-
2022-09-21 17:24:28
Viper17 offline high -voltage inverter
Features
800 V Snowpasses The strong power segment low -frequency shake PWM operation electromagnetic interference
operating frequency:
—L type 60 kHz
] - H type is 115 kHz
265 volt voltage under the power lt; 50 MW
The adjustable setting limit current
adjustable accurate overvoltage [ 123]
保护
车载软启动故障后安全自动重启滞后热停堆
应用程序
PDA、摄像机、剃须刀的适配器,手机、 Video games LCD/PDP TV auxiliary power supply, display, audio system, computer, industrial set -top box, DVD player and recorder, white product.
Explanation
This device is a solid power segment of an 800 -volt offline converter, a PWM control, two -level over -current protection, overvoltage and overload protection, lagging heat protection, softness, soft protection, softness Start and automatically restart safely to eliminate any fault conditions. Sudden mode operation and very low equipment consumption can help meet the energy conservation regulations for standby.
Advanced frequency jitter reduces the cost of EMI filter. The brown out function is embedded in high -pressure start.
Figure Figure
Typical power
Typical circuit
Back scanning application (basic)[
[ 123]
Anti -excitement Operation description
viper17
is a high -performance low -voltage PWM controller chip with 800V avalanche The power part with a strong voltage.The controller includes: oscillator with jitter characteristics, a boot circuit characteristics with soft startup, pulse width modulation logic, current restricted circuit, adjustable setting value, second current circuit, emergency mode management , Brown output circuit, ultraviolet low level circuit, and automatic restart circuit and thermal protection circuit.
The current limit setting value is controlled by the control sales. Urban mode operation guarantees that high operations in the spare mode can help the realization of energy conservation and norms.
All faulty protection adopts an automatic restart mode, which is extremely low to prevent the integrated circuit from being overheated.
The power segment and gate driver
The power part uses the solid N -channel MOSFET to ensure the safe operation capabilities of the high DV/DT within the specified rated energy range and the high DV/DT. The minimum BVDSS value of the power supply part is 800 V, and the typical RDS (open) is 20Ω at 25 ° C.
Integrated sensor network structure allowsIt is not lossless current sensing.
The grid drive is designed to provide the controlling grille current during power -power and control, to minimize the co -mode electromagnetic interference. Under the UVLO conditions, the internal drop -down circuit keeps the gate at a low level to ensure that the power supply part cannot be connected
unexpectedly.
High -voltage startup generator
High -voltage current generator supply power through the drain. Only at the input of the large -capacity capacitor voltage higher than the VDrain_ start threshold, usually 80VDC. when?
The high -voltage current generator is opened, and the IDD_CH current (3 mAh typical value) is transmitted to a capacitor transmitted to the VDD pin. In the automatic restart mode after the fault, the IDD_CH current is reduced to 0.6 mA, a typical value. In order to have a slow work cycle during the restart stage.
Power -powered soft start
If the input voltage rises to the starting level of the device (VDrain_Start), the VDD voltage begins to increase the voltage due to the IDD current generated by internal high voltage (see Table 6) in internal high voltage (see Table 6) Start the circuit. If the VDD voltage reaches the VDDON threshold (~ 14V), the power MOSFET starts the switch, and the high -voltage current generator turns off the integrated circuit. Diodes) generate voltage that is sufficient to maintain operation.
The size of the CVDD capacitor must be sufficient to avoid fast discharge and maintain the required voltage value higher than the VDDOFF threshold. In fact, the capacitance value is too low to terminate the switching operation before the controller receives any energy from the auxiliary winding.
The following formulas can be used for the calculation of VDD capacitors:
Formula 1
tssaux is the time required for auxiliary voltage stability. This time the application is based on the output level configuration (transformer, output) estimated capacitance, etc.). During the startup of the converter, the leakage current limit gradually increases to the maximum value. In this way, the stress on the secondary diodes is greatly reduced.
It also helps to prevent transformers from saturation. Soft startup time lasts 8.5 MS. This function is achieved for each attempt to start a converter or failure.
Start IDD current
Sequence map: Normal power -powered and power -off sequence
] Soft start: Time Preface Figure
Power off operation
When the inverter is disconnected, once the input voltage is too low, the system will lose the system will lose it will lose the system. Adjust the peak current limit. When the voltage drops to the VDDOFF threshold (typical 8V) power MOSFET closedBecause the integrated circuit is interrupted, the VDD voltage is reduced. After that, if the vehicle recognition number is lower than the VDrain U Start (a typical 80 volt), the power supply is prohibited from being closed. This function helps prevent converters from trying to restart the monotonous attenuation of the output voltage when the system is powered off.
