an electronic ballast applied to a discharge lamp, in particular, a power circuit unit for outputting a boosted DC voltage by receiving a commercial exchange, and in response to a pair of switching drive signals switching the boosted DC voltage to discharge the lamp A half-bridge inverter for driving, an inverter driver for generating a pair of switching driving signals having a predetermined dead time and a 180 degree phase difference between switching on periods, and a high and low cycle repeated in a predetermined period in a microprocessor The digital control unit for providing a signal and the inverter driving unit receive a signal provided from the digital control unit so that the frequency shift is circulated so that the discharge lamp is stably lit. In particular, it maintains the discharge lamp stably even when the microprocessor malfunctions by maintaining the operation without any difficulty until the normal operation is performed by the watch dog function in the microprocessor even if the microprocessor malfunctions or goes down. .

Description

Electronic ballast for discharge lamps {ELECTRONIC BALLAST FOR GAS DISCHARGE LAMP}

The present invention relates to an electronic ballast for keeping a discharge lamp lit, and is particularly suitable for stably maintaining a metal halide lamp. When the metal halide lamp is turned on by the electronic ballast, sparks or acoustic resonance are generated. A method of preventing and stably lighting the discharge lamp is disclosed in US Pat. No. 56,80015. This method continuously varies a predetermined cycle by the microprocessor to keep the discharge lamp on. In other words, the driving frequency and waveforms are generated by the microprocessor and supplied to the inverter circuit. However, the frequency for driving a metal halide lamp with a low wattage of less than 100W is usually more than 100KHz. When creating a waveform by a microprocessor, the clock frequency should be 20 MHz or higher. This is an expensive problem but has a weak point due to the high clock frequency, which is very weak to external noise. In the case of high-voltage discharge lamps, high voltages of several to several tens of KV are required to start lighting. If this signal flows into the microprocessor operating by 5V, the microprocessor malfunctions or goes down and the ballast is destroyed. In some cases, the discharge lamp may be turned off due to disturbance of the microprocessor due to external noise inflow.

The first object of the present invention is to solve the problems of the prior art, the basic waveform of the drive unit of the drive is performed by the analog method and the microprocessor is high in the range of several tens of microseconds using a low clock frequency of about 4MHz The present invention provides an electronic ballast for discharging lamps, which outputs a LOW signal and uses the signal to cause the frequency shift in the inverter driver to be circulated so that the discharge lamp can be stably lit.

It is a second object of the present invention to provide an electronic ballast for a discharge lamp that can sustain the discharge of the lamp without any trouble until the microprocessor malfunctions or is down by noise until it is revived by the watch dog function. .

A third object of the present invention is to provide an electronic ballast for a discharge lamp that simplifies and enhances a circuit through a microprocessor for complex functions such as start-up and protection mode operation.

A fourth object of the present invention is to realize a ballast having a relatively large output since the dead time can be arbitrarily adjusted in driving an inverter.

The final object of the present invention is to provide an electronic ballast for the discharge lamp to protect the ballast in the event of overheating, no load, and the like.

In order to achieve the above object, the present invention provides a power supply circuit unit which receives a commercial AC and outputs a boosted DC voltage, and a half for driving a discharge lamp by switching the boosted DC voltage in response to a pair of switching driving signals. A bridge type inverter, an inverter driver for generating a pair of switching driving signals having a predetermined dead time and a 180 degree phase difference between the switching on periods, and a high frequency at a predetermined period in the microprocessor to shift the frequency of the driving signal. The frequency control unit of the digital control unit and the inverter driving unit which provide a LOW repeated signal are supplied to the base of the transistor by being charged and discharged by a resistor and a capacitor by receiving a high and low LOW repeated signal from a microprocessor. Analog in frequency by varying the resistance of the crystal element The discharge lamp is stably lit in such a way that the shift is repeated. In particular, even if the microprocessor malfunctions or goes down, the watchdog function in the microprocessor continues to operate only with the signal of the inverter drive unit until normal operation. To keep the discharge lamp steady.

In addition, the device of the present invention can arbitrarily adjust the dead time of the discharge lamp, so that it can be applied to a relatively large number of watts, and the constant power control by the dead time control for the increase in output which is the end of the life of the discharge lamp and the unevenness of the output according to the manufacturer. You can do When the start of the discharge lamp fails to start for a certain time or overheats the ballast, or when the microprocessor does not operate normally for a certain time, the auxiliary power is turned down to the ground voltage level. It is characterized by.

