DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates electronic power regulation and control and more particularly to a power regulation system, apparatus and method to control speed and voltage regulation of resistor and/or inductor and/or capacitor (R-L-C) loads using a TRAIC device.

BACKGROUND

[002] A variety of alternating current (AC) power regulating circuits are known in the art in which AC power to a load (e.g., fluorescent lamps, motors, etc.) is regulated through control of an AC electronic switch such as a thyristor, interconnecting the source of the AC power and the load. Conventionally, the best way to regulate and control AC power to loads such as dimming of lamps, speed control of motor or ceiling fan and the like, is done using a TRIAC device.

[003] The TRAIC is a three terminal semiconductor device of a thyristor family that may be used as the AC electronic switch because of its bi-directional conduction and high power characteristics. The TRAIC includes two main terminals and a gate terminal and is triggered to the ON state by supplying current through the gate terminal. The current flows in opposite directions depending upon the relative polarity on the main terminals of the TRAIC. The TRAIC remains in the ON state until the main terminal polarity changes or until the main terminal current drops below the holding current or zero crossing which further enables the TRAIC to turn OFF thereby blocking current to the load.

[004] The prior art document, US 6057674 A wherein an apparatus and methods for AC power regulation primarily intended for inductive loads (e.g., fluorescent lights, motors, etc.) which provide substantial reduction in power consumption while also providing a leading power factor, reduced harmonic distortion, reduced crest factor and reduced noise. The system is self-adjusting for a wide range of loads and can reduce power consumption by 25 percent in lighting loads while producing minimal reduction in light output. The system utilizes a TRIAC and parallel capacitor bank in series with the load. The TRIAC is turned on in response to a near-zero differential voltage measured across the TRIAC and is turned off near the peak of each AC half cycle by shunting current around the TRIAC. The capacitor absorbs the inductive turn-off voltage spike caused by the collapsing magnetic field in the ballast at the instant of TRIAC turn-off. This energy, in turn, provides longer on-period for the lamp, thereby permitting more light and increased operating efficiency. The turn-off time is adjusted to regulate power at a reduced level responsive to line voltage, load current and load power-sense signal

[005] The prior art document, US 4390795 A discloses an electronic switching system for inductive loads in A.C. circuits, comprising a TRIAC switch in series with an inductive load such as transformer or motor, etc. across an A.C. voltage. The control voltage for the TRIAC switch is provided by a smaller, lower power TRIAC driver, which has a light emitting diode controlled by an optically isolated transistor. The optically isolated transistor is provided with electrical pulses each a half cycle of voltage by means of a zero crossing detector. Since it is impossible to know precisely what the power factor of the load is, the triggering of the TRIAC driver is provided at zero voltage on both the upward and downward crossing. These pulses, amplified by the transistor, control the TRIAC driver. The load current will lag the voltage by some angle, dependent on the power factor, and the current will stop at its zero point. The TRIAC driver has its control voltage at the zero of voltage and, therefore, has a control ready to ignite the TRIAC as soon as the current in the reverse direction passes to zero.

[006] The prior art document, US 5477111Adiscloses a dimmer for controlling the power delivered to a load from a source of line voltage and alternating current, comprising a TRIAC having an input terminal, output terminal and a gate, the TRIAC being responsive to triggering gate currents applied at selectable phase angles during each half cycle of the alternating current to deliver selectable amounts, corresponding to the phase angle at which the triggering gate current is applied, of proportional power to the load, the dimmer including a circuit which regulates the duration during which the triggering gate current is applied to the TRIAC, said circuit being capable of applying triggering gate currents of different durations to said TRIAC.

[007] The prior art document, US 7180250 B1 discloses a TRIAC-based, low voltage AC dimmer comprising a lighting load to be controlled; a source of low AC voltage for powering the lighting load; a step-up transformer connected to said source of low AC voltage for converting said low AC voltage to a higher AC voltage; a TRIAC coupled in series with the lighting load; adjustable trigger control circuit means coupled to said step-up transformer and to said TRIAC for triggering said TRIAC into a conduction state to thereby provide adjustable control of a portion of said source of low AC voltage applied to said lighting load; and an AC voltage regulator coupled across a secondary winding of said step-up transformer, said AC voltage regulator comprising a bi-directional transient suppressor in series with a resistor.

[008] The hitherto TRIAC based AC load regulation is generally achieved by voltage phase control. In this method, voltage zero-crossings are detected and TRIAC is triggered after addition of some delay. This method is function as long as the load is resistive since the voltage and current are in phase with each other. So the TRIAC is conducted on every gate trigger and turns off at current zero-cross which is in phase with voltage zero-cross. However such a method is not function when an inductive load is regulated using TRIAC device.

