Convertible Bonds: A Complete Dissection
The hybrid security offering bond downside protection and equity upside simultaneously — structure, payoff mechanics, delta hedging, from Airbnb's textbook case to Korean governance controversies.
1. What Is a CB?
A convertible bond (CB) is a hybrid security combining the characteristics of both debt and equity. The holder receives interest payments until maturity and holds the option to convert into shares when the stock price rises.
Convertible Bond = Bond + Equity Option Hybrid
A CB simultaneously provides bond downside protection and equity upside participation. Issuers raise capital at low coupons; investors capture capital gains when the stock rises.
Low coupon (0–2%) financing. Upon conversion, debt becomes equity → lower leverage ratio.
Principal protection (bond) + capital gain on stock upside (equity). Asymmetric return profile.
During market disruptions when IPO/follow-on windows are closed, CBs often become the only ECM funding mechanism.
2. Structure & Mechanics
Understanding a CB starts with five key terms. Conversion price and conversion ratio form the foundation of the CB return structure, while coupon and maturity define the bond dimension.
전환가격
Price at which the bond converts to shares. Set at 30–40% premium to current share price.
전환비율
Number of shares received per bond. = Face value / Conversion price
전환프리미엄
Premium of conversion price over current share price. Higher = less likely to convert.
쿠폰
Lower than straight bonds (0–2%). The conversion option substitutes part of the coupon.
만기
Typically 3–7 years. If not converted, repaid at par.
Convertible Bond vs Straight Bond
| Feature | Convertible Bond | Straight Bond |
|---|---|---|
| Coupon | 0–2% (low) | Market rate |
| Principal protection | Yes (if not converted) | Yes |
| Equity upside | Yes (conversion option) | None |
| Dilution risk | Yes (upon conversion) | None |
| Complexity | High (embedded option) | Low |
3. Payoff Diagram
The CB payoff is a non-linear structure that behaves either like a bond or like equity depending on the share price level. Delta (Δ) quantifies this transition.
Convertible Bond Payoff Diagram
CB value composition by share price scenario — Bond floor (downside protection) + Equity option value (upside participation)
Share price above conversion price → acts like equity. Exercise conversion → capital gain. Issuer: no repayment needed
Share price near conversion price → mixed bond+option value. Ambiguous zone for conversion.
Share price below conversion price → acts like bond. Principal + interest protected. 'Seatbelt' engaged
4. Investor Types
CBs attract not a single investor base but three distinct investor types, each with different strategies and objectives.
CB Specialist Funds
Hedge funds investing exclusively in CBs. Bond yield + equity upside.
Delta Hedge Funds
Buy CB and short the underlying stock to maintain delta-neutral position. Target volatility profits.
Credit Investors
Portfolio diversification into safer hybrid than high-yield. Conversion option is a bonus.
5. Case Studies
Real CB issuances illustrate how this instrument is used across vastly different contexts — from crisis rescue to asset leverage to governance abuse.
Airbnb CB
2020$2B CB at 0% coupon (April 2020, COVID worst point). Conversion price $28 → IPO price $68 → investors 143% return
The CB textbook: issuer raises capital at 0% interest, investors participate in equity upside. When ECM markets were closed during COVID, CBs were the only funding window.
MicroStrategy CB
2020–2024$7B+ total CB issuance → fund Bitcoin purchases. CB investors = indirect BTC long
Extreme example of using CBs as an asset leverage tool. Low coupons (0–0.625%) to buy massive BTC. Risk of covenant breach during BTC crashes was highlighted.
Korean CB — Hanwha Affiliate
2022Private CB issued to related parties at below-market terms → minority shareholder loss → FSS investigation → tighter third-party allocation rules
In Korea's market, CBs are sometimes misused to expand controlling shareholder stakes. When Refixing (downward conversion price adjustment) + third-party allocation are combined, minority shareholder dilution can be severe.