Load sensing method for a single switch partial resonance inverter circuit

Abstract

A load sensing method for a single-switch partial resonant inverter circuit comprising the steps of a time dependent control of the load (22) by determination of a to time (40), a t1 time (42), a t2 time (44), a t3 time (46), a t4 time (48), a t5 time (50) and a t6 time (52) and further comprising the steps of generating a S1 number (54) S2 number (56) and a S3 number (58) from time value t1 (42), time value t2 (44), time value t3 (46) and time value t4 (48); calculation of an R1 number (60) and R2 number from the S1, S2 and S3 values (54, 56, 58); identification of a load on the inductor (18) if the determined R1 number (60) and R2 number (62) are less than or equal to a predetermined threshold value (64), determination of safe heating if the number of R1 (60) and the number of R2 (62) is greater than the predetermined threshold value (66); the single-switch partial resonance inverter circuit (34) is in safe heating (72), identification of the no load on the inductor (18) in the case (68) the S1 number (54) is equal to the 0 when determining of approximate number R1 and the number R2 (60, 62).

Description

[0001] LOAD SENSING METHOD FOR A SINGLE SWITCH PARTIAL RESONANCE INVERTER CIRCUIT

[0002] TECHNICAL FIELD

[0003] The invention relates to a load sensing method for a single switch partial resonant inverter circuit that detects metal or pot.

[0004] BACKGROUND OF THE ART

[0005] Induction heating is widely used in industry for heating, melting and surface hardening of metals. However, it also has a field of use in bonding, melting, heat treatment, cooking and similar areas for metal-containing materials. The usage areas of induction technology are gathered in three main groups as industrial, medical, and household applications. In order to develop induction-based technologies, academic and industrial researchers work on the design of power electronic circuits, design of magnetic elements and control techniques. Although the basic working principles are the same, all induction applications have different features and requirements.

[0006] Industrial applications require high output power and reliability, while medical applications require low output power and precise control. For domestic induction cookers, the challenge is the expectation of wide load range (pot variety), high efficiency and low cost. The main components of classical induction heating systems are the rectifier and the resonant inverter. There are different resonant inverter topologies in the literature depending on the balance between cost and performance.

[0007] US2018269863 discloses smart power modules for resonant converters. The invention includes a single-switch half-resonant inverter circuit applied in induction heating application in a conventional configuration. It comprises a smart power module; a power switch, a freewheel device, and a controller circuit including a gate drive circuit and one or more power switch protection circuits. In one embodiment, the power switch is an isolated gate bipolar transistor (IGBT) device, the freewheeling device is a PN junction diode, and the controller circuit is implemented as a semiconductor integrated circuit (IC). The power module implements protection functions for the power switching device where the protection circuits are formed on the controller circuit IC and co-packaged with the power switch. In some embodiments, the control circuit in the power module includes an active soft-start circuit which is activated to realize soft-start of the power switch. In other embodiments, the control circuit in the power module includes an active turn-on pulse control circuit to detect for abnormal system input signal pulse events and block system undesired input pulses.

[0008] BRIEF DESCRIPTION OF THE INVENTION

[0009] The object of the invention is to develop a load sensing method for a single-switch partial- resonant converter circuit and a single-switch partial resonance inverter circuit to meet the low-cost product expectation commonly in induction-heated hobs.

