Patent Grant
9703311
Field of the Disclosure
The present invention relates generally to power conversion systems, and in particular but not exclusively, relates to an interface circuit including a reference pin for use in a power conversion system.
Background
Operation of a power conversion systems is usually controlled by a controller that may be designed as an integrated circuit module with pins or terminals coupled to sense data received from inputs and outputs of the power conversion system. The controllers generate control signals for the active elements/components of the power conversion systems to regulate the output in response to the data sensed through the pins or terminals. A common example of a power conversion system may include a switched mode power converter, and can be used in a wide variety of applications such as battery chargers or household appliances.
The cost of the controllers that are used to generate control signals for the power conversion systems can vary as a function of the complexity of the control circuitry, the semiconductor area required for the internal circuits of the controller, as well as the number of pins or terminals that are utilized by the controllers. In general, as additional functions for controllers for power conversion systems are added, corresponding additional pins or terminals are added to the integrated circuit module of the controller. As a consequence, each additional function that is added to a power converter controller generally translates into an additional pin on the power converter controller chip, which translates into increased costs and additional external components. Another consequence of providing additional functionality to a power converter controller is that sometimes there is often a substantial increase in power consumption of the controller as the number of functions of the power convert controller increases.
Flexibility in defining multiple modes of operation by an end customer is an asset in power converter controller integrated circuits. Different modes of operation in some applications may include output voltage range, frequency of operation, or any other adjustable feature of the controller. Mode selection by the end customer is usually realized through selecting specific external circuitry or components coupled to a “mode define” terminal of the integrated circuit that requires adding an extra pin or terminal to the controller integrated circuit, which translates into extra cost.
In almost all analog controlled power converters, a precise reference current source is required for charging a timing capacitor in an oscillator circuit that is used for an internal clock and/or in the filter circuits included in the analog controlled power converters. A dedicated pin or terminal of the controller is usually assigned to provide precise reference trimming for a precise reference current that is utilized in all conditions of operation.
Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention.
Reference throughout this specification to “one embodiment”, “an embodiment”, “one example” or “an example” means that a particular feature, structure or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, “one example” or “an example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures or characteristics may be combined in any suitable combinations and/or subcombinations in one or more embodiments or examples. Particular features, structures or characteristics may be included in an integrated circuit, an electronic circuit, a combinational logic circuit, or other suitable components that provide the described functionality. In addition, it is appreciated that the figures provided herewith are for explanation purposes to persons ordinarily skilled in the art and that the drawings are not necessarily drawn to scale.
In a wide variety of controllers for power converters, a precise oscillator is required for the timing circuitry. In an analog controller design, the precise oscillator is provided through a very accurate current source charging a timing capacitor. In an integrated circuit controller including a timing oscillator or other control blocks that require an accurate current source, the accurate precise current source is designed inside the integrated circuit. In some mixed signal controller integrated circuits the accurate precise current source could be achieved by adding trim bits to the controller that would consume more die area and would also increase the cost because of increased the final testing time.
To avoid the extra effort and cost of providing the trimming bits, an alternative analog design solution is to add a reference pin (R-pin) to the controller integrated circuit, which may produce a very accurate reference current by loading an internal band gap circuit having high accuracy (e.g., ±4% tolerance) with a precision resistor (e.g., ±1% tolerance). The resulting accurate current can then be mirrored and utilized for instance in timing circuitry of a clock oscillator, a filter circuit, or the like. However, this accurate precise reference current would be required continuously for the functionality of the integrated circuit, and the external reference pin would remain dedicated to generating the accurate reference current continuously throughout the operation of the circuit. Many system control applications require an option of operational mode detection, which is programmed by the customer through an external circuit or component coupled to an external pin. The integrated circuit pin is dedicated only to generate a precise reference current, and therefore limits the overall function set that could be implemented in a given product.
As will be discussed, methods and apparatuses for programming a power converter controller with an external programming terminal having multiple functions are disclosed. In one example, a power converter controller with a single external programming terminal having multiple functions is introduced. A user is allowed to program two or more different characteristics of the power converter controller using the same single external programming terminal. Furthermore, in one example, external programming circuitry that is coupled to the external programming terminal may be reutilized during normal operation of the power converter to generate the accurate reference current. In addition to the power consumption savings during normal operation, there is also a savings in space and size by reutilizing and sharing common circuit components for the two or more programmable functions of the power converter controller in accordance with the teachings of the present invention.
