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 … 4 1.2 Characteristics … 4 1.3 Applications 1.4 Absolute Maximum Ratings and Reference Output Capacities 1.5 Equivalent Circuit and Dimensions … 4 … 4 … 4 2.1 Block Diagram … 5 2.2 Pin Function Description … 5 3.1 Start-up Circuit … 6 3.2 On-trigger Circuit … 7 3.3 Partial Resonance … 7 3.4 Standby Mode Control … 8 3.5 Output Voltage Control … 9 3.6 Soft Drive Circuit … 9 3.7 Circuit for Load Shorts … 10 3.8 Collector Pin (pin 7) … 10 3.9 Thermal Shut-down Circuit (TSD) … 10 3.10 Over-voltage Protection Circuit (OVP) … 10 … 11 … 11 … 12 5.1 Design Flow Chart … 13 5.2 Main Transformer Design Procedure … 13 5.3 Main Transformer Design Examples 5.4 Selection of Constants for Peripheral Components … 15 … 18 … 19 … 19 … 19 2. Block Diagram 3. Operation Description 3.11 Malfunction Prevention Circuit (patent applied for) 3.12 Over-current Protection Circuit 4. Standard Circuit 5. Design Procedures 6. Cooling Design 6.1 Junction Temperature and Power Losses 6.2 Junction Temperature and Thermal Resistance 6.3 Cautions for Cooling Design 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. Outline 1.1 Introduction 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 Maximum output capacity Po［W］ Absolute maximum ratings Model Peak input voltage Peak input current Vin［V］ Iin［A］ 90V to 276VAC 180V to 276VAC 7 100 150 10 150 225 MR2920 900 MR2940 Input voltage range Maximum output capacity and input voltage range differ with design conditions. 1.5 Equivalent Circuit and Dimensions φ3.2 20.0±0.2 5.0±0.2 12.0 4.2 Collector Z/C 4 Vcc 5 Vin 2.4±0.2 6 Emitter/OCL 2.54±0.2 6×1.7±0.3=15.24±0.3 4.2±0.5 7.6±0.5 GND IC1 11.8 3 3.0±0.2 F/B ±0.5 Q1 2 16.7±0.3 1 8.0 7 +0.2 -0.1 0.7 +0.3 -0.1 2.7±0.2 0.7±0.2 4.5±0.5 Shindengen Electric MFG.CO.,LTD - 4 - MR2900 Application Note 2. Block Diagram 2.1 Block Diagram Vcc 4 Unlatch comparator UVLO comp Vin Collector 5 7 Start-up circuit UVLO comparator Start-up circuit OVP comparator VUL VCC(start) /VCC(stop) VCC(startup off) /VCC(startup on) R VOVP Z/C 1 Q Thermal Shutdown circuit Zero current detection circuit S Q1 Soft drive circuit S Q On-dead timer R Excess current detection comparator Standby circuit VTH(OCL) Vref IF/B F/B 2 Restart timer Burst current limit comparator ON range timer VTH(burst limit) 3 6 GND Emitter/OCL 2.2 Pin Function Description Pin number Abbreviation 1 Z/C Trigger input pin 2 F/B Feedback signal input pin 3 GND 4 Vcc IC power supply pin 5 Vin Start pin 6 7 Emitter /OCL Collecter Description Zero detection voltage: 0.35V Standby: Up to 4.5V in standby mode. ton(min) to ton(max): 1.5V to 4.5V/0μs to 25μs Standby: Oscillation stopped at up to 0.8V. Standby: Oscillation started at 1.8V or higher. GND pin Main switching device emitter and current detection pin Main switching device collector pin Oscillation start voltage: Vcc≧14V Oscillation stop voltage: Vcc≦8.5V Excess voltage latching voltage:Vcc=20V Current supplied Vin→Vcc at start-up Start-up circuit OFF:Vcc≧14V Start-up circuit ON: Vcc≦7.6V Excess current detection threshold:0.6V Excess current detection threshold at standby: 50mV Shindengen Electric MFG.CO.,LTD - 5 - MR2900 Application Note 3. Operation Description 3.1 Start-up Circuit 【Conventional 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. Start-up current IC Start-up current flows even during steady-state operation, resulting in losses. 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. 