A method for monitoring the ESR of output capacitor of boost converter

Abstract

The present invention belongs to the technical field of capacitor health monitoring and discloses a method for monitoring the ESR of a boost converter output capacitor, comprising: sampling the inductor current i L (t) and output voltage v o (t), obtain the AC component v o_ac (t); The proportion of time D that the inductor current is not zero on +D off Calculate the load resistance R o value; according to the output voltage v o (t) and load resistance R o With the inductor current i L The value of (t) is fitted to the capacitor current i C (t) waveform; according to the capacitor current i C (t) and the output voltage AC component v o_ac The method provided by the present invention does not need to add additional sampling points, does not affect the normal operation of the converter, is applicable to both CCM and DCM modes, and provides a basis for capacitor health monitoring.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitor health monitoring, and in particular to a method for monitoring ESR of an output capacitor of a Boost converter. Background Art

[0002] Due to the advantages of high efficiency, small size, and low noise, power electronic converters have been widely used in military, aerospace, and industrial fields. In power electronic converters, in order to obtain a higher quality output voltage, capacitors must be used to filter out high-frequency noise, among which electrolytic capacitors are the most commonly used. A survey pointed out that electrolytic capacitors are the power devices with the highest failure rate in power electronic converters. After the electrolytic capacitor has been used for a period of time, the equivalent series resistance (ESR) of the capacitor will increase, and the capacitance (C) of the capacitor will decrease. When the two change to a certain extent, it can be considered that the capacitor has failed. The failure of the capacitor will cause the operation of the converter and the system to fail. In industry, the equivalent series resistance (ESR) and capacitance (C) of the electrolytic capacitor are important indicators used to measure the health of the capacitor. Boost converters are widely used in the fields of new energy generation, computer power supply, and communication power supply. And because the equivalent series resistance (ESR) of the output capacitor after aging changes significantly and is easy to monitor, monitoring the equivalent series resistance (ESR) of the output capacitor of the boost converter is crucial to assessing its health. However, the existing Boost converter output capacitor ESR identification process is complicated and requires a high-precision trigger sampling circuit to sample the instantaneous value of the output voltage at a specific moment, so it is impossible to provide a simple and universal capacitor health monitoring method. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a method for monitoring the ESR of an output capacitor of a Boost converter, which can monitor the ESR online in real time and monitor the health status of the electrolytic capacitor.

[0004] The present invention adopts the following technical solutions to solve the above technical problems:

[0005] A method for monitoring the ESR of an output capacitor of a Boost converter comprises the following steps:

[0006] Step A), sampling the inductor current i L (t) and output voltage v o (t), and the output voltage v o (t) The output voltage AC component v is obtained by high-pass filtering and synchronous sampling o_ac (t);

[0007] Step B), the inductor current i L (t) The proportion of time D during which the inductor current is not zero after passing through the Switch module on +Doff When its value is 1, the converter is in CCM working state, and when its value is less than 1, the converter is in DCM working state;

[0008] Step C), according to the average inductor current I L and the output voltage mean V o With duty cycle D on The proportion of time D that the inductor current is not zero after the switch tube is turned off off The load resistance R is calculated using different formulas in different states. o The value of

[0009]

[0010] Step D), according to the output voltage v o (t) and load resistance R o With the inductor current i L The value of (t) is fitted to the capacitor current i C (t) waveform;

[0011]

[0012] Where g(t) is the pulse width D off , with an amplitude of 1 and a period of 1 / f s Rectangular pulse signal.

[0013] Step E), according to the inductor current i C (t) and the AC component of the output voltage v o_ac (t) value is used to calculate the equivalent series resistance (ESR) value of the filter capacitor.

[0014]

[0015] Where T = 1 / f s .

[0016] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0017] 1. The present invention is applicable to both CCM and DCM modes;

[0018] 2. The present invention does not need to monitor the PWM drive pulse signal of the power switch device, and does not require cumbersome calculations;

[0019] 3. For the Boost converter with dual-loop control of output voltage and current, the present invention does not need to introduce new sampling points;

[0020] 4. The circuit is simple and does not require a high-precision trigger sampling circuit. It can achieve accurate monitoring of ESR and has important practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the method for monitoring the ESR value of an output capacitor in the present invention;

[0022] Figure 2 This is a working waveform diagram of the Boost circuit of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0024] Figure 1 A schematic diagram of a method for monitoring the ESR of a Boost converter output capacitor provided by the present invention includes the following steps:

