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| Input voltage autosensing Provision for Standby mode operation Partial Resonance Power Supply IC Module MR2900 Series 2002/03/01 Tentative Application Note MR2900 Application Note Cautions When Using This Document 1. The circuit diagrams and parts tables provided for reference purposes in this document are for the use of persons with basic circuit design knowledge to aid in understanding the product. As such they do not constitute a guarantee of output, temperature, or other characteristics, or characteristics or safety as determined by the relevant authorities. 2. The products noted in this document are semiconductor components for use in general electronic equipment and for general industrial use. Consideration has been given to ensure safety and reliability as appropriate for the importance of the systems used by the customer. Please contact Shindengen's sales section if any points are unclear. 3. Fail-safe design and safety requirements must be considered in applications in which particularly high levels of reliability and safety are required (eg nuclear power control, aerospace, traffic equipment, medical equipment used in life-support, combustion control equipment, various types of safety equipment). Please contact our sales department if anything is unclear. 4. Shindengen takes no responsibility for losses or damage incurred, or infringements of patents or other rights, as a result of the use of the circuit diagrams and parts tables provided for reference purposes in this document. 5. The circuit diagrams and parts tables provided for reference purposes in this document do not guarantee or authorize execution of intellectual property rights, or any other rights, of Shindengen or third parties. 6. Systems using Shindengen products noted in this document and which are strategic materials as defined in the Foreign Exchange and Foreign Trade Control Law or the Export and Trade Control Law require export permission under the relevant legislation prior to export. Inquiries: Functional Devices Division, Device Sales Department, Device Sales Section Ph Fax 03-5951-8131 03-5951-8089 Thank you July 1st, 1995 Shindengen Electric MFG.CO.,LTD -2- MR2900 Application Note Contents 1. Outline 1.1 Introduction 1.2 Characteristics 1.3 Applications 1.4 Absolute Maximum Ratings and Reference Output Capacities 1.5 Equivalent Circuit and Dimensions 2. Block Diagram 2.1 Block Diagram 2.2 Pin Function Description 3. Operation Description 3.1 Start-up Circuit 3.2 On-trigger Circuit 3.3 Partial Resonance 3.4 Standby Mode Control 3.5 Output Voltage Control 3.6 Soft Drive Circuit 3.7 Circuit for Load Shorts 3.8 Collector Pin (pin 7) 3.9 Thermal Shut-down Circuit (TSD) 3.10 Over-voltage Protection Circuit (OVP) 3.11 Malfunction Prevention Circuit (patent applied for) 3.12 Over-current Protection Circuit 4. Standard Circuit 5. Design Procedures 5.1 Design Flow Chart 5.2 Main Transformer Design Procedure 5.3 Main Transformer Design Examples 5.4 Selection of Constants for Peripheral Components 6. Cooling Design 6.1 Junction Temperature and Power Losses 6.2 Junction Temperature and Thermal Resistance 6.3 Cautions for Cooling Design ... ... ... 19 19 19 ... ... ... ... 13 13 15 18 ... ... ... ... ... ... ... ... ... ... ... ... ... 6 7 7 8 9 9 10 10 10 10 11 11 12 ... ... 5 5 ... ... ... ... ... 4 4 4 4 4 The values presented in this document are based on tentative specifications as of June 29th, 2001, and may change in future Shindengen Electric MFG.CO.,LTD -3- MR2900 Application Note 1.1 Introduction 1. Outline The MR2900 Series IC modules are designed for both 200V and autosensing input with a burst-mode switching function at microloads. These modules are of the partial resonance type, and are comprised of a switching device optimized for both 200V and autosensing power supply input, and a control IC. They are designed to provide the following power supply characteristics. 1.2 Characteristics 1. An ultra high-speed IGBT with 900V resistance ensures high efficiency and low noise at partial resonance. 