A ripple current generating circuit

Abstract

The present invention provides a ripple current generating circuit. It comprises a direct current source U, a first inductor (1), lossless ripple current generator (100) and output terminals connecting two pins of the measured capacitor, including a positive terminal J+ and a negative terminal J-. The output of the DC source U has a positive pole and a negative pole. The lossless ripple current generator (100) contains at least one pulse width modulation P; The output terminal and the inductors L are connected in series and then in parallel to the DC source U. The lossless ripple current generator (100) and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is returned almost losslessly to the direct current source U or the measured capacitor; The maximum duty cycle of the pulse width modulation control circuit is less than 0.5; A display circuit (200) is further connected in parallel between the positive terminal J+ and the negative terminal J-, and the display circuit (200) has the following properties: It contains the first resistor R1, the first capacitor C1, the first diode D1 and the first light-emitting diode LED. The first resistor R1, the first diode D1 and the first light-emitting diode LED are connected in parallel, whereby The first light-emitting diode (LED) and the first diode D1 are connected in antiparallel. The parallel two-terminal network is called a parallel network (24). A distinction is made between the terminals of the parallel network (24) and the two-terminal network of the first diode D1. The parallel network (24) and the first capacitor C1 are connected in series to form a two-terminal network in series. The two-terminal network is simply referred to as a series network, and the two terminals of the series network are, respectively, the first terminal (1) and the second terminal (2) of the display circuit (200).

Description

Technical field

[0001] The present invention relates to a ripple current generating circuit and, more particularly, to a ripple current generating circuit for an aging test of an electrolytic life. Background technology

[0002] Switching power supplies are currently widely used. For applications where the input power is below 75 W and the power factor (PF) is not required, the flyback switching power supply offers a fascinating advantage. It is described in these two applications, CN 1 05 242 737 A and CN 1 05 302 217 A, for a ripple current generating circuit. At the same time, there are no effective test methods and instruments for controlling the rated ripple current of electrolytic capacitors. It also provides a technical solution for supplying a ripple current generating circuit. At low cost and low energy consumption, it provides high-frequency ripple current for testing electrolytic capacitors. The following "electrolytic capacitors" are referred to as "electrolytic capacitors."

[0003] The above two applications are presented in order, namely A (CN 1 05 242 737 A) and B (CN 1 05 302 217 A). There are still problems with the above two applications: When the measured electrolysis unit is close to failure, and the equivalent series resistance (ESR) increases sharply, the electrolysis unit's performance is close to the unusable edge. If it doesn't stop there, the electrolysis unit will enter an accelerated failure mode. If the electrolysis unit fails, the electrolysis unit may be bombed. Then, cleaning becomes difficult, causing many related errors and increasing losses. The bombed field-effect transistor Q may also cast a shadow on the test equipment operators, making them unwilling to operate the machine.

[0004] In Patent Application A, the DC power source and inductor are responsible for the power supply. A transformer, a diode, a field-effect transistor, and a pulse-width modulator control the circuit to form a core body of the circuit according to the method of the claims. Their function is to generate a ripple current, and then the consumed electrical energy is returned losslessly to the DC power source or electrolytic capacitor through the second winding. The ripple current and the consumed lossless electrical energy are referred to as a lossless ripple current generator circuit, which is simply referred to as a lossless ripple current generator.

[0005] In Patent Application B, the DC power source and the first inductor are responsible for the power supply. The second inductor, a first diode, a second diode, two field-effect transistors, and a pulse-width modulator control the circuit to form a core body of the circuit according to the method of the claims. Their function is to generate a ripple current, and then the consumed electrical energy is fed back into the DC power source or electrolytic capacitor with almost no loss through the second inductor, a first diode, and a second diode. The ripple current and the consumed lossless electrical energy are referred to as a lossless ripple current generator circuit, which is also simply referred to as a lossless ripple current generator.

[0006] The technical term "lossless ripple current generator" used in the following contents and claims has the same meaning as the corresponding circuits in the above-mentioned patents A and B, namely the circuit: It generates ripple current and the consumed electrical energy is fed back into the DC source or the measured electrolysis with almost no loss.