【MR2000 Start-up Circuit】 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. Start-up current switched off following start-up, thus eliminating the need for start-up resistors. 5 Vin pin Control coil Vcc(startup off) /Vcc(startup on) 14.5V/7.2V 4 Vcc pin 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 【Vin】 VCC(stop) =8.5V VCC(startup on) =7.6V 【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 0.2V 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. 【VZ/C】 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. 【IC】 The on-trigger detection voltage (0.2V) incorporates a 50mV hystersis to increase noise resistance. 【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. On timing delayed with CR time constant. Emitter/OCL pin Resonating condenser 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. 7 6 Collector pin 1 Z/C pin R 3 GND pin C Turn-on delay Damping begins at the resonance frequency determined by LP and C. 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. 【VCE】 The use of partial resonance is effective in permitting a simple circuit configuration with improved efficiency and noise reduction. 【Secondary rectification diode current】 【IC】 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. Drain pin 7 Z/C pin Emitter/OCL pin 6 1 F/B pin 2 4.5V (TYP) Switched from 0.6V to 0.05V 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. 3 Output voltage error detection feedback signal Standby signal (external signal) Fig.3.5 Standby Mode Control VF/B(burst stop) =0.8V 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. VF/B(burst start) =1.8V 【VF/B】 【IC】 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. 【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 Normal operation Fig.3.7 Standby Signal Receive Sequence Shindengen Electric MFG.CO.,LTD - 8 - 3.5 Output Voltage Control (normal operation) 5Vref The MR2000 Series controls output voltage with the ON range proportional to the voltage at the F/B pin. 200μA When the voltage at the F/B pin is 1.5V the ON range is 0µs, and is controlled in a linear manner so that when the voltage is 4.5V the ON range is 25µs. A current of 200µA=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. F/B pin 2 Output voltage controlled by varying impedance of photocoupler. ON range ton［μs］ Droop resistor 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. Output voltage error detection feedback signal 25 0 1.5 4.5 Feedback voltage VF/B［V］ Fig.3.8 Output Voltage Control 3.6 Soft Drive Circuit (patent applied for) Gate voltage supply matched to collector current. 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). 【VGE】 Gate charge remains unchanged even when collector current is small. Gate charge spikes reduced. 【IG】 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. 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 150°C (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) On-trigger disabled during this period. 2.5μs 0.2V 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 2.7μs (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. 