To illustrate,
As shown in the depicted example, multifunction interface module 140 may be coupled through its data lines 125 to the power conversion system block 120 to communicate data with the system in accordance with the teachings of the present invention. The multi function interface module 140 receives a supply voltage Vsupply coupled to terminal 135 and has a reference ground 101. The multifunction interface module 140 could be interfaced either at the input referenced to the input ground, at the output referenced to the output ground, or included in the controller unit of the power conversion system block 120 and referenced to the controller ground.
In one example, multifunction interface module 140 includes a single external programming terminal 142, through which multiple functions of the power conversion system block 120 may be programmed in accordance with the teachings of the present invention. In the example, the single external programming terminal 142 is coupled to an external programming circuit 145 through which a programming current 144 is conducted. In one example, the external programming circuit 145 includes a single component, such as a resistor 146 having one or more different resistance values that can be selected to provide different programming information in accordance with the teachings of the present invention.
In one example, multifunction interface module 160 includes a single external programming terminal 162 that is coupled to an external programming circuit 165, which in one example could include a single component such as a resistor 166 having one or more different resistance values that can be selected to provide different programming information in accordance with the teachings of the present invention. In one example, a programming current 164 is conducted through the external programming circuitry 165, and is utilized to program multiple functions of the system. The multifunction interface module 160 may communicate to the USB port 180 through the terminals 171 and 172, which are coupled to the data terminals D+ 182 and D− 183 of the USB port 180 in accordance with the teachings of the present invention. In one example, the ground reference G 161 of multifunction interface module 160 is coupled to the ground reference 151 of the external programming circuitry 165, which is coupled to the return connect RTN 184 of the USB port 180.
In particular, as shown in the depicted example, a bandgap block 215 is coupled to receive the supply voltage Vsupply from terminal 235 to generate an accurate bandgap voltage VBG 218 that is applied to programming terminal 242. As shown in the depicted example, the external programming circuit 245, which in one example includes programming resistor 246, is coupled to programming terminal 242 to receive the accurate bandgap voltage VBG 218. In the example, the programming resistor 246 of programming circuit 245 has a tight tolerance such that the accurate programming current 244 is conducted through programming resistor 246.
In the example, the accurate programming current 244 passes through a first current mirror 220, which is mirrored to pass a current 225, which is substantially equal to programming current 244, through a second current mirror 230. In the example, first current mirror 220 has a 1:1 current mirror ratio such that mirrored current 225 is substantially equal to or representative of the programming current 244. In one example, second current mirror 230 has an adjustable ratio, which may be selected to be K:1, where K≧1. In the example, a current comparator 260 is coupled to receive the current 225 on its first input terminal 261, and compares current 225 to an internal current source IINT 265 coupled to second input terminal 262 of current comparator 260. In the depicted example, the internal current source IINT 265 is coupled to sink current to ground G 201. In one example, it is appreciated that the internal current source IINT 265 does not necessarily need to be an accurate high cost current source, and a lower cost unregulated current source may be sufficient.
In the depicted example, the current 225 received on terminal 261 of comparator 260 is a function or mode/parameter select current. Depending on the resistance value selected for programming resistor 246 of programming circuit 245, current 225 may have a value of either VBG/1×R or VBG/K×R. In response to comparing current 225 to the internal unregulated current source 265, the current comparator 260 generates a signal 268, which may be a logic high or a logic low.
In the example, mode selector block 270 is coupled to receive the signal 268 to select a parameter or mode of operation of a power conversion system in response to the signal 268. In one example, an enable or activation signal is coupled to be received at terminal 275 to enable mode selector block 270 to select a mode of operation. In one example, the enable or activation signal received at terminal 275 is enabled during startup or power up to select between two modes/parameters of operation, which in one example is either mode A or mode B. In one example, modes A and B may correspond to two different ranges of a power converter output voltages, such as for example 5-12 VDC or 5-20 VDC. Thus, in the example, mode selector block 270 generates a ratio select signal 272 to select between modes A and B in response to signal 268 in accordance with the teachings of the present invention. In another example, it is appreciated that there may be more than two modes to select, and that signal 268 may have more than two different values for mode selector block 270 to select from when generating ratio select signal 272 in accordance with the teachings of the present invention.