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

2A is a power supply circuit diagram of a preferred embodiment according to the present invention.

2B is a view illustrating an inverter and an inverter driving circuit in accordance with a preferred embodiment of the present invention.

2C is a digital control unit of the preferred embodiment of the present invention.

Figure 3A is a waveform diagram of the output and drive signal of a preferred embodiment according to the present invention.

3B is a waveform diagram of a frequency shift unit according to the present invention.

<Description of the code | symbol about the principal part of drawing>

100: power supply circuit section 12: current detection section

14 boost unit 16 auxiliary power unit

200: inverter unit 300: inverter drive unit

32: drive signal generator 34: frequency shift unit

36: inverter drive unit 400: digital control unit

42: lamp lighting detection unit 44: high voltage cut-off unit

46: drive signal blocking unit 48: power off protection unit

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention through an embodiment of the present invention.

1 schematically shows a circuit configuration of a block diagram of an electronic ballast for a discharge lamp according to the present invention. The ballast of the present invention is largely composed of the power circuit unit 100, the inverter unit 200, the inverter driver 300, the digital control unit 400.

Referring to FIG. 2A, the power supply circuit unit 100 includes a varistor V1, a fuse F, a filter, a full-wave rectifying diode D1, D2, D3, and D4, a current detector 12, and a boost unit 14. And an auxiliary power supply unit 16. The commercial AC power outputs the first DC voltage V1 through the full-wave rectifying diodes D1-D4 through the EMI suppression filter.

The current detector 12 includes a current transformer CT, diodes D8 and D9, and a capacitor C4. When the load current is detected, it is rectified by the diodes D8 and D9, smoothed by the capacitor C4, and output to the inverter driver through the terminal 6.

The boost section 14 includes a PFC control circuit, a smoothing input capacitor C1, a transformer T1, a switching element Q1, a resistor R2, a diode D5, and a smoothing output capacitor C2. It consists of. The boost unit 14 performs high frequency switching of the first DC voltage V1 to the switching element Q1 and boosts the voltage to the transformer T1 to output the second DC voltage V2 as the main operating voltage. The transformer T1 includes a first winding T1 / 1 and a second winding T1 / 2.

The auxiliary power supply unit 16 includes diodes D3, D4, D6 and D7, resistors R1 and R10, capacitors C3, C10, C11 and C12, and a regulator REG zener diode ZD1. The auxiliary power source uses half-wave rectification and smoothing of the power induced in the secondary coil T1 / 2 of the transformer T1 during high-speed switching of the switching element Q1. That is, the voltage passing through the diode D6 and the direct current first voltage V1 are combined with the voltage stepped down by the resistor R1 to output the direct current third voltage V3, which is protected from the power supply through the terminal 5. It is sent to the part 48 and is used to protect the circuit by lowering to the ground voltage during the protection mode operation. In addition, the DC third voltage V3 is used as a power source of the PFC control circuit by smoothing the capacitor C3 through the inserted diode D7 to prevent current from flowing in the reverse direction. The inverter driving unit power is rectified by the diode (D3), smoothed by the capacitor (C10), and then rectified by the regulator (REG), which is a constant voltage device, smoothed by the capacitor (C11), and output as a DC fourth voltage (V4). The power supply is stepped down by the resistor R10 and the zener diode ZD1 through the diode D4, smoothed by the capacitor C12, and output as the DC fifth voltage V5.

Referring to FIG. 2B, the inverter unit 200 includes switching elements Q2 and Q3, diodes D1 and D2, varistors V2 and V3, capacitors C13 and C14, and a ballast inductor T2. . The ballast inductor T2 includes three windings T2 / 1, T2 / 2 and T2 / 3. Inverter unit 200 is a half-bridge inverter, the switching elements (Q2, Q3) are alternately operated to create a load waveform diagram as shown in Figure 3A to turn on the discharge lamp with an alternating current of high frequency.

The inverter driver 300 includes a drive signal generator 32, a frequency shifter 34, and an inverter driver 36. This shifted waveform generates a reference waveform of frequency F1 in the gate waveform diagrams of Q2 and Q3 of FIG. 3A in the drive signal generator 32 and gradually increases analogously from frequency F1 to F2 in the frequency shifter 34. To make it and supply it to the inverter drive unit 36 to operate the inverter unit 200.

