CN218276654U

CN218276654U - Double-isolation driving power amplifier circuit

Info

Publication number: CN218276654U
Application number: CN202222347186.0U
Authority: CN
Inventors: 焦洁; 谭玉良; 陈磊; 郭丽华
Original assignee: Shandong Huabo Electric Co ltd
Current assignee: Shandong Huabo Electric Co ltd
Priority date: 2022-09-02
Filing date: 2022-09-02
Publication date: 2023-01-10
Anticipated expiration: 2032-09-02

Abstract

The utility model belongs to the technical field of medical equipment, in particular to a double-isolation driving power amplifier circuit, which comprises a PWM wave generator, an isolation transformer, an isolation driving module, an MOS tube and a power amplifier transformer which are connected in sequence according to the transmission direction of the PWM wave; the PWM wave generator is used for outputting PWM waves; the isolation transformer is used for filtering the PWM wave output by the PWM wave generator; and the isolation driving module is used for isolating the back electromotive force at the side of the power amplifier transformer and amplifying the PWM wave filtered by the isolation transformer and then controlling the grid of the MOS tube to enable the drain and the source of the MOS tube to generate on-off switching to drive the power amplifier transformer. The utility model discloses an isolation transformer and isolation drive module's dual isolation has reduced the influence of vary voltage leakage inductance and electromagnetic interference to the PWM ripples that PWM wave generator produced, makes MOS pipe work under on off state, has reduced the loss of MOS pipe and has generated heat, makes switching frequency more stable, and power amplifier transformer output waveform is more level and smooth.

Description

Double-isolation driving power amplifier circuit

Technical Field

The utility model belongs to the technical field of medical equipment, concretely relates to two isolation drive power amplifier circuits.

Background

A high-frequency electric knife (high-frequency surgical instrument) is an electric surgical instrument for replacing a mechanical surgical knife to cut tissues. The tissue is heated when high-frequency high-voltage current generated by the tip of the effective electrode contacts with the body, so that the tissue is separated and coagulated, and the aims of cutting and hemostasis are fulfilled. The existing power amplifier circuit for generating high-frequency high-voltage current by a high-frequency electrotome generates PWM (pulse width modulation) waves by a pulse width modulator, and then drives a signal isolation through an isolation transformer or directly controls a grid (g) of an MOS (metal oxide semiconductor) tube by the PWM waves generated by the pulse width modulator without isolation so that a drain (d) and a source(s) of the MOS tube generate on-off switches to drive a boosting or reducing transformer (transformer for short).

The isolation transformer utilizes the electromagnetic induction principle to enable a primary input end and a secondary output end to generate electrical isolation, and filters input PWM waves to drive a grid (g) of the MOS tube, so that the peak voltage generated at the moment of switching off the PWM waves generated by the pulse width modulator due to the influence of back electromotive force and electromagnetic interference generated at the moment of switching off leakage inductance of the transformer can be reduced.

Normally, the MOS transistor works in a switching state, and switches between a cut-off region and a full-on region at a high frequency, and since a linear region is passed through during the switching process, the MOS transistor in the linear region acts as a variable resistor, and thus a switching loss is generated. The MOS tube works in a linear region due to long rising edge or falling edge time of the MOS tube or insufficient voltage of a driving grid electrode (g). The peak voltage generated by leakage inductance is composed of oscillation waveforms with about several megafrequencies, the rising edge of the PWM wave becomes wider, so that the MOS tube switch works in a linear region, the MOS tube is heated due to the fact that the MOS tube loss is increased under the heavy load condition, and the MOS tube is easy to burn out; if the peak voltage is too large, the MOS tube will be broken down, and the oscillating peak voltage will make the transformer switch frequency unstable, resulting in unsmooth output waveform and noise.