In one example, the ratio select signal 272 from mode selector block 270 is coupled to be received by second current mirror 230 to control the ratio selection of the second current mirror 230, which in one example is K:1, where K≧1.
In the example, second current mirror 230 generates a mirrored current 237 of current 225 having the selected ratio K:1, where K≧1, in response to ratio select signal 272. In the example, the mirrored current 237 is coupled to be received by a timing circuit 250. In the example, mirrored current 237 is an accurate precise current and therefore is a fixed accurate precise reference current. In one example, timing circuit 250 may utilize mirrored current 237 to accurately and precisely generate timing information for the power conversion system, which may be achieved for example by charging a timing capacitor of an internal oscillator, clock, or the like.
In the example, it is appreciated that even if there is a change in programming current 244, which occurs in response to a change in the selection of a mode of operation due to a change in the resistance value of resistor 246 of programming circuit 245, the second current mirror 230 ratio is also changed accordingly at startup to offset (compensate) the change in programming current 244 and maintain current 237 at the precise unchanged value. In other words, in one example, the current 237 remains constant or unchanged for each of the plurality of modes of operation that may be selected. For instance, when the resistance value of programming resistor 246 is changed from 1×R to K×R, programming current 244 changes from VBG/1×R to VBG/K×R. However, at the same time, when the ratio select signal 272 from mode selector block 270 changes from mode A to mode B, and the selected ratio of second current mirror 230 simultaneously changes by a factor of K from 1:1 to K:1, which offsets (compensates) the change in programming current 244, and maintains the precise reference current 237 at unchanged value for the timing circuit 250, whether programming resistor 246 is 1×R or K×R in accordance with the teachings of the present invention. In other words, the precise reference current 237 remains constant or unchanged whether mode A or mode B is selected in accordance with the teachings of the present invention. Thus, it is appreciated that multifunction interface module 240 not only enables programming of mode A or mode B, but multifunction interface module 240 also provides the precise reference current 237, which can used by timing circuit 250 whether mode A or mode B is selected in accordance with the teachings of the present invention.
In the depicted example, a current mirror 1, 320, a current mirror 2, 330, and a precise reference voltage follower 380 are coupled to terminal 335 to receive the supply voltage Vsupply. As shown in the example depicted in
As shown in the depicted example, precise reference voltage follower 380 is coupled to single external programming terminal 342. In one example, precise reference voltage follower 380 is coupled to generate a precise voltage at single external programming terminal 342 that follows a tight value of a reference voltage VREF 385 coupled to be received by precise reference voltage follower 380. For instance, in one example, precise reference voltage follower 380 is coupled to receive reference voltage VREF 385 from an internal bandgap circuit. In one example, the precise value of the voltage on single external programming terminal 342 remains tight or substantially equal to the reference voltage VREF 385, regardless of any change in current 344 that may happen through the user selected external programming circuit 345 and programming resistor 346.
In the example, current 344 may change based on the user selected resistance value of programming resistor 346 of external programming circuit 345 from VREF/1×R to VREF/K×R. In one example, the second current mirror (current mirror 2, 330) has a selectively adjustable current ratio of K:1, where K≧1. In one example, the adjustable current ratio of K:1 can be implemented by adjusting the total silicon area and size of a device included in second current mirror (current mirror 2, 330) to realize a desired ratio K:1. For instance, the total silicon area and size of the device in second current mirror (current mirror 2, 330), and therefore the current mirror ratio, may be adjusted by selectively coupling one or more of a plurality of transistors or devices in parallel in response to a ratio select signal 372 generated by mode selector block 370 in response to signal 368 from current comparator 360.
As shown in the example of
In the example illustrated in
In one example, current mirror 2, 330 generates a mirrored current 337 having the selected ratio in response to ratio select signal 372. In the example, the mirrored current 337 is coupled to be received by a timing circuit 350. In the example, mirrored current 337 is an accurate precise current and therefore is a fixed accurate precise reference current. In one example, timing circuit 350 may utilize mirrored current 337 to accurately and precisely charge an internal timing capacitor of an internal oscillator, clock, or the like.