The drive signal generator 32 includes a drive signal generator IC U2, resistors R13-R21, a variable resistor R22, and a capacitor C17. The basic frequency setting is determined by the resistors R21 and R22 and the capacitor C17 connected to the terminals RT and CT of the inverter driving signaling IC U2, and the inverter driving signal generating IC ( U2 alternately generates pulse signals at terminals E2 and E1 output to resistors R13 and R14. At this time, the dead time of the active signal section is determined by the voltage applied to the terminal DT of the signal generator IC U2 for driving the inverter. The basic dead time divides the voltage of the reference voltage terminal Vref by the resistors R17 and R19. It is set by applying. The constant output control is executed by the dead time controlled according to the voltage applied to the non-inverting terminal of the OP AMP of the inverter driving signal generating IC U2 in accordance with the magnitude of the load current. It supplies the reference voltage (Vref) to the inverting terminal of the OP AMP of the inverter driving signal generation IC (U2) as the basic voltage through the resistor (R15), and feeds back through the resistor (R16) at the output terminal of the OP AMP to invert When the load current is increased, the current of the current detection unit of FIG. 2A increases, and the voltage of the non-inverting terminal in the 0P AMP of the inverter driving signal generating IC U2 is increased through the terminal 6, thereby increasing the dead time. As a result, the output is lowered to control the constant power. Dimming control is realized by controlling the frequency by adjusting the variable resistor R22.

The frequency shift section 34 is composed of resistors R23, R24, R25, capacitor C18, and transistor TR4. The resistor R24 is connected between the connection point of the resistors R22 and R21 and the collector of the transistor TR4 and the emitter of the transistor TR4 is connected to the ground point. A capacitor C18 and a resistor R23 are respectively connected in parallel between the base of the transistor TR4 and the ground point. The resistor R25 is connected between the terminal 7 connected to the terminal P2 of the microprocessor U3 and the base of the transistor TR4. The operation of this circuit is as follows. Frequency determination is based on the change of the resistance value connected to the terminal RT of the driving signal generator IC U1. That is, the terminal P2 of the microprocessor U3 of FIG. 2C outputs oscillated waveforms of HIGH and LOW within about several tens of microseconds as shown in FIG. 3B. The frequency shift part 34 supplied with the waveform to the terminal 7 drives the base of the transistor TR4 to a waveform as shown in FIG. 3B while charging and discharging the resistors R25 and R23 and the capacitor C18. . As a result, by controlling the current flowing through the resistor R24, as a result, as shown in FIG. 3A, the frequency gradually changes from F1 to F2, and the waveform changes analogously and this change is repeated periodically. This shift in frequency at the gate for a short time is repeated to keep the discharge lamp, especially the metal halide lamp, steady on.

The inverter drive unit 36 is composed of an inverter driver IC U1, diodes D5, D6, and D7, resistors R11 and R12, and a capacitor C15. The inverter drive unit receives an alternate driving signal based on the ground point from the driving signal generator 32 and converts the driving signal into a signal capable of driving the switching elements Q2 and Q3 to drive the inverter unit 200.

Referring to FIG. 2C, the digital control unit 400 includes a microprocessor U3, a lamp lighting detection unit 42, a high voltage breaking unit 44, a driving signal blocking unit 46, and a power cut protection unit 48. . Microprocessor (U3) has a built-in program, and the function of each terminal is as follows and the clock uses an internal clock.

1. P0: Outputs a signal to protect the ballast when there is no lamp or at start-up failure. That is, if the terminal P3 does not change from HIGH to LOW even after a certain time elapses, a HIGH signal is output.

2. P1: Output terminal for protection during abnormal operation as a micro. If a certain time elapses, HIGH signal is output unconditionally. This signal is absent if the processor is down.

