TWI362170B - Integrated circuit and related method for determining an operation mode - Google Patents

Description

Ι3δ2170 IX. Description of the invention: [Technical field of the invention] The present invention relates to the determination of a mode of operation (〇perati〇nm〇de). The method and related circuits, in particular, the mode of operation used in a power supply Decision Method and Related Circuits [Prior Art] • In order to reduce the package size, the pin count of the integrated circuit is also as small as possible. Therefore, the concept of a multi-function pin has been created. The power management integrated circuit in the power supply also requires a multi-function pin to reduce packaging costs. For example, the company 'Supertex' - a company based in California, produces a light emitting diode (LED) driver (ddver) IC, HV9910B, which has a multi-function pin RT. Please refer to #1 and 2, which are the two light emitting diode (LED) drive systems recommended in the HV9910B product datasheet, and the IQ is HV9910B. For detailed system operation of Figures 1 and 2, please refer to the HV9910B product data sheet. Briefly, when the power switch α is turned on, the inductor 1 starts to store energy, and the current Iled flows from the power source VIN through the LEDs: LEDN, inductor L, power switch Qi, and resistor Rcs. When the current ILED is large to a preset level, when the power switch Qi is turned off, the inductor L begins to discharge. The current Iled flows through the circuit formed by the 1362170 LEDl.XEDn, the inductor L, and the diode D. When the power switch Qi is turned off after the shutdown, it depends on the operating mode. • Figure 1 is for operation in Pulse Width Modulation (PWM) mode and Figure 2 is for fixed off time (c〇nstant 〇ff_time) mode. The difference between Figure 1 and Figure 2 is only the connection of the resistor RT. • If ICl is judged from the multi-function pin RT, the RT-side of the resistor is fixedly connected to the ground wire (GND). As shown in Figure 1, the Bellow ICi will operate the entire LED drive system in pulse width modulation (pulse width). M〇dulati〇n, pwM) Mode ' makes the switching frequency fPWM approximately a fixed value. If % is from the multi-function pin RT, the high-voltage (such as 12 volts) signal from the GATE pin can be discriminated, as shown in Figure 2, then (^ will cause the entire led drive system to operate at a fixed off time. (C〇nstant 〇ff_time) mode, so that the closing time φ time T〇FF is about a fixed value. The resistance value of the resistor RT is also used to determine the switching frequency fPWM in the pulse width modulation (PWM) mode. Or the off time T0FF in the constant 〇ff_time mode. In other words, the multi-function pin RT is not only used to determine the working mode of the working iCi, but also used to determine the switching time of the power switch Qi. Such a multi-function pin RT design may have an adverse effect on the internal circuit design of the IC 1 8 1362170. SUMMARY OF THE INVENTION An embodiment of the present invention provides an integrated circuit including a controller and a multi-function connection. a foot and a mode judging circuit. The controller is for controlling a power switch and can be set to operate in one of several working modes. The working mode includes a first operating mode φ and a second operating mode. The multi-function pin can be connected to an external resistor, and the mode determining circuit detects a signal of the multi-function pin. The signal represents a resistance value of the external resistor. When the resistance value is in a first range, the mode determining circuit operates the controller in a first operating mode; when the resistance value is in a second range, the mode The judging circuit operates the controller in a second operating mode. The working modes are all used for power conversion. B. One embodiment of the present invention provides an operating mode determining method. An integrated circuit is provided, which has a plurality of The function pin is connected to an external resistor, and the resistance value of the external resistor is detected through the multi-function pin. When the resistance value is less than a first preset resistance value, the integrated circuit is firstly operated. a mode, controlling a power switch to perform power conversion, and when the resistance value is greater than the first preset resistance value, causing the integrated circuit to be different from the first working mode In the second mode of operation, the power switch is controlled to perform power conversion. 9 1362170 [Embodiment] The above and other objects, features, and advantages of the present invention will become more apparent and appreciated. For example, and in conjunction with the drawings, a detailed description is as follows: FIG. 3 is a light-emitting diode (1) ght-emitation diode 'LED' driving system 200 implemented in accordance with the present invention. Unlike the integrated circuit IC1 in FIG. 1 and FIG. 2, the integrated circuit 1 in FIG. 3 (: 2 determines whether the IC 2 operates in the pWM mode or the fixed off time depending on the magnitude of the resistance of the resistor RT ( The constant off_time mode controls the switching of the power switch Qi and converts the energy to drive the LEDs LEDi.leDn. As for the power switch Qi, the current price measuring resistor Rcs, the inductor ^ capacitor CIN and C〇UT in Fig. 3 The operation and principle between the diode D and the LED diode Lu's are similar to those of the corresponding elements in Fig. 1, so the explanation is omitted and not described here. In the embodiment, when the resistance value of the resistance ^ is greater than ^, the '% will operate in the phase ((7), 〖. (10)), and the second time is the closing time T〇FF, that is, the power switch & Ding: Γ; time: 'all are about a fixed time. And this solid is determined by the resistance value of the resistor RT. ^ 〇 217 〇 in the embodiment of Figure 3, ohms, τ The resistance value is less than 8·5仟2 and the sinking will be (4) in the Weiwei mode, so that the switching frequency f, the force rate: Qilian King twenty-two number two open between the moment the piece goods are a vehicle about a fixed frequency. ^ A resistance value of the determined size. ^ Cloth Frequency 'will be by the resistor

