 |
Electronic Components Datasheet Search |
|
|
Electronic Components Datasheet Search |
|
HV9910BNG-G-M901 Datasheet(PDF) 6 Page - Microchip Technology |
|
||||||||||||||||||||||||||||||
HV9910BNG-G-M901 Datasheet(HTML) 6 Page - Microchip Technology |
|
|
6 / 15 page  HV9910B DS20005344A-page 6 2015 Microchip Technology Inc. 3.0 APPLICATION INFORMATION HV9910B is optimized to drive buck LED drivers using open-loop, peak current mode control. This method of control enables fairly accurate LED current control without the need for high side current sensing or the design of any closed loop controllers. The IC uses very few external components and enables both Linear and PWM-dimming of the LED current. A resistor connected to the RT pin programs the fre- quency of operation (or the off-time). The oscillator pro- duces pulses at regular intervals. These pulses set the SR flip-flop in the HV9910B which causes the GATE driver to turn on. The same pulses also start the blank- ing timer, which inhibits the reset input of the SR flip- flop and prevent false turn-offs due to the turn-on spike. When the FET turns on, the current through the induc- tor starts ramping up. This current flows through the external sense resistor RCS and produces a ramp volt- age at the CS pin. The comparators are constantly comparing the CS pin voltage to both the voltage at the LD pin and the internal 250mV. Once the blanking timer is complete, the output of these comparators is allowed to reset the flip-flop. When the output of either one of the two comparators goes high, the flip flop is reset and the GATE output goes low. The GATE goes low until the SR flip-flop is set by the oscillator. Assuming a 30% ripple in the inductor, the current sense resistor RCS can be set using: Constant frequency peak current mode control has an inherent disadvantage – at duty cycles greater than 0.5, the control scheme goes into subharmonic oscilla- tions. To prevent this, an artificial slope is typically added to the current sense waveform. This slope com- pensation scheme will affect the accuracy of the LED current in the present form. However, a constant off- time peak current control scheme does not have this problem and can easily operate at duty cycles greater then 0.5. This control scheme also gives inherent input voltage rejection, making the LED current almost insensitive to input voltage variations. However, this scheme leads to variable frequency operation and the frequency range depends greatly on the input and out- put voltage variation. HV9910B makes it easy to switch between the two modes of operation by changing one connection (see Section 3.3 “Oscillator”). 3.1 Input Voltage Regulator HV9910B can be powered directly from its VIN pin and can work from 8.0 - 450VDC at its VIN pin. When a volt- age is applied at the VIN pin, the HV9910B maintains a constant 7.5V at the VDD pin. This voltage is used to power the IC and any external resistor dividers needed to control the IC. The VDD pin must be bypassed by a low-ESR capacitor to provide a low impedance path for the high frequency current of the output GATE driver. HV9910B can also be operated by supplying a voltage at the VDD pin greater than the internally regulated voltage. This will turn off the internal linear regulator of the IC and the HV9910B will operate directly off the voltage supplied at the VDD pin. Please note that this external voltage at the VDD pin should not exceed 12V. Although the VIN pin of the HV9910B is rated up to 450V, the actual maximum voltage that can be applied is limited by the power dissipation in the IC. For exam- ple, if an 8-pin SOIC (junction to ambient thermal resis- tance Rθ,j-a = 128°C/W) HV9910B draws about IIN = 2.0mA from the VIN pin, and has a maximum allowable temperature rise of the junction temperature limited to about ∆T = 100°C, the maximum voltage at the VIN pin would be: In these cases, to operate the HV9910B from higher input voltages, a Zener diode can be added in series with the VIN pin to divert some of the power loss from the HV9910B to the Zener diode. In the above exam- ple, using a 100V Zener diode will allow the circuit to easily work up to 450V. The input current drawn from the VIN pin is a sum of the 1.0mA current drawn by the internal circuit and the cur- rent drawn by the GATE driver.The GATE driver depends on the switching frequency and the GATE charge of the external FET). In the above equation, fS is the switching frequency and QG is the GATE charge of the external FET (which can be obtained from the data sheet of the FET). 3.2 Current Sense The current sense input of the HV9910B goes to the non-inverting inputs of two comparators. The inverting terminal of one comparator is tied to an internal 250mV reference, whereas the inverting terminal of the other comparator is connected to the LD pin. The outputs of both these comparators are fed into an OR GATE and the output of the OR GATE is fed into the reset pin of the flip-flop. Thus, the comparator which has the lowest voltage at the inverting terminal determines when the GATE output is turned off. RCS 0.25V orVLD 1.15 ILED A ------------------------------------ = VIN MAX T Rja – -------------- 1 IIN ------ 100 C 128 CW --------------------------- 1 2mA ------------- 390V = = = IIN 1.0mA Qg fs + |
Similar Part No. - HV9910BNG-G-M901 |
|
Similar Description - HV9910BNG-G-M901 |
|
|
|
Link URL |
| Privacy Policy |
| ALLDATASHEET.COM |
| Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
