CN2473854Y - Electronic ballast - Google Patents

Abstract

The utility model discloses an electronic ballast, which comprises a rectification circuit, a half-bridge inverter circuit, a soft start circuit, a high-frequency double-pump circuit and an abnormal protection circuit. The output end of the inverter circuit is connected to the input end of the soft start circuit, the output end of the soft start circuit is connected to the input end of the high frequency double pump circuit, the output end of the high frequency double pump circuit is connected to the output end of the rectifier circuit, abnormal protection The input end of the circuit is connected to the output end of the half-bridge inverter circuit, and the output end of the abnormal protection circuit is connected to the control end of the half-bridge inverter circuit. The utility model has long service life and wide voltage adaptable range.

Description

electronic ballast

The utility model relates to an electronic ballast for controlling the delayed start and lighting of fluorescent lamps.

There are many kinds of electronic ballasts available, mainly including ordinary bridge rectifier electrolytic capacitor filter electronic ballasts, flow-by-flow filter electronic ballasts, high-frequency double-pump electronic ballasts, etc. The performance of these electronic ballasts is Poor, fluctuating voltage adaptability range is narrow, once abnormal situation occurs, the above-mentioned electronic ballasts are easily damaged, so the existing electronic ballasts have a short service life despite their low cost; and the existing electronic ballasts The inverter often interferes with the power grid due to its own high-frequency oscillation, which affects the normal work.

The purpose of the utility model is to provide an electronic ballast with long service life and wide voltage adaptability range.

In order to achieve the above object, the utility model includes a rectifier circuit, a half-bridge inverter circuit, a soft start circuit and a high-frequency double-pump circuit. The input end of the starter circuit is connected, the output end of the soft start circuit is connected to the input end of the high-frequency double-pump circuit, the output end of the high-frequency double-pump circuit is connected to the output end of the rectification circuit, and it is characterized in that it also includes an abnormality protection circuit, The input end of the circuit is connected with the output end of the half-bridge inverter circuit, and the output end of the circuit is connected with the control end of the half-bridge inverter circuit; when an abnormal situation occurs, the half-bridge is controlled by the abnormal protection circuit The oscillator in the inverter circuit stops vibrating.

The abnormality protection circuit includes a sampling voltage divider formed by serially connecting capacitor C7, voltage dividing resistors R9 and R10, a rectifier diode D13, a differential circuit composed of a resistor R11 and a capacitor C12, a bidirectional trigger tube D14, and a resistor R12 , R13, capacitor C13 is an integral circuit composed of thyristor Q3 and diode D15, one end of the sampling voltage divider is the input end of the abnormal protection circuit, the other end is grounded, the series connection point of the voltage dividing resistor R9 and the resistor R10 is passed through the rectifier diode D13, the differential circuit composed of resistor R11 and capacitor C12 is connected to the trigger terminal of bidirectional trigger D14, and the output terminal of bidirectional trigger D14 is connected to the control pole G of thyristor Q3 through the integration circuit composed of resistors R12, R13 and capacitor C13 connection, the cathode of the thyristor is grounded, the anode of the thyristor is connected to the power supply through the resistor R7, and the anode of the thyristor is connected to the anode of the diode D15, and the cathode of the diode D15 is used as the output terminal of the abnormal protection circuit.

An instantaneous overvoltage protection circuit is connected in series between the rectification circuit and the input AC power supply, and the circuit is composed of a fuse FU and a varistor RV.

As a further improvement to the utility model, an anti-electromagnetic interference circuit is connected in series between the instantaneous overvoltage protection circuit and the rectifier circuit. The circuit is composed of a capacitor C1 and an inductor L1, and the inductor L1 and the capacitor C1 are connected to form an inverted "L" filter circuit.

Due to the abnormal protection circuit and instantaneous overvoltage protection circuit, it will not damage the electronic ballast in abnormal state or overvoltage phase error, thus greatly prolonging the service life; at the same time, it is also equipped with anti-electromagnetic interference circuit, that is, It can suppress the interference signal in the power grid from affecting the normal operation of the electronic ballast, and filter and attenuate the electromagnetic interference generated by the electronic ballast itself, so as to ensure that the power grid is not polluted.

Below in conjunction with accompanying drawing and embodiment the utility model is described further.

Fig. 1 is a schematic block diagram of the utility model;

Fig. 2 is the schematic circuit diagram of the utility model.