Therefore, the multi-function RT RT mode of operation is also used to determine not only the switching time of the power switch Qi used to determine the operating IC2. = Application design of IC2's multi-function pin rt in Figure 3, 输出 2 Figure 1Cl's multi-function pin RT input and output circuit will have the following two problems. The output circuit of the L% multi-function pin RT requires a high voltage circuit. Because the pin GATE is used to turn the power switch on or off, its output double is often high voltage, such as 12 volts. Since the second figure towel ic, the multi-function pin RT is connected to the pin gate, the output circuit of the buckle 1 transmitted through the multi-function pin RT has to use a high-voltage circuit to receive the pin GATE. The transmitted high voltage 〇 2 volts signal. 2. The input and output circuits of the iq's multi-function pin ruler may be interfered by the high frequency switching signal. The IQ pin GATE will output a high frequency signal to turn the power switch on or off. q "#IC" is applied to the fixed off 1362170 time (constant off-time) mode operation of Figure 2, such high frequency signals will pass through. The connection of the resistor RT enters the multi-function pin RT, which in turn affects the fixed off-time control circuit connected to the multi-function pin RT. Therefore, the ICi needs some additional protection measures to prevent the input and output circuits of the multi-function pin from being affected. The interference of the high-frequency signal outputted by the pin GATE. The multi-function pin RT of IQ in Fig. 3 does not have the problem of Φ described above. The input and output circuit of the multi-function pin RT of ic2 can use the low-voltage circuit, 4 Such as 5 volt circuit. This is because IC2's multi-function pin RT, the non-buck operation mode is the constant off-time mode or the gas is smashed to the ground power line (GND), not A voltage (12 volt) signal is received. As is known to those of ordinary skill in the art, low voltage (like 5 volt) circuits can be designed with relatively small wafer faces than high voltage (like 12 volts) circuits. Product, so use low-voltage circuit comparison • There is e to save the cost of the chip area. The same reason 'regardless of the operating mode, the constant off-time mode or the PWM mode, as shown in Figure 3, as many as IC2 The function pin RT and the pin GATE are knife-off, so the 1C2 multi-function pin RT is not interfered by the high-frequency signal output by the pin GATE. Therefore, the IC2 does not have to cost to set the south-frequency signal. Fig. 4 is a partial circuit diagram of the embodiment of Fig. 3. The integrated circuit IC2 has a controller 202, a mode judging circuit 204, and a voltage setting 12 1362170 fixed circuit 206. The controller 202 is connected The foot GATE controls the switching of the power switch Qi in Fig. 3. The Wu-type judging circuit 2〇4_current flowing through the multi-function pin RT also equally detects the resistance value of the resistor Rt. The resistance value, the mode judging circuit 2〇4 sends out the mode signal Smode, and the setting controller 202 operates in one of several working modes. For example, when the resistance value of the resistor RT is greater than 85 ohms, the mode judges The circuit 204 sets the controller 202 to operate in the fixed off time mode, and also sends the time signal STIME according to the detected resistance value of the resistor RT to determine the off time T0FF. When the resistance of the resistor RT is less than 8.5 ohms The mode determination circuit 204 sets the controller 202 to operate in the PWM mode, and also sends a time signal STIME according to the detected resistance value of the resistance, and determines the switching frequency fpwM 0. The voltage setting circuit 206 follows the mode signal SM0DE. To set the voltage VRT of the multi-function pin RT. As shown in Fig. 4, the voltage setting circuit B 206 includes a multiplexer 2062 whose three servo inputs receive fixed voltages VREFH, Vref, and Vref1, respectively. In this embodiment, 'Vrefh, Vrefq, and Vrefl are 1 volt, 〇6 volt, and 0.2 volt, respectively. According to the mode signal SM0DE, the multiplexer 2062 selects one of the fixed voltages Vrefh, VrEFO, and VrefL as the reference voltage Vref, and outputs it to the comparator 2064. The comparator 2064 is connected to the switch Qc such that the voltage VRT of the multi-function pin RT is maintained at approximately equal to the reference voltage VREF. Moreover, the current IRT flowing through the resistor RT also flows through the 13 1362170 switch Qc, which is detected by the mode judging circuit 204. Figure 5 is a flow chart of a method of an embodiment which can be used as an operational basis for the circuit of Figure 4. Please refer to Figure 4 and Figure 5 at the same time. Step 502 shows that when IC2 of Figure 4 is started to be connected to the power supply, it must wait for a settling time, wait for the power supply to stabilize, and the fixed voltages VREFH, VreFO, and VrefL are stably generated before entering other step. In step 504, the mode judging circuit 204 causes the multiplexer 2062 to select the fixed voltage VREF0 as an output through the mode signal Smode, and thus the voltage VRT of the multi-function pin RT is approximately equal to the fixed voltage VREF0. The mode determining circuit 204 detects the current IRT flowing through the multi-function pin RT in step 506, and compares whether the IRT is less than a predetermined current value Irto in step 508. In the embodiment of Fig. 4, the fixed voltage VREF0 is 0.6 volts, and the preset current value Irto is 7 〇 micro-amper. Therefore, the mode judging circuit 204 is equivalent to determining in step 506 whether the resistance value of the resistor RT is greater than 8.5 ohms (~0.6 V/70 uA). If the resistance value of the resistor RT is determined to be greater than 8.5 ohms in step 506, the mode determining circuit 204 determines that the IC2 should operate in the fixed off time mode, and then proceeds to step 510; if the determination result is no, the mode determining circuit 204 determines that the IC2 should Operating in PWM mode, then proceeding to step 520.