[0007] Further, the problem is solved in patents CN 1 05 676 937 B and CN 1 05 676 936 B, and the technical solution is summarized as follows: A display circuit is inserted into the loop of the DC power source U and the measured capacitor. The display circuit consists of the inductor L and the LED in parallel. The current direction of the DC power source U, which provides power through inductor L, is opposite to the forward direction of the LED. When the measured inductor is normal, the excitation current of the switching transistor Q substantially does not appear in the inductor L, and the LED does not light up; when the ESR of the measured capacitor increases sharply, the excitation current of Q appears in L, and Q is turned off. At this time, the excitation current flowing through L cannot be abruptly changed, and it can flow through LED continuously, and the LED is driven to emit light and then remind the user.

[0008] The two patent applications mentioned above are abbreviated in order of appearance: existing patent C (CN 1 05 676 937 B) and patent D (CN 1 05 676 936 B). There are also problems in them.

[0009] The inductor L is used to isolate the power supply and the measured capacitor, so that the DC power source only supplies DC current, while the measured capacitor supplies high-frequency ripple current. This requires the inductor L to have a large inductance. If the inductor L has a moderate inductance, it is used to achieve the display circuit. Because a large inductance can cause problems for the display circuit. That is, the ESR of the measured capacitor will rise slightly, and the display circuit will start to display, which is inconvenient to use.

[0010] Therefore, we hope to use a ripple current generating circuit. The inductor L is used only to isolate the power supply, and the DC power source is used only to provide the DC current. The inductor L is not responsible for providing an indication signal. The signal indicating that the electrolysis is invalid is then provided by other circuits, so that the equipment or operator can shut down in time. Content of the invention

[0011] The present invention aims to solve the deficiencies of the existing method for generating ripple current and provides a ripple current generating circuit. The inductor L is used only to isolate the power supply. Then, the signal indicating that the measured capacitor is invalid is provided by other circuits. It is inexpensive, the display circuit is simple, and it is convenient to use.

[0012] The present invention provides a ripple current generating circuit. Solution 1: It comprises a DC power source, a first inductor, a lossless ripple current generator, and output terminals connecting two pins of the measured capacitor, including a positive terminal and a negative terminal. The output of the DC power source has a positive terminal and a negative terminal. The lossless ripple current generator includes at least one pulse width modulation circuit.

[0013] The output terminal and the inductors are connected in series and then in parallel to the DC power source.

[0014] The lossless ripple current generator and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is returned to the DC source or the measured electrolysis with almost no loss.

[0015] The maximum duty cycle of the pulse width modulation control circuit is less than 0.5;

[0016] A display circuit is further connected in parallel between the positive terminal and the negative terminal. The display circuit has the following characteristics: It contains the first resistor, the first capacitor, the first diode, and the first light-emitting diode. The first resistor, the first diode, and the first light-emitting diode are connected in parallel, and the first light-emitting diode and the first diode are connected in antiparallel. The two-terminal network formed in parallel is called a parallel network. The terminals of the parallel network and the two-terminal terminal of the first diode are distinguished. The parallel network and the first capacitor are connected in series to form a two-terminal network. The two-terminal network is simply called a series network, and the two terminals of the series network are respectively the first terminal and the second terminal of the display circuit.

[0017] The present invention provides a ripple current generating circuit. Solution 2: It comprises a DC power source, a first inductor, a lossless ripple current generator, and output terminals connecting two pins of the measured capacitor, including a positive terminal and a negative terminal. The output of the DC power source has a positive terminal and a negative terminal. The lossless ripple current generator includes at least one pulse width modulation circuit.

[0018] The output terminal and the inductors are connected in series and then in parallel to the DC power source.

[0019] The lossless ripple current generator and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is returned to the DC power source or the measured capacitor with almost no loss.

[0020] The maximum duty cycle of the pulse width modulation control circuit is less than 0.5;

[0021] A display circuit is further connected in parallel between the positive and negative terminals. The display circuit has the following characteristics: It contains the first resistor, the second resistor, the first and second capacitors, the first diode, the second diode, and the first light-emitting diode. The connection relationship is: The second resistor and the first LED are connected in series to form a first two-terminal network. The first network and the second capacitor are simultaneously connected in parallel with the first resistor to form a second two-terminal network. The second network and the second diode are connected in series to form the third two-terminal network. The third network has the following properties: The direction of the second diode and the first LED is the same. The third network is connected in antiparallel with the first diode to form the fourth two-terminal network, and the fourth network is connected in series with the first capacitor to form a two-terminal network. The two-terminal network is called a series network. The two terminals of the series network are the first terminal and the second terminal, respectively.

