Narrow-pulse-width large-current laser driving circuit capable of being automatically turned off based on energy compression

Abstract

The invention relates to the technical field of circuit optimization design, in particular to a narrow-pulse-width large-current laser driving circuit capable of being automatically turned off based on energy compression, which is obtained based on improvement of a switch discharge type laser driving basic topology circuit and comprises a booster circuit, a switch unit and a discharge loop. A PMOS (P-channel Metal Oxide Semiconductor) tube is used as a control tube of a discharge loop and an isolation device between a booster circuit and the discharge loop, the booster circuit adopts a booster chip to convert 5V input into 100V output to a discharge capacitor, so that the circuit does not need high-voltage input, meanwhile, the PMOS tube is placed at the front end of the LD laser in the discharge loop, and a half-bridge driver is not needed due to the adoption of the PMOS tube, so that the cost is reduced. And meanwhile, the source electrode of the PMOS tube is connected with the discharge capacitor, the PMOS tube is automatically turned off after the discharge of the capacitor is finished, and the pulse width of the output pulse is not influenced by the external pulse because the PMOS tube is automatically turned off. And the discharge loop uses multi-channel output to improve the output pulse peak value. The defects of an existing laser driving circuit are overcome through structural optimization.

Description

Technical Field

[0001] This invention relates to the field of circuit optimization design technology, specifically to a narrow pulse width high current laser driving circuit based on energy compression and automatic shutdown. Background Technology

[0002] For a long time, voltage source-series resonant or voltage source-switching discharge designs have been commonly used in high-current, narrow-pulse-width laser drive circuit designs. Most designs using the switching discharge type employ NMOS transistors as switches. However, if the switch is placed at the rear end of the LD laser, common-cathode drive cannot be achieved, even though most commercially available lasers are common-cathode, such as Osram, Esselida's 4-line, and Xinliang Photonics' 8-line and 16-line diode lasers. Placing the switch at the front end of the LD laser requires a half-bridge driver, increasing cost and requiring multiple pulse inputs, thus raising performance requirements. The pulse current output by both series resonant and switching discharge types is related to the initial voltage of the discharge capacitor; a higher initial voltage results in a higher output current, placing higher demands on the external voltage source. In the switching discharge type drive circuit, the external charging power supply is directly connected to the LD laser after the switch is turned on, significantly affecting the waveform of the output pulse. In existing designs, the pulse width of the input pulse signal has a significant impact on the pulse width of the output pulse current. When the pulse width of the input pulse signal is too large, it will cause the peak value of the output to decrease. Summary of the Invention

[0003] The purpose of this invention is to provide a narrow pulse width high current laser driving circuit based on energy compression and automatic shutdown, aiming to achieve a laser driving circuit with output peak value unaffected by external power supply and output pulse width unaffected by input pulse signal, while being compatible with multi-line LD lasers on the market.

[0004] To achieve the above objectives, the present invention provides a narrow pulse width high current laser driving circuit based on energy compression and automatic shutdown, which is obtained by improving the basic topology of switch discharge laser driving circuit, including a boost circuit, a switching unit and a discharge circuit.

[0005] The boost circuit includes the section from the DC-5V input to the source of Q1; the switching unit uses a PMOS switch; and the discharge circuit is a multi-channel output circuit.

[0006] The boost circuit section uses the DC-DC boost chip LT8331.

[0007] All PMOS switches are controlled by the same pulse signal. An inverter U3 is connected to the pulse signal input side, and the output power supply of inverter U3 is 5V.

[0008] When the pulse input is high, transistor Q4 is turned on and MOSFET Q1 is turned on when the gate input is low. The 100V voltage of the boost circuit is applied to the energy storage capacitors C1 and C2 through Q1. At the same time, the pulse signal is converted into a low level by inverter U3 and input to transistors Q5 and Q6 respectively. When Q5 and Q6 are turned off, Q2 and Q3 are also in the cut-off state.

[0009] When the pulse input is low, transistor Q4 is cut off, MOSFET Q1 is also cut off, the connection between the boost circuit and energy storage capacitors C1 and C2 is broken, and the outputs Q5 and Q6 of inverter U3 get a high level and are in the conducting state, and then Q3 and Q2 are turned on.

[0010] The discharge circuit adopts a dual-channel parallel structure, with Q2 and Q3 simultaneously conducting and discharging.