[0010] In order to achieve the aforementioned purposes, invention relates to a load sensing method for a single-switch partial resonant inverter circuit comprising the steps of connecting a main power circuit to a DC phase line in such a way that one or more of an inductor, a resistor and a capacitor formed on the inductor on which a load is disposed, provides a partial resonance circuit on a circuit path; forming a single-switch partial-resonant inverter circuit by making a single-switching of one or more of a semiconductor switch to connected the partial resonant circuit and a free pass diode connected to the semiconductor switch; time-dependent control of the load in the single-switch partial resonance inverter circuit by determining a to time for the first moment when the semiconductor switch turns off in a closed position, a t1 time for the first moment when the inductor current reaches its maximum value, t2 time for the first moment when the voltage between the terminals of the semiconductor switch exceeds the DC bus voltage, a t3 time for the first moment when the semiconductor switch voltage reaches its maximum value, a t4 time for the second moment when the voltage across the terminals of the semiconductor switch exceeds the DC bus voltage, determining a t5 time for the first moment the free pass diode turns on and a t6 time for the first moment when the semiconductor switch turns on under zero voltage characterized in that further comprising the steps of subtracting the t2 time value from the t1 time value to find a number S1 ; subtracting the time value t3 from the time value t4 to find a number S2; subtracting the t1 time value from the t3 time value to find an S3 number; determining an R1 number by dividing the found S2 number by the S1 number and an R2 number by dividing the S3 number by the S1 number; identifying that there is a load on the inductor if the determined number of R1 and number of R2 are less than or equal to a predetermined threshold value; identifying safe heating of the single-switch partial resonance inverter circuit if the number of R1 and the number of R2 are greater than the predetermined threshold, when determining approximately the number of R1 and R2 , identification of no load on the inductor in the case that the number of S1 is equal to the number 0. Thus, a load sensing can be implemented by a load sensing method based on an operating single-switch partial resonance inverter circuit.

[0011] In a preferred embodiment of the invention the load heated on the inductor is a pan or a cooking pot. The load can be of any type, depending on the state of the heating or cooking process on an induction hob.

[0012] A preferred application of the invention comprising the step of identifying a load on the inductor as ferromagnetic when a magnetic field is formed depending on the load for the case where the numbers of R1 and R2 are less than or equal to the predetermined threshold value. Thus, according to the developed load sensing method, it is explained that when the condition is less than or equal to the predetermined threshold value, the induction heating stove circuit is completed with the load placed on the inductor and a ferromagnetic effect can be achieved if the load is a material that provides electromagnetic conductivity. In addition, by checking the ferromagnetic effect, the recognition of the load and the type of the load can be processed. In this way, the cooking temperature can be adjusted according to the type of load.

[0013] A preferred application of the invention the step of identifying a load on the inductor as nonferromagnetic when a magnetic field is not formed depending on the load for the case where the numbers of R1 and R2 are less than or equal to the predetermined threshold value. Thus, according to the subject matter load sensing method, when the condition is less than or equal to the predetermined threshold value, the load rest on the inductor completes the induction heating stove circuit and a ferromagnetic effect cannot be achieved if the load is a material that does not provide electromagnetic conductivity. In addition, by checking at the absence of ferromagnetic effect, the recognition of the load and the type of the load can be determined. In this way, the cooking temperature can be adjusted according to the type of load.

[0014] A preferred application of the invention the S2 number and the S3 number are set equal to each other regardless of whether there is a load on the inductor. Thus, according to the subject matter load sensing method, a mathematical equation is expressed for any situation; In addition, with this equation, it can be determined that the sum of the t1 time value and t4 time values is equal to 2 times the t3 time value.

[0015] A preferred application of the invention comprising the step of determining the time values of t1 and t2 are equal to each other when the resistance formed in the inductor is equal to the number 0. Thus, in a situation where there is no resistance in the circuit, it is determined that t1 time coincides with t2 time, that is, the semiconductor switch cannot switch to active conduction.

[0016] A preferred application of the invention comprising the step of determining that the t1 and t2 time values are not equal to each other when the resistance formed in the inductor is not equal to the number 0. Thus, when a resistance occurs in the circuit, it is determined that the semiconductor switch both turns on under zero voltage and turns off at different times, that is, the switch operates in a single switching function.

[0017] BRIEF DESCRIPTION OF THE FIGURES

[0018] Figure 1 is the illustration of the loaded circuit diagram of the load sensing method for a single switch partial resonant inverter circuit of the invention.

[0019] Figure 2 is the illustration of the equivalent circuit diagram of the load sensing method for a single-switch partial resonant inverter circuit of the invention.