[0022] Preferably, solutions 1 and 2 have the properties: the first LED is a generator in the optocoupler, namely the LED in the optocoupler.

[0023] The working principle is explained in detail in conjunction with the example embodiment.

[0024] The advantageous effects of the invention are: It provides high-frequency ripple current; the inductor is used only to isolate the power supply and is not responsible for providing an indicator signal. Before the electrolysis fails, the current flows in the generator's LED or the LED in the optocoupler. The optocoupler outputs an isolated signal to warn the user or the circuit, and the preset ESR before the electrolysis fails can be set. Description of appendix Fig. is a schematic diagram of a first embodiment of technical solutions of the present invention; Fig. is a schematic diagram of a first embodiment of the display circuit according to the first technical solutions of the present invention; Fig. is a first schematic equivalent diagram of a first embodiment of the display circuit according to the first technical solutions of the present invention; Fig. is a second schematic equivalent diagram of a first embodiment of the display circuit according to the first technical solutions of the present invention; Fig. is a third schematic equivalent diagram of a first embodiment of the display circuit according to the first technical solutions of the present invention; Fig. is a schematic diagram of a path of a charging current generated by the DC power source U of Figure 1; Fig. is a waveform diagram of the drive voltage Ugs from the grid and source of the switching transistor Q in Fig. ,an excitation current il of a main power stage and an operating current i out of the measured capacitor. Fig. is a schematic diagram where the operating current i out of the measured capacitor in Fig. forms a voltage drop on ESR of the measured capacitor; Fig. is a schematic diagram of a second embodiment of technical solutions of the present invention; Fig. is a schematic diagram of a second embodiment of the display circuit according to the second technical solutions of the present invention; Fig. is a first schematic equivalent diagram of a second embodiment of the display circuit according to the second technical solutions of the present invention; Fig. is a second schematic equivalent diagram of a second embodiment of the display circuit according to the second technical solutions of the present invention; Fig. is a third schematic equivalent diagram of a second embodiment of the display circuit according to the second technical solutions of the present invention; Detailed implementationFirst embodiment

[0025] A ripple current generating circuit in Fig. is according to solution 1 and it includes a DC current source U, the first inductor 1_and lossless ripple current generator and output terminals connecting two pins of the measured capacitor, including a positive terminal J+ and a negative terminal J-.The output of the DC current source U has a positive pole and a negative pole.The lossless ripple current generator 100 includes at least one pulse width modulation P;

[0026] The output terminal and the inductors L are connected in series and then in parallel to the DC source U.

[0027] The lossless ripple current generator 100 and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is fed back into the DC power source U or the measured capacitor with almost no loss.

[0028] The maximum duty cycle of the pulse width modulation control circuit is less than 0.5;

[0029] A display circuit 200 is further connected in parallel between the positive terminal J+ and the negative terminal J-. The schematic diagram of the display circuit 200 is shown in Fig. The display circuit 200 has the following characteristics: It includes the first resistor R1, the first capacitor C1, the first diode D1, and the first light-emitting diode LED. R1, D1, and LED are connected in parallel, and LED and D1 are connected in antiparallel. The parallel two-terminal network formed is called a parallel network 24. The terminals of the parallel network 24 are distinguished by the anode of the first diode D1 and the cathode of the first diode D1. The parallel network 24 and the first capacitor C1 are connected in series to form a two-terminal network. The two-terminal network is simply referred to as a series network, and the two terminals of the series network are, respectively, the first terminal 1 and the second terminal 2 of the display circuit.

[0030] Obviously, the first terminal 1 is connected to the positive terminal J+, and the second terminal 2 is connected to the negative terminal J-; if the first terminal 1 is connected to the negative terminal J- and the second terminal 2 is connected to the positive terminal J+, the circuit is also functional.

[0031] In antiparallel connection it shows:anode of the first diode D1 and cathode of the first LED are connected and also cathode of the first diode D1 and anode of the first LED are connected.

[0032] The first capacitor C1 is referred to as C1, and the first resistor R1 is referred to as R1. The first LED is referred to as LED, and other devices are similar.