2. An ultra high-speed IGBT with 900V resistance simplifies design for autosensing power supply input. 3. Very low power consumption at micro-loads (in burst mode). 4. Onboard start-up circuit eliminates the need for start-up resistors. 5. Soft drive circuit achieves low noise levels. 6. Excess current protection function (ton limit, primary current limit). 7. Excess voltage protection and thermal shut-down function. 8. Power supply circuits may be constructed with a minimum of external components. 9. The use of a full mold package provides benefits in insulation design. 1.3 Applications TVs, displays, printers, VTR, DVD, STB, air-conditioners, refrigerators, and other electrical appliances, and office equipment. 1.4 Absolute Maximum Ratings and Reference Output Capacities Absolute maximum ratings Model MR2920 MR2940 Peak input voltage VinV 900 Peak input current IinA 7 10 Maximum output capacity PoW Input voltage range 90V to 276VAC 100 150 180V to 276VAC 150 225 Maximum output capacity and input voltage range differ with design conditions. 1.5 Equivalent Circuit and Dimensions 3.2 20.00.2 Collector Z/C 7 1 3.00.2 2 Q1 IC1 4 5 6 Emitter/OCL Vcc Vin 2.40.2 11.8 0.5 +0.2 -0.1 5.00.2 4.2 12.0 F/B GND 8.0 3 16.70.3 4.20.5 7.60.5 2.70.2 2.540.2 6x1.70.3=15.240.3 0.7 +0.3 -0.1 4.50.5 0.70.2 Shindengen Electric MFG.CO.,LTD -4- MR2900 Application Note 2.1 Block Diagram 2. Block Diagram Vcc 4 Start-up circuit UVLO comparator Start-up circuit Vin Collector 5 7 Unlatch comparator UVLO comp OVP comparator VUL VCC(start) /VCC(stop) R Q S VCC(startup off) /VCC(startup on) VOVP Z/C 1 Thermal Shutdown circuit Zero current detection circuit On-dead timer Standby circuit Q1 Soft drive circuit S Q R Excess current detection comparator Vref F/B 2 IF/B VTH(OCL) Restart timer ON range timer Burst current limit comparator 3 GND VTH(burst limit) 6 Emitter/OCL 2.2 Pin Function Description Pin number 1 Abbreviation Z/C Trigger input pin Description Zero detection voltage: 0.35V Standby: Up to 4.5V in standby mode. ton(min) to ton(max): 1.5V to 4.5V/0s to 25s Standby: Oscillation stopped at up to 0.8V. Standby: Oscillation started at 1.8V or higher. Oscillation start voltage: Vcc14V Oscillation stop voltage: Vcc8.5V Excess voltage latching voltage:Vcc=20V Current supplied VinVcc at start-up Start-up circuit OFF:Vcc14V Start-up circuit ON: Vcc7.6V Excess current detection threshold:0.6V Excess current detection threshold at standby: 50mV 2 3 4 F/B GND Vcc Feedback signal input pin GND pin IC power supply pin 5 6 7 Vin Emitter /OCL Collecter Start pin Main switching device emitter and current detection pin Main switching device collector pin Shindengen Electric MFG.CO.,LTD -5- MR2900 Application Note 3.1 Start-up Circuit In conventional start-up circuits employing a start-up resistor, current continues to flow following power supply start-up, thus wasting power and reducing efficiency, particularly during standby. See Fig.3.1 Comparison of Start-up Circuits - Conventional Start-up Circuit. In the MR2000 Series start-up circuit the start-up current is supplied from the input voltage at power supply start-up, and is shut-off when the power supply is in operation. The start-up circuit supplies a current of 12mA (typical) from the IC internal constant current source until the voltage at the Vcc pin reaches 14V (typical). This current is consumed internally in the IC as well as being used as the charging current for the condenser connected externally between the Vcc pin and GND. This design allows a stable start-up only minimally dependent upon input voltage. When the voltage at the Vcc pin reaches 14V (typical) the start-up circuit is disconnected, the start-up current no longer flows and oscillation begins simultaneously. The current consumed in the IC is then supplied from the control coil. See Fig.3.1 Comparison of Start-up Circuits MR2000 Start-up Circuit. 3. Operation Description Conventional Start-up Circuit Start-up current IC Start-up current flows even during steady-state operation, resulting in losses. MR2000 Start-up Circuit Start-up current switched off following start-up, thus eliminating the need for start-up resistors. 