[0025] Step A), sampling the inductor current i L (t) and output voltage v o (t), and the output voltage v o (t) The AC component v is obtained by high-pass filtering and synchronous sampling. o_ac (t);

[0026] Step B), the inductor current i L (t) The proportion of time D during which the inductor current is not zero after passing through the Switch module on +D off When its value is 1, the converter is in CCM working state, and when its value is less than 1, the converter is in DCM working state;

[0027] Step C), according to the average inductor current I L and the output voltage mean V o With duty cycle D on The proportion of time D that the inductor current is not zero after the switch tube is turned off off The load resistance R is calculated using different formulas in different states. o The value of

[0028]

[0029] Step D), according to the output voltage v o (t) and load resistance R o With the inductor current i L The value of (t) is fitted to the capacitor current i C (t) waveform;

[0030]

[0031] Where g(t) is the pulse width D off , with an amplitude of 1 and a period of 1 / f sRectangular pulse signal.

[0032] Step E), according to the inductor current i C (t) and the AC component of the output voltage v o_ac (t) value is used to calculate the equivalent series resistance (ESR) value of the filter capacitor.

[0033]

[0034] Where T = 1 / f s .

[0035] Figure 2 is a working waveform diagram of the Boost circuit in the present invention when the load is resistive, wherein Figure 2 (a) is CCM mode, Figure 2 (b) is DCM mode. The present invention provides a simulation result of the equivalent series resistance of the output capacitor of the Boost converter. The simulation conditions are: input voltage V in =10V, inductance L f =240μH, capacitance C = 120μF, switching frequency f s =20kHz, sampling frequency fc = 10MHz. First, the circuit operation simulation is performed. After the operation stops, the inductor current i L (t), output voltage v o (t) and its AC component v o_ac (t), duty cycle of inductor current D on The proportion of time D that is not zero after the switch tube is turned off off Imported into Matlab Workspace, according to the duty cycle D on The proportion of time D that is not zero after the switch tube is turned off off The value of determines the working mode of the Boost circuit and calculates the load R o The value of the output capacitor current i is then obtained by current fitting. c (t), and finally the data is processed and calculated to obtain the equivalent series resistance ESR value of the output capacitor. The simulation results under different conditions are shown in Table 1. It can be seen that the method for monitoring the ESR value of the output capacitor of the Boost circuit provided by the present invention has a high tracking accuracy.

[0036] Table 1

[0037] ESR actual value / Ω 0.2 0.4 0.2 0.4 Duty cycle D 0.5 0.5 0.5 0.5 <![CDATA[R L / Oh]]> 10(CCM) 10(CCM) 100(DCM) 100(DCM) ESR calculation value / Ω 0.2003 0.3977 0.1985 0.3947

[0038] The advantage of the Boost circuit output capacitor ESR value monitoring method provided by the present invention is that no new measurement point needs to be introduced, the method is simple and easy to implement, and is applicable to both CCM and DCM modes.

[0039] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0040] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for monitoring the ESR of a boost converter output capacitor, characterized in that: The following steps are involved: Step A), sampling the inductor current i L (t) and output voltage v o (t), and make the output voltage v o (t) The output voltage AC component v is obtained by high-pass filtering and synchronous sampling o_ac (t); Step B), the inductor current i L (t) The proportion of time D during which the inductor current is not zero after passing through the Switch module on +D off When its value is 1, the converter is in CCM working state; when its value is less than 1, the converter is in DCM working state; Step C), according to the average inductor current I L , output voltage average V o , duty cycle D on , the proportion of time D that the inductor current is not zero after the switch is turned off off The value of the inductor current and the proportion of time D when the inductor current is not zero on +D off The load resistance R is calculated using the following formula o The value of Step D), according to the output voltage v o (t) and load terminal resistance R o and the inductor current i L The value of (t) is fitted to the capacitor current i C (t) waveform; Step E), calculating the ESR value of the output capacitor of the Boost converter according to the following formula; Where T = 1 / f s .

2. The monitoring method according to claim 1, characterized in that: In step D, the output voltage v o (t) and load terminal resistance R o and the inductor current i L The value of (t) is fitted to the capacitor current i C The waveform of (t) is simulated according to the following formula: Where g(t) is the pulse width D off , amplitude is 1, period is 1 / f s rectangular pulse signal.

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