[0033] C1 and the parallel network 24 are connected in series to form the display circuit 200. Since the circuit is a series circuit, the functions are the same after a position change. Therefore, Solution 1 contains a variety of series processes, but the functions are as follows: (a) The cathode of D1 is facing down, C1 is on the upper side, as shown in 2-1, the anode of D1 is connected to one terminal of C1, and the other terminal of C1 is the first terminal 1 of the display circuit and the cathode of D1 is the second terminal 2 of the display circuit; (b) The cathode of D1 is down, C1 is down, as shown in 2-2, the cathode of D1 is connected to one terminal of C1, and the anode of D1 is the first terminal 1 of the display circuit and the other terminal of C1 is the second terminal 2 of the display circuit; (c) The cathode of D1 is facing up, C1 is facing up, as shown in 2-3, the cathode of D1 is connected to one terminal of C1, and the other terminal of C1 is the first terminal 1 of the display circuit; and the anode of D1 is the second terminal 2 of the display circuit; it is exactly the same as the method of 2-2 of (b) above, terminal 1 of (b) is equal to terminal 2 of (c), and terminal 2 of (b) is equal to terminal 1 of (c). That is, terminals 1 and 2 of the Fig. are swapped, which is exactly the same as (b) the Fig. is. (d) The cathode of D1 is facing up, C1 is facing down, as shown in 2-4, the anode of D1 is connected to one terminal of C1, and the other terminal of C1 is the second terminal 2 of the display circuit; and the cathode of D1 is the first terminal 1 of the display circuit; it is exactly the same as the method of 2-1 of (a) above, terminal 1 of method (a) is equal to terminal 2 of (d), and terminal 2 of method (a) is equal to terminal 1 of (d). That is, terminals 1 and 2 of (d) are reversed, which is exactly the same as (a) of the Fig. is.

[0034] That is, the only effective connection method is only the above (a) of 2-1 and (b) of 2-2. C1 and network 24 are connected in series. Since the circuit is a series circuit, the functions are the same after a position change, which is a known technique. In (b) of 2-2, C1 of (a) of 2-1 is exchanged with network 24. That is, (a) of 2-1 and (b) of 2-2 are essentially equivalent. Namely, in the first technical solution, the display circuit 200 includes the above four connection modes.

[0035] The LED is Φ3mm highlighted in red. For convenience, the light-emitting diode is simply referred to as LED, and the model is 3AR2UD. The capacitor C1 is a 333 / 500V chip capacitor, and the nominal capacity is 0.033 uF. D1 is 1N4148, and R1 is 22K. The switching power supply is constructed according to 2-1 as the display circuit and is in Fig. installed.The lossless ripple current generator 100 adopts the technical solution 1 of the first embodiment of patent A. Inductor L assumes an inductance of 1 mH. It is wound with a wire diameter of 0.6 mm.

[0036] The measured capacitor is the electrolysis of nominal 450B×C47MEFC18×25 and the nominal withstand voltage is 450V, the ripple current is 1.2A, and the DC power source U is set to 311V DC.After the circuit of the first embodiment is set up, the air gap of the magnetic core is adjusted so that the ripple current of the measured capacitor is 1.2A and the LED does not emit light.

[0037] Since the failed electrolytic capacitor is difficult to obtain, an adjustable resistor is inserted in series with the capacitor measured above to simulate the electrolytic capacitor whose performance has been affected. The adjustable range of the adjustable resistor here is 0-39 Ω. If the adjustable resistor is 5 Ω, it means that the ESR of a 47uF / 400V electrolytic capacitor increases from about 0.5 Ω to 5.5 Ω, and the electrolytic capacitor performance is close to the unusable edge.

[0038] At this time, LED 1 emits light, and the average operating current is actually measured at 1.6 mA. By selecting capacitors C1 with different capacitances, the sensitivity of the display is initially adjusted. The capacitance of capacitor C1 is small, resulting in low sensitivity, while the capacitance of capacitor C1 is large, resulting in high sensitivity. Since the LED emits light with a forward voltage drop of 1.6 V to 2.2 V, resistor R1 can be connected in parallel across two terminals of the LED to adjust the sensitivity. In this example, if R1 uses a resistance of 1.6 K, the voltage across two terminals of R1 will be less than 1.6 V at a peak current of 1 mA or less.

