START CONTROL DEVICE FOR A PEAK CURRENT CONTROLLED CONVERTER.
The start-up current limiting device for analog converters, featuring a synchronized PWM-controlled insulated gate field effect transistor, addresses the issue of uncontrolled inrush current by adjusting the current limitation setting, ensuring stable and controlled peak currents during startup and steady-state operation.
Patent Information
- Application Number
- FR2021014079
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2021-12-21
- Publication Date
- 2025-05-30
- Estimated Expiration
- 2041-12-21
AI Technical Summary
Commercial analog converters often experience uncontrolled inrush current during startup due to the lack of effective current control, leading to unsatisfactory initial conditions and potential current jumps during the transition to steady state.
A start-up current limiting device comprising an insulated gate field effect transistor, a current measuring resistor, a tuning capacitor, and an adjustment resistor synchronized with a PWM signal, which operates in two phases: a linear decrease in transistor resistance during startup and saturation during steady-state operation.
The solution effectively controls the inrush current during startup, reducing peak currents and ensuring stable operation by adjusting the current limitation setting based on the PWM signal, thus overcoming the limitations of commercial analog converters.
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Abstract
Description
Title of the invention: Start-up control device for a peak current controlled converter.
[0001] The invention relates to a start-up control device for a controlled converter (for example switching power supply) in peak current (or which result from the same principle, i.e. a measurement of the current which serves as a modulating wave in place of the triangular or sawtooth signal of the traditional voltage control) by a commercial controller on which the adjustment of the current limitation is external.
[0002] The start-up of a converter equipped with a commercial controller is almost systematically uncontrolled, a consequence of the initialization time of the soft-start function. This shortcoming causes an uncontrolled inrush current.
[0003] Work is known dealing with digitally controlled converters which, by nature, do not have these characteristics of non-control of the current in the initial start-up phase.
[0004] [Fig-1] schematically represents the classic structure of an analog converter 2 (step-down) on the basis of control by measurement of the current which serves as a modulating wave, in this case by peak current.
[0005] Converter 2 is powered by a source 1, and powers a load 3.
[0006] The converter 2 includes an input filter FE which makes it possible to ensure the performance emission and susceptibility forms with respect to source 1.
[0007] The converter 2 comprises a switch module MI comprising power switches to ensure energy conversion (based on the principle of switching power supplies).
[0008] The converter 2 comprises a voltage loop module LV and a current loop module BC which allow the comparison to be carried out and then the generation of the pulse width modulation by a PWM module.
[0009] The converter 2 includes a soft-start module DD for clean starting, i.e. starting monotonously and controlling the inrush current.
[0010] In the example of [Fig. 1], the input filter FE comprises a coil or inductance Se and a capacitor Ce, and the output filter FS comprises a coil or inductance Ss and a capacitor Cs.
[0011] The switch module MI comprises an inverter INV, and two insulated gate field effect transistors M_T, M_B.
[0012] The PWM module for generating pulse width modulation comprises a comparator C and an RS flip-flop A2, and the soft start module DD includes a switch Sss, a capacitor Css and a source Source_I.
[0013] The BT voltage loop module comprises a source Vref, a switch Sref, two impedances ZI and Z2, and a corrector PI, and the BC current loop module comprises a shunt resistor Rshunt or current measuring resistor and a gain GI.
[0014] At startup, the switch Sss, of the soft start module DD, is closed. The output voltage of the converter 2 follows the image of the voltage of the point Ref which evolves according to a ramp produced by the couple Source_I and Css. When the ramp reaches a voltage close to the reference voltage Vref corresponding to the image of the output voltage level (after the filter FS) of the steady state of the converter 2, the switch Sss opens and the switch Sref closes. The system goes into steady state, the PWM signal, corresponding to the pulse width modulation signal varies in order to obtain VFB = Vref, with VFB representing the input voltage of the PI comparator of the LV voltage loop module.
[0015] Current analog controllers do not fully satisfy the control of the starting current.
[0016] Almost systematically, for current commercial analog converters, the start of the startup is not controlled. The initial conditions of the converter are not satisfactory (integrating effect of the corrector). This initialization time generates a current demand despite the existing DD soft start module. To a lesser extent, the transition between startup and steady state can generate a current jump.
[0017] An aim of the invention is to overcome the problems mentioned above, and in particular to control the inrush current when starting a converter controlled by current measurement serving as a modulating wave.
[0018] According to one aspect of the invention, there is provided a starting current limiting device for a converter controlled by current measurement serving as a modulating wave by external current limiting adjustment, the device comprising: - an insulated gate field effect transistor comprising a source, a drain and a gate; - a current measuring resistor connected between the source and the drain; - a tuning capacitor placed between the grid and ground; and - an adjustment resistor connected to the grid and receiving a voltage of synchronized control on a pulse width modulation signal of the current measurement controlled converter which serves as a modulating wave.
[0019] According to one embodiment, the device is configured to operate in two phases:
[0020]
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[0028]
[0029]
[0030]
[0031] - a first phase corresponding to the start-up of the converter, during which the internal resistance of the transistor decreases linearly to a saturation value; - a second phase corresponding to the operation of the converter during which the transistor is saturated. There is also provided, according to another aspect of the invention, a current measurement controlled converter serving as a modulating wave comprising: - an input filter module; - a switch module; - a current loop module connected to a device according to one of the preceding claims; - a voltage loop module; - a pulse width modulation module; - a soft start module; and - an output filter module. For example, the converter configured to be controlled in peak current mode. Also provided, according to another aspect of the invention, is a switching power supply comprising a converter as previously described. The invention will be better understood by studying a few embodiments described as non-limiting examples and illustrated by the appended drawings in which the figures: [Fig.l] schematically illustrates a current measurement controlled converter serving as a modulating wave by external current limitation adjustment, according to the state of the art; [Fig.2] schematically illustrates a starting current limiting device for a converter controlled by current measurement serving as a modulating wave by external current limiting adjustment, according to one aspect of the invention; [Fig.3] schematically illustrates a converter provided with a device of [Fig.2], according to one aspect of the invention; [Fig.4] schematically illustrates the operation of a converter of [Fig.l], according to the state of the art; [Fig.5] schematically illustrates the operation of a converter of [Fig.3], according to one aspect of the invention; and [Fig.6] schematically illustrates the production of the control signal of the device, according to one aspect of the invention. In all figures, elements with identical references are similar. [Fig.2] schematically represents a current limiting device of startup for converter controlled by current measurement serving as modulating wave by external current limitation adjustment, according to one aspect of the invention.