5 Vin pin Vcc(startup off) /Vcc(startup on) 14.5V/7.2V Vcc pin Control coil 4 Fig.3.1 Comparison of Start-up Circuits In the case of an instantaneous power failure or a load short, oscillation is stopped when the voltage at the Vcc pin reaches 8.5V, and when this voltage drops to 7.6V the start-up circuit operates again and the voltage at the Vcc pin then begins rising. See Fig.3.2. Incorporation of the functions described above improve efficiency, particularly during standby, and reduces the number of start-up resistors required, thus reducing the overall number of components. VCC(startup off) =VCC(Start) =14.0V VCC(stop) =8.5V VCC(startup on) =7.6V Vin VCC VCE VOUT Instantaneous power failure Load short Fig.3.2 Start-up Circuit Operation Sequence Shindengen Electric MFG.CO.,LTD -6- 3.2 On-trigger Circuit The MR2000 Series employs current-critical operation to detect energy bursts at the secondary side of the main transformer and switch on the main switching device. Energy discharge timing is detected at the negative edge of the control coil voltage waveform (0.2V in the diagram at right), and the main switching device switched on for current-critical operation. The on-trigger detection voltage (0.2V) incorporates a 50mV hystersis to increase noise resistance. 0.2V VZ/C IC Secondary rectification diode current VCE Control coil voltage Fig.3.3 On-trigger Operation Sequence 3.3 Partial Resonance In current-critical switching power supplies (RCC), damping begins at the resonance frequency (determined by the primary inductance LP of the main transformer and the resonating condenser C) when the secondary current in the circuit formed by connecting the resonating condenser between the collector and GND of the main switching device reaches 0A. The discharge current of the resonating condenser flows through the primary coil and returns energy to the input. Adjustment of the CR time constant applied to the Z/C pin (see diagram at right) allows the main switching device to be turned on at the trough of the damping voltage waveform, thus permitting a reduction in turn-on losses. In a circuit using partial resonance, the energy stored in the resonating condenser during the OFF period of the main switching device is returned to the input, thus permitting a reduction in turn-on losses. This allows the connection of a large-capacity condenser between the collector and GND of the main switching device, and thus permits a reduction in noise. The use of partial resonance is effective in permitting a simple circuit configuration with improved efficiency and noise reduction. VCE On timing delayed with CR time constant. Collector pin 1 3 Z/C pin R GND pin C Emitter/OCL pin Resonating condenser 7 6 Turn-on delay Damping begins at the resonance frequency determined by LP and C. IC Secondary rectification diode current Fig.3.4 Partial Resonance Shindengen Electric MFG.CO.,LTD -7- 3.4 Standby Mode Control (patent applied for) The MR2000 Series is able to switch between two methods of output voltage control - normal operation and the standby mode, in a single power supply. The standby mode supported by this IC employs the burst method for intermittent operation under light loads to reduce oscillation frequency and switching losses, and is effective in reducing the standby input voltage under micro-loads. A unique characteristic of this IC is the use of the burst mode for intermittent operation without stopping IC control, and thus minimizing output ripple. The Z/C pin is clamped to a voltage of 4.5V (typical) or less by an external signal to allow selection of standby mode control. The standby mode is cleared (ie restored to the normal mode) by clearing the clamp voltage on the Z/C pin, and applying a voltage of 4.5V (typical) or higher. In normal operation the ON range of the main switching device is controlled in a linear manner in relation to voltage variation at the F/B pin, while in standby mode operation the Emitter/OCL pin current detection threshold value is switched from 0.6V for the normal mode to 0.05V for the standby mode. The collector current is fixed at a peak value by the