Automatically restart operation
If the inverter is powered off, the vehicle recognition number is higher than the VDrain U Start, the starting order is not prohibited. Typical value is 4.5 V). This means that the high -voltage startup generator restarts the VDD. Only when the VDD voltage is lower than the VDDRESTART, the capacitor is charged. The above scenarios are described as described by the power off due to faults. After the failure, the charging current is 0.6 mAh (typical values), not the 3 mAh (typical value) stage of the normal startup converter. This function is to ensure the failure with the low VDDRESTART threshold (4.5 V). The IC's restarting attempt has a long duplication rate, the converter is safe, and the extremely low power throughput.
Short -circuit events.
Sequence map: After short circuit
oscillator
The switching frequency is fixed in the inside to 60 kHz or 115 kHz. In these two cases, the modulation of the switching frequency is about ± 4 kHz (60 kHz version) or ± 8 kHz (115kHz version) at 250Hz (typical) rate, so the expansion effect generated will be The energy distribution is on multiple sidelines with the same energy but smaller amplitude.
The current mode conversion of the current limit is that the device is a current mode converter: the drain current is sensing and converted to the voltage. Compare this voltage on the feedback tube foot, through a sider, one cycle and one cycle.
Viper17 has a default current limit value IDLIM. The designer can adjust the electrical specifications according to it, and the minimum current depression required to start the IDLIM adjustment by the RLIM resistor connected to the controller: No RLIM without RLIM Or at high RLIM (ie 100 kΩ), the current limit is fixed to the default value overvoltage protection (OVP). This device can monitor the output voltage of the inverter. This operation is completed by the CONT PIN to complete the voltage generated by the auxiliary winding. To perform the output voltage monitor, the control pin must be connected to the AUX through the AUX through the RLIM and ROVP. 3 The controller recognizes the voltage four consecutive times.
This special function uses an internal counter to reduce noise and prevent locking errors. The counter does not trigger OV in a oscillator cycle at a timePosted when a signal.
The resistance of the resistance to KOVP will be given by the following formulas:
Equation 2
Where:
VOVP is the OVP thresholdVOUT OVP is the output voltage value of the OVP converter set by the designer
NAUX is the number of auxiliary winding turns
NSEC is the number of second windings [123 ]
VDSEC is the positive voltage of the two -level diode
VDAUX is the auxiliary diode forward voltage
ROVP and Rlim to form an output compressor
According to the required required required Idlim, fixed RLIM, ROVP can be calculated through the following formulas:Formula
The resistance value should be ensured Within the scope of the rated ability.
Figure OVP timing figure
Feedback and overload protection (OLP) Viper17 is a current mode converter: feedback pipe control PWM operation, control the emergencies, control the emergencies Mode and activate the overload protection of the device.
When the feedback foot voltage is between VFB-BM and VFB-Lin (0.5 V and 3.3 V, typical values), the drain current is induced and converted to anti-PWM comparators. Lean pin.
This voltage compares the circular basis through the voltage on the feedback foot. When these two voltages are equal, the PWM logical command switch off the power MOSFET. The drain current is always limited to the IDLIM value.
In the case of overload, when the reaction of the feedback for the incident increases higher than VFBúlin, the drain current is limited to the default IDLIM value or
Published on a continuous pipe foot through a resistor. Pulse width modulation comparator is disabled (using RLIM) pulse width.
At the same time, the internal current generated began to charge the feedback capacitor charging (CFB). When the feedback voltage reaches the VFB-OLP threshold, the converter is turned off, and the ICHARGE value is reduced to 0.6 ma. In the first start phase of the flower, the output voltage after the soft start time (the typical value is 8.5 ms) can force the feedback pin voltage to rise to the threshold of the VFB_OLP closing the converter itself.
To avoid this incident, it must be loaded according to the output. Network feedback further amend the stability of the compensation circuit. The figure shows two different feedback networks.
Time from VFB VFB-Lin to device shutdown (vfb-lin) time vfb_olp) Can be calculated by CFB value, use
Formula:
In the figure, a capacitor connected to the FB pin (CFB) is used as a circuit Some compensation feedback circuits are also used as components delayed OLP, because the time required for capacitor charging (see equations 5). After the start time, the typical value of 8.5 ms. During this period, the feedback voltage is fixed at VFBúlin, and the output capacitor cannot reach its nominal value. The controller interpreter is an overload. In this case, OLP delay helps to avoid incorrect device closing during startup.
