DE202007004225U1 - Circuit for generating ignition voltage impulse, has high-voltage circuit with controllable electronic switch, charging condenser and voltage-dependent switch, and circuit output is connected by electronic switch with charging condenser - Google Patents

Abstract

The circuit has high-voltage circuit (S2) with a controllable electronic switch (Q1), a charging condenser (C3) and a voltage-dependent switch (D1). The circuit output (B) is connected by the electronic switch with the charging condenser. The low-voltage circuit (S1) receives the drive impulses and is coupled over a couple element (U2) with the high-voltage circuit. The control input (G) of the electronic switch is connected by the voltage-dependent switch with the couple element. An independent claim is also included for the photo-spectrometric measuring system for determination of the individual components.

Description

BACKGROUND THE INVENTION

The The present invention relates to an electronic circuit for generating an ignition pulse to the ignition a gas discharge lamp.

In photospectrometric measuring systems, e.g. for apsorption measurements in liquid chromatographs, become common Gas discharge lamps, e.g. Deuterium lamps, used as light source. Gas discharge lamps are ignited by means of a voltage pulse or ignition pulse. Between the anode and the cathode of such a light source is formed after the ignition process a glowing plasma.

to Generation of the voltage pulse, a circuit can be provided which a low voltage circuit or driver circuit for generating a low voltage pulse and a high voltage circuit for Generation of the actual ignition pulse includes. It is known to use relays, e.g. Reed relays as separators between the driver circuit and the high voltage circuit provided.

EPIPHANY

It Object of the present invention is an electronic circuit for generating an ignition pulse to the ignition to indicate a gas discharge lamp. The task is solved by the characteristics of the independent Claims. Advantageous embodiments are in the dependent claims cited.

In an embodiment is a circuit for generating a Zündspannungsimpulses on a Circuit output for connection to a gas discharge lamp, disclosed which is a high voltage circuit with a controllable electronic Switch a charging capacitor and a voltage-dependent switch wherein the circuit output of the circuit via the electronic Switch is connected to the charging capacitor. Next, the Circuit a low-voltage circuit, which a low voltage pulse driver receives and this one over Coupling element transmits to the high voltage circuit. Here is the control input of the electronic switch over the voltage dependent switch connected to the coupling element. When applying the driver pulse a current is driven into the coupling element, which leads to a output side voltage drop of the coupling element leads. As a result This voltage drop is the voltage-dependent switch conductive and so that the controllable electronic switch abruptly controlled. As a result of this sudden switching is in the charging capacitor stored electric charge transmitted as ignition voltage pulse to the gas discharge lamp. This circuit allows It's a very short ignition pulse (e.g., shorter as a microsecond).

In another embodiment is the coupling element realized as an optocoupler, which input side has a photodiode and the output side one or more optically having the photodiode coupled photosensitive elements, so that at current flow through the photodiode, a voltage at the output of the optocoupler is generated. This is the low voltage side galvanically completely decoupled from the high voltage side. This makes it possible to use this circuit in security-sensitive environments. Next, this circuit has no mechanical elements, for example Relay, whereby the circuit is subject to virtually no aging and thus over its entire service life a variety of identical ignition pulses can generate.

In another embodiment the low-voltage side has a logic module which connects to receives a drive pulse from its input and in response to it its output a current through the associated photodiode of the optocoupler drives. Since the logic module at its entrance is very high impedance, the logic device can duch very low power Circuits are controlled, for example, a microcontroller.

In another embodiment is another capacitor to the output side photosensitive elements of the optocoupler connected in parallel. This codenser builds Generation of a drive pulse via a certain time (e.g., 20-30 milliseconds) a voltage (e.g. 7V for two photosensitive elements), wherein the voltage-dependent switch is designed so that it reaches a certain threshold voltage (Eg 6.8V) of the other capacitor turns on and thus a circuit of the controllable electronic switch causes.

In another embodiment the logic device is inverting, the anode of the photodiode of the optocoupler with the output of the logic module and the cathode the photodiode over one or more resistances connected to a low voltage for supplying the low voltage circuit is.

In a further embodiment, the controllable electronic switch is designed as a high-voltage field-effect transistor, which connects the charging capacitor to the switching output via its source-drain path, so that when at circuit of the source-drain path an electric charge stored in the charging capacitor abruptly in the ignition voltage pulse is transferred.