current detection threshold value, and the burst mode is selected. Burst mode control is such that oscillation occurs when the voltage at the F/B pin is 1.8V (typical) or higher, and is stopped when this voltage is 0.8V (typical) or lower. Drain pin 7 Z/C pin Emitter/OCL pin 6 Switched from 0.6V to 0.05V Output voltage error detection feedback signal 1 F/B pin 2 3 4.5V (TYP) Standby signal (external signal) Fig.3.5 Standby Mode Control VF/B(burst stop) =0.8V VF/B(burst start) =1.8V VF/B IC VOUT ripple As output voltage control in the standby mode fixes the Fig.3.6 Standby Mode Control Sequence drain current peak value for each oscillation cycle, the duty ratio of the oscillating and non-oscillating intervals is varied to ensure a constant voltage. Standby mode start 0.2V 4.5V(TYP) Standby mode clear VZ/C IC IOUT Normal operation Standby mode Fig.3.7 Standby Signal Receive Sequence Normal operation Shindengen Electric MFG.CO.,LTD -8- 3.5 Output Voltage Control (normal operation) The MR2000 Series controls output voltage with the ON range proportional to the voltage at the F/B pin. When the voltage at the F/B pin is 1.5V the ON range is 0s, and is controlled in a linear manner so that when the voltage is 4.5V the ON range is 25s. A current of 200A=IF/B (typical) flows at the F/B pin, and the impedance of the photocoupler transistor connected externally between the F/B pin and GND is varied with the control signal from the secondary output detection circuit, thus controlling the ON range of the main switching device to produce a constant voltage. The maximum ON range is adjusted by setting the maximum value for the voltage at the F/B pin using a resistor connected externally between the F/B pin and GND. 5Vref 200A F/B pin Droop resistor 2 Output voltage controlled by varying impedance of photocoupler. Output voltage error detection feedback signal ON range tons 25 0 1.5 4.5 Feedback voltage VF/BV Fig.3.8 Output Voltage Control 3.6 Soft Drive Circuit (patent applied for) The MR2000 Series supplies the main switching device gate drive voltage from two separate drive circuits. A voltage exceeding the threshold value for the main switching device is supplied from the first drive circuit at the leading edge of the drive voltage waveform to switch on the main switching device with the optimum timing. The drive voltage is then supplied gradually by the second drive circuit (see Fig.3.9). Supply of drive voltage in this manner reduces drive losses, as well as reducing noise due to gate charge current and discharge current when the resonating condenser is switched on. Gate voltage supply matched to collector current. VGE Gate charge remains unchanged even when collector current is small. Gate charge spikes reduced. IG Reactive charge reduced under light load. Large resonating condenser discharge current. Damping of resonating condenser discharge current. IC Conventional drive circuit MR2000 drive circuit Fig.3.9 Comparison of Drive Circuits Shindengen Electric MFG.CO.,LTD -9- 3.7 Circuit for Load Shorts The MR2000 Series is designed so that when droop occurs under excessive load, output voltage drops, and control coil voltage drops in proportion. When the control coil voltage falls below 4.5V (typical) the standby mode is selected and the Emitter/OCL pin threshold voltage changes from 0.6V to 0.05V, thus limiting the collector current to approximately 1/10th of its previous value. This design permits a reduction in the stress on the MR2000 Series IC in the case of a load short, and control of the short-circuit current in the secondary diode and load circuit. 4.5V(TYP) VZ/C ICP limited when VZ/C falls below 4.5V (typical). IC Load short VOUT VCC Fig.3.10 Circuit for Load Shorts 3.8 Collector Pin (pin 7) The collector pin on the main switching device. The transformer is designed, and the resonating condenser adjusted, to ensure that VCE(max) is less than 900V. Depending upon input conditions, the collector pin may be subjected to reverse bias for a period during partial resonance. This IC employs an ultra high-speed IGBT in the main switching device. This device differs from MOSFET devices in that it has no body diode structure, thus requiring connection of an external high-speed diode between the Collector and Emitter/OCL pins. 3.9 Thermal Shut-down Circuit (TSD) The MR2000 Series incorporates a thermal shut-down circuit. The onboard IC is latched at 150C (typical) and oscillation is then stopped. Unlatch is achieved by momentarily dropping the voltage at the Vcc pin to VUL (unlatch voltage) or lower. 