[009] For reactive (mainly inductive) AC load regulations using the TRAIC there are many problems encountered as the voltage and current in a reactive load are out of phase. Also asymmetric triggering of the TRIAC device introduces direct current (DC) load that results in prolonged conduction and unexpected current zero-cross on TRIAC. Thus the conventional power control system and the method of phase control does not guarantee precise and accurate performance.

[0010] Thus, in view the hitherto drawbacks of the voltage phase control, there exists a dire need to provide an improved power control system for achieving load regulation independent of the type of load.

SUMMARY OF THE INVENTION

[0011] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0012] The main object of the present invention is to provide a current based TRAIC regulation (CTR) system to obviate the drawbacks of a TRAIC regulation achieved by voltage phase control.

[0013] Another object of the present invention is to provide power control system for achieving AC load regulation independent of the type of load.

[0014] Yet another object of the present invention is to provide a method of fetching current status through TRIAC and thereby regulate the voltage based on the current status or the TRIAC state.

[0015] In one implementation, the present invention provides a method for achieving load regulation wherein the load is at least one of a resistive load and/or inductive load and/or capacitive load. The method is a new approach of getting status of current through TRIAC and thereby control TRIAC based on the TRIAC current.

[0016] In one implementation, the present invention provides method for AC load regulation by getting status of current through TRIAC and its subsequent switching based on the current through TRIAC.

[0017] In one implementation, the present invention provides a current based triode for alternating current (TRIAC) regulation system. the system comprises at least one current source electrically coupled with at least one load and at least one triode for alternating current (TRIAC);at least one digital circuit for controlling the TRIAC as per prescribed regulation mechanism by generating delayed pulses for a gate triggering. The system is characterized in that, it comprises at least one current zero-cross detection circuit electrically coupled to the TRIAC and the adapted to monitor the TRIAC to detect TRIAC’s conduction state and the time of commutation; and at least one pulse generation circuit, electrically coupled to the current zero-cross detection circuit and the digital circuit, and adapted to generate electrical pulses on detection of the current passing through the TRIAC is zero or crosses zero; and transmit the electrical pulses to the digital circuit for the regulation of the TRIAC.

[0018] In one implementation, the present invention provides an apparatus for regulating a triode for alternating current (TRIAC) connected to at least one load is disclosed. The apparatus comprises at least one current zero-cross detection circuit electrically coupled to the TRIAC and the adapted to monitor the TRIAC to detect TRIAC’s conduction state and the time of commutation based on the current passing through the TRIAC; and at least one pulse generation circuit, electrically coupled to the current zero-cross detection circuit and at least one digital circuit associated with the TRIAC, and adapted to: generate electrical pulses on detection of the current passing through the TRIAC is zero or crosses zero; transmit the electrical pulses to the digital circuit for the regulation of the TRIAC.

[0019] In one implementation, the present invention provides a method for regulating a triode for alternating current (TRIAC) connected to at least one load. The method comprises:
• monitoring the current passing through the TRIAC;
• detecting TRIAC’s conduction state and the time of commutation to determine a moment when the current reaches or crosses the zero mark threshold, TRIAC exits conduction state;
• generating electrical pulses based on the determination of the current reaches or crosses the zero mark threshold, TRIAC exits conduction state;
• transmit the electrical pulses to at least one digital circuit for the regulation of the TRIAC;
• regulating the triode for alternating current (TRIAC) connected to the load.

[0020] As compared to the prior-art techniques, the present invention a current based TRIAC regulation (CTR) detects current zero-cross instead of voltage and hence any kind of a load can be effectively and precisely controlled using TRIAC. The present invention provides an innovative way to detect the moment at which the TRIAC exits conduction state when current through it reaches zero and thereby generate pulses on every current zero-cross, which makes the CTR unique and simple for implementation along with being cost effective.

[0021] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0022] Figure 1 illustrates a block diagram of a current based TRIAC regulation (CTR) technique, in accordance with an embodiment of the present subject matter.

[0023] Figure 2 illustrates a practical implementation of the CTR circuit diagram, in accordance with an embodiment of the present subject matter.

[0024] Figure 3 illustrates a wave form generated for a CTR behavior under full load condition, in accordance with an embodiment of the present subject matter.

[0025] Figure 4 illustrates a waveform generated for a CTR behavior under Load regulation with reduced duty cycle, in accordance with an embodiment of the present subject matter.