[0020] Figure 3 is a flowchart illustration of the load sensing method for a single-switch partial resonance inverter circuit of the invention.

[0021] Figure 4 is a graphical representation of the single-switch inverter current and voltage forms for the load sensing method for a single-switch partially resonant inverter circuit of the invention.

[0022] Figure 5 is the equivalent circuit diagram illustration of the load sensing method for a singleswitch partial resonance inverter circuit of the invention in the operating mode between t6 and tO time interval.

[0023] Figure 6 is the equivalent circuit diagram illustration of the load sensing method for a single switch partial resonance inverter circuit of the invention in the operating mode between tO and t5 time interval.

[0024] Figure 7 is the equivalent circuit diagram illustration of the operation mode continuation in the time interval t0 to t5 of the load sensing method for a single-switch partial resonance inverter circuit of the invention. Figure 8 is the continuation of the equivalent circuit diagram for the load sensing method for a single switch partial resonant inverter circuit of the invention in the operating mode between t5 and t6 time interval.

[0025] DETAILED DESCRIPTION OF THE INVENTION

[0026] In this detailed explanation, the subject matter invention is explained without any limitation and only with reference to examples to better explain the development.

[0027] Figure 1 shows the loaded circuit diagram of the load sensing method for a single-switch partial resonant inverter circuit of the invention. A main power circuit (10) includes a singleswitched partial resonance inverter (34) that detects one or more loads (22) connected to a direct current phase (14) on circuit paths (16). In the equivalent circuit, a partial resonant circuit (26) is formed by connecting one or more of a resonant circuit equivalent inductance (18), a resistor formed on the inductor (resonant circuit equivalent resistance) (20), and a resonant circuit capacitor (24) provided on the inductor (18). A single switching (32) is formed by connecting the partial resonance circuit (26) by one or more one or more of an insulated gate bipolar transistor (28) as the semiconductor switch (28) and a free pass diode (30) as an internal circuit element of thus, a single switched partial resonance inverter circuit (34) is obtained in the main power circuit (10).

[0028] Figure 2 shows the equivalent circuit diagram of the load sensing method for a single-switch partial resonant inverter circuit of the subject matter invention. Figure 3 shows the flowchart of the load sensing method for a single-switch partial resonant inverter circuit of the invention. In the equivalent circuit of the single-switch partial resonant inverter circuit in Figure 2; single switch partial resonant invertor (34) providing a single switch (32) from free pass diode (30) connected to the transistor (28) is formed from from a resonant circuit equivalent resistor (REQ) (20) connected in series resonance (RLC) in circuit paths (16) connected to a direct current phase voltage (12), the resonant circuit equivalent inductance (LEQ) (18), from the resonant circuit capacitor (CRES)(24) and from an isolated gate bipolar transistor (28) as a semiconductor switch connected to a series resonant RLC. In the load sensing method for a single-switch partial resonance inverter circuit, which is the subject of the invention in Figure 3, firstly, a tO time (40) for the first moment when the insulated gate bipolar transistor goes into a closed state is determined by the current (ILEQ) of the coil (inductor) current (ILEQ). a t1 time for the first moment (42) a t2 time (44) for the first moment when the voltage across the terminals of the insulated-gate bipolar transistor exceeds the direct current bus voltage, the first moment when the switch voltage (VCE) reaches its maximum value (the current on the inductor equals zero A t3 time (46) for the first moment when the free pass diode turns on, a t4 time (48) for the second moment when the voltage between the terminals of the semiconductor switch exceeds the DC bus voltage, a t5 time (50) for the first moment when the free transition diode turns on and a t6 time 52 is determined for the first moment when the switch (insulated gate bipolar transistor) opens under zero voltage. Then, by subtracting t1 time value from t2 time value, an S1 number (54) is found, t4 time value is subtracted from t3 time value, an S2 number (56) and t3 time value is subtracted t1 time value and an S3 number (58) is found. Thus, the time difference number sequence is obtained. After S1 , S2 and S3 numbers (54) (56) (58) are found, an R1 number (60) is made by dividing the S2 number (56) by the S1 number (54) and an R2 number is obtained by dividing the S3 number (58) by the S1 number (54). number (62) is obtained. Thus, a series of proportional numbers is found. For example, the string R1 and R2 numbers (60, 62). Then, the R1 and R2 numbers (60, 62) are compared (64) (66) (68) with a predetermined fixed number of the method of the invention. Here, as the number of comparisons, the previously determined number is 30. Here, it can be determined that if the number of R1 (60) and the number of R2 (62) are less than or equal to 30 (64), there is a load on the inductor (70). 66), the single-switch partial resonance inverter circuit is provided to operate in safe heating (72).