3.10 Over-voltage Protection Circuit (OVP) The MR2000 Series incorporates an over-voltage protection circuit (OVP). Latching occurs when the control coil voltage exceeds 20V (typical), and secondary output over-voltage protection then operates indirectly. Unlatch is achieved in the same manner as for the overheat protection circuit. Shindengen Electric MFG.CO.,LTD - 10 - 3.11 Malfunction Prevention Circuit (patent applied for) The use of current-critical operation in the MR2000 Series ensures that the main transformer does not become saturated provided the droop setting is optimized. On the other hand, at start-up, and in the case of a load short, the output voltage is very much less than the set voltage. As the control coil voltage is proportional to the output voltage it also reaches an extremely small value, and the on-trigger timing may be incorrectly detected due to the ringing voltage while the device is OFF and switched on before the current-critical point. To counter this problem, the MR2000 Series incorporates a circuit to prevent on-trigger malfunction at start-up, and in the case of a load short. This function disables the on-trigger for a period of 2.7s (typical) after the main switching device in the IC is switched OFF (on-dead time). This prevents incorrect detection due to the ringing voltage while the device is OFF. This design permits detection of the point at which the transformer secondary current is 0A at start-up, and in the case of a load short. The main switching device is then switched on at this point, allowing abnormal oscillation to be controlled. On-trigger disabled during this period. 2.5s 0.2V VZ/C Enlarged view IC Secondary rectification diode VZ/C IC Secondary rectification diode VCE VOUT Fig.3.11 Comparison of Drive Circuits 3.12 Over-current Protection Circuit Body diode A current detection resistor is connected between the Emitter/OCL pin and GND to detect current between the emitter of the main switching device and the emitter current detection pin. 7 Resonating condenser 6 Collector pin Emitter/OCL pin During stable operation the main switching device Current detection current is limited by pulse-by-pulse operation with the resistor 0.6V threshold value. The leading edge clamp function prevents malfunctioning and thus prevents incorrect detection at Fig.3.12 Current Detection Resistor turn-on. During standby, the 50mV threshold value is selected and the oscillation noise from the transformer due to burst oscillation is reduced. Shindengen Electric MFG.CO.,LTD - 11 - MR2900 Application Note Standard circuit/Parts list 4. Standard Circuit L F101 C101 N L101 C103 R101 T101 D201 C102 C104 C105 C108 R102 R103 C109 PC101 6 IC101 2 3 R105 D104 C111 R104 PC102 1 D105 D106 C203 D102 7 5 4 C107 R106 C204 R207 IC201 R204 D103 R206 PC101 R201 R202 R203 PC102 TR201 R208 SW201 R209 D101 C106 C201-1 C201-2 L201 VO C202 R205 GND R210 Shindengen Electric MFG.CO.,LTD - 12 - MR2900 Application Note 5.1 Design Flow Chart 5. Design Procedures Specifications determined Main transformer design Refer to: 5.2 Main Transformer Design Procedure 5.3 Main Transformer Design Examples Selection of primary circuit components Refer to: 5.4 Selection of Constants for Peripheral Components Reexamination Cooling design Trial manufacture Operational checks Problems found No problems Completion 5.2 Main Transformer Design Procedure This design procedure provides an example of an electrical design procedure. Ensure that design of insulation materials, insulation configuration, and structure are in accordance with the necessary safety standards as determined by the relevant authorities. 