[0026] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0027] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0028] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0029] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0030] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0031] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0032] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0033] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0034] In one implementation, a TRIAC is used as an AC electronic switch to regulate a load wherein the load is inductive and/or resistive and/or capacitive.

[0035] In one implementation, a method involves measuring current through TRAIC and the voltage regulation based on the measured current or the TRAIC state so as to achieve a load regulation independent of the type of load.

[0036] In one implementation, the method for measuring current through TRIAC and the voltage regulation based on the measured current or the TRIAC state is disclosed. Conventionally, the current applications using TRIAC encounter a problem of using variable resistors to control regulation which require manually changing the resistance which is prevented by measuring current through TRAIC and voltage regulation based on the measured current.

[0037] In one implementation, the present invention provides a current based TRAIC regulation system that is used in microcontroller and remote control based applications.

[0038] Referring now to figure 1, the figure 1 illustrates a block diagram of a current based TRIAC regulation (CTR) technique, in accordance with an embodiment of the present subject matter. In one implementation, the CTR may include an Alternating current (AC) source. The AC source may be 110VAC/230VAC, however, the person skilled in that art may understand that a varying ranges of AC source may be used in the present invention. The CTR may be connected to a load. The load may be any inductive/capacitive/resistive load. The CTR techniques may further include a TRIAC. The TRIAC may consists of a TRIAC with snubber. It may be understood by the person skilled in the art that any existing TRIAC and a compatible snubber available in the art may be used for the implementation of this CTR technique. The CTR may further include a gate triggering circuit having a microcontroller as one of the component. The gate triggering circuit is a digital circuit which can be any microcontroller controlling TRIAC based on the desired regulation. Controller takes input, processes them and generates delayed pulses for gate triggering. The CTR further comprises a current zero-cross detection block or module to monitors the state of TRIAC. The CTR also comprise a pulse generation circuit gives pulse every time current through TRIAC crosses zero.

[0039] In one implementation, the CTR is characterized in that having the current zero-cross detection block/module adapted to monitor the state of TRIAC. Based on the TRIAC’s conduction state and the time of commutation the Zero-crossing of current is detected.

[0040] In one implantation, the CTR is characterized in that having the pulse generation circuit gives pulse every time current through TRIAC crosses zero. These pulses are passed on to Gate Triggering Circuit block. Now depending on the level of the desired regulation Gate can be triggered with some delay.

[0041] Referring now to figure 2, the figure 2 illustrates a practical implementation of the CTR circuit diagram, in accordance with an embodiment of the present subject matter. In one implementation, the figure 2 is the practical implementation circuit of CTR. As shown in figure 2, the person skilled in the art may understand that the circuit is not much different from the prior Voltage phase control circuit available in the art. It is only a few components and their location in the circuit that changes the complete control mechanism. Further, it may be also understood that the isolation at U1 is optional and could depend on the application needs.