During gas discharge lamps a spark high voltage (for example greater than 450V for a deuterium lamp) is needed the operating voltage after ignition is many times lower (For example, 82 volts for a deuterium lamp). Therefore contains the circuit in a further embodiment an operating voltage supply, which (over other elements, such as a low resistance and a Diode which prevents reverse current flow through the ignition pulse) connected to the circuit output.

In another embodiment is the voltage-dependent Switch realized as a Zener diode.

In another embodiment is the circuit together with a gas discharge lamp, for example a deuterium lamp, in a photospectrometric measuring system for Determination of individual components of a substance to be analyzed integrated.

DESCRIPTION THE DRAWINGS

The The invention will be further described below with reference to the drawings explains where the same reference signs are the same or functionally identical or similar Refer to features.

1 shows an electrical circuit diagram according to a preferred embodiment of the invention, and

2 shows a diagram of the voltage curve of one with the embodiment of 1 generated ignition pulse.

1 shows an electronic circuit with a low voltage part S1, which is coupled via an optocoupler U2 with a high voltage part S2. The low voltage part has a logic module U1 with inverting output (eg of the type 74LVC06) whose input is connected to a controllable input voltage U _IN to ground. In addition, this input is connected via a pull-up resistor RS to the supply voltage of the low voltage part to ground, eg 5V. The output of the logic device U1 is connected via the cathode input of the optocoupler U2 (eg of the type TLP191B) to a network connected to the anode input of the optocoupler comprising a first resistor R1, a second resistor R2 and a first capacitor C1 to the supply voltage 5V of the low voltage part the first resistor R1 and the second resistor R2 are connected in series, the first resistor R1 is connected to the cathode input and the second resistor R2 is connected to the supply voltage, and the first capacitor C1 connects the connection point of these resistors R1 and R2 to the ground. This capacitor causes a temporal acceleration of the current through the input-side photodiode of the opto-coupler U2 at power.

The Input-side photodiode of the optocoupler U2 is optically with a output-side network of two series-connected photodetectors (Photosensitive elements) and parallel connected resistor of the optocoupler is coupled, so that when current flows through the Photoresistor a voltage on this network and thus at the output of the optocoupler is generated. Input and output of the optocoupler U2 are thus galvanically separated from each other. This will be a from galvanic isolation of the driver circuit from the high voltage circuit reached.

The high voltage part S2 has a high voltage field effect transistor FET-Q1 (eg of the type 2SK2884), which at its drain D with a second supply voltage of 450V, hereinafter also referred to as ignition supply voltage, and in parallel via a third capacitor C3, hereinafter also as Charging capacitor C3 designated, is connected to ground. The source S of the FET Q1 is connected via a fourth resistor R4 and a second diode D2 to the ignition output B of the electronic circuit. The ignition output is connected to the anode of a (in 1 not shown) deuterium lamp connected. The gate G of the FET is directly connected to an output of the optocoupler U2, and is further connected via a second capacitor C2 to the other output of the optocoupler. Between gate G and source S, a third resistor R3 is connected.

Of the Exit B is still over a third diode D3 and a (small) fifth resistor R5 having a third supply voltage of 85V, also referred to below as operating supply voltage, connected. This supply voltage is on with a fourth Capacitor C4 connected to ground.

The input A of the electronic circuit is, for example, from a (in 1 not shown) microcontroller, which turns on the logic device U1 at a certain time by generating a voltage pulse U _IN , as a result of which the output of the logic device U1 drives a current in the photodiode of the input side of the optocoupler U2. The photodetek generates the light generated by the photodiode Tornetzwerk the output side of the optocoupler a voltage of about 7 volts, which drops above the internal resistance, and thus via the parallel connected to the second capacitor C2. This process takes a certain amount of time, eg 20-30 milliseconds. The Zener diode D1 connected between this capacitor and the gate G of the field effect transistor Q1 prevents a correspondingly slow switching through of the field effect transistor Q1. The zener diode D1 blocks up to a certain voltage and switches over when this voltage is exceeded, for example at 6.8 V abruptly, so that a current flows via the third resistor R3 connected between gate and source; the voltage across R3 and thus between gate and source causes the field effect transistor Q1 abruptly turns on and discharges the charging capacitor C3 charged to 450V via the fourth resistor R4 and the second diode D2 (the third resistor R3 also ensures that in the case of blocking (ie no ignition operation) Gate and source of FET Q1 are at the same potential and the FET blocks with it).