As shown in Figures 1 and 2, the utility model includes an instantaneous overvoltage protection circuit 1, an anti-electromagnetic interference circuit 2, a rectifier circuit 3, a half-bridge inverter circuit 4, an abnormal protection circuit 7, a soft start circuit 5 and a high-frequency dual The pump circuit 6, the instantaneous overvoltage protection circuit 1, the anti-electromagnetic interference circuit 2 and the rectification circuit 3 are sequentially connected in series, and the output terminal of the rectification circuit 3 outputs the operating voltage of other circuits, and the output terminal 4 of the half-bridge inverter circuit is connected to the soft The input end of the starting circuit 5 is connected, the output end of the soft start circuit 5 is connected with the input end of the high-frequency double-pump circuit 6, the output end of the high-frequency double-pump circuit 6 is connected with the output end of the rectification circuit 3, and the abnormal protection circuit 7 is input end is connected with the output end of the half-bridge inverter circuit 4, and the output end of the abnormal protection circuit 7 is connected with the control end of the half-bridge inverter circuit 4; when an abnormal situation occurs, the abnormal protection circuit 7 controls the half-bridge inverter circuit The oscillator in 4 is stopped. The abnormality protection circuit 7 includes a sampling voltage divider formed by serially connecting a capacitor C7, a voltage dividing resistor R9, and R10, a rectifier diode D13, a differential circuit consisting of a resistor R11 and a capacitor C12, a bidirectional trigger tube D14, and a resistor R12 , R13, capacitor C13 composed of integral circuit, thyristor Q3 and diode D15, one end of the sampling voltage divider is the input end of the abnormal protection circuit 7, the other end is grounded, the series connection point of the voltage dividing resistor R9 and the resistor R10 is rectified The differential circuit composed of diode D13, resistor R11 and capacitor C12 is connected to the trigger terminal of bidirectional trigger D14, and the output terminal of bidirectional trigger D14 is connected to the control pole G of thyristor Q3 through the integration circuit composed of resistors R12, R13 and capacitor C13. connected, the cathode of the thyristor is grounded, the anode of the thyristor is connected to the power supply through the resistor R7, and the anode of the thyristor is connected to the anode of the diode D15, and the cathode of the diode D15 is used as the output end of the abnormal protection circuit 7.

The working principle of the circuit is described as follows in conjunction with accompanying drawing 2: The instantaneous overvoltage protection circuit 1 is composed of a fuse FU and a varistor RV. The value is approximately infinite, so that the electronic ballast can work normally. When the AC input voltage increases sharply due to wrong phase connection or other reasons, when the rated load voltage of the varistor RV is exceeded, the varistor value will decrease instantly. The current through it suddenly increases a lot, exceeding the fusing current value of the fuse FU, and the fuse FU is blown, which protects the electronic ballast circuit from being burned.

The anti-electromagnetic interference circuit 2 is composed of a capacitor C1 and an inductor L1, and the inductor L1 and the capacitor C1 are connected to form an inverted "L" filter loop. The circuit not only suppresses the interference from the power grid, but also attenuates the electromagnetic interference generated by the electronic ballast itself, so as to ensure that the power grid is not polluted.

The bridge rectifier circuit 3 is composed of diodes D1-D4, and the filter circuit is composed of diodes D11, D12 and capacitors C11 and C12 in the high-frequency double-pump circuit. It superimposes the rectified original pulsating DC voltage and the high-frequency voltage of the high-frequency double-pump circuit to form a DC voltage with small ripples, which provides a working DC voltage for the half-bridge inverter.

The half-bridge inverter circuit 4 is composed of diodes D5-D8, resistors R1-R6, capacitors C2-C4, switch tubes Q1, Q2, pulse transformer T and ballast coil L2. After the power supply is turned on, first, a base trigger current is provided by the resistors R1 and R4 to turn on the switch tube Q2, and the oscillation is established by the positive feedback coupling of the pulse transformer T and the inductance, and a current flows through the winding N3 of the pulse transformer T, and the ballast coil L2, filaments f1, f2 charge capacitors C5, C6. Since the winding N3 of the pulse oscillation transformer T is in the same phase as the winding N1, the base of the switching tube Q1 is turned on due to the forward bias voltage, and the charges stored in the capacitors C5 and C6 are discharged through the switching tube Q1. At the same time, the winding N1 of the pulse oscillation transformer T is opposite to the phase of the winding N2, and the signal voltage induced on the winding N2 is opposite to the polarity of the originally applied forward bias voltage, which prompts the switching tube Q2 to turn from the conduction state to In the cut-off state, one oscillation cycle is completed, so that the switching tubes Q1 and Q2 quickly establish oscillation. After the circuit oscillation is established, the two ends of the series resonant capacitors C5 and C6 generate a very high frequency AC voltage, which excites the fluorescent lamp to start and ignite.

The starting voltage of the soft start circuit 5 is divided by the series capacitors C5 and C6, and the thermistor RT is connected in parallel with the capacitor C6. During the preheating period of the lamp, the thermistor RT is equivalent to a short circuit. The preheating current passes through the capacitor C5 and the thermistor RT. The current passes through the capacitors C5 and C6, which immediately causes LC series resonance, and a very high resonance voltage is applied at both ends of the lamp tube, which breaks down the lamp tube and ignites it. The process of the thermistor RT from low resistance to high resistance is the process in which the preheating current preheats the filament to the electron emission temperature before it is ignited. Through this process, the sputtering of the cathode emission material is avoided and the lamp life is extended. life.