Similar to step 504, in step 510, the mode determining circuit 204 transmits the voltage VRT 14 1362170 of the multi-function pin RT to the fixed voltage Vrefh through the voltage setting circuit 206. In the embodiment of Fig. 4, the fixed voltage Vrefh is 1 volt. The mode decision circuit 204 then detects the current IRT flowing through the multi-function pin RT in step 512. In step 514, mode decision circuit 204 begins to cause controller 202 to operate in a fixed off time mode. The mode judging circuit 204' also controls the off time T?ff in the fixed off time mode in accordance with the current current IRT' as shown in step 516. For example, when the current 1RT is about 93.747 microamperes, it means that the resistance of the resistor RT is about 10.667 ohms (~1V/93.747uA), so that the off time T〇FF is about 0.5 microseconds; When the current IRT is about 0.93747 microamperes, it means that the resistance of the resistor rt is about 0.0667 megaohms (~1V/0.93747uA), which makes the off time T0FF about 50 罇 seconds. In step 520, the mode judging circuit 204 transmits the voltage vrt of the multi-function pin RT to the fixed voltage Vref1 through the voltage setting circuit 206. In the embodiment of Fig. 4, the fixed voltage VREFL is 〇.2 volt. The mode judging circuit 204 then detects the current Irt flowing through the multi-function pin RT in step 522. In step 524, mode decision circuit 204 begins to cause controller 202 to operate in PWM mode. The mode decision circuit 204' also controls the switching frequency fPWM in the PWM mode in accordance with the current current 1RT' as shown in step 526. For example, 'Integrated circuit IC2 can be designed so that when the current Irt is about 30 microamperes' means that the resistance of the resistor Rt is about 6.667 ohms (~0.2V/30uA), and the integrated circuit IQ is open 15 1362170. The frequency fpwM is about 30 kHz (KHz); each material weeping + Li Du Tian Tian Dian · Irt is about 200 = female training ' means resistance R (four) resistance is about 1 仟 ohm 2ν / 2_A), integrated The on-rate of the circuit IC2 is f_ kHz (KHz). It can be seen from the above embodiment that '8.5 ohm is a voltage watershed (w fine hed). A resistor with a resistance value & 8 5 ohms can cause Φ IC2 to operate in a fixed off-time mode, and the resistance of resistor Rt may be as large as 1.0667 million ohms. A resistor core with a resistance value smaller than 85 ohms can operate 1C2 in PWM mode, and the resistance of resistor Rt may be as small as 1 ohm. It can be inferred that in this embodiment, the usable resistance value of the resistor Rt ranges from 1 仟 ohm to 1.0667 mega ohms, and the maximum and minimum differences are about one thousand (three times cubic). In the above embodiment, as the operating mode changes, the voltage VRT of the multi-function pin RT also changes. Thereby, the problem that the current Irt may be excessively varied can be solved. From another point of view, if the voltage Vrt of the multi-function pin RT is maintained at a fixed 'will not change as the working mode changes', IQ will be quite difficult to design because IQ will need to be able to detect the size. Variations up to 10 times the square current IRT. It can be seen from the foregoing embodiment that as the operating mode changes, the voltage VRT of the multi-function pin RT is switched, and the magnitude change of the current IRT is reduced to a quadratic multiple of 10 (from 0.93747 microamperes to 200 microamperes). IQ's current sensing capability of 1362170 can be considerably reduced, and a better design. It can be seen from the explanation that the embodiment disclosed above can make the output of the multi-function pin RT use a low-voltage circuit, so that the output of the multi-function pin RT can be protected from high-frequency signals, and the current IRT can be solved. It may be a problem of excessive variation. However, the present invention is not limited to the light-emitting diode driving system disclosed in the above embodiments, and is not limited to the above effects. Although the present invention has been disclosed in the above preferred embodiments, the present invention is not intended to limit the invention, and any of the ordinary skill in the art to which the present invention pertains may be made without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims. * [Simple description of the drawings] Figures 1 and 2 show two conventional light-emitting diode drive systems. Figure 3 is a diagram of a light emitting diode drive system implemented in accordance with the present invention. Figure 4 is a partial circuit diagram of an embodiment of Figure 3. Figure 5 is a flow chart of a method of an embodiment which can be used as an operational basis for the circuit of Figure 4. 17 1362170