【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 - Standard circuit/Parts list MR2900 Application Note 4. Standard Circuit L101 L T101 R101 C103 F101 C102 C104 L201 VO D201 C101 N C201-2 R205 C201-1 C106 D101 C202 GND C105 C108 C203 D102 R102 R103 PC101 7 5 6 C109 PC101 D103 R202 4 IC101 2 C107 R206 R106 1 3 R105 R201 R203 C204 D105 D106 D104 PC102 R207 IC201 R208 TR201 SW201 R209 R210 R204 C111 R104 PC102 Shindengen Electric MFG.CO.,LTD - 12 - MR2900 Application Note 5. Design Procedures 5.1 Design Flow Chart Specifications determined Main transformer design Selection of primary circuit components Reexamination Refer to: 5.2 Main Transformer Design Procedure 5.3 Main Transformer Design Examples Refer to: 5.4 Selection of Constants for Peripheral Components 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 Minimum input voltage Rated output voltage Rated output current Maximum output current Efficiency Abbreviation Unit Reference value VAC(min) V Vo V ― ― Io A ― Io(max) A ― kHz 25k～50kHz 0.80～0.85 η Minimum oscillation frequency f(min) Duty ratio 0.50～0.70 D Control coil voltage VNC 15～17V V 2 Effective cross-sectional area of transformer core Ae Magnetic flux density variation ΔB mT α A/mm Coil current density ― mm 250～320mT 2 2 4～6A/mm 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 × VAC(min) [V] 2 Maximum DC input voltage VDC(max) = 2 ×VAC(max) [V] 3 Oscillation cycle T(max) = 1 [s] f(min) 4 Maximum ON period ton(max) = D f(min) [s] 5 Maximum OFF period toff(max) = NS1 ×VDC(min) × tON(max) + tq NP × (VO1 +VF1) [s] 6 Resonance period tq = 7 Maximum load power PO(max) = VO × IO(max) [W] 8 Maximum output power (reference value) PL = 1.3 × PO(max) [W] 9 Peak collector current ICP = 2 × PL η×VDC(min) × D [A] 10 Primary coil inductance LP = VDC(min) × ton(max) ICP [H] 11 Number of turns in primary coil 9 NP = VDC(min) × ton(max) ×10 ΔB × Ae 12 Core gap 2π LP × Cq 2 lg = 4π ×10 −10 [s] [Turn] × Ae × NP 2 [mm] LP 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 (VO1 +VF1) × NP × ( 1 - ton(max) - tq) f(min) NS1 = VDC(min) × ton(max) [Turn] 14 Number of turns in non-control output coil NS2 = NS1 × VO2 +VF2 VO1 +VF1 [Turn] 15 Number of turns in control coil NC = NS1 × VNC +VFNC VO1 +VF1 [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 = 2 × D × PO α× 3 ×η×VDC(min) × ton(max) × f(min) [mm ] 17 Secondary coil size ANS = 2 × 1 − D − (tq × f(min)) × IO α × 3 × (toff(max) − tq) × f(min) [mm ] 2 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 AC90～276V 85% Oscillation frequency at droop 29.6kHz Duty ratio TON/T=0.655 Rated output VO1：DC135V, 0.45A VO2：DC35V,0.40A Total output 81.2W VO3：DC16V,0.40A Droop output 110.36W (rated output x 1.36) 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 ×VAC(min) =1.2 × 90 =108 ［V］ Ensure that ton(max) is 29μs or less. ton(max) = D = 0.655 3 = 22.13 ［μs］ f(min) 29.6 ×10 ICP = 2 × PL 2 ×110.36 = = 3.67 ［A］ η×VDC(min) × D 0.85 ×108 × 0.655 Droop output (rated total output x 1.36) calculated as PL Substitute -6 × LP = VDC(min) ton(max) = 108 × 22.13 ×10 = 651.24 ［μH］ 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 ΔB=310mT in equation 11. The maximum rating for ΔB for PC40 at 100°C is 390mT. ΔB has been derated to 310mT in this example. 9 -6 9 NP = VDC(min) × ton(max) ×10 = 108 × 22.13 ×10 ×10 = 59.3 ≅ 59 ［Turn］ ΔB × Ae 310 ×130 The gap (Ig) is calculated using equation 12 in 5.2.2. lg = 4π ×10 × Ae × NP 2 = 4 × 3.14 ×10 −10 ×130 × 59 2 = 0.87 ［mm］ LP 0.65 ×10 - 3 -10 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) × NP × ( 1 - ton(max) - tq) f(min) NS1 = VDC(min) × ton(max) (135 +1) × 59 × ( = Calculation assumes tq =2.5μs. 1 − 22.13 ×10 −6 − 2.5 ×10 −6 ) 29.6 ×10 3 = 30.73 ≅ 31 ［Turn］ 108 × 22.13 ×10 −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 2.5μs. This calculation verifies the effectiveness of this value in terms of LP and the resonance condenser Cq (C108) as previously calculated. tq = 2π LP × Cg 2π 0.65 ×10 −3 ×1000 ×10 −12 = = 2.53 ［μs］ 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 × VO2 +VF2 = 31 × 35 +1 = 8.20 ≅ 8 ［Turn］ VO1 +VF1 135 +1 NS3 = NS1 × VO3 +VF3 = 31 × 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 × VNC +VFNC = 31 × 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 density（α）set at 6A/mm , ANP = = Adjust current density in accordance with conditions of use and structure of the transformer. 