[0042] As shown in figure 2, the CTR circuit diagram comprises the following components/ parts, however, it may be understood by the person skilled in the art that the functioning and working of these components as explained below is mere for the understanding purpose and may be changed depending on the knowledge of the person skilled in the art to achieve the same purpose and similar functionality to achieve the present invention.
• AC Source – V1 is the 230 VAC / 50Hz Source. The connections of LINE and NEUTRAL are of particularly importance for avoiding electrical shocks. As mostly non-isolated power supplies are preferred for consumer electronics, it is recommended to design the NEUTRAL as the GND reference in the circuit, this brings the digital voltage in the circuit almost same as NEUTRAL and hence avoids shock while using human interfaces on the device.
• Load – Motor M1 in Figure 2. Though CTR is most efficient for Reactive loads, any load can be controlled with it. Let us take an Inductive load as it is always a case of most issues. For our discussion let us take a mediocre inductive load, such as a motor, with 200mH and some series resistance associated with it, say 20 Ohms. Now practically inductance of a coil cannot be guaranteed overall production batches. Even a few mH of change can change the point of maximum regulation in case of Voltage phase control technique. Here the Load impedance is around 62.8 Ohms.
• TRIAC – TRIAC Q1 and Snubber circuit R5 and C2 in Figure 2. The TRIAC should be selected with current rating higher than the load current and considerable (di/dt)c. Also the TRIAC selected should have higher Blocking voltage rating, higher than the peak input voltage, 400V in our case. Value of R5 and C2 also depends on the load.
• Gate Triggering Circuit – The PIC controller and the switches form the Gate Triggering Circuit. The controller must have an external interrupt source on which current zero-crossing pulses can trigger an ISR, a Timer to generate delay, GPIs to take desired regulation inputs & a GPO to generate Gate triggering pulses output. SW1 and SW2 can be used for controlling the regulation.
• Current zero-cross detection – The capacitor C1 is the main component in Current zero-cross detection. Firstly, let us understand its functioning in the circuit. As TRIAC can be turned ON by triggering its gate and turns OFF when current through it crosses zero. When TRIAC is in non-conducting state the whole source voltage appears across it and when TRIAC is conducting voltage across it is almost zero i.e., it is as good as short. As capacitor C1 is placed in parallel (neglecting inductor L1) to TRIAC the voltage across C1 is same as that of TRIAC. So from the moment the TRIAC stops conducting the capacitor starts charging and voltage across it builds up, this causes the current also to flow through resistor R1, R2, R3, bridge D1 and opto-coupler U1 path. The role of D1 and U1 will be discussed in pulse generation circuit description. Now when TRIAC gate is triggered and it enters conduction state, the charge in C1 discharges through L1 and Q1, so L1 serves to limit the current and di/dt through Q1 from C1. Also the discharging of capacitor through TRIAC makes sure that TRIAC turns ON always on every gate trigger. Now it is clear that on every current-zero cross the capacitor will be charged and when TRIAC is conducting it is short. From this it is also obvious that the impedance of capacitor should be much higher than the impedance of load as it appears in series with load when TRIAC is not conducting, in our case it is around 3.1 MOhms for 1nF capacitor. Whereas the impedance of inductor L1 should be much lesser than the impedance of load as it is in series with load when TRIAC is conducting but should be enough to limit di/dt while C1 discharge, in our case it is around 0.0000314 Ohms.
• Pulse generation Circuit – Diode Bridge D1 and Opto-coupler U1 forms Pulse generation circuit. As discussed on every current zero-cross through TRIAC the voltage across capacitor C1 builds but this voltage is alternating. So D1 changes alternating voltage to direct. Opto-couple can be replaced by a transistor.

[0043] In one implementation, in order to achieve the present invention, the person skilled in the art may understand that for successful working of the circuit as provided in the figure 2, the calculation of values for the two major components C1 and L1 is critical. To achieve the same, ¬the component selection of the components C1 and L1 is critical.

[0044] In one implementation, for C1 Capacitor selection, the major selection parameter is its impedance. Impedance of C1 capacitor should be greater than the load impedance. Also important is its size and standard values available. The formula for its calculation is same:
Xc = 1/2?fC;
Where Xc – Impedance of capacitor >> Load Impedance
f – Frequency of input AC
C – Value of capacitor in Farads

[0045] In one implementation, for C1 Capacitor selection, the inductor selection depends on value of C1, TRIAC ratings and Load. As discussed above the impedance of L1 should be negligible as compared to Load impedance. The formula for calculating inductance of an inductor is same:
XL = 2?fL;
Where XL – Impedance of inductor << Load Impedance

[0046] In one implementation, while choosing L the max commutating (di/dt)TRIACmax of TRIAC should also be considered. Assuming that the C1 is charged equal to input AC voltage peak, the value of L should be such that, (di/dt)TRIACmax>> Vpeak/L.

[0047] Referring now to figure 3, the figure 3 illustrates a waveform generated for a CTR behavior under full load condition, in accordance with an embodiment of the present subject matter. In one example, the figure 3 illustrates a case 1 of a full load condition. The waveforms in figure 3 are an example of an inductive load. Here CTR detects zero-crossing at, say instance 6(ms), and immediately triggers the gate. As soon as the gate is triggered TRIAC turns ON and starts conducting. Now it can be seen that current is mostly on the negative side. This can be adjusted by triggering gate at the 90degree phase point of voltage,, in case of pure inductive load, just by gradually shifting gate triggers till the time between two zero-crossing is half the time period. This would adjust the current equally on positive and negative cycles. The person skilled in the art would understand the process after reading the complete description and the claims disclosed in the present invention.

[0048] Referring now to figure 4, the figure 4 a waveform generated for a CTR behavior under Load regulation with reduced duty cycle, in accordance with an embodiment of the present subject matter. In one example, the figure 4 illustrates a case 2 of load regulation with reduced duty cycle. The load can be regulated by introducing delay between zero-crossing detection and the next gate trigger to TRIAC. The waveform in figure 4 is an example of reduced duty cycle operation. As can be seen the current through the load can be controlled more accurately and incessantly with CTR technique. The person skilled in art would be able to appreciate the benefits of CTR over the traditional ways of controlling TRIAC.