3. P2: Output terminal for frequency shift. Repeat HIGH and LOW in tens of microseconds.

4. P3: Input terminal to check lamp ON / OFF. HIGH indicates lamp OFF and LOW indicates lamp ON.

5. P4: Output terminal to stop driving signal. Outputting HIGH stops the drive signal.

6. P5: Output terminal to stop high voltage start signal. High output stops the high voltage start signal.

The lamp lighting detecting unit 42 is composed of a varistor V4, a diode D8, resistors R26 and R27, a capacitor C16, and a transistor TR1. When the lamp is turned on, the voltage is induced in the third winding T2 / 3 of the ballast of the inverter unit 200, and the voltage is rectified by the diode D8 and smoothed by the capacitor C16 to turn on the transistor TR1. Make terminal (P3) of (U3) LOW and recognize it as lit. However, if terminal P3 is HIGH, the lamp is turned off.

The high voltage blocking unit 44 includes a transistor TR2, diodes D9 and D10, and a resistor R28. This works in two ways: That is, when power is supplied to the ballast, the high voltage generator of the inverter unit 200 generates a high voltage. When the lamp is turned on, a detection signal is generated by the lighting detector 42 to turn on the transistor TR2 via the diode D9. The high voltage is cut off by bringing the signal of the high voltage generator of (10) to the ground level. This high voltage interrupter also operates when there is a HIGH signal at terminal P5 of microprocessor U3.

The driving signal blocking section 46 is composed of a transistor TR3. This is operated when the microprocessor is in the start mode operation or the protection mode operation. When the terminal P4 becomes HIGH, the driving signal output is stopped.

The power cut-off protection unit 48 includes diodes D11, D12, and D13, resistors R32-R35, thyristors SCR, zener diodes ZD2, capacitors C19, transistors TR5, and temperature switches TS. It is composed of The DC third voltage V3 is connected to the anode of the thyristor SCR through the terminal 5. The cathode of the thyristor (SCR) is connected to the ground point. The resistors R32 and R33 are connected in series between the terminal 5 and the ground point, and the temperature switch TS is connected in parallel to the resistor R33. An anode of the diode D11 is connected to the connection point of the resistors R32 and R33, and the cathode is connected to the gate of the thyristor SCR. Resistors R34 and R35 are connected in series between the terminal 5 and the ground point, and a capacitor C19 is connected in parallel to the resistor R35. The collector and emitter of transistor TR5 are connected between the connection point of resistors R34 and R35 and the ground point. The base of the transistor TR5 is connected via a resistor R31 at the terminal P1 of the microprocessor U3. The connection points of the resistors R34 and R35 are connected to the cathode of the zener diode ZD2 and the anode is connected to the anode of the diode D13. The cathode of the diode D13 is connected to the gate of the thyristor SCR. The cathode of diode D12 is connected to the gate of thyristor SCR and the anode of diode D12 is connected via resistor R30 at terminal P0 of microprocessor U. The operation of this circuit outputs HIGH signal to the terminal P0 by the built-in program when the lamp does not turn on even after the first predetermined time elapses, that is, when the lamp ON / OFF check terminal P3 does not change from HIGH to LOW. The thyristor SCR is turned on, thereby lowering the auxiliary third DC voltage V3 of FIG. 2A to the ground voltage level to stop all operations of the PFC control circuit and the inverter driver 300 to protect the ballast. Second, when the ballast is abnormally overheated, the temperature switch TS is turned from the ON state to the OFF state, and the thyristor SCR is turned on to stop the operation of both the PFC control circuit and the inverter driver 300. Thirdly, if the microprocessor (U3) malfunctions due to external noise and does not return to normal even after a certain period of time, the protected mode is protected. After a predetermined time, the terminal P1 outputs a HIGH signal. As a result, the transistor TR5 is turned on and the voltage of the capacitor C19 becomes the ground voltage so that the thyristor SCR is not turned on. However, if the microprocessor malfunctions, the terminal P1 does not go high even after a certain time. Accordingly, the third DC voltage V3 formed at the terminal 5 charges the capacitor C19 to a voltage divided by the resistors R34 and R35. The high voltage generating circuit and the inverter driving circuit operate normally until the charging voltage exceeds the voltage of the zener diode ZD2. However, if the capacitor (C19) voltage exceeds the Zener diode (ZD2) voltage after a longer time, the thyristor (SCR) is turned on to make the DC third voltage (V3) to the ground voltage and stop all operations of the ballast. Protect.

