Datasheet LT8316 (Analog Devices) - 13
| Manufacturer | Analog Devices |
| Description | 600VIN Micropower No-Opto Isolated Flyback Controller |
| Pages / Page | 26 / 13 — APPLICATIONS INFORMATION. Output Power. Selecting a Transformer. Table 1. … |
| File Format / Size | PDF / 1.5 Mb |
| Document Language | English |
APPLICATIONS INFORMATION. Output Power. Selecting a Transformer. Table 1. Predesigned Transformers — Typical Specifications
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link to page 13 LT8316
APPLICATIONS INFORMATION
Example: A 12V output voltage is generated from a where VIN = 400V input that can drop as low as VIN(MIN) = 250V. If a transformer with primary-to-secondary turns ratio η = Efficiency ≈ 80% NPS = 10 is selected to supply a maximum output current (VOUT + VF ) • NPS I D ≈ OUT(MAX) = 2A, then the duty cycle is DVIN(MIN) ≈ 33% and (V ) • N the sense resistor is calculated R OUT + VF PS + VIN SNS = 133mΩ. A 120mΩ resistor is selected. ISW(MAX) = Max. switch current limit = 100mV/RSNS A more accurate value for RSNS can be obtained by finding The calculated power is approximate, and does not take D experimentally with an oscilloscope and electronic load. into account timing variations caused by circuit parasitics. The actual output power must be evaluated on the bench.
Output Power
Example: Consider a 12V output converter with a VIN(MIN) Compared with a buck or a boost converter, a flyback con- of 250V and a VIN(MAX) of 500V. With a ten-to-one primary- verter has a complicated relationship between the input to-secondary winding ratio (NPS = 10) and a sense resis- and output currents. Boost converters have relatively con- tor RSNS = 120mΩ, the maximum power output is 33W stant maximum input current regardless of input voltage, at VIN(MAX) = 500V but lowers to 28W at VIN(MIN) = 250V. while buck converters have relatively constant maximum output current regardless of input voltage, owing to the
Selecting a Transformer
fact that they have continuous input and output currents respectively. A flyback converter, however, has both dis- Transformer specification and design is possibly the continuous input and output currents. The duty cycle most critical part of successfully applying the LT8316. In affects both input and output currents, making it hard to addition to the usual list of guidelines dealing with high- predict maximum output power. frequency isolated power supply transformer design, the following information should be carefully considered. The following equation calculates output power: Analog Devices has worked with several leading magnetic POUT = 0.5 • η • VIN • D • ISW(MAX) component manufacturers to produce pre-designed fly- back transformers for use with the LT8316. Table 1 shows the details of these transformers.
Table 1. Predesigned Transformers — Typical Specifications TRANSFORMER PART LPRI NUMBER (µH) NP:NS:NT ISOLATION VENDOR TARGET APPLICATIONS
11328-T078 670 8:1:1 Reinforced Sumida 100V–600V to 12V/3A 11328-T080 670 4:1:0.5 Reinforced Sumida 100V–600V to 24V/1.5A 11328-T073 670 2:1:0.25 Reinforced Sumida 100V–600V to 54V/0.7A 11328-T061 600 5:1:1 Basic Sumida 200V–450V to 15V/2A 11338-T195 1000 14:1:1.7 Basic Sumida 100V–400V to 7V/2A 11328-T074 500 8:1:1 Reinforced Sumida 100V–450V to 12V/3A 15364-T008 1500 20:1:2.4 Reinforced Sumida 25V–450V to 5V/1A 11328-T086 70 4:1:0.5 Reinforced Sumida 30V–260V to 24V/3A 00399-T239 2800 6:1:0.7 Functional Sumida 90V–500V to 16.8V/0.4A 750317463 440 8:1:1 Reinforced Wurth Elektronik 100V–600V to 12V/4A 750317589 670 8:1:1 Reinforced Wurth Elektronik 100V–600V to 12V/3A 750317464 440 4:1:0.5 Reinforced Wurth Elektronik 100V–600V to 24V/2A 11328-T060 800 18:1:3 Reinforced Sumida 140V–450V to 5V/7A Rev. 0 For more information www.analog.com 13 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts
APPLICATIONS INFORMATION
Example: A 12V output voltage is generated from a where VIN = 400V input that can drop as low as VIN(MIN) = 250V. If a transformer with primary-to-secondary turns ratio η = Efficiency ≈ 80% NPS = 10 is selected to supply a maximum output current (VOUT + VF ) • NPS I D ≈ OUT(MAX) = 2A, then the duty cycle is DVIN(MIN) ≈ 33% and (V ) • N the sense resistor is calculated R OUT + VF PS + VIN SNS = 133mΩ. A 120mΩ resistor is selected. ISW(MAX) = Max. switch current limit = 100mV/RSNS A more accurate value for RSNS can be obtained by finding The calculated power is approximate, and does not take D experimentally with an oscilloscope and electronic load. into account timing variations caused by circuit parasitics. The actual output power must be evaluated on the bench.