[0049] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention enables regulation of loads by getting current flow through TRIAC and the voltage regulation based on the current flow or the TRIAC state.
2. The present invention obviates the drawback of conventional techniques of using TRIAC and variable resistors to control regulation which require manually changing of resistance.
3. The present invention can be easily used in microcontroller and remote control based applications.
,CLAIMS:1. A current based triode for alternating current (TRIAC) regulation system, the system comprising:
at least one current source electrically coupled with at least one load and at least one triode for alternating current (TRIAC);
at least one digital circuit for controlling the TRIAC as per prescribed regulation mechanism by generating delayed pulses for a gate triggering; and
characterized in that, the system comprises:
at least one current zero-cross detection circuit electrically coupled to the TRIAC and the adapted to monitor the TRIAC to detect TRIAC’s conduction state and the time of commutation; and
at least one pulse generation circuit, electrically coupled to the current zero-cross detection circuit and the digital circuit, and adapted to:
generate electrical pulses on detection of the current passing through the TRIAC is zero or crosses zero;
transmit the electrical pulses to the digital circuit for the regulation of the TRIAC.

2. The current based triode for alternating current (TRIAC) regulation system as claimed in claim 1, wherein the current zero-cross detection circuit is adapted to detect a moment when the current reaches or crosses the zero mark threshold, TRIAC exits conduction state.

3. The current based triode for alternating current (TRIAC) regulation system as claimed in claim 2, wherein the TRIAC exits conduction state is detected based on the TRIAC’s conduction state and the time of commutation.

4. The current based triode for alternating current (TRIAC) regulation system as claimed in claim 1, wherein the current zero-cross detection circuit comprises at least one capacitor wherein an impedance of the capacitor is greater than the load impedance and is calculated based on:
Xc = 1/2?fC;
Wherein, Xc – Impedance of capacitor >> Load Impedance
f – Frequency of input AC
C – Value of capacitor in Farads

5. The current based triode for alternating current (TRIAC) regulation system as claimed in claims 1 and 4, wherein the current zero-cross detection circuit comprises at least one neglecting inductor depending on the value of the capacitor, the TRIAC ratings and the load, and is calculated based on:
XL = 2?fL;
Where XL – Impedance of inductor << Load Impedance

6. An apparatus for regulating a triode for alternating current (TRIAC) connected to at least one load, the apparatus comprising:
at least one current zero-cross detection circuit electrically coupled to the TRIAC and the adapted to monitor the TRIAC to detect TRIAC’s conduction state and the time of commutation based on the current passing through the TRIAC; and
at least one pulse generation circuit, electrically coupled to the current zero-cross detection circuit and at least one digital circuit associated with the TRIAC, and adapted to:
generate electrical pulses on detection of the current passing through the TRIAC is zero or crosses zero;
transmit the electrical pulses to the digital circuit for the regulation of the TRIAC.

7. The apparatus as claimed in claim 6, wherein the digital circuit is adapted for controlling the TRIAC as per prescribed regulation mechanism by generating delayed pulses for a gate triggering.

8. The apparatus as claimed in claim 6, wherein the current zero-cross detection circuit is adapted to detect a moment when the current reaches or crosses the zero mark threshold, TRIAC exits conduction state.

9. The apparatus as claimed in claim 6, wherein the TRIAC exits conduction state is detected based on the TRIAC’s conduction state and the time of commutation.

10. The apparatus as claimed in claim 6, wherein the current zero-cross detection circuit comprises at least one capacitor wherein an impedance of the capacitor is greater than the load impedance and is calculated based on:
Xc = 1/2?fC;
Wherein, Xc – Impedance of capacitor >> Load Impedance
f – Frequency of input AC
C – Value of capacitor in Farads

11. The apparatus as claimed in claim 6 and 10, wherein the current zero-cross detection circuit comprises at least one neglecting inductor depending on the value of the capacitor, the TRIAC ratings and the load, and is calculated based on:
XL = 2?fL;
Where XL – Impedance of inductor << Load Impedance

12. A method for regulating a triode for alternating current (TRIAC) connected to at least one load, the method comprising:
monitoring the current passing through the TRIAC;
detecting TRIAC’s conduction state and the time of commutation to determine a moment when the current reaches or crosses the zero mark threshold, TRIAC exits conduction state;
generating electrical pulses based on the determination of the current reaches or crosses the zero mark threshold, TRIAC exits conduction state;
transmit the electrical pulses to at least one digital circuit for the regulation of the TRIAC;
regulating the triode for alternating current (TRIAC) connected to the load.