CN102665369B - High-power electronic ballast - Google Patents

Abstract

The invention relates to a high-power electronic ballast which uses active secondary detection technology to suppress surge current and realize soft start, including an EMI filter circuit, a rectifier circuit, an MCU control circuit, a sampling detection circuit, and a half-bridge inverter circuit , the output end of the rectifier circuit is connected to one end of the first inductance L11, the other end of the first inductance L11 is respectively connected to the drain D of the field effect transistor QE, and the anode of the diode D11, and the cathode of the diode D11 is respectively connected to the second resistor R12 One end is connected to one end of the first resistor R11, and the other end of the second resistor R12 is respectively connected to one end of the third resistor R13 and the sampling detection circuit. When the power is turned on, the startup surge current is suppressed through the resistor R11. In the second detection, when the voltage reaches 400V, the control circuit sends an instruction to make the half-bridge inverter circuit work, so as to realize the real suppression of surge current and soft start.

Description

High Power Electronic Ballast

technical field

The invention relates to the technical field of high-power electronic ballasts, in particular to a high-power electronic ballast which uses active secondary detection technology to suppress surge current and realize soft start.

Background technique

High-power electronic ballasts generally adopt active power factor correction technology. When starting up and powering on, a large surge current will be generated due to the charging of the filter capacitor. At present, there are the following three schemes for suppressing the surge current impact of startup in high-power HID electronic ballasts on the market:

The first is to use a single negative temperature coefficient NTC thermistor to suppress the surge current impact at the moment of power on, as shown in Figure 1. At the moment of power on, the resistance of the NTC thermistor is relatively high, which is used to A lower inrush current is generated when it is turned on, and the thermistor will heat up naturally under normal working conditions, and its resistance value will drop to the working resistance value accordingly, which can avoid more consumption. For low-power electronic ballasts, the operating current is small and the loss is not large, but in high-power electronic ballasts, the self-consumption is relatively large and the temperature rise is also large, which is obviously not suitable. Especially when the power supply is turned off and turned on again quickly, the thermistor has not cooled completely, and the function of surge suppression will be lost, thus losing the protection of the electronic ballast.

The second is to place a relay (or bidirectional triode thyristor) in parallel with the resistor R at the front end of the bridge rectifier, as shown in Figure 2. When starting up, the inrush current is suppressed through R, and after the capacitor C1 is charged through the delay circuit, the relay pulls in, and the resistor R is bypassed by the relay, thereby reducing the power consumption during full operation. This is a common method for current high-power electronic ballasts to suppress surge currents. However, when the voltage is low, due to the constant power characteristic of the electronic ballast with active power factor correction, the current passing through the relay contacts will increase, so that the relay contacts may be melted, thus shortening the life of the relay. Shorten, indirectly reduce the service life of electronic ballasts.

The third is to use a relay (or bidirectional triode thyristor) in parallel with the resistor R in the active power factor correction circuit to suppress the surge impact at the moment the power is turned on, as shown in Figure 3, due to the active power of the electronic ballast The factor correction generally adopts the step-up method, which is raised to 400V, so that in normal operation, the current through the relay contact is greatly reduced, and the service life of the relay is increased. However, with this method of connection, when the input power is turned on, the PFC circuit will increase the voltage across the electrolytic capacitor C1 to 400V in a short period of time. In order to achieve a better surge current suppression effect, the value of the resistor R is often It will reach about 10 ohms. When the moment of connection is near the peak value of the alternating current, when the voltage across the capacitor C1 reaches 400V, the instantaneous voltage amplitude across the resistor R may reach more than 100V. At this time, the source and drain of the MOSFET tube The voltage value between the poles reaches more than 500V, which exceeds the withstand voltage value of the MOSFET tube, which may damage the MOSFET tube and shorten the service life of the electronic ballast.

Contents of the invention

The object of the present invention is to provide a high-power electronic ballast which adopts active secondary detection technology to suppress surge current and realize soft start, thereby prolonging the service life of the ballast and the HID lamp tube.