[0011] This invention provides a narrow-pulse-width, high-current laser drive circuit based on energy compression and automatic shutdown. It is an improvement on the basic topology of a switch-discharge laser drive circuit, comprising a boost circuit, a switching unit, and a discharge circuit. This invention uses a PMOS transistor as the control transistor for the discharge circuit and as an isolation device between the boost circuit and the discharge circuit. The boost circuit uses a boost chip to convert a 5V input to a 100V output to the discharge capacitor, eliminating the need for a high-voltage input. Simultaneously, the PMOS transistor is placed at the front end of the LD laser in the discharge circuit; because of the use of PMOS, a half-bridge driver is unnecessary. Furthermore, the source of the PMOS transistor is connected to the discharge capacitor, and the PMOS transistor automatically turns off when the capacitor discharges. Because the PMOS transistor automatically turns off, the output pulse width is unaffected by external pulses. The discharge circuit uses a multi-channel output to improve the output pulse peak value. This invention addresses the shortcomings of existing laser drive circuits through structural optimization. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of a narrow pulse width high current laser driving circuit based on energy compression and automatic shutdown according to the present invention.

[0014] Figure 2 This is a schematic diagram of the basic topology of a switch-discharge type.

[0015] Figure 3 This is a schematic diagram comparing capacitor discharge with different channel numbers in an embodiment of the present invention.

[0016] Figure 4 This is a schematic diagram illustrating the effect of the input pulse width on the output pulse width in an embodiment of the present invention. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0018] Please see Figure 1 This invention provides a narrow pulse width high current laser driving circuit based on energy compression and automatic shutdown, which is obtained by improving the basic topology of switch discharge laser driving circuit, including a boost circuit, a switching unit and a discharge circuit.

[0019] like Figure 2 The diagram shows a basic topology for a switch-discharge type laser drive. VCC is the high-voltage power supply, and R1 is a current-limiting resistor, restricting the current flowing through the LD laser below the stimulated emission threshold. C1 is the energy storage capacitor, and D1 and R2 protect the LD diode and eliminate reverse overshoot across the LD laser. When the pulse input is low, Q1 is off, and VCC charges the energy storage capacitor C1 through R1, forming a charging circuit (VCC-R1-C1). When the pulse input is high, Q1 is on, and C1 rapidly discharges, providing a pulsed current to the LD laser, forming a discharge circuit (C1-LD-Q1).

[0020] Specifically, the present invention addresses Figure 2 The improvements are as follows:

[0021] 1. The circuit of this invention has its own boost circuit, so no external high voltage input is required. It only needs to provide the voltage that powers the chip of the boost circuit.

[0022] 2. In the circuit of this invention, the power supply for charging the capacitor is isolated from the capacitor during discharge, preventing the charging power supply (in this invention, a boost circuit) from being interrupted. Figure 2 The influence of the external high-voltage power supply (VCC) on the discharge circuit.

[0023] 3. In the discharge circuit, the circuit of this invention... Figure 2 The traditional NMOS switch is replaced with a PMOS switch. After the switch is replaced with a PMOS switch, the PMOS can be automatically turned off. This eliminates the need for an additional pulse input for control, and the pulse output is not affected by the external pulse width. This design allows the driver to be compatible with most common cathode lasers on the market.

[0024] 4. The discharge circuit of this invention has multiple discharge paths, and the output pulse can increase the pulse peak value without affecting the pulse width compared to single-path discharge.

[0025] The present invention will be further described below with reference to the embodiments:

[0026] like Figure 1 As shown, in this embodiment, the boost circuit uses the DC-DC boost chip LT8331. The boost circuit includes the portion from the DC-5V input to the source of Q1, which is composed of the LT8331 and its peripheral circuitry. The 100V voltage required for the charging circuit is output from the SW1 and SW2 pins of the LT8331. The output voltage is adjusted by changing the ratio of R1 and R2. The formula is as follows. The function of the boost circuit is to input a 5V voltage and output a 100V voltage. Using a boost chip can stably output a 100V high voltage to boost the initial discharge voltage of the energy storage capacitors C1 and C2 to 100V. Integrating the boost circuit into the driver circuit reduces the requirements for using the driver circuit; only 5V is needed to meet the circuit's operating conditions. Furthermore, the chip's output voltage is relatively stable. The chip has high integration, small size, and can achieve high-efficiency voltage conversion.

[0027] In this invention, all PMOS switches are controlled by the same pulse signal. When the pulse input is high, transistor Q4 conducts, and MOSFET Q1 conducts when its gate is low. The 100V voltage from the boost circuit is applied to the energy storage capacitors C1 and C2 through Q1. Energy flows from the boost chip to the energy storage capacitors, forming a charging circuit: "LT8331(SW1\SW2)--Q1--C1\C2--GND". The boost circuit and the charging circuit are connected by PMOS transistor Q1. Simultaneously, the pulse signal is converted to a low level by inverter U3 and input to transistors Q5 and Q6, which are not conducting. This further causes Q2 and Q3 to be cut off, and diode U2 receives no current. When the pulse input is low, transistor Q4 is cut off, and therefore MOSFET Q1 is also cut off. The connection between the boost circuit and the energy storage capacitors C1 and C2 is broken, and the boost circuit does not participate in the subsequent energy storage capacitor discharge process, so it has no impact on the output result. The outputs Q5 and Q6 of inverter U3 are high and in a conducting state. Then, Q3 and Q2 conduct the energy stored in the energy storage capacitor and release it rapidly in nanoseconds to form a current pulse. The process of the energy storage capacitor releasing energy to the LD diode forms a discharge circuit "C1\C2--Q2\Q3--R5--U2--GND".