Chinese patent document CN1024734C (CN 92109533.3) discloses a double-isolation driving circuit for a power VMOS transistor for switching a Pulse Width Modulation (PWM) integrated circuit chip, which is characterized in that a full-bridge circuit composed of semiconductor triodes is connected to an output terminal of a PWM integrated device, a high-frequency transformer for isolating a control voltage from a high voltage of a main circuit is connected to the output terminal of the PWM integrated device after the PWM device is isolated from the transformer, and a secondary terminal of the transformer is connected to the power VMOS transistor after passing through a shaping circuit, wherein the shaping circuit is composed of an inverter with a source threshold, a voltage comparator and a totem-type driving circuit. Therefore, the ideal drive waveform with steep waveform transition and purification can be obtained, and the circuit has low power consumption and high efficiency. The principle of the patent is that before the VMOS tube controller is isolated by the transformer, the inductive load of the transformer is also isolated by the PWM device by a full-bridge circuit so as to avoid the influence of the inductive device on the PWM device and ensure that the load of the PWM is basically resistive; meanwhile, the waveform transmitted by the transformer is shaped and interference signals are suppressed, so that the driving waveform is idealized finally. The technical scheme is only used for solving the influence of the high-frequency isolation transformer on the waveform generated by the PWM device, and the influence of the leakage inductance of the transformer in the power amplifier circuit on the PWM waveform cannot be solved.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a two isolation drive power amplifier circuit, in order to reduce the spike voltage that transformer leakage inductance produced, electromagnetic interference and rising fall along response time to MOS pipe and power amplifier circuit power supply and output waveform's influence, increase isolation drive module on transformer isolation module's basis, under isolation transformer and isolation drive module dual isolation, power amplifier transformer leakage inductance and electromagnetic interference have been reduced to the influence of the PWM ripples that PWM wave generator produced, thereby the waveform of drive MOS pipe grid (g) is more level and smooth under the messenger high frequency condition, and make MOS pipe work under on-off state, MOS pipe loss reduces, generate heat and reduce, make switching frequency more stable, power amplifier transformer output waveform is more level and smooth.

In order to achieve the above object, the utility model provides a following technical scheme: a double-isolation driving power amplifier circuit comprises a PWM wave generator, an isolation transformer, an isolation driving module, an MOS tube and a power amplifier transformer which are sequentially connected according to the transmission direction of the PWM wave;

the PWM wave generator is used for outputting PWM waves;

the isolation transformer is used for generating electrical isolation and filtering the PWM wave output by the PWM wave generator;

and the isolation driving module is used for isolating the back electromotive force at the side of the power amplifier transformer, amplifying the PWM wave filtered by the isolation transformer and controlling the grid of the MOS tube, so that the drain and the source of the MOS tube are switched on and off to drive the power amplifier transformer.

Compared with the prior art, the beneficial effects of the utility model are that: the utility model discloses in, isolation transformer can make primary input end and secondary output produce electrical isolation and filter the PWM ripples of input by utilizing the electromagnetic induction principle.

The isolation driving module can isolate the electromotive force induced by the isolation transformer, the peak voltage caused by leakage inductance can be reduced through the isolation driving module, and the PWM wave is amplified, so that the time of rising edge and falling edge of the PWM wave is shortened, and sufficient current and output voltage are provided, so that the MOS transistor can charge and discharge the grid capacitor more quickly to shorten the transition period, the MOS transistor works in a switching state, and the loss and the heat of the MOS transistor are reduced.

Under the dual isolation of the isolation transformer and the isolation driving module, the influence of leakage inductance of the power amplifier transformer and electromagnetic interference on PWM waves generated by the PWM wave generator is reduced.

The technical proposal of the utility model is also that: the PWM wave generator includes a pulse width modulator.

The technical proposal of the utility model is also that: the isolation driving module comprises a gate driver. The grid driver can effectively amplify the driving signal of the controller, so that the grid capacitance of the MOS tube can be charged and discharged more quickly, the power-on time of the MOS tube on the grid is shortened, the loss of the MOS tube is reduced, and the switching efficiency is improved. In addition, the gate driver is used as an isolation driving module, and an isolation layer is integrated between the input circuit and the output circuit and is physically isolated by distance and an insulating material. The control signal may pass through the isolation layer in a variety of ways during transmission, and the isolation layer may prevent any significant leakage current from flowing from one side of the isolation layer to the other. Since one input die can be isolated from multiple output dies, which in turn can be isolated from each other, the output common can be freely shifted up from the input common or other output common until the limits of the isolation technique are reached, and the strength of the isolation layer can also be used to enhance the system's ability to withstand surges, lightning strikes, and other abnormal events that may damage the system.