[0029] In addition, in the process of determining the number of R1 and R2 (60, 62), in the case where the number of R1 and R2 (60, 62) goes to an infinite number, that is, when the number of S1 is equal to the number 0 (68), it is determined that there is no load on the inductor (74). Here, the load (22) heated on the inductor (18) is a pot or a cooking vessel. In addition, in the case where the numbers of R1 and R2 (60, 62) are less than or equal to the number 30, when a magnetic field is formed depending on the load (22) placed on the inductor (18), it can be determined that the load (22) is ferromagnetic and R1 and R2 are For the case where the numbers (60, 62) are less than or equal to the number 30, when the magnetic field does not form due to the load (22) placed on the inductance (36), it is ensured that the load (22) is not ferromagnetic. With the method of the invention, regardless of whether there is a load (22) on the inductor (18), the number of S2 (56) and the number S3 (58) provide mathematical equality to each other. In addition, with the method according to the invention, in case the resonant circuit equivalent resistance (20) is equal to the number 0, it can be determined that the time values of t1 and t2 are equal to each other, and in the case that the equivalent resistance of the resonant circuit (20) is not equal to the number 0, it can be determined that the time values of t1 and t2 are not equal to each other. The subject of the invention is used in the following formulas in the load sensing method for the single-switch partial resonance inverter circuit of the induction heated hob;

[0030] • Damping coefficient,

[0031]

[0032] With the help of the related circuit equations, (20) and (18) values related to the circuit and the pot characteristic can be reached from there.

[0033] Figure 4 shows the single-switch inverter current and voltage forms for the load sensing method for a single-switch partial resonance inverter circuit, which is the subject matter of the invention. In the graph of single-switch inverter current and voltage forms, the states of the circuit elements are given according to the working moments of the semiconductor switch (T) (28) at the time intervals tO and t6 when the semiconductor switch (T) (28) is open (H) and closed (L). In addition, in the graphs, the status of current changes (ISSI) (36) in a single switch inverter between tO and t6 time intervals were examined; It has been determined that the switch switches to its initial state in the closed (L) state at tO time, the coil current (ILEQ) (19) reaches the maximum value (Imax) at t1 time, and the direct current (DC) bus voltage of the semiconductor switch (28) at t2 time. Also shown here is the moment t3 at which the voltage of the semiconductor switch (VCE) (29) reaches the maximum value (Vmax) relative to the voltage variations (VSSI) (38) in the single-switch inverter. It is also shown in the graphs that the second moment when the voltage between the ends of the semiconductor switch (28) exceeds the DC bus voltage is t4, the first moment when the free transition diode turns on (ID) is t5, and the moment when the semiconductor switch (28) opens under zero voltage is t6. Figure 5 shows the equivalent circuit diagram of the load sensing method for a single-switch partially resonant inverter circuit of the invention in the operating mode in the time interval t6 to tO. Figure 6 shows the equivalent circuit diagram of the load sensing method for a singleswitch partially resonant inverter circuit of the invention in the operating mode in the time interval t0 to t5. Figure 7 shows the equivalent circuit diagram of the operation mode continuation in the time interval tO to t5 of the load sensing method for a single switch partial resonant inverter circuit of the invention. Figure 8 shows the equivalent circuit diagram continuation of the load sensing method for a single-switch partially resonant inverter circuit of the invention in the operating mode in the time interval t5 to t6. Here, operating modes with single switching (32) for a single-switched resonance inverter can be examined in four operating stages in a range. The time interval t6 < t < tO, which is the conduction time of the semiconductor T, is modeled as a series RL circuit consisting of the equivalent circuit resistor (20) and the equivalent circuit inductor (18) connected via the circuit path (16) to the DC phase voltage (12), while tO The resonance occurring between the inductor (18) and the capacitor (24) in the time interval < t < t5 is analyzed as a series RLC circuit, and in the time interval t5 - 16, when the free pass diode (30) is in conduction, it is modeled as a series RL circuit.