[0032] The device comprises an insulated gate field effect transistor MOFSET comprising a source S, a drain D and a gate G; - a current measuring resistor Rshunt_2 connected between the source S and the drain D; - a Ctime adjustment capacitor placed between the grid G and ground; and - an adjustment resistor Rtime connected to the grid G and receiving a voltage Control synchronized to a PWM pulse width modulation signal of the current-controlled converter which serves as a modulating wave.
[0033] The principle is based on the linear operation of the MOSFET. We act on the gain of the current measurement (variable resistance Rvariable2).
[0034] During a first phase, at t=0, the insulated gate field effect transistor MOFSET is controlled slowly and synchronously to the PWM signal (it is the time constant of the resistor / capacitor pair which makes it possible to adjust more or less slowly the decay time of the resistance Rvariable2 of the MOSFET transistor and therefore the linear operation time. The choice of the Rtime / -Ctime pair makes it possible to adjust the time desired to limit the starting current. This adjustment makes it possible to control the evolution of the signal Vgs (control voltage between gate G and source S of the MOSFET transistor). Its internal resistance Rvariable2 decreases linearly until its saturation value (Rvariable2_sat « Rshunt_2).
[0035] During a second phase, the MOFSET transistor is saturated, the shunt resistor Rshunt_2 is almost short-circuited, and the current measurement is governed by the shunt or current measurement resistor Rshunt, of the current loop module BC, which ensures full performance of the converter.
[0036] This solution is independent of the time constants of the assembly because the synchronization signal is the PWM signal.
[0037] [Fig. 3] schematically represents a converter provided with a device of [Fig. 2], in this case a converter according to [Fig. 1] in which the current loop module BC further comprises a device of [Fig. 2] according to one aspect of the invention.
[0038] [Fig.4] schematically represents the operation of a converter of [Fig.l], in which, during an entire initialization phase (start-up), the voltage V comp of the signal COMP is at the high limit. The current limitation is achieved by the limit of Icrête (well beyond the maximum current necessary for the load and its dynamics).
[0039] [Fig.4] represents a conventional operation with a duty cycle maximum of 50%.
[0040] In comparison, [Fig.5] schematically represents the operation of a converter of [Fig.3], according to one aspect of the invention, in which the originality is to act on the transient part (initialization time) without intervening on the permanent regime.
[0041] [Fig.5] shows the effects of limiting the peak current at startup thanks to the Ipeak Stop limit which has become adjustable over time. This limit is imposed well below the steady state during the startup phase, which makes it possible to reduce the duty cycle and therefore the peak currents throughout the converter.
[0042] As shown in [Fig.6], the control signal Cmde is produced from the PWM signal. A monostable, i.e. a circuit that stores a level change in memory, allows the signal to be shaped to obtain the operation described below. Depending on the configuration of the monostable, in the absence of a certain number of PWMs (e.g.: stopping the converter), it can reset itself in order to prepare a new start if necessary.
[0043] As shown in [Fig.6]: - in phase 0: delay (1.3ms in this example) due to the threshold voltage VGS(th) of the MOSFET transistor. This delay has no impact on operation. - in phase 1: linear operation of the MOSFET transistor. The equivalent resistance at Rshunt_2 decreases, which allows the current limitation setting to be increased. - in phases 2 and 3: the MOSFET transistor is saturated. The current limitation setting becomes fixed and allows the current required for the load to be supplied (continuation of start-up and steady state).
[0044] The solution overcomes the initialization problem of most commercial analog controllers in order to control without compromise the amplitude of the currents in the converter and more precisely the input current on which there are significant constraints.
Claims
Claims
1. A starting current limiting device for a current measurement-controlled converter serving as a modulating wave by external current limiting adjustment, the device comprising: • an insulated gate field effect transistor (MOFSET) comprising a source (S), a drain (D) and a gate (G); • a current measuring resistor (Rshunt_2) connected between the source (S) and the drain (D); • an adjustment capacitor (Ctime) arranged between the gate (G) and ground; and • an adjustment resistor (Rtime) connected to the gate (G) and receiving a control voltage (Cmde) synchronized to a pulse width modulation signal (PWM) of the current measurement-controlled converter which serves as a modulating wave.
2. Device according to claim 1, configured to operate in two phases: • a first phase corresponding to the start-up of the converter, during which the internal resistance of the transistor (MOFSET) decreases linearly to a saturation value; • a second phase corresponding to the operation of the converter during which the transistor (MOFSET) is saturated.
3. Current measurement controlled converter serving as a modulating wave comprising: • an input filter module (FE); • a switch module (MI); • a current loop module (BC) connected to a device according to one of the preceding claims; • a voltage loop module (BT); • a pulse width modulation module (MLI); • a soft start module (DD); and • an output filter module (FS).
4. Converter according to claim 3, configured to be controlled in peak current mode.
5. A switching power supply comprising a converter according to claim 4.