The technical scheme of the utility model also: the isolation driving module comprises a triode. The triode is a semiconductor device for controlling current and has the function of current amplification; the triode has a certain isolation effect, can reduce the loop leakage inductance, limits the peak voltage in the minimum loop, plays a role in isolating the back electromotive force at the transformer side, reduces the influence on the driver, and can accelerate the time for turning off the MOS tube when the driving capability of the driver is insufficient.

The technical proposal of the utility model is also that: the power supply is connected with the input end of the MOS tube.

The technical advantages of the utility model reside in that:

the driving MOS tube is switched on and off in the charging and discharging process of the gate capacitance of the MOS tube, and is switched between a cut-off region and a complete conduction region at high frequency. The reduction of the heat loss of the MOS tube requires that the PWM wave trigger pulse has a sufficiently fast rising and falling speed, a sufficiently large pouring current can be provided at the moment of switching on, a gate-source capacitance discharge loop with as low impedance as possible can be provided during switching off so as to reduce the switching loss, and a drive circuit can ensure a sufficiently large and stable gate-source voltage during the conduction period so as to reduce the conduction loss. During the turn-off period, a certain negative voltage is arranged between the grid electrode and the source electrode, so that the error conduction caused by interference is avoided.

The isolation transformer can electrically isolate the primary input end from the secondary output end by utilizing the electromagnetic induction principle and filter the input PWM wave.

The isolation driving module can isolate the leakage inductance counter electromotive force generated by the step-up transformer, the peak voltage caused by leakage inductance can be reduced through the isolation driving module, the time of the rising edge and the falling edge of a PWM wave is shortened, and sufficient current and output voltage are injected, so that the MOS tube can charge and discharge a grid capacitor more quickly to shorten the transition period, the MOS tube is enabled to work in a switch state, and the loss and the heat of the MOS tube are reduced.

Drawings

Fig. 1 is a schematic structural diagram of a dual-isolation driving power amplifier circuit according to the present invention;

fig. 2 is a circuit diagram of a dual-isolation driving power amplifier circuit according to embodiment 1 of the present invention;

FIG. 3 is a waveform diagram generated by directly driving a MOS transistor by a PWM wave generator without adding an isolation module;

FIG. 4 is a waveform diagram generated by adding an isolation transformer between the PWM wave generator and the MOS transistor to drive the MOS transistor;

FIG. 5 is an enlarged view of a waveform diagram generated by adding an isolation transformer between a PWM wave generator and an MOS transistor to drive the MOS transistor;

FIG. 6 is a waveform diagram generated by adding an isolation transformer and an isolation driving module between the PWM wave generator and the MOS transistor to drive the MOS transistor;

FIG. 7 is an enlarged view of a waveform diagram generated by adding an isolation transformer between a PWM wave generator and an MOS transistor and driving the MOS transistor by an isolation driving module;

in the figure, a 100PWM wave generator, a 200 isolation transformer, a 300 isolation driving module, a 400MOS tube, a 500 power amplifier transformer and a 600 power supply are provided.

Detailed Description

The present invention is described in detail below with reference to the attached drawings:

example 1

As shown in fig. 1, the dual-isolation driving power amplifier circuit includes a PWM wave generator 100, an isolation transformer 200, an isolation driving module 300, a MOS transistor 400 and a power amplifier transformer 500, which are connected in sequence according to a transmission direction of a PWM wave, wherein an input end of the MOS transistor 400 is connected to a power supply 600.

The PWM wave generator 100 outputs a PWM wave. In this embodiment, the PWM wave generator 100 is a pulse width modulator.