2 × D × PO α × 3 ×η ×VDC(min) × ton(max) × f(min) 2 2 × 0.655 × 81.2 = 0.210 ［mm ］ 6 × 3 × 0.85 ×108 × 22.13 ×10 −6 × 29.6 ×10 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 ×VDC(min) × tON(max) + tq = 31 ×108 × 22.13 ×10 + 2.5 ×10 −6 = 11.73 ［μs］ NP × (VO1 +VF1) 59 × (135 +1) ANS1 = 2 × 1 − D − (tq × f(min)) × IO1 2 × 1 − 0.655 − (2.5 ×10 −6 × 29.6 ×10 3 ) × 0.45 2 = = 0.165 ［mm ］ α × 3 × (toff(max) − tq) × f(min) 6 × 3 × (11.73 ×10 −6 − 2.5 ×10 −6 ) × 29.6 ×10 3 ANS2 = 2 × 1 − D − (tq × f(min)) × IO2 2 × 1 − 0.655 − (2.5 ×10 −6 × 29.6 ×10 3 ) × 0.40 2 = = 0.146 ［mm ］ α × 3 × (toff(max) − tq) × f(min) 6 × 3 × (11.73 ×10 −6 − 2.5 ×10 −6 ) × 29.6 ×10 3 ANS3 = 2 × 1 − D − (tq × f(min)) × IO3 2 × 1 − 0.655 − (2.5 ×10 −6 × 29.6 ×10 3 ) × 0.40 2 = = 0.146 ［mm ］ α × 3 × (toff(max) − tq) × f(min) 6 × 3 × (11.73 ×10 −6 − 2.5 ×10 −6 ) × 29.6 ×10 3 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=37［Turn］ 0.50mmφ NP2=22［Turn］ 0.50mmφ 1 12 NP1 2 NS2 3 11 NS3 10 5 8 NP2 NS2=8［Turn］ 0.30mmφ×2wires NC NS3=4［Turn］ 0.30mmφ×2wires NP2 NS2 NS3 NS1 NC=4［Turn］ 0.20mmφ NC 6 NS1 7 NP1 NS1=31［Turn］ 0.30mmφ×2wires Spacer Spacer Primary inductance (LP): 0.65mH (between transformer pins ① and ③) 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 C107 C108 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 47μF and 100μF 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. C109 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. C111 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. R102 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. R103 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] R104 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. R105 This resistor compensates for droop due to input voltage. Adjust on the basis of droop characteristics. A value of approximately 50kohms is appropriate. R106 This resistor limits current at the Z/C pin. A value of approximately 20kohms is appropriate. D102 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. D106 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 ×150 × NC NP (assume an initial compensation voltage of 150V) 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 150°C. 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=150°C (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 ×ID The temperature increase (ΔTj) due to power losses (PD) is expressed as, ΔTj +Ta ≦Tj(max) and if TSD=150°C (typical) and TSD(min)=120°C are assumed, PD is limited so that the following equation is satisfied. ΔTj+Ta≦TSD(min) 6.2 Junction Temperature and Thermal Resistance Tj may be calculated as follows using the thermal resistance θja. Tj =( PD ×θja) +Ta θja is the thermal resistance in the vicinity of the junction, and is expressed as follows. θja =θjc +θcf +θfa 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). Abbreviation Unit θja θjc ℃/W ℃/W θcf ℃/W θfa ℃/W 6.3 Cautions for Cooling Design Thermal shutdown (TSD) is a protective function which stops and latches operation at 150°C 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 100°C. Shindengen Electric MFG.CO.,LTD - 19 -