Based on the above considerations, the OLP delay time must be long enough to transmit the initial output voltage, and only when the output voltage is in a stable state. The output transient time depends on the output value capacitor and load.
When the circuit stability calculation value of the circular fluidized bed capacitor is too low, it cannot ensure that there is sufficient OLP delay, you can use an alternative compensation network
Use this alternative compensation network, the Polar (FPFB (FPFB (FPFB (FPFB (FPFB (FPFB , FPFB1) and zero (FZFB) are introduced as the reasons CFB and CFB1 and resistance RFB1.
CFB CFB is higher than FZB and FPFB1 in frequency. This rod is usually used to compensate for high -frequency zero points caused by ESR (the resistance of the equivalent number reflux conversion replacement capacitor). Considering the scheme, the formulas in the figure of these poles and zero frequencies
The formulas are as follows:
Formula
Formula
]
Formula
RFB (DYN) is a dynamic resistance seen by FB pin.
CFB1 capacitor fixed OLP delay, usually the results of CFB1 are much higher than CFB.
Formula 5 can still be used to calculate the OLP delay time, but CFB1 must consider replacing the circulating fluid bed. Using an alternative compensation network, the designer can meet the stability of the loop and sufficient OLP delay time in all cases.
FB pin configuration
fb pins configuration
] When there is no load or an emergency mode operation under a very light load, when the voltage on the feedback pin is reduced to lower than the sudden mode threshold VFBBM 50 MV, the power MOSFET cannot be opened anymore. If the voltage on the feedback pin exceeds VFBBM. The voltage of the PWM comparator is irreversible by the input of the feedback pin to a certain value through the resistance of the feedback pin to a certain value, resulting in the minimum value, which is 90 mAh (typical values) for the drainage peak.
When the load is reducedAt this time, the feedback circuit will reduce the feedback pins voltage. When the voltage is less than 50mv, the VFBBM MOSFET stops the switch. After the MOSFET stops, as the result of the feedback reaction of the energy output stop, the feedback pin voltage increases and surpass the VFBBM threshold MOSFET power device to start switching again.
Figure shows this behavior called an emergency. The time period of the system alternate power MOSFET switch to the time period when the power MOSFET does not switch. The power output during the switching period exceeds the non -switch cycle of the non -processing power that has no power to process the power of the load power. The advantage of this emergencies operation is that the average switching frequency is more than the normal operating frequency, up to about 100 Hz, which reduces all frequencies to the minimum related loss.
Emergency mode sequence map, light load management
Brown protection power off protection protection is a non -lock -off shutdown function launched under power conditions detected Improving.
Brown OUT comparator reference VBRTH internally, 0.45 V typical values, and disable the voltage of the BR pins below this internal reference voltage, the pulse width is used. Turn off the conditional power MOSFET below. Before the browning state appears, the VDD voltage continues to oscillate between the VDDON and the UVLO threshold, and there is a voltage lag to improve the noise resistance.
When the voltage on the pin is higher than that of the reference voltage plus the previously said voltage lag.
The Brown Out comparator also has current lag. IBRHYST can set the VINON threshold and VINOFF threshold to select the resistor of the frequency division to the BR pins by appropriate methods.Browning protection: BR external settings and time sequencing diagrams
Fixed the VINON and vinoff level. The following relationship can be used for calculations of resistance RH and RL [ 123]
Formula
Formula
In order to make this function work normally, the vehicle recognition number must be less than the minimum power supply and vehicle recognition number. Enter the minimum voltage of the minimum voltage and maximum load on a large capacitor.
BR pins are a high impedance input that connects to high value resistance, so it is easy to pick up noise. When the converter works or sends the device unexpectedly during the ESD test.
You can use a small film capacitor (such as 1-10 NF) to bypass the ground to prevent any such faults. If the brown out function is not used, the pin must be connected to the GND.
Second -level overcurrent protection and hiccup mode Viper17 prevent short circuit, short -circuit secondary winding or anti -gratitude transformers hard saturationEssence For example, when an abnormal leaky current exceeds 0.6 A, the call condition will be called.
In order to distinguish the first signal of actual faults and interference (for example, the interference caused by the ESD test) entered the warning status " after a signal. If the signal does not stick to the subsequent switching cycle