[0039] Note: The conduction voltage drop of the white LED is about 3.0V, and the conduction voltage drops of the red and green LEDs are also different, and the conduction voltage drop of the illuminator in the optocoupler is about 1.1V. The illuminator in the optocoupler is also an LED.

[0040] Working principle: When the electrolysis in Fig. is normal, then ESR is 0.5 Ω and there is only a ripple voltage across the measured capacitor. For example, when the lossless ripple current generator 100 is fully loaded, the duty cycle is close to 0.5.

[0041] The path of the charging current generated by the DC source U is in the path in Fig. shown, which is pure DC current to supplement the loss of the lossless ripple current generator. In this process, the charging current is DC, and at this time the LED does not emit light.

[0042] If the measured capacitor is normal, such as the above-mentioned 47 uF / 400 V electrolysis, its ESR at 65 kHz is 0.5 Ω, namely, if the switching transistor Q is working normally, the excitation current i1 of the main power stage is as in Fig. shown, and then Ugs is drive voltage of grid and source of the switching transistor Q. The demagnetization current of D3 is i2 and the operating current of the measured capacitor is i out The voltage drop caused by the current across the ESR of the measured capacitor is shown in the Fig. .There is a fluctuating high frequency ripple current between terminal 1 and 2.The waveform is the same as the waveform i out in Fig. If the ESR of the measured capacitor is small, the peak value of the high-frequency ripple current is also small. Selecting the appropriate R1 is not enough to emit light in LEDs.

[0043] When the ESR of the measured capacitor increases from about 0.5Ω to 5.5Ω, the performance of the measured capacitor is close to the unusable edge.If the voltage drop of i out has risen to ESR, a fluctuating high-frequency ripple current exists between terminals 1 and 2 so that the LED can conduct and emit light.

[0044] C1 has a capacitance of 0.033 uF, and its capacitance is small, but at a frequency of 65 kHz, its capacitive reactance is 73.8 Ω, allowing the LED to conduct and emit light. Value engineering of C1: At the operating frequency of the lossless ripple current generator 100, its capacitive reactance is greater than five times the expected ESR of the measured capacitor. When the capacitive reactance of C1 is close to the ESR, C1 shares a large ripple current, so the ripple current obtained from the measured capacitor is insufficient. When the capacitive reactance of C1 is greater than ten times the expected ESR of the measured capacitor, the ripple current obtained from the measured capacitor is closer to the design value.

[0045] The working principle of the invention is not complicated. The capacitance of C1 is small. C1 has the function of passing high frequency and blocking low frequency. When the ESR of the measured capacitor increases, the voltage drop across the ESR generated by the lossless ripple current generator 100 increases synchronously. Then, the generated high frequency voltage increases with the aging of the electrolytic capacitor. C1 has the function of passing high frequency. When the high frequency voltage across the ESR reaches a certain threshold, the LED lights up, and R1 is set to adjust the threshold. That is, the voltage drop is lower than the LED voltage generated by the current at the terminals of R1, and the high frequency ripple voltage forms the current through the capacitor C1, preventing the LED from turning on. The LED cannot be redistributed to R1, so the LED does not light up.

[0046] In this way, the LED will light up, achieving the purpose of the invention and reminding the user that the ESR of the measured capacitor has increased to the point where the user can proceed to the next step. In this example, the operating current of the lossless ripple current generator 100 is reduced to 30%, the LED continues to light up, and the operating current is reduced to 0.36 mA. The use of a high-brightness LED is still noticeable.

[0047] At this time, the electrolysis can still function, but the electrolysis is already under high heat. Because the excitation current of the main power stage has a high calorific value on the ESR, which in this case is 0.22 W, this already accelerates aging. Under normal circumstances, in tens of hours to hundreds of hours, the ESR increases rapidly, causing the heat to continue to rise until failure occurs, the capacity is lost, and a series of failures such as the explosion of the switching transistor.

[0048] The circuit of 2-2, 2-3 and 2-4 can make the circuit 200 of Fig. which can also work.It can be seen that the four circuits of the first embodiment can achieve the object of the invention.