5.2.1 Standard Design Conditions Abbreviation Minimum input voltage Rated output voltage Rated output current Maximum output current Efficiency Minimum oscillation frequency Duty ratio Control coil voltage Effective cross-sectional area of transformer core Magnetic flux density variation Coil current density VAC(min) Vo Io Io(max) f(min) D VNC Ae B V mm mT A/mm 2 2 Unit V V A A kHz Reference value 0.800.85 25k50kHz 0.500.70 1517V 250320mT 46A/mm 2 Note that the above values are for reference only, and should be adjusted to suit load conditions. Shindengen Electric MFG.CO.,LTD - 13 - 5.2.2 Standard Design Calculations 1 Minimum DC input voltage VDC(min) = 1.2 x VAC(min) [V] 2 Maximum DC input voltage VDC(max) = 2 xVAC(max) T(max) = 1 f(min) [V] 3 Oscillation cycle [s] 4 Maximum ON period ton(max) = D f(min) toff(max) = NS1 xVDC(min) x tON(max) + tq NP x (VO1 +VF1) tq = 2 LP x Cq 2 [s] 5 Maximum OFF period [s] 6 Resonance period [s] 7 Maximum load power Maximum output power (reference value) Peak collector current PO(max) = VO x IO(max) PL = 1.3 x PO(max) ICP = 2 x PL xVDC(min) x D [W] 8 [W] 9 [A] 10 Primary coil inductance LP = VDC(min) x ton(max) ICP 9 NP = VDC(min) x ton(max) x10 B x Ae [H] 11 Number of turns in primary coil [Turn] 12 Core gap lg = 4 x10 -10 x Ae x NP 2 LP [mm] The gap Ig is the center gap value. Review transformer core size and oscillation frequency and redesign if Ig is 1mm or greater. 13 Number of turns in control output coil Number of turns in non-control output coil Number of turns in control coil (VO1 +VF1) x NP x ( 1 - ton(max) - tq) f(min) NS1 = VDC(min) x ton(max) NS2 = NS1 x VO2 +VF2 VO1 +VF1 NC = NS1 x VNC +VFNC VO1 +VF1 [Turn] 14 [Turn] 15 [Turn] Consider the secondary diode forward voltage for each output when determining the number of turns in an output coil. VFNC is the control coil voltage rectification diode forward voltage. The reference value for determining the control coil voltage VNC(min) is 15V to 17V. If the VNC(min) value is too small, start-up characteristics may deteriorate and start-up may become difficult. If the VNC(min) value is too large, the over-voltage latch stop voltage VOP is able to be reached easily. Check the VNC(min) voltage in an actual circuit during the design process to determine its optimum value. Shindengen Electric MFG.CO.,LTD - 14 - 16 Primary coil size ANP = ANS = 2 x D x PO x 3 xxVDC(min) x ton(max) x f(min) 2 x 1 - D - (tq x f(min)) x IO x 3 x (toff(max) - tq) x f(min) [mm ] 2 17 Secondary coil size [mm ] 2 ANC=0.2mm dia. is recommended for the NC coil for ease of calculation. 5.3 Main Transformer Design Examples 5.3.1 Initial Setup Input voltage Efficiency Oscillation frequency at droop Duty ratio AC90276V 85% 29.6kHz TON/T=0.655 Rated output Droop output VO1DC135V, 0.45A VO2DC35V,0.40A VO3DC16V,0.40A 110.36W (rated output x 1.36) Total output 81.2W 5.3.2 Primary Inductance (LP) Calculations Primary inductance (LP) calculated using equations 1, 4, 9, and 10 in 5.2.2. VDC(min) =1.2 xVAC(min) =1.2 x 90 =108 V ton(max) = D = 0.655 3 = 22.13 s f(min) 29.6 x10 ICP = 2 x PL 2 x110.36 = = 3.67 A xVDC(min) x D 0.85 x108 x 0.655 Ensure that ton(max) is 29s or less. Substitute -6 x LP = VDC(min) ton(max) = 108 x 22.13 x10 = 651.24 H ICP 3.67 Primary inductance LP =0.65mH. 5.3.3 Calculation of Number of Turns in Primary Coil (NP), and Gap (Ig) The number of turns in the primary coil is calculated using equation 11 in 5.2.2. Specifications require the use of PC40 EER39L steel in the transformer core. 2 Substitute Ae=130mm and B=310mT in equation 11. 9 -6 9 NP = VDC(min) x ton(max) x10 = 108 x 22.13 x10 x10 = 59.3 59 Turn B x Ae 310 x130 Droop output (rated total output x 1.36) calculated as PL The maximum rating for B for PC40 at 100C is 390mT. B has been derated to 310mT in this example. The gap (Ig) is calculated using equation 12 in 5.2.2. lg = 4 x10 -10 x Ae x NP 2 = 4 x 3.14 x10 -10 x130 x 59 2 = 0.87 mm LP 0.65 x10 - 3 The number of turns in the primary coil is NP=59, and the gap Ig=0.87mm. The gap (Ig) calculated above is a reference value. During trial manufacture, adjust the gap (Ig) in relation to the value found in the calculations, and ensure that it is appropriate to the primary inductance value. The number of turns has been rounded to the nearest integer, however this value may be adjusted as necessary. Shindengen Electric MFG.CO.,LTD - 15 - 5.3.4 Calculation of Number of Turns in Secondary Coil (NS1) The number of turns in the secondary coil is calculated using equation 13 in 5.2.2. (VO1 +VF1) x NP x ( 1 - ton(max) - tq) f(min) NS1 = VDC(min) x ton(max) (135 +1) x 59 x ( = Calculation assumes tq =2.5s. 1 - 22.13 x10 -6 - 2.5 x10 -6 ) 29.6 x10 3 = 30.73 31 Turn 108 x 22.13 x10 -6 The number of turns in the secondary coil is therefore NS1=31. 