In order to realize the purpose of the above invention, the present invention adopts the following technical solutions: a high-power electronic ballast, including a series EMI filter circuit and a rectifier circuit connected in series, the output end of the rectifier circuit is connected to one end of the first inductance L11, the first The other end of the inductor L11 is respectively connected to the drain D of the field effect transistor QE and the anode of the diode D11, which is characterized in that: the gate G of the field effect transistor QE is connected to the MCU control circuit through the PFC boost circuit, and the negative poles of the diode D11 are respectively It is connected with one end of the second resistor R12 and one end of the first resistor R11, the other end of the second resistor R12 is respectively connected with one end of the third resistor R13 and the sampling detection circuit 40, and the other end of the first resistor R11 is respectively connected with the first capacitor The positive pole of C11 is connected to the half-bridge inverter circuit, and a pair of normally open contacts of the relay K are connected in parallel at both ends of the first resistor R11; the half-bridge inverter circuit is connected to one end of the second inductance L12, and the second inductance L12 The other end is respectively connected with one end of the second capacitor C12 and one end of the HID lamp, one end of the rectifier circuit, the substrate and source S of the field effect transistor QE, the other end of the third resistor R13, the negative electrode of the first capacitor C11, the half One end of the bridge inverter circuit is grounded; the other end of the second capacitor C12 and the other end of the HID lamp are grounded; the output signal of the PFC boost circuit and the sampling detection circuit is sent to the MCU control circuit, and the MCU control circuit passes the half-bridge inverter The variable control circuit controls the work/stop of the half-bridge inverter circuit.

The field effect transistor QE is a P-channel enhanced insulated gate field effect transistor.

When the power is turned on, the start-up surge current is suppressed through the resistor R11, and the sampling circuit detects the total voltage of the resistor R11 and the capacitor C11 for the first time. Due to the change of the sampling position, the sampling voltage is no longer in the traditional sense. voltage of C1. When the total voltage reaches 400V, the active power factor correction circuit automatically completes the control of 400V to ensure that the MOSFET will not be broken down. At the same time, the control circuit issues a command to make the relay pick up and bypass the resistor R11; after that, the sampling circuit conducts a second Detection, (at this time, because R11 is bypassed, the detection value is the terminal voltage of capacitor C11. At this time, the voltage may be lower than 400V, and the active power factor correction circuit automatically adjusts the voltage to 400V). When the voltage reaches 400V, the control The circuit issues instructions to make the half-bridge inverter circuit work, so as to realize the suppression of inrush current and soft start in the true sense.

Description of drawings

1-3 are schematic circuit diagrams of three specific solutions in the prior art;

Fig. 4 is a schematic circuit diagram of the present invention.

Detailed ways

A high-power electronic ballast, which includes an EMI filter circuit 10, a rectifier circuit 20, an MCU control circuit 50, a sampling detection circuit 40, a half-bridge inverter circuit 60, a first inductor L11, a second inductor L12, a diode D11, Field effect transistor QE, first resistor R11, second resistor R12, third resistor R13, relay K, first capacitor C11, second capacitor C12 and HID lamp, EMI filter circuit 10 and rectifier circuit 20 connected in series, rectifier circuit The output terminal of 20 is connected to one end of the first inductance L11, and the other end of the first inductance L11 is respectively connected to the drain D of the field effect transistor QE and the anode of the diode D11, and it is characterized in that: the gate G of the field effect transistor QE passes through The PFC boost circuit 30 is connected to the MCU control circuit 50, the cathode of the diode D11 is respectively connected to one end of the second resistor R12 and one end of the first resistor R11, and the other end of the second resistor R12 is respectively connected to one end of the third resistor R13 and the sampling The detection circuit 40 is connected, and the other end of the first resistor R11 is respectively connected to the positive pole of the first capacitor C11 and the half-bridge inverter circuit 60, and a pair of normally open contacts of the relay K are connected in parallel to the two ends of the first resistor R11; The bridge inverter circuit 60 is connected to one end of the second inductance L12, the other end of the second inductance L12 is respectively connected to one end of the second capacitor C12 and one end of the HID lamp, one end of the rectifier circuit 20, the substrate of the field effect transistor QE and The source S, the other end of the third resistor R13, the negative electrode of the first capacitor C11, and one end of the half-bridge inverter circuit 60 are all grounded; the other end of the second capacitor C12 and the other end of the HID lamp are all grounded.