The high-frequency dual-pump circuit 6 includes diodes D9-D12 and capacitors C8-C11. In a short time after the power is turned on, large-capacity capacitors C10, C11 and diodes D9-D12 form a parasitic diode capacitor filter circuit to make electronic ballast The device starts working. After the lamp is ignited and enters steady-state operation, part of the high-frequency current returns to the power supply through capacitors C8 and C9, while the other part is rectified and filtered by capacitors D9 and C10 and diodes D10 and C11 to generate positive and negative auxiliary voltages ±ΔV, and The 100HZ pulsating DC output from the above-mentioned full-wave rectification circuit is superimposed through diodes D11 and D12 respectively to form a DC voltage with small ripples, which is used as the power supply voltage of the half-bridge inverter. The purpose of setting this circuit is to make the lamp current crest factor less than 1.7, while the power factor is greater than 0.93, and the THD index reaches the H level.

When the abnormality protection circuit 7 is in a normal state, because the sampling signal is small, the bidirectional trigger D14 cannot reach its breakdown voltage, so the protection circuit cannot be activated and will not affect the operation of the ballast. When there are abnormal conditions such as aging of the lamp tube, air leakage, disconnection between the lamp and the ballast, and filament fusing, the output power of the electronic ballast will increase by 1 to 2 times the normal value, and the abnormal state protection circuit will pass through the capacitor C7 and Divider resistors R9 and R10 obtain the sampling voltage, which is rectified by diode D13, and the differential circuit breaks down bidirectional trigger D14 after differentiation, and then sends it to the integrating circuit, so that the thyristor Q3 is turned on, resulting in the base drive current of triode Q1 It will be grounded through the thyristor Q3, so that the oscillator stops vibrating, and the electronic ballast stops working. After the lamp returns to normal, after disconnecting the power supply for a few seconds, then reconnecting the power supply, the electronic ballast will work normally directly, so as to protect the electronic ballast from being damaged in an abnormal state and prolong the service life of the electronic ballast. life.

Claims (4)

1; a kind of electric ballast; comprise rectification circuit (3); half-bridge inversion circuit (4); soft starting circuit (5) and high frequency dual-pump circuit (6); the output of rectification circuit (3) provides the working power of each circuit; the output of half-bridge inversion circuit (4) is connected with the input of soft starting circuit (5); the output of soft starting circuit (5) is connected with the input of high frequency dual-pump circuit (6); the output of high frequency dual-pump circuit (6) is connected with the output of rectification circuit (3); it is characterized in that: also comprise abnormity protection circuit (7); the input of this circuit is connected with the output of described half-bridge inversion circuit (4), and the output of this circuit is connected with the control end of described half-bridge inversion circuit (4).

2; electric ballast according to claim 1; it is characterized in that: described abnormity protection circuit (7) comprises by electric capacity (C7); divider resistance (R9; R10) be connected in series the sampling voltage divider that forms successively; rectifier diode (D13); by resistance (R11); the differential circuit that electric capacity (C12) is formed; two-way trigger tube (D14); by resistance (R12; R13); the integrating circuit that electric capacity (C13) is formed; controllable silicon (Q3) and diode (D15); one end of sampling voltage divider is the input of this abnormity protection circuit; other end ground connection; the serial connection point of divider resistance (R9) and resistance (R10) is through rectifier diode (D13); resistance (R11) is connected with the trigger end of two-way trigger tube (D14) with the differential circuit that electric capacity (C12) is formed; the output of two-way trigger tube (D14) is through resistance (R12; R13) be connected with the control utmost point (G) of controllable silicon (Q3) with the integrating circuit that electric capacity (C13) is formed; the silicon controlled minus earth; the silicon controlled anode links to each other with power supply through resistance (R7); this silicon controlled anode connects the anode of diode (D15) simultaneously, and the negative electrode of diode (D15) is as the output of this abnormity protection circuit.

3, electric ballast according to claim 1 is characterized in that: be connected in series instantaneous overvoltage crowbar (1) between described rectification circuit (3) and the input ac power, this circuit is made up of fuse (FU) and piezo-resistance (RV).

4, according to claim 2 or 3 described electric ballasts; it is characterized in that: be serially connected with anti-electromagnetic interference circuit (2) between described instantaneous overvoltage crowbar (1) and the rectification circuit (3); this circuit is made up of electric capacity (C1) and inductance (L1), and inductance (L1) and electric capacity (C1) connect into down the filter circuit of " L ".

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