5.3.5 Verification of Resonance Time (tq) The calculation above assumes a resonance period (tq) of 2.5s. This calculation verifies the effectiveness of this value in terms of LP and the resonance condenser Cq (C108) as previously calculated. tq = 2 LP x Cg 2 0.65 x10 -3 x1000 x10 -12 = = 2.53 s 2 2 If the calculated value differs, change tq and recalculate. Conditions are therefore satisfied. Note that the calculation assumes a resonance condenser Cq of 1000pF. 5.3.6 Calculation of Number of Turns in Secondary Coils (NS2, NS3) The numbers of turns NS2 and NS3 in the secondary coils are calculated using equation 14 in 5.2.2. NS2 = NS1 x VO2 +VF2 = 31 x 35 +1 = 8.20 8 Turn VO1 +VF1 135 +1 NS3 = NS1 x VO3 +VF3 = 31 x 16 + 0.6 = 3.78 4 Turn VO1 +VF1 135 +1 The numbers of turns in the secondary coils are NS2=8 and NS3=4. 5.3.7 Calculation of Number of Turns in Control Coil (NC) A value of between 15V and 17V is optimum for Vcc. This design assumes Vcc=16V, and the number of turns in the control coil is calculated using equation 15 in 5.2.2. NC = NS1 x VNC +VFNC = 31 x 16 +1 = 3.88 4 Turn VO1 +VF1 135 +1 For ease of handling, a 0.2mm dia. wire is recommended for the control coil. Shindengen Electric MFG.CO.,LTD - 16 - 5.3.8 Calculation of Wire Size for Primary Coil (NP) Coil size is calculated using the rated output power. Cross-sectional area of the primary coil is calculated using equation 16 in 5.2.2. 2 With current densityset at 6A/mm , ANP = 2 x D x PO x 3 x xVDC(min) x ton(max) x f(min) Adjust current density in accordance with conditions of use and structure of the transformer. = 2 2 x 0.655 x 81.2 = 0.210 mm 6 x 3 x 0.85 x108 x 22.13 x10 -6 x 29.6 x10 3 A diameter of 0.50mm is therefore appropriate for the wire size of the primary coil. 5.3.9 Calculation of Wire Size for Secondary Coils (NS1, NS2, NS3) Cross-sectional area of the secondary coil is calculated in the same manner as in 5.3.8 using equation 17 in 5.2.2. toff(max) is first calculated using equation 5 in 5.2.2. -6 toff(max) = NS1 xVDC(min) x tON(max) + tq = 31 x108 x 22.13 x10 + 2.5 x10 -6 = 11.73 s NP x (VO1 +VF1) 59 x (135 +1) ANS1 = 2 x 1 - D - (tq x f(min)) x IO1 2 x 1 - 0.655 - (2.5 x10 -6 x 29.6 x10 3 ) x 0.45 2 = = 0.165 mm x 3 x (toff(max) - tq) x f(min) 6 x 3 x (11.73 x10 -6 - 2.5 x10 -6 ) x 29.6 x10 3 2 x 1 - D - (tq x f(min)) x IO2 2 x 1 - 0.655 - (2.5 x10 -6 x 29.6 x10 3 ) x 0.40 2 = = 0.146 mm x 3 x (toff(max) - tq) x f(min) 6 x 3 x (11.73 x10 -6 - 2.5 x10 -6 ) x 29.6 x10 3 2 x 1 - D - (tq x f(min)) x IO3 2 x 1 - 0.655 - (2.5 x10 -6 x 29.6 x10 3 ) x 0.40 2 = = 0.146 mm x 3 x (toff(max) - tq) x f(min) 6 x 3 x (11.73 x10 -6 - 2.5 x10 -6 ) x 29.6 x10 3 ANS2 = ANS3 = The wire sizes for the secondary coils are therefore as follows. NS1: 0.32mm dia. x 2 wires NS2: 0.29mm dia. x 2 wires NS3: 0.29mm dia. x 2 wires NP1=37Turn 0.50mm NP2=22Turn 0.50mm 1 NP1 2 NP2 3 5 NC 6 NS1 NS2 12 11 NS3 10 8 7 NS2=8Turn 0.30mmx2wires NS3=4Turn 0.30mmx2wires NC NP2 NS2 NS3 NS1 NP1 Spacer Spacer NC=4Turn 0.20mm NS1=31Turn 0.30mmx2wires Primary inductance (LP): 0.65mH (between transformer pins and ) Gap Ig: 0.87mm The structure of the transformer requires that all turns in coil NS1 be in a single layer. Fig.5.1 Transformer Specifications and Coil Structure Shindengen Electric MFG.CO.,LTD - 17 - 5.4 Selection of Constants for Peripheral Components 5.4.1 Values of Constants for MR2900 Peripheral Components (see 4. Standard Circuit on P12) Component Constant This is the power supply voltage rectification condenser. If this value is small