The field effect transistor QE is a P-channel enhanced insulated gate field effect transistor.

The working process of the present invention is: the mains AC220V passes through the EMI filter circuit 10, which is the electromagnetic interference filter circuit to filter and suppress the electromagnetic interference of the power grid. The voltage circuit 30 is the power factor correction circuit for power supply, the input signal of the MCU control circuit 50 is provided by the PFC boost circuit 30 and the sampling detection circuit 40, and the gate G of the MOSFET tube, that is, the field effect transistor QE, is connected with the PFC boost circuit 30, The drain D is connected to the anode of the diode D11, and the source S is grounded. After being boosted by diode D11, it is divided into two circuits, one of which passes through resistors R12 and R13 in series and flows to the ground, and the sampling circuit takes a signal from the middle of R12 and R13 and sends it to the MCU control circuit 50; the other passes through the relay K connected in parallel with the first resistor R11 To the positive terminal of the first capacitor C11 , the negative terminal of C11 is grounded, the half-bridge inverter circuit 60 is connected in parallel with both ends of C11 , and is controlled by the half-bridge inverter control circuit 70 . The positive terminal of the output of the half-bridge inverter circuit 60 is connected to the second inductor L12, and the negative terminal is grounded. The other end of L12 is connected in series with the HID lamp, the other end of the HID lamp is grounded, and the second capacitor C12 is connected in parallel to both ends of the HID lamp.

The present invention can well solve the troubles caused by the three methods in the background technology, and adopts the active secondary detection technology of the relay to suppress the start-up surge current and realize the soft start of the high-power electronic ballast, so that the ballast can be extended device and HID lamp life.

Claims (2)

1. A high-power electronic ballast, comprising a series connection of an EMI filter circuit (10) and a rectification circuit (20), the output end of the rectification circuit (20) is connected to one end of the first inductance L11, and the first inductance L11 The other end is respectively connected to the drain D of the field effect transistor QE and the anode of the diode D11, which is characterized in that: the gate G of the field effect transistor QE is connected to the MCU control circuit (50) through the PFC boost circuit (30), and the diode D11 The negative electrode of the second resistor R12 is connected with one end of the second resistor R12 and one end of the first resistor R11 respectively, the other end of the second resistor R12 is connected with one end of the third resistor R13 and the sampling detection circuit (40) respectively, and the other end of the first resistor R11 Connect with the positive pole of the first capacitor C11 and the half-bridge inverter circuit (60) respectively, and a pair of normally open contacts of the relay K are connected in parallel at the two ends of the first resistor R11; the half-bridge inverter circuit (60) and the second One end of the inductance L12 is connected, the other end of the second inductance L12 is respectively connected with one end of the second capacitor C12 and one end of the HID lamp, one end of the rectifier circuit (20), the substrate and the source S of the field effect transistor QE, the third The other end of the resistor R13, the negative pole of the first capacitor C11, and one end of the half-bridge inverter circuit (60) are all grounded; the other end of the second capacitor C12 and the other end of the HID lamp are all grounded; The PFC boost circuit (30) and sampling detection circuit (40) output signals to the MCU control circuit (50), and the MCU control circuit (50) controls the half-bridge inverter circuit ( 60) work/stop. 2. The high-power electronic ballast according to claim 1, characterized in that: said field effect transistor QE is a P-channel enhanced insulated gate field effect transistor.

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