The built-in program of the digital controller operates in the following modes. When the power is applied, the microprocessor executes the start-up mode and generates and stops the high voltage and driving signals by repeating the terminals P4 and P5 several times LOW and HIGH at regular intervals. If it does not turn on, it is determined that there is no lamp or the lamp is heated and the terminal (P4, P5) is made HIGH for several minutes to stop the generation of high voltage and driving signal. Next, go back to the beginning and repeat the above process twice as an example. If it still does not turn on, the lamp is considered to be absent and the terminal (P0) is set to HIGH to disconnect the ballast's auxiliary power. When the lamp is turned on during any of the above periods, only P5 is made HIGH to stop the high voltage and continue to output the drive signal. If the microprocessor U3 does not operate normally due to external noise, a high voltage and a driving signal are generated only by the analog circuit. In other words, even if the microprocessor is down, the inverter drive unit and the high voltage generating circuit are operated so that the start signal is generated and turned on, and even if the microprocessor is down after being turned on, the analog circuit is revived by the watchdog function. Keeps on because it continues to operate. However, when the microprocessor is down for a long time, the power cut protection unit is operated to protect the ballast by stopping it. In all of this, the watchdog function is performed.

According to the present invention, the waveform that drives the inverter is analogized in the inverter driver, and the microprocessor provides only a signal capable of shifting the frequency, so that the watchdog can be watched even if the microprocessor malfunctions or is down by noise. It can keep the discharge lamp on without any problem until it comes to life again, and the clock frequency can be reduced as low as 4MHz, so it is relatively strong against noise and provides a reliable ballast. In addition, the present invention has a feature to configure the ballast to increase the function and simplify the circuit, because the complex logic of the start mode or other protection mode is performed by the microprocessor.

In addition, the present invention can arbitrarily adjust the dead time of the oil signal section of the inverter drive unit to realize a ballast having a relatively high output. Its output is rated at the rated output, and a low-cost ballast can be realized by using various protection modes by only an 8-pin microprocessor.

In addition, the present invention has a characteristic of protecting the ballast by stopping the operation of the ballast when the microprocessor does not operate normally for a certain period of time during start-up and protecting the ballast in case of abnormality such as overheating and no load.

Claims (10)

A power supply circuit unit for outputting a boosted DC voltage by inputting commercial AC; A half bridge inverter unit for driving a discharge lamp by switching the boosted DC voltage in response to a pair of switching driving signals; An inverter driving circuit unit for generating a pair of switching driving signals having a predetermined dead time between the switching on periods and having a phase difference of 18 degrees; And An electronic ballast for a discharge lamp, characterized in that the microprocessor has a digital control section for generating a signal in which the HIGH and LOW are repeated at regular intervals. The electronic ballast of claim 1, wherein the driving circuit unit is configured to cycle the frequency shifted by receiving a signal in which the HIGH and LOW cycles are repeated from the digital controller at a predetermined cycle. The method of claim 1, wherein the driving circuit unit continues to operate while the microprocessor of the digital controller resumes operation by the watchdog function of the microprocessor when the microprocessor of the digital controller malfunctions or is down for some reason. Electronic ballasts for discharge lamps. The electronic ballast of claim 1, wherein the driving circuit unit can arbitrarily adjust a dead time. The electronic ballast of claim 1, wherein the driving circuit unit performs constant output control by dead time control by current detection of the power supply circuit unit. The electronic ballast of claim 1, wherein the driving circuit unit is capable of starting and maintaining lighting even when the digital control unit stops operating. The method of claim 1, wherein the digital control unit repeats the operation and stop several times at a predetermined time interval for several seconds when starting the discharge lamp, and after the start stop for several minutes when the start is not started The electronic ballast for a discharge lamp, characterized in that to stop the operation of the ballast if the above process is repeated again several times and still does not start. The electronic ballast of claim 1, wherein the digital controller includes a circuit capable of operating and stopping the high voltage start signal and the drive signal when starting the discharge lamp. The electronic lamp of claim 1, wherein the digital control unit protects the ballast by stopping the operation of the ballast by stopping the auxiliary power when the microprocessor is down and does not return to normal operation even after a predetermined time elapses. ballast. The ballast of claim 1, wherein the digital control unit stops the operation of the ballast by interrupting the auxiliary power supply in case of abnormality, such as overheating of the ballast, starting failure, and the microprocessor being down and not returning to normal operation even after a predetermined time elapses. An electronic ballast for discharge lamps, characterized in that the protection.