[0034] The operating mode in Figure 5 starts in the range of t6 < t < tO, when the T semiconductor switch is opened under zero voltage (ZVT) and continues until the T switch (32) is closed. It can be used in the following equations for the analysis of the operation of the RL circuit;

[0035] The operating mode in Figure 6 and Figure 7 starts in the range tO < t < t5, with the semiconductor T closed, and the resonance takes place between LEQ and CRES (18) (24) and is analyzed as a series RLC circuit. In addition, the following equations can be used for ILEQ current;

[0036] In addition to the above equations, the following circuit equations can be used to calculate the switch (32) voltage VCE;

[0037] The operating mode and equations of the equivalent circuit in Figure 6 and Figure 7 in the range are given. In this range, (series RLC circuit mode) coil 18 current ILEQ and switch 32 voltage VCE reach their maximum values. Also, when the coil 18 current ILEQ reaches the maximum value of ILEQmax, the derivative of the current ILEQ is zero, (at t=t1 ). As a result, the maximum coil 18 current ILEQmax can be obtained using the following equations;

[0038] The maximum power level of the single switch partial resonance inverter (34) is limited by the maximum breakdown voltage level of the power switch (28). When the VCE switch voltage reaches its maximum VCEmax, the current ILEQ is zero (t = t3). As a result, the maximum switch voltage can be obtained using the following equations;

[0039] When series resonance occurs between LEQ and CRES (18) (24), the switch voltage VCE exceeds the DC link voltage VDC (12) in two instants. (t2 and t4). TRES and <nd can be obtained using the following equations;

[0040] In the range t5 < t < t6 of the equivalent circuit in Figure 8, T starts with the opening of the D diode (30) connected in anti-parallel to the power switch 28. The free return of current or energy over the source (12) is performed by a D power diode (30). The diode (30) current is expressed as the conduction time TD and the diode peak current IDPEAK. The following equations for the operation of the RL circuit can be used. REFERENCE NUMBERS

[0041] 10 Main power circuit

[0042] 12 DC phase voltage (VDC)

[0043] 14 DC phase line

[0044] 16 Circuit path

[0045] 18 Inductor / Equivalent inductance (LEQ)

[0046] 19 ILEQ

[0047] 20 Resistor / Equivalent resistance (REQ)

[0048] 22 Load

[0049] 24 Capacitors (CRES)

[0050] 26 Partial resonance circuit

[0051] 28 Semiconductor switch (T)

[0052] 29 Switch voltage (VCE)

[0053] 30 Free pass diode (D)

[0054] 31 Diode current (ID)

[0055] 32 Single switching

[0056] 34 Single switching partial resonance inverter

[0057] 36 Single-switch inverter current (ISSI)

[0058] 38 Single switch inverter voltage (VSSI)

[0059] 40 The first moment of the switch in the closed state tO

[0060] 42 Maximum initial moment of inductor current t1

[0061] 44 The first moment when the DC link voltage of the switch passes (t2)

[0062] 46 Switch voltage maximum initial moment t3

[0063] 48 Second moment when the switch crosses the DC link voltage t4

[0064] 50 Diode first moment in conduction t5

[0065] 52 The first moment when the key is opened in ZVT t6

[0066] 54 S1 number (t2 minus t1 )

