Switching Power Supply Startup Circuit Stabilization
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Solution Overview
Problem
In switching power-supply apparatuses, using a small capacity capacitor for the power-supply voltage can lead to start-up failures due to rapid voltage drops when the control circuit is initiated, causing repeated starting and stopping of the control circuit.
Innovation Solution
The apparatus employs a starting circuit that supplies a first constant current when the power-supply voltage is below a threshold voltage and a second, higher constant current when the voltage exceeds this threshold, with the first constant current being maintained during the control circuit's startup to stabilize the power-supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a small capacity capacitor is used for the power-supply voltage, then the starting speed of the control circuit is improved and cost is reduced, but the power-supply voltage drops rapidly causing start-up failures
Solution Approach 1:
The starting circuit performs preliminary action by proactively supplying a first starting current to the control circuit before the power-supply voltage drops. This advance current supply ensures the control circuit has sufficient power to start up reliably, preventing the voltage drop issue that would otherwise cause start-up failures.
Solution Approach 2:
The starting circuit changes the current parameter dynamically by supplying a first starting current when the control circuit needs to start up, and then switching to a second starting current when the power-supply voltage exceeds a threshold. This parameter change allows optimization of both starting speed and reliability under different operating conditions.
2Reliability
If a constant current circuit supplies starting current continuously, then the control circuit can start reliably, but power loss increases during normal operation
Solution Approach 1:
The starting circuit employs periodic action by operating in different modes: it supplies a first starting current during start-up phase, then switches to supplying a second starting current when the power-supply voltage exceeds the threshold. This periodic switching reduces power loss during normal operation while maintaining reliability during start-up.
Solution Approach 2:
The starting circuit is designed to be dynamic rather than static, automatically adjusting the starting current it supplies based on the power-supply voltage level. When voltage is low, it supplies higher current; when voltage exceeds threshold, it supplies lower current. This dynamic behavior optimizes both reliability and energy efficiency.
3Reliability
If the starting circuit supplies high current continuously, then the control circuit starts reliably, but the capacitor cannot be small capacity
Solution Approach 1:
The starting circuit uses periodic action to supply high current only when necessary (when power-supply voltage is below threshold), and reduces current supply when voltage is sufficient. This allows the use of a smaller capacity capacitor while maintaining reliable start-up, as the high current is not needed continuously.
Solution Approach 2:
The invention extracts the high current supply function from continuous operation and applies it only during the specific period when needed for reliable start-up. By separating the high current requirement from continuous operation, the capacitor capacity can be reduced while maintaining start-up reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration prevents power-supply voltage drops until the voltage generated in the transformer's tertiary winding reaches operating levels, ensuring stable operation and preventing start-up failures even with small-capacity capacitors.
Implementation Method 1
a first constant current circuit that supplies a first starting current to the control circuit when the power supply voltage is equal to or lower than a first threshold voltage
Implementation Method 2
a second constant current circuit that supplies a second starting current to the control circuit when the power supply voltage is larger than the first threshold voltage
Implementation Method 3
a transformer T having a primary winding P1, a secondary winding S1 and a tertiary winding P2
Data Source
AI summary
A switching power-supply apparatus includes: a control circuit that controls on-and-off switching of a switching element; a first rectifying-and-smoothing circuit that smoothes a voltage generated in a secondary winding; and a second rectifying-and-smoothing circuit that smoothes a voltage generated in a tertiary winding as a power supply voltage, a starting circuit that supplies as a starting current: a first constant current to the control circuit when the power supply voltage is equal to or lower than a first threshold voltage, which is lower than a starting voltage of the control circuit; a second constant current, which is greater than the first constant current, to the control circuit when the power supply voltage is larger than the first threshold voltage and is equal to or lower than the starting voltage; and the first constant current to the control circuit while the control circuit is started up.