Output Power
Example: Consider a 12V output converter with a VIN(MIN) Compared with a buck or a boost converter, a flyback con- of 250V and a VIN(MAX) of 500V. With a ten-to-one primary- verter has a complicated relationship between the input to-secondary winding ratio (NPS = 10) and a sense resis- and output currents. Boost converters have relatively con- tor RSNS = 120mΩ, the maximum power output is 33W stant maximum input current regardless of input voltage, at VIN(MAX) = 500V but lowers to 28W at VIN(MIN) = 250V. while buck converters have relatively constant maximum output current regardless of input voltage, owing to the
Selecting a Transformer
fact that they have continuous input and output currents respectively. A flyback converter, however, has both dis- Transformer specification and design is possibly the continuous input and output currents. The duty cycle most critical part of successfully applying the LT8316. In affects both input and output currents, making it hard to addition to the usual list of guidelines dealing with high- predict maximum output power. frequency isolated power supply transformer design, the following information should be carefully considered. The following equation calculates output power: Analog Devices has worked with several leading magnetic POUT = 0.5 • η • VIN • D • ISW(MAX) component manufacturers to produce pre-designed fly- back transformers for use with the LT8316. Table 1 shows the details of these transformers.
Table 1. Predesigned Transformers — Typical Specifications TRANSFORMER PART LPRI NUMBER (µH) NP:NS:NT ISOLATION VENDOR TARGET APPLICATIONS
11328-T078 670 8:1:1 Reinforced Sumida 100V–600V to 12V/3A 11328-T080 670 4:1:0.5 Reinforced Sumida 100V–600V to 24V/1.5A 11328-T073 670 2:1:0.25 Reinforced Sumida 100V–600V to 54V/0.7A 11328-T061 600 5:1:1 Basic Sumida 200V–450V to 15V/2A 11338-T195 1000 14:1:1.7 Basic Sumida 100V–400V to 7V/2A 11328-T074 500 8:1:1 Reinforced Sumida 100V–450V to 12V/3A 15364-T008 1500 20:1:2.4 Reinforced Sumida 25V–450V to 5V/1A 11328-T086 70 4:1:0.5 Reinforced Sumida 30V–260V to 24V/3A 00399-T239 2800 6:1:0.7 Functional Sumida 90V–500V to 16.8V/0.4A 750317463 440 8:1:1 Reinforced Wurth Elektronik 100V–600V to 12V/4A 750317589 670 8:1:1 Reinforced Wurth Elektronik 100V–600V to 12V/3A 750317464 440 4:1:0.5 Reinforced Wurth Elektronik 100V–600V to 24V/2A 11328-T060 800 18:1:3 Reinforced Sumida 140V–450V to 5V/7A Rev. 0 For more information www.analog.com 13 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Package Description Typical Application Related Parts