[0067] 56 S2 number (t4 minus t3)

[0068] 58 S3 number (t3 minus t1 )

[0069] 60 R1 number (S2 divided by S1)

[0070] 62 Number of R2 (S3 divided by S1 )

[0071] 64 If less than or equal to a threshold value

[0072] 66 If greater than a threshold value

[0073] 68 S1 equals 0

[0074] 70 A load on the inductor

[0075] 72 Safe heating

[0076] 74 No load on the inductor

Claims

CLAIMS1) A load sensing method for a single-switch partial resonant inverter circuit comprising the steps of connecting a main power circuit (10) to a DC phase line (14) in such a way that one or more of an inductor (18), a resistor (20) and a capacitor (24) formed on the inductor (18) on which a load (22) is disposed, provides a partial resonance circuit (26) on a circuit path (16); forming a single-switch partial-resonant inverter circuit (34) by making a single-switching (32) of one or more of a semiconductor switch (28) to connected the partial resonant circuit (26) and a free pass diode (30) connected to the semiconductor switch (28); time-dependent control of the load (22) in the single-switch partial resonance inverter circuit (34) by determining a tO time (40) for the first moment when the semiconductor switch turns off in a closed position, a t1 time (42) for the first moment when the inductor current reaches its maximum value, t2 time (44) for the first moment when the voltage between the terminals of the semiconductor switch exceeds the DC bus voltage, a t3 time (46) for the first moment when the semiconductor switch voltage reaches its maximum value, a t4 time (48) for the second moment when the voltage across the terminals of the semiconductor switch exceeds the DC bus voltage, determining a t5 time for the first moment the free pass diode turns on and a t6 time (52) for the first moment when the semiconductor switch turns on under zero voltage characterized in that further comprising the steps of subtracting the t2 time value (44) from the t1 time value (42) to find a number S1 (54); subtracting the time value t3 (46) from the time value t4 (48) to find a number S2 (56); subtracting the t1 time value (42) from the t3 time value (46) to find an S3 number (58); determining an R1 number (60) by dividing the found S2 number (52) by the S1 number (54) and an R2 number (62) by dividing the S3 number (58) by the S1 number (54); identifying that there is a load on the inductor (18) (70) if the determined number of R1 (60) and number of R2 (62) are less than or equal to a predetermined threshold value (64); identifying safe heating (72) of the single-switch partial resonance inverter circuit if the number of R1 (60) and the number of R2 (62) are greater than the predetermined threshold (66), when determining approximately the number of R1 and R2 (60, 62), identification (74) of no load on the inductor (18) in the case (68) that the number of S1 is equal to the number 0.2) A load sensing method according to claim 1 , wherein the load (22) heated on the inductor (18) is a pan or a cooking pot.3) A load sensing method according to Claim 1-2, comprising the step of identifying a load on the inductor (18) as ferromagnetic when a magnetic field is formed dependingon the load (22) for the case (64) where the numbers of R1 and R2 (60, 62) are less than or equal to the predetermined threshold value.4) A load sensing method according to Claim 1-2, comprising the step of identifying a load on the inductor (18) as non-ferromagnetic when a magnetic field is not formed depending on the load (22) for the case (64) where the numbers of R1 and R2 (60, 62) are less than or equal to the predetermined threshold value.5) A load sensing method according to any one of the preceding claims, wherein the S2 number (56) and the S3 number (58) are set equal to each other regardless of whether there is a load (22) on the inductor (18).6) A load sensing method according to any of the preceding claims, comprising the step of determining the time values of t1 and t2 (40) (42) are equal to each other when the resistance (20) formed in the inductor (18) is equal to the number 0.7) A load sensing method according to Claim 6, comprising the step of determining that the t1 and t2 time values (40) (42) are not equal to each other when the resistance (20) formed in the inductor (18) is not equal to the number 0.

Images