[0049] In the first embodiment, the display circuit 200 includes four methods. Accordingly, the ripple current generating circuit of the present invention also includes four methods. This was disclosed in Patent A. Various changes to the original connection relationship will not be repeated here. The display circuit 200 is added therein, which can also achieve the purpose of the invention. Simply put, the proposal is summarized only in a general "first embodiment." In the first embodiment, the current flowing through the LED is not direct current, but a high-frequency current with the same frequency as the ripple current generator. If the LED lead is long, the electromagnetic radiation cannot be ignored. If the LED is replaced by the illuminator of the optocoupler, the output current of the optocoupler also appears periodically, which is an unstable signal.This can cause problems for subsequent circuits. The second embodiment shows a solution. Second embodiment

[0050] A ripple current generating circuit in Fig. is according to solution 2 and it includes a DC current source U, the first inductor L and lossless ripple current generator and output terminals connecting two pins of the measured capacitor, including a positive terminal J+ and a negative terminal J-.The output of the DC current source U has a positive pole and a negative pole.The lossless ripple current generator 100 includes at least one pulse width modulation P;

[0051] The output terminal and the inductors L are connected in series and then in parallel to the DC source U.

[0052] The lossless ripple current generator 100 and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is fed back into the DC power source U or the measured capacitor with almost no loss.

[0053] The maximum duty cycle of the pulse width modulation control circuit is less than 0.5;

[0054] A display circuit 200 is further connected in parallel between the positive terminal J+ and the negative terminal J-. The schematic diagram of the display circuit 200 is shown in Fig. The display circuit 200 has the following characteristics: It includes the first resistor R1, the second resistor R2, the first capacitor C1, the second capacitor C2; the first diode D1 and the second diode D2, and the first light-emitting diode LED. R2 and LED are connected in series, forming the first two-terminal network 21. The two-terminal network 21, C2, and R1 are connected in parallel, forming the second two-terminal network 22. The two-terminal network 22 and D2 are connected in series, forming the third two-terminal network 23. The third two-terminal network 23 has the following function: D2 and LED have the same direction. The third two-terminal network 23 and D1 are connected in antiparallel, forming the fourth two-terminal network 24. The fourth two-terminal network 24 and C1 are connected in series, forming a series network. The two ports of the serial network are the first port 1 and the second port 2.The series network is also the main body of circuit 200.

[0055] Obviously, the first terminal 1 is connected to the positive terminal J+, and the second terminal 2 is connected to the negative terminal J-; if the first terminal 1 is connected to the negative terminal J- and the second terminal 2 is connected to the positive terminal J+, the circuit is also functional.

[0056] The second diode D2 and the first LED are in the same direction. In the third network 23, when R1 is open, the capacitor C2 is equivalent to direct current. The current flowing from the lower end of the third network 23 to the LED passes through D2, then flows out of the upper end of the third network 23. Both D2 and the LED are in a forward conduction state. This connection is called the same direction, which is like a diode with a larger voltage drop. Its cathode is the cathode of the third network 23. Direct current can flow out from the cathode of the network, and its anode is the anode of the third network 23. Direct current can flow in from the anode of the network.

[0057] The third network 23 is connected antiparallel to the first diode D1, i.e. the cathode of the third network 23 is connected to the anode of D1, and the anode of the third network 23 is connected to the cathode of D1

[0058] In the above-mentioned second technical solution 2, several connection relationships are included as described below.

[0059] There are two connection relationships between R2 and LED: (a) the cathode of the LED is connected to one end of R2 as in network 21 in Fig. shown; (b) The anode of the LED is connected to one end of R2 as shown in network 21 in Fig. shown;

[0060] These two are equivalent. Network 21, C1, and R1 are connected in parallel to form a two-terminal network 22, and network 22 is connected in series with diode D2. In network 22, when R1 is open, capacitor C2 is equivalent to direct current, and network 22 is a diode, which has unidirectional conductivity. The cathode of the LED is the cathode of the second network 22. Direct current can flow out from the cathode of the network. The anode of the LED is the anode of the third network 23. Direct current can flow in from the anode of the network. Since the series connection is in the same direction, there are two possibilities: (a) The cathode of network 22 is connected to the anode of D2, see Fig. ; (b) The anode of network 22 is connected to the cathode of D2, see Fig. ;

[0061] The fourth network 24 is connected in series with the first capacitor C1, and there are also two possibilities: (a) The D1 anode of network 24 is connected to the C1 end, see Fig. . (b) The D1 cathode of network 24 is connected to the C1 end, see Fig. ;

[0062] As in the first embodiment, in the second embodiment, there are three independent series circuits and each series circuit has two ways, a total of eight connection methods, in fact, they are also equivalent.