The isolation transformer 200 is used for generating electrical isolation and filtering the PWM wave output by the PWM wave generator 100.

The isolation driving module 300 is configured to isolate the back electromotive force at the side of the power amplifier transformer 500, amplify the PWM wave filtered by the isolation transformer 200, and control the gate of the MOS transistor 400, so that the drain and the source of the MOS transistor 400 are switched on and off to drive the power amplifier transformer 500. In this embodiment, the isolation driving module 300 is a gate driver, and the specific model is a gate driving module IXDN609SI.

Specifically, fig. 2 is a circuit diagram of a dual-isolation driving power amplifier circuit, a pulse width modulator (u 1) generates four paths of PWM waves with same phase and opposite phases in pairs, the PWM waves respectively output two sets of PWM waves with opposite phases through two isolation transformers 200 (T1A, B), the isolation transformers 200 use the electromagnetic induction principle to electrically isolate a primary input end from a secondary output end and filter the input PWM waves to drive a gate (g) of a MOS transistor 400, so as to reduce peak voltage generated at the moment when the PWM waves generated by the pulse width modulator (u 1) are turned off due to the influence of back electromotive force and electromagnetic interference generated at the moment when the leakage inductance of the power amplifier transformer 500 is turned off.

The four PWM waves outputted from the isolation transformer 200 (T1A, B) then pass through the isolation driving module 300 (U2A, B, C, D), and the isolation driving module 300 (U2A, B, C, D) can shorten the time of the rising edge and the falling edge of the waveform and output the four PWM waves with more stable high voltage and high current.

The PWM peak voltage driven after double isolation is small, the driving current and voltage are more suitable for the conduction condition of the grid (g) of the MOS tube 400, and finally the PWM waveform after double isolation drives the grid (g) of the MOS tube 400 (Q1A, B, C, D), so that the drain (D) and the source(s) of the MOS tube 400 (Q1A, B, C, D) are quickly conducted and quickly cut off to work in a switching state, the heating condition of the MOS tube 400 (Q1A, B, C, D) under heavy load is reduced, and then the electromagnetic induction principle of the power amplifier transformer 500 (T2) is used for realizing boosting or reducing voltage to generate the needed pulse waveform.

Analyzing the working principle:

without the isolation transformer 200 and the isolation driving module 300, the driving waveforms across the gate (g) and the source(s) of the MOS transistor 400 are measured, as shown in fig. 3 below.

The PWM waveform of fig. 3 is a waveform without adding the isolation transformer 200 and the isolation driving module 300, and it can be seen that waveforms at both ends of the gate (g) and the source(s) of the MOS transistor 400 obviously generate a large peak voltage noise at the turn-off instant of the MOS transistor 400 due to leakage inductance of the power amplifier transformer 500, as shown in blocks 1 'and 2' of fig. 3, the reason that the block 1 'of fig. 3 generates a peak voltage is caused by the turn-off of the waveform of block 2' of fig. 3, and thus it can also be seen that the peak voltage generated by the leakage inductance interferes with the waveform and the power supply which do not work, and the like, where the low level waveform represents the turn-off of the PWM wave, the high level represents the work of the PWM wave, and the two paths of waveforms are complementary driving waveforms, and the circuit is a waveform generated by directly driving the MOS transistor 400 by the SG3525 pulse width modulation chip.

(II) adding the isolation transformer 200 without the isolation driving module 300, and measuring the driving waveforms at the two ends of the gate (g) and the source(s) of the MOS transistor 400 and the amplified waveforms, as shown in FIGS. 4 and 5.

Fig. 4 shows the measured driving waveforms at the gate (g) and the source(s) of the MOS transistor 400 with the isolation transformer 200 added and without the isolation driving module 300, and it can be seen that the peak voltage in the box 1 ″ of fig. 4 is significantly reduced, and fig. 5 shows the waveform after the waveform is amplified, and it can be seen that the rising edge time in the box 2 ″ of fig. 5 is about 400ns, and the rising edge is relatively wide. Compared with the circuit of the present invention, the circuit corresponding to fig. 4 and 5 does not have the isolation driving module 300.