[Main component symbol description] IC, IC2

RT

fpWM

TpwM

L

D 200 204 2062 2064

Vrt

Rj

CS GATE T〇FF

Qi

Cin C〇UT LED!... LEDn 202 206

VreFH VreFO VreFL

Qc Integrated body f-channel multi-function pin switch frequency switch period inductor diode diode light-emitting diode drive system mode judgment circuit multiplexer comparator voltage resistor pin off time power switch capacitor light-emitting diode controller voltage setting circuit fixed Voltage switch 18 1362170

RT current

19

Claims (1)

1362170 X. Patent application scope: 1. An integrated circuit comprising: a controller 'for controlling a power switch, the controller can be set to operate in one of several working modes, The working mode includes a first working mode and a second working mode; a multi-function pin for connecting to an external resistor; and a mode determining circuit for detecting the multi-function a signal of the foot, the nickname represents the resistance value of the external resistor of § 玄, when the resistance value is in the first range, the controller is operated in a first working mode, and when the value of the resistor is at a second In the range, the controller is operated in a second mode of operation; wherein the modes of operation are all used for power conversion. 2. The integrated circuit of claim 1, wherein the first operating mode is a pulse width modulation (PWM) mode, and the second operating mode is a fixed off time (c) 〇nstant off-time) mode. 3. The integrated circuit of claim 2, wherein the resistance value of the external resistor is used to determine an operating frequency of the pulse width modulation (PWM) mode, or the fixed The off time of the constant off-time mode. 20 丄 4. The integrated circuit as described in claim 1 of the patent scope, further includes: 0 虔 δ 疋 疋 circuit 'When the mode judging circuit decides to make the controller in '^第" Before the mode or the second working mode, the voltage diode circuit causes the voltage of the multi-function pin to be substantially a first fixed voltage: the mode determining circuit determines to operate the controller in the first working mode/ The electric star setting circuit makes the voltage of the multi-function pin substantially a first solid voltage; when the mode judging circuit determines to operate the controller in the first working mode, the electric castle setting circuit makes the multi The function pin is electrically connected to a third fixed voltage; and the first fixed voltage is between the second and second fixed voltages. 5. The integrated circuit of claim 1, wherein the power-on relationship is used for a power conversion (p〇wer c〇n system. 6. - an operation mode determining method, including: An integrated circuit 'haves a multi-function pin connected to an external through-multi-function pin to detect the resistance value of the external resistor. When the resistance value is less than a first 'one and the first working mode t , causing the integrated circuit to control a power switch for power conversion; when the resistance value is greater than the first predetermined resistance value, the difference is different from the first operational mode Working mode, control the power 21 υυζι /υ switch to carry out the power conversion. The fan (4) 6 (4) operation mode verification method - the resistance value step of the block resistance, to go to 'Hai. The hybrid voltage is roughly - Detecting the current flowing through the external resistor. The bunker; and the other package: the operation mode determining method as described in claim 7 of the patent application, when the resistance value is less than the first preset resistance value, The voltage of the foot is substantially - a second fixed voltage, wherein the second = is lower than the first fixed voltage; and - the solid voltage is when the resistance value is greater than the first predetermined resistance value, the multi-function foot is The voltage is substantially a third fixed voltage, wherein the third fixed is still at the first fixed voltage. 9. The operating mode determining method according to claim 6, wherein the first working mode is a pulse The width modulation (叩 mod-, PWM) mode, and the second operation mode is a constant off-time mode. 10. The operation mode determination method according to claim 9 of the patent application scope, further includes There is: 22 1362170 according to the resistance value of the external resistor to determine the switching time of the power switch. 11. The operating mode determining method according to claim 6, wherein the power-on relationship is used to drive the number Light-emitting diodes (LEDs). twenty three