operation at start-up readily becomes intermittent, and if it is too large start-up time becomes excessive. A value of between 47F and 100F is appropriate. This condenser determines the resonance frequency. Select the value on the basis of noise and efficiency etc. A value of between 820pF and 2200pF is appropriate for autosensing power supplies of between 75W and 150W capacity. This condenser is incorporated to deal with noise at pin 2. A value of approximately 4700pF is appropriate. Also beneficial in gain phase adjustment, however frequency response deteriorates if the value is too large. This is the partial resonance adjustment condenser. Adjust so that turn-on occurs at the resonance trough. Turn-on occurs earlier if this value is small, and later if it is large. A value of between 10pF and 33pF is appropriate. This is the current limiting damper resistor for C108. A value up to a few ohms is appropriate. Select the value on the basis of noise and efficiency etc. This is the over-current detection resistor. It determines the droop point. Calculate the resistance value as follows. [0.60 (over-current threshold voltage) / Droop point collector current at minimum input] Adjust on the basis of droop characteristics. Set to a value slightly higher than the droop point set with R103. A value of a few tens of kohms is appropriate. This resistor compensates for droop due to input voltage. Adjust on the basis of droop characteristics. A value of approximately 50kohms is appropriate. This resistor limits current at the Z/C pin. A value of approximately 20kohms is appropriate. This corresponds to the body diode for the main switching device (ultra high-speed IGBT). Select a high-speed diode in the 900V, 1A class. This is a Zener diode to compensate for droop due to input voltage. Select a diode for a Zener voltage at least equal to that found with the following equation. Zener voltage =1.3 x150 x NC NP (assume an initial compensation voltage of 150V) C107 C108 C109 C111 R102 R103 R104 R105 R106 D102 D106 R105 and D106 are additional components for autosensing input specifications. Shindengen Electric MFG.CO.,LTD - 18 - MR2900 Application Note 6. Cooling Design Tj(max) for the MR Series is 150C. As operation of the MR Series is accompanied by an increase in temperature associated with power losses, it is necessary to consider the type of heat sink to be used. While a design which ensures that Tj(max) is not exceeded is of absolute importance, the overheat protection function (TSD=150C (typical)) must be also considered in any design. The extent to which Tj is derated in a design is therefore extremely important in improving reliability. 6.1 Junction Temperature and Power Losses The majority of power losses during operation of the MR Series are associated with the internal MOSFET. If the majority of power losses are considered as ON losses, they may be expressed by the following equation. PD =VDS xID The temperature increase (Tj) due to power losses (PD) is expressed as, Tj +Ta Tj(max) and if TSD=150C (typical) and TSD(min)=120C are assumed, PD is limited so that the following equation is satisfied. Tj+TaTSD(min) 6.2 Junction Temperature and Thermal Resistance Tj may be calculated as follows using the thermal resistance ja. Tj =( PD xja) +Ta ja is the thermal resistance in the vicinity of the junction, and is expressed as follows. ja =jc +cf +fa Abbreviation Thermal resistance between junction and vicinity. Thermal resistance between junction and case. Thermal resistance between case and fins (contact thermal resistance). Thermal resistance between case and fins (contact thermal resistance). 6.3 Cautions for Cooling Design Thermal shutdown (TSD) is a protective function which stops and latches operation at 150C in the event of abnormal heating of the MR1520. Circuit design therefore requires a cooling design in which temperature has been sufficiently derated. Shindengen recommends that cooling design be such that case temperature does not exceed 100C. ja jc cf fa Unit /W /W /W /W Shindengen Electric MFG.CO.,LTD - 19 - |
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