- 您现在的位置：买卖IC网 > Sheet目录1211 > DM300021 (Microchip Technology)MODULE PWR DSPICDEM MC1H HV 3PHS
Set Up and Operation
1.4.7.2
ISOLATED VOLTAGE FEEDBACK
There are many different ways that the two isolated voltage feedback signals can be
provided. Clearly, the DC level must be correctly maintained while still giving sufficient
bandwidth. The bandwidth is especially important for the |VAC| signal in order to
ensure low harmonics are produced by the active PFC. Power supply consumption
should also be as low as possible. All the above requirements can be met by the use
of an inexpensive PIC ? microcontroller, along with two additional low current
optocouplers.
In this case, an 8-pin PIC12C671 microcontroller was chosen, as it has the necessary
ADC on-board and is low cost. Full advantage could be taken of the on-board 4 MHz
RC clock. Three different methods for representing the magnitude of the two signals
were considered. In all cases, only two optocouplers were required.
? A serial communication interface – A simplified two-wire SPI (Clock and Data
Out). It would operate as a master with the dsPIC device as the slave. Given the
PIC12C671 does not have a hardware SPI module, the interface would be
reproduced in software. The code latency was to be used for ADC acquisition and
conversion timing. This was the method chosen and the code is given in
Appendix B along with a diagram showing the transmission data cycle.
Note:
The clock and data signals for the SPI interface are inverted due to the
opto-isolators. The user code should account for this by sampling the data
on the falling clock edge and inverting the received data.
? Pulse width modulation at constant frequency – This was rejected partly due to
concerns over distortion of the pulse width by economic optocouplers. Also, it was
thought that it would not be possible to provide the required bandwidth, while
maintaining the 8-bit resolution of the captured data, given the lack of a hardware
PWM module.
? Frequency modulation – This was considered given that the pulse distortion by
the optocouplers ceased to be an issue. However, concerns about how the band-
width of the feedback could be maintained over the 8-bit data range led to its
rejection.
The actual hardware is described below:
? U34 – The PIC12C671. Note that the PIC12C671 is reset whenever the RESET
line is asserted, as this pin has been configured as the MCLR. This allows correct
synchronization of the SPI with the dsPIC device to be established. The RESET
line must be asserted for a minimum pulse width of 2 μ s.
? R12, R15, R122 – These form a potential divider so that the maximum expected
voltage on |VAC|_SENSE is 4.5V.
? C43 – This acts to smooth out any noise spikes on the |VAC|_SENSE_POINT in
combination with R12, R15 and R122.
? R10, R13, R14, R140, R141 – These form a potential divider so that the maximum
expected voltage on BUS_SENSE is 4.5V. Note that HALF_BUS_SENSE is used
? C57 – This acts to filter out any noise spikes on the DC bus voltage sensing
circuit.
? D40, D42 – Clamping diodes to protect the PIC12C671 inputs.
? 2003 Microchip Technology Inc.
DS70096A-page 25
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
DM300022
MODULE PWR DSPICDEM MC1L LV 3PHS
DM320002
BOARD EXPANSION PIC32 I/O
DM320003-2
KIT EVAL PIC32 USB II STARTER
DM320003
BOARD DEMO USB PIC32 OTG
DM320005
BOARD EXPANSION FOR PIC32 KIT
DM320011
BOARD AUDIO DEV FOR PIC32
DM330015
KIT STARTER MOTR CTRL DSPIC33E
DM330021
KIT DEMO DSPIC33 MCLV
相关代理商/技术参数
DM300021
制造商:Microchip Technology Inc 功能描述:MODULE dsPICDEM MC1H 3 PHASE
DM300022
功能描述:开发板和工具包 - PIC / DSPIC Low V Pwr Module RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM300023
功能描述:开发板和工具包 - PIC / DSPIC dsPICDEM SMPS Buck Demo Brd RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM300024
功能描述:开发板和工具包 - PIC / DSPIC dsPICDEM 1.1 GP RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM300027
功能描述:开发板和工具包 - PIC / DSPIC 16-bit Starter Demo Board RoHS:否 制造商:Microchip Technology 产品:Starter Kits 工具用于评估:chipKIT 核心:Uno32 接口类型: 工作电源电压:
DM-3-000-K
制造商:PacTec 功能描述:Case, Plastic; ABS; Black; 11.46 in.; 3.38 in.; 10.4 in.; UL 94-HB Rated 制造商:PacTec 功能描述:ENCLOSURE, DESKTOP, PLASTIC, BLACK; Enclosure Type:Desktop; Enclosure Material:Plastic; Body Color:Black; External Height - Imperial:3.38"; External Height - Metric:86mm; External Width - Imperial:10.4"; External Width - Metric:264mm;RoHS Compliant: Yes
DM-300-C
制造商:Greenlee Textron Inc 功能描述:DMM 1000V RMS
DM-301
制造商:Labfacility Limited 功能描述:SENSOR PT100 THIN FILM 2X2.3MM CL B 制造商:LABFACILITY 功能描述:SENSOR, PT100, THIN FILM, 2X2.3MM, CL B 制造商:LABFACILITY 功能描述:TEMPERATURE RTD SENSOR, -70C to +500C, 100 OHM; Sensing Temperature Min:-70C; Sensing Temperature Max:+500C; Resistance:100ohm; Sensor Terminals:Through Hole; Temperature Sensing Range:-70C to +500C ;RoHS Compliant: Yes