[0063] The lossless ripple current generator 100 adopts technical solution 1 of the first embodiment of patent B. Inductor L has an inductance of 1 mH. It is wound with a wire diameter of 0.6 mm. Inductor L2 is a power inductance of approximately 1.3 mH, and the air gap is adjustable.

[0064] The measured capacitor is a nominal 450B×C47MEFC18×25 electrolytic capacitor with a nominal withstand voltage of 450V, a ripple current of 1.2A, and a DC power source U set to 420V DC. The component parameters of the display circuit 200 are: Capacitor C1 is a 473 / 500V chip capacitor with a nominal capacitance of 0.047uF. Capacitor C2 is a 104 / 16V chip capacitor. D1 and D2 are each 1N4148, and R2 is 1K. R1 is 10K, and LED is 3AR2UD.

[0065] After the circuit of the second embodiment is set up, the air gap of the magnetic core is adjusted so that the ripple current of the measured capacitor is 1.2 A and the LED does not emit light.

[0066] Since the failed electrolytic capacitor is difficult to obtain, an adjustable resistor is inserted in series with the capacitor measured above to simulate the electrolytic capacitor whose performance has been affected. The adjustable range of the adjustable resistor here is 0-39 Ω. If the adjustable resistor is 4.5 Ω, this means that the ESR of a 47uF / 400V electrolytic capacitor increases from about 0.5 Ω to 5.5 Ω, and the electrolytic capacitor performance is close to the unusable limit.

[0067] At this time, the LED emits Fig. Light, and the average value of the operating current is actually measured at 1.9 mA.

[0068] Working principle: If the measured capacitor is in Fig. normal, then ESR is 0.5 Ω and there is only a ripple voltage across the measured capacitor.The path of the charging current generated by the DC source U is in the path in Fig. shown, which is pure DC current to supplement the loss of the lossless ripple current generator. In this process, the charging current is DC, and at this time the LED does not emit light.

[0069] If the measured capacitor is normal, such as the above-mentioned 47 uF / 450 V electrolysis, its ESR at 65 kHz is 0.5 Ω, namely, if the switching transistor Q1 and Q2 are working normally, the excitation current il of the main power stage is as in Fig. shown, and then Ugs is the drive voltage of the grid and source of the switching transistor Q1 and Q2. The demagnetization current of D3 and D4 is i2 and the operating current of the measured capacitor i out is the voltage drop formed by the current at the ESR of the measured capacitor, which is Fig. There is a fluctuating high-frequency ripple current between terminal 1 and 2. The waveform is the same as the waveform of i out , in Fig. If the ESR of the measured capacitor is small, the peak value of the high-frequency ripple current is also small. Selecting the appropriate R1 is not enough to produce light emission from an LED.

[0070] When the ESR of the measured capacitor increases from about 0.5Ω to 5.0Ω, the performance of the measured capacitor is close to the unusable edge.If the voltage drop of i out has risen to ESR, a fluctuating high-frequency ripple current exists between terminals 1 and 2 so that the LED can conduct and emit light.

[0071] C1 has a capacitance of 0.047uF, and its capacitance is small, but at a frequency of 65kHz, its capacitive reactance is 52.1Ω, which is enough to allow the LED to conduct and emit light. Value engineering of C1: At the operating frequency of the lossless ripple current generator 100, its capacitive reactance is greater than five times the expected ESR of the measured capacitor. When the capacitive reactance of C1 is close to the ESR, C1 shares a large ripple current, so the ripple current obtained from the measured capacitor is insufficient. When the capacitive reactance of C1 is greater than ten times the expected ESR of the measured capacitor, the ripple current obtained from the measured capacitor is closer to the design value.

[0072] The circuit of Fig. can switch the circuit 200 from Fig. replace, which can also work. It can be seen that the four circuits of the second embodiment can achieve the object of the invention. In the content of the second embodiment, the display circuit 200 includes the eight processes. Accordingly, the ripple current generating circuit of the present invention also includes eight processes. This was stated in Patent B. Various changes in the original connection relationship will not be repeated here. Therein, the display circuit 200 is added, which can also realize the purpose of the invention. Simply put, the proposal is summarized only in a general "the second embodiment."