After the discharging process of the charging capacitor C3, the lamp is finally supplied via the fifth resistor R5 and the third diode D3 with a constant 85V of the third supply voltage. The output voltage U _OUT at the output B thus shows a short-time voltage pulse of over 450V and subsequently (after a decay process, see 2 ) a largely constant voltage of (slightly less than) 85V. The third diode prevents a reverse current flow in the discharge phase and the second diode D2 prevents a reverse current flow in the phase of the constant voltage supply.

2 shows an exemplary voltage waveform U _IN in volts with the embodiment 1 generated ignition pulse over the time t in milliseconds. At time t1, the through-connection of FET Q1 begins. Within a pulse duration tp of about 800 nanoseconds, a voltage with a peak value of 537.5 volts builds up at the output B at time t2, which then abruptly drops to about 350V. After ignition, the anode voltage (output B) drops continuously to 82V (PWM control).

• RS = 4,64 kΩ
• R1 = 31,6 Ω
• R2 = 100 Ω
• R3 = 464 Ω
• R4 = 464 Ω
• R5 = 5 Ω
• C1 = 220 nF
• C2 = 470 nF
• C3 = 66 nF (Hochspannung 1 KV)
• C4 = 66 μF (Hochspannung 400V)

Below is a list of exemplary values for the in 1 shown components. It is clear that the components can be realized as concentrated elements or as networks of concentrated elements. For example, the charging capacitor C3 can be formed from two parallel capacitors of 33 nF each.

• RS = 4.64 kΩ
• R1 = 31.6 Ω
• R2 = 100 Ω
• R3 = 464 Ω
• R4 = 464 Ω
• R5 = 5 Ω
• C1 = 220 nF
• C2 = 470 nF
• C3 = 66 nF (high voltage 1 KV)
• C4 = 66 μF (high voltage 400V)

Claims (10)

Circuit for generating an ignition voltage pulse (U _OUT ) at a circuit output (B) for connection to a gas discharge lamp, comprising: - a high-voltage circuit (S2) having a controllable electronic switch (Q1), a charging capacitor (C3) and a voltage-dependent switch (D1) in which the circuit output (B) is connected to the charging capacitor (C3) via the electronic switch (Q1), - a low-voltage circuit (S1) for receiving a drive pulse which is coupled to the high-voltage circuit (S2) via a coupling element (U2), - Wherein the control input (G) of the electronic switch (Q1) via the voltage-dependent switch (D1) is connected to the coupling element. The circuit of claim 1, wherein the coupling element is realized as an optocoupler (U2), which on the input side a Photodiode has and on the output side one or more optically with the photodiode has coupled photosensitive elements, so that at current flow through the photodiode a voltage at the output of Optocoupler (U2) is generated. The circuit of claim 2, wherein the low voltage circuit (S1) has a logic device (U1), with an input for recording the drive pulse and an output for connection to the photodiode of the opto-coupler (U2), so that when applying the drive pulse a Current is driven through the photodiode of the optocoupler (U2) and daduch generated light is incident on the photosensitive elements. A circuit according to claim 2 or 3, wherein another one Kodensator (C2) to the photosensitive elements of the optocoupler (U2) is connected in parallel, so that this coder (C2) after Generation of a driving pulse builds up a voltage, wherein the voltage-dependent Switch (D1) is designed so that when it reaches a certain Voltage at the other capacitor (C2) turns on and thus a Switching through the controllable electronic switch (Q1) causes. A circuit according to claim 4, wherein the logic device (U1) is inverting, the cathode of the Photodiode of the optocoupler (U2) connected to the output of the logic device (U1) and the anode of the photodiode via one or more resistors (R1, R2) to a low voltage (5V) for supplying the low voltage circuit. A circuit according to claim 1 or one of the preceding claims, wherein the controllable electronic switch (Q1) is a field-effect transistor which connects the charging capacitor (C3) to the switching output (B) via its source-drain path, so that when the source-drain is switched through A distance stored in the charging capacitor elektische charge in the ignition voltage pulse (U _OUT ) is transferred. A circuit according to claim 1 or one of the preceding Claims, wherein the circuit output (B) via another circuit (R5, D3) with a substantially constant Operating voltage supply is connected. The circuit of claim 1 or any of the preceding Claims, where the voltage-dependent Switch (D1) is implemented as a Zener diode. A photospectrometric measuring system for determining individual constituents of a substance to be analyzed, comprising: a gas discharge lamp for illuminating the substance to be analyzed, and a circuit connected to the gas discharge lamp for generating an ignition voltage pulse (U _OUT ) according to one of the preceding claims. A photospectrometric measuring system according to claim 9, wherein the gas discharge lamp is a deuterium lamp.