And (iii) adding the isolation transformer 200 and the isolation driving module 300, and measuring the driving waveforms at the two ends of the gate (g) and the source(s) of the MOS transistor 400 and the amplified waveforms, as shown in fig. 6 and 7.

The waveform of fig. 6 is the driving waveform measured across the gate (g) and the source(s) of the MOS transistor 400 with the addition of the isolation transformer 200 and the isolation driving module 300, and it can be seen that the peak voltage of the box 1'″ of fig. 6 is significantly reduced, and the rising edge time of the box 2' ″ of fig. 7 is about 50ns, which is one eighth of the rising edge time of fig. 5.

And (4) conclusion: as can be seen from the above measured fig. 3-7, after the isolation transformer 200 and the isolation driving module 300 are doubly isolated, the influence of the peak voltage, the electromagnetic interference and the response time of the rising edge and the falling edge generated by the leakage inductance of the power amplifier transformer 500 on the power supply and the output waveform of the MOS transistor 400 and the power amplifier circuit is reduced.

The waveform of the gate (g) of the driving MOS transistor 400 is smoother under high frequency conditions, so that the MOS transistor 400 works in a switching state, the loss of the MOS transistor 400 is reduced, the heat generation is reduced, the switching frequency is stable, and the output waveform of the power amplifier transformer 500 is smoother.

Example 2

The difference from embodiment 1 is that the isolation driving module 300 is a triode.

The utility model discloses an application prospect: leakage inductance is an important index of a switching transformer, has a great influence on the performance index of switching power, and is easy to break down the switching device due to overvoltage caused by the existence of the leakage inductance and the generation of counter electromotive force at the moment when the switching device is cut off.

The leakage inductance can also form an oscillation loop with distributed capacitance in the circuit and distributed capacitance of a transformer coil, so that the circuit generates oscillation and radiates electromagnetic energy outwards to cause electromagnetic interference.

In addition, the MOS tube works in a linear region easily due to leakage inductance and the pulse width of the rising edge and the falling edge generated by the device, so that the loss is serious, the MOS generates heat seriously, and the MOS tube is easy to burn out under heavy load.

And the utility model discloses can reduce the recoil that power amplifier transformer leaks and feels to the influence of MOS pipe, reduce the radiation for drive MOS pipe etc. Therefore the circuit has apparent help to switching power supply circuits such as high frequency circuit and power push-pull circuit or inverter circuit, reduces power amplifier circuit's loss, protection MOS pipe and power chip, and high frequency output is more stable, helps improving medical circuit's safety.

Claims

1. The utility model provides a two keep apart drive power amplifier circuit which characterized in that: the power amplifier comprises a PWM wave generator (100), an isolation transformer (200), an isolation driving module (300), an MOS (metal oxide semiconductor) tube (400) and a power amplifier transformer (500) which are sequentially connected according to the transmission direction of the PWM wave;

the PWM wave generator (100) is used for outputting a PWM wave;

the isolation transformer (200) is used for generating electrical isolation and filtering the PWM wave output by the PWM wave generator (100);

the isolation driving module (300) is used for isolating back electromotive force at the side of the power amplifier transformer (500), amplifying the PWM wave filtered by the isolation transformer (200) and controlling the grid of the MOS tube (400) so that the drain and the source of the MOS tube (400) are switched on and off to drive the power amplifier transformer (500).

2. The dual isolation driver circuit of claim 1, wherein: the PWM wave generator (100) comprises a pulse width modulator.

3. The dual isolation driver circuit of claim 1, wherein: the isolated driving module (300) comprises a gate driver.

4. The dual isolation driver circuit of claim 1, wherein: the isolation drive module (300) includes a triode.

5. The dual isolation driver circuit of claim 1, wherein: the power supply (600) is further included, and the power supply (600) is connected with the input end of the MOS tube (400).