[0073] The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiments should not be construed as the limiting invention. It will be obvious to those skilled in the art that various improvements and refinements may be made without departing from the spirit and scope of the invention. For example, a resistor is added in the first diode; the resistor R1 in Fig.Instead, it is directly connected in parallel with diode D1. For example, in a DC power source, the ammeter is directly connected, and the mechanical ammeter cannot output an external electrical signal, which is not applicable. The digital ammeter itself is more complicated and expensive than the present invention and does not conform to the ideal solution principle of TRIZ. These modifications and refinements are also considered to be within the scope of the present invention, and the scope of the present invention is defined by the scope of the claims.

Claims

[1] The present invention provides a ripple current generating circuit. It comprises a direct current source U, a first inductor (1), lossless ripple current generator (100) and output terminals connecting two pins of the measured capacitor, including a positive terminal J+ and a negative terminal J-. The output of the DC source U has a positive pole and a negative pole. The lossless ripple current generator (100) contains at least one pulse width modulation P; The output terminal and the inductors L are connected in series and then in parallel to the DC source U. The lossless ripple current generator (100) and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is returned almost losslessly to the direct current source U or the measured capacitor; The maximum duty cycle of the pulse width modulation control circuit is less than 0.5; A display circuit (200) is further connected in parallel between the positive terminal J+ and the negative terminal J-, and the display circuit (200) has the following properties: It contains the first resistor R1, the first capacitor C1, the first diode D1 and the first light-emitting diode LED. The first resistor R1, the first diode D1 and the first light-emitting diode LED are connected in parallel, whereby The first light-emitting diode (LED) and the first diode D1 are connected in antiparallel. The parallel two-terminal network is called a parallel network (24). A distinction is made between the terminals of the parallel network (24) and the two-terminal network of the first diode D1. The parallel network (24) and the first capacitor C1 are connected in series to form a two-terminal network. The two-terminal network is simply referred to as a series network, and the two terminals of the series network are, respectively, the first terminal (1) and the second terminal (2) of the display circuit (200). [2] A ripple current generating circuit comprises a DC current source U, a first inductor L, a lossless ripple current generator (100), and output terminals connecting two pins of the measured capacitor, including a positive terminal J+ and a negative terminal J-. The output of the DC current source U has a positive pole and a negative pole. The lossless ripple current generator (100) includes at least one pulse width modulator P; The output terminal and the inductors L are connected in series and then in parallel to the DC source U. The lossless ripple current generator (100) and the output terminals are connected in parallel to generate ripple current. The consumed electrical energy is fed back into the DC power source U or the measured capacitor with almost no loss. The maximum duty cycle of the pulse width modulation control circuit is less than 0.

5. A display circuit (200) is further connected in parallel between the positive terminal J+ and the negative terminal J-, and the display circuit (200) has the characteristics: It includes the first resistor R1, the second resistor R2, the first capacitor C1 and the second capacitor C2, the first diode D1 and the second diode D2, and the first light-emitting diode LED. The connection relationship is: The second resistor R2 and the first light-emitting diode LED are in series to form a first two-terminal network (21). The first network (21) and the second capacitor C2 are simultaneously connected in parallel with the first resistor R1 to form a second two-terminal network (22). The second network (22) and the second diode D2 are in series to form the third two-terminal network (23).The third network (23) has the following characteristics: the direction of the second diode D2 and the first light-emitting diode LED is the same. The third network (23) is connected in antiparallel with the first diode D1 to form the fourth two-terminal network (24). The fourth network (24) is connected in series with the first capacitor C1 to form a two-terminal network. The two-terminal network is called a series network. The two terminals of the series network are the first terminal (1) and the second terminal (2), respectively. [3] A ripple current generating circuit according to claim 2 has the property: The first resistor R1 is changed to be parallel to the first diode D1. [4] A ripple current generating circuit according to claim 1 to 3 has the property: There is another resistor C1 which is in series with the first diode D1. [5] A ripple current generating circuit according to claims 1 to 3 has the property: The first light-emitting diode is a generator in the optocoupler, namely the light-emitting diode in the optocoupler.

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