In the example, it is appreciated that even when there is a change in current 344, which occurs for example when the resistance value of programming resistor 346 is changed from K×R (mode A) to 1×R (mode B), current 344 changes from VREF/K×R (mode A) to VREF/1×R (mode B). However, at the same time, when the ratio select signal 372 from mode selector block 370 changes from mode A to mode B, and the selected ratio of second current mirror 330 simultaneously changes by a factor of K from 1:1 to K:1, which offsets the change in current 344, and maintains the precise reference current 337 at an unchanged value for the timing circuit 350 whether programming resistor 346 is 1×R or K×R in accordance with the teachings of the present invention. In other words, the precise reference current 337 remains unchanged whether mode A or mode B is selected in accordance with the teachings of the present invention. In one example, the precise reference current 337 is coupled to be received by timing circuit 350 to charge an internal timing capacitor of an internal oscillator/clock. Thus, it is appreciated that multifunction interface module 340 not only enables programming of mode A or mode B, but multifunction interface module 340 also provides the precise reference current 337, which can be used by timing circuit 350 whether mode A or mode B is selected in accordance with the teachings of the present invention.
As shown in the example depicted in
Activation and deactivation of the ratio scale transistor MP1431 in current mirror 2430 is through the pull up of the gate of transistor MP1431 through transistor MP2432 to turn off transistor MP1431, or through the pull down of the gate of transistor MP1431 through transistor MP4434 to turn on transistor MP1431. In the depicted example, by turning off transistor MP1431 through transistor MP2432, mode A is selected and the ratio of current mirror 2430 is 1:1. By turning on transistor MP1431 through transistor MP4434, mode B is selected and the ratio of current mirror 2430 is K:1, where K>1.
Activation signals 472A and 472B for the gate pull up and pull down through transistors MP2432 and MP4434, respectively, are generated by the mode select block 470. In the depicted example, mode select block 470 is implemented with a latch or flip-flop. In the example of
In the example shown in
The current 444 from supply voltage Vsupply through the portion 430A of current mirror 2430 and through a precise reference voltage follower block 480 is passed to a single external programming terminal 442 of multifunction interface module 440. In one example, precise reference voltage follower block 480 is coupled to receive a reference voltage VREF 485 to set the voltage at external programming terminal 442 to VREF. An external programming circuit 445, which includes a user selected programming resistor 446, is coupled to a single external programming terminal 442 to receive reference voltage VREF and conduct current 444. In one example current 444 is based on the user selected programming resistor 446, which has a user selected resistance value of either 1×R or K×R. As such, current 444 could be either VREF/(1×R) or VREF/(K×R), which may be used to select current mirror 2430A ratio of 1:1 or K:1. In other examples, it is appreciated that the programming resistor 446 could be selected from more than two options to select more than two different ratios for current mirror 2430 in accordance with the teachings of the present invention.
As shown in the depicted example, precise reference voltage follower block 480 includes of an operational amplifier 483 having a non-inverting input 481 that is coupled to receive precise reference voltage VREF 485. The inverting input 482 of operational amplifier 483 is coupled to receive the voltage on single external programming terminal 442 to keep the voltage on single external programming terminal 442 virtually equal to the precise voltage reference VREF 485 received at the non-inverting input 481 of operational amplifier 483. Output 484 of the operational amplifier 483 is coupled to be received by the base of a bipolar transistor 486, which conducts current 444 that passes from the supply voltage Vsupply terminal 435 through portion 430A of current mirror 2430 to the user selected programming resistor 446 of external programming circuitry 445 coupled to single external programming terminal 442 in accordance with the teachings of the present invention.
Current mirror 1420 with a 1:1 ratio mirrors any current changes in current 444 due to the user selected programming resistor 446 to mirrored current 425, which is conducted through transistor MP6466 to node 463 of current comparator 460. Current comparator 460 compares mirrored current 425 from PMOS transistor MP6466 with an internal unregulated current source IINT 465.