[0028] When the pulse input is high, Q1 conducts, the boost circuit is connected to the charging circuit through Q1, and the charging circuit operates. At this time, the discharging circuit is not conducting. When the pulse input is low, Q1 is cut off, the charging circuit is not conducting, the boost circuit is isolated, and the discharging circuit operates. When the charging circuit is operating, C1 and C2 operate in the charging circuit; when the discharging circuit is operating, C1 and C2 operate in the discharging circuit.

[0029] The U3 uses the SN74LVC1G04 model, which uses PMOS and does not require additional pulse signal control. When the capacitor discharge ends, the PMOS can be automatically turned off, and the laser can be directly connected to ground, making it compatible with common cathode lasers on the market.

[0030] The discharge circuit adopts a dual-channel parallel structure, with Q2 and Q3 conducting and discharging simultaneously. The multi-channel discharge structure can greatly increase the output pulse peak value without increasing the pulse width. In traditional laser drive circuits, a single laser has only one switching transistor, and all capacitor discharges pass through this switching transistor. In this case, increasing the capacitor increases the output peak value, but the output pulse width also increases. With parallel multi-channel output, a laser can have multiple switching transistors, with each capacitor corresponding to one switching transistor. In this case, increasing the capacitor will not change its output pulse width, but it can improve the output peak value.

[0031] Figure 3 This figure shows a comparison of the results of single-channel dual 500pF capacitors (red), dual-channel dual 500pF capacitors (blue), and single-channel single 1uF capacitors (green) in this embodiment. As can be seen from the figure, the discharge effect of the dual-channel dual 500pF capacitors is significantly higher than the other two peak values, while the result for the single-channel capacitor remains unchanged.

[0032] In this invention, PMOS transistors replace most of the NMOS transistors in traditional circuits in the discharge circuit, thus enabling common-cathode driving of multi-line LD lasers. The use of PMOS transistors also allows for automatic shutdown of the discharge circuit, preventing the pulse width of externally input pulse signals from affecting the output pulse width. The sources of PMOS transistors Q2 and Q3 are connected to the energy storage capacitor. When the energy storage capacitor finishes discharging, its voltage drops, and the source voltages of Q2 and Q3 also drop synchronously, achieving automatic shutdown of the PMOS transistors. When the discharge circuit does not shut down with the input pulse, the output pulse width will not be affected by an excessively long input pulse width. Figure 4 The effect of different input pulse widths on the output waveform when using an NMOS transistor as the switching transistor in the discharge circuit is shown. The input pulse widths are 27ns (purple), 30ns (red), 35ns (green), and 40ns (blue). It can be seen that the larger the input pulse width, the larger the output pulse width, and the output waveform is severely distorted when the input pulse width reaches a certain level.

[0033] The above description discloses only one or more preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A narrow-pulse-width, high-current laser driving circuit based on energy compression and automatic shutdown, characterized in that, The circuit is based on an improved topology of a switch-discharge laser driver, including a boost circuit, a switching unit, and a discharge circuit. The boost circuit includes the section from the DC-5V input to the source of Q1; the switching unit uses a PMOS switch; and the discharge circuit is a multi-channel output circuit.

2. The narrow pulse width high current laser driving circuit based on energy compression with automatic shutdown as described in claim 1, characterized in that, The boost circuit section uses the DC-DC boost chip LT8331.

3. The narrow pulse width high current laser driving circuit based on energy compression with automatic shutdown as described in claim 2, characterized in that, All PMOS switches are controlled by the same pulse signal. An inverter U3 is connected to the pulse signal input side, and the output power supply of inverter U3 is 5V.

4. The narrow pulse width high current laser driving circuit based on energy compression with automatic shutdown as described in claim 3, characterized in that, When the pulse input is high, transistor Q4 is turned on and MOSFET Q1 is turned on when the gate input is low. The 100V voltage of the boost circuit is applied to the energy storage capacitors C1 and C2 through Q1. At the same time, the pulse signal is converted into a low level by inverter U3 and input to transistors Q5 and Q6 respectively. When Q5 and Q6 are turned off, Q2 and Q3 are also in the cut-off state. When the pulse input is low, transistor Q4 is cut off, MOSFET Q1 is also cut off, the connection between the boost circuit and energy storage capacitors C1 and C2 is broken, and the outputs Q5 and Q6 of inverter U3 get a high level and are in the conducting state, and then Q3 and Q2 are turned on.

5. The narrow pulse width high current laser driving circuit based on energy compression with automatic shutdown as described in claim 4, characterized in that, The discharge circuit adopts a dual-channel parallel structure, with Q2 and Q3 simultaneously conducting and discharging.

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