If the mirrored current 425 through transistor MP6466 is greater than the current of current source IINT 465, current IINT 465 is sinked to ground 401, and the gate 463 of PMOS transistor MP7467 is pulled high and therefore MP7467 remains off. As a result, terminal R of the mode select block 470, which is coupled to the first input 471B of NOR1 gate 471 is pulled low. The second input 471A of NOR1 gate 471, which is received from the output 473C of NOR2 gate 473 is also low, and the signal Qbar 472A at the output 471C of NOR1 gate 471 goes high, which in turn latches the signal Q 472B at the output 473C of NOR2 gate 473 at low. As a result, with the signal Qbar 472A latched high and the signal Q 472B latched low, PMOS transistor MP2432 is turned off, and PMOS transistor MP4434 is turned on. With PMOS transistor MP4434 turned on, the gate of PMOS transistor MP1431 is pulled down, which turns on PMOS transistor MP1431 in parallel with PMOS transistor MP3433, mode B is selected and the ratio of second current mirror (current mirror 2430) is therefore K:1 because the combined current flow in current 444 of PMOS transistor MP1431 and PMOS transistor MP3433 is K times greater than the current flow of just PMOS transistor MP3433. The current 444 is then mirrored through PMOS transistor MP8438 to generate a current 437. In one example, current 437 is a precise current that may be received by timing circuit as a precise reference current to generate an accurate oscillating signal or clock signal in accordance with the teachings of the present invention. In one example, it is appreciated that increased current ratio for current mirror 2430 offsets (compensates) for the increased current 444 through programming resistor 446 due to a K times lower resistance value selected for programming resistor 446, and that the precise reference current 437 received by the timing circuit, to for example charge a timing capacitor for internal clock oscillator, remains precisely fixed in accordance with the teachings of the present invention.
If the mirrored current 425 through transistor MP6466 is less than the current of current source IINT 465, (in one example the mirrored current 425 could be either 30 uA or 10 uA compared to current source 465 IINT=20 uA), the gate of PMOS transistor MP7467 is pulled low through current source IINT 465, and PMOS transistor MP7467 turns on to sink current Ibias 469 to ground. P-channel transistor MP7467 therefore pulls up terminal R 468 of the mode select block 470 to high. This results in the signal Qbar 472A at the output 471C of NOR1 gate 471 to go low, which in turn latches the signal Q 472B at the output 473C of NOR2 gate 473 at high. As a result, with the signal Qbar 472A latched low and the signal Q 472B latched high, PMOS transistor MP2432 is turned on, and PMOS transistor MP4434 is turned off. With PMOS transistor MP2432 turned on, the gate of PMOS transistor MP1431 is pulled up, which turns off PMOS transistor MP1431. As a result, mode A is selected and the ratio of second current mirror 2430 is therefore 1:1 because all of current 444 is conducted through PMOS transistor MP3433 since PMOS transistor MP1431 is turned off.
In one numerical example K=3, R=12.4 kΩ, the current through transistor MP6466 is 30 uA, K×R=38.3 kΩ, the current in transistor MP6466 is 10 uA), and IINT=20 uA, where IINT 465 is not required to be an expensive precise regulated current source. In an example application in which multifunction interface module 440 is included with a power conversion system, used for example in a cellphone charger, a 1×R selection results in a mode B selection that may define a charger output voltage range of 5-12 VDC, and user defined K×R selection results in a Mode A selection that may define an output voltage range of 5-20 VDC. In one example, the selected mode as indicated with signal Qbar 472A and signal Q 472B may be communicated to the power conversion system through for example data lines 125, as illustrated for example in
The above description of illustrated examples of the present invention, including what is described in the Abstract, are not intended to be exhaustive or to be limitation to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible without departing from the broader spirit and scope of the present invention. Indeed, it is appreciated that the specific example voltages, currents, frequencies, power range values, times, etc., are provided for explanation purposes and that other values may also be employed in other embodiments and examples in accordance with the teachings of the present invention.
These modifications can be made to examples of the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. The present specification and figures are accordingly to be regarded as illustrative rather than restrictive.
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| Number | Date | Country | |
|---|---|---|---|
| 20160274618 A1 | Sep 2016 | US |
